Laser Illumination Device with Beam Expander for Compact Projectors
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Solution Overview
Problem
Current illumination devices in projectors using laser light sources face challenges in reducing size and weight while maintaining high light-use efficiency and minimizing luminance non-uniformity, as they require large optical systems for light path unification and are prone to speckle noise.
Innovation Solution
The illumination device employs a configuration with a light source section having multiple laser sources emitting different wavelengths, a parallelizing optical system to convert light beams into a single path, an expanding optical system to increase beam diameters, and a uniformizing optical system to enhance in-plane intensity distribution, along with a coupling optical system to reduce beam divergence, allowing for a smaller optical system size and improved light-use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a large-scaled optical system is constructed for light path unification using laser sources, then light-use efficiency is improved, but device size and weight increase
Solution Approach 1:
The optical system is divided into separate functional modules: individual collimator lenses for each laser source, a central light path unifying optical system, and an expanding optical system. This segmentation allows each component to be optimized independently and the overall system to be more compact while maintaining high light-use efficiency through proper optical path management.
Solution Approach 2:
The patent employs an expanding optical system that increases the beam diameter of unified light in the optical path direction. This dimensional change allows the light path unifying optical system to be smaller while still achieving high light-use efficiency, as the expanded beam can be properly directed and utilized in the projection path.
2Volume of moving object
If a compact optical system is used for light path unification, then device size is reduced, but light-use efficiency decreases
Solution Approach 1:
Collimator lenses are placed immediately after each laser source to convert divergent light into parallel beams before the light enters the light path unifying optical system. This preliminary collimation action allows the subsequent optical system to be more compact while maintaining high light-use efficiency, as parallel beams are easier to direct and combine without loss.
Solution Approach 2:
The expanding optical system increases the beam diameter in the optical path direction, allowing a compact light path unifying optical system to achieve high light-use efficiency. The dimensional expansion occurs at the appropriate stage in the optical path, enabling compact design without sacrificing efficiency.
3Illumination intensity
If laser light sources are used for illumination, then color reproducibility is improved, but speckle noise and luminance non-uniformity increase
Solution Approach 1:
The expanding optical system increases the beam diameter of unified light in the optical path direction. This dimensional expansion reduces the density of coherent laser light, thereby suppressing speckle noise and luminance non-uniformity while preserving the excellent color reproducibility inherent to laser light sources.
4Loss of energy
If multiple light path unifying optical systems are used to handle multiple light sources, then light-use efficiency is improved, but device complexity increases
Solution Approach 1:
Multiple light paths from different laser sources are merged into a single unified optical path using a centralized light path unifying optical system. This combining approach maintains high light-use efficiency by properly directing all light beams through a single path, while reducing device complexity compared to having separate optical systems for each light source.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables a smaller-sized projector with improved light-use efficiency and reduced luminance non-uniformity, effectively addressing the challenges of size reduction and speckle noise, resulting in enhanced display quality.
Implementation Method 1
a collimator lens 12R, 12G, and 12B, respectively, serve to convert respective incident lights derived from the three types of laser sources (the red, the green, and the blue laser sources 11R, 11G, and 11B) into the parallel lights
Implementation Method 2
the dichroic prisms 131 and 132, serve to perform the color composition (the light path unification) on the parallel lights derived from the three types of laser sources
Implementation Method 3
an expander lens 16 serves to expand a beam diameter of each of the parallel lights which have been subjected to the color composition in the dichroic prisms 131 and 132
Implementation Method 4
a fly-eye lens 17 serves to uniformize an in-plane intensity distribution of each of the parallel lights which have had a beam diameter thereof expanded by the expander lens 16
Data Source
AI summary
An illumination device includes: a light source section having plural kinds of light sources, in which the light sources emits light beams having different wavelengths; a parallelizing optical system parallelizing each of the light beams entered from the light sources, and allowing each of the parallelized light beams to exit therefrom; a light path unifying optical system unifying the parallelized light beams exited from the parallelizing optical system into a single light path; an expanding optical system expanding a beam diameter of each of the parallelized light beams unified into the single light path, and allowing each of the expanded and parallelized light beams to exit therefrom; and a uniformizing optical system uniformizing an in-plane intensity distribution in each of the expanded and parallelized light beams exited from the expanding optical system.