Watch Crown Rotation Sensing Using Laser Interference
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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 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 inputs, then measurement precision can be achieved, but device complexity and manufacturing difficulty increase due to the need for precise optical treatments or features on rotating surfaces
Solution Approach 1:
The patent extracts and removes the requirement for optical treatments or features from the rotating surface. By using a laser beam that reflects off the natural surface of the rotating component, the invention eliminates the need for adding optical features, markers, or treatments to the rotating part, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent replaces traditional mechanical or complex optical encoding systems with a laser-based optical sensing system. Instead of using encoders, resolvers, or mechanically complex optical features, the invention uses a laser beam reflected from the rotating surface to detect rotational motion, simplifying the overall system
2Volume of moving object
If compact design is implemented in wearable devices, then device size is reduced, but space for optical sensing components becomes limited
Solution Approach 1:
The patent merges the laser source and the optical detection functionality into a single integrated optical sensing system. The laser module both emits the laser beam and detects the reflected light, eliminating the need for separate transmitter and receiver components, thereby reducing the space required for optical sensing components in compact wearable devices
Solution Approach 2:
The laser module serves multiple functions: it emits the laser beam for illumination, acts as the light source for the optical sensing system, and detects the reflected light to determine rotational characteristics. This multi-functionality reduces the number of components needed and minimizes the space required for optical sensing in compact devices
3Measurement precision
If high precision rotation sensing is achieved using laser-based systems, then measurement accuracy improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements a self-aligning mechanism where the laser beam is directed to reflect back along its incident path. The optical sensing system automatically detects the reflected light that returns to the laser source, creating a self-contained alignment system that reduces the need for high-precision manual alignment during manufacturing
Solution Approach 2:
Instead of directing the laser beam perpendicular to the rotating surface (conventional approach), the patent directs the laser beam at an oblique angle so that the reflected light returns along the incident path. This inverted approach simplifies the optical path and reduces alignment requirements, as the reflection naturally follows the incident path back to the source
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, occupying minimal space and simplifying manufacturing processes, while allowing for precise control of device functions based on rotational inputs.
Implementation Method 1
the laser module may be a vertical cavity surface emitting laser, the vertical cavity surface emitting laser may detect a difference in frequency between the emitted laser beam and the reflected portion of the laser beam
Implementation Method 2
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
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.