Optical Sensor Self-Test Using Internal Reference Target
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Solution Overview
Problem
Optical sensors used in safety systems, such as light curtains and 3D cameras, require frequent performance monitoring due to hazardous operating conditions, but existing methods are not suitable for continuous operation and often require periodic maintenance, making it challenging to test sensor performance without interrupting normal operation.
Innovation Solution
An optical sensor system with a test light source and reference target within the housing, where the test light source periodically emits light at a known wavelength, which is reflected back to the photosensitive devices, allowing a logic circuit to determine the distance and compare it to a predetermined threshold to verify correct operation, enabling continuous performance testing without interrupting normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic maintenance testing is used to monitor sensor performance, then device complexity is reduced, but reliability of continuous monitoring is insufficient for safety systems
Solution Approach 1:
The patent combines the test light source, reference target, and performance evaluation logic directly within the optical sensor housing. This integration allows continuous self-testing without external equipment, resolving the contradiction by embedding monitoring capabilities within the sensor itself, thereby improving reliability without proportionally increasing overall system complexity.
Solution Approach 2:
The optical sensor performs self-diagnosis by using its own components (test light source, reference target, photosensitive devices) to automatically monitor its performance. The sensor generates test signals, measures its own response, and evaluates its health status without requiring external testing equipment or manual intervention, thus improving continuous monitoring reliability while keeping the system simple.
2Measurement precision
If a reference light source is used to test pixel array performance, then measurement precision is improved, but the sensor cannot operate continuously without interruption
Solution Approach 1:
The patent enables continuous operation by implementing periodic self-testing during normal sensor operation. The test light source periodically emits test signals while the sensor continues its primary function of detecting external light. This allows continuous monitoring of sensor health without interrupting productivity, as the testing occurs during regular operational cycles rather than requiring separate maintenance windows.
Solution Approach 2:
The sensor performs periodic self-testing by activating the test light source at regular intervals during normal operation. This periodic action allows continuous monitoring of sensor performance over time while maintaining continuous productivity, as the brief test cycles are embedded within the ongoing operational sequence rather than halting it.
3Measurement precision
If external testing equipment is used to monitor sensor performance, then measurement precision is improved, but ease of operation is reduced due to setup complexity
Solution Approach 1:
The patent merges all testing components (light source, reference target, photosensitive devices, logic circuit) within the sensor housing into a single integrated unit. This eliminates the need for external testing equipment and complex setup procedures, resolving the contradiction by making the sensor self-contained and easy to operate while maintaining measurement precision through its built-in reference target and comparison logic.
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 regular and non-intrusive testing of optical sensor performance, ensuring continuous monitoring and maintenance of safety system reliability, even in applications with infrequent maintenance schedules, by using a test light source and reference target to verify correct operation without affecting normal operation.
Implementation Method 1
The test light source is periodically pulsed on to emit light at a known wavelength
Implementation Method 2
one or more photosensitive devices configured to convert light to electrical signals
Implementation Method 3
The light is reflected from the reference target back to at least a portion of the photosensitive devices
Data Source
Figure 1
Figure 2
AI summary
A system to test operation of an optical sensor (50) is disclosed. The optical sensor (50) includes one or more photosensitive devices (80) configured to convert light to electrical signals. A test light source (60) and a reference target (76) are included within the housing (52) of the optical sensor (50). The test light source (60) is mounted proximate to the photosensitive devices (80) and the reference target (76) is positioned opposite from the test light source (60). The test light source (60) is periodically pulsed on to emit light (62) at a known wavelength. The light (62) is reflected from the reference target (60) back to at least a portion (82) of the photosensitive devices (80). A logic circuit uses the reflected light (64) which is received at the portion (82) of the photosensitive devices (80) to determine the distance between the light source (60) and the reference target (76). This calculated distance is compared against the known distance to verify correct operation of the optical sensor (50).