Patterned Passive Infrared Lens for Directional People Counting
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Solution Overview
Problem
Traditional passive infrared sensors struggle to determine the direction of travel of individuals passing through their field of view, making it difficult to accurately count the number of people entering or exiting an area.
Innovation Solution
A sensor device incorporating a passive infrared sensor and a lens with an asymmetric obstruction that directs infrared radiation unevenly, allowing the control circuit to analyze sensor signals and determine the direction of travel and count individuals based on threshold values or machine learning algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a traditional passive infrared sensor is used to detect individuals passing through an area, then the sensor can detect the presence of individuals, but the direction of travel of individuals cannot be determined
Solution Approach 1:
The patent applies asymmetry by introducing an asymmetric obstruction pattern on the lens that is not symmetric with respect to the optical axis. This asymmetric pattern causes the sensor to receive different amounts of infrared radiation from individuals traveling in different directions, thereby enabling direction detection without adding complex mechanical moving parts or multiple sensors. The asymmetric obstruction creates direction-dependent signal characteristics that allow the single sensor to distinguish travel directions.
2Measurement precision
If traditional passive infrared sensors are used, then the sensors are inexpensive, but they cannot accurately count the number of people entering or exiting an area due to inability to determine direction
Solution Approach 1:
The asymmetric obstruction pattern on the lens creates direction-dependent signal characteristics that enable accurate person counting. By analyzing the temporal profile of infrared radiation signals with respect to the asymmetric obstruction pattern, the system can determine whether an individual is entering or exiting the monitored area, thereby achieving accurate bidirectional person counting with a single passive infrared sensor.
Solution Approach 2:
The patent applies local quality by creating different optical transmission characteristics at different locations on the lens surface through the asymmetric obstruction pattern. Different regions of the lens have different levels of obstruction, which creates spatially varying response characteristics that correspond to different travel directions, enabling the system to locally distinguish between entering and exiting individuals.
3Loss of information
If an asymmetric obstruction is added to the lens to enable direction detection, then the direction of travel can be determined, but the manufacturing complexity increases
Solution Approach 1:
The asymmetric obstruction pattern can be manufactured using standard optical fabrication techniques such as photolithography and deposition processes. The obstruction pattern is formed by depositing opaque material in specific non-symmetric regions of the lens, which is a well-established manufacturing process. This approach maintains compatibility with existing industrial lens manufacturing capabilities while achieving the desired asymmetric optical characteristics for direction detection.
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
Effectively detects the passage and direction of individuals, enabling accurate counting of people entering or exiting an area, improving security and logistical management.
Implementation Method 1
The passive infrared sensor can sense infrared radiation emitted by individuals as they pass within the field of view of the passive infrared sensor
Implementation Method 2
a lens that focuses infrared radiation from individuals onto the passive infrared sensor
Data Source
AI summary
A sensor device includes a passive infrared sensor, a control circuit, and a lens that directs infrared radiation onto the passive infrared sensor. The lens includes an obstruction that asymmetrically blocks transmission of infrared radiation through the lens. The control circuit is configured to determine the direction of crossing of individuals passing in front of the sensor device based on sensor signals from the passive infrared sensor.