JPS61214864A - Binarizing system - Google Patents

Abstract

PURPOSE:To binarize faithfully whatever characters or patterns are written on an original by comparing a signal which is differentiated digitally by the MTF processing with a read picture signal to binarize the signal. CONSTITUTION:The output of an image sensor 3 is digitized by an A/D converter 10, and an output signal (a) of the sensor 3 expressed with 16 gradations is branched into two, and one is sent to an MTF processing operation part 11, and the other is sent to an amplitude limiting ROM 12. The operation part 11 has a function to differentiate digitally the input signal and outputs a signal having a waveform (b). The ROM 12 uses the input of the signal (a) as the address to output a reference signal (c). Signals (b) and (c) are inputted to a comparator 13, and the comparator 13 compares signals inputted to terminals A and B with each other, and the high level is outputted for A<=B, and the low level is outputted for A>B. Thus, a binary signal outputted from the comparator 13 has a waveform B to binarize faithfully characters written on the original.

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to a binarization method, and in particular, to a binarization method that makes it possible to obtain accurate binarized signals. be.

(Prior Art) A conventional binarization method will be explained using FIGS. 3 and 4. Here, it is assumed that the numerals in FIG. 3 and FIG. 4 correspond.

Now, the characters of manuscript 1 are rloIJ as shown in the figure.
, and is read by an image sensor 3 such as a COD, for example, along a reading line 2 indicated by a dashed line. A solid line a in FIG. 4(a) shows a read image signal waveform when the original 1 is read along the reading line 2 by the image sensor 3.

After the read image signal a is output from the image sensor 3, it is branched, and one is input to an integrating circuit 4 and integrated.

The waveform of the output signal of the integrating circuit 4 is as shown by the dotted line in FIG.

On the other hand, the other branched signal is directly input to the inverting input terminal of the comparator 5. The comparator 5 compares the magnitudes of the input signals a and b, and outputs a binary signal C having a waveform as shown in FIG. 4(b).

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

A small length of white part sandwiched between the black parts of the characters on the document when viewed in the reading direction, and a small length of white and black part that comes after the dark part of the document, that is, part A in FIG. When the conventional apparatus is used to binarize the white part, there is a problem in that it cannot be detected and is dropped from the binarized signal C, as is clear from the waveform in FIG. As a result, there is a problem in that the reproduced recorded image is distorted or chipped.

The present invention has been made to solve the above-mentioned problems.

(Means and operations for solving the problems) In order to solve the above problems, the present invention provides means for converting the read image signal into a digital image signal in a method of binarizing the read image signal. means for branching a digital image signal; means for subjecting one of the branched signals to MTF processing;
It is characterized in that it is equipped with a comparison means that inputs the F-processed signal and the other branched signal and outputs a signal obtained by comparing both signals, thereby preventing distortion or chipping of the recorded image. There is.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

Further, FIG. 2 shows waveforms of signals at each part in FIG. 1.

In this embodiment, the image sensor 3 is the same as the original 1 shown in FIG.
The explanation will be based on the assumption that the same part of the image is being read. Also,
It is assumed that each line in FIG. 1 is a line capable of transmitting a 4-bit signal.

The output of the image sensor 3 has the waveform of the signal a shown by the solid line in FIG. 2(A). This waveform is shown in Figure 4 (
The waveform of the read signal a in a) is the same as that of the read signal a.

The output signal a of the image sensor 3, which is digitized by the A/D converter 10 and expressed in 16 gradations and 4 bits, is branched, and one is divided into MTF (Modu-ratio
n Transfer Function) is sent to the processing calculation unit 11, and the other is sent to the amplitude limiting ROM 12.

The MTF processing calculation unit 11 has a function of digitally differentiating an input signal. That is, if a signal a having the waveform shown in FIG. 2A is input, when the signal a rises, it is increased in the positive direction, and when it falls, it is increased in the negative direction. When the slope of the input signal is zero, the value increased at the time of rising or falling is maintained as it is. Therefore, the signal a of the waveform shown in FIG.
When the signal is input to the TF processing calculation unit 11, the MTF processing calculation unit 11 outputs a signal having a waveform as shown in signal b (indicated by a dotted line) in FIG. 2 (A>).

Note that the MTF processing calculation unit 11 is a well-known means, for example, [R1coh Technical Rep
ortNo, 3. May 1980J No. 25-3
Page 1 or “Same Report No. 6.
November.

1981J, pages 37-42.

On the other hand, the amplitude limiting ROM 12 has a function of outputting the data (reference signal C) shown in Table 1 using the input of the signal a as an address.

Table 1 In other words, when the input signal is at a level from O to 7, it is used as the reference signal C and a signal at level 6 is output, and when the input signal level is C or higher, a signal at level B is output. do. Also, when the input signal level is from 8 to B, each
Outputs signals at levels up to A. Note that this data is just an example, and it goes without saying that it can be modified and used as appropriate.

The signal C output from the MTF processing calculation unit 11 and the reference signal C output from the amplitude limiting ROM 12 are sent to a comparator 13.
Enter. This comparator 13 compares the magnitude of the signal input to the A terminal and the signal input to the B terminal, so that A≦
When B, an H level signal is output, and when A>8, an L level signal is output.
This is a comparator that outputs a level signal.

Therefore, the binary signal d output from the comparator 13 has the waveform shown in FIG. 2(B), which is a faithful binary representation of the characters written on the original 11. Also,
Small noises are removed.

In the above embodiment, the read image signal a is amplitude limited R
Although the input is input to the OM 12, the amplitude is limited, and the input is input to the comparator 13, the present invention is not limited to this.
12 is omitted and the read image signal a is directly sent to B of the comparator 13.
Those skilled in the art will readily understand that input may be made to the terminal.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) The present invention compares a signal digitally differentiated by MTF processing, that is, a signal with thin line emphasis, and a read image signal, and converts it into a binary value. Even if it is written, please follow this faithfully 2
It can be converted into value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
FIG. 3 is a block diagram showing an example of a conventional system, and FIG. 4 is a waveform diagram of signals in the main part of FIG. 3. 1... Original, 3... Image sensor, 10... A
/D converter, 11... MTF processing calculation unit, 12...
Amplitude limiting ROM, 13... comparator agent Michito Hiraki and one other person Figure 1 Figure 3 Figure 4rlI4

Claims (2)

[Claims] (1) In a method of binarizing a read image signal, means for converting the read image signal into a digital image signal, means for branching the digital image signal, means for performing MTF processing on one of the branched signals, and the MTF.
A binarization method characterized by comprising a comparison means that receives the processed signal and the other branched signal as input and outputs a signal obtained by comparing both signals. (2) The binarization method according to claim 1, wherein the other branched signal is amplitude-limited and inputted to the comparison means.