Increased accuracy and resolution for optic position sensors

• US 5,978,418 A
• Filed: 07/19/1996
• Issued: 11/02/1999
• Est. Priority Date: 07/19/1996
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Greve, James E., Gilbert, Ted B., Gustus, Jeffery S.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Bayard, Emmanuel
• Application Number:
  US08/683,925
• Time in Patent Office: 1,201 Days
• Field of Search: 375/369, 375/342, 375/316, 375/333, 375/262, 375/261, 375/260, 375/216, 341/90, 341/97, 341/74, 341/13, 341/68, 341/69, 341/70, 356/359, 356/43, 356/45, 356/136, 356/128, 356/386, 356/356
• US Class Current: 375/242
• CPC Class Codes: G01D 5/34794 Optical encoders using the Vernier principle, i.e. incorporating two or more tracks having a (n, n+1, ...) relationship

Abstract

An optic position sensor provides a data encoding method which improves the resolution capability of the sensing system. The data pattern of the sensor comprises a series of data signals having a start bit, digital data bits, an analog bit region (12) and a stop bit. The digital data bits may be a Manchester Encoded, Gray Coded data signal pattern. The analog data bit region (12) comprises a vernier track (10) which will produce a signal peak that moves linearly with position. The detection of the position of the vernier track (10) or bit relative to its range or region (12) provides a measurement of the percent of travel that has occurred within and between the discernible resolution of the digital data bits of the data signal, to provide resolution capability of approximately one part in sixteen thousand.

Claims

1. A position sensor mask of a high resolution position sensor having a resolution magnitude of at least 1×

10^-4 and which encodes a signal and enables high resolution detection and decoding of the encoded signal, the mask comprising a start bit, digital data bits, analog data bit, and a stop bit.

2. The position sensor mask in accordance with claim 1, wherein the digital data bits comprise Manchester Encoded, Gray Coded data bits.

3. The position sensor mask in accordance with claim 1, wherein the analog data bit comprises a vernier track.

4. A method of encoding a signal for high resolution detection of a resolution magnitude of at least 1×

10^-4 and decoding of the encoded signal, comprising the steps of;

providing a mask having a start bit, digital data bits, analog data bit, and stop bit; and

displacing the mask to effect uniquely and continuously an output signal whereby the output signal is an encoded signal representing the displacement of the encoded mask.

5. The method in accordance with claim 4, wherein the digital data bits comprise Manchester Encoded, Gray Coded data bits.

6. The method in accordance with claim 4, wherein the analog data bit comprises a vernier track.

7. A method of detecting and decoding with high resolution of a resolution magnitude of at least 1×

10^-4 a received encoded signal, comprising steps of;

receiving the encoded signal and detecting data bits of said signal;

detecting the data bits to discern a pattern of data bits comprising a start bit, digital data bits, analog data bit, and stop bit; and

determining the position of the analog data bit relative to a range of possible positions for the analog data bit to provide a measurement of the amount of travel occurring within and between the discernible resolution of the digital data bits of the encoded signal.

8. The method in accordance with claim 7, wherein the digital data bits comprise Manchester Encoded, Gray Coded data bits.

9. The method in accordance with claim 7, wherein the analog data bit comprises a vernier track.

10. The method in accordance with claim 7, further comprising the step of filtering the received encoded signal in order to enhance the ability to accurately measure the location of data bit peaks.

11. A method of signal encoding, detecting and decoding with high resolution of a resolution magnitude of at least 1×

10^-4, comprising the steps of;

providing a mask having a start bit, digital data bits, analog data bit, and stop bit;

displacing the mask to effect uniquely and continuously an encoded signal representing the displacement of the encoded mask;

receiving the encoded signal and detecting data bits of said signal;

detecting the data bits to discern a pattern of data bits comprising the start bit, digital data bits, analog data bit, and stop bit; and

determining the position of the analog data bit relative to a range of possible 107,005 positions for the analog data bit to provide a measurement of the amount of travel occurring within and between the discernible resolution of the digital data bits of the encoded signal.

12. The method in accordance with claim 11, wherein the digital data bits comprise Manchester Encoded, Gray Coded data bits.

13. The method in accordance with claim 11, wherein the analog data bit comprises a vernier track.

14. The method in accordance with claim 11, further comprising the step of filtering the received encoded signal in order to enhance the ability to accurately measure the location of data bit peaks.

15. The method in accordance with claim 11, wherein the method comprises an optical position sensor.

16. The method in accordance with claim 15, further comprising the steps of providing a controlled light source to illuminate a portion of the mask, and receiving the light after encoding by the mask and transmitting the encoded light to a detector for detection of the data bits.