5B-2-2 
Figure 2 - Reflection Light Amount Image 
4 METHOD OF RECORDING CRACK 
The vehicle where the automatic measurement device had been 
installed was developed about 20 years ago. The device by which 
then crack situation is understood uses the slit camera and 35mm 
roll film. Roads are produced with the illumination installed in the 
vehicle and the shadow of the shining on crack is produced. The 
slit camera takes a picture of the shadow of the crack (The speed 
fed according to the velocity of the car changes into the film). The 
generation situation of the crack was understood from the film 
taken a picture. 
The Komatus Engineering Co., LTD developed another kind of 
device by the digitalization of the measurement device. The 
reflection record by a digital method uses the laser and the optical 
detection sensor. The laser is scanned in the direction of the road 
crossing at high speed in the spot. The change in the reflection 
light amount of the spot laser is caught and the optical detection 
sensor is recorded as line surface information in the direction of 
the road crossing. The distance signal obtained when the vehicle 
runs is recorded at the same time. Recorded surface information is 
treated with a special player as one scanning lines and is 
recognized by displaying it at the same time by the plural as a 
respect image (pavement road). 
Figure 3 - Laser Irradiation Entrance 
Figure 4 - Irradiated Laser 
5 CRACK IMAGE 
Information acquired with the optical detection sensor is recorded 
on the W-VHS tape (tape to record the high picture quality 
reflection). Even the maximum at the recording time of the tape 
can be recorded regardless of the running speed of the car. The 
monitor as seen from sky by eyes projects the image of the road. 
This digital image differs from 35mm roll film, is not damaged, 
and is not torn off. Moreover, advancement, the retreat, and the 
stop can be freely done with the remote control button of a video 
device. 
Figure 5 shows the crack image of the vertical direction (direction 
of progress). Figure 6 shows a horizontal crack image. The crack 
Line B 
Line A 
Crack 
Reflection Light Amount Image 
Line A 
Bright 
Dark 
Line B 
Bright 
Dark