| 摘要 |
PROBLEM TO BE SOLVED: To obtain a cemented lens constituted by cementing the bonding surfaces of at least two lenses with a cement and improved so that stress caused on the bonding surfaces of the lenses due to a difference between the linear expansion coefficients of the cemented lenses is absorbed by the elasticity of the cement layer. SOLUTION: As for this cemented lens, the radii of curvature of the bonding surfaces of two lenses are made different from each other so that the gap at the circumferential part of the bonding surface is larger than the gap on the optical axis. The cement layer has flexible elasticity. The cemented lens satisfies a conditional expression (1). (1)|Δα×D/d|<0.03, whereinΔα: the difference between the linear expansion coefficients of the two cemented lenses, D: the diameter of the bonding surface and d: the thickness of the cement layer on the outermost circumference of the bonding surface.
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