Polaroid

While not an official biography, the following is reprinted with the kind permission of the Royal Society.

by F.W. Campbell, F.R.S.†

Erasmus Bartholin (1625-1698) was sent, in 1669, a transparent crystal from Iceland (Iceland spar) and, by rotating the crystal, he discovered that objects seen through it appeared double. He correctly deduced that light traveling through the crystal was refracted at two different angles. Today, these are still called the ordinary and extraordinary rays. The explanation required the genius of Thomas Young (1773-1829) to account for them some 150 years later: the two rays were polarized at right angles to each other. William Nicol (1768-1851) had the ingenious idea of cementing two crystals of Iceland spar together with Canada balsam so that each ray was separated at right angles. The resulting Nicol prism could then be used to measure the angle of polarization of compounds, which later resulted in a profound understanding of many aspects of chemistry.

Today, Nicol prisms are still very expensive, bulky and of limited aperture. Edwin Land, when a Harvard freshman, conceived the idea that a polarizer might be made by lining up a myriad of tiny crystals (iodoquinine sulphate) in the same direction and embedding them in transparent plastic which, when set, prevented the crystals from drifting apart. The new polarizer was patented in 1929. With his Harvard physics instructor, George Wheelwright III, he set up the Land-Wheelwright Laboratories in 1932. He established the Polaroid Corporation in Boston in 1937. Thus the word Polaroid was born and entered the dictionary.

The trademark was coined by the Smith College art scholar, Clarence Kennedy, with whom Land collaborated in the early 1930s to produce 3-D photographs of Renaissance sculpture. Like many photographers, Land had a great interest in classical art. (When I watched him taking pictures on a sunny afternoon inside King’s College Chapel, Cambridge, in 1973, I was surprised at how long he took to compose each one; the end result was most impressive artistically. Although a shy person, he did not hesitate to lie on the floor watched by the passing tourists while he photographed the vaulted ceiling. As he stood up, I was handed one of his many shots; it included my eyes looking down at him.)

When Edwin and Helen were reading daily in the New York Public Library, they came across the work of an English physician, Dr William Bird Herapath. In 1852 he had found that dogs treated with quinine had microscopic crystalline needles in their urine. He observed that overlapping perpendicular needles were black where they crossed, whereas parallel needles were clear. From that observation Land invented the first sheet polarizer, the J sheet. The crystals also had a magnetic dipole moment, so that if a suspension is placed in a very strong magnetic field they become oriented to form a uniform dichroic layer. If the aligned crystals are suspended in a polymer, they set.

After making the first samples of synthetic polarizers Land and his wife returned to Harvard. Although still a freshman, he gave a lecture at an invited Physics Colloquium and was given a personal laboratory. Terre (Helen) Land assisted him in this experimental work at a time when women were not normally allowed in Physics Laboratories.

This exciting new polarizer had many advantages: it was inexpensive, thin and could be cut easily to any size and shape to fit the application. When two are crossed a very high extinction coefficient results, suitable for scientific use. For maximum light transmission, a low-coefficient version is available for viewing stereoscopic aluminum screens; these screens preserve the angle of polarization.

Stereoscopic (3-D) cinemas were very popular in the 1950s and were practical only because the Polaroid spectacles were so cheap; the audience liked to steal the magic spectacles believing that they would enhance stereoscopic vision outside the cinema! As television developed, the stereo-cinema became less popular, although the technique still has many important scientific uses.

When I visited Edwin in 1960 he took me to a table covered with all the different types of Polaroid. He handed me a pair of scissors and said ‘ Help yourself, you might come up with a new application.’ I did! This was typical of Land, for he wanted to help the research of others as well as his own.

It was on this occasion that he told me that his original reason for developing Polaroid was to prevent car accidents at night in towns like New York. Before dipped headlamps were devised, the glare from oncoming vehicles obscured pedestrians crossing the street. Headlamps were to be fitted with a visor oriented at 90 degrees. Unfortunately, this meant doubling the headlamp wattage, which would increase fuel consumption. Car makers were not willing to raise the cost of cars, so Land’s humanitarian concern for the safety of pedestrians failed to be implemented.

However, serendipity came to his rescue or, to quote Louis Pasteur (1854), ‘Chance favours the prepared mind.’ One of his colleagues went fishing and took a scrap of Polaroid with him. He came rushing back with a large trout and explained to Land that you could see through the reflection of the sky on the surface of the pool and locate the position of the large leading trout. Initially, Polaroid spectacles were sold only in the ubiquitous fish-and-gun shops in the USA, but they quickly became popular with the public as Polaroid sunglasses, as they are known today.

Another popular use is in photography, as a screw-on filter, to darken the sky and enhance the contrast of the clouds (the blue sky opposite the Sun is highly polarized, the clouds are not). Indeed, his first contract was with Kodak to make Polaroid; Kodak would make the screw-on filter mount. Suddenly Land and his team were faced with all the difficulties of manufacturing optically high-quality Polaroid on a very large scale. After intense activity and ingenuity, they met the deadline. In these early days of making polarizers Land began to work with Howie Rogers. Independently and together they made many significant inventions in polarizers, plastic optics and photographic systems.

The latest wide-scale use of Polaroid is to remove the glare from light falling on the ubiquitous visual display terminal or unit (VDU). A 1/4-wave retardation plate is cemented on one side of a sheet of Polaroid and that side is placed against the terminal screen. Light hits the glass screen and is reflected back through the 1/4-wave plate a second time. It has now undergone a 90 degree shift in orientation and thus is extinguished by the second outgoing passage through the Polaroid. This dramatically reduces the eye-strain due to specular reflection from the convex glass front surface of a VDU. We have come a long way in the history of light (1625-1991) from Bartholin, Young and Nicol to Edwin Land.

Of course, Land had to overcome many human as well as scientific problems to produce the final mass production of Polaroid. For example, to make the first sheet polarizer he had to use the 10000 gauss electromagnet in Columbia Physics Laboratory. After he made the polarizer work, he showed the results to the head of the department who then gave him permission to use the electromagnet as well as a key to the room. Before getting the key, Land had taken the elevator to the sixth floor, walked out of the window and along a ledge on the outside of the building and through another window to gain access to the room containing the electromagnet. It is just as well he did not suffer from acrophobia.

One can speculate that it was this frustration with administrators that led him to set up his own company with himself as Chief Administrator -- an elegant and simple solution to a problem that faces all creative scientists and engineers, even to this day!