PURPOSE: To absorb the radial thermal stress of a plastic lens due to temperature variation and to prevent variation in the radius of curvature of the lens, by fitting a deformation absorbing sleeve fixedly in the plastic lens installed in a lens frame.

CONSTITUTION: When the temperature of the plastic lens body 40 held in the lens frame 30 of a lens holder is varied, the plastic lens body 40 expands and contracts according to repetitive cooling and heating operation and the thermal stress generated radially is absorbed by the elastic deformation of the deformation absorbing part 34 of the lens frame 30 and the flange part 61 of the deformation absorbing sleeve 60, preventing the variation in the radius of curvature of the plastic lens body 40. Therefore, when the plastic lens body 40 is installed in the lens frame 30, the need to specially increase the clearance to the lens frame 30 including the clearance of the fitting to the deformation absorbing sleeve 60 is eliminated.