Intrinsic and induced aberrations can be important contributors to the total aberration content of a lens. Theory for induced aberrations has been explored and recently advanced. Macros for calculating and targeting intrinsic and induced aberrations have been written. We briefly discuss wave aberration theory and induced aberration theory, including algorithmic advancements. We demonstrate the application of the recent theory and new macros in lens optimization.
Refractive infrared optical designs have traditionally covered modest FOVs in one spectral band. The design of a fast, extreme fisheye lens imaging 360° azimuth by 120° elevation over the full 3-12 micron band is described. The various relevant tradeoffs that were explored are detailed and the advantages and disadvantages of each approach are discussed. In particular, the applicability of reflective and diffractive solutions is described.
We report on the design, fabrication, and on-sky performance of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of "monolithic" powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. Finally, we present performance results from observations with FISICA at the KPNO 4-m telescope and comparisons of FISICA performance to other available IFUs on 4-m to 8-m-class telescopes.
Freeform Optical surfaces are defined as any non-rotationally symmetric surface or a symmetric surface that is rotated about any axis that is not its axis of symmetry. These surfaces offer added degrees of freedom that can lead to lower wavefront error and smaller system size as compared to rotationally symmetric surfaces. Unfortunately, freeform optics are viewed by many designers as more difficult and expensive to manufacture than rotationally symmetric optical surfaces. For some freeform surfaces this is true, but a designer has little or no feedback to quantify the degree of difficulty for manufacturing a surface. This paper describes a joint effort by Optical Research Associates (ORA) and the Precision Engineering Center (PEC) at North Carolina State University to integrate metrics related to the cost and difficulty of manufacturing a surface into the merit function that is used during the design of an optical system using Code V. By incorporating such information into the merit function, it is possible to balance optical performance and manufacturability early in the design process.
We discuss the design, fabrication, assembly, and testing of the prototype Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) Integral Field Unit (IFU). FISICA is intended for large telescopes with f/numbers close to f/15, such as the KPNO 4-m and GTC 10.4-m telescopes. It implements an image slicing approach, wherein the initial image plane is optically sliced into thin strips and the strips are optically rearranged end-to-end, whereupon the composite slit image is fed into a conventional spectrograph. We divide the field of view into 22 slices, while accommodating the entire f/15 viewing solid angle. The all-reflective instrument resides in a cryogenic dewar at the initial focal plane, and places the composite slit image output precisely at the initial focus, allowing it to interface to the existing FLAMINGOS spectrograph. The mirrors were diamond turned using various tool geometries and state-of-the-art, multi-axis tool control. The mirrors are made from a single billet of aluminum, and the optical bench and mounts are made of the same alloy as the mirrors for optimum performance during cryogenic cooling. We discuss the key design efforts, emphasizing tradeoffs among performance, volume, fabrication difficulty, and alignment requirements. We describe the fabrication, and present preliminary laboratory test results.
We report on the design and status of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of “monolithic” powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. We also discuss plans for first-light observations on the KPNO 4-meter telescope in July 2004.
Modeling the effects of stress birefringence is critical for polarization sensitive optical systems. Optical design and optomechanical software tools to model stress birefringence are discussed and illustrated for three examples. The first example compares retardance in calcium fluoride lenses as a function of shape. The second example discusses the modeling of a beam splitter in an LCD projector. Lastly, stress birefringence modeling tools are demonstrated in detail in the design of focusing and collimating lenses for a WDM wavelength selective switch. The wavelength selective switch, operating over the telecom C-band (1530-1561nm), employs a liquid crystal polarization modulator to select the output fiber for each input channel. Over the operational temperature range, CTE mismatches between the glasses and mounting materials induce stress in the optical elements creating cross-talk between the output optical fibers. Cross-talk is computed as a function of temperature for several potential design concepts.
Telecommunication wavelength division multiplexing systems (WDM) demand high fiber-to-fiber coupling to minimize signal loss and maximize performance. WDM systems, with increasing data rates and narrow channel spacing, must maintain performance over the designated wavelength band and across a wide temperature range. Traditional athermal optical design techniques are coupled with detailed thermo-elastic analyses to develop an athermal optical system under thermal soak conditions for a WDM demultiplexer. The demultiplexer uses a pair of doublets and a reflective Littrow-mounted grating employed in a double-pass configuration to separate nine channels of data from one input fiber into nine output fibers operating over the C-band (1530 to 1561.6 nm). The optical system is achromatized and athermalized over a 0 degrees C to 70 degrees C temperature range. Detailed thermo-elastic analyses are performed via a MSC/NASTRAN finite element model. Finite element derived rigid-body positional errors and optical surface deformations are included in the athermalization process. The effects of thermal gradients on system performance are also evaluated. A sensitivity analysis based on fiber coupling efficiency is performed for radial, axial, and lateral temperature gradients.