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Патент USA US2114163

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April 12,
INTENSITY METER
L_ F'.FORB|RD
ULTRAVIOLET
' RAYS
Original Filed May 23, 1936
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Patented Apr. 12,
2,114,163
UNITED STATES PATENT OFFICE
2,114,163
m'rnNsrrr
- METER
»
aus
Fon unmvromr
Lester F. Bird, Newark, N. .IJ/assigner to Han
ovia Chemical and Manufacturing-Company,
Newark, N. J., a corporation of New Jersey
L v
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-
Application May 23, 1936, Serial No. 81,411
_
Renewed November 12, 1937 y
8 (Halma.
This invention relates to devices for indicating
the intensity’of ultraviolet rays; and more par
ticularly to a meter suitable for the measurement
of ultravioletfrays in a -therapeutic region and
5 such regions that are useful in _the production of
vitamin D‘and sunburn.
.
The meters which have heretofore been em
ployed in the measurement of ultraviolet rays
have been found unreliable and unsatisfactory in
10 that such meters are responsive to undesired
regions of the spectrum or else theydo not re
spond uniformlyI to the desired regions. Meters
of the type heretofore used have employed sodium
cells, uranium cells, barrier type photocells, and
l5 other devices with or without filters.
It is an object of this linvention to provide a
(Cl. Z50-84)
the primary photocell is definitely divided into
two portions, that due to the short ultraviolet
and that due to the effects of the long. ultraviolet
and stray visible radiations.
With a mercury v
arc light source the response of the cell is about 5
60% from ultraviolet below 3200 Angstrom units
and about 40% from stray visible and long ultra
violet. It is obvious if the stray visible and the
long ultraviolet component is eliminated from the
resultant response the indication will be only due 1o
to the desired wavelengths. Exactly this result
is secured and since the second cell responds only
to those> radiations that are stray in the fluores
cent system its response is combined with that ofl
the first cell so as to eliminate the undesired com- 15
ponent so thatV all of the readings of the meter
metering device for ultraviolet rays which is uni
are due to desired wavelengths.
formly sensitive to ‘ultraviolet energy lying be
The essential features of the meter are briefly
tween 2000 "and 3200 Angstrom units, and which as follows:
'
20 is unresponsive to all other regions of a spectrum.
First, the employment of iluorescent glasses in 20
That is, the meter will not respond to any radia-y' a balanced system with photocells.
tions above 3200 Angstrom units.
Second, the ñuorescent glass exposed directly
à A further object is the provision of a device.
-~for measuring 'short ultraviolet rays which is
¿5 simple in operation and positively reliable -inas
Y much as it is incapable of indicating the radia
. 'tions in any other region of the spectrum.
In accordance with my invention two photo
cells are mounted within a common holder and
to the radiations.
Third, the elimination ofthe undesired radia
tions by transmission and absorption.
l
25
Fourth, the conversion by means of fluores
cence of the desired radiations to put them into a
condition that is useful for measurement and also
to secure-thereby the useful radiations in a me
30 arranged to receive light from separate optical ichemical direction so that they are separated from 30
systems. The nature of the cells and their re
the unwanted radiations.
spouse» characteristics are not important except
Fifth, the elimination from the indications of
that they must be responsive to light in the visible the meter the enects due to the unwanted radia
_
spectrum. The optical systems may or may not tions so that the response _is purely that which is
35 be similar, but the response of one photocell must
result in part at least from any short ultraviolet
components inthe light incident on thereceiver
while the response of the other cell must be en
tirely the result of the long ultraviolet and visible
40 components of the incident light. The optical
system associated with the first photocell is com
posed in part of a specially formed piece of
fluorescent glass in which the incident light falls
directly upon the surface. l'I'he voptical system
45 associated with the second photocell may employ
a similar piece of fluorescent glass but in this case '
the glass is covered with a filter that excludes the
short ultraviolet from the surface, or again, it
may have only the filter over the cell without the
50 fluorescent glass.
p
desired.
-
»
35
Measurements are made in the simplest manner
<upon a light source. A balancing filter is em
ployed such as a piece of window glass (cut ofi
about 3300 Angstrom units) or a piece of pyrex
glass (cut oil' about 3050 Angstrom units) or a 40
piece of corex glass (cut off about 2800 Angstrom
units) and it is placed over the light receiver so
as to ñlter allV of the incident light to both re
ceivers. The response of the instrument is then
balanced to read zero. All of the responses due to 45
light that passes the filter are thus eliminated
from the reading. 'I'he filter is then removed
allowing the incident light to fall directly upon
the receivers.
'
.
Should there be a component present in the 50
light that was not transmitted by the balancing
The fluorescent glasses are combined with their
photocells so that they receive only the ñuorescent - filter there will then be a deflection of the indi
li'ght from the glasses but none of the incident cator since the system is no longer balanced. I_f
light except the unavoidable stray radiations. all of the incident light is transmitted by the illter
.55 'I'he arrangement is such that the response of the system is balanced after the removal of the 55
2
.
2,114,108
nlter and no deflection occurs. The upper limit
of sensitivity of the meter is set by the limit of
transmission of the balancing filter. Since ñlters
are available with cut-offs at almost any desired
` wavelength in this 'region the meter can be em
ployéd for a number of purposes.
Measurements have been made with this meter
on various kinds of light sources such as the sun,
ultraviolet sun lamps, carbon arcs, incandescent
lamps, quartz and glass mercury arc lamps of
various ages and deterioration, high voltage dis
charge tubes, etc. The necessary requirements
must be met in these measurements that the filter
have a sharper cut-off than the light that is being
15 measured if the results are to be reasonably ac
curate. 'I’his restriction is especially applicable
to measurements made upon sunshine.
v
' These and'other objects which will later appear,
are accomplished by the simple and practical con
struction and arrangement of parts hereinafter
described and exhibited in the accompanying -
drawing, forming part hereof, and in which:
Figs. l and 2 are diagrammatic views of the
ultraviolet ray indicating device' embodying my
26 invention, and
Fig. 3 is a perspective view of the indicating
in all light of wavelengths below about 4300
Angstrom units: but because of its thickness and
transparency, in the lvisible and long ultraviolet
region, it does not convert Alight energy in these
regions into iiuorescence as efficiently as it does
in shorter ultraviolet. For instance, the 4 mil
limeter thickness employed in this receiver is
quite transparent to iong ultraviolet at 3660
Angstrom units, since about 40% passes the glass.
However, at about 3200 Angstrom units the con 10~
version efficiency reaches totality and below this
point it is practically uniform and complete. All
of these shorter wavelengths are completely ab
sorbed on the surface of this glass, or at least
within a very short thickness near the surface. 15
Since this glass is somewhat responsive to the
long ultraviolet and part of the visible light, the
combination of this glass and cell are only par
tially able to select the desired wavelengths for
measurement. The unwanted portion of the re 20
sponse is due to the long ultraviolet. and visible
portions of the light.
.
In operation, when a balancing ñlter I2 is
placed over glass 5, the response is entirely due
to long wavelengths, which is not desired in the» 25
result. By balancing out this part of the reading,
when the filter I2 is removed, the result is en
device.
`
tirely due to the desired short wavelength. Since
Referring to the drawing, in Fig. 2, the device the balancing filter I2 is placedover both> cells
is shown to comprise a shell I having inthe upper simultaneously and removed from both at the 30
30 wall thereof openings 2 and 8, the shell being'
same time, the balance of the long ultraviolet and
connected by means of a cord 4 to an indicating visible regions continues after the balancing ñlter
meter I3, for example which can be of any type I2 is removed. In other words, the balancing
` that has surment sensitivity.
filter I2 is first placed over both openings 2 and
Covering opening 2 in the shell is a disc 5 of 3 to obtain a balance in the indicating meter I3, 35
35 ñuorescent glass, and vcovering'the opening 8 is
after which the illter I2 is removed and the bal
a disc 8 of window glass. Mounted on the back ance will continue. The balance is obtained by
of the disc 5, but spaced from the edges thereof, adjusting the potentiometer I0 and II.
is an absorber 1, and positioned behind the ab
Current flows from >photocell disc 8 through
sorber 1 is a photocell disc 8. Also positioned contacts 24 and 28 to the microammeter I8. The 4.0
40 behind the glass disc 6 is a photocell 9, the photo
resistance I0, Il is connected across the meter.
cells 8 and 9 extending beyond the edges of discs Disc
9 is connected to the moving arm of resist
5 and 8. For balancing purposes there is pro
ance II so that its potential opposes that from
vided a potentiometer III and II.
disc 8 in the meter. An adjustment of the pointer
Special attention must be given to the fluoresc
20 varies the deñection produced by the balanc
ing glass disc 5 as it is due to the characteristics
'
`
of this glass that the desired selection of wave ing photo disc 8.
-The
device
described
above
is
effective
for
al
lengths is obtained. The glass found most useful most all types of artificial sources of ultraviolet
for this purpose is a piece of fiuorescing uranium
but is rather uncertain and unreliable
glass about 4 millimeters thick and 35 millimeters radiations,
in a variable light source such as the sun light. 50
in
diameter,
the
edges
being
ground
and
polished
50
I have found that the form of my invention such
to a true conic section at 45 degrees. The open
ing 2 is less than the smallest diameter of the as shown in Fig. l, which is the preferred form,
glass 5 so as to prevent light from directly reach ` is equally effective with sun light as with artincial
ing the extremities of glass 6. It is apparent light sources.
In the form of the invention shown in Fig. 1, 55
55 that light generated within glass 5 is free to pass the device comprises a shell I having openings 2
through it to the edge where the action of the
bevel is to completely reflect the light at right and 3 therein, and an electrical system and meter
as above described in connection with Fig. 2.
angles.
,
Covering the opening 2 is a disc 5 of fluorescent
On the back surfaces of the glass 5, as stated glass, having mounted on the back thereof an
above,
there
is
attached
or
painted
an
absorbing
60
absorber 1, and mounted adjacent thereto a pho
surface, the vehicle of which has nearly the same tocell disc 8, as heretofore described. Covering ‘
index of lrefraction as the glass 5. Should this the opening 3 is a similar arrangement compris
absorbing surface be completely opaque and have
ing a disc 5' of ñuorescent glass having mounted
exactly the same index of refraction as the glass
l on the back thereof an absorber 1', and posi 65
65 5, there would be no reflection from the rear sur
face of the glass. The opaque layer 1 extends tioned adjacent thereto a photocell disc 8'. A
piece of filter glass I 2' is arranged to be moved
over the rear surface of glass 5 to a position
cover the opening 3 or to be moved to a posi
directly behind the upper edge of the bevel. This to
tion
whereby all of the rays strike directly upon
arrangement prevents any of the direct incident
the fluorescent glass 5'. 'I‘he filter I2’ is made 70
light
upon
glass
5
from
reaching
the
photocell
8.
70
It has been found that cellulose acetate lacquers, from the same kind of glass as the filter I2 de
in connection with Fig. 2.
shellacs, India lnk having a shellac base, etc. are scribed
In operation, in measuring the intensity of
f substances suitable for the absorbing surfaces de
short ultraviolet rays', the filter glass I2’ is
scribed above.
moved
to an out of the way position so that all 75
The glass 5 is of such a nature that it ñuoresces
75
of the light rays strike directly upon the ?uores
cent glasses 5 and 5’. Since the two systems
connected with l and l' are identically the same,
the meter i3 can then be balanced. The nlter
which is transparent to visible and long ultra
violet radiations and opaque to ultraviolet radia
tions below 3200 Angstrom units, said glass hav
ing a front light receiving surface and a rear
I glass I2' is then moved to cover` the ñuorescent ‘ surface, absorbing material covering the rear 5
glass 5' so that the short ultraviolet rays will surface of said glass. means adjacent the front
strike only the ñuorescent glass' 5.
'This will
cause an unbalance in the meter I3, and the
readings thereof will indicate the intensity of
10 the short ultraviolet rays being measured.
'I'he foregoing disclosure is to be regarded as
descriptive and illustrative only, and not as re
strictive or limitative of the invention, of which
obviously an embodiment may be constructed
surface of the glass for shielding portions of said
front surface so that the area of the front sur
face exposed to light radiations is less than the
area of the rear surface covered by the absorb- l0
ing material, said absorbing material being ca
pable of absorbing .visible and long ultraviolet
radiations transmitted through said glass, a piece ’
of glass which is opaque to ultraviolet radiations
l5 including many modiñc'ations without departing
from the general scope herein indicated and
denoted in the appended claims. _" _
Having' thus described my invention, what I
below 3200 Angstrom units, photocells positioned l5
and arranged to receive radiations through said
last mentioned glass and fluorescence from said
, claim as new and desire to secure by Letters
trical circuit including said photocells and said
indicating meter, and a filterl adapted to_cover 20
both of said glasses to enable balancing of the
meter, said filter being glass which is opaque to
ultraviolet radiations below 3200 Angstrom units.
20 Patent, is:
i
'
-
1. In a device for indicating the intensity of
ultraviolet rays, a piece of fluorescent glass
which is transparent to visible and long ultra
violet radiations and?’opaque to ultraviolet radia
25 tions belowg3200 Angstrom units, said glass'hav
fluorescent glass, an indicating meter, an elec
4. In a device for indicating the intensity of
ultraviolet rays, a light receiving surface com- 25
ing a front light receiving surface and a rear
prising a piece of fluorescent glass which is trans
surface, said glass having bevelled and polished
parent to visible and long ultraviolet _radiations
and opaque to ultraviolet radiations below 3200
Angstrom units and having edges, said glass hav
edges, means adjacent the front surface of the
' glass for shielding said edges from light radia
30 tions, absorbing material capable of absorbing
visible and long ultraviolet radiations trans
mitted through said glass covering areas of the
rear surfaces of said glass equal at least to the
area of the front surface of the glass exposed
35 to light radiations, a piece of glass which is
Vopaque to ultraviolet radiations below 3200 Ang
strom units, said pieces of glass being positioned
to receive substantially the same amount of radi
ations from the light source, photocells posi
40 tioned and arranged 'to receive radiations
through saidllast mentioned piece of glass and
ing a front light receiving surface and a rear 30
surface, an absorber positioned behind the rear
surface of said glass to absorb visible and long
ultraviolet radiations transmitted through the
glass, means for shielding the edges of the glass
from incident light at right angles to said front 35
surface oi' the glass, a piece of glass opaque to
ultraviolet radiations below 3200 Angstrom units,
vphotocells positioned and arranged to receive
radiations through said last mentioned piece of
glass and fluorescence from said iiuorescent glass. 40
an indicating meter, an electrical circuit includ
fluorescence from said iluorescentglass, an in
ing said photocells and said indicating meter,
' dicating meter, an electrical circuit including
and means for adjusting said meter so that
when said lpiece of fluorescent glass is exposed
45 a filter adapted to cover both of said glasses to” to ultraviolet radiations the meter will indicate 45
enable balancing of the meter, said mter being only those radiations below 3200 Angstrom units.
5. In a device for indicating the intensity of
a piece of glass which is opaque to ultraviolet
ultra violet rays, a pair of light receiving surfaces
radiations below 3200 Angstrom units.
2. In _a device-for indicating the intensity of comprising pieces of fluorescent glass _transparent
50 ultraviolet rays, a piece of Ifluorescent glass to visible and long ultraviolet radiations and 50
opaque to ultraviolet radiations below 3200 Ang
which is transparent to visible and long ultra
strom units, said glasses being positioned to re
violet radiations and opaque to ultraviolet radia
ceive substantially the same amount of radiations
tions vbelow 3200 Angstrom units, said glass hav
ing a front light receiving surface and a rear from the source of radiations, absorbers 4positioned behind said glasses to absorb visible and 55
55 surface _and edges, means adjacent the front sur
face of the glass for shielding said edges from long ultraviolet radiations transmitted through
light radiations, absorbing material covering an the glasses, said absorbers being spaced from the
said photocells and said indicating meter, and
area of the rear surface of said glass equal at edges of said glasses to provide an area through
least to the area of the front surface of the glass . which visible radiations can pass, photocells
60 exposed to light radiations, said absorbing mate
rial being capable of absorbing visible and long
ultraviolet radiations transmitted through said
glass, a piece of glass which is opaque to ultra
violet radiations below 3200 Angstrom umts,
*65 photocells positioned and arranged to receive
\radiations through said last mentioned glass and
fluorescence from said fluorescent glass, an indi
cating meter, an electrical circuit including said
photocells-'and said indicating meter, and a filter
70 adapted to cover both of said glasses to enable
balancing of the meter, said filter being glass
which is opaque to,_`_ultraviolet radiations below
3200 Angstrom units. "" ""
3. In a device for indicating the intensity of
¿5 ultraviolet rays, a piece of fluorescent glass
mounted in position to receive fluorescence from 60
said glasses, an indicating meter, `an electrical
circuit including said photocells and said indicat
ing meter, and a filter adapted to be moved to
cover one of said fluorescent glasses, said filter
being a piece of glass which is opaque to ultra- 65
violet radiations below 3200 Angstrom units.
6. In a device for indicating the intensity of
ultra violet rays, a p_air of light receiving surfaces y
comprising pieces of fluorescent glass transparent
to visible and long ultraviolet radiations and 70
opaque to ultraviolet radiations below 3200 Ang
strom units and having edges, said glasses being
- positioned to
receive substantially the same
amount of radiations from the source of radia
tions,`said glasses having front receiving sur- 75
4
2,114,168
faces and rear surfaces, means for shielding the
edges of said pieces of glass, the edges of said
pieces of glass being bevelled and polished. ab
sorbing material capable of absorbing visible and
long ultraviolet radiations transmitted throußh
said glasses, said absorbing material covering
areas of the rear surfaces of said glasses equal
to the areas of said glasses exposed to light radi,
ations and spaced from the edges of the rear sur
faces of said glasses to provide areas through
which reflected ñuorescence can pass, photocells
mounted and arranged to receive radiations re
ñected by said bevelled edges, an indicating me
ter, an electric circuit including said photocells
15 and said indicating meter, and a filter adapted to
be moved to cover one of said ñuorescent glasses,
said filter being a piece of glass which is opaque
to ultraviolet radiations below 3200 Angstrom
units.
`
'1. In s. device for indicating the intensity oi:l
ultraviolet rays. a pair of light receiving sur
faces‘comprising pieces of iluorescent'glass trans
parent to visible and long ultraviolet radiations
andl opaque to ultraviolet radiations below 3200
Angstrom units and having edges, said glasses
being positioned to receive substantially the same
amount of radiations from the source of racha»
`tions, said glasses having front receiving surfaces
and rear surfaces, means for shielding the edges
80 of said pieces of glass, the edges of said pieces of
glass being bevelled and polished, absorbing ma
terial capable of absorbing visible and long ultra
violet radiations transmitted through said
glasses, said absorbing material covering areas
35 of the rear surfaces of said glasses equal Itc'the
areas of said glasses exposed to light radiations,
and spaced from the edges of the rear surfaces
of said glasses to provide areas through which
reflected iluorescence can pass, photoceils mount.
40 ed and arranged to receive fluorescence reflected
by said bevelled edges, an indicating meter, an
electric circuit including said photocells and said
indicating meter, a filter adapted to be moved to
cover one of said nuorescent glasses, said filter
being a piece of glass which is opaque to ultra
violet radiations, and means for adjusting said
indicating meter so that when said fllter covers
one of said iluorescent glasses the meter will in
dicate only ultraviolet radiations below 3200 Ang
10
strom units.
8. In a device for indicating the intensity of
ultraviolet rays, a light receiving' surface com
prising a i'lrst piece of ñuorescent glass which is
transparent to visible and long ultraviolet radia
tions and opaque to ultraviolet radiations below 15
3200 Angstrom units and having edges, said glass _
having a front light receiving surface and a rear .
surface, the edges of said glass being bevelled and
polished. and an absorber positioned behind the
rear surface of said glass to absorb visible and
long ultraviolet radiations transmitted through
the glass, said absorber being lspaced from the
edges of said rear surface to provide an area
through which reñected fluorescence can pass,
the edges of the glass being shieldedfrom inci
dent light at right anglesto said front and rear
surfaces of the glass, a second _piece of glass
which is opaque to ultraviolet radiations below
3200 Angstrom units, photocells positioned and
arranged to receive incident radiations through
said second piece of glass and fluorescence from
said first piece of glass, an indicating meter, and
an electrical circuit including said photocells
and said indicating meter, means for adjusting
said meter so that when said piece of fluorescent
glass is exposed to light radiations the meter _
will indicate only those radiations below 3200
Angstrom umts.
'
LESTERF. BIRD.
/
40
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