1. A novel method to set up and calibrate goniophotometer
Ziyi Wu University of Arizona (520) December

2. Overview
This presentation introduced a novel method to set up and calibrate goniophotometer which I did for Grote Industries in Summer 2011.
The goal for this project is to use an alternative method to set up a goniophotometer which greatly reduces budget, time and space.
This goniophotometer is used for first round test before sent to product evaluation department for official testing, therefore, up to 8% of error is allowed for this setup.
The content of this presentation is approved by Grote Industries.

3. What is goniophotometer?
A Goniophotometer is a device used for measurement of the light emitted from an object at different angles.
The use of goniophotometer has been increasing in recent years with the introduction of LED-lighting technology in automotive industry.
There is a government regulation which limits the light emitted from vehicle lamps at different angle.

4. What is goniophotometer?
Figure 1. GO-HD5 goniophotometer by EVERFINE Corp.

5. The traditional goniophotometer setup
Setting up a goniophotometer can be a costly project in terms of budget, time, and space: the system must be isolated inside a black tunnel and baffles are used in the tunnel in order to block the stray light.
Figure 2. The traditional goniophotometer setup

6. My setup for goniophotometer
Figure 3. My goniophotometer setup

7. Baffle design
Baffle 1 and baffle 2 have same structural and materials.
The board is made with plastic for its light weight and low-cost.
The frame which holds the white board is made with T-slotted aluminum profile.
The back surfaces (face to detector) of both baffle is painted to flat black for better anti-reflectivity.
four rollers with brakes under the frame so that it can be move to any desired location.
Figure 4. Flat black surface of the baffle 1 and 2

8. Baffle design
Baffle 3 is essentially a mini black tunnel designed for the detector only.
A tube which extended out is the only opening for this box and it will block any stray light passed through baffle 1 and baffle 2.
The box is made with plastic board painted in black on both surfaces and the frame is made with flat black T-slotted aluminum profile.
Figure 5. Isometric view of baffle 3

9. Alignment and calibration
The alignment and calibration of my setup is rather easy due to the mobility of each baffle
place the laser on the goniophotometer with no rotation angle.
placed a two white boards to cover the windows on baffle 1 and 2.
Calibrate baffle 1 until the laser is hitting its midpoint, then fix the position of baffle 1
Remove the cover on baffle 1 to allow laser to pass through it.
Calibrate baffle 2 until the laser is hitting its midpoint, then fix the position of baffle 2
Calibrate baffle 3 until the reading from the detector reach its maximum, then fix the position of baffle 3

10. Comparison with traditional setup
My setup
Traditional setup
Cost
dollars
>5000 dollars
Build time
1 week
1 month
Environment
Normal indoor environment
Black tunnel required
Recyclability
All frames are re-useable
None
Mobility
All baffles are moveable
Calibration
Required when baffles are moved
Once per year
Test error
20 degree
20 degree

11. Questions and comments