Abstract: A modulated reflectance measurement system includes lasers for generating an intensity modulated pump beam and a UV probe beam. The pump and probe beams are focused on a measurement site within a sample. The pump beam periodically excites the measurement site and the modulation is imparted to the probe beam. For one embodiment, the wavelength of the probe beam is selected to correspond to a local maxima of the temperature reflectance coefficient of the sample. For a second embodiment, the probe laser is tuned to either minimize the thermal wave contribution to the probe beam modulation or to equalize the thermal and plasma wave contributions to the probe beam modulation.

Abstract: A method is disclosed for determining the inactive doping concentration of a semiconductor region using a PMOR method. In one aspect, the method includes providing two semiconductor regions having substantially the same known as-implanted concentration but known varying junction depths. The method includes determining on one of these semiconductor regions the as-implanted concentration. The semiconductor regions are then partially activated. PMOR measures are then performed on the partially activated semiconductor regions to measure (a) the signed amplitude of the reflected probe signal as function of junction depth and (b) the DC probe reflectivity as function of junction depth. The method includes extracting from these measurements the active doping concentration and then calculating the inactive doping concentration using the determined total as-implanted concentration and active doping concentration.

Abstract: A probe is presented that includes a light source, a coherent fiber bundle, and a pattern selector. The pattern selector is disposed between the light source and the proximal end of the coherent fiber bundle. The pattern selector includes at least one patterned zone through which light from the light source passes to project at least one fringe set onto a surface. Each of the at least one fringe sets has a structured-light pattern. The probe further includes an imager for obtaining at least one image of the surface and a processing unit that is configured to perform phase-shift analysis on the at least one image. A method for projecting a plurality of fringe sets suitable for phase-shift analysis on a surface using a probe is presented.

Abstract: A probe includes an insertion tube and a plurality of light emitters disposed on the distal end of the insertion tube. The probe further includes at least one intensity modulating element through which light from the plurality of light emitters is passed to project a plurality of fringe sets onto a surface. Each of the plurality of fringe sets intern have a structured-light pattern that is projected when one emitter group of at least one of the plurality of light emitters is emitting. The probe further includes an imager for obtaining at least one image of the surface and a processing unit that is configured to perform phase-shift analysis on the at least one image. A method for projecting a plurality of fringe sets suitable for phase-shift analysis on a surface using a probe is also presented.

Abstract: A technique includes providing an optical source signal to an optical fiber to produce a backscatter signal. A receiver is provided to detect the backscatter signal. During an acquisition period in which the backscatter signal is present, a sensitivity of the receiver is varied with respect to time to regulate an input signal range of an amplifier of the receiver.

Abstract: An opto-electronic assembly and testing method are disclosed. A housing of the opto-electronic assembly is coupled to a window to form an optical chamber. A retro-reflector can be coupled to the housing. A radiation source can be disposed on or about the retro-reflector. The radiation source can emit radiation into the optical chamber through at least a portion of the retro-reflector. A detector can sense a level of the radiation in the optical chamber. A controller coupled to the detector can signal an error condition when the level of the radiation exceeds a threshold associated with the presence of obscurants on the window. Optionally, the controller can be coupled to the radiation source for selectively emitting pulses of radiation into the optical chamber and detecting data bits corresponding to the pulses of radiation.

Abstract: A reflection characteristic measuring apparatus capable of scanning a specimen surface of a sheet specimen at a high speed is provided. The reflection characteristic measuring apparatus includes a group of illuminating and light-receiving systems for directing illuminating light onto the specimen surface of the sheet specimen held by a specimen holding roller pair and for receiving reflected light from the specimen surface. The illuminating and light-receiving systems measure a spectral characteristic of the received reflected light. The illuminating and light-receiving systems are disposed over one-dimensional arrays of color samples which extend in the longitudinal direction of the sheet specimen, and scan the one-dimensional arrays in a direction opposite to a direction in which the sheet specimen is transported.

Abstract: A method and apparatus for biomedical subsurface imaging and measurement of thickness, elastic and optical properties of industrial and biomedical materials based on laser Photo-Thermo-Acoustic (PTA) frequency-swept heterodyne depth profilometry, In particular, the invention relates to biomedical imaging and measure of tissue and tumour thickness, L, speed of sound, cs, acoustic attenuation coefficient, ?, optical absorption coefficient, ?a, and optical scattering coefficient, ?s.

Abstract: A voltage sensor capable of single-point or simultaneous multi-point contactless voltage measurement has an electro-optic transducer, a surface plasmon resonance (SPR) and an optical system. The electro-optic transducer is operable to translate an electric field dependent on the voltage in a device under test field to a variation in refractive index. The surface plasmon resonance (SPR) transducer is juxtaposed with the electro-optic transducer and is operable to translate the variation in the refractive index of the electro-optic transducer to a variation in reflectivity. The optical system is configured to illuminate the SPR transducer with incident light at a surface plasmon resonance-inducing angle of incidence and to detect light reflected by the SPR transducer at a single point or at multiple points within a region.

Abstract: A sensor and method for surface plasmon resonance sensing, wherein a small variation of the refractive index of an ambient medium results in a large variation of loss of a sensing mode. The surface plasmon resonance sensor comprises an antiguiding waveguide including a core characterized by a refractive index and a reflector surrounding the core. The reflector has an external surface and is characterized by a band gap and a refractive index higher than the refractive index of the core. A coating is deposited on the external surface of the core, the coating defining with the ambient medium a coating/ambient medium interface. In operation, the coating is in contact with the ambient medium, and the antiguiding waveguide is supplied with an electromagnetic radiation to (a) propagate a mode for sensing having an effective refractive index lower than the refractive index of the core and higher than a refractive index of an ambient medium and (b) produce surface plasmons at the coating/ambient medium interface.

Abstract: This application describes designs, implementations, and techniques for controlling propagation mode or modes of light in a common optical path, which may include one or more waveguides, to sense a sample.

Abstract: A spectrophotometric scanner suitable for producing spectral reflectance images of surfaces of samples for a plurality of wavelength bands is disclosed. The spectrophotometric scanner comprises a scanner head for collecting spectral reflectance data, a positioning mechanism for positioning the scanner head in relation to a surface, and a computing device for controlling the mechanism and recording and analyzing the spectral reflectance data. The computing device directs the positioning mechanism to position the scanner head on a row of locations in a grid of locations of the surface; directs the scanner head to measure spectral reflectance data for each location in the row of locations; records and analyzes the spectral reflectance data; and produces spectral reflectance images from the spectral reflectance data. A light source in the scanner head comprises a plurality of sequentially controllable LEDs, each producing light in a different wavelength band.

Abstract: The invention is directed to systems and methods of digital signal processing and in particular to systems and methods for measurements of thermoreflectance signals, even when they are smaller than the code width of a digital detector used for detection. For example, in some embodiments, the number of measurements done is selected to be sufficiently large so as to obtain an uncertainty less than the code width of the detector. This allows for obtaining images having an enhanced temperature resolution. The invention is also directed to methods for predicting the uncertainty in measurement of the signal based on one or more noise variables associated with the detection process and the number of measurement iterations.

Abstract: Rotating polygon mirrors are configured such that angles formed by a rotation axis and mirror surfaces differs from one another in the mirror surfaces in order to shift a collecting point of a scanning light flux in a sub-scanning direction in association with rotation at constant angular speed. A collecting point position forming optical system is configured such that the collecting point is moved in an inspection range Zr in a height direction Z. The XYZ scanning is performed by moving the inspection object in the sub-scanning direction such that the collecting point shifted in the sub-scanning direction and the height direction is linearly scanned in the height direction of the inspection object in synchronization with the rotation of the rotating polygon mirror at the constant angular speed, and the an appearance positional coordinate of the inspection object is determined by a confocal method to perform the appearance inspection.

Abstract: An optical measurement apparatus and method a method for performing modulation spectroscopy measurement of a sample comprising: delivering an incident probe beam to a sample at a known spot; modulating reflectance of the probe beam with a pump beam which periodically forms a pump beam spot on the sample coincident with the probe beam spot; and monitoring a reflected probe beam with a detector: wherein the incident probe and pump beams are collinear; and wherein the incident beams are directed to be collinear by reflecting a beam from a facet of an optical waveguide transmitting the other beam.

Abstract: Two optical signals are autocorrelated by causing them to be incident on a metal surface, where they generate a second (or higher) harmonic signal. The resulting harmonic signal is detected by a photomultiplier tube or the like. The harmonic signal generation on the metal surface is phase-matched and dispersion free and can be performed over a wide range of wavelengths.

Abstract: A flow-through gas cell and a method for passing a sample gas through a flow-through gas cell for spectroscopy are disclosed. In an embodiment, a flow-through gas cell is disclosed. The gas cell includes a substantially cylindrical interior cavity. The interior cavity comprises an inner surface that is reflective. In addition, the gas cell includes a gas inlet and a gas outlet. In the gas cell, a source is disposed on a side of the gas cell, and a detector is disposed on the same side of the gas cell as the source. The source emits electromagnetic radiation, and the detector detects electromagnetic radiation. The gas cell further includes mirrors disposed on opposing ends of the interior cavity.

Abstract: Radiation is projected onto a plurality of targets on a substrate. By assuming that the overlay error derivable from asymmetry varies smoothly across the substrate, the number of targets measured can be reduced. This may result in a smaller area of the scribe lane being used by targets for each layer of the substrate.

Abstract: A system and method for identifying explosive or other target materials includes the steps of irradiating a first location and a second location spaced apart from the first location from a sample suspected of including explosives with ultraviolet, visible or infrared light, measuring reflected light emanated from the first sample location (R1) and reflected light emanated from the second sample location (R2), and calculating a normalized difference in reflectivity (?R/ R), wherein R=(R1+R2)/2 is an average reflectivity. A differential reflection spectrum (DRS) is then generated for the sample where ?R=R2?R1 is the difference of the reflectivities of the first and the second sample location. One or more explosives if present are identified in the sample based on comparing the DRS for said sample to at least one reference DRS.

Abstract: A modulated reflectance measurement system includes lasers for generating an intensity modulated pump beam and a UV probe beam. The pump and probe beams are focused on a measurement site within a sample. The pump beam periodically excites the measurement site and the modulation is imparted to the probe beam. For one embodiment, the wavelength of the probe beam is selected to correspond to a local maxima of the temperature reflectance coefficient of the sample. For a second embodiment, the probe laser is tuned to either minimize the thermal wave contribution to the probe beam modulation or to equalize the thermal and plasma wave contributions to the probe beam modulation.

Abstract: Method for determining a mean radiation power P rad 0 _ of electromagnetic radiation of a radiation source, the radiation being intensity-modulated with modulation frequency ?0, in a predetermined time interval.

Abstract: The invention relates to a method for determining a characteristic of a semiconductor sample forming a surface. The method comprises the steps: simultaneously illuminating an area on the surface of a semiconductor sample with superimposed exciting light beams with a plurality of wavelengths, modulating the light beam of the different wavelengths with the same frequency, but different phases, selecting a modulation function and its phases in such a way, that the sum of the photon fluxes of all light beams at all times lies within a tolerance range, the tolerance range being considerably smaller than the sum of all photon fluxes, simultaneously phase-dependent measuring of the components of the surface photo voltage caused by the different light beams and determining the characteristic of the semiconductor sample from the relationships between the components and the respective wavelengths. Furthermore a device for carrying out such a method is described.

Abstract: A modulated reflectance measurement system includes lasers for generating an intensity modulated pump beam and a UV probe beam. The pump and probe beams are focused on a measurement site within a sample. The pump beam periodically excites the measurement site and the modulation is imparted to the probe beam. For one embodiment, the wavelength of the probe beam is selected to correspond to a local maxima of the temperature reflectance coefficient of the sample. For a second embodiment, the probe laser is tuned to either minimize the thermal wave contribution to the probe beam modulation or to equalize the thermal and plasma wave contributions to the probe beam modulation.

Abstract: A pulse stretcher includes a first prism and a second prism positioned opposite each other. A first coupling prism is optically coupled to the first prism with a partially reflective interface that directs a beam towards the second prism in a helical path. The first prism and the first coupling prism form a beamsplitter. A recirculating prism (or a reflective element) reflects the beam from the first prism into the second prism. Mirrors are positioned around the first and second prisms to permit recirculation of the beam through the first and second prisms. The beam recirculates through the first and second prisms using two or more helical paths. The pulse stretcher can be incorporated into a lithographic system.

Abstract: A measuring apparatus comprising a measuring chip, an optical incidence system, a photodiode array, a differentiation part, and a computation part. The differentiation part differentiates an optical detection signal output from each light-receiving element, in a direction where light-receiving elements are juxtaposed, at intervals of outputs of two adjacent light-receiving elements. The computation part specifies a reference light-receiving element, then judges whether or not values of the optical detection signals of a first predetermined number of light-receiving elements increase monotonously in directions going to both sides, and computes a position of a dark line on the basis of a value obtained by differentiating the outputs of a second predetermined number of light-receiving elements sandwiching the reference light-receiving element when it is judged that the values of the optical detection signals increase monotonously, in the above-described direction.

Abstract: A polarization modulation photoreflectance technique has been developed for optical characterization of semiconductor quantum confined structures. By using a tunable laser source in conjunction with polarization state modulation, a single beam modulation spectroscopy technique may be used to characterize the optical response of semiconductor materials and structures. Disclosed methods and instruments are suitable for characterization of optical signatures of quantum electronic confinement, including resolution of excitonic states at the band edge or other direct or indirect critical points in the band structure. This allows for characterization of semiconductor quantum well structures, for characterization of strain in semiconductor films, and for characterization of electric fields at semiconductor interfaces.

Abstract: An apparatus for characterizing multilayer samples is disclosed. An intensity modulated pump beam is focused onto the sample surface to periodically excite the sample. A probe beam is focused onto the sample surface within the periodically excited area. The power of the reflected probe beam is measured by a photodetector. The output of the photodetector is filtered and processed to derive the modulated optical reflectivity of the sample. Measurements are taken at a plurality of pump beam modulation frequencies. In addition, measurements are taken as the lateral separation between the pump and probe beam spots on the sample surface is varied. The measurements at multiple modulation frequencies and at different lateral beam spot spacings are used to help characterize complex multilayer samples. In the preferred embodiment, a spectrometer is also included to provide additional data for characterizing the sample.

Abstract: A coefficient of a function that relates a measurement from a wafer to a parameter used in making the measurement (such as the power of a beam used in the measurement) is determined. The coefficient is used to evaluate the wafer (e.g. to accept or reject the wafer for further processing), and/or to control fabrication of another wafer. In one embodiment, the coefficient is used to control operation of a wafer processing unit (that may include, e.g. an ion implanter), or a heat treatment unit (such as a rapid thermal annealer).

Abstract: A surface plasmon resonance enzyme sensor including a sensing part 6 having an optically transparent base 1, a thin metal film 2 made of gold or silver, and a film 4 provided on the metal thin film 2 causing electron transfer reaction with both the thin metal film and the enzyme is provided.

Abstract: A Mach-Zehnder interferometer includes a continuous arm defining a first optical path having a length and a non-continuous arm having first and second parts with a trench defined therebetween, the non-continuous arm defining a second optical path the length of which differs from that of the first optical path. A phase shifter is selectively movable between a first position in which the phase shifter introduces no phase shift to a signal traveling along the second optical path and at least a second position at which the phase shift introduces a phase shift to the optical signal traveling along the second path relative to a signal traveling through the first optical path. A M×M optical switch using such a Mach-Zehnder interferometer.

Abstract: Achromatic optics may be employed in spectroscopic measurement systems. The achromatic optics comprises a spherical mirror receiving a beam of radiation in a direction away from its axis and a pair of lenses: a positive lens and a negative meniscus lens. The negative meniscus lens corrects for the spherical aberration caused by off-axis reflection from the spherical mirror. The positive lens compensates for the achromatic aberration introduced by the negative lens so that the optics, as a whole, is achromatic over visible and ultraviolet wavelengths. Preferably, the two lenses combined have zero power or close to zero power. By employing a spherical mirror, it is unnecessary to employ ellipsoidal or paraboloidal mirrors with artifacts of diamond turning which limit the size of the spot of the sample that can be measured in ellipsometry, reflectometry or scatterometry.

Abstract: Described herein is an optical measurement instrument for a living body, comprising light incident means for simultaneously applying incident light of a wavelength in a visible-infrared region to a plurality of incident positions on the surface of a subject, light detection means for simultaneously detecting lights obtained by allowing the incident light to pass through the subject, at a plurality of detection positions on the surface of the subject, and imaging means for imaging information on the inside of the subject using detected signals outputted from the light detection means. The light incident means includes light modulation means for intensity-modulating the incident light applied to the plurality of incident positions with modulation frequencies respectively different every the respective incident positions.

Abstract: A micro-photoreflectance technique has been developed for performing non-destructive analysis of III-V optoelectronic devices. By using a significantly reduced spot size (for example, 10 micrometers), various compositional features of the device may be analyzed and the Franz-Keldysh oscillations appearing in the micro-photoreflectance wavelength spectra (such as those beyond the barrier/SCL wavelength in an EML structure) may be analyzed to provide information regarding the physical characteristics of the device, such as the electric field and p-i junction placement within an exemplary EML device structure.

Abstract: An apparatus and method for transmitting a hazardous electromagnetic beam (10). A hazardous beam (10) and a non-hazardous beam (12) are generated and directed along respective paths which are substantially parallel and either at least partially coincident or in close proximity so that an object will traverse the path of the non-hazardous beam (12) immediately before it is impinged by the hazardous beam (10). Any disturbance of the non-hazardous beam (12) by an object is detected and the hazardous beam (10) is disabled in response to a predetermined disturbance.

Abstract: An apparatus measures a property of a layer (such as the sheet resistance of a conductive layer or thermal conductivity of a dielectric layer that is located underneath the conductive layer) by performing the following method: (1) focusing the heating beam on the heated a region (also called "heated region") of the conductive layer (2) modulating the power of the heating beam at a predetermined frequency that is selected to be sufficiently low to ensure that at least a majority (preferably all) of the generated heat transfers out of the heated region by diffusion, and (3) measuring the power of another beam that is (a) reflected by the heated region, and (b) modulated in phase with modulation of the heating beam. The measurement in act (3) can be used directly as a measure of the resistance (per unit length) of a conductive line formed by patterning the conductive layer.

Abstract: The invention relates to a method and to a corresponding device for detecting spectral reflectance, an illuminating device arranged in a stationary fashion being used to apply to measuring fields moving relative to the measuring system radiation which differs in strength as a function of the relative speed, and the radiation reflected by the measuring fields being further processed after photoelectric conversion to derive measured variables. It is the object of the present invention to develop such a method as well as a corresponding device so that the optical reflectance-measuring system can be optimally adapted to different relative speeds given a prescribed measuring field size.

Abstract: In an image-wise exposure apparatus, a mirror array device includes a plurality of small mirrors which are two-dimensionally arrayed and are movable between ON-positions where each of the small mirrors reflects light impinging thereupon along an operative optical path so that the reflected light impinges upon a photosensitive material and OFF-positions where each of the small mirrors reflects light impinging thereupon along an inoperative optical path so that the reflected light does not impinge upon the photosensitive material. An initializing image signal which intends to cause all the small mirrors of the mirror array device to be set in the respective OFF-positions is input into the mirror array device, and an initial amount of light on the operative optical path at the time the initializing image signal is input into the control circuit is measured.

Abstract: The invention relates to a confocal laser imaging system and method. The system includes a laser source, a beam splitter, focusing elements, and a photosensitive detector. The laser source projects a laser beam along a first optical path at an object to be imaged, and modulates the intensity of the projected laser beam in response to light reflected from the object. A beam splitter directs a portion of the projected laser beam onto a photodetector. The photodetector monitors the intensity of laser output. The laser source can be an electrically scannable array, with a lens or objective assembly for focusing light generated by the array onto the object of interest. As the array is energized, its laser beams scan over the object, and light reflected at each point is returned by the lens to the element of the array from which it originated. A single photosensitive detector element can generate an intensity-representative signal for all lasers of the array.

Abstract: A dual beam tunable spectrometer comprises a radiation source, generating means, a detector, and a shutter arrangement. The radiation source generates an incident radiative beam. The generating means, which includes an acousto-optic tunable filter, receives the incident radiative beam and generates therefrom a reference beam and a sample beam. The detector detects at least part of the reference beam, and detects at least part of the sample beam emitted from a sample following illumination of the sample with the sample beam. The shutter arrangement includes a first shutter selectively permitting passage therethrough of the part of the reference beam and a second shutter selectively permitting passage therethrough of the part of the sample beam. The shutter arrangement opens the first shutter and closes the second shutter to permit the detector to detect only the part of the reference beam.

Abstract: An apparatus for measuring local carrier concentration in a preselected area of a semi-conductor is shown and described. An exciting light (preferably a laser) alters the sample's band-gap by photo injecting electron hole pairs in the area being measured. Because of the Franz-Keldysh effect, the photo injected carriers alter the sample's reflectivity. An optical fiber conducts a broad band source of probing light to the excited area on the sample. The sample reflects some of the broad band light back into a fiber that conducts the reflected light to an optical analyzer. The optical analyzer includes a dispersive element that disperses the reflected light onto a linear array of detectors. The analyzer thus simultaneously samples multiple wavelengths in the reflected spectrum. From the resulting samples, a computer deconvolutes the spectral line shape into a measurement of the local electric field and the local carrier concentration.

Abstract: The microreflectometer system, forming a 0.01 mm.sup.2 area spot, scans a mirror coating for defects of a mirror having a diameter of about 30 centimeters. Tens of thousands of reflectivity measurements are automatically taken as a computer controlled three dimension stage having the test mirror therein is selectively controlled. The reflectivity of each measurement either relative or absolute is used to determine the condition of the coating.

Abstract: A method and apparatus for thermowave analysis employs a single laser beam, which has an additive, two-frequency, intensity modulation, and is directed onto the object. The amplitude of the mixed frequency of the discrete modulation frequencies, which is not contained in the exciting beam, is analyzed as response signal. By obtaining a reference signal from the exciting beam and forming the difference between this exciting beam and the measurement signal, noise suppression and a lowering of the limit of sensitivity are achieved in an advantageous manner.

Abstract: A reflectance meter having improved noise immunity for measuring photometric quantities is disclosed. The device includes noise reduction techniques for eliminating the effects of ambient and artificial light upon the measurement signal. A gated modulator provides frequency shifting of desired information to a carrier frequency so that undesired signals may be filtered out. A gated demodulator provides a means to demodulate the information contained in frequency spectrum near the gate or chopping frequency.

Abstract: A method and apparatus for enhancing a holographic image in order to create an eerie spiritual visual image which can be used in conjunction with religious pictures in hologram form or an eerie visual image of decorative scenes for home or office furnishing purposes or Halloween or other scary situations. A holographic film incorporating an image therein is placed between two plates of optically transparent material such as glass. A direct source of illumination of the image through candlelight set at the focal point distance in front of the hologram film, within its focal plane and at a location no lower than the lowermost point of the holographic image creates the enhanced image and eerie effect in a dark room.

Abstract: The invention relates to a dosimeter wherein the substances to be detected color a chemical sensor layer. The degree of coloration of the chemical sensor layer is measured by a photometric diffusion-reflectance measuring device. This dosimeter is improved with respect to a measurement occurring during the time that the contaminant substance is effective. The foregoing is accomplished with the dosimeter of the invention in that the dosimeter has a measuring chamber which receives a diffusion element and with a light impermeable wall portion which closes off the diffusion element while at the same time being permeable to the substance to be detected. A light source and a photosensor are arranged in the measuring chamber.

Abstract: A method and associated apparatus for measuring the intensity decay time of an optical cavity is particularly useful for accurate measurement of cavities of the type that include highly reflective mirrors. In the method, apparatus is provided for generating at least one pulse of laser light having a bandwidth that exceeds the resonant frequency spacing of the optical cavity and for directing that pulse into the cavity. The intensity of the light within the cavity is then measured and the amount of time is determined for such intensity to decay from a first predetermined value to a second predetermined value.

Abstract: In a surface reflectance meter for directing light to a surface, receiving light reflected from the surface and measuring the rate of change of light flux upon withdrawal of a light chopper from the optical path, a fault detection means which detects and indicates a fault in the flux rate of change measurement is disclosed. In the preferred embodiment the rate of change of flux is detected by measuring the time for the light intensity to increase from a first to a second predetermined intensity and the fault detector means detects and indicates a fault when the light intensity does not reach the second predetermined intensity within a predetermined period of time. The surface reflectance meter is reset for repetition of the measurement upon indication of a fault. This invention is useful in portable surface reflectance meters which must be hand held to the surface to be measured, because instability in holding the meter to the surface can cause the fault.

Abstract: A single meter measures the gloss and the distinctness of image (DOI) of a painted surface for quality evaluation of the finish. A DOI signal is obtained by a prior method of focusing the reflected image of a moving shutter onto a slit and measuring the light passing through the slit. The rate of increase of the resulting signal is used as a measure of DOI. The same signal is integrated over a preset time period covering the upper part of the signal rise to yield a value proportional to gloss.

Abstract: A retroreflectivity measuring system measures performance data relating to a reflective surface, such as a highway stripe or marking containing reflective glass beads. A laser beam illuminates a portion of the reflective surface with radiation of a predetermined wavelength, the laser being incident on the surface at an incidence angle i. The incident laser beam is then reflected back, at least partially, at a particular observation angle o that is separated from the incidence angle by a divergence angle .delta.. A telephotomultiplier aimed at the illuminated area receives the reflected laser beam at the observation angle o. A preferred telephotomultiplier includes a telescope, a narrow pass optical filter for passing basically only the wavelength of the laser beam, and a sensitive photoelectric device, such as a multiplier phototube. The laser and the telephotomultiplier may be mounted on a servo-motor driven frame in order to scan the target area from a moving vehicle.

Abstract: An apparatus for detecting defects in a laser mirror by using a laser beam in order to detect any possible changes in reflectivity over the surface of the mirror. A laser beam is split by a beam splitter into one portion for scanning the mirror to be inspected and which is reflected therefrom to produce a reflection signal, the remaining portion of the beam providing a reference signal. A computer receives both signals and on the basis of comparison thereof determines the condition of the mirror because there will be incorrect reflection of the laser beam from any region of the mirror which is defective.