JP2005007643A - Quantity of light control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quantity of light control device which can improve the precision of quantity of light adjustment of light beams. <P>SOLUTION: An image formation apparatus 100 includes a light scanning device 10 with a laser array 12 which has 32 LDs and a single MPD 20 for detecting a quantity of light of laser beams, laser driving devices D1-D32, the quantity of light control devices C1-C32, and change-over switches SW1-SW32. The change-over switch changes over in accordance with a switch change-over signal from a controller 102 whether the MPD 20 is to be connected to the quantity of light control device or grounded. The controller 102 grounds the MPD 20 so as to discharge electric charges accumulated in the MPD 20 for a period of time other than a quantity of light control period of time, and connects the quantity of light control device corresponding to the LD to be controlled and the MPD 20 with each other so that the quantity of light control is carried out during the quantity of light control period of time. The quantity of light control device carries out the quantity of light control to make the quantity of light a target quantity of light on the basis of a detection signal from the MPD 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light amount control device, and more specifically, to a light amount control device that is used in an optical scanning device or the like that scans a light beam emitted from a plurality of light emitting units on a surface to be scanned, and performs light amount control of the light beam. Relates to the device.
[0002]
[Prior art]
In recent years, in an image forming apparatus adopting an electrophotographic method, both an image forming apparatus for forming a monocolor image and an image forming apparatus for forming a full color image have a higher image forming speed and a higher resolution of the formed image. The demand for is getting higher. In order to achieve such high speed and high resolution, an optical scanning device having a high speed (high frequency) image clock signal, a polygon mirror that rotates at high speed, and a laser driver that modulates the laser beam at high speed. is required. However, it is technically difficult to transmit a high-frequency clock signal without deterioration, and devices such as transmission cables and laser drivers become expensive. In addition, the polygon motor for rotating the polygon mirror has a shorter life or increased noise due to heat generation due to an increase in current consumption due to a load such as windage loss of the polygon mirror as the rotation speed is increased. There is also a problem such as, and there is a limit to increasing the rotational speed.
[0003]
In view of this, a technique has been proposed in which an image is formed by increasing the number of emission points from which a laser beam is emitted and simultaneously scanning a plurality of laser beams. For example, by using a laser light source including two laser diodes (hereinafter referred to as “LD”) capable of emitting two laser beams from one chip, the rotational speed of the polygon mirror is set to 1 Compared to a laser light source that emits a single laser beam, it can be halved (1/2), thereby reducing the scanning speed on the photosensitive drum. The frequency can also be lowered.
[0004]
By the way, in an electrophotographic image forming apparatus using a laser, in order to scan with a stable light amount of the laser beam, the light amount control of the laser beam, that is, APC (Auto Power Control) control is performed for each scan. . Usually, the light intensity control is performed by detecting the amount of light emitted from the laser beam by a sensor such as a monitor photodiode (hereinafter also referred to as “MPD”) (usually disposed inside the LD package and detecting the back beam of the LD. Sensor), convert the current value according to the monitored light amount into voltage, and compare it with the reference voltage according to the target light amount, so that the LD light amount becomes the target light amount and feedback. This is done by controlling.
[0005]
In mono-color and full-color image forming apparatuses that require high speed and high resolution, it is necessary to increase the number of laser beams of a light source mounted in the optical scanning apparatus and perform light amount correction within one scanning period.
[0006]
As the number of laser beams is increased, the number of laser beams for controlling the amount of light simultaneously increases. However, in general, an LD package having a laser having a plurality of light emitting points has one MPD for each LD package. In many cases, the light quantity control for each laser beam is inevitably performed in time series by switching the laser beam to be lit.
[0007]
In order to simultaneously control the light quantity of a plurality of laser beams, the number of MPDs corresponding to the number of lasers is arranged outside the laser without providing the MPD in the LD package or without using the MPD in the package. However, as the number of laser beams increases, the cost for MPD increases and the apparatus becomes larger, which is not realistic. Therefore, even if the MPD is arranged outside without providing the MPD in the LD package or without using the MPD in the LD package, the laser beam to be lit is switched using a single MPD. Therefore, it is necessary to control the light amount in time series.
[0008]
There is a technique described in Patent Document 1 as a technique for performing light quantity control by switching lighting of a plurality of LDs. FIG. 18 shows an optical writing device described in Patent Document 1. The optical writing device shown in FIG. 18 includes a light emitting unit 200 having a plurality (four) of LDs and an LD array 204 in which one light receiving unit (MPD) 202 is housed in one package. Accordingly, LD drive control circuits 210 to 216 and changeover switches 218 to 224 each including an LD drive unit 206 and an APC control unit 208 are provided. A plurality of laser beams emitted from the light emitting unit 200 of the LD array 204 are collimated by a collimator lens (not shown), deflected by a polygon mirror 226, and rotated in a predetermined direction (sub-scanning direction) via an fθ lens 228. A main scan is performed on the photosensitive drum 230 in the axial direction of the photosensitive drum 230. The GAVD 232 that performs overall control of the apparatus is based on a synchronization detection signal (Start of Scan signal: hereinafter referred to as an SOS signal) from a photodetector 234 provided outside the main scanning writing area. To decide.
[0009]
When performing APC control of each LD, the GAVD 232 outputs a DATA signal and an APC signal to any one of the LD drive unit 206 and the APC control unit 208 so that each LD is individually turned on to execute the APC control. At the same time, only the changeover switch corresponding to the lighted LD is turned on, and the output current from the light receiving unit 202 is input only to the corresponding APC control unit 208.
[0010]
In this way, since the output current from the single light receiving unit 202 is switched and used for light amount control, it is advantageous in terms of switching speed compared to switching after converting the output current to voltage, and the light amount control is speeded up. It is effective from the viewpoint.
[0011]
[Patent Document 1]
JP 2001-150726 A
[0012]
[Problems to be solved by the invention]
However, the technique described in Patent Document 1 has the following problems. With respect to this problem, a case where APC control is performed for two LDs will be described with reference to FIG. As shown in FIG. 19, the selector switches SW1 and SW2 (for example, the selector switches 218 and 220 in FIG. 18) are in an open state during the image forming process and when the SOS signal is detected, so that the light receiving unit 202 is connected anywhere. In this state, the laser beam is received, and charges (MPD charges) corresponding to the accumulated light amount received are accumulated in the light receiving unit 202. When the changeover switch SW1 is turned on and the APC control of the first LD is started, the current from the light receiving unit 202 is indicated by the dotted line in FIG. (MPD current) becomes larger than the current corresponding to the actual light amount of the laser beam, and the accuracy of APC control deteriorates.
[0013]
This phenomenon becomes more prominent as the number of laser beams increases. When the number of laser beams is small, such as one, the charge accumulated in the light receiving unit 202 is quickly emitted in a very short time when the APC control unit 208 and the light receiving unit 202 are connected at the start of APC control. Therefore, even in the APC control period for each line, it is possible to adjust the light amount within the APC control time after the discharge of the charge. On the other hand, when the number of laser beams is large, for example, in an LD array that emits four laser beams, the amount of light incident on the light receiving unit 202 in the image region is quadrupled. 4 times, and no charge can be released within a predetermined APC control period. Accordingly, since more current than the current corresponding to the actual light amount is input to the APC control unit 208, the same state as when the light is emitted with a large power is obtained, and the light emission amount of the LD is controlled to be lowered. As a result, the amount of light may be insufficient.
[0014]
The present invention has been made to solve the above-described problems, and is a light quantity control device capable of improving the accuracy of light quantity adjustment of a light beam, and in particular, includes a light source that emits a plurality of light beams. It is an object of the present invention to provide a light quantity control device capable of improving the accuracy of light quantity adjustment for each light beam even when the light quantity adjustment of the plurality of light beams is performed with a smaller number of light receiving elements.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is provided with scanning means for scanning a light beam modulated on the basis of image data on the image carrier, and an image formed on the image carrier. A light amount control device for controlling an amount of light beam used in an image forming apparatus that forms an image by transferring to a recording medium, the light emission means including a light emitting unit for emitting the light beam, and the light emission A light detection means for detecting the light quantity of the light beam emitted from the unit; a light quantity control means for controlling the light quantity so that the light quantity of the light beam becomes a predetermined light quantity based on a detection result of the light detection means; Charge accumulation preventing means for preventing charge from being accumulated in the light quantity detection means at least when light quantity control by the light quantity control means is started is provided.
[0016]
The light quantity control device includes a scanning unit that scans a light beam modulated on the basis of image data on the image carrier, and forms an image by transferring the image formed on the image carrier to a recording medium. Used in forming equipment.
[0017]
The light quantity control device includes a light emitting unit including a light emitting unit that emits a light beam. As this light emitting means, for example, a surface emitting laser light source or the like is used.
[0018]
The light detection means detects the light amount of the light beam emitted from the light emitting unit. The detected light quantity is photoelectrically converted and output to the light quantity control means.
[0019]
The light quantity control means controls the light quantity so that the light quantity of the light beam becomes a predetermined light quantity based on a detection result of the light detection means, for example, a current value or a voltage value corresponding to the detected light quantity.
[0020]
This light amount control is performed, for example, in a period other than the image forming period in one scanning period by the scanning unit. However, when the light detecting unit is in an open state where it is not connected anywhere, it is detected by the light detecting unit during the image forming period. In some cases, charges corresponding to the light quantity of the light beam accumulated in the light detection means. In such a state, when the light detection means and the light quantity control means are connected at the start of the light quantity control and the light quantity control is performed, a light quantity larger than the light quantity of the light beam actually emitted from the light emitting means will be detected. In some cases, the amount of light cannot be accurately controlled.
[0021]
Therefore, the charge accumulation preventing means sets a state in which no charge is accumulated in the light quantity detecting means at least when the light quantity control means starts the light quantity control means.
[0022]
As described above, the light amount control can be performed accurately by setting the state in which no charge is accumulated in the light detection means at the start of the light amount control.
[0023]
Specifically, as described in claim 2, the charge accumulation preventing unit includes a switching unit that connects or grounds the light detection unit with the light amount control unit, and a light amount control period other than the light amount control period by the light amount control unit. The switching unit is controlled so that the light detection unit is grounded at least during a predetermined period immediately before the light amount control is started, and the light detection unit is connected to the light amount control unit during the light amount control period. And a switching control means.
[0024]
According to the present invention, since the light detection means is grounded for at least a predetermined period immediately before the light quantity control is started except for the light quantity control period by the light quantity control means, the charge accumulated in the light detection means during the image forming period or the like. Is released. Thereby, since the charge is not accumulated at the start of the light amount control, the light amount control can be performed accurately.
[0025]
It should be noted that the light detection means may always be grounded during a period other than the light amount control period, or if the time is sufficient to release the accumulated charge, light is emitted only during the period immediately before the light amount control is started. The detection means may be grounded.
[0026]
According to a third aspect of the present invention, the charge accumulation preventing means includes a switching means for connecting or disconnecting the light detection means with the light quantity control means, and a period other than the light quantity control period by the light quantity control means. The switching is performed so that the light detection unit is connected to the light amount control unit at least for a predetermined period immediately before the light amount control is started, and the light detection unit is connected to the light amount control unit during the light amount control period. And a switching control means for controlling the means.
[0027]
According to the present invention, since the light detection means is connected to the light quantity control means at least during a predetermined period other than the light quantity control period by the light quantity control means, the light detection means accumulates during the image forming period. The charge that has been made is released. Thereby, since the charge is not accumulated at the start of the light amount control, the light amount control can be performed accurately.
[0028]
It should be noted that the light detection means may always be connected to the light quantity control means during a period other than the light quantity control period, or just before the light quantity control is started if the time is sufficient to release the accumulated charge. The light detection means may be connected to the light quantity control means only during this period.
[0029]
According to a fourth aspect of the present invention, the charge accumulation preventing unit blocks the light beam incident on the light detecting unit during a period other than the light amount control period by the light amount control unit, and during the light amount control period. The light detection unit may be a blocking unit that causes the light beam to enter the light detection unit.
[0030]
According to the present invention, since the light beam incident on the light detection means is interrupted during a period other than the light quantity control period by the light quantity control means, no charge is accumulated in the light detection means at the start of the light quantity control. Light amount control can be performed accurately.
[0031]
According to a fifth aspect of the present invention, the light emitting unit includes a plurality of light emitting units and a plurality of the light amount control units corresponding to the light emitting units, and the light amount control by the light amount control unit is performed for each light emitting unit. It is good also as a structure performed sequentially.
[0032]
As described above, when the light emitting unit includes a plurality of light emitting units and a plurality of light amount control units, and each light amount control is performed using a single light detection unit, the light detection unit accumulates in the light detection unit during an image forming period. Although the amount of charge increases according to the number of light emitting units, the charge accumulation preventing unit does not accumulate charges in the light detecting unit when the light amount control starts, so that the light amount control of each light emitting unit can be performed accurately.
[0033]
Note that the light amount control of each light emitting unit may be performed entirely within one scanning period, or may be performed in a plurality of scanning periods. In addition, a plurality of light detection means may be provided, but the effect of the present invention becomes remarkable when the number of light detection means is smaller than the number of light emitting units.
[0034]
Further, when sequentially performing the light amount control, only the light amount control means performing the light amount control is connected to the light detection means, and the light amount control means not performing the light amount control is disconnected from the light detection means. . Thereby, the detection result of the light detection means during the light quantity control period is input only to the light quantity control means performing the light quantity control, so that the light quantity control can be performed accurately.
[0035]
In the image forming apparatus according to the present invention, for example, a plurality of the light emitting unit, the light amount control unit, the charge accumulation preventing unit, the image carrier, and the scanning unit are provided for each color. It is possible to apply to.
[0036]
In this case, since a scanning unit or the like is provided for each color, the light amount control of each light emitting unit may be performed independently.
[0037]
Further, as described in claim 7, the invention can be applied to an image forming apparatus provided with a plurality of the image carriers for each color. In this case, since the light beam for each color is scanned on each image carrier by a single scanning means, when there are a plurality of light emitting units, the light amount control of each light emitting unit does not end within one scanning period. There is a case. In this case, light amount control may be performed for each color divided into a plurality of scanning periods.
[0038]
Further, as described in claim 8, it is also possible to apply to an image forming apparatus provided with a plurality of the light emitting means for each color.
[0039]
Also in this case, since the light beam for each color is scanned on each image carrier by a single scanning unit for a plurality of light emitting units, the light amount control of each light emitting unit may not be completed within one scanning period. . In this case, for example, the light amount control may be performed in a plurality of scanning periods for each color.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a case where the present invention is applied to an optical scanning apparatus that performs scanning exposure on a photosensitive drum with a plurality of laser beams will be described.
[0041]
(First embodiment)
FIG. 1 is a plan view showing a schematic configuration of an optical scanning device 10 according to the present embodiment. As shown in the figure, the optical scanning device 10 is mounted on a circuit board 14 and emits a plurality of laser beams, and a surface emitting laser array 12 and a polygon that scans the plurality of laser beams in the main scanning direction. And a mirror 24.
[0042]
As described above, the laser array 12 generates a plurality of laser beams. In FIG. 1, only one laser beam is illustrated for the sake of simplicity. The surface emitting laser array 12 that can be easily arrayed can generate several tens of laser beams, and the arrangement of the laser beams is not limited to one row but is arranged two-dimensionally. Is also possible. The laser array 12 according to the present embodiment is two-dimensionally arranged as shown in FIG. 2, and the number of LDs is 32. Hereinafter, these LDs are referred to as first LD to thirty-second LD, and laser beams emitted from these LDs are referred to as first laser beam to thirty-second laser beam.
[0043]
The laser beam emitted from the laser array 12 is converted into substantially parallel light by the collimator lens 16. The half mirror 18 separates a part of the laser beam and guides it to the MPD 20. Unlike the edge emitting laser, the laser array 12 cannot emit a laser beam (back beam) from the rear side of the resonator. Therefore, in order to obtain a monitor signal for light quantity control, a part of the laser beam emitted from the laser array 12 is separated by the half mirror 18 and then guided to the MPD 20 as described above.
[0044]
On the other hand, the laser beam that has passed through the half mirror 18 is imaged into a long line in the main scanning direction in the vicinity of the reflecting surface of the polygon mirror 24 by the cylindrical lens 22 having power only in the sub-scanning direction, and is incident on the polygon mirror 24. The
[0045]
The polygon mirror 24 is rotated by a motor (not shown) and deflects and reflects the incident laser beam in the main scanning direction. The laser beam deflected and reflected by the polygon mirror 24 is imaged on a photosensitive drum (not shown) in the main scanning direction by the fθ lens 26 having power only in the main scanning direction, and substantially on the photosensitive drum. An image is formed so as to move at a constant speed. The laser beam that has passed through the fθ lens 26 is imaged on the photosensitive drum by a cylindrical mirror 28 having power only in the sub-scanning direction, and an electrostatic latent image corresponding to the image signal of the corresponding color is formed on the photosensitive drum. Formed on top.
[0046]
Further, since the optical scanning device 10 needs to synchronize the scanning start on each reflecting surface of the polygon mirror 24, the pickup mirror 30 that reflects the laser beam before the scanning starts, and the laser reflected by the pickup mirror 30 A main scanning synchronization sensor (hereinafter referred to as “SOS sensor”) 32 for detecting the beam, and the writing timing in the main scanning direction is synchronized by the SOS signal output from the SOS sensor 32.
[0047]
Next, the configuration of the image forming apparatus 100 to which the optical scanning device 10 is applied will be described with reference to FIG. As shown in the figure, the image forming apparatus 100 includes a controller 102, an image processing apparatus 104, laser drive apparatuses D1 to D32, light amount control apparatuses C1 to C32, changeover switches SW1 to SW32, and the optical scanning apparatus 10 described above. It is configured to include.
[0048]
The controller 102 controls the overall operation of the image forming apparatus 100, and includes various control signals including an image signal indicating an image to be formed and a reset signal for resetting each related unit before starting image formation. Is output to the image processing apparatus 104, and a switch switching signal indicating the switching timing of the laser beam to be subjected to light amount control is output to the changeover switches SW1 to SW32. In addition, let the switch switch signal output to each of switch SW1-SW32 be a 1st switch switch signal, a 2nd switch switch signal, ... 32nd switch switch signal.
[0049]
The image processing device 104 generates a first video signal to a thirty-second video signal indicating the on / off state of each laser beam based on the image signal input from the controller 102, and outputs the first video signal to the thirty-second video signal to the laser driving devices D1 to D32. A role of outputting a light amount control start signal for instructing the start of execution of light amount control to the light amount control devices C1 to C32 based on the SOS signal output from the SOS sensor 32 of the optical scanning device 10, and a laser A light amount control reference voltage signal for setting a reference voltage corresponding to a level at which a plurality of (32 in this embodiment) laser beams emitted from the array 12 indicate a predetermined target light amount is supplied to the light amount control devices C1 to C1. It has the role of outputting to C32 and instructing the setting of the reference voltage. The light quantity control start signal output to each of the light quantity control devices C1 to C32 is a first light quantity control start signal, a second light quantity control start signal,..., A 32nd light quantity control start signal.
[0050]
Further, the laser driving devices D1 to D32 output a laser driving signal (laser driving current value) based on the video signal input from the image processing device 104 to the corresponding LD of the laser array 12 to turn on / off the laser beam. As a result, the role of executing image formation by the optical scanning device 10 and the laser in which the light amount of each laser beam becomes the target light amount based on differential signals (described later) input from the light amount control devices C1 to C32 during light amount control. And a role of setting a drive current value.
[0051]
Further, the light amount control devices C1 to C32 are differential signals for setting the light amount of each laser beam emitted from the laser array 12 based on a light amount detection signal (described later) input from the MPD 20 of the optical scanning device 10 as the target light amount. Is output to the laser driving devices D1 to D32 at a timing according to the light amount control start signal input from the image processing device 104.
[0052]
As shown in FIG. 3, each of the change-over switches SW1 to SW32 includes one input terminal E and three output terminals F to H. The input terminals E are connected to the output terminals of the MPD 20, respectively. Connected to each of the control devices C1 to C32, the output terminal G is in an open state where it is not connected anywhere, and the output terminal H is grounded. The input terminal E is selectively connected to any one of the output terminals F to H according to a switch switching signal input from the controller 102. Accordingly, when the input terminal E is connected to the output terminal F, the output terminal of the MPD 20 is connected to the light quantity control device C1, and when the input terminal E is connected to the output terminal G, the output terminal of the MPD 20 is anywhere. When the input terminal E is connected to the output terminal H, the output terminal of the MPD 20 is grounded.
[0053]
In this embodiment, the input terminal E is connected to the output terminal F when the switch switching signal is at a high level, the output terminal of the MPD 20 is connected to the light amount control device, and the input terminal E is connected when the switch switching signal is at a low level. Is connected to the output terminal H, and the output terminal of the MPD 20 is grounded. In addition, during the light amount control, only the switch switching signal corresponding to the LD that is subject to the light amount control among the first switch switching signal to the thirty-second switch switching signal is controlled to be high level, and the other switch switching signals are controlled to be low level. The Thereby, MPD20 is connected with one light quantity control apparatus at the time of light quantity control. The first light amount control start signal to the thirty-second light amount control start signal are substantially the same as the first switch change signal to the thirty-second switch change signal, and during the light amount control, the first light amount control start signal to the thirty-second light amount control start signal. Among them, only the light quantity control start signal corresponding to the LD of the light quantity control target is controlled to be high level, and the other light quantity control start signals are controlled to be low level.
[0054]
FIG. 4 shows a circuit configuration of the light quantity control device C1. The light quantity control devices C2 to C32 have the same configuration. As shown in FIG. 4, the light quantity control device C1 includes an amplifier 106 configured by an operational amplifier (so-called operational amplifier) and a resistor, and a comparator 108 configured by an operational amplifier. Here, the output terminal F of the changeover switch SW1 is connected to the input terminal of the amplifier 106, and one input terminal of the comparator 108 is connected to the output terminal of the amplifier 106. The reference voltage as a light amount control reference voltage signal set by an instruction from the image processing apparatus 104 is applied to the other input terminal of the comparator 108.
[0055]
In the light quantity control device C1 configured as described above, when the light quantity control is instructed, that is, the first light quantity control start signal becomes high level, the first switch switching signal becomes high level, and the input of the changeover switch SW1 When the end E is connected to the output end F, the light amount of the laser beam emitted from the LD that is the light amount control target of the laser array 12 is converted into a current by the MPD 20, and this is input to the amplifier 106 as a light amount detection signal. . The amplifier 106 converts the input current into a voltage in a predetermined range. Then, the converted voltage is compared with the reference voltage by the comparator 108, so that a difference signal having a level corresponding to the difference from the reference voltage is output from the comparator 108 to the laser driving device D1.
[0056]
In the laser driving device D1, the level of the difference signal input from the light amount control device C1 is 0 (zero), that is, the light amount of the laser beam to be controlled matches the target light amount. The light quantity of the laser beam is adjusted.
[0057]
In addition to the configuration shown in FIG. 4, the light quantity control device C1 has a period during which the execution of the light quantity control indicated by the light quantity control start signal and the switch switching signal input from the image processing apparatus 104 is permitted, and A circuit for controlling the differential signal to be output to the laser driving device D1 only during the period from the switching timing of the laser beam to be controlled to the next switching timing is also included, but this is not shown in the figure. To do.
[0058]
Next, the APC control operation of the image forming apparatus 100 according to the present embodiment will be described with reference to FIG.
[0059]
In the optical scanning device 10 according to the present embodiment, since only one MPD 20 is provided for the laser array 12, the light amount adjustment of each laser beam is not performed at the same time, and is performed while individually controlled for lighting.
[0060]
As shown in FIG. 5, the APC control according to the present embodiment is performed in an area other than the image area in which image formation is performed within one scanning period (denoted as “SOS interval” in the figure). (Indicated as 'APC area' in the figure).
[0061]
During image formation, the first light quantity control start signal to the thirty-second light quantity control start signal and the first switch change signal to the thirty-second switch change signal are all at a low level, and the input end E of the changeover switch SW1 is the output end. Connected to H and grounded.
[0062]
When the image formation is completed, the first light quantity control start signal is set to the high level by the image processing device 104, and the first switch switching signal is set to the high level by the controller 102 almost in synchronization with this. Further, the first LD is turned on by the laser driving device D1 substantially in synchronization with the first light amount control start signal and the first switch switching signal becoming high level. Thereby, the input terminal E of the changeover switch SW1 is connected to the output terminal F, the MPD 20 and the light quantity control device C1 are connected, the first laser beam is detected by the MPD 20, the light quantity is converted into a current, and the light quantity control apparatus. Input to C1.
[0063]
Then, a difference signal corresponding to the difference between the voltage corresponding to the detected light amount and the reference voltage is output to the laser driving device D1 by the light amount control device C1.
[0064]
In the laser driving device D1, the light amount of the laser beam is adjusted so that the level of the difference signal input from the light amount control device C1 becomes 0 (zero). Thereby, the light quantity of the first laser beam is adjusted so as to match the target light quantity.
[0065]
It should be noted that the timing for starting the light amount control is to avoid the rotation angle at which the reflected light from the polygon mirror 24 directly returns to the laser array 12 in order to avoid the adverse effect of the reflected light from the polygon mirror 24 directly returning to the laser array 12. It is good to do it at the timing.
[0066]
When the APC control of the first LD is finished, as shown in FIG. 5, the first light quantity control start signal and the first switch switching signal are set to low level, and the first LD is turned off. Then, the second light quantity control start signal and the second switch switching signal are set to the high level, the second LD is turned on, and APC control is performed on the second LD in the same manner as described above. In the same manner, APC control up to the 32nd LD is sequentially performed.
[0067]
Thus, in the APC area, the first light quantity control start signal to the thirty-second light quantity control start signal and the first switch switching signal to the thirty-second switch switching signal are selectively set to the high level and the first LD to the thirty-second LD are selectively set. APC control is performed in order. As described above, the MPD 20 and any one light amount control device and the MPD 20 are connected to perform the APC control. When the MPD 20 and a plurality of light amount control devices are connected, only one laser beam is turned on during the APC control. This is because the output current from the MPD 20 is diverted to the plurality of light quantity control devices, and the light quantity control device subject to APC control determines that the light quantity is low and cannot perform APC control accurately.
[0068]
As described above, by connecting only the input end of the light quantity control device corresponding to the LD to be APC controlled to the MPD 20 and grounding the input end of the other light quantity control device, as shown in FIG. The output current of the MPD 20 at the time of laser lighting in the SOS search region for detecting a signal (denoted as “MPD current” in the figure) flows all to the ground side, that is, the output terminal H side of the changeover switch. For this reason, charges are not accumulated in the MPD 20, and the light amount can be accurately adjusted even when the light amounts of a plurality of laser beams are adjusted by a single MPD 20.
[0069]
In the present embodiment, since the input terminal E of the changeover switches SW1 to SW32 is connected to either the output terminal F or the output terminal H, the output terminal G may be omitted.
[0070]
(Second Embodiment)
Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, and the detailed description is abbreviate | omitted.
[0071]
FIG. 6 shows a schematic configuration of the image forming apparatus 110 according to the present embodiment. The only difference between the image forming apparatus 110 and the image forming apparatus 100 of FIG. 3 is the configuration of the changeover switches SW1 to SW32.
[0072]
As illustrated in FIG. 6, the changeover switches SW <b> 1 to SW <b> 32 are either in a state where the input terminal E is connected to the output terminal F or disconnected in accordance with the switch switching signal. In this embodiment, when the switch switching signal is at a high level, the input terminal E is connected to the output terminal F to connect the MPD 20 and the light quantity control device, and when the switch switching signal is at a low level, the input terminal E is anywhere. It becomes an open state that is not connected.
[0073]
Next, the APC control operation of the image forming apparatus 110 according to the present embodiment will be described with reference to FIG.
[0074]
As shown in FIG. 7, during image formation, only the first switch switching signal is at a high level, the other switch switching signals are at a low level, and any of the first light quantity control start signal to the 32nd light quantity control start signal is selected. Is also at a low level. Therefore, the input terminal E of the changeover switch SW1 is connected to the output terminal F, and the MPD 20 and the light quantity control device C1 are connected. The other change-over switches SW2 to SW32 are in an open state.
[0075]
When the image formation is completed, the first light quantity control start signal is set to a high level by the image processing device 104, and the first LD is turned on by the laser driving device D1. As a result, the first laser beam is detected by the MPD 20, and the amount of light is converted into a current and input to the light amount controller C1. Then, a difference signal corresponding to the difference between the voltage corresponding to the detected light amount and the reference voltage is output to the laser driving device D1 by the light amount control device C1.
[0076]
In the laser driving device D1, the light amount of the laser beam is adjusted so that the level of the difference signal input from the light amount control device C1 becomes zero. Thereby, the light quantity of the first laser beam is adjusted so as to match the target light quantity.
[0077]
When the APC control of the first LD is completed, as shown in FIG. 7, the first light quantity control start signal and the first switch switching signal are set to low level, and the first LD is turned off. As a result, the input terminal E of the changeover switch SW1 is in an open state where it is not connected anywhere. Then, the second light quantity control start signal and the second switch switching signal are set to the high level, and the second LD is turned on. Thereby, the input terminal E of the changeover switch SW2 is connected to the output terminal F, and the MPD 20 and the light quantity control device C2 are connected. Then, APC control is performed for the second LD in the same manner as described above. In the same manner, APC control up to the 32nd LD is sequentially performed. Then, after the APC control of the 32nd LD is completed, the first switch switching signal becomes high level again, and the MPD 20 and the light quantity control device C1 are connected.
[0078]
As described above, in the area other than the APC area, that is, in the image area and the SOS search area, the change-over switch SW1 is always connected to the light quantity control device C1, so that the MPD 20 All of the output current flows to the light quantity control device C1 side. For this reason, as shown in FIG. 7, no charge is accumulated in the MPD 20, and even when the light amounts of a plurality of laser beams are adjusted by a single MPD 20, the light amount can be adjusted accurately. Since the APC control is not started unless the light amount control start signal becomes high level, the APC control does not malfunction even if the output current of the MPD 20 is input to the light amount control device, and there is no particular problem.
[0079]
(Third embodiment)
Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same part as 2nd Embodiment, and the detailed description is abbreviate | omitted.
[0080]
FIG. 8 shows a schematic configuration of the image forming apparatus 120 according to the present embodiment. The image forming apparatus 120 is different from the image forming apparatus 110 in FIG. 6 in that a shutter mechanism 122 and a shutter control device 124 for controlling the shutter mechanism 122 are provided. Since other configurations are the same as those of the image forming apparatus 110, description thereof is omitted. In FIG. 8, the internal configuration of the switch change signal and the changeover switches SW1 to SW32 is omitted.
[0081]
As shown in FIGS. 9A and 9B, a shutter mechanism 120 is provided in front of the MPD 20. The shutter mechanism 122 is driven by a shutter control device 124 including a stepping motor 126 and a drive circuit 128 that drives the stepping motor 126.
[0082]
The shutter control device 124 opens and closes the shutter mechanism 122 according to a shutter control signal from the controller 102. In the present embodiment, the shutter control device 124 is configured so that the shutter mechanism 122 is opened when the shutter control signal is at a high level, that is, the position indicated by the dotted line in FIGS. 9A and 9B. It is rotated so that Thereby, the laser beam L reflected by the half mirror 18 enters the MPD 20. Further, the shutter control device 124 is configured so that the shutter mechanism 122 is in a closed state when the shutter control signal is at a low level, that is, the shutter mechanism 122 is at a position indicated by a solid line in FIGS. 9A and 9B. To rotate. Thereby, it is possible to prevent the laser beam L reflected by the half mirror 18 from entering the MPD 20.
[0083]
Next, the APC control operation of the image forming apparatus 120 according to the present embodiment will be described with reference to FIG.
[0084]
As shown in FIG. 10, during image formation, the first switch switching signal to the 32nd switch switching signal and the first light amount control start signal to the 32nd light amount control start signal are all at a low level. The shutter control signal is at a low level. Accordingly, the change-over switches SW1 to SW32 are in the open state, but the shutter mechanism 122 is in the closed state, so that the incidence of the laser beam on the MPD 20 is blocked and no charge is accumulated in the MPD 20.
[0085]
When the image formation is completed, the controller 102 sets the first switch switching signal to the high level, the image processing device 104 sets the first light quantity control start signal to the high level, and the first LD is turned on by the laser driving device D1. In synchronism with this, the shutter control signal becomes high level, and the shutter mechanism 122 is opened. As a result, the first laser beam is detected by the MPD 20, and the amount of light is converted into a current and input to the light amount controller C1. Then, a difference signal corresponding to the difference between the voltage corresponding to the detected light amount and the reference voltage is output to the laser driving device D1 by the light amount control device C1.
[0086]
In the laser driving device D1, the light amount of the laser beam is adjusted so that the level of the difference signal input from the light amount control device C1 becomes zero. Thereby, the light quantity of the first laser beam is adjusted so as to match the target light quantity.
[0087]
When the APC control of the first LD is completed, as shown in FIG. 10, the first light quantity control start signal and the first switch switching signal are set to low level, and the first LD is turned off. Then, the second light quantity control start signal and the second switch switching signal are set to the high level, and the second LD is turned on. Thereby, the input terminal E of the changeover switch SW2 is connected to the output terminal F, and the MPD 20 and the light quantity control device C2 are connected. Then, APC control is performed for the second LD in the same manner as described above. In the same manner, APC control up to the 32nd LD is sequentially performed. Then, after the APC control of the 32nd LD is completed, the shutter control signal becomes low level again, and the incidence of the laser beam on the MPD 20 is blocked.
[0088]
In this way, in the area other than the APC area, that is, in the image area and the SOS search area, the shutter mechanism 122 is always closed. Therefore, even if the changeover switches SW1 to SW32 are open as shown in FIG. Charges are not accumulated, and even when the light amounts of a plurality of laser beams are adjusted with a single MPD 20, the light amount can be adjusted accurately.
[0089]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, and the detailed description is abbreviate | omitted.
[0090]
The image forming apparatus according to the present embodiment is the same as the image forming apparatus 100 shown in FIG. 3, but in this embodiment, the input terminals E of the changeover switches SW1 to SW32 are connected to any of the output terminals F to H. It is different in that it can be in a state of being made.
[0091]
In this embodiment, when the switch switching signal is at the first high level, the input terminal E is connected to the output terminal F, the output terminal of the MPD 20 is connected to the light amount control device, and when the switch switching signal is at the low level. When the input terminal E is connected to the output terminal H, the output terminal of the MPD 20 is grounded, and the input terminal E is the output terminal when the switch switching signal is a second high level lower than the first high level and higher than the low level. Connected to G, the output terminal of MPD 20 is opened. The switch switching signal is not limited to the above, and any signal may be used as long as the input terminal E is selectively connected to any one of the output terminals F to H.
[0092]
Next, the APC control operation of the image forming apparatus 100 according to the present embodiment will be described with reference to FIG.
[0093]
As shown in FIG. 11, during the image formation, the first switch switching signal to the 32nd switch switching signal are all at the second high level, and the first light quantity control start signal to the 32nd light quantity control start signal are any. Is also at a low level. For this reason, the input terminals E of the changeover switches SW1 to SW32 are all connected to the output terminal G, and the output terminal of the MPD 20 is in an open state. Therefore, as shown in FIG. 11, the MPD 20 is in a state where charges are accumulated.
[0094]
The first switch switching signal is at the low level at the time point ta after the predetermined period has elapsed after the image formation is finished, and the first switch switching signal is set to the first high level by the controller 102 at the time point tb after the predetermined period has elapsed. At the same time, the first light quantity control start signal is set to high level by the image processing device 104, and the first LD is turned on by the laser driving device D1. Thus, once the first switch switching signal goes low and the input terminal E of the switch SW1 is connected to the output terminal H, the charge accumulated in the MPD 20 is transferred to the ground side as shown in FIG. Released.
[0095]
Then, the first laser beam is detected by the MPD 20, the light amount is converted into a current and input to the light amount control device C1, and the light amount control device C1 responds to the difference between the voltage corresponding to the detected light amount and the reference voltage. The difference signal is output to the laser driving device D1.
[0096]
In the laser driving device D1, the light amount of the laser beam is adjusted so that the level of the difference signal input from the light amount control device C1 becomes zero. Thereby, the light quantity of the first laser beam is adjusted so as to match the target light quantity.
[0097]
When the APC control of the first LD is finished, as shown in FIG. 11, the first switch switching signal becomes the second high level, the first light quantity control start signal becomes the low level, and the first LD is turned off. As a result, the input terminal E of the changeover switch SW1 is again opened. Then, the second light quantity control start signal and the second switch switching signal are set to the first high level, and the second LD is turned on. Thereby, the input terminal E of the changeover switch SW2 is connected to the output terminal F, and the output terminal of the MPD 20 and the light amount control device C2 are connected. Then, APC control is performed for the second LD in the same manner as described above. In the same manner, APC control up to the 32nd LD is sequentially performed.
[0098]
As described above, in the areas other than the APC area, that is, in the image area and the SOS search area, the MPD 20 is in an open state and charges are accumulated. However, after the image formation is completed and before the APC control is started, the MPD 20 Since the accumulated charge is released by grounding the output terminal once, the APC control is not started in the state where the charge is accumulated in the MPD 20, and the light quantity of the plurality of laser beams is adjusted by the single MPD 20. Even in this case, the light amount can be accurately adjusted.
[0099]
(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same part as 2nd Embodiment, and the detailed description is abbreviate | omitted.
[0100]
The image forming apparatus according to this embodiment is the same as the image forming apparatus 110 shown in FIG.
[0101]
Next, the APC control operation of the image forming apparatus 110 according to the present embodiment will be described with reference to FIG.
[0102]
As shown in FIG. 12, during image formation, the first switch switching signal to the 32nd switch switching signal and the first light amount control start signal to the 32nd light amount control start signal are all at a low level. For this reason, the input terminal E of the changeover switches SW1 to SW32 is not connected anywhere, and the output terminal of the MPD 20 is in an open state. Accordingly, as shown in FIG. 12, the MPD 20 is in a state where charges are accumulated.
[0103]
The first switch switching signal becomes a high level at the time ta after the lapse of a predetermined period after completion of the image formation, and the first light quantity control start signal is set to a high level by the image processing device 104 at a time tb after the lapse of the predetermined period. The first LD is turned on by the laser driving device D1. As described above, after the image formation is completed, the first switch switching signal is set to the high level from the time ta before the APC control is started so that the input terminal E of the selector switch SW1 is connected to the output terminal F. As a result, as shown in FIG. 12, the charge accumulated in the MPD 20 is released to the light quantity control device C1 side. Since the APC control is not started unless the light quantity control start signal becomes high level, the APC control does not malfunction even if the output current of the MPD 20 is input to the light quantity control device C1, and there is no particular problem.
[0104]
Then, the first laser beam is detected by the MPD 20, the light amount is converted into a current and input to the light amount control device C1, and the light amount control device C1 responds to the difference between the voltage corresponding to the detected light amount and the reference voltage. The difference signal is output to the laser driving device D1.
[0105]
In the laser driving device D1, the light amount of the laser beam is adjusted so that the level of the difference signal input from the light amount control device C1 becomes zero. Thereby, the light quantity of the first laser beam is adjusted so as to match the target light quantity.
[0106]
When the APC control of the first LD is completed, as shown in FIG. 12, the first switch switching signal and the first light quantity control start signal become low level, and the first LD is turned off. As a result, the input terminal E of the changeover switch SW1 is again opened. Then, the second light quantity control start signal and the second switch switching signal are set to the first high level, and the second LD is turned on. Thereby, the input terminal E of the changeover switch SW2 is connected to the output terminal F, and the output terminal of the MPD 20 and the light quantity control device C2 are connected. Then, APC control is performed for the second LD in the same manner as described above. In the same manner, APC control up to the 32nd LD is sequentially performed.
[0107]
As described above, in the areas other than the APC area, that is, in the image area and the SOS search area, the MPD 20 is opened and charges are accumulated. However, after the image formation is completed, the MPD 20 is Since the light quantity control device is connected, the charge accumulated in the MPD 20 can be released to the light quantity control device side. Accordingly, the APC control is not started in a state where charges are accumulated in the MPD 20, and the light amount can be accurately adjusted even when the light amounts of a plurality of laser beams are adjusted with a single MPD 20.
[0108]
(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described. In this embodiment, another embodiment of the image forming apparatus will be described. In addition, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.
[0109]
In the above embodiment, an image forming apparatus for forming an image of one color by one optical scanning apparatus has been described. In the present embodiment, a multicolor image forming apparatus for forming an image of a plurality of colors will be described. .
[0110]
FIG. 13 shows a schematic configuration of a multicolor image forming apparatus to which the present invention is applied. As shown in FIG. 13, the multicolor image forming apparatus 130 includes developing units 40Y, 40M for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 40C and 40K are arranged side by side (in order from right to left in FIG. 13).
[0111]
Since these developing units 40Y, 40M, 40C, and 40K have the same configuration, only the developing unit 40Y will be described here, and description of the other developing units 40M, 40C, and 40K will be omitted. For members in the developing units 40M, 40C, and 40K that are the same as members in the developing unit 40Y, the letter Y at the end of the reference numerals given to the members in the developing unit 40Y is replaced with an alphabet representing each color. A description will be given with reference numerals.
[0112]
The developing unit 40Y includes an optical scanning device 10Y that irradiates a light beam based on yellow image data in the direction of arrow A in FIG. 13, a cylindrical photosensitive drum 42Y that rotates at a constant speed in the direction of arrow B in FIG. Has been. The optical scanning device 10Y has the same configuration as the optical scanning device 10 shown in FIG.
[0113]
Further, as shown in FIG. 13, a charger is disposed on the upstream side of the rotation direction (see arrow B in FIG. 13) of the photosensitive drum 42Y from the irradiation position of the light beam by the optical scanning device 10Y (see arrow A in FIG. 13). 44Y is disposed to uniformly charge the photosensitive drum 42Y. The photosensitive drum 42Y uniformly charged by the charger 44Y is rotated in the direction of arrow B in FIG. 13 to perform sub-scanning of the light beam, and a latent image is formed on the photosensitive drum 42Y.
[0114]
Further, on the downstream side in the rotation direction of the photosensitive drum 42Y with respect to the light beam irradiation position by the optical scanning device 10Y, development that supplies yellow toner to the photosensitive drum 42Y is opposed to the peripheral surface of the photosensitive drum 42Y. A container 46Y is provided. The toner supplied from the developing unit 46Y is attached to the portion irradiated with the light beam by the optical scanning device 10Y. As a result, a yellow toner image is formed on the photosensitive drum 42Y.
[0115]
For the developing units 40M, 40C, and 40K, magenta, cyan, and black toner images are formed on the photosensitive drums 42M, 42C, and 42K, respectively.
[0116]
On the downstream side in the rotation direction of the photosensitive drums 42Y, 42M, 42C, and 42K (positions depending on the axis of the photosensitive drums 42Y, 42M, 42C, and 42K) from the arrangement positions of the developing units 46Y, 46M, 46C, and 46K, An endless belt-shaped intermediate transfer body 48 is disposed.
[0117]
The intermediate transfer member 48 is stretched around a plurality of conveyance rollers 50 and is conveyed in the direction of arrow D in FIG. By this conveyance, the intermediate transfer member 48 is guided in the order of the photosensitive drums 42Y, 42M, 42C, and 42K, and the yellow, magenta, cyan, and black toner images are sequentially superimposed, and the multi-color toner is formed on the surface of the intermediate transfer member 48. An image is formed.
[0118]
That is, the intermediate transfer body 48 is transferred by superimposing all the single-color images of yellow, magenta, cyan, and black developed on the respective photoconductive drums 42Y, 42M, 42C, and 42K in one pass, so that a multicolor toner image is transferred. Formed. Thereafter, the transfer roller 53 batch-transfers one sheet at a time from a tray (not shown) to the recording sheet 52 conveyed in the direction of arrow P in FIG.
[0119]
Note that the toner remaining on the surface of the photosensitive drums 42Y, 42M, 42C, and 42K after the toner image is transferred to the intermediate transfer member 48 is removed by a photosensitive drum cleaner (not shown). Further, an intermediate transfer body cleaner (not shown) is also provided on the intermediate transfer body 48 after transferring the multicolor toner image to the recording paper 52 so that the toner remaining on the surface of the intermediate transfer body is removed. It has become.
[0120]
As described above, in the multicolor image forming apparatus 130, as the optical scanning device is provided for each of a plurality of colors, four circuits as shown in FIG. 3 are provided for each color. The present invention can also be applied to such a multicolor image forming apparatus 130, and the amount of light can be adjusted accurately, so that a color image with good image quality can be obtained.
[0121]
(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described. In this embodiment, another embodiment of the optical scanning device will be described. In addition, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.
[0122]
In the above embodiment, the case where only one laser array is provided in the optical scanning device has been described. However, in this embodiment, two laser arrays for forming an image with two colors in the optical scanning device are provided. The form in the case of being provided is demonstrated.
[0123]
FIG. 14 shows the configuration of the optical scanning device 10B according to the present embodiment. The same parts as those of the optical scanning device 10 in FIG.
[0124]
As shown in FIG. 14, an optical scanning device 10B according to the second embodiment includes a surface emitting laser array 12B that is attached to a circuit board 14B and emits a plurality of laser beams, a collimator lens 16B, and a beam splitter. 17 and the cylindrical mirror 28B are different from the optical scanning device 10 according to the first embodiment. Since the configuration of the laser array 12B is the same as that of the laser array 12, a detailed description thereof is omitted here.
[0125]
The laser beam emitted from the laser array 12B is made into substantially parallel light by the collimator lens 16B, and is emitted from the laser array 12 by the beam splitter 17 disposed in the middle part between the collimator lens 16 and the half mirror 18, and is collimated. The optical path is matched with the laser beam that is made substantially parallel light by the lens 16.
[0126]
Thereafter, the laser beam is partly separated by the half mirror 18 and guided to the MPD 20.
[0127]
On the other hand, the laser beam that has passed through the half mirror 18 is imaged by the cylindrical lens 22 in the vicinity of the reflecting surface of the polygon mirror 24 into a long line in the main scanning direction and is incident on the polygon mirror 24.
[0128]
The polygon mirror 24 is rotated by a motor (not shown) and deflects and reflects the incident laser beam in the main scanning direction. The laser beam deflected and reflected by the polygon mirror 24 is imaged on the second photosensitive drum (not shown) in the main scanning direction by the Fθ lens 26, and substantially the same on the second photosensitive drum. The image is formed so as to move at high speed. Then, the laser beam that has passed through the Fθ lens 26 is imaged on the second photosensitive drum by the cylindrical mirror 28B, and an electrostatic latent image corresponding to the image signal of the corresponding color is formed on the second photosensitive drum. Formed.
[0129]
The optical scanning device 10B according to the present embodiment is configured to use the two laser arrays 12 and 12B as described above, but the SOS signal is the same as that of the optical scanning device 10 according to the first embodiment. The output from the SOS sensor 32 according to the laser beam emitted from the laser array 12 is applied, and the writing timing in the main scanning direction of each of the two colors is synchronized by the SOS signal.
[0130]
The configuration of the image forming apparatus to which the optical scanning device 10B according to the present embodiment is applied is substantially the same as the configuration of the image forming apparatus 100 (see FIG. 3) according to the first embodiment. Although detailed description of the laser beam is omitted, two systems of laser drive devices D1 to D32, light amount control devices C1 to C32, and changeover switches SW1 to SW32 are provided and input to these, respectively. Each signal is different in that two systems are provided.
[0131]
As described above, in a configuration in which a plurality of laser arrays are provided in a single optical scanning device, the number of laser beams increases, so that there is not enough time to perform APC control for all the laser beams within one scanning period. Sometimes. In such a case, APC control may be executed for each laser array. That is, in one scanning period, APC control of all laser beams of one laser array is performed, and in the next scanning period, APC control of all laser beams of another laser array is performed. In this manner, APC control can be reliably performed by assigning a laser array that performs APC control to each scan.
[0132]
As described above, the present invention can also be applied to an image forming apparatus including an optical scanning device including a plurality of laser arrays, and the amount of light can be adjusted with high accuracy, so that a color image with high image quality can be obtained. .
[0133]
(Eighth embodiment)
Next, an eighth embodiment of the present invention will be described. In the present embodiment, a mode in which an image of a plurality of colors is formed by one optical scanning device will be described. In addition, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.
[0134]
FIG. 15 shows an image forming apparatus 140 as an image forming apparatus according to the present invention. The image forming apparatus 140 includes three conveyance rollers 50, an endless intermediate transfer body 48 wound around the conveyance rollers 50, and a transfer roller 53 disposed to face the conveyance rollers 50 with the intermediate transfer body 48 interposed therebetween. ing.
[0135]
In order to form a black (K) monochromatic image on the side of the intermediate transfer member 48 along the moving direction of the intermediate transfer member 48 when the intermediate transfer member 48 is driven to rotate (direction of arrow A in FIG. 15). Development unit 40K, development unit 40C for forming a cyan (C) single color image, development unit 40M for forming a magenta (M) single color image, development for forming a yellow (Y) single color image Units 40Y are sequentially arranged at substantially equal intervals.
[0136]
Although not shown in detail in FIG. 15, each developing unit 40 includes a photosensitive drum 42 that is arranged so as to be orthogonal to the moving direction of the intermediate transfer body 48, and the periphery of each photosensitive drum 42. In addition, the electrostatic latent image formed on the photosensitive drum 42 by the charger for charging the photosensitive drum 42 and the optical scanning device 60 is developed with toner of a predetermined color (K or C or M or Y). A developing device for forming a toner image, a transfer device for transferring the toner image formed on the photosensitive drum 19 to the intermediate transfer member 48, and a cleaning device for removing the toner remaining on the photosensitive drum 19 are arranged in this order. Has been.
[0137]
The toner images of different colors formed on the photosensitive drums 42 of the individual developing units 40 are respectively transferred to the intermediate transfer body 48 so as to overlap each other on the belt surface of the intermediate transfer body 48. As a result, a color toner image is formed on the intermediate transfer body 48, and the formed color toner image is transferred to the recording paper 52 fed between the transport roller 50 and the transfer roller 53. Then, the recording paper 52 is sent to a fixing device (not shown), and the transferred toner image is fixed. As a result, a color image (full color image) is formed on the recording paper 52.
[0138]
The optical scanning device 60 includes a laser array 12 composed of at least four LDs, and at least four light beams for forming single-color images of K, C, M, and Y are emitted from the laser array 12. Each is injected. At least four light beams emitted from the laser array 12 are collimated by the collimator lens 16 disposed on the beam emission side of the laser array 12, and then are reflected on the same reflecting surface of the single polygon mirror 24. Each is incident. The laser array 12 may include four or more LDs. In this case, a plurality of LDs are assigned to each color.
[0139]
The polygon mirror 24 has a regular polygonal column shape, and a plurality of reflecting surfaces are formed on the side surfaces by mirror finishing. The polygon mirror 24 rotates at a high speed by transmitting a driving force of a motor (not shown), and deflects and scans at least four light beams incident on the same reflecting surface along the main scanning direction.
[0140]
An Fθ lens 26 having power only in the main scanning direction is disposed on the light beam emission side of the polygon mirror 24, and the light beam deflected and reflected by the polygon mirror 24 is substantially equal on the outer peripheral surface of the photosensitive drum. It is refracted by the fθ lens 26 so that it moves at high speed and the image forming position in the main scanning direction coincides with the outer peripheral surface of the photosensitive drum. A separation mirror 36 is disposed on the light beam emission side of the fθ lens 26, and at least four light beams incident on the separation mirror 36 are on the side where the corresponding developing unit 40 is positioned by the separation mirror 36. Reflected to.
[0141]
In the vicinity of the developing units 40K, 40C, 40M, and 40Y, a cylindrical mirror 38 having power only in the sub-scanning direction is disposed. At least four light beams emitted from the separation mirror 36 are respectively reflected by the cylindrical mirror 38 so that the image forming positions in the sub-scanning direction coincide with the photosensitive drum 42, and the photosensitive drum of the corresponding developing unit 40. 42 are respectively irradiated. The cylindrical mirror 38 also has a surface tilt correction function that conjugates the outer peripheral surfaces of the polygon mirror 24 and the photosensitive drum 42 in the sub-scanning direction.
[0142]
The optical scanning device 60 includes a single MPD 20 as in the above embodiment, and APC control of each laser is performed according to the amount of light detected by the MPD 20.
[0143]
As described above, in the case of a configuration including a laser array that emits a plurality of laser beams with a single optical scanning device, the APC control is performed for all the laser beams within one scanning period by increasing the number of laser beams. May have insufficient time. In this case, APC control may be executed for each LD assigned to each color. That is, in one scanning period, APC control of an LD assigned to a certain color is performed, and in the next scanning period, APC control of an LD assigned to another color is performed. In this way, by assigning an LD that performs APC control for each scan, APC control can be reliably performed.
[0144]
As described above, the present invention can also be applied to an image forming apparatus including a plurality of image forming units and one optical scanning device, and the amount of light can be adjusted accurately, so that a color image with good image quality can be obtained. it can.
[0145]
(Ninth embodiment)
Next, a ninth embodiment of the present invention will be described. In this embodiment, another embodiment of the optical scanning device will be described. In addition, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.
[0146]
In the present embodiment, a mode in which a single optical scanning device including a plurality of laser arrays for each color and a plurality of image forming units for each color will be described.
[0147]
FIG. 16 shows an outline of an image forming apparatus 150 to which the present invention is applied. The image forming apparatus 160 includes four developing units 40 (yellow developing unit 40Y, magenta developing unit 40M, cyan developing unit 40C, and black developing unit 40K) corresponding to each color signal constituting a color image signal. Are configured in the same manner and each include a photosensitive drum 42 as an image carrier.
[0148]
Further, the image forming apparatus 150 is an optical scanning device 62 for irradiating a predetermined exposure scanning position 64 on the surface of the photosensitive drum 42 (hereinafter referred to as the drum surface) included in each developing unit with a laser beam. It has.
[0149]
In each developing unit, the photosensitive drum 42 is rotated at a predetermined angular velocity in the direction of arrow (1) in FIG. 16 by a motor (not shown). As a result, the laser beam emitted from the optical scanning device 62 is repeatedly scanned on the drum surface along the axial direction (main scanning direction) of the photosensitive drum 42 (details will be described later).
[0150]
In each developing unit, a charger 44 is provided slightly upstream of the exposure scanning position 64 along the drum rotation direction indicated by the arrow (1) in FIG. 16, so that the drum surface is uniformly charged. ing. As a result, the surface of the drum uniformly charged by the charger 44 is exposed and scanned with laser light, thereby removing the charged charges other than the image portion and leaving the charge in the image portion. A latent image is formed.
[0151]
Further, a developing device 46 is provided slightly downstream of the exposure scanning position 64 along the drum rotation direction indicated by the arrow (1) in FIG. The developing unit 46 is filled with toner charged to a polarity opposite to that of the electrostatic latent image, and the electrostatic latent image formed on the drum surface is colored in each color (cyan, magenta, yellow, and black). The toner, which is the charged fine particles, is electrostatically attached to form a visible image (toner image).
[0152]
Further, a transfer device 66 is provided below the photosensitive drum 42 in FIG. 16, and an intermediate transfer member 48 for transferring the toner image is sandwiched between the transfer device 66 and the photosensitive drum 42. The intermediate transfer body 48 is transported in order by the transport rollers in the direction of the arrow (2) in FIG. 16 in the developing units Y, M, C, and K. Further, the transfer unit 66 in each developing unit applies charges to the intermediate transfer member 48 and sequentially transfers the toner images for each color to the intermediate transfer member 48 by the electrostatic force.
[0153]
Further, a fixing device 68 is disposed downstream of the intermediate transfer body 48 on which the toner image for each color has been transferred in the direction indicated by the arrow (2) in FIG. In the fixing device 68, the recording sheet 52 for recording an image is sandwiched and conveyed in the direction of the arrow (3) in FIG. 16, and the toner image transferred to the intermediate transfer member 48 by applying heat or pressure is recorded on the recording sheet. 52 is fused.
[0154]
A cleaner 70 for removing toner remaining on the photosensitive drum 42 after transfer is provided at the rearmost end of the rotation direction of the photosensitive drum 42 of each developing unit (the direction indicated by the arrow (1) in FIG. 16). ing.
[0155]
FIG. 17 shows an outline of the optical scanning device 62 viewed from the direction of arrow A in FIG. The optical scanning device 62 includes a polygon mirror having a regular polygonal prism shape having a side surface (reflecting surface) that is mirror-finished for reflecting laser light, and rotating at a constant speed in the direction of the arrow (1) in FIG. 24 is provided. In the present embodiment, a case where the number of side surfaces of the polygon mirror 24 is 12 will be described as an example.
[0156]
Further, in the optical scanning device 62, the fθ lens 26 composed of a plano-convex lens and a plano-concave lens with the polygon mirror 24 as the center, and a cylindrical mirror 38 for refracting and reflecting the laser beam to the photosensitive drum 42. Are arranged in order in the vertical direction of FIG.
[0157]
Further, the optical scanning device 62 includes each color (Y, Y) including an LD 72A that emits a laser beam modulated based on each color signal constituting a color image signal and an LD driver (LDD) 72B that drives the LD 72A. M, C, and K) corresponding to the four laser light sources 74Y, 74M, 74C, and 74K are arranged side by side on the left side of FIG. 2 with respect to the polygon mirror 24 (hereinafter, four laser light sources 74Y, 74M, 74C, and 74K are collectively referred to as a laser light source 74). The laser light source 74 may be a laser array that emits a plurality of laser beams as described in the above embodiment.
[0158]
A collimator lens 76 and a half mirror 77 are disposed on the optical axis X of each laser beam emitted from the laser light source 74. These collimator lenses 76 convert the laser light from the laser light source 74 into parallel light beams and condense them to a predetermined beam diameter, and the laser light passes through as condensed light beams. The half mirror 77 reflects a part of the laser light that has passed through the collimator lens 76 and guides it to the MPD 20.
[0159]
Each laser beam emitted from the laser light source 74 passes through the collimator lens 76 and the half mirror 77 and enters the polygon mirror 24. A part of the laser light is reflected by the half mirror 77 toward the MPD 20. The laser beams emitted from the laser light sources 74M and 74C are incident on the polygon mirror 24 via the reflecting mirrors 78 arranged on the respective optical axes X, and thereby the laser beam is emitted. Each laser beam from the light sources 74C and 74K is incident on the polygon mirror 24 from a direction opposite to each other. Similarly, each laser beam from the laser light sources 74M and 74Y is incident on the polygon mirror 24 from a direction opposite to each other. become.
[0160]
The polygon mirror 24 is driven and controlled by a drive control IC 79. The drive control IC 79 is for performing drive control of a motor (not shown) for rotationally driving the polygon mirror 24, and includes a phase locked loop (PLL) 79A, a drive circuit 79B, and an amplifier 79C in order. Connected and integrated circuit.
[0161]
A hall element (not shown) is connected to the phase synchronization controller 79A via an amplifier 79C, and a reference clock signal generator (not shown) that outputs a reference clock signal (CLK) that serves as a reference for the rotational speed of the motor is connected. ing. The phase synchronization control unit 79A includes a phase of a Hall signal output from the Hall element as a signal indicating a rotation frequency of the motor (rotation frequency signal) in order to rotate the motor at a constant speed at a constant speed, A predetermined PLL control signal is output to the drive circuit 79B so that the phase of the reference clock signal from the reference clock signal generator 61 is in a phase locked state with a predetermined phase difference.
[0162]
The drive circuit 79C supplies an excitation current proportional to the signal voltage of the PLL control signal input from the phase synchronization control unit 79A to the stator coil group of the motor.
[0163]
As a result, the motor is controlled to accurately rotate at a constant speed by appropriately increasing / decreasing its rotation speed by PLL control using the reference clock signal and the hall signal. As a result, the polygon mirror 24 is rotated at a constant speed to continuously change the incident angle of the laser beam on each reflecting surface, thereby deflecting the laser beam and sending it to the cylindrical mirror 38 side, along the main scanning direction. The photosensitive drum 42 in each developing unit can be irradiated.
[0164]
Each laser beam incident on the polygon mirror 24 is reflected and deflected by the reflection surface of the polygon mirror 24, passes through the fθ lens 26, and is guided to the corresponding cylindrical mirror 38. Here, the laser light emitted from the laser light sources 74C and 74K is deflected and scanned sequentially in the direction of the arrow (2) in FIG. 17 (CK main scanning direction) by the polygon mirror 24, and the laser light emitted from the laser light sources 74Y and 74M. Are deflected and scanned in order in the direction of arrow (3) in FIG. 17 (YM main scanning direction) by the polygon mirror 24, and bidirectional scanning in opposite directions is performed.
[0165]
The laser light guided to the cylindrical mirror 38 is reflected by the cylindrical mirror 38 and further guided to the exposure scanning position 64 on the drum surface in each of the developing units by the corresponding reflecting mirror 38A. Therefore, the laser beam is scanned at a constant speed on the drum surface by the action of the fθ lens 26. Each optical path of the laser beam is indicated by arrows 80Y, 80M, 80C and 80K.
[0166]
Further, in the optical scanning device 62, there are lasers in the vicinity of the deflection scanning start position in the CK main scanning direction (arrow 2 direction in FIG. 17) and the YM main scanning direction (arrow 3 direction in FIG. 2), respectively. Synchronous detectors (SOS sensors) 82CK and 82YM for detecting laser light to synchronize the timing of main scanning start (Start of Scan; SOS) with light, and for guiding the laser light to the respective SOS sensors 82CK and 82YM Reflecting mirrors 84CK and 84YM are provided. Each of the SOS sensors 82CK and 82YM is provided with a sensor unit that senses laser light. When the laser light is not sensed, a high level signal (hereinafter referred to as H signal) is output to sense the laser light. In this case, a low level signal (hereinafter referred to as L signal) is output.
[0167]
Thus, the SOS signal (C + K) output from the SOS sensor 82CK is output from the laser light source 74C due to the optical path length difference between the laser light from the laser light source 74C and the laser light from the laser light source 74K to the SOS sensor 82CK. The SOS signal (C) based on the detection of the laser light and the SOS signal (K) based on the detection of the laser light from the laser light source 74K are combined in time series. Similarly, the SOS signal (Y + M) output from the SOS sensor 82YM is output from the laser light source 74Y due to the optical path length difference between the laser light from the laser light source 74Y and the laser light from the laser light source 74M to the SOS sensor 82YM. The SOS signal (Y) based on the detection of the laser light and the SOS signal (M) based on the detection of the laser light from the laser light source 74M are combined in time series.
[0168]
When APC control is performed with a single MPD for a plurality of laser light sources as in the above configuration, there may be insufficient time to perform APC control for all laser beams within one scanning period. When a laser light source including a plurality of LDs is used as each laser light source, time is particularly short. In this case, APC control may be executed for each laser light source. That is, in one scanning period, APC control of all laser beams of one laser light source is performed, and in the next scanning period, APC control of all laser beams of other laser light sources is performed. Thus, by assigning a laser light source that performs APC control to each scan, APC control can be reliably performed.
[0169]
As described above, the present invention can also be applied to an image forming apparatus including an optical scanning device including a plurality of laser light sources, and the amount of light can be adjusted with high accuracy, so that a color image with high image quality can be obtained. .
[0170]
In the above embodiment, the case where the light quantity control of a plurality of laser beams is performed by a single MPD has been described. Applicable.
[0171]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to improve the accuracy of light amount adjustment of a light beam, and in particular, the light source that emits a plurality of light beams is provided, and the number of light beams is smaller than the number of light beams. Even when the light amount adjustment of a plurality of light beams is performed by the light receiving element, an effect that the accuracy of the light amount adjustment for each light beam can be improved is obtained.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic configuration of an optical scanning device according to a first embodiment.
FIG. 2 is a schematic view showing a configuration of a laser array according to the first embodiment.
FIG. 3 is a block diagram illustrating a configuration of the image forming apparatus according to the first embodiment.
FIG. 4 is a circuit diagram showing a partial configuration of a light amount control apparatus according to the first embodiment.
FIG. 5 is a time chart for explaining an APC control operation of the image forming apparatus according to the first embodiment;
FIG. 6 is a block diagram illustrating a configuration of an image forming apparatus according to a second embodiment.
FIG. 7 is a time chart for explaining an APC control operation of the image forming apparatus according to the second embodiment.
FIG. 8 is a block diagram illustrating a configuration of an image forming apparatus according to a third embodiment.
FIG. 9A is a top view illustrating a schematic configuration of a shutter mechanism according to a third embodiment. (B) is a side view of (A).
FIG. 10 is a time chart for explaining the operation of initial APC of the image forming apparatus according to the third embodiment.
FIG. 11 is a time chart for explaining an APC control operation of the image forming apparatus according to the fourth embodiment.
FIG. 12 is a time chart for explaining an APC control operation of the image forming apparatus according to the fifth embodiment.
FIG. 13 is a diagram illustrating a schematic configuration of an image forming apparatus according to a sixth embodiment.
FIG. 14 is a diagram illustrating a schematic configuration of an optical scanning device according to a seventh embodiment.
FIG. 15 is a diagram illustrating a schematic configuration of an image forming apparatus according to an eighth embodiment.
FIG. 16 is a diagram illustrating a schematic configuration of an image forming apparatus according to a ninth embodiment.
FIG. 17 is a diagram illustrating a schematic configuration of an image forming apparatus according to a ninth embodiment.
FIG. 18 is a diagram illustrating a schematic configuration of an image forming apparatus according to a conventional example.
FIG. 19 is a time chart for explaining an APC control operation of an image forming apparatus according to a conventional example.
[Explanation of symbols]
10 Optical scanning device
12 Laser array (light emitting means)
16 Collimator lens (scanning means)
19 Photosensitive drum (image carrier)
20 MPD (light detection means)
22 Cylindrical lens (scanning means)
24 Polygon mirror (scanning means)
26 fθ lens (scanning means)
100 Image forming apparatus
102 Controller (switching control means)
104 Image processing apparatus
122 Shutter mechanism (blocking means)
124 Shutter control device
C1-C32 light quantity control device (light quantity control means)
SW1-SW2 changeover switch (switching means)

Claims (8)

The image forming apparatus includes a scanning unit that scans a light beam modulated on the basis of image data on an image bearing member, and forms an image by transferring an image formed on the image bearing member to a recording medium. A light quantity control device for controlling the light quantity of the light beam,
A light emitting means comprising a light emitting section for emitting the light beam;
A light detecting means for detecting the amount of light beam emitted from the light emitting unit;
A light amount control means for controlling the light amount so that the light amount of the light beam becomes a predetermined light amount based on a detection result of the light detection means;
Charge accumulation preventing means for preventing charge from being accumulated in the light quantity detection means at least when light quantity control by the light quantity control means is started;
A light quantity control device comprising: The charge accumulation preventing means includes a switching means for connecting or grounding the light detection means with the light quantity control means, and at least a predetermined period immediately before starting the light quantity control other than the light quantity control period by the light quantity control means. And a switching control means for controlling the switching means to connect the light detection means to the light quantity control means during the light quantity control period. 1. The light quantity control device according to 1. The charge accumulation preventing means includes a switching means for connecting or disconnecting the light detection means to or from the light quantity control means, and at least a predetermined amount immediately before the light quantity control other than the light quantity control period by the light quantity control means is started. And a switching control means for controlling the switching means so that the light detection means is connected to the light quantity control means, and the light detection means is connected to the light quantity control means during the light quantity control period. The light quantity control device according to claim 1. The charge accumulation preventing unit blocks the light beam incident on the light detection unit during a period other than the light amount control period by the light amount control unit, and the light beam is incident on the light detection unit during the light amount control period. The light quantity control device according to claim 1, wherein the light amount control device is a blocking means. 2. The light emitting unit includes a plurality of light emitting units, a plurality of the light amount control units corresponding to the light emitting units, and sequentially performs light amount control by the light amount control unit for each light emitting unit. The light quantity control device according to claim 1. 6. The light quantity control device according to claim 1, wherein a plurality of the light emitting means, the charge accumulation preventing means, the image carrier, and the scanning means are provided for each color. 6. The light quantity control device according to claim 1, wherein a plurality of the image carriers are provided for each color. 8. The light quantity control device according to claim 7, wherein a plurality of the light emitting means are provided for each color.

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