Projection optical system and projecting apparatus provided...

Optical: systems and elements – Lens – With field curvature shaping

Reexamination Certificate

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C359S649000, C359S726000, C359S753000, C359S682000, C359S784000, C359S740000

Reexamination Certificate

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07012758

ABSTRACT:
A projection optical system includes from the enlargement side a first lens unit, a mirror which is an optical path bending member, a second lens unit, and a third lens unit. The projection optical system is designed so that a condition (1), 5.5<T12/FL<12.0, is fulfilled. Here, T12is the air equivalent distance between the first lens unit and the second lens unit, and FL is the overall focal length of the projection optical system. By fulfilling the condition (1), it is unnecessary that the diameter of the first lens unit be extremely large. It is also unnecessary to change the lens shape to prevent interference between the first lens unit and the second lens units, so that an increase in the cost of the projection optical system can be suppressed.

REFERENCES:
patent: 5442484 (1995-08-01), Shikawa
patent: 5745297 (1998-04-01), Kaneko et al.
patent: 6144503 (2000-11-01), Sugano
patent: 6542316 (2003-04-01), Yoneyama
patent: 6624952 (2003-09-01), Kuwa et al.
patent: 2004/0233547 (2004-11-01), Sugano
patent: 2003-248169 (2003-09-01), None

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