Patent ID: 7653275

Claim:
An optical device for laser light comprising: a first optical member having a light-exit end at which light exits the first optical member; a second optical member having a light-entrance end which abuts said light-exit end through a protective medium and from which said light enters the second optical member; and said protective medium is arranged between said light-exit end and said light-entrance end, and suppresses fixing together of the light-exit end and the light-entrance end, wherein said protective medium contains fluoride, wherein said protective medium is realized by a film formed on only one of the light-exit end and the light-entrance end, and wherein said film is a multilayer film constituted by layers including a lowermost layer and an uppermost layer, a first degree of adhesiveness between the uppermost layer and the other of the light-exit end and the light-entrance end is lower than a second degree of adhesiveness between adjacent ones of the layers, and a third degree of adhesiveness between the lowermost layer and said one of the light-exit end and the light-entrance end.