JPH05292311A - Original reader - Google Patents

Abstract

PURPOSE:To set automatically a binarization threshold level for binarization processing with an assumption for reading the objects of plural kinds of originals having a photograph or a mark attached on a part of the original in which the position of the photograph or the mark corresponds to the color of a character part when the original is read and the read signal is subjected to the binarization processing. CONSTITUTION:The position of a photograph or a mark is detected by a photograph position detection means 12 or a mark position detection means 12' based on picture data from a photoelectric conversion means 10. Then the binarization threshold level setting means 13 sets a binarization threshold level based on the position information. Moreover, the picture data obtained till the binarization threshold level is set are once stored in a picture storage means 14 and after the binarization threshold level is set, a binarization processing means 15 applies the binarization processing to the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus for reading a document and binarizing it, and particularly to a document or a part of which a photograph or a mark is attached, and the photograph position or the mark position and the color of a character portion Relates to a target of reading a plurality of types of documents.

[0002]

2. Description of the Related Art In a conventional document reading apparatus, a document P such as a form recorded horizontally is conveyed in a vertical direction (in the direction of a black arrow in the figure) as shown in FIG. Then, the image of one row in the horizontal direction illuminated by the illumination lamp 101 at a predetermined position is received by the horizontally long CCD 103 as the photoelectric conversion means through the lens 102 and photoelectrically converted. The photoelectrically converted image data for one column in the horizontal direction is subjected to main scanning in the horizontal direction and A / D converted in synchronization with the horizontal synchronizing signal. In the meantime, the original P is conveyed in the vertical direction (sub-scanning), and the image for one row in the horizontal direction is photoelectrically converted and A / D converted at a new position. By repeating such main scanning and sub scanning, the document P
Are all photoelectrically converted and A / D converted.

The image data digitized by A / D conversion is binarized for each pixel by comparison with a predetermined binarization threshold value, and is read as black and white image data. In such a conventional document reading apparatus, shading correction is performed for the purpose of correcting sensitivity variations of CCD pixels and nonuniformity of illumination light. For this, a standard (constant density) white plate is read, and a correction coefficient is calculated and stored for each pixel so that the A / D conversion data has a constant value. Then, when the document is actually read, the A / D conversion data is multiplied by the correction coefficient to correct it.

[0004]

However, in such a conventional document reading apparatus, the binarization threshold value for the binarization process is fixed or manually input from the outside and set. However, when a plurality of types of originals written with inks of various colors are binarized (black-and-white) with a constant binarization threshold, characters may be blurred depending on the color type. Or, there was a problem of being crushed.

That is, since the data output from the CCD as the photoelectric conversion means is not constant with respect to the color of the ink or the like used, if this is binarized with a constant binarization threshold value, the CCD output is If it is small, it becomes light, and if it is large, it becomes dark. Therefore, the present invention is premised on that a plurality of types of originals, to which a photograph or a mark is attached, and whose photograph position or mark position and the color of the character portion correspond, are to be read. It is an object of the present invention to provide a document reading device capable of optimally and automatically setting a binarization threshold for.

[0006]

Therefore, in the present invention, a photograph is partly attached, and the photograph position corresponds to the color of the character portion (including characters, symbols, figures, ruled lines, etc.). When a plurality of types of originals to be read are to be read, a means for detecting a photograph position and a means for setting a binarization threshold value based on the detected photograph position are provided.

In addition, when a mark (including a bar code, a hole, etc.) is provided in a specific area, and a plurality of types of originals in which the mark position in the specific area and the color of the character part correspond to each other are to be read. Is provided with a means for detecting the mark position and a means for setting a binarization threshold value based on the detected mark position.

[0008]

In the above arrangement, when reading a document in which the photograph position (or the mark position in the specific area) and the color of the character portion of the document have a one-to-one correspondence, the photograph position (or mark position) is changed. 2 for the binarization processing according to the detection result
The binarization processing suitable for each color is performed by changing the binarization threshold value.

The image data obtained until the photograph position (or mark position) is detected is temporarily stored in an image storage means such as an image memory, and is binarized by detecting the photograph position (or mark position). Binarization processing may be performed after the optimization of the values. Alternatively, instead of using the image storage means, a pre-scan is performed prior to the main scan, a photo position (or mark position) is detected by this pre-scan, a binarization threshold value is set, and a main scan thereafter The binarization process may be performed by.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a document reading device (scanner) according to the present invention.
The structural example of is shown. An insertion port 2 for a document P such as a document is formed at the upper end of the box 1, and a discharge port 3 for the document P is formed at the lower end.

Inside the box 1, there are a plurality of pairs of conveying rollers 5 for nipping and conveying the original P downward along a downward conveying path 4 from the insertion opening 2 to the ejection opening 3, and both front and back surfaces of the original P. , Two lamps 6 for illuminating the original P, two mirrors 7 for reflecting light from both front and back surfaces of the document P, two lenses 8 for condensing the reflected light, and the condensing light. Two Cs as photoelectric conversion means for receiving light and converting photoelectrically
CD10 and is provided.

Therefore, when the document P is inserted through the insertion slot 2, the CCD 10 receives the reflected light from the document P at a predetermined position while being transported by the transport roller 5, and the main scanning direction (direction orthogonal to the transport direction). Photoelectric conversion is performed for each line. Then, this is repeated with the carrying direction as the sub-scanning direction, and all the images of the document P are photoelectrically converted. Next, a document to be read by the document reading apparatus according to the present invention will be described.

Reference numerals A, B and C in (1) of FIG. 2 are examples of an original in which a photograph (face photograph) is partly attached, and the photograph position and the character color (red, blue, green) are 1. Corresponds to one-to-one. A ', B', and C'in (2) of FIG. 2 are examples of documents with marks in the specific area (near the upper end), and the mark position (horizontal position) and the character position in the specific area are shown. The colors (red, blue, green) have a one-to-one correspondence.

As described above, a plurality of types of originals in which the photograph position or mark position and the color of the character portion have a one-to-one correspondence may be used. Of course, in the case of colors of similar colors (for example, green and yellowish green), the photograph or mark may be at the same position. Further, even if different colors have similar values after photoelectric conversion, a photograph or a mark may be present at the same position.

Next, a configuration example of the signal processing circuit in the document reading apparatus according to the present invention will be described with reference to FIG. The image data photoelectrically converted by the photoelectric conversion means 10 is digitized by the A / D converter 11. Based on this digital image data, the photographic position or mark position is detected by the photographic position detecting means 12 or mark position detecting means 12 'which will be described later. Then, based on this position information, the binarization threshold value setting means 13 sets the binarization threshold value.

On the other hand, an image storage means 14 such as an image memory for storing digital image data up to the photograph position or the mark position.
The image accumulating means 14 is provided with a FIFO method, and after the binarization threshold value is determined, the latest image data is stored and the binarization processing means is sequentially executed from the oldest image data.
Output image data to 15. Thereby, the binarization processing means 15 compares the image data with the binarization threshold value and performs the binarization process.

It should be noted that, without using the image accumulating means 14, the photograph position or the mark position is detected by the pre-scan prior to the main scan, the optimum binarization threshold value is set, and then the second scan is performed. Binarization processing may be performed using a threshold value. In this pre-scan, scanning may be performed coarsely (that is, resolution may be reduced) to increase the speed.

(1) Specific example in case of photograph position A concrete example of the photograph position detecting means 12 will be described. When the image of the original with a part of the photograph attached is viewed in the window 3 × 3 area as shown in FIG. 4, the character portion is a binary area, so that the luminance changes greatly. Since the portion of the photograph is a gradation area, there is no great change in luminance.

Utilizing this characteristic, the maximum luminance Lmax and the minimum luminance Lmin in the 3 × 3 area are detected, and the following 1) to
If all the conditions of 3) are satisfied, it is determined to be a photograph, and the photograph position is finally detected based on this. 1) Lmax-Lmin <L1 (no brightness difference) 2) Lmin <L2 (area is not all white) 3) Lmax> L3 (area is not all black) L1, L2 and L3 are constants and are shown in FIG. There is a relationship as shown.

Specifically, with the circuit of FIG. 6, Lmax,
Lmin is detected. Three FIFO type line memories 21 to 23 are provided in series and each can store one line of digital image data. Therefore, every time the image data is input to the line memory 21 pixel by pixel, the image data is sequentially fed on the line memories 21 to 23. In this way, image data for 3 lines is always stored.

Further, nine latch circuits 24a are connected in series to the output sides of the line memories 21 to 23, three in series.
-24c, 25a-25c, 26a-26c are provided. Therefore, the data for each pixel is read from the output side of each of the line memories 21 to 23 every pixel clock and the first latch circuit is read.
The previous data of the first latch circuit is sent to the second latch circuits 24b, 25b, 26b to be latched, and the previous data of the second latch circuit is latched by the third latch circuit 24c. , 25c, 26c and are latched. Thus, the nine latch circuits 24a to 24c and 25a to 25
The data in the 3 × 3 area is held by c and 26a to 26c.

Here, three horizontal lines (same scanning line)
The pixels are compared in size independently for three lines to detect the maximum and minimum values in the three horizontal pixels, and the results are compared again in magnitude to obtain Lmax and Lmin. That is, the outputs of the three latch circuits 24a to 24c, 25a to 25c, and 26a to 26c arranged side by side are input to the maximum value / minimum value detection circuits 27 to 29, respectively, and the maximum value and the minimum value of the three horizontal circuits are input. Is detected and output. Then, the outputs of the three maximum value / minimum value detection circuits 27 to 29 are input to another maximum value / minimum value detection circuit 30, and the maximum value and the minimum value in the 3 × 3 area are detected to obtain Lmax.
, Lmin.

A concrete example of the maximum / minimum value detection circuit 27 is shown in FIG.
Shown in. Output a of the first latch circuit 24a and the second latch circuit
The output b of 24b is input to the comparator 31 and the selector 32.
Then, according to the comparison result of a and b by the comparator 31,
When controlling the selector 32 and detecting the maximum value MAX,
When a> b, the selector 32 outputs a, and a
When ≤b, b is output. That is, the larger value is output.

Next, the selector which is the larger of a and b
The comparator 33 compares the output d of 32 and the output c of the third latch circuit 24c.
And to the selector 34. Then, d by the comparator 33
When the maximum value MAX is detected by controlling the selector 34 in accordance with the result of comparison between c and c, when d> c, the selector 34
Output d, and when d ≦ c, output c. That is, the larger value is output. This becomes the maximum value MAX.

When the minimum value MIN is detected, the comparator 31
When the comparison result of is a> b, the selector 32 outputs b, and when a ≦ b, a is output. Then, when the comparison result of the comparator 33 is d> c, the selector 34 may output c, and when d ≦ c, the selector 34 may output d. The same applies to the other maximum / minimum value detection circuits 28 to 30.

The determination of the photograph based on Lmax and Lmin is performed by the circuit of FIG. The subtraction circuit 35 has Lmax and Lmin.
Is input and Lmax-Lmin is output. Comparison circuit 36
Compares Lmax-Lmin with a constant L1, and obtains Lmax-L
When min <L1, an H level signal is output. The comparison circuit 37 compares Lmin with a constant L2, and outputs an H level signal when Lmin <L2.

The comparison circuit 38 compares Lmax with a constant L3, and outputs an H level signal when Lmax> L3.
The outputs of these comparison circuits 36 to 38 are input to the AND circuit 39, and when all are at the H level, the AND circuit 39 outputs an H level signal. This becomes the photo discrimination signal.

The final photo position detection is performed by the circuit shown in FIG. The line number counter 40 counts the horizontal synchronizing signal SH after being cleared by the reading start signal,
The count value (the number of main scanning lines) is output to the latch circuit 42. The pixel counter 41 counts the pixel clock after being cleared by the horizontal synchronizing signal SH, and outputs the count value (the number of pixels) to the latch circuit 42.

An output signal (photograph discrimination signal) of the AND circuit 39 of the photograph discrimination unit of FIG. 8 is input to the latch circuit 42 as a latch signal. When this signal is at H level, the number of main scanning lines and The number of pixels is latched. This is output to the binarization threshold value setting means 13 (see FIG. 3) as a photograph position.

Next, a concrete example of the binarization threshold value setting means 13 will be described with reference to FIG. This binary threshold setting means 13
Is composed of a look-up table (ROM) 43 and a D / A converter 44. Look-up table (RO
M) 43 is adapted to be input with the detected photograph position (the number of lines and the number of pixels up to the photograph position) at the address side, and is stored in advance in the following manner in response to the address side input. 8-bit D of binary threshold data
Output to the / A converter 44. A comparator may be used instead of the look-up table (ROM) 43.

[Address] [Data] A ± α ... Threshold data for red ink B ± α ... Threshold data for blue ink C ± α ... Threshold data for green ink Enter a level (eg 7FH).

The 8-bit D / A converter 44 is for generating a binarization threshold value, converts the data into an 8-bit voltage signal, and inputs it to the comparator 45 as the binarization processing means 15. The comparator 45 as the binarization processing means 15
The image data is compared with the output (binarization threshold value) of the 8-bit D / A converter 44, and binarization processing is performed.

(2) Specific Example of Mark Position Detection A specific example of the mark position detection means 12 'will be described. The mark exists in a specific area of the document, for example, in the area of L to L + M in the number of main scanning lines in the vertical direction, as shown in FIG.
The horizontal position in the area differs depending on the type of document.

Therefore, the circuit of FIG. 12 counts the number of main scanning lines, cuts out the mark area (L to L + M), and detects the mark position in it by counting the number of pixel clocks. The circuit of FIG. 12 will be described with reference to the timing chart of FIG. Line number counter 51
Is counted by the horizontal start signal SH after being cleared by the reading start signal, and the count value (the number of main scanning lines)
Is output to the comparator 52.

The comparator 52 outputs the count value to L and L +.
Compared with M, when L ≦ count value ≦ L + M, an H level signal is output. Therefore, this H level signal becomes the mark area detection signal. The pixel counter 53 counts the pixel clock after being cleared by the horizontal synchronizing signal SH, and outputs the count value (the number of pixels) to the latch circuit 54.

On the other hand, the image data is input to the comparator 55 and compared with a predetermined value to detect the presence / absence of a mark. When the mark is present, the comparator 55 outputs an H level signal. The output of this comparator 55 is the AND circuit 56.
The mark area detection signal is input to the other input terminal of the AND circuit 56.

Therefore, an H level signal is output from the AND circuit 56 only when a mark is detected in the mark area, and this H level signal is input to the latch terminal of the latch circuit 24 as a latch signal. Therefore, the latch circuit
At 54, the number of pixels when the mark position rises is latched.

This is output to the binarization threshold value setting means 13 (see FIG. 3) as a mark position. Next, a concrete example of the binarized threshold value setting means 13 in this case will be described with reference to FIG. The binarization threshold value setting means 13 comprises a look-up table (ROM) 57 and a D / A converter 58.

The look-up table (ROM) 57 is adapted to input the detected mark position (the number of pixels up to the mark position) on the address side thereof. The binary threshold data stored in advance is output to the 8-bit D / A converter 58. [Address] [Data] A '± α ... Red ink threshold data B' ± α ... Blue ink threshold data C '± α ... Green ink threshold data Other areas are intermediate Enter a level (eg 7FH).

The 8-bit D / A converter 58 is for generating a binarization threshold value, converts the data into an 8-bit voltage signal, and inputs it to the comparator 59 as the binarization processing means 15. The comparator 59 as the binarization processing means 15
The image data is compared with the output (binarization threshold value) of the 8-bit D / A converter 58 to perform binarization processing.

[0041]

As described above, according to the present invention, the binarization threshold value for the binarization process is automatically used by utilizing the photograph positions or mark positions of a plurality of types of originals to be read. By setting the optimum value to, even if the color of the character part is different, the binarization process can be performed at the optimum level, and thus it is possible to prevent the character from being blurred or crushed. ..

[Brief description of drawings]

FIG. 1 is a structural diagram of a document reading apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram showing a document to be read.

FIG. 3 is a block diagram showing a configuration example of a signal processing circuit.

FIG. 4 is a diagram illustrating a method of discriminating between photographs.

FIG. 5 is a diagram for explaining a method of discriminating between photographs as well.

FIG. 6 shows Lmax and Lmi which are part of the photograph position detecting means.
Circuit diagram of n detector

7 is a diagram showing a specific example of the maximum value / minimum value detection circuit in FIG.

FIG. 8 is a circuit diagram of a photograph discriminating unit which is a part of photograph position detecting means.

FIG. 9 is a circuit diagram of a final detection unit which is a part of the photograph position detection means.

FIG. 10 is a circuit diagram showing a specific example of binarization threshold value setting means.

FIG. 11 is a diagram explaining marks.

FIG. 12 is a circuit diagram showing a specific example of mark position detection means.

FIG. 13 is a timing chart of FIG.

FIG. 14 is a circuit diagram showing a specific example of a binarization threshold value setting means for mark detection.

FIG. 15 is a diagram showing a reading scanning principle as a conventional example.

[Explanation of symbols]

 10 Photoelectric conversion means (CCD) 12 Photo position detection means 12 'Mark position detection means 13 Binarization threshold value setting means 14 Image storage means (image memory) 15 Binarization processing means

Claims (2)

[Claims] 1. An original reading device for reading an original and performing binarization processing, wherein a plurality of kinds of originals having a photograph attached to a part thereof and the photograph position and the color of a character portion correspond to each other are to be read. The document reading apparatus, further comprising means for detecting a photograph position and means for setting a binarization threshold value based on the detected photograph position. 2. A document reading apparatus for reading a document and performing binarization processing, wherein a plurality of types of marks are provided in a specific area, and a mark position in the specific area and a color of a character portion correspond to each other. An original reading apparatus, comprising: an object to be read, including means for detecting a mark position and means for setting a binarization threshold value based on the detected mark position.