This looks entirely like your depth range – what is the furthest you want to shade, and what is the nearest you want to shade?
Take the nearest of the band and map it to white; anything nearer should clamp to white.
Take the furthest of the band and map it to black; anything further should clamp to black.
Also: The image you pasted as reference doesn’t look like pure depth – either it’s depth from a different camera or it’s some combination of depth and lighting.