Single-code-channel absolute photoelectric coding and decoding system

Abstract

The invention provides a single-code-channel absolute type photoelectric coding and decoding system. The system is characterized in that the system is composed of a light source (1), a grating (2), a light beam splitter (3), an incremental code detector (4) and an absolute code detector (5), wherein the grating (2) is composed of a grating substrate (200) and a unique code channel (210). The method can be used in a system for speed closed-loop control and accurate position measurement, and can be widely used in the fields of servo systems, precise measurement, motion control, medical equipment, aerospace and the like.

Description

(I) Technical field

[0001] The invention relates to a single-code channel absolute photoelectric encoding and decoding system and a design method, which can be used in instruments for speed closed-loop control and position precision measurement, and belongs to the field of photoelectric detection technology. (II) Background technology Photoelectric encoder is a sensor based on grating measurement technology that detects and controls parameter information such as position, displacement, speed, acceleration, angle, etc. It plays an important role in the field of high-precision measurement and motion control. With the rapid development of precision measurement and intelligent manufacturing, photoelectric encoders are developing towards high precision, high reliability, high resolution and high adaptability. According to the way of receiving and processing signals, it is divided into imaging and scanning. The imaging type uses high-speed exposure to take pictures of the scale modulation signal, and uses image processing to solve the coding information of the scale code channel, but the algorithm is complex and the amount of calculation is large, resulting in insufficient real-time performance; the scanning type uses a specially designed photoelectric detector array to output scanning signals of different phases in real time, which can be used for high-speed testing. According to the encoding and decoding method, it is divided into incremental and absolute encoders. The incremental type provides precise relative displacement measurement, and the measurement of absolute position requires a zero reference point; the absolute type can achieve absolute position measurement without starting the zero return operation, without cumulative error and data will not be lost after power failure. The traditional absolute type uses photoelectric encoders or grating rulers to achieve measurement using multiple code channels, at least one code channel is used to detect precise incremental information, and at least one code channel is used to detect absolute position information. However, multiple code channels are not conducive to the miniaturization of devices, and installation yaw deviation will cause multiple code channel de-phase, resulting in measurement errors. Therefore, the present invention proposes a single code channel absolute photoelectric encoding and decoding system, in which a single code channel realizes synchronous real-time scanning measurement of absolute position and incremental position, thereby avoiding yaw de-phase caused by installation tolerance. (III) Summary of the invention The purpose of the present invention is to provide a single-code channel absolute photoelectric encoding and decoding system, which consists of a light source 1, a grating 2, an optical beam splitter 3, an incremental code detector 4, and an absolute code detector 5, wherein the grating 2 consists of a grating substrate 200 and a unique code channel 210. The object of the present invention is achieved in that: The light emitted by the light source (1) is modulated by the grating (2), and the modulated light is split by the optical beam splitter (3), and received and processed by the incremental code detector (4) and the absolute code detector (5). The modulation of the light beam component A1 by the unique code channel (210) on the grating (2) is not different, and a grating modulated light field (401) without code channel difference is formed on the photoelectric detection surface. The incremental code detector (4) collects (401) and generates a simple harmonic wave signal (402) after photoelectric conversion, and can subsequently perform interpolation and subdivision operations to obtain high-resolution incremental information. The modulation of the light beam component A2 by the unique code channel (210) is different, and a grating modulated light field (402) with code channel difference is formed on the photoelectric detection surface. The modulated light field (402) carries code channel coding information, which is collected by the absolute code detector (5) and converted into a code element signal with a logic level. After decoding according to the coding table, the absolute information of the current position can be obtained. In addition, the optical beam splitter (3) can split more types of light beams such as A3 as needed to improve measurement accuracy or verify and correct errors. (Further details and explanations are given below, including other claims and their details) The light source 1 in the system can be a collimated light source, a divergent light source, a point light source, a surface light source, a volume light source of various types and combinations thereof, and can be a multicolor light source or a complex color light source and combinations thereof. The light source carries at least two beam components A1 and A2. The grating 2 can be any type of grating, such as a rectangular grating, a sinusoidal grating, a blazed grating, a step grating, a volume grating, etc., including but not limited to a transmission grating, a reflection grating, a diffraction or interference grating. The scale substrate 200 can be made of opaque processes or materials such as steel alloy, aluminum alloy, and plated metal, or can be made of translucent or partially translucent processes or materials such as glass and plastic, including circular code disks of different radii, linear scales, and scales of other arbitrary motion trajectories and shapes. The grating 2 is a light modulator formed by a unique code channel 210 , which includes at least two different code positions 211 and 212 , including but not limited to absorption, reflection, transmission, scattering, interference or diffraction processes, materials or coatings. The code channel 210 has a uniform grating distribution, and each grating line of the code channel has no difference in modulation of the light beam component A1, and a periodic incremental signal can be generated during the grating movement. The code positions 211 and 212 of the code channel 210 modulate the light beam component A2 differently. With reference to the scale substrate 200, the intensity modulation of the light beam A2 by the code positions 211 and 212 can be opposite or the same. Each code position 211 and 212 on the code channel 210 can be encoded according to a specific encoding method, including but not limited to a random code, a pseudo-random code, an M sequence, a Gray code, an index code, etc. The optical beam splitter 3 splits the light source into at least two beam components A1 and A2, such as splitting the wavelength of the light. The optical beam splitter includes but is not limited to a dichroic mirror, a semi-transparent and semi-reflective mirror, a high-pass filter, a low-pass filter, a band-pass filter, a diffraction optical device, an interference optical device, a dispersion optical device, and an optical system composed of a combination thereof. The absolute code detector 5 is used to detect the light field 501 carrying the code channel coded information and decode the logic level signal 502 carrying the coded information. In particular, when the code positions 211 and 212 modulate the intensity of the light beam A2 in the opposite direction, setting the same threshold can achieve the equal width and phase of the incremental period and the absolute signal code position, effectively reducing the absolute and incremental fusion error. The absolute detector can output the logic signal in serial decoding or parallel decoding. The optical beam splitter 3 can split more beam components such as A3 as needed. A3 generates incremental codes with other periods in the form of incremental code detection to improve the accuracy of incremental information; it can also generate check codes in the form of absolute code detection to correct errors and reduce bit error rates; A3 can also generate reference index codes for incremental counting and resetting. (IV) Description of the drawings

[0013] Figure 1 The figure is a schematic diagram of single-track absolute coding. The coding technology is implemented on the grating scale 2. The grating 2 is composed of a scale substrate 200 and a unique code channel 210. The code channel 210 contains at least two different code positions 211 and 212. The code positions 211 and 212 on the code channel 210 are encoded according to a specific encoding method M. Each bit position m of the encoding M is i Corresponding to a grid line code position of the code channel 210, the binary coded logic 1 corresponds to the code position 211 of the code channel 210, and the binary coded logic 0 corresponds to the code position 212 of the code channel 210. Code position 211 and code position 210 are realized by different processes, materials or coatings, including but not limited to absorption, reflection, transmission, scattering, interference or diffraction. For the beam component A1, the code positions 211 and 212 of the code channel 210 do not differ, and the code channel 210 has a uniform grating distribution, and a periodic incremental signal can be generated during the grating movement. For the beam component A2, the modulation of light by the code positions 211 and 212 of the code channel 210 is different, and can carry the information of the encoding M.

[0014] Figure 2It is a schematic diagram of single-channel absolute decoding. The absolute code decoding technology consists of a grating scale 2 and an absolute code detector 5. The light beam component A2 is modulated by the unique code channel 210 of the grating 2, and the light field 502 carrying the code bit encoding difference signal is detected by the absolute code receiver 5. The absolute code detector 5 decodes the high and low level logic signals 502 carrying the encoded information through the photoelectric conversion of each sub-unit. In particular, when the intensity modulation of the light beam A2 by the code bits 211 and 212 is reversed, setting the same threshold can achieve the equal width and phase of the incremental period and the absolute signal code bit, effectively reducing the absolute and incremental fusion error. The absolute detector can read out the logic signal in serial decoding or parallel decoding.

[0015] Figure 3 The invention is a schematic diagram of a single-code channel absolute detection system, wherein the detection system realizes the detection of absolute position code and precision incremental position on the same code channel 210. The light emitted by the light source (1) is modulated by the grating (2), and the modulated light is split by the optical beam splitter (3). The modulation of the light beam component A1 by the unique code channel (210) is not different, and a grating modulated light field (401) without code channel difference is formed on the photoelectric detection surface. The incremental code detector (4) collects (401) and generates a simple harmonic wave signal (402) after photoelectric conversion, and interpolation and subdivision operations can be performed later to obtain high-resolution incremental information. The modulation of the light beam component A2 by the unique code channel (210) is different, and a grating modulated light field (402) with code channel difference is formed on the photoelectric detection surface. The modulated light field (402) carries code channel coding information, which is converted into a code element signal with a logic level after being collected by the absolute code detector (5). The absolute information of the current position can be obtained after decoding according to the coding table. In addition, the optical beam splitter (3) can split more types of light beams such as A3 as needed. A3 generates incremental codes of different periods in the manner of incremental code detection to improve the accuracy of incremental information; it can also generate check codes in the manner of absolute code detector 5 to correct errors and reduce bit error rate; optionally, A3 can also generate reference index codes for incremental counting and resetting.

[0016] Figure 4This is a schematic diagram of a transmission-type single-channel absolute photoelectric encoder and decoder system. The system consists of a light source 1, a grating 2, a beam splitter 3, an incremental channel detector 4, and an absolute channel detector 5. Light source 1 uses a two-color collimated light source, emitting narrow-band collimated blue light and narrow-band collimated red light. Grating 2 is a linear scale used to measure linear motion. Grating 2 consists of a glass substrate 200 and a surface shading layer. An equal-periodic light-transmitting channel 210 is etched on the shading layer, and a film is sequentially coated on the grating channel 210 according to the coding sequence. Beam splitter 3 is a dichroic mirror that transmits low-wavelength light and reflects high-wavelength light. The two-color collimated light emitted by light source 1 is modulated by grating 2, irradiated on the dichroic mirror, and then split and detected separately. The blue light is transmitted to the incremental code detector 4. Under the blue light, the code elements 210 and 211 have the same light field modulation effect. The light field 401 on the detection surface is periodically distributed. After photoelectric conversion, a simple harmonic wave signal 402 is generated, which can be interpolated and subdivided to obtain high-resolution incremental information. The reflected red light is irradiated to the absolute code detector 5 and converted into a code element signal with a logic level. After subsequent decoding according to the coding table, the absolute information of the current position can be obtained.

[0017] Figure 5 This is a schematic diagram of a reflective single-channel absolute photoelectric encoder and decoder system. The system consists of a light source 1, a grating 2, a beam splitter 3, an incremental code detector 4, and an absolute code detector 5. The light source 1 of this embodiment adopts a white light Lambertian point light source, which emits divergent polychromatic light. The grating 2 is a circular grating code disk for measuring rotational motion. The grating 2 is composed of a stainless steel bottom 200 and a surface reflective layer. The reflectivity of metal chromium is about 55%. There are equal-periodic code channels 210 etched on the chrome-plated layer. Different materials are deposited on the grating code channel 210 in sequence according to the coding sequence. The optical beam splitter 3 is composed of a semi-transparent semi-transparent semi-reflective mirror 301, a high reflective mirror 302, a blue light bandpass filter 311, and a red light bandpass filter 312. The semi-transparent semi-reflective mirror 301 and the high reflective mirror 302 split the complex light into transmitted light and reflected light. The transmitted light is filtered into narrow-band blue light by the blue light bandpass filter, and the reflected light is filtered into narrow-band red light by the red light bandpass filter. The complex light emitted by the light source 1 is modulated and reflected by the grating 2, and then irradiated to the optical beam splitter 3 to be split and filtered into narrow-band light sources and then detected separately. The blue light is transmitted to the incremental code detector 4, and a simple harmonic wave signal 402 is generated after photoelectric conversion, which can be interpolated and subdivided to obtain high-resolution incremental information. The reflected red light is irradiated to the absolute code detector 5, converted into a code element signal with a logic level, and the absolute information of the current position can be obtained after subsequent decoding according to the coding table. In this example, the light source 1, the optical beam splitter 3, the incremental code detector 4, and the absolute code detector 5 can be packaged together, which is conducive to miniaturization of the system and easy installation. (V) Specific implementation methods The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly. In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention. Embodiment 1: Figure 4An embodiment of a transmission type single code channel absolute photoelectric codec system is given. The system is composed of a light source 1, a grating 2, an optical beam splitter 3, an incremental code channel detector 4, and an absolute code channel detector 5. In this embodiment, the light source 1 adopts a two-color collimated light source, emitting narrow-band collimated blue light and narrow-band collimated red light. The grating 2 is a linear scale for measuring linear motion. The grating 2 is composed of a glass substrate 200 and a metal chromium reflective layer plated on the surface. The transmittance of the metal chromium is less than one ten-thousandth. An equal-periodic light-transmitting code channel 210 is etched on the chrome layer. According to the 01 pseudo-random code generated by the M sequence, the grating code channel 210 is coated in sequence. The code channel position 211 with a code value of 1 is coated with C1. The transmittance of the C1 film system to blue light and red light is the same as 98%. The code channel position 212 with a code value of 0 is coated with C2. The transmittance of the C2 film system to blue light is the same as C1, which is 98%, and the transmittance to the red light source is less than 10%. The optical beam splitter 3 is a dichroic mirror, which transmits low-wavelength light and reflects high-wavelength light. The two-color collimated light emitted by the light source 1 is modulated by the grating 2, and then irradiated on the optical dichroic mirror for beam splitting and separate detection. The blue light is transmitted to the incremental code detector 4. The code elements 210 and 211 under the blue light have the same light field modulation effect. The detection surface light field 401 is a periodic distribution. After photoelectric conversion, a simple harmonic wave signal 402 is generated, and operations such as interpolation and subdivision can be performed to obtain high-resolution incremental information. The reflected red light is irradiated to the absolute code detector 5, which is converted into a code element signal with a logic level. After subsequent decoding according to the coding principle, the absolute information of the current position can be obtained. Embodiment 2: Figure 5An embodiment of a reflective single-channel absolute photoelectric codec system is provided. The system is composed of a light source 1, a grating 2, an optical beam splitter 3, an incremental code detector 4, and an absolute code detector 5. The light source 1 of this embodiment adopts a white light Lambertian point light source, which emits divergent polychromatic light. The grating 2 is a circular grating code disk for measuring rotational motion. The grating 2 is composed of a stainless steel bottom 200 and a metal chromium reflective layer plated on the surface. The reflectivity of the metal chromium is about 55%. An equal-periodic code channel 210 is etched on the chrome-plated layer. According to the 01 pseudo-random code generated by the M sequence, different materials are deposited on the grating code channel 210 in sequence. The code channel position 211 with a code value of 1 is plated with a high-reflective material D1. The reflectivity of D1 to blue light and red light is the same as 96%. The code channel position 212 with a code value of 0 is deposited with material C2. The reflectivity of C2 material to blue light is the same as that of C1, which is 96%, and the absorption reflectivity to red light is less than 30%. The optical beam splitter 3 is composed of a semi-transparent semi-reflective mirror 301, a high reflective mirror 302, a blue light bandpass filter 311, and a red light bandpass filter 312. The semi-transparent semi-reflective mirror 301 and the high reflective mirror 302 split the complex light into transmitted light and reflected light. The transmitted light is filtered into narrow-band blue light by the blue light bandpass filter, and the reflected light is filtered into narrow-band red light by the red light bandpass filter. The complex light emitted by the light source 1 is modulated and reflected by the grating 2, and then irradiated on the optical beam splitter 3 to be split and filtered into narrow-band light sources and then detected separately. The blue light is transmitted to the incremental code detector 4. The code elements 210 and 211 have the same light field modulation effect under the blue light. The detection surface light field 401 is periodically distributed. After photoelectric conversion, a simple harmonic wave signal 402 is generated, and interpolation and subdivision operations can be performed to obtain high-resolution incremental information. The reflected red light is irradiated onto the absolute code detector 5 and converted into a code element signal with a logic level. After subsequent decoding according to the coding principle, the absolute information of the current position can be obtained. In this example, the light source 1, the optical beam splitter 3, the incremental code detector 4, and the absolute code detector 5 can be packaged together, which is conducive to the miniaturization of the system and easy installation.

Claims

1. A single-channel absolute photoelectric encoding and decoding system. Its characteristics are: The system is composed of a light source (1), a grating (2), a beam splitter (3), an incremental code detector (4), and an absolute code detector (5), wherein the grating (2) is composed of a grating substrate (200) and a unique code channel (210); in the system, light emitted by the light source (1) is modulated by the grating (2), and the modulated light is split by the beam splitter (3), and received and processed by the incremental code detector (4) and the absolute code detector (5) respectively. The unique code channel (210) on the grating (2) has no difference in modulation of the light beam component A1, and forms a grating modulated light field (401) without code channel difference on the photoelectric detection surface. The incremental code detector (4) collects (401) and generates a simple harmonic wave signal (402) after photoelectric conversion, and can subsequently perform operations such as interpolation and subdivision to obtain high-resolution incremental information. The unique code channel (210) modulates the light beam component A2 differently, and forms a grating modulated light field (402) with code channel differences on the photoelectric detection surface. The modulated light field (402) carries code channel coding information, which is collected by the absolute code detector (5) and converted into a code element signal with a logic level. After subsequent decoding according to the coding table, the absolute information of the current position can be obtained. In addition, the optical beam splitter (3) can split more types of light beams such as A3 as needed to improve measurement accuracy or check and correct errors.

2. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The light source (1) in the system can be a collimated light source, a divergent light source, a point light source, a surface light source, a volume light source of various types and combinations thereof, and can be a multicolor light source or a complex color light source and combinations thereof.

3. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The grating (2) may be a rectangular grating, a sinusoidal grating, a blazed grating, a step grating, a volume grating or any other type of grating, including but not limited to a transmission grating, a reflection grating, a diffraction or interference grating.

4. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The scale substrate (200) can be made of opaque technology or materials such as steel alloy, aluminum alloy, plated metal, etc., or can be made of translucent or partially translucent technology or materials such as glass and plastic, including circular code discs of different radii, linear scales, and other scales with arbitrary motion trajectories and shapes.

5. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The grating (2) is an optical modulator formed by a unique code channel (210), wherein the code channel (210) comprises at least two different code positions (211) and (212), including but not limited to absorption, reflection, transmission, scattering, interference or diffraction processes, materials or coatings.

6. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The code channel (210) has a uniform grating distribution, and each grating line of the code channel has no difference in the modulation of the light beam component A1, and a periodic incremental signal can be generated during the movement of the grating.

7. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The code positions (211) and (212) of the code track (210) modulate the light beam component A2 differently. With reference to the scale substrate (200), the intensity modulation of the light beam A2 by the code positions (211) and (212) can be opposite or the same. Each code bit (211) and (212) on the code channel (210) may be encoded according to a specific encoding method, including but not limited to a random code, a pseudo-random code, an M sequence, a Gray code, an index code, etc.

8. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The optical beam splitter (3) splits the light source into at least two light beam components A1 and A2, such as splitting the wavelength of the light. The optical beam splitter includes but is not limited to a dichroic mirror, a semi-transparent semi-reflective mirror, a high-pass filter, a low-pass filter, a band-pass filter, a diffraction optical device, an interference optical device, a dispersion optical device, and the like, and an optical system composed of a combination thereof.

9. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The absolute code detector (5) is used to detect the light field (501) carrying the code channel coded information and decode the logic level signal 502 carrying the coded information. In particular, when the code positions (211) and (212) modulate the intensity of the light beam A2 in the opposite direction, setting the same threshold can achieve the equal width and the same phase of the incremental period and the absolute signal code position, effectively reducing the absolute and incremental fusion error. The absolute detector can output the logic signal in a serial decoding manner or in a parallel decoding manner.

10. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The optical beam splitter (3) can separate more beam components such as A3 as needed. A3 generates incremental codes with other periods in the manner of incremental code detection to improve the accuracy of incremental information; it can also generate check codes in the manner of absolute code detection to correct errors and reduce bit error rates; A3 can also generate reference index codes for incremental counting and resetting.

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