Image forming apparatus using an electrophotographic process and image forming method

An image forming apparatus comprising:

• exposing means for exposing a photoconductor by outputting a light signal subjected to a pulse width modulation;
• developing means for developing the photoconductor to form a developed image on the photoconductor;
• transfer means for transferring the developed image onto a transfer-receiving member to form a transfer image;
• image patch creation means for creating an image patch including a minute point;
• sensor means for detecting density information of a developed image of the image patch formed on the photoconductor or a transfer image of the image patch formed on the transfer-receiving member;
• picture quality maintaining control means for changing, in a case where the density information detected by the sensor means is outside a range of a specified reference density, an exposure parameter for forming an image of the minute point so that the density information falls within the range of the specified reference density;
• and
• count means for counting a usage time,
• wherein the picture quality maintaining control means changes the exposure pattern according to an increase in a count value of the count means.

An image forming method of an image forming apparatus including a photoconductor, an exposure unit configured to expose the photoconductor by outputting a light signal subjected to a pulse width modulation, a developing unit configured to develop the photoconductor to form a developed image on the photoconductor, and a transfer unit configured to transfer the developed image onto a transfer-receiving member to form a transfer image, the image forming method comprising:

• creating an image patch including a minute point;
• detecting density information of a developed image of the image patch formed on the photoconductor or a transfer image of the image patch formed on the transfer-receiving member;
• and
• changing, in a case where the density information detected by the sensor unit is outside a range of a specified reference density, an exposure parameter for forming an image of the minute point so that the density information falls within the range of the specified reference density,
• wherein the exposure pattern is changed according to an increase of a usage time.