scispace - formally typeset
Search or ask a question
Topic

Shift-and-add

About: Shift-and-add is a research topic. Over the lifetime, 142 publications have been published within this topic receiving 1942 citations.


Papers
More filters
Journal ArticleDOI
01 Oct 2007
TL;DR: This paper describes two nonideal iris recognition systems and analyzes their performance, using a special dataset of the off-angle iris images to quantify the performance of the designed systems.
Abstract: The popularity of the iris biometric has grown considerably over the past two to three years. Most research has been focused on the development of new iris processing and recognition algorithms for frontal view iris images. However, a few challenging directions in iris research have been identified, including processing of a nonideal iris and iris at a distance. In this paper, we describe two nonideal iris recognition systems and analyze their performance. The word ldquononidealrdquo is used in the sense of compensating for off-angle occluded iris images. The system is designed to process nonideal iris images in two steps: 1) compensation for off-angle gaze direction and 2) processing and encoding of the rotated iris image. Two approaches are presented to account for angular variations in the iris images. In the first approach, we use Daugman's integrodifferential operator as an objective function to estimate the gaze direction. After the angle is estimated, the off-angle iris image undergoes geometric transformations involving the estimated angle and is further processed as if it were a frontal view image. The encoding technique developed for a frontal image is based on the application of the global independent component analysis. The second approach uses an angular deformation calibration model. The angular deformations are modeled, and calibration parameters are calculated. The proposed method consists of a closed-form solution, followed by an iterative optimization procedure. The images are projected on the plane closest to the base calibrated plane. Biorthogonal wavelets are used for encoding to perform iris recognition. We use a special dataset of the off-angle iris images to quantify the performance of the designed systems. A series of receiver operating characteristics demonstrate various effects on the performance of the nonideal-iris-based recognition system.

144 citations

Journal ArticleDOI
TL;DR: In this article, the brightest point in each image is shifted to the centre of image space and all images are superimposed, which is suitable for imaging faint astronomical objects with large optical telescopes.

143 citations

Patent
13 Mar 2013
TL;DR: In this article, a method of biometric recognition is provided, where multiple images of the face or other non-iris image and iris of an individual are acquired and the multiple images are determined to form an expected sequence of images.
Abstract: A method of biometric recognition is provided. Multiple images of the face or other non-iris image and iris of an individual are acquired. If the multiple images are determined to form an expected sequence of images, the face and iris images are associated together. A single camera preferably acquires both the iris and face images by changing at least one of the zoom, position, or dynamic range of the camera. The dynamic range can be adjusted by at least one of adjusting the gain settings of the camera, adjusting the exposure time, and/or adjusting the illuminator brightness. The expected sequence determination can be made by determining if the accumulated motion vectors of the multiple images is consistent with an expected set of motion vectors and/or ensuring that the iris remains in the field of view of all of the multiple images.

89 citations

Journal ArticleDOI
TL;DR: Novel algorithms are described which are demonstrated to convert 291 raw images per second to laser speckle contrast images and as many as 410 laser specker contrast images persecond to relative correlation time images and enable real-time imaging of blood flow dynamics.
Abstract: Though laser speckle contrast imaging enables the measurement of scattering particle dynamics with high temporal resolution, the subsequent processing has previously been much slower. In prior studies, generating a laser speckle contrast image required about 1 s to process a raw image potentially collected in 10 ms or less. In this paper, novel algorithms are described which are demonstrated to convert 291 raw images per second to laser speckle contrast images and as many as 410 laser speckle contrast images per second to relative correlation time images. As long as image processing occurs during image acquisition, these algorithms render processing time irrelevant in most circumstances and enable real-time imaging of blood flow dynamics.

76 citations

Journal ArticleDOI
TL;DR: In this article, the image quality obtainable with shift-and-add (SAA) imaging for the recovery of diffraction-limited information is quantitatively investigated using data simulating an 8m aperture at a site with near-IR seeing conditions as found on Mauna Kea.
Abstract: The image quality obtainable with shift-and-add (SAA) imaging for the recovery of diffraction-limited information is quantitatively investigated using data simulating an 8-m aperture at a site with near-IR seeing conditions as found on Mauna Kea. This is compared to the image quality obtainable from image centroiding and wavefront tip-tilt correction. For good seeing conditions, image centroiding and SAA, which tracks the image peak, show similar performance containing about 30 percent of the image power in a diffraction-limited component. However, as the seeing degrades, SAA consistently yields improved resolution maintaining significantly greater diffraction-limited information. This enhances the detection threshold by about 2 magnitudes over the seeing-limited case for the seeing range studied. By comparison, the gain due to image centroiding decreases to less than 1 magnitude at the same poor seeing limit.

65 citations

Network Information
Related Topics (5)
Image processing
229.9K papers, 3.5M citations
77% related
Pixel
136.5K papers, 1.5M citations
76% related
Wavelet
78K papers, 1.3M citations
75% related
Image segmentation
79.6K papers, 1.8M citations
71% related
Feature extraction
111.8K papers, 2.1M citations
71% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20211
20182
20172
20163
20159
20149