Spectral-Filter Image Sensor Layout for Autofocus Crosstalk Suppression
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Solution Overview
Problem
Phase-detection autofocus image sensors in compact cameras suffer from optical crosstalk due to light reflection from shields, affecting focus accuracy.
Innovation Solution
A crosstalk-suppressing image sensor design featuring a semiconductor substrate with a photodiode, an opaque layer partially covering the light-exposure region, and a spectral filter adjacent to the opaque layer, which absorbs oblique optical rays and reduces crosstalk by blocking unwanted light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shields are used to restrict illumination angles for phase detection, then phase detection capability is improved, but optical crosstalk increases due to light reflection from the shields
Solution Approach 1:
A spectral filter layer is introduced as an intermediary component between the shield structure and the photodiode. This filter selectively transmits the wavelength range of interest while blocking reflected light that causes crosstalk, thereby mediating between the phase detection requirement and the crosstalk suppression need
Solution Approach 2:
The spectral filter is applied locally at specific positions adjacent to the opaque layer, creating different optical properties in different regions. The filter allows desired light to reach the photodiode while blocking reflected light from the shield, providing localized crosstalk suppression without affecting overall phase detection capability
2Measurement precision
If opaque layers are added to block light for phase detection, then phase detection capability is improved, but device complexity increases
Solution Approach 1:
The spectral filter layer serves multiple functions simultaneously: it acts as a wavelength selector for phase detection, a crosstalk suppressor by blocking reflected light, and potentially an anti-reflective element. This multi-functionality reduces the need for additional separate components, thereby managing device complexity
Solution Approach 2:
The spectral filter is integrated with the existing sensor structure, combining the phase detection functionality with the crosstalk suppression function in a single layered structure. The filter is positioned adjacent to the opaque layer, merging multiple optical control functions into one compact arrangement
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 optical crosstalk, enhancing focus accuracy and image quality in compact cameras by ensuring only intended light reaches the photodiode, thereby improving phase-detection autofocus performance.
Implementation Method 1
a spectral filter adjacent to the opaque layer in the image-plane direction, and partially covering the light-exposure region... which absorbs oblique optical rays and reduces crosstalk by blocking unwanted light
Data Source
AI summary
A crosstalk-suppressing image sensor includes a semiconductor substrate, an opaque layer, and a spectral filter. The semiconductor substrate includes a photodiode therein and is located beneath a light-exposure region of a back surface of the semiconductor substrate. The opaque layer is on the back surface, partially covers the light-exposure region, and has an opaque-layer thickness perpendicular to an image-plane direction parallel to the back surface. The spectral filter is adjacent to the opaque layer in the image-plane direction, and partially covers the light-exposure region.