JPS6348973A - Sensitivity adjusting circuit for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To improve a reliability for a device and to improve a response characteristic to the change in the quantity of light by electronically sweeping out an unnecessary charge through the input of excessive light stored in the photosensitive part of a solid-state image pickup element and controlling an exposure time equivalently. CONSTITUTION:A timing control circuit 5 compares a light receiving level designated by a decision light receiving level signal with a decision reference level based on the decision light receiving level signal obtained from a light receiving level detection circuit 4. When the light receiving level does not exceed the decision reference level and accordingly, a practical upper limit, a control signal 51 for designating no requirement for generating a sweeping out pulse is outputted, in this case, an unnecessary stored charge sweeping circuit 6 does not output the sweeping out pulse but the solid-state image pickup element 2 outputs a video signal 21 within the practical level. When the light receiving level exceeds the decision reference level, information designating the degree of exceeding is outputting as the signal 51. the circuit 6 controls the timing for sweeping out the unnecessary storage charge correspondingly to the designation of the signal 51. In such a way, an equivalent diaphragm processing of a lens 1 can be executed through the sweeping out for the unnecessary storage charge.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a sensitivity adjustment circuit for a solid-state imaging device.

In particular, the present invention relates to a sensitivity adjustment circuit for a solid-state imaging device, which improves the sensitivity adjustment circuit for excessive light input.

[Conventional technology]

Conventionally, in solid-state imaging devices of this second type, the exposure time unit in which the photosensitive section receives light can be set to a fixed time period that is the same as one vertical drive cycle specified in the television system. If a solid-state image sensor used as a sensor in a solid-state image sensor receives excessive light input that exceeds the upper limit of the practical level of the light-receiving element in the above-mentioned time unit, its output will reach a saturation level and cannot be used as a signal. There is a problem.

In order to prevent such problems from occurring, it is necessary to limit the amount of light that is manually applied and adjust the sensitivity so that the output bell does not exceed the limit regulated by the upper limit of the practical level.

For this purpose, conventionally, an iris (
1ris) control mechanism and a circuit that adjusts the iris control mechanism to the amount of received light.

[Problem that the invention seeks to solve]

The sensitivity adjustment circuit of the conventional solid-state imaging device described above is as follows.

This requires a mechanical iris control mechanism with a complicated configuration and a circuit to drive it according to the received light level, which complicates the configuration of the light receiving lens and inevitably reduces the reliability of the solid-state imaging device itself. Further, there are disadvantages in that the response characteristics to drastic changes in the amount of light are not sufficient and the configuration of the light receiving lens is unavoidably expensive.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a means for electronically sweeping out unnecessary charges caused by excessive photopower accumulated on the photosensitive portion of a solid-state image sensor and equivalently controlling the exposure time. It is an object of the present invention to provide an inexpensive sensitivity adjustment circuit for a solid-state imaging device that can greatly improve the reliability of a solid-state imaging device by significantly simplifying the light-receiving lens FiX, and also significantly improve the response characteristics to sudden changes in light amount. be.

[Means for solving problems]

A solid-state imaging device including an uninvented circuit 1J, a solid-state imaging device including an independent photosensitive section, a memory section, and a transfer section that transfers the charge obtained in the photosensitive section to the memory section. In the sensitivity adjustment circuit.

When the charge as a signal accumulated in the photosensitive part of the solid-state image sensor includes unnecessary charge exceeding the upper limit of the practical level of the solid-state image sensor, this is determined as the light reception level prior to the transfer timing. an unnecessary accumulated charge cleaning circuit which sweeps out the unnecessary accumulated charge through the transfer section and the memory section at a timing corresponding to the above, and adjusts the formation time of the solid-state image sensor so as to equivalently correspond to the upper limit of the practical level; a received light level detection circuit that detects the received light level of the solid-state image sensor; and a sweep timing control circuit that controls the timing of sweeping out unnecessary accumulated charges in the unnecessary accumulated charge sweeping circuit in response to the received light level detected by the received light level detection circuit. It is composed of:

〔Example〕

Next, the present invention will be explained in detail in #1 with reference to the drawings.

FIG. 1 is a block diagram showing the harm-to-harm ratio of a sensitivity adjustment circuit of a conventional solid-state imaging device, and FIG. 2 is a block diagram showing the configuration of a sensitivity adjustment circuit of a conventional solid-state imaging device.

First, a conventional sensitivity adjustment circuit will be explained with reference to Figure 2.

Lens 1. Solid-state image sensor 2. This is the basic configuration of a solid-state camera f9 device with a movie amplification circuit 3RI, and a received light level detection circuit 4. The iris control circuit 7 and the iris control mechanism 8 constitute a degree adjustment circuit.

The optical image received from the lens 1 is supplied to the solid-state image sensor 2 . The solid-state imaging device 2 includes a photosensitive section that generates a charge corresponding to an input optical image, a transfer section that transfers this charge to a memory section, and the memory section, and stores the optical image received by the lens 1 into a 11L image. Convert it to a target name and convert it into video signal 2
1 and output to the video amplification circuit 3.

The video tt amplifying circuit 3rj amplifies the human power and sends it to the load circuit as an output signal 31 at a normal level.

The light reception level detection circuit 4d manually detects the level of the output signal 31, thereby determining the magnitude of the light reception level by the lens l, and supplies a determined light reception level signal 41 to the iris control circuit 7.

When the iris control circuit 7ri1 receives the judged light receiving level signal 41, it generates an iris control signal 71 with a control amount corresponding to the magnitude of the judged light receiving level indicated by this signal, and supplies this to the iris control mechanism 8.

The iris control mechanism 8rt has a function of opening and closing the lens 1 only in accordance with the amount of control specified by the iris control signal 71 via a motor or the like. For example, when the amount of light received is excessive, the lens 1 It operates to close the pattern at a preset adjustment point near the upper limit of the practical level of the solid-state image sensor 2. Therefore, the iris control signal 71 is.

The iris control circuit 7 outputs a control amount necessary and sufficient to cause the iris control mechanism 8 to adaptively control its aperture in accordance with the amount of light received by the lens 1.

Furthermore, from a different perspective, the length of the received light level detection circuit 4, iris control circuit 7, and iris control mechanism 8ri as a whole adjusts the pattern of the lens 1 according to the amount of received light.
It forms a volupe.

In this way, the sensitivity of the solid-state imaging device is adjusted. However, such sensitivity enhancement by mechanical pattern control has the drawbacks mentioned above.

Therefore, the present invention attempts to solve this drawback as follows.

The embodiment of the invention shown in FIG. Solid-state imaging device 2. Video amplification circuit 3. Received light level detection circuit 4. It is configured with a timing control circuit 5 and an unnecessary accumulated charge sweeping circuit 6, and the components other than the timing control circuit 5 and unnecessary accumulated charge sweeping circuit 6 are the same as those with the same symbols in FIG. Detailed explanation will be omitted.

The basic feature of the present invention is that even if there is an excessive light input exceeding the practical level upper limit of the solid-state image sensor 2, the unnecessary charge accumulated in the photosensitive part of the solid-state image sensor 2 exceeding the practical level upper limit is removed. , this is read out from the memory section via the transfer section and the memory section, and unnecessary accumulated charges are swept out.
This has the same effect as equivalently controlling the pattern of the lens 1 on the photosensitive section, and maintains the image signal 21 output from the solid-state imaging device 2 at a specified level.

The unnecessary accumulated charge sweeping circuit 6d supplies a sweeping pulse 61 to the solid-state image pickup device 2 to cause the above-mentioned unnecessary accumulated charges to be swept out.

FIG. 3 is a sweep pulse timing chart showing the generation timing of the sweep pulse in the embodiment of FIG.

Vertical voice j-phase pulse Pvri vertical tremor period T shown in FIG.
o every time, it is provided to the transfer section of the solid-state image sensor 2 from a television camera system or the like that uses a solid-state image pickup device, and the transfer section generates a transfer gate pulse Pa of the same period based on this vertical synchronization pulse.

The solid-state image sensor 2 transfers the signal charge accumulated in the photosensitive section to the memory section and stores it at the timing of generation of the transfer gate pulse PG.

Conventionally, in order to carry out such charge accumulation, transfer, and storage regardless of the light reception level over the entire time of the vertical motor cycle 'rO, even when the practical level upper limit of the solid-state image sensor 2 is exceeded, unnecessary charge accumulation is avoided. It was inevitable that he would do so.

Unnecessary accumulated charge sweep circuit 6rt, transfer gate pulse PG
Prior to the generation timing, in the case of FIG. 3, a sweep pulse Ps as a so-called second transfer gate pulse is generated at a time T1 earlier than the next transfer gate pulse generation, and this is applied to the transfer section of the solid-state image sensor 2. The unnecessary accumulated charges accumulated in the photosensitive section during the unnecessary accumulation time indicated by T2 are transferred to the transfer section.
It is transferred, read and swept through the memory section. In this way, only the signal charges discharged during the effective storage time T are stored in the memory section and used as video signals.

The occurrence and timing of generation of the sweep pulse Ps are determined as follows.

Based on the judgment light reception level signal obtained from the timing control circuit 5ri and the light reception level detection circuit 4, the light reception level specified by this signal is compared with the judgment reference level.The 0 judgment reference level corresponds to the upper limit of the practical level of the solid-state imaging device 2. This threshold is set in advance to determine whether the received light level exceeds the upper limit of the practical level. If the received light level does not exceed this judgment reference level and therefore does not exceed the upper limit of the practical level, a control signal 51 that specifies that generation of a sweep pulse is not required is output, and in this case, the unnecessary accumulated charge sweep circuit 6 outputs a sweep pulse. No output, solid-state image sensor 2ri
The video signal 21 is output within the practical level.

Now, when the light reception level specified by the judgment light reception level signal inputted to the timing control circuit 5 exceeds the judgment reference level, information specifying the extent to which one judgment reference level has been exceeded is outputted as the control signal 51.

Unnecessary accumulated charge sweeping circuit 6r receives this control signal 51
i. Prior to the generation of the next transfer gate pulse PG, a sweep pulse Ps is generated at the timing of the effective accumulation time Tl corresponding to the six light reception levels specified by this control signal 51, and the above-mentioned unnecessary accumulated charges are swept out. The effective accumulation time T1° shown in FIG. 3, and therefore the unnecessary accumulation time Txd, are determined in accordance with the extent to which the light reception level exceeds the upper limit of the practical level of the solid-state image sensor 2, and an equivalent lens is formed by sweeping out unnecessary accumulated charges. 1, the stamp processing is electronically processed.

In FIG. 3, an increase in T1 results in an increase in sensitivity, and an increase in T2 results in a decrease in sensitivity.

In this way, sensitivity adjustment with significant improvements in reliability and response characteristics is possible through electronic control using a simple circuit.

Note that the received light level detection circuit 4 shown in FIG. Timing control circuit 5. It is clear that the unnecessary accumulated charge sweeping circuit 6 can be implemented in the same way no matter how these are combined.

〔Effect of the invention〕

As explained above, according to the present invention, the solid-state imaging device itself is equipped with an electronic control means that sweeps out unnecessary accumulated charges caused by excessive light reception on the photosensitive portion of the solid-state imaging device and equivalently produces an aperture effect on the lens. The present invention has the effect of realizing an inexpensive sensitivity adjustment circuit for a solid-state imaging device that can significantly improve the reliability of the VC and significantly improve the response characteristics to sudden changes in the amount of light.

[Brief explanation of the drawing]

Figure 1 is a professional diagram of Kazuo's example of the sensitivity adjustment circuit of the uninvented solid-state imaging device, and Figure 2 is the sensitivity p of the conventional solid-state imaging device.
A block diagram of the 41i circuit, and FIG. 3 is an imaging pulse timing chart showing the generation timing of the sweep pulse in the embodiment shown in FIG. 1. ,3・
・Group: Video amplification circuit, 4: Received light level detection circuit, 5: River/timing control circuit, 6: Unnecessary accumulated charge sweeping circuit, 7: Iris control Circuit, 8. Old...Iris? 1lIJ #Mechanism. Agent Patent Attorney Uchihara −′・−・7 days
. Rod once

Claims (1)

[Claims] In a sensitivity adjustment circuit for a solid-state imaging device including a solid-state imaging device configured with an independent photosensitive section, a memory section, and a transfer section that transfers charges obtained in the photosensitive section to the memory section, When the charge as a signal accumulated in the photosensitive section of the solid-state image sensor includes unnecessary accumulated charge exceeding the practical level upper limit of the solid-state image sensor, this is adjusted to correspond to the light reception level prior to the transfer timing of the transfer section. A circuit for sweeping out unnecessary accumulated charge through the transfer section and the memory section at a timing to equivalently adjust the exposure time of the solid-state image sensor to correspond to an upper limit of practical level, and a light receiving level of the solid-state image sensor. A solid-state imaging device comprising: a received light level detection circuit for detecting a received light level; and a sweep timing control circuit for controlling the timing of discharging unnecessary accumulated charges in the unnecessary accumulated charge sweeping circuit in accordance with the received light level detected by the received light level detecting circuit. A sensitivity adjustment circuit for a solid-state imaging device, which adjusts sensitivity.