The ON-LINE CRYSTALLOGRAPHY Interface

As well as an ``off-line'' data analysis program, FIT2D may be used as an ``on-line'' data display and manipulation program. Figure 31, page  shows the ON-LINE CRYSTALLOGRAPHY interface. Data may be input and displayed as with the other menus, and additionally the AUTO INPUT button allows files in a sequence to be automatically input and displayed as they are saved by the data acquisition system. An optional ``alarm'' may be set which will ring if the time for an image to appear is greater than a specified length.

Figure 31: The ON-LINE CRYSTALLOGRAPHY Main Menu

EXIT: Exit Interface and return to main interfaces menu

EXCHANGE: Swap current data with the ``memory''; see Section 5.2, Page .

PRINT: Output current graphics to a PostScript file.

PREV FILE: Input ``previous'' file in a file sequence.

?: List of commands with short descriptions.

FULL: View image of full data; set the ROI to be the whole of the defined data.

UN-ZOOM: Zoom out to see more of the data. (Also changes the ADR.)

SET GEOMETRY: Define diffraction geometry i.e. beam centre, wavelength, sample to detector distance. This must be defined if the corresponding d-spacings of diffraction peaks are to be calculated.

HELP: Detailed help text.

INPUT: Input data from a file on disk. This defines the file type, and may be the size for further input using the "NEXT FILE" or "PREV FILE" commands; see Section 5.1, Page .

ZOOM IN: View a smaller region in greater detail. (Also changes the ADR.)

PEAK SEARCH: Find, display, and calculate statistics on diffraction peaks. A number of control parameters allow the peak search to be optimised to find the maximum number of genuine peaks, whilst rejecting noise and other defects. The found peaks and estimates of integrated intensities and sigmas may optionally be saved in an ASCII file.

AUTO INPUT: Automatically input files from a sequence with option of performing a peak search on input, and of setting an alarm if a new image is not available after a defined interval.

OPTIONS: Display style control menu; see Section 5.5, Page .

Z-SCALING: Automatic or fixed user control of intensity display range. It is important to consider whether fixed range scaling, or automatic re-scaling is more suitable when displaying a sequence of images; see Section 5.3, Page .

SPY-GLASS: Cursor controlled ``real-time'' zoom window.

DISPLAY: Graphical display possibilities; see Section 5.4, Page .

MOVEMENT: Easily controlled movement around an image; see Section 5.6, Page .

NEXT FILE: Input ``next'' file in a file sequence.

MASK: Interactive masking of ``bad'' data regions. These are ignored in the PEAK SEARCH command; see Section 5.7, Page .

The peak search option identifies peaks, uses centroiding (with background removal) to improve the initial peak positions, calculates D-spacing, and performs a simple box integration. This allows estimates of the number peaks with different $I/Sigma(I)$ to be displayed, and if the diffraction geometry has been defined, the number of peaks in different resolution shells, and the average $I/Sigma(I)$ in each shell is displayed. The peak positions, D-spacings and intensities may be saved to an ASCII output file for further use e.g. Input to an indexing program.

The AUTO INPUT command allows a sequence of images to be input, displayed, and optionally searched for peaks, and statistics output. Similarly the NEXT FILE and PREV FILE allow easy input of following or previous files in a sequence. (All files are assumed to be of the same format and sizes as the a file input using the INPUT button.)