Thanks for answer,
In fact, it's for a photosensor/phototransistor. I want to sense small particles and calculate the time the particle enters/exits the beam and measure the size of the particles. So it has to have relative fixed dimensions.
For some measurement techniques, I have to produce a sheeted (rectangular) laser beam in dimensions of the range of 20/30mmx1mm or 2mm. (max 0.5-3mW)
I searched on the internet already for some weeks find such low-cost laser diodes of compact systems, but without luck.
I hope someone can help...