The emergence of freeform surfaces in optical systems creates a need for new design methodologies and tools. We present a new analysis tool to facilitate spectrometer designs that leverage freeform surfaces. We demonstrate this new tool for two common all-spherical spectrometer design forms. Using insights from nodal aberration theory, this novel visualization enables the optical designer to efficiently and effectively implement freeform optical surfaces into spectrometers and other dispersive optical instrumentation.
The desire to field space-based telescopes with apertures in excess of 10 meter diameter is forcing the development of extreme lightweighted large optomechanical structures. Sparse apertures, shell optics, and membrane optics are a few of the approaches that have been investigated and demonstrated. Membrane optics in particular have been investigated for many years. The MOIRE approach in which the membrane is used as a transmissive diffractive optical element (DOE) offers a significant relaxation in the control requirements on the membrane surface figure, supports extreme lightweighting of the primary collecting optic, and provides a path for rapid low cost production of the primary optical elements. Successful development of a powered meter-scale transmissive membrane DOE was reported in 2012. This paper presents initial imaging results from integrating meter-scale transmissive DOEs into the primary element of a 5- meter diameter telescope architecture. The brassboard telescope successfully demonstrates the ability to collect polychromatic high resolution imagery over a representative object using the transmissive DOE technology. The telescope includes multiple segments of a 5-meter diameter telescope primary with an overall length of 27 meters. The object scene used for the demonstration represents a 1.5 km square complex ground scene. Imaging is accomplished in a standard laboratory environment using a 40 nm spectral bandwidth centered on 650 nm. Theoretical imaging quality for the tested configuration is NIIRS 2.8, with the demonstration achieving NIIRS 2.3 under laboratory seeing conditions. Design characteristics, hardware implementation, laboratory environmental impacts on imagery, image quality metrics, and ongoing developments will be presented.
The desire to field space-based telescopes with apertures in excess of 10 meter diameter is forcing the development
of extreme lightweighted large optics. Sparse apertures, shell optics, and membrane optics are a few of the
approaches that have been investigated and demonstrated. Membrane optics in particular have been investigated for
many years. The majority of the effort in membrane telescopes has been devoted to using reflective membrane
optics with a fair level of success being realized for small laboratory level systems; however, extending this
approach to large aperture systems has been problematic. An alternative approach in which the membrane is used as
a diffractive transmission element has been previously proposed, offering a significant relaxation in the control
requirements on the membrane surface figure. The general imaging principle has been demonstrated in 50-cm-scale
laboratory systems using thin glass and replicated membranes at long f-number (f/50). In addition, a 5-meter
diameter f/50 transmissive diffractive optic has been demonstrated, using 50-cm scale segments arrayed in a
foldable origami pattern. In this paper we discuss Membrane Optical Imager Real-time Exploitation (MOIRE)
Phase 1 developments that culminated in the development and demonstration of an 80 cm diameter, off-axis, F/6.5
phase diffractive transmissive membrane optic. This is a precursor for an optic envisioned as one segment of a 10
meter diameter telescope. This paper presents the demonstrated imaging wavefront performance and collection
efficiency of an 80 cm membrane optic that would be used in an F/6.5 primary, discusses the anticipated areal
density in relation to existing space telescopes, and identifies how such a component would be used in previously
described optical system architectures.
The spatial response of a FPA is an important attribute of image quality. A novel test station for determining detector MTF has been developed and used on LWIR FPAs. The test station focuses an illuminated pinhole aperture onto a FPA, creating a sub-pixel spot. Total system MTF is determined by scanning the spot across the FPA. Optics MTF is measured by moving the imaged spot through focus and applying phase retrieval methods. The Optics MTF is then removed from the measured total MTF to produce the detector MTF. The technique has been applied to large area LWIR FPAs.