Decay-Time Scanner Optics to Prevent Photodiode Saturation

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Solution Overview

Problem

Conventional scanners face challenges in detecting weak luminescence light intensity signals from luminescent materials with short decay times, leading to inaccurate determination of decay time characteristics due to saturation issues and light intensity losses, especially when the light sensor is close to the material.

Innovation Solution

A high sensitivity light sensor with a bias regulator, photodiode, inverting transimpedance amplifier, and PNP bipolar junction transistor configuration, along with a control unit that adjusts excitation light intensity and measurement parameters to prevent saturation and minimize light losses, allowing for accurate detection of weak luminescence signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the light sensor is placed close to the luminescent material to minimize light losses, then detection sensitivity is improved, but the photodiode saturates due to high excitation light intensity

Engineering Contradiction:

Improvedetection sensitivityVSAvoidphotodiode saturation

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The optical path is segmented into excitation light path and emission light path using a beam splitter. The beam splitter separates the high-intensity excitation light from the photodiode while allowing the weaker luminescence emission to reach the detector, thus preventing saturation while maintaining close proximity for sensitive detection

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A beam splitter acts as an intermediary optical element that selectively directs different wavelengths of light to different paths. It mediates between the high-intensity excitation source and the photodiode by reflecting excitation light away while transmitting luminescence emission to the detector

Inventive Principle:

Principle #24Intermediary (Mediator)

2Illumination intensity

If the excitation light intensity is increased to detect weak luminescence signals, then signal strength is improved, but the photodiode saturation threshold is exceeded

Engineering Contradiction:

Improveexcitation light intensityVSAvoidmeasurement accuracy

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The optical system segments excitation and emission light paths using a beam splitter, allowing high excitation intensity to be applied to the luminescent material while preventing this high-intensity light from reaching and saturating the photodiode detector

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of trying to reduce excitation light intensity to prevent saturation, the system inverts the approach by using wavelength-selective optics to separate excitation and emission paths, allowing high excitation intensity to be maintained while protecting the detector

Inventive Principle:

Principle #13The other way round (Inversion)

3Use of energy by moving object

If a light guide is used to deliver excitation light to the luminescent material, then light delivery efficiency is improved, but luminescence light losses occur during collection

Engineering Contradiction:

Improvelight delivery efficiencyVSAvoidluminescence light losses

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The beam splitter serves multiple functions: it delivers excitation light to the luminescent material while simultaneously collecting the emitted luminescence light and directing it to the photodiode, eliminating the need for separate light guides and reducing overall optical losses

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

The solution enables accurate detection of weak luminescence light intensity signals and determination of decay time characteristics with improved sensitivity and reduced light losses, enabling reliable authentication of luminescent materials even with small quantities or weak responses.

Implementation Method 1

a photodiode (1) mounted to operate in a photoconductive mode with a positive high voltage Vb applied at its cathode by means of a bias regulator (2)

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

A luminescent material typically converts energy of an exciting radiation of a given wavelength into emitted light having another wavelength

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS11307136B2Light sensor and decay-time scanner

Publication Date: 2022.04.19 SICPA HOLDING SA

AI summary

The disclosed scanner for detecting a decay time of light emitted by a luminescent material has a control unit operable to adapt the drive current, or the value of the drive voltage, powering its light source to accordingly adapt the intensity of excitation light delivered to the luminescent material so that its high sensitivity light sensor can reliably measure the luminescence light emitted in response to the excitation light, and thus accurately determine a corresponding decay time value.