Optical Transmitting Module Ghost Image Elimination
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Solution Overview
Problem
Head-mounted display devices using waveguides often produce ghost images when displaying images close to the eye, such as in stereoscopic or interactive modes, due to multiple output pupils projecting light at the same angle, leading to reduced display quality and user discomfort.
Innovation Solution
An optical transmitting module with a first lens having negative refracting power, positioned between the waveguide and the eye, and an optical element, such as a second lens with positive refracting power, to align virtual images from different beam splitters on a focal plane, eliminating ghost images by adjusting the focal plane's distance relative to the eye within a range of 25cm to 3m.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple output pupils are used to expand the eye box range, then the exit pupil dimension is magnified, but ghost images appear when displaying close-range images
Solution Approach 1:
A first lens with negative refracting power is introduced as an intermediary component between the waveguide and the user's eye. This lens mediates the light paths from multiple output pupils, causing light from adjacent pupils to converge at different virtual image locations. This separation eliminates the ghost image effect while preserving the expanded eye box benefit.
Solution Approach 2:
The patent changes the optical parameters by introducing a lens with negative refracting power. This parameter change modifies how light from multiple output pupils propagates to the eye, creating separated virtual image locations at different distances. The focal plane distance is adjusted within 25cm to 3m to optimize the separation effect and eliminate ghost images.
2Object-affected harmful factors
If clear imaging is preset to infinity or far location, then ghost image phenomenon is reduced, but close-range image display quality deteriorates
Solution Approach 1:
The patent creates dynamic virtual image locations at different distances from the waveguide for different output pupils. Instead of fixing all images at infinity or a single far location, the system dynamically positions virtual images at varying distances (within 25cm to 3m), allowing close-range display while maintaining image separation to prevent ghosting.
3Adaptability or versatility
If virtual images are displayed at close distance, then interactive and stereoscopic display is enabled, but ghost images appear reducing display quality
Solution Approach 1:
The first lens with negative refracting power acts as an intermediary that enables close-range virtual image display while maintaining image quality. It separates the light paths from multiple output pupils, ensuring that even at close distances (25cm to 3m), the virtual images from different pupils do not overlap, thus preventing ghost images and preserving display quality for interactive and stereoscopic applications.
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 eliminates ghost images, enhances display quality, and improves user comfort by aligning virtual images and avoiding distortion in real images formed from ambient light, making the head-mounted display device suitable for closer-range image display.
Implementation Method 1
a first lens 120 having a negative refracting power, positioned between the waveguide and the eye
Implementation Method 2
utilizes a waveguide as an optical component (combiner)
Implementation Method 3
an optical element, such as a second lens with positive refracting power, to align virtual images from different beam splitters on a focal plane
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
An optical transmitting module and a head mounted display device are provided. The optical transmitting module includes a waveguide and a first lens. The waveguide is located on a transmission path of an image beam. The waveguide includes a plurality of beam splitters configured to split the image beam the image beam into a first image beam and a second image beam. The second image beam reflected by the beam splitter is outputted from the waveguide, so as to display a virtual image. The first lens causes a plurality of virtual images displayed by a plurality of the second image beams reflected from different beam splitters at the same angle to coincide on a focal plane of the first lens. The head mounted display device can eliminate a ghost image phenomenon that occurs when the user observes the images displayed in a range closer to the eye.