Single code channel absolute photoelectric encoding and decoding system

Abstract

The application provides a single code track absolute photoelectric coding and decoding system, which is characterized by comprising 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 base (200) and a unique code track (210). The application can be used in a system for speed closed-loop control and position accurate measurement, and can be widely used in servo systems, precise measurement, motion control, medical equipment, aerospace and other fields.

Description

(1) Technical field

[0001] The present 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. (2) Background technology

[0002] Photoelectric encoders are sensors based on grating measurement technology that detect and control parameters such as position, displacement, velocity, acceleration, and angle. They play a vital role in 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. Based on the signal reception and processing method, they are categorized as imaging and scanning. Imaging encoders use high-speed exposure to capture the modulated signal of a scale and use image processing to decipher the encoded information within the scale's code tracks. However, the algorithm complexity and high computational effort result in limited real-time performance. Scanning encoders employ specially designed photodetector arrays to output scanning signals of varying phases in real time, making them suitable for high-speed testing. Based on the encoding and decoding method, they are categorized as incremental and absolute encoders. Incremental encoders provide precise relative displacement measurement but require a zero reference point for absolute position measurement. Absolute encoders achieve absolute position measurement without the need for a zero reference, eliminating cumulative error and ensuring data loss after power failure. Traditional absolute encoders employ multiple code tracks, either photoelectric encoders or grating scales, with at least one track for precise incremental information and at least one track for absolute position. However, multiple code channels are detrimental to device miniaturization, and installation yaw deviations can cause multiple code channels to lose phase, leading to measurement errors. Therefore, this paper proposes a single-channel absolute photoelectric encoding and decoding system. This single code channel enables simultaneous real-time scanning measurement of absolute and incremental position, thus avoiding yaw desynchronization caused by installation tolerances. (3) Summary of the invention

[0003] 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.

[0004] The object of the present invention is achieved like this:

[0005] 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 unique code channel (210) on the grating (2) modulates the light beam component A1 in a non-differential manner, forming a grating modulated light field (401) without code channel differences on the photoelectric detection surface. The incremental code detector (4) collects (401) and generates a simple harmonic wave signal (402) after photoelectric conversion. Subsequently, operations such as interpolation and subdivision can be performed to obtain high-resolution incremental information. The unique code channel (210) modulates the light beam component A2 in a different manner, forming 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. After being collected by the absolute code detector (5), it is converted into a code element signal with a logic level. Subsequently, after decoding according to a coding table, the absolute information of the current position can be obtained. In addition, the optical beam splitter (3) can split out more types of light beams such as A3 as needed, which are used to improve measurement accuracy or verify and correct errors.

[0006] (Further details and explanations are given below, including other claims and their details)

[0007] 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, or any combination thereof, and can be a polychromatic light source or a complex light source, or any combination thereof. The light source carries at least two beam components A1 and A2.

[0008] 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.

[0009] The scale substrate 200 can be made of an opaque process or material such as steel alloy, aluminum alloy, or plated metal, or a translucent or partially translucent process or material such as glass or plastic, including circular code disks of different radii, linear scales, and scales of other arbitrary motion trajectories and shapes.

[0010] The grating 2 is an optical modulator formed by a unique code channel 210 , which includes at least two different code bits 211 and 212 , including but not limited to absorption, reflection, transmission, scattering, interference or diffraction processes, materials or coatings.

[0011] The code channel 210 has a uniform grating pitch 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 grating movement.

[0012] Code positions 211 and 212 of code track 210 modulate light beam component A2 differently. With reference to scale substrate 200, code positions 211 and 212 can modulate the intensity of light beam A2 in opposite or identical directions. Each code position 211 and 212 on code track 210 can be encoded using a specific encoding scheme, including but not limited to random codes, pseudo-random codes, M-sequences, Gray codes, index codes, and the like.

[0013] The optical beam splitter 3 separates the light source into at least two beam components, A1 and A2, such as by splitting the wavelength of the light. Optical beam splitters include, but are not limited to, dichroic mirrors, semi-transparent and semi-reflective mirrors, high-pass filters, low-pass filters, band-pass filters, diffraction optical devices, interference optical devices, dispersive optical devices, and combinations thereof, and may be optical systems.

[0014] The absolute code detector 5 is used to detect the light field 501 carrying the code channel encoding information and decode it into a logic level signal 502 carrying the encoded information. Specifically, when code bits 211 and 212 modulate the intensity of light beam A2 in opposite directions, setting the same threshold ensures that the incremental period and the absolute signal code bits are of equal width and in phase, effectively reducing absolute and incremental fusion errors. The absolute detector can output logic signals using either serial or parallel decoding.

[0015] Beam splitter 3 can split additional beam components, such as A3, as needed. A3 generates incremental codes with other periods using incremental code detection to improve the accuracy of incremental information. It can also generate check codes using absolute code detection for error correction and bit error rate reduction. A3 can also generate reference index codes for incremental counting and resetting. (IV) Description of the accompanying drawings

[0016] Figure 1 This is a schematic diagram of single-track absolute encoding. The encoding technology is implemented on the scale 2, which consists of a scale base 200 and a unique code channel 210. The code channel 210 contains at least two different code positions 211 and 212. Each code position 211 and 212 on the code channel 210 is encoded according to a specific encoding method M. Each bit m of the encoding M is encoded. iCorresponding 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. The code position 211 and the 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 light beam component A1, the code positions 211 and 212 of the code channel 210 do not have differences, and the code channel 210 has a uniform grating distribution, and a periodic incremental signal can be generated during the grating movement. For the light beam component A2, the code positions 211 and 212 of the code channel 210 have differences in the modulation of light and can carry the information of the code M.

[0017] Figure 2 This is a schematic diagram of single-channel absolute decoding. Absolute code decoding technology consists of a scale 2 and an absolute code detector 5. Light beam component A2 is modulated by the unique code channel 210 of grating 2. Light field 502, carrying the code bit differential 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 coded information through photoelectric conversion of each sub-element. Specifically, when code bits 211 and 212 modulate the intensity of light beam A2 in opposite directions, setting the same threshold ensures that the incremental period and the absolute signal code bits are equal in width and phase, effectively reducing absolute and incremental fusion errors. The absolute detector can read out the logic signal using either serial or parallel decoding.

[0018] Figure 3 This is a schematic diagram of a single-code channel absolute detection system. The detection system realizes the detection of absolute position codes and precise 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 beam component A1 by the unique code channel (210) is not different, and a grating modulated light field (401) without code channel differences 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. Subsequently, interpolation and subdivision operations can be performed to obtain high-resolution incremental information. The modulation of the beam component A2 by the unique code channel (210) is different, and a grating modulated light field (402) with code channel differences is formed on the photoelectric detection surface. The modulated light field (402) carries code channel coding information. After being collected by the absolute code detector (5), it is 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. 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.

[0019] Figure 4 This is a schematic diagram of a transmissive, single-channel, absolute photoelectric encoder / 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 narrowband collimated blue light and narrowband 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 shield. Transmissive channels 210 of equal periodicity are etched into the shielding layer. These channels are then coated sequentially 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 and then incident on the dichroic mirror for separate detection. Blue light is transmitted to incremental code detector 4. Under this light, code elements 210 and 211 have the same optical field modulation effect. The light field 401 on the detection surface is periodically distributed. Photoelectric conversion generates a simple harmonic wave signal 402, which can be interpolated and subdivided to obtain high-resolution incremental information. Reflected red light is irradiated by absolute code detector 5, where it is converted into a code element signal with a logic level. Subsequent decoding according to the coding table yields the absolute information of the current position.

[0020] Figure 5 This is a schematic diagram of a reflective, single-track, absolute photoelectric encoder / decoder system. The system consists of a light source 1, a grating 2, a beam splitter 3, an incremental track detector 4, and an absolute track detector 5. In this embodiment, light source 1 utilizes a white Lambertian point light source, emitting divergent, polychromatic light. Grating 2 is a circular grating code disk used to measure rotational motion. It consists of a stainless steel base 200 and a reflective surface layer. The reflectivity of the metallic chromium is approximately 55%. A code track 210 of equal periodicity is etched into the chrome layer. Different materials are deposited sequentially on the grating code track 210 according to the coding sequence. The optical beam splitter 3 consists of a semi-transparent, semi-reflective mirror 301, a high-reflective mirror 302, a blue bandpass filter 311, and a red bandpass filter 312. The semi-transparent, semi-reflective mirror 301 and the high-reflective mirror 302 split the polychromatic light into transmitted light and reflected light. The transmitted light is filtered into narrow-band blue light by the blue bandpass filter, and the reflected light is filtered into narrow-band red light by the red bandpass filter. The polychromatic light emitted by the light source 1 is modulated and reflected by the grating 2. It then strikes the optical beam splitter 3, where it is split and filtered into narrow-band light sources and detected separately. The blue light is transmitted to the incremental code detector 4, where it undergoes photoelectric conversion to generate a simple harmonic wave signal 402, which can be interpolated and subdivided to obtain high-resolution incremental information. The reflected red light strikes the absolute code detector 5, where it is converted into a code element signal with a logic level. Subsequent decoding according to the coding table yields the absolute information of the current position. 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 beneficial to the miniaturization of the system and easy installation. (V) Specific implementation methods

[0021] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort are within the protection scope of the present application.

[0022] It should be noted that all the direction indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the direction indications also change accordingly.

[0023] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] In addition, the description such as "first", "second", etc. in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is also not within the protection scope of the present application.

[0025] Embodiment one:

[0026] Figure 4An embodiment of a transmissive single-channel absolute photoelectric encoder / decoder system is provided. The system comprises a light source 1, a grating 2, an optical beam splitter 3, an incremental channel detector 4, and an absolute channel detector 5. In this embodiment, light source 1 utilizes a two-color collimated light source, emitting narrowband collimated blue light and narrowband collimated red light. Grating 2 is a linear scale used to measure linear motion. Grating 2 comprises a glass substrate 200 coated with a reflective layer of metal chromium. The metal chromium has a transmittance of less than one ten-thousandth. Transparent channels 210 of equal periodicity are etched into the chromium layer. Films are sequentially applied onto grating channels 210 according to a 01 pseudo-random code generated by an M sequence. Channels 211 with a code value of 1 are coated with C1. The C1 film has a transmittance of 98% for both blue and red light. Channels 212 with a code value of 0 are coated with C2. The C2 film has a transmittance of 98% for blue light, the same as C1, and a transmittance of less than 10% for red light. 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 and then beam split by the dichroic mirror for separate detection. Blue light is transmitted to incremental code detector 4. Under blue light, code elements 210 and 211 have the same light field modulation effect. The detection surface light field 401 is periodically distributed. Photoelectric conversion generates a simple harmonic wave signal 402, which can be interpolated and subdivided to obtain high-resolution incremental information. The reflected red light is transmitted to absolute code detector 5, where it is converted into a code element signal with a logic level. Subsequent decoding based on coding principles yields absolute information about the current position.

[0027] Example 2:

[0028] Figure 5A system of reflective single code track absolute photoelectric encoder and decoder is given. The system is composed of light source 1, grating 2, light beam splitter 3, incremental code track detector 4, absolute code track detector 5. The light source 1 of this embodiment is a white Lambert point light source, emitting divergent complex light. The grating 2 is a circular grating code disc for measuring rotary motion, which is composed of stainless steel bottom 200 and surface chromium-coated reflective layer. The reflectivity of chromium is about 55%, and the code track 210 with equal period is etched on the chromium-coated layer. According to the 01 pseudo-random code generated by M sequence, different materials are deposited on the code track 210 in turn. The code track bit 211 with code value 1 is coated with high-reflective material D1, which has the same reflectivity of 96% for blue light and red light. The code track bit 212 with code value 0 is deposited with material C2, which has the same reflectivity of 96% for blue light as C1, and has less than 30% reflectivity for red light. The light beam splitter 3 is composed of semi-transparent semi-reflective mirror 301, high-reflective mirror 302, blue band-pass filter 311, and red band-pass filter 312. The semi-transparent semi-reflective mirror 301 and 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 band-pass filter, and the reflected light is filtered into narrow-band red light by the red band-pass filter. The complex light emitted by the light source 1 is modulated and reflected by the grating 2, and then irradiates on the light beam splitter 3 to be split and filtered into narrow-band light sources for separate detection. The blue light is transmitted to the incremental code detector 4. The code elements 210 and 211 under blue light have the same light field modulation effect, and the light field 401 on the detection surface is periodically distributed. After photoelectric conversion, the simple harmonic signal 402 is generated, and interpolation subdivision and other operations can be performed to obtain high-resolution incremental information. The reflected red light irradiates on the absolute code detector 5, and is converted into code element signal with logic level. After decoding according to the encoding principle, the absolute information of the current position can be obtained. In this example, the light source 1, light beam splitter 3, incremental code detector 4, and absolute code detector 5 can be packaged together, which is conducive to the miniaturization of the system and easy to install.

Claims

1. A single-channel absolute optoelectronic encoding and decoding system, characterized by: 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), wherein the grating (2) consists 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), the modulated light is split by the beam splitter (3), and is 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 the grating modulated light field (401) without code channel difference and generates a simple harmonic wave signal (402) after photoelectric conversion, which can be subsequently interpolated and subdivided to obtain high-resolution incremental information; the unique code channel (210) has no difference in modulation of the light beam component A2 The system has differences, and a grating modulated light field (501) with code channel differences is formed on the photoelectric detection surface. The grating modulated light field (501) with code channel differences 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 subsequent decoding according to the coding table. In addition, the optical beam splitter (3) can separate the light beam component A3, which is used to improve measurement accuracy or check and correct errors; the grating (2) is an optical modulator formed by a unique code channel (210), and the code channel (210) contains at least two different code bits, including but not limited to absorption, reflection, transmission, scattering, interference or diffraction processes, materials or coatings; the code channel (210) has a uniform grating pitch distribution, and the modulation of the beam component A1 by each grating line of the code channel does not have differences, and a periodic incremental signal can be generated during the movement of the grating.

2. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, wherein: The light source (1) in the system is 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, or a multi-color 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, wherein: The grating (2) is 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, wherein: The grating substrate (200) is made of steel alloy, aluminum alloy, plated metal, or glass or plastic, and includes circular code discs or linear scales with different radii.

5. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, wherein: The two different code positions of the code channel (210) modulate the light beam component A2 differently. With reference to the grating substrate (200), the two different code positions modulate the intensity of the light beam A2 in opposite directions or in the same direction. Each code position on the code channel (210) can be encoded according to a specific encoding method, and the encoding method includes but is not limited to a random code, a pseudo-random code, a Gray code, and an index code.

6. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, wherein: The optical beam splitter (3) separates the light source into at least two light beam components A1 and A2, and splits 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.

7. 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 a grating modulated light field (501) with code channel differences that carries code channel encoding information, and decodes a logic level signal (502) that carries the encoding information. When the intensity modulation of the light beam A2 by two different code positions is reversed, the same threshold value is set to achieve the equal width and the same phase of the incremental period and the absolute signal code position, thereby reducing the absolute and incremental fusion error. The absolute detector outputs the logic signal in a serial decoding or parallel decoding manner.

8. The single-channel absolute optoelectronic encoding and decoding system according to claim 1, characterized in that: The optical beam splitter (3) can split the light beam component A3, and A3 generates incremental codes of different periods according to the incremental code detection method, which is used to improve the accuracy of incremental information; or A3 generates a check code according to the absolute code detection method, which is used for error correction and bit error rate reduction; or A3 generates a reference index code for incremental counting and resetting.

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