3D-Integrated Optical Sensor Spectral Shift Control
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Solution Overview
Problem
Optical sensors face performance limitations due to spectral shift issues when the angle of incidence increases, particularly in ambient light and true color sensors, which existing solutions like mechanical apertures and diffusers struggle to address effectively, especially in mobile device applications where height constraints are a challenge.
Innovation Solution
A 3D-Integrated optical sensor design incorporating a semiconductor substrate, integrated circuit, wiring, a filter layer with direction-dependent transmission characteristics, a transparent spacer layer, and an on-chip diffuser, which limits spectral shift by establishing a defined working distance between the filter and diffuser, allowing for a wider field of view without the need for complex filter redesign or external components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the angle of incidence of incoming light is increased to widen the field of view, then the field of view is improved, but the spectral shift increases causing performance degradation
Solution Approach 1:
A diffuser layer is introduced as an intermediary between the optical sensor and the interference filter. This diffuser scatters incoming light at various angles, creating a distribution of incident angles on the filter that compensates for the blue-shifting effect, thereby maintaining spectral accuracy while enabling a wider field of view
Solution Approach 2:
The interference filter is redesigned with adjusted optical and material parameters, specifically modifying the thickness and refractive indices of the dielectric layers. This parameter optimization reduces the spectral shift sensitivity to angle of incidence, allowing the filter to maintain performance across a wider angular range
2Measurement precision
If mechanical apertures are mounted to limit the angle of incidence, then spectral shift is reduced, but the device height increases which is incompatible with mobile device requirements
Solution Approach 1:
The mechanical aperture system is replaced with an optical solution using a diffuser layer and optimized interference filter. This substitution eliminates the need for bulky mechanical components while achieving the same spectral control function, thereby reducing device height
Solution Approach 2:
Instead of controlling light angles through mechanical structures in the vertical dimension, the solution uses optical scattering in the horizontal dimension via the diffuser layer. This dimensional shift allows spectral control without increasing device height
3Adaptability or versatility
If diffusers are attached to optical sensors to widen field of view, then field of view is improved, but complex simulations and filter redesign are required which increases device complexity
Solution Approach 1:
The interference filter parameters (layer thickness, refractive indices) are optimized through systematic design methods to pre-compensate for the diffuser's angular scattering effect. This parameter tuning allows the filter to work effectively with the diffuser without requiring complex adaptive control systems
Solution Approach 2:
The filter design is pre-optimized during the manufacturing stage to account for the diffuser's optical properties. This preliminary design adjustment eliminates the need for complex real-time simulations or adaptive control, simplifying the overall device complexity
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 design reduces spectral shift, enhances the field of view, and maintains low z-height and process complexity, making it suitable for mobile devices while avoiding the need for mechanical apertures and external diffusers, with cost-effective manufacturing through wafer-level semiconductor processes.
Implementation Method 1
Their optical properties are due to multiple thin layers of dielectric material having different refractive indices
Implementation Method 2
multiple thin layers of dielectric material having different refractive indices
Implementation Method 3
an on-chip diffuser which limits spectral shift by establishing a defined working distance between the filter and diffuser
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~4C
AI summary
A 3D-Integrated optical sensor comprises a semiconductor substrate (100), an integrated circuit (200), a wiring (300), a filter layer (400), a transparent spacer layer (500), and an on-chip diffuser (600). The semiconductor substrate (100) has a main surface (110). The integrated circuit (200) comprises at least one light sensitive area (210) and is arranged in the substrate (100) at or near the main surface (110). The wiring (300) provides an electrical connection to the integrated circuit (200) and is connected to the integrated circuit (200), The wiring (300) is arranged on or in the semiconductor substrate (100). The filter layer (400) has a direction dependent transmission characteristic and is arranged on the integrated circuit (200). In fact, the filter layer (400) at least covers the light sensitive area (210). The transparent spacer layer (500) is arranged on the main surface (110) and, at least partly, encloses the filter layer (400). A spacer thickness is arranged to limit a spectral shift of the filter layer (400). The on-chip diffuser (600) is arranged on the transparent spacer layer (500).