The size of infrared camera systems can be reduced by collecting low-resolution images in parallel with multiple narrow-aperture lenses rather than collecting a single high-resolution image with one wide-aperture lens. We describe an infrared imaging system that uses a three-by-three lenslet array with an optical system length of 2.3 mm and achieves Rayleigh criteria resolution comparable with a conventional single-lens system with an optical system length of 26 mm. The high-resolution final image generated by this system is reconstructed from the low-resolution images gathered by each lenslet. This is accomplished using superresolution reconstruction algorithms based on linear and nonlinear interpolation algorithms. Two implementations of the ultrathin camera are demonstrated and their performances are compared with that of a conventional infrared camera.

With this work we show the use of focal plane coding to produce nondegenerate data between subapertures of an imaging system. Subaperture data is integrated to form a single high resolution image. Multiple apertures generate multiple copies of a scene on the detector plane. Placed in the image plane, the focal plane mask applies a unique code to each of these sub-images. Within each sub-image, each pixel is masked so that light from only certain optical pixels reaches the detector. Thus, each sub-image measures a different linear combination of optical pixels. Image reconstruction is achieved by inversion of the transformation performed by the imaging system. Registered detector pixels in each sub-image represent the magnitude of the projection of the same optical information onto different sampling vectors. Without a coding element, the imaging system would be limited by the spatial frequency response of the electronic detector pixel. The small mask features allow the imager to broaden this response and reconstruct higher spatial frequencies than a conventional coarsely sampling focal plane.

In the low-to-mid IR wavelength range there is a need for high performance, cost effective aspheric optics. Silicon has many advantages including high transmission and a high refractive index, but it can be very difficult to diamond turn. The resulting fabrication errors reduce efficiency and increase scattering and stray light. Wafer-based lithographic techniques can be used to make diffractive and refractive elements in both silicon and germanium. Advantages of diffractive structures such as: thinner elements, highly aspheric and even non-rotationally symmetric phase functions and chromatic compensation make this an attractive technology compared to diamond turning. In addition, wafer based fabrication makes these elements cost-effective in many applications. At Digital Optics Corporation, we have designed and fabricated wafer-based optics for use in the 1.3-14 micron range. In this paper, we will discuss the design, fabrication and evaluation of several product categories including a diffractive germanium beamshaper, a diffractive silicon aspheric lens, and a diffractive silicon spiral lens.

We have designed and built a multi-aperture thin imager using a lenslet array and a CCD imager. The thickness of the imager is significantly reduced. We will present experimental results that demonstrate high resolution imaging.