Documentation on imhol

Task: imhol
Purpose: Compute amplitude and phase images from real and imaginary
Categories: image analysis

        IMHOL computes amplitude and phase images from real and
        imaginary holographic images. The amplitude image can be debiased,
       and the phase image is computed as 0.5 * atan2(imaginary/real).

Key: in
        Two values; the real and imaginary images, respectively. These
        Wild card expansion is supported. 

Key: mag
        Up to two values; the output intensity image and
        optionally, its associated error image (which will be constant).
        Default is no output images.

Key: phase
        Up to two values; the output position angle image and optionally,
        its associated error image (which will not be constant).  These
        will be in degress, radians or microns (see OPTIONS).
        Default is no output images.

Key: sigma
        The mean standard deviation of the noise in the images.
        Required when debiasing or blanking; try to make it as accurate
        a value as possible. The default is 0.

Key: sncut
        This is the S/N ratio below which the output images
        are blanked (see also options=zero below). It is STRONGLY 
        recommended that SNCUT of at least 2 is used.
        The default is 0.

Key: pacut
        The output images are blanked if the error in the phase
        image (degrees, radians or mircrons depending on OPTIONS) is greater
        than this value.  This is active even if you don't output
        the PA image.   Note that there is no equivalent for the output
        error of the POLI image because the error is constant and
        equal to SIGMA.  Keyword SNCUT essentially takes care of this.
        The default is no position angle error based blanking.

Key: options
        Task enrichment options.  Minimum match is active.
          bias    If computing polarized intensity, do NOT remove the Ricean
                  bias in the image.  By default, the bias is removed to first
                  order with P = sqrt(P_obs**2 - sigma**2)   You should have
                  a very good reason for using this option.  See VLA memo
                  no. 161 by Patrick Leahy for more details of bias removal.
          zero    When the output pixel is clipped, by setting CLIP(1),
                  setting OPTIONS=ZERO will cause the output polarized
                  intensity image (not the position angle image) pixel to
                  be set to 0.0 rather than being masked out.   This is
                  very important if you are interested in doing statistics
                  on a region of low polarized intensity S/N ratio.  If 
                  you leave the region masked rather than zeroed, you will 
                  bias the statistics in that region -- zero is a better
                  estimate of the pixel than just excluding it from the
                  statistics (provided the clip level is sufficiently small).
                  Residual bias in the statistical results from the area then
                  depend upon how well the bias remover works and at what 
                  level clipping was performed.  See VLA memo no. 161
                  by Patrick Leahy.
          radians Output the phase image in radians instead of degrees.
          microns Output the phase image as equivalent surface error in
                  microns.
          relax   Only warn about image axis descriptor mismatches
                  instead of giving a fatal error
          bmfit   Fit focus and pointing offsets to aperture E-field maps.