JP2009025795A - Optical deflector - Google Patents

Abstract

An optical deflector capable of stably controlling the operation of optical deflection at a relatively high speed.
An optical deflector includes a deflecting unit, a vibration state detecting unit, a driving signal generating unit, a modulation timing signal generating unit, and a deflection state detecting unit. The deflecting unit deflects the light from the light source 101. The vibration state detection means detects the vibration state of the deflection means. The drive signal generation unit generates a drive signal for driving the deflection unit. The modulation timing signal generating means generates a reference time for controlling the light amount of the light source as a modulation timing signal. The deflection state detection means detects the deflection state of the deflected light generated when the light from the light source is deflected by the deflection means. The drive signal generation means generates a drive signal based on the detection information of the vibration state detection means, and the modulation timing signal generation means generates a modulation timing signal based on the detection information of the deflection state detection means.
[Selection] Figure 1

Description

The present invention relates to an optical deflector including a vibration system having a vibrating body with a light deflecting element supported so as to be able to vibrate and having a deflecting unit that deflects light from a light source by the vibrating body, and an image forming apparatus using the same. It relates to optical equipment.

As a conventional example of an optical deflector, a galvanometer mirror shown in FIG. 8 has been proposed (see Patent Document 1). This is a galvanometer mirror driven by electromagnetic force. Here, the mirror 56 is disposed on the movable plate 53, and the movable plate is supported from the silicon substrate 50 as the main body by the torsion bar 54 so as to rotate about the axis. The driving means for driving the movable plate 53 includes a planar coil 55 and permanent magnets 60 to 63. Therefore, this optical deflector is an electromagnetic type that is driven by passing a driving current through the planar coil 55 and utilizing the Lorentz force with the permanent magnet. In FIG. 8, reference numeral 51 denotes an upper glass substrate, reference numeral 52 denotes a lower glass substrate, and reference numeral 57 denotes an electrode terminal.

As another conventional example, there is the same electromagnetic type electromagnetic actuator having a total reflection mirror in a movable part (see Patent Document 2). The proposed example of Patent Document 2 focuses on the following problems. In other words, the resonance cycle of an electromagnetic actuator usually drifts with temperature or with age. Therefore, if a current having a preset resonance frequency is continuously supplied to a planar coil, it will fluctuate due to temperature changes and the passage of time. Note that the angle is not controlled constant. The purpose is to provide the following. That is, to provide an electromagnetic actuator that can be reciprocated with a resonance period without providing a separate detection means. To provide an electromagnetic actuator capable of controlling a deflection angle (amplitude) without providing a separate detection means. To provide a resonance frequency signal generation device for an electromagnetic actuator capable of outputting a resonance frequency signal corresponding to the resonance period of the electromagnetic actuator. As an achievement means, the coil is used not only for exciting the movable part but also for detecting. For the detection, an induced electromotive voltage or induced electromotive current generated in the coil is used. The timing at which the actuator passes a certain rotation angle (deflection angle) is detected as time information from the coil as detection means.
JP 07-175005 A JP 2001-305471 A

However, when an optical deflector as disclosed in Patent Document 2 is used for deflecting light that is modulated in accordance with an image signal, the temperature of the optical deflector varies depending on the content of the image signal. For this reason, the operation of the light deflection changes, which causes deterioration of the formed image. In order to form an image with high accuracy, it is necessary to follow the modulation speed of the image signal as much as possible to correct the optical deflection operation.

In view of the above problems, the optical deflector of the present invention has the following characteristics. The optical deflector includes deflection means, vibration state detection means, drive signal generation means, modulation timing signal generation means, and deflection state detection means. The deflecting means includes a vibration system having a vibrating body with an optical deflection element supported so as to be capable of vibrating, and deflects light from the light source by the vibrating body. The vibration state detection means detects the vibration state of the vibration system of the deflection means. The drive signal generation unit generates a drive signal for driving the vibration system of the deflection unit. The modulation timing signal generating means generates a reference time for controlling the light amount of the light source as a modulation timing signal. The deflection state detection means detects the deflection state of the deflected light generated when the light from the light source is deflected by the deflection means. Further, the drive signal generation means generates a drive signal based on the detection information of the vibration state detection means, and the modulation timing signal generation means generates a modulation timing signal based on the detection information of the deflection state detection means.

In view of the above problems, an optical apparatus such as an image forming apparatus and an image display apparatus according to the present invention includes the optical deflector, a light source, and a target object. The optical deflector deflects light from the light source, At least part of the light is incident on the target object. Then, an image is formed on the target object using incident light while synchronizing image data for controlling the light amount of the light source with the modulation timing signal.

According to the optical deflector of the present invention, since both the vibration state detecting unit and the deflection state detecting unit as described above are provided, the operation of the optical deflection can be controlled at high speed and stably. Therefore, for example, the optical deflection operation can be corrected in a short time with respect to the image update speed, and a stable and highly accurate optical apparatus such as an image forming apparatus or an image display apparatus can be realized.

Hereinafter, embodiments of an optical deflector according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows a configuration diagram of an optical deflector according to the present embodiment. In FIG. 1, 101 includes a light source such as a semiconductor laser, 102 includes a vibration system having a vibration body with a light deflection element such as a total reflection mirror supported so as to be able to vibrate, and deflects a light beam 201 from the light source 101 by the vibration body. The deflection means. The deflecting means 102 has at least one natural vibration mode. A plurality of natural vibration modes having vibration modes around the same axis or vibration modes around different axes may be provided. Reference numeral 103 denotes vibration state detection means for detecting the vibration state of the vibration system of the deflection means 102, and reference numeral 104 denotes drive signal generation means for generating a drive signal 203 for driving the vibration system of the deflection means 102. Reference numeral 105 denotes modulation timing signal generation means for generating a reference time for controlling the light amount of the light source 101 as the modulation timing signal 204. Reference numeral 106 denotes a deflection state detection unit that detects the state (deflection state) of the deflected light deflected by the deflection unit 102. Further, 202 is a detection signal that is detection information of the vibration state detection means that indicates the vibration state of the deflection means, 205 is a signal that is detection information of the deflection state detection means 106 that indicates the deflection state of the deflection means, and 206 is the light source of the light source. A modulation pattern signal (image signal or the like). A specific example of the deflection state detecting means 106 will be described later in the third embodiment.

In this specification, the state in which the vibration system of the deflecting means 102 is oscillating is referred to as “vibration state”. The deflecting means 102 deflects the light beam 201 from the light source 101 and moves it on a predetermined surface. This state is called a “deflection state”.

In the present embodiment, the light source 101 includes means for controlling (also referred to as modulation) the amount of light output from the light source. For example, in the case of a semiconductor laser, it is an electrode to which a control voltage or current is applied. As a method for controlling (modulating) the amount of light, a method of changing the intensity of the light amount of the light source 101 in time series, turning on and off the light source 101 repeatedly, and changing the proportion of time that the light is lit per unit time. There are methods. In the optical deflector of the present embodiment, a modulation pattern signal 206 that controls how the light source 101 should change the amount of light is input to the light source 101.

By deflecting and scanning the light beam 201 modulated from the light source 101 controlled by the modulation pattern signal 206 by the deflecting means 102, an image forming apparatus or the like can be configured by the optical deflector. At this time, a desired light deflection can be obtained by adjusting the timing at which the vibration system of the deflecting means 102 is oscillating and the timing or the reference timing for modulation of the light source 101.

As the deflecting means 102, for example, the actuator described in the background art can be used. Desirably, the deflection means 102 can obtain a desired vibration state by being driven using resonance. Resonance is that the magnitude (amplitude) of the vibration of the vibration system of the deflecting means 102 greatly depends on the frequency of the drive signal 203, and vibration occurs particularly efficiently at a specific frequency (resonance frequency). It is a phenomenon that is done. As the driving means of the deflecting means 102, it is possible to apply a driving force to the deflecting means 102 by an electrostatic system, a piezoelectric system, or the like, in addition to the electromagnetic system including the driving coil and magnet described in the background art. In the case of electrostatic driving, an electrode is formed on at least one vibrating body, and an electrode that causes an electrostatic force to act on the electrode is formed in the vicinity of the vibrating body. In the case of piezoelectric driving, a piezoelectric element is provided in a vibration system or its support part and a driving force is applied.

FIG. 2 shows a characteristic diagram of the deflecting means 102 driven using resonance. 2 is the frequency of the drive signal 203 to the deflection means 102, the vertical axis in FIG. 2A is the magnitude of the deflection angle (amplitude) of the deflection means 102, and the vertical axis in FIG. 2B is the deflection means. The phase of the vibration of 102. Here, the vibration phase represents the ratio of the vibration deviation of the deflection means 102 with respect to the drive signal 203. As can be seen from FIG. 2, the deflection angle is largest at the resonance frequency fc, and the rate of phase change is also greatest there.

This index of efficiency at resonance is called the Q value. As the Q value is larger, vibration of the vibration system of the deflecting means 102 can be generated with less input energy. In addition, since the response to signals other than the resonance frequency fc becomes insensitive, the vibration of the vibration system of the deflecting unit 102 can be easily maintained in a more stable state. However, the larger the Q value, the more easily the magnitude of vibration and the phase of vibration when the driving frequency deviates from the resonance frequency fc. This resonance frequency fc shifts sensitively due to environmental changes such as temperature.

Here, the operation will be described by considering only the configuration of the light source 101 and the deflecting means 102.
The greater the Q value of the vibration system used in the deflection means 102, the slower the response to which the actual vibration state of the vibration system of the deflection means 102 reacts when the drive signal 203 is changed. Therefore, as a method for maintaining the vibration system of the deflection means 102 using resonance in a desired vibration state, it takes a long time to correct the vibration state of the deflection means 102 when the drive signal 203 is changed. Become.

When the environmental change or the heat generation of the deflecting means 102 itself occurs greatly, the vibration state of the deflecting means 102 in the resonance state changes greatly. Therefore, it is necessary to greatly correct the vibration state of the deflecting means 102 by changing the drive signal 203.

Regarding the method of correcting the change in the vibration state due to the environmental change, since this change is relatively slow in time, the method of changing the drive signal 203 sufficiently follows the deflection means 102 to the predetermined vibration state. Can keep.

However, the method for correcting the change in the vibration state due to the heat generation of the deflecting means 102 itself is as follows. Here, a case where an optical deflector is used in an image forming apparatus will be described as an example. By controlling (modulating) the light amount of the light source 101 in correspondence with the signal of the image to be formed (the modulation pattern signal 206 of the light source 101), the light amount incident on the deflecting means 102 changes. Therefore, heat may be generated in the deflecting unit 102, and the temperature or the like may locally change. Therefore, when the deflection unit 102 is driven with the same drive signal 203, the vibration state of the deflection unit 102 may fluctuate in response to a change in the image signal (the modulation pattern signal 206 of the light source 101). As a result, the deflection state of the light deflection is changed, so that an image formed by the image forming apparatus is deteriorated.

When the drive signal 203 is changed for the purpose of suppressing the fluctuation of the vibration state of the deflecting means 102, the follow-up operation of the deflecting means 102 is slow, so that the image signal (the modulation pattern signal 206 of the light source 101) changes quickly. Can not respond. Therefore, the formed image cannot be greatly improved.

In the present invention including this embodiment, the deflection means 102 “(1) Fluctuation of a relatively long-cycle vibration state due to the environment” and “(2) Vibration state of a relatively short-cycle due to changes in image data, etc. "Variation" is controlled together by another method. According to the present invention, “(1) detects the vibration state of the deflection means 102 and corrects it with the drive signal 203 based on the information”, “(2) detects the deflection state of the optical deflection, and the information Is corrected using a modulation timing signal 204 to the light source 101 ”. In other words, for the change in the long-period deflection operation due to the environmental change in (1), the vibration state of the deflection means is corrected by the drive signal generation means, and in the short-period deflection operation due to the change in the image signal in (2). For the change, the operation of the light source is corrected by the modulation timing signal generating means.

Next, the vibration state detection unit 103 and the drive signal generation unit 104 related to the correction of the variation (1) will be described. The vibration state detection unit 103 detects the vibration state of the deflection unit 102 and outputs a detection signal 202 representing the vibration state to the drive signal generation unit 104. Any vibration state detection means 103 can be used as long as the vibration state can be monitored. For example, an electromagnetic type sensor, a capacitance type sensor, a piezoelectric type sensor, etc. incorporated in the deflecting means 102 can be mentioned. It is preferable that the reciprocating vibration of the deflecting means 102 can be detected sinusoidally. In this case, since the sensor built in the deflection means that vibrates sinusoidally generates a signal according to the displacement angle of the deflection means, the signal generated from the sensor has a sinusoidal waveform. As described above, the configuration in which the reciprocating vibration of the deflecting unit 102 is detected in a sine wave manner is suitable when a self-excited oscillation circuit described later is used.

For example, in the case of a piezoelectric sensor, the vibration state detecting means can be configured using a piezoresistor. In order to detect the displacement angle of a vibrating body using a piezoresistor, for example, when a piezoresistor is provided in a torsion spring and the vibrating body takes a certain displacement angle based on a signal output from the piezoresistor. Detect time. The piezoresistor is manufactured, for example, by diffusing phosphorus in p-type single crystal silicon. If a constant current is passed through the piezoresistor, a voltage signal is output according to the torsion angle of the torsion spring. Therefore, when measuring the displacement angle of the vibrating body, it is possible to accurately measure the displacement angle of the vibrating body by providing the piezoresistors on the plurality of torsion springs and obtaining the displacement angle of the plurality of torsion springs. it can.

The drive signal generation means 104 receives the vibration state detection signal 202 and generates the drive signal 203 based on it. The drive signal generation unit 104 generates the drive signal 203 by changing the frequency or the like so that the vibration state of the deflection unit 102 is maintained at the target vibration state.

Specifically, first, the frequency of the drive signal 203 is changed to bring the vibration into a resonance state or a certain state near the resonance. Next, the magnitude of the drive signal 203 is changed so that the amplitude of the vibration state becomes a predetermined magnitude. By repeating this, the vibration state of the deflecting means 102 can be maintained at the target state.

As a method of bringing vibration to a resonance state or a certain state near resonance, there are a method of observing the magnitude of vibration and a method of observing the phase of vibration. These utilize the characteristics described in FIG.

In the method of observing the magnitude of vibration, the frequency of the drive signal 203 is changed so that the magnitude of vibration is maximized. For example, when the frequency is slightly increased and the vibration seems to increase, the frequency is increased in that direction. If the vibration appears to decrease, the frequency is reduced. This process is repeated to find the frequency at which the magnitude of vibration becomes maximum (see FIG. 2 (a)).

The method of observing the phase of vibration is performed as follows. It is known that when the deflecting means 102 is in a resonance state, the vibration phase is shifted by 90 ° with respect to the input waveform of the driving energy. That is, the phase difference between the input waveform of the driving energy and the change in the oscillating angle can be said to be 90 ° (see FIG. 2B). The sign of the numerical value of the phase difference depends on the direction defined by the waveform and angle. Actually, the phase difference between the drive signal 203 and the signal 202 indicating the vibration state is shifted from 90 ° due to the delay of the circuit or the like. In consideration of the deviation due to the delay of the circuit, the frequency of the drive signal 203 is changed so that the drive signal 203 and the signal 202 indicating the vibration state have a certain phase difference. Thereby, the deflecting means 102 can be maintained in a resonance state or a certain state near the resonance.

The operation of correcting the variation (1) by the vibration state detection unit 103 and the drive signal generation unit 104 can be performed, for example, when the apparatus is started or periodically during the operation of the apparatus. For example, it may be performed when the magnitude of vibration falls below a reference value. Further, a thermometer may be installed in the apparatus, and this correction operation may be performed when a temperature variation of a certain level or more is detected.

Next, the deflection state detection means 106 and the modulation timing signal generation means 105 related to the correction of the variation (2) will be described. As described above, the modulation timing signal generation unit 105 generates a reference time when the light source 101 controls (modulates) the light amount as the modulation timing signal 204 and outputs it to the light source 101. This modulation timing signal 204 is generated based on a detection signal 205 (detected by the deflection state detection means 106) of the deflection state of the deflection / scanning light generated by deflecting the light beam 201 from the light source 101.

For example, when an optical deflector is used in an image forming apparatus, it is difficult to form a high-quality image as described above only by controlling the vibration state performed using the drive signal generation unit 104. The reason for this is that (1) the accuracy of detecting the vibration state of the deflecting means 102 cannot be improved so much, and (2) the image to be formed and the deflecting means 102 due to the delay of the drive signal and the modulation of the light source. There is a point that the vibration state does not correspond completely.

FIG. 3 is a diagram for explaining optical deflection on an arbitrary scanning plane due to a certain modulation signal 206. It is assumed that the deflection / scanning light 301 as shown in FIG. 3A is formed using one of the deflection / scanning directions. However, in practice, the relationship between the direction of light deflection and the modulation timing of the light source 101 may deviate from the desired one. Due to this deviation, as shown in FIG. 3B, the deflection / scanning light 301 from the light source deviates from a desired position (desired deflection angle), and the image formation pattern deviates from the position where an image is desired to be formed. It will end up.

When both of the reciprocating vibrations of the deflecting means 102 are used for image formation, a particularly significant deviation occurs. This is because the image formed by the forward deflection and the image formed by the backward deflection are shifted in opposite directions, so that the deviation is enhanced twice. For example, if FIG. 3C shows a desired light deflection, when a deviation occurs, the light deflection as shown in FIG. 3C and 3D, reference numeral 302 denotes deflection / scanning light scanned in the A direction, and reference numeral 303 denotes deflection / scanning light scanned in the B direction.

In order to solve this problem, in the present embodiment, the modulation timing signal generation unit 105 modulates the modulation timing based on the detection signal 205 of the deflection / scanning light deflection state generated by deflecting the light beam 201 from the light source 101. Correction is performed by the signal 204. Specifically, by shifting the modulation timing signal 204 on the time axis, processing for correcting the timing at which the light source 101 is modulated in accordance with the deflection state of the optical deflection is performed. That is, the modulation timing signal generation unit 105 generates a modulation timing signal so that the deflected light is in a target deflection state.

As a means for detecting the deflection state of the optical deflection, an element for optically detecting the deflection state can be used (see a third embodiment described later). For example, a photo detector, a position detection element (PSD;
position-sensing-detector), an image sensor, etc. can be used.

Since the deflection state detection means 106 directly detects the deflection state of the optical deflection, it can detect the optical deflection state with high accuracy. That is, the vibration state of the deflecting means 102 is not detected, but the position of the deflection / scanning light is detected, so that problems such as a decrease in accuracy due to a signal response do not occur. In addition, since the state of light deflection is detected, including a decrease in accuracy at the time of vibration state detection, a delay in drive signal, a delay in modulation of the light source, and the like, there are no error factors. Therefore, it is possible to detect the state of light deflection with very high accuracy.

Here, since the correction is performed based on the modulation timing of the light source 101, the state of light deflection can be finely corrected. Furthermore, since the vibration state of the deflecting means 102 is not corrected by the drive signal generating means 104 but is corrected at the modulation timing of the light source, it can be corrected in real time.

Therefore, in the present embodiment, it is possible to maintain a desired deflection state by correcting a change in the deflection state having a relatively short cycle due to a change in image data or the like at high speed.

The operation of correcting the variation (2) by the deflection state detection means 106 and the modulation timing signal generation means 105 is performed every time or at an appropriate time, for example, at a place where the deflection / scanning light reciprocated by the deflection means 102 turns back. Can do. Typically, the time interval at which the drive signal generation unit 104 updates (corrects) the drive signal is the time interval at which the modulation timing signal generation unit 105 updates (corrects) the modulation timing signal, because of the above two fluctuation characteristics. Longer than interval.

According to this embodiment, it is possible to provide an optical deflector capable of controlling the optical deflection operation at a high speed and stably to a target state by controlling both the variation (1) and the variation (2).

Note that a self-excited oscillation circuit can be used for the drive signal generation means 104 of the present embodiment. The self-excited oscillation circuit is a circuit that positively feeds back the vibration state detection signal 202 of the deflecting means 102 using an operational amplifier or the like to generate a drive signal 203. The self-excited oscillation circuit can automatically adjust the drive signal 203 so that the magnitude of the detection signal 202 is maximized. Therefore, it is resistant to external noise and the deflection means 102 can always be stably held in a resonance state or a certain state near resonance.

This circuit can be realized with a simple configuration centered on one operational amplifier. By using this self-excited oscillation circuit, when the deflecting means 102 is driven using the resonance phenomenon, the deflecting means 102 can be used as an oscillator. Therefore, it is not necessary to add a means for generating a frequency, and the drive signal generating means 104 can be configured with a small number of parts. In such a case, the vibration state detection means 103 is preferably capable of detecting the reciprocal vibration of the deflection means 102 in a sine wave manner as described above.

By using the self-excited oscillation circuit, the drive signal generation means 104 can be stably realized with a small number of components. Therefore, an optical deflector that realizes stable and accurate optical deflection with a simple configuration can be provided.

(Second embodiment)
The optical deflector according to this embodiment is characterized by the modulation timing signal generation means 105. Others are the same as the first embodiment.

In the present embodiment, the modulation timing signal generation unit 105 generates the modulation timing signal 204 using a signal synchronized with the drive signal 203. In other words, the modulation timing signal generating means generates the modulation timing signal 204 using a signal obtained by multiplying the synchronizing signal of the drive signal.

FIG. 4 is a configuration diagram illustrating the modulation timing signal generation unit 105 of the present embodiment. In FIG. 4, 401 is a pulse signal generation means, 402 is a frequency multiplication means, 403 is a phase generation means, 501 is a pulse signal, and 502 is a multiplication signal. FIG. 5 is a diagram illustrating signals in the modulation timing signal generation unit 105 of the present embodiment. In FIG. 5, the horizontal axis represents time, and the vertical axis represents signal magnitude.

Here, the pulse signal generation unit 401 generates a pulse signal 501 from the drive signal 203 of the deflection unit 102. For example, if FIG. 5A is the drive signal 203, a pulse signal 501 as shown in FIG. 5B is generated. The frequency of the pulse signal 501 matches the frequency of the drive signal 203. In FIG. 5B, the DUTY ratio is 50%, but this is not the case.

This pulse signal 501 is converted by the frequency multiplying means 402 into a frequency multiplied signal 502 of N times frequency. FIG. 5C shows a multiplied signal 502 generated from the pulse signal 501 in FIG. Here, the frequency is doubled as an example, but in practice, for example, frequencies from several hundred times to several tens of thousands times can be used.

The multiplication signal 502 is a modulation timing signal having a certain phase (an index of time deviation in one cycle of the drive signal 203) with respect to the drive signal 203 to the deflecting means 102 based on the signal 205 of the deflection state of the optical deflection. 204 (see FIG. 5D). The deflection state signal 205 of the optical deflection is input to the modulation timing signal generation means 105 regardless of the drive signal 203 directly. By adjusting the phase of the modulation timing signal 204 (for example, the signal of FIG. 5E), the modulation timing of the light source is adjusted in accordance with the phase of the vibration state of the deflecting means 102, and the deflection of the optical deflection is performed. The state can be controlled. Specifically, the phase of the modulation timing signal 204 of the light source 101 is advanced or delayed, and adjustment is performed so that desired light deflection is performed.

The modulation timing signal 204 can be easily generated by counting the multiplied signal 502 and generating a signal at a certain arbitrary count. This can be configured by a digital circuit (logic IC) such as an FPGA (Field-Programmable-Gate-Array) or a PLD (Programmable-Logic-Device). Therefore, the modulation timing can be adjusted with high accuracy in increments of the cycle of the multiplied signal 502.

The multiplied signal 502 can be used as a reference signal for modulating the light source 101 during operation of the apparatus. Specifically, the light quantity of the light source 101 can be changed according to the modulation pattern signal as the multiplication signal 502 rises and falls. Thus, since the modulation timing signal 204 can be synchronized with the drive signal 203 of the deflecting means 102, if the deflection state of the optical deflection is the same, desired light is obtained at the same deflection position for each round-trip of deflection. be able to. Here, the synchronization means that the ratio of the frequency of each repetitive signal is an integer ratio.

Thus, according to the present embodiment, it is possible to realize an optical deflector that can control the deflection state of the optical deflection with higher accuracy and stability.

(Third embodiment)
The optical deflector according to the present embodiment is characterized by a deflection state detection unit that generates a detection signal 205 of the deflection state of the optical deflection. Others are the same as those in the first or second embodiment.

In the deflection state detecting means of this embodiment, the distance between the position of the deflected light moving in one direction on the light receiving element and the position of the deflected light moving in the opposite direction is measured, and the measurement signal of the distance is used as the optical deflection signal. Used as a signal 205 for detecting the deflection state. The modulation timing signal generation means 105 that receives the detection signal 205 generates the modulation timing signal 204 so that the distance becomes a predetermined distance.

FIG. 6 is a schematic diagram for explaining the detection of the deflection state of the optical deflection in the present embodiment. In FIG. 6, 601 is a light receiving element, and 602 is a strip-shaped light receiving region. Further, 603 and 604 are deflection / scanning light, 605 is a deflection trajectory of the center of the deflection / scanning light in the longitudinal direction, 606 is the center of the deflection / scanning light 603 in the lateral direction, and 607 is the center of the deflection / scanning light 604 in the lateral direction .

The light receiving element 601 is composed of a plurality of light receiving regions 602. As shown in FIG. 6, the positions of the deflection / scanning light 603 moving in the direction X and the deflection / scanning light 604 moving in the opposite direction Y are measured along the deflection locus 605 on the light receiving element 601. As a method for detecting the positions of the deflection / scanning light beams 603 and 604, the light source 101 is modulated (ON and OFF) to form a light spot (spot) on the light receiving element. The position of the light spot on the light receiving element 601 is calculated based on the signals from the plurality of light receiving areas 602 of the light receiving element 601 and the arrangement of the light receiving areas 602. Thereby, the position 606 of the light point in the direction X and the position 607 of the light point in the direction Y can be measured, and the distance Z between the two points can be measured. This measurement distance Z is used as a signal 205 for detecting the deflection state of the optical deflection. By using this method, the deflection state of the optical deflection can be directly detected as position information, so that the deflection state of the optical deflection can be grasped with very high accuracy.

Based on the amount of deviation of the measurement distance Z from the target distance, the modulation timing signal generation means 105 generates the modulation timing signal 204. At this time, how much the modulation timing signal 204 can be shifted to correct the deviation from the target distance can be calculated from the data created in advance and stored in the modulation timing signal generation means 105. it can.

According to this embodiment, since the deflection state of the optical deflection can be detected with very high accuracy, it is possible to provide an optical deflector that realizes a more stable and highly accurate optical deflection operation.

(Fourth embodiment)
The optical deflector described in the first to third embodiments can be used in an image forming apparatus which is one of optical devices. In such an image forming apparatus, even if there is a change in the environment or a change in the image signal, it is difficult to be affected by the change, and a high-quality image can be formed.

FIG. 7 shows the configuration of the image forming apparatus of this embodiment. The surface of a vibrating body (not shown) included in the vibration system of the optical deflector 530 of this embodiment is a light reflecting surface, and the light emitted from the light source 510 is shaped by the collimator lens 520 and is reflected by the optical deflector 530. Deflected and scanned. The deflected / scanned light is imaged on the photosensitive drum 550 through the coupling lens 540, and the photosensitive drum 550 is exposed. By modulating the light emitted from the light source 510, an electrostatic latent image corresponding to the modulation signal is formed on the photosensitive drum 550.

The photosensitive member 550 rotated around the rotation axis in a direction perpendicular to the scanning direction is uniformly charged by a charger (not shown), and by scanning light on the photosensitive member 550, an electrostatic latent image is formed on the scanning portion. Is formed. Next, a toner image is formed on the image portion of the electrostatic latent image by a developing device (not shown), and an image is formed on the paper by, for example, transferring and fixing the toner image on the paper (not shown).

In the image forming apparatus of the present embodiment using the optical deflector 530 of the present invention that realizes a highly accurate and stable optical deflection operation, the optical scanning characteristic is good and a clear image can be generated. .

The light deflector of the present invention in which a light source for generating a light beam and a light deflecting element for deflecting the light beam on a vibrating body are formed can also be applied to an image display device. Here, an image display body is provided, and the optical deflector deflects light from the light source and causes at least a part of the light to enter the image display body. As described above, in the optical apparatus such as the image forming apparatus and the image display apparatus of the present invention, the optical deflector of the present invention, the light source, and the target object are included, and the optical deflector deflects light from the light source, At least part of the light is incident on the target object. Then, an image is formed on the target object using incident light while synchronizing image data for controlling the light amount of the light source with the modulation timing signal. In addition, by using the deflecting means of the optical deflector having two natural vibration modes around different axes, the light from the light source is deflected and scanned in a two-dimensional manner to enter the image display body. You can also

It is a block diagram of the optical deflector which concerns on embodiment of this invention. It is a characteristic view of the deflection | deviation means driven using resonance. It is a schematic diagram explaining the deflection | deviation and scanning light by a certain modulation signal in arbitrary surfaces. FIG. 5 is a configuration diagram of a modulation timing signal generation unit of an optical deflector according to a second embodiment. FIG. 6 is a diagram for explaining a signal in a modulation timing signal generation unit of a second embodiment. FIG. 10 is a configuration diagram illustrating a deflection state detection unit of an optical deflector according to a third embodiment. FIG. 10 is a configuration diagram illustrating an image forming apparatus according to a fourth embodiment of the present invention. It is a figure of the galvanometer mirror which is a prior art example of an optical deflector.

Explanation of symbols

101 light source
102 Deflection means
103 Vibration state detection means
104 Drive signal generation means
105 Modulation timing signal generation means
106 Deflection state detection means
202 Detection signal indicating the vibration state of the deflection means
203 Drive signal for driving deflection means
204 Light source modulation timing signal
205 Detection signal indicating deflection state of deflection means
206 Light source modulation pattern signal
510 light source
530 Optical deflector of the present invention
550 Photosensitive drum (target target)
601 Light receiving element (deflection state detection means)
602 Light receiving area (deflection state detection means)

Claims (10)

Including a vibration system having a vibrating body with an optical deflection element supported so as to be capable of vibrating, and deflecting means for deflecting light from a light source by the vibrating body;
Vibration state detection means for detecting a vibration state of a vibration system of the deflection means;
Drive signal generation means for generating a drive signal for driving the vibration system of the deflection means;
A modulation timing signal generating means for generating a reference time for controlling the light amount of the light source as a modulation timing signal;
Deflection state detection means for detecting the deflection state of the deflected light generated by the light from the light source being deflected by the deflection means;
Have
The drive signal generation means generates the drive signal based on detection information of the vibration state detection means,
The modulation timing signal generating means generates the modulation timing signal based on detection information of the deflection state detecting means;
An optical deflector characterized by that. The time interval at which the drive signal generating means updates the drive signal is longer than the time interval at which the modulation timing signal generating means updates the modulation timing signal;
2. The optical deflector according to claim 1, wherein: The vibration state detection means is means for detecting the vibration state of the deflection means sinusoidally, and the deflection state detection means is means for optically detecting the deflection state of the deflection light. The optical deflector according to claim 1 or 2. The vibration state detection means is an electromagnetic sensor, a capacitance sensor, or a piezoelectric sensor built in the deflection means,
4. The optical deflector according to claim 3, wherein the deflection state detection means is a photo detector, a position detection element, or an image sensor. The drive signal generation unit generates a drive signal by changing the frequency of the drive signal so that the deflection unit is in a target vibration state.
5. The optical deflector according to claim 1, wherein: The drive signal generation means includes a self-excited oscillation circuit, and the deflection means is driven using a resonance phenomenon.
6. The optical deflector according to claim 5, wherein: The modulation timing signal generating means generates a modulation timing signal so that the deflected light is in a target deflection state.
7. The optical deflector according to claim 1, wherein The modulation timing signal generating means generates a modulation timing signal using a signal obtained by multiplying a synchronization signal of the drive signal;
7. The optical deflector according to claim 1, wherein The deflection state detecting means measures a distance between a position of the deflected light moving in one direction on the light receiving element and a position of the deflected light moving in the opposite direction, and the modulation timing signal generating means Generate a modulation timing signal so that the distance is
8. The optical deflector according to claim 1, wherein The optical deflector according to any one of claims 1 to 9, a light source, and a target object,
The light deflector deflects light from the light source, causes at least a part of the light to enter the target object,
Forming an image on the target object using the incident light while synchronizing image data for controlling the light amount of the light source with the modulation timing signal;
An optical apparatus characterized by that.

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