Image alignment by detecting change in position of beam

A non-transitory computer-readable recording medium having stored therein instructions executable by a processor, the non-transitory computer-readable recording medium comprising:

• instructions to detect a position change of a beam with respect to a certain color in a main scanning direction, based on a change in a detection time at which the beam with respect to the certain color is detected against a reference color by a beam detecting apparatus in the image forming apparatus in the main scanning direction;
• instructions to detect a position change of the beam with respect to the certain color in a sub-scanning direction, based on a change in a detection time at which the beam with respect to the certain color is detected against the reference color by the beam detecting apparatus in the sub-scanning direction;
• and
• instructions to correct a value of at least one parameter used for alignment between an image of the reference color and an image of the certain color, based on the position changes of the beam with respect to the certain color in the main scanning direction and the sub-scanning direction.

An image forming apparatus comprising:

• a diode to irradiate a beam used in an image forming job;
• a beam detecting apparatus to detect a beam in a main scanning direction indicating a scan direction of the image forming job and to detect a beam in a sub-scanning direction indicating a progress direction of the image forming job;
• a processor;
• and
• a memory storing instructions executable by the processor,
• wherein the processor executes the instructions to:
• detect a position change of a beam with respect to a certain color in the main scanning direction, based on a change in a detection time at which the beam with respect to the certain color is detected against a reference color by the beam detecting apparatus in the main scanning direction;
• detect a position change of the beam with respect to the certain color in the sub-scanning direction, based on a change in a detection time at which the beam with respect to the certain color is detected against the reference color by the beam detecting apparatus in the sub-scanning direction;
• and
• correct a value of at least one parameter used for alignment between an image of the reference color and an image of the certain color, based on the position changes of the beam with respect to the certain color in the main scanning direction and the sub-scanning direction.