SU680460A1 - Method for focusing optical system - Google Patents

Abstract

THE OPTICAL SYSTEM FOCUSING METHOD, mainly for machining precision parts, is based on obtaining scattering structures moving relative to the image in the measurement zone. This is because the distance between the optical system and the plane of the measurement zone varies, while maintaining the angle of incidence of the light beam , the size of the scattering structures is optimized, characterized in that, in order to increase the focusing accuracy, the illumination is produced by a beam of an optical quantum generator with Scrap drops on the surface, which provide a contrast separation of the light flux into the mirror component and diffuse structure with a diffraction structure, and the change in the distance between the osh-ary system and the plane of the measurement zone leads to the disappearance of the orderly movement of individual elements of the image structure, which is observed perpendicular to pn to the reflected ray of the plane. i (LOQsh o4 ^ O5

Description

The invention relates to optics, in particular, to methods of focusing optical systems, and can be used to focus an optical system when processing precision parts with an optical quantum oscillator (laser) beam,

There is a known method of adjusting to focus, which consists in measuring the diameter of the cross section of the light spot at some distance from the G13 lens.

However, this method does not give the exact value of the location of the focus.

There is also a method of adjusting to focus, based on obtaining scattering structures moving relative to the image. In the measurement zone, which means that by changing the distance between the optical system and the plane of the measurement zone, while maintaining the GLOW, the angle of incidence of the beam is optimized. C23.

However, this method is complicated and inefficient, since the focus adjustment is made on a special element, which is then replaced on the object under study, which causes the appearance of additional errors.

The aim of the invention is to improve the accuracy of focusing.

This is achieved by the fact that according to the proposed method, the illumination of the investigated surface is produced by a laser beam with an angle of incidence on the surface, providing a contrast separation of the light flux into the mirror component and diffuse with the diffraction structure, and the change in the distance between the optical system and the plane of the measurement zone until the orderly movement of the individual elements of the image structure disappears, which is observed in the plane perpendicular to the reflected beam.

FIG. Figures 1–3 show the beam paths for different cases of focusing.

When focusing the laser light beam on the surface of the workpiece, three positions of the focal spot are possible: the focal spot is on the part surface (exact focusing case, FIG. 1 the focal spot is above the part surface (the case of underfocusing, Fig. 2). F focus spot It is located inside the material of the part (the case of refocusing, Fig. 3 I.

When a real rough surface is illuminated with a coherent monochromatic I reflection, for example, a He-Ne laser /, there is a phenomenon of decomposition of the light flux reflected from the real rough surface into a specular and diffuse component 17

J (x, ((x, zl + 2Ao ((x, 2;) co5 2irsin | 2fe (x,

where A con5i is the amplitude of the intensity of the incident wave x (X; 2) is the amplitude of the intensity of the reflected wave; F is the angle of incidence, at the angle of reflection; I is the radiation wavelength Z — the current value of the asperity height of the reflection surface profile in the selected section. The first two terms of the equation represent the mirror component of the reflection flux, the third control term characterizes the field of diffuse component by the way.

In a plane located perpendicular to the reflection plane at a distance LF, where F is the focal length of the optical system, a diffraction pattern with a system of diffraction maxima is observed, where the mirror component is a diffraction maximum of the oxygen order (Fig. 1). I), and the diffusion component is the set of diffraction maxima of higher orders (Fig. 1, (|.

The shift of the diffraction maxima relative to an arbitrarily chosen point on a rough surface moving in a plane perpendicular to the plane of incidence of the beam depends on the location of the focal spot. In the case of the location of the focal spot inside the material (Fig. 3), the direction of displacement of the diffraction maxima coincides with the movement of the reflecting surface; underfocusing (Fig. 2 /, the diffraction peaks shift and the reflecting surface moves in opposite directions. For the case of full focusing, the diffraction peaks shift randomly and does not depend on the direction of movement of the reflecting surface (Fig. 1 /.

Claims (1)

'METHOD OF FOCUSING THE OPTICAL SYSTEM, mainly for processing precision parts, based on obtaining scattering structures moving relative to the image in the measurement zone, namely, by changing the distance between the optical system and the plane of the measurement zone, while maintaining a constant angle of incidence of the light beam, achieve optimization of the size of scattering structures, characterized in that, in order to improve the accuracy of focusing, the illumination is produced by a beam of an optical quantum generator with glom incidence on the surface, providing contrasting separation of the luminous flux to the mirror and diffuse component with a diffractive structure, and the change in the distance between the optical system and the measurement plane area leads to the disappearance of the orderly movement of individual elements of the structure image, which is observed in a plane perpendicular to the reflected beam. I