Laser power control apparatus

Abstract

In a laser power control apparatus for controlling a laser power of a combination drive, first laser light Lc applied onto a first optical disk and second laser light Ld applied onto a second optical disk is collected by one photodetector 8.

1 . A laser power control apparatus for controlling an output of laser light which is exclusively applied onto a first optical disk and a second optical disk in a combination drive to record or read information thereon or therefrom, the apparatus comprising: 
 first laser light generating means for generating first laser light to be applied onto the first optical disk;    first drive current generating means for generating a drive current of the first laser light generating means;    second laser light generating means for generating second laser light to be applied onto the second optical disk;    second drive current generating means for generating a drive current of the second laser light generating means;    laser light intensity detection means for exclusively collecting the first laser light and the second laser light and generating a first laser light intensity signal which indicates an intensity of the collected laser light;    first laser light generating current control means for controlling the first laser light generating means based on the first laser light intensity signal; and    second laser light generating current control means for controlling the second laser light generating means based on the first laser light intensity signal.    
   
   
       2 . The laser power control apparatus according to  claim 1 , wherein the first laser light generating current control means includes: 
 first variable gain means for amplifying the first laser light intensity signal with a first predetermined gain, so as to offset a difference in intensity between the first laser light and the second laser light.    
   
   
       3 . The laser power control apparatus according to  claim 2 , wherein the first laser light generating current control means further includes first offset adjusting means for offset adjusting the first laser light intensity signal with a first predetermined offset value, so as to further offset a difference in intensity between the first laser light and the second laser light.  
   
   
       4 . The laser power control apparatus according to  claim 1 , wherein the second laser light generating current control means includes second variable gain means for amplifying the first laser light intensity signal with a second predetermined gain, so as to offset a difference in intensity between the first laser light and the second laser light.  
   
   
       5 . The laser power control apparatus according to  claim 4 , wherein the second laser light generating current control means further includes second offset adjusting means for offset adjusting the first laser light intensity signal with a second predetermined offset value, so as to further offset a difference in intensity between the first laser light and the second laser light.  
   
   
       6 . The laser power control apparatus according to  claim 4 , wherein the second laser light generating current control means includes an operational amplifier for amplifying the first laser light intensity signal having been amplified with the second predetermined gain, based on a difference between the amplified first laser light intensity signal and a first predetermined reference potential.  
   
   
       7 . The laser power control apparatus according to  claim 6 , wherein the first predetermined reference potential is variable.  
   
   
       8 . The laser power control apparatus according to  claim 1 , wherein the second laser light generating current control means controls the second laser light generating means based on the laser light intensity signal having been offset adjusted.  
   
   
       9 . The laser power control apparatus according to  claim 8 , wherein the second laser light generating current control means includes second variable gain means for amplifying the laser light intensity signal having been offset adjusted, with a second predetermined gain.  
   
   
       10 . The laser power control apparatus according to  claim 9 , wherein the second laser light generating current control means includes an operational amplifier for amplifying the laser light intensity signal having been amplified with the second predetermined gain, based on a different between the amplified laser light intensity signal and a second predetermined reference potential.  
   
   
       11 . The laser power control apparatus according to  claim 10 , wherein the second predetermined reference potential is variable.  
   
   
       12 . The laser power control apparatus according to  claim 2 , wherein the second laser light generating current control means includes an operational amplifier for amplifying a laser light intensity signal having been amplified with the first predetermined gain, based on a difference between the amplified first laser light intensity signal and a second predetermined reference potential.  
   
   
       13 . The laser power control apparatus according to  claim 12 , wherein the second predetermined reference potential is variable.  
   
   
       14 . The laser power control apparatus according to  claim 2 , wherein 
 the first laser light generating current control means further includes:    a sample/hold circuit for sampling and holding the first laser light intensity signal having been amplified with the first predetermined gain, and    an operational amplifier amplifies the sampled and held first laser light intensity signal based on a difference between the sampled and held first laser light intensity signal and a second predetermined reference potential.    
   
   
       15 . The laser power control apparatus according to  claim 14 , wherein the second predetermined reference potential is variable.  
   
   
       16 . The laser power control apparatus according to  claim 1 , wherein the second drive current generating means is controlled by the first laser light generating current control means.  
   
   
       17 . The laser power control apparatus according to  claim 16 , wherein the first laser light generating current control means further includes a polarity reverser for reversing a polarity of the first laser light intensity signal.  
   
   
       18 . The laser power control apparatus according to  claim 12 , wherein a polarity of the operational amplifier is variable.  
   
   
       19 . The laser power control apparatus according to  claim 12 , wherein a polarity of the operational amplifier is variable at a predetermined timing.  
   
   
       20 . The laser power control apparatus according to  claim 1 , further comprising: 
 second laser light intensity detection means for collecting the second laser light and generating a second laser light intensity signal;    a first sample/hold circuit for sampling and holding the first laser light intensity signal;    a variable gain circuit for amplifying the first laser light intensity signal with a predetermined gain;    a second sample/hold circuit for sampling and holding the first laser light intensity signal having been amplified with the predetermined gain;    a first switch for selecting one selected from the group consisting of an output from the first sample/hold circuit, an output from the second sample/hold circuit, and the first laser light intensity signal, based on the second laser light intensity signal, and outputting the selected one; and    a second switch for selecting one of an output from the first switch and the first laser light intensity signal based on the second laser light intensity signal, and outputting the selected one, wherein    the second laser light generating current control means controls the second laser light generating means based on the output from the second switch.