William T. Plummer

Photographic optical systems with nonrotational aspheric surfaces

Sections of nonrotational aspheric surfaces can be useful in a variety of optical situations. In several examples, image-forming objectives, as for photographic or electronic camera products, are described in which suitably located asymmetric pairs of refractive surfaces are devised, such that relative rotation about a displaced axis of one with respect to the other can be used to produce a focusing effect that is satisfactory for imaging purposes over reasonable fields of view and for practicable apertures and achromatic corrections. Taylor expansions about assignable reference points in any given surface of a sequence, together with suitable coordinate systems, can be employed to relate performance to shape parameters.

Unusual optics of the Polaroid SX-70 Land camera.

The unique optical system of the folding single-lens-reflex viewfinder used in the Polaroid SX-70 Land camera has required novel approaches to design and manufacture. The camera uses an unusual short-barrel taking lens with front-element focus, two plane mirrors, an eccentric reflective Fresnel focus screen, an aspheric aperture element, an aspheric concave mirror, and an aspheric eye lens. All the viewing components are tilted or decentered, and two aspheres are not figures of revolution. Beginning with J. G. Bakers computer design, special technology has been needed for producing millions of replicas of this system and controlling their quality.

Mars: Is the Surface Colored by Carbon Suboxide?

The reflection spectrum of Mars can be well matched from 0.2 through 1.6 microns (and farther) by polymers of carbon suboxide, reflection spectra for which have now been measured. We propose that the reddish color of Mars might be attributed to carbon suboxide, not the commonly considered limonite or other iron-bearing minerals.

Athermalization of a single-component lens with diffractive optics

We describe a design method to athermalize a single-material lens element by using a kinoform on one surface to keep its focal length and aberrations constant with temperature. We diamond turned and thermally tested a plastic athermat and compared it to an uncompensated conventional lens.

A mechanically generated hologram

A visually striking image phenomenon has been noticed during mechanical abrasion of a plane nickel optical surface. After the lap was removed and the surface was cleaned, two clear ghost images of the absent lap were visible in full detail, in each of four abrasion test areas. In a binocular view these ghost images were plainly situated above and below the actual optical surface, an appearance commonly associated with a reflection hologram. A theory is offered to explain the phenomenon by simple geometry.

Venus Clouds: Test for Hydrocarbons

Infrared reflection spectra of hydrocarbon clouds and frosts now give a critical test of Velikovskys prediction that Venus is surrounded by a dense envelope of hydrocarbon clouds and dusts. Venus does not exhibit an absorption feature near 2.4 microns, although such a feature is prominent in every hydrocarbon spectrum observed.

Infrasonic Resonances in Natural Underground Cavities

Several examples of acoustic resonance in the frequency range from 0.001 to 1.0 Hz have been observed in limestone caverns. In some cases, the cavern geometry is simple enough for direct application of the Helmholtz resonator theory, and good agreement is found. Three experiments are described. Spectral analysis indicates that subacoustic resonance is responsible for numerous reports of periodically fluctuating or reversing cavern winds, and that appropriate wind measurements can provide new information about chambers not accessible to exploration.

Venus Clouds: Test for Carbon Suboxide

Venus clouds absorption spectra correlation with carbon suboxide frost reflection spectra, suggesting absence of carbon suboxide in atmosphere

Free-form optical components in some early commercial products

In the period from 1973 through 1992, Polaroid introduced six different free-form aspheric optical surfaces in some unusually innovative instant photographic cameras, made in the millions. In each case these peculiar components were used to solve unusual problems of product size, shape, and function. This presentation relates how and why those surfaces were used and how they were tooled and manufactured with high quality.

The Venus spectrum: New evidence for ice

Abstract Kuiper has announced that the Venus cloud reflection spectrum shows no depression whatever at 1.93 microns, where carbon dioxide absorption is small, and has concluded that the broad absorption feature centered at 2.05 microns in an ice-cloud reflection spectrum is therefore not compatible with Venus. A critical review of his procedure shows that his use of a lunar reference spectrum to establish the continuum in this region has introduced a serious error. The actual Venus reflectivity is depressed almost 14% at 1.93 microns and even further at 2.13 microns, consistent with a 30% depression at 2.05 microns. Ice clouds are entirely compatible with such a dip, and also match the rest of the Venus infrared spectrum better than any other material tested. Kuipers spectra are not in conflict with prior measurements of water vapor on Venus, which is on the order of 0.01 precipitable em, but may very somewhat with time.