PURPOSE: To convert efficiently semiconductor laser light to a good plane wave by constituting a collimating lens of a positive meniscus lens having the concave face directed to a light source side, negative meniscus lens having the convex face directed thereto and biconvex lens and forming said lens in such a manner that the focal length and radius of curvature satisfy the specific conditions.
CONSTITUTION: The collimating lens is constituted of the 1st lens 5 which is the positive meniscus lens having the concave face directed to the light source side, the 2nd lens 6 which is the negative meniscus lens having the convex face directed to the light source side and the 3rd lens 7 which is the biconvex lens. The lens is constituted to satisfy the conditions (1) 0.9f>r2>0.3f, r2<0, (2) 2.0f>r4>1.2f where (f) is designated as the focal length of the entire system, r2, r4 are the radii of curvature of the faces of the 1st lens and 2nd lens on the side opposite from the light source. The conditions (1) are the conditions to correct the spherical aberration and astigmatism and the conditions (2) are the conditions to correct satisfactory the spherical aberration and comatic aberration. The light of a semiconductor laser is efficiently condensed and is converted to the good plane wave.
MIZUNO SADAO
ATSUTA YASUSHI
ITOU NOBORU
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