Abstract: A first heat-treating method involves monitoring at least one thermal efficiency parameter associated with an irradiance system configured to produce an irradiance flash incident on a surface of a workpiece, and automatically updating control information used by the irradiance system to produce the irradiance flash, in response to the monitoring of the thermal efficiency parameter. A second method involves predicting a heating effect of an irradiance flash to be incident upon a surface of a workpiece, in response to a measurement of a heating parameter of the surface, and pre-adjusting the irradiance flash, in response to the predicted heating effect. A third method involves measuring a temperature of a surface of a workpiece during an initial portion of an irradiance flash incident on the surface, and controlling a power of a remaining portion of the irradiance flash, in response to the temperature.

Abstract: A system for removing molten metal from a vessel is disclosed. The system includes a pump and a refractory casing that houses the pump. As the pump operates it moves molten metal upward through an uptake section of the casing until it reaches an outlet wherein it exits the vessel. The outlet may be attached to a launder. Another system uses a wall to divide a cavity of the chamber into two portions. The wall has an opening and a pump pumps molten metal from a first portion into a second portion until the level in the second portion reaches an outlet and exits the vessel.

Abstract: An apparatus, method and process directed to enabling a VIM induction furnace to be removed from a vacuum chamber while the induction furnace is still in a heated state without damaging the induction furnace. The induction furnace can include a power port that can be easily switched to an auxiliary cooling source to enable the induction furnace to be removed from the vacuum chamber while the induction furnace is still in a heated state.

Abstract: A melt metallurgical installation has a melting furnace for melting scrap metal and a charging region for the melting furnace which is located above the melting furnace. The installation further has a charging element, which has been filled with scrap metal intended for the melting furnace and can be moved in a movement direction into the charging region where it can be emptied and then moved again, in the empty state, against the movement direction out of the charging region. The charging region is enclosed by a hood such that the charging region, including the charging element which has been placed in the charging region, is closed at the top and on the sides. The hood has at least one upper extraction opening through which the waste gases and dust developing in the hood can be extracted out of the hood.

Abstract: A liquid cooling heat exchanger module filled with a cooling liquid includes a casing (10) and a cooling structure (11), and the interior of the casing (10) is hollow, and the casing (10) has an inlet (100) and an outlet (101) interconnected to the interior, and the cooling structure (11) is installed in the casing (10), and the cooling structure (11) has a vortex generating area (110) concavely formed at a position opposite to the inlet (100), such that a cooling liquid is filled from the inlet (100) into the casing (10) and impacted in the vortex generating area (110) to form a vortex, so as to achieve the effects of extending the time for the cooling liquid to stay in the heat exchanger module (1), maximizing the cooling effect of the cooling liquid, and improving the heat dissipating efficiency.

Abstract: An object of the present invention is to provide a readily produced and easily handled heat storage member. The heat storage member 1 has a rectangular plane surface of, for example, 15 (cm)×20 (cm), and has a thickness of, for example, 10 to 15 mm. The heat storage member 1 includes a gelatinous latent heat storage material 12, and a large number of highly heat conductive fillers 14 dispersed in the latent heat storage material 12. The highly heat conductive fillers 14 are mixed in the latent heat storage material 12 with a bias in dispersion density. In the rectangular plane surface of the heat storage member 1, a periodic pattern is formed in combination of cellular (cell-like) regions 10, which are demarcated by, for example, hexagonal contour lines 16 and which are periodically arrayed in the vertical and horizontal directions.

Abstract: Systems according to the present disclosure provide one or more surfaces that function as heat or power radiating surfaces for which at least a portion of the radiating surface includes or is composed of “fractal cells” placed sufficiently closed close together to one another so that a surface (plasmonic) wave causes near replication of current present in one fractal cell in an adjacent fractal cell. A fractal of such a fractal cell can be of any suitable fractal shape and may have two or more iterations. The fractal cells may lie on a flat or curved sheet or layer and be composed in layers for wide bandwidth or multibandwidth transmission. The area of a surface and its number of fractals determines the gain relative to a single fractal cell. The boundary edges of the surface may be terminated resistively so as to not degrade the cell performance at the edges.

Abstract: A heat exchanger includes a shell; a pair of tube plates provided at both ends of the shell; a plurality of heat transfer tubes supported by the tube plates and housed in the shell; and a high-temperature fluid inlet connection for introducing a high-temperature fluid into the shell. A cooling jacket having a porous structure, over which a cooling fluid is to be spread, is provided on the interior surface of the high-temperature fluid inlet connection.

Abstract: An apparatus for plugging a bore of a tube sheet, the apparatus includes cantilevered members that project radially outward from a body on the inner surface of the tube sheet. Slots can be drilled into a tube the projects into the bore and the cantilevered members set into the slots. The cantilevered members can slide radially outward from within the body, or can be pivotingly attached on an end of the body. One end of a bolt threadingly attaches to the body, and attaches on its other end to a nut circumscribing the tube sheet bore on its outer surface. A deformable collar circumscribes the bolt between the body and nut and provides a seal within the tube sheet bore. The apparatus can also be used to plug bores that do not include tubes.

Abstract: A thermal interface material (TIM) using high thermal conductivity nano-particles, particularly ones with large aspect ratios, for enhancing thermal transport across boundary or interfacial layers that exist at bulk material interfaces is disclosed. The nanoparticles do not need to be used in a fluid carrier or as filler material within a bonding adhesive to enhance thermal transport, but simply in a dry solid state. The nanoparticles may be equiaxed or acicular in shape with large aspect ratios like nanorods and nanowires.

Abstract: A non-detachable magazine lower receiver for a firearm includes a stock mount, a trigger well extending from the stock mount, and a magazine well. The trigger well is configured to receive a firing mechanism. The magazine well is configured to receive a magazine. A proximal wall of the magazine defines a retention opening that passes through a distal wall of the trigger well. The retention opening is configured to receive a magazine retention member for fixing a magazine recovered in the magazine well to the lower receiver.

Abstract: A charging handle for a firearm having a receiver has an elongated rod running from a front end to a rear end at which a crossbar portion is connected to the rod. The crossbar portion is laterally situated to each side of the elongated rod and features redirection channels on both the top and bottom surfaces and is sized, shaped, and adapted to be gripped by a shooter using the firearm. The charging handle has flexible tabs on either side of the elongated rod for securement of the charging handle within groove on the firearm receiver. Rearward force by a user on either the left, right, or both sides of the crossbar portion user disengages the tabs from the grooves and releases the charging handle thereby allowing the charging handle to freely move along the firearm receiver.

Abstract: The bolt hold-open system is a firearm bolt locking or holding mechanism for an AK-47 or similar firearm capable of automatically keeping the bolt of the firearm in an open position when the firearm magazine is empty. The bolt hold-open system includes a locking assembly and a modified magazine. The bolt hold-open system also provides a manual control for keeping the bolt in an open position and for releasing the bolt. The system prevents the bolt carrier from closing while there is an empty magazine in the gun, but can be easily activated to release the bolt when the magazine is removed or a non-empty magazine is in the magazine receiver. The system requires minimal modifications to the firearm and magazine and is easily adaptable to firearms similar to the AK-47 that fire ammunition in a wide range of calibers and configurations.

Abstract: A magazine release for installation on a carbine in place of an original sliding latch enables use of removable magazines in place of an original clamshell magazine. The magazine release features a support member having an upper portion coupled to a trigger assembly frame of the carbine in place of the original sliding latch. A lever is pivotally supported on the support member at a lower portion thereof carried beneath the trigger assembly frame. The lever is pivotal about an axis that lies transversely of a longitudinal barrel direction of the carbine, and is manually pivotable in a release direction moving a catch feature rearwardly in the longitudinal barrel direction out of a default positon into which said catch feature is biased forwardly so as to catch under a retention feature of the removable magazine. The catch feature normally retains the removable magazine in place until the lever is pivoted in the release direction.

Abstract: An apparatus for mounting and locking on a wall a firearm such as a rifle or shotgun comprising a housing assembly for supporting a firearm, a trigger and receiver guard assembly for preventing access to the trigger and receiver of the firearm, and a means for pinning the trigger and receiver guard assembly and firearm within the housing assembly while in a locked position.

Abstract: Firearms with integrated suppressors have a receiver having a forward portion defining an internal bore, a tubular body having sides defining an interior, a selected portion of the interior receiving a barrel, the barrel having a rear end removably received in the internal bore, a selected portion of the interior receiving a plurality of baffles, and wherein at least one side of the body can be disassembled into a panel to enable access to the baffles. Each of the baffles may define an aperture. The barrel may have a central bore that defines a bore axis, and the baffle apertures may be axially registered with the bore axis. At least one side of the body may have an attachment facility that removably connects an accessory to the rifle. The barrel, baffles, and body may be of monolithic or modular construction.

Abstract: A firearm suppressor can comprise a central longitudinal chamber adapted to facilitate passage of a projectile fired from a firearm through the central longitudinal chamber. The firearm suppressor can also comprise an outer chamber disposed radially outward of the central longitudinal chamber, the outer chamber being in fluid communication with the central longitudinal chamber via an opening. The firearm suppressor can further comprise a baffle disposed in the outer chamber and defining a forward portion of the outer chamber and a rearward portion of the outer chamber. The forward portion of the outer chamber can contain the opening such that discharge gases associated with the projectile enter the forward portion of the chamber and are directed backward past the baffle to the rearward portion of the outer chamber where the discharge gases are at least temporarily trapped behind the projectile to reduce or prevent alteration of a trajectory or a speed of the projectile by the discharge gases.

Abstract: An upper receiver for a firearm is provided. The upper receiver having: a hand guard section integrally formed with the upper receiver; a rail section integrally formed with the hand guard section, wherein the rail section is formed of a first material and the hand guard section is formed of a second material, wherein the second material is molded about the first material.

Abstract: A sock and sling system is presented for storing a gun within the sock in a storage state and for using as a sling connected to the gun when in a sling state. The system includes a sock extending a length from a first end to a second end and having an open interior. A pair of removable sling swivels connect the sock member to the gun. When used as a sling, the length of the sock member can be adjusted in a plurality of ways including twisting the sock member, selecting one of a number of loops to attach to or by adjusting the length of a length adjusting drawstring. In this way, a system is presented that serves the dual purpose of storing a gun in a storage state and as a sling in a sling state.

Abstract: An adapter for a QD socket is disclosed. The adapter has a connection post having a plurality of tabs movable relative to each other between a first configuration and a second configuration. The first configuration defines a maximum effective outer diameter of the connection post, and the second configuration defines a minimum effective outer diameter of the connection post. A method of modifying a quick disconnect attachment is also disclosed.

Abstract: An illuminable reticle supporting multiple optical fibers includes an electroformed foil or wire reticle segment providing a primary aiming mark; a first optical fiber having a first end, the first optical fiber being adhered to and overlaying a lower portion of the segment to provide a first illuminable aiming point along the primary aiming mark when the first optical fiber emits light from its first end; and a second optical fiber having a second end, the second optical fiber being adhered to and overlaying a lower portion of the first optical fiber to provide a second illuminable aiming point parallel with and below the first illuminable aiming point when the second optical fiber emits light from its second end.

Abstract: A method for shooting a projectile weapon involves determining the inclination of a line of sight from a vantage point to a target and a line-of-sight range to the target, then predicting a trajectory parameter at the line-of-sight range, for a preselected projectile. Using the trajectory parameter, an equivalent horizontal range may then be determined, wherein the equivalent horizontal range is the range at which the trajectory parameter would be expected to occur if the projectile were shot from the vantage point toward a theoretical target located in a horizontal plane intersecting the vantage point. The equivalent horizontal range may be utilized to compensate for ballistic drop when shooting the projectile weapon. The method may be embodied in a handheld laser rangefinder including a memory for storing ballistic data. Systems for automatic hold over adjustment in a weapon aiming device are also disclosed.

Abstract: A weapon and weapon system, and methods of manufacturing and operating the same. In one embodiment, the weapon includes a warhead including destructive elements and a guidance section with a seeker configured to guide the weapon to a target. The seeker includes a detector configured to receive a distorted signal impinging on an objective lens from the target, memory configured to store target criteria and a correction map, and a processor configured to provide a correction signal based on the distorted signal, the target criteria and the correction map to guide the weapon to the target.

Abstract: Methods and apparatus are provided for an armor mounting device capable of securely and detachably holding an armor panel to a floor. In one exemplary embodiment the armor mounting device consists of a base having a flat plate portion and a raised central portion, and a detachable clamp that includes a hold down plate and a spring loaded latch disposed within hold down plate. The spring loaded latch is connectable to the raised central portion of the base through a hole in the armor panel when the detachable clamp is juxtaposed with the base, to thereby trap the armor panel between the hold down plate and the flat plate portion of the base. A bonding agent secures the base to the floor.

Abstract: A polyurea hybrid ballistic armor formed from novel cured reaction products of various diamines and polyester diols with isocyanate curing agents. The cured reaction product can absorb large amounts of energy from ballistic projectiles, and when various hard granular particles are embedded within the cured reaction product, a strike plate effect can be realized, allowing the polyurea hybrid ballistic armor to defeat ballistic projectiles. The polyurea hybrid ballistic armor can additionally be utilized to add additional layers of protection to existing armor systems.

Abstract: A turret includes a hollow casing provided with a gun, such as a cannon. The casing includes an upper half-shell at least partially widening towards the bottom of the casing, and a lower half-shell at least partially widening towards the top of the casing; the upper half-shell and the lower half-shell meeting and widening, in at least one edge border of the casing.

Abstract: A bullet resistant shield for electric power equipment constructed from standardized modular sections configured for easy erection in the field into walls and enclosures. The modular sections may be constructed at a factory and transported to the desired location where the sections are assembled together into walls and enclosures. The modules are sized for transportation by trucks over public roadway, rail, barge and so forth. Concrete foundations may be installed prior to arrival of the modular sections to ready the site for erection of the shied structure upon arrival of the modular sections. Unlike conventional bullet resistant enclosures, these sections provide adequate ventilation to avoid overheating of air-cooled electric power equipment, such as large substation transformers. One or more electric fans may be mounted in the section to provide forced air ventilation. The wall may be positioned to allow walk-up maintenance access without the use of doors.

Abstract: A body shell of an armored vehicle includes a front face carrying a bulletproof windscreen projecting towards an outside of the body shell, at least one side wall including an opening, the side wall being integral with the front face at a strut that is defined by a part of the side wall included between an edge of the opening and a rim of the side wall situated furthest outwards at the front of the vehicle. In the armored vehicle body shell, the strut extends beyond the front face towards the outside of the body shell, and the edge of the opening is situated near the front face so that a junction between the strut and the front face of the body shell is at the vicinity of the edge of the opening which forms a rear edge of the strut.

Abstract: A system for defending against an intruder includes a building having a wall dividing first and second spaces and a nonlethal device selectively operable through the wall. The nonlethal device includes an enclosure mounted to the wall and having an access door for selectively accessing an interior compartment of the enclosure from the first space, a container of a nonlethal chemical weapon, such as a lachrymatory agent, having an outlet and located within the enclosure, a conduit extending from the container to the second space through the wall and having an inlet in fluid flow communication with the outlet of the container of nonlethal chemical weapon, and a valve operable to selectively release the nonlethal chemical weapon from the container and through the conduit to the second space to form a cloud of the nonlethal chemical weapon within the second space.

Abstract: A target for receiving projectiles is configured for mounting in a corner of a room. The target includes a front target wall including a pair of spaced apart edges having a target area located between the edges and at least one side area extending from the front wall adapted for engagement with one of the walls defining the corner.

Abstract: An example resetting gun target includes a first curved rocking member; a second curved rocking member; a connector portion joining the first rocking member and the second rocking member and maintaining a space between the first rocking member and the second rocking member; and a central target panel attached to the connector portion and situated in the space between the first curved rocking member and the second curved rocking member. The resetting gun target may further include paddle portions respectively situated at a first end and a second end of each of the first curved rocking member and the second curved rocking member.

Abstract: The invention is an explosively formed projectile (EFP). On detonation of an explosive charge, an explosively formed projectile is formed from two separate metal elements, an open-poled dished liner and a cavitation pin. The open-poled dished liner is made of a metal more dense than a metal of the cavitation pin. The cavitation pin lies on the open-poled dished liner longitudinal axis and in contact therewith. The cavitation pin has a truncated right conical shape with a base diameter to length ratio of 0.7:1 to 1.5:1. The ratio of the open-poled dished liner diameter:cavitation pin fore portion major base diameter is 2:1 to 4:1. Upon detonation, the cavitation pin leads the explosively forged liner in the explosively formed projectile assembly. The leading pin causes cavitation in water resulting in an increase in the velocity of the explosively formed projectile.

Abstract: A marine cable cutter is provided for wirelessly severing wire responsive to an electromagnetic command signal. The cutter includes an explosive package for wrapping around the wire, and a clamshell case for containing the package around the wire. The package includes a wireless receiver to receive the command signal, an electric pulse generator triggered by the receiver, an explosive initiated by the generator, and a platform for containing the receiver, generator and explosive. The clamshell case includes a pair of envelopes connected along mutual first edges by a hinge and mutual second edges by respective clamps. The envelopes pivot on the hinge to open and receive the package with disposal of the wire therein, and subsequently to close and secure by the clamps. The envelopes can be composed of sheet metal with the clamps being flanges with aligned holes for receiving bolt fasteners.

Abstract: A toy arrow that has a shaft with a head end and a tail end is described herein. A head is associated with the head end of the shaft. Fins are associated with the tail end of the shaft. Extending hooks extend outward from the sides of the head.

Abstract: Example nocks, arrowheads and/or arrowhead inserts include a tapered annular flange axially engaging a correspondingly tapered edge on a tubular arrow shaft. The tapered flange and edge help prevent the end of tubular arrow shaft from deforming radially outward when substantial axial force is applied to the nock, arrowhead and/or arrowhead insert.

Abstract: A paintball grenade that disperses a marking fluid upon impact. In one embodiment, the paintball grenade includes a flexible, resilient tube sealed at both ends. The tube includes a distended portion containing pressurized marking fluid and a side discharge port for discharging the marking fluid along a discharge axis that is approximately transverse to a longitudinal axis of the tube. A blocking member is disposed in the tube that is movable between a closed position that prevents fluid communication between the distended portion of the tube and the discharge port and an open position that allows fluid communication between the marking fluid and the discharge port. When the paintball grenade is thrown and impacts an object, this results in hydrostatic shock through the marking fluid, which moves the blocking member from the closed position to the open position, thereby discharging the marking fluid through the discharge port onto surrounding objects.

Abstract: A munition (10) with variable explosive power comprises a body (12) extending in an axial direction and housing at least first and second explosive charges (31, 32), together with a firing device (16). According to the invention, the munition further comprises a selector (50, 50?) provided with a detonating portion (52) and adapted to move between at least first and second positions, the selector being configured so that its detonating portion couples the firing device (16) to the first explosive charge in said first position and to the second explosive charge in said second position, one of the first and second explosive charges (31, 32) not being coupled to the firing device (16) in at least one of the first and second positions.

Abstract: An arrow construction system comprising a tip canister configured to receive an arrow tip and to attach to an arrow shaft. The tip canister contains a power source and sensitive electronics. The power circuit may be a battery, a primary storage capacitor, a coil and a rectifier, and/or a solar cell. The tip canister may be electrically connected to the nock via the shaft electrical conduction system. The electrical conductors may be integrated into the shaft. The wires may form a cable with standard connectors. The nock may contain a light. Alternatively, the fletching may comprise light emitting film or fibers. The circuits may include a flash circuit, an audio circuit, a radio beacon, a wireless transmitter, environmental sensors, a camera, a switch, and/or a GPS device. The switch may be activated by a current detected in a coil or by an accelerometer.

Abstract: Methods and apparatus for an acoustic source for directing acoustic energy to ensonify a container, a first sensor to detect acoustic energy from the acoustic source affected by an object in the container without contacting the container, a second sensor to confirm presence of the object, and a processing module to process the detected acoustic energy from the first and second sensors to identify the object in the container.

Abstract: A method of blasting rock at an underground blast site in which boreholes (11a, b, c) are drilled in a rock mass 10 from a drive defining face 12, each borehole is loaded with at least one charge of explosive material (13a-c, 14a-c, 15a-c), at least one detonator is placed in operative association with each charge, and a sequence of at least two initiation events is conducted to blast the rock mass, in each of which only some of the charges are initiated, by sending firing signals to only the detonators associated with said charges and in which each initiation event is a discrete user-controlled initiation event. In one of the at least two initiation events a stranded portion of the rock mass such as a pillar is created that has already been drilled and charged, and the stranded portion of the rock mass is blasted in a subsequent one or more of the at least two initiation events without personnel accessing said stranded portion.

Abstract: A measuring wheel includes a handle that can be folded into a non-use position. The wheel lies in a plane, and the handle moves in a plane coincident with the plane of the wheel between a collapsed position and an extended use position. The handle has a proximal section and a distal section that connect about a pivot point for movement between a collapsed position and the extended use position. The measuring wheel has a releasable engagement member associated with one of the handle sections that releasably holds the handle in the extended position. The releasable engagement member can be disengaged to allow the handle to be collapsed.

Abstract: A micrometer provides a quick adjustment mode and a fine adjustment mode. A spline-like rotary coupling configuration constrains the micrometer thimble and a threaded element to move together with respect to rotation, but does not constrain the position of the threaded element relative to the thimble along the measurement axis. A gear in the micrometer frame includes gear teeth that mesh with the threaded element and roll thereon along the measurement direction. A locking arrangement, when unlocked, allows the meshed gear to be rotated by a user to drive the threaded element along the measuring axis in the quick adjustment mode. When locked, the locking arrangement prevents motion of the gear to provide the fine adjustment mode, wherein the user rotates the thimble to screw the threaded element through the meshed teeth of the gear, to adjust the spindle position.

Abstract: An apparatus including a first plurality of electrodes and a second plurality of electrodes is disclosed. Each electrode of the first plurality of electrodes is configured to measure an electric field associated with a position of a moving object. The second plurality of electrodes is disposed further away from the moving object in comparison to the first plurality of electrodes. The second plurality of electrodes is configured to measure a signal associated with ambient noise.

Abstract: A system and method for sweeping electromagnetic radiation over a first coherence length and a second length over a range of wavelengths to generate an image. Electromagnetic radiation having a first coherence length is generated and swept over a range of wavelengths. Electromagnetic radiation having a second coherence length is generated and swept over a range of wavelengths. The electromagnetic radiation is splitting through a reference path and a sample path; Electromagnetic radiation returned from the reference path and the sample path is detected, wherein the detector generates output signals corresponding to the received electromagnetic radiation. In one embodiment, the output signals are processed to generate an image. The image may be interleaved with data corresponding to the electromagnetic radiation having the first coherence length and the second coherence length.

Abstract: A method includes sequentially acquiring phase-shifted images of an optical source in a plurality of predetermined positions in the z plane to form a plurality of image frame sequences; determining from the plurality of image frame sequences at least one phase-related characteristic associated with each predetermined position of the optical source in the z plane; and storing the at least one phase-related characteristic and the predetermined positions of the optical source in the z plane.

Abstract: Exemplary embodiments of the present disclosure include a combined catheter-based optical coherence tomography-two-photon luminescence (OCT-TPL) imaging system. Exemplary embodiments further include methods to detect, and further characterize the distribution of cellular components (e.g., macrophage, collagen/elastin fiber, lipid droplet) in thin-cap fibroatheromas with high spatial resolution in vivo.

Abstract: A method for determining 3D coordinates of points on a surface of the object by providing a remote probe having a probe tip and a non-contact 3D measuring device having a projector and camera coupled to a processor, projecting a pattern onto the surface to determine a first set of 3D coordinates of points on the surface, determining susceptibility of the object to multipath interference by projecting and reflecting rays from the measured 3D coordinates of the points, projecting a first light to direct positioning of the remote probe by the user, the first light determined at least in part by the susceptibility to multipath interference, touching the probe tip to the surface at the indicated region, illuminating at least three spots of light on the remote probe, capturing an image of the at least three spots with the camera, and determining 3D coordinates of the probe tip.

Abstract: A stereoscopic measurement system captures stereo images and determines measurement information for user-designated points within stereo images. The system comprises an image capture device for capturing stereo images of an object. A processing system communicates with the capture device to receive stereo images. The processing system displays the stereo images and allows a user to select one or more points within the stereo image. The processing system processes the designated points within the stereo images to determine measurement information for the designated points.

Abstract: A method is used to determine an aiming point for a sighting system used by a shooter to shoot a target. The method includes receiving a range signal that corresponds to a distance from the shooter to the target. A first position signal is received from a magnification system sensor. A first magnification setting based at least in part on the first position signal is then determined. Thereafter, a first aiming point based at least in part on both of the range signal and the first magnification setting is determined.

Abstract: An optical position-measuring device includes a measuring standard as well as a scanning unit movable relative to it along at least one measuring direction, a scanning beam path being formed between the measuring standard and scanning unit and being used to generate displacement-dependent signals. A protective cap is disposed in a manner allowing movement along an axis perpendicular to the measuring-standard plane such that in at least one operating mode, the protective cap for the most part surrounds the scanning beam path between the scanning unit and measuring standard.