A high-precision grating ruler system and measuring equipment

Abstract

The present application discloses a high-precision grating ruler system and measuring equipment. Relating to the field of ultra-precision displacement measurement, the high-precision grating ruler system comprises: a reflective grating, disposed on a first target to be measured; a grating ruler reading head, disposed on a second target to be measured relative to the reflective grating, for outputting an incremental signal and a zero-position signal upon detecting a relative displacement between the first target to be measured and the second target to be measured; and a control module, communicatively connected to the grating ruler reading head, for receiving the incremental signal and the zero-position signal, and determining the relative displacement between the first target to be measured and the second target to be measured through the incremental signal and the zero-position signal. This application solves the technical problem of limitations of ultra-precision measuring instruments such as laser interferometers and capacitive sensors in actual measurement applications in related technologies.

Description

Technical Field

[0001] The present application relates to the field of ultra-precision measurement, and more specifically, to a high-precision grating ruler system and measuring equipment. Background Art

[0002] Among related technologies, ultra-precision measuring instruments with nanometer-level accuracy include laser interferometers, capacitive sensors, and grating rulers. Laser interferometers use the laser wavelength as a displacement measurement reference, achieving high measurement accuracy and resolution. However, since the wavelength of light fluctuates with changes in the ambient refractive index and temperature, they have limitations in actual measurement applications. Capacitive sensors also have high accuracy and resolution in small-scale, unidirectional motion scenarios. However, due to the small plate area of ​​capacitive sensors used in ultra-precision measurements, their edge effects have a significant impact on measurement accuracy.

[0003] Meanwhile, most domestically produced optical scales on the market are based on the Moiré fringe imaging scanning principle, resulting in low precision. Applied to equipment such as machining machines and SMT placement machines, they cannot meet the ultra-high-precision displacement measurement needs of ultra-precision manufacturing and aerospace. High-precision optical scales with accuracy of ±0.5μm and resolutions up to 5nm are currently available abroad, but they are expensive and difficult to procure.

[0004] Furthermore, laser interferometers and optical scales each focus on different application scenarios. Laser interferometers, which trace the reference back to the wavelength of light, remain the benchmark for industrial displacement measurement and are widely used in large-scale, high-precision displacement measurement scenarios. In recent years, with the development of optical grating and optoelectronic technologies, the accuracy and resolution of optical scales have reached the same level as interferometers. Their high stability, compact structure, and cost-effectiveness have enabled them to gradually replace interferometers in some applications.

[0005] The technical core of the grating ruler lies in its precision measurement capability, which can measure linear displacement at the nanometer level. Therefore, it is mainly used in fields such as precision machining, semiconductor manufacturing, and aerospace where there is an urgent need for ultra-precision measurement technology with nanometer-level measurement accuracy.

[0006] Currently, no effective solution has been proposed to the above-mentioned problems existing in the related technologies. Summary of the Invention

[0007] The main purpose of this application is to provide a high-precision grating scale system and measuring equipment to solve the problem of limitations of ultra-precision measuring instruments such as laser interferometers and capacitive sensors in actual measurement applications in related technologies.

[0008] To achieve the above objectives, according to one aspect of the present application, a high-precision grating ruler system is provided. The system includes: a reflective grating disposed on a first target to be measured; a grating ruler reading head disposed on a second target to be measured, opposite the reflective grating, and configured to output an incremental signal and a zero position signal upon detecting a relative displacement between the first target to be measured and the second target to be measured; and a control module communicatively coupled to the grating ruler reading head, configured to receive the incremental signal and the zero position signal, and to determine the relative displacement between the first target to be measured and the second target to be measured based on the incremental signal and the zero position signal.

[0009] Furthermore, the grating scale reading head also includes: a laser for emitting an initial light beam; a zero position signal measurement module for processing the initial light beam into zero position measurement light and incremental measurement light, and converting the zero position measurement light into a zero position signal; an incremental signal measurement module for receiving incremental measurement light and converting the incremental measurement light into an incremental signal.

[0010] Furthermore, the zero-position signal measurement module includes: a collimating mirror for collimating the initial light beam into a parallel light beam; a dichroic prism for dichroicing the parallel light beam into a reflected light beam and a transmitted light beam, wherein the reflected light beam serves as the zero-position measurement light and the transmitted light beam serves as the incremental measurement light; a zero-position transmission grating for transmitting the zero-position measurement light twice, wherein the transmitted zero-position measurement light is emitted to the zero-position reflection grating and reflected by the zero-position reflection grating to the dichroic prism for transmission, and the target zero-position measurement light is obtained, wherein the zero-position reflection grating is contained in the reflection grating; and a zero-position photoelectric detector for receiving and converting the target zero-position measurement light to obtain a zero-position signal.

[0011] Furthermore, the incremental signal measurement module also includes: a right-angle prism for receiving and reflecting incremental measurement light; an incremental transmission grating for receiving vertically incident incremental measurement light and transmitting the transmitted incremental measurement light to the incremental reflection grating to form a multi-path interference signal; and a photodetector group including multiple photodetectors for receiving and converting the multi-path interference signal to obtain an incremental signal.

[0012] Furthermore, the control module also includes a first signal processing unit, which is used to normalize the amplitude of the multi-channel interference signal according to the displacement calculation formula to complete the initial phase measurement, and convert the processed multi-channel interference signal into a differential signal output with a phase difference of a preset phase value.

[0013] Furthermore, the multi-path interference signal is a three-path interference signal, and the displacement calculation formula is:

[0014] 2Ω=arctan{[-2dI1+(g+d)I2+(dg)I3] / [-2eI1+(h+e)I2+(eh)I3]}

[0015] =arctan[(C*sinδ) / (C*cosδ)]

[0016] X=(2Ω / 4π)*d

[0017] Wherein, d is the grating pitch, 2Ω is the phase shift between the reflection grating and the transmission grating in the grating scale reading head, d, e, g, h are simplified parameters related to δ1, δ2, δ3, δ1 is the initial phase of the first interference signal in the three-way interference signal, δ2 is the initial phase of the second interference signal in the three-way interference signal, δ3 is the initial phase of the third interference signal in the three-way interference signal, I1 is the intensity of the first interference signal, I2 is the intensity of the second interference signal, I3 is the intensity of the third interference signal, and the DC quantity and amplitude of the three interference signals are equal.

[0018] Furthermore, the control module also includes a second signal processing unit, which is used to perform filtering processing and peak location processing on the zero-position signal, and convert the processed zero-position signal into a differential output signal that complies with a preset format.

[0019] Furthermore, the control module also includes a laser constant current source power supply unit for supplying power to the laser.

[0020] Furthermore, the control module also includes a photodetector bias voltage stabilizing power supply unit for supplying power to the zero position photodetector and the photodetector group in the grating scale reading head.

[0021] To achieve the above-mentioned purpose, according to another aspect of the present application, a measuring device is provided, which includes the above-mentioned high-precision grating ruler system.

[0022] The present application provides a high-precision grating ruler system, comprising: a reflective grating disposed on a first target to be measured; a grating ruler reading head disposed on a second target to be measured relative to the reflective grating, for outputting an incremental signal and a zero-position signal upon detecting a relative displacement between the first target to be measured and the second target to be measured; and a control module in communication with the grating ruler reading head, for receiving the incremental signal and the zero-position signal, and determining the relative displacement between the first target to be measured and the second target to be measured based on the incremental signal and the zero-position signal. This solves the problem of limitations of ultra-precision measuring instruments such as laser interferometers and capacitive sensors in actual measurement applications in related technologies. Furthermore, the system achieves the effect of achieving submicron or even nanometer-level linear measurement accuracy and resolution by providing a low-cost, high-precision measurement system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0024] Figure 1 is a schematic diagram of a high-precision grating ruler system provided according to an embodiment of the present application; and

[0025] Figure 2 Schematic diagram of the internal design of the grating ruler reading head provided for this application;

[0026] Figure 3 Schematic diagram of the zero position measurement system provided for this application;

[0027] Figure 4 A schematic diagram of a grating ruler system for forming three-way interference signals is provided for this application. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] For ease of description, some nouns or terms involved in the embodiments of the present application are explained below:

[0032] Grating ruler: also known as grating displacement sensor, is a linear displacement measurement device that uses grating lines as a measurement reference, which can achieve nanometer-level measurement accuracy and sub-nanometer-level measurement resolution.

[0033] Grating: An optical device consisting of a large number of parallel slits of equal width and spacing, which can spatially periodically modulate the amplitude and / or phase of the incident light wave, a phenomenon also known as diffraction.

[0034] Transmission grating: Evenly spaced grooves are engraved on optical flat glass. The grooved areas are opaque to light, while the unengraved areas are slits that allow light to pass through.

[0035] Reflection grating: Equally spaced grooves are engraved on a metal mirror (or a metal layer plated on a glass substrate). Diffuse reflection occurs on the grooves, and diffraction occurs in the direction of the reflected light at the unengraved areas.

[0036] The present invention will be described below in conjunction with preferred embodiments. Figure 1 Schematic diagram of a high-precision grating ruler system provided according to an embodiment of the present application. Figure 1 As shown, the system includes the following parts:

[0037] A reflection grating is provided on the first target to be measured;

[0038] The grating ruler reading head is arranged on the second target to be measured relative to the reflective grating, and is used to output an incremental signal and a zero position signal when a relative displacement between the first target to be measured and the second target to be measured is detected;

[0039] In the grating ruler system provided in this application, the reflective grating and the reading head are respectively installed on two targets to be measured that have a relative displacement relationship. Figure 1 shown.

[0040] The control module is connected to the grating ruler reading head for receiving the incremental signal and the zero position signal, and determining the relative displacement between the first target to be measured and the second target to be measured through the incremental signal and the zero position signal. Figure 1 As shown, one side of the control module is connected to the scale readhead, providing power and control functions for the components within the scale readhead. It also processes and resolves the interference waveforms output by the scale readhead, ultimately outputting incremental and zero-position signal waveforms according to established standards. Optionally, the other end of the control module serves as a power input and signal output port.

[0041] In an optional embodiment, the grating scale reading head also includes: a laser for emitting an initial light beam; a zero position signal measurement module for processing the initial light beam into zero position measurement light and incremental measurement light, and converting the zero position measurement light into a zero position signal; an incremental signal measurement module for receiving incremental measurement light and converting the incremental measurement light into an incremental signal.

[0042] As mentioned above, the grating scale reading head in this application is integrated into a smaller size as possible. The grating scale reading head integrates the incremental transmission grating, the zero position transmission grating, the laser, the photodetector and other related optical devices to realize the incremental and zero position measurement functions.

[0043] Specifically, the grating ruler reading head mainly consists of three parts: laser, zero position signal measurement module and incremental signal measurement module. Figure 2 The internal design diagram of the grating ruler reading head provided for this application is as follows: Figure 2 As shown, the zero-position signal measurement module includes: a collimator for collimating the initial light beam into a parallel light beam; wherein the collimator is an appropriate collimator selected according to the laser light output parameters, and the light source emitted by the laser is collimated into a parallel light beam by the collimator; a beam splitter prism for splitting the parallel light beam into a reflected light beam and a transmitted light beam, wherein the reflected light beam serves as the zero-position measurement light and the transmitted light beam serves as the incremental measurement light; a zero-position transmission grating for transmitting the zero-position measurement light twice, wherein the transmitted zero-position measurement light is emitted to the zero-position reflection grating and reflected by the zero-position reflection grating to be transmitted through the beam splitter prism, thereby obtaining the target zero-position measurement light, wherein the zero-position reflection grating is contained in the reflection grating; and a zero-position photodetector for receiving and converting the target zero-position measurement light to obtain a zero-position signal.

[0044] As mentioned above, it should be noted that the zero-position reflection grating is included in the reflection grating set on the first target to be measured. The high-precision grating ruler system provided by this application adopts a one-dimensional pulse zero-position optical path, and the zero-position marks are respectively located on the transmission grating and the reflection grating. The zero-position mark is distributed with non-periodic light and dark lines, which are called zero-position coding. Figure 3 As shown, Figure 3 This is a schematic diagram of the zero-position measurement system. When the zero mark P0 on the transmission grating is fully aligned with the zero mark P1 on the reflection grating, collimated light is irradiated onto P0. The light passes through the light-transmitting portion of P0 and is incident on P1. Since the encoding of P0 and P1 is the same, the light will pass through P1 and be incident on the metal film of the reflection grating substrate, thereby returning along the original path to the detector, generating a large photocurrent. When the two are not fully aligned, the light intensity reflected back to the detector by the metal film along the original path is weak, and the photocurrent at this time is small. Therefore, during the relative movement of the transmission and reflection gratings, when passing through the zero position (the position where P0 and P1 are fully aligned), a large light pulse will be generated. The subsequent circuit can use the peak point position of this pulse as the reference zero position of the grating ruler.

[0045] In an optional embodiment, the incremental signal measurement module further includes: a right-angle prism for receiving and reflecting incremental measurement light; an incremental transmission grating for receiving vertically incident incremental measurement light and directing the transmitted incremental measurement light to the incremental reflection grating to form a multi-path interference signal; and a photodetector group including a plurality of photodetectors for receiving and converting the multi-path interference signal to obtain an incremental signal.

[0046] Specifically, the present application provides a grating ruler system that forms three-way interference signals, such as Figure 4 As shown, the incremental signal measurement module mainly includes the following three parts: a right-angle prism, an incremental transmission grating, and a photodetector group. The right-angle prism is used to reflect the transmitted light obtained by the beam splitter prism, that is, the incremental measurement light. After being reflected by the right-angle prism, the incremental measurement light is perpendicularly incident on the incremental transmission grating. According to the incremental measurement principle, the three-way interference signal is finally received by the photodetector group (photodetector 1, photodetector 2, and photodetector 3) and converted into an incremental signal after photoelectric conversion. It should be noted that this application is described in an embodiment of forming a three-way interference signal.

[0047] Specifically, the high-precision grating ruler system provided in this application is an incremental distance-coded grating ruler. It uses the dual-grating displacement measurement principle to measure relative displacement before and after a movement. It also provides a zero-position grating pair to enable the setting of a reference zero point. After the system is powered on, the reference position is determined by moving through the zero point. Displacement measurements are then performed using the reference point as the zero point. Relative displacement is calculated from the incremental signal, and absolute displacement is determined based on the zero point position.

[0048] Furthermore, the incremental measurement principle of the incremental signal measurement module is based on the grating diffraction phase shift theorem. To specifically introduce the grating diffraction phase shift theorem, the light emitted by the laser (a semiconductor laser is taken as an example here) is collimated into parallel light by the optical system, and then first incident on the transmission grating to generate 0-order and ±1-order diffraction light. The transmission grating used here adjusts the parameters of the line shape and aspect ratio according to specific contrast requirements (i.e., the requirements for the energy distribution of diffracted light at each order), and can achieve the expected intensities of the three diffracted beams of 0-order and ±1-order diffracted light to be close, and the intensity of higher-order diffracted light is much lower than the design requirements of these three orders.

[0049] The three diffracted beams then strike a reflective grating, generating secondary diffraction. The reflective grating used here also has clear design and process parameter requirements, achieving the desired suppression of the 0th-order diffracted light and higher-order diffracted light, with the diffraction energy primarily concentrated in the ±1st-order diffracted light.

[0050] The secondarily diffracted light then returns to the transmission grating, producing third-order diffraction, again generating 0th-order and ±1st-order diffraction light. At this point, interference occurs between the light rays emitted in the same direction. By placing photodetectors at specific locations, the required four-way periodic interference signal can be obtained, which can be used for subsequent displacement calculations.

[0051] The three-diffraction process and the approximate positional relationship between the grating, laser, and detector are as follows: Figure 4 As shown, the diffracted light of the suppressed order, as well as the interference and diffracted light not used in the displacement solution, are not detected in the actual system and are therefore not marked in the figure.

[0052] The following explanation explains the phase relationship of the four interference signals. The first diffraction of the transmission grating produces 0th order and ±1st order diffraction light with almost equal energy. According to the diffraction principle, there is a phase delay of φ between the 0th order and the ±1st order, and there is no phase delay between the ±1st order. When the three diffracted lights undergo a second diffraction through the reflection grating, if the two gratings produce relative motion in the X direction, according to the grating phase shift theorem, the movement of the reflection grating will introduce different phase shifts to the diffracted lights of different orders. Taking one of the lights as an example, △(+1,1) represents the phase shift introduced by the +1st order of the first diffraction in the -1st order light after the second diffraction. Similarly, after the second diffraction, there is:

[0053] △(+1,-1)=-Ω

[0054]

[0055] △(-1,+1)=+Ω

[0056] Similarly, after three diffractions, the final phase delay of the interference signal on the four photodetectors is as follows:

[0057]

[0058] It can be seen that △2 and △3 contain the same phase shift information. Therefore, in the actual system, one of them can be used to represent the two paths, so that only three photodetectors are used to collect the required signals. The intensities of the three interference signals are recorded as I1, I2, and I3, where I0 represents the DC component of the interference light and Ib represents the amplitude of the AC component. For the convenience of formula derivation, it is assumed that the DC quantity and amplitude of the three signals are equal. In the actual system, the DC quantity and AC amplitude of each of the three lights can be calibrated experimentally, and then substituted into the formula for calculation after normalization. At the same time, the initial phase of the three signals (that is, the phase difference of each signal other than the phase shift introduced by diffraction) is set to δ1, δ2, and δ3, then:

[0059] I1=I0+Ib*cos(2Ω+δ1)

[0060] I2=I0+Ib*cos(2Ω+δ2)

[0061] I3=I0+Ib*cos(2Ω+δ3)

[0062] Therefore, by solving the above equations together, we can get the solution formula for the phase shift of 2Ω:

[0063] 2Ω=arctan{[-2dI1+(g+d)I2+(dg)I3] / [-2eI1+(h+e)I2+(eh)I3]}

[0064] =arctan[(C*sinδ) / (C*cosδ)]

[0065] Wherein, d is the grating pitch, 2Ω is the phase shift between the reflection grating and the transmission grating in the grating scale reading head, d, e, g, h are simplified parameters related to δ1, δ2, δ3, δ1 is the initial phase of the first interference signal in the three-way interference signal, δ2 is the initial phase of the second interference signal in the three-way interference signal, δ3 is the initial phase of the third interference signal in the three-way interference signal, I1 is the intensity of the first interference signal, I2 is the intensity of the second interference signal, I3 is the intensity of the third interference signal, and the DC quantity and amplitude of the three interference signals are equal.

[0066] The above formula shows that by pre-measuring the DC and AC quantities in the interference signal intensity measured by the three detectors, as well as the initial phases of the three interference signals, these nine known quantities can be converted into a single sine and cosine signal with the same phase. In other words, the measured output waveform is converted into two sine and cosine signals with a constant phase difference of π within the system. The phase shift of 2Ω can then be determined by measuring the real-time phase of these two signals.

[0067] According to the derivation of the grating diffraction phase shift theorem, when the transmission grating and the reflection grating produce linear relative motion, the phase shift caused by the Doppler frequency shift measured by the photodetector is expressed as:

[0068] I(t)=I0+I*cos(4πX / d)

[0069] The phase shift 2Ω is related to the grating pitch d and the displacement X. Specifically:

[0070] X=(2Ω / 4π)*d

[0071] The aforementioned dual-grating system, after measuring the intensity and initial phase of the three interference signals, combined with the grating pitch, enables incremental measurement. Through the interference and diffraction of light, tiny displacements are significantly amplified, enabling high-precision incremental measurement.

[0072] Furthermore, the control module includes a first signal processing unit, which is used to normalize the amplitude of the multi-path interference signal according to the above-mentioned displacement calculation formula to complete the initial phase measurement. In this application, a three-path interference signal is used as an example for illustration. The first signal unit converts the processed three-path interference signal into a differential signal output with a phase difference of π.

[0073] In an optional embodiment provided herein, the laser's supply voltage and control signal, the photodetector's bias voltage, and the incremental and zero-position signals output by the photodetector all interact with the control module via cables. The control module also includes a second signal processing unit for filtering and peak locating the zero-position signal, and converting the processed zero-position signal into a differential output TTL signal conforming to a preset signal format. It should be noted that, in specific applications, the functions implemented by the first and second signal units can be implemented using an FPGA, an MCU, or purely analog circuits.

[0074] The control module also includes a laser constant current source power supply unit, which is used to power the laser and ensure the stability of the laser current, thereby ensuring the stability of the laser light intensity and preventing damage to the laser. The control module also includes a photodetector bias voltage regulated power supply unit, which is used to power the zero position photodetector and the photodetector group in the grating scale readhead, thereby ensuring the stability of the photodetector gain and thus the photoelectric conversion gain.

[0075] The present application provides a high-precision grating ruler system. Taking the currently used incremental grating pair with a pitch of 1 μm as an example, each cycle of the incremental signal represents a displacement of 500 nm. If the incremental signal is subdivided using 12-bit AD (with the peak-to-valley values ​​of the output signal as the upper and lower limits of sampling), the theoretical limit resolution of this system can reach 0.06 nm (500 / 2 / 4096 nm). Based on existing research results, the repeatability of pulsed zero-position positioning in the system can reach 15 nm (that is, the zero-position accuracy level can reach 15 nm), and the pitch repeatability of the incremental grating is 1000 nm ± 1.5 nm. Therefore, after filtering, debugging, and calibration, the repeatability limit accuracy of the incremental ranging of the grating ruler system can reach 3 nm. Therefore, the high-precision grating ruler system provided by the present application achieves submicron or even nanometer-level linear measurement accuracy and resolution. At the same time, through the solution provided by the present application, a miniaturized and highly reliable high-precision measuring device is achieved, providing a wider range of application scenarios. The high-precision grating ruler system is a relatively low-cost high-precision measuring device.

[0076] It should be noted that, based on the high-precision grating scale system provided by this application, the dimensions of the current product readhead can be reduced to 30mm*25mm*20mm. Therefore, this application's high-precision grating scale system solution enables the implementation of miniaturized, highly reliable, and low-cost high-precision grating scale products, addressing the current demand in the precision manufacturing field for nanometer-level high-precision linear displacement measurement equipment.

[0077] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0078] The embodiment of the present application also provides a measuring device, which includes the above-mentioned high-precision grating scale system. During the installation stage of the measuring device, the laser, collimator and light source holder are installed into the housing as a component after completing the collimation and dimming externally, and the light spot position is adjusted to the expected position and then fixed. The reflector frame is fixed to the housing, and then the beam splitter prism and the right-angle reflector are respectively installed on the reflector frame, and their postures are adjusted until the zero position and incremental measurement spots are vertically incident on the corresponding transmission grating. The incremental transmission grating is installed on a specific bracket, and then the bracket is installed on the front surface of the housing. By adjusting the rotation of the bracket, it is ensured that the transmission grating and the reflection grating lines are parallel. The photodetector is welded on the receiving board, and its installation posture is fine-tuned to ensure that the incremental light spot and the zero position light spot are both hit on the corresponding photodetector working surface. The cable is wrapped with a metal layer at the outlet to ensure that the shielding layer of the cable is connected to the reading head housing and grounded. Then fix the housing screws to complete the assembly of the reading head. The other end of the cable is connected to the control module, which consists of a whole PCBA and a corresponding housing. All functions are integrated on the PCBA through corresponding electronic components. Its external interface is used to connect to an external power supply and output differential signal pairs of incremental and zero positions.

[0079] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0080] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0081] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0082] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0083] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0084] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0085] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0086] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0087] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0088] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A high-precision grating ruler system, characterized in that: include: A reflection grating is provided on the first target to be measured; a grating ruler reading head, arranged on a second target to be measured relative to the reflective grating, and configured to output an incremental signal and a zero position signal when a relative displacement between the first target to be measured and the second target to be measured is detected; A control module is communicatively connected to the grating ruler reading head, and is used to receive the incremental signal and the zero position signal, and determine the relative displacement between the first target to be measured and the second target to be measured through the incremental signal and the zero position signal; the control module also includes a laser constant current source power supply unit, which is used to power the laser; the control module also includes a photodetector bias voltage stabilized power supply unit, which is used to power the zero position photodetector and the photodetector group in the grating ruler reading head; The grating ruler reading head further includes: a laser for emitting an initial light beam; a zero position signal measurement module for processing the initial light beam into zero position measurement light and incremental measurement light, and converting the zero position measurement light into the zero position signal; an incremental signal measurement module for receiving the incremental measurement light and converting the incremental measurement light into the incremental signal; The incremental signal measurement module further includes: a right-angle prism for receiving and reflecting the incremental measurement light; an incremental transmission grating for receiving the vertically incident incremental measurement light and transmitting the transmitted incremental measurement light to the incremental reflection grating to form a multi-path interference signal; and a photodetector group including a plurality of photodetectors for receiving and converting the multi-path interference signal to obtain the incremental signal. In which, the detector group includes three detectors, the multi-path interference signal is a three-path interference signal, and the three DC quantities and three AC quantities corresponding to the light intensities of the three-path interference signals corresponding to the three detectors, as well as the three initial phases corresponding to the three-path interference signals are measured. The three DC quantities, the three AC quantities and the three initial phases are converted into two sine and cosine signals with a constant phase difference of π. The relative displacement is obtained by measuring the real-time phases of the two sine and cosine signals.

2. The grating scale system according to claim 1, characterized in that: The zero signal measurement module includes: a collimating lens, used for collimating the initial light beam into a parallel light beam; a beam splitter prism, configured to split the parallel light beam into a reflected light beam and a transmitted light beam, wherein the reflected light beam serves as the zero-position measurement light and the transmitted light beam serves as the incremental measurement light; a zero-position transmission grating, configured to transmit the zero-position measurement light twice, wherein the transmitted zero-position measurement light is emitted to a zero-position reflection grating and reflected by the zero-position reflection grating to be transmitted through the beam splitter prism, thereby obtaining target zero-position measurement light, wherein the zero-position reflection grating is contained in the reflection grating; The zero position photoelectric detector is used to receive and convert the target zero position measurement light to obtain the zero position signal.

3. The grating scale system according to claim 1, characterized in that: The control module also includes a first signal processing unit for normalizing the amplitude of the multi-path interference signal according to a displacement calculation formula to complete initial phase measurement, and converting the processed multi-path interference signal into a differential signal output with a phase difference of a preset phase value.

4. The grating scale system according to claim 3, characterized in that: The displacement calculation formula is: 2Ω=arctan{[-2dI1+(g+d)I2+(dg)I3] / [-2eI1+(h+e)I2+(eh)I3]} =arctan[(C*sinδ) / (C*cosδ)]; X=(2Ω / 4π)*d; Where d is the grating pitch, is the phase shift between the reflection grating and the transmission grating in the grating scale reading head, d, e, g, h are simplified parameters related to δ1, δ2, δ3, δ1 is the initial phase of the first interference signal in the three-way interference signal, δ2 is the initial phase of the second interference signal in the three-way interference signal, δ3 is the initial phase of the third interference signal in the three-way interference signal, I1 is the intensity of the first interference signal, I2 is the intensity of the second interference signal, I3 is the intensity of the third interference signal, and the DC quantity and amplitude of the three interference signals are equal.

5. The grating scale system according to claim 1, characterized in that: The control module further includes a second signal processing unit configured to perform filtering and peak location processing on the zero-bit signal, and convert the processed zero-bit signal into a differential output signal conforming to a preset format.

6. A measuring device, characterized in that The measuring device comprises a high-precision grating ruler system according to any one of claims 1 to 5.

Images