Abstract: An optical system that can be used in an optical imaging system and displays good imaging performance with corrected chromatic aberration without increasing the number of lenses is provided by employing a lens surface with a diffractive effect. The optical system uses a lens with a concave incident surface and positive refractive power. A grating element surface 40 with positive refractive power is formed on at least one surface of the lens. The surface on which the grating element is formed is an aspherical surface with a radius of curvature that becomes bigger with increasing distance from the optical axis.

Abstract: A plurality of types of ink having different wavelength characteristics are used for multiple printing of code information. When two or more types of ink are to be printed in an overlapping manner, in a region 8 in which one type of ink 4 and another type of ink 5 are printed in the overlapping manner, the ink 4 and the ink 5 are printed so as not to completely overlap each other by using a checkered pattern 9. As a result, the multiple printing can be performed without strict constraints on the wavelength characteristics of the ink.

Abstract: An optical scanner comprising a light source unit, an optical deflector to scan a light beam from the light source unit, a first image formation optical system disposed between the light source unit and the optical deflector, and a second image formation optical system disposed between the optical deflector and the surface to be scanned, wherein the second image formation optical system comprises a first curved mirror to reflect the light beam from the optical deflector and a second curved mirror to focus the light beam from the first curved mirror on the surface to be scanned, having surface shapes of any of the group consisting of the first curved mirror having a toric surface with a convex shape in the main scanning direction, which is the direction a light beam is scanned in, and with a concave shape in the sub scanning direction, which is the direction perpendicular to the main scanning direction, and the first curved mirror having a toric surface with a concave shape in the main scanning direction and a

Abstract: An optical scanner comprising a light source unit, an optical deflector to scan a light beam from the light source unit, a first image formation optical system disposed between the light source unit and the optical deflector, and a second image formation optical system disposed between the optical deflector and the surface to be scanned, wherein the second image formation optical system comprises a first curved mirror to reflect the light beam from the optical deflector and a second curved mirror to focus the light beam from the first curved mirror on the surface to be scanned, having surface shapes of any of the group consisting of the first curved mirror having a toric surface with a convex shape in the main scanning direction, which is the direction a light beam is scanned in, and with a concave shape in the sub scanning direction, which is the direction perpendicular to the main scanning direction, and the first curved mirror having a toric surface with a concave shape in the main scanning direction and a

Abstract: The scanner optics of this invention includes a condensing lens arrangement composed of a first aspherical lens having a positive refractive power and a convex meniscus surface on the side of the scanning surface and a second toric lens of which incident surface is saddle toroidal where a point on the incident surface has a greater radius of curvature in the sub-scanning direction as the point is farther from the optical axis in the scanning direction. A laser light flux emitted from a light source is deflected and scanned by a polygon mirror so as to form an image on a scanning surface via the condensing lens arrangement.

Abstract: The optical scanner of this invention includes a light source, an optical deflector for scanning a light flux from the light source, a first image formation optical system disposed between the light source and the optical deflector, and a second image formation optical system disposed between the optical deflector and a surface to be scanned. The second image formation optical system includes a curved mirror for reflecting a light flux from the optical deflector and a correction lens for converging the light flux from the curved mirror on the surface to be scanned. A refractive power in the sub-scanning direction at the center of the correction lens in the scanning direction is different from that at the periphery thereof.