JPS5627117A - Light splitter - Google Patents

Abstract

PURPOSE: To effectively lead the split light to a photodetector even if the distance between the exit end face of the light splitter and the photodetector becomes large by providing a refracting face inclined with respect to the boundary face between the light splitter and the photodetector.

CONSTITUTION: Light incident to a refracting grating 40 is diffracted at an angle α with respect to the diffraction grating plane and reaches an end face 9 while totally reflecting on the surface of a glass plate, thence it emits at an angle θ. Hence, it splits to the two symmetrical luminous fluxes 45 and 46 at the exit end 9. If in this case a photodetector P is apart from the exit end 9, it cannot detect the split luminous fluxes. Thereupon, a transparent material 44 having a scored shape of a V shape on the face opposing to the photodetector P and having the same refractive index n₁ as that of the glass plate 2 is adhered to the end face of the glass plate 2. The V-shaped score has a vertex angle β and the vertex angle β is determined by the formula 1. Then, the light emitting from the end face becomes parallel to the glass plate 2 and enters the photodetector fairly apart from the exit end face.

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