VG20 - a new NIR absorbing optical filter glass

VG20 - a new NIR absorbing optical filter glass

Dr. Ralf Biertümpfel

14.05.2013

VG20 NIR cut-off filter, Dr. Ralf Biertümpfel 14.5.2013

SCHOTT Advanced Optics – Optische Filter 2013

Agenda

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Agenda

Introduction to absorption filter glass

NIR absorbing glasses

VG20 – properties and advantages


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SCHOTT AG

Business segments

Introduction


Optical Industries

Home Tech

Home Appliances Precision Materials

Pharmaceutical Systems Advanced Optics

Flat Glass Electronic Packaging Lighting and Imaging

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SCHOTT Advanced Optics: materials and legal regulations

IMSU

Integrated Management System for Safety and Environmental Protection

EHS

Environmental, Health and Safety Management System

RoHS

European Regulation on hazardous substances

Some of the optical filter glasses contain lead or cadmium. They are in

compliance with RoHS according to exemption 13b documented in ANNEX III

of the directive 2011/65/EU

REACH

Registration, Evaluation and Authorization of Chemical Substances

Introduction


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Absorption Filter – Optical Filter Glass – Volume Filter

Introduction


Unwanted light spectrum is absorbed and dissipated as heat

Optical filter glass is also called:

color filter

absorption filter

volume filter

Light source Filter Detector

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Introduction


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Agenda

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Agenda





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Requirements for NIR / IR absorbers



Transmitting visible light and preserve

colors.

Absorbing NIR light.

Steep transition between passband

region and blocking region.

Heat resistance –

maintain optical properties.

Suitable for imaging optics:

reproducible optical properties

high stability of refractive index

low variation of cut-off wavelength

batch to batch repeatability

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Transmittance of NIR / IR absorbers



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VG20

S8022, S8023

BG60, BG61,

BG62

BG38 to BG55

KG1, KG2,

KG3, KG5


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More details: diabatic scale of transmittance of NIR / IR

absorbers with true color vision

KG5

BG39

BG42

BG62

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Agenda

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Agenda





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VG20 has much higher absorption in the NIR

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thickness =

2 mm

thickness =

1 mm

10-5

10-8


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Smallest thickness for low transmittance at 633 nm

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True color vision:

red light is absobed, other colors transmit through the filter

VG20

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VG20 has high optical quality and is optimized

for imaging optics

nd = 1,5405

ne = 1,5426

nd = 60,6

ne = 60,2

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Environmentally Robust: Advantage of VG20 in hot and

humid conditions

High heat and humidity tests (85 °C / 85 %rH)

Clear glass as well as plastic can show surface corrosion . Typically this effect

is more dominant for blue glasses. “Normal Blue Glass” (like BG39) is a

phosphate based glass.

BG60/BG61: fluoro-phosphate glasses exhibit much less corrosion

New VG20 exhibits same environmental properties as BG60

Illustration of corrosion: Blue Glass before test

Blue Glass with severe corrosion VG20 after 250h 85 °C / 85 %rH

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VG20 is available as polished filters or as coated component

Available sizes: up to 80 mm (greater size on request)

Minimum thickness = 0.7 mm

Surface qualities

• standard = 60/40 or 5/3x0.63

• premium = 40/20 or 5/3x0.16

Wavefront deformation is low

Additional coatings:

• AR

• UV- and/or NIR-cutoff

• etc…

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SCHOTT’s VG20 uniqueness

VG20 a NIR absorbing optical glass filter


Excellent climatic resistance

Uncoated filter glass withstands more than 250 h

at 85 °C / 85% rH

VG20 is easily coated.

Climatic

resistance

Reproduc-

ability &

Repeatability

Application

Continuous production – less variation than pot melt

High stability of transmission vs. wavelength characteristics

Reproducible optical properties (refractive index & dispersion)

Negligible variations from melt to melt

True color vision

High absorption in the NIR at a small glass thickness

Applicable for laser safety, imaging optics, NVIS

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Thank you very much for your attention



© SCHOTT AG

129 years of experience

1884 SCHOTT was founded

Production of optical glasses

1886 Production of first filter glasses

1. History of Filters at SCHOTT


Source: SCHOTT AG (Glasmuseum, Jena), July 1886 Source: SCHOTT Optischer Glaskatalog, July 1886, p. 19

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History of Interference Filters

Dr. Walter Geffcken (SCHOTT) was one of the first who invented interference

filters, especially AR coatings.

1939 Patent of “Metal dielectric interference filters (Fabry Perot resonator)”

DE 716153

1940 Patent of “Coatings with reduced surface reflections” CH223344

1942 Patent of “All dielectric interference filters” using several optical films

DE742463

1. History of Filters at SCHOTT


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The new catalogue for Optical Filter Glass

3. Filter Glass Catalogue


Our new catalogue of Optical Filter Glasses has two parts

Description part

Introduction

Nomenclature

Description of glass properties

Important formulas

Background information

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© SCHOTT AG

The new catalogue for Optical Filter Glass

3. Filter Glass Catalogue


Our new catalogue of Optical Filter Glasses has two parts

Properties part

Portfolio

Guaranteed values

Detailed data

Transmittance curves

Geometry of polished filters

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© SCHOTT AG

The new Catalogue of Interference Filter

5. Interference Filter Catalogue


Our new catalogue of Interference Filters has two parts

Description part

Introduction

Basics of interference

Description filter properties

Important formulas and

definitions

Background information

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© SCHOTT AG

The new Catalogue of Interference Filter

5. Interference Filter Catalogue


Our new catalogue of Interference Filters has two parts

Properties part

Portfolio

Guaranteed values

Detailed data

Typical transmittance curves

Special filters

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VG20 - a new NIR absorbing optical filter glass

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