JPH09200781A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device with which color reproducibility is improved without requiring any complicated circuit. SOLUTION: At the time of image pickup, an additive pixel signal SCCD outputted from a color imaging device 100 is digitally converted to additive pixel data DCCD by a sample/hold(S/H) circuit 102 and an A/D converter 104 and stored/held in a frame memory 106 as they are. At the time of image reproduction, an arithmetic part 108 executes a prescribed operation processing program and color temperature correction coefficients previously stored in a program memory 112 corresponding to various photographic states and white balance correction coefficients in a ROM 108 are multiplied to the additive pixel data DCCD read out of the frame memory 106 so that proper white balance control in quick response to the real photographic state can be performed and a color difference signal can be formed and outputted. When any proper color temperature correction coefficient does not previously exist in the program memory 112, on the other hand, the color temperature correction coefficient is automatically predictively operated based on the additive pixel data DCCD in the frame memory 106 and white balance control processing is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as an electronic still camera, and more particularly to white balance adjustment.

[0002]

2. Description of the Related Art In an image pickup apparatus such as an electronic still camera or a video camera, color signals are balanced in accordance with the color temperature of illumination light so that a white object is reproduced in white to obtain color reproducibility. White balance adjustments have been made to improve it. For example, the method disclosed in Japanese Patent Laid-Open No. 5-252521 is known.

According to such a conventional technique, a single plate type with one two-dimensional color solid-state image pickup device (color CCD) is adopted, and as shown in FIG. 7, each horizontal line N, N +
1, 2 pixels are arranged for each of N + 2, ... Further, combinations of four kinds of pixel color filters of cyan (Cy), magenta (Mg), yellow (Ye) and green (G) are adjacent to each other. By providing a color filter that is arranged so as to be different between the respective horizontal lines, color imaging is performed. Such a color CCD is shown in FIG.
A matrix circuit composed of the analog circuit shown in is connected.

Each pixel signal generated in the pixel group by image pickup is read out for each horizontal line in synchronization with the horizontal scanning read-out period T _H , and a pair of sample hold circuits 2 and 4 cycle the so-called dot sequential timing. The sample is held in synchronization with τ _p . Here, each horizontal line is provided with a pixel group of the first column provided with pixel filters of cyan (Cy) and yellow (Ye) and a pixel filter of magenta (Mg) and green (G). Since the pixel group in the second column is arranged, as shown in the timing chart of FIG. 9, the pixel signals of the two pixels in the first and second columns located on the same line are mutually added (mixed). The sample and hold circuit 2 and the sample and hold circuit 4 alternately sample and hold the added pixel signal,
Color signals separated for each pixel (more accurately, for each two pixels) are obtained.

One horizontal period delay circuits 6 and 8 are connected to each sample and hold circuit 2 and 4, and the sample and hold circuits 2 and 4 and one horizontal period delay circuits 6 and 8 are gained via a switch circuit 10. Subtraction circuits 20 and 22 are provided which are connected to the control circuits 12 to 18 and which subtract predetermined output signals of the gain control circuits 12 to 19 from each other.

The 1 horizontal period delay circuits 6 and 8 output the color signals output from the sample and hold circuits 2 and 4 for 1 horizontal period T.
_After delaying by _H , the switch circuit 10 performs a switching operation so that a color signal based on the same combination of pixel filters is always input to the gain control circuits 12 to 18. As a result, as shown in FIG. 10, the subtraction circuit 20 outputs the color difference signal BY and the subtraction circuit 22.
Outputs a color difference signal R-Y, and white balance adjustment is performed by adjusting the gains of the gain control circuits 12 to 18 independently.

[0007]

In such a conventional technique, it is difficult to reduce the size of the image pickup device because an analog circuit having a complicated hardware structure is required.

Further, if the color difference signals BY and RY are not formed based on the pixel signals corresponding to the array of the pixel filters of the respective colors provided in the respective pixels of the color CCD, a false color will be displayed in the reproduced image. However, since the color filter arrangement may differ depending on the type of the color CCD used in the image pickup device, the analog circuit implemented as a hardware must be changed each time. There was a problem of not becoming.

Further, since the line complementarity is simply complemented by the one horizontal period delay circuit, the vertical reproducibility of color information is not good. Since the information amount of the finally obtained video signal becomes three times the number of pixels of the color CCD, the information amount becomes redundant, which is not rational. Since there are four color information parameters, there is a problem that the control becomes complicated.

The present invention has been made in view of these problems of the prior art, has a rational and simple circuit structure, and can easily cope with various color CCDs, and can reproduce reproduced images. The color reproducibility can be improved, etc.
It is an object of the present invention to provide an image pickup apparatus having a white balance adjustment function that has not been available in the past.

[0011]

In order to achieve such an object, the present invention provides a first pixel column composed of a plurality of pixels in which cyan and yellow pixel color filters are alternately arranged in the horizontal line direction. And a second pixel row composed of a plurality of pixels in which magenta and green pixel color filters are alternately arranged in the horizontal line direction are alternately arranged in the vertical direction, and the first and second pixels are arranged. A pair of columns is configured as each horizontal line, and pixel signals generated in the plurality of pixels are combined for each of the first and second pixel columns and pixel signals of two pixels adjacent to each other in the vertical direction are combined. By mixing and outputting, a color image pickup device that horizontally scans and reads out the addition pixel signals for each horizontal line, and the addition pixel signals that are read out from the color image pickup device are added pixel data. A / D converter for digital conversion into data, a first storage medium for storing the added pixel data output from the A / D converter in association with the pixel array of the color image sensor, and a reference color A second storage medium for pre-storing a white balance correction coefficient when photographed under a temperature light source as a reference correction coefficient, and a reference correction coefficient for the white balance correction coefficient when photographed under various light source color temperatures. A third storage medium that stores various color temperature correction coefficients corresponding to the ratio in advance, and the addition pixel data stored in the first storage medium by executing a predetermined arithmetic processing program. By multiplying the reference correction coefficient in the second storage medium and the color temperature correction coefficient corresponding to the light source color temperature at the time of shooting, which is stored in the third storage medium. It was that it comprises a calculator for the balance adjustment.

Further, when the color temperature correction coefficient corresponding to the light source color temperature at the time of photographing does not exist, the arithmetic unit obtains an addition average value for each color of the addition pixel data, and calculates the addition average value. The unknown color temperature correction coefficient satisfying the condition that the color difference signal after white balance adjustment obtained by applying the reference correction coefficient and the unknown color temperature correction coefficient becomes 0 is predicted and calculated as an automatic color temperature correction coefficient, White balance adjustment is performed by multiplying the added pixel data stored in the first storage medium by the reference correction coefficient and the automatic color temperature correction coefficient in the second storage medium.

Furthermore, the arithmetic unit performs an arithmetic mean of the color difference signals which are adjacent to each other in the vertical direction of the pixel array, with respect to the calculated color difference signals, so that the color difference signals are insufficient. The complementary color difference signal for each minute is calculated.

The color temperature correction coefficient and the calculation program are input from an external storage medium to the third storage medium.

[0015]

[Embodiment]

(First Embodiment) A first embodiment according to the present invention will be described below with reference to the drawings. Note that this embodiment relates to an electronic still camera that electronically captures an image of a subject.

The structure of the main part of this electronic still camera will be described with reference to FIG. A sample hold circuit 102 and an A / D converter 104 are serially connected in sequence to an output contact of a two-dimensional color solid-state image sensor (color CCD) 100, and
The output contact of the D converter 104 is connected to a frame memory 106 including a so-called SRAM or the like that stores data for at least one frame image. Frame memory 1
The output contact of 06 is connected to an operation unit 110 having an operation function including a microprocessor (MPU), and the output contact of the operation unit 110 is externally provided on the housing of the electronic still camera. It is connected to a terminal (terminal for plug connection with an external device) 114.

Further, nonvolatile data storing data of white balance correction coefficients Ka, Kb, Kc, Kd (hereinafter referred to as reference correction coefficient data) used in arithmetic processing for correcting variations in optical characteristics of individual cameras. A memory (hereinafter, referred to as ROM) 108 is provided, and the arithmetic unit 11
According to the command from 0, these reference correction coefficient data K
Read a, Kb, Kc and Kd. Reference correction coefficient data K
a, Kb, Kc, and Kd are coefficient values such that each color difference component (BY) and (RY) when an achromatic subject is photographed under a reference color temperature light source becomes 0, It is a unique value for each camera.

Although FIG. 1 shows that the A / D converter 104, the frame memory 106, the ROM 108, and the arithmetic unit 110 are connected to each other via individual data transfer paths, in reality, The A / D converter 104, the frame memory 106, and the ROM 108 are connected to each other via a so-called data bus extended from the arithmetic unit 110, and the arithmetic unit 110 controls based on a predetermined synchronization timing. Each of these components 104, 106, 10
Data transfer between 8 and 110 is performed.

Further, by mounting an expansion memory 106 'of the same type as the frame memory 106 on a memory expansion connector (not shown) connected to the data bus, data for a number of frame images can be stored or Instead of this, a memory card or a dedicated external storage device 106 'is connected so that pixel data for a large number of frame images can be stored.

The calculation unit 110 is a calculation processing program for executing a white balance adjustment described later and color temperature correction coefficients Ca, Cb, Cc used for the calculation processing.
Program memory 112 for storing the Cd of the data is connected, based on the calculation process program, the pixel data D _CCD in the frame memory 106 or the extended memory 106 ', the reference correction coefficient data Ka in ROM108
, Kb, Kc, Kd and the color temperature correction coefficients Ca, Cb, Cc, Cd in the program memory 112, white balance adjustment processing is performed, and a color difference signal formed based on the adjusted pixel data is applied. (BY)
And (RY) are output to the external terminal 114. For convenience of explanation, the symbol D _out in FIG. 1 indicates such a color difference signal (B-
Y) and (RY) are comprehensively shown.

Here, the color temperature correction coefficients Ca, Cb, Cc
, Cd are coefficients for obtaining an appropriate white balance correction coefficient under a light source when an achromatic subject is photographed under various color temperature light sources. That is, ROM1
Reference correction coefficient data Ka and K stored in advance in
Since b, Kc, and Kd are reference values when an achromatic subject is photographed under the reference color temperature light source, the reference correction coefficient data Ka, Kb, Kc, and Kd are the color temperature correction coefficients during actual photographing. By multiplying Ca, Cb, Cc, and Cd, appropriate white balance correction coefficients (Ca Ka), (Cb Kb), (Cc Kc), under an actual color temperature light source,
(Cd Kd) is calculated, and the white balance is adjusted to match the actual shooting. Then, these color temperature correction coefficients Ca, Cb, Cc, Cd are stored in the program memory 112 as a plurality of types of data corresponding to each color temperature in advance before photographing in order to cope with proper photographing under various color temperature light sources. Is stored.

An external storage medium such as a so-called floppy disk or memory card storing the above-mentioned arithmetic processing program and the color temperature correction coefficients Ca, Cb, Cc, Cd is provided in the casing of the electronic still camera. By mounting on a driving device (not shown) and the operator inputting a predetermined command, the arithmetic processing program and the color temperature correction coefficient Ca
, Cb, Cc, Cd are written in the program memory 112 via the arithmetic unit 110, changed to a new arithmetic processing program, and the color temperature correction coefficients Ca, Cb, Cc, C are written.
It is possible to add or change d.

However, instead of the writable and readable program memory 112, a read-only memory or a rewritable E ² PROM in which an arithmetic processing program and color temperature correction coefficients Ca, Cb, Cc, Cd are stored in advance are applied. You may.

The color CCD 100, as shown in FIG.
By forming pixel color filters of four colors of cyan (Cy), yellow (Ye), magenta (Mg), and green (G) in a predetermined array for each of a plurality of two-dimensionally arrayed pixels. It is configured to perform color imaging. Further, when the pixel signals integrated in each pixel are read out, the pixel signals in the two columns are added (mixed), and the added pixel signals are read out as pixel signals for one horizontal line.

For example, in the horizontal line of the nth row, as shown in the figure, the first pixel row in which cyan (Cy) and yellow (Ye) are alternately arranged, and magenta (Mg) and green (G) are arranged. When the pixel signal of the horizontal line of the nth column is scanned and read, the second pixel columns alternately arranged,
Due to the structure of the charge transfer path formed in the color CCD 100, (Mg + Cy), (G + Ye)
), (Mg + Cy), (G + Ye) ... And the added pixel signal S _CCD is output. That is, the added pixel signal S _CCD is a signal (Mg
+ Cy), (G + Ye), (Mg + Cy), (G + Ye)
) Is an analog signal. Similarly, the other horizontal lines are each made up of pixel groups of two columns. Therefore, the added pixel signal S _CCD output from the color _CCD 100 is output in the array shown in FIG. 4 with respect to the pixel array in FIG.

Next, the operation of the electronic still camera having such a configuration will be described with reference to the flowcharts of FIGS. 5 and 6. In addition, FIG. 5 shows an operation for shooting a still image of one frame,
FIG. 6 shows operations for white balance adjustment and the like.

In FIG. 5, when the operator presses the shutter release button, one frame of image is picked up by the color CCD 100 in step S100, whereby pixel charges corresponding to the subject image are accumulated in each pixel. Next, variables n and m are set in steps S110 to 130, and the pixel signals are read out in a predetermined order corresponding to the pixel array (n, m) in step S140. That is, in step S140, each pixel charge is transferred inside the color CCD 100, and the added pixel signal S _CCD is read in synchronization with a predetermined dot-sequential timing τp.

Next, at step S150, each sampled pixel signal S _CCD read in synchronization with the dot-sequential timing τp is sampled and held by the sample and hold circuit 102, and the sampled pixel data of a predetermined gradation is sampled by the A / D converter 104. Digitally converted into D _CCD , and in step S160, the added pixel data D _CCD is sequentially stored and held in the frame memory 106. And step S
In 170 and S180, it is determined whether or not the reading of the addition pixel signal S _CCD for one frame is completed, and after repeating the processing of steps S120 to S160 until the reading is completed, a series of imaging operations is completed.

By carrying out such an image pickup operation, the frame memory 106 holds the addition pixel data D _CCD corresponding to the array of the addition pixel signals S _CCD as shown in FIG. Also, these added pixel data D _CCD is A
Since the / D converter 104 digitally converts the added pixel data S _CCD , it is stored in the frame memory 106 without substantially performing white balance adjustment.
If you start shooting by specifying the expansion memory 106 ',
The addition pixel data D _CCD for one frame image is stored in the extension memory 106 ′. Furthermore, when the second and subsequent still images are captured, the added pixel data _DCCD corresponding to the respective second and subsequent frame images is stored in the extension memory 106 '.

When the operator finishes the photographing operation and gives an instruction to reproduce the still image, the processing shown in FIG. 6 is performed. That is, the arithmetic unit 110 executes the arithmetic processing program in the program memory 112 to perform the following processing.

In step S200, the calculation unit 110
From the ROM 108, the reference correction coefficient data Ka, Kb,
In addition to reading Kc and Kd, the addition pixel data D _CCD for the designated frame image is read from the frame memory 106 or the expansion memory 106 'in association with the pixel array.
That is, in FIG. 4, each addition pixel data D _CCD is sequentially read from the left side to the right side of each column and from the top to the bottom side of each row.

Next, in step S202, as shown in the following equations (1-a) to (1-d), the reference correction coefficient Ka is set to the added pixel data (Mg + Cy) of magenta Mg and cyan Cy, and the green G And the yellow Ye, the reference correction coefficient Kb is added to the added pixel data (G + Ye), the reference data Kc is added pixel data (Mg + Ye) between the magenta Mg and the yellow Ye, and the added pixel data (G + Cy) is added to the green G and the cyan Cy. ) _Is multiplied by the reference correction coefficient Kd to _obtain the addition pixel data P _MgCy , P _GYe , P _MgYe , and P _GCy that are basically white balance adjusted and normalized.

P _MgCy = Ka x (Mg + Cy) (1-a) P _GYe = Kb x (G + Ye) (1-b) P _MgYe = Kc x (Mg + Ye) (1-c) P _GCy = Kd × (G + Cy) (1-d) Next, in step S204, it is determined whether the light source color temperature at the time of image capturing is detected or not, and an appropriate color corresponding to the detected light source color temperature is determined. Temperature correction coefficient Ca
, Cb, Cc, Cd exist in the program memory 112, the process proceeds to step S206, and if there is no proper color temperature coefficient, step S21.
The process shifts to 2.

In step S206, the following equation (2-a
) And (2-b), the program memory 112
The appropriate color temperature correction coefficients Ca, Cb, Cc read from
Cd is the normalized addition pixel data P _MgCy , P
_GYe, P _MgYe, by multiplying the P _GCy, perform white balance adjustment corresponding to an actual shooting state, further, the color difference signals based on the addition pixel data after such white balance adjustment and (B-Y) (R -Y) is calculated.

BY = Ca * P _MgCy- Cb * _PGYe (2-a) RY = Cc * P _MgYe- Cd * _PGCy (2-b) Therefore, the above formula (1-a) ~ (1-d) and (2-a) (2-b
), The added pixel data (Mg + Cy
), (G + Ye), (Mg + Ye), (G + Cy)
Are white balance correction coefficients (Ca x Ka), (Cb x Kb), (Cc x Kc), which correspond to the actual shooting conditions.
White balance adjustment is realized by (Cd x Kd).

Next, in step S208, complementary calculation is performed for pixels for which the color difference signals (BY) and (RY) are not calculated.

That is, the color difference signals (BY) and (RY) obtained by the calculation of the above equations (2-a) and (2-b) are obtained for each horizontal line as is clear from the arrangement of FIG. Therefore, the color difference signal (RY) is not obtained for the horizontal line for which the color difference signal (BY) is obtained, and the color difference signal (RY) is obtained for the horizontal line. The color difference signal (BY) cannot be obtained for the obtained horizontal line.
More specifically, the first color difference signal (BY) calculated by the equation (2-a) corresponds to, for example, each horizontal line in the nth column and the (n + 2) th column in FIG. But
The second color difference signal (RY) calculated by the above equation (2-b) does not correspond to the horizontal lines of the (n + 1) th column and the (n + 3) th column, and conversely, It corresponds to each horizontal line in the (n + 3) th column, but does not correspond to each horizontal line in the nth column and the (n + 2) th column. In such a state, color information for all pixels cannot be obtained when the image is reproduced, and the color reproducibility is deteriorated.

Therefore, the color difference signal of the horizontal line, which cannot be obtained by the calculation of the equations (2-a) and (2-b), is given by the following equation (3-
Complementary operation is performed by a) and (3-b). (BY) _n = {(BY) _n-1 + (BY) _{n + 1} } / 2 ... (3-a) (RY) _{n + 1} = {(RY) _n + (RY) _{n + 2} } / 2 (3-b) By performing such complementary calculation, it is possible to reproduce an image having good color reproducibility in the vertical direction.

Steps S200 to S20 described above
When the calculation process of 8 is completed, next, in step S210, the calculated color difference signals (BY) and (RY) are output at a predetermined timing corresponding to the pixel array. If a monitor television or the like is connected to the external terminal 112, a color still image is reproduced and displayed.

As described above, according to this embodiment, since the color difference signals (BY) and (RY) corresponding to all the pixels are obtained by performing the complementary calculation, the color reproducibility in the vertical direction can be obtained. White balance adjustment capable of reproducing a good color image can be realized.

On the other hand, if it is determined in step S204 that the proper color temperature correction coefficient at the time of actual photographing is unknown, the process proceeds to step S212. Then, in steps S212 and S214, an appropriate color temperature correction coefficient is predicted and calculated, and then in step S216, white balance adjustment is performed based on the predicted color temperature correction coefficient (hereinafter, referred to as an automatic color temperature correction coefficient).

First, in step S212, as shown in the following equations (4-a) to (4-d), the total addition average value PA of the addition pixel data P _MgCy of magenta Mg and cyan Cy obtained in step S202 is obtained. It calculates the _MgCy, and the total average value of the added pixel data P _GYE green G and yellow Ye, all average value PA _GCy green G, and cyan G. The coefficient Total is the number of added pixel data for each color.

PA _MgCy = (ΣP _MgCy ) / Total ... (4-a) PA _GYe = (ΣP _GYe ) / Total ... (4-b) PA _MgYe = (ΣP _MgYe ) / Total ... (4-c) PA _GCye = (ΣP _GCy ) / Total ... (4-d) Next, in step S214, the equations (4-a) to
The average value PA _MgCy , PA _GYe , PA calculated in (4-d)
_{Applying MgYe} and PA _GCye to the following conditional expressions (5-a) to (5-b), and also satisfying conditional expressions (6-a) to (6-d), automatic color temperature correction coefficient for each color CAa, CAb, CAc,
Calculate CAd.

BY = CAa * PA _MgCy- CAb * PA _GYe = 0 ... (5-a) BY-CA = PA _MgYe- CAd * PA _GCy = 0 ... (5-b) Ca (MIN) ≤ CAa ≤ Ca (MAX) ... (6-a) Cb (MIN) ≤ CAb ≤ Cb (MAX) ... (6-b) Cc (MIN) ≤ CAc ≤ Cc (MAX) ... (6-c) Cd (MIN) ≤Cad ≤Cd (MAX) (6-d) That is, as shown in the above equations (5-a) and (5-b), the color difference signals (BY) and (RY) for the target image are Both 0
If the condition (achromatic color) is satisfied, the automatic color temperature correction coefficients CAa, CAb, CAc, and CAd at this time are appropriate white balance correction coefficients. Therefore, the arithmetic mean value PA _MgCy , PA for each color in the entire image
_GYe , PA _MgYe , and PA _GCye are _expressed by these equations (5-a) and (5-
b) to apply automatic color temperature correction coefficients CAa, CAb,
CAc and CAd are predictive calculations.

Further, depending on the image, the color distribution may be biased toward a certain specific color, and the automatic color temperature correction coefficients CAa, CAb, CA can be simply calculated from the equations (5-a) and (5-b).
Even if c and CAd are obtained, the balance with respect to the color temperature distribution of the actual photographing light source may be greatly disturbed, and the temperature may be adjusted to a light source temperature that is impossible in reality. In order to avoid these situations in advance, the automatic color temperature correction coefficient C
For Aa, CAb, CAc, and CAd, the color temperature correction coefficients Ca, Cb, Cc, which are provided in advance for the number of preset light sources,
The limit is set so as not to deviate from the range of Cd (see the above formulas (6-a) to (6-d)).

That is, the minimum and maximum values of the color temperature correction coefficients Ca, Cb, Cc, and Cd provided in advance are
Ca (MIN), Ca (MAX), Cb (MIN), Cb (MAX), Cc (MIN),
If Cc (MAX), Cd (MIN), and Cd (MAX), the automatic color temperature correction coefficients CAa, CAb, CAc, which are restricted within the range of the conditional expressions (6-a) to (6-d), Adopt CAd.

Next, in step S216, the added pixel signals P _MgCy , P _MgCy , P are calculated by the following equations (7-a) and (7-b).
Automatic color temperature correction coefficients CAa, C for _GYe , P _MgYe , P _GCy
White balance adjustment is performed by multiplying Ab, CAc, and CAd, and color difference signals (BY) and (R-
Y) is calculated. BY = CAa * P _MgCy- CAb * P _GYe (7-a) RY = CAc * P _MgYe- CAd * P _GCy (7-b) Next, the processes of step S208 and step S210 are performed. By doing so, the color difference signals that cannot be obtained only by the operations of the expressions (7-a) and (7-b) are complemented (see the expressions (3-a) and (3-b)). Then, these color difference signals are output via the external terminal 114.

By connecting a display device such as a monitor to the external terminal 114, an image can be reproduced and displayed.

As described above, according to this embodiment, the pixel data for each frame image obtained at the time of photographing is stored in the frame memory, and then the above-mentioned arithmetic processing is performed on the pixel data in this frame memory at the time of image reproduction. Since the color difference signals are formed and output while adjusting the white balance by using, the capacity of the frame memory can be significantly reduced, and at the same time, the number of hardware components such as the conventional horizontal delay circuit can be reduced. You can

That is, conventionally, a color C having n × m pixels is used.
In the case of performing the above-described adjustment processing and processing for color difference signal formation in a camera that captures images with a CD, in order to store and hold data of color difference signals (BY) and (RY) and luminance components. A frame memory having a storage capacity three times as large as the number of pixels n × m is required. For example, focusing on a pair of pixel color filters on the BY line shown in FIG. 7, pixel data corresponding to one frame image is obtained from pixel data of magenta (Mg) and cyan (Cy), and green (G) and yellow (Ye). Color difference signal (BY) and a color difference signal (RY) corresponding to one frame image need to be formed and stored in the frame memory, and the luminance component also corresponds to one frame image. Memory is required, the memory capacity three times that is required to reproduce one frame image.

On the other hand, according to this embodiment,
Focusing on the pair of pixel color filters on the BY line, two pairs of filters of magenta (Mg) and cyan (Cy), and green (G) and yellow (Ye) are combined into one horizontal line. Since there are as many pixels as the number of pixels, a frame memory for storing these pixel data for one frame image is sufficient, and therefore the storage capacity can be significantly reduced.

Further, according to this embodiment, the pixel data at the time of image pickup is stored in the frame memory as it is,
Since calculation processing for white balance adjustment is performed during image reproduction, redundancy of the image data amount can be avoided.

Further, according to this embodiment, the white balance correction coefficients Ka, Kb, Kc, Kd peculiar to the camera are provided.
The previously stored as reference correction coefficient data in ROM 108, the correction coefficient Ka, Kb, Kc, and each added pixel data D _CCD first time white balance adjustment of the Kd was (see step S202), further fact Color temperature correction coefficients Ca, Cb, Cc, C according to the light source color temperature of
The second white balance adjustment is performed by d (see steps S206 and S214). Since the color temperature correction coefficients Ca, Cb, Cc and Cd can be input by an external storage medium, these color temperature correction coefficients Ca, Cb, Cc and Cd are fixed and built in the camera in advance. Since it is unnecessary and can be newly added or changed, it is possible to provide an electronic still camera having excellent expandability and the like.

Even if the color temperature correction coefficients Ca, Cb, Cc and Cd corresponding to the light source color temperature assumed in advance are not set, the automatic color temperature correction coefficients CAa and CA are used.
Since b, CAc, and CAd are automatically predicted and calculated to adjust the white balance (see steps S212 to S216), there is an excellent effect that it is possible to realize proper shooting that immediately corresponds to the actual shooting state.

The automatic color temperature correction coefficients CAa, CAb,
In order to calculate CAc and CAd, step S in FIG.
In the description of 212, the addition average values PA _MgCy , PA _GYe , and PA for all the addition pixel data for one frame image
_{Although MgYe} and _PAGCy are obtained, the present invention is not limited to such arithmetic processing. For the addition pixel data within a specific range for one frame image, for example, the addition average value for the addition pixel data corresponding to a predetermined view angle range (such as within a predetermined range from the center of the frame image) is set to PA _MgCy. , PA _GYe , PA _MgYe , PA _GCy .

(Second Embodiment) Next, a second embodiment will be described. It should be noted that this is related to the electronic still camera, and the configuration of the main part will be described with reference to FIG.

In FIG. 2, the same or corresponding portions as in FIG. 1 are indicated by the same reference numerals, and the added pixel signal S _CCD read from the color _CCD 100 in which the pixel color filters similar to those in FIG. 3 are sample-held. Digital pixel data D by the circuit 102 and the A / D converter 104
_The data is converted into _CCD , and the pixel data D _CCD is made to correspond to the pixel array of the _CCD 100 and is stored and held in the frame memory 106 or the expansion memory 106 ′. Further, the RO which previously stores the reference correction coefficient data Ka, Kb, Kc and Kd for the white balance correction correction coefficient.
It is equipped with M108.

Further, this electronic still camera is also provided with a central control unit 118 having a microprocessor or the like for controlling operations at the time of photographing and image reproduction, and at the time of image reproduction, the frame memory 106 or the expansion memory 10 is provided.
The pixel data D _CCD corresponding to the frame image stored and held in 6 ′ is output to the external terminal 114 via the external output interface 116.

The above-described components are provided in the electronic still camera, and when image reproduction is performed on the monitor of the host computer 120 such as a so-called personal computer, the host computer 12 is connected to the external output terminal 114.
By connecting a predetermined input terminal 122 of 0, the pixel data D _CCD output from the electronic still camera is received.

Here, the host computer 120 previously stores data of a plurality of types of color temperature correction coefficients Ca, Cb, Cc, Cd corresponding to various light source color temperatures, and the equation (1-
The arithmetic processing program for white balance adjustment and color difference signal formation described in a) to (7-b) is supplied by a so-called floppy disk 124, memory card or the like.

Next, the operation of this embodiment will be described. The operation at the time of shooting is performed in the same manner as the flowchart of FIG. 5 described in the first embodiment each time the operator instructs one shooting, and the pixel data D corresponding to the still image of the subject is captured.
_{The CCD} is stored and held in the frame memory 106 or the expansion memory 106 '.

On the other hand, when the operator gives an instruction to reproduce an image, the central control unit 118 reads the reference correction coefficient data Ka, Kb, Kc, Kd from the ROM 108, and at the same time, outputs one frame image from the frame memory 106 or the expansion memory 106 '. Read pixel data D _CCD corresponding to, and through the output interface 116 and the external output terminal 114,
These reference correction coefficient data Ka, Kb, Kc, Kd are transferred to the host computer 120, and each pixel data DCCD is transferred to the host computer 120 in time series corresponding to the pixel array of the color _CCD 100.

Next, the host computer 120 receives the reference correction coefficient data Ka, Kb, Kc, Kd and the pixel data _DCCD and the color temperature correction coefficients Ca, Cb, Cc, C.
For d, the white balance adjustment and the color difference signals (BY) and (RY) are formed by performing the arithmetic processing of steps S200 to S210 in FIG. 6, or instead of step S206 in FIG. , Steps S212 to S21
6 calculates the automatic color temperature correction coefficient to form white balance adjustment and color difference signals (BY) and (RY), and based on these color difference signals (BY) and (RY) To play a still image on the monitor.

Therefore, the host computer 120
Performs the white balance adjustment and color difference signal forming processing based on the equations (1-a) to (7-b) by executing the arithmetic processing program stored in advance.

According to the second embodiment, the pixel data for each frame image obtained at the time of photographing is stored in the frame memory, and then the added pixel data of the frame memory is reproduced at the time of image reproduction by the host computer or the like. Since the external device of the above is configured to form the color difference signal while performing the white balance adjustment by the above calculation processing, it is possible to significantly reduce the memory capacity, and at the same time, the number of hardware components such as the conventional horizontal delay circuit can be reduced. It is possible to realize an electronic still camera that can reduce

Further, according to this embodiment, the white balance correction coefficients Ka, Kb, Kc, Kd peculiar to the camera are provided.
Are stored in the ROM 108 as reference correction coefficient data in advance, so that the color temperature correction coefficients Ca, Cb, Cc corresponding to the actual light source color temperature can be stored in an external device such as a host computer.
, Cd can be built in to perform proper white balance adjustment, and the color temperature correction coefficient C
Since a, Cb, Cc, and Cd can be newly added or changed, it is possible to provide an electronic still camera system excellent in expandability and the like.

Even if the color temperature correction coefficients Ca, Cb, Cc, Cd corresponding to the light source color temperature assumed in advance are not set, the automatic color temperature correction coefficients CAa, CA are used.
Since b, CAc, and CAd are automatically predicted and calculated to adjust the white balance (see steps S212 to S216), there is an excellent effect that it is possible to realize proper shooting that immediately corresponds to the actual shooting state.

[0068]

As described above, according to the present invention, the following effects can be obtained.

Since the white balance adjustment and the color difference signal are formed by executing the arithmetic processing program by the arithmetic unit, a complicated circuit as in the prior art is unnecessary, and the simplification and downsizing of the apparatus can be realized.

The white balance correction coefficient (reference correction coefficient) stored in the second storage medium is once normalized to the reference color temperature light source unique to the image pickup apparatus. This can be realized by performing the normalized addition pixel data based on the color temperature correction coefficient. Therefore, it is not necessary to adjust the variation of each manufactured image pickup device, and it is possible to easily obtain the proper color temperature correction coefficient data by simply inputting the data to the third storage medium after shipment. It is possible to realize white balance adjustment, and it is possible to provide an image pickup apparatus that is highly adjustable and highly expandable.

Since the mechanism for automatically calculating the automatic color temperature correction coefficient is provided, it is not always necessary to accurately manage the light source color temperature at the time of photographing. Therefore, even if various color temperature correction coefficients corresponding to various light source color temperatures are not previously built in, white balance adjustment that can be practically used is performed, and image reproduction with good color reproducibility can be realized. Exerts an excellent effect.

Further, since the complementary calculation for complementing the shortage of each color difference signal for each horizontal line is performed, the color reproducibility in the vertical direction can be improved and the image quality can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a first embodiment according to the present invention.

FIG. 2 is a block diagram showing a main configuration of a second embodiment according to the present invention.

FIG. 3 is an explanatory diagram showing, as a representative, a partial configuration of a light-receiving surface of a color CCD applied to an embodiment.

FIG. 4 is an explanatory diagram for explaining an array of added pixel signals read from a color CCD applied to the embodiment.

FIG. 5 is a flowchart showing an operation example at the time of imaging according to the embodiment.

FIG. 6 is a flowchart for explaining the operations of white balance adjustment and color difference signal formation processing during image reproduction according to the embodiment.

FIG. 7 is a color C applied to a conventional electronic still camera.
It is explanatory drawing which shows a part structure of the light-receiving surface of CD.

FIG. 8 is a block diagram showing a configuration of a conventional electronic still camera.

FIG. 9 is a color C applied to a conventional electronic still camera.
6 is a timing chart showing the output timing of an addition pixel signal read from a CD.

FIG. 10 is a timing chart showing the timing of white balance adjustment processing in a conventional electronic still camera.

[Explanation of symbols]

100 ... Color CCD, 102 ... Sample and hold circuit, 104 ... A / D converter, 106 ... Frame memory,
106 '... Extended memory, 108 ... ROM, 110 ... Arithmetic section, 112 ... Program memory, 114 ... External output terminal, 116 ... Output interface, 118 ... Central control section, 120 ... Host computer, 122 ... Input terminal,
124 ... External storage medium.

Claims (4)

[Claims] 1. A first pixel row composed of a plurality of pixels in which cyan and yellow pixel color filters are alternately arranged in the horizontal line direction, and magenta and green pixel color filters are alternately arranged in the horizontal line direction. Second pixel rows composed of a plurality of formed pixels are alternately arranged in the vertical direction, and each pair of the first and second pixel rows is configured as a horizontal line, By combining the generated pixel signals for each of the first and second pixel columns and mixing and outputting the pixel signals of two pixels that are adjacent to each other in the vertical direction, the added pixel signal for each horizontal line is obtained. A color image sensor for horizontal scanning and reading; an A / D converter for digitally converting each of the addition pixel signals read from the color image sensor into addition pixel data; and the A / D converter. A first storage medium that stores the added pixel data output in accordance with the pixel array of the color image sensor, and a white balance correction coefficient when a photograph is taken under a reference color temperature light source as a reference correction coefficient. A second storage medium which is stored in advance, and a third storage which stores in advance various color temperature correction coefficients corresponding to the ratio of the reference correction coefficient to the white balance correction coefficient when photographed under various light source color temperatures. A medium, and by executing a predetermined arithmetic processing program, the addition pixel data stored in the first storage medium is stored in the reference correction coefficient and the third storage medium in the second storage medium. And a calculation unit for performing white balance adjustment by multiplying the stored color temperature correction coefficient corresponding to the light source color temperature at the time of shooting. That the image pickup apparatus. 2. The calculation unit, when the color temperature correction coefficient corresponding to the light source color temperature at the time of photographing does not exist,
A condition that the color difference signal after white balance adjustment, which is obtained by applying the reference correction coefficient and the unknown color temperature correction coefficient to the addition average value while obtaining the addition average value for each color of the addition pixel data, is set to 0. The unknown color temperature correction coefficient that satisfies the above is subjected to predictive calculation as an automatic color temperature correction coefficient, and for the added pixel data stored in the first storage medium, the reference correction coefficient in the second storage medium and the The image pickup apparatus according to claim 1, wherein white balance adjustment is performed by multiplying by an automatic color temperature correction coefficient. 3. The deficiency of the color difference signal is calculated by performing an arithmetic mean of the color difference signals that are adjacent to each other in the vertical direction of the pixel array with respect to the calculated color difference signal. The image pickup apparatus according to claim 1 or 2, wherein the complementary color difference signal is calculated. 4. The image pickup apparatus according to claim 1, wherein the third storage medium receives the color temperature correction coefficient and the calculation program from an external storage medium.