Abstract: Light signals of first to n-th bands amplified en bloc undergo proper attenuation through an adjustable optical attenuator in conformance with attenuation in an optical fiber connected to input of an optical amplifying repeater apparatus, whereon the light signals are demultiplexed or separated into individual bands and amplified by first to n-th fixed-gain optical amplifiers (#1, . . . , #n) each having a high fixed gain in the respective bands to be subsequently multiplexed by an optical multiplexer and then sent out onto a transmission line. A monitoring light branching device extracts a part of light power of a specific monitoring wavelength, which is then fed to an adjustable attenuator control circuit which controls the attenuation factor of the adjustable optical attenuator so that the light power of the specific wavelength remains constant. The gain of the optical amplifying repeater apparatus at the specific wavelength can thus be determined.

Abstract: A tip optical element for immersion microscope objectives is constructed so that a first optical element and a second optical element are cemented to each other, and has an annular light-blocking area on a surface of one of the first optical element and the second optical element to be cemented. The tip optical element is fabricated in such a way that a beam restricting device is placed on a surface of one of the first optical element and the second optical element; a light-transmitting area transmitting an effective beam and the light-blocking area formed around the light-transmitting area are provided to the beam restricting device; and the first optical element and the second optical element are cemented to each other, with the beam restricting device sandwiched between them.

Abstract: Provided is an operation microscope capable of obtaining bright and wide range red reflex on an observation image. Further, an operation microscope suitable for an observation of a retina and a vitreous body is provided. A pair of deflection members composed of two deflection mirrors are provided as a deflection means for deflecting illumination light guided from a light source to the vicinity of an optical axis of an observation optical system and guiding it to an eye to be operated through an objective lens. The deflection mirrors are disposed to sandwich the optical axis therebetween and simultaneously guide the illumination lights to the eye to be operated at substantially the same oblique angles with respect to the optical axis from the respective opposite sides. In addition, a stereo variator is made insertable onto the observation optical axis, so that relative positions of optical axes of right and left observation fluxes can be changed.

Abstract: An optical apparatus minimizes autofluorescence and stray light as well as leakage of excitation light and efficiently utilizes illuminating light from a fluorescence illumination optical system to allow observation of a bright fluorescence image. An observation apparatus has an objective, an observation optical system unit including a variable magnification optical system, and an imaging optical system unit including an imaging lens and an eyepiece. A fluorescence illumination apparatus, which is provided separately, is removably attached to the observation apparatus. The fluorescence illumination apparatus has a light source, a collector lens unit, and a reflecting member placed between the objective and the observation optical system unit at a position displaced from the optical axis of the objective to make light from the light source incident on the objective. An excitation filter is provided between the light source and the reflecting member.

Abstract: A magnetically positioned precision holder for optical components in an optical device comprises a carrier for replaceably holding at least one optical component. The carrier is arranged in positionally adjustable fashion in a housing recess including a precision stop surface. Magnet pairs (A1/A2 and B1/B2) are oriented with identical polarity being provided in order to achieve a continuous contact pressure of the carrier (2; 3) against the stop surface (6), in such a way that the one magnet (A1, B1) is located in the recess and the corresponding magnet (A2, B2) is located in the carrier. The use of identically poled magnet pairs for movable precision holders and for precision positioning systems is also proposed.

Abstract: Disclosed is a bi-directional telescope for a laser on air telecommunication system, the telescope comprising: a primary optical surface; at least one transmitting device forming at least one transmitting beam impinging against the primary optical surface at an at least one illuminated area, the at least one transmitting beam having a corresponding axis; and a receiving device collecting the power deflected by an optical surface of the primary optical surface into a receiving beam, the receiving beam having an axis. The telescope is characterized in that the optical surface of the primary optical surface is larger than the at least one illuminated area and in that the transmitting beam axis does not coincide with the receiving beam axis. A method for receiving and transmitting optical signals through the air by a bi-directional telescope is also described.

Abstract: The invention relates to a method for providing a structure (2d) in the form of a crosshair and/or hairlines in a telescopic sight or binocular telescope, at least one transparent optical part (1d), in particular a lens of the telescopic sight or binocular telescope, being provided with the structure (2d). The structure (2d) is introduced as internal engraving into the transparent optical part (1d) by laser action.

Abstract: An apparatus and method for stabilizing an optical tube on a base wherein a tension adjuster adapted to adjust the tension between the optical tube and sideboard of the base is secured between a the optical tube and the sideboard. By turning the tension adjuster, tension can be added or reduced to stabilize the optical tube.

Abstract: The present invention concerns the structure of and methods of constructing indicating instruments with slim profiles. The indicating instrument comprises a meter movement and a circuit board. The main body of the meter movement is situated in an aperture in the circuit board. With this placement, the front end of the body of the meter movement extends a distance in front of the circuit board and the back end of the meter movement body extends a distance behind the circuit board. Through appropriate selection and arrangement of any components on the circuit board, the circuit board can be constructed such that none of its components extend beyond the distance that the meter movement extends on either side of the circuit board. In this manner the space needed for the meter movement and the circuit board and its components collapses into the same area. A light plate may be added to the circuit board and meter movement. The light plate provides a structural framework for the indicating instrument.

Abstract: An image projector (8, 68) includes a light source (14) that illuminates a three-path reflective LCD assembly (25, 74) that produces images for projection by a projection lens (27). The light source produces S-polarized light rays that are received by a spectrally selective wave plate (36) that changes a first wavelength range of light to P-polarized light rays (34) and transmits without polarization change second and third wavelength ranges of light. A plate-type transflective polarizing beam splitter (40) transmits the P-polarized first wavelength range light rays and reflects S-polarized second and third wavelength range light rays (34). The P-polarized first wavelength range light rays transmit through a field lens (421) and impinge on a first reflective LCD light valve (261).

Abstract: The present invention is so arranged as to include (a) gradation reference potential generating means including a group of output terminals whose voltages are determined in accordance with a voltage division ratio of one ladder resistor, so as to output gradation reference potentials, for example, of 1024, which is a 16 multiple of a required 64-gradations; (b) output terminal designating means including a memory for designating, among from the output terminals, an output terminal for each of the 64-gradations required, in accordance with the display modes; and (c) selecting means for selecting an output terminal that corresponds to an input gradation signal, among from the output terminals designated by the output terminal designating section, and for applying a voltage via the thus selected output terminal to a display screen.

Abstract: A projection type optical display system includes: a light source; a display panel with light-modulating pixel regions; a light control system for splitting the emitted light into light rays falling within multiple wavelength ranges and focusing the rays onto associated pixel regions according to their wavelength ranges; an optical system for forming an image on a projection plane by utilizing the light modulated; a circuit for generating image subframe data from image frame data and getting the image subframes displayed by the panel time-sequentially; and an optical shifter for shifting, on the projection plane, one of the image subframes being displayed by the panel. The optical shifter is optimized to an outgoing light ray of the panel, which falls within a wavelength range with the highest luminosity, so as to shift the ray on the projection plane an integral number of times as long as the pixel pitch of the panel.

Abstract: To provide a rear-projection type screen in which, without the need for a tape-attachment operation on the outer circumferential part of the lens sheets, the top of the Fresnel lens can be prevented from being pared by the abrasion caused by the vibration during transportation. A rear-projection type screen according to the present invention is configured from two or more overlapping sheet-like members such as a Lenticular lens sheet 1 and Fresnel lens sheet 2, in which a fixing protrusion 3 is integrally formed in the sheet-like members in such way that neither of the two sheet-like members is displaced from the state in which the two sheet-like members overlap. A protrusion, used to attach the rear-projection type screen to the main body of a rear-projection-type image display apparatus or the screen frame, may be integrally formed in the sheet-like members from which the rear-projection type screen is configured.

Abstract: The invention has for its object to provide a transmission type illumination device for a stereomicroscope capable of observing objects over a wide magnification range wherein a diffuser that provides a surface light source and an optical element having a periodical structure in a one-dimensional direction are used in combination thereby achieving illumination with reduced field variations. This device is at least made up of, in order from a light source, a collector lens, a diffuser and a convex lens 4b. In the vicinity of the lens 4b located nearest to the side of a viewing surface 5, there is provided an optical element having a periodical structure in a one-dimensional direction. With respect to the angle &agr; for splitting the incident light beam, the optical element 7 having a periodical structure in a one-dimensional direction satisfies the condition 0.5D/L<tan&agr;<0.

Abstract: A lock pin is inserted into a hole of a lens holding frame in order to lock a blur correction lens when blur correction is not executed. An optical axis of the blur correction lens and an optical axis of a photographic optical system match when the blur correction lens and the lens holding frame have fallen in the gravitational direction by their own weight and the lock pin and the hole have come into contact with each other.

Abstract: An optical film composed by laminating a light scattering film 1 scattering and transmitting light and comprising at least two phases or more different in refractive index and a reflective polarizer 2 selectively P/S converting the light. It is preferred that at least one phase of the light scattering film larger in the refractive index has a columnar structure extending in the thickness direction of the film and the transmittance of the film in the normal direction is 4% or more. The optical film is excellent in visibility, is small in light loss in order to provide an excellently visible and bright image, and has an excellent light collecting property when used in a liquid crystal display device or the like.

Abstract: A lithography apparatus having achromatic Fresnel objective (AFO) that combines a Fresnel zone plate and a refractive Fresnel lens. The zone plate provides high resolution for imaging and focusing, while the refractive lens takes advantage of the refraction index change properties of appropriate elements near absorption edges to recombine the electromagnetic radiation of different energies dispersed by the zone plate. This compound lens effectively solves the high chromatic aberration problem of zone plates. The lithography apparatus allows the use of short wavelength radiation in the 1-15 nm spectral range to print high resolution features as small as 20 nm.

Abstract: Optical bodies, comprising: a plurality of first optical layers comprising a first polymer composition that comprises (i) a polyester portion having terephthalate comonomer units and ethylene glycol comonomer units, and

Abstract: An image display apparatus includes a display having an image display surface which displays a two-dimensional image of an object including a three-dimensional object, and an image transmitting panel spaced apart from the image display surface for creating an imaging plane displaying a real image of the two-dimensional image in a space opposite to the display. The image transmitting panel and the imaging plane are non-parallel with each other.

Abstract: A solid immersion lens device and method of making. A solid immersion lens device is provided having a plurality of solid immersion lenses. The solid immersion lenses are provided in a predetermined pattern and secured so as to cause them to be in a fixed position with respect to each other.

Abstract: An illumination system and exposure apparatus and method involving illuminating a surface over an illumination field (IF) having an arcuate shape. The illumination system comprises a light source (54) for providing a light beam (100), and an optical integrator (56). The optical integrator comprises a first reflective element group (60) having an array of first optical elements (E) each having an arcuate profile corresponding to the arcuate shape of the illumination field. Each of the first optical elements has an eccentric reflecting surface (RSE) comprising an off-axis section of either a spherical surface (S) or an aspherical surface (ASE). The array of first optical elements is designed so as to form a plurality of arcuate light beams (108) capable of forming a plurality of light source images (I).

Abstract: A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is dampened in order to allow the tool to settle down and provide alignment after the tool is positioned as desired.

Abstract: The present invention has as its object to provide a thin type optical system which enables both of image information displayed on display means such as a liquid crystal display to be observed and image information of which image is substantially equal to the image observed via therethrough and which is taken by image pickup means and a compound display apparatus using such optical system.

Abstract: A head-mounted display (HMD) using retinal direct projection that provides a small size and lightweight by changing the configuration of optical components and optical arrangement. The HMD includes: a planar backlight for producing and emitting planar light; a light-speed controlling element positioned in front of the planar backlight for controlling the speed of incident light so that the light propagates parallel or near parallel to an optical axis; an image-forming element disposed in front of the light-speed controlling element for forming an image; and a Fresnel lens placed in front of the image-forming element for focusing the incoming incident onto an eyeball.

Abstract: A light guide for display devices of the head-mounted or head-up type comprises:

Abstract: A method for manufacturing a spectacle lens, in which at first a semi-finished uncut spectacle lens (hereinafter referred to as a blank) is produced, i.e. a spectacle lens having merely one finished optical surface (hereinafter described as base surface); subsequently a prescription-optimized surface is computed according to the data of a spectacle lens prescription; and then the prescription-optimized surface is finished according to the computed data. The invention is characterized by the following method steps: after the production of the semi-finished spectacle lens the base surface is measured; the prescription-optimized surface is computed and finished taking into account not only the individual data of the spectacle prescription, but also the actual shape of the base surface.

Abstract: An apparatus and method that provides for improved optical communication between at least one source and at least one destination, with reduced loss of power and superior retention of the quality of a signal when compared with the prior art. The apparatus has a body having at least one integrated optical channel along which a light signal is transmitted via an N-fold plurality of lenses. A light signal transmitted along the integrated optical channel is repeatedly refocused along the optical axis and is then highly focused at the second end. Optionally, the light signal can be switched, attenuated, filtered, tapped or monitored by positioning appropriate optical devices between the lenses.

Abstract: In a magnifying observation apparatus, simple observation conditions are set for simply acquiring a plurality of observation images. A plurality of simple observation images are acquired per the plurality of simple observation conditions set, and displayed on a simple observation image display section. A desired simple observation image is selected from among the plurality of simple observation images displayed on the simple observation image display section. The observation conditions are further set as required based on the simple observation conditions set to the simple observation image selected. An observation image acquired based on the observation conditions set is displayed.

Abstract: A method for assembling an optical disk apparatus involves disposing first and second short-cutting terminals at different faces of a housing and in parallel with a laser diode of the apparatus. In a first state of assembling, the first short-cutting terminal is shorted by a solder applied thereon. Thereafter, the apparatus is inspected in a second state of assembling in which the solder is removed from the first short-cutting terminal. After inspection, the second short-cutting terminal is shorted by a solder applied thereon. Subsequently, the solder on the second short-cutting terminal is removed.

Abstract: A semiconductor laser (41) is fixed onto a base part (22) with a submount (32) and a reference optical axis (5) is determined by the semiconductor laser (41). A groove (222) having a U-shaped section is formed on a bonding part (221), and solder (31) is applied in the groove (222) and melted and a collimator lens (42) supported by a supporting arm (61) is moved to the groove (222). A light beam emitted from the semiconductor laser (41) is guided through the collimator lens (42) to an image pickup part (7), where an image representing the state of the light beam is acquired. The collimator lens (42) is positioned with respect to the reference optical axis (5) on the basis of the image and fixed onto the base part (22) out of contact therewith, with the solder interposed therebetween. This simplifies a structure of an optical element module (11) in which the collimator lens (42) is positioned with respect to the reference optical axis (5) with high accuracy.

Abstract: An optical system including a lens (30) which is an optical part without a reflecting surface, wherein an incident optical axis (1) and an outgoing optical axis (2) does not agree with each other. An optical axis (4) of the lens (30) is not parallel with nor perpendicular to a plane including an incident position (25) of an incident light, an outgoing position of an outgoing light (55), and the incident optical axis (1) or the outgoing optical axis (2).

Abstract: An optical device for routing a plurality of optical signals between a first port and a second port is disclosed. The optical device includes a mirror array having a plurality of reflective elements. Each optical input signal is directed by a reflective element in a direction designated by a control signal. The optical device further includes a curved mirror for receiving each directed optical signal from the respective reflective element, and for reflecting each directed optical signal to the first or second port.

Abstract: An improved structure and method for building large-aperture lightweight deformable mirrors uses a hinged substrate. In addition to reduced weight, the approach provides rigidity to the mirror, which is necessary for the accurate response to actuator commands and tolerance to disturbances. No stresses are induced in the substrate due to the commanded deformation of the substrate, regardless of the magnitude of the deformation. Any stresses in the substrate structure are those induced due to forces in the face sheet, which are likely to be small using advanced nano-laminate and membrane face sheet technologies. The magnitude of the deformation (dynamic range) is limited only by the actuator stroke, and not by the stresses induced in the substrate. The design therefore accommodates small-force, large-stroke actuators, as opposed to the current designs that use large-force, small-stroke actuators.

Abstract: In a device to generate laser light, with a laser-active main resonator (2) and a coupled non-linear resonator (6), each of the two resonators (2, 6) being delimited by mirrors (8, 4; 4, 10), and one mirror (4) of the main resonator (2) being identical to a mirror (4) of the coupled non-linear resonator (6), it is provided that the non-linear resonator (6) is designed for a power loss less than 63% of the power which is coupled via the main resonator (2) and the mirror which delimits the coupled non-linear resonator (6), and the laser-active main resonator is designed so that in laser operation it has a threshold pump power which is less than one fifth, preferably less than one tenth, of the pump power which is used and using which this resonator is excited.

Abstract: A method of manufacturing a mirror for a dish reflector of a system for generating electrical power from solar radiation which includes the steps of: a) shaping a blank of defformable material to have a concave surface profile for a mirror, which step further comprises the steps of i) positioning the blank between two opposed curved former surfaces so that the former surfaces compress the blank to assume the shape of the former surfaces, ii) cutting the blank along a predetermined path of movement to separate the blank into parts, each part having a cut surface, iii) releasing the parts of the blank from the former surfaces to cause the cut parts to resume their uncompressed form, with the result that at least one of the parts defines the required concave surface, b) gluing or laminating or otherwise adhering together a back surface of a sheet of reflective glass and the concave surface of the shaped blank to form the mirror.

Abstract: An optical element 11 includes a bandpass filter made of a lamination of thin films respectively having different refraction factors so as to selectively allow light emitted from a backlight 6 to pass therethrough, and a polarizer 3, a quarter-wavelength plate 2 located between the bandpass filter 6 and the polarizer 3 so as to prevent light incident from the side of the polarizer 3 from being reflected by the bandpass filter 1 and then emitted from the side of the polarizer 3.

Abstract: A dispersive multilayer mirror (1) comprising several individual layers (2, 3) applied to a carrier substrate (4) and adjoining each other via parallel, plane surfaces having different optical constants and different thicknesses, wherein a wedge-shaped glass platelet (5) is fastened to the outermost individual layer (2) facing away from the carrier substrate (4) by optical contact.

Abstract: An objective optical element of an optical pickup apparatus has a magnification m1 satisfying the following formula for a light flux of the wavelength &lgr;1: −1/7≦m1≦−1/25 and |m1|<|M1, M1, where M1 is an optical system magnification from the first light source to the first optical information recording medium for a light flux of the wavelength &lgr;1. The objective optical element comprises a common region and an exclusive region. The exclusive region includes an exclusive diffractive structure having a function to suppress an increase of spherical aberration due to a raise of atmospheric temperature. A light flux of a wavelength &lgr;2 having passed through the exclusive diffractive structure intersects with the optical axis at a position different from the position of the converged light spot formed on the information recording plane of the second optical information recording medium.

Abstract: A method and apparatus for providing quadrature biasing for coupled-pair circuits. A QBCP-circuit for quadrature amplifiers provides a new input common-mode sense point that separates the inputs for the differential-and-common mode feedback-control loops. The QBCP circuit biases all four transistors equivalently and reduces the feedback-loop interaction, thereby simplifying the bias control system and improves the voltage-transfer frequency-response performance.

Abstract: A method and apparatus for providing matched differential MR biasing and pre-amplification. Tightly matched and well centered low-level MR bias voltage is provided directly to the sensing element for controlled input-impedance differential pre-amplification without common-mode voltage level control with loops.

Abstract: A dual mode write driver providing both a voltage mode of operation and a current mode of operation by combining the required topology in a write driver circuit to allow either current mode operation or voltage mode operation. A logic control signal is applied to an input to the dual mode write driver to cause the circuit to configure for either voltage mode operation or current mode operation. The dual mode write driver is typically used in a tape or disk drive system to write data onto a tape or disk recording medium. The dual mode write driver has a first PFET (P3) coupled to a first NFET (N1) at a first node which is connected through a resistor (R1) to a first side of a write head (L1) of the write driver, and a second PFET (P4) coupled to a second NFET (N2) at a second node which is connected through a resistor (R2) to a second side of the write head.

Abstract: A method and system for calibrating the write current of a current mode write driver having a first PFET coupled to a first NFET at a first node which is connected to a first side of a write head of the write driver, and a second PFET coupled to a second NFET at a second node which is connected to a second side of the write head. The current mode write driver also defines an INODE where a source of the first NFET is coupled to a source of the second NFET, and the current mode write driver is put in a state where all four FET devices are in an off condition. A precision resistor R is connected from the INODE I/O pin of the write driver to a positive potential VDD I/O pin of the write driver, such that a current I1 is caused to flow. Then the actual value of I1 is calculated by first measuring the voltage V across the precision resistor and then calculating the precise current from I1=V/R.

Abstract: Bi-Variant Coupled Pair (BVCP) circuits suitable for use in channel front-end low noise preamplifiers of magnetic storage devices are described. In a magnetic storage device, a BVCP circuit provides a DC bias voltage for a read transducer, low-noise amplification performance, and relatively small AC coupling capacitor values for reducing the cost of an integrated circuit (IC) in which the BVCP circuit may be embodied. The BVCP circuit also has a controllable input impedance for matching a transmission line impedance for high data rate applications.

Abstract: A voltage determination unit dynamically determines a first voltage required to maintain the rotational speed of a spindle motor (SPM) at the rated rotational speed according to a rotational state of the SPM. A CPU determines a second voltage for driving the SPM by software processing in a software control mode. A voltage generator generates the first voltage determined by the voltage determination unit as driving voltage in a hardware control mode and generates the second voltage determined by the CPU as the driving voltage in the software control mode. A driver circuit drives the SPM by the driving voltage generated with the voltage generator.

Abstract: A method and apparatus for providing a marker at the end of the adaptive self-servowrite process for adaptive formatting via the self-servowrite process. The mark is used later in the drive manufacturing process to identify the number of tracks written on the surface and thus determine the appropriate format to use in the drive.

Abstract: Disclosed is a method measuring the height of a magneto-resistive element (MRE) on a padded slider in a disc drive based on a change in the resistance of the MRE. During operation of the disc drive a biasing current is applied to the MRE head. Next a resistance value of the MRE head is calculated by determining the voltage drop across the MRE head. The resistance of the MRE head is dependent upon its temperature. The temperature of the MRE lowers as its proximity to the disc increases, as the cooler disc surface acts as a conduit drawing heat away from the MRE. This measured resistance value is compared to a threshold value. The threshold value is based upon the resistance of the MRE head at a threshold temperature, which corresponds to a specific distance away from the disc surface. If the measured resistance is lower than the threshold resistance the method outputs an indication to a user that the drive is in danger of failing.

Abstract: A main magnetic pole core of a metallic soft magnetic multi-layer film is formed on a substrate via a non-magnetic insulation film, two detecting conductor films are made contact with both side faces of the main magnetic pole core respectively, and a high-frequency signal is applied across the two detecting conductor films. When a magnetic flux passing through the main magnetic pole core changes, its impedance changes, and this change is taken out as the change in the amplitude of the high-frequency signal. A pair of electrode terminals connected to both ends of the detecting conductor films respectively, a power source terminal and a ground terminal are formed on the substrate. A semiconductor bare chip used as a high-frequency amplifier is installed so as to be opposite to these terminals, whereby the terminals of the bare chip are directly connected to the electrode terminals, power source terminal and ground terminal.

Abstract: A magnetic head includes core blocks having a medium sliding surface formed on one surface of the core blocks, the medium sliding surface having a slender convex curved shape formed along a sliding direction of a recording medium from the upstream side of the sliding direction to the downstream side, and the medium sliding surface having a magnetic gap formed thereon, wherein the medium sliding surface is shaped along a longitudinal direction thereof like a circular arc with a radius of curvature R while being shaped along a width direction like a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, so that the radius of curvature r is continuously reduced with closer distance to the downstream end of the recording medium sliding direction from a vicinity of the magnetic gap, so that by employing the above magnetic head, a long life magnetic head with small damage due to foreign material adhesion as well as small abrasion can be provided.

Abstract: A method and apparatus for forming a high conductance, high aspect ratio structure in a single low temperature copper chemical vapor deposition step. The present invention includes topographical features to increase a conformal coverage area.

Abstract: A method for forming a trimmed upper pole piece for a magnetic write head, said pole piece having a uniform width above and below a write gap layer. Prior art methods of trimming pole pieces to a final width using ion-beam etches produce pole pieces with thickness differentials due to the etch resistant nature of the alumina write-gap filling material. The present method uses NiCr, NiFeCr or Ru as write gap filling materials which have an etch rate which is substantially equal to the etch rate of the other layers forming the pole piece and are highly corrosion resistant.