Projection Lens Peripheral Portion for Eye Tracking in Holographic Displays
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Solution Overview
Problem
Existing eye tracking optical systems for holographic displays require a separate configuration of imaging lenses outside the display system, leading to occlusion issues and stringent tracking accuracy requirements, making the system complex and inefficient.
Innovation Solution
A display system that integrates a projection unit with a spatial light modulator and an eye tracking unit, where the peripheral portion of the projection lens serves as an imaging lens for eye tracking, utilizing a beam splitter for separate light paths and active illumination to achieve accurate real-time eye tracking without altering the projection optical path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate imaging lens is configured outside the display system for eye tracking, then the eye tracking function can be achieved, but the system becomes complex and the imaging lens may occlude the display
Solution Approach 1:
The projection lens is designed to perform dual functions: the central portion (first lens portion) projects display light onto the spatial light modulator, while the peripheral portion (second lens portion) images the user's eye for tracking. This multi-functionality eliminates the need for a separate imaging lens, simplifying the system structure while maintaining reliable eye tracking functionality
Solution Approach 2:
The eye tracking function is merged with the projection function by integrating the imaging capability into the projection lens itself. The camera is positioned to receive light through the second lens portion of the projection lens, combining what were previously separate optical paths into a unified system
2Object-affected harmful factors
If the imaging lens is bias placed to avoid occlusion, then display occlusion is avoided, but the frontal collection for eye image is not conducive and tracking accuracy requirements become more stringent
Solution Approach 1:
The projection lens is divided into two functional portions: the first lens portion (central area) dedicated to projection and the second lens portion (peripheral area) dedicated to eye imaging. This segmentation allows each portion to be optimized for its specific function, with the second lens portion positioned to frontally collect eye image light without causing display occlusion
3Device complexity
If the peripheral portion of projection lens is used for eye tracking, then the optical design is simplified and system is compact, but the light separation between projection and tracking paths must be achieved
Solution Approach 1:
A beam splitter is introduced as an intermediary optical element to separate the light paths. The beam splitter reflects tracking light from the second lens portion to the camera while allowing projection light to pass through, enabling clear separation of the two optical paths without complex mechanical adjustments or polarization considerations
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 simplifies the optical design, provides a compact and efficient system for holographic displays, enabling accurate eye tracking in real-time while maintaining normal projection imaging, even in dark environments, by utilizing the high pass portion of the projection lens and active infrared illumination.
Implementation Method 1
The beam splitter is configured to reflect light from the second lens portion to the camera
Implementation Method 2
The projection lens includes a first lens portion overlapping with the spatial light modulator
Implementation Method 3
An imaging optical path of the camera passes through the second lens portion
Data Source
AI summary
The embodiments of the present invention provide a display system and a display method. The display system includes a projection unit and an eye tracking unit. The projection unit includes a projection light source, a projection lens and a spatial light modulator. The projection lens is located between the projection light source and the spatial light modulator. In a direction of an optical axis of the projection lens, the projection lens includes a first lens portion overlapping with the spatial light modulator and a second lens portion not overlapping with the spatial light modulator. The eye tracking unit includes a camera. An imaging optical path of the camera passes through the second lens portion. The display system and the display method provided by the embodiments of the present invention can be advantageously used in the display field including holographic display, simplifying the optical design, and providing a compact and efficient optical system.