Image acquisition system
An image acquisition system for acquiring iris images for use in biometric recognition of a subject includes an optical system comprising a cluster of at least 2 lenses arranged in front of a common image sensor with each lens optical axis in parallel spaced apart relationship. Each lens has a fixed focus and a different aperture to provide a respective angular field of view. The lens with the closest focus has the smallest aperture and the lens with the farthest focus has the largest aperture so that iris images can be acquired across a focal range of at least from 200 mm to 300 mm.
1. An image acquisition system for acquiring iris images for use in biometric recognition of a subject, the system including an optical system comprising:
at least first and second lens systems each arranged in front of a common image sensor with each lens system including an optical axis in parallel spaced apart relationship to the optical axis of the other lens system, each lens system having a fixed focus, and a different aperture than the other lens system to provide a different angular field of view, each of the first and second lens systems comprising multiple optical elements, the first lens system having a closer focus and a smaller aperture than the second lens system, such that the image acquisition system can simultaneously acquire iris images across a focal range of at least from 200 mm to 300 mm.
2. An image acquisition system according to claim 1 comprising two, three or four fixed focus lens system.
3. An image acquisition system according to claim 1 wherein each lens system has a fixed focal length extending between approximately 4.0 mm and 5.0 mm.
4. An image acquisition system according to claim 1 wherein each lens system comprises an optical assembly have a total track length less than approximately 4.22 mm.
5. An image acquisition system according to claim 1 wherein each lens system comprises at least two lenses that simultaneously provide images over a focus range extending from 180 mm to 350 mm.
6. An image acquisition system according to claim 1 comprising at least three lens systems that simultaneously provide images over a focus range extending from 150 mm to 480 mm.
7. An image acquisition system according to claim 1 comprising at least three lens systems that simultaneously provide images over a focus range extending from 133 mm to 530 mm.
8. An image acquisition system according to claim 1 wherein each lens system comprises multiple lenses providing a focal length f approximately equal to 4.26 mm.
9. An image acquisition system according to claim 1 comprising two lens systems with aperture diameters of approximately 1.3 mm and 1.7 mm respectively.
10. An image acquisition system according to claim 1 where each lens system comprises: a front optical element and a rear optical element disposed between said front optical element and said sensor.
11. The image acquisition system of claim 10 wherein said rear optical element is spaced 0.8 mm from said sensor and wherein said front optical element is spaced 2.2 mm from the rear optical element.
12. The image acquisition system according to claim 10 wherein the optical characteristics of the optical elements of the first lens system differ from the optical characteristics of the optical elements of the second lens system only in the thickness of the respective rear optical elements.
13. An image acquisition system according to claim 10 wherein each of said front and rear optical elements is spaced apart by air.
14. An image acquisition system according to claim 10 wherein said front optical elements of the lens system are formed on a common substrate.
15. An image acquisition system according to claim 14 wherein said front optical elements comprises a molded glass.
16. An image acquisition system according to claim 10 wherein said rear optical elements for each lens system is formed on a common substrate.
17. An image acquisition system according to claim 16 wherein said rear optical elements comprise a molded glass different than material forming the front optical elements.
18. An image acquisition system according to claim 10 wherein surfaces of said front and rear optical elements facing said sensor have aspheric characteristics.
19. An image acquisition system according to claim 1 further comprising an infra-red flash.
20. An image acquisition system according to claim 1 wherein said sensor comprises an RGB sensor.
21. An image acquisition system according to claim 1 wherein said sensor comprises an RGB-IR sensor.
22. An image acquisition system according to claim 1 wherein the systems are arranged in either a regular or an irregular arrangement.
23. A smartphone including the image acquisition system according to claim 1 .