Patent ID: 8390660
Filing Date: 2013-03-05
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: a light source unit including a plurality of light sources for irradiating a multibeam composed of light beams emitted from the plurality of light sources; a light beam deflector for deflecting the multi-beam irradiated from the light source unit in a main scanning direction; an image carrier, on which an electrostatic latent image is to be drawn by the multi-beam deflected by the light beam deflector; and a timing signal generator for generating timing signals on a basis for the starts of image writing operations at the starts of the image writing operations by the plurality of light sources to start drawing an electrostatic latent image on the image carrier, the timing signal generator including a first optical sensor for receiving the light beams respectively emitted from the plurality of light sources to obtain timing signals after the light beams are deflected by the light beam deflector, the timing signal generator for generating the timing signals based on signals output from the first optical sensor; wherein: a positional relationship of the plurality of light sources with respect to the first optical sensor is so set that the timing signals corresponding to the light beams respectively emitted from the plurality of light sources can be separately generated at different timings by the timing signal generator; and the image forming apparatus further comprises: a first light emission controlling section used in a normal operation mode for executing a control to shift the starts of the image writing operations by the plurality of light sources by a first time interval to align image write starting positions of the respective light beams in the main scanning direction in the case of drawing an electrostatic latent image on the image carrier by the multi-beam irradiated from the light source unit on a basis the timing signals generated by the timing signal generator; a time interval data storage storing the first time interval used for the control in the first light emission controlling section beforehand; a test image data storage storing an image data of a test image beforehand, in which dot rows each formed by one-dot images arranged in a row in a sub scanning direction are arranged at predetermined intervals in the main scanning direction; an operation controlling section for controlling the operation of the image carrier at such a speed that the dot images adjacent in the sub scanning direction overlap; a second light emission controlling section used in a first time interval adjustment mode for drawing an electrostatic latent image of the test image on the image carrier by causing the light source unit to irradiate a multi-beam modulated by the test image data stored in the test image data storage on a basis the timing signals generated by the timing signal generator and causing the light beam deflector to deflect the multibeam with the image carrier moved by the operation controlling section, and the second light emission controlling section for executing a control to draw electrostatic latent images of a plurality of test images with different first time intervals; a developing unit for developing the electrostatic latent images of the test images drawn on the image carrier by the second light emission controlling section; a density measuring section for measuring the densities of the plurality of test images developed by the developing unit; and a first time interval adjusting section for storing the first time interval used to draw the electrostatic latent image of the test image having the lowest density out of the plurality of test images measured by the density measuring section in the time interval data storage as the first time interval used for the control in the first light emission controlling section, wherein: the first light emission controlling section executes the control to shift the starts of the image writing operations by the plurality of light sources by the first time interval to align image write starting positions of the respective light beams in the main scanning direction in the normal operation mode, using the first time interval stored in the time interval data storage by the first time interval adjusting section.