Abstract: An alignment tool including a first and a second positioning system configured for positioning and orientating a first lens and a second lens respectively, wherein a light beam is configured to be disposed through the first lens and the second lens to cast a light spot on the image plane, if the light spot does not stay stationary on the image plane when at least one of the first lens and the second lens is rotated about the central axis of the light beam, at least one of the first positioning system and the second positioning system is actuated to alter at least one of the position and orientation of at least one of the first lens and the second lens until the light spot becomes stationary on the image plane, indicating the first lens is coaxially disposed with the second lens.

Abstract: A method for measuring interfaces of an optical element, forming part of a plurality of similar elements including at least one reference optical element, the method implemented by a device, the method including: relative positioning of each reference optical element and the measurement beam, to allow a measurement of interfaces of each reference optical element; acquisition of a reference image, of each reference element; positioning of the measured optical element to allow acquisition of a measurement image, of the optical element to be measured; determining a difference of position in a field of view of the measured element with respect to each reference optical element, based on the reference and measurement images; adjusting the position of the measured optical element in the field of view to cancel the difference of position; and measuring the interfaces of the measured optical element by the measurement beam.

Abstract: A system for testing an optical surface, the system comprising a non-coherent light source, a detector, a test plate positioned between the non-coherent light source and the optical surface, the test plate separated from the optical surface by a gap, and a processor. The processer is configured to cause the non-coherent light source to illuminate the test plate and optical surface with non-coherent light, control the detector to capture an interferogram produced by interference between light reflected from the test plate and light reflected from the optical surface, and perform quantitative analysis on the interferogram to characterize aberrations in the optical surface.

Abstract: Methods for detecting defects on the surface of a sheet of material include collimating a beam of light and intersecting the collimated beam of light with a beam splitter. The beam splitter directs a first portion of the intersected beam of collimated light to illuminate a first surface of the sheet, wherein a first portion of the light illuminating the first surface is reflected and a second portion of the illuminating light is scattered by a defect. The reflected and scattered light is received with a first lens element that directs the reflected and scattered light to an inverse aperture. The reflected light is blocked by the inverse aperture and the scattered light is transmitted by the inverse aperture. The scattered light transmitted by the inverse aperture is directed with a second lens element to an imaging device.

Abstract: A sensing device includes a pressure sensor and a deformable cover. A fluid cavity engineered between the deformable cover and the pressure sensor changes shape and ultimately collapses as force is applied to the sensing device. The shape and collapse of the engineered cavity, along with the entire structure of deformable cover and the pressure sensor, govern the force vs. pressure behavior of the sensing device and can be tailored as desired. A first benefit includes providing tailored properties of the sensing device by varying the structure of the deformable cover. A second benefit includes that if too much force is applied, excess force—beyond that which is required to collapse the engineered cavity—does not produce excess pressure which would cause damage to the pressure sensor. As such the sensing device is protected from accidental, or intended, over loading.

Abstract: An ellipsometer apparatus (10) has a measurement compensation feature. The ellipsometer (10) provides for relative lateral movement between a light source assembly (12) and a specimen holder (14) via a positioner assembly (16) to provide for more accurate measurements of a thin film layer (55) on a specimen member (50).

Abstract: A camera hand-piece for medical use includes a lighting system, an optical window, a fixed part in turn having an optical system for acquiring images through an optical window, an image sensor, electronic circuits for image processing, and optionally a prism. The hand-piece has an external part, which is mobile with respect to the internal fixed part, and rotatably commutable between at least two different working positions having different optical or lighting features, which are freely selectable by an operator. In one embodiment, the lighting system for lighting the framed field is positioned in the internal fixed part of the camera hand-piece, and the mobile distal part, non comprising electronic parts, can be sterilized in an autoclave.

Abstract: The inductive power supply system comprises an input power module for receiving a stable voltage source, a storage module for storing a predetermined information, a processing module for generating a control signal according to the predetermined information and a feedback signal, a driving module for transforming the stable voltage source into a driving voltage according to the control signal, an inductive coil for electrically transmitting the driving voltage to process an inductive power transmission operation, and a feedback module for generating the feedback signal according to the driving voltage received by the inductive coil, where the predetermined information represents an initial state of the inductive power supply system comprising a sinusoidal amplitude corresponding to the driving voltage, and an intruding metal can affect another sinusoidal amplitude of the feedback signal to make the processing module correspondingly generate the control signal during the inductive power transmission operation.

Abstract: The instant disclosure describes an optical device for the interferometric analysis of the surface condition of an object, including: a light source; an optical fiber capable of receiving the incident light wave and transmitting said wave to the object; a detector capable of detecting a combination between a light wave reflected by the optical fiber and a light wave returned by the object; and in which the optical fiber has a free end in the shape of a cone, with a vertex angle of between 15 and 25 degrees, the tip of the cone having dimensions of less than 50×50 nm, and the tip of the cone being placed, while in use, at a distance of between 5 and 50 ?m from the surface of the object.

Abstract: A method for measuring spacings between optical surfaces of a multi-lens optical system includes detecting the centring state of the optical system by taking into consideration all optical surfaces of the optical system. Then the optical system is adjusted in such a way, taking the centring state into consideration, that the optical axis of the optical system is aligned as far as possible with a reference axis. In a next step the spacings between the optical surfaces are determined with the aid of a short-coherence interferometer. The measuring-light ray directed onto the optical system for this purpose runs likewise along the reference axis.

Abstract: A method and system for determining a shape of a portion of an air-bearing surface (ABS) of a head residing on a slider are described. The ABS is configured to fly at a fly height from and with a velocity with respect to a disk during normal operating conditions. The method and system include driving at least one heater residing in the head while the slider is substantially at the normal operating conditions with respect to the disk and the fly height. The shape of the portion of the ABS changes in response to the heater(s) being driven. The method and system also include performing Doppler measurements on the slider while the heater is driven. The shape may then be determined based on the Doppler measurements.

Abstract: An etching amount calculating method that can stably and accurately calculate the amount of etching even if a disturbance is added. Superposed interference light resulting from superposition of interference light of reflected light from a mask film and reflected light from the bottom of a concave portion on other interference light is received. A waveform in a predetermined time period is extracted from a superposed interference wave calculated from the superposed interference light. The period of an interference wave of the reflected light from the mask film and the reflected light from the bottom is detected from the distribution of frequencies of the extracted waveform. The steps described above are repeated while shifting the predetermined time period by a predetermined time, and the detected periods are integrated and averaged at each repetition. The etching amount of the concave portion is calculated based on the integrated and averaged periods.

Abstract: Disclosed is a method involving repeatedly measuring a pressure within a flow of processing gas that is provided in a semiconductor processing apparatus for treatment of a semiconductor substrate, such as a semiconductor wafer. The flow of processing gas is made to extend between a surface of the substrate and a surface of a processing body. From the pressure measurements the occurrence of an event that is related to a variation in the position of the substrate's surface relative to the surface of the processing body is determined.

Abstract: An algorithm and method for calculating an interferometric gap is disclosed that comprises providing an interferometric sensor having a first gap and an interferometric correlation element having a second gap placed in series with the first gap. A correlation burst waveform is generated having a plurality of features wherein the shape of the burst waveform evolves across the range of the second gap. Means are provided for tracking the features across the entire range of gaps and determining the dominant peak or dominant valley to determine the first gap.

Abstract: Methods and systems are disclosed for analyzing a scanning interferometry signal. Steps include: providing a scanning interferometry signal produced by a scanning interferometer for a first location of a test object (e.g., a sample having a thin film); providing a model function of the scanning interferometry signal produced by the scanning interferometer, wherein the model function is parameterized by one or more parameter values; fitting the model function to the scanning interferometry signal for each of a series of shifts in scan position between the model function and the scanning interferometry signal by varying the parameter values; and determining information about the test object (e.g., a surface height or height profile, and/or a thickness or thickness profile for a thin film in the test object) at the first location based on the fitting.

Abstract: A measuring device for detecting stresses of a bearing arrangement. The stresses are measured based on elastic changes in shape. The inventive measuring device includes a light source, which is directed onto a light passage, and a light sensor. The dimensions of a portion of the light that penetrates the light passage and impinges the light sensor can be modified by elastically changing the shape of the light passage.

Abstract: In one embodiment, a method of dynamic reference plane compensation, comprises impinging radiation from a first radiation source onto a surface of an object; generating an uncompensated measurement signal from radiation reflected from a first location on the surface and a second location; generating a compensation signal from radiation reflected from a third location and a fourth location on the surface; and generating a compensated measurement signal using the uncompensated measurement signal and the compensation signal.

Abstract: Micron-scale displacement measurement devices having enhanced performance characteristics are disclosed. One embodiment of a micron-scale displacement measurement device includes a phase-sensitive reflective diffraction grating for reflecting a first portion of an incident light and transmitting a second portion of the incident light such that the second portion of the incident light is diffracted. The device further includes a mechanical structure having a first region and a second region, the mechanical structure positioned a distance d above the diffraction grating, the second portion of the incident light is reflected off of the first region of the structure such that an interference pattern is formed by the reflected first portion and the reflected second portion of the incident light. The device can further include an electrode extending toward, but spaced a distance away from, the second region of the mechanical structure.

Abstract: A surface gap detector facilitates determining conformance of a surface of an object by providing a light source integrated into the detector that diffusely illuminates the surface of the object so that a user may observe the light that passes between the detector and the object when the surface of the object is aligned in substantial contact with a gap detecting edge of the surface gap detector.

Abstract: An apparatus and method measures the gap between one substantially planar object, such as a mask, and a second planar object, such as a substrate. A gapping mark is used for measuring a gap between the first and second plates. The gapping mark includes a first grating on a first surface of a first plate, the first grating having a first uniform period in a first direction. A second grating is located on the first surface of the first plate, the second grating being adjacent to the first grating in the first direction, the second grating having a second uniform period in the first direction. The gapping mark also includes a third grating on the first surface of the first plate, the third grating being adjacent to the first grating in a second direction, the second direction being substantially orthogonal to the first direction, the third grating having the second uniform period in the first direction.

Abstract: A light reflected from a semiconductor die is used for enhanced control of substrate removal from the die. According to an example embodiment of the present invention, light reflected from a semiconductor die as it is undergoing substrate removal is used to detect the progress of the substrate removal process, and the removal process is controlled therefrom. In different embodiments, the reflected light is used to detect the removal of a portion of a layer of material in the die and to detect the removal of an entire layer of material.

Abstract: This disclosure presents a non-contact precision optical device, including methods for measuring distances to an arbitrary target and various configuration geometries, for using polarization maintaining (PM) optical fiber components in a polarization diplexing scheme to construct a version of a dual chirp coherent laser radar that is immune to environmental effects.

Abstract: The present invention relates to micron-scale displacement measurement devices. A first embodiment is a device that includes a substrate and a rigid structure suspended above the substrate to form a backside cavity. Formed in the rigid structure is a reflective diffraction grating positioned to reflect a first portion of an incident light and transmit a second portion of the incident light such that the second portion of the incident light is diffracted. The device also includes a membrane positioned a distance d above the reflective diffraction grating and at least a first photo-detector for receiving interference patterns produced from the first portion of the incident light reflected from the diffraction grating and the second portion of the incident light reflected from the membrane.

Abstract: The present invention relates to micron-scale displacement measurement devices. A first embodiment is a device that includes a substrate and a rigid structure suspended above the substrate to form a backside cavity. Formed in the rigid structure is a reflective diffraction grating positioned to reflect a first portion of an incident light and transmit a second portion of the incident light such that the second portion of the incident light is diffracted. The device also includes a membrane positioned a distance d above the reflective diffraction grating and at least a first photo-detector for receiving interference patterns produced from the first portion of the incident light reflected from the diffraction grating and the second portion of the incident light reflected from the membrane.

Abstract: A method for determining the relative motion of a surface with respect to a measurement device including placing a partially transmitting object, which is part of the measuring device, adjacent to the surface; illuminating the surface with incident illumination, which does not constitute an interference pattern, such that the illumination is reflected from portions of the surface, wherein at least part of at least one of the incident and reflected illumination passes through the object; detecting the illumination reflected from the surface, and generating a detected signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.

Abstract: A gap measuring method characterized by comprising the steps of: applying a plurality of color lights to a member provided with a gap, to produce color interference fringes; obtaining respective intensities of the color lights in the images of the interference fringes taken by a color camera, at each of predetermined positions of each image, so as to compute and actual ratio among the obtained intensities of the color lights for each of the predetermined positions; and obtaining gap values of a plurality of points of the gap provided in the member, based on said actual ratio and theoretical ratios each of which is computed based on intensities of said color lights in an image corresponding to each of preliminarily set gap values.

Abstract: A method is disclosed for reconstructing an image from a total internal reflection hologram that includes the steps of arranging the hologram in relation to the first face of a coupling body, generating a substantially collimated illumination beam, directing the beam through a second face of the coupling body so that it reconstructs the image recorded in the hologram, recycling at least once the light in the illumination beam that is reflected from the hologram by redirecting it through the second face of the coupling body so that it also reconstructs the image recorded in the hologram, and scanning the illumination and recycled beams across the hologram, for the purpose of increasing the effective reconstruction efficiency of the total internal reflection hologram.

Abstract: Several embodiments of a microinterferometer are disclosed. A first embodiment of a microinterferometer for measuring the absolute distance to an object surface includes a substrate. The microinterferometer also includes a phase-sensitive, reflective diffraction grating formed on the substrate. The diffraction grating is configured to reflect a first portion of an incident light and transmit a second portion of the incident light, such that the second portion of the incident light is diffracted. The microinterferometer further includes a lens formed on the substrate for focusing the second portion of the incident light to a predetermined local distance, and a photo-detector for receiving interference patterns produced from the first portion of the incident light reflected from the diffraction grating and the second portion of the incident light reflected from the object surface.

Abstract: An interference optical system (18) leads parallel beam to a pair of opposed test surface (M1, M2). It then leads, from the test surfaces via different optical paths (C1, C2), interference fringe images formed by radiation of the parallel beam to the test surfaces (M1, M2), respectively. The interference optical system (18) has a pair of opposite reference surfaces (S1, S2) formed thereon and defined with a highly accuracy parallelism and distance. A measurement head (27) is provided with these reference surfaces (S1, S2), which are interposed between and oppose to the test surfaces (M1, M2), respectively. Imaging devices (19a, 20a) take interference fringe images that are created through interference between a light reflected at each of the test surfaces (M1, M2) and a light reflected at the corresponding reference surface (S1, S2) opposing thereto.

Abstract: A system for determining at least one condition of a seal including an optical fiber for transmitting light from a light source. The optical fiber is embedded in the seal and operatively coupled to an interferometric system. The interferometric system is operatively coupled to a processor. The interferometric system provides the processor with information relating to wear of the optical fiber, and the processor determines wear of the seal, rate of wear and remaining useful life of the seal based on the information relating to wear of the optical fiber.

Abstract: A sensor has an interferometer which measures a change in an applied environmental condition relative to a reference environmental condition. The interferometer is operated under the applied environmental condition to generate an interference spectrum. Intensities of the interference spectrum are measured at first and second wavelengths, respectively. The first and second wavelengths correspond to first and second reference intensities that are separated from one another by an odd number of extrema in the interference spectrum when the interferometer is operated under the reference condition. Measurement of the change in the applied environmental condition is based on the measured intensities and the first and second reference intensities.

Abstract: An apparatus and method of measuring the gap between one substantially planar object, such as a mask, and a second planar object, such as a substrate. The invention achieves a high degree of sensitivity, accuracy, capture range, and reliability, through a novel design of a mark located only on the mask-plate. The light is inclined to the surfaces so associated optical components do not interrupt the exposing beam used in lithography. The same optics are used as for aligning overlay. Each gapping mark on the mask-plate includes one or more two-dimensional gratings, each with period constant in the incident plane, but varying in the transverse plane. When illuminated, two images are formed of each of the two-dimensional gratings, with fringes resulting from interference between paths having traveled different distances through the gap and the mask-plate as a result of successive diffractions and reflections.

Abstract: A fiber optic wall shear stress sensor is presented. The sensor comprises a floating head supported by a physical arrangement. At least one optical fiber is positioned in an operable relationship to the floating head wherein an interferometric region is formed between the floating head and each optical fiber. The interferometric region changes in response to a shear force on the floating head.

Abstract: A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident illumination; detecting illumination reflected from the surface to form at least one detected signal; and determining the amount of relative motion parallel to the surface from said at least one detected signal, characterized in that said determining includes correcting for the effects of relative motion perpendicular to the surface.

Abstract: The present invention provides an apparatus comprising a wavelength variable light source for shifting a wavelength of light stepwise within a predetermined range and applying the light with the shifted wavelength onto a light transmissible object that is to be measured and is provided with a gap; a camera for taking an image of an interference fringe formed by the light transmitted by said object, correspondingly to each step of the shifted wavelength; an image memory for storing images taken by said camera; and means for obtaining a change in the intensity of the images taken by said camera, at each of predetermined positions of each image over said predetermined wavelength range; and means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity.

Abstract: A position of an image or shadow of a clearance measuring mark projected onto a plate with respect to a position of clearance measuring mark on a photomask is sensed as image data by a CCD camera and subjected to an image process by a processor. Based on a relative positional relationship between image or shadow of a clearance measuring mark and clearance measuring mark, the clearance between photomask and plate can be adjusted to a prescribed value by a clearance adjusting device. As a result, a clearance measuring device and method can be provided capable of accurately and inexpensively measuring the clearance between the plate and the photomask in the exposure apparatus.

Abstract: A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident illumination such that illumination is reflected from portions of the surface; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident illumination is reflected or diffracted by the object, as a reference illumination; coherently detecting the illumination reflected from the surface, utilizing the illumination reflected from or diffracted by the object as a local oscillator, to form a signal; determining the relative motion of the surface from the signal; varying the phase of the illumination reflected from or diffracted by the object with respect to that reflected from the surface; and determining the direction of relative motion parallel to the surface based on a characteristic of the signal caused by said varied relative phase.

Abstract: The invention relates to a method and device for measuring distances through the atmosphere against a target through propagation time measuring. Measuring light signals are transmitted towards a target and light pulses reflected by the target are received. The distance measuring includes a coarse measuring procedure and a fine measuring procedure. During the coarse measuring procedure at least one time point is fixed after which the measuring signal from the target can be expected to appear. During the fine measuring procedure a number of measurements are performed. The signal information collection during the fine measuring procedure takes place in a matching time space after the time point fixed during the coarse measuring. Preferably, the measuring during the coarse measuring procedure takes place with one or a few measuring pulses and measuring during the fine measuring procedure with a number of measuring light pulses.

Abstract: A speed and/or position determining device for determining the speed or position of a target object includes a head-up display for simultaneously viewing both the target object and an image of information regarding the target object. An optical projection system for projecting the information image from a light emitting display to a combining sight of the head-up display passes along a short straight optical axis between the light emitting display and the combining sight. The device may also incorporate a novel method for determining the length of a time period that elapses between the time that a radiation emitter emits a pulse of radiation and the time a reflected portion of the emitted pulse of radiation is received back at the device. The novel method makes use of one or more electronic delay modules having a plurality of tap lines. An electronic state of each of the tap lines changes as a signal input to the delay module propagates through the delay module.

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: An electronic distance meter comprises an integrated circuit from a GPS navigation receiver having a local pseudo-random number code generator for code demodulation that is connected to modulate either a polychromatic or a monochromatic light source. An optical system focuses the light on a distant target with an unknown range. Reflections from the distant target are focused on a light detector that produces a phase-delayed copy of the original pseudo-random number code. The time-of-flight to and back from the distant target is a function of the distance. The GPS receiver integrated circuit computes the range based on the code-phase delay to a precision better than one centimeter. The position of a remote target can be triangulated from several electronic distance meters each having known positions, e.g., determined by included GPS navigation receivers.

Abstract: A laser range finder includes a circular in-sight field of view which incorporates within it a magnified "TV view" of the target area with the TV view roughly approximating the rectangular shape of a standard television picture. Also within the circular field, over and under the TV view, are a target quality indicator, a range distance display, and other indicators. Within the TV view is a targeting reticle which indicates roughly the footprint of ranging laser pulses such that a target can be selected. The target quality indicator is a bar graph which displays the number of identifiable received reflected laser pulses from a series of such pulses emitted by the range finder. By aiming the range finder at various targets via the footprint reticle, repeatedly firing the range finder and monitoring the target quality graph for each firing, a user can move the range finder to find a surface proximate the target with a reflective quality sufficient to yield an accurate target range reading.

Abstract: A method and apparatus for reducing the noise of a laser range finder. The laser range finder includes a high voltage silent circuit, a logarithmic amplifier and a sun noise averaging amplifier. The high voltage silent circuit shuts down the switched power supply controller of the high voltage power supply to reduce the noise coupled from the high voltage power supply when the receiver of the laser range finder is in a receiving mode. The logarithmic amplifier provides dynamic gain control for the receiver to avoid signal saturation and improve the signal to noise ratio of the received signal. The sun noise averaging amplifier provides an amplified average sun noise which automatically adjusts the threshold voltage of detecting the distance signal from a target.

Abstract: A light-weight, hand-held range finding apparatus of the present invention includes signal emitting circuitry and lens for emitting signals, and signal receiving circuitry and lens for receiving reflected signals, which are positioned within a chamber of a housing. The housing includes an upper section to which a sighting device is attached, a front end through which the emitted signals are emitted and the reflected signals are received, a back panel having a display device attached to said housing for displaying operational selections and range findings. An actuator is mounted adjacent the upper section and is operably connected to the signal emitting circuitry. The actuator is used to select desired operational selections displayed on the display device and actuating the signal emitting circuitry.

Abstract: A method and apparatus for electro-optical distance measurement. A series of pulses provided by a laser are received as echoes by a receiver. The pulses are each produced within respective intervals having a common predetermined duration. Each pulse is time-shifted relative to the beginning of its corresponding interval. A pulse pattern comprising echo signals for each of a series of pulses is used to determine the distance to an object producing the echoes.

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: A time measurement device useful with laser range cameras and time-of-flight measuring methods includes a light transmitter responsive to start and stop signals for transmitting the light during a time interval to be measured, and a light receiver for receiving the light and for providing an output signal related to an exposure of the light during the time interval time between start and stop signals to the transmitter The output signal thus providing a measurement of the time between the start and the stop signals. The transmitter includes a light emitting diode to which an electrical current is provided for generating a constant output light source for the transmitter. The light receiver includes charged coupled devices (CCD) having a linear response to an amount of exposure to the light received from the light transmitter. As a result, the CCD provides the output signal in a linear relationship to the amount of exposure to the light, and thus a measurement of the time interval.

Abstract: A distance measuring apparatus for a vehicle including: an irradiating means for emitting and irradiating an electromagnetic wave; a receiving means for receiving a reflected wave produced when the electromagnetic wave is reflected by an obstacle and generating a receiving signal; a propagation delay time period measuring means provided with a comparison value set such that a value for a comparison reference is larger in a case in which a propagation delay time period from irradiating to receiving the electromagnetic wave is shorter than in a case in which the propagation delay time period thereof is longer for comparing the receiving signal with the comparison value, recognizing a time point at which the receiving signal is equal to or larger than the comparison value when the receiving signal is compared with the comparison value as a receive detecting time point and measuring the propagation delay time period from a time point at which the irradiating means irradiates the electromagnetic wave to the receiv

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: A distance measurement device comprising a light-sending unit for sending pulsed light toward an object of measurement where a distance thereto is measured, a light-receiving unit for receiving incident light including pulsed reflection light reflected by the object, a distance measurement unit for measuring the time from the sending of the pulsed light to the receiving of the incident light and calculating the distance to the object, and an interference detection unit for determining whether interference light exists in the incident light, based on the intensity of the incident light.