# US 5,703,721 A · Optical magnifier

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- Number: US 5,703,721 A
- Document ID: US5703721A
- Status: Granted
- Kind: A
- Application number: 08/562,666
- Filed: 1995-11-27
- Granted: 1997-12-30
- Earliest claimed: 1995-11-27
- Assignees: Eastman Kodak Company
- Inventors: Joseph R. Bietry; Lee R. Estelle; Paul D. Ludington
- Web page: https://patentgrep.com/patent/US5703721A

## CPC

- G02B 27/4216: {correcting geometrical aberrations}
- G02B 25/008: {comprising two or more lenses (G02B25/004 - G02B25/007 take precedence)}
- G02B 27/0037: {with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical magnifier, preferably having only two elements and including a rear negative surface associated with an object to be viewed, which is aspheric. The aspheric surface follows a formula having a sag which is positive to help effect correction for field curvature, astigmatism and distortion. Preferably the lens has at least one other aspheric surface and a diffractive surface. The diffractive surface is preferably on a curved surface to assist in improving the quality of the magnifier with a limited number of elements.

## Claims

### Claim 1

An optical magnifier consisting of, from a front, eye side to a rear, object side, a first biconvex element and a second element, the second element consisting of two refractive surfaces, both of which are concave toward the object side and the magnifier having a diffractive surface on either the rear surface of the first biconvex element or the front surface of the second element.

### Claim 2 (depends on 1)

An optical magnifier according to claim 1 having at least two surfaces that are aspheric.

### Claim 3

An optical magnifier comprising, from a front, eyeside to a rear, object side, a first positive element and a second element, the second element having front and rear refractive surfaces, both of which are concave toward the object side, the rear refractive surface being positioned within 5 mm of an object to be viewed from the eyeside, said rear refractive surface being an aspheric surface of negative power positioned to correct field curvature associated with the object, the aspheric surface following a formula having aspheric terms which are positive.

### Claim 4 (depends on 3)

An optical magnifier according to claim 3 wherein 0.0<S/EF<0.3, where EF is the focal length of the magnifier, S is the incremental sag of the aspheric surface at a clear aperture of the magnifier when H/EF is equal to 0.18 where H is the image height at full field.

### Claim 5 (depends on 3)

An optical magnifier according to claim 3 wherein said aspheric surface complies with the general formula: ##EQU8## wherein C, D, E, F, G and k are aspheric coefficients and wherein at least D is positive.

### Claim 6 (depends on 3)

An optical magnifier according to claim 3 wherein at least two of the surfaces are aspheric.

### Claim 7

An optical magnifier constructed according to the following table in which R.sub.1 through R.sub.4 are the radii of curvature of the magnifier from a front eyeside to a rear object side, radii R, thicknesses and distances are in millimeters, the index is for the sodium D line of the spectrum and V is the abbe number, the aspheric coefficients fit the following general formula: ##EQU9## and the diffractive surfaces are described by the following phase equation:
______________________________________ ##STR1## DISTANCE OR RADIUS THICKNESS INDEX V ______________________________________ 10 DIAPHRAGM 35.000 R.sub.1 ASPHERE 5.900 R.sub.2 ASPHERE 0.200 R.sub.3 41.8407 15.200 1.590 30.9 R.sub.4 ASPHERE ______________________________________
The coefficients for surfaces R.sub.1, R.sub.2 and R.sub.4 are:
______________________________________ SURF. C = 0.0712810 D = -0.4235000E-04 F = -0.2637200F-08 R.sub.1 k = 0.0000000 E = 0.3181400E-06 G = 0.1004800E-11 R = 1/C = 14.02898 SURF. C = D = 0.2948800E-04 F = 0.0 R.sub.2 -0.0187855 k = 0.0 E = 0.6327600E-04 G = 0.6879400E-06 R = 1/C = 11.9126 SURF. C = 0.0839447 D = 0.1068000E-02 F = -0.8642300E-05 R.sub.4 k = 0.0 E = 0.6327600E G = 0.6879400E-06 R = 1/C = 11.9126 ______________________________________
Coefficients for the diffractive surface R.sub.2 are:
______________________________________ C.sub.1 = -1.399E-03 C.sub.3 = 5.0503E-07 C.sub.5 = -2.1304E-15 C.sub.2 = -2.020E-05 C.sub.4 = -3.6217E-09 .lambda..sub.0 = 601.8 NM ______________________________________

### Claim 8

An optical magnifier constructed according to the following table in which R.sub.1 through R.sub.4 are the radii of curvature of the magnifier from a front eyeside to a rear object side, radii R, thicknesses and distances are in millimeters, the index is for the sodium D line of the spectrum and V is the abbe number, the aspheric coefficients fit the following general formula: ##EQU10## and the diffractive surfaces are described by the following phase equation:
______________________________________ ##STR2## RADIUS THICKNESS INDEX V ______________________________________ 10 DIAPHRAGM 35.000 R.sub.1 ASPHERE 6.250 1.59 30.9 R.sub.2 -138.6388 0.250 R.sub.3 24.9913 15.234 1.59 30.9 R.sub.4 ASPHERE ______________________________________
The aspheric coefficients for R.sub.1 and R.sub.4 are:
______________________________________ SURF. C = 0.0712819 D = -0.4002700E-04 F = -0.1524500E-08 R.sub.1 k = 0.0000000 E = 0.9801800E-07 G = -0.1998500E-11 VERTEX RADIUS (1/C) = 14.0288 SURF. C = 0.747032 D = 0.1950900E-02 F = -0.1629400E-04 R.sub.4 K = 0.0000000 E = 0.1495100E-03 G = 0.9862700E-06 VERTEX RADIUS (1/C) = 13.3863 ______________________________________
Coefficients for the diffractive surface R.sub.2 are:
______________________________________ C.sub.1 = -2.6839E-03 C.sub.3 = 2.5135E-07 C.sub.5 = 7.4828E-12 C.sub.2 = -6.0734E-06 C.sub.4 = -2.4004E-09 .lambda..sub.0 = 601.8 NM ______________________________________

### Claim 9

An optical magnifier constructed according to the following table in which R.sub.1 through R.sub.4 are the radii of curvature of the magnifier from a front eyeside to a rear object side, radii R, thicknesses and distances are in millimeters, the index is for the sodium D line of the spectrum and V is the abbe number, the aspheric coefficients fit the following general formula: ##EQU11## and the diffractive surfaces are described by the following phase equation:
______________________________________ ##STR3## RADIUS THICKNESS INDEX V ______________________________________ 10 DIAPHRAGM 35.000 R.sub.1 ASPHERE 6.250 1.59 30.9 R.sub.2 -143.4110 0.250 R.sub.3 24.9913 15.234 1.59 30.9 R.sub.4 ASPHERE ______________________________________
The coefficients for R.sub.1 and R.sub.4 are:
__________________________________________________________________________ SURF. 1 C = 0.714597 D = -0.4039180E-04 F = -0.1637370E-08 k = 0.0000000 E = 0.1082030E-06 G = -0.1888110E-11 VERTEX RADIUS (1/C) = 13.9939 SURF. 4 C = 0.741966 D = 0.1317330E-02 F = -0.9026310E-05 k = 0.0000000 E = 0.7626560E-04 G = 0.7396810E-06 VERTEX RADIUS (1/C) = 13.4777 __________________________________________________________________________
The coefficients for the diffractive surface R.sub.2 are:
______________________________________ C.sub.1 = -2.67278E-03 C.sub.3 = 2.73465E-07 C.sub.5 = 8/37743E-12 C.sub.2 = -6.77570E-06 C.sub.4 = -2.65724E-09 .lambda..sub.0 = 601.8 NM ______________________________________

### Claim 10

An optical magnifier constructed according to the following table in which R.sub.1 through R.sub.4 are the radii of curvature of the magnifier from a front eyeside to a rear object side, radii R, thicknesses and distances are in millimeters, the index is for the sodium D line of the spectrum and V is the abbe number, the aspheric coefficients fit the following general formula: ##EQU12## and the diffractive surfaces are described by the following phase equation:
______________________________________ ##STR4## RADIUS THICKNESS INDEX V ______________________________________ 10 DIAPHRAGM 35.000 R.sub.1 ASPHERE 5.900 R.sub.2 132.529 0.200 R.sub.3 ASPHERE 15.200 1.59 30.9 R.sub.4 ASPHERE ______________________________________
The aspheric coefficients for R.sub.1, R.sub.3 and R.sub.4 are:
__________________________________________________________________________ SURF. 1 C = 0.645765 D = 0.7594100E-05 F = -0.1161100E-08 k = 0.0000000 E = 0.2164100E-06 G = 0.2373000E-11 R = 1/C = 15.4855 SURF. 3. C = 0.0645970 D = 0.0 F = 0.0 k = 2.9610000 E = 0.0 G = 0.0 R = 1/C = 15.4806 SURF. 4 C = 0.1067486 D = 0.8380000E-03 F = -0.1320800E-04 k = 0.0000000 E = 0.9502300E-04 G = 0.1117000E-05 R = 1/C = 9.3678 __________________________________________________________________________
The coefficients for the diffractive surface R.sub.2 are:
______________________________________ C.sub.1 = -1.4600E-03 C.sub.3 = 6.2003E-07 C.sub.5 = 0.0 C.sub.2 = -3.1336E-05 C.sub.4 = -3.1047E-09 .lambda..sub.0 = 601.8 NM ______________________________________

### Claim 11

An optical magnifier constructed according to the following table in which R.sub.1 through R.sub.4 are the radii of curvature of the magnifier from a front eyeside to a rear object side, radii R, thicknesses and distances are in millimeters, the index is for the sodium D line of the spectrum and V is the abbe number, the aspheric coefficients fit the following general formula: ##EQU13## and the diffractive surfaces are described by the following phase equation:
______________________________________ ##STR5## RADIUS THICKNESS INDEX V ______________________________________ 10 DIAPHRAGM 35.000 R.sub.1 ASPHERE 5.900 1.60 38.0 R.sub.2 -282.843 0.200 R.sub.3 ASPHERE 15.200 1.59 30.9 R.sub.4 ASPHERE ______________________________________
the aspheric coefficients for R.sub.1, R.sub.3 and R.sub.4 are:
__________________________________________________________________________ SURF. R.sub.1 C = 0.0715958 D = -0.9764700E-05 F = 0.4155400E-09 k = 0.0000000 E = 0.3817900E-07 G = 0.5780800E-11 R = 1/C = 13.9673 SURF. R.sub.3 C = 0.456809 D = 0.0 F = 0.0 k = -7.5220000 E = 0.0 G = 0.0 R = 1/C = 21.8910 SURF. R.sub.4 C = 0.0943850 D = 0.6190000E-03 F = -0.1112600E-04 k = 0.0000000 E = 0.9618100E-01 G = 0.8829700E-06 R = 1/C = 10.5949 __________________________________________________________________________
The coefficients for the diffractive surface R.sub.2 are:
______________________________________ C.sub.1 = -2.1900E-03 C.sub.3 = 5.6166E-07 C.sub.5 = 0.0 C.sub.2 = -2.7000E-05 C.sub.4 = -2.4397E-09 .lambda..sub.0 = 601.8 NM ______________________________________

### Claim 12

An optical magnifier consisting of, from a front, eye side to a rear, object side:
a first biconvex element and a second element, the second element consisting of two refractive surfaces, both of which are concave toward the object side;
the magnifier having a diffractive surface on either the rear surface of the first biconvex element or the front surface of the second element;
wherein said magnifier has at least two aspheric surfaces defined by ##EQU14## where, D, E, F, G and K are aspheric coefficients and wherein each of said two aspheric surfaces has at least one aspheric coefficient that is non-zero.

### Claim 13 (depends on 12)

An optical magnifier according to claim 12 wherein the rear surface of the second element is a negative aspheric surface which follows a formula having a positive sag from a corresponding spherical curvature.

### Claim 14 (depends on 12)

An optical magnifier according to claim 12 wherein 0.0<S/EF<0.3, where EF is the focal length of the magnifier, S is the incremental sag of the negative aspheric surface at a clear aperture of the magnifier when H/EF is equal to 0.18 where H is the image height at full aperture.

### Claim 15 (depends on 13)

An optical magnifier according to claim 13 wherein said aspheric surface complies with the general formula: ##EQU15## and wherein C, D, E, F, G and k are constants and wherein D is positive.