This camera is an incredible tool for experimental scientists. Compared to available equipment today the camera has high spatial and dynamic resolution. It is possible to get higher spatial and dynamic resolution, but the cost is very high.
When a high resolution is used the time necessary for reading out the picture become large. This is the main drawback with our system. To reduce this time it was necessary to develop our own software. One of the concepts of the Macintosh Computer Operating System is using visual means for an easy-to-use user environment. The result is that all operations are performed against the screen and take unnecessary long time. Our program for camera control violates this concept although as much of the Macintosh User Interface as possible is used.
The program code is written in C-programming language and most of it is included in appendix . The read out of the CCD-chip is done through the 16-bits NU200 Interface at a speed of . Each pixel is read as a unsigned 16-bits number which gives a minimum read out time for pixels of . The microprocessor speed of our Macintosh is so operating system tasks of the computer do not cause trouble. A standard Macintosh dialogue as shown in dialogue is used to communicate with the user. To reduce programming and computational time error messages and all other user information are streamed to a standard console window instead of using proper dialogues.
The user dialogue have possibilities to read out parameters from the camera electronics. When used together with other camera control software with possibilities to show the pictures on the screen, this is very useful. A full frame picture is taken and from this is the interesting region picked out using the other software. If one picture of this region with the correct exposure time and binning factors is captured the software will read these parameters from the Camera Electronic unit and insert them in the dialogue. This function actually makes the software quite useful. The version of the Macintosh Operating system used (System 7), allows multiple programs to be open simultaneously, but it does not support multitasking. For most of the image processing another software is used. This is IP Lab from Signal Analysis.
After the user has given proper parameters in the dialogue shown in dialogue the program allocates sufficient memory for one frame. Then a loop which is repeated as many times as the user has specified in the dialogue, starts. The loop expose the CCD-chip and read out the data to the allocated memory. The memory is written to the hard disk as fast as possible. The storage format of the picture is similar to the format used in the group. The picture is saved as two lines. The first line has a specific length of 360 bytes starting as the standard format does with the grey level resolution and resolution in y- and x-direction. Then the date, time and parameters used are saved together with a text line. So far this text has been static, but as proposed in the program in appendix the user should be able to enter his own comments.
This format was chosen because most advanced image processing software is able to read raw data files with offsets. It is therefore preferable to know the offset of the data. Some software are also able to read the dimensions from the file, but usually the dimensions have to be written binary. This is included in the text in the header line assuming that dimension corresponding to the ASCII value of line feed (ASCII 10) is never used. Other improvements are suggested in the program in appendix .