SU1456779A1 - Method and apparatus for measuring parameters of roughness of slightly rough surface - Google Patents

Abstract

The invention relates to a measuring technique and can be used for the diagnosis of a slightly rough surface. The aim of the invention is to increase the accuracy and increase the sensitivity by measuring the radiation intensity gradient. In the method and apparatus implementing this method, for irradiating an object 7 along a normal, a high coherent radiation source 1 is used. In the Michelson interferometer, the object and reference waves are strictly coaxially mixed at the output of the interferometer. Subsequently, the difference in the motion of the reference and object waves is changed, to achieve cf antiphase, which is judged by the minimum intensity of the resultant field. The odor-coordinate intensity distribution in the image plane of the object, the intensity of the resulting field and the reference beam are measured, from which the distribution function is measured by the height of the M1 roughness, as well as the roughness parameters of the low-rough surface. 2 sec. f-ly, 1 ill. (With SL M / 5 7 J6

Description

This invention relates to a measurement technique and can be used to diagnose a low-rough surface.

The aim of the invention is to improve the accuracy and increase the sensitivity by measuring the intensity gradient of the radiation field.

The drawing shows a diagram of the device,. implementing method.

The device contains a source of coherent radiation I, a collimator 2 and a beam splitter 3 along the radiation, dividing the radiation into two beams, one of which explores a quarter-wave plate A oriented in that its axis forms an angle of 45 with the plane of radiation polarization , and a mirror 5, in contact with which, on the side opposite to the beam incident on it, is installed a piezoceramic displacement 6, and along the other beam there is an object holder 7, successively installed along the way out The beam has a polarizer 8, an aperture diaphragm 9, a lens 10 located so that the plane of the object holder 7 is optically aligned with the plane of the diaphragm 11 of a photoreceiver 12, and an additional beam splitter 13 mounted along the beam splitter 13A with a diaphragm 15 located in the plane optically conjugated to the plane of the object holder 7, and configured to move in this plane by means of the transverse scanning mechanism b

The method is implemented and the device operates in the following manner.

Normally irradiate the test object 7 in the holder. The beam is strictly coaxially mixed at the output of the interferometer by adjusting the mirror 5 and the beam splitter 3, Equalizes the intensities of the object and beam, changing the mutual orientation (angle between axes) of the polarizer 8 and the quarter-wave plate

4 t. With the help of piezo-ceramic

four

shifts 6 change the path difference between the reference and object beams, to achieve their antiphase nature,

vfaznost reference and object beams control the minimum intensity of the resulting beam Trmin

using a photoelectric receiver 16, choose the size of the aperture diaphragm 9 so that in the formation of the image of the object's surface

participation of all spatial-frequency components of the field corresponding to the surface structure of the object, according to

.

where d is the size of the aperture diaphragm; a is the diameter of the irradiating beam; b is the distance from the measured surface to the aperture stop; L - wavelength used

jricT04HHKa;

1, is the correlation radius of the irregularities of the surface under study.

The intensity 1pmin of the resulting beam is measured using a photoelectric receiver 12, then the object beam is overlapped and the intensity of the reference beam TO is measured. Further, according to the formula (1), the phase dispersion of the field is calculated

five

b. ,

Jl /

(one)

where 4 1rmin - the intensity of the resulting floor is minimal; (/ - phase phase dispersion;

6

  the intensity of the reference beam.

The one-coordinate intensity distribution in the beam cross section is measured by scanning the 45 field with a micron-diaphragm system. 15, a photomultiplier photoelectric device 14 in the transverse micro-room mechanism 16,

The size of the micron diaphragm selects considerably smaller sizes of the structural elements of the resulting field. According to the obtained dependencies using the formulas

 lL lM l5ii :) ((x, y) - (2)

4 kttiL i | jLzf - Г Y (х, у) (3)

the correlation moments of the phase of the object field of the third and fourth order are calculated. In relations (2) and (3), the designation. ,, means averaging, (x, y) is the local value of the objective field phase, f is the average phase.

Using the obtained values of the structural parameters of the object surface, one can judge the distribution function of the roughness heights of the low-rough surface and determine the surface roughness parameters (dispersion, heights, average roughness height, etc.).

Claims (1)

1. A method for determining the roughness parameters of a slightly rough surface, namely, that the collimated coherent radiation beam is divided into two beams of equal intensity, the reference and the measuring, illuminate the test surface with the measuring beam, align the reflected beam from the surface with the reference one, observe interference fringes and determine roughness parameters, characterized in that, in order to increase accuracy and increase sensitivity, a beam of linearly polarized coherent about the radiation, the beams are aligned until the interference bands disappear, change the path difference to obtain the minimum intensity of light radiation over the entire plane of observation, record the total intensity of the radiation -BO of the entire plane network and one-coordinate intensity distribution, overlap the measurements five 0 The beam is measured, the intensity of the reference beam is recorded, and the roughness parameters are calculated from the data obtained. 2, Device. To determine the roughness parameters of a low-rough surface, containing a source of coherent radiation, a collimator arranged successively along the radiation, and a beam splitter, which divides the radiation into two beams, a reference and a gauge, a reflector, located in the reference beam, the holder of the object under study. located in the measuring beam, and a photodetector with a diaphragm located in the region of the formation of the interference pattern, characterized in that, in order to improve accuracy and increase sensitivity, it is equipped with a quarter-wave plate located between the beam splitter and the reflector and oriented so that its optical axis forms an angle A5 ° with the radiation polarization plane, a piezoceramic moving, located in the reference beam and hidden with the reflector, sequentially arranged between the beam - divide and photoreceiver by a polarizer, aperture diaphragm, lens, installed in such a way that the plane of the object holder and the plane of the photoreceiver are optically aligned, and tion beam splitter, an additional light detector with a diaphragm arranged downstream otrazhen0 him from the radiation beam splitter mounted in a plane optically conjugated with the plane of the sample holder, and is movable in this plane. 0 five