Beam Phasing Adjustment in Optical Smoke Detectors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical beam smoke detector systems with opposing detector units, beam interference can cause false alarms due to timing phasing issues, where one detector's beam may interfere with another's signal, leading to inconsistent signal strength and increased false alarm probabilities.
Innovation Solution
The method involves adjusting the timing of beam projections within a window period around the nominal transmit interval, using pseudo-random or random number sequences to distribute the projection times, ensuring that beams from opposing units are less likely to be in phase, while maintaining consistent response times by linking the randomness to the nominal interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two detector units are installed in an opposed manner to protect larger volumes, then the protection coverage is improved, but beam interference between units causes false alarms
Solution Approach 1:
The system dynamically adjusts the timing of beam projections from opposing detector units. Instead of fixed periodic transmission, each unit varies its transmit timing within a window around the nominal interval, creating dynamic temporal separation that prevents persistent beam interference while maintaining protection coverage.
Solution Approach 2:
The invention changes the temporal parameter of beam projection by introducing random or pseudo-random timing variations within a window. This parameter change ensures that beams from opposing units do not consistently interfere with each other, reducing false alarms while maintaining the same average protection coverage.
2Ease of operation
If beam projection timing is fixed at regular intervals, then the system operation is simple, but opposing units will periodically come into phase causing signal strength variations
Solution Approach 1:
The system transitions from static fixed timing to dynamic variable timing within a window. This allows the system to maintain operational simplicity while preventing the periodic in-phase interference that occurs with fixed intervals, thereby improving signal consistency without significantly complicating the operation.
Solution Approach 2:
The invention uses periodic action with variable phase within a window. Instead of continuous transmission or completely random timing, the system employs periodic beams with random or pseudo-random timing variations within each period, maintaining rhythm while avoiding consistent interference patterns.
3Measurement precision
If beam transmission duration is extended to improve detection sensitivity, then the detection accuracy is improved, but the probability of beam interference between opposing units increases
Solution Approach 1:
By dynamically varying the timing of beam projections within a window, the system can maintain longer transmission durations for improved sensitivity while reducing interference probability. The temporal separation ensured by random timing variations allows longer beams to coexist without consistent overlap, resolving the contradiction between sensitivity and interference.
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
This approach reduces the likelihood of false alarms by minimizing the chances of opposing detector units projecting beams simultaneously, while maintaining consistent response times and ensuring the detector's accuracy in smoke detection.
Implementation Method 1
The transmitter projects a modulated beam, in this example a modulated Infrared (IR) beam, on to the retro-reflector which reflects the IR beam along the same axis back to the receiver
Implementation Method 2
Smoke in the beam path will reduce the amount of light returning to the receiver
Implementation Method 3
Smoke in the beam path will reduce the amount of light returning to the receiver
Data Source
Figure 1
Figure 2~3
AI summary
A method for adjusting the timing of beam projections in a beam detector. The method comprises projecting a beam for the purpose of detecting obscuration of the beam and, if a level of signal of the beam detected is less than a threshold for each of a number of consecutive projections or for each consecutive projection over a pre-determined time period, initiating a warning, signalling an alarm or otherwise reacting. The method further comprising adjusting the timing of projecting the beam from a nominal transmit interval 'T' to be within a window time-period 'W' extending from an amount before to an amount after the nominal transmit interval 'T'.