Passive Infrared Sensor Direction Detection Using Multi-Lenslet Array
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Solution Overview
Problem
Passive infrared sensors lack the ability to detect the direction of motion of objects due to the absence of range information, which is typically provided by active sensors like radars or laser detectors, and are generally less expensive than active sensors.
Innovation Solution
A system comprising a passive infrared sensor coupled with a lens having multiple lenslets to focus infrared energy from different directions, allowing the processor to estimate the direction of motion based on varying intensities of infrared energy detected over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive infrared sensors are used to detect moving objects, then cost is reduced compared to active sensors, but the ability to detect direction of motion is lost due to lack of range information
Solution Approach 1:
The lens is divided into multiple lenslets, each responsible for focusing infrared energy from a specific direction. This segmentation allows the system to capture spatial distribution information of infrared energy, enabling direction of motion detection while maintaining the low cost advantage of passive sensors
Solution Approach 2:
The patent transitions from a single-point detection approach to a multi-directional detection approach by arranging lenslets in a specific geometric pattern. This adds a spatial dimension to the detection capability, allowing the system to infer direction of motion from intensity variations across different lenslets without requiring active sensing
2Measurement precision
If active sensors like radars or laser detectors are used, then direction of motion can be detected based on measured ranges and angles, but the cost increases significantly
Solution Approach 1:
The patent creates an optical copy of the spatial distribution of infrared energy by using an array of lenslets to focus energy from different directions onto corresponding sensor elements. This optical copying approach replicates the directional information that would otherwise require expensive active sensing, achieving similar measurement precision at lower cost
Solution Approach 2:
The patent replaces expensive active sensing components with inexpensive passive infrared sensors combined with simple lenslet arrays. The lenslets act as disposable optical elements that provide directional information through their geometric arrangement, eliminating the need for costly radars or laser detectors while maintaining adequate measurement precision
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 the detection of the direction of motion of warm moving objects using passive infrared sensors, enhancing their functionality without the need for expensive active sensors, by leveraging the intensity variations focused by the lenslets to determine the object's trajectory.
Implementation Method 1
a lens having multiple lenslets configured to focus the infrared energy emitted by the object from different directions
Implementation Method 2
a lens having multiple lenslets configured to focus the infrared energy
Implementation Method 3
a passive infrared sensor configured to detect infrared energy emitted by the object
Data Source
AI summary
A passive infrared sensor system for detecting the direction of movement by a warm object includes a passive infrared sensor and a lens having multiple lenslets. Different lenslets may have different lens characteristics, for example, different focal lengths or thicknesses, to produce focused infrared beams of different intensities for the sensor. As a warm object, such as a person or an animal, moves from one location to another in the field of view of the sensor, the infrared energy emitted by the warm object may be focused by different lenslets having different focal lengths or thicknesses, and the sensor may detect different intensities at different times. A processor may estimate the direction of movement by performing pattern matching of the detected intensities with a database of patterns based on actual statistics or simulations of movements by warm objects in the environment monitored by the sensor, or known characteristics of the environment and the sensor.