Image Projection Optics Using Angle-Dependent Light Rejection
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Solution Overview
Problem
Conventional image projection devices struggle to effectively mitigate temperature rises in image radiation units due to external light while maintaining the quality of projected images.
Innovation Solution
The image projection device incorporates an angle-dependent light transmission unit that changes transmittance based on incidence angle, disposed in the optical path to differentiate between radiation light and external light, thereby reducing external light incidence on the image radiation unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If free-form surface mirrors are used to reflect radiation light, then the image can be projected to the driver's viewpoint, but external light is collected on the image radiation unit surface causing temperature rise and deterioration
Solution Approach 1:
A polarizing plate is introduced as an intermediary component between the image radiation unit and the free-form surface mirrors. This polarizing plate selectively transmits polarized light from the image radiation unit while blocking external light, thereby mediating the conflict between image projection and external light rejection. The polarizing plate converts the unpolarized external light into blocked energy while allowing the polarized radiation light to pass through, solving the temperature rise problem without compromising image brightness.
Solution Approach 2:
The invention changes the polarization state parameter of the light. By placing a polarizing plate in the optical path, the radiation light's polarization parameters are modified. This parameter change enables the system to distinguish between radiation light (which has specific polarization characteristics after passing through the polarizing plate) and external light (which is blocked by the polarizing plate), thereby resolving the contradiction between maintaining image brightness and preventing temperature rise.
2Temperature
If a shielding part or infrared cutoff filter is disposed near the intermediate image formation position, then external light influence is reduced, but the device complexity increases
Solution Approach 1:
The polarizing plate serves multiple functions simultaneously: it acts as a polarizer for the radiation light, a beam splitter for separating radiation light and external light paths, and a heat rejection filter for blocking external light. This multi-functionality eliminates the need for separate shielding parts or infrared cutoff filters, thereby reducing device complexity while still achieving temperature control.
Solution Approach 2:
The invention merges the functions of light polarization, beam splitting, and heat rejection into a single polarizing plate component. By combining these previously separate functions into one element, the optical system complexity is reduced while maintaining the ability to mitigate external light influence and control temperature.
3Illumination intensity
If the transmittance of the angle-dependent light transmission unit is increased to maintain image quality, then more external light also reaches the image radiation unit
Solution Approach 1:
The invention uses a composite optical system combining a polarizing plate with angle-dependent light transmission characteristics. This composite structure leverages both polarization selection and angle-dependent transmittance properties to achieve high image brightness while simultaneously blocking external light. The combination of these two light control mechanisms creates a synergistic effect that resolves the contradiction between image quality and external light rejection.
Solution Approach 2:
The angle-dependent light transmission unit utilizes curved or bent geometry to control light paths. The curvature enables different incidence angles for radiation light and external light, allowing the unit to transmit radiation light effectively while blocking external light. This geometric approach maintains image brightness without increasing external light incidence on the image radiation unit.
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 mitigates temperature rises in the image radiation unit while maintaining the quality of projected images by selectively transmitting radiation light and blocking external light.
Implementation Method 1
an angle-dependent light transmission unit of which transmittance of light in a predetermined polarization plane changes depending on an incidence angle
Implementation Method 2
a reflection-transmission unit that reflects radiation light from the image radiation unit at a front surface and transmits light from a back surface
Data Source
AI summary
An image projection device is provided that can effectively mitigate a temperature rise of an image radiation unit due to external light while maintaining the quality of a projected image. The image projection device includes an image radiation unit that radiates an image, a reflection-transmission unit that reflects radiation light from the image radiation unit at a front surface and transmits light from a back surface, and an angle-dependent light transmission unit of which transmittance of light in a predetermined polarization plane changes depending on an incidence angle. The angle-dependent light transmission unit is disposed in an optical path of the radiation light from the image radiation unit to the reflection-transmission unit.