Incremental code channel output signal compensation method and photoelectric encoder system

Abstract

The invention provides an incremental code channel output signal compensation method and a photoelectric encoder system. The photoelectric encoder is characterized in that the photoelectric encoder system is composed of an LED light source (1), a coded disc (2), a photodiode array (3) and an incremental code channel output signal compensation method (4), wherein the coded disc (2) is composed of incremental code channels (21); the photodiode array (3) is composed of incremental code channel photodiode arrays (31); light is emitted from the LED light source (1), modulated by the incremental code channel (21) and then received by the incremental code channel photodiode array (31), and an output signal is compensated and corrected by the incremental code channel output signal compensation method (4) to obtain a Lisajous circle with better quality, so that the system can still output a correct signal under the condition that the code channel is polluted or has other noise interference. The method can be used for high-precision linear displacement and angle measurement, and can be widely applied to the fields of high-precision machine tool control machining, semiconductor machining and detection and the like.

Description

(I) Technical field

[0001] The present invention relates to an incremental code channel output signal compensation method and a photoelectric encoder system, which can be widely used in the fields of machine tool control processing, semiconductor processing and precision detection. (II) Background technology

[0002] With the development of modern precision industry, especially the semiconductor industry, higher requirements have been put forward for processing accuracy in fields such as chip processing and testing and precision CNC processing. The demand for high-precision processing corresponds to high-precision positioning and detection requirements. As a displacement sensing device that uses light fields as input and output signals for precise measurement, photoelectric encoders have been widely used in precision processing and testing fields such as semiconductors with their ultra-high detection accuracy, compact system structure and long service life. At the same time, it has also promoted the continuous improvement of the detection accuracy and precision of photoelectric encoder systems.

[0003] A photoelectric encoder is a displacement or angle sensor that modulates the incident light signal through a code disc engraved with a special pattern and generates a periodic light field to measure the moving distance. It is mainly composed of an LED light source, a code disc with engraved lines, and a photodiode detection array. The incident light beam is modulated by the incremental code channel in the code disc to form a light field with a certain periodicity. The energy distribution period of the light field is W. According to the 4 signals with a phase difference of 90° output by the photodiode array: A sin+ , A sin- , A cos- , A cos+ , subtract the two signals with a phase difference of 180° to remove the even harmonic components and get A sin and A cos The two signals with a phase difference of 90° can then be used to calculate the phase corresponding to the current position through the inverse tangent (such as Figure 2 ): According to the phase The moving distance at the current time t1 relative to the previous time t0 can be calculated by using the signal period w (e.g. Figure 2 ):

[0004] In common photoelectric encoder systems, at least one incremental code channel consisting of a certain grating pattern is included. The incremental displacement information can be obtained by performing inverse tangent calculation on the incremental code channel output signal. However, due to the inevitable introduction of interference such as code channel dirt, circuit noise, and assembly error in the actual use environment, the output signal carries more clutter interference, which in turn affects the amplitude or phase difference of the output signal. When the output signal is no longer a standard Lissauer circle, the result calculated by the inverse tangent in formula (1) will have a certain deviation from the actual result, which will affect the positioning accuracy of the system.

[0005] In order to solve the above problems, the present invention discloses an incremental code channel output signal compensation method and a photoelectric encoder system, which can be used in the fields of high-precision machine tool control processing, semiconductor processing and precision detection. Figure 3 As shown, in the present invention, before using the encoder, any point in the uniform rotation process of the code disk is used as the starting point and the current point is defined as Then collect the output signal amplitude information within a continuous cycle and record it as A 1sin ~A Nsin and A 1cos ~A Ncos , and its corresponding phase is Since the code disk rotates at a constant speed, the corresponding phases are distributed at equal intervals. are mapped onto the standard Lissajous circle and the corresponding A sin and A cos Reblogged as B sin and B cos , thus establishing the mapping relationship of "output value-phase-standard value". sin and A cos The corresponding value can be found sin and B cos , since the standard value B is mapped to the standard Lissajous circle, according to The current phase can be accurately calculated, and then the accurate displacement can be calculated. If the mapping table does not divide the phase finely enough in actual use, the difference method can be used to calculate the standard value after the corresponding difference, and then the corresponding phase value can be calculated using formula (1). (III) Summary of the invention

[0006] The object of the present invention is to provide a method for arranging a photodiode array based on an optical encoder incremental code channel dirt immunity and an encoder system; the characteristics are: the encoder system is composed of an LED light source (1), a code disk (2), a photodiode array (3), and an incremental code channel output signal compensation method (4), wherein: the code disk (2) in the system is composed of an incremental code channel (21); the photodiode array (3) in the system is composed of an incremental code channel photodiode array (31). The object of the present invention is achieved in that:

[0007] like Figure 3 As shown, in the present invention, before using the encoder, any point in the uniform rotation process of the code disk is used as the starting point and the current point is defined as Then collect the output signal amplitude information within a continuous cycle and record it as A 1sin ~A Nsin and A 1cos ~A Ncos , and its corresponding phase is Since the code disk rotates at a constant speed, the corresponding phases are distributed at equal intervals. are mapped onto the standard Lissajous circle and the corresponding A sin and A cos Reblogged as B sin and B cos , thus establishing the mapping relationship of "output value-phase-standard value". sin and A cos The corresponding value can be found sin and B cos Since the standard value B is mapped to the standard Lissajous circle, the current phase can be accurately calculated according to equations (2) and (3), and then the accurate displacement can be calculated.

[0008] The LED light source (1) in the system is used to generate a stable and high-intensity initial light beam; the LED light source (1) may or may not have a lens on its surface, but it should be ensured to have a sufficient output light beam angle so that the light beam can cover the incremental code track (21) when irradiating the code disk (2); the position and angle of the LED light source (1) should be adjusted according to the structure of the actual optical encoder system so that the light beam emitted by the LED light source (1) can be received by the incremental code track photodiode array (31) after being modulated by the code disk (2); the LED light source (1) should have a narrow spectral range, and its spectral width should be less than 60nm; the LED light source (1) should have a small light-emitting size and should have a suitable spacing distance from the code disk (2), so that the light field modulated after irradiating the code disk (2) should have clear periodic characteristics;

[0009] The code disc (2) in the system is used to modulate the light beam emitted by the LED light source (1), and its substrate can be a metal or a transparent medium; when the code disc (2) rotates around its center, the incremental code track photodiode array (31) in the photodiode array (3) detects the light spot signal modulated by the incremental code track (21) and outputs the corresponding displacement increment information; the characteristic is that the incremental code track (21) in the code disc (2) is achieved by coating a coating or engraving with a certain period on the substrate material to modulate the incident light field; in the reflective optical path, the incremental code track (21) part of the code disc (2) should be coated with a layer with high reflectivity and the reflectivity should be significantly different from that of the non-code track area to ensure that the output signal has a certain contrast; in the transmissive optical path, the incremental code track (21) part of the code disc (2) should be able to ensure that the light has a certain transmittance and the transmittance should be significantly different from that of the non-code track area to ensure that the output signal has a certain contrast.

[0010] The photodiode array (3) in the system is composed of an incremental code channel photodiode array (31), which is a photodiode array comprising a signal amplification unit, a filter, an analog-to-digital conversion unit, a signal processor, and a temperature sensor, and is capable of converting an optical signal into an electrical signal for output; the system is characterized in that the width and arrangement period of the photodiodes in the incremental code channel detection unit (31) of the photodiode array (3) should be determined according to the actual light field period after being modulated by the incremental code channel (31) in the code disk (2); the position of the photodiodes in the incremental code channel detection unit (31) should be arranged according to the light field period to ensure that four sine and cosine signal outputs with a phase difference of 90° can be collected.

[0011] The incremental code channel output signal compensation method (4) in the system is used to compensate and correct the decrease in Lissajous circularity caused by code channel dirt, noise and other factors, so as to ensure the accuracy of the output result; it is characterized in that the amplitudes of the two signals constituting the Lissajous circularity are recorded separately in one incremental signal cycle, the signal in one cycle is divided according to angle according to the resolution requirement, each individually divided angle is mapped to a standard Lissajous circularity and the horizontal and vertical coordinates corresponding to the point on the standard circle are read out, thus establishing a mapping relationship between angle-actual signal amplitude-standard signal amplitude. When turning to any angle, it is only necessary to determine the standard signal amplitude according to the mapping relationship after obtaining the current signal amplitude, and the current angle can be calculated according to the standard signal amplitude, thus compensating and correcting the non-standard Lissajous circularity and being able to output accurate calculation results. (IV) Description of the drawings

[0012] Figure 1The invention discloses an incremental code channel output signal compensation method and a photoelectric encoder system structure diagram. The system structure comprises an encoder system comprising an LED light source (1), a code disk (2), a photodiode array (3), and an incremental code channel output signal compensation method (4), wherein: the code disk (2) in the system comprises an incremental code channel (21); and the photodiode array (3) in the system comprises an incremental code channel photodiode array (31).

[0013] Figure 2 It is a schematic diagram of the incremental code channel output signal and Lissauer circle. W refers to the output signal period, Ф refers to the phase value corresponding to the current position calculated by inverse tangent, and Δx refers to the displacement increment calculated according to the phase difference.

[0014] Figure 3 It is a schematic diagram of the output signal and Lissauer circle before and after compensation and correction of the signal with amplitude and phase difference. sin and A cos Indicates the output signal amplitude before compensation correction, B sin and B cos It indicates the standard signal amplitude after compensation and correction. Indicates the corresponding phase.

[0015] Figure 4 It is a specific implementation case. (V) Specific implementation methods

[0016] Figure 4 The invention provides an implementation case of the incremental code channel output signal compensation method and the photoelectric encoder system. The system is composed of an LED light source (1), a code disk (2), a photodiode array (3), and an incremental code channel output signal compensation method (4), wherein: the code disk (2) in the system is composed of an incremental code channel (21); and the photodiode array (3) in the system is composed of an incremental code channel photodiode array (31).

[0017] When the code disk rotates at a constant speed and collects the output signal amplitude information within a continuous cycle, it is recorded as A 1sin ~A Nsin and A 1cos ~A Ncos , combined with the divided phase And the standard value B corresponding to the standard Lissajous circle sin and B cos You can get an "output value A-phase -standard value B” mapping table. In normal use, if the amplitude of the output signal is detected to be (0.85, 1.1), the current corresponding standard value can be obtained from the table as (0.707, 0.707), and then the current phase value can be obtained by inverse tangent calculation according to formula (1): If the detected value cannot directly find the corresponding standard value B in the mapping table, first calculate the average value (B1) of the standard values ​​B1 and B2 corresponding to the two adjacent known phase values. 12sin ,B 12cos ), and then calculate the phase value by the inverse tangent value. If we directly use the average of the measured values ​​A1 and A2 (A 12sin ,A 12cos ) for linear interpolation will result in larger errors because the trajectory of the signal is a curve.

Claims

1. A method for compensating an incremental code channel output signal and a photoelectric encoder system; characterized in that: The optical encoder system is composed of an LED light source (1), a code disk (2), a photodiode array (3), and an incremental code channel output signal compensation method (4), wherein: the code disk (2) in the system is composed of an incremental code channel (21); the photodiode array (3) in the system is composed of an incremental code channel photodiode array (31); the light beam emitted by the LED light source (1) in the system is irradiated onto the code disk (2) and the light beam can cover the incremental code channel (21), and the light beam modulated by the code disk (2) carries the information of the incremental code channel (21); the light carrying the information of the incremental code channel (21) in the reflected light is received by the incremental code channel photodiode array (31) in the photodiode array (3) and after compensation and correction by the incremental code channel output signal compensation method (4), a signal with a good quality Lissauer circle is output.

2. The incremental code channel output signal compensation method and photoelectric encoder system according to claim 1; characterized in that: The LED light source (1) in the system is used to generate a stable and high-intensity initial light beam; the LED light source (1) may or may not have a lens on its surface, but it should be ensured to have a sufficient output light beam angle so that the light beam can cover the entire incremental code track (21) when irradiating the code disk (2); the position and angle of the LED light source (1) should be adjusted according to the structure of the actual optical encoder system so that the light beam emitted by the LED light source (1) can be received by the incremental code track photodiode array (31) after being modulated by the code disk (2); the LED light source (1) should have a narrow spectral range, and its spectral width should be less than 50nm; the LED light source (1) should have a small light-emitting size and should have a suitable spacing distance from the code disk (2), so that the light field modulated after irradiating the code disk (2) should have clear periodic characteristics.

3. The incremental code channel output signal compensation method and photoelectric encoder system according to claim 1; characterized in that: The code disc (2) in the system is used to modulate the light beam emitted by the LED light source (1), and its substrate can be a metal or a transparent medium; when the code disc (2) rotates around its center, the incremental code track photodiode array (31) in the photodiode array (3) detects the light spot signal modulated by the incremental code track (21) and outputs the corresponding displacement increment information; the characteristic is that the incremental code track (21) in the code disc (2) is achieved by coating a coating or engraving with a certain period on the substrate material to modulate the incident light field; in the reflective optical path, the incremental code track (21) part of the code disc (2) should be coated with a layer with high reflectivity and the reflectivity should be significantly different from that of the non-code track area to ensure that the output signal has a certain contrast; in the transmissive optical path, the incremental code track (21) part of the code disc (2) should be able to ensure that the light has a certain transmittance and the transmittance should be significantly different from that of the non-code track area to ensure that the output signal has a certain contrast.

4. The incremental code channel output signal compensation method and photoelectric encoder system according to claim 1; characterized in that: The photodiode array (3) in the system is composed of an incremental code channel photodiode array (31), which is a photodiode array comprising a signal amplification unit, a filter, an analog-to-digital conversion unit, a signal processor, and a temperature sensor, and is capable of converting an optical signal into an electrical signal for output; the system is characterized in that the width and arrangement period of the photodiodes in the incremental code channel detection unit (31) of the photodiode array (3) should be determined according to the actual light field period after being modulated by the incremental code channel (31) in the code disk (2); the position of the photodiodes in the incremental code channel detection unit (31) should be arranged according to the light field period to ensure that four sine and cosine signal outputs with a phase difference of 90° can be collected.

5. The incremental code channel output signal compensation method and photoelectric encoder system according to claim 1; characterized in that: The incremental code channel output signal compensation method (4) in the system is used to compensate and correct the decrease in Lissajous circularity caused by code channel dirt, noise and other factors, so as to ensure the accuracy of the output result; it is characterized in that the amplitudes of the two signals constituting the Lissajous circularity are recorded separately in one incremental signal cycle, the signal in one cycle is divided according to angle according to the resolution requirement, each individually divided angle is mapped to a standard Lissajous circularity and the horizontal and vertical coordinates corresponding to the point on the standard circle are read out, thus establishing a mapping relationship between angle-actual signal amplitude-standard signal amplitude. When turning to any angle, it is only necessary to determine the standard signal amplitude according to the mapping relationship after obtaining the current signal amplitude, and the current angle can be calculated according to the standard signal amplitude, thus compensating and correcting the non-standard Lissajous circularity and being able to output accurate calculation results.

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