Optical finger navigation module for extreme temperature operation and method for increasing life time of OFN module

• US 9,778,786 B1
• Filed: 03/21/2016
• Issued: 10/03/2017
• Est. Priority Date: 03/21/2016
• Status: Active Grant

• Current Assignee: Cloud Light Technology Limited
• Original Assignee: SAE Magnetics Limited (TDK Corporation)
• Inventors: Tong, Ka Lap, Hung, Vincent Wai
• Primary Examiner(s): SHERMAN, STEPHEN G
• Application Number:
  US15/076,646
• Publication Number:
  US 20170269760A1
• Time in Patent Office: 561 Days
• Field of Search: 345174, 345175
• CPC Class Codes: G01K 1/14 Supports; Fastening devices; Arrangements for mounting thermometers in particular locations
• CPC Class Codes: G01K 13/00 Thermometers specially adapted for specific purposes
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/0425 using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected tracking a projected light spot to determine a position on a display surface G06F3/0386

Abstract

An optical finger navigation module includes a light source mounted below a window plate formed on a housing of the module, a driver for outputting a current to the light source, an environmental sensor for sensing an environmental condition and providing a signal, and a sensor integrated circuit including a processor coupled with the environmental sensor for reading the signal and generating a compensated current that corresponds to the signal based on a compensation curve tailor-made for the light source and derived from a compensation algorithm using compensation factors. A method for increasing lifetime of the module is also disclosed.

Claims

1. An optical finger navigation module for extreme temperature operation, the module comprising:

(a) a housing comprising a top window plate and a bottom electrical substrate;

(b) a light source mounted below the top window plate;

(c) a transmitter driver for outputting a current to the light source;

(d) a photodetector and a digital signal processor for capturing and processing light signals from the light source respectively;

(e) a temperature sensor mounted on the bottom electrical substrate for sensing an ambient temperature and providing a temperature signal;

(f) a sensor integrated circuit comprising a main processor coupled with the temperature sensor for reading the temperature signal and generating a compensated current that corresponds to the temperature signal based on a compensation curve tailor-made for the light source and derived from a temperature compensation algorithm using a plurality of compensation factors;

(g) a memory coupled with the main processor for storing the compensation factors; and

(h) a capacitance sensing circuit for sensing a tracking object on top of the window plate;

(i) wherein the plurality of compensation factors comprises a high temperature factor and a low temperature factor, and each factor comprises an end-point compensation current and a mid-point compensation current, and a maximum end-point compensation current is determined by a capacity of the transmitter driver for driving the light source.

2. An optical finger navigation module comprising:

(a) a light source mounted below a window plate formed on a housing of the module;

(b) a transmitter driver for outputting a current to the light source;

(c) an environmental sensor mounted inside the housing for sensing an environmental condition and providing a signal representing the environmental condition; and

(d) a sensor integrated circuit comprising a main processor coupled with the environmental sensor for reading the signal and generating a compensated current that corresponds to the signal based on a compensation curve tailor-made for the light source and derived from a compensation algorithm using a plurality of compensation factors;

(e) wherein the environmental sensor is a temperature sensor for sensing an ambient temperature;

(f) wherein the plurality of compensation factors comprises a high temperature factor and a low temperature factor, and each factor comprises an end-point compensation current and a mid-point compensation current, and a maximum end-point compensation current is determined by a capacity of the transmitter driver for driving the light source.

3. The optical finger navigation module as claimed in claim 2, wherein the main processor is coupled with the environmental sensor via an I/O interface.

4. The optical finger navigation module as claimed in claim 2, further comprising a photodiode array and a digital signal processor for capturing and processing light signals from the light source respectively after detection of a tracking surface on the window plate.

5. The optical finger navigation module as claimed in claim 2, further comprising a memory coupled with the main processor for storing the plurality of compensation factors, each compensation factor having a memory usage of 1-2 bytes.

6. The optical finger navigation module as claimed in claim 2, further comprising an apertured sensor cover for covering the sensor integrated circuit.

7. The optical finger navigation module as claimed in claim 2, further comprising a proximity sensor for detecting a tracking object on top of the window plate.

8. The optical finger navigation module as claimed in claim 7, wherein the proximity sensor is a piezoelectric force sensor in the form of a sensing film disposed underneath a bottom electrical substrate of the module.

9. The optical finger navigation module as claimed in claim 8, wherein the piezoelectric force sensing film is electrically coupled with the electrical substrate via an electrical connection.

10. The optical finger navigation module as claimed in claim 7, wherein the proximity sensor is a capacitance sensor for detecting a capacitance change on the module using a capacitance sensing circuit.

11. The optical finger navigation module as claimed in claim 10, wherein the capacitance sensing circuit comprises a metal coating coated on an inner surface of the housing between the window plate and a bottom electrical substrate on which the light source, the environmental sensor and the sensor integrated circuit are mounted.

12. The optical finger navigation module as claimed in claim 11, wherein the metal coating is formed by physical vapor deposition, or sputtering and electro-plating deposition.

13. The optical finger navigation module as claimed in claim 2, wherein the environmental sensor is integrated into the sensor integrated circuit.

14. A method for increasing life time of an optical finger navigation module by minimizing operation time of a light source and compensating for environment variation in the optical finger navigation module having a light source and a transmitter driver for outputting a current to the light source, the method comprising:

(a) providing an environmental sensor inside a housing of the module for sensing an environmental condition;

(b) reading a signal provided by the environmental sensor that represents the environmental condition;

(c) generating a compensated current that corresponds to the signal based on a compensation curve tailor-made for the light source and derived from a compensation algorithm using a plurality of compensation factors; and

(d) controlling the transmitter driver to output the compensated current to the light source;

(e) wherein the environmental sensor is a temperature sensor;

(f) wherein the plurality of compensation factors comprises a high temperature factor and a low temperature factor, and each factor comprises an end-point compensation current and a mid-point compensation current, and a maximum end-point compensation is determined by a capacity of the transmitter driver for driving the light source.

15. The method as claimed in claim 14, further comprising:

(a) characterizing the light source at different temperatures;

(b) determining a current compensation for each temperature and producing an actual current value from the current compensation;

(c) translating the actual current value into a compensation factor; and

(d) storing the compensation factor in a memory using 1-2 bytes.

16. The method as claimed in claim 14, further comprising preparing and storing one tailor-made compensation curve for each kind of light source.

17. The method as claimed in claim 14, further comprising providing a proximity sensor for sensing a tracking object when it is placed on top of a window plate formed on the housing of the module.

18. The method as claimed in claim 17, wherein the proximity sensor is a piezoelectric force sensor in the form of a sensing film disposed underneath the housing of the module.

19. The method as claimed in claim 17, wherein the proximity sensor is a capacitance sensor for detecting a capacitance change on the module using a capacitance sensing circuit, the capacitance sensing circuit comprising a metal coating deposited on an inner surface of the housing of the module.