proximity sensor problem

[xperiae3]

hi seniors.. i bought sony xperia e3 about week ago.. from very first day i had same problem with proximity sensor. when i touch phone to my ear for answering call.. screen goes blank but when i remove ear device from ear , it remains blank.. i hav not even installed screen guard.. please guide me what to do.. its so irritating.. bought this device over other companies.. but seems backstabbed .....

[xperiae3]

hi... recently i discovered new thing regarding sensor... when my screen does not lights up when i remove it from ear.. if i clean screen from sensor area then screen lights up.. what a cheap quality of sensor.. i have been using htc and samsung smartfone from so much time but nithing happened like this before..