| 摘要 |
PURPOSE:To output an image including a middle tone stably at all times with high quality by detecting the image density of an electrostatic latent image, detecting the density of a specific pattern based on the detecting result of the image density, and correcting the density corresponding to the kind of the image based on the detected density of the specific pattern. CONSTITUTION:In response to an instruction from a CPU 15, a specific pattern generat ing circuit 22 generates a signal to form a mat black pattern to a laser driver 7, so that an image of a mat black pattern is formed on a photoreceptor 10. The density of this image is detected by a densitometer 23 and taken into the CPU 15 through an A/D converter 26. The CPU 15 compares the image density with a preset reference density data. When the detected density is lower than the reference density, the CPU 15 instructs a bias power source 14 to lower the bias output. On the other hand, if the detected density of the image is higher than the reference density, the CPU 15 instructs the bias power source 14 to raise the bias output. Thereafter, in correcting the density of an image of a middle tone, the CPU 15 forms a density correction data from the detected density data in the same manner as above, and outputs the data to a RAM 4. As a result, a digital-digital conversion is performed to an image data 1 in accordance with the density correction data, and the corrected data is input to a terminal P of a comparator 5. |
