| 摘要 |
PROBLEM TO BE SOLVED: To provide: a lens which is inexpensive and easy to process, exhibits superior transmittance for far-infrared rays, and offers good aberration correction capability; an inexpensive, high-performance far-infrared lens system comprising two such lenses and well corrected for aberrations; and an imaging optical device and digital device having the same.SOLUTION: A far-infrared lens system LN is for use in the far-infrared band and has a two-lens configuration comprising a first lens L1 and a second lens L2 in order from the object side. Each lens L1, L2 comprises a lens core having a refractive index greater than 2.0 and no greater than 3.9 for a wavelength of 10 μm, and a cover layer made of a resin material covering the lens core. At least one of lens surfaces of the lens core is a spherical surface and a surface of the cover layer that covers the spherical surface is an aspherical surface, where the cover layer has a thickness no less than 0.01 mm at a thinnest spot and no greater than 0.7 mm at a thickest spot.SELECTED DRAWING: Figure 2 |
