Photoelectric encoder

Abstract

The present application relates to a photoelectric encoder, belonging to the technical field of displacement sensors. The photoelectric encoder comprises: a grating having a circular absolute code track formed on the grating. The absolute code track is composed of a plurality of lands and a plurality of pits forming a data recording sequence, with the lands and pits having different light reflectivities. The grating has a mounting hole at its center for being mounted on a motor shaft sleeve, with the absolute code track surrounding the mounting hole; a laser reader disposed above the grating and having sensing elements corresponding to the absolute code track for reading light signals corresponding to the lands and pits; and a signal processing circuit electrically connected to the laser reader to decode the light signals to obtain a position-encoded signal. According to the photoelectric encoder of the present invention, the laser reader can obtain position information by directly reading the position information, effectively ensuring the accuracy of the grating, while reducing the complexity of the grating signal processing circuit and improving the real-time performance of signal processing.

Description

Technical Field

[0001] The present application relates to the technical field of displacement sensors, and in particular to a photoelectric encoder. Background Art

[0002] A photoelectric encoder, also known as a photoelectric shaft encoder, is a digital angle measurement device that integrates optics, mechanics, and electronics. It is a displacement sensor that converts physical quantities such as the angle, angular displacement, and angular velocity of a rotating spindle into digital signals and outputs them.

[0003] Since the optical code disc is affected by the process, high-resolution encoders cannot be realized by directly engraving the code disc. Figure 1 As shown in the figure, the system includes incremental code channels and absolute code channels. The absolute code channel is responsible for identifying the absolute position, and the incremental code channel is responsible for improving the resolution. The entire signal processing process includes signal conditioning, analog-to-digital converter (ADC) sampling, subdivision processing, data correction, and absolute signal calculation modules. The system is relatively complex. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a photoelectric encoder that digitally encodes position information, which can be directly read to obtain position information, effectively ensuring the accuracy of the grating while reducing the complexity of the grating signal processing circuit.

[0005] According to an embodiment of the present invention, a photoelectric encoder includes: a grating having a circular absolute code track provided on the grating, the absolute code track being formed into a data recording sequence by a plurality of lands and a plurality of pits, the light reflectivity at the lands and the pits being different, a mounting hole being provided at the center of the grating for being mounted on a shaft sleeve of a motor rotating shaft, and the absolute code track surrounding the mounting hole; a laser reader being provided above the grating, the laser reader being provided with sensing elements corresponding to the absolute code track for reading light signals corresponding to the lands and pits; and a signal processing circuit being electrically connected to the laser reader for decoding the light signal to obtain a position coding signal.

[0006] To elaborate, the grating is coaxial with the motor. When the motor rotates, the grating and the motor rotate at the same speed. The laser reader obtains information from the grating to determine the speed and direction of rotation of the motor. The laser reader emits a laser beam to illuminate the absolute code track on the grating. One or more "0"s are recorded on the pits, and one or more "1"s are recorded on the lands. The light signal reflected back to the laser reader at the pits is weaker than the light signal reflected back to the laser reader at the lands, so that the light signal output by the laser reader is a pulse wave modulated by the pits. The pulse waves with different strengths output from the laser reader are processed and decoded by the signal processing circuit to obtain the "0", "1" position coding signals recorded on the grating.

[0007] According to the photoelectric encoder of the embodiment of the present invention, the laser reader can obtain position information by direct reading, which can effectively ensure the accuracy of the grating, while reducing the complexity of the grating signal processing circuit and improving the real-time performance of signal processing.

[0008] According to the photoelectric encoder of the embodiment of the present invention, there is one absolute code track, the laser reader is arranged relative to the absolute code track, and the data recording sequence is the longest linear feedback register sequence code. Therefore, the encoding of position information can be completed through a single absolute code track. The laser reader can eliminate the traditional light-driven focusing system and dynamic tracking system, and can solve the problem of the small number of single-circle engravings on glass gratings and metal gratings.

[0009] According to an embodiment of the present invention, the photoelectric encoder comprises a grating comprising: a substrate; an information layer laminated on the substrate, the information layer defining a plurality of lands and pits, the lands and pits being arranged alternately; a reflective layer laminated on the information layer; and a protective layer laminated on the reflective layer. The information layer is used to record digital sequence information, and the protective layer seals the information layer within the grating to prevent contamination and damage.

[0010] Optionally, the information layer is made of a phase-change metal material, the lands are amorphous regions, and the pits are crystalline regions, so that the grating can be both readable and writable.

[0011] Optionally, the grating further comprises: a label layer, which is stacked on a side of the protective layer away from the reflective layer, so that information such as grating parameters can be printed on the label layer for easy identification.

[0012] According to an embodiment of the present invention, the photoelectric encoder comprises a sensing element comprising a laser diode for emitting a laser beam onto the absolute code track; and a photodetector electrically connected to a signal processing circuit for receiving the laser beam reflected from the absolute code track to generate a light signal. The light signal is then transmitted to the signal processing circuit for decoding and generating a position encoding signal. This allows the data sequence recorded on the grating to be read.

[0013] Optionally, the signal processing circuit includes: a radio frequency amplifier, the input end of the radio frequency amplifier is electrically connected to the photodetector, and the radio frequency amplifier is used to receive the light signal and output the amplified signal; a decoder, the decoder is electrically connected to the output end of the radio frequency amplifier, and the decoder is used to receive the amplified signal and decode the output position coding signal. The light signal is a weak signal of the longest linear feedback register V, so the radio frequency amplifier is required to amplify the signal for processing. The encoding of the grating can be encoded by the longest linear feedback register code or Gray code, so the binary data processed by the processing circuit can be decoded by a sequential lookup table to complete the serial code and converted into a recognizable position coding signal.

[0014] Optionally, the signal processing circuit further includes a signal filter, wherein an input end of the signal filter is electrically connected to the RF amplifier, and an output end of the signal filter is electrically connected to a decoder. The signal filter is configured to receive the amplified signal and output a filtered signal, and the decoder is configured to receive the filtered signal and decode and output a position-coded signal. The signal filter can filter out high-frequency noise in the amplified signal.

[0015] Optionally, the signal processing circuit further includes a level comparator, wherein the input end of the level comparator is electrically connected to the output end of the signal filter, and the output end of the level comparator is electrically connected to a decoder, the level comparator is configured to receive the filtered signal and output a pulse signal, and the decoder is configured to receive the pulse signal and decode and output a position coding signal. The level comparator performs shaping processing (or binarization processing) on the filtered signal to obtain the required standard pulse signal.

[0016] Optionally, the signal processing circuit further includes a phase processor, wherein two input terminals of the phase processor are electrically connected to the level comparator and the radio frequency amplifier, respectively, and an output terminal of the phase processor is electrically connected to a decoder. The phase processor is configured to receive and compare the pulse signal and the amplified signal to obtain a phase error parameter, and to correct the pulse signal based on the phase error parameter to output a binary data signal. The decoder is configured to receive the binary data signal and decode the output position-encoded signal. The phase processor processes the rising / falling edges and zero crossings of the pulse signal to obtain phase error information between an unfiltered pulse signal and a relatively ideal pulse signal that has been filtered and equalized, and corrects the pulse signal based on the phase error parameter, thereby making the read pulse signal more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0019] Figure 1 This is a prior art raster data reading and processing technology.

[0020] Figure 2 Schematic diagram of the connection between the photoelectric encoder 1 and the motor shaft according to an embodiment of the present invention;

[0021] Figure 3 Schematic diagram of the absolute code track of the photoelectric encoder 1 according to an embodiment of the present invention;

[0022] Figure 4 Schematic diagram of the coding sequence of the absolute code channel of the photoelectric encoder 1 according to an embodiment of the present invention;

[0023] Figure 5 A top view of a grating of a photoelectric encoder 1 according to some embodiments of the present invention;

[0024] Figure 6 Schematic diagram of the structure of the grating of the photoelectric encoder 1 according to an embodiment of the present invention;

[0025] Figure 7 FIG. 4 is a schematic diagram of a signal processing circuit of a photoelectric encoder 1 according to an embodiment of the present invention.

[0026] Reference numerals:

[0027] Photoelectric encoder 11,

[0028] Grating 10, absolute code channel 101, land 102, pit 103, mounting hole 104,

[0029] Substrate 11, information layer 12, reflective layer 13, protective layer 14, label layer 15,

[0030] Laser read head 20 , laser diode 22 , photodetector 23 , radio frequency amplifier 24 , decoder 25 , signal filter 26 , level comparator 27 , phase processor 28 , signal processing circuit 30 . DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0032] The following describes a photoelectric encoder 1 according to an embodiment of the present invention with reference to the accompanying drawings.

[0033] like Figure 2 、 Figure 3 and Figure 7 As shown, the photoelectric encoder 1 according to an embodiment of the present invention includes: a grating 10 , a laser reader 20 and a signal processing circuit 30 .

[0034] Specifically, a circular absolute code track 101 is provided on the grating 10. The absolute code track 101 is formed by a plurality of lands 102 and a plurality of pits 103 to form a data recording sequence. The light reflectivity at the lands 102 and the pits 103 is different. A mounting hole 104 is provided in the center of the grating 10 to be mounted on the shaft sleeve of the motor rotating shaft, and the absolute code track 101 surrounds the mounting hole 104; a laser reader 20 is provided above the grating 10, and a sensing element corresponding to the absolute code track 101 is provided on the laser reader 20 to read the light signals corresponding to the lands 102 and the pits 103; a signal processing circuit 30 is electrically connected to the laser reader 20 to decode the light signal to obtain a position coding signal.

[0035] The data recording sequence can be encoded using either the longest linear feedback register sequence or the Gray code. If the data recording sequence is encoded using the longest linear feedback register sequence, there is a single absolute code track 101. If the data recording sequence is encoded using the Gray code, the absolute code tracks 101 are several concentric circular code tracks along the radial direction. This arrangement reduces the number of absolute code tracks 101, allowing the laser reader 20 and grating 10 to be relatively fixed in position, eliminating the need for a traditional light-driven focusing system and dynamic tracking system. Furthermore, the reduced number of code tracks allows for a smaller diameter of the grating 10, thereby reducing the jitter amplitude of the outer circumference of the grating 10 and improving the vibration resistance of the grating 10.

[0036] To elaborate, the grating 10 is coaxial with the motor. When the motor rotates, the grating 10 rotates at the same speed as the motor. The laser reader 20 obtains information from the grating 10 to determine the speed and direction of rotation of the motor. The laser reader 20 emits a laser beam to illuminate the absolute code track 101 on the grating 10. One or more "0"s are recorded on the pit 103, and one or more "1"s are recorded on the platform 102. The light signal reflected back to the laser reader 20 at the pit 103 is weaker than the light signal reflected back to the laser reader 20 at the platform 102, so that the light signal output by the laser reader 20 is a pulse wave modulated by the pit 103. The pulse waves with different strengths output from the laser reader 20 are processed and decoded by the signal processing circuit 30 to obtain the "0", "1" position coding signals recorded on the grating 10.

[0037] According to the photoelectric encoder 1 of the embodiment of the present invention, the laser reader 20 can obtain position information by direct reading, which can effectively ensure the accuracy of the grating 10, while reducing the complexity of the signal processing circuit 30 of the grating 10 and improving the real-time performance of signal processing.

[0038] like Figure 4 and Figure 5 As shown, according to the photoelectric encoder 1 of an embodiment of the present invention, there is one absolute code track 101, the laser reader 20 is arranged relative to the absolute code track 101, and the data recording sequence is the longest linear feedback register sequence code (M sequence code), so that the encoding of position information can be completed through a single absolute code track 101. The laser reader 20 can cancel the traditional light-driven focusing system and dynamic tracking system, and can also solve the problem of the small number of single-circle engravings of the glass grating 10 and the metal grating 10.

[0039] like Figure 4 and Figure 5 The grating 10 shown as a 5-bit M-sequence code can obtain 25 positions, namely 00000, 00001, 00011, 00111, 01110, 11100, 11001, 10011, 00110, 01101, 11011, 10111, 01111, 11111, 11110, 11101, 11010, 10100, 01000, 10001, 00010, 00100, 01001, 10010, 00101, 01010, 10101, 01011, 10110, 01100, 11000, 10000. The actual number of bits of the digital recording sequence code of the grating 10 can be determined according to the specific application.

[0040] like Figure 6As shown, according to an embodiment of the present invention, a photoelectric encoder 1 includes a grating 10 comprising: a substrate 11; an information layer 12, which is stacked on substrate 11 and defines a plurality of lands 102 and a plurality of pits 103, which are alternately arranged; a reflective layer 13, which is stacked on information layer 12; and a protective layer 14, which is stacked on reflective layer 13. Information layer 12 is used to record digital sequence information, and is sealed within grating 10 by protective layer 14 to prevent contamination and damage.

[0041] Optionally, the information layer 12 is made of a phase-change metal material, the land 102 is an amorphous area, and the pit 103 is a crystalline area. In this way, the grating 10 can be readable and writable. When writing a digital recording sequence, part of the information layer 12 is changed by high-temperature laser irradiation, and the area quickly becomes liquid, and then "condenses" into an amorphous state to become an amorphous area. Since the amorphous area and the crystalline area have different light reflectivities, the digital recording sequence on the grating 10 can be read by the laser reader 20; when erasing, the amorphous area is changed by high-temperature laser irradiation and becomes a crystalline state again, thus returning to a writable state. This effectively ensures the accuracy of the grating 10, while reducing the complexity of the signal processing circuit 30 and improving the real-time performance of signal processing. At present, the pit length standard of BD optical discs can be less than 0.15u of the longest linear feedback register, that is, the resolution of the grating 10 can reach at least 0.15u of the longest linear feedback register, which is equivalent to a resolution of 2 per meter. 22 .

[0042] It should be noted that the phase change metal material is a phase change alloy layer, and the reflective layer 13 is usually an aluminum alloy layer.

[0043] like Figure 6 As shown, optionally, the grating 10 further includes: a label layer 15, which is stacked on the side of the protective layer 14 away from the reflective layer 13, so that information such as parameters of the grating 10 can be printed on the label layer 15 for easy identification.

[0044] like Figure 7 As shown, the photoelectric encoder 1 according to an embodiment of the present invention comprises a sensing element comprising a laser diode 22 for emitting a laser beam onto the absolute code track 101; and a photodetector 23 electrically connected to a signal processing circuit 30 for receiving the laser beam reflected by the absolute code track 101 to generate a light signal. The light signal is then transmitted to the signal processing circuit 30 for decoding and generating a position encoding signal. This allows the data sequence recorded on the grating 10 to be read.

[0045] like Figure 7As shown, optionally, the signal processing circuit 30 includes: a radio frequency amplifier 24, the input end of which is electrically connected to the photodetector 23, and the radio frequency amplifier 24 is used to receive the light signal and output the amplified signal; a decoder 25, which is electrically connected to the output end of the radio frequency amplifier 24, and is used to receive the amplified signal and decode the output position coding signal. The light signal is a weak signal of the longest linear feedback register V, so the radio frequency amplifier 24 is required to amplify the signal. The encoding of the grating 10 can be encoded by the longest linear feedback register code or Gray code. Therefore, the binary data processed by the processing circuit can be decoded into a recognizable position coding signal by a sequential lookup table. Among them, the radio frequency amplifier 24 includes but is not limited to an adding amplifier, a waveform equalization circuit, and a data limiting circuit.

[0046] In addition, decoder 25 can convert the processed binary data into a recognizable position-coded signal by decoding the digital record sequence through a sequential table lookup. A linear search (also known as a linear search) uses a one-by-one comparison method to find the key. Starting from the last record in the table, the key in each record is compared with a given value. If a key in a record compares to the given value, the position of the record is returned.

[0047] like Figure 7 As shown, the signal processing circuit 30 optionally further includes a signal filter 26. The input end of the signal filter 26 is electrically connected to the RF amplifier 24, and the output end of the signal filter 26 is electrically connected to the decoder 25. The signal filter 26 is configured to receive the amplified signal and output a filtered signal. The decoder 25 is configured to receive the filtered signal and decode and output a position-encoded signal. The signal filter 26 can filter out high-frequency noise in the amplified signal.

[0048] like Figure 7 As shown, the signal processing circuit 30 optionally further includes a level comparator 27, the input end of the level comparator 27 being electrically connected to the output end of the signal filter 26, and the output end of the level comparator 27 being electrically connected to the decoder 25. The level comparator 27 is configured to receive the filtered signal and output a pulse signal, and the decoder 25 is configured to receive the pulse signal and decode and output a position coding signal. The level comparator 27 performs shaping processing (or binarization processing) on the filtered signal to obtain the required standard pulse signal.

[0049] like Figure 7As shown, the signal processing circuit 30 optionally further includes: a phase processor 28, wherein the two input ends of the phase processor 28 are electrically connected to the level comparator 27 and the RF amplifier 24, respectively, and the output end of the phase processor 28 is electrically connected to the decoder 25. The phase processor 28 is used to receive and compare the pulse signal and the amplified signal to obtain a phase error parameter, and correct the pulse signal according to the phase error parameter to output a binary data signal. The decoder 25 is used to receive the binary data signal and decode and output a position encoding signal. The phase processor 28 obtains phase error information between the unfiltered pulse signal and the ideal pulse signal after filtering and equalization by processing the rising / falling edges and zero crossings of the pulse signal, and corrects the pulse signal according to the phase error parameter, thereby making the read pulse signal more accurate.

[0050] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0051] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0052] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Claims

1. A photoelectric encoder, characterized in that: include: A grating having a circular absolute code track formed thereon, wherein the absolute code track comprises a plurality of lands and a plurality of pits forming a data recording sequence, wherein the lands and the pits have different light reflectivities, a mounting hole is defined at the center of the grating for being mounted on a motor shaft sleeve, the absolute code track surrounds the mounting hole, the data recording sequence is encoded in a longest linear feedback register sequence, and the absolute code track is one; a laser reader, the laser reader being disposed above the grating and opposite the absolute code track, the laser reader being provided with a sensing element corresponding to the absolute code track for reading light signals corresponding to the lands and the pits; the sensing element comprising a laser diode and a photodetector, the laser diode being configured to emit a laser beam onto the absolute code track, the photodetector being electrically connected to a signal processing circuit, the photodetector being configured to receive the laser beam reflected by the absolute code track to generate the light signal, and transmitting the light signal to the signal processing circuit for decoding and generating a position coding signal; The signal processing circuit is electrically connected to the laser reader to obtain a position coding signal according to the decoding of the light signal. The signal processing circuit includes a radio frequency amplifier, a decoder, a signal filter, a level comparator and a phase processor. The input end of the radio frequency amplifier is electrically connected to the photodetector, and the radio frequency amplifier is used to receive the light signal and output an amplified signal; the input end of the signal filter is electrically connected to the radio frequency amplifier, and the signal filter is used to receive the amplified signal and output a filtered signal; the input end of the level comparator is electrically connected to the output end of the signal filter, and the level comparator is used to receive the filtered signal and output a pulse signal; The two input ends of the phase processor are electrically connected to the level comparator and the RF amplifier respectively, and the output end of the phase processor is electrically connected to the decoder. The phase processor is used to receive and compare the pulse signal and the amplified signal to obtain a phase error parameter, and correct the pulse signal according to the phase error parameter to output a binary data signal. The decoder is used to receive the binary data signal and decode the output position code signal.

2. The photoelectric encoder according to claim 1, wherein The grating comprises: substrate; an information layer, the information layer being stacked on the substrate, the information layer defining a plurality of the lands and the pits, the plurality of the lands and the plurality of the pits being alternately arranged in sequence; a reflective layer, the reflective layer being stacked on the information layer; A protective layer is stacked on the reflective layer.

3. The photoelectric encoder according to claim 2, characterized in that The information layer is made of a phase-change metal material, the lands are amorphous regions, and the pits are crystalline regions.

4. The photoelectric encoder according to claim 3, characterized in that The grating further comprises: The label layer is stacked on a side of the protection layer away from the reflective layer.

Images