Adjustable Pulse Width TOF Sensor for Distance Resolution
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Solution Overview
Problem
Conventional time-of-flight distance image sensors face challenges in optimizing measurement accuracy across both short and long distances within a defined measurement range, as the accuracy at short and long distances cannot be simultaneously optimized due to the fixed pulse width of the light pulse.
Innovation Solution
A distance image capturing device that includes a light source unit, a light receiving pixel unit with a photoelectric conversion device and electric charge accumulating units, and a distance image processing unit that switches between normal and detailed measurement modes to adjust the phase and width of the radiation light based on the distance to the object, allowing for improved distance resolution across the measurement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed pulse width of light is used for distance measurement, then the measurement range can be defined, but the measurement accuracy cannot be optimized for both short and long distances simultaneously
Solution Approach 1:
The patent applies dynamics by making the light pulse width adjustable rather than fixed. The control unit dynamically changes the pulse width parameter based on the measurement requirements - using wider pulses for long distances and narrower pulses for short distances, allowing the system to adapt to different measurement scenarios and optimize accuracy for each range
Solution Approach 2:
The patent changes the temporal parameter (pulse width) of the light signal to resolve the contradiction. By varying the pulse width parameter according to the target distance, the system achieves high measurement precision across different ranges - wider pulses provide better signal strength for distant objects while narrower pulses provide better temporal resolution for close objects
2Length of stationary object
If the pulse width is widened to measure longer distances, then the maximum measurement range increases, but the distance resolution at short distances deteriorates
Solution Approach 1:
The system dynamically adjusts the pulse width based on the required measurement range. When measuring long distances, the control unit sets a wider pulse width to ensure sufficient signal return. When measuring short distances, it switches to a narrower pulse width to maintain high distance resolution, thus preventing the deterioration of short-distance measurement accuracy
Solution Approach 2:
The control unit preliminarily determines the appropriate pulse width based on the expected measurement distance before actual measurement begins. This preliminary setting of parameters ensures that the optimal pulse width is already configured for the specific measurement scenario, preventing resolution loss at short distances
3Measurement precision
If the pulse width is narrowed to improve short distance resolution, then the distance resolution at short distances improves, but the maximum measurable distance decreases
Solution Approach 1:
The system employs dynamic parameter adjustment where the pulse width is narrowed specifically when short-distance measurement is required, improving resolution in that regime. When the measurement target is at long distance, the system dynamically widens the pulse width again to restore the maximum measurable distance capability, thus resolving the trade-off through conditional parameter changes
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 enhances the accuracy of distance measurement across the entire range from short to long distances by adjusting the phase and width of the radiation light, thereby improving the distance resolution and S/N ratio, especially in the detailed measurement mode.
Implementation Method 1
a photo electric conversion device that receives reflected light which the radiation light has been reflected from an object in the measurement space and background light in an environment of the measurement space, and that generates an electric charge in accordance with the received reflected light and the background light
Implementation Method 2
distance image sensors of a time of flight (hereinafter, referred to as "TOF") system measuring the distance between a measurement unit and an object on the basis of a flying time of light in a space (measurement space) using the fact that the speed of light is known
Data Source
AI summary
The present invention includes a light source unit; a light receiving pixel unit which includes a photo electric conversion device and an electric charge accumulating unit, and a distance image processing unit, when the distance is measured by an input voltage in accordance with an electric charge accumulated in the electric charge accumulating unit, that: measures a distance via a normal mode at a predetermined width of radiation light when the distance is measured by an input voltage in accordance with an electric charge accumulated in the electric charge accumulating unit, and switches to the detailed measurement mode according to the distance to the object measured via the normal mode and adjusts a phase of the radiation light radiated from the light source unit by a detailed measurement mode.