Linear Scan
A linear scan is a collection performed on two axes, usually designated Scan and Step (or X and Y). Collection proceeds by moving along the Scan axis by a user-entered amount, collecting data by triggering at a specified increment. After each scan line is collected, the Step axis is moved, usually by the same Scan Increment. The data from the collection is displayed as a 2D Image. 3D display options are also available.
Starting a Linear Scan
In Basic Mode, a Linear scan is selected when the "Linear" option is selected on the Scan Settings tab of the Controls form. In Advanced Mode, A Linear scan is started by selecting the "Linear" tab of the Scan Manager. In either case, the user must set the parameters of the Linear scan using the input fields.
- Scan Axis and Step Axis can be any pair of axes. In Basic Mode, they are always the first two linear axes.
- Focus Axis should be set to the axis that is perpundicular to the surface of the part being scanned. In Basic Mode, this is always the third linear axis.
- Scan and Step Start positions can be entered manually in Advanced Mode; in Basic Mode, they are set but not displayed.
- Scan and Step Length can be any length that will fit within the scanning tank.
- Scan and Step Increment (or Resolution as displayed in Basic Mode) can be set to any increment less than the Scan and/or Step Length, within the limits of the encoder and/or motor resolution.
- Scan Velocity and Acceleration should be set as high as possible without causing trigger overruns.
- In Advanced Mode, the user can also specify the Step Velocity and Acceleration: in Basic Mode, these are set to maximum.
Once the settings are configured, the user can press the "Start" button on the Main Form to begin the Linear scan.
Linear Scan Options
- Unidirectional Scanning
- When active, the system will only collect data in one direction. This helps eliminate backlash.
- Stream Data to Disk
- When active, data will be stored immediately to disk as the scan proceeds. This also allows for recovery of the data. In Advanced Mode, this setting is located on the "Options" tab of the Scan Manager.
Note: if "Keep Data on Disk at all times" is active in Configuration, this parameter is ignored and data is always streamed to disk.
- HTS (High Throughput Scanning)
- Duplicates scan lines, based on the value specified in HTS. will also increase the step size by the same factor, so aspect ratio is maintained.
Focus Scan
If the "Focus Scan" checkbox is enabled (or "Find Focus" on the Scan Manager in Advanced Mode), the linear scan will be duplicated multiple times, at different focus positions. The focus options are set when the scan is started. The scan will be cancelled if the user presses the "Cancel" button.
When the user clicks "Start", a dialog will appear that lets the user input the number of times to repeate the scan, and the focus increment (in nanometers) between them. The first scan will run at the current focus. If the number of repeats to make is greater than 1, another linear scan will automatically start after the first completes, adjusting the focus position based on the increment.
When adjusting the focus, the gate setup on the Digital Oscilloscope will track the change of position, moving the gates along with the signal, whether or not the "Track Focus" option is enabled. This is so the original signal will remain within the gate positions.
Note: Make sure your Z-axis is far enough away from the limits before Focus Scanning, otherwise your Focus Axis steps will not work properly.
Multi-Step Scans
Note: Multi-Step Linear scans are only available in Advanced Mode
If the "Use MultiAxes" checkbox is selected on the Linear scan page, the user can create a profile that moves multiple axes when doing the Step motion. In this way, an irregular shape such as a wedge or a curve can be scanned. The Scan Axis motion remains a linear (single-axis) motion.
The profile can be created and edited from the dialog created when "Show Profile" is pressed.
See Also: Teach and Learn Setup