SU1610252A1 - Method of measuring spatial displacements of object - Google Patents

Abstract

The invention relates to a measurement technique and can be used to control the accuracy of movement of objects. The aim of the invention is to improve the measurement accuracy by eliminating the influence of the accuracy of the beam on the measurement line on the error. For this, coherent radiation is divided into two streams — the reference and measurement, and before reflection from the object from the measurement flux, three beams are formed, the periodic structure is illuminated by the flows, moving in two mutually perpendicular planes, the interference pattern is obtained from the diffracted radiation, converted into electrical the signal and its parameters determine the movement of the object. 2 Il.

Description

The invention relates to a measurement technique, in particular, to laser interferometry, and can be used to control the accuracy of linear displacements of objects, for example, the working bodies of machine tools and measuring instruments.

The purpose of the invention is to improve the measurement accuracy by eliminating the influence of the accuracy of beam positioning along the measurement line on the error.

Figure 1 shows the beam propagation scheme; Fig. 2 is a diagram of an apparatus for implementing the proposed method for measuring the spatial movements of an object.

The device contains a periodic structure 1, created by radiators 2 and 3, photovoltaic cells 4-6, laser 7, collimator 8, beam splitter 9, shaper 10 three beams, reflectors 11 and 12. double optical wedge 13, diaphragm 14. elect (L

with

Ron oscillators 15 and 16, light-modulator 17, optical system 18, narrow-band amplifiers 19-21, phase-measuring blocks 22-24. Reference numeral 25 denotes an object whose displacement is measured.

The method is carried out as follows.

The radiation of the laser 7 through the collimator 8 is directed to the beam splitter 9 of the Michelson interferometer, where it is divided into two light beams of the EI and EO measuring and reference channels. The EI radiation of the measuring channel passes through the imaging unit 10, where it is divided into three luminous fluxes E1, E2, E3, which are directed to the measuring corner reflector 11 mounted on the object 25. Reflected from the measuring 11 and reference 12 corner reflectors the light emitted by EI and EO spatially aligned on the beam splitter 9 at an angle a.

oh oh

1GO SP

Yu

defined by the dual optical wedge 13 of the reference light wave, and directed through the restrictive stop 14 to the light modulator 17, in which radiators 2 and 3 create a moving structure with periodic structure 1 in the form of two ultrasonic waves moving mutually perpendicular. One of these streams (Е1) forms with two other (Е2 and ЕЗ) equal angles in two mutually perpendicular planes, providing spatial alignment of the diffraction orders of the output spectra of Е1, Е2 and. E1, E3, the algebraic difference of the frequencies of which is proportional to the frequency of excitation of the periodic structure in axes X and Y, respectively. In this scheme, the proportionality coefficient is equal to 1. The interfering orders of the diffraction spectra of E3 (0), E1 (-1) and E2 {0), E1 (+1) are directed to the photoconverters 4 and 5, which separate the electrical measuring signals U3 and U2. The EO radiation of the reference channel is directed to a periodic structure T at an angle a to the radiation of the measuring channel in one of these planes, and the interfering orders of the diffraction spectra of the reference and measuring channels E0 (0) and E 1 (-1) are directed to a phototransducer 6, which separates the electrical measuring signal U1.

The signals from, U2, U1, through narrowband amplifiers 19-21, tuned to fi-fa frequencies, are fed to the inputs of the phase-measuring blocks 22-24. The second inputs of blocks 22 and 23 receive signals from electronic generators 15 and 16 as reference signals, setting the excitation frequency of periodic structure 1 in directions Y and X, respectively. As a reference signal to the second input of the phase meter unit 24, the signal U2 is supplied.

As a result of the interference (optical heterodyning) of different-frequency light waves, electrical signals appear at the outputs of the corresponding photodetectors, the phase change of which is proportional to the change in a certain

Z, X, Y coordinates. To measure the coordinate, the phase of the electrical signal U1 can be measured using the reference signal U2. U1 signal phase change

multiplied by the value of I / lg get the corresponding change in the coordinate D2, the phase Change of the signals U2 and U3 is measured relative to the electrical signals of electronic generators with frequencies f2 and f i,

multiply this change, respectively, by the value of Lx / 2 and Lu / 2 l :, where Lx and Lu are the length of the acoustic waves in the X and Y directions, and the movements along the X and Y coordinates are determined. Thus,

make independent measurements of the movement of an object in space along the three axes X, Y, Z.

Claims (1)

. Invention Formula A method for measuring spatial the object's movements, namely, that coherent radiation is divided into measuring and reference flows, after reflecting the measuring flux from the object, create in a transparent medium a periodic structure moving in two mutually perpendicular planes, illuminate the medium with radiation fluxes at an angle chosen from the condition multipole diffraction from each radiation flux, convert the interfering orders of the diffracted streams into an electrical signal and determine by its parameters the movement of the object, about which, in order to improve accuracy, three light beams are formed from the measuring flux, so that one of the beams forms equal angles with two others in two mutually perpendicular planes, the magnitude of which ensures the spatial alignment of the diffraction orders of these beams on the periodic structure, so that the algebraic difference of frequencies combined in one of the directions of motion periodic structure, proportional to the frequency of excitation of the periodic structure in this direction. /. No UT, f2 , /; W, 2 FIG. 2 FIG. J j