Ceiling Mount Intrusion Detector with Arbitrary Direction Detection
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Solution Overview
Problem
Existing ceiling mount intrusion detectors are limited in their ability to detect alarm conditions in arbitrary directions due to the non-rotationally symmetric performance of pyroelectric sensors, particularly missing detections in the vertical direction.
Innovation Solution
A ceiling mount intrusion detector design incorporating a unitary Fresnel lens, formed by splicing two full Fresnel lenses together, and a dual, quad, or multi-element pyroelectric sensor, which projects a detection area pattern allowing for strong signal output in any direction, including vertical, by optimizing the lens dimensions and sensor placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual element pyroelectric sensor is used in a known ceiling mount detector, then the detector can output a strong signal when an intruder passes from one area to another along the strong X axis, but the detector will not output a signal or will output a signal too weak to be detected when the intruder passes evenly through the positive and negative areas along the weak Y axis or does not pass from one area to the other
Solution Approach 1:
The lens is divided into multiple segments or zones with different optical properties. Specifically, the lens includes a first region with a first focal length and a second region with a second focal length, allowing different spatial zones to direct infrared energy to appropriate sensor elements, thereby enabling detection from multiple directions including vertical paths.
Solution Approach 2:
Different regions of the lens are assigned different optical characteristics (different focal lengths) to optimize detection in specific directions. The first region focuses on detecting intruders moving horizontally, while the second region focuses on detecting intruders moving vertically or from other directions, ensuring each area of the lens contributes optimally to detection in its designated direction.
2Ease of manufacture
If a single Fresnel lens with fully concentric annular sections is used, then the lens structure is simple and easy to manufacture, but the pyroelectric sensor performance is non-rotationally symmetric, causing the look down area to be non-rotationally symmetric and missing detections in vertical direction
Solution Approach 1:
The lens deliberately introduces asymmetry by creating regions with different focal lengths in different spatial orientations. This asymmetric design compensates for the non-rotationally symmetric nature of the pyroelectric sensor, transforming the detection pattern into a more symmetric, omnidirectional coverage that maintains manufacturing simplicity while achieving rotational detection capability.
3Productivity
If the lens dimensions and sensor placement are optimized to achieve strong signal output in any direction including vertical, then detection efficiency is enhanced and missed alerts are reduced, but the device complexity increases due to splicing two full Fresnel lenses together
Solution Approach 1:
Two full Fresnel lenses are spliced together to form a unitary lens structure with multiple regions of different focal lengths. This merging approach enables the single lens assembly to provide omnidirectional detection capability, achieving strong signal output in any direction including vertical paths, while consolidating what would otherwise require multiple separate lens components into one integrated unit.
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
Ensures detection of intruders in any arbitrary direction with a peak-to-valley signal value sufficient to identify alarm conditions, reducing missed alerts and enhancing detection efficiency.
Implementation Method 1
A ceiling mount intrusion detector design incorporating a unitary Fresnel lens, formed by splicing two full Fresnel lenses together
Implementation Method 2
a dual element pyroelectric sensor only outputs a strong and clear signal indicative of an alarm condition when energy from an alarm condition, such as an intruder, is detected by a first element of the sensor and then by a second element of the sensor
Data Source
Figure 1A~1D
Figure 2A
Figure 2B~2C
AI summary
A ceiling mount intrusion detector with arbitrary direction detection capability is provided. The detector can include a pyroelectric sensor and a unitary Fresnel lens such that the unitary Fresnel lens includes a first piece of a first full Fresnel lens and a second piece of a second full Fresnel lens and such that the first piece and the second piece are spliced together. Due to the dimensions and location of the unitary Fresnel lens relative to the sensor, the sensor can output a signal indicative of an alarm condition when an object passes in front of the lens at any angle relative to the sensor.