| 摘要 |
PURPOSE: An imaging optical system is provided to acquire diffraction efficiency in whole viewable portion and high performance about definition and aberration. CONSTITUTION: A first lens(L1) has a positive refractive power and diffraction grating is formed on the convex phase side of the first lens in the phase side(IP). A second lens(L2) has a negative refractive power and diffraction grating is formed on the concave object side of the second lens in the object side. A third lens(L3) has the positive refractive power. A fourth lens(L4) has the positive or negative refractive power. The first lens, the second lens, the third lens, and fourth lens are arranged in order from the object side in which the subject locates to the phase side which a phase about a subject is formed.
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