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 ALSO

BP 3D	[Back Projection - 3D, using Euler angles ||]
BP CG	[Back Projection - 3D, Conjugate gradients ||*]
BP R2	[Back Projection - 2D, weighting of image series ||]
BP RP	[Back Projection - 3D, iterative, with constraints, ||*]
BP S2	[Back Projection - 2D, single tilt iterative, constrained ||]

USAGE

.OPERATION: BP W2

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

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

.ANGLES DOCUMENT FILE: ANGLES
[Enter the name of the document file containing Eulerian angles for the projections used (in order: psi, theta, phi). Only theta is actually used, psi and phi are ignored.]

.RADIUS & HEIGHT (NSLICE) 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 NSLICE dimension of resulting 3D volume.]

.RECONSTRUCTION FROM NROW1.....NROW2: 2,73
[The reconstruction is calculated between specified NROW borders. Default is NROW1=1, NROW2=NROW. The 3D output volume will have dimensions: (NSAM, NROW2-NROW1+1, HEIGHT) where NSAM is original 2D projection dimension.]

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

.3-D OUTPUT FILE: UUU101
[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. The projections do not need to have power-of-2 dimensions.

3. 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.

4. Implemented by: Paul Penczek.

SUBROUTINES

WGBP2, RDPA, FFTR_Q

CALLER

VTIL2