Head-Up Display Mirror Arrangement for Compact Optical Path
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Solution Overview
Problem
Head-up displays for mobile objects, such as automobiles, face a challenge in reducing size while maintaining an extended optical path length to minimize driver eye movement and prevent fatigue, which is contradictory to the requirement for a compact device.
Innovation Solution
A head-up display utilizing a reflection optical system with at least three mirrors, where the n-th mirror has refractive power and is arranged closest to the image reflecting surface, and the arrangement positions and angles of the mirrors are configured to satisfy specific conditional expressions to achieve a reduced device size while maintaining the optical path length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical path length is extended to increase the focal distance of the virtual image, then driver eye movement is reduced and fatigue is prevented, but the device size increases
Solution Approach 1:
The patent uses multiple mirrors (l-th, m-th, n-th mirrors) to fold the optical path into a compact three-dimensional arrangement. By reflecting light through multiple surfaces rather than using a straight linear path, the effective optical length is extended while the physical footprint remains small, resolving the contradiction between long optical path and compact device size.
Solution Approach 2:
The optical components are arranged in a nested configuration where the l-th mirror, m-th mirror, and n-th mirror are positioned within each other's spatial envelope. The light beam passes through a sequence of reflected paths that nest within the device housing, allowing extended optical path length L within a compact form factor.
2Volume of moving object
If the device size is reduced to fit limited installation space, then installation flexibility is improved, but the optical path length from image display element to image reflecting surface is insufficient
Solution Approach 1:
The patent employs multiple reflection surfaces arranged in a folded configuration, transforming a linear optical path into a multi-dimensional path. The light beam undergoes sequential reflections at the l-th mirror, m-th mirror, and n-th mirror, effectively multiplying the optical path length within the same physical space, thereby achieving sufficient optical length in a compact device.
Solution Approach 2:
The mirrors are configured with specific curvature radii (Rl, Rm, Rn) to control the light beam path. By optimizing the curvature of each mirror surface, the optical path is extended through controlled reflection geometry, allowing the light to traverse a longer effective distance while maintaining a compact physical arrangement.
3Length of stationary object
If multiple mirrors are used to extend the optical path, then the device complexity increases, but the optical path length is sufficient
Solution Approach 1:
The patent uses exactly three mirrors (l-th, m-th, and n-th) - no more, no less - to achieve the required optical path extension. This minimal sufficient approach avoids unnecessary complexity while meeting the optical path length requirement. Each mirror performs a specific function in the sequence, and removing any would fail to achieve the target optical length.
Solution Approach 2:
The patent optimizes specific parameters of the mirrors including curvature radii (Rl, Rm, Rn), reflection angles (θl, θm, θn), and spacing distances (αl, αm, αn) to achieve the desired optical path length with minimal components. By carefully controlling these parameters, the system achieves sufficient optical length using only three mirrors rather than requiring additional reflective surfaces.
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 allows for a compact head-up display that maintains the necessary optical path length, minimizing driver eye movement and preventing fatigue, while also reducing the size of the device and minimizing external light incidence and dust entry.
Implementation Method 1
a reflection optical system which reflects display light from an image display element to an observer side on an image reflecting surface
Implementation Method 2
the n-th mirror has a refractive power and is arranged closest to the image reflecting surface side along an optical path of the light beam
Data Source
AI summary
Disclosed is a head-up display capable of achieving reduction in size while securing an optical path length from an image display element to an image reflecting surface. In a head-up display, a reflection optical system has at least three or more mirrors including an l-th mirror, an m-th mirror, and an n-th mirror sequentially in this order from the image display element side along a light beam emitted from the image display element D, the n-th mirror has a refractive power and is arranged closest to the image reflecting surface side among all mirrors, the light beam emitted from the image display element D is reflected from the l-th mirror, the m-th mirror, and the n-th mirror in this order, the light beam emitted from the n-th mirror passes between the l-th mirror and the m-th mirror and reaches the image reflecting surface, and predetermined conditional expressions are further satisfied.