Time of Flight Sensor CCD Stripe Location Identification
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Solution Overview
Problem
Current time of flight distance sensors face limitations due to high noise levels, poor fill factor, and high costs, restricting their use to indoor environments and limiting their ability to differentiate between reflections from distant objects and atmospheric effects like fog, dust, and snow.
Innovation Solution
A time of flight distance measurement method involving a pulsed fan beam and a charge coupled device (CCD) sensor architecture with a self-calibration step to accurately determine the location of the illumination stripe, allowing for reliable distance measurement by transferring data through a storage region and readout section, enabling high fill factor and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge coupled device (CCD) sensor architecture is used with high fill factor, then light sensitivity and signal-to-noise ratio are improved, but the device complexity increases due to the need for precise stripe location identification and data transfer mechanisms
Solution Approach 1:
The sensor array is divided into multiple rows of pixels, with each row independently capable of capturing the illumination stripe at different positions. This segmentation allows the system to determine stripe location by identifying which row contains the stripe signal, thereby managing complexity through modular row-based processing while maintaining high fill factor benefits.
Solution Approach 2:
A storage region is introduced as an intermediary between the photosensitive image region and the readout section. This storage region temporarily holds data from the photosensitive region before it is read out, enabling the system to process and identify stripe locations without immediately increasing readout complexity, thus resolving the contradiction between high fill factor and device complexity.
2Measurement precision
If avalanche photodiodes are used to provide gain and reduce noise, then measurement precision is improved, but manufacturing cost and device complexity increase significantly
Solution Approach 1:
The patent uses standard charge coupled device pixels that can be manufactured using conventional CMOS processes rather than expensive avalanche photodiodes. These cheaper, more manufacturable pixels are sufficient when combined with the row-based stripe location identification method, achieving acceptable measurement precision without the high manufacturing cost and complexity of APD arrays.
3Measurement precision
If the illumination stripe position is not accurately determined, then distance measurement accuracy is reduced, but adding calibration mechanisms increases device complexity
Solution Approach 1:
The system performs self-calibration by automatically identifying which row contains the illumination stripe through the captured image data itself. The control circuitry analyzes the stripe position within the sensor array and uses this information to determine accurate distance measurements, eliminating the need for external calibration mechanisms while maintaining high measurement precision.
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 enables low-noise, high-resolution distance measurements over extended ranges with lower costs, improving the robustness and efficiency of time of flight sensors, allowing them to operate effectively in various environmental conditions.
Implementation Method 1
emitting a pulsed fan beam from a light emitter to illuminate a remote object with an object illumination stripe
Implementation Method 2
illuminate a remote object with an object illumination stripe
Implementation Method 3
capturing an image of the object illumination stripe as an image illumination stripe on a photosensitive image region
Data Source
AI summary
A time of flight sensor has an image region and a storage region on a device which may be a CCD. A pulse of light illuminates an object, and an image illumination stripe is recorded on the image region. In a distance determining step, the image region is clocked after emitting the pulse of light and the row in which the image illumination stripe is illuminated gives a measure of the distance to the object. The apparatus can self calibrated by emitting a pulse of light without clocking the image region.