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ENHANCED INTENSITY FROM UV LAMPS

IP.com Disclosure Number: IPCOM000010315D
Publication Date: 2002-Nov-20
Document File: 3 page(s) / 95K

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IPCOM000010314D: IP.COM

Abstract

During operation of many UV lamps or an integrated sphere together with a UV lamp, ozone is generated. Ozone absorbs UV light, resulting in decreased UV intensity. We have found that blowing N2 gas on to an Hg lamp or in an integrated sphere together with an Hg lamp, ozone generation from the lamp may be avoided or at least reduced and enhance the intensity, uniformity and stability of UV light from the lamp. The light intensity was enhanced by as much as a factor of 8.

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ENHANCED INTENSITY FROM UV LAMPS

Problem or object to be solved

During operation of many UV lamps or an integrated sphere together with a UV lamp, ozone is generated. Ozone absorbs UV light, resulting in decreased UV intensity.

We have found that blowing N2 gas on to an Hg lamp or in an integrated sphere together with an Hg lamp, ozone generation from the lamp may be avoided or at least reduced and enhance the intensity, uniformity and stability of UV light from the lamp. The light intensity was enhanced by as much as a factor of 8.

State of the art

Generation of ozone from UV lamps is a well-known fact. It is also well known that ozone absorbs UV light. Integrated spheres are used extensively for obtaining uniform light sources. However, the idea of enhancing the UV performance of UV lamps by ozone reduction has not been seen.

Disadvantage(s) of the state of the art

Commercial systems are available for elimination of ozone from UV lamps. However, the primary purpose for these systems is to reduce the concentration of toxic ozone and not to enhance the UV output from the lamps.

Short description of the idea

A mercury lamp (Hg-lamp) has been employed as a UV source for calibration of CCD cameras. The Hg lamp can generate radiation with wavelength ranging from deep UV to visible spectrum. In the UV range, there is a strong peak at 253.7 nm, which has been used for CCD camera calibration.

For obtaining a uniform light source, a UV lamp in combination with a UV sensitive integrating sphere can be used. The light from the lamp can be directed into or enclosed in the integrating sphere. As a result of multiple reflections in the sphere, a uniform light source can be obtained at the exit port of the sphere.

During the operation of the Hg lamp, ozone is generated as a by-product. Ozone is generated by photons with wavelength below ~242 nm. Ozone absorbs UV light with an absorption peak around 254 nm. The degree of UV absorption depends on the absorption coefficient, the concentration of ozone and path length through the absorbing medium, as described by the Beer-Lambert law. Furthermore, generation of ozone results in intensity variations since air fluctuations or diffusion of ozone in air would result in varying ozone concentration and thereby varying absorption of UV light.

We have found that by blowing N2 on the Hg lamp, the intensity of the 253.7 nm photons increases by up to 60%. This is believed to be caused by the reduction or elimination of ozone generated from the Hg lamp. The concentration of ozone will depend on the power of the lamp. For the Hg lamp which has been used in the current studies, ~1.5 ppm ozone was formed in the vic...