Engineering Psychology · UTSIC
A small (10 cm wide) enclosure in off-white and grey plastic with an electrical cord attached. A square opening has been cut into opposite faces of the enclosure. Mounted inside the enclosure, place at the centre of both opening so as to form a window, is a glass element that is a liquid crystal cell. This cell is cloudy but transparent. One one side of the enclosure is a black button adjacent to the point at which the electrical cord joins the enclosure.
The electrical cord is terminated with a two-pin type F plug.
Accession Number: 2024.ep.24
Alternative Name:
Primary Materials: Plastic, Glass
Markings:
Height = 5 cm, Width =10cm, Length= 2.5; The cord is ~3m long.
This is a hand-built developmental prototype of a single cholesteric liquid crystal cell. Its functioning demonstrated the suitability of such cells for use in visual occlusion headsets. When the button on the unit is pressed, current is applied to the cell, which goes from transparent to an opaque white field due to the light scattering effect of the liquid crystal cell.
This item is in good cosmetic condition and was tested as functional September 2024. Dirt and wear are superficial.
Associated Instruments:
Manufacturer: Dr. Paul Milgram
Date of Manufacture: c. 1981
This item was among a small collection of items related to the development of the PLATO visual occlusion goggles donated to the collection by Dr. Paul Milgram on September 11, 2024.
John W. Senders, Kristofferson A. B., Levison W. H., Dietrich C. W., Ward J. L. (1967). The attentional demand of automobile driving. Highway Research Record, 195, 15–32. (Archived March 5. 2025).
Paul Milgram and R Van der Horst. “Alternating-Field Stereoscopic Displays Using Light-Scattering Liquid Crystal Spectacles.” Displays 7, no. 2 (1986): 67–72.
The PLATO (Portable Liquid crystal Apparatus for Tachistoscopic Occlusion) system was developed beginning around 1981 by Professor Paul Milgram. The system is an experimental tool that permits the time controlled occlusion of one or both of a subject’s eyes. The system has various applications, including research in visual perception, neuroscience, sports psychology/training, ergonomic evaluation of interfaces, etc., in addition to its original goal for quantifying the attentional workload of various tasks.
Visual occlusion was pioneered by Dr. John Senders and collaborators in the 1960’s (cited and linked above). Milgram completed his PhD under Senders at UofT in 1980. During his post-doc research, he focused on driving tasks, as Senders had done. This research was done while working at the Institute for Perception of the Dutch Organization for Applied Scientific Research (subsequently TNO Human Factors) in Soesterberg, the Netherlands.
This hand-made cell was the initial proof of concept in this developmental process. A fully functional goggle-based system is described in Milgram, and Van der Horst 1986.
At that point, visual occlusion research relied on head mounted mechanical visors, first developed by Senders, to periodically block vision. While at TNO, Milgram developed a goggle-based system using cholesteric liquid crystals to block vision. This was proposed as an alternative to existing twisted-nematic liquid crystal devices and PLZT ceramic-based shutters. In addition to the need for light polarising layers, which significantly reduced the intensity of light transmitted, the former had a relatively slow refresh rate while the latter required very high voltages.
Milgram returned to Toronto in 1986 to take a faculty position at the Department of Industrial Engineering (currently Mechanical and Industrial Engineering) of the University of Toronto. In 1990, in Toronto, he founded Translucent Technologies Inc., which continues to develop and sell the PLATO system worldwide.
- Donated to UTSIC