Patent ID: 6965482

Claim:
A lens for multiple wavelengths condensing plural kinds of monochromatic lights respectively, the lens comprising: a lens surface sectioned into plural aspherical zones having different refractive power in a common use area for all the monochromatic lights, wherein the plural sectioned aspherical zones respectively have one common single focal point corresponding to an inherent wavelength of each of the monochromatic lights, one focal point corresponding to the inherent wavelength of one of the monochromatic lights is arranged in different position with other focal points corresponding to the inherent wavelengths of other monochromatic lights, each of the aspherical zones, with regard to each of the monochromatic lights, differs in optical path length from each other by approximately integral multiple of wavelength λ i (i is an integral number of 1, 2 . . . , meaning each of the monochromatic lights) of each of the monochromatic lights, when a difference between a maximum value and a minimum value of a wavefront aberration of each of the monochromatic lights in each of the aspherical zones is (ΔV d (λ i )) where d is an integral number of 1, 2 . . . , meaning each of the aspherical zones, the difference of a wavefront aberration in each of the aspherical zones is no more than 0.14 λ i , a ratio between differences of each of the monochromatic lights is between 0.4 and 2.5 in each of the aspherical zones, and the wavelength λ i comprises at least two kinds of wavelength selected from a group of around 790 nm, 655 nm, and 405 nm.