JP4855017B2 - Document size detection apparatus, image reading apparatus, and image forming apparatus - Google Patents

Description

The present invention relates to a document size detection device that detects a document size at a document reading unit, an image reading device including the document size detection device, and an image of a digital copying machine, a facsimile, a digital multifunction peripheral, or the like including the image reading device. about the formation equipment.

  In a conventional document reading apparatus, an infrared sensor is used as a method for detecting a document size at the time of reading a pressure plate. However, in recent years, a method for detecting a document size using a line sensor for reading a document is used without using an infrared sensor. It has become like this. When detecting the document size, not only the main scanning size but also the sub-scanning size is required. However, when the document size detection in the sub-scanning direction is performed, it is necessary to pre-scan the document surface. In this case, since it affects the scanning speed and the like, the document size detection in the sub-scanning direction is actually performed by the infrared sensor as in the past, and the method of using the line sensor read data becomes mainstream only in the main scanning direction detection. ing.

  As conventional techniques related to a document size detection method using a line sensor for reading a document, for example, the inventions described in Patent Documents 1 to 3 are known. All of these prior arts employ a method of detecting only the main scanning direction.

  Among them, the method described in Patent Document 1 judges the size of the document in the main scanning direction assuming that the inside of the document is white and the outside of the document is black when the pressure plate is opened, but if black comes in the document, The line sensor reading position is moved, and the size is detected by a white line in the document.

  The method described in Patent Document 2 is the same as the invention described in Patent Document 1 in that the original size in the main scanning direction is determined as white inside the original and black outside the original when the pressure plate is opened. It is characterized by taking the data under two conditions, when the lamp is turned on and when the lamp is extinguished, and removing the influence of ambient light.

Further, the method described in Patent Document 3 is the same as the invention described in Patent Document 1 in that the document size in the main scanning direction is determined by assuming that the inside of the document is white and the outside of the document is black when the pressure plate is opened. The main scanning document size is detected using the reading data of the line sensor at a plurality of points in the direction.
JP-A-10-257255 JP 2000-138798 A JP 2003-198809 A

  However, although the inventions described in Patent Documents 1 and 2 are effective in increasing the accuracy of document size detection from two or more types of read data, it is possible to cope with the case where the pressure plate is closed in a short time or the user's eyes. It doesn't mean that it's friendly. The invention described in Patent Document 3 is the same as the invention described in Patent Document 1 in that the document size in the main scanning direction is determined as white inside the document and black outside the document when the pressure plate is opened. It is characterized by detecting the main scanning document size using the reading data of the line sensor at multiple points, it does not mention whether the lamp is on or not, and it is simply averaged for sub-scanning Therefore, there is a high possibility of malfunction due to the lamp on / off state.

 The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to eliminate as much as possible a document size erroneous detection when the pressure plate is closed in a short time or a document size erroneous detection due to lamp on / off. In other words, the data required for detecting the document size is reduced as much as possible to prevent erroneous detection when there is a high density portion of the document at the size reading position.

To achieve the above object, a first means of the invention, optionally changing the image data acquisition range of the main scanning direction showing a submaximal become read range of the number of main scanning pixels ranging write a plurality of line memories an image data acquisition range changing means for, optionally the spacing of patches each other for the image data acquisition in the sub-scanning direction, and a patch distance changing means for changing independently of the main scanning direction, provided with a, the User chromatography the In the document size detection apparatus in which the document size detection operation is started when the document reading is started, the image data acquisition range changing unit increases the image data acquisition range in the main scanning direction as the number of reading lines increases. It is characterized by making it.
The second means is the first means, wherein the image data acquisition range changing means compares the pixel density average value for each line in the patch to indicate the state of the original in the previous line and the current line. It is determined whether or not the difference between the image density average values is equal to or less than a certain value, and when the determination result is equal to or less than the certain value, the monochrome determination for the current line is performed.
The third means is characterized in that the image reading apparatus includes the document size detecting device of the first means or the second means.
The fourth means is characterized in that the image forming apparatus includes the image reading apparatus of the third means.

  In the embodiment described later, the means for arbitrarily changing the image data acquisition range in the main scanning direction and the means for changing the image data acquisition interval arbitrarily in the sub-scanning direction and independently of the main scanning direction are: The IPU 32 corresponds to the CPU 34 and the IPU 32, respectively. In the IPU 32, the image processing module 32a, the multi-line memory 32b, and the memory control 32c are used for the functions.

According to the present invention, document size erroneous detection when the time until the pressure plate is closed for a short time, or it is possible to minimize the document size erroneous detection due Lamp / off, minimize the data necessary for the document size detection In addition, it is possible to prevent erroneous detection when there is a high density portion of the document at the size reading position.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of an image reading apparatus according to an embodiment of the present invention. The image reading apparatus mainly includes a contact glass 1, a light source (illumination lamp) 2, first to third mirrors 3, 4, 5, a lens 8, and a CCD 9. The lamp 2 and the first mirror 3 are the first one. The second and third mirrors are mounted on the carriage 6 on the second carriage 7, respectively, and move in the sub-scanning direction at a 2-to-1 speed. In such a configuration, the original 10 placed on the contact glass 1 functioning as the original placement surface is irradiated with light by the lamp 2 and reflected by the first mirror 3, the second mirror 4, and the third mirror 5. The collected light is collected by the lens 8 and imaged on the CCD 9. While the lamp 2 and the first mirror 3 travel a distance L, the second mirror 4 and the third mirror 5 travel a distance L / 2. This makes it possible to scan the entire original while keeping the optical path length of the optical system constant.

  FIG. 2 is a perspective view showing a mechanical configuration of the image reading apparatus of FIG. The first carriage 6 including the lamp 2 and the first mirror 3 is attached to the drive wire 11, and the second carriage 7 including the second mirror 4 and the third mirror 5 is wound around the pulley 12. The drive wire 11 is wound around the wire pulley 15 connected to the drive shaft 14, and the drive of the motor 18 is transmitted to the drive wire 11 by the timing pulley 16 and the timing belt 17. A position where a certain distance is returned after one end of the first carriage 6 crosses the home position sensor 13 is defined as a home position.

  FIG. 3 is a block diagram showing an electrical configuration of a part for executing a series of copying operations of a copying machine as an image forming apparatus including the image reading apparatus according to the present embodiment. The copying machine includes a scanner 31 as an image reading device, a printer 33 as an image output device, an IPU (image processing unit) 32 that performs image processing for converting image data of the read image into a visible image, and a ROM (not shown). The user inputs user instruction information such as mode setting and number designation to the CPU 34 that controls the entire image forming apparatus according to the stored program, the RAM 36 that stores data to be processed by the CPU 34, and the CPU 34. The operation unit 35 on which various information is displayed from the CPU 34 is basically configured. The operation unit 35 is an interface between the user and the copying machine, and includes a CPU 35a and a display unit 35b.

  In the copying machine having such a configuration, when a document is set on the scanner 31 and the start key of the operation unit 35 is pressed, the scanner 31 reads the document, performs a series of image processing in the IPU 32, and outputs image data to the printer 33. Output and paper discharge is performed. Necessary parameters in the scanner 31, IPU 32, and printer 33 are held in a RAM 36 of the CPU 34, and the CPU 34 sets each device. The mode information necessary for parameter setting can be specified by the user from the operation unit 35, and information is exchanged by communication between the CPU 35a and the CPU 34 in the operation unit 35.

  FIG. 4 is a block diagram showing details in the IPU 32. The IPU 32 performs desired image processing on the original reading data received from the scanner 31, but when the original size detection operation is performed, the original reading data is stored in a plurality of line memories 32b connected to the image processing module 32a. . In addition, a memory control 32c for controlling the multiple line memory 32b is also provided, and data read / write from the CPU 34 to the multiple line memory 32b can be performed.

FIG. 5 is a flowchart showing a document size detection operation sequence in the present embodiment.
In the figure, it is detected that the carriages 6 and 7 are placed at the document size detection position and the pressure plate for pressing the document against the surface of the contact glass 1 is closed, or the document size is detected when the user starts reading the document. The operation is started (step S1). The opening / closing of the pressure plate is detected by ON / OFF of the DF opening / closing sensor. When document size detection is started, first, preparations necessary for document size detection are made (step S2). In step S2, setting of the document reading timing for document size detection as shown in FIGS. 7 and 8 and preparation setting necessary for shading correction as necessary are executed. The preparation includes shading correction and the like, but since these corrections are not related to the document size detection process of the present invention, description thereof will be omitted. The preparation operation and the lighting operation of the light source lamp are not particularly specified in order, and may be performed in parallel.

When the preparation is completed in step S2, irradiation of the document is started for reading the document (step S3). In step S3 , the lamp is turned on. In the flowchart of FIG. 5, steps S2 and S3 are described as being sequentially processed, but there is no particular order, and parallel processing is also possible. When the processes in steps S2 and S3 are completed, the original is read (step S4). In the original reading process, a write enable signal for the original size is generated, the original is read within the effective period of the write enable signal, and the process is terminated.

  In step S4, a write signal for the document size is generated, image data is read within the valid period of the write signal, and the process ends. At this time, reading is performed while moving the carriages 6 and 7 while scanning the document, or reading is performed while the carriage 6 is stopped at the document size detection position, and read image data of two or more lines is acquired. May be. When reading is performed while moving the carriages 6 and 7 while scanning the document, it is possible to read images at different positions on the document, and erroneously detect the document size depending on the contents of the image data on the document. In addition, the carriage is moved to the original document reading (main scan) position in parallel with the reading, so that the time until the start of the main scan after the document size is detected can be shortened. On the other hand, if reading is performed while the carriage 6 is stopped at the document size detection position, it is possible to clearly detect the influence of external light on the document table and the change in the lighting state of the document irradiation lamp from the contents of the image data. There is also an advantage (detection is not impossible even when the carriage is moved).

  When the reading of the document is completed in step S4, the irradiation of the document is terminated (step S5). However, in the case where the main scan is started immediately after the reading of the document for size detection is completed, the processing of step S5 may not be performed, and the document irradiation lamp may be kept on. Here, the determination process is not performed. Further, the process of step S5 is not regulated in order with respect to the process of step S6 described below, and can be performed in parallel.

  When the process of step S4 is completed, the read document image data is extracted to analyze the document size (step 6). The read document image data is taken out by reading data stored in the multi-line memory 32b from the CPU. Acquisition of document image data is performed as acquisition of a plurality of patch images. Acquisition of the patch image will be described later with reference to FIGS. Next, the image data taken out in step S6 is analyzed, and the document size is determined (step S7). The document size is determined based on the analysis (black and white determination) of the extracted patch image. If the document size is successfully determined in step S7, the document size is determined in step S8. Specifically, the determination of the document size is to store the document size information in a program execution memory 36 (RAM) connected to the CPU 34. Thereafter, the document size information determined as necessary is read. To use.

After the document size is determined, the document size detection operation is completed (step S9). Analysis processing for determining (determining) the document size will be described later with reference to FIG. When the document size is determined, the document size detection operation is terminated. On the other hand, if the determination of the document size fails in step S7, the document size detection operation is completed without determining the document size (step S9 ). Examples of document size determination failures include a black document, the influence of external light on the document table, and the illumination state of the document illumination lamp (when the lamp is turned on but the light quantity is not stable) It is conceivable that the size of the document cannot be determined from the read data due to the execution of the program.

  The basic sequence of the document size detection operation in the present embodiment has been described above. It should be noted that the feature of the present invention is particularly the analysis of document image data (determination of document size) in step S107, and this analysis is performed by analyzing the patch image.

FIG. 6 is a diagram illustrating an example of the memory control 32c . Memory control 3 2c receives the image processing module 32a serves as a reference for reading one line by the line sensor from a signal (XLSYNC), and a signal indicating a read start trigger of the line sensor (XFSYNC), and a pixel clock signal (PCLK) . In addition, the CPU 24 receives four parameters indicating the main scan start, main scan width, sub-scan start, and sub-scan width indicating the memory write area. Line reference signal on the basis of these parameters (XLSYNC), and from the read start trigger signal (XFSYNC) to confirm the write position of the memory, a plurality line memories 3 2b as a write reset signal (XWRST) and the write enable signal (XWE) hand over. Different parameters are prepared corresponding to the assumed document size.

  FIG. 7 shows the timing in the sub-scanning direction, and FIG. 8 shows the timing in the main scanning direction. By having the configuration shown in FIG. 6 as the memory control, data of a plurality of patches in a two-dimensional direction as shown in FIG. 9 can be simultaneously written in the memory. A hatched portion shown in FIG. 9 is a memory write area. Although the parameters and timing are the main scanning direction and the sub-scanning direction, the sub-scanning direction in the present invention indicates not only the sub-scanning direction for document reading but also the passage of time. The horizontal axis t in FIG. 9 is an example showing the passage of time, and shows the position of the reading patch at T1 and T2.

  FIG. 7 is a diagram illustrating timings of the one-line reference signal (XLSYNC), the reading start trigger signal (XFSYNC), the write reset signal (XWRST), and the write enable signal (XWE) in the sub-scanning direction. In the write enable signal (XWE) in FIG. 7, the light is reset by the write reset signal (XWRST), and the image within the sub-scanning period of the sub start 1 of the write enable signal (XWE) by the signal (XFSYNC) indicating the reading start trigger. Write data. This scanning area is an area in which all the detection target documents enter the document. After the sub-scan period of sub-start 1, a predetermined sub-scan width is skipped and writing is performed within the sub-scan period of sub-start 2. This scanning area is an area where the inside and outside of the document are switched by the document.

  FIG. 8 is a diagram illustrating timings of the one-line reference signal (XLSYNC), the reading start trigger signal (XFSYNC), the write reset signal (XWRST), and the write enable signal (XWE) in the main scanning direction. Also in the write enable signal (XWE) shown in FIG. 8, writing is performed within the main scanning period of the main start 1 and the main start 2 in the same manner as the write enable signal (XWE) in FIG. As a result of the writing of the plurality of line memories 32b being controlled by the write enable signal (XWE), two-dimensional patch images (multiple) can be simultaneously written to the memory, that is, patch images can be obtained.

FIG. 10 is a flowchart showing the processing procedure for extracting image data in step S6 in the flowchart of FIG. In this process, as a process for the data in one patch, it is finally determined whether the target patch is determined to be white or black, but at the time of step S6, the patch is determined. It is not determined that white = original is present and black = no original is determined only by monochrome determination. Here, the patch data shown in FIG. 9 is read from the plurality of line memories 32a one by one to the RAM 36 of the CPU 34, and the pixel density average value of the nth line in the patch is sequentially calculated. When the pixel density average values of the two lines are compared and it is determined that they can be used to determine whether there is a document or not (the difference between the image density average values of the previous line and the current line is a certain value Δ or less. ), The pixel density average value (current line) is binarized to determine black and white. The monochrome determination result is adopted as the monochrome determination result of one patch. In FIG. 9, the shaded area is the memory write area. 7 and 8, the parameters and timing are described as the main scanning direction and the sub-scanning direction. However, the sub-scanning direction in this embodiment indicates not only the sub-scanning direction with respect to document reading but also the passage of time. Yes. The horizontal axis t in FIG. 9 represents the passage of time (using time as a parameter), and T1 and T2 represent reading positions corresponding to the passage of time.

In FIG. 10, the monochrome determination flow is started from step S11, and the nth line is read for the reading range of the number of main scanning pixels indicating the range (number of pixels to be read) to be read as line data from the image data of the patches on the plurality of line memories 32a. Set n = 1 indicating the reading of image data. Next, in step S12, the number N (n) of pixels in the reading line is set. Thereafter, reading is performed in units of one pixel from the multiple line memory 32a (step S13) [D (n) = MenRd], and the density of one line of pixels is added to obtain the average of the density of one line (step S14) [ Y (n) ave = ΣD (n) / N (n)]. Here, Y (n) ave represents the average value (pixel density average value of the line) of the 0th pixel to the N (n) -1 pixel of the nth line, and N (n) is the nth line. The number of pixels used for calculating Y (n) ave is indicated, and D (n) indicates the density of each pixel from the 0th pixel to the N (n) -1 pixel in the nth line. Strictly speaking, Y (n) ave adds the parameter m, and divides the sum (Σ) from m = 0 to N (n) −1 for D (n) (m) by N (n). Is the value obtained. Next, the absolute value of the difference between the pixel density average value of the previous line and the pixel density average value of the current line is obtained and compared with a predetermined constant value Δ (step S15) [| Y (n) ave− Y (n−1) ave | ≦ Δ]. In this comparison, if the value is equal to or less than a predetermined value Δ, the calculated pixel density average value can be determined to be a stable value with little influence of the original, but if it is larger than the predetermined value Δ, there is an influence of the original image at the reading position. It is determined that the situation is unstable due to external influences, and the reading range of the number of main scanning pixels is further expanded and the procedure from step S12 is performed again (step S16). If it is equal to or smaller than a certain value Δ, the black and white pixels of the patch are determined from the result [Y (n) ave ≦ TH] (steps S17, S18, S19), and the monochrome determination flow is terminated (step S20). In this embodiment, in order to eliminate the influence of lamp non-lighting that causes the lamp lighting of the scanner to be delayed, the pixel density average value of the first line in the sub-scanning direction is compared with the pixel density average value of the next line, It is preferable to compare sequentially. If the lighting of the lamp is stable, the difference between the pixel density average value of the previous line and the pixel density average value of the current line is almost zero, but the current line is brighter than the previous line in the non-lighted part. Therefore, the difference between the pixel density average values of these lines increases. Therefore , when the difference approaches zero, the pixel data is binarized, and the result is used as the result of patch monochrome determination. Such processing is performed for each patch within the patch range. In addition, when calculating the average pixel density value for each line, if the part of the line containing dust or an image of the original is read, the effect is greatly reflected and black and white determination may not be performed correctly. When the difference in the pixel density average values does not converge, it is preferable to increase the number of pixels in the main scanning direction used for calculating the average value in order to reduce the influence so that the black and white determination is performed correctly.

FIG. 11 is a flowchart showing the processing contents in the processing (determination) of analyzing the image data in step S7 in the flowchart of FIG. In this process, the black and white determination result of the patch obtained in the previous step S6 is used to determine whether or not there is an original / non-original determination. For the patch to be processed, if the determination result of whether or not there is a document is white, it is considered that there is a document, and if it is black, it is considered that there is no document. Here, L (n) IN and L (n) JUDGE are used as reading patches as shown in FIG. N in L (n) indicates the number of times of reading since the start of line sensor reading (indicating the passage of time), IN and JUDGE indicate positions in the main scanning direction, and IN is included in all originals to be detected. The main scanning position indicates the main scanning position where JUDGE switches between the inside and outside of the document depending on the document.

  In this process, the detection process is started in step S31, and the detection frequency N is set in step S32. Here, first, n = 1 is set as an initial value. Next, in step S33, it is determined whether n has exceeded the number of detections. If it has exceeded N, it is determined that detection is impossible, and the detection process is exited. The following determination is repeated until n = N (steps S34 and S35). In step S34, it is determined whether Ln (IN) is white. If the original is also black, it is determined that the lamp is off, n = n + 1 is set (step S35), and the process returns to step S33.

  When Ln (IN) is white, the determination result of L (n) JUDGE is set as a detection candidate (step S36), and the process proceeds to the next step. Then, 1 is added to n obtained as a detection candidate (step S37), and the next reading result is determined (step S38). In this determination, it is determined whether L (n) JUDGE is black. If it is white, there is a high possibility that the pressure plate has been closed. Therefore, the determination is not made here, and the result of the previous detection candidate is used as it is (step S39). If it is black, it is considered that the lamp is more stable than the previous time, so that the current determination result is used (step S40), and the document size detection process is terminated (step S41).

  In order to execute the document size detection described above, the processing procedure is described as a computer program in a general-purpose program language, and this program is recorded on an arbitrary recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, and an MO. By recording the image on a medium and causing the computer of the image reading apparatus to read it, the detection of the document size according to the embodiment of the present invention can be easily performed at the time of image reading. In addition to recording the program on a recording medium, the program can be directly read by a computer such as an image forming apparatus or an image reading apparatus via an arbitrary network such as the Internet or an intranet.

  FIG. 12 is a schematic configuration diagram showing an example of a digital copying machine according to the present embodiment. In the figure, a digital copying machine is for monochrome image formation. A main body 400, an image reading device 500 installed on the upper portion of the image forming apparatus main body 400, and an automatic document feeder (hereinafter referred to as an automatic document feeder) mounted thereon. , “ADF”) 550, a large-capacity paper feeding device 700 disposed on the right side of the image forming apparatus main body 400 in the same figure, and a sheet post-processing device disposed on the left side of the image forming apparatus main body 400 in the same figure. 800 is basically composed.

  The image forming apparatus main body 400 includes an image writing unit 410, an image forming unit 420, a fixing unit 430, a duplex conveying unit 440, a paper feeding unit 450, a vertical conveying unit 460, and a manual feeding unit 470.

  The image writing unit 410 modulates the LD, which is a light source, based on the image information of the document read by the image reading device 500, and writes laser on the photosensitive drum 421 by a scanning optical system such as a polygon mirror and an fθ lens. is there. The image forming unit 420 includes a photosensitive drum 421 and known electrophotographic imaging elements such as a developing unit 422, a transfer unit 423, a cleaning unit 424, and a charge eliminating unit provided along the outer periphery of the photosensitive drum 421. Consists of.

  The fixing unit 430 fixes the image transferred by the transfer unit 423 on the transfer paper. The double-sided conveyance unit 440 is provided downstream of the fixing unit 420 in the transfer sheet conveyance direction, and includes a first switching claw 441 that switches the transfer sheet conveyance direction to the sheet post-processing device 800 side or the double-side conveyance unit 440 side, , The reverse conveying path 442 guided by the switching claw 441, the image forming side conveying path 443 that conveys the transfer paper reversed by the reverse conveying path 442 to the transfer unit 423 again, and the reverse transfer paper after the sheet post-processing device 800. A second switching claw 445 is disposed at a branch portion between the image forming side conveying path 443 and the post processing side conveying path 444.

  The sheet feeding unit 450 includes four sheet feeding stages, and the transfer sheets stored in the sheet feeding stages selected by the pickup roller and the sheet feeding roller are drawn out and guided to the vertical conveyance unit 460. The vertical conveyance unit 460 conveys the transfer paper fed from each paper feed stage to the registration roller 461 immediately upstream in the paper conveyance direction of the transfer unit 423, and the registration roller 461 provides a visible image on the photosensitive drum 421. The transfer paper is fed into the transfer unit 423 in time with the leading edge. The manual feed portion 470 includes an openable and closable manual feed tray 471, and opens the manual feed tray 471 as needed to supply transfer paper manually. Also in this case, the transfer timing of the transfer paper is taken by the registration roller 461 and is transported.

  The large-capacity paper feeding device 700 supplies a large amount of transfer paper of the same size, and the bottom plate 702 rises as the transfer paper is consumed, so that the paper can always be picked up from the pickup roller 701. ing. The transfer paper fed from the pickup roller 701 is conveyed from the vertical conveyance unit 460 to the nip of the registration roller 461.

  The sheet post-processing apparatus 800 performs predetermined processing such as punching, alignment, stapling, and sorting. In this embodiment, the punch 801, the staple tray (alignment) 802, the stapler 803, and the shift tray 804 are used for the above functions. I have. In other words, the transfer paper carried from the image forming apparatus 400 to the paper post-processing apparatus 800 is punched one by one with the punch 801 when punching, and then if there is no particular processing, the proofing is performed. When sorting, stacking, and sorting to the tray 805, the sheets are discharged to the shift tray 804, respectively. In this embodiment, the sorting is performed by the reciprocating movement of the shift tray 804 by a predetermined amount in a direction orthogonal to the sheet conveyance direction. In addition, sorting can be performed by moving the paper in a direction orthogonal to the paper transport direction on the paper transport path.

  In the case of alignment, the transfer paper that has been punched or not punched is guided to the lower transport path 806, and the staple tray 804 is aligned in the direction perpendicular to the paper transport direction by the rear end fence. In the jogger fence, alignment in the direction parallel to the paper transport direction is performed. Here, when binding is performed, a predetermined position of the aligned sheet bundle, for example, a predetermined position such as a corner portion or two central positions is bound by the stapler 803 and discharged to the shift tray 804 by the discharge belt. In this embodiment, a pre-stack conveyance path 807 is provided in the lower conveyance path 806, and a plurality of sheets are stacked at the time of conveyance to avoid interruption of the image forming operation on the image forming apparatus main body 400 side during post-processing. Be able to.

  The image reading apparatus 500 is guided onto the contact glass 510 by the ADF 600, optically scans the stopped original, and reads the image formed by the imaging lens through the first to third mirrors, such as a CCD or CMOS. Read by the photoelectric conversion element. The read image data is subjected to predetermined image processing by an image processing circuit (not shown) and temporarily stored in a storage device. Then, it is read from the storage device by the image writing unit 410 during image formation, modulated according to the image data, and optical writing is performed.

  The ADF 550 has a double-sided reading function, and is attached to the contact glass 510 installation surface of the image reading device 500 so as to be freely opened and closed. In the ADF 550, the document placed on the document placement table 551 is automatically sent onto the contact glass 510 when the document is read.

As described above, according to this embodiment,
1) When the size is detected at a specific position, depending on the state of the document, for example, if there is a solid black patch, it is determined that there is no document. In order to avoid such a situation, since the reading range in the main scanning direction is increased as the number of reading lines increases, erroneous determination can be prevented.
2) Since the reading range is increased as the number of lines is increased, it is possible to determine how the density change in the main scanning direction has changed, and to prevent erroneous determination.
3) It is possible to prevent erroneous determination by checking whether the density change is less than a certain difference between the previous line and the current line.
There are effects such as.

1 is a cross-sectional view illustrating a schematic configuration of an image reading apparatus according to an embodiment of the present invention. 1 is a perspective view showing a mechanical configuration of an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of a digital copying machine including the image reading device illustrated in FIG. 1. It is a block diagram which shows the detail in IPU in FIG. 6 is a flowchart illustrating a document size detection processing procedure in line sensor reading according to an embodiment of the present invention. FIG. 5 is a block diagram showing an input / output state of a memory control signal in the IPU in FIG. 4. 7 is a timing chart showing input / output signal timings in the sub-scanning direction of the memory control in FIG. 6. 7 is a timing chart showing input / output signal timings in the main scanning direction of the memory control in FIG. 6. It is a figure which shows an example of the patch reading in this embodiment. It is a flowchart which shows the process sequence of the black-and-white determination in this embodiment. 6 is a flowchart illustrating a processing procedure of document size determination processing in the present embodiment. It is a schematic block diagram which shows an example of the mechanical structure of the digital copying machine of FIG.

Explanation of symbols

1 Contact glass 2 Lamp 3, 4, 5 Mirror 6, 7 Carriage 8 Lens 9 CCD
31 Scanner 32 IPU
32a Image processing module 32b Multiple line memory 32c Memory control 33 Printer 34 CPU
36 Memory (RAM)

Claims (4)

An image data acquisition range changing means changes the image data acquisition range of the main scanning direction showing a submaximal become read range of the number of main scanning pixels ranging write a plurality of line memories optionally patch each other for the image data acquisition arbitrarily intervals in the sub-scanning direction, and main to the scanning direction and the patch interval changing means for changing independently, co if provided with a document size detecting operation when the User chromatography tHE starts the reading of the original is started In the original document size detection device,
The document size detection apparatus, wherein the image data acquisition range changing means increases the image data acquisition range in the main scanning direction as the number of read lines increases. The document size detection apparatus according to claim 1,
The image data acquisition range changing unit compares a pixel density average value for each line in the patch, and a difference between the pixel density average values in the previous line and the current line indicating the state of the original is equal to or less than a predetermined value. A document size detection apparatus that performs monochrome determination for the current line when the determination result is equal to or less than a predetermined value.   An image reading apparatus comprising the document size detection apparatus according to claim 1.   An image forming apparatus comprising the image reading apparatus according to claim 4.

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