JP2015103973A - Image reading apparatus, control method of the same, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress image deterioration which can be caused by the presence of a foreign matter at the time of reading an image.SOLUTION: The image reading apparatus acquires an inter-document time between the completion of reading a preceding document and the start of reading the next document in a case where plural consecutive documents are conveyed in a predetermined direction with intervals and the respective documents are read by a reader. On the basis of the acquired inter-document time, the apparatus determines a detection method performed by a detector for detecting dust on a reading glass platen. In accordance with the determined detection method, the apparatus controls the operation of the detector.

Description

  The present invention relates to an image reading technique in which an image of a document is read by a reading unit while the document is conveyed in a predetermined direction on a reading glass.

  In the image reading apparatus, when the original is conveyed on the original glass and is read by the reading unit, the original adheres to the original glass before the start of the image reading job where the original is not read or after the image reading job. A foreign object (dust or dirt) is detected, the reading position is changed to a position to avoid the foreign object, and further, during an image reading job, the foreign object is detected in a section outside the document area between documents. There has been proposed a method for correcting a black streak image caused by the foreign matter on the output document image data (see Patent Document 1).

  Further, in black line image correction, a method has been proposed in which the time of the section outside the document area is calculated according to the reading mode, and black line image correction that can be performed according to the time is performed (Patent Document). 2).

Japanese Patent No. 4401597 Japanese Patent No. 4440081

  However, in the method of Patent Document 1, since reading is performed until the image reading job is completed at the reading position determined before the start of the image reading job, if a foreign object occurs at the reading position during the image reading job, the original image Image correction is required for the data. In addition, when a foreign matter occurs in the middle at the first determined reading position, even if there is another reading position where there is no foreign matter, reading is performed at the first determined reading position, so that the image correction is performed. It was necessary.

  Further, in the method of Patent Document 2, image correction processing is performed on the section outside the document area calculated according to the reading mode. However, as with the problem that may occur in Patent Document 1, other reading positions where no foreign matter exists are present. Even if there is, there is a need to perform image correction processing because reading is performed at the first determined reading position.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image reading technique capable of suppressing image deterioration that may occur due to the presence of foreign matter during image reading.

In order to achieve the above object, an image reading apparatus according to the present invention comprises the following arrangement. That is, an image reading device that reads an image of a document by a reading unit while conveying the document on a reading glass in a predetermined direction,
When the plurality of continuous documents are transported in the predetermined direction at intervals and the images of the respective documents are read by the reading unit, the inter-document time required from the completion of reading the preceding document to the start of reading the next document Acquisition means for acquiring;
A determination unit that determines a detection method in a detection unit that detects dust on the reading glass based on the inter-document time acquired by the acquisition unit;
Control means for controlling the operation of the detection unit according to the detection method determined by the determination means.

  ADVANTAGE OF THE INVENTION According to this invention, the image reading technique which can suppress the image degradation which may generate | occur | produce by the presence of the foreign material at the time of image reading can be provided.

1 is a cross-sectional view of an image forming apparatus according to a first embodiment. 1 is an external perspective view of an image forming apparatus according to a first embodiment. 2 is a cross-sectional view of a main part of the image reading apparatus according to Embodiment 1. FIG. 2 is a block diagram illustrating an image formation control unit according to the first embodiment. 3 is a flowchart illustrating dust detection processing according to the first embodiment. 6 is a flowchart illustrating dust avoidance processing according to the first exemplary embodiment. FIG. 6 is a schematic diagram for explaining a dust avoidance operation in the sheet document transport unit according to the first embodiment. 6 is a flowchart illustrating a reading process in which a dust avoidance level is determined based on a reading condition according to the first exemplary embodiment and a flow reading is executed. FIG. 6 is a table showing a reading condition according to the first embodiment and a dust avoidance level related thereto. FIG. 6 is a diagram illustrating an example of a reading position moving distance and time when dust detection / avoidance is performed according to the first exemplary embodiment. 10 is a flowchart illustrating processing for calculating an actual inter-sheet time according to the second exemplary embodiment. 10 is a flowchart illustrating a reading process in which a dust avoidance level is determined based on an actual paper interval time according to the second exemplary embodiment and a flow reading is performed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An image reading apparatus according to Embodiment 1 and an image forming apparatus including the image reading apparatus will be described with reference to the drawings. In this image reading apparatus, when a subject moving on the original glass is irradiated with light from the reading unit and an image of the subject is read, black streak images caused by foreign matters such as dust or dirt on the original glass are generated. A configuration for suppressing or correcting the above will be described.

<Embodiment 1>
Some image forming apparatuses equipped with an image reading apparatus include a copying machine, a printer, a facsimile, and a composite function thereof. The image reading apparatus according to the present embodiment will be described with respect to a case where the image reading apparatus is installed in a facsimile. However, the image reading apparatus may be used by being installed in an apparatus such as a copying machine or a printer. Further, the image reading apparatus may be used alone like a scanner without being installed in the image forming apparatus.

  FIG. 1 is a cross-sectional view of the image forming apparatus according to the first embodiment along the sheet conveyance direction. FIG. 2 is an external perspective view of the image forming apparatus of FIG. FIG. 3 shows a part of the image reading apparatus according to the first embodiment equipped in the image forming apparatus, and is a cross-sectional view along the document conveying direction.

<Image forming apparatus>
The image forming apparatus 100 includes an apparatus main body 101, an image reading apparatus 103 provided on the upper part of the apparatus main body 101, and an automatic document feeder (ADF: auto document feeder) 126 provided on the upper part of the image reading apparatus 103. I have.

  The automatic document feeder 126 is, for example, a sheet document D as a subject placed on a document placing table 106 (including a slide guide 106a for adjusting the width of the document and a sensor 106b for detecting that the document is placed). Are separated one by one and supplied to the image reading apparatus 103.

  The image reading device 103 serving as a reading unit reads the sheet document D sent onto the flow reading glass 109 by the automatic document feeder 126 by the image sensor unit 108 stopped moving at the sheet document reading position 109a. ing. The image sensor unit 108 can be a CIS or a CCD.

  Further, the image reading apparatus 103 reads the sheet document D (or book document) placed on the document table glass 107 by moving the image sensor unit 108 in the sub-scanning direction. The sub-scanning direction that is the predetermined direction is the left-right direction of FIGS. The main scanning direction is a direction orthogonal to the sub-scanning direction, and is the arrow B direction in FIG.

  The apparatus main body 101 of the image forming apparatus forms an image on a sheet (recording medium) based on the image reading information of the image reading apparatus 103, and thus functions as a recording apparatus.

  The image reading apparatus 103 transmits the read image to the recording apparatus main body 104 incorporated in the apparatus main body 101. The recording apparatus main body 104 is an electrophotographic printer using an LED array. The operation unit 105 (FIG. 2) includes components such as a display unit and input keys, and is a part where the user operates the image forming apparatus 100.

  In addition, the apparatus main body 101 includes a recording sheet discharge unit configured to be capable of stacking a plurality of sheets P on top of the LED head unit 110, the image forming unit 111, the cassette paper feeding unit 112, and the recording apparatus main body 104. 113 and a cartridge cover part 114 are provided. Further, the apparatus main body 101 also includes a joining unit 119 that joins the image reading apparatus 103 and the recording apparatus main body 104, a control unit 120 of the facsimile apparatus, a double-sided conveyance unit cover 122, a conveyance direction switching unit 123, and a resist conveyance unit 124. ing. In addition, the apparatus main body 101 includes an MP (multi-paper) paper feeding unit 125 and a double-sided conveyance unit 150 disposed inside the recording apparatus main body 104.

  The automatic document feeder 126 includes components such as an ADF separation unit 115, a paper discharge conveyance unit 116, a document discharge unit 117, a document pressing plate 118 that presses a book document, and a sheet document conveyance unit 121.

  In FIG. 3, a document feeding sensor 121 h and a document position detection sensor 121 i are disposed in a sheet document conveying unit 121 including a conveying path of the image reading apparatus 103. The document feed sensor 121h detects whether or not the sheet document D has been sent out from the ADF separation unit 115 and the passage of the rear end of the sheet document D. The document position detection sensor 121i is configured to detect the passage of the leading edge and the trailing edge of the sheet document D conveyed by the reading conveyance roller 121c and the like. The output is used for reading timing control.

  Next, an image formation control unit of the image forming apparatus 100 including image signal processing for processing an image signal output from the image sensor unit 108 will be described based on the block diagram of FIG.

  The image forming apparatus 100 includes a main CPU 24, a RAM 27, a ROM 28, an operation unit 105, a drive unit 44, a communication I / F (interface) 42, an image data generation unit 43, an image formation unit 111, an image processing unit 41, and an image sensor unit. 108.

  The main CPU 24 controls the entire apparatus via the data bus / system bus 210. The RAM 27 is a work area for the main CPU 24 and a temporary storage area for data. The ROM 28 is written with a firmware program for controlling the image forming apparatus 100 and a boot program for controlling the firmware program, and is used by the main CPU 24.

  The image sensor unit 108 is a photoelectric conversion device, and includes an LED 10, a light receiving sensor 13, and an AMP / A / D (amplifier / analog / digital) converter 23.

  An analog signal which is image data output from the light receiving sensor 13 is amplified by the AMP of the AMP / A / D converter 23 and converted into a digital signal by the A / D converter. In the case of 8-bit data, the converted digital signal of the image data is 0 for black, 255 for white, and 256-level luminance data (density) from 0 to 255 to the RAM 27 via the data bus and system bus 210. Saved.

  The image processing unit 41 includes a dust correction unit 411 and a dust detection unit 412, and performs dust detection processing and dust correction processing for image data stored in the RAM 27. The digital signal of the image data output from the image processing unit 41 is output to the image data generation unit 43 of the image forming apparatus 100 via the communication I / F 42. The image data generation unit 43 collects image data for one main scanning line input from the communication I / F 42 to generate image data for one page, and generates a necessary image from the generated image data for one page. Data for the size (original image area) is generated. The image data generated by the image data generation unit 43 is output to the image forming unit 111 or is reproduced by an information processing apparatus such as a host computer.

  An operation unit 105 (see also FIG. 2) of the image reading apparatus 103 displays the status of the image reading apparatus 103 and the operation status of the entire image forming apparatus 100. Further, the operation unit 105 inputs a reading command for executing processing of the image reading device 103 in accordance with an operation from the user.

<Dust detection correction processing>
FIG. 5 is a flowchart showing dust detection correction processing in document reading by flow reading.

  A processing program for executing the dust detection correction process is stored in the ROM 28, and the main CPU 24 executes this processing program to perform the following operations.

  First, when the user places a sheet document D on the document table 106 and presses the copy button of the operation unit 105, the main CPU 24 starts an image reading process (DF (flow scanning) scan). First, the main CPU 24 scans on the reading glass (at least one of the flow reading glass 109 and the document table glass 107) before reading the document or between successive documents (outside the document area) (step S101). ).

Here, the main CPU 24 controls the image sensor unit 108 to turn on the LED 10, and image data (Sd _{1 to} Sd ₇₅₀₀ ) of all main scanning pixels (N = _{1 to 7500} pixels) on the reading glass by the light receiving sensor 13. ) And is stored in the RAM 27 via the image processing unit 41.

  Next, dust detection processing is performed to detect pixels having a dust detection threshold value or less as dust from the scanned data on the reading glass (steps S102 to S110).

First, in the dust detection process, the main CPU 24 controls the dust detection unit 412 in the image processing unit 41 to sequentially store image data on the reading glass for one main scanning line stored in the RAM 27 in order from the first pixel. Remove (Sd _N ). Then, the luminance value of the image data Sd _N of the target pixel N is compared with a dust detection threshold value (for example, luminance value 200) stored in the RAM 27 (step S102).

  Note that the dust detection threshold is set according to the application and purpose, and can be set at any timing via the operation unit 105, for example.

Comparison of the results, when the brightness value of the image data Sd _N of the target pixel N is equal to or less than the dust detection threshold (luminance value 200) (YES at step S102), the main CPU24 determines that the there is dust to the target pixel N Then, the detected dust number Gm (= Gm + 1) is set (step S103). The main CPU 24 stores the dust position Gm_pos (= N (pixel number)) in the RAM 27 (step S104). Note that the initial value of the dust number Gm is 0, and is incremented by 1 every time dust is detected.

  After storing the detected dust number Gm and the dust position Gm_pos in the RAM 27, the main CPU 24 detects the detected dust width of the dust (steps S105 to S108).

  First, the main CPU 24 counts the dust width Gm_cnt (Gm_cnt = Gm_cnt + 1) using the target pixel N as a dust pixel (step S105). The initial value of the dust width Gm_cnt is 0, and the unit of the dust width is a pixel.

  After counting the dust width for one pixel, the main CPU 24 determines whether or not the target pixel N is the last pixel (N = 7500) (step S1051). If the target pixel N is not the final pixel (NO in step S1051), the main CPU 24 shifts the target pixel N by one pixel (N = N + 1) and detects the next pixel N (= N + 1) (step S106). On the other hand, if the target pixel N is the last pixel (N = 7500) (YES in step S1051), the main CPU 24 proceeds to step S108.

The main CPU24, when executing step S106, as a target pixel N the following pixel, similarly, by comparing the image data Sd _N and dust detection threshold (luminance value 200), whether there is dust in the next pixel N Is determined (step S107).

  If the main CPU 24 determines that there is dust in the next pixel N + 1 as well as the previous pixel N (YES in step S107), the main CPU 24 returns to step S105, and the main CPU 24 counts up the dust width Gm_cnt (Gm_cnt = Gm_cnt + 1). ) Similarly, it is determined whether or not it is continuous dust after the next pixel, and if it is continuous dust, the dust width Gm_cnt is counted (step S105, step S1051, step S106, and step S107).

  If it is determined that there is no dust in the next pixel N + 1 (NO in step S107), the main CPU 24 stores the dust width Gm_cnt counted so far in the RAM 27 as the dust width Gm_wid (= Gm_cnt) of the dust number Gm (step S107). S108).

  If it is determined in step S102 that the target pixel N is free of dust (NO in step S102), the main CPU 24 determines whether or not the target pixel N is the last pixel (N = 7500) (step S109). If the target pixel N is not the final pixel (NO in step S109), the main CPU 24 detects the next pixel (N = N + 1) (step S110) and returns to step S102. On the other hand, when the target pixel N is the last pixel (N = 7500) (YES in step S109), the main CPU 24 ends the series of dust detection processing (steps S102 to S110).

  When the dust detection processing is completed, the main CPU 24 determines the detected dust as a correction location. When the original reaches the reading glass, the main CPU 24 reads the image data line by line in the main scanning, and at the same time, determines the dust correction processing ( Image correction processing).

<Dust avoidance processing>
The dust avoidance process will be described with reference to FIGS.

  FIG. 6 is a flowchart showing dust avoidance processing, and FIG. 7 is an enlarged cross-sectional view of a portion of the sheet document conveying unit 121.

  Note that a processing program for executing the dust avoidance processing is stored in the ROM 28, and the main CPU 24 executes this processing program to perform the following operations.

  When dust is detected in the dust detection processing of FIG. 5, when the sheet document D is conveyed by the automatic document feeder 126 and image reading is executed by the image sensor unit 108, dust correction is executed as necessary. When dust correction is performed, a corrected image is generated in which the image of the dust detection part (location) is replaced by the surrounding image. Therefore, although the influence of dust is suppressed, its image quality is lower than that of the original scanned image. Will deteriorate. In addition, the correction result may be conspicuous depending on the content of the image (photograph, text, etc.). Furthermore, if the dust width exceeds the correction upper limit width of the dust correction unit 411, the portion cannot be corrected, and black streaks may occur in the output image.

  In order to solve such a problem as much as possible, in the first embodiment, the following dust avoidance process is executed during scanning using the automatic document feeder 126. In this method, dust detection processing is executed at a plurality of reading candidate positions, and finally a reading position used for image reading is determined based on the detection result. In other words, a reading position that avoids a position where dust is present is determined.

  First, the main CPU 24 determines whether or not there is a predetermined amount or more of dust at the current reading position (nth reading position) in the dust detection process of FIG. 5 (step S301). The prescribed amount is, for example, a determination that “there is dust” when there is one or more dust having a width of one pixel or more.

  If it is determined that there is no dust (NO in step S301), the reading position (n-th reading position) at that time is determined as the reading position used for image reading, and the reading position is stored in the RAM 27.

  On the other hand, if it is determined that there is “dust” (YES in step S301), the main CPU 24 determines whether dust detection processing has been completed at all reading candidate positions (step S302). Here, as shown in FIG. 7, the reading candidate position is a position where the image sensor unit 108 performs image reading in the sheet document conveying unit 121. As shown in FIG. 7, a plurality of reading candidate positions are determined from the upstream side of the guide, such as a first reading position and a second reading position. In the continuous scanning, a candidate reading position that is considered to be optimal is selected from the candidate reading positions, and the selected candidate reading position is determined as a reading position used for actual image reading.

  In step S302, when the dust detection processing is not completed at all the reading candidate positions (NO in step S302), the main CPU 24 acquires the next reading candidate position (step S304). The next reading candidate position may be a distance from a position serving as a common reference, or may be a distance from the current reading candidate position. For example, in the case of FIG. 7, the location of the second reading position is set at a predetermined distance (for example, 0.25 to 0.5 mm) downstream from the first reading position. When the next reading candidate position is acquired, the main CPU 24 moves the image sensor unit 108 to the acquired reading candidate position (step S305). Next, the main CPU 24 adds 1 to a variable n indicating the number of reading candidate positions (step S306). Then, the process returns to step S301, and the dust detection process of FIG. 5 is performed again at the moved reading candidate position, and the presence or absence of dust is determined based on the detection result.

  On the other hand, when dust detection processing is completed at all the reading candidate positions in step S302 (YES in step S302), that is, when it is determined that “dust is present” at all the reading candidate positions, there are more reading candidate positions. not exist. Therefore, the main CPU 24 sets the reading candidate position as the priority reading position, and moves the image sensor unit 108 to the priority reading position (step S303). The priority reading position may be, for example, the first reading position in FIG. 7 among the reading candidate positions, or may be the reading position with the least dust, the reading position with the smallest dust width, or the like. In this case, since dust exists at the determined reading position, dust correction processing is executed on the read image.

  By executing the above processing, when the processing is completed without passing through step S303 (that is, when “no dust” is determined at any reading candidate position), the automatic document feeder 126 is used, When image reading of the sheet document D is executed at the reading position stored in the RAM 27, it is possible to obtain a good image without dust correction or black streaking.

<Dust detection / avoidance processing by level>
Scanning scanning using the automatic document feeder 126 will be described with reference to FIGS.

  FIG. 8 is a flowchart showing a reading process in which the dust avoidance level is determined based on the reading conditions and the flow reading is executed. FIG. 9 is a table showing the reading conditions and the dust avoidance levels associated therewith. FIG. 10 is an example of the reading position moving distance and time when dust is detected and avoided.

  A processing program for executing the processing of FIG. 8 is stored in the ROM 28, and the main CPU 24 executes this processing program to perform the following operations.

  First, when the user places a sheet document D on the document table 106 and presses the copy button on the operation unit 105, the main CPU 24 reads the reading conditions input to the image reading device 103 via the operation unit 105. Is acquired (step S201). Here, the reading conditions include, for example, reading resolution (unit: dpi), color mode (monochrome / color), reading surface (only one side / both sides), and the like.

  Next, the main CPU 24 executes dust detection / avoidance processing in the standard operation before starting reading the document (step S202). The standard operation dust detection / avoidance processing is, for example, dust detection / avoidance processing with the contents (detection method) specified in level 3 (standard) shown in FIG. 9B. That is, there are three reading candidate positions (dust detection positions), and the interval (dust detection interval) between the reading candidate positions is set to 0.5 mm. Note that the processing contents of the dust detection / avoidance processing in this standard include, for example, the reading candidate position in consideration of other setting values such as the guide width of the sheet document conveying unit 121 and the time of first copy out (FCOT). The number and interval can be set.

  Next, the main CPU 24 determines a level (dust prevention level) for the input reading condition and stores it in the RAM 27 (step S203). This level defines the processing contents (detection location, reading candidate position interval, etc.) of dust detection / avoidance processing defined in FIG. 9B. 9A specifies the theoretical inter-sheet time (theoretical inter-document time) for the input reading conditions. Based on this, in FIG. 9B, the level associated with the corresponding time range including the specified theoretical inter-sheet time is selected. Details of the contents at each level will be described later.

  Next, the main CPU 24 initializes the value of the current reading line number n to 0 (step S204). The main CPU 24 executes reading of the document image on the nth line (step S205). Then, the main CPU 24 performs dust correction on the read image when there is dust to be corrected based on the detection result of the dust detection processing in FIG. 5 (when there is no dust to be corrected, dust correction is not performed). (Step S206). Thereafter, the main CPU 24 determines whether or not all lines have been read (step S207). If reading of all lines has not been completed (NO in step S207), the main CPU 24 increments the count of n by 1 (step S208). Thereafter, the process returns to step S205, and the main CPU 24 executes image reading of the (n + 1) th line.

  On the other hand, if all lines have been read (YES in step S207), the main CPU 24 then determines whether or not the next document remains on the document table 106 (step S209). If there is a next original (NO in step S209), the main CPU 24 executes dust detection / avoidance processing at the level determined in step S203 (step S210). After execution, the process returns to step S204.

  On the other hand, if there is no next original (YES in step S209), the process ends.

  Next, details of the level set in step S203 in FIG. 8 will be described with reference to FIG.

  For example, when the resolution of the reading condition is 100 dpi, the color mode is black and white, and the reading surface is single-sided, the theoretical inter-paper time is 50 ms from FIG. 9A, and this 50 ms is shown in FIG. 9B. Therefore, the level 0 is set. For example, when the resolution of the reading condition is 600 dpi, the color mode is color, and the reading surface is double-sided, the theoretical inter-paper time is 1500 ms from FIG. 9A, and this 1500 ms is the time in FIG. 9B. Since it falls within the range of 1340 ms, level 4 is set.

  Thus, each level is set according to the reading conditions. As an example, the level assignment in each reading condition is based on the inter-sheet time (outside the document region interval time). The inter-paper time is a section time outside the document area specified from the reading conditions, and includes various motor speeds corresponding to the reading conditions, inter-document time per line, productivity, controller image processing time, and the like. Varies with parameters. In other words, the inter-paper time can be said to be a reading interval between documents, that is, a reading interval time from the completion of reading of the preceding document to the start of reading of the next document.

  For example, if the reading interval time is the same regardless of the resolution (one line reading every 100 μs), the distance between the reading lines is wide if the resolution is low, and the motor speed can be increased accordingly. It becomes. As a result, the time is shortened with respect to the distance of the section outside the document area, and as a result, the time between sheets is also shortened. On the other hand, when the resolution is high, the distance between the reading lines is short, so the motor speed is decreased and the distance advanced every 100 μs is shortened. As a result, since the total reading time is required compared with the low resolution, the time between sheets is increased accordingly. As described above, since the time between sheets for the reading condition changes due to various factors, the level is set according to the time.

  At each level, a dust detection / avoidance process that is completed within each paper interval is defined. In the dust detection / avoidance process, the time required for each dust detection or movement between reading positions is shown in the schematic diagram of FIG.

  In the case of FIG. 10A, the dust detection time for one reading position is 20 ms, the interval between each reading position is 0.25 mm, and converted to time is 110 ms. The movement between the reading positions includes acceleration / deceleration. Therefore, when moving from the third reading position to the first reading position all at once, the number of acceleration / decelerations is reduced, so that the movement can be performed in a shorter time than when stopping at every reading position. The time in this case is 200 ms.

  In the case of FIG. 10B, the dust detection time is the same as that in FIG. 10A (20 ms), but the interval from each reading position is 0.5 mm, which is 220 ms in terms of time. It is 400 ms when moving from the third reading position to the first reading position at once, and 600 ms when moving from the fourth reading position to the first reading position at once.

  In this way, the contents of the dust detection / avoidance process at each level are determined in consideration of each time in FIG.

  For example, at level 0, the paper interval time is short and it is impossible to move to another reading position. Therefore, dust detection is performed only at one of the default reading positions as the home position, or dust detection is not performed. .

  In the case of level 1, for example, under the reading condition where the sheet interval time is 300 ms, dust detection can be performed at two locations if the interval between the reading candidate positions is shortened. If it can be executed in two places, even if it is determined that there is “dust” at the first reading position, it may be determined that there is “no dust” at the second reading position. In this case, reading is performed at the first reading position. It is possible to obtain a better image than that performed.

  Even if it is determined that “dust is present” at all reading positions, if the “priority reading candidate position” in step S303 in FIG. 6 is the first reading position, the maximum time required for dust detection / avoidance processing is 260 ms, and all operations can be completed within the paper interval. As the time between sheets increases, dust detection can be performed at more reading positions, and the possibility of determining “no dust” increases. In addition, by widening the interval between the reading positions, when there is unevenness in how dust adheres, there is an increased possibility that dust detection and reading can be performed at locations where the dust distribution is small. In particular, when the resolution specified by the reading condition is high, high-quality and high-definition image reading is required. Therefore, it is desirable to perform dust detection / avoidance processing as much as possible within the sheet interval.

  As described above, according to the first embodiment, the level of dust detection / avoidance processing (processing content) that can be executed within the time based on the inter-paper time in the section outside the document area specified from each reading condition. ) Is adaptively selected and executed. As a result, it is possible to increase the chances of acquiring better image data than the conventional technique without reducing the productivity of image reading.

<Embodiment 2>
The first embodiment is configured to select and execute a level (processing content) of dust detection / avoidance processing that is completed within the inter-sheet time specified from the reading condition input from the operation unit 105. However, the sheet interval time is not necessarily the time expected from the reading conditions, and is determined from, for example, the interval between the preceding document and the next document when a plurality of continuous documents are actually conveyed at intervals. Alternatively, the paper interval time at the reading position may be predicted or determined, and the level of dust detection / avoidance processing to be performed may be determined based on the paper interval time. In the second embodiment, this determination method will be described with reference to FIGS. 11 and 12.

  FIG. 11 is a flowchart for calculating the actual sheet interval time. FIG. 12 is a flowchart showing a reading process for executing the continuous reading for determining the dust avoidance level based on the actual paper interval time.

  The processing program for executing the processing of FIGS. 11 and 12 is stored in the ROM 28, and the main CPU 24 performs the following operation by executing this processing program.

<Paper time calculation (FIG. 11)>
The main CPU 24 determines whether or not the trailing edge of the document that has been transported in advance has turned off the document position detection sensor 121i (step S401). The document position detection sensor 121i here is, for example, a read sensor. The detection of the sensor OFF is preferably interrupted, but the sensor state may be detected each time by polling at a constant cycle.

  If sensor OFF is not detected (NO in step S401), the process waits until it is detected. On the other hand, when the sensor OFF is detected (YES in step S401), the main CPU 24 acquires the OFF time of the document position detection sensor 121i and stores it in the RAM 27 (step S402). The OFF time, the ON time described later, the reading end time, and the like may be acquired from the time (timer) set in the image reading apparatus 103, or the start time of the scanning reading scan is set to 0 and is used as a reference. It may be the time measured.

  Next, the main CPU 24 determines whether or not a subsequent document has turned on the document position detection sensor 121i (step S403). The detection of the sensor ON is preferably interrupted as in step S401, but it may be polled at a constant period to detect the sensor state each time.

  When the sensor ON is detected (YES in step S403), the main CPU 24 acquires the ON time of the document position detection sensor 121i and stores it in the RAM 27 (step S406). Then, the main CPU 24 calculates the current paper interval time from the difference between the OFF time and the ON time of the document position detection sensor 121i stored in the RAM 27, and stores it in the RAM 27 (step S407).

  On the other hand, if the sensor ON is not detected (NO in step S403), the main CPU 24 determines whether or not the preceding document has been read (step S404). This determination may be made based on, for example, read image data, or may be determined to be complete when a predetermined timing has elapsed since the document position detection sensor 121i was turned off.

  If reading of the preceding document is not completed (NO in step S404), the process returns to step S403. On the other hand, when the reading of the preceding document is completed (YES in step S404), the main CPU 24 acquires the reading end time and stores it in the RAM 27 (step S405). Then, the main CPU 24 calculates the current sheet interval time from the difference between the OFF time of the document position detection sensor 121i stored in the RAM 27 and the document reading end time, and stores it in the RAM 27 (step S407).

<Dust detection / avoidance processing by level (FIG. 12)>
First, when the user places a sheet document D on the document table 106 and presses the copy button on the operation unit 105, the main CPU 24 sets the level to be executed in the dust detection / avoidance process executed before reading the document. The “standard level” (level 3 in FIG. 9) is determined and stored in the RAM 27 (step S500).

  Next, the main CPU 24 executes dust detection / avoidance processing according to the level stored in the RAM 27 before starting reading the document (step S501). Next, the main CPU 24 initializes the value of the current reading line number n to 0 (step S502). The main CPU 24 executes reading of the document image on the nth line (step S503). Then, the main CPU 24 performs dust correction on the read image based on the detection result by the dust detection processing of FIG. 5 (when there is no dust, the dust correction is not executed) (step S504). Thereafter, the main CPU 24 determines whether or not all lines have been read (step S505). If reading of all lines has not been completed (NO in step S505), the main CPU 24 increments the count of n by 1 (step S506). Thereafter, the process returns to step S503, and the main CPU 24 executes image reading of the (n + 1) th line.

  On the other hand, if all the lines have been read (YES in step S505), the main CPU 24 then determines whether or not the next document remains on the document table 106 (step S507). If there is a next original (NO in step S507), the main CPU 24 acquires the sheet interval time stored in the RAM 27 in the process of FIG. 11 (step S508). Next, the main CPU 24 determines a level for executing the dust detection / avoidance process from FIG. 9 based on the acquired inter-sheet time (step S509). In the level determination method, the level corresponding to the time range shown in FIG. 9B is stored in the RAM 27 as an execution level from the acquired inter-sheet time.

  Then, the process returns to step S501, and dust detection / avoidance processing is executed at the level stored in the RAM 27.

  On the other hand, if there is no next original (YES in step S507), the process ends.

  As described above, according to the second embodiment, the level of dust detection / avoidance processing (processing content) that can be performed within the time interval is adaptively selected based on the interval between sheets in the actual section outside the document area. ,Run. As a result, it is possible to increase the chances of acquiring better image data than the conventional technique without reducing the productivity of image reading.

<Embodiment 3>
The present invention is not limited to the embodiment described above. In addition, the effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

  For example, the reading conditions shown in FIG. 9, the level selection corresponding to the reading conditions, and the dust detection / avoidance process may be a combination of the number of detection points and the detection interval other than those shown in the table. Furthermore, the order of avoiding operations that can be completed in a shorter time may be adopted as the end condition of the dust avoiding operation.

  In the first embodiment, the level is determined based on the theoretical inter-paper time (first time) calculated from the reading conditions. In the second embodiment, the level is determined based on the actual inter-paper time (second time). However, the level may be determined by combining these two methods. For example, when the paper interval time calculated in step S407 in FIG. 11 is longer than the theoretical paper interval time calculated in step S201 in FIG.・ You can select an avoidance method. Alternatively, even when the time comparison result is the reverse of the above, a method of selecting the level of the corresponding time range can be considered.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (9)

An image reading device that reads an image of the document by a reading unit while conveying the document in a predetermined direction on a reading glass,
When the plurality of continuous documents are transported in the predetermined direction at intervals and the images of the respective documents are read by the reading unit, the inter-document time required from the completion of reading the preceding document to the start of reading the next document Acquisition means for acquiring;
A determination unit that determines a detection method in a detection unit that detects dust on the reading glass based on the inter-document time acquired by the acquisition unit;
An image reading apparatus comprising: a control unit that controls an operation of the detection unit according to a detection method determined by the determination unit. The detection unit is configured to read the reading position on the reading glass before the document passes or while the leading edge of the next document passes from the trailing edge of the preceding document among the plurality of continuous documents. The image reading apparatus according to claim 1, wherein dust on the reading glass is detected based on an image read by the image reading apparatus. The determination means is a detection method of selecting at least one of a plurality of reading candidate positions on the reading glass and detecting the dust at the selected reading candidate position, and selecting from the plurality of reading candidate positions One of a plurality of detection methods that differ in the number of reading candidate positions to be read or the distance between the reading candidate positions is detected by a detection unit that detects dust on the reading glass based on the time between documents acquired by the acquisition unit. The image reading apparatus according to claim 1, wherein the image reading apparatus is selected as a method. The plurality of detection methods are associated with different time ranges,
The determination unit selects a detection method corresponding to a time range including the inter-document time acquired by the acquisition unit among the plurality of detection methods as a detection method in a detection unit that detects dust on the reading glass. The image reading apparatus according to claim 3. An input unit for inputting the reading condition of the document;
The image reading apparatus according to claim 1, wherein the acquisition unit acquires a time specified by a reading condition input by the input unit as the inter-document time. The image reading apparatus further comprises detection means for detecting the position of the document existing in the document transport path of the image reading apparatus,
The acquisition means calculates the time from when the detection means detects the trailing edge of the preceding document among the plurality of continuous documents until the leading edge of the next document is detected, or the trailing edge at the reading position of the preceding document. 5. The image reading apparatus according to claim 1, wherein the earlier time of the time until detection is acquired as the time between the originals. 6. Input means for inputting the reading conditions of the original;
Detection means for detecting the position of the document existing in the document transport path of the image reading apparatus;
The acquisition unit detects a first time specified by the reading condition input by the input unit and a next document after the detection unit detects a trailing edge of a preceding document among the plurality of continuous documents. 5. The image reading according to claim 1, wherein the second time is preferentially acquired as the time between documents in the second time until the leading edge is detected. 5. apparatus. A method for controlling an image reading apparatus that reads an image of a document by a reading unit while conveying the document in a predetermined direction on a reading glass,
When the plurality of continuous documents are transported in the predetermined direction at intervals and the images of the respective documents are read by the reading unit, the inter-document time required from the completion of reading the preceding document to the start of reading the next document An acquisition process to acquire;
A determination step of determining a detection method in a detection unit for detecting dust on the reading glass based on the time between documents acquired in the acquisition step;
And a control step of controlling the operation of the detection unit in accordance with the detection method determined in the determination step. A program for causing a computer to control the image reading apparatus that reads an image of the original document by a reading unit while conveying the original document in a predetermined direction on the reading glass,
The computer,
When the plurality of continuous documents are transported in the predetermined direction at intervals and the images of the respective documents are read by the reading unit, the inter-document time required from the completion of reading the preceding document to the start of reading the next document Acquisition means for acquiring;
A determination unit that determines a detection method in a detection unit that detects dust on the reading glass based on the inter-document time acquired by the acquisition unit;
According to a detection method determined by the determination unit, the program functions as a control unit that controls the operation of the detection unit.

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