Grating ruler displacement measurement method based on linear beam splitting grating and displacement sensor

Abstract

The invention provides a grating ruler displacement measurement method based on a linear beam splitting grating and a displacement sensor, the method is applied to a miniature grating ruler displacement sensor based on the linear beam splitting grating, and the method comprises the following steps: when a grating ruler and a read head module generate relative displacement, a light beam is emitted through a light source, and the emergent light beam is split through the beam splitting grating to obtain a grating ruler; one beam splitting light is incident to a measuring grating in a grating ruler, and is reflected by the measuring grating to form a Talbot image; after the Talbot image is modulated through the scanning plate, the modulated Talbot image is received through a photoelectric detector, and four paths of current signals with the phase difference of 90 degrees are generated; and current-voltage conversion, difference and subdivision processing are sequentially carried out on the four paths of current signals through the signal processing circuit, high-resolution AB signals are obtained, and the AB signals are used for determining the relative displacement of the grating ruler and the read head module. According to the invention, the application requirements of high precision, small size, low power consumption and large-range installation tolerance are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical measurement, in particular to a grating ruler displacement measurement method based on a straight-line beam-splitting grating and a displacement sensor. BACKGROUND

[0002] As a high-precision position measurement feedback component, a high-precision grating ruler displacement sensor has important applications in the high-end manufacturing industry. The grating ruler displacement sensor has great research and development difficulties due to its high precision, small size, low power consumption, and large installation tolerance, and the current domestic research foundation is relatively weak. At present, there is no unit that can develop such products, and it mainly depends on imports from abroad. With the rapid development of the high-end manufacturing industry, the research and development breakthrough of the domestic grating ruler displacement sensor has important significance.

[0003] In view of the demand of the high-end manufacturing industry for small size and high precision of the grating ruler displacement sensor, the conventional diffraction interference principle is difficult to meet. In the prior art, the relative displacement of the grating ruler is measured by a grating ruler measurement device, which uses a digital camera and an optical lens to collect the grating ruler stripes, and measures the displacement by measuring the change of light intensity with position movement. However, the structure of the digital camera and the optical lens cannot meet the application requirement of miniaturization, and has high power consumption and small installation tolerance range.

[0004] How to meet the application requirements of high precision, small size, low power consumption, and large installation tolerance range of the grating ruler displacement sensor, and realize displacement measurement has become a technical problem to be solved in the field of grating ruler displacement sensor. SUMMARY

[0005] The present application provides a grating ruler displacement measurement method based on a straight-line beam-splitting grating and a displacement sensor, which meets the application requirements of high precision, small size, low power consumption, and large installation tolerance range based on a beam-splitting grating and a Talbot imaging principle.

[0006] In the first aspect, the present application provides a grating ruler displacement measurement method based on a straight-line beam-splitting grating, which is applied to a miniature grating ruler displacement sensor based on a straight-line beam-splitting grating. The displacement sensor includes a read head module and a grating ruler. The read head module includes an optical measurement element and a signal processing circuit. The optical measurement element includes a light source, a photodetector, and a scanning plate. The scanning plate is provided with a beam-splitting grating, and the beam-splitting grating is located above the light source. The distance between the grating ruler and the scanning plate is a Talbot imaging distance. The method includes the following steps: When the grating ruler and the read head module occur relative displacement, the light source emits a light beam, the outgoing light beam is split by the beam-splitting grating to obtain two split beams, and one of the two split beams is incident to a measurement grating in the grating ruler to form a Talbot image after being reflected by the measurement grating. After the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; The four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal; the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the read head module.

[0007] According to the grating ruler displacement measurement method based on a linear beam-splitting grating provided by the application, the optical measurement element further comprises a reference positioning photodetector; the scanning plate is further provided with a plurality of scanning slits, the scanning slits comprising four first scanning slits and one second scanning slit, the light-sensitive surfaces of the four displacement measurement photodetectors being respectively aligned with the four first scanning slits, and the second scanning slit being aligned with the reference positioning photodetector; After the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; After the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; The period of the first scanning slit is T, and the distance between adjacent first scanning slits along the arrangement direction is nT+T / 4, where n is an integer, so that each displacement measurement photodetector outputs a corresponding current signal.

[0008] According to the grating ruler displacement measurement method based on a linear beam-splitting grating provided by the application, the other one of the two beams of split light is reflected by the zero grating in the grating ruler to form a converging light beam; the method further comprises: The converging light beam is modulated by the second scanning slit; The modulated converging light beam is converted into a zero current signal by the reference positioning photodetector, and the zero current signal is subjected to current-voltage conversion and subdivision processing by the signal processing circuit to output a zero signal.

[0009] According to the grating ruler displacement measurement method based on a linear beam-splitting grating provided by the application, the signal processing circuit comprises an amplification circuit and an interpolation subdivision circuit; the four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal, which comprises: The four current signals are subjected to current-voltage conversion by the amplification circuit to obtain converted four voltage signals; The converted four-way voltage signal is differentially processed by the interpolation subdivision circuit to obtain two-way voltage signals with a phase difference of 90 degrees. The two-way voltage signals are converted into the high-resolution AB signal by the interpolation subdivision circuit.

[0010] According to the grating ruler displacement measurement method based on a linear beam splitting grating provided by the present application, the converted four-way voltage signal is differentially processed by the interpolation subdivision circuit to obtain two-way voltage signals with a phase difference of 90 degrees, which comprises: The signals of two displacement measurement photodetectors set among the four displacement measurement photodetectors are differentiated; The signals of the other two displacement measurement photodetectors except the two displacement measurement photodetectors set among the four displacement measurement photodetectors are differentiated to generate the two-way voltage signals with high contrast.

[0011] According to the grating ruler displacement measurement method based on a linear beam splitting grating provided by the present application, the structure parameters of the beam splitting grating are determined by the following steps: The required diffraction angle of the beam splitting grating is calculated according to the Talbot imaging distance; Based on the required diffraction angle and the wavelength of the light source, the period of the beam splitting grating is determined by the grating equation; Based on the requirement of high transmittance, the glass material is determined as the material of the beam splitting grating; A simulation model of the beam splitting grating is established according to the period of the beam splitting grating and the material of the beam splitting grating, and the groove depth and the grating line width of the beam splitting grating are obtained by simulating and optimizing the simulation model of the beam splitting grating, so as to make the first-order diffraction efficiency highest.

[0012] In the second aspect, the present application further provides a micro grating ruler displacement sensor based on a linear beam splitting grating, which comprises a read head module and a grating ruler. The read head module comprises a light source, a photodetector group, a scanning plate, a driving circuit, an amplification circuit and an interpolation subdivision circuit; the photodetector group comprises four displacement measurement photodetectors and a reference positioning photodetector; the scanning plate is provided with a beam splitting grating and a plurality of scanning slits, the plurality of scanning slits comprise four first scanning slits and one second scanning slit; the beam splitting grating is located above the light source, the four first scanning slits are respectively aligned with the light sensitive surfaces of the four displacement measurement photodetectors, and the second scanning slit is aligned with the reference positioning photodetector. The grating ruler comprises a measurement grating and a zero grating, and the distance between the grating ruler and the scanning plate is the Talbot imaging distance.

[0013] In a third aspect, the present application also provides a grating ruler displacement measurement device based on a linear beam splitting grating, which is applied to a micro grating ruler displacement sensor based on a linear beam splitting grating; the displacement sensor comprises a read head module and a grating ruler, the read head module comprises an optical measurement element and a signal processing circuit, the optical measurement element comprises a light source, a displacement measurement photodetector and a scanning plate; the scanning plate is provided with a beam splitting grating, the beam splitting grating is located above the light source, and the distance between the grating ruler and the scanning plate is a Talbot imaging distance; the device comprises: a beam splitting module, which is used for emitting a light beam through the light source when the grating ruler and the read head module are relatively displaced, splitting the outgoing light beam through the beam splitting grating to obtain two beams of split light, and making one of the two beams of split light incident to a measurement grating in the grating ruler to form a Talbot image through reflection of the measurement grating; a displacement measurement module, which is used for modulating the Talbot image through the scanning plate, receiving the modulated Talbot image through the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees, and sequentially performing current-voltage conversion, difference and subdivision processing on the four current signals through the signal processing circuit to obtain a high-resolution AB signal; the high-resolution AB signal is used for determining the relative displacement amount of the grating ruler and the read head module.

[0014] In a fourth aspect, the present application also provides an electronic device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and the processor implements the grating ruler displacement measurement method based on a linear beam splitting grating according to any one of the above aspects when executing the computer program.

[0015] In a fifth aspect, the present application also provides a non-transitory computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the grating ruler displacement measurement method based on a linear beam splitting grating according to any one of the above aspects.

[0016] In a sixth aspect, the present application also provides a computer program product, which comprises a computer program, and the computer program is executed by a processor to implement the grating ruler displacement measurement method based on a linear beam splitting grating according to any one of the above aspects.

[0017] The micro grating ruler displacement sensor based on the linear beam-splitting grating provided by the application comprises a reading head module and a grating ruler, the reading head module comprises an optical measurement element and a signal processing circuit, the optical measurement element comprises a light source, a displacement measurement photodetector and a scanning plate, the signal processing circuit comprises a driving circuit, an amplifying circuit and an interpolation subdivision circuit; the scanning plate is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, and the distance between the grating ruler and the scanning plate is a Talbot imaging distance; the micro grating ruler displacement measurement method comprises the following steps: firstly, when the grating ruler and the reading head module are relatively displaced, a light beam is emitted by the light source, the emitted light beam is split by the beam-splitting grating to obtain two split light beams, one of the two split light beams is incident into a measurement grating in the grating ruler, and a Talbot image is formed by reflection of the measurement grating; then, after the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; further, the four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal; and the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the reading head module.

[0018] The scanning plate of the grating ruler displacement sensor is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, the distance between the grating ruler and the scanning plate is a Talbot imaging distance, the light emitted by the light source is split by the beam-splitting grating, directional propagation of the light beam is realized, the energy utilization rate is improved, and the power consumption of the light source is reduced; meanwhile, the split propagation of the transmitted light of the beam-splitting grating makes it easier to realize high-uniformity light intensity detection, improves the installation tolerance, and meets the application requirements of high precision, small size, low power consumption and large installation tolerance on the basis of the beam-splitting grating and the Talbot imaging principle. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0020] Figure 1 It is a flowchart of the grating ruler displacement measurement device method based on the linear beam-splitting grating provided by the application.

[0021] Figure 2 It is a schematic diagram of the overall structure of the micro grating ruler displacement sensor based on the linear beam-splitting grating provided by the application.

[0022] Figure 3 It is a schematic diagram of the structure of the reading head module provided by the application.

[0023] Figure 4It is the structural schematic diagram of the scanning version provided by the application.

[0024] Figure 5 It is the overall structural schematic diagram of the grating ruler provided by the application.

[0025] Figure 6a It is the Talbot image simulation result diagram of the grating ruler and the reading head module under the reference posture provided by the application.

[0026] Figure 6b It is the Talbot image simulation result diagram of the grating ruler and the reading head module under the installation tolerance 2-degree posture provided by the application.

[0027] Figure 7 It is the component layout schematic diagram of the reading head module provided by the application.

[0028] Figure 8 It is the optical path schematic diagram of the beam splitting grating provided by the application.

[0029] Figure 9 It is the microstructure schematic diagram of the beam splitting grating provided by the application.

[0030] Figure 10 It is the transmission light diffraction efficiency simulation result diagram and the reflection light diffraction efficiency simulation result diagram of the beam splitting grating in the optical simulation software provided by the application.

[0031] Figure 11 It is the comparison diagram of the beam splitting grating structure light illumination surface and the light source direct light illumination surface provided by the application.

[0032] Figure 12 It is the structural schematic diagram of the grating ruler displacement measurement device based on the linear beam splitting grating provided by the application.

[0033] Figure 13 It is the structural schematic diagram of the electronic equipment provided by the application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] In order to solve the problems in the prior art, the present application aims to provide a micro grating ruler displacement sensor and displacement measurement method based on the linear beam splitting grating structure, which can realize the technical features of high precision, small size, low power consumption and large installation tolerance at the same time, and is more suitable for the actual application requirements at the current development stage.

[0036] The application will be described below Figures 1-13 The application provides a grating ruler displacement measurement method and a displacement sensor based on a linear beam-splitting grating.

[0037] Figure 1 A flowchart of a grating ruler displacement measurement method based on a linear beam-splitting grating is provided in the application, as shown in Figure 1 The method is applied to a micro grating ruler displacement sensor based on a linear beam-splitting grating. The displacement sensor comprises a read head module and a grating ruler. The read head module comprises an optical measurement element and a signal processing circuit. The optical measurement element comprises a light source, a displacement measurement photodetector and a scanning plate. The signal processing circuit comprises a driving circuit, an amplification circuit and an interpolation subdivision circuit. The scanning plate is provided with a beam-splitting grating. The beam-splitting grating is located above the light source. The distance between the grating ruler and the scanning plate is a Talbot imaging distance. The method comprises the following steps. In step 101, when the grating ruler and the read head module are relatively displaced, the light source emits a light beam. The outgoing light beam is split by the beam-splitting grating to obtain two beams of split light. One of the two beams of split light is incident to a measurement grating in the grating ruler, and a Talbot image is formed by reflection of the measurement grating.

[0038] Specifically, first of all, it should be noted that the method is applied to a micro grating ruler displacement sensor based on a linear beam-splitting grating. The displacement sensor comprises a read head module and a grating ruler. The read head module comprises an optical measurement element and a signal processing circuit. The optical measurement element comprises a light source, a displacement measurement photodetector and a scanning plate. The signal processing circuit comprises a driving circuit, an amplification circuit and an interpolation subdivision circuit. The scanning plate is provided with a beam-splitting grating. The beam-splitting grating is located above the light source. The distance between the grating ruler and the scanning plate is a Talbot imaging distance.

[0039] Exemplarily, Figure 2 A schematic diagram of the overall structure of a micro grating ruler displacement sensor based on a linear beam-splitting grating is provided in the application, as shown in Figure 2 The left side is the mark of x, y and z coordinate axes. The micro grating ruler displacement sensor based on a linear beam-splitting grating comprises a read head module 1 and a grating ruler 2. The sensor structure is simple, which is composed of one light source, five photodetectors, one scanning plate, a signal processing circuit and a mechanical shell. Therefore, the sensor can be designed to be small in size. The overall size can reach 15 mm (millimeters) x 15 mm (millimeters). The size of the core sensing area is only 5 mm (millimeters) x 5 mm (millimeters).

[0040] Figure 3 A schematic diagram of the structure of the read head module is provided in the application, as shown in Figure 3As shown, the read head module 1 is composed of optical measurement elements and signal processing circuit, the optical measurement structure includes displacement measurement structure and reference positioning structure. The displacement measurement structure is composed of light source 104, four displacement measurement photodetectors (1051, 1052, 1053 and 1054), the first scanning slit of scanning plate 106, the reference positioning structure is composed of light source 104, reference photodetector 1055 and the second scanning slit, the signal processing circuit of the optical measurement element is composed of driving circuit 101, amplification circuit 102 and interpolation subdivision circuit 103.

[0041] Figure 4 The scanning plate provided by the present application is shown in the structural schematic diagram as Figure 4 As shown, the scanning plate is located above the light source 104 of the displacement measurement structure and the reference positioning structure, and the positioning relationship with the light source and the photodetector is realized by mechanical shell assembly. The scanning plate 106 is provided with a beam splitter grating 1061 and a plurality of scanning slits (the first scanning slits 1062, 1063, 1064, 1065 and the second scanning slit 1066), and the plurality of scanning slits include four first scanning slits (1062, 1063, 1064 and 1065) and the second scanning slit 1066; the beam splitter grating 1061 of the scanning plate corresponds to the light source 104 (that is, the beam splitter grating is located above the light source 104), the four first scanning slits (1051, 1052, 1053 and 1054) are respectively aligned with the light sensitive surfaces of the four displacement measurement photodetectors (1051, 1052, 1053 and 1054), and the second scanning slit 1056 is aligned with the reference positioning photodetector 1055.

[0042] Figure 5 The overall structure of the grating ruler provided by the present application is shown in the structural schematic diagram as Figure 5 As shown, the grating ruler 2 includes a measurement grating 201 and a zero grating 202, wherein the distance between the grating ruler 2 and the scanning plate 106 is the Talbot imaging distance. Figure 5 The front view of the measurement grating structure is shown, the microstructure is a one-dimensional grating with uniform period, the grating period is L, the grating line width is L / 2, and high-contrast measurement signals are realized through the Talbot imaging effect; wherein the zero structure schematic diagram is shown, the microstructure is a variable-pitch grating, and high-contrast zero reference signals of line convergence are realized through the optical effect of the binary diffraction element.

[0043] The Talbot imaging distance is the position of Z T =(2*p²) / λ. Wherein: p is the period of the grating, and λ is the wavelength of the incident light. At Z T , the formed image is upright and the same as the original grating structure.

[0044] The grating displacement measurement method based on the linear beam splitter grating meets the requirements of high precision, small size, low power consumption and large installation tolerance based on the beam splitter grating and the Talbot imaging principle. The Talbot imaging principle (Talbot effect), also known as self-imaging effect or Talbot effect, is an important phenomenon in optical diffraction. It describes that when a coherent light (such as a plane wave) is vertically irradiated to a periodic object (such as a grating), a clear image of the object structure will be formed spontaneously at a certain distance behind the grating (without lens), and this image will periodically repeat.

[0045] The displacement measurement method comprises the following steps: Firstly, when the grating ruler and the read head module are relatively displaced, the light beam emitted by the light source 104 is split by the beam splitter grating 1061 to obtain two split beams.

[0046] Among them, one of the two split beams is incident to the measurement grating in the grating ruler, and the Talbot image is formed by reflection of the measurement grating (arriving at the scanning slit on the scanning plate 106), and the Talbot image reaching the scanning plate 106 is as shown in Figure 6a and Figure 6b For example, Figure 6a is the Talbot image simulation result diagram of the grating ruler and the read head module in the reference attitude provided by the application, including the light intensity collected by the detector 1051, the light intensity collected by the detector 1052, the light intensity collected by the detector 1053 and the light intensity collected by the detector 1054. Figure 6b is the Talbot image simulation result diagram of the grating ruler and the read head module in the installation tolerance 2 degree attitude provided by the application, including the light intensity collected by the detector 1051, the light intensity collected by the detector 1052, the light intensity collected by the detector 1053 and the light intensity collected by the detector 1054.

[0047] Step 102, after the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photoelectric detector to generate four current signals with a phase difference of 90 degrees.

[0048] Specifically, the formed Talbot image is modulated by the scanning plate 106, and the light beam transmits through the scanning slit on the scanning plate 106 and is incident to the displacement measurement photoelectric detector 1051, 1052, 1053, 1054 and 1055.

[0049] When the grating ruler 2 is relatively displaced with respect to the read head module 1, the light intensity incident to the photoelectric detector will change to generate four measurement signals, the four measurement signals have a phase difference of 90 degrees, and the four measurement signals are converted by photoelectric conversion to generate four current signals with a phase difference of 90 degrees.

[0050] Step 103, sequentially performing current-voltage conversion, difference and subdivision processing on the four-way current signal through the signal processing circuit to obtain a high-resolution AB signal; the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the read head module.

[0051] Specifically, after obtaining the four-way current signal, further current-voltage conversion, difference and subdivision processing on the four-way current signal through the signal processing circuit to obtain a high-resolution AB signal. The "AB signal" generally refers to the two-way orthogonal pulse signal output by the encoder.

[0052] Among them, the current-voltage conversion should be to convert the current signal into a voltage signal, such as using an operational amplifier or resistance sampling, in order to facilitate subsequent circuit processing. The operational amplifier circuit directly converts the input current into the output voltage. Its gain (conversion ratio) is determined by the feedback resistor R f determines (V out =-I in *R f ), V out is the output voltage, I in is the input current, and R f is the feedback resistor. Difference processing refers to the technology of transmitting, amplifying and processing signals using differential signals. The differential signal is composed of a pair of signals with equal size and opposite polarity. For example, a differential amplifier or an instrument amplifier is used to amplify the differential signal while suppressing the common-mode signal. Subdivision processing is mainly used in incremental position / angle encoders (such as grating rulers) and is an electronic method for improving the resolution (i.e. the smallest displacement / angle change that can be detected) of the encoder output signal beyond the basic resolution provided by the physical marking (grating pitch) or the photoelectric element itself. Usually output two-way (sometimes also zero position signal) phase difference 90 degrees sine / cosine signal (A phase and B phase) or square wave signal.

[0053] These three processes are often used in series in a complete signal chain, especially in high-precision sensing and measurement systems: Signal acquisition: the sensor (such as the reading head of the grating ruler) outputs a weak current signal proportional to the physical quantity (displacement).

[0054] Current-voltage conversion: convert the weak current signal into a voltage signal (usually a sine / cosine pair) that is easy to process.

[0055] Difference processing: the converted sine / cosine voltage signal is transmitted to the subsequent processing circuit (such as the subdivision circuit) in a differential manner to resist noise and interference introduced by long cable transmission.

[0056] Subdivision processing: receive the sine / cosine signal transmitted by differential transmission (or convert it to a square wave), and use electronic methods (measure amplitude or detect edges) to interpolate and subdivide the signal, greatly improving the resolution and accuracy of the final output position or angle information.

[0057] Final output: the subdivided signal (usually a high-resolution pulse or digital position value) is sent to a counter, microcontroller, or motion controller for precise position control or measurement.

[0058] High-resolution AB signal, i.e., two orthogonal pulse signals, is the quadrature pulse output of the encoder. Based on the high-resolution AB signal, the displacement can be determined, and the process is as follows: 1. AB signal characteristic analysis Quadrature: two square waves (A, B) with a phase difference of 90 degrees, the direction is determined by the relative order of the rising / falling edges.

[0059] Resolution enhancement: the original 4 edges per cycle, if the encoder line number is N, the basic resolution is Δ = 360 degrees / (4N). After 4 times frequency, the resolution is enhanced to Δ / 4.

[0060] 2. Hardware processing circuit Direction discrimination circuit: use D flip-flop to capture the phase relationship of A and B signals: when A rising edge, if B is high → forward; B is low → reverse.

[0061] 3. Subdivision technology (software implementation) Interpolation subdivision: ADC sampling of sine / cosine AB signal, calculating phase angle θ = arctan(B / A) through arctangent operation to achieve high-multiple subdivision (such as 256 times).

[0062] Dynamic compensation: use lookup table method to correct the non-ideal quadrature of AB signal (such as 1 degree positive / negative deviation needs to be calibrated).

[0063] 4. Counter and direction logic Field-Programmable Gate Array (FPGA) or single-chip microcomputer implementation: In 4 times frequency mode, each A / B edge triggers an interrupt, and the counter counts according to the direction ±1.

[0064] 32-bit counter overflow processing: enable hardware overflow interrupt, and software extends to 64-bit variable.

[0065] Speed synchronization: timing capture counter value (such as STM32 encoder interface mode), combined with timer to calculate instantaneous speed.

[0066] 5. According to the cumulative count value of the counter, the encoder line distance, the interpolation subdivision multiple, the resolution mode, the displacement amount is calculated: For example, a 2500 line encoder (λ = 10 microns μm), 4x frequency mode + 100x subdivision → theoretical resolution 10 nanometers nm. The displacement is calculated as follows: Wherein, is the cumulative count value.

[0067] When the grating ruler 2 and the read head module 1 are relatively displaced, the Talbot image generated by the grating ruler 2 changes in phase following the displacement of the grating ruler 2. After the transmitted light is modulated by the specially designed first scanning slit, the four displacement measurement photodetectors receive the transmitted light whose intensity changes with the displacement of the grating ruler, thereby generating four current signals with a phase difference of 90 degrees, realizing the conversion from displacement to optical signal and then to electrical signal, and further realizing displacement measurement.

[0068] In this process, the microstructure of the scanning grating beam splitter 1061 is specially designed so that the ratio of the transmitted light intensity to the incident light intensity exceeds 92%, reducing the energy loss of reflected or absorbed light; the scanning grating beam splitter 1061 can achieve a first-order diffraction efficiency of more than 78%, which ensures the beam splitting effect while suppressing the generation of zero-order diffraction light and high-order diffraction light; according to the Talbot imaging working distance, the height difference between the grating ruler and the scanning plate can be obtained, and according to the layout scheme of the photodetector and the light source, the grating period of the beam splitter grating is designed so that the coincidence rate of the light illumination area of the beam splitter after beam splitting on the scanning plate and the photosensitive area of the photodetector can reach 32%, which is higher than 15% when directly incident, and the energy utilization rate is effectively improved by more than 100%.

[0069] The method provided by the embodiment is applied to a linear beam-splitting grating-based micro grating ruler displacement sensor, the linear beam-splitting grating-based micro grating ruler displacement sensor comprises a reading head module and a grating ruler, the reading head module comprises an optical measurement element and a signal processing circuit, the optical measurement element comprises a light source, displacement measurement photodetectors and a scanning plate, and the signal processing circuit comprises a driving circuit, an amplifying circuit and an interpolation subdivision circuit; the scanning plate is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, and the distance between the grating ruler and the scanning plate is a Talbot imaging distance; the method comprises the following steps: firstly, when the grating ruler and the reading head module are relatively displaced, a light beam is emitted by the light source, the emitted light beam is split by the beam-splitting grating to obtain two split light beams, and one of the two split light beams is incident on a measurement grating in the grating ruler to form a Talbot image after being reflected by the measurement grating; then, after the Talbot image is modulated by the scanning plate, the Talbot image after modulation is received by the displacement measurement photodetectors to generate four current signals with a phase difference of 90 degrees; further, the four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal; and the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the reading head module.

[0070] The scanning plate of the grating ruler displacement sensor is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, the distance between the grating ruler and the scanning plate is a Talbot imaging distance, the light emitted by the light source is split by the beam-splitting grating, directional propagation of the light beam is realized, the energy utilization rate is improved, and the power consumption of the light source is reduced; meanwhile, the split propagation of the transmitted light of the beam-splitting grating makes it easier to realize high-uniformity light intensity detection, improves the installation tolerance, and meets the application requirements of high precision, small size, low power consumption and large installation tolerance on the basis of the beam-splitting grating and the Talbot imaging principle.

[0071] According to the grating ruler displacement measurement method based on the linear beam-splitting grating, the optical measurement element further comprises a reference positioning photodetector; the scanning plate is further provided with a plurality of scanning slits, the scanning slits comprise four first scanning slits and one second scanning slit, the photosensitive surfaces of the four displacement measurement photodetectors are respectively aligned with the four first scanning slits, and the second scanning slit is aligned with the reference positioning photodetector. After the Talbot image is modulated by the scanning plate, the Talbot image after modulation is received by the displacement measurement photodetectors to generate four current signals with a phase difference of 90 degrees, which comprises the following steps: After the Talbot image is modulated by each first scanning slit, the Talbot image after modulation is received by each displacement measurement photodetector to generate four current signals. The period of the first scanning slit is T, and the distance between adjacent first scanning slits along the arrangement direction is nT+T / 4, wherein n is an integer, so that each displacement measurement photodetector outputs a corresponding current signal.

[0072] Specifically, in some embodiments, the optical measurement element further comprises a reference positioning photodetector; the scanning plate is further provided with a plurality of scanning slits, the scanning slits comprising four first scanning slits (1062, 1063, 1064 and 1065) and a second scanning slit 1066, the four first scanning slits (1062, 1063, 1064 and 1065) being aligned with the light-sensitive surfaces of the four displacement measurement photodetectors respectively, and the second scanning slit 1066 being aligned with the reference positioning photodetector.

[0073] The specific implementation process of step 102 comprises the following steps: After the Talbot image is modulated by each first scanning slit (1062, 1063, 1064 and 1065), the modulated Talbot image is received by each displacement measurement photodetector to generate four current signals, that is, the corresponding current signals output by each displacement measurement photodetector.

[0074] Wherein, the period of the first scanning slit is T, and the distance between adjacent first scanning slits along the arrangement direction is nT+T / 4, wherein n is an integer, so that each displacement measurement photodetector outputs the corresponding current signal.

[0075] The method provided by the embodiment is used to modulate the Talbot image by each first scanning slit, and the modulated Talbot image is received by each displacement measurement photodetector to generate four current signals, which facilitates subsequent processing of the four current signals by the signal processing circuit to generate the AB signal, thereby realizing effective grating ruler displacement measurement.

[0076] According to the grating ruler displacement measurement method based on a straight-line beam-splitting grating provided by the application, the other one of the two split beams is reflected by the zero grating in the grating ruler to form a converging light beam; the method further comprises: The converging light beam is modulated by the second scanning slit; The modulated converging light beam is converted into a zero current signal by the reference positioning photodetector, and the zero current signal is subjected to current-voltage conversion and subdivision processing by the signal processing circuit to output a zero signal.

[0077] Specifically, in some embodiments, the method further comprises outputting the zero signal, and the process is specifically implemented by the following steps: The other one of the two split beams after being split by the beam-splitting grating 1061 is reflected by the zero grating in the grating ruler to form a converging light beam, which reaches the second scanning slit 1066.

[0078] Further, the converging light beam is modulated by the second scanning slit 1066, and then the modulated converging light beam is converted into a zero current signal by the reference positioning photodetector 1055.

[0079] Further, the zero current signal is converted into voltage by the signal processing circuit (amplification circuit and interpolation subdivision circuit), and is subdivided to output a zero signal (Z signal).

[0080] The zero signal is also called a reference signal, an Index signal or a Marker signal, and is an important auxiliary signal in addition to the AB quadrature pulse, and is used to provide an absolute position reference point.

[0081] The method provided in the embodiment is that another one of the two beams of split light after being split by the beam splitter 1061 is reflected by a zero grating in the grating ruler to form a converging light beam, and the converging light beam is modulated by a second scanning slit; further, the modulated converging light beam is converted into a zero current signal by a reference positioning photodetector, and the zero current signal is converted into voltage by a signal processing circuit, and is subdivided to output a zero signal.

[0082] According to the grating ruler displacement measurement method based on a straight-line split beam grating, the signal processing circuit includes an amplification circuit and an interpolation subdivision circuit; four current signals are converted into voltage by the signal processing circuit in sequence, and are differentially processed and subdivided to obtain high-resolution AB signals, including: The four current signals are converted into voltage by the amplification circuit to obtain four converted voltage signals; The four converted voltage signals are differentially processed by the interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees; The two voltage signals are converted into high-resolution AB signals by the interpolation subdivision circuit.

[0083] Specifically, in some embodiments, the signal processing circuit includes an amplification circuit and an interpolation subdivision circuit. Figure 7 is a schematic diagram of the layout of components of the read head module provided in the embodiment, 1051, 1052, 1053 and 1054 are four displacement measurement photodetectors, 1055 is a reference positioning photodetector, 1074 is an illumination surface, the signal processing circuit includes an amplification circuit, a subdivision circuit and a driving circuit, and the driving circuit is used to provide a driving power supply for the operation of the sensor. Figure 7As shown, the light emitted by the light source 104 is reflected by the grating ruler 2, and the light irradiation surface 1074 covers the light sensitive surface of the photodetector, and the photodetector is arranged in a circle, corresponding to the light intensity of the Gaussian distribution of the light source, so that the photodetection with high uniformity can be realized.

[0084] Step 103 can be implemented by the following steps: First, the four-way current signal is converted into voltage by the amplification circuit to obtain the converted four-way voltage signal.

[0085] Among them, each way adopts a transimpedance amplifier (TIA) or a precision sampling resistor + operational amplifier scheme. The output voltage is V out =-I in *R f , V out is the output voltage, I in is the input current signal, and R f is the feedback resistance of the transimpedance amplifier (TIA).

[0086] Further, the converted four-way voltage signal is differentially processed by the interpolation subdivision circuit to obtain two-way voltage signals with a phase difference of 90 degrees.

[0087] For example, the two-way differential signals are obtained by differential operation of the photodetector 1052 and the photodetector 1053 signals, and differential operation of the photodetector 1051 and the photodetector 1054.

[0088] Further, the interpolation subdivision circuit converts the two-way voltage signals into high-resolution AB signals. The two-way orthogonal voltage signals (Sin / Cos) are converted into high-resolution AB signals (square waves) by the interpolation subdivision circuit, which needs to go through key steps such as signal conditioning, digital subdivision, square wave generation, etc. Finally, the resolution is improved (for example, from 1μm to 10nm).

[0089] Among them, the key steps are as follows: (1) Signal conditioning: including amplification and bias adjustment (adapting the Sin / Cos signal amplitude to the ADC input range), and anti-aliasing filtering, such as second-order low-pass filtering, with a cutoff frequency of 2 times the highest frequency of the signal (such as a signal bandwidth of 10kHz→cutoff frequency fc=20kHz).

[0090] (2) Digital subdivision: First, the look-up table method or the Coordinate Rotation Digital Computer (CORDIC) algorithm is used to quickly calculate the instantaneous phase angle.

[0091] Secondly, generating pulses according to the instantaneous phase angle change: if the instantaneous phase angle change is greater than 0, a forward pulse (A phase leading B phase by 90 degrees) is generated; if the instantaneous phase angle change is less than 0, a reverse pulse (B phase leading A phase by 90 degrees) is generated.

[0092] (3) AB signal generation: a. Direction discrimination and pulse distribution The logic rules are as follows:

[0093] b. Square wave shaping Hysteresis comparator: converting digital pulses into 3.3-volt square waves.

[0094] Jitter suppression: adding a dead time to prevent noise from triggering.

[0095] The method provided by the embodiment converts four current signals into voltage signals through an amplification circuit, differentiates the converted four voltage signals through an interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees, and converts the two voltage signals into high-resolution AB signals through the interpolation subdivision circuit, so that the calculation of the relative displacement amount based on the AB signals is facilitated, and the grating ruler displacement measurement is performed with low power consumption and high efficiency.

[0096] According to the grating ruler displacement measurement method based on a linear beam-splitting grating, the converted four voltage signals are differentiated through an interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees, which comprises: The signals of two displacement measurement photodetectors set in the four displacement measurement photodetectors are differentiated; The signals of the other two displacement measurement photodetectors except the two displacement measurement photodetectors set in the four displacement measurement photodetectors are differentiated to generate two voltage signals with high contrast.

[0097] Specifically, in some embodiments, the converted four voltage signals are differentiated through an interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees, which comprises: Firstly, the signals of two displacement measurement photodetectors set in the four displacement measurement photodetectors are differentiated; and secondly, the signals of the other two displacement measurement photodetectors (except the two displacement measurement photodetectors set) are differentiated to generate two voltage signals with high contrast.

[0098] For example, the two differential signals are obtained by differential operation of the signals of the photodetector 1052 and the photodetector 1053, and the differential operation of the signals of the photodetector 1051 and the photodetector 1054.

[0099] The method provided by the embodiment is that four-phase difference current signals output by four photodetectors of the read head module are differentially processed into two high-contrast signals with a phase difference of 90 degrees, so that four high-resolution AB signals can be output based on the two voltage signals, and then the grating ruler displacement value is obtained.

[0100] According to the grating ruler displacement measurement method based on a straight-line beam-splitting grating provided by the application, the structural parameters of the beam-splitting grating are determined by the following steps: The required diffraction angle of the beam-splitting grating is calculated according to the Talbot imaging distance. Based on the required diffraction angle and the wavelength of the light source, the period of the beam-splitting grating is determined by a grating equation. Based on the required high transmittance, the glass material is determined as the material of the beam-splitting grating. A simulation model of the beam-splitting grating is established according to the period of the beam-splitting grating and the material of the beam-splitting grating, and the groove depth and the grating line width of the beam-splitting grating are obtained by simulating and optimizing the simulation model of the beam-splitting grating, so that the first-order diffraction efficiency is the highest.

[0101] Specifically, in some embodiments, the structural parameters of the beam-splitting grating are determined by the following steps: First, the required diffraction angle of the beam-splitting grating is calculated according to the Talbot imaging distance. The required diffraction angle is the angle between the direction line and the normal line when the wave is diffracted. The imaging light path is affected by the Talbot imaging distance, and the imaging light path is designed according to the Talbot imaging distance in the embodiment. The required diffraction angle θ of the beam-splitting grating can be determined according to the imaging light path.

[0102] Further, based on the required diffraction angle and the wavelength of the light source, the period of the beam-splitting grating is determined by a grating equation. Wherein, d is the period of the beam-splitting grating, θ is the required diffraction angle, k is the required diffraction order, and λ is the wavelength of the light. The diffraction order k can meet the beam-splitting requirement by taking one order, and the wavelength λ can be freely selected within the interval that meets the diffraction effect.

[0103] The required diffraction angle θ, the diffraction order k and the wavelength λ obtained according to the Talbot imaging distance are brought into the grating equation, and the equation is solved to obtain the period d of the beam-splitting grating.

[0104] Further, based on the required high transmittance, the glass material is determined as the material of the beam-splitting grating. Specifically, to improve the transmission intensity of the beam-splitting grating and suppress the reflection intensity of the beam-splitting grating, the grating line material is selected to be a material with high transmittance, for example, the grating line material is designed to be a glass material, which maintains consistency with the grating base material while reducing redundant processes and reducing costs.

[0105] Further, a beam splitting grating simulation model is established according to the beam splitting grating period d and the beam splitting grating material (glass material), and the groove depth of the beam splitting grating and the grating line width of the beam splitting grating are obtained by simulation optimization of the beam splitting grating simulation model, so that the first-order diffraction efficiency is the highest. The simulation optimization process can be understood as setting the groove depth h and the grating line width w of the beam splitting grating as variables, iteratively optimizing the values of the groove depth h and the grating line width w of multiple groups of beam splitting gratings, and determining the values of the groove depth h and the grating line width w of the beam splitting grating corresponding to the highest first-order diffraction light efficiency as the structural parameters of the beam splitting grating.

[0106] Figure 8 is a schematic diagram of an optical path of the beam splitting grating provided by the application, as shown in Figure 8 , a beam splitting grating structure 1061 is additionally arranged at the light emitting position of the light source (i.e., on the scanning plate 106), according to the working mechanism of the beam splitting grating, the light beam 1071 passing through the beam splitting grating 1061 is split into each-order diffraction light to be incident on the grating ruler 2, by designing the microstructure parameters of the beam splitting grating, the high diffraction efficiency and specific diffraction angle of the first-order diffraction light 1072 can be realized, and then the reflected light 1073 of the grating ruler 2 is realized to be irradiated on the photosensitive surface of the photodetector in a fixed point and a fixed quantity, so that the photodetection with high energy utilization rate is realized.

[0107] Figure 9 is a schematic diagram of the microstructure of the beam splitting grating provided by the application, as shown in Figure 9 , the microstructure parameters of the beam splitting grating 1061 include: the beam splitting grating period d, the groove depth h and the grating line width w of the beam splitting grating.

[0108] Figure 10 is a simulation result diagram of the transmission light each-order diffraction efficiency and the reflection light diffraction efficiency of the beam splitting grating in the optical simulation software provided by the application, as shown in Figure 10 , the horizontal axis represents the angle (unit: degree), and the vertical axis represents the normalized light intensity, the blue line represents the curve of the reflection light intensity distribution, and the red line represents the curve of the transmission light intensity distribution. As can be seen from the diagram, the total transmission light intensity is much higher than the total reflection light intensity, the ratio of the transmission light intensity to the incident light intensity is more than 92%, which reduces the energy loss caused by the reflection light or the absorption light; the first-order diffraction light has the highest diffraction efficiency in the transmission light, which can reach more than 78% of the total transmission light intensity, and the diffraction efficiency of the zero-order diffraction light is suppressed, and the zero-order diffraction light intensity accounts for less than 2% of the total transmission light intensity, which reduces the influence of the invalid diffraction light on the photodetection.

[0109] The method provided by the embodiment can realize high diffraction efficiency and specific diffraction angle of first-order diffraction light by designing the microstructure parameters of the beam splitter grating, thereby realizing fixed-point and fixed-quantity irradiation of reflected light of the grating ruler on a photosensitive surface of a photodetector, and realizing high-energy utilization of the photodetection.

[0110] The application further provides a miniature grating ruler displacement sensor based on the linear beam splitter grating, comprising a read head module and a grating ruler. The read head module comprises a light source, a photodetector group, a scanning plate, a driving circuit, an amplification circuit and an interpolation subdivision circuit; the photodetector group comprises four displacement measurement photodetectors and one reference positioning photodetector; the scanning plate is provided with a beam splitter grating and a plurality of scanning slits, the plurality of scanning slits comprise four first scanning slits and one second scanning slit; the beam splitter grating is located above the light source, the four first scanning slits are respectively aligned with the photosensitive surfaces of the four displacement measurement photodetectors, and the second scanning slit is aligned with the reference positioning photodetector. The grating ruler comprises a measurement grating and a zero grating, and the distance between the grating ruler and the scanning plate is a Talbot imaging distance.

[0111] The application provides a linear beam splitter grating type grating ruler displacement measurement sensor based on Talbot imaging, which comprises a grating module and a read head module. The grating ruler is composed of a measurement grating component and a zero grating component. The read head module comprises a light source, a photodetector, a scanning plate, a power supply circuit and a signal processing circuit. Compared with the prior art, the sensor has small power consumption, large installation tolerance and simple structure, and can realize the application requirements of high precision, small size, low power consumption and large installation tolerance.

[0112] Embodiment 1 The read head module 1 and the grating ruler 2 are placed as shown in Figure 2 The scanning plate 106 is located above the optical element structure in the read head module 1, the grating ruler 2 is located above the scanning plate 106, the distance between the grating ruler 2 and the scanning plate 106 is a Talbot imaging distance, which makes the lower surface of the scanning plate 106 be on the Talbot imaging plane of the grating ruler 2. The light is emitted from the light source 104 in the read head module 1, the transmission light intensity ratio of the beam splitter grating 1061 on the scanning plate 106 is above 92%, which reduces the energy loss of reflected light or absorbed light; meanwhile, the transmission light intensity of the beam splitter grating on the scanning plate 106, the diffraction efficiency of the first-order diffraction light is above 78%, which suppresses the diffraction efficiency of the zero-order diffraction light and the high-order diffraction light; in addition, when the light beam after beam splitting is incident on the photosensitive surface of the photodetector through the grating ruler, the coincidence rate of the light irradiation surface 1074 and the photosensitive surface can reach 32%, which is higher than the coincidence rate of the light irradiation surface 1070 and the photosensitive surface when the light is directly emitted from the light source, Figure 11These are comparison diagrams of the beam-splitting grating structure illumination surface and the direct light-emitting illumination surface of the light source provided by this invention, as shown below. Figure 11 As shown, this effectively improves energy utilization, thereby reducing the overall power consumption of the sensor.

[0113] As can be seen in Example 1, the beam-splitting grating structure, as a beam-splitting optical element, effectively improves the energy utilization rate of the grating ruler displacement sensor and reduces the overall power consumption of the sensor.

[0114] Example 2: Reader module 1, grating ruler 2, etc. Figure 1 As shown, the scanning plate 106 is positioned above the optical element structure in the read head module 1, and the grating ruler 2 is positioned above the scanning plate 106. The distance between the grating ruler 2 and the scanning plate 106 is the Talbot imaging distance, which ensures that the lower surface of the scanning plate 106 is on the Talbot imaging plane of the grating ruler 2. Light is emitted from the light source 104 in the read head module 1. After being split by the beam splitting grating 1061 on the scanning plate 106, the center of the beam incident on the measurement area of ​​the scanning plate coincides with the center of the measurement area, and the center of the beam incident on the zero-position area of ​​the scanning plate coincides with the center of the zero-position area. Even when there is an installation tolerance between the grating ruler 2 and the read head module 1, a high degree of overlap between the illumination surface and the photodetector's photosensitive surface can still be guaranteed. Furthermore, when the installation tolerance reaches 2 degrees, the stability of the light intensity fluctuation value detected by the photodetector can still be kept within 10%, thus improving the sensor installation tolerance.

[0115] As can be seen in Example 2, the beam splitting grating structure, as a beam splitting optical element, can reduce the light intensity deviation caused by beam tilt, improve the uniformity of light intensity detection, and increase the sensor installation tolerance. Its installation tolerance independent rotation angle can reach up to 2 degrees.

[0116] The following describes the grating ruler displacement measuring device based on a linear beam-splitting grating provided by the present invention. The grating ruler displacement measuring device based on a linear beam-splitting grating described below can be referred to in correspondence with the grating ruler displacement measuring method based on a linear beam-splitting grating described above.

[0117] Figure 12 This is a schematic diagram of the grating ruler displacement measuring device based on a linear beam-splitting grating provided by the present invention. This grating ruler displacement measuring device 1200 is applied to a miniature grating ruler displacement sensor based on a linear beam-splitting grating. The displacement sensor includes a readhead module and a grating ruler. The readhead module includes optical measurement elements and signal processing circuitry. The optical measurement elements include a light source, a displacement measurement photodetector, and a scanning plate. The scanning plate is equipped with a beam-splitting grating, which is located above the light source. The distance between the grating ruler and the scanning plate is the Talbot imaging distance. The device includes: The beam splitting module 1210 is configured to emit a light beam from the light source when the grating ruler and the read head module are relatively displaced, split the emitted light beam by the beam splitting grating to obtain two split beams, and make one of the two split beams incident on a measurement grating in the grating ruler to form a Talbot image through reflection of the measurement grating. The displacement measurement module 1220 is configured to modulate the Talbot image by the scanning plate, receive the modulated Talbot image by the displacement measurement photodetector, generate four current signals with a phase difference of 90 degrees, and perform current-voltage conversion, difference, and subdivision processing on the four current signals by the signal processing circuit in sequence to obtain a high-resolution AB signal, which is used to determine the relative displacement amount of the grating ruler and the read head module.

[0118] The device provided in the embodiment is applied to a linear beam splitting grating-based miniature grating ruler displacement sensor, which includes a read head module and a grating ruler. The read head module includes an optical measurement element and a signal processing circuit. The optical measurement element includes a light source, a displacement measurement photodetector, and a scanning plate. The signal processing circuit includes a driving circuit, an amplification circuit, and an interpolation subdivision circuit. The scanning plate is provided with a beam splitting grating, which is located above the light source. The distance between the grating ruler and the scanning plate is a Talbot imaging distance. The device includes a beam splitting module 1210 configured to emit a light beam from the light source when the grating ruler and the read head module are relatively displaced, split the emitted light beam by the beam splitting grating to obtain two split beams, and make one of the two split beams incident on a measurement grating in the grating ruler to form a Talbot image through reflection of the measurement grating. Then, a displacement measurement module 1220 is configured to modulate the Talbot image by the scanning plate, receive the modulated Talbot image by the displacement measurement photodetector, generate four current signals with a phase difference of 90 degrees, and perform current-voltage conversion, difference, and subdivision processing on the four current signals by the signal processing circuit in sequence to obtain a high-resolution AB signal. The high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the read head module.

[0119] The scanning plate of the grating ruler displacement sensor is provided with a beam splitting grating, which is located above the light source. The distance between the grating ruler and the scanning plate is a Talbot imaging distance. The light emitted by the light source is split by the beam splitting grating, directional propagation of the light beam is achieved, energy utilization is improved, and power consumption of the light source is reduced. Meanwhile, the split and propagated transmitted light of the beam splitting grating is more conducive to realization of high-uniformity light intensity detection, installation tolerance is improved, and application requirements of high precision, small size, low power consumption, and large installation tolerance are met based on the beam splitting grating and the Talbot imaging principle.

[0120] According to the grating ruler displacement measurement device 1200 based on the linear beam splitting grating provided by the application, the optical measurement element further comprises a reference positioning photodetector; the scanning plate is further provided with a plurality of scanning slits, the scanning slits comprising four first scanning slits and one second scanning slit, the four first scanning slits being respectively aligned with the light-sensitive surfaces of the four displacement measurement photodetectors, and the second scanning slit being aligned with the reference positioning photodetector; The displacement measurement module 1220 is specifically configured to: After the Talbot image is modulated through each first scanning slit, the modulated Talbot image is received by each displacement measurement photodetector to generate the four current signals; Wherein, the fringe period of the first scanning slit is T, and the distance between adjacent first scanning slits along the arrangement direction is nT+T / 4, wherein n is an integer, so that each displacement measurement photodetector outputs a corresponding current signal.

[0121] According to the grating ruler displacement measurement device 1200 based on the linear beam splitting grating provided by the application, the device further comprises a zero signal output module; Another beam splitting light in the two beam splitting lights is reflected by the zero grating in the grating ruler to form a converging light beam; The zero signal output module is configured to: The converging light beam is modulated through the second scanning slit; The modulated converging light beam is converted into a zero current signal by the reference positioning photodetector, and the zero current signal is subjected to current-voltage conversion and subdivision processing by the signal processing circuit to output a zero signal.

[0122] According to the grating ruler displacement measurement device 1200 based on the linear beam splitting grating provided by the application, the signal processing circuit comprises an amplification circuit and an interpolation subdivision circuit; The displacement measurement module 1220 is further configured to: The four current signals are subjected to current-voltage conversion by the amplification circuit to obtain the four voltage signals after conversion; The four voltage signals after conversion are subjected to differential processing by the interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees; The two voltage signals are converted into the high-resolution AB signal by the interpolation subdivision circuit.

[0123] According to the grating ruler displacement measurement device 1200 based on the linear beam splitting grating provided by the application, the displacement measurement module 1220 is further configured to: Differencing signals of two of the four displacement measurement photodetectors; Differencing signals of the other two of the four displacement measurement photodetectors, except the two displacement measurement photodetectors, to generate the two high-contrast voltage signals.

[0124] According to the present application, a grating ruler displacement measurement device 1200 based on a linear beam splitting grating is provided, and the structure parameters of the beam splitting grating are determined by the following steps: According to the Talbot imaging distance, a required diffraction angle of the beam splitting grating is calculated; Based on the required diffraction angle and the wavelength of the light source, the period of the beam splitting grating is determined by a grating equation; Based on the required high transmittance, a glass material is determined as the material of the beam splitting grating; According to the period of the beam splitting grating and the material of the beam splitting grating, a simulation model of the beam splitting grating is established, and the groove depth and the grating line width of the beam splitting grating are obtained by simulating and optimizing the simulation model of the beam splitting grating, so that the first-order diffraction efficiency is the highest.

[0125] Figure 13 As shown in the structural schematic diagram of the electronic equipment provided by the present application, Figure 13 As shown in the structural schematic diagram of the electronic equipment provided by the present application, The processor 1310 can call the logical instructions in the memory 1330 to execute a grating ruler displacement measurement method based on a linear beam splitting grating, which is applied to a micro grating ruler displacement sensor based on a linear beam splitting grating; the displacement sensor includes a read head module and a grating ruler, the read head module includes an optical measurement element and a signal processing circuit, the optical measurement element includes a light source, a displacement measurement photodetector and a scanning plate; the scanning plate is provided with a beam splitting grating, the beam splitting grating is located above the light source, and the distance between the grating ruler and the scanning plate is a Talbot imaging distance; the method includes: After the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; The four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal; the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the read head module.

[0126] In addition, the logical instructions in the memory 1330 described above can be implemented in the form of a software function unit and sold or used as a separate product, which can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts of the technical solutions can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various program code storage media.

[0127] On the other hand, the present application also provides a computer program product, which comprises a computer program, the computer program can be stored on a non-transitory computer readable storage medium, and the computer program is executed by a processor, so that the computer can execute the grating ruler displacement measurement method based on a straight-line beam-splitting grating provided by the above-mentioned method, which is applied to a micro grating ruler displacement sensor based on a straight-line beam-splitting grating; the displacement sensor comprises a read head module and a grating ruler, the read head module comprises an optical measurement element and a signal processing circuit, the optical measurement element comprises a light source, a displacement measurement photodetector and a scanning plate; the scanning plate is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, the distance between the grating ruler and the scanning plate is a Talbot imaging distance; the method comprises: When the grating ruler and the read head module are relatively displaced, the light source emits a light beam, the emitted light beam is split by the beam-splitting grating to obtain two split beams; one of the two split beams is incident on a measurement grating in the grating ruler and is reflected by the measurement grating to form a Talbot image; After the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; The four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal; the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the read head module.

[0128] In another aspect, the application also provides a non-transitory computer readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a grating ruler displacement measurement method based on a linear beam-splitting grating, which is provided by the above method and applied to a micro grating ruler displacement sensor based on a linear beam-splitting grating; the displacement sensor comprises a read head module and a grating ruler, the read head module comprises an optical measurement element and a signal processing circuit, the optical measurement element comprises a light source, a displacement measurement photodetector and a scanning plate; the scanning plate is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, the distance between the grating ruler and the scanning plate is a Talbot imaging distance; the method comprises: When the grating ruler and the read head module are relatively displaced, the light source emits a light beam, the outgoing light beam is split by the beam-splitting grating to obtain two split beams; one of the two split beams is incident on a measurement grating in the grating ruler, and a Talbot image is formed by reflection of the measurement grating; After the Talbot image is modulated by the scanning plate, the modulated Talbot image is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees; The four current signals are sequentially subjected to current-voltage conversion, difference and subdivision processing by the signal processing circuit to obtain a high-resolution AB signal; the high-resolution AB signal is used to determine the relative displacement amount of the grating ruler and the read head module.

[0129] The device embodiments described above are only schematic, wherein the units shown as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the present embodiment scheme. Those skilled in the art can understand and implement without creative labor.

[0130] Those skilled in the art can clearly understand the technical solutions of the various embodiments from the above description of the embodiments, and the various embodiments can be implemented by means of software with the necessary general hardware platforms, and of course, can also be implemented by hardware. Based on such understanding, the above technical solutions, essentially or in other words, the part of the prior art that makes a contribution, can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, and the like, and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0131] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for some technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for measuring the displacement of a grating ruler based on a linear beam-splitting grating, characterized in that, An application is made to a miniature grating ruler displacement sensor based on a linear beam-splitting grating; the displacement sensor includes a readhead module and a grating ruler, the readhead module includes an optical measurement element and a signal processing circuit, the optical measurement element includes a light source, a displacement measurement photodetector, and a scanning plate; the scanning plate is provided with a beam-splitting grating, the beam-splitting grating is located above the light source, and the distance between the grating ruler and the scanning plate is the Talbot imaging distance; the method includes: When the grating ruler and the read head module are relatively displaced, a light beam is emitted through the light source. The emitted light beam is split into two beams by the beam splitting grating. One of the two beams is incident on the measuring grating in the grating ruler and is reflected by the measuring grating to form a Taber image. After the image of the Titan is modulated by the scanning plate, the modulated image of the Titan is received by the displacement measurement photodetector to generate four current signals with a phase difference of 90 degrees. The signal processing circuit sequentially performs current-to-voltage conversion, differential processing, and subdivision processing on the four current signals to obtain a high-resolution AB signal; the high-resolution AB signal is used to determine the relative displacement between the grating ruler and the read head module.

2. The grating ruler displacement measurement method based on a linear beam-splitting grating according to claim 1, characterized in that, The optical measurement element also includes a reference positioning photodetector; the scanning plate is also provided with a plurality of scanning slits, the scanning slits including four first scanning slits and two scanning slits, the four first scanning slits being aligned with the photosensitive surfaces of the four displacement measurement photodetectors respectively, and the second scanning slits being aligned with the reference positioning photodetector; The process of modulating the Talbot image using the scanning plate, receiving the modulated Talbot image via the displacement measurement photodetector, and generating four current signals with a 90-degree phase difference includes: After the image of the Titan is modulated by each of the first scanning slits, the modulated image of the Titan is received by each of the displacement measurement photodetectors to generate the four current signals. Wherein, the stripe period of the first scanning slit is T, and the spacing between adjacent first scanning slits along the arrangement direction is nT+T / 4, where n is an integer, so that each displacement measurement photodetector outputs a corresponding current signal.

3. The grating ruler displacement measurement method based on a linear beam-splitting grating according to claim 2, characterized in that, The other beam of the two split beams is reflected by the zero-position grating in the grating ruler to form a converging beam; the method further includes: The converging beam is modulated through the second scanning slit; The modulated converging beam is converted into a zero-position current signal by the reference positioning photodetector, and the zero-position current signal is processed by the signal processing circuit to perform current-voltage conversion and subdivision processing, and output a zero-position signal.

4. The grating ruler displacement measurement method based on a linear beam-splitting grating according to claim 1, characterized in that, The signal processing circuit includes an amplification circuit and an interpolation subdivision circuit; the process of sequentially performing current-to-voltage conversion, differential processing, and subdivision processing on the four current signals through the signal processing circuit to obtain a high-resolution AB signal includes: The four current signals are converted to voltage by the amplifier circuit to obtain the four voltage signals after conversion. The four voltage signals after conversion are differentially processed by the interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees. The two voltage signals are converted into the high-resolution AB signal by the interpolation subdivision circuit.

5. The grating ruler displacement measurement method based on a linear beam-splitting grating according to claim 4, characterized in that, The step of performing differential processing on the converted four voltage signals through the interpolation subdivision circuit to obtain two voltage signals with a phase difference of 90 degrees includes: The signals from two of the four displacement measurement photodetectors are differentially divided. The signals from the two displacement measurement photodetectors other than the two designated displacement measurement photodetectors are differentially divided to generate two high-contrast voltage signals.

6. The grating ruler displacement measurement method based on a linear beam-splitting grating according to claim 1, characterized in that, The structural parameters of the beam splitter grating are determined through the following steps: The required diffraction angle of the beam splitter is calculated based on the Timber imaging distance. Based on the required diffraction angle and light source wavelength, the beam splitting grating period is determined using the grating equation. Based on the requirement for high transmittance, glass material was selected as the beam splitting grating material; A beam splitter grating simulation model is established based on the beam splitter grating period and the beam splitter grating material. The groove depth and grating line width of the beam splitter grating are obtained by simulating and optimizing the beam splitter grating simulation model to maximize the first-order diffraction efficiency.

7. A miniature grating ruler displacement sensor based on a linear beam-splitting grating, characterized in that, Includes the read head module and the grating ruler; The read head module includes a light source, a photodetector group, a scanning plate, a driving circuit, an amplification circuit, and an interpolation subdivision circuit; the photodetector group includes four displacement measurement photodetectors and one reference positioning photodetector; the scanning plate is provided with a beam splitter grating and multiple scanning slits, the multiple scanning slits including four first scanning slits and one second scanning slit; the beam splitter grating is located above the light source, the four first scanning slits are respectively aligned with the photosensitive surfaces of the four displacement measurement photodetectors, and the second scanning slit is aligned with the reference positioning photodetector; The grating ruler includes a measuring grating and a zero-position grating, and the distance between the grating ruler and the scanning plate is the Talbot imaging distance.

8. A grating ruler displacement measuring device based on a linear beam-splitting grating, characterized in that, An application is made to a miniature grating ruler displacement sensor based on a linear beam-splitting grating; the displacement sensor includes a readhead module and a grating ruler, the readhead module includes optical measurement elements and signal processing circuitry, the optical measurement elements include a light source, a photodetector, and a scanning plate; the scanning plate is equipped with a beam-splitting grating, the beam-splitting grating is located above the light source, and the distance between the grating ruler and the scanning plate is the Talbot imaging distance; the device includes: The beam splitting module is used to emit a light beam through the light source when the grating ruler and the read head module are relatively displaced. The emitted light beam is split into two beams by the beam splitting grating. One of the two beam split beams is incident on the measuring grating in the grating ruler and is reflected by the measuring grating to form a Taber image. The displacement measurement module is used to modulate the Talbot image through the scanning plate, receive the modulated Talbot image through the displacement measurement photodetector, and generate four current signals with a phase difference of 90 degrees. The signal processing circuit sequentially performs current-to-voltage conversion, differential processing, and subdivision processing on the four current signals to obtain a high-resolution AB signal. The high-resolution AB signal is used to determine the relative displacement between the grating ruler and the read head module.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the grating ruler displacement measurement method based on a linear beam splitter grating as described in any one of claims 1 to 6.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the grating ruler displacement measurement method based on a linear beam splitter grating as described in any one of claims 1 to 6.

Images