Abstract: Systems, devices and methods of producing an image are provided. A electro-magnetic radiation source provides electro-magnetic radiation to a sample and a reference. A detector/interferogram unit produces at least one interferogram that is supplied to a signal processing unit. The signal processing unit extracts phase, magnitude, and/or polarization data from the supplied signals, and produces an image based on at least the extracted data.

Abstract: An imaging device can take an image of a flow field including tracer particles includes a compound-eye lens formed from a large number of monocular lenses, which take images of images taken by an imaging lens. Each of the multiple monocular lenses functions as one imaging device. This can enable measurement precision to be enhanced by suppressing the influence of ghost particles, while reducing the equipment cost by minimizing the number of imaging devices. A space for installing the imaging device can easily ensured. If a large number of imaging devices are used, not only do they require time and manpower for setting up, but there is also a possibility that the measurement precision will be degraded due to displacement of an axis of the imaging devices caused by vibration, etc. When the imaging device having the compound-eye lens is used, setup is simplified, and measurement precision can be ensured.

Abstract: A weapon-locating ladar system estimates a backward trajectory of an airborne target by using flow field measurements to follow the wake turbulence trailing the airborne target from a position at which the target is detected backwards until the wake is no longer observable. The system may use the backward trajectory to estimate the point-of-origin of the target. The system may also use the flow field measurements along the backward trajectory to classify the target. Target classification may be used to refine the point-of-origin estimate, to influence counter-fire or to adapt the flow field measurements.

Abstract: The present disclosure describes methods and systems for measuring crosswind speed by optical measurement of laser scintillation. One method includes projecting radiation into a medium, receiving, over time, with a photodetector receiver, a plurality of scintillation patterns of scattered radiation, comparing cumulative a radiation intensity for each received scintillation pattern of the received plurality of scintillation patterns, and measuring a cumulative weighted average cross-movement within the medium using the compared cumulative radiation intensities.

Abstract: A method of using a light detection system for increasing the accuracy of a precision airdrop is described. Radiation is transmitted to target areas between an airborne vehicle and a dropzone target. Scattered radiation is received from the target areas. Respective wind characteristics are determined from the scattered radiation and a wind velocity map is generated, based on the respective wind characteristics, between the airborne vehicle, and at least the dropzone target. An aerial release point for the precision airdrop is computed based on the generated wind velocity map and a location of the dropzone target.

Abstract: A velocity measuring device emitting a laser beam at a web; a photodiode converting an optical output of the laser into an electric signal; a laser driver operating the laser to alternate a first emitting interval wherein the oscillating wavelength increases and a second emitting interval wherein the oscillating wavelength decreases; a current-voltage converting/amplifying portion converting the electric current from the photodiode into a voltage; a filter portion removing a carrier wave from the output of the current-voltage converting/amplifying portion; a signal extracting portion calculating a number of interference waveforms in the output of the filter portion; and a calculator calculating the velocity of the web based on the result of the extracting portion. The laser driver operates so the absolute values for the rates of change, in respect to time, of the oscillating wavelengths during the first emitting interval and during the second emitting interval are different.

Abstract: A wind turbine includes a number of blades and an optical measurement system comprising a light source, such as a laser, an optical transmitter part, an optical receiver part, and a signal processor. The light source is optically coupled to the optical transmitter part, which includes an emission point for emitting light in a probing direction. The optical receiver part comprises a receiving point and a detector. The optical receiver part is adapted for receiving a reflected part of light from a probing region along the probing direction and directing the reflected part of light to the detector to generate a signal used to determine a first velocity component of the inflow. The emission point is located in a first blade at a first radial distance from a center axis, and the receiving point is located in the first blade at a second radial distance from the center axis.

Abstract: Two or more spatial filters are used in determining velocity based on speckle translation. A light source may be turned on, turned off, or both for a variable amount of time during operation. The velocity may then be determined with trend identification, correlation, recursive frequency estimation, or measurement bandwidth variation. A confidence level may also be calculated for the measured velocity, and the measured velocity reported or used only when the calculated confidence level meets or exceeds a given value.

Abstract: Systems and methods for laser based measurement of air parameters for use, e.g., on aircraft are disclosed. An example system includes a coherent source of radiation, a modulator, a transceiver, an optical mixer, and a measuring system. The coherent source produces a coherent radiation beam, and the modulator is configured to modulate the coherent radiation beam. The transceiver is configured to transmit the modulated radiation beam to, and receive a scattered radiation signal from a target region. The optical mixer is configured to determine a difference between the scattered radiation signal and the reference radiation beam. The measuring system is configured to determine at least one of velocity, air density, pressure, temperature, barometric altitude, angle of attack, angle of side slip, icing and turbulence based on the difference between the scattered radiation signal and the reference radiation beam.

Abstract: The present invention relates to a method of measuring web feeding velocity by using an encoder. A method of measuring feeding velocity of a web, on which a scale having a different pitch from a pitch of a mask is formed, includes: calculating a number of vibrations of a moiré image of light passing through the mask and the scale; calculating scale pitches of the fed web based on the calculated number of vibrations of the moiré image; averaging the pitches so that a change in a pitch between adjacent timings among the calculated scale pitches is minimized; extracting first signals corresponding to a plurality of phases for one pitch based on the averaged pitch; calculating second signals for forming a Lissajous circle from the signal corresponding to the plurality of phases; and calculating an angle of the Lissajous circle by the second signals for forming the Lissajous circle and then calculating the feeding velocity of the web by using the calculated angle.

Abstract: A method of analyzing pulses from a flow cytometer in which particles in a fluid pass through an excitation volume of an electromagnetic radiation and interact with the electromagnetic radiation to generate signals in the form of pulses includes generating a time-dependent pulse indicative of the characteristics of one or more particles passing through the excitation volume of the electromagnetic radiation, determining a measurement window by selecting a portion of the pulse with a starting point and an ending point above a predetermined value, and calculating a first derivative of the pulse with respect to time over the measurement window.

Abstract: Systems and methods for laser based measurement of air parameters are disclosed. An example system includes a source of radiation, an amplification system with one or more power amplification stages, a transceiver, and an optical mixer. The source produces a plurality of beams, and the amplification system is configured to amplify the beams. The transceiver is configured to transmit the modulated beam to, and receive a scattered beam from a target region. The optical mixer is configured to determine a difference between the scattered beam and a reference beam, which is used to determine a Doppler shift therefrom. In certain embodiments, the amplification system includes a fiber preamplifier and one or more fiber power amplifiers stages.

Abstract: A cell observation device is provided with a reflection interference shutter 106A which adjusts a light quantity of light emitted from a reflection interference measurement light source 106, a quantitative phase shutter 105A which adjusts a light quantity of light emitted from a quantitative phase measurement light source, a camera 110 which images reflected light from the reflection interference measurement light source 106 to generate a reflection interference image and which images transmitted light from a quantitative phase measurement light source 105 to generate a quantitative phase image, and a first extraction unit 204 and a second extraction unit 205 which extract first and second parameters from the reflection interference image generated by the camera 110. During generation of the reflection interference image, the quantitative phase shutter 105A blocks the light from the quantitative phase measurement light source 105.

Abstract: An aerial, landing, takeoff, aircraft collision avoidance system (10) that automatically operates an audible and visual display warning system within an aircraft by sensing when there is an intruder aircraft approaching on the same runway, intersecting runway, or same airway during climb, descent, and midair flight by employing a five-way interactive communication system using laser and radio wave technology and, thereby, providing added safety and protection for users of the system and oncoming aircrafts while being designed to automatically open a simultaneous three-way line of communication between pilots and air traffic controllers during crisis; identify and alert aircrafts what runways are presently in use during landings, taxiing, and takeoffs; and identify what runways are in use to taxiing aircrafts that may inadvertently cross a runway without clearance from air traffic control.

Abstract: A LIDAR device may transmit light pulses originating from one or more light sources and may receive reflected light pulses that are then detected by one or more detectors. The LIDAR device may include a lens that both (i) collimates the light from the one or more light sources to provide collimated light for transmission into an environment of the LIDAR device and (ii) focuses the reflected light onto the one or more detectors. The lens may define a curved focal surface in a transmit path of the light from the one or more light sources and a curved focal surface in a receive path of the one or more detectors. The one or more light sources may be arranged along the curved focal surface in the transmit path. The one or more detectors may be arranged along the curved focal surface in the receive path.

Abstract: A laser Doppler velocimeter uses self-mixing amplification of backreflections from scatterers below the surface of a flow. A time domain signal is divided into segments that are roughly equal to a transit time of particles through a focus of a laser beam. The segments are connected to a frequency domain through the use of an FFT algorithm to produce frequency domain data segments. Signal-to-noise ratio is enhanced through signal processing techniques using the segments to produce a final enhanced signal spectrum.

Abstract: A localized dynamic light scattering measurement system includes a beam displacer for splitting an incident beam having two orthogonal linearly polarized beam components with slightly different frequencies into two orthogonal linearly polarized output beams focused onto an object to be measured. The beam displacer cooperates with an iris to collect and recombine scattering beams each reversely backscattered at 180 degrees from the object so as to form a signal beam, which is polarized by a polarizer to produce two polarization components, thereby generating a heterodyne interference signal associated with the polarization components. A signal processing unit obtains measurement data on the object based on power spectrum or autocorrelation data corresponding to the heterodyne interference signal.

Abstract: Determining a height profile of a test object surface includes obtaining, from a scanning interferometry device, scanning interferometry data for the test object surface, calculating a coherence profile of the test object surface and a phase profile of the test object surface based on the scanning interferometry data, calculating an phase gap map based on the coherence profile and the phase profile, modifying the coherence profile based on the phase gap map to obtain a corrected coherence profile, and determining a height of the test object surface based on the corrected coherence profile.

Abstract: A device for measuring a speed of a material includes a body unit disposed at an exit side of a rolling stand and placed below a material which is transferred from the rolling stand; and a speed measuring unit installed on the body unit and constructed to measure a speed of the material transferred from the rolling stand.

Abstract: Methods for tracking the relative velocity between a vehicle and a target that uses both a measured velocity as well as an estimate of the velocity that is based on tracking the peaks in a laser vibrometer return signal.

Abstract: A displacement measuring apparatus 100 which measures a displacement amount of a moving object 102 includes a light source that irradiates the moving object 102 using luminous flux emitted from a light emitting area 101, a photo diode array 104, 105 that includes a plurality of light receiving areas in a movement direction of the moving object 102 and that forms an image of the luminous flux reflected on a plurality of indentations 103 of the moving object 102 to receive light, and a measurement unit that measures the displacement amount of the moving object 102 based on a movement amount of a light emitting area image 106 that is formed on the photo diode array 104, 105 by forming the image of the luminous flux.

Abstract: A system for assessing the flow of a fluid. The system can include a light source, a fiber-optic system optically coupled to the light source, which is arranged to provide a reference beam and an observation beam, an optical detection system arranged to receive combined light from the reference beam and the observation beam and to provide detection signals, and a data processing system arranged to communicate with the optical detection system to receive the detection signals. The data processing system can be configured to use the detection signals to determine a speckle pattern corresponding to the fluid flow, wherein the speckle pattern includes a plurality of lines, and to calculate a correlation between adjacent lines perpendicular to the flow to determine at least one of a rate of the flow and a displacement of the flow.

Abstract: A sporting device may include a proximity detector, and a housing for carrying the proximity detector. The proximity detector may comprise a single photon avalanche diode for measuring the speed of an object struck by the housing. For example, the housing may define a tennis racket.

Abstract: A laser Doppler velocimeter uses self-mixing amplification of backreflections from scatterers below the surface of a flow. A time domain signal is divided into segments that are roughly equal to a transit time of particles through a focus of a laser beam. The segments are connected to a frequency domain through the use of an FFT algorithm to produce frequency domain data segments. Signal-to-noise ratio is enhanced through signal processing techniques using the segments to produce a final enhanced signal spectrum.

Abstract: The invention relates to a device (1) for characterizing a two-phase flow in a channel (11), and to a related method.

Abstract: A laser radar system using collocated laser beams to unambiguously detects a range of a target and a range rate at which the target is moving relative to the laser radar system. Another aspect of various embodiments of the invention may relate to a laser radar system that uses multiple laser radar sections to obtain multiple simultaneous measurements (or substantially so), whereby both range and range rate can be determined without various temporal effects introduced by systems employing single laser sections taking sequential measurements. In addition, other aspects of various embodiments of the invention may enable faster determination of the range and rate of the target, a more accurate determination of the range and rate of the target, and/or may provide other advantages.

Abstract: A localized dynamic light scattering measurement system includes a beam displacer for splitting an incident beam having two orthogonal linearly polarized beam components with slightly different frequencies into two orthogonal linearly polarized output beams focused onto an object to be measured. The beam displacer cooperates with an iris to collect and recombine scattering beams each reversely backscattered at 180 degrees from the object so as to form a signal beam, which is polarized by a polarizer to produce two polarization components, thereby generating a heterodyne interference signal associated with the polarization components. A signal processing unit obtains measurement data on the object based on power spectrum or autocorrelation data corresponding to the heterodyne interference signal.

Abstract: Methods, systems and computer program products for managing frequency domain optical coherence tomography (FDOCT) image resolution. A spectrum used to acquire an image of a subject is calibrated and default dispersion correction parameters are set. Default dispersion management parameters associated with a region of the image of the subject are also set. The image of the subject is acquires after setting the default dispersion correction parameters and the default dispersion management parameters. A quality of the acquired image is compared to a quality metric for the acquired image. The dispersion correction parameters are adjusted if the quality of the acquired image does not meet or exceed the quality metric for the acquired image. The acquired image is reprocesses based on the adjusted dispersion correction parameters. The steps of comparing, adjusting and reprocessing are repeated until the acquired image meets or exceeds the quality metric for the acquired image.

Abstract: In one general aspect, an electrophoretic measurement method is disclosed that includes providing a vessel that holds a dispersant, providing a first electrode immersed in the dispersant, and providing a second electrode immersed in the dispersant. A sample is placed at a location within the dispersant between the first and second electrodes with the sample being separated from the electrodes, an alternating electric field is applied across the electrodes, and the sample is illuminated with temporally coherent light. A frequency shift is detected in light from the step of illuminating that has interacted with the sample during the step of applying an alternating electric field, and a property of the sample is derived based on results of the step of detecting.

Abstract: A system for tracking airborne organisms includes an imager, a backlight source (such as a retroreflective surface) in view of the imager, and a processor configured to analyze one or more images captured by the processor to identify a biological property of an organism.

Abstract: Present novel and non-trivial optical, laser-based measuring systems and method are disclosed. An optical, laser-based, or LIDAR measuring apparatus is comprised of a radiation receiver/transmitter, a beam-forming optical element, a beam steering device comprised of a deviation optical element and at least one actuator used to steer the deviation optical element in response to drive signal(s) from a processor.

Abstract: A fluid observation apparatus for performing a method for observing a fluid by PIV. The method for observing a fluid includes capturing an image of inorganic particles in a fluid for flow observation by irradiating the fluid for flow observation passing through a flow channel with light, the fluid for flow observation containing inorganic particles to be observed each having a planar surface, a dispersion medium to be observed, and a viscosity modifier. The fluid for flow observation is high-viscosity non-Newtonian slurry containing inorganic particles. The fluid for flow observation may be a simulated fluid for a fluid for flow analysis. The simulated fluid closely resembles the particle size of inorganic particles to be analyzed and the viscosity of the fluid for flow analysis. The fluid for flow analysis contains the inorganic particles to be analyzed and a dispersion medium to be analyzed.

Abstract: A system and method for determining a measured distance between a measuring device (20A) and an object (21), the system including a first laser source (13) for producing a first light beam (13A) having a first waveform (32) and a first frequency; a second laser source (11) for producing a second light beam (1 IA) having a second frequency, said second light beam (HA) having a second waveform (36), wherein said first frequency is chirped up at the first rate as said second frequency is chirped down at the first rate, and said second frequency is chirped up at the second rate as said first frequency is chirped down at the first rate; an optical element (15) for combining said first light beam (13A) with said second light beam (HA) into a combined light beam path (17), said optical element (15) splitting a returning portion of said combined light beam path (17) into a third light beam (24); and a single detector (23) for receiving said third light beam (24) including two different beat frequencies that are propo

Abstract: A unit pixel included in a photo-detection device, the unit pixel including a floating diffusion region in a semiconductor substrate, a ring-shaped collection gate over the semiconductor substrate, a ring-shaped drain gate over the semiconductor substrate, and a drain region in the semiconductor substrate, wherein the collection gate and the drain gate are respectively arranged between the floating diffusion region and the drain region.

Abstract: The invention relates to a method for Doppler light detection and ranging (LIDAR) measurement of speeds. A laser beam is directed at the medium to be measured, and radiation which is then emitted by the medium is measured by a detector. In order to allow better control of the dynamic range of a direct reception Doppler LIDAR apparatus, a multiplicity of laser pulses can be transmitted per measurement, and a multiplicity of laser pulses can be received by the detector per measurement. A direct reception Doppler LIDAR apparatus can be suitable for carrying out the method.

Abstract: A velocimetry system for measuring the velocity of a moving body propagating through a measurement volume includes a light source for emitting a light beam, a controller for generating a modulation pattern corresponding to a desired set of fringes to be generated in the measurement volume, and a spatial light modulator operatively connected to the controller to receive therefrom the modulation pattern. The spatial light modulator is configured to spatially modulate the light beam according to the modulation pattern in order to generate the desired set of fringes in the measurement volume. Also provided are a light detector for measuring the energy of the light scattered by the moving body as it intersects the fringes, and a data analysis unit operatively connected to the light detector and adapted to determine the velocity of the moving body from at least one fringe characteristic and the energy of the scattered light measured.

Abstract: Provided is a measuring apparatus that includes: a semiconductor laser device that emits a laser light beam to an object to be measured; a driving unit that provides a driving signal for modulation drive of the semiconductor laser device; a first detection unit that detects a first electrical signal that corresponds to the intensity of the laser light beam modulated due to the self-coupling effect, in a first half-cycle of the driving signal; a second detection unit that detects a second electrical signal that corresponds to the intensity of a second laser light beam modulated due to the self-coupling effect, in a second half-cycle of the driving signal being in an opposite phase of the first half-cycle; a calculation unit that calculates a difference between the first and second electrical signals; and a measuring unit that measures a change in the state of the object based on the calculated difference.

Abstract: Three-dimensional surface illumination using curved laser sheets is described for optical flow measurements over conformal curved surfaces. The illumination method is applicable to many different optical-based flow visualization and measurement techniques, particularly for particle image velocimetry. An alignment sheet increases the accuracy of determining the position and movement of particles used in optical-base fluid flow techniques.

Abstract: A device for the interferometric measuring of an object, including a source to generate a source beam, a beam splitting device to split the source beam into a measuring beam and a reference beam, an optic interference device and a first detector, which cooperate such that the measuring beam reflected by the object at least partially is at least partially interfered as the receiver beam and the reference beam on a detector area of the first detector. The beam splitting device splits the source beam into a measuring beam, a first partial reference beam, and at least one second partial reference beam. There is at least one second detector embodied such that the first receiver beam is interfered with the first partial reference beam on a detection area of the first detector and the second partial receiver beam with a second partial reference beam on a detection area of the second detector, each with the formation of an optic interference.

Abstract: An information processing apparatus using a design and evaluation method for a device or an apparatus concerning microscopic particles in conformity with dual mechanics is provided, and this apparatus may be utilized as an evaluation apparatus for evaluating whether or not quantum computers can be realized; wherein the dual mechanics is universal mechanics constructed by combining classical mechanics and novel wave mechanics and may be applicable to all particles ranging from microscopic to macroscopic particles. As a result, it is possible to prevent making useless efforts for realizing quantum computers that are judged to be impossible to realize and to pitch those efforts that might be wasted on the above realization into developing other effective technologies.

Abstract: A Lidar measurement device for vehicular traffic surveillance and method for use of same are disclosed. In one embodiment, video circuitry acquires video of a field of view having a target therein. A steerable laser progressively scans the field of view to identify targets. The steerable laser then progressively, repeatedly scans a sub-field of the field of view containing the target. A processing circuit portion determines target data of the target based upon range and time measurements associated with reflected laser range-finding signals from the scans of the sub-field. The processing circuit then integrates the target data into the video such that the video may displayed with an image of the target and target data, such as a speed measurement, associated therewith.

Abstract: A method of laser-based speed determination includes determining, via a digital scan of a field of view, a location of a target, directing, via a laser-aiming device, a laser from a laser device to the determined location, and determining a speed of the target via light reflected from the target to the laser device.

Abstract: The range image sensor is a range image sensor which is provided on a semiconductor substrate with an imaging region composed of a plurality of two-dimensionally arranged units (pixel P), thereby obtaining a range image on the basis of charge quantities QL, QR output from the units. One of the units is provided with a charge generating region (region outside a transfer electrode 5) where charges are generated in response to incident light, at least two semiconductor regions 3 which are arranged spatially apart to collect charges from the charge generating region, and a transfer electrode 5 which is installed at each periphery of the semiconductor region 3, given a charge transfer signal different in phase, and surrounding the semiconductor region 3.

Abstract: One of first and second beams (28) of corresponding first and second light (13) are projected into an atmosphere (20) and at least one physical property of the atmosphere (20) is detected from the interference pattern (47) generated from the resulting scattered light (30). The first and second beams (20) are selected responsive to either a detected signal-to-noise ratio (SNR) or a detected aerosol-to-molecular ratio (AMR). The wavelength (740) of the first light (13) provides for either molecular or aerosol scattering, whereas the wavelength (738) of the second light (13) provides for primarily only aerosol scattering. In accordance with a second aspect, scattered light (30) from one or more beams (28) of substantially monochromatic light (13) projected into the atmosphere (20) and received from a plurality of interaction regions (17) or measurement volumes (52) provides for determining wind power (P*) within a region of the atmosphere (20).

Abstract: Exemplary embodiments of apparatus, method and computer accessible medium can be provided which can facilitate a determination of at least one characteristic of a structure. For example, it is possible to use at least one first arrangement which can be structured to provide at least one first transmitted radiation along a first axis and at least one second transmitted radiation along a second axis. The first and second transmitted radiations can impact the structure and generate respective first and second returned radiation. The first and second axis can be provided at a predetermined angle with respect with one another which is greater than 0. Further, at least one second arrangement can be provided which can be configured to receive data associated with the first and second returned radiations, and determine at least one relative velocity between the structure and the first arrangement along the first and second axes.

Abstract: A laser radar system using collocated laser beams to unambiguously detects a range of a target and a range rate at which the target is moving relative to the laser radar system. Another aspect of various embodiments of the invention may relate to a laser radar system that uses multiple laser radar sections to obtain multiple simultaneous measurements (or substantially so), whereby both range and range rate can be determined without various temporal effects introduced by systems employing single laser sections taking sequential measurements. In addition, other aspects of various embodiments of the invention may enable faster determination of the range and rate of the target, a more accurate determination of the range and rate of the target, and/or may provide other advantages.

Abstract: A maintenance system for an assembly comprises a storage medium containing an as-built computer-aided design model of the assembly, a displaying means for displaying the as-built computer-aided design model, a metrology device for measuring a location of at least one characteristic of the assembly and creating as-built data regarding the location, and a replacing means for replacing a part of the assembly with a replacement part. The replacing means determines the location for the replacement part on the assembly by analyzing the as-built computer-aided design model and the data created by the metrology device.

Abstract: A system and method for measuring wind velocities are provided. A laser wind velocimeter with a radiation source includes a fiber laser. All optical signals, transmitted and received, are conveyed by optical fibers. An amplifier amplifies a source laser, which is then transmitted to one or more transceivers. The one or more transceivers, each projecting along a different axis, and each with a single optical fiber input/output interface act as both the transmission device to focus the radiation at a target region, and as the receiving system for collecting reflected radiation. The one or more transceivers transmit radiation to the target region.

Abstract: Provided is a measuring apparatus including: a driving unit that outputs first and second driving signals each having an opposite phase; a first semiconductor laser device, driven by the first driving signal, that emits a first laser beam to an object to be measured; a second semiconductor laser device, disposed near the first device and driven by the second driving signal, that emits a second laser beam to the object; a first detection unit that detects a first electrical signal that corresponds to the intensity of the first laser beam modulated due to the self-coupling effect; a second detection unit that detects a second electrical signal that corresponds to the intensity of the second laser beam modulated due to the self-coupling effect; a calculation unit that calculates differences between the first and second electrical signals; and a measuring unit that measures a state change of the object from the difference.

Abstract: A probe detection system (74) for use with a scanning probe microscope comprises both a height detection system (88) and deflection detection system (28). As a sample surface is scanned, light reflected from a microscope probe (16) is separated into two components. A first component (84) is analysed by the deflection detection system (28) and is used in a feedback system that maintains the average probe deflection substantially constant during the scan. The second component (86) is analysed by the height detection system (88) from which an indication of the height of the probe above a fixed reference point, and thereby an image of the sample surface, is obtained. Such a dual detection system is particularly suited for use in fast scanning applications in which the feedback system is unable to respond at the rate required to adjust probe height between pixel positions.