JPS5877375A - Profile compesating system - Google Patents

Abstract

PURPOSE:To make the profile clearer, by compensating the profile of the front and tail edges of a changing point in one sample unit to the changing point of a picture signal. CONSTITUTION:A picture signal from a photoelectric converter 1 is held at a sample hold circuit 2 and its output A is inputted to a differential amplifier 9 and a sample hold circuit 3. The output A is delayed by one sample at sample hold circuits 3, 4, its output B is inputted to the differential amplifier 9, and delayed by one sample at sample hold circuits 5, 6, and its output C is inputted to the differential amplifier 9. The outputs A, B, C are inputted to the differential amplifier 9 to operate an output 10: B-alpha[(A-B)-(B-C)], where; alpha is coefficient of compensation, allowing to obtain the picture signal output 10 after profile compensation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an outline correction method for correcting and enhancing an output image signal from a photoelectric converter in which the outline becomes unclear due to the characteristics of the elements of the photoelectric converter. A conventional contour correction method is shown in FIG. In Figure 1, 11 is the input, 1
2 is an output, and 13 is a buffer amplifier, which is composed of a simple differentiation circuit. The change point of the image signal is differentiated by C and R, and the image signal is emphasized depending on the size of the time constant. Therefore, this method cannot predict the change point and only emphasizes the trailing edge of the change point. Furthermore, since the DC component is cut by a capacitor, there is a drawback that the image signal is not transmitted faithfully. The purpose of the present invention is to use a sample-and-hold circuit to predict where the image signal from a photoelectric converter will change with respect to a change point, and to correct it for one cycle before and after the change point. This is contour correction in units of one sample.

A feature of the present invention is that in a method for correcting the outline of an image signal read by a photoelectric converter, a signal A obtained by quantizing the output of the photoelectric converter by a predetermined pulse train is provided, and the signal A is converted into one pulse of the pulse train. A signal B delayed by an interval is given, a signal C is given which is delayed by one pulse interval of the pulse train, and a differential amplifier generates a signal B-α ((A-B) = (B- C)) The purpose of α is to perform contour correction by giving a constant.

Signal B is obtained by sampling and holding signal A using a pulse train that is shifted by a phase of π from the pulse train, and then sample-holding the signal using the original pulse train. Signal C is also obtained from signal B by a similar procedure.

Examples will be described below with reference to the drawings.

FIG. 2 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a time chart for explaining its operation.
Ru. In FIG. 2, reference numeral 0 indicates reflected light from a document, and the reflected light is converted into electrical energy by a photoelectric conversion element of a photoelectric converter 1. In FIG. The image signal output from the photoelectric converter 1 becomes a held signal by the sample-and-hold circuit 2 driven by the 8 first pulses. Let this output be A.

Next, the image signal A is driven by the second pulse of 7 to the sample-and-hold circuit of 3, and the 10th pulse of 8 to drive the sample-and-hold circuit of 4 to delay the output A by one sample and change the output to B. shall be. Similarly to the above, output B is delayed by one sample using a 5.6 sample-and-hold circuit, and output C is obtained. Output 10=B-α((A-B)-(B-C)) (α: correction coefficient) is calculated using 9 differential amplifiers for each output A, B, C, and the image signal output 10 is contour-corrected. get. .

FIG. 3 shows a time chart. From the top, 8 first pulses, output A, output B, output C, and 10 contour-corrected picture numbers are output, and each output A, B, and C is one sample at the timing of the 8 first pulses. The image signal calculated by the 9 differential amplifiers becomes the output 10 after being delayed by 100 ms. α is a correction coefficient that determines the rate of contour correction.

As explained above, in the first embodiment, it is predicted where the image signal from the photoelectric converter will change at the change point, and contour correction is performed at the leading and trailing edges of the change point in units of samples. . For this reason, it has the effect of sharpening the outline of lowercase letters and photographs that contain a large number of high frequency components, and also has the advantage of being able to faithfully transmit image signals because the circuit configuration is DC-coupled.

Note that the sample-and-hold circuit explained in FIG. 2 may be an analog type circuit that uses a commonly used capacitor as a hold element, or it may be an analog type circuit that uses a commonly used capacitor as a hold element, or it may be an analog type circuit that uses a sensor output level signal that is converted into a digital signal by A/D conversion of the sensor output. It is clear that similar effects can be obtained by using a circuit in which ' is held by a flip-flop circuit or the like, and the calculation by the differential amplifier 9 is performed by a digital arithmetic unit.

The present invention has the advantage that the leading edge and the trailing edge of the changing point of the image signal are corrected on a sample-by-sample basis, and that the image signal can be faithfully transmitted because the circuit configuration is DC-coupled.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional contour correction, FIG. 2 is a circuit diagram of an embodiment of the present invention, and FIG. 3 is a time chart for explaining its operation. 11; input, 12; output, 13; buffer amplifier, C; ° capacitor, R; resistor,
0; Reflected light, 1; Photoelectric converter, 2.3, 4.5, 6; Sample and hold circuit,
7; second pulse; 8; first pulse; 9; differential amplifier; 10; contour-corrected image signal output; A; output A, B; output B, C; output C0; patent applicant Oki Electric Kogyo Co., Ltd. Patent Application Agent Patent Attorney Megumi Yamamoto −

Claims (1)

[Claims] In a method for correcting the contour of an image signal read by a photoelectric converter, a signal A obtained by quantizing the output of the photoelectric converter using a predetermined pulse train is provided, and the signal A is converted to the pulse train. A signal B delayed by one pulse interval of the pulse train is given, a signal C is given which is delayed by one pulse interval of the pulse train, and a differential amplifier generates a signal B-α((A-B)-(B- C) A contour correction method characterized by performing contour correction by giving α a constant.