Note: Descriptions are shown in the official language in which they were submitted.
CA 02486807 2004-11-22
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Optical Array Converting ITV Radiation
This invention is an optical array converting UV radiation, especially
contained in sunlight.
The spectral characteristic of the transmission of the filter is similar to
the sensitivity of human
skin to sun burning. That sensitivity is described by the widely recognized
Diffey Standard,
also called also the Erythema Action Spectrum.
The Roberston Berger UV meter has been widely used over the past two decades
to measure
W in good approximation of the Diffey/Erythemal Spectral Response. This
stationary device
is based on a phosphore convertor screen as the principle means to reach a
spectral response
close to the Erythemal/Diffey Curve.
By now there are a few UV hand-held measuring devices known on the market that
are
targeting monitoring of UV radiation for avoiding sunburning. CASIO Computer
Ltd.
manufactures a device called "CASIO UC-120 UV", which has an optical array
containing
absorptive filter made of material similar to Schott UG-11 and a photodiode.
The spectral
characteristic of the device doesn't match the Diffey Standard. The device
illuminated by
sunlight is too sensitive to UV-A, that has low burning power.
US patent 5,196,705 describes a device measuring the intensity and dose of UV.
The device has
an optical array containing: an absorptive filter made of material similar to
Schott UG- 11, a
photo- luminescentive material and a photodiode. The spectral characteristic
of the device
doesn't match the Diffey Standard. The device is too sensitive to UV-A
comparing to its
sensitivity to W-B. Several others solutions for biologically oriented
monitors of UV
radiation were also proposed, among them: US patent 5,036,311 describes a UV-
monitoring
system in which a light sensing element is placed under a curved optical
element with
interference .filters imposed on its surface.
US patent 5,401,970 describes a UV-monitoring device which incorporates a UV-B
sensor and
a VIS sensor. The UV-B detector involved is described to be based on a
phosphor convertor
screen.
CA 02486807 2004-11-22
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Description of the invention
The invention solves the problem of constructing a device equipped with an
optical array
converting UV, visible and IR radiation that has the spectral characteristic
of the transmission
similar to the Diffey Standard.
Definition of the relative internal transmission of a set of filters:
.rre~ ~t(~)-Tint(a.)~Tint(310) (1)
where:
wavelength in nano-meters
Tree ,nt(~) relative internal transmission for ~, wavelength
Tint() internal transmission for ~, wavelength
T;nt(310) internal transmission for 310nm wavelength
Note that the total internal transmission of the set of absorptive filters is
equal to the product of
internal transmissions of each consecutive filter.
Definition of the relative transmission of a set of filters:
Tre1 (~)-T(~)/T(310) (2)
where:
wavelength in nano-meters
Trel(~) relative transmission for ~, wavelength
T(~,) transmission for 7~ wavelength
T(310) transmission for 310nm wavelength
The Diffey spectral characteristics will be denoted as D(7~) (3)
where: ~, wavelength in nano-meters
In the first solution the array contains a system of absorptive filters to
block visible and IR
radiation, a system of interference filters modifying transmission of LTV
and/or blocking visible
and IR radiation, scattering elements, elements forming the light beam.
Interference filter/filters
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is/are made of layers of materials having high and low LTV refractive indexes.
According to the
invention one of the system of interference filters has layers made of Hafnium
oxide and/or
Zirconium oxide. A collimator placed in the optical path forms the light beam.
The collimator
can have surfaces highly absorbing light. At the beginning of the optical path
a scatterer is
placed to achieve non-directional characteristic of the array. The scatterer
can be made of
PTFE.
In the second solution the array contains the first system of absorptive
filters to partly block
W-A, the second system of absorptive filters to block visible and IR radiation
and
may contain scattering elements and/or system/systems of interference
filter/filters.
The first system of absorptive filters has internal relative transmission
Tre1",t(~); between 0 and
0.2 for 7~=290nm, between 0.34 and 0.7 for ~,=300nm, between 0.5 and 0.8 for
~,=320nm,
between 0.04 and 0.36 for 7~=330nm, between l0E-3 and 0.1 for ~,=340nm,
between 7* l0E-6
and 0.02 for ~.=350nm, between 2*l0E-7 and 7*l0E-3 for ~,=360nm, between 2*l0E-
7 and
7* l0E-3 for ~,=370nm, between 2* l0E-5 and 0.03 for 7~=380nm ,.between 2* l0E-
3 and 0.14
for ~,=390nm. The total optical thickness of the first system of absorptive
filters is between 0.5
and 2mm.
The second system of absorptive filters has internal relative transmission
Ttel,nt(~): between 0
and 0.3 for 7~=290nm, between 0.7 and 0.8 for ~,=300nm, between 1 and 1.3 for
~,=320nm,
between 1 and 1.4 for 7~=330nm, between 1 and 1.3 for 7~=340nm, between 1 and
1.12 for
7~=350nm, between 0.6 and 0.8 for 7~=360nm, between 0.14 and 0.3 for ~.=370nm,
between l0E-
3 and 0.015 for ~,=380nm, between l0E-10 and l0E-6 for ~,=390nm. The total
optical thickness
of the first system of absorptive filters is between 0.5 and l Omm.
At the beginning of the optical path a scatterer is placed to achieve non-
directional
characteristic of the array. The scatterer can be made of PTFE. In the optical
path additional
system/systems of interference filters can be placed to block visible and IR
radiation andlor to
modify transmission in UV range.
In another embodiment the internal transmissions are arranged slightly
differently. In the third
solution, the array contains the first system of absorptive filters to partly
block UV-A, the
second system of absorptive filters to block visible and 1R radiation and
CA 02486807 2004-11-22
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may contain scattering elements and/or system/systems of interference
filter/filters. The first
system of absorptive filters has internal relative transmission Tret;nt(~):
between 0 and 0.6 for
~,=290nm, between 0.1 and 1.5 for 7~=300nm, between 0.2 and 2.0 for ~,=320nm,
between l0E-4
and l0E-1 for ~,=330nm, between l0E-2 and 1.0 for ~,=340nm, between l0E-8 and
0.1 for
~,=350nm, between l0E-9 and l0E-2 for ~,=360nm, between l0E-9 and l0E-2 for
~,=370nm,
between l0E-6 and 0.1 for 7~=380nm, between l0E-4 and 0.1 for ~,=390nm.
The second system of absorptive filters has internal relative transmission
Trel;nt(~): between 0
and 0.7 for 7~=290nm, between 0.3 and 1.5 for 7~=300nm, between 0.5 and 2 for
7~=320nm,
between 0.5 and 3 for ~,=330nm, between 0.5 and 2 for ~,=340nm, between 0.5
and 1.7 for
~,=350nrn, between 0.1 and 1.5 for ~,=360nm, between 0.01 and 1 for ~.=370nm,
between l0E-5
and l0E-1 for ~,=380nm, between l0E-12 and l0E-2 for ~,=390nm.
At the beginning of the optical path a scatterer is placed to achieve non-
directional
characteristic of the array. The scatterer can be made of PTFE. In the optical
path additional
system/systems of interference filters can be placed to block visible and IR
radiation and/or to
modify transmission in UV range.
This invention allows producing a cheap and simple optical array with a
spectral characteristics
in the UV-A and UV-B range following the human skin sensitivity described by
Diffey
Standard. The scatterer ensures non-directional characteristics of the array.
Other standards of
skin sensitivity to UV-A and W-B burning can also be easily followed.
Brief Description of the Drawings
The invention is presented on the block diagrams where Fig. 1 presents the
construction of
the version 1 of the optical array, Fig. 2 presents the construction of
another variant of the
invention presented on Fig. 1, Fig. 3 presents the construction of the version
2 of the optical
array, Fig. 4 presents the construction of the of the version 3 of the optical
array. Fig. 5 presents
Tre1(~)*D(310)/T'el(310) for optical array from Fig. 2 in comparison with the
Diffey Standard
D(~,), Fig. 6 presents T'et(~,)*D(310)/T'el (310) for optical array from Fig.
3 in comparison with
the Diffey Standard D(~,), Fig. 7 presents Tre1(~)*D(310)/Trei(310) for
optical array from Fig. 4
in comparison with the Diffey Standard D(7~).
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Description of the version 1
The array contains: the layer 1 that scatters light, a collimator 2 an
absorptive filter 3 that
makes a system of absorptive filters, a set of interference filters 4 that
makes a system of
interference filters. The absorptive filter 3 is made of material transparent
to LTV and
blocking visible and IR radiation. That property has M1 material, with a
characteristics
presented in the table below.
In that example a scatterer 1 is made of PTFE, and the absorptive filter 3 is
a piano-parallel
plate, 8mm thick, made of M1 material Schott UG-11 like. The set of
interference filters 4 that
is placed on the absorptive filter's 3 surface consists of 38 layers of
Hafnium oxide and/or
Zirconium oxide and Silica oxide.
The scatterer 1 ensures non-directional characteristics of the array. The
collimator 2 forms the
light beam. To achieve desired spectral characteristics the light beam passes
through the
absorptive filter 3 and the interference filter 4.
In the other variant of the version 1, that is shown on the Fig. 2, the array
contains: the layer 5
that scatters light, a collimator 6, absorptive filter 7 that makes a system
of absorptive filters
and a first set of interference filters 8 and a second set of interference
filters 9 that both make a
system of interference filters. The absorptive filter 7 is made of material
transparent to UV and
blocking visible and IR radiation. That property has M1 material, with a
characteristics
presented in the table below.
In that example a scatterer 5 is made of PTFE, and absorptive filter 7 is a
piano-parallel plate,
8mm thick, made of M1 material, Schott UG-11 like. The first set of
interference filters 8 and
the second set of interference filters 9 are placed on the absorptive filter's
7 surfaces and
together consists of 62 layers of Hafnium oxide and/or Zirconium oxide and
Silica oxide.
The scatterer 5 ensures non-directional characteristics of the array. The
collimator 6 forms the
light beam. To achieve desired spectral characteristics the light beam passes
through the first
interference filter 8, the absorptive filter 7 and the second interference
filter 9.
CA 02486807 2004-11-22
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On the Fig. 5 chart the Tre;(~,)*D(310)/TTei (310) characteristics of the
array is plotted as a
broken line, the Diffey Standard is plotted as a solid line. On the chart
these two curves are
close to each other in the 310-325nm range.
Description of the version 2
The array contains: the layer 10 that scatters light, a first absorptive
filter I 1 that makes a
first system of absorptive filters, a second absorptive filter 12 that makes a
second system
of absorptive f hers. The frst absorptive filter I 1 is made of material
transparent to UV
with decreasing transmission when the wavelength is changed from 320 to 3SOnm,
the
second absorptive filter 12 is made of material transparent to UV and blocking
visible
and IR radiation. That property have materials M2 and MI respectively, with
characteristics
presented in the table below.
In that example a scatterer 10 is made of PTFE, the first absorptive f lter 11
is a plano-parallel
plate, l.Smm thick, made of M2 material, Schott GG-19 like, the second
absorptive filter 12 is
a plano-parallel plate, 8 mm thick, made of M1 material, Schott UG-I 1 like.
The scatterer 10 ensures non-directional characteristics of the array. To
achieve desired
spectral characteristics the light beam passes through the first absorptive
filter 11 and the
second absorptive filter 12.
On the Fig. 6 chart Trel(~)*D(310)/TTeI (310) characteristics of the array is
plotted as a broken
line, the Diffey Standard is plotted as a solid line.
Description of the version 3
The array contains: a first absorptive filter 13 that makes a first system of
absorptive filters, a
second absorptive filter 14 that makes a second system of absorptive filters
and a first set of
interference filters 1 S and a second set of interference filters 16 that both
make a system of
interference filters. The first absorptive filter 13 is made of material
transparent to UV with
decreasing transmission when wavelength is changed from 320 to 3SOnm, the
second
absozptive filter 14 is made of material transparent to UV and blocking
visible and- IR radiation.
That property have materials M2 and M1 respectively, with characteristics
presented in the
table below. Interference filters axe constricted to block visible and IR
radiation andfor to
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modify transmission characteristics in W.
In that example the first absorptive filter 13 is a piano-parallel plate,
1.5mm thick, made of
M2 material, Schott GG-19 like. The second absorptive filter 14 with
interference filters 15, 16
placed on the filter 14 surfaces are made together by Schott as Schott DUG-11
filter.
To achieve desired spectral characteristics the light beam passes through the
first absorptive
filter 13, the first interference filter 1 S, the second absorptive filter 14
and the second
interference filter 16.
On the Fig. 7 chart Trei(~,)*D(310)/Tr'l (310) characteristics of the array is
plotted as a broken
line, the Diffey Standard is plotted as a solid line.
TABLE of relative internal transmission TTe;nt(~)
~.[nm] 290 300 310 320 330 340 350
Ml glass,Minimal value0 0.7 1 1.0 1.0 1.0 1.0
8 mm thick
Maximal value0.3 0.8 1 I .3 1.4 1.3 1.12
-
M2 glass,Minimal value0 0.34 1 0.5 0.04 l0E-3 7* l0E-6
1.5 mm
thick Maximal value0.2 0.7 1 0,8 0.36 0.1 0.02
~f~l 360 370 380 390
Ml glass,Minimal value0.6 0.14 l0E-3 l0E-10
8 mm thick
Maximal value0.8 Q,3 0.015 l0E-6
M2 glass,Minimal value2* I OE-72* l0E-72* I OE-52* I OE-3
1.5 mm
thick Maximal value7*l0E-3 7*l0E-3 0.03 0.14
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Data in tables above are TTet",t(~) characteristics of plano-paralel plates
made of M1, M2 with
given thickness.
The exact values of T'el,nt(~,) are described in the example constructions.
These data are
example values and it is obvious that the invention is not restricted to them.
The optical array in the example constructions has the spectral
characteristics similar to human
skin sensitivity to UV contained in sunlight. Fig. 5 presents
TTe~(~,)*D(310)/TTet (310) chart for
optical array from Fig. 2 in comparison with the Diffey Standard D(~,), Fig. 6
presents
Tre~(~,)*D(310)/Tret (310) chart for optical array from Fig. 3 in comparison
with the Diffey
Standard D(~,), Fig. 7 presents TTe~(~,)*D(310)/Trei (310) chart for optical
array from
Fig 4 in comparison with the Diffey Standard D(~,). The biggest discrepancies
between the
characteristics and the Diffey Standard are for LTV-C that is absent in
sunlight and W-A that
has a minimal burning power comparing with total burning power of sun LTV.
