Recording apparatus

Abstract

To solve the problem that, when a medium end is detected using one light emitting element and one light receiving element, a medium end position cannot be detected with high accuracy because a detection voltage across a threshold is generated due to an environmental change occurring during scanning of a recording medium, such as floating of the medium end or external light.SOLUTION: A recording device causes a sensor unit to scan a detection target, the sensor unit including a light emitting unit that emits light toward the detection target, a plurality of light receiving units including a first light receiving unit and a second light receiving unit that detect reflected light of the light, and an aperture member that is provided between the plurality of light receiving units and the detection target and includes an opening that restricts input of the reflected light to the light receiving units. Then, the end of the recording medium included in the detection target is detected based on a differential signal obtained by differentially amplifying signals from the first light receiving part and the second light receiving part. Here, the plurality of light receiving parts are arranged side by side in the scanning direction of the sensor unit, and the first light receiving part and the second light receiving part receive the reflected light from the detection target through the same opening of the aperture member.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a recording device. [Background technology]

[0002] When performing borderless printing with an inkjet recording device, poor accuracy in detecting the edge position of a recording medium such as paper can lead to issues such as dirt inside the device and the creation of blank spaces at the edges of the recording medium. A typical method for detecting the edge position of a recording medium (hereinafter referred to as the media edge position) in such a recording device is as follows: A light-emitting element such as an LED and a light-receiving element such as a phototransistor that converts an optical signal into an electrical signal are used. The light-emitting element irradiates light, which is reflected by the recording medium, and the light-receiving element detects the reflected light. The media edge position is then detected based on the detection signal. This detection method is prone to degradation in detection accuracy due to environmental fluctuations such as dirt on the recording medium.

[0003] Patent Document 1 describes an image forming apparatus equipped with a media sensor having a light-emitting element and a light-receiving element, which detects the edge position of a medium based on the detection signal of the light-receiving element when the detection target position of the media sensor is moved relative to the paper. Specifically, the document describes a configuration in which the current value for paper edge detection is obtained by determining the current value to be passed through the light-emitting element for each position on the paper, thereby reducing the influence of environmental fluctuations and accurately detecting the edge position of the medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 16-182361 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes a method for detecting the position of a medium edge using one light-emitting element and one light-receiving element. When using one light-emitting element and one light-receiving element in this way, environmental fluctuations that occur during scanning of the recording medium, such as lifting of the medium edge or external light, can cause a detection voltage that crosses the threshold. As a result, it is not possible to reduce the effects of environmental fluctuations, and there is a problem in that the position of the medium edge cannot be detected with high accuracy.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a technique for reducing the influence of environmental fluctuations and detecting the position of a medium edge with high accuracy. [Means for solving the problem]

[0007] In order to achieve the above object, a recording device according to one aspect of the present invention has the following configuration: a sensor unit including a light emitting unit that irradiates light toward a detection target, a plurality of light receiving units including a first light receiving unit and a second light receiving unit that detect reflected light of the light, and an aperture member that is provided between the plurality of light receiving units and the detection target and has an opening that limits input of the reflected light to the light receiving units; a scanning means for scanning the sensor unit over the detection target; a detecting means for detecting an edge of a recording medium included in the detection target based on a differential signal obtained by differentially amplifying signals from the first light receiving unit and the second light receiving unit, the plurality of light receiving units are arranged side by side in the scanning direction of the scanning means, The first light receiving portion and the second light receiving portion receive the reflected light through the same opening of the aperture member. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the influence of environmental fluctuations and detect the medium edge position with high accuracy.

[0009] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are designated by the same reference numerals. [Brief explanation of the drawings]

[0010] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. [Figure 1] 1 is a block diagram illustrating the configuration of an inkjet printing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the mechanism of a carriage on which a print head of an inkjet recording apparatus according to an embodiment is mounted, as viewed from above. [Figure 3] FIG. 4 is a conceptual diagram illustrating the operation of the sensor unit according to the embodiment. [Figure 4] 6A and 6B are diagrams illustrating details of the operation of the sensor unit when detecting the edge position of the paper. [Figure 5] 10A and 10B are diagrams illustrating an example of selection of a light receiving element in a light receiving element array. [Figure 6] 10A and 10B are diagrams for explaining the influence of the diameter of the light receiving aperture on the detection area. [Figure 7] 5A and 5B are diagrams showing examples of the shape of an aperture of an aperture member. [Figure 8] 4A and 4B are diagrams showing examples of connections between a light-receiving element array, a selector, and a differential amplifier of a sensor unit according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0012] First, the terms used in this embodiment are defined as follows. ·"record" In this specification, "recording" does not only refer to the formation of meaningful information such as characters or figures, but also to the formation of images, designs, patterns, etc. on a recording medium, or the processing of a medium, regardless of whether the information is meaningful or insignificant, or whether it is visible to humans or not. "Recording media" Recording media refers not only to paper used in general recording devices, but also to a wide range of materials that can accept ink, such as cloth, plastic film, metal plates, glass, ceramics, wood, and leather. ·"ink" The term "ink" should be broadly interpreted in the same way as the definition of "recording" above, and refers to a medium containing a recording material that can be applied to a recording medium to form an image, design, pattern, etc., or to process the recording medium, or to treat the ink. It is a liquid in physical properties. The ink treatment mentioned above refers to, for example, solidification or insolubilization of the coloring material in the ink applied to the recording medium. ·"nozzle" Unless otherwise specified, the term "nozzle" refers to an ejection port. Inside the nozzle there is a communicating liquid path and an element that generates energy used to eject ink. ·"scanning" In order to record on a recording medium, a recording head scans the recording medium to perform recording. Here, the term "scanning" refers to the head movement during acceleration and deceleration for recording or related to recording. "Round Trip Record" The term "reciprocating printing" refers to printing while performing the above-mentioned "printing" or "scanning" back and forth on the paper surface. The terms "reciprocating scanning," "reciprocating printing," "bidirectional scanning," and "bidirectional printing" also refer to the same things.

[0013] FIG. 1 is a block diagram illustrating the configuration of an inkjet recording apparatus 120 according to an embodiment of the present invention.

[0014] The sensor unit 117 has a light-emitting unit 105 and a light-receiving element array 102, and a signal output from the light-receiving element array 102 is output to a differential amplifier (differential amplification unit) 104 via a selector 103. The differential amplifier 104 can amplify or differentially amplify a signal from a light-receiving element (light-receiving sensor) selected in the light-receiving element array 102 depending on the setting of the selector 103, and sends the amplified signal to the main controller 101. An example circuit of the sensor unit 117 will be described later with reference to FIG. 8. The main controller 101 receives the signal from the differential amplifier 104 via an analog input unit 106 and a digital input unit 107. The digital input unit 107 is also connected to an interrupt controller 108 inside the main controller 101 and issues an interrupt signal to the CPU 112 according to predetermined interrupt conditions. When the CPU 112 receives this interrupt signal, it processes the interrupt signal with priority over any ongoing processing, allowing it to respond more immediately to the signal input to the digital input unit 107. The light emitting unit 105 is driven by a pulse width modulation signal output from a PWM (pulse width modulation unit) 116 in the main controller 101 via a digital output unit 109, and the amount of light emitted is controlled by pulse width modulation.

[0015] The print head 110 is driven via a head driver 111 in response to an image signal to be recorded. The print head 110 scans over the recording medium by being driven by a motor 115. The scanning position of the print head 110 is detected based on a signal from a position encoder sensor 113 input to a digital input unit 114, and the scanning position is managed by a pulse counter 118 in the main controller 101.

[0016] FIG. 8 is a diagram showing an example of connections between the light receiving element array, the selector, and the differential amplifier of the sensor unit 117 according to the embodiment.

[0017] A photodetector array 801 composed of multiple sensors corresponding to the photodetector array 102 is disposed within the sensor unit 117. FIG. 8 shows a sensor unit including a total of 64 sensors, each with 16 photodetectors 802 arranged in four columns. Each photodetector 802 is connected to a selector 803 within the sensor unit 117. This selector 803 corresponds to the selector 103 in FIG. 1. By setting this selector 803, it is possible to arbitrarily select a photodetector 802 from the photodetector array 801 to be used for detecting the media edge position. In addition, by setting the selector 803, it is possible to bundle the outputs of multiple photodetectors 802 and output them together, and the number and positions of the photodetectors 802 to be bundled can also be arbitrarily selected. For example, the outputs of 16 photodetectors from the first to sixteenth positions in the third column can be bundled and connected to the selector 803 as a photodetector, or the outputs of odd-numbered photodetectors such as the first, third, fifth, and seventh positions in the first column can be selected as photodetectors. Furthermore, the position and number of light receiving elements to be selected can be arbitrarily selected, for example, by selecting the output of the first light receiving element 802 in each of columns 1' to 4' as the light receiving element. By making it possible to select a bundle of multiple light receiving elements 802 as the light receiving element in this way, the surface area of ​​the light receiving element can be increased artificially, thereby improving the sensitivity of the light receiving element. The setting of this selector 803 can be changed by an instruction from the CPU 112, and the selection and arrangement of the light receiving elements, which will be described later, are performed in cooperation between the CPU 112 and the selector 103.

[0018] The output of the selector 803 is connected to IV converters A to D arranged in the IV converter 804 in the sensor unit 117. This allows the selector 803 to arbitrarily select which IV converter to connect the output of the light receiving element 802 or a group of multiple light receiving elements 802 to. The output of the IV converter 804 is connected to the amplifier 805, and an amplified output can be obtained from the amplifier 805. This amplifier 805 corresponds to the differential amplifier 104 in FIG. 1. The amplifier 805 includes a coarse adjustment amplifier, a fine adjustment amplifier, a differential amplifier, etc., and it is possible to arbitrarily select which amplifier to use, and also to arbitrarily select the combination of these amplifiers. However, the configuration of the amplifier 805 is not limited to the above-described configuration; for example, the amplifier 805 may include multiple amplifiers, one type of amplifier, or more types of amplifiers.

[0019] 8, the sensor unit 117 includes the selector 803, IV converter 804, and amplifier 805. However, the sensor unit 117 may include only the photodetector array 801, with the selector 803, IV converter 804, and amplifier 805 configured as external circuits. As an example of a combination for detecting the medium edge position, the outputs of the first photodetector 802 in the 1'th column and the first photodetector 802 in the 2'th column of the photodetector array 801 are selected by the selector 803 and connected to IV converter A and IV converter B of the IV converter 804, respectively. These outputs are then input to a differential amplifier in the amplifier 805, and the output obtained from the amplifier 805 can be used to detect the medium edge position, as described below. By being able to arbitrarily select the positions and number of photodetectors 802 used to detect the medium edge position in this way, it is possible to detect the medium edge position in a variety of scenarios.

[0020] FIG. 2 is a schematic diagram illustrating the mechanism of a carriage 201 carrying a print head 110 of an inkjet recording apparatus 120 according to an embodiment, as viewed from above.

[0021] The print head 110 is mounted on a carriage 201, which is carried along a main rail 203 so as to be capable of reciprocating scanning. The sensor unit 117 is also mounted on the carriage 201 and is also capable of reciprocating scanning. This allows the sensor unit 117 to scan in the width direction (X direction) of the paper 202, and the main controller 101 can detect the medium edge position based on light reflected from the paper 202, platen 204, etc. The paper 202 is carried on the platen 204. The light receiving element array 102 (light receiving element array 801 in FIG. 8) of the sensor unit 117 is arranged parallel to the scanning direction (X direction) of the carriage 201. The light emitting unit 105 is arranged at a position offset in the vertical direction (Y direction) from the light receiving element array 102. This arrangement allows the lateral width of the carriage 201, including the sensor unit 117, to be reduced.

[0022] FIG. 3 is a conceptual diagram illustrating the operation of the sensor unit 117 according to the embodiment.

[0023] 3 shows the sensor unit 117 as viewed from the side, with the light receiving elements of the light receiving element array 102 lined up in the depth direction (X direction) of the figure. The light emitting unit 105 and the light receiving element array 102 on the substrate 306 face the paper 202 or the platen 204 via an aperture member 301 of the sensor unit 117. Light emitted from the light emitting unit 105 passes through a light projecting aperture 305 and becomes light ray 302, which is projected onto the paper 202. The projected light ray 302 is reflected by the paper 202, and a portion of this light ray passes through a light receiving aperture (opening) 304 and becomes light ray 303, which is received by the light receiving element array 102. At this time, the light ray 303 utilizes diffuse reflection from the paper 202, and utilizes a reflection component that is less dependent on the reflection angle.

[0024] FIG. 4 is a diagram for explaining the details of the operation of the sensor unit 117 when detecting the edge position of the paper 202. In FIG.

[0025] The outputs of light receiving elements 404 and 405 of light receiving element array 102 are selected by selector 103 and connected to differential amplifier 104, and signal 401 output from light receiving element 404 and signal 402 output from light receiving element 405 are input to differential amplifier 104. Here, signal 401 is input to the non-inverting input terminal (+) of differential amplifier 104, and signal 402 is input to the inverting input terminal (-) of differential amplifier 104. As a result, differential amplifier 104 outputs differential signal 403 based on the difference between input signals 401 and 402.

[0026] Although light emitting unit 105 is not shown in Fig. 4, it irradiates light from the front or back direction of Fig. 4 toward paper 202 via the light-emitting aperture of aperture member 301. Light receiving elements 404, 405 detect light reflected from paper 202 via light-receiving aperture 304 of aperture member 301. Because each of light receiving elements 404, 405 is angled with respect to light-receiving aperture 304, light receiving element 404 has area 411 as its detection area on paper 202, and light receiving element 405 has area 412 as its detection area.

[0027] Next, regarding the movement of the signal, it is assumed here that the carriage 201 and sensor unit 117 are moving from the right side to the left side of the figure (in the direction of the arrow). When the sensor unit 117 moves to the top of the edge of the paper 202, the detection area 411 reaches the paper 202 first, so the light receiving element 404 detects the reflected light from the paper 202 first, and the level of the signal 401 output from the light receiving element 404 rises and is input to the non-inverting input terminal (+) of the differential amplifier 104. The signal 401 is shown over time as a detection waveform 406.

[0028] Now, let's look at the detection area 411 detected by the light receiving element 404. When the sensor unit 117 is positioned further to the right than shown in FIG. 4, the detection area 411 is located on the platen 204, which has a low reflectivity. Therefore, less reflected light enters the light receiving element 404, and the detection waveform 406 is at a low level. Next, when the sensor unit 117 moves leftward (in the direction of the arrow) in FIG. 4, the detection area 411 detects the paper 202, which has a high reflectivity, as shown in FIG. 4, and the detection waveform 406 transitions to a high level. At this time, the detection area 412 of the light receiving element 405 is still located on the platen 204, so the level of the signal 402 output by the light receiving element 405 remains low. Therefore, a level difference occurs between the signals 401 and 402. As the detection area 412 is located on the platen 204 and the detection area 411 on the paper 202 increases, the differential signal 403 output by the differential amplifier 104 becomes a high-level signal.

[0029] As the carriage 201 moves further in the direction of the arrow, the paper 202 reaches the detection area 412 of the light receiving element 405, which begins to detect the paper 202. This causes the signal 402 to transition to a high level, as shown by the detection waveform 407. As the level of the signal 402 increases in this way, the difference with the level of the signal 401, which is already at a high level, decreases, and the differential signal 403 output from the differential amplifier 104 begins to decrease. In this way, the waveform of the differential signal 403 changes to that shown by the differential waveform 408, and becomes a detection signal that becomes pulsating near the edge of the paper 202.

[0030] The rising and falling timings of this pulse-like detection signal are obtained using a threshold value 409. That is, the scanning position (position coordinates) of the carriage 201 at the timings when the detection signal exceeds the threshold value and when it falls below the threshold value are obtained and designated as Pos1 and Pos2, respectively. By taking the center coordinate of these position coordinates Pos1 and Pos2, it is possible to obtain the edge position of the paper 202 located in the center of the arrangement of the light receiving elements 404 and 405. Note that this edge position is not limited to the center coordinate of Pos1 and Pos2, and may be obtained as a position according to a preset ratio, such as a position obtained by dividing the distance between Pos1 and Pos2 by a ratio of 6:4.

[0031] The advantage of detecting the edge of the paper based on differential detection, which takes the difference between the two signals, is that it is possible to cancel out the influence of external disturbances that are commonly received by each of the light receiving elements 404 and 405, thereby enabling stable detection of the position of the edge of the medium.

[0032] To maximize the benefits of edge position detection using differential signals, it is necessary to ensure symmetry between the differential signals in optical and circuit terms and to avoid overlap between the differential signals. Without symmetry, the timing of the signal levels of signals 401 and 402 output by light-receiving elements 404 and 405 will be misaligned. When the differential amplifier 104 takes the difference, this misalignment will not cancel out and will remain. As a result, the amplitude 410 of differential waveform 408 output from differential amplifier 104 will decrease or a signal offset will occur, resulting in a lower signal-to-noise ratio of the differential signal. Furthermore, if there is overlap between the differential signals, the overlapping portions will cancel out when differential amplifier 104 takes the difference, compromising the signal strength of the original detection waveforms 406 and 407. This again leads to problems such as a decrease in amplitude 410.

[0033] To avoid such problems, photodetectors 404 and 405 for differential detection are selected from the photodetector array 102. Generally, semiconductors have large variations in characteristics, and when photodetectors are constructed using individual semiconductor devices, their sensitivity also varies widely. On the other hand, the photodetector array 102 is manufactured by forming circuits on a wafer made of the same semiconductor material using lithography. Therefore, variations in the semiconductor material between photodetectors within the photodetector array 102 are small, and dimensional variations between each photodetector can also be reduced through lithography precision. This reduces sensitivity variations between photodetectors. If the photodetector were constructed using individual semiconductors instead of this configuration, it would be necessary to provide an amplifier between the differential amplifier 104 to electrically adjust the output offset in order to reduce sensitivity variations, which would increase costs and area.

[0034] Furthermore, by selecting a light receiving element from the light receiving element array 102 and using it to detect the edge position, the positional relationship between the light receiving elements can be managed with high precision. Furthermore, the position of electronic components on the board can vary due to variations in the mounting position of the components during the soldering process, which can lead to variations in the characteristics between the light receiving elements depending on the positional relationship between the light receiving element and the light emitting element or aperture. On the other hand, when light receiving elements from the light receiving element array are selected and used, the position and characteristics of each light receiving element can be managed with high precision in the semiconductor process, reducing the impact of variations in position between the light receiving elements. Furthermore, even when light receiving elements are packaged together, rather than using a light receiving element array, positional management of the light receiving elements can be improved compared to when individual light receiving elements are arranged.

[0035] 2, the optical system is arranged such that the light-emitting units 105 are spaced apart in the direction (Y direction) perpendicular to the arrangement direction of the light-receiving element array 102, and are arranged at the same position in the X direction. This makes it possible to make the distance between each light-receiving element in the light-receiving element array 102 and the light-emitting units 105 approximately equal. This makes it possible to reduce bias in the light intensity distribution that depends on the distance from the light-emitting units 105 to the light-receiving elements, and to improve symmetry between each light-receiving element.

[0036] 4, light receiving element 404 forms detection area 411 on the detection surface via light receiving aperture 304, and light receiving element 405 similarly forms detection area 412 via the same light receiving aperture 304. These detection areas mainly spread out like the light beams shown in FIG. 4, but the extent of this spread is determined by the size and diameter of light receiving aperture 304, the distance from the light receiving element, the distance to the detection target (including at least one of paper 202 and platen 204), etc. Furthermore, by sharing a single aperture and making the aperture shape common to each light receiving element, highly symmetrical detection areas can be obtained.

[0037] FIG. 5 is a diagram illustrating an example of selection of light receiving elements in the light receiving element array 102. In FIG.

[0038] FIG. 5(a) shows a case where adjacent light receiving elements 404 and 405 are selected from the light receiving element array 102. In this case, detection areas 501 and 502 formed by the light receiving elements 404 and 405 via the light receiving aperture 304 overlap in an area 512. This reduces the amplitude of the differential signal obtained from the signals output from the light receiving elements 404 and 405. A detection waveform 513 shows the waveform of the signal 401 output from the light receiving element 404, and a detection waveform 514 shows the waveform of the signal 402 output from the light receiving element 405. The waveform of the differential signal at this time is as shown by a differential waveform 515 in FIG. 5(a). This reduces the amplitude of the differential signal obtained from the signals output from the light receiving elements 404 and 405.

[0039] In contrast, Figure 5(b) shows the case where light receiving elements 404 and 405, which are located a predetermined distance apart, are selected in the light receiving element array 102. Here, an inactive element region 503 containing a predetermined number of light receiving elements is provided between the selected light receiving elements 404 and 405. This allows the light receiving elements 404 and 405 to be spaced apart, separating the detection regions 504 and 505 and preventing the detection regions from overlapping. Detection waveform 516 shows the waveform of signal 401 output from light receiving element 404, detection waveform 517 shows the waveform of signal 402 output from light receiving element 405, and differential waveform 518 shows the differential signal output from differential amplifier 104 at this time.

[0040] The number and width of the light-receiving elements in this ineffective element region 503 are determined so that the detection regions 504, 505 formed by the light-receiving elements 404, 405 via the light-receiving aperture 304 do not overlap or the overlap width is narrow. Alternatively, they may be determined so as to ensure a region 506 with a width that does not overlap. Each detection region 504, 505 can be geometrically determined from the width of the light-receiving elements 404, 405, the distance 508 from the light-receiving element to the top surface of the aperture member 301, the opening width of the light-receiving aperture 304, and the distance 507 from the light-receiving surface side of the aperture member 301 to the surface to be detected. In addition, if there is an effect of reflection within a unit (not shown), the width of the ineffective element region 503 can be adjusted, for example, by widening it.

[0041] FIG. 6 is a diagram illustrating the influence of the diameter of the light receiving aperture 304 on the detection area.

[0042] FIG. 6A shows a case where the diameter of the light-receiving aperture 304 is larger than a predetermined amount, as indicated by reference numeral 615. The detection areas of the light-receiving elements 404 and 405 formed through the light-receiving aperture 304 expand in the scanning direction of the carriage 201, as indicated by detection areas 601 and 602. As a result, the transition ranges of the detection signals 401 and 402 output from the light-receiving elements 404 and 405 expand, as indicated by detection waveforms 603 and 604, resulting in overlap 614. As a result, the waveform of the differential signal output from the differential amplifier 104 becomes as indicated by differential waveform 605. In this case, the level of the detection waveform 604 begins to rise before the level of the preceding detection waveform 603 reaches its highest point, canceling out the rise in the level of the differential signal. As a result, the maximum amplitude cannot be achieved, as indicated by differential waveform 605, and the signal level begins to decrease. In such a case, a valid differential signal cannot be obtained from the detection signals obtained from the overlapping detection areas.

[0043] FIG. 6(b) shows a case where the diameter of the light receiving aperture 304 is smaller than that of the example of FIG. 6(a), as indicated by reference numeral 616.

[0044] The diameter 616 of the light-receiving aperture 304 is reduced so that the detection areas 606, 607 formed by the light-receiving elements 404, 405 via the light-receiving aperture 304 do not overlap, forming a gap 608, or the overlap width 614 in Figure 6(a) becomes narrower. The detection areas 606, 607 can be geometrically determined from the gap between the light-receiving elements 404, 405, the distance 508 from the light-receiving element to the top surface of the aperture member 301, the opening width of the light-receiving aperture 304, and the distance 507 from the light-receiving surface side of the aperture member 301 to the surface to be detected. In addition, if there is an effect of reflection within a unit (not shown), adjustments can be made, such as by narrowing the diameter 616 of the light-receiving aperture. A detected waveform 609 indicates the waveform of the signal 401 output from the light receiving element 404, a detected waveform 610 indicates the waveform of the signal 402 output from the light receiving element 405, and a differential waveform 611 indicates the waveform of the differential signal output from the differential amplifier 104 at this time. As indicated by an amplitude 612, this differential waveform 611 has a sufficient amplitude to obtain the scanning position of the carriage 201 by comparing it with a threshold value.

[0045] 6(a), the detection areas 601 and 602 can be prevented from overlapping by moving the positions of the light receiving elements 404 and 405 selected in the light receiving element array 102 in opposite directions toward the ends of the light receiving element array 102. In other words, by widening the space between the light receiving elements 404 and 405, the detection areas 601 and 602 can be prevented from overlapping.

[0046] FIG. 7 is a diagram showing an example of the shape of the aperture of the aperture member.

[0047] 7(a) shows a case where the diameter of the light receiving aperture 304 is reduced and light receiving elements 701 and 702 located on the outside of the light receiving element array 102 are used. As shown in FIG. 7(a), the angle of the light rays incident on the light receiving elements 701 and 702 through the light receiving aperture 304 becomes sharp, so the light that can be taken in from the detection target surface becomes too weak.

[0048] In contrast, Figure 7(b) shows an example in which the surface of the light-receiving aperture 304 has an inverse tapered shape that opens toward the light-receiving element. That is, the diameter of the light-receiving aperture 304 on the detection surface side is small, and the diameter on the light-receiving element array side is widened. This makes it possible to ensure detection areas 703 and 704 even when light-receiving elements 701 and 702 located outside the light-receiving element array 102 are used. In other words, by making the surface of the light-receiving aperture 304 as shown in Figure 7(b), it is possible to widen the range of light-receiving elements that can be selected from the light-receiving element array.

[0049] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0050] The present specification and drawings disclose the following recording device.

[0051] <Item 1> a sensor unit including a light emitting unit that irradiates light toward a detection target, a plurality of light receiving units including a first light receiving unit and a second light receiving unit that detect reflected light of the light, and an aperture member that is provided between the plurality of light receiving units and the detection target and has an opening that limits input of the reflected light to the light receiving units; a scanning means for scanning the sensor unit over the detection target; a detecting means for detecting an edge of a recording medium included in the detection target based on a differential signal obtained by differentially amplifying signals from the first light receiving unit and the second light receiving unit, the plurality of light receiving units are arranged side by side in the scanning direction of the scanning means, a first light receiving section and a second light receiving section, the first light receiving section and the second light receiving section receiving the reflected light through the same opening of the aperture member;

[0052] <Item 2> The recording device described in item 1, characterized in that the multiple light receiving units include multiple light receiving elements, the first light receiving unit includes one or more light receiving elements of the multiple light receiving elements, and the second light receiving unit includes one or more light receiving elements different from the first light receiving unit.

[0053] <Item 3> 3. The recording device according to item 2, wherein a predetermined number of light receiving elements are included between the first light receiving section and the second light receiving section.

[0054] <Item 4> Item 3. The recording device according to item 2, further comprising a selection means for selecting, from the plurality of light receiving elements, one or more light receiving elements to become the first light receiving portion and one or more light receiving elements to become the second light receiving portion.

[0055] <Item 5> 5. The recording device according to item 4, wherein the selection means selects a light receiving element so that a first detection area in which the first light receiving unit detects reflected light input through the same opening and a second detection area in which the second light receiving unit detects reflected light input through the same opening do not overlap.

[0056] <Item 6> The recording device described in any one of items 1 to 5, characterized in that the aperture member and the same opening are arranged so that a first detection area detected by the first light receiving unit by reflected light input through the same opening does not overlap with a second detection area detected by the second light receiving unit by reflected light input through the same opening.

[0057] <Item 7> The recording device described in item 4 or 5, characterized in that the selection means selects one or more light receiving elements to become the first light receiving unit and one or more light receiving elements to become the second light receiving unit based on the distance between the multiple light receiving units and the aperture member, the size of the same opening, and the distance between the aperture member and the detection target.

[0058] <Item 8> 8. The recording device according to any one of items 1 to 7, wherein the side of the same opening has a tapered shape that is wider on the side of the plurality of light receiving units and smaller on the side of the detection target.

[0059] <Item 9> The scanning device further includes an acquisition unit for acquiring a scanning position of the sensor unit scanned by the scanning unit, The detection means a differential amplifier that outputs a differential signal between a first signal output from the first light receiving unit and a second signal output from the second light receiving unit, 9. The recording device according to any one of items 1 to 8, characterized in that, during scanning by the scanning means, the edge of the recording medium is detected based on a first coordinate indicating the scanning position acquired by the acquiring means when the differential signal becomes equal to or greater than a threshold, and a second coordinate indicating the scanning position acquired by the acquiring means when the differential signal becomes equal to or less than the threshold.

[0060] <Item 10> 10. The recording device according to item 9, wherein the detection means detects the center coordinate between the first coordinate and the second coordinate as the edge of the recording medium.

[0061] <Item 11> 11. The recording apparatus according to any one of items 1 to 10, wherein the detection object includes at least one of the recording medium and a platen that supports the recording medium.

[0062] <Item 12> 12. The recording device according to any one of items 1 to 11, wherein the light emitting unit irradiates light toward the detection target through an opening different from the same opening of the aperture member.

[0063] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention. [Explanation of symbols]

[0064] 102...light receiving element array, 104...differential amplifier, 105...light emitting section, 117...sensor unit, 201...carriage, 202...paper, 204...platen, 301...aperture member, 304...light receiving aperture, 305...light emitting aperture, 404, 405...selected light receiving element

Claims

1. a sensor unit including a light emitting unit that irradiates light toward a detection target, a plurality of light receiving units including a first light receiving unit and a second light receiving unit that detect reflected light of the light, and an aperture member that is provided between the plurality of light receiving units and the detection target and has an opening that limits input of the reflected light to the light receiving units; a scanning means for scanning the sensor unit over the detection target; a detecting means for detecting an edge of a recording medium included in the detection target based on a differential signal obtained by differentially amplifying signals from the first light receiving unit and the second light receiving unit, the plurality of light receiving units are arranged side by side in the scanning direction of the scanning means, a first light receiving section and a second light receiving section, the first light receiving section and the second light receiving section receiving the reflected light through the same opening of the aperture member;

2. The recording device described in claim 1, characterized in that the multiple light receiving sections include multiple light receiving elements, the first light receiving section includes one or more light receiving elements of the multiple light receiving elements, and the second light receiving section includes one or more light receiving elements different from the first light receiving section.

3. 3. The recording apparatus according to claim 2, wherein a predetermined number of light receiving elements are included between the first light receiving section and the second light receiving section.

4. 3. The recording device according to claim 2, further comprising a selection means for selecting, from the plurality of light receiving elements, one or more light receiving elements to become the first light receiving portion and one or more light receiving elements to become the second light receiving portion.

5. The recording device described in claim 4, characterized in that the selection means selects a light receiving element so that a first detection area in which the first light receiving unit detects reflected light input through the same opening and a second detection area in which the second light receiving unit detects reflected light input through the same opening do not overlap.

6. The recording device described in claim 1, characterized in that the aperture member and the same opening are arranged so that a first detection area detected by the first light receiving unit by reflected light input through the same opening and a second detection area detected by the second light receiving unit by reflected light input through the same opening do not overlap.

7. The recording device described in claim 4, characterized in that the selection means selects one or more light receiving elements to become the first light receiving unit and one or more light receiving elements to become the second light receiving unit based on the distance between the multiple light receiving units and the aperture member, the size of the same opening, and the distance between the aperture member and the detection object.

8. 2. The recording apparatus according to claim 1, wherein the side surface of the same opening has a tapered shape that is wider on the side of the plurality of light receiving sections and narrower on the side of the detection target.

9. The scanning device further includes an acquisition unit for acquiring a scanning position of the sensor unit scanned by the scanning unit, The detection means a differential amplifier that outputs a differential signal between a first signal output from the first light receiving unit and a second signal output from the second light receiving unit, The recording device according to claim 1, characterized in that, during scanning by the scanning means, the edge of the recording medium is detected based on a first coordinate indicating the scanning position acquired by the acquisition means when the differential signal becomes equal to or greater than a threshold value, and a second coordinate indicating the scanning position acquired by the acquisition means when the differential signal becomes equal to or less than the threshold value.

10. 10. The recording apparatus according to claim 9, wherein the detecting means detects the center coordinate between the first coordinate and the second coordinate as the edge of the recording medium.

11. 2. The recording apparatus according to claim 1, wherein the detection object includes at least one of the recording medium and a platen that supports the recording medium.

12. 2. The recording apparatus according to claim 1, wherein the light emitting unit irradiates the light toward the detection target through an opening different from the same opening of the aperture member.

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