Photoelectric detection unit, photoelectric encoder system, and motor

Abstract

This application discloses a photoelectric detection unit, a photoelectric encoder system, and a motor, wherein the photoelectric detection unit is used to detect scanning fringes that characterize grating displacement and convert them into an electrical signal characterizing grating disk displacement, wherein the electrical signal generated by the scanning fringes has harmonic components, and the geometric shape of the photoelectric detection unit is defined to be used to suppress the harmonic components. This application provides a photoelectric detection unit, a photoelectric encoder system, and a motor that have high area utilization efficiency, a high signal-to-noise ratio, reduced measurement errors, and can more effectively remove harmonic components.

Description

[Technical Field]

[0001] The present invention relates to the field of photoelectric sensors, and more particularly to photoelectric detection units, photoelectric encoder systems, and motors. [Background technology]

[0002] A photoelectric encoder is a sensor that uses a grating to achieve displacement-to-digital signal conversion, converting the amount of mechanical displacement on the output shaft into a pulse or digital signal via photoelectric exchange. Here, the amount of mechanical displacement may be linear displacement or rotational displacement (i.e., the rotation angle of the output shaft). The photoelectric encoder consists of a light source, a grating disk or linear grating, and a photoelectric detection device. A grating disk is a device that makes multiple slits in a circular disk of a certain diameter, and a linear grating is a device that makes multiple slits in a long plate of a certain length. Since the grating disk (or linear grating) moves synchronously with the output shaft (the type of motion is rotation or translation), the light emitted from the scanning unit forms a periodic scanning light pattern on the grating disk (or linear grating), and the scanning light pattern is detected by the photoelectric detection device to obtain an electrical signal that characterizes the amount of mechanical displacement of the grating disk (or linear grating), and further motion information of the output shaft, such as rotation angle, rotational speed, and translational displacement and velocity.

[0003] The electrical signals obtained by a photoelectric detection device detecting a scanning light pattern contain many harmonic components, which introduce noise into subsequent signal processing. These harmonic components can be removed or suppressed by designing the shape of the photoelectric detection unit included in the photoelectric detection device. A US patent, publication number US7268883B2, titled "Optoelectronic harmonically filtered detector system for a scanning unit," with reference to Figures 3-5, describes in its specification how the elements of a single photoelectric detector in an embodiment of the invention are shaped according to a desired harmonic suppression effect. However, the embodiments shown in the invention, for example in the embodiments shown in Figures 3 and 5, have complex curved elements in their geometric shape, requiring a single photoelectric detection unit to be divided into multiple segments along the lateral direction. Each segment is defined by a single function, and the geometric shape can be defined by combining multiple functions corresponding to multiple segments. When the shape needs to be adjusted, the function of each segment must be redefined, resulting in low adjustment efficiency. Furthermore, in the embodiment shown in Figure 3, both ends of the geometric shape are sharp, making machining difficult. If adjustment is necessary, the function of each segment must be redefined.

[0004] However, in actual products, it is often necessary to adjust the shape of the photoelectric detection unit in order to improve the installation density and area utilization rate of the photoelectric detection unit, or to eliminate shapes that are difficult to process, such as sharp angles.

[0005] Therefore, a photoelectric detection unit is needed that has a high area utilization rate, can easily remove sharp angles, and has high graphic adjustment efficiency. A photoelectric encoder system and motor including such a photoelectric detection unit are also required. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The objective of this invention is to provide a photoelectric detection unit, a photoelectric encoder system, and a motor that have high area utilization efficiency, facilitate the removal of sharp angles, and have high graphic adjustment efficiency. [Means for solving the problem]

[0007] To achieve the above objective, the photoelectric detection unit provided in the first embodiment is used to detect scanning fringe white spots characterizing grating displacement and convert them into electrical signals characterizing the relative displacement of the grating, wherein the period of the gaps in the grating is P, where the geometric shape of the photoelectric detection unit includes a first edge and a second edge, and the two vertices of the first edge and the second edge overlap each other to form a closed graphic, the geometric shape of the photoelectric detection unit is shown below, and the geometric shape of the photoelectric detection unit is after a sector-to-rectangle transformation, the first edge The edge is described by a first descriptive function, the second edge is described by a second descriptive function, or the geometric shape of the photoelectric detection unit is shown below, the first edge is described by the first descriptive function, the second edge is described by the second descriptive function, and the first descriptive function includes a first gradient function and a first harmonic rejection function, the second descriptive function includes a second gradient function and a second harmonic rejection function, and the difference between the first descriptive function and the second descriptive function is a function directly proportional to cosω0x, where ω0 = 2π / P, and x is a coordinate value taken along the grating periodic direction.

[0008] A photoelectric detection system provided in a second embodiment includes a light source, a grating having a plurality of measurement gaps and a gap period of P, and a photoelectric detection device capable of forming a relative displacement with respect to the grating, wherein the light source projects scanning fringe spots characterizing the relative displacement onto the photoelectric detection device, a plurality of photoelectric detection units are formed in the photoelectric detection device, the photoelectric detection unit includes a photoelectric detection device for detecting the scanning fringe spots and converting them into an electrical signal characterizing the relative displacement, and a processing circuit for converting the electrical signal into the relative displacement, wherein the geometric shape of the photoelectric detection unit includes a first edge and a second edge, and the two vertices of the first edge and the second edge overlap each other to form a closed graphic. The geometric shape of the photoelectric detection unit is formed as follows, and after the geometric shape of the photoelectric detection unit is transformed from sector to rectangle, the first edge is described by a first descriptive function and the second edge is described by a second descriptive function, or the geometric shape of the photoelectric detection unit is formed as follows, the first edge is described by a first descriptive function and the second edge is described by a second descriptive function, the first descriptive function includes a first gradient function and a first harmonic rejection function, the second descriptive function includes a second gradient function and a second harmonic rejection function, and the difference between the first descriptive function and the second descriptive function is a function directly proportional to cosω0x, where ω0 = 2π / P, and x is a coordinate value taken along the grating periodic direction.

[0009] The motor provided in the third embodiment is characterized by having the above-mentioned photoelectric detection system.

[0010] The embodiments of the present invention will become clearer with reference to the drawings above, and these drawings are used to interpret the embodiments of the present invention. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing a photoelectric encoder system according to one embodiment of the present invention. [Figure 2]It is a schematic diagram of a linear grating. [Figure 3] It is a schematic diagram showing a plurality of photoelectric detection units according to the first embodiment of the present invention. [Figure 4] It is a schematic diagram showing a single photoelectric detection unit according to the first embodiment of the present invention. [Figure 5] It is a schematic diagram showing two rows of photoelectric detection units according to the first embodiment of the present invention. [Figure 6] It is a schematic diagram of the principle of designing a geometric shape as shown in Figure 3 using a harmonic removal function, a slope function, and a center line adjustment function. [Figure 7] It is a schematic diagram showing a photoelectric detection unit according to the second embodiment of the present invention. [Figure 8] It is a schematic diagram showing a photoelectric detection unit according to the third embodiment of the present invention. [Figure 9] It is a schematic diagram showing a photoelectric detection unit according to the fourth embodiment of the present invention. [Figure 10] It is a schematic diagram showing a photoelectric detection unit according to the fifth embodiment of the present invention. [Figure 11] It is a schematic diagram showing a photoelectric detection unit according to the sixth embodiment of the present invention. [Figure 12] It is a schematic diagram showing a photoelectric detection unit according to the seventh embodiment of the present invention. [Figure 13] It is a schematic diagram of the principle of designing the geometric shape of a photoelectric detection unit using a harmonic removal function, a slope function, and a center line adjustment function. [Figure 14] It is a schematic diagram of the principle of designing the geometric shape of another photoelectric detection unit using a harmonic removal function and a slope function. [Figure 15] It is a schematic diagram of the principle of designing the geometric shape of another photoelectric detection unit using a harmonic removal function and a tilt function. [Figure 16] It is a schematic diagram of the principle of designing the geometric shape of yet another photoelectric detection unit using a harmonic removal function and a slope function. [Figure 17] It is a block diagram showing the configuration of a motor according to one embodiment of the present invention. [Modes for carrying out the invention]

[0012] The following description clearly and completely describes the technical solutions in embodiments of the present invention with reference to the drawings. It is clear that the described embodiments represent only some, and not all, embodiments of the present invention.

[0013] Typically, the modules of embodiments of the present invention described and shown in the drawings can be installed and configured in various different arrangements. Therefore, the detailed description of embodiments of the present invention provided below in the drawings does not limit the scope of the present invention for which protection is sought, but rather illustrates only preferred embodiments of the present invention. All other embodiments derived from embodiments of the present invention, without requiring creative work by those skilled in the art, are all within the scope of protection of this application.

[0014] The terms “including,” “having,” and other synonymous terms used in the various embodiments of the present invention below are used to indicate specific features, numbers, steps, operations, elements, modules, or combinations of the foregoing, and should not be understood as excluding the existence of one or more other features, numbers, steps, operations, elements, modules, or combinations of the foregoing, or increasing the possibility of one or more features, numbers, steps, operations, elements, modules, or combinations of the foregoing.

[0015] Furthermore, terms such as "first," "second," and "third" used in the embodiments of the present invention are used solely to distinguish between descriptions and cannot be understood as indicating or implying relative importance.

[0016] All terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the various embodiments of the present invention belong, unless otherwise specifically limited. Such terms (limited to those in commonly used dictionaries) shall not be interpreted as having the same meaning as in the context of the relevant technical field, or as having an ideal or full meaning, unless explicitly limited in the various embodiments of the present invention.

[0017] Referring to Figure 1, the photoelectric detection system 10 provided in an embodiment of the present invention includes a scanning unit 11 having a light source 111 and a collimating lens 112, an output shaft 13, and a grating disk 14 having gaps 141 that rotate synchronously with the output shaft 13, a photoelectric detection device 15, and a signal processing circuit 16, where the gaps 141 are periodically arranged light-transmitting fringes, more specifically, the periodically arranged fringes form periodically arranged transparent and opaque regions on the grating disk 14 ("transparent regions" are i.e., the "gaps"). The grating disk 14 can rotate in sync with the output shaft 13. Light emitted from the light source 111 is formed into parallel light by the collimating lens 112. As the grating disk 14 rotates, the parallel light passes through the grating disk 14 and forms periodically changing striped white spots (referred to as "scanning striped white spots" in the preceding text) on the photoelectric detection device 15. The photoelectric detection device 15 detects the scanning striped white spots and forms an electrical pulse signal. By processing the electrical pulse signal, information such as the current rotation angle, number of rotations, and rotation speed of the output shaft can be obtained.

[0018] The scanning unit 11 is not limited to the light source 111 and the collimating lens 112, but may also use other collimating light sources or scanning gratings, as long as they can form parallel light, and the specific form of the scanning unit 11 is not limited here. The grating disk 14 does not necessarily rotate synchronously in accordance with the output shaft 13, and the photoelectric detection device 15 may rotate synchronously in accordance with the output shaft 13. If a relative displacement is formed between the grating disk 14 and the photoelectric detection device 15, this relative displacement can be used to measure various information related to the rotation angle of the output shaft.

[0019] The photoelectric detection system 10 may take other forms and may include other components. For example, if the photoelectric detection system is used to detect the magnitude or velocity of translational displacement, it may include a light source, a linear grating, a photoelectric detection device and other corresponding components. The embodiments of this application are not limited to specific forms of the photoelectric detection system 10. In this patent application, when the term "grating" is used, it means including at least a disk-type grating (i.e., a grating disk) and a linear grating.

[0020] The grating disk 14 has M gaps 141, and the distance from the center of the rotation axis of the photoelectric detection device 15 is R (in this case, the photoelectric detection device 15 can be considered as a single point, and as is commonly used in the industry, the midpoint of the light-receiving part of the photoelectric detection device 15 can be taken, and the distance from this midpoint to the center of the rotation axis is R), then the period P of the gaps is 2πR / M. In a preferred embodiment, the shape of the gaps is sector-shaped or nearly sector-shaped, with two side edges eventually intersecting the center of the grating disk, although the shape of the top and bottom two edges may be standard circular arcs. Such shapes can be transformed from a shape in polar coordinates to a standard rectangle in Cartesian coordinates after a sector-to-rectangle transformation, and currently common harmonic suppression methods are based on grating gaps with a standard rectangular shape. However, in actual use, the length of the gaps in the grating is generally larger than the size of the photoelectric detection device 15, meaning that the shape of the two edges at the top and bottom ends of the grating gaps does not affect the light distribution projected onto the photoelectric detection device 15. Therefore, the shape of the two edges at the top and bottom ends of the grating gaps can be straight or other curves. Also, because the gaps in the grating are densely packed, the length of the gaps in a single grating is much larger than its width, so the gaps in a single grating can be considered rectangular. Even in the grating, using rectangular gaps instead of fan-shaped gaps results in a slightly lower harmonic suppression effect, and measurements can be performed similarly, but the intensity of the fundamental frequency component of the final electrical signal is slightly weaker. For this reason, the gaps 141 in the grating disk 14 can be approximated as fan-shaped. The light emitted from the light source 111 passes through the grating disk 14 and generates scanning fringe spots with a spatial period of P. Viewed from a single period, the geometric shape of a single spot is a sector or similar sector, and is projected onto the photoelectric detection device 15. The light perceived by each point in the photoelectric detection device 15 is a square wave light wave.

[0021] When the photoelectric detection system 10 is used to detect the magnitude and velocity of translational displacement, a linear grating is used. Referring to Figure 2, Figure 2 shows a linear grating 14a. Such gratings are generally used to measure translational displacement, and this linear grating has gaps 141a, and the period P of the gaps 141a can be calculated as L / M, where L is the total length of the grating and M is the total number of slits. Light emitted from the light source passes through the linear grating 14a, forms striped white spots, and is projected onto the corresponding photoelectric detection device, and the light sensed by each point in the photoelectric detection device 15 is a square wave light wave.

[0022] Referring to Figure 3, Figure 3 is a schematic diagram showing a plurality of photoelectric detection units according to the first embodiment of the present invention. The photoelectric detection device 15 includes a plurality of photoelectric detection units, and Figure 3 shows four of these photoelectric detection units 151, 152, 153, and 154 outputting sensor signals S1 to S4, respectively. It should be noted that when used in conjunction with a grating disk, the shapes of the photoelectric detection units 151, 152, 153, and 154 shown in Figure 3 differ slightly from the shapes of the actually manufactured photoelectric detection units, as they obtain the shape of the actually manufactured photoelectric detection units after undergoing a rectangle-sector transformation. In actual operation, the shape shown in Figure 3 is generally designed using mathematical formulas, and then the shape of the actually manufactured photoelectric detection unit is obtained after a rectangle-sector graphic transformation. The mathematically designed shape is a symmetrical, elongated "snapie" shape centered on the graphic center, as shown in Figure 3. After the rectangle-to-sector graphic conversion is performed, the shape of the actually manufactured photoelectric detection unit is similar to this "snapie" shape, but slightly deformed based on the "snapie" shape shown in Figure 3. These are common methods for those skilled in the art, so no further explanation is provided. For a photoelectric detection device used in conjunction with a linear grating 14a, it is possible to directly design the shape shown in Figure 3 (a "snapie" symmetrical around the shape center) using mathematical formulas and then manufacture the photoelectric detection device without the need to perform a rectangle-to-sector graphic conversion.

[0023] The sensor signals S1 to S4 generally have a predetermined phase difference from one another, preferably a 90-degree phase difference between adjacent signals among S1 to S4. S1 to S4 are input to the signal processing circuit 16 for processing, thereby obtaining physical quantities such as the rotation angle, rotation period, and rotation speed of the rotating shaft.

[0024] If the photoelectric detection device 15 is used with a linear grating 14a instead of the grating disk 14, signals S1 to S4 can be input to the corresponding signal processing circuit for processing, enabling the acquisition of physical quantities such as translational displacement and velocity, and a determination of whether or not the object moves to a specific position.

[0025] For the sake of simplicity, the following embodiments will describe a single photoelectric detection unit whose shape is a "snapy" symmetrical with respect to the graphic center, as shown in Figure 4. As those skilled in the art will understand, when the photoelectric detection device 15 is used in conjunction with a grating disk, the photoelectric detection unit designed according to the embodiments of this application needs to be fabricated in the photoelectric detection device 15 after a rectangle-to-sector transformation. When the photoelectric detection device 15 is used in conjunction with a linear grating 14a, the rectangle-to-sector transformation is not necessary, and the unit can be fabricated directly in the photoelectric detection device 15. Rectangle-to-sector transformation and its inverse transformation, i.e., sector-to-rectangle transformation, are both common techniques in the field of graphic transformation. Rectangle-to-sector transformation is used to transform graphics in a Cartesian coordinate system to graphics in a polar coordinate system, and sector-to-rectangle transformation is used to transform graphics in a polar coordinate system to graphics in a Cartesian coordinate system. A detailed explanation will be omitted here. U.S. Patent US7268883B2 can also be referenced for specific algorithms.

[0026] Referring to Figure 3, if W is the width of the widest part of the photoelectric detection unit 151 and d is the minimum gap width between adjacent photoelectric detection units (e.g., 151 and 152), then the following should be satisfied:

[0027] P=N(W+d) (3)

[0028] Here, P is the grating gap period, N is the number of photoelectric detection units that need to be placed in a single row within one grating gap period, and N is an integer greater than or equal to 1. Since the grating gap period extends in the X direction, the X direction is called the "grating period direction".

[0029] Since the scanning light wave sensed by each point in the photoelectric detection device 15 is a square wave, it can be expanded as a superposition of a fundamental frequency light wave (fundamental frequency component) and odd-numbered harmonic components.

[0030] rect(t)=A0+A1 / π·cos(ω0t)+A3 / π·cos(3ω0t)+A5 / π·cos(5ω0t)

[0031] Here, A0 is the average value after the square wave has been integrated with respect to time, and A i The amplitudes of each harmonic are given by the following, and the angular velocity of the fundamental frequency light wave is as follows:

[0032] ω0 = 2π / P

[0033] Based on the orthogonality of trigonometric functions, as shown in Figure 4, if the height value h in the Y direction of a single photoelectric detection unit 151 changes along the X axis in the COS(ω0x) manner, then when a square wave is irradiated, the electrical signal output from the single photoelectric detection unit 151 will have a non-zero fundamental frequency component, but all other harmonic components will be zero. In this way, multiple harmonic components can be suppressed or removed. This is a common method for harmonic suppression in this field, so an explanation will be omitted.

[0034] In conventional technology, the method for realizing that the height value of a single photoelectric detection unit 151 in the Y direction changes along the X axis using the COS(ω0x) method is complex and requires segmentation. That is, the x-coordinate range related to the shape of a single photoelectric detection unit 151 is segmented, and a shape edge change function is set for each segment. In other words, the x-coordinate range related to a single photoelectric detection unit 151 is divided into several segments, and a function indicating how the shape edge changes is set for each segment. If the shape of the optical detection unit needs to be adjusted due to reasons such as the appearance of hard-to-manufacture shapes like sharp angles at the vertices of the geometric shape, resulting in a large empty area around the sensor and low area utilization, it is necessary to re-select the shape edge function, resulting in low adjustment efficiency.

[0035] Herein, based on one embodiment of the present invention, a simple and easy-to-operate shape edge setting method is provided, making it easy to adjust the shape of the photoelectric detection unit and obtain a good shape according to specific requirements.

[0036] Referring to Figure 4, according to one embodiment of the present invention, the outer edges of the geometric shape of the photoelectric detection unit 151 include a first edge L1 and a second edge L2, and the first edge L1 and the second edge L2 are described by a first descriptive function and a second descriptive function, respectively. That is, in the embodiment of the present invention, the geometric shape of the photoelectric detection unit 151 includes two edges, and the two edges are described by one descriptive function, forming a closed geometric shape.

[0037] When describing the first edge L1 and the second edge L2 using descriptive functions, the variables on the X and Y axes of the descriptive functions are x and y, respectively. When x is at its minimum value, it corresponds to vertex A of the geometric shape, and when x is at its maximum value, it corresponds to vertex B of the geometric shape. As x changes from the minimum to the maximum value, y also changes continuously, forming a curve between the two vertices (if x and y are discrete values, this "continuous change" is actually a "preliminary continuous change" between very closely spaced discrete values). Thus, the first and second descriptive functions form the first edge L1 and the second edge L2 between the two vertices, respectively.

[0038] Furthermore, in one embodiment of the present invention, both the first and second descriptive functions include a slope function, a midline adjustment function, and a harmonic rejection function. Here, the harmonic rejection function is used to ensure that the difference between the first and second descriptive functions changes in the COS(ω0x) manner for any x value, the slope function is used to cause the photoelectric detection unit to have a constant orientation, and the midline adjustment function is used to adjust the midline of the shape of the photoelectric detection unit as needed, thereby fine-tuning the outer contour of the photoelectric detection unit. Preferred embodiments of the above functions are as follows, where y arc1 is the first descriptive function, and y arc2 This is the second descriptive function.

[0039] y arc1 =kx+A1COS(ω0x)+A2SIN(2ω0x) (1)

[0040] y arc2 =kx-A1COS(ω0x)+A2SIN(2ω0x) (2)

[0041] Here, ω0 = 2π / P, where P is the period of the grating gap. ω0 is the angular velocity of the fundamental frequency component contained in the square wave light wave. In the example shown in Figure 4, A1 = 80, A2 = 5, P = 240, and k = 2.

[0042] As those skilled in the art will understand, A1 and A2 are constants that are actually related to the size of the photoelectric detection unit, and they change depending on the size of the photoelectric detection unit. Those skilled in the art can select appropriate parameters according to the desired size of the photoelectric detection unit and other actual circumstances. Generally, if the size of the photoelectric detection unit is on the order of microns, then A1 and A2 are also on the order of microns, and if the size of the photoelectric detection unit is on the order of nanometers, then A1 and A2 are also on the order of nanometers. In this patent application, the grating period P is exemplary as a unitless constant such as 240 and 256, which means that the size of the photoelectric detection unit is also a unitless constant, and in this case A1 and A2 are also unitless constants. Such values ​​are merely examples and will be interpreted and explained in relation to the technical solutions of the embodiments of this patent. In actual applications, the values ​​of A1 and A2 can be adjusted according to the actual size value of P.

[0043] In equations (1) and (2), kx is the gradient function, and when k=0, the shape shown in Figure 3 deteriorates to the shape shown by the two X-rays in Figure 6(a), that is, the shape in which the gradient of the overall shape becomes 0. The shape shown in Figure 3 corresponds to k≠0, in which case the shape has a significant gradient, and this gradient contributes to placing the photoelectric detectors more densely within the limited space. At this time, the photoelectric detection unit 151 is actually tilted off by an α angle with respect to the Y direction, where 0≦α<90° and as follows.

[0044] k = tan(90-α) = H / D (10)

[0045] H is the height of the photoelectric detection unit 151 in the Y direction, and D is the width of the photoelectric detection unit 151 in the X direction, i.e., the difference between the maximum and minimum values ​​of the range of possible values ​​of x. Preferably, D = P / 2, so that the light projected through the gaps 141 in the grating covers just one photoelectric detection unit, at which point the harmonic rejection effect is highest. Here, for a photoelectric detection unit 15 with only one row of photoelectric detection units 151-154, the height H of the photoelectric detection unit 151 is usually less than half the height of the grating, to ensure that the photoelectric detection units 151-154 are in the position where the light is most concentrated. Depending on the required values ​​of H and D, an appropriate k value can be calculated. Empirically, a preferred range for k is 1 to 10.

[0046] It should be noted that while densely packed photoelectric detection units can be obtained by using a function that changes monotonically within the range of x (e.g., kx) as the slope function, the slope function is not limited to this form. Designers can select an appropriate slope function as needed. The slope function may also be a function that does not change monotonically within the range of x, if necessary, to obtain a photoelectric detection unit with a special curved shape. Furthermore, even when using a function that changes monotonically within the range of x, the slope function is not limited to a linear function kx, but may be a monotonically changing function of other forms, to obtain a photoelectric detection unit that is approximately long but has more shape changes at the edges as intended by the designer.

[0047] Furthermore, in calculation formulas (1) and (2), A2SIN(2ω0x) is the intermediate line adjustment function, and its function is to adjust the shape of edges L1 and L2 of the geometric shape of the photoelectric detection unit. Its specific function will be explained with reference to Figure 6. Note that other functions can also be used as the intermediate line adjustment function, and in order to maintain the closure at vertices A and B of the L1 and L2 curves, the function only needs to satisfy the condition that y is 0 when x is at its maximum and minimum values, for example, A2SIN(3ω0x), A2SIN(4ω0x), or other functions. The designer can adjust the shape of the photoelectric detection unit by adjusting the function form or the coefficients preceding it.

[0048] Furthermore, in calculation formulas (1) and (2), ±A1COS(ω0x) is the harmonic rejection function. Its effect is that by subtracting calculation formula (2) from calculation formula (1), a function directly proportional to COS(ω0x) can be obtained, and in this case, the height of the photoelectric detection unit will exhibit a change in COS(ω0x) within the entire range of x-value variation of the photoelectric detection unit. When a square wave is projected onto a photoelectric detection unit 151 having such a change in height, the electrical signal output from a single photoelectric detection unit 151 will have a non-zero fundamental frequency component, but all other harmonic components will be zero. In this way, multiple harmonic suppressions or rejections are achieved. The harmonic rejection function may have other forms, as long as a function directly proportional to COS(ω0x) can be obtained when subtracting calculation formulas (1) and (2). Different forms of harmonic rejection functions can also be used to adjust the edge of the photoelectric sensor unit.

[0049] Referring to Figure 4, the photoelectric detection unit 151 extends along the Y direction, while the scanning fringe white spots are incident on the photoelectric detection unit from the X direction.

[0050] Therefore, the desired height of a single photoelectric detection unit 151 in the Y direction can be obtained by the difference between the first description function and the second description function, i.e., by the above calculation formulas (1) to (2).

[0051] y arc1 -yarc2 = 2A1COS(2π / P·x) (11)

[0052] Specifically, in the embodiment shown in FIG. 4, the signals after suppressing the harmonic components output from the photoelectric detection units 151, 152, 153, and 154 are as follows respectively.

[0053] F1(x) = l·A1COS(2π / P·x + 0) (12)

[0054] F2(x) = l·A1COS(2π / P·x + 0.5π) (13)

[0055] F3(x) = l·A1COS(2π / P·x + π) (14)

[0056] F4(x) = l·A1COS(2π / P·x + 1.5π) (15)

[0057] Here, l is a constant. The actions of the coefficients A1 and A2 are respectively for adjusting the differences between the cosine function and the sine function in the above formulas (1) and (2). Specifically, up to the photoelectric detection unit 151, y arc1 and y arc2 both include the linear function kx. Therefore, it can be ensured that the geometric shape of the photoelectric detection unit 151 extends in the Y direction, and the coefficient k is used to adjust the inclination of the photoelectric detection unit. The coefficient A1 can adjust the width W of a single photoelectric detection unit 151, and the coefficient A2 can adjust the magnitudes of the apex angles and the flatness near the apex angles at the apexes A and B of the photoelectric detection unit 151.

[0058] Referring to FIG. 5, FIG. 5 shows that the photoelectric detection device 15 includes two columns of photoelectric detection units. The first column of photoelectric detection units includes four of the photoelectric detection units 151, 152, 153, and 154, and the second column of photoelectric detection units includes the other four photoelectric detection units 155, 156, 157, and 158.

[0059] Referring to Figure 6, Figure 6 is a schematic diagram illustrating the principle of designing the shape shown in Figure 3 using a harmonic rejection function, a slope function, and a mid-line adjustment function.

[0060] As shown in Figure 6(a), the X-rays are divided into two lines, upper and lower, which are curves corresponding to the harmonic rejection functions A1COS(ω0x) and -A1COS(ω0x), respectively. The Y line corresponds to the slope function kx, and the Z line corresponds to the mid-line adjustment function A2SIN(2ω0x). Here, A1=55, A2=15, k=5 / 3, P=256, and ω0=2π / P. In the shape enclosed by the two X-rays in Figure 6(a), the distance between the two X-rays changes according to the cosine function as x changes, which is the fundamental reason for achieving harmonic suppression or rejection. However, in practice, the shape enclosed by the two X-rays in Figure 6(a) is generally not used directly because the shape needs to maintain a constant orientation to improve the utilization rate of the sensor area or to simplify subsequent calculation algorithms.

[0061] Since the cosine function and the sine function differ in phase by only 90 degrees, the harmonic rejection function may also be the sine function. With technological advancements, it is possible to achieve harmonic rejection to some extent, or on a constant plane, without excluding the fact that the distance between the two upper and lower X-rays changes according to other functions. In this case, this function can be used directly as the harmonic rejection function instead of the cosine or sine function in the above embodiment, and the shape of the photoelectric detection unit can be designed using the shape adjustment method disclosed in the embodiment of this application.

[0062] In Figure 6(b), the two upper and lower X-rays correspond to kx + A1COS(ω0x) and kx - A1COS(ω0x), respectively. This is equivalent to adding kx to the curves A1COS(ω0x) and -A1COS(ω0x), respectively, and introducing a slope into the graphic composed of the two X-rays in Figure 6(a). Therefore, a function capable of producing such an effect is called a "slope function". Here, the midpoint Y of the shape in Figure 6(b) is kx, and the "midpoint" means that at each possible value of x, the distance in the y-direction from the midpoint Y to the two upper and lower X-rays (corresponding to the upper and lower outer edges of the shape, respectively) is A1COS(ω0x).

[0063] In Figure 6(c), the Z line is a curve obtained by substituting A2SIN(2ω0x) into the Y line in Figure 6(b), and it is also a midpoint of the shape. That is, for each possible value of x, the y-direction distance from line Z to the two upper and lower X lines is A1COS(ω0x). Clearly, the effect of substituting A2SIN(2ω0x) is to fine-tune the midpoint Y in the shape of Figure 6(b), thereby enabling fine-tuning of the outer edge of the shape. A function that can produce such an effect is called a "midpoint adjustment function". In this case, the two upper and lower curves X in Figure 6(c) correspond to kx+A1COS(ω0x)+A2SIN(2ω0x) and kx-A1COS(ω0x)+A2SIN(2ω0x), respectively.

[0064] Figures 6(a) to 6(c) show an example illustrating the principle of adjusting the shape of a photoelectric detection unit according to an embodiment of the present invention. The principle involves using a gradient function to make the shape "upright" or obtain other orientations, and then fine-tuning the shape's midline by taking an appropriate midline adjustment function, thereby adjusting the curvature of each part of the shape's edge. In this method, the designer selects an appropriate gradient function to obtain the approximate orientation based on the desired shape's schematic, and then fine-tunes the shape's outer edge curve by selecting an appropriate midline adjustment function until the desired shape is obtained. Generally, when it is necessary to make the shape "upright," the gradient function is a function that changes monotonically within the range of possible values ​​of x, and the rate of change of this function determines the degree to which the shape is "upright." If the range of possible values ​​of x is symmetrical with respect to the x-axis origin, an odd function can be used as the gradient function. The midline adjustment function is used as needed, and if the harmonic rejection function can be combined with the gradient function to obtain the appropriate shape, the midline adjustment function may not be used. Next, we will show some other examples of slope functions and midline adjustment functions with reference to Figures 13 to 15.

[0065] In the preferred embodiments shown in calculation formulas (1) and (2), the shape can be finely adjusted by adjusting parameters A1 and A2. Referring to Figures 7 to 12, the influence of coefficients A1 and A2 in calculation formulas (1) and (2) on the shape of the photoelectric detection unit will be explained.

[0066] In Figure 7, the possible values ​​for each parameter are k=1, A2=5, A1=42, and P=268. In Figure 8, the possible values ​​for each parameter are k=1, A2=10, A1=42, and P=268. In Figure 9, the possible values ​​for each parameter are k=1, A2=20, A1=42, and P=268.

[0067] As is clear from Figures 7-9, if the other coefficients do not change, the flatness near the vertex angle can be easily adjusted by adjusting the coefficient A2. If A1 = 42 and does not change, the flatness gradually deteriorates as the value of A2 gradually increases from 5, 10, and 20. Therefore, the first descriptive function yarc1 and the second descriptive function y arc2 This allows for the rapid acquisition of the desired flatness of the geometric shape of the photoelectric detection unit 151. Furthermore, when the flatness is good, the manufacturing of the photoelectric detection unit 151 becomes easier, and when multiple such photoelectric detection units 151 are arranged in a row, the space utilization rate increases.

[0068] In Figure 10, the possible values ​​for each parameter are k=1, A2=10, A1=35, and P=268. In Figure 11, the possible values ​​for each parameter are k=1, A2=10, A1=30, and P=268. In Figure 12, the possible values ​​for each parameter are k=1, A2=10, A1=20, and P=268.

[0069] As is clear from Figures 10-12, if the other coefficients do not change, the width W of the photoelectric detection unit 151 can be easily adjusted by adjusting coefficient A1, and a desired width W shape can be obtained.

[0070] If the other coefficients remain unchanged, the width W can be easily adjusted by adjusting coefficient A1. If A2 = 10 and remains unchanged, the width W gradually narrows as the value of A1 gradually decreases from 35, 30, and 20. As the width W narrows, the vertex angle of the photoelectric detection unit becomes acutely sharp, and acute angles are difficult to process during manufacturing. Therefore, it is necessary to select an appropriate A1 to avoid acute angles at the vertex and obtain the desired width W of the photoelectric detection unit 151.

[0071] Figures 13 to 16 show examples using other forms of slope functions and mid-line adjustment functions.

[0072] In Figure 13(a), the two X-rays are curves corresponding to the harmonic rejection functions A1COS(ω0x) and -A1COS(ω0x), respectively, and the Y line is the slope function (5 / 3)x-0.0001x 3The curve corresponds to the mid-line adjustment function A2SIN(2ω0x), and the Z line is the curve corresponding to the mid-line adjustment function A2SIN(2ω0x). Here, A1=55, A2=15, P=256, and ω0=2π / P. In Figure 13(b), the two upper and lower X-rays are A1COS(ω0x) and -A1COS(ω0x) respectively, with a slope function (5 / 3)x-0.0001x 3 The curve obtained by superimposing these two values ​​is such that the Y line in Figure 13(b) coincides with the Y line in Figure 13(a), and the slope function is (5 / 3)x-0.0001x 3 This is the corresponding curve, and in fact, it is the midpoint line of the shape shown in Figure 13(b). As can be seen from the above, the combination of the harmonic rejection function and the slope function already yields a good shape, and the slope and thickness of this shape are suitable for the lateral arrangement of multiple photoelectric detection units, and there are no obvious acute angles, so such a shape can be used. In Figure 13(c), the midpoint line adjustment function A2SIN(2ω0x) is inserted, and line Z is the midpoint line. By comparing line Z with the midpoint line Y in Figure 13(b), it can be seen that the midpoint line shape is adjusted, which further changes the shape of the two curves above and below. The shape shown in Figure 13(c) is also a shape suitable for use.

[0073] In Figure 14(a), the two X-rays are curves corresponding to the harmonic rejection functions A1COS(ω0x) and -A1COS(ω0x), respectively, and the Y line is the slope function -0.0001x 3 This is the corresponding curve. Here, A1=55, P=256, and ω0=2π / P. In Figure 14(b), the two upper and lower X-rays are A1COS(ω0x) and -A1COS(ω0x) respectively, with a slope function of -0.0001x. 3 The curve obtained by superimposing the two is such that the Y line in Figure 14(b) coincides with the Y line in Figure 14(a), and the slope function is -0.0001x 3This is a curve that corresponds to the shape shown in Figure 14(b), and is actually the midpoint of the shape shown in Figure 14(b). The shape shown in Figure 14(b) is similar to a rectangle and is easy to arrange in some cases (if this shape is used, one row can contain only two photoelectric detection units within one grating period. Generally, it is desirable for a photoelectric detection device to contain four photoelectric detection units within one grating period for the sake of simplicity in subsequent algorithms, and the shape shown in Figure 14(b) can be arranged in two rows to satisfy this requirement, or one can arrange only two photoelectric detection units within each grating period without pursuing the sake of simplicity in subsequent algorithms), and is a usable shape that does not have hard-to-manufacture sharp angles.

[0074] In Figure 15(a), the two X-rays are curves corresponding to the harmonic rejection functions A1COS(ω0x) and -A1COS(ω0x), respectively, and the Y line is the slope function -0.01x 2 This is the corresponding curve. Here, A1=55, P=256, and ω0=2π / P. In Figure 15(b), the two upper and lower X-rays are A1COS(ω0x) and -A1COS(ω0x) respectively, with a slope function of -0.01x. 2 The result obtained by superimposing these values ​​is that the Y line in Figure 15(b) coincides with the Y line in Figure 15(a), and the slope function is -0.01x 2 This is the corresponding curve, and in practice, it is the midpoint of the shape shown in Figure 15(b). The shape shown in Figure 15(b) does not have sharp corners that are difficult to manufacture, is a usable shape, and a suitable method can be realized that includes four photoelectric detection units within one grating period by leaving two rows.

[0075] In Figure 16(a), the two X-rays are curves corresponding to the harmonic rejection functions A1COS(ω0x) and -A1COS(ω0x), respectively, and the Y line is the slope function (5 / 3)x-0.01x 2 -0.0001x 3 This is the corresponding curve. Here, A1=55, A2=15, P=256, and ω0=2π / P. In Figure 16(b), the two upper and lower X-rays are A1COS(ω0x) and -A1COS(ω0x) respectively, with a slope function (5 / 3)x-0.01x 2-0.0001x 3 The result obtained by superimposing these is that the Y line in Figure 16(b) coincides with the Y line in Figure 16(a), and the slope function is (5 / 3)x-0.01x 2 -0.0001x 3 This is a corresponding curve and is actually the midpoint of the shape shown in Figure 16(b). The shape shown in Figure 16(b) has no sharp corners that are difficult to manufacture, and the upper and lower ends of the shape are of different sizes, so that the larger end of the mirror image shape obtained by inverting the shape vertically by 180 degrees fits perfectly into the empty area below the shape. In this way, a pair of shapes are arranged repeatedly in the horizontal direction, which improves the density of the arrangement and enables a suitable method to include four photoelectric detection units within one grating period.

[0076] As technology advances, the field of optical sensors may give rise to other requirements regarding the shape and orientation of photoelectric detection units, all of which can be easily designed by the methods disclosed in the embodiments of this application.

[0077] As should be understood, the values ​​of P and the function parameters in each of the above embodiments are illustrative only, and in accordance with the principles disclosed in the embodiments of the present application, those skilled in the art can adjust the function parameters used based on the grating period P actually used and the size, arrangement, and density of the required shape.

[0078] In one embodiment, referring to Figure 17, the present invention provides a motor 100, on which a photoelectric detection system 10 is arranged.

[0079] Specifically, referring to Figures 1, 3, and 13, the photoelectric detection system 10 includes a scanning unit 11 having a light source 111 and a collimating lens 112, an output shaft 13, a grating disk 14 having a measuring gap 141 that rotates synchronously with the output shaft 13, a photoelectric detection device 15, and a signal processing circuit 16, where the gap 141 is a periodically arranged light-transmitting fringe, more specifically, the periodically arranged fringe forms periodically arranged transparent and opaque regions ("transparent regions" are i.e., the "gap") on the grating disk 14, and the grating disk 14 can rotate synchronously with the output shaft 13. In the scanning unit 11, light emitted from the light source 111 passes through the collimating lens 112 to form parallel light, and as the grating disk 14 rotates, the parallel light passes through the grating disk 14 to form a pulse signal to the photoelectric detection device 15, and by processing the pulse signal, information such as the angle, number of rotations, and rotation speed of the output shaft can be reflected.

[0080] The photoelectric detection system 10 may take other forms and may include other components. For example, if the photoelectric detection system is used to detect the magnitude and velocity of translational displacement, it may include a light source, a linear grating, a photoelectric detection device and other corresponding components. The embodiments of this application are not limited to specific forms of the photoelectric detection system 10.

[0081] The photoelectric detection device 15 is used to detect scanning light characterizing the displacement of the grating disk 14 and convert it into an electrical signal characterizing the rotational displacement of the grating disk 14, wherein the photoelectric detection device 15 includes a plurality of photoelectric detection units 151, the geometric shape of the photoelectric detection unit 151 includes a first edge L1 and a second edge L2, the first edge L1 is described by a first description function, the second edge L2 is described by a second description function, both the first and second description functions include a gradient function, a midline adjustment function and a harmonic rejection function, and the photoelectric detection unit removes harmonic components by the difference between the first and second description functions and suppresses the harmonic components.

[0082] The embodiments disclosed herein are merely preferred examples of the present invention and, naturally, do not limit the scope of the claims of the present invention. Accordingly, equivalent modifications made based on the claims of the present invention still fall within the scope of the present invention.

[0083] (Note) (Note 1) A photoelectric detection unit, The photoelectric detection unit is used to detect scanning fringe spots that characterize the grating displacement and convert them into an electrical signal that characterizes the relative displacement of the grating, wherein the period of the gap in the grating is P, where, The geometric shape of the photoelectric detection unit includes a first edge and a second edge, and the two vertices of the first edge and the second edge overlap each other to form a closed graphic. The geometric shape of the photoelectric detection unit is shown below, and after the geometric shape of the photoelectric detection unit is transformed from sector to rectangle, the first edge is described by the first description function, the second edge is described by the second description function, or the geometric shape of the photoelectric detection unit is shown below, the first edge is described by the first description function, the second edge is described by the second description function, and A photoelectric detection unit characterized in that the first description function includes a first gradient function and a first harmonic rejection function, the second description function includes a second gradient function and a second harmonic rejection function, and the difference between the first description function and the second description function is a function directly proportional to cosω0x, where ω0 = 2π / P, and x is a coordinate value taken along the grating periodic direction.

[0084] (Note 2) The photoelectric detection unit according to Appendix 1, characterized in that the first description function further includes a first intermediate line adjustment function, and the second description function further includes a second intermediate line adjustment function.

[0085] (Note 3) The photoelectric detection unit according to Appendix 1, characterized in that both the first harmonic rejection function and the second harmonic rejection function are functions selected from the group consisting of sine and cosine functions.

[0086] (Note 4) The photoelectric detection unit according to Appendix 3, characterized in that the first harmonic rejection function is A1cosω0x, the second harmonic rejection function is -A1cosω0x, and A1≠0.

[0087] (Note 5) The photoelectric detection unit according to Appendix 2, characterized in that both the first intermediate line adjustment function and the second intermediate line adjustment function are functions selected from the group consisting of sine and cosine functions.

[0088] (Note 6) The photoelectric detection unit according to Appendix 2, characterized in that both the first and second intermediate line adjustment functions are A2sin2ω0x and A2≠0.

[0089] (Note 7) The photoelectric detection unit according to Appendix 1, characterized in that both the first slope function and the second slope function are functions that monotonically increase within the range of possible values ​​of x in the closed graphic.

[0090] (Note 8) The photoelectric detection unit according to Appendix 7, characterized in that the range of possible values ​​for x in the closed graphic is symmetric with respect to the origin of the x-axis, and both the first slope function and the second slope function are odd functions within the range of possible values ​​for x in the closed graphic.

[0091] (Note 9) The photoelectric detection unit according to Appendix 8, characterized in that both the first slope function and the second slope function are kx and k≠0.

[0092] (Note 10) The photoelectric detection unit according to Appendix 1, characterized in that the scanning stripe white spots enter the photoelectric detection unit from the first edge and exit from the second edge to suppress harmonic components attached to the scanning light signal.

[0093] (Note 11) The first description function described above is, y arc1 =kx+A1COS(ω0x)+A2SIN(2ω0x) (1), The second descriptive function is, y arc2 =kx-A1COS(ω0x)+A2SIN(2ω0x) (2), The photoelectric detection unit according to any one of the appendices 1 to 10, characterized in that k ≠ 0 and A1 ≠ 0.

[0094] (Note 12) A photoelectric detection system, Light source and A grating having multiple measurement gaps and a gap period of P, A photoelectric detection device can form a relative displacement between the photoelectric detection device and the grating, and the light source projects scanning fringe white spots that characterize the relative displacement onto the photoelectric detection device, and a plurality of photoelectric detection units are formed in the photoelectric detection device, and the photoelectric detection units detect the scanning fringe white spots and convert them into electrical signals that characterize the relative displacement. The circuit includes a processing circuit for converting the electrical signal into the relative displacement, Here, The geometric shape of the photoelectric detection unit includes a first edge and a second edge, and the two vertices of the first edge and the second edge overlap each other to form a closed graphic. The geometric shape of the photoelectric detection unit is shown below, and after a sector-to-rectangle transformation is performed on the geometric shape of the photoelectric detection unit, the first edge is described by the first description function, and the second edge is described by the second description function, or the geometric shape of the photoelectric detection unit is shown below, the first edge is described by the first description function, and the second edge is described by the second description function, A photoelectric detection system characterized in that the first description function includes a first gradient function and a first harmonic rejection function, the second description function includes a second gradient function and a second harmonic rejection function, and the difference between the first description function and the second description function is a function directly proportional to cosω0x, where ω0 = 2π / P, and x is a coordinate value taken along the grating periodic direction.

[0095] (Note 13) A motor characterized by having the photoelectric detection system described in Appendix 12.

Claims

1. A photoelectric detection unit, The photoelectric detection unit is used to detect scanning fringe spots that characterize the grating displacement and convert them into an electrical signal that characterizes the relative displacement of the grating, wherein the period of the gap in the grating is P, and here, The geometric shape of the photoelectric detection unit includes a first edge and a second edge, and the two vertices of the first edge and the second edge overlap each other to form a closed graphic. The geometric shape of the photoelectric detection unit is shown below, and after the geometric shape of the photoelectric detection unit is transformed from sector to rectangle, the first edge is described by the first description function, the second edge is described by the second description function, or the geometric shape of the photoelectric detection unit is shown below, the first edge is described by the first description function, the second edge is described by the second description function, and The first description function includes a first slope function and a first harmonic rejection function, the second description function includes a second slope function and a second harmonic rejection function, and the difference between the first and second description functions is cosω ０ It is a function directly proportional to x, where ω ０ A photoelectric detection unit characterized by having a coefficient of 2π / P, where x is a coordinate value taken along the grating periodic direction.

2. The photoelectric detection unit according to claim 1, characterized in that the first description function further includes a first intermediate line adjustment function, and the second description function further includes a second intermediate line adjustment function.

3. The photoelectric detection unit according to claim 1, characterized in that both the first harmonic rejection function and the second harmonic rejection function are functions selected from the group consisting of sine and cosine functions.

4. The first harmonic rejection function is A １ cosω ０ x is such that the second harmonic rejection function is -A １ cosω ０ x and A １ The photoelectric detection unit according to claim 3, characterized in that ≠ 0.

5. The photoelectric detection unit according to claim 2, characterized in that both the first intermediate line adjustment function and the second intermediate line adjustment function are functions selected from the group consisting of sine and cosine functions.

6. Both the first intermediate line adjustment function and the second intermediate line adjustment function are A ２ sin 2ω ０ x, and A ２ ≠ 0, The photoelectric detection unit according to claim 2, characterized by this.

7. The photoelectric detection unit according to claim 1, characterized in that both the first slope function and the second slope function are functions that monotonically increase within the range of possible values ​​of x in the closed graphic.

8. The photoelectric detection unit according to claim 7, characterized in that the range of possible values ​​for x in the closed graphic is symmetric with respect to the origin of the x-axis, and both the first slope function and the second slope function are odd functions within the range of possible values ​​for x in the closed graphic.

9. The photoelectric detection unit according to claim 8, characterized in that both the first slope function and the second slope function are kx and k ≠ 0.

10. The photoelectric detection unit according to claim 1, characterized in that the scanning stripe white spots enter the photoelectric detection unit from the first edge and exit from the second edge to suppress harmonic components attached to the scanning light signal.

11. The first descriptive function is, 9 ａｒｃ１ THIS IS １ RO(ω ０ 8)0 ２ 10(2ω ０ 9) (1)であり、 The second descriptive function is, 9 ａｒｃ２ 10.00 １ RO(ω ０ 8)0 ２ 10(2ω ０ 9) (2)であり、 Here, k ≠ 0, A １ A photoelectric detection unit according to any one of claims 1 to 10, characterized in that ≠ 0.

12. A photoelectric detection system, Light source and A grating having multiple measurement gaps and a gap period of P, A photoelectric detection device can form a relative displacement between the photoelectric detection device and the grating, and the light source projects scanning fringe white spots that characterize the relative displacement onto the photoelectric detection device, and a plurality of photoelectric detection units are formed in the photoelectric detection device, and the photoelectric detection units detect the scanning fringe white spots and convert them into electrical signals that characterize the relative displacement. The circuit includes a processing circuit for converting the electrical signal into the relative displacement, Here, The geometric shape of the photoelectric detection unit includes a first edge and a second edge, and the two vertices of the first edge and the second edge overlap each other to form a closed graphic. The geometric shape of the photoelectric detection unit is shown below, and after the geometric shape of the photoelectric detection unit is transformed from sector to rectangle, the first edge is described by the first description function and the second edge is described by the second description function, or the geometric shape of the photoelectric detection unit is shown below, the first edge is described by the first description function and the second edge is described by the second description function, The first description function includes a first slope function and a first harmonic rejection function, the second description function includes a second slope function and a second harmonic rejection function, and the difference between the first and second description functions is cosω ０ It is a function directly proportional to x, where ω ０ A photoelectric detection system characterized by the equation = 2π / P, where x is a coordinate value taken along the grating periodic direction.

13. A motor characterized by having the photoelectric detection system described in claim 12.

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