Active Optical Engine Using Polarization Switching for Wider FOV
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Solution Overview
Problem
Existing near-eye display systems face challenges in expanding the field of view (FOV) without increasing the size, weight, and power consumption of projectors, which is particularly problematic for small, lightweight, and energy-efficient devices like head-mounted displays and smart glasses.
Innovation Solution
The use of an active optical engine that includes an active wave plate to switch light beam polarization and a polarizing beam splitter to redirect light beams through multiple optical paths, allowing for 1D or 2D pupil expansion, thereby enhancing the FOV without significant increases in projector size, weight, or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the projector size is increased to expand the field of view, then the FOV is improved, but the device weight and power consumption increase
Solution Approach 1:
The optical system is divided into multiple discrete optical elements (wave plates, beam splitters, mirrors, lenses) arranged in specific optical paths. This segmentation allows the FOV to be expanded through optical path manipulation rather than increasing projector size, directly resolving the contradiction between FOV and device weight.
Solution Approach 2:
The patent introduces multiple optical paths (first optical path, second optical path, third optical path) that manipulate light in different spatial dimensions. By using polarization-based beam splitting and wave plate rotation, the system expands the effective FOV without proportionally increasing the physical footprint of the projector, thus resolving the contradiction between FOV area and device weight.
2Area of stationary object
If the projector size is increased to expand the field of view, then the FOV is improved, but the power consumption increases
Solution Approach 1:
The optical system segments the light path into multiple polarization-based paths using beam splitters and wave plates. This allows FOV expansion through optical path diversity rather than increasing projector power output, resolving the contradiction between FOV and power consumption.
Solution Approach 2:
The system changes the polarization parameter of light using wave plates (converting between linear and circular polarization) to create multiple usable optical paths from a single light source. This parameter manipulation enables FOV expansion without increasing the power consumption of the projector.
3Area of stationary object
If active wave plates are used to switch polarization states, then the FOV is expanded through multiple optical paths, but the device complexity increases
Solution Approach 1:
The wave plates serve multiple functions: they convert linear polarization to circular polarization, enable beam splitting via the PBS, and control the activation of different optical paths. This multi-functionality reduces the need for separate components for each function, thereby managing device complexity while expanding FOV.
Solution Approach 2:
The polarizing beam splitter acts as an intermediary that separates light paths based on polarization state. This intermediary component enables the system to manage complexity by providing a clear mechanism for routing light through different optical paths without requiring complex switching mechanisms.
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 a wide, immersive FOV in near-eye display systems while maintaining a compact and energy-efficient design, supporting better geometries and longer battery life.
Implementation Method 1
an active wave plate that is configured to transition between an activated state and a deactivated state. The active wave plate is configured to convert the light beam output by the projection optics device from the first polarization to a second polarization when in the activated state
Implementation Method 2
a PBS that is configured to redirect light beams having the first polarization and to allow light beams having the second polarization to pass therethrough
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
In an embodiment, an apparatus is disclosed that includes at least one processor configured to determine a target coupling-out facet, identify an optical path to the target coupling-out facet, identify an active wave plate corresponding to the optical path, determine a target state of the active wave plate that corresponds to the optical path, set the active wave plate to the identified target state and cause a projection device to project a light beam comprising an image field of view component along the identified optical path.