Head-Mounted Display MEMS Mirror Orthogonal Scanning
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Solution Overview
Problem
Current head-mounted display devices using two-dimensional MEMS mirrors for laser beam scanning suffer from image dragging phenomena and limited field of view due to scanning frequency and angle limitations.
Innovation Solution
A head-mounted display device incorporating a projection device with a first and second MEMS mirror element and a relay optical element group, where the MEMS mirrors control scanning in orthogonal directions, allowing for increased scanning angles and frequencies, and an optical waveguide to ensure the light beam is converged onto the optical pupil, thereby enhancing the field of view and reducing image dragging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-dimensional MEMS mirror is used to perform scanning in two directions simultaneously, then the device structure is simplified, but the scanning frequency and scanning angle are limited causing image dragging phenomenon and small field of view
Solution Approach 1:
The patent divides the single two-dimensional MEMS mirror into two separate one-dimensional MEMS mirror elements. Each MEMS mirror element is responsible for scanning in one specific direction, allowing independent optimization of scanning frequency and angle for each axis, thereby eliminating the mutual constraint that limited the bi-axial mirror's performance.
Solution Approach 2:
The patent transitions from a two-dimensional scanning approach using one mirror to a separable orthogonal scanning approach using two mirrors. By decomposing the 2D scanning function into two independent 1D scanning functions along orthogonal axes, the system achieves higher scanning frequencies and larger scanning angles without increasing overall device complexity.
2Device complexity
If a two-dimensional MEMS mirror is used to perform scanning in two directions simultaneously, then the device structure is simplified, but the scanning angle is limited causing small field of view
Solution Approach 1:
The patent divides the single two-dimensional MEMS mirror into two separate one-dimensional MEMS mirror elements. Each MEMS mirror element is responsible for scanning in one specific direction, allowing independent optimization of scanning frequency and angle for each axis, thereby eliminating the mutual constraint that limited the bi-axial mirror's performance.
Solution Approach 2:
The patent transitions from a two-dimensional scanning approach using one mirror to a separable orthogonal scanning approach using two mirrors. By decomposing the 2D scanning function into two independent 1D scanning functions along orthogonal axes, the system achieves higher scanning frequencies and larger scanning angles without increasing overall device complexity.
3Device complexity
If the light beam is not properly converged onto the optical pupil, then the optical system is simpler, but the image quality and uniformity are poor
Solution Approach 1:
The patent introduces a relay optical element group as an intermediary component between the MEMS mirror elements and the optical waveguide. This relay optical system includes lenses or mirrors that precisely control the light beam path, converge the beam onto the optical pupil, and ensure uniform illumination, thereby improving image quality without significantly complicating the overall optical system.
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 effectively increases the scanning angle and frequency, reducing image dragging and expanding the field of view while ensuring the light beam fills the optical pupil, improving image quality and uniformity.
Implementation Method 1
since the projection device of the head-mounted display device respectively controls scanning and imaging of the light beam in a first direction and a second direction through vibration of the first MEMS mirror element and the second MEMS mirror element
Implementation Method 2
after a laser light source emits laser light, the laser light is scanned and projected to a screen through a two-dimensional MEMS mirror
Implementation Method 3
through the relay optical element group, the light beam is coupled into the optical waveguide of the head-mounted display device, and is transmitted to the human eye through the optical waveguide for imaging
Implementation Method 4
The relay optical element group is located on the transmission path of the light beam and between the second MEMS mirror element and the optical pupil
Implementation Method 5
The optical waveguide is located on the transmission path of the light beam and has a first surface and a second surface opposite to each other, wherein the first surface is located between the relay optical element group and the second surface
Data Source
AI summary
A head-mounted display device including a projection device and an optical waveguide is provided. The projection device has an optical pupil located on a second surface of the optical waveguide, and includes a light source, a first MEMS mirror element, a second MEMS mirror element, and a relay optical element group. The relay optical element group has a first axis equivalent focal length corresponding to a first parallel light beam and has a second axis equivalent focal length corresponding to a second parallel light beam. The first parallel light beam and the second parallel light beam travel along an optical axis of the relay optical element group, and a value of the first axis equivalent focal length is different from a value of the second axis equivalent focal length. The head-mounted display device may provide good image quality and a large field of view.