CN104596424A - Two dimension displacement measurement device which uses double frequency laser and diffraction grating - Google Patents

Abstract

A two-dimensional displacement measurement device using a dual-frequency laser and a diffraction grating involves an ultra-precise displacement measurement technology and a grating displacement measurement system, which consists of a scale grating and a reading head. components, scanning spectroscopic grating components, X-direction detection components, Z-direction detection components, and signal processing components; the device is based on the principle of Michelson interferometer, the principle of multi-diffraction grating interference and the principle of optical beat frequency, and can realize displacement in the X and Z directions. Simultaneous measurement has the advantages of compact structure, strong anti-interference ability, low requirement for the backward zero-order diffraction intensity of the scale grating, and no coupling between X-direction and Z-direction measurement. It can achieve nanometer or even higher measurement resolution, and can be applied to multi-freedom High-precision displacement measurement.

Description

A two-dimensional displacement measurement device using a dual-frequency laser and a diffraction grating

technical field

The invention relates to an ultra-precise displacement measurement technology and a grating displacement measurement system, in particular to a two-dimensional displacement measurement device using a dual-frequency laser and a diffraction grating.

Background technique

In recent years, ultra-precision measurement has become a research hotspot in the field of measurement in the world. Considering the influence of factors such as measurement range, accuracy, system size, and working environment, the demand for high-precision measurement using a small-volume multi-degree-of-freedom measurement method is becoming more and more prominent in modern displacement measurement. In the field of semiconductor processing, the positioning accuracy and motion accuracy of the mask table and workpiece table in the lithography machine are the main factors that limit the line width of semiconductor chip processing. In order to ensure the positioning accuracy and motion accuracy of the mask table and workpiece table, lithography In the machine, a high-precision, large-range dual-frequency laser interferometer measurement system is usually used for displacement measurement. At present, the line width of existing semiconductor chips on the market has approached 14nm, and the ever-increasing semiconductor processing requirements pose a greater challenge to ultra-precision displacement measurement technology, and the dual-frequency laser interferometer measurement system is vulnerable due to its long optical path measurement. Environmental impact, and there are a series of problems such as large system volume and high price, which make it difficult to meet new measurement requirements.

In response to the above problems, major companies and research institutions in the field of ultra-precision measurement at home and abroad have devoted a lot of energy to research, and one of the main research directions includes the development of new displacement measurement systems based on diffraction gratings. After decades of development, the displacement measurement system based on the diffraction grating has produced many research results, which have been disclosed in many patents and papers.

German HEIDENHAIN company's patent US4776701 (disclosure date: October 11, 1988) proposes a method for measuring X-direction displacement by using a beam passing through a refraction grating and a reflection grating to achieve coherent superposition and optical phase shifting. In this method, the phase shift of the interference signal is realized by adjusting the structural parameters of the grating itself, and the measurement results are not affected by the displacement in the Y direction and the Z direction. Since this method does not require additional phase shifting elements, the volume of the system is small, but this method can only be used for displacement measurement in the X direction.

The patent US7362446B2 (published on April 22, 2008) of the Netherlands ASML company proposes a position measurement unit that uses the principle of grating diffraction encoder and interferometer to measure the displacement of the scale grating in the X direction and the Z direction. The unit can measure 6 degrees of freedom of the platform at the same time; through the special prism structure design, the optical components such as light splitting, phase shifting and light combining of the position measurement unit except the scale grating are combined into a whole, so as to reduce the size and quality of the unit , the purpose of compact structure; the measurement light of the grating diffraction encoder used by the position measurement unit to measure the X-direction displacement of the scale grating comes from the diffracted light of the scale grating, and the measurement light of the interferometer used to measure the Z-direction displacement of the scale grating also comes from the scale grating. Diffraction light, but originating from the diffraction of different beams, is discrete. This method can realize displacement measurement in X direction and Z direction at the same time, but the positions of interferometer and grating diffraction measurement are different, and the structure of prism group is complicated.

In the paper "Design and construction of a two-degree-of-freedom linear encoder for nanometric measurement of stage position and straightness. Precision Engineering 34 (2010) 145-155" jointly published by Japanese scholar Wei Gao and Tsinghua University scholar Zeng Lijiang et al. A two-dimensional grating measuring device using the principle of diffraction grating interference. The laser light emitted by the laser is divided into measurement light and reference light by the polarization beam splitter prism, and the two are respectively incident on the scale grating and the reference grating and undergo reverse diffraction. , using the phase shifting of the subsequent optical path, the interference signals can be received on the four groups of detector surfaces. By processing the interference signal, the displacement information of the grating reading head relative to the scale grating in the X direction and the Z direction can be decoupled. In order to realize the phase shift of the signal, this method introduces a lot of phase shifting and optical combining devices, which are large in size; and when the reading head and the grating move in the Z direction, the range of the interference area becomes smaller, which is not conducive to a larger range in the Z direction. Measurement.

In the patents CN102937411A (disclosure date, February 20, 2013) and CN102944176A (disclosure date, February 27, 2013) of Tsinghua University scholar Zhu Yu, a two-dimensional grating measurement system designed using the principle of diffraction grating interference is proposed, and the introduction of The beat frequency signal is generated by the dual-frequency laser, which enhances the anti-interference ability of the measurement signal. In this group of patents, when the reading head moves in the Z direction relative to the scale grating, the range of the interference area becomes smaller, which is not conducive to the measurement of a larger range in the Z direction.

The patents CN102865817A (disclosure date January 9, 2013) and US8604413B2 (disclosure date December 10, 2013) of Mitutoyo Corporation of Japan propose a structure of a two-dimensional displacement sensor, which can realize multidimensional displacement measurement, but The entire system adopts a transmission method, and uses optical devices such as prisms for refraction, so the system is relatively large.

In the patent CN103604376A (published on February 26, 2014) by Hu Pengcheng, a scholar of Harbin Institute of Technology, a kind of anti-optical frequency aliasing grating interferometer system is proposed, and the dual-frequency laser emitted by the laser is transmitted separately in space. setting, eliminating the optical frequency aliasing and the corresponding periodic nonlinear error, and can realize the measurement of three-dimensional displacement; in the patent CN103644849A (disclosure date March 19, 2014) of Harbin Institute of Technology scholar Lin Jie et al., by introducing the self The principle of collimation proposes a three-dimensional displacement measurement system, which can realize Z-direction displacement measurement with a large range, but it is not conducive to improving the quality of the interference signal due to the large number of beam splitting times.

Contents of the invention

In order to solve the limitations of the above solutions, adapt to and meet the aforementioned measurement requirements, the present invention uses the typical Michelson interference principle, multi-diffraction grating interference principle and optical beat frequency principle to design a simple and compact structure, small volume, anti-interference ability Strong two-dimensional displacement measurement device using dual-frequency laser and diffraction grating. When the reading head of the device is displaced in the horizontal direction (X direction) and vertical direction (Z direction) relative to the scale grating, high-precision two-dimensional displacement real-time measurement can be realized.

Technical scheme of the present invention is as follows:

A two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating, including a scale grating and a reading head, and the reading head includes a dual-frequency laser light source, a Z-direction interference component, a scanning spectroscopic grating component, an X-direction detection component, and a Z-direction detection component , signal processing components; dual-frequency laser light sources include dual-frequency lasers, beam splitters, and polarizer A; Z-direction interference components include polarization beam splitters, 1/4 wave plate A, reflective components, 1/4 wave plate B, and polarizer B The scanning spectroscopic grating component includes a scanning spectroscopic grating and an aperture; the plane where the grating lines of the scanning spectroscopic grating is located is parallel to the plane where the grating lines of the scale grating are located; the scanning spectroscopic grating is a one-dimensional grating, and the scale grating has backward zero-order diffracted light, and The equivalent grating periods of the scanning spectroscopic grating and the scale grating in the X direction are equal; the X direction is parallel to the plane where the grating lines of the scanning spectroscopic grating are located, and is perpendicular to the direction of the scanning spectroscopic grating grating lines; the Z direction is the direction of the scanning spectroscopic grating. The direction perpendicular to the plane where the grating line is located; the equivalent grating period refers to the period of the grating in a certain direction; the dual-frequency orthogonally polarized light emitted by the dual-frequency laser enters the beam splitter, and the reflected light passes through the polarizer A and then enters Z The beat frequency signal formed is used as a reference signal for Z-direction measurement. The transmitted light is incident on the polarization beam splitter and divided into reference light and measurement light; After reflection, it passes through 1/4 wave plate A, polarizing beam splitter prism, and polarizing plate B to enter the Z-direction detection part in sequence; after passing through 1/4 wave plate B, the measurement light enters the scanning spectroscopic grating along the Z direction, and is scanned and split After the grating is diffracted, the diffracted beam enters the scale grating and undergoes reverse diffraction. The reverse diffracted light passes through the scanning spectroscopic grating to diffract and split, and nine measuring beams and other stray beams are obtained; among the nine measuring beams, eight of them propagate in pairs In the same way, four sets of interference signals are formed when incident on the X-direction detection part, and the displacement of the reading head relative to the scale grating in the X-direction is obtained after the signal processing unit is resolved; the other of the nine measuring beams is the measuring beam returning along the incident direction It passes through the 1/4 wave plate B, and is reflected by the polarization beam splitter prism, and then enters the Z-direction detection part through the polarizer B; the beat frequency signal formed by the encounter of the reference light and the measurement light incident on the Z-direction detection part is used as the Z-direction measurement One of the measurement signals, the reference signal and the measurement signal measured in the Z direction are resolved by the signal processing unit to obtain the displacement of the reading head relative to the scale grating in the Z direction.

When the scanning spectroscopic grating is a one-dimensional rectangular grating, the scale grating includes the following structural arrangements: ①The scale grating is a one-dimensional rectangular grating, and its grating line direction is parallel to the grating line direction of the scanning spectroscopic grating; ②The scale grating is a two-dimensional rectangular grating , and its two grid line directions are respectively parallel and perpendicular to the grid line direction of the scanning spectroscopic grating; ③ the scale grating is a two-dimensional rectangular grating, and its two grid line directions are respectively 45° to the grid line direction of the scanning spectroscopic grating.

A diaphragm is added to the scanning spectroscopic grating part, and the diaphragm is located between the scanning spectroscopic grating and the X-direction detecting part.

When the wavelength λ=632.8nm of the measurement light emitted by the dual-frequency laser and transmitted through the scanning spectroscopic grating, ① a group of optimal parameters for the scanning spectroscopic grating to adopt a one-dimensional rectangular grating are grating period d=10 μm, grating step height h=488nm, The grating step width a=3.567 μm; ②The parameters of the scale grating include: (a) when the scale grating adopts a one-dimensional rectangular grating, and the direction of the grating lines is parallel to the direction of the grating lines of the scanning spectroscopic grating, a group of preferred parameters is the grating Period d=10 μm, grating step height h=488nm, grating step width a=3.567 μm; (b) when the scale grating adopts a two-dimensional rectangular grating, and its two grid line directions are respectively parallel and parallel to the grid line direction of the scanning spectroscopic grating When vertical, a set of preferred parameters are the grating period d ₁ =d ₂ =10 μm in the direction of the two grid lines, the height of the grating step h=159 nm, and the width of the grating step in the direction of the two grid lines a ₁ =a ₂ =5.67 μm; (c) When the scale grating adopts a two-dimensional rectangular grating, and its two grid line directions are respectively 45° to the grid line direction of the scanning spectroscopic grating, a set of preferred parameters is the grating period d ₁ in the two grid line directions = d ₂ =7.07 μm, grating step height h=159 nm, and grating step width a ₁ =a ₂ =4.01 μm in the direction of two grating lines.

The present invention is a two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating proposed by utilizing the principle of a typical Michelson interferometer, the principle of multi-diffraction grating interference and the principle of optical beat frequency, and has the following innovations and outstanding effects:

1. By placing the scale grating and the scanning spectroscopic grating in parallel, and the equivalent grating period of the two in the X direction is equal, and the scale grating has the setting of the backward zero-order diffracted light, it can provide measurement signals for the X direction and the Z direction at the same time, Furthermore, the displacement of the reading head relative to the scale grating in the X and Z directions is measured at the same time, and the optical 2 subdivision is realized. With a suitable electrical subdivision card, nanometer precision measurement can be realized.

2. The Z-direction measurement adopts the optical beating frequency principle of dual-frequency laser, which reduces the requirements for the zero-order diffraction intensity of the scale grating backward, reduces the power requirements for the laser, and enhances the anti-interference ability of the signal at the same time, which can realize Z-direction high Accuracy measurement.

3. Since the displacement measurement in the X direction utilizes the spectroscopic characteristics of the scanning spectroscopic grating and the scale grating itself to achieve coherent superposition and optical phase shifting, no additional phase shifting and combining devices are required, which not only reduces the structure size, but also avoids phase shifting and combining Errors caused by optical devices.

4. By placing the scale grating and the scanning spectroscopic grating in parallel, and setting the equivalent grating periods of the two in the X direction to be equal, it is possible to make the reading head move relative to the scale grating in the Z direction without affecting the measurement of the interference area in the X direction. range, so it can provide a larger Z-direction measurement range.

5. When detecting the displacement, there is no coupling relationship between the X-direction and Z-direction measurement signals, which simplifies the subsequent signal processing method and reduces the error introduced by signal processing.

6. The X-direction and Z-direction measurement signals can be exported through optical fibers, which can further reduce the volume of the reading head, especially when the period of the grating is designed to be on the order of microns, the two-dimensional displacement measurement device has a compact structure, small size, and high quality. The advantage of being light and easy to apply.

Description of drawings

Fig. 1 is a structural schematic diagram of a two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating according to the present invention.

Fig. 2a is a schematic diagram of the placement of the scanning spectroscopic grating parallel to and perpendicular to the grating lines of the scale grating according to the present invention.

Fig. 2b is a schematic diagram of the placement method of the scanning spectroscopic grating and the direction of the scale grating at 45° according to the present invention.

Fig. 3a is a schematic structural diagram of a one-dimensional rectangular grating applied in the present invention.

Fig. 3b is a schematic structural diagram of a two-dimensional rectangular grating applied in the present invention.

Fig. 4 is a schematic diagram of the optical path transmission direction of an embodiment of a two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating according to the present invention.

Part number description in the figure: 1-dual-frequency laser light source, 2-Z-direction interference component, 3-scanning spectroscopic grating component, 4-scale grating, 5-X-direction detection component, 6-Z-direction detection component, 7-signal processing Components; 11-dual-frequency laser, 12-splitter prism, 13-polarizer A; 21-polarization beamsplitter, 22-1/4 wave plate A, 23-reflection component, 24-1/4 wave plate B, 25- Polarizer B; 31-scanning spectroscopic grating, 32-diaphragm.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

A two-dimensional displacement measurement device using a dual-frequency laser and a diffraction grating, including a scale grating 4 and a reading head, the reading head includes a dual-frequency laser light source 1, a Z-direction interference component 2, a scanning spectroscopic grating component 3, and an X-direction detection component 5 , Z-direction detection part 6, signal processing part 7; Dual-frequency laser source 1 includes dual-frequency laser 11, beam splitter 12, polarizer A13; Z-direction interference part 2 includes polarization beam-splitter prism 21, 1/4 wave plate A22, reflector Component 23, 1/4 wave plate B24, polarizer B25; Scanning spectroscopic grating component 3 comprises scanning spectroscopic grating 31, diaphragm 32; The spectroscopic grating 31 is a one-dimensional grating, and the scale grating 4 has backward zero-order diffracted light, and the equivalent grating periods of the scanning spectroscopic grating 31 and the scale grating 4 in the X direction are equal; the X direction is the grid line of the scanning spectroscopic grating 31 The plane where it is located is parallel to and perpendicular to the direction of scanning the grating lines of the spectroscopic grating 31; the Z direction is the direction perpendicular to the plane where the grating lines of the scanning spectroscopic grating 31 are located; the equivalent grating period refers to the period of the grating in a certain direction; the dual-frequency laser The dual-frequency orthogonally polarized light emitted by 11 enters the beam splitter 12, and its reflected light passes through the polarizer A13 and then enters the Z-direction detection part 6. The formed beat frequency signal is used as a reference signal for Z-direction measurement, and its transmitted light enters After arriving at the polarization beam splitter 21, it is divided into reference light and measurement light; the reference light passes through the 1/4 wave plate A22, and after being reflected by the reflection component 23, it passes through the 1/4 wave plate A22, the polarization beam splitter 21, and the polarizer in turn B25 is incident to the Z-direction detection part 6; the measurement light is incident on the scanning spectroscopic grating 31 along the Z direction after passing through the 1/4 wave plate B24, and after being diffracted by the scanning spectroscopic grating 31, the diffracted beam is incident on the scale grating 4 and undergoes reverse diffraction. The back-diffraction light is diffracted and split through the scanning spectroscopic grating 31 to obtain nine measuring beams and other stray beams; among the nine measuring beams, eight of them propagate in the same direction two by two, and enter the X-direction detection component 5 to form four sets of interference signals , the displacement of the reading head relative to the scale grating 4 in the X direction is obtained after being solved by the signal processing unit 7; the other measuring beam returning along the incident direction in the nine measuring beams passes through the 1/4 wave plate B24, and is determined by After being reflected by the polarizing beam splitter prism 21, it passes through the polarizer B25 and enters the Z-direction detection part 6; the beat frequency signal formed by the meeting of the reference light and the measurement light incident on the Z-direction detection part 6 is used as a measurement signal for the Z-direction measurement, and the Z-direction measurement The reference signal and measurement signal of the signal processing unit 7 are resolved to obtain the displacement of the reading head relative to the scale grating 4 in the Z direction.

In a two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating of the present invention, when the scanning spectroscopic grating 31 is a one-dimensional rectangular grating, its scale grating 4 includes the following structural arrangements: ① the scale grating 4 is a one-dimensional rectangular grating, And its grid line direction is parallel to the grid line direction of the scanning spectroscopic grating 31; 2. the scale grating 4 is a two-dimensional rectangular grating, and its two grid line directions are respectively parallel and vertical to the grid line direction of the scanning spectroscopic grating 31; 3. the scale grating 4 is a two-dimensional rectangular grating, and its two grid line directions are respectively 45° to the grid line direction of the scanning spectroscopic grating 31 .

In a two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating of the present invention, an aperture 32 is added to the scanning spectroscopic grating component 3 , and the aperture 32 is located between the scanning spectroscopic grating 31 and the X-direction detection component 5 .

A kind of two-dimensional displacement measuring device using dual-frequency laser and diffraction grating of the present invention, when the wavelength λ=632.8nm of the measuring light that passes through the scanning spectral grating 31 emitted by the dual-frequency laser 11, ① scan one part of the spectral grating 31 The set of optimal parameters is grating period d=10 μm, grating step height h=488nm, grating step width a=3.567 μm; ②The parameters of the scale grating 4 include: (a) when the scale grating 4 adopts a one-dimensional rectangular grating, and its grid lines When the direction is parallel to the grid line direction of the scanning spectroscopic grating 31, one group of preferred parameters are grating period d=10 μm, grating step height h=488nm, grating step width a=3.567 μm; (b) when the scale grating 4 adopts two-dimensional When a rectangular grating, and its two grid line directions are respectively parallel and perpendicular to the grid line direction of the scanning spectroscopic grating 31, a set of preferred parameters are the grating period d ₁ =d ₂ =10 μm in the two grid line directions, and the grating step height h=159nm, grating step width a ₁ =a ₂ =5.67μm in two grating line directions; (c) when the scale grating 4 adopts a two-dimensional rectangular grating, and its two grating line directions are respectively the same as the grating of the scanning spectroscopic grating 31 When the line direction is 45°, a set of optimal parameters are the grating period d ₁ =d ₂ =7.1 μm in the direction of the two grid lines, the height of the grating step h=159nm, and the width of the grating step in the direction of the two grid lines a ₁ =a ₂ = 4.01 μm.

Taking the scale grating 4 and the scanning spectroscopic grating 31 as a one-dimensional rectangular grating as an example, when a two-dimensional displacement measuring device using a dual-frequency laser and a diffraction grating of the present invention is implemented, as shown in Figure 4, the dual-frequency The dual-frequency orthogonally polarized light OP containing wavelengths λ ₁ and λ ₂ emitted by the laser 11 is incident on the beam splitting prism 12, and its reflected light is incident on the Z-direction detection component 6 after passing through the polarizer A13, and the formed beat frequency signal is used as the Z-direction One path of the reference signal measured, its transmitted light OP1 is incident on the polarization beam splitter prism 21, and the polarization beam splitter prism 21 is set so that the light beam OP1 is incident on the polarization beam splitter prism 21. ₁ measurement light OP2-2 and reference light OP2-1 whose vibration direction is perpendicular to the XZ plane (s-wave) and whose wavelength is _λ2 .

The measurement light OP2-2 passes through the 1/4 wave plate B24 and enters the scanning spectroscopic grating 31, and then diffracts to produce three measuring beams of -1 grade OP3-1, 0 grade OP3-2, and +1 grade OP3-3; the three beams After the measurement beam is incident on the scale grating 4, back diffraction occurs, and five measurement beams [-1, +1] grade OP3-13, [0, -1] grade OP3-21, [0, 0] grade OP3-22 are obtained , [0, +1] level OP3-23, [+1, -1] level OP3-31 and other stray light beams; the five measuring beams are incident on the scanning beam splitting grating 31 and then diffracted again, the diffracted light The stray beam is blocked by the aperture 32 arranged between the scanning grating 31 and the X-direction detection part 5, and the unblocked measuring beam has [-1, +1, -1] levels OP3-131, [0,- 1, 0] level OP3-212, [-1, +1, 0] level OP3-132, [0, -1, +1] level OP3-213, [+1, -1, 0] level OP3-312 , [0, +1, -1] level OP3-231, [+1, -1, +1] level OP3-313, [0, +1, 0] level OP3-232 and [0, 0, 0] Grade OP3-222 has a total of nine bundles.

[-1, +1, -1] grade OP3-131 and [0, -1, 0] grade OP3-212, [-1, +1, 0] grade OP3-132 and [0 , -1, +1] level OP3-213, [+1, -1, 0] level OP3-312 and [0, +1, -1] level OP3-231, [+1, -1, +1] Two pairs of stage OP3-313 and [0, +1, 0] stage OP3-232 have the same propagation direction, incident on the X-direction detection component 5 to form four groups of interference signals, and the changes of the four groups of interference signals are only related to the relative The displacement of the scale grating 4 in the X direction is related. The four sets of interference signals are received by the X-direction detection part 5 and processed by the signal processing unit 7 to obtain two mutually orthogonal electrical signals. 4 Displacement occurring in the X direction.

The placement of the 1/4 wave plate A22 can be set such that the angle between the fast axis direction and the X-Z plane is 45°, the reference light OP2-1 passes through the 1/4 wave plate A22, and is reflected by the reflective member 23 and then passes through the 1/4 wave plate again. 4 wave plate A22, whose polarization direction is rotated by 90° and incident on the polarization beam splitter prism 21 for transmission, after passing through the polarizer B25, it is finally incident on the Z-direction detection component 6 as the reference light for Z-direction measurement; 1/4 wave plate B24 The placement method can be set so that the angle between the fast axis direction and the X-Z plane is 45°, the measurement light OP2-2 passes through the 1/4 wave plate B24, scans the spectroscopic grating 31, is reflected by the scale grating 4, and passes through the scanning spectroscopic grating again 31, which is the [0, 0, 0] grade OP3-222 of the measuring beam returning along the incident direction among the nine measuring beams, which is transmitted through the 1/4 wave plate B24 again, and the polarization direction is rotated by 90° and enters the polarization beam splitter prism Reflection occurs on 21, and after passing through the polarizer B25, it finally enters the Z-direction detection part 6 as the measurement light for Z-direction measurement; the beat frequency signal formed by the meeting of the reference light and the measurement light incident into the Z-direction detection part 6 is used as the Z-direction measurement One way measurement signal, and the beat frequency signal only contains the displacement information of the reading head relative to the scale grating 4 in the Z direction; After calculation, the displacement of the reading head relative to the scale grating 4 in the Z direction is obtained.

In order to improve the quality of the beat frequency signal received by the Z-direction detection component 6, it is necessary to make the energy of the measuring light and the reference light incident on the Z-direction detection component 6 approximately equal, so in specific implementation, the reflection component 23 is set as a partial reflection device, The energy of the measuring light received by the Z-direction detecting component 6 and the energy of the reference light are approximately equal.

In the specific implementation process, in order to further reduce the volume of the reading head, the dichroic prism 12, the polarizer A13, the polarization beam splitter 21, the 1/4 wave plate A22, the 1/4 wave plate B24, the reflective part 23, the polarizer B25, can adopt Integrated structure.

In the specific implementation process, in order to reduce the volume of the reading head and at the same time reduce the influence of the heat dissipation of the dual-frequency laser 11 on the detector, the optical fiber can be used to transmit the beam emitted by the dual-frequency laser 11 to the optical path.

Referring to Fig. 2 a, it is a schematic diagram of the placement mode of the scanning beam-splitting grating 31 of the present invention parallel to and perpendicular to the grid line direction of the scale grating 4, wherein the scanning beam-splitting grating 31 is a one-dimensional rectangular grating, the scale grating 4 is a two-dimensional rectangular grating, and the scanning beam-splitting grating 31 It is placed parallel to the scale grating 4 , and the two grating lines of the scale grating 4 are parallel to and perpendicular to the grating line directions of the scanning spectroscopic grating 31 .

Referring to Fig. 2 b, it is a schematic diagram of the placement mode of the scanning beam-splitting grating 31 and the direction of the scale grating 4 grid lines of the present invention at 45°, wherein the scanning beam-splitting grating 31 is a one-dimensional rectangular grating, the scale grating 4 is a two-dimensional rectangular grating, and the scanning beam-splitting grating 31 It is placed parallel to the scale grating 4 , and the directions of the two grating lines of the scale grating 4 are respectively 45° to the direction of the grating lines of the scanning spectroscopic grating 31 .

Referring to FIG. 3 a , it is a schematic diagram of a one-dimensional rectangular grating structure applied in the present invention, wherein the parameters are: grating period d, grating step height h, and grating step width a.

Referring to Fig. 3b, it is a schematic diagram of a two-dimensional rectangular grating structure applied in the present invention, in which the parameters are: two directional grating periods d ₁ and d ₂ , grating step height h, and two directional grating step widths a ₁ and a ₂ .

Claims (4)

1. one kind uses the two-dimensional displacement measurer of double-frequency laser and diffraction grating, comprise scale grating (4) and read head, it is characterized in that: described read head comprises dual-frequency laser source (1), Z-direction interference part (2), scanning spectro-grating parts (3), X to exploring block (5), Z-direction exploring block (6), Signal Processing Element (7); Described dual-frequency laser source (1) comprises two-frequency laser (11), Amici prism (12), polaroid A (13); Described Z-direction interference part (2) comprises polarization splitting prism (21), quarter wave plate A (22), reflection part (23), quarter wave plate B (24), polaroid B (25); Described scanning spectro-grating parts (3) comprise scanning spectro-grating (31), diaphragm (32); The grid line place plane of described scanning spectro-grating (31) is parallel with the grid line place plane of scale grating (4); Described scanning spectro-grating (31) is one-dimensional grating, and scale grating (4) has backward zero order diffracted light, and scanning spectro-grating (31) is equal with scale grating (4) equivalent screen periods in the X direction; Described X-direction is parallel with the grid line place plane of scanning spectro-grating (31), and perpendicular to scanning the direction of spectro-grating (31) grid line; Described Z-direction is the direction with the grid line place plane orthogonal of scanning spectro-grating (31); Described equivalent screen periods refers to the grating cycle in one direction; The double frequency crossed polarized light of described two-frequency laser (11) outgoing incides Amici prism (12), its reflected light incides Z-direction exploring block (6) through after polaroid A (13), the road reference signal that the beat signal formed is measured as Z-direction, its transmitted light is divided into reference light and measures light after inciding polarization splitting prism (21); Described reference light is through quarter wave plate A (22), and after being reflected by reflection part (23), incide Z-direction exploring block (6) through quarter wave plate A (22), polarization splitting prism (21), polaroid B (25) successively; Scanning spectro-grating (31) is incided along Z-direction after described measurement light transmission quarter wave plate B (24), after scanning spectro-grating (31) diffraction, diffracted beam incides scale grating (4) and reverse diffraction occurs, reverse diffraction light, through scanning spectro-grating (31) diffraction light splitting, obtains nine bundle measuring beams and other spuious light beams; In nine described bundle measuring beams, wherein eight to restraint the direction of propagation between two identical, incide X and form four groups of interference signals to exploring block (5), obtain read head after being resolved by signal processing unit (7) relative to scale grating (4) in the displacement of X to generation; Another measuring beam returned along incident direction in described nine bundle measuring beams through quarter wave plate B (24), and incides Z-direction exploring block (6) through polaroid B (25) after being reflected by polarization splitting prism (21); Incide the reference light of Z-direction exploring block (6) and measure light and to meet the road measuring-signal measured as Z-direction of beat signal formed, the reference signal that Z-direction is measured and measuring-signal pass through to obtain after signal processing unit (7) resolves the displacement that read head occurs in Z-direction relative to scale grating (4).

2. a kind of two-dimensional displacement measurer using double-frequency laser and diffraction grating as claimed in claim 1, it is characterized in that: when described scanning spectro-grating (31) is for one dimension rectangular raster, scale grating (4) comprises following structure arrangement mode: 1. scale grating (4) is one dimension rectangular raster, and its grid line direction is parallel with the grid line direction of scanning spectro-grating (31); 2. scale grating (4) is two-dimensional rectangle grating, and two grid line direction is parallel and vertical with the grid line direction of scanning spectro-grating (31) respectively; 3. scale grating (4) is two-dimensional rectangle grating, and two grid line direction is at 45 ° with the grid line direction of scanning spectro-grating (31) respectively.

3. a kind of two-dimensional displacement measurer using double-frequency laser and diffraction grating as claimed in claim 1, it is characterized in that: in described scanning spectro-grating parts (3), set up diaphragm (32), and diaphragm (32) is positioned at scanning spectro-grating (31) and X between exploring block (5).

4. a kind of two-dimensional displacement measurer using double-frequency laser and diffraction grating as claimed in claim 1, it is characterized in that: when the wavelength X=632.8nm of the measurement light through scanning spectro-grating (31) of two-frequency laser (11) outgoing, 1. described scanning spectro-grating (31) adopts one group of preferred parameter of one dimension rectangular raster to be screen periods d=10 μm, grating steps height h=488nm, grating steps width a=3.567 μm; The parameter of 2. described scale grating (4) comprising: (a) is when scale grating (4) employing one dimension rectangular raster, and its grid line direction with scanning spectro-grating (31) grid line direction parallel time, one group preferred parameter is screen periods d=10 μm, grating steps height h=488nm, grating steps width a=3.567 μm; B () is when scale grating (4) employing two-dimensional rectangle grating, and two grid line direction is parallel with time vertical with the grid line direction of scanning spectro-grating (31) respectively, and one group preferred parameter is the screen periods d in two grid line directions ₁=d ₂=10 μm, grating steps height h=159nm, two grid line directions grating steps width a ₁=a ₂=5.67 μm; C () adopts two-dimensional rectangle grating when scale grating (4), and when two grid line direction is at 45 ° with the grid line direction of scanning spectro-grating (31) respectively, one group preferred parameter is that the screen periods in two grid line directions is d ₁=d ₂=7.07 μm, grating steps height h=159nm, two grid line direction grating steps width a ₁=a ₂=4.01 μm.