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Document Type and Number:
Japanese Patent JP6851843
Kind Code:
PROBLEM TO BE SOLVED: To obtain a projection optical system having good telecentricity on a reduction conjugate side and giving a long back focus and good optical performance.SOLUTION: The projection optical system is disposed on a reduction conjugate side and projects an image displayed by an image display element to an enlargement conjugate side, and the projection optical system includes three lenses immobile along the optical axis direction on a side closest to the reduction conjugate side. The three lenses include, successively from the enlargement conjugate side to the reduction conjugate side, a meniscus first lens having a convex surface on the enlargement conjugate side, a second lens having negative refractive power, and a third lens having positive refractive power, in which the second lens and the third lens are cemented to form a cemented lens, and a radius of curvature G1R2 of a lens surface on the reduction conjugate side of the first lens, a radius of curvature G2R1 of a lens surface on the enlargement conjugate side of the second lens, a focal distance FG3 of the third lens, and a focal distance FG of the synthesized system from the first lens to the third lens are each appropriately set.SELECTED DRAWING: Figure 1

Ryo Iijima
Application Number:
Publication Date:
March 31, 2021
Filing Date:
February 07, 2017
Export Citation:
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Canon Inc
International Classes:
G02B15/20; G02B13/04; G02B13/18
Domestic Patent References:
Foreign References:
Attorney, Agent or Firm:
Takuma Abe
Sogo Kuroiwa

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