Solid-State Imaging Device Distance Measurement Background Light
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Solution Overview
Problem
Conventional solid-state imaging devices using the pulse phase method face limitations in measuring distances accurately due to a narrow dynamic range and low tolerance to intense background light, particularly at long distances or in outdoor environments with strong background illumination.
Innovation Solution
A solid-state imaging device with a light receiving circuit that includes a counter circuit to count the number of light pulses, a comparison circuit to set a threshold, and a storage circuit to store the time signal when the count value exceeds the threshold, allowing for accurate distance measurement even in intense background light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pulse phase method is used for distance measurement, then the distance to far objects can be measured with high resolution, but the dynamic range becomes narrow and the tolerance to intense background light decreases
Solution Approach 1:
The pixel is divided into multiple independent photoelectric conversion units (first photodiode and second photodiode), each capable of independently performing photoelectric conversion. This segmentation allows different units to handle different light intensity ranges, thereby expanding the dynamic range while maintaining measurement precision for distant objects.
2Measurement precision
If the pulse phase method is used for distance measurement, then the distance to far objects can be measured with high resolution, but the tolerance to intense background light decreases
Solution Approach 1:
A time gate control circuit is introduced as an intermediary to control the photoelectric conversion timing. This circuit generates time gate control signals that enable photoelectric conversion only during specific time windows when reflected light is expected, effectively filtering out intense background light that occurs at other times while maintaining accurate distance measurement capability.
3Measurement precision
If the light source intensity is intensified to measure far objects with high resolution, then the measurement precision improves, but the sensitivity to intense background light decreases
Solution Approach 1:
The system employs periodic pulsed illumination and synchronized periodic time-gated detection. The light source emits light in periodic pulses, and the photoelectric conversion is activated in synchronized periodic time windows. This periodic action allows the system to maintain high measurement precision for distant objects while naturally filtering out continuous intense background light through temporal separation.
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
Enables wide-range distance measurement and accurate distance determination in environments with intense background light, overcoming the limitations of the pulse phase method by increasing the dynamic range and tolerance to background noise.
Implementation Method 1
a light receiving element for performing photoelectric conversion of converting received light into an electrical signal
Data Source
AI summary
A plurality of pixels in a solid-state imaging device each include: a light receiving circuit that includes a light receiving element performing photoelectric conversion, sets, by an exposure signal, a photoelectric time for performing the photoelectric conversion, and outputs a light reception signal depending on whether or not incident light has reached the pixel within the photoelectric time; a counter circuit that counts, as a count value, the number of times the incident light has reached the pixel, based on the light reception signal; a comparison circuit that sets a value corresponding to the count value as a threshold, and sets a comparison signal to an on state in the case where the count value is greater than the threshold; and a storage circuit that stores, as a distance signal, a time signal when the comparison signal is in the on state.