Triple beam splitter prism and preparation method thereof

The invention relates to a triple beam splitter prism, which comprises a first triangular prism and a second triangular prism which are overlapped and overlapped surfaces of which are partially glued, the first triangular prism comprises a first incident surface, a first emergent surface and a first gluing surface; the second triangular prism comprises a second gluing surface, a second emergent surface and a third emergent surface; the included angle between the first incident plane and the first emergent plane is theta1 which is larger than 90 degrees and larger than arcsin1/n1, the included angle between the second gluing plane and the third emergent plane is theta2 which is larger than 90 degrees and larger than arcsin1/n2, n2 is the refractive index of the second triangular prism, and n3 is the refractive index of the second triangular prism. A cementing layer close to one side of the first emergent surface and one side of the second emergent surface and an uncemented air layer far away from one side of t