Patent ID: 7640068
Filing Date: 2009-12-29
Classification: G01C,G01S

Abstract:
1. A method of controlling a surveying instrument, the surveying instrument comprising: a base, a measuring unit mounted relative to the base, and an actuator control unit for controlling an orientation of the measuring unit relative to the base, the measuring unit comprising a lens and a detector having plural detector segments; the method comprising: receiving first light through the lens and forming a first spot of the first light on the detector, wherein the first light is modulated light having an intensity which is modulated according to a first time pattern; receiving second light through the lens and forming a second spot of the second light on the detector, wherein the second light is modulated light having an intensity which is modulated according to a second time pattern; processing light intensity signals produced by the plural detector segments based on the first and second time patterns and generating a first control signal indicative of a position of the first spot on the detector, and a second control signal indicative of a position of the second spot on the detector; controlling, in a first control mode, the actuator control unit to change the orientation of the measuring unit relative to the base in a first angular direction based on the first signal and to change the orientation of the measuring unit relative to the base in a second angular direction based on the second signal.