Abstract: A mounting device having a mounting assembly for mounting a pair of goggles to a helmet is provided. The mounting assembly is configured to provide at least three degrees of freedom of movement using one or more actuation mechanisms for locking and unlocking a position of the mounting device. The number of actuation mechanisms is less than a number of degrees of freedom. In some aspects, the number of actuation mechanisms is one. A rotation base connects the mounting assembly to the helmet, and a goggle linkage connects the mounting assembly to the goggles. Various single actuation mechanisms, including a sliding mechanism, a friction-based wire/brake mechanism, and a floating friction brake mechanism, are provided.

Abstract: An object of the present invention is to provide a projection apparatus capable of appropriately performing control relating to a rotation state and/or a movement state of a projection lens. A projection apparatus according to an aspect of the present invention includes a housing; a light source; a control unit; and a projection lens attached to the housing, the projection lens having a holder, a detection unit that detects a rotation state of the holder, an emission optical system, and a locking mechanism unit that brings rotation of the holder into a locked state or an unlocked state. The projection lens is displaceable between a first position at which a rotation state of the holder is a housed state in which the emission optical system faces the housing and a second position at which the emission optical system does not face the housing by rotating the holder. The second position includes an upper position at which the emission optical system faces an upper side in a vertical direction.

Abstract: The application is directed to a locking adjustment assembly for an optical aiming device. The locking adjustment assembly is usable across different optical platforms regardless of the focal length of a particular optical platform. The locking adjustment assembly is operationally configured to be reset to a zero position. The locking adjustment assembly may also provide an automatic lock at a zero position.

Abstract: Disclosed is an optical scope including an objective lens, an eyepiece lens, and a reticle, wherein a field lens having negative power is disposed in at least one of a front and a back of the reticle disposed on an image formation surface of the objective lens to increase eye-relief.

Abstract: A night vision goggles aided flight simulator system (100) and method for simulating night flight operations. The system comprises a computer (5) programmed with flight simulator software to calculate a flight simulator image (A1,A2); a projection screen (1) configured to receive the flight simulator image (A1,A2); a light projector (2) configured to project the flight simulator image (A1,A2) onto the projection screen (1); and a view tracking device (3) configured to measure a viewing vector (V) of a night vision device (4). The system (100) is configured to mask the projected flight simulator image (A1,A2) as a function of the measured viewing vector (V).

Abstract: A light collecting device is adapted to collect and guide light to a light sensor. The device includes a monocular collecting module including at least one light collector configured to collect light from the environment of the device, a binocular collecting module including a first and a second distant light collector configured to collect light from the environment of the device, and an optical waveguide configured to guide the light collected from the monocular and binocular collecting modules to a light sensor.

Abstract: Universal electronic exchange system for eyepieces, especially for coupling to telescopes or similar, which comprises: an automated rotary device provided with a rotary plate of the revolver type provided with a plurality of eyepiece holders intended to receive different sizes of eyepieces, and actuation means for said rotary plate, an electronic unit for selecting the eyepiece to be used capable of receiving a selection signal generated by a user, determining the aligned position in respect to the optical axis and sending a command signal to an electronic unit for controlling the rotation and stopping of the rotary plate, which in turn is capable of processing the speed, angular path of rotation, and stopping position of the eyepiece to be used, and sending a command signal to the actuation means of said rotary plate for positioning and aligning with precision said eyepiece with the optical axis.

Abstract: An electronic binoculars includes: first and second imaging units with a predetermined horizontal distance therebetween disposed in a housing; optical members that guide image light beams to the first and second imaging units; a sensor that detects angular acceleration or acceleration acting on the housing; an image processor that processes image signals produced by the first and second imaging units and corrects the image signals in terms of the change in motion of the housing in accordance with the angular acceleration or acceleration detected by the sensor; and first and second displays with a horizontal distance therebetween disposed in the housing, the first and second displays displaying the image signals processed by the image processor.

Abstract: The invention provides a decentration optical system comprising at least five optical surfaces. The optical surfaces are each decentered with respect to an axial chief ray in the Y-Z plane in the XYZ coordinate space, and at least one surface is decentered in the X-Z plane orthogonal to the Y-Z plane. At least two of the multiple optical surfaces are rotationally asymmetric surfaces, and at least one of the at least two rotationally asymmetric surfaces is a rotationally asymmetric surface having an X odd-numbered degree term.

Abstract: Focusing devices and methods for controlling a focal position of an objective lens assembly in a night vision optical device are provided. The focusing device includes an objective lens assembly positioned at a first or second focus position from an imaging device and a binary focus controller, coupled to the objective lens assembly, configured to translate the objective lens assembly relative to the imaging device to either the first or second focus position. The objective lens assembly is translated to either the first or second focus position in response to an orientation of the night vision optical device.

Abstract: A system includes a displacement sensor, an actuator connected to the displacement sensor, and a feedback unit. The displacement sensor is configured to measure at least one of a relative position and a relative orientation between the displacement sensor and the target object. The feedback unit receives a signal from the displacement sensor related to the measured relative position or relative orientation and controls the actuator to move the displacement sensor on the basis of variations in the received signal arising due to a change in environmental conditions.

Abstract: An optical module for head mounted displays and other applications comprises: an optical substrate and optical superstrate having inter-engaging ridged surfaces. A reflective layer is formed on at least one of the surfaces. An index matching material may be located between the surfaces. A region that receives a projected image, from a projector, directs rays launched from the projector onto the ridged surfaces, so that in use a viewer perceives an augmented image. The augmented image comprising reflected rays from the projector and transmitted rays from an object located on an opposite side of the module to that of the viewer.

Abstract: A binocular telescope with internal focusing and two cylindrical barrel tubes, each fastened to a bridge and accommodating an objective lens, a focusing lens, a prism system for image inversion and an eyepiece. The prism system is configured so that the optical axis of the eyepieces is offset relative to the optical axis of the objective lenses. The bridge is provided with two cylindrical apertures in which the barrel tubes are mounted parallel to one another, each rotatable about the optical axis of its objective. Each barrel tube comprises a rotary sleeve, an objective tube and an eyepiece tube. The bridge is one piece and has a small length compared to the barrel tube length. The rotary sleeves are inserted into the apertures and the objective tubes and eyepiece tubes are connected to the rotary sleeves such that they lie rotatable on the upper and lower sides of the bridge.

Abstract: A riflescope high speed, coarse and fine adjustment assembly that includes a riflescope with an erector tube located inside a scope body. Formed on the scope body is a mounting surface with a lead screw slot located adjacent to the proximal end of the erector tube. Located over the mounting surface is an adjustment plate with a perpendicularly aligned post member located thereon. Located inside the post member is a threaded lead screw with threaded head that connects to the post member and a lower non-threaded neck that extends into a slot formed on the mounting surface. The adjustment plate is affixed along its front edge while the plate's opposite rear section is detached and free to move up or down. Disposed over the adjustment plate is a cover plate with a fine adjustment lever that selectively rises and lowers the rear edge of the cover plate. Attached to the cover plate is a detent plate. Attached over the detent plate is a coarse adjustment dial.

Abstract: This is a microscope observation system comprising a microscope, a camera unit, a light-amount adjustment unit for controlling adjustment parts included the microscope in order to suppress the amount of reflected light of a specimen image formed on the camera unit, a camera adjustment unit for controlling an adjustment part group of the camera unit in order to adjust image signals photo-electrically converted by the camera unit to a desired state, a light measurement unit for measuring the brightness of the specimen, a display unit for displaying a captured image, a control unit for controlling continuous display speed indicating the continuous display interval of an image continuously displayed on the display unit and at least one of an observation position shifting unit for changing the observation position or observation magnification of the specimen or an observation state detection unit for detecting the observation position or the observation magnification.

Abstract: Provided is a binocular loupe capable of adapting to current vision of a worker of a medical operation or precise operation in operating. The binocular loupe has frame means, a pair of binocular loupe bodies, attaching means for fixing the binocular loupe bodies to the frame means, focus adjusting means for adjusting a focal length of each of the binocular loupe bodies, and supporting means for detachably attaching the focus adjusting means to eyepiece portions of the binocular loupe bodies.

Abstract: Provided is a device for improving the focus of an object viewed using a night vision instrument.

Abstract: Binoculars include first and second lens barrels. A bridge interconnects the lens barrels. First and second optical systems are accommodated in respectively the lens barrels. First and second focus lenses are included in respectively the first and second optical systems, for focus adjustment by moving in an optical axis direction. An operation barrel is secured to the bridge, and externally rotatable and movable in the optical axis direction between a focus adjusting position and a diopter adjusting position. A focus adjuster with gear teeth and screw threads moves the first and second focus lenses simultaneously in the optical axis direction when the operation barrel is rotated in the focus adjusting position. A diopter adjuster, including gear teeth, an intermediate rod and screw threads, moves the second focus lens in the optical axis direction when the operation barrel is rotated in the diopter adjusting position.

Abstract: An optical device may include at least one optical element and a coupling section adapted to control relative movement between the at least one optical element and the coupling section. The coupling section may include an engaging element and a detent mechanism adapted to adjustably lock the at least one optical element in a plurality of rotational positions. The rotational positions may include rotational positions around a first axis that is substantially perpendicular to a second axis of the at least one optical element, the second axis being a substantially longitudinal axis of the at least one optical element.

Abstract: A projector device, includes: a projector unit, including a light source and a projection lens whose focal position is variable, that projects an image upon a projection surface with a light flux outputted from the light source that passes through the projection lens; an image-capturing unit, including a photographic lens whose focal position is variable, that captures an image of a subject with a light flux from the exterior that passes through the photographic lens; and a single drive source that generates drive force for changing both the focal position of the projection lens and the focal position of the photographic lens.

Abstract: A telescope having a focus display includes a tube assembly, a sensor and a focus display. The tube assembly has a first tube and a second tube connected within the first tube. The first tube has an opening. The sensor is provided on the second tube. The focus display is provided in the opening of the first tube. The focus display is provided with a screen, a processing unit and an electromagnetic sensing unit. The electromagnetic sensing unit, the processing unit and the screen are electrically connected with each other. When the first tube is telescopically moved with respect to the second tube, the electromagnetic sensing unit receives and senses the change in the electromagnetic field of the sensor. The processing unit then calculates the displacement and displays the data on the screen, so that the user can focus the telescope to obtain the clearest image.

Abstract: Binoculars having a center-focusing function and an individual-focusing comprise a telescopic base provided at an end thereof with a control sleeve which is connected to a left lens system in a left barrel and a right lens system in a right barrel through an adjusting portion disposed in the telescopic base. When a user pushes the control sleeve so that the control sleeve is forced to shift toward the adjusting portion, the user can rotate the control sleeve to simultaneously actuate the adjusting portion, so as to adjust focuses of the left and right lens systems. When the user pulls the control sleeve so that the control sleeve is forced to shift away from the adjusting portion, the user can rotate the control sleeve to simultaneously actuate the adjusting portion, so as to adjust a parallax between one and the other of the left and right lens systems.

Abstract: Binoculars have a digital camera function. The binoculars comprise observation optical-systems, an imaging-block, an indicating-device, and an imaging-block direction changing device. The objective optical-systems have objective optical-systems having first- and second-light axes, at the front-face, and have ocular optical-systems at the rear-face. The imaging-block has an imaging-lens, and an imaging-device. The imaging-lens forms an image on an imaging-surface of the imaging-device, and has a third-light axis. The imaging-device captures the image formed on the imaging surface. The indicating-device has an indicating-surface on which images are indicated, and is located on one of the top- and bottom-face.

Abstract: The binoculars include a pair of displaceable optical elements, which are at least parts of objective optical systems, respectively, a focusing mechanism used to move the displaceable optical elements for focusing, a pair of guide rails that guide the displaceable optical elements, respectively, when they are moved. The pair of guide rails have inclined portions, at least parts thereof, which incline with respect to the optical axes of the objective optical systems, respectively. A pair of engagement portions are formed on a pair of frames of the displaceable optical elements, respectively. The engagement portions are engaged with the guide rails, respectively. When the displaceable optical elements are moved for focusing with the pair of engagement portions being engaged with the inclined portions of the pair of guide rails, respectively, a distance between the optical axes of the pair of displaceable optical elements changes, thereby a convergence value being compensated.

Abstract: Binoculars which include a pair of observation optical systems each having an objective optical system, an erecting optical system and an eyepiece optical system. The binoculars include a focusing mechanism that is used to move a part of the observation optical system for focusing, and a convergence value compensating mechanism that compensates for a convergence value by displacing displaceable optical elements which are at least parts of the objective optical systems, respectively, in association with actuation of the focusing mechanism. In this structure, a distance between optical axes of the eyepiece optical systems is adjustable in line with a width between eyes of a user. A maximum value of a distance between optical axes of the displaceable optical elements is smaller than a minimum value of the distance between the optical axes of the eyepiece optical systems.

Abstract: The invention aims at providing a pair of binoculars making it possible to easily perform a focusing operation and a diopter adjustment, and efficiently perform an assembling operation. The present invention provides a pair of binoculars having a pair of supporters for supporting adjustment lenses provided between a pair of ocular optical systems and a pair of objective optical systems so as to be capable of moving forward and backward along the optical axis, a focusing gear for performing a focusing operation by moving said pair of supporters forward or backward at the same time in the direction of optical axis, a diopter adjuster for performing a diopter adjustment by moving one supporter forward or backward in the direction of optical axis as keeping the other supporter stationary, and a focusing and diopter adjusting unit having a changeover gear for changing over the focusing gear and the diopter adjuster to each other.

Abstract: An imaging optical device, in particular binoculars or a telescope, comprises, in addition to a casing, an optical system with at least two optical components, the distance of which relative to one another is adjustable for focus setting of the optical system. This adjustment is effected by an adjusting device, which is coupled with at least one of the two components. The position of the optical components relative to each other is detected and, by the aid of a processor, converted into a focal length of the optical system and then outputted as a focal length via an output device. In this way, the distance of an object sighted by the optical device can be determined conveniently.

Abstract: A monocular or binocular optical system that is capable of automatically adjusting a diopter setting upon or during a change in magnification in a way that acts to preserve focus and a corresponding method for adjusting a diopter setting to preserve focus upon or during a change in magnification.

Abstract: A focusing optic can be axially displaced along the optical axis in a housing with the aid of coarse and fine drives. The coarse drive includes a coarse belt drive by which the coarse drive and the focusing optic cooperate actively with one another and the fine belt drive is provided for connecting the fine drive and the focusing optic.

Abstract: A multi-focal night vision apparatus is disclosed. The apparatus can include a receptor for receiving light reflected off of and emitted from objects in an image field of the night vision apparatus and a set of optical elements for focusing the light onto the receptor. The optical elements can include a field lens having a first portion for focusing far field objects and a second portion for simultaneously focusing near field objects.

Abstract: A binocular telescope with a photographing function includes a pair of telescopic optical systems, a casing for receiving the telescopic optical systems, and the casing has outer-side end portions. A camera system includes a photographing optical system, and a solid-state image sensor arranged behind and aligned with the photographing optical system, and an electronic control system electronically controls an operation of the camera system. The electronic control system is supplied with electric power from the batteries through an electric power source circuit board. The batteries and the electric power source circuit board are provided at the outer-side end portions of the casing, such that the weight is balanced between the outer-side end portions of the casing.

Abstract: A mechanism for focal adjustment and dipotric deviation adjustment in binoculars. The mechanism includes: a first focal adjustment lens system; a second focal adjustment lens system; a focal adjustment shaft that performs a focal adjustment by causing the first focal adjustment lens system and the second focal adjustment lens system to move along optical axes thereof; and a dioptric deviation adjustment shaft that performs a dioptric deviation adjustment by causing the first focal adjustment lens system to move along the optical axis. The focal adjustment shaft and the dioptric deviation adjustment shaft both are housed within a bridge casing set between the first lens barrel and the second lens barrel. The dioptric deviation adjustment shaft is linked with the first focal adjustment lens system. The focal adjustment shaft is linked with the second focal adjustment lens system and the dioptric deviation adjustment shaft.

Abstract: A pair of variable-powered binoculars include a pair of objective lens systems; a pair of prism systems, each of the prism system inverting an image that advances through the corresponding objective lens systems, from an inverted image to an erecting image; a pair of concave adjusting lenses, each of the concave adjusting lenses placed between a focus formed by the corresponding objective lens system and the corresponding prism system, so that each of the concave adjusting lenses is movable along the optical axis formed by the corresponding objective lens system and the corresponding prism system; and a pair of ocular lens systems, each of the ocular lens systems placed on the optical axis, so that each ocular lens system is movable along the optical axis closer to or away from the corresponding concave adjusting lens, synchronizing with a movement of the corresponding concave adjusting lens.

Abstract: A viewing apparatus includes a viewing optical system having a positive objective optical system and a positive eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the positive eyepiece optical system; a photographing optical system, provided independently from the viewing optical system, for photographing the object image viewed through the positive eyepiece optical system; a first focusing mechanism for changing an image focal point of the object image formed through the positive objective optical system of the viewing optical system; a second focusing mechanism for changing an image focal point of an object image formed through the photographing optical system; an association mechanism which interconnects the first focusing mechanism with the second focusing mechanism; and an indicia indication optical system for selectively indicating the object image and an indicia image in a field of view viewing through the positive eyepiece optical s

Abstract: The night vision goggle training apparatus simulates the size, feel and handling of actual night vision goggles. A narrow band-width green filter is positioned over the viewing port, to simulate nighttime viewing conditions. The image intensification system used in night vision goggles is eliminated; limiting use of the training goggles to daytime use. The out of balance weight of the night vision goggles is identical to actual night vision goggles. Brightness control is simulated by attenuation filters that fit over the objective lens. The blooming effect of lights is simulated with a star filter. A thin, fine mesh screen is used to simulate reduced acuity, scintillation and ghosting effects during low light or rapid motion, which occur during use of actual night vision goggles. The objective focus and diopter adjustment are identical to night vision goggles.

Abstract: A telescope comprising a lens (3) and a focussing member (5) which can be displaced by means or a focussing adjustment ring (12), whereby the basic position thereof can be adjusted by a lockable diopter adjustment ring (13), also comprising a reversing system (4) and an eyepiece (6), characterised in that a cam disk (20) for displacement of the focusing member (5) is associated with the diopter adjustment ring (13) when the eyepiece (6, 7, 8) is used with modifiable enlargement, whereby said cam disk (20) can be displaced by a value which is dependent upon the diopter adjustment and modification of the enlargement of the eyepiece.

Abstract: An imaging optical device, in particular binoculars or a telescope, comprises, in addition to a casing, an optical system with at least two optical components, the distance of which relative to one another is adjustable for focus setting of the optical system. This adjustment is effected by an adjusting device, which is coupled with at least one of the two components. The position of the optical components relative to each other is detected and, by the aid of a processor, converted into a focal length of the optical system and then outputted as a focal length via an output device. In this way, the distance of an object sighted by the optical device can be determined conveniently.

Abstract: A focusing optic can be axially displaced along the optical axis in a housing with the aid of coarse and fine drives. The coarse drive includes a coarse belt drive by which the coarse drive and the focusing optic cooperate actively with one another and the fine belt drive is provided for connecting the fine drive and the focusing optic.

Abstract: An optical device comprises a lens barrel and a casing. The casing has two casing sections that are movable relative to each other. A distribution cable is provided in the casing, and extends between the casing sections. The distribution cable is loosely wound around the lens barrel, whereby a movement of the distribution cable, caused by a relative movement of the casing sections, is absorbed by the loosely wound portion of the distribution cable.

Abstract: A telescope includes a main tube having an objective lens and an eyepiece, and a focuser located between the objective lens and the eyepiece; a mode switching mechanism located in front of the eyepiece and including an external switch lever and an internal flip mirror fixedly connected to the switch lever; a digital image store device located behind the main tube for receiving and processing incoming video and audio signals, storing the processed signals on a memory, and displaying the video signals on a liquid crystal display; and a focusing control device located between the main tube and the digital image store device. By operating the switch lever, optical axes of the telescope and the digital image store device can be brought to parallel with each other for the digital image store device to receive and record images exactly the same as those being viewed with the telescope.

Abstract: A terrestrial telescope with digital camera includes objective lenses, an imaging element located downstream of the objective lenses, a retractable optical-path-splitting means between the objective lenses and the imaging element, and an optical system for observing an optical image divided from the optical path of the imaging optical system by the optical-path-splitting means. An imaging position correction means is further provided which includes an optical element that is inserted into the optical axis of the imaging optical system to correct any change in the image-formation position when the optical-path-splitting means is retracted from the optical path of the imaging optical system during imaging.

Abstract: An optical system is capable of enhancing vision of low vision individuals using a simple adjustment mechanism that requires a minimum length of travel to effect a desired adjustment. First and second substantially perpendicular mirrors are mounted in a cluster for pivotable movement. An entrance mirror is pivoted in response to pivoting movement of the mirror cluster so as to ensure proper convergence when the object to be viewed is close to the objective lens or lenses in a binocular system. The system also includes an objective lens and an eyepiece lens and is readily mounted to a conventional eyeglasses frame.

Abstract: A software application for organizing and editing image data files created through digital photography has a first portion thereof based on a computing platform; and a second portion thereof distributed to a device memory on a digital photographic device. The second portion of the software is used to organize and contain captured images, including annotation to individual ones of the captured images as photographic sessions bounded in one or more session containers according to programmable rules, and wherein the session containers appear as fully editable and annotate-able electronic documents containing the images of the session and captions associated to individual ones of the session images upon upload to the computing platform.

Abstract: A binocular comprising left and right lens units, a support base for connecting the left and right lens units, and a diopter adjusting ring and a focus adjusting ring disposed on the support base. The base is formed with an opening at a center thereof and the diopter adjusting ring and the focus adjusting ring are disposed side by side in the opeining.

Abstract: A viewing apparatus includes a viewing optical system having a positive objective optical system and a positive eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the positive eyepiece optical system; a photographing optical system, provided independently from the viewing optical system, for photographing the object image viewed through the positive eyepiece optical system; a first focusing mechanism for changing an image focal point of the object image formed through the positive objective optical system of the viewing optical system; a second focusing mechanism for changing an image focal point of an object image formed through the photographing optical system; an association mechanism which interconnects the first focusing mechanism with the second focusing mechanism; and an indicia indication optical system for selectively indicating the object image and an indicia image in a field of view viewing through the positive eyepiece optical s

Abstract: In an optical viewer instrument with a photographing function, there is provided a telescopic lens system for observing objects, and a digital camera system including a solid-state image sensor and a photographing lens system associated with each other such that an object is formed as a photographed image on the solid-state image sensor through the photographing lens system. A manually-operable focussing mechanism is associated with the telescopic lens system and the photographing lens system such that the object is brought into focus through the telescopic lens system, and such that the object is brought into focus through the photographing lens system. Optical parameters are selected such that predetermined conditions are fulfilled, whereby the focussing of the telescopic lens system and the focusing of the photographing lens system can be suitably and properly performed by the focussing mechanism.

Abstract: A trinocular apparatus is provided for sighting and photographing subjects in the field. The trinocular apparatus comprises a binocular viewing system and a third barrel focusing a common image on an image capturing device mounted to the binocular viewing system. Focusing for both the binocular system and the third barrel is managed by a common focusing apparatus. In a preferred embodiment images are captured electronically, and the trinocular apparatus includes apparatus for storing and transferring captured images.

Abstract: An adjustable eyepiece for a viewing device includes a diopter ring with at least one cam follower mounted to the diopter ring and a cam sleeve axially aligned with the diopter ring. The cam sleeve is positioned around a tubular portion of the diopter ring and has at least one cam pathway formed in the cam sleeve. Each cam follower that is mounted to the diopter ring is positioned in a cam pathway such that the cam sleeve may be secured in at least two axial positions relative to the diopter ring. In one embodiment of the invention, three cam pathways are formed in the cam sleeve as L-shaped slots, which may be used in combination with three cam followers to secure the cam sleeve in two axial positions relative to the diopter ring.

Abstract: Binoculars includes: a first focal adjustment lens system; a second focal adjustment lens system; a focal adjustment shaft that performs a focal adjustment by causing the first focal adjustment lens system and the second focal adjustment lens system to move along optical axes thereof; and a dioptric deviation adjustment shaft that performs a dioptric deviation adjustment by causing the first focal adjustment lens system to move along the optical axis.

Abstract: A binocular includes a right and left lens barrels respectively having a right and left telescope optical systems. The right and left telescope optical systems include focus arrangement structures in which both eyepiece lenses are simultaneously moved the same distance with respect to each objective lenses. There are provided two diopter correction structures independently and separately in the right and left telescope optical systems. In one diopter correction structure, a left objective lens is adjusted with respect to a right objective lens to correct a diopter difference between the two telescope optical systems on a manufacture process. In the other diopter correction structure, the location of the right objective lens is adjusted along the optical axis direction on an usual operation by an observer.