Projection Optical System with Free Curved Surfaces for Tilted Virtual Image
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Solution Overview
Problem
Conventional head-up display devices face challenges in minimizing their cubic capacity while maintaining necessary capabilities and displaying a tilted virtual image plane, leading to increased size and reduced effective pixels due to trapezoidal video distortion.
Innovation Solution
A projection optical system incorporating an eyepiece optical system with a free curved surface lens and a free curved surface concave mirror, which tilts the virtual image plane by adjusting the conjugation points for far and near distances, and tilts the liquid crystal display panel opposite to the Scheimpflug principle to correct trapezoid distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional head-up display device uses a horizontally long virtual image with a curved mirror to ensure light flux size, then the light flux coverage is improved, but the mirror size increases and the cubic capacity of the device cannot be reduced
Solution Approach 1:
The patent employs free curved surfaces on both the lens and concave mirror to achieve asymmetric light flux control. The curved surfaces enable efficient light gathering in the vertical direction while maintaining compact horizontal dimensions, resolving the contradiction between light flux size and device volume.
Solution Approach 2:
The patent uses a rotationally asymmetric optical configuration where the virtual image has different dimensional requirements in horizontal and vertical directions. The free curved surface lens and concave mirror are designed with asymmetric curvatures to match this requirement, allowing compact device volume while ensuring adequate light flux in the critical vertical direction.
2Shape
If a head-up display device tilts the virtual image plane using the Scheimpflug principle, then the tilted virtual image is achieved, but trapezoidal video distortion occurs and the number of effective pixels decreases
Solution Approach 1:
The patent uses free curved surfaces with specifically designed rotationally asymmetric profiles to tilt the virtual image plane while maintaining uniform pixel mapping. The curved surfaces correct the trapezoidal distortion that would otherwise result from simple planar tilting, preserving image quality and effective pixel count.
Solution Approach 2:
The patent applies different curvature characteristics to different regions of the lens and mirror surfaces. The free curved surfaces are designed with position-dependent optical powers that locally compensate for the tilting effect, ensuring that each region of the virtual image plane maintains proper pixel density and geometric accuracy.
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 minimal optical setup that supports a tilted virtual image plane, reducing the device's size and maintaining image quality by correcting distortion and increasing the number of effective pixels.
Implementation Method 1
The eyepiece optical system includes a free curved surface lens and a free curved surface concave mirror in order from the image forming unit side along an emission direction of image light
Implementation Method 2
the eyepiece optical system includes a free curved surface lens and a free curved surface concave mirror in order from the image forming unit side along an emission direction of the image light
Data Source
AI summary
It is an object of the present invention to provide a projection optical system having a minimal optical configuration while ensuring necessary capabilities and a head-up display device having a tilted virtual image plane. The head-up display device according to the present invention includes an image forming unit to emit image light containing image information and an eyepiece optical system to display a virtual image by reflecting the image light. While a virtual image plane is tilted to display a virtual image in a range from a far distance to a near distance, a point on the image forming unit conjugating to a far point on the virtual image plane is optically farther from a light flux entering the image forming unit than a point on the image forming unit conjugating to a near point on the virtual image plane.