Solid-State Imaging Element Structure for Spectral Ripple Suppression
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Solution Overview
Problem
Conventional solid-state imaging elements experience significant ripple in spectral spectra due to interference between light reflected by the light receiving surface and the color filter, which degrades accuracy in applications like biometric authentication and vegetation surveys.
Innovation Solution
A solid-state imaging element with a surface layer thicker than half the coherence length of incident light, a filter layer that transmits target light and reflects the rest, and a photoelectric conversion layer, optionally including antireflection films, silicon dioxide, transparent resin, or stress relaxation layers, and surface plasmon resonance or Fabry-Perot filters, to minimize optical path differences and reduce ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a color filter is used to transmit desired wavelength light, then spectral spectrum can be obtained, but ripple occurs due to interference between reflected light from the light receiving surface and reflected light from the color filter
Solution Approach 1:
A surface layer is introduced as an intermediary component between the incident light and the color filter. This surface layer has a thickness of 0.5 micrometers or more, which is designed to be equal to or greater than the coherence length of incident light, thereby suppressing interference effects and reducing ripple in the spectral spectrum while maintaining the color filter's wavelength selection function.
Solution Approach 2:
The thickness of the surface layer is specifically controlled to be 0.5 micrometers or more, matching the coherence length of incident light. This parameter change transforms the optical path difference between reflected light waves, causing them to fall outside the coherence length range and thus suppressing interference. Additionally, an antireflection film may be applied to further reduce reflectance and minimize interference effects.
2Object-generated harmful factors
If the surface layer thickness is increased to suppress ripple, then interference is reduced, but device complexity increases
Solution Approach 1:
Instead of adding multiple complex layers, the solution changes the thickness parameter of the existing surface layer to be 0.5 micrometers or more. This single parameter adjustment effectively suppresses ripple by ensuring the optical path difference exceeds the coherence length of incident light, maintaining device simplicity while achieving the desired effect.
Solution Approach 2:
The surface layer is designed as a simple, thin film structure that can be easily formed during manufacturing. By using a straightforward thickness specification (0.5 micrometers or more) rather than complex multilayer structures, the solution reduces manufacturing complexity and cost while effectively addressing the ripple problem.
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 effectively suppresses ripple in spectral spectra, enhancing accuracy in biometric authentication and vegetation surveys by reducing interference and maintaining signal quality.
Implementation Method 1
the surface layer may include an antireflection film. This brings about an action that a reflectance of the surface layer is reduced.
Implementation Method 2
there is a possibility that the ripple will become large due to interference between light reflected by a light receiving surface of the solid-state imaging element and light reflected by the color filter
Implementation Method 3
a photoelectric conversion layer that photoelectrically converts the predetermined target light transmitted through the filter layer
Data Source
AI summary
A ripple is suppressed in a solid-state imaging element that obtains a spectral spectrum. The solid-state imaging element includes a surface layer, a filter layer, and a photoelectric conversion layer. In the solid-state imaging element, the surface layer has a thickness exceeding a half of a coherence length of incident light. Furthermore, in the solid-state imaging element, the filter layer transmits predetermined target light of the incident light transmitted through the surface layer and reflects a rest of the incident light transmitted through the surface layer to the surface layer. Furthermore, in the solid-state imaging element, the photoelectric conversion layer photoelectrically converts the predetermined target light transmitted through the filter layer.