Light Pulse Compression for High Contrast Time-of-Flight Imaging
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Solution Overview
Problem
Time-of-flight-based systems face limitations in achieving high demodulation contrast due to parasitic effects and theoretical maximum constraints, which affect the quality of distance information acquisition in real-time three-dimensional imaging applications.
Innovation Solution
Implementing light pulse compression techniques with a duty cycle of less than 50% and coordinating modulation of the light source with pixel sampling to enhance demodulation contrast, achieving synchronous demodulation and increasing the demodulation contrast to at least 90%, while minimizing phase non-linearity and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a modulated light wave is emitted with conventional duty cycle, then the system can operate continuously, but the demodulation contrast is limited to below 63% due to theoretical maximum constraints and parasitic effects
Solution Approach 1:
The patent applies periodic action by using pulsed light emission with duty cycles less than 50% instead of continuous modulation. The light source emits periodic pulses synchronized with the pixel sampling rate, creating discrete measurement opportunities that eliminate the theoretical demodulation contrast limit of conventional continuous modulation systems.
Solution Approach 2:
The patent changes the duty cycle parameter from conventional values (typically 50% or higher) to less than 50%, and optimizes the pulse width and frequency parameters. This parameter optimization enables the demodulation contrast to exceed the conventional 63% maximum, achieving greater than 90% contrast as stated in the patent.
2Reliability
If the integration period is extended to improve signal strength, then more photons are collected, but the demodulation contrast decreases due to the inverse relationship between integration period and demodulation contrast
Solution Approach 1:
The patent uses periodic pulsed illumination with duty cycles less than 50% to create distinct measurement windows. This periodic action allows the system to collect photons during each pulse while maintaining high demodulation contrast through the brief integration period required for each pulse, resolving the trade-off between signal strength and contrast.
Solution Approach 2:
The patent applies preliminary action by pre-synchronizing the light pulse emission with the pixel sampling timing. The control unit coordinates the light source modulation with the detector array sampling to ensure that each pulse coincides with the optimal sampling window, maximizing both signal collection and demodulation contrast simultaneously.
3Productivity
If continuous illumination is used to maintain constant measurement capability, then the system can continuously acquire data, but phase non-linearity and distortion increase
Solution Approach 1:
The patent replaces continuous illumination with periodic pulsed illumination at optimized duty cycles. This periodic action maintains continuous data acquisition capability through high-frequency pulsing while eliminating phase non-linearity and distortion that occur with continuous modulation, as each pulse provides a clean, well-defined measurement reference.
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 light pulse compression technique significantly increases demodulation contrast and reduces phase non-linearity and distance calculation errors, enabling more precise three-dimensional imaging and data acquisition with improved signal strength and accuracy.
Implementation Method 1
Time-of-flight techniques, for example, can facilitate fast optical acquisition of distance information. In TOF systems, the time that light needs to travel from the measurement system to the scene and back again corresponds directly to the distance R.
Implementation Method 2
The control unit also is coupled to the detector array and is operable to coordinate modulation of the light source with sampling of pixels in the detector array so as to provide synchronous demodulation.
Data Source
AI summary
Time-of-flight (TOF) based systems using light pulse compression are described and, in some cases, can help increase demodulation contrast. Further, light pulse shaping techniques are described that, in some cases, can help reduce phase non-linearity and distance-calculation errors. The techniques can be used, for example, in measurement systems, as well as imaging systems in which a time-of-flight and/or distance information is obtained. The time-of-flight and/or distance information can be used to reconstruct and display a three-dimensional image of a scene. The light compression techniques also can be used to provide reference signals.