Color Sensor Dark Photocurrent Cancellation via Differential Amplifier

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Solution Overview

Problem

Conventional color sensors are adversely affected by dark current voltage offset and temperature variation, leading to decreased DC response and reduced temperature robustness due to the non-linear voltage response caused by dark current and temperature changes.

Innovation Solution

A system and method that incorporates a differential amplifier circuit to cancel the dark current voltage offset by subtracting the dark photocurrent offset voltage from the photocurrent voltage, thereby stabilizing the voltage response and enhancing temperature robustness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a conventional color sensor uses a transimpedance amplifier to convert photocurrent to voltage, then the voltage level is suitable and linearity is maintained, but dark current voltage offset occurs that adversely affects DC response

Engineering Contradiction:

Improvevoltage levelVSAvoidDC response

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The invention segments the measurement process by introducing a separate dark sensor circuit that independently measures dark current, allowing the signal path to be divided into light-containing signal and dark current component for separate processing

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dark sensor circuit acts as an intermediary that measures and characterizes the dark current offset, which is then used by the differential amplifier to compensate and cancel the offset in the main sensor output

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the color sensor operates over a temperature range, then adaptability is improved, but the slope of linearity varies with temperature due to dark current offset rate changes

Engineering Contradiction:

Improvetemperature range operationVSAvoidslope of linearity

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The system dynamically adapts to temperature changes by continuously measuring dark current with the dark sensor and using differential amplification to cancel the temperature-dependent offset, maintaining stable linearity across varying temperatures

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The dark sensor provides feedback information about dark current levels that is used to compensate the main sensor output, creating a closed-loop system that maintains stable characteristics despite temperature variations

Inventive Principle:

Principle #23Feedback

3Measurement precision

If dark current is measured and canceled using a differential amplifier circuit, then DC response is improved and temperature robustness is enhanced, but device complexity increases

Engineering Contradiction:

ImproveDC responseVSAvoidcircuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention creates a copy of the sensor circuit (dark sensor) that is dedicated to measuring only the dark current component, allowing the offset to be characterized and canceled without affecting the main measurement path

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent merges the light sensor and dark sensor circuits into a single integrated color sensor device, sharing common components such as the differential amplifier and power supply while maintaining separate measurement functions

Inventive Principle:

Principle #5Merging (Combining)

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

The solution effectively cancels the dark current voltage offset, improving the DC response and temperature robustness of color sensors by maintaining a constant slope in the voltage response across varying temperatures.

Implementation Method 1

At the heart of a color sensor is a photodetector. The purpose of the photodetector is to capture and convert electromagnetic radiation into an electronic signal.

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

a transimpedance amplifier is used to convert the photocurrent into a voltage signal

Methodology Applied

Scientific EffectTransimpedance conversion:

Implementation Method 3

The differential amplifier circuit receives the first and second voltages and outputs a final output that cancels contributions of the offset voltage in the first voltage due to the dark photocurrent

Methodology Applied

Scientific EffectDifferential amplification:

Data Source

PatentUS7773134B2System and method for canceling dark photocurrent in a color sensor circuit

Publication Date: 2010.08.10 GODO KAISHA IP BRIDGE 1

AI summary

A system and method for canceling dark photocurrent in a color sensor circuit is disclosed. A color sensor is described including a color sensor circuit, a dark color sensor circuit, and a differential amplifier circuit. The color sensor circuit receives photocurrent from a color component of a light input. The color sensor circuit outputs a first voltage indicating intensity of the color component. The dark color sensor circuit receives dark photocurrent and outputs a second voltage indicating an offset voltage. The differential amplifier circuit is coupled to the color sensor circuit and to the dark color sensor circuit. The differential amplifier circuit receives the first and second voltages and outputs a final output that cancels contributions of the offset voltage in the first voltage due to the dark photocurrent.