Optical: systems and elements – Prism – With reflecting surface
Patent
1990-07-31
1991-10-08
Arnold, Bruce Y.
Optical: systems and elements
Prism
With reflecting surface
359691, 359676, 359652, 359708, G02B 1500
Patent
active
050548972
ABSTRACT:
A plastic zoom lens has a first group of lenses having negative refracting power and arranged on an object side of the zoom lens; a second group of lenses having positive refracting power and arranged on an image side of the zoom lens; and a device for changing a focal length of the plastic zoom lens by changing a distance between the first and second groups of lenses. The first group of lenses have a first lens group composed of a negative plastic lens having a large curvature face on the image side thereof and at least one aspherical surface and a positive plastic lens having a large curvature face on the object side thereof. The negative and positive plastic lenses are sequentially arranged from the object side of the zoom lens. The first group of lenses further have at least one negative lens arranged on the object side of the first lens group. The second group of lenses have a second lens group composed of a positive plastic lens having a large curvature face on the object side thereof and a negative plastic lens having a large curvature face on the image side thereof. The positive and negative plastic lenses are sequentially arranged from the object side of the zoom lens. The second group of lenses further have at least one positive lens arranged on each of the object and image sides of the second lens group.
REFERENCES:
patent: 4516839 (1985-05-01), Tokumaru
patent: 4653873 (1987-03-01), Kawamura
patent: 4699474 (1987-10-01), Ozawa
patent: 4999007 (1991-03-01), Aoki et al.
Arnold Bruce Y.
Dang Hung Xuan
Ricoh & Company, Ltd.
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