Holographic Head-Mounted Display Using Spatial Light Modulator
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) are bulky due to the need for complex lenses to achieve high-quality, wide-field-of-view images, and holographic HMDs face issues with image quality, speckle, and limited image size due to pixel size and computational load limitations of spatial light modulators (SLMs).
Innovation Solution
A head-mounted display design utilizing a high spatial coherence light source, a beam expanding/diverging element, and a spatial light modulator (SLM) to create a converging scanning beam axis or wave front, allowing the SLM to generate holographic images with a large angular size without requiring small pixel SLMs, thus eliminating the need for large lenses and achieving a lightweight design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional eye piece lenses are used to re-image the display module, then the display appears at a comfortable viewing distance, but the device becomes bulky and heavy
Solution Approach 1:
The patent extracts and eliminates the bulky eye piece lenses from the HMD system by using a holographic display approach. Instead of requiring lenses to re-image the display module, the invention uses an SLM to generate holographic images that can be viewed at comfortable distances without traditional optical imaging components, thereby removing the source of bulk and weight.
Solution Approach 2:
The patent replaces the mechanical/optical lens-based imaging system with a computational holographic system. Instead of using physical lenses to focus and re-image light, the invention uses an SLM to modulate light phases and amplitudes computationally, substituting a mechanical optical system with a programmable optical modulator approach.
2Manufacturing precision
If complex lenses are used to display high quality images with wide field of view, then image quality and FoV improve, but the device becomes very bulky
Solution Approach 1:
The patent changes the fundamental parameters of the display system by using an SLM that can dynamically modulate light phase and amplitude. Instead of relying on fixed optical properties of complex lenses, the invention uses programmable parameter control through the SLM to achieve high image quality and wide field of view, allowing software-based optimization without adding physical bulk.
Solution Approach 2:
The patent transitions from a 2D display requiring complex lenses for 3D imaging to a true 3D holographic display that encodes depth information in the light field. By using the SLM to modulate both phase and amplitude of light waves, the system creates volumetric images that provide high quality and wide FoV without the need for bulky lens assemblies.
3Area of stationary object
If SLM pixel size is reduced to achieve large holographic images, then image size increases, but manufacturing precision becomes extremely difficult
Solution Approach 1:
The patent employs a dynamic approach where the SLM can be reconfigured programmatically to change the effective pixel size and holographic image parameters. Instead of relying on fixed, ultra-fine physical pixel dimensions, the system uses dynamic phase and amplitude modulation to achieve large holographic images, allowing the effective resolution to be adjusted through control signals rather than physical fabrication changes.
4Manufacturing precision
If SLM resolution is increased to achieve ideal holographic images, then image quality improves, but computational load increases very high
Solution Approach 1:
The patent applies partial action by using an SLM that modulates only the necessary parameters (phase and/or amplitude) required for holographic image generation, rather than attempting to control every possible light property. This selective modulation approach achieves sufficient image quality while keeping computational requirements manageable by focusing on the essential degrees of freedom needed for holography.
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
The design enables a lightweight HMD with a large field of view and high image quality by using a converging beam to reduce the angular size limitations of SLMs, allowing for a more compact and efficient holographic display system suitable for virtual and augmented reality applications.
Implementation Method 1
a beam expanding/diverging element (10)
Implementation Method 2
a beam expanding/diverging element (10)
Implementation Method 3
a beam converging element (11) that converges the expanded light beam into a viewing zone
Implementation Method 4
a beam converging element (11) that converges the expanded light beam into a viewing zone
Implementation Method 5
The spatial light modulator (12) adds a phase pattern and/or an amplitude pattern to the light beam to generate a holographic virtual image
Implementation Method 6
The spatial light modulator (12) adds a phase pattern and/or an amplitude pattern to the light beam to generate a holographic virtual image
Data Source
AI summary
A head mounted display device includes a light source that emits a high coherence light beam, a beam expansion/diverging element that expands the light beam emitted by the light source, and a beam converging element that converges the expanded light beam into a viewing zone. The light beam from the beam converging element is incident onto a spatial light modulator (SLM), and the SLM is configured to add a phase pattern and/or an amplitude pattern to the light beam to generate a virtual image that is visible to a user wearing the head mounted display device. The light converging element creates a beam or scanning beam axis that converges towards the eye, which enables a large field of view for a virtual or holographic image to be displayed.