A unified reconstruction framework for both parallel-beam and variable focal-length fan-beam collimators by a Cormack-type inversion of exponential Radon transform

1999 ◽  
Vol 18 (1) ◽  
pp. 59-65 ◽  
Author(s):  
J. You ◽  
Z. Liang ◽  
G.L. Zeng
Keyword(s):  
Radon Transform ◽  
Focal Length ◽  
Parallel Beam ◽  
Exponential Radon Transform

Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM

1983 ◽  
Vol 41 ◽  
pp. 376-377
Author(s):  
Richard L. McConville
Keyword(s):  
Field Strength ◽  
Electron Probe ◽  
Spherical Aberration ◽  
Focal Length ◽  
Objective Lens ◽  
Parallel Beam ◽  
Tilt Axis ◽  
X Ray ◽  
Small Probe ◽  
Specimen Height

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.

Noise properties of the inverse π-scheme exponential radon transform

2002 ◽  
Author(s):  
Emil Sidky ◽  
Chien-Min Kao ◽  
Patrick J. La Riviere ◽  
Xiaochuan Pan
Keyword(s):  
Radon Transform ◽  
Exponential Radon Transform
Sign in / Sign up

Export Citation Format

Share Document