LENS-FIELD CENTER ALIGNMENT FOR HIGH-RESOLUTION ELECTRON-MICROSCOPY

In the objective lens alignment in transmission electron microscopy, t here is usually some discrepancy between the incident beam directions required to satisfy the voltage-center condition or the coma-free cond ition. This is because an incident beam direction is found for the ref erence point conjugate to the screen center, while the reference point is usually not located alone the lens-field axis. In this report it i s demonstrated that the voltage-center alignment keeping the coma-free condition can be carried out by finding an object point on the lens-f ield axis. We propose to call this technique a lens-field center align ment. Since most microscopes have the deflector below the objective le ns needed for this technique, the lens-field center alignment can be u sed in most microscopes.