SU872959A1 - Touch-free photometric method of measuring transparent sample roughness height - Google Patents

Description

(54) CONTACTLESS PHOTOMETRIC METHOD

MEASUREMENTS OF SURFACE ROUGHNESS HEIGHT The invention relates to a control measurement technique and can be used, in particular, to control the surface quality, determine the roughness height, select pa- rial technological processes for creating polished surfaces in various industries. A known method for measuring the surface roughness height of transparent samples. The test surface is precoated with a thin highly reflective aluminum or silver layer reproducing its microrelief, and then the chromatic order l method is used. The disadvantage of the known method is that when measuring. The degree of reproducibility of the microrelief of the indicated layer always remains unclear, since the thickness of this layer may be an order of magnitude greater than the height of the surface roughness. TRANSPARENT SAMPLES The closest technical solution to the invention is a non-contact photometric method for measuring the surface roughness height of transparent and opaque samples, consisting of sending a monochromatic radiation flux at an angle relative to its normal to the sample surface not exceeding 10 and determining the signals from diffuse and nojmoro flows reflected from the sample surface. The roughness height is judged by the formula r-l-il where X is the wavelength of the monochromatic radiation flux; ZG 3.1416 - known constant; lvtt -nOAH "signals from diffuse and full fluxes reflected from the measured surface;

Lying rms height

roughness.

When measuring transparent samples using this method, the surface to be measured is precoated with a thin layer (but not transparent) of aluminum or silver, reproducing its microrelief

However, the known method is characterized by insufficient accuracy of the .314 and complexity of the measurement process, since the operation of applying this layer on the surface being measured is very laborious. In addition, the operation reduces the accuracy of the measurement T The mean square roughness height of the sample surface to be measured; the wavelength of the monochromatic radiation flux is known constant; the refractive index of the sample material for this wavelength; The specular reflection coefficients of the measured and opposite surfaces of the sample are determined, for example, by the Fresnel formulas, in the initial position of the sample; J is the transmittance of the measured surface and the thickness of the sample in its initial position; T. Tzff, l Signals from diffuse and total fluxes reflected from surfaces in its initial position are the specular reflection coefficients of the sample being measured and opposite to the measured surfaces of the sample, determined, for example, by the Fresnel formulas with the sample turned upside down; T is the transmittance of the opposite measured surface and thickness

Research institutes due to the distortions introduced by the layer pd) and reproduction of the microrelief, and in a number of cases make the samples unsuitable for use.

The aim of the invention is to improve the accuracy and simplify the measurement process.

The goal is achieved by the fact that, after determining the signals, the sample is inverted so that the radiation flux falls on the opposite surface of the sample, the signals from the diffuse and full fluxes reflected from the sample surfaces are determined, and the roughness height is judged by inverting it. position; signals from diffuse and full fluxes reflected from surfaces when the sample is turned upside down. The drawing shows a schematic diagram of the installation for the implementation of the proposed method. The installation contains radiation sources 1 (laser), a screen 2, radiation traps 3 and 4, a photometric ball 5 in which holes 6–9 are made, a photodetector 10 and a sample 1 with a measured surface 12 and a surface 13 that restricts it and is opposite to the measured one . The proposed method is carried out as follows. The monochromatic beam of radiation from the radiation source 1 falls through the holes 8 and 9 of the photometric container 5 onto the measured surface 12 of sample II at an angle of 5-10 to its normal. The radiation passing through 11 is trapped by trap 4, and the flow reflected by sample 11 enters the photometric ball 5 where it integrates and creates on the receiving surface of the photodetector 10 through the opening 6 illumination proportional to the magnitude of the reflected flux emitted through the opening 7 of the ball and caught by trap 3, i.e. the screen 2 does not block this hole; an illumination is created on the receiving surface, proportional to the magnitude of the differential flow reflected by the sample 11. The cover of the screen 2 should be the same with the coating of the inner surface of the walls of the ball. Then the sample 11 is turned over and installed so that the radiation beam first falls on another surface 13 and then, after passing through the thickness of the sample 11, irradiates the measured surface 12. Repeat 8729 5 10 6 sequence of operations, find the full and diffuse reflected samples flow of poly. and recording signals "ff | polX LIFP of the LNF postzgayuschie from the photodetector 10, proportional to the surface T created on its surface; illumination from the flux of Fdiff, F is full of Polkts 5 entering the photometric ball. 5. a system of two equations, a formula is obtained for determining the roughness height

"with

one

full flows reflected from surfaces in its original position; rj - mirror coefficients

reflections of the measured and opposite measured surfaces of the sample, defined, for example, by Fresnel formulas, with the sample turned upside down} Tj is the transmittance of the protivopolozhnye measured Invention Non-contact photometric, method for measuring the roughness height of the surface of transparent samples, consisting in A monochromatic radiation flux at an angle relative to its normal to the sample surface, not exceeding lO, is detected on the sample surface and determines signals from diffuse and total fluxes, trazhennyh from poR - mean square height of roughness measured by a surface of the sample; ,.,% is the wavelength of the monochromatic radiation flux;

the surface and thickness of the sample when it is inverted in position;

WAI | f 1 polyp signals from diffuse and 1 full fluxes reflected from surfaces in the inverted position of the sample.

In the case of r r, j. g, 5 g and T

thirty

 T (C T formula is greatly simplified. I4T

, 1416 - known constant; n - refractive index

sample material at this wavelength;

G, g are the mirror reflection coefficients and; Zeroma and O. ZDiFs poltsa. Epoli-1 sample surfaces, with the chain that improves the accuracy and simplifies the measurement process, after determining the signals, turn the sample so that the radiation flux falls on the opposite measured surface of the sample, while determining the signals from diffuse and full fluxes reflected from the sample surfaces, and the roughness height is judged by the formula 787295 opposite to the measured sample surfaces, determined, for example, by Fresnel formulas, in the initial position. 5 samples; the transmittance of the intended surface and the thickness of the sample in its initial position; 10 Diffuse and full fluxes reflected from surfaces in its initial position; IS rj, rlj are the specular reflection coefficients of the measured and opposite measured surface of the sample, defined, for example, 20 (by the Fresnel formulas for the inverted position of the sample; Tn is the transmittance anti-swayable measured surface and the thickness of the sample in its inverted position; IFPP PAH diffuse and —full fluxes reflected from the surfaces in the inverted position of the specimen. understanding of the expertise of L. Koehier W, F. Multiple-Beam Fringes of the Equal Chromatic Order, Journ. of the Optical Soc. of Amer., 1953, o 1. 43, 9, p. 738-749. 2. USSR Author's Certificate 654853 CL G O B 11/30, 1979 (prototype).

Claims (3)

Claims A non-contact photometric method for measuring the surface roughness of transparent samples, which consists in sending a monochromatic radiation flux to the surface of the sample at an angle relative to the normal to it, not exceeding 10 ° ₄₅ and determining signals from the diffuse and total fluxes reflected from the sample surfaces, o which is characterized in that, in order to increase the accuracy and simplify the measurement process, after determining the signals, the sample is turned over so that the radiation flux falls on the opposite my sample surface, determines at the same time signals from the full flow and diffuse reflected from the sample surface, but the roughness height is judged by the formula • 1 ί-Л \ -г ^П л л V 1 rlj Rdiff -4- ^ 1-A ri. _d Zpoln- »And ¹ 1 g ₄ / ^and FULL Where R _CK is the root mean square height of the roughness of the measured surface of the sample; X is the wavelength of the monochromatic radiation flux; ЗГ = 3,1416 - known constant; n is the refractive index of the sample material at this wavelength; g - mirror coefficients 2 reflections of the verified and 7 872959 8 ^t < ^Г <»<4 of the opposite measured surfaces of the sample, defined, for example, by Fresnel formulas, in the initial position. 5 samples; - transmittance of the measured surface and thickness of the sample in the first ^: its initial position; 10 - signals from diffuse and full flows reflected from surfaces in its initial position; fifteen -coefficients of specular reflection of the measured and opposite measured surfaces of the sample, determined, for example, 20 with Fresnel formulas with the inverted position of the sample; - transmittance of the anti-slip measured surface and the thickness of the sample with its inverted position; ^{signals from} diffuse and full flux reflected from surfaces when the sample is inverted.