Patent ID: 9290028
Filing Date: 2016-03-22
CPC Classification: B41J

Claim Text:
1. An image forming apparatus which reads 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 unit configured to obtain pattern data of the test pattern to form the test pattern on the recording medium; 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 move the recording medium or the receiving unit at a constant speed; an intensity data obtaining unit configured to obtain intensity data on the reflected light which is received from a scanning position of the light by the light receiving unit while the light moves over the test pattern; a threshold value setting unit configured to set an upper-limit threshold value and a lower-limit threshold value to respective two points having a same distance from a derivative point, the derivative point being a point in a derivative of the intensity data whose slope is closest to zero; and a determination unit configured to determine an edge position based on a first-main-scanning position where the intensity data corresponds to the upper-limit threshold value and a second main-scanning position where the intensity data corresponds to the lower-limit threshold value.