Patent ID: 9280053
Filing Date: 2016-03-08
CPC Classification: G03F

Claim Text:
1. A focusing system comprising: a transmissive optical element arranged to receive and focus a light beam, said transmissive optical element having a first thermal lens power having a first value and a first absorption; and a reflective thermal lens compensating plate arranged to receive said light beam at least indirectly from a light beam source and reflect said light beam before said light beam reaches said transmissive optical element, said reflective thermal lens compensating plate having a second thermal lens power having a second value and a second absorption; wherein the sign of said first value and said second value are opposite to one another and wherein a material for said reflective thermal lens compensating plate is chosen so that said second absorption relates to said first absorption and a relative absolute magnitude of said first value and said second value such that a thermal lens of said thermal lens compensating plate substantially completely compensates for a thermal lens of said transmissive optical element.