SU1631271A1 - Method of checking transparent optical parts - Google Patents

Description

one

(21) 4479570/28

(22) 06.30.88

(46) 02.28.91. Bul № 8

(72) L.I.Dadenko, Yu.B.Pasko,

V.K. Rezunkov and V.P. Tetera

(53) 537.7 (088.8)

(56) USSR Author's Certificate No. 1456776, cl. G 01 B 11/24, 1987.

(54) METHOD FOR CONTROL OF TRANSPARENT OPTICAL PARTS

(57) The invention relates to a measurement technique. The aim of the invention is to improve the accuracy of monitoring the parameters of transparent optical parts by pre-setting the acousto-optic cell to the Bragg diffraction mode and measuring the parameters of the parts while increasing the signal-to-noise ratio of the informative signal. Before installing the monitored part, the acousto-optic cell is tuned to the Bragg diffraction mode and the frequency f0 of acoustic oscillations is recorded. After the part is installed, the frequencies of acoustic oscillations f, f corresponding to Bragg diffraction modes for two informative beams from the part being monitored are recorded. The frequencies ft, fg are used in determining the radii of curvature, and the frequency Ј0 and the diameter of the part being monitored are used in determining the wedge shape. 2 yut.

a ss

(L

The invention relates to a measurement technique and can be used to measure a wide range of curvature of surfaces and a wedge shape of transparent optical parts.

The aim of the invention is to improve the accuracy of monitoring the parameters of transparent optical parts by pre-setting the acousto-optic cell to the Bragg diffraction mode and measuring the parameters of the parts at an increased signal-to-noise ratio of the informative signal.

FIG. Figure 1 shows the general case of the path of refracted rays in a transparent, controlled part with a wedge shape; in fig. 2 is a diagram of a device for monitoring transparent optical parts implementing the proposed method.

The device (see Fig. 2) contains a source of monochromatic radiation and a monitored piece 2 arranged sequentially in the direction of the radiation, an acousto-optic cell 3 located along the propagation path of the radiation transmitted through the monitored piece 2. Further, in the direction of the diffracted beam, a focusing lens 4 and a photodetector 5 are located for recording the signal. In addition, the circuit contains a tunable frequency generator of 6 electrical signals.

O5

with y

316

The acousto-optic cell 3 is an optically active element made, for example, of a paratellurite single crystal of a certain orientation with a piezoelectric transducer for a given frequency range. At the same time, the output of an electric signal tunable in frequency 6 is connected to an acousto-optic cell 3.

The device works as follows.

The acousto-optic cell 3, for example, in the case of wedge type control, is set so that the direction of monochromatic radiation is normal to the direction of propagation of acoustic oscillations, the Bragg angle is measured by the corresponding angle 90 of the frequency of acoustic oscillations f, according to

D.- fi ° | - 2V

(one)

where V is the speed of sound propagation in the acousto-optic cell; Ol is the monochromatic wavelength.

whom radiation;

f is the frequency of acoustic oscillations;

S) - Bragg angle.

Then, between the radiation source 1 and the acousto-optic cell 3, a controlled transparent part 2 is installed and guided to two parts of its surface, one of which is necessarily located on the edge of the part, monochromatic radiation, the direction of which can be considered parallel to the optical axis.

In this case, at the angles of incidence on the part 2 of monochromatic beams (X; (see Fig. 1), the angles of refraction at the exit of the part are determined by the expressions

Ы "tf; (n-i) -ny ± е„, (2)

where n is the refractive index of the controlled part. The sign of the ntf term in Eq. (2) depends on the ratio of the angles of incidence of the radiation beam onto the wedge-shaped face and the angle of the wedge shape. For this case, the angle of incidence of the beam (X on the face with the wedge shape J is greater than the wedge shape. For the opposite

Q

Q

five

five

g

Q

one

But the ratio of the angles of,, -, / and the first and second members of the right-hand side of equation (2) is reversed. The sign of the angle QQ is assumed to be positive if its direction coincides with the sign of the angle of exit of the radiation passing through the test piece 2 (Y.

After aligning the acousto-optic cell 3 with respect to the incident radiation and installing the optical part 2 between the monochromatic radiation source and the acousto-optic cell 3, the frequency of the acoustic oscillations supplied to the opto-optical cell 3 is changed by the generator 6 until the Bragg diffraction mode transmitted through the detail of the acousto-optic array is reached cells 3. At the same time, the radiation beam 1 emitted from part 2 forms, with the normal to the direction of propagation of acoustic oscillations in cell 3, the Bragg angle b | with the frequency of acoustic oscillations f j.

Then equation (2) will be

0, 00 | i (n - 1) - njf, (3)

where X is the distance from beam axis 1

to the optical axis.

For convenience of calculations, choose the value of X (close to half the diameter of the part D:

X

D 2

(four)

The diameter of the part 2 is measured and the monochromatic radiation at the edge of the part is directed to the distance X from the optical axis. The Bragg angle in this case is УЈ and the frequency of acoustic oscillations is f%.

The radius of curvature of the part being monitored is calculated by the formula

R 2yd (n-1.)

(five)

fl (ft-fe)

where d is the distance between the axes of the beams

incident radiation. The wedge shape of part 2 is determined by the formula

X-4-G4 O 2nV L1

 Of

Jlfl

1 2d 2J

(6)

In the proposed method, the direction parallel to the co51 is allowed.

fight of beams on the controlled part at an angle to the optical axis of the part. The expression for R and J does not change, only d is multiplied by 1 / cosft, where () is the angle between the direction of the beams and the optical axis.

Direction to the controlled part of the beams at an angle to each other is also allowed. However, in this case the expressions for R and Y are much more complicated.

In the proposed method of monitoring transparent optical parts, the accuracy of measuring the radius of curvature and wedge shape of optical parts is improved compared to traditional methods, since the accuracy of determining the parameters is determined by the accuracy of determining the frequency of acoustic oscillations while ensuring an increase in the signal-to-noise ratio of the informative signal.

Claims (1)

Invention Formula The method of control of transparent optical parts, consisting in 0 2716 two monochromatic radiation beams per monitored part and the subsequent direction of the received information beams to the acoustic cell, forming Bragg diffraction modes for each of the monochromatic radiation beams and determining the radii of curvature and wedge shape of the optical part from the distance between the centers of the beams from the monitored part and value frequencies of fj, f "acoustic oscillations corresponding to the Bragg diffraction mode for each of the beams, which are different That, in order to increase the measurement accuracy, prior to installation of the component to the acoustooptic In the cell, the Bragg diffraction mode is formed with respect to the incident radiation and the frequency f, acoustic oscillations are fixed, one of the sections is selected at the edge of the part, and the part wedge shape is determined using the part diameter and frequency частоты. Phage. one FIG. 2