**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**

- Only the theta angle from the angular document file is used.
Two remaining angles (psi and phi) are ignored.
- 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.
- Implemented by: Paul Penczek.

**SUBROUTINES**- WGBP2, RDPA, FFTR_Q

**CALLER**- VTIL2

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