Photodetection Device Self-Diagnosis Using Switched Light Paths
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Solution Overview
Problem
Current photodetection devices lack a reliable self-diagnosis function to detect faults in their light-receiving sections, which can lead to inaccurate distance measurements and operational failures.
Innovation Solution
A photodetection device and system incorporating a light-receiving section with a photodiode, switches, and a signal generator, controlled by a controller to generate and detect pulse signals, allowing for self-diagnosis by analyzing the timing and voltage changes at specific nodes, thereby identifying faults such as current imbalances or voltage stuck states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a BIST function is implemented using light reflected within the housing, then self-diagnosis capability is improved, but the complexity of the device increases
Solution Approach 1:
The light-receiving section is designed to perform dual functions: detecting external reflected light during normal operation and detecting internal reflected light during self-diagnosis. The same hardware components (photodetector, switches, signal generator) are reused for both measurement and diagnosis purposes, eliminating the need for separate diagnostic hardware and reducing overall device complexity.
Solution Approach 2:
The system performs self-diagnosis by using its own light-emitting section to generate test light and its own light-receiving section to detect the reflected light. The controller automatically controls the switches and monitors the output without requiring external diagnostic equipment, enabling the device to self-test and self-diagnose faults.
2Measurement precision
If multiple switches are added to control light paths for self-diagnosis, then fault detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The light path is segmented into multiple controllable paths using switches. The first switch controls the path for external light detection, while the second switch controls the path for internal reflected light detection. This segmentation allows precise control over which light path is active, enabling accurate fault detection by isolating specific components and paths during diagnosis.
Solution Approach 2:
The switches are dynamically controlled by the controller to change the light path configuration based on the operational mode (normal measurement or self-diagnosis). During self-diagnosis, the controller activates the second switch to route internal reflected light to the light-receiving section, while during normal operation, the first switch is activated for external light detection. This dynamic switching enables flexible and accurate fault detection without permanent structural complexity.
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 effective self-diagnosis and fault detection in the light-receiving sections, ensuring accurate distance measurements and prolonged device operation by identifying and reporting faults, thus preventing operational failures.
Implementation Method 1
The photodetector is configured to detect light reflected by a measurement object of the light emitted from the light-emitting section
Data Source
AI summary
A photodetection device according to the present disclosure includes: a light-receiving section including a light-receiving element, a first switch, a second switch, and a signal generator, the first switch that couples the light-receiving element to a first node by being turned on, the second switch that applies a predetermined voltage to the first node by being turned on, and the signal generator that generates a pulse signal on the basis of a voltage at the first node; a controller that controls operations of the first switch and the second switch; a detector that detects a timing at which the pulse signal is changed, on the basis of the pulse signal; and an output section that outputs a detection signal corresponding to a detection result by the detector when the second switch is turned on.