Image Sensor Pixel Charge Accumulation for Weak Light Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image sensors face challenges in detecting weak light intensities, leading to poor signal-to-noise ratios and saturation issues when detecting alternating light components, such as excitation and fluorescence in spectroscopic measurements, where the intensity of incident light can vary significantly by wavelength.
Innovation Solution
An image sensor with a configuration of photoelectric conversion, charge accumulation, and readout gates allows for selective signal amplification of pixels by transferring and accumulating charges from the photoelectric conversion portion to a charge accumulation portion, enabling individual control over the number of charge transfers and readouts, thereby enhancing signal quality while minimizing the influence of alternating light components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light amount of incident light on the pixel is increased, then the detection signal becomes stronger, but the pixel becomes saturated and the magnitude of the detection signal does not correspond to the intensity of the incident light
Solution Approach 1:
The patent applies dynamic control by varying the integration time for each pixel based on detected light intensity. Pixels detecting weak light undergo multiple integration cycles to amplify their signals, while pixels detecting strong light use shorter integration times to prevent saturation. This dynamic adjustment of integration periods allows the system to maintain optimal signal levels across all pixels, resolving the contradiction between signal strength and linearity.
2Measurement precision
If the signal amount of all pixels is uniformly increased, then pixels detecting weak light intensity achieve sufficient signal levels, but pixels detecting other wavelengths become saturated
Solution Approach 1:
The patent implements local quality control by assigning different integration times to different pixels based on their individual light intensity requirements. Each pixel's integration period is independently adjusted according to the specific wavelength and intensity it detects. This localized optimization allows weak light pixels to accumulate sufficient signal through extended integration while strong light pixels maintain shorter integration times, preventing saturation and ensuring all pixels operate within their linear detection ranges.
3Object-affected harmful factors
If gated imaging is used to remove excitation light, then the influence of excitation light is reduced, but the signal of fluorescent light needs to be enhanced through pulsed integration
Solution Approach 1:
The patent employs periodic action through pulsed integration, where the image sensor performs multiple cycles of light detection and signal accumulation. During each cycle, the sensor alternates between integration periods for capturing fluorescent light and non-integration periods for removing excitation light effects. By repeating this periodic process multiple times and accumulating signals, the system effectively filters out excitation light interference while building up sufficient fluorescence signal strength through constructive accumulation across multiple pulses.
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 allows for selective amplification of signal amounts in pixels detecting weak light intensities, improving the signal-to-noise ratio and enabling accurate detection of specific light components, even when incident light is alternating and of varying intensities.
Implementation Method 1
each pixel includes a photoelectric conversion portion for generating a charge in an amount according to an intensity of incident light
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An image sensor 5 includes a plurality of pixels 10. Each pixel 10 includes a photoelectric conversion portion 11, a reset gate 12 for controlling removal of a charge accumulated in the photoelectric conversion portion 11, a charge accumulation portion 13, an accumulation gate 14 for controlling a transfer of the charge from the photoelectric conversion portion 11 to the charge accumulation portion 13, and a readout gate 16 for controlling readout of the charge from the charge accumulation portion 13. The reset gate 12 removes the charge generated in the photoelectric conversion portion 11 by incidence of excitation light. The accumulation gate 14 transfers the charge generated in the photoelectric conversion portion 11 by incidence of fluorescence to the charge accumulation portion 13. The readout gate 16 performs control for reading out the charge after the charge transfer to the charge accumulation portion 13 is performed n times. The number n of the charge transfers is set for each pixel 10. Thus, an image sensor capable of selectively increasing signal amounts of pixels of a part of a plurality of pixels, and detecting only one of two light components being alternately incident is realized.