Abstract: A scanning image displayer, including a beam provider emitting a laser beam; a beam scanner including a two-dimensional drive deflecting mirror, deflectively scanning the beam in a main scanning direction and a sub-scanning direction; and an optical element including a reflection surface before the two-dimensional drive deflecting mirror, deflecting the beam in a direction of the two-dimensional drive deflecting mirror such that the beam obliquely enters a mirror thereof. The two-dimensional drive deflecting mirror deflectively scans the beam to project the beam onto a surface to be projected, and the light intensity of the beam is controlled according to image information to form an image. A flat surface of a substrate where the mirror is formed is located parallel or almost parallel to an optical axis of the beam, and the reflection surface is located so as not to receive the beam deflectively scanned by the two-dimensional drive deflecting mirror.

Abstract: A laser scanner system for removing a coating from a surface.

Abstract: Disclosed is an evaluation device of an optical writing device, comprising: the optical writing device; a light reception section; a drive section; and a control section to light each light emitting element in a previously set lighting pattern based on a light amount; to drive the drive section to move the light reception section to a position opposite to the light emitting element to be lit; to calculate characteristic data based on a light amount value of the light received by the light reception section; to calculate a first calculation value based on the characteristic data for each light emitting element; to calculate a second calculation value different from the first calculation value based on the characteristic data; to calculate a third calculation value based on the first calculation value and the second calculation value; and to instruct the display section to display the third calculation value.

Abstract: A laser projection device includes: an incidence optical system condensing laser light, a scanning device deflect the laser light in a first scanning direction and a second scanning direction with a mirror, and a projection optical system guiding the deflected light to a surface to be scanned. The scanning device performs the deflection in the first scanning direction by resonant driving and performs the deflection in the second scanning direction by non-resonant driving. The incidence optical system has different optical powers in the first scanning direction and the second scanning direction, and makes light incident on the scanning device in a convergent state in the first scanning direction and in a substantially parallel light state in the second scanning direction. The projection optical system has a negative optical power in the first scanning direction.

Abstract: An optical scan unit (10) is configured to include a light source (11), a divergent light conversion element (12) having such positive power as to convert divergent light from the light source (11) into convergent light to form a spot on a projection plane, an optical deflector (13) deflecting a light beam from the divergent light conversion element (12) to a first scan direction and a second scan direction which is orthogonal to the first scan direction, and a deflection angle conversion element 14 (14) having such negative power as to convert a deflection angle of the light deflected by the optical deflector (13).

Abstract: A disclosed surface emitting laser device includes an oscillator structure including an active layer, semiconductor multilayer reflection mirrors sandwiching the oscillator structure, an electrode provided on an emitting surface where light is emitted in a manner such that the electrode surrounds an emitting region, and a dielectric film formed in at least one region outside a center part of the emitting region so that a refractive index of the region outside the center part of the emitting region is less than the refractive index of the center part of the emitting region. When viewed from an emitting direction of the light, a part of the electrode overlaps a part of the dielectric film.

Abstract: A disclosed surface-emitting laser element includes a substrate, multiple semiconductor layers stacked on the substrate including a resonator structure including an active layer, a semiconductor multilayer mirror on the resonator structure, and a confined structure where a current passage region is enclosed by at least an oxide generated by oxidation of part of a selective oxidation layer containing aluminum, an electrode provided around an emission region, and a dielectric film provided in a peripheral portion within the emission region and outside a central portion of the emission region to make a reflectance of the peripheral portion lower than that of the central portion. The dielectric film is arranged such that a reflectance of a high-order transverse mode in a second direction is higher than that in a first direction, and a width of the current passage region in the first direction is greater than that in the second direction.

Abstract: A scanning optical apparatus includes a light source, a deflecting element for deflecting a beam of light emitted from the light source, an optical device for causing the beam of light emitted from the light source to be imaged into a linear shape long in the main scanning direction on the deflecting surface of the deflecting element. The optical device is comprised of a first optical element and a second optical element, and a third optical element for causing the beam of light deflected by the deflecting element to be imaged into a spot-like shape on a surface to be scanned. The third optical element includes a single lens, the opposite lens surfaces of which both include a toric surface of an aspherical surface shape in the main scanning plane, the curvatures of the opposite lens surfaces in the sub scanning plane being continuously varied from the on-axis toward the off-axis in the effective portion of the lens.

Abstract: Briefly, in accordance with one or more embodiments, a scanned beam display may utilize one or more post-scan optics while at least partially maintaining an infinite focus, or nearly infinite focus, property of the display. The display may comprise a light source to generate a light beam, a scanning platform to generate a raster scan from the light beam projected as a projected image, one or more post-scan optics to at least partially adjust the projected image, and one or more collimating optics to focus the light beam from the light source, the one or more collimating optics having a selected focal length to at least partially provide infinite, or nearly infinite focus, of the projected image at or beyond a selected distance.

Abstract: A scanning type image display apparatus includes a light source unit for emitting a laser beam, a scanning mirror for scanning the laser beam two-dimensionally in a first direction and a second direction that intersects the first direction, and a control unit for controlling driving of the scanning mirror. The control unit drives the scanning mirror such that a scanning frequency in the first direction is higher than a scanning frequency in the second direction, and varies a scanning amplitude in the first direction by varying the scanning frequency in the first direction in synchronization with a period of the scanning frequency in the second direction.

Abstract: An optical scanning apparatus that includes a light source unit having plural main light sources that are two-dimensionally arranged in the main scanning direction and the sub scanning direction, and plural sub light sources that are arranged between rows of the main light sources aligned in the main scanning direction. The optical scanning apparatus also includes an optical system configured to scan light emitted from the light source unit on a scanning object to form an image on the scanning object, and a control apparatus configured to adjust a main scanning direction image position by controlling two of the main light sources that are juxtaposed to each other with respect to the main scanning direction and adjust a sub scanning direction image position by controlling a main light source and a sub light source that are adjacent to each other.

Abstract: An optical scanning device includes a light source, a deflector, and an optical system including an elongated optical element that focuses deflected luminous flux on a surface of a medium to be scanned. The optical element is supported by a first elastic member and reinforced by a reinforcing member arranged outside a beam effective range along a length of the optical element. The optical element is pressed by a pressing member in a pressing direction orthogonal to a deflection direction, and biased by a second elastic member in a direction opposite to the pressing direction. The pressing member and the second elastic member control a posture of the optical element at a substantially central part in a main scanning direction.

Abstract: Fiber optic scanner and method for transmitting and receiving optical signals and range imaging camera including fiber optic scanner. The fiber optic scanner includes a light guide array including individual light guides arranged such that a first end has first ends of the individual light guides arranged in an image plane of collimating optics and a second end has second ends of the individual light guides arranged in a circular manner. A central light guide includes a first end arranged at a center of the circularly arranged second ends of the individual light guides and a motor driven reflector arranged to guide light emerging from the circularly arranged ends of the individual light guides into the central light guide.

Abstract: A laser beam is periodically deflected before being directed into a sample volume. The beam is deflected at a frequency such that the beam makes one or more passes through the sample volume while data are collected from the sample volume. The amplitude of motion of the beam, the dwell time of the beam at any given point, and the Gaussian intensity profile of the beam cooperate to produce an effective flat topped illumination profile for the light that is incident on specimens in the sample volume. The total photon exposure at any given point in the sample volume is a function of both the beam intensity and the dwell time at that location. Therefore, a longer dwell time and lower intensity at the edge of the profile are in balance with a shorter dwell time and higher intensity at the center of the profile.

Abstract: An optical pattern uses a single rotating component. The rotating component includes a number of deflection sectors. Each sector deflects an incident optical beam by a substantially constant angular amount although this amount may vary from one sector to the next. The rotating component may be combined with an imaging lens group that produces, for example, image points, spots, or lines displaced along a line locus.

Abstract: An optical scanning device includes a coupling optical system, a light source including a plurality of light emitting units for emitting light beams, and a deflector including a deflecting surface for deflecting the light beams. The coupling optical system is arranged on an optical path between the light source and the deflector so that the light beams enter the deflector at an angle with respect to a normal direction of the deflecting surface in a sub-scanning direction. The light emitting units are arranged two-dimensionally, and a distance between two light emitting units at opposite ends in a main scanning direction is smaller than a distance between two light emitting units at opposite ends in the sub-scanning direction.

Abstract: In an image forming apparatus provided with an optical beam scanning apparatus according to the invention, an optical beam scanning apparatus of an overillumination scanning optical system includes a semiconductor laser device as a light source, a pre-deflection optical system, a polygon mirror, and a post-deflection optical system, with a width of the luminous flux made incident on the polygon mirror being wider than a width of one reflecting surface forming the polygon mirror, wherein at least two sheets of flat plate for transmitting the luminous flux scanned by the polygon mirror are provided in the post-deflection optical system. In accordance with an image forming apparatus provided with an optical beam scanning apparatus according to the invention, not only a wave front aberration on a photoconductive drum can be suitably corrected, but suitable beam diameter and beam profile can be obtained on the photoconductive drum.

Abstract: A plastic optical element for use in an optical scanning device including light effective portions that focus light, and at least one link portion that connects the light effective portions in the sub-scanning direction, the link portion forming a border arc having a curvature radius R of 2 mm or greater and contacting the light effective portions such that the tangent of the light effective portion at the connection point of the light effective portion and the border arc matches the tangent of the border arc at the connection point.

Abstract: If inclination correction of scanning line is performed while the incident position of the laser beam is not suitable, the shape of a spot of the laser beam which forms an image on a photosensitive drum may not be uniform depending on the scanning position of the laser beam. The housing is provided with a U-shaped groove to which the convex portion of a lens hold member that holds the lens is engaged. With the position of the convex portion adjusted, the convex portion is attached and secured in the U-shaped groove. Thus, the installation position of the lens to an optical path of the laser beam is adjusted, and the lens can be rotated and adjusted in order to correct an inclination or a bending of scanning line.

Abstract: An optical deflector is disclosed which is capable of preventing unnecessary reflection by a member disposed behind a reflecting portion. The optical deflector includes a substrate portion, a reflecting portion can swing about a swinging motion axis with respect to the substrate portion, and an aperture stop portion which includes an aperture and blocks at least part of a light beam other than a light beam entering the aperture among an incident luminous flux to the optical deflector. The aperture allows passage of the incident luminous flux toward the reflecting portion and that of an emergent luminous flux reflected by the reflecting portion. At least part of an aperture rim of the aperture stop portion has a shape that makes the width of the aperture narrower from a light-beam-incoming side toward a reflecting portion side.

Abstract: A disclosed vertical cavity surface emitting laser device emits light orthogonally in relation to a substrate and includes a resonator structure including an active layer; and semiconductor multilayer reflectors disposed in such a manner as to sandwich the resonator structure between them and including a confinement structure which confines an injected current and transverse modes of oscillation light at the same time. The confinement structure has an oxidized region which surrounds a current passage region. The oxidized region is formed by oxidizing a part of a selective oxidation layer which includes aluminum and includes at least an oxide. The selective oxidation layer is at least 25 nm in thickness. The semiconductor multilayer reflectors include an optical confinement reducing section which reduces optical confinement in a transverse direction. The optical confinement reducing section is disposed on the substrate side in relation to the resonator structure.

Abstract: An optical scanning apparatus having a low-height optical box and accurately arranged reflecting mirrors, and an image forming apparatus using the same. The imaging optical system includes: an imaging optical element which a scanning beam transmits off a profile center thereof in a sub-scanning direction during guiding a beam from a light source to a scanning surface by an imaging optical system via a deflector; a first mirror which deflects the beam transmitted the imaging optical element to fold an optical path toward the edge-surface-A side where within the sub-scanning section, the edge surface A is one of the edge surfaces of the imaging optical element closer to a passing position of the scanning beam; and a second mirror. The second mirror is disposed between the deflection unit and imaging optical element so that the second mirror exists across a plane including the edge surface A.

Abstract: F-theta lenses, included in scanning lens systems, are arranged on a main scanning plane facing an optical deflector and substantially linearly symmetrically on the main scanning plane with reference to a rotational center of the optical deflector. Each f-theta lens has a no-power portion in the main scanning direction. Synchronization-detecting light passes through the no-power portion of the f-theta lens, thus enabling reduction in color shift due to temperature variation in an image forming apparatus without increasing the cost and complexity in controlling color shift.

Abstract: A laser scanning unit for a laser printer includes a frame connected to a casing, an optical system module installed on the frame directly for generating laser beams according to print data, an optical scanning module fixed on the frame for reflecting the laser beams generated by the optical system module, a curved lens for reflecting the laser beams reflected from the optical scanning module, and a reflector module installed on the frame directly for reflecting the laser beams reflected from the curved lens to an organic photo conductor.

Abstract: An optical scanning device includes a light source, a deflector, and an optical system including an elongated optical element that focuses deflected luminous flux on a surface of a medium to be scanned. The optical element is supported by a first elastic member and reinforced by a reinforcing member arranged outside a beam effective range along a length of the optical element. The optical element is pressed by a pressing member in a pressing direction orthogonal to a deflection direction, and biased by a second elastic member in a direction opposite to the pressing direction. The pressing member and the second elastic member control a posture of the optical element at a substantially central part in a main scanning direction.

Abstract: A two-dimensional scanning projector causing a light beam to scan in a first direction and a second direction orthogonal to the first direction, comprising: a first deflector which deflects the light beam in the first direction; and a scanning optical system arranged between the first deflector and a scanned surface, wherein the first deflector is arranged such that a rotation axis of the first deflector is inclined, in a plane including an optical axis of the scanning optical system and the second direction, by a first angle with respect to the second direction, and the light beam is incident on the first deflector such that, in the plane including the optical axis and the second direction, a chief ray of the light beam entering a center of a projected image is obliquely incident on the first deflector to form a second angle with respect to the optical axis.

Abstract: A technique capable of achieving reduction in space of allocating an optical system and improvement of an optical characteristic of a scan light in an optical scanner that scans a light flux from a light source on each of a photosensitive surface of a plurality of photoconductors in a main-scanning direction is provided.

Abstract: An optical scan apparatus is configured to include a light source emitting a light beam; a vibration mirror deflecting the light beam emitted from the light source to scan a scan area; a drive unit driving the vibration mirror; and an optical imaging system focusing the light beam deflected by the vibration mirror on a predetermined focus position, and having optical power to correct a displacement of the focus position which occurs due to a deformation of the vibration mirror caused by its own vibration.

Abstract: A casing 20 of a mobile phone body is provided with a sub-liquid-crystal display panel 23, a projector lens 26, a light source 35 including an LED. The sub-liquid-crystal display panel 23 and the projector lens 26 are movable between a normal position contained within the casing 20 and a raised position raised from the normal position. The sub-liquid-crystal display panel 23 is fixed at the raised position roughly perpendicularly to the light axis Q between the-sub-liquid-crystal display panel 23 and the light source 35 so that the light axis of the projector lens 26 is substantially aligned with the light axis Q. The illumination light from the light source is set to be parallel rays.

Abstract: In an image forming apparatus provided with an optical beam scanning apparatus according to the invention, an optical beam scanning apparatus of an overillumination scanning optical system includes a semiconductor laser device as a light source, a pre-deflection optical system, a polygon mirror, and a post-deflection optical system, with a width of the luminous flux made incident on the polygon mirror being wider than a width of one reflecting surface forming the polygon mirror, wherein at least two sheets of flat plate for transmitting the luminous flux scanned by the polygon mirror are provided in the post-deflection optical system. In accordance with an image forming apparatus provided with an optical beam scanning apparatus according to the invention, not only a wave front aberration on a photoconductive drum can be suitably corrected, but suitable beam diameter and beam profile can be obtained on the photoconductive drum.

Abstract: A surface emitting laser element is disclosed. The surface emitting laser element includes a resonator structural body including an active layer, first and second semiconductor distributed Bragg reflectors which sandwich the resonator structural body, and a confinement structure which can confine an injection current and a lateral mode of oscillation light at the same time by being formed with selective oxidation of a layer to be selectively oxidized containing aluminum in the first semiconductor distributed Bragg reflector. A thickness of the layer to be selectively oxidized is 28 nm, and a temperature when an oscillation threshold current becomes a minimum value is approximately 17° C.

Abstract: An optical scanning device includes a light source for emitting first light beams, a deflecting unit that deflects the first light beams as second light beams having scanning lines that are substantially arc shaped, a scanning lens disposed in a light path of one of the second light beams, and a light-blocking member interposed between the deflecting unit and the scanning lens. The light-blocking member blocks reflected light generated from the one of the second light beams when the second light beam enters the scanning lens. The light-blocking member protrudes toward the second light beam path along at least a scanning area of the second light beam, and includes a protruding edge section curving in substantially a same arc shape as the scanning line.

Abstract: An optical scanner includes a rotation control unit to change a number of revolutions of a rotary deflector to change a ratio of a scan speed of a light beam scanned on the surface of a latent image bearing member to a linear velocity of the latent image bearing member in accordance with a change in a linear velocity of the latent image bearing member, an inclination adjustment unit to adjust inclination of a scan line relative to a reference scan line on the latent image bearing member, an inclination adjustment unit controller to adjust the inclination adjustment unit based on the ratio, and a scan initiation unit to initiate scanning of the light beam on the surface of the latent image bearing member after adjustment of inclination is completed and the rotary deflector starts rotating at a constant speed for writing a latent image.

Abstract: Some embodiments of the present invention provide adapters for use in posterior imaging systems. The adapters include lens set configured to adapt the posterior imaging system to operate as an anterior imaging system. Related optical coherence tomography systems and anterior imaging systems are also provided herein.

Abstract: A light source unit includes a holder, a light source, coupling lens, and a support member. The light source is supported by the holder and projects a light beam against a target. The coupling lens adjusts an optical axis of the light beam. The support member contacts the holder and the coupling lens to fix the coupling lens in place on the holder after the coupling lens adjusts the optical axis of the light beam. The holder and the coupling lens are adhered to the support member using an adhesive agent. An optical scanner includes a rotary deflector to deflect and scan the light projected from the light source unit, a scan optical element to focus the light deflected by the rotary deflector, and the light source unit. An image forming apparatus includes the optical scanner.

Abstract: Disclosed is a method for manufacturing a surface-emitting laser device that emits laser light in a direction perpendicular to a substrate. The method includes manufacturing a laminated body in which a lower reflecting mirror, a resonator structure including an active layer, and an upper reflecting mirror including a selectively oxidized layer are laminated on the substrate; etching the laminated body from an upper surface to form a mesa structure having at least the selectively oxidized layer exposed at a side surface; and mounting the laminated body on a tray having a front surface shaped to follow a warpage of the laminated body at an oxidation temperature and selectively oxidizing the selectively oxidized layer from the side surface of the mesa structure, thereby generating a confinement structure in which a current passing region is surrounded by an oxide.

Abstract: An image reading apparatus comprises an original placement portion on which an original is to be placed, optical unit for optically scanning the original on the original placement portion while moving relative to the original placement portion and a guide member that guides movement of the optical unit. The optical unit includes a sliding member having a screw portion that slides in contact with the guide member and a screw hole portion to which the sliding member is mounted. The screw portion of the sliding member is plastically deformable and screwed into the screw hole portion while being plastically deformed.

Abstract: A laser light projector includes a laser beam generated by a laser light source, a scanner associated with the laser light source and having one or more moving mirrors capable of scanning the laser beam along X-Y coordinates, a scan-fail monitor and a safety-lens. The safety-lens includes a plurality of powers arranged for increasing the safety of the projected light within audience areas by increasing beam divergence in the audience, while keeping beam divergence low above the heads of the audience, thus allowing mirror targeting to occur.

Abstract: An optical device includes an optical component that reflects or shapes a light beam. In a particular embodiment, the optical device can include a bending moment generating structure that generates a bending moment in a supported portion of the optical component. The optical device can also include an adjusting mechanism that adjusts the bowing amount of the optical component by adjusting the bending moment of the bending moment generating structure.

Abstract: A scanning optical device, comprises a light source to emit a light beam; a deflecting section to deflect the emitted light beam so as to scan; an optical element to make the scanning light beam to converge; and a correcting mechanism to correct an attitude of the optical element so as to adjust a convergence position of the scanning light beam; wherein at least a part of the correcting mechanism is arranged between the deflecting section and the optical element.

Abstract: A process for enhancing an illusion created by a mirror labyrinth containing a series of interreflective mirrors includes the placement of a rotatable mirrored stile rotating about a vertical axis within the mirror labyrinth to interact with the series of interreflective mirrors to enhance the illusion created by the mirror labyrinth. The rotatable mirrored stile preferably has a motor drive mechanism mountable to a floor or ceiling of a mirror maze. A polygonal post is mounted to the drive mechanism to define a rotational axis with the post defining from two to eight rotationally degenerate faces. At least one of the rotationally degenerate faces is mirrored.

Abstract: A winged rotatable mirrored stile is provided having a post mounted to define a vertical rotational axis in a mirror labyrinth. A plurality of wings extends radially from the post with each of the wings, at least one wing face supporting a mirror. A mirror labyrinth is provided that includes multiple fixed position interreflective mirrors and a rotatable mirrored stile sharing reflections with the multiple fixed position interreflective mirrors to enhance the disorienting and therefore amusement value of the labyrinth.

Abstract: An optical scanning device includes a light source, a deflector, and an optical system including an elongated optical element that focuses deflected luminous flux on a surface of a medium to be scanned. The optical element is supported by a first elastic member and reinforced by a reinforcing member arranged outside a beam effective range along a length of the optical element. The optical element is pressed by a pressing member in a pressing direction orthogonal to a deflection direction, and biased by a second elastic member in a direction opposite to the pressing direction. The pressing member and the second elastic member control a posture of the optical element at a substantially central part in a main scanning direction.

Abstract: Scanning projection device PJ two-dimensionally deflects a beam emitted from light source unit 1 and performs scanning with deflection element 3, and projects the beam obliquely on screen SC with projection optical system 7. By defining a range of an incident angle to screen SC properly, projection optical system 7 does not disturb an observation of images, and a correction of a spot shape does not become difficult. Further, by defining a ratio of scan-angle magnifications between in the vertical direction and the horizontal direction properly, difference in resolution between in the vertical direction and the horizontal direction can be reduced, and a high-quality and excellent image can be displayed, even when a beam obliquely projected.

Abstract: An imaging lens good in mass-productivity, compact, low in manufacturing cost, good in aberration performance is provided by effectively correcting aberrations without greatly varying the variation of the thickness of a curing resin. An imaging device having such an imaging lens and a portable terminal are also provided. A third lens (L3) has a flat surface on the object side, a convex surface near the optical axis on the image side, and a concave aspheric surface around the peripheral portion within the region where a light beam passes. Therefore, it is possible to reduce the other optical aberrations such as distortion and simultaneously to design the imaging lens so that the astigmatism takes on a maximum value at the outermost portion. Hence, the resolutions at low to middle image heights are high. In addition, such a shape does not cause a large variation of the thickness of the third lens (L3) from the region along the axis to the periphery.

Abstract: An optical scanning unit that includes a first optical device that forms collimated light from light radiated from a light source, a second optical device that focuses the collimated light onto a deflector, and an imaging optical device that focuses light deflected by the deflector onto an exposure object. The optical scanning unit further includes a refraction unit and a diffraction unit, and the power of the refraction unit is ?r, the power of the diffraction unit is ?d, and the ratio ?r/?d is such that 0.5<?r/?d<1.3.

Abstract: Provided are forward-imaging optical coherence tomography (OCT) systems and probes.

Abstract: This invention relates to a method of three-dimensional targeting, by galvano motor scanning head means using a combination of pre-objective and post-objective scanning techniques whereby a collimated input to collimated output beamexpander (2, 3) is used to size a beam or laser beam input into said galvano motor scanning head and a flat-field or f-Theta or telecentric lens (6) or lenses are used to focus said beam or laser beam at a target plane and where altering the separation of the elements (2, 3) within said beamexpander will alter the beam or laser beam from a collimated to a converging or diverging output into said galvano motor scanning head to alter the focal distance to said target plane.

Abstract: An optical scanner that may assemble the lens design for varying the focus and resolution, having a light source, a reflection compound mirror, a charge coupled device, a basic objective lens and a compound lens. The basic objective lens is designed by simulation software. According to the lens design theory, the compound lens is designed. By incorporating the basic objective lens and the compound lens, different resolutions such as 1200 dpi, 1600 dpi and 2400 dpi of the optical scanner are obtained without redesigning the lens device, the current specification of the optical scanner is also varied.

Abstract: An optical lens device of image scanner includes a diaphragm and plural lenses. The plural lenses, diaphragm, and image induction element are linearly arranged for defining an optical path between the document and the image induction element. Wherein, among the plural lenses, the one that is most close to the manuscript is called the first lens, and the other one that is most close to the image induction element is called the last lens, and the distance between the last lens and the image induction element is called BFL, and the length of the image induction element is called image height, and the total optical length between the document and the image induction element is called TT, and the effective focus length of the optical lens device is called EFL. If the optical lens device fulfills following conditions: the diameter of the last lens/the diameter of the first lens>1; EFL/image height<0.9; and BFL/TT<0.