JPH06141233A - Auto iris device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to realize an auto iris device that can perform good iris control even when the background has a significantly different brightness level compared to the main subject. A means for measuring the brightness level of an imaged video signal, a means for obtaining a brightness level distribution of the entire imaged screen from the brightness data, and a means for weighting the brightness level distribution according to each brightness level. , Means for removing a component having a high frequency and a small amplitude with respect to the brightness level distribution, and an average value and / or a maximum value of the brightness levels of the image signal picked up from the brightness level distribution after the weighting and the removal processing are performed. An auto iris device that has a means for obtaining and controls the iris using the average value and / or the maximum value, and is not affected by the image input whose brightness level is extremely different from that of the main subject, so excessive iris correction is performed. This can be avoided, and good iris control can always be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto iris device such as a television camera.

[0002]

2. Description of the Related Art FIG. 4 shows a block diagram of the prior art. The details of the conventional technique will be described below with reference to FIG. The light incident from the lens 1 having the iris control mechanism is photoelectrically converted by the image sensor 2, amplified by the video signal processing circuit 3, and then subjected to various kinds of video processing and output as a video signal. The auto iris system is a system that keeps the average value / maximum value of the brightness level of the main subject on the screen at a constant value, but in the conventional method, the average value of the video signal amplified by the video signal processing circuit 3 in FIG. It is inputted to the maximum value extraction circuit 4, and the average value and the maximum value of the video signal of the entire screen are extracted,
An iris signal generation circuit 5 generates an iris control signal from this information, the control signal and a reference signal 6 are compared and amplified by a differential amplifier 7, and the lens 1
Iris was being controlled. With this feedback system, when the brightness of the entire screen is higher than a predetermined value, the iris is closed, and when it is low, the iris is opened and the brightness can be kept constant.

[0003]

The prior art has the following problems (1) to (3). (1) When an extremely high level image input such as backlight is present in the background of the main subject over a certain range,
In the conventional method, since the average value of the entire screen is used for the processing, the average level is calculated to be higher than necessary, and the iris correction causes the main subject to be dark. (2) When there is a video input with a sharp peak such as a light source in the background of the main subject, the conventional method performs processing using the maximum value of the entire screen, so the maximum value is calculated higher than necessary, When iris correction is performed, the main subject becomes dark and sunk. (3) When the background has an extremely low brightness level compared to the main subject, the average level of the entire screen is used for processing in the conventional method, so the average level is calculated lower than necessary,
When iris correction is performed, the main subject will fly white. It is an object of the present invention to eliminate these drawbacks and to realize an auto iris device that can perform good iris control even when the background has a significantly different brightness level compared to the main subject.

[0004]

In order to achieve the above object, the present invention comprises means for measuring the brightness level of a picked-up video signal, means for obtaining the brightness level distribution of the entire imaged screen from the brightness data, A means for weighting the brightness level distribution according to each brightness level, a means for removing a component with a high frequency and a small amplitude from the brightness level distribution, and a brightness level after the weighting and removal processing It is configured to have a means for obtaining an average value and / or a maximum value of the luminance level of the image signal picked up from the distribution, and to control the iris using the average value and / or the maximum value.

[0005]

As a result, since it is not affected by the image input whose brightness level is extremely different from that of the main subject, it is possible to avoid excessive iris correction and always perform good iris control.

[0006]

1 is a block diagram showing the outline of one embodiment of the present invention. 2 and 3 are explanatory views showing the processing contents of this embodiment. The contents of this embodiment will be described below with reference to FIGS. 1, 2, and 3. In FIG. 1, a lens 1, an image pickup device 2, a video signal processing circuit 3, an average value / maximum value extraction circuit 4, an iris signal generation circuit 5, a reference signal 6 and a differential amplifier 7 are shown in a block diagram of the prior art. It is similar to
The luminance distribution creating circuit 8, the level adaptive processing circuit 9, and the filtering processing circuit 10 are the features of the present invention. The brightness distribution creating circuit 8 obtains a brightness distribution from the video signal amplified by the video signal processing circuit 3, and the level adaptation processing circuit 9 weights the brightness distribution according to the brightness level. The average value / maximum value extraction circuit 4 finds the average value and the maximum value of the brightness level of the screen from the brightness distribution after weighting and removal processing is performed by removing the components with high amplitude and small amplitude, and the average value and the maximum value. To control the iris.

Here, processing contents of the luminance distribution creating circuit 8, the level adaptation processing circuit 9, and the filtering processing circuit 10,
The effects will be described with reference to FIGS. 2 and 3. FIG. 2 shows processing when the background has an extremely low luminance level as compared with the main subject. FIG. 2A shows a result of creating a luminance distribution from a picked-up video signal, the horizontal axis indicates the luminance level, and the vertical axis indicates the area, that is, the number of samples for each level. When the brightness level of the background is extremely lower than that of the main subject, a large distribution peak exists in the low-luminance portion in addition to the distribution of the main subject as shown in (a). When the average value of the entire screen is calculated as it is, the value becomes A0, which is lower than the average luminance level of the main subject portion.
In order to remove the influence of the background having an extremely low brightness level, the weighting process according to the brightness level shown in FIG. 2B is performed. That is, the brightness distribution is multiplied by a function in which the weighting coefficient of the low brightness part is reduced. The result is shown in FIG. When the average value is calculated from the brightness distribution weighted according to the level, the value becomes A1, which is closer to the average brightness level of the main subject portion compared to A0.

FIG. 3 shows a process when there is an image input of an extremely high level such as backlight or an image input having a sharp peak such as a light source in the background of the main subject. Figure 3
(A) shows the result of creating a luminance distribution from the imaged video signal. In addition to the distribution of the main subject, there are peaks with a large back light distribution and peaks with a small light source distribution in the high brightness portion. become. Therefore, if you proceed as it is,
The average value of the brightness level is A0 and the maximum value is M0. The average value A0 and the maximum value M0 are higher than the brightness level of the main subject part. Therefore, in order to remove the influence of the backlight and the light source, the weighting process according to the brightness level is performed as shown in the example of FIG. That is, the brightness distribution is multiplied by a function with a small weighting coefficient for the low brightness part and the high brightness part. The result is shown in FIG. This can eliminate the influence of backlight. Since the influence of the light source appears in the maximum value, it cannot be removed only by weighting processing according to the level. Therefore, the filtering process is performed next. In this processing method, a threshold level is determined and the value is set to 0 when the area is less than this. The result of the filtering process is shown in FIG. This can eliminate the small distribution peaks of the light source.

As described above, when the average value and the maximum value are calculated from the luminance distribution subjected to the weighting processing and the filtering processing according to the level, the average value A0 becomes A1 and the maximum value M0 becomes M1. , Closer to the brightness level of the main subject part. The above problem can be solved by controlling the iris using the average value and the maximum value obtained by the above method. In addition, although the case where the iris is controlled by using the average value and the maximum value has been described in the present embodiment, it is needless to say that the present invention is similarly applicable to the case where the iris is controlled by using the average value or the maximum value.

[0010]

According to the present invention, the luminance distribution is obtained from the luminance data of the imaged image signal, the luminance distribution is weighted according to the luminance level, and the iris control is performed using the weighted data. It is possible to avoid the influence of a video input having a brightness level extremely different from that of a subject. In addition, when weighting according to the brightness level, there is no special restriction on the position of the main subject on the screen, so good iris control can be performed even if the main subject is off the center of the screen. it can.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the processing contents of the present invention.

FIG. 3 is an explanatory diagram showing the processing content of the present invention.

FIG. 4 is a schematic block diagram of a conventional technique.

[Explanation of symbols]

1: lens, 2: image sensor, 3: video signal processing circuit,
4: average value / maximum value extraction circuit, 5: iris signal generation circuit, 6: reference signal, 7: differential amplifier, 8: luminance distribution creation circuit, 9: level adaptation processing circuit, 10: filtering processing circuit.

Claims (1)

[Claims] 1. In a camera device having an auto iris system for automatically adjusting the iris of a lens, a means for measuring a brightness level of a captured video signal, a means for obtaining a brightness level distribution of an entire imaging screen from the brightness data, A means for weighting the brightness level distribution according to each brightness level, a means for removing a component with a high frequency and a small amplitude from the brightness level distribution, and a brightness level after the weighting and removal processing An auto iris device comprising means for obtaining an average value and / or a maximum value of a brightness level of a video signal imaged from a distribution, and controlling the iris using the average value and / or the maximum value.