The proximity sensor on your Android reads how close your face is to your device whilst making a call. By turning off the display, it eliminates the risk of accidental "button pushing" which can occur when your face touches the screen. In order to turn the proximity sensor off, your phone must first be rooted (software installed that allows you to access the phone's operating system) before you download any program that will let you disable it.
Open the "Market" icon on your device to take you to the Android Market. Search for a program called "Hardware Disabler" and download the free version onto your device.
Install the downloaded program and now search the Android Market again for "Android Sensor Box." Download the free version and install.
Open the "Android Sensor Box" program to find out the name of the driver which powers the proximity sensor. Once you have located it, you can close the program.
Open "Hardware Disabler." Check the box next to the name of the driver which powers the proximity server to disable it. Reboot your phone to make sure the process is completed.
Be careful when gaining root access not to tamper with any other drivers which may affect your phone's hardware.