Image forming apparatus with density correction function and density correction method

An image forming apparatus with a correction function for correcting density of an image, comprising:

• an image bearing member configured to convey the image in a first direction while bearing the image;
• and
• a controller configured to perform a bias correction and a y correction for the density,
• wherein:
• the controller includes:
• a test patch generator configured to generate a test patch on the image bearing member, the test patch including a first test patch and a second test patch;
• a first density sensor configured to detect density of the first test patch to output a first detection signal corresponding to the density of the first test patch;
• a second density sensor configured to detect density of the second test patch to output a second detection signal corresponding to the density of the second test patch;
• a selector configured to compare the first detection signal with the second detection signal to select one of the first detection signal and the second detection signal as a bias-correction detection signal used for the bias correction while selecting another detection signal as a γ-correction detection signal used for the γ correction;
• and
• an adjuster configured to adjust the density by performing the bias correction based on the one detection signal and the γ correction based on the other detection signal, and
• the image bearing member bears the first and second test patches at positions separated in a second direction intersecting with the first direction.