Two of the many applications for microlens arrays are fill factor improvement in focal plane arrays and collimation of laser diode arrays. Most lenslet arrays made for fill factor improvement consist of immersion lenses that themselves do not have a 100% fill and the evaluation of such lenses is not representative of their use in an imaging system. Alternative designs are investigated. Anamorphic optics are required to correct for the astigmatism present in laser diode output. An array of micro-optics with toroidal refractive surfaces can be used to collimate or focus the light. We report on the fabrication and evaluation of such anamorphic micro-optics.
Spectrometers that include extended-range linear InGaAs arrays make it possible to measure optical signals to 2500 nm. Available arrays, however, have more than 100 times the dark current as that of conventional arrays, which are limited to 1700 nm. This behavior leads to non-linearity in a short-wave infrared spectroradiometer used to monitor spectral radiance of an integrating sphere uniform source. A method of improving linearity in an extended-range InGaAs array is presented. The non-linearity is corrected using a multi-point calibration at a number of lamp power levels whereby the calibration factor for each wavelength point depends on the lamp power in the integrating sphere. An algorithm in the spectroradiometer software chooses the correct calibration factors and reports the system spectral radiance values accordingly. This method reduced error by more than a factor of two.
Miniature optical systems utilizing arrays of lenses had been conceived by the early part of this century. More recent uses for multi-aperture optics have included Hartmann wavefront sensing and agile beam steering. To support our own research efforts in micro-optics, Adaptive Optics Associates, Inc., developed first-order raytrace software that is capable of modeling multi-aperture systems. The graphical user interface at the heart of this software gives a CAD-like utility to the program, which is a powerful tool for the micro-optics design engineer. The article discusses the benefits of such an interface. Several examples of micro-optics systems taken from available literature are analyzed. The results, including inter-lens effects, are discussed during a slide presentation given at the 1993 Annual Meeting of the Society of Photo-Optical Instrumentation Engineers, held at San Diego, California. The presentation documents and analyses various microoptics designs and demonstrates the capabilities of the software.Recently, AOA has added "real" optics as well as the ability to examine the image plane using a virtual detector that provides a histogram of rays striking each pixel. Future developments will include three-dimensional systems and diffractive elements, such as binary optics.
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