Optical positional encoder comprising immediately adjacent detectors

• US 4,691,101 A
• Filed: 06/19/1985
• Issued: 09/01/1987
• Est. Priority Date: 06/19/1985
• Status: Expired due to Term

• Current Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Leonard, Mark G.
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/747,084
• Time in Patent Office: 804 Days
• Field of Search: 250/231 SE, 250/237 G, 340/347 P, 324/175, 356/395
• US Class Current: 250/231.16
• CPC Class Codes: H03M 1/301 Constructional details of parts relevant to the encoding mechanism, e.g. pattern carriers, pattern sensors

Abstract

An optical shaft encoder has a light detector configuration that includes the function of a phase plate. The light detectors are one-half the width of a code wheel transmissive section and are arranged in groups of four so that each group corresponds to one pitch of the code wheel. The light detectors are interdigitated such that they are adjacent to one another and receive information from two channels. One light beam illuminates the four light detectors producing four electrical signals. The physical layout of the light detectors causes the output signals to be phase shifted 90° from each other. These signals are combined electronically in pairs forming quadrature push pull signals.

Claims

1. An optical encoder for indicating the rotational movement of a shaft, comprising:

an emitter means for emitting a light beam along a light path;

a light modulation means concentrically attached to the shaft and placed in the light path for modulating the light beam in response to the rotation of the shaft; and

a detector means, positioned in the light path, for detecting said modulated light beam with individual light detectors located immediately adjacent to one another and for generating more than one output signal in response to the rotation of the shaft wherein the output signals have substantially the same shape and are delayed from each other by approximately integer multiples of 360°

divided by the number of signals.

2. An optical encoder as in claim 1 further comprising at least one output channel formed from a plurality of the output signals.

3. An optical encoder as in claim 2 wherein the light modulation means comprises an optical track positioned to cross the light path, the optical track having alternating transmissive and non-transmissive sections operative for modulating the light beam in response to the rotating shaft.

4. An optical encoder as in claim 3 wherein the individual light detectors are arranged into groups.

5. An optical encoder as in claim 4 wherein each group of light detectors has substantially the same dimensions as one transmissive section plus one non-transmissive section.

6. An optical encoder as in claim 5 wherein the individual light detectors each have substantially the same shape and size.

7. An optical encoder as in claim 6 wherein each of the transmissive sections have substantially the same shape and size.

8. An optical encoder as in claim 7 wherein individual light detectors located a distance of one transmissive section plus one non-transmissive section apart have their outputs signals connected together forming coupled outputs.

9. An optical encoder as in claim 8 further comprising an electrical means for converting the coupled outputs into n/2 output channels where n equals the number of light detectors in one group.

10. An optical encoder as in claim 9 wherein each group of light detectors consists of four individual light detectors.

11. An optical encoder as in claim 10 wherein the outputs of the individual light detectors have substantially identical shapes and are delayed from each other by approximately integer multiples of 90°

.

12. An optical encoder as in claim 11 wherein the emitter means comprises an LED and a collimating lens.

13. An optical encoder as in claim 12 wherein:

the individual light detectors are located in an array having two ends; and

a dummy light detector is located at each end of the array.

14. An optical encoder as in claim 13 wherein the light detectors are photodiodes.

15. An optical encoder as in claim 14 wherein each of the light detectors have a trapezodial shape.

16. An optical encoder as in claim 1 further comprising:

a second track on the light modulation means with transmissive and non-transmissive sections aligned to modulate a light beam; and

a second detector means, positioned in the light path for receiving the light beam modulated by the second track, and for generating index signals that reach their extreme amplitude at least once during each revolution of the shaft.

17. An optical encoder as in claim 16 wherein:

the second detector means comprises individual light detectors located immediately adjacent to one another wherein the individual light detectors have outputs; and

the outputs of alternate light detectors are connected together thereby forming two output index signals.

18. An optical encoder as in claim 17 wherein the size and shape of the light detectors and transmissive sections are operative for the two output signals reaching their extreme amplitude at least once during each revolution of the shaft.

19. An optical encoder as in claim 18 further comprising an electical means coupled to the output index signals for producing an index pulse in response to the extreme amplitudes of the output index signals.

20. An optical encoder for indicating the rotational movement of a shaft, comprising:

an emitter means for emitting a light beam along a light path;

a light modulation means concentrically attached to the shaft and placed in the light path for modulating the light beam in response to the rotation of the shaft; and

a detector means, positioned in the light path, for receiving the modulated light beam with individual light detectors located immediately adjacent to one another and for generating index signals that reach their extreme amplitude at least once during each revolution of the shaft.

21. An optical encoder as in claim 20 wherein:

the outputs of alternate light detectors are connected together thereby forming two output index signals.

22. An optical encoder as in claim 21 wherein the light modulation means comprises an optical track positioned to cross the light path, the optical track having alternating transmissive and non-transmissive sections operative for modulating the light beam in response to the rotating shaft.

23. An optical encoder as in claim 22 wherein the size and shape of the light detectors and transmissive sections are operative for the two output signals reaching their extreme amplitude at least once during each revolution of the shaft.

24. An optical encoder as in claim 23 further comprising an electrical means coupled to the output index signals for producing an index pulse in response to the extreme amplitudes of the output index signals.

25. An optical encoder for indicating an object'"'"'s movement along a route, comprising:

an emitter means for emitting a light beam along a light path;

a light modulation means located next to the emitter means and in the light path for modulating the light beam in response to the object'"'"'s movement along the route; and

a detector means, positioned in the light path, for receiving the modulated light beam with individual light detectors located immediately adjacent to one another and for generating more than one signal in response to the object'"'"'s movement along the route wherein the signals have substantially the same shape and are delayed from each other by approximately integer multiples of 360°

divided by the number of signals.

26. An optical encoder as in claim 25 further comprising at least one output channel formed from a plurality of the output signals.

27. An optical encoder as in claim 26 wherein the light modulation means comprises an optical track positioned on the light modulation means to cross the light path, the optical track having alternating transmissive and non-transmissive sections and being operative for modulating the light beam in response to movement along a route.

28. An optical encoder as in claim 27 wherein the individual light detectors are arranged into groups.

29. An optical encoder as in claim 28 wherein each group of light detectors has substantially the same dimensions as one transmissive section plus one non-transmissive section.

30. An optical encoder as in claim 29 wherein the individual light detectors each have substantially the same shape and size.

31. An optical encoder as in claim 30 wherein each of the transmission sections have substantially the same shape and size.

32. An optical encoder as in claim 31 wherein individual light detectors located a distance of one transmissive section plus one non-transmissive section apart have their outputs connected together forming coupled outputs.

33. An optical encoder as in claim 32 further comprising an electrical means for converting the coupled outputs into n/2 output channels where n equals the number of light detectors in one group.

34. An optical encoder as in claim 33 wherein each group of light detectors consists of four individual light detectors.

35. An optical encoder as in claim 34 wherein the outputs of the individual light detectors have substantially identical shapes and are delayed from each other by approximately integer multiples of 90°

.

36. An optical encoder as in claim 35 wherein the emitter means comprises an LED and a collimating lens.

37. An optical encoder as in claim 36 wherein:

the individual light detectors are located in an array having two ends; and

a dummy light detector is located at each end of the array.

38. An optical encoder as in claim 37 wherein the light detectors are photodiodes.

39. An optical encoder as in claim 38 further comprising:

a second track on the light modulation means with transmissive and non-transmissive sections aligned to modulate a light beam; and

a second detector means, positioned in the light path, for receiving the light beam modulated by the second track, and for generating index signals that reach their extreme amplitude at least once during each excursion across the route.

40. An optical encoder as in claim 31 wherein:

the second detector means comprises individual light detectors located immediately adjacent to one another wherein the individual light detectors have outputs; and

the outputs of alternate light detectors are connected together thereby forming two output index signals.

41. An optical encoder as in claim 40 wherein the size and shape of the light detectors and transmissive sections are operative for the two output signals reaching their extreme amplitude at least once during each excursion across the route.

42. An optical encoder as in claim 41 further comprising an electical means coupled to the output index signals for producing an index pulse in response to the extreme amplitudes of the output index signals.

43. An optical encoder for indicating an object'"'"'s movement along a route, comprising:

an emitter means for emitting a light beam along a light path;

a light modulation means located next to the emitter means and in the light path for modulating the light beam in response to the object'"'"'s movement along a route; and

a detector means, positioned in the light path, for receiving the modulated light beam with detectors located immediately adjacent to one another and for generating index signals that reach their extreme amplitude at least once during each excursion across the route.

44. An optical encoder as in claim 43 wherein:

the outputs of alternate light detectors are connected together thereby forming two output index signals.

45. An optical encoder as in claim 44 wherein the light modulation means comprises an optical track positioned to cross the light path, the optical track having alternating transmissive and non-transmissive sections operative for modulating the light beam in response to movement along a route.

46. An optical encoder as in claim 45 wherein the size and shape of the light detectors and transmissive sections are operative for the two output signals reaching their extreme amplitude at least once during each revolution of the shaft.

47. An optical encoder as in claim 46 further comprising an electical means coupled to the output index signals for producing an index pulse in response to the extreme amplitudes of the output index signals.