JPH08336070A - Image pickup device - Google Patents

Abstract

PURPOSE: To prevent blooming in the case of picking up a high luminance object. CONSTITUTION: A video signal from an image pickup element is fed to a photometry circuit A6 in usual image pickup, a photometry signal is generated from a mean luminous quantity of a designated area of an image pickup face and a system controller 8 applies a prescribed VSUB voltage to the image pickup element 3 via a VSUB voltage control circuit 17. In the case of picking up a high luminance object, since an aperture detected by an iris encoder 12 is small, the system controller 8 controls a photometry circuit changeover circuit 16 to select a photometry circuit B15 to decrease the VSUB voltage in response to a photometry signal in response to the mean luminous quantity of the high luminance area of the image pickup face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device used in a VTR or the like with a built-in camera.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing the structure of a conventional image pickup apparatus. In FIG. 7, 1 is a taking lens, 2 is an iris for adjusting the amount of incident light, 3 is an image formed on the image pickup surface by the taking lens 1, and the light amount of which is adjusted by the iris 2 is photoelectrically converted into an image. An image pickup device such as a CCD for converting into a signal, 4 is an AGC circuit for giving a gain to the video signal output from the above-mentioned image pickup device 5, and 5 is a predetermined signal processing for the video signal to convert it into a standardized video signal. The signal processing circuit 6, which divides the image pickup screen of the image pickup device 3 into a plurality of regions, gates the image luminance signal obtained from the AGC circuit 4 to extract the image luminance signal corresponding to the designated region. The photometric circuits A and 7 for integrating the extracted signals to obtain the average light amount thereof are digital signals capable of processing the photometric signals output from the photometric circuit A6 by a system control circuit 8 described later. An A / D converter for converting the Le signal.

Reference numeral 11 is an iris motor for driving the iris 2, 10 is an iris drive circuit for driving the iris motor 11, and 9 is an iris control signal (digital signal) output from a system control circuit 8 described later.
Is converted into an analog signal and given to the iris drive circuit 10, 12 is an iris encoder composed of a Hall element or the like for detecting the aperture of the iris 2, that is, an aperture value, and 13 is the iris encoder 12 The A / D converter for converting the iris encoder output (analog signal) output from the device into a digital signal that can be processed by the system control circuit 8, and 8 is a microcomputer that comprehensively controls the entire video camera system. The system control circuit 14 is a VSU for generating the VSUB voltage applied to the image sensor 3.
It is a B fixed voltage generation circuit.

Next, the operation will be described. Shooting lens 1
The optical image from is photoelectrically converted by the image sensor 3 via the iris 2. The video luminance signal output from the image pickup device 3 is input to the AGC circuit 4 to have a predetermined gain, and then sent to the signal processing circuit 5, and at the same time, the signal processing circuit 5 serves as a video luminance signal for controlling exposure. It is input to the photometric circuit A6 before being input to. The photometric circuit A6 integrates the video luminance signal corresponding to the designated area on the image pickup screen to obtain the average light amount. This average light quantity is converted into a digital signal by the A / D converter 7 and input to the system control circuit 8 as a photometric signal.

The system control circuit 8 generates an exposure control signal by performing an operation so that the level of the digitally converted photometric signal falls within a predetermined range. This calculated exposure control signal is the D / A converter 9
Is input to the iris drive circuit 10 through the iris drive circuit 10, and the iris drive circuit 10 applies a voltage to the iris motor 11 to control the opening amount of the iris 2 to perform exposure control.

The photometry circuit A6 performs center-weighted average photometry. The center-weighted average photometry will be described below. The center-weighted average photometry is one of the methods for generating the above-described photometric signal. As shown in FIG. 5, the screen has a screen central portion A, a screen backlight portion B, an upper screen portion C, and three gate frames. In this method, the video luminance signal is integrated in each gate frame to obtain the average light amount, and the integrated values indicating the three average light amounts are added at a predetermined ratio to generate a photometric signal.

For example, if the addition ratio of the screen central part A: screen backlight part B: screen upper part C is 50:30:20, the signal is [(screen central part A × 50) + (screen backlight part B ×
30) + (upper part of the screen C × 20)] / 100.

As the VSUB voltage applied to the image pickup device 3, the fixed voltage generated by the VSUB fixed voltage generation circuit 14 is used.

[0009]

However, in the above-described conventional image pickup apparatus, an extremely bright subject 100 such as sunlight enters the upper portion C of the screen in FIG. 5 and a dark subject enters the central portion A of the screen. In this case, since the exposure is center-weighted average photometry, the exposure is controlled mainly to match the exposure to the subject in the central portion A of the screen. For this reason, the iris is likely to open, and there is a problem that blooming as shown in FIG. 6 occurs when the sunlight is captured because the sunlight on the upper portion C of the screen is extremely bright.

The present invention has been made in view of the above problems, and it is an object of the present invention to obtain an image pickup device in which blooming does not occur even when an image of an extremely bright object such as sunlight is picked up. To do.

[0011]

According to the present invention, there is provided an image pickup device for photoelectrically converting incident light to output a video signal, a diaphragm adjusting means for controlling the amount of light incident on the image pickup device, and an image pickup surface of the image pickup device. First photometric means for generating a first photometric signal based on a video signal obtained from a predetermined area, and second photometric means based on a video signal obtained from an area with the highest brightness on the imaging surface of the image sensor. Second to generate a signal
And a detecting means for detecting the aperture value of the aperture adjusting means, and the first and second detecting means according to the detection of the detecting means.
Selecting means for selecting one of the photometric means and the first or second photometric means selected by the selecting means.
Alternatively, there is provided voltage control means for applying a VSUB voltage having a magnitude corresponding to the second photometric signal to the image pickup device.

[0012]

According to the present invention, when a normal subject is imaged, the VSUB voltage having a magnitude corresponding to the first photometric signal from the first photometric means is applied to the image sensor. Also,
When an extremely bright subject such as sunlight is imaged, it is detected by the detection unit that the subject is imaged with high brightness, and in response to the detection, the selection unit causes the second photometric unit. Is selected, and the voltage control means lowers the VSUB voltage in response to the second photometric signal.
This can eliminate blooming.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the block diagram of FIG. 1, the flowchart of FIG. 2 and the VSUB voltage explanatory diagram of FIG. 1 to 13 in FIG. 1 are configured the same as 1 to 13 in FIG. 7 showing a conventional example.

In FIG. 1, reference numeral 15 divides the image pickup screen into a plurality of areas, and gates the video luminance signal obtained from the AGC circuit 4 to select the highest luminance area on the image pickup screen. A photometric circuit B, 16 which designates and extracts a video luminance signal corresponding to the designated area and integrates the extracted signals to obtain an average light amount thereof is two photometric circuits, the photometric circuit A6 and the photometric circuit B15. Is selected by the system control circuit 8 and a photometry circuit switching circuit 17 is used for controlling the VSUB voltage applied to the image sensor 3 by the system control circuit 8.
It is a SUB voltage control circuit.

FIG. 2 is a flowchart showing the processing contents in the system control circuit 8. Next, the processing contents of steps S1 to S7 will be described. Step S1 ... The output value of the iris encoder 12 is A / D as to whether the iris 2 is in a small iris state.
Judgment is made from the value obtained through the converter 13. Step S2 ... When the iris 2 is not in the small aperture state, the photometry circuit switching circuit 16 is controlled to select the photometry circuit A6. Step S3 ... The above-mentioned center-weighted average photometry is performed by the photometry circuit A6. Step S4 ... Controls the VSUB voltage control circuit 17 and determines to increase the VSUB voltage applied to the image sensor 3.

Step S5 ... When the iris is in the small aperture state, the photometry circuit switching circuit 16 is controlled to select the photometry circuit B15. Step S6 ... Peak photometry described later is performed by the photometry circuit B15. Step S7 ... Controls the VSUB voltage control circuit 17 and determines to decrease the VSUB voltage applied to the image sensor 3.

Next, the VSUB voltage will be described with reference to FIG. The VSUB voltage is the potential barrier of the pixel P well portion shown in the pixel portion potential schematic diagram of FIG. Shows a schematic sectional view of the pixel portion, and is a horizontal direction (PD to VCCD) and a vertical direction (PD to S) of the schematic sectional view of the pixel portion
It shows the potential of UB). Blooming means that when an image of a subject 100 having an extremely high brightness such as the sun is picked up as shown in FIG. 6, the signal generated in the light receiving section in the schematic sectional view of the pixel section becomes excessive and the signal charge is read out by the reading section. This is a phenomenon in which the image quality is impaired by overcoming the potential barrier, flowing into the VCCD, and overflowing into the surrounding pixels.

In response to this blooming, the VSUB voltage applied to the image pickup device 3 is set so that the potential barrier of the pixel P well portion is lower than the potential barrier of the reading portion (A → B), so that the electric charge overflowing from the light receiving portion is directed in the SUB direction. It is possible to suppress the sweeping out to the VCCD and consequently suppress blooming.

Next, a specific operation will be described with reference to FIGS. 1, 2 and 3. In FIG. 1, the optical image from the taking lens 1 is photoelectrically converted by the image sensor 3 via the iris 2. The video luminance signal output from the image sensor 3 is
After being input to the AGC circuit 4 and having a predetermined gain, it is sent to the signal processing circuit 5 and is also sent to the photometric circuit switching circuit 16 before being input to the signal processing circuit 5 as a video luminance signal for controlling exposure. Is entered. A photometric signal is generated by the photometric circuit A6 or photometric circuit B15 selected there.

When a normal subject that is not an extremely bright subject such as sunlight is imaged, the iris encoder 12 determines in step S1 in FIG. 2 that the subject is not in the small aperture state. Based on this judgment, the system control circuit 8
In step S2, the photometric circuit switching circuit 16 is controlled to select the photometric circuit A6, and in step S3, the center-weighted average photometry processing is performed in this photometric circuit A6.

Next, in step S4, the system control circuit 8 outputs VS indicated by A in FIG. 3 based on the photometric signal obtained from the photometric circuit A6 through the A / D converter 7.
A UB voltage is generated and this VSUB voltage is applied to the image sensor 3 via the VSUB voltage control circuit 17.

Also, an extremely bright subject 1 such as sunlight.
When 00 is imaged, it is determined in step S1 that the aperture is in the small aperture state, and the system control circuit 8 controls the photometry circuit switching circuit 16 in step S5 to control the photometry circuit B.
15 is selected so that the photometric circuit B15 performs peak photometric processing in step S6.

Here, the peak photometry is one of the methods for generating a photometric signal for controlling the exposure, and as shown in FIG. 4, a plurality of photometric signals are arranged in the vertical and horizontal directions on the screen. A method of generating a gate frame, integrating and obtaining an average light amount of a video brightness signal in each gate frame, detecting the integrated value with the highest brightness from each integrated value, and generating a photometric signal from the detected value Is.

In step S7, the system control circuit 8 controls the VS indicated by B in FIG. 3 based on the photometric signal obtained from the photometric circuit B15 via the A / D converter 7.
A UB voltage is generated and this VSUB voltage is applied to the image sensor 3 via the VSUB voltage control circuit 17.

In other words, when the subject 100 having extremely high brightness such as sunlight is imaged, the conventional center-weighted average photometry system is changed to the peak photometry system so that the blooming on the screen can be extremely extreme. The iris 2 is controlled so that the subject 100 having high brightness is exposed. For this reason, the iris 2 is more likely to be closed than in the case where center-weighted average photometry is conventionally performed, and the amount of signal charge stored in the light receiving portion of the pixel portion potential schematic diagram of FIG. 3 is suppressed, and overflows to the VCCD. At the same time as it becomes difficult to output, the VSUB voltage applied to the image pickup device 3 is made lower than the read-out portion potential barrier as shown in B of FIG. . This makes it possible to obtain a stable video signal without blooming, which has been a problem in the past.

[0026]

As described above, according to the present invention,
Even when a subject with extremely high brightness such as sunlight is imaged, it is possible to obtain a stable video signal without blooming on the imaging screen.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the embodiment.

FIG. 3 is a configuration diagram for explaining a VSUB voltage applied to an image sensor.

FIG. 4 is a configuration diagram for explaining peak photometry.

FIG. 5 is a configuration diagram for explaining center-weighted average photometry.

FIG. 6 is a configuration diagram showing blooming.

FIG. 7 is a block diagram showing a conventional imaging device.

[Explanation of symbols]

 2 Iris 3 Image sensor 6 Photometric circuit A 8 System control circuit 12 Iris encoder 15 Photometric circuit B 17 VSUB Voltage control circuit

Claims (3)

[Claims] 1. An image pickup device for photoelectrically converting incident light to output a video signal, aperture adjusting means for controlling the amount of incident light to the image pickup device, and an image obtained from a predetermined area on an image pickup surface of the image pickup device. A first photometric means for generating a first photometric signal based on the signal; and a second photometric signal for generating a second photometric signal based on a video signal obtained from a region having the highest brightness on the imaging surface of the image sensor. Photometric means, detection means for detecting the aperture value of the aperture adjustment means, selection means for selecting one of the first and second photometric means according to the detection of the detection means, and the selection means. VS having a magnitude corresponding to the first or second photometric signal obtained from the first or second photometric means
An image pickup apparatus comprising: a voltage control unit that applies a UB voltage to the image pickup element. 2. The image pickup apparatus according to claim 1, wherein the first photometric means generates the first photometric signal by a center-weighted average photometric method. 3. The second photometric means generates the second photometric signal by a peak photometric method.
The imaging device described.