JP2702982B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus using an image pickup device such as an image pickup tube or a solid-state image pickup device.

[Conventional technology]

FIG. 4 schematically shows a plan view of an interline transfer CCD solid-state imaging device, which is one type of solid-state imaging device.
No. 254892). Driving of this element is performed as follows. First, the video signal charges of the entire screen photoelectrically converted and stored in the pixels 1 arranged regularly in the horizontal and vertical directions are read out and stored in a vertical CCD register 2 which is temporarily transferred in a vertical direction during a vertical blanking period. I do. The video signal charges read into the vertical CCD register 2 are transferred by one line every horizontal retrace period to the horizontal CCD register 3 for transferring in the horizontal direction, and are sequentially read from the output unit 4 during the subsequent horizontal video period. go. The arrow in the figure indicates the transfer direction of the video signal charge.

In recent years, there has been a strong demand for higher resolution such as a high-definition television system (HD system), and an increase in the number of pixels of a solid-state imaging device has been studied accordingly. However, in the conventional CCD solid-state image pickup device having only one row of the horizontal CCD registers 3 as shown in FIG. 4, the transfer speed is increased according to the driving frequency of the horizontal CCD registers by the increase in the number of pixels, and cannot be driven at present. .

For this reason, as shown at 3, 3 'in FIG. 5, a method has been adopted in which two rows of water body CCD registers are provided, and reading is performed at an increased transfer rate in each row (IEICE Technical Report ED87-174).

[Problems to be solved by the invention]

In the solid-state image pickup device shown in FIG. 5, the video signals output separately from the two output sections 4, 4 'are passed through buffer amplifiers 7, 7' as shown in FIG. The signal is converted into a television signal by the post-signal processing circuit 8 and output.

If there is a difference between the gains of the two circuit systems from the solid-state imaging device output units 4 and 4 'to the synthesizing circuit 10, a difference also occurs in each video signal level included in the synthesized signal.
For example, when a uniform wall is photographed, a vertical striped false signal appears, and the image quality is significantly degraded.

Therefore, in this method, it is necessary to finely adjust the gain of the two circuit systems, which causes an increase in mass production cost.
In addition, this adjustment currently requires a complicated operation while photographing a special subject, and also causes a problem such as a need to readjust when the environmental temperature changes.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an element structure and a driving method capable of automatically adjusting a gain while performing normal shooting.

[Means for solving the problem]

In order to achieve the above object, the present invention uses a solid-state imaging device having a structure capable of outputting a reference signal necessary for comparing gains from each output terminal at least during a time when a video signal is not output. .

Each signal output separately to different terminals of the solid-state imaging device is regrouped by a subsequent circuit to synthesize a video signal.
The reference signal portion included in the recombined synthesized signal is taken out, the levels are compared, and the gain of each circuit system before the synthesis is adjusted so that these reference signal levels become substantially the same.

[Action]

In the image pickup device and the image pickup apparatus according to the present invention, a reference signal necessary for measuring the gain of a circuit system through which a video signal from each output terminal passes can be obtained at any time without photographing a special subject. In addition, the gain of the video signal from each output terminal is automatically adjusted, and the difference in video signal level can be reduced.

Therefore, it is possible to suppress deterioration in image quality caused by a difference in video signal level. Also, fine adjustment of the gain of the circuit system is automatically performed without using a special subject,
Fine adjustment at the time of production becomes unnecessary, and mass production cost can be reduced.
Further, since the gain adjustment is automatically performed, a complicated readjustment operation performed while photographing a special subject, which is necessary each time the environmental temperature changes, becomes unnecessary.

〔Example〕

 A first embodiment of the present invention is shown in FIGS.

FIG. 1 shows an example of a solid-state imaging device structure according to the present invention. The reference signal generating circuit 5 generates a reference signal required for gain comparison, and the generated reference signal is distributed so that it can be output from each output terminal. It differs from the structure of the conventional solid-state imaging device in FIG. 5 in that the sorting circuits 6 to 6 ″ are newly provided.

FIG. 3 shows an example of a signal processing circuit for converting the output signal of the image pickup device into a television signal according to the present invention. The signal gain comparison circuit compares the levels of the two divided output signals.
11 in that a gain adjustment amount operation storage circuit 12 for controlling the gain of at least one of the output signals and a gain controller 9 are provided.

The video signal charges stored in the pixel 1 and read out to the vertical CCD register 2 by the element shown in FIG. 1 are sequentially transferred to the horizontal CCD register 3 every horizontal blanking period as in the conventional case. On the other hand, at the same time, a reference signal charge is generated every horizontal period by a reference signal generation circuit 5 comprising a normal CCD charge injection circuit (Japanese Patent Laid-Open No. 59-172195) and the like, and the reference signal charge is supplied to the distribution circuit CCD 6 ″. When the vertical CCD register 2 is driven to transfer the video signal charges, the reference signal charges transferred into the distribution circuit CCD 6 ″ are also transferred to the vertical CCDs 6 and 6 for the distribution circuit similarly to the video signal charges. ′ Through the horizontal CCD register 3,
Transfer to 3 '. The video signal and the reference signal charge transferred into the horizontal CCD registers 3, 3 'are sequentially output to the output units 4, 3, as schematically shown in FIGS. 2 (b) and 2 (c) during the subsequent horizontal video period.
Read from 4 '.

Next, the signals output to the two output sections 4 and 4 'of the solid-state imaging device are passed through buffer amplifiers 7 and 7' shown in FIG. FIG. 2 (d) schematically shows the recombined composite signal waveform. By the way, for example, when the gain of the circuit passing through the buffer amplifier 7 'is higher (lower) than that of the circuit passing through the buffer amplifier 7, a difference occurs in the level of the reference signal 13 included in the composite signal in proportion thereto. Therefore, the signal gain comparison circuit 11 takes the long-term average of each reference signal to reduce the influence of noise, and then detects the gain difference between the two circuit systems. Then, this value is compared with the value already stored in the gain adjustment amount calculation storage circuit 12,
The gain of the gain controller 9 is reduced (increased) by a sufficiently small gain value in accordance with the comparison result, and the state at that time is stored in the gain adjustment amount calculation storage circuit 12.
Similarly, when the comparison and adjustment of the gain are repeated in each horizontal period, the gains of the two circuits are substantially the same, and a composite signal having no gain difference is obtained. After that, the signal processing circuit 8 as in the prior art
To convert to TV signal and output.

As described above, in the image pickup apparatus shown in FIG. 3, the level difference after synthesizing the video signals read out in two parts is automatically reduced, and almost no difference occurs. Therefore, it is possible to suppress deterioration in image quality caused by a difference in video signal level. Further, since the fine adjustment of the gain of the circuit system is automatically performed without using a special subject, the fine adjustment at the time of production becomes unnecessary and the mass production cost can be reduced. Further, since the gain adjustment is automatically performed, a complicated readjustment operation performed while photographing a special subject, which is necessary each time the environmental temperature changes, becomes unnecessary.

In the gain adjustment at the time of turning on the power, it is desirable to shorten the apparatus start-up time by omitting the averaging operation for reducing noise, or increasing the gain value to be adjusted for adjustment to be larger than usual.

It is apparent that the gain may be adjusted by a method such as obtaining the reference signal level ratio by the signal gain comparison circuit 11 and multiplying one of the signals of the two circuit systems by the reciprocal of the reference signal level ratio.

 7 and 8 show a second embodiment of the present invention.

FIG. 7 shows another example of the solid-state image pickup device structure according to the present invention, in which several video signals used in several scanning lines (three scanning lines in FIG. 7) of a television system to be used (three in FIG. 7). (3) output terminals and read out simultaneously, and a reference signal can be output from each output terminal similarly to the element of FIG.

The video signal charge accumulated in the pixel 1 by the element of FIG. 7 and the reference signal charge generated by the reference signal generator 5 are, for example, a set of signals for three horizontal periods as in the element of FIG. The video signal charges and the reference signal charges transferred into the horizontal CCD registers 3 to 3 "are sequentially transferred into the horizontal CCD registers 3 to 3".
Are sequentially read from the output units 4 to 4 ″.
The signal for the screen is read out every one field period of the television system to be used (however, when increasing the signal accumulation time to increase the sensitivity, the signal is adjusted to the cycle).

Next, the signals output to the output sections 4 to 4 "of the solid-state imaging device are converted into digital signals through buffer amplifiers 7 to 7" and AD converters 21 to 21 "shown in FIG. In 11,11 ", after the long term average of the reference signal converted into the digital signal is reduced to reduce the influence of noise, the level ratio of the averaged three reference signals is obtained. This value is compared with the value stored in the gain adjustment amount operation storage circuits 12, 12 "and stored again, while the gain controller 9, 9" (multiplier) multiplies the conversion signal by the reciprocal of the stored level ratio. After adjusting the gain to convert the signal into a signal having no gain difference, the signal is stored in the image memory circuit 22. Then, the time adjustment circuit 23 sequentially reads out the signals from the image memory circuit 22 in accordance with the order of the television system to be used, and outputs the signals to the signal processing circuit 8.
To convert to TV signal and output.

As described above, in the image pickup apparatus shown in FIG. 8, since the gain difference of the circuit system is automatically corrected by the subsequent circuit, a television signal having no level difference can be obtained. Therefore, in the present embodiment, similarly to the first embodiment, it is possible to suppress the deterioration of the image quality caused by the difference in the video signal level. Also, fine adjustment of the circuit system gain at the time of production becomes unnecessary, and mass production cost can be reduced. Furthermore, the complicated readjustment work required every time the environmental temperature changes is not required. Further, in this embodiment, since the correct gain adjustment can be performed immediately after the detection of the reference signal level, the apparatus can be started up at a very high speed.

The reading speed of the signals from the horizontal CCD registers 3 to 3 "may be arbitrarily selected within a range in which the signal charges for one screen of the image sensor can be read in one field period of the television system to be used. The frequency of the output signal is reduced, and the signal band at the time of reading can be narrowed, so that the effect of random noise generated by the output amplifier can be reduced by narrowing the signal band, and the signal-to-noise ratio of the signal can be increased. In addition, it is desirable that the signal reading speed be low in terms of the fact that the AD converter is inexpensive at a lower speed than at a higher speed.

The gain controllers 9, 9 ″ are provided before the AD converter, and multiply the output signal of the image sensor 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 by the method.

In the above embodiment, only the case where the reference signal is output for each signal of one horizontal video period has been described, but for each field period. The injection may be performed at an arbitrary time, such as every few minutes or when a certain operation such as a switch operation is performed, to adjust the gain. Further, the reference signals from each output terminal need not always be output simultaneously, and may be output sequentially at different times.

In order to reduce the influence of noise when the signal gain comparison circuit detects the level of the reference signal, it is better to increase the level of the reference signal. However, from the point of view of the dynamic range of the subsequent circuit, it is desirable that the level of the reference signal be set in a range from the white level of the video signal to about three times the white level.

In the first embodiment, a digital circuit similar to that of the second embodiment may be used.

If the image pickup device used has a structure capable of outputting the same reference signal from each output terminal as shown in FIG. 9 in addition to the devices shown in FIGS. It is clear that a structure for outputting the data may be used.

Furthermore, an interline transfer CCD is used as the structure of the image sensor.
Although the description has been made using the solid-state imaging device, it is apparent that other types of CCD solid-state imaging device, MOS solid-state imaging device, imaging tube, and the like may be used.

The case where the solid-state imaging device has the reference signal generating circuit has been described above. The video signal when uniform light is applied to the screen is used as the reference signal, and FIGS. Operate the circuit shown to adjust the gain. By storing the state at that time, the gain adjustment can be simplified even in a camera using a conventional image sensor.

〔The invention's effect〕

As described above, when the imaging device and the imaging device according to the present invention are used, a reference signal necessary for measuring a gain of a circuit system through which a video signal from each output terminal passes can be used even if a special subject is not captured. You can always get it. In addition, the gain of the video signal from each output terminal is automatically adjusted, and the difference in video signal level can be reduced.

Therefore, it is possible to suppress deterioration in image quality caused by a difference in video signal level. Further, since the fine adjustment of the gain of the circuit system is automatically performed without using a special subject, the fine adjustment at the time of production becomes unnecessary and the mass production cost can be reduced. Further, since the gain adjustment is automatically performed, it is not necessary to perform a complicated readjustment operation while photographing a special subject which is required every time the environmental temperature changes.

[Brief description of the drawings]

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 the imaging device of the embodiment, and FIG.
4 and 5 are schematic diagrams of a conventional interline transfer CCD solid-state imaging device, FIG. 6 is a block diagram showing the structure of a conventional imaging device, and FIG.
FIG. 9 is a schematic view of a solid-state imaging device according to a second embodiment of the present invention, FIG. 8 is a block diagram showing the structure of an imaging device of the embodiment, and FIG. 9 is a solid-state imaging device of still another embodiment according to the present invention. It is a schematic diagram of an element. Reference Signs List 1 ... pixel, 2 ... vertical CCD register, 3 ... horizontal CCD register, 4 ... output unit, 5 ... image sensor, 9 ... gain controller, 10 ... combining circuit, 11 ... signal gain comparison circuit , 12 ... Gain adjustment amount calculation storage circuit.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenji Takahashi 1-280 Higashi Koikebo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-1-114174 (JP, A) JP-A-62 −57374 (JP, A)

Claims (3)

(57) [Claims] 1. An image pickup apparatus using a solid-state image pickup device that converts incident light into an electric signal and divides a video signal into two or more rows of horizontal charge transfer elements and outputs the signal. A reference signal generation circuit, a distribution circuit that distributes the reference signal charge generated by the reference signal generation circuit to each of the two or more horizontal charge transfer element columns, and at least a part of the time during which the video signal is not output. An imaging apparatus having a structure in which the two or more reference signals are output from output terminals of the two or more horizontal charge transfer element columns at a time. 2. A solid-state image pickup device for converting incident light into an electric signal and outputting video signals of two or more scanning lines of a television system in two or more rows of horizontal charge transfer element rows. A reference signal generation circuit for generating a reference signal charge in the imaging device; a distribution circuit for distributing the reference signal charge generated by the reference signal generation circuit to each of the two or more rows of the horizontal charge transfer element rows; Wherein at least a part of the time during which no is output, the two or more reference signals are output from the output terminals of the two or more horizontal charge transfer element columns. . 3. The image pickup apparatus according to claim 1, wherein the magnitude of the level of the reference signal is in the range of 1 to 3 times the magnitude of the white level of the video signal. .