Advanced Texture OMP-0362G MetroPro Application AdvText.app This booklet is a quick reference; it assumes that you are familiar with MetroPro and the instrument. Information on MetroPro is provided in MetroPro Quick-Start Guide, OMP-0469, and the MetroPro Reference Guide, OMP-0347. For information on the instrument, please refer to the applicable Zygo Corporation manual. Information herein is applicable as of MetroPro version 7.15.0. The Advanced Texture Application The MetroPro Advanced Texture Application provides a complete set of controls, plots, and results, to measure and quantify the surface texture of a test part. It can be used with any of Zygo Corporation’s microscopes, including the NewView and Maxim. The application is ideal for measuring surfaces that are subject to wear, including disk drive media, magnetic tape, machined metal, and films. It can also be used for any surface in which you want to visualize and measure the components of surface texture. Through digital filtering of the test data, the surface characteristics of the test part are broken down into waviness, roughness, and high frequency results. For most results, letters are used to indicate the result’s classification; I refers to input or nonfiltered data; W refers to waviness data, or the more widely spaced component of surface texture; R refers to roughness data, or the smaller irregularities of the surface; and HiF refers to high frequency data, or the finer surface irregularities. The application is licensed as part of standard MetroPro. For information on licensing, see the MetroPro Quick-Start Guide. The Advanced Texture Application: • Displays graphics and numeric results of the test surface as input, waviness, and roughness data. • Provides simple to use and apply filtering tools. • Includes advanced surface analysis options, such as the peaks and valleys analysis, bearing ratio results, summits analysis, and volume results. 1 ADVANCED TEXTURE APPLICATION Guidelines • Use a System Error File - It is recommended that you create a system reference file for the objective in use and then subtract this file from the measurement. • Set Light Level with Several Fringes in View - For the most accurate measurements, set the light level (press F5) when there are several fringes in the field of view. • Save Your Changes - To preserve changes made to the application, select the Save Application command from the Application Window menu. In the File Handler, click the Current Selection box, enter a name for the file, ending with “.app” and press Enter, then click Done. Making Measurements 1. Power-up the instrument, start MetroPro, and open the application by clicking on the AdvText.app icon. 2. Click the Objective button until it displays the objective in use. Set the applicable controls within the Objective Working Distance (in mm) Measure Cntrl and Analyze Cntrl 2.5X 5X 10X 20X 50X icons. (See “Establishing Filer 10.3 mm 9.3 mm 7.4 mm 4.7 mm 3.4 mm Settings” and “Software Controls” in this booklet.) Microscope Controls - NewView 5000 3. Place the test part on the stage under the objective. Position the objective at its working distance from the part. Don’t crash the objective into the part or the stage. 4. Set the Zoom knob to the desired setting; ensure that the software Image Zoom control is set to match. Position the filter tray to FOCUS. Press the F5 key to adjust the light level. Focus the microscope for a sharp image; there should be visible fringes. 5. If there are not visible fringes, adjust for tilt in the part. To do this, press the F4 key to open the Light Level window, adjust the stage tip and tilt until the Peak Intensity readout is Typical microscope shown, actual controls may vary maximized, and press Enter to close the window. 6. Adjust the stage to center the area of interest in view. Place the filter tray to MEAS, press F5 again to adjust the light level. Refocus for high contrast fringes. 7. Fine-tune focus and stage tip and tilt for surface detail, to null or minimize the number of fringes, and to center the darkest fringe. 8. Press the F1 key or click the MEASURE button to measure. 2 ADVANCED TEXTURE APPLICATION Filtering - the Key to Analyzing the Surface Texture The Advanced Texture application uses digital filtering to separate data into waviness, roughness, and high frequency components. In auto mode, the software arbitrarily sets the low and high filter settings only as a starting point. It is strongly recommended that you enter your own values for the filter settings, as graphic displays and results are directly affected. The use of the terms “frequency” and “wavelength” as they relate to filtering is shown below: Term Waviness Roughness High Frequency Frequency low middle (mid) high Wavelength long moderate short One analogy to filtering is sifting dirt or sand. The size of the holes and number of screens determine what you end up with; two screens divide material into three different grades. It is similar with Advanced Texture, except the number of filters (up to two) and the filter size (frequency or wavelength) are software selectable. If both low and high filters are used, data is divided into waviness, roughness, and high frequency, which in some instances may represent noise. If just a low filter is used, data is separated into waviness and roughness. Establishing Filter Settings 1. Click the Analyze Cntrl icon to access the filter controls. Make a measurement with High Filter and Low Filter controls set to “Off”. Observe what happens when the High Filter and Low Filter controls are set to “Auto” by clicking the Analyze button (or F2). 2. Use the Filter Freq (or Filter Wavelen) result displayed in the main window as a gauge and enter your own parameters in the corresponding control. Change the High Filter and Low Filter controls to “Fixed”. Click the Analyze button to reanalyze the data. Try different settings and observe the effects on the results. The exact filter values to enter vary due to the test part, the objective, and your testing criteria. The R/W Profile window serves as a visual aid in observing filtering effects. (See “R/W Profile” in this booklet.) 3 ADVANCED TEXTURE APPLICATION Using Filter Frequency Settings The Advanced Texture FFT filter frequencies are designed to do two things: • The High Frequency filter is meant to filter out noise (high frequencies) • The Low Frequency filter is meant to filter out overall part shape (low frequencies) What you will have left, when these frequencies are set properly for your part, is data pertaining to the roughness or texture of your part. How do I get there? The easiest way to go about it is: 1. Set the Remove control to Cylinder if you are trying to look at roughness attributes. 2. Set filter setting to FFT Auto. This means that the software will choose a high and a low frequency limit based on the frequencies that make up your data. 3. Click Analyze. 4. Open up Analyze Attributes. Here you will see what frequencies the software chose. These may not be optimal (and usually aren’t), but they are good starting points for the next steps. 5. Enter these frequencies into the control boxes for High Filter Freq and Low Filter Freq. 6. Set High FFT Filter and Low FFT Filter controls to Fixed. 7. Click Analyze again. Nothing should change at this point. 8. Now you are ready to start tweaking frequencies to get the roughness data that you are looking for. Hints for tweaking these values are: Low Filter Freq- If this value is set too low, you will see overall surface form errors in your Roughness Map. If this value is set too high, you will start to see the texture/roughness of the part in your Waviness Map. Set this number so that the part form shows up in the Waviness Map and that the texture of the part is shown in the Roughness Map. High Filter Frequency- If this value is set too low, you will see a lot of your texture and roughness missing from the map. If this value is set too high, you will have noise spikes (if they are present) swamping the roughness data. This usually shows itself as a plot of only one color. It is often necessary to set this value as high as it will allow. There are limits on both of these frequency values defined by the field of view and the camera resolution. When you hit either of these limits, MetroPro will tell you so. If you have been using a contact profilometer in the past, you may want to look at the High Freq value being related to your probe tip size. Often our noncontact methods will be able to see more roughness on a part because at high magnifications we can see deeper into skinny trenches and pits that a larger probe tip cannot. 4 ADVANCED TEXTURE APPLICATION AdvText.app To open the application, click on the AdvText.app icon. If the icon is not on the MetroPro base window, then use the Load Application command from the MetroPro Window menu to first load the application icon. The Advanced Texture Screen 5 ADVANCED TEXTURE APPLICATION Roughness/Waviness Map This is the main window shown on page 4; it shows the original measured input data side-by- side with the roughness and waviness data obtained through filtering. Item Description H Swedish height, or the roughness between two predefined reference lines. The upper reference line exposes 5% of the data and the lower line exposes 90%. Ha The average surface height, or average deviation, of all points from a plane fit to the high frequency data.