JP2003116049A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately make an exposure control even in a case of a backlight by applying to a television, for example, in an image pickup device. SOLUTION: A backlight level indicating the degree of a backlight is detected by a luminance level in an area of a low luminance level and a luminance level in the other area, and the brightness is increased in correspondence to this backlight level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device,
For example, it can be applied to television. The present invention detects a back light intensity indicating the degree of back light based on the brightness level of a region having a low brightness level and the brightness level of another region, and performs exposure control so as to increase brightness according to the back light intensity. This makes it possible to appropriately control the exposure even in the case of backlight.

[0002]

2. Description of the Related Art Conventionally, in an image pickup apparatus such as a television camera, a predetermined evaluation value (so-called photometric value) indicating the brightness of an image pickup result is detected by signal processing an output signal of an image pickup element, Squeeze based on this evaluation value,
The exposure is controlled by controlling the charge storage time of the image sensor and the gain of the AGC circuit.

In the image pickup apparatus, the luminance signal obtained by performing signal processing on the output signal of the image pickup element is integrated (average photometry), and further, the result of weighting processing of the luminance signal with a large weight set at the center of the screen is integrated. By this (center-weighted metering or spot metering with the center focused), such an evaluation value is generated. In so-called multi-pattern photometry and multi-segment photometry, the screen is divided into a plurality of areas, the average contrast of the entire image is obtained from the difference in the brightness level between these areas, and this contrast is used as the evaluation value. Has been done.

[0004]

However, even with such various photometric methods, there is a problem that it is difficult to properly control the exposure in the case of backlight, and in this case, the subject is imaged due to underexposure. .

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose an image pickup apparatus capable of appropriately performing exposure control even in the case of backlight.

[0006]

In order to solve such a problem, in the invention of claim 1, the backlight intensity indicating the degree of backlighting is determined by the average brightness level of a region having a low brightness level and the average brightness level of other regions. Backlight intensity detecting means for detecting
In the exposure control for backlight correction, a control unit for controlling the exposure is provided so as to increase the brightness of the image pickup result according to the backlight intensity.

According to the structure of claim 1, the backlight intensity detecting means for detecting the backlight intensity indicating the degree of backlight by the average luminance level of the region having the low luminance level and the average luminance level of the other regions, and the backlight compensation. In the exposure control of (1), by providing a control unit for controlling the exposure so as to increase the brightness of the imaging result according to the backlight intensity, even when the backlight location is arranged at various locations on the screen depending on the composition. The exposure can be controlled appropriately so as to deal with the backlight. Accordingly, it is possible to provide an imaging device capable of appropriately controlling exposure even in the case of backlight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate.

(1) Configuration of the Embodiment FIG. 2 is a block diagram showing the configuration of the television camera according to the embodiment of the present invention. In this television camera 1, the lens 2 is C by a predetermined magnification and diaphragm.
Incident light is collected on the imaging surface of the CD solid-state image sensor (CCD) 3, and the diaphragm 4 controls the amount of light incident on the CCD solid-state image sensor 3 from the lens 2 by driving the iris driving circuit 5. The iris drive circuit 5 is a central processing unit (CP
The amount of aperture of the diaphragm 4 is changed by the control of U) 9. As a result, in the television camera 1, the central processing unit 9 controls the diaphragm 4 to control exposure.

The CCD solid-state image pickup device 3 is a single-plate type color image pickup device in which complementary color system color filters are arranged on the image pickup surface, and a color signal corresponding to the color filter is generated by driving a timing generator (TG) 6. The result of continuous imaging is output.

The timing generator 6 processes a predetermined reference clock to generate and output various reference signals necessary for the operation of each section of the television camera 1. In this process, the timing generator 6
Under the control of the central processing unit 9, the timing of the drive signal output to the CCD solid-state image pickup device 3 is switched so that the charge accumulation time of the CCD solid-state image pickup device 3 can be changed. As a result, in the television camera 1, the central processing unit 9 can control the charge storage time to control the exposure.

The sample and hold circuit (S / H) 7 has a C
The output signal of the CD solid-state image sensor 3 is subjected to correlated double sampling and output. An AGC (Automatic Gain Control) circuit 8 amplifies the output signal of the sample hold circuit 7 with a predetermined gain instructed by a central processing unit (CPU) 9 and outputs the amplified signal. As a result, in the television camera 1, the central processing unit 9 controls the gain of the AGC circuit 8 to control exposure.

Analog-to-digital conversion circuit (A / D) 9
A is an image data D1 obtained by the image pickup result by performing an analog-digital conversion process on the output signal of the AGC circuit 8.
Is output. In the camera signal processing circuit 10, after receiving the image data D1 and performing various processing required for the television camera 1 by the camera signal processing unit 10A, the luminance signal Y and the color difference signals RY and BY are obtained. Convert and output. In the television camera 1, the luminance signal Y and the color difference signals RY and BY are output to various video equipment as external equipment.

In this series of processing, the camera signal processing unit 10A corrects the gamma of the image data D1 by the gamma correction circuit (γ) 11 and outputs it. In the gamma correction process, the gamma correction circuit 11 switches the correction characteristic under the control of the central processing unit 9.

The multi-division AE detection circuit 12 integrates the image data D1 output from the analog-digital conversion circuit 9A in field units to obtain the image data D1.
The detection value indicating the brightness of the imaging result of 1 is detected and output. In this processing, the multi-division AE detection circuit 12
By executing the integration processing with the output signal of the timing generator 6 as a reference, as shown in FIG.
For each area formed by dividing one screen by the image data D1 into seven equal parts in the horizontal direction and the vertical direction,
The detection value based on the average value of the brightness level is detected and output.
It should be noted that, in the following, for each area divided in this manner, reference is made to the start side of raster scanning, and each area is indicated by a code made up of letters and numbers that are continuous in the horizontal and vertical directions, respectively.

The central processing unit 9 controls the diaphragm, the charge storage time, and the gain of the AGC circuit by executing a predetermined processing procedure based on the detection value output from the multi-division AE detection circuit 12, and thereby, The exposure control process is executed. At the same time, the characteristics of the gamma correction circuit 11 are switched. In this processing, the central processing unit 9 detects the degree of back light by executing the processing procedure of FIG. 1, sets a parameter to be used for exposure control based on the detection result, executes the exposure control processing by this parameter, and The characteristics of the correction circuit 11 are switched.

That is, the central processing unit 9 shifts from step SP1 to step SP2 and detects the region having the lowest brightness level based on the detection value output from the multi-division AE detection circuit 12. Incidentally, in the composition as shown in FIG. 3, for example, it is considered that the region D6 at the lowermost central portion of the person is detected as the region having the lowest brightness level.

Subsequently, the central processing unit 9 carries out step S
Moving to P3, the detection value of the region having the lowest brightness level detected in step SP1 is multiplied by a predetermined value k of 1 or more, and the multiplication result is set as a threshold value. Thereby, for example, the detection value of the area D6 described above with reference to FIG.
In case of 6, the central processing unit 9 has a value k × PD6 (k>
Set the threshold according to 1).

Subsequently, the central processing unit 9 judges the detection value of the area adjacent to the area detected in step SP2 on the basis of this threshold value.
An area where it can be determined that the same portion as the area detected in step 3 is imaged is detected. In this processing, for example, as shown by the arrow in FIG. 4, when the area D3 is detected as the area having the lowest brightness level in step SP2, the central processing unit 9 starts the raster scanning with respect to this area D2. The detection values of the regions that are successively adjacent in the counterclockwise direction are determined. Further, when the detection value of the adjacent area is determined and the area equal to or smaller than the threshold value is detected, as shown in FIG.
Similarly, the detection value is determined based on the threshold value. In addition, in the example shown in FIG. 5, in the determination described above with reference to FIG.
This is processing for the area C2 when it is determined that the area C2 is equal to or less than the threshold value. The central processing unit 9 repeats this processing until no adjacent area below the threshold value is detected.

The central processing unit 9 executes the following step SP
In step 5, the same object as the region with the lowest brightness level detected in step SP2 is imaged based on the determination result obtained by sequentially determining the detection values adjacent to the region equal to or less than the threshold value with the threshold value. The area that can be determined to be being detected is detected. As a result, the central processing unit 9 is operated as shown in FIG.
In the example shown in (1), the areas C4 to C6, D2 to D6, and E4 to E6 of the region due to the backlight of a person are detected as the areas of low brightness level.

Subsequently, the central processing unit 9 executes step S
Moving to P6, the average brightness level of the low brightness level region thus detected is detected. Here, the central processing unit 9 detects the average brightness level by calculating the average value of the detection values for the low brightness level region. Thus, in the example shown in FIG. 6, the areas C4 to C6 and D2 are respectively
To D6, E4 to E6, the detection value which is the average luminance level is set to P
With C4 to PC6, PD2 to PD6, PE4 to PE6, KL = (PC4 + PC5 + PC6 + PD2 + PD3
+ PD4 + PD5 + PD6 + PE4 + PE5 + PE6)
The average luminance level KL of the low luminance level region is detected by the calculation processing of / 11.

Subsequently, the central processing unit 9 executes step S
Moving to P7, for areas other than the low brightness level area,
Calculate the average brightness level. Thus, in the example described above with reference to FIG. 6, the detection is performed by averaging the detection values for the hatched area in FIG. 7. Specifically, in this case, the central processing unit 9
Areas A0-A6, B0-B6, C0-C3, D0, D
1, E0 to E3, F0 to F6, G0 to G6 are the average luminance levels, and the detected values are PA0 to PA6, PB0 to PB6,
PC0 to PC3, PD0, PD1, PE0 to PE3, P
In F0 to PF6 and PG0 to PG6, KH = (PA
0 + PA1 + PA2 + PA3 + PA4 + PA5 + PA6
+ PB0 + PB1 + PB2 + PB3 + PB4 + PB5 +
PB6 + PC0 + PC1 + PC2 + PC3 + PD0 + P
D1 + PE0 + PE1 + PE2 + PE3 + PF0 + PF
1 + PF2 + PF3 + PF4 + PF5 + PF6 + PG0
+ PG1 + PG2 + PG3 + PG4 + PG5 + PG6)
This average luminance level is calculated by the calculation processing of / 38.

Subsequently, the central processing unit 9 carries out step S
Moving to P8, the backlight intensity indicating the degree of backlight is detected for the low brightness level region. Here, the central processing unit 9
Divides the average luminance level KL of the low luminance level region detected in step SP6 by the average luminance level KH of the other region detected in step SP7, and the backlight intensity is calculated by the average luminance level ratio KL / KH. To calculate.

By these processes, the central processing unit 9
Is configured to classify an image pickup result into regions, identify a region that is determined to be backlight, and detect the degree of backlight in this region. By the way, even in the low-brightness level region detected in this way, the backlight may not be backlit. Therefore, the central processing unit 9 detects in this way in step SP9 according to a series of determination processing results described later. It is determined whether it is necessary to correct the exposure control parameter based on the back light intensity.

If a negative result is obtained here, the central processing unit 9 moves to step SP10 and ends this processing procedure. On the other hand, if a positive result is obtained in step SP9, the central processing unit 9 moves to step SP11 to correct the exposure control parameter AEref and also to correct the parameter for setting the gamma correction characteristic.

Among these corrections, regarding the processing for correcting the exposure control parameter AEref, the central processing unit 9 corrects the parameter AEref according to the back light intensity by the characteristic curve shown in FIG. That is, when the backlight intensity is 2.0 or less, the brightness level difference between the bright portion and the dark portion in the imaged result is not so large, and therefore exposure control is performed in the same manner as normal exposure control, and sufficient brightness is obtained. A desired subject can be imaged. This allows
In this case, the central processing unit 9 corrects the exposure control parameter AEref by multiplying it by 1.

On the other hand, when the backlight intensity increases, the difference in brightness level between the bright portion and the dark portion in the image pickup result increases accordingly, so that a dark image is picked up in a portion having a low brightness level. As a result, in this case, the central processing unit 9 gradually increases the multiplication value corresponding to the increase in the backlight intensity, and multiplies the exposure control parameter AEref by the multiplication value to correct the exposure value. On the other hand, if the exposure is controlled too much by such a correction,
The central processing unit 9 stops increasing the multiplication value when the backlight intensity becomes 4.0 or more due to the large saturation of the bright portion, and the multiplication value causes the exposure control parameter AE to be reduced.
It is corrected by multiplying by ref.

Therefore, the exposure control parameter AEref is a control target value for the exposure control, and the central processing unit 9 controls the exposure so that the exposure amount increases in accordance with the backlight intensity. ing.

On the other hand, of these corrections, the central processing unit 9 sets the control parameters for the γ correction according to the characteristic curve shown in FIG. Here, as shown in FIG. 10, when the backlight intensity is 2.0 or less, the parameter is set so that the gamma correction is performed by the gamma characteristic applied to a normal television camera.

On the other hand, when the backlight intensity exceeds 2.0, by contrast with the characteristics of the normal gamma correction applied to such a normal television camera, the backlight level is reduced at a low luminance level. The parameters are corrected so that the gamma characteristic is switched so as to raise the brightness level. Further, when the backlight intensity increases above the value 4.0, the parameters are corrected so that the correction for raising the brightness level above the current level is stopped at such a low brightness level.

As a result, the central processing unit 9 switches the gamma correction characteristic according to the back light intensity so as to extend the gradation at the low brightness level which is observed by being lowered by the back light. Further, when the backlight intensity exceeds a certain value, the processing for expanding the tone according to such backlight intensity is maintained at a certain value, thereby preventing an unnatural tone in the imaging result.

When the control parameters are set in this way, the central processing unit 9 moves to step SP12,
After the photometric parameters are corrected by executing a predetermined processing procedure, the process proceeds to step SP10 to end this processing procedure.

FIG. 11 is a flow chart showing a processing procedure for determining whether or not the above-mentioned correction processing is necessary. The central processing unit 9 executes this processing procedure concurrently with the above-mentioned processing procedure. That is, the central processing unit 9
In the processing procedure shown in FIG.
From step 15 to step SP16, an area having the highest brightness level is detected from the detection value of each area detected by the multi-division AE detection circuit 12, and the brightness level MAX of this area is equal to or higher than a predetermined threshold value TH1. To determine. If a negative result is obtained here, in this case, since a dark place as a whole is being imaged and there is no light source having a high brightness level that forms a backlight in the screen, the process proceeds to step SP17. Here, the central processing unit 9 determines that the above-mentioned control parameter correction is not necessary, moves to step SP18, and ends this processing procedure.

On the other hand, when a positive result is obtained in step SP16, the central processing unit 9 determines in step SP1.
It moves from 6 to step SP19. Here, the central processing unit 9 detects an area having the lowest brightness level than the detection value of each area detected by the multi-division AE detection circuit 12, and whether the brightness level MIN of this area is equal to or lower than a predetermined threshold value TH2. Judge whether or not. If a negative result is obtained here, in this case, a bright place as a whole is imaged, and there is no portion with a low brightness level such as due to backlight in the screen, so the processing moves to step SP17, and is described above. After determining that the correction of the control parameter is not necessary, the process proceeds to step SP18 and this processing procedure is ended.

On the other hand, when a positive result is obtained in step SP19, the central processing unit 9 determines in step SP1.
It moves from 9 to step SP9A. Here, the central processing unit 9 determines whether or not the number of low brightness level areas NUM detected in step SP5 is equal to or greater than a predetermined value TH3. If a negative result is obtained here, in this case, the area of low brightness level is a narrow and limited range, and the user
Since this is the case where the low brightness level area is not mainly photographed, the process proceeds to step SP17, and after it is determined that the correction of the control parameter is not necessary, the process proceeds to step SP18 to end this processing procedure. To do.

On the other hand, when a positive result is obtained in step SP20, the central processing unit 9 determines in step SP2.
Move from 0 to step SP21. Here, as shown in FIG. 12, the central processing unit 9 calculates the distance DT between the center of the low-brightness level region detected in step SP5 and the center of the screen, and whether this distance DT is equal to or less than a predetermined value TH4. To determine. If a negative result is obtained here, in this case, the area with the low brightness level is the corner of the screen, and it is the case where the user does not take an image of this area with the low brightness level. After moving to step SP17 and determining that the correction of the control parameter is not necessary,
The process moves to step SP18 and this processing procedure is ended.

As a result, the central processing unit 9 erroneously does not control the exposure due to the control parameter of the backlight.

FIG. 13 is a flow chart showing in detail the photometric parameter correction process, which is the process procedure of step SP12 of FIG. In this processing procedure, the central processing unit 9 performs steps SP31 to SP3.
Then, the process shifts to step 2 to execute the photometric frame position setting process, which is the setting of the area used for photometry.

Here, FIG. 14 is a plan view showing a region used for photometry which is set by the central processing unit 9 when the correction process of the photometry parameter is not executed.
The central processing unit 9 generally takes a first image in the region A0 to G1 which is almost one-third of the upper side of the image pickup result, which often captures the sky.
The frame WIN0 of is set. In addition, when the sky is photographed in this way, the second frame W is formed in an area excluding the areas C3 to E4 which are biased downward from the center of the screen in which the subject is often assigned.
IN1 is set, and the third frame WIN2 is set in the central areas C3 to E4 of the screen.

The central processing unit 9 further values K0, K1, K for these frames WIN0-WIN2, respectively.
A weighting coefficient of 2 is set, and the detection value of each area obtained from the multi-division AE detection circuit 12 is set to the weighting coefficient K0, K.
The photometric value is detected by weighting with 1 and K2 and adding. The central processing unit 9 executes the exposure control processing so that this measured value matches the above-mentioned control parameter AEref.

On the other hand, in the processing of step SP32, as shown in FIG. 15, the third frame WI surrounds the low brightness level region detected in step SP5.
Set N2. For this reason, in FIG. 15, the frame WIN2 is shown as a rectangle, but by setting the frame WIN2 so as to surround the low brightness level area,
In N2, for example, as shown in FIG. 16, it is set in various shapes according to the low brightness level region. As a result, the central processing unit 9 controls the exposure by focusing on the portion judged to be the backlight.

The first and second frames WIN0 and WIN
1 is set in the same manner as in the normal case.

After executing the photometric frame position setting process in this way, the central processing unit 9 proceeds to step SP33 and sets the weighting coefficient for each frame. Here, the central processing unit 9 uses the characteristic curve shown in FIG.
After the weighting coefficient K2 for IN2 is corrected, the weighting coefficient of each of the weighting coefficients K0 to K2 is corrected by so-called normalization processing by the amount of the change in the size of the third frame WIN2 from the normal state, and this step SP33 Execute the process.

That is, the central processing unit 9 weights the weighting coefficient K2 with the multiplication value 1 in the range where the backlight intensity is 2.0 or less, and thereby calculates the photometric value by the weighting processing similar to the normal processing. To do so. On the other hand, when the backlight intensity increases to a value of 2.0 or more, the multiplication value is increased according to the backlight intensity, and the weighting coefficient K2 is weighted by the multiplication value. When the backlight intensity increases to a value of 4.0 or more, the increase of the multiplication value according to the backlight intensity is stopped and the weighting coefficient K2 is weighted. As a result, the central processing unit 9 shifts the focus of the photometric processing used for the exposure control to the area of low brightness level.

In the central processing unit 9, the increase of the multiplication value according to the back light intensity is determined by the exposure control parameter AEr.
set to correspond to an increase in the multiplication value in ef,
Thus, for the other weighting factors K0 and K1,
By increasing the weighting coefficient by a specific weighting coefficient K2 without increasing it at all, the degree of increase in the photometric value becomes smaller with respect to the increase in the exposure control parameter AEref due to the backlight intensity. Exposure is controlled by increasing the amount of light.

When the weighting coefficient is set in this way, the central processing unit 9 moves to step SP34, sets the corresponding weighting coefficient in the area of each frame set in step SP32, and moves to step SP35. Return to the processing procedure of.

In this exposure control, the central processing unit 9 weights and adds the detection values of the respective areas output from the multi-division AE detection circuit 12 by the weighting coefficient set in this way, and thereby detects the photometric value. . As a result, the central processing unit 9 detects the back light intensity based on the detection value of each region output from the multi-division AE detection circuit 12 by executing the above-described series of processing procedures, and then according to the back light intensity. The functional block of the backlight detection circuit 14 is configured to correct the characteristics of the gamma correction circuit 11, control the photometric processing, and calculate the weighting coefficient for exposure control. Further, the central processing unit 9 is configured to form a functional block of a multiplication circuit 16 that weights the control parameter AEref for exposure control with a weighting coefficient. Further, the functional block of the photometric value calculation circuit 19 for calculating the photometric value indicating the brightness of the subject is constructed by the frame and the weighting coefficient set by the backlight intensity detection circuit 14 as described above.

The central processing unit 9 calculates the difference value between the photometric value thus obtained and the weighting result of the control parameter AEref, and the photometric value matches the weighting result of the control parameter AEref by this difference value. Calculate the exposure control amount required for. Further, the exposure control amount is divided into aperture control, accumulated charge control, and gain control of the AGC circuit 8 to control the corresponding circuit block. As a result, the central processing unit 9 causes the photometric value and the control parameter A
A functional block including a comparison circuit 17 that calculates a difference value from the weighted result of Eref, a control value calculation circuit 18 that calculates a control amount from the difference value, and a control value distribution circuit 19 that distributes this control value to each circuit block. It is designed to make up.

(2) Operation of the Embodiment With the above-described configuration, in this television camera 1 (FIG. 2), the output signal of the CCD solid-state image pickup device 3 is processed by the sample hold circuit 7, and then the AGC circuit 8 is used. The analog-digital conversion circuit 9 is amplified with a predetermined gain.
The image data D1 is generated by the analog-digital conversion processing by A. In the television camera 1, this image data D1 is processed by the camera signal processing circuit 10 to generate a luminance signal Y, color difference signals RY and BY,
Output to external device. As a result, in the television camera 1, for example, the image pickup result by the television camera 1 can be monitored by the monitor device, and the image pickup result can be recorded by the video tape recorder or the like.

In the television camera 1, in such a process, the image data output from the analog-digital conversion circuit 9A is input to the multi-division AE detection circuit 12, where one screen of the image pickup result is displayed in 7 × 7. A brightness level is detected for each area divided into areas, and this brightness level is input to the central processing unit 9 as a detection value.
Further, in the television camera 1, the detection values obtained from each of the areas are the frames WIN0 to WIN2 set on the screen.
For each area (FIG. 14), each frame WIN0-WIN2
Are weighted and added by the weighting coefficient set to, and the photometric value indicating the brightness of the image pickup result is detected.

In the television camera 1, this photometric value and the control parameter AEre which is the control target of the exposure control are set.
A difference value with respect to f is calculated, and a control amount of exposure control required to correct this difference value is calculated. Further, this control amount is distributed to each part to control the diaphragm 4 of the lens 2, the charge storage time of the CCD solid-state image sensor 3 and the gain of the AGC circuit 8, whereby the photometric value is set to the control parameter AEref.
The exposure control process is executed so as to match with. As a result, the television camera 1 can obtain a desired subject image pickup result with appropriate brightness.

In the television camera 1, in such a process, the area having the lowest brightness level is detected from the brightness levels of the areas output from the multi-division AE detection circuit 12 (FIGS. 1 and 3), and further, A threshold value is set on the basis of the brightness level of this area, and an area continuous with the area of the lowest brightness level is detected, whereby the area of the lowest brightness level is detected (FIGS. 4 to 6).

In the television camera 1, when the area thus detected is smaller than the predetermined area, it is determined that the arrangement of the normal light source is the case (not the backlight) (FIG. 11), and the above-mentioned operation is performed. The exposure is controlled by the photometric value detected with reference to the frames WIN0 to WIN2 and by the above-mentioned control parameter AEref, so that the processing of the exposure control in the case of back light is not erroneously executed, and the appropriate brightness is set. A desired subject can be imaged.

Further, when the area having the highest brightness level and the area having the lowest brightness level are detected from the brightness levels of the respective areas thus detected, and the brightness levels of these areas are equal to or lower than the predetermined brightness levels, respectively. , If the brightness is equal to or higher than a predetermined brightness level, the exposure control is performed by the photometric value detected based on the above-described frames WIN0 to WIN2 and by the control parameter AEref. It is configured such that the desired subject can be imaged with appropriate brightness without performing the execution.

Further, even when the center of the area of low brightness level detected based on the threshold value is more than the predetermined distance from the center of the screen, the photometry detected based on the above-mentioned frames WIN0 to WIN2. The exposure is controlled by the value and by the above-mentioned control parameter AEref, so that the processing of the exposure control in the case of backlighting is not executed by mistake, and a desired subject can be imaged with appropriate brightness. ing.

On the other hand, when all of the above four conditions are satisfied, it is judged that the image is picked up by the backlight, and the brightness of the image pickup result is increased so as to correct the backlight.

That is, in the television camera 1, the back light intensity indicating the degree of back light is detected by the average brightness level of the low brightness area detected based on the threshold value and the average brightness level of the other areas. (FIGS. 1 and 7), the parameter AEref which is a control target according to the backlight intensity.
The exposure control is performed so as to increase the brightness of the image pickup result. As a result, the television camera 1 appropriately determines the degree of backlight even when the backlight is arranged at various locations on the screen depending on the composition of the user, and controls the brightness of the imaging result according to the determination result. Therefore, the exposure can be appropriately controlled even in the case of backlight.

In the television camera 1, such a back light intensity is obtained by the ratio of the average brightness level of the area having a low brightness level to the average brightness level of the other area, whereby the portion having a high brightness level is exposed to the sun. In this case, even if the light source is an indoor light source, etc., the degree of backlight can be appropriately expressed, and thus exposure control can be appropriately performed.

Further, the exposure control is performed so as to increase the brightness of the image pickup result only when the backlight intensity is within a predetermined range. That is, when the back light intensity is lower than a predetermined value, the contrast of the image pickup result is small. In this case, if the exposure control is performed to make the image pickup result brighter, the brightness of the entire screen may be increased. It will be displayed naturally. On the contrary, if the backlight is controlled to increase the brightness of the screen more than the current level when the backlight intensity is equal to or higher than a predetermined value, it is possible to capture an image in which the brightness level is saturated in a wide range of a high brightness level area. The result is obtained. As a result, the television camera 1 is configured to effectively avoid the occurrence of discomfort in the image pickup result and correct the backlight.

Further, in the television camera 1, the frame used for the calculation of the photometric value is moved and the size of the frame is changed according to the region of low luminance level detected in this way (FIG. 14-). 15). As a result, in the television camera 1, the area on which the emphasis is related to the processing of photometry is switched corresponding to the area where the exposure is controlled so that the brightness becomes appropriate due to the backlight, and the size of this area is changed.
This also enables appropriate exposure control.

The weighting coefficient set in the frame in this way is changed according to the back light intensity (FIG. 9), whereby the area of low luminance level, which is an area to be emphasized compared to other areas, is changed. When the average brightness level is low, focus more on this area of low brightness level to perform photometry.
The exposure control process is switched, and this also enables more appropriate exposure control.

In the television camera 1, even in the case of changing the weighting coefficient, as in the case of the control parameter AEref, the weighting coefficient of the part to be emphasized is increased in accordance with the backlight intensity only within a predetermined range, and Therefore, the excessive correction is prevented, and the unnaturalness in the imaging result is effectively avoided.

When the exposure control is performed so as to correct the backlight in this way, the television camera 1 has a characteristic of gamma correction so that the gradation is extended in a portion having a low brightness level according to the backlight intensity. Changed (Figs. 9 and 1)
0). That is, at the time of backlighting, a portion with a low brightness level is crushed and displayed. Thus, by expanding the gradation at a portion with a low brightness level according to the backlight level, the contrast at a location with a low brightness level is increased. Can be emphasized, which makes it possible to obtain a high-quality imaging result as if the dynamic range were expanded at first glance.

However, in this case, if the gradation is extended also on the high luminance level side, the high luminance portion is saturated and displayed, so-called white crushing. As a result, the television camera 1 is capable of effectively avoiding color crushing by outputting gradation only in a portion having a low luminance level and outputting a high quality image pickup result.

Further, by correcting the gamma characteristic as described above only when the backlight intensity is within a predetermined range, it is possible to prevent the image pickup result from being uncomfortable due to excessive correction.

(3) Effects of the Embodiments According to the above configuration, the backlight level indicating the degree of backlighting is detected by the brightness level of the low brightness area and the brightness level of the other area, and the backlight level is determined. Accordingly, by performing the exposure control so as to increase the brightness, the exposure control can be appropriately performed even in the case of backlight.

At this time, the backlight intensity is set by the ratio of the average brightness level of the low brightness area and the average brightness level of the other area, so that the high brightness level is caused by the sun or the indoor light source. Even in such cases, the degree of back light can be appropriately expressed, and thus exposure control can be appropriately performed.

When the backlight intensity is equal to or higher than a predetermined value, it is possible to prevent the excessive correction and correct the backlight by stopping the increase in the brightness of the image pickup result.

Further, a weighting coefficient for the image pickup result is set according to the back light intensity, and the image pickup result is processed by this weighting coefficient to detect the photometric value, thereby averaging the areas of low luminance level, which are the areas to be emphasized. When the brightness level is low, the exposure control process can be switched so that the area of the low brightness level is more heavily weighted for photometry, which also allows more appropriate exposure control.

Further, in accordance with the region of low luminance level detected in this way, the region for setting the weighting coefficient is switched, the position where the emphasis is given in the exposure control is moved, and further, the region where the emphasis is given in the exposure control is changed. By varying the size, the exposure can be appropriately controlled also by this.

By executing the processing for increasing the brightness of the image pickup result by setting the parameter which is the control target value according to the backlight intensity, the backlight can be corrected by the simple processing.

If the brightness level of the area with the highest brightness level is less than or equal to the predetermined value, or if the brightness level of the area with the lowest brightness level is greater than or equal to the predetermined brightness level, the brightness level of the area with the lowest brightness level is used as a reference. If the area of the predetermined brightness level or lower is equal to or smaller than the predetermined area, and the center of the area of the predetermined brightness level or lower is equal to or larger than the center of the screen by a predetermined distance or more, the exposure control process by the backlight intensity is performed. By canceling, it is possible to effectively avoid erroneous backlight compensation.

By switching the gamma correction characteristic so as to extend the gradation of the region having a low luminance level in accordance with the backlight intensity, it is possible to output a high-quality imaged result with an expanded dynamic range. it can.

(4) Other Embodiments In the above-mentioned embodiments, the case where the judgment of the backlight, the detection of the backlight intensity, and the detection of the photometric value are executed by setting the area of 7 × 7 has been described. The present invention is not limited to this, and the area may be set by various division numbers,
Further, an area may be set for each process, and detection of a photometric value may be performed in pixel units instead of setting such an area.

Further, in the above-mentioned embodiment, the case where the backlight intensity is detected by the ratio of the average brightness level of the area having the low brightness level and the average brightness level of the other areas has been described. Not limited to this, the point is to calculate the value indicating the degree of backlighting based on the average luminance level of the low luminance level area and the average luminance level of the other area. For example, the difference value between these two luminance levels and the difference value The backlight intensity may be detected by a division value obtained by dividing by any of the luminance levels.

Further, in the above-mentioned embodiment, the case where the weighting coefficient is set corresponding to the frame to perform the photometry is described, but the present invention is not limited to this, and for example, a value which continuously changes due to smoothing processing is It can be widely applied to the case where the weighting coefficient is set to change.

Furthermore, in the above-described embodiment, the case where the characteristics of gamma correction, the frame setting of photometry, the setting of the weighting coefficient, and the like are also changed according to the backlight intensity has been described, but the present invention is not limited to this and is necessary. These processes may be omitted according to the above.

Further, in the above embodiment, the CCD
Although the case of using the solid-state image sensor has been described, the present invention is not limited to this, and can be widely applied to the case of using the solid-state image sensor of CMOS.

Further, in the above-mentioned embodiments, the case where the present invention is applied to the image pickup device of the single plate type has been described, but the present invention is not limited to this and can be widely applied to the image pickup device of the three plate type. .

Further, in the above-mentioned embodiments, the case where the present invention is applied to the image pickup apparatus by the television camera is described, but the present invention is not limited to this, and the recording function of, for example, a camera-integrated video tape recorder is provided. To an image pickup device having the same, an image pickup device giving priority to a still image pickup function such as an electronic still camera, an image pickup device having a communication function such as a mobile phone, and an image pickup device integrated with a personal computer It can be widely applied.

[0081]

As described above, according to the present invention, the backlight level indicating the degree of backlighting is detected by the brightness level of the low brightness level area and the brightness level of the other area, and the brightness is determined according to the backlight level. By controlling the exposure so as to increase the brightness, the exposure can be appropriately controlled even in the case of backlight.

[Brief description of drawings]

FIG. 1 is a flowchart showing a processing procedure of a microcomputer in a television camera according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a television camera according to an embodiment of the present invention.

FIG. 3 is a plan view for explaining a region in the television camera of FIG.

FIG. 4 is a plan view for explaining determination of a brightness level of a peripheral area.

FIG. 5 is a plan view for explaining determination of processing following FIG.

FIG. 6 is a plan view showing a region having a low luminance level.

FIG. 7 is a plan view showing another region.

FIG. 8 is a characteristic curve diagram for explaining control parameter setting.

FIG. 9 is a characteristic curve diagram for explaining correction of characteristics of gamma processing.

FIG. 10 is a characteristic curve diagram for explaining a gamma characteristic.

FIG. 11 is a flowchart for explaining a backlight determination process.

12 is a plan view for explaining the processing procedure of FIG. 11. FIG.

FIG. 13 is a flowchart for explaining a photometric process.

FIG. 14 is a plan view showing a normal frame setting.

FIG. 15 is a plan view showing frame setting.

FIG. 16 is a plan view showing another example of frame setting.

FIG. 17 is a characteristic curve diagram for explaining setting of weighting coefficients.

[Explanation of symbols]

1 ... Television camera, 3 ... CCD solid-state image sensor, 4 ... Aperture, 8 ... AGC circuit, 9 ... Central processing unit, 10 ... Camera signal processing circuit, 11 ... Gamma correction circuit, 12 ... ... Multi-division AE detection circuit

Claims (13)

[Claims] 1. An image sensor, brightness level detection means for detecting a brightness level of the image result for each area obtained by dividing one screen of an image result of the image sensor, and brightness levels of the respective areas. A region detection unit that determines a region having a low luminance level, an average luminance level of the region having a low luminance level, and an average luminance level of another region, and a backlight intensity that detects a backlight intensity indicating a degree of backlight. A detection unit and a control unit that performs exposure control so as to increase the brightness of the imaging result in accordance with the backlight intensity in the exposure control for backlight correction. 2. The image pickup apparatus according to claim 1, wherein the backlight intensity is a ratio of an average brightness level of the area having the low brightness level to an average brightness level of another area. 3. The image pickup apparatus according to claim 1, wherein the exposure control means stops increasing the brightness of the image pickup result when the backlight intensity is equal to or higher than a predetermined value. 4. The weighting coefficient setting means for setting a weighting coefficient for the image pickup result according to the backlight intensity, and the luminance level of the image pickup result being weighted and added by the weighting coefficient to obtain the image pickup value. The image pickup apparatus according to claim 1, further comprising: a photometric value detection unit that detects a photometric value indicating the resulting brightness; and an exposure control unit that controls exposure so that the photometric value becomes a predetermined value. 5. The image pickup apparatus according to claim 4, wherein the control unit switches the region in which the weighting coefficient is set, in accordance with the region having the low brightness level detected by the region detection unit. . 6. The control unit according to claim 1, wherein the control unit moves a position to be emphasized in the exposure control according to a region having a low brightness level detected by the region detection unit. Imaging device. 7. The control means varies the size of an area to be emphasized in the exposure control according to the area having the low brightness level detected by the area detecting means. The imaging device according to. 8. The control means processes the image pickup result to detect a photometric value indicating the brightness of the image pickup result, and a control target of the image pickup result according to the backlight intensity. The image pickup apparatus according to claim 1, further comprising a parameter setting unit that sets a value, and an exposure control unit that controls the exposure so that the photometric value becomes the control target value. 9. The control means executes the exposure control of the backlight correction when the brightness level of the highest brightness level among the brightness levels of the respective areas is equal to or higher than a predetermined value. The image pickup apparatus according to claim 1. 10. The control means executes the exposure control of the backlight correction when the brightness level of the lowest brightness level of the brightness levels of the respective areas is equal to or lower than a predetermined brightness level. The image pickup apparatus according to claim 1. 11. The backlight unit controls the backlight when the area having a predetermined brightness level or lower based on the brightness level of the area having the lowest brightness level among the brightness levels of the areas has a predetermined area or more. The image pickup apparatus according to claim 1, wherein exposure control for correction is executed. 12. The control means, of the brightness levels of the respective areas, the center of the area having a predetermined brightness level or lower based on the brightness level of the area having the lowest brightness level is a predetermined distance or less from the center of the screen. In case of
The image pickup apparatus according to claim 1, wherein the exposure control for the backlight correction is executed. 13. The image pickup apparatus according to claim 1, wherein the control unit extends the gradation of a region having a low luminance level in the gamma correction of the image pickup result according to the backlight intensity.