Douglas S. Goodman

Large-field scanning laser ablation system

A large-field scanning imaging system has been developed to perform imaging ablation using 308-nm excimer laser light. A 1 x Dysonlike lens images a portion of the mask onto a portion of the substrate to be ablated. The lens has a field of 12 mm and a numerical aperture of 0.05, providing a resolution of about 6 μm. A mirror system comprising a roof and a plane mirror, with all three surfaces mutually orthogonal, ensures that the mask and the substrate have identical orientations. A common stage is used to hold the mask and the substrate. The stage is scanned in a serpentine manner to transfer the entire image. The illuminated region is diamond-shaped, and adjacent scans overlap by half its width to ensure uniformity. Illumination uniformity is provided by a light tunnel in the illumination system. Alignment is performed by optically combining images of mask marks and substrate marks formed by a pair of microscope objectives, one viewing the mask and the other viewing the substrate. The substrate is leveled, focused, and registered relative to the image of the mask by a stage with six degrees of freedom.

Imaging limitations related to the skew invariant

It is the aim of this paper to call attention to and to suggest practical applications in imaging of the long known but neglected skeew invariant. For a ray passing through a rotationally symmetric optical system whose axis is the z- axis of a Cartesian coordinate system, the quantity S=n((beta) x-ay) where n is the refractive index and ((alpha) ,(beta) ) are direction cosines, is constant. Despite the generality of this result and the strength of the constrain that it expresses, this result is little used by optical designers, except with non-imaging systems. The skew invariant precludes perfect imaging of more than one object plane (except for the well-known special case of afocal system). With one perfect imaging plane, the skew invariant limits the quality possible on another plane. For a lens that images one plane the upper limits of imaging at another are restrained by the invariant. Similar restraints exist with two imperfectly images planes. Additional applications are speculated upon.

Description and applications of high-brightness multi-laser-diode system

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 105 W/cm2) 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.

High-brightness multilaser source

This paper discusses a high-brightness multi-laser source developed at Polaroid for such applications as coupling light to fibers, pumping fiber lasers, pumping solid state lasers, material processing, and medical procedures. The power and brightness are obtained by imaging the nearfields of up to eight separate multi-mode lasers side by side on a multi-faceted mirror that makes the beams parallel. The lasers are microlensed to equalize the divergences in the two principal meridians. Each laser is aligned in a field- replaceable illuminator module whose output beam, focused at infinity, is bore-sighted in a mechanical cylinder. The illuminators are arranged roughly radially and the nearfields are reimaged on the mirror, which is produced by diamond machining. The array of nearfields is linearly polarized. A customizable afocal relay forms a telecentric image of the juxtaposed nearfields, as required by the application. The lasers can be of differing powers and wavelengths, and they can be independently switched. Light from other sources can be combined. The output can be utilized in free space or it can be coupled into a fiber for transport or a fiber laser for pumping. A linearly polarized free space output can be obtained, which allows two units to be polarization combined to double the power and brightness.

Compact finger imager

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.

LINE RATIO AND IMAGE FORMATION IN PHOTOLITHOGRAPHIC PROJECTORS

The line ratio l (the ratio of the subresolution line image irradiance extremum normalized to the aberration-free case) is explored as a means of assessing aberration balance and as a line-imaging criterion for a photolithographic projection system.

Applications of cylinders in Vs

Two previous papers treated a general purpose optomechanical system in which optical elements are mounted in cylinders that are located in Vs. The present paper presents several applications of this system. Knowledge of the first two papers is assumed.

Formerly novel optics: a collection of optical tidbits

Thefirst birefringent optical element was the calcite trilobite eye, 540,000,000 years ago. One type was a hexagonal array of from one to several thousand lenslets of calcite crystals, oriented to produce no double images. At each molt new eyes were grown. Some trilobite eyes were calcite with spherical aberration correction resulting from a gradient index. (Some trilobites were blind.) Reference: Richard Fortey, Trilobite!, Knoff, New York, 2000

More cylinders in Vs

This paper considers a variety of techniques for an optomechanical system in which optical elements are mounted on cylinders that are located in Vs.

Design and implementation of a multilaser-based initializer for phase-change optical disks

This paper deals with the opto-mechanical configuration of a newly developed high-speed initializing system for phase change recording media such as CD-RW, DVD-RAM, and DVD-RW. The mechanical layout of the system that ensured the mechanical alignment of each diode laser to be field replaceable. With the unique optical configuration implemented, up to six field- replaceable high-power diode lasers of wavelength 840 nm can be simultaneously installed onto this newly developed system. When all six diode lasers were installed, the internal anamorphic optical system can project the near-field intensity distribution of the high power diode lasers into a large 180 micrometer by 3 micrometer spot size while maintaining enough initialization laser power and providing large depth of focus. In this operational configuration, the system is capable of converting the standard outer diameter of 120 mm phase change optical disk from its originally sputtered amorphous state to initialized crystalline state in less than 20 seconds, which is approximate 2 to 3 times faster than todays commercially available system.