Photodiode-Augmented IR Sensor Sunlight False Positive Reduction
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Solution Overview
Problem
Conventional pyroelectric infra-red (PIR) motion sensors often produce false positive signals due to transient rays of light from the sun, limiting their effectiveness in outdoor use during daylight hours.
Innovation Solution
A photodiode-augmented IR sensor system that combines an IR element with an ambient light-sensing element, using a Fresnel lens to detect both IR radiation and visible light, allowing for the differentiation between true motion and false positives by analyzing the presence or absence of IR and visible light simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional PIR motion sensor is used to detect IR radiation, then motion detection capability is provided, but false positive signals occur due to transient sunlight rays
Solution Approach 1:
The patent combines a PIR sensor and a photodiode into a single sensor unit, allowing simultaneous detection of IR radiation and visible light. The processor analyzes both signals together to distinguish true motion from false positives caused by sunlight, thereby improving reliability while eliminating harmful false signals.
Solution Approach 2:
The photodiode provides feedback information about visible light intensity to the processor. When the processor detects high visible light intensity from the photodiode coinciding with an IR signal from the PIR sensor, it identifies the IR signal as a false positive and suppresses it, thus improving motion detection accuracy.
2Adaptability or versatility
If conventional PIR motion sensors are used outdoors during daylight, then motion detection is attempted, but reliability deteriorates due to sunlight interference
Solution Approach 1:
By merging PIR and photodiode sensors in one unit, the system gains the ability to operate reliably outdoors during daylight. The photodiode monitors visible light conditions, and when sunlight is detected, the processor compensates for its interference on the PIR sensor, enabling accurate motion detection in previously unsuitable conditions.
Solution Approach 2:
The photodiode acts as an intermediary that monitors visible light intensity and provides information to the processor about sunlight conditions. This intermediary data allows the processor to interpret PIR signals correctly in the presence of sunlight, improving reliability in outdoor daylight environments.
3Reliability
If PIR sensors are placed indoors away from windows, then false positives from sunlight are reduced, but adaptability to outdoor use is limited
Solution Approach 1:
The combined PIR-photodiode sensor unit enables outdoor deployment by providing built-in sunlight discrimination capability. The photodiode detects visible light from sunlight, allowing the processor to distinguish true motion from false positives even when the sensor is exposed to direct sunlight outdoors, thus improving adaptability without sacrificing reliability.
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 accurate detection of motion while minimizing false positives from sunlight, allowing the sensor to function effectively during daylight hours and improving its reliability in various environmental conditions.
Implementation Method 1
A photodiode-augmented IR sensor includes a Fresnel lens
Implementation Method 2
an IR element configured to generate a first output in response to received infra-red (IR) radiation
Implementation Method 3
an ambient light-sensing element configured to generate a second output in response to received visible light
Data Source
AI summary
Methods and apparatus relating to a photodiode-augmented infrared (IR) motion sensor are provided. The IR motion sensor can be used to sense mid-IR range radiation emitting from a person. Within the IR motion sensor, incident mid-IR range radiation impinges on an IR sensing element situated behind a Fresnel lens. Thus, when the person crosses a particular region in the range of the IR motion sensor, the IR sensing element detects a change in radiation signature, and can subsequently notify another system, such as a security system, of the change. The IR motion sensor also includes an ambient light-sensing element configured to provide information used to perform a quality check, such as to rule out “false positive” outputs, on information output from the IR sensing element.