Wide-angle lens assembly and method
First Claim
Patent Images
1. A wide angle lens system comprising:
- a combination of a first lens and a second lens which are respectively selected from a first group of discrete bi-concave lenses which have an aspherical surface on one face thereof and are fabricated respectively corresponding to each of horizontal viewing angles covered by the wide-angle lens system, and from a second group of identical bi-convex lenses which are provided with aspherical surfaces on both faces thereof and are fabricated respectively corresponding to each of horizontal viewing angles covered by the wide-angle lens system, said first lens and said second lens being aligned along an optical axis from an object side to an image side such that the first lens is positioned on the object side with respect to the second lens, the aspherical surface of the first lens being faced to the object side, wherein;
the combination of the first lens and the second lens provides a wide angle view and satisfies the following conditions;
0.65f2<
bf<
0.8f2-1.8f2<
-1.1f2, andwhere f1 is a focal distance of the first lens, f2 is a focal distance of the second lens, and bf is a distance of back focus from the second lens to a focus point thereof in each discrete combination of the first lens and the second lens.
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Abstract
A low-cost wide-angle lens assembly being comprised of a decreased number of lenses yet capable of properly correcting optical aberrations. The second lens in each lens group from the minimum to the maximum horizontal viewing angle is commonly used, and the first lens in each lens group from a reference angle to the maximum horizontal viewing angle is commonly used, thus reducing the total number of required lenses. Aberrations are favorably corrected by satisfying predetermined conditions as to focal distances and back focuses of the lenses.
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Citations
3 Claims
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1. A wide angle lens system comprising:
a combination of a first lens and a second lens which are respectively selected from a first group of discrete bi-concave lenses which have an aspherical surface on one face thereof and are fabricated respectively corresponding to each of horizontal viewing angles covered by the wide-angle lens system, and from a second group of identical bi-convex lenses which are provided with aspherical surfaces on both faces thereof and are fabricated respectively corresponding to each of horizontal viewing angles covered by the wide-angle lens system, said first lens and said second lens being aligned along an optical axis from an object side to an image side such that the first lens is positioned on the object side with respect to the second lens, the aspherical surface of the first lens being faced to the object side, wherein; the combination of the first lens and the second lens provides a wide angle view and satisfies the following conditions; 0.65f2<
bf<
0.8f2-1.8f2<
-1.1f2, andwhere f1 is a focal distance of the first lens, f2 is a focal distance of the second lens, and bf is a distance of back focus from the second lens to a focus point thereof in each discrete combination of the first lens and the second lens.
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2. A wide-angle lens system comprising:
a combination of a first lens, a second lens, and a third lens which are respectively selected from a first group of identical bi-concave lenses that have an aspherical surface on one face thereof and are fabricated respectively corresponding to each of horizontal viewing angles covered by the wide-angle lens system, a second group of identical bi-convex lenses which are provided with aspherical surfaces on both faces thereof and are fabricated respectively corresponding to each of horizontal viewing angles, and a third group of discrete negative meniscus lenses which are fabricated respectively corresponding to each of horizontal viewing angles, the first, second, and third lenses being aligned along an optical axis from an object side to an image side such that said third lens is positioned on the object side in relation to the first lens, with a convex face of the third lens facing to the object side and concave face thereof to the image side, whereas said second lens is positioned on the image side in relation to the first lens, the aspherical surface of the first lens being faced to the object side, wherein the combination of the first, second, and third lenses satisfies the following conditions; 0.65f2<
bf<
0.8f2-1.8f2<
f1<
-1.1f2-14.0f2<
f0<
-5.5f2where f0 is a focal distance of the third lens, f1 is a focal distance of the first lens, f2 is a focal distance of the second lens, and bf is a distance of back focus from the second lens to a focus point thereof in each discrete combination of the first, second and third lenses.
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3. A method of fabricating lens systems which cover individual segments of a horizontal viewing angle ranging from 70°
- to 120°
, wherein;from viewing angle of 70°
to a first prescribed viewing angle, the lens system comprises a combination of two lenses which are respectively selected from a first lens group and a second lens group, whereas;from a second prescribed viewing which is greater than said first prescribed viewing angle to a viewing angle of 120°
, the lens system comprises a combination of three lenses which are respectively selected from the first lens group, the second lens group, and a third lens group, comprising the steps of;fabricating lenses of the first lens group respectively corresponding to individual segments of the viewing angle, said lenses being bi-concave lenses and having an aspherical surface on one side thereof; fabricating lenses of the second lens group respectively corresponding to individual segments of the viewing angle, said lenses being bi-concave lenses and having aspherical surfaces on both sides thereof; fabricating lenses of the third lens group respectively corresponding to individual segments of the viewing angle, said lenses being discrete negative meniscus lenses; constructing lens systems corresponding to each individual segment of the horizontal viewing angle from the viewing angle of 70°
to said first prescribed viewing angle by combining a fit lens and a second lens respectively selected from the first lens group and the second lens group, and by arranging said first and second lenses along an optical axis from an object side to an image side such that said first lens is positioned on the object side in relation to the second lens, with the aspherical surface of the first lens facing to the object side, wherein;the second lens is an identical type in any of the lens systems corresponding to each of the horizontal viewing angles, and the combination of the first lens and the second lens satisfy the following conditions; 0.65f2<
bf<
0.8f2-1.8f2<
f1<
-1.1f2,where f1 is a focal distance of the first lens, f2 is a focal distance of the second lens, and bf is a distance of back focus from the second lens to a focus point thereof in each discrete combination of the first and second lenses; and constructing lens systems corresponding to each individual segment of the horizontal viewing angle from said second prescribed viewing angle to the viewing angle of 120°
by combining a fist lens, a second lens, and a third lens, respectively selected from the first lens group, the second lens group, and the third lens group, and by arranging the first, second, and third lenses along the optical axis from the object side to the image side such that the third lens is positioned on the object side in relation to the first lens, with a convex side of the third lens facing to the object side and a concave side thereof to the image side, whereas the second lens is positioned on the image side in relation to the first lens, the aspherical surface of the first lens being faced to the object side, wherein;the second lens is of the same type as the second lens that is used in the lens systems of two-lens combination corresponding to each of the horizontal viewing angles from 70°
to the first prescribed viewing angle, as well as is common to all of the lens systems corresponding to each of the horizontal viewing angles from the second prescribed viewing angle to the viewing angle of 120°
;the first lens is of the same type as the first lens that is used in the lens system of two-lens combination for covering said first prescribed viewing angle, as well as is common to all of the lens systems corresponding to each of the horizontal viewing angles from the second prescribed viewing angle to the viewing angle of 120°
;the combinations of the first, second, and third lenses satisfy the following conditions; 0.65f2<
bf<
0.8f2-1.8f2<
f1<
-1.1f2-14.0f2<
f0<
-5.5d2,where f0 is a focal distance of the third lens.
- to 120°
Specification