JPS59149575A - Preprocessing circuit - Google Patents

Abstract

PURPOSE:To convert a picture element signal of a proper density level into a binary coded pattern and to deliver the pattern by deciding whether a picture pattern on a form has a proper density level or not by a density checking circuit and on the basis of the peripheral binary coded pattern. CONSTITUTION:A form is scanned by a sensor, and the picture image of the slip undergoes the photoelectric conversion to obtain a video signal. This video signal is stored in a shift register 11 after an A/D conversion 10. The output of the register 11 is stored in an X-Y direction register 12. Three picture element signals a-c are stored in the X and Y direction registers 12a and 12b respectively. The signals a-c of the X direction are delivered to a main density compensating circuit 13: while the signals a-c of the Y direction are delivered to a secondary density compensating circuit 14 respectively. These circuits 13 and 14 compensate the density respectively. In other words, the proper level of the signal (b) is decided from the white level difference between signals (a) and (c). It is checked 15 whethr the proper levels M and S delivered from the circuits 13 and 14 are proper or not. Then a proper level is binary coded 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a preprocessing circuit used in an optical character reading device.

[Technical background of the invention and its problems]

Generally, an optical character reading device (hereinafter referred to as OCR) is equipped with a line image sensor (hereinafter referred to as line sensor) such as an N CCD image sensor. is scanned. That is, the image on the form is focused on a line sensor via a lens, and then photoelectrically converted and then sent to a binarization circuit.

By the way, in OCR as described above, when a photoelectrically converted analog video signal is converted into a binary pattern, the binary image is compared to the original pattern (image pattern on the form) before being converted. may not be partially reproduced.

This is thought to be caused by the resolution performance of the lens, the spatial frequency characteristics of the line sensor, etc. in particular,
For example, in No. 4 Turn 1 as shown in FIG. 1, the video signals at the time of scanning the life ta and the line tb are shown in FIG. 2(A).

This is a signal as shown in φ). That is, in the line ta, there is a hole 1a as shown in FIG. 1, and in the line tb, there is a thin line part 1b. Therefore, as shown in FIG. 2(A), in the video signal of line ta, a sign at point a, which is close to the white (that is, the color of the form paper) level, is generated.

Further, as shown in FIG. 2 (0), a signal at point b that approaches the black level is generated in the video signal on line tb. However, point a has not reached the white level, and point b has not reached the sufficiently black level region 1. Therefore, the video signal of each line ta, tb is sliced at the level S, 7' in Fig. 1.
P turn 1 is photoelectrically converted and binarized...?
In the turn, the hole portion 1a is crushed and the thin wire portion 1b is cut.

In conventional OCR, when converting photoelectrically converted video,
Although the signal is sent to a binarization circuit via a preprocessing circuit, it has not been possible to completely eliminate the above-mentioned phenomenon.

[Purpose of the invention]

This invention was made in view of the above circumstances, and its purpose is to convert video signals photoelectrically converted in OCR into two
To provide a preprocessing circuit capable of obtaining a binarized pattern that can reliably reproduce the original pattern on a form to be read when converting to a digitized pattern.

[・Summary of the invention]

According to the present invention, in OCR, an image signal obtained by optically scanning a form is stored in an XY register having registers in the scanning direction and the transport direction. Based on the X-direction and Y-direction image signals output from the XY register, respective density appropriate signals are output from the main density and sub-density correction circuits. For each density appropriateness signal output from the main density and sub-density correction circuits, the density check circuit performs density adequacy determination processing based on the binarized pattern of the image signal. In this way, it is possible to obtain an appropriate binarization f-turn for the image pattern on the form.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. , FIG. 3 is a block diagram showing the configuration of a preprocessing circuit according to the present invention. In the figure, numeral 10 is an analog-to-digital converter (hereinafter referred to as an A/D converter) that converts a photoelectrically converted analog video signal into a digital signal. This video signal is an analog signal obtained by photoelectrically converting characters on a form to be read. 1 is a shift register that stores, for example, two scans of digital signals output from the A/D converter 10. A register 12 stores signals for three pixels in the x and X directions at the output of the shift register 11.

The main density correction circuit 13 outputs an appropriate density signal in the X direction from the three pixel signals in the X direction (scanning direction for the form) output from the register 12 . Further, the sub-density correction circuit 14 outputs a density appropriate signal in the Y direction from the three pixel signals in the Y direction (transfer direction of the form). 15 is a density check circuit that outputs X, Y from the main and sub-degree correction circuits 13 and 14;
Check the density of the direction density signal.

The binarization circuit 16 converts the optimized density signal output from the density check circuit 15 into a binarized signal. 17 is a shift register that stores the signal binarized by the 1.binarization circuit 16 for one scan.

The register 18 is a 3×3 virtual memory, for example, and outputs a binarized pixel signal based on the output of the shift register 17 to the density check circuit 15.

The operation of this configuration will be explained. first,
The form is scanned multiple times by a line sensor (not shown), and a video signal is obtained by photoelectrically converting the image (characters, etc.).

This video signal is converted into a digital signal by an A/D converter 1o and stored in a shift register 1no. As shown in FIG. 4, this shift register 11 includes registers 11a and 11b for two scans, that is, two registers for two scans on the form.
Stores the signal corresponding to a row of images. The output of the shift register 11 is stored in the X and Y direction Lucister 12. The register 12 includes registers 12a and 12b in a cross configuration as shown in FIG. ) will be stored.

When the pixel signal is stored in the register 12 in this way, the 3-pixelization code a ''-c in the X direction from the register 12a
is output to the main density correction circuit 13.

Three pixel codes a to C in the Y direction are output from the register 12b to the image density correction circuit 14. The main density and image density correction circuits 13 and 14 are circuits having the same functions, and perform density correction as described below. For example, as shown in FIG. 6(A), three pixel code IL
” If the difference between the white levels of signal a and signal C is large, the contrast will be large and the influence on the signal will be large. If it is above the straight line connecting signal C, the appropriate level of the signal is determined so that it is emphasized to white.In addition, in the case of Fig. 6 (B), the signal is emphasized to black. The appropriate level is determined so that the
In the case of Figure (C), the white waveform surrounded by black is shown. The appropriate level of signal bi is determined by the difference between the white level of signals a and c and the level of signal S. . In this case, the appropriate level is determined so that the signal is emphasized to white. In the case of () in Fig. 6, the situation is the opposite of that in Fig. (C).

The signal levels of the respective waveforms shown in Figures 6) to (9) depend on the performance of the optical system and line sensor, and are determined experimentally and statistically. Here, each of the waveforms shown in FIG. 2 (A, ) and CB) is as shown in FIG. 6 (A).

(B) The contrast of the multi-line edges is emphasized and the line edges do not widen, and as shown in Figures 6 (c) and (1), there are no crushed holes or breaks in the thin line areas. The appropriate level is determined so that it disappears.

The density check circuit 15 checks whether each of the appropriate levels M and S output from the main density and image density correction circuits 13 and 14 is valid.

The appropriate level output from the concentration check circuit 15 is 2.
The data is binarized by the digitization circuit 16. In this case, the binarization method of the binarization circuit 16 is a fixed slice method with a fixed threshold value or a floating method with a variable threshold value.

A dynamic slice method may also be used. The signal P that has been binarized by the binarization circuit 16 is output to the shift register 17 and the register 18 of each storage company for one scanning, as shown in FIG. A virtual matrix is formed in the register 18, and the output thereof is supplied to the quadruple check circuit 15. 1. For example, in the case of a figure as shown in Fig. 8, the register 12a of the register 12 stores a waveform as shown in Fig. 7), and the register 12b stores a waveform as shown in Fig. 70). Suppose that In this case, the waveform shown in FIG. 6 highlights the register 12h to white, and the register 12b
is highlighted to black. The density check circuit 15 detects the above-mentioned contradiction, makes a judgment based on the binarization pattern supplied from the register 18, and outputs a valid and appropriate level. That is, in the case of the figure shown in FIG. 8, only 18d of the register 18 shows a black signal, and 18a to 18
All c become white signals (18eil-1l: pixels to be optimized). Based on the pattern status of the virtual matrix, the density check circuit 15 determines that the output S is inappropriate based on the output M of the main density correction circuit 13 and the output S of the image density correction circuit 14, and outputs the output M as an appropriate level. I will do it. Note that such determination processing is performed based on statistical data, and does not always yield the same results.

In this way, the image pattern on the form is checked by the density check circuit 15 based on the surrounding binarized pattern.
It is determined whether the concentration level is appropriate. and,
A pixel signal with an appropriate density level is sent from the density check circuit 15 to the binarization circuit 16, where it is converted into a binarized pattern and output. Therefore, in the image pattern on the form, the loops (
1a) in Figure 1 is crushed, still has a thin line (1b in Figure 1)
It is possible to reliably prevent a situation where a cut occurs.

〔Effect of the invention〕

As described in detail above, according to the present invention, when converting a photoelectrically converted video signal into a binary pattern in OCR, a binary pattern is generated that can reliably reproduce the original or turn on the form to be read. pattern can be obtained.

Therefore, high quality image patterns can be obtained,
This provides the effect of realizing reliable reading processing.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a pattern for explaining the operation of a conventional preprocessing circuit, and Fig. 2 (A), 03) is a diagram showing a waveform of a video signal to explain the operation of a conventional preprocessing circuit. 3 is a block diagram showing the configuration of a preprocessing circuit according to an embodiment of the present invention, and FIG. 4 is a block diagram specifically showing the configuration of the shift register 1 and register 12 in FIG. 5 is a block diagram showing the configuration related to the operation of the concentration check circuit 15 in FIG. 3, FIGS. 6) to C) are diagrams for explaining the operation of the preprocessing circuit in FIG. figure(
A), Φ) are diagrams for explaining the operation of the circuit in FIG.
FIG. 8 is a diagram showing an example of a diagram for explaining the operation of the circuit of FIG. 5. 11.17...Shift register, 12.18...Register, 13...Main density correction circuit, 14...Sub-density correction circuit, 15...Density check circuit, 16...2
Value circuit. Applicant's agent Patent attorney Takehiko Suzue No. 6 (A) CB) No. (A) ? (C) (D) 7 Figure (B) 8 Figure Kazuo Wakasugi, Commissioner of the Patent Office1. Indication of the case Special No. 58-13983 No. 2, name of the invention Preprocessing circuit 3, person making the amendment Relationship to the case Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. 4, Agent April 26, 1982 Day 7, Amendment (1) Book F + B, page 11, line 15 to line 16, 1st 6 i (A to (C) are "stop" [Fig. 6 (B) to CD) I am corrected.

Claims (1)

[Claims] In a preprocessing circuit that converts image signals obtained by optically scanning a form into a binary pattern, output from an XY register that stores each image signal in the scanning direction and transport direction of the form. density correction means for outputting appropriate density signals based on each of the above-mentioned image signals; and density determination for performing density appropriateness determination processing on the image signals output from the density correction means based on the binarization pattern. A preprocessing circuit comprising: means.