Patent ID: 6025955
Filing Date: 2000-02-15
Classification: G03F,Y10S

Abstract:
An optical member for light having a wavelength of not more than 400 nm, wherein OH group concentration distribution of said optical member is symmetrical with respect to an optical axis thereof, and wherein a root mean square value measured by the following measuring method is not more than 0.004 times a wavelength of a prove light, said measuring method comprising the steps of:illuminating said optical member with said prove light having a wavelength of 633 nm along said optical axis thereof and measuring refractive indexes of said optical member in said optical axis;fitting even-order polynomials including Zero-order polynomial to the measured refractive indexes by a least square method to minimize the differences between the fitted even-order polynomials and the measured refractive indexes; andcalculating said root mean square value of the differences between the measured refractive indexes and the even-order polynomials.