Projection Screen Leakage Light Control via Intermediary Optical Member
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Solution Overview
Problem
Image display apparatuses face a challenge in reducing noise caused by leakage light, which decreases their merchantability due to limitations in diffraction efficiency of transmission-type holograms, leading to 0-order light being projected onto surfaces other than the intended screen.
Innovation Solution
Incorporating a first optical member downstream of the irradiated member on the light path, which reflects or diffuses the 0-order light, reducing leakage by using a combination of transmission-type diffusion HOE and reflection-type mirror HOE to control the incidence angle and redirect unwanted light internally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a transmission-type hologram is used for the screen, then the screen can be thin and lightweight, but leakage light (0-order light) is projected onto surfaces other than the intended screen, causing noise and decreasing merchantability
Solution Approach 1:
A first optical member is introduced as an intermediary element between the output section and the screen. This optical member selectively reflects or diffuses the 0-order light (leakage light) while allowing the diffracted image-forming light to pass through, thereby mediating between the thin-screen requirement and the noise-reduction requirement
Solution Approach 2:
The first optical member is designed with spatially varying optical properties - it has different reflectivity and diffusivity characteristics for different regions of the light spectrum and different incident angles, enabling it to selectively handle 0-order light versus image-forming light based on local optical quality requirements
2Object-generated harmful factors
If the diffraction efficiency of the transmission-type hologram is increased to reduce leakage light, then less noise is generated, but the manufacturing precision and complexity of the hologram increase
Solution Approach 1:
The optical system is segmented into multiple functional components: the transmission-type hologram for image formation and the first optical member for leakage light control. This segmentation allows each component to be optimized independently - the hologram for image quality and the optical member for noise reduction - rather than requiring the hologram alone to perform both functions at high precision
3Object-generated harmful factors
If additional optical members are added to control leakage light, then noise is reduced, but the device complexity and component count increase
Solution Approach 1:
The first optical member is designed to perform multiple functions simultaneously: it reflects 0-order light to prevent noise, diffuses some light to improve screen uniformity, and allows image-forming light to pass through. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving noise reduction
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 significantly reduces leakage light, enhancing image quality, contrast, and transparency by minimizing noise that affects merchantability and simplifying the attachment process while potentially reducing component count and costs.
Implementation Method 1
a first optical member that is disposed downstream of the irradiated member on a light path of the projection light, and reflects or diffuses a portion of the projection light that has transmitted through the irradiated member
Implementation Method 2
a first optical member that is disposed downstream of the irradiated member on a light path of the projection light, and reflects or diffuses a portion of the projection light that has transmitted through the irradiated member
Data Source
AI summary
An image display apparatus according to one embodiment of the present disclosure includes: an output section that outputs projection light along a predetermined axis; an irradiated member to be irradiated with the projection light; and a first optical member that is disposed downstream of the irradiated member on a light path of the projection light, and reflects or diffuses a portion of the projection light that has transmitted through the irradiated member.