Solid-State Imaging Device Driving Method for Smear Reduction
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Solution Overview
Problem
Solid-state imaging devices face challenges in reducing smear and image blur, particularly when miniaturizing CCD chips, as smear occurs due to light leakage and charge diffusion, leading to increased noise and decreased dynamic range, and current methods to mitigate these issues, such as narrowing the vertical CCD width, result in temporal resolution degradation.
Innovation Solution
A driving method for solid-state imaging devices that involves holding and adding signal charges from different fields within a frame to synchronize charge accumulation times, using a Bayer pattern of color filters, and performing weighted averaging to match signal charge accumulation times, thereby reducing smear and preventing image blur during motion capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the vertical CCD width is narrowed to suppress smear, then smear is reduced, but temporal resolution degrades causing image blur
Solution Approach 1:
The pixel array is divided into multiple independent vertical CCD units (first vertical CCD, second vertical CCD, etc.), each handling different color components. This segmentation allows each vertical CCD to be optimized independently - they can be narrowed to reduce smear while maintaining overall image quality through the combined output of multiple units.
Solution Approach 2:
The patent transitions from a single vertical CCD architecture to a multi-vertical-CCD architecture, adding dimensional complexity to the charge transfer system. This allows the problem of smear reduction to be addressed in one dimension (narrowing individual CCDs) while compensating in another dimension (using multiple parallel CCDs to maintain temporal resolution and color information).
2Ease of manufacture
If the chip size is miniaturized to increase chips per wafer, then manufacturing cost is reduced, but smear increases due to shorter charge transfer paths
Solution Approach 1:
By segmenting the pixel array into multiple vertical CCDs that read out charges in parallel, the patent enables shorter individual charge transfer paths within each vertical CCD. This allows miniaturization of the overall chip while maintaining adequate charge transfer distance within each segmented unit, thus reducing smear even as chip size decreases.
Solution Approach 2:
The patent uses multiple vertical CCDs performing partial readout operations simultaneously. Each vertical CCD handles a portion of the total pixel array, allowing the charge transfer path in each unit to be optimized independently. This partial action approach enables shorter transfer paths that reduce smear while maintaining overall imaging performance through parallel processing.
3Measurement precision
If multiple fields are used to maintain temporal resolution, then temporal resolution is preserved, but smear increases due to extended charge accumulation time
Solution Approach 1:
The patent segments the frame into multiple fields, with each field being read out by a dedicated vertical CCD unit. This segmentation allows simultaneous parallel readout of multiple fields, maintaining temporal resolution by capturing different time moments concurrently rather than sequentially, thus preventing smear that would occur with extended sequential accumulation.
Solution Approach 2:
By using multiple vertical CCDs to read out multiple fields in parallel, the system maintains continuous imaging action without temporal gaps. Each vertical CCD continuously captures and transfers charges from its assigned field, ensuring that the useful imaging action continues uninterrupted across all fields, thereby maintaining temporal resolution while avoiding the smear that would result from extended single-field accumulation.
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 method effectively suppresses smear and maintains temporal resolution, ensuring clear images even when capturing moving objects by synchronizing charge accumulation and reducing light and charge leakage.
Implementation Method 1
The photodiode 901 converts incident light to a charge
Data Source
AI summary
The present invention is to provide a driving method for a solid-state imaging device which suppresses increase of smear and occurrence of image blur when imaging a moving object.In the driving method, for each row of the color filters arranged in the Bayer pattern, for a pixel, a signal charge is held in a first holding unit, which is generated in a preceding field period temporally preceding a predetermined field out of two different fields temporally equidistant from the predetermined field, a first signal charge is held in a second holding unit, which is generated within the predetermined field, the signal charge held in the first holding unit and a signal charge which is generated in a following field period are added, and a second signal charge obtained by the addition and the first signal charge are respectively outputted to outside of the solid-state imaging device.