US 20050089078 A1
Method and apparatus are provided for visibly outlining the energy zone to be measured by a radiometer. The method comprises the steps of providing a laser sighting device on the radiometer adapted to emit more than two laser beams against a surface whose temperature is to be measured and positioning said laser beams about the energy zone to outline said energy zone. The apparatus comprises a laser sighting device adapted to emit more than two laser beams against the surface and means to position said laser beams about the energy zone to outline said energy zone. The laser beams may be rotated about the periphery of the energy zone. The laser beams may be rotated about the periphery of the energy zone. In another embodiment, a pair of laser beams are projected on opposite sides of the energy zone. The laser beams may be further pulsed on and off in a synchronized manner so as to cause a series of intermittent lines to outline the energy zone. Such an embodiment improves the efficiency of the laser and results in brighter laser beams being projected. In yet another embodiment, a primary laser beam is passed through or over a beam splitter or a diffraction grating so as to be formed into a plurality of secondary beams which form, where they strike the target, a pattern which defines an energy zone area of the target to be investigated with the radiometer. Two or more embodiments may be used together. A diffraction device such as a grating may be used to form multiple beams. In a further embodiment, additionally laser beams are directed axially so as to illuminate the center or a central are of the energy zone.
87. In a hand-held temperature measuring instrument comprising a radiometer having a field of view which includes a target surface temperature measurement area, and separate spaced apart independent lasers for aiming said radiometer at said area, all mounted on a common support, each laser directing a visible laser beam onto said measurement surface area to identify the radiometer field of view, the improvement comprising a beam splitter illuminated by at least one of said lasers to project a pattern of more than two laser light spots onto said temperature measurement area to indicate the radiometer field of view.
This is a continuation-in-part application of both pending U.S. patent application Ser. No. 08/764,659 filed on 11 Dec. 1996 and Ser. No. 08/617,265 filed on 18 Mar. 1996 in the names of Milton B. Hollander and W. Earl McKinley for Method and Apparatus for measuring Temperature Using Infrared Techniques, the latter of which, is a continuation-in-part application of U.S. application Ser. No. 08/348,978 filed on 28 Nov. 1994, now U.S. Pat. No. 5,524,984 which in turn was a continuation-in-part application of then copending U.S. patent application Ser. No. 08/121,916 filed 17 Sep. 1993, now issued as U.S. Pat. No. 5,368,392, on 29 Nov.
1. Field of the Invention
The present invention relates generally to a method and apparatus for more accurately measuring the temperature of a surface using infrared measurement techniques and, more particularly, to such a method and apparatus which utilizes a laser sighting device which is adapted to project at least a circumscribing laser sighting beam or beams for more clearly defining the periphery of the energy zone from which the temperature is measured. Generally speaking, this has been accomplished by directing the laser beam about the periphery of the energy zone; by the use of three or more stationary laser beams which are focused on the periphery of the energy zone; or by the use of a controlled single laser beam directed towards three or more predetermined locations on the periphery of the energy zone. In the alternative embodiment, a single laser beam may be rotated around the periphery of the energy zone using, for example, slip rings. In another embodiment, the single rotating laser may be pulsed on and off in a synchronized manner in order to produce a series of intermittent lines outlining the energy zone, thus increasing the efficiency of the laser by concentrating its total wattage in a smaller area, causing a brighter beam. Further, the circumscribing beam or beams may be used in conjunction with an additional beam directed at and defining a central spot, or larger central area, of the energy zone.
In yet another method and embodiment, at least one laser beam is subdivided by passing it through a diffraction grating, for example, into a plurality of three or more subdivision beams which can form a pattern of illuminated spot areas on a target whose energy zone is to be investigated with a radiometer. Herein “a plurality” means three or more, e.g. six or twelve.
2. Description of the Prior Art
Remote infrared temperature measuring devices (commonly referred to as infrared 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 infrared radiometers use optical reflection and/or refraction principles to capture the radiated energy from a given surface. The infrared 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.
Examples of such infrared radiometers are illustrated at pages J-1 through J-42 of the Omega Engineering Handbook, Volume 2B. See, also, U.S. Pat. No. 4,417,822 which issued to Alexander Stein et al. on Nov. 29, 2983 for a Laser Radiometer; U.S. Pat. No. 4,527,896 which issued to Keikhosrow Irani et al. on Jul. 9, 1985 for an Infrared Transducer-Transmitter for Non-Contact Temperature Measurement; and U.S. Pat. No. 5,169,235 which issued to Hitoshi Tominaga et al. for Radiation Type Thermometer on Dec. 8, 1992. Also see Baker, Ryder and Baker, Volume II, Temperature Measurement in Engineering, Omega Press, 1975, Chapters 4 and 5.
When using such radiometers to measure surface temperature, the instrument is aimed at a target or “spot” 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 infrared 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 insure 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, there have been no means of accurately determining the perimeter of the actual energy zone unless it is approximated by the use of a “distance to target table” or by actual physical measurement.
Target size and distance are critical to the accuracy of most infrared thermometers. Every infrared instrument has a field of view (FOV), an angle of view in which it will average all the temperatures which it sees. Field of view is described either by its angle or by a distance to size ratio (D:S). If the D:S=20:1, and if the distance to the object divided by the diameter of the object is exactly 20, then the object exactly fills the instrument's field of view. A D:S ratio of 60:1 equals a field of view of 1 degree.
Since most infrared thermometers have fixed-focus optics, the minimum measurement spot occurs at the specified focal distance. Typically, if an instrument has fixed-focus optics with a 120:1 D:S ratio and a focal length of 60″ the minimum spot (resolution) the instrument can achieve is 60 divided by 120, or 0.5″ at a distance of 60″ from the instrument. This is significant when the size of the object is close to the minimum spot the instrument can measure.
Most general-purpose infrared thermometers use a focal distance of between 20″ and 60″ (50 and 150 cm); special close-focus instruments use a 0.5″ to 12″ focal distance. See page Z54 and Z55, volume 28, The Omega Engineering Handbook, Vol. 28. In order to render such devices more accurate, laser beam sighting devices have been used to target the precise center of the energy zone. See, for example, pages C1-10 through C1-12 of The Omega Temperature Handbook, Vol. 27. Various sighting devices such as scopes with cross hairs have also been used to identify the center of the energy zone to be measured. See, for example, Pages C1-10 through C1-21 of The Omega Temperature Handbook, Vol. 27.
The use of a laser to pinpoint only the center of the energy zone does not, however, provide the user with an accurate definition of the actual energy zone from which the measurement is being taken. This inability frequently results in inaccurate readings. For example, in cases where the area from which radiation emits is smaller than the target diameter limitation (too far from or too small a target), inaccurate readings will occur.
One method used to determine the distance to the target is to employ an infrared distance detector or a Doppler effect distance detector or a split image detector similar to that used in photography. However, the exact size of the energy zone must still be known if one is to have any degree of certainty as to the actual area of the surface being measured. This is particularly true if the energy zone is too small or the surface which the energy zone encompasses is irregular in shape. In the case where the surface does not fill the entire energy zone area, the readings will be low and, thus, in error.
Similarly, if the surface is irregularly shaped, the readings will also be in error since part of the object would be missing from the actual energy zone being measured.
Thus, the use of a single laser beam only to the apparent center of the energy zone does not insure complete accuracy since the user of the radiometer does not know specifically the boundaries of the energy zone being measured.
As will be appreciated, none of the prior art recognizes this inherent problem o offers a solution to the problems created thereby.
Proposals have ben made in the prior art for indicating an energy zone area of a target surface by means visible to the eye of the target.
A first kind of such indication utilizes multi-spectral light, as evidenced for example in the Japanese Publication No. S57-22521 which teaches the use of an incandescent light source to outline an energy zone at the target. Japanese Publication No. 62-12848 suggests a similar use of multi-spectral light to outline an energy zone at the target. Reference is made to Japanese case JP 63-145928.
Further, U.S. Pat. No. 4,494,881 EVEREST also suggests using a multi-spectral light source together with a beam splitter arrangement which permits the infra-red received beam and the multi-spectral light to utilize the same optical arrangement. EVEREST teaches the use of a visible light source such as an incandescent lamp or strobe light which is projected against the target surface, the temperature of which is to be measured. This adds additional energy to the same energy zone where the temperature measurement is to be taken, and this destroys accuracy. When EVEREST uses a beam splitter, the incandescent light beam causes the beam splitter to act as a radiator of infrared energy. When EVEREST uses a Fresnel lens, the light tends to, elevate the temperature of the Fresnel lens, which in turn reflects back to the infra-red detector.
This manner of indication, utilizing incoherent multi-spectral light, has the disadvantage amongst others that the multi-spectral light itself has a heat factor which can cause incorrect reading by the energy detecting means of the apparatus.
A laser is Light Amplification by Stimulated Emission of Radiation. This device was invented in 1960 to produce an intense light beam with a high degree of coherence. Atoms in the material emit in phase. Laser light is used in holography. A light beam is coherent when all component waves have the same phase. A laser emits coherent light, but ordinary electric incandescent light is incoherent in which atoms vibrate independently.
It is not possible simply to substitute a laser for an incandescent light source, because the incandescent beam is incoherent in nature, so that when projected parallel and in close proximity to the boundaries of the invisible infra-red zone, incandescent light inside the infra-red zone is reflected as heat energy. Moving the incandescent beam well away from the infra-red zone clearly does not permit accurate delineation of the target zone.
A second kind of energy zone indicator utilizes coherent laser light, as evidenced for example in U.S. Pat. No. 4,315,150 of DERRINGER, which is directed to a targeted infrared thermometer in which a laser is provided to identify the focal point, i.e., the center, of the energy zone, but there is nothing in DERRINGER to suggest causing more than two laser beams to outline the energy zone.
U.S. Pat. No. 5,085,525 BARTOSIAK ET AL teaches use of a laser beam to provide a continuous or interrupted line across a target zone to be investigated, but there is no suggestion to outline a target zone, nor to indicate a central point or central area of the target zone.
German patent publications of interest include:
All of the above noted prior art is hereby incorporated into this case by reference thereto.
Against the foregoing background, it is a primary object of the present invention to provide a method and apparatus for measuring the temperature of a surface using infrared techniques.
It is another object of the present invention to provide such a method and apparatus which provides more accurate measurement of the surface temperature than provided by the use of techniques heretofore employed.
It is yet another object of the present invention to provide such a method and apparatus which permits the user visually to identify the location, size nd temperature of the energy zone on the surface to be measured.
It is still yet another object of the present invention to provide such method and apparatus which employs a heat detector and a laser beam or beams for clearly outlining the periphery of the energy zone of the surface.
It is a still further object of the present invention to provide a method and apparatus which permits the use of a single laser beam which is subdivided by passing it through, or over, a beam splitter, holographic element or a diffraction grating, thereby to form a plurality of three or more subdivision beams which provide a pattern where they strike a target whose energy zone is to be investigated.
It is still further object of the invention to provide a method and apparatus which utilizes not only a beam or beams for outlining the energy zone, but also an additional beam or beams directed at and illuminating an axial central spot, or larger central area, of the energy zone.
For the accomplishment of the foregoing objects and advantages, the present invention, in brief summary, comprises a method and apparatus for visibly outlining the energy zone to be measured by a radiometer. The method comprises the steps of providing a radiometer with a detector and a laser sighting device adapted to emit at least one laser beam against a surface whose temperature is to be measured and controlling said laser beam towards and about the energy zone to outline visibly said energy zone. The beam is controlled in such a fashion that it is directed to three or more predetermined points of the target zone. This can be done mechanically or electrically.
Another embodiment of this invention employs a plurality of three or more laser beams to describe the outline and optionally also the center of the energy zone either by splitting the laser beam into a number of points through the use of optical fibres or beam splitters or a diffraction device or the use of a plurality of lasers. One embodiment of the apparatus comprises a laser sighting device adapted to emit at least one laser beam against the surface and means to rotate said laser beam about the energy zone to outline visibly said energy zone. This rotation can be by steps or continuous motion.
Another embodiment consists of two or more stationary beams directed to define the energy zone. The three or more laser beams could each be derived from a dedicated laser to each beam or by means of beam splitters. This can be accomplished by mirrors, optics, a diffraction grating, and fibre optics.
Another embodiment consists of a laser beam splitting device that emits one laser beam which is split into a plurality of three or more beams, by a diffraction grating, for example, to outline the energy zone and optionally to indicate a central spot or larger central area of the energy zone.
In a still further embodiment, the temperature measurement device comprises a detector for receiving the heat radiation from a measuring point or zone of the object under examination. Integral to the equipment is a direction finder, i.e. a sighting device using a laser beam as the light source and incorporating a diffractive optic, i.e. a holographic component such as a diffraction grating, or a beam splitter, with which the light intensity distribution is also shown and the position and size of the heat source is indicated. The marker system relates to a predetermined percentage, e.g. 90%, of the energy of the radiated heat.
The method includes visually outlining and identifying the perimeter of the energy zone by projecting more than two laser beams to the edge of the 90% energy zone to mark out the limits of the surface area under investigation, for example, by a series of dots or spots which form a pattern.
Two or more embodiments may be used together or alternately.
The foregoing and still other objects and advantages of the present invention will be more apparent from the detailed explanation of the preferred embodiments of the invention in connection with the accompanying drawings, wherein:
FIGS. 9A-C illustrate alternative configurations of the outlines which can be projected using the apparatus of the present invention;
Traditionally, prior art radiometers have long employed laser sighting devices and direction finders to assist in the proper aim and alignment of the instrument.
The actual size and shape of the energy zone E is determined by the optics of the radiometer and the distance between the radiometer and the target. Each radiometer has a defined angle of vision or “Field of view” which is typically identified in the instrument's specification sheet. The size of the energy zone E is predetermined when the field of view is known in conjunction with the distance to the target. Obviously, the further the radiometer is held from the target (i.e., the greater the distance), the larger the energy zone E.
This can be expressed in a “distance to spot size zone”. For example, with a “distance to spot size zone” of 40:1 the periphery of the energy zone would have a 1″ diameter at a distance of 40″ or, at a distance of 20″ the diameter of the energy zone would be ˝″. The manufacturer of the pyrometer usually provides field of view diagrams for determining the energy zone at specific distances.
As can readily be appreciated, however, such laser aiming devices are merely able to identify the center of the energy zone being measured and not the outer periphery, as distinct from the diameter, of the actual energy zone from which the measurement is being taken. The further away from the surface the radiometer 10 is positioned, the larger the energy zone E. Thus, depending upon the size and configuration of the surface 20, the actual energy zone E may, conceivably, include irregular shaped portions of the surface 20 or even extend beyond the edges of the surface. Of course, in such instances, the resultant measured temperature would be inaccurate. Without knowing the outer perimeter of such energy zone E, the user of the radiometer 10 would have no knowledge of such fact and the resultant readings could be inaccurate.
The present invention provides a means for visibility defining the energy zone E so that the user of the radiometer 10 can observe the actual energy zone being measured to determine where it falls relative to the surface being measured. In the various embodiments of this invention, a fine laser line or lines is projected against the surface being measured and such line or lines is positioned so as to encompass the periphery of the energy zone E. Of a rotating laser beam is employed, positioning can be effected, alternatively by moving either the laser itself or the laser beam emitted from the laser or from a laser beam splitter.
If the perimeter of the energy zone E cold be identified on the object by the movement of the laser beam in a path about the circumference of the energy zone E, the user would be able quickly and accurately to determine if the energy zone from which the measurement was being taken was fully on the surface to be measured and whether its surface was of the type which would provide an otherwise accurate measurement.
The periphery of the energy zone E is identified as a function of the stated “field of view” of the particular radiometer as identified in its specifications and the distance between the radiometer and the target. Identification of the size and shape of the energy zone is easily done using conventional mathematical formulae. Once identified, the laser beams are then projected about the periphery of the energy zone E in accordance with the methods and apparatus hereinafter described. One simple “aiming” approach is to project the laser beam at the same angle as the field of view of the radiometer emanating from the same axis or, alternatively, by mechanically adjusting the laser beam angle in accordance with the “distance to spot size ratio” calculations. In either event, the periphery of the energy zone E would be identified by the laser beams.
It should be appreciated that the laser aiming device 12 may be an integral part of the radiometer 10 or, alternatively, a separate unit that may be mounted on or near the radiometer 10.
Alternatively, a prism can be used in place of the mirror 30 with predetermined angles to cause the prism to function as the reflecting mirror surface and, thereby, direct the laser beam about the perimeter of the energy zone.
The rotation of the laser beam may be effected using beam splitter or fiber optic techniques as shown in
It will, of course, be appreciated that the energy zones E may assume configurations other than the circular configuration shown in
The laser sighting device 1000 of
The laser 1012 is powered with power source 1018. Slip rings 1016 are provided to facilitate rotation of the laser 1012. Upper and lower counterweights 1015A and 1015B, respectively are provided above and below the laser 1012 and a return spring 1019 is also provided.
The laser 1012 of the sighting device 1000 in
A modified version of the laser sighting device of
The laser sighting device 1100 of
Adjustment screw 1217 is further provided for controlling the position of the motor 1221 and, as such, the direction of the laser beam 1214. A swivel ball 1222 is provided about the outward end of the laser 1212 which is seated in swivel ball seat 1220. Spring washer 1218 is further provided adjacent the swivel ball 1222.
The laser sighting device 1200 operates in substantially the same manner as the sighting devices depicted in
At least two laser sighting devices 1312 are provided on opposite sides of the radiometer 1300. Device 1312 includes a pair of lasers 1314 provided within the laser sighting devices 1312 positioned on each side of the radiometer approximately 180 degrees apart which are adapted to project a pair of laser beams (not shown) toward a target on either side of the energy zone to be measured by the radiometer. In this manner, the laser beams are used to define the outer periphery of the energy zone being measured by the radiometer 1300.
In an alternate embodiment, the lasers depicted in
The apparatus of any one of FIGS. 2,3,4,6,8,11,12,13 and 18 may further include means for projecting a laser beam axially to strike the surface zone to be measured, e.g. in
In a practical form of construction, the laser beam generator 1401 and the diffraction grating support 1404 and the radiometer would conveniently be carried on a support structure, not shown, to provide a hand-held apparatus aimed at a selected area, or areas, to be investigated. Thus a method of identifying the extent of a radiation zone on a region whose temperature is to be measured may comprise the steps of providing a sighting device for use in conjunction with said radiometer, said device including means for generating a laser beam, splitting said laser beam into a plurality of three or more components by passing said beam through or over diffraction grating means, and directing said beam components towards said region so as to form a plurality of illuminated areas on said region where said beam components impinge on said region, and determining temperature at said region with said radiometer. Preferably, the diffraction grating means is such as to cause the laser beam to be sub-divided into a plurality of three or more beams which form illuminated areas arranged at intervals on a circle or other closed geometric figure on the region.
Having thus described the invention with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.