Optical Sensor Isolation via Barrier Walls
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Solution Overview
Problem
Existing physiological monitoring devices face challenges in accurately and reliably measuring physiological parameters due to issues with optical sensor design, including optical isolation of light sources and detectors, secure skin contact, and movement during exercise, which affect accuracy and battery life.
Innovation Solution
The design incorporates optical sensor arrangements with spaced apart light sources and detectors, mounted in transparent lenses or epoxy layers within a caseback, and uses barrier walls and opaque layers to ensure optical isolation, along with adjustable protrusion mechanisms for secure skin contact and reduced movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light sources and photodiodes are positioned close together in the optical sensor, then the device size is reduced and power consumption is lowered, but optical isolation becomes difficult and measurement accuracy deteriorates
Solution Approach 1:
The optical sensor is divided into separate functional zones: a light source region with LEDs and a detector region with photodiodes, physically separated by barrier walls extending from the caseback. This segmentation allows close positioning while maintaining optical isolation through the partition structure.
Solution Approach 2:
Barrier walls and opaque layers are introduced as intermediary structures between the light sources and photodiodes. These intermediaries block direct light paths while allowing the components to remain in close proximity, solving the optical isolation problem without increasing overall device complexity.
2Measurement precision
If the optical sensor is firmly positioned against the skin, then light transmission through tissue is improved and ambient light interference is reduced, but movement during exercise increases and comfort decreases
Solution Approach 1:
The optical sensor assembly is designed with adjustable protrusion capability, allowing it to dynamically adapt between firm contact mode (for accurate measurement) and relaxed mode (for comfort during exercise). The sensor can be positioned to protrude slightly from the caseback to maintain consistent skin contact despite movement.
Solution Approach 2:
Only the optical sensor portion protrudes from the caseback to maintain skin contact, while the rest of the device remains comfortable against the wrist. This localized protrusion ensures measurement accuracy without compromising overall device comfort or stability during exercise.
3Measurement precision
If the optical sensor protrudes from the caseback, then skin contact is improved and measurement accuracy increases, but device waterproofing becomes more difficult and structural integrity is compromised
Solution Approach 1:
The barrier walls serve as intermediary structures that extend from the caseback interior to the exterior surface, creating optical isolation while maintaining the caseback's structural integrity. These walls allow the optical sensor to be positioned at the surface without creating openings that would compromise waterproofing.
Solution Approach 2:
The caseback is designed as a continuous protective shell that encapsulates the optical sensor assembly. The barrier walls and opaque layers are integrated into this shell structure, maintaining waterproofing while allowing the sensor to contact the skin through the shell's surface.
4Ease of manufacture
If multiple optical components are integrated into a single lens or epoxy layer, then manufacturing is simplified and device complexity is reduced, but optical isolation between components becomes more difficult
Solution Approach 1:
The optical sensor assembly is segmented into distinct light source and detector regions, with barrier walls creating separate optical zones within the lens or epoxy layer. This segmentation allows simplified manufacturing through single-lens or epoxy encapsulation while maintaining optical isolation through the partition structure.
Solution Approach 2:
Different regions of the single lens or epoxy layer are assigned different optical functions: some regions transmit light from LEDs while other regions direct light to photodiodes. The barrier walls create local optical properties that ensure isolated light paths despite the unified encapsulation structure.
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 configuration enhances the accuracy, reliability, and durability of physiological monitoring devices by ensuring that only reflected light is detected, improving battery life and maintaining device integrity during exercise.
Implementation Method 1
Optical energy emitted by the light sources passes through the skin of the targeted tissue region, is scattered, partially absorbed, and is reflected by blood flowing through arteries
Implementation Method 2
The reflected optical energy is in effect modulated in accordance with blood flow in the targeted area and detected by the photo detector
Implementation Method 3
one or more associated optical detectors that receive a portion of the optical energy emitted by the light sources
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Described herein are systems and methods for optically isolating components of an optical sensor in physiological monitoring devices worn by a user to sense, measure, and/or display physiological information. An optical sensor may be mounted in the rear face of the device, emit light proximate a targeted area of a user's body, and detect light reflected from the targeted area. Optically isolating structure may be located at least partially between one or more components of the optical sensor to ensure that light detected by the sensor is light reflected from the targeted area rather than light emitted directly from a light source and/or ambient light. The optically isolating structure may, in some cases, extend between a contact surface of the monitoring device to a base portion of the sensor components or a surface of a circuit board to which the sensor components are mounted.