I need to detect a very light tube (like a plastic test-tube) running down a ramp. The tube is made of glossy, transparent plastic that may or may not be printed with an irregular company logo or other information. No guarantees on whether it is overall opaque or transparent to IR or any other wavelength, so I don't want to rely on a light gate mechanism.
I'm thinking I can look for a spike in the reflected light level and trigger a one-shot that gives me an indicator pulse (100ms would be nice).
I could design one myself but surely there must be a standard part for this sort of application? I've looked around Omron et al, but all the sensors I can find are light gates. Any cheap, small reflective sensors of the type I'm describing? Distance between sensor and object can be controlled fairly tightly (certainly within 1cm, probably less).
I have considered using one of those IrDA transceivers that have a prepackaged LED, photoFET and amplifier, but they're heavily filtered to reject signals outside the IrDA carrier area and I just want simplicity :)