End detection method and liquid dispensing device

Abstract

This technology provides high-precision detection of the edges of a media. [Solution] The system is equipped with multiple light-receiving units, and differential output is obtained from the outputs of the multiple light-receiving units. The differential output is adjusted by adjusting the light-receiving sensitivity of the light-receiving units using an adjustment unit.

Description

Technical Field

[0001] The present invention relates to an end detection method and a liquid ejection device.

Background Art

[0002] When performing borderless printing with an inkjet recording apparatus, it is common to perform recording while detecting the end of a recording medium with the recording apparatus.

[0003] In Patent Document 1, a method of detecting the end of a medium using an optical sensor including a pair of light emitting elements and light receiving elements has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when detecting a recording medium with a conventional optical sensor, for example, the output voltage may change due to environmental variations that occur during scanning of the medium, such as floating of the medium end or external light. Therefore, there has been a problem that the end of the medium cannot be detected with high accuracy.

[0006] Therefore, the present invention provides a technique for detecting the end of a medium with high accuracy.

Means for Solving the Problems

[0007] Therefore, the edge detection method of the present invention is an edge detection method for detecting the edge of a sheet of paper in the width direction using a detection means provided on a carriage that is movable in the width direction of the sheet of paper, wherein the detection means comprises a light-emitting unit, a first light-receiving unit including a plurality of light-receiving elements that receive reflected light from the light-emitting unit, a second light-receiving unit positioned at a distance in the width direction from the first light-receiving unit and including a plurality of light-receiving elements that receive reflected light from the light-emitting unit, and a differential amplifier circuit unit that differentially amplifies the output signals of the first light-receiving unit and the second light-receiving unit, and is characterized by comprising an adjustment step of adjusting the differential output of the differential amplifier circuit unit, an acquisition step of acquiring the differential output of the differential amplifier circuit unit adjusted by the adjustment step while moving the carriage, and a detection step of detecting the edge of the sheet of paper based on the change in the differential output with respect to the position of the carriage obtained by the acquisition step. [Effects of the Invention]

[0008] According to the present invention, a technology for detecting the edges of a medium with high precision can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is an external perspective view showing a liquid dispensing device. [Figure 2] This is a block diagram of the control unit for the liquid dispensing device. [Figure 3] This diagram shows the hardware configuration of the liquid dispensing device. [Figure 4] This diagram illustrates the concept of recording medium edge detection operation in a liquid dispensing device. [Figure 5] This is a diagram conceptually illustrating the adjustment process. [Figure 6] This is a flowchart illustrating the recording process. [Figure 7] This diagram illustrates a method for adjusting the light-receiving sensitivity in the light-receiving section. [Figure 8] This diagram shows how to adjust the amplification factor of the differential amplifier circuit in the light-receiving section. [Figure 9] This diagram shows the method for adjusting the current in the light emission intensity adjustment circuit of the light-emitting section. [Modes for carrying out the invention]

[0010] (First embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

[0011] Figure 1 is an external perspective view showing the liquid ejection device 100 according to this embodiment. The liquid ejection device 100 is an inkjet recording device that records an image on paper by alternately repeating the recording operation of ejecting liquid ink from a moving liquid ejection head and transporting a recording medium. However, the present invention is also applicable to various liquid ejection devices other than inkjet recording devices.

[0012] Furthermore, "recording" includes not only cases where meaningful information such as characters and figures is formed, but also broadly cases where images, patterns, etc. are formed on a recording medium, or where the medium is processed, regardless of whether it is meaningful or not, and does not depend on whether or not it is manifested in a way that can be perceived visually by humans.In addition, in this embodiment, a sheet of paper is assumed as the "recording medium," but it may also be cloth, plastic film, etc.

[0013] The liquid dispensing device 100 has an overall flat rectangular parallelepiped shape and includes a cut paper feeding section 104 for setting the recording medium, a roll paper feeding section 103, an ink supply section 105 for supplying ink, and a waste liquid tank section 106 for inserting the waste liquid tank.

[0014] The liquid dispensing device 100 is equipped with an operation unit 102 that receives input from the operator. The operation unit 102 includes a touch panel display that accepts input from the operator and displays information to the operator. The liquid dispensing device 100 is also equipped with a notification unit 101 that can provide audible notifications for operations performed on each part.

[0015] FIG. 2 is a block diagram of the control unit of the liquid ejection device 100. The control unit 200 includes a CPU 213, a ROM 214, a RAM 215, an adjustment unit 209, and an encoder 210. The control unit 200 moves the detection unit 201 onto the end of the recording medium using the scanning unit 202. On the end of the recording medium, the control unit 200 lights the light emitting unit 204 of the detection unit 201 to irradiate the recording medium with light. The light reflected by the recording medium is received by the first light receiving unit 205, the second light receiving unit 206, or the third light receiving unit 207, and an output signal is output to the control unit 200 via an output switching amplifier (differential amplifier circuit unit) 208. The control unit 200 adjusts the output signals of the detection unit 201 and the density sensor 211 to a signal level suitable for detecting the end of the recording medium using the adjustment unit 209. After adjustment, the control unit 200 moves the detection unit 201 from above the recording medium toward the end using the scanning unit 202, and acquires the coordinates of the end position of the recording medium with the encoder 210 based on the obtained output signal.

[0016] FIG. 3 is a diagram showing the hardware configuration of the liquid ejection device 100. The liquid ejection device 100 includes a carriage 300 movable in the width direction of the recording medium. The liquid ejection device 100 scans a carriage 300 on which a detection unit 201 having a light receiving unit 212 and a light emitting unit (LED light source) 204, a density sensor 211, and a nozzle group 305 are mounted in the scanning direction 307. Further, the liquid ejection device 100 conveys a recording medium 308 in the conveyance direction 310 on a platen 309. The scanning direction 307 and the conveyance direction intersect. The detection unit 201 is provided at one end in the scanning direction of the carriage 300, and detects the end A, end B of the recording medium 308, or the end position at the leading end in the conveyance direction. The density sensor 211 is provided at the other end in the scanning direction of the carriage 300, and can perform density detection of the recording medium 308.

[0017] FIG. 4 is a diagram showing the concept of the recording medium end detection operation in the liquid ejection device 100. Here, the light emitting unit 204 is omitted. The light receiving unit 212 of the detection unit 201 includes a first light receiving unit 205, a second light receiving unit 206, and a third light receiving unit 207. The output voltage 404 of the first light receiving unit 205, the output voltage 405 of the second light receiving unit 206, and the output voltage 417 of the third light receiving unit 207 are input to the output switching amplifier 208. The control unit 200 can switch the output method to differential mode or single mode and output. FIG. 4(a) shows detection in differential mode, and FIG. 4(b) shows detection in single mode (first operation mode). In single mode, based on the ground (0V), the signal level of the output signal (single-ended output signal) is determined by the output voltage 417 of the third light receiving unit 207. In differential mode (second operation mode), the potential difference between the output voltage 404 of the first light receiving unit 205 and the output voltage 405 of the second light receiving unit 206 becomes the signal level of one output signal (differential output signal).

[0018] When the output switching amplifier 208 is set to differential mode, when the detection unit 201 is moved in the scanning direction 407 above the recording medium 308, a differential output 406 is output (see FIG. 4(a)). In differential mode, a differential output 406 is output from the output voltage 404 from the first light receiving unit 205 and the output voltage 405 of the second light receiving unit 206.

[0019] At the position 409 where the detection unit 201 is arranged above the recording medium 308, both the output voltage 404 of the first light receiving unit 205 and the output voltage 405 of the second light receiving unit 206 become high (H) (since there is no difference), and the differential output 406 becomes low (L). At the position 410 where the detection unit 201 is arranged on the end of the recording medium 308, the output voltage 404 from the first light receiving unit 205 becomes high (H), and the output voltage 405 from the second light receiving unit 206 becomes low (L) (since a difference occurs), and the differential output 406 becomes high (H). At the position 411 where the detection unit 201 is not arranged above the recording medium 308, both the output voltage 404 of the first light receiving unit 205 and the output voltage 405 of the second light receiving unit 402 become low (L) (since there is no difference), and the differential output 406 becomes low (L).

[0020] In this way, a predetermined threshold voltage 412 is set for changes in the differential output 406, a position 413 where the threshold voltage 412 is exceeded and a position 414 where the threshold voltage 412 is not exceeded are detected, and the midpoint 415 between them is detected as the edge position of the recording medium 308.

[0021] When the output switching amplifier 208 is set to single mode, a single output 418 is output when the detection unit 201 is moved to the top of the recording medium 308 in the scanning direction 407 (see Figure 4(b)). In single mode, a single output 418 is output, which is the output voltage 417 from the third light receiving unit 207 inverted. At position 409, where the detection unit 201 is positioned on the top of the recording medium 308, the output 417 of the third light receiving unit 207 becomes high (H), and the single output 418 becomes low (L). At position 410, where the detection unit 201 is positioned on the edge of the recording medium 308, the output 417 of the third light receiving unit 207 changes, and the single output 418 also changes. At position 411, where the detection unit 201 is not positioned on the top of the recording medium 308, the output 417 of the third light receiving unit 207 becomes low, and the single output 418 becomes high.

[0022] In this way, a threshold voltage 419 is set for changes in the single output 418, and the position 420 where the threshold voltage 419 is exceeded is detected and identified as the end position.

[0023] When detection is performed in differential mode, the voltage levels of the output voltage 404 of the first light-receiving unit 205 and the output voltage 405 of the second light-receiving unit 402 may be generally lower due to manufacturing variations or variations in the reflectivity characteristics of the object being read. In this case, the difference in voltage levels between when the recording medium 308 is read and when the platen 309 is read becomes smaller, and the voltage level of the differential output 406 also becomes lower. As a result, the differential output 406 may not exceed the threshold voltage 412, or if it does, the excess may be only slight, making it impossible to accurately detect the edge position of the recording medium 308 from the midpoint 415.

[0024] Therefore, in this embodiment, before performing edge detection in differential mode, output adjustment is performed in single mode, and the sensor is moved based on the position detection result of the paper edge in single mode to adjust the differential output. The method is described below.

[0025] Figure 5 is a conceptual diagram illustrating the adjustment operation in this embodiment. Figure 5(a) shows the adjustment in differential mode, and Figure 5(b) shows the adjustment in single mode.

[0026] In single mode, the light-emitting unit 204 (not shown in Figure 5) is lit to illuminate the recording medium, and while the carriage is moved, the reflected light from the recording medium and the platen 306 is received by the third light-receiving unit 207. In this case, for example, if the recording medium has low reflectivity, the output voltage of the third light-receiving unit 207 changes from the H level to the L level of the relatively low output voltage 512', and the single output changes from the L level to the relatively low H level of the single output 513'. In such cases, the sensitivity is adjusted by the adjustment unit 209 (see Figure 2). Specifically, the sensitivity of the third light-receiving unit 207 is adjusted so that the high level (H) of the single output exceeds the threshold voltage 419 and is approximately twice the value of the original output 513'. α shown in the figure is the correction amount for the single output.

[0027] Then, based on the sensitivity adjustment of the third light-receiving unit 207, the sensitivity of the first light-receiving unit 205 and the second light-receiving unit 206 is adjusted to correct the differential output. In the case of a recording medium with low reflectivity, the first light-receiving unit 205 will produce output results such as output voltage 506' or output voltage 506'', and the second light-receiving unit 206 will produce output voltage results such as output voltage 507' or 507''. The differential output will be a differential output 508' or differential output 508''. In the case of an ideal recording medium, the output voltage of the first light-receiving unit 205 will be 506, and the output voltage of the second light-receiving unit 206 will be 507. The differential output will be a differential output 508. Therefore, correction is performed so that the output voltage in the case of a recording medium with low reflectivity becomes the output voltage in the case of an ideal recording medium. A threshold value of 509 is set as the threshold, and the sensitivity is adjusted so that the differential output is approximately twice the value of the threshold value of 509. β shown in the figure is the amount of differential output correction.

[0028] In this way, by adjusting the sensitivity of the third light-receiving unit 207 in advance, and then adjusting the sensitivity of the first light-receiving unit 205 and the second light-receiving unit 206 in accordance with the sensitivity adjustment of the third light-receiving unit 207, high-precision detection using a differential method becomes possible. Although the explanation described adjusting the sensitivity of the light-receiving unit, the amount of light emitted by the light-emitting unit 204 may also be adjusted, or the amplification factor of the output switching amplifier 208 may be adjusted.

[0029] Figure 6 is a flowchart illustrating the recording process in this embodiment. The series of processes shown in Figure 6 are performed by the CPU 213 of the liquid dispensing device 100 loading the program code stored in the ROM 214 into the RAM 215 and executing it. Alternatively, some or all of the functions of the steps in Figure 6 may be implemented by hardware such as an ASIC or electronic circuit. The symbol "S" in the description of each process indicates a step in the flowchart. The recording process in this embodiment will now be described using the flowchart in Figure 16.

[0030] When a recording command is received and the recording process begins, CPU213 in S601 feeds the recording medium into the recording unit. In S602, CPU213 irradiates light onto the fed recording medium and adjusts the single output based on the reflected light. In S603, with the single output adjusted, CPU213 performs edge detection on the edge of the recording medium in single mode. In S604, CPU213 adjusts the differential output based on the edge position identified by the single output. In S605, CPU213 performs edge detection on the recording medium in differential mode. In S606, CPU213 starts recording on the recording medium based on the edge position information acquired in S605. Specifically, while detecting the edge of the recording medium in differential mode with the differential output adjusted, it adjusts the recording position according to the changes in the detected edge position. This process ends when all recording scans are completed.

[0031] Figure 7 shows a method for adjusting the light receiving sensitivity in the light receiving unit 212. Hereinafter, an example of sensitivity adjustment in this embodiment will be described. Note that the first light receiving unit 205, the second light receiving unit 206, and the third light receiving unit 207 each constitute a part of the light receiving unit 212.

[0032] The light-receiving unit 212 has multiple light-receiving elements 701, which are arranged in a two-dimensional array in the direction 702 in which the light-receiving unit 212 scans and in the direction 703 in which the recording medium is transported. The adjustment unit 209 (see Figure 2) can freely set which light-receiving elements 701 to be used for output from among the multiple light-receiving elements 701 arranged in the light-receiving unit 212. When multiple light-receiving elements 701 are selected and set by the adjustment unit 209 (see Figure 2), the result of adding the outputs of each selected light-receiving element 701 is output. If a large number of light-receiving elements 701 are selected, the light-receiving sensitivity will be high, and if a small number of light-receiving elements 701 are selected, the light-receiving sensitivity will be low. In this way, the adjustment unit 209 (see Figure 2) can adjust the light-receiving sensitivity by changing the number of light-receiving elements in the light-receiving unit 212.

[0033] In this manner, the device is equipped with multiple light-receiving elements, and a differential output is obtained from the outputs of the multiple light-receiving elements. The differential output is then adjusted by adjusting the light-receiving sensitivity of the light-receiving element using the adjustment unit 209. This makes it possible to provide a technology for detecting the edge of a medium with high precision.

[0034] (Second embodiment) A second embodiment of the present invention will be described below with reference to the drawings. Since the basic configuration of this embodiment is the same as that of the first embodiment, only the characteristic configurations will be described below.

[0035] Figure 8 shows a method for adjusting the amplification factor of the output switching amplifier 208 of the light receiving unit 212 in this embodiment. Below, as an example of sensitivity adjustment in this embodiment, a method for adjusting the amplification factor of the output switching amplifier 208 will be described. The output switching amplifier 208 is capable of amplifying and outputting the signal received from the light receiving unit 212 according to the instructions of the adjustment unit 209 (see Figure 2).

[0036] In other words, the output switching amplifier 208 can amplify the voltage difference between the input terminals input from the light receiving unit 212 and output it. The amplification factor of the output switching amplifier 208 can be controlled by the adjustment unit 209.

[0037] Thus, the system is equipped with multiple light-receiving units, acquires a differential output from the outputs of the multiple light-receiving units, and adjusts the differential output by adjusting the amplification factor of the output switching amplifier using an adjustment amount derived from the differential output. This makes it possible to provide a technology for detecting the edge of a medium with high precision.

[0038] (Third embodiment) A third embodiment of the present invention will be described below with reference to the drawings. Since the basic configuration of this embodiment is the same as that of the first embodiment, only the characteristic configurations will be described below.

[0039] Figure 9 shows the current adjustment method of the light emission amount adjustment circuit 901 of the light emission unit 204 (see Figure 3). Below, as an example of sensitivity adjustment in this embodiment, the current adjustment method of the light emission amount adjustment circuit 901 of the light emission unit 204 will be described. The light emission amount adjustment circuit 901 adjusts the amount of current under control from the adjustment unit 209 and supplies current to the light emission unit 204, thereby adjusting the amount of light emitted in the light emission unit 204.

[0040] Thus, the device is equipped with multiple light-receiving units, and a differential output is obtained from the outputs of the multiple light-receiving units. The differential output is then adjusted by adjusting the amount of light emitted in the light-emitting unit 204 using an adjustment unit. This makes it possible to provide a technology for detecting the edge of a medium with high precision.

[0041] (Other embodiments) In the embodiments described above, an example was explained in which the light receiving unit 212 was divided into three parts: a first light receiving unit 205, a second light receiving unit 206, and a third light receiving unit 207. In other embodiments, a configuration in which the light receiving unit 212 is divided into two parts, a first light receiving unit and a second light receiving unit, will be described. First, the second light receiving unit detects the recording medium in single mode, and the sensitivity of the single output signal is adjusted based on the detection result. Subsequently, the sensitivity of the first light receiving unit is adjusted based on the sensitivity adjustment of the second light receiving unit, and the differential output between the first and second light receiving units is corrected.

[0042] Thus, the detection unit may be divided into two parts, a first light receiving unit and a second light receiving unit, and the differential output may be corrected.

[0043] This embodiment includes the following methods and configurations.

[0044] (Method 1) An edge detection method for detecting the edge of a sheet of paper in the width direction, using detection means provided on a carriage that is movable in the width direction of the paper, The detection means comprises a light-receiving unit including a light-emitting unit, a first light-receiving unit including a plurality of light-receiving elements that receive reflected light from the light-emitting unit, a second light-receiving unit including a plurality of light-receiving elements that are positioned at a distance in the width direction from the first light-receiving unit and receive reflected light from the light-emitting unit, and a differential amplifier circuit unit that differentially amplifies the output signals of the first light-receiving unit and the second light-receiving unit. An adjustment step to adjust the differential output of the differential amplifier circuit section, The acquisition step involves acquiring the differential output of the differential amplifier circuit section adjusted by the adjustment step while moving the carriage, A detection step for detecting the edge of the paper based on the change in differential output with respect to the position of the carriage obtained by the acquisition step, An end detection method characterized by having the following features.

[0045] (Method 2) The edge detection method according to Method 1, wherein the adjustment step involves changing the number of light-receiving elements used as the first light-receiving unit and the number of light-receiving elements used as the second light-receiving unit among the plurality of light-receiving elements of the light-receiving unit, thereby adjusting the differential output of the differential amplifier circuit.

[0046] (Method 3) The edge detection method according to method 1, wherein the adjustment step involves adjusting the amplification factor of the differential amplifier circuit.

[0047] (Method 4) The adjustment step involves adjusting the amount of light emitted from the light-emitting section using the end detection method described in Method 1.

[0048] (Method 5) A second acquisition step involves acquiring the output signal of a third light-receiving unit, which includes a plurality of light-receiving elements that receive reflected light from the light-emitting unit, while moving the carriage. A derivation step for deriving the end position based on the output signal of the third light receiving unit acquired in the second acquisition step, It further possesses, The adjustment step involves adjusting the differential output based on the end position derived in the derivation step, according to one of methods 1 to 4 of the end detection method.

[0049] (Method 6) The end detection method according to method 5, wherein the third light-receiving unit includes a light-receiving element different from the first light-receiving unit and the second light-receiving unit among the plurality of light-receiving elements of the light-receiving unit.

[0050] (Method 7) The end detection method according to method 5, wherein the third light-receiving unit includes the same light-receiving element as the first light-receiving unit or the second light-receiving unit among the plurality of light-receiving units of the light-receiving unit.

[0051] (Method 8) An edge detection method according to any one of methods 1 to 7, further comprising the step of recording an image on the paper by discharging liquid from a recording unit mounted on the carriage while moving the carriage, based on the information of the edge of the paper detected in the detection step.

[0052] (Method 9) The end detection method according to method 1, wherein the concentration is detected using the concentration sensor provided in the carriage.

[0053] (Method 10) The edge detection method according to any one of methods 1 to 9, wherein the detection step involves detecting the midpoint between the position where the differential output exceeds a predetermined threshold and the position where it falls below the predetermined threshold as the edge of the paper.

[0054] (Method 11) A transport means for transporting a recording medium, A moving means for moving a carriage in a scanning direction intersecting the transport direction in which the recording medium is transported by the transport means, A detection means comprising: a light-emitting unit provided at the end of the carriage in the scanning direction and irradiating light toward the recording medium; a light-receiving unit having a plurality of light-receiving elements that receive reflected light from the recording medium; and an amplification circuit unit that amplifies the output signal from the light-receiving unit. The system includes an adjustment means for adjusting the output signal from the detection means, and a control means for controlling the detection means, A method for detecting the end of a liquid dispensing device, comprising: In the first operating mode of the amplification circuit, the first light receiving unit of the light receiving unit receives reflected light from the recording medium transported by the transport means, and the first adjustment step adjusts the output signal from the detection means using the adjustment means. The control means performs a switching step of switching the first operating mode of the amplification circuit to a second operating mode different from the first operating mode, In the second operating mode, the second adjustment step involves adjusting the output signal from the detection means when a second light-receiving unit, which is different from the first light-receiving unit and is provided in the light-receiving unit, receives reflected light from the recording medium, based on the adjustment in the first adjustment step, and the adjustment means adjusts the output signal from the detection means. In the second operating mode, an edge detection step is performed in which the edge of the recording medium is detected by the output signal from the detection means adjusted in the second adjustment step, An end detection method characterized by having the following features.

[0055] (Composition 1) Equipped with a liquid ejection head, a carriage that can move in the width direction of the paper, The detection means provided on the carriage, A liquid dispensing device comprising, The detection means includes a light-emitting unit, a first light-receiving unit including a plurality of light-receiving elements that receive reflected light from the light-emitting unit, and a second light-receiving unit positioned at a distance in the width direction from the first light-receiving unit and including a plurality of light-receiving elements that receive reflected light from the light-emitting unit. It includes a differential amplifier circuit that differentially amplifies the output signals of the first light receiving unit and the second light receiving unit, A liquid dispensing device further comprising an adjustment means for adjusting the differential output of the differential amplifier circuit.

[0056] (Configuration 2) An acquisition means for acquiring the differential output of the differential amplifier circuit section adjusted by the adjustment means while moving the carriage, A detection means for detecting the edge of the paper based on the change in differential output with respect to the position of the carriage, obtained by the acquisition means, A liquid dispensing device according to configuration 1, further comprising the above.

[0057] (Composition 3) The liquid dispensing device according to configuration 1 or 2, wherein the adjustment means adjusts the differential output of the differential amplifier circuit by changing the number of light-receiving elements used as the first light-receiving unit and the number of light-receiving elements used as the second light-receiving unit among the plurality of light-receiving elements of the light-receiving unit.

[0058] (Composition 4) The liquid dispensing device according to configuration 1 or 2, wherein the adjusting means adjusts the amplification factor of the differential amplifier circuit.

[0059] (Composition 5) The liquid dispensing device according to configuration 1 or 2, wherein the adjusting means adjusts the amount of light emitted from the light-emitting section.

[0060] (Composition 6) The system further comprises a conveying means for conveying the aforementioned paper in a conveying direction intersecting the width direction, A liquid dispensing device according to any one of configurations 1 to 5, which records an image on a sheet of paper by alternately repeating a recording scan, in which a liquid is dispensed from the liquid dispensing head while moving the carriage to record an image on the sheet of paper based on information about the edge of the sheet of paper detected by the detection means, and transport by the transport means. [Explanation of Symbols]

[0061] 100 Liquid dispensing device 205 1st light receiving section 206 2nd light receiving section 207 Third light receiving section 208 Output Switching Amplifier 209 Adjustment section 213 CPU

Claims

1. An edge detection method for detecting the edge of a sheet of paper in the width direction, using detection means provided on a carriage that is movable in the width direction of the paper, The detection means comprises a light-receiving unit including a light-emitting unit, a first light-receiving unit including a plurality of light-receiving elements that receive reflected light from the light-emitting unit, a second light-receiving unit including a plurality of light-receiving elements that are positioned at a distance in the width direction from the first light-receiving unit and receive reflected light from the light-emitting unit, and a differential amplifier circuit unit that differentially amplifies the output signals of the first light-receiving unit and the second light-receiving unit. An adjustment step to adjust the differential output of the differential amplifier circuit section, The acquisition step involves acquiring the differential output of the differential amplifier circuit section adjusted by the adjustment step while moving the carriage, A detection step for detecting the edge of the paper based on the change in differential output with respect to the position of the carriage obtained by the acquisition step, An end detection method characterized by having the following features.

2. The edge detection method according to claim 1, wherein the differential output of the differential amplifier circuit is adjusted in the adjustment step by changing the number of light-receiving elements used as the first light-receiving unit and the number of light-receiving elements used as the second light-receiving unit among the plurality of light-receiving elements of the light-receiving unit.

3. The edge detection method according to claim 1, wherein the adjustment step involves adjusting the amplification factor of the differential amplifier circuit.

4. The end detection method according to claim 1, wherein the adjustment step involves adjusting the amount of light emitted from the light-emitting section.

5. A second acquisition step involves acquiring the output signal of a third light-receiving unit, which includes a plurality of light-receiving elements that receive reflected light from the light-emitting unit, while moving the carriage. A derivation step for deriving the end position based on the output signal of the third light receiving unit acquired in the second acquisition step, It further possesses, The end detection method according to claim 1, wherein the adjustment step adjusts the differential output based on the end position derived in the derivation step.

6. The end detection method according to claim 5, wherein the third light-receiving unit includes a light-receiving element different from the first light-receiving unit and the second light-receiving unit among the plurality of light-receiving elements of the light-receiving unit.

7. The end detection method according to claim 5, wherein the third light-receiving unit includes the same light-receiving element as the first light-receiving unit or the second light-receiving unit among the plurality of light-receiving units of the light-receiving unit.

8. The edge detection method according to claim 1, further comprising the step of recording an image on the paper by discharging liquid from a recording unit mounted on the carriage while moving the carriage, based on the information of the edge of the paper detected in the detection step.

9. The end detection method according to claim 1, wherein the concentration is detected by a concentration sensor provided in the carriage.

10. The edge detection method according to claim 1, wherein in the detection step, the midpoint between the position where the differential output exceeds a predetermined threshold and the position where it falls below the predetermined threshold is detected as the edge of the paper.

11. A transport means for transporting a recording medium, A moving means for moving a carriage in a scanning direction intersecting the transport direction in which the recording medium is transported by the transport means, A detection means comprising: a light-emitting unit provided at the end of the carriage in the scanning direction and irradiating light toward the recording medium; a light-receiving unit having a plurality of light-receiving elements that receive reflected light from the recording medium; and an amplification circuit unit that amplifies the output signal from the light-receiving unit. The system includes an adjustment means for adjusting the output signal from the detection means, and a control means for controlling the detection means, A method for detecting the end of a liquid dispensing device, comprising: In the first operating mode of the amplification circuit section, the first light receiving section of the light receiving section receives reflected light from the recording medium transported by the transport means, and the first adjustment step adjusts the output signal from the detection means using the adjustment means. The control means performs a switching step of switching the first operating mode of the amplification circuit to a second operating mode different from the first operating mode, In the second operating mode, the second adjustment step involves adjusting the output signal from the detection means when a second light receiving unit, which is different from the first light receiving unit and is provided in the light receiving unit, receives reflected light from the recording medium, based on the adjustment in the first adjustment step, and the adjustment means adjusts the output signal from the detection means. In the second operating mode, an edge detection step is performed in which the edge of the recording medium is detected by the output signal from the detection means adjusted in the second adjustment step, An end detection method characterized by having the following features.

12. Equipped with a liquid ejection head, a carriage that can move in the width direction of the paper, The detection means provided on the carriage, A liquid dispensing device comprising, The detection means includes a light-emitting unit, a first light-receiving unit including a plurality of light-receiving elements that receive reflected light from the light-emitting unit, and a second light-receiving unit positioned at a distance in the width direction from the first light-receiving unit and including a plurality of light-receiving elements that receive reflected light from the light-emitting unit. It includes a differential amplifier circuit that differentially amplifies the output signals of the first light receiving unit and the second light receiving unit, A liquid dispensing device further comprising an adjustment means for adjusting the differential output of the differential amplifier circuit.

13. An acquisition means for acquiring the differential output of the differential amplifier circuit section adjusted by the adjustment means while moving the carriage, A detection means for detecting the edge of the paper based on the change in differential output with respect to the position of the carriage, obtained by the acquisition means, The liquid dispensing device according to claim 12, further comprising the following:

14. The liquid dispensing device according to claim 12, wherein the adjustment means adjusts the differential output of the differential amplifier circuit by changing the number of light-receiving elements used as the first light-receiving unit and the number of light-receiving elements used as the second light-receiving unit among the plurality of light-receiving elements of the light-receiving unit.

15. The liquid dispensing device according to claim 12, wherein the adjustment means adjusts the amplification factor of the differential amplifier circuit.

16. The liquid dispensing device according to claim 12, wherein the adjusting means adjusts the amount of light emitted from the light-emitting section.

17. The system further comprises a conveying means for conveying the aforementioned paper in a conveying direction intersecting the width direction, A liquid dispensing device according to claim 12, which records an image on a sheet of paper by alternately repeating a recording scan, in which a liquid is dispensed from the liquid dispensing head while moving the carriage to record an image on the sheet of paper, based on information of the edge of the sheet of paper detected by the detection means, and transport by the transport means.

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