| 摘要 |
PURPOSE:To suppress a shift small between incident luminous flux and projecting luminous flux at the time of zero adjustment or to align the incident luminous flux and projecting luminous flux completely with each other by rotating and adjusting at least one of 1st and 2nd prisms around an axis of rotation. CONSTITUTION:The 1st prism 10 is arranged by having its incident end surface 11 in parallel to a plane obtained by rotating a vertical plane S by theta counterclockwise around an intersection line (m) and its projection surface 12 in parallel to a plane obtained by rotating the vertical surface S by theta counterclockwise around the intersection line (m). Then the 2nd prism 20 is so arranged so that its incidence end surface 21 is parallel to the projection end surface 12 of the 1st prism 10 and the projection end surface 21 is parallel to the incidence end surface 11 of the 1st prism 10 at the time of the zero adjustment. For the purpose, the 1st prism 10 is rotated and adjusted to adjust finely the direction of luminous flux according to the relation between the incidence angle and deviation angle. Consequently, the shift between the incident luminous flux and projecting luminous flux is suppressed low or eliminated at the time of the zero adjustment.
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