Optical Element with Matching Grating Pitches for HMD Light Enlargement
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Solution Overview
Problem
In head-mounted displays, miniaturization and efficient image light enlargement are challenging, especially when using fine laser beams, as existing optical elements struggle to sufficiently enlarge image light to match the pupil diameter, leading to usability issues.
Innovation Solution
An optical element comprising a first light guide with a semitransmissive reflective film and diffraction elements with grating patterns of the same pitch and orientation, allowing for the enlargement of image light by diffraction and reflection, enabling image light to be incident to the pupil effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If two diffraction gratings are used to enlarge image light, then image light enlargement is achieved, but the structure becomes complex and difficult to manufacture
Solution Approach 1:
The patent combines multiple diffraction gratings into a single integrated optical element with multiple grating structures formed on one substrate. This merging approach maintains the image light enlargement function while reducing structural complexity and manufacturing difficulty compared to using separate diffraction gratings.
Solution Approach 2:
The optical element integrates multiple functions including diffraction, reflection, and light guidance within a single component. The grating structures perform both diffraction and reflection functions, eliminating the need for separate optical elements and simplifying the overall system.
2Volume of moving object
If a laser scanning method is used for miniaturization, then device size is reduced, but image light becomes too small to match pupil diameter
Solution Approach 1:
The patent changes the optical parameters of the laser beam through diffraction and reflection by the grating structures. The gratings alter the beam's direction, size, and distribution to transform the small laser-scanned image light into a larger output that matches the pupil diameter while maintaining the miniaturized device architecture.
3Area of moving object
If image light is enlarged using existing optical elements, then image light size increases, but precise adjustment of image light position relative to pupil becomes necessary
Solution Approach 1:
The optical element is designed to automatically adjust and optimize the image light position and size through its integrated grating structures. The diffraction and reflection geometries are configured to self-align the output beam with the pupil diameter, eliminating the need for manual or active position adjustment by the user.
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 optical element effectively enlarges image light, ensuring it reaches the pupil, thereby improving usability and display quality in head-mounted displays without the need for precise adjustment of image light position relative to the pupil.
Implementation Method 1
a first diffraction element that is provided in a section of the first incidence section, and is provided with a plurality of gratings, which are arranged at a predetermined pitch
Implementation Method 2
a semitransmissive reflective film that is provided in the inside of the first light guide
Implementation Method 3
light that propagates through the first light guide and reaches the second diffraction element is sequentially emitted at the same angle as the incidence angle while being repeatedly reflected by the semitransmissive reflective film and the reflective film
Implementation Method 4
a second diffraction element that is provided in at least a section of the first emission section, and is provided with a plurality of gratings, which are arranged at a predetermined pitch
Data Source
AI summary
An optical element includes a light guide is provided with a incidence section and a emission section, a semitransmissive reflective film is provided in the inside of the light guide, a first diffraction element is provided in the incidence section, and is provided with a plurality of gratings, a second diffraction element is provided in the emission section, and is provided with a plurality of gratings, and a reflective film is provided in the incidence section in a periphery of the first diffraction element, in which the pitch of the plurality of gratings of the first diffraction element is equivalent to the pitch of the plurality of gratings of the second diffraction element, and each extension direction of the plurality of gratings of the first diffraction element is the same direction as each extension direction of the plurality of gratings of the second diffraction element.