Short technical description.

Electronics

The SemAfore is a passive digitizer listening to the analogue slow scan signal going to the recording CRT when the PHOTO button is pressed. It digitizes this image with the same resolution as the scanning system gives, which varies with microscope and recording time but is typically 1900 x 1400 pixels. The image is recorded with 256 grey levels. One such image file takes 2.66 Mb of disk space.

The SemAfore does not in any way control the SEM. Its only connection to the SEM is via an existing socket. This means that the installation does not require any rewiring or soldering.

The A/D and D/A converters of the digitizer have a 12 bit resolution, which results in superb image quality. Electrically balanced connection with the SEM eliminates ground noise without sacrificing linearity.

Calibration is controlled by software, there are no trimmers to adjust. The digitizer board supports a thorough closed-loop self-test and an 'oscilloscope function' for troubleshooting the cabling.

Software

The 'state of the art' 32-bit program exploits the full power of 32-bit processors used in modern PC's. It also benefits from the multiprocessing and memory management capabilities of the 32-bit Windows operating systems.

Operation

The PC display will show the image as it is being recorded and stored in the RAM system memory. When the recording is finished the brightness and contrast can be adjusted in real time. A histogram is provided as assistance for the more advanced grey scale processing. Included are functions for automatic optimising of contrast and brightness and for enhancing the dark, the medium or the bright parts of the image. Basic convolution filters are available for sharpening the image or for removing noise.

The recorded image normally contains many more pixels than can be displayed on a PC screen. The advantage of this is that smaller parts of the image can be magnified and still retain a good image quality. This zoom function magnifies any selected area to full screen size. The zooming process can be repeated on already magnified images. The SemAfore has a full Windows multi-document interface, where several images can be viewed at the same time. The magnified image can be stored and printed like the original image.

The image can be sent back to the camera unit of the SEM and photographed in original or processed form. You can print it with any Windows compatible graphics printer e.g. a laser, inkjet, bubble or dye sublimation printers.

The image magnification can easily be calibrated against the micron bar or a magnification standard. Once done the displayed scale and magnification is correct for any type of zooming. When the image is printed, the real magnification ratio (paper to specimen) is automatically calculated and printed.

Objects can also be measured by drawing a line across the object which automatically displays the distance in micrometers. Similarly the surface area can be measured by tracing the perimeter of an area with the mouse cursor.

A grid with calibrated and selected grid spacing can be displayed on the image.

The object counting function works by clicking on the selected objects which then are marked and the total number of counted objects displayed. Three different types of objects can simultaneously be counted.

Image storage

A most important feature of SemAfore is the image archiving system. The database, based on the relational database engine MS Jet, allows storing images together with descriptive data. Image files can easily be found by looking in the thumbnail gallery or by searching the database. Images can be opened directly from the database gallery and stored from SemAfore without going through intermediate files. Thumbnail images are stored in the database, but the actual image files are kept separately. This makes it possible to manage up to 50 000 images within one database.

The SemAfore image database supports storage on optical disks (including CD-R) and network file servers.

Besides using the image database, you can read and store images on a disk in different file formats. The default format is BMP (Windows bitmap), but most other common formats are available, including TIFF and JPEG.

Support for sending images by e-mail is included in the SemAfore program.

Technical questions from anywhere in the world can be directed to us by e-mail sales@jeol.se or fax +46 8 29 16 47.