Optical Three-Dimensional Coordinate Sensor System and Method Thereof

• US 20120013486A1
• Filed: 07/19/2010
• Published: 01/19/2012
• Est. Priority Date: 07/19/2010
• Status: Active Grant

• Current Assignee: National Chiao Tung University (Government of The Republic of China)
• Original Assignee: National Chiao Tung University (Government of The Republic of China)
• Inventors: Chao, Paul C.P., Lin, Tzu-Yang, Chen, Wei-Dar
• Granted Patent: US 8,513,585 B2
• Time in Patent Office: Days
• US Class Current: 341/13
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• 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 17/943 using a plurality of optical emitters or detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/94108 making use of reflection
• CPC Class Codes: H03K 2217/94111 having more than one emitter
• CPC Class Codes: H03K 2217/94112 having more than one receiver

Abstract

The present invention relates an optical three-dimensional coordinate sensor system and method thereof. A plurality of light-emitting modules produce a plurality of light signals, and then a plurality of reflected light signals reflected by an object are received by a plurality of photodetectors. After receiving the reflected light signals, the photodetectors generate a plurality of photocurrents. A plurality of active pixel circuits receive the photocurrents and transform the photocurrents to a plurality of reflective optical voltages. A plurality of differential amplifier circuits (DAC) compare the reflective optical voltages and the background voltages, and then output a plurality of DAC output voltages of the reflected light signals. Afterward, a processing module detects the DAC output voltages and uses an algorithm to calculate the top three of the DAC output voltages to determine the three-dimensional coordinate of the object.

Claims

1. An optical three-dimensional coordinate sensor system, comprising:

a plurality of light-emitting modules emitting a plurality of light signals to an object;

a plurality of sensing modules, comprising;

a plurality of photodetectors receiving a plurality of reflected light signals reflected by the object to generate a plurality of photocurrents;

a plurality of active pixel circuits (APCs) connected to the photodetectors for receiving the photocurrents and transforming the photocurrents to a plurality of reflective optical voltages, each of the APCs comprising at least one active transistor within a pixel unit cell;

a plurality of sampling circuits connected to the APCs for sampling and storing the reflective optical voltages, each of the sampling circuits comprising a sampling transistor and a capacitor; and

a plurality of differential amplifier circuits (DACs) connected to the sampling circuits for receiving the reflective optical voltages, each of the DACs subtracting the reflective optical voltage from a background voltage and multiplying a differential gain thereto, the DACs outputting a plurality of DAC output voltages of the reflected light signals; and

a processing module connected to the sensing modules for detecting the DAC output voltages and using an algorithm to calculate top three of the DAC output voltages to determine a three-dimensional coordinate of the object.

2. The optical three-dimensional coordinate sensor system as claimed in claim 1, wherein each of the APCs is a 2-transistor-APC (2T-APC), the 2T-APC comprising a reset transistor, a row select transistor and a storage capacitor;

a source of the reset transistor is connected to a Vdd, a drain of the reset transistor is connected to a drain of the row select transistor, and a source of the row select transistor is connected to the storage capacitor.

3. The optical three-dimensional coordinate sensor system as claimed in claim 2, wherein the reset transistor and the row select transistor are PMOS transistors.

4. The optical three-dimensional coordinate sensor system as claimed in claim 2, wherein the 2T-APC operates in a plurality of modes sequentially.

5. The optical three-dimensional coordinate sensor system as claimed in claim 4, wherein the plurality of modes comprise a reset mode, in which the reset transistor is switched ON and pre-charges a node Va to 3.3V;

also, the row select transistor is switched ON.

6. The optical three-dimensional coordinate sensor system as claimed in claim 5, wherein the plurality of modes comprise an integration mode, in which the reset transistor is switched OFF and the node Va drops because of a plurality of photo-carriers discharging a photocurrent capacitor C_PD.

7. The optical three-dimensional coordinate sensor system as claimed in claim 6, wherein the plurality of modes comprise a readout mode, in which the row select transistor is switched OFF and an output voltage of the row select transistor is readout.

8. The optical three-dimensional coordinate sensor system as claimed in claim 1, wherein each of the sensing modules is a 3×

3 polymer photo-detector (PPD) array to realize the determination of the three-dimensional coordinate of the object.

9. The optical three-dimensional coordinate sensor system as claimed in claim 1, wherein the light-emitting modules are a plurality of light-emitting diodes (LEDs).

10. The optical three-dimensional coordinate sensor system as claimed in claim 8, wherein a radiant flux detected by the PPD is proportional to cos θ

×

Ω

, where Ω

=A_PPD cos θ

/[d²+(x−

x*)²+(y−

y*)²] is a solid angle spanned by the PPD to the object, d is a distance between the object and the PPD, θ

is an angle between the PPD and the object, A_PPD is an area of the PPD pixel, and α

is a proportionality factor.

11. The optical three-dimensional coordinate sensor system as claimed in claim 10, wherein the photocurrent is proportional to the radiant flux, and the photocurrent satisfies the following condition:

12. The optical three-dimensional coordinate sensor system as claimed in claim 11, wherein the top three of the DAC output voltages satisfy the following condition:

13. An optical three-dimensional coordinate sensing method, comprising the following steps:

emitting a plurality of light signals to an object by a plurality of light-emitting modules;

receiving a plurality of reflected light signals reflected by the object and generating a plurality of photocurrents by a plurality of photodetectors;

receiving the photocurrents and transforming the photocurrents to a plurality of reflective optical voltages by a plurality of active pixel circuits (APCs);

sampling and storing the reflective optical voltages by a plurality of sampling circuits;

subtracting the reflective optical voltages from a plurality of background voltages and multiplying differential gains thereto to output a plurality of differential amplifier circuit (DAC) output voltages of the reflected light signals by a plurality of differential amplifier circuits (DACs); and

detecting the DAC output voltages and using an algorithm by a processing module to calculate top three of the DAC output voltages to determine a three-dimensional coordinate of the object.

14. The optical three-dimensional coordinate sensing method as claimed in claim 13, wherein the step of receiving the photocurrents and transforming the photocurrents further comprises the following step:

providing a 2-transistor-APC (2T-APC) to operate in a plurality of modes sequentially.

15. The optical three-dimensional coordinate sensing method as claimed in claim 14, wherein the plurality of modes comprise a reset mode, in which the reset transistor is switched ON and pre-charges a node Va to 3.3V;

also, the row select transistor is switched ON.

16. The optical three-dimensional coordinate sensing method as claimed in claim 15, wherein the plurality of modes comprise an integration mode, in which the reset transistor is switched OFF and the node Va drops because of a plurality of photo-carriers discharging a photocurrent capacitor C_PD.

17. The optical three-dimensional coordinate sensing method as claimed in claim 16, wherein the plurality of modes comprise a readout mode, in which the row select transistor is switched OFF and an output voltage of the row select transistor is readout.

18. The optical three-dimensional coordinate sensing method as claimed in claim 13, wherein the step of calculating the three-dimensional coordinate further comprises the following step:

detecting a radiant flux by a polymer photo-detector (PDD), the radiant flux being proportional to cos θ

×

Ω

, wherein Ω

=A_PPD cos θ

/[d²+(x−

x*)²+(y−

y*)²] is a solid angle spanned by the PPD to the object, d is a distance between the object and the PPD, 0 is an angle between the PPD and the object, A_PPD is an area of the PPD pixel, and α

is a proportionality factor.

19. The optical three-dimensional coordinate sensing method as claimed in claim 18, wherein the photocurrent is proportional to the radiant flux, and the photocurrent satisfies the following condition:

20. The optical three-dimensional coordinate sensing method as claimed in claim 19, wherein the top three of the DAC output voltages satisfy the following condition: