Camera Light Source Over-Current Protection Circuit
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Solution Overview
Problem
Time of flight (ToF) cameras face the risk of eye damage due to over-currents in their light sources, which can lead to abnormal operations and harm human subjects, as existing protection methods are inadequate in managing high current levels effectively.
Innovation Solution
A camera system with a light source protection function that includes a light source driver converting power to pulse current, a current measurement unit, an amplitude controller, a smoothing circuit, and a comparator controller to adjust and interrupt power when the current exceeds a threshold, ensuring safe operation and alerting managers of potential hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a higher current is supplied to the light source to improve optical power density and depth measurement quality, then the measurement precision and image quality are improved, but the risk of eye damage increases due to potential over-current conditions
Solution Approach 1:
The patent applies preliminary action by measuring the current supplied to the light source before it reaches dangerous levels. The current measurement unit continuously monitors the current, and the comparator compares it against a predetermined threshold value in advance, allowing the system to prevent over-current conditions before they can cause eye damage while maintaining high current operation for improved depth measurement quality
Solution Approach 2:
The patent implements feedback by creating a closed-loop control system where the current measurement unit continuously monitors the light source current, compares it with the threshold value, and provides feedback to the light source driver controller. When the current exceeds the threshold, the system automatically reduces the current back to safe levels, enabling the light source to operate at high currents for improved measurement precision while maintaining safety through continuous feedback control
2Device complexity
If a conventional current measurement method is used where the measured current is transmitted directly to the comparator, then the device complexity is reduced, but a malfunction occurs when the measured current exceeds the comparator's operating range
Solution Approach 1:
The patent applies preliminary action by introducing an amplitude control circuit before the comparator that pre-processes the measured current signal. This circuit limits the current amplitude to within the comparator's safe operating range before comparison occurs, preventing malfunctions while maintaining the overall simplicity of the protection circuit structure
Solution Approach 2:
The patent uses an amplitude control circuit as an intermediary component between the current measurement unit and the comparator. This intermediary element conditions the measured current signal by controlling its amplitude, ensuring that the comparator receives signals within its operating range without requiring complex redesign of the entire protection circuit
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 system effectively prevents eye damage by adjusting and interrupting over-currents, providing accurate subject information and enhanced safety through adjustable reference values and real-time monitoring.
Implementation Method 1
a light source (10) configured to emit light to a subject
Implementation Method 2
a smoothing circuit (70) configured to smooth the pulse current of which the amplitude is controlled by the amplitude controller
Data Source
AI summary
Provided is a camera using a light source having a subject eye protection function. The camera includes a light source driver installed between a power supply and a light source for emitting light to a subject and configured to convert electric power supplied by the power supply to a pulse current, a light source driver controller configured to control the light source driver to be turned on or off such that the light source driver converts the electric power supplied by the power supply to the pulse current, a current measurement unit configured to measure the pulse current supplied to the light source, an amplitude controller configured to control an amplitude of the pulse current measured by the current measurement unit, a smoothing circuit configured to smooth the pulse current of which the amplitude is controlled by the amplitude controller, and a comparator controller configured to control the electric power supplied by the power supply to be interrupted in a case in which the smooth current smoothed by the smoothing circuit is greater than a preset threshold value.