Pin Hole Optical Filtering for Sensor Saturation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensor systems face challenges in efficiently measuring distances to objects at large distances due to saturation issues with detectors under high ambient light conditions and the need for expensive avalanche photo diodes.
Innovation Solution
A sensor system utilizing single-photon CMOS silicon photo-multipliers with a pin hole and optical elements to image laser radiation at a fixed distance, combined with a diffusor to scatter laser radiation and reduce saturation, allowing for efficient time-of-flight distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional detectors are used for distance measurement, then the system can operate, but the detectors saturate under high ambient light conditions at large distances
Solution Approach 1:
A pin hole is introduced as an intermediary optical element between the ambient light source and the detector. This pin hole selectively transmits only the laser radiation while blocking the broader spectrum ambient light, thereby preventing detector saturation while maintaining distance measurement capability
Solution Approach 2:
The detector surface is optimized to have different properties for different wavelength ranges. The pin hole creates a localized beam path that maintains high intensity for the laser wavelength while the detector's spectral response is tuned to be highly sensitive only to this specific wavelength, rejecting ambient light
2Reliability
If avalanche photo diodes are used to avoid saturation, then detector reliability improves, but the system cost increases significantly
Solution Approach 1:
The patent replaces expensive avalanche photo diodes with much cheaper silicon-based photo-multipliers. By introducing the pin hole to pre-filter ambient light before it reaches the detector, the system achieves saturation resistance without requiring expensive specialized detectors, making the system cost-effective
Solution Approach 2:
The pin hole serves as a simple, low-cost intermediary that performs the critical function of ambient light rejection, enabling the use of inexpensive detectors while maintaining system reliability
3Measurement precision
If the detector is positioned to capture reflected laser radiation, then distance measurement is enabled, but ambient light also reaches the detector causing saturation
Solution Approach 1:
A pin hole is positioned in the optical path between the ambient light environment and the detector. This intermediary element allows the collimated laser beam to pass through while blocking the divergent ambient light, enabling time-of-flight measurement without ambient light interference
Solution Approach 2:
The optical path is segmented into a dedicated laser beam path through the pin hole and a blocked ambient light path. This spatial segmentation separates the useful signal (laser radiation) from the harmful interference (ambient light) before they reach the detector
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
Enables cost-effective and high-resolution distance measurement up to 300 meters with reduced detector saturation, using less expensive single-photon CMOS silicon-based photo-multipliers and minimizing the impact of ambient light.
Implementation Method 1
detect a proportion of the laser radiation that is reflected back at at least one object illuminated by the laser radiation
Implementation Method 2
an optical element to image the laser radiation to at least one image point at a fixed distance in an optical far field of the sensor system
Implementation Method 3
the detector is designed to measure a time-of-flight of the reflected laser radiation
Implementation Method 4
A pin hole in front of the detector. A diameter of the pin hole corresponds approximately to a size of the image point
Data Source
AI summary
A sensor system and a method for operating a sensor system are disclosed. In an one embodiment, the sensor system includes a light source configured to emit laser radiation and an optical element configured to image the laser radiation to at least one image point at a fixed distance in an optical far field of the sensor system. A detector is configured to detect a proportion of the laser radiation reflected back at at least one object illuminated by the laser radiation. A pin hole is located in front of the detector, a diameter of the pin hole corresponds to a size of the image point within a factor of 2.