Pulsed Optical Distance Sensor Background Noise Correction
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Solution Overview
Problem
Existing 3D CMOS image sensors for distance measurement face challenges in accurately detecting distance due to corruption from unwanted background light and object reflectivity, requiring multiple image captures which limits bandwidth and increases energy usage, potentially violating eye safety standards.
Innovation Solution
An optical distance measuring device with a pulsed radiation source and capacitive pixel sensor elements that capture radiation reflections and background light in overlapping detection periods, allowing for simultaneous measurement of distance, reflectance, and background components in a single cycle, reducing the need for multiple laser pulses and energy usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple image captures are performed to correct for background light and reflectivity, then measurement precision is improved, but productivity decreases due to limited bandwidth
Solution Approach 1:
The patent employs periodic pulsed illumination with alternating phases: during the first phase, the light source emits pulses to capture reflected light containing distance information; during the second phase, the light source remains dark to capture only background light. This periodic action enables simultaneous acquisition of multiple measurement components within a single measurement cycle, resolving the contradiction between precision and speed by eliminating the need for multiple sequential captures.
2Measurement precision
If multiple image captures with different exposure times are performed, then measurement precision is improved, but use of energy increases due to multiple laser pulses
Solution Approach 1:
The illumination operates in periodic pulses only during the first detection phase, remaining completely dark during the second detection phase. This periodic action with alternating emission and darkness enables the system to capture both reflected light and background light using a single pulsed illumination event, thereby reducing energy consumption by eliminating redundant laser pulses while maintaining measurement precision.
3Measurement precision
If multiple image captures are performed to correct for background light, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses periodic pulsed illumination alternating between emission and darkness phases, combined with overlapping detection periods that capture different light components. This approach enables background light correction and distance measurement to be performed simultaneously within a single measurement cycle using the same hardware, thereby improving precision without increasing device complexity.
4Measurement precision
If laser energy is doubled for serial reflectance correction, then measurement precision is improved, but object-affected harmful factors increase due to eye safety concerns
Solution Approach 1:
The illumination system operates with periodic pulses only during the first detection phase and remains completely dark during the second detection phase. This periodic action enables the system to capture background light without additional laser energy, thereby reducing total laser radiation exposure by half while maintaining measurement precision through the alternating emission and darkness phases.
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 significantly increases measurement speed and reduces radiation energy by half, while ensuring eye safety by eliminating the need for unnecessary laser pulses, thereby enhancing the reliability and efficiency of distance measurement systems.
Implementation Method 1
detecting different amounts of radiation in two overlapping detection periods during the radiation pulse period to capture reflections of the radiation pulse at the object surface
Implementation Method 2
Complementary metal oxide semiconductor (CMOS) image sensor technology provides effective options for recording measurement signals in real time at high speed
Data Source
AI summary
The present invention describes an optical distance measuring device having a pulsed radiation source that is implemented to transmit, in a temporally contiguous radiation pulse period, a radiation pulse having a pulse duration tp that is shorter than the radiation pulse period, and to transmit no radiation pulse in a temporally contiguous dark period. Further, the optical distance measuring device includes a detector for detecting different amounts of radiation in two overlapping detection periods during the radiation pulse period to capture reflections of the radiation pulse at an object surface and a background radiation and/or in two overlapping detection periods during the dark period to capture background radiation. The optical distance measuring device further includes an evaluator determining a signal depending on a distance of the optical distance measuring device to an object based on the detected amount of radiation. Further, the present invention provides a method for optical distance measurement and for multiple sampling.