Fourier Transform Light Mixing Illuminator for Uniform Color Output
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Solution Overview
Problem
Existing light mixing devices using diffusers and light scramblers are inefficient and costly due to increased etendue, leading to energy inefficiencies and difficulties in collecting mixed light effectively.
Innovation Solution
An optical device that focuses light from an array of light emitting elements to a Fourier plane, where zero spatial frequency components of different wavelengths overlap, and a mask is used to selectively block higher spatial frequency components, allowing for efficient color mixing without the need for aggressive light scramblers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If aggressive light scramblers and diffusers are used to mix light, then color mixing quality is improved, but energy efficiency deteriorates and device complexity increases
Solution Approach 1:
The patent transforms the light mixing problem from spatial domain to frequency domain by using a Fourier transforming optic. Instead of physically scrambling light paths through diffusers, the invention uses spatial frequency filtering where the Fourier plane separates different spatial frequencies, allowing selective blocking of higher frequencies while maintaining zero-frequency components. This dimensional transformation resolves the contradiction by achieving color mixing without aggressive spatial scrambling.
Solution Approach 2:
The patent changes the parameter space by working in the spatial frequency domain rather than direct spatial domain. By Fourier transforming the light field, the system can selectively modify spatial frequency parameters - blocking higher frequencies while preserving zero-frequency components - to achieve uniform color mixing without the energy losses associated with traditional spatial scrambling methods.
2Illumination intensity
If aggressive light scramblers are used to spread light, then color mixing quality is improved, but light collection efficiency deteriorates due to increased etendue
Solution Approach 1:
The patent resolves the etendue problem by transforming to the frequency domain. The Fourier transforming optic creates a plane where spatial frequencies are separated, allowing selective filtering without increasing the physical spread of light. This maintains the light bundle's spatial coherence while achieving frequency-based mixing, thereby preserving collection efficiency.
3Illumination intensity
If light is spread to overlap on the imaging plane, then color mixing is achieved, but device complexity and cost increase due to need for high numerical aperture optics
Solution Approach 1:
The patent eliminates the need for complex high-NA optics by working in the frequency domain. The Fourier transforming optic naturally separates spatial frequencies, allowing simple aperture masks to perform the mixing function that would otherwise require complex high-numerical-aperture optical systems. This dimensional transformation simplifies the overall optical architecture.
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 approach enables efficient and uniform color mixing with minimal power loss, achieving a bright and spatially homogenized light output that can be projected onto an object, improving energy efficiency and reducing costs compared to traditional methods.
Implementation Method 1
An optical device is employed that focuses the light from the elements to a Fourier plane of the device, wherein the light emitting elements are arranged so that at least the zero spatial frequency components of light of the different wavelengths from the elements substantially overlap in a region at the Fourier plane
Implementation Method 2
An optical device is employed that focuses the light from the elements to a Fourier plane of the device
Implementation Method 3
A mask is used that selectively blocks some of spatial frequency components of light from the elements without blocking the zero spatial frequency components of light from reaching the object
Data Source
AI summary
One embodiment of the invention is directed to a light mixing illuminator for illuminating an object, comprising an array of light emitting elements wherein at least some of the elements emit light of different wavelengths. An optical device is employed that focuses the light from the elements to a Fourier plane of the device, wherein the light emitting elements are arranged so that at least the zero spatial frequency components of light of the different wavelengths from the elements substantially overlap in a region at the Fourier plane. An objective is used to project the region onto the object. A mask is used that selectively blocks some of spatial frequency components of light from the elements without blocking the zero spatial frequency components of light from reaching the object.