Abstract: A total-focus imaging apparatus comprises a variable-focus lens unit with a focal position thereof changeable at high speeds, a CCD element, a microcomputer and a liquid-crystal display unit. The microcomputer includes an image memory, an image processing circuit and a control circuit. The variable-focus lens unit and the CCD element allow an object of observation to be photographed to generate a number of images with the focal positions thereof slightly different from each other and the image to be stored in the image memory. Pixels each brought to a focus are selected by the image processing circuit from pixels of the images to generate an image of the observation object comprising only pixels each brought to a focus. Such an image is then displayed on the liquid-crystal display unit. Thus, an image of the observation object which is all but completely brought to a focus can be presented in a semi-real-time manner.

Abstract: A temperature compensating focuser and method for use, with a telescope includes providing a temperature sensor adapted to measuring temperature at the telescope body, a lens support for one of the focus optics and a control. The control includes a motor adjusting the support to modify a distance between the focus optics of the telescope in response to changes in temperature sensed by the temperature sensor. The control may further include a learning mode for establishing a temperature coefficient of the telescope. The control may further include a memory for storing a relative position of the lens support and a temperature value when power is removed from the control. The control adjusts the lens support according to the relative position and temperature values in memory and temperature sensed by the temperature sensor when power is restored to the control.

Abstract: An optical communication device which has an optical module including an optical element and a lens system optically coupled through a space and housed in a package, a supporting member for supporting the optical module, and a fixing member directly placed over the optical module for removably fixing the optical module on the supporting member, wherein the optical module is securely sandwiched between the supporting member and the fixing member, and a method of fixing the optical module for use in the optical communication device.

Abstract: A fly eye lens has cells in an optical functional portion, and first, second, and third positioning portions on an outer edge. The first and second positioning portions are located in a region of a plane normal to the optical axis of the lens, divided by a first reference line extending through a center of thermal expansion and located in the plane. The first and second positioning portions have side surfaces located on the first reference line. The third positioning portion has a side surface located on a second reference line intersecting the first reference line, extending through the center of thermal expansion, and located in the plane. Even when the fly eye lens thermally expands, the position of the center of thermal expansion does not change in an optical system, and desired optical performance can be continuously achieved.

Abstract: A technique for controlling the coefficient of thermal expansion of composite structural members (16, 18, 20, 22) in an optical assembly (10) to maintain precise alignment between optical components (26, 28). The technique includes measuring the coefficient of thermal expansion of each composite structural member (16, 18, 20, 22) and identifying a target structural member having the highest coefficient of thermal expansion. A small end portion of the non-target structural members (16, 18, 20, 22) is removed and replaced with a spacer member (38). The spacer member (38) is made of a material so that the combination of the coefficient of thermal expansion of the spacer member (38) and the structural member (16, 18, 20, 22) matches the target coefficient of thermal expansion. Additionally, the thickness of the spacer member (38) is selected so that the overall length of each of the structural members is the same.

Abstract: A method and apparatus for centering an optical component, such as a lens element, within an optical bore sleeve. The optical component has an outer perimeter, and the optical bore sleeve has an inner perimeter for receiving the outer perimeter of the optical component. A plurality of deformable ridges are interposed between the outer perimeter of the optical component and the inner perimeter of the sleeve for aligning the optical component and the sleeve along a common optical axis as the ridges are deformed upon insertion of the optical component into the sleeve.

Abstract: Several embodiment of an athermalizing apparatus is described. In one embodiment, the athermalizing apparatus includes a lens element and a support member coupled to the lens element. The support member has a sloped outer surface and a first coefficient of thermal expansion (“CTE”). The athermalizing apparatus further includes a rib member having a substantially complementary sloped surface that bears on the sloped outer surface of the support member. The rib member has a second CTE. The sloped outer surface of the support member forms a ramp angle with respect to an optical axis of the lens element. A radial expansion of the support and/or rib member causes an axial displacement of the support member as a function of the ramp angle.

Abstract: A lens barrel includes an optical element having a light-transmissive surface which is deformed by own weight thereof and/or by being supported, and a plurality of protrusive parts which support the optical element. The plurality of protrusive parts are disposed in such a way as to enable the light-transmissive surface of the optical element to be deformed symmetrically with respect to a plane which includes an optical axis.

Abstract: A package for housing optical components where the enclosure has two enclosures. The first enclosure for the optical components (the optical enclosure) provides necessary alignment and hermeticity as well as a heat pipe to dissipate heat generated by the optical component. The second enclosure for the electronic components (the electronic enclosure) provides proper hermeticity and heat dissipation devices (e.g., a Peltier cooling device). The first enclosure can sit atop the second enclosure or vice versa. In an embodiment, a heat sink can be attached to the top of the dual-enclosure assembly.

Abstract: An endoscopic optical system includes an elongate metal housing with a circular opening in its end in which a transparent window is received. The window has a cylindrical outer edge surface which is metallized over at least part of its area and is opposed to the cylindrical internal surface of the opening. An annular solder joint is provided in the gap between the opposed cylindrical surfaces. The solder joint has a thickness in the direction perpendicular to the window which is only a proportion of the thickness of the window.

Abstract: An optical apparatus having a temperature compensating function includes an optical element holding frame arranged to hold an optical element, a support member arranged to support the optical element holding frame for movement in a direction of an optical axis and having a cam for moving the optical element holding frame in the direction of the optical axis, and a correction member arranged to expand or contract in a direction orthogonally intersecting the optical axis according to temperature variation, wherein the optical element holding frame rotates in association with expansion or contraction of the correction member so as to be moved in the direction of the optical axis along the cam of the support member.

Abstract: In a process for the correction of non-rotationally-symmetrical image errors in an assembly, e.g., an objective with optical elements, particularly lenses, several Peltier elements are arranged on at least one of the optical elements, distributed over its periphery, and are differently driven electrically in order to act on the temperature distribution in the optical element. A respective temperature-conducting connection is provided between the Peltier elements and the optical element. The invention also relates to an objective with optical elements, particularly lenses, and Peltier elements.

Abstract: A lens-fitted film unit is provided with a thermally expandable axial distance adjusting member which has a thermal expansion coefficient greater than plastic lens elements of a taking lens held by an axially movable lens holder and disposed between the lens holder and a stationary shutter cover and which expands or contracts in accordance with a change in ambient temperature to change an axial distance between the lens holder and a film plane so as thereby to shift a focal point of the taking lens in an axial direction to compensate a variation of the focal length of the taking lens due to a change in refractive power of the plastic lens element which is caused by axial expansion or axial contraction of the plastic lens element due to the change in ambient temperature.

Abstract: An optical mounting for an optical component includes an inner, preferably multi-part, portion that abuts the optical component and an outer frame, which are connected together by a plurality of spring hinge beams. The spring hinge beams and other portions of the optical mounting are produced galvanoplastically.

Abstract: A thermal compensation system for an optical lens that has a focus adjustment with visible focus distance numerals and a juxtaposed index line for identifying the focus distance. The index line is provided on an internal ring slidably mounted to rotate circumferentially with respect to a barrel portion of the optical lens that includes the focus distance numerals. An actuator mounted within the optical lens includes a wax motor that is responsive to temperature changes and mechanical lever that engages both the wax motor and the ring for causing circumferential movement of a ring in response to actuation movement of the wax motor as caused by temperature changes. Further, an adjustment cam is provided for adjusting the relative positions of the wax motor and lever for calibrating the temperature responsive movements of the ring bearing the index line.

Abstract: An imaging system with beam focus adjustment, includes an emitter which emits a beam of radiation along a beam path and an optical assembly, having a focus adjustment mechanism, configured to focus the emitted beam on a medium to be imaged. A medium support member supports the medium on its support surface during imaging. A sensor generates temperature data representing a detected temperature of the medium support member and a controller controls the focus adjustment mechanism in accordance with the temperature data to adjust the focus of the emitted beam on the medium.

Abstract: An optical component mounting device and method is disclosed where the optical components are disposed within a thin-walled tube and the tube is configured to produce an interference fit within the cylindrical opening of a mounting sleeve. The optical components are secured to the tube such that their optical axes coincide with the tube longitudinal axis. Mating of the optical mounting assembly to external reference surfaces precisely locates and aligns the optical axes with respect to an external reference axis. The optical mounting assembly provides at least two degrees of freedom to the optical components for facilitating alignment.

Abstract: An optical-element supporting device arranged to support and set one or a plurality of optical elements in respective predetermined positions in an optical axis direction, includes ring frames mounted respectively on the plurality of optical elements and each having a plurality of projections protruding in the optical axis direction, and a pinching structure for pinching the ring frames being piled up in the optical axis direction (the pinching structure comprising, for example, a lens barrel member which accommodates the ring frames mounted on the optical elements and leaf springs mounted near an end part of the lens barrel member in the optical axis direction), wherein the projections of the ring frames and respective pinching positions of the pinching structure are axially aligned in parallel with the optical axis direction.

Abstract: A hybrid optical barrel as a projection optical unit includes a plurality of cell groups disposed in series along an optical axis, each cell group including at least a cell unit and each cell unit including a lens and a cell holding the lens. The optical barrel also includes a connecting barrel member carrying the plurality of cell groups, the connecting barrel member being made of a material with a CTE<3.0 ppm.degree.C. such as Invar, Ultra Low Expansion.TM. glass, Zerodur glass, or silicon carbide. The connecting barrel member may comprise a plurality of sub-barrels disposed in series along the optical axis. Alternatively, the connecting barrel member may comprise a plurality of spacing members. Therefore, during an axial displacement of the optical barrel caused by a temperature change, relative axial dimensions of the sub-barrels or the spacing members remain substantially constant, thereby reducing an overall displacement of the lenses within the plurality of cell groups.

Abstract: A coupler system (13) for mounting a projection lens (15) to a cathode ray tube (16) in a projection television (10) is provided. The system includes a first member (20) composed of a heat and chemical resistant plastic and a second member (22) composed of metal. The second member (22) is mounted to the periphery (18) of the faceplate (17) of the cathode ray tube (16) to provide a high level of heat transfer from the tube. The second member also absorbs x-rays emitted by the tube. The first member can be readily molded from high performance plastic resins and thus reduces the overall cost of the coupler system compared to couplers composed entirely of metal.

Abstract: In a lens system including a thermal compensation mechanism that compensates for unwanted positional shifts between two tenses in the lens system resulting from changes in a temperature of the lens system, a bias mechanism is provided to bias elements of the lens system together. The bias force exerted by the bias mechanism on the thermal compensation mechanism insulates the lenses from effects of a dynamic environment, and ensures that a distance between the lenses along the optical axis will change with temperature of the lens system to provide necessary compensation. In an exemplary embodiment, the bias mechanism is a cylinder with a helical cut along its length that laterally surrounds a portion of the compensation mechanism, and provides a bias force in a direction parallel to the optical axis to urge angled interfaces of the compensation mechanism into abutment.

Abstract: A projection television lens system having a device that distorts for telescopically adjusting an A/B assembly, the tubular member that carries the A and B lens elements within a focus mount of a projection television lens system. Additionally, at one end of the lens, there is provided a fixed mounting site, i.e. a mounting site which is fixed in position with respect to the CRT 9 assembly. A device is then provided which connects the fixed mounting site to the tubular member. The thermal and structural characteristics of the device are selected so that the device itself distorts in response to temperature changes and thereby moves the A and B lens elements toward or away from the C element in response to, respectively, increased or decreased ambient temperature. In the most preferred embodiment, the fixed mounting site is on the focus mount at the image side of the lens assembly.

Abstract: An extender lens group removably incorporated in a zoom lens equipped with a temperature compensating feature for increasing the prim-lens focal length to achieve increased magnification is comprised of a front extender lens sub-group including four lens elements and a rear extender lens sub-group including two lens elements, the front extender lens sub-group including two positive bi-convex lens elements each of which has a strong curvature at the subject side surface followed by an overall positive doublet comprising a positive bi-convex lens element with a strong curvature at the subject side surface and a negative bi-concave lens element with a strong curvature at the image side surface and the rear extender lens sub-group including an overall positive doublet comprising a bi-concave lens element with a strong curvature at the image side surface and a positive meniscus lens element with a concave surface on the subject side.

Abstract: A window structure includes a housing, a window received into the housing, and a mounting support joining the window to the housing. The mounting support has an outer support ring joined to the housing, where the outer support ring has a coefficient of thermal expansion of about that of the housing, and an inner support ring joined to the window, where the inner support ring has a coefficient of thermal expansion of about that of the window. The inner support ring is joined to the outer support ring by a single-segment or multi-segment ring with a gradation in thermal expansion coefficient, but is not radially aligned with the outer support ring. The result is a large reduction in the stresses and strains otherwise imposed on the window.

Abstract: Several embodiment of an athermalizing apparatus is described. In one embodiment, the athermalizing apparatus includes a lens element and a support member coupled to the lens element. The support member has a sloped outer surface and a first coefficient of thermal expansion ("CTE"). The athermalizing apparatus further includes a rib member having a substantially complementary sloped surface that bears on the sloped outer surface of the support member. The rib member has a second CTE. The sloped outer surface of the support member forms a ramp angle with respect to an optical axis of the lens element. A radial expansion of the support and/or rib member causes an axial displacement of the support member as a function of the ramp angle.

Abstract: A filter clamp for retaining a filter, comprising a frame having an aperture to accommodate the filter, a clamp member having a clamp opening for alignment with the aperture when the clamp is in a mounted position, and a connector having a plurality of openings spaced about the aperture of the frame and mating protrusions spaced about the clamp opening of the clamp member. At least two protrusions extend through their mating openings and have their free ends formed at an angle to the openings so as to retain the clamp member in a mounted position containing the filter between the periphery and the frame while allowing the clamp member to move laterally, longitudinally and upwardly in relation to the frame sufficient amounts to accommodate expansion and contraction of the filter.

Abstract: An optical gun sight system for an M1A2 Abrams Main Battle Tank supported in a lower housing which may be attached to the fixed internal upper housing in the turret of the tank. An adapter plate is provided which has two sets of openings, one to align with the openings in the upper housing and the other to align with openings in the lower housing. An alignment mechanism allows for fine adjustment of the lower housing relative to the upper housing. Operating buttons, knobs and filter wheel are conveniently located on or beneath the front face of the lower housing. A thermal imaging system includes an objective lens for receiving an image of a target object, an eyepiece lens for viewing the image of the object, and a compensator lens movably located between the objective and eyepiece lenses for providing a thermal image of the object.

Abstract: A beam projecting apparatus which includes a light source emitting a laser beam; and a beam projecting device which includes a beam projecting portion from which the laser beam is projected outwardly so that the laser beam has a beam waist position at a predetermined position apart from the beam projecting apparatus. The beam projecting apparatus further includes a beam waist position adjusting optical system which is disposed along a light path from the light source to the beam projecting portion, at least one lens element of the beam waist position adjusting optical system being movable along an optical axis thereof; a temperature detecting device for detecting a temperature in the beam projecting apparatus; and a controller for controlling a movement of the at least one lens element in association with the temperature detected by the temperature detecting device so that a deviation of the beam waist position from the predetermined position due to a temperature change is minimized.

Abstract: An optical element and a scanning optical apparatus using the same capable of correcting for image plane re-positioning caused by internal distortion of the optical element, particularly, refractive index distribution caused by forming the optical element by plastic molding. The optical element has an internal refractive index distribution such that the focal length calculated based on the curvature of the plane thereof, the refractive index of the material, and the thickness along the optical axis, is shorter than the focal length actually measured. The element may be used in the scanning optical apparatus, may be provided with planes of different curvatures in a generating line and a line perpendicular thereto, and may be longer in the generating line.

Abstract: An optical unit provided between a plurality of light sources and a deflecting system in a multiple beam scanning optical system in which the appropriate intensity and appropriate intensity distribution of each beam on the scanned surface change are maintained regardless of foreseen changes in ambient temperature. The optical unit includes a condenser lens which condenses the beams emitted from the light sources and an aperture which regulates diameters of beams projected from the condenser lens. A connecting member which connects the condenser lens and the aperture at a distance corresponding to a focal length of the condenser lens.

Abstract: An arrangement is provided for fixing components of an optical system such as lenses, mounting rings, and the like. The components which are guided radially in the tube are held in the axial direction under pretensioning in an elastic manner. The arrangement is designed for fixing components in the axial direction in which the pretensioning force can be varied in definable steps. This is done by providing that a detachable fastening ring and also the tube have catch elements at concentric circumferential surfaces, which catch elements are constructed as complementing locking elements. Under axially directed force, the catch elements of the fastening ring can be engaged in the catch elements at the tube and the catch elements can be disengaged in the opposite force direction. The pretensioning force which is exerted by the fastening ring on the components to be held depends upon the extent to which the catch elements of the fastening ring and of the tube overlap.

Abstract: An anti-fogging lens device, having a plural number of optical glass lens elements mounted within a lens barrel, including a first lens element located in a foremost position on the side of a subject and a second lens element located behind and at a space from the first lens element. A spacer ring is fitted in the lens barrel to set apart the first and second lens elements by a gap space of a predetermined width. The spacer ring is formed of a material having higher thermal conductivity than the lens elements and, on the inner peripheral side thereof, provided with a moisture depositing surface which is formed in a non-flat shape to increase its surface area. The lens barrel is fitted in a cylindrical member, and a seal pocket, to be packed with a seal material, is formed between the lens barrel and the cylindrical member to stop clearances between these two members with a secure hermetical seal.

Abstract: A projection optical system of a projection exposure apparatus according to the present invention has a plurality of optical members made of glass materials at least one of which has a temperature characteristic of index of refraction different from that of the other glass material. Further, a temperature control device for controlling a temperature of at least one of the optical members is provided. An imaging characteristic of the projection optical system is controlled. The imaging characteristic to be controlled is a non-linear magnification or curvature of field. The temperature control device sets the temperature to be controlled to a variable target temperature determined in accordance with the imaging characteristic of the projection optical system. An exposing operation for transferring a mask pattern to a photosensitive substrate is started after the temperature of the optical member to be controlled reaches a predetermined allowable range of the target temperature.

Abstract: An optical member is bonded to one surface of a holder. At least a pair of grooves are formed on the surface of the holder to leave an elevated portion which is smaller than the optical element in width. The optical member is bonded to the surface of the holder only at the elevated portion.

Abstract: A light source device has a semiconductor laser element, a collimator lens, a lens barrel for holding the collimator lens, first and second lens barrel support member and a laser support member. The lens barrel support members are formed of the same type of material as that of the lens barrel and engage the lens barrel at a surface parallel to the optical axis of the collimator lens. The laser support member is formed of a different type material from that of the lens barrel support members, and joins the lens barrel support members at a surface perpendicular to the optical axis of the collimator lens.

Abstract: A light source package includes a light source, a lens for collimating the light from the light source, and a support member for supporting the light source and the lens so that the optical axis of the lens is set to a desired position relative to the light source. The support member includes a compensating device for compensating the lens for deviation of the optical axis of the lens resulting from a difference in the coefficients of linear thermal expansion between the lens and the support member when the ambient temperature changes.

Abstract: A lens position adjusting apparatus for adjusting an axial position of a rearmost lens group of a plurality of lens groups provided in a focal length variable lens upon assembly of the focal length variable lens is provided. The lens position adjusting apparatus includes a lens frame, a lens frame holder and an engagement tooth array portion. The lens frame holds the rearmost lens group. The lens frame holder engages with the lens frame through a threaded engagement. The engagement tooth array portion is formed along a rear end of the lens frame. The engagement tooth array portion consists of a plurality of engaging teeth. Each of the engaging teeth extends in a direction substantially parallel to an optical axis facing towards a rear of the focal length variable lens.

Abstract: An elongated optic (12) is supported within a cylindrical housing (18) by a pair of support rods (14) passing through the cylindrical housing (18). A resilient retention spring (16) diametrically opposed to each support rod (14) presses the elongated optic (12) against the support rod (14) to prevent movement by the elongated optic (12) while allowing the elongated optic (12) to expand and contract. Contact between the support rods (14) and the resilient retention spring (16) is minimized to prevent inhibiting the internal reflectivity of the elongated optic.

Abstract: A glass lens and a plastic lens are secured such that the glass lens is retained in a predetermined position with reference to a lens barrel and against a reference surface provided in the lens barrel. The plastic lens is held by a resilient ring-shaped portion of the lens barrel against the glass lens, thus locating the plastic lens in a predetermined position with reference to both the lens barrel and the glass lens. The glass lens is retained against the reference surface by a retaining member positioned opposite the reference surface.

Abstract: A wide angle objective system is described for, inter alia CCD cameras, which system is compact, inexpensive and satisfactorily corrected. It comprises a front meniscus lens (L.sub.1), a thick convex-concave central lens element (L.sub.2) and a biconvex lens element (L.sub.3), the two last-mentioned elements preferably being cemented together, the pupil (P) being present at the area of the exit surface (4) of the second lens element and the first and the third element (L.sub.1,L.sub.3) being made of, for example PMMA and the second element (L.sub.2) being made of, for example PC.

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 barrel for holding an assembly or group of lens elements is molded as an integral member from a thermoplastic resin material such as polycarbonate, and at least two of the lens elements have different diameters. The lens barrel includes an outer cylindrical wall portion having a uniform diameter and a uniform wall thickness, and a lens holder portion integrally extending from an inner surface of the outer cylindrical wall portion. The lens holder portion is formed in accordance with the different diameters of the lens elements such that wall thickness is substantially uniform.

Abstract: The housing 2 is integrally formed with a cylindrical support portion 6. A cylindrical bore 30a is formed through the support portion 6. An inner diameter of the bore 30a is made substantially equal to an outer diameter of the semiconductor laser 4. The semiconductor laser 4 is therefore supported in the bore 30a. A lens barrel 7 holds therein a collimator lens 5. The outer diameter of the lens barrel 7 is also substantially equal to the inner diameter of the bore 30a. The lens barrel 7 is also supported in the bore 30a.

Abstract: In an ultraviolet exposure apparatus, substances contained in an atmosphere contacting a lens surface are reduced, the substances generating accumulations on the lens surface. Openings are formed in the wall of a lens barrel to allow the atmosphere to be replaced by a proper gas. The proper atmospheric gas may be a gas not containing oxygen such as a nitrogen gas, or clean air obtained by intentionally generating accumulations by applying ultraviolet light to source air. A ultraviolet light source is preferably cooled by a cooling system different from the cooling system of a lens optical system.

Abstract: In a connecting mechanism which connects two members, one of the two members is provided with an elastically deformable engaging portion, and the other member is provided with a contact surface which is brought into contact with the elastically deformable engaging portion, which is elastically deformed at a front end. The two members are engaged with each other by elastically deforming the elastically deformable engaging portion so that the latter comes into contact with the contact surface. The elastically deformable engaging portion and the contact surface are shaped such that the engagement force of the two members during a connecting operation is stronger than the engagement force when the connecting operation is completed.

Abstract: The invention provides a photographic lens which uses a low-hygroscopicity resin lens component as a constitutional component, is made compact without incurring some expense, and enables the optical properties to be kept stable to an atmospheric humidity change. The photographic lens is of the single-focus or varifocallength type that comprises a plurality of lens components among which at least one or more lens components are resin lens components, wherein at least one of the resin lens components is formed of a low-hygroscopicity resin. For instance, the invention is applicable to a single-focus lens comprising four lens components, i.e., a positive meniscus lens component convex on the object side, a double-concave lens component, a double-convex lens component and a negative meniscus lens component convex on the image surface side.

Abstract: A lens plate is provided with many lenses, and a base plate is provided with many LED arrays and driving ICs arranged at respective opposite ends of the base plate. The lens plate and the base plate are positioned in place relative to each other by spacers. The base plate has a thermal conductive layer and a thermal preserving layer over the layer. Grooves are formed in the preserving layer between the driving ICs and the LED arrays.

Abstract: In the optical coupling system where the space between projection lens and CRT is connected with a liquid, this invention aims to offer a projection lens unit wherein the angle of CRT relative to the optical axis of projection lens (tilt angle) may be changed by quite a simple operation; thereby the CRT tilt angle can be reset to an optimum when the angle of projection oblique to a screen shifts. Namely, a first housing and a second housing in which an optical coupling liquid is contained and sealed are coupled together with an watertight structure like a piston and cylinder and fixed, and a ring cam for regulating the relative space and tilt is held between the two housings; by fastening the two housings together with bolts, etc. the two housings can be set at a desired relative positioning.

Abstract: A lens apparatus in which plural lenses, each having a different expansion coefficient to others, are adhered to each other at their lens surfaces and some of the plural lenses, which has a smaller expansion coefficient than other lenses and the number of which is fewer than the total number of the plural lenses, are coupled with a lens barrel so that all of the plural lenses are supported by the lens barrel.

Abstract: A mechanism for adjusting the diopter setting of a finder assembly which has an objective optical system and an eyepiece optical system, includes an object side image forming position adjusting device which adjusts the position where an image is to be formed by the objective optical system. The mechanism effectively compensates for any change that occurs in the position where an image is formed by the objective optical system due to temperature or humidity variations. Thus, the problem of plastic lenses having their focal lengths extended in a hot and humid environment is solved by the invention.