Abstract: A lens device which is applied to a projection type image display apparatus includes an outer tube and an inner tube forming a tube structure having an optical lens and a thermal react material such as bimetallic sheet disposed between the outer tube and the inner-tube. Lens focus is corrected by moving a relative position between the outer tube and the inner tube in an optical axis direction to thereby maintain an initially set focus position to obtain an image of high picture quality.

Abstract: A lens holding device and a lens system equipped with the holding device are simple in structure and low in cost. The lens holding device includes a cylindrical lens barrel that is structured as one body with a single plastic lens and has an inside diameter larger than the effective diameter of the plastic lens. A holding ring, made from an impermeable substance, holds at least one lens that has been inserted into the lens barrel and fixes the position of the lens. The holding ring covers the edge surface of the lens barrel.

Abstract: An imaging system including a Gaussian light source, such as a laser diode, an image plane, and an optical system located between the light source and the image plane. The optical system has an optical axis, a first principal focus and a second principal focus. The image plane is located at the second principal focus of the optical system. The optical system creates a Gaussian intensity profile on the image plane whose e.sup.-2 intensity diameter on such plane is substantially constant even when the Gaussian light source being imaged by the optical system shifts along the optical axis.

Abstract: The present invention is an instrument (10) which includes a tubular section (12) having a wall (13) made of a material exhibiting superelastic characteristics and a delivery tube (14) having a bore (15) through which the tubular section (12) passes. The instrument (10) may be adapted for use in medical/dental and non-medical procedures. The superelastic character of the wall material is used in combination with the delivery tube (14) to alternately restrict the shape of the wall (13) and allow it to change to its unconstrained shape. Thus, the wall (13) can be sufficiently deformed to permit the tubular section (12) to pass in and out of and through the delivery tube (14) while at the same time enabling the tubular section (12) to have a shape when extended outside of the delivery tube (14) that is sufficiently bent or curved to be suitable for performing a desired function, for example a medical or dental procedure inside a patient's body.

Abstract: A projection TV set apparatus includes a lens, a mirror sleeve for holding the lens, and a buffer material provided at a connecting portion between the lens and the mirror sleeve and having a smaller modulus of elasticity than the lens. Also, a projection lens assembly for a projection TV set apparatus which is arranged in front of a light source of the projection TV set apparatus includes a mirror sleeve and at least one lens fitted inside the mirror sleeve having projections formed at at least three locations in the radial direction on the outer circumference of the lens to contact a connecting portion of the mirror sleeve.

Abstract: An integrally-driven type optical head (1) in which a laser optical system (20) provided with a semiconductor laser (22) and a light receiving device is mounted in a moving part of an actuator (50). In this optical head, the moving part (5) is constituted by uniting a heat radiator (10) made of a metal or the like with a heat insulator (9) made of a plastic or the like. The heat conduction bonding of the heat radiator to the semiconductor laser is performed. A coil of the actuator is securely fixed to this heat radiator through the heat insulator. Thereby, heat generated from the semiconductor laser is transferred to the heat radiator and is then radiated from the surface of the heat radiator to the external space of the optical head. Further, in case where heat is generated by the coil when the actuator operates, the laser optical system can be prevented from being heated, because of the fact that the heat conductivity between the coil and the laser optical system is low.

Abstract: A zoom lens device includes an imaging device for converting light from an object to an electrical signal, a zoom lens and a focusing lens disposed between the object and the imaging device, a zooming adjusting circuit for adjusting a movement of the zoom lens, focus adjusting circuits for adjusting movements of the focusing lens, correcting circuits for outputting an adjustment value in response to adjustment of the zoom lens, a temperature detecting circuit for detecting a temperature around the object, and a coefficient circuit for correcting a correction value of the correcting circuit based on an output signal of the temperature detecting circuit.

Abstract: Fitting holes are formed on a line of extension or a substantially vertical bisector in an arranging direction of a pair of lenses of a plastic plate formed integrally with at least the pair of lenses. Correspondingly, bosses are formed protruding from a base body using an adherable material so that a height thereof is larger than a sum of a thickness of the plastic plate and a thickness of a stop plate. Even after attaching the stop plate and the plastic plate to the base body, the bosses are protrudable from the plastic plate. Thus, the plastic plate and the stop plate are fixed in a sandwiched state between the base body and an adhesive agent. The plastic lens having a poor adhesion with the adhesive agent can be surely fixed without increasing the number of parts, and an instability of a positional accuracy due to environmental changes is obviated.

Abstract: A lens barrel holding apparatus for fixing a lens barrel having at least one optical element. The apparatus fixes a lens barrel to a lens barrel holding bed. The lens barrel has a flange portion formed along the circumferential direction of the outer peripheral portion of the lens barrel. The lens barrel holding bed has a cylindrical recess of a diameter larger than the outer diameter of the flange portion. The apparatus includes a plurality of bar-like first supporting members for coupling the bottom surface of the recess and the flange portion together. Also included is a second supporting member that has at least three bar members disposed on the upper part of the flange portion along the circumferential direction of the flange portion so as to surround the lens barrel. The at least three bar members are coupled to the flange portion and to the lens barrel holding bed.

Abstract: A thermally compensating lens mount (40) comprises an axially symmetric housing (42) that is formed from an inner layer of a first material (44) having a low coefficient of thermal expansion (CTE) to an outer layer of a second material (46) having a high CTE. The longitudinal cross-section of the housing (42) has a barrel shaped geometry along the symmetry axis (47) so that differential thermal expansion of the first and second materials (44, 46) decreases the length of the housing (42) along its axis of symmetry (47) by an amount determined by the CTEs of the inner and outer layers (44, 46), their thicknesses, and the geometry of the barrel shape.

Abstract: Unwanted positional shifts between two objects, such as lenses, are precisely compensated during thermal changes by use of a passive mechanical system. Materials with differing coefficients of thermal expansion and angled interfaces transforms a longitudinal dimensional change into a fine transverse dimensional change to precisely control movement as a function of temperature thereby maintaining, e.g., lens focus. Compensation movement can be to reduce or increase the spacing between objects such as lenses during a thermal change.

Abstract: A refractive lens element (16) with a very thin edge thickness is mounted to withstand gun shock loads by utilizing a cell cradle (14) that is contoured to conform to the lens element surface profile (24). The lens is employed in a system having a rectangular clear aperture (26) which when projected on the circular lens defines four lens segments (36a-36d) outside of the clear aperture. The cell cradle has an opening (26) conforming to the clear aperture and carries a compliant padding (40) coextensive with the lens segments outside of the clear aperture to support the lens axially. The lens perimetrical edge (20) is bonded to the cell with a compliant bond material (44) to secure the lens in a radially symmetric position.

Abstract: In a camera lens group having both glass and plastic lenses mounted in a lens frame, where at least one of the lenses is movable along the optical axis, a spacing member and a resiliently deformable member are each arranged in an interval between lenses in the lens group. The resiliently deformable member biases one of the lenses away from the spacing member, and the spacing member reduces the range of possible movement of the movable lens.

Abstract: An apparatus for setting the rotational torque of a screw mechanism including a frictional member which is positioned between a lens frame and a lens frame holder. The frictional member can be made of natural fiber, sponge, rubber, or styrene foam.

Abstract: An optical mounting system is configured so as to locate a 360.degree. shoulder all around the optical element periphery in both the object and image sides of the optical element. The shoulder allows expansion or contraction of the optical element both in the thickness direction of the optical element and in the direction normal to the optical axis when installed in the mounting assembly. Three small metal clips are used to maintain centering of the optics, the thermal expansion and contraction of these clips being coordinated with the clip geometry so that the optical material remains centered without induced stress or free play at either room temperature or at the operating temperature.

Abstract: A lens mounting system (36) comprises a lens mount (53) having a cylindrical inner surface to define an internal cavity. An annular mounting member (46) projects into the cavity and has a fixed forward facing mounting surface (48). A mounting ring (52) threadedly engaged with the inner surface is selectively movable between a withdrawn position distant from the mounting member (46) and an advanced position adjacent thereto. A lens (40) for the system includes a forward facing optical surface (42), a rearward facing optical surface (44), and an annular mounting member (46) at an interface between the first optical surface (42) and the second optical surface (44).

Abstract: An electro-optic imager, used for exposing photosensitive media, wherein a modulator, e.g. an array of PLZT light valves, is used to modulate one or more light beams. Temperature control is applied to the modulator to reduce or eliminate variations in response characteristics which would otherwise change the color balance of the final print from the desired color balance.

Abstract: In an image device wherein rays from LED arrays are guided through single lenses to form an image, LED arrays are arranged on a base plate, single lenses are arranged on a lens plate, the distance between the base plate and the lens plate is kept constant by using a spacer, and the coefficients of thermal expansion of the lens plate, base plate and spacer are made virtually identical to each other.

Abstract: An imaging optical system for compensating for changes of temperature according to the present invention corrects a focal point for an entire optical system due to temperature change by changing a relative distance between a lens and a light receiving element. To this end, a correcting member, which expands and contracts due to temperature change, is disposed between the lens and the light receiving element. Moreover, the coefficient of thermal expansion is set to such a value so as to be able to substantially correct for the focal point change. According to another aspect of the present invention, the optical system includes a lens system which has at least a positive lens and a negative lens in order to offset the effect of the temperature change.

Abstract: An optical head assembly includes a light beam source and collimating optics mounted in an active, thermally-compensated assembly. A collimating optics mount preferably in the form of a flexure plate having a three-point elastic hinge is supported on a base plate by a respective number of equally-spaced actuators. The motion of the flexure plate is thereby over constrained and allows the operation of the elastic hinge to benefit from elastic averaging such that motion of the flexure plate may be effected by the actuators individually or in combination. Controlled flexure plate motion may be implemented to compensate for thermal shifts in system focal length, while maintaining radial and angular alignment of the collimating optics relative to the beam source, according to the influence of the individual actuators.

Abstract: A laser telescope is provided for reducing undesired laser thermal lensing effects which would otherwise impair the intensity and quality of a laser beam passing therethrough. An outer barrel is mounted in a chamber within a housing by ball bearings which hold the outer barrel longitudinally fixed but permits rotation of the outer barrel about its longitudinal axis. An inner barrel is coaxially situated within the outer barrel and includes a threaded outer surface which is threaded into a threaded inner surface of the outer barrel. A first lens is mounted adjacent one end of the chamber and a second lens is mounted in the inner barrel. A laser beam is directed through the laser telescope along the common axis of the chamber, the outer barrel, and the inner barrel. The lens spacing in the barrels is sensed and actuates a drive motor in proportion to the error between the sensed lens spacing and the desired lens spacing.

Abstract: The described joint (1, 3, 2) consists of at least three joint parts preferably with different material composition and thus different thermal expansion coefficients .alpha.. For optimum compensation of the deformation differences acting predominantly radially, which result with a temperature change, it is proposed to provide between a first joint part--for example an optical lens (1)--and a second joint part--for example a lens mounting (2)--at least one further joint part as intermediate ring (3), the ring thickness-dimensioning thereof and the material selection thereof (thermal expansion coefficient .alpha..sub.R) being carried out in such a manner that the aforementioned deformation phenomena, which are material-specific and caused by temperature change, in the joint (1, 3, 2) compensate themselves in such a manner that a stress-free or low-stress mounting, for example of microoptics (1) for use in polarization-optical instruments, can be realized.

Abstract: A system for maintaining desired temperature control of a specimen observed under a microscope includes an objective lens heater comprising a heating element placed within a heat sleeve, which surrounds the objective lens casing. When an electric current is applied, the heating element is activated, heating the objective lens to a desired temperature. The heated objective lens may be used in combination with a stage heater to ensure that the specimen will be maintained at a desired physiological temperature during observation.

Abstract: In a first preferred embodiment of a thermal rotary actuator constructed according to the present invention, an actuator body includes first and second spaced, parallel linear actuator elements each linear actuator element having a respective predetermined coefficient of thermal expansion (CTE) and respective first and second ends defining the linear actuator element length. The linear actuator elements, in response to a selected temperature differential therebetween, are thereby subject to a predetermined length differential. Means are provided for effecting the selected temperature differential in the first and second linear actuator elements to thereby effect the predetermined length differential. First yoke means, attached to the first ends of the first and second linear actuator elements, include fixing means for fixing the first ends in a predetermined spatial relationship, and means for flexibly attaching said fixing means to the reaction structure.

Abstract: Beam scanning system that incorporates an actively-controlled optical head, wherein a light beam source and collimating optics are mounted in an active, thermally-compensated assembly. A collimating optics mount preferably in the form of a flexure plate having a three-point elastic hinge is supported on a base plate by a respective number of equally-spaced actuators. The motion of the flexure plate is thereby over constrained and allows the operation of the elastic hinge to benefit from elastic averaging such that motion of the flexure plate may be effected by the actuators individually or in combination. Controlled flexure plate motion may be implemented to compensate for thermal shifts in system focal length, while maintaining radial and angular alignment of the collimating optics relative to the beam source, according to the influence of the individual actuators.

Abstract: An athermalized optical system and method are disclosed. A thermally compensating portion of the optical system is employed to compensate for mechanical and optical thermal effects in the entire optical system. In the preferred embodiment, the optical system comprises an imaging system having a laser diode light source, a collimating lens, a rotating mirror, a scan lens and a media transport. Temperature compensation of the imaging system is obtained by varying the spacing between the laser diode and the collimating lens to decollimate the laser light beam as a function of the system wide temperature effects.

Abstract: A ball lens assembly constructed of a lens holder formed with a press-fit hole having a circular section and a ball lens press-fitted with the press-fit hole of the lens holder. The lens holder is formed by sintering stainless steel powder. As the lens holder is formed by sintering, a force for press-fitting the ball lens into the lens holder can be suppressed to thereby effectively prevent breakage of the ball lens.

Abstract: An athermalized beam source and collimator assembly includes a collimator lens spaced from a novel circular foldback flexure plate by a lens barrel. The circular foldback flexure plate incorporates a circular foldback flexure adjacent the beam source mount to isolate the beam source from the ambient environment and to athermalize the assembly. The beam source mount and circular foldback flexure plate are composed of a material that is identical in composition and CTE as the portion of the beam source that is attached to the beam source mount. The temperature of the beam source may then be maintained by a thermal element mounted to the back surface of the flexure plate, without the occurrence of mechanical strain at the interface between the beam source and beam source mount.

Abstract: Apparatus for providing athermalized collimation of a light beam source by a light beam collimator includes beam source support for fixing the beam source at a predetermined position thereon and for thereby defining a light beam optical axis; collimator support for aligning the collimator at a beam collimator position on the optical axis; and thermal compensator operatively connected between the beam source support and the collimator support. The thermal compensator is operable to selectively displace the collimator along the optical axis and thereby displace the collimator. In a particular feature of the invention, the thermal compensator comprises a composite laminate construction of fiber strands, wherein the coefficient of thermal expansion .alpha. of the thermal compensator is determined by the alignment of the fiber strands.

Abstract: An image-reading device comprises a lens unit array comprising an array of distributed refractive index plastic cylindrical lens elements and plastic plates, adhering the distributed refractive index plastic cylindrical lens elements therebetween, and a plastic case containing and holding the lens unit array. The difference in the thermal expansion coefficients of the plates of the lens unit array and the plastic case is 5.0.times.10.sup.-5 cm/cm/.degree. C. or below, or more preferably, 3.0.times.10.sup.-5 cm/cm/.degree. C. or below. The plastic case is formed by connecting, in a longitudinal arrangement, a plurality of case segments formed by an injection molding.

Abstract: An athermally compensated printhead includes a laser diode having predetermined characteristics for generating a beam of light, a diode mount, cooling means, a collimator lens, and a len mount. The diode mount is formed of a predetermined material with a predetermined coefficient of thermal expansion for mounting the laser diode in the printhead. The cooling means is used to maintain the laser diode at a substantially constant operating temperature for longer life and to avoid wavelength changes. The collimator lens has characteristics which provide predetermined changes in focal length versus changes in ambient temperature over a predetermined temperature range. The len mount is formed of a predetermined material having a predetermined coefficient of thermal expansion for mounting the collimator lens adjacent a first major surface of the diode mount to receive the beam of light from the laser diode.

Abstract: Apparatus for the soundproofing of moving picture cameras with a soundproof mounting of the camera skeleton supporting the parts of the camera mechanism which generate noise and vibrations in a camera housing, which has a lens holder, to which interchangeable lenses can be fastened, whereby for the soundproof mounting of the camera skeleton in the camera housing, there are several soundproofing connecting elements between the camera skeleton and the camera housing, at least some of which have a directional natural rigidity.

Abstract: A scanning optical system has a light source for emitting a light beam; a condenser lens for changing the light beam from the light source to a parallel light beam; a connection holding member for supporting the light source and the condenser lens; a deflector for deflecting an approximately parallel light beam transmitted from the condenser lens at an equiangular velocity; and a lens for optical scanning for scanning a scanned face at an approximately equal speed while converging the light beam deflected by the deflector and forming an image in the shape of a spot on the scanned face, the lens for optical scanning being formed by a plastic material for optics.

Abstract: A focus compensating lens structure wherein a lens means for collimating laser light produced by a source has an index of refraction which varies with temperature and wavelength to compensate for temperature effects on the wavelength of light produced by the laser source and the length of the mounting on which the source and lens are disposed.

Abstract: A mount for mounting a lens in an optical scanning device includes a tubular portion having a first surface which rotatably supports the lens. A second surface includes a plurality of arcuate supports. An annular spring is supported by the arcuate supports and is bent at the points of contact with the supports to extend outwardly beyond the supports to bias the mount and the lens against the scanning device in which it is mounted.

Abstract: An optical assembly comprises a light beam source, a collimating lens, and a passive thermally-compensated structure. Concentric rings of dissimilar material are supported by a baseplate and arranged to support a flexure plate at a predetermined distance above the baseplate. The collimating lens is mounted on the flexure plate. A difference in the thermal coefficient of expansion of the rings is chosen so that the flexure plate moves to compensate for thermal shifts in system focal length, while maintaining radial and angular alignment of the lens relative to the laser diode source, so as to provide controlled axial movement of the collimating lens.

Abstract: A scanner includes a light source for producing a light beam and a multifaceted polygon for directing the light beam to a spot on a surface to be scanned, such as at the surface of a photoreceptor or a document to be read, that is located at a predetermined location relative to the polygon and for moving the spot across the surface along a scan line or predetermined length. The scanner also includes a post-facet lens system with first and second elements configured to compensate for field curvature and wobble without compensating for scanner non-linearity. They are composed of plastic, the surfaces of the elements having curvature in both the scan plane and the cross-scan plane as well as less magnification than existing post-facet lens systems.

Abstract: Installing of an optical component on a housing case. One side of the optical component to be installed is abutted to a reference surface formed on the housing case for positional regulation thereof. A heat-fusible protrusion is formed on the housing case at the position which is opposed to the reference surface and has a vertical length enough to be beyond the top surface of the optical component seated on the housing case. Heat is applied to at least a part of the fusible protrusion to be fused onto the optical component with abutting the one side of the optical component to the reference surface. The fused portion is let to be hardened for regulating the position of the other end of the optical component, whereby the optical component is fixed onto the housing case with regulating the posture thereof in the direction crossing to the reference surface.

Abstract: A thermally and mechanically stable muzzle reference system collimator asbly. The assembly comprises a muzzle reference system collimator and an adaptor plate to adapt the muzzle reference system collimator to the muzzle of a gun. The muzzle reference system collimator and adaptor plate are made up of materials having a low coefficient of thermal expansion. The adaptor plate is bonded to the gun barrel through materials which are capable of absorbing, rather than transmitting, the shock of firing to the muzzle reference system collimator and its fragile internal optical components.

Abstract: A heat sterilizable electronic video endoscope is provided in which a lens system is mounted by the use of elements such as metal spacers, which are not adversely affected by heat. Similarly, the electronic circuitry is arranged in the center of the endoscope and is formed of heat resistant material. In addition, glass fibers are provided which surround the lens system and the electronic circuitry to further protect it from the heat of sterilization. The light fibers themselves are made of glass and are not adversely affected by the heat sterilizing process. In addition, a sterilizable sheath may be provided which will extend over the endoscope and has an accordion shaped extension to extend along the electrical cable and light cable for those situations where it is not possible to resterilize the endoscope for a second procedure. In addition, a removable handle can be provided over the sheath which facilitates positioning the endoscope during an operative procedure or investigation.

Abstract: Lenses, which include at least one plastic lens, are supported in a lens barrel by a lens holding structure which includes shoulder surfaces and inner circumferential surfaces of a lens barrel, at least one annular elastic member, and a retainer ring. The lenses are radially positioned in coaxial alignment with the lens barrel by the inner circumferential surfaces of the lens barrel, and axially positioned in engagement with the shoulder surfaces by the elastic member and the retainer ring. The elastic member elastically presses one of the lenses against one of the shoulder surfaces, and the retainer ring is threadedly mounted on the outer end of the lens barrel end holds the other lens against the other shoulder surface. Annular spacers may be disposed between the outer circumferential edges of the lenses and the inner circumferential surfaces of the lens barrel, for holding the lenses in coaxial alignment with the lens barrel.

Abstract: An optical mirror is kinematically mounted at its sides on one fixed point and two movable points which points are supported by a frame spaced from the mirror. One of the movable points is a ball on a cantilevered arm which rests in a cone or groove in the mirror, the other movable point is a mechanical flexure prelaod mounting or a pneumatic preload mounting, which mountings serve to apply constant preload to such mirror. The mirror is made of ceramic material, of low thermal expansion or contraction and has water cooling passages therein. The frame is made of metal of higher thermal expansion or contraction. However such mirors, when reflecting a high intensity laser beam can thermally expand relative to the frame and must do so with minimal deformation from the desired optical contour thereof which result is accomplished by the resilient and constant preload mountings of the present invention.

Abstract: An optical coupling system in which the space between a CRT and a projecting lens, both of which are optically coupled together, is filled with a specific liquid has been employed in the optical system of a projection-type television. In such a system an increase in the temperature of the CRT increases causes the temperature of the specific liquid or optical coupling liquid to increase, resulting in a variation in the refractive index of the liquid which causes a projected image to be defocused. In order to correct such a defocusing of the image, a single lens in contact with the liquid is allowed to move by a small amount in the optical axis direction. In other words, the external periphery of the signal lens is supported by a layer composed of a rubber-like elastic body. In such an arrangement, the volume expansion of the liquid can be utilized to move the single lens by a small amount. The defocusing of the image is thus corrected.

Abstract: A scanning optical system has a light source for emitting a light beam; a condenser lens for changing the light beam from the light source to a parallel light beam; a connection holding member for supporting the light source and the condenser lens; a deflector for deflecting an approximately parallel light beam transmitted from the condenser lens at an equiangular velocity; and a lens for optical scanning for scanning a scanned face at an approximately equal speed while converging the light beam deflected by the deflector and forming an image in the shape of a spot on the scanned face, the lens for optical scanning being formed by a plastic material for optics.

Abstract: Mounts for plastic lens elements of differing diameters or materials include a separate V-block for mounting each lens element, wherein the V-blocks for lens elements of a smaller diameter converge at angles less than V-blocks for lens elements of a larger diameter, the angles of convergence being selected so that the centers of the lens elements remain aligned with an optical axis perpendicular to both of the lens elements upon thermal expansion of the lens elements.

Abstract: A scanning optical apparatus comprises a first imaging optical system for imaging a light beam collimated by a collimating optical system so as to form a linear image. The first imaging optical system includes a vari-focal lens using liquid crystal. A scanning deflector is provided for deflecting a light beam which has emerged from the first imaging optical system and for scanning a target with the light beam in a first direction. Electric circuit is provided for varying focal length of the vari-focal lens by generating changes in orientation properties of crystal liquid of the vari-focal lens in synchronization with the timing of scanning of the deflector. A second imaging optical system is provided for imaging a light beam deflected by the scanning deflector on the target. The second imaging optical system is adapted to maintain a geometrically conjugate relationship between the scanning deflector and the target in a second direction perpendicular to the first direction.

Abstract: An optical magnifying lens installed in the hub of a plier-grip or similar instrument and which also holds the instruments's mating halves together in a snugly rotatable position.

Abstract: Laser light emitted from a light source is deflected in a predetermined direction by a rotary polygonal mirror to scan the surface of a photosensitive medium. A correction lens corrects the focal point of the laser light deflected by the rotary polygonal mirror. The correction lens is formed by cutting a circular lens along a plane off the optical axis thereof and removing a segment of shorter arc therefrom. The correction lens is held by a lens holder by way of being pressed by a pressing member both in the radial direction and in the direction of the optical axis thereof to the lens holder.

Abstract: Device for connecting two components of a motion-picture camera. A thermal expansion compensation pendulum (Rost pendulum) (3) is disposed between the two components (10, 11), said pendulum being composed of a first element (31) connected with one component (11), a second element (32) connected with the component (10), and at least one intermediate element having axial and/or radial play between both elements (31, 32) and being connected therewith. The coefficient of thermal expansion of the intermediate element or elements (33) is a multiple of the coefficients of thermal expansion of the first and second elements.