JP2017109857A - Double feed detection device, double feed detection method, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double feed detection device, a double feed detection method, and a control program, capable of restraining wrong detection of double feed while suppressing increase of a device cost or a device size.SOLUTION: A double feed detection device comprises: an ultrasonic oscillator outputting ultrasonic waves; an ultrasonic receiver disposed facing the ultrasonic oscillator and outputting a signal acceded to the received ultrasonic waves; a filter 143 capable of changing a passage frequency band to either one of a first frequency band including a peak frequency of the ultrasonic waves output by the ultrasonic oscillator, or a second frequency band including no peak frequency; a setting part setting the passage frequency band of the filter; and a detection part detecting occurrence of sheet double feed on the basis of the signal value treated by using the filter. The setting part sets the passage frequency band of the filter to the second frequency band when the signal value of the signal treated by using the filter set to the first frequency band is larger than a threshold value for abnormality determination.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a double feed detection device, a double feed detection method, and a control program, and more particularly, to a double feed detection device, a double feed detection method, and a control program for detecting double feed using an ultrasonic oscillator and an ultrasonic receiver.

  An apparatus such as a scanner that conveys an original and reads an image of the conveyed original has a function of detecting whether or not a multi-feed in which a plurality of originals are conveyed is generated. In general, a multifeed detection device such as a scanner includes an ultrasonic oscillator that outputs an ultrasonic wave and an ultrasonic receiver that outputs a signal corresponding to the received ultrasonic wave, and the ultrasonic receiver when a document is conveyed Detects double feed based on the signal output by. However, such a multifeed detection device usually has a converter using a switching method such as a DC-DC (Direct Current) converter. Such a converter may generate switching noise, and if the ultrasonic receiver receives this switching noise together with the ultrasonic wave output from the ultrasonic oscillator, there is a possibility that double feed cannot be detected correctly.

  Equipped with an ultrasonic transmitter and an ultrasonic receiver, based on the reception level of ultrasonic waves received by the ultrasonic receiver, it detects the overlap of sheets passing between the ultrasonic transmitter and the ultrasonic receiver A duplicate detection apparatus is disclosed. This duplication detection device extracts the maximum reception level from the reception levels of ultrasonic waves when the drive frequency of the ultrasonic waves transmitted by the ultrasonic transmitter is changed. Then, the duplication detection device automatically sets the ultrasonic driving frequency when the maximum reception level is obtained as the optimum driving frequency for the duplication detection of the sheet-like object (see Patent Document 1).

JP 2009-73604 A

  In a double feed detection device, it is desired to suppress erroneous detection of double feed while suppressing an increase in device cost or device size.

  An object of the present invention is to provide a double feed detection device, a double feed detection method, and a control program capable of suppressing erroneous detection of double feed while suppressing an increase in device cost or device size.

  The double feed detection device according to one aspect of the present invention includes an ultrasonic oscillator that outputs ultrasonic waves, an ultrasonic receiver that is disposed opposite to the ultrasonic oscillator and outputs a signal corresponding to the received ultrasonic waves, A filter capable of changing the pass frequency band to either the first frequency band including the peak frequency of the ultrasonic wave output from the ultrasonic oscillator and the second frequency band not including the peak frequency, and a setting for setting the pass frequency band of the filter And a detection unit that detects the occurrence of double feeding of paper based on the signal value of the signal processed using the filter, and the setting unit includes a filter set in the first frequency band. It is determined whether or not the signal value of the processed signal is equal to or less than the abnormality determination threshold value. If the signal value is greater than the abnormality determination threshold value, the pass frequency band of the filter is set to the second frequency band.

  The double feed detection method according to one aspect of the present invention includes an ultrasonic oscillator that outputs ultrasonic waves, an ultrasonic receiver that is disposed opposite to the ultrasonic oscillator and outputs a signal corresponding to the received ultrasonic waves, A multifeed in a multifeed detection apparatus comprising: a filter capable of changing a pass frequency band to either a first frequency band including a peak frequency of ultrasonic waves output from an ultrasonic oscillator or a second frequency band not including a peak frequency. A detection method includes: setting a pass frequency band of a filter; and detecting the occurrence of double feeding of paper based on a signal value of a signal processed using the filter. It is determined whether or not the signal value of the signal processed using the filter set in the frequency band is equal to or lower than the abnormality determination threshold value. To set the frequency band.

  A control program according to one aspect of the present invention includes an ultrasonic oscillator that outputs an ultrasonic wave, an ultrasonic receiver that is disposed opposite to the ultrasonic oscillator and outputs a signal corresponding to the received ultrasonic wave, and an ultrasonic wave A control program to be executed by a multifeed detection device having a filter capable of changing a pass frequency band to either a first frequency band including a peak frequency of ultrasonic waves output from an oscillator or a second frequency band not including a peak frequency And setting the pass frequency band of the filter, and causing the double feed detection device to detect that the double feed of the paper has occurred based on the signal value of the signal processed using the filter, and set , It is determined whether or not the signal value of the signal processed using the filter set in the first frequency band is equal to or less than the abnormality determination threshold value. Setting the pass frequency band of the filter in the second frequency band.

  According to the present invention, the double feed detection device can suppress erroneous detection of double feed while suppressing an increase in device cost or device size.

1 is a perspective view showing a document conveying device 100 according to an embodiment. 4 is a diagram for explaining a conveyance path inside document conveying apparatus 100. FIG. 2 is a block diagram illustrating a schematic configuration of a document conveying apparatus 100. FIG. 2 is a diagram illustrating a schematic configuration of a storage device 150 and a CPU 160. FIG. It is a flowchart which shows the example of operation | movement of a setting process. It is a figure for demonstrating a 2nd ultrasonic signal and a noise component. 5 is a flowchart illustrating an example of an operation of document reading processing. It is a flowchart which shows the example of operation | movement of a double feed determination process. It is a figure for demonstrating the characteristic of a 2nd ultrasonic signal. FIG. 10 is a block diagram illustrating a schematic configuration of another document feeder 200. 2 is a diagram showing a schematic configuration of a processing circuit 250. FIG.

  Hereinafter, an original conveying apparatus according to an aspect of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  FIG. 1 is a perspective view showing a document conveying device 100 configured as an image scanner.

  The document conveyance device 100 is an example of a double feed detection device, and includes a lower casing 101, an upper casing 102, a document table 103, a discharge table 105, operation buttons 106, and the like.

  The upper casing 102 is disposed at a position covering the upper surface of the document conveying apparatus 100, and is engaged with the lower casing 101 by a hinge so as to be opened and closed when the document is blocked, for example, when cleaning the inside of the document conveying apparatus 100. Yes.

  The document table 103 is engaged with the lower housing 101 so that a document can be placed thereon. The document table 103 is provided with side guides 104a and 104b that are movable in a direction perpendicular to the document conveyance direction. Hereinafter, the side guides 104a and 104b may be collectively referred to as a side guide 104.

  The discharge table 105 is engaged with the lower casing 101 by a hinge so as to be rotatable in the direction indicated by the arrow A1, and holds the discharged document when it is opened as shown in FIG. Is possible.

  The operation button 106 is disposed on the surface of the upper casing 102 and, when pressed, generates and outputs an operation detection signal.

  FIG. 2 is a diagram for explaining a transport path inside the document transport apparatus 100.

  The conveyance path inside the document conveyance device 100 includes a first document detection sensor 111, feed rollers 112a and 112b, brake rollers 113a and 113b, a second document detection sensor 114, an ultrasonic oscillator 115a, an ultrasonic receiver 115b, and a first. Conveying rollers 116a and 116b, first driven rollers 117a and 117b, a third document detection sensor 118, a first imaging device 119a, a second imaging device 119b, second conveying rollers 120a and 120b, second driven rollers 121a and 121b, and the like. Have.

  Hereinafter, the feeding rollers 112a and 112b may be collectively referred to as a feeding roller 112. Further, the brake rollers 113a and 113b may be collectively referred to as a brake roller 113. The first transport rollers 116a and 116b may be collectively referred to as the first transport roller 116. The first driven rollers 117a and 117b may be collectively referred to as a first driven roller 117. Further, the second transport rollers 120a and 120b may be collectively referred to as the second transport roller 120. In addition, the second driven rollers 121a and 121b may be collectively referred to as the second driven roller 121.

  The upper surface of the lower casing 101 forms a lower guide 107a of the document conveyance path, and the lower surface of the upper casing 102 forms an upper guide 107b of the document conveyance path. In FIG. 2, an arrow A2 indicates the conveyance direction of the document. Hereinafter, upstream means upstream in the document transport direction A2, and downstream means downstream in the document transport direction A2.

  The first document detection sensor 111 has a contact detection sensor disposed on the upstream side of the feeding roller 112 and the brake roller 113, and detects whether or not a document is placed on the document table 103. The first document detection sensor 111 generates and outputs a first document detection signal whose signal value changes depending on whether the document is placed on the document table 103 or not.

  The second document detection sensor 114 has a contact detection sensor disposed on the downstream side of the feeding roller 112 and the brake roller 113 and on the upstream side of the first conveying roller 116 and the first driven roller 117, and the document is located at that position. Whether or not exists is detected. Second document detection sensor 114 generates and outputs a second document detection signal whose signal value changes depending on whether or not a document exists at that position.

  The ultrasonic oscillator 115a and the ultrasonic receiver 115b are arranged in the vicinity of the document conveyance path so as to face each other across the conveyance path. The ultrasonic oscillator 115a outputs an ultrasonic wave. On the other hand, the ultrasonic receiver 115b receives the ultrasonic wave that has been oscillated by the ultrasonic oscillator 115a and passed through the document, and generates and outputs a first ultrasonic signal that is an electrical signal corresponding to the received ultrasonic wave. Since the ultrasonic receiver 115b also receives ultrasonic waves based on noise output from components other than the ultrasonic oscillator 115a, the first ultrasonic signal generated by the ultrasonic receiver 115b includes a noise component. Hereinafter, the ultrasonic oscillator 115a and the ultrasonic receiver 115b may be collectively referred to as an ultrasonic sensor 115.

  The third document detection sensor 118 has a contact detection sensor arranged on the downstream side of the first conveying roller 116 and the first driven roller 117 and on the upstream side of the first imaging device 119a and the second imaging device 119b. It detects whether or not a document exists at the position. Third document detection sensor 118 generates and outputs a third document detection signal whose signal value changes depending on whether or not a document exists at that position.

  The first image pickup device 119a has a reduction optical system type image pickup sensor including an image pickup element by a CCD (Charge Coupled Device) arranged linearly in the main scanning direction. This image sensor reads the back side of the document and generates and outputs an analog image signal. Similarly, the second image pickup device 119b includes a reduction optical system type image pickup sensor including an image pickup element using a CCD arranged linearly in the main scanning direction. This image sensor reads the surface of a document and generates and outputs an analog image signal. Note that only one of the first imaging device 119a and the second imaging device 119b may be arranged to read only one side of the document. Further, a CIS (Contact Image Sensor) of the same-magnification optical system type having an image pickup element of CMOS (Complementary Metal Oxide Semiconductor) can be used instead of the CCD. Hereinafter, the first imaging device 119a and the second imaging device 119b may be collectively referred to as an imaging device 119.

  The document placed on the document table 103 is conveyed in the document conveyance direction A2 between the lower guide 107a and the upper guide 107b as the feed roller 112 rotates in the direction of arrow A3 in FIG. . The brake roller 113 rotates in the direction of arrow A4 in FIG. When a plurality of documents are placed on the document table 103 by the functions of the feed roller 112 and the brake roller 113, only the documents that are in contact with the feed roller 112 among the documents placed on the document table 103 are displayed. Are separated. As a result, the operation of the document other than the separated document is restricted (preventing double feeding). The feed roller 112 and the brake roller 113 function as a document separation unit.

  The document is fed between the first conveying roller 116 and the first driven roller 117 while being guided by the lower guide 107a and the upper guide 107b. The document is fed between the first imaging device 119a and the second imaging device 119b by the first conveying roller 116 rotating in the direction of the arrow A5 in FIG. The document read by the imaging device 119 is discharged onto the discharge table 105 when the second transport roller 120 rotates in the direction of arrow A6 in FIG.

  FIG. 3 is a block diagram illustrating a schematic configuration of the document conveying apparatus 100.

  In addition to the configuration described above, the document conveying apparatus 100 includes a first image A / D converter 140a, a second image A / D converter 140b, an ultrasonic detection circuit 141, a driving device 146, an interface device 147, and a storage device 150. And a CPU (Central Processing Unit) 160 and the like.

  The first image A / D converter 140a converts the analog image signal output from the first imaging device 119a from analog to digital, generates digital image data, and outputs the digital image data to the CPU 160. Similarly, the second image A / D converter 140b performs analog-to-digital conversion on the analog image signal output from the second imaging device 119b, generates digital image data, and outputs the digital image data to the CPU 160. Hereinafter, these digital image data are referred to as read images.

  In addition to the ultrasonic sensor 115, the ultrasonic detection circuit 141 includes a front-stage amplifier 142, a filter 143, a rear-stage amplifier 144, a peak hold circuit 145, and the like.

  The intensity of the ultrasonic wave output from the ultrasonic oscillator 115 a can be changed by the CPU 160 and is set by the CPU 160. The CPU 160 changes the number of drive pulses of the ultrasonic oscillator 115a, thereby changing the number of ultrasonic oscillations output from the ultrasonic oscillator 115a and changing the intensity of the ultrasonic waves. Alternatively, the CPU 160 changes the amplitude of the ultrasonic wave output from the ultrasonic oscillator 115a by changing the oscillation voltage applied to the ultrasonic oscillator 115a, thereby changing the intensity of the ultrasonic wave.

  The preamplifier 142 amplifies the first ultrasonic signal output from the ultrasonic sensor 115 and outputs the amplified first ultrasonic signal to the filter 143. The first amplification factor by the pre-stage amplifier 142 can be changed by the CPU 160 and is set by the CPU 160.

  The filter 143 applies a band-pass filter that passes a signal in a predetermined frequency band to the signal output from the pre-stage amplifier 142 and outputs the signal to the post-stage amplifier 144. The pass frequency band that the band pass filter passes can be changed by the CPU 160 and set by the CPU 160. The passing frequency band set when the document conveying apparatus 100 is started is the first frequency band including the peak frequency of the ultrasonic wave output from the ultrasonic oscillator 115a. The peak frequency is the frequency at which the amplitude of the ultrasonic wave output from the ultrasonic oscillator 115a is the largest, and is the center frequency of the oscillation frequency of the ultrasonic oscillator 115a.

  The pass frequency band changed by the CPU 160 after the document conveying apparatus 100 is activated includes a second frequency band that does not include the peak frequency. For example, when the peak frequency is 300 kHz, the first frequency band is in the range of 275 kHz to 325 kHz, and the second frequency band is in the range of 325 kHz to 375 kHz. A plurality of bands may be determined in advance as the second frequency band. For example, in addition to the range of 325 kHz to 375 kHz, a range of 225 kHz to 275 kHz, a range of 375 kHz to 425 kHz, a range of 175 kHz to 225 kHz, etc. are determined as the second frequency band.

  The post-stage amplifier 144 amplifies the signal output from the filter 143 and outputs the amplified signal to the peak hold circuit 145. The second amplification factor by the post-stage amplifier 144 can be changed by the CPU 160 and is set by the CPU 160.

  The peak hold circuit 145 generates a second ultrasonic signal obtained by taking peak hold on the signal output from the post-stage amplifier 144 and outputs the second ultrasonic signal to the CPU 160. The peak hold circuit 145 generates a second ultrasonic signal by holding the maximum value of the signal output from the post-stage amplifier 144 for a certain hold period.

  The driving device 146 includes one or a plurality of motors, and rotates the feeding roller 112, the brake roller 113, the first conveying roller 116, and the second conveying roller 120 according to a control signal from the CPU 160, thereby performing an original conveying operation. Do.

  The interface device 147 has an interface circuit conforming to a serial bus such as a USB, for example, and is electrically connected to an information processing device (not shown) (for example, a personal computer, a portable information terminal, etc.) to display a read image and various information Send and receive. Instead of the interface device 147, a communication unit including an antenna that transmits and receives wireless signals and a wireless communication interface device that transmits and receives signals through a wireless communication line according to a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network).

  The storage device 150 includes a memory device such as a random access memory (RAM) and a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk and an optical disk. In addition, the storage device 150 stores computer programs, databases, tables, and the like used for various processes of the document feeder 100. The computer program may be installed in the storage device 150 from a computer-readable portable recording medium using a known setup program or the like. Examples of the portable recording medium include a CD-ROM (compact disk read only memory) and a DVD-ROM (digital versatile disk read only memory). Further, the storage device 150 stores the read image.

  CPU 160 operates based on a program stored in storage device 150 in advance. Instead of the CPU 160, a digital signal processor (DSP), a large scale integration (LSI), or the like may be used. Instead of the CPU 160, an application specific integrated circuit (ASIC), a field-programming gate array (FPGA), or the like may be used.

  The CPU 160 includes an operation button 106, a first document detection sensor 111, a second document detection sensor 114, a third document detection sensor 118, a first imaging device 119a, a second imaging device 119b, a first image A / D converter 140a, The second image A / D converter 140b, the ultrasonic detection circuit 141, the driving device 146, the interface device 147, the storage device 150, and the like are connected to control these components. The CPU 160 performs drive control of the drive device 146, document reading control of the imaging device 119, and the like, and acquires a read image. The CPU 160 performs setting control of the ultrasonic detection circuit 141, double feed detection processing, and the like.

  FIG. 4 is a diagram illustrating a schematic configuration of the storage device 150 and the CPU 160.

  As illustrated in FIG. 4, the storage device 150 stores programs such as a setting program 151, a control program 152, an image generation program 153, and a detection program 154. Each of these programs is a functional module implemented by software operating on the processor. The CPU 160 functions as the setting unit 161, the control unit 162, the image generation unit 163, and the detection unit 164 by reading each program stored in the storage device 150 and operating according to each read program.

  FIG. 5 is a flowchart showing an example of the setting processing operation of the ultrasonic detection circuit 141.

  Hereinafter, an example of setting operation of the ultrasonic detection circuit 141 will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 160 in cooperation with each element of the document feeder 100 based on a program stored in the storage device 150 in advance. The operation flow shown in FIG. 5 is executed when the apparatus is activated. Note that the operation flow shown in FIG. 5 may be executed at an arbitrary timing when the document reading process is not executed, periodically or in accordance with an instruction from the user.

  First, the setting unit 161 performs initial setting of the ultrasonic detection circuit 141 (step S101). The setting unit 161 sets the output of the ultrasonic wave by the ultrasonic oscillator 115a to OFF when the document feeder 100 is activated. The setting unit 161 sets the pass frequency band of the filter 143 to the first frequency band, sets the intensity of the ultrasonic wave output from the ultrasonic oscillator 115a to the initial value, and sets the first amplification factor of the preamplifier 142 and The second gain of the post-stage amplifier 144 is set to an initial value. Furthermore, the setting unit 161 sets the double feed determination threshold value to an initial value. The double feed determination threshold is a threshold for detecting that the double feed of the paper has occurred by the detection unit 164 comparing with the signal value of the second ultrasonic signal.

  Next, the setting unit 161 acquires the second ultrasonic signal output from the ultrasonic detection circuit 141 (step S102). The second ultrasonic signal is generated from the first ultrasonic signal output from the ultrasonic receiver 115b in a state where the ultrasonic oscillator 115a does not output an ultrasonic wave. The second ultrasonic signal is processed by using the filter 143 set to the first frequency band after the first ultrasonic signal is amplified by the preamplifier 142 with the first amplification factor of the initial value. Thus, the signal is amplified with the second amplification factor of the initial value.

  Next, the setting unit 161 determines whether or not the signal value of the acquired second ultrasonic signal is equal to or less than the abnormality determination threshold value (step S103). The abnormality determination threshold is set to a value larger than the signal value of the second ultrasonic signal measured in a previous experiment in a state where the ultrasonic oscillator 115a does not output ultrasonic waves. The abnormality determination threshold value is, for example, a signal value of the second ultrasonic signal measured in a previous experiment in a state where the ultrasonic oscillator 115a does not output an ultrasonic wave, and the ultrasonic oscillator 115a outputs an ultrasonic wave. Is set to an intermediate value of the signal value of the second ultrasonic signal.

  When the signal value of the second ultrasonic signal is larger than the abnormality determination threshold value, the setting unit 161 determines that the signal value of the second ultrasonic signal is abnormal (step S104).

  When the setting unit 161 determines that the signal value of the second ultrasonic signal is abnormal, the setting unit 161 sets the pass frequency band of the filter 143 to the second frequency band (step S105). This process is executed every time it is determined in step S103 that the signal value of the second ultrasonic signal is larger than the abnormality determination threshold value. The setting unit 161 sequentially selects a band close to the first frequency band from the predetermined second frequency band, and sets it as the pass frequency band of the filter 143.

  When the pass frequency band of the filter 143 is set to the second frequency band, the setting unit 161 sets the double feed determination threshold, the intensity of the ultrasonic wave output from the ultrasonic oscillator 115a, the first amplification factor by the pre-stage amplifier 142, or The second amplification factor by the post-stage amplifier 144 is changed (step S106).

  The setting unit 161 is a value that is smaller than the double feed determination threshold (initial value) when the pass frequency band is set to the first frequency band when the pass frequency band is set to the second frequency band. Change to

  Alternatively, the setting unit 161 sets the ultrasonic intensity when the pass frequency band is set to the second frequency band as the ultrasonic intensity when the pass frequency band is set to the first frequency band (initial value). ) Change to be larger.

  Alternatively, the setting unit 161 sets the first gain or the second gain when the pass frequency band is set to the second frequency band as the first gain or the second gain when the pass frequency band is set as the first frequency band. 2 Change to be larger than the amplification factor (initial value).

  Note that the setting unit 161 may change at least one of the double feed determination threshold, the intensity of the ultrasonic wave, the first amplification factor, or the second amplification factor. In addition, the setting unit 161 may change a plurality or all of the double feed determination threshold value, the ultrasonic intensity, the first amplification factor, or the second amplification factor. In that case, the parameter combination to be set is stored in the storage device 150 in advance, and the setting unit 161 reads the parameter combination from the storage device 150 and sets the parameter combination.

  Next, the setting unit 161 returns the process to step S102, and repeats the processes of steps S102 to S106 until the signal value of the second ultrasonic signal becomes equal to or less than the abnormality determination threshold value.

  On the other hand, when the signal value of the second ultrasonic signal is equal to or less than the abnormality determination threshold value in step S103, the setting unit 161 determines that the signal value of the second ultrasonic signal is normal (step S107), and the series. This step is finished.

  In step S101, the setting unit 161 may set the output of the ultrasonic wave from the ultrasonic oscillator 115a to ON. In this case, the abnormality determination threshold value is set to a value larger than the signal value of the second ultrasonic signal in a state where the ultrasonic oscillator 115a outputs an ultrasonic wave, which is measured by a prior experiment. In this case, the second ultrasonic signal acquired by the setting unit 161 in step S102 is generated from the first ultrasonic signal output by the ultrasonic receiver 115b while the ultrasonic oscillator 115a outputs the ultrasonic wave. .

  Hereinafter, the significance of changing each parameter of the ultrasonic detection circuit 141 according to the flowchart shown in FIG. 5 will be described.

  FIG. 6 is a diagram for explaining the second ultrasonic signal and the noise component.

  The horizontal axis in FIG. 6 indicates the frequency, and the vertical axis indicates the signal value. The signal 601 is an example of a second ultrasonic signal generated in a state where the ultrasonic oscillator 115a outputs an ultrasonic wave. The signal 602 is an example of a second ultrasonic signal generated in a state where switching noise is generated from the DC-DC converter that does not output the ultrasonic wave from the ultrasonic oscillator 115a and supplies a voltage to the pre-stage amplifier 142. It is.

  In the example shown in FIG. 6, the peak frequency of the ultrasonic wave output from the ultrasonic oscillator 115a is approximately 300 kHz. The signal value of the second ultrasonic signal 601 has a peak at 300 kHz and gradually decreases as the distance from 300 kHz increases. The signal value of the second ultrasonic signal 601 has a particularly large value in the range of a 50 kHz width A centering on 300 kHz. Although not shown, the signal value of the second ultrasonic signal 601 has a value greater than 0 in the range of 200 kHz to 400 kHz, and is 0 in the range of 200 kHz or less and 400 kHz or more.

  On the other hand, the peak frequency of switching noise generated from the DC-DC converter is also approximately 300 kHz. The signal value of the second ultrasonic signal 602 has a peak at 300 kHz, and decreases sharply away from 300 kHz. The signal value of the second ultrasonic signal 602 has a particularly large value in the range of 5 kHz width B centering on 300 kHz, and is 0 in the range of 275 kHz or less and 325 kHz or more.

  In general, a DC-DC converter can achieve the highest power supply efficiency by using a switching frequency of about 300 kHz. On the other hand, when the switching frequency of the DC-DC converter is set to about 300 kHz, switching noise (ripple noise) having a frequency of about 300 kHz is generated and affects the second ultrasonic signal. However, the amplitude (level) and frequency of switching noise vary depending on manufacturing variations such as cable homing for each device, or the temperature, humidity, etc. of the environment in which the device is used. Therefore, even when the switching frequency of the DC-DC converter is set to about 300 kHz that can maximize the power supply efficiency, the influence on the second ultrasonic signal is sufficiently small, and erroneous detection of double feeding may not occur. There is also.

  Therefore, the setting unit 161 sets the pass frequency band of the filter 143 to the first frequency band F1 (275 kHz to 325 kHz) having a 50 kHz width A centering on the peak frequency (300 kHz) of the ultrasonic wave when the apparatus is activated (FIG. 5). Step S101). On the other hand, when the signal value of the second ultrasonic signal is larger than the abnormality determination threshold, the setting unit 161 is affected by the switching noise of the DC-DC converter and becomes abnormal. Determine (see step S104). In this case, the setting unit 161 sets the pass frequency band of the filter 143 to the second frequency band F2 (325 kHz to 375 kHz) having a 50 kHz width that does not include the ultrasonic peak frequency (300 kHz) (see step S105). Since the second frequency band F2 does not include the switching frequency of the DC-DC converter, the second ultrasonic signal is not affected by the switching noise of the DC-DC converter.

  However, as shown in FIG. 6, in the second frequency band F2, the signal value of the second ultrasonic signal 601 generated in a state where the ultrasonic oscillator 115a outputs an ultrasonic wave also decreases. Therefore, the setting unit 161 allows the double feed determination threshold, the intensity of the ultrasonic wave output from the ultrasonic oscillator 115a, and the first amplification so that the double feed can be correctly detected even if the signal value of the second ultrasonic signal 601 is small. The rate or the second gain is changed (see step S106). As a result, the document feeder 100 can correctly detect double feeding without being affected by the switching noise of the DC-DC converter.

  Note that switching noise can be eliminated by providing a regulator between the DC-DC converter and the pre-stage amplifier 142, but in that case, the regulator increases device cost and device size. Further, it is possible to change the frequency band of the second ultrasonic signal by changing the frequency of the ultrasonic wave output from the ultrasonic oscillator 115a, but by providing a circuit for changing the frequency of the ultrasonic wave. Device cost and device size increase. On the other hand, since the variable bandwidth filter has a small cost difference and size difference from the fixed band filter, the document conveying apparatus 100 can suppress erroneous detection of double feed while suppressing an increase in apparatus cost or apparatus size. it can.

  FIG. 7 is a flowchart illustrating an example of an operation of document reading processing of the document conveying device 100.

  Hereinafter, an example of the operation of the original reading process of the original conveying apparatus 100 will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 160 in cooperation with each element of the document feeder 100 based on a program stored in the storage device 150 in advance. The operation flow shown in FIG. 7 is periodically executed.

  First, the control unit 162 waits until the operation button 106 for instructing reading of a document is pressed by the user and an operation detection signal for instructing reading of the document is received from the operation button 106 (step S201). ).

  Next, the control unit 162 determines whether or not a document is placed on the document table 103 based on the first document detection signal received from the first document detection sensor 111 (step S202).

  If no document is placed on the document table 103, the control unit 162 returns the process to step S 201 and waits until a new operation detection signal is received from the operation button 106.

  On the other hand, when a document is placed on the document table 103, the control unit 162 drives the driving device 146 to rotate the feed roller 112, the brake roller 113, the first transport roller 116, and the second transport roller 120. Then, the document is conveyed (step S203).

  Next, the image generation unit 163 causes the imaging apparatus 119 to read the conveyed document, and obtains a read image via the A / D converter 140 (step S204).

  Next, the image generation unit 163 transmits the read image to an information processing device (not illustrated) via the interface device 147 (step S205). Note that when not connected to the information processing apparatus, the image generation unit 163 stores the read image in the storage device 150.

  Next, the control unit 162 determines whether or not a document remains on the document table 103 based on the first document detection signal received from the first document detection sensor 111 (step S206).

  When the document remains on the document table 103, the control unit 162 returns the process to step S203 and repeats the processes of steps S203 to S206. On the other hand, if no document remains on the document table 103, the control unit 162 ends the series of processes.

  FIG. 8 is a flowchart illustrating an example of the operation of the double feed determination process.

  Hereinafter, an example of the operation of the multi-feed determination process of the document conveying apparatus 100 will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 160 in cooperation with each element of the document feeder 100 based on a program stored in the storage device 150 in advance. The operation flow shown in FIG. 8 is periodically executed during document conveyance.

  First, the detection unit 164 acquires a second ultrasonic signal from the ultrasonic detection circuit 141 (step S301).

  Next, the detection unit 164 determines whether or not the signal value of the acquired second ultrasonic signal is less than the double feed determination threshold (step S302).

  FIG. 9 is a diagram for explaining the characteristics of the second ultrasonic signal.

  In the graph 900 of FIG. 9, the solid line 901 indicates the characteristics of the second ultrasonic signal when a single original is being conveyed, and the dotted line 902 indicates the second ultrasonic signal when the original is double fed. Show the characteristics. The horizontal axis of the graph 900 indicates time, and the vertical axis indicates the signal value of the second ultrasonic signal. Due to the occurrence of double feeding, the signal value of the ultrasonic signal of the dotted line 902 is lowered in the section 903. Therefore, it is possible to determine whether or not a document double feed has occurred depending on whether or not the signal value of the second ultrasonic signal is less than the double feed determination threshold.

  If the signal value of the second ultrasonic signal is less than the double feed determination threshold value, the detection unit 164 determines that a document double feed has occurred (step S303). In that case, the detection unit 164 notifies the user that an abnormality has occurred through an unillustrated speaker, LED (Light Emitting Diode), or the like as an abnormality process, and ends a series of steps. On the other hand, when the signal value of the ultrasonic signal is equal to or greater than the double feed determination threshold, the detection unit 164 determines that no double feed of the document has occurred (step S304) and ends the series of steps. As described above, the detection unit 164 compares the signal value of the second ultrasonic signal with the double feed determination threshold value to detect that the double feed of the paper has occurred.

  As described above in detail, when the document conveying apparatus 100 operates according to the flowcharts shown in FIGS. 5, 7, and 8, and the signal value of the second ultrasonic signal is larger than the abnormality determination threshold, the ultrasonic detection circuit 141, the pass frequency band of the filter 143 is changed. This makes it possible to suppress erroneous detection of double feeding while suppressing an increase in device cost or device size.

  FIG. 10 is a block diagram showing a schematic configuration of an original conveying apparatus 200 according to another embodiment.

  The document conveying device 200 includes a processing circuit 250 in addition to the units included in the document conveying device 100. The processing circuit 250 is a DSP, LSI, ASIC, FPGA, or the like, and executes setting processing and double feed detection processing of the ultrasonic detection circuit 141 instead of the CPU 160.

  FIG. 11 is a diagram showing a schematic configuration of the processing circuit 250. The processing circuit 250 includes a setting circuit 251 and a detection circuit 254. Each of these units may be configured by an independent integrated circuit, a microprocessor, firmware, and the like.

  The setting circuit 251 is an example of a setting unit. The setting circuit 251 executes initial setting of the ultrasonic detection circuit 141. The setting circuit 251 transmits an ultrasonic control signal to the ultrasonic oscillator 115a so that the output of the ultrasonic wave from the ultrasonic oscillator 115a is set to OFF when the document conveying apparatus 200 is activated. The setting circuit 251 transmits a band setting signal to the filter 143 so that the pass frequency band of the filter 143 is set to the first frequency band. The setting circuit 251 transmits an ultrasonic intensity setting signal to the ultrasonic oscillator 115a so that the intensity of the ultrasonic wave output from the ultrasonic oscillator 115a is set to an initial value. In addition, the setting circuit 251 transmits a first amplification factor setting signal to the front-stage amplifier 142 so that the first gain of the front-stage amplifier 142 is set to an initial value, and sets the second gain of the rear-stage amplifier 144 to an initial value. The second gain setting signal is transmitted to the post-stage amplifier 144 so as to set. Furthermore, the setting unit 161 transmits a threshold setting signal to the detection circuit 254 so as to set the double feed determination threshold to an initial value.

  The setting circuit 251 receives the second ultrasonic signal from the ultrasonic detection circuit 141. When the signal value of the received second ultrasonic signal is larger than the abnormality determination threshold, the setting circuit 251 transmits a band setting signal to the filter 143 so as to set the pass frequency band of the filter 143 to the second frequency band. . Then, the setting circuit 251 transmits an ultrasonic intensity setting signal to the ultrasonic oscillator 115a so as to change the intensity of the ultrasonic wave output from the ultrasonic oscillator 115a. The setting circuit 251 transmits a first amplification factor setting signal to the front-stage amplifier 142 so as to change the first gain of the front-stage amplifier 142, and changes the second gain of the rear-stage amplifier 144 so as to change the second gain. A second gain setting signal is transmitted to the amplifier 144. Furthermore, the setting circuit 251 transmits a threshold setting signal to the detection circuit 254 so as to change the double feed determination threshold.

  The detection circuit 254 is an example of a detection unit. The detection circuit 254 receives the second ultrasonic signal from the ultrasonic detection circuit 141. When the signal value of the second ultrasonic signal is less than the double feed determination threshold, the detection circuit 254 transmits a detection signal indicating that double feed has been detected to the CPU 160.

  As described above in detail, in the document conveying apparatus 200, as in the document conveying apparatus 100, it is possible to suppress erroneous detection of double feed while suppressing an increase in apparatus cost or apparatus size.

100 Document Conveying Device 115a Ultrasonic Oscillator 115b Ultrasonic Receiver 142 Preamplifier 143 Filter 144 Postamplifier 161 Setting Unit 164 Detection Unit

Claims (8)

An ultrasonic oscillator that outputs ultrasonic waves;
An ultrasonic receiver that is disposed opposite to the ultrasonic oscillator and outputs a signal corresponding to the received ultrasonic wave;
A filter capable of changing a pass frequency band to any one of a first frequency band including a peak frequency of an ultrasonic wave output from the ultrasonic oscillator and a second frequency band not including the peak frequency;
A setting unit for setting a pass frequency band of the filter;
A detection unit that detects that a double feed of paper has occurred based on a signal value of the signal processed using the filter;
The setting unit determines whether a signal value of the signal processed using the filter set in the first frequency band is equal to or less than an abnormality determination threshold value, and the signal value is the abnormality determination threshold value. If greater, set the pass frequency band of the filter to the second frequency band;
A double feed detection device characterized by that. The detection unit detects that double feeding of paper has occurred by comparing the signal value of the signal with a threshold for determination of double feeding,
The multifeed detection device according to claim 1, wherein the setting unit changes the multifeed determination threshold when the pass frequency band of the filter is set to the second frequency band.   The multifeed detection device according to claim 1, wherein the setting unit changes the intensity of the ultrasonic wave output from the ultrasonic oscillator when the pass frequency band of the filter is set to the second frequency band. . An amplifier that amplifies the signal output from the ultrasonic receiver;
The multifeed detection device according to any one of claims 1 to 3, wherein the setting unit changes an amplification factor of the amplifier when the pass frequency band of the filter is set to the second frequency band.   The setting unit determines whether or not the signal value is equal to or less than the abnormality determination threshold based on the signal output by the ultrasonic receiver in a state where the ultrasonic oscillator outputs an ultrasonic wave. The multifeed detection device according to any one of claims 1 to 4.   The setting unit determines whether the signal value is equal to or less than the abnormality determination threshold based on the signal output by the ultrasonic receiver in a state where the ultrasonic oscillator is not outputting ultrasonic waves. The multifeed detection device according to any one of claims 1 to 4. An ultrasonic oscillator that outputs ultrasonic waves, an ultrasonic receiver that is arranged opposite to the ultrasonic oscillator and outputs a signal corresponding to the received ultrasonic waves, and a peak frequency of the ultrasonic waves that the ultrasonic oscillator outputs A filter capable of changing a pass frequency band to any one of a first frequency band including the peak frequency and a second frequency band not including the peak frequency,
Set the pass frequency band of the filter,
Detecting the occurrence of double feeding of paper based on the signal value of the signal processed using the filter,
In the setting, it is determined whether or not the signal value of the signal processed using the filter set in the first frequency band is equal to or less than an abnormality determination threshold, and the signal value is greater than the abnormality determination threshold. If larger, set the pass frequency band of the filter to the second frequency band;
A double feed detection method characterized by that. An ultrasonic oscillator that outputs ultrasonic waves, an ultrasonic receiver that is arranged opposite to the ultrasonic oscillator and outputs a signal corresponding to the received ultrasonic waves, and a peak frequency of the ultrasonic waves that the ultrasonic oscillator outputs A control program to be executed by a multifeed detection device having a filter capable of changing a pass frequency band to any one of a first frequency band including the first frequency band and a second frequency band not including the peak frequency,
Set the pass frequency band of the filter,
Based on the signal value of the signal processed using the filter, the double feed detection device is caused to detect that a double feed of paper has occurred,
In the setting, it is determined whether or not the signal value of the signal processed using the filter set in the first frequency band is equal to or less than an abnormality determination threshold, and the signal value is greater than the abnormality determination threshold. If larger, set the pass frequency band of the filter to the second frequency band;
A control program characterized by that.

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