Optical Sensor Synchronization Using a Changing Calibration Target
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Solution Overview
Problem
Existing camera calibration methods are prone to errors due to unsynchronized recording, which are difficult to detect and result in inaccurate calibration parameters, especially in multi-camera systems.
Innovation Solution
A calibration target with controllable illuminants, such as LEDs, is used to modify its optical appearance over time, allowing for the detection of temporal offsets and synchronization of optical sensors by analyzing the chronological sequence of light events in sensor images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTP protocol or synchronization line is used to synchronize cameras, then simultaneous recording is improved, but device complexity and cost increase
Solution Approach 1:
A calibration chart with temporally varying optical appearance serves as an intermediary medium to transfer synchronization information between cameras. Instead of direct electronic synchronization, the calibration chart encodes temporal reference information through its changing appearance, allowing cameras to independently determine their temporal offset by analyzing the sequence of optical states observed
Solution Approach 2:
The patent replaces electronic/mechanical synchronization systems (PTP protocol, synchronization lines) with an optical information encoding system. The calibration chart uses optical signals (light emission, reflection, or display changes) to convey temporal synchronization information, eliminating the need for complex electronic synchronization infrastructure
2Device complexity
If calibration is performed without synchronization, then device complexity is reduced, but measurement precision deteriorates due to temporal offsets
Solution Approach 1:
The calibration chart provides feedback information about temporal offset through its optical appearance. By analyzing which optical states are captured and in what sequence, cameras can determine their relative timing offsets and correct their calibration data accordingly, transforming an uncontrolled variable into a measurable and correctable parameter
Solution Approach 2:
The calibration chart dynamically changes its optical parameters (emission state, reflected light, displayed pattern) over time. This temporal variation in optical parameters encodes synchronization information, allowing cameras to distinguish between simultaneous and non-simultaneous captures by analyzing the sequence of optical states observed
3Ease of operation
If calibration target is stationary, then ease of operation is improved, but reliability deteriorates due to undetected temporal offsets
Solution Approach 1:
The calibration chart changes its optical appearance through light emission, reflection, or display changes over time. This temporal variation in optical state provides detectable feedback that reveals synchronization status, allowing users to identify temporal offsets through the sequence of optical patterns captured in calibration images
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 reliable and efficient synchronization and calibration of multiple optical sensors by detecting and correcting temporal offsets, ensuring accurate calibration parameters without additional hardware synchronization lines.
Implementation Method 1
The light or the appearance that previously occurred at the first position can occur at the second point in time at the second position (and in particular no longer at the first position). It is also proposed that the light is emitted, for example, by a respective LED or LED arrangement in the area of the first position or in the area of the second position.
Data Source
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Figure 3~4
AI summary
A method for synchronizing several optical sensors (1, 2, 3) during a calibration of the sensors (1, 2, 3) comprising the steps of: sensing (100) a calibration target (4) by the sensors (1, 2, 3) at a first time point, modifying (200) an optical appearance of the calibration target (4) for the sensors (1, 2, 3), and sensing (300) the calibration target (4) by the sensors (1, 2, 3) at a second time point following the first time point and the modification, wherein the modification of the optical appearance comprises emitting light in an area at a first position (405) of a plurality of predefined positions (401-411) on the calibration target (4) at the first time point and not emitting light in the area at the first position (405) of the plurality of predefined positions (401-411) on the calibration target (4) at the second time point.