JP2000069354A - Television camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend dynamic range by mutually adding three kinds of video signals, i.e., a video signal generating no void, a video signal corresponding to longer than one field of exposure time for a solid-state image pickup element and a video signal generating no gradation. SOLUTION: A solid-state image pickup element 2 outputs a signal which is exposed and photoelectrically converted in two periods, based on a reading pulse and a CDS/AGC circuit 4 processes the outputted signal to obtain a signal 1 of one horizontal scanning period. Respective signals, repeatedly recorded in respective video recording parts 10 to 12 and stored as newest video signals, are simultaneously outputted at each field and outputted through an adder 13 and a multiplier 14 and a video signal part of a brighter subject is weighted by a video signal photographed by a field of a shorter exposure period to obtain an arithmetic mean. A video signal part of a darker subject is weighted by a video signal photographed by the field of a longer exposure period to obtain an arithmetic mean.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device (C)
The present invention relates to a television camera device using a CD and a video storage element (memory).

[0002]

2. Description of the Related Art FIG. 4 shows a configuration of a conventional television camera. 21 is a lens, 22 is a solid-state image sensor, 23 is correlated double sampling (CDS) or automatic gain control (AG).
C) AGC circuit for performing C), 24 is an analog / digital (A / D) converter, 25 is a digital signal processor (DSP), 26 is a microcomputer, and 27 is a solid-state image sensor Driver, 2
Reference numeral 8 denotes a digital / analog (D / A) converter.

Next, the operation will be described. Light from the subject passes through the lens 21 and is driven by the solid-state imaging device driver 27, and is photoelectrically converted by the solid-state imaging device 22. The output of the solid-state imaging device 22 is subjected to sampling and gain control by a CDS / AGC circuit 23, converted to a digital signal by an A / D converter 24, and subjected to gamma correction and color correction by a DSP 25. The signal is converted into an analog signal by the A converter 28 and converted into a video signal. The microcomputer 26 is a DSP2
5 and the exposure time of the solid-state imaging device 22 is controlled via the solid-state imaging device driver 27.

[0004]

In the prior art, for example, since the light source is behind the subject, when the background is brighter than the subject, that is, in a so-called backlight state, if the exposure time of the solid-state imaging device is shortened, the Does not provide a sufficient amount of light, and the subject is imaged in a black-out condition, with the subject being darkened on the monitor screen. Further, when the exposure time of the solid-state imaging device is lengthened, the amount of light in the background is saturated, and only a white image appears on a portion behind the subject on the monitor screen, resulting in an overexposed state.

SUMMARY OF THE INVENTION An object of the present invention is to provide a television camera which does not cause underexposure or overexposure which causes image quality deterioration.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a television camera having a solid-state imaging device, which stores video signals obtained by exposing the solid-state imaging device during a plurality of exposure periods. And outputting the stored video signals, and weighting each portion of the output video signal. The weighting is performed for a portion having a higher video signal level according to the video signal level of each portion. Is weighted by a video signal having a shorter exposure period, a portion having a smaller video signal level is weighted by a video signal having a longer exposure period, and the weighted video signals are added.

[0007] For a subject having a large contrast difference such as a backlight state, a video signal free from overexposure and obtained by shortening the exposure time of the solid-state image sensor to less than one field, and the exposure time of the solid-state image sensor. By adding video signals without blackouts, which are obtained by making the length of the image longer than one field, an image with a wide dynamic range can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. 1 is a lens. Reference numeral 2 denotes a solid-state imaging device.
Reference numeral 3 denotes a solid-state imaging device driver that drives the solid-state imaging device 2. Reference numeral 4 denotes a CDS / AGC circuit for performing correlated double sampling (CDS) and automatic gain control (AGC), and performs CDS processing and AGC processing on the output of the solid-state imaging device 2. 5
Is an analog / digital (A / D) converter.
The analog output of the GC circuit 4 is converted into a digital signal.
Reference numeral 6 denotes a digital signal processor (DSP).
The output of the D converter 5 is subjected to gamma correction and color correction processing. 7
Is a microcomputer (hereinafter referred to as a microcomputer),
Each control of the DSP 6 and the solid-state imaging device 2, particularly, control relating to the exposure time thereof is performed. A memory driver 8 controls the memory 9. Reference numeral 9 denotes a memory for recording an output signal of the DSP 6. Reference numerals 10, 11 and 12 are video recording units in the memory 9. Reference numeral 13 denotes an adder for adding outputs of the video recording units 10, 11, and 12. A multiplier 14 multiplies the output of the adder 13 by 1/3. 15 is a digital / analog (D /
A) The converter converts the output signal of the multiplier 14 from digital to analog.

The operation will be described below. Light passing through the lens 1 is photoelectrically converted by the solid-state imaging device 2. The solid-state imaging device driver 3 sets the exposure time interval of the solid-state imaging device 2 to two-field or one-field intervals or the solid-state imaging device 2
Is switched in a predetermined repetition order to any one of less than one field using the electronic shutter function of. The output of the solid-state imaging device 2 is a CDS / AGC circuit 4, A
The image signals are sequentially processed by the / D converter 5 and the DSP 6, and are recorded in the video recording units 10, 11, and 12 in the memory 9 for each of the video signals exposed during the two-field period, the one-field period, or the period less than one field. You. The signals recorded in the video recording units 10, 11 and 12 are output for each field, arithmetically averaged through an adder 13 and a multiplier 14, and output through a D / A converter 15.

Next, as shown in FIG. 2, for example, when a bright subject and a dark subject appear together on the screen,
The exposure time of the solid-state imaging device 2 and the detailed operation of the memory 9 in the embodiment of the television camera of the present invention will be described with reference to the timing chart of FIG. 3 and FIG.

In FIG. 3, reference numeral 16 denotes a vertical synchronization pulse, 1
7 is a read pulse of the solid-state imaging device 2, 18 is a shutter pulse of the solid-state imaging device 2, and 19 is a CDS / AGC circuit 4.
Reference numeral 20 denotes a signal output of the D / A converter 15. As a signal 19a for one horizontal scanning period, a signal obtained by subjecting the solid-state imaging device 2 to exposure during both the period 16a and the period 16b and performing photoelectric conversion is output by a readout pulse 17a.
The output signal is obtained by being processed by the CDS / AGC circuit 4. Signal 19b for one horizontal scanning period
Indicates that a signal obtained by exposing the solid-state imaging device 2 during the period 16c and photoelectrically converted is output by a readout pulse 17b.
The output signal is obtained by being processed by the CDS / AGC circuit 4. Signal 19c for one horizontal scanning period
Is a signal obtained by exposing the solid-state imaging device 2 in a period after the shutter pulse 18a in the period 16d and photoelectrically converting the signal. The readout pulse 17c outputs the signal, and the output signal is processed by the CDS / AGC circuit 4. It is obtained by doing.

The signal 19a obtained as described above is
After being processed by the A / D converter 5 and the DSP 6, the data is recorded as digital video data in the video recording unit 10 in the memory 9.
Recording and output operations of the memory 9 are controlled by the microcomputer 7. Similarly to the above operation, the signal 19b is recorded as digital video data in the video recording unit 11 and the signal 19c is recorded in the video recording unit 12 as digital video data. Video recording unit 10, 1
The signals recorded repeatedly as 1 and 12 and recorded and held as the latest video signals are simultaneously output for each field, and are passed through an adder 13 and a multiplier 14 so that the video signal portion of a brighter subject is exposed more. An arithmetic mean weighted by a video signal captured in a field having a short period is performed. For a video signal portion of a darker subject, arithmetic averaging of weighted video signals in a field having a longer exposure period is performed. The signal thus arithmetically averaged passes through the D / A converter 15 and is output as a video signal 20 for one horizontal scanning period.

[0013]

According to the present invention, even for a subject having a large contrast difference such as a backlit state, a video signal free from overexposure and obtained by shortening the exposure time of the solid-state imaging device to less than one field. Exposure time 1 of the solid-state imaging device
A wide dynamic range is obtained by adding the three types of video signals of a field video signal and a video signal in which the solid-state imaging device has an exposure time longer than one field and in which no blackout occurs. A television camera can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a block configuration of an embodiment of a television camera according to the present invention.

FIG. 2 is a diagram illustrating an example of a screen in which a bright subject and a dark subject are imaged together.

FIG. 3 is a waveform chart for explaining the operation of one embodiment of the television camera of the present invention.

FIG. 4 is a diagram showing an example of a block configuration of a television camera according to the related art.

[Explanation of symbols]

1: lens, 2: solid-state imaging device (CCD), 3: solid-state imaging device driver, 4: CDS / AGC circuit, 5: analog / digital (A / D) converter, 6: digital signal processor, 7: micro Computer (microcomputer), 8:
Memory driver, 9: memory, 10, 11, 12: video recording unit, 13: adder, 14: multiplier, 15: digital /
Analog (D / A) converter.

Claims (1)

[Claims] In a television camera having a solid-state imaging device, a video signal obtained by exposing the solid-state imaging device during a plurality of exposure periods is stored, and the stored video signal is output. Weighting each portion of the output video signal, and the weighting is performed by using a video signal having a shorter exposure period for a portion having a higher video signal level according to the video signal level of each portion; A television camera characterized in that a portion having a smaller level is weighted with a video signal having a longer exposure period and the weighted video signal is added.