Light intensity control circuit for an optical scanning unit

A light intensity control circuit for an optical scanning device, in which an intensity of a beam emitted by a laser diode is modulated in accordance with an image signal, said image signal including information about gradation levels of an image to be formed by said scanning device on a photoconductive surface, said control circuit comprising:

• a first circuit for setting a first intensity value of said beam to correspond to a minimum gradation level of an image to be formed, said minimum gradation level corresponding to a white image;
• a second circuit for setting a second intensity value of said beam to correspond to a maximum gradation level of said image to be formed, said maximum gradation level corresponding to a black image;
• said beam having 256 different intensity levels between said minimum gradation level and said maximum gradation level;
• and
• a driving circuit for driving said laser diode such that said intensity of said beam is determined in accordance with said image signal and a difference between said first intensity value and said second intensity value.

A method of setting an intensity of a laser beam used in a laser scanning unit for forming an image on a photoconductive surface in accordance with an image signal, said method comprising the steps of:

• determining a first intensity value of said beam which corresponds to a minimum gradation level of an image to be formed;
• determining a second intensity value of said beam which corresponds to a maximum gradation level of said image to be formed;
• setting an intensity of said beam in accordance with said image signal and a difference between said first intensity value and said second intensity value;
• holding an image signal while said intensity of said beam is being set;
• and
• holding a succeeding image signal while said intensity of said beam is being set.

A light intensity control circuit for an optical scanning device, in which an intensity of each pixel of a beam emitted by a laser diode is modulated in accordance with an image that includes information about a gradation level of said each pixel, said control circuit comprising:

• a first circuit for setting a first intensity value of said beam corresponding to a minimum gradation level of said pixel, said minimum gradation level of said each pixel corresponding to a white image;
• a second circuit for setting a second intensity value of said beam corresponding to a maximum gradation level of said pixel, said maximum gradation level of said each pixel corresponding to a black image;
• said beam comprising 256 different intensity levels corresponding to 256 gradation levels of said each pixel, said gradation levels of said each pixel extending between said white image and said black image;
• and
• a driving circuit for driving said laser diode such that said intensity of said beam for each said pixel is determined in accordance with said image signal and a difference between said first intensity value and said second intensity value.