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http://hdl.handle.net/11375/25209
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DC Field | Value | Language |
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dc.contributor.advisor | Xu, Chang-qing | - |
dc.contributor.author | Mohamed, Mahmoud | - |
dc.date.accessioned | 2020-01-24T19:18:58Z | - |
dc.date.available | 2020-01-24T19:18:58Z | - |
dc.date.issued | 2020 | - |
dc.identifier.uri | http://hdl.handle.net/11375/25209 | - |
dc.description.abstract | Micro-/pico-projectors are exciting technology as they represent a core enabling technology for the future growth of portable devices. They are currently involved in many fields such as automotive, defence & aerospace, healthcare, and media/entertainment. Solving the issue of speckle noise in such small projectors has been a challenge until now, as most of the effective techniques for speckle suppression are not suitable for such small sizes. The purpose of this dissertation is exploring and applying practical solutions for reducing the laser speckle noise for a handheld laser projector (micro-/pico-projectors). The first method is to introduce a laser source with low-level speckle noise. The source is designed based on end pumping of two cascaded laser crystals in the same cavity. The first crystal is Nd: YVO4 and the second is Nd: GdVO4 crystal. The output power ratio is adjusted mechanically to be 1:1. The output optical to optical efficiency is close to 50%. The output power at 1:1 power ratio has the lowest speckle noise level. The laser source is compact. Such a laser source is promising for micro-/pico-projectors. The second method is to reduce the laser speckle noise by a simple, low cost and compact optical method. Our novel method is to vibrate a lens with a small focal length in just one dimension (1D) in front of an optical diffuser. The method reduced the speckle noise by 81.25% and 75.6% for laser diode (LD) and diode-pumped solid-state (DPSS) laser sources, respectively. Finally, an optimisation was performed as follows: First, two laser sources are blended under specific conditions. Second, by adding another vibrating lens with a direction of vibration orthogonal to that of the first lens. Afterwards, the two optimisations are tested with a real pico-projector engine setup. The speckle contrast ratio was < 5%. | en_US |
dc.language.iso | en | en_US |
dc.title | SPECKLE SUPPRESSION IN HANDHELD LASER PROJECTION DISPLAYS | en_US |
dc.type | Thesis | en_US |
dc.contributor.department | Engineering Physics | en_US |
dc.description.degreetype | Thesis | en_US |
dc.description.degree | Doctor of Philosophy (PhD) | en_US |
dc.description.layabstract | Projection display technology today has garnered a large amount of interest due to its vast market. The display technology has evolved alongside the development of various light sources for their light engines. For example, the technology started with the use of a conventional lamp, progressed to light-emitting diodes, and recently has arrived at laser sources. Laser-based projection displays have caught the attention of those seeking to develop display technologies due to many advantages for projection, thanks to the intrinsic properties of the laser. Laser projectors have significant benefits that include high brightness, wide colour gamut, long lifetime and high electrical to optical efficiency. There have been multiple types of laser-projector created to satisfy the requirements of the intended applications. A large scale and high-power laser projector will be used in applications requiring a big screen, large audiences, and wide-open spaces found in a cinema or theatre. A mini projector on the other hand will typically be used for home cinema, while micro-/pico-projectors are intended for personal use. Although laser projectors up until now have been useful, they are expensive and have safety concerns. Moreover, laser projectors encounter a technical problem due to the high coherence of the laser source. This issue is known as “speckle” noise. Speckle noise results in a reduction of the quality of images generated with laser-based projectors. Many types of research have been conducted to reduce the laser speckle noise to be lower than human eye perception limits. As a result, most of these speckle reduction techniques are applied to large scale projectors, and a few of them have been successfully applied for smaller projectors, such as micro-/pico- projectors. | en_US |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Mohamed_Mahmoud_Talaat_2020January_PhD.pdf | 2.66 MB | Adobe PDF | View/Open |
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