Optical: systems and elements – Lens – Selective magnification by exchanging or adding a lens...
Patent
1998-12-17
2000-09-26
Epps, Georgia
Optical: systems and elements
Lens
Selective magnification by exchanging or adding a lens...
359672, 359673, 359674, G02B 1502
Patent
active
061249815
ABSTRACT:
An attachment lens satisfactorily corrects aberrations by using a diffraction surface. The attachment lens is installed on an image surface side of a master lens unit (M) serving as a photographic optical system, and it extends a focal length of the master lens unit (M) toward a longer focal length side. The attachment lens has a diffraction surface (D) which is composed of a diffraction grating shaped rotationally symmetrical with respect to an optical axis and which has a negative refractive power with respect to a diffracted light ray of a design order of diffraction. The attachment lens is adapted to satisfy a conditional expression given below when a height of an axial paraxial ray incident upon the diffraction surface, which has the negative refractive power, from an optical axis is denoted as h.sub.D, and a height of a pupil paraxial ray incident upon the diffraction surface, which has the negative refractive power, from the optical axis is denoted as H.sub.D :
REFERENCES:
patent: 5044706 (1991-09-01), Chen
patent: 5543966 (1996-08-01), Meyers
patent: 5726809 (1998-03-01), Griffith
patent: 5884108 (1999-03-01), Kamo et al.
patent: 5930043 (1999-07-01), Ogawa
Canon Kabushiki Kaisha
Epps Georgia
Thompson Timothy
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