SPECIAL PURPOSE SUNGLASSES FOR PILOTS

This paper describes special-purpose sunglasses with lenses for use when flying a jet aircraft. The purpose of these sunglasses is to enable the pilot to see easily in highly contrasting situations. In particular, the pilot needs to view outside the cockpit into a highly illuminated scene and at the same time look at a dimly illuminated instrument panel. Also, when the pilot is viewing instruments in the intermediate field of vision, these sunglasses reduce glare caused from the high illumination in the far field of vision.

Some pilots experience the problem of not being able to see clearly the instruments when there is stark contrast between the high outside illumination and the dim illumination from the instrument panel. This situation frequently occurs at altitudes between 35,000 and 45,000 ft. over clouds. Moreover, this problem is exacerbated as the pilot ages.

The two illustrations below show the dramatic difference between stark and balanced lighting conditions inside the cockpit of a jet. The first, Figure 1(a), illustrates the lighting conditions that a pilot experiences when high contrast exists between the illumination outside and inside the cockpit. As this photograph illustrates, this lighting condition makes the instruments difficult to see clearly. By contrast, Figure 1(b) illustrates the lighting condition when the illumination is more balanced; when illumination is balanced by means of the special-purpose sunglasses, details both outside and inside the cockpit are seen easily. (Note: This effect in the photograph was achieved by using a flash but simulates the balance that the special purpose-sunglasses achieve for the pilot.)

Figures 1(a) and 1(b): Photographs of the Tulsa Technology Center’s B727.

The need for special-purpose sunglasses has made more apparent by a thorough examination of the attributes of existing products, two of which are discussed here. Uniformly dark sunglasses do not reduce the contrast; they reduce the outside illumination to a comfortable level, but they can render the instrument panel too dark to see easily and result in the viewing conditions shown in Figure 1(a). Vignetted sunglass lenses, on the other hand, also do not satisfactorily address the problem of contrast; vignetted sunglasses—lenses that have a gradient in the tinting that are dark at the top and lighten towards the bottom—assist in the overall balancing of illumination between outside and inside the cockpit, but they can permit too much light to enter a pilot’s eyes, which, in turn, causes glare when the pilot views the instruments. (Note: Neither figure above illustrates the problem of glare.)

The special-purpose sunglasses shown in Figure 2, below, render details in different fields of vision to be seen easily by balancing the illumination received by the eyes; they accomplish this effect by using dark tinting in the far field of vision, no tinting in the intermediate field of vision, and medium tinting in the near field of vision.

Figure 2: Special-purpose sunglasses for reducing the contrast between outside and inside the cockpit of a jet aircraft. The large dark area on the lenses is for distant viewing, the clear area is for viewing the instrument panel and the gray area is for near viewing (patent pending).

In addition to improving the pilot’s ability to see in stark lighting situations, these special-purpose sunglasses have the potential of improving safety because they permit the pilot to see more clearly and with less eye strain.

Ray Hobbs, Ph.D.
Tulsa OK
20 July 2007