Laser navigation sensor

• US 7,742,514 B1
• Filed: 10/31/2006
• Issued: 06/22/2010
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Sanders, Steven
• Primary Examiner(s): Harvey, Minsun
• Assistant Examiner(s): Stafford, Patrick
• Application Number:
  US11/591,015
• Time in Patent Office: 1,330 Days
• Field of Search: 372/38.02, 372/38.01, 372/38.07
• US Class Current: 372/38.02
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261

Abstract

The apparatus includes a diode laser, a current source interconnected with the diode laser, and four limiting circuits. The first limiting circuit limits peak current flowing to an anode connection of the diode laser. The second limiting circuit limits peak current flowing from a cathode connection of the diode laser, wherein the first and second limiting circuits are independent from each other. The third limiting circuit limits average current flowing through the diode laser. Finally, the fourth limiting circuit limits average current flowing through the diode laser, wherein the third and fourth limiting circuits are independent from each other. Other embodiments and features are also disclosed.

Claims

1. An apparatus comprising:

a diode laser;

a current source interconnected with the diode laser;

a first limiting circuit in the current source configured to monitor and limit peak current flowing to an anode connection of the diode laser;

a second limiting circuit in the current source configured to monitor and limit peak current flowing from a cathode connection of the diode laser, wherein the second limiting circuit is independent from the first limiting circuit;

a third limiting circuit in the current source configured to monitor and limit average current flowing through the diode laser; and

a fourth limiting circuit in the current source configured to monitor and limit average current flowing through the diode laser, wherein the fourth limiting circuit is independent from the third limiting circuit.

2. The apparatus of claim 1, further comprising:

a first register configured to hold peak current limit data to be applied by the first limiting circuit to configure the first limiting circuit to limit peak current flowing to the anode connection to maintain eye-safe operation;

a second register configured to hold peak current limit data to be applied by the second limiting circuit to configure the second limiting circuit to limit peak current flowing from the cathode connection to maintain eye-safe operation; and

a third register being configured to hold average current limit data to be applied by the third limiting circuit.

3. The apparatus of claim 2, wherein the first limiting circuit comprises a first current limiter circuit, the second limiting circuit comprises a second current limiter circuit, and the third limiting circuit comprises a first switch circuit.

4. The apparatus of claim 3, wherein the first current limiter circuit receives a first analog control signal from a first digital-to-analog converter coupled to the first register, and the second current limiter circuit receives a second analog control signal from a second digital-to-analog converter coupled to the second register.

5. The apparatus of claim 4, further comprising:

an average current monitor circuit coupled in between the first current limiter circuit and the laser diode, wherein the first switch circuit is controlled by two control signals, the two control signals being a third analog control signal from a third digital-to-analog converter coupled to the third register and a fourth analog control signal received from the average current monitor circuit.

6. The apparatus of claim 5, wherein the fourth circuit includes modulation control circuitry and a second switch circuit which is controlled by said modulation control circuitry.

7. The apparatus of claim 6, further comprising register setting and checking circuitry that is configured to dynamically modify and verify the data in said three registers based on a time-dependent duty cycle of a control signal from the modulation control circuitry.

8. The apparatus of claim 2, further comprising:

a first temperature sensor configured to monitor changes in operating temperature;

a first compensation circuit controlled by an output signal from the first temperature sensor and configured to modify the peak current limit data read from the first register and to modify the average current limit data read from the third register;

a second temperature sensor configured to monitor changes in operating temperature; and

a second compensation circuit controlled by an output signal from the second temperature sensor and configured to modify the peak current limit data read from the second register.

9. The apparatus of claim 2, further comprising:

a first supply voltage sensor configured to monitor changes in power supply voltage;

a first compensation circuit controlled by an output signal from the first supply voltage sensor and configured to modify the peak current limit data read from the first register and to modify the average current limit data read from the third register;

a second supply voltage sensor configured to monitor changes in the power supply voltage; and

a second compensation circuit controlled by an output signal from the second supply voltage sensor and configured to modify the peak current limit data read from the second register.

10. The apparatus of claim 1, wherein the current source is manufactured on a single silicon die.

11. A method comprising:

emitting laser light from a laser device;

providing current to and receiving current from the laser device;

monitoring and limiting peak current flowing to an anode connection of the laser device;

monitoring and limiting peak current flowing from a cathode connection of the laser device in an independent manner from said limiting of peak current flowing to the anode connection;

monitoring and limiting time-averaged current flowing to the anode connection of the laser device; and

monitoring and limiting time-averaged current flowing from the cathode connection of the laser device in an independent manner from said limiting of time averaged current flowing to the anode connection.

12. The method of claim 11, further comprising:

holding peak current limit data in a first register to configure a first current limiter to limit the peak current flowing to the anode connection to maintain eye-safe operation; and

holding peak current limit data in a second register to configure a second current limiter to limit the peak current flowing from the cathode connection to maintain eye-safe operation; and

holding average current limit data in a third register to be applied by a first switch to limit the time-averaged current flowing to the anode connection.

13. The method of claim 12, further comprising converting the data from the registers to analog signals.

14. The method of claim 13, further comprising:

controlling the first switch circuit by comparing two control signals, the two control signals being an analog control signal derived from the data in the third register and another analog control signal received from an average current monitor circuit.

15. The method of claim 14, dynamically modifying and verifying the data in said three registers based on a time-dependent duty cycle of a control signal from modulation control circuitry.

16. The method of claim 12, further comprising:

monitoring changes in operating temperature by a first temperature sensor;

modifying the peak current limit data read from the first register and the average current limit data read from the third register based on an output signal from the first temperature sensor;

monitoring changes in operating temperature by a second temperature sensor; and

modifying the peak current limit data read from the second register based on an output signal from the second temperature sensor.

17. The method of claim 12, further comprising:

monitoring changes in supply voltage by a first supply voltage sensor;

modifying the peak current limit data read from the first register and the average current limit data read from the third register based on an output signal from the first supply voltage sensor;

monitoring changes in supply voltage by a second supply voltage sensor; and

modifying the peak current limit data read from the second register based on an output signal from the second supply voltage sensor.

18. An integrated circuit comprising:

a first limiting circuit in the current source configured to monitor and limit average current flowing through the diode laser; and

a second limiting circuit in the current source configured to monitor and limit average current flowing through the diode laser, wherein the second limiting circuit is independent from the first limiting circuit.

19. The integrated circuit of claim 18, wherein the first limiting circuit comprises a first switch, and further comprising a third register configured to hold average current limit data to be applied by the first switch.

20. The integrated circuit of claim 19, wherein the second limiting circuit comprises a second switch, and further comprising modulation control circuitry which controls said second switch.