AxoScan™

The Mueller Matrix

The "Mueller Matrix" Advantage

Unlike "partial" or "incomplete" polarimeters that only measure a particular subset of polarization parameters, the AxoScan and AxoStep both measure the full Mueller matrix. The 16 elements of the Mueller matrix contain all possible polarization properties of a sample. This is extremely important in situations where your real-world sample does not conform to the assumptions made by the measurement system.

As an example, measuring a stacked layer of retarders will create "elliptical retardance" if any of the layers are not perfectly aligned to each other. A system designed for measuring "linear retardance" or "birefringence" will fail to see the effects of that misalignment and will give the wrong result. But the Mueller matrix cannot be fooled, and the AxoScan will give the correct measurement.

Our easy-to-use software automatically converts the Mueller matrix into the meaningful parameters of transmittance, polarizer properties (diattenuation and polarizance), retardation, and depolarization. Axometrics also offers a wide range of application-specific software for numerous industries.

And as new applications come up, you don’t need to worry about obsolescence. Since the Mueller matrix already contains all possible polarization properties, new applications are a simple matter of installing new analysis software for your existing measurement system.

If your product depends on optical polarization, we likely already have analysis software for your application. Contact us to find out.

Applications

Applications

Because the Mueller matrix contains all possible polarization properties of a sample, there are too many AxoScan applications to list. The list below highlights some of the most common applications, but be sure to visit our Applications page for additional information.

If you don’t see your application listed, please feel free to contact us to discuss your measurement requirements. If the measurement involves polarization, we’ve probably helped someone make similar measurements.

Polarizer properties
Accurately measure the polarizer axis angle and polarizer efficiency (diattenuation magnitude) of polarizers. Determine whether the output state is linear, circular, or some elliptical state in between. Also determine whether the input and output states are the same. In some applications, retardation films are laminated to polarizer films for field-of-view compensation or for creating circular polarizers. Our multi-layer analysis software can be used to determine the properties of the individual layers.

Retarder properties
Accurately measure the retarder fast-axis angle and retardance magnitude. Also determine whether the fastest-propagating state is linear, circular (optical rotation), or elliptical. Measuring retardance as a function of tilt angle allows calculation of the out-of-plane retardance (Rth) and indicatrix tilt angle (β), and characterizes c-plates.

Liquid crystal parameters testing
Simultaneously measure the cell gap, top and bottom alignment directions, twist angle, and top and bottom pre-tilt angles of any mode of liquid crystal. Measurement can be applied to test cells, commercial panels, or polymerized films.

Generalized Ellipsometry
Measuring a sample in reflection provides the necessary data (ψ and Δ) for calculating the refractive index and thickness of thin films. Because the AxoScan measures the full Mueller matrix, the measurement is not limited to isotropic films. Uniaxial and biaxial anisotropic films and substrates can be measured without difficulty.

Stress-Induced Birefringence
AxoScan can accurately measure retardance levels below 0.1 nm.  Measuring an XY map of the retardance and fast-axis orientation of a sample reveals stress-induced birefringence patterns.  AxoScan is widely used in testing injection-molded plastic optics and thick glass optics to reveal this phenomenon.

Biological Samples
Aligned collagen fibers create significant levels of linear retardation. AxoScan is used in the selection of tissues for use in manufacturing heart valves to ensure the fiber alignment is properly aligned to the valve geometry.

Reflective Devices
The VRTF fixture allows testing of samples in either transmission or reflection. AxoScan is widely used in testing reflective devices such as LCOS imagers, transflective LCD panels, cholesteric filters, and light recycling films.

Polarization Ray-Tracing
One of the great strengths of the Mueller matrix is its ability to be used in Polarization Ray Tracing simulations. Using the measured Mueller matrix of a complex sample, it is possible to predict how that sample would change any input polarization state. For example, our software can predict what a sample would look like when placed between any two arbitrary linear, elliptical, or circular polarizers. Our measurement data files can be imported into several third-party lens design, polarization ray tracing, and liquid crystal design software packages.

Models

Models

Fixtures

OPMF - Out-of-Plane Measurement Fixtures

Used around the world in both R&D and QC labs, the OPMF-1 is most common mounting fixture for AxoScan. The OPMF automatically tilts and rotates a sample for measuring polarization properties as a function of field-of-view. Measuring at multiple incident angles is critical for many applications:

• Polar angle and azimuth angle maps for field-of-view (FOV) analysis
• Industry-standard out-of-plane retardance parameters (R0, Rth and Beta)
• Relative 3D refractive index ellipse of transmissive samples
• Pre-tilt measurements of light crystal (LC) displays and films
• Cell gap measurement of vertically aligned LC

The OPMF-1 has a tilt angle (polar angle) range is -55° to +55°, and rotation angle (azimuth angle) is continuous 0° to 360°

The OPMF-2 extends the maximum tilt angle to 75°.  This extended tilt range is typically useful in R&D applications for field-of-view studies.

XY200 - Motorized XY Scan Table

The XY200 fixture automatically performs XY maps of samples up to 200mm square, and includes software for analyzing the measurement polarization property maps.  The included XYViewer software has features for:

• Statistically analyzing distributions of the sample
• Cross-section plots
• Masking out of range pixels
• Data export to spreadsheets
• User setup of binned color tables for go / no-go applications for quality control

VRTF - Transmission and Reflection Fixture

The VRTF-1 can automatically reconfigure between transmission and reflection modes, enabling a very wide range of applications. Tilt angles from 15° to 90° in reflection, and from -45° to 45° in transmission are possible. The MSRS option provides full 360° rotation of the sample, and the optional XY50 stage allows XY maps of areas up to 50 mm x 50 mm.

The VRTF is our most flexible fixture, allowing a wide range of applications in polarimetry and ellipsometry:

• Polar angle and azimuth angle maps for field-of-view (FOV) analysis
• Industry-standard out-of-plane retardance parameters (R0, Rth and Beta)
• Relative 3D refractive index ellipse of transmissive samples
• Pre-tilt measurements of light crystal (LC) displays and films
• Cell gap measurement of vertically aligned LC
• XY maps and cross-section line scans up to 50 mm in either transmission or reflection
• Refractive index measurements
• Thin film thickness measurements
• LCOS and reflective display testing

FSVM - Free Standing Vertical Mount

The FSVM is a simple mounting fixture for measuring samples in transmission at normal incidence. The fixture includes an adjustable reference edge for repeatably setting the sample orientation.

OBHM - Optics Bench Horizontal Mounts

The Optics Bench Horizontal Mounts are suitable for researchers wanting the mount the AxoScan on an optics bench. This provides maximum flexibility in many R&D applications.