22. A method for detecting particles comprising: imaging a plurality of particles using a first point spread function that changes as a function of the axial location of a particle, wherein the imaging returns an image; estimating a first plurality of point spread function dictionary coefficients of the image using a Matching Pursuit algorithm with a point spread function dictionary that includes a plurality of point spread function responses corresponding to a different particle position; determining a first region within which the particles are located in the image from the first plurality of point spread function dictionary coefficients; estimating a second plurality of point spread function dictionary coefficients of the image using a Convex Optimization algorithm with a second point spread function dictionary that includes a plurality of point spread function responses corresponding to different particle position; and determining a location of the particles in the image from the second plurality of coefficients.
22. A method for detecting particles comprising: imaging a plurality of particles using a first point spread function that changes as a function of the axial location of a particle, wherein the imaging returns an image; estimating a first plurality of point spread function dictionary coefficients of the image using a Matching Pursuit algorithm with a point spread function dictionary that includes a plurality of point spread function responses corresponding to a different particle position; determining a first region within which the particles are located in the image from the first plurality of point spread function dictionary coefficients; estimating a second plurality of point spread function dictionary coefficients of the image using a Convex Optimization algorithm with a second point spread function dictionary that includes a plurality of point spread function responses corresponding to different particle position; and determining a location of the particles in the image from the second plurality of coefficients. 24. The method according to claim 22 , wherein the spatial resolution of the point spread function responses in the second point spread function dictionary is greater than the spatial resolution of the point spread function responses in the first point spread function dictionary.