SU1211604A1 - Arrangement for measuring object displacements - Google Patents

Abstract

The invention relates to measurement technology and can be used for precision measurements of the sizes of balls, cube cylinders and other bodies of regular geometric shape. The aim of the invention is to provide measurement of the size of objects by measuring the distance between reflectors of any shape. The device contains measuring and auxiliary lasers with common mirrors, two photodetectors, two frequency meters, each of which is associated with a corresponding photodetector, an auto-tuning system and a piezocorrector connected to it, mounted on one of the mirrors, an additional laser measured, the distance between the object of measurement and a mirror coaxial with the first laser, the second piezo-corrector, placed on the second mirror, and a switch installed between the auto-tuning system and the piezo correctors. The device allows recording the change in the distance between the reflectors of various geometric shapes as a change in the difference in the beat frequencies of the measurement and auxiliary lasers 1 sludge. Ф S

Description

The invention relates to a measurement technique and can be used for precision measurements of the sizes of balls, cylinders, cubes and other bodies of regular geometric shape used as reference samples when creating density units based on solids.

The aim of the invention is to provide measurement of the dimensions of objects by measuring the distance between reflectors of any shape.

The drawing shows a diagram of the device.

The device contains reflectors 1 and 2, which form the auxiliary laser resonator with the active element 3. The auxiliary laser is optically coupled through the mirror 4 to a photo receiver 5 connected to the automatic frequency control system 6 (AFC | auxiliary laser electrically connected via a switch 7 with piezocorrectors 8 and 9 placed on reflectors 1 and 2. The active element 10 forms with reflector 1 and a reflecting element mounted on the surface of the object to be measured 11 (or the reflecting surface of the volume kta 11), the first measuring laser. The active element 12 forms a second measuring laser with the reflector 2 and the surface of the measured object 1. Both measuring lasers are optically coupled to the auxiliary laser and photodetectors 16 and 17 through mirrors 4, 13, 14 and 15, connected to frequency counters 1-8 and 19.

The device works as follows.

Initially, the value of the do parameter — the diameter of the object to be measured 11 in its initial position is determined. To do this, use the scanning mode of reflectors 1 and 2, carried out when an object to be measured between sneMBHTaMii 10 and 12 is measured using the piezocorrectors 8 and 9 connected alternately via switch 7 to the AFC system 6 of the auxiliary laser, which generates a control signal for scanning. In this case, the bases of the auxiliary (bo) and measuring (L. | and Lj.) Lasers are determined by the formulas

WITH

7 liters

L. - „Ь, L ,, where with

L) oh th. ye ch

C 2 & C

C (1)

2 speed of light;

intermode spacing for auxiliary and measurement lasers, respectively.

The relative measurement error of the intermode intervals when using serial devices is in the order of 10 - 10.

After measuring the intermode intervals, the feedback circuit of the AFC 6 auxiliary laser closes, maintaining the base of its resonator unchanged with a relative error of about 1-10 (which can be done by the LPC system or the external absorbing cell, as in industrial LH lasers -77 and LG-149). From the measured values of the bases of the auxiliary resonators and measuring lasers, do is determined from the ratio

 LO - L - L

(2)

The dp of determining the true configuration of the object 11 is performed by measuring its dimensions in several sections, the number of which depends on the degree of deviation of the shape of the object 11 under study from the correct geometrical one. After this measurement, do the frequencies of the beats fof and foj of the measuring and auxiliary lasers measured by optical heterodyning systems consisting of mirrors 4, 13, 14, and 15 and the photodetectors 16 and 17 are measured. The frequencies of the beats are recorded with frequency meters 18 and 19, they are equal:

fo, f -fo; fo2 2 O,

where f 1 f jL is the generation frequency of the measuring lasers in the initial position of the object 11; fo is the frequency of generation.

auxiliary laser.

After that, the object I1 is smoothly transferred to a new position in which the generation frequencies of the measuring lasers change in accordance with the change in the bases of the resonators of the measuring lasers, caused by the change in the size of the measured object

m 11. These new values of frequencies will be denoted by f and f Ij, and the frequencies of the institutes biv will be f ;, f fo H-fj, f f,,. The beat frequencies are measured again.

The desired size dj of the new section of the object 11 of measurements is found as the algebraic sum of the previously found value dg and its change Ado, determined from the expression

D (1 „

foi-

2DL

foi - foz

 02

0

The error of the moving mechanism of the object 11 is not included in the measurement error, because it leads to opposite changes in the generation frequencies of the measuring lasers, which are fully compensated for.

The measurement procedure is repeated for all necessary sections of the measured object 11.

The following estimate of the requirements for the stability of the laser frequency as a function of the required measurement error follows from the relation C3):

.)one..

do

or

 "about

(four)

where (S -f is the relative instability of the laser frequency during a single measurement cycle. Using the ratios known from probability theory, one can estimate the required stability of the laser for a series of measurements:

 ,,

,

)

ten

15

25

thirty

35

40

{,AT 5

where n is the number of measurements in the series;

6 - standard deviation of the measured value,

Given the value of the average quadratic deviation; do 0.1 m; 0.5 m, we obtain for -h 25 an estimate of the relative frequency instability of the laser B – H, which can be realized by a frequency auto-tuning system, bp of the measured value ud for a series of measurements h. At some position of the object 11, Hsj HpiaJKeiujH is determined:

1 (d; -l-3)

vp-d

I-1

, (61

20

Claims (1)

where ud is the average value in the series. Invention Formula A device for measuring the movement of objects, containing a measuring and auxiliary lasers with two common reflectors, two photoelectric receivers, two frequency meters, each of which is associated with a corresponding photodetector, an automatic tuning system, and a piezocorrector mounted on it from reflectors, characterized in that, in order to provide measurement of the sizes of objects, it is equipped with an additional measuring laser, designed to be installed between the object of measurement and one of the reflectors coaxially A second laser, a second piezocorrector mounted on another reflector, and a switch connected between the self-tuning system and piezocorrectors.