Patent ID: 8724187

Claim:
A collimator lens which converts, into convergent light, a light beam of divergent light emitted from a light source in which an emission wavelength changes according to temperature, comprising: a first face which faces the light source on a light path and on which the light beam is incident; a second face which is placed opposite to the first face and from which the light beam exits; and a diffractive structure which is formed on at least one of the first face and the second face; wherein in a case where divergent light emitted from a position P 1 at a distance S 1 from the second face enters the second face and imaging is performed at a position P 2 at a distance S 2 from the first face, in a temperature range of 0° C. to 60° C. and in a range of the emission wavelength of the light source which changes within the temperature range, and when a minimum value of a wavefront aberration of an image, which is generated at the position P 2 by the divergent light emitted from the position P 1 in a range of 0<S 1 /S 2 ≦50, is WF 1 , and when a minimum value of a wavefront aberration of an image, which is generated at the position P 2 when parallel light satisfying S 1 =∞ enters the second face, is WF 2 , a relationship of WF 1 <WF 2 is satisfied.