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  1. Article ; Online: Improved digital image correlation for in-plane displacement measurement.

    Mudassar, Asloob Ahmad / Butt, Saira

    Applied optics

    2014  Volume 53, Issue 5, Page(s) 960–970

    Abstract: Electronic speckle photography (ESP) for in-plane displacement (IPD) and deformation measurements is well known with its more modern form, digital image correlation (DIC). Two speckle images of an optically rough surface before and after deformation, ... ...

    Abstract Electronic speckle photography (ESP) for in-plane displacement (IPD) and deformation measurements is well known with its more modern form, digital image correlation (DIC). Two speckle images of an optically rough surface before and after deformation, called reference and test images, are recorded and processed for IPD or deformation measurement of the test image with respect to the reference image. The reliability of ESP in measurements depends strongly on the postprocessing of the two images by DIC, which we have referred to as conventional DIC. In this paper, we are proposing a small but useful modification in the existing DIC methods by introducing some additional steps, which drastically improves the results obtained with the existing techniques. The modification to the conventional DIC method has been referred to as modified DIC. Computer-simulated and experimental results have been presented to validate the superiority of modified DIC over conventional DIC methods.
    Language English
    Publishing date 2014-02-10
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4522
    ISSN (online) 1539-4522
    DOI 10.1364/AO.53.000960
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Application of Principal Component Analysis in Automatic Localization of Optic Disc and Fovea in Retinal Images.

    Mudassar, Asloob Ahmad / Butt, Saira

    Journal of medical engineering

    2013  Volume 2013, Page(s) 989712

    Abstract: A retinal image has blood vessels, optic disc, fovea, and so forth as the main components of an image. Segmentation of these components has been investigated extensively. Principal component analysis (PCA) is one of the techniques that have been applied ... ...

    Abstract A retinal image has blood vessels, optic disc, fovea, and so forth as the main components of an image. Segmentation of these components has been investigated extensively. Principal component analysis (PCA) is one of the techniques that have been applied to segment the optic disc, but only a limited work has been reported. To our knowledge, fovea segmentation problem has not been reported in the literature using PCA. In this paper, we are presenting the segmentation of optic disc and fovea using PCA. The PCA was trained on optic discs and foveae using ten retinal images and then applied on seventy retinal images with a success rate of 97% in case of optic discs and 94.3% in case of fovea. Conventional algorithms feed one patch at a time from a test retinal image, and the next patch separated by one pixel part is fed. This process is continued till the full image area is covered. This is time consuming. We are suggesting techniques to cut down the processing time with the help of binary vessel tree of a given test image. Results are presented to validate our idea.
    Language English
    Publishing date 2013-05-23
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2741632-X
    ISSN 2314-5137 ; 2314-5137 ; 2314-5129
    ISSN (online) 2314-5137
    ISSN 2314-5137 ; 2314-5129
    DOI 10.1155/2013/989712
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Snakes with Coordinate Regeneration Technique: An Application to Retinal Disc Boundary Detection.

    Mudassar, Asloob Ahmad / Butt, Saira

    Journal of medical engineering

    2013  Volume 2013, Page(s) 852613

    Abstract: A modified snake method based on the novel idea of coordinate regeneration is presented and is tested on an object with complex concavities and on retinal images for locating the boundaries of optic discs, where the conventional snake methods fail. We ... ...

    Abstract A modified snake method based on the novel idea of coordinate regeneration is presented and is tested on an object with complex concavities and on retinal images for locating the boundaries of optic discs, where the conventional snake methods fail. We have demonstrated that the use of conventional snake method with our proposed coordinate regeneration technique gives ultimate solution for finding the boundaries of complex objects. The proposed method requires a Gaussian blur of the object with a large kernel so that the snake can be initialised away from the object boundaries. In the second and third steps the blurring kernel size is reduced so that exact boundaries can be located. Coordinate regeneration is applied at each step which ultimately converges the snake (active contour) to exact boundaries. For complex objects like optic discs in retinal images, vessels act as snake distracters and some preimage processing is required before the proposed technique is applied. We are demonstrating this technique to find the boundary of optic discs in retinal images. In principle, this technique can be extended to find the boundary of any object in other modalities of medical imaging. Simulation results are presented to support the idea.
    Language English
    Publishing date 2013-10-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2741632-X
    ISSN 2314-5137 ; 2314-5137 ; 2314-5129
    ISSN (online) 2314-5137
    ISSN 2314-5137 ; 2314-5129
    DOI 10.1155/2013/852613
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Displacement sensor for indoor machine calibrations.

    Mudassar, Asloob Ahmad / Butt, Saira

    Applied optics

    2013  Volume 52, Issue 15, Page(s) 3461–3472

    Abstract: This paper presents a simple displacement sensor for indoor machine calibrations. The sensor, which is placed in the path of a diverging laser beam, consists of two plane mirror pieces laterally displaced with the line joining their centers initially ... ...

    Abstract This paper presents a simple displacement sensor for indoor machine calibrations. The sensor, which is placed in the path of a diverging laser beam, consists of two plane mirror pieces laterally displaced with the line joining their centers initially held perpendicular to the optical axis of the beam during the displacement of the sensor with one of the mirrors always traveling along the optical axis of the laser beam. The optical signals from the two mirrors are combined and a simple detector at the interference plane counts the fringes during the sensor displacement. The sensor could be mounted on the moving head of any mechanical machine, e.g., the lathe machine for displacement calibration. The device has been tested over a range of 10 cm beyond a distance of 150 cm from a diverging laser source giving an accuracy of 1.1015 μm. Theoretical modeling, simulation, and experimental results are presented which establish that the proposed sensor can be used as a promising displacement measuring device.
    Language English
    Publishing date 2013-05-20
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4522
    ISSN (online) 1539-4522
    DOI 10.1364/AO.52.003461
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article: Extraction of Blood Vessels in Retinal Images Using Four Different Techniques.

    Mudassar, Asloob Ahmad / Butt, Saira

    Journal of medical engineering

    2013  Volume 2013, Page(s) 408120

    Abstract: A variety of blood vessel extraction (BVE) techniques exist in the literature, but they do not always lead to acceptable solutions especially in the presence of anomalies where the reported work is limited. Four techniques are presented for BVE: (1) BVE ... ...

    Abstract A variety of blood vessel extraction (BVE) techniques exist in the literature, but they do not always lead to acceptable solutions especially in the presence of anomalies where the reported work is limited. Four techniques are presented for BVE: (1) BVE using Image Line Cross-Sections (ILCS), (2) BVE using Edge Enhancement and Edge Detection (EEED), (3) BVE using Modified Matched Filtering (MMF), and (4) BVE using Continuation Algorithm (CA). These four techniques have been designed especially for abnormal retinal images containing low vessel contrasts, drusen, exudates, and other artifacts. The four techniques were applied to 30 abnormal retinal images, and the success rate was found to be (95 to 99%) for CA, (88-91%) for EEED, (80-85%) for MMF, and (74-78%) for ILCS. Application of these four techniques to 105 normal retinal images gave improved results: (99-100%) for CA, (96-98%) for EEED, (94-95%) for MMF, and (88-93%) for ILCS. Investigations revealed that the four techniques in the order of increasing performance could be arranged as ILCS, MMF, EEED, and CA. Here we demonstrate these four techniques for abnormal retinal images only. ILCS, EEED, and CA are novel additions whereas MMF is an improved and modified version of an existing matched filtering technique. CA is a promising technique.
    Language English
    Publishing date 2013-12-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2741632-X
    ISSN 2314-5137 ; 2314-5137 ; 2314-5129
    ISSN (online) 2314-5137
    ISSN 2314-5137 ; 2314-5129
    DOI 10.1155/2013/408120
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Improved collimation testing technique.

    Mudassar, Asloob Ahmad / Butt, Saira

    Applied optics

    2012  Volume 51, Issue 26, Page(s) 6429–6440

    Abstract: Laser collimation is an essential part of many experimental setups including optical coherent processors, image transformers, Fourier transform generators, and 4f-based optical systems. A device is required to test the collimation of lasers in such ... ...

    Abstract Laser collimation is an essential part of many experimental setups including optical coherent processors, image transformers, Fourier transform generators, and 4f-based optical systems. A device is required to test the collimation of lasers in such experiments. We are proposing a modification in the existing two-lens-system (TLS)-based collimation testing technique in which a combination of a convex and a concave lens is placed in space between the collimating lens and the first grating of the conventional setup. In the proposed method, we change the position of the second TLS component, placing it between the two gratings. The proposed idea not only reduces the size of the system but also gives improved results. Theoretical modeling and simulated and experimental results are presented to support our idea.
    Language English
    Publishing date 2012-08-21
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4522
    ISSN (online) 1539-4522
    DOI 10.1364/ao.51.006429
    Database MEDical Literature Analysis and Retrieval System OnLINE

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