Refractive Lenslet Arrays Research Articles

Shack–Hartmann wavefront sensor with the precorrected holographic lenslet array

The method of the dynamic range expansion of the Shack–Hartmann wavefront sensor is discussed. It is based on the use of nonlinear dual focus holographic lenslet arrays with the aberration precompensation. The data concerning the optical setup and the technique of adaptive lenslet array producing based on nonlinear holographic recording phenomenon are represented. On the example of spherical wavefronts it is shown, that the use of three lenslet arrays with different amount of the aberration precompensation allows expanding approximately in five times the dynamic range of the sensor four times greater with preserving the specified sensitivity in comparison with the corresponding refractive lenslet array.

The magic lens

We present an automatic approach to design and manufacture passive display devices based on optical hidden image decoding. Motivated by classical steganography techniques we construct Magic Lenses , composed of refractive lenslet arrays, to reveal hidden images when placed over potentially unstructured printed or displayed source images. We determine the refractive geometry of these surfaces by formulating and efficiently solving an inverse light transport problem, taking into account additional constraints imposed by the physical manufacturing processes. We fabricate several variants on the basic magic lens idea including using a single source image to encode several hidden images which are only revealed when the lens is placed at prescribed orientations on the source image or viewed from different angles. We also present an important special case, the universal lens , that forms an injection mapping from the lens surface to the source image grid, allowing it to be used with arbitrary source images. We use this type of lens to generate hidden animation sequences. We validate our simulation results with many real-world manufactured magic lenses, and experiment with two separate manufacturing processes.

Low-cost microoptical modules for mcm level optical interconnections

A multichannel free-space microoptical module for dense MCM-level optical interconnections has been designed and fabricated. Extensive modeling proves that the module is scalable with a potential for multi-Tb/s/spl middot/cm/sup 2/ aggregate bit rate capacity while alignment and fabrication tolerances are compatible with present-day mass replication techniques. The microoptical module is an assembly of refractive lenslet-arrays and a high-quality microprism. Both components are prototyped using deep lithography with protons and are monolithically integrated using a vacuum casting replication technique. The resulting 16-channel high optical-grade plastic module shows optical transfer efficiencies of 46% and inter-channel cross talks as low as -22 dB, sufficient to establish workable multichannel MCM-level interconnections. This microoptical module was used in a feasibility demonstrator to establish intra-chip optical interconnections on a 0.6 /spl mu/m CMOS optoelectronic field programmable gate array. This optoelectronic chip combines fully functional digital logic, driver and receiver circuitry and flip-chipped VCSEL and detector arrays. With this test-vehicle multichannel on-chip data-communication has been achieved for the first time to our knowledge. The bit rate per channel was limited to 10 Mb/s because of the limited speed of the chip tester.

Aberration-correction results from a segmented microelectromechanical deformable mirror and a refractive lenslet array

Quadratic aberration is successfully corrected with a segmented microelectromechanical deformable mirror in conjunction with a refractive lenslet array. Use of the lenslet array greatly improves the effective fill factor of the correcting element. Experimental results show correction approaching the diffraction limit for an extreme spherical aberration.

Pattern transfer for diffractive and refractive microoptics

Pattern transfer technologies developed for very large and ultra-large scale integrated (VLSI and ULSI) circuit processing can be adapted to fabricate high fidelity microstructures for planar diffractive and refractive optical elements (DOEs and ROEs). Lithographic, dry-etching, and material deposition techniques used to pattern continuous and stepped microoptical surface relief structures in dielectric, metallic, and semiconductor materials are reviewed. Examples are given of multilevel DOEs, analog refractive lenslet arrays, and subwavelength structures.

Binary optics: A VLSI-based microoptics technology

Binary optics technology applies VLSI and ULSI processing techniques to the field of microoptics to enable the fabrication of unique wavefront engineering devices from x-ray to IR wavelengths. The nested character of these stepped diffractive surface relief structures, coupled with submicron linewidths and precise etch depths, puts stringent demands on process tolerances. We summarize our efforts to produce high-optical-quality diffractive and refractive microoptics with this technology. We also describe novel techniques developed to fabricate the deep structures needed to form high-aspect-ratio gratings and analog refractive lenslet arrays, including thick resist processing and deep anisotropic etching.

A REFLECTIVE SHACK-HARTMANN WAVEFRONT SENSOR FOR ADAPTIVE OPTICS

ABSTRACT We describe a new wavefront sensor based on the efficient Shack-Hartmann quad cell system. The key improvement to existing designs is a modified lenslet array. The traditional refractive lenslet array is replaced with a segmented reflective system that allows individual control of each subaperture. This system has produced diffraction limited slope correction of the six 1.83 m mirrors of the MMT using a 9.9 V magnitudeguide star and significant image improvement on guide stars as faint as 11.3 V magnitude, limited by the readout noise of the CCD quad cell detector. Recent experiements with an improved detector diffraction limited imaging on guide stars as faint as 15th magnitude. This optimized wavefront sensor, equally applicable to filled aperture telescopes, promises to extend the amount of sky coverage available for adaptive correction in the near IR.