Light Scanning Apparatus, Method of Controlling the Same and Image Forming Apparatus Equipped with the Same

A light scanning apparatus which makes a light beam scan along a main scanning direction on an effective scanning region which has a predetermined width, comprising:

• a light source which emits the light beam;
• a deflector which includes an oscillation mirror which oscillates about an oscillatory axis which is orthogonal or approximately orthogonal to the main scanning direction, deflects the light beam emitted from the light source using the oscillation mirror, and makes the light beam scan a second scanning range which contains but extends beyond a first scanning range which corresponds to the effective scanning region;
• a detector which detects the scanning light beam which moves through a position which is outside the first scanning range but is within the second scanning range, and outputs a signal;
• and
• a controller which controls a mirror drive signal fed to the oscillation mirror based on the output signal from the detector and accordingly adjusts the amplitude of the oscillation mirror,
• wherein the controller stops driving the oscillation mirror when confirming based on the output signal that the oscillation mirror is under abnormal control,
• wherein the controller detects a change of the amplitude of the oscillation mirror in accordance with the output signal and stops driving the oscillation mirror in accordance with the result of the detection.

An apparatus for forming an image, comprising:

• a latent image carrier which has an effective scanning region which has a predetermined width along a main scanning direction;
• an exposure unit which scans a light beam on the effective scanning region so as to form a latent image;
• an exposure controller which controls the exposure unit;
• and
• a developing unit which develops the latent image with toner to form a toner image, wherein
• the exposure unit includes:
• a light source which emits the light beam;
• a deflector which has an oscillation mirror which oscillates about an oscillatory axis which is orthogonal or approximately orthogonal to the main scanning direction, deflects the light beam emitted from the light source using the oscillation mirror, and makes the light beam scan a second scanning range which contains but extends beyond a first scanning range which corresponds to the effective scanning region;
• and a detector which detects the scanning light beam which moves through a position which is outside the first scanning range but is within the second scanning range, and outputs a signal, and
• the exposure controller controls a mirror drive signal fed to the oscillation mirror based on the output signal from the detector and accordingly adjusts the amplitude of the oscillation mirror, meanwhile stops driving the oscillation mirror when confirming based on the output signal that the oscillation mirror is under abnormal control,
• wherein the exposure controller detects a change of the amplitude of the oscillation mirror in accordance with the output signal and stops driving the oscillation mirror in accordance with the result of the detection.

A method of controlling a light scanning apparatus, which deflects a light beam from a light source along a main scanning direction using an oscillation mirror which resonates and makes the light beam scan on an effective scanning region, according to which while the oscillation mirror is driven so that the light beam scans a second scanning range which contains but extends beyond a first scanning range corresponding to the effective scanning region, a detector detects this scanning light beam which moves passed a position which is within the second scanning range but outside the first scanning range, a mirror drive signal fed to the oscillation mirror is controlled in accordance with a signal which the detector outputs, and the amplitude of the oscillation mirror is accordingly adjusted, the method comprising:

• detecting a reciprocal light beam, which moves from the effective scanning region via the detector and returns back to the effective scanning region via the detector, for every oscillation cycle of the oscillation mirror and outputting a signal;
• and
• stopping the driving of the oscillation mirror upon confirmation based on the output signal that the oscillation mirror is under abnormal control;
• detecting a change of the amplitude of the oscillation mirror in accordance with the output signal;
• and
• stopping the driving of the oscillation mirror in accordance with the result of the detection.