Hitachi Microscope & Magnifier S-4800 Manual De Usuario
3
-
108
3.10.2 Condenser Lens Setting and Image Quality
Probe current is adjusted by changing the Cond Lens 1 value.
To increase probe current, select a lower Cond Lens 1 value (larger spot size).
Information necessary for setting of Cond Lens 1 is as follows.
(1) Resolution:
Probe current is adjusted by changing the Cond Lens 1 value.
To increase probe current, select a lower Cond Lens 1 value (larger spot size).
Information necessary for setting of Cond Lens 1 is as follows.
(1) Resolution:
The electron beam size is smaller with a higher excitation value of Cond Lens 1. However,
image resolution also depends on the S/N ratio of the image and on the ease of focusing and
astigmatism correction.
image resolution also depends on the S/N ratio of the image and on the ease of focusing and
astigmatism correction.
(2) S/N ratio:
The signal to noise ratio is better with lower excitation values of Cond Lens 1.
(3) Charging:
Charging of insulator specimens is greater at smaller excitation values of Cond Lens 1.
(4) Signal source:
Generally the backscattered electron imaging needs higher probe current than the secondary
electron imaging. X-ray analysis needs much higher probe current.
electron imaging. X-ray analysis needs much higher probe current.
3.10.3 Objective Lens Aperture Size and Image Quality
The objective lens aperture has four openings: 100, 50, 50 and 30 micrometers (numbered 1, 2,
3 and 4).
For normal operation, use number 2 or 3 (50 micrometers). The electron optical column of S-
4800 is designed to achieve highest resolution with 50 micrometers aperture.
When a larger probe current is required, for example X-ray analysis, use number 1 (100
micrometers). Resolution may degrade with this large aperture.
Use number 4 (30 micrometers) to reduce probe current, for example to reduce charging.
Resolution is not improved but the depth of focus is better with the smallest aperture
.