Unusual optics of the Polaroid SX-70 Land camera

Abstract

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. Baker's computer design, special technology has been needed for producing millions of replicas of this system and controlling their quality.

Measuring aspheres quickly: tilted wave interferometry

“…2 Some of the first freeform elements have been introduced by Polaroid in their SX-70 cameras presented in 1972. 3 Well-known examples for aspheres are also the Schmidt plate installed in 1960 in the 2-m Alfred-Jensch-Telescope of the observatory in Tautenburg, aspheric pickup heads for optical data storage, 4 and aspheric lenses for eyewear. Moritz von Rohr (1868 to 1940) is usually credited with the design of the first aspheric lenses for Zeiss eyeglasses.…”

Metrology of freeform shaped parts

“…One of the first examples in mass production is the Polaroid SX-70 folding Single Lens Reflex camera shown in Figure 4, which was on the market in 1972 [135]. Because of its peculiar off-axis viewing optical system, two freeform optical components were used for distortion correction in its optical design.…”

Solution to the bundle-to-bundle mapping problem of geometric optics using four freeform reflectors

“…With the appearance of computer controlled machining, it became possible to make a surface with any almost any profile on a lathe. Early freeform designs include a progressive spectacle lens designed in the late 1950s by Kanolt [10] and the Polaroid SX-70 folding camera [11] whose key components were mostly patented in the early 1970s, e.g. [12][13][14].…”