High-resolution optical encoder with phased-array photodetectors

• US 6,564,168 B1
• Filed: 09/14/2000
• Issued: 05/13/2003
• Est. Priority Date: 09/14/1999
• Status: Expired due to Term

• Current Assignee: Immersion Corporation
• Original Assignee: Immersion Corporation
• Inventors: Hasser, Christopher J.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): VO, HIEN XUAN
• Application Number:
  US09/661,580
• Time in Patent Office: 971 Days
• Field of Search: 702/163, 235/492, 235/487, 235/488, 235/441, 250/231.14, 736/50
• US Class Current: 702/163
• CPC Class Codes: G01D 5/34 the beams of light being detected by photocells
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders
• CPC Class Codes: G01D 5/366 Particular pulse shapes

Abstract

Embodiments of high-resolution optical encoders having phased-array photodetectors and integrated on semiconductor chips. Emitters, detectors, and encoders disks are described which can be easily produced with semiconductor processes, such as a detector array provided with lens to collimate light and enhance detection. Integrated sensor chips include an array of photodetectors that receive energy from a beam emitted from an emitter and modulated by an encoder disk, analog-to-digital converters, state machines, counters, a communication module, a sensor processing unit, and a force computation unit. One embodiment includes low resolution and high resolution modes and an emitter controlled by sensor circuitry. A detector for an optical encoder can be provided on a single chip that includes a first array of photodetectors used for absolute sensing of a moving object, and a second array of photodetectors used for incremental sensing of the moving object.

Claims

1. A sensor device comprising:

an array of a plurality of photodetectors that receive energy from a beam of electromagnetic energy, said photodetectors operative to output signals indicating detection of energy from said beam; and

a mode selection circuit communicatively coupled to said array of photodetectors, wherein said mode selection circuit is operable to select a first mode in which each of said detectors independently provides a signal,

said mode selection circuit being operable to select a second mode in which at least two of said photodetectors are grouped to provide a signal.

2. A sensor device as recited in claim 1 further comprising an emitter control circuit that controls an emitter to output said beam such that less power is consumed in said second mode than in said first mode.

3. A sensor device as recited in claim 2 wherein said emitter control circuit controls said emitter to pulse said beam with a greater off-time in said second mode than in said first mode.

4. A sensor device as recited in claim 2 wherein said emitter control circuit controls said emitter to emit said beam at a lower intensity in said second mode than in said first mode.

5. The sensor device of claim 1 wherein said signal output by said grouped photodetectors provides a lower sensing resolution than in said first mode.

6. The sensor device of claim 1 wherein less power is consumed by said sensor device in said second mode than in said first mode.

7. A detector for an optical encoder, the optical encoder detecting motion of a moving member, the detector comprising:

a first array of a plurality of photodetectors that receive energy from a beam emitted by an emitter of said optical encoder, each of said photodetectors operative to output a signal indicating a detection of energy from said beam, wherein said first array is used for absolute sensing of said moving member; and

a second array of a plurality of photodetectors that receive energy from said beam emitted by said emitter, each of said photodetectors operative to output a signal indicating a detection of energy from said beam, wherein said second array is used for incremental sensing of said moving member;

wherein said first array and said second array of photodetectors are included on a single semiconductor integrated circuit chip.

8. A detector as recited in claim 7 wherein an encoder disk modulates said energy from said emitted beam onto said first array and said second array.

9. A detector as recited in claim 8 wherein said encoder disk includes a Gray code pattern for modulating light onto said first array of photodetectors, and a slot pattern for modulating light onto said second array of photodetectors.

10. An integrated sensor processing device comprising:

a photodetector array for outputting one or more analog signals;

at least one analog-to-digital converter for converting the analog signals to digital signals;

at least one state machine for receiving the digital signals, and outputting pulse and direction signals;

a counter for using the pulse and direction signals to determine a position of a moving member, the position being relative to a start point of the moving member;

a communication module for providing the position to a controller; and

a mode selection circuit coupled to the photodetector array, wherein the mode selection circuit is operable in any one or more of a first mode and a second mode,

the first mode for providing a first signal, and the second mode for providing a second signal that is lower in resolution than the first signal.

11. An integrated sensor processing device detecting motion of a moving member, the sensor processing device comprising:

an array of a plurality of photodetectors that receive energy from a beam of electromagnetic energy emitted from an emitter, each of said photodetectors operative to output a signal indicating a detection of energy from said beam;

at least one analog-to-digital converter coupled to said array of photodetectors, said analog-to-digital converter converting said signals from said photodetectors to digital signals;

at least one state machine coupled to said at least one analog-to-digital converter, said state machine outputting pulse and direction signals;

a counter coupled to said analog-to-digital converter that receives said pulse and direction signals and determines a position of said moving member from said pulse and direction signals, said position relative to an initial start point of the moving member;

a communication module coupled to said counter and providing said position to a controller;

wherein said integrated sensor processing device is provided on a single integrated circuit chip; and

digital logic circuitry coupled to said at least one analog-to-digital converter, wherein said digital logic circuitry can select a first digital signal having a high resolution, and wherein said digital logic circuitry can select a second digital signal having a resolution lower than the first digital signal such that the amount of power consumed is reduced.

12. An integrated sensor processing device as recited in claim 11 wherein said digital logic circuitry selects said first digital signal having the steepest slope at the present position of said moving member.

13. An integrated sensor processing device as recited in claim 11 wherein said at least one analog-to-digital converter includes a multi-level analog-to-digital converter.

14. An integrated sensor processing device as recited in claim 13 wherein said multi-level analog-to digital converter is used with said digital logic circuitry and at least one other analog-to-digital converter is a single level comparator, and wherein said digital logic circuitry reads said digital signals only from said multi-level analog-to-digital converter when said moving member is moving under a threshold velocity.