Recording device

Abstract

The objective is to improve the accuracy of edge detection of the media. [Solution] The sensor unit receives signals through two inputs: a digital input and an analog input. When the input of the digital input changes, the signal is acquired by the analog input to obtain a signal level corresponding to the threshold of the digital input. Based on the acquired signal level, the detection result from the digital input is corrected.

Description

Technical Field

[0001] The present invention relates to a recording apparatus.

Background Art

[0002] When performing borderless printing with an inkjet type image recording apparatus, if the detection accuracy of the media edge position is poor, there are problems such as inducing dirt inside the machine and generating margins. A general method for detecting the media edge position in a recording apparatus is as follows. Using a light emitting element such as an LED and a light receiving element that converts an optical signal into an electrical signal, such as a phototransistor, the media edge position is detected based on a detection signal generated by the reflected light from the media. This detection method is likely to deteriorate in detection accuracy due to the influence of environmental variations such as dirt on the media.

[0003] In Patent Document 1, a calibration method and a main body configuration for reducing the influence of environmental variations are disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, a detection method for media using a pair of light emitting elements and light receiving elements has been proposed. When using a pair of light emitting elements and light receiving elements, for example, regarding environmental variations that occur during the scanning of the media, such as floating at the media edge or external light, the voltage exceeding the threshold changes, so it cannot be reduced. Therefore, there was a problem that the media edge could not be detected with high accuracy. Also, in the case of detection by high-speed scanning according to printing, it is effective to use interrupt processing by a digital input unit for speed improvement, but there is a concern of being affected when the threshold of the digital input unit fluctuates, which has been a factor deteriorating the accuracy.

[0006] This invention has been made in view of the above-mentioned problems, and aims to improve the accuracy of edge detection of a medium. [Means for solving the problem]

[0007] The present invention is characterized by comprising: a light-emitting unit that irradiates light onto a sheet of paper; a sensor unit that receives light from the sheet of paper by the light-emitting unit and has a first light-receiving unit and a second light-receiving unit arranged in the width direction of the sheet of paper; the light-emitting unit and the first and second light-receiving units and is configured to be reciprocally scannable in the width direction of the sheet of paper; an analog input unit that takes signals from the first and second light-receiving units as input; a digital input unit that converts the signals from the first and second light-receiving units into digital inputs with a threshold value; an analog signal acquisition unit that acquires the input of the analog input unit when the input of the digital input unit changes; and a correction means that corrects the threshold value of the digital input unit based on the result of the analog signal acquisition unit when the digital input changes. [Effects of the Invention]

[0008] By applying the contents of this invention, it is possible to improve the accuracy of edge detection of the medium. [Brief explanation of the drawing]

[0009] [Figure 1] This is a system configuration diagram related to the implementation. [Figure 2] This is a diagram illustrating the structure of the implementation mechanism. [Figure 3] This is a diagram showing the configuration of the units involved in the implementation. [Figure 4] This is a differential waveform in practice. [Figure 5] This is a differential waveform for fluctuations in the actual operation. [Figure 6] This explains the threshold in practice. [Figure 7] This diagram illustrates how to obtain the interrupt level in practice. [Figure 8] This diagram illustrates the acquisition of position correction values ​​in the implementation phase. [Figure 9] This is a flowchart of the correction process using an offset amplifier in practice. [Figure 10] This is an array sensor configuration in an embodiment. [Modes for carrying out the invention]

[0010] (First embodiment) Figure 1 is a system diagram of a configuration to which the present invention is applied. The sensor unit 120 consists of a light-emitting unit 105 and two light-receiving units 102 and 103, each connected to a differential amplifier 104. The differential amplifier 104 functions as a differential amplifier and sends a differential amplified signal, which is the difference in signal strength between the two light-receiving units 102 and 103, to the main controller 101. The main controller 101 receives the signal from the differential amplifier 104 with an analog input unit 106 and a digital input unit 107. The digital input unit 107 is internally connected to an interrupt controller 108 and issues an interrupt signal to the CPU 112 according to predetermined interrupt conditions. When the CPU 112 receives an interrupt signal, it prioritizes processing the interrupt signal over the currently running process, enabling a more immediate response.

[0011] Next, Figure 2 shows the mechanical configuration of the device. The print head 110, which ejects ink and records images on the recording medium, is mounted on a carriage 201 that can scan back and forth. The sensor unit 120 is also mounted on the carriage 201 and is also capable of scanning back and forth. As a result, the sensor unit 120 can manipulate the paper 202 in the width direction and perform detection operations. With respect to the paper 202, the light-receiving elements 102 and 103 of the sensor unit 120 are arranged parallel to the scanning direction of the carriage 201, and the light-emitting part 105 is arranged vertically.

[0012] Figure 3 shows the operation diagram of the sensor unit 120. The light ray 301 emitted from the light-emitting unit 105 is reflected by the paper 202 and received by the light-receiving units 102 and 103. The light from the light-emitting unit 105 is emitted radially, but here only the portion of the light ray that is effective for reception is shown. Optical windows, apertures, etc. may be used in the sensor unit 120 when forming such light rays. Figure 3 shows the sensor unit viewed in a cross-section in the width direction of the paper 202, and the light ray 301 is projected perpendicular to the width direction.

[0013] Figure 4 shows the detection flow based on the output signal from the differential amplifier 104. The signal flow for the position 411 obtained by the position encoder sensor 113 is shown in 401. The transition of this signal 401 with respect to the positional relationship between the sensor unit 120, particularly the light receivers 102 and 103, and the paper 202 will be explained in sections 406 to 410. When the sensor unit 120 is in the relationship shown in Figure 4(b) with respect to the paper 202, the amount of light received by the light receivers 102 and 103 is small, so the difference is small, and the output signal 401 of the differential amplifier 104 is also small, resulting in the state of period 406. Subsequently, when the positional relationship becomes the state shown in Figure 4(c), reflected light from the paper 202 is received by the light receiver 103, so the signal of the light receiver 103 increases and the signal difference with 102 becomes large. Therefore, the output signal 401 of the differential amplifier 104 becomes larger, resulting in the state of period 407. Subsequently, when the state shown in Figure 4(d) is reached, the paper 202 enters the entire range of the light receiving unit 103, so the signal of the light receiving unit 103 no longer increases, and the output signal of the differential amplifier 104 also no longer increases, resulting in state 408. This state continues until the state shown in Figure 4(e). Subsequently, when the state shown in Figure 4(f) is reached, reflected light from the paper 202 is received by the light receiving unit 102, causing the signal of the light receiving unit 102 to increase. As the difference with the already high signal of the light receiving unit 103 begins to decrease, the signal of the differential amplifier 104 decreases, resulting in state 409. Subsequently, when the state shown in Figure 4(g) is reached, the paper 202 enters the entire range of the light receiving unit 102, so the signal of the light receiving unit 102 no longer increases, and the output signal of the differential amplifier 104 also no longer decreases, resulting in state 410. The output signal 401 of the differential amplifier 104 is input to the analog input section 106 and the digital input section 107 of the main controller 101, and the digital input signal is as shown in 403. The digital input section 107 has a threshold for distinguishing between digital 0s and 1s, and the relationship with respect to signal strength is as shown in 402. When the output signal 401 of the differential amplifier 104 falls below the threshold 402, the digital signal 403 becomes LOW, or 0, and when the output signal 401 of the differential amplifier 104 exceeds the threshold 402, it becomes HIGH, or 1.For such an acquired digital signal 403, by taking the central position 502 of the rising edge position 404 and the falling edge position 405, the end position of the paper 202 can be detected.

[0014] The advantage of the method of taking the center of the pulse is that, as shown in FIG. 5, even when the signal intensity of the output signal 401 of the differential amplifier 104 fluctuates as 501, both the rising edge position 404 and the falling edge position 405 are affected by 503 and 504 respectively, so they can be canceled at the central position 502. The sensor signal generally easily changes in intensity depending on conditions, and by taking such a method, it becomes easier to obtain a stable detection result.

[0015] On the other hand, the influence when the threshold value 402 fluctuates is shown in FIG. 6. The threshold value 402 depends on the digital input section 107 of the main controller 101 and has individual variations. In addition to fixed variations such as individual variations, variable factors such as environmental temperature and changes over time may also have an impact. In any case, when the threshold value 402 varies as 601 or 602, the positions at which interrupts are detected in relation to the output signal 401 of the differential amplifier 104 will be different as 605 and 606, and even though the signal is the same 401, the results will be different. Also, the threshold values are called VIH, VIL, etc. for rising and falling respectively, and it is common for the threshold value 402 to be different. Therefore, the influence from variable factors is also different for each, and it cannot be expected that the fluctuations in the threshold value can be canceled by a uniform influence as shown in FIG. 5.

[0016] Therefore, to avoid variations like those in 605 and 606, correction is performed in two steps: first, by acquiring a threshold and then correcting based on the deviation from the target. Figure 7 shows how to acquire the threshold. First, move to the inspection position (S701). The positional relationship is as shown in Figure 7(b), so that either the light-receiving elements 102 or 103 is on top of the paper 202 in order to obtain a differential signal. Next, light-emitting parts are turned on, and the PWM 116 that controls their intensity is set to the minimum value and then gradually increased (Figure 7(c)). As a result, there is no reflected light at the light-receiving part 102 which is not on the paper 202, so the received signal does not increase (PD0, 702), whereas at the light-receiving part 103 which is on the paper 202, the reflected light becomes stronger and the signal becomes stronger (PD1, 703). As a result, the differential signal between the light-receiving parts becomes larger, and the output signal 401 of the differential amplifier 104 also increases. At this time, the state of the interrupt controller 108 from the digital input 107 is monitored, and if the level is LOW, the PWM 116 is further increased. Accordingly, the output signal 401 of the differential amplifier 104 also increases, and at a certain point it exceeds the threshold 402. When this happens, the level of the digital input 107 becomes HIGH (S703). When the CPU 112 detects that the level of the digital input has changed, it functions as an analog signal acquisition unit and acquires the level of the analog input at that time (S704). The signal when the level of the digital input 107 changes in this way corresponds to the threshold 402, and in this way the internal threshold 402 can be known. The internal threshold 402 obtained in this way is used as the detection threshold Vth_p as the threshold voltage acquired for correction.

[0017] The correction method using the threshold value obtained next is shown in FIG. 8. First, in the flow of S801 to S810 in FIG. 8(b), the displacement amount per signal intensity is calculated. First, move to the origin position of the position correction (S801). The positional relationship is as shown in FIG. 8(a), and both the light receiving elements 102 and 103 are out of the paper 202. The signal obtained from the differential amplifier at this time corresponds to the point 802 in the transition 801 obtained throughout the flow. Next, start the acquisition of the analog input unit 106 (S802). Then start the constant speed driving of the carriage (S803). At this time, if the driving speed of the carriage 201 is made as low as possible, it is preferable because it is easy to obtain many acquisition points of the analog input unit 106. Next, continue driving while continuing the acquisition of the analog input unit 106, and stop the driving of the carriage when reaching the position correction end position (S804) (S805). The positional relationship at this time is as shown in FIG. 8(g), and corresponds to 806 in the signal transition 801. Next, the CPU 112 stops the acquisition of the analog input unit 106 (S806). The analog input acquired so far corresponds to the period 808 with respect to the signal transition 801. Next, analyze this acquisition period 808 and extract the data in the rising period (S807). The extraction of this period may be performed, for example, by calculating the arrival points of 90% and 10% with respect to the maximum value and using the period between them. Here, the signal level of 90% with respect to the maximum value is S90, the position at that time is P2, the signal level of 10% with respect to the maximum value is S10, and the position at that time is P1. Next, calculate the displacement amount per signal intensity within this period (S809). The calculation is performed as (P2 - P1) / (S90 - S10). Using this correction value, calculate the position correction value from the detection threshold value Vth_p acquired in S707 of FIG. 7. Let the threshold value before correction be Vth_0, and the position acquisition value correction value Pos_p due to the threshold deviation amount is calculated as Pos_p=(Vth_P - Vth_0)×(P2 - P1) / (S90 - S10). By adding this correction value Pos_p to the central position 502 of the pulse acquired from the sensor in FIG. 4, the threshold deviation amount is corrected by the amount converted into the position deviation, and a position detection value with less variation can be obtained.

[0018] (Second Embodiment) Next, Figure 9 shows a second embodiment in which the threshold deviation is corrected using an offset amplifier. The main controller 101 outputs an analog signal based on digital settings from the CPU 112 and has a D / A C901 that functions as an analog signal output unit. The output signal from the D / A C901 is connected to an offset amplifier 902 located between the differential amplifier 117 and the analog input unit 106 and the digital input unit 107. The offset amplifier 902 can increase or decrease the output signal of the differential amplifier 117 by the amount of the output signal of the D / A C901, thereby correcting the threshold deviation. For the setting, the setting value of the D / A C901 is set to VTH_N obtained in S705 in Figure 7, so that the threshold deviation is absorbed by the offset amplifier 902. In this way, the output of the differential amplifier 117 and the operation of the interrupt controller 108 connected to the digital input unit 107 can absorb the threshold deviation.

[0019] Next, Figure 10 shows a third embodiment, a configuration using a sensor unit consisting of an array 1001 of multiple light-receiving elements 1002. The connection state 1005 of the light-receiving elements 1002 is set by a selector (not shown). In this example, four elements 1003 of the light-receiving elements 1002 at one end are connected to one side of the differential amplifier 117, and four elements 1004 of the light-receiving elements 1002 at the other end are connected to the other side of the differential amplifier 117. As a result, the four elements 1003 and 1004 at both ends operate in accordance with 102 and 103 in Embodiment 1, respectively. Furthermore, if it is desired to increase the received light intensity level, the sensitivity can be increased by increasing the number of elements from 4 to 5, for example. Also, if it is desired to adjust the position of the reflected light rays, instead of selecting elements at both ends, it is possible to select four elements starting from one end, and adjust the position of the sensitivity region. By adopting this array 1001 configuration, the positional function can be controlled by the element selection state of the light-receiving elements 1002, allowing for flexible control of the signal state depending on the operating conditions. [Explanation of Symbols]

[0020] 102,103 Light receiving part 105 Light-emitting part 106 Analog Input Section 107 Digital Input Section 108 Interrupt Controller 117 Sensor Unit 401 Output signal of differential amplifier 402 threshold

Claims

1. A light-emitting unit that illuminates the paper, The light received from the paper by the light-emitting unit, and the first light-receiving unit and the second light-receiving unit arranged in the width direction of the paper, A sensor unit having the light-emitting part and the first and second light-receiving parts, configured to be able to reciprocately scan in the width direction of the paper, An analog input unit that receives signals from the first and second light receiving units as input, The system includes a digital input unit that converts the signals from the first and second light receiving units into digital inputs using a threshold value. An analog signal acquisition unit that acquires the input of the analog input unit when the input of the digital input unit changes, A recording device characterized by having a correction means for correcting the threshold value of the digital input unit based on the results of the analog signal acquisition unit when the digital input changes.

2. A position acquisition means for acquiring the position of the aforementioned sensor unit, A differential amplifier unit that takes signals from the first and second light receiving units as input and outputs a differentially amplified signal, The system includes the position acquisition means, the analog input unit, and the detection means for detecting the edge position of the paper based on the digital input unit. The analog input section receives the signal from the differential amplifier section as input. The recording apparatus according to claim 1, characterized in that the digital input unit receives the signal from the differential amplifier unit as a digital input with a threshold value.

3. An analog signal output section that outputs an analog signal, An offset amplifier that takes the signals from the analog signal output unit and the differential amplifier unit as inputs, and outputs the signal from the differential amplifier unit with an offset based on the signal from the analog signal output unit, It has, The recording device according to claim 2, characterized in that the correction means corrects a threshold value for signal strength.

4. The recording device according to claim 1, characterized in that the light-receiving unit is configured as an array consisting of a plurality of light-receiving elements.

5. When the level of the digital input section changes, the input of the analog input section is acquired. The recording device according to claim 1, characterized in that the correction means corrects the threshold based on the acquired signal.

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