IRIS IMAGE DEFINITION ESTIMATION SYSTEM USING THE ASTIGMATISM OF THE CORNEAL REFLECTION OF A NON-COAXIAL LIGHT SOURCE
First Claim
1. A novel iris image definition estimation system using an astigmatism of the corneal reflection of a non-coaxial light source where virtual images of a light source are measured by a sensor and used for focus adjustment, comprising:
- a non-coaxial light source which produces an incident light deviating from an optical axis which is transmitted into a cornea at an oblique angle;
a meridional virtual image and a sagittal virtual image formed behind the cornea due to astigmatism of corneal reflection;
a sensor which captures a composite glint area formed by the meridional and the sagittal virtual images, and subsequently provides information to adjust the a direction of focusing.
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Abstract
An iris image definition estimation system using the astigmatism of the corneal reflection of a non-coaxial light source to assess both the resolution of the iris patterns and the direction of focus adjustment. The corneal reflection results in two virtual images on the meridional and the sagittal planes. These virtual images are formed behind the cornea and close to the iris. Yet, both are projected onto the same location and result in a composite glint area. In addition, the shape of the glint area of a non-coaxial light source varies with different camera focus settings. Furthermore, due to the high intensity of the glint area, the shape can be easily observed, and the size and the shape of the glint area can be used to determine the resolution of the iris image and the direction of focus adjustment, respectively.
113 Citations
8 Claims
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1. A novel iris image definition estimation system using an astigmatism of the corneal reflection of a non-coaxial light source where virtual images of a light source are measured by a sensor and used for focus adjustment, comprising:
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a non-coaxial light source which produces an incident light deviating from an optical axis which is transmitted into a cornea at an oblique angle; a meridional virtual image and a sagittal virtual image formed behind the cornea due to astigmatism of corneal reflection; a sensor which captures a composite glint area formed by the meridional and the sagittal virtual images, and subsequently provides information to adjust the a direction of focusing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification