Patent US5900993A successfully refreshed from Google Patents.
US5900993A
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US
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Lens systems for use in fingerprint detection
Assignee: Cross Match Technologies Inc
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Filing: 1997-05-09
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Granted: 1999-05-04
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Expires: 2017-05-09
Abstract
Abstract Lens systems for use in fingerprint detection systems employing frustrated total internal reflection are provided. The systems include an aperture stop and three lens units. The first lens unit has a positive power, is located on the object side of the aperture stop, and forms a telecentric pupil for the lens system. The second lens unit has a positive power, is located on the image side of the first lens unit, and forms a real image of the object. In certain embodiments, the third lens unit is located between the first and second lens units and has substantially afocal cylindrical power. In other embodiments, the third lens unit serves to correct the field curvature of the image contributed by the first and second lens units.
Inventors
- 👤 Ellis Betensky
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 15:30
CPC Classifications
G; G06; G06V; G06V40/00; G06V40/10; G06V40/12; G06V40/13; G06V40/1324
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
134 words
An optical system having an optical axis, said system forming an image of an object and comprising: a) a prism having a first surface for contacting the object and a second surface, said first surface being oriented with respect to the optical axis at an angle greater than the angle of total internal reflection of the surface; b) an aperture stop; c) a first lens unit having a positive power between the aperture stop and the prism for forming a telecentric entrance pupil; d) a second lens unit having a positive power on the image side of the aperture stop for forming a real image of the object; and e) a third lens unit between the first and second lens units, said third lens unit having cylindrical power, said cylindrical power being substantially afocal.
Claim 2
Dependent Claim
134 words
An optical system having an optical axis, said system forming an image of an object and comprising: a) a prism having a first surface for contacting the object and a second surface, said first surface being oriented with respect to the optical axis at an angle greater than the angle of total internal reflection of the surface; b) an aperture stop; c) a first lens unit having a positive power between the aperture stop and the prism for forming a telecentric entrance pupil; d) a second lens unit having a positive power on the image side of the aperture stop for forming a real image of the object; and e) a third lens unit between the first and second lens units, said third lens unit having cylindrical power, said cylindrical power being substantially afocal.
Claim 3
Dependent Claim
17 words
The optical system of claim 1 wherein the first lens unit comprises at least one aspherical surface.
Claim 4
Dependent Claim
17 words
The optical system of claim 1 wherein the first lens unit consists of a single lens element.
Claim 5
Dependent Claim
17 words
The optical system of claim 1 wherein the second lens unit comprises at least one aspherical surface.
Claim 6
Dependent Claim
17 words
The optical system of claim 1 wherein the second lens unit consists of a single lens element.
Claim 7
Dependent Claim
22 words
The optical system of claim 1 wherein the third lens unit comprises an optical surface which is adjacent to the aperture stop.
Claim 8
Dependent Claim
17 words
The optical system of claim 1 wherein the third lens unit consists of a single lens element.
Claim 9
Dependent Claim
28 words
The optical system of claim 1 wherein the cylindrical power of the third lens unit is used to reduce the size of the image in one direction only.
Claim 10
Dependent Claim
32 words
The optical system of claim 1 wherein the cylindrical power of the third lens unit serves to reduce the field curvature of the image contributed by the first and second lens units.
Claim 11
Dependent Claim
136 words
An optical system having an optical axis, said system forming an image of an object and comprising: a) a prism having a first surface for contacting the object and a second surface, said first surface being oriented with respect to the optical axis at an angle greater than the angle of total internal reflection of the surface; b) an aperture stop; c) a first lens unit having a positive power between the aperture stop and the prism for forming a telecentric entrance pupil; d) a second lens unit having a positive power for forming a real image of the object, said second lens unit being on the image side of the first lens unit; and e) a third lens unit for correcting the field curvature of the image contributed by the first and second lens units.
Claim 12
Dependent Claim
136 words
An optical system having an optical axis, said system forming an image of an object and comprising: a) a prism having a first surface for contacting the object and a second surface, said first surface being oriented with respect to the optical axis at an angle greater than the angle of total internal reflection of the surface; b) an aperture stop; c) a first lens unit having a positive power between the aperture stop and the prism for forming a telecentric entrance pupil; d) a second lens unit having a positive power for forming a real image of the object, said second lens unit being on the image side of the first lens unit; and e) a third lens unit for correcting the field curvature of the image contributed by the first and second lens units.
Claim 13
Dependent Claim
17 words
The optical system of claim 10 wherein the first lens unit comprises at least one aspherical surface.
Claim 14
Dependent Claim
17 words
The optical system of claim 10 wherein the first lens unit consists of a single lens element.
Claim 15
Dependent Claim
17 words
The optical system of claim 10 wherein the second lens unit comprises at least one aspherical surface.
Claim 16
Dependent Claim
17 words
The optical system of claim 10 wherein the second lens unit consists of a single lens element.
Claim 17
Dependent Claim
15 words
The optical system of claim 10 wherein the third lens unit has a negative power.
Claim 18
Dependent Claim
16 words
The optical system of claim 10 wherein the third lens unit has an overall meniscus shape.
Claim 19
Dependent Claim
15 words
The optical system of claim 10 wherein the third lens unit comprises an aspherical surface.
Claim 20
Dependent Claim
17 words
The optical system of claim 10 wherein the third lens unit consists of a single lens element.
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