Abstract: A coated, embrittlement resistant optical fiber thermometer fiber is disclosed, which can be a sapphire or silica fiber with a metallic coating which prevents the fiber from becoming brittle at high temperature, and enhances transmission of radiation through the fiber. The coating can be applied over a thin "conductive" film attached to the fiber exterior using vacuum metallization, sputtering, or organo-metallic deposition. The coating may comprise pure platinum electroplated over a thin conductive film. The fiber may include a first end terminating in a blackbody radiator in a furnace and a second end terminating at a receptor apparatus. A coated fiber of the present invention provides a hermetic seal around the fiber to prevent its exposure to hydroxyl ions in the atmosphere. Fibers of the invention will remain flexible even after exposure to temperatures well over 1000 degrees Centigrade. The coating also prevents unwanted external radiation from entering the fiber.

Abstract: A radiant thermometer for detecting infrared rays coming from an object along an optical axis to determine its temperature is provided with an improved aiming system. An exterior housing supports an interior housing that mounts the detector having an opening for receiving the infrared rays. A visible sighting light source is provided in the exterior housing behind the detector. A peripheral lens system is mounted between the interior and the exterior housing to provide a cone shaped transmission of light having a larger field angle than a field angle of the detector. The cone shaped transmission of light is capable of being focused on the optical axis for aiming the radiant thermometer.

Abstract: A thermal radiation sensor is joined with a shutter that is adapted for reversible interruption of radiation from an object to the sensor. The shutter includes an integral electrically operated heater for maintaining a portion of the shutter at a predetermined temperature as a thermal reference for the sensor. The sensor is alternatively exposed to radiation from the object and the thermal reference portion of the shutter, and provides a first signal representative of the radiation that it receives from the object and a second signal representative of the radiation that it receives from the reference portion. An electronic circuit is connected to the sensor for receiving the first and second signals, for calculating the temperature of the object, and for providing a signal representative of the calculated temperature.

Abstract: A probe has an inlet and outlet by which a fluid flows over an optical sensing element in the sensing probe. Broad band optical radiation is supplied to the element and radiation transmitted through the optical sensing element is supplied to three photodiodes responsive respectively to radiation at different wavelengths. The transmission characteristic of the optical sensing element varies in different ways with change in temperature and pressure respectively. A store of temperature and pressure against amplitude of radiation at different wavelengths is addressed by the outputs of the photodiodes to give an indication of pressure and temperature at the sensing element.

Abstract: A device for the measurement of a temperature in a relatively low range having the lower limit of below 100.degree. C. is proposed. The device is suitably used for measuring a temperature of a substrate 4 during a sputtering treatment in a vacuum environment. Infrared rays radiated from the substrate 4 in a vacuum chamber 1 are collected by an optical lens 13 mounted in a freely movable probe 10 via a mirror (15) provided in a hood 14 attached to a front end of the probe (10) for deflecting the incident rays to the lens 13. The collected rays are led outside the chamber 1 to a sensor through a fluoride fiber 8 optically connected to the lens 13. The fiber 8 is enveloped in an air-tight manner within a metal bellows 9.

Abstract: A monitor for measuring the temperature distribution of a product (12) including a plurality of ball lenses (14) lying in a lenticular array (18) across the product (12). A signal processor (22) is connected to a photodiode array (20). Each photodiode in the array (20) is connected by a separate optical fiber (16) to one of the ball lenses (14).

Abstract: A solid state laser visible light source (26) passes light through a scanning mechanism (22) otherwise used to convey radiation from a target (12) to a detector (28) of a scanning radiation sensor (10) to mark with light a line (16) which is continuous when the sensor (10) is operating in a continuous mode, but when the sensor is operated in a spot mode in which a plurality of spots along a scan line are to be individually measured, a control (30) causes the light source to turn on and off at the correct times in the scan cycle to cause the light source (26) to mark the plural spots on the scan line (16). A CCD camera (40) with an automatic gain control circuit (46) is used in conjunction with a band pass light filter (36) to substantially enhance viewability of the image of the light markings (16) on the target (12) on a display (44).

Abstract: Pyrometric temperature measurement of molten masses arranged in a vacuum involve the problem that the material of the molten mass deposits on mirrors, windows and other optical means so that the radiation, on its way to the pyrometer, is ever more absorbed. For preventing vapor depositions in the path of radiation, a matter filter having a rotating vane wheel is arranged between the container for the molten mass and the pyrometer. The radiation passes through the gaps between the vanes. Molecules of the molten material are caught by the vanes. Accordingly, a mirror behind the matter filter is kept free of undesired vaporization and transmits radiation to the pyrometer.

Abstract: A disposable cone channel insertion probe is adapted for use in combination with an infrared thermometer. The probe has a generally frusto-conical hollow body portion, an inner reflective surface, and a flange projecting radially outward from the rearward end of the probe. The infrared thermometer also includes a mechanism for retaining the probe and optics for further focusing and collimating the infrared light from the probe to an infrared sensor.

Abstract: An optical fiber is installed to pass through a plurality of measurement places. Predetermined positions in the optical fiber are set at a predetermined temperature. When an optical signal is radiated on the optical fiber, Raman scattering occurs at various portions of the optical fiber. The intensities of the Raman scattered light components depend on temperatures. Backscattered light components of the Raman scattered light are sampled and stored in a memory. A temperature distribution on the optical fiber is obtained on the basis of the stored data. The temperatures of the mesurement places can be specified on the basis of the predetermined temperature on the obtained temperature distribution as a reference. The temperatures of the measurement places can be corrected on the basis of the predetermined temperature.

Abstract: A radiation clinical thermometer has a probe with an optical guide and an infrared sensor, a detection signal processing section, a body temperature operating section, and a display unit. A filter correction system for setting a correction value based on the transmission wavelength characteristics of a filter is also provided. The body temperature operating section receives infrared data, temperature-sensitive data, which takes into account the temperature equilibrium between the optical guide and the infrared sensor, and a correction value from the filter correction section so as to calculate body temperature data.

Abstract: A clinical thermometer which employs an infrared sensor and is constructed so as to prevent the occurrence of a temperature measurement error caused by a change in temperature of a tip portion (of a housing a temperature measuring portion) during temperature measurement. In one embodiment a heat insulator is attached to the tip portion to prevent a rise in temperature of the tip portion. In a second embodiment, the tip portion is formed of a metal of good heat conductivity in the shape of a net for example to improve the heat radiating property of the tip portion, thereby preventing a rise in temperature of the tip portion. In a third embodiments, a temperature sensor is attached to the tip portion to correct a temperature measurement error caused by a change in temperature of the tip portion.

Abstract: Tympanic temperature measurements are obtained from the output of a thermopile mounted in an extension from a housing. The housing has a temperature display thereon and supports the electronics for responding to sensed radiation. The thermopile is mounted in a highly conductive can which includes a radiation guide and thermal mass. The guide provides a narrow field of view due to a fairly high emissivity. Electronics determine the target temperature as a function of the temperature of the hot junction of the thermopile determined from the cold junction temperature and a thermopile coefficient. The tympanic temperature is adjusted to provide an indication of core temperature.

Abstract: An infrared thermometer (10) with a fixed aperture (99), focusable remote pickup head (12) conveys infrared light (16) from a target (14) to a photosensor (52) of a defocused sensor head (20). The remote pickup head (12) has a reimaging lens (84) and means for selectively adjusting the focus of the lens (84) relative to the target (14) after the pickup head has been fixedly mounted. The aperture setting is kept fixed during the focus adjustment to eliminate the need to recalibrate after the focus adjustment. The defocused sensor head (20) has a defocused relay lens (50) which is selectively out of focus to convey a slightly blurred, out of focus image of the output end of the fiber optic cable (18) to the photosensor (52) to reduce noise, average the light signal and reduce calibration difficulties due to high intensity spots in the image field and to make the unit less susceptible to misfocusing.

Abstract: A medical diagnostic method and apparatus employs differential radiation detection apparatus for remotely detecting temperature differentials between a plurlity of areas on the surface of an object having a plurality of lenses which each focus a beam of radiation from a corresponding area of the body onto a radiation detector in such a way that not more than one field of view reaches the detector at any time.

Abstract: An improved apparatus and means for measuring temperatures inside enclosures or conduits containing hot gases laden with entrained solids using a pyrometer. The improvement involves an optical access port consisting of a high strength sight tube, a safety valve, a double sight glass, various purge connections and provisions for optical alignment. A dynamic purge system keeps the optical sight path clear during normal operation, and clears the path if it begins to become occluded during operational upsets within the enclosure or conduit. The improved optical access port is mounted on the exterior wall of the vessel or conduit.

Abstract: Tympanic temperature measurements are obtained from the output of a thermopile mounted in an extension from a housing. The housing has a temperature display thereon and supports the electronics for responding to sensed radiation. A disposable plastic sheet taken from a tape of such sheets stretches over the end of the extension between side posts. The thermopile is mounted in a highly conductive thermal mass which includes a waveguide tube. A low conductivity gaseous environment surrounding the thermopile extends through the tube. The electronics include an EEPROM in which both calibration and characterization information may be stored during a calibration procedure through an optical coupling. A capacitor and transistor associated with a switch form a simple watchdog circuit.

Abstract: A radiation thermometer comprises a housing (1) within which is mounted a radiation detector system including a radiation sensor (2) positioned to receive radiation through a window (5) in the housing. The radiation detector system generates an electrical signal related to the sensed radiation. An optical signal generator (11, 14) is responsive to the electrical signal from the radiation detector system (9) and an internal housing temperature detector to generate a modulated optical signal whose frequency is related to the electrical signal from the radiation sensor and whose mark-space ratio is related to the signal from the internal temperature detector. The housing (1) is connectable with an optical waveguide, such as an optical fibre (16), into which the optical signal is coupled in use. A power source (13) is mounted within the housing (1) and is connected to the detector system (9).

Abstract: A radiation clinical thermometer includes a probe, a detection signal processing section, a body temperature operating section, and a display unit. A filter correction section for setting a correction value based on the transmission wavelength characteristics of a filter is arranged. The body temperature operating section receives infrared data, temperature-sensitive data, and the correction value from the filter correction section so as to calculate body temperature data.

Abstract: An infrared thermometer (10) with a fixed aperture (99), focusable remote pickup head (12) conveys infrared light (16) from a target (14) to a photosensor (52) of a defocused sensor head (20). The remote pickup head (12) has a reimaging lens (84) and means for selectively adjusting the focus of the lens (84) relative to the target (14) after the pickup head has been fixedly mounted. The aperture setting is kept fixed during the focus adjustment to eliminate the need to recalibrate after the focus adjustment. The defocused sensor head (20) has a defocused relay lens (50) which is selectively out of focus to convey a slightly blurred, out of focus image of the output end of the fiber optic cable (18) to the photosensor (52) to reduce noise, average the light signal and reduce calibration difficulties due to high intensity spots in the image field and to make the unit less susceptible to misfocusing.

Abstract: A catoptric type radiation thermometer having a catoptric type optical system is provided with a light receiving member for receiving an infrared ray emitted from an object to be measured. The infrared ray is periodically prevented and allowed to pass by a shutter blade fixed to an optical chopper supported by a bimorph cell vibrated by an AC signal. The optical chopper is arranged in such a manner that the longitudinal direction thereof is perpendicular to an optical axis of the optical system and the transverse direction is parallel to the axis and that one end of the chopper is supported at the outside of the passageway of the infrared ray.

Abstract: The infrared thermometer optical chopper includes a planar shutter having infrared radiation transmissive and infrared reflective portions arranged on the shutter, and a mechanism for rotating the shutter sequentially through a series of stop positions in which the transmissive and reflective portions are sequentially aligned with the internal optics of the infrared thermometer. A mechanism is also preferably provided for sensing the positioning of the shutter at the stop positions, to determine whether the shutter stop position alignment is in an infrared radiation transmissive phase or in an infrared radiation reflective phase.

Abstract: A device, for simulating temperature effects at the interface of a head-to-medium interface, is comprised of a unitary block of material which transmits radiation in the infrared (IR) region of the electromagnetic spectrum and which has a wear-resistant property substantially approximating that of the material of an actual magnetic head to be simulated. The unitary block is shaped to have (1) a first forwardly facing surface substantially approximating the dimensions and contour of the working surface of the head to be simulated, and (2) a second rearwardly facing surface substantially approximating the dimensions and contour of a light-transmitting surface of a positive spherical lens the focal plane of which coincides with the forwardly facing surface. Sapphire is selected as a material having a suitable IR-transmitting property and a wear-resistant-property commensurate with one wear-resistant properties of alloy and ferrite materials commonly used in the manufacture of a video magnetic head.

Abstract: In the case of a system for detecting excessively heated wheel bearings and/or wheel tires of rail vehicles, a device is inserted into the path of the beam extending from a measuring point to a heat radiation sensor that distorts the resulting image and, in particular, widens it at least uniaxially. This device also serves to detect the measuring point when wheel axles shift in an axial direction. A system of this type may be formed by using a distorting optical device (6) which permits the imaging of a correspondingly widened field (4).

Abstract: A high speed infrared temperature measuring device which consists of a lens barrel in an instrument housing, a sensor in the lens barrel to read an infrared target signal, a processing circuit for the signal, an automatic circuit for the thermoelectric cooler and a black body compensation circuit and means to read and record the processed signal.

Abstract: A laser thermal testing method and system for use in testing a fire alarm system which has a plurality of heat-sensors which are remotely distributed throughout a protected area. The laser thermal testing system includes a first laser and a second laser. The first laser generates an aiming beam of coherent electromagnetic radiation in the visible spectrum. The laser thermal testing system also includes a movable reflector which reflects the aiming beam. The movable reflector is optically coupled to the first laser. The movable reflector is first moved in order to align the aiming beam in an aligned position so that the aiming beam is reflected onto one of the heat-sensors. The movable reflector is then fixedly secured in the aligned position. The second laser generates a heating beam of coherent electromagnetic radiation in the infrared spectrum.

Abstract: Laser pyrometer techniques are utilized to accurately image a true temperature distribution on a given target without touching the target and without knowing the localized emissivity of the target. The pyrometer utilizes a very high definition laser beam and photodetector, both having a very narrow focus. The pyrometer is mounted in a mechanism designed to permit the pyrometer to be aimed and focused at precise localized points on the target surface. The pyrometer is swept over the surface area to be imaged, temperature measurements being taken at each point of focus.

Abstract: A method of measuring a furnace temperature in a hot isostatic pressing unit, including the steps of condensing a thermal radiation beam from an end portion of a closed-end tube in a high-pressure furnace of the hot isostatic pressing unit by an optical system, feeding the radiation beam from the optical system to a detector to measure the temperature in the furnace, wherein the optical system includes a solid lens having an incoming surface formed by a spherical surface with center at a temperature measurement objective point and having an outgoing surface formed by a spherical surface with center at a light collecting point, so as to condense a radiant energy from the temperature measurement objective point. In another aspect of the invention, the steps further comprising removing a wavelength of absorption by a low b.p. metal gas vaporized from a treatment material in the furnace or a capsule glass.

Abstract: An improved optical system for a radiation thermometer is provided wherein a range finding system is coincident with the optical system of the infrared measurement. The finder optical system can utilize various forms of focusing members.

Abstract: In a pyrometer system, a pyrometer provides output signals to a processor indicative of the temperature of rotating blades in a gas-turbine engine. The processor includes a synchronization unit and a gate controlled by the synchronization unit. After monitoring the output of the pyrometer to identify which parts of the output signal arise from radiation from the blades and which arise from the combustion chamber, the synchronization unit is set in synchronism with the blade signals and the gate is controlled to pass signals from the blade and to interrupt signals arising from the combustion chamber. The output of the processor is thereby indicative of blade temperature and is insensitive to combustion chamber radiation.

Abstract: A radiation probe includes an optionally cooled tube 10 with a window 22 at one end, and can be traversed across a gas turbine engine combustion chamber 20 by drive means 26. A radiation detector 28 simultaneously measures radiation intensity at a plurality of wavelengths, at each of a succession of positions during the traverse. From this data, local values of radiation levels, grey and non grey absorption coefficients, local temperature and local gas composition and soot concentration are calculated, using a recurrence formula which relates intensities at neighboring positions.

Abstract: The present invention relates to an optical system of a radiation thermometer in which the measuring optical system and the finder optical system can be focused. The central portion of the sub-mirror in Cassegrainian type optical system is used as a finder lens of the finder optical system. The third mirror is located between the main and sub-mirrors in order to reflect the light passed through the central portion of the sub-mirror. The light reflected on the third mirror is used for finder observation.

Abstract: In one form of the present invention, an emissive substance radiates electromagnetic radiation as a function of temperature. The radiation is transmitted by a waveguide to a sensor which measures the intensity of the radiation and infers the temperature of the emissive substance therefrom.

Abstract: A remote passive condition sensor apparatus such as a temperature or humidity sensor apparatus. A corner cube reflector at a remote location, where it is not feasible to have electrical connections or batteries, receives and reflects back radiant energy to an optical readout instrument. Condition responsive elements in the corner reflector affect the amount of reflected radiant energy as a function of the condition sensed.

Abstract: An apparatus for measuring the temperature in a heating system comprising a cooking pot with cooking material positioned on a hot plate where a radiation receiver is arranged at a distance from the wall of the cooking pot and aligned with it, which receiver produces a temperature measurement signal corresponding to the temperature of the cooking material in the cooking pot. The temperature measurement signal is derived from a detected radiation area on the wall of the cooking pot which corresponds to the radiation measuring field of the radiation receiver. The effect of different distances of the cooking pot from the radiation receiver is automatically compensated for by aligning the center axis of the radiation measurement field at an acute angle to the support surface of the hot plate, so that the distance of the center of the detected radiation area from the bottom of the cooking pot increases with an increasing distance of the wall of the cooking pot from the radiation receiver.

Abstract: In an apparatus wherein an infrared sensor is incorporated opposite to an opening formed at a predetermined position of a housing, a distance keeping member for keeping a constant distance from a temperature measuring portion is further mounted on another predetermined position of the housing, and an output signal from the infrared sensor responding to the infrared rays from the temperature measuring portion is supplied to a temperature measuring circuit whose operational state is selected by a temperature measurement control switch, and the temperature of the temperature measuring portion is displayed on a display unit which is driven by the output signal from the temperature measuring circuit.

Abstract: The present invention relates to an optical system of a radiation thermometer in which the measuring optical system and the finder optical system can be focused. The central portion of the sub-mirror in Cassegrainian type optical system is used as a finder lens of the finder optical system. The third mirror is located between the main and sub-mirrors in order to reflect the light passed through the central portion of the sub-mirror. The light reflected on the third mirror is used for finder observation.

Abstract: A pyrometer for viewing the blades of an engine has a forward lens which produces a first image of the blades in an image plane P.sub.1. Rearwardly of the image plane P.sub.1 is an assymetric faceted lens assembly having a central region with a long focal length, and an outer annular region of shorter focal length. The outer region of the rear lens assembly forms a second image of the first image in a second image plane P.sub.2. The inner region forms a third image of the forward surface of the first lens in the second image plane P.sub.2. A disc mask is fixed centrally to the forward surface of the first lens, and an annular mask is located in the first image plane P.sub.1. The forward end of a fibre-optic cable is located in the second image plane P.sub.2 and comprises a central bundle of fibres which receives the second image, and two outer bundles which receive different parts of the third image.

Abstract: A slight tube assembly, in combination with a sensing instrument, such as an optical pyrometer, for use in continuously monitoring the temperature of the first row of rotating blades in large gas turbines, particularly the type used in industry. Temperature data received by the pyrometer unit is fed to a control circuit, which regulates fuel input to the tubine to control the firing temperature. The key to obtaining reliable blade temperature data in the practice of this invention is the position of the sight tube in the turbine, which enables the pyrometer to "view" the rotating blades along a direct line of sight that penetrates a hot gas duct, but not the turbine section of the engine.

Abstract: Hand-held instrument for measuring the temperature of a target without contact with the target. The instrument utilizes a microprocessor and a digital display to calculate and indicate different temperature functions. Compensation is included for the effects of emissivity and ambient temperature changes which otherwise could result in inaccurate readings. Temperature trend direction liquid crystal arrow(s) actuated by the microprocessor are included in the display.

Abstract: A heating system for heating a rapidly rotating article, including strobe means capable of emitting radiant energy and positioned to radiate energy onto the article, a light source positioned to illuminate a temperature-sensing means on the article, light detector means to measure changes in the light reflected by the temperature-sensing means and control means to energize the strobe means in response to reflected light from the detector means.

Abstract: An induction heating cooking apparatus contains a cooker main unit (1), comprising a connector (17) attached to an operation part (7) of the cooker main unit (1) in a freely attachable/detachable manner. A probe (13) containing a thermistor therein is coupled to the connector (17). The probe (13) is inserted into the foodstuff to be cooked in a cooking pan (5), and the thermistor detects the temperature thereof. A light emitting device (23) installed in the connector (17) outputs a light signal in response to the output from the thermistor. This light signal is introduced into the cooker main unit (1) through a light transmitting part (25) formed at a bottom part (19) of the connector (17) and another light transmitting part (27) formed in the operation part (7), being received by a light receiving device (29). In response to the output from the light receiving device (29), a driving circuit drives an inverter.

Abstract: This invention provides an apparatus for measuring the temperature of the contents of a saucepan in a heating system comprising a saucepan and its contents placed on and heated by a heating element. The invention provides saucepans having radiating surfaces encircling the pan in a transition area between the bottom and side wall of the pan, a radiation sensor with a focusing device aligned with the radiating surface of the saucepan placed on the heating element, and provides for the radiation sensor to be spaced from the radiating surface at a distance corresponding to the focal point of the radiation focusing device.

Abstract: To be of most use as an input signal for the control system of a gas turbine aeroengine, a pyrometer-derived turbine blade temperature signal should represent the average temperature of the hottest parts of the blades with fast and accurate response when the average temperature of the hottest parts changes with engine conditions. The invention achieves this by providing the pyrometer with an optical system adapted to give the pyrometer's photo-diode a large field of view which is rectangular at the face of the turbine rotor and which extends an integer number of inter-blade passage widths in the circumferential direction and a portion of the length of the blade aerofoils in the radial direction.

Abstract: Optical quotient thermometers are disposed on the operative end of pusher rods used to push coke from coke oven chambers. The actual value of the optical quotient temperature is measured by the thermometer on two closely-adjacent wavelengths and a quotient signal is produced from the top measured volumes which is converted in a measuring head secured to the pusher rod. An electrical signal is delivered by a converter in the measuring head by wires extending along the pusher rod to a point externally of the oven chamber to a recording and/or evaluating facility where the signal is recorded.

Abstract: A method and apparatus is disclosed for detecting thermal waves. This system is based on the measurement of the change in reflectivity at the sample surface which is a function of the changing surface temperature. The apparatus includes a radiation probe beam that is directed on a portion of the area which is being periodically heated. A photodetector is aligned to sense the intensity changes in the reflected radiation probe beam which results from the periodic heating. These signals are processed to detect the presence of thermal waves.

Abstract: A method and apparatus for determining a temperature profile along a single optical fiber. The temperature profile is determined by measuring the output power spectral distribution. By measuring n points along the spectral power distribution curve, n "resolution elements" of temperature can be determined.

Abstract: An optical fiber temperature thermometer uses a thermochromic substance having optical absorption peaks which vary with temperature within a first waveband, and having substantially constant absorption with temperature in a second waveband. The radiation employed is in a wide band to include the first and second wavebands, and the radiation, reflected and attenuated as a result of the passage through the thermochromic substance, is split into two selected beams and filtered in narrow band pass filters for the first and second wavebands, to supply optical signals to respective detectors whose outputs are divided to produce a ratio signal representative of the temperature. The sensor is sufficiently compact for biomedical use, and, being unaffected by electromagnetic fields, is useful in regions of high tension or in microwave heating.

Abstract: In a radiation pyrometer in a gas turbine engine, non-uniformly distributed changes in transparency of an optical element in the system, e.g. contamination of pyrometer objective lens L.sub.1 by combustion products from the turbine can be automatically detected. Lens L.sub.1 focusses radiation from target T onto an additional lens L.sub.2, which in turn focusses it onto the end E of the fibre-optic bundle F. Considered reciprocally, lens L.sub.2 images the end E of fibre-optic F into L.sub.1, so that although each optical fibre in end E receives radiation from all parts of target T, each fibre is imaged into a corresponding discrete area of L.sub.1. Fibre-optic bundle F comprises two (or more) sub-bundles F.sub.1 and F.sub.2 forming complementary sub-areas of end E and each sub-bundle is provided with its own photodetector P.sub.1, P.sub.2 and associated pre-amplifier A.sub.1,A.sub.2 adjusted so that their outputs A.sub.1 S.sub.1 and A.sub.2,S.sub.2 are matched at the non-contamination condition.

Abstract: A method for the structural, superficial and deep analysis of a body is disclosed. The method includes scanning the body to be examined using a modulated excitation radiation beam so as to impart a thermal modulation to the body. The thermal modulation is then measured on the side of the body distal to the side exposed to the beam. The amplitude as well as the phase of the measured thermal modulation is used to determine the thickness and structure of the body. A device for accomplishing the above described method is also disclosed.