Abstract: A projection zoom lens is configured by a first group having a negative refractive force, a second group having a positive refractive force, a third group having a positive refractive force, an aperture diaphragm, a fourth group having a positive refractive force, and a fifth group having a positive refractive force. The groups are arranged in aforementioned order from an enlarged-side to a reduced-side in the projection zoom lens, wherein the reduced-side is telecentric, wherein the first group is configured by a first sub-lens group having a positive or a negative refractive force, a second sub-lens group having a negative refractive force, and a third sub-lens group having a negative refractive force, wherein the sub-lens groups are arranged sequentially from the enlarged-side to form a focusing group, wherein the second group to the fifth group constitute a zooming group.

Abstract: An imaging optical system includes a positive or negative first lens group including a negative lens element closest to the object, a diaphragm, and a positive second lens group. The negative lens element closest to the object has an object-side aspherical surface including a paraxial convex surface, a paraxial curvature that is the greatest within the effective aperture, and a portion within the effective aperture having a curvature less than ½ of the paraxial curvature. These conditions are satisfied: R1/f<1.35 D1/f>0.4 ?2.5<f1/f<?1.3 V>56 “f” designates the overall focal length; f1, R1 and D1 respectively designate the focal length, paraxial radius of curvature of an object-side surface, and thickness, of the negative lens element closest to the object; and V designates the Abbe number regarding the d-line of a lens element, within the second lens group, closest to the diaphragm.

Abstract: An imaging optical system includes a positive or negative first lens group including a negative lens element closest to the object, a diaphragm, and a positive second lens group. The negative lens element closest to the object has an object-side aspherical surface including a paraxial convex surface, a paraxial curvature that is the greatest within the effective aperture, and a portion within the effective aperture having a curvature less than ½ of the paraxial curvature. These conditions are satisfied: R1/f<1.35 D1/f>0.4 ?2.5<f1/f<?1.3 V>56 “f” designates the overall focal length; f1, R1 and D1 respectively designate the focal length, paraxial radius of curvature of an object-side surface, and thickness, of the negative lens element closest to the object; and V designates the Abbe number regarding the d-line of a lens element, within the second lens group, closest to the diaphragm.

Abstract: An imaging optical system includes a positive or negative first lens group including a negative lens element closest to the object, a diaphragm, and a positive second lens group. The negative lens element closest to the object has an object-side aspherical surface including a paraxial convex surface, a paraxial curvature that is the greatest within the effective aperture, and a portion within the effective aperture having a curvature less than ½ of the paraxial curvature. These conditions are satisfied: R1/f<1.35 D1/f>0.4 ?2.5<f1/f<?1.3 V>56 “f” designates the overall focal length; f1, R1 and D1 respectively designate the focal length, paraxial radius of curvature of an object-side surface, and thickness, of the negative lens element closest to the object; and V designates the Abbe number regarding the d-line of a lens element, within the second lens group, closest to the diaphragm.

Abstract: An imaging optical system includes a positive or negative first lens group including a negative lens element closest to the object, a diaphragm, and a positive second lens group. The negative lens element closest to the object has an object-side aspherical surface including a paraxial convex surface, a paraxial curvature that is the greatest within the effective aperture, and a portion within the effective aperture having a curvature less than ½ of the paraxial curvature. These conditions are satisfied: R1/f<1.35 D1/f>0.4 ?2.5<f1/f<?1.3 V>56 “f” designates the overall focal length; f1, R1 and D1 respectively designate the focal length, paraxial radius of curvature of an object-side surface, and thickness, of the negative lens element closest to the object; and V designates the Abbe number regarding the d-line of a lens element, within the second lens group, closest to the diaphragm.

Abstract: An imaging optical system includes, at the vicinity of the optical axis, a positive first lens element having an object-side convex surface, a negative second lens element having an object-side concave surface, a positive third lens element having an image-side convex surface, and a fourth lens element having an image-side concave surface. The fourth lens element is provided with aspherical surfaces on both sides such that a combined refractive power thereof has an increasingly weaker negative refractive power toward the outer periphery thereof. The following conditions (1) and (2) are satisfied: 38<?d1??d2<80??(1), and ?1.2<r3/f<?0.6??(2), wherein ?d1 and ?d2 designate the Abbe numbers at the d-line of the first and second lens elements, respectively, r3 designates the radius of curvature of the object-side surface of the second lens element, and f designates the focal length of the imaging optical system.

Abstract: An individual identifying/attribute authenticating system includes a portable terminal possessed by a buyer of a good or service and an authenticating terminal set at a seller of the good or service. The portable terminal includes at least a component that generates an electronic signature by using a signature key and a component that transmits an electronic certificate and the electronic signature to the authenticating terminal. The authenticating terminal includes at least a component that judges whether or not the electronic signature is legitimate, a component that acquires an attribute information listed in the electronic certificate, in a case in which the electronic signature is legitimate, and a component that judges whether or not the attribute information satisfies a sales restricting condition of the good or service.