hi Dice, I've experimented with SMD LED with 3 of them in serial, they worked much better, 3 times brighter than 1, but the problem is 2 batteries do not provide enough voltage or power for 3 LEDs, so I had to use a DC power supply to power them.
I'm thinking to have my colleague design a voltage conversion circuit to raise the voltage of 2 batteries from 3V to 4.5V or 5V.

What exact model numbers / company did you get your Surface mount LEDs from?  Are they at the right wave length (940 nm)?

I don't think that you can raise voltage in a DC circuit but you can always throw in more batteries. I am using AG13 button cells in my sword model, 3 of them give me 4.5 volts, and could drive 5 small LEDs if I needed them to.

Cheers.

James.

sorry for replying late, the model of LED's I used are also from Vishay, they are tiny LEDs, sorry I forgot the model number, I got them as a few samples by asking Vishay's office in China, I'm sure you can also find it out from Vishay's office in your country?

You are right, using more batteries or higher voltage batteries are much easier, I was just thinking 3 or more batteries would be too heavy for a pen, but it's better than a complicated circuit.