This paper describes a robust liquid crystal alignment layer that can be applied to the interior surfaces of a preformed cavity. In this paper, we describe a method of infusing a dye into a microcavity to produce an effective photodefinable alignment layer. Additionally, we demonstrate that after the application of a diffused RM layer, the alignment of the liquid crystal can be rendered insensitive to subsequent light exposure. In this work we make clear the effect of the RM is not stabilizing the azodye layer, but becomes the stable alignment layer. This is demonstrated by using the process described above with the additional step of realigning of the azodye layer to be perpendicular to the surface through photo-bleaching; and showing the alignment of the LC is unaffected by this process. This versatile alignment layer method, offers significant promise for new photonics applications.
Accommodation–convergence mismatch is still an unsolved issue within the field of augmented reality, virtual reality, and three-dimensional systems in general. Solutions suggested to correct the focus cue in recent years require additional bandwidth, or compromise the image resolution. Our simple approach to overcome this issue is by using an eye-tracking system and electronic lenses. We propose an electronic hybrid lens system composed of segmented phase profile liquid crystal and Pancharatnam phase lenses. For practical application, eye tracking is necessary for measuring the toe-in of the user’s pupil to calculate the object depth. This information is used to determine the required diopteric power of the hybrid system. The optical performance and imaging quality of the proposed hybrid system are evaluated.
Microbolometers are the dominant technology for uncooled thermal imaging and recently devices based on a direct birefringence measurement of a 1 μm-thick liquid crystal (LC) transducer pixel have been shown to have comparable sensitivity to current microbolometers. A modified approach for increasing device sensitivity to the temperature-dependent indices of refeaction is use of an LC resonant cavity in an etalon structure. The measured quantity is the transmission of a visible wavelength through the etalon which requires no thermal contact with the IR absorbing cavity. In this paper a detailed device design is proposed for a LC resonant cavity between dielectric mirrors. The dielectric mirror materials beneath the cavity were chosen to be compatible with existing VLSI processing. The mirror materials above the cavity were chosen to have high transmittance for the 8-14 μm LWIR band and the visible probe wavelength. The performance of this design was evaluated numerically and is shown to yield 31% change in transmitted intensity over the 200 mK temperature range considered when pixel thickness is 470 nm. For comparison, a 1 μm-thick LC pixel based on direct birefringence measurement is expected to yield a 1.6% transmission change over the same range. The etalon device represents a 19x increase in sensitivity with thinner pixels – this leads to lower pixel thermal mass and faster thermal response times.
A low f /# lens and zoom lens system based on Pancharatnam phase are presented. The design, fabrication, and characterization of these devices are shown. The unique characteristics of these devices is made possible by the use of azo-dye photoalignment to align reactive mesogens. The wavelength dependence on the image quality is evaluated and shown to be satisfactory from red light to near infrared machine vision systems. A demonstration device is shown with a 4x zoom ratio.
An uncooled thermal imager is being developed based on a liquid crystal (LC) transducer. Without any electrical connections, the LC transducer pixels change the long-wavelength infrared (LWIR) scene directly into a visible image as opposed to an electric signal in microbolometers. The objectives are to develop an imager technology scalable to large formats (tens of megapixels) while maintaining or improving the noise equivalent temperature difference (NETD) compared to microbolometers. The present work is demonstrating that the LCs have the required performance (sensitivity, dynamic range, speed, etc.) to enable a more flexible uncooled imager. Utilizing 200-mm wafers, a process has been developed and arrays have been fabricated using aligned LCs confined in 20×20-μm cavities elevated on thermal legs. Detectors have been successfully fabricated on both silicon and fused silica wafers using less than 10 photolithographic mask steps. A breadboard camera system has been assembled to test the imagers. Various sensor configurations are described along with advantages and disadvantages of component arrangements.
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