JPH02266675A - Automatic sensitivity control method for solid-state imaging device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic sensitivity control circuit for a solid-state imaging device.

2. Description of the Related Art In recent years, imaging devices using solid-state imaging devices, that is, solid-state imaging devices, have come to be used as solid-state cameras in home video cameras, etc., taking advantage of their small size, light weight, and long lifespan. As cameras become more popular, there is an increasing demand for multifunctional video cameras. One of them is automatic sensitivity control of solid-state imaging devices. Sensitivity control of video cameras has normally been performed by mechanically opening and closing the lens diaphragm, but recently automatic sensitivity control, which electrically controls the charge accumulation time of the solid-state image sensor, has come into use. Ta.

An automatic sensitivity control circuit for a conventional solid-state imaging device as described above will be described below with reference to the drawings.

FIG. 2 shows the configuration of an automatic sensitivity control circuit of a solid-state imaging device. In FIG. 2, 4 is a solid-state image sensor;
is a signal processing circuit, 6 is an integration circuit, 7 is an amplitude comparison circuit, 8
is a drive pulse signal generation circuit.

FIG. 3 is a waveform diagram of signals for automatic sensitivity control of the solid-state imaging device. In FIG. 3, 9 is a vertical blanking pulse, 10 is a signal charge readout pulse, and 11 is a solid-state image sensor output signal.

The optical signal received by the solid-state image sensor 4 is converted into an electrical signal (hereinafter referred to as a solid-state image sensor output signal) by photoelectric conversion, and is input to the signal processing circuit 5, where it is converted into a video signal. is also input, and the time in field 1 shown in FIG. 3 is converted into a DC voltage level corresponding to the amount of output signal from the solid-state image sensor during the period t12. Next, the optical signal converted to a DC voltage level is compared with a threshold value that determines appropriate sensitivity by an amplitude comparison circuit 7,
The output is taken into the drive pulse generation circuit 8 at time t12. The drive pulse generation circuit generates a signal charge readout pulse at time t13 of field 2 according to the output of the amplitude comparison circuit, thereby changing the charge accumulation time of the solid-state image sensor and controlling the amount of output signal from the solid-state image sensor. do. In other words, when a solid-state image sensor output signal higher than the threshold value is detected, the charge accumulation time is shortened (and when a solid-state image sensor output signal lower than the threshold value is detected, the charge accumulation time is increased to increase the sensitivity). This operation is repeated for each field to perform sensitivity control.

As described above, the solid-state image sensor output signal is fed back to the drive pulse generation circuit, and every field (1/60 second)
By controlling the charge accumulation time of the solid-state image sensor, automatic sensitivity control that maintains a constant appropriate sensitivity can be performed electrically.

Problems to be Solved by the Invention However, with the above configuration, the error in the video output signal level with respect to the appropriate sensitivity level becomes large due to the frequency characteristics of the integrating circuit that converts the solid-state image sensor output signal into a DC voltage level signal. It had the disadvantage of being stored away.

In view of the above drawbacks, the present invention provides an automatic sensitivity control circuit that can suppress flickering and control errors.

Means for Solving Problems The present invention includes a refining circuit that receives a photoelectric conversion signal from a solid-state image sensor as an input, an output of the integrating circuit as a first input, and a threshold voltage that determines appropriate sensitivity as a second input. an amplitude comparison circuit that receives the output of the amplitude comparison circuit as an input, and a drive pulse generation circuit that receives the output of the amplitude comparison circuit as an input and generates a drive pulse for the solid-state image sensor, , is input to the drive pulse generation circuit, and is configured to change the charge accumulation time of the solid-state image sensor and control the sensitivity.

Effect: With this configuration, the frequency characteristics of the integrating circuit (,
It is possible to suppress flickering and control errors, and to suppress images that periodically repeat brightness and darkness.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

The configuration of the automatic sensitivity control circuit of the solid-state imaging device in the embodiment of the present invention is the same as the configuration of the automatic sensitivity control circuit of the conventional solid-state imaging device (as shown in FIG. 2, the solid-state imaging device 4, signal processing It is composed of a circuit 5, a refinement circuit 6, an amplitude comparison circuit 7, and a drive pulse generation circuit 8.

FIG. 1 is a waveform diagram of signals for automatic sensitivity control of a solid-state imaging device in an embodiment of the present invention. In FIG. 1, 1 is a vertical blanking pulse, 2 is a signal charge readout pulse, and 3 is a vertical blanking pulse.
is the solid-state image sensor output signal.

The operation of the automatic sensitivity control circuit of the solid-state imaging device configured as described above will be explained.

During the period from time t11 to time t12, which is the vertical scanning period of field 1, the amplitude comparison circuit 7 compares the output of the integrating circuit 6 which receives the output signal of the solid-state image sensor 4 with a threshold value for setting appropriate sensitivity. . And time t1
2, the amplitude comparison circuit output is detected. Based on the detected result, the drive pulse generation circuit 8 generates a series of unnecessary charge pulses at time t'3 for setting the charge accumulation time of the solid-state image sensor, and generates a pulse for the next field (field 2).
Set the charge accumulation time. Here, once the charge accumulation time is set by the sensitivity control, the sensitivity control is not performed between multiple fields and the position of the unnecessary charge readout pulse does not change, so the charge accumulation time is fixed. and,
After a plurality of fields (in the figure, the n-th field), sensitivity control is performed again in the same manner as above. Time t. 2, the amplitude comparison circuit output is detected and the drive pulse generation circuit 8
, the unnecessary charge read pulse is output at time t. 3, and set the charge accumulation time of the next field (field n+1). As described above, the unnecessary charge readout pulse is determined again for each plurality of fields, the charge accumulation time is set, and the sensitivity is controlled.

As described above, according to this embodiment, in the automatic sensitivity control circuit of the solid-state imaging device, sensitivity control is performed by changing the charge accumulation time of the solid-state imaging element for each plurality of fields, so that the frequency characteristics are adjusted in the integrating circuit. It is possible to obtain a stable DC voltage that does not depend on the voltage, suppressing flickering of the video output signal and sensitivity control errors.

Effects of the Invention As described above, according to the present invention, sensitivity control is performed by changing the charge accumulation time of the solid-state image sensor for each plurality of fields in the automatic sensitivity control circuit of the solid-state image sensor.
Flickering of the video output signal and sensitivity control errors can be suppressed, and the practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram of signals for automatic sensitivity control of a solid-state imaging device in an embodiment of the present invention, FIG. 2 is a configuration diagram of an automatic sensitivity control circuit of a conventional solid-state imaging device, and FIG. 3 is a diagram of a conventional solid-state imaging device. 3 is a waveform diagram of signals for automatic sensitivity control of the device. FIG. 1.9...Vertical blanking pulse, 2,10
...Signal charge read pulse, 3, 11...
・Solid-state image sensor output signal, 4...Solid-state image sensor, 5.Old...signal processing circuit, 6...Integrator circuit,
7... Amplitude comparison circuit, 8... Drive pulse signal generation circuit. Name of agent: Patent attorney Shigetaka Awano Haga 1 person II 2
figure

Claims (1)

[Claims] an integrating circuit that receives a photoelectric conversion signal from an image sensor as an input; an amplitude comparing circuit that uses the output of the integrating circuit as a first input and a threshold voltage that determines appropriate sensitivity as a second input; A drive pulse generation circuit is provided that generates a drive pulse for the image pickup device using an output as an input, and the output of the amplitude comparison circuit is inputted to the drive pulse generation circuit for each plurality of fields, and the charge accumulation time of the image pickup device is An automatic sensitivity control circuit for a solid-state imaging device, characterized in that the circuit changes the sensitivity of a solid-state imaging device.