Holographic Image Projector Using Coupling Prism
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Solution Overview
Problem
Current heads-up display (HUD) systems, particularly in vehicles, face challenges with power consumption, contrast limitations, and inefficient optical power usage due to reliance on LED backlit LCDs and mirror matrices, and existing LCOS-based holographic projectors are bulky and costly, lacking flexibility in perceived distance and resolution.
Innovation Solution
An image projector system utilizing a spatial light modulator with a reflective phase manipulating surface and a coupling prism to increase angular separation of diffraction components, allowing for a more compact and efficient holographic display with improved contrast and resolution, including a method to control LCOS devices for generating diffraction profiles and compensating for distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LED backlit LCDs are used in HUD systems, then the display can show useful information to drivers, but the device consumes significant power and has limitations in contrast and dynamic range
Solution Approach 1:
The patent replaces the LED backlit LCD system with a holographic projection system using an SLM (spatial light modulator) and laser source. This substitution eliminates the need for high-power LED backlights and LCD panels, achieving superior contrast and brightness efficiency through optical interference patterns that create images without requiring continuous high-energy illumination.
Solution Approach 2:
The patent utilizes phase modulation of light waves through the SLM to create holographic images. By controlling the phase of light pixels rather than their intensity directly, the system achieves high contrast ratios and efficient light utilization, as the phase information is converted into spatial intensity distributions through diffraction and interference.
2Power
If mirror matrices (DLP projectors) are used in HUD systems, then the display can provide image projection, but the optical power usage is inefficient for sparse information displays
Solution Approach 1:
The patent changes the fundamental operating parameters from intensity modulation (DLP) to phase modulation (SLM). This parameter change enables more efficient optical power usage because phase-modulated light can be diffracted to create images with minimal energy loss, and the system can dynamically adjust the diffraction efficiency to match the sparsity of displayed information.
Solution Approach 2:
The patent employs temporal multiplexing with sequential projection of different wavelength components (red, green, blue lasers) to create full-color holographic displays. This periodic action allows efficient use of optical power by projecting monochromatic holograms sequentially, each optimized for its wavelength, rather than attempting to project all colors simultaneously with reduced efficiency.
3Reliability
If LCOS based holographic projectors are used, then the system can generate holographic images, but the lensing systems are complicated, costly and bulky
Solution Approach 1:
The patent extracts and eliminates the bulky lensing system from conventional LCOS holographic projectors by using a digital micromirror device (DMD) or SLM in a configuration that requires minimal optical elements. The system uses the diffraction properties of the modulator itself and simple Fourier optics to form holographic images, removing the need for complex lens assemblies while maintaining image quality.
Solution Approach 2:
The patent transitions from 2D spatial modulation to 3D spatial-frequency domain modulation by using the full capabilities of the SLM to control both amplitude and phase across the wavefront. This dimensional expansion in the optical control space enables simplified optical paths, as the system can encode image information in the phase domain and let diffraction naturally perform the Fourier transform to create the holographic image.
4Measurement precision
If pixel size is reduced to increase resolution, then the lateral extent of the intermediate image can be constrained, but phase flicker increases and contrast is reduced
Solution Approach 1:
The patent applies preliminary phase correction and optimization algorithms to the pixel phase values before hologram generation. By pre-compensating for phase flicker effects and optimizing the phase distribution across pixels, the system can use smaller pixels for higher resolution without suffering from increased phase flicker, thereby maintaining high contrast in the displayed holographic images.
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 solution enables a more compact, cost-effective, and high-resolution holographic display with enhanced contrast and variable perceived distance, suitable for vehicle HUDs, reducing the need for bulky lensing systems and improving image quality by increasing angular dispersion and suppressing zero-order diffraction components.
Implementation Method 1
a spatial light modulator having a reflective phase manipulating surface, the spatial light modulator being responsive to an electric control signal to generate a two-dimensional phase profile on the reflective phase manipulation surface to diffract the optical input beam into a diffracted beam having a plurality of diffraction components angularly separated
Implementation Method 2
a coupling prism having at least a first surface and being positioned such that at least a first subset of the diffraction components is refracted through the first surface to the imaging system; wherein upon refraction through the first surface, an angular separation of the first subset of diffraction components is increased
Data Source
AI summary
A holographic display image projector system including an input light source for generating an at least partially coherent optical input beam and an imaging system for transforming an image representation in the Fourier domain into a corresponding holographic image in the spatial domain. The image projector includes a spatial light modulator having a reflective phase manipulating surface and being responsive to an electric control signal to generate a two-dimensional phase profile on the reflective phase manipulation surface to diffract the optical input beam into a diffracted beam having a plurality of diffraction components angularly separated in a first dimension. A coupling prism having a first surface positioned such that a first subset of the diffraction components is refracted through the first surface to the imaging system, wherein upon refraction, an angular separation of the first subset of diffraction components is increased by at least a factor of 2.