part present detection? what sensor??

Hi. I need to come up with an application for detecting a very tiny metal nut on a part. The part is at a distance of 200mm and is 1 cm in diameter. I have been using a Balluff a PhotoElectric Sensor http://www.balluff.ca/Balluff/us/ProductsChannel/Product+Detail/en/ProductDetail.htm?ProductID=BOS+26K-PA-1LHC-S4-C&ProductGroupGuid={8BF459B2-B1E0-4064-8C67-6F14F05FFD2E}&ProductGroupName=Photoelectric%20Sensors

but I find the Laser light beam is too spread. I tried the SICK http://www.mysick.com/eCat.aspx?go=DataSheet&Cat=Row&At=Fa&Cult=English&Category=Produktfinder&ProductID=7010

and it seems to work perfect(small light beam) but they cost $450 each. Does anyone know of a Type a sensor that may work in place of the SICK?

I have had good luck with these guys

http://www.keyence.com/

I have a Keyence salesman that comes by with a case of their sensors products. Most of the time he can solve any problem I have out of his case. If not he will ship me a sample to "try before you buy"

I think its worth a shot.

edit:
I like this one.
http://www.keyence.com/products/sensors/lasercompact/lvs31/lvs31.php

We use to demo an Aromat (Matsushita) fiber optic sensor that would count the columns on the Lincoln Memorial on a penny. The sensitivity could be set so that it would do this reliably. So I would look for this type of sensor which should be available from several manufacturers including Keyence, Sunx, etc.. I have also had good results with Keyence sensors.

I second (or third) the Keyence suggestion. They will let you borrow a sensor for 15 days to test your application. They have a complete line of fiber optic sensor cables and heads to match a wide variety of environments and there controllers are easy to setup and use. With that said, they can be a bit costly.

You may also want to look at IFM Efector. They compete with Keyence very well in these types of application and can be a bit more cost effective.

My understanding is Banner Engineering is the world leader in photoelectric sensing technology.

http://www.clrwtr.com/Banner-Engineering-Sensors.htm
http://www.clrwtr.com/Banner-Part-Sensing-Sensors.htm

I would suggest looking into the Banner QS18 laser series:
http://info.bannersalesforce.com/xpedio/groups/public/documents/literature/66981.pdf

We use these all over and they work great for us. Being able to see that little red dot really helps with the setup. The cutoff point is adjustable via a small screw (personally I prefer that over the "teach" mode that some other sensors have). You'd need the Class 2 laser which has a 250mm range. The literature claims a 1mm spot size. Pricewise, I think you're looking at $150-200.