Abstract: A telecentric imaging optical system has first and third lens systems each having a positive power, and a second lens system having a negative power. In the imaging optical system, the second lens system is disposed between the first and the third lens systems. The imaging optical system satisfies the following inequalities:f1/2.5<-f2<2.multidot.f1f3/2.5<-f2<2.multidot.f3where f1 is the focal length of the first lens system, f2 is that of the second lens system and f3 is that of the third lens system. A rear focal point of a composite lens system consisting of the first and the second lens systems substantially coincides with the front focal point of the third lens system. The telecentric imaging optical system has a large variable power ratio.

Abstract: An apparatus for recording an image with a plurality of laser beams on a recording surface comprises a plurality of laser source units each generating a laser beam and a first lens for directing the laser beam from each one of the plurality of laser source units to the recording surface. In the apparatus, the laser source units are each disposed on a holding member in such a manner that the principal ray of the laser beam therefrom passes through a front focal point of the first lens. Thus, the apparatus is advantageous in that it is not necessary to employ an enlarged lens despite increase in the number of the laser source units, or the channel numbers.

Abstract: An apochromat optical system for a photoengraving process comprises a first lens group which includes a first lens having a positive power, a second lens made of Kultz flint glass having a negative power and a third lens in the form of a meniscus having a positive power. The first to third lenses are successively disposed in order starting from the object side. A second lens group includes the substantially same configuration of lenses as in the first lens group. The lenses of the first and second lens groups are approximately symmetrical with respect to the stop. Accordingly, the system has a high aperture ratio and small curvature of a saggital and meridional image field which can reduce an astigmatic difference in a peripheral part of an image.

Abstract: A telecentric image-forming optical system comprising a first lens group including a double-convex lens, a meniscus lens whose convex side faces an object or a plano-convex lens, and a double-concave lens arranged in this order; and a second lens group including a double-convex lens, a meniscus lens whose convex side faces an image or a plano-convex lens, and a double-concave lens arranged in this order, wherein the secondary focal point of the first lens group and the principal focal point of the second lens group substantially coincide with each other in the vicinity of a double-convex lens. The telecentric image-forming optical system is compact and forms an image which is large sized in relation to the compact length of the system.

Abstract: An optical non-contact detection of profile errors of a surface or surfaces of an article, such as an industrial product is carried out by a coherent signal bea of light introduced along an imaginary plane and projected onto the surface of the article at a large angle of incidence. The signal beam of light is reflected from the surface toward the same imaginary plane and traveled past optical system toward a photosensitive material on which a separate reference beam of light is projected. A hologram of the surface is formed on the photosensitive material, which is used for an analysis of the profile errors of the surface.

Abstract: The image-forming magnification of a telecentric optical system, for use in an exposure apparatus such as a projecting apparatus, a laser plotter and the like is determined by the focal length ratio. An error in processing and arranging lenses necessitates adjustment of the image-forming magnification. According to the present invention, the magnification may be greatly varied. According to the present invention, a lens movable along the optical axis and having a positive focal length is placed at a position corresponding to the point at which the focal points of two lens groups coincide with each other. The image-forming magnification ratio can be varied by moving the lens while the distance between an object and an image is kept constant. Characteristic features of telecentric optical systems are maintained.

Abstract: An optical system for use in a flying spot scanning apparatus. The optical system includes a laser tube, an optoelectronic integrated circuit which divides a laser beam into a plurality of beams and individually modulates the beams, a focusing lens for focusing the beams, a deflection mirror for reciprocatingly deflecting the beams to scan a recording medium, a concave mirror receiving the beams thereon, and a recording medium disposed optically behind the concave mirror. The recording medium is fed in a predetermined direction while the beams are scanned across the recording medium.