Optical print head and image forming apparatus

An image forming apparatus, comprising:

• a photoreceptor;
• and
• an optical writing unit that writes an image onto the photoreceptor by optical beam, wherein
• the optical writing unit includes:
• a plurality of light-emitting elements that are connected to a plurality of current supply lines in one-to-one correspondence, the current supply lines branching from a first power line at different branch positions in a longitudinal direction thereof;
• a plurality of holding elements that are provided in one-to-one correspondence with the light-emitting elements;
• a signal writing unit that writes a luminance signal into each of the holding elements, the luminance signal being represented by a voltage indicating a light emission amount of a corresponding one of the light-emitting elements;
• a second power line that is different from the first power line, and supplies a reference voltage to each of the holding elements, the reference voltage being a reference when the signal writing unit writes the luminance signal into the holding element;
• and
• a plurality of driving drivers that are provided in one-to-one correspondence with the current supply lines, and each control a current supplied to a corresponding one of the current supply lines from the first power line, in accordance with a voltage that is held in a corresponding one of the holding elements when the signal writing unit has written the luminance signal into the corresponding one of the holding elements, wherein
• the signal writing unit includes a signal output subunit that outputs the luminance signal, and
• a power source that supplies the reference voltage to the second power line is common with a power source that supplies a voltage to the signal output subunit.