AUTOMATIC CALIBRATION TECHNIQUE FOR TIME OF FLIGHT (TOF) TRANSCEIVERS

• US 20110181892A1
• Filed: 01/25/2011
• Published: 07/28/2011
• Est. Priority Date: 01/27/2010
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Golden, Philip, Ritter, David W., Craddock, Carl Warren
• Granted Patent: US 8,274,037 B2
• Time in Patent Office: Days
• US Class Current: 356/614
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: G01J 9/00 Measuring optical phase difference devices or arrangements for controlling the phase of light beams G02F1/01; Determining degree of coherence; Measuring optical wavelength spectrometry G01J3/00
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: H01L 31/101 Devices sensitive to infrared, visible or ultraviolet radiation

Abstract

A system and method for automatically calibrating a Time-of-Flight (TOF) transceiver system for proximity/motion detection, is provided. Moreover, the system comprises a component that senses a signal (e.g., current or voltage) at an light emitting diode (LED), an attenuator, a signal injector at a sensor and a switching circuit that toggles between a normal mode (e.g., when signal from the sensor is input to the sensor front end) and a calibration mode (e.g., when signal from the attenuator is input to the sensor front end). During the calibration mode, the sensor front end identifies the phase delay error within the signal path, including board and/or package parasitic, and accounts for the phase delay error during proximity/motion detection in the normal mode.

Claims

1. An apparatus, comprising:

a light emitting diode (LED) driver circuit for generating an electrical signal;

a LED that transmits light based on the electrical signal;

a driver sensing component that senses the electrical signal;

an attenuation component for attenuating the sensed driver signal; and

a measurement component for measuring a phase of the attenuated signal.

2. The apparatus of claim 1, further comprising:

a calibration bridge that switches an input of a front end of the apparatus based on a current mode of operation.

3. The apparatus of claim 2, wherein the calibration bridge provides a disparate electrical signal generated by an optical sensor to the input of the front end, during a normal mode of operation.

4. The apparatus of claim 2, wherein the calibration bridge provides the attenuated signal to the input of the front end, during a calibration mode of operation.

5. The apparatus of claim 2, wherein the current mode of operation is switched at least one of automatically, dynamically, periodically or at a predefined time.

6. The apparatus of claim 1, wherein the driver sensing component senses a voltage signal at the LED.

7. The apparatus of claim 1, wherein the driver sensing component senses a current signal at the LED.

8. The apparatus of claim 1, wherein a front end of the apparatus utilizes the phase measurement to accurately identify at least one of proximity or motion of an object in a sense field.

9. The apparatus of claim 1, wherein the driver sensing component, the attenuation component, the measurement component and an LED driver reside within a single IC.

10. The apparatus of claim 1, wherein the phase measurement includes a phase error contributed by at least one of an analog circuit, a digital processing circuit, a LED driver, board parasitics, or package parasitics.

11. A method, comprising:

sensing an electrical signal at a light emitting diode (LED);

attenuating the sensed driver signal; and

identifying a phase delay error based on the attenuated sensed driver signal.

12. The method of claim 11, further comprising:

generating an electrical signal;

determining a phase measurement associated with the electrical signal;

using the electrical signal to generate light;

causing the light to reflect from an object;

receiving at least a portion of the reflected light; and

determining a phase delay for the reflected light based on the phase measurement.

13. The method of claim 12, further comprising:

detecting at least one of a position or presence of the object based on the phase delay.

14. An apparatus, comprising:

an integrated circuit (IC) chip having at least one sense pin;

the IC for sensing an electrical signal for driving a light emitting diode (LED);

an attenuator that provides an attenuated version of the sensed signal;

a switch that selectively coupling the attenuator with a sensor front end; and

the sensor front end that calculates a phase error introduced in a signal path traversed by the electrical signal, based on the attenuated version of the sensed driver signal.

15. The apparatus of claim 14, further comprising:

a resistor externally connected to the at least one sense pin.

16. The apparatus of claim 14, wherein the attenuator is a V/I (voltage to current) attenuator or an I/I (current to current) attenuator.

17. The apparatus of claim 14, wherein the switch provides the attenuated version of the signal to the sensor front end, during a calibration mode.

18. The apparatus of claim 14, wherein the switch provides a signal received from an optical sensor to the sensor front end, during a normal operation mode.

19. The apparatus of claim 18, wherein the sensor front end calculates a phase delay based on the signal received from the optical sensor.

20. The apparatus of claim 19, wherein the sensor front end automatically corrects the phase delay based on the phase error, wherein the corrected phase delay is utilized to identify at least one of proximity or motion of an object.