Abstract: An imaging-lens substantially consists of a first-lens-group, a stop and a second-lens-group in this order from object-side. The first-lens-group substantially consists of three or less lenses including a negative-lens arranged closest to object-side and a positive-lens arranged on image-side of the negative-lens. The first-lens-group includes a negative-lens having a meniscus-shape with its convex-surface facing object-side and a positive-lens cemented on the negative-lens in this order from object-side. The second-lens-group substantially consists of five or less lenses including a cemented-lens of two lenses of a positive-lens and a negative-lens and a single-lens having positive-refractive-power, and which is arranged on image-side of the cemented-lens.

Abstract: A zoom lens including, from an object: a front group having negative power; and a rear group having positive power, the rear group including, from the object, a positive lens, a negative lens having a concave surface facing the object, a cemented positive lens constructed by a negative lens and a positive lens, and a cemented lens constructed by a positive lens and a negative lens, the rear group further including a focusing group disposed to the object side of the positive lens La for focusing from infinity to a close object by moving from the object side to an image side, a distance between the front group and the rear group being varied thereby zooming from a wide-angle end state to a telephoto end state, and given condition being satisfied, thereby providing a downsized zoom lens having wide angle of view and excellent optical performance with fewer lenses.

Abstract: The endoscope objective lens is configured such that focusing from the farthest object to the nearest object is achieved by moving at least one lens group other than the most object-side lens group along the optical axis. One of the at least one lens group to be moved during focusing is a negative lens group. The one negative lens group that is moved during the focusing consists of a cemented lens that is formed by a positive lens and a negative lens cemented together in this order from the object side. The cemented surface of the cemented lens is oriented such that the concave surface faces the object side. Given conditional expressions are satisfied.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (?1+?2)/2>60 where n1 and ?1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and ?2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: There is provided a lens module, including: a first lens having positive refractive power, an object-sided surface thereof being convex; a second lens having negative refractive power, an image-sided surface thereof being concave; a third lens having positive refractive power; a fourth lens having negative refractive power, an image-sided surface thereof being convex; and a fifth lens having negative refractive power, an image-sided surface thereof being concave, wherein the fourth lens satisfies Conditional Expression 1, f ? ? 4 f < - 3.0 [ Conditional ? ? Expression ? ? 1 ] where f is an overall focal distance of an optical system and f4 is a focal distance of the fourth lens.

Abstract: A lens apparatus includes an optical system including multiple lens units, the optical system including: a first lens unit which is disposed closest to an object side in the optical system and is rotatable about a point in a vicinity of an optical axis of the optical system; and at least one lens unit which is movable in a direction including a component in a direction perpendicular to the optical axis. The following conditional expression is satisfied: 1.0<ft/|f1|<2.2, where ft represents a focal length of the optical system at a telephoto end, and f1 represents a focal length of the first lens unit. At least one of rotation of the first lens unit or movement of the at least one lens unit in the direction including the component in the direction perpendicular to the optical axis changes an image formation position in the direction perpendicular to the optical axis.

Abstract: An inner focus lens system comprising lens units each composed of at least one lens element, wherein a most object side lens unit is provided and is fixed with respect to an image surface in focusing, and the conditions: BF/Y<1.7 and (L×FNo)/f<2.2 (BF: a distance from an image side surface apex of a most image side lens element to the image surface, Y=f×tan ?, L: an overall length of lens system, FNo: a F-number of lens system, f: a focal length of lens system, ?: a half view angle of lens system) are simultaneously satisfied, or only the condition: (L×FNo)/f<2.0 (L: the overall length of lens system, FNo: the F-number of lens system, f: the focal length of lens system) is satisfied.

Abstract: An optical image capturing system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element. The first lens element with positive refractive power has a convex object-side surface. The second through seventh lens elements all have refractive power. The sixth lens element has an object-side surface and an image-side surface which are both aspheric. The seventh lens element has an object-side surface and an image-side surface which are both aspheric, its wherein the image-side surface of the seventh lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof.

Abstract: An imaging lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. The first lens element with negative refractive power has a convex object-side surface and a concave image-side surface. The second lens element has positive refractive power. The third lens element has refractive power. The fourth lens element with refractive power has an object-side surface and an image-side surface being aspheric. The fifth lens element with positive refractive power has an object-side surface and an image-side surface being aspheric. The sixth lens element with negative refractive power has a concave image-side surface, wherein at least one reflection point is formed on the image-side surface thereof.

Abstract: Disclosed herein is an imaging lens, including: a first lens having positive (+) power and being biconvex; a second lens having negative (?) power and being concave toward an image side; a third lens having positive (+) power and being biconvex; a fourth lens having positive (+) power and being convex toward the image side; and a fifth lens having negative (?) power and being concave toward the image side, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are sequentially disposed from an object side.

Abstract: Fabricating optical devices can include mounting a plurality of singulated lens systems over a substrate, adjusting a thickness of the substrate below at least some of the lens systems to provide respective focal length corrections for the lens systems, and subsequently separating the substrate into a plurality of optical modules, each of which includes one of the lens systems mounted over a portion of the substrate. Adjusting a thickness of the substrate can include, for example, micro-machining the substrate to form respective holes below at least some of the lens systems or adding one or more layers below at least some of the lens systems so as to correct for variations in the focal lengths of the lens systems.

Abstract: A method comprises depositing an optical filter layer on a glass wafer, then cutting the wafer into dice. The dice are positioned on a carrier and encapsulated in a molding compound to form a reconstituted wafer, and the wafer is back-ground and polished. Lens faces are positioned on opposing surfaces of the glass dice and spacers are positioned on one side of the wafer. The wafer is then cut into lens modules, each having two side-by-side lenses with an opaque molding compound barrier between. The individual modules are attached to devices that require dual lenses, such as, e.g., proximity sensors that use a light source and a light receiver or detector.

Abstract: There are provided an inner focus lens consisting of a first lens group, an aperture diaphragm, and a second lens group in order from an object side. The first lens group has a positive first lens element, a positive second lens element, and a negative third lens element; or a positive first lens element, a positive second lens element, a positive third lens element, and a negative fourth lens element, in order from the object side. One lens element in the second lens group is moved with respect to an image surface in focusing, some of the lens elements thereof are moved in a direction perpendicular to an optical axis. The inner focus lens satisfies 0.2<|fF/fO|<3.0 (fF: a focal distance of a focus lens, fO: a synthetic focal distance of the lens elements moving in the direction perpendicular to the optical axis).

Abstract: There are provided an inner focus lens consisting of a first lens group, an aperture diaphragm, and a second lens group in order from an object side. The first lens group has a positive first lens element, a positive second lens element, and a negative third lens element, or has a positive first lens element, a positive second lens element, a positive third lens element, and a negative fourth lens element, in order from the object side. One lens element in the second lens group is moved with respect to an image surface in focusing. The second lens group has five or more lens elements, and has a configuration including a negative lens element, a positive lens element, and a positive lens element in order from the object side.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (v1+v2)/2>60 where n1 and v1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and v2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: An imaging lens includes a plurality of lenses, wherein a surface on an image side of a lens on an object side and a surface on the object side of a lens on the image side of two lenses arranged adjacently and separately from each other face each other across an air space, the air space is termed an air lens, a shape of the air lens is defined such that the surface on the image side of the lens on the object side is taken as a surface on the object side of the air lens and the surface on the object side of the lens on the image side is taken as a surface on the image side of the air lens, and an air lens positioned on a most object side and an air lens positioned on a most image side each have a biconvex shape.

Abstract: A focus control device includes a first focus-lens group, a second focus-lens group, a wobbling control unit that generates a first wobbling control signal used to control a wobbling motion of the first focus-lens group and generates a second wobbling control signal used to control a wobbling motion of the second focus-lens group, and a phase control unit that controls the phase of the first and second wobbling control signals, wherein the phase control unit corrects the phase of the first wobbling control signal to cause the first focus-lens group to make a first target wobbling motion and corrects the phase of the second wobbling control signal to cause the second focus-lens group to make a second target wobbling motion.

Abstract: A projection lens for projecting an image beam is provided. The image beam is converted by a light valve from an illumination beam irradiating the light valve. The projection lens includes a first lens group, a second lens group, and a third lens group. The first lens group is disposed on a transmission path of the image beam, and has a first optical axis. The second lens group is disposed on both a transmission path of the illumination beam and the transmission path of the image beam, and between the light valve and the first lens group. The second lens group has a second optical axis. The second optical axis is inclined with respect to the first optical axis. The third lens group is disposed on the transmission path of the image beam, and between the first lens group and the second lens group. A projection apparatus is also provided.

Abstract: An imaging lens includes: a movable lens group with total positive refractive power, including first and second sub lens groups; and an ever-fixed lens group that is ever-fixed. The imaging lens has first and second focusing modes for focusing operation in first and second focus ranges, respectively. The first focus range covers from an object at an infinite distance to an object at a first finite distance, and the second focus range covers from an object at a second finite distance shorter than the infinite distance to an object at a third finite distance shorter than the first finite distance. The first sub lens group is configured to be fixed and the second sub lens group is configured to travel, during each of the first and second focusing modes. Traveling of the movable lens group toward object plane allows switching from the first to second focusing modes.

Abstract: A single focal length lens system comprising a front lens unit, an aperture diaphragm, and a rear lens unit, wherein the front lens unit is composed of three or less lenses including a negative lens located closest to the object side and a positive lens located on the image side relative to the negative lens, and does not move along an axis in focusing, the rear lens unit includes a focusing lens unit moving along the axis and a fixed lens unit not moving along the axis in focusing, and the conditions: 0.4<fW/fGF<1.5, 0.9<fW/T1<4.5, and ?0.3<fW/fG1<0.3 (fW, fGF, fG1: focal lengths of the entire single focal length lens system, the focusing lens unit, the front lens unit, T1: an axial distance from an object side lens surface of the negative lens to the aperture diaphragm) are satisfied.

Abstract: An imaging lens having reduced susceptibility to thermally-induced stress birefringence for imaging an object plane to an image plane; comprising a plurality of lens elements. The lens element that experiences a highest optical power density is fabricated using a glass having a negligible susceptibility to thermal stress birefringence as characterized by the thermal stress birefringence metric.

Abstract: An inner focus lens system comprising a first lens unit and subsequent lens units, wherein an aperture diaphragm is provided, the first lens unit is: fixed with respect to an image surface in focusing; and composed of five or more lens elements including a first positive lens element located closest to the object side and a second positive lens element, the subsequent lens units include at least a first focusing lens unit located closest to the object side and a second focusing lens unit, at least one of the first focusing lens unit and the second focusing lens unit is composed of two or less lens elements, at least one lens element is provided on the image side relative to the aperture diaphragm, and the condition: NF1?NF2 (NF1, NF2: the number of lens elements constituting the first, second focusing lens unit) is satisfied.

Abstract: The invention is directed to correcting compound lens forms for 3rd and 5th order ray aberrations. All lens design forms have limiting aberrations. The proposed classes of lenses can be corrected for all 3rd and 5th order ray aberrations. The limiting aberrations are seventh order or higher. A variety of these lenses are disclosed here for the sake of example. These lens design forms can be used in various applications including the objective lens for an endoscope or other optical instrument.

Abstract: An imaging mechanism includes: an imaging device; a light receiving section that is provided on one surface of the imaging device; a cover member that covers the one surface of the imaging device and the light receiving section; and a lens unit that has a plurality of lenses including a plano-convex lens having a flat portion and a lens barrel, and that is optically coupled to the light receiving section, the lens barrel fixing the plurality of lenses, wherein the plano-convex lens having the flat portion is provided at a closest position to the imaging device in the plurality of lenses such that the flat portion faces the imaging device, and the flat portion protrudes from an end of the lens barrel toward the imaging device and is fixed to the cover member.

Abstract: An optical image capturing system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element. The first lens element with positive refractive power has a convex object-side surface. The second through fifth lens elements all have refractive power. The fifth lens element has a convex image-side surface. The sixth lens element with positive refractive power has both of the object-side and image-side surfaces thereof being aspheric. The seventh lens element with negative refractive power has a concave image-side surface and both of the object-side and image-side surfaces thereof being aspheric. The image-side surface of the seventh lens element changes from concave at a paraxial region to convex at a peripheral region.

Abstract: Embodiments are disclosed herein related to the construction of optical elements for an RGB camera system. One disclosed embodiment provides a wide-angle lens construction, comprising a first, negative stage, and a second, positive stage positioned behind the first, negative stage along an optical axis of the lens construction. The second, positive stage further comprises a first positive lens substage, a first negative lens substage, a second positive lens substage, and a second negative lens substage.

Abstract: An optical system includes a positive lens unit, wherein the positive lens unit includes an optical element containing a base material and minute particles that are mixed with the base material and have Abbe number that is lower than that of the base material, and the minute particles are higher in density at a peripheral portion of the optical element than on an optical axis of the optical element.

Abstract: This invention provides an injection-molded plastic optical lens comprising, in order from a center to an edge thereof: an optical effective portion, a connecting portion and a peripheral portion that are concentrically formed; wherein the lens has an outer diameter D, the optical effective portion has an edge thickness ET1 and a central thickness CT, the connecting portion has a minimum thickness ET2, and the plastic optical lens satisfies the following relations: CT?0.30 mm and ET2/ET1<1.0. At least one lens element with refractive power can be disposed at each of the object side and the image side of the plastic optical lens of the present invention to form an optical lens assembly.

Abstract: An endoscope for oblique viewing including an image pickup device, a front lens group having a positive refractive power, a prism disposed on the CCD side of the front lens group, and a rear lens group disposed on the CCD side of the prism and having a positive refractive power.

Abstract: An optical system for an endoscope includes a negative lens-group, an aperture diaphragm and a positive lens-group in this order from an object side, wherein the negative lens-group includes a negative first-lens and a negative second-lens in this order from the object side; and wherein the optical system meets conditional expressions (1) and (2): 0.05<H(100)×(nd01?1)/Rf01<0.38??(1) and 0.5<enp/FL<2.5??(2), where: H(100) is a height at which a principal ray with a field angle of incidence of 100 degrees falls on a surface on the object side of the first lens; Rf01 is a curvature radius of the surface on the object side of the first-lens; nd01 is a refractive index of the first-lens; FL is a focal length of an entire system; and enp is a distance between an entrance pupil and the surface on the object side of the first lens.

Abstract: There is provided herein an optical system for a tip section of a multi-sensor endoscope, the system comprising: a front-pointing camera sensor; a front objective lens system; a side-pointing camera sensor; and a side objective lens system, wherein at least one of said front and side objective lens systems comprises a front and a rear sub-systems separated by a stop diaphragm, said front sub-system comprises, in order from the object side, a first front negative lens and a second front positive lens, said rear sub-system comprises, in order from the object side, a first rear positive lens, an achromatic sub-assembly comprising a second rear positive lens and a third rear negative lens, wherein the following condition is satisfied: f(first rear positive lens)?1.8f, where f is the composite focal length of the total lens system and f(first rear positive lens) is the focal length of said first rear positive lens.

Abstract: A first lens unit performing communication with an image pickup apparatus with a first voltage and a second lens unit performing communication with the image pickup apparatus with a second voltage are selectively attached to the image pickup apparatus. The image pickup apparatus includes a controller configured to operate with a third voltage different from at least one of the first and second voltages to output a signal for the communication with the first and second lens units, and a determiner configured to determine the type of the lens unit attached to the image pickup apparatus. The controller is configured to produce, as a voltage of the signal for the communication, from the third voltage, one of the first and second voltages corresponding to a determination result of the determiner.

Abstract: There are provided an inner focus lens consisting of a first lens group, an aperture diaphragm, and a second lens group in order from an object side. The first lens group has a positive first lens element, a positive second lens element, and a negative third lens element, or has a positive first lens element, a positive second lens element, a positive third lens element, and a negative fourth lens element, in order from the object side. One lens element in the second lens group is moved with respect to an image surface in focusing. The second lens group has five or more lens elements, and has a configuration including a negative lens element, a positive lens element, and a positive lens element in order from the object side.

Abstract: Provided is a lens module for imaging an object on an image plane. In the order from the object side to the image side of the lens module, the lens module includes a first lens made of glass and having positive refraction power, a second lens made of plastic and having negative refraction power, a aperture stopper, a third lens having positive refraction power, and a fourth lens having negative refraction power. The lens module satisfies the following formula: Vd1?Vd2?35; wherein, Vd1 is the Abbe number of the first lens in d light and Vd2 is the Abbe number of the second lens in the d light.

Abstract: A fish eye lens system and a photographing apparatus including the same, the fish eye lens system including, in an order from an object side to an image side: a first lens group having a negative refractive power; an aperture stop; and a second lens group having a positive refractive power, wherein the first lens group includes, in the order from the object side to the image side, a (1-A)-th lens group having a negative refractive power, a (1-B)-th lens group having a negative refractive power, and a (1-C)-th lens group including at least one positive lens, and wherein the (1-B)-th lens group is moved to perform focusing.

Abstract: An optical system for an endoscope includes a negative lens-group, an aperture diaphragm and a positive lens-group in this order from an object side, wherein the negative lens-group includes a negative first-lens and a negative second-lens in this order from the object side; and wherein the optical system meets conditional expressions (1) and (2): 0.05<H(100)×(nd01?1)/Rf01<0.38??(1) and 0.5<enp/FL<2.5??(2), where: H(100) is a height at which a principal ray with a field angle of incidence of 100 degrees falls on a surface on the object side of the first lens; Rf01 is a curvature radius of the surface on the object side of the first-lens; nd01 is a refractive index of the first-lens; FL is a focal length of an entire system; and enp is a distance between an entrance pupil and the surface on the object side of the first lens.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (?1+?2)/2>60 where n1 and ?1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and ?2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: An imaging lens includes: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power which is formed in a concave shape on both sides thereof; a third lens having a positive refractive power which is formed in a meniscus shape in which a concave surface is directed toward the side of an object; and a fourth lens having a negative refractive power in which a convex surface is directed toward the object side, which are sequentially disposed from the object side to the image side, wherein the imaging lens satisfies the following conditional expressions (1), (2), (3), (4) and (5): 0.40<f1/|f2|<0.80??(1) 0.80<|f2|/f3<1.50??(2) 0.90<f/|f4|<2.00??(3) 2.60<|(R2?R3)/f1|<4.00??(4) ?d1??d2>25.

Abstract: A taking lens system comprises a frontmost lens unit, a rearmost lens unit, and a plurality of lens units arranged between the frontmost lens unit and the rearmost lens unit. One of the plurality of lens units is a first focusing lens unit. During focusing from an infinite object distance to a close object distance, only the first focusing lens unit moves toward the image side in a first shooting mode, and at least two lens units in the taking lens system move in a second shooting mode. In the state in which the taking lens system is focused on an object at infinity, the positions of the first focusing lens unit and at least one lens unit in the taking lens system in the first shooting mode are different from those in the second shooting mode. The taking lens system satisfies the condition Mn1>Mn2.

Abstract: An optical system includes, in order from an enlargement conjugate side to a reduction conjugate side via a largest air gap, a front unit having a negative power, and a rear unit having positive power. The optical system satisfies 1.75<Ndn1<2.05, 0.02<?gFn1?(0.6438?0.001682×?dn1)<0.08, and 2.5<|fn1/F|<5.0, where fn1 represents a focal length of a negative lens in the front unit, Ndnl represents a refractive index of a material of the negative lens, ?dn1 represents an Abbe number of the material of the negative lens, ?gFn1 represents a partial dispersion ratio of the material of the negative lens, and F represents a focal length of the optical system.

Abstract: Provided is an optical system for a thermal image microscope. The optical system includes an image forming unit and a relay unit. The image forming unit forms a focus. The relay unit elongates an optical path. Here, the image forming unit includes six lenses. The relay unit includes two lenses. Aspherical surfaces of the lenses are all convex surfaces.

Abstract: This invention is a wide field surveillance, monocentric, refractive optical system with inherent features being, non-mechanical, compact, high resolution, a field of view up to two Pi steradians solid angle. The optics design uses a single optical system and multiple flat image collection devices. Multiple fiber plates translate and map the image off of the curved image surface to the flat image collection devices. The fiber plates also act to translate the image into a larger volume as compared to the curved image surface, allowing required volume for the multiple image collection devices. This invention uses a single refractive optical system with multiple CCD or CMOS detectors. Advantages over prior art are simple optical system, rugged optics, high resolution and single optics which is easily manufactured.

Abstract: The lens control device includes a wobbling controller that performs a wobbling operation for moving a predetermined drive lens minutely back and forth along the optical axis, an optical reduction controller that performs an optical canceling operation for moving a different drive lens minutely back and forth along the optical axis, to reduce change in magnification of a subject image which can be caused by the wobbling operation, the subject image being formed via the predetermined drive lens, and a controller that controls the optical reduction controller to perform the optical canceling operation for the change in magnification caused by the wobbling operation when a predetermined condition is not satisfied, and controls the optical reduction controller not to perform the optical canceling operation for the change in magnification caused by the wobbling operation when the predetermined condition is satisfied.

Abstract: A single focal length lens system comprising: at least a front lens unit having positive or negative power, and being fixed in focusing; a focusing lens unit having positive power, and moving along an optical axis in focusing; and a rear lens unit having negative power, and being fixed in focusing, wherein the focusing lens unit includes: a cemented lens of a negative lens and a positive lens; and a positive single lens located on the image side relative to the cemented lens and having an aspheric surface, the rear lens unit is composed of one single lens, and the condition: ?0.5<fW/fGR<?0.1 (fW, fGR: focal lengths of the entire single focal length lens system, the rear lens unit) is satisfied.

Abstract: Provided is a small-sized five-element image pickup lens which ensures a sufficient lens speed of about F2 and exhibits various aberrations being excellently corrected. The image pickup lens is composed of, in order from the object side, a first lens with a positive refractive power, including a convex surface facing the object side; a second lens with a negative refractive power, including a concave surface facing the image side; a third lens with a positive or negative refractive power; a fourth lens with a positive refractive power, including a convex surface facing the image side; and a fifth lens with a negative refractive power, including a concave surface facing the image side. The image-side surface of the fifth lens has an aspheric shape, and includes an inflection point at a position excluding an intersection point with the optical axis.

Abstract: A single focal length lens system comprising a front lens unit, an aperture diaphragm, and a rear lens unit, wherein the front lens unit is composed of three or less lenses including a negative lens located closest to the object side and a positive lens located on the image side relative to the negative lens, and does not move along an axis in focusing, the rear lens unit includes a focusing lens unit moving along the axis and a fixed lens unit not moving along the axis in focusing, and the conditions: 0.4<fW/fGF<1.5, 0.9<fW/T1<4.5, and ?0.3<fW/fG1<0.3 (fW, fGF, fGF: focal lengths of the entire single focal length lens system, the focusing lens unit, the front lens unit, T1: an axial distance from an object side lens surface of the negative lens to the aperture diaphragm) are satisfied.

Abstract: Provided are a wafer scale lens, which is so short in an optical total length with respect to an image height that it can correct an aberration satisfactory, and an optical system including the wafer scale lens and having a thin lens element on the side closest to the image. The optical system includes a first lens having a positive refractive power relative to an object, and a second lens arranged on the side of the image of the first lens and having a recessed shape on the side of the object. At least one lens is arranged on the side of the second lens.

Abstract: An endoscope objective lens unit includes a front lens group and a rear lens group with a diaphragm interposed therebetween. The front lens group includes a first lens and a second lens, and the rear lens group includes a third lens, a fourth lens and a fifth lens. The endoscope objective lens unit satisfies following expressions (1A) to (4): (1A) ?3 <SF ?1; (2) ?3 <Fr/Ff <?1.1; (3) ?1.6 <Ff/f <?0.6; and (4) Ff/f1 <1.6, where SF is a shape factor, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

Abstract: It is preferable that an image forming optical system includes in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a subsequent lens group having a positive refractive power as a whole, and that the third lens group includes only a cemented lens having a negative refractive power, which includes a positive lens and a negative lens in order from the object side. Moreover, it is preferable that a cemented surface of the cemented lens in the third lens group has a shape which is convex toward an image side.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, an aperture stop, and a rear lens group. In the optical system, the rear lens group includes a second lens unit configured to move during focusing. The first lens unit includes n positive lenses (n is an integer greater than 1) and one or more negative lenses. With an order of an optical member counted from the object side towards the image side being indicated by i (i is an integer equal to or greater than 1), a refractive index and an Abbe number of a material of an i-th positive lens of the first lens unit with respect to d-line light (Ndi, ?di), maximum and minimum values of the Abbe number ?di (max(?di), min(?di)), a minimum value of the refractive index Ndi (min(Ndi)), a focal length of the first lens unit (fp), and a focal length of the entire optical system (f) are appropriately set.