A linescan is a separate single-line horizontal scan that is executed independently of the normal image frame. A linescan has its own dwell and interpixel delay which can be significantly different from the dwell and interpixel delay assigned to the frame. The user can assign the linescan to execute before, at the middle of, or after the frame is acquired. Refer to the configuration examples for descriptions of common applications of linescans. The SEM Linescan Preferences panel is shown below:

Other Preferences General Scan Generate SEM Image • SEM Linescan • X-ray Image X-ray Probe TEM Image Micron Marker File Formats Hardware Setup

• Channel Options

  • Physical Channel. The physical source for the linescan data. The linescan appears as an overlay on the image window for the lowest numbered Logical Channel enabled in SEM Image Preferences, but the source for the linescan data is selected separately here.

    Physical channels are the actual analog or digital signal inputs to the 4pi system. There are 4 analog inputs labeled ADC A - ADC B, 4 TTL counter inputs labeled CNTR 1 - CNTR 4, and 8 SCA inputs labeled SCA 1 - SCA 8. Read more about Physical Channels in the SEM Image Preferences.

  • Mirror. Read about the Mirror setting in the SEM Image Preferences.

  • Acquire. Read about the Acquire menu in the SEM Image Preferences.

  • Display. Read about the Display menu in the SEM Image Preferences.

  • Dwell. Read about the Dwell setting in the SEM Image Preferences.

  • Delay. This is, for the line scan, equivalent to the (inter-)pixel delay specified in Scan Generate Preferences. It is the settling time allowed for the beam, plus the input source instrument being used. Before the linescan begins, a horizontal and vertical retrace delay is executed to give the beam time to be positioned.

  • Name. The name given to a stand alone linescan window.

• Sequence Options

  Linescans are presently limited to a single horizontal scan across the image area, vertically centered. The scan may be set to be performed before, after, or in the middle of the image acquisition as described below:

  • Image First. The image is completely acquired before the linescan runs, for each frame.

  • Linescan First. The linescan is executed before image acquisition begins.

  • Linescan when passing. The image is acquired down to the line where the linescan will occur, then the linescan runs, and then the image acquisition picks up on the next line. This requires no vertical repositioning of the beam, and may be useful for samples that change over time, but in the latter case could cause a discontinuity since the image scan is suspended for the duration of the linescan.

• Miscellaneous Options

  • Overlay on Image. (currently always selected) Determines whether to overlay a graph of the linescan data on the lowest logical channel's image window.

  • Set Color. This button accesses the operating system's color-picking services, and allows the line-profile color to be set.

  • View %. Enter a number between 0 and 100 to set the physical size of the line profile within the image window as a percentage of the half-height image window size. The default is 95%.