JP3584658B2 - Document size detector - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a document size detecting device such as a digital copying machine.
[0002]
[Prior art]
In document size detection in a conventional copying machine or the like, a difference between a pixel of interest and a pixel ahead of a predetermined pixel is calculated in order to prevent erroneous detection due to the influence of noise or dust as disclosed in Japanese Patent Application Laid-Open No. 2-277038. Is determined. The above-described determination is performed each time the next pixel comes, and when the number of times exceeding the threshold value has continuously occurred a predetermined number of times, the position is set as the document edge. The document size is detected based on the result. That is, the difference between the white pixel of the document and the black pixel outside the document several pixels ahead is determined, and it is confirmed that the threshold value is exceeded. If the state occurs a predetermined number of times in a row, the position is defined as the document edge. Algorithm. Here, in order to detect a document edge by the above method, white pixels must be continuous at the edge of the document and black pixels must be continuous outside the document.
[0003]
[Problems to be solved by the invention]
In the above-mentioned conventional method, it is conceivable to increase the number of times that the threshold value must be continuously exceeded in order to reduce the influence of noise and dust. However, if the number of times that the threshold must be continuously exceeded is increased, the number of pixels that must continuously exceed the threshold increases by the increased number. That is, the number of white pixels that must be at the edge of the document increases. In this case, when characters or lines are present in pixels that must continuously exceed the threshold value, that is, there is a problem that an edge cannot be detected for a document having characters or lines at the edge of the document. .
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a document size detecting device that does not cause erroneous detection due to noise or dust when detecting a document edge.
It is another object of the present invention to provide a document size detecting device capable of correctly detecting a document edge even for a document having characters, lines, or the like at the document end.
[0005]
Means and action for solving the problem
According to the present invention (claim 1), a pixel of interest (6-1 in FIG. 6), a pixel (6-2 in FIG. 6) a predetermined number of pixels (M pixels) before the pixel of interest, and an equal interval (L Calculation means (4-2 in FIG. 4, 6-6 to 6 in FIG. 6) for calculating respective differences from a plurality of pixels (6-3, 6-4,... In FIG. 6) sequentially positioned at pixel intervals). -9) and comparing means (4-3 in FIG. 4 and 6-10 to 6--6 in FIG. 6) for comparing each difference obtained by the arithmetic means with a threshold and detecting a case where all the differences exceed the threshold. 13, 6-14) and when all the differences exceed the threshold value as a result of the comparison by the comparing means, the target pixel position is set as a temporary edge, and the position of the target pixel is shifted in the main scanning direction and the temporary edge position when if the all the difference obtained by the comparing means exceeds the threshold value has continued for a predetermined number of times Characterized by comprising an edge detection means for detecting a document edge (4-6 of FIG. 4).
According to the present invention, since there are a plurality of pixels that have a difference from the pixel of interest by the calculating means and a wide range, noises and noises can be increased without increasing the predetermined number of times (N in FIG. 7) in which pixels exceeding the threshold value appear continuously. It can be less susceptible to garbage. In addition, since a plurality of pixels that take the difference from the target pixel are arranged at equal intervals, all the pixels within the range where the pixel that takes the difference exists need not have the same data continuously. When a pixel different from the original background such as a line is included, the original edge can be detected when the pixel comes to a section where the density comparison is not performed.
[0006]
Further, the present invention (claim 2) provides a calculation means (5-2 in FIG. 5) for obtaining a difference between a target pixel and a previous pixel, and a comparison for detecting a case where the difference obtained by the calculation means exceeds a threshold value. Means (5-3 in FIG. 5) , an address counter (5-4 in FIG. 5) indicating the position of the target pixel in the main scanning direction, and a predetermined value for holding the value of the address counter when the difference exceeds a threshold value. A shift register (5-5 in FIG. 5) having a number of storage capacities, and a difference between a maximum address and a minimum address among a predetermined number of addresses held in the shift register is within a predetermined range. And edge detecting means (5-6 in FIG. 5) for setting the latest address to the document edge .
According to the present invention, when a density change exceeding a threshold value within a predetermined range is more than a predetermined number of times, the portion is detected by the edge detection means as the document edge, whereby the edge detection means of the invention (claim 1) is detected. It is possible to detect a document edge having many lines or many fine characters at the document end which is difficult to detect.
[0007]
Further, the present invention (claim 3) is a document size detecting device having a configuration in which the two inventions (claims 1 and 2) are combined. That is, the present invention is obtained by (1) first arithmetic means for calculating respective differences between a pixel of interest and a plurality of pixels equidistant from a pixel preceding by a predetermined number of pixels, and the first arithmetic means. A first comparing means for comparing each difference with a threshold value and detecting a case where all the differences exceed the threshold value; the temporary edge position when if the pixel position is a temporary edge, all of said difference obtained by said comparing means and said calculating means being transferred to the position of the pixel of interest in the main scanning direction exceeds a threshold value has continued for a predetermined number of times A first document edge detecting means having a first edge detecting means for detecting an image as a document edge, (2) a second calculating means for calculating a difference between a target pixel and a previous pixel, and a second calculating means thereof Exceeds the threshold Second comparison means for detecting a case, the address counter indicating the position of the target pixel in the main scanning direction, when the difference exceeds a threshold value, holds the value of the address counter, a shift register having a storage capacity of a predetermined number And a second edge detecting means for setting the latest address to a document edge when a difference between a maximum address and a minimum address among a predetermined number of addresses held in the shift register falls within a predetermined range. And (3) size discriminating means for performing size detection using the larger one of the two document edge positions detected by the first and second document edge detecting means as a document edge. It is characterized by having.
According to the present invention, the larger one of the two document edges detected by the first document edge detecting means and the second document edge detecting means is determined as the document edge by the size determining means, so that various types of documents can be processed. Document size can be accurately detected.
[0008]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 is a side view of an image reading unit of a copying machine that realizes the present invention.
The image reading unit includes a document table 1 for placing a document, a document holder 2 having a white document cover surface, and a sensor 10 including a switch for turning on and off in a closed state by opening and closing the document holder 2. An open / closed state detection sensor 11 that is turned on when the document holder 2 is closed is attached.
Further, inside the image reading unit, a light source 3 for irradiating the image surface of the original 9 with light while moving in the sub-scanning direction indicated by the arrow A, and mirrors 4, 5, 6 and lenses for reflecting light reflected on the image surface And a CCD image sensor 8 which receives the light via an LED 7 and converts the light into an electric signal.
A document size detection unit, which will be described later with reference to FIG. 3, is provided at a stage subsequent to the CCD image sensor 8, and detects the presence or absence and size of the document based on an image signal obtained by scanning with the light source 3.
[0009]
When a document is to be placed on the document table 1 and the document press is to be closed, at a predetermined angle, the actuator attached to the mounting portion of the document press is pressed and the sensor (PH1) 10 is turned on. When the sensor 10 is turned on, reading of the original in a state in which the original pressing is closed is performed. In this closed state, the reflection of light from the white document cover surface of the document holder 2 does not reach the CCD image sensor 8. Therefore, a portion of the original 9 that is off the surface is detected as black, and a portion of the original surface where there is no printing has a detection value corresponding to the density of the background of the original. In the case of a document whose normal background is printed on white paper, a portion of the document surface where no printing is performed is detected as white. The reading of the original in the closed state of the original pressing is performed in order to obtain the size of the original whose background is white.
[0010]
When the document holder 2 is completely closed, the sensor (PH2) 11 is turned on. After the sensor 11 is turned on, the original is read for the second original size detection. In this case, a portion of the document 9 that is off the surface is detected as white, and a portion of the document surface that is not printed has a detection value corresponding to the density of the background of the document. The reading of the document in the fully closed state of the document pressing is performed in order to determine the size of the document using paper with a colored background.
The document size detection unit extracts a document edge from each image data obtained in each process of document reading scanning for the first and second document size detections.
[0011]
Next, a configuration and an operation for detecting the document size from the image data read in the closed state and the fully closed state of the above-described document presser 2 will be described with reference to FIGS. 1, 4, and 5. FIG. As shown in FIG. 1, the document size detection device detects edges by two detection devices, a first document edge detection unit 1-1 and a second document edge detection unit 1-2. The first document edge detection unit 1-1 attempts to detect an edge portion from a difference between image data obtained by reading an unprinted margin around the document surface and image data read from a portion outside the document surface. The second document edge detection unit 1-2 determines whether characters or lines are drawn or dust is attached to the margin around the document surface, and the margin portion and the portion outside the document surface. This is to enable detection even when an edge cannot be detected.
[0012]
First, as shown in FIG. 4, the first document edge detection unit 1-1 is configured by a D flip-flop for holding data necessary for obtaining a difference between input image data and a target pixel. The subtracted data delay unit 4-1 calculates a difference between each pixel of interest and a plurality of pixels equally spaced from the pixel before the predetermined number of pixels, and compares each subtraction result with a threshold value. A comparator 4-3 for judging whether all the differences exceed the threshold value, and a counter 4 for counting how many consecutive times that all the differences exceed the threshold value in the comparator 4-3. -4, an address counter 4-5 that counts the number of pixels of the target pixel since the rise of the main scanning synchronization signal. If the counter 4-4 generates a predetermined number of times, the position of the target pixel is determined. Tsu is constituted by the edge detection unit 4-6 to di.
[0013]
The data of the pixels 6-2, 6-3, 6-4,... Taking the difference from the target pixel 6-1 include the pixel 6-2 before the target pixel 6-1 and the pixel 6-2, as shown in FIG. Data of Q-1 pixels at intervals of L pixels from 6-2, ie, a total of Q pixels. These pixels are extracted from a predetermined delay output terminal provided in the data delay section 4-1. As shown in FIG. 6, the subtractor 4-2 in FIG. 4 includes subtractors 6-6 to 6-9 for calculating a difference between the Q pixel and the target pixel. The comparator 4-3 in FIG. 4 includes the comparators 6-10 to 6-13 and the AND circuit 6-14 in FIG.
Outputs of the subtractors 6-6 to 6-9 are supplied to inputs of the comparators 6-10 to 6-13, respectively, and are compared with threshold values. The comparators 6-10 to 6-13 output "H" when the output of the subtractor exceeds the threshold. The output of each of the comparators 6-10 to 6-13 is applied to an AND circuit 6-14, and when all the outputs of the comparators are at "H", "H" is output. That is, the comparator 4-3 outputs “H” when all the differences between the Q data and the target pixel exceed the threshold value, and outputs “L” when at least one of the differences does not exceed the threshold value.
[0014]
The counter 4-4 counts the number of times the output of the comparator 4-3 is continuously "H". When the value of the counter 4-4 reaches a predetermined value, the counter 4-4 outputs "H", and otherwise outputs "L". The edge detection unit 4-6 holds the value of the address counter 4-5 when the output of the counter 4-4 becomes "H". The held value of the address counter 4-5 is updated as needed when the output of the counter 4-4 becomes "H", and is determined as a document edge when the main scanning synchronization signal becomes "L". It is a mechanism that works.
[0015]
The edge detection described above is performed twice, as described above, in a state in which the document press is almost closed and a state in which the document press is fully closed. In the state where the original is closed, the edge of the original with white background can be detected, and in the state where the original is fully closed, the edge of the original with black background can be detected. The edge detection unit 4-6 can detect a document edge that could not be detected by using the larger one of the two document edges obtained in the first and second detections as the document edge. Therefore, in this embodiment, the edge can be detected regardless of the density of the background of the document.
[0016]
Further, according to the first document edge detection unit 1-1, as shown in FIG. 7, since there are a plurality of pixels that take a difference from the pixel of interest and in a wide range, the number of times pixels exceeding the threshold value appear continuously (see FIG. 7). 7) can be made less susceptible to noise and dust without increasing N). In addition, since a plurality of pixels that take the difference from the target pixel are arranged at equal intervals, all the pixels within the range where the pixel that takes the difference exists need not have the same data continuously. Even if a pixel different from the original background, such as a line, is included, the original edge can be detected when the pixel comes to the section where the density comparison is not performed in FIG.
[0017]
Next, as shown in FIG. 5, the second document edge detection unit 1-2 includes a data delay unit 5-1 for holding data of a pixel immediately before the pixel of interest, a pixel of interest and a pixel preceding the pixel. Subtractor 5-2 which takes the difference from the data, a comparator 5-3 which compares the difference with a threshold, and an address counter 5-4 which counts the number of pixels of the pixel of interest since the rise of the main scanning synchronization signal. If the difference exceeds the threshold value, the value of the address counter 5-4 is held, and the shift register 5-5 and the shift register 5 hold the latest predetermined number of addresses whose difference has exceeded the threshold value. If the difference between the maximum address and the minimum address among the predetermined number of addresses of -5 is within a predetermined range, the edge detection means 5-6 uses the latest address as the document edge.
[0018]
The data delay unit 5-1 takes out the target pixel and the preceding pixel, obtains the difference between them by the subtracter 5-2, compares the obtained difference with a predetermined threshold by the comparator 5-3, When there is a difference, the value of the address counter 5-4 (which indicates the position in the main scanning direction by counting the main scanning synchronization signal) is input to the shift register 5-5 by the comparison output. The shift register 5-5 performs a shift operation by an appropriate synchronizing signal, and when a comparator output indicating a difference equal to or larger than a threshold value from the comparator 5-3 frequently occurs, the values of a large number of address counters are held and compared. Where the output of the device is not so large, the number of values of the address counter in the shift register 5-5 is reduced. The edge detection unit 5-6 calculates the difference between the maximum and minimum address counter values held in the shift register 5-5, and if the difference falls within a predetermined range, the latest address is determined. It is held as a document edge. By repeating such an operation, the document edge is determined when the main scanning synchronization signal becomes "L" while updating the document edge.
[0019]
The fact that the difference between the maximum address and the minimum address falls within the predetermined range means that, as shown in FIG. That is, the change occurs more than a predetermined number of times. Such an occurrence occurs more than a predetermined number of times in a portion of a document where characters are printed. In other words, the second edge detection unit 3-2 performs a process of finding the outermost portion of the printed portion of the character while detecting the printed portion of the character, and determining a nearby point as the document edge. You are doing it. For an original having many lines or fine characters at the end of the original, if a density change exceeding a threshold value within a predetermined range is more than a predetermined number of times, a second detection device using that portion as the document edge Since the document edge is searched while paying attention to characters and lines, the document edge that is difficult to be detected by the first detection device can be detected.
[0020]
The size discriminating section 1-3 in FIG. 1 determines the larger one of the two document edges output from the first edge detecting section 1-1 and the second edge detecting section 1-2 as the document edge. A document edge that could not be detected by one can be detected.
[0021]
【The invention's effect】
According to the present invention (claim 1), since there are a plurality of pixels that have a difference from the pixel of interest by the arithmetic means and in a wide range, noise and dust are not increased without increasing the predetermined number N in which pixels exceeding the threshold value appear continuously. Can be hardly affected. In addition, since a plurality of pixels that take the difference from the target pixel are arranged at equal intervals, all the pixels within the range where the pixel that takes the difference exists need not have the same data continuously. When a pixel different from the original background such as a line is included, the original edge can be detected when the pixel comes to a section where the density comparison is not performed.
[0022]
Further, according to the present invention (claim 2), when a density change exceeding a threshold value within a predetermined range is more than a predetermined number of times, the portion is detected as a document edge, so that there are many lines at the document end. A document edge having many small characters can be detected.
[0023]
Further, according to the present invention (claim 3), the two different edge detection methods of the first document edge detecting means and the second document edge detecting means are used, and the larger of the two detected document edges is used as the document edge. By using the edge, a document edge that cannot be detected by only one of them can be detected, and the document size can be accurately detected.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a document size detecting device according to an embodiment of the present invention; FIG. 2 is a diagram showing a configuration of a main part of an image reading unit of a copying machine; FIG. FIG. 4 is a diagram showing a configuration of a first document edge detection unit. FIG. 5 is a diagram showing a configuration of a second document edge detection unit. FIG. 6 is a diagram showing a first document edge detection. FIG. 7 is a diagram for explaining the operation of the first document edge detector. FIG. 8 is a diagram for explaining the operation of the second document edge detector. Description】
1-1: First document edge detecting section, 1-2: Second document edge detecting section, 1-3: Size discriminating section, 4-1: Data delay section, 4-2: Subtractor, 4-3: Comparison 4-4 counter, 4-5 address counter, 4-6 edge detector, 5-1 data delay unit, 5-2 subtractor, 5-3 comparator, 5-4 address Counter, 5-5... Shift register, 5-6.

Claims (3)

Calculating means for calculating a difference between the pixel of interest and a pixel which is a predetermined number of pixels before the pixel of interest and a plurality of pixels sequentially positioned at equal intervals from the pixel;
A comparing unit that compares each difference obtained by the arithmetic unit with a threshold, and detects a case where all the differences exceed the threshold;
When all the differences exceed the threshold value as a result of the comparison by the comparing unit, the target pixel position is set as a temporary edge, and the position of the target pixel is shifted in the main scanning direction, and the position obtained by the arithmetic unit and the comparing unit is obtained. A document size detection device comprising: edge detection means for detecting the temporary edge position as a document edge when a predetermined number of times when all the differences exceed the threshold value . Calculating means for calculating the difference between the target pixel and the previous pixel;
Comparing means for detecting a case where the difference obtained by the calculating means exceeds a threshold value;
An address counter representing the position of the pixel of interest in the main scanning direction;
A shift register that holds a value of an address counter when the difference exceeds a threshold and has a predetermined number of storage capacitors;
Edge detection means for setting the latest address to a document edge when a difference between a maximum address and a minimum address of a predetermined number of addresses held in the shift register is within a predetermined range. An original size detecting device, comprising: First arithmetic means for calculating respective differences between the target pixel and a plurality of pixels spaced at equal intervals from the pixel before the predetermined number of pixels, and comparing each difference obtained by the first arithmetic means with a threshold value; A first comparing means for detecting a case where all the differences exceed the threshold value; and a case where all the differences exceed the threshold value as a result of the comparison by the first comparing means, the target pixel position is set as a temporary edge, and the main scanning is performed. Detecting the temporary edge position as a document edge when a predetermined number of times that all of the differences obtained by the calculation means and the comparison means exceed a threshold while moving the position of the pixel of interest in the direction, First document edge detecting means having edge detecting means;
A second calculating means for calculating a difference between the target pixel and the previous pixel; a second comparing means for detecting a case where the difference obtained by the second calculating means exceeds a threshold value; An address counter that indicates the position, a shift register that holds a value of the address counter when the difference exceeds a threshold, and has a predetermined number of storage capacities; and a maximum number of addresses of a predetermined number of addresses held in the shift register. When the difference between the address and the smallest address falls within a predetermined range, a second document edge detecting means having second edge detecting means using the latest address as a document edge ;
Before SL document size detection apparatus characterized by comprising a size determining means for performing the size detected as should the original edge larger of the two document edge position detected by the first and second document edge detection means.

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