Abstract: An image forming apparatus includes an image forming unit configured to form an image on a sheet. The image forming unit includes a photosensitive member; a charger configured to charge the photosensitive member based on a charging potential; an exposure unit configured to expose the photosensitive member charged by the charger to light to form an electrostatic latent image on the photosensitive member, an exposure intensity of the exposure unit being controlled based on an exposure condition; a developing sleeve configured to develop the electrostatic latent image; and one or more processors configured to perform operations including controlling the image forming unit to form a line test image and a width test image.

Abstract: An image forming apparatus includes: a toner image former that forms a toner image on an outer peripheral surface of a photosensitive rotating body and that transfers the toner image having been formed onto a transfer receiving object; a detector that detects a grayscale abnormality of the toner image on the photosensitive rotating body or the transfer receiving object; a cleaner that cleans the outer peripheral surface of the photosensitive rotating body; and a hardware processor that causes the cleaner to clean when the detector detects the grayscale abnormality at a same position in a main scanning direction per circumferential length of the photosensitive rotating body in a sub-scanning direction.

Abstract: A printing system includes a printing unit, an operation unit, and a control unit. The printing unit prints an image on a sheet, conveys the sheet to a reading unit, and performs adjustment for printing an image on the sheet based on an image read by the reading unit. The control unit performs an operation of controlling to execute a manual adjustment function for adjusting predetermined adjustment items based on adjustment values received via the operation unit after authentication of an operator. The control unit performs another operation of controlling to execute an automatic adjustment function for adjusting the predetermined adjustment items based on the image read by the reading unit without the authentication of the operator.

Abstract: An image forming apparatus and method for color registration are provided. The image forming apparatus according to an example includes a communication device to receive print data, a print engine including a plurality of photosensitive drums, and a processor to control the print engine to print the received print data on a plurality of printing papers, and to form a predetermined pattern for color registration in an inter-paper distance section between two of the plurality of printing papers on a paper feeding path.

Abstract: An apparatus which forms an electrostatic latent image by exposing a charged photosensitive member with light. The apparatus identifies a pixel which has density value less than a threshold value and is sandwiched in a predetermined direction between two pixels having density values greater than or equal to the threshold value in image data, generates screen image data by screen processing on the image data, and outputs, for each of one pixel of the two pixels sandwiching the identified pixel and a pixel adjacent to the one pixel in the predetermined direction, an adjusted density value the screen image data.

Abstract: One embodiment is directed to a compact system for scanning electromagnetic imaging radiation, comprising a first waveguide and a second waveguide, each of which is operatively coupled to at least one electromagnetic radiation source and configured such that output from the first and second waveguides is luminance modulated and scanned along one or more axes to form at least a portion of an image.

Abstract: An image forming apparatus includes: an image bearing member to rotate; a charging member to charge a surface of the image bearing member; a charging voltage applying portion to apply an alternating-current voltage having a predetermined charging frequency to the charging member; and an exposing portion to perform image exposure and background exposure. A plurality of modes are settable for the image forming apparatus, and the plurality of image forming modes include image forming modes different in a background potential difference which is a potential difference between a surface potential of the image bearing member after the surface of the image bearing member is charged and before the charged surface is exposed by the exposing portion and a surface potential of a portion of the surface of the image bearing member which has been subjected to the background exposure.

Abstract: An image forming apparatus include a latent image bearer, charger, latent image forming unit, developing unit, receiver unit, transfer unit, information acquisition unit, and correction unit. The charger charges the latent image bearer with a predetermined charging potential. The latent image forming unit forms an electrostatic latent image on the latent image bearer. The developing unit develops the electrostatic latent image to form a toner image. The receiver unit receives the toner image from the talent image bearer. The transfer unit applies a predetermined transfer bias to transfer the toner image to the receiver unit. The information acquisition unit acquires residual image generation determination information.

Abstract: In an optical scanning device, light emitting start timings of light emitting parts with respect to a reference light emitting part are stored in a storage part. In a correction mode, a light emitting timing correction control part performs first control for allowing positions of beam spots of the light beams emitted from the light emitting parts to be equal to each other, second control for allowing a light emitting part LD4 to emit a light beam at a plurality of different start timings and patch images to be formed on a intermediate transfer belt 281, and third control for correcting light emitting start timings of light emitting parts LD2 to LD4 on the basis of the start timing of the light emitting part LD4 at which the patch images has the highest concentration.

Abstract: An image forming apparatus includes a feed tray having a placement surface on which a sheet is placed. The feed tray includes a fixed table, an extension table, and a sensor. The extension table is capable of being pulled out along and being accommodated in the fixed table. The sensor is disposed on the fixed table and detects whether or not the sheet is placed on the extension table in a situation in which the extension table is pulled out.

Abstract: An optical scanning device according to an embodiment includes a light source, a MEMS mirror, a MEMS-mirror driving unit, a control unit, and a sensor. The light source radiates a plurality of laser beams that scan a photoconductive drum. The MEMS mirror includes a reflection surface that reflects the plurality of laser beams radiated from the light source. The MEMS-mirror driving unit reciprocatingly moves the MEMS mirror. The sensor supplies a horizontal synchronization signal to the control unit by detecting the laser beam reflected on the reflection surface when the MEMS mirror reaches a predetermined position. After detecting the horizontal synchronization signal supplied from the sensor, the control unit performs the auto power control of the light amount of at least one laser beam among the plurality of laser beams.

Abstract: An image forming apparatus includes a rotating polygon mirror configured to rotate and reflect the first laser beam and the second laser beam, a first generation unit configured to generate a first signal based on timings at which the respective first laser beams, a second generation unit configured to generate a second signal for determining a timing to form an electrostatic latent image on the second image bearing member with the second laser beam based on the first signal and a correction value, and a calculation unit configured to calculate the correction value based on the output of the detection unit, in which the calculation unit calculates the correction value based on the signal output from the detection unit in a period of time that has passed until the rotating polygon mirror reaches steady rotation since it has started to be driven to rotate.

Abstract: A decoloring apparatus comprises a decoloring unit configured to carry out a decoloring processing which decolors the color of an image formed on a paper with a decolorable color material; a scanner configured to scan the papers to which the decoloring processing is carried out; a memory configured to store data of a predetermined image indicating a predetermined form formed on the paper; a conveyance section configured to convey the paper scanned by the scanner to a plurality of paper discharging positions; and a control section configured to determine whether or not the scan image generated by the scanner is consistent with the predetermined image, and to drive the conveyance section to respectively convey the papers on each of which the scan image is consistent with the predetermined image and the papers on each of which the scan image is not consistent with the predetermined image to different positions.

Abstract: A converter includes a feedback part, a pulse width modulation (PWM) controller and a PWM generator. The feedback part is configured to output a feedback signal based on a driving voltage. The PWM controller is configured to output a PWM control signal based on the feedback signal and a first compensation signal. The PWM generator is configured to control the driving voltage based on the PWM control signal. The first compensation signal is determined according to an occurrence of a predetermined pattern of an input image data.

Abstract: An image capturing unit includes a sensor unit that image-captures a predetermined area including a subject; and a reference chart unit that is arranged in the predetermined area and captured with the subject by the sensor unit.

Abstract: An object is to accurately determine a factor that drops the quantity of laser light. An image forming apparatus is provided, which has: a laser diode that includes a front side emission point to which drive current is supplied and from which rear light is emitted; a photosensitive drum to which the rear light is emitted; a detection portion that detects a value on a surface potential of the photosensitive drum; and a determination portion that determines an abnormality of the laser diode, and the detection portion detects, a plurality of times, a value on the surface potential of a portion of the photosensitive drum to which the rear light is emitted, and the determination portion determines whether the laser diode is abnormal based on a change amount of the value on the surface potential detected by the detection portion.

Abstract: The invention is concerning the writing controlling apparatus that includes an acquiring unit configured to acquire a plurality of light amounts of a light source driven while changing an input current in non-effective scanning periods during which an image carrier is not irradiated with light from the light source, as a plurality of output results; a detecting unit configured to detect characteristics of the light source using the output results thus acquired; and a correcting unit configured to correct a current to be applied to the light source based on the characteristics thus detected.

Abstract: There is provided an image forming apparatus including: an image forming section including a photosensitive body, and an LED array configured to expose the photosensitive body; and a controller configured to: make a judgment of a dew-condensation state of the LED array, and change a power supply state of the LED array based on the dew-condensation state.

Abstract: An image forming apparatus may include a laser scanning unit which irradiates light to a photosensitive body to form an image; a feedback information provision unit which provides feedback information used to control optical power of the laser scanning unit; and a main controller which controls the optical power of the laser scanning unit by adjusting a voltage that is applied to the laser scanning unit by using the feedback information. The main controller performs primary optical power control by comparing a density of a sample patch formed on the photosensitive body by the laser scanning unit, the density received from the feedback information provision unit, with a target density that is previously stored and performs secondary optical power control by comparing a feedback voltage received from the feedback information provision unit with the target voltage obtained during the primary optical power control.

Abstract: An image forming apparatus improved in the accuracy of detecting a time period over which a laser beam is scanned. A laser beam emitted from a laser light source is deflected by a polygon mirror such that the laser beam scans a photosensitive drum. The deflected laser beam is guided onto the photosensitive drum via an imaging lens. A mode hop detection unit detects a mode hop of the laser beam. An image pulse generation section detects a main scanning magnification of an electrostatic latent image formed on the photosensitive drum. When a mode hop is detected, the main scanning magnification in a next scanning cycle is corrected using a correction value stored in a storage unit and used most lately, whereas when no wavelength variation has not detected, the main scanning magnification in the next scanning cycle is corrected using the latest correction value.

Abstract: An image forming apparatus includes a photoconductor, a charger to charge the photoconductor, a multi-beam scanning unit, a development unit, and a transfer unit. The multi-beam scanning unit includes a vertical cavity surface emitting laser as a light source having light emitting elements arrayed in main and sub-scanning directions by setting an interval between light emitting elements adjacently disposed at a center portion of the scanning unit in the sub-scanning direction narrower than an interval between other light emitting elements adjacently disposed at other portions of the scanning unit in the sub-scanning direction, a deflecting element to deflect light emitted from the light emitting elements to scan the surface of photoconductor by an interlace scan, and a light intensity adjustment unit to adjust light intensity of the light emitting elements adjacently disposed at the center portion relative to a light intensity of other light emitting elements adjacently disposed at other portions.

Abstract: An image forming apparatus includes a temperature sensor detecting an operating ambient temperature of the polygon motor, and a controller controlling the polygon motor and the paper feed mechanism. If the temperature detected by the temperature sensor is equal to or greater than a preset temperature, the controller controls, before operation for giving a command to start image formation is performed, the polygon motor to rotate; increases, in response to the operation, a rotational speed of the polygon motor up to a rated speed; and controls the paper feed mechanism to start conveying a sheet of paper at a time when a period of time variable depending on the detected temperature has elapsed, the period of time being preset to be shorter as the detected temperature increases, in expectation of a time required for the rotational speed of the polygon motor to reach the rated speed.

Abstract: An image forming apparatus comprises a light source, a photosensitive member and a control unit. The light source turns on in response to a driving current supplied based on image data. An electrostatic latent image is formed on the photosensitive member by exposing the photosensitive member to a light beam output from the light source turned on. The control unit controls the value of the driving current supplied to the light source in accordance with a driving state of the light source so that the value of the driving current supplied to the light source differs and changes with the passage of time in accordance with the driving state of the light source prior to the driving current being supplied to the light source.

Abstract: An image forming apparatus according to one aspect controls a light source such that first and second laser beams emitted from first and second light emitting elements respectively are incident on a BD sensor successively, and measures the time interval between two BD signals, output from the BD sensor, that correspond to the first and second laser beams and. When performing the measurement, the image forming apparatus controls the light powers of the first and second light beams so as to be light powers determined in advance using APC. According to this, measurement errors when measuring the interval between the light beams emitted from the two light emitting elements are suppressed, and correction accuracy for the image writing start positions for the multiple light emitting elements is improved.

Abstract: A light beam scanning device which is capable of performing high-accuracy light amount control without complicated control even when the device includes a laser diode having non-linear I-L characteristics. Gain circuits set the amount of light to be emitted from the laser diode. A PD circuit board detects the amount of the emitted light. A laser controller controls the amount of the emitted light by adjusting drive current applied to the laser diode based on a detection output from the PD circuit board. A CPU corrects data for correcting the drive current. The CPU decides a light amount correction range for correcting the light amount based on the correction data, calculates the slope of the I-L characteristics in the light amount correction range based on light amounts at two points within the light amount correction range and drive currents associated with the respective light amounts, and corrects the correction data using the calculated slope.

Abstract: An electrophotographic image forming apparatus that are capable of reducing the variation of the rise time of the laser light source due to the temperature change of the laser light source with a simple configuration. A laser light source emits a laser beam according to a driving signal in order to expose an image bearing member. A voltage detection unit detects terminal voltage of the laser light source. A drive unit has a voltage source that can control output voltage and supplies current corresponding to the output voltage of the voltage source to the laser light source when making the laser light source emit the laser beam according to the driving signal. A control unit controls the voltage source so that the output voltage of the voltage source generates current overshot to a target current based on the detection result of the voltage detection unit.

Abstract: A scanning optical apparatus includes a light beam detection unit, a reference signal generation unit, and a returned light detection unit. The light beam detection unit decides whether the light beam reflected by the reflecting surface of a polygon mirror has entered the BD sensor, through comparison between an output value of the BD sensor and a predetermined first threshold. The reference signal generation unit generates a scan start reference signal in response to the decision that the light beam has entered the BD sensor. The returned light detection unit decides whether the light beam reflected by the reflecting surface has entered the internal light sensor, through comparison between an output value of the internal light sensor and a second threshold corresponding to light beam intensity higher than the intensity of the light beam reflected by the reflecting surface and corresponding to the first threshold.

Abstract: An optical writing device for forming an electrostatic latent image on a photoreceptor by exposing the photoreceptor to light modulated in accordance with image data. The optical writing device has: a substrate; a light-emitting-element array including a plurality of light-emitting elements supported by the substrate to be arranged in a main-scanning direction; and a light-receiving-element array substantially in parallel to the light-emitting-element array, the light-receiving-element array including a plurality of light-receiving elements supported by the substrate to be arranged in the main-scanning direction. For light-quantity measurement of one of the light-emitting elements, at least an output value output from one of the light-receiving elements of which center is located in a different position, with respect to the main-scanning direction, from a center of the one of the light-emitting elements is used.

Abstract: A light-emitting chip includes: a substrate; plural light-emitting elements arrayed in line on the substrate, each of the light-emitting elements including a light-emitting region having a length in an array direction of the array different from a length in a direction orthogonal to the array direction; and a light-up current supplying interconnection including plural connecting portions, each of the connecting portions being provided on the light-emitting region of a corresponding one of the light-emitting elements in a shorter direction of the light-emitting region either the array direction or the direction orthogonal to the array direction, each of the connecting portions being connected to an electrode provided on the light-emitting region, the light-up current supplying interconnection supplying a current for lighting up to the plural light-emitting elements through the plural connecting portions.

Abstract: An embodiment of the image processing apparatus for controlling the lighting of a line head that is driven with binary data and performs exposure with subline lighting to thereby form images, includes: a subline generating unit that generates a plurality of sublines from a same image data; an inclination correcting unit that exposes the generated sublines so as to generate correction image data used to correct an inclination of an exposure position; a gradation control unit that controls the lighting of sublines based on the correction image data generated by the inclination correcting unit to express gradation; and a light intensity correction unit that corrects and controls the light intensity based on the correction image data generated by the inclination correcting unit, wherein an output of the gradation control unit and an output of the light intensity correction unit are input into the line head in parallel.

Abstract: An image forming apparatus including: a light scanning portion that lights a plurality of beams, and scans a surface to be scanned of an image carrier to form an electrostatic latent image; a detection portion that detects at least one lighted beam; an abnormality detection portion that transmits data to the light scanning portion via a transmission-line, causes the light scanning portion to light a beam, and detects abnormality of the transmission-line based on the detected beam; and a setting portion that sets a number of beams to be lighted in the case of the formation of the electrostatic latent image so that an amount of light of the detected beam in the case of abnormality detection of the transmission-line is equal to or more than a minimum amount of light of the detected beam in the case of the formation of the electrostatic latent image.

Abstract: There is provided an exposure device including: plural exposure heads having plural light-emitting elements arranged in a first direction, the plurality of exposure heads also being arranged in the first direction; plural temperature detecting units for detecting temperature arranged at both ends in the first direction of each of the plural exposure heads; and a correction unit for correcting quantities of light emitted from the exposure heads based on temperature data detected by the temperature detecting units.

Abstract: An image forming apparatus includes a VCSEL that includes a plurality of light sources emitting light beams, an image processing unit, and write control units that send a sub-scanning start reference signal indicating a reference for starting image formation in a sub-scanning direction and start a control of driving the light sources for each of a plurality of colors when receiving image data from the image processing unit. The write control units perform a control of outputting the sub-scanning start reference signal at timing of any of a plurality of areas divided by the number of lines scanned simultaneously in a scan cycle in a main-scanning direction.

Abstract: A printing control apparatus to control a printing operation includes a web server connection unit to connect with a web server of a pre-set address and receive environmental information of an area where the printing apparatus is located, and a controller to transmit a printing control signal corresponding to the received environmental information and printing data to a printing apparatus. Accordingly, a transfer voltage is adjusted according to the environmental information of the area where the printing apparatus is located, so that the effect of the environment on the printing quality can be minimized and thus the printing quality can be improved.

Abstract: An image forming apparatus is provided. The image forming apparatus includes a semiconductor laser that emits a laser beam, a light power of the laser beam being controllable by a current applied to the semiconductor laser; a scanner unit that exposes a photosensitive element by scanning the photosensitive element using the laser beam; a light power detection unit that detects a light power of the laser beam; a current control unit that controls the current applied to the laser based on the light power of the laser beam; a home position detection unit that detects whether the laser beam is positioned at a scan home position; and a continuous illumination unit that commences continuous illumination of the laser at a time which is prior to a forecast time at which the home position detection unit is forecast to detect the laser beam.

Abstract: A method and system for compensating for temperature changes is disclosed that includes a mounting bar, a plurality of imaging chips adaptively mounted on the mounting bar, each imaging chip including a plurality of imaging elements, and a temperature determiner to determine a temperature of the mounting bar. A control module enables and disables at least one imaging element based on the determined temperature of the mounting bar.

Abstract: In an image forming apparatus, a separating unit separates each laser beam into a first laser beam used for measuring light intensity and a second laser beam used for scanning a photosensitive element, a photoelectric converting unit measures a light intensity of each of the first laser beams and outputs a voltage indicative of the light intensity. A control unit controls a light intensity of each of the laser beams based on a common drive current and a corresponding one of a current correction value, which is set by each of the laser beams to correct a light intensity of a corresponding one of the laser beams based on a corresponding one of the voltages output by the photoelectric converting unit.

Abstract: An optical scanning device includes n-odd (n?2) light sources disposed at different positions at least in a sub-scanning direction, a pixel forming part in which one pixel is depicted by light beams emitted from m-odd (n?m?2) light sources of the n-odd light sources and a distance of adjacent light sources for emitting the light beams in the sub-scanning direction is less than 5 ?m, and a light source driving control part configured to control an emitting state of the light sources for depicting the one pixel and conduct an emission driving control for moving a gravity center of the one pixel in the sub-scanning direction.

Abstract: Emission windows are prevented from being contaminated and are cleaned easily. The emission windows for emitting light beams are disposed on a housing of a laser exposure device having optical elements arranged inside for exposing a photoreceptor, and the upper surface of the housing is provided with a slidable shutter with openings. An image forming apparatus includes guide rails independent of the laser exposure device to movably guide predetermined cleaning brushes in the longitudinal direction of the emission windows. When the cleaning brushes are mounted on the guide rails and moved toward the inner side of the apparatus, the cleaning brushes touch a slant portion of a rib and the shutter is moved to the right to align the openings with the emission windows. While the cleaning brushes touch a longitudinally extending portion, the emission windows are exposed to enable the cleaning of the exposed window using the cleaning tool.

Abstract: According to an aspect of the invention, a control method for an exposure shutter of an image forming apparatus includes, opening the shutter only to a slit glass for monochrome when monochrome printing is performed, and opening the shutter to slit glasses for monochrome and color when color printing is performed.

Abstract: An optical scanning apparatus includes a plurality of light sources capable of emitting light. A detection unit detects a light quantity of the light emitted from the plurality of light sources. A control unit controls drive current of a light source designated as a control object based on a detection result obtained by the detection unit. The control unit controls the drive current based on an activation state of the light source designated as the control object and an activation state of a light source other than the control object.

Abstract: A drive signal for driving a semiconductor laser is generated on the basis of an image signal inputted in synchronism with a pixel clock. A bias signal to the semiconductor laser is generated at a timing earlier than the drive signal by a predetermined time. The bias signal is disabled in synchronism with the leading edge of the drive signal.

Abstract: A light emitting device includes: a plurality of light emitting elements that emit light to have luminosity depending on the magnitude of a driving signal; a plurality of holding units that are respectively disposed in the plurality of light emitting elements, and respectively hold the driving signal to maintain a magnitude regulated such that the luminosity of the plurality of light emitting elements becomes uniform; and a plurality of supply units that are respectively disposed in the plurality of light emitting elements, and supply the driving signal, which is held by the holding units to have a certain magnitude for a period of time according to a gradation of light to be emitted, to a corresponding light emitting element.

Abstract: In an optical control apparatus, a semiconductor laser emits a laser beam having a power corresponding to an energizing current. A light power detecting device detects a light power of the laser beam. A monitor voltage generating device generates a monitor voltage set based on the light power. A reference voltage generating device generates a reference voltage set based on a target light power of the laser beam. A current control device controls the energizing current such that the monitor voltage approaches the reference voltage based on a deviation of the monitor voltage from the reference voltage. A pseudo voltage input device inputs a predetermined pseudo voltage to the current control device instead of the monitor voltage under a predetermined condition such that a variation range of the deviation lies within a predetermined range.

Abstract: An image forming apparatus includes an electrophotographic photoconductive body for forming an electrostatic latent image thereon; an exposure device for exposing the electrophotographic photoconductive body to form an electrostatic latent image; a storage device for storing information related to potential characteristics at a plurality of areas divided on a surface of the electrophotographic photoconductive body in advance; an information obtaining device for obtaining the information related to potential characteristics, wherein light quantities exposed by the exposure device are determined according to the information related to potential characteristics stored by the storage device and the information related to potential characteristics obtained by the information obtaining device.

Abstract: A light emitting device includes: a plurality of light emitting elements that emit light to have luminosity depending on the magnitude of a driving signal; a plurality of holding units that are respectively disposed in the plurality of light emitting elements, and respectively hold the driving signal to maintain a magnitude regulated such that the luminosity of the plurality of light emitting elements becomes uniform; and a plurality of supply units that are respectively disposed in the plurality of light emitting elements, and supply the driving signal, which is held by the holding units to have a certain magnitude for a period of time according to a gradation of light to be emitted, to a corresponding light emitting element.

Abstract: An imaging apparatus for imaging on a recording medium is improved to permit the imaging power to be balanced between various groups of individual radiation sources with a low outlay and high accuracy. Two or more imaging heads that respectively include a multiplicity of individual radiation sources that can be electrically driven individually with light beams directed onto a radiation-sensitive layer of the recording medium. A drive moves the recording medium and the radiation sources relative to one another. A control device controls the power of the light beams of the radiation sources separately for each imaging head. A least one light guide is provided that guides a portion of the light beams emanating from the radiation sources to the receiver surface of a photoelectric sensor, which sensor is connected to the control device.

Abstract: A control system for a cooling fan of a laser printer enables selection of fan speed based on the actual degree of usage of the printer. The system provides first and second sets of fan speeds where each set contains information corresponding to a plurality of fan speeds. Information regarding the current operational condition of the fuser of the printer is periodically obtained, preferably during a preset interval. The fan is then operated at one of the fan speeds of the first or second set of fan speeds, with the selection of the first or second set and the selection of one of the fan speeds based on the current operational condition of the fuser. In this manner, the speed of the fan is substantially continuously controlled based on the operational condition of the printer.

Abstract: A plurality of first base images are formed from a base color output in accordance with a predetermined adjustment value. A plurality of first correction images are formed on the first base images from a correction color to be a subject for correction output in accordance with a predetermined adjustment value. The first correction images are displaced within a predetermined range. The first adjustment value is determined from changed adjustment values. The second base images are formed from the base color output in accordance with the predetermined adjustment value, and the second correction images are formed from the correction color output in accordance with a plurality of adjustment values determined based on the first adjustment value. The second adjustment value having an extreme is determined from a plurality of adjustment value candidates. Finally, the adjustment value for the correction color is corrected to the determined second adjustment value.

Abstract: To provide an image forming apparatus capable of preventing a fluctuation in image density immediately after the light quantities are corrected, and a method for controlling the same, when light quantity measurement is carried out at time t1, the controller CPU calculates the light quantity correction value ND. Herein, it is assumed that the light quantity correction value ND calculated previously, which is the light quantity correction value before light quantity measurement at time t1, is NDold, and the light quantity correction value ND calculated based on the light quantity measurement value at time t1 is NDnew. When the light quantity correction NDnew is calculated, the controller CPU varies the light quantity correction value ND from the light quantity correction value NDold a plurality of times by a predetermined variation value ? in the direction approaching the light quantity correction value NDnew for each of the printing sheets.