Below is a picture with projector off
http://img211.imageshack.us/img211/5347/54808149.jpg

Below is the picture with projector on
http://img208.imageshack.us/img208/8580/66363017.jpg

Rear DI:

webcam with ir bandpass filter

epson projector with hot mirror.

I have put hot mirror still the projector brightness is affecting the blobs.I changed projector brightness.It worked fine.But when you open a window the brightness increases since window has white background.So the screen has some fluctuating brightness.I wonder how brightness is captured by camera.Since it can see only ir rays?

So what must be done so that changing brightness is not captured by camera?

hm, looks like your IR Illuminators are weak,

I hope you have remowed the IR Filter before putting in the Bandpass.

cant find any other issue

I had a similar problem with my Rear DI setup where the projector light was turning off the IR illuminators since they have photosensors on them. If your illuminators are darkness-triggered make sure to cover (or just rip out) the sensor on the illuminators.