Patent ID: 9434145
Filing Date: 2016-09-06
CPC Classification: B32B,G02B,Y10T

Claim Text:
1. A method for forming an optical element, the method comprising: a) depositing a first multilayer thin film coating to form a first coated surface on a first transparent substrate that is substantially flat, wherein, for incident light at an angle of incidence exceeding 5 degrees, the first multilayer thin film coating has a filter characteristic that transmits light of a first wavelength band and reflects light of a second wavelength band, wherein the first coated surface has a first surface form, and wherein the first substrate further has a second surface that is opposite the first coated surface, wherein the second surface has a second surface form after the coating is deposited; and b) bonding the second surface of the first substrate to a third surface of a second transparent substrate to form the optical element, wherein the third surface has a third surface form prior to bonding and wherein the first coated surface of the optical element has a fourth surface form after bonding, wherein the difference between the fourth surface form and the third surface form is less than the difference between the first surface form and the third surface form and wherein the difference between the fourth and the third surface forms and between the first and the third surface forms is calculated with respect to sagitta deviation, or with respect to surface irregularity, or with respect to both sagitta deviation and surface irregularity and is expressed as an absolute value.