JPH0278382A - Image pickup device - Google Patents

Abstract

PURPOSE:To adjust the gain automatically while applying usual photographing by outputting a reference signal required for comparing gains from each output terminal at least at part of time within the time not outputting a video signal. CONSTITUTION:A video signal charge stored in a picture element 1 and read out in a vertical CCD register 2 is transferred sequentially to a horizontal CCD register 3 for each horizontal blanking period. Simultaneously a reference signal generating circuit 5 generates a reference signal charge for each horizontal period and the reference signal charge is transferred to a distributing circuit CCD 6''. When the register 2 is driven to transfer the video signal charge, the reference signal charge transferred in the CCD 6'' is transferred sequentially in registers 3, 3' through the vertical CCD 6, 6' for the distribution circuit. The video signal and the reference signal charge transferred in the register 3, 3' are read out sequentially from output sections 4, 4' for the succeeding horizontal video period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an imaging device using an imaging device such as an imaging tube or a solid-state imaging device.

[Conventional technology]

A plan view of an interline transfer CCD solid-state imaging device, which is a type of solid-state imaging device, is schematically shown in FIG.
0-254892). This element is driven as follows. First, pixels 1 are arranged regularly in the horizontal and vertical directions.
Is it photoelectrically converted? The video signal charge of the entire screen multiplied by 9 is:
Vertical CCD that transfers data once in the vertical direction during the vertical retrace period
Read and store in register 2. The video signal charge read into the vertical CCD register 2 is transferred to the horizontal CCD register 3, which transfers it in the horizontal direction, one line at a time every horizontal retrace period, and sequentially output to the output section 4 during the subsequent horizontal video period.
I'm going to read it from there. Arrows in the figure indicate the transfer direction of video signal charges.

Incidentally, in recent years, there has been a strong demand for higher resolution such as in high-definition television systems (HD systems), and accordingly, studies are underway to increase the number of pixels of solid-state image sensors.

However, in a conventional COD solid-state image pickup device having only one row of horizontal CCD registers 3 as shown in FIG. 4, the drive frequency of the horizontal CCD registers and the transfer speed increase as the number of pixels increases, and it cannot be driven at present.

Therefore, as shown at 3 and 3' in Figure 5, the water body CC
A method is used in which two rows of D registers are provided and the transfer speed in each row is increased for reading (IEICE Technical Report ED87-174).
.

[Problem to be solved by the invention]

In the solid-state image pickup device shown in FIG. 5, the video signals output after being divided into two output sections 4 and 4' pass through buffer amplifiers 7 and 7' as shown in FIG. After that, the signal processing circuit 8 converts it into a television signal and outputs it.

By the way, from the solid-state imaging probe output parts 4, 4' to the synthesis circuit 10
If there is a difference in the gain of the two circuit systems up to this point, there will also be a difference in the level of each video signal included in the recombined composite signal. For example, when photographing a negative-looking wall, vertical striped false signals appear, resulting in a significant deterioration in image quality.

Therefore, in this method, it is necessary to delicately adjust the gains of the two circuit systems, which causes an increase in mass production costs. In addition, this adjustment currently requires complicated work while photographing a special subject, and also poses problems such as readjustment being required when the environmental temperature changes.

SUMMARY OF THE INVENTION An object of the present invention is to provide an element structure and a driving method that allow automatic gain adjustment while performing normal imaging.

[Means to solve the problem]

In order to achieve the above object, the present invention provides video (at least part of the time during which the S number is not output).

A solid-state imaging probe is used that has a structure that allows the standard (V'1) required for comparing gains to be output from each output terminal.

The signals output separately to different terminals of the solid-state image sensor are then recombined in a subsequent circuit to synthesize a video signal. The reference signal portions included in this recombined composite I= signal are extracted and their levels are compared, and the gains of each circuit system before composition are adjusted so that these reference signal levels are approximately the same.

[Effect]

In the image pickup device and image pickup device according to the present invention, the reference signal necessary to set the gain of the circuit system through which the video signal from each output terminal passes to 8 (8) can be obtained at any time without photographing a special subject. It can automatically adjust the gain of the video signal from each output terminal to reduce differences in video signal levels.

Therefore, deterioration in image quality that occurs when there is a difference in video signal level can be suppressed. Furthermore, since fine adjustment of the gain of the circuit system is automatically performed without using a special subject, fine adjustment during production is not necessary, and early production costs can be reduced. Furthermore, since gain adjustment is performed automatically, there is no need for the complicated readjustment work that was required each time the environmental temperature changed while photographing a special subject.

〔Example〕

A first embodiment of the invention is shown in FIGS. 1-3.

FIG. 1 shows an example of the structure of a solid-state image sensor according to the present invention, which includes a reference signal generation circuit 5 that generates a reference (No. The structure of the conventional solid-state image pickup device shown in FIG. 5 differs in that circuits 6 to 6' are newly provided for the allocation.

FIG. 3 is an example of a signal processing circuit according to the present invention that converts an output signal of an image sensor into a television signal. A signal gain comparison circuit 1 that compares the levels of two divided signals is shown in FIG.
1 and a gain adjustment amount calculation storage circuit 12 for controlling the gain of at least one of the output signals thereof.
This circuit differs from the conventional circuit in that a gain controller 9 and a gain controller 9 are provided.

In the device shown in FIG. 1, the video signal charges accumulated in the pixel 1 and read out to the vertical CCD register 2 are sequentially transferred to the horizontal CCD register 3 every horizontal retrace period, as in the conventional case. On the other hand, at the same time, a normal CCDtft charge injection circuit (Japanese Patent Laid-Open No. 59-172
195) etc., a reference signal charge is generated every horizontal period, and the distribution is distributed to the circuit CC.
The reference signal charge is transferred to D6'. and vertical CO
When the D register 2 is driven to transfer the video signal charge, the reference signal charge transferred to the circuit CCD 6' is also distributed.
Similar to the video signal charge, the distribution is vertical C0D6.6 for the circuit.
' and then sequentially transferred into the horizontal CCD register 3°3'. The video signal and reference signal charge transferred into the horizontal COD registers 3, 3' are transferred to the horizontal video period shown in FIG.
As schematically shown in b) and (Q), the data are sequentially read out from the output units 4 and 4'.

Next, the signals outputted separately to the two output sections 4 and 4' of the solid-state image pickup device pass through buffer amplifiers 7 and 7' shown in FIG. 3, and are recombined into one by a synthesis circuit 1o. The recombined composite signal waveform is schematically shown in FIG. 2(d). For example, if the circuit passing through the buffer amplifier 7' has a higher (lower) gain than the circuit passing through the buffer amplifier 7, a difference will occur in the level of the reference signal 13 included in the composite signal in proportion to the gain. Therefore, in the signal gain comparison circuit 11, after taking a long-term average of each reference signal to reduce the influence of noise,
Detects the gain difference between two circuit systems.

Then, this value is compared with a value already stored in the gain adjustment edge calculation storage circuit 12, and the gain of the gain controller 9 is lowered (increased) by a sufficiently small gain value according to the comparison result, and the state at that time is It is stored in the adjustment amount calculation storage circuit 12. By repeating the gain comparison and adjustment for each horizontal period, the gains of the two circuits become almost the same, and a composite signal with no difference in gain is obtained. Thereafter, as in the conventional case, the signal processing circuit 8 converts the signal into a television signal and outputs it.

In this manner, in the imaging device f't shown in FIG. 3, the level difference after combining the video signals read out in two parts is automatically reduced, and almost no difference occurs. Therefore, deterioration in image quality that occurs when there is a difference in video signal level can be suppressed.

Further, since fine adjustment of the gain of the circuit system is automatically performed without using a special subject, fine adjustment during production is unnecessary, reducing the number of bankruptcies. Furthermore, since gain adjustment is performed automatically, there is no need for the complicated readjustment work that was required each time the environmental temperature changed while photographing a special subject.

Note that the averaging operation for reducing noise is omitted when adjusting the gain when the power is turned on. Alternatively, it is desirable to speed up the device start-up time by making the gain value adjusted for adjustment larger than usual. It is obvious that the adjustment may be made by multiplying one of the circuit system signals by the reciprocal of the reference signal level ratio.

7 and 8 show a second embodiment of the present invention.6 FIG. 7 shows another example of the structure of a solid-state image sensor according to the present invention, in which several scanning lines (in FIG. 7, three The video signal used in the book's scanning line is divided into several output terminals (three in Figure 7) and read out simultaneously, and the reference signal can be output from each output terminal like the device in Figure 1. Different from conventional element structure.

The video signal charges accumulated in the pixel 1 and the reference signal charges generated by the reference signal generator 5 in the device shown in FIG.

Similar to the device shown in FIG. 1, signals for three horizontal periods, for example, are combined into a set and sequentially transferred into the horizontal CCD registers 3 to 3'. The video signal charge and the reference signal charge transferred into the horizontal CCD registers 3 to 3' are sequentially read out from the output sections 4 to 4'' in the following period (for example, slowly over 3 horizontal periods). The signal is read out every 1 field period of the TV system used (however, the '#7' of the signal
When increasing the sensitivity by increasing the integration/opening time, adjust it to that cycle).

Next, the signals output separately to the output sections 4 to 4'' of the solid-state imaging probe are converted into digital signals through buffer amplifiers 7 to 7' and AD converters 21 to 21' shown in FIG. In the comparator circuit 11.11', after taking a long-term average of the reference signals converted into digital signals and reducing the influence of noise, the level ratio of the three averaged reference signals is determined.This value is calculated by gain g4'l11m. While the memory circuit 12.12' compares the stored value with a certain value and stores it again, the gain controller 9.9' (multiplier) multiplies the converted signal by the reciprocal of the stored level ratio to adjust the gain. After converting the signal into a signal with no difference, the signal is stored in the image memory circuit 22. Then, the time adjustment circuit 23 sequentially reads out the signal from the image memory circuit 22 in accordance with the order of the television system used, and the signal processing circuit 8 converts it into a television signal. Output.

In this manner, in the image pickup apparatus shown in FIG. 8, gain differences in the circuit system are automatically compensated for by the subsequent circuit, so that a television signal with no level difference can be obtained. Therefore, in this embodiment as well, as in the first embodiment, it is possible to suppress deterioration in image quality that occurs when there is a difference in video signal level. Further, fine adjustment of the circuit gain during production is not necessary, and mass production costs can be reduced. Furthermore, the complicated readjustment work required every time the environmental temperature changes becomes unnecessary. Further, in this embodiment, since the correct gain N4 adjustment can be performed immediately after the reference signal level is detected, the device can be started up very quickly.

Note that the reading speed of the signals from the horizontal COD registers 3 to 3' may be arbitrarily selected within a range that allows signal charges for one screen of the image pickup device to be read out during one field period of the television system used. However, the slower the reading speed, the lower the frequency of the output signal, and the narrower the signal band during reading. Therefore, by narrowing the signal band, it is possible to reduce the influence of random noise generated by the output amplifier and increase the S/N ratio of the signal. Furthermore, since low-speed AD converters are cheaper than high-speed AD converters, it is desirable that the signal readout speed be slow.

Also, the gain controllers 9 and 9' are installed before the AD converter, and either multiply the output signal of the imaging probe by the reciprocal of the detected gain ratio, or increase or decrease the gain value by a sufficiently small value as in the first embodiment. It is obvious that the adjustment may be made in the following manner.

In the above embodiments, the reference signal is output only for each signal of one horizontal video period, but it can be output at any arbitrary time, such as every one field period, every few minutes, or when some operation such as a switch operation is performed. The reference signals from each output terminal do not always need to be output at the same time, and may be output sequentially at different times.

Furthermore, in order to reduce the influence of noise when detecting the level of the reference signal with the signal gain comparison circuit, it is better to increase the level of the reference signal. However, from the viewpoint of the dynamic range of the subsequent circuit, it is desirable to set the level of the reference signal within a range from approximately the white level of the video signal to approximately three times the white level.

Further, in the first embodiment, a digital circuit similar to that in the second embodiment may be used.

In addition to the image sensors shown in Figs. 1 and 7, the image sensors used are those shown in Figs.
It is clear that as long as the structure is such that the same reference signal can be output from each output terminal as illustrated in the figure, even a structure that divides the screen into left and right halves and outputs them is acceptable.

Furthermore, the structure of the image sensor is an interline transfer CCD.
Although the explanation has been made using a solid-state image sensor, there are other types of COD solid-state image sensor and MO5 solid-state image sensor.

It is obvious that an image pickup tube or the like may also be used.

The case where the solid-state image sensor has a reference signal generation circuit has been described above.
Operate the circuit shown in the figure to adjust the gain. By storing the state at that time, gain adjustment can be simplified even in a camera using a conventional image sensor.

〔Effect of the invention〕

As described above, by using the image sensor and image pickup device according to the present invention, the reference signal necessary to measure the gain of the circuit system through which the video signal from each output terminal passes can be obtained without photographing a special subject. available at any time.

Moreover, it is possible to automatically adjust the gain of the video signal from each output terminal to reduce differences in video signal levels.

Therefore, deterioration in image quality that occurs when there is a difference in video signal level can be suppressed. Furthermore, since fine adjustment of the gain of the circuit system is automatically performed without using a special subject, fine adjustment during production is not necessary and mass production costs can be reduced. Furthermore, since gain adjustment is performed automatically, there is no need to perform complicated readjustment work while photographing a special subject every time the environmental temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a solid-state imaging device according to a first embodiment of the present invention, FIG. 2 is a block diagram of an imaging device according to the same embodiment, and FIG.
The figure is a signal timing diagram of the same embodiment, and FIGS. 4 and 5 are schematic diagrams of a conventional interline transfer CCD solid-state image sensor.
FIG. 6 is a block diagram showing the structure of a conventional imaging device, FIG. 7 is a schematic diagram of a solid-state imaging device according to a second embodiment of the present invention, and FIG. 8 is a block diagram showing the structure of an imaging device of the same embodiment. The block diagram shown in FIG. 9 is a schematic diagram of a solid-state image sensor according to still another embodiment of the present invention. 1... Pixel, 2... Vertical CCD register, 3...
Horizontal CCU register, 4...Output section, 5...Image sensor, 9...Gain controller, 10...Composition circuit, 11...Signal gain comparison circuit, 12...Gain adjustment! It calculation memory circuit. Tsuta 1 zu kudzu 2 tsuta ni ni ni yowushi II! J7] J! ] Figure 3 Figure 4 ¥ 5 Figure 6 Figure 7 Figure 8 Figure 9 (phantom (b)

Claims (1)

[Scope of Claims] 1. In an imaging device using an imaging device such as an imaging tube or a solid-state imaging device that converts incident light into an electrical signal, at least part of the time during which no video signal is output, An imaging device characterized by having a structure capable of outputting a reference signal necessary for comparing signal gains. 2. In an imaging device that uses an imaging device such as an image pickup tube or a solid-state imaging device that converts incident light into an electrical signal, the video signal used by two or more scanning lines of the television system used in the imaging device is An imaging device characterized by having a structure that allows output to be divided into two or more output terminals. 3. An image sensor that outputs a video signal from the image sensor by dividing it into two or more output terminals, and comparing the signal gain from each of the output terminals during at least part of the time during which no video signal is output. a drive circuit that drives the image sensor so as to output a reference signal necessary for the image pickup; a synthesis circuit that combines the signals separately output from each output terminal and synthesizes a video signal used for the image output; A signal gain comparison circuit that detects and compares the level of the reference signal output from the terminal, and a gain adjustment circuit and gain that adjusts the video signal level output from each output terminal based on the information obtained by the signal gain comparison circuit. 2. The imaging device according to claim 1, further comprising an adjustment amount calculation storage circuit. 4. The signal gain comparison circuit is provided after the synthesis circuit,
4. The imaging apparatus according to claim 3, wherein the gain adjustment circuit is provided before the synthesis circuit. 5. The signal gain comparison circuit is a circuit that detects the magnitude relationship between the level of the reference signal output from one of the output terminals and the level of the reference signal output from each of the other output terminals, The gain adjustment circuit and the gain adjustment amount calculation storage circuit output a signal serving as the large (small) reference when the level of the reference signal output from each of the other output terminals is larger (smaller). 5. The imaging apparatus according to claim 4, wherein the circuit resets the gain of the circuit system connected to each output terminal to be smaller (larger) by a sufficiently small fixed amount. 6. In the imaging device according to claim 2, the imaging device is arranged so that video signals used in two or more scanning lines of a television system used in the imaging device are divided into two or more output terminals and read out simultaneously. A drive circuit for driving, an AD converter for converting the read signal into a digital signal, an image memory circuit for temporarily storing the signal converted to the digital signal, and an image memory circuit for temporarily storing the signal converted to the digital signal, An imaging device characterized by having a time adjustment circuit that sequentially reads out video signals. 7. In the image pickup device according to claim 6, the drive circuit controls the image pickup device to output a reference signal from each output terminal during at least part of the time during which no video signal is output. A signal gain comparison circuit for detecting the level ratio of a reference signal included in the signal read from the image sensor is provided after the AD conversion, and the signal converted to the digital signal is An imaging device comprising: a gain adjustment circuit that corrects a level difference between signals output from each of the output terminals by multiplying by a reciprocal of a ratio of levels of the detected reference signals. 8. In the imaging device according to claims 1 to 5 and 7, the level of the reference signal is set in a range from approximately the white level of the video signal to about three times the white level. An imaging device characterized by: