1. Field of the Invention
The present invention relates to electric lamps and more particularly, but not by way of limitation, to a lamp having a treated lense to reduce peripheral glare primarily for use as automobile or vehicle driving lamps, spotlights or the like.
2. History of the Prior Art
There is a well developed history of utilization of lamps for spotlights or driving lamps where the lamp includes an internal parabolic reflecting surface for collecting the light emission from a bulb or resistive element located near the focus of the parabolic surface, collimating the light into a beam which is directed through the lense or suitable transparent media to illuminate a specific viewing area.
Since the lense is usually refractive and the parabolic surface is often slightly open to provide a desired beam pattern, there exists peripheral illumination outside of the beam width in which the light is less intense and which is even desirable for many ordinary uses.
However, when such lamps are used as driving lights for vehicles in fog, smoke or rainy conditions, reflection from the peripheral illumination is distractive and actually impairs visibility in the desired viewing area.
A particularly successful attempt was made to overcome the above disadvantages by the patent to Hulbert, U.S. Pat. No. 3,754,135, issued Aug. 21, 1973, for "Light Treating Means." The Hulbert device teaches the treating of the light by coating specific areas of the lense with a blue translucent pigment whereby the teaching indicates that a "light mixing" takes place which serves to change the color spectrum and to reduce glare. While glare is in fact reduced by the Hulbert device, a great amount of peripheral illumination is still present which can and does present some problems when the lamp is used in conditions of fog, smog, rain or on wet surface.
On the other hand, by utilizing the blue mixed light, there is an enhancement in color differentiation and object identification within the illuminated beam pattern of light.
Another problem exists with the Hulbert device when used as a vehicle head lamp that is that the primary beam is surrounded by a reflected blue halo during use in highly reflective environments which can be distractive to approaching motorists as well as to the driver of the vehicle. Also, since the Hulbert lamp appears blue during daylight conditions as well as when used in a highly reflective environment, its use is prohibited under many state laws in which blue has been adopted for use by law enforcement vehicles only.