Distance Measuring Device Using Damped Oscillation Waveforms
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Solution Overview
Problem
Existing distance measuring devices using pulses of light face challenges with high production costs due to the need for expensive, power-consuming, and heat-generating A/D converters with high sampling frequencies, and require complex bias voltage adjustments for avalanche photodiodes.
Innovation Solution
A distance measuring device incorporating an avalanche photodiode, an amplifier circuit, a differential amplifier, damping circuits, and an A/D converter, where the signal path allows direct current signals, and the damping circuits convert pulse signals into damped oscillation waveforms, enabling effective sampling with a lower sampling frequency and simplified bias voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high sampling frequency A/D converter is used to directly sample narrow pulse waveforms, then measurement precision is improved, but device cost, power consumption, and heat generation increase significantly
Solution Approach 1:
An LC damping circuit is introduced as an intermediary between the photodetector and the A/D converter. This damping circuit transforms the narrow pulse waveform into a damped oscillation waveform with longer duration, enabling the use of a lower sampling frequency A/D converter while maintaining measurement precision. The damping circuit acts as a mediator that reconciles the conflict between pulse width and sampling requirements.
Solution Approach 2:
The patent changes the waveform parameter of the pulse signal by introducing damping. The narrow pulse waveform is transformed into a damped oscillation waveform with different temporal characteristics (longer duration, exponentially decaying amplitude). This parameter change allows the A/D converter to operate at a lower sampling frequency while still capturing sufficient information for accurate distance measurement.
2Measurement precision
If a high sampling frequency A/D converter is used to directly sample narrow pulse waveforms, then measurement precision is improved, but device cost increases significantly
Solution Approach 1:
The LC damping circuit serves as a cost-effective intermediary that enables the use of a lower sampling frequency A/D converter. By transforming the pulse waveform into a damped oscillation waveform, the system can employ more affordable A/D converters with lower sampling frequencies, significantly reducing production costs while maintaining measurement precision.
Solution Approach 2:
The patent employs a simple LC damping circuit implementation using standard electronic components (inductors and capacitors) that are relatively inexpensive. This approach replaces the need for expensive high sampling frequency A/D converters, achieving cost reduction through the use of cheaper, more readily available components.
3Measurement precision
If a high sampling frequency A/D converter is used to directly sample narrow pulse waveforms, then measurement precision is improved, but heat generation increases significantly
Solution Approach 1:
The LC damping circuit acts as an intermediary that enables the system to use a lower sampling frequency A/D converter. Since power consumption and heat generation are reduced by using a lower sampling frequency converter, the damping circuit mediates between the need for precise measurement and the desire to minimize thermal output.
Solution Approach 2:
By changing the waveform parameter from a narrow pulse to a damped oscillation waveform, the system reduces the data rate requirements, which in turn reduces the power consumption and heat generation of the A/D converter while maintaining the necessary measurement precision.
4Measurement precision
If bias voltage is finely adjusted for each avalanche photodiode product, then measurement precision is improved, but device complexity and production cost increase
Solution Approach 1:
The patent implements a self-service approach by incorporating an automatic bias voltage adjustment circuit that automatically determines and sets the optimal bias voltage for each avalanche photodiode. This eliminates the need for manual fine adjustment by technicians, reducing adjustment complexity and production cost while maintaining detection sensitivity.
Solution Approach 2:
The automatic bias voltage adjustment circuit employs feedback mechanisms to monitor and adjust the bias voltage based on the actual performance of the avalanche photodiode. This feedback-based approach ensures optimal detection sensitivity while eliminating the complexity of manual adjustment processes.
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 configuration achieves high accuracy and cost-effectiveness by increasing sampling points with damped oscillation waveforms and simplifying bias voltage adjustments, reducing production costs and power consumption.
Implementation Method 1
an avalanche photodiode, which detects pulsed light that is reflected from an object to be measured
Implementation Method 2
an amplifier circuit, which converts electric current output from the avalanche photodiode into a voltage pulse signal
Implementation Method 3
damping circuits, which convert the pulse signals from the differential amplifier into signals with a damped oscillation waveform
Data Source
Figure 1
AI summary
A distance measuring device is provided at low cost. The distance measuring device includes an avalanche photodiode 101, a TIA 103, a differential amplifier 104, damping circuits 105, 106, and an A/D converter 107. The avalanche photodiode 101 detects pulsed light that is reflected from an object to be measured. The TIA 103 is an amplifier circuit that converts electric current output from the avalanche photodiode 101 into a voltage signal. The differential amplifier 104 is arranged in a rear stage of the TIA 103 and differentially amplifies the voltage signal. The damping circuits 105, 106 are arranged in a rear stage of the differential amplifier 104 and convert the pulse signals from the differential amplifier 104 into signals with a damped oscillation waveform. These signals are A/D converted by the A/D converter 107. The signal path from the avalanche photodiode 101 to the A/D converter 107 allows a direct current signal to pass therethrough.