High-resolution optical encoder with phased-array photodetectors

• US 20040061502A1
• Filed: 03/18/2003
• Published: 04/01/2004
• Est. Priority Date: 09/14/1999
• Status: Active Grant

• Current Assignee: Immersion Corporation
• Original Assignee: Immersion Corporation
• Inventors: Hasser, Christopher J.
• Granted Patent: US 6,928,386 B2
• Time in Patent Office: Days
• US Class Current: 324/332
• 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. 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; and

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.

2. An integrated sensor processing device as recited in claim 1 wherein said single integrated circuit chip is a semiconductor chip.

3. An integrated sensor processing device as recited in claim 1 wherein said communication module includes digital circuitry for providing serial data to said controller.

4. An integrated sensor processing device as recited in claim 1 wherein said controller is a microprocessor.

5. An integrated sensor processing device as recited in claim 4 wherein said sensor processing device is included in a haptic feedback device coupled to a host computer, and wherein said microprocessor is local to said haptic feedback device and separate from said host computer.

6. An integrated sensor processing device as recited in claim 1 further comprising:

a sensor processing unit coupled to said counter and determining a velocity of said moving member; and

a force computation unit coupled to said sensor processing unit and determining a force to be output by at least one actuator coupled to said force feedback computation unit.

7. An integrated sensor processing device as recited in claim 6 wherein said sensor processing device is included in an interface device coupled to a host computer, and wherein said controller is microprocessor of said host computer.

8. An integrated sensor processing device as recited in claim 1 further comprising digital logic circuitry coupled to said at least one analog-to-digital converter on said integrated circuit chip, said digital logic circuitry selecting one of said digital signals to provide a higher resolution than said other digital signals.

9. An integrated sensor processing device as recited in claim 8 wherein said digital logic circuitry selects said digital signal having a steepest slope at the present position of said moving member.

10. An integrated sensor processing device as recited in claim 8 wherein said at least one analog-to-digital converter includes a multi-level analog-to-digital converter.

11. An integrated sensor processing device as recited in claim 10 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.

12. A sensor device for detecting motion of a moving member, the sensor device comprising:

an emitter that emits a beam of electromagnetic energy;

a moving member having an encoder pattern;

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

a mode selection circuit coupled to said array of photodetectors, wherein said mode selection circuit can select a high resolution mode in which each of said detectors provides said signal independently to permit a higher sensing resolution, and wherein said mode selection circuit can select a low resolution mode in which at least two of said photodetectors are considered grouped and wherein said signals output by said grouped photodetectors are combined to achieve a lower sensing resolution than in said high resolution mode, wherein less power is consumed by said sensor device in said low resolution mode than in said high resolution mode.

13. A sensor device as recited in claim 12 further comprising an emitter control circuit that controls said emitter to output said beam such that less power is consumed in said low resolution mode than in said high resolution mode.

14. A sensor device as recited in claim 13 wherein said emitter control circuit controls said emitter to pulse said beam with a greater off-time in said low resolution mode than in said high resolution mode.

15. A sensor device as recited in claim 13 wherein said emitter control circuit controls said emitter to emit said beam at a lower intensity in said low resolution than in said high resolution mode.

16. A sensor device as recited in claim 13 wherein said low resolution mode is used to sense a position of a non-force-feedback mouse, and wherein said high resolution mode is used to sense a position of a force feedback mouse.

17. 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 first 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.

18. A detector as recited in claim 17 wherein an encoder disk modulates said energy from said emitted beam onto said first array and said second array.

19. A detector as recited in claim 18 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.