Image forming apparatus with laser scanning device and method of aligning the laser scanning device

An apparatus comprising:

• a light source to emit a laser beam;
• a resonant scanning mirror to reflect the laser beam emitted from the light source, and scan the reflected laser beam in a plurality of scanning directions,
• wherein the resonant scanning mirror is movable into a least a predetermined reference position;
• a plurality of detectors to detect the reflected laser beam during the scanning of the reflected laser beam, and generate synchronizing signals for each of the plurality of scanning directions;
• a light blocking unit, separate from the plurality of detectors and spaced between the plurality of detectors and the resonant scanning mirror, to restrict paths over which the reflected laser beam is incident on the plurality of detectors to a plurality of predetermined paths,
• wherein the laser beam passes the light blocking unit with each scan in one direction;
• and
• an alignment checking unit to check an alignment of the resonant scanning mirror based on the synchronizing signals generated by the plurality of detectors when the reflected laser beam is incident on the plurality of detectors over the plurality of predetermined paths,
• wherein the laser beam is incident on the at least one detector only when the resonant scanning mirror is disposed at a reference position and is operating normally, and when the resonant scanning mirror is deviated from the reference position, or when a scanning area of the laser beam is asymmetrical with respect to a center line, even though the resonant scanning mirror is disposed at the reference position but is not operating normally, the light blocking unit prevents the laser beam from being incident on the at least one detector.

A method of aligning an image forming apparatus comprising:

• emitting a laser beam from a light source so that the laser beam is incident on a resonant scanning mirror and is reflected by the resonant scanning mirror;
• oscillating the resonant scanning mirror to scan the reflected laser beam in a plurality of scanning directions;
• restricting, at a position separate from and spaced from the resonant scanning mirror and at least one detector, a path over which the reflected laser beam is incident on the at least one detector to a predetermined path,
• wherein said restricting occurs at each scan in one direction;
• detecting a synchronizing signal generated by the at least one detector when the reflected laser beam is incident on the at least one detector over the predetermined pat,
• wherein the laser beam is incident on the at least one detector only when the resonant scanning mirror is disposed at a reference position and is operating normally, and when the resonant scanning mirror is deviated from the reference position, or when a scanning area of the laser beam is asymmetrical with respect to a center line, even though the resonant scanning mirror is disposed at the reference position but is not operating normally, the light blocking unit prevents the laser beam from being incident on the at least one detector;
• determining a time difference between detection times of two synchronizing signals generated by the at least one detector;
• comparing the time difference with a preset reference time;
• determining whether the resonant scanning mirror is aligned correctly based on a result of the comparison;
• and
• displaying an indication of whether the resonant scanning mirror is aligned correctly.

A laser scanning device comprising:

• a light source to emit a laser beam;
• a resonant scanning mirror to reflect the laser beam emitted from the light source and alternately scan the reflected laser beam in a first scanning direction between a first scan end point and a second scan end point, and a second scanning direction between the second scan end point and the first scan end point;
• a first detector to detect the reflected laser beam and generate a first synchronizing signal when the reflected laser beam is approaching the first scan end point while being scanned in the second scanning direction, and a second synchronizing signal when the reflected laser beam is receding from the first scan end point while being scanned in the first scanning direction;
• and
• a first light blocking unit, separate from and spaced from the first detector and the resonant scanning mirror, to prevent the reflected laser beam from being incident on the first detector during the scanning of the reflected laser beam,
• wherein the laser beam passes the first light blocking unit while scanning in one direction, and
• wherein the laser beam is incident on the first detector only when the resonant scanning mirror is disposed at a reference position and is operating normally, and when the resonant scanning mirror is deviated from the reference position, or when a scanning area of the laser beam is asymmetrical with respect to a center line, even though the resonant scanning mirror is disposed at the reference position but is not operating normally, the first light blocking unit prevents the laser beam from being incident on the first detector.