Distance Image Sensor Subframe Timing Control
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Solution Overview
Problem
Existing distance measurement devices face limitations in achieving high distance resolution across various measurement ranges due to background light noise and signal saturation.
Innovation Solution
A distance image measurement device and method that employs a light source generating pulsed light, with a pixel circuit having multiple charge readout regions and control electrodes, allowing for controlled charge transfer and voltage detection, and calculating distance based on detection signals. The device shifts the timing of control pulses relative to the generation of pulsed light across subframe periods to reduce background noise and improve resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light source continuously irradiates the target with pulsed light sequences, then the distance measurement range is expanded, but background light noise increases and distance resolution degrades
Solution Approach 1:
The light source irradiates the target with pulsed light in periodic subframe periods rather than continuously. By dividing the frame period into multiple subframe periods and controlling the light source to emit pulses only during specific subframes, the system reduces background light noise accumulation while maintaining expanded distance measurement range. This periodic illumination approach directly addresses the contradiction by limiting exposure time while preserving measurement capabilities.
Solution Approach 2:
The frame period is segmented into multiple subframe periods (first to N-th subframe periods), and the charge readout regions are divided into multiple regions (first to M-th regions). This segmentation allows different time windows to capture different distance ranges, enabling the system to expand measurement range while reducing noise by only activating specific segments during specific subframes based on the measurement requirements.
2Adaptability or versatility
If multiple charge readout regions are provided to expand distance measurement range, then various distance ranges can be measured, but device complexity increases
Solution Approach 1:
Each charge readout region is designed to serve multiple distance measurement ranges through the subframe period mechanism. By controlling which charge readout region accumulates charge during which subframe period, the system enables each hardware component to perform multiple measurement functions, thereby expanding the overall measurement range without proportionally increasing device complexity.
Solution Approach 2:
The system uses periodic subframe periods to control charge transfer to different readout regions. During the first subframe period, charge is transferred to the first charge readout region; during the second subframe period, charge is transferred to the second charge readout region, and so on. This temporal multiplexing allows multiple measurement ranges to be captured using the same physical hardware, reducing complexity compared to having dedicated hardware for each range.
3Productivity
If the second duration is set equal to or longer than the first duration to ensure complete charge transfer, then charge transfer efficiency is improved, but measurement time increases
Solution Approach 1:
The charge transfer process is organized into periodic subframe periods, where each subframe period handles a specific portion of the charge transfer task. By distributing the charge transfer across multiple timed subframes rather than requiring a single extended period, the system maintains high transfer efficiency while managing the total measurement time through parallel processing of different distance ranges in different subframes.
Solution Approach 2:
The control pulses are designed to be applied in advance during specific subframe periods to prepare the charge transfer before the actual measurement phase. By pre-positioning charges in appropriate readout regions during earlier subframe periods, the system ensures efficient charge transfer is ready when needed, reducing the time required during the critical measurement phase.
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 enhances distance resolution and reduces errors caused by background light, enabling accurate distance measurement across a wide range while preventing signal saturation.
Implementation Method 1
a photoelectric conversion region configured to convert light into charge
Data Source
AI summary
A distance image sensor includes a light source that generates pulsed light, a light source control means for controlling the light source, a pixel circuit including a photoelectric conversion region, charge readout regions, a charge discharge region, and control electrodes, a charge transfer control means for sequentially applying a control pulse to the control electrodes, and a distance calculation means for reading voltages of the charge readout regions as detection signals and repeatedly calculating a distance on the basis of the detection signals, and the charge transfer control means sets timings of the control pulses so that delay times of the control pulses with respect to a generation timing of the pulsed light is shifted to a time differing between the four types of subframe periods in one frame period.