Optical Filter Radial Refractive Index Circular Sun Image
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Solution Overview
Problem
Current optical filters used in devices simulating natural light struggle to produce a spatially uniform luminance and angular profile that replicates the characteristics of sunlight, leading to unwanted ghost images and non-circular sun shapes, which compromise the realistic reproduction of a clear sky and sun.
Innovation Solution
An optical filter with a radial profile of refractive index and cylindrical elements that prevents light cross-talk between channels, ensuring a substantially constant angular luminance within a defined cone and zero elsewhere, eliminating ghost images and allowing for a circular sun image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a tandem mixer with square or rectangular lenses is used, then the device complexity is reduced and manufacturing is simplified, but the sun image produced is not circular and additional filters are required
Solution Approach 1:
The patent applies spheroidality by using circular lenses instead of square or rectangular ones in the tandem mixer. This curvature change directly produces a circular sun image in the far field, eliminating the need for additional spatial filters and diffusers that would be required to correct the shape when using rectangular lenses.
2Shape
If additional spatial filters and diffusers are used to correct ghost images and shape, then the sun image quality is improved, but the device complexity and manufacturing costs increase
Solution Approach 1:
The patent extracts and removes the problematic additional spatial filters and diffusers from the optical system. By using circular lenses from the outset, the design eliminates the need for these corrective components, thereby reducing device complexity and manufacturing costs while maintaining high image quality.
Solution Approach 2:
The patent applies preliminary action by correctly selecting circular lenses at the design stage, which prevents the formation of ghost images and non-circular sun shapes before they occur. This proactive approach eliminates the need for corrective measures downstream, simplifying the overall system.
3Shape
If circular lenses are used in the tandem mixer, then the sun image is circular and additional filters are eliminated, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by modifying the lens geometry parameter from square/rectangular to circular. This change simplifies the optical path and eliminates the need for additional corrective components, thereby reducing overall manufacturing precision requirements despite the inherent precision needed for circular lens fabrication.
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 solution achieves a sharp, circular sun image in contrast to a clear sky, eliminating the need for additional spatial filters and diffusers, while maintaining high luminance uniformity and industrial scalability.
Implementation Method 1
The channels have a refractive index whose value decreases starting from a maximum refractive index along a radially outward direction away from a channel axis passing through a centre of gravity of a section of the channel, so that a radial profile of refractive index of the channels is defined. The radial profile of refractive index of the channels is configured such that the light rays crossing any channel of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face of the channel exit the channel with substantially parallel directions.
Data Source
AI summary
The present invention relates to an optical filter (100) comprising a substantially flat entry surface (101), a substantially flat exit surface (102) parallel to the entry surface, a plurality of channels (103) made of a material substantially transparent to light, wherein the channels (103) of the plurality of channels comprise an entry face (104), an exit face (105) and a lateral surface extending perimetrically between the entry face (104) and the exit face (105) over a length (L) of the channels (103), are arranged side by side and parallel to each other so as to define a plurality of interspaces between adjacent channels (103), have a channel axis (Y) incident to the entry (101) and exit (102) surface, and are arranged with the entry face (104) substantially overlapping the entry surface (101) and with the exit face (105) substantially overlapping the exit surface (102), at least one element of optically absorbing and/or non-transparent material (108, 109; 109′) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light between adjacent channels (103) of the plurality of channels and so as to reduce the passage of light parallel to the channels and externally thereto, or at least a first element of optically absorbing material (108) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light between adjacent channels (103) of the plurality of channels (103) and at least a second element of optically non-transparent material (109; 109′) configured and arranged with respect to channels (103) so as to reduce and/or substantially prevent the passage of light parallel to the channels (103) and externally thereto through interspaces between adjacent channels (103); wherein the channels (103) have a refractive index whose value decreases starting from a maximum refractive index (na) along a radially outward direction away from the channel axis (Y) passing through a centre of gravity of a section of the respective channel (103), so as to define a radial profile of refractive index of the channels, and wherein the radial profile of refractive index of the channels (103) is configured such that the light rays crossing any channel (103) of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face (104) of the channel exit the exit face (105) of the channel with substantially parallel directions.