High-precision grating ruler system and measuring equipment

Abstract

The invention discloses a high-precision grating ruler system and measuring equipment. The high-precision grating ruler system relates to the field of ultra-precision displacement measurement, and comprises a reflection grating arranged on a first to-be-measured target; the grating ruler reading head is arranged on the second to-be-measured target opposite to the reflection grating and is used for outputting an increment signal and a zero signal under the condition that relative displacement of the first to-be-measured target and the second to-be-measured target is detected; and the control module is in communication connection with the grating ruler reading head and is used for receiving the increment signal and the zero signal and determining the relative displacement between the first to-be-measured target and the second to-be-measured target through the increment signal and the zero signal. According to the invention, the technical problem of limitation of ultra-precision measurement instruments such as a laser interferometer and a capacitive sensor in actual measurement application in the prior art is solved.

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] In the related technologies, ultra-precision measuring instruments with nanometer-level precision include laser interferometers, capacitive sensors, and grating rulers. Among them, laser interferometers use the laser wavelength as the displacement measurement reference, which can achieve higher measurement accuracy and resolution. However, since the wavelength of light fluctuates with the refractive index and temperature of the environment, it has limitations in actual measurement applications. Capacitive sensors also have high accuracy and resolution in small-range unidirectional motion scenarios, but capacitive sensors used for ultra-precision measurement have a smaller plate area, so their edge effects have a greater impact on measurement accuracy.

[0003] At the same time, most domestic grating rulers on the market are based on the principle of moiré fringe imaging scanning, with low accuracy. They are used in mechanical processing machine tools, SMT placement machines and other equipment, and cannot meet the ultra-high precision displacement measurement needs in ultra-precision manufacturing and aerospace. There are currently high-precision grating ruler products with an accuracy of ±0.5μm and a resolution of up to 5nm abroad, but they are expensive and difficult to purchase.

[0004] Furthermore, laser interferometers and grating rulers focus on different application scenarios. Laser interferometers trace the reference to the wavelength of light and are still the reference for industrial displacement measurement. They are widely used in large-scale, high-precision displacement measurement scenarios. In recent years, with the development of grating and optoelectronic technology, the accuracy and resolution of grating rulers have been in the same echelon as interferometers. Their high stability, compact structure and high cost-effectiveness have enabled them to gradually replace interferometers in some application fields.

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

[0006] Currently, no effective solution has been proposed for 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 ruler system and measuring equipment to solve the problem that ultra-precision measuring instruments such as laser interferometers and capacitive sensors in related technologies have limitations in actual measurement applications.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a high-precision grating ruler system is provided. The system comprises: a reflection grating, which is arranged on a first target to be measured; a grating ruler reading head, which is arranged on a second target to be measured relative to the reflection 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; and a control module, which is connected to the grating ruler reading head in communication, 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.

[0009] Furthermore, the grating ruler 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 collimator, used to collimate the initial light beam into a parallel light beam; a beam splitter, used to split the parallel light beam into a reflected light beam and a transmitted light beam, wherein the reflected light beam is used as the zero-position measurement light and the transmitted light beam is used as the incremental measurement light; a zero-position transmission grating, used to transmit the zero-position measurement light twice, the transmitted zero-position measurement light is emitted to the zero-position reflection grating and reflected by the zero-position reflection grating to the beam splitter prism for transmission, and the target zero-position measurement light is obtained, wherein the zero-position reflection grating is contained in the reflection grating; a zero-position photoelectric detector, used to receive and convert 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 incident the transmitted incremental measurement light on the incremental reflection grating to form a multi-path interference signal; a photodetector group, including multiple photodetectors, for receiving and converting multi-path interference signals to obtain incremental signals.

[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 ruler 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 ruler reading head.

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

[0022] Through the present application, a high-precision grating ruler system is provided, including: a reflection grating, arranged on a first target to be measured; a grating ruler reading head, arranged on a second target to be measured relative to the reflection grating, for outputting 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, which is in communication connection 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 through the incremental signal and the zero position signal, thereby solving the problem of limitations of ultra-precision measuring instruments such as laser interferometers and capacitive sensors in the related art in actual measurement applications. Thus, the effect of achieving sub-micron or even nanometer-level linear measurement accuracy and resolution is achieved by providing a low-cost high-precision measurement system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the 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 the present application. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present 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 solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present 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 comprising 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 the convenience 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 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 modulate the amplitude and / or phase of the incident light wave, also known as diffraction.

[0034] Transmission grating: Equally spaced grooves are cut on optical flat glass. The grooved areas are opaque to light, while the uncut 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 is a schematic diagram of a high-precision grating ruler system provided according to an embodiment of the present application, such as Figure 1 As shown, the system includes the following parts:

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

[0038] The grating ruler reading head is arranged on the second target to be measured opposite 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 the present 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 grating ruler reading head, which is used to power the components in the grating ruler reading head and provide control functions, and at the same time process and solve the interference waveform output by the grating ruler reading head, and finally output the incremental signal and zero position signal waveform according to the established standard. Optionally, the other end of the control module is a power input & 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 the present 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 includes 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, which is used to collimate 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 through the collimator. A beam splitter, which is used to split the parallel light beam into a reflected light beam and a transmitted light beam, wherein the reflected light beam is used as the zero-position measurement light, and the transmitted light beam is used as the incremental measurement light; a zero-position transmission grating, which is used to transmit the zero-position measurement light twice, and the transmitted zero-position measurement light is emitted to the zero-position reflection grating and reflected by the zero-position reflection grating to the beam splitter prism for transmission, and the target zero-position measurement light is obtained, wherein the zero-position reflection grating is contained in the reflection grating; a zero-position photoelectric detector, which is used to receive and convert 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 mark is respectively located on the transmission grating and the reflection grating. The zero-position mark is distributed with non-periodic light and dark lines, which is called zero-position coding. Figure 3 As shown, Figure 3 This is a schematic diagram of the zero position measurement system. When the zero position mark P0 on the transmission grating is completely aligned with the zero position mark P1 on the reflection grating, collimated light is irradiated onto P0, and the light passes through the light-transmitting part 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, and then return along the original path to be incident on the detector, generating a large photocurrent. When the two are not completely 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 completely aligned), a large light pulse will be generated, and the subsequent circuit can use the peak point position of the pulse as the reference zero position of the grating ruler.

[0045] In an optional embodiment, 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 incident the transmitted incremental measurement light on the incremental reflection grating to form a multi-path interference signal; a photodetector group, including multiple photodetectors, for receiving and converting multi-path interference signals to obtain incremental signals.

[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 splitting prism, that is, the incremental measurement light. The incremental measurement light is reflected by the right-angle prism and vertically 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, photodetector 3) and becomes an incremental signal after photoelectric conversion. It should be noted that the present application is described in an embodiment of forming a three-way interference signal.

[0047] Specifically, the high-precision grating ruler system provided by the present application belongs to an incremental distance-coded grating ruler, which uses the dual-grating displacement measurement principle to measure the relative displacement before and after movement, and at the same time provides a set of zero-position grating pairs to achieve the setting of the reference zero point. Therefore, after the system is powered on, the reference position is determined by moving through the zero point, and then the displacement measurement is performed with the reference point as the zero point, the relative displacement is calculated by the incremental signal, and the absolute displacement is determined in combination with 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 used as an example here) is collimated as parallel light by the optical system and then first incident on the transmission grating to generate 0th and ±1st 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 each order of diffracted light). It can be expected that the intensities of the three diffracted light beams of 0th and ±1st orders are close, and the intensity of higher-order diffracted light is much lower than the design requirements of these three orders.

[0049] The three diffracted lights are then incident on the reflection grating, resulting in secondary diffraction. The reflection grating used here also has clear requirements for design parameters and process parameters, and the suppression of the 0th order diffraction light and the higher order diffraction light is achieved as expected, and the diffraction energy is mainly concentrated in the ±1st order diffraction light.

[0050] The second diffracted light then returns to the transmission grating, producing third diffraction, and also producing 0th order and ±1st order diffracted light again. At this time, interference will occur between the light rays emitted in the same direction. By setting a photodetector at a specific position, the required 4-way periodic interference signal can be obtained, which can be used for subsequent displacement calculation.

[0051] The three-dimensional diffraction process and the approximate positional relationship between the grating, laser, and detector are shown in the figure. 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 explains the phase relationship of the 4 interference signals. The first diffraction of the transmission grating produces 0th and ±1st order diffraction lights 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, so 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. Here, 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 ruler 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] From the above formula, we can know that by measuring the DC and AC quantities in the light intensity of the interference signal measured by the three detectors in advance, as well as the initial phase of the three interference signals, these nine known quantities can be converted into a sine and cosine with the same phase. That is, in the system, the measured output waveform is converted into two sine and cosine signals with a constant phase difference of π, and then the phase shift 2Ω at this time is obtained by measuring the real-time phase of the two signals.

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

[0068] I(t)=I0+I*cos(4πX / d)

[0069] Among them, the phase shift 2Ω is related to the grating pitch d and the displacement X, specifically:

[0070] X=(2Ω / 4π)*d

[0071] Therefore, relying on the aforementioned dual grating system, after measuring the intensity and initial phase of the three-way interference signal, combined with the grating pitch, incremental measurement can be achieved. Through the interference and diffraction of light, the tiny displacement is greatly amplified, thereby achieving high-precision incremental measurement.

[0072] Furthermore, the control module includes a first signal processing unit, which is used to normalize the amplitudes of the multi-path interference signals 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 explanation. The first signal unit converts the processed three-path interference signals into a differential signal output with a phase difference of π.

[0073] In an optional embodiment provided by the present invention, the power supply voltage and control signal of the laser, the bias voltage of the photodetector, the incremental signal and the zero-position signal output by the photodetector are all interacted with the control module through cables. The control module also includes a second signal processing unit for filtering and peak positioning 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 the functions implemented by the first signal unit and the second signal unit can be implemented in specific applications by means of FPGA, MCU or pure analog circuits.

[0074] The control module also includes a laser constant current source power supply unit, which is used to power the laser to ensure the stability of the laser current, thereby ensuring the stability of the laser light intensity and avoiding damage to 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, thereby ensuring the stability of the photodetector gain, thereby ensuring the stability of the photoelectric conversion gain.

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

[0076] It should be noted that based on the high-precision grating ruler system provided by this application, the external dimensions of the current product reading head can be compressed to 30mm*25mm*20mm. Therefore, the high-precision grating ruler system solution of this application realizes the implementation of miniaturized, highly reliable, and low-cost high-precision grating ruler products, solving the current demand for nano-level high-precision linear displacement measurement equipment in the field of precision manufacturing.

[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 ruler system. During the installation stage of the measuring device, the laser, collimator and light source seat are installed into the housing as a component after completing the collimation and dimming externally, and the 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 is parallel to the reflection grating line. The photodetector is welded on the receiving board, and its installation posture is fine-tuned to ensure that the incremental spot and the zero 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 housing of the reading head 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. The control module consists of a whole PCBA plus a corresponding shell. 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 increment and zero position.

[0079] 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 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 may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include 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 generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. 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 capable of directing a computer or other programmable data processing device to operate 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 A 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 operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0083] In a typical configuration, a computing device includes one or more processors (CPU), 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 include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. 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 disk read-only memory (CD-ROM), digital versatile disk (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 temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0086] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[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 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 may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0088] The above are only 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 modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should 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 arranged on the first target to be measured; A grating ruler reading head is arranged on the second target to be measured opposite 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; The control module is communicatively connected with the grating ruler reading head, and is used 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.

2. The grating ruler system according to claim 1, characterized in that: The grating ruler reading head also includes: a laser for emitting an initial beam; A zero-position signal measurement module, used for processing the initial light beam into a zero-position measurement light and an incremental measurement light, and converting the zero-position measurement light into the zero-position signal; The incremental signal measurement module is used to receive the incremental measurement light and convert the incremental measurement light into the incremental signal.

3. The grating ruler system according to claim 2, characterized in that: The zero signal measurement module comprises: A collimator lens, used for collimating the initial light beam into a parallel light beam; A beam splitter prism, used for splitting the parallel light beam into a reflected light beam and a transmitted light beam, wherein the reflected light beam is used as the zero-position measurement light, and the transmitted light beam is used as the incremental measurement light; A zero-position transmission grating, used for transmitting the zero-position measurement light twice, wherein the transmitted zero-position measurement light is emitted to a zero-position reflection grating and is reflected by the zero-position reflection grating to be transmitted by the beam splitter prism, and a target zero-position measurement light is obtained, 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.

4. The grating ruler system according to claim 2, characterized in that: The incremental signal measurement module also includes: A right-angle prism, used for receiving and reflecting the incremental measurement light; An incremental transmission grating, used 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; The photoelectric detector group includes a plurality of photoelectric detectors, and is used to receive and convert the multi-path interference signal to obtain the incremental signal.

5. The grating ruler system according to claim 4, characterized in that: 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.

6. The grating ruler system according to claim 5, characterized in that: The multi-channel interference signal is a three-channel interference signal, and 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; Among them, 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 interference signals, δ2 is the initial phase of the second interference signal in the three interference signals, δ3 is the initial phase of the third interference signal in the three interference signals, 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.

7. The grating ruler system according to claim 1, characterized in that: The control module also includes a second signal processing unit, which is used to perform filtering 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.

8. The grating ruler system according to claim 2, characterized in that: The control module also includes a laser constant current source power supply unit, which is used to supply power to the laser.

9. The grating ruler system according to claim 3 or 4, characterized in that: 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.

10. A measuring device, characterized in that: The measuring device comprises a high-precision grating ruler system as described in any one of claims 1 to 9.

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