System and method for screening semiconductor lasers
View Patent ↗A system and method are provided for screening a semiconductor laser. The method includes: (i) operating the laser at a first of a number of drive currents; (ii) acquiring a number (N) of frames of data from a sensor in an optical navigation system (ONS) receiving speckle pattern in light from the laser reflected from a surface proximal to the ONS, the sensor data including differential signal values; (iii) calculating an average differential signal value (AVG) for the N frames of data; (iv) sorting the N frames of data across a plurality of bins including a Bin_0 for frames of data having a differential signal value within a predetermined amount of the AVG; and (v) determining if a number of frames of data in any bins other than Bin_0 exceed a predetermined threshold, and if so recording the drive current.
1. A method of screening a semiconductor laser comprising:
(a) operating the laser at a first of a number (D) of discrete drive currents in a range of drive currents;
(b) acquiring a number (N) of frames of data from a sensor in an optical navigation system (ONS) receiving speckle pattern in light from the laser reflected from a surface proximal to the ONS, the sensor data including differential signal values;
(c) calculating an average differential signal value (AVG value) for the N frames of data;
(d) sorting the N frames of data across a plurality of bins, the plurality of bins including at least a Bin — 0 for frames of data having a differential signal value within a predetermined amount of the AVG value; and
(e) determining if a number of frames of data in any of the plurality of bins other than Bin — 0 exceed a predetermined threshold, and if the number of frames of data in any of the plurality of bins exceed the predetermined threshold, recording the drive current.
2. A method according to claim 1 , wherein if the laser drive current is less than a predetermined maximum in the range of drive currents increasing the drive current to another of the number (D) of discrete drive currents repeating (b) through (e) until drive current equals the predetermined maximum.
3. A method according to claim 2 , further comprising determining from the recorded drive currents an state of polarization (SOP) unstable zone.
4. A method according to claim 3 , further comprising programming a controller in the ONS to drive the laser in a drive current range outside of the SOP unstable zone.
5. A method according to claim 4 , further comprising determining the drive current range is below a predetermined maximum.
6. A method according to claim 3 , further comprising repeating (b) through (e) until over a predetermined range of ambient temperatures to determine the SOP unstable zone over the range of ambient temperatures.
7. A method according to claim 1 , further comprising calculating a root mean square (RMS) value of the differential signal values for the N frames of data at each drive current, and determining a state of polarization (SOP) unstable zone from the RMS value.
8. A method according to claim 1 , wherein there is movement between the ONS and the surface during data acquisition.
9. A computer-readable medium, containing a set of instructions that causes a computer to perform a process comprising:
(a) operating a laser for use in an optical navigation system (ONS) at a first of a number (D) of discrete drive currents in a range of drive currents;
(b) acquiring a number (N) of frames of data from a sensor in an optical navigation system (ONS) receiving speckle pattern in light from the laser reflected from a surface proximal to the ONS, the sensor data including differential signal values;
(c) calculating an average differential signal value (AVG value) for the N frames of data;
(d) sorting the N frames of data across a plurality of bins, the plurality of bins including at least a Bin — 0 for frames of data having a differential signal value within a predetermined amount of the AVG value; and
(e) determining if a number of frames of data in any of the plurality of bins other than Bin — 0 exceed a predetermined threshold, and if the number of frames of data in any of the plurality of bins exceed the predetermined threshold, recording the drive current.
10. A computer-readable medium according to claim 9 , wherein if the laser drive current is less than a predetermined maximum in the range of drive currents the process further comprises increasing the drive current to another of the number (D) of discrete drive currents repeating (b) through (e) until drive current equals the predetermined maximum.
11. A computer-readable medium according to claim 10 , wherein the process further comprises determining from the recorded drive currents a state of polarization (SOP) unstable zone.
12. A computer-readable medium according to claim 11 , wherein the process further comprises programming a controller in the ONS to drive the laser in a drive current range outside of the SOP unstable zone.
13. A computer-readable medium according to claim 12 , wherein the process further comprises determining the drive current range is below a predetermined maximum.
14. A computer-readable medium according to claim 11 , wherein the process further comprises repeating (b) through (e) until over a predetermined range of ambient temperatures to determine the SOP unstable zone over the range of ambient temperatures.
15. A computer-readable medium according to claim 9 , wherein the process further comprises calculating a root mean square (RMS) value of the differential signal values for the N frames of data at each drive current, and determining a state of polarization (SOP) unstable zone from the RMS value.
16. A system for screening a semiconductor laser comprising:
a laser driver configured to operate the laser at a first of a number (D) of discrete drive currents in a range of drive currents;
a sensor array configured to receive a speckle pattern in light from the laser reflected from a surface proximal to the sensor array and generate differential signal values in response thereto; and
a computer configured to:
(a) acquire a number (N) of frames of data from the sensor array, the data including differential signal values;
(b) calculate an average differential signal value (AVG value) for the N frames of data;
(c) sort the N frames of data across a plurality of bins, the plurality of bins including at least a Bin — 0 for frames of data having a differential signal value within a predetermined amount of the AVG value;
(d) determine if a number of frames of data in any of the plurality of bins other than Bin — 0 exceed a predetermined threshold, and if the number of frames of data in any of the plurality of bins exceed the predetermined threshold record the drive current.
17. A system according to claim 16 , wherein the computer is further configured to determine if the laser drive current is less than a predetermined maximum in the range of drive currents, increase the drive current to another of the number (D) of discrete drive currents and repeating (a) through (d) until drive current equals the predetermined maximum.
18. A system according to claim 17 , wherein the computer is further configured to determine from the recorded drive currents a state of polarization (SOP) unstable zone, and to program a controller in the laser driver to drive the laser in a drive current range outside of the SOP unstable zone.
19. A system according to claim 16 , wherein the computer is further configured to calculate a root mean square (RMS) value of the differential signal values for the N frames of data at each drive current, and determining a state of polarization (SOP) unstable zone from the RMS value.
20. A system according to claim 16 , further comprising a number of actuators to provide relative motion between the sensor array and the surface during data acquisition.