Method and apparatus for determining pattern position and image forming system including the same

A method of detecting a test pattern position of an image forming apparatus when light is irradiate onto and subsequently reflected from a recording medium, the method comprising:

• obtaining, by a processor, at least one first detected data set of the reflected light which is received from a scanning position of the light by a light receiving unit while a reading unit moves relatively with respect to the recording medium before the test pattern is formed;
• obtaining, by the processor, at least one second detected data set of the reflected light which is received by the light receiving unit when the light moves over the test pattern at generally the same scanning position as the scanning position while the reading unit moves relatively with respect to the recording medium after the test pattern is formed;
• subtracting, by the processor, a value comparable to a local minimum value of the at least one second detected data set from each of the at least one first detected data set and the at least one second detected data set, and
• calculating, by the processor, a proportion of the subtracted at least one second detected data set relative to the subtracted at least one first detected data set to align local maximum values of the subtracted at least one second detected data set such that the local maximum values are generally constant.

An image forming system configured to read a test pattern formed by ejecting liquid droplets onto a recording medium to adjust an ejection timing of the liquid droplets, comprising:

• an image forming apparatus including,
• a reading unit including
• a light emitting unit configured to irradiate a light onto the recording medium, and
• a light receiving unit configured to receive a reflected light from the recording medium,
• a relative movement unit configured to relatively move the recording medium or the reading unit at a constant speed;
• and
• a processor configured to,
• at least one first detected data set of the reflected light which is received from a scanning position of the light by the light receiving unit while the reading unit moves relatively with respect to the recording medium before the test pattern is formed,
• obtain at least one second detected data set of the reflected light which is received by the light receiving unit when the light moves over the test pattern at generally the same scanning position as the scanning position while the reading unit moves relatively with respect to the recording medium after the test pattern is formed,
• subtract a value comparable to a local minimum value of the at least one second detected data set from each of the at least one first detected data set and the at least one second detected data set, and
• determine a proportion of the subtracted at least one second detected data set relative to the subtracted at least one first detected data set to align local maximum values of the subtracted at least one second detected data set such that the local maximum values are generally constant.