A high-precision grating scale signal phase mutual correction algorithm and reading head system

Abstract

The present invention provides a high-precision grating scale code signal phase mutual correction algorithm and a reading head system, which is characterized in that: the high-precision grating scale reading head system is composed of a collimated light source (1), a scale grating (2), an indicator grating (3), a photodiode array (4), and a code signal phase mutual correction algorithm (5); through the code signal phase mutual correction algorithm (5), the photodiode array (4) can generate an output signal with correct phase information according to the relative displacement of the scale grating (2). The present invention can be used for the measurement of high-precision micro displacements and can be widely used in the fields of precision semiconductor manufacturing, precision displacement measurement, precision motion control, closed-loop feedback control of CNC machine tools, etc.

Description

(I) Technical field

[0001] The present invention relates to a high-precision grating scale signal phase mutual correction algorithm and a reading head system, which can be used for high-precision micro-displacement measurement such as precision semiconductor manufacturing, precision displacement measurement, precision motion control, and closed-loop feedback control of CNC machine tools, and belongs to the field of photoelectric detection technology. (II) Background technology

[0002] In modern industry, people have put forward higher and higher requirements for the accuracy, speed, resolution and reliability of displacement measurement. As a high-precision linear displacement sensor, the grating ruler not only has better performance in the above indicators, but also has a lower manufacturing cost, making it widely used in fields such as CNC machining technology. With the rapid development of CNC machining technology, the technical level of grating rulers has been greatly improved.

[0003] The grating ruler uses a high-precision long grating (scale grating) as the measurement reference. When the scale grating overlaps with the grating on the reading head (indicator grating), the light field after passing through the two gratings will form a moiré pattern. Figure 2 ). According to the geometric shading principle, the fringe spacing W and direction of the moiré fringe Satisfies the following equation:

[0004]

[0005] Where d1, d2 and θ are the two grating pitches and their angle respectively.

[0006] Formulas (1) and (2) represent the general pattern of moiré fringes (also called oblique moiré fringes). Depending on the values ​​of d1, d2 and θ, the fringes will also present different patterns: when d1 is equal to d2 and θ approaches 0, the moiré fringes are almost perpendicular to the direction of the grid lines, and the fringe spacing W = d / θ. This type of fringes is called transverse moiré fringes; when d1 is close to d2 and θ is equal to 0, the moiré fringes are parallel to the direction of the grid lines, and the fringe spacing W = d2 / Δd. This type of fringes is called longitudinal moiré fringes. In the above two patterns, since the parameters on the denominator are small, the fringe spacing W is much larger than the grid pitch d. When there is a small relative displacement of the scale grating and the indicator grating of the scale ...

[0007] The scale grating of an absolute optical scale contains incremental and absolute tracks, and correspondingly, there are also incremental and absolute tracks on the indicator grating. When the system is turned on, the low-precision absolute position information can be quickly obtained by reading the unique position code on the scale grating through the absolute track on the indicator grating. Then, the high-precision position information is obtained through the moiré fringes obtained through the incremental track on the indicator grating. Since there is no need to find a reference zero position, the absolute optical scale has higher reliability and work efficiency. For reflective optical scales, the scale grating is mostly made of steel, and the light source and photoelectric detection device are located on the same side of the scale grating, which also allows the scale grating to be directly installed on the base surface of the system to be tested. This not only saves installation space, but also allows it to be used in a large range of test scenarios.

[0008] In the early grating scale, the moiré fringes were usually light gate moiré fringes (when d1 = d2 and θ = 0). According to formula (1), the spacing of the light gate moiré fringes tends to infinity, so four-field scanning is required to obtain the light field information of the incremental code channel. Four-field scanning requires four collimated light sources, and the incremental code channel of the indicator grating needs to open four windows aligned with the collimated light sources. The grating pitch of each window is the same as that of the scale grating, and the grating lines of each window differ by 1 / 4 of the grating pitch in sequence. There is a photoelectric detection device at the rear end of each window to receive the four-phase light intensity signal. Corresponding to the four-field scanning, the incremental window of the single-field scanning indicator grating only needs to open one window, and the fringes formed are longitudinal moiré fringes or transverse moiré fringes. The photoelectric detection device at the rear end of the window uses a densely arranged photodiode array, and the adjacent photodiodes receive moiré fringe signals with a phase difference of 1 / 4. Since the incremental window of the single-field scanning only needs to open one window, it is small in size and easy to integrate. In addition, multiple photodiodes are used for detection in each phase of single-field scanning, and the average effect between photodiodes in the same phase can effectively reduce the impact of dirt or random errors. In addition, the failure rate and adjustment difficulty of single-field scanning are significantly reduced compared with four-field scanning.

[0009] The present invention adopts Figure 1 The system block diagram shown is a single-field scanning reflective absolute grating ruler. Since the moiré fringes at the third incremental code track (41) on the photodiode array (4) are periodic sinusoidal signals A, in use, it is necessary to convert the sinusoidal signals into high and low level signals A' through threshold comparison, and judge the displacement of the scale grating (2) relative to the indicator grating (3) according to the rise / fall of the signal A'.

[0010] Due to factors such as assembly, light source attenuation, optical path dirtiness, random fluctuations, etc., the amplitude or background of the Moire fringe sine wave signal is weakened. When the discrimination threshold remains unchanged, a square wave signal with a low duty cycle (such as Figure 3Or due to factors such as assembly, light leakage, random fluctuations, etc., the amplitude or background of the moiré fringe sine wave signal is enhanced. When the discrimination threshold remains unchanged, a square wave signal with a high duty cycle will be generated (such as Figure 4 In both cases, the phase corresponding to the rising / falling edge of signal A' will deviate from the designed value, thereby obtaining erroneous displacement information.

[0011] In order to solve the above problems, the present invention discloses a high-precision grating scale signal phase mutual correction algorithm and a reading head system, which can be used for high-precision micro-displacement measurement and can be widely used in precision semiconductor manufacturing, precision displacement measurement, precision motion control, closed-loop feedback control of CNC machine tools and other fields. Figure 1 As shown, the present invention can make the rising edge of the square wave output by the third absolute code channel (42) and the reference signal M of the moiré fringe signal of the third incremental code channel (41) aligned with the zero phase through the design of a special photodiode array (4). Signal A and signal M are input as input signals into the code channel signal phase mutual correction algorithm (5). Whenever the algorithm detects the rising edge of signal M, the voltage value of signal A at this time is recorded as the discrimination threshold L', and the updated discrimination threshold L' is fed back to the photodiode array (4). The photodiode array (4) outputs a signal A" with correct phase and duty cycle according to the updated discrimination threshold L'. This improves the accuracy and reliability of the grating scale system. (III) Summary of the invention

[0012] The purpose of the present invention is to provide a high-precision grating ruler reading head system, which is composed of a collimated light source (1), a reflective grating (2), a transmissive grating (3), a photodiode array (4), and a code channel signal phase mutual correction algorithm (5).

[0013] The objective of the present invention is achieved in this way: the photodiode array (4) generates an output signal for the light field irradiated thereon along with the relative displacement of the scale grating (2), wherein the third incremental code channel (41) generates an incremental sine wave signal A, generates an incremental square wave signal A' according to a set discrimination threshold L, and generates an absolute square wave signal M according to the third absolute code channel (42); the signal A and the signal M generated by the photodiode array (4) are input into a code channel signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) adjusts the discrimination threshold L' in real time according to the states of the signal A and the signal M, and feeds back to the photodiode array (4), the photodiode array (4) generates an incremental square wave signal A" with a correct phase corresponding to the duty cycle and the rising / falling edge according to the updated discrimination threshold L', thereby achieving real-time correction of the code channel signal phase.

[0014] The collimated light source (1) in the system can be any one of a light source system formed by a light emitting diode (LED) and a special lens or a laser after collimation / expansion. The collimated light source (1) is characterized in that the collimated light source (1) has a relatively small beam divergence angle, and the half-maximum full width of the beam divergence angle is less than 10°; the collimated light source (1) has a relatively narrow spectral range, or is a monochromatic light source, and the half-maximum full width of the spectrum is less than 35nm; the collimated light source (1) has a relatively large aperture, and can simultaneously illuminate the first incremental code track (21) and the first absolute code track (22) on the scale grating (2); the beam direction of the collimated light source (1) forms an angle with the vertical direction of the plane where the scale grating (2) is located, and the smaller pair of angles formed is between 45° and 10°.

[0015] The scale grating (2) in the system is a reflective grating that can undergo one-dimensional relative displacement with the collimated light source (1) and the photodiode array (4), and can generate a light field that changes with the relative displacement and project it onto the indicator grating (3); the characteristic is that the scale grating (2) uses a metal material as a substrate, and is plated with periodic polished metal stripes, which can reflect the incident light beam; the stripe period (grating pitch) in the first incremental code track (21) area on the scale grating (2) is between 20 μm and 50 μm; correspondingly, the width of a single stripe is half of the stripe period (grating pitch), and is between 10 μm and 2 5μm; in the first absolute code track (22) area of ​​the scale grating (2), the stripes are distributed in a randomly coded form, the width of a single stripe is the same as the stripe width (grid pitch) in the first incremental code track (21) area, between 20μm and 50μm, each reflection stripe in the first absolute code track (22) area must be aligned with a stripe in the first incremental code track (21) area, and the width of a single stripe must be greater than the grid pitch in the first incremental code track (21) area; the direction of the stripes in the first incremental code track (21) and the first absolute code track (22) area must be consistent with the displacement direction of the scale grating (2).

[0016] The indicator grating (3) in the system is a transmission grating fixed in position relative to the collimated light source (1) and the photodiode array (4), and is capable of filtering the light field reflected by the scale grating (2); the indicator grating (3) is characterized in that the indicator grating (3) uses a glass material as a substrate, on which periodic dielectric stripes are plated, and is capable of transmitting the incident light beam; the stripes in the second incremental code channel (31) area on the indicator grating (3) are distributed in an anti-phase manner relative to the stripes in the first incremental code channel (21) area on the scale grating (2), that is, at the stripes in the first incremental code channel (21), there should be no stripes at the corresponding position in the second incremental code channel (31), and vice versa; the second incremental code channel (31) on the indicator grating (3) is 1) The period (pitch) of the stripes in the area is between 20 μm and 50 μm; correspondingly, the width of a single stripe is half of the period (pitch) of the stripe, which is between 10 μm and 25 μm; the period and width of the stripes in the area of ​​the second incremental code track (31) on the indicator grating (3) must be consistent with the period and width of the stripes in the area of ​​the first incremental code track (21) on the scale grating (2); the area of ​​the second absolute code track (32) on the indicator grating (3) is a transparent window, and the width of the window must be an integer multiple of the width of the stripes in the area of ​​the first absolute code track (22) on the scale grating (2); the direction of the stripes in the areas of the second incremental code track (31) and the second absolute code track (32) on the indicator grating (3) must be consistent with the displacement direction of the scale grating (2).

[0017] The photodiode array (4) in the system is a one-dimensional photodiode array including a transimpedance amplifier (TIA) and a signal processing unit, and is capable of generating an output signal according to changes in a light field irradiated thereon; the third incremental code channel (41) region on the photodiode array (4) is used to generate an incremental sine wave signal A, an incremental square wave signal A', and an incremental square wave signal A"; when the photodiode array (4) does not receive the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5), the third incremental code channel (41) region thereon generates an incremental square wave signal A' according to a preset discrimination threshold L; each time the photodiode array (4) receives the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5), the third incremental code channel (41) region thereon generates an incremental square wave signal A" with a duty cycle of 50% according to the fed back discrimination threshold L'; The pixel spacing in the third incremental code track (41) region on the photodiode array (4) must be consistent with 1 / 4 of the spacing of the moiré fringes irradiated thereon; the third absolute code track (42) region on the photodiode array (4) is used to generate an absolute square wave signal M; the rising / falling edge of the absolute square wave signal M generated by the third absolute code track (42) region on the photodiode array (4) must be aligned with the edge of the image of the first absolute code track (22) region on the scale grating (2); the pixel spacing in the third absolute code track (42) region on the photodiode array (4) must be consistent with 1 / 2 of the image width of the grating fringes in the first absolute code track (22) region on the scale grating (2); the fringes direction in the second incremental code track (31) and second absolute code track (32) regions on the indicator grating (3) must be consistent with the displacement direction of the scale grating (2).

[0018] The photodiode array (4) and the code channel signal phase mutual correction algorithm (5) in the system form a set of negative feedback adjustment modules, which can generate an incremental square wave signal A" with a duty cycle of 50% as the scale grating (2) is displaced; the signal processing unit in the photodiode array (4) includes a single threshold comparator, which can convert the incremental sine wave signal A into an incremental square wave signal A' or an incremental square wave signal A" according to a preset discrimination threshold L or a discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5); after the system is turned on, when the photodiode array (4) does not receive the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5), the signal processing unit thereon uses the preset discrimination threshold L as a basis. The quasi-voltage Vref, the discrimination threshold L can be any one of the system default value or the last reference voltage recorded before the system was shut down last time; when the photodiode array (4) receives the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5), the signal processing unit thereon uses the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5) as the reference voltage Vref; the single threshold comparator on the photodiode array (4), when the voltage of the input signal is higher than the reference voltage Vref, the comparator outputs a high level, and when the voltage of the input signal is lower than the reference voltage Vref, the comparator outputs a low level; the single threshold comparator on the photodiode array (4) can realize the sine wave signal to the reference voltage according to the reference voltage. The conversion of the square wave signal; the code channel signal phase mutual correction algorithm (5) includes a hysteresis comparator and a latch, which can record the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M in real time, and generate a discrimination threshold L'; the hysteresis comparator on the code channel signal phase mutual correction algorithm (5) outputs a high level when the voltage of the input signal is higher than the set upper comparison threshold VIH, and outputs a low level when the voltage of the input signal is lower than the set lower comparison threshold VIL. When the voltage of the input signal is between the set upper comparison threshold VIH and the lower comparison threshold VIL, the level output by the comparator remains unchanged. The hysteresis comparator can effectively avoid unnecessary level flipping caused by the noise of the input signal. ; The upper comparison threshold VIH and the lower comparison threshold VIL of the hysteresis comparator on the code channel signal phase mutual correction algorithm (5) are determined according to the high level VH and the low level VL of the input square wave signal, usually the upper comparison threshold VIH = (2 / 3) × VH + (1 / 3) × VL, the lower comparison threshold VIL = (1 / 3) × VH + (2 / 3) × VL; the latch on the code channel signal phase mutual correction algorithm (5) can respond to the level flip of the hysteresis comparator output signal in real time, and temporarily maintain the voltage value of the input signal when the level flips; the latch on the code channel signal phase mutual correction algorithm (5) can record the voltage value of the maintained incremental sine wave signal A, generate the discrimination threshold L', and feed it back to the photodiode array (4) in real time;The negative feedback module, which is composed of a photodiode array (4) and a code channel signal phase mutual correction algorithm (5), generates an incremental square wave signal A" with a duty cycle of 50% by recording the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M as a discrimination threshold L'.

[0019] When the system is affected and the light intensity irradiated on the photodiode array (4) is weakened, the amplitude or background of the incremental sine wave signal A generated by the third incremental code channel (41) thereon will decrease. Under the premise that the discrimination threshold L remains unchanged, the duty cycle of the generated incremental square wave signal A' will be less than 50%, and the phase corresponding to the rising / falling edge of the incremental square wave signal A' will deviate from the designed value. The incremental sine wave signal A generated by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M generated by the third absolute code channel (42) are input into the code channel. In the signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) will record in real time the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M; the code channel signal phase mutual correction algorithm (5) will generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A, and feed it back to the photodiode array (4); the photodiode array (4) will generate an incremental square wave signal A" with a duty cycle of 50% according to the discrimination threshold L', and the phase corresponding to the rising / falling edge of the signal A" will be consistent with the design value, thereby realizing the correction of the phase signal.

[0020] When the system is affected and the light intensity irradiated on the photodiode array (4) increases, the amplitude or background of the incremental sine wave signal A generated by the third incremental code channel (41) thereon will increase. Under the premise that the discrimination threshold L remains unchanged, the duty cycle of the generated incremental square wave signal A' will be greater than 50%, and the phase corresponding to the rising / falling edge of the incremental square wave signal A' will deviate from the designed value. The incremental sine wave signal A generated by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M generated by the third absolute code channel (42) are input into the code channel. In the signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) will record in real time the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M, and the code channel signal phase mutual correction algorithm (5) will generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A, and feed it back to the photodiode array (4); the photodiode array (4) will generate an incremental square wave signal A" with a duty cycle of 50% according to the discrimination threshold L', and the phase corresponding to the rising / falling edge of the signal A" will be consistent with the design value, thereby realizing the correction of the phase signal. (IV) Description of the drawings

[0021] Figure 1It is the block diagram of the high-precision grating ruler reading head system. The high-precision grating scale reading head system comprises a collimated light source (1), a scale grating (2), an indicator grating (3), a photodiode array (4), and a code channel signal phase mutual correction algorithm (5); wherein the scale grating (2) comprises a first incremental code channel (21) and a first absolute code channel (22), the indicator grating (3) comprises a second incremental code channel (31) and a second absolute code channel (32), and the photodiode array (4) comprises a third incremental code channel (41) and a third absolute code channel (42); the photodiode array (4) can generate an incremental sine wave signal A and an absolute square wave signal M; the code channel signal phase mutual correction algorithm (5) can receive the incremental sine wave signal A and the absolute square wave signal M output by the photodiode array (4) to generate a discrimination threshold value L'; the photodiode array (4) can receive a preset discrimination threshold value L and a discrimination threshold value L' output by the code channel signal phase mutual correction algorithm (5) to generate an incremental square wave signal A' and an incremental square wave signal A".

[0022] Figure 2 It is the moiré pattern produced by the overlap of two black and white gratings with different grating pitches and grating line directions. According to the principle of geometric shading, the spacing W and direction of the moiré fringes Satisfying the equations shown in formulas (1) and (2), according to the relationship between the grating pitches d1, d2 and the angle θ, the moiré fringes are divided into oblique moiré fringes (d1≠d2, θ≠0), transverse moiré fringes (d1=d2, θ≠0), longitudinal moiré fringes (d1≠d2, θ=0), and light-gate moiré fringes (d1=d2, θ=0). In the case of transverse moiré fringes and longitudinal moiré fringes, when θ or Δd is small, the spacing W of the moiré fringes is much larger than the grating pitch d, thereby realizing the amplification of the displacement signal.

[0023] Figure 3 It is the system output signal condition and correction means when the light intensity is weakened. When the system is affected and the light intensity is weakened, under the premise that the discrimination threshold L remains unchanged, the incremental square wave signal A' generated is an error signal with a duty cycle less than 50%. In the present invention, the code channel signal phase mutual correction algorithm (5) will record the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M in real time, and generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A. The incremental square wave signal A" generated according to the discrimination threshold L' is a correct signal with a duty cycle equal to 50%.

[0024] Figure 4It is the system output signal condition and correction means when the light intensity is enhanced. When the system is affected and the light intensity is weakened, under the premise that the discrimination threshold L remains unchanged, the generated incremental square wave signal A' is an error signal with a duty cycle greater than 50%. In the present invention, the code channel signal phase mutual correction algorithm (5) will record the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M in real time, and generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A. The incremental square wave signal A" generated according to the discrimination threshold L' is a correct signal with a duty cycle equal to 50%. (V) Specific implementation methods

[0025] Embodiment 1:

[0026] Figure 3 An embodiment of a high-precision grating scale code channel signal phase mutual correction algorithm and a reading head system is provided. The high-precision grating reading head system is composed of a collimated light source (1), a scale grating (2), an indicator grating (3), a photodiode array (4), and a code channel signal phase mutual correction algorithm (5). The photodiode array (4) includes a third incremental code channel (41) and a third absolute code channel (42), wherein the third incremental code channel (41) can generate an incremental sine wave signal A with the relative displacement of the scale grating (2), and generate an incremental square wave signal A' according to a set discrimination threshold L, and the third absolute code channel (42) can generate an absolute square wave signal M with the relative displacement of the scale grating (2).

[0027] When the system is affected and the light intensity irradiated on the photodiode array (4) is weakened, the amplitude or background of the incremental sine wave signal A generated by the third incremental code channel (41) thereon will decrease. Under the premise that the discrimination threshold L remains unchanged, the duty cycle of the generated incremental square wave signal A' will be less than 50%, and the phase corresponding to the rising / falling edge of the incremental square wave signal A' will deviate from the designed value. The incremental sine wave signal A generated by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M generated by the third absolute code channel (42) are input into the code channel. In the signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) will record in real time the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M; the code channel signal phase mutual correction algorithm (5) will generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A, and feed it back to the photodiode array (4); the photodiode array (4) will generate an incremental square wave signal A" with a duty cycle of 50% according to the discrimination threshold L', and the phase corresponding to the rising / falling edge of the signal A" will be consistent with the design value, thereby realizing the correction of the phase signal.

[0028] Embodiment 2:

[0029] Figure 4An embodiment of a high-precision grating scale code channel signal phase mutual correction algorithm and a reading head system is provided. The high-precision grating reading head system is composed of a collimated light source (1), a scale grating (2), an indicator grating (3), a photodiode array (4), and a code channel signal phase mutual correction algorithm (5). The photodiode array (4) includes a third incremental code channel (41) and a third absolute code channel (42), wherein the third incremental code channel (41) can generate an incremental sine wave signal A with the relative displacement of the scale grating (2), and generate an incremental square wave signal A' according to a set discrimination threshold L, and the third absolute code channel (42) can generate an absolute square wave signal M with the relative displacement of the scale grating (2).

[0030] When the system is affected and the light intensity irradiated on the photodiode array (4) increases, the amplitude or background of the incremental sine wave signal A generated by the third incremental code channel (41) thereon will increase. Under the premise that the discrimination threshold L remains unchanged, the duty cycle of the generated incremental square wave signal A' will be greater than 50%, and the phase corresponding to the rising / falling edge of the incremental square wave signal A' will deviate from the designed value. The incremental sine wave signal A generated by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M generated by the third absolute code channel (42) are input into the code channel. In the signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) will record in real time the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M, and the code channel signal phase mutual correction algorithm (5) will generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A, and feed it back to the photodiode array (4); the photodiode array (4) will generate an incremental square wave signal A" with a duty cycle of 50% according to the discrimination threshold L', and the phase corresponding to the rising / falling edge of the signal A" will be consistent with the design value, thereby realizing the correction of the phase signal.

Claims

1. A high-precision grating scale signal phase mutual correction algorithm and a reading head system; characterized by: The high-precision grating scale reading head system comprises a collimated light source (1), a scale grating (2), an indicator grating (3), a photodiode array (4), and a code channel signal phase mutual correction algorithm (5), wherein: the scale grating (2) in the system comprises a first incremental code channel (21) and a first absolute code channel (22); the indicator grating (3) in the system comprises a second incremental code channel (31) and a second absolute code channel (32); the photodiode array (4) in the system comprises a third incremental code channel ( 41) and a third absolute code track (42); in the system, the collimated light source (1) irradiates the collimated light beam to the first incremental code track (21) and the first absolute code track (22) on the scale grating (2), and the scale grating (2) reflects the light beam to form a special light field distribution, superimposes the second incremental code track (31) and the second absolute code track (32) on the indicator grating (3) and transmits, and finally irradiates the third incremental code track (41) and the third absolute code track (42) on the photodiode array (4). 2); the photodiode array (4) will generate an output signal for the light field irradiated thereon along with the relative displacement of the scale grating (2), wherein the third incremental code channel (41) generates an incremental sine wave signal A, and the single threshold comparator thereon can receive a default discrimination threshold L to generate an incremental square wave signal A', or receive a discrimination threshold L' output by a code channel signal phase mutual correction algorithm (5) to generate an incremental square wave signal A", wherein the third absolute code channel (42) generates an absolute square wave signal M; the code channel signal phase mutual correction algorithm (5) can receive the incremental sine wave signal A output by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M output by the third absolute code channel (42) to calculate and generate the discrimination threshold L'; the incremental square wave signal A" generated by the negative feedback module composed of the photodiode array (4) and the code channel signal phase mutual correction algorithm (5) is a correct square wave signal with a duty cycle of 50% and a phase corresponding to the rising / falling edge consistent with the design value.

2. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: The collimated light source (1) in the system can be any one of a light source system formed by a light emitting diode (LED) and a special lens or a laser after collimation / expansion. The collimated light source (1) has a relatively small beam divergence angle, and the half-maximum full width of the beam divergence angle is less than 10°. The collimated light source (1) has a relatively narrow spectral range, or is a monochromatic light source, and the half-maximum full width of the spectrum is less than 35nm. The collimated light source (1) has a relatively large aperture and can simultaneously illuminate the first incremental code track (21) and the first absolute code track (22) on the scale grating (2). The beam direction of the collimated light source (1) forms an angle with the vertical direction of the plane where the scale grating (2) is located, and the smaller pair of angles formed is between 45° and 10°.

3. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: The scale grating (2) in the system is a reflective grating that can undergo one-dimensional relative displacement with the collimated light source (1) and the photodiode array (4), and can generate a light field that changes with the relative displacement and project it onto the indicator grating (3); the characteristic is that the scale grating (2) uses a metal material as a substrate, and is plated with periodic polished metal stripes, which can reflect the incident light beam; the stripe period (grating pitch) in the first incremental code track (21) area on the scale grating (2) is between 20 μm and 50 μm; correspondingly, the width of a single stripe is half of the stripe period (grating pitch), and is between 10 μm and 2 5μm; in the first absolute code track (22) area of ​​the scale grating (2), the stripes are distributed in a randomly coded form, the width of a single stripe is the same as the stripe width (grid pitch) in the first incremental code track (21) area, between 20μm and 50μm, each reflection stripe in the first absolute code track (22) area must be aligned with a stripe in the first incremental code track (21) area, and the width of a single stripe must be greater than the grid pitch in the first incremental code track (21) area; the direction of the stripes in the first incremental code track (21) and the first absolute code track (22) area must be consistent with the displacement direction of the scale grating (2).

4. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: The indicator grating (3) in the system is a transmission grating fixed relative to the collimated light source (1) and the photodiode array (4), and is capable of filtering the light field reflected by the scale grating (2); the indicator grating (3) is characterized in that the indicator grating (3) is made of glass as a substrate, on which periodic dielectric stripes are plated, and is capable of transmitting the incident light beam; the stripes in the second incremental code track (31) area on the indicator grating (3) are distributed in an anti-phase manner relative to the stripes in the first incremental code track (21) area on the scale grating (2), that is, at the stripes in the first incremental code track (21), there should be no stripes at the corresponding position in the second incremental code track (31), and vice versa; the second incremental code track (31) on the indicator grating (3) is The period (pitch) of the stripes in the area is between 20 μm and 50 μm; correspondingly, the width of a single stripe is half of the period (pitch) of the stripe, and the width is between 10 μm and 25 μm; the stripes in the second incremental code track (31) area on the indicator grating (3) must be consistent with the period and width of the stripes in the first incremental code track (21) area on the scale grating (2); the second absolute code track (32) area on the indicator grating (3) is a transparent window, and the window width must be an integer multiple of the width of the stripes in the first absolute code track (22) area on the scale grating (2); the direction of the stripes in the second incremental code track (31) and the second absolute code track (32) areas on the indicator grating (3) must be consistent with the displacement direction of the scale grating (2).

5. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: The photodiode array (4) in the system is a one-dimensional photodiode array including a transimpedance amplifier (TIA) and a signal processing unit, and is capable of generating an output signal according to changes in a light field irradiated thereon; the third incremental code channel (41) region on the photodiode array (4) is capable of receiving a discrimination threshold L and a discrimination threshold L', and is used to generate an incremental sine wave signal A, an incremental square wave signal A', and an incremental square wave signal A"; the pixel spacing in the third incremental code channel (41) region on the photodiode array (4) is to be consistent with 1 / 4 of the spacing of the moiré fringes irradiated thereon; the third absolute code channel (42) on the photodiode array (4) is The invention relates to a photodiode array (4) and a photodiode array (5). The photodiode array (4) and the photodiode array (6) are provided with a third absolute code channel (42) region for generating an absolute square wave signal M. The rising / falling edge of the absolute square wave signal M generated by the third absolute code channel (42) region on the photodiode array (4) must be aligned with the edge of the image of the first absolute code channel (22) region on the scale grating (2). The pixel spacing in the third absolute code channel (42) region on the photodiode array (4) must be consistent with 1 / 2 of the image width of the grating stripes in the first absolute code channel (22) region on the scale grating (2). The stripe direction in the second incremental code channel (31) and the second absolute code channel (32) region on the indicator grating (3) must be consistent with the displacement direction of the scale grating (2).

6. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: The photodiode array (4) and the code channel signal phase mutual correction algorithm (5) in the system form a set of negative feedback adjustment modules, which can generate an incremental square wave signal A" with a duty cycle of 50% as the scale grating (2) is displaced; the signal processing unit in the photodiode array (4) includes a single threshold comparator, which can convert the incremental sine wave signal A into an incremental square wave signal A' or an incremental square wave signal A" according to a preset discrimination threshold L or a discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5); after the system is turned on, when the photodiode array (4) does not receive the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5), the signal processing unit thereon will set the preset discrimination threshold L As the reference voltage Vref, the discrimination threshold L can be any one of the system default value or the last reference voltage recorded before the system was shut down last time; when the photodiode array (4) receives the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5), the signal processing unit thereon uses the discrimination threshold L' fed back by the code channel signal phase mutual correction algorithm (5) as the reference voltage Vref; the single threshold comparator on the photodiode array (4) outputs a high level when the voltage of the input signal is higher than the reference voltage Vref, and outputs a low level when the voltage of the input signal is lower than the reference voltage Vref; the single threshold comparator on the photodiode array (4) can realize positive The conversion of the sine wave signal to the square wave signal; the code channel signal phase mutual correction algorithm (5) includes a hysteresis comparator and a latch, which can record the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M in real time, and generate a discrimination threshold L'; the hysteresis comparator on the code channel signal phase mutual correction algorithm (5) outputs a high level when the voltage of the input signal is higher than the set upper comparison threshold VIH, and outputs a low level when the voltage of the input signal is lower than the set lower comparison threshold VIL. When the voltage of the input signal is between the set upper comparison threshold VIH and the lower comparison threshold VIL, the level of the comparator output remains unchanged. The hysteresis comparator can effectively avoid the noise of the input signal. Unnecessary level flip; the upper comparison threshold VIH and the lower comparison threshold VIL of the hysteresis comparator on the code channel signal phase mutual correction algorithm (5) are determined according to the high level VH and the low level VL of the input square wave signal, usually VIH = (2 / 3) × VH + (1 / 3) × VL, VIL = (1 / 3) × VH + (2 / 3) × VL; the latch on the code channel signal phase mutual correction algorithm (5) can respond to the level flip of the hysteresis comparator output signal in real time, and temporarily maintain the voltage value of the input signal when the level flips; the latch on the code channel signal phase mutual correction algorithm (5) can record the voltage value of the maintained incremental sine wave signal A, generate the discrimination threshold L', and feed it back to the photodiode array (4) in real time;The negative feedback module, which is composed of a photodiode array (4) and a code channel signal phase mutual correction algorithm (5), generates an incremental square wave signal A" with a duty cycle of 50% by recording the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M as a discrimination threshold L'.

7. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: When the system is affected and the light intensity irradiated on the photodiode array (4) is weakened, the amplitude or background of the incremental sine wave signal A generated by the third incremental code channel (41) thereon will decrease. Under the premise that the discrimination threshold L remains unchanged, the duty cycle of the generated incremental square wave signal A' will be less than 50%, and the phase corresponding to the rising / falling edge of the incremental square wave signal A' will deviate from the designed value. The incremental sine wave signal A generated by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M generated by the third absolute code channel (42) are input into the code channel. In the signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) will record in real time the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M; the code channel signal phase mutual correction algorithm (5) will generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A, and feed it back to the photodiode array (4); the photodiode array (4) will generate an incremental square wave signal A" with a duty cycle of 50% according to the discrimination threshold L', and the phase corresponding to the rising / falling edge of the signal A" will be consistent with the design value, thereby realizing the correction of the phase signal.

8. The high-precision grating scale signal phase mutual correction algorithm and reading head system according to claim 1; characterized in that: When the system is affected and the light intensity irradiated on the photodiode array (4) increases, the amplitude or background of the incremental sine wave signal A generated by the third incremental code channel (41) thereon will increase. Under the premise that the discrimination threshold L remains unchanged, the duty cycle of the generated incremental square wave signal A' will be greater than 50%, and the phase corresponding to the rising / falling edge of the incremental square wave signal A' will deviate from the designed value. The incremental sine wave signal A generated by the third incremental code channel (41) on the photodiode array (4) and the absolute square wave signal M generated by the third absolute code channel (42) are input into the code channel. In the signal phase mutual correction algorithm (5), the code channel signal phase mutual correction algorithm (5) will record in real time the voltage value of the incremental sine wave signal A corresponding to the rising / falling edge of the absolute square wave signal M, and the code channel signal phase mutual correction algorithm (5) will generate a discrimination threshold L' equal to the voltage value of the recorded incremental sine wave signal A, and feed it back to the photodiode array (4); the photodiode array (4) will generate an incremental square wave signal A" with a duty cycle of 50% according to the discrimination threshold L', and the phase corresponding to the rising / falling edge of the signal A" will be consistent with the design value, thereby realizing the correction of the phase signal.

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