Head-mounted illumination systems are often used by dentists, surgeons, ophthalmologists, and other practitioners when performing examinations and medical procedures. Certain advantages of such systems is that they leave the hands free while projecting illumination in the same direction the user is looking.
Most head-mounted illumination systems use standard flashlight technology; that is, a filament-based lamp in conjunction with a back reflector. Such an arrangement does not provide very uniform illumination. Even those systems which use very expensive and precision reflectors have difficulty producing a clean and uniform beam of light and the illumination, to the extent that it is uniform, is not maintained over a long focal range. Reflector-based systems also produce considerable stray light, and are therefore inefficient.
A uniform, intense illumination area can be produced using a fiber-optic illuminators, in which case a high-intensity light source feeds an optical fiber bundle. However, the user must be constantly attached via a tether to the heavy fiber bundle which is, in turn, anchored to an illuminator box that must be plugged into a power outlet. Thus, the mobility and comfort of the wearer is significantly reduced.
An ordinary imaging illuminator, using a standard bulb and an imaging lens, may alternatively be employed, but this arrangement exhibits a low collection efficiency and produces a relatively dim light beam. The magnified image of the bulb filament in the illumination plane also tends to produce a very uneven light structure.
Commonly assigned U.S. Pat. No. 5,440,642 improves upon the prior art by providing a head-mounted lighting assembly which produces a uniform, intense and adjustable light beam. The assembly may be easily mounted upon a head of a user, either on a headband or a spectacle frame. However, due to the heat-dissipation aspects of the configuration disclosed therein, the illumination system requires a subassembly including a low-pass heat filter which tends to reduce the light output while blocking forwarding-projecting heat. The base of the assembly described in the '462 patent must be disconnected with a plurality of screws, which causes bulb replacement to be somewhat cumbersome.
The need continues to remain, therefore, for a compact, portable, lightweight illumination system wherein the majority of heat dissipation occurs through the middle portion of the assembly for more uniform cooling. A preferred design would eliminate technical problems associated with bulb replacement and reduce the number of optical components for higher efficiency. When mounted on the head of a user via a headband or spectacle frames, an improved implementation should prevent contact with a user's forehead while providing additional degrees adjustment for enhanced operational flexibility.