Method for automatically adjusting the optical axis of a laser resonator

Laser apparatus comprising:

• a laser tube having a first mirror at a first end thereof and a second mirror at a second end thereof,
• an actuator,
• a fixed plate positioned at said first end of said laser tube and connected to an actuator,
• a movable plate, connected to said actuator, which supports said first mirror and moves back and forth relative to said fixed plate by virtue plate of said actuator,
• a measuring circuit for measuring an output power level of light from said laser tube, wherein said measuring circuit produces a first output power level and produces, after the moveable plate is moved, a second output power level,
• a comparison circuit for comparing said first and second output power levels and for producing a difference signal representing a sign of a difference between said first and second output power levels, and
• a control circuit for controlling movement of said actuator such that said actuator moves said moveable plate an incremental amount in a first direction after said measuring circuit provides said first output power level and before said measuring circuit provides said second output power level, and said actuator subsequently moves said moveable plate an incremental amount in said first direction if said second output power level is larger than said first output power level and moves said moveable plate an incremental amount in a second direction opposite said first direction if said second output power level is less than said first output power level.