CCD Image Sensor Charge Routing for Dynamic Range

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Solution Overview

Problem

Conventional Charge Coupled Device (CCD) image sensors face limitations in dynamic range due to charge packet amplification, leading to blooming and reduced ability to detect signals in both bright and dark regions, necessitating separate output amplifiers that compromise image quality.

Innovation Solution

A CCD image sensor design featuring a charge directing switch that routes charge packets to either a charge multiplying shift register or a bypass shift register based on packet size, allowing for non-destructive sensing and adaptive gain application to maintain dynamic range and prevent blooming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If charge multiplication is applied to amplify small charge packets, then detection sensitivity is improved, but dynamic range is reduced causing blooming in bright regions

Engineering Contradiction:

Improvedetection sensitivityVSAvoiddynamic range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The image sensor is divided into multiple output channels (first output channel with charge multiplication, second output channel without charge multiplication). Each channel handles different signal ranges, allowing the system to simultaneously capture both dark and bright regions without blooming while maintaining detection sensitivity for small signals.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If a single output amplifier is used, then device complexity is reduced, but the ability to handle both bright and dark regions simultaneously is compromised

Engineering Contradiction:

Improvenumber of output amplifiersVSAvoidsimultaneous bright and dark region handling

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The output stage is segmented into multiple amplifiers (first output amplifier for multiplied charge packets, second output amplifier for non-multiplied charge packets). This segmentation enables independent optimization of each amplifier for its specific signal range, allowing simultaneous handling of bright and dark regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A dynamic selection mechanism is implemented that automatically routes charge packets to the appropriate output channel based on their magnitude. This dynamic routing ensures that small charge packets are amplified while large charge packets are directly read out, enabling adaptive handling of varying signal conditions.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If charge packets are routed through the charge multiplying shift register, then small signals are amplified, but large charge packets cause blooming into adjacent pixels

Engineering Contradiction:

Improvesignal amplificationVSAvoidblooming effect

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The charge packet processing path is segmented into two separate routes: one through the charge multiplying shift register for small charge packets, and another direct route for large charge packets. This segmentation prevents blooming by excluding large charge packets from the charge multiplication process while still providing amplification for small signals.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A dynamic routing mechanism is implemented that selectively directs charge packets to different processing paths based on their magnitude. This dynamic selection prevents blooming by automatically routing large charge packets away from the charge multiplying shift register while maintaining signal amplification for small charge packets.

Inventive Principle:

Principle #15Dynamics

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 dynamic range and noise performance of CCD image sensors by selectively applying gain to charge packets, ensuring accurate detection of both small and large signals without blooming, thereby improving image quality in mixed bright and dark regions.

Implementation Method 1

Charge multiplication occurs in charge multiplying HCCD shift register 110 through the application of large electric fields to the gate electrodes (not shown) overlying HCCD shift register 110 during charge transfer. The large electric fields produce a signal larger than originally collected in the pixels in pixel array 100.

Methodology Applied

Scientific EffectImpact ionization: Avalanche Breakdown

Implementation Method 2

A non-destructive sense node is connected to an output of the horizontal shift register

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS9136305B2Method of producing an image sensor having multiple output channels

Publication Date: 2015.09.15 SEMICON COMPONENTS IND LLC

AI summary

A method for producing an image sensor includes providing a horizontal shift register electrically connected to a pixel array for receiving charge packets from the pixel array. A non-destructive sense node is provided that is connected to an output of the horizontal shift register. A charge directing switch is provided that is electrically connected to the non-destructive sense node. The charge directing switch includes first and second outputs. A charge multiplying horizontal shift register is provided that is electrically connected to the first output of the charge directing switch. A bypass horizontal shift register or an amplifier is provided that is connected to the second output of the charge directing switch.