In these ways illustrated above, the contour of every optical depth 
is photographed with a uniform rate of contraction(or magnification), 
but there are some weak points in each method. Namely, the method of 
cutting the object by a vertical plane light beam directly has a defect 
that the contour can not be photographed in the concave part of the 
object. The II-type and III-tyb6 have the same defect that there are 
cases of some dead surfaces on the object; in the example Shove, the 
end parts of the contours on the cylindrical surface are nissing.(this 
was described in the paper***reported in 1963. ) 
Although it is certain that the 
contours run though the nissing 
area, their parts cannot be seen 
through the small camera lens, 
being hidden by other parts of 
the object. In the comparision 
between the contour photographed 
  
by the II-type and the contour 
by the III-typoe, the former is 
Fig.ll. Ortho-contour photo- 
better than the latter in their Braph by the cutting method 
E pb ey SESS E . 
shape, because it be considerd so that the mechanism of the TI-iype is 
simper than the III-type, but the sharpness of the contour by the III- 
type was better than one of the II-type. This may be considerd because 
the light source system is kept in a constant condition, and to keep in 
a constant condition means that the distances a and b showed in Fig 
9 should not be changed during the centerpivot c are scaning on the 
bench I. The most important factor which affects the accuracy of this 
method is the width of the slit, because the irregular variation of the 
contour seems to have been caused by the imperfect precision of the 
whole equiment which is almost hand nade.