SU55017A1 - Device for measuring the radii of curvature of concave spherical surfaces - Google Patents

Description

According to the invention, the following device is proposed for determining the radii of curvature of concave spherical surfaces, as well as deviations of concave surfaces from spherical shape.

Ball III, for example, from a ball bearing with a diameter of 1% -4 mm after preliminary polishing with a crocus on a drop of resin (sometimes it is desirable to follow, aluminizing it with the reflecting surface of the ball) is set in the I plate so that it protrudes above the mirror surface of the plate on the M part of its diameter or, in any case, to an amount that can be further measured.

If a sufficiently distant light source is projected onto this ball (a distance ten times larger than the ball diameter), then the imaginary image of the source (spotlight) will be the same (or not, but known to us) the plane of the knife H, which is the edge of the plate P, removed from the light point by 1-3 mm.

Some conventional illuminator Mada aperture O, not shown in the drawing, sends a beam of light to a concave mirror 3, giving an image of a circular hole O on the ball W. From the side of the ball, mirror 3 is represented by a disk, therefore at the focus of the ball (at a distance M diameter from the front surface) will be a reduced image of the mirror 3, and a beam of a sufficiently large aperture will emerge from the resulting point light into space.

The mirror 3 partially (below the horizontal diameter) shields the product AND, which is irrelevant for the study. Since mirror 3 is located almost on the axis of the illuminating beam, at its high apertures we can only be considered with spherical aberration of the ball W. A simple calculation shows that this aberration is negligible for most cases, and in special cases it can be taken into account.

Focusing the knife H on the image of the light point 5j, we, first, observe the errors of the product according to the shadow pattern and, secondly, measure the distance from the plane of the knife to any point on the surface of the product (in this case the product is a concave test glass, lens or polishing cup) and thereby measuring the radius of curvature of the product (and in other cases, the vertex distance of the system) with corrections known to us. Since the sensitivity of focusing with a knife is high enough, it all comes down to the need to accurately measure the distance from the blade of the knife to the spherical surface.

In those cases where it is desirable to have a slit-like illumination of a high aperture, a polished cylinder is used instead of a ball.

In general, the proposed device is a rigid, aligned system moving in space as a whole. As the diameter of the ball or the diaphragm mirror 3, we get the opportunity to resize the light of the point.

The subject matter of the invention.

A device for measuring the radii of curvature of concave spherical surfaces and investigating deviations from their shape by the shadow method, characterized by using a high radius of a ball of small radius rigidly connected with a knife as a point illuminator so that the dot coincides with the plane of the knife.

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