Patent ID: 6672109
Filing Date: 2004-01-06
Classification: C03B,C03C,G03F,Y10S

Abstract:
A silica glass member, which is a silica glass member for use with a light having a specific wavelength of 250 nm or shorter,in which the difference in the maximum and the minimum values of hydroxyl group concentration as measured in a plurality of points within a plane vertical to an optical axis whose center is the crossing point of its optical axis with the optical axis of the silica glass member is 50 ppm or lower; in which the plurality of signed birefringence values obtained based on the birefringence values measured on several points within a plane vertical to an optical axis whose center is the crossing point of its optical axis with the optical axis of the silica glass member and the direction of the fast axis fall within a range of from âˆ’2.0 to +2.0 nm/cm, wherein said plurality of signed birefringence values of said silica glass member are expressed based on the formulae as follows: âˆ’2.0&lE;Bij&lE;2.0 nm/cmâ€ƒâ€ƒ(1) Bij=&Sum;k=1h&it;â€ƒ&it;Aijkh(2)â€ƒwhere, in formula (1) and (2) above, i represents the number of said silica glass members L (i=1, 2, . . . m; 2&lE;m), j represents the number of concentrical virtual circles C present on an effective cross section vertical to the optical axis of said silica glass member L, each having a center on said optical axis and different from each other in radius from said optical axis (j=1, 2, . . . n; 1&lE;n), k represents the number of measuring points located on the circumference of said concentrical circles C (k=1, 2, . . . h; 1&lE;h), Aijk represents the signed birefringence value at the kth measuring point Pijk located on the circumference of a concentrical circle Cij of a silica glass member Li, and Bij represents the mean signed birefringence value corresponding to the arithmetic mean of the signed birefringence values of the measuring points located on the circumference of a concentrical circle Cij of a silica glass member Li.