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Digital Camera Patent Abstract
A digital camera for portable equipment includes a light emitting
device; an electrically-driven light quantity controller for controlling
a quantity of light emitted from the light emitting device; and
a system controller which drives the light quantity controller and
the light emitting device and controls operations of the light quantity
controller and the light emitting device. In a state where the light
emitting device is ON, the system controller turns the light emitting
device OFF when the system controller drives the light quantity
controller to capture an object image.
Digital Camera Patent Claims
What is claimed is:
1. A digital camera for portable equipment, comprising: a light
emitting device; an electrically-driven light quantity controller
for controlling a quantity of light emitted from said light emitting
device; and a system controller which controls operations of said
light quantity controller and said light emitting device, wherein,
in a state where said light emitting device is ON, said system controller
turns said light emitting device OFF when said system controller
drives said light quantity controller to capture an object image.
2. The digital camera for portable equipment according to claim
1, wherein said light emitting device comprises at least one high-intensity
LED.
3. The digital camera for portable equipment according to claim
1, wherein said light quantity controller comprises a mechanical
diaphragm which is driven by said system controller.
4. A digital camera for portable equipment, comprising: a light
emitting device; an electrically-driven light quantity controller
for controlling a quantity of light emitted from said light emitting
device; and a system controller which drives said light quantity
controller and said light emitting device and controls operations
of said light quantity controller and said light emitting device,
wherein, when an object image is captured in a state where said
light emitting device is ON, said system controller drives said
light quantity controller to prevent light from passing through
said light quantity controller after turning said light emitting
device OFF before completion of an exposure.
5. The digital camera for portable equipment according to claim
4, wherein said light emitting device comprises at least one high-intensity
LED.
6. The digital camera for portable equipment according to claim
4, wherein said light quantity controller comprises an electrically-driven
diaphragm which is driven by said system controller.
7. A digital camera for portable equipment, comprising: an imaging
device; a light emitting device; a light quantity controller for
controlling a quantity of light emitted from said light emitting
device; and a system controller which drives said imaging device,
said light quantity controller and said light emitting device, controls
operations of said imaging device, said light quantity controller
and said light emitting device, and determines a optimum exposure
time in accordance with an image signal of an object image captured
by said imaging device, wherein said system controller determines
said optimum exposure time with said light emitting device remaining
on when an object image is captured with said light emitting device
remaining on, and wherein, in a state where said light emitting
device is ON, said system controller turns said light emitting device
OFF when said system controller drives said light quantity controller
to stop down a photographing lens of said digital camera, and turns
said light emitting device ON after completion of said driving of
said light quantity controller.
8. The digital camera for portable equipment according to claim
7, wherein said system controller drives said light quantity controller
to stop down said photographing lens and subsequently determines
said optimum exposure time after turning said light emitting device
ON after completion of said driving of said light quantity controller,
and wherein, when an exposure is started at said optimum exposure
time, said system controller turns said light emitting device OFF
immediately after a lapse of said optimum exposure time, and thereafter
said system controller drives said light quantity controller to
prevent light from passing through said light quantity controller
to complete said exposure.
9. The digital camera for portable equipment according to claim
7, wherein said light emitting device comprises at least one high-intensity
LED.
10. The digital camera for portable equipment according to claim
7, wherein said light quantity controller comprises an electrically-driven
diaphragm which is driven by said system controller.
11. A digital camera for portable equipment, comprising: an imaging
device; a light emitting device; an electrically-driven mechanical
shutter for controlling a quantity of light emitted from said light
emitting device; and a system controller which drives said imaging
device, said mechanical shutter and said light emitting device,
controls operations of said imaging device, said mechanical shutter
and said light emitting device, and determines a optimum exposure
time in accordance with an image signal of an object image captured
by said imaging device, wherein, when an object image is captured
with said light emitting device turned ON at a low intensity, said
system controller determines said optimum exposure time with said
light emitting device remaining ON at said low intensity, controls
said light emitting device to remain ON at a high intensity at a
commencement of an exposure, and drives said mechanical shutter
to fully shut after turning said light emitting device OFF before
completion of said exposure.
12. The digital camera for portable equipment according to claim
11, wherein said system controller determines a underexposure-prevention
time, at which said system controller turns said light emitting
device OFF and commences to drive said mechanical shutter, so that
said mechanical shutter is approximately half shut upon a lapse
of said optimum exposure time.
13. A digital camera for portable equipment, comprising: an imaging
device; a light emitting device; an electrically-driven mechanical
shutter for controlling a quantity of light emitted from said light
emitting device; and a system controller which drives said imaging
device, said mechanical shutter and said light emitting device,
controls operations of said imaging device, said mechanical shutter
and said light emitting device, and determines a optimum exposure
time in accordance with an image signal of an object image captured
by said imaging device, wherein, when an object image is captured
with said light emitting device turned ON, said system controller
determines said optimum exposure time with said light emitting device
remaining ON, subsequently determines a underexposure-prevention
time, at which said system controller turns said light emitting
device OFF while said system controller commences to drive said
mechanical shutter after said imaging device commences an exposure
operation, so that said mechanical shutter is approximately half
shut at a lapse of said optimum exposure time, and subsequently
commences to drive said mechanical shutter after turning said light
emitting device OFF upon a lapse of said underexposure-prevention
time from said commencement of said exposure operation.
14. The digital camera for portable equipment according to claim
13, wherein said light emitting device comprises at least one high-intensity
LED.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a digital camera which
is suitable for being incorporated in a portable device such as
a cellular phone or a personal digital assistant.
[0003] 2. Description of the Related Art
[0004] Various kinds of portable devices in which a digital camera
is incorporated such as cellular phones and personal digital assistants
(PDAs) have been developed. Such a digital camera has become increasingly
sophisticated, and a digital-camera equipped personal digital assistant
provided with high-intensity LEDs as a light emitting device has
been proposed in Japanese laid-open patent publication No. 2003-259182.
It has been desired in recent years for a digital camera incorporated
in a portable device be equipped with a diaphragm device for enlarging
the scope of exposure control and a mechanical shutter adapted to
meet the demand for high-quality images.
[0005] However, in the case where an object image is captured with
one or more high-intensity LEDs remaining lit, the peak current
increases since a current for driving the high-intensity LED and
a current for driving the diaphragm device are simultaneously passed
through the high-intensity LED and the diaphragm device, respectively.
An increase in the peak current may cause the voltage which is supplied
to other electronic parts to drop and may damage the battery. On
the other hand, a high-output/large-capacity battery is generally
bulky and thus undesirable to be adopted as a power source of a
small and lightweight portable device.
SUMMARY OF THE INVENTION
[0006] The present invention has been devised in view of the problems
mentioned above, and provides a digital camera for portable equipment
which is provided with an electrically-driven light quantity controller
and a light emitting device capable of remaining on, wherein the
peak current at the time of capturing an object image is prevented
from increasing upon operating the light quantity controller and
the light emitting device.
[0007] Additionally, the present invention provides a digital camera
for portable equipment which is provided with an electrically-driven
diaphragm or shutter mechanism and a light emitting device capable
of remaining on, wherein a correct exposure is obtained while preventing
the peak current from increasing upon operating the light emitting
device and the diaphragm or shutter mechanism.
[0008] According to an aspect of the present invention, a digital
camera for portable equipment is provided, including a light emitting
device; an electrically-driven light quantity controller for controlling
a quantity of light emitted from the light emitting device; and
a system controller which controls operations of the light quantity
controller and the light emitting device. In a state where the light
emitting device is ON, the system controller turns the light emitting
device OFF when the system controller drives the light quantity
controller to capture an object image.
[0009] It is desirable for the light emitting device to include
at least one high-intensity LED.
[0010] It is desirable for the light quantity controller to include
a mechanical diaphragm which is driven by the system controller.
[0011] In an embodiment, a digital camera for portable equipment
is provided, including a light emitting device; an electrically-driven
light quantity controller for controlling a quantity of light emitted
from the light emitting device; and a system controller which drives
the light quantity controller and the light emitting device and
controls operations of the light quantity controller and the light
emitting device. When an object image is captured in a state where
the light emitting device is ON, the system controller drives the
light quantity controller to prevent light from passing through
the light quantity controller after turning the light emitting device
OFF before completion of an exposure.
[0012] It is desirable for the light emitting device to include
at least one high-intensity LED.
[0013] It is desirable for the light quantity controller to include
an electrically-driven diaphragm which is driven by the system controller.
[0014] In an embodiment, a digital camera for portable equipment
is provided, including an imaging device; a light emitting device;
a light quantity controller for controlling a quantity of light
emitted from the light emitting device; and a system controller
which drives the imaging device, the light quantity controller and
the light emitting device, controls operations of the imaging device,
the light quantity controller and the light emitting device, and
determines a optimum exposure time in accordance with an image signal
of an object image captured by the imaging device. The system controller
determines the optimum exposure time with the light emitting device
remaining on when an object image is captured with the light emitting
device remaining on. In a state where the light emitting device
is ON, the system controller turns the light emitting device OFF
when the system controller drives the light quantity controller
to stop down a photographing lens of the digital camera, and turns
the light emitting device ON after completion of the driving of
the light quantity controller.
[0015] It is desirable for the system controller to drive the light
quantity controller to stop down the photographing lens and subsequently
determine the optimum exposure time after turning the light emitting
device ON after completion of the driving of the light quantity
controller. When an exposure is started at the optimum exposure
time, the system controller turns the light emitting device OFF
immediately after a lapse of the optimum exposure time, and thereafter
the system controller drives the light quantity controller to prevent
light from passing through the light quantity controller to complete
the exposure.
[0016] It is desirable for the light emitting device to include
at least one high-intensity LED.
[0017] It is desirable for the light quantity controller to include
an electrically-driven diaphragm which is driven by the system controller.
[0018] In an embodiment, a digital camera for portable equipment
is provided, including an imaging device; a light emitting device;
an electrically-driven mechanical shutter for controlling a quantity
of light emitted from the light emitting device; and a system controller
which drives the imaging device, the mechanical shutter and the
light emitting device, controls operations of the imaging device,
the mechanical shutter and the light emitting device, and determines
a optimum exposure time in accordance with an image signal of an
object image captured by the imaging device. When an object image
is captured with the light emitting device turned ON at a low intensity,
the system controller determines the optimum exposure time with
the light emitting device remaining ON at the low intensity, controls
the light emitting device to remain ON at a high intensity at a
commencement of an exposure, and drives the mechanical shutter to
fully shut after turning the light emitting device OFF before completion
of the exposure.
[0019] The system controller can determine a underexposure-prevention
time, at which the system controller turns the light emitting device
OFF and commences to drive the mechanical shutter, so that the mechanical
shutter is approximately half shut upon a lapse of the optimum exposure
time.
[0020] In an embodiment, a digital camera for portable equipment
is provided, including an imaging device; a light emitting device;
an electrically-driven mechanical shutter for controlling a quantity
of light emitted from the light emitting device; and a system controller
which drives the imaging device, the mechanical shutter and the
light emitting device, controls operations of the imaging device,
the mechanical shutter and the light emitting device, and determines
a optimum exposure time in accordance with an image signal of an
object image captured by the imaging device. When an object image
is captured with the light emitting device turned ON, the system
controller determines the optimum exposure time with the light emitting
device remaining ON, subsequently determines a underexposure-prevention
time, at which the system controller turns the light emitting device
OFF while the system controller commences to drive the mechanical
shutter after the imaging device commences an exposure operation,
so that the mechanical shutter is approximately half shut at a lapse
of the optimum exposure time, and subsequently commences to drive
the mechanical shutter after turning the light emitting device OFF
upon a lapse of the underexposure-prevention time from the commencement
of the exposure operation.
[0021] It is desirable for the light emitting device to include
at least one high-intensity LED.
[0022] According to an aspect of the present invention, although
the digital camera includes a light emitting device and an electrically-driven
mechanical shutter, the peak current for driving these devices can
be minimized.
[0023] According to another aspect of the present invention, an
exposure value which is substantially the same as a correct exposure
value determined before the commencement of an exposure can be obtained.
[0024] The present disclosure relates to subject matter contained
in Japanese Patent Application No. 2004-051471 (filed on Feb. 26,
2004) which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The present invention will be described below in detail
with reference to the accompanying drawings in which:
[0026] FIG. 1 is a schematic block diagram of components of an
embodiment of a digital camera for portable equipment according
to the present invention;
[0027] FIG. 2 is a timing chart illustrating the timing of various
events when the digital camera performs a typical imaging process
of the prior art (in which a high-intensity LED remains lit for
a predetermined period of time);
[0028] FIG. 3 is a timing chart illustrating the timing of various
events when the digital camera performs a typical imaging process
of the prior art (in which a high-intensity LED remains lit for
a predetermined period of time and a diaphragm shutter is actuated);
[0029] FIG. 4 is a timing chart illustrating the timing of various
events when the digital camera performs an imaging process according
to a first embodiment of the present invention;
[0030] FIG. 5 is a flow chart showing operations in the first embodiment
of the imaging process;
[0031] FIG. 6 is a timing chart illustrating the timing of various
events when the digital camera performs an imaging process according
to a second embodiment of the present invention;
[0032] FIG. 7 is a flow chart showing operations in the second
embodiment of the imaging process;
[0033] FIG. 8 is a timing chart illustrating the timing of various
events when the digital camera performs an imaging process according
to a third embodiment of the present invention; and
[0034] FIG. 9 is a flow chart showing operations in the third embodiment
of the imaging process.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] FIG. 1 shows elements of an embodiment of a digital camera
for portable equipment according to the present invention. This
digital camera is incorporated in a portable such as a PDA or a
cellular phone. The circuitry which operates exclusively for primary
functions of the portable device (i.e., not for functions of the
digital camera) are not shown in FIG. 1 for the purpose of simplifying
the drawing.
[0036] The digital camera is provided with a photographing lens
11 including a mechanical diaphragm shutter (electrically-driven
light quantity controller) 13 which serves as a diaphragm and a
shutter. The diaphragm shutter 13 serves as a light quantity controller.
The digital camera is provided with a CCD image sensor (image pick-up
device) 15, a diaphragm-shutter drive circuit 17 and a CCD drive
circuit 19. An object-image-forming light bundle which is passed
through the photographing lens 11 and the diaphragm shutter 13 is
focused on the CCD image sensor 15 to be formed as an object image
thereon. The diaphragm shutter 13 is driven by the diaphragm-shutter
drive circuit 17, while the CCD image sensor 15 is driven by the
CCD drive circuit 19. When not energized, the diaphragm shutter
13 is held at rest in a moving range thereof between a fully opened
position and a fully closed position. Upon being energized, the
diaphragm shutter 13 operates to make the shutter blades thereof
move in a direction to open or shut the shutter blades.
[0037] The digital camera is provided with a system control circuit
(system controller) 21 which controls operations of the diaphragm-shutter
drive circuit 17 and the CCD drive circuit 19. The system control
circuit 21 comprehensively controls the overall operations of the
digital camera.
[0038] The digital camera is provided with an AFE (analog front
end) 23. The CCD image sensor 15 converts the received object light
into an electric charge pixel by pixel, accumulates (integrates)
the electric charges, and converts the accumulated electric charges
into an analogue image signal to output this signal to the AFE 23.
[0039] The CCD image sensor 15 is driven by the CCD drive circuit
19 in accordance with signals (e.g., a vertical driving signal,
a horizontal driving signal and a sweep signal) output from the
CCD drive circuit 19. Each of the vertical driving signal and the
horizontal driving signal sequentially shifts each pixel signal
of the CCD image sensor 15, while the sweep signal sweeps the electric
charge accumulated at each pixel therefrom to a substrate. Electric
charges are not accumulated (integrated) during the time the sweep
signal is output from the CCD drive circuit 19, and commence accumulation
immediately after the CCD drive circuit 19 stops outputting the
sweep signal. A time interval between the moment at which the CCD
drive circuit 19 stops outputting the sweep signal and the moment
at which the CCD drive circuit 19 outputs a subsequent vertical
synchronization signal corresponds to an exposure time (integral
action time or accumulation time for capturing one image). The sweep
signal is output in synchronization with the vertical synchronization
signal which is output at predetermined intervals from the system
control circuit 21. After the diaphragm shutter 13 is shut immediately
before the vertical synchronization signal is output, the electric
charges accumulated by the light receiving elements of the CCD image
sensor 15 are output to the AFE 23 as an electric analogue signal
over two fields.
[0040] The analogue image signal is converted into a digital signal
at the AFE 23, and subsequently this digital signal is converted
into an image signal having a predetermined format via a signal
processing circuit 25 to be displayed as a visual image on an LCD
monitor 27 and stored in an internal memory 29.
[0041] The digital camera is provided with a high-intensity LED
(light emitting device) 31 which serves as a light emitting device
at a time of exposure. The high-intensity LED 31 is not a type of
light-emitting device which flashes like a flash lamp but a type
of light-emitting device which lights up and is capable of remaining
on. The system control circuit 21 controls the light-emitting operation
of the high-intensity LED 31 via the LED drive circuit 33 so that
the high-intensity LED 31 lights up when an image is captured under
certain conditions, e.g., in low light. The portable device in which
the present embodiment of the digital camera is incorporated is
provided with a release button 35 which is operated to start an
imaging process. Upon the release button 35 being operated, operations
for the imaging process are performed by the system control circuit
21.
[0042] The system control circuit 21 selects a camera mode from
among various camera modes such as digital camera mode, high-intensity
LED lighting mode and moving-image mode (video mode) in response
to operations of a group of manual operation switches (not shown;
e.g., a mode selection switch) provided on the portable device.
In digital camera mode, the CCD image sensor 15 is generally driven
in a manner similar to that of a camcorder, so that visual images
captured at predetermined intervals are displayed on the LCD monitor
27.
[0043] Basic prior-art imaging processes of the digital camera
will be hereinafter discussed with reference to the timing charts
shown in FIGS. 2 and 3. These timing charts illustrate the timing
of various events when the digital camera performs a typical conventional
imaging process using the high-intensity LED 31. The high-intensity
LED 31 is used in the imaging process shown in FIG. 2. In the imaging
process shown in FIG. 3, not only the high-intensity LED 31 but
also the diaphragm shutter 13 are used. Firstly, the imaging process
shown in FIG. 2 will be discussed hereinafter.
[0044] Upon the release button 35 being half depressed, a power
supply 37 of the portable device feeds a driving current to an imaging
circuit (which includes the CCD image sensor 15, the CCD drive circuit
19, the AFE 23, and the signal processing circuit 25) so that the
imaging process starts. In the case where the release button 35
is not capable of being half-depressed and subsequently fully-depressed
due to the construction thereof, the release button 35 can be operated
in conjunction with another operational button, e.g., half-depressing
the release button 35 halfway could be equivalent to the case where
the digital camera mode is selected in the portable device. In this
state, a current I1 is fed to the imaging circuit. This causes the
high-intensity LED 31 to light up in synchronization with the vertical
synchronization signal which is firstly output after the half-depression
of the release button 35. The power supply current necessary for
energizing the light-intensity LED 31 is represented by I2 (see
FIG. 2).
[0045] During a half depression of the release button 35, a driving
signal for driving the CCD image sensor 15 continues to be output
from the CCD drive circuit 19 to be input to the CCD image sensor
15, so that the CCD image sensor 15 repeats an electric-charge integrating
operation and an electric-charge readout operation to output analogue
image signals at predetermined intervals from the time when the
vertical synchronization signal is firstly output after the half-depression
of the release button 35. The analogue image signals output from
the CCD image sensor 15 are processed via the AFE 23 and the signal
processing circuit 25 to be displayed as visual image on the LCD
panel 27. An optimum exposure time (electronic shutter time) is
determined from the output analogue image signal by the signal processing
circuit 25 and the system control circuit 21. The system control
circuit 21 determines an exposure time for the CCD drive circuit
19 via serial communication so that the optimum exposure time is
obtained. The exposure time refers to the integral action time or
accumulation time of the CCD image sensor 15 in a state where the
diaphragm shutter 13 is open.
[0046] Immediately after the release button 35 is fully depressed,
electric charges are accumulated during the exposure time between
the moment at which the CCD drive circuit 19 stops outputting the
sweep signal, that the CCD drive circuit 19 outputs in synchronization
with the vertical synchronization signal which is firstly output
after the full-depression of the release button 35, and the moment
at which the subsequent vertical synchronization signal is output
from the system control circuit 21. Subsequently, the accumulated
electric charges are read out in synchronization with the subsequent
vertical synchronization signal to be stored in the internal memory
29 and displayed as a visual image on the LCD monitor 27.
[0047] In the above described imaging process in which the diaphragm
shutter 13 is not actuated, the peak current (peak value of the
power supply current) Imax is the sum of the current I1 and the
current I2 (i.e., "I1+I2" shown in FIG. 2), since both
the power supply current I1 for driving the imaging circuit and
the power supply current 12 for energizing the high-intensity LED
31 are necessary.
[0048] Another typical conventional imaging process in which the
high-intensity LED 31 and the diaphragm shutter 13 are actuated
will be hereinafter discussed with reference to FIG. 3.
[0049] Upon the release button 35 being half depressed, the power
supply 37 feeds a driving current to an imaging circuit (which includes
the CCD image sensor 15, the CCD drive circuit 19, the AFE 23, and
the signal processing circuit 25) so that the imaging process starts.
In the case where the release button 35 is not capable of being
half-depressed and subsequently fully-depressed due to the construction
thereof, the release button 35 can be operated in conjunction with
another operational button, e.g., half-depressing the release button
35 halfway could be equivalent to the case where the digital camera
mode is selected in the portable device. In this state, the current
I1 is fed to the imaging circuit so that the imaging circuit operates.
Thereafter, the high-intensity LED 31 lights up in synchronization
with the vertical synchronization signal which is firstly output
after the half-depression of the release button 35. The power supply
current necessary for energizing the light-intensity LED 31 is represented
by I2 (see FIG. 3).
[0050] During a half depression of the release button 35, a driving
signal for driving the CCD image sensor 15 continues to be output
from the CCD drive circuit 19 to be input to the CCD image sensor
15, so that the CCD image sensor 15 repeats an electric-charge integrating
operation and an electric-charge readout operation to output analogue
image signals at predetermined intervals from the time when the
vertical synchronization signal is firstly output after the half-depression
of the release button 35. The analogue image signals output from
the CCD image sensor 15 are processed via the AFE 23 and the signal
processing circuit 25 to be displayed as a visual image on the LCD
panel 27.
[0051] Immediately after the release button 35 is fully depressed,
a mechanical-shutter speed starts being clocked from the moment
at which the vertical synchronization signal is firstly output after
the full-depression of the release button 35, and the diaphragm
shutter 13 is driven to shut so that the mechanical-shutter speed
elapses at the moment at which the diaphragm shutter 13 is half
shut. Subsequently, the accumulated electric charges are read out
in synchronization with the vertical synchronization signal which
is firstly output after the diaphragm shutter 13 is fully shut,
and are output as an analogue image signal.
[0052] In the above described imaging process in which the high-intensity
LED 31 is lit while the diaphragm shutter 13 is actuated, the current
I1 and the current I2 are fed to the imaging circuit and the high-intensity
LED 31 upon a half depression of the release button 35, and a current
I3 is fed to the diaphragm shutter 13 when the diaphragm shutter
13 is driven. Accordingly, the peak current becomes the sum of the
current I1, the current I2 and the current I3 (i.e., "I1+I2+I3")
in the case shown in FIG. 3, thus becoming very large.
[0053] A feature of the present embodiment of the digital camera
for portable equipment according to the present invention is that
the high-intensity LED 31 and the diaphragm shutter 13 can be actuated
while preventing the peak current Imax from becoming large.
First Embodiment
[0054] A first embodiment of the imaging process performed by the
present embodiment of the digital camera for portable equipment
according to the present invention will be hereinafter discussed
with reference to the timing chart shown in FIG. 4 and the flow
chart shown in FIG. 5.
[0055] Control waits for the release button 35 to be half depressed
(step S11). Upon the release button 35 being half depressed (if
YES at step S11), the imaging circuit (which includes the CCD image
sensor 15, the CCD drive circuit 19, the AFE 23, and the signal
processing circuit 25) is turned ON (step S12), and the high-intensity
LED 31 is lit in synchronization with the vertical synchronization
signal which is firstly output after the half-depression of the
release button 35 (step S13). Due to the operations at steps S12
and S13, the CCD image sensor 15 is driven by the CCD drive circuit
19 while the AFE 23, the signal processing circuit 25 and the LCD
monitor 27 are actuated so that the object image captured by the
CCD image sensor 15 is displayed on the LCD monitor 27.
[0056] Subsequently, using intensity data which is calculated by
the signal processing circuit 25 on every field from the pixel signal
obtained from the CCD image sensor 15, the system control circuit
21 determines an optimum electronic shutter time T0 for obtaining
correct exposure while making corrections to the electronic shutter
time over several fields, and sets the CCD drive circuit 19 for
the determined optimum electronic shutter time T0 (step S14).
[0057] The high-intensity LED 31 is turned OFF in synchronization
with the vertical synchronization signal (step S15), the diaphragm
shutter 13 is stopped down to a predetermined aperture setting from
a full-aperture state via the diaphragm-shutter drive circuit 17
(step S16), and the high-intensity LED 31 is turned ON again upon
completion of the stop-down operation of the diaphragm shutter 13
(step S17). This is the case where the object brightness is great;
the depth of field can be increased by stopping down the diaphragm
shutter 13.
[0058] In a state where the high-intensity LED 31 is lit while
the diaphragm shutter 13 is stopped down to a predetermined aperture
setting, the system control circuit 21 determines and sets an exposure
time T1 for obtaining correct exposure in a manner similar to that
at step S14 (step S18), and control waits for the release button
35 to be fully depressed (step S19). Even during the time control
waits for the release button 35 to be fully depressed, a process
for indicating an image signal obtained with the set exposure time
T1 as a visual image on the LCD monitor 27 is repeated. During this
time, the exposure time can be sequentially varied by detecting
intensity data at regular time intervals.
[0059] Upon the release button 35 being fully depressed (if YES
at step S19), an exposure process, in which control waits for the
exposure time T1 to elapse from the moment at which the vertical
synchronization signal is firstly output after the full-depression
of the release button 35, is performed in synchronization with the
vertical synchronization signal. Immediately after the exposure
time T1 elapses, the high-intensity LED 31 is turned OFF (step S20),
and subsequently, the diaphragm shutter 13 is fully shut (step S21).
[0060] In synchronization with the vertical synchronization signal
which is firstly output after the diaphragm shutter 13 is fully
shut, the CCD image sensor 15 stops integrating electric charges
and subsequently pixel signals are read out as still image data
from the CCD image sensor 15 over two fields (step S22). The read
pixel signals are processed via the AFE 23 and the signal processing
circuit 25 to be written in the internal memory 29 as digital image
data having a predetermined format.
[0061] Upon completion of the readout of the pixel signals, the
diaphragm shutter 13 is fully opened (step S23), and the power source
for the imaging circuit is turned OFF (step S24) to complete the
imaging process (END).
[0062] Variations (rise and fall) of the power supply current in
time sequence in the first embodiment of the imaging process performed
by the present embodiment of the digital camera for portable equipment
according to the present invention will be discussed hereinafter.
[0063] The power supply current I1 continues to be fed to the imaging
circuit from the moment at which the release button 35 is turned
ON (half depressed) to the moment at which the vertical synchronization
signal is firstly output after the release button 35 is turned ON.
[0064] The power supply current I1+I2 commences to be fed to the
imaging circuit upon the high-intensity LED 31 being turned ON.
[0065] When the diaphragm shutter 13 is driven to stop down the
photographing lens 11, the power supply current I1+I3 is fed to
the imaging circuit because the diaphragm shutter 13 is driven after
the high-intensity LED 31 is turned OFF.
[0066] Subsequently, the power supply current I1+I2 is fed to the
imaging circuit because the high-intensity LED 31 is turned ON again
after the diaphragm shutter 13 is stopped down to a predetermined
aperture setting.
[0067] Subsequently, the power supply current I1+I3 is fed to the
imaging circuit during a closing operation of the diaphragm shutter
13 because the diaphragm shutter 13 is fully shut shortly after
the high-intensity LED 31 is turned OFF upon completion of an exposure.
[0068] Upon the diaphragm shutter 13 being fully shut, the power
supply current I1 is fed to the imaging circuit during a readout
of pixel signals. Upon completion of this readout, the power supply
current I1+I3 commences to be fed to the imaging circuit, and continues
to be fed during the time the diaphragm shutter 13 is driven to
fully open. Thereafter, only the power supply current I1 is fed
to the imaging circuit immediately after the diaphragm shutter 13
is fully opened.
[0069] In the first embodiment of the imaging process, the diaphragm
shutter 13 and the high-intensity LED 31 are not driven simultaneously,
and therefore the peak current is limited to the current I1+I3,
or the current I1+I2 in the case where the power supply current
I2 for lighting the high-intensity LED 31 becomes greater than the
power supply current I3 for driving the diaphragm shutter 13.
Second Embodiment
[0070] In the above described first embodiment of the imaging process,
although the high-intensity LED 31 is turned OFF immediately after
a lapse of the exposure time (exposure time) T1, the CCD image sensor
15 continues to be exposed until the diaphragm shutter 13 is fully
shut, which results in slight overexposure. A second embodiment
of the imaging process performed by the present embodiment of the
digital camera for portable equipment according to the present invention,
wherein an imaging operation at correct exposure is achieved with
less power consumption, will be hereinafter discussed with reference
to the timing chart shown in FIG. 6 and the flow chart shown in
FIG. 7.
[0071] Control waits for the release button 35 to be half depressed
(step S31). Upon the release button 35 being half depressed (if
YES at step S31), the imaging circuit (which includes the CCD image
sensor 15, the CCD drive circuit 19, the AFE 23, and the signal
processing circuit 25) is turned ON (step S32), and the high-intensity
LED 31 is lit with a low intensity L1 in synchronization with the
vertical synchronization signal which is firstly output after the
half-depression of the release button 35 (step S33). Namely, the
CCD image sensor 15 is driven by the CCD drive circuit 19 with the
high-intensity LED 31 remaining on with the low intensity L1, while
the AFE 23, the signal processing circuit 25 and the LCD monitor
27 are actuated so that the object image captured by the CCD image
sensor is displayed on the LCD monitor 27.
[0072] Subsequently, using intensity data which is calculated by
the signal processing circuit 25 on every field from the pixel signal
obtained from the CCD image sensor 15, the system control circuit
21 determines an exposure time T1 and an aperture value for obtaining
correct exposure while making corrections to the exposure time and
the aperture value over several fields, and sets the CCD drive circuit
19 for the determined exposure time T1 and the determined aperture
value (step S34). Control waits for the release button 35 to be
fully depressed while repeating the imaging process performed with
the calculated exposure time T1 (step S35).
[0073] Upon the release button 35 being fully depressed (if YES
at step S35), the sweep signal is output from the CCD drive circuit
19 for a period of time T5 in synchronization with the vertical
synchronization signal which is firstly output after the full-depression
of the release button 35 (step S36). The period of time T5 is determined
from the following equation:
T5=T6-T1-(T4/2)
[0074] T4 represents a mechanical-shutter shutting operation time
(the time necessary for the diaphragm shutter 13 to be fully shut
from the fully-open position thereof). T6 represents field time
(the time interval between two vertical synchronization signals).
[0075] Immediately after the period of time T5 elapses, the high-intensity
LED 31 is turned ON at the high intensity L2 to stay lit for a period
of time T2, and is subsequently turned OFF immediately after a lapse
of the period of time T2 (step S37). The period of time T2 is determined
from the following equation:
T2=T1-T3-(T4/2)
L2=L1.times.(T1/T2)
[0076] T3 represents the mechanical delay time (lag time between
a startup of the diaphragm shutter 13 and the actual commencement
of shutting operation of the diaphragm shutter 13.
[0077] The power supply current for making the high-intensity LED
31 remain lit with the low intensity L1 is represented by I2, and
the power supply current for making the high-intensity LED 31 remain
lit with a high intensity L2 is represented by I4. The power supply
current I2 is smaller than the power supply current I4. Therefore,
the light emitted from the high-intensity LED 31 with the high intensity
L2 is brighter than the light emitted from the high-intensity LED
31 with the low intensity L1.
[0078] Immediately after a lapse of the period of time T2, the
system control circuit 21 sends a shutting signal to the diaphragm-shutter
drive circuit 17, and consequently, the diaphragm shutter 13 is
fully shut (step S38). Although the diaphragm shutter 13 commences
to be energized to fully shut via the diaphragm-shutter drive circuit
17 immediately after the period of time T2 elapses, the diaphragm
shutter 13 actually commences to shut immediately after a lapse
of the mechanical delay time T3, and is fully shut immediately after
a lapse of the mechanical-shutter shutting operation time T4.
[0079] Immediately after a lapse of the mechanical-shutter shutting
operation time T4, pixel signals are read out as still image data
from the CCD image sensor 15 over two fields to be written in the
internal memory 29 as digital image data (step S39). Thereafter,
the diaphragm shutter 13 is driven to fully open (step S40), and
the power source for the imaging circuit is turned OFF (step S41)
to complete the imaging process (END).
[0080] Variations (rise and fall) of the power supply current in
time sequence in the second embodiment of the imaging process performed
by the present embodiment of the digital camera for portable equipment
according to the present invention will be discussed hereinafter.
[0081] The power supply current I1 continues to be fed to the imaging
circuit from the moment at which the release button 35 is turned
ON (half depressed) to the moment at which the vertical synchronization
signal is firstly output after the release button 35 is turned ON.
Upon the high-intensity LED 31 being turned ON, the power supply
current I1+I2 commences to be fed to the imaging circuit because
the high-intensity LED 31 is turned ON to remain lit with the low
intensity L1 in synchronization with the vertical synchronization
signal which is firstly output immediately after the high-intensity
LED 31 is turned ON.
[0082] Upon the release button 35 being fully depressed, the power
supply current I1+I4 commences to be fed to the imaging circuit
because the high-intensity LED 31 is turned ON to remain lit with
the high intensity L2 in synchronization with the vertical synchronization
signal which is firstly output after the full-depression of the
release button 35.
[0083] Subsequently, the power supply current I1+I3 is fed to the
imaging circuit because the diaphragm shutter 13 is actuated to
be fully shut while the high-intensity LED 31 is turned OFF immediately
after a lapse of the period of time T5+T2 from the moment at which
the aforementioned first vertical synchronization signal is output.
[0084] Subsequently, the power supply current I1 is fed to the
imaging circuit because the current fed to the diaphragm shutter
13 is cut off immediately after the high-intensity LED 31 is turned
OFF.
[0085] Upon the diaphragm shutter 13 being fully shut, the power
supply current I1 is fed to the imaging circuit during a readout
of pixel signals. Upon completion of this readout, the power supply
current I1+I3 commences to be fed to the imaging circuit, and continues
to be fed during the time the diaphragm shutter 13 is driven to
fully open. Thereafter, only the power supply current I1 is fed
to the imaging circuit immediately after the diaphragm shutter 13
is fully opened.
[0086] In the second embodiment of the imaging process, the diaphragm
shutter 13 and the high-intensity LED 31 are not driven simultaneously,
and therefore the peak current is limited to the current I1+I3,
or the current I1+I4 in the case where the power supply current
I4 for lighting the high-intensity LED 31 becomes greater than the
power supply current I3 for driving the diaphragm shutter 13.
[0087] Moreover, an object image can be captured at correct exposure
because the high-intensity LED 31 is turned ON to remain lit with
the high-intensity L2 (which is greater in brightness than the low-intensity
L1) during an exposure so that a correct exposure is attained with
the exposure time T1 that is set on condition that the high-intensity
LED 31 remains lit with the low intensity L1 over the entire exposure
time.
[0088] In the second embodiment of the imaging process shown in
FIG. 7, the high-intensity LED 31 can be replaced by a plurality
of LEDs so that all the LEDs are turned ON when emitting light with
the high intensity L2 and that a portion (e.g., a half) of all the
LEDs are turned ON (or OFF) when emitting light with the low intensity
L1.
Third Embodiment
[0089] A third embodiment of the imaging process performed by the
present embodiment of the digital camera for portable equipment
according to the present invention, wherein an imaging operation
at correct exposure is achieved while minimizing the peak current,
will be hereinafter discussed with reference to the timing chart
shown in FIG. 8 and the flow chart shown in FIG. 9.
[0090] Control waits for the release button 35 to be half depressed
(step S51). Upon the release button 35 being half depressed (if
YES at step S51), the imaging circuit (which includes the CCD image
sensor 15, the CCD drive circuit 19, the AFE 23, and the signal
processing circuit 25) is turned ON (step S52), and the high-intensity
LED 31 is turned ON in synchronization with the vertical synchronization
signal which is firstly output after the half-depression of the
release button 35 (step S53). Due to the operations at steps S52
and S53, the CCD image sensor 15 is driven by the CCD drive circuit
19, while the AFE 23, the signal processing circuit 25 and the LCD
monitor 27 are actuated so that the object image captured by the
CCD image sensor 15 is displayed on the LCD monitor.
[0091] Subsequently, in a manner similar to that at step S34 shown
in FIG. 7, the system control circuit 21 determines an exposure
time T1 and an aperture value for obtaining correct exposure, and
sets the CCD drive circuit 19 for the determined exposure time T1
and the determined aperture value (step S54). Control waits for
the release button 35 to be fully depressed while repeating the
imaging process performed with the calculated exposure time T1 in
a manner similar to that at step S35 shown in FIG. 7 (step S55).
[0092] Upon the release button 35 being fully depressed (if YES
at step S55), control waits for an exposure time T7 to elapse from
the moment at which the vertical synchronization signal is firstly
output after the full-depression of the release button 35. Immediately
after the exposure time T7 elapses, the high-intensity LED 31 is
turned OFF. The exposure time T7 is determined from the following
equation:
T2=T1-T3-(T4/2)
T7=(T1+T2)/2
[0093] T3 represents the mechanical delay time, and T4 represents
the mechanical-shutter shutting operation time.
[0094] Note that the exposure time T1, which represents a calculated
optimum exposure time, is determined to obtain correct exposure
if the diaphragm shutter 13 is half shut upon a lapse of the period
of time T1 in a state where the high-intensity LED 31 remains lit
during exposure. Therefore, if the high-intensity LED 31 is turned
OFF while the diaphragm shutter 13 starts to be energized to fully
shut immediately after the exposure time T7 elapses, the diaphragm
shutter 13 commences to shut immediately after a lapse of the mechanical
delay time T3; and subsequently, the exposure time T1 elapses at
the moment the diaphragm shutter 13 commences to shut, thus resulting
in a substantially correct exposure. However, if the high-intensity
LED 31 is turned OFF while the diaphragm shutter 13 starts to be
energized to fully closed immediately after the exposure time T1
elapses, the exposure time is extended by the sum of the mechanical
delay time T3 and the mechanical-shutter shutting operation time
T4, which results in overexposure. On the other hand, if the high-intensity
LED 31 is turned OFF while the diaphragm shutter 13 starts to be
energized to be fully closed at a predetermined period of time T3+T4
(the sum of the mechanical delay time T3 and the mechanical-shutter
shutting operation time T4) before the exposure time T1 elapses,
the exposure time T1 elapses upon the diaphragm shutter 13 being
half shut, which results in underexposure.
[0095] Immediately after the exposure time T7 elapses, the diaphragm
shutter 13 is fully shut (step S57). Upon the diaphragm shutter
13 being fully shut, pixel signals are read out as still image data
from the CCD image sensor 15 over two fields, and are processed
via the AFE 23 and the signal processing circuit 25 to be written
in the internal memory 29 as digital image data and, at the same
time, are displayed as visual image on the LCD monitor 27 for a
predetermined period of time (step S58).
[0096] Thereafter, the diaphragm shutter 13 is driven to fully
open (step S59), and the power source for the imaging circuit is
turned OFF (step S60) to complete the imaging process (END).
[0097] Variations (rise and fall) of the power supply current in
time sequence in the third embodiment of the imaging process performed
by the present embodiment of the digital camera for portable equipment
according to the present invention will be discussed hereinafter.
[0098] The power supply current I1 continues to be fed to the imaging
circuit from the moment at which the release button 35 is turned
ON (half depressed) to the moment at which the vertical synchronization
signal is firstly output after the release button 35 is turned ON.
[0099] Upon the high-intensity LED 31 being turned ON, the power
supply current I1+I2 commences to be fed to the imaging circuit.
[0100] When the diaphragm shutter 13 is fully shut upon completion
of an exposure, the power supply current I1+I3 is fed to the imaging
circuit because the diaphragm shutter 13 is driven after the high-intensity
LED 31 is turned OFF.
[0101] Thereafter, the power supply current I1 is fed to the imaging
circuit during a readout of a still image data. Upon completion
of the readout of the still image data, the power supply current
I1+I3 commences to be fed to the imaging circuit, and continues
to be fed during the time the diaphragm shutter 13 is driven to
fully open. Thereafter, only the power supply current I1 resumes
to be fed to the imaging circuit immediately after the diaphragm
shutter 13 is fully opened.
[0102] In the third embodiment of the imaging process, the diaphragm
shutter 13 and the high-intensity LED 31 are not driven simultaneously,
and therefore, the peak current is limited to the current I1+I3,
or the current I1+I2 in the case where the power supply current
I2 for lighting the high-intensity LED 31 becomes greater than the
power supply current I3 for driving the diaphragm shutter 13.
[0103] Moreover, in the third embodiment of the imaging process,
an object image can be captured at correct exposure because the
exposure time T7, upon a lapse of which the high-intensity LED 31
is turned OFF while the diaphragm shutter 13 is actuated to be fully
shut, is set between the exposure time T1 which causes overexposure
and the exposure time T2 which causes underexposure.
[0104] Although the above described embodiment of the digital camera
for portable equipment is provided with the CCD image sensor 15
as an image pick-up device, the CCD image sensor 15 can be replaced
by a CMOS image sensor.
[0105] Although the above described embodiment of the digital camera
for portable equipment is provided with the diaphragm shutter 13
as a light quantity controller, the diaphragm shutter 13 can be
replaced by a diaphragm and a shutter which are provided independently
of each other. Additionally, the above described embodiment of the
digital camera for portable equipment can be provided with a light
quantity controller which moves or rotates an ND filter.
[0106] Obvious changes may be made in the specific embodiments
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. |