IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
UP-0478484
(2006-06-29)
|
등록번호 |
US-7570426
(2009-08-24)
|
발명자
/ 주소 |
- Rodgers, Wayne
- Erlandson, Robert E.
- Hargis, C. Bryon
- Murphy, Neil
|
출원인 / 주소 |
- The Johns Hopkins University
- The Eddy Company
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
4 인용 특허 :
17 |
초록
▼
Techniques for filtering light include, along a central optical axis, an entrance window; a first polarizer, a narrowband polarization-changing material, a second polarizer, and an exit window. The optical paths through the filter are substantively unscattered and pass through unstressed components
Techniques for filtering light include, along a central optical axis, an entrance window; a first polarizer, a narrowband polarization-changing material, a second polarizer, and an exit window. The optical paths through the filter are substantively unscattered and pass through unstressed components between the polarizers. The polarization-changing material changes polarization for a narrow wavelength band on the order of about 0.01×10-9 meters and does not condense on optical windows and polarizers during the operational lifetime. An aspect ratio, defined by a distance from the entrance window to the exit window divided by an optical aperture for the entrance window, is less than 4/1. This filter thus transmits light substantively unattenuated in the narrow wavelength band up to a maximum acceptance angle greater than 5 degrees. Combined with optics and imaging detectors, it is suitable for wide area surveillance, including daylight surveillance for combustion like forest fire and missile plume.
대표청구항
▼
What is claimed is: 1. An apparatus for wide-angle narrowband filtering of optical energy comprising: an optical entrance window for admitting light to the apparatus; a first polarizer to determine a first polarization state of light transmitted through the first polarizer and separated a first dis
What is claimed is: 1. An apparatus for wide-angle narrowband filtering of optical energy comprising: an optical entrance window for admitting light to the apparatus; a first polarizer to determine a first polarization state of light transmitted through the first polarizer and separated a first distance no less than zero from the optical entrance window along a central optical axis; a second polarizer oriented to substantively block light having the first polarization state and separated a second distance, greater than the first distance, from the optical entrance window along the central optical axis; a narrowband polarization-changing material disposed between the first polarizer and the second polarizer; and an optical exit window for transmitting light away from the second polarizer separated a third distance, no less than the second distance, from the optical entrance window along the central optical axis; wherein the polarization-changing material changes polarization for a narrow wavelength band width on the order of about 0.01×10-9 meters; the polarization-changing material does not condense on optical windows and polarizers during an operational lifetime for the apparatus; no optical window between the first polarizer and second polarizer is subject to a polarization-inducing stress; a negligible portion of light transiting the apparatus incident at an incident direction less than a maximum acceptance angle from the central axis is scattered into a different direction; and an aspect ratio, defined by a distance from the optical entrance window to the optical exit window divided by an optical aperture for the optical entrance window, is less than 4/1, whereby the apparatus transmits light in the narrow wavelength range in each of a plurality of directions up to the maximum acceptance angle around the central axis and a tangent of the maximum acceptance angle is equal to half of a reciprocal of the aspect ratio and the maximum acceptance angle is greater than 7 degrees; and wherein: the polarization-changing material is a metal vapor that rotates polarized light in the narrow wavelength band when subjected to a magnetic field; and the apparatus further comprises a magnet to produce the magnetic field; and a heater to heat a particular component that contacts the metal vapor to prevent condensation of metal from the metal vapor onto the particular component; wherein: the apparatus further comprises an inner chamber of walls that encloses the metal vapor, the walls of the inner chamber include a first inner optical window and a second inner optical window; the first inner optical window admits polarized light transmitted through the first polarizer; the second inner optical window transmits light to impinge on the second polarizer; and the heater is configured to heat the first inner optical window and the second inner optical window to prevent condensation of metal from the metal vapor onto the first inner optical window and the second inner optical window; wherein: the apparatus further comprises a vacuum chamber that encloses the inner chamber and the first polarizer; the optical entrance window forms a portion of a wall of the vacuum chamber; and a vacuum pressure in the vacuum is selected so that connective heat loss from the inner chamber is sufficiently low that metal does not condense from the metal vapor onto the first inner optical window and the second inner optical window; and wherein: the first polarizer is located inside the vacuum chamber, blocking from the inner chamber first inner optical window spurious polarization introduced into the light admitted by the optical entrance window by a stress on the optical entrance window that results from a pressure difference between the vacuum pressure in the vacuum chamber and a pressure outside the vacuum chamber. 2. An apparatus as recited in claim 1, wherein the apparatus further comprises a light imaging detector separated a fourth distance, not less than the third distance, from the optical window along the optical axis direction. 3. An apparatus as recited in claim 2, wherein the optical exit window is an aperture of the light imaging detector, whereby the fourth distance equals the third distance. 4. An apparatus as recited in claim 2, wherein the operational lifetime of the apparatus is more than 100 hours. 5. An apparatus as recited in claim 2, wherein light is sufficiently unattenuated inside the apparatus, so that the light imaging detector detects signals of interest within the narrow wavelength band width. 6. An apparatus as recited in claim 2, wherein light is sufficiently unscattered inside the apparatus, so that the light imaging detector produces an image of light received through the optical entrance window within a basic field of view defined by the maximum acceptance angle rotated around the central optical axis, whereby the basic field of view of the apparatus is a cone having an apex at the optical exit window and an angle of more than 14 degrees. 7. An apparatus as recited in claim 6, further comprising a lens to reduce an arrival angle of light into the basic field of view, whereby an apparatus field of view is greater than the basic field of view. 8. An apparatus as recited in claim 7, wherein the lens collects sufficient light within the narrow wavelength band for combustion to be detected by the light imaging detector. 9. An apparatus as recited in claim 1, wherein the vacuum chamber encloses both the first polarizer and the second polarizer. 10. An apparatus as recited in claim 1, wherein the apparatus has a volume that is not greater than 1000 cubic centimeters. 11. An apparatus as recited in claim 1, wherein the apparatus has a mass that is not greater than one kilogram. 12. An apparatus as recited in claim 1, wherein the narrow wavelength band width overlaps an optical wavelength associated with a local minimum in intensity of a daylight spectrum. 13. An apparatus as recited in claim 12, wherein the optical wavelength associated with the local minimum in intensity of the daylight spectrum corresponds to a solar Fraunhofer absorption line. 14. An apparatus as recited in claim 1, wherein the narrow wavelength band width overlaps an optical wavelength associated with a relatively high intensity in a combustion spectrum. 15. An apparatus as recited in claim 14, wherein the narrow wavelength band width overlaps an optical wavelength associated with a relatively high intensity in a combustion spectrum of potassium. 16. An apparatus as recited in claim 14, wherein the narrow wavelength band width overlaps optical emissions from combustion of a metal coinciding with at least one Fraunhofer line. 17. An apparatus as recited in claim 1, wherein the polarization-changing material is a Potassium vapor. 18. An apparatus as recited in claim 1, wherein the first polarizer and the second polarizer are subjected to mechanical stress less than a stress threshold above which polarization state of light induced by a polarizer changes over the operational lifetime for the apparatus. 19. An apparatus as recited in claim 1, wherein the first polarizer is the same as the optical entrance window. 20. An apparatus as recited in claim 1, wherein the second polarizer is the same as the optical exit window. 21. An apparatus for wide-angle narrowband filtering of optical energy comprising: an optical entrance window for admitting light to the apparatus; a first polarizer to determine a first polarization state of light transmitted through the first polarizer and separated a first distance no less than zero from the optical entrance window along a central optical axis; a second polarizer oriented to substantively block light having the first polarization state and separated a second distance, greater than the first distance, from the optical entrance window along the central optical axis; a narrowband polarization-changing material disposed between the first polarizer and the second polarizer; and an optical exit window for transmitting light away from the second polarizer separated a third distance, no less than the second distance, from the optical entrance window along the central optical axis; wherein the polarization-changing material changes polarization for a narrow wavelength band width on the order of about 0.01×10-9 meters; the polarization-changing material does not condense on optical windows and polarizers during an operational lifetime for the apparatus; no optical window between the first polarizer and second polarizer is subject to a polarization-inducing stress; a negligible portion of light transiting the apparatus incident at an incident direction less than a maximum acceptance angle from the central axis is scattered into a different direction; and an aspect ratio, defined by a distance from the optical entrance window to the optical exit window divided by an optical aperture for the optical entrance window, is less than or equal to 2/1, whereby the apparatus transmits light in the narrow wavelength range in each of a plurality of directions up to the maximum acceptance angle around the central axis and a tangent of the maximum acceptance angle is equal to half of a reciprocal of the aspect ratio and the maximum acceptance angle is greater than or equal to 4 degrees; and wherein: the polarization-changing material is a metal vapor that rotates polarized light in the narrow wavelength band when subjected to a magnetic field; and the apparatus further comprises a magnet to produce the magnetic field; and a heater to heat a particular component that contacts the metal vapor to prevent condensation of metal from the metal vapor onto the particular component; wherein: the apparatus further comprises an inner chamber of walls that encloses the metal vapor, the walls of the inner chamber include a first inner optical window and a second inner optical window; the first inner optical window admits polarized light transmitted through the first polarizer; the second inner optical window transmits light to impinge on the second polarizer; and the heater is configured to heat the first inner optical window and the second inner optical window to prevent condensation of metal from the metal vapor onto the first inner optical window and the second inner optical window; wherein: the apparatus further comprises a vacuum chamber that encloses the inner chamber and the first polarizer; the optical entrance window forms a portion of a wall of the vacuum chamber; and a vacuum pressure in the vacuum is selected so that convective heat loss from the inner chamber is sufficiently low that metal does not condense from the metal vapor onto the first inner optical window and the second inner optical window; and wherein: the first polarizer is located inside the vacuum chamber. blocking from the inner chamber first inner optical window spurious polarization introduced into the light admitted by the optical entrance window by a stress on the optical entrance window that results from a pressure difference between the vacuum pressure in the vacuum chamber and a pressure outside the vacuum chamber. 22. A system for detecting combustion sources in daylight, comprising: a wide field-of-view narrowband magneto-optic filter comprising: an optical entrance window for admitting light to the filter; a first polarizer to induce a first polarization state of light transmitted through the first polarizer and separated a first distance from the optical window along a central optical axis; a second polarizer oriented to substantively block light having the first polarization state and separated a second distance, greater than the first distance, from the optical window along the central optical axis direction; a narrowband polarization-changing material disposed between the first and second optical polarizers; and an optical exit window for transmitting light out of the filter separated a third distance, greater than the second distance, from the optical window along the central optical axis; an optical coupler configured to direct light into the optical entrance window of the filter from a surveillance area where combustion detection is desirable; a light imaging detector configured to receive light from the optical exit window of the filter and produce image data; and a data processor to process image data from the light imaging detector to determine where combustion is evident in the surveillance area; wherein the material changes polarization for a narrow wavelength band width on the order of about 0.01×10-9 meters that overlaps an optical wavelength associated with a local minimum in intensity of a daylight spectrum and overlaps an optical wavelength associated with a relatively high intensity in a combustion spectrum; no optical window between the first polarizer and second polarizer is subject to a polarization-inducing stress; an aspect ratio, defined by a distance from the optical entrance window to the optical exit window divided by an optical aperture for the optical entrance window, is less than 4/1; and the light imaging detector produces an image of an simultaneous field of view that has a size in a range from about 14 degrees to about 100 degrees;and wherein: the polarization-changing material is a metal vapor that rotates polarized light in the narrow wavelength band when subjected to a magnetic field; and the apparatus further comprises a magnet to produce the magnetic field; and a heater to heat a particular component that contacts the metal vapor to prevent condensation of metal from the metal vapor onto the particular component; wherein: the apparatus further comprises an inner chamber of walls that encloses the metal vapor, the walls of the inner chamber include a first inner optical window and a second inner optical window; the first inner optical window admits polarized light transmitted through the first polarizer; the second inner optical window transmits light to impinge on the second polarizer; and the heater is configured to heat the first inner optica1 window and the second inner optical window to prevent condensation of metal from the metal vapor onto the first inner optical window and the second inner optical window; wherein: the apparatus further comprises a vacuum chamber that encloses the inner chamber and the first polarizer; the optical entrance window forms a portion of a wall of the vacuum chamber; and a vacuum pressure in the vacuum is selected so that convective heat loss from the inner chamber is sufficiently low that metal does not condense from the metal vapor onto the first inner optical window and the second inner optical window; and wherein: the first po1arizer is located inside the vacuum chamber. blocking from the inner chamber first inner optical window spurious polarization introduced into the light admitted by the optical entrance window by a stress on the optical entrance window that results from a pressure difference between the vacuum pressure in the vacuum chamber and a pressure outside the vacuum chamber. 23. An apparatus for wide-angle narrowband filtering of optical energy, comprising: a central optical axis extending left to right; a magnet that produces a magnetic field; a vapor chamber having an input window and an output window and enclosing a metal vapor, the metal vapor including a polarization changing material tat, when subjected to the magnetic field, changes polarization for a narrow wavelength bandwidth on the order of about 0.01×10-9 that overlaps an optical wavelength associated wit a local minimum in intensity of a daylight spectrum and overlaps an optical wavelength associated wit a relatively high intensity in a combustion spectrum; a heater tat heats the vapor chamber input and output windows; a vacuum chamber, having an input window and an output window, tat encloses the vapor chamber so as to shut in the vapor chamber all around; a first polarizer, inside the vacuum chamber, to determine a first polarization of light transmitted there-though; and a second polarizer oriented to substantively block light having the first polarization; wherein the vacuum chamber input window, the first polarizer, the vapor chamber input window, the vapor chamber output window, the second polarizer, and the vacuum chamber output window are arranged along the optical axis in that order from left to right, so that the optical energy traverses the windows and polarizers in that order; and wherein the first polarizer is located inside the vacuum chamber, blocking from the vapor chamber input window spurious polarization introduced into the light traversing the vacuum chamber input window by a stress thereon that results from a pressure difference between a vacuum pressure in the vacuum chamber and a pressure outside the vacuum chamber.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.