Method for adjusting recording head, and image forming apparatus

A method for adjusting a recording head that is a method for adjusting discharge timing of a plurality of head modules in the recording head formed by joining the plurality of head modules each of which has a nozzle array in which a plurality of nozzles for discharging droplets are arranged at different positions in a first direction, wherein the plurality of head modules are joined in a second direction intersecting with the first direction,

• the recording head including a complementary region where a nozzle belonging to one of the head modules adjacent to each other in the second direction and a nozzle belonging to the other of the head modules complement each other to record a dot row aligned in the second direction,
• the method comprising:
• a first measurement step of measuring a complementary region recording shift amount that is a recording shift amount in the first direction in the complementary region in a joined portion between a first head module and a second head module that are the head modules adjacent to each other;
• a second measurement step of measuring a first non-complementary region recording shift amount that is a recording shift amount in the first direction in a non-complementary region other than the complementary region in a nozzle array in the first head module, and a second non-complementary region recording shift amount that is a recording shift amount in the first direction in a non-complementary region other than the complementary region in a nozzle array in the second head module;
• and
• a timing adjustment step of adjusting discharge timing of at least one of the first head module and the second head module according to the complementary region recording shift amount that is measured in the first measurement step, and the first non-complementary region recording shift amount and the second non-complementary region recording shift amount that are measured in the second measurement step,
• wherein adjustment is performed in the timing adjustment step so that the complementary region recording shift amount after being adjusted becomes a value between the first non-complementary region recording shift amount and the second non-complementary region recording shift amount.