JPS6355113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical character reading device. More specifically, the present invention relates to an optical character scanning device that converts an address written on a letter into a binary video signal.

Conventionally, flying point scanning devices, etc. have been used in this type of device, and these devices
Not only when the background color of the paper surface in the scanning area is white, but even when the background color is colored, if there is no major unevenness in the background color, the automatic gain adjustment (AGC) By keeping the level of the conversion signal constant and quantizing it using a predetermined threshold, it was possible to easily convert the address written within the scanning area into a binary video signal. However,
When scanning a letter with a window or a label and converting the address information written on the window or label into a binary video signal, the optical reflectance of the window or label is , or the scanning area may include a portion of the paper surface with high reflectance other than windows and labels. In particular, if you use a pre-scan to detect the window position or the addressee's position in advance and then spread the main scan based on this position information to retrieve address information, the window with address information written in the main scan's scanning area This is the case when parts other than labels are included. In such a case, the reflectance of the window or label itself does not work as a standard for AGC control, so it is impossible to extract the address inside the window or label, or even if it can be extracted, it will be extracted to the level of paper noise. This caused a problem where the data could not be read.

The present invention has been made in view of the above drawbacks, and
The purpose of this is to detect the position of the addressee on the letter by using known technology, such as the technology described in Japanese Patent Application No. 142240/1982, and to scan the area corresponding to the addressee. By adjusting the amplification degree of AGC based on the level of the photoelectric conversion signal obtained from the center of the scanning area among the photoelectric conversion signals obtained from the scanning area, it is possible to detect areas other than windows and labels in the scanning area. Another objective of the present invention is to provide an optical character scanning device that can accurately extract the address written on the label as a binary video signal.

Hereinafter, the present invention will be explained in detail with reference to FIGS. 1 to 6.

FIG. 1 is a diagram showing an example of a letter with a window. In this case, the position of the addressee may be detected using the technique described in Japanese Patent Application No. 142,240/1986, or the known window detection technique (Japanese Patent Application No. 13818) to detect the addressee's position, but in any case, we will proceed with the discussion assuming that rectangle ABCD in the diagram has been determined by the pre-scan as the area to be main scanned. 10 is the entire letter, 11 is a window surrounded by WXYZ, 12 is the addressee, and 13 is the paper area within the window that has low reflectance in the visible range, such as blue, where addressee 12 is written. . 14 surrounded by ABCD
15 is a scanning area (main scan area), and 15 is a paper surface area other than the window, which has a higher reflectance than the white paper surface area 13. A scanning area 14 indicates an area in which the optical character scanning device scans the letter 10, and the scanning is started from point B in the direction of arrow a, and is sequentially repeated in the direction of arrow b.

Figure 2A shows how a letter 1 is scanned using a conventional character scanning device.
This figure shows a figure obtained from a binary video signal when scanning over 0 (FIG. 1). 14a shows a figure obtained when the paper surface portion 13, which has a lower reflectance than the paper surface portion 15 in FIG. 1, is regarded as a type of character signal. That is, since the amplification degree of the photoelectric conversion signal is controlled based on the reflected light from the paper surface portion 15 having a high reflectance, it is determined that the paper surface portion 13 having a low reflectance contains some information that is all black. As is clear from this figure, the conventional character scanning device cannot extract the figure corresponding to the addressee name 12 in FIG. 1.

FIG. 2B shows an area targeted for AGC, which is predetermined in the present invention, and the area is indicated by diagonal lines surrounded by a rectangle STUV.
Further, TC ₁ indicates a gate pulse signal that limits the AGC target area. In order to facilitate the explanation below, the areas surrounded by the rectangles ASVD, STUV, and TBCU are respectively defined as scanning areas.

FIG. 3 is a block diagram showing one embodiment of the present invention. In the figure, 10 is a letter, 20 is a conveyance path, 30 is a scanning section, 40 is a photoelectric conversion section, 50 is a control section, 60
Reference numeral denotes a photoelectric conversion signal processing section, 70 a discrimination section, and 80 a pre-scanning section for detecting the addressee position. The letter 10 is conveyed along the conveyance path 20 in the conveyance direction c, that is, from top to bottom in FIG. 3 at a constant speed. The scanning unit 30 starts from point B in FIG.
A scanning area 14 of a rectangle ABCD is scanned with flying points 31. Scattered light 32 on the letter 10 is focused on the photoelectric conversion unit 30. The photoelectric conversion unit 30 converts the scattered light 3
Based on the strength of 2, it is converted into an electrical signal. A photoelectric conversion signal obtained by scanning and photoelectric conversion is guided to a scanning signal processing section 60 by 12. An example of the signal on 12 is shown in FIG. 5A. This signal shows a photoelectric conversion signal when scanning HK in FIG. 1. The photoelectric conversion signal processing section 60
It is composed of an AGC circuit 61, a gate circuit 62, a gate pulse generation circuit 63, and a binarization circuit 64. The AGC circuit 61 adjusts the degree of amplification of the photoelectric conversion signal derived from 12 based on the level of the AGC control signal derived from 14. That is, the amplification degree of the AGC is adjusted based on the photoelectric conversion signal level in the scanning area in FIG. 2B, so that the address in the window can be read. The signal obtained by this circuit is led to the binarization circuit 64 through 13. 13
An example of the above signal is shown in FIG. 5D. Gate circuit 6
Reference numeral 2 applies a gate to the photoelectric conversion signal led by 12 based on the gate pulse signal led by 15. The signal obtained by this circuit is led to the AGC circuit 61 through 14. 14
An example of the above signal is shown in FIG. 5c. The gate pulse generation circuit 63 generates a gate pulse by using the signal on the circuit 16 derived from the control section 50. In other words, as shown in Figure 2B
This generates the gate pulse of _TC1 . The signal obtained by this circuit is led to the gate circuit 62 through 15. An example of the signal on 15 is shown in Figure 5B.
Also shown. Note that details of this circuit will be described later.

The binarization circuit 64 converts the photoelectric conversion signal led by 13 into an electrical binary video signal using a predetermined threshold value. This binarized signal is led to the discrimination section 70 through 17, where it is subjected to character recognition processing. An example of the signal on 17 is shown in FIG. 5E. It should be noted that although this block diagram includes a known binarization circuit 64, it is included for convenience of explanation and need not be included in this block.

FIG. 4 shows an embodiment of the gate pulse generation circuit 63. This circuit consists of an astable multivibrator circuit () 631 and an astable multivibrator circuit () 632. The astable multivibrator circuit ( ) 631 is
161, for example, a pulse having a pulse width t1 is generated at the falling timing of a start pulse that is output every time the scanning area is scanned from bottom to top. This t1 is equal to t(T) minus t(B) at TC ₁ shown in FIG. 5B. An example of a signal on 161 is shown in FIG. Astable multivibrator ()632
generates a pulse having a pulse width t2 at the falling timing of the pulse guided by 161. This t2 corresponds to TC ₁ shown in FIG. 5B. It should be noted that although this circuit uses two unstable multivibrator circuits, it can also be easily implemented using a counter circuit.

As described above in detail, according to the present invention, the document is a letter with a window or a letter with a label, and the window part,
Even if the optical reflectance of the label part is lower than that of the surrounding paper area, a gate circuit and gate pulse generation circuit can be added and the video signal of this part can be used as a reference.
Make AGC work. This allows the address written on the window or label to be converted into an accurate binary video signal. Although an AGC circuit is used to keep the photoelectric conversion signal level constant in one embodiment of the present invention, it can also be easily done by automatically changing the threshold level according to the scanning output from the window or label. I would like to add that it goes without saying that this can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of writing on a sheet of paper to be scanned;
FIG. 2A is a diagram showing a figure of a binary video signal obtained by a conventional device, FIG. 2B is a diagram showing an example of a scanning area targeted by an AGC circuit, and FIG.
A block diagram showing one embodiment of the present invention, FIG.
FIG. 5 is a diagram showing an example of a gate pulse generation circuit, FIG. 5 is a diagram showing various signal waveforms in an embodiment of the present invention, and FIG. 6 is a diagram showing signal waveforms in the gate pulse generation circuit.

Claims (1)

[Claims] 1. A scanning means for scanning the character writing surface on a sheet of paper;
gate pulse generating means for generating a gate pulse indicating a predetermined range within a scanning area; gate means for passing a photoelectric conversion signal in accordance with the gate pulse; and photoelectric conversion in accordance with the signal obtained by the gate means. Optical character scanning comprising variable amplification means for changing the amplification degree of a signal, and a binarization circuit for generating a binary signal by comparing the signal from the variable amplification means with a predetermined threshold value. Device.