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Title:
IMAGING OPTICAL SYSTEM AND IMAGING APPARATUS
Document Type and Number:
WIPO Patent Application WO/2017/209220
Kind Code:
A1
Abstract:
An imaging optical system includes a first lens having a concave image side surface and a negative refractive power; a second lens having a convex object side surface and a positive refractive index; a third lens having a concave object side surface and a negative refractive power; a fourth lens having a convex image side surface and a positive refractive power; and a fifth lens having a convex object side surface and a positive refractive power in the order from the object side to the image side, optionally includes a lens on the image side of the fifth lens. The imaging optical system satisfies conditional expressions [1] 1.94 < n2 < 2.20 and [2] 15.0 <ν2 < 20.0, where ν2 and n2 represents an Abbe number and a refractive index of a lens material of the second lens L2 at d-line, respectively.

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Inventors:
OHASHI KAZUYASU (JP)
Application Number:
PCT/JP2017/020365
Publication Date:
December 07, 2017
Filing Date:
May 31, 2017
Export Citation:
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Assignee:
RICOH CO LTD (JP)
OHASHI KAZUYASU (JP)
International Classes:
G02B9/60; G02B9/62; G02B13/00; G02B13/04
Foreign References:
JPH09166748A1997-06-24
JP2013047753A2013-03-07
US6222685B12001-04-24
JPH09166748A1997-06-24
JP2000180718A2000-06-30
JP2003131126A2003-05-08
Other References:
"Modern Lens Design", 1 January 1992, MCGRAW-HILL, INC, ISBN: 978-0-07-059178-3, article WARREN J. SMITH: "Modern Lens Design", pages: 25 - 27, XP055152035
OHARA CORPORATION: "OHARA Optical Glass Chart 2015", 1 January 2015 (2015-01-01), XP055397510, Retrieved from the Internet [retrieved on 20170809]
HOYA CORPORATION: "HOYA Glass catalogue 2015 Abbe diagram", 8 May 2015 (2015-05-08), XP055397717, Retrieved from the Internet [retrieved on 20170810]
Attorney, Agent or Firm:
SAKAI, Hiroaki (Toranomon Mitsui Building 8-1, Kasumigaseki 3-chome, Chiyoda-k, Tokyo 13, JP)
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