JP5451047B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device used in an image forming apparatus such as a laser beam printer. More specifically, the present invention relates to an optical scanning device that deflects and scans laser light using a deflection mirror (hereinafter referred to as a MEMS mirror) manufactured by a micro electro mechanical system technology.

  Conventionally, Japanese Patent Application Laid-Open No. 2005-195869 has been proposed as an optical deflecting device in which a MEMS mirror reciprocates by resonance vibration. An optical deflecting device using a MEMS mirror has the following characteristics compared to an optical deflecting device using a rotating polygon mirror such as a polygon mirror. That is, it is possible to greatly reduce the size of the optical deflecting device, to reduce power consumption, and to prevent the mirror surface from tilting theoretically. In particular, an optical deflecting device having a MEMS mirror manufactured from a Si (silicon) single crystal by a semiconductor process has characteristics such as theoretically no metal fatigue and excellent durability.

  FIG. 14 shows the configuration of an optical scanning device proposed in Japanese Patent Laid-Open No. 2005-195869 (Patent Document 1).

  The laser beam emitted from the laser light source 162 is guided to the MEMS mirror 651 through the collimator lens 631 and the cylindrical lens 632. The MEMS mirror 651 is reciprocated by driving means (not shown) to deflect and scan the laser beam.

  Most of the deflection-scanned laser beam forms an image on the surface to be scanned via the scanning lens 166 and the folding mirror 168, and is used for image writing.

  In addition, a part of the laser beam that has been deflected and scanned is changed in direction by the pre-sensor mirrors 169a and 169b and is incident on the light receiving sensors 160a and 160b, respectively. The incident light is detected by the light receiving sensors 160a and 160b, Output a signal. Reference numeral 161 denotes an optical box to which the various components described above are attached.

Based on the electrical signals output from the light receiving sensors 160a and 160b, the deviation of the resonance frequency of the MEMS mirror 651 and the driving frequency of the driving means (not shown) is monitored, and the driving frequency and amplitude of the driving means (not shown) are changed. Control is performed to obtain a desired deflection operation.
JP 2005-195869 A

  However, in the above conventional example, when the drive of the MEMS mirror 651 is controlled based on the outputs from the light receiving sensors 160a and 160b, the deflection of the laser beam is performed by the reciprocating operation of the MEMS mirror 651. For this reason, the laser beam deflected and scanned is incident twice on each of the light receiving sensors 160a and 160b in one cycle of the reciprocation of the MEMS mirror 651. In this case, the two laser beams incident on each light receiving sensor are scanned in both directions. As described above, when the electrical signal at the timing when the laser beam is incident on the light receiving sensor is used as the control signal in the configuration in which the scanning directions are opposite to each other, the light receiving surface of a general light receiving sensor has a certain width, so The incident angle is different from the position where the laser beam having the opposite direction starts to enter the light receiving surface. In other words, the method of detecting the timing of starting incidence on the light receiving surface detects the laser beam when the deflection angle of the MEMS mirror is different, and there is a problem that accurate detection and control cannot be performed.

  As one solution to this problem, a method using a two-divided sensor can be considered. The two-divided sensor has two light receiving sensors arranged close to each other in the scanning direction, and outputs a signal when the outputs of the two light receiving sensors that are sequentially output as a laser beam passes over them are intersected. Is. Therefore, it is possible to detect a laser beam deflected at the same deflection angle even when the laser beam is scanned from either the left or right direction. However, the two-divided sensor is disadvantageous in that it is more expensive than a normal light receiving sensor.

  In view of the above-mentioned problems, the invention according to the present application is a low-cost laser beam that is deflected and scanned at the same deflection angle even when the laser beam is deflected and scanned bidirectionally by an optical deflector in which the MEMS mirror reciprocates. The purpose is to detect with two light receiving sensors. It is another object of the present invention to provide an optical scanning device that can realize optical scanning at a substantially constant speed in an image region by using a MEMS mirror at a low cost.

  In order to achieve the above object, the invention according to the present application constitutes an optical scanning device as follows.

A laser light source that emits laser light, and a deflector that deflects the laser light emitted from the laser light source and scans the surface to be scanned , the first deflection direction being opposite to the first deflection direction. and reciprocates in a second deflection direction, a deflecting device for deflecting the laser beam emitted from the laser light source, a deflector and a driving device for driving the deflection element, are deflected and scanned by the pre-Symbol deflector receiving the laser beam, possess a light receiving sensor for outputting based thereon, and a controller for controlling the drive of the deflection device according to prior Symbol driving device, a first deflection direction during one cycle of the reciprocating operation of the deflection element in the optical scanning device deflecting the laser beam scanning the surface to be scanned, and, for scanning the surface to be scanned deflects the laser beam in a second deflection direction opposite to the first deflection direction, the controller Said In the period up to before the deflection direction by deflecting the laser beam by deflecting the laser beam in the second polarization direction after scanning the scanning surface for scanning the scanning surface, first by the deflector a first timing which the laser beam that will be deflected and scanned in the deflection direction of output changes of the light receiving sensor by incident light amount is reduced to the photodetection sensor, the deflection in the deflection direction of the second by the deflector a second timing the amount of light the laser light that will be scanned is incident to the light receiving sensor output of the light receiving sensor changes by increasing, for controlling the drive of the deflection device according to the driving device based on.

A laser light source that emits laser light, a deflector that deflects and scans the laser light emitted from the laser light source, a deflection element that reciprocates and deflects the laser light emitted from the laser light source, and the deflection element A deflector having a driving device for driving the laser beam, an imaging lens that forms an image of a laser beam deflected and scanned by the deflector on a surface to be scanned, a holding member that holds the deflection element, and the deflector. a single detection member for detecting the deflection scanning laser beam, one light-receiving sensor for receiving the laser beam deflected and scanned by the deflector, regulatory you regulate the laser light incident on the light receiving sensor in the optical scanning device having a single detection member, a and a section, the restricting portion is formed integrally with the front Symbol holding member, the light receiving sensor is the deflection element of the holding member The side that is fixed is fixed to the opposite side, it is arranged at a position apart than the deflection element relative to the imaging lens.

  As described above, according to the present invention, even when the laser beam is deflected and scanned bidirectionally by the reciprocating operation of the deflecting element, the laser beam when deflected and scanned with the same deflection angle can be accurately measured with an inexpensive configuration. It can be detected well.

  The best mode for carrying out the present invention will be described below in detail based on embodiments with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be changed as appropriate according to the device to which the invention is applied and various conditions. The present invention is not intended to be limited to the following embodiments.

  FIG. 1 is a perspective view showing an optical scanning device according to a first embodiment to which the present invention can be applied. In the figure, 1 is a laser light source unit, 2 is a cylindrical lens, 3 is a reflection mirror that reflects a laser beam before entering the deflection element, and 4 is a MEMS mirror that is a deflection element that deflects and scans the laser beam in the main scanning direction. Reference numeral 5 denotes a scanning lens as an imaging lens. Reference numerals 6a and 6b denote pre-sensor mirrors which are first and second reflecting members arranged one by one near both ends of the scanning lens 5 in the main scanning direction, and 7a and 7b denote pre-sensor lenses. 8 is a light receiving sensor, and 9a and 9b are a first restricting portion and a second restricting portion of a restricting member having a slit disposed in front of the light receiving sensor 8. Reference numeral 10 denotes a MEMS mirror holder as a holding member that holds the MEMS mirror 4, and 11 denotes an optical box that holds the various optical components described above. The MEMS mirror holder 10 holds the MEMS mirror 4 and the light receiving sensor 8, and the MEMS mirror 4, the light receiving sensor 8, the MEMS mirror holder 10, and the like form an integral MEMS mirror unit 12.

  FIG. 2 is an exploded perspective view of the MEMS mirror unit 12. In the figure, 21 is a core made of a material having high magnetic permeability, and 22 is a coil. Here, the core 21 and the coil 22 constitute a drive device that drives the MEMS mirror 4. The core 21 and the coil 22 are fixed to the MEMS mirror holder 10 by adhesion, press fitting, or the like. Reference numeral 23 denotes a permanent magnet, which is fixed to the MEMS mirror 4 by adhesion or the like. Reference numeral 24 denotes an electric circuit board on which the light receiving sensor 8 is mounted, and is fixed to the MEMS mirror holder 10 with a screw or the like (not shown).

  FIG. 3 shows the configuration of the MEMS mirror 4 that is a deflection element. The MEMS mirror 4 is formed by etching a silicon wafer, and includes a first movable element 31, a second movable element 32, an outer frame 33, a pair of first torsion springs 34, and a pair of second torsion springs. It consists of 35. Here, the 1st needle | mover 31 has played the role of the reflective mirror which reflects a laser beam. The first torsion spring 34 connects the first mover 31 and the second mover 32, and the second torsion spring 35 connects the second mover 32 and the outer frame 33. The permanent magnet 23 is fixed to the second movable element 32 by adhesion or the like. Here, the first mover 31, the second mover 32, the first torsion spring 34, and the second torsion spring 35 form a vibration system having two vibration modes, and one of their natural frequencies is the other. It is configured to be approximately doubled.

  4 is a cross-sectional view of the MEMS mirror unit 12 cut along a cutting line AA in FIG. As shown in the figure, a core 21 is disposed at a position facing the permanent magnet 23, and a coil 22 is wound around the core 21. The permanent magnet 23, the core 21, and the coil 22 constitute an electromagnetic actuator. When a current is passed through the coil 22, torque acts on the permanent magnet 23 and the second movable element 32 is driven. Here, the deflector is comprised by the MEMS mirror 4 and the electromagnetic actuator.

  Next, the operation of the present optical scanning device will be described with reference to FIG. FIG. 5 schematically shows an optical system including two restricting portions of the optical scanning device. The laser light source unit 1 emits a laser beam L1 that is substantially parallel or has a desired convergence rate. The laser beam L1 passes through the cylindrical lens 2 and is condensed only in the sub-scanning direction (the normal direction of the paper surface in FIG. 5) that is substantially perpendicular to the main scanning direction. Further, the laser beam L1 whose direction is changed by the reflection mirror 3 is incident on the MEMS mirror 4 as a line image that is long in the main scanning direction. The laser beam is deflected and scanned by the MEMS mirror 4 that is driven to swing back and forth by the electromagnetic actuator described above, and forms an image on the scanned surface S through the scanning lens 5. Further, a part of the laser beam deflected and scanned by the MEMS mirror 4 is incident on the pre-sensor mirrors 6a and 6b, which are two reflecting members respectively disposed in the vicinity of both ends of the scanning lens 5 in the main scanning direction. It is changed and returned to the arrangement side of the MEMS mirror 4. The laser beams reflected by the pre-sensor mirrors 6a and 6b pass through the slit between the first restricting portion 9a and the second restricting portion 9b of the restricting member and enter one light receiving sensor 8. Here, a detection member is constituted by one light receiving sensor 8 and a restricting member having a first restricting portion 9a and a second restricting portion 9b arranged in front of the light receiving sensor 8.

  The deflection scanning of the laser beam is performed by a reciprocating operation by swinging around the rotation axis of the MEMS mirror 4. Therefore, when the laser beam is deflected and scanned in the direction of the arrow F (first deflection direction) at a certain time, the laser beam is incident on the light receiving sensor 8 via the pre-sensor mirror 6a that is the first reflecting member. After the oscillation of the MEMS mirror 4 reaches the maximum swing angle, the deflection direction of the laser beam is reversed, and the laser beam is deflected and scanned in the direction of the arrow R (second deflection direction). Then, a laser beam enters the light receiving sensor 8. Thereafter, the laser beam passes through the region incident on the scanning lens 5 to form the scanning line S on the surface to be scanned, and then enters the light receiving sensor 8 through the pre-sensor mirror 6b which is the second reflecting member. Thereafter, the MEMS mirror 4 reaches the maximum swing angle, the deflection direction is reversed again, and enters the light receiving sensor 8 again via the pre-sensor mirror 6b. Therefore, for each reciprocation of the MEMS mirror 4, the light receiving sensor 8 has four incident laser beams, and the light receiving sensor 8 generates four signal outputs each time. That is, it is possible to detect the incident timing (time) of four times of the laser light beam during one cycle by the reciprocating operation of the MEMS mirror 4.

  In this embodiment, by combining the two frequency components and driving the MEMS mirror 4, optical scanning at a substantially constant angular velocity is realized in the image region (region passing through the scanning lens 5). FIG. 6 shows a controller for controlling the driving of the MEMS mirror 4. In the figure, reference numerals 61 and 62 denote arbitrary waveform generators that generate sine waves of frequencies f (first frequency) and 2f (second frequency). The frequencies f and 2f are frequencies that substantially match the two natural frequencies of the vibration system described above, and in this embodiment, f = 2000 Hz (2f = 4000 Hz) as an example. The phase and amplitude of each sine wave can be arbitrarily changed by a command from the calculation unit 63. The two sine waves generated by the arbitrary waveform generators 61 and 62 are added by the adder 64 and then amplified by the amplifier 65, so that a current flows through the coil 22. The calculation unit 63 controls the phase and amplitude of each sine wave of the arbitrary waveform generators 61 and 62 so that the four signal outputs 66 from the light receiving sensor 8 have a desired time interval. In this way, the controller ensures that the time intervals (four time intervals per cycle) of the laser beam passing through the single light receiving sensor 8 via the pre-sensor mirrors 6a and 6b are each a desired set time. The drive of the drive device is controlled.

  Next, a method for controlling the MEMS mirror 4 of this embodiment will be described in detail.

  The deflection angle θ of the MEMS mirror 4 driven with two frequency components is expressed as follows.

here,
A1: Amplitude of first vibration motion ω1: Angular frequency of first vibration motion φ1: Phase of first vibration motion A2: Amplitude of second vibration motion ω2: Angular frequency of second vibration motion φ2: First Phase t 2 of vibration motion: Indicates a time when an arbitrary time within one cycle of the first vibration motion is used as a reference.

here,
A1 = 1, A2 = 0.2, φ1 = φ2 = 0,
ω1 = 2π × 2000 [Hz], ω2 = 2π × 4000 [Hz]
Then, the deflection angle θ and the angular velocity θ ′ are as shown in FIG. 7A shows the deflection angle θ on the vertical axis and time on the horizontal axis, and FIG. 7B shows the angular velocity θ ′ on the vertical axis and time on the horizontal axis. Represents one period.

  The thick line in FIG. 7A is the deflection operation of the MEMS mirror 4 expressed by Expression (1), and is closer to a sawtooth wave than a sine wave (indicated by a thin line). As shown in FIG. 7B, a substantially constant angular velocity is realized in which a change in angular velocity is smaller than that of a sine wave in a part of an image area (a range of about 0.18 to 0.32 msec in this embodiment). doing.

  In FIG. 7A, reference numerals 71 and 72 respectively denote a light receiving sensor in which the laser beam reflected by the pre-sensor mirrors 6a and 6b passes through the first edge of the first restricting portion 9a or the second edge of the second restricting portion 9b. 8 is a position where the light enters the beam. Here, the angles formed by the positions where the laser light beams are incident on the pre-sensor mirrors 6 a and 6 b before entering the light receiving sensor 8 with respect to the amplitude center of the MEMS mirror 4 are θ 1 and θ 2, respectively.

Here, assuming that the target values for a total of four times during one cycle in which the laser beam enters the light receiving sensor 8 via the pre-sensor mirrors 6a and 6b are t10, t20, t30, and t40, in this embodiment,
t10 = 0.052 msec
t20 = 0.154 msec
t30 = 0.346msec
t40 = 0.448msec
It becomes.

  In actual control, four output times (t1, t2, t3, t4) are periodically monitored during one cycle from the light receiving sensor 8. A1, A2, φ1, and φ2 are changed so that they coincide with the target values t10, t20, t30, and t40 or fall within a predetermined allowable deviation range.

  By performing such control, optical scanning at substantially constant speed is always realized in the image area.

  When a deflection element that reciprocates by resonance vibration as described above is used, a laser beam that is deflected and scanned in both directions during one cycle is incident on the light receiving sensor 8 twice.

  Here, the effect of the edge of the restricting portion will be described. If a single light receiving sensor 8 detects the position at the same deflection angle of a laser beam deflected and scanned in both directions using the MEMS mirror 4 without providing a restricting portion, the light incident on the light receiving surface of the light receiving sensor 8 will be described. It is necessary to detect the start timing and the incident end timing. However, it is very difficult to detect the incident end timing sharply only at the end of the light receiving surface in terms of manufacturing accuracy of the light receiving sensor and its package. For this reason, in the configuration in which the restricting portion is not provided, there is a problem in that the light receiving sensor cannot accurately detect the laser beam when deflected at the same deflection angle. Therefore, in this embodiment, a restricting member having a restricting portion is provided separately from the light receiving sensor, and the light receiving sensor detects the timing at which the laser beam passes through the edge of the restricting portion, thereby deflecting at the same deflection angle. The light receiving sensor can accurately detect the laser beam at that time. Furthermore, when the restricting part is molded from a resin material, it is difficult to spread the resin material cleanly to the ridge line when the angle of the restricting part is 90 degrees or an acute angle during molding, and the ridge line of the restricting part is accurate. There is a problem that it cannot be molded well. Therefore, in this embodiment, the resin material is molded into a shape having a tapered surface so that the angle of the restricting portion becomes an obtuse angle. And the edge shape which has an accurate straight line is obtained by using the one ridgeline which makes the obtuse angle of a taper surface as an edge of a control part. With this configuration, the light receiving sensor detects the timing at which the laser beam deflected by the deflector passes through a highly accurate edge (one ridge line of the tapered surface), so that the incident start timing and the incident end timing are sharply detected. Making it possible. Furthermore, the temperature change can be achieved by arranging the restricting portion so that one edge of the taper surface that is the edge coincides with the direction (sub-scanning direction) perpendicular to the main scanning direction in which the laser beam is deflected by the deflector. Even when the laser beam is shifted in the sub-scanning direction and enters the light receiving sensor due to misalignment of various optical components due to factors such as these, the timing of passing through the edge of the laser beam can be prevented from shifting. As described above, the feature of the present embodiment is the same by using a restricting member having a restricting portion even when a laser beam deflected and scanned in both directions using the MEMS mirror 4 is input to one light receiving sensor 8. That is, the laser beam can be detected by one light receiving sensor 8 twice per one regulating portion when deflected at a deflection angle of 2 mm. Accordingly, it is possible to provide an optical scanning device that can realize optical scanning at a substantially constant speed within the image region by the MEMS mirror at a low cost.

  A detection method using one light receiving sensor 8 and one regulating unit will be described with reference to FIGS. 8 and 9. FIG. 8 schematically shows an optical system including one regulating unit of the present optical scanning device. The difference from the optical system described with reference to FIG. 5 is whether two restriction parts, the first restriction part 9a and the second restriction part 9b, are provided or only one restriction part called the restriction part 9a is provided. Therefore, since the same configuration is used as the optical system other than the restricting portion, the description is omitted. FIG. 9 shows the laser beam before and after passing through the edge of one restricting portion 9a and the output of the light receiving sensor 8 corresponding thereto. 8 is a light receiving sensor, 9a is a restricting portion, 203a and 203b are laser beams, and three beams are described for each laser beam. Among the three light beams, two broken lines are light beams before and after passing through the edge of the restricting portion 9a, and a thick line is a light beam that is detected and calculated as a timing (time) of passing through the edge of the restricting portion 9a, and θa, θa ′ is the incident angle of the laser beam. The lower graph in FIG. 9 is a graph showing the output from the light receiving sensor 8 over time, with the horizontal axis representing time and the vertical axis representing the output from the light receiving sensor 8. In FIGS. 9A and 9B, the scanning direction of the laser beam is reversed, and the time axis direction of the graph is also reversed accordingly. When the laser beam 203a scans from the light receiving sensor 8 side toward the restricting portion 9a as shown in FIG. 9A, light is received at time ta in the figure until the laser beam 203a passes the edge of the restricting portion 9a. A laser beam 203a is incident on the sensor 8 to output a signal. Thereafter, after passing through the edge of the restricting portion 9a, the laser beam 203a is blocked by the restricting portion 9a and no signal is output as shown at time tb in the figure. Since this behavior is exhibited, the first timing (time) of passing the edge of the laser beam restricting portion 9a is the fall time of the output signal of the light receiving sensor 8. Specifically, as shown in the lower graph of FIG. 9A, the time tdown at the moment when the output from the light receiving sensor 8 falls below a certain slice level SL is set as the timing (time) for passing the edge of the laser beam restricting portion 9a. The light receiving sensor 8 detects.

  When the laser light beam 203b scans from the restricting portion 9a toward the light receiving sensor 8 as shown in FIG. 9B, the time until the laser light beam 203b passes the edge of the restricting portion 9a is as indicated by time tc in the figure. The laser beam 203b incident on the light receiving sensor 8 is blocked by the restricting portion 9a. Therefore, no signal is output because the laser beam 203b is not incident on the light receiving sensor 8. After that, when passing through the edge of the restricting portion 9a, the laser beam 203b is incident on the light receiving sensor 8 as shown at time td in the figure, and a signal is output. Since this behavior is exhibited, the second timing (time) when the laser beam passes through the edge of the restricting portion 9a is the rise time of the output signal of the light receiving sensor. Specifically, as shown in the lower graph of FIG. 9B, the time tup at the moment when the output of the light receiving sensor exceeds a certain slice level SL is received as the timing (time) when it passes through the edge of the laser beam restricting portion 9a. The sensor 8 detects.

  When this method is used, θa≈θa ′, and the timing (time) at which the laser beam passes through the edge of the restricting portion 9a of the laser beam incident at substantially the same angle can be processed regardless of which side the laser beam scans. That is, both the timings when the bidirectional laser light beams deflected at the same deflection angle pass can be accurately detected by the single light receiving sensor 8.

  FIG. 10 shows an outline when the signal processing method is used in a detection member including a restriction member having two restriction portions 9a and 9b. FIG. 10A is a graph showing the deflection angle of one cycle of the MEMS mirror 4 and the output from the light receiving sensor 8. The upper side is a graph showing the relationship between the deflection angle of the MEMS mirror 4 and the scanning time, and the lower side is a graph showing the relationship between the output from the light receiving sensor 8 and the scanning time. In the graph showing the deflection angle, θma is the deflection angle of the MEMS mirror 4 when the laser beam on one end side in the scanning direction passes the edge of the restricting portion 9a, and θmb is the restricting portion on the laser beam on the other end side in the scanning direction. This is the deflection angle of the MEMS mirror 4 when passing through the edge 9b. FIG. 10B and FIG. 10C are enlarged views of the periphery of the light receiving sensor 8 of FIG. 5 schematically showing an optical system including two restricting portions of the optical scanning device. FBD and RBD are directions in which the laser beam deflected and scanned in the F direction and the R direction (direction opposite to the F direction) by the MEMS mirror 4 scans the light receiving sensor 8.

  Signal processing in one cycle will be described in order. First, the laser beam FBD deflected and scanned in the F direction by the MEMS mirror 4 passes through the edge of the restricting portion 9a when the deflection angle becomes θma, and a signal is output from the light receiving sensor 8 ((1) in the figure). ). At this time, since the laser beam FBD scans in the F direction on the light receiving sensor 8 as shown in FIG. 10B, the first timing (time) of passing the edge of the laser beam restricting portion 9a is the time of the light receiving sensor 8. Falling signal. Thereafter, the laser beam RBD whose deflection direction is reversed in the R direction passes through the edge of the restricting portion 9a when the deflection angle becomes θma again, and a signal is output from the light receiving sensor 8 ((2) in the figure). At this time, since the laser beam RBD scans in the R direction on the light receiving sensor 8 as shown in FIG. 10C, the second timing (time) of passing the edge of the laser beam restricting portion 9a is the time of the light receiving sensor 8. Rise signal. Then, the laser beam RBD deflected in the R direction as it is passes through the edge of the restricting portion 9b when the deflection angle becomes θmb, and a signal is output from the light receiving sensor 8 ((3) in the figure). At this time, since the laser beam RBD scans in the R direction on the light receiving sensor 8, the third timing (time) of passing the edge of the laser beam restricting portion 9 b is a falling signal of the light receiving sensor 8. The laser beam FBD whose deflection direction is reversed again in the F direction passes through the edge of the restricting portion 9b when the deflection angle becomes θmb again, and a signal is output from the light receiving sensor 8 ((4) in the figure). . At this time, since the laser beam FBD is scanned in the F direction on the light receiving sensor 8, the fourth timing (time) of passing the edge of the laser light regulating portion 9b is a rising signal of the light receiving sensor 8.

  By this method, there are two each of the first to fourth timings (time) at which four laser beams pass through the edge per cycle of the reciprocating operation of the MEMS mirror ((1) and (2) in the figure, The laser beam deflected at the same deflection angle at the timing (time) of (3) and (4)) can be detected by the light receiving sensor, and a signal can be output. Therefore, the controller can process the four times output as signals from the light receiving sensor and control the driving of the MEMS mirror by the driving device so that each of the times becomes a desired set time. Here, a configuration is shown in which the controller controls the driving of the MEMS mirror based on a total of four timings when the laser light passes through the edges of the two restricting portions in both directions. However, even if the controller controls the driving of the MEMS mirror based on a total of two timings when the laser beam has passed in both directions through the edge of one restricting portion as shown in FIGS. Any system can be used as long as the driving of the MEMS mirror is stable. As described above, according to the configuration of the present embodiment, even when the MEMS mirror driven by combining a plurality of frequencies as described above is used, the controller performs MEMS based on the timing at which the laser light passes through the edge of the restricting portion. By controlling the driving of the mirror, the substantially uniform speed control of the deflection angle can be performed with high accuracy.

  As shown in FIG. 2, in this embodiment, a restricting member including restricting portions 9 a and 9 b is integrally molded with a resin material in the MEMS mirror holder 10 that holds the MEMS mirror 4. However, in order to obtain the effects described so far, the configuration is not limited to this, and the MEMS mirror holder 10 and the restriction portions 9a and 9b may be configured separately as shown in FIG. . However, as shown in FIG. 2, if the restriction member provided with restriction parts 9 a and 9 b is integrally molded with a resin material in the MEMS mirror holder 10, the restriction member provided with the restriction part and the MEMS mirror holder The manufacturing cost can be kept low as compared with the case where these are molded separately. Further, since the restricting portion and the MEMS mirror holder are generally often formed of a resin material, the MEMS mirror holder 10 that holds the restricting member including the restricting portions 9a and 9b and the MEMS mirror 4 as in this embodiment. And the relative positions of the edges of the restricting portions 9a and 9b with respect to the rotation axis of the MEMS mirror 4 are difficult to shift. Therefore, the influence of thermal expansion due to changes in the temperature environment is very slight, and deterioration in isokineticity can be suppressed.

  Further, the driving device and the light receiving sensor 8 are also integrally fixed to the MEMS mirror holder 10 and unitized as a MEMS mirror unit 12. Thereby, compared with the case where the light receiving sensor and the MEMS mirror are held by separate holding members, the manufacturing cost can be reduced. Further, when the control as in this embodiment is performed, the angle with respect to the rotation axis center of the MEMS mirror 4 when the laser beam deflected and scanned by the MEMS mirror 4 enters the light receiving sensor 8 must always be constant. Don't be. Otherwise, the target times t10, t20, t30, and t40 themselves change and the substantially constant speed as expected cannot be obtained. Therefore, in the case where the light receiving sensors are arranged at both ends outside the image area as in the conventional example described above, for example, when the temperature environment changes, the position of the light receiving sensor 8 is caused by the thermal expansion of the holding member that holds the MEMS mirror unit. (Angle) changes, resulting in deterioration of isokineticity. Here, the holding member that holds the MEMS mirror unit corresponds to the optical box 11 in the present embodiment, and the optical box is typically molded of a resin material in many cases. However, if the light receiving sensor 8 is formed as a unit integrated with the MEMS mirror 4 as in this embodiment, the relative position of the light receiving sensor 8 with respect to the rotation axis of the MEMS mirror 4 is difficult to shift. Therefore, the influence of thermal expansion due to changes in the temperature environment is very slight, and deterioration in isokineticity can be suppressed.

  Furthermore, as shown in FIG. 2, in this embodiment, the light receiving sensor 8 is assembled on the side of the MEMS mirror holder 10 opposite to the side on which the MEMS mirror 4 is fixed. The light receiving sensor 8 is disposed at a position away from the MEMS mirror 4 with respect to the scanning lens 5. With such a configuration, the assembly workability of the MEMS mirror unit 12 is improved, and the MEMS mirror 4 and the light receiving sensor 8 can be arranged close to each other in the sub-scanning direction. Therefore, it is possible to provide an optical scanning device that has good assembly workability and can be miniaturized.

  In this embodiment, as a component part of the MEMS mirror unit 12, a restriction member including a restriction portion is integrally formed in one MEMS mirror holder 10, and the MEMS mirror 4 and the light receiving sensor 8 are fixed. However, this MEMS mirror holder 10 may be composed of a plurality of parts for the convenience of manufacturing. In short, it is only necessary that the holding part for holding the MEMS mirror 4 and the regulating part are integrally molded, Moreover, the MEMS mirror 4 and the light receiving sensor 8 should just be unitized.

  In the present embodiment, there are two types of laser light beams that are detected by the light receiving sensor 8 when the MEMS mirror 4 is deflected and scanned in both directions and is deflected at the same deflection angle. Then, the two laser beams are reflected by a pre-sensor mirror disposed one by one near both ends of the scanning lens and are incident on one light receiving sensor. However, it is not limited to this. The point is that the laser beam, which is deflected and scanned in both directions by the reciprocating motion of the MEMS mirror, is input to the controller using the rising time and the falling time of the timing (time) at which the laser beam passes through the edge. Any configuration that can accurately detect the laser beam at the time may be used. Therefore, as shown in FIG. 12, one of the detected laser beams may be a laser beam that is folded back by the pre-sensor mirror 6 c, and the other may be a laser beam that is directly incident from the MEMS mirror 4.

  Further, in this embodiment, the pre-sensor mirrors 6a and 6b (reflection mirrors) are used as the reflection member, but the present invention is not limited to this as long as the member has a reflection function. For example, it may be a reflective prism having two reflective surfaces.

  FIG. 13 shows a MEMS mirror unit according to a second embodiment to which the present invention can be applied. In the figure, 81 is an electric circuit board, and 82 is a connector mounted on the electric circuit board 81. Since other configurations are the same as those in the first embodiment, description thereof is omitted.

  In this embodiment, the core 21 for driving the MEMS mirror 4, the coil 22, and the light receiving sensor 8 are mounted on one electric circuit board 81.

  Specifically, the coil 22 is wound around the core 21. The core 21 is fixed to the electric circuit board 81 by means such as adhesion, caulking, or screwing. The coil 22 is connected to a land (not shown) of the electric circuit board 81 by soldering or the like.

  The connector 82 is connected to the coil 22, the output terminal of the light receiving sensor 8, the power source for the light receiving sensor, and the like, and is connected to a control circuit (not shown) via a harness (not shown).

  In the configuration of this embodiment, in addition to the effects of the first embodiment, the number of components can be reduced by mounting the MEMS mirror driving coil 22 and the light receiving sensor 8 on one electric circuit board 81. Further, by integrating the interface between the coil 22 and the light receiving sensor 8 in the connector 82, a MEMS mirror unit with good assembling workability can be provided.

  Note that the configuration of the present embodiment is not limited to that described above. In short, it is only necessary that the electric components constituting the electromagnetic actuator such as the core 21 and the coil 22 and the light receiving sensor 8 are mounted on the same electric circuit board 81. That is, other components such as all or part of the control unit may be present on the electric circuit board 81 as a matter of course.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example at all, All the deformation | transformation are possible within the technical thought of this invention.

1 is a perspective view illustrating an optical scanning device according to Embodiment 1. FIG. 1 is an exploded view of a MEMS mirror unit according to Embodiment 1. FIG. 1 is a front view of a MEMS mirror according to Example 1. FIG. FIG. 2 is a cross-sectional view of the MEMS mirror unit according to the first embodiment taken along line AA. FIG. 3 is a conceptual diagram illustrating an optical system including two restricting units of the optical scanning device according to the first embodiment. FIG. 3 is a conceptual diagram illustrating a control unit that controls driving of the MEMS mirror according to the first embodiment. (A) The conceptual diagram showing the relationship between the deflection angle in the deflection | deviation operation | movement of the MEMS mirror which concerns on Example 1, and time. (B) The conceptual diagram showing the relationship between the angular velocity and time in the deflection | deviation operation | movement of the MEMS mirror which concerns on Example 1. FIG. FIG. 3 is a conceptual diagram illustrating an optical system including one regulating unit of the optical scanning device according to the first embodiment. (A) 1st explanatory drawing showing the relationship between the output from a light receiving sensor at the time of using one control part, and scanning time. (B) 2nd explanatory drawing showing the relationship between the output from a light receiving sensor at the time of using one control part, and scanning time. (A) Explanatory drawing showing the relationship between the scanning time at the time of using the two control parts which concern on Example 1, and the deflection angle of a MEMS mirror, or the output from a light receiving sensor. (B) The 1st explanatory view showing the detection method in the photo acceptance unit at the time of using two control parts concerning Example 1. FIG. (C) 2nd explanatory drawing showing the detection method in the light reception sensor at the time of using the two control parts which concern on Example 1. FIG. FIG. 9 is a perspective view illustrating an optical scanning device according to a modification example of Example 1. FIG. 9 is a conceptual diagram illustrating an optical system according to another modification of Example 1. FIG. 6 is a perspective view illustrating a MEMS mirror unit according to Embodiment 2. Explanatory drawing showing the optical scanning device of a prior art example.

Explanation of symbols

1 Laser light source unit 4 MEMS mirror (deflection element)
8 Light Receiving Sensor 9a First Restriction Part 9b Second Restriction Part

Claims (15)

A laser light source for emitting laser light;
A deflector that deflects laser light emitted from the laser light source and scans a surface to be scanned , and reciprocates in a first deflection direction and a second deflection direction opposite to the first deflection direction. A deflector that deflects the laser light emitted from the laser light source, and a drive device that drives the deflector;
Receiving the laser beam deflected and scanned by the pre-Symbol deflector, a light receiving sensor for outputting based thereon,
A controller for controlling the drive of the deflection device according to prior SL drive,
Have a first and deflecting the laser beam in the deflection direction during one cycle of the reciprocating operation of the deflection element to scan the scanning surface, and the laser in a second deflection direction opposite to the first deflection direction In an optical scanning device that deflects light and scans the surface to be scanned ,
In the period from when the laser beam is deflected in the first deflection direction to scan the surface to be scanned and before the laser beam is deflected in the second deflection direction to scan the surface to be scanned, the output of the light receiving sensor and the first timing is changed by the amount of light the deflector laser beam that will be deflected and scanned in the first direction of deflection by the incident to the light receiving sensor is reduced, the by the deflector the output of the light receiving sensor and the second timing is changed by the amount of light the laser light that will be deflected and scanned in the second polarization direction enters into the light receiving sensor is increased, the deflection element according to the driving device based on An optical scanning device characterized by controlling driving. A restricting portion that is provided on the downstream side of the light receiving sensor with respect to the first deflection direction and restricts the laser light deflected and scanned by the deflector from entering the light receiving sensor;
The first timing is a timing at which laser light deflected and scanned in the first deflection direction is incident on the light receiving unit and the regulating unit, and the second timing is the second deflection direction. The optical scanning device according to claim 1, wherein the laser beam deflected and scanned at a timing is incident on the light receiving unit and the regulating unit. The controller further includes a period from when the laser beam is deflected in the second deflection direction to scan the surface to be scanned and before the laser beam is deflected in the first deflection direction to scan the surface to be scanned. A third timing at which the output of the light receiving sensor changes due to a decrease in the amount of light incident on the light receiving sensor by the laser beam deflected and scanned in the second deflection direction by the deflector; and Based on a fourth timing at which the output of the light receiving sensor changes due to an increase in the amount of light incident on the light receiving sensor by the laser beam deflected and scanned in the first deflection direction, The optical scanning device according to claim 1, wherein the driving is controlled. Another control part provided on the upstream side of the light receiving sensor with respect to the first deflection direction, and configured to restrict the laser light deflected and scanned by the deflector from entering the light receiving sensor;
The third timing is a timing at which laser light deflected and scanned in the second deflection direction is incident on the light receiving unit and the regulating unit, and the fourth timing is the first deflection direction. The optical scanning device according to claim 1, wherein the laser beam deflected and scanned at a timing is incident on the light receiving unit and the regulating unit. The deflection element includes two movable elements and a torsion spring that connects the two movable elements, and one of the two movable elements is a reflecting mirror that reflects laser light. the optical scanning apparatus according to any one of claims 1 to 4. The controller controls the driving of the reflecting mirror of the deflecting element by the driving device by synthesizing the first frequency and the second frequency twice as high as the first frequency. 6. The optical scanning device according to claim 5 , wherein the reflecting mirror of the deflection element deflects and scans the laser light at a substantially equal angular velocity in a partial section in one cycle. A holding member for holding the deflection element;
The regulating unit, an optical scanning apparatus according to any one of claims 1 to 6, characterized in that it is molded integrally with the holding member. The optical scanning device according to claim 7 , wherein the holding member and the restricting portion are molded of a resin material. The optical scanning apparatus according to claim 7 or 8 wherein the light receiving sensor, characterized in that it is fixed to the holding member. An imaging lens for imaging the laser beam deflected and scanned by the deflector on the surface to be scanned;
The light receiving sensor is assembled on the side of the holding member opposite to the side on which the deflection element is fixed, and is disposed at a position away from the deflection element with respect to the imaging lens. The optical scanning device according to claim 9 . The drive device is fixed to the holding member, the light receiving sensor and the driving device optical scanning apparatus according to claim 9 or 10, characterized in that it is mounted on the same electrical circuit board. A laser light source for emitting laser light;
A deflector that deflects and scans laser light emitted from the laser light source, and includes a deflection element that reciprocates and deflects laser light emitted from the laser light source, and a driving device that drives the deflection element. And
An imaging lens that forms an image on the surface to be scanned with the laser beam deflected and scanned by the deflector;
A holding member for holding the deflection element;
One detection member that detects the laser beam deflected and scanned by the deflector, and controls one laser sensor that receives the laser beam deflected and scanned by the deflector and the laser beam that is incident on the light sensor. and one sensing member having a regulatory unit you,
In an optical scanning device having
The restricting portion is formed integrally with the front Symbol holding member, wherein the side where the light receiving sensor is a deflection element of the holding member is fixed is fixed to the opposite side, the deflection element relative to the imaging lens An optical scanning device characterized in that the optical scanning device is disposed at a position farther than the distance .   The optical scanning device according to claim 9, wherein the holding member and the restricting portion are molded of a resin material. The optical scanning device according to claim 12 or 13 , wherein the driving device is fixed to the holding member, and the driving device and the light receiving sensor are mounted on the same electric circuit board. An imaging lens that forms an image on the surface to be scanned with the laser beam deflected and scanned in the main scanning direction by the deflector;
The restricting portion passes a first edge that restricts laser light incident on the light receiving sensor through the vicinity of one end of the imaging lens in the main scanning direction and a vicinity of the other end of the imaging lens in the main scanning direction. to the optical scanning apparatus according to any one of claims 12 to 14, characterized in that it comprises a second edge for regulating the laser light incident on the light receiving sensor.

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