CN105203031A - Quadruple optical subdivision two-axis heterodyne grating interferometer - Google Patents

Abstract

A quadruple optical subdivision two-axis heterodyne grating interferometer comprises a double-frequency laser, a first 50% unpolarized polarization beam splitter, a first plane mirror, a second plane mirror, a first interfering module, a second interfering module, a first photoelectric receiver, a second photoelectric receiver, a grating scaleplate and a signal processing module. The quadruple optical subdivision two-axis heterodyne grating interferometer can measure the displacement of a grating in the horizontal direction and in the vertical direction at the same time, the displacement measurement stroke in the vertical direction is substantially increased, the optical subdivision multiple can reach quadruple, and high resolution is achieved while the measurement result is kept stable.

Description

The diaxon heterodyne grating interferometer of four times of optical fines

Technical field

The invention belongs to diaxon displacement measurement system, particularly a kind of diaxon heterodyne grating interferometer of four times of optical fines.

Background technology

Main two kinds at present, the instrument that micro-nano accurate displacement is measured: laser interferometer and grating interferometer.Laser interferometer take wavelength as benchmark, can obtain very high resolution, but is easily subject to the impact of the factor such as environment, light source due to wavelength, and its application is restricted.And grating interferometer just compensate for the shortcoming of laser interferometer, it is using screen periods as benchmark, and measurement result is not subject to the impact of environment and wavelength substantially, has been widely used in the fields such as machining tool, robot, biologic medical.But the precision of grating interferometer and resolution are also slightly poorer than laser interferometer, certain structures measuring error when grating alignment is not good is large.

In order to solve the problem, Chinese scholars has carried out large quantifier elimination, patent CN10293711A as people such as Tsing-Hua University Zhu Yu discloses a kind of dual-frequency grating interferometer system, the straight-line displacement of level and vertical both direction can be measured simultaneously, but this system is subject to the restriction of spot diameter and photelectric receiver area, this problem of solution that the Lin Jie of Harbin Institute of Technology etc. are artificial discloses patent CN10360077 and proposes a kind of diaxon grating interference instrument system using double-frequency laser, but this system can only realize twice optical fine, resolution is not high, and the measuring beam of this structure and reference beam are asymmetric light path in optical interference circuit parts, make when environment changes such as temperature, measuring beam and reference beam change in optical path length inconsistent, thus result is impacted.

Summary of the invention

In order to solve the problem, the object of this invention is to provide a kind of diaxon heterodyne grating interferometer of four times of optical fines, this instrument can measure the displacement of grating vector direction (horizontal direction) and grating normal (vertical direction) simultaneously, not only the displacement measurement range of in the vertical direction is increased considerably, and optical fine multiple reaches 4 times, while maintenance measurement result is stable, obtain high resolving power.

Technical solution of the present invention is as follows:

A kind of diaxon heterodyne grating interferometer of four times of optical fines, its feature is, comprise: two-frequency laser, 50% unpolarized light splitting piece, the first plane mirror, second plane mirror, first intervention module, the second intervention module, the first photelectric receiver, second photelectric receiver, grating scale and signal processing module.Described intervention module is the N10715A intervention module of Agilent company, comprise polarization splitting prism, first right-angle prism, second right-angle prism, the 3rd right-angle prism, the first quarter-wave plate, second quarter-wave plate, 3rd plane mirror, the 4th plane mirror, the 5th plane mirror.Comprise orthogonal two linearly polarized lights by the light beam of two-frequency laser outgoing, there is fixing frequency difference in two polarized lights, the light beam of laser emitting is first through 50% unpolarized light splitting piece.Unpolarized light splitting piece wherein light beam out impinges perpendicularly on the first intervention module through the first catoptron, the reflecting surface of the first catoptron and the angle of scale grating normal are the half of the Littrow angle of grating scale corresponding wavelength, the angle between the normal direction of light and grating scale is made to be the Littrow angle of grating scale, incide grating scale diffraction Hou Yuan road by the first intervention module the first measuring beam first time out with Littrow angle to return, being reflected by the first intervention module afterwards incides on grating scale with Littrow angle again, after former road returns, the first measuring beam is coupled to optical fiber together with the first reference beam reflected by intervention module, electric signal is converted into photelectric receiver through optical fiber light-guiding, the first signal is obtained by data processing module process.In like manner, the second intervention module is impinged perpendicularly on through the second catoptron by 50% light splitting piece another light beam out, angle between the normal direction of light and grating scale is the Littrow angle of grating scale, incide grating scale Hou Yuan road by the second intervention module the second measuring beam first time out with Littrow angle to return, second measuring beam and the first measuring beam are in the both sides of grating normal respectively, second measuring beam incides with Littrow angle on grating scale again through the second intervention module reflection again, after former road returns, the second measuring beam is coupled to optical fiber together with the second reference beam reflected by the second intervention module, electric signal is converted into photelectric receiver through optical fiber light-guiding, secondary signal is obtained by data processing module process.The displacement on grating level and vertical direction can be obtained according to the first signal and secondary signal demodulation.

Especially, the first measuring beam and the second measuring beam are not only applicable to the situation of Littrow angle incidence, are equally applicable to the situation of m rank Bragg angle incidence, and m rank Bragg angle can be drawn by following formula:

$\mathrm{\θ}=asin\left(\frac{m\mathrm{\λ}}{2d}\right)$

In formula, λ is optical maser wavelength, and d is screen periods.M is positive integer, and m is larger, and the optical fine multiple of grating interference instrument system is larger.

Technique effect of the present invention:

The present invention can measure the displacement on grating horizontal direction and vertical direction simultaneously, make measuring beam through scale optical grating diffraction twice by using intervention module, first measuring beam and the second measuring beam combine the optical fine that can realize four times, improve the resolution of grating interferometer when screen periods is identical with electronic fine-grained multiple.This light path measuring beam and reference beam footpath altogether before intervention module simultaneously, in intervention module, measuring beam and reference beam are symmetrically distributed, the impact caused measuring beam and reference beam during temperature variation in intervention module is the same, improves the stability of system and the reliability of measurement result.Through experiment test, move in the horizontal direction of speed to be 10mm/s range be 8mm, error is ± 80nm, and in 23 seconds, grating interferometer drift is 7nm, and laser interferometer drift is 14nm.

Accompanying drawing explanation

Fig. 1 is the diaxon heterodyne grating interferometer of four times of optical fines

Fig. 2 is the light channel structure schematic diagram of intervention module

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the invention is described in further detail.

A kind of diaxon heterodyne grating interferometer of four times of optical fines as shown in Figure 1, comprise: two-frequency laser 1,50% light splitting piece 4, first plane mirror 6, second plane mirror 7, first intervention module 14, second intervention module 15, first photelectric receiver 19, second photelectric receiver 18, grating scale 10, signal processing module 20 and high-accuracy mobile platform 11.Comprise orthogonal two linearly polarized lights by the light beam of two-frequency laser 1 outgoing, there is fixing frequency difference in two polarized lights, is first divided into folded light beam and transmitted light beam through 50% unpolarized light splitting piece 4 by the light beam of two-frequency laser 1 outgoing.Described folded light beam vertically incides the first intervention module 14 after the first catoptron 6 reflects, angle between the normal direction of light and grating scale 10 is the Littrow angle of grating scale, incide grating scale 10 diffraction Hou Yuan road by the first intervention module 14 the first measuring beam first time out with Littrow angle to return, being reflected by the first intervention module 14 afterwards incides on grating scale 10 with Littrow angle again, after former road returns, the first measuring beam is coupled to optical fiber together with the first reference beam reflected by intervention module 14, electric signal is converted into the electric receiver 19 of light first through optical fiber light-guiding, processed by data processing module 20 and obtain the first signal.In like manner, the second intervention module 15 is impinged perpendicularly on through the second catoptron 7 by 50% light splitting piece 4 another light beam out, angle between the normal direction of light and grating scale 10 is the Littrow angle of grating scale, incide grating scale 10 Hou Yuan road by the second intervention module 15 the second measuring beam first time out with Littrow angle to return, second measuring beam and the first measuring beam are respectively in the both sides of grating normal, second measuring beam reflects through the second intervention module 15 and again incides with Littrow angle on grating scale 10, after former road returns, the second measuring beam is coupled to optical fiber together with the second reference beam reflected by the second intervention module 15, turn 18 through optical fiber light-guiding to the second photelectric receiver and turn to electric signal, processed by data processing module 20 and obtain secondary signal.The displacement on grating level and vertical direction can be obtained according to the first signal and secondary signal demodulation.

Described intervention module be the N10715A intervention module of Agilent company as shown in Figure 2, comprise polarization splitting prism 31, first right-angle prism 32, second right-angle prism 35, the 3rd right-angle prism 33, first quarter-wave plate 36, second quarter-wave plate 34, the 3rd plane mirror 37, the 4th plane mirror 38 and the 5th plane mirror 39.The light beam impinging perpendicularly on intervention module is divided into p light and s light through polarization splitting prism 31, the s light being polarized Amici prism 31 reflection is reference light, successively through the first right-angle prism 32, polarization spectroscope 31, 3rd plane mirror 37, first quarter-wave plate 36, second right-angle prism 35, first quarter-wave plate 36, 3rd plane mirror 37, polarization splitting prism 31, second quarter-wave plate 34, 4th plane mirror 38, second quarter-wave plate 34, polarization splitting prism 31, 3rd right-angle prism 33, polarization splitting prism 31, second quarter-wave plate 34, 5th plane mirror 39, second quarter-wave plate 34, polarization splitting prism 31, be parallel to incident light but depart from certain distance and export, p light through polarization splitting prism 31 transmission is measurement light, successively through the second quarter-wave plate 34, grating scale 10, second quarter-wave plate 34, polarization splitting prism 31, 3rd right-angle prism 33, polarization splitting prism 31, second quarter-wave plate 34, grating scale 10, second quarter-wave plate 34, polarization splitting prism 31, 3rd plane mirror 37, first quarter-wave plate 36, second right-angle prism 35, first quarter-wave plate 36, 3rd plane mirror 37, polarization splitting prism 31, first right-angle prism 32, polarization splitting prism 31, output coaxial with reference light, be coupled to optical fiber together, be transmitted to photelectric receiver.

In embodiment, grating scale 10 adopts reflective high-diffraction efficiency grating, cycle is 561.8nm, through four times of optical fines and 1024 times electronic fine-grained, the theoretical resolution of grating interferometer is 0.137nm, higher than the theoretical resolution 0.154nm of the corresponding product of Agilent company.

Claims (3)

1. a diaxon heterodyne grating interferometer for four times of optical fines, is characterized in that comprising: two-frequency laser (1), 50% unpolarized light splitting piece (4), the first plane mirror (6), the second plane mirror (7), the first intervention module (14), the second intervention module (15), the first photelectric receiver (19), the second photelectric receiver (18), grating scale (10), signal processing module (20) and high-accuracy mobile platform (11);

First the light beam of described two-frequency laser (1) outgoing is divided into folded light beam and transmitted light beam through described 50% unpolarized light splitting piece (4), described folded light beam vertically incides the first intervention module (14) after the first plane mirror (6) reflection, the incident angle of the light beam exported from the first intervention module (14) and grating scale (10) is the Littrow angle of grating scale, incide grating scale (10) diffraction Hou Yuan road by the first intervention module (14) the first measuring beam first time out with Littrow angle to return, being reflected by the first intervention module (14) afterwards incides on grating scale (10) with Littrow angle again, after former road returns, the first measuring beam is coupled and receives through optical fiber light-guiding to the first photelectric receiver (19) and be converted into electric signal together with the first reference beam reflected by the first intervention module (14), processed by data processing module (20) and obtain the first signal, in like manner, after the second plane mirror (7) reflects, the second intervention module (15) is vertically incided by described transmitted light beam, angle between the normal direction of light and described grating scale (10) is the Littrow angle of grating scale, incide grating scale (10) Hou Yuanlu by the second intervention module (15) the second measuring beam first time out with Littrow angle to return, second measuring beam and the first measuring beam are respectively in the both sides of grating normal, second measuring beam incides with Littrow angle on grating scale (10) again through the second intervention module (15) reflection again, after former road returns, second measuring beam is coupled through optical fiber light-guiding together with the second reference beam reflected by the second intervention module (15), turn (18) through the second photelectric receiver receive and be converted into electric signal, processed by data processing module 20 and obtain secondary signal, according to the first signal and secondary signal demodulation, obtain the displacement on grating level and vertical direction.

2. the diaxon heterodyne grating interferometer of four times of optical fines according to claim 1, angle between the normal that it is characterized in that the first described measuring beam and the second measuring beam and described grating scale (10), namely incident angle is Littrow angle or m rank Bragg angle, and m rank Bragg angle is stated by following formula:

$\mathrm{\θ}=asin\left(\frac{m\mathrm{\λ}}{2d}\right)$

In formula, λ is optical maser wavelength, and d is screen periods, and m is larger, and the optical fine multiple of grating interference instrument system is larger.

3. the diaxon heterodyne grating interferometer of four times of optical fines according to claim 1, is characterized in that the first described intervention module and the second intervention module are the N10715A intervention module of Agilent company.