Single-Ended CTIA Pixel With Dynamic Reset for Two-Color Imaging

Solution Overview

Problem

Conventional CTIA unit cell circuits are limited in their ability to handle varying ambient light conditions, as they are typically optimized for either bright or low light scenarios due to fixed integration levels, preventing them from effectively capturing two-color, dual-polarity images.

Innovation Solution

The CTIA unit cell circuit employs an image detector with an opposing pair of image sensors and a switching network that allows for dynamically setting reset levels, enabling integration in both positive and negative directions, and includes a CTIA switch, low reset switch, high-reset biasing switch, and high-reset cut-off switch to manage photocurrent and prevent blooming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the image detector uses low capacitance components, then sensitivity in low ambient light is improved, but the ability to store charge in bright ambient light deteriorates

Engineering Contradiction:

ImprovesensitivityVSAvoidcharge storage capacity

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent implements dynamic reset level adjustment by introducing multiple reset levels (first reset level and second reset level) that can be selectively switched based on ambient light conditions. The switching network changes the reset level of the CTIA unit cell dynamically, allowing low reset level for bright light scenes (enabling high charge storage) and high reset level for low light scenes (maximizing sensitivity), thus resolving the contradiction between charge storage capacity and sensitivity.

Inventive Principle:

Principle #15Dynamics

2Quantity of substance

If the CTIA unit cell is optimized for bright ambient light, then charge storage capacity is improved, but sensitivity in low ambient light deteriorates

Engineering Contradiction:

Improvecharge storage capacityVSAvoidsensitivity

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent implements dynamic reset level adjustment by introducing multiple reset levels (first reset level and second reset level) that can be selectively switched based on ambient light conditions. The switching network changes the reset level of the CTIA unit cell dynamically, allowing low reset level for bright light scenes (enabling high charge storage) and high reset level for low light scenes (maximizing sensitivity), thus resolving the contradiction between charge storage capacity and sensitivity.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If a single reset level is used in the CTIA unit cell, then device complexity is reduced, but adaptability to different ambient light conditions deteriorates

Engineering Contradiction:

Improvereset level configurationVSAvoidambient light condition adaptability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic reset level adjustment by introducing multiple reset levels (first reset level and second reset level) that can be selectively switched based on ambient light conditions. The switching network changes the reset level of the CTIA unit cell dynamically, allowing low reset level for bright light scenes (enabling high charge storage) and high reset level for low light scenes (maximizing sensitivity), thus resolving the contradiction between charge storage capacity and sensitivity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent makes the CTIA unit cell multi-functional by enabling it to operate in both bright light mode and low light mode through the switching network. The same CTIA unit cell structure serves multiple purposes by dynamically adjusting its reset level, eliminating the need for separate optimized circuits for different lighting conditions and thereby improving adaptability without proportionally increasing complexity.

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 configuration enables two-color, dual-polarity image capturing with a larger dynamic range and reduced noise, allowing for high-density image capture with low power consumption, surpassing the limitations of conventional CTIA pixels.

Implementation Method 1

The image detector is configured to detect light having a first color and light having a second color different from the first color, and to generate a photocurrent in response to detecting the light

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11356622B1Single-ended capacitive trans-impedance amplifier (CTIA) unit cell for two-color applications

Publication Date: 2022.06.07 RAYTHEON CO

AI summary

An image capturing device is provided, which includes a capacitive trans-impedance amplifier (CTIA) unit cell. The CTIA unit cell includes an image detector and a switching network. The image detector is configured to detect light having a first color and light having a second color different from the first color, and to generate a photocurrent in response to detecting the light. The switching network includes a CTIA switch, a CTIA low reset switch, and a CTIA high-reset biasing switch. The CTIA switch sets a first reset level of the CTIA unit cell to a first voltage in response invoking a first switching state of the CTIA low-reset switch and sets a second reset level of the CTIA to a second voltage greater than the first voltage level in response to invoking a second switching state of the CTIA low-reset switch.