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

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.