Watch Crown Rotation Sensing Using Laser Doppler Detection
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Solution Overview
Problem
Existing wearable electronic devices face challenges in accurately detecting rotational inputs with high precision and efficiency, particularly in compact designs, due to the need for precise optical treatments or features on rotating surfaces.
Innovation Solution
The implementation of a laser-based optical sensing system that directs a laser beam onto a rotating surface at an oblique angle, utilizing vertical-cavity surface-emitting lasers (VCSELs) to detect changes in frequency of the reflected light, allowing for accurate determination of rotational speed and direction without requiring optical treatments or features on the rotating surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical sensing mechanisms are used to detect rotational movements, then measurement precision can be achieved, but the device complexity and manufacturing difficulty increase due to the need for precise optical treatments or features on rotating surfaces
Solution Approach 1:
The patent replaces traditional mechanical encoders or resolvers with a laser-based optical sensing system. A laser beam is directed onto the rotating crown assembly, and the reflected light is detected to determine rotational speed and direction. This substitution eliminates the need for complex mechanical components and precise optical treatments on the rotating surface, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent utilizes changes in the frequency of reflected laser light as a parameter to detect rotational motion. By measuring the Doppler shift or frequency modulation of the reflected beam, the system can accurately determine rotational speed and direction without requiring physical features on the rotating surface. This parameter-based approach simplifies the rotating component design while preserving measurement accuracy.
2Measurement precision
If precise optical treatments or features are added to rotating surfaces for accurate detection, then measurement precision improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces mechanical encoders or resolvers with a laser-based optical sensing system. A laser beam is directed onto the rotating crown assembly, and the reflected light is detected to determine rotational speed and direction. This substitution eliminates the need for complex mechanical components and precise optical treatments on the rotating surface, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent utilizes changes in the frequency of reflected laser light as a parameter to detect rotational motion. By measuring the Doppler shift or frequency modulation of the reflected beam, the system can accurately determine rotational speed and direction without requiring physical features on the rotating surface. This parameter-based approach simplifies the rotating component design while preserving measurement accuracy.
3Volume of moving object
If compact design is implemented in wearable devices, then device size is reduced, but the ability to accommodate precise sensing mechanisms is compromised
Solution Approach 1:
The patent replaces mechanical encoders or resolvers with a laser-based optical sensing system. A laser beam is directed onto the rotating crown assembly, and the reflected light is detected to determine rotational speed and direction. This substitution eliminates the need for complex mechanical components and precise optical treatments on the rotating surface, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent utilizes changes in the frequency of reflected laser light as a parameter to detect rotational motion. By measuring the Doppler shift or frequency modulation of the reflected beam, the system can accurately determine rotational speed and direction without requiring physical features on the rotating surface. This parameter-based approach simplifies the rotating component design while preserving measurement accuracy.
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 solution enables robust and highly accurate rotation sensing, reducing the need for precision optical treatments and allowing for simpler manufacturing, while occupying minimal space, thereby enhancing user interaction with wearable devices.
Implementation Method 1
the reflected portion of the beam reflected from the sensing surface of the crown assembly... based at least in part on a difference in frequency between the emitted beam and the reflected portion of the beam
Data Source
AI summary
An electronic watch includes a housing and a crown assembly including a rotatable actuation member. The rotatable actuation member includes a knob external to the housing and configured to receive a rotational input and a shaft assembly coupled to the knob and positioned at least partially within the housing, the shaft assembly defining a sensing surface configured to rotate in response to the rotational input. The electronic watch further includes an optical sensing system configured to detect the rotational input, the detecting including directing light onto the sensing surface, receiving reflected light from the sensing surface, and producing a signal corresponding to a rotational motion of the sensing surface, the signal based at least in part on an interference between the light directed onto the sensing surface and the reflected light.