Distance Measuring Device Random Modulation ToF
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Solution Overview
Problem
Existing distance measuring devices based on time of flight (ToF) measurement face a trade-off between maximum measuring distance and distance resolution, where decreasing the frequency of intensity-modulated light to extend the maximum measuring distance results in a decrease in distance resolution.
Innovation Solution
The proposed distance measuring device employs a light source, photoelectric converter, charge accumulator, timing controller, delay controller, and distance calculator, using a square wave modulation signal with randomly selected high and low level periods to calculate the time difference and distance, allowing for extended maximum measuring distance without compromising resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the frequency of intensity-modulated light is decreased to extend the maximum measuring distance, then the maximum measuring distance is improved, but the distance resolution deteriorates
Solution Approach 1:
The invention segments the measurement process into multiple accumulation periods, where electric charges are accumulated over multiple cycles of the modulation signal. This allows the system to effectively integrate signals over a longer time period, extending the maximum measurable distance while maintaining resolution through the segmented accumulation approach rather than requiring a single long-period signal
Solution Approach 2:
The invention employs periodic accumulation of electric charges over multiple periods of the modulation signal. By accumulating charges during multiple high-level periods and comparing them across different accumulation periods, the system achieves extended measurement range while preserving distance resolution through the periodic integration process
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 approach enables the device to measure distances up to twice the previous maximum without reducing resolution, by varying the delay period and using multiple reference timing signals to accurately determine the time difference and distance, while maintaining high measurement accuracy across different ranges.
Implementation Method 1
a photoelectric converter configured to receive light from the target space within reception time period and produce an amount of electric charges corresponding to an intensity of the received light
Data Source
AI summary
The distance measuring device includes a light source (1), a light-receiving sensor (2), a timing controller (5), a distance calculator (6), and a delay controller (8). The timing controller (5) outputs a modulation signal and plural reference timing signals. The modulation signal is a square wave signal having high and low level periods appearing alternately. Each of the high and low level periods has its length randomly selected from integral multiples of a predetermined unit time period. The reference timing signals include a signal having the same waveform as that of the modulation signal and a signal having the same waveform as that of the inverted modulation signal. The light source (1) varies an intensity of the light in concordance with the modulation signal. The delay controller (8) delays the plural reference timing signals by the delay period (Td) to create plural timing signals respectively. The light-receiving sensor (2) accumulates the electric charges generated within the reception time period, with regard to each of the timing signals. The distance calculator (6) calculates the time difference (τ) from amounts of the electric charges respectively associated with the timing signals, and calculates a distance (L) to the target (3) on the basis of the time difference (τ) and the delay period (Td).