1530 
served through the camera, and the height of 
a frame carring the light sources is adjusted 
until high fringe visibility on the plane panel 
is obtained in the same height of the camera. 
With the adjustment the “same distance con- 
dition” is satisfied. The fringe visibility dif- 
fers along the vertical direction at this stage. 
The fringe visibility is made uniform by back 
and forth adjustment of the camera, and thus 
the optical alignment of the system is com- 
pleted. 
The / and d are calibrated finally using a 
standard object as shown in Figure 4. The 
distances between the fiducial marks are 
made exactly the same. Very thin wings are 
stretched beyond the standard object to touch 
the grating surfaces, so it is possible to count 
the fringe order which corresponds to each 
fiducial mark without ambiguity. A picture of 
the standard object is shown in Figure 5. 
Three equations are rewritten for the depth 
of three fiducial marks from Equation 1. 
hi = Ni (dis, = N1) 
ha = Na l/((d/IS, — Na) (2) 
hs = Na l/(dlS, — Na) 
Il 
ha Te hi 
(3) 
haha m... 
Because ha — hi 2 ha — hs - H, d/S, is ob- 
tained as follows: 
d/S, 2 [NX Ni + Ns) — 2NiNs]/ 
[2N2 — (N1 * N3)] (4) 
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1975 
  
  
  
  
  
— N — H — = HH — > 
— h4 — 
bz— h ia 
  
  
Fıc. 4. Standard object for calibration of d 
and /. 
Substituting d/S, in one of the Equation 3, / is 
obtained. 
RESULTS 
A setof pictures ofa living body with natural 
skin is shown in Figure 6. The forward facing 
pictures from a stereo pair with a 400 mm 
base length. The contour step is approxi- 
mately 4.5 mm. Another stereo pair (Figure 7) 
is presented as a comparison of fringe visibil- 
ity. The object is a mannequin.