Patent ID: 7214917

Claim:
A position measuring instrument capable of irradiating a target with measuring light to determine a distance, a direction, and a position of the target on the basis of light reflected from the target, the position measuring instrument having a rotating unit and a fixed unit, and comprising: a light source unit for emitting measuring light; and a light receiving unit for receiving reflected light; and wherein said rotating unit comprises: a reflecting mirror capable of reflecting in at least a vertical and horizontal direction; a vertical driving motor for driving the reflecting mirror up and down; a horizontal driving motor for driving the reflecting mirror side to side; a rotary encoder for measuring a vertical rotating angle of said reflecting mirror; and a rotary encoder for measuring a horizontal rotating angle of said reflecting mirror; and further comprising a distance measuring unit for measuring a distance from the position measuring instrument to the target, and a slant measuring unit for correcting a position of said target based on a measurement of an inclination of the rotating unit and a measurement of a rotational backlash of the rotating unit.