Patent ID: 9062959
Filing Date: 2015-06-23
Classification: G01B,G01M

Abstract:
1. A wavelength scanning interferometer for an aspheric surface measurement, characterized by, comprising a translation platform ( 1 ), a measured aspheric surface ( 2 ), a first mirror group ( 3 ), a light splitter ( 4 ), a beam expander ( 6 ), a tunable laser ( 7 ), an imaging lens ( 8 ), a CCD camera ( 9 ), a reference plane mirror ( 10 ), an image card ( 11 ), a computer ( 12 ) and a data card ( 13 ), wherein the measured aspheric surface ( 2 ) is fixed on the translation platform ( 1 ), the measured aspheric surface ( 2 ), the first mirror group ( 3 ), the light splitter ( 4 ), the imaging lens ( 8 ) and the CCD camera ( 9 ) are coaxially placed in sequence, the reference plane mirror ( 10 ) is arranged at the bottom of the light splitter ( 4 ), the CCD camera ( 9 ), the image card ( 11 ), the computer ( 12 ) and the data card ( 13 ) are connected in sequence, the beam expander ( 6 ) is connected with the tunable laser ( 7 ), and the translation platform ( 1 ) and the tunable laser ( 7 ) are connected with the data card ( 13 ) respectively; a light beam emitted by the tunable laser ( 7 ) is expanded by the beam expander ( 6 ) to become a parallel light beam with wavefront divided into two beams by the light splitter ( 4 ), one beam is incident on the reference plane mirror ( 10 ) to become a reference light, and the other beam is focused by the first mirror group ( 3 ) and then is incident on the measured aspheric surface ( 2 ), the lights reflected by the reference mirror ( 10 ) and the measured aspheric surface ( 2 ) are re-superposed on the light splitter ( 4 ) to form interference; interference fringes are acquired by the CCD camera ( 9 ) after passing through the imaging lens ( 8 ), and encounter optical-electric conversion in the CCD camera ( 9 ) and then analogue-digital conversion in the image card ( 11 ), and finally enter into the computer ( 12 ) which performs signal processing so as to obtain an optical path difference and surface shape information; wherein, when in use, wavelengths of a light source are scanned and interference fringes are recorded, so as to calculate an absolute optical path difference of a cat eye position, which is recorded as OPDc, and calculate an absolute optical path difference of a vertex sphere position, which is recorded as OPDa; then distance d between the vertex sphere position and the cat eye position is a curvature radius of the vertex sphere of the measured surface: R0=OPDa−OPDc.