Transimpedance Imaging Readout for Fast Stable Peak Voltage Capture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing solid-state imaging devices face limitations in high-speed readout of voltage values corresponding to incident light amounts due to the need for a large-capacity capacitor and the time required for output voltage stabilization in the readout circuit.
Innovation Solution
The implementation of a solid-state imaging device configuration that includes photodiodes, charge-voltage converting circuits, pre-holding circuits, transimpedance amplifiers, peak holding circuits, and post-holding circuits, which allow for the conversion and holding of voltage values as currents, enabling high-speed and accurate readout by stabilizing potential differences and suppressing capacity-related speed reductions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large-capacity capacitor is connected to the input terminal of the readout circuit, then the output voltage value becomes steady with high accuracy, but the readout speed decreases due to the time required for voltage stabilization
Solution Approach 1:
The readout circuit is divided into two independent paths: a first readout circuit for reading dark current values and a second readout circuit for reading signal values. Each circuit has its own capacitor (first capacitor C1 and second capacitor C2), allowing them to operate independently without interfering with each other's charging/discharging cycles, thus resolving the speed-accuracy trade-off
Solution Approach 2:
The dark current value is read out in advance before the signal value. The first readout circuit completes its charging and discharging cycles for the dark current measurement before the second readout circuit begins its operation for the signal measurement. This preliminary action allows the signal readout to start without waiting for the dark current readout to complete, improving overall readout speed
Solution Approach 3:
The readout operation is performed periodically in two phases: first reading the dark current value, then reading the signal value. This periodic alternating operation allows both capacitors to be charged and discharged in sequence, ensuring accurate measurements while maintaining high readout speed through efficient time management
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 the readout of voltage values corresponding to incident light amounts with high accuracy and speed, improving sensitivity and stability by using transimpedance amplifiers to convert and hold peak voltage values effectively.
Implementation Method 1
photodiodes which generate charge quantities corresponding to incident light amounts
Implementation Method 2
a transimpedance amplifier which inputs voltage values held and output by the pre-holding circuits as currents, and outputs voltage values converted based on a transimpedance from the currents flowing in accordance with change quantities to the input voltage values from a reference voltage value
Data Source
AI summary
A solid-state imaging device 1 includes photodiodes PD1 to PDN, charge-voltage converting circuits 101 to 10N, pre-holding circuits 201 to 20N, a transimpedance amplifier 30, a peak holding circuit 50, and a post-holding circuit 60. The charge-voltage converting circuit 10n inputs charges generated at the photodiode PDn and outputs a voltage value corresponding to the input charge quantity. The pre-holding circuit 20n holds the output voltage value from the charge-voltage converting circuit 10n and outputs the output voltage value as a current. The transimpedance amplifier 30 inputs voltage values successively output form the pre-holding circuits 201 to 20N as currents and outputs voltage values converted based on a transimpedance from the currents flowing in accordance with change quantities to the input voltage values from a reference voltage value. The peak holding circuit 50 holds and outputs a peak hold voltage of the output voltage values from the transimpedance amplifier 30.