Asymmetric Light Guiding Prism for Ghost Image Prevention
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Solution Overview
Problem
Attachable image display devices with small and thin light guiding prisms often generate ghost images due to light reflection, which interferes with the user's field of view.
Innovation Solution
The ocular optical system incorporates a light guiding prism with specific side inclinations and a positive refractive emission surface, diverting reflected light away from the pupil to prevent ghost image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the light guiding prism is made small and thin, then the field of view is not significantly interrupted, but light reflected off the side of the light guiding prism enters the pupil and generates ghost images
Solution Approach 1:
The patent applies asymmetry by configuring the light guiding prism with non-parallel side surfaces having different inclination angles. Specifically, the first side surface has a first inclination angle and the second side surface has a second inclination angle that differs from the first, creating an asymmetric structure that directs reflected light away from the pupil while maintaining a compact prism size.
Solution Approach 2:
The patent applies local quality by giving different optical properties to different parts of the light guiding prism. The side surfaces are configured with specific inclination angles tailored to their local positions, where the first side surface has a specific inclination relative to the optical axis and the second side surface has a different inclination, optimizing light control at each location.
2Device complexity
If the light guiding prism is made small and thin, then the device becomes more compact, but light reflection from the sides enters the pupil causing ghost images
Solution Approach 1:
The asymmetric configuration of side surfaces with different inclination angles allows the prism to be compact while preventing ghost images. The first side surface inclined at a first angle and the second side surface inclined at a second angle create asymmetric light reflection paths that diverge from the pupil, enabling compact design without sacrificing optical performance.
Solution Approach 2:
The patent changes the geometric parameters of the light guiding prism by specifying different inclination angles for different side surfaces. The first side surface has a first inclination angle and the second side surface has a second inclination angle, optimizing the balance between compactness and ghost image prevention through parameter optimization.
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 reduces or eliminates ghost images by ensuring that reflected light is diverted from the user's pupil, maintaining a clear field of view.
Implementation Method 1
The emission portion includes an emission surface that has a positive refractive power, and the emission surface emits the image light reflected off the reflection surface
Implementation Method 2
The light guiding prism serves to guide, to the front of the eye of the user, image light from the display element
Implementation Method 3
a reflection surface off which the image light from the display element 2 is reflected to the emission portion 4
Data Source
AI summary
An ocular optical system includes a light guiding prism that guides image light from a display element and an emission portion that emits the image light guided by the light guiding prism. The light guiding prism includes a plurality of sides arranged to surround a light path of the image light, and a reflection surface off which the image light is reflected to the emission portion. The plurality of sides include a first side that is arranged on an opposite side of a first plane including first and second optical axes and that is situated between the emission portion and the reflection surface, wherein the first optical axis is a portion of the image light before the image light is reflected off the reflection surface, and the second optical axis is a portion of the image light after the image light is reflected off the reflection surface.