Stereoscopic Camera Calibration Target with Strobe Illumination
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Solution Overview
Problem
Stereoscopic cameras often experience discrepancies between set and actual interocular distances, leading to noticeable artifacts when images are combined or superimposed, due to calibration errors and limitations in equipment precision and human registration.
Innovation Solution
A calibration target with planar, parallel surfaces and color-coded illumination points, controlled by circuitry to set strobe frequencies based on camera settings, is used to capture image sequences that allow for determining actual camera settings, enabling accurate alignment and calibration of stereoscopic cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stereoscopic cameras use standard calibration methods, then calibration can be performed, but calibration accuracy is insufficient due to equipment precision limitations and human registration errors
Solution Approach 1:
The patent introduces a specialized calibration target as an intermediary object between the stereoscopic cameras. This target features precisely manufactured planar surfaces with known geometric relationships and distinct illumination points that serve as reference markers. By using this intermediary calibration target, the system achieves accurate interocular distance measurement without being limited by the cameras' own precision constraints or human registration errors.
Solution Approach 2:
The patent employs strobe illumination with controllable frequency and duration as a parameter change mechanism. By adjusting the strobe frequency and pulse width, the system optimizes the visibility and detectability of illumination points on the calibration target. This parameter control enables precise capture of calibration data even when cameras have varying shutter speeds and frame rates, thereby improving measurement accuracy independent of equipment limitations.
2Ease of operation
If stereoscopic cameras are calibrated with fixed interocular distances, then setup is simplified, but artifacts appear when images are combined due to actual distance discrepancies
Solution Approach 1:
The patent implements a feedback mechanism where the calibration target is captured by the stereoscopic cameras, and the captured images are processed to calculate the actual interocular distance. This measured value is then fed back to update the camera calibration parameters. The system iteratively adjusts the calibration settings based on the measured discrepancies, ensuring that the final calibration accurately reflects the true physical configuration of the cameras, thereby eliminating image artifacts.
Solution Approach 2:
The patent performs preliminary calibration by capturing images of the calibration target before actual stereoscopic recording. This preliminary action allows the system to determine the actual interocular distance and convergence settings in advance. By pre-calibrating the cameras using the known geometry of the calibration target, the system establishes accurate transformation parameters that will be applied during subsequent recording, preventing artifacts from appearing in the final images.
3Ease of manufacture
If calibration targets use simple geometric patterns, then manufacturing is easier, but detection precision is reduced
Solution Approach 1:
The patent applies local quality by using uniformly colored or distinctively colored illumination points on the calibration target. Each illumination point has a specific color or intensity characteristic that enhances its detectability by the camera sensors. This local differentiation allows the system to precisely identify and locate each point even when the overall target structure is simple, thereby maintaining high measurement precision while keeping manufacturing straightforward.
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 method improves calibration accuracy, ensuring proper alignment of stereoscopic cameras with the scene and reducing artifacts in recorded images by determining actual interocular distances and convergence settings.
Implementation Method 1
Each of the first illumination points comprises a light emitting diode controlled by the circuitry
Implementation Method 2
circuitry that sets a strobe frequency of the first and second illumination points
Data Source
AI summary
A stereoscopic camera calibration target includes: first illumination points on a first surface; second illumination points on a second surface, the first and second surfaces being planar, parallel to each other, and spaced from each other; and circuitry that sets a strobe frequency of the first and second illumination points. A method includes: moving a calibration target in front of a stereoscopic camera, the calibration target comprising first points on a first surface and second points on a second surface, the first and second surfaces being planar, parallel to each other, and spaced from each other; capturing, using the stereoscopic camera, an image sequence of the calibration target, the image sequence comprising pairs of left and right images of at least some of the first and second points; determining a calibration value for the stereoscopic camera using the image sequence; and processing the image sequence using the calibration value.