| 摘要 |
PURPOSE:To obtain a uniform brightness distribution as a plane light source by constituting a light device so that respective groove wall surfaces of a Fresnel surface facing the linear light source side increases in inclination gradually away from the linear light source. CONSTITUTION:Couples of linear light sources 1 and photoconductors 2 are arranged at right and left symmetrical positions and the Fresnel surface 2b of the photoconductor 2 is so constituted that its respective groove wall surfaces increase in inclination gradually away from the linear light sources 1. Therefore, the incident angle of light on the respective groove wall surfaces of the Fresnel surface 2b from the linear light sources 1 decreases away from the linear light sources 1, so the spread of its reflected light decreases away from the linear light sources 1. Further, this operation even on light incident on the Fresnel surface 2b after being reflected totally by the top surfaces 2c of the photoconductors 2 temporarily is similar. Consequently, the uniform brightness distribution is obtained as the surface light source and the thickness is reduced. |
