JPH0362684A - Automatic iris controller for video camera - Google Patents

Abstract

PURPOSE:To easily control automatic iris of a video camera by storing plural kinds of rules of the control mode in response to the level of the video signal and generating the control signal. CONSTITUTION:A peak value of the video signal obtained from an image pickup means is detected by a peak detection circuit 12 and the peak value and the video signal are fed to a control signal generating means 16 to control the incident luminous quality of the image pickup means based on the control signal. In this case, the generating means 16 stores plural kinds of rules of the control mode in response to the level of the video signal and generates a control signal based on 1st and 2nd weight coefficients resulting from a difference between a level of the video signal and the peak level and on how much the level of the video signal is suited to the plural kinds of rules.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an auto iris control device for a video camera suitable for application to a digital video camera.

[Keystone of the invention]

The present invention provides a peak detection circuit for detecting the peak value of a video signal obtained from an imaging means, a control signal generation means to which the peak value detected by the peak detection circuit and the video signal are supplied, and a control signal generation means for the control signal generation means. In the auto iris control device that controls the amount of light incident on the imaging means based on a control signal from the image pickup means, the control signal generation means includes a storage device that stores a plurality of rules for control modes depending on the level of the video signal. The first and second weighting coefficients are based on the level value of the video signal and the difference between the level value and the peak value, and the signal obtained based on the degree to which the level of the video signal conforms to multiple types of rules. On the basis of the,
By generating a control signal, the auto iris of the video camera can be easily controlled.

[Conventional technology]

In a conventional auto iris circuit, a circuit as shown in FIG. 4, for example, is used to obtain data on the amount of exposure or amount of incident light. In FIG. 4, (2) is a non-additive mixing (NAM) circuit (2), which receives red, blue and green signals R, G from an imaging means (not shown) such as a CCD of a color video camera; B are input terminals (1R) and (I
G), (IB). This NAM circuit (2)
Of the red, blue, and green signals R, G, and B supplied to this, the color signal with the highest level is selected and output.

The color signal from this NAM circuit (2) is supplied to a peak detection circuit (3) and an average value detection circuit (4).

The detection outputs from these detection circuits (3) and (4) are as follows:
The mixture is supplied to a mixing circuit (5) which is made of a potentiometer and can vary the mixing ratio, and its mixing output is output to an output terminal (6).

The input/output characteristics of the peak detection circuit (3) described above are as shown by the solid line curve (7) in FIG. 5, and the human output characteristics of the average value detection circuit (4) are shown by the broken line in FIG. as shown in curve (8). In Fig. 5, the horizontal axis represents the area ratio in the imaging screen of the subject corresponding to the white peak (100 IRE) with respect to the background whose light intensity corresponds to the bedscale level (OIRE) of the video signal. This is hereinafter referred to as APL (average picture level). The vertical axis represents the level (voltage) of the detection output from each detection circuit (3), (4) in mV.

As is clear from this Figure 5, the APL on the horizontal axis is approximately 38
The curves intersect at the % position, and by varying the mixing ratio of the mixing circuit (5), both lines (7) and (8)
This results in input/output characteristics corresponding to the curve located in the region between . Since the control operation of the auto iris changes in response to such changes in characteristics, the mixing ratio of the mixing circuit (5) is varied depending on the shooting conditions, subject, etc. to enable auto iris mode switching. There is.

[Problem to be solved by the invention]

By the way, if you try to configure the auto iris control circuit of a video camera based on the conventional analog circuit described above using a digital circuit, it will be impractical because you will have to process huge amounts of data at extremely high speed. .

In view of this, the present invention proposes an auto-iris control device for a video camera that can easily control the auto-iris of a video camera.

[Means to solve the problem]

The present invention includes a peak detection circuit (12) that detects the peak value of a video signal obtained from an imaging means, and a control signal generation means (12) to which the peak value detected by the peak detection circuit (12) and the video signal are supplied. 16) and the control signal generating means (16), the control signal generating means (16) controls the amount of light incident on the imaging means based on the control signal from the control signal generating means (16). comprising a storage device storing a plurality of types of rules of the aspect, first and second weighting coefficients based on the level value of the video signal and the difference between the level value and the peak value;
A control signal is generated based on a signal obtained depending on how well the level of a video signal conforms to a plurality of types of rules.

[Effect]

According to the present invention, the control signal generating means (16) has a plurality of M rules for control modes depending on the level of the video signal.
first and second weighting coefficients based on the level value of the video signal and the difference between the level value and the peak value, and the level of the video signal according to multiple types of rules. A control signal is generated based on the signal obtained by the matching heel.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIG. (16) is a ROM, here a 1M bit E
PROM (erasable programmable ROM).

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

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 the peak detection circuit (12), and the ROM (
16) as an address signal.

The peak detection circuit (12) detects a video signal (
A circuit that detects the peak value of the level of the signal with the highest level among the red, blue, and green signals for each field period, and is composed of a digital NAM circuit (13) and a digital sampling/holding circuit (14). There is. Then, the digital color signal from the NAM circuit (11) described above is supplied to the NAM circuit (13), and the output of the NAM circuit (13) is transmitted to the NAM circuit (13) itself and the sampling and hold circuit (14). is supplied to.Also,
A vertical synchronization signal related to the red, blue, and green signals R, G, and B supplied to the A/D conversion circuit (10) described above is supplied as a clear pulse to the NAM circuit (13), and is also supplied as a sampling pulse. , is supplied to the sampling and holding circuit (14).The digital peak value PV (4) obtained from the sampling and holding circuit (14) is supplied to the sampling and holding circuit (14).
bits) are supplied to the ROM (16).

(15) is an address counter which divides the imaging surface of the above-mentioned imaging means into, for example, 16×16 matrix-like pixels, and based on the horizontal synchronization signal and vertical synchronization signal from the synchronization signal generation means supplied to the imaging means. In synchronization with the scanning of the imaging means, 16 of the ROMs (16) provided corresponding to 16×16 matrix pixels are
An 8-bit address signal specifying an X16f-specific address is generated, and this is supplied to the ROM (16).

Then, as described later, 16X1 of the imaging surface of the imaging means
Depending on the brightness of the subject image at six pixels and the difference between that brightness and the peak brightness value for each field,
Using fuzzy reasoning, a digital control signal for the iris mechanism is created and stored in this ROM (16), and the level of the highest level color signal among the red signal, blue signal and green signal from the imaging means is determined. and its peak value 1
The digital control signal is read out according to the distribution in 6×16 pixels.

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

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

The following three human parameters are used to control the iris of the video camera. However, the above 16X1
Let any pixel among the six pixels be pixel X.

(a) Address (position) of pixel X (b) Data of pixel X (brightness of subject image) (c)
The data of pixel X (difference between the brightness of the subject image and the peak value of that brightness for each field) is shown in Figure 2 A to D for these three input parameters and the iris control signal. Give the fuzzy set as shown. Figure 2 A shows the position members and -ship functions, such as "lower", "slightly lower", and "around the middle".
There are seven labels available: , "slightly above" and "above".

Figure 2B shows the brightness membership functions: "very dark", "dark", "slightly dark", and "normal".
, "Somewhat bright", "Bright", "Very bright" 7
Street labels are provided.

Figure 2 C shows the difference from the peak value (the difference from the peak brightness value)
The following four labels are available: "very small,""small,""slightlysmall," and "approximately equal."

The second diagram shows the membership function of the control amount, and has seven labels: ``largely closed,''``closed,'' ``slightly closed,'' ``do not move much,'' ``slightly opened,''``opened,'' and ``widely opened.'' has been done.

Next, set the rules to control Iris. This rule is expressed, for example, in the following words, taking into consideration the empirical rules for controlling the iris of a video camera. Here, the input indicates the brightness of the subject image.

Rule (1-1) If the input is approximately equal to the peak value and the input is dark, open the iris wide.

Rule (1-2) If the human power is approximately equal to the peak value and the input is bright, Rule (1-3) The iris should not be moved much.

Human power is almost equal to the peak value and has very good human resources. If so, squeeze the iris a little.

By using such a rule, it becomes possible to control the peak value of the iris. If the iris control is to be brought closer to average value control, the following rule may be added to the above rule.

Rule (2-1) If the human power is slightly smaller than the peak value and the input is dark, open the iris wide.

Rule (2-2): If the human power is slightly smaller than the peak value and the input is bright, the iris will not move much.

In addition, when shooting outdoors, there is often a bright sky above the subject image, and in order to exclude this from being controlled by the iris, each of the above rules includes the following: All you have to do is add a sentence that says ``.

Next, we will create an algorithm to calculate the actual control amount of the iris from the actual address of the pixel X and the two data.
This will be explained using the rules (1-1) to (1-3) above. Assume that the difference from the actual peak value is a and the actual brightness is b. First, please refer to Figure 3 A! ! To be more specific, consider how well the input a matches the rule (1-1), ``near the peak value.'' Suppose that it is derived from the fuzzy set shown in FIG. 2C and is 0.5. Next, when input, the matching with "dark" of rule (1-1) is checked and it is 0. In this case, the weight for the control amount "open wide" is O.

Next, referring to FIG. 3B, looking at rule (1-2), the matching with input a is 0.5, and the matching with input a is 0.7. In this case, the smaller value of 0.5 is adopted, and the membership function of "do not move much" of the control amount is removed by 0.5.

Next, referring to FIG. 3B, from rule (1-3), a membership function of "slightly narrowed down", which is cut down by 0.3, is obtained.

This is the end of the fuzzy theory, but the actual iris control value is a definite value. In order to obtain this, the center of gravity of the membership function (where the area is expressed as %) is
Be wary of asking.

〔Effect of the invention〕

According to the present invention described above, it is possible to obtain an auto-iris control device for a video camera that can easily control the auto-iris. Furthermore, according to the present invention, the method of controlling the auto-iris can be set through software simulation, making it easy to add or change rules in fuzzy inference, and requiring only a small circuit scale. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing fuzzy sets of each parameter, Fig. 3 is a diagram showing fuzzy inference, and Fig. 4 is a summary of the conventional example. 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, (14) is a sampling/holding circuit, (15) is an address counter, and (16) is a ROM. (17) is a D/A conversion circuit, and (18) is a low-pass filter. Agent Hidemori Matsukuma

Claims (1)

[Claims] A peak detection circuit that detects a peak value of a video signal obtained from an imaging means, a control signal generation means to which the peak value detected by the peak detection circuit and the video signal are supplied, and control from the control signal generation means. Based on the signal
In the auto iris control device for controlling the amount of light incident on the imaging means, the control signal generating means includes a storage device storing a plurality of types of rules for control modes depending on the level of the video signal; The first and second levels based on the level value and the difference between the level value and the peak value.
The auto iris for a video camera is characterized in that the control signal is generated based on a weighting coefficient of Control device.