Image Sensor Conversion Gain Control via Selective Capacitance

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Solution Overview

Problem

Existing image sensors face inefficiency in adjusting conversion gain without reducing the light receiving area, as adding elements to adjust gain typically minimizes the light reception area, necessitating a method to adjust gain based on light intensity without affecting the light reception area.

Innovation Solution

The image sensor incorporates a photodiode, a sensing node, a read-out circuit, and capacitors with a conversion gain control line that can be selectively connected to a ground line or output line based on control signals, allowing for adjustment of conversion gain without altering the light receiving area by varying the effective capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If additional elements are provided in a pixel to adjust the conversion gain, then the conversion gain can be adjusted according to light intensity, but the area that the light receiving region takes in the entire pixel is reduced

Engineering Contradiction:

Improveconversion gain adjustment capabilityVSAvoidlight receiving area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The patent merges the conversion gain control line with the existing pixel structure, making the control line serve dual purposes: as part of the pixel circuit and as a capacitance adjustment mechanism. This integration allows conversion gain adjustment without adding separate dedicated elements that would occupy additional space.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The conversion gain control line is designed to perform multiple functions: it serves as a control line for adjusting conversion gain and simultaneously acts as one of the capacitor electrodes. This multi-functionality eliminates the need for separate capacitor structures, thereby preserving light receiving area while enabling conversion gain adjustment.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If the light receiving area is reduced to accommodate additional elements, then conversion gain adjustment is enabled, but the light sensitivity and signal-to-noise ratio deteriorate

Engineering Contradiction:

Improveconversion gain adjustment capabilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

By merging the conversion gain control line with the pixel structure and using it as a capacitor electrode, the patent eliminates the need for separate elements that would reduce light receiving area. This preserves light sensitivity and signal-to-noise ratio while enabling conversion gain adjustment.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the electrical parameters (capacitance values) of the pixel circuit by selectively connecting different capacitances to the sensing node through the conversion gain control line. This allows dynamic adjustment of conversion gain without physical changes to the light receiving structure, thereby maintaining signal-to-noise ratio.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the light receiving area is reduced to accommodate additional elements, then conversion gain adjustment is enabled, but the manufacturing complexity increases

Engineering Contradiction:

Improveconversion gain adjustment capabilityVSAvoidpixel structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the conversion gain control line with the existing pixel circuit structure, eliminating the need for separate capacitor electrodes and control lines. This integration reduces the number of manufacturing steps and simplifies the overall pixel structure while maintaining conversion gain adjustment functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The conversion gain control line is designed to serve multiple functions within the pixel structure, acting both as a control line and as a capacitor electrode. This multi-functionality reduces the total number of elements that need to be manufactured and assembled, thereby simplifying the manufacturing process.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enables the image sensor to increase or decrease conversion gain without reducing the light receiving area, thereby enhancing signal-to-noise ratio at high light levels and increasing sensitivity at low light levels, improving overall image processing efficiency.

Implementation Method 1

a photodiode configured to convert an optical signal into photogenerated charge

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS9019410B2Image sensors comprising photodiodes and image processing devices including the same

Publication Date: 2015.04.28 SAMSUNG ELECTRONICS CO LTD

AI summary

An image sensor may include a photodiode configured to convert an optical signal into photogenerated charge, a sensing node adjacent to the photodiode and configured to sense the photogenerated charge, a read-out circuit configured to convert the photogenerated charge into an electrical signal and to output the electrical signal through an output line, and/or at least one capacitor formed between the sensing node and a conversion gain control line. The conversion gain control line corresponding to the at least one capacitor may be selectively connected to a ground line or the output line based on at least one control signal.