SU380946A1 - INTERFEROMETER FOR QUALITY CONTROL OF THE FLAT OPTICAL SURFACE DETAILS - Google Patents

Description

one

The invention relates to optical measuring instruments, more specifically to interferometers for monitoring the quality of a flat optical surface of a part.

A known interferometer is used to control the quality of a flat optical surface of a part, which contains an illumination and observation system and an optical separation device in the form of a Dove prism, which makes it possible to estimate the curvature of interference fringes by the nonial alignment of several mutually rotated strip images.

The known interferometer has several disadvantages. In the interferometer, the boundaries separating the adjacent areas in which mutually rotated images of the band are observed serve as Dowe prism side faces, which have a finite length, and the backlight is realized through a diaphragm, which also has finite dimensions. Therefore, the border separating the neighboring areas has the form of a dark strip, the width of which is the greater, the greater the length of the Dow prisms and the angular diameter of the diaphragm. The observed interfaces and interference fringes lie in different planes. Parallax takes place between the images of the strip observed through the Dove prisms and the sections of the strip observed outside the Dove prisms. All this reduces the accuracy of control.

The proposed interferometer differs from the known one in that it is equipped with two positive lenses installed behind the focal plane of the observational system, and the separation optical device is located between these lenses and is designed as a double image system consisting of a beam-splitting cube dividing the light flux into two a branch, a pentaprism, located in one of the branches, a prism, the main section of which has the form of a parallelogram, installed so that its two parallel faces are perpendicular beams to the beams in both branches x, and the face is inclined to the beams of the face facing the pentaprism and has areas of mirror coatings in the form of rectangles, and a wedge located on the inclined face of the prism, the angle of which is equal to the angle of inclination of this face

to beams of rays.

Due to these differences, the width of the borders of the strip into sections with mutually rotated images is almost zero, the plane of the strip image passes

across the interfaces, and there is no parallax between the strip images at different sites, which improves the control accuracy. FIG. 1 shows the optical layout.

the proposed interferometer; in fig. 2 -

the section along the A-A in FIG. one; in fig. 3 is a view of the interferometer field of view.

The interferometer contains an illumination system that includes a source of monochromatic radiation 1, a condenser 2, a diaphragm 3, and negative lenses 4 vi. 5, lens 6, standard 7, a beam-splitting nlastin S, a separating optical device consisting of a beam-splitting cube 5, a pentaprism 10, a prism 11, a wedge 12, mirror coatings 13 in the form of rectangles, and an observation system - a positive lens 14.

The interferometer works as follows.

The source / monochromatic radiation through the condenser 2 illuminates the aperture 3 located in the focal plane of the lens 4. Lens 5 projects the image of the diaphragm 3 into the focal plane of the lens 6. A parallel beam of radiation, striking the lens, falls on the reference surface of the standard 7 and on the monitored surface of the part 15 The rays reflected from these surfaces interfering with each other form an interference pattern localized in the gap between these surfaces. The beam splitting plate 8 directs the rays reflected from the reference and controlled surfaces into a dual image system consisting of the beam-splitting cube 9, pentaprism 10, prism 11 and wedge 12. The lens 5 and lens 6 build an image of the interference pattern in the front focal plane of the lens 14.

If, in the observed interference pattern, bands of equal thickness are directed perpendicularly parallel to the sides of the mirror rectangles, and the strip images observed in the outermost rectangles are aligned with the strip itself, then the pictures observed in the middle rectangles are offset twice in relation to the strip the big arrow of the curvature of the strip at this point. The high control accuracy is achieved due to the increased sensitivity of the eye to the nonial alignment, as well as due to the displacement of the image in the mirror rectangles, by a double value.

Subject invention

Interferometer to control the quality of the flat optical surface of the part, which contains the lighting and observation systems and the separation optical device,

characterized in that, in order to increase the accuracy of control, it is equipped with two positive lenses installed behind the focal plane of the objective of the observation system, and the separation optical

The device is located between these lenses and is made in the form of a double image system consisting of a beam-splitting cube dividing the luminous flux into two branches, a pentaprism located in one of the branches, a prism, the main section of which has the form of a parallelogram installed so that its two the parallel faces are perpendicular to the beam of beams in both branches x, and the face is inclined to the beam of beams facing the pentaprism and has areas of mirror coatings in the form of rectangles and a wedge located on the inclined face of the prism, l which is equal to the angle of inclination of this face to the beam of rays.