JP3097086B2 - Video camera auto iris control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera auto iris control device suitable for application to a digital video camera.

[Conventional technology]

In a conventional auto iris circuit, for example, a circuit as shown in FIG. 4 is used in order to obtain data of an exposure amount or an incident light amount. In FIG. 4, (2) is a non-additive mixing (NAM) circuit (2), to which red, blue, and green signals R, G, and G from imaging means (not shown) such as a CCD of a color video camera. B is the input terminal (1R), (1G),
(1B). In the NAM circuit (2), a color signal having the highest level among the red, blue and green signals R, G and B supplied thereto is selected and output.

The color signal from the NAM circuit (2) is supplied to a peak detection circuit (3) and an average value detection circuit (4). Each detection output from the detection circuits (3) and (4) is supplied to a mixing circuit (5) composed of a potentiometer and capable of changing a mixing ratio, and the mixed output is output to an output terminal (6). .

The input / output characteristics of the above-described peak detection circuit (3) are as shown by a solid line curve (7) in FIG. 5, and the input / output characteristics of the average value detection circuit (4) are indicated by a broken line in FIG. Curve of (8)
As shown in FIG. In FIG. 5, the horizontal axis represents the area ratio of the subject corresponding to the white peak (100 IRE) in the video screen with respect to the background corresponding to the pedestal level (0 IRE) of the video signal in%. This is called APL
(Average picture level). The vertical axis represents the level (voltage) of the detection output from each of the detection circuits (3) and (4).
It is expressed in units of mV.

As is clear from FIG. 5, the APL on the horizontal axis is about 38%
The curves intersect at the position of, and by changing the mixing ratio of the mixing circuit (5), the input / output characteristics corresponding to the curves located in the region between the curves (7) and (8) are obtained. Will be obtained. Since the control operation of the auto iris changes according to such a change in the characteristics, the mode ratio of the auto iris can be switched by changing the mixing ratio of the mixing circuit (5) according to the photographing conditions and the subject. .

[Problems to be solved by the invention]

By the way, when an auto iris control circuit of a video camera based on the conventional analog circuit described above is to be constituted by a digital circuit, an enormous amount of data must be arithmetically processed at an extremely high speed, which is not practical.

In view of such a point, the present invention intends to propose a video camera auto iris control device which can easily control the video camera auto iris.

[Means for solving the problem]

An automatic iris control device for a video camera according to the present invention includes an image pickup unit, an iris unit for adjusting the amount of light incident on the image pickup unit, and a screen unit period of a digital video signal obtained by digitizing a video signal from the image pickup unit. Peak detecting means for detecting a peak value of each level, and iris control signal generating means for supplying an iris control signal to the iris means based on the level of the digital video signal and the peak value of the digital video signal per screen unit period In the iris control signal generation means, the brightness based on the level of the digital video signal for each of a plurality of pixels obtained by dividing the imaging surface of the imaging means into a matrix, The brightness of the digital video signal from the peak detection means for each screen unit period, based on the level of the video signal. The difference between the peak value of the brightness based on the peak value of the pixel, the position of the plurality of pixels, and each membership function of the control amount of the iris control signal are set in advance, and the brightness, the brightness and the peak value of the brightness According to the combination of the difference and the label of each membership function of the positions of the plurality of pixels, a plurality of rules for selecting the label of the membership function of the control amount are set in advance,
The iris control signal generating means includes: a brightness for each of the plurality of rules; a difference between the brightness and the peak value of the brightness; and an actual value of each of the positions of the plurality of pixels; Calculate each matching coefficient between the difference from the value and the membership function of the label of each membership function of the plurality of pixel positions, and select the smallest matching coefficient among the matching coefficients for each rule of the plurality of rules. Then, as a weighting coefficient for the control amount for each rule, the waveform is deformed according to the weighting coefficient for the control amount for each rule so as to cut off the upper part of the waveform of the membership function of the label of the control amount for each rule. Calculate the barycenter of the area of the membership function of the label of the waveform-deformed control amount for each rule, determine the final value of the control amount of the iris control signal, and write The storage unit supplies an address signal based on the level of the digital video signal and a peak value of the digital video signal for each screen unit period and a position signal indicating a position of a plurality of pixels to the storage unit. The iris control signal is read out from the control unit and supplied to the iris means.

[Action]

According to this aspect of the invention, the amount of light incident on the imaging unit is adjusted by the iris unit, and the peak detection unit
The peak value of the level of the digital video signal obtained by digitizing the video signal from the imaging means is detected for each screen unit period, and the level of the digital video signal and the screen of the digital video signal are detected by the iris control signal generation means. An iris control signal is supplied to the iris means based on the peak value for each unit period.

In the iris control signal generating means, the brightness based on the level of the digital video signal for each of a plurality of pixels obtained by dividing the imaging surface of the imaging means into a matrix, and the level of the digital video signal for each of the plurality of pixels Of the brightness based on the peak value of the brightness based on the peak value of the level of the digital video signal from the peak detection unit for each screen unit period, the position of a plurality of pixels, and the control amount of the iris control signal. Is set in advance, and the label of the membership function of the control amount is selected according to the combination of the brightness, the difference between the brightness and the peak value of the brightness, and the label of each membership function at the positions of the plurality of pixels. A plurality of rules are set in advance.

Then, the iris control signal generating means includes a brightness for each of the plurality of rules, a difference between the brightness and a peak value of the brightness, and an actual value of each of a plurality of pixel positions, brightness,
Calculate each matching coefficient between the difference between the brightness and the peak value of the brightness and the membership function of the label of each membership function of the positions of the plurality of pixels, and among the matching coefficients for each rule of the plurality of rules, The smallest matching coefficient is selected and used as a weighting coefficient for the control amount for each rule. According to the weighting coefficient for the control amount for each rule, the upper part of the waveform of the membership function of the label of the control amount for each rule is displayed. The waveform is deformed so that it is cut off, the center of gravity of the area of the membership function of the label of the control amount whose waveform is deformed for each rule is calculated, the final value of the control amount of the iris control signal is determined, and stored in the storage unit. In addition, an address signal and a plurality of pixels based on the level of the digital video signal and the peak value of the digital video signal for each screen unit period are provided. A position signal indicating the position is supplied to the storage unit, reads out the determined value of the control amount of the iris control signal from the storage unit, and supplies to the iris unit.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. (16) ROM, 1Mbit EPROM here
(Erasable programmable ROM).

(10) is an A / D conversion circuit to which red, blue, and green signals R, G, and B from imaging means (not shown) such as a CCD of a color video camera are respectively input to an input terminal (1R), (1G), (1
B) and digitized respectively.

The digital red, blue and green signals from the A / D conversion circuit (10) are supplied to the digital NAM circuit (11), and among these color signals, the highest level digital color signal (5-bit signal) is output. The digital color signal is supplied to a peak detection circuit (12) and is also supplied to a ROM (16) as an address signal.

The peak detection circuit (12) is a video signal (or a signal having the highest level among red, blue and green signals) from the imaging means.
The circuit detects the peak value of the level for each field period, and comprises a digital NAM circuit (13) and a digital sampling and holding circuit (14). Then, the digital color signal from the above-mentioned NAM circuit (11) is
3), the output of the NAM circuit (13) is supplied to the sampling and holding circuit (14), and the output of the sampling and holding circuit (14) is output to the NAM circuit (1).
3) supplied to. Also, the vertical synchronizing signals related to the red, blue and green signals R, G, B supplied to the A / D conversion circuit (10) are supplied to the NAM circuit (13) as clear pulses, and sampling is performed. Sampling as pulse
It is supplied to the hold circuit (14). And the digital peak value obtained from the sampling and holding circuit (14)
PV (5 bits) is supplied to the ROM (16) as an address signal.

(15) is an address counter which divides the imaging surface of the above-mentioned imaging means into, for example, 16 × 16 matrix pixels, and supplies a horizontal synchronization signal and a vertical synchronization signal from a synchronization signal generation means to supply the imaging means. Based on the above, in synchronization with the scanning of the imaging means, an 8-bit address signal for specifying 16 × 16 addresses of the ROM (16) provided corresponding to the 16 × 16 matrix pixels, ie, , 16x16 matrix-like pixel signals, which are supplied to the ROM (16).

Then, as described later, 16 × 16
A digital control signal for the iris mechanism is created using fuzzy inference according to the brightness of the subject image at each pixel and the difference between the brightness and the peak value of the brightness for each field. And read out the digital control signal according to the level of the highest level of the red signal, the blue signal, and the green signal from the imaging means and the distribution of the peak value in 16 × 16 pixels. To do.

The digital control signal read from the ROM (16) is supplied to a D / A conversion circuit (17), converted into an analog signal, and then supplied to an iris mechanism (not shown) through a low-pass filter (18). Is done.

Next, with reference to FIGS. 2 and 3, a method of determining a digital control signal to be stored in the ROM (16) using fuzzy inference will be described.

The following three are adopted as input parameters for controlling the iris of the video camera. However, the above 16 × 16
An arbitrary pixel among the pixels is defined as a pixel x.

(A) Address (position) of pixel x (b) Data of pixel x (brightness of subject image) (c) Difference data of pixel x (brightness of subject image
The difference between the brightness and the peak value of each field) For each of the three input parameters and the iris control signal, a fuzzy set as shown in FIGS. 2A to 2D is given. FIG. 2A shows the membership function of the position, and seven kinds of labels, “lower”, “slightly lower”, “center”, “slightly upper”, and “upper” are prepared.

FIG. 2B shows the membership function of brightness, "very dark", "dark", "slightly dark", "normal", "slightly bright", "bright", "very bright".
7 labels are prepared.

FIG. 2C shows the membership function of the difference from the peak value (the difference between the brightness and the peak value). The membership functions of "very small", "small", "slightly small" and "almost equal" are shown. Four kinds of labels are prepared.

FIG. 2D shows the membership function of the controlled variable, in which seven labels of “close widely”, “close”, “close a little”, do not move much, “open a little”, “open” and “open a lot” are shown. It is prepared.

Next, a rule for controlling the iris is set.
This rule is expressed by, for example, the following words in consideration of a rule of thumb in iris control of a video camera.
Here, the input indicates the brightness of the subject image.

If such a rule is used, the iris peak value can be controlled. If the control of the iris is to be made closer to the average value control, the following rule is added to the above rule.

In outdoor shooting, there is often a bright sky above the subject image. To exclude this from the control target of the iris, the above-mentioned rules require that “the middle or lower part of the imaging surface of the imaging means be hit. You can add a sentence that says

Next, an algorithm for obtaining the actual control amount of the iris from the two data of the actual pixel x will be described using the above-described rules (1-1) to (1-3). It is assumed that the difference between the actual brightness and the peak value is a and the actual brightness is b. First, referring to FIG. 3A, the input a is a rule (1
Consider how much the input of -1) is almost equal to the peak value. It is assumed that the value is 0.5 derived from the fuzzy set shown in FIG. 2C. Next, when the matching between the input b and “dark” in the rule (1-1) is checked, it is 0. In this case, the weight for the control amount “open greatly” is zero.

Next, referring to FIG. 3B, looking at the rule (1-2), matching with the input a is 0.5 and matching with the input b is 0.7. In this case, the smaller of 0.5 is adopted, and the membership function of `` do not move much '' of the control amount is set to 0.
Cut off with 5.

Next, referring to FIG. 3C, looking at the rule (1-3), matching with the input a is 0.5 and matching with the input b is 0.3. In this case, the smaller 0.3 is adopted, and the membership function of "squeezing iris a little" of the control amount is
Sharp off at 0.5.

Although the fuzzy theory ends here, the actual iris control value is a definite value. In order to obtain this, as shown in FIG. 3D, the center of gravity (where the area is halved) of the membership function cut off by each weight is obtained and stored in the ROM (16). Then, an address signal based on the level of the digital video signal and a field period of the digital video signal, that is, an address signal based on a peak value for each screen unit period, and a position signal indicating the positions of 16 × 16 matrix pixels are stored in the ROM (16). ) To read the fixed value (digital value) of the control amount of the iris control signal from the ROM (16), and supply it to the D / A converter (17) to convert it to an analog value. It is supplied to the iris mechanism through a low-pass filter (18).

〔The invention's effect〕

According to the present invention described above, it is possible to obtain an auto iris control device for a video camera capable of easily controlling the auto iris. Further, according to the present invention, it is possible to set the control method of the auto iris by simulation on software, easily add or change rules in fuzzy inference, and reduce the required circuit scale. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a fuzzy set of each parameter, FIG. 3 is a diagram showing a state of fuzzy inference, and FIG. FIG. 5 is a curve diagram showing the input / output characteristics of the conventional detection circuit. (10) is an A / D conversion circuit, (11) is a NAM circuit, (12) is a digital peak value detection circuit, (13) is a digital NAM circuit, (1)
4) Sampling and holding circuit, (15) Address counter, (16) ROM, (17) D / A conversion circuit, (18)
Is a low-pass filter.

Claims (1)

(57) [Claims] 1. An image pickup means, an iris means for adjusting the amount of light incident on the image pickup means, and a level peak for each screen unit period of a digital video signal obtained by digitizing a video signal from the image pickup means. Peak detecting means for detecting a value of the digital video signal, and iris control signal generating means for supplying an iris control signal to the iris means based on a level of the digital video signal and a peak value of the digital video signal for each unit screen period. In the iris control signal generating means, brightness based on the level of the digital video signal for each of a plurality of pixels obtained by dividing the imaging surface of the imaging means into a matrix, The peak of the brightness based on the level of the video signal in the level of the digital video signal per screen unit period from the peak detection means. Each membership function of the difference between the peak value of the brightness based on the value, the positions of the plurality of pixels and the control amount of the iris control signal is set in advance, and the brightness, the brightness and the peak value of the brightness are set. And a plurality of rules for selecting a label of the membership function of the control amount are set in advance according to a difference between the iris control signal generating means and the iris control signal generating means. The brightness of each of the plurality of rules, the difference between the brightness and the peak value of the brightness, and the actual values of the positions of the plurality of pixels, and the brightness, the brightness and the brightness Calculating each matching coefficient between the difference from the peak value and the membership function of the label of each membership function of the positions of the plurality of pixels, The smallest matching coefficient among the matching coefficients for each rule of the plurality of rules is selected as a weighting coefficient for the control amount for each rule, and according to the weighting coefficient for the control amount for each rule, The waveform of the membership function of the label of the control amount for each rule is deformed so as to cut off the upper part of the waveform, and the center of gravity of the area of the membership function of the label of the control amount that is waveform-deformed for each rule is calculated. The determined value of the control amount of the iris control signal is determined and stored in a storage unit, and the address signal based on the level of the digital video signal and the peak value of the digital video signal for each screen unit period, respectively. Also, a position signal indicating the positions of the plurality of pixels is supplied to the storage unit, and the control unit determines the control amount of the iris control signal from the storage unit. Read the value, auto iris control device of the video camera, characterized in that it has to be supplied to said iris means.