Bibliographic Details
| Title: |
Decoherent Focusing Design and Advanced Passive Speckle Reduction for Laser Illumination Systems |
| Authors: |
Lapchuk, A., Prygun, O., Manko, D., Gorbov, I., Morozov, Y. |
| Publication Year: |
2024 |
| Collection: |
Physics (Other) |
| Subject Terms: |
Physics - Optics |
| More Details: |
To effectively apply passive speckle reduction methods, it is essential to use an illumination system that maximally exploits the non-ideal temporal coherence and angular diversity (spatial coherence reduction) of laser light. This study examines the necessary conditions for these factors to act independently to achieve maximum speckle reduction. A novel design for decoherent focusing of laser illumination into a rectangular, uniformly lit spot is proposed. The design is based on an array of rectangular prisms of varying heights and a Fresnel lens comprising crossed 1D cylindrical Fresnel lenses with flat facets. Mathematical modelling demonstrates that such a lens can effectively focus a Gaussian beam into a rectangular uniform illuminated spot, even for lenses with a high numerical aperture (NA = 0.2). A planar implementation of this lens is also proposed. The comb-like spectrum of a laser diode is shown to limit the capabilities of passive methods, as it is challenging to generate a significant number of decorrelated laser sub-beams beyond the available spectral modes. Experimental results confirm that applying a slight modulation (~15%) to the laser diode current during intensity integration transforms the comb spectrum into a continuous one. This enables the generation of an unlimited number of decorrelated laser beams, independent of the laser's spectral modes, to achieve the desired number for a specific optical device.
Comment: 13 pages, 13 figures, 3 tables, 10 equations |
| Document Type: |
Working Paper |
| Access URL: |
http://arxiv.org/abs/2412.13869 |
| Accession Number: |
edsarx.2412.13869 |
| Database: |
arXiv |
