How to read signal (1.5 - 2 V) with Arduino Nano digital input

Hello everyone.

I am beginner in electronics. I must read a 1.5 - 2 V DC voltage with Arduino Nano. Since the Nano accepts 3 - 5 V s HIGH and lower than 2 V as LOW, I cannot read 1.5 V as HIGH and 0.5 V or lower as LOW.

How can I solve my problem? Should I use someking of gain, amplifier?? Any advice welcome!