As you pointed out, there are lenses that do what you want.  As you found out,
there are cheap lenses for visual uses, and then there are expensive lenses for
industrial, scientific and other high-end uses.  I don't believe that you'll
find anything in the middle ground yet.  There aren't any high-volume
mid-quality uses for these, and so no one is producing them.  (speculation on my
part, this may not be the case)

Hopefully someone will prove me wrong.  Until then, you might try and look at
the problem again.

My understanding is that your requirement is:
Produce a line of light, at a 90 degree angle with a sharp/well defined line.

You don't tell us the distance to these sensors.  I'll assume it's only a few
yards (if it were more you wouldn't be able to use a cheap laser, which you
point out is acceptable).

Why not use a regular LED?  You can get some very high power leds for little
more than a very cheap laser.  You might even be able to find one with a lens
that projects a 90 degree cone.  If so, just place something in front of it with
a slit.  You may have to make your detectors a little more sensitive, but with a
modulated light beam it should be easy to deal with.

Are there any specific reasons to use a laser?

-Adam

Jinx wrote:
>
> I'm revisiting an old project that I abandoned mainly because of the cost
> of one component. Hopefully someone has practical experience of a
> cheaper source for it or can suggest an alternate method. I've looked
> at mirrors (specifically the scanner from a laser printer) but would prefer
> to avoid the extra power requirements and moving parts. Audible noise
> and/or vibration are considerations, as well as obtaining the most even
> light spread possible
>
> I need to make an arc of at least 90 degrees with either a red or IR laser,
> about 5mW. The lasers are no problem to get at low cost, but the line
> generator lens has so far been tricky. I got a plastic one for $2 which is
> about 7mm across with ridges that make a fairly passable line, but
> quite a bit of the light is being scattered you couldn't really call it a
> sharp line. For intruder detection or something like that it'd be OK but
> my target is a series of small detectors 10m away. As each detector
> picks up the laser light , the PIC will produce an increasing tone so the
> definition of the beam has to be quite good. Some reasonable quality
> optics are needed, and that's when I've found the price goes up. Wrong
> place to comparison shop, but the only reference I have to these is the
> RS catalogue, and both red and IR lasers + LG are around NZ$900. A
> local laser supplier was cheaper but it still would've stung. With a
> perfectly suitable laser pointer available for next-to-nothing surely an
> LG lens shouldn't be THAT expensive
>
> TIA
>
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