JP2009020404A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner in which jitter at a vibration is reduced even when variation in the characteristic of a vibration system, such as a temperature change, a change with time or machining accuracy when manufactured, is present, and to provide an image forming apparatus. <P>SOLUTION: The optical scanner comprises: the vibration system 100 having a rocking body and a torsion spring; a reflection mirror formed on the rocking body; a light source 131 which generates a light beam; a coil 161 which applies driving force to the vibration system 100; a light receiving element 140 which clocks time when the rocking body takes a dislocation angle θ BD; a driving control part 600 which controls the coil 161; and a control gain adjuster 620 which adjusts the control gain of the driving control part 600, wherein the driving control part 600 calculates the time difference 153 between the time 151 detected by the light receiving element 140 and a target time 152, and controls the vibration system 100 on the basis of the time difference 153, and the control gain adjuster 620 adjusts the control gain on the basis of the time difference 153 and sets the control gain to the driving control part 600. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical scanning device and an image forming apparatus. In particular, the present invention relates to an optical deflection apparatus having an oscillating body such as a micro oscillating structure. The present invention also relates to an image forming apparatus such as a scanning display, a laser beam printer, and a digital copying machine using the optical deflection apparatus.

  Conventionally, various optical deflectors (optical scanning devices), which are oscillating bodies in which a reflecting mirror is driven to resonate, have been proposed. The resonant oscillator can be significantly reduced in size compared to an optical scanning optical system using a rotating polygonal mirror such as a polygon mirror. In addition, the features such as low power consumption, theoretically no surface tilt, especially the oscillator made of Si single crystal manufactured by semiconductor process is theoretically free from metal fatigue and excellent in durability, etc. (For example, Patent Document 1). Such a resonant oscillator is hereinafter referred to as a resonant optical deflector.

  Further, in the resonance type optical deflector, since the deflection angle (displacement angle) of the reflecting mirror changes sinusoidally in principle, the angular velocity is not constant. In order to correct this characteristic, the following method has been proposed (for example, see Japanese Patent Application No. 2006-035491). In this specification, the deflection angle of the reflecting mirror and the scanning angle of the scanning light deflected / scanned by the reflecting mirror have a fixed relationship and can be treated equally, so the deflection angle (displacement angle) and the scanning angle are equivalent. Used in meaning.

  In the method described in Japanese Patent Application No. 2006-035491, a resonance type optical deflector having two oscillators is used, vibration at a fundamental frequency is applied to one oscillator, and vibration at an integral multiple of the fundamental frequency is applied to the other oscillator. It is the structure which generates. By generating vibrations having a fundamental frequency and twice the fundamental frequency, substantially sawtooth drive can be realized. FIG. 13 shows a resonance type optical deflector that realizes substantially sawtooth driving.

  The vibration system 400 includes oscillators 401 and 402, torsion springs 411 and 412, a support part 421, a drive part 420, a light source 431, first and second light receiving elements 441 and 442, and a drive control part 450. Reference numeral 432 denotes a light beam from the light source 431, and reference numeral 433 denotes scanning light reflected by the oscillator 401. This vibration system has a fundamental frequency and a resonance frequency that is an integral multiple of the fundamental frequency, and is driven at a combined frequency of the fundamental frequency and a frequency that is an integral multiple of the fundamental frequency. When driving at a combined frequency of the fundamental frequency and a frequency that is, for example, twice the fundamental frequency, the oscillating body 401 having a reflecting surface is driven by substantially sawtooth drive, and the deflection angle thereof changes in angular velocity compared to sine wave drive. Achieves less light deflection. The drive control unit 450 generates a drive signal necessary for realizing the target vibration waveform, and the drive unit 420 drives the vibration system 400.

  FIG. 14 shows a drive control unit 450 of Japanese Patent Application No. 2006-035491. In the figure, reference numerals 351 and 352 denote arbitrary waveform generators that generate sine waves of 2000 Hz and 4000 Hz. The phase and amplitude of each sine wave can be arbitrarily changed by a command from the calculation unit 454. The two generated sine waves are added by an adder 370 and then amplified by an amplifier 380, and a current is supplied to a driving unit 420 such as a coil. Torque is applied to the driving unit 420 such as a permanent magnet attached to the rocking body 402 by the current flowing through the driving unit 420 such as a coil to drive the rocking body 402.

The first and second light receiving elements 441 and 442 are arranged like the light receiving elements 141 and 142 shown in FIG. Outputs 451 from the first and second light receiving elements 441 and 442 become a value 453 obtained based on a preset reference value 452 and are taken into the calculation unit 454. The calculation unit 454 outputs an operation amount 455 to the arbitrary waveform generators 351 and 352 so that the outputs 451 of the first and second light receiving elements 441 and 442 indicate arbitrary values. That is, the phase and amplitude of each sine wave of the arbitrary waveform generators 351 and 352 are controlled so that the scanning light 433 of the optical deflecting device passes through the first and second light receiving elements 441 and 442 at an arbitrary time desired. To do.
JP 57-8520 A

  Since the resonance frequency of the oscillator manufactured by the above semiconductor process is determined by the processing accuracy of the material and shape of the movable plate and the elastic support portion, the resonance frequency, moment of inertia, and torsion of the oscillator manufactured are determined by the material and processing accuracy. Solid differences occur in the spring constant of the spring. Therefore, if all the manufactured oscillators are to be driven with the same drive frequency and the same control gain, the driveable ones must be selected and used, which may reduce the yield.

  Further, when the oscillator having this individual difference is controlled by the drive control unit 450 having the same drive frequency and the same control gain, the oscillatory motion is caused by the individual difference of the inertia of the oscillator and the spring constant of the torsion spring. Jitter may increase.

  Furthermore, the moment of inertia of the oscillator, the spring constant of the torsion spring, the natural frequency, and the like change due to temperature changes and secular changes. Therefore, when the control is performed by the drive control unit 450 in which the same control gain is set, there is a problem that the jitter of the oscillating motion increases due to the temperature change or aging change of the oscillating body.

  The present invention has been made in view of the above points, and an optical scanning device capable of selecting a control gain that reduces a deviation between a vibration waveform of a rocking body and a target vibration waveform and improving the accuracy of optical scanning. It is another object of the present invention to provide an image forming apparatus.

  In order to solve the above problems, an optical scanning device and an image forming apparatus of the present invention have the following configuration.

  (1) A vibration system having one or more oscillating bodies and one or more torsion springs connected to the oscillating bodies, a reflection mirror formed on at least one of the oscillating bodies, and a light beam are generated. Time is measured when at least one of the light source, the driving means for applying a driving force to the vibration system in order to perform a vibration motion at a predetermined frequency, and at least one of the oscillating bodies forms at least one displacement angle. And a scanning controller that controls the driving unit based on the time measured by the displacement angle detecting unit, and scans the light by irradiating the light beam on the reflecting mirror. The apparatus includes a control gain adjustment unit that adjusts a control gain of the drive control unit, and the drive control unit has a predetermined time within one cycle of the frequency as a reference or origin time, A time difference between at least one time when the oscillator makes at least one predetermined displacement angle and a preset time is calculated, and based on the time difference, the amplitude and phase of the vibration waveform of the vibration motion At least one is controlled, The said control gain adjustment means adjusts the said control gain based on the said time difference, The optical scanning apparatus characterized by the above-mentioned.

  (2) A vibration system having one or more oscillating bodies and one or more torsion springs connected to the oscillating bodies, a reflection mirror formed on at least one of the oscillating bodies, and a light beam. Time when at least one of the light source, the driving means for applying a driving force to the vibration system in order to cause the vibration motion at a predetermined frequency, and the oscillator to form different first and second displacement angles is set. Displacement angle detection means for measuring, and drive control means for controlling the drive means based on the time measured by the displacement angle detection means, and scanning the light by irradiating the light beam on the reflection mirror The optical scanning device includes a control gain adjusting unit that adjusts a control gain of the drive control unit, and the drive control unit has a predetermined time within one cycle of the frequency as a reference or origin time. , A plurality of times when one of the oscillating bodies forms the first displacement angle and a different time when one of the oscillating bodies forms the second displacement angle. A time difference between at least two times and a set time is calculated, and at least one of amplitude and phase of a vibration waveform of the vibration motion is controlled based on the time difference, and the control gain adjusting means is configured to control the control based on the time difference. An optical scanning device characterized in that a gain is adjusted and set in the drive control means.

  (3) An image forming apparatus including the optical scanning device according to (1) or (2), wherein the control gain adjusting unit sets the control gain in the drive control unit other than during image formation. An image forming apparatus.

  According to the present invention, even when individual differences occur in the moment of inertia of the oscillator, the spring constant of the torsion spring, the natural frequency, etc. in the manufacturing process, the deviation between the oscillation of the oscillator and the target vibration waveform is minimized. A control gain can be selected. Therefore, it is possible to improve jitter in the vibration motion of the rocking body. Furthermore, in the past, oscillators that deviated from a certain range of resonance frequency were regarded as defective because of increased jitter. However, setting a control gain suitable for individual differences between oscillators reduces jitter and improves yield. can do.

  Furthermore, even when the moment of inertia of the oscillator, the spring constant of the torsion spring, the natural frequency, etc. change due to temperature change or secular change, a control gain that minimizes the deviation between the oscillation waveform of the oscillator and the target vibration waveform is set. You will be able to choose. As a result, the vibration of the oscillating body approaches the target vibration waveform, so that the accuracy of optical scanning can be improved.

  An embodiment of the optical deflecting device (optical scanning device) of the present invention will be described in detail below. The first embodiment is configured as a resonance type optical deflecting device having one oscillator and the third embodiment is having two oscillators. Hereinafter, more specific embodiments of the present invention will be described with reference to the drawings.

  In the first embodiment, a vibration system is constituted by one rocking body and at least one torsion spring connected to the rocking body. A reflection mirror is formed on the oscillator. The displacement angle measuring unit has at least one light receiving element (displacement angle measuring means) disposed at a position irradiated with the scanning light when the oscillating body with the reflection mirror takes a certain displacement angle. Further, the scanning light may be directly incident on the light receiving element, or may be incident on the light receiving element via at least one reflecting member. That is, it is sufficient that at least one light receiving element is arranged so as to receive and detect scanning light having a certain deflection angle (scanning angle) with a certain oscillating body with a reflecting mirror.

  The optical deflecting device of Example 1 will be described. The vibration system of the optical deflecting device according to the first embodiment includes one oscillator and at least one torsion spring coupled to the oscillator, and can generate an oscillation motion at the fundamental resonance frequency. The light deflection apparatus further includes a drive unit (drive means) that operates the vibration system, a reflection mirror formed on the oscillating body, and a light source that irradiates the light beam, and irradiates the reflection mirror with the light beam. And scan the light.

  A block diagram of an optical deflecting device according to the present embodiment is shown in FIG. The vibration system 100 includes a rocking body 102, and a torsion spring 112 that connects the rocking body 102 and the support portion 121 is provided.

  The drive control unit (drive control means) 600 applies (applies) a driving force to the oscillator 102 to simultaneously excite the natural vibration mode of the vibration system 100 by electromagnetic, electrostatic, piezoelectric, or the like. In this embodiment, it is assumed that the drive control unit 600 sends a signal for controlling the coil 161 to pass an appropriate current. Torque acts on the permanent magnet 162 attached to the oscillating body 102 by the current flowing through the coil 161 to drive the vibration system 100. The oscillator 102 has a reflecting mirror on the surface, and scans the light beam 132 from the light source 131. The scanning light 133 passes through the light receiving element 140 twice in each cycle of reciprocating scanning. The drive control unit 600 generates a drive signal to the coil 161 based on the time that the scanning light 133 passes through the light receiving element 140 twice. Reference numeral 620 denotes a control gain adjuster (control gain adjusting means) described later.

  FIG. 2 shows the deflection angle (scanning angle) of the optical deflection apparatus according to this embodiment. The oscillator 102 has a reflecting mirror on the surface, and scans the light beam 132 from the light source 131. The light deflection apparatus has a light receiving element 140, and the light receiving element 140 is disposed at a position of a deflection angle (position of θBD) smaller than the maximum deflection angle of the light deflection apparatus. In FIG. 2, the light receiving element 140 is arranged in the direct scanning optical path of the optical deflecting device. However, as described above, the light receiving element 140 is arranged in the optical path of the scanning light further deflected by another reflecting mirror (reflecting member) or the like. May be.

The deflection angle θ (measured here with reference to the position of the scanning center 160 as shown in FIG. 2) of the optical deflection apparatus of the present embodiment is the amplitude, angular frequency, and phase of the vibration motion A, ω, φ, When the time when the appropriate time is the origin or the reference time is t, it can be expressed as the following equation.
θ (t) = Asin (ωt + φ) Equation 2

The light receiving element 140 is arranged at a desired position where the scanning light 133 is irradiated, and the amplitude of the vibration motion is such that the scanning light 133 passes over the light receiving element 140 at two different times within one cycle of the vibration motion. , Adjust the phase. In this way, the desired deflection angle θ of the optical deflecting device can be obtained. At this time, the two times are as follows when the deflection angle corresponding to the position of the light receiving element 140 is θBD (see FIG. 2).
At certain times t1 and t2,
θ (t1) = θ (t2) = θBD Equation 3

  By controlling the two times t1 and t2 to be desired times t10 and t20 by the drive control unit 600, the amplitude and phase of the vibration motion can be uniquely determined. More specifically, the drive control unit 600 controls the amplitude and phase of the oscillating motion by controlling an appropriate current to flow through the coil 161 in order to set the two times to arbitrary times.

  Here, in the optical deflecting device of the present embodiment, only the amplitude A of the oscillating motion needs to be controlled, and when it is not necessary to control the phase φ, it is only necessary to consider the relative time between the two times t1 and t2. . Specifically, for example, t10 out of target times (set times) t10 and t20 through which the scanning light 133 passes through the light receiving element 140 is set as a reference time. The drive signal is controlled by the drive control unit 600 so that the detected relative time tA = t2−t1 when the scanning light 133 passes through the light receiving element 140 becomes the target relative time tA0 = t20−t10, whereby the amplitude A of the vibration motion is set. Can be controlled.

Assuming that time difference ΔtA between tA and tA0, ΔtA is expressed as follows.
ΔtA = tA−tA0 = (t2−t1) − (t20−t10) Equation 4

The control method of the present embodiment will be described in detail. Obtained in advance the coefficients M _A representing a change in the control parameter X is detected relative time the scanning light 133 and the light receiving element 140 when changes minutely from the target value is passed through tA = t2-t1 including amplitude A of the optical deflecting device deep. This is expressed as follows.

Therefore, the operation amount ΔA of the amplitude of the reflecting mirror can be obtained by the following equation based on the time difference ΔtA between the detected relative time tA and the target relative time tA0.

  The manipulated variable ΔA is calculated from the time difference ΔtA by the above relational expression. And the output of the drive control part 600 is changed based on the value. By repeating the above control, tA converges to the target relative time tA0, and a desired deflection angle θ can be obtained.

  The above process will be described with reference to the block diagram of FIG. FIG. 3 is a block diagram for explaining the control of the optical deflection apparatus according to the present embodiment. The scanning beam 133 (deflected light) passes through the light receiving element 140 by deflecting the light beam 132 from the light source 131 by the vibration system 100 driven by the drive unit 120 of the light deflector. The drive control unit 600 calculates a time difference 153 by subtracting the detection time 151 detected by the light receiving element 140 from the target time 152. Further, as shown in Expression 7, the operation amount 155 is calculated by calculating with the calculator 154 based on the time difference 153, and the controller 161 and the amplifier 180 apply the operation amount 155 to the coil 161 (drive means) of the drive unit 120 of the optical deflector. Generate the input signal. In this case, since t10 is set as the reference time, the operation amount 155 for the controller 610 shown in FIG.

  In addition to the above configuration, in this embodiment, the time difference ΔtA (153) is input to the control gain adjuster 620 (shown in FIGS. 1 and 3), and the control gain adjuster 620 controls the controller based on the time difference ΔtA. A signal for adjusting the control gain 610 is output to adjust the control gain.

  Here, the amplitude and angular frequency of the vibration motion are A and ω, respectively, and the time when an arbitrary reference time within one cycle of the vibration motion is the origin (0) is t. At this time, the deflection angle θ of the optical deflector according to the present embodiment can be expressed as shown in Equation 2. However, φ = 0 is set. Here, assuming that A = 1 and ω = 2π × 2000, the deflection angle θ of the optical deflection apparatus according to this embodiment is as shown in FIG. FIG. 4 is a graph showing a time change of the deflection angle θ of the optical deflecting device according to the present embodiment.

  At this time, if the light receiving element 140 is arranged at 80% of A, that is, at a position where the deflection angle θ is 0.8, the time when the deflection angle θ is 0 (scanning center 160) is 0 is as follows. . That is, the target times t10 and t20 for the scanning light 133 to pass through the light receiving element 140 are 0.074 msec and 0.176 msec. These target times are obtained and stored in advance (this is the same in the following embodiments). Accordingly, the drive signal is controlled by the drive control unit 600 so that the two times t1 and t2 during which the scanning light 133 passes through the light receiving element 140 becomes the above value, whereby the deflection angle θ of the optical deflector shown in FIG. Obtainable.

  In the present embodiment, the light receiving element 140 is disposed at a position where the deflection angle θ is 0.8 from the scanning center 160 of the optical deflecting device, but an arbitrary deflection angle θ may be used. In this embodiment, the time when the deflection angle θ is 0 is set to 0. However, an arbitrary time of one cycle of the angular frequency of the first vibration motion may be set as the origin (0).

  When the detection times t1 and t2 are expressed as in Expression 3, the amplitude A of the vibration motion can be set to a desired A if the controller 610 can control the t2-t1 to be 0.102 msec. In this embodiment, since one value is determined, A can be obtained by this method.

  Let tA be the difference between t2 and t1. tA = t2-t1. A difference between the target value tA0 of tA and tA is defined as a time difference ΔtA. ΔtA = tA−tA0 = (t2−t1) − (t20−t10). As for ΔtA, the operation amount ΔA of the amplitude A can be calculated by Expression 7. The manipulated variable ΔA is input to the controller 610, and a signal input to the coil 161 (driving means) of the driving unit 120 of the optical deflecting device is generated by the amplifier 180 to drive the vibration system 100.

  In this embodiment, t10 and t20 are determined values, but may be values having a certain range.

Ｎは測定回数であり、任意に値を定めることができる。この評価関数Ｊを最小にするように、制御ゲイン調整器６２０が制御器６１０の制御ゲインを決定する構成を以下に述べる。 Here, when the average value measured N times is used as the evaluation function, and the time difference ΔtA at the k-th measurement (k-th measurement) is ΔtA (k), the evaluation function J is, for example, as follows: I will represent it.

N is the number of measurements, and can be arbitrarily determined. A configuration in which the control gain adjuster 620 determines the control gain of the controller 610 so as to minimize the evaluation function J will be described below.

When the controller 610 is a PI controller, if the input to the controller 610 is ΔA and Adef is a fixed value, the output is expressed by the following equation.
KA (1 + KA ′ / s) ΔA + Adef Equation 9
KA and KA ′ are control gains, and KA ′ means the reciprocal of the integration time of the PI controller. s is a Laplace operator. In the present embodiment, a configuration in which only KA is adjusted using the evaluation function J without adjusting and changing KA ′ is shown.

  FIG. 5 is a flowchart illustrating a process for determining the control gain KA using the evaluation function J.

  x control gain candidates KAi (i is a natural number from 1 to x) are determined in advance, and a signal for setting the control gain value of the controller 610 so that KA = KAi is sequentially set one by one. , And sent from the control gain adjuster 620 to the controller 610. For example, initially, i = 1 and KA = KA1 are set (steps S101 and S102) (hereinafter, “step” is omitted).

  First, with the control gain KA set to KAi (for example, KA1 when i = 1), the operation amount 155 (ΔA) is calculated by sending the time difference ΔtA to the calculator 154. Then, the controller 610 and the amplifier 180 generate a signal to be input to the coil 161 (drive means) of the drive unit 120 of the optical deflection apparatus, and drive the vibration system 100. After the vibration motion of the vibration system 100 is controlled and a fixed time has elapsed (S103, when the vibration motion can be regarded as a steady state), the evaluation function J is calculated using the value obtained by measuring the detected time difference ΔtA N times. Calculate (S104). However, in this embodiment, N = 1. At that time, a set of the value of the evaluation function J and the value of the control gain KA at that time is stored in the control gain adjuster 620 (S105).

  Next, it is confirmed whether all control gain candidates have been set as control gains (check whether i is greater than x) (S107). If there is a control gain candidate that has not yet been set, the process returns to S102. That is, the control gain adjuster 620 sends a signal to the controller 610 to reset the control gain of the controller 610 to a different control gain candidate (for example, 1 is added to i (S106), and KA = KA2). Then, the control gain is reset (S102). After setting the control gain, the operation amount 155 is calculated by sending the time difference ΔtA to the computing unit 154, and a signal input to the coil 161 (driving means) of the driving unit 120 of the optical deflector by the controller 610 and the amplifier 180 is obtained. Generate and drive the vibration system 100. At that time, the evaluation function J is calculated (S104), and the set of the value of the evaluation function J and the value of the control gain KA at that time is stored in the control gain adjuster 620 (S105).

  The above process is repeated x times, and all control gain candidates are actually set as control gains. When all control gain candidates are set as control gains (if YES in S107), a set of x evaluation function J values and control gain values at that time is stored in the control gain adjuster 620. ing. The control gain adjuster 620 compares the values of the evaluation functions J (S108), and sends a signal for setting the control gain value when the evaluation function J is minimum to the controller 610 (S109). Thereafter, after a predetermined time has elapsed (S110), light deflection is performed using the control gain set as described above.

  In the above description, a set of the values of the control gain KA and the evaluation function J is stored in the control gain adjuster 620 for all x sets, and the control gain KA that minimizes the evaluation function J is stored in the stored set. Selected and set. However, the control gain adjuster 620 may perform the following operation by storing only one set of the value of the evaluation function J and the value of the control gain KA at that time. That is, only when the control gain KA is changed and the value of the evaluation function J at that time is smaller than the value of the evaluation function J stored in the storage unit (storage means) of the control gain adjuster 620, the evaluation is performed. This is an operation of overwriting and storing the set of the function J and the control gain KA in the storage device. At this time as well, the control gain KA that minimizes the evaluation function J can be obtained.

  In this embodiment, the controller 610 is a PI controller, and one optimal control gain value is determined. Here, the controller 610 may be a P controller. In this case, by setting KA ′ to 0, the controller 610 can be realized with the same configuration as in the present embodiment.

  In this embodiment, the control gain KA 'is not adjusted, and only the KA is adjusted. When both KA and KA ′ are changed, only the combination of control gains is increased, and the configuration of this embodiment can be applied without changing the basic configuration. For example, if x control gains KA candidates and y control gains KA 'candidates are defined, x x y combinations of control gains may be tried.

In this embodiment, the time difference is defined as ΔtA = tA−tA0 = (t2−t1) − (t20−t10), and the evaluation function J is defined as Equation 8. However, the time difference at the time of the k-th measurement is defined as Δt1 (k) = t1−t10, Δt2 (k) = t2−t20, N is the number of times of measurement, m is a natural number, and Wi is a weight that is 0 or more. As a real number, the evaluation function J may be defined as follows.

  Although the measurement error can be reduced by increasing the value of N in Expression 8 and Expression 10, the measurement time becomes longer. Also, by reducing the value of N, the period for changing the control gain is shortened, and the jitter of the vibration motion of the vibration system may increase. In view of the above, it is necessary to determine the value of N.

  In the present embodiment, the operation of waiting for a certain period of time (S103 and S110 in FIG. 5) is based on the possibility that the vibration motion is in a transient state with the change of the control gain. When calculating the evaluation function J, in order to ignore the measured value in the transient state, an operation of waiting for a certain time to pass is added. Therefore, when the transient state is extremely short or negligible, the operation of waiting for a certain time may be omitted. The same applies to the other embodiments.

  An optical deflecting device according to Embodiment 2 of the present invention will be described. The configuration of the optical deflection apparatus is basically the same as that of the first embodiment, except for the following points.

  The cycle in which the drive control unit 600 controls the vibration system 100 is a first cycle, and the cycle in which the control gain adjuster 620 changes the control gain is a second cycle. At this time, in this embodiment, the second period is set longer than the first period.

  The second period is a period in which the control gain is changed by the control gain adjuster 620 using the value of the time difference ΔtA. When the control gain of the controller 610 is changed by the control gain adjuster 620, a signal to be input to the coil 161 of the driving unit 120 of the optical deflector is generated by the controller 610 and the amplifier 180 using the changed control gain, The vibration system 100 is driven. The control gain is changed, the time difference ΔtA when the oscillating motion of the oscillating body 102 reaches a steady state after a certain time has elapsed is measured, and the evaluation function J is calculated.

  The vibration motion of the oscillating body 102 immediately after the control gain is changed may not be in a steady state due to the influence of the control gain before the change or the control gain is changed. Therefore, the evaluation function J calculated using ΔtA immediately after the control gain change cannot always evaluate the steady state jitter state.

  Therefore, by setting the second control period to be longer than the first control period, the value of the evaluation function J corresponding to the changed control gain can be obtained.

  In this embodiment, a vibration system is constituted by two oscillating bodies and a plurality of torsion springs arranged on the same axis for connecting the oscillating bodies in series. A reflection mirror is formed on at least one oscillator. The displacement angle measuring unit includes a first light receiving element (displacement angle measuring means) arranged at a position irradiated with the scanning light when the oscillating body with the reflecting mirror takes the first displacement angle. Furthermore, the oscillating body with the reflection mirror has a second light receiving element arranged at a position irradiated with the scanning light when the second displacement angle is taken. The first and second light receiving elements may be different elements or the same element. Further, the scanning light may be directly incident on the light receiving element, or may be incident on the light receiving element via at least one reflecting member. In other words, at least one light receiving element can detect and detect the scanning light in which the oscillating body with the reflection mirror takes the first and second displacement angles and becomes the first and second deflection angles (scanning angles). It suffices if they are arranged.

  Next, the optical deflecting device of this embodiment will be described. The vibration system of the optical deflecting device of the present embodiment includes two oscillating bodies and a plurality of torsion springs connecting the oscillating bodies in series. Also, a first vibration motion (first periodic driving force) that moves at a separated fundamental resonance frequency (first frequency) and a second vibration that moves at a resonance frequency (second frequency) that is an integral multiple of the first vibration motion (first periodic driving force). Movement (second periodic driving force) can be generated (applicable). The optical deflection apparatus further includes a driving unit that operates the vibration system, a reflection mirror formed on at least one of the oscillators, and a light source that irradiates the light beam, and irradiates the reflection mirror with the light beam. And scan the light.

  FIG. 6 shows a block diagram of the optical deflecting device according to this embodiment. The vibration system 100 includes oscillating bodies 101 and 102, and a torsion spring 111 that connects the oscillating bodies 101 and 102 in series and a torsion spring 112 that connects the oscillating body 102 and the support portion 121 are provided.

  The drive control unit (drive control means) 600 applies a driving force that simultaneously excites a plurality of natural vibration modes of the vibration system 100 to the oscillator 102 by electromagnetic, electrostatic, piezoelectric, or the like. In the present embodiment, it is assumed that the drive control unit 600 sends a signal for controlling the coil 161 to pass an appropriate current. Torque acts on the permanent magnet 162 attached to the oscillating body 102 by the current flowing through the coil 161 to drive the vibration system 100. The oscillator 101 has a reflection mirror on the surface, and scans the light beam 132 from the light source 131. The scanning light 133 passes through the first and second light receiving elements 141 and 142 twice in each cycle of reciprocating scanning. The drive control unit (drive control means) 600 generates a signal for causing an appropriate current to flow to the coil 161 based on the time during which the scanning light 133 passes through the first and second light receiving elements 141 and 142 twice.

  FIG. 7 shows the deflection angle (scanning angle) of the optical deflecting device of this embodiment. The oscillator 101 has a reflection mirror on the surface, and scans the light beam 132 from the light source 131. The optical deflection apparatus has two light receiving elements, and the first and second light receiving elements 141 and 142 are arranged at positions of deflection angles (positions θBD1 and θBD2) smaller than the maximum deflection angle of the optical deflection apparatus. In FIG. 7, the first and second light receiving elements 141 and 142 are arranged in the direct scanning optical path of the optical deflecting device. However, as described above, the scanning light further deflected by another reflecting mirror (reflecting member) or the like is used. The first and second light receiving elements 141 and 142 may be disposed in the optical path.

The deflection angle θ (measured here with reference to the position of the scanning center 160 as shown in FIG. 7) of the optical deflection apparatus of the present embodiment can be expressed as the following equation. The amplitude, angular frequency, and phase of the first vibration motion are A1, ω1, and φ1, respectively, the amplitude, angular frequency, and phase of the second vibration motion are A2, ω2, and φ2, and the appropriate time is the origin or reference time. T is the time.
θ (t) = A1sin (ω1t + φ1) + A2sin (ω2t + φ2) Equation 11

In addition, the deflection angle θ of the optical deflecting device is such that the amplitude and angular frequency of the first vibration motion are A1 and ω1, respectively, the amplitude and angular frequency of the second vibration motion are A2 and ω2, and the relative phases of the two frequencies are respectively. φ, where t is a time when an appropriate time is a reference time, and can be expressed as the following equation.
θ (t) = A1sin (ω1t) + A2sin (ω2t + φ) Equation 12
Or θ (t) = A1sin (ω1t + φ) + A2sin (ω2t) Equation 13

  Equation 13 corresponds to the case where the phase on the fundamental wave ω1 side may be controlled during control. Expressions 11 and 12 and 13 differ only in the form of expression depending on how the reference or origin time is taken, and are expressions including four unknown values (for example, in Expression 12 and Expression 13) φ can be expressed as φ1-φ2 or φ2-φ1).

Here, the first and second light receiving elements 141 and 142 are arranged at desired positions where the scanning light is irradiated. Then, the amplitudes of the first and second vibration motions so that the scanning light passes over the first and second light receiving elements 141 and 142 at four different desired times within one cycle of the first vibration motion. , Adjust the phase. Thus, four unknown values are determined. This makes it possible to obtain a desired deflection angle θ of the optical deflection device. At this time, these four times are as follows when the deflection angles corresponding to the positions of the first and second light receiving elements 141 and 142 are θBD1 and θBD2 (see FIG. 7), respectively.
At certain times t1 and t2,
θ (t1) = θ (t2) = θBD1 Equation 14
At certain times t3 and t4
θ (t3) = θ (t4) = θBD2 Equation 15

  The drive controller 600 controls the four times t1, t2, t3, and t4 to be the desired times t10, t20, t30, and t40, respectively, and thereby the amplitude and phase of the first and second vibration motions. Can be determined uniquely. More specifically, the drive control unit 600 controls each of the first and second vibration motions by controlling an appropriate current to flow through the coil 161 in order to set the four times to arbitrary times. Control amplitude, phase or relative phase.

  When the deflection angle θ of the optical deflecting device is expressed by only one term of Expression 11, the scanning light passes over the first or second light receiving element 140, 141 at least at two desired times. In addition, the amplitude and phase of the first or second vibration motion may be adjusted.

  Here, in the optical deflecting device, when the amplitudes of the first and second vibration motions and the relative phase between the first vibration motion and the second vibration motion are to be controlled, four times t1, The relative time of t2, t3, and t4 may be considered. Specifically, for example, t10 out of target times t10, t20, t30, and t40 through which the scanning light 133 passes through the first and second light receiving elements 141 and 142 is set as a reference time. Three detection relative times t2-t1, t3-t1, and t4-t1 during which the scanning light 133 passes through the first and second light receiving elements 141 and 142 become target relative times t20-t10, t30-t10, and t40-t10. Thus, the drive signal is controlled by the drive control unit 600. As a result, the amplitudes of the first and second vibration motions and the relative phases of the first vibration motion and the second vibration motion can be controlled.

When the time differences between the detected relative time and the target relative time are Δt2, Δt3, and Δt4, the time differences Δt2, Δt3, and Δt4 are expressed as follows.
Δti = (ti−t1) − (ti0−t10), (i = 2, 3, 4) Equation 16

The control method of the present embodiment will be described in detail. When the control parameter X including any one of A1, A2, and φ of the optical deflecting device slightly changes from the target value, the relative time of the scanning light 133 passing through the first and second light receiving elements 141 and 142 A coefficient and a matrix M representing changes in t2-t1, t3-t1, and t4-t1 are obtained in advance. These are expressed as follows:

Accordingly, the operation amounts ΔA1, ΔA2, and Δφ of the amplitude and phase of the reflecting mirror are time differences between the detected relative times t2-t1, t3-t1, t4-t1 and the target relative times t20-t10, t30-t10, t40-t10. From Δt2, Δt3, and Δt4, the following equation is obtained.

  From the above relational expressions, the operation amounts ΔA1, ΔA2, and Δφ are calculated from the time differences Δt2, Δt3, and Δt4. And the output of the drive control part 600 is changed based on the value. By repeating the above control, the detected relative times t2-t1, t3-t1, and t4-t1 converge to the target relative times t20-t10, t30-t10, t40-t10, and a desired deflection angle θ is obtained. Can do.

  The above process will be described with reference to the block diagram of FIG. The deflected light (scanning light) 133 passes through the first and second light receiving elements 141 and 142 by deflecting the light beam 132 from the light source 131 by the vibration system 100 driven by the drive unit 120 of the light deflector. The drive control unit 600 calculates the time difference 153 (Δt2, Δt3, Δt4) by subtracting the detection time 151 detected by the first and second light receiving elements 141, 142 from the target time 152. Thick arrows 151, 152, and 153 in FIG. 8 indicate that several pieces (three in this case) of time information are transmitted. Further, as shown in Expression 19, the operation amount 155 is calculated by performing a matrix operation by the arithmetic unit 154 based on the time difference 153, and the controllers 611 and 612, the adder 170, and the amplifier 180 are used to calculate the operation amount 120 of the optical deflection device 120. A signal to be input to the driving means (coil 161) is generated. In this case, since t10 is set as the reference time, the operation amount 155 to the controller 611 shown in FIG. 8 is not one, or the operation amount 155 to the controller 612 is not two. Become one. That is, the phase difference φ between the two frequencies can be adjusted by either the controller 611 or the controller 612.

  In addition to the above configuration, in this embodiment, the time differences Δt2, Δt3, and Δt4 are input to the control gain adjuster 620. The control gain adjuster 620 outputs a signal for adjusting the control gains of the controllers 611 and 612 based on the time differences Δt2, Δt3, and Δt4, thereby adjusting the control gain.

  The light deflecting device of this embodiment has two light receiving elements 141 and 142 as displacement angle detecting means. The two light receiving elements 141 and 142 are provided to detect that the scanning light 133 reflected by the reflection mirror of the oscillator 101 of the optical deflector is positioned at two different deflection angles (scanning angles). . However, the two light receiving elements 141 and 142 are not necessarily used. That is, for example, a reflecting plate is installed at the position of the second light receiving element 142 in FIG. 7, and the scanning light 133 is deflected by the reflecting plate, and the deflected light is transmitted directly or through at least one reflecting member. 141 may be adopted. Also in this case, four different timings (time) can be detected in one cycle of the vibration motion by using one light receiving element. By setting these four timings (time) to t1, t2, t3, and t4, respectively, this embodiment can be applied to an optical deflecting device having only one light receiving element.

  An optical deflecting device according to this embodiment will be described. The vibration system 100 including the oscillating bodies 101 and 102 and the torsion springs 111 and 112 has two vibration modes, but is adjusted so that one of those frequencies is approximately twice the other. As an example, the inertia moments of the oscillators 101 and 102 are I1 and I2, and the spring constants of the torsion springs 111 and 112 are k1 / 2 and k2 / 2. The two natural angular frequencies are ω1 = 2π × 2000 [Hz] (first frequency) and ω2 = 2π × 4000 [Hz] (second frequency).

  The deflection angle θ of the optical deflection apparatus according to the present embodiment is expressed as shown in Expression 11. Here, when A1 = 1, A2 = 0.2, φ1 = 0, φ2 = 0, ω1 = 2π × 2000, and ω2 = 2π × 4000, the time change of the deflection angle θ of the optical deflector according to the present embodiment. Is as shown in FIG. The deflection angle θ shown by a solid line in FIG. 9 is closer to a sawtooth wave than a sine wave (shown by a broken line), and can move at a substantially constant angular velocity in a certain region. In this embodiment, A1 = 1, A2 = 0.2, φ1 = 0, φ2 = 0, ω1 = 2π × 2000, and ω2 = 2π × 4000, but the change amount of the angular velocity of the deflection angle is substantially smaller than that of the sine wave. Any A1, A2, φ1, φ2, ω1, and ω2 that are reduced in the equiangular velocity region may be used.

  At this time, if the first and second light receiving elements 141 and 142 are arranged at positions symmetrical to the scanning center 160 of the optical deflecting device in which 80% of A1, that is, the deflection angle θ is 0.8, respectively, as follows. Become. That is, desired target times t10, t20, t30, and t40 (see FIG. 9) for the scanning light 133 to pass through the first and second light receiving elements 141 and 142 are 0.052 msec, 0.154 msec, 0.346 msec, 0 .448 msec. Therefore, the drive signals are controlled by the controllers 611 and 612 so that the detection times t1, t2, t3, and t4 during which the scanning light 133 passes through the first and second light receiving elements 141 and 142 become the desired values. Thus, the deflection angle θ of the optical deflecting device indicated by the solid line in FIG. 9 can be obtained. In the present embodiment, the first and second light receiving elements 141 and 142 are arranged at symmetrical positions from the scanning center 160 of the optical deflecting device in which the deflection angle θ is 0.8, but even at an arbitrary deflection angle θ. Good.

  A more specific method of controlling the deflection angle θ in the present embodiment will be described below.

  For the times t1, t2, t3, and t4, a relative time based on t1 is considered. The operation amounts ΔA1, ΔA2, and Δφ of the amplitude and the phase of the reflecting mirror are three detection relative times t2-t1, t3-t1, t4-t1, and three target relative times t20-t10, t30-t10, t40-t10. The time differences Δt2, Δt3, and Δt4 are obtained by Expression 19. The manipulated variables ΔA1, ΔA2, and Δφ of the amplitudes A1 and A2 and the relative phase φ can be calculated from Expression 19 and the values of the time differences Δt2, Δt3, and Δt4. The manipulated variables ΔA1, ΔA2, and Δφ are input to the controllers 611 and 612, and a signal input to the coil 161 of the driving unit 120 (driving unit) of the optical deflector is generated by the amplifier 180 to drive the vibration system 100.

  Further, the time differences Δt 2, Δt 3 and Δt 4 are sent to the control gain adjuster 620. Based on these Δt2, Δt3, and Δt4, the control gain adjuster 620 sends a signal for changing the control gain to the controllers 611 and 612 so that the evaluation function having Δt2, Δt3, and Δt4 as variables becomes an optimum value. send.

  In the present embodiment, t1, t2, t3, t4, t10, t20, t30, and t40 are determined values, but may be values having a certain range. Although t20-t10, t30-t10, and t40-t10 are determined values, they may be values having a certain range. In this embodiment, t1, t2, t3, t4, t10, t20, t30, and t40 are handled as times, but a counter value based on a certain clock may be used. These are the same in other embodiments.

ここで、本実施例ではＮ＝１、ｍ＝２、Ｗｉ＝１とする。また、ｎ＝３であり、評価関数Ｊは以下のように表される。

この評価関数Ｊを最小にするような、制御器６１１，６１２の制御ゲインを決定する。 When N is the number of measurements, n is the number of the time differences, m is a natural number, and Wi is an arbitrary real number greater than or equal to 0 representing the weight, an evaluation function J using the time differences Δt2, Δt3, and Δt4 as variables is as follows: I will express it in

Here, in this embodiment, N = 1, m = 2, and Wi = 1. Further, n = 3, and the evaluation function J is expressed as follows.

Control gains of the controllers 611 and 612 are determined so as to minimize the evaluation function J.

When the controllers 611, 612 constitute a PI controller for each of A1, A2, and φ, the inputs to the controllers 611, 612 are ΔA1, ΔA2, and Δφ, and A1def, A2def, and Aφdef are fixed values. Then, each output is expressed by the following formula.
K1 (1 + K1 ′ / s) ΔA1 + A1def Equation 22
K2 (1 + K2 ′ / s) ΔA2 + A2def Equation 23
K3 (1 + K3 ′ / s) Δφ + φdef Equation 24
K1, K2, K3, K1 ′, K2 ′, and K3 ′ are control gains, and K1 ′, K2 ′, and K3 ′ represent reciprocals of the integration time of the PI controller. s is a Laplace operator. In the present embodiment, a configuration is shown in which K1 ′, K2 ′, and K3 ′ are not adjusted, and only K1, K2, and K3 are adjusted using the evaluation function J.

  Predetermined x control gain candidates K1p (p is a natural number from 1 to x), y control gain candidates K2q (q is a natural number from 1 to y), z control gain candidates K1r (r is 1) The natural number from to z is set as the control gain of the controllers 611 and 612. This combination is x × y × z.

  Here, it demonstrates using the flowchart of FIG. The control gain is set to one set of control gain candidates. For example, in step S201 (hereinafter simply referred to as S201), p = q = r = 1, K1 = K11, K2 = K21, and K3 = K31 (S202, S203, S204). In this state, the operation amount 155 is calculated by sending the time differences Δt2, Δt3, Δt4 (153) to the calculator 154. Then, the controller 611, 612, the adder 170, and the amplifier 180 generate a signal to be input to the coil 161 of the driving unit 120 (driving means) of the optical deflection apparatus, and drive the vibration system 100.

  After changing the control gain, the vibration motion of the vibration system 100 is controlled, and after a predetermined time has elapsed (S205), the evaluation function J is calculated using the values obtained by measuring the time differences Δt2, Δt3, and Δt4 N times (S206). In this embodiment, since N = 1, the value measured once is used. At that time, a set of the value obtained by calculating the evaluation function J and the values of the control gains K1, K2, and K3 at that time is stored in the control gain adjuster 620 (S207).

  Next, the control gain adjuster 620 sends a signal to reset the control gains of the controllers 611 and 612 to different control gain candidates to the controllers 611 and 612 to reset the control gain. 1 is added to r (S208), and while r is less than z, the process returns to S204. For example, by setting K3 = K32, one set of the next control gain is K1 = K11, K2 = K21, K3. = K32.

  After setting the control gain, the operation amount 155 is calculated by sending the time differences Δt2, Δt3, Δt4 (153) to the calculator 154. Then, the controller 611, 612, the adder 170, and the amplifier 180 generate a signal to be input to the drive unit 120 (drive means) of the optical deflector, and drive the vibration system 100. After a predetermined time has elapsed (S205), the evaluation function J is calculated (S206), and the set of the evaluation function J value and the control gain values K1, K2, and K3 at that time is stored in the control gain adjuster 620 (S207). ).

  The above process is repeated x × y × z times, and all control gain candidates are actually set as control gains. Through the steps S208 to S215, all combinations of control gain candidates can be set. Even if it is not the same as the process of S208 to S215, the combination of the control gain of xxyxz should just be performed. By performing the processing up to S 215, a set of x × y × z evaluation function J values and control gain values at that time is stored in the control gain adjuster 620. The control gain adjuster 620 compares the values of the evaluation functions J (S216), and sends a signal for setting the control gain value when the evaluation function J is minimum to the controllers 611 and 612 (S217). ). After a predetermined time has elapsed (S218), light deflection is performed using the control gains K1, K2, and K3 set as described above.

  In this embodiment, all the combinations of the control gains K1, K2, and K3 and the evaluation function J are stored in the control gain adjuster 620, and the control gain combination that minimizes the evaluation function J is selected and set. . However, the control gain adjuster 620 may perform the following operations by storing only one set of the evaluation function J and the control gain at that time. That is, only when the control gains K1, K2, and K3 are changed and the value of the evaluation function J at that time is smaller than the value of the stored evaluation function J, the set of the evaluation function J and the control gain is changed to the previous one. The operation of overwriting and storing the value of is performed. Similarly, control gains K1, K2, and K3 that minimize the evaluation function J can be obtained.

  In this embodiment, the controllers 611 and 612 are PI controllers, and one optimal control gain group is determined. Here, the controllers 611 and 612 may be P controllers. In that case, by setting K1 ′, K2 ′, and K3 ′ to 0, the controller 611 and 612 can be realized with the same configuration as in the present embodiment. it can.

  In the present embodiment, the control gains K1 ', K2', and K3 'are not adjusted, and only K1, K2, and K3 are adjusted. Even when all the control gains of K1 ′, K2 ′, and K3 ′ are changed in addition to K1, K2, and K3, only the combination of the control gains is increased, and the basic configuration remains unchanged. Can be applied. For example, if the number of control gains K1 ′, K2 ′, and K3 ′ is x ′, y ′, and z ′, there are x × y × z × x ′ × y ′ × z ′ combinations. Should be considered.

  In this embodiment, the time difference is defined as Δti = (ti−t1) − (ti0−t10), (i = 2, 3, 4), and the evaluation function J is defined as Equation 20. However, the time difference may be defined as Δti = ti−ti0, (i = 1, 2, 3, 4), and the evaluation function J of Expression 20 may be used. In this case, n = 4.

  Further, even when the time difference Δti (i = 2, 3, 4) is set as shown in FIG. 11 such as Δt2 = t2−t1, Δt3 = t3−t2, Δt4 = t4−t3, the evaluation is similarly performed. The control gain can be adjusted using the function J. In the evaluation function J of Expression 20, since weighting is performed using Wi, the present invention can be applied even when the definition of Δti is different from the present embodiment. When changing the definition of Δti, it is also necessary to change the matrix operations shown in Equation 18 and Equation 19.

  Japanese Patent Application No. 2006-035491 discloses a relational expression for obtaining ΔA1, ΔA2, Δφ1, and Δφ2 from Δti when Δti = ti−ti0 (i = 1, 2, 3, 4). Based on this relational expression, when the time difference is defined as Δti = ti−ti0 (i = 1, 2, 3, 4), a control gain that sets the evaluation function J to an optimum value may be obtained. Also in this case, it is necessary to change the matrix operations shown in Expression 18 and Expression 19 in accordance with the change in the definition of Δti.

  In this embodiment, a control gain that sets the evaluation function J to an optimum value is set. However, even if the evaluation function J is optimal, if the value of at least one certain time difference (for example, Δt2) deviates from the set range, there is a possibility that the desired optical scanning may not be realized. is there. Even if the evaluation function J in this case is optimum (minimum), the desired optical scanning cannot be realized, so that the value of the control gain is inappropriate.

  Therefore, when this time difference Δti is out of the set range or each time difference, the value of the control gain at that time is given to the controllers 611 and 612 regardless of the value of the evaluation function J at that time. An operation of not resetting may be performed.

  In this case, the time difference is set to have a means for comparing the set time. When the time difference deviates from the set range, the set of the evaluation function J value and the control gain value at that time is not stored, or the control gain is not used even if stored. It is necessary to have a means for storing. The same applies to other embodiments.

  In this embodiment, three control gains are changed. As a method for optimizing the evaluation function J without limiting the number of control gains to be changed, the following method can be cited in addition to the methods performed in the first to third embodiments. For example, experimental design method, quality engineering method, response surface method, sensitivity analysis, Newton method, quasi-Newton method, steepest descent method, conjugate gradient method, neural network method, annealing method, tabu search method, genetic algorithm method and so on. The method of the optical deflecting device in the present invention is not limited. When a large number of control gains are changed, an optimization method may be selected in consideration of solution convergence and calculation time. The same applies to the other embodiments.

  By using the above method for optimizing the evaluation function J, the number of times of changing the control gain can be reduced. As a result, the time required for gain adjustment can be shortened, and an optimum gain can be obtained quickly.

  An image forming apparatus according to Embodiment 4 of the present invention will be described. The block diagram of the optical deflecting device of this embodiment is the same as that shown in FIG. 1 or FIG. The configuration is the same as that shown in FIG. 3 or FIG.

  The overall appearance configuration of the present embodiment is shown in the perspective view of FIG. The light emitted from the light source 131 is shaped by the collimator lens 520 and then deflected one-dimensionally by the vibration system 100 driven by the drive unit 120 of the light deflection apparatus. The scanning light forms an image on the photosensitive drum 540 through the coupling lens 530. Two light receiving elements 141 and 142 are disposed at the deflection angle of the vibration system 100 outside the range that defines the effective area of the photosensitive drum 540. Then, the angular velocity of the deflection angle θ of the vibration system 100 of the optical deflection apparatus is controlled to be substantially equal angular velocity in a predetermined region (substantially equal angular velocity region) by the control method described in the first, second, third, etc. To do. As a result, by providing the coupling lens 530 with a so-called fθ function, optical scanning can be performed at a substantially constant speed on the effective area of the photosensitive drum 540. According to this embodiment, since the change in the angular velocity is smaller than that in the case of driving with a sine wave, good printing can be performed.

  In FIG. 12, the two light receiving elements 141 and 142 are arranged, but as described above, the two light receiving elements may not be used. That is, if it has at least one light receiving element, a reflecting plate is installed at the position of the deflection angle to be detected, and the scanning light is deflected by the reflecting plate, and the deflected light is directly or through at least one reflecting member. It is good also as a structure which passes the light receiving element.

  In the present embodiment, any of the configurations shown in the first to third embodiments may be used for adjusting the control gain. In the image forming apparatus according to the present exemplary embodiment, the timing for adjusting the control gain and obtaining the optimum control gain is set to a timing other than the time of image formation.

  Adjusting the control gain may increase the jitter of the vibration system 100 as described above. As a result, performing control gain adjustment during image formation may reduce the accuracy of image formation. Therefore, in this embodiment, the evaluation function J is optimized except when the image is formed, specifically, when the photosensitive drum 540 of the image forming apparatus is not performing image formation at the time of multiple rotations or cleaning. Adjust the control gain.

  As the number of control gains to be adjusted increases and as the number of control gain candidates increases, the control gain adjustment time becomes longer. If the number of combinations of control gains increases, the control gain adjustment time also increases, and therefore the first printout time may increase. Therefore, it is necessary to determine the number of control gains, the number of combinations of control gain candidates, the number of times of measurement N, the optimization method of the evaluation function J, and the like so that the gain adjustment is completed within the previous multi-rotation time of the image forming apparatus.

1 is a block diagram illustrating a configuration of an optical deflecting device according to Embodiment 1. FIG. 6 is a plan view of a deflection angle of the optical deflecting device according to Embodiment 1. FIG. FIG. 3 is a block diagram illustrating control of the optical deflection apparatus according to the first embodiment. 6 is a graph showing a change with time of a deflection angle of the optical deflection apparatus according to the first embodiment. 6 is a flowchart for describing processing for determining a control gain using an evaluation function according to the first embodiment. FIG. 9 is a block diagram illustrating a configuration of an optical deflecting device according to a third embodiment. 6 is a plan view of a deflection angle of an optical deflecting device according to Embodiment 3. FIG. FIG. 9 is a block diagram for explaining control of an optical deflection apparatus according to Embodiment 3. 12 is a graph showing a change with time of the deflection angle of the optical deflecting device according to Example 3. 12 is a flowchart for describing processing for determining a control gain using an evaluation function according to a third embodiment. 12 is a graph showing a change with time of the deflection angle of the optical deflecting device according to Example 3. FIG. 10 is a top perspective view illustrating scanning of a light deflection apparatus according to a fourth embodiment onto a photosensitive drum. It is a block diagram which shows the structure of the optical deflection apparatus which concerns on a prior art example. It is a block diagram explaining control of the optical deflection apparatus concerning a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Vibration system 101,102 Oscillator 111,112 Torsion spring 120 Drive part (drive means)
121 Supporting part 131 Light source 132 Light beam 133 Scanning light 140 Light receiving element (displacement angle measuring means)
141 1st light receiving element (displacement angle measurement means)
142 Second light receiving element (displacement angle measuring means)
160 Scanning Center 161 Coil (Drive Unit)
162 Permanent magnet (drive means)
170 Adder 180 Amplifier 420 Driver (Driver)
431 Light source 432 Scanning light 441 First light receiving element (displacement angle measuring means)
442 Second light receiving element (displacement angle measuring means)
450 Drive control unit (drive control means)
454 Calculator 520 Collimator lens 530 Coupling lens 540 Photosensitive drum 600 Drive control unit (drive control means)
610 Controller 611, 612 Controller 620 Control gain adjuster

Claims (9)

A vibration system having one or more oscillating bodies and one or more torsion springs connected to the oscillating bodies; a reflection mirror formed on at least one of the oscillating bodies; and a light source for generating a light beam; Displacement for measuring time when at least one of the driving means for applying a driving force to the vibration system and causing the oscillating body to make vibration motion at a predetermined frequency and at least one displacement angle. An optical scanning device comprising: an angle detection unit; and a drive control unit that controls the drive unit based on a time measured by the displacement angle detection unit, and irradiates the light beam onto the reflection mirror to scan the light. And
A control gain adjusting means for adjusting a control gain of the drive control means;
When the predetermined time within one cycle of the frequency is set as a reference or origin time, the drive control means has at least one time when the oscillating body forms at least one predetermined displacement angle. Calculating a time difference from the set time, and controlling at least one of the amplitude and phase of the vibration waveform of the vibration motion based on the time difference;
The optical scanning device characterized in that the control gain adjusting means adjusts the control gain based on the time difference and sets the control gain in the drive control means. A vibration system having one or more oscillating bodies and one or more torsion springs connected to the oscillating bodies; a reflection mirror formed on at least one of the oscillating bodies; and a light source for generating a light beam; In order to measure a time when at least one of the driving means for applying a driving force to the vibration system to cause the vibration system to perform a vibration motion at a predetermined frequency and at least one of the oscillators have different first and second displacement angles. And a drive control means for controlling the drive means based on the time measured by the displacement angle detection means, and scanning the light by irradiating the light beam onto the reflection mirror. Because
A control gain adjusting means for adjusting a control gain of the drive control means;
When the predetermined time within one cycle of the frequency is set as a reference or origin time, the drive control means is configured so that different times when one of the oscillating bodies forms the first displacement angle are different from each other. Calculating a time difference between a set time and at least two of a plurality of times when one of the moving bodies forms the second displacement angle, and vibration of the vibration motion based on the time difference Control at least one of the amplitude and phase of the waveform;
The optical scanning apparatus characterized in that the control gain adjustment means adjusts the control gain based on the time difference and sets the control gain in the drive control means.   The vibration system can simultaneously generate a first vibration motion that moves at a first frequency that is a fundamental frequency and a second vibration motion that moves at a second frequency that is an integer multiple of the fundamental frequency. And the driving means is capable of applying a first periodic driving force having the first frequency and a second periodic driving force having the second frequency to the vibration system. The optical scanning device according to claim 2.   4. The optical scanning device according to claim 1, wherein a period in which the control gain is adjusted by the control gain adjusting unit is longer than a period in which the oscillator is controlled by the drive control unit. .   The control gain adjusting means includes means for calculating an evaluation function using the time difference as a variable, and means for setting the control gain in the drive control means based on the calculated evaluation function. The optical scanning device according to claim 1. When the control gain is set and the time difference is measured k times, the time difference value is Δti (k), N is the number of times of measurement, n is the number of the time differences, m is a natural number, and Wi is a weight of 0 or more. The optical scanning apparatus according to claim 5, wherein the evaluation function is represented by the following expression when an arbitrary real number is:

The control gain adjustment means has storage means,
The storage means stores a plurality of control gain values and a plurality of evaluation function values corresponding to the plurality of control gains obtained by the equation 1,
The control gain adjusting unit selects an evaluation function having a minimum value from the plurality of evaluation functions stored by the storage unit, and drives the control gain corresponding to the evaluation function having the minimum value. The optical scanning device according to claim 6, wherein the optical scanning device is set in a control unit.   The control gain adjusting means does not set the value of the control gain at this time as the control gain of the drive control means regardless of the value of the evaluation function when the value of the time difference is out of the set range. 8. An optical scanning device according to claim 5, wherein An image forming apparatus comprising the optical scanning device according to claim 1,
The image forming apparatus, wherein the control gain adjusting unit sets the control gain in the drive control unit except during image formation.

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