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Digital Camera Patent Abstract
A digital camera having a camera-shake compensation mechanism and
a luminance compensation processor is provided. The camera-shake
compensation mechanism compensates for a camera-shake by adjusting
a relative relation between positions of an optical axis of a photographing
optical system and a center of an image of an imaging device. The
luminance compensation processor compensates for luminance information
of pixels of the imaging device, which are outside an image circle
of the photographing optical system during a camera-shake compensation
operation performed by the camera-shake compensation mechanism.
Digital Camera Patent Claims
1. A digital camera, comprising: a camera-shake compensation mechanism
that compensates for a camera-shake by adjusting a relative relations
between positions of an optical axis of a photographing optical
system and a center of image of a imaging device; and a luminance
compensation processor that compensates for luminance information
of pixels of said imaging device, which are outside an image circle
of said photographing optical system during a camera-shake compensation
operation performed by said camera-shake compensation mechanism.
2. A digital camera according to claim 1, wherein said luminance
compensation processor comprises: a detecting processor that counts
the number of times each of said pixels is determined as being outside
the image circle in said camera-shake compensation operation that
is repeated at a predetermined period by said camera-shake compensation
mechanism during an electric-charge accumulating period of said
imaging device; and a luminance information amplifier that amplifies
the luminance information of said pixels based on factors that are
obtained for each of said pixels in accordance with the number of
times each of said pixels is determined as being outside the image
circle, the number of times being counted by said detecting processor.
3. A digital camera according to claim 2, wherein said detecting
processor comprises: a distance calculator that calculates a distance
from a center of the image circle to a pixel of said imaging device;
a comparator that compares the distance calculated by said distance
calculator and a radius of the image circle; and a determination
processor that determines whether the pixel is positioned outside
the image circle in accordance with a result of a comparison carried
out by said comparator.
4. A digital camera according to claim 1, wherein said camera-shake
compensation mechanism comprises: a camera-shake detector that detects
a quantity of camera-shake; and a drive mechanism that moves said
imaging device in a plane perpendicular to the optical axis, so
that the camera-shake detected by said camera-shake detector is
counteracted.
5. A digital camera according to claim 1, wherein said luminance
compensation processor compensates for the luminance information
based on the time in which each of said pixels has been outside
an image circle of said photographing optical system during a camera-shake
compensation operation performed by said camera-shake compensation
mechanism.
6. A digital camera according to claim 5, wherein said luminance
compensation processor further compensates for the luminance information
with respect to a distance from the optical axis to a pixel of said
imaging device when said imaging device is moved by the camera-shake
compensation operation.
7. A digital camera, comprising: a camera-shake compensation mechanism
that compensates for a camera-shake by moving an imaging device
with respect to an optical axis of a photographing optical system;
a calculator that calculates a distance from the optical axis to
a pixel of said imaging device when said imaging device is moved
by a camera-shake compensation operation of said camera-shake compensation
mechanism; and a luminance compensation processor that compensates
for luminance information of the pixel based on the distance calculated
by said calculator.
8. A method of luminance compensation, comprising steps of: detecting
a distance from an optical axis to a pixel of an imaging device
while the imaging device is moved by a camera-shake compensation
operation performed by a camera-shake compensation mechanism of
a digital camera; and compensating for luminance of the pixels by
amplifying the luminance value in accordance with the distance.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a digital camera provided
with camera-shake compensation functionality (anti-shake functionality).
[0003] 2. Description of the Related Art
[0004] Conventionally, some digital cameras are provided with camera-shake
compensation functionality. In a conventional camera-shake compensation
operation (or a blur compensation operation) of the camera-shake
compensation functionality, a camera-shake (a direction and the
quantity of the camera-shake) of the digital camera, for example,
is obtained by using a gyro-sensor. A solid-state imaging device
(e.g., CCD) or a compensation optical system (which is a part of
a photographing optical system) is then moved to counterbalance
the detected camera-shake. Thereby, the camera-shake that results
from hand-held shake and the like are compensated, and a satisfactory
image is obtained.
SUMMARY OF THE INVENTION
[0005] In general, the solid-sate imaging device is placed at a
position where the center of an effective area of the solid-sate
imaging device is concentric with the center of an image circle
of the photographing optical system, and the photographing optical
system is also optically designed in order to include the effective
area of the solid-sate imaging device within the image circle. Here,
the image circle is defined as an outermost circular area that is
able to receive light more than a predetermined quantity of light
(for example, 50 percent or more) compared to the quantity of light
received on the-optical axis of the photographing optical system.
Namely, outside the image circle of an optical image formed by the
photographing optical system, the luminance and sharpness are substantially
low compared to the luminance and sharpness obtained within the
image circle.
[0006] However, when the solid-sate imaging device or the compensation
optical system is operated in accordance with the above-described
camera-shake compensation operation, the relative relations between
the image circle position and the solid-sate imaging sensor position
change, thereby a part of the solid-sate imaging device occasionally
exceeds the range of the image circle. As described above, since
the luminance of the optical image outside the image circle is low,
the quality of an image deteriorates although a blur of the image
is compensated.
[0007] In order to overcome the above problem, making the image
circle substantially large enough to keep the solid-sate imaging
device within the image circle even when relative relations between
the photographing optical system and the solid-state imaging device
are varied during the camera-shake compensation, has been contemplated.
However, in order to enlarge the size of the image circle, the dimensions
of the photographing optical system should also be increased, thereby
this approach runs against the trend to reduce camera size.
[0008] An object of the present invention is to reduce the size
of a digital camera provided with camera-shake compensation functionality.
[0009] According to the present invention, a digital camera is
provided that comprises a camera-shake compensation mechanism and
a luminance compensation processor.
[0010] The camera-shake compensation mechanism compensates for
a camera-shake by adjusting a relative relation between positions
of an optical axis of a photographing optical system and a center
of an image of an imaging device. The luminance compensation processor
compensates for luminance information of pixels of the imaging device,
which are located outside an image circle of the photographing optical
system during a camera-shake compensation operation performed by
the camera-shake compensation mechanism.
[0011] For example, the luminance compensation processor comprises
a detecting processor and a luminance information amplifier. The
detecting processor counts the number of times each of the pixels
is determined as being outside the image circle in the camera-shake
compensation operation. This is repeated every predetermined period
by the camera-shake compensation mechanism during an electric-charge
accumulating period of the imaging device. The luminance information
amplifier amplifies the luminance information of the pixels based
on factors that are obtained for each of the pixels in accordance
with the number of times each of the pixels is determined as being
outside the image circle, which is counted by the detecting processor.
[0012] The detecting processor may comprise a distance calculator,
a comparator, and a determination processor. The distance calculator
calculates a distance from a center of the image circle to a pixel
of the imaging device. The comparator compares the distance calculated
by the distance calculator and a radius of the image circle. The
determination processor determines whether the pixel is positioned
outside the image circle in accordance with a result of a comparison
carried out by the comparator.
[0013] The camera-shake compensation mechanism may comprise a camera
shake-detector and a drive mechanism. The camera-shake detector
detects the quantity of a camera-shake. The drive mechanism moves
the imaging device in a plane perpendicular to the optical axis,
so that the camera-shake detected by the camera-shake detector is
counterbalanced.
[0014] For example, the luminance compensation processor compensates
the luminance information with respect to the time that each of
the pixels has been outside an image circle of the photographing
optical system during a camera-shake compensation operation, performed
by the camera-shake compensation mechanism.
[0015] Further, the luminance compensation processor may also compensate
the luminance information with respect to the distance from the
optical axis to a pixel of the imaging device, when the imaging
device is moved by the camera-shake compensation operation.
[0016] Further, according to the present invention, a digital camera
is provided that comprises a camera-shake compensation mechanism,
a calculator, and a luminance compensation processor.
[0017] The camera-shake compensation mechanism compensates for
a camera-shake by moving an imaging device with respect to an optical
axis of a photographing optical system. The calculator calculates
a distance from the optical axis to a pixel of the imaging device
when the imaging device is moved by a camera-shake compensation
operation of the camera-shake compensation mechanism. The luminance
compensation processor compensates for luminance information of
the pixel based on the distance calculated by the calculator.
[0018] Furthermore, according to the present invention, a luminance
compensation method is provided. The method comprises steps of detecting
a distance from an optical axis to a pixel of an imaging device
while the imaging device is moved by a camera-shake compensation
operation performed by a camera-shake compensation mechanism of
a digital camera, and compensating for the luminance of the pixel
by amplifying the luminance value in accordance with the distance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The objects and advantages of the present invention will
be better understood from the following description, with reference
to the accompanying drawings in which:
[0020] FIG. 1 is a front view of a digital camera to which an embodiment
of the present invention is applied;
[0021] FIG. 2 is a perspective view of the digital camera shown
in FIG. 1;
[0022] FIG. 3 is a block diagram of the digital camera;
[0023] FIG. 4 schematically illustrates a relative relation between
an image circle of a photographing lens and a CCD;
[0024] FIG. 5 is a flowchart of a luminance compensation operation;
[0025] FIG. 6 is a flowchart of a camera-shake compensation operation;
[0026] FIG. 7 schematically illustrates a relative relation between
the image circle and the CCD, which is moved in the camera-shake
compensation operation;
[0027] FIG. 8 is a flowchart of a luminance compensation subroutine;
and
[0028] FIG. 9 is a flowchart of a luminance compensation operation
of an alternate embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention is described below with reference
to the embodiments shown in the drawings.
[0030] FIG. 1 is a front view of a digital camera to which an embodiment
of the present invention is applied. FIG. 2 is a perspective view
from the rear side of the digital camera shown in FIG. 1. A power
button (Pon) 11 is provided on the rear side of the digital camera
1, and is used to control the On/Off state of the camera. On the
top face, a release button 13 is provided. Reflected light from
an object comes into the digital camera 1 through a photographing
lens 10, so that an image of the object is formed on an imaging
surface of a CCD (which will be described later). Image data obtained
by the CCD is subjected to a predetermined image processing and
then reproduced on an LCD 16, which is provided on the rear side
of the digital camera 1. Further, a start and an end of the camera-shake
compensation operation are controlled by an operation of an anti-shake
button 14.
[0031] Note that, in the present embodiment, a first direction
"x" is defined as a direction that is perpendicular to
an optical axis "OP" of the photographing optical system,
and further the first direction "x" corresponds to a horizontal
direction when the digital camera 1 is held in the normal position.
A second direction "y" is defined as a direction perpendicular
to the optical axis "OP" and to the first direction "x",
so that the second direction "y" corresponds to a vertical
direction when the digital camera 1 is held in the normal position.
Further, a third direction "z" coincides with the optical
axis "OP".
[0032] Inside the digital camera 1, a first angular velocity sensor
26 and a second angular velocity sensor 27 are provided. The first
angular velocity sensor 26 is a sensor for detecting the angular
velocity about the y-axis (the axis along the second direction "y").
The second angular velocity sensor 27 is a sensor for detecting
the angular velocity about the x-axis (the axis along the first
direction "x"). A gyroscope sensor is an example of the
first and second angular velocity sensor 26 and 27.
[0033] FIG. 3 is a block diagram of the digital camera 1. A switch
11a is switched on and switched off in connection with an operation
of the power button (Pon) 11. When the switch 11a is turned on,
the electrical power is then supplied to all of the circuits in
the digital camera 1.
[0034] When the release button 13 is half depressed, a photometry
switch 12a is turned on and a photometry process starts. Further,
when the release button 13 is fully depressed, a release switch
13a is turned on so that an image capturing process starts. An anti-shake
switch 14a is switched On and switched Off in connection with an
operation of the anti-shake button 14. A camera-shake compensation
operation, which will be described later, starts when the anti-shake
switch 14a is switched on and ends when the anti-shake switch 14a
is switched off.
[0035] An AE component 23 carries out a photometry operation for
an object, so that an exposure value is calculated, and a stop value
and exposure time (electric-charge accumulating period), which are
required for the image capturing operation, are calculated from
the exposure value. An AF component 24 carries out a distance measurement
so that the digital camera 1 is brought into focus by moving the
photographing lens 10 along the optical axis "OP" in accordance
with a result of the measurement.
[0036] When the above-described release switch 13a is turned On,
control signals from a CPU 20 are output to a CCD driver 21. Further,
CCD drive signals are fed to the CCD 39a from the CCD driver 21,
in accordance with the control signals from the CPU 20. Namely,
an optical image formed on the imaging surface of the CCD 39a through
the photographing lens 10 is subjected to photoelectrical conversion
so that image data is output from the CCD 39a. The image data from
the CCD 39a is then subjected to A/D conversion and predetermined
image processing in an image-processing unit 22, and is then stored
in an image memory 50.
[0037] An angular velocity detecting component 25 includes the
first angular velocity sensor 26, the second angular velocity sensor
27, and an amplifier/high-pass filter circuit 28. Each of the first
and second angular velocity sensors 26 and 27 detects angular velocity
components about the y-axis and the x-axis for every regular interval
(e.g., 1 ms). The amplifier/high-pass filter circuit 28 amplifies
signals relating to the angular velocity components and then cuts
off null voltage and removes a panning component of the first and
second angular velocity sensor 26 and 27, and finally outputs the
amplified and filtered analog signals to terminals A/D0 and A/D1
of the CPU 20, as a first and second angular velocity components
"vx" and "vy".
[0038] The analog signals of the first and second angular velocity
components "vx" and "vy", which are input from
the terminals A/D0 and A/D1 of the CPU 20, are converted to the
digital signals in the CPU 20. Further, the signals are subjected
to an integral process, so that the quantity of the camera-shake
which is induced during the regular interval (1 ms), is calculated
by using a transformation coefficient, which takes the focus length
and so on into consideration. Namely, displacement in the first
direction "x" of the digital camera 1 is calculated in
accordance with the output from the first angular velocity sensor
26. Further, displacement in the second direction "y"
of the digital camera 1 is calculated in accordance with the output
from the second angular velocity sensor 27.
[0039] The CPU 20 calculates coordinates of a position S, where
the CCD 39a ought to be moved and which corresponds to the above-calculated
quantity of the camera-shake, for each of the first direction "x"
and the second direction "y". In the present embodiment,
a coordinate value of the position S in the first direction "x"
is referred to as "sx", and a coordinate value in the
second direction "y" is referred to as "sy".
The motion of a movable section 30a, including the CCD 39a, is performed
by electromagnetic force, as described later. Further, the movement
of the movable section 30a to the position P is carried out by an
actuator driver 29, which is controlled by signals of a first PWM-duty
"dx" and a second PWM-duty "dy". The first PWM-duty
"dx" controls the motion in the first direction "x"
and the second PWM-duty "dy" controls motion in the second
direction "y". Namely, the first and second PWM-duty "dx"
and "dy" correspond to the components of the drive force
applied to the movable section 30a, in the first and second directions
"x" and "y".
[0040] An anti-shake device 30 is a device that compensates for
a camera-shake, by moving the CCD 39a to the above-calculated position
S, in order to counteract a shake of the digital camera 1 induced
by the hand-held shake. The anti-shake device 30 comprises the movable
section 30a that includes the CCD 39a and a fixed portion 30b. The
movable section 30a is designed to move within a movable area. The
movable section 30a is supported by a support mechanism (not shown)
so as to be movable in the first direction "x" and the
second direction "y".
[0041] The motion in the first direction "x" of the movable
section 30a of the anti-shake device 30 is carried out by an actuator
that is comprised of a first drive coil 31a provided on the movable
section 30a, and a first drive magnet 33b and a first drive yoke
35b provided on the fixed portion 30b. Further, the movement in
the second direction "y" of the movable section 30a of
the anti-shake device 30 is carried out by an actuator that is comprised
of a second drive coil 32a provided on the movable section 30a,
and a second drive magnet 34b and a first drive yoke 36b provided
on the fixed portion 30b. Namely, the motion of the movable section
30a is operated by controlling the directions and values of electric
current supplied to the first and second drive coils 31a and 32a.
[0042] The first and second drive coils 31a and 32a are connected
to the actuator driver 29. Therefore, the motion of the movable
section 30a of the anti-shake device 30 is controlled by the actuator
driver 29, which is controlled by a signal having the first PWM-duty
"dx" from the terminal PWM0 of the CPU 20 and a signal
having the second PWM-duty "dy" from the terminal PWM1
of the CPU 20.
[0043] The position P of the movable section 30a is detected by
a Hall device 44b and a Hall device signal processor 45 which are
used in cooperation with a position-sensing magnet 41a and position-sensing
yoke 43b. The information of the detected position P is input to
terminals A/D2 and A/D3 of the CPU 20. The information includes
a first position signal "px" and a second position signal
"py", as components of the first direction "x"
and the second direction "y". The first and second position
signals "px" and "py" are subjected to an A/D
conversion through the terminals A/D2 and A/D3. A component of the
position P in the first direction "x" after the A/D conversion
is referred to as a variable "pdx", and a component of
the position P in the second direction "y" after the A/D
conversion is referred to as variable "pdy". The PID (proportional
integral derivative) control is performed based on the data including
the detected position P(pdx, pdy) and the objective position S(sx,
sy), which indicates a destined position of the movable section
30.
[0044] FIG. 4 schematically shows a relative relation between the
image circle of the photographing lens 10 and the CCD 39a. The center
of the image circle 100 is aligned with the optical axis "OP"
of the photographing lens 10. The effective pixel area 101 is a
rectangular area formed of the effective pixels of the CCD 39a.
When the anti-shake switch 14a is in the OFF state and the camera-shake
compensation functionality is at rest, the movable section 30a is
placed at a position where the optical axis OP penetrates a center
101c of the effective pixel area 101. The center 101c is an intersection
point between two diagonal lines of the effective pixel area 101.
In the present embodiment, the position of the movable section 30a
and the CCD 39a on this occasion is-referred to as "the center
of motion". Further, the photographing lens 10 is optically
designed so that the image circle 10 includes the effective pixel
area 101 of the CCD 39a when the CCD 39a is positioned at the center
of motion.
[0045] As described above, in the present embodiment, the camera-shake
of the digital camera 1, which is induced by the hand-held shake,
is eliminated by motion of the CCD 39a. Namely, the quantity of
the anti-shake motion of the CCD 39a depends on the magnitude of
the camera-shake. Thus, on some occasions, a part of the CCD 39a,
i.e. some of the pixels of the CCD 39a, are outside the image circle
100 of the photographing optical system in accordance with the camera-shake.
Accordingly, the CPU 20 carries out a luminance compensation operation
(which will be detailed below) during an electric-charge accumulating
period in order to compensate for luminance information of the pixels
of the CCD 39a that are outside the image circle 100.
[0046] FIG. 5 is a flowchart of the luminance compensation operation,
which is carried out during an electric-charge accumulating period
of the CCD 39a. The electric-charge accumulating period takes place
when the release button 13 is fully depressed to turn on the release
switch 13a and the image capturing process is started. In Step S100,
a variable "n", which indicates the number of times the
camera-shake compensation has been carried out, is preset as "1".
Further, a variable "Gi" which is incremented each predetermined
interval for each of the pixels and that indicates the amount of
time each of the pixels is outside the image circle 100 during the
electric-charge accumulating period, is preset to "0".
Here the suffix "i" of the variable "Gi" corresponds
to a variable "i" that identifies each of the effective
pixels (which will be discussed later). Further, the variable "Gi"
finally correlates with the total time in which each of the pixels
has been outside the image circle 100 during the electric-charge
accumulating period. In Step S102, the camera-shake compensation
operation is then executed.
[0047] FIG. 6 is a flowchart of the camera-shake compensation operation.
In Step 200, the first and second angular velocity components "vx"
and "vy", which are output from the angular velocity detecting
component 25, are input to the CPU 20 through the terminals A/D0
and A/D1, and are converted to digital signals from analog signals.
In step S202, the first and second position signals "px"
and "py" of the movable section 30a, which are detected
by the Hall device 44b and calculated by the Hall device signal
processor 45, are input to the CPU 20 through the terminals A/D2
and A/D3 and are converted from analog signals to digital signals.
Thereby, the current position P(pdx, pdy) is obtained.
[0048] In Step S204, the state of the anti-shake switch 14a is
checked to determine whether the anti-shake mode has been set. When
the anti-shake mode has not been set, the position S(sx, sy), which
is an objective position of the movable section 30a to be moved,
is set as the center of motion of the movable section 30a in Step
S206. On the other hand, when the anti-shake mode has been set,
the position S(sx, sy) of the movable section 30a is then calculated
in Step S208 from the first and second angular velocity components
"vx" and "vy", which are obtained in Step S200.
[0049] In Step S210, the drive force required for the movement
of the movable section 30a is calculated from the position S(sx,
sy) and the current position P(pdx, pdy), which were obtained in
Step S206 and Step S208. Namely, the first PWM-duty "dx"
and the second PWM-duty "dy", which are required for driving
the first and second drive coil 31a and 32a, are calculated. In
Step S212, the first drive coil 31a and the second drive coil 32a
are driven by the actuator driver 29 in accordance with the first
PWM-duty "dx" and the second PWM-duty "dy",
so that the movable section 30a is actuated. The operations in Steps
S210 and S212 are carried out by using a normal PID automatic control,
which in general includes proportional, integral, and derivative
calculations.
[0050] When the camera-shake compensation operation ends, the process
returns to Step S102 of FIG. 5 and then proceeds to Step S104. In
Step S104, whether an electric-charge accumulating period has elapsed
is determined. The period is calculated by the CPU 20 when the release
button 13 is half depressed and the photometry switch 12a is turned
on. Whether the electric-charge accumulation period has elapsed
is determined by-using the following Eq. (1).
n.multidot..DELTA.t.ltoreq.Ts (1)
[0051] In Eq. (1), ".DELTA.t" denotes a period in which
the camera-shake compensation operation is repeated and "Ts"
denotes the electric-charge accumulating period. When it is determined
that the electric-charge accumulating period has not passed, the
process proceeds to Step S106.
[0052] In Step S106, the variable "i", which identifies
each of the effective pixels and which indicates an effective pixel
that is currently being subjected to a determination as to whether
the effective pixel is outside the image circle 100, is preset to
"1". The process then proceeds to Step S108, so that the
variable "i" and the total number "M" of the
effective pixels of the CCD 39a are compared. Namely, whether all
of the effective pixels have been subjected to this process is checked.
When the process has not been carried out for all of the effective
pixels, the process proceeds to Step S110.
[0053] In Step S110, whether a pixel that is currently being processed
is positioned outside the image circle 100 is determined. With reference
to FIG. 7, a process of Step S110 is explained. The pixel "Pi"
in FIG. 7 is a pixel that is currently being processed (the suffix
"i" represents the above variable "i"). Further,
a circle 102 describes the outermost periphery of the light beams
that are made incident into the photographing lens 10. Whether the
pixel "Pi" is positioned outside the image circle 100
is determined based on Eq. (2).
R.ltoreq.{square root over ((x.sub.i+x.sub.L).sup.2+(y.sub.i+y.sub.L).sup.-
2)} (2)
[0054] In Eq. (2), the variable "x.sub.i" denotes a distance
between the center 101c of the effective pixel area 101 and the
pixel "Pi", in the first direction "x". Further,
the variable "y.sub.i" denotes a distance between the
center 101c of the effective pixel area 101 and the pixel "Pi",
in the second direction "y". The variable "X.sub.L"
denotes a distance between the center 100c of the image circle 100
and the center 101c of the effective pixel area 101, in the first
direction "x". The variable "x.sub.L" corresponds
to the first direction (x) component "sx" of the position
"S", where the CCD 39a is moved to, in accordance with
the quantity of the camera-shake. Similarly, the variable "y.sub.L"
denotes a distance between the center 100c of the image circle 100
and the center 101c of the effective pixel area 101, in the second
direction "y". The variable "y.sub.L" corresponds
to the second direction (y) component "sy" of the position
"S", where the CCD 39a is moved in accordance with the
quantity of the camera-shake. Further, "R" denotes the
radius of the image circle 100, which is arbitrarily selected based
on the photographing lens characteristics and required image quality.
[0055] The right-hand side of Eq. (2) represents a one-line distance
"PL" from the center 101c to the pixel "Pi".
Whether the pixel "Pi" is positioned outside the image
circle 100 is determined by comparing the distance "PL"
with the radius "R".
[0056] When it is determined in Step S110 that the pixel, which
is currently being processed, is positioned outside the image circle
100, the process proceeds to Step S112, and the variable "Gi"
(which indicates the amount of times the pixel "Pi" has
been counted outside the image circle 100) is incremented by "1",
and then proceeds to Step S114. Note that, when it is determined
in Step S110 that the current pixel is positioned inside the image
circle 100, Step S112 is skipped and the process jumps to Step S114.
In Step S114, the variable "i" is incremented by "1".
The process then returns to Step S108 and the above-described processes
are repeated.
[0057] When it is determined in Step S108 that the value of the
variable "i" exceeds the total number "M" of
the effective pixels, the process proceeds to Step S116, since the
process of Step S110 and Step S112 has been carried out for all
of the effective pixels of the CCD 39a after the execution of the
camera-shake compensation operation. In Step S116, the variable
"n" (the number of camera-shake compensation processes
that have been carried out) is incremented by "1" and
the process then returns to Step S102, so that the above-described
processes are repeated.
[0058] When it is determined in Step S104 that the electric-charge
accumulating period of the CCD 39a has passed, as a result of Eq.
(1), the process proceeds to Step S118. In Step S118, the luminance
compensation subroutine is carried out. In the luminance compensation
subroutine, a luminance-correcting factor is calculated and the
luminance of each pixel is corrected by the luminance-correcting
factor.
[0059] FIG. 8 is a flowchart of the luminance compensation subroutine.
In Step S300, a variable "i" which identifies each of
the effective pixels and which indicates an effective pixel that
is currently being subjected to the luminance compensation process,
is set to "1". In Step S302, whether the luminance compensation
subroutine has already been carried out for all of the effective
pixels is determined by comparing the value of the variable "i"
with the total number "M" of the effective pixels in the
effective pixel area 101 of the CCD 39a.
[0060] When it is determined in Step S302 that there still remains
a pixel or pixels that have not been processed, the process proceeds
to Step S304. In Step S304, the luminance-correcting factor "Ki"
for compensating for the luminance of the pixel "Pi" is
calculated. The luminance-correcting factor is given by Eq. (3).
Note that, a coefficient "k" in Eq. (3) is a predetermined
luminance-correcting constant. 1 Ki = k Gi t Ts ( 3 )
[0061] Next, the process proceeds to Step S306 and the luminance
information of the pixel "Pi" is compensated based on
the calculated luminance-correcting factor "Ki". For example,
the luminance of the pixel "Pi" is amplified at the image-processing
unit 22 by using the luminance-correcting factor "Ki",
which is calculated in the CPU 20. The variable "i" is
then incremented by "1" in Step S308 and the process returns
to Step S302 to repeat the above-described processes. On the other
hand, when it is determined in Step S302 that the processes from
Step S304 to Step S306 have already been carried out for all of
the effective pixels, the present luminance compensation subroutine
ends. Further, the process then returns to Step S118 of FIG. 5,
so that the luminance compensation operation ends.
[0062] As described above, according to the present embodiment,
the luminance of the effective pixels of the CCD 39a that are located
outside the image circle 100 of the photographing lens 10 is amplified.
Therefore, enlargement of the photographing lens 10 is not required
for the image circle 100 to sufficiently cover the maximum drive
range of the CCD 39a, which is dependent to the mechanical structure
of the movable section 30a. Namely, according to the present embodiment,
an increase in the size of the photographing lens 10 of the digital
camera 1 having the camera-shake compensation functionality is not
required, while increasing the quality of an image obtained through
the camera-shake compensation.
[0063] In the present embodiment, the luminance is amplified or
corrected in accordance with the total time an effective pixel of
the CCD 39a has been outside the image circle during the camera-shake
compensation process, (this time correlates with the number of times
each of the effective pixels is determined as being outside the
image circle during the electric-charge accumulating period). However,
information used in the luminance compensation is not limited to
the above information. A distance of each effective pixel from the
optical axis "OP" during the camera-shake compensation
can also be incorporated into the correction of the luminance of
the effective pixels. Namely, a distance related factor that can
substantially counterbalance the luminance distribution (distribution
of quantity of light) along the radial direction due to the characteristics
of the lens system is introduced into Eq. (3), in place of the factor
"Gi". For example, when the luminance distribution is
defined as f(r) (where "r" is the radius), the distance
related factor includes function .alpha.x (1-f(r)), where .alpha.
is a lens dependent constant. More specifically, as shown in the
flowchart of FIG. 9, in Step S113, the value of the distance related
factor Fi(PL) is calculated for each of the effective pixels "Pi"
by calculating Fi(PL)+.alpha..times.(1-- f(PL)) in turn. Further,
in this alternate embodiment, the distance related factor Fi (PL),
instead of "Gi", is multiplied in Eq. (3) in Step S304
of the luminance compensation subroutine shown in FIG. 8, so that
the information relating to distance is included in the factor "Ki".
Namely, in the alternate embodiment, Eq. (4) is used in place of
Eq. (3). 2 Ki = k Fi ( PL ) t Ts ( 4 )
[0064] Here, the processes in the flowchart of FIG. 9 are the same
as those in FIG. 5, except for Step S100 and Step S112, which have
been replaced by Step S101 and Step S113, and Step S110 which has
been deleted. Note, in Step S101, the factor Fi(PL) is initialized
to Fi(PL)=0 in place of the factor "Gi".
[0065] Note that, in the present embodiment, the camera-shake compensation
operation is carried out during repetition of the luminance compensation
operation, which is repeated every one ms after the release switch
13a is turned on. However, the procedure is not limited to that
of the above-embodiment. The luminance information and the position
information for each pixel may be stored in a memory while repeating
the camera-shake compensation operation for every ms after the release
switch 13a is turned on, so that the luminance can be corrected
with respect to the data stored in the memory after the electric-charge
accumulating period has passed.
[0066] Further, the factor "Ki" for each of the effective
pixels can also be stored in the image memory 50 in relation with
the image data, so that the luminance correction of the image data
can be performed in an external device, such as a computer, after
transmitting the image data and the factors "Ki" to the
device.
[0067] Further, in the present embodiment, a digital camera that
compensates for the camera-shake by driving the CCD 39a is chosen
as an example. However, it is not restricted to this type of camera.
The present embodiment can also be applied to a digital camera of
the type having a camera-shake compensation optical system as a
part of the photographing lens system, which is driven in order
to counterbalance the detected camera-shake.
[0068] Although the embodiments of the present invention have been
described herein with reference to the accompanying drawings, obviously
many modifications and changes may be made by those skilled in this
art without departing from the scope of the invention.
[0069] The present disclosure relates to subject matter contained
in Japanese Patent Application No. 2004-186499 (filed on Jun. 24,
2004) which is expressly incorporated herein, by reference, in its
entirety. |