| 摘要 |
PURPOSE:To suppress the spread of a light source and to save space, to increase the utilization efficiency of illumination light, and to imprint a sharp image by using an optical element which has a concave incidence surface and a convex projection surface for a data carrier and projecting irradiation light. CONSTITUTION:A data imprinting device 1 consists of a base plate 10 fixed to a rear cover 3, a lamp 11 fixed to the base plate 10, a prism 12, a liquid- crystal plate 13, and a circuit unit 14. The prism 12 has the concave incidence surface S1 and convex projection surface S2, has negative refracting power on the whole, and projects the convergent illumination light of a lamp 11 from a surface S3. The negative refracting power of the surface S1 reduces the image of the filament of the lamp 11 viewed from the plate 13 to eliminate the need to leave a large gap between the plate 13 and lamp 11, and the positive refractive power of the surface S2 prevents the unnecessary spread of the illumination luminous flux; and the aspherical shapes of the surfaces S1 and S2 improve the illumination efficiency. Consequently, the space is saved and the blurring of an imprinted data image to make the image sharp.
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