Pulse Data Recorder Digital Switch Readout Circuit
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Solution Overview
Problem
Current photon counting systems, such as lidar and medical imaging applications, face limitations in range measurement, intensity information, and high noise levels due to analog circuits and Geiger-mode APDs, which restrict their effectiveness for soft targets and spatial/temporal coverage.
Innovation Solution
A pulse data recorder with an all-digital readout circuit that records the state of a digital switch at each pulse of a clock, allowing for high-speed operation and ultra-high time resolution intensity measurements, using a first-in first-out buffer to store the state of the switch, eliminating the need for analog-to-digital conversion and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog sample and hold circuits are used to store photon counts, then intensity information can be captured, but the number of samples is limited to about 40 due to analog cell size and bandwidth requirements
Solution Approach 1:
The patent replaces analog sample and hold circuits with a digital switching and memory system. Each pixel uses a digital switch controlled by a clock signal to transfer photon count data to memory locations, eliminating the need for analog waveform storage and enabling significantly more samples to be stored with high temporal resolution.
Solution Approach 2:
The patent creates digital copies of photon arrival data in memory, where each clock cycle captures the state of digital switches corresponding to different time intervals. This allows multiple time-resolved samples to be stored without the bandwidth and cell size constraints of analog systems.
2Measurement precision
If high bandwidth analog circuits are used for photon detection, then high temporal resolution can be achieved, but noise levels increase and the system is only useful for hard targets
Solution Approach 1:
The patent replaces high bandwidth analog circuits with digital switching circuits that operate at lower bandwidth but achieve equivalent or better temporal resolution through precise clocked sampling. This digital approach significantly reduces noise while maintaining the ability to resolve photon arrival times with high precision.
Solution Approach 2:
The patent uses periodic clock signals to control digital switches that sample photon arrival data at regular intervals. This periodic sampling approach achieves high temporal resolution without requiring continuous high bandwidth analog processing, thereby reducing noise while maintaining measurement precision.
3Measurement precision
If Geiger-mode APDs are used for photon counting, then single photon detection is possible, but range measurement and intensity information are limited
Solution Approach 1:
The patent segments the detection process into multiple time-resolved samples using clocked digital switches, where each sample captures photon arrival information for a specific time interval. This segmentation preserves both the sensitivity of single-photon detection and the ability to extract range and intensity information from the time distribution of detected photons.
Solution Approach 2:
The patent adds a time dimension to photon detection by recording photon arrivals in multiple time-resolved memory locations. This transforms the detection capability from simple photon counting to four-dimensional data (spatial position, time of arrival, intensity, and range information derived from time distribution).
4Measurement precision
If LIDAR systems are placed in Low Earth Orbit to achieve closer range to surface, then detection sensitivity improves, but the ability to collect data with spatial and temporal coverage is limited due to orbital speed
Solution Approach 1:
The patent enables continuous high-speed photon counting and time-resolved data acquisition that can operate effectively from moving platforms. The digital clocked sampling system maintains accurate time stamps for photon arrivals even during rapid platform motion, allowing LIDAR systems to achieve both detection sensitivity and extensive spatial-temporal coverage without requiring orbital deployment.
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 high frame rates, digital noise reduction, and maximum utilization of high-speed, low-power digital integrated circuit technologies, providing precise time and intensity information for photon arrival records.
Implementation Method 1
the state of a switch is set in response to the occurrence of an event
Data Source
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AI summary
A pulse data recorder system and method are provided. Upon the arrival or occurrence of an event or signal, the state of a digital switch is set. Upon receiving a pulse from a readout clock, the state of the switch is stored in a buffer memory, and the state of the switch is reset. As the readout clock is run, a time history of the state of the switch is obtained. The pulse data recorder can feature a plurality of unit cells, for use in imaging or other multiple pixel applications.