HUD Projection Optics With Folded Light Path for Uniform Luminance
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Solution Overview
Problem
Head-up displays mounted on vehicles face challenges in achieving compact design while maintaining image quality, as increasing the size of the spatial modulation element leads to protrusion and deteriorated mountability, and existing solutions fail to effectively suppress luminance unevenness.
Innovation Solution
A projection device with a plurality of light sources arranged in a specific direction, a lens that redirects light to a common region on the spatial modulation element, and a first reflective optical member that deflects light to an arbitrary point at a predetermined angle, reducing protrusion and luminance unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the size of the spatial modulation element is increased to increase the size of the virtual image, then the virtual image size is improved, but the amount of protrusion of the backlight unit increases and mountability deteriorates
Solution Approach 1:
The patent transitions from a series arrangement (one-dimensional layout) to a folded optical path configuration (multi-dimensional spatial arrangement). By introducing reflective optical members to fold the optical path, the system achieves the required optical path length for large spatial modulation elements without increasing the protrusion thickness in the normal direction, thus resolving the contradiction between virtual image size and mountability.
2Area of moving object
If the size of the spatial modulation element is increased to increase the virtual image size, then the virtual image size is improved, but the thickness of the lens must be increased to ensure optical path length
Solution Approach 1:
The patent uses reflective optical members to fold the optical path in additional spatial dimensions, allowing the optical path length to be extended without increasing the thickness of the lens in the normal direction. This enables large spatial modulation elements to be used while maintaining compact lens thickness.
3Device complexity
If a reflector is merely arranged to face the liquid crystal display at a predetermined angle, then the device structure is simplified, but luminance unevenness cannot be suppressed
Solution Approach 1:
The patent applies local quality by designing reflective optical members with position-dependent reflective properties. Different regions of the reflective optical members have different orientations and reflective characteristics, allowing each local region to redirect light from light source elements to specific regions on the spatial modulation element. This ensures uniform luminance distribution across the entire display area while maintaining a relatively simple overall structure.
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 enhances the mountability of the head-up display on vehicles by minimizing protrusion and ensures uniform luminance, allowing for a more compact and effective display system.
Implementation Method 1
a lens that changes an optical path of light emitted from each of the plurality of light sources such that the light emitted from each light source reaches substantially the same region of an incident surface of the spatial modulation element
Implementation Method 2
a first reflective optical member that deflects the light emitted from the lens toward the spatial modulation element, the first reflective optical member having a shape that deflects light emitted from the lens so as to be incident on an arbitrary point on the incident surface of the spatial modulation element at a predetermined reference incident angle
Data Source
AI summary
A projection device includes: a plurality of light sources arranged in a first direction; a spatial modulation element that modulates incident light into image information and emits the image information; a lens that changes an optical path of light emitted from each of the plurality of light sources such that the light emitted from each light source reaches substantially the same region of an incident surface of the spatial modulation element; and a first reflective optical member that deflects the light emitted from the lens toward the spatial modulation element, the first reflective optical member having a shape that reflects light emitted from the lens so as to be incident on an arbitrary point on the incident surface of the spatial modulation element at a predetermined reference incident angle.