JPH06245151A - Video camera equipment - Google Patents

Abstract

PURPOSE:To reproduce a high illuminance portion and a low illuminance portion of an object in an excellent way by selecting a charge storage time of an image pickup element a predetermined long time and a predetermined short time and adding both picture signals simultaneously. CONSTITUTION:A charge storage time of an image pickup element 1 is controlled to be a long time up to one pattern scanning period and a predetermined short time within one pattern scanning period for each field by an image pickup element drive control circuit 2. A long time stored picture of a low illuminance portion and a short time stored picture of a high illuminance portion via an A/D converter 3 are processed simultaneously by a field memory 4 reading a picture with a delay of one field. Then a portion of a predetermined level or over in the long time stored picture signal is clipped by a high level compression conversion section 5 or 6 and both picture signals are added by an adder section 7. Thus, the low illuminance portion and the high illuminance portion are reproduced in an excellent way without white level and black level distortion even in the case of picking up an object with a large contrast difference.

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 for obtaining a television signal.

[0002]

2. Description of the Related Art Conventionally, when a television signal is obtained by imaging a subject with high contrast (large contrast),
The light amount is adjusted as a whole by changing the diaphragm of the lens optical system for forming an incident image on the image pickup element or by using a light amount attenuation optical filter called an ND filter to create an appropriate light amount state. However, also in this method, when the contrast of the image is strong, when trying to reproduce the high illuminance portion better, the low illuminance portion has a low signal, and the signal level difference becomes small, which is a so-called blackout phenomenon. On the other hand, if it is attempted to reproduce the low illuminance part better, the amount of light incident on the image sensor is inevitably increased, so that the high illuminance part exceeds the dynamic range of the image sensor itself, and a correct signal cannot be obtained. , The so-called whiteout phenomenon.
In this way, when simultaneously capturing the low-illuminance part and the high-illuminance part of a large-contrast subject, there are many restrictions on the simultaneous reproduction of the low-illuminance part and the high-illuminance part, and the input / output characteristics of the signal processing circuit of the camera device are

[0003]

A so-called gamma characteristic is provided to increase the gain in the low illuminance portion and decrease the gain in the high illuminance portion. However, when the dynamic range of the image pickup device itself is exceeded, it cannot be dealt with, and since the circuit gain differs depending on the signal level, there is a drawback that the S / N changes depending on the signal level, and a great improvement has not been obtained.

[0005]

In the above-mentioned prior art,
When a subject having a high illuminance portion and a low illuminance portion is imaged, it is difficult to obtain both illuminance portions in the best state on the same screen, and even if it is obtained, the S / N greatly varies depending on the signal level. . The present invention eliminates these drawbacks, images a subject having a high illuminance portion and a low illuminance portion,
The objective is to realize a television camera device that can reproduce both illuminance parts well.

[0006]

In order to achieve the above object, the present invention sets the charge accumulation time of the image pickup device of the television camera device to a predetermined long time up to one screen scanning period for each screen. The drive is controlled to be repeated for a predetermined short time within one screen scanning period, and the first image signal obtained by the long-time accumulation and the second image signal obtained by the short-time accumulation are synchronized, A low illuminance portion and a high illuminance portion are reproduced at the same time by compressing or clipping signals of a predetermined level or more of image signals in long-term storage and adding them. FIG. 1 is a block diagram showing the overall configuration of the present invention. In FIG. 1, reference numeral 1 is an image sensor, and 2 is a drive control circuit for operating the same, which controls the storage time of the image sensor 1 for each screen (for example, one field) between a long time and a short time. Reference numeral 3 is an A / D converter that converts the output signal of the image sensor 1 into a plurality of bits of data, and 4 is a memory such as a field memory, which delays the output signal of the A / D converter 3 by one field. . Reference numerals 5 and 6 are high-level compression conversion units, which operate the high-level compression conversion unit on the side to which a signal of a field having a long storage time is supplied by the drive control circuit 2 to compress signals of a predetermined level or higher. Convert. Reference numeral 7 denotes an adder, which adds the outputs of the high-level compression conversion units 5 and 6 which alternately output the high-level compression-converted signal and the non-high-level compression-converted signal. Reference numeral 8 denotes a D / A converter, which is an addition unit 7
Change the output to analog signal.

[0007]

The operation of the present invention will be described. Regarding the storage time of the image pickup device, charges are stored for a relatively long time in a certain field and short time in the next field. At this time, since the sensitivity of the image sensor 1 is determined by the charge accumulation time, the image signal is obtained from the image sensor 1 in a state where the sensitivity is increased during long time accumulation and decreased during short time accumulation. These signals are divided into two after A / D conversion, one signal is delayed and synchronized, and the high-level signal component of the high-sensitivity signal (the signal during long-term storage) is converted into the high-level compression conversion unit 5.
Alternatively, data compression conversion is performed at 6, and the two data are added at the addition unit 7, and an analog signal is obtained by the D / A conversion circuit 8. As a result, when capturing a large-contrast object, the low-illuminance portion is reproduced by the high-level-compressed signal for long-time accumulation and the high-illuminance portion is reproduced by the short-time accumulation signal, so that white and black are crushed. Both the low illuminance portion and the high illuminance portion can be reproduced simultaneously and satisfactorily.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. An image sensor 1 converts an optical image from a subject into an electric signal. The drive control circuit 2 applies a bias and a drive pulse to the image sensor 1 to perform two-dimensional scanning and read out as a two-dimensional signal. Reference numeral 10 is a correlated double sampling circuit for improving noise generated in the low frequency band generated from the image sensor 1, 16 is a signal amplifier circuit, 3 is an A / D converter for converting an analog signal into a digital signal of a plurality of bits, 4 Is a field memory, 5 and 6 are high-level compression conversion units, 7 is a data addition unit, and the addition output data is D
In addition to the A / A converter 8, the analog output signal is amplified by an amplifier 15
Is output from the output terminal 9 via. On the other hand, of the output pulses of the drive control circuit 2 that controls the drive of the image sensor 1, the shutter pulse that controls the storage time of the image sensor 1 is supplied to the gate circuit 11, and the output of the field determination circuit 12 outputs the field in each field. The generation timing of the shutter pulse is controlled. In addition, the drive control circuit 2 described above,
Field discrimination circuit 12 and field memory 4, A
Driving circuit 1 for driving the D / D converter 3, the D / A converter 8 and the like
4 and the amplifier 15 are supplied with the pulse from the television sync signal generator 13.

This operation will be described below. The number of bits of the image signal obtained by the image sensor 1 is reduced by the correlated double sampling circuit 10 to reduce low frequency noise, amplified by the amplifier 16 to an appropriate level, and bit noise is not a problem in the A / D converter 3. , Digital signal data of 8 to 9 bits, for example. On the other hand, the image sensor 1 is driven by the drive circuit 2, but an electronic shutter pulse that determines the charge accumulation time is also generated, and if this electronic shutter pulse is applied to the image sensor 1, the accumulation time should be shortened. If the shutter pulse is not applied, the mode can be set to the accumulation for one field period. Therefore, if the gate circuit 11 supplies the shutter pulse to the image pickup device 1 every other field, a field with high sensitivity and a field with low sensitivity can be created every other field.

The high-sensitivity and low-sensitivity repeated imaging output signal for each field is processed by the above-mentioned path, and if the image data stored in the field memory 4 is read out just one field later, it is delayed by one field. It is possible to synchronize the image data of the high sensitivity field and the image data of the low sensitivity field. Of these data, the high-level compression conversion unit 5 or 6 performs field conversion on the field data when the sensitivity is high, and the data conversion is performed to compress the high-illuminance part, that is, the high-level data. With respect to the field data of, the processing such as loosening the compression degree of the high level data is performed, and the compression degree of the high level compression conversion unit 5 or 6 is set in two ways for each field (in the high sensitivity field and the low sensitivity field). It is set to switch to the compression degree of. Then, after adding these two data in the addition unit 7, D /
The A converter 8 converts the analog signal into an analog signal, and the sync signal generator 1
The output signal is output from the output terminal 9 as a television camera output signal via a processing amplifier 15 for mixing the composite synchronizing signal for converting into a normal television signal supplied by the signal 3 of FIG.

As described above, when a large contrast object having a low illuminance portion and a high illuminance portion is imaged by the above-mentioned configuration, the low illuminance portion is used for signal data of a high-sensitivity field in which a high level signal component is compressed (for a long time). High-illuminance area is reproduced with signal data of the low-sensitivity field (signal during short-time accumulation) in the low-light area and high-light area at the same time. Can be reproduced.

[0012]

According to the present invention, when a subject having a large difference in contrast is imaged, both the low illuminance part and the high illuminance part can be reproduced well on the monitor, and a large S / N deterioration occurs. Since this can be realized without causing the above, for example, in a use such as a furnace monitoring camera, it is possible to monitor both a dark place and a bright place with one camera.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 image sensor 2 image sensor drive control circuit 3 A / D converter 4 field memory 5,6 high level compression converter 7 data adder 8 D / A converter

Claims (2)

[Claims] 1. A television camera device having a two-dimensional photoelectric conversion image pickup device for converting an optical image from a subject into an electric signal, a circuit for driving the image pickup device, and a circuit for processing an electric signal output from the image pickup device. , The charge accumulation time of the image pickup device is controlled to be a predetermined long time up to one screen scanning period for each screen and a predetermined short time repetitive operation within the one screen scanning period, A television camera device characterized in that a first image signal obtained by storage and a second image signal obtained by the short-time storage are synchronized, and these signals are added to obtain a television signal. 2. The television camera device according to claim 1, wherein before the first and second image signals are added,
A television camera device characterized in that a signal of a predetermined level or higher of an image signal in the above long-term storage is compressed or clipped.