JPH0486074A - Video image pickup device - Google Patents

Abstract

PURPOSE:To automatically execute the narrowing-down correction and automatic gain control(AGC) of a fine area part on an image pickup screen by executing control so as to automatically hold the narrowing-down amount of incident light quantity to the image pickup screen at the photometric case of the fine area. CONSTITUTION:As a full screen photometric means to execute the entire photometry of the image pickup screen, photometry weighting circuits 12 and 14 and detection circuits 13 and 15 are provided, as a fine area photometric means to execute the photometry of the fine area on the image pickup screen, BLK circuits 32 and 37 and detection circuits 33 and 38 are provided, and as a switching means to switch the output of the full screen photo-metric means and the output of the fine area photometric means, changeover switches 35 and 40 are provided. When switching to the output of the fine area photometric means, the narrowing-down amount for the quantity of light made incident to the image pickup screen, and the correcting amount of the AGC at an AGC circuit 5 are automatically switched and controlled to a hold mode. Thus, the narrowing-down correction and AGC of the fine area part on the image pickup screen can be automatically executed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] [Summary of the Invention] The present invention enables switching between overall photometry of an imaging screen and photometry of a minute area, and enables photometry of a minute area. To provide a video imaging device that can automatically perform aperture correction and automatic gain control for a minute area on the imaging screen by controlling the aperture amount of the amount of light incident on the imaging screen to be automatically held. It is.

[Conventional technology]

A conventional video imaging device (so-called video camera) using an imaging device such as a CCD (charge-coupled device J)
, there is a so-called aperture correction (auto iris) function that can automatically narrow down the amount of light incident on the CCD to an appropriate amount, and a so-called auto gain control (that automatically adjusts the level of the output signal from the CCD). A G
C) Some are equipped with 4tlltifC, etc.

FIG. 3 shows a block diagram of a schematic configuration for performing auto iris and AGC in a conventional video imaging device.

In the video imaging device equipped with the auto iris and AGC functions shown in FIG. An image is formed through an aperture 2 on an imaging screen (on a CCD) of an imaging device 3 configured with a CCD or the like. The auto iris and AGC are controlled based on the video signal obtained from the output of the imaging device 3 via the signal processing circuit 4.

That is, in the AGC control described above, the video signal via the signal processing circuit 4 is transmitted to the AGC controlling the AGC.
It is sent to the photometric weighting circuit 12 via the circuit 5. The photometry weighting circuit 12 performs weighting (top weighting) processing on signals obtained from the upper part of the image capture screen, and center-weighted photometry processing that intensively measures signals obtained from the center of the image capture screen. Here, the upper weighting process in the photometry weighting circuit 12 means that the upper part of the imaging screen has a high probability of receiving light from a bright object such as the sky, so information from the upper part of the imaging screen is This process is performed to reduce the overall amount of information by weighting the information. Furthermore, the center-weighted photometry processing is a process in which information at the center of the image capture screen is mainly photometered, assuming that there is a high probability that the subject to be photographed will normally be located at the center of the image capture screen. The output of this photometric weighting circuit 12 is
The signal is sent to the detection circuit 13. [Detection circuit] 3 performs, for example, average value detection of the output of the photometric weighting circuit 12, and
Extract only the C (DC) component.

The output of this detection circuit 13 is supplied to the inverting input terminal of the comparator 10. At this time, the voltage supplied to the non-inverting input terminal of the comparator 10 is the base Y$ lightning voltage for AGC adjustment from the variable voltage source 11. The comparator 10 compares the voltage supplied to the inverting input terminal with the AGC adjustment reference voltage supplied to the non-inverting input terminal,
A signal resulting from this comparison is sent to the AGC circuit 5. In the AGC circuit, the gain of the video signal from the signal processing circuit 4 is controlled based on the output of the comparison result of the comparator 10. The AGC circuit 5 automatically performs gain control of the video signal, so that the video signal at a constant level is output from the output terminal 9.

In this way, after AGC control is performed, aperture control is performed. That is, in this aperture control, the video signal passed through the signal processing circuit 4 is passed through the photometry weighting circuit 14 which performs the same upper weighting processing and center weighted photometry processing as described above.
sent to. The output of the photometric weighting circuit 14 is sent to a detection circuit 15, from which an average value detection output, for example, of the output of the photometry weighting circuit 14 is taken out. The output of the detection circuit 15 is supplied to the inverting input terminal of the comparator 7. At this time, the voltage at the non-inverting input terminal of the comparator 7 is the reference voltage for controlling the aperture by the variable voltage source 8, and the output of the comparator 7 is amplified and then drives the aperture 2. The signal is sent to the iris drive motor 6. Therefore, the comparator 7 compares the voltage supplied to the inverting input terminal with the aperture control reference voltage supplied to the non-inverting input terminal, and drives the iris drive motor 6 based on the comparison result. It has become.

By controlling the drive of the aperture 2 in this way,
Aperture control of the amount of light incident on the imaging device 3 is performed.

The image signal (video signal) obtained by performing the aperture correction and AGC as described above is outputted from the output terminal 9.

[Problems to be Solved by the Invention] By the way, when a subject is photographed using the above-mentioned conventional video imaging device equipped with the auto-iris AGC function, for example, the upper part of the imaging screen may be a bright subject like the sky. When shooting in a fixed pattern, such as when the subject you want to photograph is in the center of the image capture screen, the above-mentioned upper imprinting, center-weighted metering, etc. work effectively, making it possible to obtain good images. become able to.

However, when shooting using the above-mentioned conventional video imaging device, the shots are usually taken with various subjects or under various shooting conditions. There may be cases where you want to do something like this. In this case, there are many cases where the above-described pattern does not apply. In this way, if the above-described prescribed pattern is not applied, almost no effect of the above-mentioned aperture correction or AGC can be obtained.

Further, depending on the subject, there may be cases where it is desired to perform aperture correction or AGC only on a small area portion within an arbitrary range of the image pickup screen. However, in the above-mentioned conventional video imaging apparatus, it is not possible to automatically correct only a small arbitrary area of the imaging screen, so it is usually necessary to switch to a manual correction operation. That is, in the case of a conventional video imaging device, for example, in the case of manual aperture correction, the photographer must use an external knob or switch of the video device to change the aperture according to his/her preference. However, this manual aperture correction and the like has disadvantages in that it is often difficult to adjust and the operation may take a long time.

The present invention has been proposed in view of the above-mentioned circumstances, and an object of the present invention is to provide a video imaging device that can automatically perform aperture correction and AGC for a small area on an imaging screen. It is something.

[Means for Solving the Problems] A video imaging device of the present invention has been proposed to achieve the above-mentioned object, and includes a full-screen photometer for performing overall photometry of the imaging screen; and a switching means for switching between the output of the full screen photometry means and the output of the small area photometry means. When switching to the output of the area photometry means, the aperture amount of the amount of light incident on the imaging screen is automatically switched to the hold mode.

[Effect]

According to the present invention, since the present invention has a micro-area photometer that performs photometry on a micro-area of the imaging screen, it is possible to automatically perform aperture correction and AGC in a micro-area, and when measuring a micro-area, the imaging screen is Since the aperture amount of the amount of incident light is automatically switched to the hold mode, it is possible to obtain a good video signal.

〔Example〕

Embodiments to which the present invention is applied will be described below with reference to the drawings.

1V shows a block diagram of a schematic configuration of a video imaging apparatus according to an embodiment of the present invention.

The video imaging apparatus of this embodiment shown in FIG. 1 includes a photometry weighting circuit 12, which is a full-screen photometry means for performing overall photometry of the imaging screen of the imaging device 3, which is composed of, for example, a CCD (charge-coupled device). 14, a detection circuit 13.15, a BLK circuit 32.37 and a detection circuit 33.38, which are small area photometry means for measuring a small area of the imaging screen, and the output of the full screen photometry means and the small area photometry. A changeover switch 35°40 is a switching means for switching between the output of the means and the output of the means.
When the output obtained from the changeover switches 35 and 40 is switched to the output of the micro area photometry means, the amount of aperture of the amount of light incident on the imaging screen (the amount of aperture by the aperture 2) and the AGC circuit. The AGC correction amount in step 5 is automatically switched to the hold mode. In addition,
In FIG. 1, the same components as those in FIG. 3 described above are given the same reference numerals and their explanations will be omitted.

That is, in the aperture amount control shown in FIG. 1, the video signal from the signal processing circuit 4 is sent to the photometry weighting circuit 14 of the full screen photometry means, and is also sent to the BLK circuit 32 of the small area photometry means. It is ready to be sent. Here, the BLK circuit 32 is a circuit for erasing (blanking) all other information while leaving only the information of a part of the imaging screen as the minute area. It is controlled according to the pulse of That is, the blanking pulse generation circuit 31 generates a blanking pulse depending on which part of the imaging screen the minute area covers.

Further, the range to be blanked by the BLK circuit 32 can be set to any part of the imaging screen, but in this embodiment, considering practical ease of use, for example, For example, 2 μsec in the horizontal direction indicated by the minute portion 101 in the center of the image capture screen lOO in FIG.
, for example, in a range of about 0°76 m5ec in the vertical direction. For reference, FIG. 2 shows a range 102 where center-weighted metering is performed in a conventional video imaging device.
is also shown. The range 102 in this conventional device is
H/3 for the width H in the horizontal direction with respect to the imaging screen 100
The width is in a range of about V/2 with respect to the width V in the vertical direction, and is much larger than the minute portion 101 in this embodiment. Further, the range where the upper part is molded is a width range of approximately V/4 of the upper part of the imaging screen 100 with respect to the vertical width (3) of the imaging screen 100. The output of the BLK circuit 832 is sent to the detection circuit 33. This detection circuit 33 is different from the detection circuit 15,
Considering that the signal to be supplied is a signal of the above-mentioned minute area and that the effect of aperture correction is sufficiently obtained, it is designed to have characteristics of peak detection (peak-hold detection). .

In this way, the signal obtained from the detection circuit 33 is sent to the mixer 34, and the mixer 34 passes the signal through the photometric weighting circuit 14 and the detection circuit 15, which are similar to the conventional configuration shown in FIG. It is mixed with the resulting signal. At this time, in the mixing in the mixer 34, in this embodiment, the mixing ratio of the outputs of the detection circuits 15 and 33 is set to, for example, 2:1. The output of this mixer 34 is sent to the selected terminal 35B of the changeover switch 35. In addition, the changeover switch 35
The output of the detection circuit 15 is supplied to the selected terminal 35C. Here, in the mixer 34, the detection circuit 3
The outputs of 3 and 15 are mixed by the changeover switch 35 from the output of the detection circuit I5 to the output of the detection circuit 33.
This is to ensure a smooth response when switching to the output of the mixer 34 (the output of the mixer 34), and the output of the detector 15 supplied to the mixer 34 is
It is designed to act as a brake.

As described above, when a photographer or the like wishes to perform aperture correction in a minute area, for example, the changeover switch 35 can be adjusted in response to an operation such as a user control switch.
is switched so that the selected terminal 35B is selected, the aperture control loop is switched to the BLK circuit 32. The path is switched to the detection circuit 33, and the control of the aperture 2 is
This is done based on the information obtained through the micro area photometry. This makes it possible to perform photometry under special conditions, such as during highlights or backlighting, and corrects the exposure of the small area to the appropriate level.

Also, at the same time as (or prior to) the above-mentioned aperture amount control,
In the AGC performed, the video signal via the AGC circuit 5 is sent to the photometry weighting circuit 12 and also to the BLK circuit 37 of the small area photometry means. This 1i
The BLK circuit 37 also operates in the same manner as the BLK circuit 32 described above. The output of this BLK circuit 37 is sent to a detection circuit 38 having the same peak detection characteristics as the detection circuit 33 described above.

Further, the output of the detection circuit 38 is mixed with the output of the detection circuit 13 in a mixer 39. The output of the mixer 39 is sent to the selected terminal 40B of the changeover switch 40, and the output of the detection circuit 13 is supplied to the selected terminal 35C at this time.

Therefore, when a photographer or the like wishes to perform AGC correction in the minute area during highlights or backlighting, for example, he or she can switch the selector switch 40 to the selected terminal 40B by operating the user control switch or the like. By switching so that the above BL is selected, the AGC control loop
The path is switched to the K circuit 37 and the detection circuit 38, and the AG
Control of the C circuit 5 is performed based on the information obtained by this micro area photometry. As a result, the minute area portion can be corrected to the appropriate exposure. Note that the switching of the changeover switches 35 and 40 may be performed in conjunction with each other.

By the way, as mentioned above, when performing micro-area photometry, only a portion of the image capturing screen is handled, so when shooting a wide-angle camera, the aperture correction and AGC changes drastically due to so-called vanning or subject movement. There is. That is, for example, if a video signal obtained when the aperture or AGC fluctuates rapidly is reproduced, there is a risk that the brightness of the screen will fluctuate drastically.

In order to eliminate the widening that causes such problems, in the video imaging device according to the embodiment of the present invention, the aperture amount and the AG
It has a function to hold the gain of C. That is, in the video imaging apparatus of this embodiment, in order to perform the micro area photometry, for example, the user switch is operated to select the selected terminals 35B, 40B of the changeover switch 35, 40.
is selected, then, for example, after about one second, the selected terminals 36N,
Control is performed such that selected terminals 36H and 36H are selected from 41N. This switches to hold mode.

Here, the aperture amount and the AGC hold function will be explained separately.

That is, when holding the aperture amount, first, the aperture amount of the aperture 2 is detected using, for example, the Hall element 42 as the aperture amount detection means. Here, for example,
The aperture amount of the aperture 2 is a certain amount, and when you want to fix (hold) this aperture amount, that is, when you want to hold the aperture position of the aperture 2, the aperture position of the aperture 2 at this time is determined by the Hall element 42. It is detected and taken out as an electric signal, and this electric signal is taken into the microcomputer 70 of the hold circuit 50. The microcomputer 70 selects the selected terminal 3 using the changeover control switch 36.
When 6N is selected, the value taken in by the A/D converter 71 is output as is. At this time, when the selected terminal 36H is selected by the changeover control switch 36 and the hold mode is entered (that is, the changeover selection switch 36 is switched approximately 1 second after the changeover switch 35 is operated in accordance with the operation of the user switch). time), the microcomputer 70 controls this changeover control switch 36.
The output value of the A/D converter 71 immediately before switching is held in the hold processing circuit 72 and outputted. In this case, even if the input from the Hall element 42 to the microcomputer 70 changes, the microcomputer 70
The output of will be a constant held earlier. The output of this microcomputer 70 is sent to a non-inverting input terminal of a comparator 53 via a D/A converter 51. The comparator 53 compares the output value of the Hall element 42 and the output value of the D/A converter 51. The output of the comparator 53 is sent to the inverting input terminal of the comparator 7 via the changeover control switch 36 whose selected terminal 36H is selected. As a result, the aperture control loop is constructed as follows: Hall element 42 -> microcomputer 70 -> comparator 53 -> comparator 7 -> iris drive motor 6 -> Hall element 42. Therefore, if the output from the microcomputer 70 remains unchanged (if it is held), the output of the Hall element 42 will also be kept constant, and the aperture position of the aperture 2 will be held. Become.

In addition, when holding the AGC, the control signal to the AGC circuit 5 is sent to the A/D of the microcomputer 60.
If the signal is taken into the converter 61 and the selected terminal 41N is selected by the changeover control switch 41, the control signal is output as is.

On the other hand, when holding, A immediately before this hold
The output value of the /D converter 61 is held as it is by the processing circuit 6.
2 to hold and output. The held output of the microcomputer 60 at this time is sent to the AGC circuit 5 via the D/A converter 52 and the changeover control switch 40 whose selected terminal 41H has been selected.

As a result, the AGC circuit 5 is controlled by this held output.

As described above, the video imaging apparatus of this embodiment includes a full-screen photometry means (photometry weighting circuit 12.14 and a detection circuit 13.15) that performs overall photometry of the imaging screen, and a Micro area photometry means (B
LK circuit 32.37 and detection circuit 33.38), a changeover switch 35.40 for switching between the output of the full screen photometry means and the output of the small area photometry means, and an aperture setting by the aperture 2 during the small area photometry. and a changeover control switch 36, 41 and a hold circuit 50 that automatically switch and control the AGC correction amount in the AGC circuit 5 to a hold mode. can be done automatically. In other words, the detection circuits 33 and 38 that perform peak hold are provided,
The response is improved by mixing the detection output in a minute area and the detection output for the whole screen, and the aperture 2 is controlled by the photometry output in a minute area, and it also has a hold function, which allows for aperture correction and A.
Since the GC is automatically corrected and controlled, the photographer can control the exposure so that the subject he or she wants to photograph has the correct exposure, and is not affected by the size of the subject on the west side. Automatic control becomes possible. Further, full-screen photometry and small-area photometry can be switched, for example, by simply operating a single user control switch. Furthermore, even under special conditions such as so-called highlights or backlight, or regardless of the size of the subject, light conditions, etc., aperture correction and AGC are possible. Furthermore, since all corrections are made automatically, the operation is easy, the response when making corrections is quick, and the photographer can freely adjust the aperture to any location, ensuring appropriate image quality. It will be possible to secure the following.

〔Effect of the invention〕

In the video imaging device of the present invention, it is possible to switch between overall photometry of the imaging screen and photometry of a minute area, and when measuring a minute area, the aperture amount of the amount of light incident on the imaging screen is automatically adjusted. By controlling the camera to hold the image, it is possible to automatically perform aperture correction and AGC for a small area on the image capture screen, ensuring appropriate correction even under special conditions such as highlights and backlighting. became possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a video imaging device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining an imaging screen,
FIG. 3 is a block diagram showing a schematic configuration of a conventional video imaging device.

Claims (1)

[Scope of Claims] Full-screen photometry means for photometry of the entire imaging screen; Micro-area photometry means for measuring the light of a minute area of the imaging screen; The output of the full-screen photometry means and the small-area photometry means. and a switching means for switching between the output of the switching means and the output of the micro area photometry means, and when the output obtained from the switching means is switched to the output of the micro area photometry means, the aperture amount of the amount of light incident on the imaging screen is automatically set to the hold mode. A video imaging device characterized in that switching control is performed.