Patent Publication Number: US-2021188589-A1

Title: Medium conveying apparatus for generating image based on pulse signal whose cycle varies according to rotation of dc motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of prior Japanese Patent Application No. 2019-229606, filed on Dec. 19, 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     Embodiments discussed in the present specification relate to medium conveyance. 
     BACKGROUND 
     In a medium conveying apparatus such as a scanner, a DC: motor may be used as a motor for conveying a medium. The DC motor is low cost and can easily adjust the speed. However, the rotation speed varies by an external factor such as a load variation. Therefore, in an image acquired by imaging the conveyed medium, an inter-lengthening in the sub-scanning direction may occur. 
     An image reading apparatus in which a feed roller is rotatably driven by a DC motor to continuously feed a document in a conveyance path, and sequentially transfer and store one page of data read by an image sensor to a line buffer by one line, is disclosed (Japanese Unexamined Patent Publication (Kokai) No. H6-54132). The image reading apparatus performs a reading operation by an image sensor every time a photo interrupter located to face a part of a disc mounted to be integrally rotatable to a rotation shaft of the DC motor detects a through hole provided in the disc and outputs a detection signal. 
     SUMMARY 
     According to some embodiments, a medium conveying apparatus includes a conveyance roller to convey a medium, a DC motor to drive the conveyance roller, a processor to rotate the DC motor, an encoder to output a first pulse signal whose cycle varies according to a rotation speed of the DC motor, and an imaging device to acquire an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant. The processor detects a number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal, and discards images acquired by the imaging device in the same number of pulses as difference between the detected number of pulses and a reference number, in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pulses exceeds the reference number. 
     According to some embodiments, a medium conveying apparatus includes a conveyance roller to convey a medium, a DC motor to drive the conveyance roller, a processor to rotate the DC motor, an encoder to output a first pulse signal whose cycle varies according to a rotation speed of the DC motor, and an imaging device to acquire an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant. The processor detects a number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal, and generates an input image using images acquired by the imaging device in a reference number of pulses, among images acquired by the imaging device in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pulses exceeds the reference number. 
     According to some embodiments, a method for generating an image includes conveying a medium by a conveyance roller, driving the conveyance roller by a DC motor, rotating the DC motor, outputting a first pulse signal whose cycle varies according to a rotation speed of the DC motor by an encoder, acquiring an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant by an imaging device, detecting a number of pukes of the second pulse signal included in a predetermined cycle of the first pulse signal, and discarding images acquired by the imaging device in the same number of pukes as difference between the detected number of pulses and a reference number, in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pukes exceeds the reference number. 
     According to some embodiments, a method for generating an image includes conveying a medium by a conveyance roller, driving the conveyance roller by a DC motor, rotating the DC motor, outputting a first pulse signal whose cycle varies according to a rotation speed of the DC motor by an encoder, acquiring an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant by an imaging device, detecting a number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal, and generating an input image using images acquired by the imaging device in a reference number of pulses, among images acquired by the imaging device in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pulses exceeds the reference number. 
     According to some embodiments, a computer-readable, non-transitory medium stores a computer program. The computer program causes a medium conveying apparatus including a conveyance roller to convey a medium, a DC motor to drive the conveyance roller, an encoder to output a first pulse signal whose cycle varies according to a rotation speed of the DC motor, and an imaging device to acquire an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant, to execute a process including rotating the DC motor, detecting a number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal, and discarding images acquired by the imaging device in the same number of pulses as difference between the detected number of pulses and a reference number, in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pulses exceeds the reference number. 
     According to some embodiments, a computer-readable, non-transitory medium stores a computer program. The computer program causes a medium conveying apparatus including a conveyance roller to convey a medium, a DC motor to drive the conveyance roller, an encoder to output a first pulse signal whose cycle varies according to a rotation speed of the DC motor, and an imaging device to acquire an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant, to execute a process including rotating the DC motor, detecting a number of pukes of the second pulse signal included in a predetermined cycle of the first pulse signal, and generating an input image using images acquired by the imaging device in a reference number of pulses, among images acquired by the imaging device in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pulses exceeds the reference number. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a medium conveying apparatus  100  according to an embodiment. 
         FIG. 2  is a diagram for illustrating a conveyance path inside the medium conveying apparatus  100 , 
         FIG. 3  is a schematic diagram for illustrating a DC motor  121 , etc. 
         FIG. 4  is a block diagram illustrating a schematic configuration of the medium conveying apparatus  100 . 
         FIG. 5  is a diagram illustrating schematic configurations of the storage device  140  and the processing circuit  150 . 
         FIG. 6  is a flowchart illustrating an operation example of the medium reading processing. 
         FIG. 7  is a flowchart illustrating an operation example of the image acquisition processing. 
         FIG. 8  is a graph showing a second pulse signal included in a predetermined cycle. 
         FIG. 9A  is a schematic diagram for illustrating that a cycle of a first pulse signal varies. 
         FIG. 9B  is a schematic diagram for illustrating that a cycle of a first pulse signal varies. 
         FIG. 10  is a graph showing a relationship between the first pulse signal and the second pulse signal. 
         FIG. 11  is a schematic diagram illustrating an example of an input image. 
         FIG. 12  is a diagram illustrating a schematic configuration of another processing circuit  250 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are not restrictive of the invention, as claimed. 
     Hereinafter, a medium conveying apparatus, a method and a computer-readable, non-transitory medium storing a computer program according to an embodiment, will be described with reference to the drawings. However, it should be noted that the technical scope of the invention is not limited to these embodiments, and extends to the inventions described in the claims and their equivalents. 
       FIG. 1  is a perspective view illustrating a medium conveying apparatus  100  configured as an image scanner. The medium conveying apparatus  100  conveys and images a medium being a document. The medium is a thin medium, such as a paper, or a thick medium, such as a thick paper, a card, a booklet or a passport. The medium conveying apparatus  100  may be a fax machine, a copying machine, a multifunctional peripheral (MFP)), etc. A conveyed medium may not be a document but may be an object being printed on etc., and the medium conveying apparatus  100  may be a printer etc. 
     The medium conveying apparatus  100  includes a lower housing  101 , an upper housing  102 , a medium tray  103 , an ejection tray  104 , an operation device  105 , and a display device  106 . 
     The upper housing  102  is located at a position covering the upper surface of the medium conveying device  100  and is engaged with the lower housing  101  by hinges so as to be opened and closed at a time of medium jam, during cleaning the inside of the medium conveying device  100 , etc. 
     The medium tray  103  is engaged with the lower housing  101  in such a way as to be able to place a medium to be conveyed. The ejection tray  104  is engaged with the lower housing  101  in such a way as to be able to hold an ejected medium. 
     The operation device  105  includes an input device such as a button, and an interface circuit acquiring a signal from the input device, receives an input operation by a user, and. outputs an operation signal based on the input operation by the user. The display device  106  includes a display including a liquid crystal or organic electro-luminescence (EL), and an interface circuit for outputting image data to the display, and displays the image data on the display. 
       FIG. 2  is a diagram for illustrating a conveyance path inside the medium conveying apparatus  100 . 
     The conveyance path inside the medium conveying device  100  includes a first sensor  111 , a feed roller  112 , a brake roller  113 , a first conveyance roller  114 , a second conveyance roller  115 , a second sensor  116 , a first imaging device  117   a,  a second imaging device  117   b,  a third conveyance roller  118  and a fourth conveyance roller  119 , etc. The numbers of each roller is not limited to one, and may be plural. The first imaging device  117   a  and the second imaging device  117   b  may be collectively referred to as imaging devices  117 . 
     A top surface of the lower housing  101  forms a lower guide  107   a  of a conveyance path of a medium, and a bottom surface of the upper housing  102  forms an upper guide  107   b  of the conveyance path of a medium. An arrow Al in  FIG. 2  indicates a medium conveying direction. An upstream hereinafter refers to an upstream in the medium conveying direction A 1 , and a downstream refers to a downstream in the medium conveying direction A 1 . 
     The first sensor  111  is located on an upstream side of the feed roller  112  and the brake roller  113 . The first sensor  111  includes a contact detection sensor and detects whether or not a medium is placed on the medium tray  103 . The first sensor  111  generates and outputs a first medium signal whose signal value changes between a state in which a medium is placed on the medium tray  103  and a state in which a medium is not placed. 
     The feed roller  112  is provided on the lower housing  101  and sequentially feed media placed on the medium tray  103  from the lower side. The brake roller  113  is provided in the upper housing  102  and is located to face the feed roller  112 . 
     The first conveyance roller  114  is provided on the lower housing  101 . The second conveyance roller  115  is provided in the upper housing  102 , and is located to face the first conveyance roller  114 . The first and second conveyance rollers  114  and  115  are examples of conveyance rollers, are located on the downstream side of the feeding roller  112  and the brake roller  113  in the medium conveying direction A 1 , and convey the medium fed by the feeding roller  112  and the brake roller  113  to the imaging device  117 . 
     The second sensor  116  is located on the downstream side of the first conveyance roller  114  and the second conveyance roller  115  and on the upstream side of the imaging device  117  in the medium conveying direction A 1 . The second sensor  116  detects whether or not the medium exists at the position. The second sensor  116  includes a light emitter and a light receiver provided on one side with respect to the conveyance path of the medium, and a reflection member such as a mirror provided at a position facing the light emitter and the light receiver with the conveyance path in between. The light emitter emits light toward the conveyance path. On the other hand, the light receiver receives light projected by the light emitter and reflected by the reflection member, and generates and outputs a second medium signal being an electric signal based on intensity of the received light. Since the light emitted by the light emitter is shielded by the medium when the medium is present at the position of the second sensor  116 , the signal value of the second medium signal is changed in a state where the medium is present at the position of the second sensor  116  and a state where the medium is not present. The light emitter and the light receiver may be provided at positions facing one another with the conveyance path in between, and the reflection member may be omitted. 
     The first imaging device  117   a  is an example of an imaging device, and includes a line sensor based on a unity-magnification optical. system type contact image sensor (CIS) including an imaging element based on a complementary metal oxide semiconductor (CMOS) linearly located in a main scanning direction. Further, the first imaging device  117   a  includes a lens for forming an image on the imaging element, and an AID converter for amplifying and analog-digital (A/D) converting an electric signal output from the imaging element. The first image pickup device  117   a  images a front surface of a conveyed medium, in accordance with control from a processing circuit to be described later. 
     A second pulse signal including a continuous pulse whose cycle is constant is input to the first imaging device  117   a  from a pulse generator described later. The first imaging device  117   a  acquires an image acquired by imaging the conveyed medium in response to the pulse of the input second pulse signal. In other words, the first imaging device  117   a  acquires a line image of the conveyed medium imaged by the line sensor, for each timing at which a pulse occurs in the second pulse signal (for each rising timing of the pulse). Specifically, a pixel count of a line image in a vertical direction (subscanning direction) is 1, and a pixel count in a horizontal direction (main scanning direction) is larger than  1 . 
     Similarly, the second imaging device  117   b  is an example of an imaging device, and includes a line sensor based on a unity-magnification optical system type CIS including an imaging element based on a CMOS linearly located in a main scanning direction. Further, the second imaging device  117   b  includes a lens for forming an image on the imaging element, and an A/D converter for amplifying and A/D converting an electric signal output from the imaging element. The second imaging device  117   b  generates and outputs an input image acquired by imaging a back surface of the conveyed medium, in accordance with control from a processing circuit to be described later. 
     The second pulse signal is input to the second imaging device  117   b  from the pulse generator. The second imaging device  117   b  acquires an image acquired by imaging the conveyed medium in response to the pulse of the input second pulse signal. In other words, the second. imaging device  117   b  acquires a line image of the conveyed medium imaged by the line sensor, for each timing at which a pulse occurs in the second pulse signal (for each rising timing of the pulse). 
     The first imaging device  117   a  and the second imaging device  117   b  are examples of an imaging device. Only either of the first imaging device  117   a  and the second imaging device  117   b  may be located in the medium conveying apparatus  100  and only one side of a medium may be read. Further, a line sensor based on a unity-magnification optical system type CIS including an imaging element based on charge coupled devices (CCDs) may be used in place of the line sensor based on a unity-magnification optical. system type CIS including an imaging element based on a CMOS. Further, a line sensor based on a reduction optical system type line sensor including an imaging element based on CMOS or CCDs. 
     The third conveyance roller  118  is provided on the lower housing  101 . The fourth conveyance roller  119  is provided in the upper housing  102 , and is located to face the third conveyance roller  118 . The third, fourth conveyance rollers  118 ,  119  are examples of the conveyance rollers, are located on the downstream side of the imaging device  117  in the medium conveying direction A 1 , and convey the medium conveyed by the first, second conveyance rollers  114 ,  115  to the ejection tray  104 . 
     A medium placed on the medium tray  103  is conveyed between the lower guide  107   a  and the upper guide  107   b  in the medium conveying direction Al by the feed roller  112  rotating in a direction of an arrow A 2  in  FIG. 2 . When a medium is conveyed, the brake roller  113  rotate in a direction of an arrow A 3 . By the workings of the feed roller  112  and the brake roller  113 , when a plurality of media are placed on the medium tray  103 , only a medium in contact with the feed roller  112 , out of the media placed on the medium tray  103 , is separated. Consequently, the medium conveying apparatus  100  operates in such a way that conveyance of a medium other than the separated medium is restricted (prevention of multi-feed). 
     The medium is fed between the first conveyance roller  114  and the second conveyance roller  115  while being guided by the lower guide  107   a  and the upper guide  107   b.  The medium is fed between the first imaging device  114   a  and the second imaging device  114   b  by the first conveyance roller  114  and the second conveyance roller  115  rotating in directions of an arrow A 4  and an arrow A 5 , respectively. The medium read by the imaging device  117  is ejected on the ejection tray  104  by rotating the third conveyance roller  118  and the fourth conveyance roller  119  in the directions of arrows A 6  and A 7 , respectively. 
       FIG. 3  is a schematic diagram for illustrating a DC motor  121  and an encoder  122 . 
     As shown in  FIG. 3 , the medium conveying apparatus  100  includes the DC motor  121  and the encoder  122 . 
     The DC motor  121 , for example, includes a modulation circuit for PWM (Pulse Width Modulation) modulating a predetermined voltage so as to be a speed specified by the processing circuit to be described later, and rotates according to the voltage acquired by PWM demodulation by the modulation circuit. The DC motor  121  drives and rotates the first to fourth conveyance rollers  114 ,  115 ,  118 , and  119  to convey the medium by a control signal from the processing circuit. The DC motor  121  may drive only some of the rollers among the first to fourth conveyance rollers  114 ,  115 ,  118 , and  119 . The DC motor  121  may also drive and rotate the feed roller  112  and/or the brake roller  113  to feed the medium. 
     The encoder  122  includes a disc  123 , a light emitter  124  and a light receiver  125 . The disc  123  is provided on a rotation axis of the DC motor  121 , to rotate in accordance with the rotation of the DC motor  121 . A plurality of slits  126  (light transmission hole) is formed on the disc  123 . The emitter  124  and the light receiver  125  is provided to face each other across the disc  123 . The light emitter  124  irradiates light toward the disc  123 . On the other hand, the light receiver  125  generates and outputs a first pulse signal which is an electrical signal corresponding to an intensity of the received light. The signal value of the first pulse signal is a relatively large value (High) while receiving light emitted by the light emitter  124  from the slit  126 , and is a relatively small value (Low) while the light emitted by the light emitter  124  is blocked by the disk  123 . For convenience,  FIG. 3  shows the disc  123  including twelve slits  126 , although the actual disc  123  includes hundreds of slits. 
     The graph  300  of  FIG. 3  shows an example of a waveform of the first pulse signal schematically. The horizontal axis of the graph  300  indicates time, the vertical axis indicates voltage of the first pulse signal. The length T of one cycle of the first pulse signal indicates the length of a cycle from when one end of a particular slit  126  in the disc rotation direction passes between the light emitter  124  and the light receiver  125  until one end of the next slit  126  in the disc rotation direction passes between the light emitter  124  and the light receiver  125 . In other words, the length T of the cycle of the first pulse signal varies according to a rotation speed of the DC motor  121 . Therefore, the medium conveying apparatus  100  can measure the rotation speed of the DC motor  121  using the first pulse signal. 
       FIG. 4  is a block diagram illustrating a schematic configuration of the medium conveying apparatus  100 . 
     The medium conveying apparatus  100  further includes a pulse generator  131 , a second motor  132 . an interface device  133 , a storage device  140 , a processing circuit  150 . etc., in addition to the configuration described above, 
     The pulse generator  131  generates a second pulse signal and outputs it to the imaging device  117  and the processing circuit  150 . The length of one cycle of the second pulse signal is set to a length capable of conveying the medium by a distance corresponding to one pixel at a preset resolution when the DC motor  121  is rotated at a reference speed which is the reference rotation speed. Thus, the medium conveying device  100  can generate the input image with a preset resolution by combining the line images acquired by imaging at the timing that each pulse of the second pulse signal occurs when the DC motor  121  rotates at the reference speed. 
     The second motor  132  drives and rotates the feed roller  112  and the brake roller  113  to feed the medium by a control signal from the processing circuit  150 . The second motor  132  is a DC motor. The second motor  132  may be a stepping motor. The feed roller  112  and the brake roller  113  may also be driven by separate motors. The second motor  132  may also drive some of the rollers among the first to fourth conveyance rollers  114 ,  115 ,  118 , and  119 . 
     For example, the interface device  133  includes an interface circuit conforming to a serial bus such as universal serial bus (USB), is electrically connected to an unillustrated information processing device (for example, a personal computer or a mobile information terminal), and transmits and receives an input image and various types of information. Further, a communication module including an antenna transmitting and receiving wireless signals, and a wireless communication interface device for transmitting and receiving signals through a wireless communication line in conformance with a predetermined communication protocol may be used in place of the interface device  133 . For example, the predetermined communication protocol is a wireless local area network (LAN). 
     The storage device  140  includes a memory device such as a random access memory (RAM) or a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. Further, the storage device  140  stores a computer program, a database, a table, etc., used for various types of processing in the medium conveying apparatus  100 . The computer program may be installed on the storage device  140  from a computer-readable, non-transitory medium such as a compact disc read only memory (CD-ROM), a digital versatile disc read only memory (DVD-ROM), etc., by using a well-known setup program, etc. 
     The processing circuit  150  operates in accordance with a program previously stored in the storage device  140 . The processing circuit  150  is, for example, a CPU (Central Processing Unit), The processing circuit  150  may be a digital signal processor (DSP), a large scale integration (LSI), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc. 
     The processing circuit  150  is connected to the operation device  105 , the display device  106 , the first sensor  111 , the second sensor  116 , the imaging device  117 , the DC motor  121 , the encoder  122 , the pulse generator  131 , the second motor  132 , the interface device  133  and the storage device  140 , etc., and controls each of these units. The processing circuit  150  drives the DC motor  121  and the second motor  132 , to generate an input image by acquiring line images from the imaging device  117 , and transmits the input image to the information processing apparatus via the interface device  133 . In particular, the processing circuit  150  discards a part of the line images among the line image acquired by the imaging device  117 , based on the first pulse signal generated by the encoder  122 , generates an input image from the line images that are not discarded. 
       FIG. 5  is a diagram illustrating schematic configurations of the storage device  140  and the processing circuit  150 . 
     As shown in  FIG. 5 , the storage device  140  stores a control program  141 , an image generating program  142  and a detection program  143 , etc. Each of these programs is a functional module implemented by software operating on a processor. The processing circuit  150  reads each program stored in the storage device  140  and operates in accordance with each read program. Consequently, the processing circuit  150  functions as a control module  151 , an image generating module  152  and a detection module  153 . 
       FIG. 6  is a flowchart illustrating an operation example of medium reading processing in the medium conveying apparatus  100 . 
     Referring to the flowchart illustrated in  FIG. 6 , an operation example of the medium reading processing in the medium conveying apparatus  100  will be described below. The operation flow described below is executed mainly by the processing circuit  150  in cooperation with each element in the medium conveying apparatus  100 , in accordance with a program previously stored in the storage device  140 . The operation flow illustrated in  FIG. 6  is periodically executed. 
     First, the control module  151  stands by until an instruction to read a medium is input by a user by use of the operation device  105 , and an operation signal instructing to read the medium is received from the operation device  105  (step S 101 ). 
     Next, the control module  151  acquires the first medium signal from the first sensor  111  and determines whether or not a medium is placed on the medium tray  103  based on the acquired first medium signal (step S 102 ). 
     When a medium is not placed on the medium tray  103 , the control module  151  returns the processing to step  5101  and stands by until newly receiving an operation signal from the operation device  105 . 
     On the other hand, when the medium is placed on the medium tray, the control module  151  drives and rotates the second motor  132 , rotates the feed roller  112  and the brake roller  113  to feed the medium. Further, the control module  151  drives and rotates the DC motor  121 , rotates the first to fourth conveyance rollers  114 ,  115 ,  118 , and  119  to convey the medium (step S 103 ). 
     The control module  151  performs a feedback control of the DC motor  121 , so that the rotation speed of the DC motor  121  follows the command value such as a preset voltage value. As described above, the disc  123  of the encoder  122  is attached to the rotation shaft of the DC motor  121 , the encoder  122  outputs the first pulse signal which varies according to the rotation speed of the DC motor  121 . The control module  151  detects the cycle of the first pulse signal output from the encoder  122  every predetermined feedback control cycle, for example, every 500 ns, and controls the DC motor  121  so that the voltage value acquired by converting a frequency into a voltage coincides with the command value. Although, the DC motor  121  can easily perform the speed adjustment at a low cost, the rotation speed of the DC motor  121  varies by an external factor such as a load variation. However, the rotation speed of the DC motor  121  changes a rotation speed corresponding to the command value after a predetermined cycle, by the above feedback control. Thus, the control module  151  controls the rotation speed of the DC motor  121  so that the cycle of the first pulse signal output from the encoder  122  follows the command value. 
     Next, the image generating module  152  determines whether or not the front end of the medium has passed the position of the second sensor  116  and waits until the front end of the medium passes the position of the second sensor  116  (step S 104 ). The image generating module  152  periodically acquires the second medium signal from the second sensor  116  and determines whether or not the medium is present at a position of the second sensor  116  based on the acquired second medium signal. When a signal value of the second medium signal changes from a value indicating nonexistence of a medium to a value indicating existence of a medium, the image generating module  152  determines that the front end of the medium has passed through the position of the second sensor  116 . 
     When the front end of the medium passes through the position of the second sensor  116 , the image generating module  152  causes the imaging device  117  to start imaging (step S 105 ). 
     Next, the processing circuit  150  executes the image acquiring processing (step S 106 ), In the image acquiring processing, the detection module  153  detects the number of pulses of the second pulse signal included in each cycle of the first pulse signal. The image generating module  152  acquires line images from the imaging device  117 , and discards the line images based on the number of pulses detected by the detection module  153 . Details of the image acquisition processing will be described later. 
     Next, the image generating module  152  combines the line images that are not discarded among the line images acquired in the image acquiring process to generate an input image S 107  of steps). 
     Next, the image generating module  152  transmits the generated input image to the information processing device via the interface device  133  (step S 108 ). When not being connected to the information processing device, the image generating module  152  stores the input image in the storage device  140 . 
     Next, the control module  151  determines whether or not the medium remains on the medium tray  103  based on the first medium signal acquired from the first sensor  111  (step S 109 ). When a medium remains on the medium tray  103 , the control module  151  returns the processing to step S 106  and repeats the processing in steps S 106  to S 109 . 
     On the other hand, when a medium does not remain on the medium tray  103 , the control module  151  stops the DC motor  121  and the second motor  132  (step S 110 ), and ends the series of steps. 
       FIG. 7  is a flowchart illustrating an operation example of the image acquisition process. 
     The flow of operation shown in  FIG. 7  is performed in the step  5106  of the flow chart shown in  FIG. 6 . 
     First, the image generating module  152  determines whether or not one cycle of the second pulse signal has elapsed (step S 201 ). The image generating module  152  periodically receives the second pulse signal from the pulse generator  131 , determines that one cycle of the second pulse signal has elapsed when a next pulse occurs (rises) after a specific pulse occurs (rises), in the received second pulse signal. When one cycle of the second pulsed signal has not elapsed, the image generating module  152  proceeds the processing to step S 205 . 
     On the other hand, when one cycle of the second pulse signal has elapsed, the image generating module  152  determines whether or not the pulse included in the elapsed cycle is a discard pulse (step S 202 ). The discard pulse is a pulse for discarding the line image acquired by the imaging device  117 , among the pulses included in the second pulse signal, and is determined in the processing of step S 208  to be described later. The discard pulse in current cycle of the first pulse signal is determined when the immediately preceding cycle has elapsed. When the current cycle of the first pulse signal is the first cycle, the image generating module  152  determines that the pulse included in the current cycle is not the discard pulse. Further, the image generating module  152  determines that the pulse included in the current cycle is not the discard pulse when the discard pulse is not determined since the number of pulses detected by the detection module  153  is equal to or less than the reference number, in the immediately preceding cycle. 
     When the pulse included in the current cycle is not the discard pulse, the image generating module  152  acquires a line image acquired by the imaging device  117  in the pulse from the imaging device  117 , and stores it in the storage device  140  (step S 203 ). 
     On the other hand, when the pulse included in this cycle is the discard pulse, the image generating module  152  discards the line image acquired by the imaging device  117  in the pulse (step S 204 ), The image generating module  152  once acquires the line image from the imaging device  117 , and discards the acquired line image without storing in the storage device  140 . The image generating module  152  may discard the line image without acquiring the line image from the imaging device  117 . 
     Next, the detection module  153  determines whether or not one cycle of the first pulse signal has elapsed (step S 205 ). The detection module  153  receives the first pulse signal periodically from the encoder  122 , and determines that one cycle of the first pulse signal has elapsed when a next pulse occurs (rises) after a specific pulse occurs (rises) in the first pulse signal received. When one cycle of the first pulse signal has not elapsed, the detection module  153  returns the processing to step S 201 . 
     On the other hand, when one cycle of the first pulse signal has elapsed, the detection module  153  detects a number of pulses of the second pulse signal included in the elapsed cycle of the first pulse signal (step S 206 ). The detection module  153  detects, as the number of pulses of the second pulse signal included in the cycle of the first pulse signal, the number of pulses occurred in the second pulse signal from when a pulse included in the elapsed cycle occurs to when a. next pulse occurs in the first pulse signal. 
     Next, the image generating module  152  determines whether or not the number of pulses detected by the detection module  153  exceeds a reference number (S 207  of steps). The reference number is preset to the number of pulses of the second pulse signal included in one cycle of the first pulse signal when a medium is not conveyed. When the number of pulses detected by the detection module  153  is equal to or less than the reference number, the image generating module  152  proceeds the processing to step S 209 . 
     On the other hand, when the number of pulses detected by the detection module  153  exceeds the reference number, the image generating module  152  determines discard pulses for discarding the line images acquired by the imaging device  117 , among the pulses of the second pulse signal included in the next cycle of the first pulse signal (step S 208 ). The image generating module  152  determines the same number of pulses as difference between the number of pulses detected by the detection module  153  and the reference number, i.e. a number acquired by submitting the reference number from the number of pulses detected by the detection module  153 , among the pulses of the second pulse signal included in the next cycle of the first pulse signal, to the discard pulses. in other words, the image generating module  152  determines the same number of pulses as a number exceeding the reference number, among the pulses of the second pulse signal included in the next cycle of the first pulse signal, to the discard pulse. Further, the image generating module  152  determines the discard pulse so as to discard the image intermittently in the next cycle. 
     Thus, when the number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal exceeds the reference number, the image generating module  152  discards the images acquired by the imaging device  117  in the same number of pulses as difference between the detected number of the pulses and the reference number, in the next cycle of the predetermined cycle of the first pulse signal. In other words, when the number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal exceeds the reference number, the image generating module  152  acquires only images acquired by the imaging device  117  in the reference number of pulses, among the images acquired by the imaging device  117  in the next cycle of the predetermined cycle of the first pulse signal. 
       FIG. 8  is a graph showing a second pulse signal  801  to  808  included in a predetermined cycle of the first pulse signal. The horizontal axis of each graph indicates time, the vertical axis indicates magnitude of voltage of the second pulse signal. In the example shown in  FIG. 8 , the number of pulses of the second pulse signals  801  to  808  included in the predetermined cycle of the first pulse signal is  5  to  12 , respectively. The reference number in the first pulse signal is assumed to be  4 . 
     The image generating module  152  determines, for each of the second pulse signals  801  to  808 , the number of the discard pulses of the second pulse signal included in the next cycle of the first pulse signal to  1  to  8 , respectively. Thus, the number of line images acquired by the image generating module  152  in the next cycle of the first pulse signal is expected to be four. 
     The image generating module  152  determines the pulse corresponding to the second pulse p 2  among the pulses p 1  to p 5  of the second pulse signal  801  as the discard pulse of the next cycle. The image generating module  152  determines the pulses corresponding to the second. and fourth pulses p 2  and p 4  among the pulses p 1  to p 6  of the second pulse signal  802  as the discard pulses of the next cycle. The image generating module  152  determines the pulses corresponding to the second, fourth, and sixth pulses p 2 , p 4 , and p 6  among the pulses p 1  to p 7  of the second pulse signal  803  as the discard pulses of the next cycle. Further, the image generating module  152  determines the pulses corresponding to the second, fourth, sixth, and eighth pulses p 2 , p 4 , p 6 , and p 8  among the pulses p 1  to p 8  of the second pulse signal  804  as the discard pulses of the next cycle. 
     Thus, when the number of pulses of the second pulse signal included in the cycle of the first pulse signal is equal to or less than twice the reference number, the image generating module  152  determine the discard pulse so that the discard pulse is not continuous Thus, the image generating module  152  can discard the line image so that the characters, etc., included in the medium in the input image do not disappear. 
     The image generating module  152  determines the pulses corresponding to the second, third, fifth, seventh, and ninth pulses p 2 , p 3 , p 5 , p 7 , and p 9  among the pulses p 1  to p 9  of the second pulse signal  805  as the discard pulses of the next cycle. The image generating module  152  determines the pulses corresponding to the second, third, fifth, sixth, eighth, and tenth pulses p 2 , p 3 , p 5 , p 6 , p 8 , and p 10  among the pulses p 1  to p 10  of the second pulse signal  806  as the discard pulses of the next cycle. The image generating module  152  determines the pulses corresponding to the second, third, fifth, sixth, eight, ninth, and eleventh pulses p 2 , p 3 , p 5 , p 6 , p 8 , p 9 , and p 11  among the pulses p 1  to p 11  of the second pulse signal  807  as the discard pulses of the next cycle. The image generating module  152  determines the pulses corresponding to the second, third, fifth, sixth, eighth, ninth, eleventh, and twelfth pulses p 2 , p 3 , p 5 , p 6 , p 8 , p 9 , p 11 , and p 12  among the pulses p 1  to p 12  of the second pulse signal  808  as the discard pulses of the next cycle. 
     Thus, when the number of pulses of the second pulse signal included in the cycle of the first pulse signal is greater than twice the reference number, the image generating module  152  determines the discard pulses so that the pulses not discarded are not continuous and are scattered (are dispersed at substantially equal intervals). Thus, the image generating module  152  can discard the line images so that a straight line extending in the oblique direction in the input image does not become zigzag. 
     Next, the image generating module  152  determines whether or not the entire conveyed medium has been imaged (S 209  of steps). The image generating module  152 , for example, acquires the second medium signal periodically from the second sensor  116  and determines whether or not the medium exists at the position of the second sensor  116  based on the acquired second medium signal. The image generating module  152  determines that the rear end of the medium has passed through the position of the second sensor  116  when the signal value of the second medium signal changes from the value indicating existence of a medium to the value indicating nonexistence of a medium. The image generating module  152  determines that the entire medium has been imaged when a predetermined time has elapsed after the rear end of the medium has passed through the position of the second sensor  116 . 
     When the entire conveyed medium has not been imaged, the image generating module  152  returns the processing to step  5201  and repeats the processing of step S 201  to S 209 . On the other hand, when the entire conveyed medium has been imaged, the image generating module  152  ends the series of steps. 
     After the image acquisition processing, in step S 107 , the image generating module  152  generates the input image using the line images acquired in step S 203  and stored in the storage device  140 , that is, the line images that are not discarded in step S 204 . In other words, when the number of pulses of the second pulse signal included in each cycle of the first pulse signal exceeds the reference number, the image generating module  152  generates the input image using images acquired by the imaging device  117  in the reference number of pulses, among the images acquired by the imaging device  117  in the next cycle of the first pulse signal. 
     Hereinafter, the technical significance of discarding the line images acquired by the imaging device  117  in accordance with the number of pulses detected by the detection module  153 , will be described. 
       FIG. 9A  and.  FIG. 9B  are schematic diagrams for illustrating that the cycle of the first pulse signal output from the encoder  122  varies due to a load variation when the medium passes through the respective conveyance rollers. 
     In the exemplary embodiment shown in  FIG. 9A , the conveyed medium P is a booklet such as a passport read in a state where pages including a photograph is opened, and has a plurality of regions having different thicknesses. The medium P has a first region having a relatively thin thickness (left side in the drawing) and a second region having a relatively thick thickness (right side in the drawing) across a stitched portion.  FIG. 9A  shows a state in which, after the first region of the medium P passes between the first conveyance roller  114  and the second conveyance roller  115 , the second region of the medium P is about to be fed between the first conveyance roller  114  and the second conveyance roller  115 . In the state shown in  FIG. 9A , the imaging device  117  reads the first area of the medium P. 
     When the front end portion, the stitched portion or the rear end portion of the medium P pass between the first conveyance roller  114  and the second conveyance roller  115 , the rotation speed of the DC motor  121  varies due to the load change when the first conveyance roller  114  and the second conveyance roller  115  bite the respective portions of the medium P. Also, when the front end portion, the stitched portion or the rear end portion of the medium P pass between the third conveyance roller  118  and the fourth conveyance roller  119 , the rotation speed of the DC motor  121  varies due to the load change when the third conveyance roller  118  and the fourth conveyance roller  119  bite the respective portions of the medium P. 
       FIG. 9B  is a graph showing an example of first pulsed signal  901  output from the encoder  122 . The horizontal axis of the graph of  FIG. 9B  indicates time, the vertical axis indicates magnitude of voltage of the first pulsed signal. Since the puke of the first pulse signal  901  occurs according to the rotation of the DC motor  121 , the cycle of the first pulse signal  901  varies according to the rotation speed of the DC motor  121 , 
     At time t 0 , the medium P is not yet fed between the first conveyance roller  114  and the second conveyance roller  115 , the rotation speed of the DC motor  121  is kept at a constant reference speed by feedback control by the control module  151 . Therefore, the cycle of the first pulse signal  901  maintains a constant reference length T 0 . 
     At time t 1 , the front end portion of the medium P is bitten by the first conveyance roller  114  and the second conveyance roller  115 , the rotation speed of the DC motor  121  is slowed due to the load change, the cycle of the first pulse signal  901  changes to the length T 1  which is longer than the reference length T 0 . Since feedback control does not work immediately even when the cycle of the first pulse signal  901  at time t 1  changes long, the rotation speed of the DC motor  121  does not return to the original for a while, the cycle remains a length T 1  for a while. 
     At time t 2 , the cycle of the first pulse signal  901  returns to the reference length T 0  again, by the feedback control by the control module  151 . 
     Since the second conveyance roller  115 , the second imaging device  117   b  and the fourth conveyance roller  119  located on the upper side of the conveyance path, are movably provided upward, they moves upward in accordance with the thickness of the medium P in conveyance. The medium P fed between the reading surface of the first imaging device  117   a  and the reading surface of the second imaging device  117   b  by the first conveyance roller  114  and the second conveyance roller  115  is read by each of the imaging device  117 . Also, when the front end portion of the medium P passes through the third conveyance roller  118  and the fourth conveyance roller  119  while the imaging device  117  is reading the medium P, the cycle of the first pulse signal  901  varies in the same manner as the variation at time t 1  to t 2  due to the load change. 
     At time t 3 , the stitched portion of the medium P is bitten by the first conveyance roller  114  and the second conveyance roller  115 , the rotation speed of the DC motor  121  is slowed due to the load change, and the cycle of the first pulse signal  901  changes to the length T 2  which is longer than the reference length T 0 . Since the thickness of the second region is greater than the thickness of the first region, the load variation when the second region is bitten by the first conveyance roller  114  and the second conveyance roller  115 , is larger than the load variation when the first region is bitten by the first conveyance roller  114  and the second conveyance roller  115 . As a result, the length T 2  of the cycle of the first pulse signal  901  at time t 3  is longer than the length T 1  of the cycle of the first pulse signal  901  at time t 1 . 
     At time t 4 , the cycle of the first pulse signal  901  returns to the reference length T 0  again by the feedback control by the control module  151 . 
     Also, when the stitched portion of the medium P passes through the third conveyance roller  118  and the fourth conveyance roller  119 , the cycle of the first pulse signal  901  varies in the same manner as the variation at time t 3  to t 4  due to the load change. Also, when the rear end portion of the medium P passes through the first conveyance roller  114 , the second conveyance roller  115 , the third conveyance roller  118  and the fourth conveyance roller  119 , the cycle of the first pulse signal  901  varies in the same manner as the variation at time t 0  to t 2  due to the load change. 
       FIG. 10  is a graph showing a relationship between the first pulse signal and the second pulse signal. The horizontal axis of each graph indicates time, and the vertical axis indicates magnitude of voltage of each signal. The upper graph of  FIG. 10  shows an example of a first pulse signal  1001 , and the lower graph shows an example of a second pulse signal  1002 . The reference number in the first pulse signal is assumed to be  4 . 
     As described above, the rotation speed of the DC motor  121  varies due to the load change when the medium passes through the conveyance roller, the cycle of the first pulse signal varies. In the example shown in  FIG. 10 , in period c 1  and period c 2 , the rotation speed of the DC motor  121  is kept at a constant reference speed by feedback control by the control module  151 . On the other hand, in period c 3 , period c 4  and period c 5 , the rotation speed of the DC motor  121  is slower than the reference speed due to the load change. Therefore, in the first pulse signal  1001  shown in  FIG. 10 , the cycle in period c 1  and period c 2 . maintains a constant reference length T 0 , the cycle in period c 3 , period c 4  and period c 5  changes to a length  12 . longer than the reference length T 0 . 
     On the other hand, the cycle of the second pulse signal is constant. In the example shown in  FIG. 10 , period c 1  and period c 2 , the number of pulses of the second pulse signal  1002  included in one cycle of the first pulse signal  1001  is four which is the reference number, On the other hand, period c 3 , period c 4  and period c 5 , the number of pulses of the second pulse signal  1002  included in one cycle of the first pulse signal  1001  is six more than the reference number, Since the pulses of the first pulse signal  1001  occurs according to the rotation of the DC motor  121 , the conveyance distance of the medium is constant in each period cl to period c 5  which is one cycle of the first pulse signal  1001 . Therefore, an input image generated by combining the line images imaged in all pulses of the second pulse signal  1002  included in period c 3 , period c 4  and period c 5 , extends. 
     The image generating module  152  can generate an image that is not extended, by discarding the line images acquired by the imaging device  117  in two pulses, among the pulses of the second pulse signal  1002  included in period c 3 , period c 4  and period c 5 . 
     When the image generating module  152  extracts images to be discarded after gathering together all the line images acquired by the imaging device  117  in period c 3 , period c 4  and period c 5 , the processing time required for extraction is increased, and the processing load of the image acquisition processing is increased. Therefore, in period c 3  in which the load change occurs, the image generating module  152  determines a discard pulses for discarding the line images in the cycle of next period c 4 , without discarding the line image. The image generating module  152  discards the line images the acquired by the imaging device  117  in the determined discard pulse, at the timing of acquiring each line image acquired by the imaging device  117 , in the cycle of next period c 4 . Similarly, the image generating module  152  determines the discard pulses for discarding the line images in the cycle of next period c 5 , in period c 4 , and discards the line images acquired by the imaging device  117  in the determined discard pulse, in the cycle of next period c 5 , 
     Although the extension occurs in the region corresponding to the cycle in which the load variation occurs in the input image, the region corresponding to one cycle in the input image is sufficiently small, the occurrence of the extension is not conspicuous. The image generating module  152  can generate an input image in which the extension is not conspicuous while reducing the processing load of the image acquisition process by preventing the occurrence of the extension in the region corresponding to the cycle after the cycle in which the load change occurs. 
     Further, as described above, since feedback control does not work immediately after the load fluctuation occurs, the varied cycle keeps the changed length for a while. Therefore, the length of the next cycle of the cycle in which the load fluctuation occurs is likely to be the same as the length of the cycle in which the load fluctuation occurs. The image generating module  152  accurately generate an input image that is not extended, while reducing the processing load of the image acquisition processing, by determining the number of line images to be discarded in the next cycle in accordance with the number of pulses of the second pulse signal included in the cycle in which the load change occurs. 
       FIG. 11  is a schematic diagram illustrating an example of an input image generated by the image generating module  152 , 
     The input image  1101  is an example of an input image generated without discarding the line images when the load change occurs. In the input image  1101 , the load variation occurs and the rotation speed of the DC motor  121  is slowed when the line L 1  is imaged, and the rotation speed of the DC motor  121  returns to the reference speed under feedback control when the line L 2  is imaged. Therefore, the extension in a region from the line L 1  to the line L 2  in the input image  1101  occurs. 
     The input image  1102  is an example of an input image in which line images are discarded when a load change occurs. In the input image  1102 , the load variation occurs and the rotation speed of the DC motor  121  is slowed when the line L 3  is imaged, and the rotation speed of the DC motor  121  returns to the reference speed under feedback control when the line L 4  is imaged. However, in the input image  1102 , a part of the line images among the line images corresponding to a region from the line L 3  to the line L 4  is discarded. Therefore, the occurrence of the extension in the region from the line L 3  to the line IA in the input image  1102  is suppressed. 
     As described in detail above, when the number of pulses of the second pulse signal for defining the image acquisition timing exceeds the reference number, included in each cycle of the first pulse signal which varies according to the rotation speed of the DC motor  121 , the medium conveying device  100  reduces the number of image acquisition in the next cycle. Therefore, the medium conveying device  100  can more easily generate an appropriate image while conveying the medium using the DC motor  121 . 
     The medium conveying apparatus  100  can convey a plurality of types of media having various thicknesses, including media having a plurality of regions having different thicknesses, such as a passport in an open state, using the DC motor  121  which is low cost, and suitably image the media. Therefore, the medium conveying apparatus  100  can generate an appropriate input image while reducing the equipment cost. 
     Further, the medium conveying device  100  uses, as the second pulse signal input to the imaging device  117 , a signal whose cycle is constant, rather than a signal synchronized with the first pulse signal output from the encoder  122 . Therefore, the medium conveying apparatus  100  can generate the second pulse signal using the pulse generator  131  which is low cost, and generate an appropriate input image while reducing the equipment cost. 
     Further, since the medium conveying device  100  generates an input image while discarding, the line images acquired by the imaging device  117  in the medium reading processing, the medium conveying device  100  can generate an appropriate input image in real time. Thus, the information processing apparatus connected to the medium conveying apparatus  100  does not need to correct the input image, the user can acquire an appropriate input image earlier, the medium conveying apparatus  100  can improve the convenience of the user. Further, since the information processing device connected to the medium conveying apparatus  100  does not need to correct the input image, the information processing device can smoothly perform the display processing of the image, thereby can improve the business efficiency of the user. 
     The image generating module  152  may discard the line image acquired by the image pickup device  117  in the number of pulses of the difference between the number of pulses detected by the detection module  153  and the reference number, only when the number of detected pulses is an integer multiple of the reference number. In that case, when the detected number of pulses exceeds the reference number and the detected number of pulses is not an integer multiple of the reference number, the image generating module  152  may combine all the line images acquired by the imaging device  117  in the cycle, thereafter, correct the image by a linear interpolation method. The image generating module  152  generates a corrected image having a reference number of lines from the combined image acquired by combining all the line images. The image generating module  152  extracts, for each line in the corrected image, an image of the nearest neighbor line at the upper side and an image of the nearest neighbor line at the lower side of the position corresponding to each line from the combined image, and generates an image of each line from the extracted two images by a linear interpolation method. Thus, the image generating module  152  can generate an input image in which the extension is more accurately modified, 
     The image generating module  152  may transmit information indicating an area in which the line image is discarded in the input image to the information processing apparatus via the interface device  133 , together with the generated input image. Thus, when a predetermined image processing is performed on the input image, the information processing device can perform image processing with emphasis on an area in which the line image is discarded in the input image or except for an area in which the line image is discarded in the input image. 
     Further, when the difference between the number of pulses detected by the detection module  153  and the reference number exceeds the upper limit number, the image generating module  152  may stop conveying and imaging the medium, and omit generating an input image. In that case, the image generating module  152  notifies the user of a warning by displaying information indicating that an abnormality has occurred to the display device  106  or transmitting the information to the information processing device via the display or interface device  133 . Thus, the image generating module  152  can notify the user of the warning when the rotation speed of the DC motor  121  is slowed so that the input image cannot be suitably generated. 
       FIG. 12  is a diagram illustrating a schematic configuration of a processing circuit  250  in a medium conveying apparatus according to another embodiment, The processing circuit  250  is used in place of the processing circuit  150  in the medium conveying apparatus  100  and executes the medium reading processing in place of the processing circuit  150 . The processing circuit  250  includes a control circuit  251 , an image generating circuit  252  and a detection circuit  253 , etc. Note that each unit may be configured by an independent integrated circuit, a microprocessor, firmware, etc. 
     The control circuit  251  is an example of a control module and has a function similar to the control module  151 . The control circuit  251  receives the operation signal from the operation device  105 , the first medium signal from the first sensor  111 , and outputs a control signal to the DC motor  121  and the second motor  132  to control the conveyance of the medium in response to the received signals. 
     The image generating circuit  252  is an example of an image generating module and has a functions similar to the image generating module  152 . The image generating circuit  252  receives the second medium signal from the second sensor  116 , the second pulse signal from the pulse generator  131 , the detection result of the number of pulses of the second pulse signal included in each cycle of the first pulse signal from the detection circuit  253 . The image generating circuit  252  acquires line images from the imaging device  117  or discards the acquired line images in response to the received information, generates the input image, and transmits the generated input image to the information processing apparatus via the interface device  133  or stores it in the storage device  140 . Further, the image generating circuit  252  outputs, the number of pulses of the second pulse signal received in a predetermined cycle to the detection circuit  253 . 
     The detection circuit  253  is an example of a detection module, and has a functions similar to the detection module  153 . The detection circuit  253  receives the first pulse signal from the encoder  122 , the number of pulses of the second pulse signal from the image generating circuit  252 , detects the number of pulses of the second pulse signal included in each cycle of the first pulse signal based on the received information. The detection circuit  253  outputs the detection result to the image generating circuit  252 . 
     As described in detail above, the medium conveying apparatus can suitably control the feeding of the medium, even when using the processing circuit  250 . 
     According to the embodiment, the medium conveying apparatus, the method, and the computer-readable, non-transitory medium storing the control program, can more easily generate an appropriate image in the medium conveying apparatus for conveying the medium using the DC motor. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.