Pancake HMD Optics Using Diffractive Elements for Wider Field of View
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Solution Overview
Problem
Conventional HMD lens systems in VR or AR devices face challenges in optimizing optical performance due to design constraints, particularly in achieving a compact form factor while providing enhanced depth of field, field of view, and stereoscopic imaging.
Innovation Solution
Incorporating diffractive optical elements into the lens system, which are part of a catadioptric or pancake optical configuration, to direct and refract light based on polarization, allowing for a compact and efficient optical design that enhances depth perception and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional lens systems are used in HMD, then optical performance can be maintained, but the device size and complexity increase
Solution Approach 1:
The patent combines refractive and diffractive optical elements into a single integrated lens system. The diffractive optical element is positioned in optical contact with the refractive lens, merging their functions to achieve compactness while maintaining optical performance. This integration allows the system to provide both the focusing capability of refractive optics and the chromatic aberration correction of diffractive optics within a unified structure.
Solution Approach 2:
The patent employs a composite optical system that utilizes both refractive and diffractive optical elements. The diffractive element introduces periodic surface structures that create diffraction effects, while the refractive lens provides conventional focusing. This composite approach leverages the complementary strengths of both optical mechanisms to achieve compact design with reduced chromatic aberration and improved depth of field.
2Volume of moving object
If lens systems are designed for compact form factor, then device portability improves, but optical performance such as depth of field and field of view deteriorates
Solution Approach 1:
The patent utilizes the wavelength-dependent properties of diffractive optical elements to change optical parameters dynamically. By designing the diffractive structure with specific pitch and geometry, the system achieves different focal lengths for different wavelengths, creating a chromatic dispersion effect that can be leveraged to expand the effective field of view and depth of field within a compact form factor. The diffractive element's parameters are optimized to provide enhanced angular separation of wavelengths.
3Ease of manufacture
If conventional optical elements are used, then manufacturing is simpler, but chromatic aberration increases
Solution Approach 1:
The diffractive optical element acts as an intermediary component that mediates the chromatic aberration problem. Positioned between the refractive lens and the display element, it introduces a controlled diffraction effect that counteracts the chromatic dispersion of the refractive lens. The periodic structure of the diffractive element creates wavelength-dependent path length differences that compensate for the refractive index variations causing chromatic aberration.
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 implementation of diffractive optical elements improves the immersive experience by providing a larger field of view and reducing chromatic aberration, resulting in a more effective VR or AR system with improved stereoscopic imaging.
Implementation Method 1
Incorporating diffractive optical elements into the lens system, which are part of a catadioptric or pancake optical configuration, to direct and refract light based on polarization
Implementation Method 2
direct and refract light based on polarization
Implementation Method 3
catadioptric or pancake optical configuration, to direct and refract light
Data Source
AI summary
An optical system of a head-mounted display (HMD) system that includes a diffractive optical element coupled to a display, for example, via lamination or a suitable optically clear adhesive. The optical system may include a reflective polarizer and a quarter-wave plate that, together with the diffractive optical element, form a catadioptric or “pancake” configuration that focuses light from a display system to an eye of a user of the head mounted display system.