Abstract: An infrared presence detector system includes a focal plane array and a processor coupled to the focal plane array. The array includes a first radiant energy sensor and a plurality of second radiant energy sensors, with the first and second radiant energy sensors configured to convert incident radiation into an electrical signal. The processor is coupled to the focal plane array, and is configured to control the focal plane array in a sleep mode, wherein the first radiant energy sensor is energized and the plurality of second radiant energy sensors are de-energized, and an active mode, wherein at least the plurality of second radiant energy sensors are energized when the first radiant energy sensor detects a presence.

Abstract: A detection element, a manufacturing method thereof and a flat panel detector are disclosed. The detection element includes: a base substrate; a photodiode on the base substrate, the photodiode includes: a first electrode on the base substrate; a photoelectric conversion layer on a side of the first electrode away from the base substrate; a transparent electrode and a second electrode electrically connected with the transparent electrode on a side of the photoelectric conversion layer away from the first electrode. Besides, an orthographic projection of the photoelectric conversion layer on the base substrate completely falls within an orthographic projection of the first electrode on the base substrate; the photoelectric conversion layer includes a sidewall, an orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate is at least partially overlapped with an orthographic projection of the second electrode on the base substrate.

Abstract: A medication assurance system for verification of both the medication and the patient is disclosed. A portable spectrometer is used to obtain a light spectrum of the medication. A subject identification or biometric device is used to identify the patient. A controller coupled to the portable spectrometer and the subject identification device identifies the medication by performing a chemometric analysis of the light spectrum. Based on the medication identified and the patient identified, the controller can determine if the medication is to be taken by the patient.

Abstract: A system is provided for determining personal ultra-violet (UV) radiation measurements, comprising: a measurement device configured to measure UV irradiation; and a terminal device configured to receive or capture an output of the measured UV irradiation from the measurement device and to determine a specific user's personal UV exposure risk level based on at least the measured sun irradiation and information of a skin type of the specific user. The measurement device configured to measure UV radiation exposure includes a surface that includes a plurality of different sections that each have a different sensitivity to UV radiation exposure, and each of the plurality of different sections are configured to display a different color in response to the UV radiation exposure.

Abstract: Metrology targets and method of using the metrology targets for measurement of critical dimension, overlay or scanner aberration are disclosed. A target may include an unresolved grid having a plurality of lines spaced equally apart from each other according to a pre-determined pitch distance and at least one resolved feature tilted at an angle with respect to the unresolved grid. The method may indentify multiple regions of interest (ROIs) and determine a series of center points between the ROIs as the ROIs are being shifted. Critical dimension, overlay or scanner aberration may be calculated by analyzing the series of center points between the ROIs.

Abstract: An optical sensor includes a visible light sensor includes a visible light sensing transistor and an infrared light sensor includes an infrared light sensing transistor, wherein the visible light sensing transistor receives a first driving voltage through a first driving voltage line, the infrared light sensing transistor receives a second driving voltage through a second driving voltage line, and the visible light sensing transistor and the infrared light sensing transistor receive a reference voltage through a reference voltage line.

Abstract: The invention relates to a spectral detector for measuring properties of light over portions of the electromagnetic spectrum including cholesteric liquid crystal material and switching means capable of varying the pitch of the helix of the cholesteric liquid crystal material, so that the position of the transmission wavelength band is adjusted in response to the switching means. The spectral detector may further include at least one light direction selecting structure for selecting light incident on the spectral detector having a certain angle of incidence. This invention also relates to a lighting system including the spectral detector of the invention.

Abstract: An infrared cut filter removable (ICR) module control apparatus includes a photoresistor, first to sixth electronic switches, an ICR module, a comparator, and a central processing unit (CPU). A first terminal of the photoresistor is connected to a power supply through a resistor. A second terminal of the photoresistor is grounded, and connected to the second to fourth electronic switches and the CPU through the first electronic switch. The second electronic switch is connected to the fifth and sixth switches. A node between the third and fourth switches is connected to a first input terminal of the ICR module and the non-inverting terminal of the comparator. A node between the fifth and sixth switches is connected to a second input terminal of the ICR module and the inverting terminal of the comparator. The CPU is connected to the output terminal of the comparator and connected to the first electronic switch.

Abstract: A device for non-destructive testing of a component by analyzing radiation dissipation when the component is stressed by mechanical stresses. The device includes measuring means for determining a surface radiation field of the component. The measuring means are integrated in a flexible housing for covering a region of the surface of the component to be tested. The device enables an initial crack upon stress concentration on a surface of the component and the presence of a crack upon propagation of the crack to be detected. The disclosed embodiments are useful for non-destructive testing of aircraft components, but may be used in all industrial sectors where testing the integrity of components is important, such as the automotive, railway, marine and nuclear industries.

Abstract: The invention relates to a method for manufacturing a spectral detector including a photo detector array and cholesteric liquid crystal material for measuring properties of light over portions of the electromagnetic spectrum. By exposing the cholesteric liquid crystal material for different exposure intensities or exposure times of ultraviolet radiation at different positions on the cholesteric liquid crystal material in a controlled way, portions of the cholesteric liquid crystal material are obtained, each having, in general, its own optical transmission. This invention also relates to a spectral detector manufactured by the inventive method.

Abstract: The invention relates to a spectral detector for measuring properties of light over portions of the electromagnetic spectrum including cholesteric liquid crystal material and switching means capable of varying the pitch of the helix of the cholesteric liquid crystal material, so that the position of the transmission wavelength band is adjusted in response to the switching means. The spectral detector may further include at least one light direction selecting structure for selecting light incident on the spectral detector having a certain angle of incidence. This invention also relates to a lighting system including the spectral detector of the invention.

Abstract: A technique for providing high-contrast images of defects in solar cells and solar panels, by illuminating each cell under inspection with broadband infrared radiation, and then forming an image of radiation that is secularly reflected from the cell. Multi-junction solar cells have a metal backing layer that secularly reflects the illumination back into an appropriately positioned and aligned camera, selected to be sensitive to infrared wavelengths at which the solar cell materials are relatively transparent.

Abstract: A device (1) for monitoring exposure to radiation (L), particularly ultraviolet radiation, at least comprising cholesteric liquid crystal material (3) having a photo-isomer sable compound, such that during use, a light reflection band of the cholesteric liquid crystal material (3) can be modified upon exposure to the radiation to be monitored. The invention also provides a method for monitoring exposure to radiation.

Abstract: A thermal imaging device is provided for converting an image in the terahertz radiation range to the visible range. In one embodiment, the device includes a converter having a thermochromic liquid crystal layer mounted on a sapphire base. In another embodiment, the device includes a thermal absorption layer including a metal selected from the group of iron, aluminum, tin, and copper. In a further embodiment, the device has an light source shaped as an annulus for illuminating a rearward surface of the converter, configured to permit visible light rays to pass through the annulus for capture by a digital detector. In a final embodiment, the device has a thermal adjustment device for adjusting the temperature of the thermochromic liquid crystal layer to an optimal temperature.

Abstract: A calibration standard specimen is provided to have formed therein calibrating patterns of a lattice shape discontinuously arrayed, and particular alignment patterns respectively disposed near the calibrating patterns so that the positioning of the specimen can be made to match the calibrating patterns to the measurement points.

Abstract: A monitoring device, process and system use an image recording device for recording an image falling on the eyes of the user of the device. The monitoring device includes a display and a signal processor with which at least the image signals recorded by the image recording device can be evaluated. An input medium and a storage medium are used for storing and retrieving information about the topology of the building. An instantaneous position of the user of the device is determined by evaluating the image signals sent by the image recording device by pattern recognition.

Abstract: An imaging system illuminates body tissue with infrared light to enhance visibility of subcutaneous blood vessels, and generates a video image of the body tissue and the subcutaneous blood vessels based on reflected infrared light. The system includes an infrared light source for generating the infrared light and a structure for diffusing the infrared light. The diffusing structure includes one or more layers of diffusing material for diffusing the light. The system further includes a video imaging device for receiving the infrared light reflected from the body tissue and for generating a video image of the body tissue based on the reflected infrared light.

Abstract: A method of evaluating the surface of a material that has a distinguishable infrared spectrum comprising (a) positioning an infrared fiber optic probe to be in contact with a surface of the sample or material at a region of interest for detecting attenuated total reflectance or within a sufficient distance from the surface of the region for detecting reflection, (b) detecting mid- or near-infrared radiation attenuated total reflectance or reflection off of the surface of the sample or the material, (c) analyzing the infrared radiation from step (b) for at least one of peak height, peak area, frequency and chemometric parameters, and (d) actuating the removal device when a signal from the infrared fiber optic probe is between pre-selected values for at least one of peak height, peak area, frequency and chemometric parameters for the sample of the material.

Abstract: A method and apparatus for improving detection of radiation emitted from object that includes a radiation detection sensor with a substrate and an array of columns protruding from a top surface of the substrate. A radiation sensitive layer, such as TLC, and a thermal conversion material, such as an absorber, are disposed upon a top surface of the columns within the array thereby producing an array of radiation detectors. The columns provide thermal isolation between the radiation detectors and the substrate, and spatial separation of columns within the array provide radiant and thermal isolation between the radiation detectors upon the tops of individual columns. Producing an image of the array of radiation detectors allows detection of the radiation emitted from an object.

Abstract: Systems and methods for thermal sensing and imaging using the electro-optic effect. A thermal detection system comprises a temperature sensing element that includes an electro-optic (EO) material layer having a length axis and characterized by a temperature dependent index of refraction, an electrical mechanism for inducing a chance in the index of refraction, a laser beam propagating lengthwise through EO layer for probing the refraction index change, and a light intensity meter for measuring a laser beam intensity change caused by the temperature dependent refraction index change. Thermal imaging is obtained by using a pixel array of such thermal sensing elements. The intensity reading may be done in either a cross-polarizer or a Mach Zehnder Interferometry reading configuration.

Abstract: A self-compensating correlated double sampling circuit for a pixel image signal and a method to process the same. In the circuit, the analog signal generated by the photosensor of the pixel array accessed by a row selection transistor is buffered through a source follower amplifier and coupled to a column in the array. The analog signal from the selected column line is fed through a CDS circuit which is then input to the sample and hold circuit of the ADC. The main purpose of the CDS circuit is to reduce the noise and non-uniformity caused by the non ideal effects associated with the signal path from the photosensor through the CDS circuit. This is accomplished by sampling the signal and a reference level and then performing the subtraction on the two samples and the ADC ramp through the same signal path.

Abstract: A chemical imaging system is provided which uses a near infrared radiation microscope. The system includes an illumination source which illuminates an area of a sample using light in the near infrared radiation wavelength and light in the visible wavelength. A multitude of spatially resolved spectra of transmitted, reflected, emitted or scattered near infrared wavelength radiation light from the illuminated area of the sample is collected and a collimated beam is produced therefrom. A near infrared imaging spectrometer is provided for selecting a near infrared radiation image of the collimated beam. The filtered images are collected by a detector for further processing. The visible wavelength light from the illuminated area of the sample is simultaneously detected providing for the simultaneous visible and near infrared chemical imaging analysis of the sample. Two efficient means for performing three dimensional near infrared chemical imaging microscopy are provided.

Abstract: An optical apparatus includes at least an image display device, a light source for illuminating the image display device, a light-receiving device for receiving the light reflected from the eye of an observer, and a calculation device for calculating the line of sight of the observer based on the output of the light-receiving means. At least part of the illuminating light from the light source is utilized as the illuminating light for illuminating the eye of the observer.

Abstract: A description is given of a switching device 1 comprising a transparent substrate 3, a switching film 5 of gadolinium having a thickness of 200 nm and a palladium layer (7) having a thickness of 10 nm. Under the influence of hydrogen gas, a transparent semiconductive layer (5) of GdH.sub.x (x>2) is formed which can be converted into a non-transparent layer of GdH.sub.x (x<2) by means of evacuation. The conversion between both compositions is reversible, and this phenomenon can for example be used in an optical switching element, a hydrogen sensor and thin displays.

Abstract: Changes-with-time in the voltages of exposed and unexposed portions of a liquid crystal recording layer with respect to a photoconductive layer having a varying dark current value are found by varying an applied voltage, and the applied voltage and the value of a dark current through the photoconductive layer are determined such that when the voltage of the unexposed portion of the liquid crystal recording layer reaches the threshold voltage of the liquid crystal recording layer, the difference in voltage between the exposed and unexposed portions of the liquid crystal recording layer reaches a maximum, so that information is recorded with the photoconductive layer and at the applied voltage, where a potential difference is obtained, which is at least one half of the difference (maximum contrast) in the voltages applied on the liquid crystals at the exposed and unexposed portions of the liquid crystal recording layer.

Abstract: A non-volatile memory device which includes a recording medium, a heating means for heating the recording medium, a reading means for reading the information stored in the recording medium, and the recording medium containing a liquid crystal compound.

Abstract: A thermal imaging system (10) contains a focal plane array (30) including a plurality of thermal sensors (32) mounted on a substrate (62). Each thermal sensor (32) includes a film layer (34) of infrared sensitive material which is both electronically and thermally isolated from the associated integrated circuit substrate (62). An image may be formed on the film layer (34) in response to infrared radiation from a scene (12). Electromagnetic radiation (22) from a source (visible light or near infrared) (20) is used to reproduce or transfer the image from the thermal sensors (32) onto the first surface (68) of the substrate (62). A thermoelectric cooler/heater (66) may be provided to optimally adjust the temperature of the substrate (62) to improve overall image quality.

Abstract: An infrared (IR) radiation transducer integrates an IR detector array with a liquid crystal (LC) readout. The IR detector is preferably a pixelized bolometer array, but other detectors such as pyroelectric materials are possible. To modulate the LC in response to detected IR radiation, a modulating section is provided that includes a charge injection structure which injects electrical charge in response to the detected IR radiation, and a charge transfer structure that transfers the injected charge to the LC readout section. During its active phase the charge transfer layer is depleted of majority charge carriers, and the charge injection and transfer mechanism operates in a manner analogous to a bipolar transistor. A visible readout is obtained by directing readout light through the LC, where it is modulated in accordance with the detected IR image. The transducers are small and light weight enough to be incorporated into a pair of goggles, for which no separate cooling is required.

Abstract: A thin-film transistor using hydrogenated amorphous silicon (a-Si:H), and particularly a thin-film device such as a thin-film transistor having high conductivity, large drivability and high process margin, and a display panel using the same transistors. The object of the invention is to reduce defects due to shorts between the gate and the source or between the gate and the drain, to prevent signal line defect even in case defects develop due to shorts, and to expand the design margin and process margin in the array. A capacity is connected to the gate electrode of the channel side and a voltage is applied to the gate electrode via the capacity.

Abstract: A combined optical imaging/display device employs a liquid crystal light valve (LCLV) with a charge coupled device (CCD) input, and a photosensitive CCD or charge injection device (CID) array for receiving an input image and developing a corresponding signal pattern. The signal pattern is applied as an input to the CCD after amplifying it and manipulating it as desired. The CCD and photosensitive array are provided on a common substrate; their cells may be arranged in alternating rows or in separate arrays. The invention is applicable to active vision enhancement goggles.

Abstract: A camera system providing color night vision for use in reconnaissance, or he like. The system includes a first lens, a mirror subassembly for splitting the lens image into three images, a filter subassembly for respectively filtering the three images through a red filter and a green filter and a blue filter first and second and third intensifiers having respective first and second and third camera units which view the three images and send three image signals in series to a display monitor where the color image is viewed.

Abstract: This invention is concerned with a thermal imaging optical system finding utility as an individual weapon sight. The system comprises an infra-red objective lens including a chopper blade together with front and back elements with an adjustable element therebetween. Infra-red radiation is received by the objective lens which also incorporates an internal substantially collimated plane polarized visible light source which illuminates a liquid crystal. The path of the infra-red and visible light which is directed to the liquid crystal cell, is repeatedly interrupted by the chopper blade. Changes in the liquid crystal cell due to the infra-red radiation transmitted by the objective lens are caused to modulate the plane polarized visible light transmitted through the liquid crystal cell to generate a visible image. This image passes through a relay inverting system and is detected by a visible light detector and viewed through an eyepiece.

Abstract: An electromagnetic imager device can detect electromagnetic images, for example, in the infrared, millimeter and microwave wavelengths and convert these images into useful wavelengths which imaging devices, such as a camera, can record. The electromagnetic imager includes an interferometer having one arm thereof filled with a gaseous mixture. The particular gaseous mixture used, improves the accuracy of the device by enhancing the probability of an exchange of kinetic energy for molecular internal energy during molecular collision. The electromagnetic image is absorbed in an internal mode of the molecular species in the gas over an absorption depth. The absorption of the electromagnetic energy causes heating in the gas which, in turn, causes local changes in the index of refraction in the focal plane of the gas. These changes in the index of refraction phase modulate the phase front of the laser beam passing through the gas.

Abstract: A reflective matrix mirror visible to infrared converter light valve (5) includes a liquid crystal medium (60) for spatially modulating an incident infrared beam by polarization rotation, a photosubstrate (30) for receiving an incident visible wavelength image (115) and for controlling the polarization rotation of the liquid crystal medium (60) responsively to the visible image (115), and a reflective matrix mirror (40). The reflective matrix mirror (40) is positioned between the liquid crystal medium (60) and the photosubstrate (30) and reflects the incident infrared beam (125) back through the liquid crystal medium (60) such that the infrared beam (125) passes through the liquid crystal medium twice and is polarization rotated responsively to the visible wavelength image (115). A polarizer (90) positioned exteriorly of the liquid crystal medium (60) converts the polarization rotation of the infrared beam (125) into output intensity modulation to produce an infrared image (130).

Abstract: The liquid crystal is written with a laser beam. The laser beam generated by a laser source is applied through an optical control unit such as galvanometer mirrors to the liquid crystal. The intensity of the laser beam applied to the liquid crystal is controlled by a laser beam intensity varying unit. A writing control unit controls the mechanical displacement caused by the optical axis control unit and controls the laser beam intensity varying unit. The laser beam energy applied to the liquid crystal can be maintained constant, thus enabling a constant written line width even during acceleration and deceleration of the optical axis control unit.

Abstract: It is known to use liquid crystal cells for thermal imaging. However, the sensitivity of the liquid crystal cell is reduced due to the walls of the cell absorbing some of the incident radiation and locally heating the crystal thereby producing localized changes in phase. Liquid crystal materials which have sufficient surface tension to form a film without forming a part of a cell are disclosed where the pitch of the helix of the film exhibits a strong temperature dependence. In one embodiment the liquid crystal film is mounted wtihin a Fabry-Perot resonant cavity so that detection of the change in the crystal due to a change in temperature is enhanced.

Abstract: The liquid crystal is written with a laser beam. The laser beam generated by a laser source is applied through an optical control unit such as galvanometer mirrors to the liquid crystal. The intensity of the laser beam applied to the liquid crystal is controlled by a laser beam intensity varying unit. A writing control unit controls the mechanical displacement caused by the optical axis control unit and controls the laser beam intensity varying unit. The laser beam energy applied to the liquid crystal can be maintained constant, thus enabling a constant written line width even during acceleration and deceleration of the optical axis control unit.

Abstract: An infrared imaging system includes a film of dichroic liquid crystal coated on a membrane, first means for forming an infrared image on the membrane, second means for illuminating the membrane with visible light, and third means for deteching variations in elliptical polarization of the light after reflection from or transmission through the membrane to provide a visible image.

Abstract: A thermal image is created in a thermostatically controlled liquid crystal cell (4) containing a two-frequency nematic or cholesteric (3). This is addressed with an alternating potential whose frequency can be swept through the cross-over frequency. By appropriate choice of frequency within this range the thermal image is converted to a phase image which in its turn is converted to a contrast image in conventional manner.

Abstract: A thermal imager includes an infrared sensitive light valve and a light source arranged to illuminate the full responsive area of the valve. The imager also includes an optical stage having focussing optics for forming an infrared image upon the surface of the valve and a chopper for modulating infrared radiation from a scene. Modulated light from the valve is read out in parallel by a detector array, and frame signals corresponding to alternate positions of the chopper are subtracted to provide uniformity correction. The light valve may comprise an infrared sensitive optically active liquid crystal cell and an analyzer adjusted to near extinction. An optical processor comprising a lens and an apodized stop filter lies in the light path between the valve and the detector array. The light source may comprise an array of light emitting diode elements and the filter a number of corresponding off-axis stop regions.

Abstract: A device for transforming information in electrical form into optical form, where the optical information consists of light intensity, light polarization or spectral composition varying with time. The transformation of information takes place from electrical into optical form by means of optical modulators, e.g. liquid crystals, and the transformation from optical form into electrical form is arranged to be carried out with photo-detectors, the device comprising components to control or sense said optical modulators in one, two or three-dimensions with time, and to sense or control said photo-detectors.

Abstract: An infrared imaging system is disclosed which provides a two-dimensional visible image of the temperature profile of a radiating infrared source remotely located from the system. The invention is preferably implemented as a small hand-held instrument which can be held at a user's eye for sighting at a source of radiation and for viewing the temperature profile thereof. The system comprises an objective lens operative to focus an infrared image of a radiating source onto a surface of a liquid crystal structure, with the opposite surface of the structure being visually viewable by way of an eyepiece. The liquid crystal structure is biased preferably by a closed loop temperature control to be sensitive to an intended infrared spectrum of interest and to be substantially non-responsive to ambient temperatures.

Abstract: Luminosity values of a structure carrying information, in particular grey scale values, are transformed into corresponding isochromates. The transformation is effected by optically imaging the information carrying structure onto a layer of liquid crystals. By this means, a thermogram corresponding to the information carrying structure produced in the layer of liquid crystals, so that the luminosity values of the structure carrying information is transformed into isotherms in the layer of liquid crystals, and the isotherms are converted into isochromates as a result of the colour/temperature behaviour of the layer of liquid crystals.

Abstract: The invention provides a liquid crystal imaging system which employs a transitory thermo-optic effect to permit notably the reproduction of T.V. images. This transitory effect is characterized by the fleeting appearance of scattering cybotactic zones in the transparent liquid phase of a mesomorphic material, at the very beginning of the transition to a nematic transparent ordered phase. The duration of the scattering period can be considerably shortened by subjecting the mesomorphic material layer to the action of an alternating electrical field.

Abstract: A liquid heating device particularly adapted to the heating of sealed bottles containing liquids which are maintained in sterile condition until used, such as dialysates and the like. The device employs sealed bottles having a temperature sensitive element in intimate contact with the liquid being heated, which changes to a predetermined color and hue as the desired temperature is obtained. This color is compared with a color standard using a single source of light which is reflected against the indicator and the standard. The light reflected from these elements is photoelectrically compared, and the operation of the heating element is interrupted when a match is made. An independent timer interrupts said operation in the event of a failure of the photoelectric comparison.

Abstract: A viewing system for improving an image, and particularly designed for use with infrared and low light level inputs. A viewing system having first and second electrodes mounted in spaced relation with a gap therebetween, an electric power source for producing an electric field in the gap attracting electrons toward one electrode and positive charge toward the other, a photoresponsive layer on the gap face of the first electrode with radiation directed onto the layer through the first electrode producing an electrostatic charge image at the gap, and a plurality of electrophoretic particles dispersed in a dielectric liquid in the gap, with the particles being selectively deposited at the second electrode as a function of the electrostatic charge image. In the preferred embodiment, the deposited particles are viewed with a dark field illumination system whereby light is scattered to the viewing position by the deposited particles. Cascaded systems and systems incorporating image intensifiers are also disclosed.

Abstract: An instant image display element for X-rays or the like comprises a laminate of an optically transparent plate 3, an optically transparent electrode 4, a deformable elastomer layer 5, a flexible insulating mirror film 6, an ionizable liquid 7 which absorbs X-rays and emits positive and negative ions in proportion to the ray intensity, and an X-ray permeable plate electrode 8. When a potential is developed across the electrodes 4, 8 and an X-ray pattern is projected through electrode 8 and into the liquid 7, the emitted ions of one polarity migrate to the mirror film 6, and cause the elastomer layer 5, and the mirror film 6 along with it, to deform in a pattern corresponding to the X-ray pattern. Such deformation may be optically projected for readout by a Schlieren system or the like.

Abstract: The invention provides a liquid crystal imaging system which employs a transitory thermo-optic effect to permit notably the reproduction of T.V. images. This transitory effect is characterized by the fleeting appearance of scattering cybotactic zones in the transparent liquid phase of a mesomorphic material, at the very beginning of the transition to a nematic transparent ordered phase. The duration of the scattering period can be considerably shortened by subjecting the mesomorphic material layer to the action of an alternating electrical field.

Abstract: The invention is a temperature stabilizing device employing a liquid crys wherein the crystal is itself stabilized to provide a thermal viewing element.

Abstract: An infrared imaging system includes a film of dichroic .[.liquid crystal.]. .Iadd.material .Iaddend.coated on a membrane, first means for forming an infrared image on the membrane, second means for illuminating the membrane with visible light, and third means for detecting variations in elliptical polarization of the light after reflection from or transmission through the membrane to provide a visible image.