Folded Camera Prism Light Blocking Element Stray Light
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Solution Overview
Problem
Folded cameras face the challenge of stray light entering the lens due to the prism intersecting the full camera cone of vision, leading to double-reflected stray light (DRSL) that can reach the image sensor, causing image quality issues.
Innovation Solution
The implementation of a light blocking element, such as a facet or cover, positioned between the lens and the prism, or on the prism's surfaces, to prevent DRSL from reaching the image sensor, including tilted facets and opaque masks to redirect or block stray rays effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the prism intersects the full camera cone of vision to enable compact folded camera design, then the camera size is reduced, but double-reflected stray light reaches the image sensor causing image quality degradation
Solution Approach 1:
The solution segments the optical path by introducing light blocking elements (such as facets or covers) that divide the camera cone of vision into valid image-forming rays and stray light paths. These blocking elements are positioned to intercept only the double-reflected stray light while allowing legitimate light rays to reach the sensor, thus resolving the contradiction between compact size and stray light prevention.
Solution Approach 2:
Light blocking elements serve as intermediary components between the prism and the image sensor. These intermediaries selectively block harmful double-reflected stray light rays without interfering with the primary optical path, enabling the compact folded camera design to maintain image quality by mediating between the space-saving prism configuration and the need for stray light rejection.
2Object-affected harmful factors
If light blocking elements are added to prevent stray light, then image quality is improved, but device complexity increases
Solution Approach 1:
The light blocking elements are merged with existing optical components rather than being completely separate additions. For example, facets are integrated into the prism structure itself, and covers are combined with the lens assembly. This merging approach prevents stray light while minimizing the increase in device complexity by utilizing existing structural elements for dual purposes.
Solution Approach 2:
The light blocking elements serve multiple functions: they block double-reflected stray light, maintain the compact folded optical path, and can be designed to work with the existing prism and lens structures. By making these elements multi-functional, the solution improves image quality without proportionally increasing device complexity, as the same structural elements perform both stray light blocking and optical path management.
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 construction effectively prevents double-reflected stray light from reaching the image sensor, enhancing image quality by ensuring only intended light rays form images on the sensor, thereby improving camera performance within size constraints.
Implementation Method 1
a reflecting element such as a prism that folds an optical path from a first optical path to a second optical path that is substantially orthogonal to the first optical axis
Implementation Method 2
Reflection surface 102c is typically covered with a reflective material (e.g. a metal or dielectric) such that the majority of light (more than 90%, or more than 99% or more than 99.9%) is reflected off the surface
Implementation Method 3
Light arriving to entrance and exit surfaces 102a and 102b will pass through with some refractions, and may have some reflections due to change of refractive index of prism transparent material and air
Implementation Method 4
in particular in some cases may suffer from total internal reflection (TIR), as known in the art
Data Source
AI summary
Folded cameras comprising a lens having a lens optical axis, an image sensor and a prism for folding light from a first optical path to a second optical path along the lens optical axis towards the image sensor, wherein the camera has a full camera cone of vision, wherein the prism intersects the full camera cone of vision, and wherein a camera has a construction that prevents double reflected stray light from reaching the image sensor.