Optical Sensor Focus Adjustment with ToF and Pose Fusion
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Solution Overview
Problem
Existing autofocus methods in optical sensing systems, particularly in digital pens or stylus devices, struggle to dynamically adjust focusing distance quickly and accurately in dynamic environments, leading to out-of-focus images and impaired positional marker decoding.
Innovation Solution
A hybrid autofocus methodology combining open-loop and closed-loop techniques, utilizing a Time-of-Flight sensor for initial distance measurement and image-based adjustments, supplemented by positional sensors and sensor fusion to rapidly adjust focusing distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional autofocus methods are used in optical sensing systems, then the system can maintain focus under static conditions, but the system cannot dynamically adjust focusing distance quickly enough in dynamic environments
Solution Approach 1:
The system performs preliminary distance measurement using a Time-of-Flight sensor before image acquisition. This preliminary action provides an advance estimate of the focusing distance, allowing the optical system to pre-adjust focus before the actual imaging moment, thereby enabling faster response in dynamic environments while maintaining image sharpness.
Solution Approach 2:
The patent introduces an intermediary processing system that fuses data from multiple sensors (Time-of-Flight distance sensor, inertial measurement unit, and optical sensor). This intermediary fusion process reconciles the conflicting requirements of fast adjustment and reliable focus by combining predictions from inertial data with actual distance measurements, enabling smooth and accurate focusing distance adjustments.
2Reliability
If the focusing distance is not dynamically adjusted, then the system maintains a simple control mechanism, but the optical sensor acquires out-of-focus images in dynamic environments
Solution Approach 1:
The patent merges multiple existing components (Time-of-Flight sensor, inertial measurement unit, optical sensor, and processing system) into an integrated autofocus system. By combining these components that already exist in the optical sensing system, the patent achieves reliable image sharpness without proportionally increasing overall device complexity, as the components work synergistically rather than adding separate dedicated autofocus mechanisms.
Solution Approach 2:
The system uses its own existing sensors (Time-of-Flight and inertial measurement unit) to provide the focusing distance information needed for autofocus. Rather than requiring external or dedicated autofocus components, the system serves its own focusing needs using data already being collected for other functions, thereby maintaining simplicity while achieving reliable focus.
3Measurement precision
If multiple sensors are used for distance measurement and focus adjustment, then the focusing distance can be adjusted accurately, but the processing time and computational load increase
Solution Approach 1:
The system performs preliminary distance measurement and pose estimation using Time-of-Flight and inertial sensors before image acquisition. This preliminary action provides advance information about the required focusing distance, allowing the system to prepare focus adjustments in advance and reduce processing time during actual image capture, thereby maintaining measurement precision while minimizing time loss.
Solution Approach 2:
The patent implements a feedback mechanism where the processing system continuously monitors distance measurements from multiple sensors and dynamically adjusts the focusing distance based on fused sensor data. This feedback loop enables the system to maintain accurate focus by continuously comparing actual distance measurements with predicted values and making real-time corrections, balancing measurement precision with efficient processing.
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
Enables fast, accurate, and reliable focusing distance adjustments even in dynamic conditions, ensuring sharp images for precise positional marker decoding and maintaining image quality.
Implementation Method 1
utilizing a Time-of-Flight sensor for initial distance measurement
Data Source
Figure 1
Figure 1A~1B
Figure 2A
AI summary
There is described a method of adjusting a focusing distance of an optical sensing system (OS) with respect to a surface (S) to be imaged by an optical sensor (C) of the optical sensing system (OS). The method comprises setting (420) an initial focusing distance of the optical sensing system (OS). The method further comprises acquiring (430) an image of the surface (S) using the optical sensor (C), processing (470) the image acquired by the optical sensor (C) to extract a distance-related metric therefrom and derive an estimate of the distance separating the optical sensor (C) from the surface (S) based on the distance-related metric, and adjusting (420) the focusing distance of the optical sensing system (OS) based on the thus derived estimate of the distance. Processing (470) the acquired image additionally relies on positional measurements (460) provided by positional sensors (PS), which positional measurements (460) are indicative of a pose or change of pose of the optical sensor (C) with respect to the surface (S). Processing (470) may especially include sensor fusion to provide a fast output indicative of the pose of the optical sensor (C) and thus of the focusing distance.