Light deflector driving system, and light deflector driving method

Abstract

To provide a light deflector driving system and the like that, even when reflecting a change in offset (or amplitude), can prevent the generation of abnormal vibration in a light deflector.SOLUTION: A light deflector driving method includes: a change instruction input step S20 of receiving input of an instruction to change at least one of a first driving signal corresponding to a first driving voltage applied to an actuator that oscillates a mirror part of a light deflector around an oscillation axis and a second driving signal corresponding to a second driving voltage; determination steps S21, S23 of, when input of the instruction is received, determining the timing when voltage is minimized for a driving signal to be changed of the first driving signal and the second driving signal; and change reflection steps S25, S27 of, when the timing when the voltage is minimized is determined for the driving signal to be changed, reflecting the change on the driving signal to be changed.SELECTED DRAWING: Figure 16

Description

[Technical field]

[0001] The present invention relates to an optical deflector driving system and an optical deflector driving method, and in particular to an optical deflector driving system and an optical deflector driving method that can suppress the occurrence of abnormal vibrations in an optical deflector even when a change in offset (or amplitude) is reflected (as a result, can suppress the appearance of striped patterns in an image drawn by light scanned by the optical deflector). [Background technology]

[0002] An image projection system is known in which an offset is applied to a drive signal (drive voltage) applied to an optical deflector (actuator) to change the vertical position (offset amount) of an image drawn by light scanned by the optical deflector (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-54752 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, after investigations by the present inventors, they found that in Patent Document 1, if a change in offset (or amplitude) is reflected at the timing when an instruction to change the offset (or amplitude) is input, the waveform of the drive signal (drive voltage) becomes distorted before and after the change, and unnecessary frequency components (unintended frequency components) contained in the edges of the drive signal (drive voltage) with the distorted waveform cause abnormal vibrations in the optical deflector, which causes striped patterns to appear in the image drawn by the light scanned by the optical deflector.

[0005] The present invention has been made to solve such problems, and aims to provide an optical deflector driving system and an optical deflector driving method that can suppress the occurrence of abnormal vibrations in an optical deflector even when a change in offset (or amplitude) is reflected (and, as a result, can suppress the appearance of striped patterns in an image drawn by light scanned by the optical deflector). [Means for solving the problem]

[0006] The optical deflector driving system of the present invention comprises a mirror unit and an actuator that oscillates the mirror unit around an oscillation axis, and applies a driving voltage corresponding to a driving signal to the actuator.The optical deflector driving system comprises a timing determination unit that, when an instruction to change the driving signal is input, determines the timing at which the voltage of the drive signal to be changed will be the smallest, and a change reflection unit that reflects the change in the drive signal to be changed when it is determined that this is the timing at which the voltage of the drive signal to be changed will be the smallest.

[0007] With this configuration, even when a change in the offset (or amplitude) is reflected, it is possible to suppress the occurrence of abnormal vibrations in the optical deflector (as a result, it is possible to suppress the appearance of stripes in the image drawn by the light scanned by the optical deflector).

[0008] This is because, rather than reflecting the change in offset (or amplitude) at the timing when an instruction to change the offset (or amplitude) is input, the change is reflected in the drive signal to be changed when it is determined that the timing is when the voltage of the drive signal to be changed is at its smallest, thereby making it possible to remove unnecessary frequency components (unintended frequency components) that cause abnormal vibrations in the optical deflector.

[0009] In the optical deflector driving system, the instruction to change may be an instruction to change the amplitude.

[0010] In the optical deflector driving system, the instruction to change may be an instruction to change an offset.

[0011] In addition, in the optical deflector driving system described above, the instruction to make the change is offset level data representing an offset amount, and the optical deflector driving system further includes an offset division unit that divides the offset amount by a rise time or a fall time, and the change reflection unit may gradually reflect the change in the driving signal to be changed each time the divided time elapses. In addition, in the above optical deflector driving system, the driving signal includes a first driving signal and a second driving signal, the driving voltage includes a first driving voltage and a second driving voltage, the first driving signal corresponds to the first driving voltage and the second driving signal corresponds to the second driving voltage, the actuator has a first driving unit driven by the first driving voltage and a second driving unit driven by the second driving voltage, and when an instruction to change at least one of the first driving signal and the second driving signal is input, the timing determination unit may determine the timing at which the voltage of the drive signal to be changed among the first driving signal and the second driving signal is smallest. In the optical deflector driving system, the first driving section may be a first piezoelectric cantilever, and the second driving section may be a second piezoelectric cantilever. In the optical deflector driving system, the first driving signal and the second driving signal may be AC ​​waveforms that are out of phase with each other.

[0012] The optical deflector driving method of the present invention comprises a change instruction input step of inputting an instruction to change a drive signal corresponding to a drive voltage applied to an actuator that oscillates a mirror portion of an optical deflector around an oscillation axis, a determination step of determining, when the instruction is input, the timing at which the voltage of the drive signal to be changed will be the smallest, and a change reflection step of reflecting the change in the drive signal to be changed when it is determined that this is the timing at which the voltage of the drive signal to be changed will be the smallest.

[0013] With this configuration, even when a change in the offset (or amplitude) is reflected, it is possible to suppress the occurrence of abnormal vibrations in the optical deflector (as a result, it is possible to suppress the appearance of stripes in the image drawn by the light scanned by the optical deflector).

[0014] This is because, rather than reflecting the change in offset (or amplitude) at the timing when an instruction to change the offset (or amplitude) is input, the change is reflected in the drive signal to be changed when it is determined that the timing is when the voltage of the drive signal to be changed is at its smallest, thereby making it possible to remove unnecessary frequency components (unintended frequency components) that cause abnormal vibrations in the optical deflector.

[0015] In the optical deflector driving method, the instruction to change may be an instruction to change the amplitude.

[0016] In the optical deflector driving method, the instruction to change may be an instruction to change an offset.

[0017] Furthermore, in the above optical deflector driving method, the instruction to make the change is offset level data representing an offset amount, and the method further includes an offset division step of dividing the offset amount by a rise time or a fall time, and the change reflection step may reflect the change in stages in the drive signal to be changed each time the divided time elapses. Effect of the Invention

[0018] The present invention makes it possible to provide an optical deflector driving system and an optical deflector driving method that can suppress the occurrence of abnormal vibrations in an optical deflector even when a change in offset (or amplitude) is reflected (and, as a result, can suppress the appearance of striped patterns in an image drawn by light scanned by the optical deflector). [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of an optical deflector driving system 10 according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a perspective view of a single-axis non-resonant / single-axis resonant type optical deflector 1. [Diagram 3] 3A is a schematic diagram showing an end face of the optical deflector of FIG. 2 taken along line II, and FIG. 3B is a schematic diagram showing an end face of the optical deflector of FIG. 2 taken along line II-II. [Figure 4] 13 is an example of a third driving voltage Vx1 (driving signal P) and a fourth driving voltage Vx2 (driving signal N). [Diagram 5] 1A shows a state in which a piezoelectric actuator of an optical deflector is not in operation, and FIG. 1B shows a state in which the piezoelectric actuator is in operation. [Figure 6] FIG. 1 is a diagram showing how an image p is drawn on a screen member 20 by laser light Ray scanned (raster scanned) by an optical deflector 1 (condenser lens 14, correction mirror 18, and projection lens 23 are omitted). [Figure 7] 7 is a diagram showing the relationship between the drive voltage applied to the optical deflector 1 (see FIG. 7(a)) and the oscillation angle of the mirror section 2 (see FIG. 7(b)). [Figure 8] 13 is an example of an image p with different vertical widths that is drawn on the screen member 20. [Figure 9] 13 shows an example of an image p that is rendered on the screen member 20 at different vertical positions (offset amounts). [Figure 10] 2 is a diagram illustrating an example of a functional configuration of an optical deflector driving system 10. [Figure 11] 2 illustrates an example of a functional configuration of a video signal processing unit 116. [Figure 12] 13 is a sequence diagram of a process in which the MEMS driver 108 swings the mirror unit 2 around the second axis X. FIG. [Figure 13] 13 is a timing chart showing examples of signals when the vertical width of video p is reduced. [Figure 14] FIG. 1 is a diagram for explaining a problem found by the present inventors. [Figure 15] FIG. 1 is a diagram for explaining a problem found by the present inventors. [Figure 16] 11 is a sequence diagram of a process for changing the vertical width of an image drawn on a screen member 20 while suppressing the occurrence of abnormal vibrations in an optical deflector 1. FIG. [Figure 17] 11 is a sequence diagram of a process for changing the offset amount of an image drawn on a screen member 20 while suppressing the occurrence of abnormal vibration in an optical deflector 1. FIG. [Figure 18] 13 is an example (time chart) of each signal when video p is offset upward. [Figure 19] FIG. 13 is an enlarged view of the area within the dotted circle of the fifth signal N. [Figure 20] 13 is a timing chart showing examples of signals when the vertical width of a video p is enlarged. [Figure 21] 13 is an example (time chart) of each signal when video p is offset downward. [Figure 22] FIG. 13 is a diagram illustrating a modified example of the fifth signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an optical deflector driving system 10 according to an embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, corresponding components are given the same reference numerals, and duplicated explanations will be omitted.

[0021] FIG. 1 is a schematic diagram of an optical deflector driving system 10 according to an embodiment of the present invention.

[0022] 1, the optical deflector driving system 10 includes a light source 12, a condensing lens 14 that condenses light (e.g., laser light) emitted by the light source 12, a correction mirror 18, an optical deflector 1 that two-dimensionally (horizontally and vertically) scans the laser light Ray condensed by the condensing lens 14 and reflected by the correction mirror 18, a screen member 20 on which an image is drawn by the laser light Ray scanned by the optical deflector 1, and a projection lens 23 that projects the image drawn on the screen member 20. Note that the optical deflector driving system 10 may have any configuration as long as it includes an optical deflector that draws an image by scanning the light emitted by the light source 12.

[0023] The light source 12 is, for example, a laser diode (LD) that emits laser light having an emission wavelength in the blue region. The laser light from the light source 12 is collected (for example, collimated) by a collecting lens 14, and is reflected by a correction mirror 18 to enter the optical deflector 1 (mirror section 2). The correction mirror 18 is provided to prevent distortion of the image drawn on the screen member 20. The correction mirror 18 may be omitted.

[0024] The optical deflector 1 scans the laser light focused by the focusing lens 14 two-dimensionally (horizontally and vertically). An image is drawn on the screen member 20 by the laser light scanned by the optical deflector 1. The screen member 20 is, for example, a rectangular phosphor plate. The phosphor plate is a wavelength conversion member that converts at least a part of the laser light Ray scanned by the optical deflector 1 into light of a different wavelength (for example, light in the yellow range). The image drawn on the screen member 20 is projected by the projection lens 23.

[0025] The optical deflector 1 is, for example, a MEMS scanner. Driving methods for the optical deflector are roughly classified into piezoelectric, electrostatic, and electromagnetic types, and any of these may be used. In addition, the piezoelectric type is roughly classified into one-axis non-resonant / one-axis resonant type, two-axis non-resonant type, and two-axis resonant type, and any of these may be used.

[0026] As a representative example, a piezoelectric type (single-axis non-resonant / single-axis resonant type) optical deflector 1 will be described below.

[0027] FIG. 2 is a perspective view of the optical deflector 1 of a single-axis non-resonant / single-axis resonant type.

[0028] The optical deflector 1 includes a mirror section 2, a pair of first piezoelectric actuators 31 and 32, a first support section 4, a pair of second piezoelectric actuators 51 and 52, and a second support section 6. Note that the optical deflector 1 may have any configuration as long as unintended abnormal vibration (abnormal resonance) occurs in the optical deflector 1 when a change in offset (or amplitude) is reflected in a drive signal (drive voltage).

[0029] The mirror section 2 includes a circular reflecting surface 2a that reflects incident light, and a circular reflecting surface support 2b that supports the reflecting surface 2a.

[0030] The reflecting surface support 2b is made of a silicon substrate. A pair of torsion bars 21 and 22 are connected to the reflecting surface support 2b and extend outward from both ends thereof.

[0031] The first piezoelectric actuators 31, 32 are each formed in a semicircular arc shape and are arranged with a gap between them so as to surround the mirror portion 2. One end of each of the first piezoelectric actuators 31, 32 is connected to face each other with one torsion bar 21 in between, and the other end of each of the first piezoelectric actuators 31, 32 is connected to face each other with the other torsion bar 22 in between.

[0032] The first support part 4 is formed in a rectangular frame shape, and is provided so as to surround the mirror part 2 and the first piezoelectric actuators 31, 32. The first support part 4 is connected to the outside of the center positions of the arc parts of the first piezoelectric actuators 31, 32, and supports the mirror part 2 via the first piezoelectric actuators 31, 32.

[0033] The second piezoelectric actuators 51, 52 are disposed opposite to each other across the first support part 4. The second piezoelectric actuators 51, 52 have their tips connected to a pair of both sides of the first support part 4 in a direction perpendicular to the torsion bars 21, 22.

[0034] The second support part 6 is formed in a rectangular frame shape and is provided so as to surround the first support part 4 and the second piezoelectric actuators 51, 52. The second support part 6 is connected to a pair of other ends of the second piezoelectric actuators 51, 52 on the sides not connected to the first support part 4. In this way, the second support part 6 supports the first support part 4 via the second piezoelectric actuators 51, 52.

[0035] Next, a detailed configuration of the first piezoelectric actuators 31 and 32 will be described. The first piezoelectric actuators 31 and 32 each include a first piezoelectric cantilever 31A or 32A configured to bend and deform by piezoelectric driving. In detail, one of the first piezoelectric actuators 31 and 32 includes one first piezoelectric cantilever 31A, and the other of the first piezoelectric actuators 31 and 32 includes the other first piezoelectric cantilever 32A. The first piezoelectric actuators 31 and 32 can swing the mirror section 2 around the first axis Y relative to the first support section 4 via the torsion bars 21 and 22 due to bending and deformation of the first piezoelectric cantilevers 31A and 32A.

[0036] Next, the detailed configuration of the second piezoelectric actuators 51, 52 will be described. The second piezoelectric actuators 51, 52 each include a pair of second piezoelectric cantilevers 51A-51D, 52A-52D configured to bend and deform by piezoelectric driving. In detail, one second piezoelectric actuator 51 of the pair of second piezoelectric actuators 51, 52 is configured with one second piezoelectric cantilever 51A-51D consisting of four piezoelectric cantilevers. The other second piezoelectric actuator 52 of the pair of second piezoelectric actuators 51, 52 is configured with the other second piezoelectric cantilever 52A-52D consisting of four piezoelectric cantilevers.

[0037] The second piezoelectric cantilevers 51A-51D on one side are arranged side by side at a predetermined interval so that their ends are adjacent to each other and their length directions are the same, and the mirror section 2 is swingable around a second axis X (an axis perpendicular to the first axis Y, but it does not have to be exactly perpendicular). The second piezoelectric cantilevers 51A-51D on one side are connected to the adjacent piezoelectric cantilevers so as to be folded back. The second axis X is an example of an oscillation axis in the present invention.

[0038] The other second piezoelectric cantilevers 52A-52D, like the one second piezoelectric cantilevers 51A-51D, are arranged such that both ends are adjacent to each other so that the length direction is the same, and the mirror portion 2 is arranged side by side at a predetermined interval so as to be swingable around the second axis X. The other second piezoelectric cantilevers 52A-52D are connected to the adjacent piezoelectric cantilevers so as to be folded back.

[0039] In this way, the one second piezoelectric actuator 51 and the other second piezoelectric actuator 52 are formed by the one second piezoelectric cantilevers 51A to 51D and the other second piezoelectric cantilevers 52A to 52D which form them, respectively, in a so-called meandering shape (or bellows shape).

[0040] Of the second piezoelectric cantilevers 51A to 51D on one side and the second piezoelectric cantilevers 52A to 52D on the other side, the cantilever (hereinafter referred to as the "first second piezoelectric cantilever") 51A, 52A arranged on the mirror section 2 side (first support section 4 side) has one end (free end) of the cantilever not connected to the adjacent second piezoelectric cantilever (hereinafter referred to as the "second second piezoelectric cantilever") 51B, 52B connected to the outer periphery of the first support section 4.

[0041] Similarly, the piezoelectric cantilever (hereinafter referred to as the "fourth second piezoelectric cantilever") 51D, 52D arranged on the second support portion 6 side among one of the second piezoelectric cantilevers 51A-51D and the other second piezoelectric cantilever 52A-52D has one end (free end) on the side not connected to the adjacent second piezoelectric cantilever (hereinafter referred to as the "third second piezoelectric cantilever") 51C, 52C connected to the inner circumference of the second support portion 6.

[0042] As a result, the first support portion 4 is able to swing about the second axis X relative to the second support portion 6 due to bending deformation of the second piezoelectric cantilevers 51A to 51D and 52A to 52D that constitute the second piezoelectric actuators 51 and 52.

[0043] Hereinafter, among the pairs of second piezoelectric cantilevers 51A to 51D, 52A to 52D, the piezoelectric cantilevers arranged in odd positions counting from the mirror portion 2 (the first second piezoelectric cantilever 51A, 52A and the third second piezoelectric cantilever 51C, 52C) will be referred to as the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C.

[0044] Furthermore, of the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C, the one included in one of the second piezoelectric cantilevers 51A to 51D is referred to as one odd-numbered second piezoelectric cantilever 51A, 51C, and the one included in the other second piezoelectric cantilever 52A to 52D is referred to as the other odd-numbered second piezoelectric cantilever 52A, 52C.

[0045] Similarly, of the pairs of second piezoelectric cantilevers 51A to 51D, 52A to 52D, the piezoelectric cantilevers arranged in even numbers counting from the mirror portion 2 (the second second piezoelectric cantilever 51B, 52B and the fourth second piezoelectric cantilever 51D, 52D) are referred to as the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D.

[0046] Furthermore, of the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D, the one included in one of the second piezoelectric cantilevers 51A to 51D is referred to as the one even-numbered second piezoelectric cantilever 51B, 51D, and the one included in the other second piezoelectric cantilever 52A to 52D is referred to as the other even-numbered second piezoelectric cantilever 52B, 52D.

[0047] Fig. 3 shows a schematic end view of the optical deflector 1. Fig. 3(a) shows an end view taken along line II in Fig. 2. However, in Fig. 3(a), the second support portion 6 is omitted. Fig. 3(b) shows an end view taken along line II-II in Fig. 2. However, in Fig. 3(b), the second support portion 6 and the third second piezoelectric cantilever 51C, 52C and the fourth second piezoelectric cantilever 51D, 52D of the pair of second piezoelectric cantilevers 51A to 51D, 52A to 52D are omitted.

[0048] The third second piezoelectric cantilevers 51C and 52C have the same configuration as the first second piezoelectric cantilevers 51A and 52A. Similarly, the fourth second piezoelectric cantilevers 51D and 52D have the same configuration as the second second piezoelectric cantilevers 51B and 52B.

[0049] Each of the first piezoelectric cantilevers 31A, 32A constituting the first piezoelectric actuators 31, 32 and each of the pairs of second piezoelectric cantilevers 51A-51D, 52A-52D constituting the second piezoelectric actuators 51, 52 is a piezoelectric cantilever having a structure in which a lower electrode L1, a piezoelectric body L2 and an upper electrode L3 are laminated on a layer of a support B as a strain-generating body (cantilever main body).

[0050] The detailed structure of the piezoelectric cantilever is such that a lower electrode L1, a piezoelectric body L2, and an upper electrode L3 are laminated on a layer of a support B, and an interlayer insulating film M1 is provided so as to surround the lower electrode L1, the piezoelectric body L2, and the upper electrode L3. An upper electrode wiring W is laminated on the interlayer insulating film M1, and a passivation film M2 is provided so as to surround the upper electrode wiring W.

[0051] As described below, the upper electrode wirings W include a first driving upper electrode wiring Wy, a second driving odd upper electrode wiring Wo, a second driving even upper electrode wiring We, a first detection upper electrode wiring Wmy, and a second detection upper electrode wiring Wmx, and when there is no need to particularly distinguish between these, they will be referred to as the upper electrode wiring W.

[0052] The piezoelectric body L2 of each of the piezoelectric cantilevers 31A, 32A, 51A to 51D, and 52A to 52D is bent and deformed by piezoelectric driving when a driving voltage is applied between the upper electrode L3 and the lower electrode L1. The piezoelectric cantilevers 31A, 32A, 51A to 51D, and 52A to 52D are bent and deformed in accordance with the bending deformation of the piezoelectric body L2.

[0053] In addition, the connection portion between adjacent piezoelectric cantilevers of each pair of second piezoelectric cantilevers 51A to 51D, 52A to 52D constituting the second piezoelectric actuator 51, 52 is a portion where the support bodies B of the adjacent piezoelectric cantilevers are integrally connected, and no layer of piezoelectric body L2 or upper electrode L3 is provided at the connection portion.

[0054] First detection units 71y, 72y and second detection units 71x, 72x are provided on the first support unit 4. The first detection units 71y, 72y are disposed on the first support unit 4 at the center of a side parallel to the second axis X of the first support unit 4 (a side perpendicular to the longitudinal side of each of the second piezoelectric cantilevers 51A to 51D, 52A to 52D).

[0055] The second detection units 71x, 72x are disposed on the first support unit 4 at the center of a side parallel to the first axis Y of the first support unit 4. The first detection units 71y, 72y and the second detection units 71x, 72x are provided separately from each other in a plan view.

[0056] The first detection units 71y, 72y are provided as sensors for detecting a first vibration transmitted to the first support unit 4 when the mirror unit 2 is swung around the first axis Y relative to the first support unit 4 by piezoelectric driving of the first piezoelectric actuators 31, 32. The second detection units 71x, 72x are provided as sensors for detecting a second vibration transmitted to the first support unit 4 when the first support unit 4 is swung around the second axis X relative to the second support unit 6 by piezoelectric driving of the second piezoelectric actuators 51, 52.

[0057] The first detection units 71y, 72y and the second detection units 71x, 72x, like the first piezoelectric cantilevers 31A, 32A and the second piezoelectric cantilevers 51A-51D, 52A-52D, have a structure in which a lower electrode L1, a piezoelectric body L2, and an upper electrode L3 are laminated on a layer of a support B constituting the first support unit 4. Note that the first detection units 71y, 72y and the second detection units 71x, 72x also have an interlayer insulating film M1, an upper electrode wiring W, and a passivation film M2, like the piezoelectric cantilevers 31A, 32A, 51A-51D, 52A-52D.

[0058] When the first support 4 is bent and deformed by the first vibration or the second vibration being transmitted to the first support 4, the piezoelectric bodies L2 of the first detection units 71y, 72y and the second detection units 71x, 72x output voltages according to the amount of deformation of the bent support 4. The optical deflector 1 can detect the vibration transmitted to the first support 4 based on the voltage value at this time.

[0059] It was found through a previous experiment that the first support section 4 of the optical deflector 1 of this embodiment is prone to bending deformation at the center of each of the two sides parallel to the second axis X when the mirror section 2 is oscillated around the first axis Y. For this reason, the first detection sections 71y and 72y are disposed at the center of the two sides. It was also found through a previous experiment that the first support section 4 is prone to bending deformation at the center of each of the two sides parallel to the first axis Y when the mirror section 2 is oscillated around the second axis X. For this reason, the second detection sections 71x and 72x are disposed at the center of the two sides.

[0060] The optical deflector 1 has, on the second support portion 6, lower electrode pads 61a, 62a, first upper electrode pads 61b, 62b, second upper electrode pads for odd numbers 61c, 62c, second upper electrode pads for even numbers 61d, 62d, a first detection electrode pad 61e, and a second detection electrode pad 62e.

[0061] One of the lower electrode pads 61a, 62a is electrically connected to the lower electrode L1 of the first piezoelectric cantilever 31A, the lower electrode L1 of the second piezoelectric cantilever 51A-51D, and the lower electrode L1 of the first detection units 71y, 72y. The other of the lower electrode pads 61a, 62a is electrically connected to the lower electrode L1 of the other first piezoelectric cantilever 32A, the lower electrode L1 of the other second piezoelectric cantilever 52A-52D, and the lower electrode L1 of the second detection units 71x, 72x.

[0062] In this manner, the lower electrode pads 61a, 62a are used as electrode pads common to the first piezoelectric actuators 31, 32, the second piezoelectric actuators 51, 52, the first detection portions 71y, 72y, and the second detection portions 71x, 72x.

[0063] One of the first upper electrode pads 61b, 62b, the first upper electrode pad 61b, is electrically connected to the upper electrode L3 of one of the first piezoelectric cantilevers 31A. The other of the first upper electrode pads 61b, 62b, the first upper electrode pad 62b, is electrically connected to the upper electrode L3 of the other first piezoelectric cantilever 32A.

[0064] One of the odd-numbered second upper electrode pads 61c, 62c is electrically connected to the upper electrode L3 of one of the odd-numbered second piezoelectric cantilevers 51A, 51C. The other of the odd-numbered second upper electrode pads 61c, 62c is electrically connected to the upper electrode L3 of the other odd-numbered second piezoelectric cantilever 52A, 52C.

[0065] One of the even-numbered second upper electrode pads 61d, 62d is electrically connected to the upper electrode L3 of one of the even-numbered second piezoelectric cantilevers 51B, 51D. The other of the even-numbered second upper electrode pads 61d, 62d is electrically connected to the upper electrode L3 of the other even-numbered second piezoelectric cantilever 52B, 52D.

[0066] The first detection electrode pad 61e is electrically connected to the upper electrodes L3 of the first detection units 71y and 72y. The second detection electrode pad 62e is electrically connected to the upper electrodes L3 of the second detection units 71x and 72x.

[0067] With the electrical connections as described above, when a drive voltage is applied between the upper electrode L3 and the lower electrode L1, the piezoelectric body L2 laminated between the upper electrode L3 and the lower electrode L1 is bent and deformed by the piezoelectric drive. This causes the support B (piezoelectric cantilever) to bend and deform in response to the bent and deformed piezoelectric body L2.

[0068] As described later, in the first support 4, a voltage generated from the first detection units 71y, 72y by a piezoelectric effect caused by bending deformation due to the transmitted vibration is output as a potential difference between the first detection electrode pad 61e and one of the lower electrode pads 61a. Similarly, a voltage generated from the second detection units 71x, 72x by a piezoelectric effect caused by bending deformation of the first support 4 is output as a potential difference between the second detection electrode pad 62e and one of the lower electrode pads 61a.

[0069] The pair of lower electrode pads 61a, 62a, the first piezoelectric cantilever 31A, 32A, the second piezoelectric cantilever 51A-51D, 52A-52D, the first detection portion 71y, 72y, and the lower electrode L1 of the second detection portion 71x, 72x are formed by shaping a metal thin film (two-layer metal thin film in this embodiment, hereinafter also referred to as a lower electrode layer) on a silicon substrate using a semiconductor planar process. As the material of this metal thin film, for example, titanium (Ti), titanium dioxide (TiO2) or titanium oxide (TiOx) with an adjusted oxidation amount is used for the first layer (lower layer), and platinum (Pt), LaNiO3 or SrRuO3 is used for the second layer (upper layer).

[0070] In this case, the lower electrodes L1 of the first piezoelectric cantilevers 31A, 32A are formed on almost the entire surface of the support B of the first piezoelectric cantilevers 31A, 32A. The lower electrodes L1 of the second piezoelectric cantilevers 51A-51D, 52A-52D are formed on almost the entire surface of the support B of the second piezoelectric cantilevers 51A-51D, 52A-52D (the entire surface including the straight portions and connecting portions along which the piezoelectric cantilevers extend).

[0071] The lower electrodes L1 of the first detection portions 71y, 72y are formed on a portion of the support B of the first support 4 where the first detection portions 71y, 72y are disposed. The lower electrodes L1 of the second detection portions 71x, 72x are formed on a portion of the support B of the first support 4 where the second detection portions 71x, 72x are disposed. Similarly, on the second support 6, the lower electrodes L1, the interlayer insulating film M1, the upper electrode wiring W, and the passivation film M2 are provided.

[0072] The lower electrode pads 61a, 62a are electrically connected to the lower electrodes L1 of the first piezoelectric cantilevers 31A, 32A, the lower electrodes L1 of the second piezoelectric cantilevers 51A-51D, 52A-52D, the lower electrodes L1 of the first detection portions 71y, 72y, and the lower electrodes L1 of the second detection portions 71x, 72x via the lower electrodes L1 formed on the second support portion 6 and the first support portion 4, as described above.

[0073] The piezoelectric bodies L2 of the first piezoelectric cantilevers 31A, 32A, the second piezoelectric cantilevers 51A-51D, 52A-52D, the first detection parts 71y, 72y, and the second detection parts 71x, 72x are formed separately from one another on the lower electrodes L1 of the respective piezoelectric cantilevers by shaping one layer of piezoelectric film (hereinafter also referred to as piezoelectric layer) on the lower electrode layer using a semiconductor planar process. As the material of this piezoelectric film, for example, lead zirconate titanate (PZT), which is a piezoelectric material, is used.

[0074] In this case, the piezoelectric body L2 of the first piezoelectric cantilevers 31A, 32A is formed on almost the entire surface of the lower electrode L1 of each of the first piezoelectric cantilevers 31A, 32A. The piezoelectric body L2 of the second piezoelectric cantilevers 51A-51D, 52A-52D is formed on almost the entire surface of the lower electrode L1 in the extending portion (straight portion) of each of the second piezoelectric cantilevers 51A-51D, 52A-52D. The piezoelectric body L2 of the first detection parts 71y, 72y is formed on almost the entire surface of the lower electrode L1 of each of the first detection parts 71y, 72y. The piezoelectric body L2 of the second detection parts 71x, 72x is formed on almost the entire surface of the lower electrode L1 of each of the second detection parts 71x, 72x.

[0075] The "first upper electrode pads 61b, 62b, the second upper electrode pads for odd numbers 61c, 62c, the second upper electrode pads for even numbers 61d, 62d, the first detection electrode pad 61e, and the second detection electrode pad 62e", the "upper electrodes L3 of the first piezoelectric cantilevers 31A, 32A, the second piezoelectric cantilevers 51A-51D, 52A-52D, the first detection parts 71y, 72y, and the second detection parts 71x, 72x", and the upper electrode wiring W that connects them are formed by shaping a metal thin film (one layer of metal thin film in this embodiment. Hereinafter, it is also referred to as the upper electrode layer) on the piezoelectric layer using a semiconductor planar process. The material of this metal thin film is, for example, platinum (Pt), gold (Au), aluminum (Al), or an aluminum alloy (Al alloy), etc.

[0076] In this case, the upper electrodes L3 of the first piezoelectric cantilevers 31A, 32A, the second piezoelectric cantilevers 51A to 51D, 52A to 52D, the first detection portions 71y, 72y, and the second detection portions 71x, 72x are formed over almost the entire surface of the piezoelectric body L2 for each piezoelectric cantilever or each detection portion.

[0077] The first upper electrode pads 61b, 62b are respectively connected to the upper electrodes L3 of the first piezoelectric cantilevers 31A, 32A via the first driving upper electrode wiring Wy as described above. The odd-numbered second upper electrode pads 61c, 62c are respectively connected to the upper electrodes L3 of the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C via the second driving odd upper electrode wiring Wo as described above. The even-numbered second upper electrode pads 61d, 62d are respectively connected to the upper electrodes L3 of the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D via the second driving even upper electrode wiring We as described above.

[0078] The first detection electrode pad 61e is electrically connected to the upper electrodes L3 of the first detection units 71y and 72y via the first detection upper electrode wiring Wmy as described above. The second detection electrode pad 62e is electrically connected to the upper electrodes L3 of the second detection units 71x and 72x via the second detection upper electrode wiring Wmx as described above.

[0079] 3, the first driving upper electrode wiring Wy, the second driving odd-numbered upper electrode wiring Wo, the second driving even-numbered upper electrode wiring We, the first detection upper electrode wiring Wmy, and the second detection upper electrode wiring Wmx are provided so as to be separated from one another in a plane. The upper electrode wiring W is insulated by an interlayer insulating film M1 formed between the upper electrode L3, and when the upper electrode wiring W is to be electrically connected to the upper electrode L3, a conductive member (e.g., an electrode via, etc.) is formed in the interlayer insulating film M1 so as to electrically connect the upper electrode wiring W to the upper electrode L3.

[0080] Moreover, the passivation film M2 is formed on the upper electrode wiring W so as to surround the upper electrode wiring W by using a semiconductor planar process.

[0081] The reflecting surface support 2b, the torsion bars 21 and 22, the support B, the first support 4, and the second support 6 are integrally formed by shaping a semiconductor substrate (silicon substrate) made up of multiple layers. The semiconductor substrate is shaped using a semiconductor planar process and a MEMS process that utilize photolithography, dry etching, or the like.

[0082] Next, the operation of the optical deflector 1 of this embodiment will be described. First, the case where the mirror portion 2 is oscillated around the first axis Y with respect to the first support portion 4 by the first piezoelectric actuators 31 and 32 will be described.

[0083] In this case, the optical deflector 1 applies drive voltages to the first piezoelectric actuators 31 and 32. Specifically, in one first piezoelectric actuator 31, a first drive voltage Vy1 is applied between one first upper electrode pad 61b and one lower electrode pad 61a to drive one first piezoelectric cantilever 31A. In addition, in the other first piezoelectric actuator 32, a second drive voltage Vy2 is applied between the other first upper electrode pad 62b and the other lower electrode pad 62a to drive the other first piezoelectric cantilever 32A. Here, the first drive voltage Vy1 and the second drive voltage Vy2 are AC voltages (e.g., sine wave, sawtooth wave, etc.) that are in opposite phase or out of phase with each other.

[0084] At this time, the oscillation voltage components of the first drive voltage Vy1 and the second drive voltage Vy2 are applied so that the angular displacement between one first piezoelectric cantilever 31A and the other first piezoelectric cantilever 32A occurs in opposite directions in the vertical directions of the first piezoelectric actuators 31, 32 (the upward direction U in Figure 1 and the opposite downward direction).

[0085] For example, when one of the first piezoelectric actuators 31 is displaced upward when oscillating around the first axis Y, one of the first piezoelectric cantilevers 31A is displaced upward. When one of the first piezoelectric actuators 31 is displaced downward, one of the first piezoelectric cantilevers 31A is displaced downward.

[0086] Similarly to the first piezoelectric actuator 31, when the other first piezoelectric actuator 32 is displaced upward, the other first piezoelectric cantilever 32A is displaced upward. When the other first piezoelectric actuator 32 is displaced downward, the other first piezoelectric cantilever 32A is displaced downward.

[0087] In the optical deflector 1 of this embodiment, a large deflection angle is obtained when swinging around the first axis Y by "displacing one of the first piezoelectric actuators 31 upward while displacing the other first piezoelectric actuator 32 downward" or by "displacing one of the first piezoelectric actuators 31 downward while displacing the other first piezoelectric actuator 32 upward." In this way, in this embodiment, the mirror section 2 can be swung around the first axis Y, and optical scanning with a predetermined first deflection angle can be performed at a predetermined first frequency Fy.

[0088] Next, a case where the first support portion 4 is swung about the second axis X relative to the second support portion 6 by the second piezoelectric actuators 51, 52 will be described.

[0089] In this case, the optical deflector 1 applies drive voltages to the second piezoelectric actuators 51 and 52. Specifically, in one of the second piezoelectric actuators 51, a third drive voltage Vx1 is applied between one of the odd-numbered second upper electrode pads 61c and one of the lower electrode pads 61a to drive one of the odd-numbered second piezoelectric cantilevers 51A and 51C. At the same time, in one of the second piezoelectric actuators 51, a fourth drive voltage Vx2 is applied between one of the even-numbered second upper electrode pads 61d and one of the lower electrode pads 61a to drive one of the even-numbered second piezoelectric cantilevers 51B and 51D.

[0090] Furthermore, in the other second piezoelectric actuator 52, a third drive voltage Vx1 is applied between the other odd-numbered second upper electrode pad 62c and the other lower electrode pad 62a to drive the other odd-numbered second piezoelectric cantilevers 52A and 52C. At the same time, in the other second piezoelectric actuator 52, a fourth drive voltage Vx2 is applied between the other even-numbered second upper electrode pad 62d and the other lower electrode pad 62a to drive the other even-numbered second piezoelectric cantilevers 52B and 52D.

[0091] Here, the third drive voltage Vx1 and the fourth drive voltage Vx2 are AC voltages (e.g., sine wave, sawtooth wave, etc.) in opposite phases to each other. FIG. 4 shows an example of the third drive voltage Vx1 and the fourth drive voltage Vx2. In FIG. 4, the sawtooth wave shown by the solid line is an example of the third drive voltage Vx1. Hereinafter, the third drive voltage Vx1 is also referred to as the first drive signal P. In addition, in FIG. 4, the sawtooth wave shown by the dashed dotted line is an example of the fourth drive voltage Vx2. Hereinafter, the fourth drive voltage Vx2 is also referred to as the second drive signal N. Note that the third drive voltage Vx1 and the fourth drive voltage Vx2 may be AC ​​voltages (e.g., sine wave, sawtooth wave, etc.) in phase with each other. The angle of view and the deflection direction of the image projected by the optical deflector drive system 10 can be changed by changing the amplitude and offset amount of at least one of the two drive signals (first drive signal P, second drive signal N). This makes it possible to control the angle of oscillation and the offset angle.

[0092] At this time, the oscillation voltage components of the third drive voltage Vx1 and the fourth drive voltage Vx2 are set so that the angular displacements of the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D occur in opposite directions with respect to the vertical direction of the second piezoelectric actuators 51, 52 (the upward direction U in Figure 1 and the opposite downward direction).

[0093] For example, when the tips of the second piezoelectric actuators 51, 52 are displaced upward (direction U shown in FIG. 1) during oscillation around the second axis X, the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C are displaced upward, and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D are displaced downward. To displace the tips of the second piezoelectric actuators 51, 52 downward, the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C are displaced downward, and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D are displaced upward.

[0094] As a result, the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, and 52C and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, and 52D are bent and deformed in directions opposite to each other.

[0095] Fig. 5 is a diagram showing the operation of one of the second piezoelectric actuators 51 of the optical deflector 1. Fig. 5(a) shows a state in which one of the second piezoelectric actuators 51 is not in operation, and Fig. 5(b) shows a state in which one of the second piezoelectric actuators 51 is in operation.

[0096] 5(b), the fourth second piezoelectric cantilever 51D generates a downward angular displacement at its tip, with the base end connected to the second support part 6 as a fulcrum. The third second piezoelectric cantilever 51C generates an upward angular displacement at its tip, with the base end connected to the tip of the fourth second piezoelectric cantilever 51D as a fulcrum.

[0097] The second piezoelectric cantilever 51B generates a downward angular displacement at its tip, with the base end connected to the tip of the third piezoelectric cantilever 51C as a fulcrum. The first piezoelectric cantilever 51A generates an upward angular displacement at its tip (connected to the first support 4), with the base end connected to the tip of the second piezoelectric cantilever 51B as a fulcrum. As a result, in the second piezoelectric actuator 51, an angular displacement is generated that is the sum of the magnitudes of the bending deformations of the second piezoelectric cantilevers 51A to 51D.

[0098] Therefore, the first support unit 4 can be swung around the second axis X, and optical scanning can be performed at a predetermined second deflection angle at a predetermined second frequency Fx. At this time, by applying an AC voltage having a frequency near the mechanical resonance frequency of the first support unit 4 including the second piezoelectric actuators 51, 52 as a drive voltage to resonantly drive the second piezoelectric actuators 51, 52, optical scanning can be performed at a larger deflection angle.

[0099] Furthermore, when the first support portion 4 is swung around the second axis X, it is not necessary to apply an AC voltage as described above, and a DC voltage may be applied. In this case, the magnitude of the bending deformation generated in the second piezoelectric cantilevers 51A-51D, 52A-52D changes linearly according to the magnitude of the DC voltage. Therefore, unlike the case where an AC voltage is applied to resonantly drive the piezoelectric cantilevers, for example, an arbitrary output can be obtained from the second piezoelectric actuators 51, 52 by controlling the magnitude of the DC voltage.

[0100] In this way, in the optical deflector 1, when it oscillates around the second axis X, the deflection angle can be controlled linearly according to the magnitude of the DC voltage applied as the drive voltage, so that any deflection angle can be obtained at any speed.

[0101] In addition, the second piezoelectric actuators 51 and 52 are each formed in a meandering shape (or a bellows shape). This allows the bending deformation of each piezoelectric cantilever to accumulate. Therefore, the second piezoelectric actuators 51 and 52 can easily obtain a larger deflection angle than the first piezoelectric actuators 31 and 32.

[0102] For this reason, in this embodiment, when the optical deflector 1 is oscillated by the first piezoelectric actuators 31, 32, in order to obtain as large a deflection angle as possible, the frequency that changes the upward or downward displacement of the first piezoelectric actuators 31, 32, i.e., the first frequency Fy, is set to a resonant frequency determined by the structure and material, etc., of the optical deflector 1 (particularly, the piezoelectric cantilever, etc.).

[0103] In addition, the second piezoelectric actuators 51, 52 are formed in a meandering shape (or a bellows shape) and are more likely to oscillate than the first piezoelectric actuators 31, 32. For this reason, the second frequency Fx is set sufficiently lower than the first frequency Fy. In this embodiment, for example, the first frequency Fy is set to 30 kHz, and the second frequency Fx is set to 60 Hz.

[0104] FIG. 6 is a diagram showing how an image p is drawn on a screen member 20 by laser light Ray scanned (raster scanned) by the optical deflector 1 (condenser lens 14, correction mirror 18, and projection lens 23 are omitted).

[0105] As described above, by the mirror portion 2 swinging about the first axis Y relative to the first support portion 4, the laser light Ray from the light source 12 incident on the mirror portion 2 is scanned in a first direction (e.g., a horizontal direction) as shown in FIG. 6.

[0106] In addition, as a result of the mirror portion 2 oscillating about the second axis X relative to the second support portion 6, the laser light Ray from the light source 12 incident on the mirror portion 2 is scanned in a second direction (e.g., a vertical direction) as shown in FIG.

[0107] FIG. 7 is a diagram showing the relationship between the drive signal applied to the optical deflector 1 (see FIG. 7(a)) and the oscillation angle of the mirror section 2 (see FIG. 7(b)).

[0108] In the optical deflector 1, when the displacement amounts of the alternately arranged cantilevers (the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D) are the same, that is, when the voltages of the first drive signal P and the second drive signal N are the same, the mirror section 2 is located at the reference position (= angle 0°. See FIG. 7(b)). The movement (oscillation) of the mirror section 2 about the second axis X is the same as the differential signal of the two signals (signal obtained by subtracting the second drive signal N from the first drive signal P) when viewed from the drive signal. In other words, when the differential signal is 0V, the mirror section 2 is located at the reference position (= angle 0°. See FIG. 7(b)).

[0109] As described above, an image p is drawn on the screen member 20 by the laser light Ray scanned by the optical deflector 1.

[0110] In this case, by changing the amplitude of at least one of the first drive signal P and the second drive signal N (see FIG. 4), it is possible to change the vertical width (see symbols H1 to H3 in FIG. 8) of the image p drawn on the screen member 20 by the laser light Ray scanned by the optical deflector 1, as shown in FIG. 8. FIG. 8 shows examples of images p with different vertical widths drawn on the screen member 20.

[0111] Furthermore, by changing the offset (offset amount) of at least one of the first drive signal P and the second drive signal N (see FIG. 4), it is possible to change the vertical position (offset amount) of the image p drawn on the screen member 20 by the laser light Ray scanned by the optical deflector 1, as shown in FIG. 9. FIG. 9 shows examples of images p drawn on the screen member 20 with different vertical positions (offset amounts).

[0112] Next, an example of the functional configuration of the optical deflector driving system 10 will be described.

[0113] FIG. 10 shows an example of the functional configuration of the optical deflector driving system 10. As shown in FIG.

[0114] As shown in FIG. 10, the optical deflector driving system 10 includes an image signal input unit 102 , an image signal processing unit 116 , an image signal storage unit 104 , a MEMS driving unit 108 , a sensor signal input unit 110 , and a light source driving unit 114 .

[0115] To the video signal input unit 102, a video signal output from an external device (not shown) connected to the video input unit 102 is input.

[0116] The video signal storage unit 104 stores the video signal (video) input to the video signal input unit .

[0117] The video signal processing unit 116 is, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), and generates a drive signal for driving the optical deflector 1 (first piezoelectric actuators 31, 32, second piezoelectric actuators 51, 52) and a drive signal for driving the light source 12 in order to draw the video signal (video) stored in the video signal storage unit 104 on the screen member 20.

[0118] At that time, the video signal processing unit 116 adjusts, for example, a drive signal that drives the optical deflector 1 so that the sensor signals (e.g., voltages detected by the first detection units 71y, 72y and the second detection units 71x, 72x) input to the sensor signal input unit 110 match target values ​​(feedback control).

[0119] The MEMS driving unit 108 D / A converts (and amplifies) the drive signal for driving the first piezoelectric actuator generated by the video signal processing unit 116, and applies it to the optical deflector 1 (first piezoelectric actuators 31, 32) as a first drive voltage Vy1 and a second drive voltage Vy2. The MEMS driving unit 108 also D / A converts (and amplifies) the drive signal for driving the second piezoelectric actuator generated by the video signal processing unit 116, and applies it to the optical deflector 1 (second piezoelectric actuators 51, 52) as a third drive voltage Vx1 (first drive signal P) and a fourth drive voltage Vx2 (second drive signal N).

[0120] The light source driving section 114 D / A converts (and amplifies) the driving signal for driving the light source generated by the video signal processing section 116 and applies it to the light source 12 .

[0121] Next, an example of the functional configuration of the video signal processing unit 116 will be described.

[0122] FIG. 11 shows an example of the functional configuration of the video signal processing unit 116.

[0123] 11, the video signal processing unit 116 includes a waveform generating unit 81, a calculating unit 82, a timing determining unit 83, an amplitude control unit 84, an offset dividing unit 85, an offset level control unit 86, a first adding unit 87, and a second adding unit 88. These are realized by the video signal processing unit 116 (CPU or DSP) executing a predetermined program. Note that some or all of these may be realized by hardware.

[0124] The waveform generating unit 81 outputs waveform data. Figures 13(a), 18(h), 20(a) and 21(h) are examples of the waveform data. The waveform data is, for example, a 60 Hz sawtooth wave. The waveform data is, for example, stored in advance in a storage unit (not shown) such as a memory.

[0125] The calculation unit 82 outputs the amplitude data, the time data, and the offset level data. An example of the amplitude data is shown in Fig. 13(b) and Fig. 20(b). The amplitude data represents the amplitude of the drive signal.

[0126] The time data includes time data (rise time) that indicates the rise time and time data (fall time) that indicates the fall time. Figures 18(b) and 21(b) are examples of the time data (rise time), and Figures 18(c) and 21(c) are examples of the time data (fall time). Specifically, the time data (rise time) represents time t2 in Figures 18(h) and 21(h), and the time data (fall time) represents time t1 in Figures 18(h) and 21(h). Figures 18(a) and 21(a) are examples of offset level data. The offset level data represents the offset amount (offset).

[0127] The timing judgment unit 83 judges the timing at which the voltage of the drive signal to be changed is smallest. The timing judgment unit 83 also outputs a first signal P (see FIG. 13(c)) and a first signal N (see FIG. 13(d)). The first signal P represents the same amplitude as the amplitude represented by the amplitude data. Similarly, the first signal N represents the same amplitude as the amplitude represented by the amplitude data. The timing judgment unit 83 also outputs a fourth signal P (see FIG. 21(f)) and a fourth signal N (see FIG. 18(g)). The fourth signal P is a continuous pulse that rises every offset / t2. Similarly, the fourth signal N is a continuous pulse that rises every offset / t1.

[0128] The amplitude control unit 84 generates a second signal P (see FIG. 13(e)) and a second signal N (see FIG. 13(f)), and outputs the generated second signal P and second signal N. The second signal P is generated by adjusting the amplitude of the waveform data (see FIG. 13(a)) to the same amplitude as the amplitude represented by the first signal P. Similarly, the second signal N is generated by adjusting the amplitude of waveform data that has been phase-inverted (reversed by 180 degrees) from the waveform data (see FIG. 13(a)) to the same amplitude as the amplitude represented by the first signal N.

[0129] The offset division unit 85 divides the offset amount "offset" represented by the offset level data output by the calculation unit 82 by the rise time t2 or the fall time t1. The offset division unit 85 outputs a third signal P (see FIG. 21(d)) and a third signal N (see FIG. 18(e)). The third signal P represents the offset amount "offset" represented by the offset level data / rise time t2. The third signal N represents the offset amount "offset" represented by the offset level data / fall time t1.

[0130] The offset level control unit 86 counts up the numerical value represented by the fifth signal N output from the offset level control unit 86 by a predetermined amount (for example, 1) each time a divided time (for example, offset amount offset / fall time t1) elapses (for example, when reflecting the offset amount shown in FIG. 18(j)). Note that the offset level control unit 86 may also count down the numerical value represented by the fifth signal N output from the offset level control unit 86 by a predetermined amount (for example, 1) each time a divided time (for example, offset amount offset / rise time t2) elapses (for example, when reflecting the offset amount shown in FIG. 21(j)).

[0131] The first adder 87 outputs the second signal P input thereto as is as the first drive signal P. However, when the fifth signal P is input thereto, the first adder 87 adds the fifth signal P to the second signal P (to reflect the change) and outputs the second signal P after this addition (after the change is reflected) as the first drive signal P.

[0132] The second adder 88 outputs the second signal N input thereto as is as the second drive signal N. However, when the fifth signal N is input thereto, the second adder 88 adds the fifth signal N to the second signal N (to reflect the change) and outputs the second signal N after this addition (after reflecting the change) as the second drive signal N.

[0133] Next, a process in which the MEMS driver 108 swings the mirror unit 2 around the second axis X will be described.

[0134] Fig. 12 is a sequence diagram of a process in which the MEMS driver 108 swings the mirror section 2 around the second axis X. Fig. 13 is an example (time chart) of each signal when the vertical width of the image p is reduced.

[0135] First, a process in which the MEMS driver 108 swings the mirror section 2 around the second axis X when drawing an image p having a vertical width H1 shown in FIG. 8(a) will be described.

[0136] 12, it is assumed that the waveform data (see FIG. 13(a)) output by the waveform generating unit 81 is input to the timing determining unit 83 and the amplitude controlling unit 84 (steps S1 and S2). It is also assumed that the amplitude data (see FIG. 13(b)) representing the amplitude h1 output by the calculating unit 82 is input to the timing determining unit 83 (step S3).

[0137] First, when the timing determination unit 83 receives amplitude data representing an amplitude h1 (step S3), it outputs a first signal P (see FIG. 13(c)) and a first signal N (see FIG. 13(d)) representing the same amplitude as the amplitude h1 represented by the amplitude data (step S4). The first signal P and the first signal N output by the timing determination unit 83 are input to the amplitude control unit 84 (step S4).

[0138] Next, when the first signal P and the first signal N are input to the amplitude control section 84 (step S4), the amplitude control section 84 generates a second signal P (see FIG. 13(e)) and a second signal N (see FIG. 13(f)) (step S5), and outputs the generated second signal P and second signal N (steps S6 and S7). The second signal P is generated by adjusting the amplitude of the waveform data (see FIG. 13(a)) to the same amplitude as the amplitude h1 represented by the first signal P. Similarly, the second signal N is generated by adjusting the amplitude of the waveform data (see FIG. 13(a)) whose phase is inverted (180 degrees inverted) to the same amplitude as the amplitude h1 represented by the first signal N. The second signal P output by the amplitude control section 84 is input to the first adder 87 (step S6). Meanwhile, the second signal N output by the amplitude control section 84 is input to the second adder 88 (step S7).

[0139] When the second signal P is input to the first adder 87 (step S6), the first adder 87 outputs the second signal P as is (step S8). The second signal P output by the first adder 87 is input to the MEMS driver 108 (step S8).

[0140] On the other hand, when the second signal N is input to the second adder 88 (step S7), the second adder 88 outputs the second signal N as is (step S9). The second signal N output by the second adder 88 is input to the MEMS driver 108 (step S9).

[0141] When the second signal P with amplitude h1 is input to the MEMS driving unit 108 (step S8), the MEMS driving unit D / A converts (and further amplifies) the second signal P with amplitude h1 and applies it to the optical deflector 1 as a third driving voltage Vx1 (first driving signal P) (step S11). When the second signal N with amplitude h1 is input to the MEMS driving unit (step S9), the MEMS driving unit D / A converts (and further amplifies) the second signal N with amplitude h1 and applies it to the optical deflector 1 as a fourth driving voltage Vx2 (second driving signal N) (step S12).

[0142] This causes the mirror section 2 to swing within a range according to the amplitude h1 represented by the amplitude data, centered on the second axis X. This causes an image p with a vertical width H1 shown in FIG.

[0143] Next, the problems that the present inventors have found will be described.

[0144] 14 and 15 are diagrams for explaining the problem found by the present inventors.

[0145] The vertical width of the image drawn on the screen member 20 can be changed, for example, as shown in Fig. 8 by changing the amplitude of the drive signals (for example, the second signal P and the second signal N). Also, the offset amount of the image drawn on the screen member 20 can be changed, for example, as shown in Fig. 9 by adding or subtracting the fifth signal P (and the fifth signal N) to the second signal P (and the second signal N).

[0146] The optical deflector 1 has multiple natural vibration modes, and a resonance phenomenon occurs when a signal containing a frequency component close to the natural vibration frequency is applied to the optical deflector 1. Since the resonance phenomenon produces a large displacement of the optical deflector 1 (mirror section 2) with a small applied voltage, the drive signal (drive voltage) applied to the optical deflector 1 needs to be a signal that does not induce uncontrolled resonance (abnormal vibration).

[0147] However, the inventors have found through their research that if a change in the offset (or amplitude) is reflected at the timing when an instruction to change the offset (or amplitude) is input, the waveform of the drive signal (drive voltage) becomes distorted before and after the change (see FIG. 14), and unnecessary frequency components (unintended frequency components) contained in the edges of the drive signal (drive voltage) with the distorted waveform cause abnormal vibrations in the optical deflector 1, which in turn causes a striped pattern (see FIG. 15) to appear in the image p drawn by the light scanned by the optical deflector 1.

[0148] Next, a process for changing the vertical width of the image drawn on the screen member 20 while suppressing the occurrence of abnormal vibrations in the optical deflector 1 will be described.

[0149] FIG. 16 is a sequence diagram of a process for changing the vertical width of an image drawn on the screen member 20 while suppressing the occurrence of abnormal vibration in the optical deflector 1.

[0150] Below, we will explain the process of changing the vertical width of the image drawn on the screen member 20, by changing (reducing) the vertical width H1 of the image p shown in Figure 8(a) to the vertical width H2 of the image p shown in Figure 8(b).

[0151] In the following, it is assumed that the processing of steps S1 to S12 shown in FIG. 12 is executed, so that an image p having a vertical width H1 shown in FIG. 8(a) is drawn on the screen member 20.

[0152] First, when amplitude data (see FIG. 13(b)) representing an amplitude h2 different from the amplitude data representing the currently input amplitude h1 is input to the timing determination unit 83 (step S20), the timing determination unit 83 determines whether or not it is the timing at which the voltage of the second signal P (see FIG. 13(e)) becomes smallest (step S21). The amplitude data representing the amplitude h2 different from the amplitude data representing the currently input amplitude h1 is input, for example, by the user performing a predetermined operation. The amplitude data representing the amplitude h2 different from the currently input amplitude data representing the amplitude h1 is an example of an instruction to change the amplitude of the present invention.

[0153] The timing determination unit 83 waits until the timing when the voltage of the second signal P is smallest (see symbol P1 in FIG. 13(e)) arrives (step S21: NO). Since such timing coincides with the timing when the voltage in the waveform data is smallest, it can be obtained from the waveform data.

[0154] When the timing determination unit 83 determines that it is the timing when the voltage of the second signal P is smallest (see symbol P1 in FIG. 13(e)) (step S21: YES), it outputs the first signal P (see FIG. 13(c)) that represents the same amplitude as the amplitude h2 represented by the amplitude data (step S22). The first signal P output by the timing determination unit 83 is input to the amplitude control unit 84 (step S22).

[0155] Furthermore, the timing determination unit 83 determines whether or not it is the timing at which the voltage of the second signal N (see FIG. 13(f)) is at its smallest (step S23). The timing determination unit 83 waits until the timing (see symbol P2 in FIG. 13(f)) at which the voltage of the second signal N (see FIG. 13(f)) is at its smallest arrives (step S23: NO). Since the second signal N has a waveform that is in opposite phase to the waveform data, such timing coincides with the timing at which the voltage in the waveform data is at its largest, and can be obtained from the waveform data.

[0156] When the timing determination unit 83 determines that it is the timing at which the voltage of the second signal N is smallest (see symbol P2 in FIG. 13(f)) (step S23: YES), it outputs the first signal N (see FIG. 13(d)) that represents the same amplitude as the amplitude h2 represented by the amplitude data (step S24). The first signal N output by the timing determination unit 83 is input to the amplitude control unit 84.

[0157] Next, when the first signal P is input to the amplitude control section 84 (step S22), it generates a second signal P (see FIG. 13(e)) with an amplitude h2 (step S25) and outputs the generated second signal P with the amplitude h2 (step S26). The second signal P with the amplitude h2 is generated by adjusting the amplitude of the waveform data (see FIG. 13(a)) to the same amplitude as the amplitude h2 represented by the first signal P. Step S25 is an example of a change reflecting section of the present invention. The second signal P output by the amplitude control section 84 is input to the first adder 87 (step S26).

[0158] Furthermore, when the first signal N is input to the amplitude control section 84 (step S24), it generates a second signal N (see FIG. 13(f)) with an amplitude h2 (step S27) and outputs the generated second signal N with the amplitude h2 (step S28). The second signal N with the amplitude h2 is generated by inverting the phase of the waveform data (see FIG. 13(a)) (by 180 degrees) and adjusting the amplitude of the waveform data to the same amplitude as the amplitude h2 represented by the first signal N. Step S27 is an example of a change reflecting section of the present invention. The second signal N with the amplitude h2 output by the amplitude control section 84 is input to the second adder 88 (step S28).

[0159] When the second signal P is input to the first adder 87 (step S26), the first adder 87 outputs the second signal P as is (step S29). The second signal P output by the first adder 87 is input to the MEMS driver 108 (step S29).

[0160] On the other hand, when the second signal N is input to the second adder 88 (step S28), the second adder 88 outputs the second signal N as is (step S30). The second signal N output by the second adder 88 is input to the MEMS driver 108 (step S30).

[0161] When the second signal P with amplitude h2 is input to the MEMS driving unit 108 (step S29), the MEMS driving unit D / A converts (and further amplifies) the second signal P with amplitude h2 and applies it to the optical deflector 1 as a third driving voltage Vx1 (first driving signal P) (step S31). When the second signal N with amplitude h2 is input to the MEMS driving unit (step S30), the MEMS driving unit D / A converts (and further amplifies) the second signal N with amplitude h2 and applies it to the optical deflector 1 as a fourth driving voltage Vx2 (second driving signal N) (step S32).

[0162] This causes the mirror section 2 to swing about the second axis X within a range according to the amplitude h2 represented by the amplitude data, thereby rendering an image p having a vertical width H2 as shown in FIG.

[0163] As described above, the change in amplitude is not reflected at the timing when the instruction to change the amplitude is input (step S20), but if it is determined that the voltage of the drive signal to be changed (second signal P, second signal N) is at its smallest (step S21: YES, step S23: YES), the change is reflected in the drive signal to be changed (steps S25, S27). From the timing when the instruction to change the amplitude is input to the timing when the voltage of the drive signal to be changed (second signal P, second signal N) is at its smallest, the drive signal is driven while maintaining the amplitude before the change.

[0164] This makes it possible to prevent abnormal vibrations from occurring in the optical deflector 1 even when changes in amplitude are reflected (as a result, it is possible to prevent stripes from appearing in the image drawn by the light scanned by the optical deflector).

[0165] The above describes the process of changing (reducing) the vertical width H1 of the image p shown in Fig. 8(a) to the vertical width H2 of the image p shown in Fig. 8(b) by using the signals shown in Fig. 13, but the present invention is not limited to this. For example, by using the signals shown in Fig. 20, the vertical width H1 of the image p shown in Fig. 8(a) can be changed (enlarged) to the vertical width H3 of the image p shown in Fig. 8(c). Fig. 20 shows an example (time chart) of each signal when enlarging the vertical width of the image p.

[0166] Next, a process for changing the offset amount of the image drawn on the screen member 20 while suppressing the occurrence of abnormal vibration in the optical deflector 1 will be described.

[0167] Fig. 17 is a sequence diagram of a process for changing the offset amount of the image drawn on the screen member 20 while suppressing the occurrence of abnormal vibration in the optical deflector 1. Fig. 18 is an example (time chart) of each signal when the image p is offset upward.

[0168] Hereinafter, as a process for changing the offset amount of the image drawn on the screen member 20, a process for offsetting the image p shown in FIG. 9(a) upward as shown in FIG. 9(b) will be described.

[0169] In the following, it is assumed that the processing of steps S1 to S12 shown in Fig. 17 is executed, so that the image p shown in Fig. 9(a) is drawn on the screen member 20. Note that steps S1 to S12 shown in Fig. 17 are similar to steps S1 to S12 shown in Fig. 12.

[0170] First, when offset level data (see FIG. 18(a)) and time data (see FIG. 18(b) and FIG. 18(c)) that represent an offset amount different from the offset data that represents the offset amount currently input are input to the offset division unit 85 (step S40), the offset division unit 85 outputs a third signal N (see FIG. 18(e)) (step S41). The offset level data that represents an offset amount different from the offset data that represents the offset amount currently input is input by, for example, a predetermined operation by the user. The offset level data that represents an offset amount different from the offset data that represents the offset amount currently input is an example of an instruction to change the offset of the present invention. The third signal N represents the offset amount (offset) / fall time t1 represented by the offset level data. The third signal N output by the offset division unit 85 is input to the timing determination unit 83 (step S41).

[0171] When the third signal N is input to the timing determination unit 83, the timing determination unit 83 determines whether or not it is the timing when the voltage of the second signal N (see FIG. 18(l)) is smallest (step S42). The timing determination unit 83 waits until the timing when the voltage of the second signal N is smallest (see symbol P3 in FIG. 18(l)) arrives (step S42: NO).

[0172] When the timing determination unit 83 determines that it is the timing at which the voltage of the second signal N is smallest (see symbol P3 in FIG. 18(l)) (step S42: YES), it outputs a fourth signal N (see FIG. 18(g)) (step S43). The fourth signal N is a continuous pulse that rises every offset amount offset / fall time t1. The fourth signal N output by the timing determination unit 83 is input to the offset level control unit 86.

[0173] The offset level control unit 86 counts up the numerical value represented by the fifth signal N outputted from the offset level control unit 86 by a predetermined amount (e.g., 1) each time the divided time (offset amount offset / fall time t1) elapses (step S44: YES), that is, each time the fourth signal N rises (see FIG. 18(g)) (step S45).

[0174] The offset level control unit 86 repeats the processes of steps S44 to S46 (step S47: NO) until the count-up reaches offset (step S47: YES). As a result, as shown in Fig. 19, the fifth signal N becomes a stepped signal that is counted up by a predetermined amount every time the divided time (offset amount offset / fall time t1) elapses. The fifth signal N output by the offset level control unit 86 is input to the second adder 88.

[0175] When the fifth signal N is input to the second adder 88 (step S46), the second adder 88 adds the fifth signal N to the second signal N (reflecting the change; step S48), and outputs the second signal N after this addition (after reflecting the change) as the second drive signal N (step S9). At that time, the fifth signal N input to the second adder 88 is a stepped signal that is counted up by a predetermined amount each time a divided time (offset amount offset / fall time t1) elapses (see FIG. 19), so that the change is reflected in the drive signal (second signal N) to be changed in stages (gradually). Step S48 is an example of a change reflecting unit of the present invention. The second signal N output by the second adder 88 is input to the MEMS drive unit 108 (step S9).

[0176] When the second signal N reflecting the change is input to the MEMS driving unit 108 (step S9), the MEMS driving unit 108 D / A converts (and further amplifies) the second signal N reflecting the change and applies it to the optical deflector 1 as a fourth driving voltage Vx2 (second driving signal N) (step S12). When the second signal P is input to the MEMS driving unit 108 (step S8), the MEMS driving unit 108 D / A converts (and further amplifies) the second signal P and applies it to the optical deflector 1 as a third driving voltage Vx1 (first driving signal P) (step S11).

[0177] This makes it possible to offset the image p shown in FIG. 9(a) upward as shown in FIG. 9(b).

[0178] As described above, rather than reflecting the change in offset at the timing when an instruction to change the offset is input (step S40), if it is determined that the voltage of the drive signal to be changed (e.g., second signal N) is at its smallest (step S42: YES), the change is reflected in the drive signal to be changed in stages (gradually) (steps S43 to S47).

[0179] This makes it possible to prevent abnormal vibrations from occurring in the optical deflector 1 even when a change in the offset is reflected (as a result, it is possible to prevent stripes from appearing in the image drawn by the light scanned by the optical deflector).

[0180] The above describes the process of offsetting the image p shown in Fig. 9(a) upward as shown in Fig. 9(b) by using the signals shown in Fig. 18, but the present invention is not limited to this. For example, the image p shown in Fig. 9(a) can be offset downward as shown in Fig. 9(c) by using the signals shown in Fig. 21. Fig. 21 shows an example (time chart) of each signal when offsetting the image p downward.

[0181] As described above, according to this embodiment, even when a change in the offset (or amplitude) is reflected, it is possible to suppress the occurrence of abnormal vibrations in the optical deflector 1 (as a result, it is possible to suppress the appearance of striped patterns in the image drawn by the light scanned by the optical deflector).

[0182] This is because, rather than reflecting the change in offset (or amplitude) at the timing when an instruction to change the offset (or amplitude) is input, when it is determined that the timing is when the voltage of the drive signal to be changed is at its smallest, the change is reflected in the drive signal to be changed, thereby making it possible to remove unnecessary frequency components (unintended frequency components) that cause abnormal vibrations of the optical deflector 1.

[0183] Next, a modified example will be described.

[0184] FIG. 22 is a diagram illustrating a modified example of the fifth signal.

[0185] In the above embodiment, the process of steps S44 to S47 (the process of reflecting the change in the offset) is performed in one cycle, but the present invention is not limited to this. For example, as shown in Fig. 22, the process of steps S44 to S47 (the process of reflecting the change in the offset) may be performed in multiple cycles.

[0186] The numerical values ​​shown in the above embodiments are all examples, and it goes without saying that suitable numerical values ​​different from these can be used.

[0187] The above-described embodiments are merely examples in all respects. The present invention should not be construed as being limited by the description of the above-described embodiments. The present invention can be implemented in various other forms without departing from the spirit or main characteristics thereof. [Explanation of symbols]

[0188] 1...optical deflector, 2...mirror portion, 2a...reflective surface, 2b...reflective surface support, 4...first support portion, 6...second support portion, 10...optical deflector drive system, 12...light source, 14...condensing lens, 18...correction mirror, 20...screen member, 21, 22...torsion bar, 23...projection lens, 31...first piezoelectric actuator, 31A...first piezoelectric cantilever, 32...first piezoelectric actuator, 32A...first piezoelectric cantilever, 51...second piezoelectric actuator, 51A ...second piezoelectric cantilever, 51B...second piezoelectric cantilever, 51C...second piezoelectric cantilever, 51D...second piezoelectric cantilever, 52...second piezoelectric actuator, 52A...second piezoelectric cantilever, 52B...second piezoelectric cantilever, 52C...second piezoelectric cantilever, 52D...second piezoelectric cantilever, 61a...lower electrode pad, 61b...first upper electrode pad, 61c...second upper electrode pad for odd numbers, 61d...second upper electrode pad for even numbers, 61e...first detection electrode pad, 62a...lower electrode pad, 62b...first upper electrode pad, 62c...second upper electrode pad for odd numbers, 62d...second upper electrode pad for even numbers, 62e...second detection Electrode pad, 71x...second detection unit, 71y...first detection unit, 72x...second detection unit, 72y...first detection unit, 81...waveform generation unit, 82...calculation unit, 83...timing determination unit, 84...amplitude control unit, 85...offset division unit, 86...offset level control unit, 87...first adder unit, 88...second adder unit, 102...video signal input unit, 104...video signal storage unit, 108...MEMS drive unit, 110...sensor signal input unit, 114...light source drive unit, 116...video signal processing unit, B...support, Fx...second frequency, Fy...first frequency, H1 to H3...vertical width, L1...lower electrode, L2...piezoelectric body, L3...upper electrode, M1...interlayer insulating film, M2...passivation film

Claims

1. A mirror portion; an actuator that swings the mirror portion around a swing axis, an optical deflector driving system that applies a driving voltage corresponding to a driving signal to the actuator, a timing determination unit that, when an instruction to change the drive signal is input, determines a timing at which the voltage of the drive signal to be changed becomes smallest; a change reflecting unit that reflects the change in the drive signal to be changed when it is determined that the timing has come when the voltage of the drive signal to be changed will be the smallest.

2. 2. The optical deflector driving system according to claim 1, wherein the instruction to change is an instruction to change amplitude.

3. 2. The optical deflector driving system according to claim 1, wherein the instruction to change is an instruction to change an offset.

4. the instruction to change is offset level data representing an offset amount, An offset division unit that divides the offset amount by a rise time or a fall time, 2 . The optical deflector driving system according to claim 1 , wherein the change reflecting unit reflects the change in a stepwise manner in the driving signal to be changed each time the divided time period elapses.

5. the drive signals include a first drive signal and a second drive signal; the driving voltages include a first driving voltage and a second driving voltage; the first drive signal corresponds to the first drive voltage; the second drive signal corresponds to the second drive voltage; the actuator has a first drive section driven by the first drive voltage and a second drive section driven by the second drive voltage, The optical deflector driving system according to claim 1, characterized in that, when an instruction to change at least one of the first drive signal and the second drive signal is input, the timing determination unit determines the timing at which the voltage of the drive signal to be changed, among the first drive signal and the second drive signal, is the smallest.

6. the first actuator is a first piezoelectric cantilever; 6. The optical deflector driving system according to claim 5, wherein the second driving section is a second piezoelectric cantilever.

7. 6. The optical deflector driving system according to claim 5, wherein the first driving signal and the second driving signal are AC waveforms out of phase with each other.

8. a change instruction input step of inputting an instruction to change a drive signal corresponding to a drive voltage applied to an actuator that swings a mirror portion of the optical deflector around a swing axis; a determination step of determining, when the instruction is input, a timing at which the voltage of the drive signal to be changed becomes smallest; and when it is determined that this is the timing at which the voltage of the drive signal to be changed is at its smallest, reflecting the change in the drive signal to be changed.

9. 9. The method of driving an optical deflector according to claim 8, wherein the instruction to change is an instruction to change amplitude.

10. 9. The method of driving an optical deflector according to claim 8, wherein the instruction to change is an instruction to change an offset.

11. the instruction to change is offset level data representing an offset amount, An offset division step of dividing the offset amount by a rise time or a fall time, 9. The optical deflector driving method according to claim 8, wherein the change reflecting step reflects the change in the drive signal to be changed in a stepwise manner each time the divided time period elapses.

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