Replacement LCD not working, getting blur ( not solid color )

I get an iphone4 on piece, and try to assembly by myself.
phone stuck boot on apple logo and I see the corner of apple logo on lcd from white getting blur ( not solid color )

I don't know it's the original lcd or not but if the issue from the un-matching type LCD or digitizer, how I identify the LCD before I buy it for replacement

please help and really appreciate if you can give advice