Triangulation Scanner Dynamic Exposure for High Dynamic Range
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Solution Overview
Problem
Triangulation scanners face challenges such as camera array saturation from bright sunlight, difficulty in capturing dense detail with high 3D accuracy, obtaining high-dynamic-range 3D images, and determining color reflectance characteristics of objects in three dimensions.
Innovation Solution
A triangulation scanner system that includes a projector capable of projecting light at varying levels and a camera with integrated circuits and memories to store signals from light reflections, allowing a processor to determine 3D coordinates based on the projected light patterns and stored signals, while also considering the relative pose of the projector and camera, and using multiple cameras for enhanced accuracy and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the camera uses a single exposure time to capture reflected light, then the device complexity is reduced, but the dynamic range of captured images is limited and cannot handle both bright and dark regions simultaneously
Solution Approach 1:
The camera dynamically adjusts exposure time for different regions of the image based on local brightness conditions. The processor divides the image into multiple regions and assigns different exposure times to each region, allowing the system to adapt to varying light conditions across the scene without requiring multiple physical cameras or complex hardware modifications.
Solution Approach 2:
The image captured by the camera is segmented into multiple regions with different exposure characteristics. By dividing the image into bright regions, dark regions, and intermediate regions, the system can apply different exposure times to each segment, effectively capturing high dynamic range information while using a single camera sensor.
2Measurement precision
If the projector emits high light levels to improve signal detection in bright conditions, then the measurement accuracy is improved, but the camera array becomes saturated and loses the ability to detect subtle light variations
Solution Approach 1:
The system dynamically adjusts the projector light level based on environmental conditions and camera response. In bright outdoor conditions, the projector emits higher light levels to maintain signal strength, while in darker conditions or when the camera is near saturation, the light level is reduced. This dynamic adjustment allows the system to maintain measurement precision without causing camera saturation.
Solution Approach 2:
The system uses feedback from the camera's detected signal strength to adjust the projector's light emission. When the camera detects that the reflected light signal is too weak (in bright conditions), the projector increases its light output. Conversely, when the signal is too strong or the camera approaches saturation, the projector reduces its output, creating a closed-loop control system that maintains optimal signal levels.
3Measurement precision
If multiple cameras are used to capture light reflections from different angles, then the measurement accuracy and detail density are improved, but the device complexity and cost increase
Solution Approach 1:
Instead of using multiple cameras simultaneously, the system uses a single camera that captures images at different exposure times in rapid succession. This periodic capture approach allows the system to reconstruct high-detail 3D information by processing multiple temporal snapshots, achieving accuracy comparable to multi-camera systems while avoiding the complexity of synchronizing and calibrating multiple devices.
4Productivity
If the camera uses short exposure time to capture fast-moving objects, then the productivity is improved, but the measurement precision decreases due to insufficient light collection
Solution Approach 1:
The system dynamically adjusts the exposure time based on the detected motion of the object or scanner. When fast motion is detected, the exposure time is shortened to freeze the motion and avoid blur, maintaining productivity. When motion is slow or stationary, the exposure time is extended to collect sufficient light, maintaining measurement precision. This dynamic adaptation allows the system to optimize both speed and accuracy based on real-time conditions.
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 system effectively avoids camera array saturation, captures high-dynamic-range 3D images, and determines color reflectance characteristics, improving the accuracy and detail of 3D measurements.
Implementation Method 1
the optical detector operable to produce signals in response to light levels reflected from a first point on the object
Data Source
AI summary
A triangulation scanner system and method of operation is provided. The system includes a projector that projects a first pattern of light at a first light level during first time intervals and project the first pattern of light at a second light level during second time intervals, the second light level being different than the first light level. A first camera has a first photosensitive array, the first photosensitive array having a first pixel with an optical detector, a first memory, and a second memory. The first memory storing a first stored signal from the optical detector during the first time intervals, the second memory storing a second signal from the optical detector during the second time intervals. A processor determines three-dimensional coordinates of the first point based at least in part on the projected first pattern of light, the first stored signal, and the second stored signal.