Patent US1890459A successfully refreshed from Google Patents.
Patent US4917458A successfully refreshed from Google Patents.
US4917458A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cornea shape measuring apparatus
Assignee: Canon Inc
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Filing: 1989-08-01
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Granted: 1990-04-17
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Expires: 2009-08-01
Abstract
Abstract A cornea shape measuring apparatus which is provided with first and second substantially ring-like index marks disposed at different positions in the direction of the optic axis and projected onto the cornea of an eye to be examined and in which the corneal reflection images of the first and second index marks are detected by a first position detector and the shape of the cornea is measured without depending on the working distance.
Inventors
- 👤 Isao Matsumura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 11:10
CPC Classifications
A; A61; A61B; A61B3/00; A61B3/10; A61B3/107
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
137 words
A cornea shape measuring apparatus, comprising: first and second substantially ring-like index marks adapted to be positioned a finite distance opposite an eye to be examined, said first index mark being adapted to be spaced from said second index mark in a direction of an optic axis; an imaging optical system for receiving corneal reflection images of said first and second index marks; a light position detector adapted to be provided on an image surface of said imaging optical system; and calculating means for calculating the radius of curvature of the cornea on the basis of: (i) distance between said first index mark and said second index mark in the direction of the optic axis; (ii) radii of the images of said first and second index marks; and (iii) radii of said first and second index marks.
Claim 2
Dependent Claim
137 words
A cornea shape measuring apparatus, comprising: first and second substantially ring-like index marks adapted to be positioned a finite distance opposite an eye to be examined, said first index mark being adapted to be spaced from said second index mark in a direction of an optic axis; an imaging optical system for receiving corneal reflection images of said first and second index marks; a light position detector adapted to be provided on an image surface of said imaging optical system; and calculating means for calculating the radius of curvature of the cornea on the basis of: (i) distance between said first index mark and said second index mark in the direction of the optic axis; (ii) radii of the images of said first and second index marks; and (iii) radii of said first and second index marks.
Claim 3
Dependent Claim
21 words
A cornea shape measuring apparatus according to claim 1, wherein said first and second index marks are concentric ring-like index marks.
Claim 4
Dependent Claim
30 words
A cornea shape measuring apparatus according to claim 1, wherein said first and second index marks are integral with each other and displaceable in the direction of the optic axis.
Claim 5
Dependent Claim
25 words
A cornea shape measuring apparatus according to claim 1, wherein at least one of said first and second index marks is a ring-like light source.
Claim 6
Dependent Claim
21 words
A cornea shape measuring apparatus according to claim 4, wherein said first and second index marks are two ring-like light sources.
Claim 7
Dependent Claim
43 words
A cornea shape measuring apparatus according to claim 1, wherein said first and second index marks are point-like light sources disposed on predetermined circumferences in two different planes in the direction of the optic axis and in a plurality of predetermined meridian directions.
Claim 8
Dependent Claim
27 words
A cornea shape measuring apparatus according to claim 6, wherein said first and second index marks are disposed in the directions of east, west, south and north.
Claim 9
Dependent Claim
29 words
A cornea shape measuring apparatus according to claim 1, wherein said imaging optical system is an object side telecentric optical system provided with stop on the focal plane thereof.
Claim 10
Dependent Claim
21 words
A cornea shape measuring apparatus according to claim 8, wherein said imaging optical system includes an image side telecentric optical system.
Claim 11
Dependent Claim
19 words
A cornea shape measuring apparatus according to claim 8, wherein the aperture of said stop is variable in size.
Claim 12
Dependent Claim
32 words
A cornea shape measuring apparatus according to claim 10, wherein the brightness of said index marks is controlled in response to a variation in the size of the aperture of said stop.
Claim 13
Dependent Claim
19 words
A cornea shape measuring apparatus according to claim 1, wherein said first and second index marks differ in radius.
Claim 14
Dependent Claim
20 words
A cornea shape measuring apparatus according to claim 1, wherein said first and second index marks are equal in radius.
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) | 1993-04-16 | 1993-10-16 | 1994-04-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-04-16 | 1997-10-16 | 1998-04-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-04-16 | 2001-10-16 | 2002-04-17 | $7700.00 | Window Closed / Lapsed |