| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive plastic aspherical collimator lens the aspherical surface shape which can be easily measured with accuracy of 1/10 of a light source wavelength. SOLUTION: The plastic aspherical collimator lens, is a single lens, the surface on the collimated light outgoing side is molded to a quadric spheroid surface which has a positive refractive power and which is shown by a prescribed expression, and the surface on the light source side is spherical, and the collimator lens is molded of resin by an injection molding method. The cone constant (k) of the spheroid surface, the correction coefficient r1 /nf of a sine condition and the under correction coefficient (n-1)k of the spherical aberration satisfy the following conditions; -1<k<0, 0.20<r1 /nf<0.40 and -0.45<(n-1)k<-0.22. Besides, the lens thickness (d), the cone constant (k) of the spheroid surface and the correction coefficient r1 /nf of the sine condition satisfy the following conditions so as to reduce the sensitivity of aberration due to decentering; 1<=d<=2, -0.9<k<=-0.65 and 0.360<=r1 /nf<=0.399.
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