Buffer Capacitor Acquisition Circuit for Short-Pulse Photodetector Signals
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Solution Overview
Problem
Conventional imaging system acquisition circuits are inadequate for active imaging systems where photodetectors emit intense currents for very short durations, requiring high energy supply to ensure accurate light flux measurement while maintaining limited energy availability.
Innovation Solution
The acquisition circuit incorporates a buffer capacitor with at least equal capacitance to the integration capacitor, along with additional electronic switches to manage and store the current emitted by the photodetector, allowing efficient energy use and precise measurement of short-duration current pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional integrator pixel architecture is used, then the circuit can perform data acquisition, but it requires large energy supply to handle intense short-duration currents from photodetectors in active imaging systems
Solution Approach 1:
The acquisition circuit is segmented into two distinct capacitor components: a first integration capacitor for charge accumulation and a second buffer capacitor for voltage stabilization. This segmentation allows each capacitor to be optimized for its specific function, reducing overall energy consumption while maintaining measurement accuracy during short-duration intense current pulses from photodetectors
Solution Approach 2:
The second buffer capacitor acts as an intermediary element between the photodetector and the first integration capacitor. It buffers the intense short-duration current, preventing direct impact on the integration capacitor and reducing the energy required to maintain stable voltage levels during acquisition
2Measurement precision
If the integration capacitor is directly connected to the photodetector, then the circuit is simple, but it cannot maintain perfect measurement of light flux during very short acquisition windows
Solution Approach 1:
The capacitor function is segmented into two separate components with distinct roles: the first integration capacitor accumulates charge from the photodetector, while the second buffer capacitor maintains voltage stability. This segmentation enables precise light flux measurement during short acquisition windows by ensuring stable voltage reference throughout the integration process
Solution Approach 2:
The second buffer capacitor serves as an intermediary that stabilizes the voltage at the photodetector output before charge transfer to the integration capacitor. This intermediary buffer ensures that voltage fluctuations during intense short-duration current pulses do not compromise measurement precision
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 configuration enables precise acquisition of short scenes with reduced energy consumption, maintaining high measurement precision and linearity, suitable for both active and passive imaging applications.
Implementation Method 1
photodetector 1 delivers a current that charges integration capacitor C1
Implementation Method 2
integration capacitor C1 connected between the first input terminal of amplifier 2 and an output terminal S of amplifier 2
Data Source
AI summary
The acquisition circuit comprises a second and third electronic switch connected in series between a photodetector and a first input terminal of an amplifier. A reference voltage is applied to a second input terminal of the amplifier, the reference voltage being applied between the photodetector and the second electronic switch by means of a fourth electronic switch. An integration capacitor and a first electronic switch are connected in parallel between the first input terminal and an output terminal of the amplifier. A buffer capacitor is connected between a common terminal of the second and third electronic switches and a secondary voltage. The electrical capacitance of the buffer capacitor is at least equal to that of the integration capacitor.