US 7,621,636 B2 · Working distance and alignment sensor for a fundus camera

Abstract

In embodiments of optical arrangements of a working distance sensor in a fundus camera that can improve the determination of a correct working distance as well as the transverse positioning of the camera a number of near infrared light sources are arranged to project a number of near infrared illumination beams into the visible light illumination path of the fundus camera and a live view of the retina under near infrared illumination is captured and displayed on a monitor. These embodiments of optical arrangements and associated methods will enable an operator to directly determine if there is any undesirable flare or other artifact appearing within a designated region on the infrared retina view as a result of a wrong alignment of the fundus camera with respect to the eye in terms of not only the working distance but also the horizontal and vertical positions. Pattern recognition algorithms can be used to further enhance the positioning sensitivity of the working distance sensor. An additional iris alignment sensor can be added to achieve a coarse alignment and also function as a measure to determine if the dilation of the iris size is sufficient for different mode of fundus imaging.

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Drawings

Claims34

Dependent claims

A method comprising:

projecting light from a near infrared light source into an annular visible light illumination path of a fundus camera to form a near infrared illumination beam;
spatially filtering the near infrared illumination beam to form an annular near infrared illumination beam substantially overlapping the annular visible light illumination path, with the annular visible light illumination path configured so that visible light projected into the annular visible light illumination path forms an annular visible light illumination beam that illuminates the retina of an eye of a subject;
focusing the annular near infrared illumination beam and the annular visible light illumination beam to an annular ring at the cornea region of the eye of a subject;
and
tapping a portion of a near infrared imaging beam, formed when the annular near infrared illumination beam is reflected from the cornea and/or retina of the eye of a subject, to form a tapped portion directed to a sensor that forms a near infrared image of the cornea and/or retina of the eye, and where the annular near infrared illumination beam and the near infrared imaging beam do not overlap at the cornea region when a working distance value between an objective lens and the anterior surface of the eye is correct so that only an image of the retina is formed at the sensor.

2 more elements

A system comprising:

means for projecting light from a near infrared light source into an annular visible light illumination path of a fundus camera to form a near infrared illumination beam;
means for spatially filtering the near infrared illumination beam to form an annular near infrared illumination beam substantially overlapping the annular visible light illumination path, with the annular visible light illumination path configured so that visible light projected into the annular visible light illumination path forms an annular visible light illumination beam that illuminates the retina of an eye of a subject;
means for focusing the annular near infrared illumination beam and the annular visible light illumination beam to an annular ring at the cornea region of the eye of a subject;
and
means for tapping a portion of a near infrared imaging beam, formed when the annular near infrared illumination beam is reflected from the cornea and/or the retina of the eye of the subject to form a tapped portion directed to a sensor that forms a near infrared image of the cornea and/or retina of the eye, and where the annular near infrared illumination beam and the near infrared imaging beam do not overlap at the cornea region when a working distance value between an objective lens and the anterior surface of the eve is correct so that only an image of the retina is formed at the sensor.

2 more elements

A system comprising:

a plurality of near infrared light sources;
a mounting structure for holding said light sources;
a projecting optical element adapted to project near infrared light from the light sources into an annular ring-shaped visible light illumination path of a fundus camera to form a plurality of near infrared illumination beams, with the annular ring-shaped visible light illumination path configured so that visible light projected into the annular ring-shaped visible light illumination path forms an annular ring-shaped visible light illumination beam that illuminates the retina of the eye of a subject;
an aperture structure for spatially filtering the near infrared illumination beams to cause the near infrared illumination beams to substantially overlap the annular ring-shaped visible light illumination path;
an optical relay system configured to focus the annular ring-shaped visible light illumination beam to a focused visible light annular ring at the cornea of the eye of a subject and to focus the near infrared illumination beams to a plurality of focused infrared light spots around an annular ring that substantially overlaps the focused visible light annular ring at the cornea region of the eye of a subject;
an optical element that taps a portion of a near infrared imaging beam, formed when the plurality of the near infrared illumination beams are reflected from the cornea and/or retina of the eye;
and
a sensor, positioned to receive a tapped portion of the near infrared illumination beam, that forms a near infrared image of the of the cornea and/or retina and where the near infrared illumination beam and the near infrared imaging beam do not overlap at the cornea when a working distance value between an objective lens and the anterior surface of the eye is correct so that only an image of the retina is formed at the sensor.

5 more elements

A system comprising:

a first plurality of infrared light sources;
a mounting structure for holding said light sources in said plurality;
a projecting optical element adapted to project infrared light from the light sources in the first plurality into an annular ring-shaped visible light illumination path of a fundus camera to form a plurality of first infrared illumination beams with the annular ring-shaped visible light illumination path configured so that visible light projected into the annular ring-shaped visible light illumination path forms an annular ring-shaped visible light illumination beam that illuminates the retina of the eye of a subject;
an aperture structure for spatially filtering the plurality of first infrared illumination beams to cause the near infrared illumination beams to substantially overlap the annular ring-shaped visible light illumination path;
a first optical relay system configured to focus the annular ring-shaped visible light illumination beam to a focused visible light annular ring at the cornea region of the eye of the subject and to focus the near infrared illumination beams to a number of focused light spots around an annular ring that substantially overlaps with the focused visible annular ring at the cornea region of the eye;
a first optical element that taps a portion of the plurality of first infrared illumination beams reflected from the cornea and/or retina of the eye of a subject to form a first infrared imaging beam where the plurality of first infrared illumination beams and the first infrared imaging beam do not overlap at the cornea when a working distance value between an objective lens and the anterior surface of the eye is correct so that only an image of the retina is formed at a sensor;
a second plurality of near infrared light sources aligned to illuminate the iris of the eye and form a second near infrared imaging beam reflected from the iris;
and
a second optical element for tapping a portion of the second near infrared imaging beam reflected from the iris of the eye.

6 more elements

Dependencies are inferred from the claim text.

Description7,422 words

Summary665 words

#One or more embodiments relate to a fundus camera for retina imaging. In particular, they relate to a fundus camera with a working distance detecting means so that the captured retina image is free from undesirable flair, artifact or ghost images.

#When imaging the retina (or fundus, these terms will be used interchangeably) of an eye, some of the illumination light beam from a light source may be reflected and/or scattered from the cornea, the iris and the crystalline lens of the eye. It is possible that this undesired reflected and/or scattered light resulting from the interaction of the illumination light beam with the anterior segment of the eye can be mixed with the imaging beam which comprises desired light reflected/scattered from the retina of the eye for photographic imaging or observational purposes. This undesirable mixing can result in the appearance of flair light, artifact, haze or ghost images on the retina image.

#To get rid of these undesirable effects, an annular ring-shaped illumination light with a selected annular width and a numerical aperture can be focused at the cornea region to illuminate a large area of the retina, and the imaging path can be designed to occupy a space inside of the annular ring on the cornea. When the eye is properly positioned the illumination path has no overlap with the imaging path at the cornea, iris and crystalline lens so that light from the illumination beam will not be reflected and/or scattered into the imaging beam. However, to ensure that there is no undesirable effect on the retina image, a correct working distance between the objective lens of the fundus camera and the patient's eye must be maintained.

Brief description of the drawings14 figures

#FIG. 1 shows one embodiment, in which near infrared light sources are arranged to project near infrared beams into the visible ring illumination path;

#FIG. 2 shows one embodiment of the retina imaging path along with at least a portion of the near infrared retina imaging beam being tapped to form an image of the retina onto a near infrared CCD.

#FIG. 3(a) shows an example of the space occupied respectively by the illumination path and the retina imaging path. When the eye is well positioned, there is no overlap of the illumination path with the imaging path at the cornea, the iris and the crystalline lens. Therefore, illumination light scattered by these tissues will not get into the imaging path.

Detailed description6,124 words

#Various embodiments of the invention will be described where one embodiment is an optical arrangement of a working distance sensor in a fundus camera (note that the word fundus and retina are used interchangeably), and the associated method, in which one or more near infrared light sources such as a number of LEDs (light emitting diodes) are arranged to project a number of near infrared illumination beams into the visible light illumination path of the fundus camera. The near infrared beams may or may not substantially overlap with the visible illumination beam.

#Due to the fact that the iris will generally not constrict when illuminated by near infrared light, a live view of the retina under near infrared illumination can be captured by a near infrared image sensor and displayed on a monitor before a visible retina image is taken. This live near infrared retina image can serve two purposes. Firstly, it will enable the operator to have a live view of the retina under near infrared illumination which preferably shows the same region as will be photographed with visible light. Therefore, the operator can identify the area of interest and make adjustments for the area to be photographed. Secondly, because the near infrared beams follow substantially the same path as the illumination beam of visible light, viewing the near infrared retina image will enable the operator to directly find out if there is any undesirable flair or any other artifact appearing within a designated region on the near infrared retina view as a result of wrong positioning of the fundus camera with respect to the eye in terms of not only the axial working distance but also the horizontal and vertical positions.

#In one embodiment, this designated region on the near infrared live image can be selected to correspond to a clear visible image without flair or other artifact by correcting for any intended or unintended overlap or non-overlap of the near infrared illumination beam with the visible illumination beam and by correcting for any dispersion-induced-difference in the working distance resulting from the difference in the operating wavelength of the visible and the near infrared spectrum.

Facts

Application

11/621,943Filed 10 Jan 2007

Published

US 2008/0165322 A110 Jul 2008

Granted

24 Nov 2009

Term ends

5 Jun 2027

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 146 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

A61B 3/12
Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions: for looking at the eye fundus,…
A61B 3/102
Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions: for optical coherence tomography [OCT]
A61B 3/152
With means for aligning, spacing or blocking spurious reflection ; with means for relaxing: for aligning
A61B
Medical diagnosis and surgery

Timeline

10 Jan 2007Application filedUS 11/621,943
4 Jun 2007Assigned to Clarity Medical Systems, Inc.assignment of assignor's interest
10 Jul 2008PublishedUS 2008/0165322 A1
14 Oct 2009Assigned to Pinto Investment Partners, L.P.security agreement
24 Nov 2009GrantedUS 7,621,636 B2
9 May 2013Assigned to Clarity Medical Systems, Inc., Retcam, Inc.release of security interest
4 Sep 2013Assigned to Comerica Bank, A Texas Banking Associationsecurity agreement
11 Aug 2017Assigned to Clarity Medical Systems, Inc.release of security interest
12 Oct 2026TodayWithin its term
5 Jun 2027Term endsEstimated, includes 146 days of adjustment

Working distance and alignment sensor for a fundus camera

Life of this patent

Working distance and alignment sensor for a fundus camera

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims34

Description7,422 words

Drawings

Classification4 codes

Life of this patent

Description7,422 words