CW-ToF Camera Pixel Row Phase Delay for Moving Object Depth Imaging
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Solution Overview
Problem
Continuous Wave (CW) Time-of-Flight (ToF) camera systems face inaccuracies and blurring in generated image frames due to object movement and the time required for multiple modulation frequency processing, which leads to reduced accuracy and increased blurring, especially when imaging non-static scenes.
Innovation Solution
The implementation of a CW-ToF camera system that introduces phase delays between rows of pixels within a single image frame, allowing charge accumulation over the same time period, thereby reducing integration time and sacrificing spatial resolution for increased speed, enabling more accurate depth imaging with reduced blurring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple modulation frequencies are used to resolve phase wrapping, then measurement precision is improved, but loss of time increases due to sequential processing
Solution Approach 1:
The pixel array is divided into multiple banks, where each bank is assigned a different modulation frequency. This allows simultaneous acquisition of multiple frequency data in a single snapshot, eliminating the sequential processing time while maintaining the ability to resolve phase wrapping through multi-frequency analysis.
Solution Approach 2:
The patent introduces a spatial dimension to frequency multiplexing by assigning different frequencies to different spatial regions (banks) of the pixel array. This transforms the time-multiplexed frequency acquisition into a space-multiplexed approach, enabling parallel measurement of multiple frequencies simultaneously.
2Measurement precision
If sequential charge accumulation for each row is performed, then spatial resolution is maintained, but productivity decreases due to extended integration time
Solution Approach 1:
The pixel array is segmented into multiple banks along the row direction, with each bank handling a subset of rows. This segmentation allows parallel charge accumulation across banks while maintaining sufficient spatial resolution within each bank, thereby increasing overall frame rate without significant loss of image quality.
Solution Approach 2:
Different regions (banks) of the pixel array are assigned different modulation frequencies, creating local variations in measurement parameters. This allows each bank to operate independently with optimized settings, enabling parallel processing while maintaining overall system performance and spatial resolution where needed.
3Measurement precision
If integration time is extended to capture moving objects accurately, then measurement precision is improved, but object movement causes blurring
Solution Approach 1:
The system uses periodic modulation of laser light at different frequencies across multiple banks, allowing rapid acquisition of depth information in a single snapshot. This periodic sampling captures the scene before significant movement occurs, maintaining image sharpness while achieving accurate depth measurements through the multi-frequency phase analysis.
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 allows for the production of depth images with reduced inaccuracies and blurring by utilizing phase delays between rows of pixels, resulting in faster readout times and improved accuracy when imaging moving objects, such as those on conveyor belts.
Implementation Method 1
Light impacting upon each pixel causes electrical charges to accumulate on the pixels
Data Source
AI summary
There is provided a continuous wave time of flight, CW-ToF, camera system comprising: a laser for emitting laser light; an imaging sensor, the image sensor comprising a pixel array for accumulating charge based on incident light comprising reflected laser light off an object, the pixel array comprising a plurality of rows of pixels; and a control system coupled to the imaging sensor and configured to control the pixel array to: identify at least a first row and a second row of the plurality of rows, wherein the first row and the second row are adjacent one another in the pixel array; accumulate charge in the pixels of the first row using a first integration setting for a first time period; accumulate charge in the pixels of the second row using a second integration setting for the first time period; and read out a set of charge samples, wherein the first row contains a first charge from accumulating using the first integration setting and the second row contains a second charge from accumulating using the second integration setting, and wherein the second integration setting is phase delayed relative to the first integration setting.