Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
1998-11-24
2001-10-30
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06309069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for and methods of personal identification. It has particular utility in relation to apparatuses which are required to capture an image of anterior features of an eye and display an image to the eye simultaneously. Such an apparatus might be used in an authentication device which captures an image of an iris of a user.
2. Related Art
Apparatuses for capturing an image of a persons' eye at the same time as providing a display for viewing by the person's eye are known. For example, IriScan Inc. market a System 2000EAC™ authentication apparatus. Another example is the pupillometer apparatus disclosed in international patent application WO 92/05736.
The former apparatus comprises an iris pattern capture unit and an identification code generation unit. The iris pattern capture unit has a housing having two apertures. An infra-red illumination source is arranged to project visible and infra-red light through the first aperture to illuminate a person's eye. A camera, installed within the apparatus is arranged such that its field of view is through the second aperture. In using the apparatus the person looks through the second aperture at a display which reproduces the image seen by the camera. At the same time, light from the illumination source is reflected from the person's eye through the second aperture towards the camera. The display enables the person to position his eye such that it is in focus and located in the centre of the field of view of the camera.
In practice it is found that the user must position his or her eye within a narrow range of distances from the device in order for a successful capture of an image of the user's eye to be achieved.
A fovea-centred eye fundus scanner is disclosed in European Patent Application 0 126 549. Because the apparatus uses scanning optics to examine the fundus (retina and choroid) of an eye, it is complex and bulky.
SUMMARY OF THE INVENTION
These are two of the problems addressed by the present invention, which provides an apparatus for providing an information signal characteristic of an eye, said apparatus comprising:
a housing having an entrance window;
an illumination source mounted on the housing, and operable to illuminate the eye over an area outside the pupil; and
an image capture device mounted within the housing, in optical communication with said entrance window, and operable to provide an image signal representing one or more features of the anterior of the eye responsive to the incidence of light from the illumination source reflected from the eye;
an optical device;
wherein, in use, visible light travels along a first optical path via the optical device to the eye to provide a visible image to be viewed by the eye and light from the illumination source and reflected from the eye travels along a second optical path via the optical device to said image capture apparatus;
wherein said optical device is arranged to interact with at least one of said illumination light and said visible light such that substantially all illumination light of a predetermined type travels further along said second optical path towards said image capture apparatus, and a significant proportion of said visible light travels further along said first optical path towards the eye.
The terms ‘optical’ and ‘light’ as used herein relate to electromagnetic radiation in the infra-red, visible and ultra-violet portions of the electromagnetic spectrum, i.e. having wavelengths in the range 10 nm to 1 mm.
Because most of the illumination light of the predetermined type arrives at the image capture apparatus, the present invention achieves a number of advantages.
Firstly, since more light is received at the image capture apparatus, the aperture of the optical arrangement associated with it can be reduced. This has the result that the depth of focus of the image capture apparatus is increased. Thus, the constraints placed on where the eye must be positioned in relation to the apparatus in order to provide a satisfactorily focused image are relaxed.
Secondly, the time of exposure may be reduced, thereby reducing the need for the person to remain still whilst the image is captured.
Thirdly, the present invention also allows a satisfactory image to be captured in situations where less light to which the image capturing apparatus is responsive is available. This is beneficial since safety considerations limit the light that can directed towards the eye. It is also useful in reducing the power requirement of the apparatus, this being a particular advantageous in relation to portable equipment powered by batteries.
Those skilled in the art will realise that the above advantages could be realised individually or in combination. Generally, providing more light to an image capture apparatus improves the quality of the resultant image.
Any increase in the proportion of said user light of a predetermined type which is incident upon the image capture apparatus (in comparison to known apparatuses) leads to some improvement in performance. However, it is preferred that more than 75% of the user light of a predetermined type travels further along the optical path towards the image capture apparatus.
In addition to the above, allowing the visible light to pass substantially unattenuated towards the user increases the apparent brightness of the display. This means that the amount of power consumed by the apparatus is reduced; a particularly useful feature in portable apparatuses. It is preferred that more than 75% of the visible light travels further along the optical path towards the user.
The anterior feature of the eye might be the iris, cornea, sclera, or eyelids or a comnbination of two or more of these.
The apparatus may be adapted to be brought by the user to his own eye or to the eye of another person or animal. Alternatively, the apparatus may be fixed in place, requiring the person whose eye is being investigated to align his head accordingly.
In some cases, the visible image seen by the eye might simply be a view through the apparatus. In others, a display means provides the visible image or overlays a partial display on that already present to provide the visible image. This has the advantage that information can be provided to the eye at the time of use of the apparatus. Looked at another way, the user image capture unit can be operated whilst the eye is viewing information on the display.
One example of the use of a display involves the provision of an display which shows the image being received by the image capture apparatus. This is advantageous since it allows the person to move his head in order to improve the quality of the image captured.
In preferred embodiments the visible light directed towards the eye and the light directed towards the image capture apparatus have different spectra. This does not mean that the light directed towards the image capture apparatus necessarily lies outside the visible region of the electromagnetic spectrum. For example, the display might be created using red, blue and green LEDs which emit light in narrow spectral bands, the image capture apparatus receiving visible light which falls outside those bands but within the visible portion of the electromagnetic spectrum.
In advantageous versions of those embodiments the optical device comprises a wavelength selective reflector effective to reflect either said visible light or said light of a different spectrum, and to allow the passage of the other. Such reflectors are economical and their use allows the components of the apparatus to be conveniently located. The selectivity can, for example, be achieved using metallic coatings or coatings of dielectric material(s).
Since the illumination light is incident upon the eye, the apparatus is more comfortable in use if the predetermined type of light substantially consists of non-visible light.
Preferably, the predetermined type of light substantially consists of near infra-red light (i.e. having a wavelength betwee
Gifford Maurice M
McCartney David J
Seal Christopher H
British Telecommunications public limited company
Manuel George
Nixon & Vanderhye P.C.
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