JP4900352B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus having a document conveying device that automatically conveys a document to a document reading position. More specifically, the present invention relates to an image reading apparatus that controls the reading timing of a document with high accuracy.

  2. Description of the Related Art Conventionally, there is an original reading apparatus equipped with an ADF (Auto Document Feeder) for automatic reading of a plurality of originals. The ADF includes a paper feed tray on which a document before reading is placed and a paper discharge tray on which the document after reading is placed. When at least one document is placed on the paper feed tray, the ADF starts from the upper document. The sheets are conveyed one by one toward the document reading position. The original is read by the scanner at the original reading position and conveyed to the paper discharge tray.

In the ADF, as described above, the original is read while being conveyed. Therefore, the reading start timing of the document is measured by detecting the leading edge of the document while the document is being conveyed. For example, a stepping motor capable of accurate positioning control is adopted as an ADF document transport motor, and a document sensor for detecting passage of paper is disposed in a document transport path. Then, the document reading position is at a certain position after the document passes the document sensor (for example, Patent Document 1).
JP 2006-33549 A

  However, the conventional image reading apparatus described above has the following problems. That is, in the reading method using ADF, the document sensor that detects the document starts reading after a certain step after detecting the leading edge of the document, and performs a certain step after detecting the trailing edge of the document. After a while, the reading is finished. Therefore, in order to read the document accurately, it is important that the document sensor detects the leading edge or the trailing edge of the document with high accuracy.

  The signal level of the document sensor is read each time a predetermined interrupt signal is detected. The interval between the interrupt signals is larger than the motor step interval. That is, the interrupt signal interval corresponds to several motor steps. Therefore, when the signal level of the document sensor changes between one interrupt signal and the next interrupt signal, the change in the document sensor cannot be recognized immediately, and an error of several steps occurs. As a result, the reading accuracy of the original document is degraded.

  The present invention has been made to solve the problems of the conventional image reading apparatus. That is, an object of the present invention is to provide an image reading apparatus that can accurately detect the reading timing of an original during automatic conveyance.

  An image reading apparatus for solving this problem is a reading unit that reads a document, a stepping motor that drives a conveyance roller that conveys the document, and an upstream side of the reading unit in the document conveyance direction. A sensor for detecting the passage of the signal, a line signal output means for outputting a pulse signal having a period corresponding to the reading time for one line by the reading means, and a motor drive signal for outputting a drive signal for the stepping motor synchronized with the pulse signal The output means, the interrupt signal output means for outputting an interrupt signal having a period corresponding to a predetermined number of pulses of the pulse signal, and the number of steps corresponding to the number of pulses of the drive signal are counted while the sensor output is at the first level. A counting means, a reset means for resetting the counter value of the counting means before the counting means starts counting, The output level of the sensor in response to the only signal, a determination means for determining whether or not the edge of the original has passed based on the output level, and the movement of the original from the position of the sensor to the reading position of the reading means Determining means for determining the reading timing of the reading means based on a value obtained by subtracting the counter value of the counter means at the time when the determination means determines that the document has passed from the number of steps. It is characterized by comprising.

  The image reading apparatus of the present invention has a function of automatically conveying and reading a document. The original is conveyed to the reading position of the reading means by a conveying roller driven by a stepping motor. The conveyance of the original is detected by a sensor. In the image reading apparatus, the number of steps (reference step number) necessary for moving the document from the position of the sensor to the reading position of the reading unit is defined. Then, when the sensor detects the document, the image reading apparatus determines the reading timing of the reading unit based on the reference step number. The read timing includes a read start timing and a read end timing.

  More specifically, the image reading apparatus counts the number of steps corresponding to the number of pulses of the drive signal for the stepping motor while the output of the sensor is at the first level. Further, the image reading apparatus acquires the output level of the sensor based on an interrupt signal having a period corresponding to a predetermined number of pulses of the pulse signal. The acquisition timing may be, for example, every pulse of the interrupt signal or every few pulses. Thereafter, based on the output level of the sensor, it is determined whether or not the end of the document has passed. For example, if the sensor output is the first level, it may be determined that the end of the document has passed unconditionally. If the output is the first level continuously for a predetermined number of times, the end of the document may be determined. It may be determined that has passed. When it is determined that the edge of the document has passed, based on the value obtained by subtracting the “counter value when it is determined that the edge of the document has passed” from the “reference step number”. Determine the read timing.

  That is, the image reading apparatus of the present invention counts the number of steps after the end of the document passes (that is, the sensor changes to the first level), and determines the reading timing based on the count value. Therefore, in the image reading apparatus of the present invention, the error is within a distance corresponding to one step. Therefore, the leading edge detection or trailing edge detection of the document becomes highly accurate as compared with the conventional technique (the error is within a distance corresponding to the period (several steps) of the interrupt signal).

  In addition, the image reading apparatus of the present invention includes a second count unit that counts the number of steps corresponding to the number of pulses of the drive signal while the output of the sensor is at the second level, and before the count of the second count unit starts, Second reset means for resetting the second count means, and the reset means has a counter value of the second count means equal to or greater than a threshold when the sensor output level changes from the second level to the first level. In this case, it is better to reset the counting means.

  In other words, the image reading apparatus includes the second count unit that counts up between the second levels in which the output level of the sensor is different from the first level. The reset means does not reset the count means when the counter value of the second count means is smaller than the threshold value. That is, when the counter value of the second count means is smaller than the threshold value, it is considered that the period of the second level is short and the sensor value is instantaneously changed due to noise or the like. Therefore, the reset means ignores such a short-term change, thereby avoiding the influence of variations in sensor output level. Thereby, the reading timing of the original can be detected with higher accuracy.

  Further, the second reset unit of the image reading device described above is configured to switch the second count unit when the count value of the count unit is equal to or greater than a threshold when the output level of the sensor changes from the first level to the second level. Better to reset.

  That is, in an image reading apparatus having a counting means that counts up when the sensor is at the first level and a second counting means that counts up when the sensor is at the second level, one of the counting means detects passage of the leading edge of the document and reads it. It is possible to increase the accuracy of the start timing and to detect the passage of the trailing edge of the document with the other counting means, thereby increasing the accuracy of the reading end timing. Therefore, even in the second reset means, when the counter value of the count means that counts up at the first level is smaller than the threshold value, the influence of variations in the output level of the sensor is avoided by not resetting. Thereby, both the reading start timing and the reading end timing of the document can be detected with higher accuracy.

  According to the present invention, an image reading apparatus that can detect the reading timing of a document during automatic conveyance with high accuracy is realized.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying an image reading apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a multi-function machine having a telephone function, a scanner function, a printer function, a copy function, a facsimile function, and the like.

[First embodiment]
[Overall configuration of MFP]
As shown in FIG. 1, the MFP 100 of the first embodiment includes an image forming unit 10 that prints an image on a sheet, and a document reading unit 20 that reads a document image. In addition, an operation panel 40 having a liquid crystal display 41 and a button group 42 is provided on the front side of the document reading unit 20, and the operation panel 40 can display an operation status and input a user operation. . The image forming method of the image forming unit 10 may be an electrophotographic method or an ink jet method. Further, even if a color image can be formed, it may be dedicated to a monochrome image.

[Configuration of the document reader]
As shown in FIG. 2, the document reading unit 20 includes a scanner unit 21 that reads an image of a document and an ADF (Auto Document Feeder) 22 that automatically conveys the document. The scanner unit 21 includes two platen glasses 23 and 24 located on the upper surface thereof, and a CCD unit 25 located therein.

  The CCD unit 25 includes a CCD sensor 251, an optical element 252 made of a lens, and a light source 253 made of a cold cathode tube. The reflected light of the light source 253 is guided to the optical element 252 and imaged on the CCD sensor 251. Then, it is converted into an electric signal by the CCD sensor 251. The reading unit is not limited to the CCD system, but may be a CIS (Contact Image Sensor) system, for example.

  The ADF 22 includes a document tray 221 on which a document before reading is placed and a discharge tray 222 on which the document after reading is placed. Specifically, the document tray 221 is disposed above the discharge tray 222. Then, the ADF 22 takes out the originals placed on the original tray 221 one by one, reads the originals, and then discharges the originals onto the discharge tray 222. Further, the ADF 22 covers the upper portion of the scanner unit 21 so that it can be opened and closed, and also functions as a document pressing cover for the document placed on the document placement table including the platen glasses 23 and 24.

  As a document reading method, there are a flat bed (document fixed scanning) method and an ADF (document moving scanning) method. In the case of the flat bed system, documents are placed one by one on a platen glass 24 (hereinafter referred to as “FB glass 24”). In this state, the CCD unit 25 moves in the sub-scanning direction (the direction orthogonal to the main scanning direction, the direction of arrow A in FIG. 2), and at that time, the image of the document is read line by line in the main scanning direction. On the other hand, in the case of the ADF method, the originals are collectively placed on the original tray 221. Then, the CCD unit 25 is moved to a position facing the platen glass 23 (hereinafter referred to as “ADF glass 23”) and fixed. In this state, the document is conveyed to a position (reading position) facing the ADF glass 23, and at that time, the image of the document is read line by line in the main scanning direction.

  Next, the ADF 22 will be described in detail. Inside the ADF 22, there are provided various rollers such as a suction roller 271, a separation roller 272, a transport roller 273, 274, and a paper discharge roller 275, and a document presser 278 facing the ADF glass 23, and thereby the document tray 221 and A substantially U-shaped conveyance path that connects the discharge tray 222 is provided. The ADF 22 includes an ADF motor 28 that drives various rollers, and the ADF motor 28 automatically rotates the various rollers to automatically convey the original. For the ADF 28, a stepping motor capable of accurate positioning control is adopted.

  Specifically, the transport path of the ADF 22 starts from the document tray 221, is taken into the ADF 22 by the suction roller 271 and the separation roller 272, makes a U-turn via the transport rollers 273, 274, and the document presser 278 and the ADF glass 23. , And a path toward the discharge tray 222 through the discharge roller 275. Then, the image of the document is read at the reading position.

  In addition, the ADF 22 includes a document sensor 29 that detects the document S passing through the conveyance path. In this embodiment, the document sensor 29 is arranged at a position in the document conveyance direction where a document passing between the reading roller and the conveyance roller 274 that finally conveys the document to the reading position can be detected. Based on the output level of the document sensor 29, it can be detected that the leading or trailing edge of the document has passed.

  The image reading unit 20 measures the document reading start timing by detecting the leading edge of the document. In addition, the document reading end timing is measured by detecting the trailing edge of the document. Specifically, the document sensor 29 starts reading after a certain period after detecting the leading edge of the document, and ends reading after a certain period after detecting the trailing edge of the document. . That is, the document reading timing is determined based on the signal from the document sensor 29.

[Electric configuration of copier]
Next, the electrical configuration of the multifunction machine 100 will be described. As illustrated in FIG. 3, the copying machine 100 includes a CPU 31, a ROM 32, a RAM 33, an NVRAM (nonvolatile memory) 34, and an ASIC 30. The ASIC 30 is electrically connected to the image forming unit 10, the document reading unit 20, the operation panel 40, and the like.

  The ROM 32 stores various control programs for controlling the copying machine 100, various settings, initial values, and the like. The RAM 33 is used as a work area from which various control programs are read or as a storage area for temporarily storing image data. The CPU 31 controls each component of the copying machine 100 while storing the processing result in the RAM 33 or NVRAM 34 according to the control program read from the ROM 32.

  FIG. 4 shows a functional configuration of the ASIC 30 focusing on the relationship with the image reading unit 20. The ASIC 30 includes a control unit 301 that controls the CCD unit 25 and the ADF motor 28, a sensor reception unit 303 that receives a signal from the document sensor 29, an ON counter 304 that counts the number of steps of the ADF motor 28, and an OFF counter 305 (counting). And an example of the second counting means). Note that the ON counter 304 is a counter that counts up on condition that the output level of the document sensor 29 is high (ON level), and the OFF counter 305 is that the output level of the document sensor 29 is low (OFF level). It is a counter that counts up on the condition that

  The control unit 301 outputs a drive signal for the ADF motor 28 to control the ADF motor 28, and outputs a drive signal for the CCD unit 25 to control the CCD unit 25. Further, the control unit 301 acquires the output level of the document sensor 29 and the counter value of the ON counter 304 to the OFF counter 305 when instructed to read the document by the ADF method, and reads the CCD unit 25 based on these. The start timing and reading end timing are determined. A method for obtaining the reading timing will be described later.

[ADF reading process]
Next, the procedure of the operation of the multifunction peripheral 100 (ADF reading process) when receiving a document reading command by the ADF method will be described with reference to the flowchart of FIG. It is assumed that at least one document is placed on the document tray 221 of the ADF 22.

  First, each roller in the ADF 22 is driven by the ADF motor 28 (S101). As a result, the originals are taken into the ADF 22 one by one by the suction roller 271 and moved along the conveyance path via the separation roller 272, the conveyance rollers 273 and 274.

  Next, it is determined by the document sensor 29 whether or not the leading edge of the document has passed (S102). More specifically, in the process of S102, the timing at which the leading edge of the document passes is detected. If the leading edge of the document has passed (S102: YES), the reading start timing is determined (S103). That is, the timing at which the leading edge of the document reaches the reading position is measured. Then, when the reading start timing comes, reading of the original by the CCD unit 25 is started (S104).

  Next, it is determined by the document sensor 29 whether or not the trailing edge of the document has passed (S105). More specifically, in the process of S105, the timing at which the trailing edge of the document passes is detected. If the trailing edge of the document has passed (S105: YES), the reading end timing is determined (S106). That is, the timing at which the trailing edge of the document reaches the reading position is measured. Then, when the reading end timing is reached, reading of the original by the CCD unit 25 is ended (S107). Details of the method for determining the document reading start timing and the document reading end timing will be described later.

  After reading the document and discharging the document to the discharge tray 222, if there is no document on the document tray 221, the ADF motor 28 is stopped and the conveyance of the document is ended (S108). After the conveyance of the original is completed, this process is terminated.

[How to determine the document reading start timing]
Next, a method for determining the document reading start timing in the multifunction peripheral 100 of the present embodiment will be described with reference to the timing chart of FIG.

  As shown in FIG. 6, the ASIC 30 of the multi-function peripheral 100 outputs a pulse signal (hereinafter referred to as “reading line end signal”) having a period corresponding to the reading time for one line by the CCD unit 25 (line signal output). Example of means). Further, a driving signal for the ADF motor 28 (hereinafter referred to as “motor driving pulse signal”) is output in synchronization with the reading line end signal (an example of motor driving signal output means). It is assumed that the ADF motor 28 of this embodiment has an excitation phase mode of 2w1-2 phase and is driven by one step with one pulse of the read line end signal.

  Furthermore, the ASIC 30 outputs an interrupt signal having a period corresponding to a predetermined number of pulses (four pulses in this embodiment) of the read line end signal (an example of an interrupt signal output unit). In response to this interrupt signal, the CPU 31 acquires the signal level of the document sensor 29. Based on the acquired signal level, the passage of the leading edge and the trailing edge of the document is determined.

  The ON counter 304 is counted up while the document sensor 29 is outputting a high level (ON level). The OFF counter 305 is counted up while the document sensor 29 is outputting a low level (OFF level). In addition, the ON counter 304 and the OFF counter 305 add a predetermined number of steps for each pulse of the motor drive pulse signal, and store it in the respective read registers. Saving to the read register may be the timing of the read line end signal or the timing of the interrupt signal. The ADF motor 28 of this embodiment has an excitation phase mode of 2w1-2 phase, and is added step by step.

  The counter value of the ON counter 304 is reset to 0 when the document sensor 29 changes from the OFF level to the ON level. On the other hand, the counter value of the OFF counter 305 is reset to 0 when the document sensor 29 changes from the ON level to the OFF level.

  The procedure for determining the document reading start timing will be described below. In the present embodiment, when the signal level of the document sensor 29 read in synchronization with the interrupt signal is continuously ON three times, it is determined that the document sensor 29 is completely turned on. Further, it is assumed that image reading by the CCD unit 25 is started 16 steps after the document sensor 29 is turned ON, and the step number “16” is “reference step number” (position of the sensor for detecting passage of the document). Is stored in the ROM 32 as the number of steps required to move the document from the reading position to the reading position of the reading means.

  First, the ON counter 304 counts the number of motor steps driven after the time when the document sensor 29 changes to ON ((A) in FIG. 6). The ON counter 304 is counted up from 0 because the document sensor 29 is reset when the document sensor 29 changes from the OFF level to the ON level. On the other hand, the OFF counter 305 stops counting from the time when the document sensor 29 changes to ON.

  Thereafter, the reading line end interrupt software process detects the ON level of the document sensor 29 at the time (1) in FIG. The ON level is detected for the first time, then the second time is detected at the time point (2), and the third time is detected at the time point (3). Then, since the ON of the document sensor 29 is detected three times continuously at the time (3) in FIG. 6, it is determined that the document sensor 29 is completely turned on (an example of a determination unit). ).

When it is determined that the document sensor 29 is ON, the counter value is read from the read register of the ON counter 304. Then, based on the counter value, the number of remaining steps until the image reading at the time (3) in FIG. 6 is started is calculated (an example of a determination unit). Specifically, it is obtained by the following equation (I).
(Remaining steps) = (Reference step number)-(Counter value) (I)
In the example of FIG. 6, since the counter value is 10, the remaining 6 steps are 16-10. As a result, image reading is started at a time point (B) six steps after a time point (3) in FIG.

  That is, in the MFP 100 of this embodiment, the number of steps of the ADF motor 28 is counted from when the document sensor 29 is turned on, that is, from when the leading edge of the document is detected. Based on the counter value, the document reading start timing is determined. For this reason, the document reading start timing is determined with reference to the time point (A) when the document sensor 29 changes to ON. As a result, in this embodiment, the maximum error of the reading start timing is within one step corresponding to the cycle of the motor drive pulse signal.

  On the other hand, in the conventional procedure, when it is determined that the document sensor 29 is completely turned on at the time (3) in FIG. 6, the time point (1) when the document sensor 29 is detected for the first time is detected. As a reference, the remaining number of steps is calculated as 16-8 and 8 steps. For this reason, image reading is started at a time point (C) 8 steps after a time point (3) in FIG. As a result, there is an error in two steps from when the document sensor 29 is turned on until the next interrupt signal is output. That is, in the conventional procedure, the maximum error in the reading start timing is the number of steps (4 steps in FIG. 6) corresponding to the period of the interrupt signal. From this, it can be seen that the reading start timing of the multifunction device 100 of the present embodiment is more accurate than the conventional one.

  In the MFP 100 according to the present embodiment, one step of the ADF motor 28 is incremented by one for each step, taking the 2w1-2 phase, which is the finest excitation phase mode, as an example. Absent. For example, if the excitation phase mode is 2-2 phase, the count is incremented by 8 per step as shown in FIG. In addition, if the excitation phase mode is the w1-2 phase, the count is incremented by two. If the excitation phase mode is 1-2 phase, count up by four. Further, when the excitation phase mode is switched during the operation of the ADF motor 28, the count-up number is switched according to the switched excitation phase mode.

[How to determine the document reading end timing]
Next, a method of determining the document reading end timing in the multifunction peripheral 100 of the present embodiment will be described with reference to the timing chart of FIG.

  The document reading end timing determination method is the same as the document reading start timing determination method except that the on / off level is opposite. That is, when the signal level of the document sensor 29 read in synchronism with the interrupt signal is continuously OFF three times, it is determined that the document sensor 29 is completely turned off. Further, it is assumed that the image reading is finished 16 steps after the document sensor 29 changes to OFF.

  First, the OFF counter 305 counts the number of motor steps driven after the time when the document sensor 29 changes to OFF ((A) in FIG. 8). Note that the OFF counter 305 is reset from 0 because the document sensor 29 is reset when the document sensor 29 changes from the ON level to the OFF level. On the other hand, the ON counter 304 stops counting from the time when the document sensor 29 changes to OFF.

  Thereafter, at time (3) in FIG. 8, the document sensor 29 is detected to be OFF three times in succession, and it is determined that the document sensor 29 is completely turned OFF. Therefore, the counter value is read from the read register of the OFF counter 305. Then, based on the counter value, the number of remaining steps until the end of image reading at the point (3) in FIG. 8 is calculated. In the example of FIG. 8, since the counter value is 10, the remaining 6 steps are 16-10. Thus, the image reading is completed at the time (B), which is six steps after the time (3) in FIG.

  As described above, by providing the OFF counter for the OFF level in addition to the ON counter 304 for the ON level, even if it is the document reading end timing, it can be obtained by the same procedure as the document reading start timing. it can. Even if there is only one counter, it is possible to improve the accuracy of the timing of either the document reading start timing or the reading end timing.

[Second form]
The multifunction machine of the second embodiment sets a threshold value as a condition for resetting the ON counter 304 and the OFF counter 305 in consideration of output variations of the document sensor 29 caused by noise or the like. This is different from the first embodiment. Note that the hardware configuration of the copying machine is the same as that of the first embodiment, and a description thereof will be omitted.

  The MFP of this embodiment stores a threshold value (hereinafter referred to as “reset threshold value”) in the ROM 32 for determining whether or not to reset the ON counter 304 to the OFF counter 305. The counter value of the ON counter 304 is reset when the counter value of the OFF counter 305 is acquired at the timing when the document sensor 29 changes from the OFF level to the ON level, and the counter value is larger than the reset threshold value. On the other hand, the counter value of the OFF counter 305 is reset when the counter value of the ON counter 304 is acquired at the timing when the document sensor 29 changes from the ON level to the OFF level, and the counter value is larger than the reset threshold.

  That is, the document sensor 29 may instantaneously change to the ON level or OFF level due to the influence of noise or the like. At this time, if the ON counter 304 or the OFF counter 305 is reset in response to the instantaneous change, the determination of the reading timing is adversely affected. Therefore, it is determined whether or not it is such an instantaneous change, and if it is an instantaneous change, control is performed so as not to reset.

  Hereinafter, the counter clearing procedure of this embodiment will be described with reference to the timing chart of FIG. In this embodiment, the reset threshold is 3.

  First, at the time of FIG. 9A, the document sensor 29 changes from the OFF level to the ON level. Therefore, the counter value of the OFF counter 305 is “12”, which is larger than the reset threshold. For this reason, it can be determined that the change has occurred after being continuously at the OFF level for a predetermined period or longer, and the ON counter 304 is reset.

  Next, at the time of FIG. 9B, the document sensor 29 changes from the ON level to the OFF level. Therefore, the counter value of the ON counter 304 is “2”, which is smaller than the reset threshold. Therefore, it can be determined that the change is instantaneous, and the OFF counter 305 is not reset.

  Next, at the time of FIG. 9C, the document sensor 29 is changed from the ON level to the OFF level. Therefore, the counter value of the ON counter 304 is “4”, which is larger than the reset threshold. Therefore, it can be determined that the change has been made after the ON level has been continuously ON for a predetermined period or longer, and the OFF counter 305 is reset.

  Next, at the time of FIG. 9D, the document sensor 29 is changed from the OFF level to the ON level. Therefore, the counter value of the OFF counter 305 is “2”, which is smaller than the reset threshold. Therefore, it can be determined that the change is instantaneous, and the ON counter 304 is not reset.

  Thus, in the case of an instantaneous change (ON between (A) and (B) in FIG. 9, OFF between (C) and (D)), the number counted is small. Therefore, when the number of counts is small, the influence of instantaneous changes due to noise or the like is avoided by not resetting. Thereby, the reading timing of the original can be detected with higher accuracy. In this embodiment, the reset threshold is common to the ON counter 304 and the OFF counter 305, but the reset threshold may be provided separately.

  As described in detail above, the multifunction peripheral 100 according to the present embodiment counts the number of steps of the ADF motor 28 while the output of the document sensor 29 is ON. In response to the interrupt signal, the output level of the document sensor 29 is acquired, and passage of the end of the document is determined based on the output level. Then, the reading start timing of the CCD unit 25 is obtained by subtracting the “counter value when it is determined that the leading edge of the document has passed” from the “reference step number” corresponding to the number of steps from the document sensor 29 to the reading position. Determined based on the value.

  That is, the count value of the counter 304 at the time when the edge of the document passes (that is, when it is determined that the document sensor 29 has changed to the ON level) is obtained, and the value obtained by subtracting the count value from the reference step number is read. The remaining number of steps to the position. Therefore, in the multi-function device 100, the error is within a distance corresponding to one step. Therefore, the document reading timing during automatic conveyance is highly accurate.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention is not limited to a multi-function machine, and can be applied to any apparatus having an automatic document conveyance function and a reading function, such as a copying machine, a scanner, and a FAX.

  Further, in the embodiment, the high level (ON level) is set when the document sensor 29 detects a document, and the low level (OFF level) is set when no document is detected. That is, the low level may be set when the document sensor 29 detects a document, and the high level may be set when it is not detected.

  In the embodiment, the signal level of the document sensor 29 is read every time an interrupt signal is detected. However, the present invention is not limited to this. For example, the interrupt signal may be read by detecting a predetermined number of times.

  In the embodiment, it is determined that the document sensor 29 is turned on when the signal level of the read document sensor 29 is continuously ON three times. However, the present invention is not limited to this. For example, it may be determined that it is turned on immediately after being turned on once. Further, even if it is discontinuous, it may be determined that the signal has been turned ON by the fourth or more ON level detection.

1 is a diagram illustrating an appearance of a multifunction machine according to an embodiment. FIG. 2 is a cross-sectional view illustrating a schematic configuration of an image reading unit of a multifunction machine. 1 is a block diagram showing an electrical configuration of a multifunction machine according to an embodiment. It is a block diagram which shows the function structure of ASIC which paid its attention to the relationship with an image reading part. 6 is a flowchart showing a procedure for reading an original in the ADF method. 6 is a timing chart showing an on / off state of a sensor signal and a state of a counter (2w1-2 phase) at the time of determining a document reading start timing. 6 is a timing chart showing an on / off state of a sensor signal and a state of a counter (2-2 phase) at the time of determining a document reading start timing. 6 is a timing chart showing an on / off state of a sensor signal and a state of a counter (2w1-2 phase) at the time of determining a document reading end timing. It is a timing chart which shows the ON / OFF state of a sensor signal at the time of determination of counter clear, and the state of a counter (2w1-2 phase).

Explanation of symbols

10 Image forming unit 20 Document reading unit 22 ADF
25 CCD unit 28 ADF motor 29 Document sensor 30 ASIC
304 ON counter 305 OFF counter 100 MFP

Claims (5)

Reading means for reading a document;
A stepping motor that drives a conveying roller that conveys the document;
A sensor located upstream of the reading means in the document conveying direction and detecting passage of the document;
Line signal output means for outputting a pulse signal having a period corresponding to a reading time for one line by the reading means;
Motor drive signal output means for outputting a drive signal for the stepping motor synchronized with the pulse signal;
Interrupt signal output means for outputting an interrupt signal having a period corresponding to a predetermined number of pulses of the pulse signal;
Counting means for counting the number of steps corresponding to the number of pulses of the drive signal while the output of the sensor is at the first level;
Second counting means for counting the number of steps corresponding to the number of pulses of the drive signal while the output of the sensor is at the second level;
If the counter value of the second counting means at the time when the output level of the sensor changes from the second level to the first level before the counting means starts counting, the counter value of the counting means Reset means for resetting
Second reset means for resetting the second count means before the second count means starts counting;
Determining means for acquiring an output level of the sensor in response to the interrupt signal and determining whether or not an end portion of the document has passed based on the output level;
It defines the number of steps required to move the document to the reading position of the reading means from the position of the sensor, of the count means when the document by said determining means from the number of steps is determined to have passed An image reading apparatus comprising: a determination unit that determines a reading timing of the reading unit based on a value obtained by subtracting a counter value. The image reading apparatus according to claim 1 ,
The second reset means resets the second count means when the counter value of the count means is equal to or greater than a threshold value when the output level of the sensor changes from the first level to the second level. A characteristic image reading apparatus. In the image reading device according to any one of claims 1 to 2 ,
The image reading apparatus according to claim 1, wherein the determination unit acquires an output level of the sensor every time the interrupt signal is generated. In the image reading apparatus according to any one of claims 1 to 3 ,
The image reading apparatus according to claim 1, wherein the determination unit determines that the leading edge of the document has passed when the output level of the sensor is the first level for a predetermined number of times. In the image reading device according to any one of claims 1 to 4 ,
The determination unit determines that the trailing edge of the document has passed when the output level of the sensor is the second level continuously for a predetermined number of times.

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