Improvements of Ortho-contour Photography 
31 
have treated these beams as to obey the optical law of paraxial ray. Some in 
consistencies are naturally expected. The conjugate relation of F and S might 
not be held concerning the lenses Li and L 2 , and if the quality of the two lenses 
is not very good, the illuminating beams might come out of planes. In order to 
avoid the latter defect we are intending to adopt cylindrical lenses for Li and L 2 
in the next attempt. The second installation we have actually constructed is 
shown in Photo. 1. As it is a test construction, it can not be said to be smart, 
Photo 1. 
being superfluous in some parts and insufficient in others. Ortho-contour photo 
graphs taken with this equipment is shown in Photo. 2. The contours are far 
clearer compared with those shown in the previous report. However, we have 
not yet checked the accuracy of them. It seems that some testing are needed by 
comparing the contours with those derived through the ordinary photogrammetry 
or by checking contours of simple shaped objects by calculation. 
Further attempt considerable 
We have an intention of making the method applicable to all non-topographic 
objects, at least, as large as a building, in future. In the present attempt we 
fixed the slits S 0 , Si, and S 2 on a rigid plate S, but there is no need of doing so, 
we can arrange, instead, the three groups Si-Li, S 0 ~L 0 , and S 2 -L 2 separately in 
proper positions and directions, and give Si, S 0 , and S 2 parallel shifts of the same 
speed by synchronous motors. The connection among the groups can be made 
only by lead wire, and this means that there are no great difficulties for us in 
taking a large triangle AS1LS2 when we work on a large object. In the present 
experiment, however, in order to catch the consecutive contours it is necessary to 
give shifts to the object or to the whole installation so as the optical depth of the