| 摘要 |
PURPOSE:To obtain aberration-free imaging by setting the projection angle from the object point on the optical axis at a prescribed value and so forming multiorder aspherical faces in such a manner that the sum of the optical path lengths by the 1st reflection and the 2nd refection attains a constant value. CONSTITUTION:In the constitution wherein the light from an object point A reflects at the point P of the 1st refection mirror 1, thence it reflects again at the point Q of the 2nd reflection mirror 2 and passes the imaging point B on the optical axis, such multiorder aspherical faces 3, 4 by which the length of optical path (b+c+d) is made always constant are formed. If in this case a projection angle alpha is smaller than the constant value, no imges are formed at the imaging point B and since this results in the disturbed sharpness of the images, beam stoppers 8, 9 are provided to the front and rear end faces of this optical control system. |
