WO2014128657A1

WO2014128657A1 - Apparatus for observing eye and a method thereof

Info

Publication number: WO2014128657A1
Application number: PCT/IB2014/059154
Authority: WO
Inventors: Shyam VASUDEVA RAO; Harinarayanan SATHYANARAYANAN; Bharath HEGDE; Manjunath MEGHALPURA CHANDRASHEKARAIH
Original assignee: Forus Health Pvt. Ltd.
Priority date: 2013-02-25
Filing date: 2014-02-21
Publication date: 2014-08-28

Abstract

The present disclosure is related to an apparatus for capturing retina and cornea images of eye and for measuring refractive power of eye. The apparatus comprises an objective lens, illumination unit, projection unit, fixation unit, movable mirror and image sensor. The illumination unit projects illumination beam onto eye when the movable mirror is placed at the intersection of illumination unit and the image sensor. The image sensor captures image of illuminated retina and computing system connected to image sensor makes a complete image of retina. The projection unit projects a target pattern in a ring form onto eye when movable mirror is placed at intersection of projection unit and image sensor. The fixation unit coupled to projection unit projects a fixation image. The movable mirror couples target pattern and fixation image onto eye. The image sensor captures image of ring that is projected onto retina surface to determine refractive power.

Description

APPARATUS FOR OBSERVING EYE AND A METHOD THEREOF

TECHNICAL FIELD

The present disclosure is related to an ophthalmic apparatus. In particular, the present disclosure relates to a unified apparatus for capturing retina and cornea images of eye and for measuring refractive power of the eye.

BACKGROUND Ophthalmic apparatuses have been known to observe eye by projecting a light onto a fundus of the eye and receiving the light reflected thereby forming an image of the retina on the imaging surface. There are several ophthalmic apparatus, each designed to perform a specific functionality.

Presently, for observing and capturing the eye fundus and for measuring refracting power of the eye at the same time, there is a need to install two apparatuses an eye refractometer as illustrated in Fig.la and an eye fundus camera as illustrated in Fig.3.

Fig. la illustrates the diagram of a refractometer 104 in accordance with an embodiment of the prior art. The refractometer comprises a fixation unit 121 with a light source 122, a light-passing screen 123 with an image that is focused by a simple or compound lens 125 and subsequent lenses to form an image visible to the eye of the subject, who is requested to focus the eye 101 on that perceived image. The refractometer 104 also comprises a projection unit 113 which includes a source 114 of Infrared (IR) light, and a barrier 115 containing a transparent slit in the form a circle as shown in Fig.lb. The structured IR light emerging from the barrier 115 is merged with the fixation beam by the hot mirror 117, and both are deflected into the main optical path by the polarizing mirror 105. The combined beam is further focused by the objective lens 103, from where it passes to the eye 101. The part of the returning IR light whose polarization is unchanged is reflected again by the polarizing mirror 105, while the changed part passes through the polarizing mirror 105, creating an image in the image sensor 107. The geometry of this image is analyzed by a computing system connected to the sensor to determine refractive power of the eye 101. Fig.2 illustrates the diagram of a fundus camera 204 in accordance with an embodiment of the prior art. The fundus camera 204 comprises IR source 214 and a flash source 222 which serves for illumination of the fundus of the eye 101. Their paths are merged by the hot mirror 217 and deflected into the main optical path by the polarizing mirror 105. The white light flash from the source 222 passes through the hot mirror 217, reflects from the polarizing mirror 105, illuminates the fundus, and creates a focused image in the sensor 107.

As a result of installing two apparatus for performing two separate functionalities, more space is needed for the installation, leading to an increased expense. The separate cost of the separate devices includes the cost for non-removable components that are similar or identical in each, such as the objective lens, the sensor, the patient chinrest that stabilizes head and eye position, etc. A customer who needs both functions must pay for these repetitions. The separate space, power and digital connectivity required by the separate devices represent twice the infrastructure cost of a single device, and may exceed the space or funding available. The patient who needs both observations must be moved from one device to the other, adding stress to the experience (particularly for the physically or mentally challenged) and time to both the user experience and clinical manpower use. The user must adjust and focus each device separately, though the required relation between the eye and the sensor may be similar or identical.

In any cost effective single apparatus that aims in integrating the functionalities of capturing and measuring the anatomical, physiological and information processing related to the retina image and anterior segment (cornea) image as well as refractive power of the eye, utilizes a laser source, infra-red light emitting diode (LED) source, image sensor, several collimator, wedge, lenses, axicon lens, hot and cold mirrors, polarizer, etc. One of the basic requirements to measure the refractive power of the eye is to project a pattern (usually a ring or circle) on the retina and observe its deformation. In the existing prior art, a ring is projected on to the surface of the retina through the eye lens is formed by a beam originating from the laser source. But, this ring would get projected non-uniformly with varying thickness and inconsistent brightness, mainly due to any other polarizer which is placed in the optical path which is required for retina and anterior segment imaging purpose. The error in determination of the refractive power will be erroneous since its calculation is dependent on the ring.

Though the optical components, the polarized laser source in combination with a wedge is best suited for measuring the refractive power of eye. Unfortunately, the laser light gives only specular reflections from the surface of the retina, resulting in a noisy ring pattern for the purpose of measurements. On the other hand, the wedge will also affect the quality of the retina image by causing glare, if it is in the optical path during retina image capture mode. Hence, there exists a need for a single cost effective apparatus for capturing the retina and cornea images, for measuring the refractive power of the eye and for adaptive optics.

SUMMARY This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In an embodiment, the present disclosure provides an apparatus for observing eye. The apparatus comprises an objective lens, an illumination unit, a projection unit, a fixation unit, a movable mirror and an image sensor. The illumination unit is configured to illuminate the eye through the objective lens with an illumination beam. The projection unit is configured to project a target pattern on the retina of the eye through the objective lens. The fixation unit is coupled to the projection unit to project a fixation image on the retina of the eye through the objective lens. The image sensor is configured to receive an image of the retina of the eye through the objective lens when at least one of the eye is illuminated by the illumination unit and a target pattern is projected on the retina of the eye by the projection unit. The movable mirror performs at least one of coupling the target pattern and the fixation image into the objective lens when placed at the intersection of the projection unit and the sensor and allowing projection of the illumination beam onto the eye when placed at the intersection of the illumination unit and the sensor.

In an embodiment, the present disclosure provides a method for observing eye. The method comprises illuminating the eye with an illumination beam by an illumination unit when a movable mirror is placed at the intersection of the illumination unit and a sensor. The method further comprises projecting a target pattern on a retina of the eye when the movable mirror is placed at the intersection of the projection unit and the sensor. The fixation unit is coupled to the projection unit to project a fixation image on the retina of the eye. The movable mirror couples the target pattern and the fixation image into an objective lens. The sensor receives an image of the retina of the eye by the sensor when at least one of the eye is illuminated by the illumination unit and the target pattern is projected on the retina of the eye.

In an embodiment, the present disclosure provides an apparatus for observing eye. The apparatus comprises an objective lens, an illumination unit, a projection unit, a fixation unit, a movable flip-mirror, a polarizing mirror and a sensor. The illumination unit illuminates the eye through the objective lens with an illumination beam. The projection unit is configured to project a target pattern on the retina of the eye through the objective lens. The fixation unit is coupled to the projection unit to project a fixation image on the retina of the eye through the objective lens. The movable flip-mirror is placed at the intersection of the illumination unit and the projection unit. The movable flip-mirror is configured to rotate in at least one of clockwise direction and anticlockwise direction. The movable flip-mirror is rotated in the clockwise direction when the projection unit projects the target pattern onto the retina of the eye. The movable flip-mirror couples the target pattern and the fixation image into the objective lens. The movable flip-mirror when rotated in the anti-clockwise direction allows the projection of the illumination beam onto the eye. The sensor receives an image of the retina of the eye through the objective lens when the eye is illuminated by the illumination unit and the target pattern is projected on the retina of the eye by the projection unit. The sensor provides an in focus image of the target pattern projected on the retina of the eye. In an embodiment, the present disclosure provides a method for observing eye. The method comprises illuminating the eye with an illumination beam by an illumination unit when the movable flip-mirror is rotated in anti-clockwise direction. The method further comprises projecting a target pattern on retina of the eye by a projection unit when the movable flip-mirror is rotated in clockwise direction. Upon projecting the target pattern, a fixation image is projected on the retina of the eye by a fixation unit, wherein the fixation unit is coupled to the projection unit. The target pattern and the fixation image are coupled by the movable flip mirror into an objective lens when the movable flip-mirror is rotated in the clockwise direction. The sensor receives an image of the retina of the eye when at least one of eye is illuminated by the illumination unit and the target pattern is projected on the retina of the eye. Upon receiving the image of the retina the sensor configured in the imaging unit provides an in focus image of the target pattern projected on the retina of the eye.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features and characteristic of the disclosure are set forth in the appended claims. The embodiments of the disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings.

Figs.la-lb illustrates a refractometer in accordance with an embodiment of the prior art;

Fig.2 illustrates a fundus camera in accordance with an embodiment of the prior art; Fig.3a illustrates a unified apparatus for measuring refractive power of eye in accordance with one embodiment of the present disclosure; Fig.3b illustrates a unified apparatus for capturing retina and cornea images of eye in accordance with one embodiment of the present disclosure;

Fig.4a illustrates a unified apparatus for measuring refractive power of eye in accordance with another embodiment of the present disclosure;

Fig.4b illustrates a unified apparatus for capturing retina and cornea images of eye in accordance with another embodiment of the present disclosure;

Fig.5 shows a flowchart illustrating method for observing eye in accordance with one embodiment of the present disclosure; and

Fig.6 shows a flowchart illustrating method for observing eye in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims.

The present disclosure provides a unified apparatus for capturing retina and cornea images of eye and for measuring refractive power of eye. Fig.3a illustrates a unified apparatus 600 for measuring refractive power of eye in accordance with one embodiment of the present disclosure. The unified apparatus 600 comprises an objective lens 103, a movable mirror 606, an image sensor 107, a refractometry system 603 and a fundus camera system 602. The refractometry system 603 comprises a projection unit 607 and a fixation unit 609. The fundus camera system comprises an illumination unit. The movable mirror 606 is placed at the intersection of the projection unit 607 and the image sensor 107. In an embodiment, the movable mirror 606 is the polarizing mirror. The movable mirror 606 when placed at the intersection of the projection unit 607 and the image sensor 107, the refractometry system 603 becomes operational and the fundus camera system 602 becomes inactive. The unified apparatus 600 performs the functionality of the refractometer. The projection unit 607 is provided with an illuminator 611, an annular aperture 613, a hot and cold mirror 615, and a projective relay lens 617. The illuminator 611 provides a beam of infrared radiation. The annular aperture 613 shapes the beam of the infrared radiation into a target pattern. The annular aperture 613 allows the infrared radiation beam in a ring shaped form. The ring shaped beam of the infrared radiation is the target pattern. The target image pattern is projected onto the eye 101 through the hot and cold mirror 615, the projective relay lens 617, the movable mirror 606 and the objective lens 103.

The fixation unit 609 is coupled to the projection unit 607. The fixation unit 609 is provided with a fixation focus lens 619. The fixation unit 609 is configured to provide a fixation image. The fixation unit 609 is also provided with an illumination source for example a light emitting diode for illuminating the fixation image. The fixation image is projected onto the eye 101 through the fixation focus lens 619, the hot and cold mirror 615, the projective relay lens 617, the movable mirror 606 and the objective lens 103. Upon projection of the fixation image onto the eye 101, eye 101 relaxes and provides a focussing point for the eye 101. The fixation focus lens 619 is used to adopt the fixation image to the refractive power of the eye 101. For example, the fixation image may be adopted with the fixation focus lens 619 to -5 dioptre optical power to 5 dioptre of the eye 101.

In an embodiment, the movable mirror 606 couples the target image pattern and the fixation image and directs the coupled target pattern and the fixation image received into the objective lens 103. The image sensor 107 captures the image of the ring that is projected onto the retina surface to analyse the dimensions for determining the refractive power of the eye 101. A computing system is connected to the image sensor 107. The computing system receives the image of the ring, approximates the image and the implied curvature of the cornea and reports the refraction properties of the eye 101 in terms of convergence.

In an embodiment, the ring shape that is produced on retina of the eye 101 is dependent on eye lens characteristics. The advantage of projecting the ring shape on the retina of the eye 101 increases the sensitivity for measuring the optical strength of the eye 101. An in focus image of the target pattern projected on the retina is created through the cornea, the objective lens 103 and an image sensor lens in the image sensor 107. An out of focus image of the target pattern projected on the cornea is projected on the image sensor 107 through the objective lens 103 and the image sensor lens. The out of focus image of the target pattern on the cornea and the in focus image of the target image pattern on the retina provides information of the alignment of the eye 101 with respect to the unified apparatus 600 and the position of the eye 101 with respect to the unified apparatus 600 may be adjusted to improve the alignment. In an embodiment, the image sensor 107 is connected to the computing system which is provided with a memory and a processor. The computing system is programmed to process the in focus and out of focus images so as to determine the relative position and to adjust the unified apparatus 600 to optimize the alignment. For a good alignment, the computing system is programmed with a preconfigured code to check whether the imaged target ring of the retina and the imaged target ring of the cornea are concentric. The application software of the computing system is provided with a preconfigured code to calculate spherical power, cylindrical power and the axis of the eye 101 with the image of the target received from the image sensor 107. When the unified apparatus 600 and the eye 101 are correctly aligned, the computing system calculates the spherical power, cylindrical power and the axis of the eye 101. The computing system is also programmed with a preconfigured code to check the retinal views on different scale.

In an embodiment, the refractive power of eye 101 is measured using a calibration mode technique and an online measurement mode technique. In the calibration mode, firstly a ring is projected on the retina surface after passing rays as illustrated in the Fig.3a, through a set of standard lens with known dioptres having either spherical powers and/or cylindrical powers at different orientations. Upon projecting the ring on the retina, the image of the ring is captured by the image sensor 107. The image sensor 107 obtains best fit ellipses corresponding to each set of cylindrical and spherical diopters. In the online measurement mode, firstly a ring is projected on the retina surface of eye 101 whose refractive power in terms dioptres is to be measured. Upon projecting the ring on the retina, the image of the ring is captured by the image sensor 107. The computing system computes major axis, minor axis and orientation with respect to x-axis and obtains a refractive power of the eye by searching for the dioptre matching to the major axis, minor axis and orientation.

Fig.3b illustrates a unified apparatus 600 for capturing cornea and retina images of eye in accordance with one embodiment of the present disclosure. The unified apparatus 600 comprises an objective lens 103, a movable mirror 605, an image sensor 107, a refractometry system 603 and a fundus camera system 602. The refractometry system 603 comprises a projection unit 607 and a fixation unit 609. The fundus camera system comprises an illumination unit 621. The movable mirror 605 is placed at the intersection of the projection unit 607 and the image sensor 107. In an embodiment, the movable mirror 605 is the polarizing mirror. The movable mirror 605 when placed at the intersection of the projection unit 607 and the image sensor 107, the refractometry system 603 becomes inactive and the fundus camera system 602 becomes operational.

The illumination unit 621 comprises one or more light emitting diode (LED) illuminators. A first LED illuminator 623 configured in the illumination unit 621 provides an alignment beam with infrared radiation and a second LED illuminator 625 configured in the illumination unit 621 provides a beam of white light radiation. The alignment beam is used to align the eye 101 with the unified apparatus 600. The illumination unit 621 also comprises a hot-cold mirror 627 to combine the alignment beam of the infrared radiation with the beam of the white light radiation to form the illumination beam. The illumination beam is projected onto the eye 101 through the movable mirror 605 and the objective lens 103. The illumination unit 621 projects the illumination beam onto the eye through the hot-cold mirror 627 and the movable mirror 605 directs the illumination beam without any deviation onto the eye through the objective lens 103. The image sensor 107 is provided with an image sensor lens. The image sensor receives the image of the illuminated retina through cornea of the eye 101, the objective lens 103 and the movable mirror 605. A computing system connected to the image sensor is used to make a complete image of the retina. By changing focal position of the image sensor 107, the focal plane may be adjusted so that the cornea of the eye 101 can be imaged on the image sensor 107. The image sensor lens and the image sensor 107 may therefore be moveable and/or provided with moveable lens elements to adjust the focal position. The one or more illuminators configured in the illumination unit 621 uses the short illumination flash to illuminate the cornea so that the pupil of the eye 101 has no time to close itself in response to the visible white light. The image of the cornea may be processed by the computing system. In this way, the retina and the cornea are imaged using the unified apparatus 600.

In an embodiment, for capturing color images of retain or cornea, a collimated visible light is used to illuminate the retina or cornea of the eye 101 and the same is passed through the hot and cold mirror 627, the movable mirror 605, the objective lens 103 and eye 101 lens of pupil. The reflected rays from either the retina or cornea are captured by the image sensor 107 and associated computing system through the objective lens 103 and the movable mirror. 605. In an embodiment, the hot mirror 627 reflects infrared rays while transmitting visible light rays.

Fig.4a illustrates a unified apparatus 500 for capturing retina and cornea images of eye in accordance with another embodiment of the present disclosure. The unified apparatus 500 comprises an objective lens 503, a polarizing beam splitter 505, an image sensor 507, a movable flip-mirror 509, an illumination unit 511, a projection unit 215 and a fixation unit 216. The movable flip-mirror 509 is placed at the intersection of the projection unit 113 and the illumination unit 511. The movable flip-mirror 509 is rotated either manually or with the help of a motor in order to get it to the right position for the right operation. In an embodiment, the movable flip-mirror 509 is configured to rotate in clockwise and anticlockwise direction. The illumination unit 511 comprises one or more light emitting diode (LED) illuminators. A first LED illuminator 214 configured in the illumination unit 511 provides an alignment beam with infrared radiation and a second LED illuminator 222 configured in the illumination unit 511 provides a beam of white light radiation. The alignment beam is used to align the eye 501 with the unified apparatus 500. The illumination unit 511 also comprises a hot-cold mirror 217 to combine the alignment beam of the infrared radiation with the beam of the white light radiation to form the illumination beam. The illumination beam is projected onto the eye 101 through the polarizing beam splitter 505 and the objective lens 503. As an example, the polarizing beam splitter 505 is a wire grid polarizer. When the illumination unit 511 projects the illumination beam, the movable flip- mirror 109 is rotated in the anticlockwise direction so that, the illumination beam is facilitated onto the polarizing beam splitter 105 without any deviation. The polarizing beam splitter 505 directs the illumination beam onto the eye 501 through the objective lens 103. The sensor 507 is provided with an image sensor lens. The sensor receives the image of the illuminated retina through cornea of the eye 501, the objective lens 503 and the wire grid polarizer 505. The computing system connected to the sensor is used to make a complete image of the retina. By changing focal position of the image sensor 507, the focal plane may be adjusted so that the cornea of the eye 501 can be imaged on the image sensor 507. The one or more illuminators configured in the illumination unit 511 uses the short illumination flash to illuminate the cornea so that the pupil of the eye 501 has no time to close itself in response to the visible white light. The image of the cornea may be processed by the computing system. In this way, the retina and the cornea are imaged using the unified apparatus 500.

Fig.4b illustrates a unified apparatus 500 for measuring refractive power of eye in accordance with another embodiment of the present disclosure. The unified apparatus 500 comprises an objective lens 503, a polarizing beam splitter 505, an image sensor 507, a movable flip-mirror 510, an illumination unit 511, a projection unit 215 and a fixation unit 216. The projection unit 215 is provided with an illuminator 514, an annular aperture 515, a hot and cold mirror 517, and a projective relay lens 519. The illuminator 514 provides a beam of infrared radiation. The annular aperture 515 shapes the beam of the infrared radiation into a target pattern. The annular aperture 515 allows the infrared radiation beam in a ring shaped form. The ring shaped beam of the infrared radiation is the target pattern. The target image pattern is projected onto the eye 501 through the hot and cold mirror 517, the projective relay lens 519, the movable flip-mirror 510, the polarizing beam splitter 505 and the objective lens 503. The movable flip-mirror 510 is rotated in clockwise direction to a 45 degree position when the projection unit 215 projects the target pattern onto the eye 501.

The fixation unit 216 is coupled to the projection unit 215. The fixation unit 216 is provided with a fixation focus lens 525 and a flip-mirror 527. The fixation unit 216 is configured to provide a fixation image 523. The fixation unit 216 is also provided with an illumination source 522 for example a light emitting diode for illuminating the fixation image 523. The fixation image 523 is projected onto the eye 501 through the flip-mirror 527, the fixation focus lens 525, the movable flip-mirror 510, the polarizing beam splitter 505 and the objective lens 503. Upon projection of the fixation image 523 onto the eye 501, eye 501 relaxes and provides a focussing point for the eye 501. The fixation focus lens 525 is used to adopt the fixation image 523 to the refractive power of the eye 501. For example, the fixation image 523 may be adopted with the fixation focus lens 525 to -5 dioptre optical power to 5 dioptre of the eye 501 through the flip- mirror 527, the projective relay lens 519, the movable flip-mirror 510 and the polarizing beam splitter 505.

In an embodiment, the movable flip-mirror 510 couples the target image pattern and the fixation image 523 and provides it to the polarizing beam splitter 505. The polarizing beam splitter 505 directs the coupled target pattern and the fixation image 523 received from the movable flip-mirror 510 into the objective lens 503. The image sensor 507 captures the image of the ring that is projected onto the retina surface to analyse the dimensions for determining the refractive power of the eye 501. The image sensor provides an in focus image of the target pattern projected on to the eye 501.

Fig.5 shows a flowchart illustrating method for observing eye in accordance with one embodiment of the present disclosure. At step 501, the movable mirror 605 is placed at the intersection of the illumination unit 621 and the image sensor 107. When the movable mirror 605 is placed at the intersection of the illumination unit 621 and the image sensor 107, the refractometer system 603 is inactive and the fundus camera system 602 is operational. At step 503, the illumination unit 621 illuminates the eye by an illumination beam. The movable mirror 605 directs the illumination beam onto the eye through the objective lens 103. At step 505, the image sensor 107 captures the image of the illuminated retina through cornea of the eye 101, the objective lens 103 and the movable mirror 605. The computing system connected to the image sensor is used to make a complete image of the retina. At step 507, the movable mirror 606 is placed at the intersection of the projection unit 607 and the image sensor 107. When the movable mirror 606 is placed at the intersection of the projection unit 607 and the image sensor 107, the fundus camera system 602 becomes inactive and the refractometer system 603 becomes operational. At step 509, the projection unit 607 projects the target pattern on a retina of the eye when the movable mirror 606 is placed at the intersection of the projection unit 607 and the image sensor 107. The fixation unit 609 coupled to the projection unit 607 projects a fixation image on the retina of the eye. At step 511, the movable mirror 606 couples the target pattern and the fixation image onto the eye through the objective lens 103. At step 513, the image sensor 107 captures the image of the ring that is projected onto the retina surface to analyse the dimensions for determining the refractive power of the eye 101.

Fig.6 shows a flowchart illustrating method for observing eye 101 in accordance with another embodiment of the present disclosure. At step 601, the movable flip-mirror 509 placed at the intersection of the illumination unit 511 and the projection unit 215 is rotated in anticlockwise direction so that the illumination beam is projected onto the eye 501 by the illumination unit 511 without any deviation at step 603. At step 605, the movable flip-mirror 509 is rotated in the clockwise direction. At step 607, the target image pattern is projected on the eye 501 by the projection unit 215. The fixation unit 216 coupled to the projection unit 215 projects the fixation image 523 onto the eye 501 at step 609. At step 611, the unified apparatus 500 is aligned with the eye. At step 613, the image sensor 507 receives the image of the retina for measuring refractive power of the eye 501.

Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

CLAIMS:

1. An apparatus for observing an eye comprising:

an objective lens;

an illumination unit configured to illuminate the eye through the objective lens with an illumination beam; a projection unit configured to project a target pattern on the retina of the eye through the objective lens; a fixation unit coupled to the projection unit to project a fixation image on the retina of the eye through the objective lens; an image sensor for receiving an image of the retina of the eye through the objective lens when at least one of the eye is illuminated by the illumination unit and a target pattern is projected on the retina of the eye by the projection unit; and

a movable mirror configured to perform at least one: couple the target pattern and the fixation image into the objective lens when placed at the intersection of the projection unit and the sensor; and allow projection of the illumination beam onto the eye when placed at the intersection of the illumination unit and the sensor.

2. The apparatus as claimed in claim 1 further comprises a computing system connected to the image sensor to process the image of the retina of the eye to create characteristic information about the eye.

3. The apparatus as claimed in claim 1, wherein the illumination unit comprises a first infrared light emitting diode (LED) illuminator to provide an alignment beam with infrared radiation and a white light LED illuminator to provide a beam of white light radiation.

4. The apparatus as claimed in claim 3, wherein the illumination unit comprises a first hot-cold mirror to combine the alignment beam of the infrared radiation with the beam of the white light radiation into the illumination beam.

5. The apparatus as claimed in claim 1, wherein the projection unit is provided with a second infrared LED illuminator for providing a projection beam of infra-red radiation and an annular aperture for shaping the projection beam of infra-red radiation into the target pattern.

6. The apparatus as claimed in claim 1, wherein the fixation unit comprises an electrically focusable lens for adapting the fixation image to optical power of the eye.

7. A method for observing an eye comprising:

illuminating the eye with an illumination beam by a illumination unit when a movable mirror is placed at the intersection of the illumination unit and a image sensor; projecting a target pattern on a retina of the eye when the movable mirror is placed at the intersection of the projection unit and the image sensor; projecting a fixation image on the retina of the eye by a fixation unit, wherein the fixation unit is coupled to the projection unit; coupling the target pattern and the fixation image by the movable mirror into an objective lens; and receiving an image of the retina of the eye by the image sensor when at least one of the eye is illuminated by the illumination unit and the target pattern is projected on the retina of the eye.

8. The method as claimed in claim 7, wherein the sensor processes the image of the retina of the eye to create characteristic information about the eye.

9. An apparatus for observing an eye comprising:

an objective lens;

an illumination unit to illuminate the eye through the objective lens with an illumination beam; a projection unit to project a target pattern on a retina of the eye through the objective lens; a fixation unit coupled to the projection unit to project a fixation image on the retina of the eye through the objective lens; an image sensor for receiving an image of the retina of the eye through the objective lens when at least one of the eye is illuminated by the illumination unit and a target pattern is projected on retina of the eye by the projection unit; and a movable flip-mirror placed at the intersection of the illumination unit and the projection unit is configured to rotate in at least one of clockwise direction and anticlockwise direction, wherein the movable flip-mirror when rotated in the clockwise direction couples the target pattern and the fixation image into the objective lens, wherein the movable flip-mirror when rotated in the anti-clockwise direction allows projection of the illumination beam onto the eye.

10. The apparatus as claimed in claim 9, wherein the movable flip-mirror is rotated in the clockwise and anticlockwise direction by at least one of manually and a motor.

11. The apparatus as claimed in claim 9 is provided with a polarizing beam splitter placed between the objective lens and the sensor to direct the illumination beam onto the eye when the eye is illuminated by the illumination unit and to direct the coupled target pattern and the fixation image received from the movable flip-mirror into the objective lens.

12. The apparatus as claimed in claim 11, wherein the polarizing beam splitter is a wire grid polarizer.

13. A method for observing an eye comprising:

illuminating the eye with an illumination beam by a illumination unit when a movable flip mirror is rotated in anti-clockwise direction; projecting a target pattern on a retina of the eye by a projection unit when the movable flip-mirror is rotated in clockwise direction; projecting a fixation image on the retina of the eye by a fixation unit, wherein the fixation unit is coupled to the projection unit; coupling the target pattern and the fixation image by the movable flip mirror into an objective lens; and receiving an image of the retina of the eye by an image sensor when at least one of the eye is illuminated by the illumination unit and the target pattern is projected on the retina of the eye.

14. The method as claimed in claim 13 further comprises placing the movable flip-mirror at the intersection of the illumination unit and the projection unit.