|
Digital Camera Patent Abstract
A digital camera includes an image pickup device which converts
incident light of an object image into an electrical signal during
an exposure operation; a processor which captures the electrical
signal, and thereafter generates a digital image from the electrical
signal; a battery checking device which performs a battery check
process for determining whether a battery voltage of the digital
camera is lower than a predetermined voltage level; a controller
which forcibly terminates the exposure operation when the battery
checking device determines that the battery voltage drops below
the predetermined voltage level during the exposure operation, and
subsequently makes the processor start capturing the electrical
signal in order to generate a backup digital image; and a warning
device which warns a user that the exposure operation is forcibly
terminated due to a shortage of the battery voltage and that the
backup digital image is underexposed, in the case where the exposure
is forcibly terminated.
Digital Camera Patent Claims
What is claimed is:
1. A digital camera comprising: an image pickup device which converts
incident light of an object image into an electrical signal during
an exposure operation; a processor which captures said electrical
signal, and thereafter generates a digital image from said electrical
signal; a battery checking device which performs a battery check
process for determining whether a battery voltage of said digital
camera is lower than a predetermined voltage level; a controller
which forcibly terminates said exposure operation when said battery
checking device determines that said battery voltage drops below
said predetermined voltage level during said exposure operation,
and subsequently makes said processor start capturing said electrical
signal in order to generate a backup digital image; and a warning
device which warns a user that said exposure operation is forcibly
terminated due to a shortage of said battery voltage and that said
backup digital image is underexposed, in the case where said exposure
is forcibly terminated.
2. The digital camera according to claim 1, further comprising
an indicator on which at least one of said digital image and a determined
result of said battery checking device are indicated, wherein said
backup digital image and an underexposure warning indication are
both indicated on said indicator in the case where said exposure
is forcibly terminated.
3. The digital camera according to claim 1, wherein said battery
checking device performs said battery check process during exposure
at a shutter speed one of equal to and slower than a flash sync
speed, and does not perform said battery check process during exposure
at a shutter speed faster than said flash sync speed.
4. The digital camera according to claim 3, further comprising:
an inverse calculating device for calculating back an amount of
underexposure with respect to a correct exposure from a timing of
said forced termination of said exposure operation and a optimum
shutter speed; and a data storing device for storing said backup
digital image and corresponding data of said amount of underexposure.
5. The digital camera according to claim 4, wherein said backup
digital image is visually indicated on said indicator together with
said corresponding data of said amount of underexposure.
6. The digital camera according to claim 1, further comprising
a release button which starts said exposure operation upon being
depressed, wherein said battery checking device performs said battery
check process during said exposure operation when said digital camera
is in a bulb mode, in which said exposure continues as long as said
release button is held down.
7. The digital camera according to claim 1, further comprising
a remote-control signal receiver which receives a remote control
signal transmitted from a remote controller provided independently
of said digital camera, wherein said battery checking device performs
said battery check process during said exposure when said digital
camera is in a remote-control bulb mode, in which said exposure
continues as long as said remote-control signal receiver receives
said remote control signal.
8. The digital camera according to claim 1, wherein said predetermined
voltage level is determined by determining a battery type of said
battery via a difference in voltage between said battery under a
loaded state and said battery under a non-loaded state.
9. A digital camera comprising: an image pickup device which converts
incident light of an object image into an electrical signal during
an exposure operation; a processor which captures said electrical
signal, and thereafter generates a digital image from said electrical
signal; a battery checking device which performs a battery check
process for determining whether a battery voltage of said digital
camera is lower than a predetermined voltage level; and a controller
which forcibly terminates said exposure operation when said battery
checking device determines that said battery voltage drops below
said predetermined voltage level during said exposure operation,
and subsequently makes said processor start capturing said electrical
signal in order to generate a backup digital image, wherein said
battery checking device performs said battery check process during
exposure at a shutter speed one of equal to and slower than a flash
sync speed, and does not perform said battery check process during
exposure at a shutter speed faster than said flash sync speed.
10. The digital camera according to claim 9, further comprising
a warning device which warns a user that said exposure operation
is forcibly terminated due to a shortage of said battery voltage
and that said backup digital image is underexposed, in the case
where said exposure is forcibly terminated.
11. The digital camera according to claim 9, further comprising
an indicator on which at least one of said digital image and a determined
result of said battery checking device are indicated, wherein said
backup digital image and an underexposure warning indication are
both indicated on said indicator in the case where said exposure
is forcibly terminated.
12. The digital camera according to claim 9, further comprising:
an inverse calculating device for calculating back an amount of
underexposure with respect to a correct exposure from a timing of
said forced termination of said exposure operation and a optimum
shutter speed; and a data storing device for storing said backup
digital image and corresponding data of said amount of underexposure.
13. The digital camera according to claim 12, wherein said backup
digital image is visually indicated on said indicator together with
said corresponding data of said amount of underexposure.
14. The digital camera according to claim 9, further comprising
a release button which starts said exposure operation upon being
depressed, wherein said battery checking device performs said battery
check process during said exposure operation when said digital camera
is in a bulb mode, in which said exposure continues as long as said
release button is held down.
15. The digital camera according to claim 9, further comprising
a remote-control signal receiver which receives a remote control
signal transmitted from a remote controller provided independently
of said digital camera, wherein said battery checking device performs
said battery check process during said exposure when said digital
camera is in a remote-control bulb mode, in which said exposure
continues as long as said remote-control signal receiver receives
said remote control signal.
16. The digital camera according to claim 9, wherein said predetermined
voltage level is determined by determining a battery type of said
battery via a difference in voltage between said battery under a
loaded state and said battery under a non-loaded state.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a digital camera having
an exposure mode (e.g., bulb mode) that is used for long exposures
(e.g., an exposure for several seconds or longer).
[0003] 2. Description of the Related Art
[0004] Some digital cameras have an exposure mode in which the
shutter remains open for several seconds or longer, e.g., a bulb
mode in which the shutter remains open as long as the shutter release
button is held down or a slow shutter mode in which the shutter
is released at a shutter speed slower than a normal shutter speed.
Prior to an exposure operation (photographing operation) in such
an exposure mode, a battery check process is generally performed
to prevent the camera from malfunctioning due to a battery voltage
drop of the digital camera. In the battery check process it is determined
whether the battery voltage is below a predetermined voltage level
(battery-check level), and an exposure operation is allowed to be
performed only when it is determined that the battery voltage is
equal to or higher than the battery-check level. If it is determined
that the battery voltage is lower than the battery-check level,
a warning (e.g., a warning indication) is issued in order to warn
the user that the battery is flat (i.e., having insufficient power)
to urge the user to replace the battery with a new one, and/or prohibits
further use of the flat battery.
[0005] However, there is a possibility of the battery voltage dropping
below the battery-check level during exposure in slow shutter mode
or bulb mode, even if it is determined that the battery voltage
is equal to or higher than battery-check level before exposure.
This is because the exposure time in such an exposure mode is usually
much longer than a normal exposure time. In conventional digital
cameras, all the operations are forcibly terminated once the battery
voltage drops below the battery-check level even during exposure,
which makes it impossible to capture a desired digital image in
such circumstances. Consequently, a photographing operation in such
a long exposure mode ends up in failure.
SUMMARY OF THE INVENTION
[0006] The present invention provides a digital camera which makes
it possible to secure a digital image even if a shortage of the
battery power is detected during exposure.
[0007] The present invention has been devised from the standpoint
that digital images captured by a digital camera can be subjected
to correction via digital image processing. If an exposure is forcibly
terminated due to the battery voltage dropping during exposure,
a digital image is secured from the electrical signal which has
been accumulated in the image pickup device until moment at which
the exposure is forcibly terminated, and the digital image thus
obtained is subjected to digital image processing to thereby prevent
a photographing operation from ending up in failure.
[0008] According to an aspect of the present invention, a digital
camera is provided, including an image pickup device which converts
incident light of an object image into an electrical signal during
an exposure operation; a processor which captures the electrical
signal, and thereafter generates a digital image from the electrical
signal; a battery checking device which performs a battery check
process for determining whether a battery voltage of the digital
camera is lower than a predetermined voltage level; a controller
which forcibly terminates the exposure operation when the battery
checking device determines that the battery voltage drops below
the predetermined voltage level during the exposure operation, and
subsequently makes the processor start capturing the electrical
signal in order to generate a backup digital image; and a warning
device which warns a user that the exposure operation is forcibly
terminated due to a shortage of the battery voltage and that the
backup digital image is underexposed, in the case where the exposure
is forcibly terminated.
[0009] It is desirable for the digital camera to include an indicator
on which at least one of the digital image and a determined result
of the battery checking device are indicated. The backup digital
image and an underexposure warning indication are both indicated
on the indicator in the case where the exposure is forcibly terminated.
[0010] It is desirable for the battery checking device to perform
the battery check process during exposure at a shutter speed one
of equal to and slower than a flash sync speed, and not to perform
the battery check process during exposure at a shutter speed faster
than the flash sync speed.
[0011] It is desirable for the digital camera to include an inverse
calculating device for calculating back an amount of underexposure
with respect to a correct exposure from a timing of the forced termination
of the exposure operation and a correct shutter speed, and a data
storing device for storing the backup digital image and corresponding
data of the amount of underexposure.
[0012] It is desirable for the backup digital image to be visually
indicated on the indicator together with the corresponding data
of the amount of underexposure.
[0013] It is desirable for the digital camera to include a release
button which starts the exposure operation upon being depressed,
wherein the battery checking device performs the battery check process
during the exposure operation when the digital camera is in a bulb
mode, in which the exposure continues as long as the release button
is held down.
[0014] It is desirable for the digital camera to include a remote-control
signal receiver which receives a remote control signal transmitted
from a remote controller provided independently of the digital camera,
wherein the battery checking device performs the battery check process
during the exposure when the digital camera is in a remote-control
bulb mode, in which the exposure continues as long as the remote-control
signal receiver receives the remote control signal.
[0015] It is desirable for the predetermined voltage level to be
determined by determining a battery type of the battery via a difference
in voltage between the battery under a loaded state and the battery
under a non-loaded state.
[0016] In another embodiment, a digital camera is provided, including
an image pickup device which converts incident light of an object
image into an electrical signal during an exposure operation; a
processor which captures the electrical signal, and thereafter generates
a digital image from the electrical signal; a battery checking device
which performs a battery check process for determining whether a
battery voltage of the digital camera is lower than a predetermined
voltage level; a controller which forcibly terminates the exposure
operation when the battery checking device determines that the battery
voltage drops below the predetermined voltage level during the exposure
operation, and subsequently makes the processor start capturing
the electrical signal in order to generate a backup digital image,
the battery checking device performs the battery check process during
exposure at a shutter speed one of equal to and slower than a flash
sync speed, and does not perform the battery check process during
exposure at a shutter speed faster than the flash sync speed.
[0017] It is desirable for the digital camera to include a warning
device which warns a user that the exposure operation is forcibly
terminated due to a shortage of the battery voltage and that the
backup digital image is underexposed, in the case where the exposure
is forcibly terminated.
[0018] In the digital camera according to the present invention,
since the processor commences to capture an electrical signal from
the image pickup device at the same time an exposure is forcibly
terminated in the event that the battery voltage drops below a predetermined
voltage level during exposure, a backup digital image can be reliably
obtained from the electrical signal which has been accumulated in
the image pickup device until the forced termination of the exposure.
Although the backup digital image thus obtained turns out to be
an underexposed image, the backup digital image can be subjected
to digital image processing to produce a corrected digital image
as if it had been captured at correct exposure. Accordingly, even
if the digital camera lapses into a shortage of battery power during
exposure (especially during a long exposure), the worst case scenario
in which no digital image data during exposure remains can be prevented
from occurring. In addition, since the backup digital image obtained
when an exposure is forcibly terminated is visually indicated together
with a warning of underexposure on a display monitor, this warning
can warn the user that the backup digital image has resulted in
underexposure due to a shortage of battery power.
[0019] Additionally, in the case where a shutter speed is slower
than a flash-sync speed, the backup digital image is visually indicated
together with the amount of underexposure (and the amount of exposure
compensation) on the display monitor, so that the user can correct
the backup digital image via digital image processing with reference
to the amount of underexposure (and the amount of exposure compensation)
as appropriate.
[0020] The present disclosure relates to subject matter contained
in Japanese Patent Application No.2004-107071 (filed on Mar. 31,
2004) which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be described below in detail
with reference to the accompanying drawings in which:
[0022] FIG. 1 is a basic block diagram of a control system of an
embodiment of a digital camera according to the present invention;
[0023] FIGS. 2A, 2B, 2C and 2D show a flow chart of a routine "CAMERA
MAIN PROCESS" performed in the digital camera having the control
system shown in FIG. 1;
[0024] FIGS. 3A, 3B and 3C show a flow chart of a subroutine "EXPOSURE
PROCESS" performed in the routine "CAMERA MAIN PROCESS"
shown in FIG. 2D;
[0025] FIG. 4 is a timing chart showing various events when it
is detected that the battery is flat during exposure in bulb mode;
and
[0026] FIG. 5 is a timing chart showing various events when it
is detected that the battery is flat during exposure in slow shutter
mode.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] An embodiment of a digital camera the control system which
is shown in FIG. 1 is provided with a battery-power check device.
The control system is provided with a CPU (controller) 11 and a
DPU (processor) 12 for comprehensively controlling the overall operations
of the digital camera. The CPU 11 and the DPU 12 are interconnected
to each other via a bus line.
[0028] The control system is provided with a battery 20, a power
circuit 21, an external flash 22, a diaphragm control circuit 23,
a TTL light modulating device 24, an electronic beeper 25, a distance-measuring-area
superimposing device 26, a mode select dial 27, various switches
28, a lens CPU 31 provided in a photographing lens of the digital
camera, an AFIC (auto focus integrated circuit) 32 and a retractable
built-in flash 33 which are all connected to the DPU 12. The DPU
12 mutually communicates with the CPU 11. The DPU 12 operates by
receiving commands from the CPU 11, and sends the CPU 11 information
of various operating statuses and settings of peripheral circuits
and elements which are connected to the DPU 12.
[0029] The battery 20 is used as a power source of the digital
camera, and is connected to each of the DPU 12 and the power circuit
21. One type of battery, which serves as the battery 20, is selected
by the user from among different types of batteries such as an alkaline
battery, a lithium battery (e.g., CR-V3) and a nickel metal hydride
(Ni-MH) battery. The power circuit 21 continuously supplies power
to the CPU 11 and the DPU 12, and controls the power supply to a
built-in flash 33, a mirror motor driver 35, an AF motor driver
38 and a DSP 13 of the control system, in accordance with a power-supply
control command input from the DPU 12.
[0030] The DPU 12 is provided with a voltage monitoring terminal
12a which is connected to the battery 20 to monitor the terminal
voltage of the battery 20 (hereinafter referred to simply as "battery
voltage"), specifically, respective battery voltages under
a non-loaded state and a loaded state. The battery voltage that
the DPU 12 inputs via the voltage monitoring terminal 12a is output
to the CPU 11 through an analog output terminal 12b of the DPU 12.
The CPU 11 incorporates an A/D converter 11c for converting the
battery voltage output from the analog output terminal 12b of the
DPU 12 into a digital signal, and compares this digital signal with
a predetermined voltage level (battery-check level) to determine
whether the battery voltage is lower than the battery-check level.
Since various types of batteries can be selectively used as the
battery 20 in the present embodiment of the digital camera as mentioned
above, the CPU 11 determines which type of battery is currently
used, and sets an appropriate battery-check level in accordance
with the type of battery currently used (currently under load).
Battery type of the battery 20 can be set not only automatically
by the CPU 11 but also manually by the user.
[0031] The external flash 22 which is detachably mounted to a camera
body of the digital camera communicates with the DPU 12, and discharges
under control of the DPU 12. The diaphragm control circuit 23 makes
a stop-down mechanism (not shown) start stopping down a diaphragm
of the photographing lens in accordance with a control signal input
from the DPU 12, and outputs EE pulses to the DPU 12 in association
with the stop-down operation of the diaphragm. The DPU 12 senses
and counts the EE pulses, and outputs a control signal immediately
after the count reaches the number of EE pulses which is determined
by an AE arithmetic operation. Upon receiving this control signal,
the diaphragm control circuit 23 makes the stop-down mechanism stop
moving to maintain the f-number of the photographing lens at an
f-number corresponding to an appropriate aperture value Av. The
TTL light modulating device 24 directly receives light which is
emitted from either the built-in flash 33 or the external flash
22 and reflected by an object to be incident on the photographing
lens, and outputs a signal corresponding the received light to the
DPU 12. The electronic beeper 25 emits beep tones as a warning in
accordance with a control signal input from the DPU 12. The distance-measuring-area
superimposing device 26 is provided with a plurality of LEDs which
are turned ON in accordance with a control signal input from the
DPU 12 to indicate a plurality of distance measuring areas (e.g.,
a plurality of AF frames) in the viewfinder. The mode select dial
27 is a hand-operated member which is manually operated to select
a desired exposure mode from among various exposure modes (e.g.,
programmed AE mode, aperture priority AE mode and shutter priority
AE mode) or a setting mode from among various setting modes (e.g.,
ISO speed setting mode, image size (image quality) setting mode,
white balance setting mode and remote control mode). The mode select
dial 27 outputs a dial position signal, detected using a coding
plate (not shown), to the DPU 12 upon being set to one of a plurality
of switching positions corresponding to the aforementioned exposure
modes and setting modes. The various switches 28 include an AF button
switch, a photometering mode switch (lever switch) and a drive mode
switch, and each of the various switches 28 outputs a status thereof
to the DPU 12. Various settings are carried out via positional information
on the mode select dial 27 or by manually turning an AV dial 48
and/or a TV dial 49 while depressing associated switches of the
various switches 28.
[0032] The lens CPU 31 that is provided in the photographing lens
(not shown) is supplied with power from the battery 20 via the DPU
12, and communicates with the DPU 12 and the CPU 11 via a series
of electrical contacts provided on a mounting surface of a lens
mount ring on the photographing lens. The lens CPU 31 stores lens
data of the photographing lens such as data on focal length, full
aperture value and minimum aperture value, and such lens data is
read by the DPU 12 and the CPU 11. The AFIC 32 detects a focus state
of an object image included in a specific distance measuring area
selected from among the aforementioned plurality of distance measuring
areas or in each of the aforementioned plurality of distance measuring
areas, and converts the received light bundle of the object into
an electrical video signal to output the same to the CPU 11. The
CPU 11 performs a distance measuring operation in accordance with
the video signal input from the AFIC 32. The recharging operation
and the discharging operation of the built-in flash 33 are controlled
by the DPU 12, and the built-in flash 33 outputs a recharge completion
signal to the DPU 12 immediately after the flash voltage reaches
a predetermined charge level.
[0033] The CPU 11 is provided therein with an internal ROM 11a
in which various programs regarding capabilities of the digital
camera and other data are written, and an internal RAM 11b in which
various parameters, lens data and other data are temporarily stored.
In addition to the lens CPU 31 and the AFIC 32, a sixteen-segment
photometering IC 34, the mirror motor driver 35, a mirror switch
37, the AF motor driver 38, an AF control photo-interrupter 40,
a remote-control-light receiving IC (remote-control signal receiver)
41, an EEPROM 42, a shutter-leading-curtain magnet 43, a shutter-trailing-curtain
magnet 44, an external indicator 45, a viewfinder internal indicator
46, a remote-controller/self-timer indication LED 47, the Av dial
48, the Tv dial 49, various switches 50, a shutter release button
51 and the DSP 13 are all connected to the CPU 11.
[0034] The sixteen-segment photometering IC 34 divides a photographing
area into sixteen photometering areas, and is capable of performing
a photometering operation on each photometering area. On each of
the sixteen photometering areas which is selected in accordance
with a sensor selection signal input from the CPU 11, the sixteen-segment
photometering IC 34 outputs an electrical signal corresponding to
the amount of light received by each photometering area as information
on an object brightness value By to the CPU 11. The CPU 11 performs
an exposure operation using this information on the object brightness
value By, an ISO speed information Sv (speed value) and other information
to determine a optimum value Ev, a optimum shutter speed Tv (time
value) and a optimum aperture value Av. The CPU 11 further calculates
the number of EE pulses corresponding to the correct aperture value
Av which are output from the diaphragm control circuit 23 in association
with the stop-down operation of stop-down mechanism (not shown).
[0035] The mirror motor driver 35 controls the operation of a mirror
motor 36 to move up and down a quick-return mirror (not shown) in
accordance with a mirror drive signal input from the CPU 11. The
CPU 11 detects whether the quick-return mirror is in an upper (raised)
position (or a lower position) from a state of the mirror switch
37 (mirror-position indication signal). The AF motor driver 38 drives
an AF motor 39, and controls the operation thereof in accordance
with an AF drive signal input from the CPU 11 to move a focusing
lens group of the photographing lens to an in-focus position by
rotation of the AF motor 39. The AF photo-interrupter 40 outputs
AF pulses to the CPU 11 in association with rotation of the AF motor
39, and the CPU 11 stops the driving of the AF motor 39 via the
AF motor driver 38 immediately after the number of the AF pulses
output from the AF photo-interrupter 40 reaches the number of AF
pulses which is determined by an AF arithmetic operation. The remote-control-light
receiving IC 41 receives a release command (remote-control release
signal) from a supplied remote controller (not shown), and outputs
a release signal to the CPU 11 during standby upon receiving the
release command from the remote controller.
[0036] The EEPROM 42 serves as a memory in which various data concerning
photographing operations and adjustments on the camera are stored,
and such data is read out by the CPU 11 at an appropriate time.
The shutter-leading-curtain magnet (ESMg1) 43 and the shutter-trailing-curtai-
n magnet (ESMg2) 44 are energized and controlled by the CPU 11.
When the shutter-leading-curtain magnet 43 and the shutter-trailing-curtain
magnet 44 are energized, a leading curtain and a trailing curtain
of the mechanical shutter (focal plane shutter) are opened by magnetic
force, respectively. The leading curtain and the trailing curtain
of the mechanical shutter become free from the magnetic force and
start moving immediately after the passage of electric current through
the shutter-leading-curtain magnet 43 and the shutter-trailing-curtain
magnet 44 is shut off, respectively. Each of the external indicator
45 and the viewfinder internal indicator 46 is provided with an
LCD panel for visually indicating various information in accordance
with an indication signal input from the CPU 11, and an LED serving
as a backlight of the LCD panel which illuminates the LCD panel
from behind the LCD panel in accordance with an illumination signal
input from the CPU 11. The remote-controller/self-timer indication
LED 47 is turned ON by the CPU 11 upon receiving a release command
signal from the supplied remote controller or flashes ON and OFF
during operation of a self-timer in a self-timer mode to inform
the user of the time of a shutter release.
[0037] The Av dial 48 is a manual operation member which is mainly
operated to set an f-number (manual f-stop setting) of the photographing
lens, while the Tv dial is a manual operation member which is operated
to set a shutter speed. Information on these settings manually determined
by the user are output to the CPU 11. Various settings for image
capturing and playback can also be made by rotating the Av dial
48 and the Tv dial 49 in combination with one or more of the various
switches 28 or the setting of the mode select dial 27. In the present
embodiment of the digital camera, the bulb mode can be selected
by rotating the Tv dial 49 up to the slowest shutter speed side.
When both the bulb mode and the remote-control photographing mode
are selected, the digital camera is in a remote-control bulb mode
in which the shutter remains open as long as the remote-control-light
receiving IC 41 receives a remote-control release signal from the
supplied remote controller. When the bulb mode is selected and the
remote-control photographing mode is not selected, the shutter remains
open as long as the shutter release button 51 is held down (as long
as a release switch SWR is ON). The remote-control bulb mode can
be freely selected and canceled by operating the mode select dial
27 as mentioned above. The various switches 50 include a main switch
SWM, a lid opening/closing sensor switch for sensing whether the
lid for a memory insertion slot of an image storing device (data
storing device) 64 is open or closed, and other switches. The shutter
release button 51 is a two-stage button wherein a photometering
switch SWS and a release switch SWR are turned ON when the shutter
release button 51 is half depressed and fully depressed, respectively.
[0038] Power supply to the DSP (digital signal processor) 13 is
controlled by the DPU 12 and the power circuit 21. The DSP 13 communicates
with the CPU 11 to perform image processing in accordance with control
signals and various data input from the CPU 11 while there is a
power supply to the DSP 13 from the power supply 21. A flash memory
61, a CCD image sensor 62, an image display monitor 63 and the image
storing device 64 are electrically connected to the DSP 13. Control
programs (firmware) and other programs for the DSP 13 are written
in the flash memory 61. The CCD image sensor 62 is positioned behind
the shutter. The CCD image sensor 62 converts an object image formed
thereon through the photographing lens into electrical signal (pixel
data), and outputs the same to the DSP 13 in accordance with control
signals input from the DSP 13. The DSP 13 performs various image
processing operations on the electrical signal input from the CCD
image sensor 62 to generate a digital image capable of being visually
indicated on the image display monitor 63. This visual image is
indicated on an LCD panel of the image display monitor 63 and also
stored as image data in the image storing device 64 at the same
time by control of the DSP 13. When storing the image data, the
image storing device 64 stores Exif data in regard to the image
data at the same time. The DSP 13 also reads the image data stored
in the image storing device 64 in order to display the read image
data on the image display monitor 63 as a visual image. The image
display monitor 63 is composed of an LCD panel and a backlight for
illuminating the LCD panel from behind the LCD panel, and is fixed
to, e.g., the back of the digital camera. The image storing device
64 is a removable memory which is manually removable from the digital
camera through the aforementioned memory insertion slot of the image
storing device 64 which can be closed by the lid of the memory insertion
slot as mentioned above. The image storing device 64 can be any
removable nonvolatile memory such as a flash memory or a micro HD
drive.
[0039] Operations of the present embodiment of the digital camera
according to the present invention will be hereinafter discussed
with reference to FIGS. 2A, 2B, 2C, and 2D.
[0040] FIGS. 2A, 2B, 2C and 2D show a flow chart of the camera
main process which is performed in the present embodiment of the
digital camera and controlled by the CPU 11 in accordance with programs
written in the internal ROM 11a of the CPU 11. This process is performed
when the battery 20 is loaded in the camera.
[0041] In the camera main process, firstly the CPU 11 initializes
each I/O port and other ports upon the battery 20 being loaded into
the camera (step S2), and further initializes constants and correction
values which are used for the internal RAM 11b and various processes
(step S4). Subsequently, the CPU 11 shuts off the power supply to
peripheral circuits via the DPU 12 and the power circuit 21 to bring
the camera into a power-off state (step S6), and turns OFF all the
LCDs (the external indicator 45 and the viewfinder internal indicator
46) provided on the camera (step S8). Immediately after the camera
falls into a power-off state at step S6, a photometric timer is
turned OFF if the photometric timer has been started (at step S50)
in a photometric-timer ON loop process shown in FIG. 2C (if control
returns to step S6 from the photometric-timer ON loop process).
[0042] [Main Switch Off Loop Process]
[0043] The ON/OFF state of each switch is input (step S10), and
it is determined whether the main switch SWM is ON (step S12). If
the main switch SWM is OFF (if NO at step S12), an interrupt of
a 250 ms timer is enabled, and the 250 ms timer is started (step
S14). Subsequently, control enters a CPU standby mode (sleep mode)
and waits for the 250 ms timer to expire (step S16). Immediately
after a lapse of 250 ms, control cancels the CPU standby mode so
that the CPU 11 starts operating (step S18). The operations at steps
S10 through S18 are repeated as long as the main switch SWM is OFF.
The 250 ms timer sets a period for periodically determining whether
the main switch SWM is ON. Upon the main switch SWM being turned
ON (if YES at step S12), the CPU 11 again shuts OFF the power supply
to peripheral circuits via the DPU 12 and the power circuit 21 to
bring the camera into a power-off state (step S20). When the camera
falls into a power-off state at step S20, the aforementioned photometric
timer is turned OFF if it has been started (at step S50) in the
photometric-timer ON loop process shown in FIG. 2C (if control returns
to step S6 from the photometric-timer ON loop process).
[0044] Subsequently, a battery check process is performed (step
S22). In this battery check process which is performed for the first
time after the power of the camera is turned ON, a battery type
determining operation in which the type of the loaded battery 20
is determined from the difference in voltage between the battery
20 under a non-loaded state and the battery 20 under a loaded state
is performed, and an appropriate battery check level which corresponds
to the type of the battery 20 is determined. Note that "under
a non-loaded state" refers to a state where the battery 20
supplies power only to the CPU 11, the DPU 12 and the DSP 13, and
that "under a loaded state" refers to, e.g., a state where
the AF motor 39 is driven. If it is detected that the difference
in voltage between the battery 20 under a non-loaded state and the
battery 20 under a loaded state is below a predetermined reference
level, the battery 20 is determined as a Ni-MH battery, and the
battery-check level is set at a level appropriate for a Ni-MH battery
(rated as 1.2 volts), subsequently this battery-check level is compared
with the battery voltage under a loaded state. On the other hand,
if it is detected that the difference in voltage between the battery
20 under a non-loaded state and the battery 20 under a loaded state
is equal to or greater than the aforementioned reference level,
the battery 20 is determined as a type other than Ni-MH battery,
and the battery-check level is set to another level for a non-Ni-MH
battery (rated as 1.5 volts), and subsequently this battery-check
level is compared with the battery voltage under a loaded state.
[0045] In the present embodiment of the digital camera, for each
type of battery a plurality of battery-check levels having different
voltage levels in stages are pre-stored in a memory: a power-low
level (for determining that the battery is nearly flat), an empty
level (for determining that the battery is flat), a half level (for
determining that the remaining battery power is half the power of
the fully-charged battery), and a BULB level (used during exposure
in bulb mode). As a result of comparing battery-check level with
the battery voltage under a loaded state, a power-low flag is set
to 1 if the battery voltage under a loaded state is below the power-low
level or the BULB level. The BULB level is predetermined to be higher
than the power-low level because the exposure time in the bulb mode
is indefinite. In a battery check process which is performed for
the second time or more, after the power of the camera is turned
ON, the aforementioned battery type determining operation is not
performed, so that the battery voltage under a loaded state is compared
with the battery-check level which has been already determined to
correspond to the type of the battery 20 in the firstly performed
battery check process. Although the battery type determining operation
which is automatically performed by the CPU 11 has been discussed
above, the user of the digital camera can manually operate a setting
device such as a setting switch to enter information on the type
of the loaded battery 20 into the camera.
[0046] [Photometric Timer Off Loop Process]
[0047] After the completion of the battery check process at step
S22, various information necessary prior to an exposure operation
(e.g., the number of available frames, battery check result, image
size and white balance) are indicated on the external indicator
45 (step S24), ON/OFF states of all switches are input (step S26),
and it is determined whether the main switch SWM is ON (step S28).
Control returns to step S6 if it is determined at step S28 that
the main switch SWM is not ON (if NO at step S28). If the main switch
SWM is ON (if YES at step S28), the CPU 11 performs data communications
with the lens CPU 31 to input lens data (step S30), and further
performs data communications with the DSP 13 (step S32). In the
data communications at step S32, camera data such as ON/OFF states
of each switch and the result of the battery check process are sent
from the CPU 11 to the DSP 13, while DSP data such as the number
of available frames and the time of the photometric timer are sent
from the DSP 13 to the CPU 11.
[0048] Subsequently, an interrupt of the photometering switch SWS
is enabled (step S34), an interrupt of a 250 ms timer is enabled,
and this 250 ms timer is started (step S36). Subsequently, control
enters the CPU standby mode (sleep mode) (step S38). Subsequently,
it is determined whether an interrupt of the photometering switch
SWS has occurred (step S40). If no interrupt of the photometering
switch SWS has occurred (if NO at step S40), control waits for the
250 ms timer to expire, and cancels the CPU standby mode so that
the CPU 11 starts operating immediately after a lapse of 250 ms
(step S42). Thereafter control returns to step S24. If it is determined
that an interrupt of the photometering switch SWS has occurred (if
YES at step S40), the battery check process is performed (step S44),
and whether the battery 20 is available is determined on the basis
of the power-low flag (step S46). The power-low flag is set to 0
if it is determined in the battery check process at step S44 that
the battery 20 is OK (available) and is set to 1 if the battery
20 is not OK (not available), respectively. If it is determined
at step S44 that the battery 20 is not OK (if NO at step S46), control
returns to step S20 so that the operations at steps 20 through step
S46 are repeated. In this case, high-power-consumption operations
of the camera such as a photometering operation, a distance measuring
operation and an exposure operation are prohibited from being performed.
If it is determined at step S44 that the battery 20 is OK (if YES
at step S46), the battery power commences to be supplied to peripheral
circuits via the DPU 12 and the power circuit 21 (step S48), the
photometric timer is started (step S50), and control enters the
photometric timer ON loop process, which starts at step S52. The
time of the photometric timer is determined based on data which
is input from the DSP 13 in the data communications performed at
step S32.
[0049] [Photometric Timer on Loop Process]
[0050] In the photometric timer ON loop process, firstly ON/OFF
states of all switches are input (step S52), and it is determined
whether the main switch SWM is ON (step S54). Control returns to
step S6 if it is determined at step S54 that the main switch SWM
is not ON (if NO at step S54). If the main switch SWM is ON (if
YES at step S54), the CPU 11 performs data communications with the
lens CPU 31 to input lens data (step S56).
[0051] Subsequently, the information on object brightness value
By which is output from the sixteen-segment photometering IC 34
is converted into a digital signal to be input to the CPU 11 (step
S58), and an AE (automatic exposure) arithmetic operation is performed
in accordance with the input lens data, the obtained digital value
of the object brightness value By and other values (step S60). In
the AE arithmetic operation, a correct exposure value Ev, a correct
shutter speed Tv (time value) and a correct aperture value Av are
calculated, and also the number of EE pulses corresponding to the
correct aperture value Av is calculated. After the completion of
the AE arithmetic operation, the calculated photometric values (TV
and Av), the number of available frames and other information necessary
for making an exposure such as battery check result are indicated
on both the external indicator 45 and the viewfinder internal indicator
46 (step S62), and also the same calculated photometric values are
sent to the DSP 13 via data communication between the CPU 11 and
the DSP 13 (step S64). Subsequently, a 125 ms timer is started (step
S66), an interrupt of the release switch SWR is enabled (step S68),
and control returns to step S52 to perform the photometric timer
ON loop process if it is determined that the 125 ms timer which
is started at step S66 has expired (if YES at step S70). The 125
ms timer sets a period for periodically performing a photometering
process (step S58) and the AE arithmetic process (step S60). If
the 125 ms timer which is started at step S66 has not yet expired
(if NO at step S70), it is determined whether the photometric timer
has expired (step S72), and control returns to step S20 if the photometric
timer has expired (if YES at step S72). However, if control enters
the photometric timer ON loop process after a two-second photometric
timer is started at step S90, control returns to step S20 after
two seconds of the two-second photometric timer elapses.
[0052] If the photometric timer has not yet expired (if NO at step
S72), it is determined whether the photometering switch SWS is ON
(step S74). If the photometering switch SWS is ON (if YES at step
S74), an AF process is performed (step S92). If the photometering
switch SWS is not ON (if NO at step S74), or after the completion
of the AF process at step S92, it is determined whether an interrupt
of the release switch SWR has occurred (step S76). If no interrupt
of the release switch SWR has occurred (if NO at step S76), control
returns to step S70 to wait a command for releasing the shutter
until the 125 ms timer or the photometric timer expires.
[0053] If an interrupt of the release switch SWR has occurred (if
YES at step S76), the battery check process is performed (step S78),
and whether the battery 20 is OK is determined on the basis of the
power-low flag (step S80). If it is determined at step S80 that
the battery 20 is not OK (if NO at step S80), control returns to
step S20, at which the camera is brought into a power-OFF state,
and prohibits operations of the camera such as a photometering operation,
a distance measuring operation and an exposure operation from being
performed. If it is determined at step S80 that the battery 20 is
OK (if YES at step S80), a mirror-up process, an exposure process
(see FIGS. 3A, 3B and 3C) and a mechanism charging process are performed
in that order (steps S82, S84 and S86). Subsequently, it is determined
whether the power of the battery 20 has become very low during exposure
(step S88).
[0054] If it is determined that the power of the battery 20 has
become very low during exposure (if YES at step S88), the backup
digital image, together with a warning indication is indicated on
the LCD panel of the image display monitor 63 via the DSP 13, and
a similar warning indication is indicated on the external indicator
45 in a manner so that the indication flashes ON and OFF (step S94).
This warning indication indicates that the backup digital image
has resulted in underexposure because the exposure was forcibly
terminated during exposure due to a shortage of battery power. Subsequently,
the amount of underexposure of the backup digital image is also
indicated on the LCD panel of the image display monitor 63. These
indicating operations warn the user that the battery 20 is nearly
exhausted (nearly flat). Subsequently, the power of the camera is
turned OFF via the DPU 12 and the power circuit 21 (step S98), and
control returns to step S24. If it is detected at step S88 that
the power of the battery 20 has not become very low during exposure
(if NO at step S88), the two-second photometric timer is started
at step S90, and control returns to step S20 after two seconds of
the two-second photometric timer elapses.
[0055] The exposure process will be hereinafter discussed with
reference to the flow chart shown in FIGS. 3A, 3B and 3C and the
timing charts shown in FIGS. 4 and 5. The exposure process is performed
immediately after the mirror-up operation at step S82 if it is determined
at step S80 that the battery 20 is OK. FIG. 4 is a timing chart
showing various events when it is detected that the power of the
battery 20 becomes very low during exposure in bulb mode, while
FIG. 5 is a timing chart showing various events when it is detected
that the power of the battery 20 becomes very low during exposure
in slow shutter mode.
[0056] In the exposure process, firstly a command for starting
an exposure is output to the DSP 13 to make the CCD image sensor
62 start accumulating electric charges via the DSP 13 (step S200;
time t1 shown in FIGS. 4 and 5). The amount of accumulated charges
to the CCD image sensor 62 increases with the passage of time. Subsequently,
a hardware timer (Tv counting timer) for measuring an exposure time
is set at the correct shutter speed (time value) Tv obtained in
the AE arithmetic operation performed at step S60 (step S202), and
the power supplied to the shutter-leading-curtain magnet 43 is shut
off so that the leading curtain of the shutter starts moving (step
S204; time t2 shown in FIGS. 4 and 5).
[0057] Subsequently, the Tv counting timer that is set at step
S202 is started (step S206), and it is determined whether the correct
shutter speed Tv is equal to or slower than a flash sync speed (e.g.,
{fraction (1/150)} sec), at which the shutter is fully open (step
S208). In the case where bulb mode (which requires an operation
of the shutter release button 51) or the remote-control bulb mode
is currently selected, the correct shutter speed Tv will be determined
as being equal to or slower than the flash sync speed.
[0058] [Normal Exposure]
[0059] In an exposure operation in which the shutter is released
at a shutter speed Tv faster than the flash sync speed, i.e., in
a normal exposure operation, the battery check process does not
have to be performed during exposure because there is little possibility
of the battery voltage suddenly dropping during exposure immediately
after the battery voltage is determined to be equal to or higher
than the battery-check level. In the present embodiment of the digital
camera, if it is determined that the correct shutter speed Tv is
not either equal to or slower than the flash sync speed (if NO at
step S208), it is determined whether the Tv counting timer has expired
(step S288). Control repeats the operation at step S288 until the
Tv counting timer expires (if NO at step S288). Upon expiration
of the Tv counting timer (if YES at step S288), the power supplied
to the shutter-trailing-curtain magnet 44 is shut off (step S290),
and control returns to the camera main process, i.e., proceeds to
step S86 shown in FIG. 2D.
[0060] [Long Exposure]
[0061] Contrary to the above described normal exposure operation,
in an exposure operation in which the shutter is released at a shutter
speed Tv is equal to or slower than the flash sync speed, i.e.,
in a long exposure operation, there is a possibility of the battery
voltage suddenly dropping during exposure even shortly after the
battery voltage is determined to be equal to or higher than the
battery-check level. Accordingly, the battery check process is periodically
performed even during exposure. Namely, if it is determined that
the correct shutter speed Tv is equal to or slower than the flash
sync speed (if YES at step S208), a 15.6 ms timer is started (step
S210), and an 8.5 ms timer for measuring a flash trigger timing
is started (step S212). The 15.6 ms timer is a hardware timer for
periodically checking an ON/OFF state of the main switch SWM and
an ON/OFF state of a memory-insertion-slot lid switch during an
exposure in bulb mode (or remote-control bulb mode), and the exposure
time is measured by counting the number of times the operation of
the 15.6 ms timer has been carried out with a software counter.
Subsequently, it is determined whether the Tv counting timer has
expired (step S214). It is determined that the Tv counting timer
has expired during the operation of the 8.5 ms timer at step S214
only when the correct shutter speed Tv is in a range of {fraction
(1/45)} to {fraction (1/150)} seconds. If the Tv counting timer
is already expired (if YES at step S214), the power supplied to
the shutter-trailing-curtain magnet 44 is shut off so that the trailing
curtain of the shutter starts moving (step S216). Control skips
the operation at step S216 if the Tv counting timer has not yet
expired. Subsequently, it is determined whether the 8.5 ms timer
that has been started at step S212 has expired (step S218). If it
is detected at step S218 that the 8.5 ms timer has not yet expired
(if NO at step S218), the operations at steps 214 through 218 are
repeated until the 8.5 ms timer expires.
[0062] Upon the expiration of the 8.5 ms timer (if YES at step
S218), it is determined whether conditions necessary for allowing
the external flash 22 to discharge are satisfied (i.e., whether
the external flash 22 is connected to the camera, whether the external
flash 22 is fully charged, etc.) (step S220). If it is determined
that such necessary conditions are satisfied (if YES at step S220),
an X-contact trigger for the external flash 22 is turned ON to thereby
cause the external flash 22 to discharge (step S222). Control skips
the operation at step S222 if the aforementioned necessary conditions
are not satisfied (if NO at step S220).
[0063] Subsequently, it is determined whether the built-in flash
33 is in a predetermined popped-up position (raised position) (step
S224). If the built-in flash 33 is in the popped-up position (if
YES at step S224), it is determined whether conditions necessary
for allowing the built-in flash 33 to discharge are satisfied (i.e.,
whether the built-in flash 33 is fully charged, whether the built-in
flash 33 is prohibited from discharging, etc.) (step S226). If such
necessary conditions are satisfied (if YES at step S226), a trigger
for the built-in flash 33 is turned ON to thereby cause the built-in
flash 33 to discharge (step S228), and control proceeds to step
S232. Control skips the operation at step S228 and proceeds to step
S232 if the aforementioned necessary conditions are not satisfied
(if NO at step S226).
[0064] Subsequently, it is determined whether the bulb mode is
currently selected by the Tv dial 49 (step S232). If the bulb mode
is currently selected (if YES at step S232), it is determined whether
the remote-control exposure mode is currently selected (step S234).
[0065] [Bulb Mode That Requires an Operation of the Shutter Release
Button]
[0066] If it is determined that the remote-control exposure mode
is not currently selected (if NO at step S234), this means that
the camera is in the middle of performing an exposure operation
in bulb mode, and accordingly, control proceeds to step S236 so
that the shutter remains open as long as the shutter release button
51 is held down.
[0067] More specifically, control waits for the 15.6 ms timer to
expire (if NO at step S236). When the 15.6 ms timer expires (if
YES at step S236), a software counter for counting the number of
times the operation of the 15.6 ms timer has been performed is increased
by one (step S237), the 15.6 ms timer is restarted (step S238),
and the battery voltage is converted into a digital voltage value
(A/D converted voltage value) (step S240). At step S240, the A/D
converted voltage value is stored in the RAM 11b as a battery voltage
value `batt-ad`.
[0068] It is determined whether the battery voltage value `batt-ad`
is lower than the BULB level (step S242). If the battery voltage
value `batt-ad` is lower than the BULB level (if YES at step S242),
a power-low during exposure flag is set to 1 (step S252), a command
for stopping the exposure operation is output to the DSP 13 (step
S249; time t3 shown in FIG. 4), and the power supplied to the shutter-trailing-curtain
magnet 44 is shut off so that the trailing curtain of the shutter
starts moving (step S250; time t4 shown in FIG. 4). This forcibly
terminates the exposure operation.
[0069] Upon inputting the exposure-operation stopping command (time
t3 shown in FIG. 4), the DSP 13 forcibly terminates the accumulating
operation of the CCD 62 to start capturing electrical signals from
the CCD 62 which have been accumulated until the forced termination
of the exposure operation. The electrical signals thus captured
are subjected to image processing in the DSP 13 to be formed (generate)
a backup digital image capable of being indicated on the image display
monitor 63. This backup digital image is stored in the image storing
device 64 as image data by the DSP 13 (time t5 shown in FIG. 4),
and is indicated, together with the aforementioned underexposure
warning indication, on the LCD panel of the image display monitor
63 (via the DSP 13 in the process at step S94 when control returns
thereto after the completion of the mechanism charging process performed
at step S86). At the same time, the aforementioned similar underexposure
warning indication is also indicated on the external indicator 45
(and also on the viewfinder internal indicator 46).
[0070] If the battery voltage value `batt-ad` is not lower than
the BULB level (if NO at step S242), it is determined whether the
lid for the memory insertion slot of the image storing device 64
is open from a state of the memory-insertion-slot lid switch (step
S244). If this lid is not open (if NO at step S244), it is determined
whether the main switch SWM is OFF (step S246). If the main switch
SWM is not OFF (if NO at step S246), it is determined whether the
photometering switch SWR or the release switch SWS is ON (step S248).
If at least one of the photometering switch SWR and the release
switch SWS is ON (if YES at step S248), control returns to step
S236.
[0071] The operations at steps S236 through S248 continue to be
performed once every 15.6 milliseconds unless the battery voltage
value `batt-ad` becomes lower than the BULB level, unless the lid
opening/closing sensor switch senses that the lid for the memory
insertion slot of the image storing device 64 is open, unless the
main switch SWM is turned OFF, or unless both the photometering
switch SWR and the release switch SWS are turned OFF. If the lid
for the memory insertion slot of the image storing device 64 is
open (if YES at step S244), if the main switch SWM is OFF (if YES
at step S246) or if both the photometering switch SWR and the release
switch SWS are OFF (if NO at step S248), even though the battery
voltage value `batt-ad` is equal to or higher than the BULB level,
control proceeds to step S249 so that a command for stopping the
exposure operation is output to the DSP 13 (step S249), and subsequently
the power supplied to the shutter-trailing-curtain magnet 44 is
shut off so that the trailing curtain of the shutter starts moving
(step S250).
[0072] This completes the exposure operation, and accordingly,
the DSP 13 forcibly terminates the accumulating operation of the
CCD 62 to start capturing electrical signals from the CCD 62 to
thereby obtain a digital image (correct digital image) capable of
being indicated on the image display monitor 63 while storing the
digital image in the image storing device 64 as image data.
[0073] [Remote-Control Bulb Mode]
[0074] If it is determined at step S234 that remote-control exposure
mode is currently selected (if YES at step S234), this means that
the camera is in the middle of performing an exposure operation
in bulb mode using the supplied remote controller, i.e., remote-control
bulb mode, and accordingly, the shutter remains open as long as
the remote-control-light receiving IC 41 receives a remote-control
release signal from the supplied remote controller. In this case,
control proceeds to step S254 at which a 260 ms timer for continuously
detecting the remote-control release signal is started. The 260
ms timer serves as a timer for detecting the remote-control release
signal, which is transmitted from the supplied remote controller
once every 250 milliseconds as long as a release button provided
on the supplied remote controller is held down. Subsequently, the
battery voltage is converted into a digital voltage value (A/D converted
voltage value), which is in turn stored in the RAM 11b as a battery
voltage value `batt-ad` (step S256), and it is determined whether
the battery voltage value `batt-ad` is lower than the BULB level
(step S258).
[0075] If the battery voltage value `batt-ad` is lower than the
BULB level (if YES at step S258), the power-low during exposure
flag is set to 1 (step S270), a command for stopping the exposure
operation is output to the DSP 13 (step S249; time t3 shown in FIG.
4), and the power supplied to the shutter-trailing-curtain magnet
44 is shut off so that the trailing curtain of the shutter starts
moving (step S250; time t4 shown in FIG. 4). This forcibly terminates
the exposure operation. Immediately after the DSP 13 inputs the
exposure-operation stopping command (time t3 shown in FIG. 4), the
DSP 13 forcibly terminates the accumulating operation of the CCD
62 to start capturing electrical signals from the CCD 62 which have
been accumulated until the forced termination of the exposure operation.
The electrical signals thus captured are subjected to image processing
in the DSP 13 to generate a backup digital image capable of being
indicated on the image display monitor 63. This backup digital image
is stored in the image storing device 64 as image data by the DSP
13 (time t5 shown in FIG. 4). In the process at step S94 in the
camera main process shown in FIG. 2D, the backup digital image and
the aforementioned underexposure warning indication are both indicated
on the LCD panel of the image display monitor 63 via the DSP 13.
At the same time, the aforementioned similar underexposure warning
indication is also indicated on the external indicator 45 (and also
on the viewfinder internal indicator 46).
[0076] If the battery voltage value `batt-ad` is not lower than
the BULB level (if NO at step S258), it is determined whether the
lid for the memory insertion slot of the image storing device 64
is open from a state of the memory-insertion-slot lid switch (step
S260). If this lid is not open (if NO at step S260), it is determined
whether the main switch SWM is OFF (step S262). If the main switch
SWM is not OFF (if NO at step S262), it is determined whether the
remote-control-light receiving IC 41 has received the remote-control
release signal (step S264). If the remote-control-light receiving
IC 41 has not received the remote-control release signal (if NO
at step S264), it is determined whether the 260 ms timer has expired
(step S266). If the 260 ms timer has not yet expired (if NO at step
S266), control returns to step S264 to wait for either the 260 ms
timer to expire or the remote-control-light receiving IC 41 to receive
the remote-control release signal. If the 260 ms timer expires (if
YES at step S266), it is determined whether the photometering switch
SWR or the release switch SWS is ON (step S268). If at least one
of the photometering switch SWR and the release switch SWS is ON
(if YES at step S268) or if the remote-control-light receiving IC
41 receives the remote-control release signal before the 260 ms
timer expires (if YES at step S264) control returns to step S254
to repeat the operations at steps S254 through S268. If the lid
for the memory insertion slot of the image storing device 64 is
open (if YES at step S260), if the main switch SWM is OFF (if YES
at step S262), if the remote-control-light receiving IC 41 does
not receive the remote-control release signal before the 260 ms
timer expires or if both the photometering switch SWR and the release
switch SWS are not ON (if NO at step S268), control proceeds to
step S249. At the operations at steps S249 and S250, a command for
stopping the exposure operation is output to the DSP 13, and the
power supplied to the shutter-trailing-curtain magnet 44 is shut
off so that the trailing curtain of the shutter starts moving. The
DSP 13 forcibly terminates the accumulating operation of the CCD
62 to start capturing electrical signals from the CCD 62 to thereby
obtain a digital image (correct digital image) capable of being
indicated on the image display monitor 63 while storing the digital
image in the image storing device 64 as image data.
[0077] [Slow Shutter Mode]
[0078] The operations which are performed when it is determined
at step S232 that bulb mode is selected have been discussed above.
Operations which are performed in the case where a shutter speed
Tv is equal to or slower than the flash sync speed and where the
bulb mode is not selected (if NO at step S232), i.e., operations
which are performed in slow shutter mode, will be discussed hereinafter.
In the slow shutter mode, control proceeds to step S272 to perform
an exposure operation at a shutter speed Tv which is manually set
by the Tv dial 49 or a calculated correct shutter speed Tv. More
specifically, firstly the battery voltage is converted into a digital
voltage value (A/D converted voltage value), which is in turn stored
in the RAM 11b as a battery voltage value `batt-ad` (step S272),
and subsequently it is determined whether the battery voltage value
`batt-ad` is lower than the power-low level (step S274).
[0079] If the battery voltage value `batt-ad` is lower than the
power-low level (if YES at step S274), the power-low during exposure
flag is set to 1 (step S292), a command for stopping the exposure
operation is output to the DSP 13 (step S293; time t3 shown in FIG.
5), and the power supplied to the shutter-trailing-curtain magnet
44 is shut off so that the trailing curtain of the shutter starts
moving (step S294; time t4 shown in FIG. 5). This forcibly terminates
the exposure operation.
[0080] Immediately after the DSP 13 inputs the exposure-operation
stopping command (time t3 shown in FIG. 5), the DSP 13 forcibly
terminates the accumulating operation of the CCD 62 to start capturing
electrical signals from the CCD 62 which have been accumulated until
the forced termination of the exposure operation. The electrical
signals thus captured are subjected to image processing in the DSP
13 to be formed (generate) a backup digital image capable of being
indicated on the image display monitor 63.
[0081] Subsequently, the CPU (inverse calculating device) 11 calculates
the timing of the forced termination of the exposure operation via
the value of the Tv software counter which counts the number of
times the operation of the 15.6 ms timer has been carried out and
the remaining time of the 15.6 ms timer, and calculates the amount
of underexposure which corresponds to the calculated timing in forced
termination of the exposure operation (step S296). Subsequently,
this data of the amount of underexposure is transmitted to the DSP
13 (step 298; time t5 shown in FIG. 5), and control returns to the
camera main process, i.e., proceeds to step S86 shown in FIG. 2D.
When storing(writing) image data in the image storing device 64,
the DSP 13 writes the backup digital image data in the image storing
device 64 together with the data of the amount of underexposure
in the form of Exif data upon receiving the data of the amount of
underexposure from the CPU 11 (time t6 shown in FIG. 5).
[0082] This amount of underexposure and this backup digital image
are indicated, together with the aforementioned underexposure warning
indication, on the LCD panel of the image display monitor 63 in
the process at step S94 when control returns thereto from the operation
at step S298. At the same time, the aforementioned similar warning
indication is also indicated on the external indicator 45 (and also
on the viewfinder internal indicator 46).
[0083] If the battery voltage value `batt-ad` is not lower than
the power-low level (if NO at step S274), it is determined whether
the lid for the memory insertion slot of the image storing device
64 is open from a state of the memory-insertion-slot lid switch
(step S276). If this lid is not open (if NO at step S276), it is
determined whether the main switch SWM is OFF (step S278). If the
main switch SWM is not OFF (if NO at step S278), it is determined
whether the Tv counting timer has expired (step S280). If the Tv
counting timer has not yet expired (if NO at step S280), the Tv
software counter is decreased by one (step S282), and control waits
for the 15.6 ms timer to expire (if NO at step S284), and when the
15.6 ms timer expires (if YES at step S284), the 15.6 ms timer is
restarted (step S286), and control returns to step S272.
[0084] The operations at steps S272 through S286 continue to be
performed once every 15.6 milliseconds unless the battery voltage
value `batt-ad` becomes lower than the power-low level, unless the
lid for the memory insertion slot of the image storing device 64
is opened, unless the main switch SWM is turned OFF, or unless the
time value (shutter speed) Tv elapses. If the lid for the memory
insertion slot of the image storing device 64 is open (if YES at
step S276), if the main switch SWM is OFF (if YES at step S278)
or if the time value (shutter speed) Tv elapses (if YES at step
S280), even though the battery voltage value `batt-ad` is equal
to or higher than power-low level (even if NO at step S274), control
proceeds to step S249 so that a command for stopping the exposure
operation is output to the DSP 13 (step S249), and subsequently
the power supplied to the shutter-trailing-curtain magnet 44 is
shut off so that the trailing curtain of the shutter starts moving
(step S250).
[0085] This completes the exposure operation, and accordingly the
DSP 13 forcibly terminates the accumulating operation of the CCD
62 to start capturing electrical signals from the CCD 62 to thereby
obtain a digital image (correct digital image) capable of being
indicated on the image display monitor 63 while storing the image
in the image storing device 64 as image data.
[0086] In the above illustrated embodiment of the digital camera,
although an underexposure warning indication and information of
the amount of underexposure of the backup digital image are indicated
to warn the user of a shortage of the battery power in the case
where an exposure operation is forcibly terminated during exposure,
it is possible for only the underexposure warning indication be
indicated, or for information of the amount of exposure compensation
be further calculated to be indicated together with the underexposure
warning indication and the amount of underexposure of the backup
digital image. If the data of the amount of exposure compensation
is indicated together with the warning indication, the amount of
exposure compensation can be used as a reference when a backup digital
image is compensated due to underexposure by a predetermined image
processing software, which saves the user's time and trouble.
[0087] Although the user is informed that an exposure operation
is forcibly terminated during exposure and that the backup digital
image has resulted in underexposure by flashing ON and OFF an underexposure
warning indication in the above illustrated embodiment of the digital
camera, the user can be informed of the same information in another
manner, e.g., by driving the electronic beeper 25 to generate beep
tones as a warning sound.
[0088] Obvious changes may be made in the specific embodiment of
the present invention described herein, such modifications being
within the spirit and scope of the invention claimed. It is indicated
that all matter contained herein is illustrative and does not limit
the scope of the present invention. |