OPTICAL PROXIMITY DETECTORS

• US 20150145764A1
• Filed: 09/24/2014
• Published: 05/28/2015
• Est. Priority Date: 11/27/2013
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Ritter, David W., Hiromi, Itaru, Golden, Philip V., Bhardwaj, Pradeep, Herbst, Steven
• Granted Patent: US 9,250,714 B2
• Time in Patent Office: Days
• US Class Current: 345/156
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 7/4913 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: G01S 7/4915 Time delay measurement, e.g. operational details for pixel components signal extraction and conditioning G01S7/493; Phase measurement
• CPC Class Codes: G06F 3/0304 Detection arrangements using opto-electronic means constructional details of pointing devices not related to the detection arrangement using opto-electronic means G06F3/033; optical digitisers G06F3/042
• CPC Class Codes: H03K 17/941 using an optical detector H03K17/968 takes precedence
• CPC Class Codes: H03K 2217/94108 making use of reflection
• CPC Class Codes: H03K 2217/94116 increasing reliability, fail-safe

Abstract

Described herein are optical proximity detectors, methods for use therewith, and systems including an optical proximity detector. Such optical proximity detectors include an analog front-end and a digital back-end. In certain embodiments, the digital back-end includes a dynamic gain and phase offset corrector, a cross-talk corrector, a phase and magnitude calculator, and a static phase offset corrector. The dynamic gain and phase offset corrector corrects for dynamic variations in gain and phase offset of the analog front-end due to changes in temperature and/or operating voltage levels. The crosstalk corrector corrects for electrical and/or optical crosstalk associated with the analog front-end. The phase and magnitude calculator calculates phase and magnitude values in dependence on the corrected versions of digital in-phase and quadrature-phase signals received from the analog front-end. The static phase offset corrector corrects for a static phase offset of the optical proximity detector.

Claims

1. An optical proximity detector, comprising:

a driver that produces a drive signal, having a carrier frequency, for use in driving a light source to thereby cause the light source to emit light having the carrier frequency;

a light detector that produces a light detection signal indicative of a magnitude and a phase of a portion of the light emitted by the light source that reflects off an object and is incident on the light detector,

an analog front-end including

amplification circuitry that receives the light detection signal and outputs an amplitude adjusted light detection signal;

one or more analog-to-digital converters (ADCs) that

receive the amplitude adjusted light detection signal, or in-phase and quadrature-phase signals produced therefrom, and

output a digital light detection signal, or digital in-phase and quadrature-phase signals; and

a digital back-end including a dynamic gain and phase offset corrector that during an operational mode of the optical proximity detector

receives the digital light detection signal from the analog front end and produces digital in-phase and quadrature-phase signal therefrom, or receives the digital in-phase and quadrature-phase signals from the analog front end,

corrects for dynamic variations in gain and phase offset caused by a portion of the analog front-end, and

outputs dynamic gain and phase offset corrected digital in-phase and quadrature-phase signals.

2. The optical proximity detector of claim 1, further comprising:

a calibration reference signal generator that produces a calibration reference signal having a same phase as the drive signal produced by the driver and having a magnitude within a dynamic range of the analog front-end;

wherein during a calibration mode of the optical proximity detector

the calibration reference signal, produced by the calibration reference signal generator, is provided to the analog front-end; and

the digital back-end

determines an actual magnitude and an actual phase of an IQ vector corresponding to the digital in-phase and quadrature-phase signals;

determines a difference between the actual magnitude of the IQ vector and an expected magnitude of the IQ vector in order to determine a zero-phase gain offset;

determines a difference between the actual phase of the IQ vector and an expected phase of the IQ vector in order to determine a zero-phase phase offset; and

determines, based on the zero-phase gain offset and the zero-phase phase offset, a transfer function for use by the dynamic gain and phase offset corrector during the operational mode of the optical proximity detector.

3. The optical proximity detector of claim 1, wherein:

the portion of the analog front-end, for which the dynamic gain and phase offset corrector corrects for dynamic variations in gain and phase offset, includes the amplification circuitry;

the amplification circuitry of the analog front-end includes a fixed gain amplifier and one or more variable gain amplifiers downstream of the fixed gain amplifier; and

the dynamic variations in gain and phase offset caused by the amplification circuitry are due to dynamic variations in at least one of temperature or operating voltage associated with the amplification circuitry.

4. The optical proximity detector of claim 3, wherein the dynamic gain and phase offset corrector also corrects for dynamic variations in gain and phase offset of at least one of the light source or the light detector.

5. The optical proximity detector of claim 1, wherein:

the portion of the analog front-end, for which the dynamic gain and phase offset corrector corrects for dynamic variations in gain and phase offset, has a transfer function that includes a nominal portion corresponding to a nominal response of the portion of the analog front-end and a dynamic portion corresponding to a dynamic gain offset and a dynamic phase offset of the portion of the analog front-end; and

the dynamic gain and phase offset corrector has a transfer function that is substantially equal to an inverse of the dynamic portion of the transfer function of the portion of the analog front-end.

6. The optical proximity detector of claim 1, wherein the digital back-end also includes:

a cross-talk corrector that

receives the dynamic gain and phase offset corrected digital in-phase and quadrature-phase signals from the dynamic gain and phase offset corrector,

corrects for at least one of electrical crosstalk and optical crosstalk, and

outputs crosstalk corrected digital in-phase and quadrature-phase signals.

7. The optical proximity detector of claim 6, wherein the digital back-end also includes:

a phase and magnitude calculator that determines a phase value and a magnitude value in dependence on the crosstalk corrected digital in-phase and quadrature-phase signals.

8. The optical proximity detector of claim 7, wherein the digital back-end also includes:

a static phase offset corrector that

receives the phase value determined by the phase and magnitude calculator, corrects for a static phase offset associated with the analog front-end, and

outputs a corrected phase value indicative of a distance between the optical proximity detector and an object off of which light, emitted by a light source driven by the driver, reflected and is incident on the light detector.

9. The optical proximity detector of claim 8, wherein the static phase offset corrector also corrects for a static offset associated with at least one of the light source or the light detector.

10. The optical proximity detector of claim 1, wherein the digital back-end also includes a gain adjustment controller that produces a gain adjustment signal that is used to adjust a gain of one or more variable gain amplifiers of the amplification circuitry of the analog front-end.

11. A method for use by an optical proximity detector including an analog front-end and a digital back-end, the method comprising:

(a) producing a drive signal having a carrier frequency;

(b) driving a light source with the drive signal to thereby cause the light source to emit light having the carrier frequency;

(c) producing an analog light detection signal indicative of a magnitude and a phase of a portion of the light emitted by the light source that reflects off an object and is incident on a light detector;

(d) amplifying the analog light detection signal using amplification circuitry of the analog front-end to thereby produce an amplitude adjusted analog light detection signal;

(e) producing, in dependence on the amplitude adjusted analog light detection signal, digital in-phase and quadrature-phase signals; and

(f) correcting for dynamic variations in gain and phase offset caused by a portion of the analog-front end to thereby produce dynamic gain and phase offset corrected digital in-phase and quadrature-phase signals.

12. The method of claim 11, wherein steps (a) through (f) are performed during an operational mode of the optical proximity detector, and further comprising, during a calibration mode of the optical proximity detector:

producing a calibration reference signal having a same phase as the drive signal used for driving the light source;

providing the calibration reference signal to the analog front-end;

determining an actual magnitude and an actual phase of an IQ vector corresponding to digital in-phase and quadrature-phase signals received from the analog front-end, or filtered versions thereof;

determining a difference between the actual magnitude of the IQ vector and an expected magnitude of the IQ vector in order to determine a zero-phase gain offset;

determining a difference between the actual phase of the IQ vector and an expected phase of the IQ vector in order to determine a zero-phase phase offset; and

determining, based on the zero-phase gain offset and the zero-phase phase offset, a transfer function for use in correcting for dynamic variations in gain and phase offset at step (g) during the operational mode of the optical proximity detector.

13. The method of claim 11, wherein steps (a) through (f) are performed during an operational mode of the optical proximity detector, and further comprising, during a calibration mode of the optical proximity detector:

causing the light detector to be non-responsive to light incident on the light detector from outside the optical proximity detector,

producing the drive signal having the carrier frequency,

driving the light source with the drive signal to thereby cause the light source to emit light having the carrier frequency,

producing an analog detection signal indicative of electrical and optical crosstalk;

amplifying the analog detection signal using the amplification circuitry of the analog front-end to thereby produce an amplitude adjusted analog detection signal;

producing, in dependence on the amplitude adjusted analog detection signal, digital in-phase and quadrature-phase signals; and

storing crosstalk error data indicative of electrical and optical crosstalk for use during the operational mode.

14. The method of claim 11, wherein:

the portion of the analog front-end, for which dynamic variations in gain and phase offset are corrected for at step (f), includes amplification circuitry used to perform the amplifying at step (d); and

the dynamic variations in gain and phase offset caused by the amplification circuitry are due to dynamic variations in at least one of temperature or operating voltage associated with the amplification circuitry.

15. The method of claim 14, wherein the portion of the analog front-end, for which dynamic variations in gain and phase offset are corrected for at step (f), also includes at least one of the light source or the light detector.

16. The method of claim 14, wherein:

the amplification circuitry, used to perform the amplifying at step (d), has a transfer function that includes a nominal portion corresponding to a nominal response of the amplification circuitry and a dynamic portion corresponding to a dynamic gain offset and a dynamic phase offset of the amplification circuitry; and

at step (f) the correcting for dynamic variations in gain and phase offset is performed using digital circuitry having a transfer function that is substantially equal to an inverse of the dynamic portion of the transfer function of the amplification circuitry.

17. The method of claim 11, further comprising:

(g) correcting for at least one of electrical crosstalk and optical crosstalk to thereby produce crosstalk corrected digital in-phase and quadrature-phase signals.

18. The method of claim 17, further comprising:

(h) determining a phase value and a magnitude value in dependence on the crosstalk corrected digital in-phase and quadrature-phase signals.

19. The method of claim 18, further comprising:

(i) correcting for a static phase offset associated with the analog front-end to thereby produce a phase value indicative of a distance to the object.

20. The method of claim 18, wherein steps (a)-(d) are performed by the analog front-end of the optical proximity detector, steps (f)-(i) are performed by the digital back-end of the optical proximity detector, and step (e) is performed by either the analog front-end or the digital back-end of the optical proximity detector.

21. A system, comprising:

a driver that produces a drive signal, having a carrier frequency, for use in driving a light source to thereby cause the light source to emit light having the carrier frequency;

a light detector that produces a light detection signal indicative of a magnitude and a phase of a portion of the light emitted by the light source that reflects off an object and is incident on the light detector.

an analog front-end that receives the light detection signal and outputs a digital light detection signal or digital in-phase signal and quadrature-phase signals produced therefrom; and

a digital back-end that receives the digital light detection signal from the analog front end and produces digital in-phase and quadrature-phase signals therefrom, or receives the digital in-phase and quadrature-phase signals from the analog front end,

the digital back end including

a dynamic gain and phase offset corrector that receives that digital in-phase and quadrature-phase signals and outputs dynamic gain and phase offset corrected digital in-phase and quadrature-phase signals;

a cross-talk corrector that receives the dynamic gain and phase offset corrected digital in-phase and quadrature-phase signals and outputs crosstalk corrected digital in-phase and quadrature-phase signals; and

a phase and magnitude calculator that determines a phase value and a magnitude value in dependence on the crosstalk corrected digital in-phase and quadrature-phase signals; and

a static phase offset corrector that receives the phase value determined by the phase and magnitude calculator, corrects for a static phase offset associated with the analog front-end, and outputs a corrected phase value indicative of a distance between the optical proximity detector and an object off of which light, emitted by the light source driven by the driver, reflected and is incident on the light detector.

22. The system of claim 21, further comprising:

a subsystem capable of being enabled and disabled; and

a comparator or processor that receives corrected phase value from the static phase offset corrector of the digital back-end and selectively enables or disables the subsystem in dependence thereon.

23. The system of claim 22, wherein the subsystem is selected from the group consisting of:

a touch-screen,

a display,

a backlight,

a virtual scroll wheel,

a virtual keypad,

a navigation pad,

a camera,

a sensor,

a central processing unit (CPU), or

a mechanical actuator.