| Popis: |
A model of long-exposure image blur due to atmospheric turbulence has been developed using a parallel processor to convolve the input image with the turbulence point spread function (PSF). The model uses two basic dimensionless parameters--the turbulence strength parameter and the sampling factor--to calculate the turbulence-degraded PSF. The turbulence strength parameter is the ratio of the optics diameter to the atmospheric coherence diameter, and the sampling factor is the product of the image pixel spacing (sampling interval) and the cutoff spatial frequency defined by the diffraction-limited incoherent optical transfer function (OTF). The turbulence OTF is computed using the turbulence strength parameter for a given optical system, slant path, and turbulence condition. Then, by taking advantage of the band-limited nature of the incoherent OTF, the turbulence PSF for the imaging system is expressed as a Hankel transform with finite limits and is evaluated numerically. The convolution requires one frame time (1/30 second) for each point in the PSF kernel, thus a 25-point convolution (5 x 5 kernel) of an entire image (512 x 512 pixels) is completed in less than one second. |
