One can conclude from this simple test that with careful plotting, the 
static mode of operation would result in an accuracy 11.5 times higher than 
the dynamic mode, This very large amount of discrepancy may be attributed to 
the plotter part of the instrument in which the mechanical back-lash, etc. 
are the principal error-contributing factors in the dynamic mode. 
Accuracy of micrography 
  
Current studies were emphasized on two things: 
(a) Errors in scale-affinity vis-a-vis magnification, and 
(b) Rotation errors. 
It has been observed (see for example, Ghosh and Nagaraja, 1976) that 
scale distortion is by far the most significant of all possible distortions 
contained in a micrograph. All other distortions combinedly contribute 
to about one fourth of this error. A study of this aspect was then worth- 
while. 
The other aspect, i.e., of image rotation as a function of magnifica- 
tion, being peculiar to EM systems was of particular interest. The results 
of the studies on these two aspects are presented in Tables 3 and 4. The 
data for Table 4 are extracted from Table 3. 
TABLE 3 
Studies on magnification and rotation of micrographs 
  
Instrument for micrography: JEOL - JSM - 25 S II 
Instrument for measurement observations:  Stereotope (Modified) 
Diffraction grating replica grid used, 2160 lines per mm. 
Same 5 x 5 unit square used. Each observation repeated 10 times 
Tilt: 0? for all micrographs. Rotation: 0° for all micrographs 
  
  
  
Magnification Image Rotation 
Nominal Actual (from test) Std. Errors Angle Scd. Errors 
in x : Mx In x (in degrees) 
In y : My In y 
1200 T2650 EI 69.9 0.5 
1800 I9 £109 70.4 +0.4 
+ 
2700 2815.3 E19 71.0 +0.3 
+2 
4200 ig sans 70.8 +0.2 
+ 
6000 S150: dec 70.5 £0.2 
9000 9279: Ios 70.0 $0.1 
* 
12000 n FAT c 69.8 £0. 1 
  
222