Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
SIGHTING SYSTEM AND METHOD FOR TEMPERATURE MEASURING
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates generally to a method and apparatus for
measuring
the temperature of a surface using infra-red measurement techniques and, more
particularly, to
such a method and apparatus which utilises a sighting device which is adapted
respectively to
aim or to project or to sense circumscribing laser or light beams for defining
or showing all, or
part, of the energy zone of the target, the temperature of which is to be
measured.
DESCRIPTION OF THE PRIOR ART
Remote infra-red temperature measuring devices (commonly referred to as infra-
red pyrometers or radiometers) have been used for many years to measure the
temperature of
a surface from a remote location. Their principle of operation is well known.
All surfaces at
a temperature above absolute zero emit heat in the form of radiated energy.
This radiated
energy is created by molecular motion which produces electromagnetic waves.
Thus, some of
the energy in the material is radiated in straight lines away from the surface
of the material.
Many infra-red radiometers use optical reflection and/or refraction principles
to capture the
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radiated energy from a given surface. The infra-red radiation is focused upon
a detector,
analyzed and, using well known techniques, the surface energy is collected,
processed and the
temperature is calculated and displayed on an appropriate display.
OBJECTS OF THE INVENTION
When using such radiometers to measure surface temperature, the instrument is
aimed at a target area within the energy zone on the surface on which the
measurement is to be
taken. 'The radiometer receives the emitted radiation through the optical
system and is focused
upon an infra-red sensitive detector which generates a signal which is
internally processed and
converted into a temperature reading which is displayed.
The precise location of the energy zone on the surface as well as its size are
extremely important to ensure accuracy and reliability of the resultant
measurement. It will be
readily appreciated that the field of view of the optical systems of such
radiometers is such that
the diameter of the energy zone increases directly with the distance to the
target. The typical
energy zone of such radiometers is defined as where 90% of the energy focused
upon the
detector is found. Heretofore, determining the size of the actual energy zone
is approximated
by the use of a distance to target table or by actual physical measurement.
It is accordingly a principal object of the present invention to provide a
sighting
apparatus, for use with or for incorporation into or onto a remote infra-red
temperature
measuring radiometer, which permits coinciding of the thermometer's field of
view with a
visible desired area of a target the temperature of which is to be measured.
A second object of the invention is to provide such a sighting apparatus which
is
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entirely independent of, and does not interfere with, the optical system of
the thermometer.
A third object of the invention is to provide such a sighting apparatus which
is
readily mountable on, and dismountable from, the thermometer.
A fourth object is to coincide the line of sight of the system with the line
of optical
field of view, to allow more accurate sighting when aiming at different
targets.
SUMMARY OF THE INVENTION
Against the foregoing background, in general terms a first form of the present
invention provides a sighting system, for temperature measuring apparatus
using infra-red
techniques, which utilises a laser generator to provide a laser beam which
becomes at least three
laser sub-beams spaced about a center line, which sub-beams are aimed onto a
reflector
arranged within the field of view of the radiometer, said reflector being
selected to (a) transmit
infra-red light, and (b) reflect laser light and visible light, said reflector
being positioned to
direct the sub-beams to the target in such a manner as to provide small
visible illuminated areas
(e.g. 'spots') disposed about the center of that area of the target whose
temperature is to be
measured.
In a further feature, the apparatus is arranged to provide additionally a
further sub-
beam, which is axial to the above mentioned sub-beams and which accordingly
provides an
illuminated 'spot' at the center of the target area.
In a second form, light rays emanating from an area of the target, concentric
with
the area whose temperature is to be measured, are passed to a reflector which
again is selected
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to (a) transmit infra-red light and (b) reflect visible light. Infra-red rays
emanating from the
selected target area pass unchanged through said reflector and are
concentrated by an infra-red
lens into an infra-red detector. Visible light rays emanating from the
concentric area are
deflected by the reflector to an optical system such as an angled mirror which
directs them to
an optical sighting device such as a sighting telescope.
The invention thus concerns, firstly, a sighting system for temperature
measuring
which comprises, for inclusion in an optical path between a selected area of a
target, whose
temperature is to be measured and a radiometer which assesses that
temperature, a deflector
which is transparent to infra-red rays emanating from the target area but is
reflective of laser
light rays, and means for generating a plurality of laser light beams onto
said deflector so as to
be directed by said deflector along said optical path to strike the target and
visually identify at
least an outline of said selected area.
Secondly, the invention concerns a sighting system for temperature measuring
which comprises, for inclusion in an optical path between a selected area of a
target, whose
temperature is to be measured, and a radiometer which assesses that
temperature, a deflector
which is transparent to infra-red rays emanating from the target area but is
reflective of visual
light rays, and an optical sighting means positioned to receive light rays
from said deflector for
viewing and thereby visually identifying at least an outline of said selected
area of the target.
Thirdly, the invention concerns a method, for visually identifying at least an
outline of a selected area of a target whose temperature is to be measured by
passage of infra-
red rays along an optical path from said selected area to a radiometer, said
method comprising
deflecting into said optical path, by means of a deflector which is
transparent to infra-red rays,
a plurality of laser beams to strike the target to at least outline said
selected area visually.
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Fourthly, the invention concerns a method, for visually identifying at least
an
outline of a selected area of a target whose temperature is to be measured by
passage of infra-
red rays along an optical path from said selected area to a radiometer said
method comprising
deflecting out of said optical path, by means of a deflector which is
transparent to infra-red rays,
light rays emanating from said selected area of the target, and passing said
deflected light rays
to an optical sighting means.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and still other obj ects and advantages of the present invention
will
be apparent from the detailed explanation of the preferred embodiments of the
invention in
connection with the accompanying drawings, wherein:
Fig. 1 is a schematic longitudinal section of a first embodiment of the
invention
utilising laser light for target illumination;
Fig. 2 is a front elevation of a part of a target on which a pattern of spats
is
provided by the apparatus;
Fig. 3 is a schematic longitudinal section of a second embodiment of the
invention
utilising visible light for target sighting;
Fig. 4 is a front elevation of part of a target to be sighted;
Fig. 5A is a diagrammatic side elevation of the improved sighting system
utilising
a laser;
Fig. 5B is an elevation to show the pattern of laser light dots received on
the
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target;
Fig. 6A is a diagrammatic side elevation of the improved sighting system
utilising
a sighting telescope;
Fig. 6B is an elevation to show the view of the target obtained with the
system of
Fig.6A.
An important aspect of the invention is that it provides, for use with a
radiometer
adapted to assess the temperature of a selected area of a target, an
attaclxable and separable
module which can visually delineate that selected area, as by an outline or a
field of view
corresponding to all or part of the selected area, by insertion of a visual-
light or laser-light
deflecting means into an infra-red path between the selected area of the
target and the heat
sensing means of the radiometer, without changing or disturbing the normal
operation of that
infra-red path and said heat sensing means.
BRIEF pESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to figures 1 and 2 of the drawings, there is shown a first
embodiment
of apparatus in accordance with the invention. A laser generator module 1
produces a single
laser beam 2 which is passed through a beam-splitting means 3 which may be,
for example, a
diffraction grating, a beam splitter or a prism. The beam-splitting means 3 is
constructed so as
to cause the single laser beam 2 to be sub-divided into a plurality of
divergent sub-beams, and
specifically into twelve sub-beams 3a which are symmetrically arranged in a
circle, and a single
central sub-beam 3b. The plurality of sub-beams 3a , 3b pass to a mirror 4
disposed at 45
degrees to direct them onto an infra-red filter/mirror 7 which as properties
of (a) transmitting
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infra-red rays, and (b) reflecting laser light. Means (not shown) may be
provided to adjust the
position of the mirror 4 mechanically, e.g. by a motor drive or adjusting
screw.
The temperature measuring apparatus is shown only schematically, and includes
an infra-red detector S associated with an infra-red lens 6.
A target 8, whose temperature is to be measured, sends infra-red rays towards
the
infra-red lens 6, and this concentrates the received rays onto the detector 5.
The area 9 of the
target which is sensed by the combination 5-6 is circular. The infra-red
filter/mirror 7 directs
the collection of sub-beams 3a, 3b towards the same circular area of the
target, and defines that
circular area on the target by a circle of illuminated 'spots' 11. The central
sub-beam 3b also
strikes the center of the target area at 10. It is to be noted that the
central sub-beam 3b can be
omitted, and then only the circular arrangement of sub-beams 3a used.
For the user of the apparatus, it is then immediately apparent which circular
area
of the target is being measured for temperature because that area is outlined
by clearly visible
spots 11.
Referring to figures 3 and 4 of the drawings, the sighting method is
effectively
reversed. A sighting telescope 12 is disposed in alignment with a light-
reflecting mirror 13
which reflects to the telescope 12 the light rays 14 which are directed to it
by an infra-red
filter/mirror 15 which has the properties of (a) transmitting infra-red rays,
and (b) reflecting
visible light.
Here again, the temperature measuring apparatus is shown only schematically,
and
includes an infra-red detector 16 associated with an infra-red lens 17. The
target 18, whose
temperature is to be measured, sends infra-red rays towards the infra-red lens
17, and this
concentrates the received rays onto the detector 16. The area 19 of the target
which is sensed
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by the combination 16-17 is circular. A concentric, but slightly smaller, area
20 of the target
sends visible rays 14~ to the infra-red filter/mirror 15, so that the user
viewing through the
sighting telescope 12 sees the circular area 20 and thus knows that the heat-
sensing means is
centered appropriately on that part of the target which is to be sensed for
temperature
measurement.
In both embodiments, the filter 7 or 15 could have optical properties such
that it
transmits infra-red energy in the bandwidth of 8 to 14 microns.
It is a further feature of the invention that the detecting and aligning
system
consisting of items l, 3, 4 and 7 in figs. 1 and 2, and consisting of items
12, 13 and 15 in figs.
3 and 4, could be made mountable and dismountable with respect to the
remainder of the
apparatus.
An essential feature, common to both of the embodiments described, is the use
of light/laser mirror means inserted into the infra-red transmission path for
deflecting the
'sighting' rays into or out of the infra-red path without affecting the
latter.
In both embodiments, the goal to be achieved is to ensure coincidence between
what the user sees, and the area of the target which is being sensed for
temperature, i.e. to
provide easy and accurate aiming of the radiometer. It is an advantage that
this sighting system
does not interfere with the radiometer's own optical system. As a result, the
sighting system
can be manufactured independently of the radiometer, and, can be added to the
radiometer as
required, and this provides better control of manufacturing and stock.
Fig. 5A shows a laser sighting system and in detail shows how the sighting
system
is designed. The laser module 101 provides a collimated laser beam 102. The
laser beam hits
a Diffraction Grating Lens 103. The diffraction grating lens splits the
collimated laser beam
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into a number of laser beams which are deflected on an angle. The accumulation
of the spread
laser beams provides a laser circle affect. The spread laser beams hit a 45
degree angle mirror
104 which reflects the laser beams to an infra-red filter 107. The infra-red
filter 107 has optical
properties such that it transmits the infra-red energy in the bandwidth of 8
to 14 microns; and
it reflects visible light as well as laser light. Because of such properties
the spread of laser
beams is reflected off the infra-red filter and projects a series of laser
dots on the target being
measured 108 to form a laser circle 111. The actual field of view 109 of the
thermometer may
be slightly larger than the laser circle 111. If there were no diffraction
grating lens 103 then the
laser module would project a single laser dot 110 which is an indication of
the center of the
target being measured. The infra-red energy from the target goes through the
infra-red filter 107
and is collected by the infra-red lens 106. The infra-red lens then focuses
the incoming energy
on the active area of the infra-red detector 105.
In a further embodiment, Figs. 6A, 6B show a sighting system that instead of
using a laser module, uses a sighting scope 112. The rest of the sighting
system is the same in
Figs. 5A, SB. The sighting scope viewing area 113 is slightly smaller than the
actual field of
view of the thermometer 109.
In both embodiments of sighting systems, the object is to coincide the
thermometer's field of view with the line of sight for more accurate aiming.
Another advantage
of the design is that the sighting system does not interfere with the
thermometer's optical
apparatus. As a result the infra-red thermometer can be manufactured
independently of the
sighting system. The sighting system can be added later on as required. This
provides better
control of manufacturing and stock.
