Optoelectronic encoder with a multilayer grating structure

Abstract

The application discloses a photoelectric encoder with a multilayer grating structure and relates to the technical field of encoders. The photoelectric encoder comprises a rotating shaft and a shell, the rotating shaft is inserted into the shell, a dynamic grating disc is arranged on the outer ring of the rotating shaft, an installation base is arranged in the shell, a fixed grating assembly, a photoelectric detection assembly, a signal processing unit and a light source module are arranged on the installation base respectively, the light source module, the dynamic grating disc, the fixed grating assembly, the photoelectric detection assembly and the signal processing unit are arranged in sequence along the direction of the light path, and the photoelectric detection assembly and the signal processing unit are electrically connected. An inner ring dynamic grating group and an outer ring dynamic grating group are arranged on the dynamic grating disc in sequence from the shaft center to the outside, and the dynamic grating disc is a phase grating. The application realizes the radial multilayer grating structure through the inner and outer ring dynamic grating disc structure, eliminates the influence of installation eccentricity, realizes the axial multilayer grating structure through the fixed grating assembly and the delay assembly, eliminates the influence of stray light and other interferences, and retains the effective angular displacement signal output through the combination of the two.

Description

Technical Field

[0001] This invention relates to the field of encoder technology, specifically to a photoelectric encoder with a multilayer grating structure. Background Technology

[0002] An optical encoder is a precision sensor that converts angular displacement into digital pulses, and it is widely used in CNC machine tools, robotics, aerospace, and other fields. Its core principle is to measure displacement using the moiré fringes or diffraction interference of a grating. Internally, the optical encoder uses a bearing-connected bushing system and incorporates a light source. Mechanical components create a sealed internal space, ensuring resistance to contamination.

[0003] However, existing photoelectric encoders generally suffer from the following problems: the installation of the moving grating code disk is prone to errors, especially eccentricity, which introduces periodic measurement errors and severely affects accuracy. Existing solutions often use dual-reading heads with aligned diameters, which are bulky, costly, and require extremely high installation consistency. Furthermore, in industrial environments, stray light and multiple internal reflections can enter the detector, reducing the signal-to-noise ratio and causing subdivision errors. Current methods to improve resolution use high-density single-layer gratings, but such encoders are more sensitive to environmental interference and installation errors. Summary of the Invention

[0004] The technical problem to be solved by this invention is that encoders are easily affected by installation misalignment and stray light interference, resulting in unstable measurement accuracy. The invention provides a photoelectric encoder with a multi-layer grating structure.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A multilayer grating structure photoelectric encoder includes a rotating shaft and a housing. One end of the rotating shaft is inserted into the housing. A movable grating disk is fitted around the outer ring of the rotating shaft. A mounting base is provided inside the housing. A fixed grating assembly, a photoelectric detection assembly, a signal processing unit, and a light source module are respectively mounted on the mounting base. The light source module, the movable grating disk, the fixed grating assembly, the photoelectric detection assembly, and the signal processing unit are arranged sequentially along the direction of the optical path. The photoelectric detection assembly and the signal processing unit are electrically connected. The moving grating disk has an inner ring moving grating group and an outer ring moving grating group arranged sequentially from the axis outwards, and the moving grating disk is a phase grating; The inner ring moving grating assembly has several inner ring grooves along the circumferential direction of the axis. The outer ring moving grating assembly has several outer ring grooves along the circumferential direction of the axis. The fixed grating assembly includes an inner ring fixed grating group and an outer ring fixed grating group, which are aligned and arranged on the same plane. The inner and outer ring grooves are arranged alternately. The position of the inner ring fixed grating group corresponds to the position of the inner ring moving grating group, and the position of the outer ring fixed grating group corresponds to the position of the outer ring moving grating group. The mounting base is provided with the inner ring fixed grating group and the outer ring fixed grating group respectively.

[0006] A movable grating disk is fixedly mounted on the outer ring of the rotating shaft by fasteners or adhesive bonding. The movable grating disk rotates synchronously with the rotating shaft. A mounting base is fixed inside the housing. The light source module emits detection light, which shines towards the movable grating disk. After passing through the movable grating disk, the light continues to shine on the fixed grating assembly located on the other side. After being modulated by the fixed grating assembly, it reaches the photodetector assembly. The photodetector assembly converts the light signal into an electrical signal and transmits it to the signal processing unit for processing. The signal processing unit can be located on the side or bottom of the mounting base and is electrically connected to the photodetector assembly via wires. The inner and outer movable grating groups are concentric ring structures. The movable grating disk as a whole is a phase grating, that is, its surface is completely transparent. Light modulation is achieved through surface microstructures. The inner groove is a rectangular cross-section microgroove formed on the surface of the transparent disk by photolithography. The inner groove and the protrusions between adjacent inner grooves together form a periodic phase structure. The cross-sectional shape, depth, and grating pitch of the outer groove are exactly the same as those of the inner groove. However, the inner and outer grooves are not aligned circumferentially, but rather staggered. This staggered arrangement creates a radially complementary spatial phase structure between the inner and outer moving grating groups. Both the inner and outer fixed grating groups are amplitude-type gratings, located on the same horizontal plane, and their positions correspond vertically to the inner and outer moving grating groups on the moving grating disk, respectively. Furthermore, the inner and outer fixed grating groups are perfectly aligned spatially.

[0007] Furthermore, the inner ring fixed grating assembly includes a first inner ring fixed grating disk, a second inner ring fixed grating disk, and an inner ring delay component, with the inner ring delay component placed on one side of the second inner ring fixed grating disk; The inner ring delay assembly includes an inner ring boss, on which a first reflector is disposed; A photoelectric detection component is arranged on one side of the first inner ring fixed grating disk.

[0008] Both the first and second inner ring fixed grating disks are miniature amplitude grating sheets mounted on a mounting base. They are used to receive the positive and negative first-order diffracted light generated by the inner ring moving grating group, respectively. The first inner ring fixed grating disk is positioned in the optical path of the positive first-order diffracted light, and its transmission window allows the positive first-order diffracted light to pass directly through and continue propagating forward to the photodetector. The second inner ring fixed grating disk is positioned in the optical path of the negative first-order diffracted light, and the inner ring delay component is located in the optical path after the negative first-order diffracted light passes through the second inner ring fixed grating disk. After passing through the second inner ring fixed grating disk, the negative first-order diffracted light is obliquely incident on the first reflector at the top of the inner ring boss. After reflection, it changes direction and is incident on the photodetector located on one side of the first inner ring fixed grating disk. This causes the negative first-order diffracted light to travel a longer optical path than the directly transmitted positive first-order diffracted light, thus achieving a phase delay. The two beams of light converge and interfere at the receiving surface of the photodetector, and finally, after processing by the signal processing unit, the detection result of the inner ring anti-interference is obtained.

[0009] Furthermore, the outer ring fixed grating assembly includes a first outer ring fixed grating disk, a second outer ring fixed grating disk, and an outer ring delay component, with the outer ring delay component placed on one side of the second outer ring fixed grating disk; The outer ring delay assembly includes an outer ring boss, and a second reflector is provided on the outer ring boss; A photoelectric detection component is arranged on one side of the first outer ring fixed grating disk.

[0010] The first outer ring fixed grating disk receives the positive first-order diffracted light generated by the outer ring moving grating group, and the second outer ring fixed grating disk receives the negative first-order diffracted light generated by the outer ring moving grating group. The optical path principle is the same as that of the inner ring fixed grating group. The outer ring delay component is located on the optical path after the negative first-order diffracted light passes through the second outer ring fixed grating disk. After passing through the second outer ring fixed grating disk, the negative first-order diffracted light is obliquely incident on the second reflecting mirror on the top of the outer ring boss. After reflection, the light changes direction and is incident on the photodetector component located on one side of the first outer ring fixed grating disk. The photodetector component is used to receive the signal after the interference of the positive and negative first-order diffracted light from the outer ring.

[0011] Furthermore, the photoelectric detection component includes an inner ring receiver and an outer ring receiver, which are respectively placed on a mounting base and electrically connected to a signal processing unit.

[0012] The inner ring receiver is located below the inner ring fixed grating group. It is used to receive the optical signal after interference of the positive and negative first-order diffraction beams of the inner ring and convert it into an inner ring electrical signal. The outer ring receiver is located below the outer ring fixed grating group. It is used to receive the optical signal after interference of the positive and negative first-order diffraction beams of the outer ring and convert it into an outer ring electrical signal. Both the inner and outer ring receivers are photodiodes. The two signals are independent of each other. The output terminals of the inner and outer ring receivers are electrically connected to the signal processing unit through wires, respectively, to transmit the inner ring electrical signal and the outer ring electrical signal to the signal processing unit for subsequent processing.

[0013] Furthermore, the signal processing unit includes a protective housing, inside which are respectively arranged an inner differential amplifier, an outer differential amplifier, and a total differential amplifier. The input terminal of the inner differential amplifier is electrically connected to the output terminal of the inner receiver, the input terminal of the outer differential amplifier is electrically connected to the output terminal of the outer receiver, and the input terminal of the total differential amplifier is electrically connected to the output terminals of the inner and outer differential amplifiers respectively. The protective housing is placed on a mounting base.

[0014] The protective casing protects the internal circuitry from electromagnetic interference. The inner-ring electrical signal output from the inner-ring receiver enters the inner-ring differential amplifier. Due to the delay structure of the inner-ring fixed grating group, the inner-ring receiver actually receives a signal that has undergone optical domain differential processing, formed by the interference of the positive and negative first-order diffracted light. The inner-ring differential amplifier further amplifies and conditions this signal, outputting a clean inner-ring differential signal. Similarly, the outer-ring electrical signal output from the outer-ring receiver enters the outer-ring differential amplifier, and after amplification and conditioning, outputs a clean outer-ring differential signal. Finally, the clean inner-ring differential signal and the outer-ring differential signal are transmitted together to the main differential amplifier. Because the inner and outer moving grating groups are spatially offset by half a grating pitch, the inner-ring differential signal and the outer-ring differential signal are out of phase in the useful signal component, but in phase in the common-mode error component caused by eccentricity. After the main differential amplifier performs a subtraction operation on the two signals, the amplitude of the useful signal is doubled due to the out-of-phase subtraction, and the eccentricity error is canceled out by the in-phase subtraction. Finally, the total differential amplifier outputs a high signal-to-noise ratio angular displacement encoded signal with eccentricity error eliminated.

[0015] Furthermore, the light source module includes an inner ring light-emitting component and an outer ring light-emitting component, which are respectively placed on the mounting base. The inner ring light-emitting component corresponds to the inner ring moving grating group, and the outer ring light-emitting component corresponds to the outer ring moving grating group.

[0016] The inner ring light-emitting component is vertically aligned with the inner ring moving grating group, and the probe light emitted by it illuminates the code track area of ​​the inner ring moving grating group perpendicularly. The outer ring light-emitting component is vertically aligned with the outer ring moving grating group, and the probe light emitted by it illuminates the code track area of ​​the outer ring moving grating group perpendicularly. The use of dual light sources ensures that the inner and outer ring light signals are independent from the source, providing a physical basis for subsequent independent photoelectric conversion and differential processing.

[0017] Furthermore, the inner ring light-emitting component includes an inner ring light-emitting diode and a first collimating lens, with the light-emitting end of the inner ring light-emitting diode facing the first collimating lens; The outer ring light-emitting component includes an outer ring light-emitting diode and a second collimating lens, with the light-emitting end of the outer ring light-emitting diode facing the second collimating lens; The inner ring light-emitting diode, the first collimating lens, the outer ring light-emitting diode, and the second collimating lens are respectively placed on the mounting base.

[0018] The light-emitting end of the inner ring LED faces the first collimating lens. The flat side of the first collimating lens faces the inner ring LED, and the convex side faces the moving grating disk. The diverging light emitted by the inner ring LED is converted into parallel light after passing through the first collimating lens and is directed perpendicularly towards the inner ring moving grating assembly. The structure and optical path of the outer ring light-emitting assembly are exactly the same as those of the inner ring light-emitting assembly. The inner ring LED, the first collimating lens, the outer ring LED, and the second collimating lens are all fixedly mounted on the mounting base using their respective light source mounting brackets.

[0019] Furthermore, the photoelectric encoder also includes a bearing, which is located on one side of the housing and is fitted onto the outer ring of the shaft.

[0020] The bearing is installed at the opening on one side of the housing. Its outer ring is fixed to the housing, and its inner ring is fitted onto the outer ring of the rotating shaft. The rotating shaft is precisely rotatably connected to the housing through the bearing, which ensures that the rotating shaft can rotate freely and also ensures the radial and axial positioning accuracy of the rotating shaft, thereby ensuring the stability of the gap between the moving grating disk and the fixed grating assembly.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, an inner and outer ring spatial inversion structure is achieved by using an inner ring moving grating group and an outer ring moving grating group. The detection data of the inner and outer rings are subtracted by a total differential amplifier, so that the effective data of the inner and outer rings are superimposed, while the error data is canceled out, effectively eliminating the periodic error introduced by the installation eccentricity. 2. This invention uses a phase grating and inner and outer ring delay components to enable one beam of light to reach the photodetector directly, while the delay components delay the arrival of another beam of light at the photodetector, thus realizing an inner and outer ring time-inverted structure. The data is processed by inner and outer ring differential amplifiers to eliminate error data and effectively suppress common-mode interference such as stray light and DC drift. 3. This invention achieves a radial multi-layer grating structure through the moving grating disk structure of the inner and outer rings, eliminating the influence of installation eccentricity. Furthermore, it achieves an axial multi-layer grating structure through the fixed grating assembly and the delay assembly, eliminating the influence of stray light and other interference. The combination of the two makes the data obtained by the photoelectric encoder more accurate. Moreover, the diffraction interference of the phase grating itself has an optical subdivision effect, which can achieve high resolution with a lower grating line density. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure of the moving grating disk of the present invention; Figure 3 for Figure 2 A magnified view of part A of the view; Figure 4 This is a schematic diagram of the inner ring fixed grating assembly of the present invention; Figure 5 This is a schematic diagram of the structure of the fixed grating assembly of the present invention; Figure 6 This is a schematic diagram of the signal processing unit of the present invention; Figure 7 This is a schematic diagram of the structure of the light source module of the present invention.

[0023] In the diagram: 1. Rotating shaft; 2. Moving grating disk; 21. Inner ring moving grating assembly; 211. Inner ring groove; 22. Outer ring moving grating assembly; 221. Outer ring groove; 3. Fixed grating assembly; 31. Inner ring fixed grating assembly; 311. First inner ring fixed grating disk; 312. Second inner ring fixed grating disk; 313. Inner ring delay assembly; 3131. Inner ring boss; 3132. First reflector; 32. Outer ring fixed grating assembly; 321. First outer ring fixed grating disk; 322. Second outer ring fixed grating disk; 323. Outer ring delay assembly; 32 31. Outer ring boss; 32. Second reflector; 4. Housing; 5. Photoelectric detection assembly; 51. Inner ring receiver; 52. Outer ring receiver; 6. Signal processing unit; 61. Inner ring differential amplifier; 62. Outer ring differential amplifier; 63. Total differential amplifier; 64. Protective shell; 7. Light source module; 71. Inner ring light-emitting assembly; 711. Inner ring light-emitting diode; 712. First collimating lens; 72. Outer ring light-emitting assembly; 721. Outer ring light-emitting diode; 722. Second collimating lens; 8. Mounting base; 9. Bearing. Detailed Implementation

[0024] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example: Figures 1-7 As shown, the present invention provides a technical solution: a photoelectric encoder with a multilayer grating structure.

[0026] like Figures 1-3 As shown, a multi-layer grating structure photoelectric encoder includes a rotating shaft 1 and a housing 4. One end of the rotating shaft 1 is inserted into the housing 4. A movable grating disk 2 is fitted around the outer ring of the rotating shaft 1. A mounting base 8 is provided inside the housing 4. A fixed grating assembly 3, a photoelectric detection assembly 5, a signal processing unit 6, and a light source module 7 are respectively provided on the mounting base 8. The light source module 7, the movable grating disk 2, the fixed grating assembly 3, the photoelectric detection assembly 5, and the signal processing unit 6 are arranged sequentially along the direction of the optical path. The photoelectric detection assembly 5 and the signal processing unit 6 are electrically connected. The moving grating disk 2 is provided with an inner ring moving grating group 21 and an outer ring moving grating group 22 arranged sequentially from the axis outwards. The moving grating disk 2 is a phase grating. The inner ring moving grating group 21 has several inner ring grooves 211 along the circumferential direction of the axis; The outer ring moving grating group 22 is provided with a plurality of outer ring grooves 221 along the circumferential direction of the axis; The fixed grating assembly 3 includes an inner ring fixed grating group 31 and an outer ring fixed grating group 32, which are aligned on the same plane. The inner ring groove 211 and the outer ring groove 221 are arranged alternately. The position of the inner ring fixed grating group 31 corresponds to the position of the inner ring moving grating group 21, and the position of the outer ring fixed grating group 32 corresponds to the position of the outer ring moving grating group 22. The mounting base 8 is provided with the inner ring fixed grating group 31 and the outer ring fixed grating group 32 respectively.

[0027] A movable grating disk 2 is fixedly mounted on the outer ring of the rotating shaft 1 by fasteners or adhesive bonding. The movable grating disk 2 rotates synchronously with the rotating shaft 1. An installation base 8 is fixed inside the housing 4. The light source module 7 emits detection light and shines it in the direction of the movable grating disk 2. After passing through the movable grating disk 2, the light continues to shine on the fixed grating assembly 3 located on the other side. After being modulated by the fixed grating assembly 3, it reaches the photoelectric detection assembly 5. The photoelectric detection assembly 5 converts the light signal into an electrical signal and transmits it to the signal processing unit 6 for processing. The signal processing unit 6 can be disposed on the side or bottom of the mounting base 8 and electrically connected to the photoelectric detection component 5 via wires. The inner ring moving grating group 21 and the outer ring moving grating group 22 are concentric ring structures. The moving grating disk 2 is a phase grating as a whole, that is, its surface is completely transparent, and light modulation is achieved through surface microstructures. The inner ring groove 211 is a rectangular cross-section microgroove formed on the surface of the transparent disk by photolithography. The protrusions between the inner ring groove 211 and the adjacent inner ring groove 211 together constitute a periodic phase structure, and the cross-sectional shape, depth and grating pitch of the outer ring groove 221 are exactly the same as those of the inner ring groove 211. However, the inner ring groove 211 and the outer ring groove 221 are not aligned in the circumferential direction, but are staggered. This staggered arrangement makes the inner ring moving grating group 21 and the outer ring moving grating group 22 form a radial phase complementary structure in spatial phase. Both the inner ring fixed grating group 31 and the outer ring fixed grating group 32 are amplitude-type gratings, located on the same horizontal plane, and their positions are vertically aligned with the inner ring moving grating group 21 and the outer ring moving grating group 22 on the moving grating disk 2, respectively. Furthermore, the inner ring fixed grating group 31 and the outer ring fixed grating group 32 are arranged in perfect spatial phase alignment.

[0028] like Figure 4 As shown, the inner ring fixed grating group 31 includes a first inner ring fixed grating disk 311, a second inner ring fixed grating disk 312 and an inner ring delay component 313, with the inner ring delay component 313 placed on one side of the second inner ring fixed grating disk 312. The inner ring delay assembly 313 includes an inner ring boss 3131, and a first reflector 3132 is provided on the inner ring boss 3131; A photoelectric detection component 5 is arranged on one side of the first inner ring fixed grating disk 311.

[0029] The first inner ring fixed grating disk 311 and the second inner ring fixed grating disk 312 are both miniature amplitude grating sheets, mounted on the mounting base 8. They are used to receive the positive first-order diffracted light and the negative first-order diffracted light generated by the inner ring moving grating group 21, respectively. The first inner ring fixed grating disk 311 is disposed in the optical path of the positive first-order diffracted light, and its light-transmitting window allows the positive first-order diffracted light to pass directly through and continue to propagate forward to the photodetector component 5. The second inner ring fixed grating disk 312 is disposed in the optical path of the negative first-order diffracted light, and the inner ring delay component 313 is located in the optical path after the negative first-order diffracted light passes through the second inner ring fixed grating disk 312. After passing through the second inner ring fixed grating disk 312, the negative first-order diffracted light is obliquely incident on the first reflecting mirror 3132 on the top of the inner ring boss 3131. After reflection, the light changes direction and is incident on the photodetector component 5 located on one side of the first inner ring fixed grating disk 311. This causes the negative first-order diffracted light to travel a longer optical path than the directly transmitted positive first-order diffracted light, thus achieving a phase delay. The two beams converge and interfere on the receiving surface of the photodetector 5, and finally, after processing by the signal processing unit 6, the detection result of the inner ring anti-interference is obtained.

[0030] like Figure 5 As shown, the outer ring fixed grating group 32 includes a first outer ring fixed grating disk 321, a second outer ring fixed grating disk 322 and an outer ring delay component 323, with the outer ring delay component 323 placed on one side of the second outer ring fixed grating disk 322. The outer ring delay component 323 includes an outer ring boss 3231, and a second reflector 3232 is provided on the outer ring boss 3231; A photoelectric detection component 5 is arranged on one side of the first outer ring fixed grating disk 321.

[0031] The first outer ring fixed grating disk 321 is used to receive the positive first-order diffracted light generated by the outer ring moving grating group 22, and the second outer ring fixed grating disk 322 is used to receive the negative first-order diffracted light generated by the outer ring moving grating group 22. The optical path principle is the same as that inside the inner ring fixed grating group 31. The outer ring delay component 323 is located on the optical path after the negative first-order diffracted light passes through the second outer ring fixed grating disk 322. After passing through the second outer ring fixed grating disk 322, the negative first-order diffracted light is obliquely incident on the second reflecting mirror 3232 on the top of the outer ring protrusion 3231. After reflection, the direction is changed and it is incident on the photodetector component 5 located on one side of the first outer ring fixed grating disk 321. The photodetector component 5 is used to receive the signal after the interference of the positive and negative first-order diffracted light of the outer ring.

[0032] like Figures 5-6 As shown, the photoelectric detection component 5 includes an inner ring receiver 51 and an outer ring receiver 52. The inner ring receiver 51 and the outer ring receiver 52 are respectively placed on the mounting base 8, and the inner ring receiver 51 and the outer ring receiver 52 are respectively electrically connected to the signal processing unit 6.

[0033] The inner ring receiver 51 is located below the inner ring fixed grating group 31 and is used to receive the optical signal after interference of the positive and negative first-order diffraction light of the inner ring and convert it into an inner ring electrical signal. The outer ring receiver 52 is located below the outer ring fixed grating group 32 and is used to receive the optical signal after interference of the positive and negative first-order diffraction light of the outer ring and convert it into an outer ring electrical signal. Both the inner ring receiver 51 and the outer ring receiver 52 are photodiodes, and the two signals are independent of each other. The output terminals of the inner ring receiver 51 and the outer ring receiver 52 are electrically connected to the signal processing unit 6 through wires, respectively, and the inner ring electrical signal and the outer ring electrical signal are transmitted to the signal processing unit 6 for subsequent processing.

[0034] like Figure 6 As shown, the signal processing unit 6 includes a protective housing 64. Inside the protective housing 64 are an inner differential amplifier 61, an outer differential amplifier 62, and a total differential amplifier 63. The input terminal of the inner differential amplifier 61 is electrically connected to the output terminal of the inner receiver 51, the input terminal of the outer differential amplifier 62 is electrically connected to the output terminal of the outer receiver 52, and the input terminal of the total differential amplifier 63 is electrically connected to the output terminals of the inner differential amplifier 61 and the outer differential amplifier 62. The protective housing 64 is placed on the mounting base 8.

[0035] The protective casing 64 protects the internal circuitry from electromagnetic interference. The inner ring electrical signal output from the inner ring receiver 51 enters the inner ring differential amplifier 61. Due to the delay structure of the inner ring fixed grating group 31, the inner ring receiver 51 actually receives a signal that has undergone optical domain differential processing, formed by the interference of the positive and negative first-order diffracted light. The inner ring differential amplifier 61 further amplifies and conditions this signal, outputting a clean inner ring differential signal. Similarly, the outer ring electrical signal output from the outer ring receiver 52 enters the outer ring differential amplifier 62, and after amplification and conditioning, outputs a clean outer ring differential signal. Finally, the clean inner and outer differential signals are transmitted together to the total differential amplifier 63. Because the inner moving grating group 21 and the outer moving grating group 22 are spatially offset by half a grating pitch, the inner and outer differential signals are out of phase in the useful signal components, but in phase in the common-mode error component caused by eccentricity. After the total differential amplifier 63 performs a subtraction operation on the two signals, the amplitude of the useful signal is doubled due to the out-of-phase subtraction, while the eccentricity error is canceled out by the in-phase subtraction. Ultimately, the total differential amplifier 63 outputs a high signal-to-noise ratio angular displacement encoded signal with eccentricity error eliminated.

[0036] like Figure 7 As shown, the light source module 7 includes an inner ring light-emitting component 71 and an outer ring light-emitting component 72. The inner ring light-emitting component 71 and the outer ring light-emitting component 72 are respectively placed on the mounting base 8. The inner ring light-emitting component 71 corresponds to the inner ring moving grating group 21, and the outer ring light-emitting component 72 corresponds to the outer ring moving grating group 22.

[0037] The inner ring light-emitting component 71 is vertically aligned with the inner ring moving grating group 21, and the probe light emitted by it is perpendicularly illuminating the code track area of ​​the inner ring moving grating group 21. The outer ring light-emitting component 72 is vertically aligned with the outer ring moving grating group 22, and the probe light emitted by it is perpendicularly illuminating the code track area of ​​the outer ring moving grating group 22. The use of dual light sources ensures that the inner and outer ring light signals are independent from the source, providing a physical basis for subsequent independent photoelectric conversion and differential processing.

[0038] like Figure 7 As shown, the inner ring light-emitting component 71 includes an inner ring light-emitting diode 711 and a first collimating lens 712, with the light-emitting end of the inner ring light-emitting diode 711 facing the first collimating lens 712; The outer ring light-emitting component 72 includes an outer ring light-emitting diode 721 and a second collimating lens 722, with the light-emitting end of the outer ring light-emitting diode 721 facing the second collimating lens 722; The inner ring light-emitting diode 711, the first collimating lens 712, the outer ring light-emitting diode 721, and the second collimating lens 722 are respectively placed on the mounting base 8.

[0039] The light-emitting end of the inner ring LED 711 faces the first collimating lens 712. The planar side of the first collimating lens 712 faces the inner ring LED 711, and the convex side faces the moving grating disk 2. The divergent light emitted by the inner ring LED 711 is converted into parallel light after passing through the first collimating lens 712 and is directed perpendicularly towards the inner ring moving grating group 21. The structure and optical path of the outer ring light-emitting assembly 72 are exactly the same as those of the inner ring light-emitting assembly 71. The inner ring LED 711, the first collimating lens 712, the outer ring LED 721, and the second collimating lens 722 are all fixedly mounted on the mounting base 8 through their respective light source mounting seats.

[0040] like Figure 1 As shown, the photoelectric encoder also includes a bearing 9, which is located on one side of the housing 4 and is sleeved on the outer ring of the rotating shaft 1.

[0041] The bearing 9 is installed at the opening on one side of the housing 4. Its outer ring is fixed to the housing 4, and its inner ring is fitted onto the outer ring of the rotating shaft 1. The rotating shaft 1 is precisely rotatably connected to the housing 4 through the bearing 9, which ensures that the rotating shaft 1 can rotate freely and also ensures the radial and axial positioning accuracy of the rotating shaft 1, thereby ensuring the stability of the gap between the moving grating disk 2 and the fixed grating assembly 3.

[0042] Working principle of the invention: During operation, the rotating shaft 1 drives the movable grating disk 2 to rotate. The inner ring light-emitting component 71 and the outer ring light-emitting component 72 emit collimated light, which passes through the corresponding inner ring movable grating group 21 and outer ring movable grating group 22, respectively, and then enters the corresponding inner ring fixed grating group 31 and outer ring fixed grating group 32. After the parallel light passes through the movable grating disk 2 of the phase grating structure, two main diffracted beams are generated in the inner and outer rings, respectively. For the inner optical path, the positive first-order light directly passes through the first inner fixed grating disk 311 to reach the inner receiver 51, while the negative first-order light is diffracted by the second inner fixed grating disk 312, reflected and delayed by the first reflecting mirror 3132, and then reaches the inner receiver 51. The two beams have a fixed phase difference. Similarly, the outer optical path is delayed by the second reflecting mirror 3232. After the two delayed beams reach the outer receiver 52, the inner differential amplifier 61 and the outer differential amplifier 62 perform differential processing on the two signals with opposite phases to eliminate common-mode interference such as stray light and DC drift in the optical path. Since the inner ring slots 211 and the outer ring slots 221 are arranged alternately, when the moving grating disk 2 is installed off-center, the periodic errors generated by the inner ring moving grating group 21 and the outer ring moving grating group 22 are out of phase. After the signals processed by the inner and outer rings are transmitted to the total differential amplifier 63 for subtraction, the periodic errors introduced by the off-center cancel each other out, and only the amplified effective angular displacement signal is output.

[0043] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photoelectric encoder with a multilayer grating structure, characterized in that: The photoelectric encoder includes a rotating shaft (1) and a housing (4). One end of the rotating shaft (1) is inserted into the housing (4). A moving grating disk (2) is fitted around the outer ring of the rotating shaft (1). An installation base (8) is provided inside the housing (4). A fixed grating assembly (3), a photoelectric detection assembly (5), a signal processing unit (6), and a light source module (7) are respectively provided on the installation base (8). The light source module (7), the moving grating disk (2), the fixed grating assembly (3), the photoelectric detection assembly (5), and the signal processing unit (6) are arranged sequentially along the direction of the optical path. The photoelectric detection assembly (5) and the signal processing unit (6) are electrically connected. The moving grating disk (2) is provided with an inner ring moving grating group (21) and an outer ring moving grating group (22) from the axis outward. The moving grating disk (2) is a phase grating. The inner ring moving grating group (21) has several inner ring grooves (211) along the circumferential direction of the axis. The outer ring moving grating group (22) has several outer ring grooves (221) along the circumferential direction of the axis. The fixed grating assembly (3) includes an inner ring fixed grating group (31) and an outer ring fixed grating group (32), which are aligned on the same plane. The inner ring groove (211) and the outer ring groove (221) are arranged alternately. The position of the inner ring fixed grating group (31) corresponds to the position of the inner ring moving grating group (21). The position of the outer ring fixed grating group (32) corresponds to the position of the outer ring moving grating group (22). The mounting base (8) is provided with the inner ring fixed grating group (31) and the outer ring fixed grating group (32).

2. The photoelectric encoder with a multilayer grating structure according to claim 1, characterized in that: The inner ring fixed grating group (31) includes a first inner ring fixed grating disk (311), a second inner ring fixed grating disk (312), and an inner ring delay component (313), wherein the inner ring delay component (313) is placed on one side of the second inner ring fixed grating disk (312); The inner ring delay assembly (313) includes an inner ring boss (3131), on which a first reflector (3132) is provided. A photoelectric detection component (5) is arranged on one side of the first inner ring fixed grating disk (311).

3. The photoelectric encoder with a multilayer grating structure according to claim 2, characterized in that: The outer ring fixed grating group (32) includes a first outer ring fixed grating disk (321), a second outer ring fixed grating disk (322), and an outer ring delay component (323), wherein the outer ring delay component (323) is placed on one side of the second outer ring fixed grating disk (322); The outer ring delay assembly (323) includes an outer ring boss (3231), on which a second reflector (3232) is provided. A photoelectric detection component (5) is arranged on one side of the first outer ring fixed grating disk (321).

4. The photoelectric encoder with a multilayer grating structure according to claim 3, characterized in that: The photoelectric detection component (5) includes an inner ring receiver (51) and an outer ring receiver (52). The inner ring receiver (51) and the outer ring receiver (52) are respectively placed on the mounting base (8). The inner ring receiver (51) and the outer ring receiver (52) are respectively electrically connected to the signal processing unit (6).

5. The photoelectric encoder with a multilayer grating structure according to claim 4, characterized in that: The signal processing unit (6) includes a protective shell (64). Inside the protective shell (64) are an inner differential amplifier (61), an outer differential amplifier (62), and a total differential amplifier (63). The input terminal of the inner differential amplifier (61) is electrically connected to the output terminal of the inner receiver (51). The input terminal of the outer differential amplifier (62) is electrically connected to the output terminal of the outer receiver (52). The input terminal of the total differential amplifier (63) is electrically connected to the output terminals of the inner differential amplifier (61) and the outer differential amplifier (62). The protective shell (64) is placed on the mounting base (8).

6. The photoelectric encoder with a multilayer grating structure according to claim 5, characterized in that: The light source module (7) includes an inner ring light-emitting component (71) and an outer ring light-emitting component (72). The inner ring light-emitting component (71) and the outer ring light-emitting component (72) are respectively placed on the mounting base (8). The inner ring light-emitting component (71) corresponds to the inner ring moving grating group (21), and the outer ring light-emitting component (72) corresponds to the outer ring moving grating group (22).

7. A photoelectric encoder with a multilayer grating structure according to claim 6, characterized in that: The inner ring light-emitting component (71) includes an inner ring light-emitting diode (711) and a first collimating lens (712), with the light-emitting end of the inner ring light-emitting diode (711) facing the first collimating lens (712). The outer ring light-emitting component (72) includes an outer ring light-emitting diode (721) and a second collimating lens (722), with the light-emitting end of the outer ring light-emitting diode (721) facing the second collimating lens (722). The inner ring light-emitting diode (711), the first collimating lens (712), the outer ring light-emitting diode (721), and the second collimating lens (722) are respectively placed on the mounting base (8).

8. The photoelectric encoder with a multilayer grating structure according to claim 7, characterized in that: The photoelectric encoder also includes a bearing (9), which is located on one side of the housing (4) and is fitted onto the outer ring of the rotating shaft (1).

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