JP2010006069A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out the operation of forming a latent image good in an image forming apparatus which forms the latent image to an effective image area by scanning a light on the effective image area of a latent image carrier using an oscillating deflection mirror face. <P>SOLUTION: The image forming apparatus is equipped with a latent image forming means which scans the light from a light source in a second scan size wider than a first scan size corresponding to the effective image area of the latent image carrier by the deflection mirror face, and a detecting means which detects the scanning light present within the second scan size and out of the first scan size. The deflection mirror face oscillates by a maximum amplitude angle θmax. Given that an amplitude angle of the deflection mirror face corresponding to the detecting means is θs (<θmax) and an amplitude angle of the deflection mirror face corresponding to an effective image area end part is θir (<θs), the latent image formation operation is controlled on the basis of a second detection signal obtained by making the deflection mirror face pass the amplitude angle θs while keeping the light source turned on when moving the deflection mirror face so that an amplitude angle θ of the deflection mirror face approaches the amplitude angle θir from the maximum amplitude angle θmax. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for forming a latent image in an effective image area by scanning a light beam from a light source on an effective image area of a latent image carrier by a vibrating deflection mirror surface. .

  An apparatus that forms a latent image by deflecting a light beam emitted from a light source by a deflector and scanning the beam on a latent image carrier such as a photosensitive drum has been conventionally known. For example, in the image forming apparatus described in Patent Document 1, a semiconductor laser is used as a light source, and a light beam having a light intensity corresponding to an image signal is emitted from the semiconductor laser. The light beam thus subjected to light modulation is deflected by a deflector such as a polygon mirror and then guided to the latent image carrier through an optical element such as a lens to perform main scanning on the latent image carrier. Scan in the direction. As a result, a latent image corresponding to the image signal is formed on the latent image carrier.

  In this image forming apparatus, a light detection sensor such as a photosensor is disposed on the scanning path of the light beam in order to form a good image. That is, the light detection sensor detects that the light beam has scanned the start point side of the scanning path, and the light modulation start timing is adjusted based on the detection result. Thus, the conventional apparatus controls the latent image forming operation by detecting the scanning start point of the light beam.

JP 63-102545 A (page 5, FIG. 1)

  By the way, although the technique which uses a vibration mirror other than a polygon mirror as a deflector is proposed, there exists the following differences with respect to an operating characteristic with the apparatus of patent document 1. FIG. That is, with respect to the light beam deflected by the polygon mirror, the light beam can be moved only in the direction corresponding to the rotation direction of the polygon mirror, and light scanning in the reverse direction is impossible. On the other hand, in the vibrating mirror, the deflecting mirror surface vibrates and the light beam from the light source can be reciprocated in the main scanning direction. Therefore, the latent image formation is favorably performed by controlling the latent image forming operation in consideration of the characteristics of the vibrating mirror, instead of controlling the latent image forming operation by directly applying the technique described in Patent Document 1. Is desired. However, in the past, this point has not been sufficiently considered.

  A vibration mirror manufactured using a micromachining technique has been proposed. In this apparatus, an optical deflector in which a drive coil, a deflection mirror surface and a ligament are integrally formed on a frame is processed using a photolithographic technique and an etching technique on a substrate such as quartz, glass, or silicon. In the oscillating mirror equipped with this optical deflector, when a voltage is applied to the drive coil, the deflection mirror surface oscillates about the oscillation axis substantially orthogonal to the main scanning direction and enters the deflection mirror surface. Deflection of the light beam. Further, in this type of oscillating mirror, in order to widen the scanning area, the frequency of the drive signal applied to the drive coil is substantially matched with the resonance frequency of the oscillating mirror, thereby causing the deflection mirror surface to oscillate in resonance. For this reason, if the resonance frequency fluctuates in accordance with the use environment of the vibrating mirror, for example, a change in temperature, the resonance frequency and the driving frequency do not match, and as a result, the vibration amplitude changes. Therefore, when a vibrating mirror that resonates and vibrates is used, it is particularly important to ensure that the vibrating mirror vibrates reliably and to capture fluctuations in the vibration amplitude for good latent image forming operation. It becomes important. However, in the prior art, sufficient consideration has not been given to these points.

  The present invention has been made in view of the above problems, and uses an oscillating deflection mirror surface to scan a light beam on an effective image area of a latent image carrier to form a latent image in the effective image area. In the present invention, the latent image forming operation is favorably performed.

  In order to achieve the above object, an image forming apparatus according to the present invention converts a light beam from a light source into an effective image area by a latent image carrier having an effective image area having a predetermined width in the main scanning direction and a vibrating deflection mirror surface. The second scanning area wider than the corresponding first scanning area can be scanned in the main scanning direction, and the scanning light beam of the first scanning area is guided to the effective image area to form a latent image in the effective image area. A latent image forming unit that detects a scanning light beam that moves within the second scanning region and out of the first scanning region and outputs a signal; and a drive signal having a predetermined frequency is latent. A control means for controlling the latent image forming operation based on the detection signal and the drive signal output from the detection means and for deflecting based on the drive signal is provided to the image forming means to vibrate the deflection mirror surface at the frequency. The plane surface vibrates at the maximum amplitude angle θmax, the amplitude angle of the deflection mirror surface corresponding to the detection means is θs (<θmax), and the amplitude angle of the deflection mirror surface corresponding to the end of the effective image area is θir (<θs ), The control means passes the amplitude angle θs while turning on the light source when moving the deflection mirror surface so that the amplitude angle θ of the deflection mirror surface approaches the maximum amplitude angle θmax from the amplitude angle θir. While obtaining one detection signal, after confirming the reversing operation of the deflection mirror surface based on the drive signal, the deflection mirror surface is moved so that the amplitude angle θ of the deflection mirror surface approaches the amplitude angle θir from the maximum amplitude angle θmax. The second detection signal is obtained by passing the amplitude angle θs while the light source is turned on, and the latent image forming operation is controlled based on the second detection signal.

  Further, the image forming method according to the present invention provides a latent image carrier having an effective image area of a predetermined width in the main scanning direction and a light beam from a light source to the effective image area by a deflection mirror surface that vibrates at a maximum amplitude angle θmax. The second scanning area wider than the corresponding first scanning area can be scanned in the main scanning direction, and the scanning light beam of the first scanning area is guided to the effective image area to form a latent image in the effective image area. A latent image forming means, and a detection means for detecting a scanning light beam that moves within the second scanning area and out of the first scanning area and outputs a signal. An image forming method for forming a latent image by executing a forming operation, and in order to achieve the above object, the amplitude angle of the deflection mirror surface corresponding to the detecting means is θs (<θmax), and the end of the effective image area Of the deflection mirror surface corresponding to When the amplitude angle is θir (<θs), the drive signal having a predetermined frequency is supplied to the latent image forming means to vibrate the deflection mirror surface at the frequency, and the amplitude of the drive signal has a maximum value. Based on the second step for confirming this, the third step for outputting the detection signal from the detecting means through the amplitude angle θs while the light source is turned on, and the detection signal obtained in the third step after the second step. And a fourth step of controlling the latent image forming operation.

  In these inventions (image forming apparatus and image forming method), a drive signal having a predetermined frequency is applied to the latent image forming means, and the deflection mirror surface vibrates at the frequency. That is, the amplitude angle of the deflection mirror surface increases as the amplitude of the drive signal increases, and the amplitude angle of the deflection mirror surface becomes maximum corresponding to the maximum value of the amplitude of the drive signal. On the contrary, the amplitude angle of the deflection mirror surface decreases as the amplitude of the drive signal decreases. Therefore, information on the vibration state of the deflecting mirror surface can be obtained by monitoring the drive signal. Therefore, the latent image forming operation is not controlled by only the detection signal output from the detecting means, but the latent image forming operation is performed by the detection signal from the detecting means while considering the vibration state of the deflection mirror surface obtained from the drive signal. Is controlling. As a result, the latent image forming operation can be performed satisfactorily.

  As described above, since the deflection mirror surface vibrates in the present invention, for example, the amplitude angle of the deflection mirror surface 651 is changed from θir (the amplitude angle of the deflection mirror surface corresponding to the effective image area) to θmax (the maximum amplitude angle of the deflection mirror surface). In addition, if the light source is turned on while θmax changes to θir, the detection signal is output twice from the detection means. However, the inversion operation of the deflection mirror surface can be confirmed based on the information indicating whether or not the amplitude of the drive signal has reached the maximum value. Accordingly, the latent image forming operation can be controlled based on the detection signal output from the detection means after the drive signal amplitude takes the maximum value, that is, the scanning start point of the light beam, and the apparatus using the polygon mirror as a deflector The latent image forming operation can be satisfactorily controlled similarly to the above. Further, the detection signal for controlling the latent image forming operation is once for one scan, and the controllability can be improved.

  In the above invention, the detection signal is obtained from the detection means in the forward movement period. In this case, after confirming the reversing operation of the deflection mirror surface based on the drive signal, the light source is turned on when the deflection mirror surface is moved so that the amplitude angle θ of the deflection mirror surface approaches the amplitude angle θir from the maximum amplitude angle θmax. The second detection signal can be obtained by passing the amplitude angle θs as it is. Then, by controlling the latent image forming operation based on the second detection signal, the same effect as described above can be obtained. Further, after the first detection signal is output, the light source may be turned off until the amplitude angle θ of the deflection mirror surface reaches the maximum amplitude angle θmax. Thus, by turning off the light source after the detection of the first detection signal, stray light is prevented from being generated at a position outside the first scanning region after the detection of the first detection signal, and ghost generation is effectively suppressed. be able to. As a result, a better latent image can be formed in the effective image area.

  Further, by turning off the light source after the amplitude angle θ of the deflecting mirror surface passes the amplitude angle θs and before reaching the amplitude angle θir, the light source lighting time in the backward movement period can be shortened. As a result, stray light generation can be more effectively suppressed.

  Furthermore, in order to form a latent image satisfactorily, it is desired to confirm that the deflection mirror surface has vibrated well. Therefore, the latent image forming operation may be executed after confirming the vibration operation of the deflection mirror surface based on the first detection signal and the second detection signal. As described above, by using the first and second detection signals, the vibration operation of the deflecting mirror surface can be surely confirmed, and the latent image forming operation can be favorably performed. Note that the latent image forming operation may be stopped when the vibration operation of the deflection mirror surface is not confirmed. Thus, it is possible to reliably prevent an inappropriate latent image forming operation from being executed.

1 is a diagram illustrating a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. FIG. 2 is a main scanning sectional view showing a configuration of an exposure unit in the image forming apparatus of FIG. 1. The figure which shows the scanning area | region of the light beam in the exposure unit of FIG. FIG. 2 is a diagram showing a configuration of an exposure unit and an exposure control unit of the image forming apparatus in FIG. 1. The graph which shows the relationship between a mirror drive signal and the amplitude of a deflection | deviation mirror surface. 6 is a flowchart showing a latent image forming operation in the first embodiment. The timing chart which shows the sensing operation in 1st Embodiment. The figure which shows typically the ON / OFF state of the laser in the sensor vicinity. 10 is a flowchart showing a latent image forming operation in the second embodiment. The figure which shows the sensing operation of the scanning light beam in the modification of 2nd Embodiment. The figure which shows the sensing operation of the scanning light beam in the modification of 3rd Embodiment. FIG. 6 is a diagram showing another embodiment of the image forming apparatus according to the present invention.

  FIG. 1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This image forming apparatus is a so-called four-cycle color printer. In this image forming apparatus, when a print command is given to the main controller 11 from an external device such as a host computer in response to an image formation request from the user, the engine controller 10 responds to the print command from the CPU 111 of the main controller 11. The engine unit EG is controlled to form an image corresponding to the print command on a sheet such as copy paper, transfer paper, paper, and OHP transparent sheet.

  In this engine unit EG, a photosensitive member 2 (corresponding to a “latent image carrier” of the present invention) is provided so as to be rotatable in the arrow direction (sub-scanning direction) in FIG. A charging unit 3, a rotary developing unit 4, and a cleaning unit (not shown) are arranged around the photoconductor 2 along the rotation direction. A charging controller 103 is electrically connected to the charging unit 3 and applies a predetermined charging bias. By applying this bias, the outer peripheral surface of the photoreceptor 2 is uniformly charged to a predetermined surface potential. Further, the photosensitive member 2, the charging unit 3, and the cleaning unit integrally constitute a photosensitive member cartridge, and the photosensitive member cartridge is integrally detachable from the apparatus main body 5.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 2 charged by the charging unit 3. The exposure unit 6 corresponds to the “latent image forming means” of the present invention, and exposes the surface of the photosensitive member 2 with a light beam L in accordance with an image signal to generate an electrostatic latent image corresponding to the image signal. Form. The specific configuration and operation of the exposure unit 6 will be described in detail later.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. That is, in this embodiment, the developing unit 4 is configured as a support frame 40 that is rotatably provided around the axis, and a cartridge that is detachable with respect to the support frame 40, and for yellow that contains toner of each color. A developing unit 4Y, a magenta developing unit 4M, a cyan developing unit 4C, and a black developing unit 4K are provided. Then, based on a control command from the developing device controller 104 of the engine controller 10, the developing unit 4 is rotationally driven and these developing devices 4Y, 4M, 4C, 4K are selectively brought into contact with the photosensitive member 2. Alternatively, when positioned at a predetermined developing position facing each other with a predetermined gap, toner is applied to the surface of the photoreceptor 2 from a developing roller provided in the developing unit and carrying toner of a selected color. As a result, the electrostatic latent image on the photoreceptor 2 is visualized with the selected toner color.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 that is stretched over a plurality of rollers 72, 73, and the like, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction by rotationally driving the roller 73. It has.

  In the vicinity of the roller 72, a transfer belt cleaner (not shown), a density sensor 76 (FIG. 2), and a vertical synchronization sensor 77 (FIG. 2) are arranged. Among these, the density sensor 76 is provided facing the surface of the intermediate transfer belt 71 and measures the optical density of the patch image formed on the outer peripheral surface of the intermediate transfer belt 71. The vertical synchronization sensor 77 is a sensor for detecting the reference position of the intermediate transfer belt 71, and is a synchronization signal output in association with the rotational drive of the intermediate transfer belt 71 in the sub-scanning direction, that is, a vertical synchronization signal. It functions as a vertical sync sensor for obtaining Vsync. In this apparatus, in order to align the operation timing of each part and to accurately superimpose the toner images of the respective colors, the operation of each part of the apparatus is performed by using the vertical synchronization signal Vsync and a horizontal synchronization sensor described later (FIGS. 3 to 5). Is controlled on the basis of a detection signal and a horizontal synchronization signal Hsync output from the signal.

  When transferring a color image to a sheet, each color toner image formed on the photoreceptor 2 is superimposed on the intermediate transfer belt 71 to form a color image and taken out from the cassette 8 one by one. The color image is secondarily transferred onto the sheet conveyed along the conveyance path F to the secondary transfer region TR2.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet, the timing of feeding the sheet to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. Are sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet on which the color image is formed in this way is conveyed to the discharge tray portion 51 provided on the upper surface portion of the apparatus main body 5 via the fixing unit 9 and the discharge roller 82. Further, when images are formed on both sides of the sheet, the sheet on which the image is formed on one side as described above is switched back by the discharge roller 82. As a result, the sheet is conveyed along the reverse conveyance path FR. Then, it is put again on the transport path F before the gate roller 81. At this time, the image is transferred to the surface of the sheet that is in contact with the intermediate transfer belt 71 and transfers the image in the secondary transfer region TR2. The surface is the opposite of the surface. In this way, images can be formed on both sides of the sheet.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing image data given from an external device such as a host computer via the interface 112, and reference numeral 106 is executed by the CPU 101. A ROM for storing calculation data, control data for controlling the engine unit EG, and the like, and a reference numeral 107 are RAMs for temporarily storing calculation results in the CPU 101 and other data.

  3 is a main scanning sectional view showing the structure of the exposure unit provided in the image forming apparatus of FIG. 1, FIG. 4 is a view showing a scanning region of the light beam in the exposure unit of FIG. 3, and FIG. It is a figure which shows the structure of the exposure unit and exposure control part of an apparatus. Hereinafter, the configurations and operations of the exposure unit 6 and the exposure control unit 102 will be described in detail with reference to these drawings.

  The exposure unit 6 has an exposure housing 61. A single laser light source 62 is fixed to the exposure housing 61, and a light beam can be emitted from the laser light source 62. As shown in FIG. 5, the laser light source 62 is electrically connected to a light source driving unit 1021 of the exposure control unit 102. Then, a light source driving signal corresponding to the image signal is given from the light source driving unit 1021 to the laser light source 62. As a result, the laser light source 62 is ON / OFF controlled based on the light source driving signal, and a light beam modulated in accordance with the image data is emitted forward from the laser light source 62. Further, as will be described later, the laser light source 62 is ON / OFF controlled at the end of the scanning region in order to acquire the horizontal synchronization signal Hsync, and at this time, a light beam is emitted forward from the laser light source 62.

  Further, the laser light source 62 emits a light beam for monitoring the light quantity to the rear simultaneously with the emission of the light beam forward. The light beam is received by a sensor 621 provided in the case of the laser light source 62. The sensor 621 includes a photodiode and is electrically connected to the APC circuit unit 1022 of the exposure control unit 102. Therefore, when the laser light source 62 is turned on, an exposure light beam is emitted forward, and at the same time, a rear emission light beam is incident on the sensor 621, and a signal corresponding to the light amount of the light beam is given to the APC circuit unit 1022. It is done. Then, the APC circuit unit 1022 controls the light source driving unit 1021 so that the light amount of the light beam from the laser light source 62 matches the reference light amount by comparing the preset reference light amount and the detected light amount of the sensor 621.

  Further, in the exposure housing 61, a collimator lens 631, a cylindrical lens 632, a deflector 65, a scanning lens are used to scan and expose the light beam from the laser light source 62 onto the surface (not shown) of the photoreceptor 2. 66 is provided. That is, the light beam from the laser light source 62 is shaped into collimated light of an appropriate size by the collimator lens 631 and then incident on the cylindrical lens 632 having power only in the sub-scanning direction Y. Then, by adjusting the cylindrical lens 632, the collimated light is imaged in the vicinity of the deflection mirror surface 651 of the deflector 65 in the sub-scanning direction Y. Thus, in this embodiment, the collimator lens 631 and the cylindrical lens 632 function as the beam shaping system 63 that shapes the light beam from the laser light source 62.

  The deflector 65 is formed by using a micromachining technique in which a micromachine is integrally formed on a semiconductor substrate by applying a semiconductor manufacturing technique, and includes a vibrating mirror that resonates and oscillates. That is, in the deflector 65, the light beam can be deflected in the main scanning direction X by the deflecting mirror surface 651 that resonates and vibrates. More specifically, the deflection mirror surface 651 is pivotally supported around a swing shaft (torsion spring) that is substantially orthogonal to the main scanning direction X, and swings in accordance with an external force applied from the operating portion 652. Swing around the axis. The actuating unit 652 applies an electrostatic, electromagnetic or mechanical external force to the deflecting mirror surface 651 based on the mirror driving signal from the mirror driving unit 1023 of the exposure control unit 102 to cause the deflecting mirror surface 651 to act as a mirror driving signal. (Fig. 6). However, as shown in FIG. 6, the deflecting mirror surface 651 vibrates with a time difference ΔTd from the input of the mirror drive signal. That is, there is a phase shift amount ΔTd between the mirror drive signal and the vibration of the deflecting mirror surface 651, which is stored in advance in the ROM 106. Note that any driving method such as electrostatic attraction, electromagnetic force, or mechanical force may be employed as the driving method by the operating unit 652, and since these driving methods are well known, description thereof is omitted here.

The light beam deflected by the deflecting mirror surface 651 of the deflector 65 is deflected toward the scanning lens 66 at the maximum amplitude angle θmax as shown in FIG. In this embodiment, the scanning lens 66 is configured so that the F values are substantially the same in the entire effective image region IR of the photoreceptor 2. Accordingly, the light beam deflected toward the scanning lens 66 is focused on the effective image area IR on the surface of the photosensitive member 2 through the scanning lens 66 with substantially the same spot diameter. As a result, a line-shaped latent image extending in the main scanning direction X is formed on the effective image area IR of the photosensitive member 2 by scanning the light beam in parallel with the main scanning direction X. In this embodiment, the scanning region (the “second scanning region” of the present invention) SR2 that can be scanned by the deflector 65 is used for scanning the light beam on the effective image region IR as shown in FIG. The scanning area (the “first scanning area” of the present invention) is set wider than SR1. Further, the first scanning region SR1 is located at a substantially central portion of the second scanning region SR2, and is substantially symmetric with respect to the optical axis. Further, the symbol θir in the figure indicates the amplitude angle of the deflection mirror surface 651 corresponding to the end of the effective image region IR, and the symbol θs indicates the amplitude angle of the deflection mirror surface 651 corresponding to the horizontal synchronization sensor described below. Show. That is, the amplitude angles θir, θs, and θmax have the following relationship:
θir <θs <θmax
have.

  In this embodiment, as shown in FIG. 3, both end sides of the scanning path of the scanning light beam are guided to the horizontal synchronization sensors 60A and 60B by the folding mirrors 69a and 69b. These folding mirrors 69a and 69b are arranged at both ends of the second scanning region SR2, and a scanning light beam moving in a position outside the first scanning region SR1 in the second scanning region SR2 is used as a horizontal synchronization sensor. The light is guided to 60A and 60B. A signal is output from the horizontal synchronization sensors 60A and 60B at a timing when the scanning light beam is received by the horizontal synchronization sensors 60A and 60B and passes through the sensor position (amplitude angle θs). The folding mirrors 69a and 69b are disposed substantially symmetrically with respect to the optical axis when the light beam scans the substantial center of the effective image region IR. Therefore, it can be considered that the horizontal synchronization sensors 60A and 60B are arranged substantially symmetrically with respect to the optical axis.

  Scanning light beam detection signals from the horizontal synchronization sensors 60A and 60B are transmitted to the measurement unit 1024 of the exposure control unit 102, and the measurement unit calculates a scanning time for scanning the effective image region IR with the light beam. The scanning time calculated by the measuring unit 1024 is transmitted to the mirror driving unit 1023, and the mirror driving unit 1023 changes the driving condition of the mirror driving signal for driving the deflecting mirror surface 651 in accordance with the transmitted scanning time. It can be set. Further, in this embodiment, the horizontal synchronization sensors 60A and 60B are used as horizontal synchronization reading sensors for obtaining a synchronization signal when the light beam scans the effective image area IR in the main scanning direction X, that is, the horizontal synchronization signal Hsync. It is functioning. Hereinafter, the scanning light beam sensing operation by the sensors 60A and 60B will be described in detail with reference to the drawings.

  FIG. 7 is a flowchart showing a latent image forming operation in the first embodiment of the image forming apparatus according to the present invention. FIG. 8 is a timing chart showing the scanning light beam sensing operation in the first embodiment, and FIG. 9 is a diagram schematically showing the ON / OFF state of the laser in the vicinity of the sensor. Here, the sensor 60A side of the scanning area will be described, but the same applies to the sensor 60B side.

  In this embodiment, the latent image forming operation for one line is completed (step S1), and when the scanning light beam passes through the effective image region IR, the light source drive signal falls to L level and the laser light source 62 is turned off. (Step S2). Thereafter, it is determined whether or not the voltage amplitude of the mirror drive signal has reached a maximum value (step S3). That is, as shown in FIG. 8, when the voltage amplitude of the mirror drive signal reaches the maximum value at the timing tm, the deflection mirror surface 651 performs the reverse operation with a delay of the phase shift amount ΔTd. Therefore, after the determination of “YES” in step S3, the laser light source 62 is turned on after a further time (ΔTd + T4) has elapsed (step S4). That is, as shown in FIG. 8, the extinguishing state is maintained until the amplitude angle of the deflecting mirror surface 651 reaches θs after the elapse of time (T2 + T3 + T4) from the start of extinguishing. Thus, in the first embodiment, the laser light source 62 is turned on after confirming the inversion operation of the deflecting mirror surface 651 based on the drive waveform of the mirror drive signal. The on / off state of the laser light source 62 and the moving state of the deflecting mirror surface 651 at this time (T2 + T3 + T4) will be described in detail with reference to FIGS.

  This time T2 is the time required for the amplitude angle θ of the deflection mirror surface 651 to move from θir to θs. Time T3 is the time required for the amplitude angle θ of the deflecting mirror surface 651 to move from θs to θmax. That is, while the deflection mirror surface 651 is moving so that the amplitude angle θ of the deflection mirror surface 651 approaches the maximum amplitude angle θmax from the amplitude angle θir (the forward movement period), the laser light source 62 is kept off. Yes. Therefore, the deflection angle θ of the deflection mirror surface 651 passes through the amplitude angle θs without emitting a light beam from the laser light source 62 during the forward movement period (T2 + T3). As a result, no detection signal is output from the sensor 60A. That is, in this embodiment, the output of the detection signal from the sensor 60A is prohibited during the forward movement period.

  When the time ΔTd further elapses after the amplitude of the mirror drive signal reaches the maximum value at the timing tm, the amplitude angle θ of the deflecting mirror surface 651 becomes the maximum amplitude angle θmax, and the deflecting mirror surface 651 moves in an inversion operation. The direction is reversed. Then, the deflection mirror surface 651 moves so that the amplitude angle θ of the deflection mirror surface 651 approaches the amplitude angle θir from the maximum amplitude angle θmax. Thus, in the initial stage (time T4) during the reverse movement (return period), the deflection mirror surface 651 moves while the laser light source 62 is turned off.

  When the time (T2 + T3 + T4) has passed since the start of turning off, the light source drive signal rises to the H level, the laser light source 62 is turned on, and APC control (light quantity adjustment) by the APC circuit unit 1022 is started (step S5). . Here, when the deflecting mirror surface 651 is operating well, the light beam from the laser light source 62 is scanned by the deflecting mirror surface 651 and the detection signal Hsync is transmitted at the timing when it passes the sensor position (amplitude angle θs). Output from sensor 60A. In this case, “YES” is determined in the step S6, the process proceeds to a step S7, and the APC control is ended.

  When the time T5 elapses from the start of lighting of the laser light source 62 (step S8), the light source drive signal falls to the L level, and the laser light source 62 is turned off (time T6; step S9). Thereafter, the process returns to step S1, and the next latent image forming operation is started based on the detection signal Hsync. That is, the light source drive signal corresponding to the image signal is supplied from the light source drive unit 1021 to the laser light source 62 in synchronization with the detection signal Hsync, and the laser light source 62 is turned on according to the image signal (time T7). As a result, a latent image corresponding to the image signal is formed in the effective image area IR of the photoreceptor 2.

  If the deflection mirror surface 651 does not vibrate well, “NO” is determined in the step S5. For example, the resonance frequency of the deflector 65 fluctuates with a change in the use environment, resulting in a mismatch between the resonance frequency and the drive frequency. As a result, the vibration amplitude may be greatly reduced. Further, a failure of the deflector 65 may occur. As described above, if the latent image forming operation is performed while the vibration operation of the deflecting mirror surface 651 is in a defective state, the image quality is deteriorated. Therefore, in this embodiment, when the detection signal is not detected (determined as “NO” in Step S6), the light amount adjustment and the latent image forming operation are stopped (Step S10).

  As described above, according to this embodiment, information on the vibration state of the deflecting mirror surface 651 can be obtained by monitoring the mirror drive signal, and the sensors 60A and 60B are taken into consideration while considering the vibration state of the deflecting mirror surface 651. The detection signal from the horizontal sync signal Hsync is used as a horizontal sync signal Hsync, and the latent image forming operation is controlled by the horizontal sync signal Hsync. In particular, in the first embodiment, the latent image forming operation is controlled based on the detection signal Hsync output from the sensors 60A and 60B after the amplitude of the mirror drive signal reaches the maximum value, that is, the scanning start point of the light beam. The latent image forming operation can be satisfactorily controlled similarly to the apparatus using the polygon mirror as a deflector. Further, the detection signal Hsync for controlling the latent image forming operation is once per scan, and the controllability can be improved.

  In addition, the laser light source 62 is turned off during the total of the forward movement period and the initial stage of the backward movement period (T2 + T3 + T4). Also in the backward movement period, the laser light source 62 is turned off after the amplitude angle θ of the deflecting mirror surface 651 passes the amplitude angle θs and before the amplitude angle θir is reached. That is, since the laser light source 62 is turned on only at a timing necessary to obtain one detection signal (horizontal synchronization signal) Hsync after the reversing operation of the deflecting mirror surface 651, stray light is effectively generated. As a result, deterioration in image quality due to the occurrence of ghost can be suppressed.

  By the way, in the first embodiment, the detection signals are prohibited from being output from the sensors 60A and 60B during the forward movement period, but the detection signals are obtained from the sensors 60A and 60B even during the forward movement period. Also good. Hereinafter, the second embodiment will be described with reference to FIGS. 10 and 11.

  FIG. 10 is a flowchart showing a latent image forming operation in the second embodiment of the image forming apparatus according to the present invention. FIG. 11 is a diagram showing a scanning light beam sensing operation in the second embodiment. In the second embodiment, the latent image forming operation for one line is completed (step S11), and when the scanning light beam passes through the effective image region IR, the light source drive signal falls to L level and the laser light source 62 is turned off. (Step S12). Thereafter, the time T2 elapses (step S13), and the light-off state is maintained until the amplitude angle of the deflecting mirror surface 651 reaches θs.

  Then, after the time T2, the light source drive signal rises to H level and the laser light source 62 is turned on (step S14). Here, when the deflection mirror surface 651 vibrates well, the light beam (first light beam) from the laser light source 62 is scanned by the deflection mirror surface 651 and passes through the sensor position (amplitude angle θs). At the timing, the first detection signal H1 is output from the sensor 60A (60B). In this way, the detection signal is obtained from the sensor 60A (60B) in the forward movement period (T2 + T3). If “YES” is determined in the step S15, the process proceeds to a step S16 so that the APC control by the APC circuit unit 1022 is started. That is, the APC circuit unit 1022 controls the light source driving unit 1021 so that the detection signal from the sensor 621 of the laser light source 62 matches the preset reference light amount.

  In this embodiment, in order to continue the APC control, the laser light source 62 is continuously turned on (time T3). For this reason, the detection of the second detection signal and the APC control are executed as follows. That is, after the scanning light beam passes through the sensor 60A (60B), the scanning direction is reversed by the deflecting mirror surface 651 that is reversed at the maximum amplitude angle θmax. Here, also in the second embodiment, as in the first embodiment, it has been detected that the amplitude of the mirror drive signal has reached the maximum value (step S17), and the inversion operation of the deflecting mirror surface 651 has been confirmed. The second detection signal H2 from the sensor 60A (60B) is detected above (step S18). Then, the second detection signal H2 is output from the sensor 60A (60B) at a timing when the scanning light beam (second light beam) moves toward the effective image region IR and passes the sensor position (amplitude angle θs). Therefore, “YES” is determined in the step S18, the process proceeds to a step S19, and the APC control is ended.

  When the time (T3 + T4) elapses from the start of lighting of the laser light source 62 (step S20), the light source drive signal falls to the L level and the laser light source 62 is turned off (time T5; step S21). Thereafter, returning to step S1, the second detection signal H2 is set as the horizontal synchronization signal Hsync, and the next latent image forming operation is started based on the horizontal synchronization signal Hsync. That is, a light source driving signal corresponding to the image signal is given from the light source driving unit 1021 to the laser light source 62 in synchronization with the second detection signal Hsync, and the laser light source 62 is turned on according to the image signal (time T6). As a result, a latent image corresponding to the image signal is formed in the effective image area IR of the photoreceptor 2.

  If the deflection mirror surface 651 does not vibrate well, as in the first embodiment, “NO” is determined in step S15 and step S18, and the latent image forming operation is stopped (step S22).

  As described above, also in the second embodiment, as in the first embodiment, the detection signal H2 output from the sensors 60A and 60B after the amplitude of the mirror drive signal takes the maximum value is used as the horizontal synchronization signal Hsync. Yes. Then, since the latent image forming operation is controlled based on the signal Hsync (H2), that is, the scanning start point of the light beam, the latent image forming operation can be controlled satisfactorily in the same manner as the apparatus using the polygon mirror as a deflector. Can do.

  The first detection signal H1 is detected in addition to the second detection signal H2, and it is confirmed that the deflection mirror surface 651 vibrates well based on these two detection signals H1 and H2, and then the next latent image is obtained. The forming operation is being executed. Therefore, the latent image can be formed reliably with the vibration of the deflecting mirror surface 651 always good. Further, it is possible to detect that a defect has occurred in the deflector 65 based on these detection signals, and when the vibration operation of the deflecting mirror surface 651 is not confirmed, the latent image forming operation is stopped. For this reason, it is possible to reliably prevent an inappropriate latent image forming operation from being executed.

In the second embodiment, the lighting state is maintained after the time T2 has elapsed until the amplitude angle of the deflecting mirror surface 651 becomes smaller than θs in the backward movement period. However, as shown in FIG. 12, for example, the laser light source 62 is turned off after the first detection signal H1 is detected, and thereafter, until the time (T4 + T5) passes and the amplitude angle of the deflecting mirror surface 651 reaches θs. The laser light source 62 may be turned on. That is, the amplitude angle θ of the deflection mirror surface 651 is θs <θ ≦ θmax at a position outside the first scanning region SR1 (amplitude angle θ: θir <θ <θmax).
During this time, the laser light source 62 may be turned off. As a result, the laser light source 62 is turned on only at the timing necessary for the detection of the first and second detection signals H1, H2 by the sensor 60A, while the laser light source 62 is turned off at other timings, so the first scanning region SR1. Generation of stray light at a position outside the range is suppressed, and ghost generation can be effectively suppressed. As a result, a better latent image can be formed in the effective image area IR.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the first and second embodiments, the sensors 60A and 60B are arranged corresponding to each of both end portions of the second scanning region SR2, but the number and arrangement of the sensors are limited to this. It is not a thing. For example, as shown in FIG. 13, the scanning light beam may be detected by a single horizontal synchronization sensor 60C and folding mirrors 69c to 69e.

  In the above embodiment, the vibrating deflection mirror surface 651 is formed by using a micromachining technique. However, the method of manufacturing the deflection mirror surface is not limited to this, and the vibrating deflection mirror surface is used. The present invention can be applied to all image forming apparatuses that deflect a light beam and scan the light beam on a latent image carrier.

  2 ... photosensitive body (latent image carrier), 6 ... exposure unit (latent image forming means), 10 ... engine controller (control means), 60A, 60B, 60C ... horizontal synchronization sensor (detection means), 62 ... laser light source, 651 ... deflection mirror surface, H1 ... first detection signal, H2, Hsync ... horizontal synchronization signal (detection signal), IR ... effective image area, L ... light beam, SR1 ... first scanning area, SR2 ... first scanning area, X: Main scanning direction

Claims (6)

A latent image carrier having an effective image area of a predetermined width in the main scanning direction;
The oscillating deflection mirror surface is configured so that the light beam from the light source can be scanned in the main scanning direction in a second scanning region wider than the first scanning region corresponding to the effective image region. A latent image forming means for guiding a scanning light beam to the effective image area to form a latent image in the effective image area;
Detecting means for detecting a scanning light beam that moves within the second scanning region and at a position outside the first scanning region and outputting a signal;
A drive signal having a predetermined frequency is applied to the latent image forming means to vibrate the deflection mirror surface at the frequency, and the latent image forming operation is controlled based on the detection signal output from the detection means and the drive signal. Control means for
Based on the drive signal, the deflection mirror surface vibrates at a maximum amplitude angle θmax,
When the amplitude angle of the deflection mirror surface corresponding to the detection means is θs (<θmax) and the amplitude angle of the deflection mirror surface corresponding to the end of the effective image area is θir (<θs),
The control means includes
While the deflection mirror surface is moved so that the amplitude angle θ of the deflection mirror surface approaches the maximum amplitude angle θmax from the amplitude angle θir, the first detection signal is obtained by passing the amplitude angle θs while the light source is turned on. ,
After confirming the reversal operation of the deflection mirror surface based on the drive signal, the light source is moved when the deflection mirror surface is moved so that the amplitude angle θ of the deflection mirror surface approaches the amplitude angle θir from the maximum amplitude angle θmax. An image forming apparatus characterized in that the second detection signal is obtained by passing the amplitude angle θs while being lit, and the latent image forming operation is controlled based on the second detection signal.   The image forming apparatus according to claim 1, wherein after the first detection signal is output, the control unit turns off the light source until the amplitude angle θ of the deflection mirror surface reaches a maximum amplitude angle θmax.   3. The image forming apparatus according to claim 1, wherein the control unit turns off the light source until the amplitude angle θ of the deflection mirror surface reaches the amplitude angle θir after the second detection signal is output.   4. The control unit according to claim 1, wherein the control unit executes the latent image forming operation after confirming a vibration operation of the deflection mirror surface based on the first detection signal and the second detection signal. The image forming apparatus described.   4. The image forming apparatus according to claim 1, wherein when the vibration operation of the deflection mirror surface is not confirmed, the control unit stops the latent image forming operation. 5. A latent image carrier having an effective image area of a predetermined width in the main scanning direction and a deflection mirror surface that vibrates at a maximum amplitude angle θmax causes a light beam from the light source to be wider than the first scanning area corresponding to the effective image area. A latent image forming unit configured to be able to scan in the main scanning direction in two scanning regions, and to form a latent image in the effective image region by guiding a scanning light beam of the first scanning region to the effective image region; A latent image forming operation is performed by an image forming apparatus including a detection unit that detects a scanning light beam that moves within the second scanning region and out of the first scanning region and outputs a signal. An image forming method for forming a latent image
When the amplitude angle of the deflection mirror surface corresponding to the detection means is θs (<θmax) and the amplitude angle of the deflection mirror surface corresponding to the end of the effective image area is θir (<θs),
A first step of applying a drive signal having a predetermined frequency to the latent image forming means to vibrate the deflection mirror surface at the frequency;
A second step of confirming that the amplitude of the drive signal has taken a maximum value;
After the second step, a third step of passing the amplitude angle θs while the light source is turned on and outputting a detection signal from the detection means;
An image forming method comprising: a fourth step of controlling a latent image forming operation based on the detection signal obtained in the third step.

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