Laser Power Calibration in an Optical Disc Drive

Abstract

Various systems, methods, and programs embodied on a computer-readable medium are provided for calibrating a laser power in an optical disc drive. In one embodiment, a range of reflectivity of an optical disc in the optical disc drive is established. A calibration pattern of marked segments is written to the optical disc and the reflectivity of the marked segments is measured. An average reflectivity is generated for each one of a plurality of laser power settings within the range of reflectivity, thereby obtaining a curve that depicts the average reflectivity with respect to the laser power settings. The laser power setting at a knee of the curve is identified and a slope of the curve at a position on the curve where the average reflectivity decreases as the laser power settings increase is determined. The laser power setting is calculated that results in a predefined darkness based upon the laser power setting at the knee and based upon the slope.

1 - 49 . (canceled) 
   
   
       50 . A method for calibrating an optical disc drive, comprising the steps of:
 writing a calibration pattern of marked segments to an optical disc;   measuring at least one reflectivity of the marked segments for each one of a plurality of laser power settings, thereby obtaining a curve that depicts the reflectivity with respect to the laser power settings using the at least one reflectivity for each one of the laser power settings;   identifying the laser power setting at a knee of the curve; and   calibrating the optical disc drive based at least in part upon the laser power setting at the knee.   
   
   
       51 . The method of  claim 50 , wherein the step of identifying the laser power setting at the knee of the curve further comprises the steps of:
 detecting at least one of the reflectivities that falls to the right of the knee of the curve; and   detecting at least one of the reflectivities that falls to the left of the knee of the curve.   
   
   
       52 . The method of  claim 50 , further comprising the steps of setting the laser power setting at a value relative to the location of the knee of the curve to write a label on an optical disc. 
   
   
       53 . The method of  claim 50 , further comprising the steps of:
 determining a slope of the curve at a position on the curve where the reflectivity decreases as the laser power settings increase; and   identifying the laser power setting at an ankle of the curve; and   wherein the step of determining the slope of the curve further comprises determining the slope of the curve between the knee and the ankle.   
   
   
       54 . The method of  claim 50 , wherein the step of writing the calibration pattern of marked segments to the optical disc further comprises writing an array of marked segments to the optical disc, wherein the array of marked segments includes marked segments written by the laser at multiple laser power settings. 
   
   
       55 . The method of  claim 54 , wherein the array of marked segments is written in a stair step configuration. 
   
   
       56 . The method of  claim 50 , further comprising the step of adjusting the at least one reflectivity of the marked segments to account for noise due to process variation in a coating on a label surface of an optical disc. 
   
   
       57 . A laser power calibration system for calibrating an optical disc drive, comprising:
 a processor circuit having a processor and a memory;   a laser operatively coupled to the processor circuit, the laser being adapted to write a label to a label surface of an optical disc placed in the optical disc drive;   a sensor operatively coupled to the processor circuit, the sensor being adapted to measure a reflectivity at designated segments on the optical disc;   a laser power calibration system stored in the memory and executable by the processor, the laser power calibration system comprising:   logic that writes a calibration pattern of marked segments to the label surface of the optical disc;   logic that measures at least one reflectivity of the marked segments for each one of a plurality of laser power settings, thereby obtaining a curve that depicts the reflectivity with respect to the laser power settings using the at least one reflectivity for each one of the laser power settings;   logic that identifies the laser power setting at a knee of the curve; and   logic that calibrates the optical disc drive based at least in part upon the laser power setting at the knee.   
   
   
       58 . The laser power calibration system of  claim 57 , wherein the laser power calibration system further comprises logic that sets the laser power setting at a value relative to the location of the knee of the curve to write the label to the label surface of the optical disc. 
   
   
       59 . A method for calibrating an optical disc drive, comprising the steps of:
 writing a calibration pattern of marked segments to an optical disc;   measuring a reflectivity of each of the marked segments;   generating an average reflectivity for each one of a plurality of laser power settings, thereby obtaining a curve that depicts the average reflectivity with respect to the laser power settings;   identifying the laser power setting at a knee of the curve; and   calibrating the optical disc drive based at least in part upon the laser power setting at the knee.   
   
   
       60 . The method of  claim 59 , wherein the step of identifying the laser power setting at the knee of the curve further comprises the steps of:
 detecting at least one of the average reflectivities that falls to the right of the knee of the curve; and   detecting at least one of the average reflectivities that falls to the left of the knee of the curve.   
   
   
       61 . The method of  claim 59 , further comprising the steps of setting the laser power setting at a value relative to the location of the knee of the curve to write a label on an optical disc. 
   
   
       62 . The method of  claim 59 , further comprising the steps of:
 determining a slope of the curve at a position on the curve where the average reflectivity decreases as the laser power settings increase; and   identifying the laser power setting at an ankle of the curve; and   wherein the step of determining the slope of the curve further comprises determining the slope of the curve between the knee and the ankle.   
   
   
       63 . The method of  claim 59 , wherein the step of writing the calibration pattern of marked segments to the optical disc further comprises writing an array of marked segments to the optical disc, wherein the array of marked segments includes marked segments written by the laser at multiple laser power settings. 
   
   
       64 . The method of  claim 63 , wherein the array of marked segments is written in a stair step configuration. 
   
   
       65 . The method of  claim 59 , further comprising the step of adjusting the reflectivity of each of the marked segments to account for noise due to process variation in a coating on a label surface of an optical disc. 
   
   
       66 . A laser power calibration system for calibrating an optical disc drive, comprising:
 a processor circuit having a processor and a memory;   a laser operatively coupled to the processor circuit, the laser being adapted to write a label to a label surface of an optical disc placed in the optical disc drive;   a sensor operatively coupled to the processor circuit, the sensor being adapted to measure a reflectivity at designated segments on the optical disc;   a laser power calibration system stored in the memory and executable by the processor, the laser power calibration system comprising:
 logic that writes a calibration pattern of marked segments to the label surface of the optical disc; 
 logic that measures the reflectivity of each of the marked segments; 
 logic that generates an average reflectivity for each one of a plurality of laser power settings, thereby obtaining a curve that depicts the average reflectivity with respect to the laser power settings; 
 logic that identifies the laser power setting at a knee of the curve; and 
 logic that calibrates the optical disc drive based at least in part upon the laser power setting at the knee. 
   
   
   
       67 . The laser power calibration system of  claim 66 , wherein the logic that identifies the laser power setting at the knee of the curve further comprises:
 logic that detects at least one of the average reflectivities that falls to the right of the knee of the curve; and   logic that detects at least one of the average reflectivities that falls to the left of the knee of the curve.   
   
   
       68 . The laser power calibration system of  claim 66 , wherein the laser power calibration system comprising further comprises logic that sets the laser power setting at a value relative to the location of the knee of the curve to write a label on an optical disc. 
   
   
       69 . The laser power calibration system of  claim 66 , wherein the laser power calibration system comprising further comprises:
 logic that determines a slope of the curve at a position on the curve where the average reflectivity decreases as the laser power settings increase; and   logic that identifies the laser power setting at an ankle of the curve; and   wherein the logic that determines the slope of the curve further comprises determines the slope of the curve between the knee and the ankle.   
   
   
       70 . The laser power calibration system of  claim 66 , wherein the laser power calibration system comprising further comprises logic that adjusts the reflectivity of each of the marked segments to account for noise due to process variation in a coating on the label surface of the optical disc.