356 
In this case , the overlapping part of images should 
be disposed by the image processing ,and necessary 
to equalize the size of two images for merge two 
images to one. These processes require many time 
and very complicated to compare with the case of 
line camera data processing. 
And to equalize a image size , it is necessary to 
knew the distance between a subject and a Camera . 
If not , it is difficult to measure the true size of 
a subject from a image data. Photo 1. shows 
a sample of image data of a tie bolt and spring. 
Also , it is necessary to get the distance when to 
measure the width of a subject . 
  
But to measure the length of a direction cross the 
scanning line of a line camera with right angles , it 
just depends on the traveling speed and the incline 
angle of a line camera , when the scanning rate of 
nt 
a line camera is fixed . 
  
According to the specifications of the line camera 
  
    
ea a 
and the result of some experiments in the field , in E mme ia 
case of using DDR, it is possible to get a line of PHOTO 1. Picture of tie bolt and 
image data ( 512 pixels per line ) which width is ; spring by the line camera 
about 0.8 millimeters at the speed of 30 kilometers 
per hour ( about 10,000 lines of image data can 
record in one second ) (Table 1) . : 
ES 
= 
TABLE 1. SPECIFICATIONS of the LINE CAMERA 
" 
  
it 
  
  
| PIXEL SIZE 13u X134 
3. THE WAY OF INSPECTION OF LOOSENESS 
LINE SIZE 912 PIXELS 
B DOT CLOCK 8 MHz 
Under the normal condition , the upper plate of 
spring touches the lower one . But , in case of DATA OUTPUT 8 BIT DIGITAL 
looseness , two plates will be separated. (Figure 6 ,P LINE SCAN RATE =10, 000 scan /sec 
hoto 2 and Photo 3 ) 
The width of a slit between those two plates 
depends on the torque of the tie bolt for 
the fastener . When lighting from over a part of 
  
  
  
  
  
  
EEE EEE 
eer ura mea ane rame 
the fastener , the slit of spring becomes 
  
a shade , and it’s width is expressed by the number 
TIGHT LOOSEN 
of lines on the image recorded by a line camera. =. 
   
  
Therefore , it’s possible to check the loosen spring o 
f rail fasteners in automatically , if the NARROW Th 
software can detect the spring and can count the uu» — 
line number of those. > 
How to measure the size of subject form image 
data by Line Camera is as follows. 
  
The line camera is set up diagonally and set the 
  
  
  
lights over subjects to make clear light and Figure 6. Shape of tight and 
shade (figure 7) , so the width oft spring is loosen spring 
able to describe as following expression . 
HE A Se se 
W=D-T 
W : lines of shade part 
D : lines of standard thickness of spring plate 
T : lines between the edge of upper and lower plate of spring 
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop "From Pixels to Sequences”, Zurich, March 22-24 1995 
  
BH 5 = x