Patent ID: 9244375
Filing Date: 2016-01-26
CPC Classification: G02B,G03G

Claim Text:
1. An image forming apparatus comprising: a light source including a light emitting element which emits a light beam for forming an electrostatic latent image on a photosensitive member; a rotating polygon mirror configured to be rotationally driven and to deflect a light beam emitted from the light source to scan the photosensitive member; a light receiving element for receiving a light beam emitted from the light emitting element; a current supply unit configured to supply a current to the light emitting element, wherein the current supply unit supplies the light emitting element with a bias current regardless of image data and supplies the light emitting element with a switching current to be superimposed on the bias current based on the image data for a time period in which at least the light beam scans the photosensitive member; a removal unit configured to remove a dark current component from a light receiving result of the light receiving element, wherein the dark current component is output from the light receiving element in a state in which the switching current is not supplied from the current supply unit to the light emitting element; an output unit configured to output a first comparison voltage corresponding to a first target light amount and a second comparison voltage corresponding to a second light amount larger than the first target light amount; a charging/discharging unit including a first capacitor and a second capacitor and configured to charge or discharge the first capacitor based on a comparison result of a voltage obtained by removing the dark current component from an output of the light receiving element which receives the light beam with the first comparison voltage and to charge or discharge the second capacitor based on a comparison result of a voltage obtained by removing the dark current component from an output of the light receiving element which receives the light beam with the second comparison voltage; and a bias current control unit configured to calculate a threshold current value based on voltage values of the first capacitor and the second capacitor and to set a value obtained by multiplying the threshold current value by a correction coefficient equal to or less than one to a value of the bias current, wherein the bias current control unit sets a value of the bias current using a first correction coefficient as the correction coefficient for a predetermined time period from when a state in which the first capacitor and the second capacitor are not charged, then changes the correction coefficient to a second correction coefficient larger than the first correction coefficient, and sets a value of a bias current obtained by using the second correction coefficient, and wherein the current supply unit supplies the light emitting element with a bias current obtained by using the second correction coefficient and the switching current, and thus the electrostatic latent image is formed.