Abstract: A zoom lens according to the present invention includes sequentially from an object side: a first lens group having negative refractive power, and a second lens group having positive refractive power, and performs a magnification change operation by changing a gap between the adjacent lens groups. The zoom lens has specific optical characteristics represented by four expressions relating to the second lens group.

Abstract: A communication device includes a zoom lens that collects signal light.

Abstract: A communication device includes a zoom lens that collects signal light.

Abstract: A zoom lens according to the present invention includes sequentially from an object side: a first lens group having negative refractive power, and a second lens group having positive refractive power, and performs a magnification change operation by changing a gap between the adjacent lens groups. The zoom lens has specific optical characteristics represented by four expressions relating to the second lens group.

Abstract: A zoom lens includes a first and a second lens group respectively having negative and positive refractive power, and changes a focal length by changing a distance between the first and the second lens group. The second lens group includes a first lens having positive refractive power and a convex surface, a second lens having positive refractive power, an aspheric surface, and a convex surface, a third lens having negative refractive power, a fourth lens having positive refractive power, and a fifth lens including one lens or more having positive refractive power. The third and the fourth lenses are connected, and the zoom lens satisfies Nd21>1.8 and ?d24>80, where Nd21 is a refractive index of the first lens of the second lens group at a d-line, and ?d24 is an Abbe number of the fourth lens of the second lens group at a d-line.

Abstract: A zoom lens includes a first and a second lens group respectively having negative and positive refractive power, and changes a focal length by changing a distance between the first and the second lens group. The second lens group includes a first lens having positive refractive power and a convex surface, a second lens having positive refractive power, an aspheric surface, and a convex surface, a third lens having negative refractive power, a fourth lens having positive refractive power, and a fifth lens including one lens or more having positive refractive power. The third and the fourth lenses are connected, and the zoom lens satisfies Nd21>1.8 and ?d24>80, where Nd21 is a refractive index of the first lens of the second lens group at a d-line, and ?d24 is an Abbe number of the fourth lens of the second lens group at a d-line.

Abstract: A toner supply bias voltage that is a vibrating voltage comprising an a.c. voltage and a d.c. voltage is applied to a toner supply roller. The d.c. voltage of toner supply bias voltage is changed in dependence upon a variation in the value of developing bias voltage. The lowering in the density at the leading end part of an image, the lowering in the density at the trailing end part of an image, and the uneven developing can be eliminated by satisfying the relationships100.ltoreq..vertline.VB.vertline..ltoreq..vertline.VSR.vertline.,2(.vertline.VSR-VB.vertline.+50).ltoreq..vertline.VPP.vertline..ltoreq.2.ve rtline.VSR.vertline. andf.gtoreq.v/lare satisfied, where VB is a developing bias voltage (unit: Volt), VSR is a d.c. voltage of the toner supply bias voltage (unit: Volt), VPP is a peak-to-peak value of the a.c.

Abstract: A developing apparatus includes a developing roller having a surface on which a layer of a non-magnetic single component developing agent (toner) is adapted to be formed, a toner supply roller held in contact with the developing roller so as to electrify the toner and also to supply the toner to the developing roller, and a toner regulating blade for regulating the toner on the developing roller so as to form a film of the toner thereon. The toner regulating blade is formed into a generally L-shape, and with a simple construction, the thickness of the toner layer, formed on the developing roller, can be stabilized, and also a torque of the developing roller can be reduced, and the degradation of a printed image is suppressed, thereby stabilizing the printed image.

Abstract: A nonmagnetic single component developing device comprises a developing roller having an outer surface on which a layer of a nonmagnetic single component developer composed of nonmagnetic toner is formed, a toner supply roller arranged in rear of the developing roller and made into contact therewith, for agitating and supplying the toner, a toner regulating blade arranged above the developing roller and made into press-contact therewith, for regulating a volume of the toner. The toner supply roller is electroconductive, and is applied thereto with an a.c. voltage so as to prevent lowering of the density in the leading and trailing end parts of an image so as to obtain a uniform image characteristic.

Abstract: A developing apparatus has a toner reservoir for holding a non-magnetic toner, a toner supply roller including a supply surface for receiving the toner from the toner reservoir and electrifying the toner thereon, an electrostatic latent image carrier including a curved or flat latent image surface on which a latent image formed by an electrostatic voltage distribution thereon is developed by the toner transferred from the supply surface, and a toner seal surface arranged adjacent to the toner supply roller to contact a remaining part of the toner on the supply surface after the latent image development so that the remaining part of the toner is taken into the toner reservoir. The respective frictional coefficients between the toner seal surface and the toner and between the toner particles are selected to prevent a disturbance of toner condition between the toner and the toner seal surface.

Abstract: A developing unit, an image-transfer unit and a fixing unit are located in that order in a vertically long housing from the bottom to the top of the housing, and a ventilation passage different from a sheet conveying passage, is formed having an inlet opening formed in the bottom part of the housing and the outlet opening formed in the top part of the housing and extending by way of the developing unit, the image-transfer unit and the fixing unit. Air in the ventilation passage is warmed up by extra heat from the fixing unit so as to induce an ascending air stream which expels NOx and ozone generated by corona discharge and which cools the fixing unit. With this arrangement, the necessity of a ventilating fan can be eliminated so as to miniaturize the electrophotographic printing apparatus and to reduce the cost while eliminating noise caused by a ventilating fan.