Axometrics, Inc.
103 Quality Circle, Suite 215
Huntsville, AL 35806
Phone: (256) 704-3332
Fax: (256) 971-2073
E-Mail:
Website: http://www.axometrics.com
AxoStepTM
Imaging Mueller Matrix Polarimeter
OPERATOR’S SOFTWARE MANUAL
©2012 Axometrics, Inc. All rights reserved.
AxoStep, AxoScan, Axometrics and the Axometrics logo are trademarks of Axometrics, Inc.
Please read these instructions completely and carefully before operating the Mueller Matrix Polarimeter. If you have any questions, or experience any difficulties, please contact Axometrics or the representative from whom the instrument was purchased.
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Axometrics, Inc.
AxoStep Polarimeter, Rev 3.0
CONTENTS
1 Introduction 4
1.1 Installed Software 4
1.2 Instrument Files Directory 4
2 The AxoStep Viewer Graphical User Interface (GUI) 5
2.1 Main Image 5
2.2 Options Tab 7
2.3 Registration Tab 8
2.3.1 Manual Registration 9
2.3.2 Auto Registration 9
2.3.3 Define a reference angle 9
2.4 Mask Tab 10
2.4.1 Threshold Mask. 11
2.4.2 Selected Area 11
2.5 Measurement Tab 11
2.5.1 Single Measurement 12
2.5.2 Tilt Scan Measurements 13
2.5.3 Wavelength Scan Measurements 14
2.5.4 Rotation Scan Measurements 15
2.5.5 XY Scan Measurements 16
2.6 XY Stage Tab 16
2.7 Calibration Tab 17
2.7.1 Automatic Calibration 18
2.7.2 Advanced Calibration Functions 20
2.7.3 Before Version 1.9.0 22
2.8 Polarimeter Coordinate System 23
2.9 Toolbars 25
2.9.1 Basic Tools 25
2.9.2 measurement information 25
2.9.3 Cross section plots 26
2.9.4 Poincare sphere 28
2.9.5 3D plot 28
2.9.6 Statistics 30
2.9.7 reduced parameters 31
2.9.8 edge detection 31
2.9.9 Optical Gauging Measurement 32
2.9.10 image measurements 32
2.9.11 user defined Calculation 32
2.9.12 Launch AxoStep 33
2.9.13 Auto Calibrate 33
2.9.14 launch tip tilt controller 34
2.9.15 launch X-y controller 35
2.9.16 Image through Crossed Polarizer 37
2.9.17 Pitch Measurement Utility 37
2.9.18 apply retardance order 37
2.9.19 Rth calculation 37
2.9.20 LCD tools 38
2.9.21 Mapping selection 38
2.10 Menu Bar 39
2.10.1 File menu 39
2.10.2 Edit menu 40
2.10.3 view menu 41
2.10.4 Tools menu 42
2.10.5 hardware menu 44
2.10.6 Help menu 44
2.11 Special Notes on Testing Polarization Elements 44
2.11.1 CAL-VIS-1 Reference Retarder 44
2.11.2 CAL-VIS-2 Reference Polarizer 45
3 LCD Production 46
3.1 Define a Pixel 46
3.2 Perform a Test Measurement 48
3.3 Define your output Regions 48
3.3.1 Configure the Output Regions 50
3.4 Configure the Robots. 52
3.5 x,y Coordinates Setup 53
3.5.1 Discrete Holes 57
3.6 Tilt, Rotation Angles 57
3.7 Wavelengths. 59
3.8 Perform a Test Measurement 60
4 Appendix 63
4.1 Reduced Parameters 63
4.1.1 Retardance 64
4.1.2 Diattenuation 65
4.2 Calculated Parameters 66
4.3 A Note about Retardance Order and “Unwrapping” 68
1 Introduction
The AxoStep™ Imaging Mueller Matrix Polarimeter is an optical instrument for capturing and image of all of the polarization properties of a sample. A sequence of intensity images are acquired as retarders rotate within the Polarization State Generator and the Polarization State Analyzer heads. These images are then processed to calculate the 16 two dimensional arrays that comprise the Mueller Matrix Image of the sample which characterizes all of the polarization transformations for that sample. A single or sequence of Mueller Matrix Images can be saved to a file for analysis in other computer programs.
A Mueller Matrix image is generally identical to an XY map of Mueller Matrices obtained using an AxoScan system. There are two superficial features that distinguish a Mueller Matrix Image from a Mueller Matrix XY Map
1. The Mueller Matrix Image is generally contains a much larger grid of points (usually greater than 100x100), and will always be arranged in a rectangular array.
2. The Mueller Matrix image generally measures a much smaller area (less than 2cm) than a typical XY map.
Nevertheless, apart from these superficial features, the data contained in a Mueller Matrix image and the data contained XY map is identical.
1.1 Installed Software
The following software has been installed on the Control Unit computer:
· Licensed copy of Microsoft Windows™ operating system
· AxoStep Engine and related configuration files
· AxoStep Viewer and related configuration files
· Any optional Axometrics’ Software
This manual describes all of the features in the AxoStep Viewer software package which is used to analyze Mueller Matrix Image datasets, and can control the AxoStep Engine via TCP/IP communication for performing basic measurement tasks.
While installing additional software (such as data analysis software, word processors, etc.) on the dedicated Control Unit computer is unlikely to affect the polarimeter, Axometrics discourages installing additional software, especially software that may run background processes causing the instrument program to compete for system resources thereby degrading instrument performance.
In the event of a catastrophic computer problem it may be necessary to reinstall the operating system or reformat the hard drive. Please contact Axometrics for detailed instructions or assistance.
1.2 Instrument Files Directory
All AxoStep instrument program files and support files are located at the following directory:
C:\AxoView\Current Version
Do not change directory locations or filenames.
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2 The AxoStep Viewer Graphical User Interface (GUI)
The AxoStep Viewer GUI is the main control program which acquires data, provides data visualization (2D image, 3D image, cross section plot and on the Poincaré sphere), streams the measurements to disk, and creates measurement reports.
The AxoStep Viewer can be used to analyze individual Mueller Matrix Image datasets as well as scans of multiple ones. Each Mueller Matrix Image is a multiple dimensional dataset containing 38 individual data images consisting of 16 images corresponding to the Mueller Matrix elements and 22 images corresponding to Reduced Parameter Images (Such as Retardation, Diattenuation, etc).
The main screen of the AxoStep Viewer GUI is shown in the following figure.
2.1 Main Image
On the front panel of the AxoStep Viewer program is the main image window.
Current Image: Allows the user to select between multiple Mueller Matrix Image datasets that are currently available (such as multiple images from a scan measurement).
Parameter to Plot: Allows the user to select between multiple parameters to show, like elements of Mueller Matrix and calculated parameters from Mueller Matrix Image that are currently available.
Current Parameter: Shows the parameter that is currently selected. The user can change how the current parameter to be shown (like adjusting the data range) on the Options Tab (described below). The user can also directly change the value on the color map to adjust the data range. The user needs to adjust the data range in order to see some feature on some samples. Otherwise the feature cannot be seen on the intense background.
Cursor Location: Shows the location of the cursor in units of pixels or actual units. User can select which unit is shown on the Program Options from the Tools menu. For showing the actual units (µm or mm), user needs to set what objective is using on the Calibration Tab of AxoStep Engine.
Parameter Value: Shows the parameter value at the current cursor location.
Convenient Buttons: Allows the user to access the frequently used buttons. The details about each button will be described in the following sections.
Parameter Category: Allows the user to choose which kind of parameters to plot, reduced parameter (like total retardance) or calculated parameter (like Rth).
Picture Controls: The following picture controls are available.
Cursor Control: Generates the cross-hair cursor shown in the image above.
Zoom in control: Allows the user to zoom into a selected area.
Drag control: Allows the user to drag the magnified view.
Line control: Draws a line on the image.
Box control: Selects a rectangular region in the image.
Circle control: Selects a circular region in the image.
Unzoom control: Returns the view to the full image.
2.2 Options Tab
Sometimes the user needs to adjust the data range in order to see some features on some samples. Otherwise the features cannot be seen on some background. Options tab shown below provides the controls to adjust the data range.
Smart Autoscale: Set the data range on the image to be following scales.
Range (Max-Min): Set the data range on the image to be possible maximum and minimum value.
Standard Deviation: Set the image scale to be ±N standard deviations from the mean value. A value of 0 means to autoscale over the full range.
Percentage: Set the image scale such that N percent of the pixels lie within the color range.
Sort Images: Sort the scanned or multiple images in the different order, like Tilt Angle, Rotation Angle, Wavelength, XY scan, etc.
2.3 Registration Tab
In order to calculate Rth or LC cell parameters from tip-tilt measurements, sometimes user needs to perform the registration (alignment) for multiple images from a scan measurement or multiple single measurements. The controls in the Registration tab are shown below.
2.3.1 Manual Registration
Delta X: Set the number of pixels to translate in the X-direction.
Delta Y: Set the number of pixels to translate in the Y-direction.
Translate: Translate the current image by Delta X and Delta Y.
: Translate the current image step by step.
Define Point: Define a reference point using the current cursor location.
Select the reference point on or near a clear reference feature in the image.
Translate to point: Translate the current point to the location of the reference point.
Change images and move the cursor to the same reference feature in the new image. When you press the Translate to Point button, the new image will align with the previous image. Repeat this procedure for each image in the scan dataset.
2.3.2 Auto Registration
Auto registration uses a Fourier transform correlation algorithm (http://en.wikipedia.org/wiki/Phase_correlation) to automatically register all the images currently available.
Auto Registration Type: The user can select between 1 dimensional correlation along X or Y (used on images that are only variable in 1-dimension, such as striped retarders) and generalized 2-dimensional correlation (used on images that are variable in 2-dimension, such as LCD pixels).
Registration Parameter: The user needs to select the parameter that will be used to perform the image correlation. It is recommended to select a parameter that has high contrast that does not change appreciably from image to image (such as transmittance on LCD cells, or retardance orientation on patterned retarders)
Reference Image for Registration: This is the image that the others will be aligned to. This image will not be translated.
Auto Register: Perform the auto registration process.
2.3.3 Define a reference angle
The user can define a reference angle so that the orientations, such as Retardance and Diattenuation Orientation, can be clearly shown with respect to a clear reference feature in the image. After the reference angle is defined, the user can select the User Defined Orientation (Retardance, Diattenuation and Polarizance) from Parameter to Plot list to be shown in current image.
Define Angle: Define the reference angle by drawing a straight line using Line Control.
Coordinates: Choose a coordinate (AxoStep or Image) in which the angle is given.
2.4 Mask Tab
Use the Mask tab to define a masked area where data points within that area are ignored so that the user can focus on the important part of data images. There are two mask types available.
1. Threshold Mask: The masked pixels are defined by the measurement values of the image. Masked data points can either be inside a parameter range, or outside a parameter range.
2. Selected Area Mask: The masked pixels are either inside, or outside an area selected by the user using either the box tool or circle tool.
Apply Mask: Applies the currently defined mask to all of the data sets in memory.
Create New Mask: Creates a mask based on the parameters set by the user (Any mask currently in memory will be erased). The Apply Mask box is automatically checked when the user presses the Create New Mask Button.
Combine with current mask: When the user presses this button, the mask created by the current parameters is multiplicatively combined with the mask currently in memory.
Clear Mask: Clears the current mask from memory.
2.4.1 Threshold Mask.
Max and Min define the range for the threshold mask.
In Range will keep all pixels that are within the range defined by Max and Min. Pixels outside of this range will be masked.
Out of Range keep all pixels that are outside the range defined by Max and Min. Pixels within this range will be masked.
Mask Parameter is the parameter in which the range defined by Max and Min is applied to. The threshold range will be taken from the dataset currently displayed (shown in the Current Image selector on the main front panel)
2.4.2 Selected Area
The Selected Area tab will create a mask defined by an area selected by the user using either the box tool or circle tool. The masked area can either be inside the selected area or outside the selected area.
2.5 Measurement Tab
The controls for making basic measurements are available on the Measurement Tab. The controls in the measurement tab are shown below.
Note, the AxoStep Engine must be running to be able to perform measurements. Usually calibration is required before measuring samples. See Calibration section for the details.
2.5.1 Single Measurement
Single measurements can be performed by setting the desired Wavelength, Number to Average, Rotation Angle, Tilt Angle and Position, and pressing the Measure Once button.
Note, the Tip-Tilt stage is required for setting Rotating and Tilt Angle. The XY Scan stage is required for setting the XY Position.
Once the Measure Once button is pressed, the AxoStep engine will perform a single measurement, and the Tilt and Rotation Corrections are performed and the Reduced Parameters are calculated. A file dialog box will appear prompting the user to save the data as a *.cmmi file. Then, a file dialog box will appear prompting the user to choose: add the measured data to the Current Image pull-down menu, or replace the images in the Current Image pull-down menu with measured data. The data will be the Current Image on the main front panel.
Wavelength: Allows the user to set the wavelength at which the measurement is performed.
Number to Average: Allows the user to select the number of images that will be acquired at every step of retarder rotation to calculate the Mueller Matrix. The larger number provides lower noise, higher measurement repeatability and longer measurement.
Note, the Number to Average is different from the Measurement Steps in AxoStep Engine. The Measurement Step is the times of retarder rotation to perform a complete measurement. The default value of Measurement Steps is 40, which is the best value for most of measurements.
Rotation Angle: Allows the user to set the rotation angle at which the measurement is performed.
Tilt Angle: Allows the user to set the tilt angle at which the measurement is performed.
X position: Allows the user to set the x position at which the measurement is performed.
Y position: Allows the user to set the y position at which the measurement is performed.
Use Current Position: The measurement is performed at current position.