| 摘要 |
PURPOSE: To accurately stick four triangle prisms together to constitute a dichroic prism constituting the color synthesizing means or the like of the optical system of a projection display device. CONSTITUTION: Out of four triangle prisms 910a-910d constituting the dichroic prism and having the same refractive index and the cross-section of rectangular equilateral triangle, a first triangle prism 910c and a second triangle prism 910a are made longer than a third triangle prism 910b and a fourth triangle prism 910d, and the first and the third triangle prisms are stuck together in a state of having a difference in level at one end, and an exposing side face 910f is formed. The second and the fourth triangle prisms are stuck together in the state of having the difference in the level on the same end side, and the exposing side face 910e is formed. The first and the third triangle prisms and the second and the fourth triangle prisms are stuck together in the state where exposing side face 910j orthogonal to the exposing side face 910f is formed on the end side of the first triangle prism. |
