Multi-Tap Pixel Circuit for Real-Time Fluorescence Lifetime Imaging
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Solution Overview
Problem
Conventional fluorescence lifetime imaging methods are limited by slow acquisition speeds and high costs, making real-time imaging infeasible, especially in applications involving moving objects or requiring high frame-rates, due to issues with photon detection rates, photon loss, and complex data handling.
Innovation Solution
A pixel circuit using a center-of-mass method (CMM) for fluorescence lifetime estimation, combined with a multi-tap pixel circuit and compressive analog-to-digital (ADC) conversion, which allows for high-speed imaging by sampling electrons at multiple locations and reducing data processing cycles, enabling efficient photon acquisition and data handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-correlated single photon counting (TCSPC) is used for fluorescence lifetime imaging, then measurement precision is improved, but productivity deteriorates due to slow acquisition speed
Solution Approach 1:
The patent divides the pixel array into multiple independently controllable regions with separate readout paths, allowing simultaneous acquisition from multiple segments. This segmentation enables parallel processing of fluorescence lifetime data, significantly increasing overall acquisition speed while maintaining measurement precision through dedicated timing circuits in each segment.
Solution Approach 2:
The patent implements preliminary time-gating before full photon detection, where a fast initial gate captures the early fluorescence decay portion to establish timing reference. This preliminary action allows subsequent full-frame acquisition to proceed at higher speeds without sacrificing lifetime measurement accuracy, as the timing calibration is already established.
2Reliability
If high frame-rates are implemented for redundant imaging, then reliability is improved, but loss of time increases due to extended acquisition duration
Solution Approach 1:
The patent maintains continuous photon detection across multiple frames by eliminating dead time between acquisitions through overlapping readout buffers and continuous integration cycles. This continuity allows high frame-rates to be achieved without extending total imaging time, as the system continuously accumulates useful signal data without interruption or idle periods.
Solution Approach 2:
The patent introduces a temporal dimension to the pixel readout by implementing multi-layer buffering where different frames are stored in different temporal layers. This allows simultaneous processing of multiple frames in parallel temporal streams, achieving high frame-rates for redundant imaging while keeping total acquisition time constant through temporal multiplexing.
3Measurement precision
If conventional time-resolved imaging methods are used, then measurement precision is maintained, but device complexity increases due to sophisticated equipment requirements
Solution Approach 1:
The patent merges the fluorescence lifetime measurement function directly into the standard CMOS image sensor pixel circuit, combining photodetection, timing measurement, and data storage in a single integrated pixel unit. This integration eliminates the need for separate external timing equipment while maintaining measurement precision through on-pixel timing circuits that operate synchronously with the image sensor readout.
Solution Approach 2:
The patent implements self-service timing measurement where each pixel autonomously measures its own fluorescence decay timing using local integration capacitors and transfer gates. The pixel circuit independently performs the time-gating operation and stores the timing-resolved signal without requiring external timing control, thereby reducing device complexity while preserving measurement precision through distributed autonomous measurement.
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 enables real-time fluorescence lifetime imaging with a wide dynamic range and high-speed data processing, overcoming limitations of existing methods by improving frame-rates and reducing costs through efficient photon economy and data compression.
Implementation Method 1
receiving at a pixel circuit a fluorescent light input emitted from a material
Implementation Method 2
performing a center-of-mass method (CMM) calculation using the two electrical outputs; and determining a lifetime parameter (τ) based on the CMM calculation
Data Source
AI summary
A pixel circuit that includes: a substrate body having a channel influenced by an electric field; an aperture in communication with the channel for receiving a fluorescent light input and moving electrons through the substrate body; and a plurality of sampling devices adapted to be switched on simultaneously to sample the moving electrons.