Fresnel Lens Sensing Device Flame-Resistant Housing
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Solution Overview
Problem
Existing sensing devices with Fresnel lenses, when used with passive infrared sensors, fail to provide flame-resistant performance, leading to high costs due to the need for isolated driving circuits.
Innovation Solution
A sensing device with a housing made from flame-resistant material, incorporating a non-isolated driving circuit and a Fresnel lens, which transmits light to a glass window sensor, ensuring flame resistance without blocking light and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Fresnel lens is used with a passive infrared sensor to implement human body induction, then the sensing function is achieved, but the device fails to pass flammability tests and requires expensive isolated driving circuits
Solution Approach 1:
The housing is divided into a lens holder and a sensor chamber that are physically separated. The lens holder contains the Fresnel lens and can be made of flame-resistant material, while the sensor chamber houses the passive infrared sensor. This segmentation allows the optical path to be isolated from the electronic components, enabling the use of flame-resistant materials in the lens holder without requiring the entire housing to be flame-resistant, thus eliminating the need for expensive isolated driving circuits.
Solution Approach 2:
A reflective plate is introduced as an intermediary element between the Fresnel lens and the passive infrared sensor. The reflective plate redirects infrared light from the lens to the sensor, allowing the lens to be positioned closer to the external environment where flame-resistant material can be used, while the sensor remains in a protected chamber. This intermediary structure enables the decoupling of the flame-resistant optical component from the electronic sensor components.
2Reliability
If a flame-resistant housing is used to enclose the sensor and circuit board, then flame-resistant performance is achieved, but light transmission to the sensor may be blocked
Solution Approach 1:
The housing is segmented into distinct functional zones: a lens holder made of flame-resistant material that can be positioned close to heat sources, and a sensor chamber that houses the passive infrared sensor. The segmentation allows the flame-resistant portion to handle thermal exposure while the sensor portion remains protected, maintaining both flame resistance and optimal light transmission conditions.
Solution Approach 2:
The optical path is extended into a three-dimensional configuration using a curved reflective plate that redirects infrared light at angles. This dimensional change in the light path allows the Fresnel lens to be positioned in a location optimized for flame-resistant material usage, while the sensor receives adequate infrared energy through the redirected optical path, maintaining sensing effectiveness.
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
The solution provides effective flame-resistant performance while lowering costs by using a non-isolated circuit and maintaining the ability to sense human presence, even in environments with heat from lighting devices.
Implementation Method 1
a Fresnel lens arranged above the sensor and configured to transmit light to the sensor
Implementation Method 2
a sensor provided with a glass window to transmit light and configured to sense light incident upon the sensor
Implementation Method 3
The sensor is a passive infrared sensor
Data Source
AI summary
The application relates to a sensing device and a lighting device. The sensing device comprises a sensor provided with a glass window to transmit light and is configured to sense light incident upon the sensor; a circuit board, wherein one side of the circuit board is provided with the sensor; a Fresnel lens arranged above the sensor and configured to transmit light to the sensor; and a housing made from a flame-resistant material, wherein the housing comprises an accommodation space configured to accommodate the sensor and the circuit board, and the housing is provided with a center hole to expose the glass window. By adopting the technical solution, the sensor has flame-resistant performance.