Abstract

The optical Fourier transform (FT) lens is the basic part of optical information processing. Now most available FT lenses^1-3 belong to those used with the monochromatic laser light source, the most commonly used wavelengths being 633 or 488 nm or with a white light source. Their aberrations are both corrected for a given wavelength of light. The image quality of those lenses will much deteriorate while they are used in a light of wave-length which is not determined during design. With the availability of laser light sources, we hope to obtain another kind of FT lens whose monochromatic aberrations are corrected for more than one wavelength at the same time but without achromatism in the sense of meeting the needs of modern optical information processing and holography. Such a lens is called a FT lens used alternatively with different light sources, with almost the same level of aberration correction for any wavelength over the given 486-656-nm spectral range. When the light source used is changed, its aberrations are almost completely invariant with wave-length, and this characteristic is called the stability of aberrations with wavelength. To our knowledge, the only reference⁴ in this field shows design data, but the design details are not discussed. The design of this doublet type lens with small air separation is described with emphasis on the choice of glass, the distribution of power, the amount of longitudinal chromatic aberration introduced, and the stability of aberrations with wavelength.

© 1988 Optical Society of America