JP5640122B2 - Micro-electromechanical component mirror drive device, projector and drive circuit - Google Patents

Description

  The present invention relates to a projector that draws a screen by deflecting laser light using a deflection element that operates by resonance.

  A projector that scans the screen two-dimensionally by using a small and highly efficient laser as a light source, deflecting the laser beam with a mirror, and changing the angle of the mirror is drawing attention in terms of small size and power saving. ing. It is also conceivable to use deflection by an electro-optic crystal. The deflection element needs to operate at a high frequency, and it is advantageous to use resonance in order to operate with low power.

  As an example, when a micro electro mechanical system mirror (MEMS mirror) is used, an operating frequency of, for example, 15 kHz to 30 kHz in the horizontal direction and 60 Hz in the vertical direction is required. By operating the MEMS mirror in the resonance mode, further lower power consumption can be realized.

  For example, Patent Document 1 discloses a MEMS mirror technique, and Patent Document 2 discloses a projector using a MEMS mirror.

JP 2003-84226 A JP 2008-151887 A

  When used in the resonance mode, a change in the amplitude, frequency, and phase of the vibrational motion of the MEMS occurs due to disturbances such as vibration, resulting in a change in display screen size and an image shift.

  The present invention includes means for driving the MEMS, means for monitoring the operating state of the MEMS in operation by the driving means, and control means for perturbing the MEMS driving waveform in accordance with the change in the state. It is possible to stabilize the operating state in a short time.

  The MEMS mirror driving method of the present invention has means for detecting the MEMS operation cycle, has means for averaging and maintaining the MEMS operation cycle in a stable operation state, and a sudden change in the MEMS operation cycle due to disturbance is observed. In this case, the MEMS operation and the drive waveform are forcibly synchronized by applying a correction pulse having the same period as the MEMS operation period due to the disturbance as the forced synchronization mode.

  Further, the MEMS mirror driving method of the present invention has means for detecting the MEMS operation cycle, has means for averaging and holding the MEMS operation amplitude in the stable operation state, and a sudden change in the MEMS operation amplitude due to disturbance is present. When observed, the amplitude of the MEMS drive waveform to be applied next is changed according to the observed MEMS operation amplitude.

  In addition, the MEMS mirror driving method of the present invention is characterized in that, when a change in the MEMS operating frequency is observed, monitoring of the MEMS operating amplitude and feedback control are temporarily stopped.

  The MEMS mirror driving circuit according to the present invention has a means for detecting the MEMS operation period, a means for averaging and maintaining the MEMS operation period in the stable operation state, and when a sudden change in the MEMS operation period due to a disturbance is observed. As a forced synchronization mode, there is provided means for applying a correction pulse having the same period as the MEMS operation period due to the disturbance.

  The MEMS mirror driving circuit of the present invention has means for detecting the MEMS operation amplitude, has means for averaging and holding the MEMS operation amplitude in the stable operation state, and a sudden change in the MEMS operation amplitude due to disturbance is present. When observed, it has means for changing the amplitude of the MEMS drive waveform to be applied next in accordance with the observed MEMS operation amplitude.

  The laser scanning projector according to the present invention has a means for detecting the MEMS operation period, a means for averaging and maintaining the MEMS operation period in a stable operation state, and a sudden change in the MEMS operation period due to a disturbance. Includes a MEMS mirror driving circuit having means for applying a correction pulse having the same period as the MEMS operation period due to the disturbance as the forced synchronization mode.

  Further, the laser scanning projector of the present invention has means for detecting the MEMS operation amplitude, has means for averaging and holding the MEMS operation amplitude in the stable operation state, and abrupt changes in the MEMS operation amplitude due to disturbance. When observed, a MEMS mirror drive circuit having means for changing the amplitude of the MEMS drive waveform to be applied next in accordance with the observed MEMS operation amplitude is provided.

  According to the present invention, when the MEMS mirror is driven, the operation state can be stabilized in a short time.

FIG. 1 is a diagram showing the influence of a disturbance accompanied by a change in operating frequency. FIG. 2 is a diagram illustrating a method of correcting a change in operating frequency. FIG. 3 is a circuit block diagram for correcting a change in operating frequency. FIG. 4 is a diagram showing the influence of a disturbance accompanied by a change in amplitude. FIG. 5 is a diagram illustrating a method of correcting a change in amplitude. FIG. 6 is a circuit block diagram for correcting the amplitude change.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the first embodiment, a case where the MEMS operating frequency is changed due to a disturbance will be described. As an example, consider a case changes in operating conditions that has occurred as shown in FIG. 1 due to a disturbance. That is, when a disturbance that extends the period of the MEMS operation as shown in part A of FIG. 1 is mixed, the drive waveform is stepped out. Therefore, the MEMS operation in which the period is extended by the part A returns to the original period over time, and the drawing is in a shifted state during that period.

  In the present invention, as shown in FIG. 2, when the operation state of the MEMS is monitored and a step-out signal is received, the next MEMS operation waveform is appropriately changed to recover from the early step-out state. Plan. More specifically, it has means for detecting the MEMS operation cycle, has means for averaging and maintaining the MEMS operation cycle in the stable operation state, and when a sudden change in the MEMS operation cycle due to disturbance is observed. Applies the correction pulse having the same period as the MEMS operation period due to the disturbance as the forced synchronization mode, thereby forcibly synchronizing the MEMS operation and the drive waveform.

  This will be described with reference to the circuit diagram of FIG. The MEMS mirror 32 is driven by the drive waveform generated by the drive waveform generator 31. The driving state of the MEMS mirror 32 is input as an analog signal and converted into a pulse by the pulsing circuit 33. The operation period of the pulsed MEMS mirror 32 is measured by a period counter 34.

  The measured value is averaged and held by the moving averager 35. The measured MEMS operation cycle and the average cycle held by the moving averager 35 are compared by the comparator 36. If the difference is large, the selector 37 sets the drive waveform generation cycle as the cycle. Set the measured MEMS operating period. If the difference is small, the target setting value is set by the selector 37.

  When the comparison result of the comparator 36 is large, no value is input to the moving averager 35. Since the moving average value and the target setting value are substantially the same, the target setting value may be used as an input to the comparator 36 without using the moving average unit 35.

In this example, a case where a sine wave is used as a drive waveform is shown, but when a resonance is used, a rectangular wave may be used. In this case, the drive waveform is the same waveform as the reference clock in the figure.

  In the second embodiment, a case where the MEMS operation amplitude changes due to a disturbance will be described. As an example, consider a case in which a change in the operating state as shown in FIG. 4 occurs due to a disturbance.

  That is, even when a disturbance that increases the amplitude of the MEMS operation, such as part A of FIG. 4, is mixed, it takes time to return to the original amplitude.

  In the present invention, as shown in FIG. 5, it has means for monitoring the MEMS operation amplitude and means for maintaining the normal state of the MEMS operation amplitude, and compares the MEMS operation amplitude with the operation amplitude in the normal state. When the change is large, the amplitude of the input waveform is changed to correct the amplitude of the next drive waveform.

  This will be described with reference to the circuit block diagram of FIG. The MEMS mirror 32 is driven by the drive waveform generated by the drive waveform generator 31. The driving state of the MEMS mirror 32 is input as an analog signal, and the amplitude measuring unit 61 measures the amplitude in the period. The measured amplitude value is averaged and held by the moving averager 35.

  The measured MEMS drive amplitude and the average amplitude held by the moving averager are compared by a comparator 36. If the difference is large, the measured amplitude is used as the gain of the drive waveform generator 31. Based on the value, the value converted by the gain converter 62 is used, and when the difference is small, the target setting value is set. As an example of the gain converter 62, an object obtained by multiplying the difference from the average amplitude by a coefficient can be considered. Further, instead of inputting the average value to the comparator 36, a target set value may be used.

In general, the phenomenon of Example 1 and Example 2 overlaps due to disturbance. That is, the frequency and amplitude change due to disturbance. Further, when the drive frequency is different, the amplitude is changed because the resonance frequency is deviated. By combining the first and second embodiments, it is possible to correct them. In this case, since the change of the driving frequency causes an amplitude change, when the change of the MEMS operation cycle is observed, the feedback by the amplitude monitor is stopped, and the control by the amplitude feedback is performed after the operation frequency is stabilized.

31 Drive is a meter generator 32 MEMS mirror 33 Pulse generator 34 Period counter 35 Moving averager 36 Comparator 37 Selector 61 Amplitude measuring device 62 Gain converter

Claims (5)

Detection means for detecting the micro-electromechanical component operating cycle;
If the change in pre-Symbol microelectromechanical components operating cycle Ru good disturbance detected by the detecting means is greater than a predetermined value, it is applied to apply a substantially correction pulse having the same period as the microelectromechanical component operation cycle by the disturbance A microelectromechanical component mirror driving device. 2. The micro electro mechanical component mirror driving device according to claim 1, wherein when the detecting means detects a change in micro electro mechanical component operating frequency, monitoring of micro electro mechanical component operating amplitude and feedback control are temporarily stopped . The 請 Motomeko 1 or 2 comprising a microelectromechanical component mirror according projector. And fine small electronic machine parts mirror,
A drive waveform generator for generating a drive waveform for driving the microelectromechanical component mirror;
A pulsing circuit for converting the driving state of the micro-electromechanical component mirror into a pulse;
A period counter for measuring an operation period of the micro-electromechanical component mirror pulsed by the pulse circuit;
A moving averager that averages and holds values measured by the period counter;
A comparator that compares the measured operating period of the micro-electromechanical component mirror with the average period held by the moving averager;
Based on the comparison result of the comparator, the driving circuit comprising, a selector for setting the measured duty cycle of the micro electronic mechanical parts mirror as the period of the drive waveform generation. A micro-electromechanical component mirror,
A drive waveform generator for generating a drive waveform for driving the microelectromechanical component mirror;
An amplitude measuring instrument for measuring the amplitude of the drive waveform ;
A moving averager which was holding averaging the measured amplitude value by the pre-Symbol amplitude measuring instrument,
A comparator that compares the measured operational amplitude of the micro-electromechanical component mirror with the average amplitude held by the moving averager;
A drive circuit comprising: a selector that sets the measured operation amplitude of the micro-electromechanical component mirror as the amplitude of the drive waveform generation based on the comparison result of the comparator.

Images