Laser Radar Projector Using Object Features as Fiducial Points
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Solution Overview
Problem
Existing laser projection systems require retro-reflective or cooperative targets for precise 3D location and light reflectivity information, which is time-consuming, degrades precision, and limits their application due to the need for target placement, and struggles with weak optical feedback signals from object features.
Innovation Solution
A targetless laser radar projector system that uses a pulsed laser beam, time-of-flight measurement, and high-sensitivity optical feedback to detect object features as fiducial points, separating the output and feedback beams to suppress stray light and enhance signal detection, allowing for precise 3D digitizing and projection without external targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retro-reflective reference targets are used to provide distinguishable optical feedback signals, then the reliability of laser projection is improved, but the ease of operation deteriorates due to time-consuming and labor-intensive target placement requirements
Solution Approach 1:
The system uses object features themselves (corners, holes, fasteners, edges) as fiducial points instead of requiring separate retro-reflective targets. The object serves its own feature detection needs, eliminating the need for external target placement while maintaining reliable feature detection for laser projection alignment
Solution Approach 2:
The patent extracts and removes the requirement for retro-reflective reference targets from the system. By detecting features directly on the object surface using the laser beam itself, the system eliminates the separate target component and its placement procedure, simplifying operation while maintaining reliability
2Measurement precision
If retro-reflective targets are placed on the object surface, then the measurement precision of 3D location is improved, but the manufacturing precision deteriorates due to placement inaccuracies affecting target position reliability
Solution Approach 1:
The object's existing features serve as the measurement reference points, eliminating the need for separate targets whose placement precision would compromise manufacturing accuracy. The laser system detects features inherent to the object itself, ensuring that measurement references are integral to the workpiece rather than externally applied
Solution Approach 2:
Instead of placing targets on the object to create reference points, the system inverts the approach by having the laser beam detect and identify features that already exist on the object surface. This inversion eliminates the source of placement error while maintaining the ability to establish precise 3D location references
3Object-affected harmful factors
If the maximum allowed laser beam power of 5 milliwatts is used, then the safety compliance is improved, but the detection sensitivity deteriorates due to weak optical feedback signals from object features
Solution Approach 1:
The system employs optical feedback by detecting the light reflected from object features back into the beam path. This feedback mechanism allows the system to use the same low-power laser beam for both projection and detection, maintaining safety compliance while enabling feature detection through the returned optical signal
Solution Approach 2:
The same laser beam serves dual functions: projecting the template pattern and providing the optical feedback signal for feature detection. This multi-functionality allows the system to maintain low power output for safety while still achieving adequate detection sensitivity by utilizing the reflected light from object features
4Device complexity
If the same beam path is used for both output laser beam and received feedback light, then the device complexity is reduced, but the measurement precision deteriorates due to stray light interference with weak feedback signals
Solution Approach 1:
The system segments the optical paths by spatially separating the outgoing laser beam from the incoming feedback signal using beam steering mirrors. This segmentation allows each beam to be optimized independently - the outgoing beam for projection and the incoming feedback light for detection - while maintaining overall system compactness through the shared optical platform
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 high-precision 3D digitizing and projection with improved sensitivity and dynamic range, allowing the use of object features as fiducial points, reducing human error, and providing real-time verification in manufacturing processes.
Implementation Method 1
A time of flight measurement system calculates the elapsed time of flight and distance traveled of pulses from the laser, to points on the object surface, and back via the signal light feedback beam to the detector
Implementation Method 2
A first optical signal detector at the laser projector receives the feedback signal light beam and converts it into a digital image signal that corresponds to the detected feedback signal light
Data Source
AI summary
A 3D pulsed laser projection system scans an object to produce a dense 3D point cloud and projects a laser light beam onto an object as a glowing template. A high-sensitivity optical feedback system receives and detects a feedback beam of the output beam light diffusely reflected from the object. The feedback light and projected beam share the same beam path between steering mirrors and the object. A light suppression component controls stray scattered light, including ambient light, from being detected. A time-of-flight measurement subsystem provides a distance-to-object measurement for projected pulses. An acousto-optical modulator, variable gain detected signal amplification and variable photo-detector power together produce a dynamic range for detected reflected feedback signals of at least 100,000, and up to 500,000. Optical fiber cables spatially filter scattered light and isolate the photo-detectors thermally. The laser is preferably pulsed at least 50 kHz, with sampling of the projected and feedback reflected optical pulse signals at a sampling rate of up to 10 gigasamples per second.