Title: Electronic still camera and information recording appartus
Abstract: An electronic still camera is provided with a photographic image capturing device that outputs image data by capturing a subject image passing through a taking lens, an analytic image capturing device provided at a position adjacent to the position that is conjugate with the photographic image capturing device relative to the taking lens that receives light forming the subject image and outputs image data for scene analysis, an analyzing circuit that performs scene analysis of the subject image based upon the image data for scene analysis output by the analytic image capturing device and an image processing circuit that performs image processing based upon the results of the scene analysis output by the analyzing circuit. The gradation curve, and the R gain and the B gain for white balance adjustment are determined based upon the results of the scene analysis using the image data for scene analysis output by the image capturing device for scene analysis provided separately from the photographic image capturing device.
Patent Number: 6,940,556 Issued on 09/06/2005 to Tamune
| Inventors:
|
Tamune; Michihiro (Yokohama, JP)
|
| Assignee:
|
Nikon Corporation (Tokyo, JP)
|
| Appl. No.:
|
291936 |
| Filed:
|
April 15, 1999 |
Foreign Application Priority Data
| Apr 16, 1998[JP] | 10-106548 |
| Current U.S. Class: |
348/350; 348/223.1; 348/254; 348/267 |
| Intern'l Class: |
H04N 009/73; H04N 009/07; H04N 005/23.2; H04N 005/20.2; G03B 013/00 |
| Field of Search: |
348/267,223.1,350,254
|
References Cited [Referenced By]
U.S. Patent Documents
| 4623932 | Nov., 1986 | Inoue et al.
| |
| 4647979 | Mar., 1987 | Urata.
| |
| 4887121 | Dec., 1989 | Pritchard.
| |
| 5262867 | Nov., 1993 | Kojima.
| |
| 5434640 | Jul., 1995 | Takagi et al.
| |
| 5438363 | Aug., 1995 | Ejima et al.
| |
| 5523785 | Jun., 1996 | Muramoto.
| |
| 5602412 | Feb., 1997 | Suzuki et al.
| |
| 5625434 | Apr., 1997 | Iwane.
| |
| 5808681 | Sep., 1998 | Kitajima.
| |
| 5995144 | Nov., 1999 | Sasakura.
| |
| 6072526 | Jun., 2000 | Hashimoto et al.
| |
| 6157781 | Dec., 2000 | Konno et al.
| |
| 6160581 | Dec., 2000 | Higashihara et al.
| |
Primary Examiner: Garber; Wendy R.
Assistant Examiner: Hannett; James M.
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
1. A single lens reflex type electronic still camera, comprising:
a viewfinder device to which a subject image passing through a taking lens is
guided by a quick return mirror;
a photographic image capturing device provided at a stage to the rear of the
quick return mirror, that captures the subject image and outputs color image data;
an analytic image capturing device provided at a position that is substantially
conjugate with said photographic image capturing device relative to the taking
lens, that receives light forming the subject image guided to said viewfinder device
from the quick return mirror and outputs color image data for scene analysis;
an arithmetic operation circuit that is supplied with the color image data for
scene analysis output by said analytic image capturing device, and calculates in
advance parameters including coefficients and gains to be utilized for image processing
based upon the color image data for scene analysis; and
an image processing circuit that performs image processing on the color image
data output by said photographic image capturing device using the parameters calculated
at said arithmetic operation circuit.
2. A single lens reflex type electronic still camera, comprising:
a viewfinder device to which a subject image passing through a taking lens is
guided by a quick return mirror;
a photographic image capturing device provided at a stage to the rear of the
quick return mirror, that captures the subject image and outputs color image data;
an analytic image capturing device provided at a position that is substantially
conjugate with said photographic image capturing device relative to the taking
lens, that receives light forming the subject image guided to said viewfinder device
from the quick return mirror and outputs color image data for scene analysis;
an arithmetic operation circuit that is supplied with the color image data for
scene analysis output by said analytic image capturing device, and calculates in
advance parameters including coefficients and gains to be utilized for image processing
based upon the color image data for scene analysis; and an image processing circuit
that calculates parameters such as coefficients and gains to be utilized for various
types of image processing based upon image data corresponding to at least a specific
area among photographic image data output by said photographic image capturing
device and performs image processing on the photographic image data using the parameters; and
an analyzing circuit that performs scene analysis on the subject image based
upon the color image data for scene analysis output by said analytic image capturing
device and determines the specific area based upon results of the scene analysis.
3. An information recording apparatus comprising:
at least a first image capturing device and a second image capturing device that
output image data by capturing a subject image passing through a taking lens;
an analyzing circuit that performs scene analysis on the subject image using
image data output by, at least, either said first image capturing device or said
second image capturing device; and
an image processing circuit that performs image processing on image data output
by, at least, either said first image capturing device or said second image capturing
device based upon scene analysis results obtained at said analyzing circuit; wherein:
said analyzing circuit calculates a gradation (γ) curve based upon brightness
values in the image data for scene analysis; and
said image processing circuit corrects photographic image data based upon the
gradation curve.
4. An information recording apparatus according to claim 3, wherein:
said image capturing device utilized for scene analysis is divided into a plurality
of areas each having a plurality of pixels receiving the subject image and said
analyzing circuit calculates the gradation curve based upon image data for scene
analysis output from the plurality of areas.
5. An information recording apparatus comprising:
at least a first image capturing device and a second image capturing device that
output image data including color information by capturing a subject image passing
through a taking lens;
an analyzing circuit that performs scene analysis on the subject image using
image data output by, at least, either said first image capturing device or said
second image capturing device; and
an image processing circuit that performs image processing on image data output
by, at least, either said first image capturing device or said second image capturing
device based upon scene analysis results obtained at said analyzing circuit; wherein:
the image data for scene analysis output by said image capturing device for scene
analysis contain RGB signals, said analyzing circuit calculates gains for white
balance adjustment based upon the RGB signals and said image processing circuit
corrects photographic image data based upon the gains for white balance adjustment.
6. An information recording apparatus comprising:
at least a first image capturing device and a second image capturing device that
output image data by capturing a subject image passing through a taking lens;
an analyzing circuit that performs scene analysis on the subject image using
image data output by, at least, either said first image capturing device or said
second image capturing device; and
an image processing circuit that performs image processing on image data output
by, at least, either said first image capturing device or said second image capturing
device based upon scene analysis results obtained at said analyzing circuit; wherein:
said image processing circuit calculates parameters including coefficients and
gains to be utilized for various types of image processing based upon image data
corresponding to, at least, a specific area among photographic image data output
by said image capturing device for photographing; and
said analyzing circuit determines the specific area based upon scene analysis results.
7. An information recording apparatus according to claim 3, wherein
the information recording apparatus is an electronic still camera.
8. An information recording apparatus according to claim 7, wherein
said first image capturing device and said second image capturing device have
different numbers of pixels from each other, and image data output by an image
capturing device having a smaller number of pixels are input to said analyzing circuit.
9. An information recording apparatus according to claim 5, wherein
the information recording apparatus is an electronic still camera.
10. An information recording apparatus according to claim 9, wherein
said first image capturing device and said second image capturing device have
different numbers of pixels from each other, and image data output by an image
capturing device having a smaller number of pixels are input to said analyzing circuit.
11. An information recording apparatus according to claim 6, wherein
the information recording apparatus is an electronic still camera.
12. An information recording apparatus according to claim 11, wherein
said first image capturing device and said second image capturing device have
different numbers of pixels from each other, and image data output by an image
capturing device having a smaller number of pixels are input to said analyzing
circuit.
Description
INCORPORATION BY REFERENCE
The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 10-106548, filed Apr. 16, 1998
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic still camera and an information
recording apparatus that record a subject as electronic image data.
2. Description of the Related Art
There are single lens reflex type electronic still cameras in the prior art.
A single lens reflex type electronic still camera is provided with a viewfinder
device to which a subject image passing through a taking lens is guided by a quick
return mirror, an image capturing device such as a CCD that is provided at a stage
to the rear of the quick return mirror to capture the subject image and output
image data, an image processing circuit that performs image processing such as
white balance adjustment and γ control on the image data output by the image
capturing device, a compression circuit that compresses data having undergone image
processing by adopting a method such as JPEG to store them in a storage medium
such as a flash memory and a monitor that displays data that has undergone the
image processing. In the image processing circuit, based upon the image data output
by the image capturing device, parameters including the R gain and the B gain for
white balance adjustment or the gradation curve for γ control using a preset
algorithm are calculated.
In such a single lens reflex type electronic still camera, the number of pixels
at the image capturing device has been steadily increasing over the years to exceed
a million or even two million pixels, resulting in a tendency for a longer period
of time required for image processing. In particular, when calculating the gradation
curve for γ control to achieve high quality image processing, a significant
length of time is required for the analysis of a photographic scene. In addition,
a large-scale, complex image processing circuit is required. Moreover, the length
of time required for calculating the R gain and the B gain for white balance adjustment
also increases when the number of pixels at the image capturing device becomes
large. It is to be noted that these problems may likewise occur in various other
types of electronic still cameras having an image capturing device with the number
of pixels exceeding 1˜2 million.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electronic still camera and
an information recording apparatus that are capable of reducing the length of time
required for image processing which is implemented by analyzing the photographic scene.
In order to achieve the object described above, the electronic still camera according
to the present invention comprises a photographic image capturing device that outputs
image data by capturing a subject image passing through a taking lens, an analytic
image capturing device provided at a position adjacent to the position that is
conjugate with the photographic image capturing device relative to the taking lens,
that receives the subject image and outputs image data for scene analysis, an analyzing
circuit that performs scene analysis of the subject image based upon the image
data for scene analysis output by the analytic image capturing device and an image
processing circuit that performs image processing on the image data output by the
photographic image capturing device based upon the results of the scene analysis
output by the analyzing circuit.
It is desirable that the number of pixels at the analytic image capturing device
be smaller than the number of pixels at the photographic image capturing device.
The analyzing circuit is capable of calculating parameters such as coefficients
and gains to support various types of image processing performed by the image processing circuit.
The analytic image capturing device may be divided into a plurality of areas
each having a plurality of pixels which receive light forming the subject image
so that the analyzing circuit can calculate the parameters based upon image data
for scene analysis output from the plurality of areas.
The analyzing circuit is capable of calculating a gradation (γ) curve based
upon the brightness value indicated by the image data for scene analysis, and the
image processing circuit is capable of correcting photographic image data based
upon the gradation curve. In this case, too, the analytic image capturing device
may be divided into a plurality of areas so that the analyzing circuit can calculate
the gradation curve based upon image data for scene analysis output from the plurality
of areas.
The image data for scene analysis output by the analytic image capturing device
contain RGB signals, the analyzing circuit calculates the gains for white balance
adjustment based upon the RGB signals and the image processing circuit corrects
the photographic image data based upon the gains for white balance adjustment.
The parameters mentioned above may be calculated at the image processing circuit
instead of at the analyzing circuit. In this case, the image processing circuit
calculates parameters such as coefficients and gains to be used in various types
of image processing based upon the image data corresponding to, at least, a specific
area among the photographic image data output by the photographic image capturing
device, and the analyzing circuit determines the specific area based upon the results
of the scene analysis.
The present invention may be adopted in a single lens reflex type electronic
still camera. Namely, a single lens reflex type electronic still camera according
to the present invention comprises a viewfinder device to which a subject image
passing through a taking lens is guided by a quick return mirror, a photographic
image capturing device provided at a stage to the rear of the quick return mirror
that outputs image data by capturing the subject image, an analytic image capturing
device provided at the position adjacent to the position which is conjugate with
the photographic image capturing device relative to the taking lens, that receives
the subject image guided to the viewfinder device and outputs image data for scene
analysis, an arithmetic operation circuit to which the image data for scene analysis
output by the analytic image capturing device are input so that it can calculate
in advance parameters such as coefficients and gains to be used for image processing
and an image processing circuit that performs image processing on the image data
output by the photographic image capturing device by using the parameters calculated
at the arithmetic operation circuit.
In the single lens reflex type electronic still camera, too, the parameters mentioned
earlier may be calculated at the image processing circuit instead of at the analyzing
circuit. Namely, such a single lens reflex type electronic still camera should
be provided with an image processing circuit that calculates parameters such as
coefficients and gains to be used for various types of image processing based upon
image data corresponding to, at least, a specific area among photographic image
data output by the photographic image capturing device and performs image processing
on the photographic image data using these parameters and an analyzing circuit
that performs scene analysis of the subject image based upon the image data for
scene analysis output by the analytic image capturing device and determines the
specific area based upon the results of the analysis.
The information recording apparatus according to the present invention comprises,
at least, a first image capturing device and a second image capturing device that
output image data by capturing a subject image passing through a taking lens, an
analyzing circuit that performs scene analysis on the subject image by using the
image data output by, at least, either the first image capturing device or the
second image capturing device, an analyzing circuit that performs scene analysis
of the subject image by using the image data output by, at least, either the first
image capturing device or the second image capturing device and an image processing
circuit that performs image processing on the image data output by, at least, either
the first image capturing device or the second image capturing device based upon
the results of the scene analysis performed by the analyzing circuit.
It is desirable that the first and second image capturing devices have different
numbers of pixels from each other and that image data output by the image capturing
device having the smaller number of pixels be input to the analyzing circuit.
The analyzing circuit is capable of calculating parameters such as coefficients
and gains for various types of image processing to be performed at the image processing circuit.
It is desirable that the image capturing device to be employed for scene analysis
be divided into a plurality of areas so that the analyzing circuit can perform
scene analysis based upon image data for scene analysis output from the plurality
of areas. A plurality of pixels are provided in each divisional area.
The analyzing circuit is capable of calculating a gradation (γ) curve based
upon the brightness value indicated by the image data for scene analysis, and the
image processing circuit is capable of correcting the photographic image data based
upon the gradation curve.
The image capturing device employed for scene analysis may be divided into a
plurality of areas. Each area has a plurality of pixels receiving the subject image
light. The analyzing circuit is capable of calculating the gradation curve based
upon image data for scene analysis output from the plurality of areas.
The image data for scene analysis output by the image capturing device employed
for scene analysis contain RGB signals, the analyzing circuit calculates the gains
for white balance adjustment based upon the RGB signals and the image processing
circuit is capable of correcting the photographic image data based upon the gains
for white balance adjustment.
Alternatively, the image processing circuit may calculate parameters
such as coefficients and gains to be used for various types of image processing
based upon image data corresponding to, at least, a specific area among the photographic
image data output by the image capturing device employed for photographing and
the analyzing circuit may determines the specific area based upon the results of
the scene analysis.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates the structure of a single lens reflex type electronic still
camera in an embodiment of the present invention;
FIG. 2 is a block diagram of one embodiment of the signal processing system
in the single lens reflex type electronic still camera;
FIG. 3 presents an example of the image capturing device for scene analysis;
FIG. 4 illustrates the color filter in the image capturing device for scene
analysts and also presents an example in which grouping into 16 blocks is implemented;
FIG. 5 is a flowchart illustrating a program that is started up with a half-press switch;
FIGS. 6A˜6D illustrate gradation curves;
FIG. 7 is a flowchart illustrating a program that is started up with a full-press switch;
FIG. 8 is a flowchart illustrating another program that is started up with the
half-press switch; and
FIG. 9 shows a person against a red background.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following is an explanation of the embodiments of the present invention given
in reference to the drawings. As illustrated in FIG. 1, the single lens reflex
type electronic still camera in this embodiment is provided with a camera main
body
70, a viewfinder device
80 that may be attached to and detached
from the camera main body
70 and an interchangeable lens
90 provided
with an internal taking lens
91 and an internal aperture
92, that
may be attached to and detached from the main body
70. Subject light travels
through the interchangeable lens
90 to enter the camera main body
70,
is led to the viewfinder device
80 by a quick return mirror
71 which
is at the position indicated by the dotted line before a shutter release operation
and an image is formed at a viewfinder mat
81. This subject image is further
guided to an ocular lens
83 by a pentaprism
82. In addition, the
subject image passes from the pentaprism
82 to a prism
84 and an
optical element
85 and is formed on the photosensitive surface of an image
capturing device for scene analysis
86. After a shutter release operation,
on the other hand, the quick return mirror
71 rotates to the position indicated
by the solid line and the subject light travels via an aperture
72 to form
an image on an image capturing device for photographing
73. The image capturing
device for scene analysis
86 is provided at a position adjacent to the position
that is conjugate with the image capturing device for photographing
73 relative
to the taking lens
91.
FIG. 2 is a circuit block diagram of the embodiment. When a half-press switch
11 is operated, the analytic image capturing device
86 starts an
electrical charge storage or accumulation, and when the accumulation ends, the
analytic image capturing device
86 outputs RGB image data for scene analysis
to an analyzing circuit
10. The analyzing circuit
10 converts the
image data to a digital signal, and performs scene analysis of a photographic scene
based upon the digital image signal. The results of the analysis are transferred
to an image data control circuit
21.
If, on the other hand, a full-press switch
12 is operated, the quick return
mirror rotates upward, the subject light from the interchangeable lens
90
forms an image on the photosensitive surface of the photographic image capturing
device
73 and a signal electrical charge corresponding to the brightness
of the subject image is accumulated at the photographic image capturing device
73. The signal electrical charge accumulated at the photographic image capturing
device
73 undergoes analog processing such as gain control at an analog
signal processing circuit
22, and then it is converted to a digital signal
at an A/D conversion circuit
23. The signal that has undergone the digital
conversion is then supplied to an image processing circuit
24 where it undergoes
image processing such as white balance adjustment, contour compensation and γ
control to become formatted, and it travels through a frame memory controller
25
to be temporarily stored at a frame memory
26. The various parameters used
in the image processing performed by the image processing circuit
24 are
calculated in advance at the scene analyzing circuit
10 and are stored within
the memory in the control circuit
21.
The image data stored in the frame memory
26 are processed into image
data for display by a display image generating circuit
27 and are displayed
on an external monitor
28 such as an LCD as the photographic results. In
addition, the image data stored in the frame memory
26 undergo data compression
at a specific ratio through a method such as JPEG at a compression circuit
29
and are recorded in a camera internal memory (storage medium)
30 such as
a flash memory.
Next, a detailed explanation is given on the image capturing device for scene
analysis
86 and the scene analyzing circuit
10. The image capturing
device for scene analysis
86 may be constituted of, for instance, a single
two-dimensional CCD having 480 separate pixels provided over 24 columns (across)×20
rows (down) as illustrated in FIG. 3. On the front surface of the image capturing
device
86, an RGB color filter
861 which is divided into a total
of 480 blocks over 24 columns (across)×20 rows (down) in correspondence to
the 480 pixels, as illustrated in FIG. 4, is provided. The 480-block RGB filter
is grouped into 16 blocks; B
11, B
12 . . . B
43 and B
44
each having 6 columns (across)×5 rows (down) filter elements, to be utilized
for scene analysis. The image capturing device
86 is divided into 16 areas
each having 30 pixels. In this context, scene analysis refers to an analysis related
to the information on the brightness of the photographic scene, the RGB signal
distribution state and the like.
Next, the procedure through which the gradation curve is determined by analyzing
a scene is explained in reference to FIGS. 5˜7. When the half-press switch
11 is operated, the program illustrated in FIG. 5 is started up, and in
step S
1, the image capturing device for scene analysis
86 accumulates
an electrical charge achieved by the subject light with its image formed on the
photosensitive surface of the image capturing device for scene analysis
86
over a specific length of time before sequentially outputting the accumulated RGB
image data to the scene analyzing circuit
10. In step S
2, the brightness
value Yij (i=1˜20, j=1˜24) for each of the 480 pixels is calculated,
and in step S
3, the full average value Yave is calculated. In step S
4,
a block average brightness value Yave 1˜Yave 16 for the 16 individual blocks
B
11˜B
44 are calculated. Then the operation advances to step
S
5 in which the differences among the block average brightness values Yave
1˜Yave 16 are calculated and the absolute value Yabs of the largest brightness
difference is calculated. In step S
6, the absolute value Yabs and a preset
threshold value Ymax are compared with each other to perform scene analysis. Then,
in step S
7, a decision is made with respect to which of the four gradation
curves prepared in advance as illustrated in FIGS. 6A˜6D is to be used based
upon the results of the scene analysis as explained below.
(1) If the absolute value Yabs of the largest brightness difference is smaller
than the preset threshold value Ymax, the photographic scene is determined to be
a halftone preference type. In the case of the halftone preference type, the S-shaped
gradation correction curve illustrated in FIG. 6A is used. This assures a halftone gradation.
(2) When the absolute value Yabs of the largest brightness difference is equal
to or larger than the preset threshold value Ymax, the difference Ydiff(i) between
the full pixel average brightness Yave and the average brightness Yave(i) in each
block is calculated as follows.
Here, i represents an integer within the range of 1˜16.
A check is performed to ascertain whether or not there are a plurality of contiguous
blocks in each of which Ydiff(i) is smaller than a preset threshold value Yhilight
or there are a plurality of contiguous blocks in which Ydiff(i) is larger than
a preset threshold value Yshadow, and based upon the results of the check, the
scene is analyzed, as described below. It is to be noted that; threshold value
Yhilight
(2-1) If there are a plurality of contiguous blocks for each of which Ydiff(i)
is smaller than the threshold value Yhilight, the scene is determined to be the
highlight preference type. In the case of the heighlight preference type, the gradation
correction curve illustrated in FIG. 6B is used. This assures gradation from halftone
through highlight.
(2-2) If there are a plurality of contiguous blocks in each of which Ydiff(i)
is larger than the threshold value Yshadow, the scene is determined to be the shadow
preference type. In the case of the shadow preference type, the gradation correction
curve illustrated in FIG. 6C is used. This assures gradation from shadow through halftone.
(2-3) If there are a plurality of contiguous blocks for each of which Ydiff(i)
is smaller than the threshold value Yhilight and there are a plurality of contiguous
blocks for each of which the Ydiff(i) is larger than the threshold value Yshadow,
the scene is determined to be the highlight-shadow preference type. In the case
of the highlight-shadow preference type, the gradation correction curve illustrated
in FIG. 6D is used. This assures gradation in the shadow area and the highlight area.
Then, in step S8, the pitches or inclinations and the γ values
of the individual gradation curves are calculated by using the full brightness
average value Yave, the block average brightness values Yave 1˜Yave 16 and
Ydiff(i), and the ultimate gradation curve is determined using these data. In step
S9, the gradation curve thus calculated is transferred to the photographic
control circuit 21. The control circuit 21 then stores the gradation
curve in its memory. The operations in steps S1˜S9 described
above are repeated until the full-press button is operated in step S10.
When the full-press button 12 is operated, the quick return mirror swings
upward and the program with the photographing sequence illustrated in FIG. 7 is
started up. In step S21, a light reception signal is accumulated at each
pixel in the image capturing device 73, and when the accumulation is completed,
the accumulated electrical charges at all the pixels are sequentially output. In
step S22, the image data thus output are processed at the analog signal
processing circuit 22, and are then converted to digital image data at the
AD conversion circuit 23 before they are input to the image processing circuit
24. Next, the operation proceeds to step S23, in which the image
data undergo gradation correction by using a gradation curve calculated in advance
at the scene analyzing circuit 10 and stored in memory. It is to be noted
that the image processing circuit 24 also engages in white balance adjustment
and the like. When the image processing is completed, the operation proceeds to
step S24, in which the image data that have undergone image processing are
temporarily stored in the frame memory 26. In step S25, the image
data are compressed at the compression circuit 29 through the JPEG method,
and then, in step S26, the compressed image data are stored in the storage
medium 30.
As explained above, when the half-press switch 11 is operated, the scene
analyzing circuit 10 calculates the gradation curve which is then transferred
to the control circuit 22 to be stored in its memory in this embodiment.
The calculation for the gradation curve is executed repeatedly while the half-press
switch 11 is being operated, and the memory contents are overwritten with
the latest data. Then, when the full-press switch 12 is operated and an
image is formed of the subject light at the photographic image capturing device
73, the image capturing device 73 accumulates electrical charges
achieved by the subject light over a specific length of time and then outputs them
sequentially. Since the image processing circuit 24 performs the gradation
correction using the gradation curves that are stored in memory in advance, it
is not necessary to calculate the gradation curve using the photographic image
data themselves, whose volume is very large, so that the length of time required
for gradation correction processing can be reduced.
Next, the procedure that is taken to calculate the R gain and the B gain to
be utilized for white balance adjustment based upon the results of the scene analysis
is explained in reference to the flowchart in FIG. 8. In step S31, electrical
charges achieved by the subject light received at the image capturing device for
scene analysis 86 are accumulated over a specific length of time, and then
the RGB image data for scene analysis are sequentially output to the scene analyzing
circuit 10. In step S32, matching processing, in which the difference
in the color characteristics between the image capturing device for scene analysis
86 and the image capturing device for photographing 73 is performed.
The matching processing may be achieved through processing in which matrix calculation
is performed for a matrix constant of, for instance, 3×L (L≧3) and
raw RGB data, for instance.
In step S33, using the RGB signals (brightness values) corresponding to
all the 480 pixels, an R gain full pixel average value Rgave and a B gain full
pixel average value Bgave are calculated. The method for calculating the R gain
and the B gain using the individual brightness values indicated by the RGB signals
is of the known art, and therefore its explanation is omitted. In step S34,
R gain block average values Rgave1˜Bgave16 and the B gain block average values
Bgave1˜Bgave16 for the 16 individual blocks B11˜B44 are calculated.
Then the operation proceeds to step S35, in which absolute values Rgdif1˜Rgdif16
of the gain differences between the R gain full pixel average value Rgave and the
R gain block average values Rgave1˜Rgave16 and absolute values Bgdif1˜Bgdif16
of the gain differences between the B gain full pixel average value Bgave and the
B gain block average values Bgave1˜Bgave16 are calculated based upon the
following equation.
Here, i represents an integer within the range of 1˜16.
In step S36, each of the absolute values Rgdif1˜Rgdif16 of the gain
differences is compared with a threshold value Rdifmax and each of the absolute
values Bgdif1˜Bgdif16 of the gain differences is compared with a threshold
value Bdifmax. Based upon these comparisons, the R gain and the B gain for white
balance are determined as described below.
(1) If the absolute values Rgdif1˜Rgdif16 of the gain differences are all
smaller than the threshold value Rdifmax, the R gain full pixel average value Rgave
is selected as the R gain. If the absolute values Bgdif1˜Bgdif16 of the gain
differences are all smaller than the threshold value Bdifmax, the B gain full pixel
average value Bgave is selected as the B gain.
(2) If any of the absolute values. Rgdif1˜Rgdif16 of the gain differences
is equal to or larger than the threshold value Rdifmax, the blocks having absolute
values indicating gain differences smaller than the threshold value Rdifmax are
selected, and the average value calculated based upon the total of the absolute
value(s) Rgdif(i) of the gain difference(s) corresponding to one or a plurality
of such blocks, is set as the R gain. If any of the absolute values Bgdif1˜Bgdif16
of the gain differences is equal to or larger than the threshold value Bdifmax,
the blocks having absolute values indicating gain differences smaller than the
threshold value Bdifmax are selected, and the average value calculated based upon
the total of the absolute value(s) Bgdif(i) of the gain difference(s) corresponding
to one or a plurality of such blocks, is set as the B gain.
In step S37, the R gain and the B gain thus calculated are transferred
to the photographic control circuit 21. The control circuit 21 then
stores the R gain and the B gain in its memory. Subsequently, the operation in
steps S31˜S37 are repeated until the full-press button is operated
in step S38.
When the full-press button 12 is operated, the quick return mirror swings
upward and the program with the photographing sequence illustrated in FIG. 7 is
started up. In step S21, a light reception signal is accumulated at each
pixel in the image capturing device 73, and when the accumulation is completed,
the accumulated electrical charges at the pixels are sequentially output. In step
S22, the image data thus sent out are processed at the analog signal processing
circuit 22 and are then converted to digital image data at the AD conversion
circuit 23 before they are input to the image processing circuit 24.
Next, the operation proceeds to step S23, in which white balance adjustment
is performed for the image data by using the R gain and the B gain calculated in
advance at the scene analyzing circuit 10 and stored in memory. It is to
be noted that the image processing circuit 24 performs other types of image
processing such as γ control using the gradation curves and the contour compensation.
As described above, when the half-press switch 11 is operated, the R gain
and the B gain for white balance adjustment are calculated at the scene analyzing
circuit 10, which are then transferred to the control circuit 21
to be stored in its memory in this embodiment. The calculation of the R gain and
the B gain is executed repeatedly while the half-press switch is being operated
so that the memory contents at the memory are overwritten with the latest data.
Then, when the full-press switch 12 is operated and the subject light forms
an image at the photographic image capturing device 73, the image capturing
device 73 accumulates electrical charges achieved by the subject light over
a specific length of time and sequentially outputs them. The image processing circuit
24 performs white balance adjustment using the R gain and the B gain that
are stored in memory in advance on the image data. Thus, it is not necessary to
calculate the R gain and the B gain for white balance adjustment by using the photographic
image data themselves, whose volume is very large, so that the length of time required
for white balance adjustment can be reduced. In addition, in a scene with a person
against a red sign RB as a background as illustrated in FIG. 9, white balance adjustment
can be achieved by excluding the area that is predominantly red so that the color
of the persons skin and the like can be expressed more faithfully.
While the analyzing circuit 10 and the control circuit 21 are
illustrated separately in FIG. 2, the present invention is configured so that the
programs in FIG. 5 and FIG. 7 or the programs in FIG. 5 and FIG. 8 are executed
by a single microprocessor.
It is to be noted that the gradation curve and the R gains and the B gains for
white balance adjustment may be calculated at the scene analyzing circuit 10
and transferred to the control circuit 21 for accumulation so that both
the high quality image processing using the gradation curve and the white balance
adjustment are executed using these parameters.
In addition, in the explanation given above, the gradation curve, and the R gain
and the B gain are calculated at the analyzing circuit 10 based upon the
image data from the image capturing device for scene analysis 86 to be transferred
in advance to the photographic control circuit 21 for accumulation. However,
white balance adjustment may be achieved in the following manner, instead. Based
upon the results of scene analysis, a block in which the absolute value of the
gain difference is smaller than the threshold value is selected and the information
related to the position of the block is transferred to the control circuit 21.
At the control circuit 21, the photographic image data within the area corresponding
to the block positional information among the image data from the photographic
image capturing device 73 are taken in from the image processing circuit
24 to calculate the R gain and the B gain for white balance adjustment.
In other words, the scene analyzing circuit 10 only calculates the area
corresponding to the image data required for calculating the R gain and B gain.
By calculating in advance the image area at the photographic image capturing device
73 to be utilized for the image processing based upon scene analysis results
obtained at the image capturing device for scene analysis 86 provided at
a position adjacent to the position that is conjugate with the position of the
image capturing device for photographing 73 in this manner, the image processing
performed based upon the results of the scene analysis can be completed within
a shorter period of time compared to the prior art, as in the embodiment described earlier.
In addition, the present invention is ideal for application in various other
types
of electronic still cameras and information recording apparatuses with a large
number of pixels (e.g., one million pixels or more) in addition to single lens
reflex type electronic still cameras.
Furthermore, in an electronic still camera or an information recording
apparatus provided with at least a pair of image capturing elements each receiving
a subject image that has been coloristically separated, a scene analysis may be
performed by using the entirety of or a portion of the image data at one of the
image capturing elements.
In this case, the scene analysis may be implemented by using the image data corresponding
to a specific portion, with the number of pixels at the image capturing elements
set equal to each other. While the explanation is given above on the gradation
curve and the gains for white balance adjustment, image processing may be implemented
using parameters other than these based upon the results of scene analysis.
*
