The SPIE/OSA Student Chapter at Michigan Technological University have developed demonstrations
and workshops for science and engineering outreach. The practical approach to holography promotes the
study of photonic related sciences in high school and college-aged students. An introduction to laser
safety, optical laboratory practices, and basic laser coherence theory is given in order to first introduce the
participants to the science behind the holograms. The students are then able to create a hologram of an
item of their choice, personalizing the experience. By engaging directly, the students are able to see how
the theory is applied and also enforces a higher level of attention from them so no mistakes are made in
their hologram. Throughout the course participants gain an appreciation for photonics by learning how
holograms operate and are constructed through hands on creation of their own holograms. This paper
reviews the procedures and methods used in the demonstrations and workshop while examining the
overall student experience.
Advancements in laser diode technology have lead to the utilization of lasers in pico-projector
systems. These proposed devices would need to take full advantage of the coherent source, while still
providing full RGB color. Previous work has been completed analyzing 532 nm green diodes in
conjunction with hadamard-matrix diffusers for reducing the disruptive speckle noise caused by
coherent sources. In addition to the speckle, many small form factor laser diodes have aspheric or nonsymmetric
beam shapes upon excitation. Non-circular beam shapes are difficult, if not impossible, to
collimate properly. Collimation and beam symmetry is vital in order to keep the bulk of the sources
power in the lower order diffractive modes that form from beam shaping optics such as diffusers and
micro-lens arrays. Because of these requirements and unique diode structure, generic spherical lenses
will not suffice, leading to new techniques for beam collimation. This paper looks at creating the proper
beam shape through the use of multimode fiber optics. The output wave from the fiber is then passed
through a diffuser. Speckle contrast measurements will be analyzed for both rotating and stationary
instances of the diffuser. In addition, other techniques for creating more functional beam shapes will be
evaluated in comparison with a fiber optic setup.
In order to produce future generation micro-projection systems that can function independently or in conjunction with
small personal communication devices lasers are the preferred source of illumination over LEDs. Lasers are much
brighter and require less power than LEDs allowing for larger screen sizes and smaller battery requirements. In order to
illuminate the spatial light modulator used in the micro-projection system micro-optical elements are used within the
illumination path of a projector system to shape the RGB laser sources. Due to the diffractive nature of the optical
elements and the high coherence of the lasers a speckle pattern is produced in the final image reducing the overall image
quality. Diffractive diffusers are typically used in combination with micro-lens arrays in a time varying fashion in an
attempt to reduce the spatial coherence of the laser sources and hence reduce the speckle. Previous reduction techniques
have successfully used pseudo-random hadamard matrix diffusers to greatly minimize the contrast of the pattern. This
paper examines new reduction methods involving diffractive diffusing elements and presents measurements in the
reduction of speckle contrast for each technique.
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