We demonstrate reconstruction of multi-element homogeneous lens systems as single GRIN lenses by smoothing their paraxial ray paths, followed by calculation of the required index distribution, to serve as optimization starting points.
I present the results of an optical design study into the performance benefits of non-rotationally symmetric “freeform” gradient-index (GRIN) media on a pupil-relay head-mounted display. A range of design variants are presented based on freeform-GRIN lenses consisting of ternary base-material combinations that are enabled by recent developments in additive manufacture. The optical performance of these designs is compared to homogeneous solutions comprising combinations of spherical, aspheric, toric, and freeform surfaces. I show that freeform-GRIN media represent powerful degrees of freedom for aberration correction in tilted and off-axis optical systems, performing comparably to homogeneous freeform optics while illustrating significant potential reductions in lens count and mass.
We present a model for the optical design of gradient-index (GRIN) media of general rotationally symmetric form, based on any number of constituent materials. This is achieved by modelling the relative composition of the medium as a function of space in a form that may be readily converted to refractive index and its derivatives, and is also suitable for optimisation in lens design software. This model is used in the optical design of a singlet GRIN eyepiece where we demonstrate equivalent performance to a multi-element homogeneous design. We show the potential of such media for correction of both chromatic and monochromatic aberrations. Whilst conventional optical systems depend on a set of homogeneous media bounded by discontinuous surfaces, such arbitrary GRIN media introduce the scope for a class of continuous optical systems where the majority of optical work is performed by GRIN media. We explore concepts for the optical design of such systems.
Many infrared systems operate in extreme environments (such as space or military), which require stable optical performance over an extended temperature range. We present a model for the first-order optical design of athermal, radial gradient-index (GRIN) systems, based on a form of the thermo-optic glass coefficient adapted to inhomogeneous material combinations. We find that radial GRIN components can significantly reduce the optical power balance of athermal, achromatic systems, thus reducing aberration contributions from individual lens elements and improving overall performance. This introduces the scope for a class of GRIN multispectral infrared imaging solutions. We apply this enhanced first-order modeling technique to generate starting points for optimization of a short wave to long wave infrared (SWIR/LWIR) multispectral optical design. An example of SWIR/LWIR optical design for a weapon sight application is generated and shown to have significantly reduced mass and improved performance compared with a conventional non-GRIN solution.
Military infrared systems generally must exhibit stable optical performance over a wide operating temperature range. We present a model for the first-order optical design of radial gradient-index systems, based on a form of the thermo-optic glass coefficient adapted to inhomogeneous material combinations. We find that GRIN components can significantly reduce the optical power balance of athermal, achromatic systems, which introduces the scope for a new class of broadband infrared imaging solutions. This novel first-order modelling technique is used to generate a starting point for optimisation of a SWIR/LWIR multispectral optical design.
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