Head-Up Display Light Guide Layout for Easier Pupil Expansion
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Solution Overview
Problem
The manufacturing of a pupil expansion type hologram for head-up displays is challenging due to the need for fine processing of the light guide body, which is difficult to achieve.
Innovation Solution
A head-up display system that includes a light guide body with a coupling region, a first expansion region, and a second expansion region, where the light flux is incident and replicated in both horizontal and vertical directions, allowing for easier manufacturing by reducing the diffraction power of the second expansion region, and is inclined with respect to the windshield to prevent stray sunlight from reaching the observer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a pupil expansion type hologram is used for head-up display, then the visual recognition region can be expanded, but fine processing of the light guide body becomes difficult and manufacturing becomes challenging
Solution Approach 1:
The light guide body is divided into multiple functional regions: a coupling region for receiving light from the display, a first expansion region for expanding the light flux in a first direction, and a second expansion region for expanding the light flux in a second direction. This segmentation allows each region to be optimized independently, reducing the overall manufacturing difficulty while achieving pupil expansion in multiple directions.
Solution Approach 2:
Different regions of the light guide body are assigned different diffraction powers tailored to their specific functions. The first expansion region has a higher diffraction power optimized for expansion in the first direction, while the second expansion region has a lower diffraction power optimized for expansion in the second direction. This local optimization reduces the need for uniformly fine processing across the entire light guide body.
2Area of stationary object
If the light guide body is designed with high diffraction power in all regions, then the visual recognition region expands effectively, but the manufacturing precision requirements increase significantly
Solution Approach 1:
The patent applies different diffraction powers to different regions of the light guide body based on their specific functional requirements. The first expansion region uses higher diffraction power for effective light flux expansion, while the second expansion region uses lower diffraction power, thereby reducing the overall manufacturing precision requirements while maintaining effective visual recognition region expansion.
Solution Approach 2:
By segmenting the light guide body into regions with different diffraction characteristics, the patent avoids the need for uniformly high precision processing across the entire component. Each segment can be manufactured with precision levels appropriate to its specific function, reducing the overall manufacturing difficulty.
3Device complexity
If the light guide body is positioned perpendicular to the windshield, then the optical path is simplified, but stray sunlight can reach the observer and cause dazzle
Solution Approach 1:
The light guide body is positioned at an asymmetric angle relative to the windshield normal, specifically inclined by a predetermined angle in the vertical direction. This asymmetric positioning blocks stray sunlight from reaching the observer's eye while still allowing the virtual image to be displayed correctly through the windshield.
Solution Approach 2:
The patent converts the potentially harmful effect of sunlight entering the optical system into a beneficial filtering mechanism. By positioning the light guide body at an inclined angle, the structure that could potentially transmit stray light instead blocks it, using the geometry to filter out harmful sunlight while maintaining the desired optical function.
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 system enables easy manufacturing of the light guide body and effectively displays a virtual image superimposed on the real view, preventing observer dazzle from sunlight while maintaining high diffraction efficiency.
Implementation Method 1
a light guide body that guides the light flux to the light-transmitting member
Implementation Method 2
A light beam at a center of the light flux emitted from the display is incident while being inclined with respect to a normal direction of the incident surface
Implementation Method 3
the light flux incident on the incident surface of the light guide body and changed in a traveling direction is replicated into a plurality of light fluxes in a horizontal direction of the virtual image visually recognized by the observer, and then the replicated light fluxes are further replicated in a vertical direction of the virtual image
Data Source
AI summary
A head-up display system includes a display that emits a light flux and a light guide body that guides the light flux to the light-transmitting member. A light beam at a center of the light flux emitted from the display is incident while being inclined with respect to a normal direction of the incident surface of the light guide body. The light flux incident on the incident surface of the light guide body is changed in a traveling direction in the light guide body, the light flux is replicated into a plurality of light fluxes in a horizontal direction of the virtual image, and then the replicated light fluxes are further replicated in a vertical direction of the virtual image to be emitted from the emission surface so as to expand the visual recognition region. A light beam at a center of the light fluxes emitted from the light guide body is emitted toward the light-transmitting member while being inclined with respect to a normal direction of the emission surface of the light guide body.