JPS61157181A - Image pickup device - Google Patents

Abstract

PURPOSE:To remove bad influences to a screen when essential accumulating time is made variable by controlling the gain of the video signal and correcting the control condition of the accumulating time. CONSTITUTION:The titled device, as an action mode of an image pick-up element 1, has the same standard mode as the usual video camera in which the accumulating time is made into the vertical period of the television signal, and the mode at the time of short seconds to execute the vertical transfer of the photodetecting part only on the way of the vertical period, and by a switch 113, the above-mentioned action mode is changed over by changing over the output of a synchronizing signal generating circuit 112. When the mode at the time of short seconds is executed, compared with the output of a voltage divider 121 of the standard mode, the output of a voltage divider 120 of the mode at the time of short seconds is set to a high voltage approximately for the product of the period of the initial T3 of the vertical period and Vsat only. Thus, in the television signal obtained as an output of an image pickup element 1, the luminance level of an object on the screen is kept constant regardless of the action mode of the image pickup element 1.

Description

[Detailed description of the invention] (Technical field) The present invention relates to an imaging device using a solid-state imaging device.

(Prior Art) When a solid-state image sensor, such as a COD (charge-coupled device), is used in a television camera, by changing the driving method of the solid-state image sensor, the field (or frame) time of the television signal can be changed. It has been proposed in the past that the accumulation time can be shortened.

For example, in a solid-state image sensor called a frame transfer type, the charge in the light receiving part that performs photoelectric conversion and charge accumulation is removed by vertical transfer once in the middle of the vertical period, and then the remaining vertical period is effectively A driving method that operates as an accumulation time is proposed, for example, in Japanese Patent Application Laid-Open No. 55-61098.

According to the above method, for example, in an NTSC TV camera, the accumulation time is usually 1/60 seconds, but this can be changed to 1/120 seconds, 11500 seconds, etc., so when a large amount of light is incident, Also, the aperture is not small and the image of a high-speed moving object is not blurred. however,
When performing the above-mentioned operation, when eliminating the charge accumulated in the middle of the vertical period without extracting it as a signal, especially when the actual accumulation time is shortened, the amount of charge to be eliminated is For example, if the actual accumulation time t1 is 11500 seconds, the ratio of the accumulation time t2 of the charge to be removed and tl is t2/l 1= (1/6O-11500)/1150
If the charge accumulated at tl is at the standard level, then at t2, the charge 7.3 times the standard level is accumulated. When such a large amount of charge is accumulated, it is very difficult to eliminate it all so that it does not affect the actual accumulation time. In particular, the amount of charge generated in so-called highlighted areas on the screen is extremely large, and when vertical transfer is performed to discharge charge in the middle of the vertical period, a large amount of charge remains and is transferred to the output screen. The negative effects of this will appear.

In addition, this remaining charge is output from the image sensor as
This becomes 4 to 10 times the signal level (about the saturation signal level of the image pickup device), leading to an abnormal response of the signal processing circuit or malfunction of gain control or aperture control.

Furthermore, an imaging device has been proposed in which charges in both the light receiving section and the storage section are removed during the vertical period. In this case, no output signal is obtained during the period before the intermediate transfer, and aperture control, gain control, etc. become inaccurate.

(Objective) It is an object of the present invention to propose a solid-state imaging device that can eliminate the drawbacks of the conventional example described above and at the same time eliminate the adverse effects on the screen when the substantial storage time is varied.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a frame transfer type CCD solid-state imaging device to which the present invention can be applied. 1 is a frame transfer type CCD solid-state imaging device; 2 is a light receiving unit that photoelectrically converts incident light from an imaging optical system (not shown) and accumulates charge;
Reference numeral 3 denotes a storage unit that transfers the charge from the light receiving unit 2 and reads it out every horizontal period; 4 a horizontal register that horizontally transfers the charge transferred from the storage unit 3 every horizontal period by φT; and 5 a horizontal register. DG is a gate provided along the register 4; DG is a gate provided along the register 4; and t*/<rear; DR is an overflow drain.

FIG. 2(a) shows the drive waveform of the frame transfer CCD image sensor 1 in the short time mode, and φ is the light receiving part 2.
．． φS is the storage section 3, φT is the horizontal shift register section 4, φ
R indicates each drive waveform of the charge-voltage converter 5.

IV is the vertical period of the television signal, and T2 is the substantial storage period.

At the beginning of the vertical period, the charges in the light receiving section 2 are vertically transferred and transferred to the storage section 3 by the vertical transfer pulses indicated by ■ and ■, and thereafter, by the pulse indicated by ■, one line at a time in one horizontal period.
The signal is transferred to the horizontal register 4, and is transferred horizontally to the charge-voltage converter 5 by the pulse 2 during the horizontal period, where it is converted into a charge voltage by the pulse 2 and taken out as an output.

After photoelectric conversion and charge accumulation in the light receiving section 2 during the T1 period, only the light receiving section is vertically transferred by the pulse (2), and the charges accumulated during the T1 period are removed from the light receiving section. After that, T
The charges received and accumulated during the two periods are vertically transferred to the storage section 3 by the pulses (1) and (2). The following operations are similar to those described above. Incidentally, in the standard mode in which the accumulation period is about one field period as shown in FIG. 2(b), the pulses marked with (■) in FIG. 2 are omitted. In the short time mode, only the light receiving section 2 performs vertical transfer due to the pulse (■), and when removing the charge accumulated in the T1 period, the amount of charge accumulated in T1 is larger than that in T2, so it cannot be completely removed. It will remain.

FIG. 3 shows the output waveform of the image thus obtained.

Vsat is the saturated output voltage of the image sensor, Vav is the standard average output voltage of the image sensor, and TBLK is the vertical blanking interval.

As described above, the remaining charge that could not be eliminated in the vertical transfer before the actual accumulation period T2 is output, and an output at the Vsat level is generated during the initial period 73111 of the vertical period. When T3 is short, it does not appear on the screen, but since Vsat is extremely large, about 3 to 5 times as large as Vav, it has a large adverse effect on signal processing, aperture control, gain control, etc.

FIG. 4 shows a first embodiment of the present invention. 101 is an imaging optical system including an imaging lens, an optical filter, etc., 102 is an aperture, 103 is a sample hold circuit that converts the discrete output from the image sensor 1 into a continuous signal, and 104 processes the output of the sample hold circuit 103, 111 is a signal processing circuit that synthesizes signals; 110 is an aperture drive circuit that drives an aperture;
Reference numeral 112 denotes a drive circuit that drives the image sensor 1, and 112 an accumulation time control that generates drive pulses for the image sensor 1, drive pulses for the sample and hold circuit 103, signal processing synchronization pulses, television synchronization signals, etc. as shown in the second figure. A synchronizing signal generating circuit 113 as a means is a switch for switching the small power mode of the synchronizing signal generating circuit and changing the operating mode of the image pickup device 1.

The image sensor 1 has two operating modes: a standard mode similar to a normal video camera in which the storage time is the vertical period of the television signal, and a short time mode in which only the light receiving section performs vertical transfer in the middle of the vertical period. , the operation mode is switched by switching the output of the synchronizing signal generating circuit 112 using the switch 113.

The subject image passes through an imaging optical system 101 and an aperture 102, is photoelectrically converted by an image sensor l, is output in accordance with a synchronization signal, is made continuous by a sample hold circuit 103, is signal processed by a signal processing circuit 104, and is synchronized at the same time. The television signal is combined with the synchronization signal from the signal generation circuit 112 and output to the television signal output terminal 114.

115 is an amplification circuit, IIS is a smoothing circuit that smoothes the output of the amplification circuit 115, 117 is an error amplification circuit that compares the smoothed output with a reference level and forms an error signal, and 118 is the output of this error amplification circuit. This is a transistor whose impedance changes depending on the amplifier 115.
The video input level is changed and the gain is adjusted as a result.

120 and 121 are voltage dividers that output a reference level, one of which is input to the error amplification circuit 117 as the reference level. Further, the output level of 120 is higher than the output level of 121.

Reference numeral 119 is a switch serving as a correction means for performing the switching, and a switch 113 for switching the operation mode of the image sensor.
Switches in conjunction with switching.

That is, when the switch 113 is on the short-second mode side, the output of the voltage divider 120 is input to the error amplification circuit 117, and when the switch 113 is on the standard mode side, the output of the voltage divider 121 is input to the error amplification circuit 117. Switch 119 to
Switch.

When performing the short-second time mode with the operation shown in FIG.
The voltage is set to be higher by the product of at. As a result, it was confirmed that the brightness level of the object on the screen in the television signal obtained as the output of the image sensor can be kept constant regardless of the operating mode of the image sensor 1.

Other examples of the configuration in which the video signal level of the imaging device is controlled by adjusting the gain AL include a configuration in which the video signal level of the imaging device is controlled by adjusting the sensitivity of the imaging device itself.

Further, as a method for adjusting the sensitivity of such an image pickup device, for example, a method of changing a target voltage in an image pickup device such as an image pickup tube is known.

These gain adjustment methods have the advantage of extremely good responsiveness compared to methods in which the video signal level is changed using an aperture, a shutter, or the like.

Although the reference level is configured to be changed by the switch 119, the actual storage time is changed continuously or stepwise, and the reference voltage is also changed continuously or stepwise in accordance with the change. You may
The present invention includes such devices, and is also effective in devices in which the video signal level of the imaging means is controlled by an aperture or by a shutter.

Further, the shutter includes not only a mechanical or physical shutter but also an electronic shutter, that is, one that controls the storage time.

Of course, it is also effective for controlling the amount of photocharge formed by using a combination of two or three of aperture, shutter, and accumulation time control depending on the video signal level, thereby controlling the video signal level in %IJ. It is.

In the above embodiment, in the short time mode of the image sensor, only the light receiving section performs vertical transfer in the middle of the vertical period, but the charges in both the light receiving section and the storage section are eliminated in the middle of the vertical period. The present invention can also be implemented in this manner.

In this case, the reference voltage in the short time mode is set to a voltage lower than that in the standard mode.

FIG. 5 is a diagram showing a second embodiment of the present invention, and shows a modification of the short time mode. In this embodiment, in synchronization with the high-speed vertical transfer of High-speed vertical transfer is performed, therefore, charges in the light receiving section and storage section are collected in the horizontal shift register 4 and overflow occurs. This overflowed charge flows into the drain DR via the gate or barrier DG and is discharged.

Therefore, the output of the charge-voltage converter 5 is missing at the [stock] part. In this case, as described above, the reference voltage in the short time mode is corrected by a switch or the like using a correction means so that it has a lower value than in the standard mode.

In addition, other types of image sensors, such as interline type C
Various types of CDs, MO3 image pickup devices, image pickup tubes, etc. that are capable of storage time control have been considered, and the present invention can be applied when the output characteristics of the image pickup device are different in the short exposure mode and in the standard mode.

(Effects) According to the present invention, even if the actual storage time of the image sensor is set short, the influence of unnecessary charges on the screen can be removed.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of frame transfer type COD, Figure 2 (a) is an explanatory diagram of short-time mode, Figure 2 (b) is an explanatory diagram of standard mode, and Figure 3 is an illustration of unnecessary signals in short-time mode. Explanatory drawing, FIG. 4 is a diagram showing a configuration example of the imaging device of the present invention, FIG. 5 is a timing chart of the second embodiment of the present invention, 102---One aperture, 1--------- 1 image sensor, 120.121---1 voltage divider, 113.119---switch, 112---1 synchronous signal generator. 116---Smoothing circuit, 117---Error amplification circuit, 115---One-amplification circuit,

Claims (1)

[Scope of Claims] An imaging device that converts an optical image into an electrical signal; An accumulation time control unit that variably controls the accumulation time of photoelectric charges in the imaging device; and Controlling the gain of the video signal according to the output of the imaging device. An imaging apparatus comprising: a control means for controlling the accumulation time; and a correction means for correcting a control state by the control means according to an output of the accumulation time control means.