Compact Light Engine Polarisation Separation
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Solution Overview
Problem
Existing light engine designs for projectors require additional components and increased complexity to produce red, green, and blue light, as they need to pass blue light to the phosphor wheel while separating excitation and emitted light, leading to larger and more costly systems.
Innovation Solution
A light engine that incorporates a wavelength conversion device with a polarisation converter and a dichroic element capable of separating light based on both wavelength and polarisation, allowing output light of the same colour as the source light by changing the polarisation of excitation light reflected by a phosphor wheel, resulting in a more compact and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a dichroic element is used to separate excitation light and emitted light from the phosphor wheel, then the light separation function is achieved, but the device complexity and size increase
Solution Approach 1:
The invention divides the light separation function into two distinct mechanisms: the dichroic element handles wavelength-based separation (reflecting converted light, passing excitation light), while the polarisation converter handles polarisation-based separation (reflecting p-polarised light, transmitting s-polarised light). This segmentation of functions allows each component to be optimised for its specific task, reducing the need for complex multi-functional elements and thereby reducing overall device complexity while maintaining reliable light separation.
Solution Approach 2:
The polarisation converter acts as an intermediary component between the phosphor wheel and the dichroic element. It modifies the polarisation state of the light before it reaches the dichroic element, enabling the dichroic element to perform both wavelength separation and polarisation-dependent routing. This intermediary function simplifies the overall system architecture by allowing the dichroic element to be more selective in its optical path control.
2Adaptability or versatility
If additional components are added to produce red, green, and blue light separately, then the colour generation capability is improved, but the device size and cost increase
Solution Approach 1:
The invention merges the functions of multiple light sources and colour generation mechanisms into a single phosphor wheel system excited by one blue light source. The phosphor wheel contains multiple phosphor materials that convert the blue excitation light into different colours (green, red, yellow) simultaneously or sequentially. The dichroic element and polarisation converter work together to separate and route these colours to the appropriate output paths, eliminating the need for separate laser diodes or LED modules for each colour and significantly reducing device size.
Solution Approach 2:
The phosphor wheel serves multiple functions: it acts as a wavelength converter (converting blue light to other colours), a colour separator (different phosphor segments produce different colours), and a polarisation modulator (when combined with the polarisation converter). The dichroic element also performs dual functions of wavelength filtering and polarisation-dependent routing. This multi-functionality reduces the total number of components needed while maintaining full colour generation capability.
3Use of energy by moving object
If the dichroic element passes all blue light to the phosphor wheel, then the excitation efficiency is maximised, but the ability to reflect blue light for direct output is lost
Solution Approach 1:
The dichroic element is designed with local quality characteristics: it has high transmittance for blue light in the p-polarisation state (allowing efficient excitation of the phosphor wheel) while maintaining high reflectance for blue light in the s-polarisation state (enabling direct blue light output when needed). This local differentiation of optical properties based on polarisation state allows the single dichroic element to serve dual purposes: maximising excitation efficiency when s-polarised light is used, and providing direct blue light output when p-polarised light is used, without requiring separate optical paths or additional components.
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 solution enables a more compact and cost-effective light engine by using polarisation to separate light paths, reducing the need for additional components and improving the balance and fabrication of the phosphor wheel, while maintaining the generation of required colours.
Implementation Method 1
a blue laser excites the phosphor wheel to generate green or red colour light. The phosphor wheel normally has some fan segments which contain different types of phosphor to convert the exciting blue light to a green, yellow or red colour.
Implementation Method 2
The blue excitation light 302 incident on such segments is absorbed by the phosphor and converted light 303 (typically green or red) is emitted.
Implementation Method 3
the wavelength conversion device further comprises a polarisation converter, either attached to or positioned behind the wheel configured to set at least some of the output light to a second polarisation, different from the first polarisation
Implementation Method 4
a dichroic element, arranged to receive the reflected output light, the dichroic element being configured to direct light of the first polarisation differently from light of the second polarisation
Implementation Method 5
A reflective type of phosphor wheel is often used, such that the excitation light and the emitted light stay on one side of the phosphor wheel.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
A light engine comprises: a wavelength conversion device, receiving source light of a first wavelength range and a first polarisation, generating light of a second wavelength range from a portion of the received source light, at least a portion of the second wavelength range being non- overlapping with the first wavelength range, the wavelength conversion device reflects output light comprising the generated light and comprises a polarisation converter that sets at least some of the output light to a second polarisation, different from the first polarisation; and a dichroic element, that receives the reflected output light and directs light of the first polarisation differently from light of the second polarisation.