Patent ID: 6460768
Filing Date: 2002-10-08
Classification: G06K

Abstract:
An improved motor-spin monitoring circuit for use with a motor directing a coherent light beam source within an optical system comprising:a motor-spin monitor capable of starting and stopping such light beam source, said monitor including a voltage sensor connected with the drive terminals of such motor for producing a first input signal proportional to the back EMF across the motor's excitation winding; a current sensor connected with the drive terminals of such motor for producing a second input signal proportional to the current through such excitation winding; and a comparator for differentially comparing either side of said first input signal to produce an output signal representative of a predefined voltage condition in such winding, and for comparing either side of said second input signal to produce a second output signal representative of a predefined current condition in such winding; said monitor being responsive to said first and said second output signals by stopping such light beam source upon condition that either one or both of said output signals meet(s) predefined criteria indicating that the motor has stopped spinning.