These edit boxes and spin buttons allow you to set the true image size (scan area size) in nanometers for the scan. Currently only square areas are implemented, i.e. the controls for setting the image-size in Y-direction are disabled. The reason for this lies in its simpler implementation.

The maximum scan area size is physically limited by the DAC calibration factor and the DAC-range, i.e.:

Example: for a common value of 139.9 pm/DACbit the max. area size would be: 139.1 * ( 2^16 ) = 9116 nm

Selecting the Rectangular scan area checkbox (not yet implemented), you are allowed to enter a rectangular scan area. If not selected, the controls for entering the scan area Y-size are disabled.

These controls allow you to set the scan resolution for the scan (i.e. the number of pixels that the scan will consist of in X- and Y-direction).

The scan resolution values can only be entered as a multiple of 4. The range is between 4 and 2048 pixels (hard-coded).

	Note
	The scan resolution is not related to the spectroscopy grid resolution (only in Full-Scan spectroscopy mode). The spectroscopy grid resolution is configured on the Grid tab.

You can operate the tip speed controls to set the tip speed in nm/s.

The minimum tip speed is limited by the user setting for the limited tip speed. This is done on the Digital tab, see that section for more details.

The maximum tip speed is limited both by physical and user constraints. Therefor a distinction is made between the maximum tip speed as set by you, and the physically maximally possible tip speed. The latter will be referred to within Camera context as the maximum attainable tip speed. You can set the maximum tip speed on the Digital tab.

The tip speed is physically limited by the number of tip jumps that are made between two pixels (see section Steps on the Digital tab for detail on inter-pixel tip jumps.

When in auto-calculated jumps mode, the maximum speed that can be attained is moving from one pixel to the next in one jump. The maximum attainable tip speed in this case is:

Where ELECTRONICS_WAIT is the time to send and execute one tip movement command (this time is hard-coded as 39 μs, after being experimentally determined).

However when auto-jump calculation is not selected, it is the user who requires a number of tip jumps to be taken in between two pixels. Given the number of jumps required, the maximum attainable tip speed is:

In case of auto-jump calculation selected and using the common DAC calibration factor 139.1, the maximum attainable tip speed for a scan area 1000 x 1000 nm and resolution of 100 pixels:

The scale of the tip speed slider runs from min. user tip speed to max. user tip speed. If the maximum attainable tip speed is larger then the max. user tip speed, a yellow light will appear, making you aware that you are not using the full possible tip speed range.

If the max. attainable tipspeed is lower than the max. user defined tipspeed, the light will turn grey. The tip speed range will always be between min. user defined tip speed and max. attainable tip speed.

Furthermore, it is possible to display the tip speed scale in either linear or logarithmic form. This is controlled from the Digital tab.

The spectroscopy dropdown control determines whether spectroscopy measurements are taken during a digital scan.

The dropdown list provides the following choices:

When selecting one of the spectroscopy modes, pressing the Scan button will execute a scan using the spectroscopy mode as selected on the Grid tab. If No spectroscopy is selected, a scan will be made without performing any spectroscopy measurements.

With the Single Spectrum button you can perform one spectroscopy measurement. When you press this button Camera will do one spectroscopy measurement at the current tip location being the current offset position, and using the IV spectrum specification. Camera will open a scan document containing only one pixel. You can open the corresponding spectrum via the image context menu.

The scan rotation controls allow you to rotate the scan area with an angle lying between -90 and 90 deg. However, the software takes scan area boundaries into account, so the actual range that the scan area might be rotated might be less. The scan area boundaries are either the physical boundaries (see Scan Area Panel), or user-set scan area size when selected on the Digital tab.

	Note
	Definition: A positive rotation angle rotates the scan area counter clock-wise.

The X- and Y-offset controls allow you to set the scan area offset in X- and Y-direction. When selecting a new offset position, the tip will move to the new position with the tip speed selected on the Scan Area Panel.

The ranges for the X-and Y-offset sliders are determined by the physical scan size (see Scan Area Panel) and will range from [-Max_physical_scan_size / 2, +Max_physical_scan_size / 2] in both X- and Y-direction.

However the scan size might be limited by the rotation of the scan area. One can imagine that the maximum offset for a 45 deg rotated scan area is less then that for a scan area with zero rotation.

By adjusting the Z-offset you can bring the Z-feedback output to zero as close as possible. This allows you to increase the resolution of the recorded Z-position by using a larger ADC-gain for the Z-ADC than would otherwise be possible.

There are several reasons for having a (varying) Z-offset.

The Z-offset signal is generated by the Z-mixer and fed into one input of the Z high voltage amplifier. The other input of the Z high voltage amplifier is the Z-feedback output signal. The output of the Z-high voltage amplifier is the sum of both inputs, multiplied by the gain of the HV amplifier module.

You can control the Z-offset as follows:

	Caution
	In the Manual mode, be careful in making large steps while the tip is close to the sample. The feedback might be set too slow to keep the tip away from the sample, leading to a crash.

The following variables can be displayed:

Right-click in the Measurement info panel to get the Measurement Info Panel Configuration panel that lets you select which items to display and in what order.

Figure 6.12. Digital Scan Mode: Measurement Info Configuration Panel

There are two main variants to an IV Measurement: a linear sweep and a cyclic sweep (linear or cyclic voltammetry). The latter can be upgoing oe downgoing.

A linear IV spectrum measurement proceeds as follows:

A cyclic IV spectrum measurement proceeds as follows:

A force-distance spectrum measurement proceeds as follows:

These radio buttons allow you to select one of four spectroscopy modes

Single Spectrum is selected from the Scan Area panel.

In this mode, spectroscopy measurements are taken on each of the scan grid points. i.e. the spectroscopy grid has the same size and resolution as the scan grid. Grid coordinates are displayed in the table when the number of scan grid points are less then 1000.

In Sub-Grid spectroscopy mode, you can define a sub-grid consisting of points of the (larger), for which spectroscopy measurements will be taken. When this mode is selected, the controls for defining the grid become enabled. The sub-grid is defined by entering the following 3 pairs of parameters:

Figure 6.16. Digital Scan Mode: Spectroscopy Grid (not to scale)

Example Suppose we have a scan grid of 1000 x 1000 nm, resolution 200 x 100 pixels.

When defining the following values:

We have defined a spectroscopy grid with upper left coordinate at (50, 50), with scan points every 5th scan grid point, 10 spectroscopy grid points wide and 5 high.

In nm the dimensions/coordinates will then be:

Grid Table The coordinates of each spectroscopy grid point are displayed in the table (both in Full-Scan and Sub-Grid mode). When the number of spectroscopy grid points exceeds 1000, no point coordinates are displayed.

Grid coordinates are displayed with X- and Y-offset as well as scan rotation angle taken into account. You might however be interested in viewing these coordinates uncluttered (i.e. without offset and rotation angle incorporated). This is possible by selecting the checkboxes No Offset and No rotation. When selected, the table will show the coordinates without these values being taken into account.

	Important
	The actual spectroscopy grid used when performing a scan will always incorporate the actual offset and scan rotation, even when one of these checkboxes is selected.

In this mode, Camera will perform consecutive spectroscopy measurements in one particular point, being the tip offset position.

In this mode spectroscopy will be taken at user-defined grid points. You can enter grid positions (in nm). Camera will find the nearest scan grid point, and appoint this as a grid point for spectroscopy measurement.

User-defined points can be entered, modified and removed using the four buttons next to the Grid table, or by selecting grid points in a scan document.

Any grid points that are invalid (i.e. lying outside the scan area ) will be marked red in the table and will not be taken into account when performing a scan.

	Important
	User-defined spectroscopy points are not stored in persistent data or otherwise.

The raster of Quick Selection enables you to create a spectroscopy grid using the mouse (not yet implemented)

If the extra mixer is factory-provided with a slew rate limiter, and component values are as shown below, you can compute the slew rate for a voltage change larger than 0.25 Volt as folllows:

Figure 6.19. Digital Scan Mode: Digital Tab: Extra Mixer Slew rate

In the Steps section you can control the number of tip jumps between two scan pixels. The idea is as follows:

Figure 6.22. Digital Scan Mode: Digital Tab: Steps

Given the fact that it takes a certain amount of time to command the tip from one place to another (due to response time of the electronics), we can introduce a tip speed by commanding the tip to locations between one pixel and the next.

If ΔTE is the time needed to order the tip to move a certain distance, a tip speed vtip can be maintained by sending ΔX / ΔTE commands to move the tip to positions in the two pixels. Each movement is referred to as a jump within Camera electronics.

Given a tip speed vtip , the number of jumps to take in between two pixels is :

With the Auto checkbox you can select auto-calculation of inter-pixel tip jumps. The number of jumps to take, given the tip speed selected in the Scan Area panel, is calculated according to the formula described above.

If the Auto checkbox is unselected, you can enter the number of jumps in the edit box.

If the number of jumps is less then required to maintain the requested tip speed, the tip will make number of jumps you have entered, however while maintaining the requested tip speed. This means that after each jump, the Camera software will wait the corresponding amount of time.

If the number of jumps is greater than the outcome of the formula for the current requested tip speed, the tip speed cannot be maintained. The tip will make the requested amount of jumps in between pixels, but the tip speed will be correspondingly lower.

This section allows you to select either straight line or a Zig-Zag backward stroke. The backward stroke is the movement the tip makes to return from the end-of-scan position (lower left corner) to the start-of-scan position (upper left corner). The backward stroke consists of (2 * X-resolution) pixels.

During the backward stroke, at each pixel position the ADC channels are read, but no spectroscopy measurements are taken.

The results of the backward stroke are displayed as an extra line for both the R2L and L2R image.

The tip speed slider scale radio button lets you change the tip speed slider behaviour between linear and logarithmic.

This section allows you to set user-defined limits for both the tip speed and the scan area size.