JPH05207482A - Automatic level setting device, automatic level controller and image pickup device - Google Patents

Abstract

PURPOSE:To attain the setting of an automatic level in an excellent way by integrating color information and brightness information so as to solve a problem of a conventional device in which an iris is too much open even to an object with a low brightness resulting in causing an unnatural picture with respect to the automatic level setting of a video camera or the like. CONSTITUTION:The device is provided with an object brightness calculation circuit 14 calculating a brightness of an object and with a setting brightness calculation circuit 15 referring to a brightness setting table from a chromaticity signal and an object brightness signal and calculating the setting brightness. Through the constitution above, the chromaticity and the brightness of an object are processed impartially, the brightness of the object being a criterion of indoor or outdoor for each color is set, and it is prevented that an iris is too much open with respect to an object in which a close relation is in existence between a color and a spectral reflectance like a green color of grass at an outdoor place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic level setting device for reproducing a beautiful image in a video camera or the like, an automatic level control device and an image pickup device using the same.

[0002]

2. Description of the Related Art In recent years, with the spread of video cameras, means for following photographing conditions have become more and more important in order to obtain beautiful colors. Among them, controlling the aperture of the video camera according to the brightness of the subject is also important for obtaining a natural image.

In a conventional automatic level control device for a video camera (hereinafter abbreviated as ALC), there is a method for enabling backlight compensation in addition to control for keeping the average luminance of a recorded image constant. It is disclosed in JP-A-2-268080. The conventional automatic level setting device will be described below.

FIG. 5 is a block diagram showing the structure of a conventional automatic level setting device. In FIG. 5, reference numeral 52 denotes a frame memory that stores an image signal for one screen, 51 indicates that the image signal for one screen is written in the frame memory 52, and the image signal stored in the frame memory 52 is divided into five areas. Is a screen dividing circuit that outputs the averaged luminance for each region from the image signal divided into regions, and 55 is the averaged luminance for each region sent from the adder 53. It is a frame memory to store,
Reference numeral 54 denotes a photometric value calculation circuit that writes the averaged brightness for each area to the frame memory 55 from the adder 53, reads out the averaged brightness for each area according to the set program, and calculates the set brightness. is there.

The operation of the automatic level setting device constructed as above will be described below. First, the screen division circuit 51 writes the image signal in the frame memory 52. Next, the screen division circuit 51 reads out an image signal for each set area from the frame memory 52 and adds it to the adder 53.
Send to. The adder 53 calculates the addition average brightness for each area from the image signal sent from the screen division circuit 51 for each area. The photometric value calculation circuit 54 calculates the brightness averaged for each area sent from the adder 53 and adds the averaged brightness to the frame memory 5
Write to 5. Further, the photometric value calculation circuit 54 reads the brightness averaged for each area from the frame memory 55 and calculates the set brightness value according to a preset program.

[0006]

However, in the above configuration, since the diaphragm control is performed only by the brightness information, it is not possible to determine the shooting condition of the backlight condition from the distribution of the brightness signal and perform the retrograde correction. However, for subjects with low brightness such as greenery of plants, there is a problem that the aperture is opened more than necessary and an unnatural image is formed.

The present invention solves the above problems and provides an excellent automatic level setting device, automatic level control device, and image pickup device capable of obtaining a natural and beautiful image by integrating color information and luminance information. The purpose is to provide.

[0008]

In order to achieve this object, an automatic level setting device of the present invention comprises a sampling circuit for obtaining image data suitable for calculating an automatic level set value from a color-separated image signal. , A diaphragm value input terminal for receiving the diaphragm value signal F of the video camera, and a sampling luminance signal Y and a sampling chromaticity signal ((BY) / Y, (RY) / Y) from the sampled image data. A signal conversion circuit for calculating, a subject luminance calculation circuit for calculating the sampled subject luminance HY from the aperture value signal F and the sampling luminance signal Y, and a sampling chromaticity signal ((BY)
/ Y, (RY) / Y) and a set brightness calculation unit that calculates a set brightness value from the sampled subject brightness signal HY.

Then, the automatic level setting device is incorporated in the automatic level control device and the image pickup device.

[0010]

With this configuration, when the set brightness is calculated, the chromaticity and the brightness of the subject are treated equally, and the set brightness can be given by arbitrarily dividing the three-dimensional space composed of the chromaticity and the brightness. .. This makes it possible to set the brightness of the subject, which is the judgment boundary between indoor and outdoor, for each color.
It is possible to give a low set brightness value to green, which has low brightness, and give a high set brightness value to yellow, which has high brightness.

As a result, the aperture control is performed as usual for a normal subject, and the aperture is controlled for a subject having a close relationship between color and spectral reflectance, such as greenery in the outdoors. It is possible to realize an automatic level setting device and an automatic level control device that can prevent the open position from opening too much (or closing too close). Moreover, the image pickup apparatus using this can reproduce a beautiful image.

[0012]

(Embodiment 1) An embodiment of the automatic level setting device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an automatic level setting device according to an embodiment of the present invention.

In FIG. 1, 11 is a sampling circuit for obtaining image data suitable for calculation of a set luminance value of automatic level setting from an image signal subjected to color separation, and 12 receives an aperture value signal F of a video camera. An aperture value input terminal 13 is a sampling luminance signal Y and a sampling chromaticity signal ((B−Y) /
Y, (RY) / Y) is a signal conversion circuit, 14 is a subject brightness calculation circuit that calculates the sampled subject brightness HY from the aperture value signal F and the sampling brightness signal Y, and 15 is a sampling Chromaticity signal ((B-
Y) / Y, (RY) / Y) and a sampled subject brightness signal HY, which is a set brightness calculation unit that outputs a set brightness value signal. 151 is a sampling brightness mainly for the sampling chromaticity signal and the sampled subject brightness signal. A signal evaluation circuit that evaluates whether a signal is good or bad based on the signal.
Reference numeral 2 denotes an average value calculation circuit that calculates the average value of each of the sampling chromaticity signal and the sampled subject luminance signal, which are good data in the signal evaluation circuit 151.
Reference numeral 3 internally has a luminance setting value table having a three-dimensional space composed of chromaticity and luminance as an expression space, and is designated by the average sampling chromaticity and the average sampling subject luminance signal from the average value calculation circuit 152. It is a set brightness calculation circuit that draws a brightness set value table by points and outputs a brightness set value signal.

The operation of the automatic level setting device configured as described above will be described. First, the sampling circuit 11 samples the color-separated image signal according to a sampling rule suitable for calculating the preset brightness value of the automatic level setting device set in advance. As an example of the image data created by the sampling circuit 11, it is possible to divide the screen into several blocks and consider the average value of the luminance signal and the color difference signal for each block. The signal conversion circuit 13 includes the sampling circuit 11
Image data from the sampling luminance signal Y and sampling chromaticity signals ((BY) / Y, (RY) /
Y) and are calculated. The subject luminance calculation circuit 14 calculates the sampled subject luminance HY from the sampling luminance signal Y from the signal conversion circuit 13 and the aperture signal F input from the aperture value input terminal 12. Normally, this sampled subject brightness HY is given by HY = F ² * Y when the f value is used as the aperture signal. The set brightness calculation unit 15 calculates the set brightness value using the sampling chromaticity signal and the sampling subject brightness signal. First, the signal evaluation circuit 151 evaluates the quality of the signal based on the sampling chromaticity signal and the sampling subject luminance signal, mainly based on the sampling luminance signal. For example, when the sampling luminance signal is higher than the highest luminance setting value and when the sampling luminance signal is lower than the lowest luminance setting value, it is determined as a defective signal. Next, the average value calculation circuit 152 calculates each average value using the sampling chromaticity signal and the sampling subject luminance signal which are good data in the signal evaluation circuit 151. The set luminance calculation circuit 153 is based on the points designated by the average sampling chromaticity and the average sampling subject luminance signal from the average value calculating circuit 152, and is set in the three-dimensional space constituted by the chromaticity and luminance held inside. The set brightness is obtained by drawing the set brightness table having the expression space as.

The difference between the automatic level setting device according to the present embodiment and the conventional automatic level setting device will be described with reference to the drawings. FIG. 4 is a conceptual diagram for explaining how the conventional automatic level setting device operates. A plane CP1 in FIG. 4 represents a state of the image signal when the video camera changes its direction from a normal subject to a subject having a low spectral reflectance. The plane CP2 represents the state of the image signal after being automatically adjusted to the standard setting value Yset of luminance by the conventional automatic level setting device.

Now, when the video camera quickly shoots from a normal subject such as a building and puts a subject having a low spectral reflectance, for example, green C on the tree, on the screen, the brightness of the screen decreases. The average brightness of the screen is Y1.
Here, Y1 <Yset. Since it is not backlit, the brightness distribution of the screen at this time is the same as that of a normal subject. Therefore, since the brightness set by the conventional automatic level setting device remains Yset, the average brightness of the screen is set to Yset in the aperture of the video camera.
To open. Therefore, as the green color of the tree changes from C1 to C2 when the aperture is opened, the color difference of the green C of the tree changes from ΔC _L to ΔC _H. This change reproduces the deep green green of the tree to a bright, bright and unnatural green.

The present invention can reduce this phenomenon by the principle described below. FIG. 2 is a conceptual diagram for explaining the principle of the present invention. FIG. 2 is a three-dimensional space that expresses the chromaticity and brightness of a subject. For example, the green distribution of trees occupies a certain area (area A) of this space. Of course, this area changes greatly depending on the brightness of the light source, and the green of the tree cannot always be identified. However, the area occupied by the green of the tree under normal outdoor light can be sufficiently set. Therefore, considering the above shooting conditions, the point specified by the average sampling chromaticity signal and the average sampling subject luminance signal is the area A.
Will be inside. In this case, if the set brightness is set to a value smaller than the set brightness value Yset for normal shooting, it is possible to prevent the above-described change to an unnatural image. By setting various kinds of set brightness using such subject brightness and color information, it is possible to adjust brightness more naturally with respect to those having a correlation between color and brightness as compared with the conventional automatic level setting device.

The signal used as the aperture value signal may not be the f value if it is set so as to be consistent with the calculation rule in the subject brightness calculation circuit 14. Although not described here intentionally, a timing generator is provided as necessary to synchronize the input timing of the aperture signal with the timing of the average luminance calculation so that the aperture and the image signal correspond accurately. It can also be configured to time the circuit. The same applies to the following examples.

(Embodiment 2) An embodiment of the video control apparatus of the present invention will be described below with reference to the drawings.
FIG. 3 is a block diagram showing the configuration of the video camera.

In FIG. 3, 1 is a diaphragm for adjusting the amount of light, 2 is a solid-state image sensor for converting an optical image into an electric signal, and 3 is a color separation circuit for color-separating the signal from the solid-state image sensor. Reference numeral 10 is an automatic level setting device for calculating a set luminance value from a color-separated signal, and 4 is a signal suitable for encoding a video signal by subjecting the color-separated signal to camera process processing such as γ correction. Is a process & matrix circuit for converting into 5 and 5 is a diaphragm sensor for detecting the opening degree of the diaphragm, and 6 is an average from the signals color-separated by the color separation circuit 3 while judging the quality of the signal as necessary. Reference numeral 7 denotes an average brightness calculation circuit for calculating brightness, and reference numeral 7 denotes a difference calculation circuit for calculating a difference between the average brightness signal from the average brightness calculation circuit 6 and the set brightness value signal from the set brightness calculation circuit 10. 8 is a diaphragm driver luminance difference signal from the difference calculation circuit 7 controls the throttle to zero.

The operation of the video camera configured as described above will be described. First, the light from the subject is attenuated by the diaphragm 1 to form an image on the solid-state image sensor 2. The solid-state image pickup device 2 photoelectrically converts an optical image formed on the surface thereof into an electric signal and outputs the electric signal to the color separation circuit 3. The color separation circuit 3 converts the video signal photoelectrically converted by the solid-state image sensor 2 into a color separation signal. The color separation signal generated by the color separation circuit 3 is sent to the automatic level setting device 10, the average luminance calculation circuit 6 and the process & matrix circuit 4. The automatic level setting device 10 receives the color separation signal from the color separation circuit 3 and the aperture signal F from the aperture sensor and calculates the set luminance value according to the procedure shown in the first embodiment. The average luminance calculation circuit 6 calculates the average sampling luminance using the good data.

The difference calculation circuit 7 includes an automatic level setting device 1
It receives a set brightness value signal from 0, receives the average brightness signal from the average brightness calculation circuit 6, calculates the difference, and outputs it to the aperture driver 8 as a brightness deviation signal. The diaphragm driver 8 controls the diaphragm 1 so as to open and close the diaphragm 1 so that the brightness deviation signal becomes zero. On the other hand, the process & matrix circuit 4 receives a correction color separation signal for which white balance correction has been performed from a white balance circuit (not shown), and performs necessary correction and conversion such as γ correction to an encoder (not shown). The encoder sends it to a video signal. The video signal is sent to a recording system (not shown) and recorded on a video tape.

According to the video camera of the present embodiment, the aperture control can determine not only the brightness but also the aperture setting value including the color of the subject. As a result, the aperture control is performed as usual for normal subjects, but the aperture is too wide open for subjects that have a close relationship between color and spectral reflectance, such as greenery in the outdoors. (Or close too much) can be prevented.

[0024]

As described above, according to the present invention, the automatic level setting device internally has the set value table in which the expression space is a three-dimensional space composed of chromaticity and luminance, and the chromaticity and the subject luminance signal are set. It is configured with chromaticity and brightness by providing a set brightness calculation unit that calculates the set brightness by pulling the setting value table according to the points specified by, and treating the chromaticity and brightness of the subject equally when performing the set brightness calculation. The set luminance can be given by arbitrarily dividing the three-dimensional space described above. Therefore, it becomes possible to set the brightness of the subject, which is the judgment boundary between indoor and outdoor, for each color. For example, a low set brightness value is given to green with low brightness, and a high set brightness value is given to yellow with high brightness. It becomes possible to do.

As a result, the aperture control is performed as usual for a normal subject, and the aperture is controlled for a subject having a close relationship between color and spectral reflectance, such as greenery in the outdoors. It is possible to realize an automatic level setting device and an automatic level control device that can prevent the open position from opening too much (or closing too close). Although a video camera has been described as an example here, the present invention can be applied to general image pickup devices such as electronic still cameras involving photoelectric conversion, and a beautiful image can be obtained with such an image pickup device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an automatic level setting device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram for explaining the principle of operation of the automatic level setting device of the present invention.

FIG. 3 is a block diagram showing a configuration of a video camera according to a second embodiment of the present invention.

FIG. 4 is a conceptual diagram for explaining problems of the conventional automatic level setting device.

FIG. 5 is a block diagram showing a configuration of a conventional automatic level setting device.

[Explanation of symbols]

 1 Aperture 2 Solid-state imaging device 3 Color separation circuit 4 Process & matrix circuit 5 Aperture sensor 6 Average brightness calculation circuit 7 Difference calculation circuit 8 Aperture driver 10 Automatic level setting device 11 Sampling circuit 12 Aperture value input terminal 13 Signal conversion circuit 14 Subject brightness Calculation circuit 15 Set brightness calculation unit 151 Signal evaluation circuit 152 Average value calculation circuit 153 Set brightness calculation circuit 51 Screen division circuit 52 Frame memory 53 Adder 54 Photometric value calculation circuit 55 Frame memory

Claims (7)

[Claims] 1. A sampling circuit for obtaining image data suitable for automatic level setting value calculation from color-separated image signals, an aperture value input terminal for receiving an aperture value signal of a video camera, and sampled image data. A signal conversion circuit that calculates at least a sampling luminance signal, a subject luminance calculation circuit that calculates a sampling subject luminance from an aperture value signal and a sampling luminance signal, and a setting luminance calculation that calculates a set luminance from image data and a sampled subject luminance signal Automatic level setting device consisting of parts. 2. The automatic level setting device according to claim 1, wherein the signal conversion circuit calculates a sampling chromaticity signal and a sampling luminance signal from the sampled image data. 3. The automatic level setting device according to claim 2, wherein the set luminance calculation unit uses a sampling chromaticity signal and a sampling subject luminance signal. 4. The automatic level setting device according to claim 2, wherein the set luminance calculation unit uses a sampling chromaticity signal, a sampling luminance signal, and a sampled subject luminance signal. 5. The set luminance calculation unit includes a signal evaluation circuit that evaluates whether the signal is good or bad mainly based on the sampling luminance signal based on the sampling chromaticity signal and the sampled subject luminance signal, and sampling performed by the signal evaluation circuit as good data. An average value calculation circuit that calculates each average value using a chromaticity signal and a sampled subject luminance signal, and a plane or curved surface that is not parallel to the chromaticity plane in a three-dimensional space composed of chromaticity and luminance A set brightness calculation circuit that internally has a determination table having an outdoor / indoor separation plane, and obtains the set brightness by drawing the table according to the points specified by the average sampling chromaticity and the average sampling subject brightness signal from the average value calculation circuit The automatic level setting device according to claim 4, comprising: 6. An average value for calculating an average sampling brightness from good data by receiving sampling brightness from the automatic level setting device according to claim 1 and a sampling circuit in the automatic level setting device. An automatic level control device comprising: a calculation circuit; and a difference calculation circuit that calculates the difference between the average sampling brightness from the average value calculation circuit and the set brightness from the set value calculation circuit. 7. An image pickup apparatus using the automatic level setting device according to claim 1 or the automatic level control device according to claim 6.