Type of sensor to sense glass marbles at close proximity??

Hi all,

I was wondering if any of these sensors would be any use to detect a glass marble at a close proximity, say 0 - 3 cm away?

Maxbotix LV-EZ0

Sharp GP2Y0A21YK IR Proximity Sensor

QRD1114 IR emitted / Phototransistor

I got info on these here: http://bildr.org/2011/03/various-proximity-sensors-arduino/ but am not sure how well any of them would work for me? The first one is ultrasonic so would be great only I think it works better at a bigger distance. The third one has the exact range I need except I am worried it will shine through the marble and not work properly.

Any help would be greatly appreciated

Edit:

I might be off the mark here but would this work?

Adafruit VCNL4000 proximity / light sensor

http://www.ebay.ie/itm/Adafruit-VCNL4000-Proximity-Light-Sensor-Break-Out-/181661322202?pt=DE_Computer_Sonstige&hash=item2a4bdbcbda

The VCN and the QRD work on the same principle. If you need to know the relative distance, I think the VCN would be better for you, and you get an easy interface to the Arduino.

As to whether it will work with glass marbles… You’ll have to test.

Most light reflects from spectral surfaces quite well, but angles are important. Since you are looking at a sphere, the number of angles is infinite, which may or may not be helpful in your application.

Thanks very much.

I think I will have to just get one and try it alright. I don't need to know the distance, just that there is a marble there or not.