Ring 
flash 
  
  
  
LASER | |110° 
  
  
  
  
  
  
  
  
X 20 X 100 
Objective Objective 
Fig. 1 
cone (110? in this case). Surrounding the source is a ring flash lamp which 
provides a useful locating image. Such a high intensity point source is 
essential when recording the positions of the probe of a three-axis measuring 
machine, for example, where many 
exposures are required of the probe 
positions on the same plate, without ; 
the background becoming overexposed. To left 4 J To right 
camera \ camera 
This system was used in the trials T a \ / 
with the UMK 10FP cameras, and worked —- \ / A 
extremely well. hag 
—- 
— 
A much simpler source may be used Mount to 
if a small aperture is being used on fit 3- axis 
the camera, since a f/22 lens at 10x machine 
principle distance will only resolve 
0.25mm on the object, and a much 
larger "point source" may be used. Double 
Fig. 2 shows a system where the fibre 
"point" is the end of a 0.25mm 
plastic fibre optic. This, however, \ 
does not have such a high numerical il 
aperture, and so two fibres are used, 
one providing the source for each 
camera. Provided that the fibres stay 
© Lamp 
probe 
in the same relative position no 
allowance for their separation need L 
be made. There is also the advantage 2 PN \ 
that the source is much less bulky, 
as the source of light (here a // N 
tungsten halogen bulb) can be remote 
from the machine, Fibre relay sources x tent 
may be even more advantageous with 
laser sources because of the greater Mirror 
bulk of the laser. 
Fig.2 
Testin hotogrammetric cameras against three-axis measuring m in 
As has already been described, one objective of the work is to provide for 
the convenient verification and calibration of multi-axis measuring machines. 
Some of these machines can claim to be accurate to a few micrometres, so that 
initially the existing methods of photogrammetry are not likely to show up 
189 
| 
| 
N 
I 
d 
I 
m 
if 
il: 
ih 
E 
m 
d 
d 
i 
{1 
Ii 
fl 
i 
I 
I 
i 
IM 
n 
IR 
I 
HM 
i 
| 
n 
if 
i 
i 
i 
1 
im 
| 
4 
i 
Hi 
li 
"i 
M 
ii 
1 
| 
in 
i 
I 
"M 
| 
ld 
| 
n 
n 
il 
Fi 
Ii 
ji 
i 
iil 
v 
fil 
i 
ii 
Hii 
i 
ji 
ul 
n 
| 
I | 
ji 
Hl 
Un 
ER 
EEE EEE TE RR ERE