Solid-State Imaging Device Dummy Photodiode Noise Suppression
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Solution Overview
Problem
Existing solid state imaging devices face challenges in suppressing noise caused by scattered radiation and scintillation light entering peripheral regions, leading to inaccurate radiation images due to charge generation in these areas.
Innovation Solution
Incorporation of a dummy photodetecting section with dummy photodiodes adjacent to the outer edges of the primary photodetecting section, which accumulates and discharges noise charges to prevent their entry into the main photodetecting section, using integrating and holding circuits to manage and output charge values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shielding member is provided to block radiation on the peripheral region, then radiation incidence on the photodetecting section is improved, but scattered radiation from the Compton effect causes noise in the peripheral region
Solution Approach 1:
The patent introduces a dummy photodetecting section as an intermediary component between the scintillator layer and the main photodetecting section. This dummy section acts as a mediator that intercepts and absorbs scattered radiation and scintillation light before they can reach the peripheral regions of the main photodetecting section, thereby preventing noise generation without compromising the main imaging function.
Solution Approach 2:
The patent converts the harmful scattered radiation and scintillation light into a beneficial effect by using the dummy photodetecting section to deliberately absorb these photons. The dummy section transforms the harmful radiation into a useful function by preventing it from reaching and interfering with the main photodetecting section, thus converting a negative factor into a positive noise-reduction mechanism.
2Adaptability or versatility
If the area of the peripheral region is increased, then device functionality is improved, but noise from scattered radiation and scintillation light is greatly enhanced
Solution Approach 1:
The patent segments the photodetecting section into a main photodetecting section for imaging and a separate dummy photodetecting section for noise absorption. This segmentation allows the peripheral region area to be increased for enhanced device functionality while the dummy section is strategically positioned to absorb scattered radiation, preventing noise enhancement in the main imaging area.
3Area of stationary object
If charges are generated in the peripheral region, then more detection coverage is achieved, but charge accumulation in photodiode junction capacitance causes noise in the radiation image
Solution Approach 1:
The patent extracts the noise-generating function from the main photodetecting section by introducing a dedicated dummy photodetecting section. This extracted component specifically handles charge generation from scattered radiation and scintillation light in the peripheral region, preventing these charges from accumulating in the main photodiode junction capacitance and causing noise in the radiation image.
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
Effectively suppresses the influence of charge generation in peripheral regions, resulting in improved accuracy and clarity of radiation images by isolating and discharging noise charges within the dummy photodetecting section.
Implementation Method 1
a photodiode which generates charges as much as incident light intensity
Implementation Method 2
a scintillator layer which is provided so as to cover the photodetecting section and generates scintillation light in response to incidence of radiation
Implementation Method 3
charges generated in the peripheral region may move from the generation position and be accumulated in a junction capacitance portion of a photodiode
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
A solid state imaging device 1 includes a photodetecting section 10, a signal readout section 20, a controlling section 30, dummy photodetecting sections 11 and 12 including dummy photodiodes, discharging means for discharging junction capacitance portions of the dummy photodiodes, and a scintillator layer 50 provided so as to cover the photodetecting section 10. The dummy photodetecting section 11 is disposed so as to neighbor the first row (the upper side of the photodetecting section 10) of the photodetecting section 10 and has a length equivalent to the length of the photodetecting section 10 in the left-right direction. The dummy photodetecting section 12 is disposed so as to neighbor the M-th column of the photodetecting section 10 (the lower side of the photodetecting section 10) and has a length equivalent to the length of the photodetecting section 10 in the left-right direction.