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BP W2 - Back Projection - 2D, filtered weighted

(09/17/94)

PURPOSE

Calculates 2-dimensional weighted back projection reconstruction for single-tilt geometry using built-in Parzen filter function. The dimensions of projections do not have to be powers of two.

SEE ALSO

BP 3 [Back Projection - 3D, iterative]
BP 3D [Back Projection - 3D, using Euler angles, ||]
BP 3E [Back Projection - 3D, using Euler angles]
BP CTF [Back Projection - 3D, CTF correction, ||]
BP GW [Back Projection - weighted, arbitrary geometry]
BP GW3 [Back Projection - weighted, arbitrary geometry, 3 angles]
BP MEM2 [Back Projection - 2D maximum entropy method]
BP R2 [Back Projection - 2D, R**2 weighting of the image series]
BP RP [Back Projection - 3D, iterative, with constraints, ||]
BP S2 [Back Projection - 2D, single tilt iterative, with constraints]
BP WX [Back Projection - weighted, X]
BP WY [Back Projection - weighted, Y]
BP XY [Back Projection - simple for single axis & conical tilting]

USAGE

.OPERATION: BP W2

.ENTER TEMPLATE FOR 2-D IMAGE NAME: PRJ***
[Enter the prefix of the projection file series.]

.SELECTION DOC FILE: SELECT
[Enter the name of the document file containing projection file numbers in the first column.]

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

.RADIUS OF RECONSTRUCTED OBJECT, HEIGHT OF THE SLICE: 45,30
[The reconstruction is calculated for the circle only and within the slab of specified height. This height is NSLICE dimension of resulting 3D volume.]

.RECONSTRUCTION FROM NROW1 TO NROW2: 2,73
[The reconstruction is calculated between specified nrow borders. Default is nrow1=1, nrow2=nrow. 3D volume will have dimensions: NSAM, NROW2-NROW1+1, height of the slice where NSAM is original 2D projection dimension.]

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

.3-D OUTPUT FILE: UUU101
[Name of the output file.]

NOTES

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

  2. The projections do not have to have power-of-2 dimensions.

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

  4. Implemented by: Paul Penczek.

SUBROUTINES

WGBP2, RDPA, REPRWB, PREPSL_2, BPRJ2, BCKC2, BCKC0

CALLER

VTIL2

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