Advances in computer technology have dramatically increased raytrace speeds in optical engineering software. Increases in raytrace speed have, in turn, led to new methods for evaluating optical system performance. Designers traditionally evaluate imaging system performance with spot diagrams, MTF plots, ray aberration plots, and distortion plots. These tools are invaluable for two reasons: (1) they provide the information experienced designers need to make design decisions, and (2) they require only a coarse sampling of rays. However, these tools are an indirect representation of imaging system performance. The designer must `wait and see' how the lens performs in situ. With today's computers and optical engineering software, it is now possible to evaluate imaging system performance visually as well as numerically--prior to lens fabrication. This paper will discuss the benefits of visual characterization for various practical optical systems. Distortion, diffraction, imagery with 3D objects, and other optical phenomenon will be evaluated.
Optical elements which are made out of macro gradient refractive material are represented by lines, as opposed to points, on the glass map (n<SUB>d</SUB> Vs. v<SUB>d</SUB> diagram). Thus, optical designers need account for gradient dispersion as well as gradient index. A dispersion model for the material must be readily available and optical design programs must be capable of defining and maintaining this relationship before and during optimization, simplifying user input and confining the material to walk a well defined path on the glass map. Thinking in terms of lines on the glass map for arbitrary glass families yields a simple dispersion model based on least squares fitting of Buchdahl coefficients. This paper introduces the concept of glass lines and outlines a technique to construct a dispersion model for any contiguous family of gradient refractive material.
Recent breakthroughs in IR detector array and cryocooler technology have made it possible to convert the concepts of optimum, passive, IR sounding to a practical satellite-borne instrument: the Atmospheric Infrared Sounder (AIRS), a grating array IR spectrometer
temperature sounder. AIRS, together with the Advanced Microwave Sounding Unit and the Microwave Humidity Sounder, will form a complementary sounding system for the Earth Observing System to be
launched in the year 2000. The three instruments are expected to become the new operational sounding system for the National Oceanic and Atmospheric Administration.
The baseline multiaperture echelle spectrometer for the Atmospheric IR Sounder (AIRS) is described in terms of design and applications. The functional requirements for the optical design are set forth including the 1-K measurement goal, the 3.4-15.4 spectral bandpass, and the full global coverage twice daily. The multiaperture spectrometer is compared to the cross-dispersed spectrometer, and the multiaperture model is found to permit specific adjustments to the signal-to-noise ratio. The optical design of the spectrometer is described in terms of the focal-plane constraints, the multiaperture pupil-imaging relay, the spectrometer collimator, and the grating format and efficiency. The multiaperture design is found to have a good spectral-response function, and a 1.2 percent signal change is noted for a 95-percent unpolarized scene. The AIRS instrument is illustrated in its deployment configuration and is concluded to be capable of fulfilling the performance requirements.