Laser Scanning Safety Circuit for Sync-Loss Shutdown
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Solution Overview
Problem
Existing laser scanning devices face challenges in ensuring reliable operation of safety circuits during abnormal firmware operations, particularly in Class 3R classification, where the risk of laser exposure is higher in stationary states, and there is a need to prevent laser emission during abnormal conditions to meet safety standards.
Innovation Solution
A scanning optical device with a safety circuit that includes a protection circuit connected to a switch, which automatically switches to an OFF state if a synchronizing signal is not received for a predetermined time, independent of firmware control, ensuring reliable safety even in abnormal firmware operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a firmware-based safety control system is used to manage laser emission, then the device can be designed for Class 3R safety classification, but the reliability of the safety circuit deteriorates when firmware abnormalities occur
Solution Approach 1:
A hardware protection circuit is introduced as an intermediary between the firmware control system and the laser emission. This protection circuit monitors the synchronizing signal and independently controls the switch to prevent laser emission when abnormalities are detected, ensuring safety without relying solely on firmware reliability
Solution Approach 2:
The patent replaces the purely software-based (firmware) safety control mechanism with a hardware-based protection circuit. This substitution ensures that safety functions operate independently of firmware conditions, providing reliable protection even when firmware abnormalities occur
2Reliability
If the laser is controlled to emit only during rotation, then safety requirements for Class 3R are satisfied, but the response time of the safety circuit to abnormal conditions deteriorates
Solution Approach 1:
The protection circuit is pre-configured with a timer that starts counting when the switch is turned ON. This preliminary timing setup allows the circuit to immediately detect when the synchronizing signal fails to appear within the expected duration, enabling rapid safety response without waiting for additional detection cycles
3Reliability
If a hardware protection circuit with timer is added, then the reliability of safety control is improved, but the device complexity increases
Solution Approach 1:
The protection circuit merges multiple functions into a single integrated hardware unit: synchronizing signal monitoring, timer operation, and switch control. By combining these functions in one circuit, the patent achieves reliable safety control while minimizing the increase in overall device 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
The solution ensures safe and reliable operation of the laser scanning device by preventing laser emission during abnormal conditions, adhering to safety standards and reducing startup time, while being hardware-based to avoid firmware intervention failures.
Implementation Method 1
a laser element; a deflector configured to deflect a light emitted from the laser element
Implementation Method 2
an output unit configured to receive the light deflected and scanned by the deflector and to output a synchronizing signal
Data Source
AI summary
A scanning optical device includes a deflector to deflect a laser light from a lase element, a detector to output a synchronizing signal, a switch provided in a supplying path which supplies a current to the laser element and to be switched to an ON state and to an OFF state. A protection circuit to which the synchronizing signal is inputted from the detector changes an output when a predetermined time depending on a time constant there of elapses, and of which the output is connected to the switch. The protection circuit changes the output, in a case in which the synchronizing signal is not inputted from the detectors for the predetermined time from when the switch is switched to the ON state by a control signal, and thereby the switch is switched to the OFF state irrespective of a state of the control signal.