Freeform optics are lenses or mirrors with surfaces having no rotational symmetry. They were conceived more than a century ago, but have recently received new attention for solving design problems. The special methods needed to manufacture them have included direct cam driven or digital grinding or milling, hot glass sagging, casting, injection molding, and fast-tool diamond turning. More recently, precision 3D printing and nanocrystalline powder compression molding have offered promising new capabilities for inexpensive high-volume commercial production in the future. Applications of freeform optics have included progressive spectacle lenses, focus adjusting devices, and aperture phase masks for special purposes. These design applications and manufacturing capabilities have been related to each other in interesting ways, and will be illustrated through a selection of patents and photographs of commercial products.
High density digital sensors combined with "digital zooming" have eliminated the need for many small magnification range zoom lenses. Instead, lens designers now must design and assess zoom lenses for ever-increasing magnification ranges. The number of zoom positions for designing and assessing must increase as well, but assessing multi-spectral Modulation Transfer Function (MTF) data for many zoom positions becomes overwhelming. In this paper an efficient and effective metric, Area-Weighted Modulation-Cycles (AWMC), is proposed and reviewed for assessing imaging properties efficiently in a zoom system.gh density digital sensors combined with "digital zooming" have eliminated the need for many small magnification range zoom lenses. Instead, lens designers now must design and assess zoom lenses for ever-increasing magnification ranges. The number of zoom positions for designing and assessing must increase as well, but assessing multi-spectral Modulation Transfer Function (MTF) data for many zoom positions becomes overwhelming. In this paper an efficient and effective metric, Area-Weighted Modulation-Cycles (AWMC), is proposed and reviewed for assessing imaging properties efficiently in a zoom system.
In the period from 1973 through 1992, Polaroid introduced six different free-form aspheric optical surfaces in some unusually innovative instant photographic cameras, made in the millions. In each case these peculiar components were used to solve unusual problems of product size, shape, and function. This presentation relates how and why those surfaces were used and how they were tooled and manufactured with high quality.
This paper describes a novel, high-brightness, multi-laser- diode system that provides great flexibility for use in a wide array of applications. The system consists of eight individual, field-replaceable laser diodes, whose outputs are optically combined to provide a collimated beam. Field replaceability of the diodes and mechanical robustness of this system make it particularly suitable for highly demanding environments. CW optical power greater than 90 Watts at 915 nm was focused to a spot size of 140 X 130 micrometer and a numerical aperture of 0.22 NA. This high CW power density (approximately 5 X 10<SUP>5</SUP> W/cm<SUP>2</SUP>) was achieved by polarization coupling of two multi-laser-diode systems. Optical power in excess of 52 W was obtained from a single-end pumped, grating stabilized Yb:fiber laser at 1100 nm. This paper will also present results on digital printing, CD-RW disk initialization and solid-state laser pumping. A unique feature of this system is the ability for direct-diode coupling to fiber, eliminating any splicing or connector- related losses.
We present the design of a compact, low-cost finger imager, to be used for enrolling and recognizing individuals based upon their finger ridge patterns. The optical system employs viewing beyond the critical angle and darkfield illumination for maximum image contrast. The optical system is afocal and telecentric, achieving corrected distortion with oblique viewing.
This paper discusses the optical and opto-mechanical design of a new laser head developed at Polaroid for printing Helios binary film for printing high quality medical hard copy images. The head is part of an external drum printer for 14' X 17' film. The pixel size is 84 X 84 μm, produced by four lasers, with the smallest printable spot 3 X 6 micrometer, to produce 4096 gray levels. Two pixels side-by-side are simultaneously printed. The head has eight independent 840 nm diode lasers manufactured by Polaroid. Each laser emits up to 1.1 W over an emission length of about 100 μm, with a particularly uniform nearfield irradiance. The lasers are microlensed to equalize the divergences in the two principal meridians. Each packaged laser is aligned in a field-replaceable illuminator whose output beam, focused at infinity, is bore-sighted in a mechanical cylinder. The illuminators are arranged roughly radially. Eight lenses image the laser nearfields on a multi-facet mirror produced by diamond machining. The mirror facets truncate the beams to give the desired pixel shapes and separations. A reducing afocal relay images the mirror onto the film. The final element is a molded aspheric lens, mounted in an actuator to maintain focus on the film. The focusing unit also comprises a triangulation-based focus sensor. The alignment procedures and fixtures were devised concurrently with the head for manufacturing simplicity. The main physical structure is a casting, into which reference surfaces are machined. All optical subassemblies are attached to this casting, with a mixture of optical alignment and self-location. Semi-kinematic cylinder-in-V methodology is utilized. The active alignment steps are done in a sequence that tends to reduce errors from previous steps.