Optical: systems and elements – Compound lens system – Telescope
Patent
1990-10-31
1992-06-23
Henry, Jon W.
Optical: systems and elements
Compound lens system
Telescope
359434, 359784, G02B 2314, G02B 912, G03B 1302
Patent
active
051248379
ABSTRACT:
A finder of a real image type has an objective lens unit having positive refracting power; a first condenser lens unit arranged in the vicinity of a focal face of the objective lens unit on an image side thereof and having positive refracting power; a relay lens unit arranged on an image side of the first condenser lens and inverting an object image provided by the objective lens and the first condenser lens rightward and leftward, and upward and downward; a second condenser lens unit having positive refracting power and arranged in the vicinity of a focal face provided on an image side of the relay lens unit by a combination system of the objective lens unit, the first condenser lens unit and the relay lens unit; and an eyepiece unit arranged on an image side of the second condenser lens unit to observe an image formed by a combination system from the objective lens unit to the second condenser lens unit. The relay lens unit is constructed by one positive lens and two negative lenses. A focal length f.sub.3k and an Abbe number .nu..sub.3k (k=1 to 3) of a k-th lens in the relay lens unit from an object side thereof, and a combined focal length f.sub.R of the relay lens unit satisfy the following conditions.
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patent: 3989349 (1976-11-01), Besenmatter et al.
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patent: 4618234 (1986-10-01), Ikari et al.
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Henry Jon W.
Ricoh & Company, Ltd.
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