Variable Capacitance Integrating Circuit for Trigger Photodiode
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Solution Overview
Problem
Conventional solid-state imaging apparatuses face challenges in optimally utilizing the trigger photodiode, particularly in X-ray imaging, where the trigger photodiode's signal is used for both detection and exposure calculation, leading to sensitivity issues and potential saturation, affecting the overall operation and performance.
Innovation Solution
The apparatus varies the charge accumulation capacitance value of the integrating circuit between high and low levels before and after detection of incident light, adjusting the sensitivity of the integrating circuit to the trigger photodiode to prevent saturation and ensure optimal utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the integrating circuit uses high sensitivity to detect incident light through the trigger photodiode, then detection accuracy is improved, but the output signal saturates when used for total exposure calculation
Solution Approach 1:
The patent applies dynamics by making the capacitance value of the integrating circuit variable rather than fixed. The control unit dynamically adjusts the capacitance value based on the operational phase: using a first (lower) capacitance value during incident light detection to prevent saturation, and a second (higher) capacitance value during total exposure calculation to improve measurement precision. This dynamic adaptation resolves the contradiction between detection accuracy and signal saturation.
Solution Approach 2:
The patent changes the parameter of capacitance value in the integrating circuit according to different operational requirements. By switching between a first capacitance value (for detection phase) and a second capacitance value (for exposure calculation phase), the system optimizes performance for each specific task, preventing signal saturation during detection while ensuring accurate total exposure measurement.
2Device complexity
If the trigger photodiode signal is used for both incident light detection and total exposure calculation, then device complexity is reduced, but optimal utilization of the trigger photodiode is compromised
Solution Approach 1:
The patent makes the integrating circuit adaptable by dynamically changing its capacitance value based on the intended use of the trigger photodiode signal. This allows the same trigger photodiode to be optimally utilized for different purposes (detection vs. exposure calculation) without requiring separate dedicated components, thus maintaining low device complexity while achieving optimal utilization through parameter adaptation.
Solution Approach 2:
By changing the capacitance parameter of the integrating circuit according to the operational phase, the system enables the trigger photodiode to serve multiple functions optimally. The control unit adjusts the capacitance value to match the current task, allowing the trigger photodiode signal to be effectively used for both incident light detection and total exposure calculation without compromising performance.
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 approach enhances the sensitivity of the integrating circuit to the trigger photodiode before light detection and reduces the risk of saturation after detection, allowing for accurate exposure calculation and optimal operation of the solid-state imaging apparatus.
Implementation Method 1
trigger photodetecting means including a trigger photodiode to generate an electric charge in an amount according to a quantity of incident light
Implementation Method 2
output means including an integrating circuit to accumulate the electric charge generated in the trigger photodetecting means, in a variable capacitance portion, and to output a value according to an amount of the electric charge accumulated in the integrating circuit
Data Source
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AI summary
A determination unit 70 determines whether there is incident light, based on an output value from an integrating circuit 62, and generates a determinated signal indicating a determinated result. A control unit 80 controls charge accumulating portions of an imaging light-receiving unit 10 whether or not to start accumulation of an electric charge, based on the determinated signal, and changes a charge accumulation capacitance value of the integrating circuit 62 of an output unit 60. Specifically, the control unit 80 varies the capacitance value for accumulation of an electric charge generated in a trigger light-receiving unit 20, depending upon the detection result on the presence/absence of incident light, to switch the sensitivity of the integrating circuit 62 to the trigger PD, thereby enabling optimal utilization of the trigger PD.