Tracker Using Segmented Image Sensor Readout for Target Detection
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Solution Overview
Problem
Conventional surveying instruments face challenges in reliably tracking moving targets due to long image capture times, which lead to target loss and increased search time, especially in bright environments with multiple light sources, and the need for precise alignment of optical axes.
Innovation Solution
A tracker system with an image sensor arrangement that takes images in illumination and non-illumination states, reading out only specific columns or rows to generate a difference image, allowing for faster target detection and reduced artefacts, and adjusting the stripe window size based on mode requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the image sensor reads out the entire imaging region to capture the target, then the completeness of target detection is improved, but the image capture time increases leading to target loss
Solution Approach 1:
The patent divides the imaging region into multiple independently readable blocks or regions. Instead of reading out the entire imaging region sequentially, the system segments the readout process into parallel block readouts, significantly reducing the total capture time while maintaining complete target detection capability.
Solution Approach 2:
The patent employs periodic illumination with the illumination unit, switching between on and off states at optimized intervals. This periodic action allows the system to capture multiple short-exposure images during one illumination cycle, reducing the effective capture time per frame while maintaining detection reliability through temporal sampling.
2Reliability
If the image capture time is extended to ensure complete target acquisition, then the detection completeness is improved, but the target moves during capture causing target loss
Solution Approach 1:
The illumination unit operates in periodic on-off cycles with durations optimized for the expected target speed. By capturing multiple rapid successive images during each illumination period, the system freezes target motion effectively while maintaining acquisition completeness through temporal sampling of the moving target's position.
Solution Approach 2:
The patent maintains continuous illumination during the target acquisition process rather than using intermittent illumination. This continuous useful action ensures that the target remains visible throughout the entire segmented readout process, allowing the system to track and acquire the complete target trajectory even as it moves rapidly across the field of view.
3Measurement precision
If multiple images are captured in bright environments with multiple light sources, then the target identification accuracy is improved, but artefacts from other light sources increase false detections
Solution Approach 1:
The illumination unit activates before the image capture begins and remains on throughout the segmented readout process. This preliminary and sustained illumination ensures that the target is consistently illuminated and properly identified across all captured images, while the controlled timing distinguishes the target's reflected light from other ambient light sources that do not follow the same temporal pattern.
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 approach enhances target detection reliability and reduces search time by minimizing image capture time, improving tracking accuracy and reducing target losses, even in dynamic environments.
Implementation Method 1
an image sensor arrangement (410) having an imaging region (415) composed of a plurality of pixels arranged in a matrix of columns and rows
Implementation Method 2
an illumination unit illuminating a target in the scene is switched on and off
Implementation Method 3
calculate a difference image section by determining a difference between the pixel values of the pixels of the image section and the other image section
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
The present invention relates to a tracker and a surveying apparatus comprising the tracker, which improve the reliability of tracking a target. The tracker comprises a an image sensor arrangement having an imaging region composed of a plurality of pixels arranged in a matrix of columns and rows. The imaging region is arranged to take an image of a scene including the target. A controller receives or generates a timing signal indicating a time duration during which an illumination unit is switched on and off, controls the imaging region to take an image of the scene when the illumination unit is switched on, and reads out a subgroup of neighboring columns or rows constituting a stripe window of the imaging region so that an image section including the target is obtained, controls the imaging region to take another image of the scene when the illumination unit is switched off, and reads out another subgroup of neighboring columns or rows constituting another stripe window of the imaging region so that another image section including the target is obtained, and calculates a difference image section by determining a difference between the pixel values of the pixels of the image section and the other image section.