Optical proximity sensors using echo cancellation techniques to detect one or more objects

• US 8,994,926 B2
• Filed: 06/07/2012
• Issued: 03/31/2015
• Est. Priority Date: 02/14/2012
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Dyer, Kenneth C.
• Primary Examiner(s): RATCLIFFE, LUKE D
• Application Number:
  US13/491,476
• Publication Number:
  US 20130208257A1
• Time in Patent Office: 1,027 Days
• Field of Search: 356 301- 315, 356 401- 41, 356 501- 515, 356 6- 22, 356/28, 356/28.5
• US Class Current: 356/4.01
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 7/4876 by removing unwanted signals G01S7/495 takes precedence

Abstract

An optical sensor includes a driver, light detector and echo canceller. The driver is adapted to selectively drive a light source. The light detector is adapted to produce a detection signal indicative of an intensity of light detected by the light detector. The echo canceller is adapted to produce an echo cancellation signal that is combined with the detection signal produced by the light detector to produce an echo cancelled detection signal having a predetermined target magnitude (e.g., zero). The echo canceller includes a coefficient generator that is adapted to produce echo cancellation coefficients indicative of distance(s) to one or more objects, if any, within the sense region of the optical sensor. The optical sensor can also include a proximity detector adapted to detect distance(s) to one or more objects within the sense region of the optical sensor based on the echo cancellation coefficients generated by the coefficient generator.

Claims

1. An optical sensor that can be used to detect the presence, proximity and/or motion of an object within the sense region of the optical sensor, comprising:

a driver adapted to selectively drive a light source;

a light detector adapted to produce a detection signal indicative of an intensity of light detected by the light detector;

an echo canceller adapted to produce an echo cancellation signal that is combined with the detection signal produced by the light detector to produce an echo cancelled detection signal, the echo canceller including a coefficient generator that is adapted to produce echo cancellation coefficients that are indicative of distance(s) to one or more objects, if any, within the sense region of the optical sensor; and

an analog-to-digital converter (ADC) that converts the echo cancelled detection signal to a digital version of the echo cancelled detection signal which is provided to the coefficient generator, wherein the ADC can be part of the echo canceller or external to the echo canceller.

2. The optical sensor of claim 1, further comprising:

a proximity detector adapted to detect distance(s) to one or more objects within the sense region of the optical sensor based on the echo cancellation coefficients generated by the coefficient generator.

3. The optical sensor of claim 1, wherein:

the light detected by the light detector includes

light transmitted by the light source that was reflected off one or more objects within the sense region of the optical sensor, and

interference light, which comprises light transmitted by the light source, and detected by the light detector, that was not reflected off an object within the sense region of the optical sensor; and

the echo cancellation signal compensates for at least a portion of the interference light included in the light detected by the light detector and is indicative of one or more objects, if any, within the sense region of the optical sensor.

4. The optical sensor device of claim 3, wherein the interference light includes one or more of the following:

specular reflections;

internal reflections;

or

light leaking under, over and/or through a barrier that separates the light detector from the light source.

5. The optical sensor device of claim 3, further comprising:

a light transmissive cover plate that covers at least one of the light detector and the light source;

wherein the interference light includes specular reflections caused by the light transmissive cover plate.

6. The optical sensor of claim 1, further comprising:

a timing controller configured to produce a transmit signal (TX) that is used to control the driver and the echo canceller.

7. The optical sensor of claim 6, wherein the transmit signal (TX) comprises a pseudo-random binary sequence.

8. The optical sensor of claim 6, wherein the coefficient generator comprises:

a delay line comprising a plurality of delay units connected one after another in series, wherein the delay line receives the transmit signal (TX), and wherein each delay unit produces a different delayed version of the transmit signal (TX);

a plurality of multipliers, each of which is configured to multiply the digital version of the echo cancelled detection signal by either the transmit signal (TX) or a different one of the delayed versions of the transmit signal produced by the delay units, to thereby produce a plurality of corresponding products; and

a plurality of accumulators, each of which receives a different one of the products produced by the plurality of multipliers, or a scaled version thereof, and outputs a different one of the echo cancellation coefficients (C₀, C₁ . . . C_M).

9. The optical sensor of claim 1, wherein the echo cancelled detection signal has a predetermined target magnitude.

10. The optical sensor of claim 9, wherein the predetermined target magnitude of the echo cancelled detection signal is zero.

11. The optical sensor of claim 9, wherein the predetermined target magnitude of the echo cancelled detection signal is a non-zero offset value.

12. An optical sensor that can be used to detect the presence, proximity and/or motion of an object within the sense region of the optical sensor, comprising:

a driver adapted to selectively drive a light source;

a light detector adapted to produce a detection signal indicative of an intensity of light detected by the light detector;

an echo canceller adapted to produce an echo cancellation signal that is combined with the detection signal produced by the light detector to produce an echo cancelled detection signal; and

a timing controller configured to produce a transmit signal (TX) that is used to control the driver and the echo canceller;

the echo canceller including

a coefficient generator adapted to produce echo cancellation coefficients that are indicative of distance(s) to one or more objects, if any, within the sense region of the optical sensor;

a delay line comprising a plurality of delay units connected one after another in series, wherein the delay line receives the transmit signal (TX), and wherein each delay unit produces a different delayed version of the transmit signal (TX);

a plurality of multipliers, each of which is configured to multiply a different one of the echo cancellation coefficients (C₀, C₁ . . . C_M) generated by the coefficient generator by either the transmit signal (TX) or a different one of the delayed versions of the transmit signal produced by the delay units, to thereby produce a plurality of corresponding products; and

a summer configured to sum the plurality of products produced by the plurality of multipliers;

wherein a sum produced by the summer is provided to a digital-to-analog converter (DAC) that converts the sum produced by the summer to the echo cancellation signal that is combined with the detection signal produced by the light detector to produce the echo cancelled detection signal, wherein the DAC can be part of the echo canceller or external to the echo canceller.

13. A method for use with an optical sensor, comprising:

(a) producing a transmit signal (TX);

(b) selectively transmitting light using the transmit (TX) signal;

(c) producing a detection signal indicative of an intensity of detected light that can include

transmitted light that was reflected off one or more objects within the sense region of the optical sensor and was detected by the optical sensor, and

interference light, which comprises transmitted light that was detected by the optical sensor, but was not reflected off an object within the sense region of the optical sensor; and

(d) producing an echo cancellation signal that is combined with the detection signal to produce an echo cancelled detection signal, wherein the producing the echo cancellation signal includes

producing a plurality of a different delayed versions of the transmit signal (TX);

multiplying a digital version of the echo cancelled detection signal by the transmit signal (TX), and by the plurality of different delayed versions of the transmit signal, to thereby produce a plurality of corresponding different products; and

separately accumulating each of the different products produced as a result of the multiplying, or scaled versions thereof, to produce echo cancellation coefficients (C₀, C₁ . . . C_M) that are indicative of distance(s) to one or more objects within the sense region of the optical sensor.

14. The method of claim 13, wherein the echo cancelled detection signal has a predetermined target magnitude.

15. The method of claim 14, wherein the predetermined target magnitude of the echo cancelled detection signal is zero.

16. The method of claim 14, wherein the predetermined target magnitude of the echo cancelled detection signal is a non-zero offset value.

17. The method of claim 13, further comprising:

(e) detecting distance(s) to one or more objects within the sense region of the optical sensor based on the echo cancellation coefficients.

18. The method of claim 13, wherein the echo cancellation signal compensates for at least a portion of the interference light detected by the optical sensor and is indicative of one or more objects, if any, within the sense region of the optical sensor.

19. The method of claim 13, wherein the producing the echo cancellation signal at step (e) includes:

multiplying each of the echo cancellation coefficients (C₀, C₁ . . . C_M) by either the transmit signal (TX), or by a different one of the plurality of different delayed versions of the transmit signal, to thereby produce a plurality of corresponding different products;

summing the plurality of products produced as a result of the multiplying to thereby produce a sum; and

converting the sum to an analog signal which is the echo cancellation signal.

20. The method of claim 19, further comprising:

(e) detecting distance(s) to one or more objects within the sense region of the optical sensor based on the echo cancellation coefficients (C₀, C₁ . . . C_M).

21. A system, comprising:

a light source;

a driver adapted to selectively drive the light source;

a light detector adapted to produce a detection signal indicative of an intensity of light detected by the light detector;

an echo canceller adapted to produce an echo cancellation signal that is combined with the detection signal produced by the light detector to produce an echo cancelled detection signal, the echo canceller including a coefficient generator adapted to produce echo cancellation coefficients that are indicative of distance(s) to one or more objects within the sense region of the optical sensor;

an analog-to-digital converter (ADC) that converts the echo cancelled detection signal to a digital version of the echo cancelled detection signal which is provided to the coefficient generator, wherein the ADC can be part of the echo canceller or external to the echo canceller; and

a proximity detector adapted to produce one or more output(s) indicative of the presence of, and distance(s) to, one or more objects within the sense region of the optical sensor based on the echo cancellation coefficients generated by the coefficient generator.

22. The system of claim 21, further comprising:

a timing controller configured to produce a transmit signal (TX) that is used to control the driver and the echo canceller.

23. The system of claim 22, wherein the coefficient generator comprises:

a delay line comprising a plurality of delay units connected one after another in series, wherein the delay line receives the transmit signal (TX), and wherein each delay unit produces a different delayed version of the transmit signal (TX);

a plurality of multipliers, each of which is configured to multiply the digital version of the echo cancelled detection signal by either the transmit signal (TX) or a different one of the delayed versions of the transmit signal produced by the delay units, to thereby produce a corresponding product; and

a plurality of accumulators, each of which receives a different one of the products produced by the plurality of multipliers, or a scaled version thereof, and outputs a different one of the echo cancellation coefficients (C₀, C₁ . . . C_M).

24. The system of claim 22, wherein the echo canceller also comprises:

a delay line comprising a plurality of delay units connected one after another in series, wherein the delay line receives the transmit signal (TX), and wherein each delay unit produces a different delayed version of the transmit signal (TX);

a plurality of multipliers, each of which is configured to multiply a different one of the echo cancellation coefficients (C₀, C₁ . . . C_M) generated by the coefficient generator by either the transmit signal (TX) or a different one of the delayed versions of the transmit signal produced by the delay units, to thereby produce a plurality of corresponding products; and

a summer configured to sum the plurality of products produced by the plurality of multipliers;

wherein a sum produced by the summer is provided to a digital-to-analog converter (DAC) that converts the sum produced by the summer to the echo cancellation signal that is combined with the detection signal produced by the light detector to produce the echo cancelled detection signal, wherein the DAC can be part of the echo canceller or external to the echo canceller.

25. The system of claim 21, wherein the echo cancelled detection signal has a predetermined target magnitude.

26. The system of claim 21, further comprising:

a comparator or processor configured to compare the one or more output(s) of the proximity detector to one of more threshold(s); and

a subsystem that is controlled based on a result of the one or more comparisons performed by the comparator or processor.