ETCH TECHNIQUE 



21 



pyramidal etch-pits, oriented relative to the X axes as shown in Fig. 5.5. 

 The actual results obtained with Z sections are more complicated than this 

 and thus indicate that the etch-pits are not exactly as idealized here. 



A 



B 



SCREEN 



LENS 



SOURCE 



Fig. 5.8 — Light transmitted thru a single set of etch-pit facets, A, is refracted as by a 

 prism, B. The three sets of facets of a Z-cut section give a three-fold etch-figure, as in C. 



^EYE 



^EYE 



SOURCE 



TOP VIEW OF 

 SECTION 



SOURCE 



A B • C 



Fig. 5.9— Light transmitted thru a pin-hole is refracted by a single set of facets, A, as 

 it would be by a prism, B. A virtual image of the pin-hole P will be observed at P'. The 

 etch-figure seen down in a Z-cut section is three-fold, as in C. 



5.41 The Reflection Method 



Figure 5.7 shows the reflection method, where a parallel beam of light 

 striking the etched surface of a Z-section is reflected from one of the three 

 sets of facets as shown in A. Each single facet reflects part of the beam by 



