Image reading device, electronic apparatus, and control method

Abstract

To adjust the amount of projection light of a light projector by using no CPU.SOLUTION: In a scanner 1, a pulse generator 51 generates a pulse signal, and a transmission type optical sensor 24 includes a light projector 24T for projecting pulsed light according to the pulse signal, and a light receiver 24R arranged to be opposite to the light projector. A peak hold circuit 91 holds a peak value of a voltage value indicating the amount of pulsed light received by the light receiver 24R. When the peak value is smaller than a reference value, a first current supply circuit 93 increases the light projection amount of pulsed light to be projected from the light projector by increasing the current to be supplied to the light projector. On the other hand, when the peak value is larger than the reference value, the first current supply circuit 93 decreases the light projection amount of pulsed light to be projected from the light projector by reducing the current to be supplied to the light projector.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present disclosure relates to an image reading device, an electronic device, and a control method. [Background technology]

[0002] In some scanners, the medium to be scanned (hereinafter sometimes referred to as the "medium to be scanned") is inserted into a transport path inside the scanner through an opening in the scanner. Some scanners into which the medium to be scanned is inserted use an optical sensor to determine whether the medium to be scanned has been inserted into the transport path. For example, when a transmissive optical sensor is used for the determination, the light projected from the light emitter is blocked by the medium to be scanned. Therefore, when the CPU (Central Processing Unit) detects a decrease in the amount of light received by the light receiver, the CPU determines that the medium to be scanned has been inserted into the transport path, and the CPU starts rotating the transport rollers.

[0003] Furthermore, scanners of the same model number are usually equipped with optical sensors of the same model number. However, because optical sensors vary from product to product, even if scanners of the same model number are equipped with optical sensors of the same model number, if the amount of light projected from the projector remains the same across multiple scanners, it may not be possible to accurately determine whether a medium to be read has been inserted into the transport path.

[0004] Therefore, in each scanner, in order to set the amount of light received by the light receiver when the medium to be read is not inserted in the transport path to the same target value across multiple scanners, the amount of light projected from the light emitter is adjusted according to the amount of light received by the light receiver (hereinafter sometimes referred to as ``light emission amount adjustment''). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-063998 Summary of the Invention [Problem to be solved by the invention]

[0006] However, because the CPU cannot operate without power supply, it is difficult for the CPU to adjust the light projection amount before power supply to the CPU begins. On the other hand, if power were supplied to the CPU before the medium to be read was inserted into the transport path in order to adjust the light projection amount by the CPU, the power consumption of the scanner would increase.

[0007] Therefore, the present disclosure proposes a technique that allows adjustment of the amount of projected light without using a CPU. [Means for solving the problem]

[0008] The image reading device disclosed herein includes a transport path, a generator, a sensor, a peak hold circuit, and a current supply circuit. A medium to be read is transported along the transport path. The generator generates a pulse signal. The sensor includes a projector that projects pulsed light corresponding to the pulse signal toward the transport path, and a light receiver disposed opposite the projector across the transport path. The peak hold circuit holds a peak value of a voltage value indicating the amount of pulsed light received by the light receiver. When the peak value is smaller than a reference value, the current supply circuit increases the current supplied to the projector, thereby increasing the amount of pulsed light projected from the projector. When the peak value is greater than the reference value, the current supply circuit decreases the amount of light projected. [Effects of the Invention]

[0009] According to the disclosed technology, the amount of light emitted can be adjusted without using a CPU. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a scanner according to a first embodiment of the present disclosure. [Figure 2]FIG. 2 is a diagram illustrating an example of the configuration of the scanner according to the first embodiment of the present disclosure. [Figure 3] FIG. 3 is a diagram illustrating a configuration example of an empty sensor according to the first embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating an example of the operation of the empty sensor according to the first embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram illustrating an example of the operation of the empty sensor according to the first embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram illustrating a configuration example of a signal processor according to the first embodiment of the present disclosure. [Figure 7] FIG. 7 is a flowchart illustrating an example of a processing procedure in the scanner according to the first embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram illustrating an example of the operation of the scanner according to the first embodiment of the present disclosure. [Figure 9] FIG. 9 is a diagram illustrating an example of the operation of the scanner according to the first embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating a configuration example of a scanner according to the second embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram illustrating a configuration example of a light projection amount adjuster according to a second embodiment of the present disclosure. [Figure 12] FIG. 12 is a flowchart illustrating an example of a processing procedure in the scanner according to the second embodiment of the present disclosure. [Figure 13] FIG. 13 is a diagram illustrating an example of the operation of the scanner according to the second embodiment of the present disclosure. [Figure 14] FIG. 14 is a diagram illustrating an example of the operation of the scanner according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, the same configurations and steps performing the same processes are denoted by the same reference numerals.

[0012] In the following, a scanner will be described as an example of an image reading device. However, the image reading device to which the disclosed technology can be applied is not limited to a scanner. For example, the disclosed technology can also be applied to image reading devices other than scanners, such as copiers. Furthermore, an image reading device is an example of an electronic device, and the electronic device to which the disclosed technology can be applied is not limited to an image reading device.

[0013] [Example 1] <Scanner configuration> 1 and 2 are diagrams illustrating an example of the configuration of a scanner according to a first embodiment of the present disclosure. Fig. 1 illustrates a side view, and Fig. 2 illustrates a front view. An example of a medium to be read that is inserted into the scanner 1 illustrated in Figs. 1 and 2 is a document containing characters and figures.

[0014] 1, scanner 1 has a feed tray 11, a lower housing 12, and an upper housing 13. Feed tray 11 is attached to upper housing 13 via a rotation axis RA1 and can be opened and closed around rotation axis RA1. Fig. 1 shows feed tray 11 in an open state, and Fig. 2 shows feed tray 11 in a closed state.

[0015] The scanner 1 also includes medium reading units 17-1 and 17-2, a CPU 21, a signal processor 50, a power supply 60, a memory 29, a pick roller 22, transmission optical sensors 24 and 25, transport rollers 26-1, 26-2, 27-1 and 27-2, transport paths P1, P2 and P3, and a flap 35. The fulcrum of the flap 35 is formed on the upper housing 13. The fulcrum of the flap 35 is located at the rear end of the flap 35, and the initial position of the flap 35 is when the leading end of the flap 35 is raised toward the upper housing 13. The pick roller 22, transport rollers 26-1, 26-2, 27-1 and 27-2, and the flap 35 are driven by a motor (not shown).

[0016] The medium reading units 17-1 and 17-2 are realized as hardware, for example, by a CIS (Contact Image Sensor) type image sensor. Examples of memory include RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), ROM (Read Only Memory), and flash memory.

[0017] The transport path P1 has an opening O1L formed on the left side of the scanner 1, an opening O1R formed on the right side of the scanner 1, an upper surface S11, and a lower surface S12. The upper surface S11 of the transport path P1 corresponds to the lower surface of the upper housing 13, and the lower surface S12 of the transport path P1 corresponds to the upper surface of the lower housing 12. In other words, the transport path P1 is formed between the upper housing 13 and the lower housing 12. The transport path P1 is also used to transport a medium to be read (hereinafter sometimes referred to as a "first medium to be read") inserted through the opening O1L. The first medium to be read is usually inserted through the opening O1L by the operator.

[0018] The transport path P2 has an opening O2 formed in the top surface of the upper housing 13, an upper surface S21, and a lower surface S22. The transport path P2 is used to transport a medium to be read (hereinafter sometimes referred to as a "second medium to be read") inserted through the opening O2. The second medium to be read placed on the feed tray 11 is inserted through the opening O2.

[0019] Here, transport path P2 merges with transport path P1 at a junction JP1 located midway along transport path P1. Furthermore, the heightwise width H1 of openings O1L and O1R of transport path P1 (i.e., the distance between the upper surface S11 and the lower surface S12) is greater than the heightwise width H2 of opening O2 of transport path P2 (i.e., the distance between the upper surface S21 and the lower surface S22). Because width H1 is greater than width H2, thicker target media are typically inserted into opening O1L, and thinner target media are typically inserted into opening O2. In other words, the thickness of the first target medium is typically greater than the thickness of the second target medium.

[0020] The transport path P3 has an opening O3 formed in the top surface of the upper housing 13, and merges with the transport path P1 at a junction JP2 located midway along the transport path P1.

[0021] The transmissive optical sensor 24 includes a light-emitter 24T and a light-receiver 24R. The light-emitter 24T and the light-receiver 24R are disposed opposite each other across the conveyance path P1, and light emitted from the light-emitter 24T toward the upper surface S11 is received by the light-receiver 24R. The light-emitter 24T is disposed on the lower surface S12 side, and the light-receiver 24R is disposed on the upper surface S11 side. When the scanner 1 is in the "operation mode," the amount of light emitted by the light-emitter 24T is kept constant at a first light-emitter amount QH under control of the CPU 21. When the scanner 1 is in the "sleep mode," which consumes less power than the operation mode, the amount of light emitted by the light-emitter 24T changes between a first light-emitter amount QH and a second light-emitter amount QL, which is smaller than the first light-emitter amount QH, at regular intervals T1 in accordance with a pulse signal output from the signal processor 50. "Sleep mode" is sometimes called "standby mode."

[0022] The transmission-type optical sensor 25 has a light-emitter 25T and a light-receiver 25R. The light-emitter 25T and the light-receiver 25R are disposed opposite each other across the conveyance path P1, and light projected from the light-emitter 25T toward the upper surface S11 is received by the light-receiver 25R. The light-emitter 25T is disposed on the lower surface S12 side, and the light-receiver 25R is disposed on the upper surface S11 side. When the scanner 1 is in the operation mode, the amount of light projected by the light-emitter 25T is kept constant at a first light-emitter amount QH under control of the CPU 21. When the scanner 1 is in the sleep mode, the light-emitter 25T is turned off.

[0023] Here, the scanner 1 does not have a "power button" for starting the supply of power to the CPU 21. The supply of power from the power supplier 60 to the CPU 21 starts when the operator of the scanner 1 opens the closed feed tray 11, or when the first medium to be read is inserted into the transport path P1 through the opening O1L and the signal processor 50 determines that the first medium to be read is present in the transport path P1. The CPU 21 becomes operable when power is supplied from the power supplier 60. When the scanner 1 is in sleep mode, power is not supplied to the CPU 21, and power is supplied to the CPU 21 when the scanner 1 is in operation mode.

[0024] <Transportation of the second read target medium> Fig. 3 is a diagram illustrating a configuration example of the empty sensor according to the first embodiment of the present disclosure, Fig. 4 and Fig. 5 are diagrams illustrating an operation example of the empty sensor according to the first embodiment of the present disclosure.

[0025] 3, the empty sensor 23 has a transmission-type optical sensor 28 and a movable member 80. The transmission-type optical sensor 28 has a light-emitter 28T and a light-receiver 28R. The light-emitter 28T and the light-receiver 28R are disposed opposite each other, and light projected from the light-emitter 28T is received by the light-receiver 28R. The amount of light projected by the light-emitter 28T is kept constant at a first light-emitter amount QH under the control of the CPU 21. The movable member 80 has an arm 81 and levers 82 and 83 connected to the arm 81. The movable member 80 is a member that can freely rotate about a rotation axis RA2.

[0026] When the second medium to be read is not placed on the feed tray 11, as shown in Figure 4, there is no second medium to be read on the transport path P2, so the light projected from the light-emitter 28T is not blocked by the lever 83 and is received by the light-receiver 28R.

[0027] When the closed feed tray 11 is opened by the operator of the scanner 1, the signal processor 50 transitions the scanner 1 from sleep mode to operating mode and starts supplying power from the power supplier 60 to the CPU 21.

[0028] When the amount of light received by the light receiver 24R (hereinafter sometimes referred to as the "first amount of received light") is equal to or greater than the threshold value THR, the CPU 21 and a controller 53 (described later) determine that the level of the first amount of received light (hereinafter sometimes referred to as the "first level of received light") is at a high level H, and when the first amount of received light is less than the threshold value THR, they determine that the first level of received light is at a low level L that is lower than the high level H. The threshold value THR is stored in advance in the memory 29.

[0029] Furthermore, when the amount of light received by the light receiver 25R (hereinafter sometimes referred to as the "second amount of light received") is equal to or greater than the threshold value THR, the CPU 21 determines that the level of the second amount of light received (hereinafter sometimes referred to as the "second light receiving level") is at a high level H, and when the second amount of light received is less than the threshold value THR, it determines that the second light receiving level is at a low level L.

[0030] Furthermore, when the amount of light received by the light receiver 28R (hereinafter sometimes referred to as the "third amount of received light") is greater than or equal to the threshold value TH1, the CPU 21 determines that the level of the third amount of received light (hereinafter sometimes referred to as the "third light receiving level") is at a high level H, and when the third amount of received light is less than the threshold value TH1, the CPU 21 determines that the third light receiving level is at a low level L.

[0031] When the feed tray 11 is open and a second medium to be read MD is placed on the feed tray 11 as shown in FIG. 5, the second medium to be read MD is inserted into the transport path P2 through the opening O2, and the lever 82 is pushed up by the second medium to be read MD. When the lever 82 is pushed up by the second medium to be read MD, the movable member 80 rotates rightward (clockwise), and the lever 83 moves from the position shown in FIG. 4 to the position shown in FIG. 5. As a result, the light projected from the light projector 28T is blocked by the lever 83, and the third light reception level decreases from high level H to low level L. When the third light reception level decreases from high level H to low level L, the CPU 21 starts rotation of the pick roller 22 and the transport rollers 26-1, 26-2, 27-1, and 27-2 and lowers the tip of the flap 35 toward the lower housing 12. The CPU 21 rotates the pick roller 22 and the conveying rollers 26-1 and 27-1 clockwise, while rotating the conveying rollers 26-2 and 27-2 counterclockwise. In addition, by lowering the tip of the flap 35 toward the lower housing 12, the conveying path P3 and the conveying path P1 are connected, and therefore, a continuous conveying path is formed by the conveying path P2, the conveying path P1, and the conveying path P3.

[0032] When the leading edge of the second medium to be read, being conveyed along conveyance path P2 by pick roller 22, passes confluence JP1 and reaches the gap between conveyance rollers 27-1 and 27-2, the second medium to be read is conveyed along conveyance path P1 in the -X direction (leftward in the figure) by conveyance rollers 27-1 and 27-2. When the second medium to be read is conveyed along conveyance path P1 in the -X direction by conveyance rollers 27-1 and 27-2 and the leading edge of the second medium to be read reaches transmission optical sensor 25, the light projected from light projector 25T is blocked by the second medium to be read, causing the second light reception level to decrease from high level H to low level L. When the second light reception level decreases from high level H to low level L, CPU 21 starts reading the second medium to be read by medium reading units 17-1 and 17-2. As the second target medium is transported in the -X direction on transport path P1, the second target medium is read by medium reading units 17-1 and 17-2. The top surface of the second target medium is read by medium reading unit 17-1, and the bottom surface of the second target medium is read by medium reading unit 17-2.

[0033] Further, as the second target medium is transported in the -X direction on transport path P1, when the leading edge of the second target medium reaches between transport rollers 26-1 and 26-2, the second target medium is further transported in the -X direction on transport path P1 by transport rollers 26-1 and 26-2. As the second target medium is transported in the -X direction on transport path P1 by transport rollers 26-1 and 26-2, the leading edge of the second target medium moves toward junction JP2 while contacting the upper surface of flap 35 as the second target medium is transported, and enters transport path P3. Therefore, after being read, the second target medium is transported in the +Z direction (upward in the figure) on transport path P3 and discharged onto the top surface of upper housing 13 through opening O3.

[0034] Furthermore, when the rear end of the last second medium to be read placed on the feed tray 11 passes the empty sensor 23, the third light receiving level increases from low level L to high level H. After the third light receiving level decreases from high level H to low level L once and then increases again from low level L to high level H, the CPU 21 stops the rotation of the pick roller 22 and the conveying rollers 26-1, 26-2, 27-1, and 27-2 after a predetermined time has elapsed since that time.

[0035] <Transportation of the first read target medium> In sleep mode, when the tip of the flap 35 is raised toward the upper housing 13 and a first medium to be read is inserted into the transport path P1 through the opening O1L in the +X direction (to the right in the figure), the light projected from the light projector 24T is blocked by the first medium to be read, causing the first light reception level to decrease from high level H to low level L. As will be described later, the signal processor 50 determines that the first medium to be read is present in the transport path P1 based on the first light reception level. Upon determining that the first medium to be read is present in the transport path P1, the signal processor 50 transitions the scanner 1 from sleep mode to operating mode and starts supplying power from the power supplier 60 to the CPU 21. Upon starting the supply of power, the CPU 21 starts rotating the transport rollers 26-1 and 27-1 counterclockwise and the transport rollers 26-2 and 27-2 clockwise. When the first medium to be read is further inserted in the +X direction and the leading edge of the first medium to be read reaches between the transport rollers 26-1 and 26-2, the first medium to be read is transported in the +X direction along the transport path P1 by the transport rollers 26-1 and 26-2.

[0036] When the first medium to be read is conveyed in the +X direction by conveyance rollers 26-1 and 26-2 and the leading edge of the first medium to be read reaches transmission-type optical sensor 25, the light projected from light projector 25T is blocked by the first medium to be read, causing the second light reception level to decrease from high level H to low level L. When the second light reception level decreases from high level H to low level L, CPU 21 temporarily stops the rotation of conveyance rollers 26-1, 26-2, 27-1, and 27-2.

[0037] After the rotation of the conveying rollers 26-1, 26-2, 27-1, and 27-2 has temporarily stopped, when the operator presses the "scan start button" (not shown) of the scanner 1, the CPU 21 again starts rotating the conveying rollers 26-1 and 27-1 counterclockwise, while starting to rotate the conveying rollers 26-2 and 27-2 clockwise. When the first medium to be read is further conveyed along the conveying path P1 in the +X direction by the conveying rollers 26-1 and 26-2 and the leading edge of the first medium to be read reaches between the conveying rollers 27-1 and 27-2, the first medium to be read is further conveyed along the conveying path P1 in the +X direction by the conveying rollers 27-1 and 27-2.

[0038] Then, when the rear end of the first target medium passes transmissive optical sensor 25, the light projected from light projector 25T is received by light receiver 25R, causing the second received light level to increase from low level L to high level H. As the first target medium is transported in the +X direction on transport path P1, the second received light level temporarily decreases from high level H to low level L, and then increases again from low level L to high level H. At this point, CPU 21 reverses the rotation direction of transport rollers 26-1, 26-2, 27-1, and 27-2, rotating transport rollers 26-1 and 27-1 clockwise and transport rollers 26-2 and 27-2 counterclockwise. This reverses the transport direction of the first target medium on transport path P1 from the +X direction to the -X direction. When the transport direction of the first medium to be read is reversed from the +X direction to the -X direction and the rear end of the first medium to be read reaches the transmissive optical sensor 25, the light projected from the light projector 25T is blocked by the first medium to be read, and the second light receiving level decreases from high level H to low level L.

[0039] When CPU 21 reverses the transport direction of the first read target medium from the +X direction to the -X direction, medium reading units 17-1 and 17-2 start reading the first read target medium. As the first read target medium is transported in the -X direction on transport path P1, the first read target medium is read by medium reading units 17-1 and 17-2. The top surface of the first read target medium is read by medium reading unit 17-1, and the bottom surface of the first read target medium is read by medium reading unit 17-2. After reading, the first read target medium is ejected from opening O1L.

[0040] Furthermore, as the first medium to be read is transported in the -X direction, when the leading edge of the first medium to be read passes the transmissive optical sensor 25, the light projected from the light projector 25T is received by the light receiver 25R, and the second light reception level increases from low level L to high level H. The CPU 21 stops the rotation of the transport rollers 26-1, 26-2, 27-1, and 27-2 after a predetermined time has elapsed from the point when the second light reception level temporarily decreases from high level H to low level L as the first medium to be read is transported in the -X direction on the transport path P1 and then increases again from low level L to high level H.

[0041] <Signal processor configuration> Fig. 6 is a diagram illustrating a configuration example of a signal processor according to the first embodiment of the present disclosure. In Fig. 6, a signal processor 50 includes a pulse generator 51, a charger / discharger 52, a controller 53, and a switch 54. The charger / discharger 52 includes a capacitor (not shown) that can store electric charge and discharge the stored electric charge. Examples of the controller 53 include a processor such as a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array).

[0042] When the scanner 1 is in the sleep mode, power is supplied from the power supply 60 to the signal processor 50. When the scanner 1 is in the operating mode, power is supplied from the power supply 60 to the CPU 21 via the switch 54. When the scanner 1 is in the sleep mode, the power consumption of the scanner 1 is, for example, about 0.3 W, and when the scanner 1 is in the operating mode, the power consumption of the scanner 1 is, for example, about 9 W.

[0043] <Scanner processing procedure> Fig. 7 is a flowchart showing an example of a processing procedure in the scanner according to the first embodiment of the present disclosure. The flowchart shown in Fig. 7 is started when the scanner 1 is in sleep mode. At the start of the flowchart shown in Fig. 7, the switch 54 is off, and no power is supplied from the power supplier 60 to the CPU 21.

[0044] In step S100, the pulse generator 51 generates a pulse signal and outputs the generated pulse signal to the projector 24T and the charger / discharger 52, and the projector 24T pulses in accordance with the input pulse signal. For example, the pulse generator 51 generates a square wave pulse signal with a duty ratio of 50%, and the projector 24T projects light (hereinafter sometimes referred to as "pulse light"), the light amount of which changes between a first light amount QH and a second light amount QL every certain time T1 in accordance with the pulse signal, toward the conveying path P1.

[0045] Next, in step S105, the controller 53 determines whether or not pulsed light is received by the photoreceiver 24R. For example, if there is a time during time T1 when the first received light level becomes high level H, the controller 53 determines that pulsed light is received by the photoreceiver 24R, and if the first received light level remains at low level L for the time T1, the controller 53 determines that pulsed light is not received by the photoreceiver 24R. If pulsed light is not received by the photoreceiver 24R (step S105: No), the process proceeds to step S110, and if pulsed light is received by the photoreceiver 24R (step S105: Yes), the process proceeds to step S115.

[0046] In step S110, the controller 53 charges the charger / discharger 52. That is, in step S110, the controller 53 controls the charger / discharger 52 so that the charge of the pulse signal output from the pulse generator 51 to the charger / discharger 52 is accumulated in the capacitor. After the processing of step S110, the processing proceeds to step S120.

[0047] On the other hand, in step S115, the controller 53 discharges the charger / discharger 52. That is, in step S115, the controller 53 controls the charger / discharger 52 to discharge the charge stored in the capacitor from the capacitor. After the processing of step S115, the processing returns to step S100.

[0048] In step S120, the controller 53 determines whether the charge amount in the charger / discharger 52, that is, the amount of charge accumulated in the capacitor of the charger / discharger 52, is equal to or greater than the threshold value THC. If the charge amount is equal to or greater than the threshold value THC (step S120: Yes), the controller 53 determines that the first target medium is present on the transport path P1, and the process proceeds to step S125. On the other hand, if the charge amount is less than the threshold value THC (step S120: No), the controller 53 determines that the first target medium is not present on the transport path P1, and the process returns to step S100.

[0049] In step S125, the controller 53 turns on the switch 54, which has been turned off, to start supplying power from the power supplier 60 to the CPU 21.

[0050] Next, in step S130, the CPU 21, which has started to supply power in step S125, keeps the amount of light projected by the projector 24T constant at the first light amount QH, thereby keeping the projector 24T constantly lit. After the process of step S130, the process procedure ends.

[0051] <Scanner operation> 8 and 9 are diagrams illustrating an example of the operation of the scanner according to the first embodiment of the present disclosure. FIG. 8 illustrates a case where pulsed light is received by the photodetector 24R before the charge amount in the charger / discharger 52 reaches the threshold THC (hereinafter, this may be referred to as "case C1"), and FIG. 9 illustrates a case where the charge amount in the charger / discharger 52 becomes equal to or greater than the threshold THC (hereinafter, this may be referred to as "case C2"). Below, an example of the operation of the scanner 1 will be described for cases C1 and C2. In both cases C1 and C2, the determinations in steps S105 and S120 (FIG. 7) are made at timings t1 to t25, each of which has a constant interval T1.

[0052] <Case C1 (Figure 8)> In FIG. 8, at each of timings t1 to t6, there is a time during time T1 when the first light reception level becomes high level H, so the controller 53 determines that the light receiver 24R is receiving pulsed light (step S105: Yes) and causes the charger / discharger 52 to discharge (step S115).

[0053] During the time T1 from timing t6 to timing t7, there is no time during which the first light-receiving level becomes high level H, and the first light-receiving level remains low level L for the time T1. Therefore, at timing t7, the controller 53 determines that the light-receiver 24R does not receive pulsed light (step S105: No) and causes the charger / discharger 52 to charge (step S110). Similarly, at each of timings t8 to t12, the controller 53 determines that the light-receiver 24R does not receive pulsed light (step S105: No) and causes the charger / discharger 52 to charge (step S110). Furthermore, at each of timings t7 to t12, the amount of charge in the charger / discharger 52 is less than the threshold value THC (step S120: No), so the process returns from step S120 to step S100.

[0054] During the time T1 from timing t12 to timing t13, there is a time when the first light receiving level becomes high level H, so at timing t13, the controller 53 determines that the light receiver 24R is receiving pulsed light (step S105: Yes) and discharges the charger / discharger 52 (step S115).

[0055] Thereafter, the operations from timing t14 to t20 are the same as those from timing t1 to t6, and the operations from timing t21 to t25 are the same as those from timing t7 to t12.

[0056] <Case C2 (Figure 9)> In FIG. 9, at each of timings t1 to t6, there is a time during time T1 when the first light reception level becomes high level H, so the controller 53 determines that the light receiver 24R is receiving pulsed light (step S105: Yes) and discharges the charger / discharger 52 (step S115).

[0057] During the time T1 from timing t6 to timing t7, there is no time during which the first light-receiving level becomes high level H, and the first light-receiving level remains low level L for the time T1. Therefore, at timing t7, the controller 53 determines that the light receiver 24R is not receiving pulsed light (step S105: No) and charges the charger / discharger 52 (step S110). Similarly, at each of timings t8 to t13, the controller 53 determines that the light receiver 24R is not receiving pulsed light (step S105: No) and charges the charger / discharger 52 (step S110). As a result, at timing t13, the charge amount of the charger / discharger 52 is equal to or greater than the threshold THC (step S120: Yes). Therefore, at timing t13, the controller 53 determines that the first read target medium is present on the transport path P1 and starts supplying power from the power supplier 60 to the CPU 21 (step S125). Furthermore, the CPU 21, which has started to supply power at timing t13, keeps the light projected by the light projector 24T constant at the first light projected amount QH from timing t13 onwards, thereby keeping the light projector 24T constantly on.

[0058] The first embodiment has been described above.

[0059] [Example 2] <Scanner configuration> 10 is a diagram showing a configuration example of a scanner according to a second embodiment of the present disclosure. A side view is shown in Fig. 10. The second embodiment differs from the first embodiment in that the scanner 1 further includes a light projection amount adjuster 90.

[0060] <Configuration of the light emission controller> 11 is a diagram illustrating a configuration example of a light emission intensity adjuster according to Example 2 of the present disclosure. In FIG. 11, a light emission intensity adjuster 90 includes a peak hold circuit 91, a subtractor 92, a first current supply circuit 93, and a second current supply circuit 94.

[0061] The peak hold circuit 91 has a resistor and a capacitor, and holds the peak value (hereinafter sometimes referred to as the "received light peak value") of the voltage value (hereinafter sometimes referred to as the "received light voltage value") indicating the first amount of received light when the scanner 1 is in sleep mode.

[0062] When the scanner 1 is in sleep mode, the subtractor 92 subtracts a reference value for the peak light-reception value (hereinafter referred to as the "reference light-reception value") from the peak light-reception value to calculate a difference value (hereinafter referred to as the "difference light-reception value") between the peak light-reception value and the reference light-reception value. The reference light-reception value is set in advance based on a target value for the light-reception voltage value (hereinafter referred to as the "target light-reception value"). For example, if the target light-reception value is 1.2 [V], the reference light-reception value is set to 1.0 [V], which is smaller than the target light-reception value, based on the resistance and capacitance of the resistor and capacitor in the peak hold circuit 91.

[0063] When the scanner 1 is in sleep mode, the first current supply circuit 93 adjusts the amount of pulsed light projected from the projector 24T by adjusting the current (hereinafter sometimes referred to as the "first supply current") supplied from the first current supply circuit 93 to the projector 24T based on the light reception differential value. When the first supply current increases, the amount of light projected by the projector 24T increases, and when the first supply current decreases, the amount of light projected by the projector 24T decreases. For example, when the light reception differential value is -0.2 [V], the first current supply circuit 93 increases the first supply current by 8 [mA], and when the light reception differential value is +0.2 [V], the first current supply circuit 93 decreases the first supply current by 8 [mA].

[0064] When the scanner 1 is in the operating mode, the second current supply circuit 94 adjusts the amount of pulsed light projected from the projector 24T by adjusting the current (hereinafter sometimes referred to as the "second supply current") supplied from the second current supply circuit 94 to the projector 24T under control of the CPU 21. When the second supply current increases, the amount of light projected by the projector 24T increases, and when the second supply current decreases, the amount of light projected by the projector 24T decreases.

[0065] <Scanner processing procedure> Fig. 12 is a flowchart showing an example of a processing procedure in a scanner according to a second embodiment of the present disclosure. As in the first embodiment, the flowchart shown in Fig. 12 is started when the scanner 1 is in sleep mode. Of the processes in the flowchart shown in Fig. 12, those that are the same as those in the flowchart shown in Fig. 7 will not be described.

[0066] Following the process of step S100, in step S200, the peak hold circuit 91 holds the peak light reception value PV [V].

[0067] Next, in step S205, the subtractor 92 calculates a light-reception difference value ΔV [V] by subtracting the light-reception reference value RV [V] from the light-reception peak value PV.

[0068] Next, in step S210, the first current supply circuit 93 determines whether the peak light-reception value PV is smaller than the reference light-reception value RV. When the light-reception differential value ΔV is a negative value, the first current supply circuit 93 determines that the peak light-reception value PV is smaller than the reference light-reception value RV. If the peak light-reception value PV is smaller than the reference light-reception value RV (step S210: Yes), the process proceeds to step S215. If the peak light-reception value PV is equal to or greater than the reference light-reception value RV (step S210: No), the process proceeds to step S220.

[0069] In step S215, the first current supply circuit 93 increases the first supply current to increase the amount of pulsed light projected from the projector 24T. After the process of step S215, the process proceeds to step S120.

[0070] On the other hand, in step S220, the first current supply circuit 93 determines whether the peak light-reception value PV is greater than the reference light-reception value RV. When the light-reception differential value ΔV is a positive value, the first current supply circuit 93 determines that the peak light-reception value PV is greater than the reference light-reception value RV. If the peak light-reception value PV is greater than the reference light-reception value RV (step S220: Yes), the process proceeds to step S225. If the peak light-reception value PV is equal to the reference light-reception value RV (step S210: No, step S220: No), the processes of steps S215 and S225 are skipped and the process proceeds to step S120.

[0071] In step S225, the first current supply circuit 93 reduces the first supply current to reduce the amount of pulsed light projected from the projector 24T. After the process of step S225, the process proceeds to step S120.

[0072] Furthermore, following the processing of step S130, in step S230, CPU 21 stops the operation of first current supply circuit 93 while starting the operation of second current supply circuit 94, thereby stopping the adjustment of the light projection amount based on the peak light-reception value and adjusting the light projection amount based on the light-reception voltage value [V]. That is, CPU 21 stops the adjustment of the light projection amount based on the peak light-reception value when power supply from power supplier 60 to CPU 21 starts in step S125, and adjusts the light projection amount based on the light-reception voltage value after power supply from power supplier 60 to CPU 21 starts. When the light-reception voltage value is smaller than light-reception target value TV [V], CPU 21 increases the second supply current by an amount corresponding to the absolute value of the difference between the light-reception voltage value and light-reception target value TV, thereby increasing the amount of light projected from light transmitter 24T. On the other hand, when the light-receiving voltage value is greater than the target light-receiving value TV, CPU 21 reduces the second supply current by an amount corresponding to the absolute value of the difference between the light-receiving voltage value and the target light-receiving value TV, thereby reducing the amount of light projected from light projector 24T. After processing step S230, the processing procedure ends.

[0073] <Scanner operation> 13 and 14 are diagrams illustrating an example of the operation of the scanner according to the second embodiment of the present disclosure. Fig. 13 illustrates a case where the peak light-receiving value PV is smaller than the reference light-receiving value RV (hereinafter, sometimes referred to as "case C3"), and Fig. 14 illustrates a case where the peak light-receiving value PV is larger than the reference light-receiving value RV (hereinafter, sometimes referred to as "case C4"). Below, an example of the operation of the scanner 1 will be described separately for case C3 and case C4.

[0074] <Case C3 (Fig. 13)> At timing tA, when the first target medium is inserted into the transport path P1 from the opening O1L toward the +X direction (to the right in the figure), the pulsed light projected from the light projector 24T is blocked by the first target medium, causing the light-receiving voltage value, which was at the target light-receiving value TV, to decrease to zero. Therefore, the peak light-receiving value PV gradually decreases in accordance with the natural discharge of the capacitor in the peak-hold circuit 91. Furthermore, as the peak light-receiving value PV gradually decreases, the first supply current gradually increases. However, because a first supply current of 4.0 mA is required for the pulsed light projected from the light projector 24T to pass through the first target medium, the light-receiving voltage value does not appear until the first supply current reaches 4.0 mA. Furthermore, because the natural discharge rate of the capacitor in the peak-hold circuit 91 is slow, it takes a considerable amount of time for the light-receiving voltage value to exceed the peak light-receiving value PV even after the first supply current reaches 4.0 mA. Therefore, even after the first supply current reaches 4.0 [mA] and the light-receiving voltage value appears, the light-receiving peak value PV continues to decrease for a while until the light-receiving voltage value reaches the light-receiving target value TV.

[0075] In this way, when the first medium to be read is inserted while the light projection amount is being adjusted based on the peak light reception value, a period of time (hereinafter sometimes referred to as "non-transmission time") can be secured between timing tA, when the first medium to be read is inserted, and timing tC, when the pulsed light passes through the first medium to be read. Also, timing tA in Figure 13 corresponds to timing t7 in Figure 9, and timing tB in Figure 13 corresponds to timing t13 in Figure 9. Also, as described above, at timing t13, controller 53 determines that the first medium to be read is present in transport path P1.

[0076] By ensuring the non-transmission time NT from timing tA to timing tC, even if the light reception voltage value increases due to light projection adjustment based on the peak light reception value, it is possible to prevent the first light reception level from becoming high level H during the period TX from timing tA (timing t7) to timing tB (timing t13) even though the first read target medium is inserted. Therefore, in the first embodiment, it is possible to prevent the first read target medium from being erroneously determined not to be inserted even though it is inserted.

[0077] <Case C4 (Figure 14)> When commercial power is connected to scanner 1 at timing tD, the light-receiving voltage value increases at timing tD, causing the light-receiving peak value PV to exceed the light-receiving reference value RV. As a result, the first supply current decreases according to the light-receiving differential value ΔV, and the light-receiving voltage value decreases in accordance with the decrease in the first supply current.

[0078] Here, since the amount of charge accumulated per pulse signal in the capacitor of the peak hold circuit 91 is small, the light receiving voltage value that becomes smaller than the light receiving target value TV at timing tD returns to the light receiving target value TV when the light receiving peak value PV becomes smaller than the light receiving reference value RV multiple times.

[0079] The second embodiment has been described above.

[0080] [Example 3] All or part of the processes described above by the CPU 21 may be realized by having the CPU 21 execute a program corresponding to each process. For example, the program corresponding to each process described above may be stored in memory 29, and the CPU 21 may read the program from memory 29 and execute it. Alternatively, the program may be stored in a program server connected to the scanner 1 via a network, downloaded from the program server to the scanner 1, and executed. Alternatively, the program may be stored in a storage medium readable by the scanner 1, read from the storage medium, and executed. Storage media readable by the scanner 1 include portable storage media such as memory cards, USB memory sticks, SD cards, flexible disks, magneto-optical disks, CD-ROMs, DVDs, and Blu-ray (registered trademark) discs. A program is a data processing method written in any language or any description method, and may be in any format, such as source code or binary code. A program is not necessarily limited to a single program, but may be distributed as multiple modules or libraries, or may achieve its function by cooperating with other programs, such as an operating system.

[0081] The third embodiment has been described above.

[0082] As described above, the image reading device (scanner 1 in the embodiment) of the present disclosure includes a transport path (transport path P1 in the embodiment), a generator (pulse generator 51 in the embodiment), a sensor (transmissive optical sensor 24 in the embodiment), a peak hold circuit (peak hold circuit 91 in the embodiment), and a current supply circuit (first current supply circuit 93 in the embodiment). A medium to be read is transported along the transport path. The generator generates a pulse signal. The sensor includes a light projector (light projector 24T in the embodiment) that projects pulsed light corresponding to the pulse signal toward the transport path, and a light receiver (light receiver 24R in the embodiment) that faces the light projector across the transport path. The peak hold circuit holds the peak value of the received light voltage, which indicates the amount of pulsed light received by the light receiver. When the peak value is smaller than a reference value, the current supply circuit increases the current supplied to the light projector, thereby increasing the amount of pulsed light projected from the light projector. Furthermore, when the peak value is greater than the reference value, the current supply circuit reduces the current supplied to the projector, thereby reducing the amount of pulsed light projected from the projector.

[0083] This allows the light amount to be adjusted without using the CPU.

[0084] The image reading device (scanner 1 in the embodiment) of the present disclosure also includes a CPU (CPU 21 in the embodiment), a charger / discharger (charger / discharger 52 in the embodiment), and a controller (controller 53 in the embodiment). The charger / discharger is capable of accumulating charge of a pulse signal and discharging the accumulated charge. The controller causes the charger / discharger to discharge charge when pulsed light is received by the light receiver, and causes the charger / discharger to accumulate charge when the pulsed light is not received by the light receiver because the pulsed light is blocked by a medium. The controller also starts supplying power to the CPU when the amount of charge accumulated in the charger / discharger reaches or exceeds a threshold. The light projector projects pulsed light before power supply to the CPU is started, but remains constantly lit after power supply to the CPU is started. The CPU stops adjusting the light projection amount based on the peak value when power supply to the CPU is started. After the supply of power to the CPU is started, the CPU adjusts the amount of pulsed light projected from the projector based on the light-receiving voltage value.

[0085] In this way, after power supply to the CPU is started, the CPU is used to adjust the amount of light emitted, so the degree of freedom in adjusting the amount of light emitted after power supply to the CPU is started can be increased compared to before power supply to the CPU is started. [Explanation of symbols]

[0086] 1. Scanner 21 CPU 24 Transmissive optical sensor 24T floodlight 24R receiver 51 Pulse Generator 52 Charger / discharger 53 Controller P1 transport path 91 Peak hold circuit 93 First current supply circuit

Claims

1. a transport path along which a medium to be read is transported; a generator for generating a pulse signal; a sensor including a light projector that projects pulsed light corresponding to the pulse signal toward the conveying path, and a light receiver that is disposed opposite the light projector across the conveying path; a peak hold circuit that holds a peak value of a voltage value that indicates the amount of pulsed light received by the photoreceiver; a current supply circuit that adjusts the amount of light projected by the transmitter by increasing a current supplied to the transmitter when the peak value is smaller than a reference value, and by decreasing the current when the peak value is larger than the reference value, thereby decreasing the amount of light projected; An image reading device comprising:

2. A CPU and a charger / discharger capable of storing charge of the pulse signal and discharging the stored charge; a controller that causes the charger / discharger to discharge the electric charge when the pulsed light is received by the light receiver, and that causes the charger / discharger to accumulate the electric charge when the pulsed light is not received by the light receiver because the pulsed light is blocked by the medium, and that starts supplying power to the CPU when the amount of the electric charge accumulated in the charger / discharger becomes equal to or greater than a threshold value; Further comprising: the light projector projects the pulsed light before the supply of power to the CPU is started, and is constantly lit after the supply of power to the CPU is started; The CPU When the supply of power to the CPU is started, the adjustment of the amount of light emitted based on the peak value is stopped; After the supply of power to the CPU is started, the amount of light emitted is adjusted based on the voltage value.

2. The image reading device according to claim 1.

3. a generator for generating a pulse signal; a sensor having a light projector that projects pulsed light in response to the pulse signal and a light receiver that is disposed opposite the light projector; a peak hold circuit that holds a peak value of a voltage value that indicates the amount of pulsed light received by the photoreceiver; a current supply circuit that increases a current supplied to the projector when the peak value is smaller than a reference value, thereby increasing an amount of the pulsed light projected from the projector, and that reduces the current when the peak value is larger than the reference value, thereby decreasing the amount of the projected light; An electronic device comprising:

4. a generator for generating a pulse signal; a sensor having a light projector that projects pulsed light in response to the pulse signal and a light receiver that is disposed opposite the light projector; a peak hold circuit that holds a peak value of a voltage value that indicates the amount of pulsed light received by the photoreceiver; A control method for an electronic device comprising: increasing the amount of the pulsed light projected from the projector when the peak value is smaller than a reference value; When the peak value is greater than the reference value, the amount of light projected is reduced. Control method.

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