JPH04505215A - Symmetric carrier frequency interferometer - Google Patents

Abstract

A symmetrical carrier frequency interferometer for measuring length, distance and speed comprises beam-deflecting and beam-splitting elements, a stationary reference mirror (8) and a movable measuring mirror (7). The optically active surfaces, which are arranged after a first polarizing layer (2), are disposed with their axes symmetrical about this layer (2). In one of the two optical paths, a lambda /2 plate (3) is located in front of a second polarizing layer inclined at 45 DEG , and a lambda /4 plate (6), the stationary reference mirror (8) and the movable measuring mirror (7) are located behind this layer in the direction of transmission. At least one reversing element (9, 10) is present in the direction of reflection.

Description

[Detailed description of the invention] Title of the invention: Symmetrical carrier frequency interferometer Technical field The present invention can be used in various industrial fields to measure length, distance and velocity. 1. Carrier frequency interferometer of the present invention, which is related to a carrier frequency interferometer capable of The meter is particularly suitable for applications where high object velocities, e.g. rotational and translational movements, occur in ultra-precise working machines. It can be advantageously used in cases where high resolution increases occur.

Conventional technology Leading measurement equipment manufacturers traditionally utilize asymmetric carrier frequency interferometers. (SPT E Vol. 480, pp. 78-83, published May 1984, USA Patent No. 4,711,547, US Pat. No. 4,752,133), standards and The measurement and measurement channels here have different temperature dependence due to the asymmetry, which is inappropriate for nanometer measuring devices. Diagonal of measurement beam relative to reference beam Line beam appearance allows placement of the reference mirror outside or above the movement path of the measuring mirror. Unacceptable return intensity to the light source compromises the stability of the light source. primary beam The possible tilt of the measurement and reference beams further affects the measurement signal. lead to the spread of music.

Disclosure of invention The object of the invention is to measure distances, lengths and velocities with great precision by simple means. An object of the present invention is to provide a carrier frequency interferometer capable of performing a carrier frequency interferometer.

The invention is based on developing a temperature-invariant carrier frequency interferometer with no feedback. laying the foundation.

According to the invention, this problem is solved by providing a beam deflection member and a beam splitting member; Fixed reference mirror and movable reference mirror? – by a symmetric carrier frequency interferometer with The carrier frequency interferometer includes an optically significant The front side of the deflection dividing layer whose effective surfaces are arranged mirror-symmetrically and tilted by a second angle of 45° A λ/2 plate is placed in one of both beam paths, and a plate of λ/2 is placed in the other partial beam path. a plate for adjusting the optical lens passage in a correspondingly equal position to a plate of λ/4 in its passing direction behind the deflection splitting layer and a fixed reference mirror; a movable measuring mirror, and at least ] reversing members in the direction of reflection. It is characterized by this.

Conveniently, the polarization splitting layer is made of a thin dielectric material and is used as a tuning plate for the optical lens. The six measurement mirrors made of quartz glass are movable one-dimensionally in the beam direction. Placed. A triple prism can be provided as the reversing member.

The special advantages of this carrier frequency interferometer according to the invention are its temperature invariance and light source. is the minimum feedback of the ray to.

BEST MODE FOR CARRYING OUT THE INVENTION According to the drawings, a preferred embodiment of the carrier frequency interferometer of the present invention has a polarization splitting layer 2. and a λ/2 plate successively arranged on the exit surface of the deflection device 1. and plate 4 and a λ/4 plate 6 and a movable measuring mirror in the optical path direction. a deflection component with a second deflection splitting layer followed by a fixed reference mirror 8; A split cube 5, and first and second triple prisms 9, 10 as reversing members It is equipped with The deflection dividing layer is made of a thin dielectric material, and the plate 4 is made of quartz glass. Consists of ? 8! The fixed mirror 7 is arranged to move linearly in the beam direction.

All components are compact when viewed from the fixed reference mirror 8 and the movable measuring mirror 7. Realizes a solidly connected unit.

A laser is utilized to perform the measurements, and the laser has two perpendicular beams of different frequencies. emits modes that are deflected from each other. The parallel laser beam generated by the deflection device is In the deflection dividing layer 2, its components A' and A' (A' is vertical and A' are linearly deflected horizontally), and they are separated into mutually parallel beam paths and The three vertically polarized components A' passing through the carrier frequency interferometer according to the invention are λ /2 plate 3, which is rotated by 90″, deflection dividing cube 5 and It passes through the λ/4 plate 6 and is reflected at the fixed reference mirror 8. λ/4 pre After passing again through port 6, the deflection plane of A' is rotated by 90° and therefore the deflection vertical The first triple prism 9, which is totally reflected by the dividing layer of the cube 5, is move the beam around twice the beam diameter and divide it into the deflection dividing cube 5. Return to layer. The beam is thus reflected twice by the fixed reference mirror 8 and is reflected at λ/4. The two passes of plate 6 rotate it by 90°, resulting in a deflection according to A'. The divided cube 5 becomes transparent. λ/2 plate 3 rotates A' to its original deflection plane let In the deflection device 1, A' is reflected and the incident beam A (f t It exits laterally parallel to f z).

Approximately similar beam paths with respect to the horizontal deflection component A' result on the basis of the symmetrical structure. . Instead of just λ/2, plate 4 makes the glass passages the same with respect to A' and A'. It is located in the beam path to hold it in place. Reflection from movable measurement mirror 7 results in displacement It acts on the frequency f2 of the beam component A' having a Doppler frequency of . deflection In splitting layer 2, A' and A' are superimposed and the carrier frequency interferometer is aligned on the same line. and are deflected perpendicularly to each other. In that case, the output beam has a frequency f and f2 ±Δf2. For example, Doppler with avalanche diode For frequency evaluation the deflection direction is superimposed by a 45@ rotated deflector.

Four passes of varying spacing (depending on the displacement of the movable measuring mirror 7) result in a solution of λ/4. image resolution is achieved. In corresponding developments and deviations of this proposal, λ/8 to λ A practical optical resolution of /16 is achieved.

summary Beam deflection element and beam splitting element, fixed reference mirror (8) and movable measurement length with mirror (7).

Symmetric carrier frequency interferometer for distance and velocity measurements. Following the first polarization splitting layer (2) The optically effective surface to be arranged is mirror-symmetrically arranged with respect to this layer (2). . λ in front of the second polarization splitting layer tilted by 45° in one of both beam paths. /2 plate (3) is arranged and a λ/4 plate is placed behind this layer in the passing direction. A rate (6), a fixed reference mirror (8) and a movable measuring mirror (7) are arranged. It is equipped with at least one reversing member (9, 10) in a certain zero reflection direction. be.

Brief description of the drawing The drawing shows a preferred embodiment of a carrier frequency interferometer according to the invention in an exploded view.

A' is the vertical polarization component of the laser beam.

A' is the horizontal polarization component of the laser beam.

f is the frequency of component A', f2 is the frequency of component A', Δf is the frequency change of component A' due to the Doppler effect.

A, (f, f,) is the incident beam, A (f, f, Δf□) indicates the output beam.

At the beam entrance.

1 Deflection device, 2 Deflection dividing layer, 5 Deflection division cube, 6　λ/4 pre-t.

7. Movable measurement mirror, 8 Fixed reference mirror.

9 First triple prism, 10 A second triple prism is arranged.

international search report

Claims (1)

[Claims] 1) Beam deflection member, beam splitting member, fixed reference mirror (8) and movable a first polarization splitting layer; The optically effective surface to be placed subsequent to (2) is mirror-symmetrical to this layer (2). one of the two beam paths in front of the second polarization splitting layer arranged at 45° and tilted by 45°. and the corresponding etc. in the other partial beam paths. A plate (4) for adjusting the optical lens passage is provided at the correct position, and A movable measuring mirror (7) is arranged behind the second polarization splitting layer in the Symmetrical carrier frequency interference characterized in that it comprises at least one reversing member in the direction Total. 2) Claims characterized in that the deflection dividing layer is formed from a thin dielectric material. Symmetrical carrier frequency interferometer according to paragraph 1. 3) The optical lens passage adjustment plate (4) is made of quartz glass. Symmetrical carrier frequency interferometer according to claim 1 or 2 characterized in . 4) Features that the measurement mirror (7) is arranged so that it can move linearly in the beam direction. A symmetrical conveying circumference according to any one of claims 1 to 3, Wavenumber interferometer. 5) A special feature characterized by providing a triple prism (9, 10) as a reversing member. Symmetrical carrier frequency interference according to any one of claims 1 to 4. Total.