This document describes the design, simulation, fabrication, and testing of a fly's eye homogenizer for use with digital micromirror devices (DMDs). It outlines the zemax simulation of the optical setup, details the mold design and fabrication process for the microlens array, and presents experimental results comparing the intensity distribution with simulation predictions. The homogenizer is concluded to provide a more collimated and uniform intensity distribution of UV light for DMDs, improving micro-machining quality. Future work is proposed to address profile irregularities and achieve better collimation.

1. Fabrication and Optimisation of
Fly’s Eye UV LED Homogenizer
for DMDs
Advisor – Proof. Y. C. Lee
Advisee – Vikram sachan (N16057211)
2018 / 07 / 23

2. Outline
• Introduction of fly’s eye homogenizer and DMD.
• Zemax simulation of optical setup.
• Mold design and fabrication.
• Experimental results and conclusions.

3. • Introduction of fly’s eye homogenizer and DMD
1. What is Fly’s Eye Homogenizer.
2. Working principle.
3. Digital Micro mirror Devices (DMDs).

4. Fly’s Eye Homogenizer
• An optical beam homogenizer divides and redirects an incident beam to provide
uniform irradiation to a plane surface. The beam homogenizer is particularly
useful in an apparatus and method for uniform laser irradiation of materials.

5. Working of Fly’s Eye Homogenizer
Light
Source

6. Digital Micro mirror Devices (DMDs)
• The digital micro mirror device, or DMD, is a micro-opto-
electromechanical system (MOEMS).

7. • Zemax simulation of optical setup
1. Simulation (Zemax Optics Studio).
2. Available Lenses and Data.
3. Simulation Results (Merit function editor).
4. Simulation Results for collimation.
5. Simulation Results of Detector D1 (For UV LED) and
Detector D3 (For Homogenizer).
6. Fly’s Eye homogenizer Parameters.

8. Simulation (Zemax Optics Studio)
1. CBT-90_UV_Ray_Files_Zemax.dat file is used.
Fig. CBD – 90 – UV LED light source ( λ
= 405 nm & 120° divergence angle).Fig. A photograph of UV LED from Luminus.

9. Fig. UV LED light source intensity profile.
Fig. Angular distribution with normalized
intensity.
Fig. Zemax optics studio screenshot
showing way to insert UV led source file.

10. Available Lenses and Data
Aspherical
lens
Radius of
curvature
(Rleft) mm
Conic (Cleft) Thickness
mm
Radius of
curvature
(Rright)mm
Conic (Cright)
L1 99.637 0 25 -18.323 -0.798
L2 20.923 -0.640 21 0 0
L3 0 0 12 -10.462 -0.626
Table 1 – Aspherical Lens Data
L3
L2
L1

11. 16.194mm
Simulation Results (Merit function editor)

12. Simulation Results
(For UV LED)
• Detector (D1)

13. Simulation Results for collimation

14. NSC Lightning Layout of Zemax Optics Studio
UV LED
L1 L2
L3
L4
D2
H
D3D1
Aspherical
lens
Radius of
curvature
(Rleft) mm
Conic (Cleft) Thickness
mm
Radius of
curvature
(Rright)mm
Conic (Cright)
L4 38.63 0 12.52 0 0
H 3.19858156 -0.5 11 3.19858156 -0.5

15. Detector (D3) – Fly’s Eye Homogenizer
Fig. Intensity Distribution –
a) False colour intensity distribution.
b) Cross-sectional view about Y axis(at
y=0).
c) Cross-sectional view about X axis axis(at
X=0).

16. • Mold design and fabrication
1. Solid works design of Homogenizer Mold and
Mold Assembly.
2. Molding, Curing and extraction process of
Homogenizer.
3. Confocal microlens profile Measurements.

17. Fly’s Eye Homogenizer Parameters
Microlens - 12X10

18. Solidworks Design of Homogenizer Mold
∅36
12mm
0.5mm
0.5mm

19. Mold Assembly
Fig. Solid works assembly view Fig. A photograph of steel mold assembly
with quartz plate (thickness = 10mm)

20. Molding Process -
1. PDMS
part A & B
4.
Vacuuming
process to
take
bubble out
2. Taken
1:1 by
weight
3. Mixed
well
around
5mins.

21. Curing Process
Curing parameters –
• Time Duration = 2hrs.
• Temperature
Gradually increase 25°C – 100°C then,
100°C – 25°C.
• Further cooling time after curing = 2hrs
Fig. Curing process

22. Fly’s Eye Homogenizer Separation from mold
PDMS
Microlens
array
Quartz
plate
10
Microlens
Fly’s Eye Homogenizer Mold

23. Confocal Microscope
Measurement for
replicated profile of
microlens arrays
Element 4X6
Confocal Microscope
Steel MoldFly’s Eye Homogenizer
Microlens Profile

24. Profile measurement under confocal microscope
• 1 microlens each time
• 50X
• Total no. of measurements
= 20.
• Time taken for each
measurement = 1hr
55mins (approximated).
Fig. Microlens
height view
Confocal Microscope

25. Aspheric Function plot
R
Z
R
Fig. Aspherical Lens
Fig. Matlab plot of aspheric function for given data
Zemax output data

26. Comparison of 2x2 element of side L and side R
Left Side (L) Right Side (R)

27. Comparison of 2x11 element of side L and side R
Left Side (L) Right Side (R)

28. Comparison of 5x6 element of side L and side R
Left Side (L) Right Side (R)

29. Comparison of 9x2 element of side L and side R
Left Side (L) Right Side (R)

30. Comparison of 9x11 element of side L and side R
Left Side (L) Right Side (R)

31. • Experimental results and conclusions
1. Experimental Setup.
2. Description of optical setup.
3. Experimental results comparison with simulation.
4. Conclusion.
5. Future Work

32. Experimental setup

33. Optical System
Detector

34. Experimental results
Measurement parameters –
Pitch = 0.05mm
Speed = 1mm/s
Time elapsed = 28hrs (approx.)
Fig. (a) shows contour display of intensity. (b) Intensity distribution of UV LED light at homogenization plane
A photograph of
actual UV light
Intensity at
homogenization
plane

35. Experimental results Comparison with Simulation
Fig. (a) Cross-sectional intensity distribution
at axis X = 0.
Fig. (a) Cross-sectional intensity distribution
at axis Y = 0.
Experiment
Simulation

36. Conclusion
• This work proposes a modification in the digital micro mirror device
(DMD). Since, fabrication of homogenizers by laser micro-machining
system is quite expensive to use and it is one-time fabrication only.
Using molding method for the manufacturing of fly’s eye UV LED
homogenizer is the cheapest way of manufacturing homogenizers. Once
the homogenizer steel mold is fabricated, we can produce any number
of homogenizers by using mold.
• The UV light used by the micro mirror devices will become more
collimated and flat top intensity distribution of UV light, hence the
quality of micro-machining of any substance will improve significantly.

37. Future Work
• PDMS Microlens profile irregularities after Demolding
process can be fixed by changing the fabricated mold
design.
• A different set of lens can be used to get more collimated
light from UV LED that decreases intensity slope and make it
more flat-top profile.

38. Future Work
• Better collimation angle can be achieved by using
different set of aspherical lenses.