Displacement measuring instrument

Abstract

To provide a displacement measuring instrument that simultaneously satisfies the conditions of being free from mechanical movement, highly accurate, having a wide measurement range, and being low-cost. [Solution] The displacement measuring device 1 includes a light source 2 that generates broadband light, a first interferometer 10 that splits the light source L11 and directs it onto a reference surface (reference side mirror 13) and a measuring surface (workpiece 9), and superimposes the reference light L13 and the measuring light L15 to generate interference light L16, a second interferometer 20 that splits the interference light and directs it onto a first reflective surface (first mirror 23) and a second reflective surface (second mirror 25), and superimposes the first reflected light L23, L26 and the second reflected light L25, L27 to generate developing light L28 that spreads in a predetermined developing direction E and whose optical path length difference changes along the developing direction E, an image sensor 3 that detects the developing light L28, and a calculation device 4 that measures the displacement of the measuring surface from the displacement of the peak position of the interference signal in the image detected by the image sensor 3.

Claims

1. A light source that generates broadband light, A first interferometer that splits the light source and directs it onto a reference surface and a measuring surface, and generates interference light by superimposing the reference light reflected from the reference surface and the measuring light reflected from the measuring surface, A second interferometer that splits the aforementioned interference light and directs it onto a first reflective surface and a second reflective surface, and superimposes the first reflected light reflected by the first reflective surface and the second reflected light reflected by the second reflective surface to generate a developed light that expands in a predetermined development direction and whose optical path length difference changes along the development direction, An image sensor that detects the unfolded light, A displacement measuring device comprising: a calculation device that measures the displacement of the measuring surface from the displacement of the peak position of the interference signal in the image detected by the image sensor.

2. The second interferometer has a beam splitter that splits the interfering light and directs it onto the first and second reflecting surfaces, The first reflected light and the second reflected light are incident on the image sensor via the beam splitter, The displacement measuring device according to claim 1, wherein at least one of the first reflective surface and the second reflective surface is an inclined mirror positioned at an angle to the deployment direction with respect to the incident optical axis.

3. The displacement measuring device according to claim 2, wherein the inclined mirror is a multi-stage inclined mirror in which a plurality of the inclined mirrors are arranged in a direction intersecting the incident optical axis and the deployment direction, and the plurality of the inclined mirrors are offset from each other in the direction of the incident optical axis.

4. The displacement measuring device according to claim 3, wherein an aperture diaphragm for narrowing the first reflected light and the second reflected light is arranged between the image sensor and the beam splitter.

5. The displacement measuring device according to claim 2, wherein a cylindrical lens is arranged that is continuous in the direction of expansion and focuses the incident light to the image sensor onto the image sensor.

6. The second interferometer has a beam splitter that splits the interfering light and directs it onto the first and second reflecting surfaces, The first reflected light and the second reflected light are incident on the image sensor without passing through the beam splitter, The displacement measuring device according to claim 1, wherein the angle of incidence of the first reflected light to the image sensor and the angle of incidence of the second reflected light to the image sensor are different from each other.

7. The displacement measuring device according to claim 6, wherein the optical path length from the beam splitter through the first reflecting surface to the image sensor and the optical path length from the beam splitter through the second reflecting surface to the image sensor are different from each other.

8. The displacement measuring device according to claim 6, wherein a cylindrical lens is arranged that is continuous in the direction of expansion and focuses the incident light to the image sensor onto the image sensor.

9. The first interferometer has a common inlet for the light source and an outlet for the interference light. The displacement measuring device according to claim 1, wherein the path of the light source from the light source to the first interferometer and the path of the interference light from the first interferometer to the second interferometer are each composed of optical fibers, and the portions of the optical fibers closest to the first interferometer are combined into a single fiber.

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