JP2009128786A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that an optical scanner in which a driving signal for an MEMS device is generated by the detected result of a BD signal has no means to detect the state of a trouble of the MEMS device, and the MEMS device is varied in characteristics due to change with lapse of time or environment such as ambient temperature, humidity or the like, a resonance frequency varies and the performance of optical scanning is deteriorated due to variance in resonance frequency. <P>SOLUTION: The optical scanner composed of a movable element which scans light by oscillation has: a means which generates a signal to drive the movable element; a means which detects the voltage of the signal; and a means which decides the trouble of the movable element on the basis of the detected voltage. The optical scanner composed of a movable element which scans light by oscillation has: a means which detects the resonance frequency of the movable element; a means which generates the signal to drive the movable element on the basis of the detected resonance frequency; and the means which detects the voltage of the generated signal, wherein the frequency of the driving signal is reset on the basis of the detected voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical scanner using MEMS technology.

  Conventionally, a polygon scanner has been widely used as a scanning mechanism of a laser beam scanning device used in a laser-beam printer or the like. The polygon scanner includes a polygonal polygon mirror that is driven to rotate about an axis, and scans the laser beam by sequentially reflecting the laser beam emitted from the laser light source on the reflecting surface of the polygon mirror.

  On the other hand, in recent years, downsizing and cost reduction of devices have been demanded.

  In response to the request, a MEMS optical scanner has been proposed instead of the polygon scanner (Patent Document 1).

  A MEMS optical scanner performs a scanning operation by using mechanical vibrations of a MEMS device using a MEMS technology that realizes miniaturization of various mechanical elements by applying technology in a semiconductor manufacturing process or the like such as silicon.

  Since the above MEMS device uses semiconductor process technology, it can be miniaturized and can be manufactured in a large amount at a time, so that the cost can be reduced.

Among current MEMS optical scanners, there is a MEMS optical scanner that generates a drive signal for a MEMS device based on a detection result of a BD (Beam Detect) signal.
JP 2006-220745 A

  In the optical scanner that generates the drive signal of the MEMS device based on the detection result of the BD signal, when the MEMS device fails, there is a first problem that there is no means for detecting the failure state.

  Further, the MEMS device has a second problem that the characteristics change due to a change with time or an environment such as ambient temperature and humidity, the resonance frequency fluctuates, and the driving efficiency of the MEMS device changes due to the fluctuation.

  As a means for solving the first problem, the optical scanner according to claim 1 is an optical scanner including a light source and a movable piece that scans light by vibration, and a signal that drives the movable piece. Generating means, means for detecting the voltage of the signal, and means for determining failure of the movable piece based on the detected voltage.

  An image forming apparatus according to claim 2 is an image forming apparatus including the optical scanner according to claim 1, and when the movable piece of the optical scanner is determined to be out of order, image formation is stopped. It has the means to make a misprint.

  As a means for solving the second problem, the optical scanner according to claim 3 is an optical scanner including a light source and a movable piece that scans light by vibration, and detects a resonance frequency of the movable piece. Means for generating a signal for driving the movable piece based on the detected resonance frequency, and means for detecting the voltage of the generated signal, and the drive signal based on the detected voltage. The frequency resetting operation is started.

  According to the present invention, in the optical scanner using the MEMS device, when the MEMS device fails in the optical scanner that generates the drive signal of the MEMS device from the detection result of the BD signal, it is possible to detect the failure state. It has the effect of becoming.

  Further, in the optical scanner using the MEMS device, when the resonance frequency fluctuates due to a change in characteristics due to a change over time or an environment such as ambient temperature and humidity, the frequency of the drive signal of the MEMS device can be reset. There is an effect.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  FIG. 2 is a block diagram of the laser beam printer.

  In this laser beam printer, a transfer material cassette 803 is mounted on the lower part of the right side surface of the main unit.

  The transfer material set in the transfer material cassette 803 is taken out one by one by a paper feed roller 804 and fed to the image forming unit by a pair of conveying rollers 805-a and 805-b.

  A transfer conveyance belt 810 that conveys a transfer material is stretched on the image forming unit by a plurality of rotating rollers, and is electrostatically attracted to the transfer conveyance belt 810 at the most upstream portion.

  In addition, the photosensitive drum 811 is linearly arranged so as to face the conveyance surface of the transfer conveyance belt to constitute an image forming unit.

  A developing unit 802 in the image forming unit includes the toner drums 811-C, 811-M, 811-Y, and 811-K, a charger, and a developer.

  A predetermined gap is provided between the charger and the developer in the housing of each of the developing units 802, and the peripheral surface of the photosensitive drum 811 is charged with a predetermined charge from the exposure unit 801 including an optical scanner through the gap. Charge uniformly.

  A MEMS optical scanner is used as the optical scanner.

  The MEMS optical scanner includes a silicon mirror, a magnet, a coil, and the like, and is driven by applying a voltage to the coil.

  The exposure unit 801 exposes the peripheral surface of the charged photosensitive drum 811 according to image information to form an electrostatic latent image, and the developing device transfers toner to the power outage portion of the electrostatic latent image. Toner image (development).

  A transfer member 807 is disposed across the conveyance surface of the transfer conveyance belt.

  The toner image formed on the peripheral surface of each photoconductive drum 811 is absorbed by the charge generated in the transferred transfer material by the transfer electric field formed by the transfer member 807 corresponding to the toner image, and is transferred to the transfer material surface. Transcribed.

  The transfer material onto which the toner image has been transferred is discharged out of the apparatus by a pair of discharge rollers 809-a and 809-b. The transfer / conveying belt 810 may be an intermediate transfer belt configured to temporarily transfer CMYK color toners and then secondarily transfer them onto a transfer material.

  FIG. 1 is a diagram for explaining the configuration of a MEMS optical scanner according to the first embodiment of the present invention. Hereinafter, the first embodiment will be described in detail with reference to FIG.

  The light source 4 is composed of a laser diode or the like, and emits a light beam that is turned on / off in accordance with a laser drive signal generated based on a video signal.

  The light beam emitted from the light source 4 irradiates the vibrating piece 5.

  The vibrating piece 5 is composed of a silicon mirror, a magnet is attached thereto, and is driven by applying a voltage to a coil (not shown).

  At this time, the vibrating piece 5 vibrates while being controlled on the basis of a drive signal such that the light beam reflected by the vibrating piece 5 scans the photosensitive drum 1.

  The drive signal is generated by the drive signal generator 7.

  The detection signal 1 from the detection circuit 6 and the control signal from the control unit 8 are input to the drive signal generation unit 7, and the drive signal generation unit 7 generates a drive signal based on these signals.

  The detection signal 1 is generated by a detection circuit 6 that detects the scanning timing of the light beam based on signals from the BD sensor 2 and the BD sensor 3.

  The voltage of the drive signal generated by the drive signal generator 7 is transmitted to the controller 8 through the voltage signal.

  The control unit 8 monitors the drive signal generation unit 7 through the input voltage signal, and performs failure determination of the resonator element 5 based on the detection result of the voltage.

  Hereinafter, an example of determining the failure of the resonator element 5 by detecting the voltage of the drive signal will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a drive signal waveform when it is not determined that the MEMS optical scanner has failed. On the other hand, FIG. 4 is a drive signal waveform when it is determined that the MEMS optical scanner is out of order.

  In the figure, Vref represents the drive signal voltage at the resonance frequency of the resonator element 5 measured in advance. Vref_max represents the maximum allowable voltage of the drive signal voltage, and Vref_min represents the minimum allowable voltage.

  In the above description, when the drive signal voltage exceeds Vref_max or falls below Vref_min, it is determined that the resonator element 5 is in failure.

  Therefore, since the waveform amplitude of the drive signal in FIG. 3 does not exceed the maximum allowable voltage Vref_max and does not fall below the minimum allowable voltage Vref_min, the resonator element 5 is not determined as a failure by the control unit 8.

  On the other hand, in FIG. 4A, since the waveform amplitude of the drive signal exceeds the maximum allowable voltage Vref_max, the vibration piece 5 is determined to be a failure by the control unit 8.

  In FIG. 4B as well, since the waveform amplitude of the drive signal is lower than the minimum allowable voltage Vref_min, the resonator element 5 is determined to be broken by the control unit 8.

  After determining that the resonator element 5 has failed, the control unit 8 causes the drive signal generation unit 7 to generate a drive signal that stops scanning through the control signal. At the same time, a misprint signal is transmitted so as to perform misprint processing to a means for controlling image formation (not shown).

  When the drive signal generation unit 7 receives the scanning stop control signal, the drive signal generation unit 7 generates a drive signal for stopping the vibration of the vibration piece 5 and transmits the drive signal to the vibration piece 5.

  The vibration piece 5 stops the vibration in response to the drive signal.

  As described above, in the first embodiment, in the MEM optical scanner, the voltage of the drive signal generated by detecting the signals from the two BD sensors is detected, and based on the magnitude of the voltage, the vibration piece 5 is detected. Determine failure.

  Further, after the failure determination, the MEMS optical scanner stops scanning, and the laser beam printer can execute misprint processing.

  FIG. 5 is a diagram showing the configuration of the MEMS optical scanner in the second embodiment of the present invention.

  In FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Since the configuration other than the configuration of FIG. 5 is the same as that of the first embodiment, the description other than that of FIG. 5 is also omitted.

  In the first embodiment, the detection signal generated by the detection circuit 6 that detects the scanning timing of the light beam based on the signals from the BD sensor 2 and the BD sensor 3 is input only to the drive signal generation unit 7 as the detection signal 1. Was not.

  In the second embodiment, the detection signal generated by the detection circuit 6 is input not only to the drive signal generation unit 7 but also to the control unit 8 as the detection signal 2.

  With this configuration, when the resonance frequency of the MEMS optical scanner has fluctuated, the fluctuation of the resonance frequency is detected based on the voltage signal from the drive signal generation unit 7, and the detection signal 2 from the detection circuit 6 is detected. Based on the above, the resonance frequency of the resonator element 5 can be calculated and reset.

  When the control unit 8 finishes calculating and resetting the resonance frequency of the resonator element 5, the control unit 8 outputs the result to the drive signal generation unit 7 as a control signal.

  Upon receipt of the control signal, the drive signal generator 7 generates a drive signal at the scanning timing obtained from the detection signal 1 from the detection circuit 6 and outputs the drive signal to the resonator element 5.

  FIG. 6 shows the state of the drive voltage when calculating and resetting the resonance frequency of the resonator element 5 when the resonance frequency of the resonator element 5 has changed.

  When the resonance frequency measured in advance has fluctuated due to an environmental change or the like, the drive voltage becomes higher than the voltage value before the fluctuation of the resonance frequency as shown in FIG. 6 (upper).

  Vref_cal in FIG. 6 is a drive voltage value at the boundary of whether or not the resonance frequency of the resonator element 5 needs to be calculated and reset.

  Specifically, when the drive voltage is equal to or lower than Vref_cal, the resonance frequency of the resonator element 5 is not calculated / reset, and when the drive voltage exceeds Vref_cal, the resonance frequency of the resonator element 5 is calculated / reset.

  Therefore, in FIG. 6 (upper), since the drive voltage exceeds Vref_cal, it is necessary to calculate and reset the resonance frequency of the resonator element 5.

  In the above case, the control unit 8 senses the fluctuation of the resonance frequency through the voltage signal from the drive signal generation unit 7, determines that the fluctuation exceeds a certain level, and detects the detection signal from the detection circuit 6. Based on 2, the resonance frequency is calculated and reset.

  By calculating and resetting the resonance frequency, the drive voltage decreases toward Vref.

  FIG. 6 (middle) and FIG. 6 (bottom) show this state.

  However, in FIG. 6 (middle), since the drive voltage still exceeds Vref_cal, it is necessary to calculate and reset the resonance frequency of the resonator element 5 again.

  The waveform of the drive voltage after resetting the resonance frequency of the resonator element 5 is shown in FIG.

  In FIG. 6 (lower), since the drive voltage is lower than Vref_cal, it is not necessary to calculate and reset the resonance frequency of the resonator element 5.

  As described above, in the second embodiment, in the MEMS optical scanner, the voltage of the drive signal generated by detecting the signals from the two BD sensors is detected, and the magnitude of the voltage fluctuation is larger than a certain level. Can calculate and reset the resonance frequency of the drive signal.

  FIG. 6 is a diagram showing the configuration of the MEMS optical scanner in the third embodiment of the present invention.

  In FIG. 6, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. However, a new code is given only to the BD sensor. Since the configuration other than the configuration of FIG. 6 is the same as that of the first embodiment, the description other than that of FIG. 6 is also omitted.

  The mirror 9 can detect the timing at which the reflected light from the mirror 9 starts scanning on the photosensitive drum 11, and the mirror 10 can detect the timing at which the reflected light from the mirror 10 ends scanning on the photosensitive drum. It is arranged.

  Furthermore, it arrange | positions so that each reflected light of the mirror 9 and the mirror 10 may be irradiated to the BD sensor 11. FIG.

  The detection circuit 6 detects the scan start timing and the scan end timing based on the signal from the BD sensor 11. The detection result is output as a detection signal 1 from the detection circuit 6 to the drive signal generation unit 7.

  As described above, the third embodiment shows that the scanning timing can be detected even in the configuration of the MEMS optical scanner including one BD sensor and two mirrors.

  Since this configuration does not require two BD sensors as in the first embodiment, the overall configuration can reduce the cost compared to the first embodiment.

  This configuration can also be applied to the second embodiment.

  FIG. 7 shows a configuration diagram of the MEMS optical scanner when the present configuration is applied to the second embodiment.

  FIG. 8 is a diagram showing the configuration of the MEMS optical scanner in the fourth embodiment of the present invention.

  In FIG. 8, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. However, a new code is given only to the BD sensor. Since the configuration other than the configuration of FIG. 8 is the same as that of the first embodiment, the description other than that of FIG. 8 is also omitted.

  The detection circuit 6 detects the scanning start timing based on the signal from the BD sensor 12. Subsequently, the scanning end timing is derived from the detected scanning start timing.

  Here, since the vibrating piece 5 is moving at a constant speed, a large amount of calculation is not required in the process of deriving the scanning end timing from the scanning start timing.

  Thereafter, the detection circuit 6 outputs the detected scanning start timing and the derived scanning end timing as the detection signal 1 to the drive signal generation unit 7.

  As described above, the fourth embodiment shows that the scanning timing can be detected even in the configuration of the MEMS optical scanner having only one BD sensor.

  Since this configuration uses only one BD sensor, the reliability is slightly inferior, but it is inexpensive.

  Further, as in the third embodiment, this configuration can also be applied to the second embodiment.

  FIG. 9 shows a configuration diagram of the MEMS optical scanner when the present configuration is applied to the second embodiment.

  FIG. 10 is a diagram in which the configuration of the fourth embodiment is applied to the configuration of the second embodiment.

It is a figure explaining the structure of the MEMS optical scanner in the 1st Example of this invention. It is a figure of the laser beam printer in connection with this invention. It is a drive signal waveform diagram when the MEMS optical scanner is operating normally. It is a drive signal waveform diagram when it is determined that the MEMS optical scanner is operating abnormally. It is a figure explaining the structure of the MEMS optical scanner in the 2nd Example of this invention. It is a figure showing the mode of calculation / resetting of the resonant frequency of the MEMS optical scanner in the 2nd Example of this invention. It is a figure explaining the structure of the MEMS optical scanner in the 3rd Example of this invention. It is the figure which applied the structure of the 3rd Example to the structure of the 2nd Example. It is a figure explaining the structure of the MEMS optical scanner in the 4th Example of this invention. It is the figure which applied the structure of the 4th Example to the structure of the 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 BD sensor 3 BD sensor 4 Light source 5 Vibrating piece 6 Detection circuit 7 Drive signal generation part 8 Control part 9 Mirror 10 Mirror 11 BD sensor 12 BD sensor

Claims (3)

  In an optical scanner comprising a light source and a movable piece that scans light by vibration, a means for generating a signal for driving the movable piece, a means for detecting the voltage of the signal, and a voltage based on the detected voltage And a means for determining failure of the movable piece.   2. An image forming apparatus comprising the optical scanner according to claim 1, further comprising means for stopping image formation and making misprinting when the movable piece of the optical scanner is determined to be faulty. apparatus.   In an optical scanner including a light source and a movable piece that scans light by vibration, means for detecting a resonance frequency of the movable piece, and means for generating a signal for driving the movable piece based on the detected resonance frequency An optical scanner comprising means for detecting the voltage of the generated signal, and starting a resetting operation of the frequency of the drive signal based on the detected voltage.

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