Illumination – Light fiber – rod – or pipe
Reexamination Certificate
1998-05-29
2002-05-07
Spyrou, Cassandra (Department: 2872)
Illumination
Light fiber, rod, or pipe
C362S559000, C362S284000, C362S293000, C385S901000
Reexamination Certificate
active
06382824
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention applies to the field of fiber optics illuminators, and more particular to those illuminators that provide a light source for solid core plastic fiber and bundled plastic or glass fibers. Recently there has been a dramatic growth in the development of large diameter solid core plastic optical fibers. An efficient, low cost means of lighting such fibers is lacking in the known fiber optics illuminators.
The principal disadvantage of currently known fiber optics illuminators is that they produce intense focused light onto the receiving end of solid core and bundled plastic fibers, which tends to heat, age and often burn the surface of the fiber ends in the illuminator, degrading them and ultimately destroying the plastic fibers prematurely. Recommended maximum continuous operating temperature for commercial plastic optical fibers is about 70 degree(s) Celsius (C.), at which point the plastic fiber ends in the illuminator tend to soften, distort and begin to melt. For greater plastic optical fiber life, continuous operational temperatures of the plastic optical fiber should be 40 degrees C. or lower. This is difficult to achieve in most fiber optic illuminators because of the light intensity into the plastic optical fiber.
Many thermal control methods are presently used to reduce the heat to protect the end of the fiber bundles in illuminators. One common method is the use of dichroic ellipsoidal reflector lamps, such as the “MR” (Miniature Reflector) halogen lamps that allow a substantial portion of the infrared energy from the lamp to pass through visible-reflectance dichroic glass reflectors instead of being reflected with the visible light into the focussed beam. Experiments have shown that such MR lamps with power as low as 42 watts will melt plastic optical fibers at the focal point within 15 seconds.
Another additional method commonly used to reduce the heat in the beam is the use of an infrared reflecting dichroic mirror between the lamp and the fiber optical fibers. This reduces the visible energy by only about 10%, and has the effect of reducing the heat load so that the 42 watt bulb will melt the plastic optical fiber ends at the focal point in about 30 seconds.
Further, some illuminators tilt an infrared-transmitting, visible-light-reflecting dichroic mirror at a 45 degree(s) angle to the optical axis, but since the mirror is near Brewster's angle, the visible beam energy is reduced by as much as 50%, and the reflected light is strongly polarized by the grazing reflection. The result is reduced thermal energy in the beam, but the technique usually only doubles the time to plastic optical fiber melting to about 60 seconds.
Further, some illuminators use a high velocity cooling fan to blow air across the end of the plastic optical fiber. This improves cooling, but such systems still do not preclude fiber burning at the focal point within a relatively short time.
After employing all of the foregoing heat removal methods, presently known, most fiber optics illuminators take the final step to prevent melting and burning of plastic optical fibers by defocusing the beam so only a portion of the energy in the visible beam strikes the plastic optical fiber. This technique is characteristic of most presently known illuminators that use 30 watt lamps or larger to illuminate plastic optical fibers. Much of the intentionally-diffused image falls outside the area of the plastic optical fibers, resulting in gross optical inefficiency from this cause alone. As a result, the optical efficiency of most typical prior art illuminators is less than 10%.
Recent fiber optics illuminators, such as disclosed in U.S. Pat. No. 5,099,399, have addressed the heat management problem by incorporating a solid core glass rod positioned in the exit aperature of the illuminator housing, wherein the glass rod attempts to dissipate the heat received from the illuminator, and thereby seperate the heat of the illuminator from the plastic optical fibers. This method is very expensive and inefficient. The glass rod needs to be long in length which substantially increases the size and length of the illuminator. The glass rod absorbs some of the infrared radiation but not enough to prevent the fiber from burning. Further, it is necessary to choose the diameter and length of the glass rod depending on the conical angle of the light emanating from the light source. These diameters and lengths of the glass rod will change according to what type of light source used. In addition, the housing of this illuminator contains cooling fins for cooling the fiber optic. Further, means of coupling fibers to such illuminators becomes a major problem and an additional cost, as an additional component, called a connector, is required to couple the glass rod to the plastic optical fibers. This type of housing is extremely expensive and does not keep the plastic fiber optic at a temperature below 40° C.
Other prior art discloses the use of a glass bundled harness, in lieu of a glass rod, for enabling plastic optical fibers to be coupled to an illuminator. The glass bundled harness loses about 40% of the light transmission, partially due to packing fraction. Further, means of coupling fibers to such illuminators becomes a major problem and an additional cost, as an additional component, called a connector, is required to couple the glass bundled harness to the plastic optical fibers.
Another fiber optic illuminator uses liquid filled lines as a means of transferring heat to cool and protect the fiber optic from degradation and premature failure. This approach is a safety concern and can be very dangerous if the liquid filled lines leak or break and the leaking liquid seeps into the electronics of the illuminator.
Prior art fiber optics illuminators, even with one or more of the forgoing heat removal methods, continue to overheat the fiber ends because the fibers are terminated in a bundle that is supported in a rubber compression bushing, much like a rubber chemical bottle stopper with a hole in the center. The bushings in this widely-used practice hold the fibers centered in the aperture of the illuminator, but the rubber is a thermal insulator that precludes the heat generated at the fiber ends from being conducted or radiated out of the fiber bundle.
The basic purpose of the present invention is to provide a fiber optics illuminator in which the focused energy falls substantially on the face of the receiving end of the solid core or bundled plastic optical fiber with minimal spillover losses, without excessive filtering losses, without rubber compression bushings, without expensive glass bundled fiber harnesses or solid core glass rods, without liquid filled cooling lines, and at operating temperatures within the plastic fiber manufacturers' recommendations.
This invention realizes the reduction of ultaviolet radiation to protect the polymeric nature of the plastic optical fiber, the removal and avoidance of dust from the optical fiber surface which provides for better light transmission and avoids burning of the dust on the light pipe surface, the maintenance of low temperatures, such as 40 degrees C. or below, at the fiber surface which avoids premature fiber degradation, thus preserving the life of the plastic optical fiber, and cost efficient componentry which allows for cost efficient fiber optic illuminators.
The prior art discloses illuminators containing a control circuit which uses a DMX controller or a master/slave circuit. DMX is a programmable language which allows the user to program the timing and sequence of the color filters or colorwheels. This method is expensive and complicated for the end user. For example, the DMX controller costs about $300 (US), without the illuminator components, and requires the end user to learn the programming language. The other prior art, the master/slave unit, adds a method of control for the color filters or colorwheels, but uses external wires to connect all the illuminators in the system. This requires the user to route exter
Costandino, Jr. Dennis Alan
Cruz, Jr. Robert Theodore
Heising Raymond Charles
Prasad Sipra Sally
Boutsikaris Leo
Bruzga Charles E.
Fiberstars Incorporated
Spyrou Cassandra
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