IR thermometer

A novel wave guide assembly for use in an IR thermometer of the type used in measuring temperature of the tympanic membrane of the ear for body temperature determinations. The assembly provides a unique arrangement of spacers and a protective sheath to create a durable yet inexpensive wave guide. The spacer includes radially offset contact points that induce moment arms to absorb shock and other forms of rough handling encountered in daily use.

IMPROVED IR THERMOMETER 
The present invention generally relates to infrared thermometers of the 
type used to measure body temperature by collecting IR emissions from a 
patient's tympanic membrane, and more specifically, a novel light wave 
guide packaging system for higher accuracy and greater durability. 
BACKGROUND OF THE INVENTION 
IR thermometers are fast becoming a staple item in health care operations 
and have revolutionized routine care procedures by eliminating or 
dramatically reducing the lag time associated with temperature 
determination in diagnosis. As opposed to prior temperature measuring 
devices such as conventional mercury thermometers, an IR thermometer is a 
sophisticated optical--electronic assembly with precision designed and 
assembled components requiring tightly toleranced and exacting 
specifications for proper operation. Attention is directed to the 
teachings of U.S. Pat. No. 4,797,840 entitled "Infrared Electronic 
Thermometer And Method For Measuring Temperature" by Jacob Fraden, for a 
general description of IR thermometer design and operative 
characteristics. The teaching of the above-identified patent is 
incorporated by reference. 
A critical aspect of IR thermometer operation is the positional arrangement 
of the wave guide and the sensor inside the body of the device. From a 
functional standpoint, the wave guide acts to collect the radiation 
emanating from the tympanic membrane of the patient's ear and accurately 
guide this radiation to the sensor with minimal external influences. The 
sensor receives the guided radiation and generates a temperature reading 
as characterized by the quantum of radiation sensed. The accuracy of the 
resulting reading depends in part on the purity of the IR radiation passed 
to the sensor by the wave guide. The performance of the thermometer will 
therefore depend in great measure on the design of the wave guide and its 
relationship with the other components of the thermometer. 
Another important consideration in system design is the durability of the 
precisely arranged components. A system that leaves the factory with 
acutely sensitive settings that are quickly lost within the first few days 
of use has significantly reduced value to the consumer. Indeed, 
thermometers that become inaccurate through the normal bumping and shaking 
encountered in daily use are of limited value regardless of the initial 
accuracy from the factory. It has, therefore, become a critical aspect of 
thermometer design to devise an arrangement of operative elements that 
incorporates a ruggedness and durability sufficient to withstand daily 
abuse in practice without significant loss of performance. 
To attain these objectives, much progress has been made in packaging the 
electronics and electro-mechanical components to withstand typical daily 
rigors of use. These are important advancements that allow greater use of 
the product at less cost and concern about abuse. Notwithstanding this 
progress, IR thermometers remain prone to loss of fidelity due to normal 
bumps. This fidelity loss is often traced to the optics discussed above, 
wherein heavy handed use causes slight but signal disruptive misalignment 
of the wave guide. Significant misalignment of the optics will 
dramatically curtail the IR thermometers accuracy. 
It was with this understanding of the problems associated with prior optic 
system design that led to the present invention. 
OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
It is an object of the present invention to provide an apparatus for 
protecting the positional integrity of an optic system used in conjunction 
with an IR thermometer. 
It is another object of the present invention to provide a packaging 
arrangement that provides shock resistance to optical elements arranged in 
an IR thermometer. 
It is a further object of the present invention to provide an arrangement 
of concentric elements and specifically delineated spaces between the 
elements to create a low impact resistant optical instrument. 
It is yet another object of the present invention to provide a shock 
resistant wave guide that is economical to manufacture and inexpensive to 
assemble. 
The above and other objects are realized in a wave guide system that 
combines precision optics with an external rigid protective sheath. The 
outer sheath is positioned concentrically around the wave guide but spaced 
therefrom, creating a precisely dimensioned gap between the wave guide and 
the outer sheath. Within this annular gap, a semi-rigid spacer is placed 
establishing line contact with both the outer sheath and the inner wave 
guide. The line contact with the inner wave guide is radially offset from 
the line contact with the outer sheath thus creating a matrix of 
perpendicular bending moments at regular intervals within the spacing 
structure. 
In accordance with the varying aspects of the present invention, a 
continuous sleeve is positioned in the annular space between the wave 
guide and the outer sheath, wherein the sleeve has plural tabs extending 
therefrom, selectively positioned to permit slight deformation in response 
to external forces, bumps or rough handling. 
The foregoing features of the present invention may be more fully 
appreciated in the context of a specific illustrative example thereof 
presented in conjunction with accompanying drawing of which:

DESCRIPTION OF THE PRESENT INVENTION 
The present invention generally provides a shock absorbing spacer to 
prevent physical distortions and damage to the light transmission medium 
in light-based analytic instruments such as IR thermometers. The spacer is 
positioned and configured within an annular gap between the transmission 
medium and an outer sheath to form a series of contact points that are 
radially offset. By positioning the supporting contact points in offset 
orientation, the impingement of external forces on the transmission medium 
are translated into bending moments along the perimeter of the 
spacer--thereby dissipating the force without distortion to the 
transmission medium. 
Turning now to the Drawing, FIG. 1 depicts the layered arrangement of the 
transmission medium (wave guide or other, depending on application), 
spacer and outer sheath. Specifically, a light transmission medium 10 
having a generally cylindrical shape is encased by a protective sheath 30 
having a generally circular inner diameter that is greater than the outer 
diameter of the transmission medium forming an annular gap therebetween. 
The spacer 20 is positioned in a snug fit in this annular gap, wherein the 
spacer has a cross-sectional shape that departs from both the outer 
surface of the transmission medium and the inner surface of the protective 
sheath. In this way, open areas are created between the spacer 20, the 
protective sheath 30 and the transmission medium. 
The arrangement of FIG. 1 is depicted in cross-section in FIG. 2A. As shown 
in cross-section, the spacer 20 is a hexagon accurately held in place 
between outer sheath 30 and the inner transmission medium 10. This 
positioning establishes contact points between the spacer and the 
protective sheath at 23; and between the spacer and transmission medium at 
24. With this arrangement, open areas are formed around the perimeter of 
the transmission medium, e.g., 25 (between the spacer and sheath) and 26 
(between the spacer and transmission medium). The location of open areas 
vis-a-vis the points of contact create moment arms along the spacer as 
depicted in FIG. 2B. It is the moment arms thereby created that act to 
absorb induced shock to the assembly by partial deflection of the 
semi-rigid spacer 20. In FIG. 2B, F(t) is the force vector imparted by the 
transmission medium and F(s) is the counteracting force vector imparted by 
the sheath. 
Representative dimensions for the components depend on the actual 
implementation of the system. For use in a IR thermometer, the 
transmission medium will typically have a diameter of 0.123/0.118 inches. 
The outer sheath will have an inner diameter of approximately 0.158/0.154 
inches. Finally, in such an arrangement, the spacer will have an 
"effective" diameter of 0.140 inches, a thickness of 0.008 inches and is 
preferably formed by extrusion using polyurethane or nylon. 
Turning now to FIG. 3A, the arrangement of FIG. 2 is shown, but now 
undergoing an external force F(1) representing a shock or bump to the 
assembly. This force acts to distort the outer protective sheath from the 
circular cross-section to a cross-section of generally elliptical shape. 
The application of this force is, however, not translated to the inner 
transmission medium. To the contrary, this medium remains circular, as the 
external force is absorbed by the counter balancing distortion of the 
spacer, and, particularly, the deflection of the semi-rigid moment arms 
within the spacer. This can be clearly seen in FIG. 3B depicting a portion 
of spacer 20 undergoing force induced deflection, via force vectors F(s) 
and F(t). 
Turning now to FIG. 4, a second inventive arrangement is shown, wherein the 
spacer 20 is completely contiguous with the transmission medium 10, but 
spaced from the outer sheath by acutely angled tabs 33. In this 
arrangement, induced forces are absorbed by the deflection of the angled 
tabs. Although only four tabs 33 are shown, the use of more tabs, 
distributed around the perimeter of the spacer 20 is contemplated. 
In FIG. 5A, a further inventive arrangement is shown, one that can be 
assembled through the use of extrusion techniques. In this arrangement, 
the spacer has an exterior surface with a star-shaped cross-section and an 
interior surface shaped to fit snugly over the transmission medium without 
open areas. In this form, the absorption of forces is accomplished via the 
flexible and/or compressible nature of the material used to form spacer 
20. Alternatively, the spacer may have an interior surface with a 
cross-section identical to that of its exterior (i.e., star shaped) 
thereby establishing open areas between the transmission medium 10 and the 
spacer 20 as depicted in FIG. 5B. In both arrangements of FIG. 5, the 
outer sheath has a generally cylindrical inner surface. 
In FIG. 6, an extrusion molding technique for making the foregoing 
arrangement of FIG. 5A is shown. In this process, the transmission medium 
10 is passed through a first die 70 having an opening shaped to correspond 
to the outer shape of the spacer. Thereafter, the extruded spacer 20 is 
fitted into a cylindrical sheath, thus forming the open areas between the 
spacer 20 and the sheath (not shown). 
The above descriptions are illustrative of the inventive concepts and many 
modifications and adaptations thereof will be readily apparent to those 
skilled in this art without departing from the scope and spirit of the 
invention.