JPH07115514A - Image reader - Google Patents

Abstract

PURPOSE:To provide an image reader able to decide correctly an area of an original placed on an original pressing plate even when there is a flaw or a dirt on the original pressing plate. CONSTITUTION:A spatial distance calculation circuit 112 calculates a position on an RGB color space based on an RGB signal of a concerned pixel and the distance of the position from a color information representing point on an original pressing plate, an original decision circuit 113 decides whether or not the concerned pixel is resident on an original based on an output of the spatial distance calculation circuit 112. A spatial frequency filter 118 outputs the result applying predetermined filtering to the concerned pixel and pixels in the vicinity, and an original decision circuit 119 decides whether or not the concerned pixel is resident on the original based on an output of the spatial frequency filter 118. A mis-decision prevention circuit 114 stores the result of decision by original decision circuits 113, 119 when the surface of the original pressing plate is read in advance and the area of the original is decided based on the storage, and the decision result by the original decision circuits 113, 119 ANDed by an AND gate 120.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, for example, an image reading apparatus having a function of detecting a document.

[0002]

2. Description of the Related Art Current copying machines such as Canon NP91
In 30, PIXEL-Dio, PIXEL-EPO, etc., the original is detected by the difference in the luminance signal between the original pressure plate and the original. That is, the document detection method of these copying machines uses the document pressure plate.
Utilizing the fact that the brightness level is extremely low when read by CCD, if the brightness level of all pixels in a certain small area exceeds a certain threshold value, it is detected as a document.

However, since a dark background such as a silver halide photograph has a brightness level that is about the same as or lower than that of the original pressure plate, the original pressure plate and the original area may not be correctly discriminated, and the original may not be detected properly. In order to solve this, there has been proposed a method of detecting a document by using the difference in the color space and the difference in the spatial frequency between the read image signal and the document pressure plate. That is, the tint information and the spatial frequency information of the read image are compared with the tint information peculiar to the original platen and the spatial frequency information of the striped pattern which are held in advance, and the original is detected based on the comparison result. It is to try. In addition, in order to improve erroneous detection due to scratches and stains on the document pressure plate in this method, based on the result of reading the surface of the document pressure plate as an image in the initial stage, the characteristic peculiar to each document pressure plate held in advance is corrected. The method of doing is also proposed.

By such a method, it is determined whether or not the original is for each pixel (or a fixed small area) represented by the read image signal,
The position and size of the document are detected based on the result, and there is a proposal described in JP-A-59-67764 for the method. The same proposal operates a counter that counts the number of output bits of the CCD line sensor in the main scanning direction and a counter that counts the number of lines in the sub scanning direction in synchronization with the reference position of the document table, and based on the determination result. By holding the count values in the main scanning direction and the sub-scanning direction, the position on the document table on which the document is placed and the document size are detected.

FIG. 20 is a view for explaining the method of detecting the position and size of a document according to the proposal, in which a document M is placed on a document table S. x and y indicate the main scanning direction and the sub scanning direction of the line sensor, and SP indicates the reference position on the document table S. In such a state, a point P1 indicating the read image signal initially determined to be the original M, a point P2 closest to the position SP in the x direction determined to be the original M, an x direction determined to be the original M Of the point P3 farthest from the position SP, and the point P4 indicating the read image signal finally determined to be the original M, the coordinates of the four points are obtained by the output bit number counters in the main scanning direction and the sub-scanning direction. Detect position and dimensions. In particular,
The minimum rectangular area that includes all four points and is parallel to x or y is the original area.

[0006]

However, the above-mentioned conventional example has the following problems. That is, even in the above-mentioned conventional example, the erroneous determination cannot be completely prevented.If the erroneous determination occurs, even if it is only one pixel, it is determined that the area larger than the actual original is the original. Will be lost. FIG. 21 is a diagram showing an example of this erroneous determination, which is affected by scratches on the document pressure plate 438,
This is an example in which the area of the original document 402 placed below it is determined to be 439.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and has the following structure as one means for solving the above problems. That is, an image reading device that optically scans a document pressed by a document pressure plate to read an image of the document, and first storage means that stores in advance the characteristics of image information on the surface of the document pressure plate,
Extracting means for extracting the characteristics of the read image information; comparing means for comparing the extraction result of the extracting means with the characteristics stored in the first storage means; and comparing results of the comparing means with the main scanning direction, Based on the accumulating means for accumulating in the sub-scanning direction, the second storing means for storing the accumulating result of the accumulating means, the accumulating result of the accumulating means and the accumulating result stored in the second storing means. The second storage means stores, in advance, the result of the image information obtained by reading the surface of the original pressure plate accumulated by the accumulating means.

[0008]

With the above structure, the comparison result of the characteristic of the read image information and the previously stored characteristic of the image information on the surface of the original plate is accumulated in the main scanning direction and the sub-scanning direction, respectively, and It is possible to provide an image reading device that determines the original area based on the result of the image information obtained by reading the surface of the original pressure plate accumulated by the accumulating means. By canceling the image information displayed, the document pressure plate and the document area can be correctly discriminated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings. In the following description, a copying machine equipped with an image reading apparatus according to an embodiment of the present invention will be described. However, the present invention is not limited to the copying machine and does not depart from the gist of the present invention. Of course, it can be implemented in various modes.

[0010]

[First Embodiment] FIG. 1 is a conceptual diagram of an apparatus showing a configuration example of a copying machine of the present embodiment. In the figure, 401 is a platen glass and 438 is a platen for pressing a document 402 between them. Numeral 403 denotes illumination, which illuminates the original document 402 and the original document 4
The reflected light from 02 passes through mirrors 404 to 406 and is imaged on the CCD 408 by the optical system 407.

Further, 409 is a motor, which is a mirror 40.
4, the mirror unit 410 including the illumination 403 is moved to the speed V
Then, the second mirror unit 41 including the mirrors 405 and 406
By driving 1 at speed V / 2 respectively,
The entire surface of 02 is scanned. An original detection unit 437, which will be described in detail later, determines whether the image read by the CCD 408 belongs to the original 402 and, if the original 402 exists, sends image information to the image processing unit 412.

An image processing unit 412 is an original detection unit 437.
The image information input from is processed and output as a print signal. 413 to 416 are semiconductor lasers and 41, respectively.
7 to 420 are polygon mirrors and 425 to 428, respectively.
Each of the photosensitive drums is a photosensitive drum, and the laser light emitted from the semiconductor laser 413 driven by the print signal from the image processing unit 412 scans the photosensitive drum 425 by the polygon mirror 417 to form a latent image on the photosensitive drum 425. Form. Similarly, the laser beams emitted from the semiconductor lasers 414 to 416 also form latent images on the photosensitive drums 426 to 428, respectively.

Numerals 421 to 424 denote developing units for developing black and white (Y), cyan (C), and magenta (M) toners, respectively, to develop the latent images formed on the corresponding photosensitive drums. To do. On the other hand, 429 to 431 are recording paper cassettes, and 432 is a manual feed tray. And then transported.

A toner image is previously formed on the photosensitive drums 428 to 425 in synchronization with the sheet feeding timing, and the toner image is transferred to the recording sheet in the order of MCYK as the recording sheet is conveyed. The recording paper on which the toner images of the respective colors have been transferred is separated from the transfer belt 434 and conveyed, and after the toner is fixed on the recording paper by the fixing device 435, the recording paper is ejected to the paper ejection tray 436 to obtain a full-color print output. .

FIG. 2 is a block diagram showing an example of the arrangement of the document detecting section 437. In the figure, 104 to 106 are amplifiers, respectively, which amplify the RGB analog image signals input from the CCD 408. Reference numerals 107 to 109 denote A / D converters, respectively, which convert the RGB analog image signals input from the amplifiers 104 to 106 into multivalued RGB digital image signals.

Reference numerals 110 and 111 respectively denote delays. The delay 110 outputs the output of the A / D converter 107 to the delay 1
10 delays the output of the A / D converter 108 by a predetermined amount, so that three CCDs, that is, CCDs 408r, 4 are provided.
Correct the spatial deviation between 08g and 408b. 112
Is a spatial distance calculation circuit, which will be described in detail later.
From the RGB signal, the position in the RGB color space indicated by them and the RG
Calculate the distance to the specified position in B space.

Reference numeral 113 denotes an original determination circuit, which will be described in detail later, and determines whether or not the pixel is on the original 402 from the output of the spatial distance calculation circuit 112. Reference numeral 118 denotes a spatial frequency filter, which will be described later in detail, and outputs a result of performing predetermined filtering on the pixel and its neighboring pixels. 1
Reference numeral 19 denotes an original determination circuit, which will be described in detail later, and determines from the output of the spatial frequency filter 118 whether the pixel is on the original 402.

Reference numeral 120 denotes an AND gate, which is the original decision circuit 11
The logical product of the determination result of No. 3 and the determination result of the document determination circuit 119 is output. Reference numeral 114 denotes an erroneous determination prevention circuit, which will be described in detail later. AND gate circuits 115 to 117 each output a logical product of the image data and the determination result from the erroneous determination prevention circuit 114.

FIG. 3 is a block diagram showing a configuration example of the spatial distance calculation circuit 112. The spatial distance calculation circuit 112 uses the RG
The spatial distance L between the predetermined point (r, g, b) on the B color space and the pixel (R, G, B) is calculated based on the following equation. L ² = (Rr) ² + (Gg) ² + (Bb) ² (1) In FIG. 3, 201 to 203 are registers, and the coordinates (r, g, b) of a predetermined point on the RGB space are preset. Has been done.

Reference numerals 204 to 206 denote subtractors, and the subtractor 204 outputs the absolute value | Rr | of the difference between the input data R of the pixel and the predetermined value R of the register 201. Similarly, the subtractor 205 outputs the absolute value of difference | Gg |, and the subtractor 206 outputs the absolute value of difference | Bb |. 207-209
Are multipliers, and square the values input from the corresponding subtractors 204 to 206.

Reference numeral 210 denotes an adder, which is a multiplier 207-209.
Add the value input from. That is, the adder 210
Outputs the spatial distance L ² . Reference numeral 211 denotes a delay, which is the output of the spatial distance calculation circuit 112 and the spatial frequency filter 118.
Take timing with the output of. FIG. 4 shows a document determination circuit 11
It is a block diagram which shows the structural example of 3.

The original determination circuit 113 determines that the pixel is on the original 402 when the pixel satisfies the following condition. L ² > λ ² (2) In FIG. 4, reference numeral 301 denotes a register in which a value on the right side of the equation (2), that is, a certain distance λ from a predetermined point (r, g, b) is preset.

Reference numeral 302 denotes a comparator, which is a spatial distance calculating circuit 11
The spatial distance L ² input from ² is compared with the distance λ ² input from the register 301, and if the condition of the expression (2) is satisfied, '1' is output. FIG. 5 is a diagram for explaining the principle of document determination based on the tint information. The predetermined point C (r, g, b) is a point representing the document pressure plate 438 in the RGB color space, and
Inside the sphere S of radius λ centered on C (r, g, b), the original pressure plate 43
It is a variation range of the result of reading 8.

That is, in this embodiment, the pixel D (R, G, B)
The spatial distance L between the point C (r, g, b) and the spatial distance calculation circuit 11
By calculating according to 2, the document determination circuit 113 determines whether or not the pixel D is within the sphere S, and when the formula (2) is satisfied, the pixel D is on the document 402. If it is determined that the expression (2) is not satisfied, it is determined that the pixel D is the result of reading the original pressure plate 438.

In the above description, an example in which the spatial distance in the RGB color space is used is described, but the present embodiment is not limited to this, and other examples such as the L ^* a ^* b ^* color space can be used. A spatial distance on the color space may be used. FIG. 6 is a block diagram showing a configuration example of the spatial frequency filter 118. In the figure, 612 is a gray scale conversion circuit, which converts the input RGB pixel data into gray scale pixel data, for example, by the following equation.

Gy = (R + 2G + B) / 4 (3) Reference numerals 601 to 607 are flip-flops F / F, which are synchronized with the pixel synchronization signal CLK and which are grayscale circuits 61.
The pixel data input from 2 is delayed by one pixel each. Reference numeral 608 denotes a multiplier, which multiplies the pixel data (pixel of interest) output from the F / F 604, that is, delayed by four pixels, by "-6", for example.

Reference numeral 609 denotes an adder, which is F / F 601-603,6
05-607 and the sum total of seven pixel data output from the multiplier 608 are output. An absolute value circuit 610 outputs the absolute value of the pixel data input from the adder 609. The output of the absolute value circuit 610 is obtained by processing the vicinity of the target pixel with the filter shown in FIG.

Reference numeral 611 is a low pass filter LPF. FIG. 8 is a block diagram showing a configuration example of the document determination circuit 119. Reference numeral 701 is a register, and a threshold value t for determining whether a document is a document is set in advance. A comparator 702 compares the data F input from the spatial frequency filter 118 with the threshold value t input from the register 701, and outputs “1” when the condition of the following equation is satisfied.

F <t (4) That is, the original determination circuit 119 determines that the pixel is on the original 402 when the pixel satisfies the condition of the expression (4). Next, the principle of document detection based on spatial frequency information will be described. In this embodiment, a striped pattern peculiar to the document pressure plate 438 is extracted from the image data to determine whether the image data belongs to the document pressure plate 438 or the document 402.

FIG. 9 is a view of the document 402 pressed by the document pressure plate 438 as viewed from the mirror unit 410 side. Further, FIG. 10 is a diagram showing an example of the image signal of the line A shown in FIG. 9 in each part of the spatial frequency filter 118, in which the vertical axis represents the luminance and the horizontal axis represents the position on the document. 10A is the output of the grayscale circuit 612, the signal of FIG. 10B is the output of the absolute value circuit 610, and the signal of FIG. 10C is the output of the LPF 611. is there.

When the line A shown in FIG. 9 is read and sent as an image signal to the document detecting section 437, the spatial frequency filter 118 filters the image signal. That is, the spatial frequency filter 118 emphasizes the signal corresponding to the original platen 438, as shown in FIG. Further, there may be a case where a region having a spatial frequency similar to that of the document pressure plate 438 is partially present in the document 402, and the spatial frequency filter 118 removes these as noises by the LPF 611, so that FIG.
An output is obtained, an example of which is shown in (c).

Therefore, in FIG. 10 (c), a signal above the threshold t indicates the original platen 438, and a signal below the threshold t indicates the original 402. In this embodiment, the original 40 is shown.
2 can be detected. 11A and 11B are views for generally explaining the principle of emphasizing the signal from the original platen. FIG. 11A shows the frequency spectrum of a general original platen, and FIG. 11B shows the frequency of a general original plate. FIG. 7C is a diagram showing a spectrum and frequency characteristics of the spatial frequency filter shown in FIG. The horizontal axis of FIG. 11 represents frequency and the vertical axis represents signal intensity. That is, when the image signal of the original platen shown in FIG. 7A is processed by the filter having the characteristic shown in FIG. 6C, the signal in the frequency band in the shaded portion of FIG. . However, in the case of the image signal of the original shown in FIG. 7B, the signal strength distribution in the pass band of the filter is rare, so the signal is not emphasized. The original pressure plate 4
By changing the size of the spatial frequency filter and the value of the coefficient according to the frequency characteristic of the striped pattern of 38,
It can be used with various document pressure plates.

However, as the use of the copying machine progresses, the surface of the original pressure plate 438 is more or less scratched or soiled. In this case, according to the above determination method, the document pressure plate 4
The tint and frequency component of 38 change due to scratches and stains, making it difficult to distinguish from the original 402 by the image signal. If left as it is, the erroneous determination as shown in FIG. 21 occurs, the flaw on the document pressure plate 438 is also determined to be a part of the document 402, and the region 439 indicated by the broken line in the figure is determined to be the document region.

Therefore, in this embodiment, the method shown in FIG. 12 is used to remove the influence of scratches and stains on the original pressure plate 438 to prevent erroneous determination and to extract the correct original area. First, when the power is turned on, the document pressure plate 438 is
Pixels that are erroneously determined to be a document are read in the main scanning direction and the sub-scanning direction by reading the front surface as an image, and the number (the number of erroneously determined pixels) is stored for each coordinate (FIG. 12A). reference). Similarly, when the document 402 is read, the pixels determined to be the document are counted in each of the main scanning direction and the sub-scanning direction (see FIG. 7B), and the erroneous determination stored in advance from the number thereof (document signal number) If the result obtained by subtracting the number of pixels is larger than a predetermined threshold value t, the coordinates are included in the original area (see FIG. 7C). After that, Figure 2
0, the points P1, P2, P3 and P4
Then, the position and size of the original 402 are detected from the coordinates of these four points.

FIG. 13 is a block diagram showing a configuration example of the erroneous determination prevention circuit 114. In the figure, reference numeral 1901 is a main scanning direction counter, 1902 is a sub scanning direction counter, and a memory corresponding to the number of pixels in each direction of the platen glass 401 is prepared as a counter, and the pixel is an original. When it is determined, it functions as a counter by adding 1 to the value of the memory corresponding to the coordinate.
For example, when it is determined that the i-th pixel in the main scanning direction from the reference position SP and the j-th pixel in the sub-scanning direction are originals, the counter x _i of the main scanning counter 1901 corresponding to the i-th pixel,
Counter y of sub-scanning counter 1902 corresponding to the j-th pixel
1 is added to _j and. The counter to be added is controlled by an address signal given from a CPU (not shown).

1905-1910, 1918 and 19
Reference numeral 20 is a tri-state gate, which outputs an input signal when the gate signals OE2, OE1, OE3, OE2 ', OE1', OE3 ', OE6 and OE7 supplied to them are' 0 '. 190
Reference numerals 3 and 1904 denote memories for respectively storing the above-described erroneous determination pixel numbers input via the tristate gates 1906 and 1909 in the main scanning direction and the sub-scanning direction. Note that these memories are synchronized by an address signal given by a CPU (not shown).

1911 and 1912 are subtractors, respectively.
The difference between the number of original signals input via the tristate gates 1905 and 1908 and the number of erroneous determination pixels input via the tristate gates 1907 and 1910, respectively, is calculated in the main scanning direction and the sub-scanning direction. This is for calculating each direction for each coordinate.

Numerals 1913 and 1914 are registers, and the threshold value t per line is set in each of the main scanning direction and the sub scanning direction. Reference numerals 1915 and 1916 denote comparators that determine whether or not the line is included in the original area in the main scanning direction and the sub-scanning direction, respectively, by comparing with thresholds t set in the registers 1913 and 1914. That is, the comparators 1915 and 1916
Outputs a signal "1" indicating that the line is included in the original area if the values input from the subtracters 1911 and 1912 are larger than the threshold value t set in the registers 1913 and 1914.

Reference numeral 1917 denotes an area extracting unit, which stores the memory 1903, 1 in response to an address signal given from a CPU (not shown).
In synchronization with the output of 904, the original area is extracted based on the maximum and minimum coordinates of the lines in the main scanning direction and the sub-scanning direction that are determined to be included in the original area, and the address information is output. A determination unit 1919 is a CPU (not shown) based on the address information of the document area input from the area extraction unit 1917 via the tristate gate 1918.
Then, it is determined whether or not the pixel indicated by the address signal given by is in the original area. This determination result is output via the tri-state gate 1920.

FIG. 14 is a flow chart showing an example of an erroneous determination prevention procedure when the power is turned on. In the figure, when the power is turned on, initial setting of the apparatus itself is executed in step S1. For example, when the mirror unit 410 or the like is set at the home position, the main scanning direction counter 1
901, sub-scanning direction counter 1902, memory 190
3,1904 is initialized to 0.

Then, in step S2, the control signal of the tristate gate of the erroneous determination prevention circuit 114 is changed to OE1 =
'0', OE2 ＝ '1', OE3 ＝ '1', OE1 '＝' 0 ', OE2' ＝
Set to "1", OE3 '= "1", OE6 = "1", OE7 = "1", start scanning in step S3 to scan one line, and in step S4, make an error by the method described above. When a determination pixel is detected and an erroneous determination pixel is detected, 1 is added to the memory corresponding to the coordinates of the pixel of each of the main scanning direction counter 1901 and the sub scanning direction counter 1902 in step S5. If no misjudged pixel is detected, the process jumps to step S6.

Subsequently, in step S6, it is determined whether or not the determination for one line is completed.
4. If it is completed, the process proceeds to step S7. 1
When the line determination is completed, it is determined in step S7 whether or not the scanning of the entire surface is completed. If it is not completed, the process returns to step S3, and if it is completed, the process proceeds to step S8.

When the scanning of the entire surface is completed, in step S8, the control signal of the tri-state gate is changed to OE1 =
'1', OE2 ＝ '0', OE3 ＝ '0', OE1 '＝' 1 ', OE2' ＝
'0', OE3 '=' 0 ', OE6 =' 0 ', OE7 =' 1 'are set to complete the erroneous determination prevention procedure, and this embodiment waits in a copyable state. The values of the main scanning direction counter 1901 and the sub scanning direction counter 1902 are stored in the memory 19 respectively.
It is stored in 03,1904.

FIG. 15 is a flow chart showing an example of an erroneous determination prevention procedure at the time of executing a copy. In the figure, when the copy start key or the like is pressed, step S2
At 1, the device itself is initialized. For example, the mirror unit 410 or the like is set to the home position, and the main scanning direction counter 1901 and the sub scanning direction counter 1902 are set.
Is initialized to 0.

Then, in step S22, the control signal of the tristate gate of the erroneous determination prevention circuit 114 is changed to OE1 =
'1', OE2 ＝ '0', OE3 ＝ '0', OE1 '＝' 1 ', OE2' ＝
Set "0", OE3 '= "0", OE6 = "0", OE7 = "1", start scanning in step S23 to scan one line, and in step S24, by the method described above,
It is determined whether or not each pixel of the read image signal is a document. If the determination result is "original", the main scanning direction counter 1901 and the sub scanning direction counter 190 are checked in step S25.
2 1 is added to the memory corresponding to the coordinates of each determination pixel. If the determination result is not "original", the process jumps to step S26.

Subsequently, in step S26, it is determined whether or not the determination for one line is completed. If not completed, the process returns to step S24, and if completed, the process proceeds to step S27. When the determination of one line is completed, in step S27,
It is determined whether or not the scanning of the entire surface is completed. If it is not completed, the process returns to step S23, and if it is completed, the process proceeds to step S28.

When the scanning of the entire surface is completed, in step S28, from the values of the main scanning direction counter 1901 and the sub scanning direction counter 1902 and the values stored in the memories 1903 and 1904 when the power is turned on,
The document area is extracted by the method described above, and the coordinates of the four corners are obtained. Then, in this embodiment, the scan is performed again to obtain the image signal in the original area.

In step S29, the initialization of the apparatus itself is executed again. For example, when the mirror unit 410 or the like is set at the home position, the main scanning direction counter 190
1, the sub-scanning direction counter 1902 is initialized to 0.
Then, in step S30, the control signal of the tri-state gate of the misjudgment prevention circuit 114 is changed to OE1 = '1', OE2 =
'1', OE3 ＝ '1', OE1 '＝' 1 ', OE2' ＝ '1', OE3 '＝
Set "1", OE6 = "1", OE7 = "0", start scanning in step S31 to scan one line, and in step S32, set each pixel of the read image signal in the original area. It is determined whether or not it is included. If the determination result is "inside the area", "1" is output in step S33, and if it is not "inside the area", "0" is output in step S34.

Subsequently, in step S35, it is determined whether or not the determination of one line is completed. If not completed, the process returns to step S32, and if completed, the process proceeds to step S36. When the determination of one line is completed, in step S36,
It is determined whether or not the scanning of the entire surface is completed. If it is not completed, the procedure returns to step S31, and if it is completed, the erroneous determination prevention procedure is completed.

Although scratches and stains on the original pressure plate 438 have been mentioned in the above description and drawings, the same applies to scratches and stains on the surface of the original platen glass 401.
Further, the timing of storing the determination result of the document pressure plate 438 is not limited to the time of turning on the power, and may be, for example, the time of resetting in the present embodiment or any time point instructed by the operator.

As described above, according to this embodiment,
In the initial setting, the image on the surface of the original pressure plate is read and the characteristics of the image are stored. Therefore, the characteristics of the surface of each original pressure plate can be stored to prevent erroneous determination, and the erroneous determination pixels are canceled based on the stored features. However, since the original area is extracted, the original pressure plate and the original area can be correctly discriminated.

[0052]

[Second Embodiment] An image reading apparatus according to a second embodiment of the present invention will be described below. In the second embodiment, the first
About the same configuration as the embodiment, the same reference numerals are given,
Detailed description thereof will be omitted. FIG. 16 is a block diagram showing a configuration example of the spatial circumference distance calculation circuit 112 of this embodiment.

In the figure, reference numerals 221 to 223 are lookup table LUTs, which are constituted by ROMs, for example. LUT221
Is the signal input to the address terminal A from the subtractor 204 |
The signal (Rr) ² corresponding to Rr | is output from the data terminal D. Similarly, the LUT 222 outputs the signal (Gg) ² to the LUT 223.
Outputs the signal (Bb) ² . As described above, according to the present embodiment, in addition to the same effect as the first embodiment, the square calculation in the spatial distance calculation circuit 112 is performed by the RO instead of the multiplier.
Since it is realized by LUT such as M, it has the effect of further reducing the cost.

[0054]

[Third Embodiment] An image reading apparatus according to a third embodiment of the present invention will be described below. In the third embodiment, the first
About the same configuration as the embodiment, the same reference numerals are given,
Detailed description thereof will be omitted. Obviously, each original plate has different scratches and stains, but the colors are slightly different. Therefore, it is difficult to determine the tint representative point C and the tint variation range λ in the color space that represents all the original pressure plates. That is, as shown in FIG. 17, a sphere S _A (representative point C (r, g, b), variation range λ) for the original pressure plate A, and a sphere S _B (representative point for the original pressure plate B). C '(r', g ',
b ') and variation range λ') are optimal.

Therefore, in this embodiment, based on the image signal of the document pressure plate 438 read when the power is turned on, the document pressure plate 4 is read.
By setting the representative point C of 38 and the variation range λ, it is intended to correspond to each original pressure plate. That is, the distribution of the image signals of the document pressure plate 438 in the color space is examined, and the point where the distribution is most concentrated is set as the representative point C,
The variation range λ is determined based on the standard deviation values of R, G, and B respectively.

FIG. 18 is a block diagram showing a configuration example of the third embodiment. The present embodiment is obtained by adding two tristate gates, a data operation circuit and a threshold value calculation circuit, the details of which will be described later, to the configuration of the first embodiment shown in FIG. However, the description of other configurations will be omitted. In FIG. 18, 131 and 132 are tristate gates, and the signals OE4 and OE5 are "0".
In the case of, the signal input is output. Signals OE4 and OE
5 becomes '0' and '1' immediately after turning on the power,
After the representative point C and the variation range λ are set, they become '1' and '0', respectively.

A data counting circuit 133 counts, for each of the RGB data input to the tri-state gate 132, the number of data of each level from 0 to 255, for example, and outputs the highest frequency level of each RGB data. That is, the representative point C (r, g, b) is output. That is,
The data counting circuit 133 includes, for example, 256 counters for each of the RGB data, and finally counts up the counter according to the value of the data, so that finally,
The number of each RGB data of the entire input image is counted.

A variation range calculator 134 determines the variation range λ ² based on the maximum standard deviation value of the RGB data calculated from the counting result of the data counting circuit 133. The output of the data counting circuit 133 is the registers 201 to 203 shown in FIG.
Respectively, and the output of the variation range calculation unit 134 is set in the register 301 shown in FIG.

FIG. 19 is a flow chart showing an example of an erroneous determination prevention procedure when the power is turned on. In the figure, when the power is turned on, the initial setting of the apparatus itself is executed in step S11, for example, the mirror unit 410 is set to the home position, and the main scanning direction counter 1
901, sub-scanning direction counter 1902, memory 190
3,1904 is initialized to 0.

Then, in step S12, the control signals of the tri-state gates 131 and 132 are changed to OE4 = '0', OE5 =.
Set to "1", and in step S13, scanning is started to scan one line. Then, step S14
Then, the data counting circuit 133 counts the data distribution of the read document pressure plate 438.

Subsequently, in step S15, it is determined whether or not counting of one line is completed, and if not completed, the process returns to step S14, and if completed, the process proceeds to step S16. When the counting of one line is completed, step S16
Then, it is determined whether or not the scanning of the entire surface is completed. If it is not completed, the process returns to step S13, and if it is completed, the process proceeds to step S17.

When the scanning of the entire surface is completed, the registers 201 to 2 of the spatial distance calculating circuit 112 are processed in step S17.
03, the representative point C is set, the variation range λ ² is set in the register 301 of the document determination circuit 113 in step S18, and the tristate gate 13 is set in step S19.
The control signals of 1,132 are set to OE4 = '1' and OE5 = '0'.

As described above, the representative point C in the registers 201 to 203 of the spatial distance calculation circuit 112 is set to the original determination circuit 1.
The variation range λ ² is set in the register 301 of No. 13, and the preparation for detecting the erroneously determined pixels of the document pressure plate 438 is completed. Subsequently, in step S20, the document pressure plate 438 is scanned again to detect erroneous determination pixels of the read document pressure plate 438, and then the erroneous determination prevention procedure ends. In addition, the same step
Since it is similar to steps S2 to S8 shown in FIG. 14, description thereof will be omitted.

As described above, the misjudgment pixels of the document pressure plate 438 are stored in the memories 1903 and 1904 of the misjudgment prevention circuit 114, and the preparation for the misjudgment prevention is completed. As described above, according to the present embodiment, in addition to the same effects as the first embodiment, it is not necessary to previously obtain and set the representative value C of the document pressure plate 438 and its variation range λ. Even if the original pressure plate 438 is replaced due to repair or the like, the representative value C and its variation range λ can be set correctly.

The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0066]

As described above, according to the present invention, the comparison results of the characteristics of the read image information and the previously stored characteristics of the image information on the surface of the original pressure plate are accumulated in the main scanning direction and the sub scanning direction, respectively. It is possible to provide an image reading apparatus that determines a document area based on the result of the image information obtained by previously reading the surface of the document pressure plate accumulated by the accumulating unit. For example, a scratch or stain on the document pressure plate is read. This has the effect of canceling image information that is erroneously determined as the original area and correctly determining the original pressure plate and the original area.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus showing a configuration example of a copying machine equipped with an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a document detection unit according to the present exemplary embodiment.

FIG. 3 is a block diagram showing a configuration example of a spatial distance calculation circuit in FIG.

FIG. 4 is a block diagram showing a configuration example of a document determination circuit 113 in FIG.

FIG. 5 is a diagram illustrating a principle of document determination based on tint information according to the present exemplary embodiment.

FIG. 6 is a block diagram showing a configuration example of the spatial frequency filter of FIG.

7 is a diagram showing the shape of the spatial frequency filter of FIG.

FIG. 8 is a block diagram showing a configuration example of a document determination circuit 119 of FIG.

FIG. 9 is a view of a document pressed by a document pressure plate as viewed from the mirror unit side.

10 is a diagram showing an example of an image signal in each unit of the spatial frequency filter of FIG.

FIG. 11 is a diagram for more generally explaining the principle of emphasizing a signal from the document pressure plate of the present embodiment.

FIG. 12 is a diagram illustrating a method of removing the influence of scratches and stains on the document pressure plate according to the present embodiment.

FIG. 13 is a block diagram showing a configuration example of an erroneous determination prevention circuit in FIG.

FIG. 14 is a flowchart showing an example of an erroneous determination prevention procedure when the power is turned on according to the present embodiment.

FIG. 15 is a flowchart showing an example of an erroneous determination prevention procedure at the time of executing copying according to the present embodiment.

FIG. 16 is a block diagram showing a configuration example of a space circumferential distance calculation circuit according to a second embodiment of the present invention.

FIG. 17 is a diagram showing that the representative color point is different depending on the original pressure plate.

FIG. 18 is a block diagram showing a configuration example of a third embodiment according to the present invention.

FIG. 19 is a flowchart showing an example of an erroneous determination prevention procedure when the power is turned on in the third embodiment.

FIG. 20 is a diagram illustrating a proposed method of detecting the position and size of a document.

FIG. 21 is a diagram showing an example of erroneous determination.

[Explanation of symbols]

 401 Document Platen Glass 402 Document 437 Document Detection Unit 438 Document Pressure Plate 112 Spatial Distance Calculation Circuit 113 Document Determination Circuit 114 Misjudgment Prevention Circuit 118 Spatial Frequency Filter 119 Document Determination Circuit 120 AND Gate 133 Data Counting Circuit 134 Variation Range Calculation Unit

Claims (3)

[Claims] 1. An image reading device for optically scanning a document pressed by a document pressure plate to read an image of the document, the first image reading device pre-storing characteristics of image information on the surface of the document pressure plate.
Storage means, extraction means for extracting the characteristics of the read image information, comparison means for comparing the extraction result of the extraction means with the characteristics stored in the first storage means, comparison results of the comparison means Accumulating means for accumulating in each of the main scanning direction and the sub-scanning direction, second storage means for storing the accumulation result of the accumulating means, accumulation result of the accumulating means and accumulation stored in the second storing means. The second storage means stores, in advance, a result accumulated by the accumulating means with respect to image information obtained by reading the surface of the original pressure plate. Image reading device. 2. The first storage means stores tint information and spatial frequency information on the surface of the original pressure plate, and the extracting means extracts tint information and spatial frequency information of image information. The image reading apparatus according to claim 1. 3. The image according to claim 1, wherein the determination unit determines the document area based on a difference between the cumulative result of the cumulative unit and the cumulative result stored in the second storage unit. Reader.