Abstract: A method for processing an image acquired through a guide consisting of a plurality of optical fibers includes, for each optical fiber, isolating on the acquired image a zone corresponding to the optical fiber, locally processing each zone individually to correct the photon flux detected in each optical fiber, then reconstructing the acquired image by eliminating the pattern caused by the optical fiber. The method also includes a sampling process for obtaining, for each optical fiber and from a sampling image, a sample injection rate which can be used for reconstructing the acquired images. The method also includes a prior step which consists in detecting the fibers from a target.

Abstract: A digital video recorder-controller apparatus (DVRC) having a network port for transmitting and receiving digitized video signals and for controlling one or more other DVRCs, and/or digital video recorders (DVRs, e.g., DVRCs operating in slave-mode). A digital video system including a networked DVRC having cameras and a networked DVR having cameras. The DVR may be remote from the DVRC, yet video signals from the cameras of the both the DVR and the DVRC can be selected, viewed, and/or recorded at the DVRC's location. A method for expanding a digital video system including providing at least one DVRC.

Abstract: An imaging device includes an illumination module comprising at least one emitter for emitting at least one excitation beam; a scanning and injection module comprising an image guide, a proximal end and a distal end of which are linked by a plurality of optical fibers; a scanning and injection optical system configured to alternately inject the at least one excitation beam into an optical fiber of the image guide from the proximal end of the image guide; a detection module comprising a detector for detecting a luminous flux collected at the distal end of the image guide, wherein at least one of the illumination module and the detection module is optically conjugated with the scanning and injection module using a conjugating optical fiber.

Abstract: An optical fiber connector has a first ferrule holding an end of a first optical fiber, a first fiber stub connected to the first ferrule, a second ferrule holding an end of a second optical fiber, and a second fiber stub connected to the second ferrule. The first fiber stub enlarges the beam diameter of light transmitted through the first optical fiber, and produces the collimated light. The second fiber stub reduces the beam diameter of the collimated light, and leads the converging light into the second optical fiber. The first and second fiber stubs are detachably connected inside a connection sleeve across a predetermined gap. First and second GI fibers contained in the first and second fiber stubs satisfy L1?L2 and L1+L2?½ pitch, wherein L1 and L2 represent the lengths of the first and second GI fibers, and one pitch is a sinusoidal period of the light transmitted therethrough.

Abstract: An endoscope system comprises an electric scope and a light source apparatus. The light source apparatus has a light source and a light control apparatus. The light control apparatus adjusts a quantity of light that is incident to the electric scope, based on a comparison between a scope characteristic that indicates a relative value of the quantity of light that can be incident to the electric scope and a light source total characteristic that indicates a relative value of the quantity of the light radiated from the light source to the electric scope.

Abstract: In part, the invention relates to a lens assembly. The lens assembly includes a micro-lens; a beam director in optical communication with the micro-lens; and a substantially transparent film. The substantially transparent film is capable of bi-directionally transmitting light, and generating a controlled amount of backscatter. In addition, the film surrounds a portion of the beam director.

Abstract: An image free from interfering structures may be generated by means of a fiber bundle of several optical fibers, when for the system of fiber bundle and sensor imaging parameters are provided, which describe the geometrical characteristics of the intensity course generated by each individual optical fiber on the sensor. In image reconstruction, for each individual optical fiber an amplitude value and/or luminosity information may be generated by fitting a function of the amplitude value and the imaging parameters of the respective optical fiber to an intensity picture of the sensor, so that an optimum amplitude and/or luminosity value may be generated considering the geometrical imaging characteristics for each individual optical fiber.

Abstract: A method and means to use randomly arranged fibers assembled together in a bundle that is capable of conveying images from an inaccessible location to a more accessible, convenient or safe location for viewing. Allows for mixing fibers of different diameters. Random distribution of fibers decreases the packing fraction, offering in exchange easiness of manufacturing and decrease in production cost. System can be also used for display units, including computer monitors, home TV, movie theatres, public display announcement boards, as airport, trains stations, highway instructions and billboard advertising. As display units, random assembled fibers are organized at the display end at the display shape, usually rectangular, from where light is emitted towards the viewer. At the illuminating end, light enters the individual fibers from multicolored lasers or other light sources which are controlled by single or multiple video boards and computers.

Abstract: A scanning fiber device of one aspect may include an actuator tube. An optical fiber may be inserted through the actuator tube. The optical fiber may have a free end portion outside of the actuator tube. A first bead may be around the optical fiber. At least part of the first bead may be within a distal portion of the actuator tube. An adhesive may be adhering the first bead to the distal portion of the actuator tube. A second bead may be around the optical fiber. At least part of the second bead may be within a proximal portion of the actuator tube. An adhesive may be adhering the second bead to the proximal portion of the actuator tube.

Abstract: An image fiber includes an image fiber body having a twisted portion which is formed by heating, softening, and twisting a portion of the image fiber body. The rate of twist in the twisted portion is made to be constant. Moreover, the rate of twist may preferably be set in a range from 3.6°/mm to 3600°/mm. In addition, the rate of twist at the beginning portion of the twisted portion and the rate of twist at the end portion of the twisted portion may preferably be set in a range from 3.6°/mm to 360°/mm. The twisted portion may be provided with a protective element.

Abstract: A system and method which integrates a mirror at the fiber tip to the fiber tip and uses a tilted flat at the exit plane to prevent astigmatism caused by the cylindrical curvature of the fiber wall and minimize reflection.

Abstract: An endoscope system of the present invention includes: an image fiber with an image fiber main body made of a plurality of cores for forming pixels and a cladding common thereto; and an optical system connected to an eyepiece side of the image fiber for causing laser light to enter the image fiber and for taking in an image from the image fiber, in which the image fiber has the cores arranged substantially uniformly over a cross-section of the image fiber main body, the cross-section being perpendicular to a longitudinal direction of the image fiber main body.

Abstract: A method for assembling an endoscope with a first tubular channel for receiving image-transmitting components and with a second channel for receiving light guides. It is proposed to introduce the light guides first into a flexible tube and to introduce the unit made up of flexible tube and light guides into the second channel.

Abstract: The amount of heat generated at a light input portion of a light guide for endoscopes constituted by a plurality of bundled optical fibers is suppressed. The light guide for endoscopes is constituted by a plurality of bundled optical fibers, for propagating an illuminating light beam, which is focused and caused to enter a light input end facet thereof, to a light output end facet thereof, to emit the illuminating light beam onto a portion to be observed. A transparent member having a sectional shape which is at least as large as the focused spot of the illuminating light beam is provided in close contact with the light input end facets of the optical fibers. The optical fibers are connected to the transparent member in a maximally densely packed state.

Abstract: A light guide for endoscopes constituted by a plurality of bundled optical fibers is formed such that it is flexible at portions where flexibility is required, and such that the durability thereof is improved. The light guide for endoscopes is constituted by a plurality of bundled optical fibers, for propagating an illuminating light beam that enters from a light input end facet thereof to a light output end facet thereof, to emit the illuminating light beam onto a portion to be observed. The light guide includes: a plurality of comparatively large diameter optical fibers; and a plurality of comparatively small diameter optical fibers which are provided at the side of the light guide toward the light output end facet thereof. Each of the comparatively large diameter optical fibers is connected to a plurality of the comparatively small diameter optical fibers.

Abstract: The invention relates to a near-field antenna comprising a dielectric shaped body having a tip. The shaped body is characterized in that at least the surface of the tip is metallized, thereby enhancing the sensitivity of devices comprising the near-field antenna, for example, spectroscopes, microscopes or read-write heads.

Abstract: When carrying out in vivo examination of a living organism, the behavior in the interior thereof is continuously observed with clear images.

Abstract: Methods of moving or vibrating cantilevered optical fibers of scanning fiber devices are disclosed. In one aspect, a method may include vibrating the cantilevered optical fiber at an initial frequency that is substantially displaced from a resonant frequency of the cantilevered optical fiber. Then, the frequency of vibration of the cantilevered optical fiber may be changed over a period of time toward the resonant frequency. Light may be directed through an end of the cantilevered optical fiber while the cantilevered optical fiber is vibrated.

Abstract: A light diffusing tip is provided. The light diffusing tip comprises a housing and a monolithic light scattering medium disposed within the housing. The monolithic light scattering medium comprises a first scattering region at a first position, the scattering region having a first scattering property and a second scattering region at a second position, the second scattering region having a second scattering property different from the first scattering property, wherein the first scattering region and the second scattering region are coextensive along a substantial portion of a length of the housing. A light diffusing applicator also is provided. The light diffusing applicator comprises at least one optical waveguide, a first termination coupled to a first end of the at least one optical waveguide, the first termination to couple to a light source and a light diffusing tip coupled to a second end of the at least one optical waveguide.

Abstract: An elongate imaging fiber bundle may include a plurality of elongate optical fibers coherently arranged in the bundle, the plurality including peripheral fibers at a periphery of the bundle and deep fibers deep to the peripheral fibers, and a coating surrounding the plurality of fibers. An exposed length of the bundle, intermediate the bundle's proximal and distal ends, may be chemically etched to be denuded of the coating, and peripheral fibers are so severed as to permit injection of light into the peripheral fibers at the exposed length. A fiberscope may include a fiber bundle having an exposed length that is denuded of the coating, and peripheral fibers are so severed in the exposed length as to permit injection of light into the peripheral fibers at the exposed length, and a light source so positioned with respect to the exposed length of the bundle as to inject light into the peripheral fibers at the exposed length.

Abstract: An elongate imaging fiber bundle may include a plurality of elongate optical fibers coherently arranged in the bundle, the plurality including peripheral fibers at a periphery of the bundle and deep fibers deep to the peripheral fibers, and a coating surrounding the plurality of fibers. An exposed length of the bundle, intermediate the bundle's proximal and distal ends, may be chemically etched to be denuded of the coating, and peripheral fibers are so severed as to permit injection of light into the peripheral fibers at the exposed length. A fiberscope may include a fiber bundle having an exposed length that is denuded of the coating, and peripheral fibers are so severed in the exposed length as to permit injection of light into the peripheral fibers at the exposed length, and a light source so positioned with respect to the exposed length of the bundle as to inject light into the peripheral fibers at the exposed length.

Abstract: An optical device and method for varying an optical characteristic of an optical beam can include a plurality of optical fibers each having an input end, an output end, and a core, wherein each of the optical fibers has an effective area and a numerical aperture, and a beam-deviating component for moving at least one of the optical fiber input ends and the optical beam relative to each other such that the optical beam selectively enters the input ends one at a time and is transmitted out the output ends one at a time, wherein at least one of the effective areas and the numerical apertures varies among the plurality of optical fibers such that the optical beam transmitted out of the output ends has a varying optical characteristic.

Abstract: An endoscope optics receiving a fiber tube to separate optic fibers running between the tubes from an image guide fitted with a distal objective lens, the objective lens being configured to look downward at an oblique angle relative to the axis of the outer tube, the distal end face of the endoscope optics being configured perpendicularly to the line of sight, where a lateral bundle portion of the optic fibers, which is to the side of the fiber tube, terminates at distally bonded fibers substantially parallel to the line of sight, in the end face. The bundle portion is enclosed at its distal end zone by a guide duct.

Abstract: In one embodiment, an apparatus includes an optical fiber made of a silica-based material. A proximal end portion of the optical fiber has an outer-layer portion. The proximal end portion can be included in at least a portion of a launch connector configured to receive electromagnetic radiation. The apparatus also includes a component that has a bore therethrough and can be made of a doped silica material. The bore can have an inner-layer portion heat-fused to the outer-layer portion of the optical fiber. The component can also have an index of refraction lower than an index of refraction associated with the outer-layer portion of the optical fiber.

Abstract: A fiberscope device is disclosed which is suitable for video imaging, laser Raman spectroscopy and laser Raman spectroscopic (i.e. chemical) imaging. The fiberscope design minimizes fiber background interference arising from the laser delivery fiber optic and the coherent fiber optic light gathering bundle while maintaining high light throughput efficiency through the use of integrated spectral filters. In the fiberscope design, the laser delivery fiber optic is offset from the coherent fiber optic light gathering bundle. The laser delivery field is captured entirely by the light gathering field of view of the coherent fiber bundle. The fiberscope incorporates spectral filter optical elements that provide environmental insensitivity, particularly to temperature and moisture.

Abstract: Embodiments relate to scanning a plurality of light beams across a corresponding plurality of zones in a field of view and collecting scattered light to enable an image of the field of view to be formed that spans the plurality of zones. According to an embodiment, a scanning endoscope tip may include structures configured to launch the plurality of scanned beams toward respective zones and receive separate light scattered from the respective beams impinging upon the respective zones. According to an embodiment, an image processor is operable to receive detection signals from corresponding light detectors and reconstruct an image of the field of view spanning the plurality of zones.

Abstract: An optical probe has a tubular outer envelope, and a shaft rotatable about a rotating axis extending longitudinal direction of the outer envelope. A light guide disposed to extend along the shaft is connected to the shaft at its leading end portion, a light deflector connected to the leading end portion of the light guide deflects light radiated from the leading end portion of the light guide, and a collecting lens converges light radiated from the light deflector outside the outer envelope. Light emitted from the light deflector is scanned along the outer envelope in response to movement of the shaft and the light deflector is connected to the shaft in a position deviated from the axis of rotation of the shaft and is movable to the shaft so that the direction of light deflected by the light deflector can be changed in this position.

Abstract: The disclosure generally relates to a method and apparatus for a fiberscope. In one embodiment, the disclosure relates to a chemical imaging fiberscope for imaging and collecting optical spectra from a sample having at least one illumination fiber for transmitting light from a first an a second light source to a distal end of a fiberscope; a dichroic mirror disposed at said distal end of the fiberscope such that light from said first light source passes substantially straight through said mirror and light of a predetermined wavelength from said second light source is substantially reflected by said mirror toward said sample to thereby illuminate said sample; and at least one collection fiber for receiving light from said illuminated sample and transmitting the received light to an optical device.

Abstract: A camera (1) has a tubular housing (3) having an emission window (7). A unitized optical fiber bundle (9) is provided on the inner surface of the housing (3) by utilizing a bundle of light guiding optical fibers on the inner surface. The unitized optical fiber bundle (9) is placed on and bonded to the inner surface of the housing (3) with the fibers bonded together by a bonding agent. An end section of the unitized optical fiber bundle (9) reaches the emission window (7) of the housing (3) to be exposed. The camera (1) has sufficient waterproof capability and is easy to produce, and capable of avoiding a decrease in the amount of light.

Abstract: Methods of reducing distortion in scanning fiber devices are disclosed. In one aspect, a method includes changing an intensity of light transmitted through a cantilevered optical fiber of a scanning fiber device. The method also includes changing a setpoint temperature for the scanning fiber device based at least in part on the change in the intensity of the light. Other methods, apparatus, systems, and machine-readable mediums are also disclosed.

Abstract: A fiber-bundle disclosed has: a bundle of a plurality of optical fibers each receives a light beam in one end and emits the light beam from the other end; and an adjuster to adjust positions of a plurality of optical fibers. The configuration can realize a wide variety of irradiation patterns easily and freely.

Abstract: A microsurgical laser probe primarily used in ophthalmic surgery provides both laser light and illumination light to a surgical site from a single light source. The laser probe has a dual core optic fiber that transmits both laser light and illumination light to the surgical site. A center core of the optic fiber transmits the laser light through the optic fiber and emits the laser light at the surgical site. The center core of the fiber is surrounded by an outer fiber core. The outer fiber core transmits illumination light through the optic fiber and emits the illumination light at the surgical site.

Abstract: A multi-cladding optical fiber includes a core that conveys visible light used by a scanner for imaging a site within a patient's body, and an inner cladding that conveys high-power light, such as infrared light, used for providing therapy to site. The distal end of multi-cladding optical fiber is driven to scan the site when imaging or rendering therapy using an actuator. High-power light is coupled into inner cladding at proximal end of optical fiber using several different techniques. Some techniques use an axicon to direct the high-power light into the inner cladding, while visible light is coupled directly into the core. Another technique uses a multimode optical fiber in a coupling relationship with the multi-cladding optical fiber, to transfer high-power light from a core of the multimode fiber into the inner cladding of the multi-cladding optical fiber.

Abstract: An electro-optical system includes an array including a plurality of optical fibers and a plurality of electrodes, and an insulator. The optical fibers are configured to transmit light, the optical fibers being mechanically coupled at distal ends in a distal arrangement and mechanically coupled at proximal ends in a proximal arrangement. The plurality of electrodes are substantially coaxially disposed with at least portions of corresponding optical fibers, the electrodes being electrically conductive, with the electrodes and optical fibers being disposed in pairs, thereby being pair components, with one of the pair components of each pair being disposed about a radial periphery of the other pair component. The insulator is disposed between the plurality of electrodes and configured to inhibit transfer of electrical energy between the plurality of electrodes.

Abstract: The invention relates to an arrangement for generating a broadband spectrum that can be used in particular as a light source for short coherence interferometry and confocal microscopy as well as endoscopic short coherence interferometry and endoscopic confocal microscopy. The arrangement comprises a laser, in particular a laser diode, for generating a short light pulse of wavelength ?P and a microstructured optical fiber (1) of high nonlinearity, that has a null dispersion of the group velocity in the vicinity of the wavelength ?P and an anomalous dispersion, as well as means for coupling the light pulse into the microstructured optical fiber.

Abstract: A medical inspection device. A housing includes a transparent plate and a first opening. A reflective layer is formed in the housing and opposes the transparent plate. The first opening is between the reflective layer and the transparent plate. A grip is connected to the first opening and extends in the exterior of the housing. An optical fiber bundle is connected to the first opening and disposed in the grip. The optical fiber bundle extends to the exterior of the grip and outputs light into the housing. The light is output to the exterior of the housing by reflection of the reflective layer and through the transparent plate. An image outside the housing is received by the optical fiber bundle through the transparent plate and by reflection of the reflective layer.

Abstract: An apparatus for treating a hollow anatomical structure can include a light delivery device. The light delivery device comprises an optical fiber that is located in a lumen of a shaft suitable for insertion into the hollow anatomical structure and has a fiber tip located proximal of a distal end of the shaft during treatment of the hollow anatomical structure. The apparatus can further include a liquid source for providing a liquid flow over the optical fiber at a predetermined liquid flow rate.

Abstract: A light diffusing tip is provided The light diffusing tip comprises a housing and a monolithic light scattering medium disposed within the housing. The monolithic light scattering medium comprises a first scattering region at a first position, the scattering region having a first scattering property and a second scattering region at a second position, the second scattering region having a second scattering property different from the first scattering property, wherein the first scattering region and the second scattering region are coextensive along a substantial portion of a length of the housing A light diffusing applicator also is provided. The light diffusing applicator comprises at least one optical waveguide, a first termination coupled to a first end of the at least one optical waveguide, the first termination to couple to a light source and a light diffusing tip coupled to a second end of the at least one optical waveguide.

Abstract: A configuration detection device includes a light-providing optical fiber, a light reflector a curvature-detecting optical fiber, and a light modulator. The light-providing optical fiber transmits detection light in a plurality of wavelength ranges that have different wavelengths from one another, The light reflector reflects the detection light as reflected light. The curvature-detecting optical fiber transmits the reflected light, and is bent together with an endoscope. The light modulator modulates at least one of the strength or the wavelength of the reflected light for each of the wavelength ranges. Based on at least one of the strength or the wavelength of the reflected light that is pre-modulated and post-modulated, and based on the distance between the light modulator and the output end of the curvature-detecting optical fiber, the configuration of the endoscope is detectable.

Abstract: A camera (1) has a tubular housing (3) having an emission window (7). A unitized optical fiber bundle (9) is provided on the inner surface of the housing (3) by utilizing a bundle of light guiding optical fibers on the inner surface. The unitized optical fiber bundle (9) is placed on and bonded to the inner surface of the housing (3) with the fibers bonded together by a bonding agent. An end section of the unitized optical fiber bundle (9) reaches the emission window (7) of the housing (3) to be exposed. The camera (1) has sufficient waterproof capability and is easy to produce, and capable of avoiding a decrease in the amount of light.

Abstract: A method for manufacturing an image fiber bundle that includes the steps of aligning a plurality of image fibers into a bundle, bonding the plurality of image fibers in at least three regions to form an image fiber bundle with a useable length and at least one useable sub-length, and inspecting the image fiber bundle for defective image fibers. The image fiber bundle includes flexible regions disposed between the bonded regions and the spacing of the bonded regions corresponds to a plurality of standardized lengths for fiberscopes.

Abstract: A method for manufacturing an image fiber bundle that includes the steps of aligning a plurality of image fibers into a bundle, bonding the plurality of image fibers in at least three regions to form an image fiber bundle with a useable length and at least one useable sub-length, and inspecting the image fiber bundle for defective image fibers. The image fiber bundle includes flexible regions disposed between the bonded regions and the spacing of the bonded regions corresponds to a plurality of standardized lengths for fiberscopes.

Abstract: An imaging system including a multi-mode fiber and a gradient index (GRIN) lens. The invention also relates to a system including a multi-mode fibre, such as a double-clad photonic crystal fibre, for transmitting an excitation signal to a sample for the purpose of imaging, and a scanning mechanism, which preferably includes a microelectromechanical system (MEMS) mirror, for reflecting the excitation signal in varying directions in order to scan the sample.

Abstract: An apparatus for controlling at least one of at least two sections of at least one fiber can be provided. The apparatus can include an arrangement which may be provided between the first and second sections of a particular continuous fiber of the fibers. A particular one of the first and second sections may be provided in a particular orientation that is perpendicular to an extension of the particular fiber. The arrangement is capable of controlling the particular fiber such that the particular one of the sections is capable of being rotated for at least 360° with respect to the particular orientation. The arrangement can include a further arrangement that is capable of at least partially wrapping the particular fiber around the second arrangement, and controlling the particular fiber such that the particular one of the sections is capable of being rotated with respect to the particular orientation during a transmission of the electro-magnetic radiation.

Abstract: A multi-core optical fiber apparatus is disclosed. The multi-core optical fiber apparatus includes a cladding comprising quartz and a plurality of cores embedded in the cladding. Each of the cores has a diameter (D) ranging from 1.3 ?m to 2.0 ?m, a numerical aperture (NA) from 0.35 to 0.45 and a refractive index profile factor (?) from 2.0 to 4.0. A center of each of the cores has a germanium content of 20 wt % to 30 wt %. An interval between adjacent cores is 3.0 ?m or more.

Abstract: An optic device, system and method for making are described. The optic device includes a first solid phase layer having a first index of refraction with a first photon transmission property and a second solid phase layer having a second index of refraction with a second photon transmission property. The first and second layers are conformal to each other. The optic device may be fabricated by vapor depositing a first layer and then vapor depositing a second layer thereupon. The first layer may be deposited onto a blank or substrate. The blank or substrate may be rotated during deposition. Further, a computer-controlled shutter may be used to alter the deposition rate of material along an axis of the optic device. Alternatively, the optic device may be moved at varying speeds through a vapor stream to alter the deposition rate of material.

Abstract: A light diffusing tip is provided. The light diffusing tip comprises a housing and a monolithic light scattering medium disposed within the housing. The monolithic light scattering medium comprises a first scattering region at a first position, the scattering region having a first scattering property and a second scattering region at a second position, the second scattering region having a second scattering property different from the first scattering property, wherein the first scattering region and the second scattering region are coextensive along a substantial portion of a length of the housing. A light diffusing applicator also is provided. The light diffusing applicator comprises at least one optical waveguide, a first termination coupled to a first end of the at least one optical waveguide, the first termination to couple to a light source and a light diffusing tip coupled to a second end of the at least one optical waveguide.

Abstract: An endoscope includes an elongated insertion section which has a distal end portion and is inserted into a body cavity. The insertion section has a rigid portion body on the distal end portion. The rigid portion body has at least one mounting hole in which each of optical members of an observation optical system and an illumination optical system is mounted. A binding portion which mechanically restricts the optical member with respect to the rigid portion body is provided on at least a part of the boundary between the mounting hole and the optical member mounted in the mounting hole.

Abstract: A microendoscope with a distal probe tip which has, in particular, a diameter of up to approximately 1 mm is provided and inside of which an optical subassembly at least provided with a micro-objective and with an image transmitting element is accommodated. An image transmitting system is connected to the optical subassembly. An image-enlarging coupling element is provided between the optical subassembly of the probe tip and the image transmitting system connected thereto. The image transmitting system connected to the coupling element has a larger active diameter than the optical subassembly that is provided with the distal objective. As a result, the distal probe tip on a handgrip has the necessary small working diameter over the entire working length, and at the beginning or inside the handgrip, the optical coupling element is coupled to an image guide or to an image transmitting system or the like having a higher pixel count and thus a larger active diameter and, therefore, a larger outside diameter.

Abstract: A probe for use in Raman spectroscopy that can be inserted into a chemical vessel through a small diameter fitting while maximizing the amount of Raman shifted radiation collected and minimizing spurious effects.