High Resolution Single Track Optical Encoder

• US 20100301195A1
• Filed: 05/31/2009
• Published: 12/02/2010
• Est. Priority Date: 05/31/2009
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Chew, Gim Eng, Ng, Chee Wai, Thor, Chung Min
• Granted Patent: US 8,097,842 B2
• Time in Patent Office: Days
• US Class Current: 250/231.13
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01D 5/34746 Linear encoders

Abstract

Disclosed are various embodiments of a single track reflective optical encoder featuring increased spatial resolution, reduced cross-talk between adjoining photodiodes, and increased amplitude output signals from individual photodiodes. With respect to prior art single track optical encoders, some photodiodes are removed from a photodiode array, while nevertheless maintaining appropriate phase relationships between pairs of A and A\, and B and B\, photodiodes. Such a configuration of photodiodes results in increased inter-photodiode spacing, and thereby permits spatial resolution to be increased while boosting current outputs from individual photodiodes. The single track optical encoder configurations disclosed herein permit very high resolution reflective optical encoders in small packages to be provided. In addition, the single track configuration reduces problems with misalignment between code scales and light detectors, permits relatively simple electronic circuitry to be used to process outputs, and reduces manufacturing, assembly, integrated circuit and encoder costs. Methods of making and using such optical encoders are also disclosed.

Claims

1. A high resolution single track reflective optical encoder, comprising:

a light emitter configured to emit light therefrom;

a plurality of photodetectors or photodiodes having leading and trailing edges arranged along a single track and a common axis to form a single track light detector, the single track light detector having disposed along the common axis pairs of A and A\ data channel light detectors and B and B\ data channel light detectors, the A and B light detectors and the A\ and B\ light detectors, respectively, being arranged to generate output signals that are 90 degrees out of phase with respect to one another, and

a code scale comprising alternating optically substantially reflective and substantially non-reflective data strips, any pair of adjoining reflective and non-reflective data strips disposed on the code scale having a combined width of X, the code scale being configured to travel along the common axis and being located and configured operably in respect of the single track light detector such that at least a portion of the light emitted from the light emitter is reflected from the code scale towards the data channel light detectors;

wherein a spacing between at least some adjoining photodetectors or photodiodes arranged along the single track and the common axis is greater than or equal to X/2, the spacing being measured between either the leading edges or the trailing edges of such adjoining photodetectors or photodiodes, the spacing being sufficiently large to prevent or inhibit cross-talk between adjoining photodiodes, the resulting optical encoder having a spatial resolution of X/2.

2. The high resolution single track reflective optical encoder of claim 1, wherein the A and B light detectors are not located adjacent one another anywhere along the common axis and the single track.

3. The high resolution single track reflective optical encoder of claim 1, wherein the A\ and B\ light detectors are not located adjacent one another anywhere along the common axis and single track.

4. The high resolution single track reflective optical encoder of claim 1, wherein widths of individual A and B light detectors are greater than or equal to X/2.

5. The high resolution single track reflective optical encoder of claim 1, wherein widths of individual A\ and B\ light detectors are greater than or equal to X/2.

6. The high resolution single track reflective optical encoder of claim 1, wherein widths of individual A, B, A\ and B\ light detectors range between about 1 microns and about 2 microns.

7. The high resolution single track reflective optical encoder of claim 1, wherein a spacing between adjoining photodetectors or photodiodes arranged along the single track and the common axis is greater than or equal to a width of each of the photodetectors or photodiodes.

8. The high resolution single track reflective optical encoder of claim 1, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, B, A\, B\).

9. The high resolution single track reflective optical encoder of claim 1, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, A\, B, B\).

10. The high resolution single track reflective optical encoder of claim 1, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, B\, A\, B).

11. The high resolution single track reflective optical encoder of claim 1, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, B, A\, B\).

12. A method of making a high resolution single track reflective optical encoder, comprising:

providing a light emitter configured to emit light therefrom;

providing a plurality of photodetectors or photodiodes having leading and trailing edges arranged along a single track and a common axis to form a single track light detector, the single track light detector having disposed along the common axis a plurality of pairs of A and A\ data channel light detectors, and B and B\ data channel light detectors, the A and B light detectors, and the A\ and B\ light detectors, respectively, being arranged to generate output signals that are 90 degrees out of phase with respect to one another;

providing a code scale comprising alternating optically substantially reflective and substantially non-reflective data strips, wherein any pair of adjoining reflective and non-reflective data strips disposed on the code scale has a combined width equal to X, the code scale being configured to travel along the common axis and being located and configured operably in respect of the single track light detector such that at least a portion of the light emitted from the light emitter is reflected from the code scale towards the data channel light detectors, and

arranging a spacing between at least some adjoining photodetectors or photodiodes disposed along the single track and the common axis such that the spacing is greater than or equal to X/2, the spacing being measured between either the leading edges or the trailing edges of such adjoining photodetectors or photodiodes, the spacing being sufficiently large to prevent or inhibit cross-talk between adjoining photodiodes, the resulting optical encoder having a spatial resolution of X/2.

13. The method of claim 12, wherein the A and B light detectors are not located adjacent one another anywhere along the common axis and the single track.

14. The method of claim 12, wherein the A\ and B\ light detectors are not located adjacent one another anywhere along the common axis and single track.

15. The method of claim 12, wherein widths of individual A and B light detectors are greater than or equal to X/2n.

16. The method of claim 12, wherein widths of individual A\ and B\ light detectors are greater than or equal to X/2n.

17. The method of claim 12, wherein widths of individual A, B, A\ and B\ light detectors range between about 1 microns and about 2 microns.

18. The method of claim 12, wherein a spacing between adjoining photodetectors or photodiodes arranged along the single track and the common axis is greater than or equal to a width of each of the photodetectors or photodiodes.

19. The method of claim 12, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, B, A\, B\).

20. The method of claim 12, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, A\, B, B\).

21. The method of claim 12, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, B\, A\, B).

22. The method of claim 12, wherein the photodetectors or photodiodes are arranged along the single track and the common axis to form a sequential pattern or a repeating sequential pattern of photodetectors or photodiodes defined by (A, B, A\, B\).

23. A method of encoding light signals generated by an optical encoder having a single track and a common axis, comprising:

emitting light from a light emitter towards a code scale;

reflecting at least a portion of the light emitted by the light emitter from the code scale, the code scale comprising alternating optically substantially reflective and substantially non-reflective data strips, wherein any pair of adjoining reflective and non-reflective data strips disposed on the code scale has a combined width equal to X, the code scale being configured to travel along the common axis;

detecting at least a portion of the light reflected from the code scale with a plurality of photodetectors or photodiodes having leading and trailing edges arranged along the single track and the common axis to form a single track light detector, the single track light detector having disposed along the common axis a plurality of pairs of A and A\ data channel light detectors, and B and B\ data channel light detectors, the A and B light detectors, and the A\ and B\ light detectors, respectively, being arranged to generate output signals that are 90 degrees out of phase with respect to one another, and

arranging a spacing between at least some adjoining photodetectors or photodiodes disposed along the single track and the common axis such that the spacing is greater than or equal to X/2, the spacing being measured between either the leading edges or the trailing edges of such adjoining photodetectors or photodiodes, the spacing being sufficiently large to prevent or inhibit cross-talk between adjoining photodiodes, the resulting optical encoder having a spatial resolution of X/2.