BACKGROUND ART

[0003] There are many different forms of lighting technology. Incandescent, fluorescent, halogen, HID (high intensity discharge) and light emitting diodes (“LEDs”) are a few examples. Incandescent lamps are a low cost relatively inefficient way of providing visible light. Fluorescent lamps are very efficient; however, their light output is relatively low.

[0004] Halogen lamps are more efficient than incandescent lamps; but, they run quite hot, still use a fair amount of energy, and emit light over a fairly specific broad spectrum, both visible and invisible. HD lamps provide a substantial amount of light energy in invisible spectra that can be useful in particular applications, such as non-destructive testing. These lamps tend to be large, run very hot, and require warm-up and cool-down time.

[0005] There are some products that utilize LEDs. LEDs are very small, run fairly cool, and are very efficient. LEDs are also available in relatively discrete spectra for specific applications requiring spectra limits, such as sources of ultraviolet or specific colours. This allows the use of light sources without filters for these applications. This keeps costs down, simplifies set-up, and improves unit efficiency.

[0006] Examples of LED light applications include multiple LEDs grouped in a single head for low power applications, such as a flashlight or a lamp for an alternative energy household. Such lamps often have many LEDs, for example 10 or more, in order to produce enough useful light energy.

[0007] Flashlights with light emitting diodes (LEDs) have advantages over flashlights with an incandescent lamp as the light source, especially in performance when the batteries deteriorate. LEDs do not lose efficiency the way incandescent lamps do when the amount of power supplied to the lamp decreases. Another advantage of LED flashlights is greater spectral content in the blue-green and blue wavelengths favorable to night vision compared to flashlights with incandescent lamps.

[0008] Others have used single or multiple LED lamps in leak detection applications. These lamps have advantages in size and power consumption; however, they also suffer from relatively low useful light energy.

[0009] Detection of leaks in systems containing fluids under pressure is often accomplished by causing visible fluorescence of fluorescent dyes that are added to the fluid in the system. Such systems may be, for example, refrigeration systems where the fluid under pressure is a refrigerant and leakage results in the fluid becoming an invisible gas upon escape. The invisibility of leaked fluid can impair detection of the leak. Addition of a fluorescent dye to the refrigerant allows easier detection of leaks by illuminating possible leakage points with radiation that causes the fluorescent dye to visibly fluoresce at the site of the leak.

[0010] Leak detection by means of use of a fluorescent dye is also used in systems other than refrigeration systems, such as automotive cooling systems and in engines having a lubricant that is under pressure.

[0011] There are many inspection lamps currently available for the purpose of illuminating potential leak sites with radiation cause visible fluorescence of fluorescent dyes. It is desirable to minimize the size, weight, cost, heat production and power consumption of such inspection lamps while having adequate output from such lamps at wavelengths suitable for causing visible fluorescence of dyes used for leak detection.

[0012] Light emitting diodes (LEDs) are used as a source of light for such inspection lamps. LEDs are more efficient at producing desired wavelengths than other light sources used in such inspection lamps. LEDs are also relatively small and produce relatively little heat. Existing LED inspection lamps have had 4 LEDs in an attempt to produce sufficient intensity at a usable distance to make a fluorescent dye fluoresce. For some situations this defeats the purpose of the LED source as additional power must be consumed and the size of the lamp is increased accordingly.

[0013] In traditional inspection lamps a broadband light source is utilized, such as an incandescent or halogen bulb. This can have an advantage over LED sources as these sources have a greater radiation output, and they emit radiation over a broad spectrum that can cause a variety of fluorescent dyes to fluoresce. LEDs have a tendency to produce light only in a narrow range of wavelengths.

[0014] However, traditional lamps suffer from a number of drawbacks. The broadband light source produces mostly radiation that is not used for detection of any fluorescent dye that has frequent use for leak detection. Also, some of the radiation may be at wavelengths normally emitted by the fluorescent materials to be detected. Filters are typically used to remove such wavelengths from the output of the inspection lamp so that light from the inspection lamp does not mask fluorescence of the fluorescent material to be detected. Radiation absorbed or reflected by filters results in heat, often necessitating means to dissipate this heat.

[0015] Alternatively, inspection lamps have been produced using electric discharge light sources since such light sources are often more efficient than incandescent light sources at producing wavelengths suitable for causing visible fluorescence of materials used for leak detection. Such inspection lamps have their own disadvantages such as the cost of the special discharge light sources, the added cost of electrical components required for operation of such light sources, a requirement for some such light sources to spend time warming up to a required elevated operating temperature in order to properly function, and the tendency of many discharge light sources to specialize in production of wavelengths not effectively utilized by all popular fluorescent dyes.

[0016] As mentioned previously, UV LEDs or LEDs that provide significant UV radiation can be used for many different applications including, for example, in inspection lamps that are used to detect fluorescent materials, such as leaks of fluids under pressure where the fluids have a suitable fluorescent dye. Unlike most light emitting diodes which have their light emitting diode (LED) chips encapsulated in epoxy packages, these light emitting diodes typically have their chips in hollow containers that lack an encapsulate. This is because the usual epoxy encapsulates are not sufficiently transparent to ultraviolet radiation or are discolored by the ultraviolet radiation produced by the LED chips. Unfortunately, the lack of an encapsulate results in a reduction of radiation output as the LED chip is surrounded by a medium (air) having a refractive index that is lower than, and worse than epoxy at being significantly different from, the refractive index of the chip material.

[0017] In an attempt to increase radiation output, ultraviolet light emitting diodes having chips encapsulated in epoxy packages are available. Epoxy has a higher refractive index than air does; so, epoxy's refractive index is closer to that of the LED chip material. Initially, ultraviolet LEDs with epoxy packages produce more radiation output than ultraviolet LEDs made with hollow containers do; however, over time, the epoxy near the LED chip is damaged by the ultraviolet radiation and this causes the output of these LEDs to significantly degrade within a few hundred hours of operation LEDs having peak wavelength as long as 420 nm, in the blue-violet range of the visible spectrum, degrade significantly after several hundred hours of operation.

[0018] There is a need to derive the full benefit of utilizing LED light sources in inspection lamps. There is also a need to retain some of the benefits of traditional light sources. Further improvements in lighting technology are desirable. It is an object of the invention to address these or other issues associated with LEDs and LED lamps.

DISCLOSURE OF THE INVENTION

[0019] In a first aspect the invention provides an inspection lamp having light emitting diodes as a source of radiation suitable for causing visible fluorescence of fluorescent materials, where said light emitting diodes are substantially non-identical in spectral characteristics of their emitted radiation, such that at least one but not all of said light emitting diodes in said inspection lamp produce wavelengths of radiation that are favorable for causing visible fluorescence of some fluorescent materials, and such that one or more different said light emitting diodes in said inspection lamp produce substantially different wavelengths of radiation which are more favorable than the wavelengths of first said light emitting diode(s) for causing visible fluorescence of some fluorescent materials other than first said fluorescent materials.

[0020] At least one light emitting diode may have a peak emission wavelength in the ultraviolet and at least one light emitting diode may have a peak emission wavelength that is visible but suitable for causing visible fluorescence of fluorescent materials.

[0021] At least one light emitting diode may produce mostly blue visible light and at least one light emitting diode may produce mostly visible violet light or ultraviolet radiation.

[0022] At least one light emitting diode may have a peak emission wavelength in the range of 425 to 480 nanometers and at least one light emitting diode may have a peak emission wavelength in the range of 360 to 430 nanometers.

[0023] The inspection lamp may have one or more lenses to collimate the radiation produced by at least some of the light emitting diodes. The radiation produced by each light emitting diode may be collimated by a separate lens associated with or mounted forward from each said light emitting diode.

[0024] The inspection lamp may have a handle. The handle may share a longitudinal axis with the inspection lamp as a whole. The handle may not share an axis with any other major portion of said inspection lamp.

[0025] The inspection lamp may accept one or more dry cells as a source of power. The inspection lamp may accept power from an external power source. The external power source may be a source of direct current with a voltage of substantially 12 volts. The external power source may be a source of alternating current with a voltage of substantially 110-125 volts. The external power source may be a source of alternating current with a voltage of substantially 220-240 volts. The inspection lamp may have one or more rechargeable cells as a source of power. The inspection lamp may have means to recharge its rechargeable cells.

[0026] The inspection lamp may have one or more dropping resistors to limit the amount of current which flows through at least one of the light emitting diodes. The inspection lamp may have non switching current regulation means to control the amount of current which flows through at least one of the light emitting diodes. The inspection lamp may have switching current regulation means to control the amount of current which flows through at least one of the light emitting diodes. The inspection lamp may be of such design that at least one of the light emitting diodes does not require separate means to limit or control the amount of current flowing through said light emitting diode.

[0027] Any of the light emitting diodes may be laser diodes. The laser diodes may be intended to normally operate in a laser mode. The laser diodes may be intended to normally operate in a non-laser mode. Oblong beams from each laser diode may be directed into different directions so as to achieve an overall beam pattern that is not oblong. The inspection lamp may have optical means to correct oblong characteristics of the beams produced by most types of laser diodes. The inspection lamp may have one more cylindrical lenses to correct oblong characteristic of the laser diodes. The inspection lamp may have optics other than cylindrical lenses to correct oblong beam characteristic of laser diodes. The inspection lamp may be of such design as to produce beams not having the oblong characteristic typical of laser diodes. In a second aspect the invention provides a module having light emitting diodes that are substantially non-identical and which produce a variety of wavelengths suitable for exciting a variety of fluorescent dyes, and suitable for replacing the bulb and/or the reflector of a flashlight so as to achieve an inspection lamp. The inspection lamp may contain one or more of the modules.

[0028] The inspection lamp may have one or more light emitting diode modules, where at least one light emitting diode module has only one type of light emitting diode but the inspection lamp as a whole includes more than one type of light emitting diode so as to produce a variety of wavelengths suitable for exciting a variety of fluorescent dyes.

[0029] In a third aspect the invention provides an inspection lamp having two or more light emitting diodes that produce radiation suitable for causing visible fluorescence of fluorescent materials, and a lens forward from each of said light emitting diodes to collimate the radiation from each light emitting diode into a beam, such that the beams of radiation individually associated with each of said light emitting diodes project forward from said lenses and merge together.

[0030] The individual beams that project forward from each lens may be parallel to each other. The individual beams may converge towards each other such that the axes of the beams intersect with each other at a specific distance forward of the lenses. The individual beams may have an angular diameter greater than any angle between any two axes of said beams, such that some area can be illuminated by all said beams at any distance from the lenses greater than distance from the lenses to the point at which the beam axes intersect.

[0031] The lenses may be comprised by a single piece of suitable transparent material. Each lens may have a center of curvature of at least one curved surface displaced from the axis of its associated light emitting diode so as to form a beam having an axis that is not parallel to said axis of said light emitting diode.

[0032] A lens assembly may have a longitudinal axis and convex lenses each having at least once curved surface with a center of curvature at a location other than on a line parallel to said lens assembly axis and passing through the center of the area of said lens, so as to be suitable as the lenses of the inspection lamp.

[0033] As stated previously for other aspects, the inspection lamp may or may have a handle, and use a variety of internal or external power sources with or without current limiting devices

[0034] The light emitting diodes may differ significantly in spectral characteristics so as to cause visible fluorescence from fluorescent substances which visibly fluoresce from the output of one or more but not all of said light emitting diodes.

[0035] Separate switches may be provided for each type of light emitting diode used within said inspection lamp.

[0036] At least one light emitting diode may have a peak wavelength that is ultraviolet and at least one light emitting diode may have a peak wavelength that is visible. At least one light emitting diode may have a peak wavelength less than 425 nanometers and at least one light emitting diode may have a peak wavelength greater than 425 nanometers.

[0037] In a fourth aspect the invention provides an LED inspection lamp having a plurality of LED sources. Each source emits electromagnetic radiation at a different peak wavelength. Each different peak wavelength causes visible fluorescence in a different leak detection dye. A lens may be associated with each LED so that radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses.

[0038] In a fifth aspect the invention provides an LED inspection lamp having a single LED for emitting electromagnetic radiation at a peak wavelength for causing visible fluorescence in a leak detection dye, and a lens associated with the LED so that substantially all of the radiation passes through the lens and is substantially directed to a target area at a target distance from the lenses.

[0039] In a sixth aspect the invention provides an LED inspection lamp having a plurality of LEDs emitting electromagnetic radiation at a peak wavelength for causing visible fluorescence in a leak detection dye, and a lens associated with each LED so that the electromagnetic radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses.

[0040] In a seventh aspect the invention provides a lens adaptor having a lens housing for attachment to an LED inspection lamp with a single LED emitting electromagnetic radiation at a peak wavelength for causing visible fluorescence in a leak detection dye, and a lens within the housing. The lens and housing are associated with the LED so that substantially all of the radiation passing through the lens from the LED is substantially directed to a target area at a target distance from the lenses.

[0041] In an eighth aspect the invention provides a lens adaptor having a lens housing and lenses. The lens housing is for attaching to an LED inspection lamp with a plurality of LEDs emitting electromagnetic radiation at a peak wavelength for causing visible fluorescence in a leak detection dye. The lenses are for associating with each LED when the lens housing is attached to the inspection lamp. Radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses.

[0042] In a ninth aspect the invention provides a lens and LED assembly for use within a flashlight casing. The assembly has a plurality of LEDs emitting electromagnetic radiation at a peak wavelength for causing visible fluorescence in a leak detection dye, and a lens associated with each LED so that the electromagnetic radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses. The assembly is shaped to fit within the flashlight casing.

[0043] In any of the aspects a lens may be movable to permit adjustment of beam characteristics. The focal length of the lenses and the distance between the lenses (or lens assembly and the light emitting diodes) may be adjustable so as to permit changing the distance at which beam size and intensity formed by each light emitting diode and each associated lens are best-formed. The distance between lens centers may be smaller than the distance between the centers of their associated light emitting diodes so that the beam components formed by each lens from its associated light emitting diode converge towards each other.

[0044] The beam components formed by each lens from its associated light emitting diode may converge towards each other so that all beam components coincide at a distance which can be changed by changing the location of the LEDs.

[0045] An inspection lamp may further incorporating means to restrict the possible adjustments to a range of adjustments where the beam elements are best-formed at the same distance forward from said inspection lamp at which said beam elements are coinciding with each other.

[0046] In a tenth aspect the invention provides a light producing assembly having two or more light emitting diodes. The assembly also has a lens forward from each of the light emitting diodes such that the light from the light emitting diodes is collimated into a beam.

[0047] In an eleventh aspect the invention provides a spot light having two or more light emitting diodes. The spot light also has a lens forward from each of the light emitting diodes such that the light from the light emitting diodes is collimated into a beam.

[0048] Each of one or more of the LEDs may be offset from the optical center of its associated lens to cause the radiation passing through the lenses to be substantially superimposed to a target area at a target distance

[0049] The spot light may have a light producing assembly. The spot light may be suitable for use as a fixed spot light. The spot light may be able to accept as a power source essentially 120 volts alternating current, 230 volts alternating current, 12 volts direct current, or 28 volts direct current, such as from a battery source.

[0050] The spot light may be able to accept direct current as a power source. The spot light may be able to accept direct current as a power source and operate even if the polarity of the direct current is reversed.

[0051] The spot light may have light emitting diodes that are essentially identical. The spot light may have light emitting diodes that produce white light. The spot light may have LEDs that produce visible light of different colors. The spot light may have light emitting diodes including red, green and blue light emitting diodes to achieve essentially white light. The spot light may be a flashlight.

[0052] The spot light may have light emitting diodes that individually produce light of different colors that combine to form light that is essentially white. The spot light may have orange, blue-green and violet light emitting diodes that are used to achieve essentially white light. The spot light may have yellow, turquoise and magenta or yellow, green and blue light emitting diodes that are used to achieve essentially white light.

[0053] The spot light may have light emitting diodes essentially of two complimentary colors that are used to achieve essentially white light. The spot light may have light emitting diodes of more than three distinct colors. The spot light may produce essentially yellow light.

[0054] The lenses may be part of a lens assembly that can be moved with respect to the light emitting diodes. The lens assembly may be part of an assembly that slides over the light emitting diodes. The spot light may have a thumbwheel for use to adjust the distance between the lens assembly and the light emitting diodes. The distance between the lenses and the light emitting diodes may be adjustable by rotating a collar that moves the lenses.

[0055] In a twelfth aspect the invention provides an LED spot light having a plurality of LEDs emitting electromagnetic radiation. The spot light also has a lens associated with each LED so that the electromagnetic radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses.

[0056] In a thirteenth aspect the invention provides a lens adaptor having a lens housing and lenses. The lens housing is for attachment to an LED spot light with a plurality of LEDs emitting electromagnetic radiation. The lenses are associated with each LED when the lens housing is attached to the spot light so that the radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses.

[0057] In a fourteenth aspect the invention provides a lens and LED assembly. The assembly has a plurality of LEDs emitting electromagnetic radiation. The assembly also has a lens associated with each LED so that the electromagnetic radiation passing through all lenses from their associated LEDs is substantially superimposed to a target area at a target distance from the lenses.

[0058] The distance between the lenses and LEDs may be adjustable so as to permit changing the distance at which beam components formed by each light emitting diode and each associated lens are best focused.

[0059] The LED locations may be changeable to permit adjustment of the convergence angle formed by each lens/LED relationship to change the best focus distance.

[0060] The distance between lens centers may be smaller than the distance between the centers of their associated light emitting diodes so that the beam components formed by each lens from its associated light emitting diode converge towards each other.

[0061] The beam components may be formed by each lens from its associated light emitting diode converge towards each other so that all beam components coincide at a distance which can be changed by changing the distance between the lenses and the LEDs.

[0062] The distance between the lenses and the light emitting diodes may be adjustable so as to permit adjustment of the distance at which beam components are focused in addition to permitting adjustment of the distance at which beam elements are coinciding with each other. The distance between the lenses and the LEDs may be adjustable by means of a thumbwheel. The distance between the lenses and the LEDs may be adjustable by rotating a collar that changes the distance between the lenses with respect to the LEDs.

[0063] A fourteenth aspect of the invention is changing the focal length of the lenses to increase the size of the spot of light by decreasing the focal length of the lenses and the distance between the lenses and LEDs or to reduce the size of the spot of light by increasing the focal length of the lenses and the distance between the lenses and LEDs.

[0064] The distance separating the LEDs from each other may be adjustable along with the distance between the lenses and the LEDs. The distance separating the LEDs and the distance between the lenses and the LEDs may both be adjusted by the same adjustment.

[0065] The lenses may be within and spaced about a single lens mount, and the LEDs may be mounted on a printed circuit board. An assembly may also have a spacer through which the LEDs project, the spacer for correctly spacing the LEDs with respect to one another for alignment with the lenses.

[0066] There may be a separator between the lenses and the LEDs, such that light from each LED cannot pass through the separator to a lens not associated with LED, and light from each LED can pass through the separator to the lens associated with that LED.

[0067] There may be a baffle that includes the spacer and the separator. The baffle and lens mount may be fixed to one another to limit relative movement of the baffle and the lens mount. The printed circuit board may be held in fixed relationship to the lens mount, with a desired distance between the lenses and their associated LEDs. The lens mount may have a tubular body extending away from the lenses, and the baffle may fit within the tubular body until the separator meets the lens mount about the lenses.

[0068] The lens mount may have a tubular body extending away from the lenses, and the printed circuit board may be fixed to the tubular body.

[0069] In a fifteenth aspect the invention provides an LED lamp including an LED source having a plurality of LED chips with each chip producing a beam of radiation. It also includes a plurality of lenses with each lens capturing a beam of radiation from an LED chip of the LED source. The lenses collimate the captured beams of radiation to produce collimated beams of radiation and the lenses merge the collimated beams of radiation at a target distance.

[0070] The LED source may be a LED cluster including the plurality of LED chips within a single encapsulant package. The lenses may be part of the encapsulant package.

[0071] In a sixteenth aspect the invention provides an LED lamp including an LED source having a plurality of LED chips with each chip producing a beam of radiation. It also includes a plurality of lenses with each lens for capturing a beam of radiation from an LED chip of the LED source. The lenses collimate the captured beams of radiation to produce collimated beams of radiation and the lenses merge the collimated beams on radiation at a target distance. The LED chips emit radiation including wavelengths of 425nm or less.

[0072] In a seventeenth aspect the invention provides an LED source including a plurality of LED chips with each chip producing a beam of radiation with at least one anode for connection, directly or indirectly, between a source of power for the LED source and one of the LED chips. The source also includes at least one cathode for connection, directly or indirectly, between a source of power for the LED source and one of the LED chips. The source further includes an encapsulant for encapsulating each of the LED chips. The encapsulated LED chips are part of a single encapsulant package. The radiation from the LED chips is emitted from the encapsulant package. The encapsulant includes a stabilizing agent; so that, the encapsulate resists degradation by radiation produced from the LED chips, while allowing desired radiation from the LED chips to pass through the encapsulant and exit the LED.

[0073] The encapsulant may include an epoxy. The stabilizing agent may include an antioxidant The antioxidant may be a hydrogen donor. The hydrogen donor may include a substituted phenol. The substituted phenol may include those with substituents in the 4- position. The substituted phenol may include those with substituents providing steric hindrance in the 2,6- position.

[0074] The antioxidant may be a hydroperoxide decomposer. The hydroperoxide decomposer may be a phosphate. The hydroperoxide decomposer may be a phosphonite. The hydroperoxide decomposer may be a sulfie. The hydroperoxide decomposer may be a dialkyldithiocarbamate. The hydroperoxide decomposer may be a dithiophosphate.

[0075] The antioxidant may include a radical scavenger. The radical scavenger may be a tetramethyl piperidine derivative.

[0076] The encapsulant may include a light stabilizer. The light stabilizer may include a quencher. The light stabilizer may include a non-UV absorber-light stabilizer. The non- UV absorber light stabilizer may be a substituted tetramethylpiperidine derivative. The substituted tetramethylpiperidine derivative may include a sebacate. The sebacate may be a bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate.

[0077] The light stabilizer may include a UV absorber. The UV absorber may include a substituted derivative of benzophenone. The substituted derivative of benzophenone may be a hydroxybenzophenone. The hydroxybenzophenone may be 2,4-dihydroxybenzophenone. The hydroxybenzophenone may be 2,2′-dihydroxy-4,4′-dimethoxybenzophenone. The 25 hydroxybenzophenone may be 2-hydroxy-4-methoxybenzophenone.

[0078] The UV absorber may be a substituted derivative of benzotriazole. The substituted derivative of benzotriazole may be a phenylbenzotriazole. The phenylbenzotriazole may be 2-(2-hydroxy-5-methylphenyl) benzotriazole. The phenylbenzotriazole may be 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol. The UV absorber may include a substituted hydroxyphenyl triazine.

[0079] The encapsulant may include a polyacrylate. The encapsulant may include a styrene. The encapsulant may include a carbonate. The encapsulant may include an urethane. The encapsulant may include an amide. The encapsulant may include an acetal. The encapsulate may include an olefin. The encapsulant may include a copolymer of two or more polyacrylates, styrenes, carbonates, urethanes, amides, acetals and olefins.

[0080] The encapsulant package may be shaped to produce, for each LED chip, a round image of the radiation emitted from each LED chip forward of the LED chip. The encapsulant package may include a plurality of lenses forward from the LED chips, wherein each lens captures a beam of radiation from an LED chip of the LED source, the lenses collimate the captured beams of radiation to produce collimated beams of radiation, and the lens merge the collimated beams of radiation at a target distance

[0081] In an eighteenth aspect the invention provides an LED lamp including an LED source of one of the other aspects, and a plurality of lenses separate from the encapsulant package, and forward from the LED chips. Each lens captures a beam of radiation from an LED chip of the LED source. The lenses collimate the captured beams of radiation to produce collimated beams of radiation. The lens merge the collimated beams of radiation at a target distance.

[0082] In a nineteenth aspect the invention provides a LED, including one or more LED chips encapsulated in an encapsulant package. The one or more LED chips have a peak emission wavelength of less than 425 nm. The encapsulant is epoxy mixed with a stabilizing agent to resist damage to the epoxy by radiation from the LED chip(s) while allowing desired radiation from the LED chips to pass through the encapsulant and exit the LED.

[0083] The encapsulant may include a mixture in which a piperidyl sebacate is combined with at least one of a benzophenone or benzotriazole in the range of 0.01-0.5 percent by weight of the encapsulate.

[0084] In a twentieth aspect the invention provides a light emitting diode having one or more LED chips encapsulated in an encapsulant package. The LED chip(s) have a peak emission wavelength of less than 425 nm. The encapsulant is epoxy mixed with a phenolic inhibitor to resist damage to the epoxy by radiation from the LED chip(s).

[0085] In a twenty-first aspect the invention provides a light emitting diode having one or more LED chips encapsulated in an encapsulant package. The LED chip(s) have a peak emission wavelength of less than 425 nm. The encapsulant is epoxy mixed with a hindered amine light stabilizer to resist damage to the epoxy by radiation from the LED chip(s).

[0086] In a twenty-second aspect the invention provides a light emitting diode having one or more LED chips encapsulated in an encapsulant package. The LED chip(s) have a peak emission wavelength of less than 425 nm. The encapsulant is epoxy mixed with a dye that absorbs radiation produced by the LED chip(s) so as to resist damage to the epoxy by radiation from the LED chip(s) while allowing desired radiation from the LED chips to pass through the encapsulant and exit the LED.

[0087] In a twenty-third aspect the invention provides a light emitting diode having one or more LED chips encapsulated in an encapsulant package. The LED chip(s) have a peak emission wavelength of less than 425 nm. The encapsulant is an acrylic. The acrylic may be polymethylmethacrylate.

[0088] In a twenty-fourth aspect the invention provides a light emitting diode having one or more LED chips encapsulated in an encapsulant package. The LED chip(s) have a peak emission wavelength of less than 425 nm. The encapsulant is a combination of an acrylic and polystyrene.

[0089] The encapsulant may be in the form of a casting resin.

[0090] The stabilizing agent may include an antioxidant.

[0091] In a twenty-fifth aspect the invention provides an LED inspection lamp using one of the LEDs of the above aspects. The LED may include additional circuitry. The additional circuitry may limit or regulate current through the LED.

[0092] The LEDs of the above aspects may be cluster LEDs having at least two LED chips. The cluster LEDs may include a domed region forward of each LED chip for optical purposes. The domed regions may have such optical properties as to form a usably collimated beam of radiation from the LED chips without additional optics. The domed regions may have such optical properties that additional optics would be used in order for a suitably collimated beam of radiation from the LED chips to be formed.

[0093] In a twenty-sixth aspect the invention provides a LED having one or more LED chips encapsulated in an encapsulant package. The LED chip(s) have a peak emission wavelength of less than 425 nm. The encapsulant package includes an inner layer surrounding the LED chip. The inner layer is an encapsulant material which is not damaged by ultraviolet radiation as easily as epoxy is. The encapsulant package also includes an outer layer which is a rigid material. The inner layer of the encapsulant package may be rigid. The inner layer of the encapsulate package may be in the form of a casting resin. The inner layer may include an acrylic. The acrylic may be polymethylmethacrylate. The inner layer may include polystyrene. The inner layer may be a polycarbonate.

[0094] In a twenty-seventh aspect the invention provides an inspection lamp, suitable for causing visible fluorescence of visibly fluorescent substances. The lamp includes at least one cluster LED as set forth in the above aspects. The LED inspection lamp may also include additional optics typically required to form a collimated beam of radiation from the cluster LED.

[0095] In a twenty-eighth aspect the invention provides an inspection lamp, suitable for causing visible fluorescence of visibly fluorescent substances. The lamp includes a cluster LED as set forth in the above aspects.

[0096] In a thirtieth aspect the invention provides an epoxy encapsulate, suitable for making LEDs having a peak wavelength of less than 425 nanometers. The encapsulant includes a stabilizing agent to resist damage to the epoxy by radiation produced by LED chips in the LEDs.

[0097] In a thirty-first aspect the invention provides a LED, suitable for use in an LED inspection lamp. The LED includes two or more LED chips with a peak wavelength of less than 425 nanometers in a single encapsulant package.

[0098] In a thirty-second aspect the invention provides a LED, suitable for use in an LED inspection lamp. The LED includes: two or more LED chips with a peak wavelength of between 425 and 450 nanometers in a single encapsulant package.

[0099] In a thirty-third aspect the invention provides a LED including one or more LED chips, an encapsulant for encapsulating one or more of the LED chips, and a stabilizing agent within the encapsulant. The stabilizing agent resists degradation of the encapsulant by radiation emitted from one or more of the LED chips.

[0100] The encapsulant may include an epoxy. The stabilizing agent may include one or more of a phenolic inhibitor, an antioxidant, a hindered amine light stabilizer, a light stabilizer other than hindered amine light stabilizers, and a light absorber that absorbs damaging wavelengths while transmitting desirable wavelengths. One or more of the LED chips emits radiation at a peak wavelength of 425 nm or less. The encapsulant may include one or more domed regions, each domed region being forward of an LED chip.

[0101] In a thirty-fourth aspect the invention provides a LED lamp including a cluster LED of one of the above aspects with domed regions, and a lens forward of each domed region of the LED. The lenses may collimate beams produced by the LED.

[0102] In a thirty-third aspect the invention provides a flashlight including a cluster LED of one of the above aspects. Other aspects and embodiments of the invention are set out elsewhere herein, or will be evident to those skilled in the art based on the principles presented herein.