Patent ID: 6917418

Claim:
An accuracy analyzing apparatus for a machine tool comprising a table, a main spindle and a feed mechanism for relatively moving the table and the main spindle along orthogonal three axes including a first axis extending along a main spindle axis and second and third axes perpendicular to each other and perpendicular to the first axis, the accuracy analyzing apparatus comprises: light projecting means attached to the main spindle for emitting a light beam having a light axis coaxial with the main spindle axis; first imaging means including an image pickup surface having a two-dimensional planar shape and placed below the light projecting means and being perpendicular to the first axis and being parallel to the second and third axes, for receiving the light beam emitted from the light projecting means by the image pickup surface and generating two-dimensional image data of the light beam; a semitransparent mirror which has a plate-like shape, which is placed between the light projecting means and the first imaging means while a plate planar face of the mirror is inclined with respect to the first and second axes and parallel to the third axis, and which transmits part of the light beam emitted from the light projecting means in an emission direction, and reflects other part of the light beam; second imaging means including an image pickup surface having a two-dimensional planar shape and placed at an opposite position to the semitransparent mirror and being parallel to the first and third axes and being perpendicular to the second axis, for receiving the reflected light beam from the semitransparent mirror by the image pickup surface and generating two-dimensional image data of the reflected light beam; and analyzing means for: receiving the two-dimensional image data generated by the first and second imaging means; calculating light receiving positions in the image pickup surfaces of the first and second imaging means on the basis of the received two-dimensional image data; estimating a light receiving position in the image pickup surface of the second imaging means where the light beam reflected by the semitransparent mirror is to be received by the image pickup surface of the second imaging means in the case where it is assumed that the axis of the main spindle coincides with the first axis, on the basis of the calculated light receiving position in the image pickup surface of the first imaging means; and comparing the estimated light receiving position with the calculated light receiving position in the image pickup surface of the second imaging means and analyzing perpendicularity of the axis of the main spindle with respect to a plane defined by the second and third axes.