JP2007266709A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus in which color rolling phenomenon incident to auto-white balance control can be avoided. <P>SOLUTION: A first OPD (optical detector) calculates integration results of all intervals in the effective region of a period for every period, a second OPD calculates partial integration results of an interval from the start of the effective region of a period to a predetermined timing in the effective region for every period. When the first OPD calculates integration results at the N-th period, such coefficients are calculated as the results obtained by multiplying the integration results from the first OPD at the N-th period by the coefficients become substantially uniform. The coefficients are corrected based on the integration results calculated by the second OPD at the N-th period and the integration results calculated by the second OPD at the (N+m)th period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus. Specifically, the present invention relates to an imaging apparatus that performs auto white balance control.

In general, in a display, white is expressed in a state where all three primary colors of red, blue, and green are emitted. For example, white may be biased to red or blue depending on the color development state of each color. Therefore, it is necessary to adjust the color development of each color so that white can be displayed correctly. This process is called white balance process. The function for automatically adjusting the white balance is called the auto white balance function.
Hereinafter, an imaging device having an auto white balance function (for example, see Patent Document 1) will be described.

  FIG. 5 is a block diagram illustrating an example of a conventional imaging device. The imaging device 101 shown here includes a solid-state imaging device 102, an AFE (Analog Front End Processor) 103, and a digital signal processing unit 104. Yes.

  The solid-state imaging device has, for example, a CCD structure, detects light from a subject through a lens 105 by a photosensor arranged in a matrix on a semiconductor substrate, generates a signal charge, and the signal charge is a vertical charge transfer register. Or an image signal of a subject is output after being transferred by a horizontal charge transfer register. In addition, red, blue, and green filters are attached to each of the optical sensors, and color photography is possible by separately detecting red, blue, and green light. Further, the solid-state imaging device operates based on a clock signal, a vertical synchronization signal, and a horizontal synchronization signal supplied from a timing generator (TG) 106. For example, an image signal for one frame is divided into an even field and an odd field by an interlace method. It is configured so that it can be output separately.

  The AFE has a CDS (Correlation Double Sampling) circuit and an AGC (Automatic Gain Control) circuit, and performs CDS on the image signal from the solid-state imaging device to remove fixed pattern noise included in the image signal, and AGC. Thus, the signal level can be stabilized.

  The digital signal processing unit is a circuit that performs automatic exposure control and auto white balance adjustment on the output signal of the AFE, and converts the signal into an image signal conforming to the output format. The analog-to-digital converter (ADC) 107, A luminance signal processing block 108, a color signal processing block 109, a microcomputer 110, an optical detector (OPD) 111, a mixing circuit (YCMIX) 112, and a digital analog converter (DAC) 113 are configured.

  The ADC digitizes the output signal of the AFE, and the luminance signal processing block is configured to perform signal processing for setting the signal level to an appropriate level as the automatic exposure control for the digitized image signal. The color signal processing block includes a primary color separation circuit 114 and a WB control circuit (white balance control circuit) 115. The primary color separation circuit extracts three primary color signals of red, blue, and green from the output signal of the ADC and performs WB control. The circuit is configured to control the signal level by multiplying these primary color signals by a coefficient given from a microcomputer.

  The OPD integrates the primary color signal obtained by multiplying the above-described coefficient by the WB control circuit for each period of the vertical synchronization signal, that is, for each field, for example, by an IIR (Infinite Impulse Response) filter. The average signal level (average level) can be calculated.

  The microcomputer includes a CPU, a ROM, and a RAM, and the CPU is configured to perform various functions by appropriately operating the RAM based on program data stored in the ROM. In particular, regarding the auto white balance control, the coefficient is generated based on the average level of each primary color signal calculated by the OPD so as to equalize the average level of these primary color signals, and is supplied to the WB control circuit. Has been.

  The mixing circuit combines the luminance signal output from the luminance signal processing block and the three primary color signals output from the color signal processing block to generate a video signal, and the DAC converts the video signal into an analog video signal. Are configured so that they can be output. Further, the TG is configured to be able to supply a clock and a synchronization signal to each part together with the solid-state imaging device based on the control of the microcomputer.

Hereinafter, the operation of the imaging apparatus configured as described above will be described.
First, light 116 from a subject enters a solid-state image sensor through a lens, and an image of the subject is formed on the light receiving surface of the solid-state image sensor. The solid-state imaging device converts this image into an electric signal, and outputs the image signal of each field in synchronization with the vertical synchronization signal supplied from the timing generator. The AFE performs CDS on the image signal output from the solid-state imaging device to remove fixed pattern noise included in the image signal, and stabilizes the signal level by AGC.

  Next, the ADC digitizes the output signal of the AFE, and the luminance signal processing block performs signal processing on the digitized image signal to set the signal level to an appropriate level as automatic exposure processing. On the other hand, the color signal processing block, the OPD, and the microcomputer perform digital signal processing as auto white balance control on the image signal digitized by the ADC as follows. FIG. 6 is a schematic diagram showing the relationship between the coefficient of auto white balance control and the time axis in the prior art.

In the digital signal processing described above, first, the primary color separation circuit extracts three primary color signals of red, blue, and green from the output signal of the ADC, and the WB control circuit detects, for example, the primary colors of red and blue among these primary color signals. The signal level is controlled by multiplying the signal by a coefficient given from a microcomputer. The OPD receives the green primary color signal and the red and blue primary color signals multiplied by the coefficients from the WB control circuit, and for each period of each vertical synchronizing signal, that is, for each field (the field is indicated by the symbol Tf in FIG. 6). And the average level of each primary color signal in each field is calculated.
The microcomputer takes in the average level of each primary color signal calculated by this OPD, and when the average level of the primary color signals of red and blue is multiplied by the above coefficient, the average level of the three primary color signals becomes the same. The coefficients to be multiplied by the primary color signals of red and blue are calculated so that the average level is uniform, and these coefficients are supplied to the WB control circuit. The white balance control is performed by the WB control circuit multiplying these coefficients by the primary color signals of red and blue.

Specifically, first, in the first field (the field whose time axis is “−2” in FIG. 6), the entire period of the effective area of the first field (the effective video signal in FIG. 6 is at a high level). The average level of each primary color signal during the period is calculated by OPD.
Next, in the second field (the field whose time axis is “−1” in FIG. 6) in the next cycle of the first field, the average level of each primary color signal calculated by OPD in the first field is multiplied. Thus, the average level of the three primary color signals is made uniform by multiplying the coefficient so that the average levels of the three primary color signals are the same, that is, the average level of each primary color signal calculated by OPD in the first field. Calculate the correct coefficient.
Thereafter, in the third field of the next period of the second field (the field whose time axis is “0” in FIG. 6), the red and blue primary color signals are multiplied by the coefficients calculated in the second field. Auto white balance control is performed.

  In the second field, a coefficient is calculated so that the average levels of the three primary color signals are the same by multiplying the average levels of the primary color signals calculated by OPD in the first field, and the second field is calculated. The average level of each primary color signal in the effective period of the field is calculated by OPD, and the average level of each primary color signal calculated by OPD in the second field is multiplied to make the average levels of the three primary color signals the same. Such a coefficient is calculated in the third field, and the calculated coefficient is multiplied by the red and blue primary color signals in the fourth field (the field of the next period of the third field). Has been done.

  Therefore, in the conventional imaging apparatus, a coefficient (new coefficient) is calculated based on the average level of each primary color signal calculated in the previous two fields, and this coefficient (new coefficient) is supplied to the WB control circuit, In the second field, the level of the primary color signal is adjusted based on the coefficient (new coefficient). Thereafter, the three primary color signals output from the color signal processing block and the image signal output from the luminance signal processing block are combined by the mixing circuit, converted into an analog signal by the DAC, and output as a video signal.

JP 2003-153285 A

However, in the auto white balance control in the conventional imaging apparatus as described above, the coefficient calculated for each field is multiplied by the primary color signal of the next field, so that the subject is fluorescent light due to this temporal shift. Auto white balance control may not function correctly when illuminated with a, and a phenomenon called color rolling may occur.
Hereinafter, the color rolling will be described in detail.

  That is, the fluorescent lamp blinks at a cycle corresponding to the power supply frequency, but the spectral characteristics of the fluorescent lamp change depending on the light emission timing within each blinking cycle, and the light from the fluorescent lamp is not always white. . Therefore, when imaging is performed with a short exposure time by the electronic shutter function of the solid-state imaging device, the imaging result is colored depending on the relationship between the exposure timing and the light emission timing of the fluorescent lamp.

  In addition, when the imaging apparatus is compatible with the NTSC (National TV Standards Committee) system and the subject is illuminated by a fluorescent lamp that is lit with a 60 Hz power supply, the field frequency of the imaging apparatus is 59.94 Hz and the fluorescent lamp power supply frequency. Since it is slightly different from 60 Hz, the phase relationship between the field of the imaging device and the flickering of the fluorescent lamp periodically changes with a relatively long period.

  In the conventional imaging apparatus, the primary color signal obtained by calculating the average level by OPD as described above and the primary color signal multiplied by the coefficient by the WB control circuit are shifted by 2 fields, so that the current field and the field after 2 are shifted. If the illumination light at the time of exposure has a different color tone, the auto white balance control does not function correctly and the image becomes colored. Since the phase relationship between the field of the imaging device and the power supply changes as described above, the color tone of the video image displayed by the video signal periodically changes in accordance with the change in the phase relationship.

  Even when the imaging apparatus is compatible with the PAL (Phase Alternating Line) system and the power supply frequency of the fluorescent lamp is 50 Hz, the field frequency and the power supply frequency of the fluorescent lamp match in the standard, but there is an error in both. Therefore, the color rolling phenomenon occurs as in the above case.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an imaging apparatus capable of avoiding a color rolling phenomenon associated with auto white balance control.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an image sensor that repeatedly captures an image of a subject in synchronization with a synchronization signal and outputs an image signal, and primary color separation that separates a plurality of primary color signals from the image signal. A first primary color signal level detection means for acquiring an average level of each primary color signal separated by the primary color separation means for the entire period of the effective area of the same period for each period of the synchronization signal; Second primary color signal level detection means for obtaining an average level of each primary color signal separated by the primary color separation means in a period from the beginning of the effective area of the same period to a predetermined timing in the effective area for each period; When the first primary color signal level detection means acquires the average level of each primary color signal in the Nth period (N: natural number), the first primary color signal level detection means acquires in the Nth period. Coefficient calculation means for calculating a coefficient such that the result obtained by multiplying the average level of each primary color signal becomes substantially uniform; and the average level and the first level of each primary color signal acquired by the second primary color signal level detection means in the Nth period. Based on the average level of each primary color signal acquired by the second primary color signal level detection means in the (N + m) period (m: natural number), the coefficient calculation means performs the first primary color signal level detection means in the Nth period. The coefficient correction unit that corrects the coefficient calculated from the average level of each primary color signal acquired by the first correction unit and the coefficient corrected by the coefficient correction unit acquired by the first primary color signal level detection unit in the Nth period. Level control means for controlling the level of each primary color signal by multiplying the average level of the primary color signal.

Here, since the coefficient calculation means calculates the coefficient based on the average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period, the coefficient calculated by the coefficient calculation means Do not depend.
That is, the average level of each primary color signal acquired by the second primary color signal level detection means (the average level of each primary color signal in the period from the beginning of the effective area of the cycle to a predetermined timing in the effective area) is displayed on the screen. The coefficient for performing white balance control is used only for detecting the temporal difference at the same position in the image, and the average level of each primary color signal acquired by the first primary color signal level detection means (the entire effective area of the period) The coefficient calculated by the coefficient calculation means does not depend on the subject.

  Further, the coefficient correction means detects the average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period and each primary color signal acquired by the second primary color signal level detection means in the (N + m) period. Based on the average level, in order to correct the coefficient calculated by the coefficient calculation means from the average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period, the Nth period and the (N + m) period , I.e., the timing at which the first primary color signal level detection means, which is the basis for the coefficient calculation means to calculate the coefficient, acquires the average level of each primary color signal (Nth period) and white balance control is performed. Accordingly, it is possible to reduce the error of the temporal coefficient due to the change in the spectral characteristics caused by the deviation of the timing ((N + m) period) when the level control means controls the level of each primary color signal.

  As described above, since the coefficient calculation means calculates the coefficient based on the average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period, the coefficient calculation means calculates The coefficient does not depend on the subject. However, between the average level of each primary color signal acquired by the first primary color signal level detection means and the average level of each primary color signal acquired by the second primary color signal level detection means, that is, in the effective region of the period. There is a possibility that the subject depends on the average level of each primary color signal in the entire period and the average level of each primary color signal in the period from the beginning of the effective area of the cycle to a predetermined timing in the effective area. . Therefore, in the coefficient correction unit, the average level of each primary color signal acquired by the second primary color signal level detection unit in the Nth period and each primary color signal acquired by the second primary color signal level detection unit in the (N + m) period. The validity of the correction is ensured by performing the correction based on the average level.

Further, the coefficient correction means acquires the average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period and the second primary color signal level detection means in the (N + m) period (m: natural number). Rather than correcting the coefficient based only on the average level of each primary color signal, the average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period, the (N + n) period (n: natural number) , N <m), the average level of each primary color signal acquired by the first primary color signal level detection means, the average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period, and the (N + n) th By performing correction based on the average level of each primary color signal acquired by the second primary color signal level detection means in a cycle, the reliability of coefficient correction can be improved.
That is, when an average level of each primary color signal that is a basis for calculating a coefficient for performing white balance control is acquired (Nth cycle), and when white balance control is performed based on the calculated coefficient (Nth + N) cycle. ), The reliability of the correction of the coefficient can be improved by reflecting the timing shift between the Nth period and the (N + n) period. .

  In the imaging apparatus of the present invention described above, since the coefficient is corrected by the coefficient correction means, when the average level of each primary color signal for calculating the coefficient for white balance control is acquired (Nth period), It is possible to reduce the timing shift at the time of white balance control (the (N + m) period) based on the calculated coefficient, reduce the coefficient error due to the change in spectral characteristics of the fluorescent lamp that changes with time, and The influence of the color rolling phenomenon accompanying white balance control can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings to facilitate understanding of the present invention.
FIG. 1 is a block diagram showing an example of an imaging apparatus to which the present invention is applied. The imaging apparatus 1 shown here includes a solid-state imaging device 2, an AFE 3, and a digital signal processing unit 4. As will be described in detail below, the image pickup apparatus of the present embodiment is particularly different from the conventional image pickup apparatus described above in that two OPDs are provided in the digital signal processing unit and the coefficient generated in the microcomputer This is the point that a function for correcting the above is added. Note that the solid-state imaging device is an example of an image sensor.

  The solid-state imaging device has a CCD structure, for example, detects light from a subject through a lens 5 by a photosensor arranged in a matrix on a semiconductor substrate, generates a signal charge, and the signal charge is a vertical charge transfer register. Or an image signal of a subject is output after being transferred by a horizontal charge transfer register. Each of the optical sensors is equipped with a red, blue, and green filter, and color photography is possible by separately detecting red, blue, and green light. Furthermore, the solid-state imaging device operates based on the clock signal, vertical synchronization signal, and horizontal synchronization signal supplied from the TG 6 so that, for example, an image signal for one frame can be divided into an even field and an odd field by an interlace method. It is configured.

  The AFE has a CDS circuit and an AGC circuit, and performs a CDS on the image signal from the solid-state image sensor to remove fixed pattern noise included in the image signal, and can be configured to stabilize the signal level by AGC. Has been.

  The digital signal processing unit is a circuit for performing automatic exposure control and auto white balance adjustment on the output signal of the AFE, and an analog-digital converter (ADC) 7, a luminance signal processing block 8, and a color signal processing block 9. The microcomputer 10, the first OPD 11 a, the second OPD 11 b, the mixing circuit (YCMIX) 12, and the digital-analog converter 13. The first OPD is an example of a first primary color signal level detection unit, and the second OPD is an example of a second primary color signal level detection unit.

  The ADC digitizes the output signal of the AFE, and the luminance signal processing block is configured to perform signal processing for setting the signal level to an appropriate level as the automatic exposure control for the digitized image signal. The color signal processing block has a primary color separation circuit 14 and a WB control circuit 15, and the primary color separation circuit extracts three primary color signals of red, blue, and green from the output signal of the ADC, and the WB control circuit outputs these primary color signals. On the other hand, the signal level can be controlled by multiplying by a coefficient given from the microcomputer. The primary color separation circuit is an example of primary color separation means.

In the first OPD, the primary color signal multiplied by the above-mentioned coefficient is integrated by the WB control circuit for each period of the vertical synchronizing signal, that is, for each field, and for the entire period of the effective area of each field, for example, by an IIR filter. Can be used to calculate an average signal level (average level) of each primary color signal over the entire period of each field, that is, an integration result for one field (for the integration region of the first OPD). (See FIG. 2).
The second OPD also applies the primary color signal multiplied by the above-mentioned coefficient by the WB control circuit within the effective area of the same period from the beginning of the effective area of each field for each period of the vertical synchronizing signal, that is, for each field. The average signal level (average level) of each primary color signal, that is, the partial integration result is calculated for the number of effective pixel start lines of each field by integrating the period up to a predetermined timing of, for example, by an IIR filter. (Refer to FIG. 2 for the integration region of the second OPD).
Here, the effective area indicates an area where an image is actually output, and the effective area indicates an area where an image can be recognized as an image sensor (see FIG. 2).
For this reason, it is desirable for the second OPD to designate an area that is not included in the effective area for a period up to a predetermined timing within the effective area.

  The microcomputer includes a CPU, a ROM, and a RAM, and the CPU is configured to perform various functions by appropriately operating the RAM based on program data stored in the ROM. In particular, regarding auto white balance control, a coefficient for equalizing the average level of each primary color signal is generated based on the integration result for one field calculated by the first OPD, and the 1 calculated by the first OPD. After correcting the coefficient generated based on the integration result for the field and the partial integration result calculated by the second OPD, the coefficient is supplied to the WB control circuit. In the present embodiment, the microcomputer plays the role of the coefficient calculation means and the coefficient correction means.

  The mixing circuit combines the luminance signal output from the luminance signal processing block and the three primary color signals output from the color signal processing block to generate a video signal, and the DAC converts the video signal into an analog video signal. Are configured so that they can be output. Further, the TG is configured to be able to supply a clock and a synchronization signal to each part together with the solid-state imaging device based on the control of the microcomputer.

Hereinafter, the operation of the imaging apparatus configured as described above will be described.
First, the light 16 from the subject enters the solid-state image sensor through the lens, and an image of the subject is formed on the light receiving surface of the solid-state image sensor. The solid-state imaging device converts this image into an electric signal, and outputs the image signal of each field in synchronization with the vertical synchronization signal supplied from the timing generator. The AFE performs CDS on the image signal output from the solid-state imaging device to remove fixed pattern noise included in the image signal, and stabilizes the signal level by AGC.

  Next, the ADC digitizes the output signal of the AFE, and the luminance signal processing block performs signal processing on the digitized image signal to set the signal level to an appropriate level as automatic exposure processing. On the other hand, the color signal processing block, the first OPD, the second OPD, and the microcomputer perform digital signal processing on the image signal digitized by the ADC as auto white balance control as follows. FIG. 3 is a flowchart of white balance control coefficient correction processing in this embodiment, and FIG. 4 is a schematic diagram showing the relationship between the white balance control coefficient and the time axis in this embodiment.

In the digital signal processing described above, first, the primary color separation circuit extracts the three primary color signals of red, blue, and green from the output signal of the ADC, and the WB control circuit uses, for example, the primary colors of red and blue among these primary color signals. The signal level is controlled by multiplying the signal by a coefficient given from a microcomputer. The first OPD and the second OPD receive the green primary color signal and the red and blue primary color signals multiplied by the coefficients from the WB control circuit, and integrate them for each period of the vertical synchronizing signal, that is, for each field. An integration result or partial integration result for one field in each field is calculated.
The microcomputer takes in the integration results and partial integration results for one field calculated by the first OPD and the second OPD, and multiplies the three primary colors by multiplying the average level of the red and blue primary color signals by the above coefficient. The coefficients multiplied by the red and blue primary color signals are calculated so that the average level of the signals is the same, that is, the average level is uniform, and these coefficients are supplied to the WB control circuit. The WB control circuit multiplies these coefficients by the red and blue primary color signals to perform auto white balance control.

The auto white balance control will be specifically described below.
That is, in the first field (the field whose time axis is “−2” in FIG. 4), the first OPD receives the primary color signal of red and blue obtained by multiplying the primary color signal of green and the coefficient from the WB control circuit. The integration result for one field is calculated for each period of each vertical synchronizing signal, that is, for each field. Such an integration result is the basic data B- _{2 for} calculating the white balance control coefficient. At the same time, the second OPD receives the green primary color signal and the red and blue primary color signals multiplied by the coefficients from the WB control circuit, and calculates a partial integration result for each period of the vertical synchronizing signal, that is, for each field. Such an integration result becomes correction reference data A- ₂ .

In the second field (the field where the time axis in FIG. 4 is “−1”) as the next field on the time axis, the white balance control coefficient using the basic data B- ₂ calculated in the first field In the same manner as the first field, the basic data B ₋₁ for calculating the white balance control coefficient in the second field and the correction reference data A ₋₁ in the second field are calculated.

Further, in the third field that is the next field on the time axis (the field in which the time axis in FIG. 4 is “0”), the correction in the third field is the same as in the first field and the second field. calculating a use reference data a, to calculate a basic correction coefficient a ₀₂ of the white balance control coefficient by comparing the correction reference data a and the correction reference data a _-2.

Then, from the ratio relationship between the basic data _{B -2} and the relative ratio _{A 12} in the relative proportions of basic data _{B -1 B 12} and the correction reference data _{A -2} and correction reference data _{A -1,} basic correction factor A _{02 is} corrected to obtain a white balance correction coefficient β, and the white balance control coefficient calculated in the second field is corrected by using the white balance correction coefficient. Auto white balance control is performed by multiplying the red and blue primary color signals by the white balance control coefficient.

In order auto white balance control is an image presupposes a still image, if the relative ratio A ₁₂ between the correction reference data A _-2 and correction reference data A _-1 is the predetermined threshold value A _thres above, that is, if it can be determined that the entire image has changed greatly relative ratio a ₁₂ and the first field second field (Fig. 3 (1) reference.) stops the correction of the automatic white balance control coefficient . This is to prevent the correction of the auto white balance control coefficient from being canceled until normal auto white balance control is necessary.
Similarly, if the relative ratio _{A 01} between the correction reference data _{A -1} and the correction reference data A is the predetermined threshold value _{A thres} above, i.e., the relative ratio _{A 01} is larger second field and the third field If (see FIG. 3 (2).) that the entire image can be determined to have changed between or, if the relative ratio _{B 12} of the underlying data _{B -2} and basic data _{B -1} is the predetermined threshold value _{B thres} more , i.e., if it can be determined that the entire image is changed by the relative ratio B ₁₂ and a large first field and the second field (Fig. 3 (3) reference.) stop correction of automatic white balance control coefficients in To do.
Further, when α = B ₁₂ / A ₁₂ and β = A ₀₂ × α and α, β, and γ are equal to or greater than predetermined threshold values, that is, when it can be determined that the entire image has changed (FIG. 3 ( In 4), the correction of the auto white balance control coefficient is stopped.

  As described above, in the imaging apparatus of the present embodiment, the white balance control coefficient is corrected using the white balance correction coefficient to derive a coefficient (new coefficient), and this new coefficient is supplied to the WB control circuit. The primary color signal level is adjusted. Thereafter, the three primary color signals output from the color signal processing block and the image signal output from the luminance signal processing block are combined by the mixing circuit, converted into an analog signal by the DAC, and output as a video signal.

In the imaging apparatus to which the present invention is applied, the white balance correction coefficient is calculated using the basic correction coefficient of the white balance control coefficient derived from the partial integration result in the first field and the partial integration result in the third field, Since the white balance control coefficient is corrected based on the white balance correction coefficient calculated in this way, the coefficient error due to the change in the spectral characteristics of the fluorescent lamp that changes with time can be mitigated, and the effect of color rolling is reduced. can do.
Note that the coefficient after correction is calculated on the hardware, and it is configured so that the result can be immediately reflected in the same field. It is possible not to occur.

  In addition, the partial integration result is used only for detecting a temporal difference at the same position in the screen, and the white balance control coefficient is calculated based on the integration result for one field. It does not depend on the subject.

Furthermore, relative to relative to the base correction coefficient of the white balance control coefficient, the relative ratio _{B 12} of the underlying data _{B -2} and basic data _{B -1} and correction reference data _{A -2} and correction reference data _{A -1} for doing the correct from the ratio relationship between the ratio a _12, it is possible to increase the credibility of corrected coefficient derived in order to reduce the time difference.

It is a block diagram which shows an example of the imaging device to which this invention is applied. It is a schematic diagram showing the integration area | region of 1st OPD and 2nd OPD. It is a schematic diagram showing the relationship between the coefficient of white balance control and a time axis in a present Example. It is a flowchart of the correction process of the coefficient of the white balance control in a present Example. It is a block diagram which shows an example of the conventional imaging device. It is a schematic diagram showing the relationship between the coefficient of automatic white balance control in a prior art, and a time axis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Solid-state image sensor 3 AFE
4 Digital Signal Processing Unit 5 Lens 6 Timing Generator 7 Analog to Digital Converter 8 Luminance Signal Processing Block 9 Color Signal Processing Block 10 Microcomputer 11a First OPD
11b Second OPD
12 Mixing Circuit 13 Digital / Analog Converter 14 Primary Color Separation Circuit 15 White Balance Control Circuit 16 Light

Claims (4)

An image sensor that repeatedly captures a subject in synchronization with the synchronization signal and outputs an image signal;
Primary color separation means for separating a plurality of primary color signals from the image signal;
First primary color signal level detection means for obtaining an average level of each primary color signal separated by the primary color separation means for the entire period of the effective area of the same period for each period of the synchronization signal;
A second primary color signal level for obtaining an average level of each primary color signal separated by the primary color separation means in a period from the beginning of the effective area of the same period to a predetermined timing in the effective area for each period of the synchronization signal Detection means;
When the first primary color signal level detection means acquires the average level of each primary color signal in the Nth period (N: natural number), the average of each primary color signal acquired by the first primary color signal level detection means in the Nth period. Coefficient calculation means for calculating a coefficient such that the result multiplied by the level is substantially uniform;
The average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period and each primary color signal acquired by the second primary color signal level detection means in the (N + m) period (m: natural number). Coefficient correction means for correcting the coefficient calculated from the average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period based on the average level;
Level control means for controlling the level of each primary color signal by multiplying the coefficient corrected by the coefficient correction means by the average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period. An imaging apparatus characterized by that. The coefficient correction means includes an average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period and a second primary color signal level detection means in the (N + m) period (m: natural number). Along with the average level of each acquired primary color signal,
The average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period, and the first primary color signal level detection means acquired in the (N + n) period (n: natural number, n <m). The average level of each primary color signal, the average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period, and each primary color acquired by the second primary color signal level detection means in the (N + n) period The coefficient calculation unit corrects the coefficient calculated from the average level of each primary color signal acquired by the first primary color signal level detection unit in the Nth period based on the average level of the signal. The imaging apparatus according to 1. The average level of each primary color signal acquired by the first primary color signal level detection means in the Nth period and each primary color signal acquired by the first primary color signal level detection means in the (N + a) period (a: natural number). The imaging apparatus according to claim 1, wherein when the ratio to the average level is equal to or greater than a predetermined value, control of the level of each primary color signal by the level control unit is stopped. The average level of each primary color signal acquired by the second primary color signal level detection means in the Nth period and each primary color signal acquired by the second primary color signal level detection means in the (N + b) period (b: natural number). The imaging apparatus according to claim 1, wherein when the ratio to the average level is equal to or greater than a predetermined value, control of the level of each primary color signal by the level control unit is stopped.

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