Full text: XVIIth ISPRS Congress (Part B5)

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three hundred rules in the Lighting Advisor 
expert system data base at the time this paper 
is being written. 
  
PENN VIDEO LIGHTING ADVISOR 
  
What is the purpose of this consultation? 
Yes: 
* LIGHTING 
* LENS CALCULATION 
* COLOR ANALYZING 
1. Use arrow keys or first letter of item to position cursor. 
2. Select all applicable responses. 
3. After making selections, press RETURN/ENTER to 
continue. 
  
  
  
  
  
PENN VIDEO LIGHTING ADVISOR 
  
What is the feature of interest? 
HOLE OR CAVITY 
RAISED SURFACE (SUCH AS A BRACKET) 
FEATURE SILHOUETTE 
FEATURE PRESENCE OR ABSENCE 
SURFACE FLAWS (CRACKS OR CAVITIES) 
FEATURE OR SURROUNDING AREA FLUORESCES 
UNDER ULTRAVIOLET LIGHT 
1. Use the arrow keys or first letter of item to position the 
Cursor. 
2. Press RETURN/ENTER to continue. 
  
  
  
  
  
  
Figure 2 
Two examples of questions asked 
in Lighting Advisor 
The Lighting Advisor uses a personal computer 
as its work station. The software is menu 
driven with help available at all times. The 
user tells Lighting Advisor about his/her 
application by answering a series of questions 
and making choices from the menus. See figure 
2. The questions pertain to the nature of the 
  
PENN VIDEO LIGHTING ADVISOR 
  
How close can you put the light source to the feature of 
interest? (in inches) 
Help ooo 
One of the factors in suggesting appro- 
priate lighting is the minimum distance 
that a light source can be placed to the 
feature. Consider any physical restric- 
tions in the process or environment. If 
you are not sure of the physical limita- 
tions, rerun the Expert System choos- 
ing a different light distance each time. 
**End- RETURN/ENTER to continue 
  
  
1. Enter a positive number. 
2. Press RETURN/ENTER to continue. 
  
  
  
  
  
  
Figure 3 
Help in understanding questions 
about an application 
application, the feature and background surface 
qualities, whether the object is moving or 
stationary during the inspection, etc. 
On-line help is available for each question at 
any menu level. One of the help screens is 
shown in figure 3. 
  
Structured 
Camera Lighting 
(Shadow Casting) 
Light / S 7 
g J 
- Shadow 
ut. 
Part 
Press ENTER to continue 
  
  
  
Figure 4 
A graphic representation of 
a suggested lighting technique 
The expert system reviews the answers given and 
returns a set of conclusions that include: 
1. The lighting technique. For example: 
Front-light field. 
2. The light source. For example: Quartz 
halogen lamp with reflector. 
3. The camera lens. For example: The 
calculated focal length is 89.6. Use a 75 
mm fixed focal length lens. Use a zoom 
lens with a focal length of 89.6 included 
as its usable range. 
4. Possible color or polarized filtration or 
special optics requirements. For example: 
Use a beam splitter. 
To help explain the Lighting Advisor 
conclusions, the system shows several color 
illustrations using the PC's graphics 
capabilities. Figure 4 shows the camera and 
light position when structured lighting is used 
to cast shadows. 
A Case Study 
This application was done two years prior to 
the development of the Lighting Advisor expert 
system. It was among many of the applications 
used to help prove and debug the expert system. 
The application requires a machine vision 
inspection of a critical dimension on an 
aluminum transmission case. The measurement 
needed is between an area on the side of the 
case and a mounting hole perpendicular to that 
plane. The arrows in figure 5 show the two 
points that the measurement is between. The 
accuracy of this distance insures that there is 
adequate clearance for the starter assembly to 
be attached. 
 
	        
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