25 September 1997 Optical design of diffraction-limited monochromatic doublets
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Abstract
In the present work we have demonstrated a family of laser focusing doublets. All members of this family are diffraction limited and their optimal performance at He-Ne laser wavelength has been investigated. Laser focusing lenses are widely used for video and optical disk systems. They are usually small with high numerical aperture operating at single wavelength. They cover a small field of view, are diffraction limited, and nearly aplanatic. The present diffraction limited family consists of six air-spaced doublets for which the F-numbers are 2, 2.5, 3, 4, 5.6 and 8. An automatic design of optical systems has been used to optimize the monochromatic spherical aberration for the axial point. The effective focal length (EFL) of the family is 100 mm and the field of view tolerance is 0.00001 rad. The performance of the doublet is shown through the Modulation Transfer Function (MTF) curve, which indicates that the optical system is diffraction limited. This is also presented from wavefront point of view by calculating the Strehl ratio of the system. The Petzval curvature is small so the system can be considered as aplanatic on axis. The overall length (OAL) of the system is small which makes it easy to handle. The most interesting member of the family is the F/2 lens due to significant improvement over a previously reported design. The F/2 system in our design has less higher order spherical aberrations compared to the existing design.
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Kamal K. Das, Hassan S. Ashour, John S. Loomis, "Optical design of diffraction-limited monochromatic doublets", Proc. SPIE 3130, Lens Design, Illumination, and Optomechanical Modeling, (25 September 1997); doi: 10.1117/12.284057; https://doi.org/10.1117/12.284057
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