| 摘要 |
PURPOSE:To prevent the malfunction dependent upon photo coupling by arranging light emission/receiving elements in a prescribed relational position determined by the refractive index and the layer thickness of a multi-layer light transmission film. CONSTITUTION:M-number light transmission films are provided between light emission element 1 and light receiving element 2. Light is incident on light emission element surface P at angle i0, and is refracted by iR in the Rth layer to be incident on the (R+1)th layer. Now, assuming that a refractive index is n under condition j+1<R, refraction angle iR is equal to Sin<-1>(nj+1/nR). Meanwhile, assuming that the R layer thickness is dR, distance L from interface Q between the jth layer and the (j+1)th layer to p is the total sum spanning R=1j of dR tan iR. Then, when nj+1<nR is defined to reflect all light on interface Q and light receiving element A' corresponding to light emission element A and light receiving prevention desired element B' are arranged inside or outside range L respectively, the malfunction of photo coupling is reduced considerably. Further, the provision of a light absorbing wall or a reflection wall in the position of distance L has a more effect. |
