JP3252979B2 - 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 APPLICATION FIELD Conventional technology Problems to be solved by the invention (FIGS. 10 to 12) Means for solving the problems (FIGS. 1 to 9) Operation (FIGS. 1 to 9) Example (1) Overall Configuration (FIG. 1) (2) Digital signal processing circuit (FIG. 2) (3) White balance adjustment (3-1) Peak level detection circuit (FIGS. 3 and 4) (3-2) Gate signal generation circuit (FIG. (5 and FIG. 6) (3-3) Level detection circuit (FIG. 7) (3-4) Central processing unit (FIGS. 8 and 9) (4) Effects of the 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 area, as shown in FIG. 10, when the fluorescent lamp K1 or the like exists in the effective area AR of the image pickup screen M, this fluorescent lamp is used. K1 may be erroneously set in the white balance adjustment area.

Further, as shown in FIG. 11, 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. 2, when a white balance adjustment area is detected, there is a method of calling a cameraman's attention by displaying a hatched pattern in this area. However, in this method, the cameraman must determine whether or not the white balance has been 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]

According to the present invention, in order to solve the above-mentioned problems, a luminance signal ADY generated from imaging signals SR, SG, and SB obtained by imaging an object in an imaging apparatus is provided. A peak level detection circuit 10 for detecting a peak level PK of ADY,
56, a gate setting circuit 10 for setting gates PK1 to PK3, LOW1 to LOW3 within a predetermined level range with the peak level as a PK reference, and gates PK1 to PK3, LO
Area setting circuits 10, 68 for detecting the signal level of the luminance signal ADY within the level range of W1 to LOW3 and setting the white balance adjustment area GT1 based on the detection result.
And white balance adjustment circuits 16 and 90 for performing white balance adjustment in the white balance adjustment area GT1, and the gate setting circuit 10 includes the area setting circuits 10 and 68.
When the size of the white balance adjustment area GT1 set by the above is equal to or smaller than a predetermined value, the gates PK1 to PK3,
The set level range of LOW1 to LOW3 is reduced.

[0012]

When the size of the white balance adjustment area GT1 set by the area setting circuits 10 and 68 is equal to or smaller than a predetermined value, the setting levels of the gates PK1 to PK3 and LOW1 to LOW3 are lowered, so that the fluorescent lamps Such a harmful portion can be excluded to set the white balance adjustment region, and thereby the white balance can be adjusted simply and reliably.

[0013]

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 the output signal of the solid-state image pickup element 2 by a sample / hold circuit (S / H) 14 by applying the correlated double sampling technique.
The resulting imaging signal S1 is converted to a VA block circuit 16
Output to

The VA block circuit 16 generates each color signal from the image pickup signal S1 and amplifies it at a predetermined amplification factor. At this time, the signal level of each color signal is corrected 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 VA 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 also generates a correction signal SH for shading correction, and generates this correction signal SH. V via a digital / analog conversion circuit (D / A) 22
Output to the A 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 an image of 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 generating 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 VA 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 detection circuit 36, where the signal levels of the respective color signals SR to SB are detected 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.

The selectors 32R to 32B select the respective color signals SR to SB in the normal operation mode and output the signals to the defect correction circuit 38. In the self-diagnosis mode, the selectors 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 circuit 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 feeds back the shading correction signals SH1 and SH2 to the VA block circuit 16 to perform shading correction.

At this time, the shading correction circuit 50
The correction signal SH1 is output via the selectors 34R-34B, and the selectors 34R-34B select and output the test signal instead of the correction signal SH1 when the selection signal SEL2 rises. 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 VA 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 (3-1) Peak Level Detection Circuit As shown in FIG. 3, the data detection circuit 54 operates in the peak balance detection circuit 5 in the white balance adjustment mode.
In step 6, a peak level is detected, and a white balance adjustment region is set based on the peak level detection result. That is, in the peak level detection circuit 56, the arithmetic circuit 58
Is 1/4 by adding the signal levels of the respective color signals SR to SB.
, A luminance signal ADY is approximately generated from the color signals SR to SB, and the luminance signal ADY is output to the peak detection circuit 62 via the selector 60.

The selector 60 selectively outputs a luminance signal ADY with reference to a window signal WHEN generated by a predetermined reference signal generation circuit, whereby a predetermined effective detection area excluding a peripheral portion of a captured image is obtained. (Corresponding to the area indicated by the symbol AR in FIG. 10).
Y is output to a low-pass filter circuit (LPF) 61.

The low-pass filter circuit 61 outputs the luminance signal A
By suppressing the high-frequency component of DY, the luminance level of a portion where the luminance level rapidly rises in the horizontal scanning direction is suppressed and output. That is, as shown in FIG. 4, in a portion such as a portion K2 (FIG. 11) where the illumination is reflected, the luminance level sharply rises in the horizontal scanning direction.

As described above, the peak level of the portion where the signal level rapidly rises in the horizontal scanning direction can be easily suppressed through the low-pass filter circuit as shown by the broken line. As a result, the peak level detection circuit 56 detects the peak level by excluding such a portion where the luminance level rises sharply, thereby enabling simple and reliable white balance adjustment.

In the low-pass filter circuit 61, the control signal ND output from the central processing unit 10 is used.
The operation is switched based on R, whereby in the operation modes other than the white balance adjustment mode, the frequency characteristics are switched and the operation is stopped as necessary.

The peak detection circuit 62 detects a peak level from the luminance signal ADY input via the low-pass filter circuit 61 and latches the detection result to a latch circuit (L) 66 via a selector 64. Thus, the peak detection circuit 56 detects the peak level of the luminance signal in the effective detection area, and stores the detection result in the latch circuit 66.

In this embodiment, the peak level detection circuit 56 detects the peak level of the color signal in another adjustment mode.
0 selects a num signal NMY (that is, a signal obtained by selecting a color signal having the highest signal level at each timing from each color signal consisting of a digital signal) instead of the output signal of the arithmetic circuit 58 as necessary. It is made to be able to output.

In response to this, the latch circuit 66 feeds back the output signal via the selector 64, whereby the selector 64 can be switched as necessary to update the latched data. I have.

(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,
While the first comparison reference PK is set based on the peak level detected by the peak level detection circuit 56,
A level lower than the first comparison reference PK by a predetermined level is set as a second comparison reference LOW.

As a result, in the comparison circuits 70 and 72, an area of the luminance level within the range from the first to the second comparison reference is detected, and this detection result is output as the level gate LVGT. Thus, in the gate signal generation circuit 68, the first and second comparison references PK
And LOW, various gate signals LVGT can be generated based on the signal level of the luminance signal ADY.

Further, in the gate signal generation 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 with the vertical synchronizing signal VD, the V counter 74 sequentially counts the horizontal synchronizing signal HD, thereby outputting a count value representing 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, 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 a 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 level gate LVGT is selectively output.

As a result, as shown in FIG. 6, in the gate signal generation circuit 68, the luminance signal ADY (FIG.
When the signal level of (A) rises sharply, a level gate is generated so that the signal level rises except for the sharp rising portion, and in the white balance adjustment mode, this level gate LVGT is applied to the gate signal GT1. (FIG. 6 (B)) is selected and output, whereby a white balance adjustment area is set.

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 selected 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. 7, 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 when the signal level of the gate signal GT1 rises, thereby selecting the color signals SR and SB in the white balance adjustment area in the white balance adjustment mode. Output.

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 and outputs it.

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 detection circuit 90, the output of the selector 110 falls to the 0 level in accordance with the operation mode, thereby stopping and controlling the subtraction processing of the subtraction circuit 106, for example, detecting data for black level adjustment. Have been made to gain. 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 the latch circuit 116 via the 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.

Thus, 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 area is cumulatively added in the field cycle via the latch circuit 116. . The selectors 118 and 120 switch the contacts at the field cycle, respectively, and thereby latch the cumulative addition results of the latch circuit 116 at the subsequent latch circuits 122 and 124 at the field cycle.

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 area is cumulatively added,
The addition results are latched to latch circuits 122 and 124, respectively, and output to the central processing unit 10. Thus, in the imaging apparatus 1, the white balance is adjusted so that the cumulative addition result becomes the zero level.

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.

Further, in this embodiment, the level detection circuit 90 supplies the output signal of the latch circuit 98 to the flip-flop circuit (FF) 126, whereby the flip-flop circuit 126 in the white balance adjustment mode.
, An output signal whose signal level rises in pixel units of the solid-state imaging device 2 in the range of the white balance adjustment region.

The counter 130 receives the output signal of the flip-flop circuit 126 via the selector 128, and counts this output signal in the field cycle, thereby
In the white balance adjustment mode, the number of pixels in the white balance adjustment area is detected. As a result, in the imaging apparatus 1, the size of the white balance adjustment area is detected based on the count result of the counter 130, thereby effectively preventing erroneous setting of the white balance.

In this embodiment, the selector 128
Switches the contacts based on a predetermined control signal CSL, whereby the level detection circuit 90 can output various count results as needed in operation modes other than the white balance adjustment mode.

With the switching of the operation of the selector 128, the selector 128 sets the comparison reference PR set by the central processing unit 10 for the output signal of the latch circuit 98.
The comparison result is output based on K. Thus, in the level detection circuit 90, various reference levels are set as necessary, and the number of pixels of each color signal exceeding the reference level can be detected.

(3-4) Central Processing Unit The central processing unit 10 adjusts the white balance by executing the processing procedure shown in FIG. 8 in the white balance adjustment mode. That is, the central processing unit 10
In step (3), when the operator for starting the white balance adjustment arranged on the operation panel is turned on, step SP
The process proceeds from step 1 to step SP2, in which the operation mode of the entire imaging apparatus 1 is set to the white balance adjustment mode, and the peak level detection result is input from the peak level detection circuit 56.

Subsequently, the central processing unit 10 proceeds to step SP 3, where the comparison reference PK and LOW of the gate signal generation circuit 68 are set. That is, after setting the peak level detected by the peak level detection circuit 56 to the first reference level PK, the central processing unit 10 sets the level lower than the first reference level PK1 by a predetermined level to the second reference level LOW1. Set to. Thus, the central processing unit 10 sets the white balance adjustment region based on the peak level detection result.

Subsequently, the central processing unit 10 proceeds to step SP4, captures the count value of the counter 130, and determines whether or not the white balance adjustment area is equal to or more than 10% of the effective area based on the count value. I do. That is, even if a portion where the luminance level rises sharply is suppressed by using the low-pass filter circuit 61, it becomes difficult to suppress the luminance level for a portion that is long in the horizontal scanning direction, such as a fluorescent lamp.

In this case, the high frequency component is suppressed in the vertical direction.
By using a two-dimensional low-pass filter circuit, the peak level can be suppressed even in a horizontally elongated portion such as a fluorescent lamp, but in this case, there is a disadvantage that the entire configuration is complicated.

Therefore, in this embodiment, as shown in FIG. 9, the first and second reference levels P set at the beginning are set.
The size of the white balance adjustment area is detected in accordance with K1 and LOW1, and when the detection area is smaller than a predetermined range, the first and second reference levels PK2 and LOW2 are sequentially updated, thereby updating the fluorescent lamp. The white balance adjustment region is set by excluding such a portion having a high luminance level.

That is, at the time of white balance adjustment, a part such as a fluorescent lamp is imaged with a relatively large area by imaging a reference white board or the like and adjusting this part to be white. In this case, the area is smaller than that of the reference portion for white balance adjustment. Therefore, by determining whether the white balance adjustment area is 10% or more of the effective area, it is possible to easily detect a portion such as a fluorescent lamp.

Based on this principle, the central processing unit 10
Returns to step SP3 if a negative result is obtained in step SP4, where the first reference level PK2 is updated to the second reference level LOW1 and then a predetermined level from the first reference level PK2. The lower level is set to the second reference level LOW2. This causes the central processing unit 10 to execute steps SP3-SP4-SP3.
The first and second reference levels are updated by repeating the processing loop LOOP1. When the white balance adjustment area is obtained by 10% or more of the effective area, a positive result is obtained in step SP4, and the processing proceeds to step SP5. Move on.

Here, the central processing unit 10 outputs a control signal to the level detection circuit 90, sets the selector 108 and the like to the white balance adjustment mode, and then executes the step SP
The process proceeds to step S6, where the cumulative addition results accumulated in the latch circuits 122 and 124 are loaded, and correction data for adjusting the amplification factor is generated so that the cumulative addition value is set to the 0 level.

Subsequently, the central processing unit 10 proceeds to step SP7 and outputs the correction data for adjusting the amplification factor to the VA block circuit 16, thereby switching the amplification factors of the red color signal and the blue color signal to perform white balance. After the adjustment, the process moves to step SP8 to end the processing procedure. Thus, by detecting the signal level difference between the red signal and the blue signal with respect to the green signal before gamma correction, it is possible to detect the deviation of the white balance with high accuracy. To adjust the white balance.

(4) Effects of the Embodiment According to the above configuration, the first and second reference levels are sequentially updated based on the peak level detection result so that the white balance adjustment area is equal to or larger than a predetermined range. Accordingly, even when there is a high-luminance level portion such as a fluorescent lamp in the effective area of the imaging screen, the white balance can be adjusted by excluding this portion, thereby easily and reliably adjusting the white balance. it can.

(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 peak level and the white balance adjustment region. However, the present invention is not limited to this. Alternatively, the peak level and the white balance adjustment region may be detected by a dedicated circuit.

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.

Further, in the above-described embodiment, a case has been described in which the sharp rise of the luminance level is suppressed by the low-pass filter circuit, and the first and second reference levels for setting the white balance adjustment area are also updated. However, the present invention is not limited to this, and the low-pass filter circuit may be omitted as necessary.

Further, in the above-described embodiment, the second reference level is set as a new first reference level, and the second reference level is set to a level lower than the first reference level by a predetermined level. Although the case of setting has been described, the present invention is not limited to this, and the first and second
Can be freely updated.

[0083]

As described above, according to the present invention, for a luminance signal generated from an image signal obtained by imaging a subject, a peak level detecting circuit for detecting a peak level of the luminance signal, A gate setting circuit for setting a gate within a predetermined level range with reference to an area setting circuit for detecting a signal level of a luminance signal within the level range of the gate and setting a white balance adjustment area based on the detection result; A white balance adjustment circuit for performing white balance adjustment in the balance adjustment area; and when the size of the white balance adjustment area set by the area setting circuit is equal to or smaller than a predetermined value, the set level range of the gate is reduced. By eliminating harmful parts such as fluorescent lights, it is possible to set the white balance adjustment area, The imaging apparatus can be realized which is capable of white balance adjustment easily and reliably.

[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 showing a peak level detection circuit.

FIG. 4 is a signal waveform diagram for describing suppression of a portion where a luminance level rapidly rises.

FIG. 5 is a block diagram showing a gate signal generation circuit.

FIG. 6 is a signal waveform diagram for describing generation of a gate signal.

FIG. 7 is a block diagram showing a level detection circuit.

FIG. 8 is a flowchart for explaining the operation of the central processing unit.

FIG. 9 is a signal waveform diagram for explaining an update operation of the level gate;

FIG. 10 is a schematic diagram used to explain erroneous adjustment of white balance.

FIG. 11 is a schematic diagram for explaining erroneous adjustment of white balance in a case where a part having a high luminance level exists.

FIG. 12 is a schematic diagram illustrating display of a white balance adjustment area.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Imaging device, 2 ... Solid-state image sensor, 10 ... Central processing unit, 16 ... VA block circuit, 20 ... Digital signal processing circuit, 54 ... Data detection circuit, 56 ...
... A peak level detection circuit, 61 a low-pass filter circuit, 68 a gate signal generation circuit, 90 a level detection circuit.

Claims (1)

(57) [Claims] 1. A peak level detection circuit for detecting a peak level of a luminance signal of a luminance signal generated from an imaging signal obtained by imaging a subject, and a gate in a predetermined level range based on the peak level
A gate setting circuit for setting the signal level of the luminance signal within the level range of the gate, an area setting circuit for setting a white balance adjustment area based on the detection result, and the white balance adjustment area, White balance tone
A white balance adjustment circuit for performing adjustment, wherein the gate setting circuit reduces the set level range of the gate when the size of the white balance adjustment area set by the area setting circuit is equal to or smaller than a predetermined value. Characteristic imaging device.