First, a date is typed into a keypad. Then, the user's helmet scans the brain for the corresponding memory, and displays it on the screen. The image is shown as though the viewer is watching through the user's eyes and listening through the user's ears.
It also appears to be able to record a memory for later viewing, as shown when Lewis watched DOR-15's takeover of the world until Lewis returns to the present, telling DOR-15 that he would have never invented her, restoring the future.
Later during the end of the film, Lewis asks Mr. Willerstein to know if he could participate in the Science Fair at school, but Willerstein gives him one more chance before he cannot participate anymore. Lewis then shows the Memory Scanner at the Science Fair, impressing him and the other staff at the school as well as winning the Science Fair.
The Memory Scanner can also read the memories of machines, shown when Lewis saw the memories of DOR-15's takeover of the world.