HK1078644B - Apparatus for rapid, accurate, non-contact measurement of the core temperature of animals and humans - Google Patents

Description

Device for rapidly and accurately measuring core temperature of animals and human bodies in non-contact manner

Technical Field

The present invention relates to temperature sensing devices, and more particularly to devices for measuring temperature based on eye black body radiation.

Background

In the livestock industry in the united states, annual livestock deaths from disease are estimated to be in the hundreds of millions of dollars. One reliable way to determine the health or presence of disease in livestock is to determine the body temperature of the animal. The body temperature of livestock can rise if infected, environmentally infected or poisoned. These elevations are the basis for veterinarians in diagnosing diseases or disease conditions in livestock. In the daily production of livestock, it is not much used to identify whether a body temperature is raised or a fever is developed due to time limitations and the need to restrain the animal's body. This deficiency in temperature assessment delays the diagnosis of the disease, thereby increasing the use of antibiotics and the loss of animals.

There is a need for rapid and accurate measurement of the core temperature of animals, particularly, but not limited to, food animals such as livestock, sheep and goats, as well as humans and horses. Core temperature, i.e. in vivo temperature, has been difficult to measure accurately without physically contacting the interior of the body.

Traditionally, to measure temperature, a medical thermometer is inserted into the rectum or mouth and must be left for several minutes to obtain a stable reading. This often requires restraint of the animal, which is time consuming and labor intensive. Typically, the body temperature of livestock is measured with a medical mercury fahrenheit thermometer or with a digital thermometer. The mercury thermometer scales from 94F to 110F, with each degree divided into 5 divisions (1/5 degrees per division). The thermometer requires the mercury to be shaken at the bulb end. The thermometer is then lubricated or moistened and inserted by hand into the rectum for its entire length. The thermometer stays in the rectum for a minimum of 3 minutes to obtain an accurate reading. Since most animals are resistant to the process, it is necessary to restrain the animal's body at this time.

In recent years, electronic digital readout has been used to make faster digital thermometers using low thermal mass temperature sensors, such as small thermocouples or thermistors. These devices still require oral or rectal insertion and restraint of the animal, but the time for accurate measurement takes only 1 minute.

Other approaches to animal temperature measurement are based on the detection of thermal radiation energy, so-called black body radiation. All heaters emit this energy in the form of a broadband spectrum, and this energy has a wavelength distribution and intensity that is proportional to the temperature. This radiant energy is measured with a non-contact microwave, millimeter (mm) wave, or Infrared (IR) wave sensor. Thermal radiation is measured very rapidly, but the thermal radiation and temperature related accuracy, in addition to instrumental errors (if any), is affected by two factors. The first factor is how accurately the temperature of the core and the surface of the radiation that can be used for measurement is related. This is often problematic on animals and humans, i.e. the skin is not a true representation of the temperature in the body. This is particularly problematic with IR where the depth of the detected radiation within the body is very shallow, substantially proportional to the temperature of the skin's exterior. The second factor, the surface emissivity, also affects the amount of thermal radiation emitted by the body at a given temperature. This results in thermal radiation-based temperature measurements that vary with the color and physical characteristics of the material being measured. In an attempt to eliminate this source of error, some IR thermal radiation thermometers use a probe that is inserted into the ear. The radiance in the ear can vary with different amounts and types of skin debris in the ear canal, which can also limit accuracy. In another version, an insert is placed in the ear of the animal to provide a constant radiance target for the IR sensor. This insert must be placed in the ear long enough before measurement to reach thermal equilibrium, which is undesirable from both cost and time considerations.

The possibility of measuring the core temperature of the animal by remote (hands-free) detection has been of great interest for the last 30 years. Previous methods are based on: (1) passive detection of the amplitude of IR or microwave energy, the radiation of which is proportional to the temperature of most materials (according to planck's law), including human or animal skin and ears (inside); (2) the use of implants and/or markers which employ contact type thermal sensors (thermistors, thermocouples, etc.) and usually have wireless means for reading data on demand; and (3) the use of an integrated temperature sensing capsule containing a temperature sensor and a radio frequency (VHF or UHF) transmitter or transponder to transmit temperature data from within the animal to an external reader. None of these prior devices or methods are entirely satisfactory due to differences in degrees, practical limitations, or other reasons. Existing passive IR radiation methods have limited accuracy (+/-1 degree or worse). These methods are based on detecting surface (skin or hide) temperature and are not suitable for accurate direct animal temperature measurement. Skin temperature is not always an accurate indication of the core temperature of an animal. Furthermore, the radiance of the skin covered by the hair is variable, providing neither an accurate skin temperature nor an indication of the core temperature when using IR.

Disclosure of Invention

The present invention provides an apparatus for measuring the core temperature of an animal or human being the object of measurement, the apparatus comprising: a sensor unit having a filter for allowing detection of only selected wavelengths of thermal radiation, and a detector for detecting selected wavelengths of thermal radiation from an eyeball of the subject and generating a signal corresponding to the radiation; wherein the sensor is not in contact with the eyeball; wherein the selected wavelength is emitted from a specific depth within the eyeball; an amplifier unit for amplifying the signal from the sensor unit and for generating an amplified signal; a data processing unit for converting the amplified signal into raw temperature data and for detecting core temperature data from the raw temperature data; and a display for displaying the core temperature data.

Drawings

Fig. 1 is a cross-sectional view of an eye of a mammal (e.g., a cow).

Fig. 2 is a block diagram of a first embodiment of the present invention.

Fig. 3 illustrates the relative radiation depths of various wavelengths emitted from the eye.

FIG. 4 illustrates yet another embodiment of the sensor unit of FIG. 1.

Detailed Description

The present invention provides rapid, accurate, non-contact measurement of electromagnetic thermal radiation and relates these measurements to the core temperature of an animal or human. The present invention overcomes the limitations of previous thermal radiation thermometers by non-contact detection of thermal radiation from only the subject's eye. The eye provides many of the desirable characteristics for making such measurements. The eye is easily visible, is usually very clean, has a high radiance, is very consistent from animal to animal, and is continually washed inside and outside with fresh body fluids that maintain the eye at near core temperatures. The wavelength of the eye radiation detected by these temperature measurements may be microwave, millimeter wave or IR (long to short wavelength). Combinations of more than one wavelength within these ranges may also be optimized to best suit the intended application.

The optimization criteria for the detected wavelengths include: (1) adapted for non-contact detection of radiation from a spot of eye size or selected portions thereof, with low sensitivity to radiation from areas outside said spot; (2) can reach the greatest depth into the eye whose radiation is detected to ensure correlation with core temperature while maintaining acceptable instrument sensitivity measurement error; (3) exempt from the natural or artificial environmental impact to measuring; and (4) measurement time of sufficient accuracy.

The method uses electromagnetic (black body) radiation of the animal eye to determine temperature accurately and quickly.

The method uses electromagnetic (black body) radiation of the animal eye to determine temperature accurately and quickly. This hands-free method is very effective and efficient for early diagnosis of disease. This facilitates rapid adoption of appropriate treatment jurisdictions and reduces overuse of antibiotics, thereby reducing antibiotic residues in meat and dairy products.

In the examples of the present specification, the method obtains an accurate core temperature indication using measured thermal electromagnetic radiation of one or more wavelengths of the animal eye. The eye can be seen from the outside of the animal and can provide an accurate indication of the core temperature, particularly when using radiation from within the eyeball.

Fig. 1 is a cross-sectional view of a mammalian (e.g., cow or human) eye. The eye is constantly being washed by body fluids and there is a constant flow of blood within the outer wall and in the orbital and eyelid areas. These all bring the eye temperature very close to the body core temperature and keep the outer surface very clean.

From the laser safety guidelines, it is known that only the visible and near infrared (400-. Similarly, radiation from these interior regions will penetrate the front of the eye and can be detected externally with appropriate sensors. Mid-infrared (1400-3000nm) and far-infrared (3000nm-1mm) are absorbed at the anterior surface of the eye, although some (1.4-2.5 microns) mid-infrared (sometimes referred to as short-wave IR) can penetrate deeper through the corneal region. The far infrared used to detect eye radiation is primarily radiation from the exposed outer surface of the eye (since radiation from the inside is absorbed by the near surface layer of the eyeball). Although this radiation is close to the core temperature, the outer surface is never sufficiently isolated from the effects of ambient temperature, wind, rain, etc. to provide an accurate correlation with the core temperature. Radiation from the lens, vitreous and retina at deeper parts of the eye meets the criteria and has a more precise correlation with the core temperature. Detecting radiation from the interior region of the eye provides a useful basis for obtaining accurate core temperature with a non-contact sensor.

Fig. 2 shows a core temperature measuring device 100 according to the invention. The sensor unit 102 includes a detector 102 and the necessary auxiliary devices to detect thermal (planck) radiation of a selected wavelength of the animal or human eye 101. The sensor unit 102 also includes various optical elements, such as lenses, mirrors, filters, etc., for focusing and filtering radiation of interest onto the detector 109, so that only the wavelengths of interest reach the detector 109. It may also include means to reduce the temperature of the detector 109 to increase the sensitivity of the detector, and it may also cool optical lenses and filters to reduce thermal radiation of all components that would be detected by the detector 109. In the example shown in fig. 2, the sensor unit 102 includes an IR filter 111, a half mirror 112, a spectral filter 113, and a parabolic reflector 114. A light shield 130, such as a rubber eyepiece, may be used to reduce extraneous heat radiation during the measurement.

In the example shown in fig. 2, the sensor unit 102 detects IR radiation in the spectral wavelength range of interest. The optical element provides a sensitive aperture that approximates the size of the eye or a selected portion thereof. The sensor unit 102 provides the aperture at a distance of a few inches or more from the front of the unit.

The sensor unit 102 also includes auxiliary sensors for sensing the temperature of the components and other desired environmental parameters to compensate for their effect on the core temperature measurement. In the example shown in fig. 2, the temperature sensor 110 obtains a temperature measurement. An Identification (ID) sensor 115 detects data required to identify the particular animal or human being measured. For example, the ID sensor 115 may be used to read a barcode tag on the animal, or it may detect a unique optical characteristic of the eye. An optional filter 111 allows a broad wavelength band of radiation of interest to reach the detector 109, but rejects radiation outside that range. The broad wavelength bands of interest include bands for eye temperature measurement and for animal identification, and may also include bands for generating visible light spots to enable the sensor 102 to be directed at the eye being measured. It also acts as a dust and water shield to protect the interior of 102 from the environment. The filter 113 passes wavelengths required for temperature sensing, and an apparatus using filters of a plurality of different wavelength bands is also part of the present invention.

The illuminated marker 120 provides a visual indication of the region of the eye 101 being examined where the core temperature measurement was taken. In other words, the marker 120 provides a visible spot on the eye corresponding to the central receiving area of the sensor unit 102. For example, when the detector unit 102 is well aligned with the eye, the marker 120 may provide a visible spot on the eye. The marker 120 allows the operator to leave the animal and know that the sensor unit 102 is aligned in the desired direction. The light spot also has an additional function of attracting the attention of the animal and thereby facilitating the measurement.

The output signal of the radiation detector 109 is sent to the amplifier-detector 103, and the amplifier-detector 103 amplifies the amplitude of the signal and detects the amplitude of the radiation from the eye. The detected signal is normalized and calibrated for the temperature of the transmitter by calibrator 106. Radiation data measured on live animals are calibrated to the rectal thermometer temperature. In these initial tests, the cows were restricted to minimize movement and to allow contact for adequate measurement. Vaccination, such as pasteuria vaccination, is a harmless means for temporarily raising the temperature of the test animals to about 5 degrees above the normal range 100-103F.

The output of the temperature sensor 110 (and any other environmental sensors) is connected to the temperature and environmental signal conditioner and control unit 104 where the signal is amplified, normalized and used to provide the correlation data needed to compensate and improve the accuracy of correlating the radiation data with the core temperature of the animal or human. For example, changes in temperature can affect the sensitivity of the detector, as well as the amplitude of extraneous thermal radiation that reaches the detector. The required corrections and compensations are made by the data correlator and computer 107. The regulator and control unit 104 may include means for maintaining the sensor unit 102 at a constant temperature, if desired. May also be cooled to improve sensitivity. For example, a thermoelectric cooler or a cryogenic liquid may be used.

The identification sensor 115 also provides data through the amplifier-detector 105 to the data correlator and computer 107, and the data correlator and computer 107 provides a visual digital readout of the core temperature, identification number, time, date, ambient temperature and other pertinent information on the display 108. The core temperature is calculated from the eye radiation amplitude at the selected wavelength and corrected for the following effects (if any): such as ambient temperature, distance from the eye to the sensor assembly 102, measured eye area and animal type, and various variables of the instrument (e.g., amplification gain, detector sensitivity, and pre-detection bandwidth). The read data is also stored in the computer 107 for later reproduction or for transfer to an external data storage device for long term storage. The display 108 may also display other information such as the rectal temperature of the animal, its feed, and other identifiers.

Fig. 3 shows the infrared and visible light emission characteristics of various regions of the eye 10. As shown, visible and near infrared (400-1400nm) wavelengths of light are focused with little attenuation through the cornea, aqueous humor, iris, lens and vitreous humor onto the retina at the back of the eye. Longer wavelengths of light, the mid and far infrared (wavelength range 1400nm to 1.0mm), attenuate very much in the cornea except for a few discrete wavelength bands, but some of the mid IR wavelengths can penetrate a considerable distance into the interior of the eye. The same is true. Thermal radiation is emitted externally from the retina-vitreous region through the lens, cornea, aqueous humor and iris at correspondingly low attenuation wavelengths. The mid IR wavelength of 1000-2400nm may also be transmitted through the sclera covering the entire eyeball, except for the portion covered by the cornea. Thus, far infrared radiation from the eye comes primarily from the surface, while weaker mid-infrared and near-infrared radiation, particularly in certain wavelength bands, will penetrate the front of the eye and be more representative of the internal eye temperature. The millimeter wave and longer wavelength radiation will represent the temperature in the deeper regions of the eye than the far infrared wavelengths. The far infrared wavelength can be used to detect radiation in the lacrimal region of the eye and correlate it with the core temperature.

For better transmission of electromagnetic radiation data from deep parts of the eye, the shorter IR wavelength range (0.8 to 1 micron) is more advantageous, but at body temperature the opposite is true, with the radiation amplitude increasing dramatically at longer wavelengths. The wavelength range to be detected is set by the type of detector 109 and the filter used before the detector, e.g. filter 111, to limit the wavelength range of radiation falling onto the detector. For wavelengths greater than about 1.5 microns, a broadband thermopile detector or some photodiodes (e.g., a cooled extended range indium arsenic photodiode detector) provide good sensitivity, typically with or without an IR filter to limit the bandwidth of the detected radiation in use. For shorter wavelengths, other photodiodes (germanium with various dopants, silicon, gallium arsenide) or photomultiplier type sensors provide excellent sensitivity, and may be preferably used in general, with or without cooling. IR filters are used to limit the range of wavelengths of radiation detected. Otherwise the radiation of several areas will be detected simultaneously. The surface radiation, representing the surface temperature of the eye, may be much larger than the deep eyeball radiation. Unless the wavelength is corrected, these surface radiations (or surface radiations) cause errors in the measurement of the desired (internal) radiation, which in most cases is most representative of the core temperature. Far IR detectors correspond exactly to the surface temperature and are generally more susceptible to environmental influences than internal radiation. In contrast, low attenuation of the eyeball at visible and near IR wavelengths is best suited for transmitting radiation back from the deep eye to the retinal region. This is desirable because the retina area is least affected by the environment and its temperature is best correlated to the core temperature. Unfortunately, the intensity of planck radiation at these short wavelengths (visible and near infrared) is problematic. In fact, blackbody radiation is very weak at live animal temperatures (300-. Even at 1000nm, the radiation at these temperatures is still weak and cannot be detected rapidly. This problem becomes: for small hand-held thermal radiation detectors, the presence or absence of IR wavelengths can be used to accurately measure the temperature of the inner eye (to the nearest 0.1k) from a distance of 30cm (12 inches) or more in an acceptably short time (a few seconds). The answer is positive: cooled extended (wavelength) range InAs photodiode detectors or equivalents may be used in either or both of the 1600-, 2400nm range, particularly in the 1600-, 1800-, and 2150-, 2350nm bands described previously. The preferred embodiment of 102 in our invention uses a photodetector of the type described having a filter capable of passing the nominal wavelength of 1600-1800 or 2150-2350nm (or both) and collection and focusing optics that establish an IR detection zone (having dimensions approaching the size of the cornea) when the detector 102 is at a selected distance, for example, 12 inches from the eye to be measured. These concepts and specifications are key elements of our invention.

Another detail of the invention is additional means to further reduce the effects of radiation from different depths in the eye, or from extraneous sources, thereby improving the accuracy of the measurement. The required thermal radiation that best correlates with the core temperature comes from the interior of the eye. But other (undesired) thermal radiation from the surface and near-surface of the eye may also be detected. These radiations may be at the same temperature as the desired internal radiation, or at a higher temperature, or at a lower temperature. In any case, it is expected that surface and near-surface radiation will vary slightly with changing ambient temperature, wind, rain, etc., resulting in measurement errors. At the wavelengths where the eye attenuates least (these are the same wavelengths as the detector filters), the internal radiation has only a perceived intensity, while the surface and near-surface radiation have much broader spectra, with the intensity increasing at longer wavelengths. By comparing the total radiation detected with a narrow band filter with the total radiation detected with a wider band filter (or without a filter), the components caused by the internal radiation are not altered (except for losses in the narrow band filter), whereas the surface radiation detected with a wide band filter is significantly increased. Knowing the spectral bandpass characteristics of the broadband filter and detector, the radiation from the surface of the eye and stray sources can be measured and the correction coefficients derived in computer 107 for internal eye temperature measurement. This coefficient, along with the amplified signal of the radiation detector and the calibration coefficient, is used to calculate the exact core temperature for each measurement in computer 107.

Fig. 4 shows a micro and millimeter wavelength detector 40, which is another embodiment of the sensor unit 102 of fig. 2. Another possibility for obtaining intra-ocular temperature data within the scope of the present invention is to detect radiation in the longer wavelength (compared to the longest IR) microwave and millimeter wave (mm) range. For the nominal 3mm (80-100GHz) range, sensitive detectors using standard radio frequency superheterodyne (mixer-oscillator) technology are available at moderate prices due to commercial and governmental concerns over this portion of the spectrum. In fact, these detectors are more sensitive than thermopiles, and can easily detect these longer wavelength, low level blackbody radiations with an accuracy of up to 0.1F or better, depending on the observation (signal accumulation) time and the wavefront bandwidth. Although antenna size, as well as near field, far field limitations of the operator, etc., can create problems in limiting the detection zone to the eye area, this problem can be overcome by making the maximum distance from the antenna to the eye to be measured a few inches and using well known antenna arrangements to provide a narrow beam. For example, even a 1 inch diameter parabolic dish antenna may have a far field beam width of about 10 degrees and a focused near field that encompasses the retinal area of an animal or human.

The antenna-detector-mixer arrangement 41 may be implemented in the form of a small integrated circuit. The antenna section picks up eye radiation of a selected wavelength, the mixer section mixes the radiation signal with the signal from oscillator 52, and the detector section converts the radiation signal to a lower frequency, amplified by amplifier 53. Both the antenna size and the oscillator frequency are functions of the desired radiation wavelength to be detected.

Detecting eye radiation at two or more wavelength bands for all wavelengths (IR, mm, and microns) may reduce the effects of ambient temperature and background radiation at a given temperature measurement. For example, a signal at a first wavelength may be compared to a signal at a second wavelength. For such an implementation, the sensor unit 102 of fig. 2 (or the antenna-mixer-detector 41 of fig. 4) may be modified to accommodate more than one radiation signal path or detector. This can be done using multiple filters and detectors. Alternatively, only one detector may be used, and a wheel or some other electromagnetic or electromechanical or magneto-optical means may be used to provide the detector with a series of filters.

While various embodiments of the invention are described herein, the scope of the invention is not limited to these embodiments, and additional embodiments do not necessarily include all of the features shown in FIG. 2. Other embodiments are also within the scope of the invention.

Claims (15)

1. An apparatus for measuring the core temperature of an animal or human being subject to measurement, the apparatus comprising:

a sensor unit having a filter for allowing detection of only selected wavelengths of thermal radiation, and a detector for detecting selected wavelengths of thermal radiation from an eyeball of the subject and generating a signal corresponding to the radiation;

wherein the sensor is not in contact with the eyeball;

wherein the selected wavelength is emitted from a specific depth within the eyeball;

an amplifier unit for amplifying the signal from the sensor unit and for generating an amplified signal;

a data processing unit for converting the amplified signal into raw temperature data and for determining core temperature data from the raw temperature data; and

and the display is used for displaying the core temperature data.

2. The apparatus of claim 1, wherein: the sensor unit detects only near infrared radiation.

3. The apparatus of claim 1, wherein: the sensor unit detects more than one wavelength.

4. The apparatus of claim 1, wherein: the sensor unit has a single optical path for a single wavelength.

5. The apparatus of claim 1, wherein: the sensor unit has one or more optical paths for detecting one or more wavelengths.

6. The apparatus of claim 1, further comprising a calibration unit for sending calibration data to the data processing unit.

7. The device of claim 1, further comprising a thermometer for measuring an ambient temperature in the vicinity of the device.

8. The apparatus of claim 1, further comprising a light shield for protecting said sensor unit from thermal radiation unrelated to radiation from said eye.

9. The apparatus of claim 1, further comprising an illuminated marker for emitting a visible light beam corresponding to the sensor unit receiving area.

10. The apparatus of claim 1, further comprising an identification sensor for detecting an identification code associated with the object.

11. The apparatus of claim 1, wherein: the filter passes wavelengths from 1000 to 2500 nm.

12. The apparatus of claim 1, wherein: the filter passes wavelengths from 1600 to 1800 nm.

13. The apparatus of claim 1, wherein: the filter passes wavelengths from 2150 to 2350 nm.

14. The apparatus of claim 1, wherein: the filter passes wavelengths from 1600 to 1800nm and from 2150 to 2350 nm.

15. The apparatus of claim 1, wherein: the sensor unit is configured to detect thermal radiation from a first bandwidth and a second bandwidth, wherein the first bandwidth is wider than the second bandwidth, and the data processing unit is further configured to compare a detected amplitude of a signal from the first bandwidth with a detected amplitude of a signal from the second bandwidth and to compensate the core temperature data according to the comparison result.