Stereoscopic photography became popular soon after the introduction of photographic processes by Daguerre and by
Talbot in 1839. Stereoscopic images were most often viewed as side-by-side left- and right-eye image pairs, using
viewers with prisms or mirrors. Superimposition of encoded image pairs was envisioned as early as the 1890s, and
encoding by polarization first became practical in the 1930s with the introduction of polarizers in large sheet form. The
use of polarizing filters enabled projection of stereoscopic image pairs and viewing of the projected image through
complementary polarizing glasses. Further advances included the formation of images that were themselves polarizers,
forming superimposed image pairs on a common carrier, the utilization of polarizing image dyes, the introduction of
micropolarizers, and the utilization of liquid crystal polarizers.
The encoding of three-dimensional image pairs by polarization was proposed as early as the 1890s, perhaps stimulated by the popularity of stereoscopic photography, the proliferation of devices for viewing side-by-side stereoscopic images, and the invention of the anaglyph. The introduction of inexpensive sheet polarizing material gave rise to new three-dimensional technologies, starting in the 1930s with 16-mm black-and-white motion pictures projected by paired projectors equipped with orthogonally oriented polarizing filters. Further advances included the introduction of color, the concept of printing left- and right-eye images on a common carrier, and most recently the development of digital photography and the utilization of polarizers in both two- and three-dimensional digital color display.
We describe a new iteration of the StereoJet process, which has been simplified by changes in materials and improved by
the conversion from linear to circular polarization. A prototype StereoJet process for producing full color stereoscopic
images, described several years ago by Scarpetti et al., was developed at the Rowland Institute for Science, now part of
Harvard University. The system was based on the inkjet application of inks comprising dichroic dyes to Polaroid
Vectograph sheet, a concept explored earlier by Walworth and Chiulli at the Polaroid Research Laboratories. Vectograph
sheet comprised two oppositely oriented layers of stretched polyvinyl alcohol (PVA) laminated to opposite surfaces of a
cellulose triacetate support sheet. The two PVA layers were oriented at +45 and -45 degrees, respectively, with respect to
the running edge of the support sheet. A left-eye and right-eye stereoscopic image pair were printed sequentially on the
respective surfaces, and the resulting stereoscopic image viewed with conventional linearly polarized glasses having +45
and -45 degree orientation. StereoJet, Inc. has developed new, simplified technology based on the use of PVA substrate
of the type used in sheet polarizer manufacture with orientation parallel to the running edge of the support. Left- and
right-eye images are printed at 0 and 90 degrees, then laminated in register. Addition of a thin layer of 1/4-wave retarder
to the front surface converts the image pair's respective orientations to right- and left-circular polarization. The full color
stereoscopic images are viewed with circularly polarized glasses.
In recent years we have noted considerable disparity in ghosting among stereoscopic images encoded by polarization and projected onto silver screens. Potential causes include inefficiency of the polarizers used in projection, errors in orientation of linear polarizers placed over paired projection lenses, misalignment of linear polarizers in 3-D viewers; and leakage of non-polarized light through each of the polarizers. With polarizing images, the efficiency of the dyes that form the polarizing images must be considered. In addition, ghosting may arise from depolarization by poor screen surfaces or by some projection equipment. Spectrophotometric measurements confirmed visual differences in blue leakage of crossed polarizing lenses from various suppliers. We also found significant differences in transmittance curves of individual polarizers. We also examined efficiencies of dye polarizers crossed with polarizers used in 3-D viewers, simulating images formed of polarizing dyes in the StereoJet process. Although antighosting measures described earlier help mitigate unwanted imagewise ghosting here, it is important to minimize all potential for the appearance of ghosts. In addition, we reviewed the relative efficiencies of linear polarizers and circular polarizers for encoding polarization of stereoscopic images. Here we compared the transmittance of the crossed pairs as functions of both wavelength and angular disparity.
We describe here advances in the development of the StereoJet process, which provides stereoscopic hardcopy comprising paired back-to-back digital images produced by inkjet printing. The polarizing images are viewed with conventional 3D glasses. Image quality has benefitted greatly from advances in inkjet printing technology. Recent innovations include simplified antighosting procedures; precision pin registration; and production of large format display images. Applications include stills from stereoscopic motion pictures, molecule modeling, stereo microscopy, medical imaging, CAD imaging, computer-generated art, and pictorial stereo photography. Accelerated aging test indicate longevity of StereoJet images in the range 35- 100 years. The commercial introduction of custom StereoJet through licensed service bureaus was initiated in 1999.
We describe the preparation of full-color stereoscopic hardcopy from digital 3-D records. Digital image records may be produced directly in digital cameras, CAD systems and by various instrumental outputs, or they may be acquired by scanning and digitizing photographic images. To produce the stereoscopic image we render the component images in terms of degree of polarization, orienting the polarization axes of the left- and right-eye images at 90 degrees to one another. We print the two images on opposite surfaces of specially prepared substrates, using dichroic inks in otherwise standard desktop inkjet printers. Software provides accurate stereoscopic registration of the paired images. The process produces 3-D images as reflection prints or as transparencies. Observers view the superimposed image pair through standard 3- D polarizing glasses. Alternatively, autostereoscopic display apparatus permits viewing without glasses. The color gamut of a typical image is shown. Image resolution depends primarily on the printer used. Applications include molecular modeling, microscopy, data visualization, entertainment, and pictorial photography.