Laser power control arrangements in electro-optical readers

Abstract

Laser power control arrangements interrupt power to a laser used in electro-optical readers upon detection of an over-power condition not conforming to preestablished regulatory standards. In one embodiment, during an operational mode, a difference between laser drive currents at two operating points is compared to a difference between laser drive currents at the same two operating points during a calibration mode. The over-power condition is recognized when the difference during the operational mode exceeds the difference during the calibration mode by a predetermined amount. In another embodiment, the laser is only energized to emit the beam at a reduced power level well below regulatory standards for staring at even if a motor drive failed.

1 - 12 . (canceled) 
   
   
       13 . A laser power control arrangement for regulating output power of a laser beam that is emitted by a laser and that is swept by a motor drive in an electro-optical reader, comprising:
 a) a motor fail circuit for detecting failure of the motor drive; and   b) a controller for energizing the laser to emit the laser beam with a reduced level of output power even if the motor drive has failed and the emitted beam is stationary, and for energizing the laser to emit the laser beam with an increased level of output power when the motor drive has not failed and the emitted beam is being swept, the reduced level being lower in output power than the increased level.   
   
   
       14 . The arrangement of  claim 13 , wherein the motor fail circuit is operative for deenergizing the laser upon detection of motor drive failure if the emitted beam has not been swept for a predetermined time period. 
   
   
       15 . A method of regulating output power of a laser beam that is emitted by a laser and that is swept by a motor drive in an electro-optical reader, comprising the steps of:
 a) detecting failure of the motor drive; and   b) energizing the laser to emit the laser beam with a reduced level of output power even if the motor drive has failed and the emitted beam is stationary, and energizing the laser to emit the laser beam with an increased level of output power when the motor drive has not failed and the emitted beam is being swept, the reduced level being lower in output power than the increased level.   
   
   
       16 . The method of  claim 15 , and the step of deenergizing the laser upon detection of motor drive failure if the emitted beam has not been swept for a predetermined time period. 
   
   
       17 . (canceled)