Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Alignment Interferometer Parallel Axis Generator

IP.com Disclosure Number: IPCOM000093495D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Bates, AD: AUTHOR

Abstract

The optics of an alignment interferometer are shown. It utilizes a prism assembly so arranged that a surface can be established parallel to and displaced in space from a reference surface by viewing interference fringes for two light beams. In drawing 1, surfaces K and F are beam-splitting coatings. Light entering surface P is split at surfaces K and F into parts that leave the prism assembly at surface E and at surfaces M and N by way of reflections at surfaces G and L respectively.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Alignment Interferometer Parallel Axis Generator

The optics of an alignment interferometer are shown. It utilizes a prism assembly so arranged that a surface can be established parallel to and displaced in space from a reference surface by viewing interference fringes for two light beams. In drawing 1, surfaces K and F are beam-splitting coatings. Light entering surface P is split at surfaces K and F into parts that leave the prism assembly at surface E and at surfaces M and N by way of reflections at surfaces G and L respectively.

The optical path lengths are the same for the two beams leaving at M and N. The axes of these two beams are parallel and lie in a plane parallel to the normal to P, the entrance face, and are at right angles to the axis of the beam entering at
P. These conditions hold independently of orientation to the entering beam for angles up to the limits imposed by vignetting at M and N, about 15 degrees. The coatings on K and F can be divided into bands of different splitting ratios, thus providing for different beam intensities leaving the exit faces.

In drawing 2, a second identical prism assembly is positioned so that the two P faces are parallel. The optical paths provide two parallel beams, the axes of which coincide only if surfaces P make the same angle with the beams. There are two positions of the top assembly that satisfy this. One is the position that makes the P surfaces parallel. For this position the optical path length through the system is the same for the two paths. When the adjustment is exact, white light interference fringes are formed. This position is well separated, and easily distinguished from, the second position in which the beam entering P, lower prism, makes a sizable nonzero angle with the plane of M, lower prism.

This system is therefore a device for establishing a surface P parallel to and displaced in space from a corresponding surface. Interference fringes beyond P, upper prism, provide a sensitive indication of the parallelism.

The system indicates parallelism of surfaces P regardless of dihedral lines, the angle between their edges at M. This condition can be established with the four-beam system of drawing 3. As shown, an entering beam divides to produce four beams. The points where the axes of these beams leave the surfaces define the corners of a square. These four points are seen as a single point on lookin...