BP W2 - Back Projection - 2D, filtered, weighted ||

PURPOSE

Calculates 2-dimensional weighted back projection reconstruction for single-tilt geometry using built-in Parzen filter function. Used at Albany for single-tilt electron tomography. See: Comparison of 'BP' operations.   Example.

SEE ALSO

BP 3D	[Back Projection - 3D, using Euler angles ||]
BP S2	[Back Projection - 2D, single tilt, iterative, constrained ||]

USAGE

.OPERATION: BP W2

.TEMPLATE FOR 2-D IMAGE FILES: PRJ***
[Enter a template for names of images in the projection file series.]

.FILE NUMBERS OR SELECTION DOC. FILE NAME: 1-700
[Enter projection file numbers or the name of the document file which contains the projection file numbers in its first register column.]

.ANGLES DOCUMENT FILE: ANGLES
[Enter name of the document file which contains Eulerian angles: psi, theta, and phi in the first three registers columns. Only theta is actually used, psi and phi are ignored.]

.RADIUS & HEIGHT OF RECONSTRUCTED OBJECT: 45,30
[The reconstruction is calculated for a cylinder parallel to the Y (nrow axis) within the slab of specified height. This height is the NZ dimension of resulting 3D volume.]

.RECONSTRUCTION RANGE IN Y: 2,73
[The reconstruction is calculated between specified Y borders. Default is NX=1, NY2=NY. The 3D output volume will have dimensions: (NX, NY2-NY1+1, NZ) where NX is original 2D projection dimension.]

.CUT-OFF FREQUENCY FOR PARZEN FILTER: 0.3
[The Parzen filter is zero for the frequencies higher then the cut-off frequency. Enter: zero for no filtering.]

.3-D OUTPUT FILE: BPW2_VOL
[Name of the output volume.]

NOTES

1. Only the theta angle from the angular document file is used. Two remaining angles (psi and phi) are ignored.

2. If the radius of the reconstructed circle is too large compared to the size of projections, a warning is printed. The reconstruction is calculated, but it is incorrect on the boundary.

3. Implemented by: Paul Penczek.

SUBROUTINES

WGBP2, RDPA, FFTR_Q

CALLER

VTIL2