HUD Test Optics for Sharp Virtual Image Capture
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Solution Overview
Problem
Conventional testing devices struggle to capture the entire image sharply due to the limited depth of field and curvature of the windshield in contact-analog HUDs, leading to blurred and distorted images, especially with larger projection distances and areas.
Innovation Solution
Incorporation of an optical element, such as a curved mirror, to redirect radiation and compensate for image curvature and astigmatism, ensuring the entire virtual image lies within the camera's depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera unit with limited depth of field is used to capture the virtual image, then the device complexity is reduced, but the image becomes blurred due to field curvature and the image cannot be captured sharply across the entire area
Solution Approach 1:
A curved mirror is introduced as an intermediary optical element between the windshield and the camera unit. This mirror compensates for the field curvature caused by the windshield, enabling the camera to capture the entire virtual image sharply without increasing the complexity of the overall testing device.
Solution Approach 2:
A curved mirror with specific radius of curvature is used to counteract the field curvature effect. The curvature of the mirror is designed to match and compensate for the curvature of the virtual image formed by the windshield, allowing the entire image to lie within the camera's depth of field.
2Area of stationary object
If the projection distance is increased to at least 5 meters for contact-analog HUDs, then the HUD area and projection surface are enlarged, but the image curvature and astigmatism increase making evaluation difficult
Solution Approach 1:
The curved mirror serves as a compensating element that counteracts the increased image curvature and astigmatism resulting from the larger projection distance. This enables accurate evaluation of the expanded HUD area despite the longer optical path.
Solution Approach 2:
The radius of curvature of the mirror is specifically designed based on the projection distance and HUD area parameters. By adjusting the mirror's curvature parameter, the system compensates for the increased field curvature and astigmatism associated with larger projection distances.
3Device complexity
If the windshield is directly illuminated by the imaging unit, then the setup is simpler, but the curved geometry causes field curvature and astigmatism that blur the image
Solution Approach 1:
The curved mirror is positioned in the illumination path to pre-compensate for the windshield's curvature effects. This intermediary element modifies the light rays before they interact with the windshield, reducing field curvature and astigmatism in the resulting virtual image.
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
Enables sharp capture and evaluation of the entire HUD image, reducing space requirements and improving measurement accuracy by aligning the image within the camera's depth of field, suitable for contact-analog HUDs with large projection distances.
Implementation Method 1
The optical element is suitable and designed to redirect the radiation from the imaging unit towards the windshield and thereby illuminate the HUD area of the windshield to generate the virtual image
Implementation Method 2
The optical element reduces the curvature of the virtual image in space (field curvature), enabling the entire image to be captured sharply by the camera unit
Implementation Method 3
In addition to field curvature, astigmatism can also be compensated for by the optical element according to the invention
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~6(b)
AI summary
The present invention relates to a testing device for a head-up display (HUD), comprising at least - an imaging unit (8), - an optical element (13), which is suitable for diverting the radiation from the imaging unit (8) in the direction of a windscreen (1) and thereby irradiating an HUD area (B) of the windscreen (1) in order to generate a virtual image (7), - a positioning device (11), which is suitable for fixing the windscreen (1) in a defined arrangement with respect to the optical element (13), and - a camera unit (12), which is suitable for capturing the virtual image (7) through the windscreen (1) from different eye positions, the optical element (13) being configured such that the entire virtual image (7) lies within the depth of field range (Δd) of the camera unit (12).