Transcript
Invisible Flame and Ultraviolet Light Viewer
The present invention relates to a portable fire imaging system for use in detecting the presence of a hydrogen flame or any flame that emits a significant amount of ultraviolet light. Hydrogen flames are typicallyinvisible to the unaided human eye. Previous methods of detecting such a flame include the use of non-imaging fire detectors. Such detectors do not produce an image of the flame and do not provide information about the size or precise location of the flame. Also, such firedetectors are not intended to be portable. Additionally, current flame imaging systems include the use of a camera or other actively powered electronic components to perform their function. This system does not use a camera or other actively powered electronic components. Therefore, this is a smaller, light weight design that does not involve cameras. This invention is a device that can present combined ultraviolet and visible light to a human for viewing by using only passive optical elements.
In this system ultraviolet and visible light passes through a magnifying lens that displays the image onto fluorescent doped fiber optics that converts the ultraviolet light into visible light. Individual light conducting fibers have a light receiving face and light emitting face. The image emitted from the fiber optic can be magnified by an eye piece. In one embodiment holey fluorescent doped optical fibers convert ultraviolet light into visible light. In its most basic embodiment this system includes a housing with a single lens in the housing and a plurality of fluorescent doped optical fibers also within the housing and those fibers optically coupled to the lens. This would be a monocular or telescope configuration. The fibers do not have to be in anholey arrangement. They do need to be fluorescent doped and capable of guiding the light reemitted by the fluorescent particles. The holey arrangement achieves waveguiding with a glass fiber that has a uniform index of refraction by using air as a medium with a smaller index of refraction and total internal reflection. Waveguiding can also be achieved with a gradient or step change in the index of refraction of the glass. Stacking a bundle of fibers into a block may still leave a holey arrangement, but the holes do not contribute to the waveguiding. Waveguiding can also be achieved by a reflective cladding. Fibers could be arranged with air spaces between the sides of the fibers to aid in internal reflection and transmission of light through the fibers, fibers could be ungraded, graded, or graded with an absorbing outer layer. The absorbing outer layer can be included to reduce cross talk between fibers.
For lighter lower cost applications a monocular or telescope configuration could be used. However, in a binocular configuration, the stereoscopic effect, which is achieved by using both eyes to view an object, allows for much better tracking of moving objects. A monocular is suited for situations where the objects being viewed are relatively stationary.
An additional option would have the fluorescent doped fibers configured in a fiber optic faceplate. In one option the fluorescent doping would utilize a material that converts ultraviolet light into green photons. Another option would provide a second lens with a second bundle of fibers. The two lenses and fiber bundles could be incorporated into a single housing which would essentially be a binocular configuration. A housing option could incorporate a tube shape in order to provide better optical viewing and shade external interfering visible light. Additional features could be incorporated such as the capabilities to zoom, or focusthe image. Also, additional filterscould tailor the system to specific applications. Also the selection of doping material can tailor the system to a specific frequency of interest. The attached figures describe some problems with existing systems and describe the invention. Figure 1 shows an ordinary passive optical imaging system for visible light. It consists of lenses and apertures.
Figure 2 shows an ordinary passive optics imaging system. This system transmits ultraviolet light that cannot be seen by the human eye. Fused silica or other specialized optics are needed to transmit the ultraviolet light without absorption.
Figure 3 shows a standard active optic electronic ultraviolet imager. This system converts an ultraviolet light image into electronic format, usually with a CCD camera, and then projects a visible light image with a small TV screen back to the human for viewing. These devices tend to be bulky, expensive and require electric power. This is one type of device that this invention intends to replace.
Figure 4 shows an ineffective use of fluorescent glass to image ultraviolet light. The fluorescent doping in the glass converts the ultraviolet light to a visible form. However, the scattering of the fluorescent process smears the image and prevents imaging with ordinary doped optical lenses.
Figure 5 shows one embodiment of the invention concept. It uses a fluorescent doped holey optical element to provide the ultraviolet imaging. The holey optical element consists of an array of parallel fluorescent doped optical fibers. Each fiber in the holey element converts ultraviolet light into visible light (green in the samples used in the prototypes). One significant difference from figure 4 is that the holey fibers channel the fluorescent light by total internal reflection to the end to form an image of pixels. In this example the fiber diameters (approximately 100 ยต m or less) are small enough to form a good pixilated image. The holey fiber element may also transmit visible light.
Figure 6 shows more details in a side view of a holey fiber optic array element.
Figure 7 shows an end view of a holey fiber optic array element.
Figure 8 shows an end view of an unclad fiber optic element. This is a less expensive option, but is less capable of guiding light than clad, and clad with coating fibers.
Figure 9 shows an end view of a clad fiber optic element. This is a somewhat more expensive option, but is more capable of guiding light than unclad fibers.
Figure 10 shows an additional option for an improved fiber optic element that is clad and has an opaque coating. The cladding improves the light wave guiding. The opaque coating reduces the cross talk between the fibers. This additional optional combination of characteristics would be especially useful in this system that does not use any active means to detect or transmit the flame image.
Figure 1: Ordinary passive optics visible light imaging system
Visible light
Basic optical
Inverted
Visible to the human eye
Figure 2: Ordinary passive optics imaging system transmits ultraviolet light that cannot be seen by the human eye
Invisible UV light, e.g. from hydrogen or alchohol flame
Fused silica optical lens
Inverted image
Invisible to the human eye
Figure 3: Electronic Ultraviolet Imager
Video screen with image
Ultraviolet light
Fused Silica optical lens
Inverted image
CCD/CMOS Camera and processor
Converted image can be seen by human eye
Figure 4: Fluorescence Glass Fluorescent glass converts Ultraviolet light to green light. The scattering of the fluorescent dopants smears the image and prevents viewing an image.
Ultraviolet light
Fluorescent Glass
Green Blob
Objects appear fuzzy and smeared to the human eye
Figure 5: Fluorescence with Holey Optics
Holey Fluorescent Optics
Ultraviolet light
Fused Silica optical lens
Inverted image
Visible image
Ultraviolet light is converted to green light all other light appears normal
Figure 6:
Scattering
Ultraviolet
Total internal reflections
Image quality visible light
Ultraviolet light is converted to green light all other light appears normal
Figure 7: Holey optic lens
Air holes for total internal reflection
Fiber
End view of the Holey Optical Element
Figure 8: Holey optics Option 1 Ungraded Glass Fiber
Fiber Optic
Figure 9: Holey optics Option 2 Graded index glass fiber for better total internal reflection
Fiber Optic
Cladding
Figure 10: Holey optics Option 3 (Concept only, not yet built) Graded index and absorbing outer layer for better total internal reflection and reduced cross-talk Fiber Optic Absorbing layer prevents cross-talk between fibers
Cladding
