Image forming apparatus including a pulse width modulator

An image forming apparatus comprising:

• pulse-width modulating means for subjecting an image-density signal to pulse-width modulation;
• image-forming means for forming an image in accordance with a pulse-width modulation signal outputted by said pulse-width modulating means;
• and
• at least two image-density-signal converting means having different characteristics for converting a multivalued image-density signal,
• wherein at least one of said image-density-signal converting means has a characteristic of converting an image-density signal corresponding to a low-density portion of the inputted image-density signal to an image-density signal of 0 or in an invisible range, and said at least two image-density-signal converting means operate in a time-sharing manner with respect to multivalued image-density signals arrayed in a main scanning direction.

An image forming apparatus comprising:

• pulse-width modulating means for subjecting an image-density signal to pulse-width modulation;
• image-forming means for forming an image in accordance with a pulse-width modulation signal outputted by said pulse-width modulating means;
• and
• at least two image-density-signal converting means having different characteristics for converting a multivalued image-density signal,
• wherein said image-forming means has light-beam scanning means for relatively scanning a light beam with respect to the photosensitive medium, and an image-forming optical system for forming a light beam spot of a predetermined size on the photosensitive medium by focusing the light beam, and wherein if it is assumed that a distance between adjacent ones of pixels in the main scanning direction at the time of forming an image in a low-density portion is dp (mm), and that the spot diameter (1/e.sup.2) of the light beam in the main scanning direction on the photosensitive medium is dB (mm), the following formula is satisfied:
• dB.ltoreq.(1/3)dp.