Patent ID: 8649019
Filing Date: 2014-02-11
Classification: G01B

Abstract:
1. A shape determining device, comprising: first and second homodyne interferometers respectively provided for front and back surfaces of an object arranged at a predetermined measurement position, the first homodyne interferometer detecting intensities of first interference light beams each obtained by interference between a first reference light beam and a first object light beam, the second homodyne interferometer detecting intensities of first interference light beams each obtained by interference between a second reference light beam and a second object light beam, the first reference light beam being obtained when light emitted from a predetermined light source is branched into a first light beam that is guided toward the front surface of the object and a second light beam is guided toward the back surface of the object, the first light beam is branched into third and fourth light beams, and the third light beam is reflected by a first reference surface, the first object light beam being obtained by reflection of the fourth light beam at a corresponding measurement site on the front surface of the object, the second reference light beam being obtained when the second light beam is branched into fifth and sixth light beams and the fifth light beam is reflected by a second reference surface, the second object light beam being obtained by reflection of the sixth light beam at the corresponding measurement site on the back surface of the object; and a thickness distribution calculator that calculates a thickness distribution of the object based on the intensities of the first and second interference light beams detected for a plurality of the measurement sites by the first and second homodyne interferometers by changing a relative position of the object in two-dimensional directions relative to the first and second homodyne interferometers, and wherein each of the first and second homodyne interferometers includes: a first optical system for non-interference light beam acquisition, the first optical system of the first homodyne interferometer, for detecting the intensity of each first interference light beam, branching the first light beam into the third and fourth light beams and then projects the third light beam onto the first reference surface and the fourth light beam onto the corresponding measurement site on the front surface of the object, so as to acquire a non-interference light beam that contains the first reference light beam and the first object light beam as mutually orthogonal polarization components, the first optical system of the second homodyne interferometer, for detecting the intensity of each second interference light beam, branching the second light beam into the fifth and sixth light beams and then projecting the fifth light beam onto the second reference surface and the sixth light beam onto the corresponding measurement site on the back surface of the object, so as to acquire a non-interference light beam that contains the second reference light beam and the second object light beam as mutually orthogonal polarization components; a second optical system for non-interference light beam branching that branches each non-interference light beam acquired by the first optical system into three or more branched non-interference light beams; a third optical system for phase shift that imparts a change in a phase difference between the orthogonal polarization components by means of a birefringent element for one or more of the three or more branched non-interference light beams for each non-interference light beam acquired so as to generate a diverse phase difference between the polarization component of the corresponding reference light beam and the polarization component of the corresponding object light beam in each of the three or more branched non-interference light beams; a fourth optical system for interference light beam extraction that extracts a polarization component having a common angle with reference to polarization directions of the corresponding reference light beam and the corresponding object light beam from each of the three or more branched non-interference light beams after the branched non-interference light beam passes through the third optical system, and thereby extracts an interference light beam between the corresponding reference light beam and the corresponding object light beam; and an interference light intensity detecting unit that detects an intensity of each interference light beam extracted by the fourth optical system, and wherein the thickness distribution calculator includes: a phase difference calculating unit that, for each of the interference light beams for which the intensity is detected by the interference light intensity detecting unit of the first and second homodyne interferometers, calculates a phase difference between the polarization components of the corresponding reference light beam and the corresponding object light beam in the corresponding non-interference light beam based on the intensity of the interference light beam; and a thickness distribution calculating unit that calculates the thickness distribution of the object based on a distribution of the phase differences calculated based on the intensities of the first and second interference light beams detected for the plurality of measurement sites by the phase difference calculating unit.