That 6 V is a nuisance, but we'll have to live with it. A typical way to interface a logic signal like the sensor outputs is to send the data over USB to the PC. This is easy with boards like this one:
This only needs a USB connection and you have 8 logic level inputs and outputs. Handy, because you'll often use more sensors, or outputs from the PC.
Unfortunately USB is 5 V, so you'll have to use a separate power supply to feed the sensor. The easiest here is a 12 V wall wart.
The sensor with the NPN mentioned in the spec is drawn at the left, with power supply and the open-collector output. An open-collector allows to connect the output to a different voltage than the power supply, which we'll do here. Connect a 4 kΩ pull-up resistor to the USB's board 5V, as drawn. If the transistor is off the resistor will pull "A" to the 5 V, so that's logic "1". If the transistor is on it will switch the output "A" to ground, that's a "0". The output "A" goes to one of the board's inputs. Ground of the sensor (coming from the wall-wart) goes to the board's ground.
FTDI, which manufactures the IC on the board, has downloadable drivers for different PC operating systems which allow you to access the ports with most current programming languages.