Mask Options Interface

Clicking on the Mask button in the Main User Interface Menu brings up the Mask Interface Menu shown below.

The menu allows the user to define various regions within a measured image which are are to be zeroed or masked out prior to an inversion. Defining a set of masks is a two step process. In the first step EUVSim is run to produce a plot of the measured image alone. The masked regions are defined on this plot and then saved. The masks are then used in the next call to EUVSim in which the full inversion should be run.

Masking out various regions of the measured image should be considered as a last resort in background removal. It should be used on background which cannot be removed by any of the normal techniques and it should only be used only when inverting a single image and not when inverting a large sequence of images.

The menu allows allows for four masks to be constructed delineating regions above, below, to the right, and to the left, of the measured image. Each mask is defined as a line (with up to 10 segments) which runs either from left to right (for top and bottom masks) or from top to bottom (for left and right masks). For a top mask all pixels above the line are zeroed out. For a bottom mask all pixels below the line are zeroed out. For a right and left mask all pixels to the right and left of the line(s) respectively are zeroed out. The lines are defined by selecting the mask definition and then left clicking on the image. NOTE: Selecting points which cause an infinte slope in any segment in the line wiil cause an error. In BOT and TOP mask definitions an infinte slope is caused by a pure vertical segment in the line and in LEFT and RIGHT mask definition an infinite slope is cause by a pure horizontal segment in the line.

In the course of describing the various options below, examples will be included of their effect on a measured image. These will all be based on the measured image shown below.

CLOSE

This button closed the window.

INPUT

This option specifies which mask is currently being defined. The options are specified in the table below.

MASK DEFINITIONS

Each of the four mask definitions have identical options and are manipulated in the same mannor. A particular mask is selected for input by setting the INPUT option above. The mask is then defined by specifing a number of points (ten or less) on the plot which define the region to be masked out. A point is selected by left clicking the mouse on the plot which will cause a + to appear on the plot and the corresponding values to be listed in in the GUI under the approprate mask definition.

The point which make up the line defining the masked region can be input in any order. Click on the ADD LINES button to connect the points with a line. Note that the line is extended to both the upper and lower X axes in the case of TOP and BOT masks and to the left and right Y axes in the case of LEFT and RIGHT masks. Clicking on DEL LINES will remove the line. DEL PTS will remove all of the selected points. To remove a single point simply erase its entry from the list then click on UPDATE to update the locations displayed on the image.

The menu below shows a TOP mask definition which was designed to remove the noise in Figure 1.

The mask itself is shown in Figure 2 with the ADD LINES option on to hilight the defined line. The effects of the mask are shown in Figure 3. The mask zeros out the measured image above the line.

The noise could just as easily have been removed using the RIGHT mask as shown in the menu below.

Figures 4 and 5 show the mask and its effect.