Patent ID: 8134780

Claim:
A prism comprising: a light incident portion that includes a first convex portion and a second convex portion, the first convex portion and the second convex portion each being a convex portion that refracts rays of light incident to a prism body and reduces a spread angle after incidence to the prism body via the convex portion to be smaller than the spread angle before the incidence, the spread angle being an angle formed between a given two of the rays, the light incident portion further including a flat incident surface on a first side of the first convex portion, the first side being opposite to a second side of the first convex portion, the second convex portion being provided on the second side; a first reflecting surface that is provided on the prism body and that is capable of reflecting a first ray of light that has entered the prism body via the first convex portion; a first emitting portion that is provided on the prism body and that emits, to the outside of the prism body, the first ray reflected by the first reflecting surface; a second emitting portion that emits, to the outside of the prism body, a second ray of light that has entered the prism body via the second convex portion; and a second reflecting surface that is provided on the prism body and that is capable of reflecting a third ray of light that has entered the prism body via the incident surface, the second reflecting surface having a first reflecting convex portion that reduces the spread angle after reflection to be smaller than the spread angle before the reflection; wherein the first reflecting surface reflects the third ray reflected by the second reflecting surface and the first ray that has entered the prism body via the first convex portion.