Displacement measuring device and displacement measuring method

Abstract

This displacement measuring device includes: a scale including a continuous portion in which a periodic pattern is formed and a discontinuous portion in which the periodic pattern is not formed; a first pattern reading unit and a second pattern reading unit that read the periodic pattern, and respectively output a first electrical signal and a second electrical signal; a signal processing unit that calculates positional displacement or angular displacement of a second member relative to a first member on the basis of the first and second electrical signals; and a storage unit that stores relative phase information between the first and second electrical signals. The first and second pattern reading units are disposed at positions where the discontinuous portion is not simultaneously read. The signal processing unit calculates displacement by using the stored phase information and the electrical signal outputted from the reading unit, of the first and second pattern reading units, that has read the continuous portion.

Description

Displacement measuring device and displacement measuring method

[0001] This disclosure relates to a displacement measuring device and a displacement measuring method.

[0002] Conventionally, displacement measuring devices that measure positional and angular displacement by reading the periodic pattern of a scale are known. Generally, in order to measure displacement over a wide range with a displacement measuring device, a long periodic pattern is required. However, the longer the periodic pattern, the more difficult it becomes to manufacture the scale.

[0003] To overcome these problems, Patent Document 1 discloses a technique for forming a long scale by joining together multiple short scales. Patent Document 2 discloses a drive control device that reads a scale adhered to or printed on the surface of a belt and controls the speed of the belt. However, with techniques like those in Patent Document 2, when forming a periodic pattern on the surface of the belt, seams are created at both ends of the scale, making it difficult to construct a periodic pattern continuously.

[0004] In discontinuous sections of the periodic pattern, the reading signal is missing, resulting in unstable displacement measurement results. Therefore, Patent Documents 1 and 2 describe providing multiple periodic pattern reading units and using pulse signals output from reading units that are not measuring discontinuous sections as external output signals. Alternatively, Patent Document 2 describes using a reference clock or dummy signal as an external output signal instead of the pulse signal output from a reading unit when it is reading a discontinuous section of the periodic pattern. Furthermore, Patent Document 1 describes a method for performing smooth tracking photography by ensuring that the pan / tilt head does not move in the opposite direction to the subject's movement.

[0005] JP-A-10-318791 Patent No. 3893300

[0006] However, when switching pulse signals output from multiple reading units at discontinuities in the periodic pattern, if the phases of each pulse signal are out of sync, a jump occurs in the signal output at the switching point. This presents a challenge in accurately measuring displacement. Furthermore, while using a reference clock or dummy signal as an external output signal at discontinuities in the periodic pattern is suitable for measuring the displacement of an object moving or rotating at a constant speed, measurement errors can become large if the displacement speed is not constant.

[0007] Therefore, the present disclosure aims to provide a displacement measuring device that can measure displacement with high accuracy even when the displacement velocity is not constant, such as when there are discontinuities in the periodic pattern.

[0008] To achieve the above objective, a displacement measuring device as one aspect of the present disclosure comprises: a scale including a continuous section on which a periodic pattern is formed and a discontinuous section on which the periodic pattern is not formed; a first pattern reading unit that reads the periodic pattern and outputs a first electrical signal; a second pattern reading unit that reads the periodic pattern and outputs a second electrical signal; a signal processing unit that calculates the positional displacement or angular displacement of a second member relative to a first member based on the first and second electrical signals; and a storage unit that stores relative phase information of the first and second electrical signals, wherein the first and second pattern reading units are positioned so as not to read the discontinuous section simultaneously, and the signal processing unit calculates the displacement using the phase information stored in the storage unit and the electrical signals output from the reading unit that reads the continuous section among the first and second pattern reading units.

[0009] According to this disclosure, even if there are discontinuities in the periodic pattern, the displacement can be measured with high accuracy even if the displacement velocity is not constant.

[0010] This is a diagram showing the displacement measuring device of Embodiment 1. This is a diagram showing the sensor of Embodiment 1. This is a diagram illustrating the periodic pattern reading unit of Embodiment 1. This is a diagram showing the scale of Embodiment 2 unfolded on a plane. This is a block diagram of the displacement measuring device of Embodiment 1. This is a diagram illustrating the input signals to the input / output unit of the integrated circuit of Embodiment 1. This is a diagram showing the displacement measuring device of Embodiment 2. This is a diagram showing the sensor of Embodiment 2. This is a diagram illustrating the index pattern reading unit of Embodiment 2. This is a diagram showing the scale of Embodiment 2 unfolded on a plane. This is a diagram illustrating the output signals of the index pattern reading unit of Embodiment 2. This is a block diagram of the displacement measuring device of Embodiment 2. This is a diagram illustrating the signal processing by analog circuitry of Embodiment 2. This is a diagram illustrating the signal processing by analog circuitry of Embodiment 2. This is a diagram illustrating the input signals to the input / output unit of the integrated circuit of Embodiment 2.

[0011] Embodiments of this disclosure will be described below with reference to the drawings. However, this disclosure is not limited to the embodiments described below. In each drawing, the same reference numeral is used for the same member or element, and redundant descriptions are omitted or simplified.

[0012] <Embodiment 1> Hereinafter, the displacement measuring device 100 in Embodiment 1 will be described with reference to Figures 1 to 6. Figure 1 is a diagram showing the displacement measuring device 100 of Embodiment 1. Figure 1(A) is a diagram showing the XZ plane of the displacement measuring device 100. Figure 1(B) is a diagram showing the YZ plane of the displacement measuring device 100.

[0013] The displacement measuring device 100 includes a scale 111. The scale 111 is fixed to the rotating body (second member) 1 (on the surface). The scale 111 is, for example, a film scale and is fixed to the rotating body 1 by adhering it with double-sided tape. In other words, the scale 111 is fixed by being attached to the surface of the rotating body 1. The scale 111 includes a periodic pattern 112 (continuous section), an index pattern 113, and discontinuous sections (discontinuous section 114a, discontinuous section 114b). The periodic pattern 112 includes a periodic pattern (first periodic pattern) 112a and a periodic pattern (second periodic pattern) 112b. Since periodic patterns 112a and 112b are included in the periodic pattern 112, they function as a continuous section in the same way as the periodic pattern 112.

[0014] Periodic patterns 112a and 112b form periodic patterns that can be read by the periodic pattern reading unit 124, which will be described later. Periodic patterns are not formed in the discontinuous portion 114a (first discontinuous portion) and discontinuous portion 114b (second discontinuous portion). Specifically, discontinuous portions 114a and 114b are the joint portions (connecting portions) in the periodic pattern when the scale 111 is fixed so as to be wrapped around the upper surface of the rotating body 1. As shown in Figure 1, discontinuous portion 114a is provided on the periodic pattern 112a side (first periodic pattern side), and discontinuous portion 114b is provided on the periodic pattern 112b side (second periodic pattern side). Furthermore, discontinuous portions 114a and 114b are configured to be in different positions in the circumferential direction.

[0015] The index pattern 113 is provided with one slit-shaped reflective portion 115. The index pattern 113 is configured such that the area other than the reflective portion 115 is a non-reflective area. The rotating body 1 is cylindrical in shape and is driven and controlled by a drive device (not shown) to rotate around its axis (an axis parallel to the X-axis) (rotating around a predetermined axis).

[0016] The displacement measuring device 100 includes a sensor 121a, a sensor 121b, and an index pattern reading unit 122 (a third pattern reading unit). The sensors 121a, 121b, and the index pattern reading unit 122 are mounted on a substrate (first component) 120 (attached to the substrate 120).

[0017] Figure 2 illustrates sensors 121a and 121b of Embodiment 1. Figure 2(A) illustrates sensor 121a. Figure 2(B) illustrates sensor 121b. Sensor 121a is configured to have a light source 123a and a first periodic pattern reading unit 124a for reading the periodic pattern 112a. For example, an LED may be used for the light source 123a. Sensor 121a is configured in which the light source 123a and the first periodic pattern reading unit 124a are mounted in the same package using a translucent resin (not shown). However, this disclosure is not limited to this embodiment, and the light source 123a and the first periodic pattern reading unit 124a may be mounted individually on the substrate 120. Sensor 121b has the same structure as sensor 121a. Specifically, the sensor 121b is configured to have a light source 123b and a second periodic pattern reading unit 124b for reading the periodic pattern 112b. Since the sensor 121b has the same structure as the sensor 121a, a detailed explanation is omitted.

[0018] Figure 3 is a diagram illustrating the periodic pattern reading unit 124 of Embodiment 1. The first periodic pattern reading unit 124a and the second periodic pattern reading unit 124b, as shown in Figure 2, have the same structure.

[0019] The periodic pattern reading unit 124 is a photodetector array that detects light emitted from the light source and reflected by the periodic pattern 112 of the scale 111. The periodic pattern reading unit 124 includes 4N (32 in Figure 3) photodetectors 125. Each photodetector is arranged at equal intervals within the periodic pattern reading unit 124.

[0020] The 4N photodetectors are cyclically assigned in the order of B(-) phase, A(+) phase, B(+) phase, and A(-) phase. In other words, there are N groups of 4-phase photodetectors (8 groups in Figure 3). The N photodetectors constituting each photodetector group are electrically connected to one another, and their outputs (currents) are added together and input to IV (current-voltage) conversion amplifiers (not shown) provided for each phase in the subsequent stage. The output of each phase IV amplifier becomes a voltage signal (sine wave signal) that changes sinusoidally in accordance with the movement of the scale 111.

[0021] The A(+) and A(-) phases are combined by a difference circuit (electrical circuit) not shown to generate an A-phase analog signal. Similarly, the B(+) and B(-) phases are combined by a difference circuit (not shown) to generate a B-phase analog signal. Finally, the periodic pattern reading unit 124 outputs A-phase and B-phase analog signals (incremental signals) with a phase difference of approximately 90°. As described above, the discontinuity 114a and discontinuity 114b are located at different positions in the circumferential direction. Therefore, the first periodic pattern reading unit 124a and the second periodic pattern reading unit 124b in this embodiment are configured to be positioned so as not to read the discontinuity simultaneously.

[0022] Figure 4 is a diagram showing the scale 111 of Embodiment 1 unfolded on a plane. Periodic patterns 112a and 112b are arranged offset to the left and right, as shown in Figure 4. That is, periodic patterns 112a and 112b are arranged on the rotating body 1 such that their periodic patterns are in different positions. In addition, the index pattern 113 is provided with one slit-shaped reflective portion 115 as described above. Periodic pattern 112a is read by the first periodic pattern reading unit 124a. Periodic pattern 112b is read by the second periodic pattern reading unit 124b. In addition, the index pattern 113 is read by the index pattern reading unit 122.

[0023] Figure 5 is a block diagram of the displacement measuring device 100 according to Embodiment 1. The displacement measuring device 100 includes an input / output unit 128, a signal processing unit 129, and a storage unit 130, all mounted on an integrated circuit 150. The integrated circuit 150 can be, for example, a microcontroller, an ASIC, or an FPGA. The integrated circuit 150, along with sensors 121a, 121b, etc., is mounted on a substrate 120. The operation and processing of the displacement measuring device 100 are controlled by the integrated circuit 150 (it comprehensively controls each component of the displacement measuring device 100).

[0024] The input / output unit 128 receives various electrical signals (the first electrical signal 131, the second electrical signal 132, the index signal 137, etc., which will be described later). It also performs a predetermined conversion process on the input electrical signals and outputs the converted information (voltage value information) to the signal processing unit 129. The details of the processing performed by the signal processing unit 129 will be described later.

[0025] The signal processing unit 129 processes the electrical signals input to the input / output unit 128 to calculate the displacement of the rotating body 1 relative to the substrate 120. Details of the processing performed by the signal processing unit 129 will be described later. The storage unit 130 consists of a storage medium such as memory (ROM or RAM) or HDD, and stores control programs, various parameter data, execution results, etc. Each process in the displacement measuring device 100 is realized by the integrated circuit 150 executing a program stored in memory.

[0026] The first periodic pattern reading unit 124a outputs a first electrical signal 131 by reading the periodic pattern 112a. Specifically, it outputs an A-phase analog signal 131a and a B-phase analog signal 131b as the first electrical signal 131. The A-phase analog signal 131a and the B-phase analog signal 131b are branched in the circuit; one is sent directly to the input / output unit 128 of the integrated circuit 150, and the other is input to the comparator 126a (signal generation unit). The comparator 126a processes (compares) the A-phase analog signal 131a and the B-phase analog signal 131b with respect to a reference voltage to generate a first pulse signal 133, which is output to the input / output unit 128. Specifically, it generates an A-phase pulse signal 133a and a B-phase pulse signal 133b as the first pulse signal 133, which are output to the input / output unit 128. The A-phase pulse signal 133a and the B-phase pulse signal 133b are input to the input / output unit 128 of the integrated circuit 150.

[0027] Similarly, the second periodic pattern reading unit 124b outputs a second electrical signal 132 by reading the periodic pattern 112b. Specifically, it outputs an A-phase analog signal 132a and a B-phase analog signal 132b as the second electrical signal 132. The A-phase analog signal 132a and the B-phase analog signal 132b are branched in the circuit; one is sent directly to the input / output unit 128 of the integrated circuit 150, and the other is input to the comparator 126b (signal generation unit). The comparator 126b processes (compares) the A-phase analog signal 132a and the B-phase analog signal 132b with respect to a reference voltage to generate a second pulse signal 134, which is output to the input / output unit 128. Specifically, it generates an A-phase pulse signal 134a and a B-phase pulse signal 134b as the second pulse signal 134, which are output to the input / output unit 128. The A-phase pulse signal 134a and the B-phase pulse signal 134b are input to the input / output unit 128 of the integrated circuit 150.

[0028] The index pattern reading unit 122 may employ, for example, a photodetector. The index pattern reading unit 122 reads the index pattern 113 and outputs a third electrical signal 135 whose voltage increases in proportion to the amount of light received. The third electrical signal 135 is processed (compared) by an analog circuit (signal generation unit) 127 mounted on the substrate 120 to generate an index signal 137. The index signal 137 is an electrical signal that is High only at the position where the index pattern reading unit 122 reads the slit-shaped reflector 115, and Low at all other locations. The index signal 137 is also input to the input / output unit 128 of the integrated circuit 150.

[0029] Thus, comparator 126a functions as a signal generation unit that compares the first electrical signal 131 to generate a first pulse signal 133. Comparator 126b functions as a signal generation unit that compares the second electrical signal 132 to generate a second pulse signal 134. Analog circuit 127 functions as a signal generation unit that processes the third electrical signal 135 to generate an index signal 137. Note that analog circuit 127 includes comparators equivalent to comparators 126a and 126b. Therefore, in addition to generating an index signal, analog circuit 127 can also output a pulse signal by comparing the input analog signal when an analog signal is input. Furthermore, at least one of comparators 126a and 126b may be an analog circuit.

[0030] The input / output unit 128 of the integrated circuit 150 has a pulse counting function that counts pulse signals input from an external source. Furthermore, the input / output unit 128 can count pulses even for input signals with frequencies of megahertz or higher. The frequency at which pulse counting is possible is faster than the internal clock frequency of the signal processing unit 129 of the integrated circuit 150, so the number of pulses can be accurately counted even when the rotating body 1 is rotating at high speed.

[0031] The input / output unit 128 counts the number of pulses of the first pulse signal 133 and the second pulse signal 134. The input / output unit 128 increments the count if phase A precedes phase B, and decrements the count if phase B precedes phase A. The input / output unit 128 counts the number of pulses n of the first pulse signal 133. １ (Number of pulses in the first pulse signal) and n pulses in the second pulse signal 134 ２ Both (second pulse counts) are counted. Then, in accordance with the instructions of the signal processing unit 129, the information of the counted pulse counts is transmitted (output) from the input / output unit 128 to the signal processing unit 129.

[0032] Furthermore, the input / output unit 128 of the integrated circuit 150 has an AD conversion function that converts the voltage of the input analog signal into a digital numerical value. In the input / output unit 128, the four analog signals 131a, 131b, 132a, and 132b of phases A and B are converted from their respective signal voltages into digital numerical information. Then, according to the instructions of the signal processing unit 129, the digitized voltage value information is transmitted from the input / output unit 128 to the signal processing unit 129.

[0033] Figure 6 is a diagram illustrating the input signals to the input / output unit 128 of the integrated circuit 150. The input / output unit 128 receives a total of nine signals: four analog signals 131a, 131b, 132a, and 132b for phase A and phase B, four pulse signals 133a, 133b, 134a, and 134b, and an index signal 137. Note that the phase B analog signals 131b, 132b, 133b, and 134b, which are not shown in Figure 6 for the sake of simplicity, are signals whose phase is shifted by approximately 90° relative to the phase A analog signals 131a, 132a, 133a, and 134a. Also, for the sake of simplicity, Figure 6 shows the case where the displacement speed is constant. However, this disclosure can also be applied when the displacement speed is not constant.

[0034] When the first periodic pattern reading unit 124a and the second periodic pattern reading unit 124b are reading the periodic pattern 112, the A-phase analog signals 131a and 132a become sinusoidal signals. At this time, the A-phase pulse signals 133a and 134a generated by the comparator 126a become square wave signals.

[0035] When the first periodic pattern reading unit 124a reads the discontinuity 114a of the periodic pattern 112a, and the second periodic pattern reading unit 124b reads the discontinuity 114b of the periodic pattern 112b, the signal amplitudes of the A-phase analog signals 131a and 132a decrease. At this time, the A-phase pulse signals 133a and 134a generated by the comparator 126a remain low, and no pulses are generated.

[0036] For the sake of simplicity, Figure 6 shows a case where only 5 pulses are output per revolution (1 rotation of the rotating body 1) for each of the A-phase pulse signals 133a and 134a. However, in reality, many pulses are generated per revolution in order to measure the displacement with high precision. Number of pulses N output per revolution by the A-phase pulse signal 133a １ The number of pulses N output per revolution by the A-phase pulse signal 134a is... ２ This is pre-stored in the memory unit 130 included in the integrated circuit 150. In the case of Figure 6, N １ = N ２ = 5.

[0037] The index signal 137 is an electrical signal that is High only when the index pattern reading unit 122 is in a position to read the slit-shaped reflector 115, and Low at all other locations. In the displacement measuring device 100, one pulse is output each time the rotating body 1 completes one rotation. The index signal 137 is used to reset the pulse count. In the input / output unit 128 of the integrated circuit 150, the pulse count n is reset in accordance with the rising edge of the index signal 137. １ and pulse count n ２ Reset each of them.

[0038] After the index signal 137 rises, when the A-phase pulse signal 133a rises, the number of pulses n of the first pulse signal 133 is reset to 1 by the signal processing unit 129. １ After the index signal 137 rises, when the A-phase pulse signal 134a rises, the number of pulses n of the second pulse signal 134 is reset to 1 by the signal processing unit 129. ２ is reset to 1.

[0039] Here, when the rotating body 1 rotates in the reverse direction, after the index signal 137 rises, when the A-phase pulse signal 133a falls, the number of pulses n of the first pulse signal 133 is reset to 5 by the signal processing unit 129. １ After the index signal 137 rises, when the A-phase pulse signal 134a falls, the number of pulses n of the second pulse signal 134 is reset to 5 by the signal processing unit 129. ２ is reset to 5.

[0040] Note that the timing for resetting the counter can be changed. For example, the timing for resetting the counter may be changed at the rise and fall of the A-phase pulse signal. Alternatively, the counter may be reset at the rise or fall timing of the B-phase pulse signal.

[0041] The phase difference Δθ between the rise of the index signal 137 and the A-phase analog signal 131a １ and the phase difference Δθ between the rise of the index signal 137 and the A-phase analog signal 132a ２ are stored in the storage unit 130 of the integrated circuit 150. The phase differences Δθ １ and the phase difference Δθ ２ include the relative phase information of the first electrical signal 131 and the second electrical signal 132. The phase differences Δθ １ and the phase difference Δθ ２ may store the values measured during calibration in the storage unit 130, or may update the values measured and stored in real time. <s

[0042] Also, in the storage unit 130, there is the joint position M of the signal output from the first periodic pattern reading unit 124a １The joint position M of the signal output from the second periodic pattern reading unit 124b. ２ This is stored in memory. In the example in Figure 6, the output signal from the first periodic pattern reading unit 124a has a gap at the position of the 4th pulse (before the 5th pulse is output). Also, the output signal from the second periodic pattern reading unit 124b has a gap at the position of the 1st pulse (before the 2nd pulse is output).

[0043] Therefore, joint position M １ = 4, joint position M ２ Set to =1 and store in the memory unit 130. Note that the seam position M １ and joint position M ２ The values ​​measured during calibration may be stored in the storage unit 130, or they may be measured in real time and the stored values ​​may be updated with each measurement.

[0044] Furthermore, the memory unit 130 contains the interval d between the signals output from the first periodic pattern reading unit 124a. １ The gap d between the signals output from the second periodic pattern reading unit 124b ２ Remember that.

[0045] In the example in Figure 6, the interval between the 4th and 5th pulses of the output signal of the first periodic pattern reading unit 124a is d. １ Furthermore, the interval between the first and second pulses of the output signal of the second periodic pattern reading unit 124b is d ２ The joint spacing is d. １ and the gap between the joints d ２ The values ​​measured during calibration may be stored in the storage unit 130, or the stored values ​​may be updated by measuring them in real time.

[0046] In this embodiment, the joint position M １ and joint spacing d １ The information is stored in the storage unit 130 as position information of the discontinuous portion 114a on the scale 111. Furthermore, the joint position M ２ and joint spacing d ２ The information of each of these is stored in the storage unit 130 as position information of the discontinuous portion 114b.

[0047] The displacement measuring device 100 starts calculating the displacement based on an external command. Alternatively, the displacement measuring device 100 calculates the displacement at predetermined time intervals. When the displacement calculation starts, the signal processing unit 129 reads the voltage values ​​of the first electrical signal 131, which are A-phase analog signals 131a and 131b, and the second electrical signal 132, which are B-phase analog signals 132a and 132b, from the input / output unit 128.

[0048] Next, the signal processing unit 129 determines the voltage value A of the A-phase analog signal 131a output from the first periodic pattern reading unit 124a. １ And the voltage value B of the B-phase analog signal 131b １ Therefore, using the following equation (1), the phase angle θ １ Calculate. Here, α in equation (1) above １ This represents the offset voltage of the A-phase analog signal 131a. β １ This represents the offset voltage of the B-phase analog signal 131b.

[0049] Similarly, the voltage value A of the A-phase analog signal 132a of the second periodic pattern reading unit 124b ２ And the voltage value B of the B-phase analog signal 132b ２ Therefore, using the following equation (2), the phase θ ２ This is calculated. Here, α in equation (2) above ２ This represents the offset voltage of the A-phase analog signal 132a. β １ This represents the offset voltage of the B-phase analog signal 132b.

[0050] Note that the atan function is computationally intensive, so the phase angle θ １ and phase angle θ ２ When calculating this, you may use a numerical table instead of the atan function.

[0051] Next, the signal processing unit 129 determines the number of pulses n of the first pulse signal 133. １ and the number of pulses n of the second pulse signal 134 ２ The input / output unit 128 reads the data. Subsequently, the signal processing unit 129 reads the phase information Δθ stored in the storage unit 130.１ , Δθ ２ And, seam position M １ M ２ Information and the joint interval d １ d ２ The information is read out. Subsequently, the signal processing unit 129 calculates the first displacement L based on the following equation (3). １ Calculate. Here, n １ = M １ In this case, the first periodic pattern reading unit 124a is reading the vicinity of the discontinuity 114a of the periodic pattern 112a, so the signal processing unit 129 of the displacement measuring device 100 determines that it is reading the discontinuity 114a and does not perform displacement calculation.

[0052] Next, the signal processing unit 129 calculates the second displacement L based on the following equation (4). ２ Calculate. Here, n ２ = M ２ In this case, the second periodic pattern reading unit 124b is reading the vicinity of the discontinuity 114b of the periodic pattern 112b, so the signal processing unit 129 of the displacement measuring device 100 determines that it is reading the discontinuity 114b and does not perform displacement calculation.

[0053] Thus, the signal processing unit 129 processes the number of pulses n １ Based on the position information of the discontinuous portion 114a, it is possible to determine whether the first periodic pattern reading unit 124a is reading the discontinuous portion 114a. Furthermore, the signal processing unit 129 determines the number of pulses n ２ Based on the position information of the discontinuous portion 114b, it is possible to determine whether the second periodic pattern reading unit 124b is reading the discontinuous portion 114b.

[0054] Next, the signal processing unit 129 calculates the displacement L based on the following equation (5). Here, n １ = M １In this case, the first periodic pattern reading unit 124a reads the joint portion (discontinuity portion 114a) of the periodic pattern 112a, so the measurement value of the second periodic pattern reading unit 124b is adopted as the displacement. In other words, when calculating the displacement L, if the first periodic pattern reading unit 124a reads the discontinuity portion 114a, the second electrical signal 132 is used as the electrical signal at that reading position. And then n ２ = M ２ In this case, the second periodic pattern reading unit 124b reads the joint portion (discontinuity portion 114b) of the periodic pattern 112b, and therefore adopts the measurement value of the first periodic pattern reading unit 124a as the displacement. In other words, when calculating the displacement L, if the second periodic pattern reading unit 124b reads the discontinuity portion 114b, the first electrical signal 131 is used as the electrical signal at that reading position.

[0055] Thus, in calculating the displacement L, the electrical signal output from the reading unit that reads the periodic pattern 112, among the first periodic pattern reading unit 124a and the second periodic pattern reading unit 124b, is used to calculate the displacement L. In other words, the signal processing unit 129 calculates the displacement L by using the first electrical signal and the second electrical signal depending on the position of the discontinuity 114a and the discontinuity 114b.

[0056] Furthermore, in other locations (continuous sections), the first displacement L １ and the second displacement L ２ The average value is adopted as the displacement. The displacement L calculated by the signal processing unit 129 is then output from the input / output unit 128 to an external device (for example, an information processing device or a server) outside the displacement measuring device 100.

[0057] As described above, the signal processing unit 129 calculates the displacement L using the electrical signals output from the reading unit of the first periodic pattern reading unit 124a and the second periodic pattern reading unit 124b that have not read the discontinuous portion of the periodic pattern 112. This makes it possible for the displacement measuring device 100 in this embodiment to avoid signal instability at the discontinuous portion.

[0058] Furthermore, the displacement measuring device 100 stores phase information Δθ in the storage unit 130. １ , Δθ ２ and the joint spacing d １ d ２ Because the displacement is calculated using this information, even when switching between the measured values ​​of multiple reading units, it is possible to suppress jumps in the measured values. As a result, the displacement measuring device 100 in this embodiment can measure displacement with high accuracy even when there are discontinuities in the periodic pattern of the scale.

[0059] Furthermore, the displacement measuring device 100 does not replace the pulse signal with a reference clock or dummy signal when calculating the displacement, and can measure the displacement even if the displacement speed is not constant. In other words, the displacement measuring device 100 in this embodiment is a device that can calculate the displacement of at least the position of the rotating body 1 relative to the substrate 120, regardless of the displacement speed.

[0060] In Embodiment 1, the case where the scale 111 has discontinuities (114a, 114b) in each of its two periodic patterns (112a, 112b) was described. However, the invention is not limited to this, and for example, the scale 111 may be configured to have one periodic pattern and one discontinuity. In this case, for example, the substrates on which sensors 121a and 121b are mounted are separate (one substrate is prepared for each sensor). Then, by changing the position (measurement position) of one of the two sensor (121a, 121b) placement positions, it is possible to avoid signal instability at the discontinuity, as described above. In this case, for example, the substrate on which sensor 121a is mounted is in the position shown in Figure 1, and the substrate on which sensor 121b is mounted is positioned at a 90° or approximately 90° angle relative to the substrate on which sensor 121a is mounted. In this way, by changing the placement positions of the two sensors (121a, 121b), even if the scale 111 has a configuration of one periodic pattern and one discontinuity, it becomes possible to measure the displacement with high accuracy regardless of the discontinuity, similar to the displacement measuring device 100 of Embodiment 1.

[0061] <Embodiment 2> The displacement measuring device 200 in Embodiment 1 will be described below with reference to Figures 7 to 15. Figure 7 is a diagram showing the displacement measuring device 200 of Embodiment 2. Figure 7(A) is a diagram showing the XZ plane view of the displacement measuring device 200. Figure 7(B) is a diagram showing the YZ plane view of the displacement measuring device 200. In the displacement measuring device 200 of Embodiment 2, detailed explanations of the same configuration and similar processing in each functional part as in the displacement measuring device 100 of Embodiment 1 will be omitted.

[0062] The displacement measuring device 200 includes a scale 211. The scale 211 is fixed on the surface of the rotating body (second member) 1. The scale 211 is, for example, a film scale and is fixed to the rotating body 1 by adhering it with double-sided tape. The scale 211 includes a periodic pattern 212 (continuous section), an index pattern 213, and discontinuous sections (discontinuous section 214a, discontinuous section 214b). The periodic pattern 212 includes a periodic pattern (first periodic pattern) 212a and a periodic pattern (second periodic pattern) 212b. Note that periodic patterns 112a and 112b are included in periodic pattern 112 and therefore function as a continuous section in the same way as periodic pattern 112. The index pattern 213 of Embodiment 2 includes an index pattern 213a (first index pattern) and an index pattern 213b (second index pattern).

[0063] Periodic patterns 212a and 212b form periodic patterns that can be read by the first periodic pattern reading unit 224a and the second periodic pattern reading unit 224b, which will be described later. Discontinuous sections 214a and 214b do not form periodic patterns. Although discontinuous section 214b is not shown in Figure 7, it has the same configuration as discontinuous section 114b in Embodiment 1. That is, discontinuous sections 214a and 214b are the joint portions (connecting portions) in the periodic pattern when the scale 211 is fixed so as to be wrapped around the upper surface of the rotating body 1. As in Embodiment 1, discontinuous section 214a is provided on the periodic pattern 212a side, and discontinuous section 214b is provided on the periodic pattern 212b side. Furthermore, discontinuous sections 214a and 214b are configured to be in different positions in the circumferential direction.

[0064] The rotating body 1 is cylindrical in shape and is driven and controlled by a drive device (not shown) to rotate about an axis (parallel to the X-axis) of the rotating body 1 (rotating around a predetermined axis). The displacement measuring device 200 includes sensors 221a and 221b. Sensors 221a and 221b are mounted on a substrate (first component) 220.

[0065] Figure 8 illustrates sensors 221a and 221b of Embodiment 2. Figure 8(A) illustrates sensor 221a. Figure 8(B) illustrates sensor 221b. Sensor 221a includes a light source 223a, a first periodic pattern reading unit 224a for reading periodic pattern 212a, and a first index pattern reading unit 222a (fourth pattern reading unit) for reading index pattern 213a. For example, an LED can be used for the light source 223a. Sensor 221a is a device in which the light source 123a and the first periodic pattern reading unit 124a are mounted in the same package using a translucent resin (not shown). However, as in Embodiment 1, the light source 223a and the first periodic pattern reading unit 224a may be mounted individually on the substrate 220.

[0066] Furthermore, sensor 221b has the same structure as sensor 221a. That is, sensor 221b has a light source 223b, a second periodic pattern reading unit 224b for reading the periodic pattern 212b, and a second index pattern reading unit 222b (fifth pattern reading unit) for reading the index pattern 213b. Since sensor 221b has the same structure as sensor 221a, a detailed explanation is omitted.

[0067] Figure 9 is a diagram illustrating the index pattern reading unit 222 of Embodiment 2. The first index pattern reading unit 222a and the second index pattern reading unit 222b included in the index pattern reading unit 222 have the same structure. The index pattern reading unit 222 is a photodetector array having a structure similar to that of the periodic pattern reading unit 224. The index pattern reading unit 222 includes 32 photodetectors 225, each of which is arranged at equal intervals.

[0068] The assignment of A(+), B(+), A(-), and B(-) phases to the photodetectors 225 can be changed based on an external command. For the index pattern reading unit 222, the 1st to 8th photodetectors from the left are assigned the B(-) phase, the 9th to 16th photodetectors are assigned the A(+) phase, the 17th to 24th photodetectors are assigned the B(+) phase, and the 25th to 32nd photodetectors are assigned the A(-) phase. The eight photodetectors constituting each photodetector group are electrically connected to each other, and their outputs (currents) are added together and input to IV (current-voltage) conversion amplifiers (not shown) provided for each phase in the subsequent stage. The A(+) and A(-) phases are combined by a difference circuit (electrical circuit) (not shown) to generate an A-phase analog signal. Similarly, the B(+) and B(-) phases are combined by a difference circuit (not shown) to generate a B-phase analog signal. Furthermore, a subsequent electrical circuit (not shown) generates a sum signal (A+B signal) and a difference signal (A-B signal) by adding the A-phase analog signal and the B-phase analog signal together.

[0069] Furthermore, the index pattern reading unit 222 is equipped with a circuit that sums the four signals of A(+), B(+), A(-), and B(-) and outputs them as a SUM signal. The SUM signal increases in proportion to the intensity of the light incident on all the photodetectors 225. In other words, the SUM signal is a signal whose signal intensity increases in proportion to the amount of light received by the index pattern reading unit 222.

[0070] Finally, the first index pattern reading unit 222a reads the index pattern 213a and outputs a difference signal 235a and a sum signal 235b as a third electrical signal. The first index pattern reading unit 222a also outputs a SUM signal as a fifth electrical signal. The second index pattern reading unit 222b reads the index pattern 213b and outputs a difference signal 236a and a sum signal 236b as a fourth electrical signal.

[0071] Figure 10 shows the scale 211 of Embodiment 2 unfolded on a plane. Periodic patterns 212a and 212b are arranged offset to the left and right, as shown in Figure 10. Similarly, index patterns 213a and 213b are also arranged offset to the left and right on the plane, as shown in Figure 10.

[0072] The index pattern 213a is provided with a reflective portion 215a. Similarly, the index pattern 213b is provided with a reflective portion 215b. The index pattern 213a is configured such that the area other than the reflective portion 215a is a non-reflective portion. Similarly, the index pattern 213b is configured such that the area other than the reflective portion 215b is a non-reflective portion. As described above, the periodic pattern 212a is read by the first periodic pattern reading unit 224a, and the periodic pattern 212b is read by the second periodic pattern reading unit 224b. The index pattern 213a is read by the first index pattern reading unit 222a, and the index pattern 213b is read by the second index pattern reading unit 222b.

[0073] Figure 11 is a diagram illustrating the output signals of the first index pattern reading unit 222a. Figure 11 shows the signals output when the first index pattern reading unit 222a reads the vicinity of the edge of the reflective portion 215a provided on the index pattern 213a while scanning the scale 211. The first index pattern reading unit 222a outputs a difference signal 235a, a sum signal 235b, and a SUM signal 238.

[0074] Figure 11(A) shows the difference signal (A-B signal). The voltage of the difference signal increases as the optical image of the reflector 215a enters the photodetector assigned to the B(-) phase of the first index pattern reading unit 222a. The signal voltage is maximum when the optical image of the edge of the reflector 215a coincides with the center of the first index pattern reading unit 222a. Subsequently, as the optical image of the reflector 215a enters the photodetector assigned to the B(+) phase of the first index pattern reading unit 222a, the voltage of the difference signal decreases, and when all photodetectors are covered by the optical image of the reflector 215a, the signal voltage becomes zero.

[0075] Figure 11(B) shows a diagram representing the sum signal (A + B signal). The voltage of the sum signal decreases as the optical image of the reflector 215a enters the photodetector assigned to the B(-) phase of the first index pattern reading unit 222a. Subsequently, when the optical image of the reflector 215a enters the photodetector assigned to the A(+) phase of the first index pattern reading unit 222a, the signal voltage begins to increase. The signal voltage becomes zero when the optical image of the edge of the reflector 215a coincides with the center of the first index pattern reading unit 222a. The signal voltage continues to increase thereafter, and reaches its maximum when the optical image of the edge of the reflector 215a coincides with the boundary between the photodetectors assigned to B(+) and A(-). Subsequently, as the optical image of the reflecting section 215a enters the photodetector assigned to the A(-) phase of the first index pattern reading section 222a, the voltage of the sum signal decreases, and when all photodetectors are covered by the optical image of the reflecting section 215a, the signal voltage becomes zero.

[0076] Figure 11(C) shows a diagram representing the SUM signal. The SUM voltage increases as the optical image of the reflector 215a enters the photodetector assigned to the B(-) phase of the first index pattern reading unit 222a, and the signal voltage reaches its maximum when all photodetectors are covered by the optical image of the reflector 215a.

[0077] Similar to the first index pattern reading unit 222a, the second index pattern reading unit 222b also outputs a difference signal 236a and a sum signal 236b as the fourth electrical signal. In this embodiment, the reflective parts 215a and 215b of the scale 211 are offset to the left and right, so the difference signals 235a and 236a and the sum signals 235b and 236b are output at different times.

[0078] Figure 12 is a block diagram of the displacement measuring device 200 of Embodiment 2. The displacement measuring device 200 includes an input / output unit 228, a signal processing unit 229, and a storage unit 230, all mounted on an integrated circuit 250. The integrated circuit 250 can be, for example, a microcontroller, an ASIC, or an FPGA. The integrated circuit 250, along with sensors 221a, 221b, etc., is mounted on a substrate 120. Similar to Embodiment 1, the operation and processing of the displacement measuring device 200 are controlled by the integrated circuit 150 (it comprehensively controls each component of the displacement measuring device 200). Note that the input / output unit 228, the signal processing unit 229, and the storage unit 230 have the same configuration and process as the input / output unit 128, the signal processing unit 129, and the storage unit 130, so a detailed explanation is omitted.

[0079] The first periodic pattern reading unit 224a outputs a first electrical signal 231 by reading the periodic pattern 212a. Specifically, it outputs an A-phase analog signal 231a and a B-phase analog signal 231b as the first electrical signal 231. The A-phase analog signal 231a and the B-phase analog signal 231b are branched in the circuit; one is sent directly to the input / output unit 228 of the integrated circuit 250, and the other is input to the comparator 226a. The comparator 226a (signal generation unit) processes (compares) the A-phase analog signal 231a and the B-phase analog signal 231b in relation to the offset voltage to generate a first pulse signal 233, which is output to the input / output unit 228. Specifically, it generates an A-phase pulse signal 233a and a B-phase pulse signal 233b as the first pulse signal 233, which are output to the input / output unit 228. The A-phase pulse signal 233a and the B-phase pulse signal 233b are input to the input / output unit 228 of the integrated circuit 250.

[0080] Similarly, the second periodic pattern reading unit 224b outputs a second electrical signal 232 by reading the periodic pattern 212b. Specifically, it outputs an A-phase analog signal 232a and a B-phase analog signal 232b as the second electrical signal 232. The A-phase analog signal 232a and the B-phase analog signal 232b are branched in the circuit; one is sent directly to the input / output unit 228 of the integrated circuit 250, and the other is input to the comparator 226b. The comparator 226b (signal generation unit) processes (compares) the A-phase analog signal 232a and the B-phase analog signal 232b in relation to the offset voltage to generate a second pulse signal 234, which is output to the input / output unit 228. Specifically, it outputs an A-phase pulse signal 234a and a B-phase pulse signal 234b as the second pulse signal 234. The A-phase pulse signal 234a and the B-phase pulse signal 234b are input to the input / output unit 228 of the integrated circuit 250.

[0081] The substrate 220 of the displacement measuring device 200 is equipped with analog circuits 227a and 227b, which process the signals output from the first index pattern reading unit 222a and the second index pattern reading unit 222b. The analog circuit 227a (signal generation unit) receives the difference signal (A-B signal) 235a, the sum signal (A+B signal) 235b, and the SUM signal 238 output from the first index pattern reading unit 222a. The analog circuit 227b (signal generation unit) receives the difference signal (A-B signal) 236a and the sum signal (A+B signal) 236b output from the second index pattern reading unit 222b. In Embodiment 2, the comparators 226a and 226b and the analog circuits 227a and 227b function as signal generation units in the same manner as in Embodiment 1.

[0082] Figure 13 is a diagram illustrating the signal processing by the analog circuit 227 of Embodiment 2. Figure 13(A) is a diagram showing the relationship between the difference signal (A-B signal) and the threshold (threshold voltage). Preferably, the threshold voltage is set to a value of about half the peak voltage of the difference signal. The threshold voltage may be generated using a voltage divider circuit, or the circuit may be configured to increase or decrease in proportion to the amount of light received by the first periodic pattern reading unit 224a.

[0083] Figure 13(B) shows the gate signal generated by the analog circuit 227. The gate signal is generated by comparing the difference signal with the threshold signal voltage as a reference. Figure 13(C) shows the sum signal (A + B signal). Figure 13(D) shows the index signal generated by the analog circuit 227. The index signal is generated when the gate signal is High and the sum signal matches the reference voltage. The pulse width of the index signal can be preset to a desired value by the design of the analog circuit 227.

[0084] Analog circuit 227a processes the difference signal 235a and the sum signal 235b and outputs an index signal 237a. Similarly, analog circuit 227b processes the difference signal 236a and the sum signal 236b and outputs an index signal 237b.

[0085] Figure 14 is a diagram illustrating the signal processing by the analog circuit 227a of Embodiment 2. Figure 14(A) is a diagram showing the relationship between the SUM signal 238 and the threshold voltage. Preferably, the threshold voltage is set to a value slightly higher than half the peak voltage of the SUM signal 238. The threshold voltage may be generated using a voltage divider circuit, or the circuit may be configured to increase or decrease in proportion to the amount of light received by the first periodic pattern reading unit 224a.

[0086] Figure 14(B) shows the discontinuity determination signal 239 generated by the analog circuit 227. The discontinuity determination signal 239 is used to determine whether the first periodic pattern reading unit 224a is reading the discontinuity 214a. The discontinuity determination signal 239 is generated by comparing the SUM signal 238 with respect to a threshold voltage. The reflection portion 215a is within the range of the periodic pattern 212a. Therefore, if the discontinuity determination signal 239 is High, the first periodic pattern reading unit 224a is not in a position to read the discontinuity 214a. Conversely, if the discontinuity determination signal 239 is Low, the first periodic pattern reading unit 224a may be in a position to read the discontinuity 214a. On the other hand, since the discontinuous portion 214a and the discontinuous portion 214b are located at different positions on the circumference, similar to Embodiment 1, when the discontinuous portion determination signal 239 is Low, the second periodic pattern reading unit 224b is not in a position to read the discontinuous portion 214b.

[0087] Figure 15 is a diagram illustrating the input signals to the input / output unit 228 of the integrated circuit 250 of Embodiment 2. The input / output unit 228 receives four analog signals 231a, 231b, 232a, and 232b for phase A and phase B, and four pulse signals 233a, 233b, 234a, and 234b. In addition, the input / output unit 228 receives two index signals 237a and 237b and a discontinuity determination signal 239. Thus, a total of 11 signals are input to the input / output unit.

[0088] Note that in Figure 15, the B-phase analog signals 231b, 232b, 233b, and 234b, which are not shown for the sake of simplicity, are signals whose phase is shifted by approximately 90° relative to the A-phase analog signals 231a, 232a, 233a, and 234a. Also, in Figure 15, for the sake of simplicity, only 10 pulses each are output per revolution for the A-phase pulse signals 233a and 234a. However, in reality, many pulses are generated per revolution in order to measure displacement with high precision. Furthermore, Figure 15 shows the case where the displacement speed is constant, similar to Embodiment 1. However, Embodiment 2 can also be applied to cases where the displacement speed is not constant, similar to Embodiment 1.

[0089] When the first periodic pattern reading unit 224a and the second periodic pattern reading unit 224b are reading periodic patterns 212a and 212b, respectively, the A-phase analog signals 231a and 232a become sinusoidal signals. At this time, the A-phase pulse signals 233a and 234a generated by the comparator 226a become square wave signals.

[0090] On the other hand, when the first periodic pattern reading unit 224a and the second periodic pattern reading unit 224b are reading the discontinuous sections 214a and 214b, the signal amplitudes of the A-phase analog signals 231a and 232a decrease. At this time, the A-phase pulse signals 233a and 234a generated by the comparator 226a remain low, and no pulses are generated.

[0091] The index signals 237a and 237b each output two pulses for each rotation of the rotating body 1. This is because the first index pattern reading unit 222a and the second index pattern reading unit 222b output pulses when they read the edge positions at two locations on the left and right of the reflecting units 215a and 215b. In the case of Figure 15, when the first periodic pattern reading unit 224a reads a range that does not include the discontinuous portion 214a (i.e., it reads a continuous portion), eight A-phase pulse signals 233a are output between the two pulses of the index signal 237a. Similarly, when the second periodic pattern reading unit 224b reads a range that does not include the discontinuous portion 214b (i.e., it reads a continuous portion), eight A-phase pulse signals 234a are output between the two pulses of the index signal 237b. The number of pulses N output by the A-phase pulse signal 233a between the two pulses of the index signal is... １ (Number of first pulses) and the number of pulses N output by the A-phase pulse signal 234a ２ The (second pulse count) is stored in advance in the memory unit 230 included in the integrated circuit 250. In the case of Figure 15, N １ = N １ = 8.

[0092] The index signal 237a corresponds to the number of pulses n of the first periodic pattern reading unit 224a. １ It is used to reset it. Similarly, the index signal 237b is used to reset the number of pulses n of the second periodic pattern reading unit 224b. ２ It is used to reset. The input / output section 228 of the integrated circuit 250 sets the number of pulses n in accordance with the rising edge of the index signals 237a and 237b. １ and pulse count n ２ Reset each of them.

[0093] After the index signal 237a rises, when the A-phase pulse signal 233a rises, the signal processing unit 229 determines the number of pulses n corresponding to the output of the first periodic pattern reading unit 224a. １This is reset to 1. Also, after the index signal 237b rises, when the A-phase pulse signal 234a rises, the signal processing unit 229 determines the number of pulses n corresponding to the output of the second periodic pattern reading unit 224b. ２ It will be reset to 1.

[0094] Here, when the rotating body 1 rotates in the opposite direction, after the index signal 237a rises, the A-phase pulse signal 233a falls, and the signal processing unit 229 determines the number of pulses n corresponding to the output of the first periodic pattern reading unit 224a. １ This is reset to 8. Also, after the index signal 237b rises and the A-phase pulse signal 234a falls, the signal processing unit 229 determines the number of pulses n corresponding to the output of the second periodic pattern reading unit 224b. ２ It will be reset to 8.

[0095] Furthermore, the timing of the counter reset can be changed. For example, the timing of the counter reset may be changed to the rising and falling edges of the A-phase pulse signal. Alternatively, the counter may be reset at the rising or falling edge of the B-phase pulse signal.

[0096] Distance information d is information about the interval between the rising edge position of the first pulse of phase A pulse signal 233a and the rising edge position of the first pulse of phase A pulse signal 234a. １ This is stored in the memory unit 230 of the integrated circuit 250. Distance information d １ This corresponds to the relative phase information of the first electrical signal 231 and the second electrical signal 232. Also, distance information d is information about the amount of movement the scale moves when the rotating body 1 completes one rotation. ２ This is also stored in the memory unit 230 of the integrated circuit 250.

[0097] Distance information d １ and distance information d ２ The values ​​measured during calibration may be stored in the storage unit 230, or the stored values ​​may be updated by measuring them in real time.

[0098] The discontinuous portion determination signal 239 rises slightly later than the first pulse of the index signal 237a. By doing so, it is possible to avoid the discontinuous portion determination signal 239 from becoming High before the number of pulses n １ corresponding to the output of the first periodic pattern reading unit 224a is reset.

[0099] The displacement measuring device 200 starts displacement calculation based on an external command. Alternatively, the displacement measuring device 200 performs displacement calculation at a predetermined time interval. When the displacement calculation is started, the signal processing unit 229 reads information on the voltage values of the A-phase analog signals 231a and 231b, which are the first electrical signals 231, and the B-phase analog signals 232a and 232b, which are the second electrical signals 232, from the input / output unit 228.

[0100] Subsequently, the signal processing unit 229 calculates the phase angle θ １ and the phase angle θ ２ from the voltage values of the A-phase analog signals 231a and 231b, which are the first electrical signals 231, and the B-phase analog signals 232a and 232b, which are the second electrical signals 232. Note that since the method for calculating the phase angle is the same as that in the first embodiment, the description thereof is omitted.

[0101] Subsequently, the signal processing unit 229 reads the number of pulses n １ of the first pulse signal 233 and the number of pulses n ２ of the second pulse signal 234 from the input / output unit 228. Subsequently, the signal processing unit 229 reads the distance information d １ , d ２ stored in the storage unit 230. Subsequently, the signal processing unit 229 calculates the first displacement L １ based on the following formula (6).

[0102] Subsequently, the signal processing unit 229 calculates the second displacement L ２ based on the following formula (7). [[ID=​​​When the discontinuity determination signal 239 is High, the first periodic pattern reading unit 224a has not read the discontinuity 214a of the periodic pattern 212a, so the measurement value of the first periodic pattern reading unit 224a is adopted as the displacement. When the discontinuity determination signal 239 is Low, the first periodic pattern reading unit 224a may have read the discontinuity 214a of the periodic pattern 212a, so the measurement value of the second periodic pattern reading unit 224b is adopted as the displacement. Also, the second displacement L ２ The value of distance information d represents the amount of movement when the rotating body 1 completes one revolution. ２ If it becomes larger than d, ２ This is subtracted. The displacement L calculated by the signal processing unit 129 is output from the input / output unit 128 to an external device (for example, an information processing device or a server) outside the displacement measuring device 200.

[0104] Furthermore, the signal processing unit 129 may calculate, for example, an angular displacement L' instead of a distance displacement L. The angular displacement L' can be calculated using the following equation (9). Here, P represents the period of the periodic pattern 212. The signal processing unit 229 calculates the displacement using the electrical signals output from the reading unit that does not read the discontinuous portion of the periodic pattern 212, among the first periodic pattern reading unit 224a and the second periodic pattern reading unit 224b, similar to Embodiment 1. As a result, the displacement measuring device 200 in Embodiment 2 can avoid signal instability at the discontinuous portion, similar to Embodiment 1.

[0105] Furthermore, the displacement measuring device 200 uses distance information d stored in the storage unit 230. １ d ２ Because the displacement is calculated using this method, even when switching between the measured values ​​of multiple reading units, it is possible to suppress jumps in the measured values. As a result, the displacement measuring device 200 in this embodiment can measure displacement with high accuracy even when there are discontinuities in the periodic pattern of the scale.

[0106] Furthermore, the displacement measuring device 200 does not replace the pulse signal with a reference clock or dummy signal when calculating the displacement, and can measure the displacement even if the displacement speed is not constant. In other words, the displacement measuring device 200 in this embodiment is a device that can calculate the positional displacement or angular displacement of the rotating body 1 relative to the substrate 120, regardless of the displacement speed.

[0107] While preferred embodiments of this disclosure have been described in detail above, this disclosure is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of this disclosure as described in the claims.

[0108] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the embodiments described above to a system or device via a network or storage medium, and by a process in which one or more processors in the computer of the system or device read and execute the program. It can also be implemented by a circuit (e.g., ASIC) that implements one or more functions. (Cross-reference to related applications) This application claims the benefit of Japanese Patent Application No. 2024-157009, filed on September 10, 2024. The contents of the aforementioned Japanese Patent Application are incorporated herein by reference in their entirety.

[0109] 100 Displacement measuring device 111 Scale 112 Periodic pattern 114 Discontinuity section 124a First periodic pattern reading section 124b Second periodic pattern reading section 129 Signal processing section 130 Storage section

Claims

1. A displacement measuring device comprising: a scale including a continuous section on which a periodic pattern is formed and a discontinuous section on which the periodic pattern is not formed; a first pattern reading unit that reads the periodic pattern and outputs a first electrical signal; a second pattern reading unit that reads the periodic pattern and outputs a second electrical signal; a signal processing unit that calculates the positional or angular displacement of a second member relative to a first member based on the first and second electrical signals; and a storage unit that stores relative phase information of the first and second electrical signals, wherein the first and second pattern reading units are positioned so as not to read the discontinuous section simultaneously, and the signal processing unit calculates the displacement using the phase information stored in the storage unit and the electrical signals output from the reading unit of the first and second pattern reading units that read the continuous section.

2. The displacement measuring device according to claim 1, wherein the scale includes at least one index pattern, the displacement measuring device further comprises a signal generation unit, at least one third pattern reading unit that reads the index pattern and outputs a third electrical signal, and an input / output unit into which the first electrical signal and the second electrical signal are input, the signal generation unit processes the first electrical signal and the second electrical signal to generate a first pulse signal and a second pulse signal, and processes the third electrical signal to generate an index signal, and the input / output unit counts the number of first pulses related to the first pulse signal and the number of second pulses related to the second pulse signal, and resets the number of first pulses and the number of second pulses using the index signal.

3. The displacement measuring device according to claim 2, characterized in that the storage unit stores the position information of the discontinuity, and the signal processing unit uses the first pulse count, the second pulse count, and the position information of the discontinuity to determine whether the first pattern reading unit and the second pattern reading unit are reading the discontinuity.

4. The displacement measuring device according to claim 1, wherein the scale includes a first index pattern and a second index pattern, the displacement measuring device further comprises a signal generation unit, a fourth pattern reading unit that reads the first index pattern and outputs a third electrical signal, a fifth pattern reading unit that reads the second index pattern and outputs a fourth electrical signal, and an input / output unit that receives the first electrical signal and the second electrical signal, the signal generation unit processes the first electrical signal and the second electrical signal to generate a first pulse signal and a second pulse signal, and processes the third electrical signal and the fourth electrical signal to generate a first index signal and a second index signal, and the input / output unit counts the number of first pulses related to the first pulse signal and the number of second pulses related to the second pulse signal.

5. The displacement measuring device according to claim 4, characterized in that the input / output unit resets the first pulse count using the first index signal and resets the second pulse count using the second index signal.

6. The displacement measuring device according to claim 4, characterized in that the second member is a rotating body that rotates around a predetermined axis.

7. The displacement measuring device according to claim 6, characterized in that the scale is fixed to the surface of the rotating body.

8. The displacement measuring device according to claim 6, characterized in that the first index signal and the second index signal output two pulses each time the rotating body rotates once.

9. The displacement measuring device according to claim 4, characterized in that the fourth pattern reading unit outputs a fifth electrical signal used as a signal for determining whether the first pattern reading unit has read the discontinuity.

10. The displacement measuring device according to claim 9, characterized in that the fifth electrical signal is a signal whose signal intensity increases in proportion to the amount of light received by the fourth pattern reading unit.

11. The displacement measuring device according to claim 1, wherein the first member is a substrate, and the first pattern reading unit and the second pattern reading unit are attached to the substrate.

12. The displacement measuring device according to claim 2, characterized in that the third pattern reading unit is attached to the first member.

13. The displacement measuring device according to claim 6, wherein the periodic pattern includes a first periodic pattern and a second periodic pattern arranged such that the periodic pattern of the second periodic pattern is different from that of the first periodic pattern, the first pattern reading unit outputs a first electrical signal by reading the first periodic pattern, and the second pattern reading unit outputs a second electrical signal by reading the second periodic pattern.

14. The displacement measuring device according to claim 6, wherein the discontinuity portion has a first discontinuity portion provided on the first periodic pattern side and a second discontinuity portion provided on the second periodic pattern side, and the first discontinuity portion and the second discontinuity portion are located at different positions in the circumferential direction.

15. The displacement measuring device according to claim 14, characterized in that the signal processing unit calculates the displacement by using the first electrical signal and the second electrical signal separately according to the positions of the first discontinuity and the second discontinuity.

16. The displacement measuring device according to claim 14, characterized in that, when the signal processing unit calculates the displacement, if the first pattern reading unit reads the first discontinuity, the electrical signal at the reading position is the second electrical signal, and if the second pattern reading unit reads the second discontinuity, the electrical signal at the reading position is the first electrical signal.

17. The displacement measuring device according to claim 1, characterized in that the signal processing unit calculates the displacement using the phase information stored in the storage unit and the electrical signals output from the reading unit that reads the continuous portion of the first pattern reading unit and the second pattern reading unit, regardless of whether the displacement velocity is constant or not.

18. A displacement measuring device comprising: a scale including a continuous section on which a periodic pattern is formed and a discontinuous section on which the periodic pattern is not formed; a first pattern reading unit that reads the periodic pattern and outputs a first electrical signal; and a second pattern reading unit that reads the periodic pattern and outputs a second electrical signal, wherein the first pattern reading unit and the second pattern reading unit are positioned so as not to read the discontinuous section simultaneously, the displacement measuring device comprising: an input step in which the first electrical signal and the second electrical signal are input; a displacement calculation step in which the displacement of the positional displacement or angular displacement of the second member relative to the first member is calculated based on the input first electrical signal and the second electrical signal; and a storage step in which relative phase information of the first electrical signal and the second electrical signal is stored, wherein the displacement calculation step calculates the displacement using the stored phase information and the electrical signals output from the reading unit of the first pattern reading unit and the second pattern reading unit that reads the continuous section.

Images