CN101135575A - Direct counting type cascade spacing changing single-grating light displacement sensor with double mirror - Google Patents

Abstract

The invention is used for solving the issue that is there is a certain angular error when the reflector of optical displacement transducer with link connection moves on guiding rail. The improvement from the invention is: two reflectors are used and respectively located at the both sides of the L-shape sliding block; the included angle range of the two reflectors is 50-70 degree.

Description

Direct census formula with double mirror becomes pitch monochromatic light grid Optical displacement sensor

Technical field

The present invention relates to a kind of absolute type displacement transducer field of anti-electromagnetic interference (EMI), be specifically related to the Optical displacement sensor that a kind of direct census formula becomes pitch monochromatic light grid structure.

Background technology

At the end of last century, at first propose several light by western developed countries such as the U.S. and pass the advanced parts project of system, some major companies become the contractor of research project, developed the optical displacement sensor of several different principle respectively, some is verified in the laboratory, and some has passed through experiment in flight test.Domestic a lot of unit has also carried out the research of this respect, and wherein the Optical displacement sensor of direct census formula change pitch monochromatic light grid structure has passed through the experiment of principle prototype.The sensor of this principle also can be used in the stronger location of electromagnetic field in the commercial production, replaces existing electromagnetic type displacement transducer, and very wide application prospect is arranged.

But in the structure of this sensor, the catoptron that is connected with the connecting rod of sensor has certain angular error when mobile on guide rail, disclosed document ([1] W.B.Spillman Jr, R.D.Laclair, R.E.Rudd, F.G.Hoff.Wavelength encoding long stroke fiber optic linear position sensor for actuatorcontrol applications.Fly-by-Light Technology Transfer Proceedings ofSPIE, 1995,2467:187-194; [2] R.D.laclair, W.B.Spillman Jr, W.W.Kuhns.Longstroke optical fiber linear position sensor for the FLASH program.Fly-by-LightTechnology Transfer Proceedings ofSPIE, 1996, not mentioning this problem 2840:137-141) solves, and the raising of just guide precision being made great efforts, this has just increased the manufacture difficulty and the cost of sensor.

Original working sensor principle is: (two optical fiber one ends are packaged together the light of wideband light source 1 by y-type optical fiber, the other end separates separately) in an optical fiber pass to collimating optical system 7, become the directional light that a certain size is arranged, incide on the grid pitch changing grating 1 by simple reflector, because moving of coupling shaft 10, make light incide positions different on the grid pitch changing grating, y-type optical fiber is got back to the light autocollimation that a wavelength should be arranged in each position, deliver in the fiber spectrometer 3 by an other optical fiber, obtain the light wavelength that autocollimation is returned, by calculating corresponding displacement.

The size of pitch grating glazing grid cycle d and the relation of simple reflector displacement x:

d(x)＝f(x) (1)

F (x) is the polynomial expression of x, can be calculated by the periodic quantity of grating deserved displacement x by this relational expression;

Wideband light source is got back to spectrometer by the grid pitch changing grating autocollimation light wavelength and incident illumination are mapped to the relational expression in corresponding cycle on the position on the grating:

d(x)*2sinθ＝λ(x) (2)

Can obtain spectral wavelength λ (x) that should the position by fiber spectrometer 3, can obtain the cycle of the grid pitch changing grating of this position by (2) formula, solve displacement with simple reflector by (1) formula again, thereby obtain the testee displacement that sensor connects by coupling shaft 10.

The design problem that existing apparatus exists is: because present simple reflector is contained on the slide block 8, when guide rail has the angle pitching owing to precision problem own, can cause the variation of θ in (2) formula, thereby make spectrum cause variation, cause the displacement x generation error of final calculating, and displacement remains unchanged in the reality.

Make a concrete analysis of as follows: referring to Fig. 2, simple reflector 11 is contained on the slide block 8, when slide block is mobile on guide rail 9, because guide rail self error, can cause that catoptron 11 has an angular error Δ α around the Z axle, behind catoptron, causing the angular error that incides the incident ray on the grating is Δ θ=2 Δ α, by formula (2) as can be known, d (x) * 2sin (θ+Δ θ)=λ (x)+Δ λ, cause the deviation delta λ of the actual spectrum that obtains by spectrometer 3, and actual calculation is calculated by (2) formula, d (x)+Δ d=(λ (x)+Δ λ)/(2sin θ), and there is deviation in the cycle of the cycle of the grating that solves with reality, calculate corresponding displacement by (1) formula again, be subjected to displacement error.

Summary of the invention

At problems of the prior art, the invention provides a kind of direct census formula with double mirror that incident angle of light can be kept constant, solve the guide precision problem and become pitch monochromatic light grid Optical displacement sensor.

Concrete architecture advances scheme is as follows:

Direct census formula with double mirror becomes pitch monochromatic light grid Optical displacement sensor, comprise sensor outer housing, collimating optical system, collimating optical system one side correspondence the catoptron on the slide block, slide block is the L type, one outer side edges cooperates with guide rail, another outer side edges is connecting coupling shaft, and the below correspondence of catoptron grid pitch changing grating; Collimating optical system opposite side correspondence y-type optical fiber, and the y-type optical fiber other end is connecting wideband light source, digital spectrometer, data acquisition process control system respectively;

Described catoptron is two, is located at the inboard both sides of L type slide block respectively, and the angle α scope of two catoptrons is 50～70 °;

Incident angle θ scope between catoptron and the grid pitch changing grating is 10～50 °.

The angle α of described two catoptrons is 56.8 °, and the incident angle θ between catoptron and the grid pitch changing grating is 23.6 °.

The present invention adopts two catoptrons, make in moving process, as long as it is constant from the angle of the radiation direction of collimating optical system 7 outgoing and grating, no matter in slide block 8 moving process, have great angle to beat, promptly when slide block on guide rail in the moving process when the Z axle has angles shifts, the double mirror structure can keep incident angle θ constant, can not cause the incident angle of light to change.This architecture advances has improved the sensor overall precision, has reduced the requirement to the guide rail machining precision.

Referring to Fig. 3, when the light that comes out from collimating optical system is parallel with grid pitch changing grating, the angle of two-face mirror and incide relational expression between the angle on the grid pitch changing grating (VLS grating):

$\mathrm{\α}=\frac{\mathrm{\π}}{4}+\frac{\mathrm{\θ}}{2}---\left(3\right)$

(3) the concrete derivation of formula is as follows:

By leg-of-mutton relation, can obtain relational expression θ ₁+ θ ₂=α, the relation that equals reflection angle by incident angle as can be known, β=π-2 (θ ₁+ θ ₂), owing to be parallel to the grating substrate from the emergent ray of colimated light system, $\mathrm{\θ}=\frac{\mathrm{\π}}{2}-\mathrm{\β},$ Can obtain relational expression (3) thus.

Can find out from the angle of two catoptrons and the relation of incident angle, because collimating optical system and grid pitch changing grating fix, so the incident light of outgoing spectrum broad can concern by keeping parallelism with grating in the colimated light system always; And two catoptrons are fixed on the slide block, so the angle between two catoptrons can not change yet, and the relation that incides between the angle α of the incident angle θ of grating and two catoptrons is determined by (3) formula.When the guide rail top shoe when the Z axle has angle to change, cause that two catoptron integral body have identical angle to change around the Z axle, but incident angle θ can not change, thereby can not have influence on the variation of spectrum.

Description of drawings

Fig. 1 is a structural representation of the present invention,

Fig. 2 is simple reflector principle analysis figure,

Fig. 3 is double mirror principle analysis figure.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described by embodiment.

Embodiment:

Referring to Fig. 1, the direct census formula with double mirror becomes pitch monochromatic light grid Optical displacement sensor and comprises sensor outer housing 6, collimating optical system 7; Collimating optical system 7 one side correspondences the catoptron on the slide block 8, and slide block 8 is the L type, and an outer side edges cooperates with guide rail 9, and another outer side edges is connecting coupling shaft 10, and the below correspondence of catoptron grid pitch changing grating 1; Collimating optical system 7 opposite side correspondences y-type optical fiber 5, and y-type optical fiber 5 other ends are connecting wideband light source 4, digital spectrometer 3, data acquisition process control system 2 respectively;

Catoptron is two, i.e. horizontal reflection mirror 12 and minor face catoptron 11, horizontal reflection mirror 12 be located on the L type slide block, the inner side edge parallel with guide rail, and minor face catoptron 11 is located at another inner side edge of L type slide block, and the angle α scope between two catoptrons is 56.8 °; The spectrum of light source is generally 600-1000nm, so adjustable angular range is 50～70 °; Become spacing grating 1 center line density and be 1000line/mm, the incident angle θ scope between two catoptrons and the grid pitch changing grating 1 is 23.6 °, and adjustable angular range is 10～50 °.

Claims (2)

1. the direct census formula that has double mirror becomes pitch monochromatic light grid Optical displacement sensor, comprise sensor outer housing, collimating optical system, collimating optical system one side correspondence the catoptron on the slide block, slide block is the L type, one outer side edges cooperates with guide rail, another outer side edges is connecting coupling shaft, and the below correspondence of catoptron grid pitch changing grating; Collimating optical system opposite side correspondence y-type optical fiber, and the y-type optical fiber other end is connecting wideband light source, digital spectrometer, data acquisition process control system respectively, it is characterized in that:

Described catoptron is two, is located at the inboard both sides of L type slide block respectively, and the angle α scope of two catoptrons is 50～70 °;

Incident angle θ scope between catoptron and the grid pitch changing grating is 10～50 °.

2. the direct census formula with double mirror according to claim 1 becomes pitch monochromatic light grid Optical displacement sensor, and it is characterized in that: the angle α of described two catoptrons is 56.8 °, and the incident angle θ between catoptron and the grid pitch changing grating is 23.6 °.

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