Abstract: A small light-emitting device is provided. A light-emitting device which is less likely to produce a shadow is provided. A structure including a switching circuit for supplying a pulsed constant current and a light-emitting panel supplied with the pulsed constant current has been conceived.

Abstract: The objective lens has a numerical aperture NA=0.6 when reproducing a DVD having a thickness of 0.6 mm and NA=0.42 when reproducing a CD having a thickness of 1.2 mm. At a boundary of NA 0.42, a slight stepped portion is formed so as to establish a phase difference. In this case, a designed wavelength is 0.635 .mu.m, and an optimum designed substrate thickness of a central portion is approximately 0.8 mm. While the DVD is reproduced, wave front aberration is on the order of 0.025.lambda., and jitter contained in the reproduction signal of the CD is equivalent to the present jitter. As a consequence, such an objective lens and an optical head with employment of this objective lens are provided, which precisely reproduce signals from the CD having the substrate thickness of 1.2 mm, and the DVD having the substrate thickness of 0.6 mm.

Abstract: A light beam recording system in which the beam is deflected after passage through a focusing element to scan a recording medium. An optical image surface correction system is employed between the deflector and recording medium for correction of the curvature of the field in the main scanning direction. The optical correction system includes an aspherical surface and deviation from a paraxial generating spherical surface to the aspherical surface.

Abstract: In a scanning optical system for deflecting a laser beam by a deflector to converge it on a scanning surface by a focusing lens, it is difficult to compensate for both an image surface curvature and a distortion aberration in the optical system. An optical system according to the present invention is designed to minimize a curvature of a meridional image surface of a focusing lens, and a sagittal image surface and distortion are compensated for by arranging an aspherical surface between the focusing lens and the scanning surface. This aspherical surface is advantageously arranged by forming a cylindrical lens, which is inserted to compensate for a tilting of the deflected surface, into an aspherical surface.

Abstract: For small type wide angle lenses for use with a compact camera, so-called inverted retrofocus lenses are often used. In this type of lens, the lens can be formed into more compact by increasing a refracting power of a rear unit of a negative meniscus with a convex surface thereof greatly curved toward an image and a front unit on the side of an object. However, this arrangement gives rise to an aberration. This aberration can be compensated by introducing at least one aspherical surface into the front unit and rear unit. In addition, this aspherical lens can be easily produced if it is formed of plastics.

Abstract: This invention relates to a wide angle lens for a compact camera using a lens shutter, in which wide angle lens, a distance from a front surface of the lens to a film surface is short. The lens is a lens of the inverted retrofocus type in which a negative meniscus lens greatly curved toward an image is arranged at the rear of a triplet lens of convex, concave and convex. The second, third and fourth lenses each comprise a plastic lens. Various aberrations are compensated and variation in focal length due to a variation in temperature is also prevented. By the formation of plastic lenses, it is possible to easily form the fourth lens into an aspherical lens.

Abstract: The present invention relates to a zoom lens system having a new structure for use with still cameras, which is wide magnification-variable and compact whose zoom ratio is about three times.A positive third lens group of a conventional zoom lens comprising three lens group, i.e. positive, negative and positive is divided into two positive lens groups to thereby decrease the refractive power of each lens group and an airspace therebetween being increased and decreased, whereby enhancing the effect of magnification-variation or rendering it possible to be utilized for correction of aberration.Further, a positive lens group having a weak refractive power is arranged between image planes to effect correction of aberration. As a result, there is obtained a zoom lens system having a new arrangement of refractive power in order of positive, negative, positive, positive and positive.

Abstract: An apparatus for detecting the density (concentration) of toner in a developer for an electrostatic recording apparatus includes an operatively moveable surface for carrying developer onto an electrostatic latent image bearing member during image development, a scraper element having at least a flat surface for scraping developer from the movable surface in a substantially steady and uniform stream along the flat face, and a substantially flat detection coil assembly having oppositely-directed faces. The coil assembly is mounted on, spaced apart from, and substantially parallel to the flat face of the scraper so that the stream of developer passes along both coil assembly faces directly after being scraped from the moveable surface, thereby enhancing the toner density detection sensitivity of the coil assembly.

Abstract: An apparatus and method for detecting the concentration of toner in a multi-component developer of an electrophotographic copying machine utilizes a source of illumination for projecting light onto the developer, and a receiving element for measuring the intensity of light of a predetermined wavelength reflected from the developer, the predetermined wavelength being of a value selected to maximize the intensity of reflected light in response to variations in toner concentration substantially independently of the reflection characteristics of the developer. The amount or concentration of toner in the developer is varied--by the addition of suitable amounts of toner--with the measured intensity of the received reflection of light of the predetermined wavelength.