JP3250676B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order. INDUSTRIAL APPLICATIONS Conventional Technology Problems to be Solved by the Invention (FIGS. 9 to 11) Means for Solving the Problems (FIG. 5) Function (FIG. 5) Example (1) Overall Configuration (FIG. 1) ( 2) Digital signal processing circuit (FIG. 2) (3) White balance adjustment (FIGS. 3 and 4) (3-1) Determination of white area (FIGS. 4 to 6) (3-2) Gate signal generation circuit ( (FIGS. 4 and 7) (3-3) Level detection circuit (FIG. 8) (4) Effects of embodiment (5) Other embodiments Effects of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus and can be applied to, for example, a television camera.

[0003]

2. Description of the Related Art Conventionally, in this type of imaging apparatus, white balance is adjusted by adjusting the amplification factor of each color signal based on the imaging result.

That is, in a white balance circuit, a peak level of a luminance signal is detected in a predetermined effective area, and a white balance adjustment area is set based on the peak level. Further, the white balance circuit detects a signal level difference between the red signal and the blue signal with respect to the green signal in the white balance adjustment area, and corrects the amplification factor of each color signal so that the signal level difference becomes zero level. I do.

That is, a portion having the highest luminance level in the image screen can be determined to be a white portion. In this case, a portion having a signal level close to the luminance level can also be considered as a white portion. Thus, the white balance circuit corrects the amplification factor of each color signal so that the white balance adjustment region is displayed in white, and performs white balance adjustment.

[0006]

However, as described above,
When white balance adjustment is performed by setting the white balance adjustment area, it is necessary to set the white balance adjustment area to 10
An area of about [%] is required.

On the other hand, when the peak level is detected to set the white balance adjustment region, as shown in FIG. 9, when the fluorescent lamp K1 or the like exists in the effective area AR of the imaging screen M, this fluorescent lamp K1 may be erroneously set in the white balance adjustment area.

Further, as shown in FIG. 10, even when light is reflected on white paper or the like prepared for white balance adjustment and a portion K2 having a high luminance level is generated, this portion is similarly adjusted for white balance. There is a risk of incorrectly setting the area. That is, in the conventional image pickup apparatus, there is a problem that the white balance cannot be reliably adjusted when the white balance adjustment area is narrow as described above, or when there is a part where the luminance level is extremely large.

FIG. 1 shows one method of solving this problem.
As shown in FIG. 1, when a white balance adjustment area is detected, there is a method of calling a photographer's attention by displaying a hatched pattern in this area. However, in this method, the cameraman must determine whether the white balance has been correctly adjusted simply by simply displaying the white balance adjustment area, and there is still a practically insufficient problem.

The present invention has been made in view of the above points, and it is an object of the present invention to propose an image pickup apparatus capable of easily and reliably adjusting a white balance.

[0011]

In order to solve this problem, in the present invention, a desired subject is imaged to obtain an image signal S1, and an image pickup apparatus 1 that outputs the image signal S1 generates the image signal S1 from the image signal S1. The luminance signal ADY is sequentially compared with predetermined reference levels L0 to L2 to obtain a frequency distribution of the luminance signal ADY in units of the reference levels L0 to L2, and the luminance level of the luminance signal ADY is changed. A histogram generation circuit 59 for generating a reference histogram, a maximum value detection circuit 64 for detecting the reference levels PK and LOW having the largest frequency distribution based on the detection results A0 to A3 of the history graph generation circuit 59;
65 and detection results PK, L of the maximum value detection circuits 64, 65
An area setting circuit 68 for setting, based on OW, an area distributed among the reference levels PK and LOW having the largest frequency distribution among the luminance signals ADY as a white balance adjustment area;
A white balance adjustment circuit 90 for detecting the signal level of the image pickup signal S1 and adjusting the white balance of the image pickup signal S1 is provided for the white balance adjustment area.

Further, in the present invention, the histograph creation circuit 59 includes a plurality of comparison circuits 62 for outputting a comparison result for each of the reference levels L0 to L2 for each pixel of the luminance signal ADY.
A to 62D and a plurality of counter circuits 63A to 63D for respectively counting the comparison results of the comparison circuits 62A to 62D.
And

Further, in the present invention, the white balance adjusting circuit 90 adjusts the white balance of a predetermined area set in the captured image of the image signal S1 and an area overlapping the white balance adjustment area.

[0014]

[Function] Reference level PK, LOW with largest frequency distribution
Is detected, and based on the detection results PK and LOW, the reference level P having the largest frequency distribution among the luminance signals ADY is detected.
If the area distributed in K and LOW is set as the white balance adjustment area, the white area can be reliably detected and selected as the white balance adjustment area.

Further, a comparison result is obtained for each reference level L0 to L2 for each pixel of the luminance signal ADY, and the comparison results are counted by the counter circuits 63A to 63D, respectively.
The white area can be easily detected.

Further, the white balance is adjusted for a white area in the effective screen by adjusting the white balance of a predetermined area set in the captured image of the image signal S1 and an area overlapping with the white balance adjustment area. can do.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

(1) Overall Configuration In FIG. 1, reference numeral 1 denotes an imaging apparatus as a whole, which drives a solid-state imaging device (CCD) 2 to image a desired subject.

That is, the image pickup apparatus 1 generates a reference signal with the timing generator (TG) 4 and drives the solid-state image pickup device 2 with the reference signal. The imaging apparatus 1 arranges a stop 6 and a zoom lens 8 in front of the solid-state imaging device 2, thereby forming an image of a subject on the imaging surface of the solid-state imaging device 2 at a desired magnification and brightness.

At this time, the central processing unit (CPU) 10
Detects the magnification of the captured image with the zoom position detection circuit 12, and switches the control of the aperture 6 based on the detection result.
Thereby, even when the magnification changes, the subject can be imaged with the brightness desired by the user.

Further, the image pickup apparatus 1 samples and holds an output signal of the solid-state image pickup element 2 by a sample / hold circuit (S / H) 14 by applying a correlated double sampling technique.
The resulting image signal S1 is transmitted to the AV block circuit 16
Output to

The AV block circuit 16 generates each color signal from the image pickup signal S1, amplifies it at a predetermined amplification rate, and corrects the signal level of each color signal at this time, so that shading correction and the like can be performed. Further, by switching the amplification rate, white balance adjustment and gain up adjustment can be performed.

Analog digital conversion circuit (A / D) 1
8 is a color signal SR output from the AV block circuit 16.
To SB are converted into digital signals and output.

The digital signal processing circuit 20 detects a signal level of each of the color signals SR to SB by a predetermined detection circuit, thereby adjusting a black set, a black balance, a white balance, an aperture, and a flare correction. And outputs the detection result to the central processing unit 10 as necessary. Thus, in the image pickup apparatus 1, by controlling each signal processing circuit in the central processing unit 10 based on the data detection result, white balance adjustment and the like can be performed.

Further, the digital signal processing circuit 20 corrects the signal level of each color signal based on the data detection result, thereby performing flare correction and generates a correction signal SH for shading correction, and generates the correction signal SH. A via a digital / analog conversion circuit (D / A) 22
Output to the V block circuit 16. Thereby, the imaging device 1
In, shading correction is performed using the correction signal SH generated by the digital signal processing circuit 20.

The video processing circuit 24 receives the color signal processed by the digital signal processing circuit 20, performs gamma processing and knee processing, and sets a pedestal level. The following encoder circuit 26 converts each color signal into a luminance signal and a color difference signal, and then converts it into a video signal and outputs it.

Thus, the image pickup apparatus 1 can pick up a desired subject and output the video signal SV.

(2) Digital Signal Processing Circuit As shown in FIG. 2, the digital signal processing circuit 20 generates various test signals by a test signal generation circuit 30 and selects selectors 32R, 32G, 32B and 34R, 34G, 3G.
4B. At this time, the test signal is switched based on the output signal of the central processing unit 10. Thus, the digital signal processing circuit 20 can adjust the AV block and the like using various test signals in the adjustment mode, and can confirm the entire operation in the self-diagnosis mode.

Further, the digital signal processing circuit 20 supplies the respective color signals SR to SB, which are digital signals, to the clamp level detecting circuit 36, and detects the signal levels of the respective color signals SR to SB at a predetermined timing. Further, the digital signal processing circuit 20 outputs this signal level detection result to a clamp circuit (not shown), thereby setting the clamp level of each of the color signals SR to SB.

In the normal operation mode, the selectors 32R to 32B select the respective color signals SR to SB and output the signals to the defect correction circuit 38. In the self-diagnosis mode, the selectors 32R to 32B switch the contacts at a predetermined timing. , The color signal SR during one horizontal scanning period of the vertical blanking period.
And selectively outputs a test signal instead of SB. On the other hand, in the adjustment mode, the selectors 32R to 32B are controlled by the central processing unit 10 to switch the contacts at a predetermined timing according to each adjustment item. Various test signals are output in place of .about.SB, so that various adjustments can be easily performed.

The automatic defect detection circuit 40 detects a defective pixel of the solid-state imaging device 2 by continuously monitoring the signal level of each color signal, and stores the position of the defective pixel in a predetermined memory circuit. The defect correction circuit 38 performs an interpolation operation at the position of the defective pixel according to the contents of the memory circuit. Thereby, the defect correction circuit 38 generates a color signal for correction from the surrounding pixels for the defective pixel, and replaces the color signal of the defective pixel with the generated color signal. Thereby, the defect correction circuit 38 is designed so that the image quality is not significantly deteriorated even when a defect occurs in the solid-state imaging device 2.

The addition circuits 42R to 42B add the flare correction signal output from the flare correction circuit 44 to each color signal, thereby correcting the flare of the captured image. The flare correction circuit 44 generates a flare correction signal based on the calculation result of the central processing unit 10, so that the image pickup apparatus 1 can perform flare correction by a simple adjustment operation.

The selectors 46R-46B are provided with an adder 42
The output signals of R to 42B are output to the subsequent video processing circuit 24. At this time, when the signal level of the selection signal SEL1 switches, the signal level of the output signal falls to 0 level by switching the contacts. Thereby, the imaging device 1
In, the input level of the video processing circuit 24 is lowered to 0 level as needed in the adjustment mode or the like, so that the circuit blocks after the video processing circuit 24 can be easily adjusted.

The low-pass filter circuit (LPF) 48
The color signal output from the defect correction circuit 38 is output after suppressing noise components by suppressing high frequency components. The shading correction circuits 50 and 52 generate the shading correction signals SH1 and SH2 based on the output signal of the low-pass filter circuit 48, and in this embodiment, the shading correction signals SH1 and SH2, respectively.
Corrects the shading of the black level and the white level.

At this time, the shading correction circuit 52
Based on the operation result D1 of the central processing unit 10, a correction signal SH2 for shading correction is created from each color signal. Thus, the digital signal processing circuit 20 returns the shading correction signals SH1 and SH2 to the AV block circuit 16 to perform shading correction. At this time, the shading correction circuit 50 outputs the correction signal SH1 via the selectors 34R to 34B. When the selection signal SEL2 rises, the selectors 34R to 34B selectively output the test signal instead of the correction signal SH1. As a result, in the image pickup apparatus 1, the shading correction signal SH1 and the test signal are selectively output as required, and the adjustment work of the AV block circuit 16 and the like can be simplified.

The data detection circuit 54 detects flare correction and white balance adjustment data by detecting the signal level and the like of the output signal of the low-pass filter circuit 48. The data detection circuit 54 stores the detection result data in the memory circuit of the defect detection circuit 38 with respect to the data for the aperture adjustment. The contents of this memory circuit are accessed from the central processing unit 10 and easily. The aperture can be adjusted.

(3) Adjustment of White Balance As shown in FIG. 3, the data detection circuit 48 controls the predetermined gate signal GT1 in the white balance adjustment mode.
Is generated, and the signal level of each of the color signals SR to SB is detected in an area determined by the gate signal GT1, and the white balance is adjusted.

That is, in the data detection circuit 48,
The detection window generation circuit 57 generates the gate signal WHGT whose signal level rises in the effective display area of the captured image, whereas the white area determination circuit 58 detects the white area of the captured image.

As shown in FIG. 4, in the data detection circuit 48, in order to detect this white area, the frequency distribution of the luminance signal is determined with reference to the luminance level, and the histogram creation circuit 59 is used.
And a histogram is created based on the luminance level. Further, the data detection circuit 48 outputs the histogram creation result to the area determination circuit 60, and obtains a predetermined reference value and a comparison result for the largest frequency, and obtains the area of the region in the captured image represented by this frequency. Is greater than or equal to a predetermined value.

That is, for example, the area K1 (FIG. 9) such as a fluorescent lamp and the area K2 (FIG. 10) where light is reflected have a high brightness level but a small area. Therefore, if the region having the highest frequency is detected, such regions K1 and K2 can be excluded.

Further, by judging whether or not the area of the region having the largest frequency is equal to or larger than a predetermined value, it is possible to judge whether or not a region sufficient for white balance adjustment can be secured. Therefore, the white balance can be easily and reliably adjusted by determining this area as a white area based on the determination result and adjusting the white balance.

Thus, in the area determination circuit 60,
When the region having the largest frequency is equal to or larger than the predetermined reference value, it is determined that a sufficient area has been obtained as a white region, and a control signal for generating a gate signal is output to the gate signal generation circuit 68.

On the other hand, the level judging circuit 61 determines, for the largest frequency, the luminance level P serving as the reference.
K and LOW are output to the gate signal generation circuit 68. Thus, the white area determination circuit 58 detects the area having the largest frequency distribution with reference to the luminance level, determines this area as a white area, and outputs a detection result.

At this time, when this region is smaller than a predetermined area,
In the white area determination circuit 58, the generation of the gate signal GT1 is stopped and controlled, and a predetermined message is displayed.
This prevents erroneous adjustment of the white balance.

In the gate signal generation circuit 68, the gate signal WHGT and the reference levels PK and LOW are used as references, within a predetermined effective area and within the white area detected by the white area determination circuit 58. Generates a gate signal GT1 whose signal level rises, so that the image pickup apparatus 1 adjusts the white balance in an area determined by the gate signal GT1.

Thus, the data detection circuit 48 selects a white balance adjustment region based on the frequency distribution detection result, and can surely perform white balance adjustment.

(3-1) Judgment of White Area As shown in FIG. 5, in the white area judgment circuit 58, the luminance signal ADY is input to the comparison circuits 62A to 62D, where the luminance signal ADY is compared with a predetermined reference level. The comparison result is detected sequentially.
Here, in the first comparison circuit 62A, a level L0 smaller than the luminance level of 100 [%] by a predetermined level is set as the reference level (FIG. 4A), and the luminance level is larger than the reference level L0. The signal level of the output signal is raised for the image data (that is, a luminance signal).

On the other hand, in the second comparison circuit 62B, in addition to the first reference level L0, a level L1 smaller than the reference level L0 by a predetermined level is set as the reference level. The signal level of the output signal is raised for the image data between the reference levels L0 and L1.
Similarly, in the third and fourth comparison circuits 62C and 62D, the third reference level L2 is selected, whereby the third reference level L2 is selected between the second and third reference levels L1 and L2, respectively.
The signal level of the output signal is raised for image data below the reference level L2.

The counter circuits 63A to 63D count the rising of the signal level for the output signals of the comparison circuits 62A to 62D, respectively. Thereby, as shown in FIG. 6, in the white area determination circuit 58, the reference level L
A histogram is created by detecting the frequency distribution of the luminance signal based on 0 to L3. On the other hand, the area determination circuit 60 and the level determination circuit 61 are formed by the maximum value detection circuit 64, the level gate setting circuit 65, and the central processing unit 10, and the maximum value detection circuit 64 detects the frequency having the largest value.

That is, the maximum value detection circuit 64 supplies the frequency detection results A0 and A1 and A2 and A3 to the comparison circuits 66A and 66B, respectively, where the comparison results S0 and S1 are detected. Further, the maximum value detection circuit 64 supplies the detection results S0 and S1 to the selectors 67A and 67B, whereby the selector 67A selects and outputs a frequency detection result having a large value from the frequency detection results A0 and A1, 67B selectively outputs a frequency detection result having a large value from the frequency detection results A2 and A3.

The comparison circuit 66C obtains the comparison result S2 with respect to the selected outputs of the selectors 67A and 67B, and the selector 67C switches the contacts based on the comparison result S2 to obtain the maximum value from the frequency detection results A0 to A3. Is detected and output. The central processing unit 10 determines whether or not the detection result is equal to or greater than a predetermined reference value. When the area of this area is equal to or less than 10% of the effective screen, a predetermined message is displayed to correct the white balance. Prevent adjustment before it happens.

On the other hand, the selector 69 is provided with the comparing circuit 6
On the basis of the comparison result S2 of FIG.
6B, and selectively outputs the comparison results S0 and S1.
1 outputs a switching signal to the selector 73 based on the selected output. In response to this switching signal, the selector 73 changes the reference levels PK and LOW used as the area determination reference for the area having the largest frequency to the reference level L.
Selective output from 0 to L2.

This selected output is output to the gate signal generation circuit 68 via the central processing unit 10, whereby the white balance adjustment region is selected with reference to the reference levels PK and LOW, and thus the level gate setting circuit 6
Reference numeral 5 is for generating a reference level required for selecting a white balance adjustment area.

(3-2) Gate Signal Generation Circuit Further, in the white balance adjustment mode, the data detection circuit 54 sets a white balance adjustment region by the gate signal generation circuit 68 shown in FIG. Here, the gate signal generation circuit 68 can generate various reference signals in accordance with the operation mode of the imaging device 1. In the white balance adjustment mode, the gate signal generation circuit 68 uses the signal level of the luminance signal ADY as a reference. GT1 is output, and a white balance adjustment region is thereby set.

That is, the gate signal generation circuit 68 supplies the luminance signal ADY to the comparison circuits 70 and 72, and outputs a comparison result based on predetermined comparison references PK and LOW. Here, the comparison references PK and LOW are set based on the output data of the central processing unit 10, and in the white balance adjustment mode,
Reference level P selected by level / gate setting circuit 65
K and LOW are set.

As a result, the comparison circuits 70 and 72 detect an area of the luminance level within the range of the reference levels PK and LOW, and output the detection result as the level gate LVGT.

Further, in the gate signal generating circuit 68, a vertical synchronizing signal VD is supplied to the V counter 74, and a horizontal synchronizing signal HD is supplied to the V counter 74 and the H counter 76.

After resetting the count value by the vertical synchronizing signal VD, the V counter 74 sequentially counts the horizontal synchronizing signal HD, thereby outputting a count value indicating a raster scanning position in the vertical scanning direction. On the other hand, after resetting the count value by the horizontal synchronizing signal HD, the H counter 76 sequentially counts predetermined clock signals, and thereby outputs a count value representing a raster scanning position in the horizontal scanning direction.

The comparison circuit 78 raises the signal level of the output signal when the count value of the V counter 74 falls within the range of the two comparison references UP and DWN based on the two comparison references UP and DWN. As a result, a gate signal whose signal level rises at a predetermined raster scanning position in the vertical scanning direction is generated. Similarly, the comparison circuit 80
When the count value of the H counter 76 falls within the range of the two comparison references LFT and RGT with reference to the two comparison references LFT and RGT, the signal level of the output signal rises. A gate signal whose signal level rises at the raster scanning position is generated.

Thus, the gate signal generation circuit 68 generates various gate signals WHGT whose signal level rises in a predetermined area of the captured image. Here, in the white bunrath adjustment mode, the gate signal WHGT rises in the effective area of the captured image.

The comparison reference U of the comparison circuits 78 and 80
P, DWN and LFT, RGT are the central processing unit 1.
Thus, the gate signal generation circuit 68 can switch the timing of the gate signal WHGT in accordance with the operation mode.

The selector 82 switches its operation based on the control signals ARE0 to ARE2 output from the central processing unit 10, and in the self-diagnosis mode or the like, the gate signal WHGT or blanking output from the comparison circuit 78 and / or 80. While selectively outputting the signal BLK, in the white balance adjustment mode, the logical sum signal of the gate signal WHGT and the level gate LVGT is output.

Thus, in the gate signal generation circuit 68, the gate LVGT (FIG. 4) such that the signal level rises when the luminance level is between the reference levels PK and LOW.
(B)), and the OR signal of the gate signal WHGT and the level gate LVGT is applied to the gate signal GT1 (FIG. 4).
(C)) to set a white balance adjustment area.

Thus, by setting the white balance adjustment region except for the portion where the luminance level rises sharply, the white balance can be adjusted except for the portion where the illumination is reflected, and the white balance can be easily and reliably adjusted. Can be.

In this embodiment, the gate signal generation circuit 68 outputs the selection output of the selector 82 to the gate circuit 86
In response to the mode switching signals MSL0 to MSL2 output from the central processing unit 10, first and second gate signals CLR and LC are output from the selected output.
H is generated. This allows the gate signal generation circuit 68 to selectively use the gate signals CLR and LCH in accordance with the operation mode, simplify the adjustment work, and check the operation mode and the like.

(3-3) Level Detection Circuit As shown in FIG. 8, the level detection circuit 90
Various signals are detected on the basis of T1. In the white balance adjustment mode, a signal level difference between a red signal and a blue signal with respect to a green signal is detected. That is, the level detection circuit 90 outputs the color signals SR
To SB to the selector 92, and outputs the selection signal via the latch circuit 94.

Here, the selector 92 switches the contacts based on the control signal output from the central processing unit 10, thereby switching the contacts of the selector 92 in this embodiment to detect the signal levels of the respective color signals SR to SB. It is made to be able to do. Thereby, the selector 92
In the white balance adjustment mode, the contacts are switched in units of fields, and the red signal SR and the blue signal SB are alternately selected and output in units of fields.

The selector 92 outputs the color signals SR to S
In addition to B, an output signal of the counter circuit 96 is input, so that a reference signal whose signal level switches every three frames can be selectively output instead of the color signals SR to SB. The gate circuit 96 outputs the selected output of the selector 92 to the latch circuit 98 during the period during which the signal level of the gate signal GT1 rises, and thereby, in the white balance adjustment mode, the red and blue color signals SR and SR of the white balance adjustment area. Selectively output SB.

On the other hand, the gate circuit 100 receives the green signal SG via the latch circuit 102 and selectively outputs the green signal SG to the latch circuit 104 during a period in which the signal level of the gate signal GT1 rises. . As a result, the level detection circuit 90 cuts out the white balance adjustment region for each of the color signals SR to SB with reference to the gate signal GT1, and outputs the white balance adjustment region.

The subtraction circuit 106 is connected to the selector 10
The output signals of the latch circuits 98 and 104 are received via the output circuits 8 and 110, and the subtraction output is output to the addition circuit 112. As a result, in the white balance adjustment mode,
The level detection circuit 90 alternately outputs a first subtraction signal obtained by subtracting a green signal from a red signal and a first subtraction signal obtained by subtracting a green signal from a blue signal in a field cycle. It has been made to be.

In the level detecting circuit 90, the output of the selector 110 is lowered to 0 level in accordance with the operation mode, thereby stopping and controlling the subtraction processing of the subtracting circuit 106, for example, detecting data for black level adjustment. It is made to be able to do. Similarly, in the level detection circuit 90, a predetermined subtraction output is input to the selector 108 in addition to the output signal of the latch circuit 98, whereby the contact point of the selector 108 is switched to detect the signal level of the subtraction output. It is made to be able to do.

The addition circuit 112 receives the output signal of the subtraction circuit 112 and sends an output signal to a latch circuit 116 via an AND circuit 114.
Is fed back as an addition input. Here, in the AND circuit 114, in the white balance adjustment mode, the clear signal CLR is input in synchronization with the vertical synchronizing signal, whereby the adding circuit 112 accumulates the output signal of the selector 108 in the field cycle. It is made to add. As a result, in the level detection circuit 90, the signal level difference between the red and blue color signals with respect to the green color signal in the white balance adjustment region is cumulatively added in the field cycle via the latch circuit 116.

The selectors 118 and 120 switch the contacts in the field cycle, respectively, and latch the accumulated addition results of the latch circuit 116 in the subsequent latch circuits 122 and 124 in the field cycle, respectively. As a result, in the level detection circuit 90, the signal level differences between the red and blue color signals with respect to the green color signal in the white balance adjustment area are cumulatively added, and the addition results are latched to latch circuits 122 and 124, respectively. Output to

Thus, in the imaging apparatus 1, the white balance is adjusted so that the cumulative addition result becomes the zero level, and the white balance adjustment area is selected based on the frequency distribution result. The balance can be adjusted.

In some cases, the clear signal CLR input to the AND circuit 114 is repeatedly input within one field. In this case, the cumulative addition results obtained based on each timing are used as latch circuits 122 and 124, respectively. Thus, the signal level of each color signal can be individually detected, for example, in the video period and the vertical blanking period. Thus, the imaging device 1 can monitor the operation state by inserting the test signal during the vertical blanking period.

(4) Effects of the Embodiment According to the above configuration, the frequency distribution result of the luminance signal is obtained based on the predetermined luminance level, and the area having the highest frequency is set as the white balance adjustment area. Thus, even when a part having a high luminance level exists in the captured image, the white balance can be adjusted by excluding this part, and thus the white balance can be easily and reliably adjusted.

(5) Other Embodiments In the above-described embodiment, a case has been described in which the operation of the data detection circuit 54 is switched to detect the white balance adjustment region. However, the present invention is not limited to this, and the present invention is not limited to this. May be used to detect the white balance adjustment region.

Further, in the above-described embodiment, the case has been described where it is determined that the white balance has been correctly adjusted when the white balance adjustment area is 10% or more of the entire effective screen. However, the present invention is not limited to this. This criterion can be set to various values as needed.

Further, in the above-described embodiment, the case where the white balance is adjusted with reference to the signal level of the green signal has been described. However, the present invention is not limited to this, and the white level is adjusted by setting each color signal to a predetermined reference level. It can be widely applied to balance adjustment.

Further, in the above-described embodiment, the case where the signal level difference of the color signal is detected before the gamma correction and the white balance is adjusted based on the signal level difference has been described. However, the present invention is not limited to this. After gamma correction, the present invention can be widely applied to a case where a signal level difference between color signals is detected and white balance is adjusted based on the signal level difference.

[0081]

As described above, according to the present invention, the frequency distribution of a luminance signal is detected on the basis of a predetermined luminance level, and the white balance is adjusted on the basis of the region having the largest frequency. Even when there is a portion where the luminance level rises sharply, the white balance can be easily and reliably adjusted.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the digital signal processing circuit.

FIG. 3 is a block diagram for explaining the white balance adjustment.

FIG. 4 is a signal waveform diagram for explaining generation of the gate signal.

FIG. 5 is a block diagram for explaining a white area determination.

FIG. 6 is a characteristic curve diagram showing a histogram.

FIG. 7 is a block diagram showing a gate signal generation circuit.

FIG. 8 is a block diagram showing a level detection circuit.

FIG. 9 is a schematic diagram for explaining erroneous adjustment of white balance.

FIG. 10 is a schematic diagram for explaining erroneous adjustment of white balance when a part with a high luminance level exists.

FIG. 11 is a schematic diagram illustrating display of a white balance adjustment area.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Imaging device, 2 ... Solid-state imaging device, 10 ... Central processing unit, 16 ... VA block, 20 ... Digital signal processing circuit, 54 ... Data detection circuit, 59 ... Histogram creation circuit, 60 ... ... area determination circuit, 61 ...
Level determination circuit 68 gate signal generation circuit.

Claims (3)

(57) [Claims] 1. An image pickup apparatus for picking up an image of a desired subject to obtain an image pickup signal and outputting the image pickup signal, wherein a luminance signal generated from the image pickup signal is sequentially compared with a predetermined reference level. By detecting a frequency distribution of the luminance signal in units of the reference level and generating a histogram based on the luminance level, a histogram generation circuit, based on a detection result of the histogram generation circuit, A maximum value detection circuit that detects the reference level having a large value, and, based on the detection result of the maximum value detection circuit, an area of the luminance signal that is distributed at the reference level having the largest frequency distribution is defined as a white balance adjustment area. Detecting a signal level of the imaging signal with respect to the area setting circuit to be set and the white balance adjustment area; An imaging apparatus comprising: a white balance adjustment circuit that adjusts a white balance of a signal. A plurality of comparison circuits for outputting the comparison result for each of the reference levels for each pixel of the luminance signal; and a plurality of counter circuits for counting the comparison results of the comparison circuit. The imaging device according to claim 1, comprising: 3. The white balance adjustment circuit according to claim 1, further comprising a white balance adjustment circuit that adjusts a white balance in a predetermined area in the captured image of the imaging signal and an area overlapping the white balance adjustment area. The imaging device according to claim 1 or 2, wherein