Photoelectric detection unit, photoelectric encoder system and electric motor

Abstract

Disclosed in the present application are a photoelectric detection unit, a photoelectric encoder system and an electric motor. The photoelectric detection unit is used for detecting scanning fringe light spots representing grating displacement and converting same into electrical signals representing grating disk displacement, wherein the electrical signals generated by the scanning fringe light spots carry harmonic components; and the geometric shape of the photoelectric detection unit is defined as being used for suppressing harmonic components. The photoelectric detection unit, the photoelectric encoder system and the electric motor in the present application have a high area utilization rate and a high signal-to-noise ratio, can reduce measurement errors, and can more efficiently eliminate harmonic components.

Description

Photoelectric detection unit, photoelectric encoder system and motor Technical Field

[0001] The present invention relates to the field of photoelectric sensing technology, and in particular to a photoelectric detection unit, a photoelectric encoder system and a motor. Background Art

[0002] A photoelectric encoder is a sensor that uses a grating to convert displacement into digital signals, converting the mechanical displacement of the output shaft into pulses or digital signals through photoelectric conversion. The mechanical displacement can be linear or rotational (i.e., the output shaft's rotation angle). A photoelectric encoder consists of a light source, a grating disk or linear grating, and a photoelectric detection device. A grating disk consists of multiple slits on a circular plate of a certain diameter, while a linear grating consists of multiple slits on a long plate of a certain length. Because the grating disk (or linear grating) moves synchronously with the output shaft (either in the form of rotation or translation), light emitted by the scanning unit passes through the grating disk (or linear grating) to form a periodic scanning light pattern. The photoelectric detection device detects this scanning light pattern, generating an electrical signal representing the mechanical displacement of the grating disk (or linear grating), and thus, information about the output shaft's motion, such as the rotation angle and rotational speed, as well as translational displacement and velocity.

[0003] The electrical signal generated by a photoelectric detection device detecting a scanning light pattern contains a significant number of harmonic components, which can introduce noise into subsequent signal processing. By designing the shape of the photoelectric detection elements within the photoelectric detection device, harmonic components can be eliminated or suppressed. U.S. Patent Publication No. US7268883B2, entitled "Optoelectronic Harmonic Filtered Detector System for a Scanning Unit," describes, with reference to Figures 3 to 5, how individual photoelectric detection elements in embodiments of the invention are shaped to achieve the desired harmonic suppression effect. However, the embodiments illustrated in the invention, such as those shown in Figures 3 and 5, have complex geometric surface elements. This requires dividing a single photoelectric detection element into multiple segments along the horizontal direction, each defined by a separate function. The geometric shape is defined by combining the functions corresponding to the multiple segments. Adjusting the shape requires redefining the function for each segment, resulting in low adjustment efficiency. Furthermore, the sharp ends of the geometric shape in the embodiment shown in Figure 3 make it difficult to manufacture, and any adjustments require redefining the function for each segment.

[0004] However, in actual products, in order to improve the arrangement density and area utilization of the photoelectric detection units, or to eliminate shapes that are difficult to process, such as sharp corners, the shapes of the photoelectric detection units often need to be adjusted.

[0005] Therefore, a photoelectric detection unit with high area utilization, easy elimination of sharp angles, and high pattern adjustment efficiency is needed, and a photoelectric encoder system and motor including such a photoelectric detection unit are also needed.

[0006] Summary of the Invention

[0007] The purpose of the present application is to provide a photoelectric detection unit, a photoelectric encoder system and a motor with high area utilization, easy elimination of sharp angles and high graphic adjustment efficiency.

[0008] To achieve the above-mentioned object, in a first aspect, a photoelectric detection unit is provided, characterized in that the photoelectric detection unit is used to detect a scanning stripe light spot representing a grating displacement and convert it into an electrical signal representing the relative displacement of the grating, the slit period of the grating is P, 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 coincide with each other to form a closed figure; the geometric shape of the photoelectric detection unit is such that: after the geometric shape of the photoelectric detection unit undergoes a sector-rectangle transformation, the first edge is described by a first description function, and the second edge is described by a second description function; or the geometric shape of the photoelectric detection unit is such that: the first edge is described by the first description function, and the second edge is described by the second description function; and the first description function includes a first slope function and a first harmonic filtering function, the second description function includes a second slope function and a second harmonic filtering function, and the difference between the first description function and the second description function is a function proportional to cosω0x, where ω0=2π / P, and x is a coordinate value taken along the grating period direction.

[0009] In a second aspect, a photoelectric detection system is provided, characterized in that it includes: a light source; a grating having a plurality of measuring slits, the slit period of the grating being P; and a photoelectric detection device, wherein a relative displacement can be formed between the photoelectric detection device and the grating, and the light source projects a scanning stripe light spot representing the relative displacement on the photoelectric detection device, and a plurality of photoelectric detection units are formed on the photoelectric detection device, and the photoelectric detection units are used to detect the scanning stripe light spot and convert it into an electrical signal representing the relative displacement; a processing circuit, wherein the processing circuit is used to convert 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 coincide with each other to form a Closed figure; the geometric shape of the photoelectric detection unit is such that: after the geometric shape of the photoelectric detection unit is transformed from a sector to a rectangle, the first edge is described by a first description function, and the second edge is described by a second description function; or, the geometric shape of the photoelectric detection unit is such that: 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 filtering function, the second description function includes a second slope function and a second harmonic filtering function, and the difference between the first description function and the second description function is a function proportional to cosω0x, where ω0=2π / P, and x is the coordinate value taken along the grating period direction.

[0010] In a third aspect, a motor is provided, characterized in that the motor is equipped with the photoelectric detection system as described above.

[0011] The embodiments of the present invention will become more apparent from the following description with reference to the accompanying drawings, which are used to explain the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is a schematic diagram of a photoelectric encoder system according to an embodiment of the present invention.

[0013] FIG2 is a schematic diagram of a linear grating.

[0014] FIG3 is a schematic diagram showing a plurality of photoelectric detection units according to a first embodiment of the present invention.

[0015] FIG4 is a schematic diagram showing a single photodetection unit according to a first embodiment of the present invention.

[0016] FIG5 is a schematic diagram showing two rows of photoelectric detection units according to a first embodiment of the present invention.

[0017] FIG6 is a schematic diagram showing the principle of using the harmonic filtering function, the slope function, and the median adjustment function to design the geometric shape shown in FIG3 .

[0018] FIG. 7 is a schematic diagram showing a photoelectric detection unit according to a second embodiment of the present invention.

[0019] FIG8 is a schematic diagram showing a photoelectric detection unit according to a third embodiment of the present invention.

[0020] FIG9 is a schematic diagram showing a photoelectric detection unit according to a fourth embodiment of the present invention.

[0021] FIG. 10 is a schematic diagram showing a photodetection unit according to a fifth embodiment of the present invention.

[0022] FIG. 11 is a schematic diagram showing a photodetection unit according to a sixth embodiment of the present invention.

[0023] FIG. 12 is a schematic diagram showing a photodetection unit according to a seventh embodiment of the present invention.

[0024] FIG13 is a schematic diagram showing the principle of designing the geometric shape of a photoelectric detection unit using a harmonic filtering function, a slope function, and a midline adjustment function.

[0025] FIG14 is a schematic diagram showing the principle of using a harmonic filtering function and a slope function to design another photoelectric detection unit geometry.

[0026] FIG15 is a schematic diagram showing the principle of designing another geometric shape of a photoelectric detection unit using a harmonic filtering function and a slope function.

[0027] FIG16 is a schematic diagram showing the principle of using the harmonic filtering function and the slope function to design another photoelectric detection unit geometric shape.

[0028] FIG17 is a block diagram showing a structure of a motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the figures is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort are intended to be within the scope of protection of this application.

[0031] Hereinafter, when the terms "including", "having" and their cognates are used in various embodiments of the present invention, they are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0032] In addition, if the embodiments of the present invention involve terms such as "first", "second", and "third", they are only used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0033] Unless otherwise defined, 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 pertain. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meaning as in the context of the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning unless clearly defined in the various embodiments of the present invention.

[0034] 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 a slit 141 that rotates synchronously with the output shaft 13, a photoelectric detection device 15 and a signal processing circuit 16, wherein the slit 141 is a periodically arranged light-transmitting stripe. More specifically, the periodically arranged stripes form periodically arranged transparent areas and opaque areas on the grating disk 14 (the "transparent areas" are the "slits" mentioned above). The grating disk 14 can rotate synchronously with the output shaft 13. The light emitted by the light source 111 passes through the collimating lens 112 to form parallel light. During the rotation of the grating disk 14, the parallel light passes through the grating disk 14 and forms a periodically changing striped light spot (referred to as the "scanning striped light spot" above) on the photoelectric detection device 15. The photoelectric detection device 15 detects the scanning striped light spot and forms an electrical pulse signal. By processing the electrical pulse signal, information such as the current rotation angle, number of turns and speed of the output shaft can be obtained.

[0035] It should be noted that the scanning unit 11 is not limited to the light source 111 and collimating lens 112. Other collimated light sources or scanning gratings, etc., can also be used as long as they can generate parallel light. The specific form of the scanning unit 11 is not limited here. The grating disk 14 does not necessarily rotate synchronously with the output shaft 13. The photoelectric detection device 15 can also rotate synchronously with the output shaft 13. As long as 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 output shaft and the rotation angle.

[0036] The photoelectric detection system 10 may also have other forms or include other components. For example, if the photoelectric detection system is used to detect the magnitude of translational displacement or translational speed, it includes a light source, a linear grating, a photoelectric detection device, and other corresponding components. The embodiments of the present application are not limited to the specific form of the photoelectric detection system 10. In this patent application document, if only "grating" is mentioned, its meaning includes at least a disk-type grating (i.e., a grating disk) and a linear grating.

[0037] The grating disk 14 has M slits 141, and the photodetector 15 is located at a distance R from the center of the rotating shaft (the photodetector 15 is considered a point; according to common industry practice, the midpoint of the photosensitive portion of the photodetector 15 can also be taken as the distance R from the center of the rotating shaft). The slit period P is 2πR / M. In a preferred embodiment, the slits are fan-shaped or fan-like, with two sides ultimately intersecting at the center of the grating disk, and the upper and lower edges can be standard circular arcs. This shape can be transformed from a polar coordinate system to a standard rectangular shape in a rectangular coordinate system through a fan-shaped-to-rectangular transformation. Common harmonic suppression methods in the industry are based on grating slits with a standard rectangular shape. However, in actual use, the length of the grating slit is generally greater than the size of the photodetector 15. This means that the shape of the upper and lower edges of the grating slit does not affect the distribution of light projected onto the photodetector 15. Therefore, the upper and lower edges of the grating slit can be straight lines or other curves. In addition, because the slits on the grating are very dense, the length dimension of a single grating slit is much larger than its width dimension, so a single grating slit can be considered as a rectangle. Even in the grating, using rectangular slits instead of fan-shaped slits can also complete the measurement, but the harmonic suppression effect is slightly worse, resulting in a slightly weaker intensity of the fundamental frequency component in the final electrical signal. Therefore, the slits 141 in the grating disk 14 can be approximately fan-shaped. After the light emitted by the light source 111 passes through the grating disk 14, it generates a scanning stripe light spot with a spatial period of P. From a single period, the geometric shape of a single light spot is fan-shaped or approximately fan-shaped. When projected onto the photoelectric detection device 15, the light sensed by each point on the photoelectric detection device 15 is a square wave.

[0038] When the photoelectric detection system 10 is used to detect the magnitude or velocity of translational displacement, a linear grating is used. Referring to FIG2 , a linear grating 14a is shown. This type of grating is typically used to measure translational displacement. This linear grating has slits 141a. The period P of the slits 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 by the light source also forms a striped light spot after passing through the linear grating 14a. This light spot is projected onto the corresponding photoelectric detection device. Each point on the photoelectric detection device 15 experiences a square wave of light.

[0039] Referring to FIG. 3 , FIG. 3 is a schematic diagram of multiple photodetection units according to a first embodiment of the present invention. The photodetection device 15 includes multiple photodetection units, with FIG. 3 showing four of these units, 151, 152, 153, and 154, which respectively output sensor signals S1-S4. It should be noted that when used with a grating disk, the shapes of the photodetection units 151, 152, 153, and 154 shown in FIG. 3 differ slightly from the shapes of the photodetection units actually manufactured. These units must undergo a rectangular-sector transformation to achieve the actual photodetection unit shape. In practice, the shape shown in FIG. 3 is typically designed using a mathematical expression, and then a rectangular-sector transformation is performed to achieve the actual shape of the photodetection unit. The mathematical expression design yields an elongated, "pea pod" shape, symmetrical about the center of the shape, as shown in FIG. However, after the rectangular-sector transformation, the actual photodetection unit shape is similar to this "pea pod" shape, but slightly modified from the "pea pod" shape shown in FIG. These are common methods used by those skilled in the art and will not be elaborated on here. Regarding the photoelectric detection device used with the linear grating 14a, the shape shown in FIG3 (a "pea pod" with centrosymmetry about the center of the shape) can be directly designed using mathematical expressions and then fabricated into the photoelectric detection device without the need for rectangular-to-sector shape conversion.

[0040] The sensor signals S1-S4 generally have a fixed phase difference with each other. Preferably, adjacent signals in S1-S4 have a phase difference of 90 degrees. By inputting S1-S4 into the signal processing circuit 16 for processing, physical quantities such as the rotation angle, rotation period, and speed of the rotating shaft can be obtained.

[0041] If the photoelectric detection device 15 is not used in conjunction with the grating disk 14 but is used in conjunction with the linear grating 14a, then S1-S4 are input into the corresponding signal processing circuit for processing to obtain physical quantities such as translation displacement and speed and to determine whether it has moved to a specific position.

[0042] In order to simplify the description, the following embodiments are all described for a single photoelectric detection unit having a shape of a "pea pod" symmetrical about the center of the graphic as shown in FIG4 . Those skilled in the art will understand that if the photoelectric detection device 15 is used in conjunction with a grating disk, the photoelectric detection unit designed according to the embodiment of the present application needs to be transformed from a rectangular to a fan-shaped shape before being fabricated onto the photoelectric detection device 15. If the photoelectric detection device 15 is used in conjunction with a linear grating 14a, it does not need to be transformed from a rectangular to a fan-shaped shape and can be directly fabricated onto the photoelectric detection device 15. The rectangular to fan-shaped transformation and its inverse transformation, i.e., the fan-shaped to rectangular transformation, are both commonly used techniques in the field of graphic transformation. The rectangular to fan-shaped transformation is used to transform a graphic in a rectangular coordinate system into a graphic in a polar coordinate system, and the fan-shaped to rectangular transformation is used to transform a graphic in a polar coordinate system into a graphic in a rectangular coordinate system, which will not be described in detail here. U.S. Patent No. 7,268,883B2 also mentions a specific algorithm for reference.

[0043] 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 conditions should be met:

[0044] P=N(W+d) (3).

[0045] Where P is the grating slit period, N is the number of photoelectric detection units required to be placed in a single row within one grating slit period, and N is an integer greater than or equal to 1. Since the grating slit period extends in the X direction, the X direction is called the "grating period direction."

[0046] Since the scanning light wave sensed by each point on the photoelectric detection device 15 is a square wave, it can be expanded into the superposition of the fundamental frequency light wave (fundamental frequency component) and the odd harmonic components:

[0047] Among them, A0 is the average value of the square wave after time integration, A i is the amplitude of each harmonic, and the angular velocity of the fundamental frequency light wave is as follows: ω0=2π / P.

[0048] According to the orthogonal relationship of trigonometric functions, referring to FIG4 , if the height h of a single photodetector unit 151 in the Y direction varies along the X-axis in a COS(ω0x) manner, then under the illumination of a square wave, the electrical signal output by the single photodetector unit 151 will have a non-zero fundamental frequency component, while all other harmonic components will be zero. This achieves the suppression or filtering of multiple harmonic components. This is a common method for harmonic suppression in the art, so it will not be described in detail.

[0049] In the prior art, the implementation method of changing the height value of a single photoelectric detection unit 151 in the Y direction in a COS(ω0x) manner along the X-axis is very complicated and needs to be performed in segments. That is, the x-coordinate range involved in the shape of a single photoelectric detection unit 151 is segmented, and a shape edge change function is set for each segment. That is, the x-coordinate range related to a single optical detection unit 151 is divided into several segments, and a function representing how the shape edge changes is set for each segment. If a shape that is difficult to make, such as an acute angle, appears at the vertex of a geometric shape, or if there is too much free space in the sensor and the area utilization rate is low, when it is desired to adjust the shape of the optical detection unit, it is necessary to reselect the shape edge function, so the adjustment efficiency is low.

[0050] Here, according to one embodiment of the present invention, a simple and easy-to-operate shape edge setting method is provided, which makes it easy to adjust the shape of the photoelectric detection unit and obtain a satisfactory shape according to specific needs.

[0051] Referring to FIG. 4 , according to one embodiment of the present invention, the outer edges of the geometric shape of the photodetection unit 151 include a first edge L1 and a second edge L2, wherein the first edge L1 and the second edge L2 are described by a first description function and a second description function, respectively. That is, according to an embodiment of the present invention, the geometric shape of the photodetection unit 151 includes two edges, each of which is described by a description function, thereby forming a closed geometric shape.

[0052] When describing the first edge L1 and the second edge L2 using a describing function, the variables of the describing function on the X-axis and Y-axis are x and y, respectively. When x takes its minimum value, it corresponds to vertex A of the geometric shape, and when x takes its maximum value, it corresponds to vertex B of the U-shaped geometric shape. As x changes from its minimum value to its maximum value, y also changes continuously, thus forming a curve between the two vertices. (When x and y take discrete values, this "continuous change" is actually a "quasi-continuous change" between closely spaced discrete values.) Therefore, the first describing function and the second describing function respectively form the first edge L1 and the second edge L2 between the two vertices.

[0053] Furthermore, in one embodiment of the present invention, the first description function and the second description function both include: a slope function, a median adjustment function, and a harmonic filtering function. The harmonic filtering function is used to ensure that for any given x value, the difference between the first description function and the second description function changes in a COS(ω0x) manner; the slope function is used to allow the photoelectric detection unit to have a certain posture; and the median adjustment function is used to adjust the shape median of the photoelectric detection unit as needed, thereby fine-tuning the outer contour of the photoelectric detection unit. A preferred embodiment of the above function is as follows, wherein y arc1is the first describing function, y arc2 is the second describing function: y arc1 =kx+A1COS(ω0x)+A2SIN(2ω0x) (1) y arc2 =kx-A1COS(ω0x)+A2SIN(2ω0x) (2)

[0054] Where ω0 = 2π / P, where P is the grating slit period. ω0 is the angular velocity of the fundamental frequency component contained in the square wave. In the example shown in Figure 4, A1 = 80, A2 = 5, P = 240, and k = 2.

[0055] Those skilled in the art will understand that A1 and A2 are actually constants related to the size of the photoelectric detection unit, and vary according to the size of the photoelectric detection unit. Those skilled in the art can select appropriate parameters based on the desired photoelectric detection unit size and other actual conditions. Generally speaking, if the size of the photoelectric detection unit is in the order of microns, then A1 and A2 are also in the order of microns; if the size of the photoelectric detection unit is in the order of nanometers, then A1 and A2 are also in the order of nanometers. In this patent application document, the grating period P is exemplarily taken as a unitless constant such as 240, 256, etc., 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. This value is only an example to explain the technical solution of the embodiment of this patent. In actual applications, the values ​​of A1 and A2 can be adjusted accordingly according to the actual size value of P.

[0056] In equations (1) and (2), kx is the inclination function. When k = 0, the shape shown in FIG3 will degenerate into the shape shown by the two X lines in FIG6(a), that is, the inclination of the entire shape is 0. The shape shown in FIG3 corresponds to k≠0. At this time, the shape has a significant inclination, which helps to place the photodetectors more densely in a limited space. At this time, the photodetection unit 151 is actually tilted at an angle α relative to the Y direction, where 0≤α<90°, and

[0057] 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, that is, the difference between the maximum and minimum values ​​of the x value range. Preferably, D = P / 2, so that the light projected through the grating slit 141 just covers a single photoelectric detection unit, and the harmonic filtering effect is best at this time. Among them, for the photoelectric detection unit 15 with only a single row of photoelectric detection units 151-154, the height H of the photoelectric detection unit 151 is usually less than 1 / 2 of the grating height to ensure that the photoelectric detection units 151-154 are where the light is most concentrated. According to the required values ​​of H and D, the appropriate k value can be calculated. According to experience, the preferred value range of k is 1-10.

[0058] It should be noted that although using a function that changes monotonically within the range of x (such as kx) as a tilt function can easily obtain densely placed photoelectric detection units, the tilt function is not limited to this form. Designers can select a suitable tilt function as needed. As needed, the tilt function can be a function that changes non-monotonically within the range of x to obtain a photoelectric detection unit with a special curved shape. In addition, even if a function that changes monotonically within the range of x is used, the tilt function is not limited to a linear function kx, but can be a monotonically changing function of other forms to obtain the photoelectric detection unit that the designer wants, which is roughly a long strip but has more morphological changes on the edge.

[0059] In the calculation formulas (1) and (2), A2SIN(2ω0x) is the median adjustment function, which is used to adjust the shape of the edges L1 and L2 of the geometric shape of the photoelectric detection unit. Its specific function will be explained in conjunction with Figure 6. In addition, other functions can also be used as the median adjustment function. In order to keep the L1 and L2 curves closed at the vertices A and B, the function should satisfy that y is 0 when x takes the maximum and minimum values. For example, A2SIN(3ω0x), A2SIN(4ω0x) or other functions can be taken. The designer can adjust the shape of the photoelectric detection unit by adjusting its function form or the coefficient in front of it.

[0060] In the calculation formulas (1) and (2), ±A1COS(ω0x) is a harmonic filtering function. Its function is that when the calculation formula (2) is subtracted from the calculation formula (1), a function proportional to COS(ω0x) can be obtained. At this time, the height of the photoelectric detection unit presents a variation form of COS(ω0x) within the entire range of x value variation of the photoelectric detection unit. When the square wave light wave is projected on the photoelectric detection unit 151 with such a height variation, the electrical signal output by the single photoelectric detection unit 151 is non-zero except for the fundamental frequency component, and all other harmonic components are 0. This achieves the suppression or filtering of multiple harmonics. The harmonic filtering function can also have other forms, as long as it satisfies the requirement that a function proportional to COS(ω0x) can be obtained when the calculation formulas (1) and (2) are subtracted. Different forms of harmonic filtering functions can also adjust the edge of the photoelectric sensor unit.

[0061] 4 , the photoelectric detection unit 151 extends along the Y direction, and the scanning stripe light spot enters the photoelectric detection unit from the X direction.

[0062] 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, that is, the above calculation formula (1)-(2):

[0063] Specifically in the embodiment shown in FIG4 , the signals output by the photoelectric detection units 151 , 152 , 153 , and 154 after suppressing the harmonic components are:

[0064] Where, l is a constant. It should be noted that the coefficients A1 and A2 are used to adjust the amplitudes of the cosine function and sine function in the above formulas (1) and (2) respectively. arc1 and y arc2 Each includes a linear function kx, thereby ensuring that the geometric shape of the photodetection unit 151 extends in the Y direction, and the coefficient k is used to adjust the slope of the photodetection unit. The coefficient A1 can adjust the width W of a single photodetection unit 151, and the coefficient A2 can adjust the vertex size and flatness near the vertex angles A and B of the photodetection unit 151.

[0065] 5 , FIG5 shows that the photoelectric detection device 15 includes two rows of photoelectric detection units. The first row of photoelectric detection units includes four photoelectric detection units 151 , 152 , 153 , and 154 , and the second row of photoelectric detection units includes another four photoelectric detection units 155 , 156 , 157 , and 158 .

[0066] 6 , which is a schematic diagram showing the principle of using a harmonic filtering function, a slope function, and a median adjustment function to design a shape as shown in FIG3 .

[0067] As shown in Figure 6(a), the X-line is divided into two upper and lower lines, representing the curves corresponding to the harmonic filtering functions A1COS(ω0x) and -A1COS(ω0x), respectively. The Y-line corresponds to the slope function kx, and the Z-line corresponds to the median 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-lines in Figure 6(a), the distance between the upper and lower X-lines changes with the cosine function as the value of x changes. This is the fundamental reason for achieving harmonic suppression or filtering. However, in practice, the shape generally requires a certain posture to improve sensor area utilization or simplify subsequent calculation algorithms. Therefore, the shape enclosed by the two X-lines in Figure 6(a) is not used directly.

[0068] Since the cosine function and the sine function differ in phase by only 90 degrees, the harmonic filtering function can also be a sine function. With technological development, it is not ruled out that varying the distance between the upper and lower X-rays according to other functions can also achieve a certain degree or aspect of harmonic filtering. In this case, such a function can be directly used to replace the cosine or sine function in the above embodiment and used as the harmonic filtering function, and the shape adjustment method disclosed in the embodiment of this application can be used to design the shape of the photoelectric detection unit.

[0069] In Figure 6(b), the upper and lower X lines correspond to kx+A1COS(ω0x) and kx-A1COS(ω0x), respectively. In other words, adding kx to the curves A1COS(ω0x) and -A1COS(ω0x) is equivalent to adding a slope to the graph formed by the two X lines in Figure 6(a). Therefore, the function that produces this effect is called a "slope function." The median Y of the shape in Figure 6(b) is kx. This "median" means that at each x value, the y-direction distance from the median Y to the upper and lower X lines (corresponding to the upper and lower edges of the shape, respectively) is A1COS(ω0x).

[0070] In Figure 6(c), line Z is the curve obtained by adding A2SIN(2ω0x) to line Y in Figure 6(b). It is also the median line of the shape. That is, at each x value, the y-direction distance from line Z to the upper and lower X lines is A1COS(ω0x), respectively. As can be seen, the effect of adding A2SIN(2ω0x) is to fine-tune the median line Y in the shape of Figure 6(b), thereby fine-tuning the outer edge of the shape. Therefore, the function that produces this effect is called the "median line adjustment function." At this point, the upper and lower curves X in Figure 6(c) correspond to kx+A1COS(ω0x)+A2SIN(2ω0x) and kx-A1COS(ω0x)+A2SIN(2ω0x), respectively.

[0071] Figures 6(a)-6(c) illustrate an example of how the shape of a photodetector unit can be adjusted according to an embodiment of the present invention. The principle is to use a tilt function to make the shape stand up or achieve another posture. Then, using an appropriate midline adjustment function, the midline of the shape is fine-tuned, thereby adjusting the curvature of each portion of the shape's edge. Using this method, designers can select an appropriate tilt function based on the desired shape's general form to achieve the general posture. Then, using an appropriate midline adjustment function, fine-tune the shape's outer curve until the desired shape is achieved. Generally speaking, if the shape is desired to stand up, the tilt function should be a function that varies monotonically within the x-value range. The speed of this function's change determines the degree of the shape's "standing up." When the x-value range is symmetric about the x-axis origin, an odd function can be used as the tilt function. The midline adjustment function is used only as needed. When combining the harmonic filtering function with the tilt function can produce the desired shape, the midline adjustment function can be omitted. Some other examples of the slope function and the median adjustment function will be given later in conjunction with Figures 13-15.

[0072] In the preferred embodiment shown in equations (1) and (2), parameters A1 and A2 can also be adjusted to fine-tune the shape. Referring to Figures 7-12, the effects of coefficients A1 and A2 in equations (1) and (2) on the shape of the photoelectric detection unit are illustrated.

[0073] In Figure 7, the values ​​of each parameter are: k=1, A2=5, A1=42, P=268; in Figure 8, the values ​​of each parameter are: k=1, A2=10, A1=42, P=268; in Figure 9, the values ​​of each parameter are: k=1, A2=20, A1=42, P=268.

[0074] It is not difficult to see from Figures 7-9 that when other coefficients remain unchanged, by adjusting the coefficient A2, the flatness near the top angle can be easily adjusted. When A1 = 42 and remains unchanged, as the value of A2 gradually increases from 5, 10, and 20, the flatness gradually deteriorates. Therefore, through the first description function y arc1 and the second describing function y arc2 , that is, the desired flatness geometry of the photoelectric detection unit 151 can be quickly obtained. It should be noted that when the flatness is better, the manufacture of the photoelectric detection unit 151 will become easier, and when multiple such photoelectric detection units 151 are arranged together, the space utilization rate will also be higher.

[0075] In Figure 10, the values ​​of each parameter are: k=1, A2=10, A1=35, P=268; in Figure 11, the values ​​of each parameter are: k=1, A2=10, A1=30, P=268; in Figure 12, the values ​​of each parameter are: k=1, A2=10, A1=20, P=268.

[0076] It is not difficult to infer from Figures 10-12 that, when other coefficients remain unchanged, by adjusting the coefficient A1, the width W of the photoelectric detection unit 151 can be easily adjusted, and a geometric shape with a desired width W can be obtained.

[0077] When other coefficients remain unchanged, the width W can be easily adjusted by adjusting coefficient A1. When A2 = 10 and remains constant, the width W gradually narrows as the value of A1 decreases from 35, 30, and 20. As width W narrows, the vertex angle of the photodetector unit rapidly becomes acute, which is difficult to manufacture. Therefore, it is necessary to select an appropriate value for A1 so that the vertex angle avoids an acute angle and achieves the desired width W of the photodetector unit 151.

[0078] 13-16 , which are examples of using other forms of the slope function and the median adjustment function.

[0079] In Figure 13(a), the two X lines are the curves corresponding to the harmonic filtering functions A1COS(ω0x) and -A1COS(ω0x); the Y line is the slope function (5 / 3)x-0.0001x 3 The corresponding curve; the Z line is the curve corresponding to the median adjustment function A2SIN(2ω0x). Where A1 = 55, A2 = 15, P = 256, ω0 = 2π / P. In Figure 13(b), the upper and lower X lines are the slope function (5 / 3)x-0.0001x superimposed on A1COS(ω0x) and -A1COS(ω0x). 3The resulting curve; the Y line in Figure 13 (b) is consistent with the Y line in Figure 13 (a), which is the slope function (5 / 3)x-0.0001x 3 The corresponding curve is actually the median line of the shape shown in Figure 13(b). It can be seen that the combination of the harmonic filtering function and the slope function has already produced a good shape. The slope and thickness of this shape are suitable for the horizontal arrangement of multiple photoelectric detection units, and there are no obvious sharp angles. This shape can be used. Figure 13(c) adds the median adjustment function A2SIN(2ω0x), and line Z is the median line. Comparing line Z with the median line Y in Figure 13(b), it can be seen that the shape of the median line has been adjusted, which leads to further changes in the shape of the upper and lower curves. The shape shown in Figure 13(c) is also a suitable shape for use.

[0080] In Figure 14(a), the two X lines are the curves corresponding to the harmonic filtering functions A1COS(ω0x) and -A1COS(ω0x); the Y line is the slope function -0.0001x 3 The corresponding curves are: A1 = 55, P = 256, ω0 = 2π / P. In Figure 14(b), the upper and lower X lines are the slope function -0.0001x superimposed on A1COS(ω0x) and -A1COS(ω0x). 3 The resulting curve; the Y line in Figure 14(b) is consistent with the Y line in Figure 14(a), which is a slope function of -0.0001x 3 The corresponding curve is actually the median line of the shape shown in Figure 14(b). The shape shown in Figure 14(b) is approximately rectangular and is easy to arrange under certain circumstances (using this shape, a single row can only contain two photoelectric detection units in one grating period. In order to simplify the subsequent algorithm, it is generally hoped that the photoelectric detection device contains four photoelectric detection units in one grating period. The shape shown in Figure 14(b) can be arranged in two rows to meet this requirement; or if the simplicity of the subsequent algorithm is not pursued, only two photoelectric detection units can be placed in each grating period). It also has no sharp angles that are difficult to make, and is also a usable shape.

[0081] In Figure 15(a), the two X lines are the curves corresponding to the harmonic filtering functions A1COS(ω0x) and -A1COS(ω0x); the Y line is the slope function -0.01x 2 The corresponding curves are: A1 = 55, P = 256, ω0 = 2π / P. In Figure 15(b), the upper and lower X lines are the slope function -0.01x superimposed on A1COS(ω0x) and -A1COS(ω0x). 2 The Y line in Figure 15(b) is consistent with the Y line in Figure 15(a), which is the slope function -0.01x 2The corresponding curve is actually the median line 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 and is a usable shape. It can also be placed in double rows to achieve the preferred approach of including four photodetection units in one grating period.

[0082] In Figure 16(a), the two X lines are the curves corresponding to the harmonic filtering functions A1COS(ω0x) and -A1COS(ω0x); the Y line is the slope function (5 / 3)x-0.01x 2 -0.0001x 3 The corresponding curves are: A1 = 55, A2 = 15, P = 256, ω0 = 2π / P. In Figure 16(b), the upper and lower X lines are the slope function (5 / 3)x-0.01x superimposed on A1COS(ω0x) and -A1COS(ω0x). 2 -0.0001x 3 The Y line in Figure 16(b) is consistent with the Y line in Figure 16(a), which is the slope function (5 / 3)x-0.01x 2 -0.0001x 3 The corresponding curve is actually the median of the shape shown in Figure 16(b). The shape shown in Figure 16(b) has no difficult-to-manufacture sharp corners, and the upper and lower ends of the shape are larger and smaller, respectively. The free space below the shape just accommodates the larger end of the mirror image of the shape after flipping it 180 degrees up and down. Repeating this pair of shapes horizontally can improve the density of the arrangement and achieve the preferred method of including four photodetection units within a single grating period.

[0083] As technology develops, the field of optically encoded sensors may generate other requirements for the shape and posture of the photoelectric detection unit, which can be conveniently designed using the method disclosed in the embodiments of this application.

[0084] It should be understood that the values ​​of P and the function parameters in the above embodiments are only exemplary. According to the principles disclosed in the embodiments of this application, technicians can adjust the function parameters used according to the actual grating period P, as well as the required shape, size, arrangement and density.

[0085] In one embodiment, referring to FIG. 17 , the present invention provides a motor 100 , which is equipped with a photoelectric detection system 10 .

[0086] 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 slit 141 that rotates synchronously with the output shaft 13, a photoelectric detection device 15, and a signal processing circuit 16. The slit 141 is a periodically arranged light-transmitting stripe. More specifically, the periodically arranged stripes form a periodically arranged transparent area and opaque area on the grating disk 14 (the "transparent area" is the "slit" mentioned above). The grating disk 14 can rotate synchronously with the output shaft 13. In the scanning unit 11, light emitted by the light source 111 passes through the collimating lens 112 to form parallel light. During the rotation of the grating disk 14, the parallel light passes through the grating disk 14 and forms a pulse signal on the photoelectric detection device 15. By processing the pulse signal, information such as the current rotation angle, number of revolutions, and speed of the output shaft can be reflected.

[0087] The photoelectric detection system 10 may also have other forms or include other components. For example, if the photoelectric detection system is used to detect the magnitude and speed of translational displacement, it may include a light source, a linear grating, a photoelectric detection device, and other corresponding components. The embodiments of the present application are not limited to the specific form of the photoelectric detection system 10.

[0088] The photoelectric detection device 15 is used to detect the scanning light representing the displacement of the grating disk 14 and convert it into an electrical signal representing the rotational displacement of the grating disk 14, wherein the photoelectric detection device 15 includes a plurality of photoelectric detection units 151, and 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, and the second edge L2 is described by a second description function; the first description function and the second description function both include: a tilt function, a midline adjustment function, and a harmonic filtering function, and the photoelectric detection unit eliminates the harmonic component by using the difference between the first description function and the second description function, thereby suppressing the harmonic component.

[0089] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope of the present invention.

Claims

1. A photoelectric detection unit, characterized in that: The photoelectric detection unit is used to detect the scanning stripe light spot representing the grating displacement and convert it into an electrical signal representing the relative displacement of the grating. The slit period of the grating is P, where: The geometric shape of the photoelectric detection unit includes a first edge and a second edge, wherein two vertices of the first edge and the second edge coincide with each other to form a closed figure; The geometric shape of the photoelectric detection unit is such that, after the geometric shape of the photoelectric detection unit is transformed from a sector to a rectangle, the first edge is described by a first description function, and the second edge is described by a second description function; or the geometric shape of the photoelectric detection unit is such that the first edge is described by the first description function, and the second edge is described by the second description function; and The first description function includes a first tilt function and a first harmonic filtering function, the second description function includes a second tilt function and a second harmonic filtering function, and the difference between the first description function and the second description function is a function proportional to cosω0x, where ω0=2π / P, and x is the coordinate value taken along the grating period direction.

2. The photoelectric detection unit according to claim 1, wherein The first describing function further includes a first center line adjustment function, and the second describing function further includes a second center line adjustment function.

3. The photoelectric detection unit according to claim 1, wherein The first harmonic filtering function and the second harmonic filtering function are both functions selected from the group consisting of a sin function and a cos function.

4. The photoelectric detection unit according to claim 3, wherein: The first harmonic filtering function is A1cosω0x, and the second harmonic filtering function is -A1cosω0x, and A1≠0.

5. The photoelectric detection unit according to claim 2, wherein: The first median adjustment function and the second median adjustment function are both functions selected from the group consisting of a sin function and a cos function.

6. The photoelectric detection unit according to claim 2, wherein: The first median adjustment function and the second median adjustment function are both A2sin2ω0x, and A2≠0.

7. The photoelectric detection unit according to claim 1, wherein The first slope function and the second slope function are both monotonically increasing functions within the range of x values of the closed graph.

8. The photoelectric detection unit according to claim 7, wherein: The x value range of the closed figure is symmetrical with respect to the origin of the x-axis, and both the first inclination function and the second inclination function are odd functions within the x value range of the closed figure.

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

10. The photoelectric detection unit according to claim 1, wherein The scanning stripe light spot enters the photoelectric detection unit from the first edge and exits from the second edge, so as to suppress the harmonic component carried by the scanning light signal.

11. [Corrected 24.01.2025 according to Rule 26] A photoelectric detection unit according to any one of claims 1 to 10, characterized in that The first description function is: arc1 =kx+A1C0S(ω0x)+A2SIN(2ω0x) (1) The second description function is: arc2 =kx-A1COS(ω0x)+A2SIN(2ω0x) (2) Among them, k≠0, A1≠0.

12. A photoelectric detection system, characterized in that: include: light source; A grating having a plurality of measuring slits, wherein the slit period of the grating is P; and a photoelectric detection device, wherein a relative displacement can be formed between the photoelectric detection device and the grating, and the light source projects a scanning stripe light spot representing the relative displacement onto the photoelectric detection device, and the photoelectric detection device is formed with a plurality of photoelectric detection units, each of which is used to detect the scanning stripe light spot and convert it into an electrical signal representing the relative displacement; a processing circuit, the processing circuit being configured to convert the electrical signal into the relative displacement; in: The geometric shape of the photoelectric detection unit includes a first edge and a second edge, wherein two vertices of the first edge and the second edge coincide with each other to form a closed figure; The geometric shape of the photoelectric detection unit is such that, after the geometric shape of the photoelectric detection unit is transformed from a sector to a rectangle, the first edge is described by a first description function, and the second edge is described by a second description function; or the geometric shape of the photoelectric detection unit is such that 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 tilt function and a first harmonic filtering function, the second description function includes a second tilt function and a second harmonic filtering function, and the difference between the first description function and the second description function is a function proportional to cosω0x, where ω0=2π / P, and x is the coordinate value taken along the grating period direction.

13. A motor, characterized in that: The motor is provided with the photoelectric detection system according to claim 12 .

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