Hitachi Microscope & Magnifier S-3400N ユーザーズマニュアル

3.10.2 

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Table 3.10-3    Objective Lens Movable Aperture and Image Quality 

 

Stop No. 

1 

2 

3 

4 

Aperture diameter

（µm） 

150 80 

50  30 

Focal depth 

Shallow 

 

 

Deep 

Probe current 

High 

 

 

Low 

Resolution Low 

 

 

High 

Application 

X-ray analysis on 

low accelerating 

voltage 

Observation and normal X-ray 

analysis 

Observations 

requiring a great 

focal depth 

 
See 3.4.2  Axial Alignment. 
 
 
3.10.4    Influence of WD in Low-vacuum Mode 
 
When observation is conducted in the low-vacuum mode, in which the specimen chamber is 
maintained at a low vacuum level, some of the primary electrons and the backscattered 
electrons that provide signals are subject to scattering by residual gas molecules, and this may 
result in a less than clear image. To ensure a clear image, the following settings may be required. 
 
(1) Accelerating voltage 

The accelerating voltage should be set as high as possible (see Table 3.10-1). 

 
(2) Probe current 

If image roughness is noticeable, the probe current should be increased (see Table 3.10-2). 

 
(3) Working distance 

To increase the sensitivity of the detector, the working distance should be minimized as 
much as possible (see Table 3.10-4). 
 

Table 3.10-4    Impact of WD in Low-vacuum Mode 

 

Working Distance (mm) 

10 

50 

Scattering of irradiation electrons 

Low 

 

High 

Scattering of backscattered electrons

Low 

 

High