Reflective Diffraction Optical Element Ghost Image Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In head-mounted displays, the 0 order diffraction ray from the reflective diffraction optical element often enters the opposite eye, causing unintended light entry and deterioration of image quality, such as ghost images.
Innovation Solution
The image display apparatus employs a first diffraction optical element with a planar or spherical interference fringe, arranged such that the normal or axis of the interference fringe intersects a plane including the direction connecting the two eyes, deflecting the 1st order diffraction ray towards the observing eye and redirecting the 0 order diffraction ray away from the observing eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflective diffraction optical element is used to deflect light, then the 1st order diffraction ray can be directed toward the observing eye, but the 0 order diffraction ray enters the opposite eye causing ghost images
Solution Approach 1:
The patent introduces a new spatial dimension by tilting the diffraction optical element relative to the optical axis. This angular arrangement in the third dimension (tilt angle θ) allows the 0 order diffraction ray to be directed away from the opposite eye while maintaining the 1st order diffraction ray path to the observing eye, thus resolving the ghost image problem without sacrificing display quality
2Ease of operation
If the diffraction optical element is arranged to direct 1st order diffraction ray to the observing eye, then image display function is achieved, but unintended light enters the opposite eye
Solution Approach 1:
The patent applies local quality by creating asymmetric tilt angles for different optical paths. The diffraction optical element is tilted at a specific angle θ relative to the optical axis, which locally modifies the light path geometry to achieve selective directionality - allowing the 1st order diffraction ray to reach the observing eye while the 0 order diffraction ray is redirected away from the opposite eye
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
This configuration effectively restricts the entry of unintended light into the opposite eye, improving image quality by ensuring the 1st order diffraction ray enters the intended eye while diverting the 0 order diffraction ray to a different height, thereby reducing ghost images and enhancing display clarity.
Implementation Method 1
a first diffraction optical element configured to deflect a proceeding direction of the image light from the image generation unit to a second direction by diffraction to cause the deflected image light to enter the one eye
Data Source
AI summary
An image display apparatus includes a light source configured to emit image light, a scanning mirror configured to reflect the image light from the light source, and a reflective diffraction optical element configured to change a direction of the image light from the scanning mirror to a different direction in addition to regular reflection. The scanning mirror is arranged at a position and a height as different from an observing point as possible. A direction of extension of an interference fringe of the reflective diffraction optical element intersects incident light from the light source.