Projection Optical System Ghost Image Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional projection display apparatuses suffer from image quality deterioration due to reflections on lens surfaces, which lead to ghost images and reduced contrast in projected and captured images.
Innovation Solution
A projection optical system is designed with a configuration where each lens surface satisfies specific conditions (1), (2), and (3) to minimize the impact of reflections, ensuring that the focal depth of ghost images is offset and the light intensity of ghost light is reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional projection optical systems are used, then the system structure is simple, but ghost images are formed and image quality deteriorates due to reflections on lens surfaces
Solution Approach 1:
The patent applies parameter changes by adjusting the curvature radius and position of lens surfaces to satisfy specific mathematical conditions. Condition (1) specifies that the curvature radius r and position d must satisfy r/d > 0.05, and condition (2) specifies that the reflected ray height H must satisfy H < f * D / (2F), where f is focal length, D is display surface half-diagonal, and F is f-number. By optimizing these parameters, the system reduces ghost image formation while maintaining a relatively simple optical structure.
2Object-affected harmful factors
If lens surfaces are designed to minimize reflections, then ghost image formation is suppressed, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific parameter ranges for lens design: curvature radius r must be greater than 0.05 times the spacing d between lens surfaces. This parameter optimization allows standard manufacturing capabilities to achieve the desired reflection suppression without requiring ultra-precision fabrication. The conditions provide practical design guidelines that balance performance with manufacturability.
Solution Approach 2:
The patent converts the harmful effect of light reflection into a beneficial design constraint. Instead of trying to eliminate reflections entirely (which would require complex anti-reflection coatings or multiple lens elements), the design accepts reflections but controls their impact by ensuring that reflected rays converge at specific locations away from the display surface. This transforms the reflection problem into a manageable geometric constraint that simplifies manufacturing.
3Manufacturing precision
If the optical system is designed with specific lens configurations, then image quality improves, but the design and optimization process becomes more complex
Solution Approach 1:
The patent provides explicit mathematical conditions that designers can directly apply: (1) r/d > 0.05 for curvature and spacing, and (2) H < f * D / (2F) for ray height control. These closed-form conditions eliminate the need for complex iterative optimization processes, allowing designers to achieve high image quality by straightforwardly applying the formulas during the design phase.
Solution Approach 2:
The patent replaces complex mechanical/optical optimization processes with mathematical modeling and analytical conditions. Instead of relying on trial-and-error mechanical adjustment or complex ray-tracing software optimization, the design uses paraxial ray tracing mathematics to derive precise design equations. This substitution simplifies the design process while maintaining high image quality standards.
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
The proposed solution effectively suppresses the formation of ghost images, thereby improving the contrast and image quality of both projected videos and captured images in projection display apparatuses.
Implementation Method 1
a plurality of lenses... projects projection light output from a video display element
Implementation Method 2
The projection light having reflected on lens surfaces of the plurality of lenses form a ray passing through the projection optical system in a backward direction
Data Source
AI summary
A projection optical system includes a plurality of lenses. The projection optical system projects projection light, to display an image formed on the video display element onto a projection target. The projection light having reflected on lens surfaces of the plurality of lenses form a ray passing through the projection optical system. Each lens surface, among the lens surfaces in the projection optical system, satisfies |X|>f/2. Where, in ray tracing using paraxial ray tracing with a marginal ray of an axial light flux passing through the projection optical system, when a first ray is a reflection of the marginal ray propagated backwards on the display surface, X denotes a distance between the display surface and a convergence plane where a reflection of the first ray on the lens surface converges, and f denotes a focal length of an entire system of the projection optical system.