PURPOSE: To prevent drop in the sensitivity in the perimeter of a wide scanning zone, by arranging two lens elements on the same plane in the lens on the side of projection point among two Fresnel lenses separated facing each other in parallel.
CONSTITUTION: The sensitivity lowers as a spot light source P on a scan line 1 is separated from the center of a lens but the decrease in the amount of transmission light is prevented by arranging two lenses 3a and 3b parallel to the scan line to reduce the incidence angle with respect to the lenses. The use of Fresnel lenses makes the equipment thinner with a larger diameter and the machinability can be improved by being made up of an acrylic resin. The point P biased to the right on the scan line 1 is located near the front of a lens element 3a-2 and emission lights (c)W(e) are allowed to pass therethrough 3a-2 with such a large transmittance that they may converge with the lens 3b toward the focus of the lens element 3a-2 and gather at the point Q on a light-receiving surface of the element 2. The same is with the point P' biased to the left. The number of the Fresnel lenses 3a may be three. The lens 3b may be composed of a plurality of lens elements. The addition of a Fresnel lens 4 is possible.
KATO NOBORU
ITO MAKOTO
UENO YOSHIAKI
| JPS58129410A | 1983-08-02 | |||
| JPS59224003A | 1984-12-15 |