ToF Sensor Pixel Charge Storage Segmentation for Stray Light
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Solution Overview
Problem
Time-of-Flight (ToF) sensing is limited by pixel saturation and stray light from close objects, which reduces dynamic range and impairs measurement accuracy.
Innovation Solution
A method and apparatus for ToF sensing that perform multiple measurements using a first modulation frequency, controlling charge carriers in photo-sensitive sensor pixels to selectively store and drain charge carriers, shaping correlation functions to reduce sensitivity to close proximity light and prevent stray light effects, allowing for distance determination based on light-intensity-independent correlation functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If close objects are measured in ToF sensing, then distance measurement is achieved, but pixel saturation occurs due to increased light reflection
Solution Approach 1:
The photo-sensitive sensor pixel is divided into multiple charge storages (first charge storage and second charge storage). Charge carriers are selectively stored in different storages based on the measured distance, allowing the sensor to handle close objects without saturation by routing their signal to the second charge storage while the first charge storage handles distant objects.
Solution Approach 2:
Different charge storages are assigned different functions based on distance ranges. The first charge storage is optimized for distant objects, while the second charge storage is optimized for close objects. This local differentiation of functionality within the pixel allows each storage to operate within its optimal dynamic range.
2Measurement precision
If close objects are measured in ToF sensing, then distance measurement is achieved, but stray light effects increase
Solution Approach 1:
The pixel is segmented into multiple charge storages that can be selectively activated. By routing charge carriers from close objects to the second charge storage, the system isolates stray light effects from the primary measurement path, reducing their impact on the overall measurement accuracy.
Solution Approach 2:
The second charge storage acts as an intermediary for handling close objects and their associated stray light. This intermediate storage allows the system to process close object signals separately, preventing stray light from contaminating the measurement of distant objects.
3Adaptability or versatility
If dynamic range is increased in ToF sensing, then measurement capability is improved, but pixel saturation occurs
Solution Approach 1:
The pixel is divided into multiple charge storages with different dynamic ranges. The first charge storage handles distant objects with lower light intensity, while the second charge storage handles close objects with higher light intensity. This segmentation allows the pixel to achieve extended dynamic range without saturating, as each storage operates within its optimal range.
Solution Approach 2:
The system changes the operational parameters of different charge storages to match the expected light intensity for different distance ranges. By adjusting which charge storage is active based on the measured distance, the system maintains optimal dynamic range utilization while preventing saturation across the entire measurement range.
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
The solution enhances ToF sensing by reducing saturation and stray light effects, improving dynamic range and measurement accuracy while determining distances with increased precision.
Implementation Method 1
charge carriers generated in the photo-sensitive sensor pixel during the at least one of the plurality of first ToF measurements by incident light
Data Source
AI summary
A method for Time-of-Flight (ToF) sensing of a scene is provided. The method includes performing, by a ToF sensor including at least one photo-sensitive sensor pixel, a plurality of first ToF measurements using a first modulation frequency in order to obtain first measurement values. A respective correlation function of each of the plurality of first ToF measurements is periodic and exhibits an increasing amplitude over distance within a measurement range of the ToF sensor. The method further includes determining a distance to an object in the scene based on the first measurement values. Performing the plurality of first ToF measurements includes for at least one of the plurality of first ToF measurements controlling the photo-sensitive sensor pixel to selectively store, in at least two charge storages of the photo-sensitive sensor pixel, part of charge carriers generated in the photo-sensitive sensor pixel during the at least one of the plurality of first ToF measurements by incident light. In addition, performing the plurality of first ToF measurements includes for the at least one of the plurality of first ToF measurements controlling the photo-sensitive sensor pixel to selectively prevent another part of the charge carriers generated during the at least one of the plurality of first ToF measurements from reaching the at least two charge storages.