JP4168865B2 - Laser control apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a laser control device that controls driving of a laser device including a laser light source including a plurality of semiconductor laser light emitting elements, and an image forming apparatus including the laser control device.

  In recent years, in image forming apparatuses such as laser printers, copiers, and facsimile machines, a laser diode and a polygon that scans the laser light in the main scanning direction are provided to form an image by irradiating and exposing a photosensitive drum with laser light. A scanner unit equipped with a mirror or the like uses a laser diode in which a laser device having a laser light source composed of a plurality of semiconductor laser light emitting elements (hereinafter also simply referred to as “semiconductor lasers”) is mounted. It has come to be. By using a laser device composed of a plurality of semiconductor lasers, an image of a plurality of rows can be formed by a single scan, so that the image forming speed can be increased.

  Since the laser diode having the above configuration generally has one laser light monitoring photodiode for a plurality of semiconductor lasers, automatic light quantity control (APC) for setting the laser light quantity of each semiconductor laser to a prescribed light quantity. : Automatic Power Control), it is not possible to energize (turn on) a plurality of semiconductor lasers constituting the laser device at the same time. For this reason, when energization of the laser device is started and started (started up), it is necessary to individually increase the energization current to the semiconductor laser.

  As described above, in a laser device including a plurality of semiconductor lasers, as a method of starting each semiconductor laser, one of the plurality of semiconductor lasers is turned on to gradually increase the amount of light, and the laser light is BD ( It is known that when the sensor is detected by a beam detect), the process shifts to line APC control, that is, the semiconductor laser is started up, and then the other semiconductor laser is turned on to start up (for example, , See Patent Document 1).

The BD sensor receives a laser beam scanned by a polygon mirror and obtains a synchronization signal for determining a writing start position of image data, and is in the vicinity of the scanning start position in the scanning range of the laser beam. And a detector that outputs a synchronization signal (hereinafter referred to as “BD signal”) when the amount of light received by the light receiving element is equal to or greater than a predetermined reference amount of received light. This reference amount of received light is the amount of light necessary to expose at least the photosensitive drum to form an electrostatic latent image.
Japanese Patent Laid-Open No. 10-166649

  However, in the method disclosed in Patent Document 1, although the BD signal is detected when the semiconductor laser is initially turned on, the process shifts to line APC control. However, the BD signal is detected for the semiconductor laser that is subsequently turned on. The process is shifted to the line APC control after a predetermined time has elapsed.

  If this elapsed time is set to be the same as the time required for the first semiconductor laser from the start of lighting until the BD signal is detected, for example, the semiconductor laser does not stand up within that time, and the amount of laser light reaches the reference light reception amount. There is a possibility that the image forming process is started in such a state that some lines are printed at a light density in the first part of the recording medium such as printing paper.

  Therefore, in order to reliably start up a semiconductor laser that will be turned on later, it is necessary to set a lighting time that allows for a certain margin. By taking such a margin, the entire laser device can be started up. The time required for this becomes long, and as a result, the time until the start of printing on the recording medium becomes long.

  Further, no matter how long the margin is expected, since the BD signal is not detected, there is no reliable guarantee that the semiconductor laser has started up. For this reason, even if an abnormality occurs in the semiconductor laser and it is in a state in which it cannot be started up, there is a possibility that it will shift to a printing operation without being detected and a good printing result may not be obtained.

  The present invention has been made in view of the above problems, and provides a laser control apparatus capable of reliably starting a laser apparatus including a plurality of semiconductor lasers in a short time, and an image forming apparatus including the laser control apparatus. With the goal.

  The laser control device according to claim 1, which has been made to solve the above problem, detects a part of the laser light from each of the laser devices including a laser light source including a plurality of semiconductor laser light emitting elements and each semiconductor laser light emitting element. One first light quantity detecting means for outputting a signal corresponding to the light quantity, an energization driving means provided for each semiconductor laser light emitting element to energize each semiconductor laser light emitting element, and a laser beam from the laser light source Is provided at a predetermined position in a scanning range in which the laser light from the laser light source is scanned by the scanning means, and the laser light is received according to the amount of light received. Based on the output signal from the second light quantity detecting means and the second light quantity detecting means for detecting the received light of the laser beam when the received light quantity is equal to or greater than a predetermined reference received light quantity. Scanning detection means for outputting a scanning detection signal indicating that the scanning of the laser beam by the means has been detected, and activation detection means for energizing the corresponding laser device to each energization driving means, Prepare.

  The energization driving means performs energization control for controlling the energization current so that the laser beam becomes a predetermined light quantity set in advance based on an output signal from the first light quantity detection means. Regardless of the output signal from the means, the energization current is gradually increased to reach the predetermined light amount, and the energization is temporarily stopped and energized again during the energization current increase period from the start of energization until the predetermined light amount is reached. Energization is started with a current that is at least equal to or greater than the energization current value at the time of the temporary stop and equal to or less than the energization current value corresponding to the predetermined light amount.

  The start detection means starts energization to the corresponding semiconductor laser light emitting element to each energization driving means so that a plurality of semiconductor laser light emitting elements are not simultaneously turned on when energization to the laser device is started. When a scanning detection signal is output from the scanning detection means to the laser light from the laser light emitting element, the energization driving means corresponding to the semiconductor laser light emitting element is temporarily stopped energizing the semiconductor laser light emitting element. Thus, it is determined that the laser device has been activated when a scanning detection signal for the laser beam is output for all the semiconductor laser light emitting elements.

  In the laser control apparatus having the above-described configuration, the amount of laser light from each semiconductor laser light emitting element gradually increases when the activation detection unit starts energizing each energization driving unit. At this time, energization to other semiconductor laser light emitting elements is temporarily stopped while one semiconductor laser light emitting element is energized. That is, energization of each semiconductor laser light-emitting element is performed so that the plurality of semiconductor laser light-emitting elements are not turned on simultaneously.

  When a scanning detection signal is output with respect to the laser beam from any one of the semiconductor laser light emitting elements, energization to the semiconductor laser light emitting element is temporarily stopped, and the remaining semiconductor laser light emitting elements are continuously energized in the same manner. And every time the scanning detection signal is output, the energization to the light emitting semiconductor laser light emitting element is temporarily stopped. In this way, when the scanning detection signal is output for the laser light from all the semiconductor laser light emitting elements, it is determined that the laser device has been activated. The predetermined amount of light is at least equal to or greater than the amount of light from the laser light source when the amount of light received by the second light amount detection means becomes the reference amount of light received.

  Therefore, according to the laser control device of the first aspect, all the semiconductor laser light emitting elements constituting the laser device are configured such that each energization driving unit energizes the corresponding semiconductor laser light emitting element to gradually increase the amount of light. Since it is determined that the laser device is activated when the scanning detection signal is output for each of the laser beams from the laser beam, the laser device can be started up reliably in a short time.

  Here, various methods of individually energizing a plurality of semiconductor laser light emitting elements are conceivable. For example, as in claim 2, each energization driving means sequentially has one corresponding semiconductor laser light emitting element as its laser. You may make it energize until a scanning detection signal is output with respect to light.

  That is, in the laser control device according to claim 2, when the start detection unit starts energizing the laser device, the energization driving unit corresponding to any one of the semiconductor laser light emitting elements is connected to the semiconductor laser light emitting element. Energization is started, and when the scanning detection signal is output from the scanning detection means to the laser light from the semiconductor laser light emitting element, the energization is temporarily stopped, and thereafter, the other semiconductor laser light emitting elements are sequentially sequentially turned on one by one. The energization by the corresponding energization driving means is started one by one, and when the scanning detection signal is output from the scanning detection means for the laser light, the energization is temporarily stopped, and the laser light from all the semiconductor laser light emitting elements is If the scanning detection signal is output, it is determined that the laser device has been activated.

  According to the laser control device having the above configuration, the plurality of semiconductor laser light emitting elements are sequentially energized one by one until the scanning detection signal is output, so that the entire laser device is finally activated. The raising can be performed reliably in a short time.

  Further, as a method of individually energizing a plurality of semiconductor laser light emitting elements, for example, as described in claim 3, each semiconductor laser light emitting element may be energized alternately and repeatedly. That is, in the laser control device according to the third aspect, when the start detection unit starts energizing the laser device, each energization driving unit alternately energizes the corresponding semiconductor laser light emitting element alternately. When a scanning detection signal is output from the scanning detection means to the laser light from one semiconductor laser light emitting element, energization to the semiconductor laser light emitting element is temporarily stopped, and thereafter, each of the other semiconductor laser light emitting elements is sequentially turned on. The energization is performed by the corresponding energization driving means one by one and once the scanning detection signal is output from the scanning detection means to the laser light, the energization is temporarily stopped, and the laser light from all the semiconductor laser light emitting elements is When the scanning detection signal is output, it is determined that the laser device is activated.

  That is, in the laser control device according to claim 2, when energization is started for one of the semiconductor laser light emitting elements for the first time, the other semiconductor laser light emission is performed until it starts up (until the scanning detection signal is output). The laser control device of the present invention (claim 3) does not energize the element, but the semiconductor laser light emitting element until the scanning detection signal is first output to any one of the semiconductor laser light emitting elements. The energization is alternately and repeatedly performed. And after a scanning detection signal is output with respect to any one semiconductor laser light emitting element, it energizes one by one one by one like the claim 2, and starts.

  Therefore, according to the laser control device of the third aspect, the laser device is activated when the scanning detection signal is output for each of the laser beams from all the semiconductor laser light emitting elements constituting the laser device. Therefore, the laser device can be reliably started up in a short time. In addition, by alternately energizing each semiconductor laser light emitting element until any one of the semiconductor laser light emitting elements starts up first, when any one of the semiconductor laser light emitting elements starts up, the other semiconductor laser light emitting elements are already present. Since the laser light quantity is a certain level, the time until the entire laser device is activated can be further shortened.

  Further, in the laser control device according to claim 3, the energization cycle for each energization drive unit when energizing each energization drive unit alternately and repeatedly is, for example, as described in claim 4. It is preferable that the laser light emitted when the means sequentially energizes the corresponding semiconductor laser light emitting elements is received by the scanning detection means during the energization period.

  In this way, the laser light from each semiconductor laser light emitting element always scans (irradiates) the second light quantity detecting means during the energization period for each cycle when the energization is repeated alternately. When the laser light quantity from any one of the semiconductor laser light emitting elements rises to such a level that it is received by the scanning detection means as a light quantity equal to or greater than the reference light reception quantity, it can be detected more quickly, and the laser device can be made shorter. It becomes possible to start in time.

  By the way, for the semiconductor laser light emitting element whose energization is temporarily stopped due to the output of the scanning detection signal, the energization may be stopped until the entire laser device is activated. Depending on the case, when the energization is temporarily stopped and energized again, an excessive current may flow to the semiconductor laser light emitting element.

  For example, the energization drive unit includes a voltage signal hold unit that holds the voltage signal from the first light quantity detection unit, and controls the energization current value in a direction in which the difference between the held voltage signal and a predetermined reference voltage is eliminated. When the energization is started and the reference voltage value is gradually increased to gradually increase the energization current to the semiconductor laser light emitting element, the voltage signal holding means When configured to hold a signal by charging a capacitor, depending on the configuration, if the semiconductor laser light-emitting element is turned off by stopping energization, the capacitor charging voltage may be discharged and decrease. . In this case, when energization is started again, the difference between the hold voltage and the reference voltage becomes large, and an excessive current may flow through the semiconductor laser light emitting element.

  Therefore, for example, as described in claim 5, the activation detection unit activates the laser device with respect to the already-detected energization drive unit that is the energization drive unit that has temporarily stopped energization due to the output of the scanning detection signal. Until completion, the energization control may be performed by energizing the corresponding semiconductor laser light emitting elements at predetermined intervals. In this case, while any of the detected energization driving means is energized, the energization by the other energization driving means is stopped.

  According to the laser control apparatus having the above-described configuration, the already-detected energization driving unit that has been de-energized once the scan detection signal is output performs energization control at a predetermined cycle even after the deactivation, so that the corresponding semiconductor each time The energization current to the laser light emitting element is controlled to become a current value corresponding to the predetermined light amount, and an excessive current to the semiconductor laser light emitting element can be prevented.

  Further, for example, as described in claim 6, the start detection means is a reference energization drive means that is an energization drive means corresponding to the semiconductor laser light emitting element to which the scan detection signal is first output after energization to the laser device is started. On the other hand, even after the scanning detection signal is output and the energization is temporarily stopped, scanning is performed by energizing for a certain period each time the scanning unit scans the scanning range a plurality of times on the basis of the output timing of the scanning detection signal. Acquisition of the scanning detection signal from the detection unit and energization control may be performed, and while the reference energization drive unit is energized, the energization by other energization drive units may be stopped.

  In this way, the reference energization driving means periodically obtains the scanning detection signal even after the scanning detection signal is output with respect to the laser light from the corresponding semiconductor laser light emitting element, so that the laser device is activated. Thereafter, the scanning position of the laser beam can be grasped based on the scanning detection signal, and a desired laser beam corresponding to the scanning position can be scanned within the scanning range.

  Also, other energization driving means other than the reference energization driving means can operate (synchronized) based on this scanning detection signal, and the laser control apparatus as a whole always performs various operations in synchronization with this scanning detection signal. It becomes possible.

  Next, the invention according to claim 7 is provided for each of the laser control devices according to any one of claims 1 to 6 and each semiconductor laser light emitting element, and is energized by a corresponding energization driving means after the laser device is activated. Modulation means for modulating the current to be generated according to the image data, a photoreceptor on which an electrostatic latent image is formed by scanning the laser light from the laser light source with the scanning means, and a surface formed on the surface of the photoreceptor. The image forming apparatus includes: a developing unit that develops the electrostatic latent image; and a transfer unit that transfers the image developed by the developing unit to a recording medium.

  According to the image forming apparatus having the above configuration, an electrostatic latent image is formed on the surface of the photosensitive member by the laser light from the laser light source controlled by the laser control apparatus according to claim 1. The time from the start of energization to the time when the laser device is activated until the electrostatic latent image is formed can be shortened, and the time until the developed image is transferred to the recording medium Can be shortened.

  Moreover, according to the image forming apparatus of the present invention, it is sufficient to determine the start of the laser device when the scanning detection signal is output for the laser light from each semiconductor laser light emitting element constituting the laser device. An electrostatic latent image can be reliably formed with a sufficient amount of laser light, and a recording medium on which a desired image is recorded reliably can be obtained.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a side sectional view showing an embodiment of a laser printer as an image forming apparatus of the present invention. As shown in FIG. 1, the laser printer 1 of this embodiment includes a feeder unit 4 for feeding a sheet 3 as a recording medium in a main body casing 2 and a predetermined image on the fed sheet 3. An image forming unit 5 and the like for forming are provided.

  The feeder unit 4 includes a paper feed tray 6 that is detachably attached to the bottom of the main casing 2, a paper pressing plate 7 provided in the paper feed tray 6, and one end side end of the paper feed tray 6. With respect to the paper feed roller 8 and the paper feed pad 9 provided above, the paper dust removing rollers 10 and 11 provided on the downstream side in the transport direction of the paper 3 with respect to the paper feed roller 8, and the paper dust removing rollers 10 and 11 And a registration roller 12 provided on the downstream side in the conveyance direction of the sheet 3.

  The sheet pressing plate 7 can stack the sheets 3 in a laminated form, and is supported so as to be swingable at the end far from the sheet feeding roller 8, so that the near end moves up and down. It is made possible, and is biased upward by a spring (not shown) from the back side. Therefore, the sheet pressing plate 7 is swung downward against the urging force of the spring, with the end far from the sheet feeding roller 8 as a fulcrum as the amount of stacked sheets 3 increases. The paper feed roller 8 and the paper feed pad 9 are disposed to face each other, and the paper feed pad 9 is pressed toward the paper feed roller 8 by a spring 13 disposed on the back side of the paper feed pad 9. . The uppermost sheet 3 on the sheet pressing plate 7 is pressed toward the sheet feeding roller 8 by a spring (not shown) from the back side of the sheet pressing plate 7, and the sheet feeding roller 8 and the sheet feeding are rotated by the rotation of the sheet feeding roller 8. After being sandwiched between the pads 9, the sheets are fed one by one. The fed paper 3 is sent to the registration roller 12 after the paper dust is removed by the paper dust removing rollers 10 and 11. The registration roller 12 includes a pair of rollers, and sends the paper 3 to the image forming unit 5 after a predetermined registration.

  The feeder unit 4 further includes a multi-purpose tray 14, a multi-purpose side feed roller 15 and a multi-purpose side feed pad 25 for feeding the sheets 3 stacked on the multi-purpose tray 14. The multi-purpose-side paper feed roller 15 and the multi-purpose-side paper feed pad 25 are arranged so as to face each other, and a spring 25a provided on the back side of the multi-purpose-side paper feed pad 25 is arranged on the multi-purpose side. The paper feed pad 25 is pressed toward the multi-purpose side paper feed roller 15. The sheets 3 stacked on the multi-purpose tray 14 are fed one by one after being sandwiched between the multi-purpose side feed roller 15 and the multi-purpose side feed pad 25 by the rotation of the multi-purpose side feed roller 15. Paper.

The image forming unit 5 includes a scanner unit 16, a process unit 17, a fixing unit 18, and the like.
The scanner unit 16 is provided in the upper part in the main body casing 2, and includes a laser diode LD (not shown in FIG. 1, see FIG. 2), a polygon mirror 19 that is driven to rotate, lenses 20 and 21, reflecting mirrors 22 and 23, and 24, and the like, as indicated by the chain line, the laser beam based on the predetermined image data emitted from the laser emission unit is polygon mirror 19, fθ lens 20, reflection mirrors 22 and 23, cylinder lens 21, reflection mirror. The light is passed or reflected in the order of 24 so as to irradiate the surface of a photosensitive drum 27 of the process unit 17 described later by high-speed scanning.

  The process unit 17 is disposed below the scanner unit 16 and is detachably mounted on the main casing 2. The process unit 17 includes a photosensitive drum 27 as a photosensitive member, a developing cartridge 28 as a developing unit, a scorotron. A mold charger 29, a transfer roller 30 as transfer means, a conductive brush 51, and the like are provided.

  The developing cartridge 28 is detachably attached to the drum cartridge 26, and includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, a toner box 34, and the like.

  The toner box 34 is filled with positively charged non-magnetic one-component toner as a developer. Examples of the toner include polymerizable monomers such as styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate. Polymerized toners obtained by copolymerization by a known polymerization method such as suspension polymerization are used. Such a polymerized toner is spherical and has very good fluidity. Such a toner is blended with a colorant such as carbon black, wax, and the like, and an additive such as silica is added to improve fluidity. The particle diameter is about 6 to 10 μm.

  The toner in the toner box 34 is agitated by an agitator 36 supported by a rotating shaft 35 provided at the center of the toner box 34 and is discharged from a toner supply port 37 opened at a side portion of the toner box 34. . Note that a toner remaining amount detection window 38 is provided on the side wall of the toner box 34 and is cleaned by a cleaner 39 supported by the rotary shaft 35.

  A supply roller 33 is rotatably disposed at a side position of the toner supply port 37, and a developing roller 31 is rotatably disposed so as to face the supply roller 33. The supply roller 33 and the developing roller 31 are in contact with each other in a state where each of them is compressed to some extent.

  The supply roller 33 has a metal roller shaft covered with a roller made of a conductive foam material. The developing roller 31 has a metal roller shaft covered with a roller made of a conductive rubber material. More specifically, the roller part of the developing roller 31 has a urethane rubber or silicone rubber coating layer containing fluorine on the surface of a roller body made of conductive urethane rubber or silicone rubber containing carbon fine particles. It is covered. A predetermined developing bias is applied to the developing roller 31 with respect to the photosensitive drum 27.

  In addition, a layer thickness regulating blade 32 is disposed in the vicinity of the developing roller 31. The layer thickness regulating blade 32 includes a pressing portion 40 having a semicircular cross section made of insulating silicone rubber at the tip of a blade body made of a metal leaf spring material. 28, the pressing portion 40 is configured to be pressed against the developing roller 31 by the elastic force of the blade body.

  The toner discharged from the toner supply port 37 is supplied to the developing roller 31 by the rotation of the supplying roller 33. At this time, the toner is positively frictionally charged between the supplying roller 33 and the developing roller 31, and further developed. The toner supplied onto the roller 31 enters between the pressing portion 40 of the layer thickness regulating blade 32 and the developing roller 31 with the rotation of the developing roller 31, where it is further sufficiently frictionally charged and constant. It is carried on the developing roller 31 as a thin layer.

  The photosensitive drum 27 is rotatably disposed at a side position of the developing roller 31 so as to face the developing roller 31. The photosensitive drum 27 is formed of a positively chargeable photosensitive layer having a drum body grounded and a surface portion made of polycarbonate or the like.

  The scorotron charger 29 is disposed above the photosensitive drum 27 at a predetermined interval so as not to contact the photosensitive drum 27. The scorotron charger 29 is a positively charged scorotron charger that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 27 to a positive polarity. ing.

  The surface of the photosensitive drum 27 is uniformly positively charged by the scorotron charger 29 and then exposed by high-speed scanning of the laser light from the scanner unit 16 to form an electrostatic latent image based on predetermined image data. Is done. Next, the electrostatic latent image formed on the surface of the photosensitive drum 27 when the toner carried on the developing roller 31 and positively charged comes into contact with the photosensitive drum 27 by rotation of the developing roller 31. That is, the surface of the photosensitive drum 27 that is uniformly positively charged is supplied to an exposed portion that is exposed to a laser beam and the potential of the photosensitive drum 27 is lowered, and is selectively carried to be visualized. By means of this, reversal development is achieved.

  The transfer roller 30 is disposed below the photosensitive drum 27 so as to face the photosensitive drum 27, and is rotatably supported by the drum cartridge 26. The transfer roller 30 is an ion conductive type transfer roller in which a metal roller shaft 52 is covered with a roller made of an elastic material to which an ionic substance such as lithium perchlorate is added. The resistance value at 22 ° C. and 50% RH is about 107 to 108.5Ω. According to the transfer roller 30, the sheet 3 can be transported satisfactorily while the electrostatic latent image formed on the photosensitive drum 27 is transferred to the sheet 3.

  The transfer roller 30 is configured such that a predetermined transfer bias is applied to the photosensitive drum 27 by a transfer bias application circuit (not shown) during transfer. Therefore, the visible image carried on the surface of the photosensitive drum 27 is transferred to the sheet 3 while the sheet 3 passes between the photosensitive drum 27 and the transfer roller 30 so as to face the transfer roller 30. .

  The conductive brush 51 is provided on the downstream side of the transfer roller 30 in the rotation direction of the photosensitive drum 27 and on the upstream side of the scorotron charger 29 so as to contact the surface of the photosensitive drum 27. The conductive brush 51 removes paper dust adhering to the surface of the photosensitive drum 27 after the transfer.

  As shown in FIG. 1, the fixing unit 18 is disposed on the downstream side of the process unit 17, and includes a heating roller 41, a pressing roller 42 that presses the heating roller 41, and the heating roller 41 and the pressing roller 42. A pair of transport rollers 43 provided on the downstream side are provided. The heating roller 41 is made of a metal and includes a halogen lamp for heating, and the toner transferred onto the paper 3 in the process unit 17 is passed between the heating roller 41 and the pressing roller 42 while the paper 3 passes between the heating roller 41 and the pressing roller 42. Then, the sheet 3 is transported to the paper discharge path 44 by the transport roller 43. The paper 3 sent to the paper discharge path 44 is sent to the paper discharge roller 45 and is discharged onto the paper discharge tray 46 by the paper discharge roller 45.

  In addition, the laser printer 1 is provided with a reverse conveyance unit 47 in order to form images on both sides of the paper 3. The reverse conveyance unit 47 includes a paper discharge roller 45, a reverse conveyance path 48, a flapper 49, and a plurality of reverse conveyance rollers 50.

  The paper discharge roller 45 includes a pair of rollers and is configured to be able to switch between forward rotation and reverse rotation. As described above, the paper discharge roller 45 rotates in the forward direction when the paper 3 is discharged onto the paper discharge tray 46, but rotates in the reverse direction when the paper 3 is reversed.

  The reverse conveyance path 48 is provided along the vertical direction so that the paper 3 can be conveyed from the paper discharge roller 45 to a plurality of reverse conveyance rollers 50 disposed below the image forming unit 5. The upstream end is disposed near the paper discharge roller 45, and the downstream end is disposed near the reverse conveyance roller 50.

  The flapper 49 is provided so as to be able to swing so as to face a branch portion between the paper discharge path 44 and the reverse conveyance path 48, and the paper reversed by the paper discharge roller 45 by excitation or non-excitation of a solenoid (not shown). 3 is configured to be able to be switched from the direction toward the paper discharge path 44 to the direction toward the reverse conveyance path 48.

  A plurality of reverse conveyance rollers 50 are provided in a substantially horizontal direction above the paper feed tray 6, and the most upstream reverse conveyance roller 50 is disposed near the rear end of the reverse conveyance path 48, and The most downstream reverse conveying roller 50 is provided so as to be disposed below the registration roller 12.

  When images are formed on both sides of the paper 3, the reverse conveying unit 47 is operated as follows. That is, when the sheet 3 having an image formed on one side is sent from the sheet discharge path 44 to the sheet discharge roller 45 by the transport roller 43, the sheet discharge roller 45 rotates forward with the sheet 3 interposed therebetween. The paper 3 is once transported to the outside (the discharge tray 46 side), and when the majority of the paper 3 is sent to the outside and the rear end of the paper 3 is sandwiched between the paper discharge rollers 45, the paper 3 rotates forward. To stop. Next, the paper discharge roller 45 rotates in the reverse direction, and the flapper 49 switches the transport direction so that the paper 3 is transported to the reverse transport path 48, and the reverse transport path 48 in the reverse direction of the paper 3. To be transported. When the conveyance of the paper 3 is completed, the flapper 49 is switched to the original state, that is, the state where the paper 3 sent from the conveyance roller 43 is sent to the paper discharge roller 45. Next, the sheet 3 conveyed in the reverse direction to the reverse conveyance path 48 is conveyed to the reverse conveyance roller 50, reversed from the reverse conveyance roller 50 in the upward direction, and sent to the registration roller 12. The paper 3 conveyed to the registration roller 12 is turned over and sent again to the image forming unit 5 after a predetermined registration, whereby a predetermined image is formed on both sides of the paper 3.

  In the laser printer 1, the toner remaining on the surface of the photosensitive drum 27 after being transferred onto the sheet 3 by the transfer roller 30 is recovered by the developing roller 31, so that the remaining toner is recovered by a so-called cleanerless system. ing. If the toner remaining on the photosensitive drum 27 is collected by such a cleaner-less method, there is no need to provide a cleaning device such as a blade or a waste toner storage means, so that the configuration of the device is simplified, the size is reduced, and the cost is reduced. Can be achieved.

  Next, the scanner unit 16 that scans the surface of the photosensitive drum 27 with laser light will be described with reference to FIG. FIG. 2 is a plan view showing a schematic configuration of the scanner unit 16. Note that the plan view of FIG. 2 displays each component in a planar manner along the path of the laser beam in order to explain the configuration of the scanner unit 16 and the outline of its operation.

  As shown in FIG. 2, the scanner unit 16 of the present embodiment includes a laser diode LD that is a laser light source. The laser light from the laser diode LD is converted into parallel light by a collimator lens 61, and then a cylinder lens. Only the sub-scanning direction is narrowed down by 62 and an image is formed on the side surface of the polygon mirror 19.

  The polygon mirror 19 as scanning means is rotated at high speed in the direction of arrow M by a motor (not shown), and the angle of the laser light is changed by the rotation of the polygon mirror 19, and the main scanning direction ( Scanning is performed at a constant cycle in the direction of arrow L). The laser light reflected by the polygon mirror 19 is subjected to distortion aberration correction by the fθ lens 20, is reflected by the reflecting mirrors 22 and 23 (see FIG. 1), and is narrowed by the cylinder lens 21 only in the sub-scanning direction. The laser light from the cylinder lens 21 is reflected by the reflecting mirror 24 and irradiates the photosensitive drum 27 provided outside the scanner unit 16.

  When the laser beam reflected by the polygon mirror 19 is applied to the reflecting mirror 63, the laser beam is reflected by the reflecting mirror 63 and irradiates the BD sensor 84. The BD sensor 84 includes a photodiode PD2 (see FIG. 4) and outputs a signal corresponding to the amount of received laser light. The BD sensor 84 detects the laser light before the start of scanning in the main scanning direction to detect polygons. It is provided for detecting a synchronization signal synchronized with the rotation speed of the mirror 19. The reflecting mirror 63 and the BD sensor 84 constitute the second light quantity detection means of the present invention. In addition, the configuration in which the laser beam from the polygon mirror 19 is reflected by the reflecting mirror 63 and received is merely an example. For example, a BD sensor 84 is provided at the position of the reflecting mirror 63 to directly receive the light from the polygon mirror 19. Needless to say, it may be.

  The laser diode LD mainly includes a laser device including a laser light source including two semiconductor lasers (first semiconductor laser LD1, second semiconductor laser LD2) (see FIG. 4), and back beams from the two semiconductor lasers LD1, LD2. And a photodiode PD1 (see FIG. 4) as a first light quantity detecting means for detecting the photosensitive drum 27. The photosensitive drum 27 is synchronized with a / BD signal described later by each laser beam from the two semiconductor lasers LD1 and LD2. The top is exposed two lines at a time. A schematic configuration example of the laser diode LD is as shown in FIG.

  As shown in FIG. 3, the laser diode LD of the present embodiment includes a base 73 provided on one surface of a stem 72, and a laser device (laser chip) 74 having light emitting points 74a and 74b on the base 73 and a photo. The diode PD1 is fixed. Two semiconductor lasers LD1 and LD2 are formed in the laser device 74. Of these, the laser light from the first semiconductor laser LD1 emits from the light emitting point 74a, and the laser light from the second semiconductor laser LD2 emits from the light emitting point. Light is emitted from 74b.

  A cap 76 is attached to the stem 72 so as to cover the base 73 on which the laser device 74 and the photodiode PD1 are placed, and a window through which the laser beams (front beams) L1 and L2 pass is provided at the front end surface of the cap 76. 77 is provided. The photodiode PD1 receives the back beams L1-b and L2-b. On the other hand, an energization terminal 78 for connecting the laser device 74 and the photodiode PD1 to the laser control device (see FIG. 4) is provided on the opposite surface of the stem 72.

  Drive control of the two semiconductor lasers LD1 and LD2 constituting the laser diode LD in the laser printer 1 of the present embodiment configured as described above will be described with reference to FIG. FIG. 4 is a schematic block diagram showing the laser control apparatus of the present embodiment. The CPU 80 plays a central role in the overall control, and various types for controlling energization to the two semiconductor lasers LD1 and LD2 in accordance with various commands from the CPU 80. The ASIC 81 that generates and outputs a control signal, and the first laser control unit 82 that controls the energization of the first semiconductor laser LD1 out of the two semiconductor lasers LD1 and LD2 constituting the laser diode LD, and the second semiconductor laser LD2 A second laser control unit 83 that controls energization, the BD sensor 84 described above for detecting a synchronization signal, an amplification circuit 85, and an AD conversion circuit 86 are provided.

  As shown in the figure, the electrical connection of the laser diode LD is such that the cathodes of the semiconductor lasers LD1 and LD2 and the cathode of the photodiode PD1 are both grounded. On the other hand, the anode of the first semiconductor laser LD1 is connected to the high-speed modulation circuit 87 in the first laser control unit 82, and the anode of the second semiconductor laser LD2 is connected to the high-speed modulation circuit 93 in the second laser control unit 83. The anode of the photodiode PD1 is connected to the switch 92 in the first laser control unit 82 and the switch 98 in the second laser control unit 83, and is connected to the ground potential via the resistor R1.

  As shown in FIG. 2, the BD sensor 84 receives laser light from each of the semiconductor lasers LD1 and LD2, and includes a photodiode PD2 that is a light receiving element. Specifically, the anode of the photodiode PD2 is grounded, and the cathode is pulled up to the power supply voltage Vcc via the resistor R2. The cathode potential (that is, the voltage across the photodiode PD2) is input as a signal corresponding to the amount of received laser light.

  A signal (voltage signal) corresponding to the amount of received light is amplified by the amplification circuit 85 at a predetermined amplification factor, and then converted into digital data by the AD conversion circuit 86 to be scanned by the scanning detection unit 81b in the ASIC 81 (the present invention). The scanning detection means). The scanning detection unit 81b compares the input digital data with the digital data corresponding to the reference light reception amount stored therein, and when the input digital data is greater than or equal to the reference light reception amount, the L level BD signal. (/ BD signal; "/" indicates negative logic). This / BD signal is input to the control unit 81a as a synchronization signal (scanning detection signal of the present invention) and used for synchronization of various controls in the control unit 81a. The reference received light amount is the amount of light necessary to expose at least the photosensitive drum 27 to form an electrostatic latent image. That is, when the amount of light received by the BD sensor 84 is equal to or greater than the reference amount of light received, an L level / BD signal is output.

  The control unit 81a (corresponding to the activation detection unit of the present invention) in the ASIC 81 controls each of the first laser control unit 82 and the second laser control unit 83 in accordance with an instruction from the CPU 80, whereby each semiconductor laser at the start of printing. It controls the energization (lighting) of the semiconductor lasers LD1 and LD2 during the start-up of LD1 and LD2 and the printing operation after the start-up. However, the following description will focus on controlling the start-up of each of the semiconductor lasers LD1 and LD2 necessary for shifting to the printing operation among various controls by the control unit 81a.

  Next, the first laser control unit 82 that controls the energization to the first semiconductor laser LD1 among the laser control units 82 and 83 that control the energization to the semiconductor lasers LD1 and LD2 will be described. As shown in the figure, the first laser controller 82 includes an LD drive current control circuit 88 that controls the value of the energization current to the first semiconductor laser LD1, and an ASIC 81 that supplies the energization current controlled by the LD drive current control circuit 88. A high-speed modulation circuit 87 as a modulation means for performing high-speed modulation with print data 1 (/ DATA1 signal; image data of the present invention) from the control unit 81a, and an enable signal 1 (/ ENB1 signal) from the control unit 81a. Accordingly, the electrical connection between the LD control enable circuit 89 that outputs a signal for permitting / disallowing energization of the first semiconductor laser LD1 and the anode of the photodiode PD1 and the peak hold circuit unit 91 is turned on / off. And the peak value of the output signal (voltage signal) from the photodiode PD1 when the switch 92 is on It includes a peak hold circuit 91 for holding, an error amplifier 90 for amplifying a difference between a predetermined reference voltage value Vref and the peak value held by the peak hold circuit 91, a.

  When the L level / ENB1 signal is input from the control unit 81a, the LD control enable circuit 89 outputs to the LD drive current control circuit 88 a signal that permits energization of the first semiconductor laser LD1. Receiving this, the LD drive current control circuit 88 supplies a current corresponding to the signal from the error amplifier 90 to the first semiconductor laser LD1 side. Specifically, the energization current value is controlled in such a direction that the output from the error amplifier 90 becomes 0 (that is, the peak value held by the peak hold circuit unit 91 is equal to the reference voltage value Vref in the error amplifier). APC control is performed. Thus, the laser light amount is controlled to be a predetermined light amount set in advance. However, even if the / ENB1 signal is at the L level, the first semiconductor laser LD1 is not energized when the / DATA1 signal is at the H level (that is, when there is no print data).

  The peak hold circuit unit 91 includes, for example, two sets of voltage follower circuits for converting input and output impedances, and a capacitor connected between each voltage follower circuit for holding the peak value. It has a typical structure. However, in the present embodiment, the charging voltage (peak value) of the capacitor is not always maintained accurately, and a discharging circuit using a resistor or the like for gradually discharging is provided. If the peak value is always held as it is without providing a discharge circuit, the smaller value is not reflected even if a smaller value is subsequently input to the peak value held at a certain timing. (It is not held). By providing the discharge circuit, when the peak value is held at a certain timing and then the switch 92 is turned off, the peak value, that is, the charging voltage of the capacitor is gradually reduced although it is slight. When the switch 92 is turned on again, the output voltage value is held as a peak value unless the output voltage of the photodiode PD1 at that time is lower than the capacitor charging voltage value.

  The switch 92 is controlled by a control signal from the control unit 81a and is turned on when the first semiconductor laser LD1 is turned on to perform APC control, and an output signal from the photodiode PD1 is input to the peak hold circuit unit 91. Note that a switch 98 provided in a second laser control unit 83, which will be described later, is also controlled by a control signal from the control unit 81a, and is turned on when the second semiconductor laser LD2 is turned on for APC control, and output from the photodiode PD1. The signal is input to the peak hold circuit unit 97.

  That is, during the APC control of the first semiconductor laser LD1, the switch 92 in the first laser control unit 82 is turned on and the switch 98 in the second laser control unit 83 is turned off. On the other hand, during the APC control of the second semiconductor laser LD2, the switch 98 in the second laser control unit 83 is turned on and the switch 92 in the first laser control unit 82 is turned off. Therefore, a signal corresponding to the amount of light of the first semiconductor laser LD1 is input to the peak hold circuit unit 91 in the first laser control unit 82, and the second semiconductor is input to the peak hold circuit unit 97 in the second laser control unit 83. Control is performed so that a signal corresponding to the amount of light of the laser LD2 is input.

  The error amplifier 90 is a well-known amplifier for amplifying the difference between the peak value from the peak hold circuit unit 91 and a predetermined reference voltage value Vref, but in this embodiment, the reference voltage value is always constant at Vref. Instead, when energization of the first semiconductor laser LD1 is started at the start of printing, the voltage is gradually increased from 0 to Vref. This is because if the reference voltage value is always kept constant at Vref, an excessive inrush current flows through the first semiconductor laser LD1 at the start of energization, and the first semiconductor laser LD1 may be destroyed.

  The increase in the reference voltage value at the start of energization continues even if the energization to the first semiconductor laser LD1 is stopped halfway. Therefore, if a relatively long energization stop period is provided after the energization is started, the reference voltage value when energization is resumed is higher than the reference voltage value when energization is stopped. Therefore, the energization current value when energization is resumed in that case is slightly higher than the energization current value when energization is stopped. The reference voltage value Vref is a value such that the laser light amount from the first semiconductor laser LD1 is a predetermined light amount sufficient to reliably form an electrostatic latent image on the surface of the photosensitive drum 27, and is APC controlled. The laser light amount when the output voltage from the photodiode PD1 (the input voltage to the error amplifier 90) is controlled to the reference voltage value Vref corresponds to the digital data input to the scanning detector 81b corresponding to the reference received light amount. More than the amount of laser light for digital data.

  On the other hand, the second laser control unit 83 that controls the energization current to the second semiconductor laser LD2 has basically the same configuration as the first laser control unit 82. That is, the second laser control unit 83 includes an LD drive current control circuit 94 that controls the value of the current supplied to the second semiconductor laser LD 2, and a current value controlled by the LD drive current control circuit 94 in the ASIC 81. According to the high-speed modulation circuit 93 as a modulation means for performing high-speed modulation with the print data 2 (/ DATA2 signal; image data of the present invention) from the control unit 81a, and the enable signal 2 (/ ENB2 signal) from the control unit 81a. An LD control enable circuit 95 that outputs a signal for permitting / disallowing energization of the second semiconductor laser LD2 and a switch for turning on / off the electrical connection between the anode of the photodiode PD1 and the peak hold circuit unit 97 98 and a peak signal holding the peak value of the output voltage from the photodiode PD1 when the switch 98 is on. It includes a hold circuit portion 97, an error amplifier 96 which amplifies the difference between the peak value and the reference voltage value Vref, which is held by the peak hold circuit 97, a.

  When the L level / ENB2 signal is input from the control unit 81a, the LD control enable circuit 95 outputs a signal indicating that energization to the second semiconductor laser LD2 is permitted to the LD drive current control circuit 94. Receiving this, the LD drive current control circuit 94 supplies a current corresponding to the signal from the error amplifier 96 to the second semiconductor laser LD2 side. Specifically, the energization current value is controlled in such a direction that the output from the error amplifier 96 becomes 0 (that is, the peak value held by the peak hold circuit unit 97 is equal to the reference voltage value Vref in the error amplifier). APC control is performed. However, even if the / ENB2 signal is at the L level, the second semiconductor laser LD2 is not energized when the / DATA2 signal is at the H level (that is, when there is no print data). The peak hold circuit unit 91 and the error amplifier 96 have the same configurations as the peak hold circuit unit 91 and the error amplifier 90 in the first laser control unit 82, respectively.

  In the first laser control unit 82, the LD drive current control circuit 88, the error amplifier 90, the peak hold circuit unit 91, and the switch 92 constitute an energization drive unit of the present invention. The LD drive current control circuit 94, the error amplifier 96, the peak hold circuit unit 97, and the switch 98 constitute the energization drive means of the present invention.

  Next, the start-up of the first semiconductor laser LD1 and the second semiconductor laser LD2 before the start of the printing operation by the laser control apparatus of the present embodiment shown in FIG. 4 will be described. For example, when image data created by a terminal device such as a personal computer (not shown) is transmitted to the laser printer 1 together with a print command, the CPU 80 rasterizes the image data and outputs it to the control unit 81a. Based on this, the control unit 81a outputs print data 1 and 2 (/ DATA1, / DATA2). However, the print data 1 and 2 cannot be output immediately after the energization of the semiconductor lasers LD1 and LD2 is started. Before the print data 1 and 2 are actually output, the lasers from the semiconductor lasers LD1 and LD2 are output. It is necessary to raise the light to a light amount sufficient to form an electrostatic latent image on the surface of the photosensitive drum 27 and to acquire a synchronization signal (/ BD signal).

  FIG. 5 is a time chart showing start-up operations of the semiconductor lasers LD1 and LD2 performed by the laser control apparatus of the present embodiment. As shown in the figure, first, the / ENB1 signal to the first laser control unit 82 is set to L level to allow energization to the first semiconductor laser LD1, and dummy data of L level is input as the / DATA1 signal, thereby 1 Energization of the semiconductor laser LD1 is started. As a result, the APC control of the first semiconductor laser LD1 starts, the energization current gradually increases, and the amount of laser light also gradually increases. In the figure, “LD1” represents the laser light amount of the first semiconductor laser LD1, and “LD2” represents the laser light amount of the second semiconductor laser LD2.

  Then, when the / BD signal from the scanning detector 81b becomes L level due to the increase in the laser light amount of the first semiconductor laser LD1, the start-up of the first semiconductor laser LD1 is completed. That is, the amount of laser light from the first semiconductor laser LD1 has increased to such an extent that the photosensitive drum 27 can be sufficiently exposed. In the following description, the fact that the / BD signal becomes L level is also simply referred to as “BD detection”.

  Thus, when BD is detected with respect to the first semiconductor laser LD1, the / DATA1 signal is set to the H level, the energization to the first semiconductor laser LD1 is temporarily stopped, and the energization to the second semiconductor laser LD2 is started. That is, the / ENB2 signal to the second laser control unit 83 is set to L level to allow energization to the second semiconductor laser LD2, and dummy data at L level is input as the / DATA2 signal, whereby the second semiconductor laser is input. Start energization to LD2. As a result, the APC control of the second semiconductor laser LD2 starts, the energization current gradually increases, and the amount of laser light also gradually increases.

  At this time, the first semiconductor laser LD1 that has already started is not stopped energizing until the second semiconductor laser LD2 starts up, but in a predetermined cycle in synchronization with the detected BD (in this embodiment, every two scans). That is, APC control is performed while detecting BD by conducting energization for a short time (every time the polygon mirror 19 performs scanning in the main scanning direction twice). Then, the energization to the second semiconductor laser LD2 is stopped while the energization to the first semiconductor laser LD1 is being performed.

  That is, after the first semiconductor laser LD1 rises, the energization of the second semiconductor laser LD2 is started and basically the second semiconductor laser LD2 is energized continuously, but the first semiconductor laser LD1 is also synchronized with the BD. In order to detect BD by energizing every two scans and performing APC control, the second semiconductor laser LD2 stops energizing during that period.

  When the BD is detected with respect to the laser beam from the second semiconductor laser LD2 by increasing the laser light amount of the second semiconductor laser LD2, the start-up of the second semiconductor laser LD2 is completed. That is, the amount of laser light from the second semiconductor laser LD2 has also increased to such an extent that the photosensitive drum 27 can be sufficiently exposed. As a result, the semiconductor lasers LD1 and LD2 are all started up, and the entire laser device 74 has been started up.

  Note that the detection of the BD for the second semiconductor laser LD2 (detecting that the / BD signal becomes L level) is performed by the first semiconductor laser LD1 because the first semiconductor laser LD1 is energized every two scans. This is done when one scan has elapsed from the energization timing. Further, in the present embodiment, the first semiconductor laser LD1 that starts energization first and completes startup corresponds to both the already-detected energization driving means and the reference energization driving means of the present invention.

  According to the laser printer 1 of the present embodiment described in detail above, the start-up is completed by first energizing the first semiconductor laser LD1 and detecting the BD, and then the second semiconductor laser LD2 Since energization is performed except when the first semiconductor laser LD1 is energized every two scans and the start-up is completed upon detection of the BD, the laser device 74 is started up, and thus the laser diode LD is started up in a short time. It can be done reliably.

  Therefore, it is possible to provide an image forming apparatus that can shorten the time from when a printing instruction is received to when the printing operation is actually started, and in which the photosensitive drum 27 is reliably exposed by the two semiconductor lasers LD1 and LD2. Thus, it is possible to obtain a recording medium on which the image is recorded reliably.

  In addition, the first semiconductor laser LD1 that has first started up maintains its rising state in order to perform APC control at a predetermined cycle (every two scans) and detect BD even after the start-up is completed and energization is temporarily stopped. In addition, the scanning position of the laser beam can be grasped based on the synchronization signal even after the printing operation is started, and a desired laser beam corresponding to the scanning position can be scanned within the scanning range.

[Second Embodiment]
In the first embodiment, first, the first semiconductor laser LD1 is continuously energized to complete the startup, and then the second semiconductor laser is energized to start the startup. In the embodiment, the two semiconductor lasers LD1 and LD2 are repeatedly energized alternately to start up both of them simultaneously.

  That is, the laser printer of this embodiment has the same hardware configuration as that of the laser printer 1 (see FIGS. 1 to 4) of the first embodiment. The difference from the first embodiment is that before the start of the printing operation. Only the starting method of each semiconductor laser LD1, LD2 is used. Therefore, in the following description, the startup method will be described.

  FIG. 6 is a time chart showing start-up operations of the semiconductor lasers LD1 and LD2. As shown in the figure, in the present embodiment, first, the / ENB1 signal to the first laser control unit 82 is set to L level to allow energization to the first semiconductor laser LD1, and dummy data of L level is input as the / DATA1 signal. As a result, energization of the first semiconductor laser LD1 is started. As a result, the APC control of the first semiconductor laser LD1 starts, the energization current gradually increases, and the amount of laser light also gradually increases.

  Here, in this embodiment, continuous energization is not performed until the first semiconductor laser LD1 starts up. When energization is performed for a certain period, the / DATA1 signal is temporarily set to H level to stop energization, and the second semiconductor laser LD2 is energized. Start energization. That is, the / ENB2 signal to the second laser control unit 83 is set to L level to allow energization to the second semiconductor laser LD2, and dummy data at L level is input as the / DATA2 signal, whereby the second semiconductor laser is input. Start energization to LD2. As a result, the APC control of the second semiconductor laser LD2 starts, the energization current gradually increases, and the amount of laser light also gradually increases.

  Also, when the second semiconductor laser LD2 is energized for a certain period, the / DATA2 signal is once set to H level to stop energization, and the energization to the first semiconductor laser LD1 is started again. In this way, when the first semiconductor laser LD1 and the second semiconductor laser LD2 are alternately energized alternately at a constant period in this way, in the present embodiment, the BD is first detected by the laser light from the first semiconductor laser LD1. Is done.

  The first semiconductor laser LD1 is completely started up by this BD detection, and thereafter the first semiconductor laser LD1 performs APC control and BD detection every two scans in synchronization with the BD signal, as in the first embodiment. I do. The second semiconductor laser LD2 is also energized in synchronization with the BD signal. However, when the first semiconductor laser LD1 is not energized and energized in a non-image area in the scanning range, APC control and BD detection are performed.

  In the present embodiment, after the start-up of the first semiconductor laser LD1 is completed, the energization of the second semiconductor laser LD2 is not performed for a while, and the energization is resumed in the non-image region, and the first semiconductor laser LD1 is started from the completion of the start-up. BD is also detected for the second semiconductor laser LD2 after scanning, and the start-up is completed.

  Therefore, according to the laser printer 1 of the present embodiment, as in the first embodiment, since both the first semiconductor laser LD1 and the second semiconductor laser LD2 have completed startup upon detection of the BD, the startup is completed in a short time. Can be done reliably.

  In addition, in the present embodiment, by alternately energizing each of the semiconductor lasers LD1 and LD2 until one of the semiconductor lasers starts up for the first time, when any one of the semiconductor lasers starts up, the other semiconductor lasers are already present. Since the laser light amount is close to a certain level (close to the startup state), it is possible to further shorten the time until both the first semiconductor laser LD1 and the second semiconductor laser LD2 are completely started up.

The embodiment of the present invention is not limited to the above-described embodiment, and it goes without saying that various forms can be adopted as long as it belongs to the technical scope of the present invention.
For example, in each of the above embodiments, the laser diode including the two semiconductor lasers, the first semiconductor laser LD1 and the second semiconductor laser LD2, has been described as an example. However, the laser diode including three or more semiconductor lasers is described. However, the present invention can be similarly applied.

  In the second embodiment, the period when the two semiconductor lasers LD1 and LD2 are alternately energized is arbitrary (constant period), but each time the semiconductor lasers LD1 and LD2 are energized alternately. The period may be such that the BD sensor 84 is always irradiated. That is, when the first semiconductor laser LD1 is first energized, the BD sensor 84 is always irradiated with laser light during the energization period, and then when the second semiconductor laser LD2 is switched to energization, the BD sensor 84 is always activated even during the energization period. Laser light is irradiated. In this way, if the BD sensor 84 is always irradiated during each energization period in the alternate energization, it becomes possible to detect the BD of each of the semiconductor lasers LD1 and LD2 more quickly.

  In each of the above-described embodiments, the case where the present invention is applied to a laser printer has been described as an example. However, the present invention is not limited to a laser printer, and a photosensitive drum is formed by a plurality of semiconductor lasers such as a copying machine and a facsimile. The present invention is applicable to any image forming apparatus configured to form an electrostatic latent image thereon.

It is a sectional side view showing the schematic structure of the laser printer of an embodiment. It is a top view which shows schematic structure of a scanner unit. It is a perspective view which shows schematic structure of a laser diode. It is a schematic block diagram which shows the laser control apparatus of embodiment. 3 is a time chart showing start-up operations of the semiconductor lasers LD1 and LD2 of the first embodiment. It is a time chart which shows the starting operation of the semiconductor lasers LD1 and LD2 of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer, 16 ... Scanner unit, 17 ... Process unit, 19 ... Polygon mirror, 20 ... f (theta) lens, 21, 62 ... Cylinder lens, 22, 23, 24, 63 ... Reflector, 27 ... Photosensitive drum, 28 ... Developing cartridge, 30 ... transfer roller, 31 ... developing roller, 61 ... collimating lens, 74 ... laser device, 81a ... control unit, 81b ... scanning detection unit, 82 ... first laser control unit, 83 ... second laser control unit, 84 ... BD sensor, 85 ... Amplifier circuit, 86 ... AD converter circuit, 87,93 ... High-speed modulation circuit, 88,94 ... LD drive current control circuit, 89,95 ... LD control enable circuit, 90,96 ... Error amplifier, 91, 97: Peak hold circuit section, 92, 98: Switch, LD: Laser diode, LD1: First semiconductor laser, LD2: First Semiconductor laser, PD1, PD2 ... photo diode, R1, R2 ... resistance

Claims (7)

A laser device comprising a laser light source comprising a plurality of semiconductor laser light emitting elements;
One first light amount detecting means for detecting a part of the laser light from each of the semiconductor laser light emitting elements and outputting a signal corresponding to the light amount;
Provided for each semiconductor laser light emitting element to energize each semiconductor laser light emitting element, and control the energization current so that the laser light has a predetermined light quantity set in advance based on the output signal from the first light quantity detecting means The energization control is performed, and at the start of energization, the energization current is gradually increased regardless of the output signal to reach the predetermined light amount, and the energization current from the start of energization until the predetermined light amount is reached. When energization is temporarily stopped during the increase period and then energized again, the energization is started with a current that is at least equal to or greater than the energization current value when the energization is stopped and less than the energization current value corresponding to the predetermined light amount. Energized drive means,
Scanning means for scanning the laser light from the laser light source in a predetermined direction at a constant period;
A second light quantity detecting means provided at a predetermined position in a scanning range in which the laser light from the laser light source is scanned by the scanning means, and receiving the laser light and outputting a signal corresponding to the received light amount; ,
Based on an output signal from the second light quantity detection means, when the received light quantity is equal to or greater than a predetermined reference received light quantity, the received light of the laser light is detected, and the scanning means scans the laser light at the fixed period. Scanning detection means for outputting a scanning detection signal indicating that the
At the start of energization of the laser device, each energization driving means is energized to the corresponding semiconductor laser light-emitting element so that the plurality of semiconductor laser light-emitting elements are not lit simultaneously. When a scanning detection signal is output from the scanning detection means in response to the laser light from the light emitting element, the energization driving means corresponding to the semiconductor laser light emitting element is temporarily stopped from energizing the semiconductor laser light emitting element. Then, activation detection means for determining that the laser device is activated when the scanning detection signal for the laser light is output for all semiconductor laser light emitting elements,
A laser control device comprising: The activation detection means includes
When energization to the laser device is started, the energization driving unit corresponding to any one of the semiconductor laser light emitting elements is energized to the semiconductor laser light emitting element, and laser light from the semiconductor laser light emitting element is emitted. On the other hand, when a scanning detection signal is output from the scanning detection means, the energization is temporarily stopped, and thereafter, the energization by the corresponding energization driving means is sequentially started for each of the other semiconductor laser light emitting elements one by one. When the scanning detection signal is output from the scanning detection means for the laser light, the energization is temporarily stopped, and when the scanning detection signal is output for the laser light from all the semiconductor laser light emitting elements, The laser control device according to claim 1, wherein it is determined that the laser device is activated. The activation detection means includes
At the start of energization of the laser device, each of the energization driving means is energized alternately and repeatedly to the corresponding semiconductor laser light emitting element, and the scanning is performed on the laser light from any one of the semiconductor laser light emitting elements. When the scanning detection signal is output from the detection means, the energization to the semiconductor laser light emitting element is temporarily stopped, and then the other semiconductor laser light emitting elements are sequentially energized one by one by the corresponding energization driving means. When the scanning detection signal is output from the scanning detection means for the laser light, the energization is temporarily stopped, and when the scanning detection signal is output for the laser light from all the semiconductor laser light emitting elements, The laser control device according to claim 1, wherein it is determined that the laser device is activated. The activation detection means includes
The period of each energization drive unit when energizing each energization drive unit alternately and repeatedly, the laser beam when each energization drive unit sequentially energizes the corresponding semiconductor laser light emitting element, respectively, The laser control apparatus according to claim 3, wherein the period is such that light is received by the scanning detection means during the energization period. The activation detection means includes
With respect to the already-detected energization driving means that is the energization driving means that has temporarily stopped energization due to the output of the scanning detection signal, until the start of the laser device is completed, the corresponding semiconductor laser light emitting element is respectively The energization control is performed by energizing at a predetermined cycle, and any energization by other energization driving means is stopped while any of the already detected energization driving means is energizing. The laser control apparatus in any one of -4. The activation detection means includes
After the energization of the laser device is started, the scanning detection signal is output to the reference energization driving unit corresponding to the energization driving unit corresponding to the semiconductor laser light emitting element from which the scanning detection signal is output first, and the energization is temporarily performed. Even after the stop, the scanning detection signal is obtained from the scanning detection unit by energizing the scanning unit for a certain period each time the scanning unit scans the scanning range a plurality of times, based on the output timing of the scanning detection signal. 6. The laser control according to claim 1, wherein energization control is performed, and energization by other energization drive means is stopped while the reference energization drive means is energized. apparatus. A laser control device according to any one of claims 1 to 6;
A modulation unit that is provided for each of the semiconductor laser light-emitting elements and modulates a current supplied by the energization driving unit corresponding to the laser device after startup according to image data;
A photoconductor on which an electrostatic latent image is formed by scanning the laser beam from the laser light source with the scanning unit;
Developing means for developing an electrostatic latent image formed on the surface of the photoreceptor;
Transfer means for transferring the image developed by the developing means to a recording medium;
An image forming apparatus comprising:

Images