JPS6238673A - Picture signal processing circuit - Google Patents

Abstract

PURPOSE:To set an always accurate dynamic range by deciding automatically a dynamic range of an analog/digital converter used for manual adjustment in a conventional circuit with the detection and control of a white/black level voltage from a picture signal. CONSTITUTION:A picture signal subject to photoelectric transducing by a photoelectric element 20 is amplified by an amplifier circuit section 30. The amplified picture signal is inputted to a detection section 60 and a digital analog converter 40. The picture signal inputted to the detection section 60 is detected for white/ black level voltage of the picture signal. The detected white/black level voltage signals are inputted respectively to each reference voltage control circuit 70, where the upper/lower limit of the dynamic range are decided automatically depending on the white/black level voltage and the result is fed to a converter 40. On the other hand, the picture signal inputted to the converter 40 is digitized according to the dynamic range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image signal processing circuit for a facsimile machine or the like. In particular, the present invention relates to an image signal processing circuit that can automatically control the dynamic range of digital-to-analog conversion during the process of digital-to-analog conversion of an analog signal that has been photo-electrically converted by a photoelectric element such as a COD.

〔overview〕

The present invention relates to a facsimile image processing method that is conventionally
The image quality was improved by installing an image processing circuit that could automatically correct the dynamic range of black-and-white signals, which was previously corrected manually.

[Conventional technology]

Conventionally, this type of image signal processing circuit has the configuration shown in FIG. 2, which includes an optical system 10, a photoelectric element 20, an amplifier section 30, a digital-analog converter 40, and a reference voltage source 50 that provides a dynamic range of the digital-analog converter. It was composed of:

In the conventional image signal processing circuit described above, when variations occur in the analog system consisting of the optical system 10, the photoelectric element 20, and the amplifier circuit section 30, this correction is manually performed.

[Problem that the invention seeks to solve]

Therefore, the dynamic range had to be manually adjusted to be optimal according to the variations in the analog system.
It had the disadvantage that it could not follow the images quickly and was not accurate.

SUMMARY OF THE INVENTION The present invention has been made to solve these conventional problems, and it is an object of the present invention to provide an image signal processing circuit that automatically corrects the variations in the analog system.

[Means for solving problems]

The present invention includes an optical system that optically detects screen information, a photoelectric conversion element that converts the detection output of this optical system into an electrical signal, and an amplifier circuit that amplifies the output signal of this photoelectric conversion element. In an image signal processing circuit equipped with a digital-to-analog converter for converting the output of the amplifier circuit into a digital signal and means for controlling the dynamic range of the digital-to-analog converter, the black and white level of the output signal from the amplifier circuit is controlled. The means for controlling the dynamic range, which includes a detecting section for detecting, is characterized in that it is configured to automatically control the dynamic range according to the output of the detecting section.

[Effect]

The white and black level detection signals detected by the detection unit are automatically given the upper and lower limits of the dynamic range for white and black respectively by the reference voltage control unit, and are digitized by the digital-to-analog converter accordingly. The disadvantages of the conventional manual method are eliminated.

〔Example〕

Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 10 is an optical system, 20 is a photoelectric element, 30 is an amplifier circuit section, 40 is a digital-to-analog converter, and 60 is a detection section for detecting the white level and black level of the output signal of the amplifier circuit section 30. , 70 is a reference voltage control unit that determines the upper and lower limits of the dynamic range of the digital-to-analog converter 40 according to the white level and black level voltages detected by the detection unit 60, and includes an optical system 10, a photoelectric element 20, and an amplifier. The circuit section 30 and the digital-to-analog converter 40 are connected vertically, and the detection section 60 and the reference voltage control section 70 are connected vertically between the amplifier circuit section 30 and the digital-to-analog converter 40.

The image signal focused on the photoelectric element 20 by the optical system 10 is converted into electricity by the photoelectric element 20.

The image signal converted into the electric 4g signal is amplified by the amplifier circuit section 30. The amplified image signal is input to the detection section 60 and the digital-to-analog converter 40.

The detection section 60 detects the white level and black level voltage of the image signal input to the detection section 60 .

The white and black level detection signals detected by the detection unit are each input to the reference voltage control unit 70, and the upper and lower limits of the dynamic range are automatically determined according to the white and black level voltages, and the digital-to-analog converter 40 is applied to On the other hand, the image signal input to the digital-to-analog converter 40 is digitized according to the above dynamic range.

〔Effect of the invention〕

As explained above, the present invention automatically determines the dynamic range of an analog-to-digital converter by detecting and controlling the white and black level voltages from the image signal, instead of the conventional method of determining the dynamic range by manual adjustment. An accurate dynamic range is always set.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a conventional device. DESCRIPTION OF SYMBOLS 10... Optical system, 20... Photoelectric element, 30... Amplification circuit part, 40... Digital-to-analog converter, 50
. . . Reference voltage source, 60 . . . Detection section, 70 . . . Reference voltage control section.

Claims (1)

[Claims] (1) An optical system that optically detects screen information, a photoelectric conversion element that converts the detection output of this optical system into an electrical signal, an amplifier circuit that amplifies the output signal of this photoelectric conversion element, and In an image signal processing circuit equipped with a digital-analog converter for converting the output of the amplifier circuit section into a digital signal and means for controlling the dynamic range of the digital-analog converter, detecting the black and white level of the output signal of the amplifier circuit section. An image signal processing circuit comprising: a detecting section, wherein the means for controlling the dynamic range is configured to automatically control the dynamic range according to the output of the detecting section.