Image forming apparatus and image method for forming toner images with optimized patch image density

An image forming apparatus comprising:

• image forming means for applying toner to an electrostatic latent image formed on a latent image carrier thereby developing the electrostatic latent image with the toner into a toner image;
• and
• density detecting means for detecting a toner density of the toner image formed as a patch image,
• characterized in that each patch image is formed under each different image forming condition varied stepwise by varying stepwise a density control factor affecting image density and then, the density control factor is optimized based on the detection results of the densities of the patch images given by the density detecting means and on a variation rate of the detection results against the density control value,
• wherein a value of the density control factor establishing either one of image forming conditions, including a first image forming condition providing a toner density of the patch image substantially equal to a predetermined density target value and a second image forming condition providing a value of the variation rate not greater than a predetermined effective variation rate, that provides a lower image density is selected as the optimum value thereof.

An image forming apparatus comprising:

• image forming means for applying toner to an electrostatic latent image formed on a latent image carrier thereby developing the electrostatic latent image with the toner into a toner image;
• and
• density detecting means for detecting a toner density of the toner image formed as a patch image,
• wherein with respect to each of a high image density level and a low image density level, each patch image is formed under each different image forming condition varied stepwise by varying stepwise a density control factor affecting image density and then, the density control factor is optimized based on the detection results of the toner densities of each set of the patch images given by the density detecting means,
• the apparatus characterized in that in the optimization of the density control factor for the low-density level based on the detection results of the toner densities of the low-density toner images formed as the patch images, a value of the density control factor providing a toner density of the patch image substantially equal to a predetermined density target value is selected as the optimum value thereof, and
• that in the optimization of the density control factor for the high-density level based on the detection results of the toner densities of the high-density toner images formed as the patch images, a value of the density control factor establishing either one of the image forming conditions that provides the lower image density is selected as the optimum value thereof, the image forming conditions including one providing a toner density of the patch image substantially equal to a predetermined density target value, and one providing a value of the variation rate of the detection results against the density control factor not greater than a predetermined effective variation rate.

An image forming method for forming a toner image by applying toner to an electrostatic latent image formed on a surface of a latent image carrier thereby developing the electrostatic latent image with the toner,

• characterized in that first and second optimization processes for a low image density level and a high image density level are performed respectively,
• that in the first optimization process, each low-density toner image as a patch image is formed under each different image forming condition varied stepwise by varying stepwise a density control factor affecting image density while respective toner densities of the patch images are detected by density detecting means and then, a value of the density control factor providing a toner density substantially equal to a predetermined density target value is selected as the optimum value thereof, and
• that in the second optimization process, each high-density toner image as a patch image is formed under each different image forming condition varied stepwise by varying stepwise the density control factor affecting the image density while respective toner densities of the patch images are detected by the density detecting means and a variation rate of the toner densities against the density control factor is found and then, out of a value of the density control factor providing a toner density substantially equal to a predetermined density target value and a value of the density control factor associated with the variation rate substantially equal to a predetermined effective variation rate, the value providing the lower image density is selected as the optimum value thereof.

An image forming apparatus comprising:

• exposure means for forming an electrostatic latent image by irradiating light beam on a surface of a charged latent image carrier;
• a toner carrier spaced away from the latent image carrier and bearing toner on its surface;
• and
• a bias applying means for applying a developing bias to the toner carrier for transferring the toner borne on the toner carrier to the surface of the latent image carrier thereby developing the electrostatic latent image with the toner,
• characterized in that patch images including high density patch images and low density patch images are formed such that the developing bias is varied stepwise for forming each high-density patch image at each different bias value and the developing bias is optimized based on the densities of the patch images, and
• that each low-density patch image is formed at each energy density value of the light beam varied stepwise as applying the optimized developing bias to the toner carrier and then the energy density of the light beam is optimized based on the densities of the patch images.