Image forming apparatus having an exposure device changing pulse width of a light beam based on pattern data of an image

An image forming apparatus comprising:

• a photo conductor;
• and
• an exposure device scanning a surface of the photo conductor by light beams emitted by a plurality of light-emitting elements so as to simultaneously form a plurality of electrostatic latent images at a plurality of positions on the photo conductor, a pitch of the light beams in a sub scanning direction being smaller than a beam diameter defined by a value of an intensity of the light beam at which an intensity level of each light beam is 1/e2 of an intensity level at a center thereof, the electrostatic latent image being formed also at a position where the plurality of light beams overlaps with each other,
• wherein the exposure device comprises:
• a pattern detection processing circuit for producing a code of a plurality of levels from image data used for performing the latent image formation in accordance with a pattern detection matrix;
• a pulse width setting circuit for setting a pulse with output from the pattern detection processing means with reference to pulse width data which designates a pulse width of each light beam previously set in response to the code of the plurality of levels;
• and
• a driver circuit which drives each of the light-emitting elements with the pulse width set by the pulse width setting means.

An image processing circuit comprising:

• a pattern detection processing circuit producing a code of a plurality of levels from image data according to a pattern detection matrix;
• a pulse width setting circuit setting a pulse with output from the pattern detection processing circuit with reference to pulse width data which designates a pulse width of each of light beams emitted by a plurality of light-emitting elements previously set in response to the code of the plurality of levels;
• and
• an exposure device which perform exposure scan on a photo conductor by the light beams emitted by the plurality of light-emitting elements so as to perform an image forming operation according to an electrophotograph method,
• wherein a plurality of electrostatic latent images are simultaneously performed at a plurality of positions on the photo conductor, a pitch of the light beams in a sub scanning direction being smaller than a beam diameter defined by a value of an intensity of the light beam at which an intensity level of each light beam is 1/e2 of an intensity level at a center thereof;
• and
• the pulse width is set with respect to the plurality of light-emitting elements performing the exposure scan;
• and
• the electrostatic latent image is formed also at a position where the plurality of light beams overlaps with each other so as to form the image with a pitch smaller than a pitch of the exposure scan in a sub scanning direction.

A processor readable program having a computer to control an image forming apparatus to perform an image forming process, said image forming apparatus comprising:

• an exposure device scanning a surface of a photo conductor by light beams emitted by a plurality of light-emitting elements so as to simultaneously form a plurality of electrostatic latent images at a plurality of positions on the photo conductor, a pitch of the light beams in a sub scanning direction being smaller than a beam diameter defined by a value of an intensity of the light beam at which an intensity level of each light beam is 1/e2 of an intensity level at a center thereof, the electrostatic latent image being formed also at a position where the plurality of light beams overlaps with each other;
• pattern detection processing means for producing odes of a plurality of levels from image data used for performing the latent image formation in accordance with a pattern detection matrix;
• pulse width setting means for setting a pulse with output from the pattern detection processing means with reference to pulse width data which designates a pulse width of each light beam previously set in response to the code of the plurality of levels;
• a driver which drives each of said light-emitting element with the pulse width set by the pulse width setting means;
• and
• toner concentration sensors which detect a toner concentration of each of the image patters formed on said photo conductor,
• said program having the computer to perform:
• a pulse width data selecting process for selecting a value of the pulse width data by forming the image pattern for each of sets of the plurality of image patterns having relative positions with respect to the pattern detection matrix and detecting the toner concentration of the image patterns formed-on said photo conductor by said toner concentration sensors so that the detected toner concentrations are equal to each other with respect to the plurality of image patterns in each set of the image patterns;
• and
• a data setting process for setting the selected pulse width data as the pulse width data referred to by said pulse width setting means.

A processor readable medium storing a program having a computer to control an image forming apparatus to perform an image forming process, said image forming apparatus comprising:

• an exposure device scanning a surface of a photo conductor by light beams emitted by a plurality of light-emitting elements so as to simultaneously form a plurality of electrostatic latent images at a plurality of positions on the photo conductor, a pitch of the light beams in a sub scanning direction being smaller than a beam diameter defined by a value of an intensity of the light beam at which an intensity level of each light beam is 1/e2 of an intensity level at a center thereof, the electrostatic latent image being formed also at a position where the plurality of light beams overlaps with each other;
• pattern detection processing means for producing a code of a plurality of levels from image data used for performing the latent image formation in accordance with a pattern detection matrix;
• pulse width setting means for setting a pulse with output from the pattern detection processing means with reference to pulse width data which designates a pulse width of each light beam previously set in response to the code of the plurality of levels;
• a driver which drives each of said light-emitting element with the pulse width set by the pulse width setting means;
• and
• toner concentration sensors which detect a toner concentration of each of the image patters formed on said photo conductor,
• said program having the computer to perform:
• a pulse width data selecting process for selecting a value of the pulse width data by forming the image pattern for each of sets of the plurality of image patterns having relative positions with respect to the pattern detection matrix and detecting the toner concentration of the image patterns formed on said photo conductor by said toner concentration sensors so that the detected toner concentrations are equal to each other with respect to the plurality of image patterns in each set of the image patterns;
• and
• a data setting process for setting the selected pulse width data as the pulse width data referred to by said pulse width setting means.

A pulse width data selecting method to be applied to an image forming apparatus which performs an image forming process comprising:

• an exposure device scanning a surface of a photo conductor by light beams emitted by a plurality of light-emitting elements so as to simultaneously form a plurality of electrostatic latent images at a plurality of positions on the photo conductor, a pitch of the light beams in a sub scanning direction being smaller than a beam diameter defined by a value of an intensity of the light beam at which an intensity level of each light beam is 1/e2 of an intensity level at a center thereof, the electrostatic latent image being formed also at a position where the plurality of light beams overlaps with each other;
• pattern detection processing circuit for producing a code of a plurality of levels from image data used for performing the latent image formation in accordance with a pattern detection matrix;
• pulse width setting circuit for setting a pulse with output from the pattern detection processing circuit with reference to pulse width data which designates a pulse width of each light beam previously set in response to the code of the plurality of levels;
• a driver which drives each of said light-emitting element with the pulse width set by the pulse width setting circuit;
• and
• toner concentration sensors which detect a toner concentration of each of the image patters formed on said photo conductor,
• said pulse width data selecting method comprising the steps of:
• forming the image pattern on said photo conductor for each of sets of the plurality of image patterns having relative positions with respect to the pattern detection matrix;
• determining the toner concentration of the image patterns formed on said photo conductor;
• and
• selecting a value of the pulse width data so that the toner concentrations are equal to each other with respect to the plurality of image patterns in each set of the image patterns.

An image forming apparatus forming an image on a recording medium by scanning a light beam at a sub scanning pitch smaller than a beam diameter of the light beam, the beam diameter being defined by a value of an intensity of the light beam at which an intensity level of the light beam is 1/e2 of an intensity level at a center thereof, said image forming apparatus comprising:

• code producing means for producing a code of a plurality of levels from image data of an image to be formed according to a detection matrix;
• image forming means for forming the image on the recording medium by scanning the recording medium by the light beam at a pitch smaller than the sub scanning pitch which is mechanically defined, the light beam having a pulse width being set to correspond to the code of the plurality of levels,
• wherein, with respect to at least three levels from among the levels to be set, the pulse width of the light beam output in response to the code of the plurality of levels is produced from image patterns having the same ON pixel density, and a plurality of test patterns having different relative position with respect to said detection matrix are formed so as to equalize concentrations of the test patterns having the same ON pixel density;
• and
• the pulse width corresponding to the remaining levels are produced from image patterns of the same ON pixel density by determining a temporary value as an initial value by interpolation using values of the pulse width corresponding to the already determined levels, and a plurality of test patterns having different relative position with respect to said detection matrix are formed so as to equalize concentrations of the test patterns having the same ON pixel density.

An image forming apparatus forming an image on a recording medium by scanning a light beam at a sub scanning pitch smaller than a beam diameter of the light beam, the beam diameter being defined by a value of an intensity of the light beam at which an intensity level of the light beam is 1/e2 of an intensity level at a center thereof, said image forming apparatus comprising:

• a code producing part producing a code of a plurality of levels from image data of an image to be formed according to a detection matrix;
• an image forming part forming the image on the recording medium by scanning the recording medium by the light beam at a pitch smaller than the sub scanning pitch which is mechanically defined, the light beam having a pulse width being set to correspond to the code of the plurality of levels,
• wherein, with respect to at least three levels from among the levels to be set, the pulse width of the light beam output in response to the code of the plurality of levels is produced from image patterns having the same ON pixel density, and a plurality of test patterns having different relative position with respect to said detection matrix are formed so as to equalize concentrations of the test patterns having the same ON pixel density;
• and
• the pulse width corresponding to the remaining levels are produced from image patterns of the same ON pixel density by determining a temporary value as an initial value by interpolation using values of the pulse width corresponding to the already determined levels, and a plurality of test patterns having different relative position with respect to said detection matrix are formed so as to equalize concentrations of the test patterns having the same ON pixel density.