1. An apparatus for generating a laser beam detection signal in a light scanning unit that causes a laser beam to be scanned across a surface of a photosensitive body of an image forming device to form an electrostatic latent image on said photosensitive body, said laser beam being scanned across said surface of said photosensitive body in at least one scanning line that has a beginning point and an end point, said laser beam detection signal being used by said image forming apparatus to control said light scanning unit so that said beginning point occurs at a desired location, said laser scanning unit including at least a laser source and means for directing said laser beam emanating from said laser source towards a range of locations, said apparatus comprising: a laser beam detecting sensor disposed at a sensor location that falls outside said range of locations; and a single integrated optical element disposed at a predetermined location that falls within said range of locations, said single integrated optical element being arranged to receive said laser beam from said directing means, to deflect said received laser beam towards said laser beam detecting sensor, and to focus said deflected laser beam on said laser beam detecting sensor, said laser beam detecting sensor in response to said laser beam being focused thereon producing a signal indicative of said laser beam being detected at said predetermined location.