Image Projection Apparatus Polarization Control for Curved Surfaces
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Solution Overview
Problem
Existing image projection apparatuses face degradation in brightness when projecting polarized image light onto asymmetrically curved surfaces, such as vehicle windshields, due to the mismatch in rotational positions between the projected and intermediate images, which affects the polarization state of light passing through plural-film optical members.
Innovation Solution
The image projection apparatus sets the image rotational position relationship between the projected and intermediate images with a difference, ensuring the polarization axis of incident light on the plural-film optical member is parallel or perpendicular to its plane of incidence, thereby suppressing unwanted polarization changes and maintaining image brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the image rotational position relationship between projected image and intermediate image is set with a difference to improve image quality on asymmetrically curved surfaces, then the brightness degradation is suppressed, but the polarization state control becomes more difficult
Solution Approach 1:
The patent applies asymmetry by intentionally setting a rotational position difference between the projected image and intermediate image, and by orienting the polarization axis at specific angles (parallel or perpendicular to the plane of incidence) rather than maintaining perfect symmetry. This asymmetric configuration optimizes image quality on asymmetrically curved surfaces like windshields while controlling polarization effects through the plural-film optical member.
Solution Approach 2:
The patent changes the polarization axis orientation parameter to be either parallel or perpendicular to the plane of incidence of light on the plural-film optical member. This parameter adjustment allows the system to maintain desired polarization states while achieving the rotational position difference, thereby controlling brightness degradation through deliberate parameter modification.
2Illumination intensity
If polarized image light is projected through a plural-film optical member with rotational position difference, then image quality on curved surfaces improves, but unwanted polarization changes occur causing brightness degradation
Solution Approach 1:
The patent applies preliminary anti-action by pre-configuring the polarization axis orientation (parallel or perpendicular to the plane of incidence) before light interacts with the plural-film optical member. This preliminary setup counteracts potential unwanted polarization changes that would otherwise occur during projection, thereby maintaining polarization state stability and preventing brightness degradation.
Solution Approach 2:
The patent makes the polarization axis orientation configuration universal by setting it to work with both s-polarized and p-polarized light components depending on the specific application requirements. This multi-functional approach allows the same optical system to maintain reliability across different projection scenarios on curved surfaces by adjusting the polarization axis relative to the plane of incidence.
3Illumination intensity
If the polarization axis is aligned parallel or perpendicular to the plane of incidence, then brightness degradation is suppressed, but the setup complexity increases
Solution Approach 1:
The patent applies local quality by optimizing the polarization axis orientation specifically at the interface where light interacts with the plural-film optical member (parallel or perpendicular to the plane of incidence). This localized optimization ensures brightness is maintained at the critical interaction point without requiring complex adjustments throughout the entire optical system, thereby managing setup complexity effectively.
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 effectively reduces the degradation in brightness of the projected image by minimizing irregular polarization state changes, ensuring a higher amount of desired polarized light is reflected, even on curved surfaces.
Implementation Method 1
a cold mirror (a plural-film optical member) reflecting image light exiting the liquid-crystal panel toward the windshield of a vehicle
Implementation Method 2
the polarization axis of the image light incident on the plural-film optical member is parallel or perpendicular to a plane of incidence of the image light with respect to the plural-film optical member
Data Source
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AI summary
An image projection apparatus includes an intermediate image forming member configured to form an intermediate image from light emitted by a light source device; and a plural-film optical member on which image light that forms the intermediate image is incident. The image projection apparatus uses the image light that is incident on the plural-film optical member to project an image, an image rotational position relationship in a rotational direction around an image center axis between the image that is projected and the intermediate image is such that a difference is present in image rotational positions, and the plural-film optical member is set in such a manner that a polarization axis of the image light incident on the plural-film optical member is parallel or perpendicular to a plane of incidence of the image light with respect to the plural-film optical member.