Photoelectric position measuring system using gratings having specified dimensions to suppress harmonics

• US 5,576,537 A
• Filed: 07/07/1994
• Issued: 11/19/1996
• Est. Priority Date: 07/15/1993
• Status: Expired due to Fees

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Holzapfel, Wolfgang, Franz, Andreas
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US08/271,641
• Time in Patent Office: 866 Days
• Field of Search: 250/237 G, 250/231.14, 250/231.16, 356/375, 33/707, 341/13, 341/31
• US Class Current: 250/237.00G
• CPC Class Codes: G01D 5/38 by diffraction gratings
• CPC Class Codes: H01L 27/1446 in a repetitive configuration
• CPC Class Codes: H01L 27/153 in a repetitive configuration, e.g. LED bars
• CPC Class Codes: H01L 31/173 formed in, or on, a common substrate

Abstract

A light source which emits light in strips is provided for illuminating a scale of a photoelectric position measuring system. The light modulated by the scale is converted into a sinusoidal scanning signal by a scanning plate. The scanning plate is a semiconductor substrate structured in strips. The width (A) of the light-emitting areas and the width (B) of the interspersed non-emitting areas of the light source is such that defined harmonics are filtered out of the scanning signal. The scanning plate is of such configuration that further harmonics are suppressed.

Claims

1. A photoelectric measuring system comprising:

a light source having a plurality of light emitting areas which are separated from each other by non-emitting areas in the measuring direction;

a movable scale having a periodic graduation positioned to receive light emitted from the light-emitting areas of the light source; and

a scanning plate used to scan the scale and generate at least one position-dependent scanning signal, the scanning plate having a plurality of light sensitive areas which are separated from each other by non-sensitive areas in the measuring direction,

wherein the light-emitting areas of the light source are dimensioned to suppress predetermined orders of harmonics and the light sensitive areas of the scanning plate are dimensioned to suppress predetermined additional orders of harmonics wherein if the predetermined orders suppressed by the light source are even ordered then the predetermined orders suppressed by the scanning plate are odd ordered and if the predetermined orders suppressed by the light source are odd ordered, then the predetermined orders suppressed by the scanning plate are even ordered.

2. A measuring system according to claim 1 wherein the scanning plate is in the form of a semiconductor substrate having a light sensitive area and the non-sensitive areas are formed by applying light-shielding bars on the light sensitive area so that the non-sensitive areas alternate with the light sensitive areas.

3. A measuring system according to claim 1 wherein the light source is in the form of a semiconductor substrate having a light emitting area and the non-emitting areas are formed by applying light shielding bar on the light sensitive areas of the substrate so that the light-emitting and non-emitting areas alternate.

4. A measuring system according to claim 2 wherein the light sensitive areas are in the form of strips.

5. A measuring system according to claim 3 wherein the light-emitting areas are in the form of strips.

6. A measuring system according to claim 1 wherein the scanning plate is a semiconductor substrate and the light sensitive areas are formed by strip-shaped PN junctions formed in the substrate.

7. A measuring system according to claim 1 wherein the light source is a semiconductor substrate and the light-emitting areas are formed by strip-shaped PN junctions formed in the substrate.

8. A measuring system according to claim 1 wherein the ratio of the widths of the light-emitting areas to the non-emitting areas is different from the ratio of the widths of the light sensitive areas to the non-sensitive areas.

9. A measuring system according to claim 1 wherein the ratio of the widths of the light-emitting areas to the non-emitting areas is 1:

2 and the ratio of the widths of the light sensitive areas to the nonsensitive areas is 1;

1.

10. A measuring system according to claim 1 wherein the light source and scanning plate are embodied on a single semiconductor substrate.

11. A measuring system according to claim 1 wherein the light source is a semiconductor substrate formed by a base body having a layer of N-type material applied to a surface of the base body and the light emitting areas are formed by strips of P-type material embedded in the N-type layer.

12. A measuring system according to claim 1 wherein the scanning plate is a semiconductor substrate formed by a base body having a layer of N-type material applied to a surface of the base body and the light sensitive areas are formed by strips of P-type material embedded in the N-type layer.

13. A photoelectric measuring system according to claim 1 wherein the light source further comprises:

a substrate;

a first layer of a first conductivity applied to a surface of the substrate; and

a second layer of a second conductivity applied to at least a plurality of portions of the surface of the first layer wherein the portions in which the second layer overlies the first layer form light emitting areas, the light emitting areas being separated from one another by non-emitting areas

wherein the second layer is applied over the entire first layer and light shielding bars are applied to the surface of the second layer wherein the bars are separated from one another by gaps exposing the second layer, the bars forming the non-emitting areas and the gaps forming the light emitting areas.

14. A photoelectric measuring system according to claim 13 wherein the gaps have a uniform width and the light shielding bars have a uniform width and the ratio of the widths of the gaps to the widths of the bars is 1:

2.

15. A photoelectric measuring system comprising:

a light source having a plurality of light emitting areas which are separated from each other by non-emitting areas in the measuring direction;

a scale having a periodic graduation positioned to receive light emitted from the light emitting areas of the light source; and

a scanning plate used to scan the scale and generate at least one positioned-dependent scanning signal, the scanning plate having a plurality of light sensitive areas which are separated from each other by non-sensitive areas in the measuring direction, wherein the light-emitting areas of the light source are dimensioned to suppress whole number multiples of the third harmonic and the light sensitive areas of the scanning plate are dimensioned to suppress even-numbered harmonics.

16. A photoelectric measuring system comprising:

a light source having a plurality of light emitting areas which are separated from each other by non-emitting areas in the measuring direction;

a scale having a periodic graduation positioned to receive light emitted from the light emitting areas of the light source; and

a scanning plate used to scan the scale and generate at least one positioned-dependent scanning signal, the scanning plate having a plurality of light sensitive areas which are separated from each other by non-sensitive areas in the measuring direction, wherein the light-emitting areas of the light source are dimensioned to suppress even-numbered harmonics and the light sensitive areas of the scanning plate are dimensioned to suppress whole number multiples of the third harmonic.

17. A photoelectric measuring system comprising:

a light source having a plurality of light emitting areas which are separated from each other by non-emitting areas in the measuring direction;

a movable scale having a periodic graduation positioned to receive light emitted from the light-emitting areas of the light source;

a scanning plate used to scan the scale and generate at least one position-dependent scanning signal, the scanning plate having a plurality of light sensitive areas which are separated from each other by non-sensitive areas in the measuring direction,

wherein the light-emitting areas of the light source are dimensioned to suppress predetermined orders of harmonics and the light sensitive areas of the scanning plate are dimensioned to suppress predetermined additional orders of harmonics wherein the light-emitting areas of the light source and the light sensitive areas of the scanning grating are disposed side by side in the same plane.

18. A photoelectric measuring system according to claim 17 wherein the light emitting areas of the light source are centrally disposed on a substrate and the light sensitive areas of the scanning plate are disposed adjacent to the light emitting areas.