| 摘要 |
PURPOSE:To obtain a small-sized, lightweight aspherical single lens which has aberrations compensated with high precision and is molded suitably by specifying the refractive index and geometric shape of the lens. CONSTITUTION:This lens is composed of aplanatic single lens which has a convex aspherical surface as its 1st surface and a concave spherical surface as the 2nd surface and also has positive refracting power and the refractive index eta is 1.8-2.2 to in-use wavelength: center thickness d1=0.5-5mm, (center thickness d1-end surface thickness d2)/center thickness d1<=15 deg., the end surface angle of the 1st surface theta1<=45 deg., and the end surface of the 2nd surface theta2<=15 deg.. This aspherical single lens has an about 2-10mm effective light beam diameter and an about 0.4-0.65 numerical aperture. When the refractive index eta is prefer ably >=1.9, aberrations to the numerical aperture NA' are easily removed. When the refractive index exceeds 2.2, the specific gravity of the lens material increases and the light-weight property of the lens is easily spoiled.
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