Abstract: A collimator lens for an optical fiber is disclosed. The collimator lens comprises a cylindrical member having an effective radius R and effective axial length L. The cylindrical member is formed of optically transparent material having refractive index n.sub.1. The cylindrical member has one circular end portion provided with a connecting portion connectable with a light emitting end face of an optical fiber and the other circular end portion provided with a fresnel lens pattern having a positive focal length F. The focal length F, the effective length L, the effective radius R and the refractive index n.sub.1 are satisfied with the following formula (I) and (II);F/L=tan {sin.sup.-1 (NA/n.sub.1 }/tan {sin.sup.-1 (NA)} (I)R.gtoreq.L.multidot.tan {sin.sup.-1 (NA/n.sub.1)} (II)in which NA is numerical aperture of the optical fiber.

Abstract: Described is a transparent electroconductive material composed of a transparent synthetic resin substrate and a transparent electroconductive film formed on the resin substrate. At least a surface portion of the resin substrate on which the electroconductive film is formed satisfies a requirement represented by the formula: F x Hv=0.4 wherein F is the mole number (.mu.mole/cm.sup.2) of a basic dye that can react with or adhere to the unit area of the surface of the synthetic resin, and Hv is the Vickers hardness as determined according to JIS Z-2244. The absolute value of the photoelasticity constant of the resin substrate below the glass transition temperature thereof is not larger than 15 Brewsters.

Abstract: An edge-lighting type light diffuser is disclosed which has a plane of light incidence, a light transmitting means and a plane of light emission. The light transmitting means is composed of a laminate of a plurality of light-transmissible plates. This structure provides a light diffuser capable of uniform plane illumination usable for sign boards, large-sized display devices, display devices for various types of machinery, and liquid crystal devices.