| Three dimensional imaging at multiple length scales is of great importance in biological research [4]. Conventional electron tomography addresses the length scale of 50nm3 to 50mum3, which lies between X-ray crystallography and light microscopy. A desirable technological advance is the scaling up of electron tomography to address large volumes on the order of 0.5mm3 at high resolution, and a major challenge in achieving such large scale reconstructions is reducing the time of acquisition. Electron tomography is typically a slow and tedious process. Recent advances in automated data acquisition using predictions of stage movement have lead to significant improvement [14] in acquisition speed. However, for very large scale high resolution imaging projects such as serial section tomography applied to brain circuit reconstruction [2], faster tomographic acquisition systems will be necessary.;In this work, a new conical electron beam control system was designed and tested on the following 3D imaging applications: high speed tomographic data acquisition without need for specimen tilt, enhancement of single axis tilt tomography with additional beam tilting, and object precession. Since tilting the beam requires only modification of current to deflection coils, the speed of beam tilt far exceeds mechanical tilting. Beam deflection also gives higher precision of changes in angle than mechanical tilt. Results are presented for each imaging application. |
