US3604786A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compact afocal magnifying lens
Assignee: Polaroid Corp
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Filing: 1969-07-22
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Granted: 1971-09-14
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Expires: 1989-07-22
Abstract
Abstract Compact six-element afocal magnifying lenses suitable for use as attachments to photographic objective lenses are described. The overall length of an afocal lens designed according to this invention is less than the focal length of the photographic objective lens with which it is to be associated. Magnifications as high as 2 power are attainable. Three elements are arranged in a positive front group, separated by a large air space from the other three elements which are arranged in a negative rear group. The outer elements in each group of three have higher Abbe values than the inner element of their respective group. High refractive indices are employed in the negative elements and moderate refractive indices in the positive elements. Chromatic and spherical aberrations, coma, astigmatism, field curvature, and distortion can be corrected. An aspheric surface is used.
Inventors
- 👤 James G Baker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 00:47
CPC Classifications
G; G02; G02B; G02B15/00; G02B13/00; G02B13/18
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
135 words
A compact magnifying lens for use with a photographic objective comprising: a front converging group of elements including a positive biconvex first element, a negative biconcave second element with a refractive index substantially higher than that of said first element, and a positive third element having a refractive index substantially lower than that of said second element; and a rear diverging group of elements containing a negative fourth element having a refractive index substantially higher than that of said third element, a positive biconvex fifth element having a refractive index substantially lower than that of said fourth element, and a negative biconcave sixth element having a refractive index substantially higher than that of said fifth element; said magnifying lens being afocal and having an overall length less than the focal length of said photographic objective.
Claim 2
Dependent Claim
135 words
A compact magnifying lens for use with a photographic objective comprising: a front converging group of elements including a positive biconvex first element, a negative biconcave second element with a refractive index substantially higher than that of said first element, and a positive third element having a refractive index substantially lower than that of said second element; and a rear diverging group of elements containing a negative fourth element having a refractive index substantially higher than that of said third element, a positive biconvex fifth element having a refractive index substantially lower than that of said fourth element, and a negative biconcave sixth element having a refractive index substantially higher than that of said fifth element; said magnifying lens being afocal and having an overall length less than the focal length of said photographic objective.
Claim 3
Dependent Claim
37 words
The compact afocal magnifying lens of claim 1 wherein said converging group and said diverging group are separated by a central air space having a thickness at least one-quarter of the overall length of said afocal lens.
Claim 4
Dependent Claim
30 words
The compact afocal magnifying lens of claim 1 wherein said first and second elements are joined as a doublet and said fifth and sixth elements are joined as a doublet.
Claim 5
Dependent Claim
23 words
The compact afocal magnifying lens of claim 1 wherein at least one surface of said first and second elements has an aspheric curvature.
Claim 6
Dependent Claim
35 words
The compact afocal magnifying lens of claim 4 wherein the first and second elements are cemented together and at least one surface at the cemented interface between said first and said second elements is aspheric.
Claim 7
Dependent Claim
64 words
The compact afocal magnifying lens of claim 1 wherein the Abbe dispersion numbers of said second, fourth and sixth elements are substantially equal, the Abbe dispersion numbers of said first and third elements are higher than those of said second, fourth and sixth elements and the Abbe dispersion number of said fifth element is lower than those of said second, fourth and sixth elements.
Claim 8
Dependent Claim
104 words
A compact magnifying lens for use with a photographic objective comprising: a front converging group of elements including a positive biconvex first element, a negative biconcave second element and a positive third element; a rear diverging group of elements including a negative fourth element, a positive biconvex fifth element and a negative biconcave sixth element; said magnifying lens being afocal and having an overall length less than the focal length of said photographic objective with said positive group and said negative group being separated by a central air space having a thickness of at least one-fourth of the overall length of said magnifying lens.
Claim 9
Dependent Claim
104 words
A compact magnifying lens for use with a photographic objective comprising: a front converging group of elements including a positive biconvex first element, a negative biconcave second element and a positive third element; a rear diverging group of elements including a negative fourth element, a positive biconvex fifth element and a negative biconcave sixth element; said magnifying lens being afocal and having an overall length less than the focal length of said photographic objective with said positive group and said negative group being separated by a central air space having a thickness of at least one-fourth of the overall length of said magnifying lens.
Claim 10
Dependent Claim
18 words
The compact afocal magnifying lens of claim 7 wherein at least one element surface has an aspheric curvature.
Claim 11
Dependent Claim
18 words
The compact afocal magnifying lens of claim 8 wherein said aspheric surface is in said front positive group.
Claim 12
Dependent Claim
34 words
The compact afocal magnifying lens of claim 9 wherein the first and second elements are cemented together and at least one surface at the cemented interface between said first and second elements is aspheric.
Claim 13
Dependent Claim
61 words
The compact afocal magnifying lens of claim 10 wherein said aspheric surface curvature is determined according to the formula: xi represents the aspheric surface height above a plane reference surface; c is the reciprocal of the radius at the optic axis; Rho is the radial distance from the optic axis; Beta and gamma are constants determined by the optical optimization desired.
Claim 14
Dependent Claim
62 words
The compact afocal magnifying lens of claim 7 wherein the Abbe dispersion nUmbers of said negative second, fourth and sixth elements are substantially equal to each other, the Abbe numbers of said positive first and third elements are greater than those of said negative elements and the Abbe number of said positive fifth element is lower than those of said negative elements.
Claim 15
Dependent Claim
19 words
The compact afocal magnifying lens of claim 1 conforming to the following design parameters, scaled to a unit length,
Claim 16
Dependent Claim
19 words
The compact afocal magnifying lens of claim 1 conforming to the following design parameters, scaled to a unit length,
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-13 | 1975-03-15 | 1975-09-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-13 | 1979-03-15 | 1979-09-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-13 | 1983-03-15 | 1983-09-14 | $7700.00 | Window Closed / Lapsed |