Curved Fabry-Perot Filter Matrix for Angle-Insensitive Imaging
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Solution Overview
Problem
Existing Fabry-Perot cavity filters are highly sensitive to the angle of incidence of electromagnetic waves, requiring multiple lithography and etching steps, and are not suitable for use in imaging applications, particularly in CMOS image sensors due to manufacturing restrictions.
Innovation Solution
A multispectral filtering matrix with Fabry-Perot filters featuring curved reflective layers and varying dielectric layer thicknesses, designed to minimize angle sensitivity and enable imaging capabilities, using methods that reduce the need for complex manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional flat Fabry-Perot filters are used, then the manufacturing process is simple, but the filter is highly sensitive to the angle of incidence of electromagnetic waves
Solution Approach 1:
The patent applies curvature to the reflective layers of the Fabry-Perot filter. Specifically, the first and second reflective layers are formed with curved surfaces (spherical or aspherical) rather than flat surfaces. This curvature compensates for the angle of incidence effect by ensuring that light rays at different angles experience appropriate optical path differences, thereby maintaining wavelength selectivity across a wider angular range while keeping the manufacturing process relatively simple.
2Reliability
If multiple lithography and etching steps are used to reduce angle sensitivity, then the angle sensitivity is reduced, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The patent uses a single curvature formation step to achieve angle insensitivity, avoiding the need for multiple lithography and etching steps. The curved reflective layers are formed using conventional lithography and etching processes followed by a curvature induction step (such as reflow or specialized deposition), which significantly reduces the number of process steps compared to alternative approaches while effectively reducing angle sensitivity.
Solution Approach 2:
The patent changes the geometric parameter of the reflective layers from flat to curved, which fundamentally alters the optical behavior of the filter. This parameter change (curvature radius) allows the filter to compensate for angle of incidence effects without requiring complex multi-step lithography and etching processes, thereby reducing both device complexity and manufacturing complexity.
3Adaptability or versatility
If variable distance between plates is used to obtain different wavelengths, then multiple wavelengths can be obtained, but the filter cannot be used in imaging applications due to manufacturing restrictions
Solution Approach 1:
The patent uses curved reflective layers with specific radius of curvature to achieve wavelength selection while maintaining a fixed plate distance. The curvature allows different regions of the filter to transmit different wavelengths at different angles of incidence, enabling multi-wavelength capability without requiring variable plate distances. This approach maintains manufacturing compatibility with imaging applications by using fixed-structure Fabry-Perot cavities that can be integrated into CMOS image sensors.
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 provides wavelength transmission independent of the angle of incidence, allowing for efficient imaging in CMOS technology with reduced manufacturing complexity and microlens requirements.
Implementation Method 1
each colour filter forming a Fabry-Perot cavity including a first reflective layer, a second reflective layer, and a Fabry-Perot cavity layer of dielectric material between the first reflective layer and the second reflective layer
Implementation Method 2
The transmission of the filter is set up by adjusting thickness of the cavity. Thus, in operation, part of the incident light corresponding to the wavelength of the filter is transmitted through the same as a coloured beam, while the rest of the incident light is reflected
Implementation Method 3
The curved surfaces allow for an angle of incidence of the radiation that is not perpendicular to the surface at any point on the surface. The curvature of the plates is chosen so that the error introduced by the fact that the angle of incidence is not perpendicular is compensated for by the difference in distance between the plates
Data Source
AI summary
A multispectral filter matrix for an electromagnetic wave, the matrix including at least a first and a second optoelectronic element, each optoelectronic element including a colour filter and a photoelectric transducer facing the filter, each colour filter forming a Fabry-Perot cavity including a first reflective layer, a second reflective layer and a Fabry-Perot cavity layer of dielectric material between the first reflective layer and the second reflective layer, the layer of dielectric material including a lower surface, in contact with the first reflective layer; the lower surface being curved, an upper surface in contact with the second reflective layer, the upper surface being curved, the average thicknesses of the two layers of dielectric material of the two filters being different.