Patent ID: 7869056

Claim:
A tilting angle measuring device for use between a reference surface, an object and a coherent light source, the tilting angle measuring device comprising: an optical device for receiving a light beam emitted by the coherent light source, and splitting the light beam into a first sub-beam and a second sub-beam, directing the first sub-beam to the reference surface such that a third sub-beam is reflected by the reference surface, directing the second sub-beam to the object such that a fourth sub-beam is reflected by the object, and processing the third and fourth sub-beams into a fifth sub-beam and a sixth sub-beam, respectively; a four-quadrant optical detector having four photoelectric converting units arranged in an array for respectively receiving the fifth and sixth sub-beams outputted by the optical device; and a computing unit electrically connected to the four-quadrant optical detector for computing a tilting angle of the object with respect to a predetermined position according to four intensity values of the sixth sub-beam.