Healy, John J.

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Healy, John J.
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Healy, John J.

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  • Publication
    Additional sampling criterion for the linear canonical transform
    (Optical Society of America, 2008-11-15)
    Healy, John J. 
    ;
    Hennelly, Bryan M. 
    ;
    Sheridan, John T. 
    The linear canonical transform describes the effect of first-order quadratic phase optical systems on a wave field. Several recent papers have developed sampling rules for the numerical approximation of the transform. However, sampling an analog function according to existing rules will not generally permit the reconstruction of the analog linear canonical transform of that function from its samples. To achieve this, an additional sampling criterion has been developed for sampling both the input and the output wave fields.
      372Scopus© Citations 43
  • Publication
    Fast linear canonical transforms
    (Optical Society of America, 2010-01-01)
    Healy, John J. 
    ;
    Sheridan, John T. 
    The linear canonical transform provides a mathematical model of paraxial propagation though quadratic phase systems. We review the literature on numerical approximation of this transform, including discretization, sampling, and fast algorithms, and identify key results. We then propose a frequency-division fast linear canonical transform algorithm comparable to the Sande–Tukey fast Fourier transform. Results calculated with an implementation of this algorithm are presented and compared with the corresponding analytic functions.
      1051Scopus© Citations 78
  • Publication
    Digital computation of the complex linear canonical transform
    (Optical Society of America, 2011-07-01)
    Liu, Changgeng 
    ;
    Wang, Dayong 
    ;
    Healy, John J. 
    ;
    Hennelly, Bryan M. 
    ;
    Sheridan, John T. 
    ;
    Kim, Myung K. 
    An efficient algorithm for the accurate computation of the linear canonical transform with complex transform parameters and with complex output variable is presented. Sampling issues are discussed and the requirements for different cases given. Simulations are provided to validate the results.
      499Scopus© Citations 11
  • Publication
    Cases where the linear canonical transform of a signal has compact support or is band-limited
    (Optical Society of America, 2008-02-01)
    Healy, John J. 
    ;
    Sheridan, John T. 
    A signal may have compact support, be band-limited (i.e., its Fourier transform has compact support), or neither (“unbounded”). We determine conditions for the linear canonical transform of a signal having these properties. We examine the significance of these conditions for special cases of the linear canonical transform and consider the physical significance of our results
      366Scopus© Citations 52
  • Publication
    Reevaluation of the direct method of calculating Fresnel and other linear canonical transforms
    (Optical Society of America, 2010-04-01)
    Healy, John J. 
    ;
    Sheridan, John T. 
    The linear canonical transform may be used to simulate the effect of paraxial optical systems on wave fields. Using a recent definition of the discrete linear canonical transform, phase space diagram analyses of the sampling requirements of the direct method of calculating the Fresnel and other linear canonical transforms are more favorable than previously thought. Thus the direct method of calculating these Transforms may be used with fewer samples than previously reported simply by making use of an appropriate reconstruction filter on the samples output by the algorithm.
      374Scopus© Citations 39