JPH11146264A - Device and method for picking up image and computer readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the lower part of a picture from being painted out in black when blue sky is settled within the upper part of a picked-up picture. SOLUTION: A camera signal processing circuit 6 prepares luminance and color difference signals 24, 22 and 23 from image signals from a CCD 3 and a dividing processing circuit 25 and an image recognizing circuit 26 detect the presence/absence of the blue sky at the upper part of the picture based on the respective signals 22-24, the illuminance of an object based on a signal 29 from an iris encoder 14, and reference value from a reference value generating circuit 28. When there is the blue sky, the AE level of an AE level setting circuit 30 is changed so as to be lighter than an ordinary level and based on this AE level, an AE control part 31A controls an iris 2 and an AGC circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus, an imaging method, and a computer-readable storage medium, and more particularly to exposure control.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration of an exposure control section for automatically performing exposure control in a conventional imaging apparatus such as a video camera. 6, reference numeral 1 denotes a photographing lens, 2 denotes an iris for adjusting the amount of incident light, and 3 denotes an image formed on the image pickup surface of the photographing lens 1 and whose light amount is adjusted by the iris 2 to be photoelectrically converted into an image pickup signal. Imaging device such as a CCD, 4 is a double correlation sampling circuit (CDS circuit) for reducing the noise of the charge stored in the imaging device 3, 5 is an AGC circuit for adjusting the gain of the imaging signal, and 6 is output from the AGC circuit 5. A camera signal processing circuit that performs predetermined signal processing on the captured image signal and converts the signal into a standardized video signal.

[0003] Reference numeral 7 divides the imaging screen as shown in FIG. 7 into a plurality of areas 1, 2, and 3, and applies a gate to a signal output from the AGC circuit 5 in order to extract an image signal corresponding to an arbitrary area. A gate circuit for applying, an integrator 8 integrates an imaging signal corresponding to a designated area on the imaging screen selected by the gate circuit 7 and obtains an average light amount, and 9 denotes a signal output from the integrator 8 which will be described later. System control circuit 1
7 is an A / D converter for converting into a digital signal that can be processed by the A / D converter 7.

[0004] Reference numeral 10 denotes a CCD drive circuit for controlling the accumulation operation, readout operation, and reset operation of the image sensor 3, reference numeral 11 denotes an iris motor for driving the iris 2, reference numeral 12 denotes an iris drive circuit for driving the iris motor 11, and reference numeral 13 denotes a system control. A D / A converter for converting a digital iris control signal output from the circuit 17 into an analog signal,
Reference numeral 4 denotes an iris encoder composed of a Hall element or the like for detecting an iris opening amount, that is, an aperture value.
An A / D converter 16 for converting a digital AGC control signal output from the system control circuit 17 into an analog control signal and supplying the analog control signal to the AGC circuit 5 , 17 are system control circuits for controlling the automatic exposure control of the conventional example, and have an AE control unit 17A. Reference numeral 18 denotes an AE_REF (reference) for determining a predetermined level when performing exposure control.

Next, the operation will be described. Shooting lens 1
Is converted photoelectrically by the imaging device 3 through the iris 2, becomes an image signal through the CDS circuit 4 and the AGC circuit 5, and is sent to the camera signal processing circuit 6. A signal for controlling the exposure is obtained by gating the luminance signal output from the AGC circuit 5 by the gate circuit 7 and integrating by the integrator 8, and the integrated output passes through the A / D converter 9 and the system control circuit. 17. The AE controller 17A controls the iris drive circuit 12 so that the level of the integrated output falls within a predetermined range defined by AE_REF18.
To control the drive current output to the iris motor 11, thereby controlling the opening amount of the iris 2. Automatic exposure control is performed by such a closed loop of iris control.

[0006] On the other hand, an exposure control system by the AGC circuit 5 is configured. Like the exposure control system by the iris 2, the level taken into the system control circuit 17 is within a predetermined range defined by the AE_REF 18. The automatic exposure control is performed in a closed loop by controlling the gain level of the AGC circuit 5 so as to fall within the range.

Next, the gate circuit 7 will be described with reference to FIG. FIG. 7 illustrates a gate frame when performing center-weighted average photometry. The center-weighted average photometry means that the central area 1 is weighted the largest, then the area 2 is weighted secondly, and then the area 3 is weighted. This is a photometry method that has been devised based on the idea that a subject is sometimes positioned at the center.

Here, an example of the photometric ratio (weighting ratio) is as follows: ratio of region 1: ratio of region 2: ratio of region 3 = 10: 5: 2. In particular, the reason why the weighting of the area 3 at the top of the screen is the smallest is that the blue sky easily enters the top of the screen when shooting outdoors, and the brightness of the blue sky is very high when the blue sky enters, so that the entire screen is very bright. This is to prevent the image from becoming dark.

[0009]

However, in the automatic exposure control system using the center-weighted average photometry described in the above-mentioned conventional example, when it is desired to mainly take an image of a subject taken at the top of the screen, the photometry ratio is displayed at the top of the screen. Therefore, there is a problem that the subject located at the top of the screen is not properly exposed.

An object of the present invention is to pay attention to the above-mentioned problems, and not to perform exposure control based only on center-weighted average photometry, but particularly to perform image recognition and determine whether or not a blue sky is included outdoors in fine weather. The purpose of this is to make it possible to perform optimum exposure control by detecting the result and effectively utilizing the detection result.

[0011]

In an image pickup apparatus according to the present invention, an image pickup means for picking up an image of a subject and outputting an image signal; an exposure control means for controlling the exposure of the image pickup means to the subject to a set value; A color temperature detecting unit that detects a color temperature from an image signal corresponding to a predetermined portion of an imaging screen of the imaging unit; and a changing unit that changes the set value for the exposure control according to the detected color temperature. Provided.

In the imaging method according to the present invention, an imaging procedure for imaging an object by an imaging means and outputting an image signal; an exposure control procedure for controlling the exposure of the imaging means to the object to a set value; A color temperature detection procedure for detecting a color temperature from an image signal corresponding to a predetermined portion of the imaging screen and a change procedure for changing the set value for the exposure control according to the detected color temperature are provided. .

In a computer-readable storage medium according to the present invention, an image pickup process for picking up an image of an object by an image pickup means and outputting an image signal; an exposure control process for controlling the exposure of the image pickup means to the object to a set value; A color temperature detection process of detecting a color temperature from an image signal corresponding to a predetermined portion of an imaging screen of the imaging unit; and a changing process of changing the set value for the exposure control according to the detected color temperature. Is stored.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The embodiment of the present invention performs image recognition, detects whether or not a blue sky is present in the upper part of the screen, and if a blue sky is present, sets the AE level to a value that is slightly brighter than when the exposure is normal. This makes it possible to obtain a good image without blackening.

FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, reference numerals 1 to 16 are the same as those explained in the conventional example of FIG. In FIG. 1, reference numeral 20 denotes a luminance / chromaticity signal generation circuit for converting a video signal output from the AGC circuit 5 into a luminance signal and a chromaticity signal;
21 is (RY) from the R signal, the B signal, and the luminance component reduction component YL output from the luminance / chromaticity signal generation circuit 20;
A color difference signal generation circuit for generating a color difference signal of (BY), 2
2 is a color difference signal (BY), 23 is a color difference signal (RY),
Reference numeral 24 denotes a luminance signal YH, and reference numeral 25 denotes a color difference signal (RY), (BY), and a luminance signal in an upper region of the screen from the luminance signal YH24 and the color difference signals (RY) 23 and (BY) 22. The division processing circuits (1) and 26 for obtaining YL are divided processing circuits (1) 2
An image recognition circuit (1) 27 for detecting whether or not the area defined by 5 contains a blue sky is a detection signal from the image recognition circuit (1) 26 indicating a blue sky (entered / not entered). is there.

Reference numeral 28 denotes a reference value generation circuit that defines three types of threshold levels of a luminance signal and a color difference signal used in the image recognition circuit (1) 26, and 29 denotes an iris encoder 1
4 is an iris encoder output for grasping an iris opening amount, 30 is an AE level setting circuit for setting an AE level according to a detection signal 27 from an image recognition circuit (1) 26, and 31 is an AE level setting circuit of the present invention. This is a system control circuit that realizes automatic exposure control, and has an AE control unit 31A.

Next, the operation will be described. AGC circuit 5
Is output to the luminance / chromaticity signal generation circuit 20 in the camera signal processing circuit 6. The luminance and chromaticity signal generation circuit 20 generates a high frequency component YH of the luminance signal, a low frequency component YL of the luminance signal, a red signal and a blue signal, and outputs them as color signals R and B, respectively. The color difference signals (RY) 23 and (BY) 22 are input to the generation circuit 21 and are generated. The luminance signal YH24, color difference signal (RY) 23, (B-
Y) 22 is sent to the division processing circuit (1) 25, and the integration of (RY), (BY), and YH in a predetermined area 3A in the upper part of the imaging screen as shown in FIG. A value is generated.

Next, the integrated values of the luminance signal YH24, the color difference signals (RY) 23, and (BY) 22 output from the division processing circuit (1) 25 are input to the image recognition circuit (1) 26. Each is compared with the threshold level from the reference value generation circuit 28. On the other hand, the iris encoder output signal 29 output from the iris encoder 14 is input to the image recognition circuit (1) 26 so that the illuminance of the subject can be grasped.

Then, the image recognition circuit (1) 26 determines whether or not the area determined by the division processing circuit (1) 25 includes a blue sky, and a detection signal 27 according to the determination.
Is input to the AE level circuit 30, and when the image includes a blue sky, the AE level is set to be slightly brighter to prevent the black portion at the lower portion of the screen from being lost.

Here, an algorithm for determining whether or not a blue sky is included in the image recognition circuit 26 will be briefly described. In general, the illuminance of a subject shows relatively high numerical values in outdoor sunlight, and the color temperature of the subject is relatively high. Conversely, with artificial lighting indoors, the illuminance of the subject is low and the color temperature is often relatively low. Accordingly, the color temperature of the subject can be specified to some extent according to the illuminance of the subject.

Therefore, while grasping the illuminance of the subject,
By defining each threshold level corresponding to the blue sky in fine weather by the reference value generation circuit 28,
At the upper part of the screen, the color difference data (R
If the integrated values of -Y) and (BY) are blue and the illuminance of the subject is high, it can be determined that the portion is a blue sky.

FIG. 3 is a block diagram showing a second embodiment of the present invention, wherein 1 to 16 and 20 to 24, 28, 2
Reference numerals 9 and 31 are the same as those described with reference to FIG. 3. In FIG. 3, reference numeral 32 divides the upper region 3A of the screen as shown in FIG.
-Y), (BY), a division processing circuit (2) for obtaining an integral value of the luminance signal YL, and 33 each determine whether or not each of the regions generated by the division processing circuit (2) 32 includes a blue sky. And an image recognition circuit (2) for recognizing the number of regions including a blue sky in the plurality of divided regions.
A number detection signal 33 outputs the number of areas containing the blue sky, and an AE level adjustment circuit 35 adjusts the AE level setting in a plurality of stages according to the number detection signal 34.

Next, the operation will be described. AGC circuit 5
Are input to the luminance / chromaticity signal generation circuit 20, and the high-frequency component YH of the luminance signal, the low-frequency component YL of the luminance signal, the color signal R, and the color signal B are input in the same manner as in FIG. Then, the color difference signal generation circuit 21 generates the color difference signals (RY) and (BY). Next, the luminance signal YH24, the color difference signal (RY) 23, (B-
Y) 22 is sent to the division processing circuit (2) 32, which divides the upper area 3A of the screen as shown in FIG. 4 into a plurality of parts, and for each of these areas (R-Y), (BY),
An integrated value of YL is generated.

Next, the integrated values of the luminance signal YH, the color difference signals (RY), and (BY) output from the division processing circuit (2) 32 are input to the image recognition circuit (2) 33, and the reference values are respectively set. The threshold level is compared with the threshold level by the value generation circuit 28. On the other hand, the image recognition circuit (2) 33 grasps the illuminance of the subject based on the iris encoder output signal 29 output from the iris encoder 14.

Then, the image recognition circuit (2) 33 detects the number of areas including blue sky in the image, and the information is input to the AE level adjustment circuit 35 as a number detection signal 34. In the AE level adjusting circuit 35, as shown in FIG. 5, by adjusting the AE level according to the number of regions including the blue sky, it is possible to prevent underexposure at the lower portion of the screen.

Each of the functional circuit portions shown in FIGS. 1 and 3 may be configured as hardware, or may be configured as a microcomputer system including a CPU, a memory, and the like. When configured in a microcomputer system, the memory constitutes a storage medium according to the present invention. The storage medium stores a program for executing processing necessary for the above-described operation. In addition, as this storage medium, RO
For example, a semiconductor memory such as an M or RAM, an optical disk, a magneto-optical disk, or a magnetic medium may be used.
M, a floppy disk, a magnetic tape, a nonvolatile memory card, or the like.

In the first and second embodiments, the case where the AE level is changed in accordance with the presence or absence of the blue sky at the upper part of the screen has been described. The AE level may be changed in accordance with the degree of the red color in the upper part. In addition, for example, in a monitoring device or the like, the AE level is changed by determining whether a predetermined color appears on a predetermined portion on the screen. It may be.

[0028]

As described above, claims 1, 7, 9
According to the invention, the exposure of the entire screen can be appropriately controlled according to the color of the subject in a predetermined portion on the screen.

According to the second, eighth and tenth aspects of the present invention, the exposure can be appropriately controlled according to the color and brightness of the subject.

According to the third aspect of the present invention, optimal exposure control can be performed even when a subject including a blue sky in fine weather is photographed, so that the accuracy of exposure control in outdoor fine weather is improved. Can be.

According to the fourth and fifth aspects of the present invention, the light amount control or the AGC control can be appropriately performed. Further, according to the invention of claim 6, since the set value can be finely adjusted according to the proportion of the object of the predetermined color, more optimal exposure control can be performed as compared with the invention of claims 1, 7, and 9. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a conceptual configuration diagram illustrating image recognition according to the first embodiment.

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a conceptual configuration diagram illustrating image recognition according to a second embodiment.

FIG. 5 is a characteristic diagram illustrating a relationship between the number of areas where blue sky detection is performed according to the second embodiment and the AE level.

FIG. 6 is a block diagram illustrating a configuration of a conventional exposure control unit.

FIG. 7 is a configuration diagram illustrating center-weighted average photometry.

[Explanation of symbols]

 2 Iris 3 Image sensor 4 CDS (Double correlation sampling circuit) 5 AGC circuit 6 Camera signal processing circuit 7 Gate circuit 8 Integrator 9 A / D converter 10 CCD drive circuit 11 Iris motor 12 Iris drive circuit 13 D / A conversion Device 14 iris encoder 15 A / D converter 16 D / A converter 20 luminance and chromaticity signal generation circuit 21 color difference signal generation circuit 22 color difference signal (BY) 23 color difference signal (RY) 24 luminance signal YH 25 division Processing circuit (1) 26 Image recognition circuit (1) 27 Blue sky detection circuit 28 Reference value generation circuit 29 Iris encoder output value 30 AE level setting circuit 31 System control circuit 32 Division processing circuit (2) 33 Image recognition circuit (2) 34 Blue sky number detection signal 35 AE level adjustment circuit

Claims (10)

[Claims] An imaging unit configured to image a subject and output an image signal; an exposure control unit configured to control exposure of the imaging unit to the subject to a set value; and an image corresponding to a predetermined portion of an imaging screen of the imaging unit. An imaging apparatus comprising: a color temperature detecting unit configured to detect a color temperature from a signal; and a changing unit configured to change the set value for the exposure control according to the detected color temperature. 2. An apparatus according to claim 1, further comprising an illuminance detecting unit for detecting the illuminance of the subject, wherein the changing unit changes the set value based on the detected color temperature and illuminance. Imaging device. 3. The method according to claim 1, wherein the changing unit changes the setting value such that the exposure is larger than a standard value when it is determined based on the color temperature and the illuminance that the blue sky is present in an upper portion of the imaging screen. The imaging device according to claim 2, wherein: 4. The image pickup apparatus according to claim 1, wherein said exposure control means includes a light amount control system for controlling a light amount from said subject to said image pickup means to a set value. 5. The imaging apparatus according to claim 1, wherein said exposure control means includes an image signal level control system for controlling a level of said image signal to a set value. 6. The imaging apparatus according to claim 1, wherein the changing unit changes the set value in accordance with a ratio of a part having a predetermined color temperature in the predetermined part of the imaging screen. 7. An imaging procedure for imaging an object by an imaging means and outputting an image signal, an exposure control procedure for controlling exposure of the imaging means to the object to a set value, and a predetermined portion of an imaging screen of the imaging means. An imaging method, comprising: a color temperature detecting procedure for detecting a color temperature from a corresponding image signal; and a changing procedure for changing the set value for the exposure control according to the detected color temperature. 8. The illuminance detection procedure for detecting the illuminance of the subject, wherein the setting value is changed based on the color temperature and the illuminance detected by the change procedure. Imaging method. 9. An imaging process for imaging a subject by an imaging unit and outputting an image signal; an exposure control process for controlling exposure of the imaging unit to the subject to a set value; and a predetermined portion of an imaging screen of the imaging unit. Computer storing a program for executing a color temperature detecting process for detecting a color temperature from a corresponding image signal, and a changing process for changing the set value for the exposure control according to the detected color temperature A readable storage medium. 10. A program for executing an illuminance detection process for detecting the illuminance of the subject, wherein the setting value is changed based on the detected color temperature and illuminance in the change process. 10. The computer-readable storage medium according to claim 9, wherein: