JPH02252371A - Auto-flickerless circuit for ccd camera - Google Patents

Abstract

PURPOSE:To reduce cost, and to prevent a malfunction by detecting flicker frequency with the video signal of an object to be image-picked up image-formed on a CCD solid-state image pickup element, and changing driving timing based on this flicker frequency. CONSTITUTION:The light of the object to be image-picked up image-formed on the CCD solid-state image pickup element 1 is converted into an electric signal, and this electric signal is made into the video signal by a signal processing circuit 2, and simultaneously, inputted to a flicker detection circuit 5, as well and the peak position of a low frequency band signal is detected, and it is decided whether periodicity exists or not, and the detection of the flicker frequency is executed. Then, a timing signal synchronized with timing frequency is outputted from a shutter switching circuit 6, and the output signal of a driving circuit 4 is outputted from a shutter circuit 7. Since an external sensor is not required, and besides, the timing of drive is synchronized with flicker, a favorable picture can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is directed to CGTV (C1osed C1rcuit).
CCD (charge coupled) used in Television) systems and video cameras, etc.
The present invention relates to an auto-flickerless circuit for a CCD camera, and more specifically to an auto-flickerless circuit for a CCD camera that automatically detects flicker under illumination such as a fluorescent lamp and improves the image of an object to be imaged.

[Conventional Examples] In recent years, CCD solid-state imaging devices have been used because of their CCTVCCD camera type, light weight, and high reliability.This CGTV camera (CCD camera) is not only used for security systems in financial institutions and convenience stores, but also for security systems in financial institutions and convenience stores.
It is also used in the FA field, such as visual sensors for robots.

The CCD camera is equipped with a drive circuit that corresponds to the shutter of a normal camera, and the CCD solid-state imaging device converts the light from the imaged object into an electrical signal in response to the drive signal of the drive circuit. Become. Further, in the CCD camera, an external sensor detects flicker caused by illumination of the object to be imaged, such as a fluorescent lamp, and obtains a shutter timing according to the detected flicker frequency, and synchronizes the drive signal of the CCD solid-state imaging element. An auto-prissureless circuit is provided to remove the

[Problems to be Solved by the Invention] However, in the auto flickerless circuit of the CCD camera, an external sensor is used to detect flicker caused by illumination such as a fluorescent lamp.

The cost was correspondingly high. In addition, the incident light of the external sensor and the incident light of the CCD solid-state imaging element may be different, and in such a case, the detected flicker frequency will be different, which may cause the CCD camera to malfunction and drive the CCD solid-state imaging element. (signals could no longer be synchronized), resulting in poor images of the subject.

This invention has been made in view of the above problems, and its purpose is to provide a flickerless circuit for a CCD camera that can reduce costs and prevent malfunctions of the CCD camera. .

[Means for Solving the Problems] In order to achieve the above object, the flickerless circuit of the CCD camera of the present invention detects flicker under illumination of an imaged object from a signal from a CCD solid-state imaging element, and flicker control means for determining whether or not the detected flicker has periodicity and outputting a control signal for controlling the shutter timing of the CCD solid-state image pickup device according to the determination result; A shutter switching means for switching the shutter timing of the image sensor, and a shutter timing signal from the shutter switching means to switch the shutter timing of the image sensor.
D. The main feature is that the present invention includes a shutter means for controlling the drive circuit of the solid-state image sensor.

[Function] With the above configuration, if the illumination of the object to be imaged is a fluorescent lamp, the image signal from the object to be imaged will be 507 or 6
A flicker frequency of 07 is detected, and a shutter timing signal corresponding to this flicker frequency is obtained. In other words, an external sensor can be omitted when detecting flicker.
In addition, since the CCD solid-state image sensor is driven by a shutter timing signal synchronized with the flicker frequency, the CC
The D-camera does not malfunction and an image of the object to be imaged can be obtained satisfactorily.

In this way, since the flicker frequency under illumination of the object to be imaged is detected from the signal from the CCD solid-state image sensor, there is no need to install a sensor outside the CCD camera, and the flicker frequency detected by Therefore, the cost of the CCD camera can be reduced and malfunctions can be prevented.

[Example] Embodiments of the present invention will be described below based on the drawings.

In FIGS. 1 and 2, a CCD solid-state image sensor 1
The electrical signal obtained is subjected to signal processing in a signal processing circuit 2, as in the conventional case, and amplified in an amplifier 3 to be output from a CCD camera. At this time, the operation of the CCD solid-state imaging element 1 is controlled by a drive signal from the drive circuit 4.

The flickerless circuit that detects the flicker frequency to obtain the shutter timing during operation includes a flicker detection section 5 that detects the flicker frequency from the video signal obtained by the signal processing circuit 2, and the CCD solid-state image sensor 1. a shutter switching circuit 6 for switching the drive signal to a signal at a predetermined timing synchronized with the detected flicker frequency;
At this predetermined timing, the output signal (
The shutter circuit 7 controls the drive signal (drive signal).

The flicker detection section 5 includes a BPF (bandwidth filter; LPF) section 5a that passes the low frequency band of the video signal obtained by the signal processing circuit 2, and a peak position detection section that detects the peak position of the low frequency band signal. 5b, an A/D converter 5c that converts this peak position signal into digital data, and a flicker frequency control unit that determines whether or not the peak position signal has periodicity based on these digital values and detects the flicker frequency. (CPU) 5d.

Next, the operation of the flickerless circuit having the above configuration will be explained.

First, the light of the imaged object focused on the CCD solid-state image sensor 1 is converted into an electrical signal, and this electrical signal is sent to the signal processing circuit 2.
Assume that the video signal is converted into a video signal.

At this time, the video signal is also input to the flicker detection circuit 5, the low frequency band (for example, around 507) of the video signal is passed through the bandpass filter section 5a, and the low frequency band (for example, around 507) is passed through the peak position detection section 5b. The peak position of the frequency band signal is detected. The peak position of the low frequency band signal is converted into a digital value and input to the control section 5d.

Then, the control unit 5d determines whether or not these detected peak positions have periodicity, and detects the flicker frequency due to the illumination of the object to be imaged. At this time, if the illumination of the object to be imaged is a fluorescent lamp or the like, the peak position is detected at a cycle of 507 (1150 (seconds)) or 607 (1/60 (second)), so the maximum common Number 0, 1H
z (1/10 (second)) is detected as the flicker frequency. The shutter switching circuit 6 outputs a timing signal that synchronizes the shutter timing of the CCD solid-state image sensor 1 with its flicker frequency of 1/10 (second). In response to this timing signal, the shutter circuit 7 outputs a control signal that controls the output signal of the drive circuit 4. That is, since the driving timing of the CCD solid-state image sensor 1 is set to be the greatest common divisor of the detected flicker frequencies, malfunctions of the CCD camera can be prevented.

In this way, since the flicker frequency is detected from the video signal from the imaged object imaged by the CCDCD solid-state image sensor, an external sensor unlike the conventional one is not required, and cost reduction can be expected. In addition, the detected flicker frequency does not differ from that due to the illumination of the object to be imaged (and because the drive timing of the CCD solid-state imaging probe is synchronized with the flicker, a good image of the object to be imaged can be obtained.

[Effects of the Invention] As explained above, according to the automatic flickerless circuit of the CCD camera of the present invention, the flicker frequency is detected from the video signal of the imaged object formed on the CCD solid-state image sensor, and this flicker is detected. Since the drive timing of the CCD solid-state image sensor is changed based on the frequency, the cost can be reduced, and malfunctions of the CCD camera can be prevented, resulting in good images of the object to be imaged. There is.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of an auto flickerless circuit for a CCD camera showing an embodiment of the present invention. FIG. 2 is a partial block diagram of the auto-flickerless circuit of the CCD camera. In the figure, 1 is a CCD solid-state image sensor, 2 is a signal processing circuit, and 3
is an amplifier, 4 is a drive circuit, 5 is a flicker detection section, 5
a is a bandpass filter (BPF; LPF) section, 5b is a peak position detection section, 5c is an A/D conversion section, and 5c is a control section (CPF).
U), 6 is a shutter switching circuit, and 7 is a shutter circuit.

Claims (3)

[Claims] (1) From the video signal captured by the CCD solid-state image sensor,
Flicker control means for detecting flicker caused by illumination or the like, determining whether or not the detected flicker has periodicity, and outputting a control signal for controlling the shutter timing of the CCD solid-state image sensor according to the determination result. A CCD camera comprising: a shutter switching means for switching the shutter timing of the CCD solid-state image sensor according to the control signal; and a shutter means for controlling a drive circuit of the CCD solid-state image sensor according to the shutter timing signal. Auto flickerless circuit. (2) The flicker control means includes a filter for obtaining the change in illumination from the video signal, a peak position detection means for obtaining a peak position due to the change in illumination, and an A/D converter for converting this signal into digital. and control for detecting the flicker frequency based on whether or not the digital peak position signal has periodicity, and outputting a control signal for switching the shutter timing of the CCO solid-state element in accordance with the detected flicker frequency. An auto flickerless circuit for a CCD camera comprising means. (3) The auto flickerless circuit for a CCO camera according to claim 2, wherein the shutter timing is the greatest common divisor of the detected flicker frequency.