Optical Sensor Cancellation of Crosstalk Interference
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Solution Overview
Problem
Time of flight (TOF) sensors face challenges in high resolution sensing due to high frequency clock signal requirements, signal aliasing, and interference from other TOF sensors and smudges, making it difficult to distinguish multiple objects and cancel crosstalk.
Innovation Solution
The optical sensor uses a processor to generate a random code for modulating a light source and sampling signal, updates a calibration value to cancel crosstalk, and adjusts sampling periods to detect phase delays, allowing for multiple object detection and interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect TOF is used to avoid high frequency clock signals, then temporal resolution is improved, but signal aliasing occurs making it difficult to distinguish multiple objects
Solution Approach 1:
The patent applies periodic action by using continuous light wave emission with periodic modulation. The light source emits continuous light waves that are modulated with a code sequence, and the detector periodically samples the reflected light. This periodic sampling allows the system to achieve high temporal resolution while avoiding signal aliasing by properly synchronizing the sampling with the modulation period, enabling clear distinction between multiple objects.
2Measurement precision
If continuous light wave is used in indirect TOF, then high resolution sensing is achieved, but interference from other TOF sensors and crosstalk occur
Solution Approach 1:
The patent applies local quality by assigning unique identification codes to different TOF sensors and using spatially selective sampling. Each sensor has a distinct code pattern, and the system samples light at specific time intervals corresponding to each sensor's active period. This allows high-resolution sensing for each sensor while preventing interference from other sensors through temporal and spatial separation of the measurement processes.
Solution Approach 2:
The patent applies preliminary action by performing calibration measurements before actual sensing. The system conducts preliminary measurements to determine the reflection characteristics of the target object and stores this information for later use. During actual sensing, the system uses these pre-obtained calibration data to compensate for environmental variations and sensor-specific characteristics, maintaining high resolution while reducing interference effects.
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 high resolution sensing similar to direct TOF systems while reducing interference and crosstalk, allowing for accurate detection of multiple objects and improving detection accuracy over conventional indirect TOF sensors.
Implementation Method 1
a light emitter is used to emit a continuous light wave
Implementation Method 2
a detector is used to detect a reflected light wave reflected by an object to be detected and reaches the detector. By calculating a phase delay of the reflected light wave from the continuous light wave, it is able to obtain a flying time.
Implementation Method 3
the processor is configured to compare a number of the reference photon events of each of the multiple exposure intervals with the event threshold to generate a random code, and modulate the light source driving signal and the sampling signal using the random code
Data Source
AI summary
There is provided an optical sensor including a light source, a first pixel, a second pixel and a processor. The first pixel generates a first output signal by receiving reflected light from an external object illuminated by the light source. The second pixel generates a second output signal by receiving reflected light from an inner surface of a package illuminated by the light source. The processor generates a random code according to the second output signal to modulate the light source, identifies whether to change an emission pattern of the light source according to a distance calculated according to the first output signal, and changes exposure intervals of the first pixel and the second pixel.