JPS62176370A - Image reader - Google Patents

Abstract

PURPOSE:To read specially thin ruled lines without destroying a thick part such as a character by darkening by adding a differentiated video signal obtained by differentiating the video signal to the video signal, amplifying and outputting. CONSTITUTION:A photoelectric transducer (CCD) 1 scans an original and converts the variable densities into an electrical signal. A differentiation circuit 2 consists of a resistance RX and a capacitor CX and forms the differentiated video signal obtained by differentiating the video signal read from the original by the photoelectric transducer 1. An amplifier circuit 3 functions as an analog emphasis circuit for adding the video signal read by the photoelectric transducer 1 and the differentiated video signal formed by the differentiation circuit 2 and amplifying. An A/D converter 4 converts the analog emphasized and amplified video signal by the amplifier circuit 3 into a digital signal and outputs.

Description

[Detailed Description of the Invention] [Summary] In an image reader, an analog emphasis circuit is provided that emphasizes a short pulse width signal in a video signal generated by scanning a document using a photoelectric conversion element. This makes it possible to read lines that are thinner than the resolution.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an image reader, and in particular to an analog enhancement circuit that allows thin ruled lines on a document to be clearly read.

[Problems to be solved by conventional technology and invention] Conventionally,
When reading, for example, thin ruled lines written on a document using an image reader or the like, as the thickness of the ruled lines gradually becomes thinner and approaches the resolution, the ruled lines may become unreadable. For example, if vertical ruled lines (only some of which are shown) and characters as shown by diagonal lines in Figure 3 (a) are scanned and read in the horizontal direction, a video signal as shown in Figure 3 (b) can be obtained. However, the amplitude of the video signal corresponding to the one on the left side of the video signal, that is, the thin ruled line, becomes small, and cannot be read at slice level 1, which is used to read ordinary characters. For this reason, slice level 2, which is smaller than the normal slice level,
If you change the reading mode to slice level 1, which is optimal for reading characters such as those shown on the right side of Figure 3 (a), the slice level will be uniformly changed from slice level 1 to slice level 2. There was a problem in that the width of the constituent lines became thicker and darker, as shown from d1 to d2 in the figure, and even collapsed.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a differentiation circuit that generates a differential video signal by differentiating the video signal when amplifying the video signal generated by scanning a document,
The differential video signal generated using this differentiating circuit is added to the original video signal, and the result is amplified, and a video signal in which a signal with a short pulse width is emphasized is output.

Means for solving the problems will be explained using the configuration diagram of one embodiment of the present invention shown in FIG.

In FIG. 1, a photoelectric conversion element (such as a CCD) 1 is
It scans a document and converts the shading into an electrical signal.

The differentiating circuit 2 differentiates the video signal output from the photoelectric conversion element 1 to generate a differential video signal.

The amplifier circuit 3 functions as an analog emphasis circuit that adds and amplifies the video' signal read by the photoelectric conversion element 1 and the differential video signal generated by the differentiator circuit 2.

The A/D converter 4 converts the video signal that has been analog emphasized and amplified by the amplifier circuit 3 into a digital signal and outputs the digital signal.

[Effect]

In FIG. 1, the video signal output from the photoelectric conversion element 1 while reading a document is input to one terminal of the amplifier circuit 3, and the differential video signal generated using the differentiating circuit 2 is similarly inputted to the above-mentioned 1 terminal. input to two terminals. The analog-enhanced video signal resulting from addition and amplification by the amplifier circuit 3 is input to an A/D converter 4, converted to a digital signal, and output.

As explained above, by adopting a configuration that generates a signal in the form of adding the video signal read using the photoelectric conversion element l and the differential video signal obtained by differentiating the video signal, it is possible to It becomes possible to generate a video signal that can be reproduced well.

〔Example〕

Next, the configuration and operation of one embodiment of the present invention shown in FIG. 1 will be described in detail.

In FIG. 1, a differentiating circuit 2 includes a resistor R and a capacitor CX, and generates a differential video signal by differentiating a video signal read from an original by a photoelectric conversion element 1. The generated differential video signal is input to one input terminal constituting the amplifier circuit 3, and the video signal read by the photoelectric conversion element 1 is input to the same input terminal via the resistor R1. . On the other hand, the output of the amplifier circuit 3 is fed back to the input by a resistor R2. Thereby, the amplifier circuit 3 operates as an adder circuit, and a signal obtained by adding the video signal and the differential video signal is output from its output terminal, and is input to the A/D converter 4 and converted into a digital signal.

Next, the operation of the configuration shown in FIG. 1 will be explained in detail using FIG. 2.

FIG. 2(a) shows thin ruled lines (left side) and characters (right side) written on the manuscript, and FIG. 2(b) shows what is shown in FIG. 2(a) by the photoelectric conversion element 1. Figure 2 (
2(c) shows a differential video signal obtained by differentiating the video signal using the differentiating circuit 2, and FIG. 2(d) shows a signal amplified by the amplifier circuit 3 and output.

The video signal (Fig. 2 (b)) read from the original (Fig. 2 (a)) by the photoelectric conversion element 1 is input to one terminal (inverting terminal) of the amplifier circuit 3 via the resistor R1. At the same time, the differential video signal (FIG. 2 (c)) obtained by differentiating the video signal through the differentiating circuit 2 is similarly inputted to one terminal as shown in the figure. Since a resistor R2 is connected between one terminal and the output terminal of the amplifier circuit 3, the video signal and differential video signal input to the amplifier circuit 3 are transmitted through the resistors R, Rz, and Rz. Signals amplified by predetermined amplification factors determined by Rx and resistor R2 (FIG. 2(d)) are added and output. This output video signal shown in Figure 2 (D) acts to emphasize the edge parts such as thin ruled lines written on the document shown in Part 2 (B), so it is shown on the left side of the figure. The amplitude value of the video signal for thin ruled lines increases and exceeds the slice level 1 used to read ordinary characters, and even when sliced using the slice level 1, it can be read satisfactorily. For this reason, thick parts such as characters become darker and are not crushed by changing the slice level to a smaller value in order to read thin ruled lines as in the past. The signal output from the amplifier circuit 3 is input to the A/D converter 4, converted into a digital signal, and output.

〔Effect of the invention〕

As described above, according to the present invention, when amplifying a video signal generated by scanning a document, a differentiating circuit is provided to generate a differential video signal by differentiating the video signal, and this differentiating circuit is used to amplify the video signal generated by scanning a document. Since the system uses a configuration that amplifies and outputs the generated differential video signal by adding it to the video signal, it is possible to read thin parts, especially thin ruled lines that are close to the resolution, without obscuring thick parts such as characters. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a waveform diagram explaining the present invention in detail, and FIG. 3 is a waveform diagram explaining the operation of a conventional analog emphasizing circuit. In the figure, 1 represents a photoelectric conversion element, 2 a differential circuit, 3 an amplifier circuit, and 4 an A/D converter. Patent Applicant Usatsuk Electronics Industry Co., Ltd. Representative Patent Attorney Fumihiro Hase (and 2 others) Emphasis on the lower part of the grass. 3 diagram

Claims (1)

[Claims] In an image reader that scans a document using a photoelectric conversion element and inputs image information using the generated video signal, the image reader scans the document and generates a video signal corresponding to the shading of the document. and an amplifier circuit that amplifies a video signal photoelectrically converted using the optoelectric conversion element, and the amplifier circuit amplifies a differential video signal generated by differentiating the video signal with a differentiating circuit. An image reader configured as an analog enhancement circuit that adds to an original video signal.