Optical position measuring device

• US 6,175,414 B1
• Filed: 11/18/1999
• Issued: 01/16/2001
• Est. Priority Date: 11/19/1998
• Status: Expired due to Term

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Huber, Walter, Holzapfel, Wolfgang, Höfer, Volker
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US09/443,238
• Time in Patent Office: 425 Days
• Field of Search: 356/375, 356/373, 250/237.G, 250/231.13, 250/231.18, 250/231.14, 337/06, 337/07
• US Class Current: 356/620
• CPC Class Codes: G01D 5/366 Particular pulse shapes

Abstract

An optical position measuring device is described for determining the relative position of two objects that are movable in a measuring direction with respect to each other. The position measuring device includes a scale having a scale reference mark structure, which is composed of n blocks arranged in the measuring direction with partial areas of varying optical characteristics. A scanning unit is also included, with a scanning reference pulse structure as well as a plurality of detector elements. Output signals are generated by the detector elements, which at a defined relative position of the two objects, have a maximum or a minimum value.

Claims

1. An optical position measuring device for determining a relative position of two objects movable with respect to each other in a measuring direction, by generating a reference pulse signal corresponding to at least one defined relative reference position, the position measuring device comprising:

a scale having a scale reference mark structure, the scale being connected to one of the two objects and the scale reference mark structure being composed of n (n=2,3,4 . . . ) blocks disposed in the measuring direction, the scale reference mark structure blocks having a plurality of sequentially arranged partial areas of varying optical characteristics disposed in the measuring direction; and

a scanning unit connected to the other of the objects and including a scanning plate with a plurality of detector elements and a scanning reference mark structure composed of n scanning reference blocks arranged sequentially in the measuring direction, the scanning reference mark structure blocks having assigned to them corresponding detector elements;

wherein at least a first group of blocks of one of the scale reference and scanning reference mark structures is configured, at the reference position in the plane of a respective other one of the scanning reference and scale reference mark structures, to supply an intensity distribution that is identical to the structure of the associated first group of blocks,

wherein at least a second group blocks of another one of the scale reference and the scanning reference mark structures, in a plane of a respective other one of the scanning reference and scale reference mark structures, supplies an intensity distribution that is complementary to the structure of the associated second group of blocks,

and wherein the detector elements are interconnected such that output signals of the detector elements of each group of blocks are connected to each other to generate a reference pulse output signal resulting from the output signals, said reference pulse output signal having a maximum or a minimum at the defined relative position of the two objects.

2. The optical position measuring device as recited in claim 1, wherein the scanning reference mark structure is a pure amplitude structure having for each scanning reference mark structure block an arrangement of partial areas with varying optical characteristics, such that one first group of scanning reference mark structure blocks includes a first arrangement of partial areas identical to a first arrangement of partial areas of associated scale reference mark structure blocks, and such that a second group of scanning reference mark structure blocks includes a second arrangement of partial areas complementary to a second arrangement of partial areas of associated scale reference mark structure blocks.

3. The optical position measuring device as recited in claim 1, wherein the scanning reference mark structure is one of a phase structure and a combined phase/amplitude structure.

4. The optical position measuring device as recited in claim 3, wherein the scanning reference mark structure is a combined phase/amplitude structure comprising transparent and non-transparent partial areas, and phase-shifting structures disposed in the transparent partial areas.

5. The optical position measuring device as recited in claim 1, further comprising connections to differentially connect the reference pulse output signal of the first and second groups of blocks.

6. The optical position measuring device as recited in claim 1, further comprising a subtraction element operating on the reference pulse output signal.

7. The optical position measuring device as recited in claim 1, wherein each block of the scale reference mark structure and each block of the scanning reference mark structure comprises a plurality of partial areas which are alternatively optically transparent and non-transparent.

8. The optical position measuring device as recited in claim 1, wherein each block of the scale reference mark structure and each block of the scanning reference mark structure comprises a plurality of partial areas that are alternatively optically reflecting and non-reflecting.

9. The optical position measuring device as recited in claim 1, wherein surfaces of the detector elements are larger than surfaces of the associated scale reference and scanning reference blocks.

10. The optical position measuring device as recited in claim 1, comprising an even number of blocks of the two groups of scale reference and scanning reference mark structures, and wherein surfaces of the scale reference and scanning reference blocks are identical.

11. The optical position measuring device as recited in claim 1, comprising an odd number of blocks of the two groups of scale reference and scanning reference mark structures, and wherein the sum of surfaces of the first group is identical to the sum of surfaces of the second group of the scale reference and scanning reference mark structures.