CS217606B1 - Interferometric length measuring apparatus - Google Patents

Abstract

The instrument comprises a light source (1), a beam splitter, a fixed reflector (3) and an adjustable reflector (8) in the form of a triple mirror. The fixed reflector produces measuring and reference beams and is also a triple mirror with two partially transmitting mirrors as dividing elements. The first and/or second reflection has a central aperture in which the test piece is located coaxial with the mirrors. Both reflectors are connected to viewers (9) and are independently adjustable relative to the test piece. The reflectors are symmetrically arranged on either side of the central axis.

Description

The present invention relates to an interferometric device. measuring the lengths of the objects to be tested by means of light waves.

In the known length measuring devices using body or non-body normal, the test item and the normal are arranged coaxially one after the other in order to prevent overturning errors of the first-order axis. In the case of longitudinal comparators for longer lengths, this arrangement is often not possible due to structural and thermal reasons. The test item and the normal are then placed next to each other and errors resulting from the first-order tilting of the axis must then be corrected or compensated. To this end, the Eppenstein principle is known in which a dot-like measuring rod serving as a normal is arranged parallel to the test item at a distance equal to the focal length of the two symmetrical lenses. The disadvantage of this method is that it cannot be applied to light-proof or non-body normals. In the prior art interferometric length measurements based on the two-beam long-distance interference principle, the reflector is arranged parallel to the test item, for example to test the measuring rods. Errors that occur when the axis is tilted are manifested as first order errors.

The purpose of the invention is to overcome the disadvantages of the known length measuring devices by means of a double-beam interferometer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device for measuring lengths by means of a double-beam interferometer, in which the light path runs parallel to the test item and avoids first-order tilting errors.

SUMMARY OF THE INVENTION The first reflector for generating the measuring and reference beams is designed as a first triple mirror with two partially transparent mirrors, wherein the first triple mirror or the second triple mirror located behind the first triple mirror is provided with a central aperture while both. the triple mirrors are connected to the aiming points in the plane of the triple point. devices and independently displaceable relative to the test item.

The present invention has the advantage that when the triple mirror is overturned relative to the test item, first-order overturn errors are compensated, leading to increased measurement inaccuracies, since the incident and reflected beams are equidistant from the measuring lines, thus changing the beam lengths as a result of flipping, the same size and the opposite.

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The invention is explained in more detail below by way of example.

The drawing shows schematically the interferometric length measuring device according to the invention.

The light beam 2 coming from a light source 1, preferably a laser, is divided into two sub beams 5, 6 by a partially transmissive first triple mirror 3 which is fixedly connected to the test item 4. The sub beam 5 is reflected parallel back to the main interferometric station 7 The partial beam 6 reaches a second triple mirror 8, which is provided with a central aperture 10 in its center, in which the test item 4 is arranged with relative displacement so that its measuring line coincides with the axis of the second triple mirror.

Claims (1)

Apparatus for interferometric measurement of lengths on test objects by means of light waves, comprising a light source, a beam splitting device, for example a reflector arranged fixed relative to the light source and a second reflector displaceable relative to the first reflector and designed as a second triple mirror; characterized in that the first reflector is embodied as the first triple mirror of the handle 8, from. In the second triple mirror 8, the partial beam 6 is reflected by a partially transmissive first triple mirror 3 to the main interferometric station 7, in which both are overlapping. partial beams 5, 6 indicated. On the second triple mirror 8, a sighting device 9 is provided in the plane of the triple point for determining the marks on the test item. If the second triple mirror 8 is overturned relative to the test item 4, the first-order tilt error is compensated because the incident beam and the reflected beam have the same distance from the measuring line of the test item 4, . ’YNALEZU .......... a dome (3) with two partially transparent mirrors, the first triple mirror (3) and / or the second triple mirror (8) located behind the first triple mirror (3) having a central aperture (10), while both triple mirrors (3, 8) are connected to the triple point plane. by means of the aiming devices (9) and mutually independently displaceable relative to the test item.