Fiber optic sensor with photochromic transducer, and corresponding method
First Claim
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1. A device for measuring the ratio between the UV irradiance and the illuminance, of an incident radiation, comprising:
- a sensor including a photochromic transducer including a material with characteristics of reversible photochromism, and at least a first optical path for guiding a light signal towards and through said photochromic material and collecting a light output signal whose value decreases when the level of absorbance of the photochromic material increases, the level of absorbance of the photocromic material depending upon said ratio of the radiation incident on said sensor;
a first source of light radiation associated with said first optical path for generating said light signal and injecting it into said first optical path;
a detector for detecting the light signal returning from said first optical path;
wherein said ratio is determined by measuring the attenuation of said light signal passing through said photochromic material.
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Abstract
A description is given of a sensor for measuring the UV fraction of a radiation, comprising a photochromic transducer consisting of a photochromic material (3) with characteristics of reversible photochromism, whose absorbance varies as a function of the UV fraction of the radiation (R) incident on the photochromic material. An optical path (7) is provided to guide a light signal through said photochromic material and collect a return light signal, whose value is proportional to the level of absorbance of the photochromic material.
70 Citations
20 Claims
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1. A device for measuring the ratio between the UV irradiance and the illuminance, of an incident radiation, comprising:
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a sensor including a photochromic transducer including a material with characteristics of reversible photochromism, and at least a first optical path for guiding a light signal towards and through said photochromic material and collecting a light output signal whose value decreases when the level of absorbance of the photochromic material increases, the level of absorbance of the photocromic material depending upon said ratio of the radiation incident on said sensor;
a first source of light radiation associated with said first optical path for generating said light signal and injecting it into said first optical path;
a detector for detecting the light signal returning from said first optical path;
wherein said ratio is determined by measuring the attenuation of said light signal passing through said photochromic material.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for measuring the ratio between the UV irradiance and the illuminance of a radiation, comprising the steps of:
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striking with said radiation a photochromic material having characteristics of reversible photochromism, whose absorbance varies as a function of said ratio;
making a light signal pass through said photochromic material;
determining said ratio by measuring the attenuation of said light signal passing through said photochromic material. - View Dependent Claims (14)
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13. A method for measuring an UV irradiance of a radiation, comprising the steps of:
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a) striking a photochromic material having characteristics of reversible photochromism, whose absorbance varies as a function of the ratio between said UV irradiance and an illuminance of said radiation, with a light beam having a wavelength such that it causes the decoloration of the photochromic material, until the decoloration of the photochromic material is achieved;
b) making a light signal pass through said photochromic material while the latter is being struck by said radiation;
c) detecting the variation with time of the attenuation of the light signal passing through said material, thus determining an attenuation curve;
d) determining the UV irradiance of said radiation from the slope of the attenuation curve;
e) repeating stages (a) (d) at intervals of time if necessary.
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15. A method for determining a ratio of UV radiation to illuminance for incident radiation, the method comprising the steps of:
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providing photochromic material with a optical path, said photochromic material having an absorbent coefficient absorbing a light signal passing through said optical path, said absorbent coefficient being variable as a function of the UV radiation in the incident radiation;
exposing said photochromic material to the incident radiation;
transmitting the light signal through said optical path;
measuring a value of the light signal after the light signal has passed through said optical path;
calculating the ratio as a function of the measured value of the light signal. - View Dependent Claims (16, 17, 18, 19, 20)
a reference value of the light signal is determined before the light signal passes through said optical path; and
said calculating of the ratio includes using said reference value.
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17. A method in accordance with claim 15, further comprising:
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irradiating said photochromic material with a light to lower said absorbent coefficient of said photochromic material, stopping said irradiating after said absorbent coefficient has been lowered; and
measuring the value of the light signal at a plurality of time points after said stopping;
using the value of the light signal at the plurality of time points in said calculating of the ratio.
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18. A method in accordance with claim 17, further comprising:
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determining an attenuation of the value of the light signal at the plurality of time points; and
using the attenuation in said calculating of the ratio.
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19. A method as claimed in claim 15, wherein
the light signal has a wavelength in the range of 520 to 620 nm. -
20. A method in accordance with claim 15, wherein:
said photochromic material is a fulgide dispersed in a polymer matrix.
Specification