Patent ID: 7944628

Claim:
An optical element unit comprising: an optical element group for projecting light along an optical axis of said optical element group and a housing having an inner housing part partly defining a first space and a light passageway between said inner housing part and a second space; said inner housing part receiving said optical element group; said optical element group comprising an ultimate optical element located in the region of said light passageway and being part of an ultimate optical element arrangement; and a load relieving device being provided adjacent to said ultimate optical element arrangement, said load relieving device partly defining said first space and said second space and at least partly relieving said ultimate optical element arrangement from loads resulting from pressure differences between said first space and said second space; said ultimate optical element arrangement comprising at least one ultimate optical element holder holding said ultimate optical element to said housing; said ultimate optical element holder having a first side facing towards said load relieving device and a second side facing away from said load relieving device, a third space being defined on said first side of said ultimate optical element holder between said ultimate optical element holder and said load relieving device, at least one of said housing, said ultimate optical element holder and said ultimate optical element providing at least a first venting passageway towards said third space from said second side of said ultimate optical element holder.