CMOS Optical Sensor Angular Response via Light Shielding
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Solution Overview
Problem
Wearable biometric monitoring devices face interference from ambient side light due to non-perfect skin contact, which reduces the Signal-to-Noise Ratio (SNR) of optical sensors.
Innovation Solution
An optical sensor based on CMOS technology with integrated light shielding means that defines a specific angular range for incident light, using metal and dielectric layers to block light outside this range and allow only light within the defined range to reach the photodetector active areas, ensuring parallel optical paths and uniform photodetector active areas for enhanced light shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the optical sensor is used in wearable devices with non-perfect skin contact, then the device can be worn comfortably, but ambient side light interferes with the detection and reduces Signal-to-Noise Ratio
Solution Approach 1:
The patent applies local quality by creating a light-transmissive structure with a specific aperture that selectively allows light from a defined volume of the user's body to reach the photodetector while blocking ambient side light. This localized optical path control improves signal quality without affecting the overall wearable comfort
Solution Approach 2:
The light-transmissive structure acts as an intermediary element between the photodetector and the user's body. It defines a preferential detection volume and filters light paths, allowing only relevant biometric light signals to reach the sensor while blocking harmful ambient light interference
2Reliability
If a light-transmissive structure with aperture mask is added to block side light, then Signal-to-Noise Ratio improves, but device complexity increases
Solution Approach 1:
The patent merges the light-transmissive structure with the existing wearable device housing or mounting structure. By integrating the aperture-containing structure into the device body rather than adding it as a separate component, the solution improves signal quality while minimizing the increase in device complexity
Solution Approach 2:
The light-transmissive structure can be implemented as a thin film or molded structure with integrated aperture patterns. This approach adds minimal bulk and complexity while effectively defining the optical detection path and blocking side light interference
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 minimizes side light interference, improving the Signal-to-Noise Ratio and enhancing the accuracy of biometric measurements by ensuring only light within a specific angular range reaches the photodetectors, thus reducing noise and improving measurement precision.
Implementation Method 1
each comprising a respective photodetector active area... designed to provide a respective output electrical signal related to incident light impinging on the respective photodetector active area
Implementation Method 2
light shielding means, that are formed in or on the multilayer structure and are made of one or more materials reflecting and/or absorbing incident light
Implementation Method 3
light shielding means, that are formed in or on the multilayer structure and are made of one or more materials reflecting and/or absorbing incident light
Data Source
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AI summary
The present invention relates to an optical sensor based on CMOS technology and comprising: a semiconductor substrate (21,31); an array of photocells (2,3), each of which includes a respective photodetector active area (11,12,22,32) that is formed in the semiconductor substrate (21,31) and is exposed on a given planar surface (13) of said semiconductor substrate (21,31), each photocell (2,3) being designed to provide a respective output electrical signal related to incident light impinging on the respective photodetector active area (11,12,22,32); a multilayer structure (23,33), that includes metal and dielectric layers and is formed on the given planar surface (13) of the semiconductor substrate (21,31); and light shielding means (14,15,24,35), that are formed in or on the multilayer structure (23,33) and are made of one or more materials reflecting and/or absorbing incident light impinging on said light shielding means (14,15,24,35); wherein each photodetector active area (11,12,22,32) is associated with a corresponding optical path (26,36) extending through the light shielding means (14,15,24,35) and directed towards said photodetector active area (11,12,22,32) to allow incident light with incident direction falling within a given direction range to reach said photodetector active area (11,12,22,32). The optical sensor is characterized in that: all the photocells (2,3) are connected in parallel to provide an overall output electrical signal related to incident light impinging on all the photodetector active areas (11,12,22,32); and all the optical paths (26,36) are parallel to a given direction thereby causing all the photodetector active areas (11,12,22,32) to be reached by incident light with incident direction parallel to said given direction.