Apparatus and method for contactless high resolution handprint capture

摘要

A system and method for contactless handprint capture is disclosed that includes an image capture device to capture handprint images of a subject hand at each of a plurality of different focal distances, with the image capture device including an imaging camera and an electro-optics arrangement having a plurality of light modulating elements and polarization sensitive optical elements having differing optical path lengths based on polarization states. A control system is coupled to the image capture device to cause the device to capture the handprint images at each of the different focal distances, with each handprint image having a depth-of-focus that overlaps with a depth-of-focus of handprint images at adjacent focal distances such that redundant handprint image data is captured. The control system registers each handprint image with positional data and creates a composite handprint image from the handprint images captured at the different focal distances.

主权项

1. A contactless biometric data collection device comprising:
an image capture device configured to capture images of a subject hand in any of a range of positions and at each of a plurality of different focal distances, each of the images comprising at least one of a palm print and a plurality of fingerprints, wherein the image capture device comprises:
an imaging camera configured to capture the images at a first image resolution level; andan electro-optics arrangement positioned between the hand and the imaging camera, the electro-optics arrangement including a plurality of light modulating elements and polarization sensitive optical elements having an optical path length that changes with different polarization states, so as to provide for capture of the images at each of the plurality of different focal distances; and a control system coupled to the image capture device, the control system being configured to:
cause the image capture device to capture the images at each of the plurality of different focal distances, each image having a depth-of-focus that overlaps with a depth-of-focus of images at adjacent focal distances such that redundant image data is captured;register each image with positional data so as to create pixel correspondence between the images and between portions of the hand;create a composite image from the registered images captured at each of the plurality of different focal distances;generate a depth map of the hand from the plurality of images captured at each of the different focal distances using one of a depth from focus algorithm and a depth from defocus algorithm;determine a 3D shape of the hand using one of the depth from focus algorithm and the depth from defocus algorithm; anddetermine a distortion map based on the 3D shape signifying local variations in convexity and concavity of the hand; andunwrap the composite image using the distortion map to generate a single, high resolution image; wherein the redundant image data includes depth data and lateral image shifts introduced by the polarization sensitive optical elements, the lateral images shifts comprising sub-pixel shifts between respective images captured at the plurality of different focal distances; and wherein the images captured by the image capture device at each of the plurality of different focal distances and with the lateral image shifts introduced therein are captured in a 3D spiral pattern.