JPH01217688A - Binarization circuit - Google Patents

Abstract

PURPOSE:To prevent a state for outputting black data due to the generation of wrinkles at the time of binarizing and to constantly attain an effective binarization by constituting a document to be read of a comparatively thin paper and setting a slice level so as to absorb a level fluctuation by the wrinkles. CONSTITUTION:According to the level change of a white level signal I obtained at the time of scanning the white paper part of the document, the slice level required for the binarization is set based on either one of white level data or data corresponding to an envelope signal E. Accordingly, when the white level fluctuation is generated according to the wrinkles at the time of carrying the document, the binarization processing by the slice level TH1 (TH1>TH2) based on the envelope signal E is executed. Namely, a level fluctuation value according to the wrinkles is situated within a range between reference values R1, R2. Thereby, even when the level fluctuation according to the wrinkles is generated, all the white level parts of the picture signal I is outputted as the white data to effectively execute the binarization processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Monthly Field of the Invention] (Field of Industrial Application) The present invention relates to a binarization device used, for example, in an optical character reading device.

(Prior Art) Conventionally, in an optical character reading device (OCR), a photoelectric scanning section scans a form to be read, and a binarization section converts an image signal obtained by photoelectric conversion processing by the photoelectric scanning section. Convert to binary signal (character pattern data). The character pattern of this binary signal is recognized by the character recognition section.

Here, the binarization part converts the image signal into a binarized signal of a black level signal using a slice level based on a white level signal. In this case, since the level of the white level signal becomes unstable due to the performance of the optical equipment of the photoelectric system scanning section, etc., shading correction processing is performed. That is, conventional O.C.
In R, a slice level based on a white level signal after shading correction is stored, and binarization processing is performed using this slice level. Specifically, as shown in 3(a), the binarization process is performed using the slice level TH determined based on the white level signal W of the image signal I.

By the way, the form to be read is transported to the photoelectric scanning unit by the transport mechanism. At this time, if the form is a relatively thin sheet of paper, wrinkles may occur in the form due to reasons such as uneven pressure on the conveyance rollers of the conveyance mechanism. When such wrinkles occur, as shown in FIG. 3(b), a portion Wa in which the white level of the image signal ■ changes occurs. Therefore, when binarized using the slice level TH as described above, a black level signal (black data) is output at the position of the waveform portion Wa, and it looks as if a vertical line has been written on a form. It becomes a state.

Although FIG. 3 actually shows a digital multilevel signal, it is shown as an analog signal waveform for convenience.

(Problem to be Solved by the Invention) In the binary force type used in conventional OCR, if wrinkles occur when the document to be read is conveyed, the white data portion becomes black due to fluctuations in the white level signal. There is a drawback that it is output as data.

Therefore, in OCR, misreading or directing may occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a binarization device that can perform reliable binarization processing even when the document to be read is made of relatively thin paper and wrinkles occur.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present invention provides a memory means for storing white level data corresponding to a white level signal corrected by a shading correction processing means, and a memory means corresponding to the white level signal. Envelope generating means for generating an envelope signal; first comparison means for comparing the level of the envelope signal with a first reference value of a low level; and a second reference value of a high level and the level of the envelope signal. The second to compare
The present invention is a binarization device equipped with a comparison means for determining a slice level, and a selection output means for selectively outputting data corresponding to either an envelope signal or a self-level signal for determining a slice level. The selection output means outputs data corresponding to the white level signal stored in the memory means when the comparison results of the first and second comparison means are the same, and outputs data corresponding to the white level signal stored in the memory means when the comparison results are different and outputs data corresponding to the envelope signal. The level of is the first. If it is between the second reference values, data corresponding to the envelope signal is output.

With such a configuration, it is possible to improve the accuracy of the binarization process even when the white level fluctuates greatly due to wrinkles occurring in the form during transportation.

(Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a binarization device in OCR of the same embodiment. The photoelectric system scanning unit 10 includes a photoelectric conversion circuit that scans the form to be read, and outputs an image signal obtained by converting light reflected from the form into an electrical signal. The amplifier circuit 11 is a circuit that amplifies the image signal output from the photoelectric scanning section IO. The A/D conversion circuit 12 is the amplifier circuit 11
This is a circuit that converts the image signal output from the camera into a digital signal. The shading correction circuit 13 is a circuit that performs shading correction processing on a digital signal corresponding to an image signal (white level signal) obtained by scanning a blank portion of a form. The register 14 is a memory that stores white level data corresponding to the shading-corrected white level signal.

On the other hand, the envelope generating circuit 15 includes an integrating circuit, etc.
This circuit generates an envelope signal from the image signal of the white level signal output from the amplifier circuit 11.

The A/D conversion circuit 1B is a circuit that converts the envelope signal output from the envelope generation circuit 15 into a digital signal. The register 17 is a memory that stores data corresponding to the envelope signal output from the A/D conversion circuit 12. The comparator 18 compares the level of the envelope signal with the level of a preset reference value R1, and when the level of the envelope signal exceeds the level of the reference value R1, the logic level is "1".
” output signal. Moreover, the comparator 19 is
The level of the envelope signal is compared with the level of a preset reference value R2, and when the level of the envelope signal exceeds the level of the reference value R2, an output signal of logic level "1" is output. Here, the level of the reference value R2 is set to a value greater than the level of the reference value R1.

The exclusive OR circuit (hereinafter referred to as EXOR circuit) 20 is
The outputs of the comparators 18 and 19 are input, and when the outputs are different, a logic level "1" is output, and when the outputs are the same, a logic level "0" is output. The multiplexer 21 selects and outputs the contents of the register 17 when the output of the EX-OR circuit 20 is at the logic level "1", and selects and outputs the contents of the register 14 when the output is at the logic level "0". and output it.

The binarization circuit 22 divides the image signal into two parts based on the slice level based on the data output from the multiplexer 21.
This is a circuit that performs value conversion processing.

Next, the operation of this embodiment will be explained. First, a blank portion of the form to be read is scanned by the photoelectric scanning unit IO. The image signal of the white level signal obtained by this scanning is applied to the A/D conversion circuit 12 via the amplifier circuit 11. A/
The D conversion circuit 12 converts the image signal into a digital signal (digital multi-value) and outputs it to the shading correction circuit 13. The shading correction circuit 13 performs shading correction processing on the white level signal to correct distortion caused by the performance of the optical equipment of the photoelectric system scanning section 10 and the like. As a result, as shown in FIG. 2(a), for example, an image signal (white level signal) (2) after shading correction is obtained. Here, the image signal I is actually converted into digital multivalue data by the A/D conversion circuit 12, but for convenience, the image signal I is
As shown in the figure, it is shown as an analog signal waveform. Shading corrected image signal (i.e. white level data)
(2) is stored in the register 14.

On the other hand, the envelope generation circuit 15 generates an envelope signal E as shown in FIG. 2(a) from the image signal output from the amplifier circuit 11. This envelope signal E is a signal for extracting level changes of the white level signal. The envelope route signal E is
The data is converted into digital multi-value data by the A/D conversion circuit 1B and stored in the register 17.

The comparator 18 compares the level of the envelope signal E and the level of the reference value R1, as shown in FIG. 2(b).

Here, the reference value R1 is a lower limit value at which the level of the envelope signal E can be used as a slice level during binarization processing. Further, the comparator 19 compares the level of the envelope signal E and the level of the reference value R2. Here, the reference value R
2 is the upper limit calculation value at which the level of the envelope signal E can be used as a slice level during binarization processing. The comparison result of comparator 18 is logic level "1" and comparator 1
9 - If the result is a logic level "0", the EX-OR circuit 20 outputs a logic level "1".

As a result, the multiplexer 21 selects the data corresponding to the envelope signal E, which is the content of the register 17, and outputs it to the binarization circuit 22. That is, if the level of the envelope signal E (change in level of the white level signal) is within the range between the reference values R1 and R2, the multiplexer 21 selects the data corresponding to the envelope signal E and transmits it to the binarization circuit 22. Output to. As a result, the binarization circuit 22 generates a slice level TH based on the data of the envelope signal E, as shown in FIG. 2(c).
Binarization processing is performed using I.

On the other hand, the comparison result of the comparator 18 is logic level "1"
If the comparison result of the comparator 19 is also at the logic level "1", the EX-OR circuit 20 outputs the logic level "0". This causes the multiplexer 21 to
The white level data corresponding to the white level signal ■ which is the content of is selected and outputted to the binarization circuit 22. That is, the level of the envelope signal E (level change of the white level signal) is the reference value R.
If it exceeds 2, the multiplexer 21 selects the white level data and outputs it to the binarization circuit 22. As a result, the binarization circuit 22, as shown in FIG. 2(d),
Binarization processing is performed using slice level TH2 based on white level data.

In this way, depending on the level change of the white level signal obtained when scanning the blank part of the form, the slice level required for the binarization process can be set to either the white level data or the data corresponding to the envelope signal. Set based on. As a result, when a white level fluctuation occurs due to wrinkles when the form is conveyed, binarization processing is performed using the slice level THI (THI>TH2) based on the envelope signal. That is, this is a case where the level fluctuation value due to wrinkles is within the range between the reference values R1 and R2.

Therefore, as shown in FIG. 2C, even if level fluctuations occur due to wrinkles, the entire white level portion of the image signal I will be output as white data due to the binarization process.

Furthermore, if the level fluctuation of the white level signal is large enough to exceed the reference value R2, it is considered that the level fluctuation is not due to wrinkles but, for example, due to dirt on the form. In this case, as shown in FIG. 2(d), black data is output by the binarization process in the level variation portion Wa.

[Effects of the Invention] As detailed above, according to the present invention, when the document to be read is made of relatively thin paper and wrinkles occur, the slice level is set so as to absorb level fluctuations due to the wrinkles. By doing so, it is possible to prevent a situation where black data is output due to the occurrence of wrinkles during the binarization process. Therefore, even if wrinkles occur when the form is transported, it is possible to always achieve reliable binarization processing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2(a) to (d) are waveform diagrams for explaining the operation of the embodiment, and FIGS. b) is a waveform diagram for explaining each conventional method. DESCRIPTION OF SYMBOLS 10... Photoelectric system scanning unit, 13... Shading correction circuit, 14.17... Register, 15... Envelope generation circuit, 18° 19... Comparator, 21...
Multiplexer, 22...binarization circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 30

Claims (1)

[Claims] In a binarization device that performs binarization processing on an image signal obtained by scanning a sheet of paper to be read using a slice level generated based on a white level signal, shading performs shading correction processing on the white level signal. a correction processing means, a memory means for storing white level data corresponding to the white level signal corrected by the shading correction processing means, and generating envelope data corresponding to an envelope signal corresponding to the white level signal. an envelope generating means; a first comparison means for comparing the level of the envelope signal with a first reference value of a low level; and a comparison means of comparing the level of the envelope signal with a second reference value of a high level. If the comparison results of the second comparison means and the first and second comparison means are the same, output the white level data stored in the memory means as data for determining the slice level. However, if the comparison results are different and the level of the envelope signal is within the range between the first and second reference values, the envelope data is output as data for determining the slice level. 1. A binarization device comprising a selection output means for selecting and outputting.