JP2600553B2 - Automatic level setting device, automatic level control device, and imaging device - Google Patents

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, an automatic level control device for reproducing a beautiful image in a video camera or the like, 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 shooting conditions in order to obtain beautiful colors has become increasingly important. Among them, control of the aperture of a video camera according to the brightness of a subject is also important for obtaining a natural image.

A conventional automatic level controller (hereinafter abbreviated as ALC) of a video camera employs a technique for enabling backlight correction in addition to controlling the average luminance of a recorded image to be constant. It is disclosed in Japanese Patent Publication No. 2-268080. Hereinafter, a conventional automatic level setting device will be described.

FIG. 5 is a block diagram showing a configuration of a conventional automatic level setting device. In FIG. 5, reference numeral 52 denotes a frame memory for storing an image signal for one screen, 51 denotes an image signal for one screen written in the frame memory 52, and divides the image signal stored in the frame memory 52 into five regions. 53 is an adder for calculating the average luminance of each area from the image signal obtained by dividing the area, and 55 is an adder for calculating the average luminance of each area sent from the adder 53. A frame memory for storing
Numeral 54 denotes a photometric value calculation circuit which writes the averaged luminance for each area from the adder 53 to the frame memory 55, reads out the averaged luminance for each area as necessary according to a set program, and calculates the set luminance. is there.

[0005] The operation of the automatic level setting device configured as described above will be described below. First, the screen division circuit 51 writes an image signal into the frame memory 52. Next, the screen division circuit 51 reads out the image signal for each set area from the frame memory 52, and
Send to The adder 53 calculates the average average luminance 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 luminance averaged for each area sent from the adder 53 to the frame memory 5.
Write 5 Further, the photometric value calculation circuit 54 reads out the luminance averaged for each area from the frame memory 55, and calculates a set luminance value according to a preset program.

[0006]

However, in the above configuration, since the aperture control is performed only with the luminance information, it is possible to determine the photographing condition in the backlight state from the state of the distribution of the luminance signal and perform the backward correction. However, there is a problem that a subject having a low luminance, such as greenery of a vegetation, opens an aperture more than necessary, resulting in an unnatural image.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides an excellent automatic level setting device, an automatic level control device, and an imaging 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 according to the present invention comprises a sampling circuit for obtaining image data suitable for calculating an automatic level setting value from a color-separated image signal. And an aperture value input terminal for receiving an aperture value signal F of a 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, an object luminance calculation circuit for calculating a sample object luminance HY from the aperture value signal F and the sampling luminance signal Y, and a sampling chromaticity signal ((B−Y)
/ Y, (R−Y) / Y) and a sampled luminance signal HY, and a set luminance calculation unit that calculates a set luminance value.

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

[0010]

With this configuration, the chromaticity and the luminance of the subject can be treated equally when performing the set luminance calculation, and the set luminance can be given by arbitrarily dividing the three-dimensional space composed of the chromaticity and the luminance. . Thereby, it becomes possible to set the luminance of the subject that is the determination boundary between indoor and outdoor for each color, for example,
It is possible to give a low setting luminance value to green with low luminance, and give a high setting luminance value to yellow with high luminance.

Thus, while the aperture control is performed as usual for a normal subject, the aperture control is performed for a subject having a close relationship between the color and the spectral reflectance, such as greenery of a vegetation outdoors. The automatic level setting device and the automatic level control device that can prevent the opening of (or closing) too much can be realized. In addition, an imaging device using this can reproduce a beautiful image.

[0012]

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

In FIG. 1, reference numeral 11 denotes a sampling circuit for obtaining image data suitable for calculating a set luminance value for automatic level setting from a color-separated image signal, and 12 receives an aperture value signal F of a video camera. Reference numeral 13 denotes an aperture value input terminal. Reference numeral 13 denotes a sampling luminance signal Y and a sampling chromaticity signal ((BY) /
Y, (RY) / Y), a signal conversion circuit 14 for calculating a sampled object luminance HY from the aperture value signal F and the sampled luminance signal Y, and 15 a sampling circuit. Chromaticity signal ((B-
Y) / Y, (RY) / Y) and a sampled luminance signal HY and a set luminance calculation unit that outputs a set luminance value signal. Reference numeral 151 denotes a sampling luminance mainly based on the sampling chromaticity signal and the sampled luminance signal. A signal evaluation circuit for evaluating the quality of the signal based on the signal;
Reference numeral 2 denotes an average value calculation circuit that calculates an average value of each using the sampled chromaticity signal and the sampled subject luminance signal which are regarded as good data by the signal evaluation circuit 151.
Reference numeral 3 has a luminance setting value table in which a three-dimensional space composed of chromaticity and luminance is used as an expression space, and is designated by the average sampling chromaticity from the average value calculation circuit 152 and the average sampling subject luminance signal. This is a setting luminance calculation circuit that outputs a luminance setting value signal by drawing a luminance setting value table according to points.

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 in accordance with a sampling rule suitable for calculating a preset luminance value of the automatic level setting device. As an example of the image data created by the sampling circuit 11, the screen can be divided into several blocks, and the average value of the luminance signal and color difference signal for each block can be considered. The signal conversion circuit 13 includes the sampling circuit 11
Receiving the image data from the sampling luminance signal Y and the sampling chromaticity signal ((BY) / Y, (RY) /
Y) is calculated. The subject brightness calculation circuit 14 calculates a sampled subject brightness HY from the sampling brightness signal Y from the signal conversion circuit 13 and the aperture signal F input from the aperture value input terminal 12. Normally, when the f-number is used as the aperture signal, the sampling subject luminance HY is given by HY = F ² * Y. The setting luminance calculator 15 calculates a setting luminance value using the sampling chromaticity signal and the sampling subject luminance signal. First, the signal evaluation circuit 151 evaluates the quality of the signal based mainly on the sampling chrominance signal and the sampling object luminance signal based on the sampling luminance signal. For example, a defective signal is determined when the sampling luminance signal is higher than the maximum luminance setting value and when the sampling luminance signal is lower than the minimum luminance setting value. Next, the average value calculation circuit 152 calculates the respective average values using the sampled chromaticity signal and the sampled subject luminance signal which have been regarded as good data by the signal evaluation circuit 151. The set luminance calculation circuit 153 is based on a point designated by the average sampling chromaticity from the average value calculation circuit 152 and the average sampling subject luminance signal, and is used to calculate a chromaticity and luminance held in the three-dimensional space. The set brightness is obtained by subtracting the set brightness table having the expression space.

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 the operation of the conventional automatic level setting device. A plane CP1 in FIG. 4 shows a state of an image signal when the video camera changes the 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 luminance setting value Yset by the conventional automatic level setting device.

Now, when the video camera pans quickly from a state where a normal subject such as a building is being photographed and a subject having a low spectral reflectance, for example, green C of a tree, is placed on the screen, the brightness of the screen decreases. The average luminance of the screen is Y1.
Here, Y1 <Yset. Since there is no backlight, the luminance distribution of the screen at this time is not different from that of a normal subject. Therefore, since the luminance set by the conventional automatic level setting device remains at Yset, the aperture of the video camera can be adjusted such that the average luminance of the screen is Yset.
Open so that. Therefore, green tree is changed from C1 to C2 by the aperture is opened, green tree change this is deep green is reproduced as a change in the bright and bright unnatural green.

The present invention can reduce this phenomenon according to the following principle. FIG. 2 is a conceptual diagram for explaining the principle of the present invention. FIG. 2 is a three-dimensional space expressing the chromaticity and luminance of a subject. For example, the green distribution of a tree occupies a certain area (area A) in this space. Of course, this area varies greatly depending on the brightness of the light source, and it is not always possible to specify the green color of the tree. However, the area occupied by the tree green under ordinary outdoor light can be set sufficiently. Therefore, considering the above-mentioned shooting conditions, the point specified by the average sampling chromaticity signal and the average sampling subject luminance signal is the area A
Will be within. 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 unnatural change to an image. By variously determining the set luminance using the subject luminance and the color information, it is possible to adjust the luminance more naturally for colors having a correlation between the color and the luminance as compared with the conventional automatic level setting device.

Note that the signal used as the aperture value signal need not be the f-number if it is set so as to be consistent with the calculation rules in the object luminance calculation circuit 14. Although not described here, a timing generator is provided as necessary to synchronize the aperture signal input timing with the average luminance calculation timing so that the aperture and the image signal correspond exactly. It is also possible to configure so as to take the timing of the circuit. These are the same in the following embodiments.

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

In FIG. 3, reference numeral 1 denotes a stop for adjusting the amount of light, 2 denotes a solid-state image sensor for converting an optical image into an electric signal, and 3 denotes a color separation circuit for color-separating a signal from the solid-state image sensor. Reference numeral 10 denotes an automatic level setting device that calculates a set luminance value from the color-separated signal. Reference numeral 4 denotes a signal suitable for performing a camera process such as gamma correction on the color-separated signal and encoding the video signal. 5 is an aperture sensor for detecting the degree of opening of the aperture, and 6 is an average while judging the quality of the signal from the signals separated by the color separation circuit 3 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, light from a subject is reduced by the aperture 1 to form an image on the solid-state imaging device 2. The solid-state imaging device 2 photoelectrically converts the 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 imaging device 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 described in the first embodiment. The average luminance calculation circuit 6 calculates an average sampling luminance using the good data.

The difference calculation circuit 7 includes the automatic level setting device 1
The set luminance value signal is received from 0, the average luminance signal is received from the average luminance calculation circuit 6, the difference is calculated, and the difference is output to the aperture driver 8 as a luminance deviation signal. The aperture driver 8 controls the aperture 1 so as to open and close the aperture 1 so that the luminance deviation signal becomes zero. On the other hand, the process & matrix circuit 4 receives a corrected color separation signal subjected to white balance correction from a white balance circuit (not shown), performs necessary corrections and conversions such as γ correction, and sends it to an encoder (not shown). And the encoder converts 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 this embodiment, it is possible to determine the aperture setting value not only for brightness but also for the color of the subject. As a result, while the aperture control is performed as usual for a normal subject, the aperture is too open for a subject having a close relationship between the color and the spectral reflectance, such as greenery of a vegetation outdoors. (Or too close) can be prevented.

[0024]

As described above, according to the present invention, the automatic level setting device has a set value table in which the three-dimensional space composed of chromaticity and luminance is used as the expression space, and the chromaticity and the luminance signal of the object are stored. A setting brightness calculation unit that calculates the setting brightness by subtracting the setting value table from the point specified by, and treats the chromaticity and brightness of the subject equally when performing the setting brightness calculation, and configures the chromaticity and brightness The set brightness can be given by arbitrarily dividing the three-dimensional space to be set. Therefore, it becomes possible to set the brightness of the subject which is a determination 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 is possible to do.

Thus, while the aperture control is performed as usual for a normal subject, the aperture control is performed for a subject having a close relationship between the color and the spectral reflectance, such as the greenery of a vegetation outdoors. The automatic level setting device and the automatic level control device which can prevent the opening of (or too close to) the device can be realized. Although a video camera has been described as an example here, the present invention can be applied to an image pickup device including photoelectric conversion such as an electronic still camera, and a beautiful image can be obtained with such an image pickup device.

[Brief description of the 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 a problem of a conventional automatic level setting device.

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

[Explanation of symbols]

 Reference Signs List 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 Setting brightness calculation unit 151 Signal evaluation circuit 152 Average value calculation circuit 153 Setting brightness calculation circuit 51 Screen division circuit 52 Frame memory 53 Adder 54 Photometric value calculation circuit 55 Frame memory

Claims (5)

(57) [Claims] 1. A sampling circuit for obtaining image data suitable for automatic level setting value calculation from a color-separated image signal, an aperture value input terminal for receiving an aperture value signal of a video camera, and A signal conversion circuit for calculating a sampling chromaticity signal and a sampling luminance signal; an object luminance calculation circuit for calculating a sampling object luminance from the aperture value signal and the sampling luminance signal; and a sampling chromaticity signal ( (BY) / Y, (RY) / Y) and Sampling
An automatic level setting device comprising: a set luminance calculating unit for calculating a set luminance from the subject luminance signal HY . 2. The setting luminance calculating section includes a sampling chromaticity signal.
2. The automatic level setting device according to claim 1 , wherein ((BY) / Y, (RY) / Y) , a sampling luminance signal Y, and a sampling subject luminance signal HY are used. 3. The setting luminance calculating section evaluates the sampling chromaticity signal and the sampling object luminance signal as good signals when the sampling luminance signal is within a predetermined range, and as a bad signal otherwise. A signal evaluation circuit to be evaluated, an average value calculation circuit that calculates respective average values using the sampled chromaticity signal and the sampled object luminance signal which are regarded as good signals by the signal evaluation circuit, and an average value from the average value calculation circuit. A setting luminance calculation circuit for obtaining a setting luminance by drawing a setting luminance table in which a three-dimensional space composed of chromaticity and luminance is used as an expression space based on a point specified by a sampling chromaticity signal and an average sampling object luminance signal The automatic level setting device according to claim 2 , comprising: 4. A automatic level setting device according to any one of claims 1 to 3, the average luminance calculator for calculating a <br/> average sampling brightness from the color separated image signals, prior to
Wherein the average sampling brightness from serial average luminance calculating unit itself
; And a difference calculation circuit for calculating a difference between the set luminance from setting the brightness calculating section of the dynamic level setting in the apparatus, the difference calculation
An automatic level control device that controls the luminance level according to the output signal from the circuit . 5. The image pickup apparatus using an automatic level control system for an automatic level setting apparatus or claim 4, wherein according to any of claims 1 to 3.