SU1747899A1 - Surface microgeometry testing method - Google Patents

Abstract

The invention relates to a control and measuring technique. The purpose of the invention is the expansion of technological capabilities by controlling the height of asperities with zero and negative profile angles. According to the method, the radiation intensities are recorded in two regions located symmetrically with the axis of the illuminating beam. The ratio of these intensities is related to the height of the microwaves. 3 il.

Description

The invention relates to a control and measuring technique and is intended for contactless control of the surface roughness of products obtained by various methods of mechanical processing.

One of the most difficult problems of modern engineering is to control the microgeometry of products using the contactless method.

Optical devices are known that make it possible to give an integral estimate of the surface roughness.

Closest to the present invention is a device for contactless measurement of surface roughness. The device comprises a photodetector having an optical position sensor in the imaging unit, light emitters located on both sides of the photodetector and having optical axes inclined at a certain angle to the optical axis of the photoreceiver. In addition, there are gates

which alternately transmit beams from light emitters onto the measured surface, a tracking control unit, which with the help of a sensor detects deviations of the position of the light spot, alternately created on the surface by each of the beams.

However, this device does not allow to determine the height of asperities of the surface with a negative and zero angle of the profile, which is due to the inability of the control unit to control the corresponding angles of inclination of the normal to the surface under investigation. In addition, the device has several sources of radiation, therefore, the difference in temporal radiative characteristics of one relative to the other leads to additional errors in determining the angle of inclination of the surface.

The purpose of the invention is the expansion of the technological capabilities of the method of controlling the surface microgeometry by means of contour, 9

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roll height of asperities with zero and negative profile angle.

This goal is achieved by controlling the surface microgeometry, which involves scanning the laser beam over the surface under investigation in a given direction and receiving the beam reflected from the surface to the photoreceiver. During the measurement, the position of the spot of light corresponding to the center of the incident beam is aligned with the extreme point of the surface at the height measurement site, the intensity distribution in the surface diffracted beam is fixed, and the depth of the profile is determined from the numerical solution of the following equation:

m - f (h); m - H / l2.

where h, h - respectively, the intensity recorded by the first and second channels of the differential photodetector:

f (h) is a function that establishes a relationship between the ratio h / l2 and the depth of the profile.

A device for measuring surface microgeometry contains radiation sources optically coupled to the object to be monitored, an optical system, and a photoreceiver node connected to the inputs of independent amplifiers. There are compute and register nodes. The outputs of the independent amplifiers are associated with a functional transducer, fixing the ratio of their intensities. which is connected via a switch to a linearly varying voltage generator, a clock pulse generator, and a counter, which determines the height of the irregularities according to the zero-organ signal; displayed on the indicator.

FIG. 1 shows the irregularities with negative and zero angle: in figure 2

- form of energy distribution: in FIG. 3 - a functional diagram of the device for monitoring microgeometry.

An example of a specific implementation of the proposed method for controlling the microgeometry of the surface of standard measures of setting profilographs-profilometers is illustrated with the help of the device (Fig. 3),

The radiation of laser 1 through the beam splitter 2 is focused on the surface under study 3 by the micro-lens 4. The reflected radiation is returned through the lens 4, the beam splitter 2 and the super-flat photodetector 5 is directed, the photodetector interface is oriented

along the optical axis of the micro-lens and perpendicular to the scanning direction. The signals from the photodetector through matching preamplifiers 6 and 7 are fed to the recording device 8. The scanned surface of the scanned beam, record the form of the energy distribution in the diffracted stream. If the beam is far to the left or right of a rectangular protrusion, then the form of the energy distribution in the diffracted beam is similar to the incident one. When the spot begins to creep onto a rectangular protrusion or trough, the distribution of energy begins to change shape. it

happens until the spot completely passes through the obstacle. The beginning and end of this process is recorded by the zero of the signal l (t) 1 - li / la. Taking into account the symmetry of the Gaussian distribution in

incident beam, you can always determine the point when the center of the beam is at the edge of the trough. In the recorded waveform, this point corresponds to the extremum of the signal t2 (to - ti) / 2, where pi 1h are the nearest points,

the corresponding zero functions I (t) (figure 2). The ratio is measured at this point v.2. The height of the asperities is associated with the signal expression

/ d (xf) dxf

11 - °°

12 °

/ ftxf) dxf

40

where (xf) y3 (xf) y9 (dt) is the complex conjugation,

(xf) +

45

 A h22

+ T77-exp (exp J J

l o / tl

(-2h)

where p is the diameter of the spot in terms of amplitude / e;

And - the amplitude of the falling floor;

A is the laser wavelength;

f is the focal distance of the microscope; xf is the coordinate of the photodetector;

h - depth, e - the basis of the natural logarithm.

Claims (1)

Solving a numerical equation for h. we find the depth (height) of the depression (protrusion) with a zero or negative angle microgeometry profile. In particular, when measuring the height of mm-irregularities on a reference measure that has a rectangular microgeometry (“0). where a is the angle of the profile (Fig. 1), height h is 0.1 microns, the intensity ratio at the point t2 at a laser wavelength of 0.83 microns is 1.306. On the basis of the obtained data from the solution of the equation, the height of asperities with a zero profile angle, which is 0.1 µm, is determined. The claims of the method of controlling the microgeometry of the surface, which consists in scanning the surface of the laser beam, recording the intensity of the radiation reflected from the surface and determining the microgeometry parameters using the registered intensity, characterized in that in order to expand technological capabilities by controlling the height of asperities with zero and negative profile angles, the intensity the reflected beam is recorded in two regions symmetrical with respect to the line perpendicular to the scanning direction, and the height of the asperities is determined by the ratio of the intensities registered in these areas. t, t Fig.Z