If you are talking about the kind of CCD sensor that is in a barcode reader, for example, then you are talking about a pretty difficult project. I've been trying to write some code that would interface to a barcode sensor on arduino, and have not been successful so far. The timing is very tight, requiring the interface code to be written in assembler.
a) Are there CCD (or CMOS) line sensors on the market which are giving a 1bit output per data element? I need only digital output (material present or not, black or white). This will eliminate the need of A/D converter, which will help for speed.
Not that I know of. The barcode sensors are not color, but they are greyscale, giving
an analog reading for each pixel. It's easy enough to convert to bits in software, but like you said, the A/D conversion is a bottleneck. It might be possible to use a fast external A/D converter - I haven't looked into that. Or maybe some kind of comparator.
b) How many elements do these sensors have? Is my assumption of 2048 realistic?
Yes. A common barcode sensor has 2088 linear pixels.
c) what is the speed of
a. serial transmission of these sensors to the µ-Controller
b. time of acquisition of the complete line
a) about 1 Mhz.
b) a couple of milliseconds
d) what kind of µ-Controller will I need to realize this. I presume that the Arduino is not the right one. Or?
With an arduino is it barely possible, due to clock speed. Something with a (much) faster clock would probably be easier. I don't know what to recommend.
e) Is it possible to read the two line sensors at the same time? This is necessary as the parts cannot be stopped during the control.
If you mean simultaneously, probably not with an arduino. However, 2msec is not a lot of time to wait. If the parts are moving, placing the two sensors at an offset could do the trick.
This would be a tough project to implement on an arduino.