Probe with a diffraction grating for +1,0 and -1 orders

• US 20030117633A1
• Filed: 11/25/2002
• Published: 06/26/2003
• Est. Priority Date: 05/23/2000
• Status: Abandoned Application

• Current Assignee: Mahr GmbH
• Original Assignee: Mahr GmbH
• Inventors: Rudolph, Markus, Gusek, Bernd
• Application Number:
  US10/296,394
• Publication Number:
  US 20030117633A1
• Time in Patent Office: Days
• US Class Current: 356/521
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/303 using photoelectric detection means
• CPC Class Codes: G01D 5/38 by diffraction gratings

Abstract

A measuring device that employs interference optics for detecting and tracking the movement of a mechanical element (4) has a light source (31) for emitting a light bundle that is capable of interference, a diffraction grating and a sensor arrangement (33). A beam path leads from the light source to the sensor arrangement (33) by way of the diffraction grating (32). The diffraction grating divides the light bundle into at least three partial components, thereby forming a light patch having three overlapping maxima, the center, zero maximum and the two minus one and plus one maxima on either side, at the optical sensor arrangement (33). The light beams for generating the three brightness maxima interfere with one another, so the resulting superposed light patch (46) contains interference bands that run in one direction or another when the diffraction grating is moved. The movement of the interference bands is detected with the sensor arrangement (33), and evaluated in an evaluation circuit. This permits a precise detection of each movement of the diffraction grating (32). The proposed arrangement utilizes virtually the entire interference pattern generated from the light emitted by the light source. This results in light-intensive interference patterns, even with low capacities of the light source (31). Thus, low-capacity components can be used.

Claims

1. A measuring device (1), particularly for measuring the surface roughness and/or the surface contour of a workpiece (3),

having a probe element (4), which is seated to move and can be brought into contact with the workpiece surface (2),

having a diffraction grating (32), which is seated to move and is connected to the probe element (4),

having a light source (31) for generating a light bundle (34) that is capable of interference and is aimed at the diffraction grating (32) for generating an interference light bundle (34a) having at least one zero maximum (0), a plus one maximum (+1) and a minus one maximum (−

1), and

having an optical sensor arrangement (33), which is exposed to the interference light bundle (34a) originating from the diffraction grating (32).

2. The measuring device according to claim 1, characterized in that the optical sensor arrangement (33) is connected to a digital evaluation device (63, 64, 65) having at least one counter (65) for detecting the number of interference fringes that have passed the sensor arrangement (33).

3. The measuring device according to claim 1, characterized in that the sensor arrangement (33) is connected to an analog evaluation device (66, 67, 68) that forms an interpolation device, which is designed to allocate a position value to the brightness detected by the sensor arrangement (33).

4. The measuring device according to claim 1, characterized in that the sensor arrangement (33) has at least two sensor elements (43, 44, 45, 46), which serve in detecting the brightness at various areas of the interference light bundle.

5. The measuring device according to claim 1, characterized in that the sensor arrangement (33) includes two sensor groups (43, 44;

45, 46), each comprising at least one sensor (43, 44;

45, 46) and being offset from one another by one-half the interference-fringe width.

6. The measuring device according to claim 1, characterized in that the probe element (4) is seated to move one-dimensionally.

7. The measuring device according to claim 1, characterized in that the diffraction grating (32) is permeable for light.

8. The measuring device according to claim 1, characterized in that the diffraction grating (32) is seated to move transversely to the light bundle (34).

9. The measuring device according to claim 1, characterized in that it includes a positioning device (16) that is designed to move the probe element (4) across the workpiece surface in a predetermined direction.

10. The measuring device according to claim 1, characterized in that it includes a force-generating device (18) for generating a measurement force.