Illumination of diffusely scattering media
First Claim
1. A method comprising:
- locating a delivery filter adjacent to a diffusely scattering sample; and
directing a beam of incident light of a predetermined wavelength through the delivery filter at a beam angle of incidence, and to the sample,the delivery filter having characteristics such that reflection of said incident light is dependent upon angle of incidence of said light at the filter, and such that at least 50% of the incident light of the predetermined wavelength which is diffusely scattered back out of the sample to arrive at the delivery filter is reflected by the delivery filter back towards the sample.
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Accused Products
Abstract
The invention provides a technique for increasing the illumination intensity of probe light in a diffusely scattering sample without increasing the power of the probe beam. Generally, an optical filter is used which permits a collimated probe beam of light to pass through to the sample, but which reflects back towards the sample much of the backscattered scattered probe light emerging at a wider range of angles. In particular embodiments a collimated laser beam is delivered to the sample through a multi-layer dielectric filter covering a portion of the sample. The filter is transmissive to the laser light at normal incidence, but reflective at shallower angles of incidence characteristic of the backscattered light.
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Citations
51 Claims
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1. A method comprising:
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locating a delivery filter adjacent to a diffusely scattering sample; and directing a beam of incident light of a predetermined wavelength through the delivery filter at a beam angle of incidence, and to the sample, the delivery filter having characteristics such that reflection of said incident light is dependent upon angle of incidence of said light at the filter, and such that at least 50% of the incident light of the predetermined wavelength which is diffusely scattered back out of the sample to arrive at the delivery filter is reflected by the delivery filter back towards the sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An optical enclosure for enhancing the intensity of incident light of a predetermined wavelength within a diffusely scattering sample, the optical enclosure comprising a delivery filter through which a beam of said incident light of the predetermined wavelength is directed to the sample at a beam angle of incidence with respect to said filter,
the delivery filter having characteristics such that reflection of said incident light of the predetermined wavelength increases at angles of incidence away from the beam angle of incidence, and such that at least 50% of the incident light of the predetermined wavelength which is scattered diffusely from the sample to arrive at the delivery filter is reflected back into the sample by the delivery filter.
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44. Apparatus for detecting one or more spectral characteristics of a diffusely scattering sample, comprising
a delivery filter adapted to allow a beam of incident light of predetermined wavelength to pass through at an incident beam angle of incidence to reach the sample, wherein the delivery filter is a multi-layer dielectric filter having a transmission characteristic coincident with the predetermined wavelength of the incident light beam at said angle of incidence, but which shifts to shorter wavelengths at higher angles of incidence such that the filter preferentially reflects back towards the sample incident light of the predetermined wavelength which is diffusely scattered from the sample; - and
the diffusely scattering sample, the apparatus being arranged such that at least 50% of the incident light of the predetermined wavelength scattered back from the sample to reach the delivery filter is reflected back towards the sample. - View Dependent Claims (45, 46, 47)
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48. A method of illuminating a diffusely scattering sample, comprising:
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covering a region of the sample with a delivery filter; and directing a beam of collimated light of a predetermined wavelength through the delivery filter and into said sample, wherein said delivery filter is adapted to reflect back to the sample at least 50% of the light of said predetermined wavelength diffusively scattered out of the sample to said delivery filter in said region. - View Dependent Claims (49, 50, 51)
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Specification