JP2009145398A - Optical scanner, light intensity controller, image forming apparatus, and light intensity control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light intensity controller that controls light intensity with high accuracy without reducing light quantity and that easily and that quickly compensates light quantity even in the occurrence of change in light quantity by abnormality of a light-emitting element in a surface-emitting semiconductor laser. <P>SOLUTION: In an electronic photographic process using a surface-emitting semiconductor laser, exposure is controlled spacially and timewisely without spectroscoping light beams by an optical system. In other words, the optical system is configured so that the light flux near both ends of the return mirror is not changed in the optical path in the direction of a photoreceptor when a light flux is emitted from the surface-emitting semiconductor laser to a polygon unit to reach a return mirror through the optical system. Then, the light flux with no optical path changed is defined as the light flux outside an image security region on the photoreceptor, with two photodetectors for light quantity control arranged on the light flux. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic system, an optical scanning device and a light quantity control device provided in the image forming apparatus.

  An optical scanning device included in an electrophotographic image forming apparatus drives a semiconductor laser in accordance with input image data, and forms an electrostatic latent image in accordance with the image data on a photoconductor. In order to achieve higher speed and higher resolution, it is necessary to rotate the polygon mirror that scans the photosensitive member with the laser beam emitted from the semiconductor laser at higher speed. Alternatively, it is necessary to increase the number of laser beams that simultaneously scan the photosensitive member by further increasing the emission points of the semiconductor laser that emits the laser beam.

  However, in order to rotate the polygon mirror at a higher speed, there are limitations when considering heat generation, noise, and the strength of the mirror itself.

  Therefore, in recent years, a configuration using a surface emitting laser array (VCSEL) as a light source capable of emitting more laser beams has been commercialized from the edge-emitting laser diode that has been conventionally used. VCSEL is an abbreviation for Vertical Cavity-Surface Emitting Laser.

  By the way, since the light output characteristics of the semiconductor laser are sensitive to changes in the ambient temperature, the light output greatly fluctuates due to changes in the ambient temperature or self-heating even when driven with a constant current. In order to cope with the temperature dependence of the light output, in the case of an edge-emitting laser diode, a photodiode called a monitor diode is generally incorporated in a semiconductor laser package. As a result, the optical output of the back light of the semiconductor laser is monitored to control the drive current so that the optical output can be kept constant. A drive circuit that performs laser light amount control of a semiconductor laser having such a feedback mechanism is called an APC (Auto Power Control) circuit (automatic light output control circuit).

  On the other hand, since the VCSEL emits light only in one direction due to its structure, the APC cannot be performed by monitoring the light output of the back light unlike the edge-emitting laser diode.

In an exposure apparatus that uses a surface-emitting semiconductor laser (VCSEL) as a light source, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 are technologies relating to the installation configuration of a photodetector for synchronization and light amount control. It is described in. In these prior art light quantity controls, a half mirror disposed between the light path connecting the light source and the polygon mirror is used to separate a part of the laser beam from the light source toward the photosensitive member. And the structure which introduce | transduces the isolate | separated laser beam to a photodiode (henceforth "PD") and detects a light quantity is proposed.
JP-A-5-035058 JP-A-5-005845 JP 2000-289251 A JP 2006-91553 A

  However, the configuration of the image forming apparatus as described above has the following problems when laser light amount control is performed by measuring the light amount of the laser beam directed from the light source to the photosensitive member instead of the back light.

  That is, in the configuration in which the laser beam emitted from the VCSEL is separated by the half mirror and the light amount is detected, the light amount for scanning the photosensitive member is halved by the separation. For this reason, the VCSEL has a weak point that the laser resonator length is short and the maximum output is structurally small, so there is a possibility that a sufficient amount of light for scanning the photoconductor cannot be obtained.

  The surface emitting semiconductor laser is composed of a plurality of light emitting elements, and the laser light is exposed as a single unit. For this reason, there has been a problem that it is difficult to control light amount correction when there is a problem of uneven light emission due to non-light emission of some light emitting elements.

  In view of the above-described conventional problems, the present invention provides an optical scanning device, a light amount control device, an image forming apparatus, and a light amount control method for the following purposes. That is, (1) high-precision light amount control without reducing the light amount is performed. (2) The light amount is corrected easily and quickly even when the light amount varies due to the abnormality of the light emitting element in the surface emitting semiconductor laser.

  In order to achieve the above object, the present invention provides an optical scanning apparatus including a scanning unit that scans a light beam from a light source and an optical system that forms an image of the light beam on a scanning surface. The optical system scans the light beam to the outside of the image formation guarantee area on the surface, and the optical system guides the light beam scanned to the outside of the image formation guarantee area to a light detection means used for light amount control of the light flux from the light source. It is characterized by having a light configuration.

  Further, the present invention is a light amount control device for controlling the light amount of a light beam scanned by the optical scanning device based on a detection signal of the light detection means, wherein the light source of the light beam is a light emission comprising a plurality of light emitting elements. A light-emission control unit configured to emit light from a plurality of different light-emitting patterns composed of at least one area when the light-emitting element group is divided into a plurality of areas; The light quantity fluctuation detecting means for measuring the light quantity of the light emission pattern based on the detection signal of the light detecting means after the light beam is emitted by the light and detecting the light quantity fluctuation, and the correcting means for correcting the detected light quantity fluctuation. It is characterized by comprising.

  According to another aspect of the present invention, there is provided an image carrier including the optical scanning device and the light amount control device according to any one of claims 4 to 7, wherein a light beam scanned by the optical scanning device is a surface to be scanned. A developing device that forms a toner image by applying toner to the electrostatic latent image formed on the surface of the image carrier, and the image carrier. And a transfer device that transfers the toner image on the surface of the body onto a transfer medium.

  Further, the present invention is a light amount control method of a light amount control device for controlling the light amount of a light beam scanned by the optical scanning device based on a detection signal of the light detection means, wherein the light emission control means includes a plurality of light emitting elements. A step of causing the light source to emit light with a plurality of different light emission patterns comprising at least one area when the light emitting element group of the light source composed of the light emitting element group is divided into a plurality of areas; The step of measuring the light quantity of the light emission pattern based on the detection signal of the light detection means after the light beam is emitted by the light emission pattern from the light source and detecting the fluctuation of the light quantity, and the correction means are detected. And a step of correcting the variation in the amount of light.

  According to the present invention, it is possible to perform light amount control with high accuracy without reducing the light amount. Further, even when the light amount varies due to an abnormality of the light emitting element in the light source, the light amount can be corrected easily and quickly.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Configuration of optical scanning device>
FIG. 1 is a schematic diagram showing a configuration of a main part of an optical scanning device according to an embodiment of the present invention.

  The front stage portion of the optical scanning device has a configuration in which the light beam emitted from the laser light emitting unit 100 reaches the polygon unit 102 through the light guide unit 101. The laser light emitting unit 100 is composed of, for example, a surface emitting semiconductor laser (VCSEL) composed of an array of 16 light emitting elements, and is a light source for exposure in which laser light composed of these plural elements is a single unit.

  The light guide unit 101 is a light beam correcting lens group, which corresponds to an aperture, a collimator lens, a cylindrical lens, and the like. Has refractive power. The polygon unit 102 is a unit that rotates at a constant speed around a shaft by a drive motor (not shown) to polarize the light beam and scan the light beam in the main scanning direction.

  In the rear stage of the optical scanning device, the laser light emitted from the polygon unit 102 passes through an fθ lens 103 having fθ characteristics. Then, the passing light forms an image on the surface of a photosensitive drum (image carrier) 106 as a surface to be scanned via a surface tilt correction lens 104 and a folding mirror 105. The folding mirror 105 is a mirror for changing the optical path of laser light in the direction of the photosensitive drum 106.

  Here, the optical scanning device according to the present embodiment is characterized in that the light beam emitted from the polygon unit 102 can be scanned to the outside of the electrostatic latent image formation guarantee region on the photosensitive drum 106, and the light beam outside the region is folded back. This is a configuration in which the light is not emitted to the mirror 105.

  That is, when the laser beam reaches the folding mirror 105, the light beam outside the electrostatic latent image formation guarantee area is not irradiated on the folding mirror 105, but goes straight outside the end portion. Therefore, the light beam outside the electrostatic latent image formation guarantee region does not change the optical path to the photosensitive drum 106 side (scanned surface side), and the two photodetectors P1 disposed on the extension line of the light beam. , P2 is reached. The photodetectors P1 and P2 detect the amount of light flux and the pattern distribution.

<Configuration of photodetector>
2A and 2B are schematic cross-sectional views showing the peripheral mechanism of the photodetectors P1 and P2 according to the present embodiment, and FIG. 2A shows a first example thereof. (B) shows a second example.

  In the first example shown in FIG. 2A, the photodetectors P <b> 1 and P <b> 2 are respectively disposed on the outer sides of both ends of the folding mirror 105. That is, the photodetectors P1 and P2 are arranged at positions where the light beam outside the electrostatic latent image formation guarantee area is directly received.

  In the second example shown in FIG. 2A, the photodetectors P <b> 1 and P <b> 2 are respectively arranged behind the folding mirror 105. That is, the light beams outside the electrostatic latent image formation guarantee area are received by the photodetectors P1 and P2 via the mirrors 108a and 108b, respectively.

  3 (a) and 3 (b) are schematic views showing the configuration of the photodetectors P1 and P2, FIG. 3 (a) is a front view thereof, and FIG. 3 (b) is a sectional view in one cell. .

  Regarding the light detectors P1 and P2 that detect the light amount and pattern distribution of the light beam, the light amount can be detected by a commonly used light amount photodetector such as a highly sensitive photodiode or a photomultiplier tube. The pattern distribution is a pattern distribution corresponding to a light emission pattern (see FIG. 5) to be described later. For this pattern distribution, a photodetector configured with the same number of elements as that of the surface emitting semiconductor laser used for the light source is used. Use to detect.

  That is, as shown in FIG. 3A, the photodetectors P1 and P2 in the present embodiment use, for example, a light emitting element Pa made of a highly sensitive photodiode as the number of surface emitting semiconductor laser elements in the laser light emitting unit 100. And the same number. The one cell has a shape imitating a small parabola as shown in FIG. 3B, and is configured to detect the amount of light in each preset area (see FIG. 5 described later). In FIG. 3B, Pb is a parabolic reflector, and Pc is a cable of the light emitting element Pa.

<Configuration of light quantity control device>
Next, a light amount control device that controls the light amount of the light beam scanned by the optical scanning device having the above configuration will be described.

  FIG. 4 is a block diagram showing a configuration of the light amount control apparatus according to the present embodiment.

  The light quantity control device is mounted, for example, in an image forming apparatus described later (see FIG. 12). The image signal processing unit 140 includes a control unit 150, an image signal input unit 161, an image processing unit 162, In addition, a PWM generator 163 is provided.

  The control unit 150 (light emission control means, light quantity fluctuation detection means) is composed of a CPU 151, a ROM 152, a RAM 153, and the like, and controls the entire operation of the light quantity control device according to the present embodiment. The ROM 152 stores a control program and necessary data for executing a light amount control process (see FIG. 7) described later, and the CPU 151 executes the control program. The RAM 153 is used as a work area for the CPU 151. In addition, the control signal is input to the control unit 150 in order to execute the light amount control processing in the present embodiment.

  Image data is input to the image signal input unit 161, and the image data is sent to the image processing unit 162. The image processing unit 162 performs image processing for optimizing the toner image (electrostatic latent image) with respect to the performance of the image forming apparatus main body, and the processed image data is stored in a memory in the image processing unit 42. Retained.

  Then, the image data to be output instructed from the control unit 150 is sent to the PWM generator 163. The PWM generator 163 sets a pulse width for controlling the laser emission time in one pixel based on the transmitted image data, and transmits a pulse signal to the laser driver 170.

  The laser driver 170 includes a circuit for switching on / off each light emitting element in the surface emitting semiconductor laser 100 in accordance with an instruction from the control unit 150 (for example, an instruction for pattern emission in FIG. 5 described later). Further, there is a circuit for adjusting the current flowing through each light emitting element in accordance with an instruction from the control unit 150 (an instruction for a light amount control process (see FIG. 7) described later).

  The controller 150 controls the light emission state of the surface emitting semiconductor laser 100 by using, for example, four types of light emission patterns shown in FIGS. FIGS. 5A to 5D are schematic views showing a light emission pattern of laser light according to the present embodiment.

  The light emission pattern <1> shown in FIG. 5A is a light emission pattern during normal image formation, and emits all 16 elements. The light emission pattern <2> shown in FIG. 5B is a pattern that emits light from only the four central elements, and the light emission pattern <3> shown in FIG. 5C is a pattern that emits light from 10 elements at an angle of + 45 °. . Pattern <4> is a pattern that emits light from 10 elements at an angle of −45 °.

<Light intensity control according to the present embodiment>
The light quantity control processing by the light quantity control device having the above configuration is such that light beams outside the electrostatic latent image formation guarantee area are received by the photodetectors P1 and P2 while scanning the laser beam with the four types of light emission patterns. For example, as shown in FIG. 6, the light amount fluctuation is analyzed and corrected for each preset area.

  FIG. 6 is a schematic diagram showing area classification of light emitting element groups in the surface emitting semiconductor laser 100.

  In the present embodiment, the light emitting element group in the surface emitting semiconductor laser 100 is classified into three areas 1 to 3 and is used as a reference for area analysis when a light amount variation occurs. That is, the light amount control process according to the present embodiment corrects the light amount only in the areas 1 to 3 in which the light amount fluctuation has occurred.

  Here, the above-described light emission pattern <1> is composed of all areas 1 to 3, light emission pattern <2> is composed of area 3, light emission pattern <3> is composed of areas 2 and 3, and light emission pattern <4> is area. Consists of 1 and 2.

  Details of the light amount control processing according to the present embodiment will be described below with reference to FIGS.

  FIG. 7 is a flowchart showing a light amount control process according to the present embodiment. FIG. 8 is an explanatory diagram for explaining a method for acquiring initial acquisition data during the initial setting operation, and FIGS. 9A to 9D are characteristic diagrams illustrating the initial acquisition data during the initial setting operation. . FIG. 10 is an explanatory diagram illustrating an example of repeated light emission pattern control, and FIGS. 11A and 11B are explanatory diagrams illustrating correction control in the present embodiment.

  First, the control unit 150 performs an initial setting operation before control, for example, when the power is turned on (step S11 in FIG. 7). In this initial setting operation, as shown in FIG. 8, the surface emitting semiconductor laser 100 emits light by 10 [HEX] from F0 to 40 [HEX] for each light emission pattern <1> to <4>, and the light amount (basic). Luminescence amount) is measured by two photodetectors P1 and P2. Further, based on the measured light quantity, an error amount of the two photodetectors P1 and P2 is calculated for each of the light emission patterns <1> to <4>. Based on these results, as shown in FIG. 9, the RAM 153 uses the current-light quantity characteristics and error characteristics of the photodetectors P1 and P2 for each of the light emission patterns <1> to <4> as initial acquisition data during the initial setting operation. Store it in memory.

  Next, at the time of image formation, the control unit 150 continuously outputs the light amount by using the light detector P1 and the light detector P2 that are spatially separated by repetitive light emission pattern control to be described later. Then, the fluctuation (spatial light quantity fluctuation) is detected (steps S12 and S13). In the repeated light emission pattern control of this embodiment, for example, four types of control patterns are created as shown in FIG. That is, the control pattern No. Are set from I to IV, and the contents are as follows.

  No. In I, the light detector P1 detects the light emission pattern <1>, and the light detector P2 detects the light emission pattern <2>.

  No. In II, the light detector P1 detects the light emission pattern <3>, and the light detector P2 detects the light emission pattern <4>.

  No. In III, the light detector P1 detects the light emission pattern <2>, and the light detector P2 detects the light emission pattern <1>.

  No. In IV, the light detector P1 detects the light emission pattern <4>, and the light detector P2 detects the light emission pattern <3>.

  Note that the control pattern and the combination thereof are not limited to this example.

  In the repeated light emission pattern control, the control pattern No. Is set as follows (step S12). That is, the control pattern No. Is X (No. = X). If X ≠ IV, the next control pattern No. Becomes X + 1. If X = IV, return to X = 1.

Regarding the temporal light quantity fluctuation, the measured value of the light emission pattern used in each of the photodetectors P1 and P2 is compared with the initial value acquired during the initial setting operation for each scan, and one scan is being performed. Monitor for fluctuations in In the present embodiment, the comparison target and how to obtain the variation are as follows.
-Initial value <1>-measured value <1>
-Initial value <2>-measured value <2>
Initial value <3> −measured value <3>
Initial value <4> −measured value <4>
Initial value <1> -initial value <3> -measured value <4> -measured value <2>
Initial value <1> -initial value <4> -measured value <3> -measured value <2>
Initial value <1> -initial value <4> -initial value <3> -measured value <2>
Initial value <1> + initial value <2> −measured value <1> + measured value <2>
Initial value <1> + initial value <3> −measured value <1> + measured value <3>
Initial value <1> + initial value <4> −measured value <1> + measured value <4>
Initial value <2> + initial value <3> −measured value <2> + measured value <3>
Initial value <2> + initial value <4> −measured value <2> + measured value <4>
Initial value <3> + initial value <4> −measured value <3> + measured value <4>
However, initial values <1> to <4> are initial values of light emission patterns <1> to <4>, respectively, and measurement values <1> to <4> are measurements of light emission patterns <1> to <4>, respectively. Value.

  In such a light quantity fluctuation detection process by repeated light emission pattern control, correction control is not performed even if a light quantity fluctuation is detected in the middle of the process, and the control waits for completion of control of all light emission patterns.

  When the control of all the light emission patterns is completed, the control unit 150 compares the measurement values in all the light emission patterns with the initial values as described above. Then, after taking into consideration the time required for one scan and the detection capabilities of the photodetectors P1 and P2, it is determined whether or not the comparison result value is within a specified error range (step S14).

  Then, the control unit 150 determines that there is no light amount fluctuation that needs to be corrected within the specified error range, and continues the light amount fluctuation detection process by repeated light emission pattern control. If it is outside the specified error range, the control unit 150 determines that there is a light amount fluctuation that needs to be corrected, and confirms the photodetector that has detected the light amount fluctuation in step S15.

  If the light detector that has detected the light amount fluctuation is one of the light detectors P1 and P2, the process proceeds to step S16, and the detected light amount fluctuation is detected by the detector error of the corresponding light detector ( It is determined whether it is within (obtained by the initial setting operation in step S11). If it is within the detector error, the light intensity fluctuation correction control is not performed, and the process returns to step S13. If it is outside the detector error quantity, the process proceeds to step S17, and the light quantity fluctuation correction control is performed. Moreover, also when the photodetector which detected the said light quantity fluctuation | variation is both photodetector P1, P2, it progresses to step S17.

  In the correction control performed by the control unit 150 in step S17, first, which of the areas 1 to 3 is the area in which the light amount variation has occurred is determined by the light amount value data in all the light emission patterns acquired by the repeated light emission pattern control. Judgment is made and correction control is performed only for that area.

  In the correction control in the present embodiment, a current value corresponding to the current light amount value is searched for from the current-light amount characteristic (see FIG. 9) for each light emission pattern set in the initial setting operation. Then, the necessary current value is corrected by adding or subtracting only the area of the difference between the current value and the initial use current value in the next scanning. That is, the correction control in the present embodiment corrects the light amount fluctuation by a correction formula obtained from the current-light amount characteristic. One example will be described with reference to FIGS. 11 (a) and 11 (b).

  For example, it is assumed that the light amount fluctuation is generated by forcibly reducing the light amount of the element in a certain area with respect to the laser light set to perform image formation at A0 [HEX] in the initial setting operation. Accordingly, for example, in the light emission pattern <3>, it is assumed that the laser light quantity is reduced from B to D as shown in FIG. 11A, and this light quantity fluctuation is detected by the photodetector P2. The correction amount of the necessary current value in this case is a value obtained by subtracting δ from the necessary current value γ, as shown in the current-light quantity characteristic of FIG. Specifically, it can be calculated by the correction formula shown in FIG. The point E in FIG. 11A indicates the pseudo detection amount after correction.

<Advantages of this embodiment>
(1) When the polygon unit 102 is irradiated with a light beam from the surface emitting semiconductor laser 100 and reaches the folding mirror 105 through the optical systems 103 and 104, the light beam near both ends of the folding mirror 105 is an optical path in the direction of the photosensitive drum 106. The optical system is configured so as not to change. The light beam whose optical path is not changed is a light beam outside the image formation guarantee area on the surface to be scanned of the photosensitive drum 106, and two photodetectors P1 and P2 for controlling the light amount are arranged on the light beam. That is, the photodetectors P1 and P2 are disposed on both ends of the folding mirror 105, respectively. With such a configuration, in the present embodiment, the light detectors P1 and P2 are positioned closest to the photosensitive drum 106 without spectrally dividing the light emitted from the surface emitting semiconductor laser 100 in order to perform light amount control. Can detect the light flux. This makes it possible to perform light amount control with high accuracy without reducing the light amount.

  (2) The light emitting element group in the surface emitting semiconductor laser 100 is divided into a plurality of areas, and the light quantity fluctuation is corrected in units of areas. Therefore, the light quantity fluctuation during scanning due to an abnormality of a part of the light emitting elements in the area. Even when this occurs, the light amount can be easily corrected. That is, the light quantity at the time of scanning is detected by the two light detectors P1 and P2, and the light quantity fluctuation is discriminated from the light quantity value data of the different light emission patterns composed of at least one area to determine the light emission state in the area within the light emission pattern. to correct. As described above, the light amount control using the two photodetectors P1 and P2 makes it possible to follow the change in the light amount both spatially and temporally, and easily and quickly correct the light amount. it can.

<Image Forming Apparatus According to this Embodiment>
Next, an image forming apparatus to which the light quantity control device having the above configuration is applied will be described with reference to FIG.

  FIG. 12 is a cross-sectional view showing a schematic internal structure of a copying apparatus which is an example of an image forming apparatus according to the present embodiment.

  As shown in FIG. 12, the copying apparatus includes an image scanner unit 201, a printer unit 200, and an operation unit 300. The image scanner unit 201 is a part that reads a document and performs digital signal processing. The printer unit 200 is a part that prints out an image corresponding to an original image read by the image scanner unit 201 on a sheet such as paper. The operation unit 300 is a part where the user performs operations related to the copying apparatus.

  In the image scanner unit 201, 202 is a document pressure plate, and a document 204 on the document table glass 203 is irradiated with light from a halogen lamp 205. Reflected light from the original is guided to mirrors 206 and 207, and an image is formed on the CCD sensor 210 by the lens 208.

  The CCD sensor 210 reads optical information from the document and sends it to the image signal processing unit 140. The first and second mirror mounts on which the halogen lamp 205 and the mirror 206 are mounted are mechanically moved in the vertical direction (sub-scanning direction) with respect to the electrical scanning direction (main scanning direction) of the CCD sensor 210. By doing so, the entire surface of the document is scanned. At this time, the first mirror stage moves at a speed v, and the second mirror stage on which the mirror 207 is mounted is moved at a speed 1 / 2v.

  The image scanner unit 201 includes a home position sensor 230 and a standard white plate 211. The home position sensor 230 detects the position of the first mirror base by detecting that the protrusion 229 attached to the first mirror base enters between the home positions. The standard white plate 211 is used to generate correction data for data read by the CCD sensor 210. The standard white plate 211 exhibits a substantially uniform reflection characteristic with respect to visible light, and has a white color in the visible.

  The image signal processing unit 140 electrically processes the image signal read by the CCD sensor 210 and sends it to the printer unit 200.

  In addition to the laser driver 170 and the surface emitting semiconductor laser 100, the printer unit 200 includes the optical scanning device, the photosensitive drum 106, the developing devices 219 to 222, the transfer drum 223, the paper cassettes 224 and 225, and the fixing device shown in FIG. 226.

  The image signal sent from the image scanner unit 201 is sent to the laser driver 170. The laser driver 170 modulates and drives the surface emitting semiconductor laser 100 according to the image signal. Laser light emitted from the surface emitting semiconductor laser 100 is exposed on the photosensitive drum 106 via the polygon unit 102, the fθ lens 103, the surface tilt correction lens 104, and the folding mirror 105 in the optical scanning apparatus of FIG.・ Scan.

  The surface of the photoconductive drum 106 is uniformly charged by the charging device 220, and an electrostatic latent image is formed on the precharged photoconductive drum 106 by exposure and scanning of the optical scanning device. The developing unit 221 develops the electrostatic latent image formed on the photosensitive drum 106 with toner.

  The transfer drum 223 winds a sheet (transfer medium) fed from the sheet cassette 224 or 225, and transfers the toner image developed on the photosensitive drum 106 onto the sheet. In this way, after the toner image is transferred, the sheet passes through the fixing device 226, is heated and fixed, and is discharged outside the apparatus.

  The object of the present invention can also be achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, a case where the functions of the above-described embodiment are realized by the following processing is also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

It is the schematic which shows the structure of the principal part of the optical scanning device which concerns on embodiment. It is a schematic sectional drawing which shows the periphery mechanism of the photodetector which concerns on embodiment. It is the schematic which shows the structure of a photodetector. It is a block diagram which shows the structure of the light quantity control apparatus which concerns on embodiment. It is a schematic diagram which shows the light emission pattern of the laser beam which concerns on embodiment. It is a schematic diagram which shows the area classification | category of the light emitting element group in a surface emitting semiconductor laser. It is a flowchart which shows the light quantity control process which concerns on embodiment. It is explanatory drawing explaining the acquisition method of the initial acquisition data at the time of initial setting operation | movement. It is a characteristic view which shows the initial acquisition data at the time of initial setting operation | movement. It is explanatory drawing explaining an example of repeated light emission pattern control. It is explanatory drawing explaining an example of the correction control in embodiment. 1 is a schematic cross-sectional view illustrating a configuration example of an image forming apparatus according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Laser light emission part 101 Light guide part 102 Polygon unit 103 f (theta) lens 104 Surface tilt correction lens 105 Folding mirror 106 Photosensitive drum 150 Control part 151 CPU
152 ROM
153 RAM
162 Image Processing Unit 163 PWM Generation Unit 170 Laser Driver P1, P2 Photodetector

Claims (9)

In an optical scanning device comprising scanning means for scanning a light beam from a light source and an optical system for forming an image of the light beam on a scanned surface,
The scanning means is configured to scan the light beam to the outside of the image formation guarantee area on the scanned surface,
The optical scanning apparatus according to claim 1, wherein the optical system is configured to guide a light beam scanned to the outside of the image formation guarantee area to a light detection unit used for light amount control of the light beam from the light source. The optical system includes an optical path changing unit that changes an optical path of a light beam by the scanning unit to the scanned surface side,
2. The optical scanning device according to claim 1, wherein the light beam scanned beyond the image formation guarantee area is a light beam whose optical path is not changed by the optical path changing unit.   3. The optical scanning device according to claim 1, wherein the light detection unit is arranged on each of both end sides of the optical path changing unit. A light amount control device for controlling the light amount of a light beam scanned by the optical scanning device according to any one of claims 1 to 3 based on a detection signal of the light detection means,
The light source of the luminous flux is composed of a light emitting element group composed of a plurality of light emitting elements,
Light emission control means for causing the light source to emit light with a plurality of different light emission patterns composed of at least one area when the light emitting element group is divided into a plurality of areas;
A light quantity fluctuation detecting means for measuring the light quantity of the light emission pattern based on a detection signal of the light detection means after the light beam is emitted from the light source with the light emission pattern, and detecting the light quantity fluctuation;
A light quantity control device comprising correction means for correcting the detected light quantity fluctuation.   The light emission control device according to claim 4, wherein the light emission control unit causes the light source to emit light with a plurality of light emission patterns during one scan of the light beam.   The light quantity control device according to claim 4, wherein the light quantity fluctuation detecting unit detects the light quantity fluctuation based on a basic light emission quantity of the light emission pattern.   The light quantity control device according to claim 4, wherein the correction unit corrects the light quantity variation by a correction formula obtained from a current-light quantity characteristic for each of the plurality of light emission patterns.   A light scanning device according to any one of claims 1 to 3 and a light quantity control device according to any one of claims 4 to 7, wherein a light beam scanned by the light scanning device is scanned. Development that forms an electrostatic latent image by forming an image on the surface of the image carrier, which is a surface, and forms toner images by applying toner to the electrostatic latent image formed on the surface of the image carrier An image forming apparatus comprising: an apparatus; and a transfer device that transfers the toner image on the surface of the image carrier to a transfer medium. A light amount control method for a light amount control device for controlling the light amount of a light beam scanned by the optical scanning device according to any one of claims 1 to 3 based on a detection signal of the light detection means,
When the light emission control means divides the light emitting element group of the light source composed of the light emitting element group composed of a plurality of light emitting elements into a plurality of areas, the light source is controlled with a plurality of different light emission patterns composed of at least one area. A step of emitting light;
A step of measuring a light amount of the light emission pattern based on a detection signal of the light detection unit after a light beam is emitted from the light source by the light emission pattern, and detecting the light amount variation;
And a correction means for correcting the detected light amount fluctuation.

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