Abstract: According to an image forming apparatus and method of the present invention, an image of an original is read by an image reader unit, a correction of gradation reproduction or a pseudo gradation processing is provided to the read image data by an image processing section. When an image corresponding to the image-processed image data is printed out on a sheet material, a gradation chart for image forming conditions is outputted, a number of gradations corresponding to the image forming conditions, the image forming conditions corresponding to the number of gradations are detected, and a test pattern for gradation reproduction is outputted based on the detected image forming condition is outputted. The test pattern is read again by the image reader unit. Newly read gradation data and gradation data of the test pattern are compared with each other, and correction data for every gradation of the plurality of the gradation is calculated.

Abstract: In a color image forming apparatus such as a color laser printer, misregistration of colors of an output image along a subscanning direction is minimized so as to prevent accumulation of color misregistrations in the output image. In the apparatus, a photosensitive drum motor and a transfer drum motor are driven by motors exclusively provided thereto. The apparatus includes a photosensitive drum motor controller and a transfer drum motor controller respectively provided for speed-controlling the photosensitive drum motor and the transfer drum motor. By these motor controllers, a phase difference between a frequency generator signal from the motor and a phase reference signal is checked. Even if the phase difference exceeds a predetermined range of phase, the motor controller controls the motor so that the phase difference quickly falls within the predetermined range of phase.

Abstract: A drive circuit for a brushless motor having a rotor formed of a permanent magnet and stator coils includes a plurality of magnetic sensors each for sensing a rotational position of the rotor of the brushless motor to generate a voltage signal in accordance with a magnitude of a magnetic flux density received from the rotor passing, power amplifiers each for converting the voltage signal from each corresponding magnetic sensor to a drive voltage having a predetermined phase and voltage value and supplying the drive voltage obtained to each corresponding stator coil, a speed control signal generating circuit for generating a speed control signal for control of the rotational speed of the brushless motor, and magnetic sensor controller for controlling the magnitude of the output voltage of each magnetic sensor in response to the speed control signal so that the output voltage of each magnetic sensor takes a value in accordance with the speed control signal.

Abstract: High and low density test patterns are formed from pattern generating unit as toner patterns on a photosensitive drum, and attached toner amounts corresponding to the test patterns are detected by toner density detecting unit under the control of a control circuit which calculates the differences between the attached toner amounts of the high and low density portions and respective target values, wherein, when the calculated differences do not fall within respective predetermined ranges, the exposure conditions of an optical system and the bias voltage of a developing unit, or the exposure amount of the optical system and the bias voltages of a charger and the developing unit, or the bias voltages of the charger and the developing unit and the light-emission period of the optical system are renewed.

Abstract: An image forming apparatus includes a scanner for scanning a light beam over an image carrier, an image forming unit for forming an image on the image carrier corresponding to the light beam scanned over the image carrier by the scanner and a movable supporting member for supporting an image forming medium and conveying the image forming medium to a position where the image on the image carrier is transferred to the image forming medium.

Abstract: In an image forming apparatus of the present invention, the adhesion amounts of developing agent on a high-density test pattern and a low-density test pattern are measured by a toner density measuring unit. On the basis of the measured adhesion amounts of developing agent on the high-density region and low-density region and the target values of the adhesion amounts, deviations of the adhesion amounts of the high-density region and the low density region are calculated. The renewal amount of contrast voltage and the renewal amount of background voltage corresponding to the high-density region deviation and low-density region deviation are inferred by an inference unit on the basis of inference data stored in a memory unit. The grid bias value and development bias value corresponding to the inferred renewal amounts of contrast voltage and background voltage are calculated. The grid bias voltage and development bias voltage are varied in accordance with the calculated grid bias value and development bias value.

Abstract: An image forming apparatus, in accordance with the present invention, forms a color image on an image bearing member. The image forming apparatus includes a charging device for electrically charging the image bearing member, an exposing device for exposing a light beam on the image bearing member so as to form a latent image on the charged image bearing member corresponding to image data to be formed, and a developing device for developing the latent image formed on the image bearing member with a developing agent including toner.

Abstract: An image forming apparatus includes a measuring for measuring an amount of a toner agent deposited on the image carrier. The measuring device has measuring section facing the image carrier, and a conductive cover plate arranged between the measuring section and the image carrier. The cover plate is applied with a voltage whose polarity is equal to the polarity of the toner so that an electric field is generated between the image carrier and the cover plate. The electric field prevents the toner, dispersed from the image carrier, from reaching the measuring section. The toner may also be kept from adhering to the elements of the measuring section by placing a transparent plate between the image carrier and the measuring device.

Abstract: A toner sensor measures the amount of toner attached onto a photosensitive drum upon development by a developing unit. A controller compares the measured toner attaching amount with a predetermined reference value, and executes processing for changing at least one of image forming conditions, for example, the charging amount by a charger, the developing bias voltage of the developing unit, the exposure amount of an optical system, and the toner density of the developing unit, on the basis of the comparison result.

Abstract: An image forming apparatus includes a scanner for scanning a light beam over an image carrier, an image forming unit for forming an image on the image carrier corresponding to the light beam scanned over the image carrier by the scanner and a movable supporting member for supporting an image forming medium and conveying the image forming medium to a position where the image on the image carrier is transferred to the image forming medium. The image forming apparatus further includes a first driver for driving the scanner, a second driver for driving the image carrier and the supporting member, a generator for generating a reference signal, a first controller for controlling the first driver to regulate the scanning speed of the scanner based on the reference signal generated by the generator and a second controller for controlling the second driver to regulate the moving speed of the image carrier and the supporting member based on the reference signal generated by the generator.

Abstract: In an apparatus for adjusting the intensity of a light beam, the light beam from a semiconductor laser is deflected to scan a photosensitive drum and is detected to generate a positional signal by a photodetector outside of the drum. The intensity of the light beam is also detected by a monitor detector and compared with a predetermined value. The comparison result is latched in a latch circuit in accordance with the positional signal and the semiconductor laser is controlled depending on the latched comparison result.

Abstract: A toner sensor measures the amount of toner attached onto a photosensitive drum upon development by a developing unit. A controller compares the measured toner attaching amount with a predetermined reference value, and executes processing for changing at least one of image forming conditions, for example, the charging amount by a charger, the developing bias voltage of the developing unit, the exposure amount of an optical system, and the toner density of the developing unit, on the basis of the comparison result. Besides the above, a shielding member is provided and is opened only during a measurement mode of the toner sensor in order to prevent the toner sensor from being contaminated by toner during a non-measurement mode.

Abstract: In an apparatus for adjusting the intensity of a light beam, a first driving current which is stepwisely increased in a first cycle is supplied to a semiconductor laser. The light beam is deflected to scan a photosensitive drum and is detected to generate a positional signal by a photodetector outside of the drum. The intensity of the light beam is also detected by a monitor detector and compared with a predetermined target intensity. The comparison result is latched in a latch circuit to determine a first drive signal. When the intensity of the light beam reaches the target intensity after the generation of the positional signal, a second drive signal is generated in a second cycle longer than the first cycle instead of the first drive signal and is supplied to the semiconductor laser. The second drive signal is determined in accordance with the comparison result latched in the latch circuit.

Abstract: An image forming apparatus having a humidity detector which is detachably attached to the main apparatus body that accommodates an image forming member. The humidity detector detects a humidity in the vicinity of the image forming member, converts the detected humidity into a relative humidity and outputs it. Based on the value of the output relative humidity, image forming conditions, such as the amount of exposure, are set. The humidity detecting unit contains a time detecting unit for detecting the time for replacement.

Abstract: In an optical unit, a light beam is emitted from a light source toward a given object. Part of the light beam is reflected by a reflecting mirror and is returned to a monitor diode which is incorporated in the light source. The reflecting mirror is arranged in an optical path along which the light beam is directed from the light source to the object, but is located outside of an image region containing an optical axis and expanding in the main scanning direction. By use of the light beam returned to the monitor diode, the deflection start position from which the light beam emitted from the light source is deflected is detected. In other words, the deflection start timing is detected. A variation in the monitor current produced by the monitor diode is utilized for controlling the light source, to thereby match the horizontal synchronization.

Abstract: In an apparatus for adjusting the intensity of a light beam, the light beam from a semiconductor laser is deflected to scan a photosensitive drum and is detected to generated a positional signal by photodetector outside of the drum. The intensity of the light beam is also detected by a monitor detector and compared with a predetermined value. The comparison result is latched in a first latch circuit in accordance with the positional signal and a driving data is determined in accordance with the latched comparison data. The driving data is also latched in a second latch circuit and the semiconductor laser is controlled depending on the latched driving data.

Abstract: In an apparatus for adjusting the intensity of a light beam, a driving current which is gradually increased is supplied to a semiconductor laser in a warming-up mode. The intensity of the light beam is detected by a monitor detector and compared with a predetermined value. The comparison result is latched in a first latch circuit and a preset drive data is determined in accordance with the latched comparison data and stored in a memory. The semiconductor laser is driven in a printing mode, in accordance with the preset drive data stored in the memory mode so that a printing condition can be established in a relatively short time. In the printing mode, the intensity of the light beam is adjusted in accordance with the comparison result obtained in the printing mode.

Abstract: An image forming apparatus has a printing side and a host side. Status signals are transmitted from the printing side to the host side and, according to the status signals, commands are transmitted from the host side to the printing side to execute printing operations. One exclusive line is added to status lines and used to inform the host side of changes in urgent statuses of the printing side.According to another aspect, an image forming apparatus has a printing side and a host side that transmits various data signals to the printing side. The printing side outputs a video clock signal whose frequencey changes in proportion to a recording density of the printing side. According to the video clock signal, the host side transmits a video data signal to the printing side.

Abstract: A laser printer includes a plurality of lenses and mirrors for scanning a laser beam to form an optical image on a photoconductive drum, a developing unit for storing a developer for developing an electrostatic latent image formed on the drum by the plurality of lenses and mirrors, and an image transfer section for transferring the image developed by the developing unit onto paper. The developer is a two-component developer consisting of a toner and a carrier. The toner densities of toner adhered to a toner hopper for replenishing the toner stored in the developing unit and of that adhered to a toner density detecting probe coaxially attached to the drum are measured by utilizing a light-emitting diode and a photodiode. In a CPU, a toner density measured by the light-emitting diode and the photodiode is compared with a first reference value, and then the measured density value is compared with a second reference value which is smaller than the first reference value.

Abstract: An image forming apparatus according to this invention includes a main charger for uniformly charging a surface of a photoconductive drum, an electrostatic latent image forming unit for forming an electrostatic latent image on the drum charged by the main charger, a developing unit for making visible the electrostatic latent image formed on the drum by the electrostatic latent image forming unit, and a transfer charger for transferring the image made visible by the developing unit onto a paper sheet. Power supply circuits supply operation voltages to the main charger and the transfer charger, and currents flowing from the power supply circuits to the main charger and the transfer charger are detected by current detectors. The current values detected by the current detectors are compared with corresponding predetermined values by comparators.