ECB Nematic

ECB – Analog Variable Retarder

Electronically controlled birefringence (ECB) is one of the most versatile nematic modes where the retardance of set wavelengths can be controlled in analog fashion. ECB’s have maximum retardance at 0 Volts and switch towards minimum retardance as voltage is increased. The birefringence change is a function of the LC tilt angle (also called the polar angle) defined as the angle created by the substrate normal to the molecule’s long axis.

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Electronically Controlled Birefringence (ECB) liquid crystal molecule diagram</p>

ECB Device Applications

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">LCVR's mounted into housing cups</p>

Liquid Crystal Variable Retarders


Tune unique retardance for each specific wavelength. Setting the retardance to halfwave for a specific wavelength creates a plane polarization rotator. Setting the retardance to quarterwave of a wavelength creates a circular polarization.

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Liquid Crystal Variable Attenuators, dark cells show high contrast ratio</p>

Liquid Crystal Variable Attenuator


LCVA’s are solid state, voltage controlled analog attenuators capable of 1000:1 contrast ratio. High extinction devices generally require compensator plate to correct for LC surface pinning common to ECB mode devices.

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">ECB cell with optic axis 45˚ to the input linear polarization between crossed polarizers</p>

Phase Control - OPL Change


The optical path length (OPL) of input polarization can be changed through voltage control. This is accomplished by aligning linear polarization with the slow axis of the variable retarder and modulating voltage.

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Semiconductor mask alignment shown in center.<br>Liquid crystal components are used for alignment in mask writing</p>

semiconductor Lithography Systems

ECB Liquid Crystal Devices
liquid crystal variable retarder

BVO ECB LC components used in laser writer mask alignment system Sub Heading

Precision ECB LC Devices
BVO Developmental Liquid Crystal Lab

Glass Eagle XG Display Glass or Polished Fused Silica
Thickness 1-2mm thick: Thin devices made with standard display glass
6-8mm thick: Low wavefront distortion devices made with fused silica
Outer Dimensions Maximum Size – 90mm | Minimum size – 12mm
Clear Aperture (CA) 2mm internal gasket & 2mm landing
Buffing Anti-parallel
Transmitted Wavefront Distortion Polished glass devices: .25 waves over clear aperture
BBAR Coatings Optional coatings
Contrast Ratio 500:1 standard , 1000:1 compensated
Switching Speed Low as 15-20mSec, 10-90% full cycle (function of cell gap thickness)
Bandwidth Visible or Near infrared
Temperature Range 10˚ C to 60˚ C
Damage Threshold 500 Watts/cm2 CW
.5 Joules/cm2 10nsec pulses @ 1064nm typical
ECB precision components are handmade devices incorporating difficult specifications. High uniformity, fast response times or compensation film stacks are typical upgrade requests. Liquid crystal attenuators provided with appropriate linear polarizers for respective bandwidth.
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Liquid crystal cell with redundant flex cable</p>
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Liquid crystal sub-assembly with potted LC device</p>
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Liquid crystal cells between crossed polarizers</p>

“off the shelf” Products – ECB Tunable Retarder

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">"Off the Shelf" ECB Liquid crystal cell between crossed polarizers. Retardance at V<sub>1</sup></p>
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">"Off the Shelf" ECB Liquid crystal cell between crossed polarizers. Retardance at V<sub>2</sup></p>

Ready for the lab

Prefilled liquid crystal cells, wired and ready to ship

features
  • Low wavefront distortion
  • No spacers in clear aperture
  • Low scattering device
  • Full wave retardance @ 700nm
  • < 2% non-uniformity over clear aperture
  • Optional compensator film
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Voltage vs Retardance

<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Voltage vs retardance curve of an ECB liquid crystal variable retarder. High uniformity cell capable of 700nm retardance.</p>

Voltage vs retardance curve of an ECB liquid crystal variable retarder. High uniformity cell capable of 700nm retardance. Click to enlarge.

volume manufacturing

   • 1mm thick cells, custom design mass production 

   • large panels up to 450mm x 350mm

   • aoi , contrast enhancement films value add

   • AR coated caps optional

   • high speed shutters

   • custom flex cable

   • lowest cost option

OEM volume components leverage the power of numbers to decrease cost. BVO builds proof of concept prototypes, verifies cell integration and after approval moves into production. BVO and customer work together to meet cost target.

Liquid Crystal Specifications & Drivers

Liquid Crystal Cell Drive Specs
  • 2 KHz carrier frequency, square wave
  • AC Drive, 0-30 Volts RMS, 50/50 duty cycle
  • DC Drive, Bipolar DC-balanced square wave
    Zero DC bias between +/- voltages required
  • Very low current devices, 15 milli amps Typical
  • Low capacitance, 35 nano farads Typical
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">LC Pi-cell driven by an unbalanced DC signal. Result is cell destruction from center out.</p>
Don’t Let This Happen To You – Zero DC Bias is Essential !
Optical Finesse LC Drivers
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Front Panel LCC2-33, Analog Liquid Crystal Controller</p>
OF-logo
<p style="color: white; background-color: rgba(0, 0, 0, 1.0); border: 2px solid #f88d2b; padding: 15px 15px 15px 15px">Back Panel LCC2-33, Analog Liquid Crystal Controller</p>
RECOMMENDED DRIVERS

Click to learn more about Optical Finesse Liquid Crystal Drivers. BVO’s recommended driver manufacturer.

LCC2-33 Analog Contoller

 LCC2-33 Manual 

 

uLC400-30 DigitalController

uLC400-30 Manual

BVO • Technical Polarization

Bolder Vision Optik (BVO) designs, consults and manufactures polarization control components. Liquid crystal devices, waveplates (retarders), achromatic waveplates and polarizers are manufactured in our Boulder, Colorado facility. BVO supplies standard, custom and OEM volume components to spec.

Design, Develop & Manufacture

OEM Equipment Manufacturers
BioSci / Medical Instrumentation
Consumer Products
Aerospace / Defense / Security
R & D , University, Research Labs
Machine Vision
Display

Bolder Vision Optik, Inc.

303.440.3327
info@bvo.global

5445 Conestoga Ct. Suite 135
Boulder, Colorado 80301
U.S.A.

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