JP4245580B2 - Mirror control circuit and optical space transmission device - Google Patents

Description

  The present invention relates to a mirror control circuit and an optical space transmission device, and more particularly to a mirror control circuit for driving a deflection angle variable mirror and an optical space transmission device equipped with the mirror control circuit.

  Optical space communication that transmits optical signals through free space can be used in areas where the use of radio waves is restricted, in addition to high-speed and large-capacity transmission, which is a feature of optical communication. In addition, it has many advantages such as easy establishment of a communication path without large-scale construction such as laying of optical fibers.

  When transmitting a high-speed signal of several hundred megabits or more per second by optical space transmission, it is necessary to increase the directivity of the light beam because the light receiving element is small and the light receiving sensitivity is low. For this reason, the optical space transmission device needs an automatic optical tracking function so that the light beam is not detached from the device even if it is affected by the tilt of the device or the vibration applied to the device.

  In the optical space transmission device, two devices that communicate between two distant points are arranged facing each other, detect the light receiving position of the optical signal transmitted from the partner device, and the detection result is the light of the partner device. Feedback is provided to the deflection system that controls the output direction of the signal. For example, the deflection system includes a drive mechanism that drives a mirror and a lens by a motor. The receiving side also has a deflection system, and is controlled in the same manner to realize automatic optical tracking between the transmitting and receiving apparatuses.

  Since the deflection system is necessary for each of the horizontal and vertical directions, when the deflection system is configured by the drive mechanism as described above, the size of the apparatus is increased and the adjustment process becomes complicated and costly. There was a problem of being expensive. Further, since the lens has a large mass, the deflection speed cannot be made too fast, and the vibration resistance is limited. For this reason, the application range such as inter-building communication is limited.

  In recent years, an automatic light beam tracking method using a micromirror (hereinafter referred to as “MEMS mirror”) manufactured by a semiconductor process called MEMS (Micro-Electro-Mechanical Systems) has been proposed (for example, see Patent Document 1). . The MEMS mirror can control the deflection angle of the MEMS mirror by an external signal and has a high resonance frequency on the order of kHz. Therefore, it is possible to reduce the size and respond faster than the conventional method in which a lens or mirror is driven by a motor.

  However, although the MEMS mirror has a high mechanical resonance frequency, it has a high Q value (a value related to vibration attenuation called sharpness), so it takes a long time to settle the mechanical vibration. When used as it is, there is a problem that the high-speed response inherent in the MEMS mirror cannot be effectively used.

  In order to reduce the influence of the mechanical resonance of the MEMS mirror, a technique has been proposed in which a frequency component corresponding to the mechanical resonance of the MEMS mirror is removed from the drive signal of the MEMS mirror by a filter circuit (for example, Patent Document 2). reference). However, the method disclosed in this document uses a filter circuit, and thus has a problem that the circuit configuration is expensive and large.

JP 2004-80253 A Japanese Patent Laid-Open No. 2004-219469, FIG.

  The present invention has been made in view of the above, and a mirror control circuit capable of suppressing resonance vibration of a deflection angle variable mirror at high speed with a low-cost circuit configuration and an optical space equipped with the mirror control circuit. An object is to provide a transmission apparatus.

In order to solve the above-described problems and achieve the object, the present invention controls the deflection angle of the mirror in a mirror control circuit that controls the deflection angle of a mirror having a variable deflection angle and having resonance characteristics. A control signal generating means for generating a control signal for generating a compensation signal for canceling the resonance vibration of the mirror, and a drive signal obtained by adding the compensation signal to a position near the change point of the control signal to the mirror Driving means for outputting and driving , wherein the control signal includes a signal that changes stepwise, the compensation signal includes a rectangular pulse, and the compensation signal sets the resonance frequency of the mirror to f and the rectangular When the pulse width of the pulse is T and the amplitude of the rectangular pulse normalized by the step amplitude of the control signal is p, the center of the rectangular pulse and the control signal are changed in steps. Time interval between change points is a substantially 1 / 4f, and characterized in that satisfy the 2p · sin (πfT) ≒ 1 .
The present invention also provides a control signal generating means for generating a control signal for controlling the deflection angle of the mirror in a mirror control circuit for controlling the deflection angle of the mirror having a variable deflection angle and having resonance characteristics. Driving means for generating a compensation signal for canceling the resonance vibration of the mirror and outputting the drive signal with the compensation signal added to a position in the vicinity of the change point of the control signal to drive the mirror; The control signal includes a signal that changes linearly with respect to time and changes in slope at a predetermined time, the compensation signal includes a rectangular pulse, and the compensation signal has a slope before and after the time. The center of the rectangular pulse is substantially coincident with the time when α, β, the resonance frequency of the mirror is f, the pulse width of the rectangular pulse is T, and the amplitude of the rectangular pulse is p, respectively. And 2p · sin (πfT) ≈ (β−α) / (2πf).

The present invention also includes a light source that emits a light beam modulated by a signal to be transmitted, a mirror that has a variable deflection angle, reflects the light beam incident from the light source, and has resonance characteristics; Based on a light receiving element that receives the light beam reflected by the mirror, an optical position detector that detects an incident position of the light beam reflected by the mirror, and an incident position detected by the optical position detector A control signal generating means for generating a control signal for controlling the mirror deflection angle, and a compensation signal for canceling the resonance vibration of the mirror, and generating the compensation signal at a position near the change point of the control signal. the additional drive signal and a driving means for driving outputs to the mirror, the control signal includes a signal which changes stepwise, the compensation signal includes a rectangular pulse, The compensation signal is the center of the rectangular pulse when the resonance frequency of the mirror is f, the pulse width of the rectangular pulse is T, and the amplitude of the rectangular pulse normalized by the step amplitude of the control signal is p. And the change point at which the control signal changes stepwise is approximately ¼f, and satisfies the condition of 2p · sin (πfT) ≈1 .
The present invention also includes a light source that emits a light beam modulated by a signal to be transmitted, a mirror that has a variable deflection angle, reflects the light beam incident from the light source, and has resonance characteristics; Based on a light receiving element that receives the light beam reflected by the mirror, an optical position detector that detects an incident position of the light beam reflected by the mirror, and an incident position detected by the optical position detector A control signal generating means for generating a control signal for controlling the mirror deflection angle, and a compensation signal for canceling the resonance vibration of the mirror, and generating the compensation signal at a position near the change point of the control signal. Driving means for outputting the added drive signal to the mirror for driving, and the control signal changes linearly with respect to time, and the inclination thereof changes at a predetermined time. The compensation signal includes a rectangular pulse, and the compensation signal has a slope before and after the time α and β, a resonance frequency of the mirror f, a pulse width T of the rectangular pulse, and the rectangular signal, respectively. When the pulse amplitude is p, the center of the rectangular pulse is substantially coincident with the time and satisfies the condition of 2p · sin (πfT) ≈ (β−α) / (2πf). And

  According to the mirror control circuit of the present invention, the control signal generation means generates a control signal for controlling the deflection angle of the deflection angle variable mirror, and the drive means cancels the resonance vibration of the deflection angle variable mirror. The compensation signal is generated and the drive signal with the compensation signal added in the vicinity of the change point of the control signal is output to the deflection angle variable mirror for driving. By simply adding a compensation signal to cancel, the resonant vibration of the variable deflection angle mirror can be suppressed at high speed, and the resonant vibration of the variable deflection angle mirror can be suppressed at high speed with a low-cost circuit configuration. It is possible to provide a simple mirror control circuit.

  Exemplary embodiments of a mirror control circuit and an optical space transmission device according to the present invention will be explained below in detail with reference to the accompanying drawings. In the following, an embodiment in which a mirror control circuit according to the present invention is applied to an optical space transmission device will be described as an example. It should be noted that the present invention is not limited by this embodiment, and all combinations of features described in the embodiment are not necessarily required for the solution means of the invention. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or that are substantially the same.

(Embodiment 1)
FIG. 1 is a diagram illustrating a schematic configuration of an optical space transmission device 100 according to the first embodiment. Here, a system that transmits a main signal in one direction from the transmission device to the reception device will be described as an example of the optical space transmission device 100.

  As shown in FIG. 1, the optical space transmission device 100 includes a transmission device 110 and a reception device 120. The transmission device 110 includes a light source 111 that emits a light beam modulated by a signal to be transmitted, a MEMS mirror 112 that has a variable deflection angle and reflects a light beam incident from the light source 111, and a resonance of the MEMS mirror 112. A drive circuit 113 that generates a compensation signal for canceling vibration, outputs a drive signal with the compensation signal added to a position near the change point of the control signal, and drives the MEMS mirror 112, and a MEMS mirror based on the incident position signal The control circuit 114 generates a control signal for controlling the deflection angle 112, and a control signal receiver 115 that receives an incident position signal from the receiving device 120 and outputs the incident position signal to the control circuit 114.

  The receiving device 120 receives a light beam reflected by the MEMS mirror 112 and an optical position detector 122 that detects an incident position of the light beam reflected by the MEMS mirror 112 and outputs an incident position signal. And a control signal transmitter 123 that transmits the incident position signal detected by the optical position detector 122 to the transmission device 110.

  Since the actual characteristics of the MEMS mirror 112 differ depending on the deflection direction, the drive circuit 113 and the control circuit 114 require circuits for two axes, but the principle is the same. For simplicity, only one axis is shown.

  The operation of the optical space transmission device 100 configured as described above will be described. In the transmission device 110, a transmission signal 201 to be transmitted is input to the light source 111, and the light source 111 is modulated and converted into an optical signal. The modulated optical signal is incident on the MEMS mirror 112 and reflected, and the propagation direction thereof is deflected in the biaxial direction, and the light beam 202 is output to the receiving device 120.

  In the reception device 120, a part of the light beam 202 input from the transmission device 110 is input to the receiver 121 and the optical position detector 122. In the receiver 121, the input light beam 202 is output as a received signal 203. The optical position detector 122 detects the incident position of the input light beam 202 and outputs the incident position signal 204 to the control signal transmitter 123. The control signal transmitter 123 transmits the input incident position signal 204 to the transmission device 110 via the transmission unit 130.

  In the transmission device 110, the control signal receiver 115 receives the incident position signal 204 input from the reception device 120 and outputs it to the control circuit 114. The control circuit 114 generates a control signal 205 for controlling the deflection angle of the light beam 202 to be a predetermined angle based on the input incident position signal 204 and outputs the control signal 205 to the drive circuit 113.

  The drive circuit 113 generates a compensation signal for suppressing the resonance vibration generated in the MEMS mirror 112 according to the waveform of the control signal 205, and further adds a compensation signal to the position near the change point of the control signal 205. A signal 206 is generated and output to the MEMS mirror 112 to drive the MEMS mirror 112.

  As the transmission means 130, since the signal communicated between the control signal transmitter 123 and the control signal receiver 115 is a low-speed signal, for example, a wire technology such as a power line or a LAN, or a wireless such as light, sound wave, or radio wave. Technology can be used. In this embodiment, it is assumed that the main signal is transmitted in one direction. However, in a bidirectional transmission system, the control signal 205 is converted into the main signal by TDM (time division multiplexing), for example. Multiplexing may be performed.

  FIG. 2 is a diagram illustrating a specific configuration example of the drive circuit 113 in FIG. As shown in FIG. 2, the drive circuit 113 generates a compensation pulse 210 and outputs the compensation pulse 210 to the delay circuit 142. The drive circuit 113 delays the input compensation pulse 210 to generate a compensation signal 210 as a synthesis circuit 144. The delay circuit 142 to be output to the delay circuit, the delay circuit 116 to delay the control signal 205 input from the control circuit 205 and output the delayed control signal 212 to the combining circuit 144, and the delay control signal 212 and the compensation signal 210. And a synthesis circuit 144 that generates a drive signal 207 and outputs the drive signal 207 to the MEMS mirror 112.

  The drive signal 207 and the control signal 205 will be described with reference to FIG. FIG. 3 is an example of a timing chart for explaining the drive signal 207 and the control signal 205. Here, a case where a step waveform is used as an example of the control signal 205 will be described. The step waveform is a general waveform when the control is performed by digital processing, and the amplitude of the step waveform indicates the amount of change in the deflection angle of the MEMS mirror 112.

  In FIG. 3, in order to cancel the resonance vibration that occurs when the MEMS mirror 112 is driven by the control signal 205, the shape of the compensation signal 211 and the time interval t2 between the control signal 205 must be set to predetermined values. . In accordance with the time interval t2, the control signal 205 is delayed by a predetermined time t1 like the delay control signal 212.

  For example, when a rectangular wave is used as the compensation signal 211, the compensation signal 211 having a predetermined pulse width T1 and pulse amplitude P1 is generated. As described above, the drive signal 207 is generated by adding (combining) the compensation signal 211 to the delay control signal 212.

Hereinafter, the compensation signal 211 will be described in detail. For example, when the compensation signal 211 and the control signal 205 have the same amplitude, f _MEMS is the resonance frequency of the MEMS mirror 112, the pulse width T1 is 1 / (6f _MEMS ), and the time interval t2 is 1 / (4f _MEMS ). Set to.

  Hereinafter, the principle that the compensation signal 211 suppresses the resonance vibration of the MEMS mirror 112 based on the transfer function of the MEMS mirror 112 will be described. The transfer function between the drive signal 207 of the MEMS mirror 112 and the tilt angle of the MEMS mirror 122 can be generally expressed by the following formula (1).

In the above formula (1), ω _MEMS (= 2πf _MEMS ) is the resonance angular frequency of the MEMS mirror 112, Q _MEMS is the Q value of the MEMS mirror 112, α is a proportional coefficient, and s is a Laplace operator. ω _MEMS , Q _MEMS , and α have different values in the two rotation axes, but the principle of resonance suppression is the same.

In the following description, for simplification of calculation, it is assumed that the above equation (1) is normalized so as to be “1” in direct current, and is treated as α = ω _MEMS ² . That is, the tilt angle of the MEMS mirror 112 changes by “1” with respect to the DC drive signal of “1”. Actually, generality is not lost because it is sufficient to multiply by a proportionality coefficient based on the characteristics of the MEMS mirror 112 to be used.

  The response Rstp (t) when the MEMS mirror 112 is step-driven is expressed by the following formula (2) by performing Laplace inverse transform by multiplying the above formula (1) by 1 / s obtained by Laplace transform of the unit step function. be able to.

In the above formula (2), L ⁻¹ [] represents Laplace inversion, and t represents time. When the parentheses [] are expanded into partial fractions and further transformed, they can be expressed as the following formula (3).

In the above formula (3), QMEMS is usually about several tens. Therefore, when approximating 1-1 / 4Q _MEMS ² = 1, the above formula (3) can be expressed as the following formula (4). .

  Therefore, Rstp (t) can be expressed as the following equation (5) by inversely transforming the above equation (4).

In the above equation (5), u (t) represents a unit step function. From 1 / 2Q _MEMS << 1, the third term on the right side can be ignored, and Rstp (t) can be expressed as in the following formula (6).

  In the above equation (6), u (t) in the first term on the right side represents a response following the drive waveform, and the second term represents a component of resonance vibration due to resonance vibration of the MEMS mirror 112. Next, the response Rpls (t) of the MEMS mirror 112 with respect to the compensation signal 211 is calculated. Rpls (t) can be calculated by obtaining a rectangular Laplace transform and multiplying the equation (1) to perform the Laplace inverse transform. When the amplitude of the rectangle is p and the pulse width is T, the Laplace transform can be expressed as the following formula (7).

  Therefore, Rpls (t) can be expressed as in the following formula (8).

  Further, Rpls (t) can be expressed as the following formula (9) in the same manner as the above formula (2).

  In the above equation (9), when the pulse width T is set to a time of about the resonance period and further transformed using time t ′ = t−T / 2 with the center of the pulse as the origin, the following equation (10) is obtained. be able to.

The origin of the time of the above formula (9) and the above formula (10) is different by T / 2, but since ω _MEMS · T / Q _MEMS << 1, the relationship as the following formula (11) is derived. can do.

Therefore, by setting the pulse width T to be 2P · sin (ω _MEMS T / 2) = 1, and setting the time interval 207 to 1 / (4f _MEMS ), Rpls (t) becomes Rstp ( It can be seen that the second term on the right side of t), that is, the resonance vibration component of the MEMS mirror 112 is canceled. When the amplitude of the compensation pulse is “1”, the pulse width T may be set to 1 / (6f _MEMS ).

FIG. 4 is a timing chart for explaining another example of the drive signal 207. In the above embodiment, as shown in FIG. 3, the case where the compensation signal 211 is added to the delay control signal 212 obtained by delaying the control signal 205 has been described, but the present invention is not limited to this. From the above formula (6) and the above formula (10), as shown in FIG. 4, for example, the same effect can be obtained for the drive signal 207 obtained by adding the compensation signal 211 in the opposite direction to FIG. be able to. The time interval t3 in this case is 1 / (4f _MEMS ), similar to the above-described t2. According to this, since it is not necessary to delay the control signal 205, it is excellent in high-speed response, and a delay circuit is unnecessary, and the drive circuit can be configured at low cost.

Next, the effect of suppressing the resonance vibration of the MEMS mirror 112 when the compensation signal is used will be described with reference to FIG. FIG. 5 is a diagram showing the result of calculating the mirror tilt angle of the MEMS mirror 112 by numerical analysis of the equation of motion of the MEMS mirror 112 when ω _MEMS = 2π · 100 and Q _MEMS = 100.

  FIG. 5A is a diagram illustrating a drive waveform and a response waveform of the MEMS mirror 112 when there is no compensation signal, that is, a response to the control signal 205. As shown in FIG. 5A, in the response waveform, resonance vibration occurs at the rising portion of the step waveform of the control signal 205.

  FIG. 5B is a diagram illustrating a driving waveform based only on the compensation signal and a response waveform of the MEMS mirror 112, that is, a response to the compensation signal 209. As shown in FIG. 5B, the response waveform resonates and oscillates in the opposite phase to the resonance component in FIG.

  FIG. 5C is a diagram illustrating a drive waveform when the compensation signal is added to the control signal and a response waveform of the MEMS mirror 112, that is, a response to the drive signal (in the case of the present embodiment) to which the compensation signal 211 is added. It is. As shown in FIG. 5C, the response waveform sufficiently suppresses the resonance vibration, and it was confirmed that the resonance vibration suppression method of the present embodiment is effective.

  In the above embodiment, the case where the rectangular wave / amplitude that is practically simple is the same as the drive waveform has been described as the compensation signal. However, the present invention is not limited to this, and the compensation signal may be a compensation signal having another waveform. It is possible to suppress the resonance vibration of the MEMS mirror 112. Although a single step waveform has been described as the control signal, the present invention is not limited to this, and a control signal having another drive waveform may be used. Hereinafter, other examples of the compensation signal and the control signal will be described.

  With reference to FIG. 6, another example of the waveform of the compensation signal will be described. FIG. 6 shows the result of numerical analysis of the response characteristics of the MEMS mirror 112 under the same conditions as in FIG. 5 when the compensation signal has another waveform.

  FIG. 6A is a response waveform of the MEMS mirror 112 when the amplitude of the compensation signal is a double rectangular wave, and FIG. 6B is an analysis result of the response waveform of the MEMS mirror 112 when the compensation signal is a triangular wave. Is shown. As shown in FIGS. 6A and 6B, it was confirmed that the resonance vibration can be suppressed in both cases where the amplitude of the compensation signal is doubled and a triangular wave is used. In particular, when the amplitude of the compensation signal is doubled, the time from the front end of the compensation signal to the rise of the step waveform can be shortened compared to the case of the amplitude “1”. The effect of being able to drive was confirmed.

In the above embodiment, a single step waveform is described as the control signal.
The present invention is not limited to this, and control signals having other drive waveforms may be used. With reference to FIG. 7, another example of the waveform of the control signal will be described. FIG. 7 shows the result of numerical analysis of the response characteristics of the MEMS mirror 112 under the same conditions as in FIG. 5 when the control signal has another waveform.

  As shown in FIG. 7, even when the control signal is a stepped step signal generally used in digital control, the resonance vibration can be similarly suppressed. When the control signal is a stepped step signal, the value “0” of the single step signal is the value before the change in each step, and the value “1” is replaced with the value after the change. The compensation signal can be obtained in the same manner as in the case of driving.

  Reference numerals 301 to 305 denote pulse portions of a compensation signal corresponding to each step. In this example, the amplitude of the compensation signal shows an example in which the difference between the value before the change and the value after the change is the same in each step. The compensation signals 304 and 305 have waveforms in the reverse direction to the compensation signals 301 to 303 because the waveform of the control signal to be compensated is a falling step. The response waveform of the MEMS mirror 112 is a waveform that closely follows the control signal without causing resonance vibration.

  Next, a case where a triangular wave is used as another example of the control signal will be described. In an initial state in which the adjustment of the light beam 202 is not completed between the transmission device 110 and the reception device 120, it is necessary to search the reception device 120 by scanning the MEMS mirror 112 with, for example, a triangular wave. When the MEMS mirror 112 is driven with a triangular wave, resonance occurs at the waveform change point, so that the position of the actual waveform is shifted from the control waveform, and it is considered that the receiving device 120 cannot be correctly searched. .

Below, the example which compensates the resonant vibration generate | occur | produced with a repetitive triangular wave with a rectangular wave is demonstrated. FIG. 8 is a diagram for explaining an example of a repeated triangular wave. As shown in FIG. 8, the repeated triangular wave has an amplitude “1” and a repetition period “2 · T _1/2 ”. The response Rtri (t) of the MEMS mirror 112 in the region “0” to “T _1/2 ” indicates the state at time “0” when the resonance vibration is suppressed before time “0”. A ramp function having an initial value and a slope that is the same as the slope of the triangular wave from “0” to “T _1/2 ” can be obtained as a drive signal. When QMEMS is sufficiently large as in the above equation (6), Rtri (t) can be approximately expressed as the following equation (12).

  In the above equation (12), the second term on the right side indicates resonance vibration, and a triangular wave is a sine wave. Therefore, the compensation signal needs to be centered on time “0”. When a rectangular compensation signal having an amplitude p and a pulse width T is used, resonance vibration in Rtri (t) can be canceled if the relationship of the following expression (13) is satisfied from the above expression (10).

FIG. 9 shows the result of numerical analysis of the response characteristics of the MEMS mirror 112 under the same conditions as in FIG. 5 when a triangular wave is used as the control signal and a rectangular wave is used as the compensation signal. As shown in FIG. 9, a response waveform in which resonance vibration is sufficiently suppressed can be obtained. When the compensation signal is not used, in order to suppress the resonance vibration component to about 1% or less, T _1/2 needs to be about 50 times 1 / f _MEMS from the above equation (12). By using, extremely high-speed scanning in about one cycle becomes possible.

The above equation (13) shows the condition of the compensation signal when the rising time and the falling time of the triangular wave are both T _1/2 . When the control signal changes linearly with respect to time, and the slope is different before and after a predetermined time, the compensation signal at the change point coincides with the time when the slope changes, and When the slopes before and after the time are α and β, the pulse width is T, and the amplitude is p, a rectangular pulse satisfying the following equation (14) is used to cancel the resonance vibration at the change point. Can do. FIG. 10 is a diagram illustrating an example of a control signal when the slope changes with time and a compensation signal for the control signal.

  In the above embodiment, a case where a single pulse is used as the compensation signal has been described. However, a pulse train having a shorter duration (compensation signal period) than the resonance period of the MEMS mirror 112 is used. You may decide. FIG. 11 is a diagram illustrating an example of a pulse train of a compensation signal.

  As described above, according to the first embodiment, the control circuit 114 generates a control signal for controlling the deflection angle of the MEMS mirror 112, and the drive circuit 112 cancels the resonance vibration of the MEMS mirror mirror 112. A compensation signal is added to the position near the change point of the control signal, and the drive signal with the compensation signal added is output to the MEMS mirror 112 to control the deflection angle of the MEMS mirror 112. By simply adding a compensation signal for canceling the resonance vibration of the mirror 112, the resonance vibration of the MEMS mirror 112 can be suppressed at high speed, and the resonance vibration of the MEMS mirror 112 can be suppressed at high speed with a low-cost circuit configuration. It becomes possible.

Further, according to the first embodiment, the control signal is composed of a signal that changes stepwise, the compensation signal is composed of a rectangular pulse, and the compensation signal has a resonance frequency of the MEMS mirror f _MEMS and the pulse width of the rectangular pulse. the T, in the case where the amplitude of the rectangular pulses normalized by the amplitude of the steps of the control signal is a p, the time interval between change points of the center and the control signal of a rectangular pulse changes stepwise, approximately 1 / (4f _MEMS ) and 2p · sin (π · f _MEMS T) ≈1 so that the MEMS mirror can be used in a simple manner using a practically simple stepped waveform and rectangular pulse. It is possible to suppress the resonance vibration.

(Embodiment 2)
FIG. 12 is a diagram illustrating a schematic configuration of the optical space transmission device 400 according to the second embodiment. The optical space transmission device 400 according to the second embodiment has a configuration in which a temperature measurement circuit 401 for performing temperature correction of a compensation signal is added to the space transmission device 100 according to the first embodiment. 11, parts having the same functions as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The resonance frequency and Q value of the MEMS mirror 112 vary with temperature. In other words, the above-described step signal (control signal) is compensated by using a rectangular compensation signal as an example. The pulse width of the compensation signal, the pulse amplitude, and the time interval between the compensation signal and the step signal rise are constant. In this case, the effect of suppressing the resonance of the MEMS mirror 112 is reduced due to the characteristic variation due to the temperature change of the MEMS mirror 112. Therefore, in the second embodiment, the compensation frequency corresponding to the measurement temperature is generated in consideration of the variation of the resonance frequency of the MEMS mirror 112 and the Q value due to the temperature, so that the MEMS mirror 112 is not affected by the temperature variation. Effectively suppresses resonance vibration.

  The temperature measurement circuit 401 measures the temperature in the vicinity of the MEMS mirror 112, that is, the temperature of the MEMS mirror itself or the surrounding temperature, and outputs the temperature measurement result to the drive circuit 402 as a temperature signal 410. Based on the temperature signal 410 input from the temperature measurement circuit 401, the drive circuit 402 generates a compensation signal 206 that cancels the resonance vibration of the MEMS mirror 112 at the temperature, and inputs the compensation signal 206 from the control circuit 114. In addition to the control signal 205, the drive signal 105 is output to the MEMS mirror 112. The drive circuit 402 stores, for example, a relationship between the temperature and the resonance frequency of the MEMS mirror 112 in advance in a table, reads the resonance frequency of the MEMS mirror 112 from the table in accordance with the input temperature signal, and outputs the resonance frequency. A compensation signal for canceling the vibration is generated.

  Note that since the MEMS mirror 112 is formed by a semiconductor process, the MEMS mirror 112 and the temperature measurement circuit 401 may be mounted (integrated) on the same semiconductor substrate. According to this, the temperature measurement accuracy can be increased as compared with the configuration in which the temperature measurement circuit 402 is arranged around the MEMS mirror 112, and the size and the number of parts can be reduced.

  As described above, according to the second embodiment, the temperature measurement circuit 401 measures the temperature in the vicinity of the MEMS mirror 112, and the drive circuit 402 generates a compensation signal based on the measured temperature. Therefore, it is possible to effectively suppress the resonance vibration of the MEMS mirror regardless of temperature fluctuation. Note that the resonance frequency of the MEMS mirror 112 may vary depending on the usage time (time variation), humidity, and the like. Therefore, the relationship between the usage time and the resonance frequency of the MEMS mirror 112, the relationship between the humidity and the resonance frequency of the MEMS mirror 112 are stored, and compensation for canceling the vibration of the resonance frequency according to the usage time and humidity. A signal may be generated. In this way, the resonance frequency of the MEMS mirror under the environmental conditions is calculated according to the environmental conditions such as temperature, humidity, and usage time, and a compensation signal for canceling the vibration of the calculated resonance frequency is generated. Thus, the resonance vibration of the MEMS mirror can always be effectively suppressed regardless of changes in environmental conditions.

(Embodiment 3)
In Embodiment 3, a display device to which the present invention is applied will be described. FIG. 13 is a diagram illustrating a configuration example of the display device 500 according to the third embodiment.

  A display device 500 according to Embodiment 3 includes a drive circuit 501, MEMS mirrors 502 to 504, light sources 505 to 507, and a screen 508. A position signal 511 is input to the drive circuit 501. The position signal 511 is a control signal for controlling the position where the light sources 505 to 507 are irradiated on the screen 508. The drive circuit 501 adds and outputs a compensation signal for suppressing resonance to each of the MEMS mirrors 502 to 504 based on the input position signal 511.

  The light sources 505 to 507 are, for example, red, green, and blue light sources. The light sources 505 to 507 are modulated by the modulation signals 512 to 514 corresponding to the respective color components, and the modulated light of each color is output toward the MEMS mirrors 502 to 504. The The MEMS mirrors 502 to 504 reflect the light incident from the light sources 505 to 507 and irradiate a predetermined position on the screen 508.

  According to the display device 500 having the above configuration, the resonance vibration of the MEMS mirrors 502 to 504 is suppressed, high-speed MEMS driving is possible, and higher-definition video can be displayed.

(Embodiment 4)
In Embodiment 4, an optical matrix switch to which the present invention is applied will be described. FIG. 14 is a diagram illustrating a configuration example of an optical matrix switch 600 according to the fourth embodiment. An optical matrix switch is a device that outputs an optical signal incident on an arbitrary input optical fiber from an arbitrary output optical fiber between a plurality of input optical fibers and a plurality of output optical fibers.

  As shown in FIG. 14, the optical matrix switch 600 according to the fourth embodiment includes an input optical fiber group 601, a collimator lens 602, an input side MEMS mirror group 603, an output side MEMS mirror group 604, and a collimator lens 605. An output optical fiber group 606, drive circuits 607 and 608, and a control circuit 609.

  An optical signal incident from an arbitrary input optical fiber 601a in the input optical fiber group 601 is converted into parallel light by a collimator lens 602 and output. Although the collimator lens is arranged for each fiber of the input optical fiber group 601, only the collimator lens 602 is illustrated in FIG. The optical signal output from the collimator lens 602 is input to the MEMS mirror 603 a corresponding to the input optical fiber 601 a in the input side MEMS mirror group 603.

  The MEMS mirror 603a reflects the incident optical signal toward the MEMS mirror 604a corresponding to the output optical fiber 606a to be output in the output side MEMS mirror group 604. The MEMS mirror 604a further reflects toward the output optical fiber 606a to be output in the output optical fiber group 606.

  The optical signal reflected by the MEMS mirror 604a is collected by the collimator lens 605 corresponding to the output optical fiber 606a, and is incident on the output optical fiber 606a and output. Although the collimator lens is arranged for each fiber of the output optical fiber group 606, only the collimator lens 605 is illustrated in FIG.

  The control circuit 609 outputs the deflection angle control signal of each MEMS mirror to the drive circuits 607 and 608 based on the setting signal 650 that indicates the output optical fiber that is the output destination of the optical signal input from the input optical fiber. The drive circuits 607 and 608 are driven by outputting a drive signal obtained by adding a compensation signal to the deflection angle control signal input to the control circuit 609 to each MEMS mirror.

  Since the optical matrix switch is used for path switching when a failure occurs in the network, it is necessary to complete the switching at high speed. According to the fourth embodiment, resonance is suppressed by the drive circuits 607 and 608, and high-speed switching is possible. Further, if there is resonance, it is possible that the light beam is transiently coupled to an unexpected output optical fiber at the time of switching, but it is possible to suppress crosstalk caused by such a cause.

  INDUSTRIAL APPLICABILITY The mirror control circuit and the optical space transmission device according to the present invention are useful when performing optical transmission using a deflection angle variable mirror such as a MEMS mirror, and various devices such as an optical transmission device, a display device, and an optical matrix switch. Is available.

1 is a diagram illustrating a schematic configuration of an optical space transmission device according to Embodiment 1. FIG. FIG. 2 is a diagram illustrating a specific configuration example of a drive circuit in FIG. 1. It is a figure which shows an example of the timing chart of a drive signal and a control signal. It is a timing chart for explaining other examples of a drive signal. It is the figure which showed the drive waveform in case there is no compensation signal, and the response waveform of a MEMS mirror. It is the figure which showed the drive waveform and the response waveform of a MEMS mirror only by a compensation signal. It is the figure which showed the drive waveform at the time of adding a compensation signal to a control signal, and the response waveform of a MEMS mirror. It is the figure which showed the response waveform of the MEMS mirror at the time of making the amplitude of a compensation signal into a square wave of 2 times. It is the figure which showed the response waveform of the MEMS mirror at the time of making a compensation signal into a triangular wave. It is a figure which shows the response waveform of a MEMS mirror at the time of setting it as another drive waveform. It is a figure for demonstrating the case where a control signal is made into the repetitive triangular wave. It is a figure which shows the response waveform of a MEMS mirror at the time of using a triangular wave as a control signal and using a rectangular wave as a compensation signal. It is a figure which shows an example of the control signal in case inclination changes temporally, and the compensation signal with respect to this control signal. It is a figure which shows an example at the time of making a compensation signal into a pulse train. FIG. 3 is a diagram illustrating a schematic configuration of an optical space transmission device according to a second embodiment. 6 is a diagram illustrating a configuration example of a display device according to Embodiment 3. FIG. FIG. 10 is a diagram illustrating a configuration example of an optical matrix switch according to a fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical space transmission apparatus 110 Transmission apparatus 111 Light source 112 MEMS mirror 113 Drive circuit 114 Control circuit 115 Control signal receiver 120 Reception apparatus 121 Receiver 122 Optical position detector 123 Control signal transmitter 400 Optical space transmission apparatus 401 Temperature measurement circuit 402 Drive circuit 500 Display device 501 Drive circuit 502, 503, 504 MEMS mirror 505, 506, 507 Light source 508 Screen 600 Optical matrix switch 601 Input optical fiber group 602 Collimator lens 603 Input side MEMS mirror group 604 Output side MEMS mirror group 605 Collimator lens 606 Output optical fiber group 607, 606 Drive circuit 609 Control circuit

Claims (7)

In a mirror control circuit for controlling the deflection angle of a mirror having a variable deflection angle and having resonance characteristics,
Control signal generating means for generating a control signal for controlling the deflection angle of the mirror;
Driving means for generating a compensation signal for canceling the resonance vibration of the mirror, and driving the drive signal by adding the compensation signal to a position near the change point of the control signal to the mirror;
Equipped with a,
The control signal includes a signal that changes stepwise, and the compensation signal includes a rectangular pulse,
When the resonance frequency of the mirror is f, the pulse width of the rectangular pulse is T, and the amplitude of the rectangular pulse normalized by the amplitude of the step of the control signal is p,
A mirror characterized in that a time interval between the center of the rectangular pulse and the change point at which the control signal changes stepwise is approximately ¼f and satisfies a condition of 2p · sin (πfT) ≈1. Control circuit. In a mirror control circuit for controlling the deflection angle of a mirror having a variable deflection angle and having resonance characteristics,
Control signal generating means for generating a control signal for controlling the deflection angle of the mirror;
Driving means for generating a compensation signal for canceling the resonance vibration of the mirror, and driving the drive signal by adding the compensation signal to a position near the change point of the control signal to the mirror;
With
The control signal includes a signal that changes linearly with respect to time and changes in slope at a predetermined time, and the compensation signal includes a rectangular pulse,
The compensation signal has a slope before and after the time α, β, a resonance frequency of the mirror f, a pulse width T of the rectangular pulse, and an amplitude of the rectangular pulse p, respectively.
The center of the rectangular pulse is substantially coincident with the time, and, 2p · sin (πfT) ≒ (β-α) / mirror control circuit according to claim satisfies the condition of (2 [pi] f). The mirror, the mirror control circuit according to claim 1 or 2, characterized in that the MEMS mirror. Temperature measuring means for measuring the temperature in the vicinity of the mirror,
It said drive means, mirror control circuit according to any one of claims 1 to 3, characterized in that to generate the compensation signal based on the measured temperature by the temperature measuring means. The mirror control circuit according to claim 4 , wherein the temperature measuring unit and the MEMS mirror are mounted on the same semiconductor substrate. A light source that emits a light beam modulated by a signal to be transmitted;
A mirror having a variable deflection angle, reflecting the light beam incident from the light source, and having resonance characteristics;
A light receiving element that receives the light beam reflected by the mirror;
An optical position detector for detecting an incident position of the light beam reflected by the mirror;
Control signal generating means for generating a control signal for controlling the mirror deflection angle based on the incident position detected by the optical position detector;
Driving means for generating a compensation signal for canceling the resonance vibration of the mirror, and driving the drive signal by adding the compensation signal to a position near the change point of the control signal to the mirror;
Equipped with a,
The control signal includes a signal that changes stepwise, and the compensation signal includes a rectangular pulse,
When the resonance frequency of the mirror is f, the pulse width of the rectangular pulse is T, and the amplitude of the rectangular pulse normalized by the amplitude of the step of the control signal is p,
The time interval between the center of the rectangular pulse and the change point at which the control signal changes stepwise is approximately 1 / 4f, and satisfies the condition of 2p · sin (πfT) ≈1 Spatial transmission equipment. A light source that emits a light beam modulated by a signal to be transmitted;
A mirror having a variable deflection angle, reflecting the light beam incident from the light source, and having resonance characteristics;
A light receiving element that receives the light beam reflected by the mirror;
An optical position detector for detecting an incident position of the light beam reflected by the mirror;
Control signal generating means for generating a control signal for controlling the mirror deflection angle based on the incident position detected by the optical position detector;
Driving means for generating a compensation signal for canceling the resonance vibration of the mirror, and driving the drive signal by adding the compensation signal to a position near the change point of the control signal to the mirror;
With
The control signal includes a signal that changes linearly with respect to time and changes in slope at a predetermined time, and the compensation signal includes a rectangular pulse,
The compensation signal has a slope before and after the time α, β, a resonance frequency of the mirror f, a pulse width T of the rectangular pulse, and an amplitude of the rectangular pulse p, respectively.
An optical space transmission device characterized in that the center of the rectangular pulse substantially coincides with the time and satisfies the condition of 2p · sin (πfT) ≈ (β−α) / (2πf).

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