JPH0698336A - Image pickup device - Google Patents

Abstract

PURPOSE:To implement white balance correction with high accuracy normally while white balance traces a change in a color temperature in a short time. CONSTITUTION:A gain of a color signal obtained from an output of an image pickup element 1 is corrected by gain control circuits 3,4 operated according to a correction signal from D/A converters 43, 44 to implement white balance control. A color signal from A/D converters 30, 31 is integrated by adders 36, 37 and holding circuits 39, 40 for each of plural areas being divisions of a screen, and when a correction signal arithmetic operation section 42 fetches the integration value in any of the usual mode fetching the integration value of all the areas and the mode fetching the integration value for the specific area only, high speed white balance correction is attained in the latter mode.

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, and more particularly to an image pickup apparatus having a white balance correction function for correcting the white balance of a video signal obtained from the output of an image pickup means.

[0002]

2. Description of the Related Art Conventionally, in an image pickup apparatus for correcting white balance using a signal obtained from an image pickup element,
In order to avoid the influence of a chromatic color subject, there is known a method of performing white balance correction using only a signal from a white or near-white subject or a signal that has a possibility of that.

For example, a Y (luminance) signal obtained from a signal processing circuit of a camera and R (red) -which is two kinds of color difference signals.
It is intended to correct the white balance by extracting only the above-mentioned signals from the Y signal and the B (blue) -Y signal and bringing the extracted color difference signal components close to zero. Hereinafter, such a method is referred to as a white extraction method.

FIG. 7 is a block diagram showing a main structure of a conventional image pickup apparatus for performing white balance control by such a white extraction method.

In the figure, reference numeral 1 is an image pickup device, which photoelectrically converts subject light incident through a lens 21 and an iris 22. Reference numeral 2 is a luminance chromaticity signal for generating a high frequency component (Y _H ) of the luminance signal, a low frequency component (Y _L ) of the luminance signal, a red (R) signal and a blue (B) signal from the signal from the image pickup device 1, respectively. This is a generation circuit, and the R signal and the B signal generated here are supplied to the gain control circuits 3 and 4, respectively. The gain control circuits 3 and 4 are digital-analog (D / A) described later.
The amplification factors thereof are controlled by the control signals output from the converters 44 and 43, and the R signal and the B signal are amplified by the controlled amplification factors.

When the signals output from the gain control circuits 3 and 4 are R'signals and B'signals, the R'signals and B'signals are input to the color difference signal generation circuit 5 together with the Y _L signal. , The color difference signals (RY), (B-
Y) is generated.

[0007] The color difference signals (R-Y), (B -Y) are input to the encoder 6 with the above-mentioned Y _H signal, is converted into a standard television signal at the encoder 6. 28 is an output terminal for outputting this standard television signal.

On the other hand, the color difference signals (R-Y), (B -Y) are each analogue - is input to digital (A / D) converter 31 and 30, Y _H signal is input to the A / D converter 32 It
The outputs of these A / D converters 30, 31, 32 are input to the switch circuits 33, 34, 35, respectively. The switch circuits 33, 34 and 35 are controlled according to the synchronizing signal S1 from the synchronizing signal generator 45 and the area designating signal S2 from the correction signal calculating section 42, and one screen is displayed as shown in FIG.
The A / D conversion output of the designated area among the plurality of areas divided into four is supplied to the adders 36, 37 and 38 in the subsequent stage.

Here, even when only color signals from a white or near white object are used, or when color information formed from color signal components from each area is weighted,
Since it is necessary to obtain the integrated value of the color signal for each of the 64 areas shown in FIG. 8, the correction signal calculation unit 42 must sequentially specify all areas W11 to W88 in FIG. I won't.

The operations of the adders 36, 37 and 38 and the holding circuits 39, 40 and 41 will be described. Holding circuits 39, 40, 41 are provided at the subsequent stages of the respective adders 36, 37, 38.
Are respectively connected, and the outputs of the adders 36, 37, 38 are once held by the holding circuits 39, 40, 41. The data held in each holding circuit 39, 40, 41 is input again to each adder 36, 37, 38 and added with the next A / D converted value. That is, a digital integration circuit is composed of one set of holding circuit and adder.

When the holding circuits 39, 40 and 41 complete the integration (accumulation) of A / D converted values for one area,
The correction signal calculation unit 42 fetches the held data, that is, the integrated value, and immediately after that, it is reset by the reset signal S3 output from the correction signal calculation unit 42.

[0012] For example, (B-Y) signal for the region W11 in FIG. 8, (R-Y) signal, when obtaining the integrated value of the Y _H signal, what the integration operation is completed, at t1 in FIG. 8 This is the timing shown, that is, this integration requires about 1/8 of the vertical synchronization period. The correction signal calculation unit 42 fetches the integrated value held by the holding circuits 39, 40, 41 at the timing of t1 and outputs the reset signal S3 to the holding circuits 39, 40, 41.

Here, since it takes some time ts to reset and specify the next area, the area that can be specified next is the area after W13. Therefore, the number of regions where the integrated value can be captured by the correction signal calculation unit 42 in one vertical synchronization period is four at maximum. That is, as shown in FIG. 9, in the first field, W11, W13, W15, W17
If the integrated value of each signal in is taken in, the integrated value of each signal in W12, W14, W16, W18 is taken in in the second field and W21 in the third field.
The integrated values of W23, W25, and W27 are acquired, and the integrated values of the respective signals in the 64 areas of the entire screen are sequentially acquired.

Therefore, in the image pickup apparatus of FIG. 7, it takes 16 fields to capture the integrated value of each signal for all the regions.

In the correction signal calculation circuit 42, after the integrated values of the respective areas are taken in as described above, these data are weighted according to whether or not they correspond to a white subject, and the average value for the entire screen is calculated. Ask. That is, 64
The average value of the integrated values of the (RY) signals for the four areas is calculated as Ravr, and the average value of the integrated values of the (BY) signals for the 64 areas is calculated as Bavr, and these average values Rav are calculated.
r and Bavr are reference values Rref and B for white balance correction.
Signals (white balance correction values) Rcont and Bco for controlling the gain control circuits 3 and 4 so as to be equal to ref.
Calculate nt. Here, the reference values Rref and Bref are the (R-Y) signal and (B-
Y) Corresponds to the average of the signals.

Then, the white balance correction value Rco
nt and Bcont control the gain control circuits 4 and 3 via the D / A converters 43 and 44, and white balance correction is performed.

[0017]

As described above, in the image pickup apparatus, from the plurality of areas obtained by dividing the above-mentioned screen,
The white balance correction value cannot be calculated unless all the integrated values of each signal are captured.

Therefore, the white balance correction speed is
It is limited by the time required to capture the integral values of all the divided areas of the entire screen. For example, when the screen is divided into 64, it takes 16 field periods as described above to capture the integrated value of the divided areas of the entire screen. When the field frequency is 1/60 second, the update value of the white balance correction value per second is 3.
The number of times is 75, and if the number of screen divisions is further increased, the time required for this update becomes longer.

Therefore, when the white balance needs to be quickly tracked due to a rapid change in color temperature or the like, the correction speed is limited, so that the white balance can follow the change in color temperature in a short time. There were times when I couldn't.

An object of the present invention is, in the apparatus for correcting the white balance of the color video signal obtained from the image pickup means as described above, the white balance can be made to follow the change of the color temperature in a short time, and It is an object of the present invention to provide an image pickup apparatus that can normally perform highly accurate white balance correction.

[0021]

[Means for Solving the Problems] Under such a purpose,
In the image pickup apparatus of the present invention, the image pickup means, the detection means for detecting the color information from the color video signal for each of the plurality of regions in the photographing screen of the image pickup means, and the color output by the detection means. Using the information, the white balance correction means for correcting the white balance of the color video signal output from the output of the image pickup means, and the mode of the white balance correction means are set as The switching means is configured to switch between the first mode and the second mode in which only the color information of a part of the plurality of areas can be used.

With the above-described structure, normally, highly accurate white balance control is performed in the first mode, and white balance correction with high followability is performed in the second mode when a rapid color temperature change is dealt with. You can

[0023]

EXAMPLE An example of the present invention will be described in detail below.

FIG. 1 is a block diagram showing the schematic arrangement of an image pickup apparatus as an embodiment of the present invention. The same constituents as those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

The main difference between the image pickup apparatus of FIG. 1 and the apparatus of FIG. 7 is that a situation change detection unit 50 for detecting a change in the situation in which the white balance should be rapidly corrected is provided. Correction signal calculation unit 42 according to information
Is to change the divided area used by.

Further, the situation detecting section 50 includes an iris position detector 51 for detecting a change in brightness of the photographing screen,
An external input circuit 52 for detecting power-on and a change in camera mode is connected, while the correction signal calculation unit 42 has a function of detecting a change in color temperature of ambient light.

FIG. 2 is a flow chart for explaining the operation according to the detection of the situation change by the situation change detecting section 50 in the image pickup apparatus of FIG. Whether or not there is a large change in color temperature, the change in color temperature, and the presence or absence of power-on are determined.

Step S1, Step S2, Step S
When a change in the situation is detected in any of No. 3, a timer (not shown) built in the correction signal calculation unit 42 is reset in step S4. Then, step S5
Monitor whether or not the timer time exceeds the predetermined value and overflows, and the process proceeds to step S7 until the timer time exceeds the predetermined value and overflows. Integral data from a specific area of a part of the plurality of divided areas, that is, a specific part of the screen is taken in. In addition, after the time measured by the timer exceeds the predetermined value and overflows, step S
Proceed to step 6, and all of the plurality of divided areas obtained by dividing the shooting screen,
That is, the integrated data from the entire screen is taken in.

FIG. 3 is a diagram showing an example of a region into which the integration data is taken in at step S7 in the region divided into 64. That is, in the step S6, the integrated value of each signal in only the area shown by hatching in FIG. 3 is fetched by the correction signal calculation unit 42, and the white balance correction value is calculated.

At this time, as a method of calculating the white balance correction value, the average of the integrated values of all the color difference signals (RY) and (BY) in the captured area is averaged, and these are used as reference values Rref and Bref. Calculate a correction value that makes them equal, or calculate a correction value that makes the calculated value by performing a weighting operation on the integral value of each region depending on whether or not it corresponds to a white subject and makes it equal to the reference values Rref and Bref. To do.

The specific region in FIG. 3, i.e. the hatched area in (R-Y), FIG. 4 shows an example of a sequence for capturing an integral value of (B-Y), Y _H signals. In this example, in the first field, the regions W11, W13, W15, W17
The integration data of each signal is captured, and the integration data of each signal of the regions W22, W24, W26, and W28 is captured in the second field.

As is apparent from FIG. 4, in this example, the time required to capture the integral data for one screen is 8
The field period is reached, and the time required for this integration is halved as compared with the case where integration data for all 64 regions are acquired. Therefore, the white balance correction speed at this time can be made twice as fast as the case where the integrated data of all 64 areas are fetched.

FIG. 5 is a diagram showing another example of the area into which the integral data is taken in in step S7 in the 64 divided areas. The hatched area in FIG. 5 is the integration data acquisition area in this example.

Also as a method of calculating the white balance correction value at this time, each signal (RY) for the captured area is obtained.
And the average of the integrated values of (BY) is used as reference values Rref and Bref.
Or a correction value equal to the reference values Rref and Bref is calculated by performing a weighting operation on the integral value of each area depending on whether or not a correction value equal to is calculated. It may be calculated.

The specific area in FIG. 5, i.e., hatched area in (R-Y), shown in FIG. 6 an example of a sequence for capturing an integral value of (B-Y), Y _H signals. In this example, in the first field, the regions W11, W33, W55, W77
The integrated data of each signal is acquired, and the integrated data of each signal of the regions W81, W63, W45, and W27 is acquired in the second field.

As is apparent from FIG. 6, in this example, the time required to capture the integral data for one screen is 4
This is a field period, and the time required for this integration is 1/4 of a minute compared to the case where integration data of all 64 areas are acquired. Therefore, the white balance correction speed at this time can be set to a speed four times as high as that in the case where the integrated data of all 64 areas are fetched.

As described above, in the image pickup apparatus of the present embodiment, normally all the divided screens (RY),
(B-Y), incorporating an integral value of Y _H signals, performs highly accurate white balance correction, only a predetermined time period specific area only when there is a sudden change in the imaging conditions (R-
Y), the fast enough to correct the speed of the white balance when there is a change in the (B-Y), by calculating the white balance correction value captures the integrated value of Y _H signals, rapid imaging situations be able to.

In the apparatus of the embodiment described in this specification, the integrated data of the color signals of all the divided areas is taken in in the normal white balance correction state, but in the normal white balance correction state. In addition, if the data is evenly distributed over the entire screen, only the integration data of a part of the area may be extracted, and if there is a sudden change in the imaging situation, the integration data may be acquired from a smaller number of specific areas. It is possible.

[0039]

As described above, according to the image pickup apparatus of the present invention, by providing the white balance correction mode in which only the color information of a part of the plurality of areas can be used,
Since white balance correction can be performed at high speed even when there is a sudden change in the situation, it is no longer necessary to take an image without white balance for a long time even when there is a sudden change in the photography situation. In addition, since the color information from many areas is normally used, highly accurate white balance correction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image pickup apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining an operation according to detection of a situation change in the image pickup apparatus of FIG.

FIG. 3 is a diagram showing an example of a specific area for capturing integration data in the image pickup apparatus of FIG.

FIG. 4 is a diagram showing an example of a sequence of capturing integration data of each signal in a specific area shown in FIG.

FIG. 5 is a diagram showing another example of a specific region in which integrated data is captured in the image pickup apparatus of FIG.

FIG. 6 is a diagram showing an example of an order in which integrated data of each signal in the specific area shown in FIG. 5 is fetched.

FIG. 7 is a block diagram showing a main configuration of a conventional image pickup apparatus that performs white balance correction using a white extraction method.

8A and 8B are diagrams for explaining division areas in the apparatus of FIG. 7 and the timing of capturing data from them.

9 is a diagram for explaining the order of capturing data from divided areas in the apparatus of FIG.

[Explanation of symbols]

 1 Image sensor 2 Luminance chromaticity signal generation circuit 3,4 Gain control circuit 5 Color difference signal generation circuit 30, 31, 32 Analog-digital converter 33, 34, 35 Switch circuit 36, 37, 38 Adder 39, 40, 41 Holding circuit 42 Correction signal calculation unit 43, 44 Digital-analog converter 45 Synchronization signal generation circuit 50 State change detection unit 51 Iris position detector 52 External input circuit

Claims (6)

[Claims] 1. An image pickup means and each of a plurality of areas in a photographing screen of the image pickup means,
A detecting means for detecting color information from the color video signal; and a white balance correcting means for correcting the white balance of the color video signal output from the output of the imaging means by using the color information output by the detecting means. The mode of the white balance correction means is a first mode in which the color information of all of the plurality of areas can be used and a second mode in which only the color information of a part of the plurality of areas can be used. An image pickup apparatus comprising: a switching unit that switches between the two. 2. The image pickup device according to claim 1, wherein the partial area in which the color information usable in the second mode is detected is a predetermined area in the plurality of areas. apparatus. 3. The correction speed in the second mode is the first speed.
2. The image pickup apparatus according to claim 1, wherein the correction speed is faster than the correction speed in the correction mode. 4. The switching means switches the white balance correction means from the first mode to the second mode when the luminance level of the color video signal changes. The image pickup apparatus according to item 1. 5. The switching means includes means for determining a change in color temperature using color information of the plurality of areas, and the white balance correction is performed when the change in color temperature is determined by the determining means. 2. The image pickup apparatus according to claim 1, wherein the means is switched from the first mode to the second mode. 6. The switching means switches the white balance correction means from the second mode to the first mode as the second mode continues for a predetermined period. Imaging device.