JP6652163B2 - MEMS mirror, MEMS scanner, head-up display, and vehicle - Google Patents

Description

  The present invention relates to a MEMS mirror, a MEMS scanner, a head-up display, and a vehicle.

  The in-vehicle head-up display is a device that displays images such as traffic information and a route to a destination in the direction of a windshield to assist a driver in driving. The in-vehicle device is required to have quality assurance (for example, 15 years) assuming long-term operation. However, there is a concern that the PZT film as a piezoelectric film used for driving a two-dimensional MEMS (Micro Electro Mechanical Systems) scanner, which is an image engine, may deteriorate in characteristics over time. In particular, when the amplitude sensitivity decreases and a desired shake angle cannot be obtained, the image size becomes smaller than the specification, which greatly affects the function of the scanner.

  In this case, the decreased amplitude sensitivity can be compensated for by increasing the drive voltage applied to the PZT film. For example, a control method has been known in which a drive voltage is increased until a desired shake angle is reached while a laser scan angle is detected by a PD provided on the side of a screen or the like.

  In addition, in order to compensate for the scanning capability reduced due to a change in characteristics of the MEMS device due to aging, a configuration has been proposed in which a changed resonance frequency is detected, and a drive voltage and a drive frequency are set based on the detected resonance frequency. (For example, see Patent Document 1).

  However, in the method of increasing the drive voltage to compensate for the decrease in the amplitude sensitivity, as in the conventional MEMS scanner disclosed in Patent Document 1, changing the drive voltage changes the drive characteristics of the device and degrades image quality. There was a problem. In addition, since it is necessary to provide the device with an extra voltage application capability assuming a decrease in sensitivity, there is a problem in that the cost is increased.

  The present invention has been made to solve such a conventional problem, and provides a MEMS mirror, a MEMS scanner, a head-up display, and a vehicle capable of obtaining a high-quality image at low cost. The purpose is to:

In order to solve the above problem, a MEMS mirror according to the present invention includes a mirror having a reflection surface, a pair of torsion beams provided on both sides of the mirror, and a rib provided on a back surface of the mirror. The mirror rotates about the axis of the pair of torsion beams, and the rib extends from one side of the linear portion extending in a direction perpendicular to the axis of the pair of torsion beams, and one side of the linear portion. A first straight portion, a second straight portion, and a third straight portion and a fourth straight portion extending from the other side of the straight portion, wherein the first straight portion is connected at one end to the first straight portion. Connected to a linear portion , the second linear portion is connected at one end to the linear portion, and the other end of the first linear portion and the other end of the second linear portion are connected to the linear portion Away from each other It is connected only with the first connection portion of the bulging down beam side arcuate, the width of the first straight portion, the width of the second straight portion, the width of the first connecting portion, Are substantially the same, the third linear portion is connected to the linear portion at one end, the fourth linear portion is connected to the linear portion at one end, and the other end of the third linear portion is connected to the linear portion. The other end of the fourth linear portion is connected to the torsion beam side only at a second arc-shaped second connecting portion bulging toward the torsion beam at a position away from the linear portion, and has a width of the third linear portion. When the width of the fourth straight portion, the width of the second connecting portion, is characterized by substantially the same der Rukoto.

  The present invention provides a MEMS mirror, a MEMS scanner, a head-up display, and a vehicle that can obtain high-quality images at low cost.

It is a block diagram of an electric machine system as an embodiment. It is a front view of a MEMS scanner with which an electromechanical system as an embodiment is provided. FIG. 7 is an explanatory diagram for detecting the amplitude of the sub-scan and the amplitude of the main scan. FIG. 3 is an explanatory diagram of a MEMS scanner. FIG. 7 is an explanatory diagram of deterioration of linearity in sub-scanning. FIG. 5 is a graph illustrating a relationship between linearity and a sub-scanning drive voltage in the MEMS scanner. FIG. 9 is an explanatory diagram illustrating sensitivity recovery processing. FIG. 4 is a graph showing a decrease in the sub-scanning amplitude sensitivity of the MEMS scanner. FIG. 4 is a graph showing recovery of amplitude sensitivity in sub-scanning of the MEMS scanner.

Hereinafter, embodiments of a MEMS mirror, a MEMS scanner, a head-up display, and a vehicle according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, an electromechanical system 10 as an embodiment of the present invention drives a MEMS scanner 2 provided in a head-up display (HUD) 1.

  The HUD 1 includes an image system 3 including a projection system, an image control system, and the like, and a MEMS scanner 2 that draws an image on a screen of the image system 3 by sweeping a laser beam two-dimensionally.

  FIG. 2 is a front view of the MEMS scanner 2 as an electromechanical element.

  The MEMS scanner 2 includes a MEMS mirror 20 and cantilevers 21 and 22 that are arranged so as to sandwich the MEMS mirror 20 and that support the MEMS mirror 20 so as to be rotatable in a direction indicated by an arrow P1 around a rotation axis L1.

  The MEMS mirror 20 has a mirror 23 having a substantially elliptical reflection surface, a rib 24, a pair of torsion beams 25a and 25b, a movable frame 26 made of Si supporting the torsion beams 25a and 25b, and provided on the back surface of the movable frame 26. The reinforcing plate 27 is provided. Further, the MEMS mirror 20 has PZT (lead zirconate titanate) films 28 and 29 as piezoelectric films for driving the mirror 23 to rotate around the rotation axis L2 in the direction of arrow P2.

  The rib 24 is provided on the back surface of the mirror 23 to prevent the mirror 23 from being twisted. Although the shape of the rib 24 is formed in a substantially Φ shape in FIG. 2, the present invention is not limited to this, and any shape may be used as long as the mirror 23 can be prevented from being twisted.

  The mirror 23 is preferably hermetically sealed in a package, and the package is preferably purged with nitrogen. The adhesive for fixing the mirror 23 in the package must not impair the function with respect to a temperature change of 95C to -40C.

  The torsion beams 25a and 25b are provided on both sides of the mirror 23 and are integrated with the movable frame 26. TO is a torsion offset between the rotation axis L2 of the mirror 23 and the central axis L3 of the mirror 23.

  The cantilever 21 is made of Si and can be twisted around the rotation axis L1. The PZT film 31 is provided at a bent portion of the crank part 30 and rotates the crank part 30 around the rotation axis L1. And

  The cantilever 22 includes a crank portion 32 made of Si and capable of being twisted about the rotation axis L1, a PZT film 33 provided at a bent portion of the crank portion 32 and driving the crank portion 32 to rotate around the rotation axis L1. And

The image system 3 includes an amplitude detector 4 that detects the amplitude θ _L1 of the deflection angle of the mirror 23 with respect to the rotation axis _L1 and the amplitude θ _L2 of the deflection angle of the mirror 23 with respect to the rotation axis L2.

FIG. 3 is an explanatory diagram for detecting the amplitude θ _L1 and the amplitude θ _L2 by the amplitude detection unit 4. The MEMS scanner 2 scans a laser beam in a vertical direction and a horizontal direction of the screen 40. PDs (photodiodes) 41 a and 41 b are provided above and below the screen 40, and PDs 42 a and 42 b are provided on the left and right of the screen 40.

The amplitude detection unit 4 calculates the amplitude θ _L1 of the deflection angle of the MEMS scanner 2 from the timing at which the laser light is incident on the PDs 41 a and 41 b and detected, the distance from the MEMS scanner 2 to the PDs 41 a and 41 b, and the distance between the PDs 41 a and 41 b. To detect. Similarly, the amplitude detection unit 4 determines the amplitude of the deflection angle of the MEMS scanner 2 based on the timing at which the laser light is incident on the PDs 42a and 42b and detected, the distance from the MEMS scanner 2 to the PDs 42a and 42b, and the distance between the PDs 42a and 42b. θ _L2 is detected.

Further, the amplitude detector 4 inputs information on the detected amplitudes θ _L1 and θ _L2 to a controller 15 described later. The control unit 15 controls the amplitude of the voltage waveform of the driving voltage applied to the MEMS scanner 2, the driving frequency, the phase difference between the voltage waveforms, and the like based on the information of the amplitude θ _L1 and the amplitude θ _L2. ing.

  FIGS. 4A to 4J are explanatory diagrams of the MEMS scanner 2. In the present embodiment, a MEMS scanner 2 having Si and a PZT film as shown in FIG. 2 is used.

  The mirror 23 is held by torsion beams 25a and 25b that are rotated by main scanning by being displaced by PZT films 28 and 29 that are piezoelectric elements.

  In the main scanning, when the sine wave driving voltage is applied to the PZT films 28 and 29, the torsion beams 25a and 25b to which the torque is applied are rotationally displaced (FIGS. 4A to 4E). .

  In the sub-scanning, when the sawtooth drive voltages (Ach, Bch) are applied to the PZT films 31, 33 of the independent cantilevers 21, 22, respectively, the cantilevers 21, 22 are deformed (displaced) (FIG. f) to (i)). As a result, the movable frame 26 is displaced, so that the mirror 23 rotates, and 2D scanning as two-dimensional scanning is realized (FIG. 4 (j)).

  As shown in FIG. 1, the electromechanical system 10 includes an applied voltage generator 11 that drives the MEMS scanner 2.

  The applied voltage generator 11 includes a main scanning drive voltage generator 12, a sub-scanning drive voltage generator 13, and a DC voltage generator 14. The main scanning driving voltage generator 12 and the sub-scanning driving voltage generator 13 constitute driving voltage applying means.

  The main scanning drive voltage generator 12 generates a main scanning sine wave driving voltage under the control of the controller 15 and applies the driving voltage to the PZT films 28 and 29 of the MEMS scanner 2. On the other hand, the sub-scanning drive voltage generation unit 13 generates a sub-scanning sawtooth drive voltage under the control of the control unit 15 and applies it to the PZT films 31 and 33 of the MEMS scanner 2.

  The DC voltage generator 14 has a function of generating a direct current (DC) constant voltage different from a drive voltage for driving the MEMS scanner 2 and applying the same to the sub-scanning PZT films 31 and 33 of the MEMS scanner 2. .

As described above, the control unit 15 outputs from the main scanning drive voltage generation unit 12 and the sub-scanning drive voltage generation unit 13 based on the information of the amplitude θ _L1 and the amplitude θ _L2 input from the amplitude detection unit 4. It controls the amplitude of the voltage waveform of the drive voltage, the drive frequency, the phase difference between the voltage waveforms, and the like. Further, the control unit 15 can change the magnitude of the DC constant voltage output from the DC voltage generation unit 14.

  Further, the control unit 15 switches on / off of voltage output by the main scanning drive voltage generation unit 12, the sub-scanning drive voltage generation unit 13, and the DC voltage generation unit 14. Specifically, when the application of the driving voltage to the PZT films 31 and 33 by the sub-scanning driving voltage generation unit 13 is off, the control unit 15 controls the PZT films 31 and 33 by the DC voltage generation unit 14. Is turned on. Here, the case where the application of the drive voltage to the PZT films 31 and 33 for sub-scanning is off is, for example, a non-use state where the power supply of the HUD1 is off.

  For this reason, the control unit 15 has means for detecting the use state of the HUD 1, and applies a DC constant voltage to the sub-scanning PZT films 31 and 33 by the DC voltage generation unit 14 when the HUD 1 is not used. It is desirable to have a configuration. This makes it possible to suppress a decrease in the sensitivity of the MEMS scanner 2 by utilizing the effect of recovering the amplitude sensitivity of the sub-scanning PZT films 31, 33, as described later.

  The applied voltage generator 11 is supplied with power from an external power supply 100 such as a vehicle-mounted power supply. It is assumed that the sensitivity recovery of the MEMS scanner 2 is performed in a state where the power is turned off when the vehicle is parked or the like. For this reason, the applied voltage generation unit 11 has a unique internal power supply 16 that can be charged, and a power supply switching unit 17 for switching the power supply source between the internal power supply 16 and the external power supply 100. Thus, the DC voltage generator 14 can be operated independently of the external power supply 100.

With reference to FIGS. 5A and 5B, description will be given of image disturbance due to deterioration of linearity in sub-scanning. The linearity is obtained, for example, by linearly approximating the time change of the deflection angle of the mirror 23 obtained by the measurement of the amplitude detection unit 4 by the least square method, and calculating the deviation amount of the deflection angle of the mirror 23 from the straight line. It is obtained as a value divided by the amplitude θ _L1 .

The main scan is driven resonantly at the resonance frequency, while the sub-scan is driven non-resonantly. This is because it is desirable that the ratio of the time for scanning in one direction in the vertical direction be as long as possible than the time for scanning in the reverse direction. For this reason, the sub-scanning has poor scanning efficiency, and the driving voltage required to obtain the desired swing angle amplitude θ _L1 is larger than that in the main scanning.

  In addition, in order to obtain good image quality in the sub-scanning, it is necessary to optimize the sub-scanning driving conditions (driving voltage, phase difference between Ach and Bch, driving frequency). The image in FIG. 5A satisfies the optimum condition. On the other hand, when the deviation is out of the optimum condition, the linearity is deteriorated, and a streak as shown in FIG. 5B appears in the image. The cause is due to resonance in the sub-scanning, and in particular, the resonance in the primary mode causes unevenness in the brightness of the image in the sub-scanning direction.

However, the amplitude sensitivity of the PZT films 28, 29, 31, and 33 decreases with the lapse of time, whereby the amplitudes of swing angles θ _L1 and θ _L2 decrease. In order to compensate for such a decrease in amplitude, it is necessary to apply a larger drive voltage to the PZT films 31 and 33 for sub-scanning than to the PZT films 28 and 29 for main scanning. For this reason, even if the drive condition for realizing high linearity with the initial value is set, the linearity is deteriorated by significantly increasing the sub-scanning drive voltage in order to compensate for the reduced swing angle θ _L1. become.

  The graph of FIG. 6 shows the result of evaluating the relationship between the linearity and the sub-scanning drive voltage (the maximum value of the sawtooth wave) in the MEMS scanner 2 of the present embodiment. That is, FIG. 6 shows that the linearity changes depending on the drive voltage, and the linearity shows a minimum value at a certain drive voltage. Note that the larger the value of the linearity, the stronger the brightness unevenness in the image.

In the configuration of the electromechanical system 10 described with reference to FIG. 1, when the drive voltage adjustment for compensating for the sensitivity drop is performed by the control unit 15 in order to obtain the desired swing angle amplitude θ _L1 , the linearity deteriorates and the image Brightness unevenness becomes strong.

  For example, under the driving conditions (the phase difference between Ach and Bch, the driving frequency) adjusted so that the linearity is 0.019 when the sub-scanning driving voltage is 30 V, when the driving voltage is changed to 36 V, the linearity becomes 0.026. Worsen.

  The cause of such a decrease in the sensitivity of the MEMS scanner 2 is considered to be charge charging and depolarization of the PZT films 31 and 33 as dielectrics.

  The term “charge” indicates that internal charges remain in the PZT films 31 and 33. When a drive voltage is applied to the charged PZT film, the effective drive voltage applied to the PZT film is lower than in the case where no charge is applied due to an electric field generated by internal charges. Further, when the depolarization of the PZT film proceeds due to heating or the like, the piezoelectricity of the PZT film is impaired.

  The present inventor has found that when a DC constant voltage of a certain magnitude or more is applied to the PZT film whose amplitude sensitivity has decreased due to charge charging or depolarization as described above, the charged charges are removed and the depolarization is performed. The found PZT film is repolarized. Further, for these reasons, it was found that by applying a DC constant voltage to the PZT film, the lowered amplitude sensitivity can be recovered.

  As described above, the effective drive voltage applied to the PZT films 31 and 33 decreases as described above, and the DC constant voltage is applied to the PZT films 31 and 33 to remove internal charges. By applying a high electric field or heating, the sensitivity recovery is accelerated.

  Since the repolarization is to repolarize the depolarized PZT films 31 and 33, it is necessary to apply a high electric field with a constant DC voltage and heat the PZT films 31 and 33 in order to align the domains. Thus, the sensitivity recovery is accelerated. It should be noted that the PZT film may be broken down when an excessively high voltage is applied.

  In other words, the speed of the sensitivity recovery depends on the electric field strength and the temperature, and by applying a DC constant voltage of a certain level or more to the MEMS scanner 2 and further placing the MEMS scanner 2 at a certain temperature or higher. Thus, the speed of sensitivity recovery can be effectively improved.

  As shown in FIG. 1, as a configuration for heating the PZT films 31 and 33, the electromechanical system 10 further includes a heater 18 for heating the MEMS scanner 2. The heater 18 heats the MEMS scanner 2 under the control of the control unit 15 when the application of the DC constant voltage to the PZT films 31 and 33 is on.

  Further, the present inventor has found that the effect of sensitivity recovery can be obtained with a higher DC constant voltage at lower temperatures and a lower DC constant voltage at higher temperatures. As a configuration for this, as shown in FIG. 1, the electromechanical system 10 further includes a temperature sensor 19 for detecting a temperature around the MEMS scanner 2. The control unit 15 can change the magnitude of the DC constant voltage output from the DC voltage generation unit 14 according to the temperature detected by the temperature sensor 19.

  As described above, the above-described sensitivity recovery may be performed when the HUD1 is not used. If the HUD 1 is an in-vehicle device, for example, it is considered that there is almost no situation in which the device is used continuously for 24 hours, for example. To perform sensitivity recovery. According to the JEDEC standard, the operating time of a vehicle is 8200 hours out of a vehicle life of 15 years, and when equalized, the actual operating time of the vehicle is less than 7%. Therefore, it is desirable to perform the recovery of the amplitude sensitivity of the MEMS scanner 2 other than the operation time of the vehicle.

  FIG. 7 is an explanatory diagram for explaining the sensitivity recovery processing by the applied voltage generator 11 shown in FIG.

  When the HUD 1 shown in FIG. 7A is used, the main scanning drive voltage generator 12 and the sub scanning drive voltage generator 13 apply a drive voltage to the MEMS scanner 2 (FIG. 7B). The voltage waveform of the sub-scanning drive voltage at this time is a sawtooth wave as shown in FIG. At this time, as shown in FIG. 7D, the amplitude sensitivity of the sub-scan of the MEMS scanner 2 is determined by the elapse of the use time of the HUD 1, that is, the sub-scanning drive voltage generating unit 13 applies the PZT films 31, 33 to the MEMS scanner 2. It decreases as the drive voltage application time elapses.

  When the HUD 1 shown in FIG. 7A is not used, the DC voltage generator 14 applies a DC constant voltage as shown in FIG. 7C to the sub-scanning PZT films 31 and 33 of the MEMS scanner 2 ( FIG. 7 (b). At this time, as shown in FIG. 7D, the amplitude sensitivity of the sub-scan of the MEMS scanner 2 increases as the HUD 1 is not used.

  Note that, as shown in FIG. 7C, it is desirable that the magnitude of the DC constant voltage output from the DC voltage generator 14 is equal to or greater than the maximum value of the drive voltage under the control of the controller 15. Thereby, the speed of the sensitivity recovery can be improved.

  FIG. 8 is a graph showing a decrease in the amplitude sensitivity of the sub-scan of the MEMS scanner 2. As a result of applying a sawtooth drive voltage to the PZT films 31 and 33 for sub-scanning and continuously driving the MEMS scanner 2 to measure a drop in amplitude sensitivity, a drop in sensitivity of about 20% occurs in 70 hours of continuous drive. I understood that.

  At this time, the ambient temperature of the MEMS scanner 2 is set to 95 ° C. by heating the heater 18 with reference to the on-vehicle conditions. The driving voltage is 30 V and the driving frequency is 52 Hz. When the drive voltage is increased by 20% to compensate for the 20% decrease in sensitivity, the drive voltage is increased from 30 V to 36 V. According to the graph of FIG. 6, the linearity is reduced from 0.019 to 0.026. Getting worse.

  FIG. 9 is a graph showing the recovery of the amplitude sensitivity of the sub scanning of the MEMS scanner 2. Here, the drop and the recovery of the amplitude sensitivity were measured assuming the driving conditions when actually mounted on a vehicle. Specifically, it is assumed that the vehicle user has driven the vehicle (using HUD1) for 3 hours and then parked the vehicle (not using HUD1) for 21 hours during 24 hours a day.

  First, as shown in FIG. 9A, when the driving voltage of the sawtooth wave is applied to the PZT films 31 and 33 for the sub-scanning and the continuous driving is performed for 3 hours, the amplitude sensitivity of the sub-scanning is reduced by 6%. did. Thereafter, when a DC constant voltage was applied to the PZT films 31 and 33 for sub-scanning for 21 hours, the amplitude sensitivity was recovered by 3% as shown in FIG. 9B.

  Further, in the case where the usage state as shown in FIG. 9 is repeated every day, the sensitivity recovery is performed if the sensitivity recovery is not performed in the product lifetime of the MEMS scanner 2 if the sensitivity is reduced by 20%. Thus, it is expected that the sensitivity decrease will be reduced by half to 10%.

  Further, when the drive voltage is increased by 10% to compensate for the 10% decrease in sensitivity, the drive voltage is increased from 30V to 33V. For this reason, according to the graph of FIG. 6, the linearity is deteriorated from 0.019 to 0.021. In comparison, it can be seen that the deterioration of the linearity is improved.

  As described above, the electromechanical system 10 of the present embodiment has a configuration in which the application of the DC constant voltage to the piezoelectric film is turned on when the application of the drive voltage to the piezoelectric film is turned off. I have. As described above, by applying a DC constant voltage to the piezoelectric film during use of the apparatus, the lowered amplitude sensitivity of the MEMS scanner 2 can be recovered. As a result, the width of change of the drive voltage for compensating for the decrease in the amplitude sensitivity can be suppressed to a small value. Obtainable.

  Further, the electric machine system 10 of the present embodiment has a chargeable internal power supply. Thus, the sensitivity of the MEMS scanner 2 can be recovered even when power is not supplied from the power supply of the vehicle or the like.

  Further, in the electromechanical system 10 of the present embodiment, the magnitude of the DC constant voltage applied to the piezoelectric film is equal to or larger than the maximum value of the sub-scanning drive voltage. Thereby, the speed of the sensitivity recovery of the MEMS scanner 2 can be improved.

  Further, the electromechanical system 10 of the present embodiment changes the magnitude of the DC constant voltage applied to the piezoelectric film according to the temperature detected by the temperature sensor 19. This makes it possible to efficiently recover the sensitivity of the MEMS scanner 2 at a higher DC constant voltage at lower temperatures and a lower DC constant voltage at higher temperatures.

  Further, in the electromechanical system 10 of the present embodiment, the heater 18 heats the electromechanical element when the application of the DC constant voltage to the piezoelectric film is on. Thereby, the speed of the sensitivity recovery of the MEMS scanner 2 can be improved.

1 HUD
2 MEMS scanner 3 Image system 4 Amplitude detector 10 Electromechanical system 11 Applied voltage generator (applied voltage generator)
12. Main scanning drive voltage generator (drive voltage applying means)
13 Sub-scanning drive voltage generator (drive voltage applying means)
14 DC voltage generator (DC voltage applying means)
15 control part (control means)
16 Internal power supply 17 Power supply switching unit 18 Heater 19 Temperature sensor 20 MEMS mirror 21, 22 Cantilever 23 Mirror 24 Rib 25a, 25b Torsion beam 26 Movable frame 28, 29 PZT film 30, 32 Crank part 31, 33 PZT film 40 Screen 41a, 41b, 42a, 42b PD
100 external power supply

JP 2009-128786 A

Claims (5)

A mirror having a reflective surface;
A pair of torsion beams provided on both sides of the mirror,
And a rib provided on the back surface of the mirror,
The mirror rotates about the axis of the pair of torsion beams,
The rib is
A linear portion extending in a direction perpendicular to the axis of the pair of torsion beams,
A first straight portion and a second straight portion extending from one side of the straight portion;
A third straight portion and a fourth straight portion extending from the other side of the straight portion;
Including
The first straight portion is connected at one end to the straight portion, the second straight portion is connected at one end to the straight portion, the other end of the first straight portion and the second straight portion. The other end of the first linear portion is connected only to the first connecting portion in an arc shape bulging toward the torsion beam side at a position away from the linear portion, and the width of the first linear portion and the second And the width of the first connecting portion is substantially the same,
The third straight portion is connected at one end to the straight portion, the fourth straight portion is connected at one end to the straight portion, and the other end of the third straight portion and the fourth straight portion The other end of the third linear portion is connected only to the second connecting portion in an arc shape bulging toward the torsion beam side at a position away from the linear portion, the width of the third linear portion, and the fourth MEMS mirrors and the width of the linear portion, the width of the second connecting portion, and wherein substantially the same der Rukoto. The linear portion extends in a direction away from the axis of the pair of torsion beams more than the first connecting portion connecting the first linear portion and the second linear portion, and 2. The MEMS mirror according to claim 1, wherein the MEMS mirror further extends in a direction away from axes of the pair of torsion beams than a second connection portion connecting the straight line portion and the fourth straight line portion. 3.   A MEMS scanner having the MEMS mirror according to claim 1.   A head-up display comprising the MEMS scanner according to claim 3.   A vehicle comprising the head-up display according to claim 4.