Head-Up Display Optics With Freeform Distortion Correction
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Solution Overview
Problem
Existing head-up display devices face challenges in compactization while maintaining required performance, particularly due to large reflecting mirrors and unsatisfied telecentric properties, especially when correcting distortions from concave mirrors and non-planar projection areas.
Innovation Solution
A projection optical system incorporating a concave lens, a free curved surface lens, and a free curved surface concave mirror, which minimizes optical configuration and corrects distortion, enabling a compact head-up display device with improved telecentric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional head-up display device uses a large reflecting mirror to project images, then the image projection area is sufficient, but the device volume becomes large and compactization is difficult
Solution Approach 1:
The patent implements a folded optical path configuration where the light flux is reflected multiple times between mirrors arranged in a nested manner. The first mirror reflects light in a first direction, then a second mirror reflects it in a second direction, allowing the optical system to be compacted while maintaining sufficient projection area. This nesting of optical paths enables the device to achieve both large projection area and compact volume.
Solution Approach 2:
The patent utilizes three-dimensional spatial arrangement of mirrors and optical components to fold the optical path in multiple directions. By arranging mirrors at different orientations and positions in 3D space, the system achieves compactization without sacrificing projection area, effectively utilizing dimensional space to resolve the contradiction between size and functionality.
2Manufacturing precision
If a head-up display device uses a concave mirror to correct distortion, then distortion correction is achieved, but the telecentric property becomes unsatisfied
Solution Approach 1:
The patent introduces a field lens positioned at a specific location in the optical path to correct telecentricity issues locally without affecting the overall distortion correction achieved by the concave mirror. The field lens has specific optical properties that compensate for the telecentric property degradation caused by the concave mirror, allowing both distortion correction and telecentric property to be satisfied simultaneously.
Solution Approach 2:
The field lens acts as an intermediary optical element between the concave mirror and the projection system. It mediates the optical path to correct the telecentric property that is degraded by the concave mirror's distortion correction function, thereby maintaining both distortion correction and telecentric property through the introduction of this intermediate component.
3Length of moving object
If the light flux is folded in the horizontal direction to achieve a thin profile, then the device becomes thinner, but the reflecting mirror becomes large
Solution Approach 1:
The patent folds the optical path in both horizontal and vertical directions using multiple mirrors arranged in a three-dimensional configuration. By utilizing vertical space and arranging mirrors at different heights and orientations, the system achieves thin profile without requiring excessively large mirrors, as the optical path folding occurs in multiple dimensions rather than solely in the horizontal plane.
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 allows for a compact head-up display device that maintains performance by reducing the size of optical components and correcting distortion, enhancing the telecentric property and overall compactness of the system.
Implementation Method 1
the eyepiece optical system generates image information to be displayed as a virtual image by reflecting image light emitted from an image forming unit
Implementation Method 2
the eyepiece optical system includes a concave lens, a free curved surface lens, and a free curved surface concave mirror disposed in order from the image forming unit side
Data Source
AI summary
An object of the present invention is to provide a compact head-up display device. The head-up display device of the present invention includes an image forming unit that emits image light containing image information, and an eyepiece optical system that displays a virtual image by reflecting the image light, in which the eyepiece optical system includes a concave lens, a free curved surface lens, and a free curved surface concave mirror disposed in order from the image forming unit side along the emission direction of the image light.