LED Array Projector Reflector Layout for Lower Light Loss
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Solution Overview
Problem
Existing image projectors using LED arrays suffer from significant light loss and low optical efficiency due to Lambertian light distribution, particularly in near-eye displays where power efficiency is critical.
Innovation Solution
Incorporating a reflective arrangement of at least three planar reflectors, preferably four, between the LED array and illumination optics to direct light through direct transmission and reflection, forming distinct illumination regions on the spatial light modulator, along with a controller to optimize LED illumination levels based on pixel data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LED array with Lambertian light distribution is used for illumination, then the device structure is simple, but optical efficiency is low with significant light loss
Solution Approach 1:
The patent introduces a reflective arrangement with multiple planar reflectors positioned at different angular orientations between the LED array and illumination optics. This adds a spatial dimension to light redirection, capturing Lambertian-emitted light from multiple angles and redirecting it towards the illumination optics, thereby converting isotropic emission into directed illumination and reducing light loss.
Solution Approach 2:
The reflective arrangement acts as an intermediary element between the LED array and illumination optics. The planar reflectors serve as mediating surfaces that intercept light from the LED array and redirect it towards the illumination optics, enabling efficient light transport without requiring modification of the LED emission characteristics or the illumination optics themselves.
2Loss of energy
If reflective arrangement with multiple planar reflectors is added to direct light, then optical efficiency is improved, but device complexity increases
Solution Approach 1:
The reflective arrangement with multiple planar reflectors serves multiple functions simultaneously: it redirects light from different angular regions of the LED array, defines illumination regions on the spatial light modulator, and works with the illumination optics to achieve efficient light transport. This multi-functionality justifies the added structural complexity by delivering comprehensive optical efficiency improvements.
3Area of stationary object
If uniform illumination is provided to entire SLM, then illumination coverage is complete, but power efficiency is low
Solution Approach 1:
The reflective arrangement creates distinct illumination regions on the spatial light modulator by using planar reflectors at specific orientations. Each LED illuminates particular regions through direct transmission and other regions via reflection, enabling selective illumination of only those SLM areas that require active imaging, thereby reducing power consumption while maintaining adequate illumination coverage.
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
Enhances optical efficiency by collecting and directing light more effectively, reducing light loss from 94% to 60%, and improving power efficiency in near-eye displays by ensuring selective illumination of image regions while conserving energy.
Implementation Method 1
a reflective arrangement comprising at least three planar reflectors, the reflective arrangement being deployed between the LED array and the illumination optics such that light from each of the LEDs illuminates a first region of the SLM by direct transmission from the LED via the illumination optics and additional regions of the SLM, distinct from the first region, via reflection in at least one of the planar reflectors
Implementation Method 2
an LED array comprising a plurality of separately-controllable LEDs for generating illumination
Data Source
AI summary
A projector for projecting an image includes an LED array (2) having separately-controllable LEDs for illuminating a spatial light modulator (SLM) (10) via illumination optics (8) with a converging beam. Projection optics (12) projects the image generated by the SLM. A reflective arrangement (16) typically having four planar reflectors, is deployed between the LED array (2) and the illumination optics (8) so that light from each of LED illuminates a first region of the SLM by direct transmission from the LED via the illumination optics and additional regions of the SLM via reflection in the planar reflectors.