JP6130734B2 - Optical deflector - Google Patents

Description

  The present invention relates to a piezoelectric drive type optical deflector.

  2. Description of the Related Art A piezoelectric drive type optical deflector manufactured using MEMS (Micro Electro Mechanical Systems) technology is known. Such an optical deflector includes a support, a mirror that reflects light, a torsion bar that is coupled to the mirror at the distal end, a torsion bar that is coupled to the support at the proximal end, and a torsion bar that is coupled to the distal end. A piezoelectric actuator that couples and rotates the torsion bar back and forth around its axis and a piezoelectric sensor that detects the rotation angle of the mirror portion, etc. are provided (Patent Documents 1 and 2).

In the optical deflector of Patent Document 1, the piezoelectric sensor is formed integrally with the mirror part at the peripheral part of the mirror part, and reciprocates together with the mirror part to detect the rotation angle of the mirror part (Patent Document 1). / Figure 1). Such an optical deflector has the following problems.
(A) Since the piezoelectric sensor reciprocates together with the mirror unit, the resonance frequency of the mirror unit is lowered.
(B) Since the signal line of the piezoelectric sensor is formed over substantially the entire length of the torsion bar, the length of the resonance line of the mirror portion is increased. Thus, the resonance frequency of the mirror part is affected by the wiring area, film quality and material of the signal line. It becomes easier to receive and the deviation from the design value increases.
(C) Since the area of the piezoelectric sensor increases, the extending portion and the contracting portion of the piezoelectric sensor appear simultaneously, and the detection output as a whole decreases.

  On the other hand, in the optical deflector of Patent Document 2, the piezoelectric sensor is arranged on the piezoelectric actuator on the base end side of the torsion bar instead of the front end side of the torsion bar (Patent Document 2 / FIGS. 16 to 18). Thereby, the above-mentioned problems (a) to (c) in the optical deflector of Patent Document 1 can be solved.

JP 2011-150055 A JP 2010-197994 A

  However, the optical deflector of Patent Document 2 has the following problems. First, the present inventor roughly divides the width of the piezoelectric actuator into 5 in the axial direction of the torsion bar, assigns numbers 5 to 5 in order toward the base end of the torsion bar, and assigns 1 to each section. ˜5 piezoelectric sensors were arranged, and the output of each piezoelectric sensor was examined. As a result, the frequency of the output peak of the first and second piezoelectric sensors almost coincided with the resonance frequency of the mirror part, but the frequency of the output peak of the third and fifth piezoelectric sensors was greatly shifted.

  In the optical deflector of Patent Document 2, the piezoelectric sensor is arranged over the entire width of the piezoelectric actuator, and therefore the output of the piezoelectric sensor corresponds to the sum of the outputs of the first to fifth piezoelectric sensors. . Therefore, the output components of the third to fifth piezoelectric sensors with low accuracy are included, and it is recognized that the accuracy of the entire output of the piezoelectric sensor is deteriorated.

  Further, when the projector is equipped with an optical deflector, it is necessary to reciprocally vibrate the mirror unit at a frequency other than the resonance frequency, so that the mirror unit at a frequency different from the resonance frequency in a predetermined frequency range including the resonance frequency. Must be detected with sufficient accuracy.

  However, in the piezoelectric sensor in the optical deflector of Patent Document 2, when the phase of the driving voltage of the piezoelectric actuator is used as a reference phase, the phase difference of the output voltage of the piezoelectric sensor with respect to the reference phase is the reciprocal vibration of the mirror unit with respect to the reference phase. It was also found that there was a large deviation from the phase difference, and the deviation amount changed according to the frequency of the reciprocating vibration of the mirror part. For this reason, it is difficult to detect the frequency of the reciprocating vibration of the mirror portion within a predetermined frequency range with sufficient accuracy.

  An object of the present invention is to provide an optical deflector that can detect the reciprocating frequency of a mirror part with sufficient accuracy in a predetermined frequency range including a resonance frequency.

  The optical deflector according to the present invention includes a support, a mirror part that reflects light on the front side, a torsion bar having a tip part coupled to the mirror part, and a base part that is coupled to the support body, and a tip part. A piezoelectric actuator coupled to the torsion bar and reciprocatingly rotating the torsion bar about its axis, and a piezoelectric sensor disposed in a region extending between the torsion bar and the piezoelectric actuator to detect strain in the region. In the axial direction of the torsion bar, the region has a length (b2, d2) from the end on the mirror portion side to the end on the opposite side of the piezoelectric actuator, and the coupling between the torsion bar and the piezoelectric actuator. In the region, the torsion of the piezoelectric sensor is set to be 20% or less of the length (b1, d1) of the portion. The length (a3, c3) of the part straddling the bar is smaller than half the width (a1, c1) of the torsion bar, and the length (a4, c4) of the part of the piezoelectric sensor straddling the piezoelectric actuator is It is characterized by being 25% or less of half the width (a1, c1) of the torsion bar.

  The inventor sets the width of the piezoelectric actuator in the axial direction of the torsion bar to which the tip of the piezoelectric actuator is coupled, in order from the mirror-side end of the piezoelectric actuator toward the opposite end, 20: 8: 26: 16. The number was divided at a ratio of 16 and the numbers 1 to 5 were assigned to the divisions in that order, and the number 1 to number 5 piezoelectric sensors were arranged, and the output of each piezoelectric sensor was examined. As a result, it was found that the output of the first piezoelectric sensor satisfies the criteria only in magnitude and phase difference.

  The inventor further examined an area where a predetermined stress (for example, 66 MPa) can be detected without a phase shift for the first division. As a result, it was confirmed that there was no phase difference deviation from the boundary between the torsion bar and the piezoelectric actuator to the piezoelectric actuator side up to a location having a length of 25% with respect to half the width (a1, c1) of the torsion bar.

  According to the present invention, the region in which the piezoelectric sensor detects the strain has a length from the mirror-side end of the piezoelectric actuator to the opposite end that is 20 times the length of the coupling portion between the torsion bar and the piezoelectric actuator. The length (a4, c4) of the portion of the piezoelectric sensor that spans the piezoelectric actuator is set to 25% or less of the half of the width of the torsion bar (a1, c1). Thus, the reciprocating frequency of the mirror part can be detected with sufficient accuracy in a predetermined frequency range including the resonance frequency.

  In the present invention, the torsion bar is coupled to the support at its base end, and the piezoelectric sensor is connected to the wiring of the support via a signal line formed at the base end of the torsion bar. It is preferable that

  According to this configuration, since the signal line from the piezoelectric sensor is not wired on the piezoelectric film of the piezoelectric actuator, it is possible to suppress noise caused by the driving voltage of the piezoelectric film of the piezoelectric actuator from being mixed into the signal line. .

In the present invention, a ground line, between the piezoelectric film and the piezoelectric film of the piezoelectric sensor of the piezoelectric actuator, and that is formed between the piezoelectric film of said piezoelectric actuator and said signal lines preferred.

  According to this configuration, the ground line can absorb noise and suppress the mixing of noise into the signal line.

  In the present invention, it is preferable that the piezoelectric film of the piezoelectric actuator has a portion extending in the range of the region in the longitudinal direction of the piezoelectric actuator on the tip end side of the piezoelectric actuator.

  According to this configuration, the piezoelectric film of the piezoelectric actuator has a portion that overlaps the piezoelectric sensor in the longitudinal direction of the piezoelectric actuator on the distal end side, whereby the reciprocating rotational driving force of the torsion bar by the piezoelectric actuator can be increased.

The block diagram of the optical scanner provided with an optical deflector. The enlarged view of the range containing the arrangement | positioning site | part of the piezoelectric sensor of the linear piezoelectric actuator of FIG. FIG. 3 is an explanatory diagram of dimensions of the piezoelectric sensor of FIG. 2. FIG. 2 is a stress distribution diagram obtained by analyzing the stress distribution of each part of the optical deflector during operation of the optical deflector of FIG. 1 with predetermined software. The principal part structure figure of the optical deflector utilized for the experiment for investigating the optimal position of a piezoelectric sensor. The output characteristic figure in the evaluation test with respect to each piezoelectric sensor of FIG. The output characteristic figure of each piezoelectric sensor in another evaluation test. The output characteristic figure which extracted a part of FIG. FIG. 9 is a structural diagram of a main part of an optical deflector used in an experiment for searching for a more appropriate region of the piezoelectric sensor based on the experimental results of FIGS. The figure which shows the relationship between the horizontal dimension ratio when the piezoelectric sensor of FIG. 9 is extended to the piezoelectric actuator side, and the phase difference of the piezoelectric sensor 151. FIG. The structure figure which looked at another light deflector by front view. FIG. 12 is an enlarged view of a range including an arrangement site of a piezoelectric sensor in the optical deflector of FIG. 11. FIG. 13 is an explanatory diagram of dimensions of the piezoelectric sensor in FIG. 12. FIG. 12 is a stress distribution diagram obtained by analyzing stress distribution of each part of the optical deflector during operation of the optical deflector of FIG. 11 with predetermined software.

  With reference to FIG. 1, the structure of the optical scanner 100 equipped with the optical deflector 1 is demonstrated roughly. The optical scanner 100 includes an optical deflector 1, a laser light source 90, and a control unit 95.

  The optical deflector 1 is manufactured using MEMS technology. The optical deflector 1 emits reflected light 92 as scanning light by increasing or decreasing a reflection angle at a constant frequency with respect to incident light 91 from the laser light source 90 as light incident from a certain direction. The optical scanner 100 displays an image on a predetermined screen (not shown) using the scanning light.

  The control unit 95 receives various input signals including the detection signal of the piezoelectric sensor 6 and controls the linear piezoelectric actuators 5 and 8 based on the input signal. Specifically, the control unit 95 controls the voltage applied to the piezoelectric film of the linear piezoelectric actuators 5 and 8. The control unit 95 further controls on / off of the laser light source 90 and, in some cases, the luminance of the laser light source 90.

  For convenience of describing the optical deflector 1 in FIG. When the light deflector 1 is referred to as up, down, left, and right, it is assumed that the light deflector 1 is up, down, left, and right when viewed from the front of FIG. Note that the vertical and horizontal directions defined for the convenience of description of the optical deflector 1 do not define the vertical and horizontal directions in the actual use of the optical deflector 1. The direction view facing the mirror surface of the mirror unit 2 at rest is parallel to the front view, and the clockwise rotation angle is arbitrary.

  The optical deflector 1 includes a mirror unit 2, two torsion bars 3, a rectangular frame 4, one linear piezoelectric actuator 5, and three linear piezoelectric actuators 8. The mirror unit 2 is disposed at the center of the rectangular frame 4. The left and right torsion bars 3 are arranged on the left and right sides of the mirror unit 2 with their axes aligned with the diameter in the left-right direction of the circular mirror unit 2. The torsion bar 3 is coupled to the peripheral edge of the mirror unit 2 at the distal end and is coupled to the inner peripheral side surface of the short side of the rectangular frame 4 at the proximal end.

  The mirror unit 2 receives incident light 91 from the laser light source 90 on a front-side mirror surface (not shown), and emits reflected light 92 in a direction according to the rotation angle around the axis of the torsion bar 3.

  On the right side of the mirror portion 2, the linear piezoelectric actuators 5 and 8 are respectively disposed above and below the base end portion of the right torsion bar 3, and the front end side is coupled to the base end side portion of the torsion bar 3. . On the left side of the mirror portion 2, the two linear piezoelectric actuators 8 are respectively disposed above and below the base end portion of the left torsion bar 3, and the front end side is coupled to the base end side portion of the torsion bar 3. .

  The structural difference between the linear piezoelectric actuator 5 and the linear piezoelectric actuator 8 is that the linear piezoelectric actuator 5 is equipped with a piezoelectric sensor 6 on the tip side, whereas the linear piezoelectric actuator 8 is equipped with a piezoelectric sensor 6. It is a point not to do.

  The linear piezoelectric actuator 8 functions as a piezoelectric actuator on the entire surface, whereas the linear piezoelectric actuator 5 functions as a piezoelectric actuator in the remaining actuator portion 9 except the piezoelectric sensor 6. The piezoelectric sensor 6 extends beyond the connecting portion between the linear piezoelectric actuator 5 and the torsion bar 3 and extends to the region of the torsion bar 3.

  When the linear piezoelectric actuator 5 is manufactured by the MEMS technique, the linear piezoelectric actuator 5 is manufactured as the linear piezoelectric actuator 8, and then a dividing groove is formed by etching at the boundary between the piezoelectric sensor 6 and the actuator portion 9. And the piezoelectric film of the actuator portion 9 are separated by a dividing groove. The piezoelectric film of the piezoelectric sensor 6 is formed simultaneously with the linear piezoelectric actuator 5 portion and the torsion bar 3 portion.

  FIG. 2 is an enlarged view of a range including the arrangement site of the piezoelectric sensor 6 of the linear piezoelectric actuator 5 in the optical deflector 1. FIG. 2 shows the range in front view of the optical deflector 1. The linear piezoelectric actuator 5 has a straight inner edge 5a and an outer edge 5b as side edges on the near side and the far side of the mirror part 2 in the front view.

  The torsion bar 3 includes a first portion 3a, a second portion 3b, and a third portion 3c in order from the distal end to the proximal end. The second portion 3b is an axial portion in which the torsion bar 3 is coupled to the linear piezoelectric actuators 5 and 8 in the axial direction. The first portion 3a and the third portion 3c are axial portions located on the distal end side and the proximal end side with respect to the second portion 3b in the torsion bar 3, respectively.

  In the linear piezoelectric actuator 8, the piezoelectric film almost reaches the straight edge 11 of the linear piezoelectric actuator 8. On the other hand, in the piezoelectric film of the actuator portion 9 of the linear piezoelectric actuator 5, the front end side of the linear piezoelectric actuator 5 is partitioned by partition lines 12 to 14.

  The dividing lines 12 and 14 are parallel to the width direction of the linear piezoelectric actuator 5, and the dividing line 13 is parallel to the longitudinal direction of the linear piezoelectric actuator 5. The lane marking 14 overlaps with the edge on the distal end side of the linear piezoelectric actuator 5, and the lane marking 12 is drawn to the base end side of the linear piezoelectric actuator 5 by the length of the lane marking 13 from the lane marking 14. The edge on the tip side of the linear piezoelectric actuator 5 is included in a joint portion between the torsion bar 3 and the piezoelectric sensor 6.

  The piezoelectric sensor 6 is disposed on the torsion bar 3 and the linear piezoelectric actuator 5 across the coupling portion between the torsion bar 3 and the linear piezoelectric actuator 5. A portion of the piezoelectric sensor 6 on the linear piezoelectric actuator 5 side exists in a rectangular region defined by the dividing lines 12 and 13.

  The piezoelectric film of the actuator portion 9 extends on the tip side of the linear piezoelectric actuator 5 so as to overlap the range of the piezoelectric sensor 6 in the longitudinal direction of the linear piezoelectric actuator 5 and extend to the location of the partition line 14. However, the area of the piezoelectric film increases, and the driving force of the linear piezoelectric actuator 5 increases.

  The signal line 19 is formed along the axis of the torsion bar 3 in the second portion 3b and the third portion 3c. The signal line 19 is connected at one end to a portion on the torsion bar 3 side of the piezoelectric sensor 6 and is connected at the other end to the signal line 20 of the rectangular frame 4. The signal line 20 is connected to an electrode (not shown) of the rectangular frame 4.

  The ground line 23 is formed in the linear piezoelectric actuator 5, the second portion 3 b and the third portion 3 c, and is connected to the ground line 25 of the rectangular frame 4. The ground line 23 is formed between the piezoelectric sensor 6 and the partition lines 12 and 13 in the linear piezoelectric actuator 5, and is formed between the partition line 14 and the signal line 19 in the second portion 3b.

  The ground line 24 is formed in the second part 3 b and the third part 3 c and is connected to the ground line 26 of the rectangular frame 4. The ground line 24 is formed between the piezoelectric sensor 6 and the signal line 19 and the edge 11 of the linear piezoelectric actuator 8 in the second portion 3b.

  Since the signal line 19 is not wired on the surface of the actuator portion 9, noise due to the drive voltage of the piezoelectric film of the actuator portion 9 is suppressed from being mixed into the signal line 19. The ground lines 23 and 24 have a function of electrostatically shielding the piezoelectric sensor 6 and the signal line 19 to the outside, and noise from the outside is suppressed from being mixed into the piezoelectric sensor 6 and the signal line 19.

  The dimensions of the piezoelectric sensor 6 will be described with reference to FIG. FIG. 3 is a view of the main part of the optical deflector 1 of FIG. In FIG. 3, the upper side is the mirror unit 2 side and the lower side is the rectangular frame 4 side.

  The dimensions of the respective parts in FIG. 3 are the dimensions of the optical deflector 1 as viewed from the direction facing the mirror part 2 when the mirror part 2 is in a stationary state, that is, when the normal line of the center is directed straight forward. Defined in The center line 35 overlaps the axis of the torsion bar 3 in the direction view.

The meaning of each dimension symbol in FIG. 3 is as follows.
a1: Half the width of the torsion bar 3 a2: Length of the piezoelectric sensor 6 in the direction perpendicular to the center line 35 in the length direction of the torsion bar 3 (a2 = a3 + a4)
a3: Length of the portion of the piezoelectric sensor 6 on the torsion bar 3 side in the direction orthogonal to the center line 35 a4: Length b1 of the portion of the piezoelectric sensor 6 in the direction orthogonal to the center line 35 on the side of the linear piezoelectric actuator 5 : Length of the second portion 3b in the direction of the center line 35 (= width of the linear piezoelectric actuator 5 = length of the coupling portion between the torsion bar 3 and the linear piezoelectric actuator 5)
b2: Distance from the boundary line between the first portion 3a and the second portion 3b in the direction of the center line 35 to the lower side (side on the third portion 3c side) of the piezoelectric sensor 6 (b2 = b3 + b4)
b3: Distance from the boundary line between the first part 3a and the second part 3b in the direction of the center line 35 to the upper side of the piezoelectric sensor 6 (side on the first part 3a side) b4: The piezoelectric sensor 6 in the direction of the center line 35 The distances a1 to a4 between the upper side and the lower side are set such that 0 <a3 <a1 and 0 <a4 ≦ 0.25 · a1. 0 <a3 <a1 means that the side on the center line 35 side of the piezoelectric sensor 6 does not reach the center line 35. b1 to b4 are set so that the relationship of 0 <b2 ≦ 0.20 · b1 is established.

  FIG. 4 shows the stress obtained by replacing the linear piezoelectric actuator 5 of the optical deflector 1 with the linear piezoelectric actuator 8 and analyzing the stress distribution of each part of the optical deflector 1 during operation of the optical deflector 1 with predetermined software. It is a distribution map.

  In the actual analysis result, the stress distribution is displayed in color. In FIG. 4, for the monochrome, the red region Cr (high stress region) of the torsion bar 3 and the blue region Cb of the mirror unit 2 are displayed. (Low stress area) is the same density and is difficult to understand. The yellow region Cy (region of stress = 66 MPa) reaches a length of 25% of a1 (FIG. 3) from the coupling line between the torsion bar 3 and the linear piezoelectric actuator 8 to the linear piezoelectric actuator 8 side. .

  FIG. 5 shows the structure of the optical deflector 105 used in an experiment for examining the optimum position of the piezoelectric sensor 6. The optical deflector 105 is obtained by modifying a partial structure of the optical deflector 1. FIG. 5 shows only the changing part of the optical deflector 1. 5, parts having the same structure shown in FIG. 2 are designated by the same reference numerals as those used in FIG. 2, description thereof is omitted, and the structural parts of the changed points are described by adding reference numerals.

  The linear piezoelectric actuator 5 has a dividing line 109 on the distal end side of the actuator portion 9 on the distal end side. In the linear piezoelectric actuator 5, the tip end side from the partition line 109 is a sensor region 110.

  In the experiment according to FIG. 5, if the length of the linear piezoelectric actuator 5 is defined as L, the length of the sensor region 110 is set to L / 3 or less. The sensor region 110 is divided into five equal parts in the width direction of the linear piezoelectric actuator 5 and sequentially from the distal end side (left side in FIG. 5) to the proximal end side (right side in FIG. 5) of the section divided into five. Give numbers 1-5.

  The piezoelectric sensors 111 to 115 are formed in the first to fifth sections of the sensor region 110, respectively, and detect distortions in the first to fifth sections. Hereinafter, the piezoelectric sensors 111 to 115 will be appropriately referred to as “sensor No. 1” to “sensor No. 5”.

  With reference to FIG. 6, the evaluation test result about the output of the piezoelectric sensors 111-115 is demonstrated. 6, the horizontal axis represents the frequency of reciprocating rotation of the mirror unit 2, and the vertical axis represents the mechanical half angle of the mirror unit 2 (a value half the reciprocating vibration rotation angle) and the sensor No. 1-No. 5 sensor output (peak value: peak to peak).

  Se1 to Se5 are sensor Nos. 1-No. 5 shows the output characteristics. Ma is a relational characteristic between the actual mechanical half angle and the frequency of the mirror unit 2.

  According to FIG. 6, the mechanical half angle of the mirror unit 2 is maximum at a frequency of 25132 Hz, and this frequency is the resonance frequency of the mirror unit 2. Sensor No. In 1, the frequency is maximum at 25132 Hz, and the output is 0.4 Vpp or more. Sensor No. 2 was the maximum at a frequency of 25132 Hz, but the output was 0.235 Vpp. It turned out to be inferior to 1.

  Sensor No. 3 has a maximum sensor output at a frequency of 25136 Hz, and the maximum output is 0.250 V. Less than 1. Sensor No. 4, the sensor output reached a maximum of 0.282 V at a frequency of 25136 Hz. Sensor No. 5, the sensor output reached a maximum of 0.143 V at a frequency of 25136 Hz.

  From the above results, sensor no. 1, No. 1 2 has a sufficient output at the resonance frequency while the frequency of the peak output matches the resonance frequency. On the other hand, sensor No. 3-No. In No. 5, the peak output frequency deviates from the resonance frequency, and the output is insufficient.

  With reference to FIG.7 and FIG.8, another evaluation test result about the output of the piezoelectric sensors 111-115 is demonstrated. 7 and 8, the horizontal axis represents the frequency of reciprocating rotation of the mirror unit 2, and the vertical axis represents the sensor No. The output phase difference of 1 etc. and the mechanical half angle of the mirror unit 2.

  In FIG. 7, R indicates the resonance frequency of the mirror unit 2. Se1 to Se5 are sensor Nos. 1-No. 5 shows the phase difference characteristics of the output No. 5. Mb represents the phase difference characteristic of the mirror unit 2. Ma is a relational characteristic between the actual mechanical half angle and the frequency of the mirror unit 2. FIG. 8 shows only Se1, Se2, Ma, and Mb extracted from FIG.

  Here, the phase difference means that the phase of the drive voltage applied to the piezoelectric film of the linear piezoelectric actuator 8 is the reference phase and the sensor No. 1-No. 5 represents the phase difference of the output of the piezoelectric sensor 5 or the phase difference of the reciprocating rotation of the mirror unit 2. In FIG. 7, Mb and Se1 are almost overlapped and are difficult to distinguish.

  From FIG. 7, it was found that Se1 and Mb are substantially the same in a sufficiently wide frequency range including the resonance frequency R with respect to the phase difference. On the other hand, it has been found that Se2 and Mb have a large deviation in the frequency range below the resonance frequency R.

  In the optical scanner 100, in order to draw a predetermined image on the screen, it is necessary to reciprocate and rotate the mirror unit 2 at a frequency other than the resonance frequency R. 1 was found to be excellent.

  The deployment area of the piezoelectric sensor 6 (FIGS. 1 to 3) of the optical deflector 1 is set as an area including only the first section, excluding the second to fifth sections. Therefore, the frequency and phase difference of the reciprocating vibration of the mirror unit 2 can be detected from the output of the piezoelectric sensor 6 with high accuracy.

  FIG. 9 shows the structure of the optical deflector 140 used in an experiment for searching for a more appropriate region of the piezoelectric sensor based on the experimental results of FIGS. The torsion bar 143 and the piezoelectric actuators 145 and 148 of the optical deflector 140 correspond to the torsion bar 3 and the linear piezoelectric actuators 5 and 8 of the optical deflector 1. The center line 141 corresponds to the center line 35 in FIG.

  The portion of the torsion bar 143 located on the distal end side of the piezoelectric actuator 145 is divided into five in the direction of the center line 141, and the five sections divided into five are sequentially numbered 1 to 5 from the mirror part side (upper side in FIG. 9). Numbered. Piezoelectric sensors 151 to 155 are arranged in each section, and numbers 1 to 5 are assigned to the piezoelectric sensors 151 to 155.

  In FIG. 9, a numerical value without “%” indicates a length. Numbers with% indicate percentages. The sections 1 to 5 and the vertical and horizontal directions of the piezoelectric sensor are defined as the direction of the center line 141 and the longitudinal direction of the piezoelectric actuator 145. The vertical dimensions of the 1st to 5th sections are 83, 74, 107, 66, and 66, and the ratio is 20: 8: 26: 16: 16.

  The lateral dimension of the first piezoelectric sensor is 186, and the lateral dimensions of the five piezoelectric sensors increase in the order of the numbers. The original edge of the piezoelectric actuator 145 on the torsion bar 3 side is parallel to the center line 141. However, in the experiment, the edge of the piezoelectric actuator 145 on the torsion bar 3 side is closer to the original position as shown in FIG. I'm drawing in. Accordingly, the first to fifth piezoelectric sensors in FIG. 9 have the same central angle with respect to the center of the mirror portion, and the original optical deflector enters the region of the piezoelectric actuator.

  Also in the output test in the piezoelectric sensors 151 to 155, the experimental results of FIGS. 6 to 8 similar to those of the piezoelectric sensors 111 to 115 (FIG. 5) were obtained.

  Further, it was examined how much the first piezoelectric sensor 151 can be extended to the piezoelectric actuator 145 side beyond the coupling line between the torsion bar 143 and the piezoelectric actuator 145. FIG. 10 shows the relationship between the horizontal dimension ratio (horizontal axis) and the phase difference deviation (vertical axis). The horizontal dimension ratio is the ratio of the length of the first piezoelectric sensor 151 extending to the piezoelectric actuator 145 side beyond the coupling line between the torsion bar 143 and the piezoelectric actuator 145 with respect to half the width of the torsion bar 143. It is. The phase difference shift is a difference between the phase difference of the actual deflection angle of the mirror unit with respect to the phase of the driving voltage of the piezoelectric actuator 145 and the phase difference of the output of the piezoelectric sensor 151 with respect to the phase of the driving voltage of the piezoelectric actuator 145. is there.

  In FIG. 10, the horizontal dimension ratio is the length e4 that the piezoelectric sensor 151 extends to the piezoelectric actuator 145 side beyond the coupling line between the torsion bar 143 and the piezoelectric actuator 145, with e1 being 1/2 of the width of the torsion bar 143. The ratio (% of e4 / e1) is shown. From FIG. 10, it was found that the phase difference on the vertical axis was maintained at 0 ° up to a horizontal dimension ratio of 25%.

  FIG. 11 is a structural view of another optical deflector 41 as viewed from the front. The main difference of the optical deflector 41 with respect to the optical deflector 1 described above is that the arc-shaped piezoelectric actuator 45 is not linear but semicircular.

  In the optical deflector 41, the mirror part 42, the torsion bar 43 and the rectangular frame 44 as a support correspond to the mirror part 2, the torsion bar 3 and the rectangular frame 4 of the optical deflector 1, respectively, and have the same structure as them. ing. The arc-shaped piezoelectric actuators 45 and 48 have the same semi-annular shape, and are arranged in line symmetry with respect to a straight line including the center of the mirror portion 42 and the axis 50 (FIG. 13) of the two torsion bars 43. The portion is coupled to the proximal end portion of the torsion bar 43.

  In the arc-shaped piezoelectric actuators 45 and 48, both end portions are distal end portions, and midpoint portions are proximal end portions. In other words, the arc-shaped piezoelectric actuators 45 and 48 have a structure in which there are two distal end portions and one proximal end portion.

  The difference in structure between the arc-shaped piezoelectric actuator 45 and the arc-shaped piezoelectric actuator 48 is the same as the difference between the linear piezoelectric actuator 5 and the linear piezoelectric actuator 8 in the optical deflector 1. Whereas the sensor 46 is equipped, the arc-shaped piezoelectric actuator 48 is not equipped with the piezoelectric sensor 46. The arc-shaped piezoelectric actuator 48 functions as a piezoelectric actuator over the entire surface, whereas the linear piezoelectric actuator 5 functions as a piezoelectric actuator in the remaining actuator portion 55 except for the piezoelectric sensor 46.

  Each torsion bar 43 has a first portion 43a, a second portion 43b, and a third portion 43c. The second portion 43 b is a portion in the axial direction of the torsion bar 43 to which the arc-shaped piezoelectric actuator 45 or the arc-shaped piezoelectric actuator 48 is coupled in the axial direction of the torsion bar 43. The first portion 43a and the third portion 43c are axial portions of the torsion bar 43 that exist on the distal end side and the proximal end side with respect to the torsion bar 43 in the axial direction of the torsion bar 43, respectively.

  The pair of connecting portions 49 are respectively arranged on the upper side and the lower side with respect to the mirror portion 42, and connect the outer peripheral side midpoint of the arc-shaped piezoelectric actuator 45 and the arc-shaped piezoelectric actuator 48 to the inner peripheral side edge of 44. doing. The torsion bars 43 and the connecting portions 49 are arranged alternately at 90 ° intervals in the circumferential direction of the mirror portion 42.

  FIG. 12 is an enlarged view of a range including the arrangement site of the piezoelectric sensor 46 in the optical deflector 41 of FIG. FIG. 12 shows the range in front view of the optical deflector 41. When viewed from the front, the arcuate piezoelectric actuator 45 has an inner peripheral line 55a and an outer peripheral line 55b on the inner peripheral side and the outer peripheral side. Since the arcuate piezoelectric actuator 45 is semicircular when viewed from the front, the inner circumferential line 55a and the outer circumferential line 55b are circumferential lines.

  In the arc-shaped piezoelectric actuator 48, the piezoelectric film almost reaches the straight edge 51 of the arc-shaped piezoelectric actuator 48. On the other hand, in the piezoelectric film of the actuator portion 55 of the piezoelectric sensor 46, the tip side of the piezoelectric sensor 46 is defined by the partition lines 52 to 54.

  The partition line 52 is set in the arc-shaped piezoelectric actuator 45 in the direction of the normal line of the inner peripheral line 55a. The partition line 53 extends a predetermined length along the inner peripheral line 55a while maintaining an equal distance from the inner peripheral line 55a. The partition line 54 overlaps the straight edge of the arc-shaped piezoelectric actuator 45.

  The dividing line 52 is drawn from the dividing line 54 to the proximal end side of the arcuate piezoelectric actuator 45 by the length of the dividing line 53. The edge of the arcuate piezoelectric actuator 45 on the front end side is included in the coupling portion between the torsion bar 43 and the piezoelectric sensor 46.

  The piezoelectric sensor 46 extends to the torsion bar 43 and the arcuate piezoelectric actuator 45 across the coupling portion between the torsion bar 43 and the arcuate piezoelectric actuator 45. The portion of the piezoelectric sensor 46 on the side of the arc-shaped piezoelectric actuator 45 is disposed in a region that defines the base end side and the outer peripheral line 55 b side of the arc-shaped piezoelectric actuator 45 by the partition lines 52 and 53.

  The signal line 59 is formed along the axis 50 of the torsion bar 43 in the second portion 43b and the third portion 43c. The signal line 59 is connected at one end to a portion of the piezoelectric sensor 46 on the torsion bar 43 side, and at the other end is connected to the signal line 60 of the rectangular frame 44. The signal line 60 is connected to an electrode (not shown) of the rectangular frame 44.

  The ground line 63 is formed in the arc-shaped piezoelectric actuator 45, the second portion 43b, and the third portion 43c, and is connected to the ground line 65 of the rectangular frame 44. The ground line 63 is formed between the piezoelectric sensor 46 and the partition line 52 and the partition line 53 in the arc-shaped piezoelectric actuator 45, and is formed between the partition line 54 and the signal line 59 in the second portion 43b.

  The ground line 64 is formed in the second portion 43 b and the third portion 43 c and is connected to the ground line 66 of the rectangular frame 44. The ground line 64 is formed in the second portion 43 b between the piezoelectric sensor 46 and the signal line 59 and the end edge 51 of the arc-shaped piezoelectric actuator 48.

  The dimensions of the piezoelectric sensor 46 will be described with reference to FIG. FIG. 13 is a front view of the optical deflector 41 of FIG. 12 as viewed in a direction rotated 90 ° clockwise, and the dimensions that each symbol means are defined by the dimensions in the direction of view. In the direction view, the upper side is the mirror part 42 side and the lower side is the rectangular frame 44 side in FIG. The axis 50 overlaps the axis of the torsion bar 43 in the direction view.

  In FIG. 13, an inner peripheral side extension line 56 and an outer peripheral side extension line 57 are extension lines obtained by extending the inner peripheral line 45a and the outer peripheral line 55b from the ends of the inner peripheral line 45a and the outer peripheral line 45b with the same curvature.

The meaning of each dimension symbol in FIG. 13 is as follows.
c1: Half the width of the torsion bar 43 c2: Length of the upper side (side on the inner peripheral line 55a side) of the piezoelectric sensor 46 (c2 = c3 + c4)
c3: Length of the upper side of the piezoelectric sensor 46 on the torsion bar 43 side along the inner peripheral extension line c4: Inner circumference of the upper side of the piezoelectric sensor 46 on the arcuate piezoelectric actuator 45 side Length d1 along the line 55a: Length d2 of the second portion 43b: Distance from the inner peripheral extension line 56 in the direction of the axis 50 to the lower side of the piezoelectric sensor 46 (side on the outer peripheral line 55b side) (d2 = d3 + d4)
d3: distance between the inner circumference 55a and the upper side of the piezoelectric sensor 46 in the direction of the axis 50 d4: distance between the upper side and the lower side of the piezoelectric sensor 46 in the direction of the axis 50 c1 to c4 are 0 <c3 <c1, 0 < It is set so that the relationship of c4 ≦ 0.25 · c2 is established. 0 <c3 <c1 means that the side of the piezoelectric sensor 46 on the center line 58 side does not reach the center line 58. d1 to d4 are set so that the relationship of 0 <d2 ≦ 0.20 · d1 is established.

  FIG. 14 shows a stress distribution obtained by replacing the arc-shaped piezoelectric actuator 45 of the optical deflector 41 with an arc-shaped piezoelectric actuator 48 and analyzing the stress distribution of each part of the optical deflector 41 when the optical deflector 41 is operated with predetermined software. FIG. From the stress distribution diagram of FIG. 14, as in the case of the stress distribution diagram of FIG. 4, a sufficiently large stress is generated in the region portion on the mirror portion 42 side at the coupling portion between the torsion bar 43 and the arcuate piezoelectric actuator 48. It is understood.

  Further, regarding the optical deflector 41, the analysis diagrams of FIGS. 6 to 8 for the optical deflector 1 are omitted, but the analysis of the optical deflector 41 in FIGS. It is easily understood that similar analysis results can be obtained.

  The area where the piezoelectric sensor 46 of the optical deflector 41 is disposed is that the arc-shaped piezoelectric actuator 45 is defined as Nos. 2 to 5 when the first to fifth segments similar to the linear piezoelectric actuator 5 of the optical deflector 1 are defined. This area is set as an area including only the first section. As a result, the frequency and phase difference of the reciprocating vibration of the mirror unit 42 can be detected from the output of the piezoelectric sensor 46 with high accuracy.

  The invention has been described with reference to embodiments. The rectangular frames 4 and 44 are examples of supports. The linear piezoelectric actuator 5 and the arc-shaped piezoelectric actuator 48 are examples of piezoelectric actuators. The signal line 60 is an example of a support wiring to which a signal line formed at the base end portion of the torsion bar is connected.

  A1 in FIG. 3 and c1 in FIG. 13 are examples of a length that is half the width of the torsion bar as viewed in the direction facing the front side of the mirror portion when stationary.

  B1 in FIG. 3 and d1 in FIG. 13 are examples of the length of the coupling portion in the axial direction of the torsion bar with respect to the coupling portion between the torsion bar and the piezoelectric actuator.

  In the embodiment, the linear piezoelectric actuator 5 and the arc-shaped piezoelectric actuator 45 are described as the piezoelectric actuators, but the piezoelectric actuator of the present invention may have a shape other than the straight line and the arc.

  In the embodiment, the portion of the piezoelectric sensor 46 on the torsion bar 43 side extends along the inner peripheral extension line 56 from the coupling portion between the torsion bar 43 and the arc-shaped piezoelectric actuator 45, but is perpendicular to the axis 50. It may extend to.

  In the embodiment, the torsion bar 3 and the torsion bar 43 are coupled to the rectangular frames 4 and 44 at the base end portions, respectively, but may not be coupled to the rectangular frames 4 and 44.

  In the embodiment, the optical scanner 100 equipped with the optical deflector is applied to the projector. However, the optical scanner equipped with the optical deflector of the present invention may be a barcode reader, a laser printer, a laser headlamp, or a head-up. It can be applied to a display or the like.

DESCRIPTION OF SYMBOLS 1,41 ... Optical deflector, 2,42 ... Mirror part, 3,43 ... Torsion bar, 4,44 ... Rectangular frame (support), 5 ... Linear piezoelectric actuator ( Piezoelectric actuator), 6, 46 ... Piezoelectric sensor, 19, 60 ... Signal line, 23, 24, 63, 64 ... Ground wire, 45 ... Arc-shaped piezoelectric actuator (piezoelectric actuator), 46. ..Piezoelectric sensor, 48... Arc-shaped piezoelectric actuator (piezoelectric actuator)

Claims (4)

A support;
A mirror part that reflects light on the front side;
A torsion bar having a tip part coupled to the mirror part;
A piezoelectric actuator that has a proximal end coupled to the support, a distal end coupled to the torsion bar, and reciprocally rotates the torsion bar about its axis;
A piezoelectric sensor that is disposed in a region extending between the torsion bar and the piezoelectric actuator and detects distortion in the region;
In the axial direction of the torsion bar, the region has a length (b2, d2) from an end on the mirror portion side to an end on the opposite side of the piezoelectric actuator, and a coupling portion between the torsion bar and the piezoelectric actuator. Is set to be 20% or less of the length (b1, d1) of
In the region, the length (a3, c3) of the portion of the piezoelectric sensor that spans the torsion bar is smaller than half the width (a1, c1) of the torsion bar, and the length of the portion of the piezoelectric sensor that spans the piezoelectric actuator. The length (a4, c4) is 25% or less of a half (a1, c1) of the width of the torsion bar. The optical deflector according to claim 1.
The torsion bar is coupled to the support at its proximal end,
The optical deflector, wherein the piezoelectric sensor is connected to a wiring of the support through a signal line formed at a base end portion of the torsion bar. The optical deflector according to claim 2, wherein
Wherein between the piezoelectric film of the piezoelectric actuator and a piezoelectric film of the piezoelectric sensor, and between the piezoelectric film of said piezoelectric actuator and said signal line, an optical deflector, wherein the ground line is formed. The optical deflector according to any one of claims 1 to 3,
The optical deflector according to claim 1, wherein the piezoelectric film of the piezoelectric actuator has a portion extending in a range of the region in a longitudinal direction of the piezoelectric actuator on a tip end side of the piezoelectric actuator.