JP2012058662A - Optical scanner and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of suppressing fluctuation in resonant frequency even if there is a manufacturing error; and to provide an image projection device having the optical scanner.SOLUTION: This optical scanner includes: a mirror section that swings about a swinging axis at a prescribed resonance frequency; beam sections supporting both ends of the mirror section; outer edge sections to which the ends of the beam sections are connected; a drive source for swinging the mirror section; mass bodies spaced from the beam section, mirror section and the outer edge sections between the mirror section and the outer edge sections; and connecting sections for connecting the mass bodies to the beam sections. The mass bodies suppress by an inertia moment generated by changes in the mass bodies by a prescribed width, the fluctuation in the resonance frequency in the beam sections caused by a change in the rigidity of the beam sections generated when the width in the direction of orthogonally crossing with the swinging axis is changed by a prescribed width.

Description

  The present invention relates to an optical scanner that is resonantly driven at a predetermined resonance frequency and scans incident light in a predetermined direction, and an image projection apparatus using the optical scanner.

  2. Description of the Related Art Conventionally, there is known an optical scanner that is resonantly driven at a predetermined resonance frequency and scans incident light in a predetermined direction. When a resonantly driven optical scanner is mass-produced, keeping the resonance frequency constant among mass-produced products is useful for improving productivity. However, in practice, the resonant frequency of mass-produced optical scanners is not constant due to manufacturing errors and the like. For example, when the optical scanner is formed by etching, the shape of the optical scanner to be formed varies due to variations in the etching rate. The variation in the shape of the optical scanner leads to the variation in the resonance frequency of the optical scanner.

  In order to improve the productivity of the optical scanner, a technique for adjusting the resonance frequency of the scattered optical scanner to keep the resonance frequency within a predetermined specification range has been proposed. For example, Patent Document 1 discloses a technique for removing a part of a movable plate of a rocking body with a laser when the twist angle of the rocking body reaches a predetermined value. That is, in Patent Document 1, the resonance frequency is adjusted by using the resonance frequency change accompanying the mass change of the oscillator. Patent Document 2 discloses a technique for maintaining a torsional natural vibration mode at a desired frequency ratio by applying a stress to a torsion spring to change the spring constant of one torsion spring.

JP 2006-39377 A JP 2005-326464 A

  The above-described conventional technique is based on the premise that the resonance frequency of mass-produced optical scanners varies. That is, by adjusting the varied resonance frequency, the resonance frequency in the adjusted optical scanner is kept constant. In other words, the conventional technique requires frequency adjustment individually for each of the mass-produced optical scanners. Therefore, the conventional technique has a problem that man-hours are increased and, consequently, costs are increased. If the variation of the resonance frequency can be suppressed, it is considered that the necessity for adjusting the frequency individually is reduced, and an increase in man-hours and costs can be avoided.

  An object of the present invention is to provide an optical scanner capable of suppressing variations in resonance frequency even when a manufacturing error or the like occurs, and an image projection apparatus including the optical scanner.

  In order to solve the above-described problem, an aspect of the present invention is an optical scanner that is resonantly driven at a predetermined resonance frequency and scans incident light in a predetermined direction, and the predetermined resonance is centered on an oscillation axis. A mirror portion oscillating at a frequency; a first torsion beam coupled to the mirror portion and extending parallel to the oscillation axis; and a first torsion beam coupled to the mirror portion and extending in a direction opposite to the first torsion beam. Two torsion beams; an end portion of the first torsion beam; an outer edge portion connected to an end portion of the second torsion beam; a drive source that swings the mirror portion; Between the mirror portion and the outer edge portion, the beam body, the mass body spaced from the mirror portion and the outer edge portion, and a connecting portion for connecting the mass body and the beam portion, the mass body, The beam portion has a width in a first direction perpendicular to the swing axis. The variation of the resonance frequency caused by the change in rigidity of the beam portion caused by the width change is suppressed by the change of the moment of inertia around the swing axis that occurs when the mass body changes the predetermined width. An optical scanner characterized by comprising:

  According to this, the mass body is connected to the beam portion by the connecting portion. The mass body is separated from the beam portion, the mirror portion, and the outer edge portion between the mirror portion and the outer edge portion. For example, when the optical scanner is manufactured by etching, the width in the first direction perpendicular to the swing axis of the beam portion changes. Then, in the beam portion, when the width in the first direction changes by a predetermined width, the rigidity of the beam portion changes. For example, considering the case where the width of the beam portion in the first direction is narrower than the design value, the rigidity of the beam portion decreases. The reduction in stiffness acts in a direction that reduces the resonant frequency of the optical scanner. Since the etching proceeds isotropically, the width (size) including the first direction of the mass body is reduced by the same amount as the reduction amount in the beam portion. The reduction in mass size reduces the moment of inertia of the optical scanner. This decrease in the moment of inertia works in the direction of increasing the resonance frequency of the optical scanner. That is, the size change also occurs in the mass portion in the same manner, so that the variation in the resonance frequency caused by the change in the width of the beam portion is suppressed. On the other hand, considering the case where the width of the beam portion in the first direction is wider than the design value, the rigidity of the beam portion increases. However, even if the rigidity is increased, the mass body is also larger in size than the design value, so that the fluctuation of the resonance frequency is suppressed as a result due to the increase of the moment of inertia of the optical scanner. Therefore, even if there is a manufacturing error in the form of beam width variation due to, for example, variations in etching rate, the resonance frequency variation caused by the stiffness change of the beam portion is caused by the change in the moment of inertia caused by the size change of the mass body. As a result, it is possible to suppress variations in the resonance frequency. As a result, for example, the resonance frequency of the optical scanner can be maintained at a desired value without individually adjusting the resonance frequency.

  In order to solve the above-mentioned problem, another aspect of the present invention is an optical scanner that is resonantly driven at a predetermined resonance frequency and scans incident light in a predetermined direction, and the predetermined scanner is centered on an oscillation axis. A mirror part that oscillates at a resonance frequency, a first torsion beam that is connected to the mirror part and extends parallel to the oscillation axis, and is connected to the mirror part and extends in a direction opposite to the first torsion beam. A beam part having a second torsion beam; an end part of the first torsion beam; an outer edge part to which the end part of the second torsion beam is connected; a drive source for swinging the mirror part; A mass body extending along the swing axis in a state of being separated from the beam portion, the mirror portion, and the outer edge portion between the mirror portion and the outer edge portion, and the mass body and the beam portion. And a torsional elastic constant K in the beam portion. The moment of inertia of the mirror portion around the swing axis is I1, the moment of inertia of the mass body around the swing axis is I2, and the beam portion has a first direction perpendicular to the swing axis. The amount of change in K that occurs when the width changes by a predetermined width is ΔK, the amount of change in I1 that occurs when the mirror section changes by the predetermined width is ΔI1, and the amount of change that occurs by the mass body changes by the predetermined width. When the amount of change in I2 is ΔI2, the mass body is formed so as to satisfy the following relational expression (Formula 1).

  In general, the resonance frequency in an optical scanner having a mirror and both support beams is expressed by the following equation, where K is the torsional elastic constant (rigidity) of the beam portion and I is the moment of inertia of the swinging portion.

  Accordingly, the first term on the left side of (Equation 1) indicates the resonance frequency of the optical scanner determined by the moment of inertia I1 of the mirror part and the torsional elastic coefficient K of the beam part. The second term on the left side of (Equation 1) indicates the resonance frequency of the optical scanner when the torsional elastic coefficient changes by ΔK and the moment of inertia of the mirror portion changes by ΔI1 due to variations in the etching rate. Therefore, the left side of the above (Equation 1) indicates the amount of fluctuation of the resonance frequency caused by the variation in the etching rate in the absence of the mass body. On the other hand, the first term on the right side of (Equation 1) indicates the resonance frequency of the optical scanner determined by the inertia moment I1 of the mirror portion, the inertia moment I2 of the mass body, and the torsional elastic coefficient K of the beam portion. The second term on the right-hand side of (Equation 1) indicates the optical scanner when the torsional elastic coefficient is ΔK, the inertia moment of the mirror is ΔI1, and the inertia moment of the mass body is ΔI2 due to variations in the etching rate. Indicates the resonance frequency. Therefore, the right side of the above (Equation 1) indicates the amount of fluctuation of the resonance frequency caused by variations in the etching rate in the presence of the mass body. Since the mass body is formed so as to satisfy the above (Equation 1), the amount of fluctuation in the resonance frequency caused by variations in the etching rate or the like is greater when the mass body is present than when the mass body is not present (left side) ( The right side is smaller. Therefore, by providing the mass body, it is possible to suppress variations in the resonance frequency. As a result, for example, the resonance frequency of the optical scanner can be maintained at a desired value without individually adjusting the resonance frequency.

  The optical scanner may be an optical scanner that further includes another configuration. That is, the mass body may be formed so as to satisfy the following relational expression (Formula 3).

  The above (Expression 3) specifies that the first term and the second term on the right side of the above (Expression 1) are equal. In other words, by providing the mass body that satisfies the above (Equation 3), even if the etching rate varies, the resonance frequency does not vary. Therefore, for example, the resonance frequency of the optical scanner can be maintained at a desired value without individually adjusting the resonance frequency.

  Further, the mass body may extend along the direction of the swing axis.

  According to this optical scanner, the mass body extends along the direction of the swing axis. Accordingly, it is possible to make the size of the optical scanner smaller in the first direction as compared with a case where the mass body extends along the first direction.

  Further, the mass body may be formed so as to extend in parallel with the swing axis and to have a constant width in the first direction.

  According to this optical scanner, the mass body is formed so as to extend parallel to the swing axis and to have a constant width in the first direction. If the mass body extends in a direction intersecting the swing axis, the amount of decrease in the moment of inertia varies depending on the position when the width of the mass body decreases. Specifically, the amount of inertia decreased due to the decrease in the mass width at a position farther from the oscillation axis than the amount of inertia decreased due to the decrease in the mass width at a position close to the oscillation axis. Becomes larger. Therefore, it becomes difficult to control the amount of change in the moment of inertia when the width of the mass body decreases. On the other hand, if the mass body extends parallel to the swing axis, the width in the first direction of the mass body is constant, so the distance between the arbitrary position in the longitudinal direction of the mass body and the swing axis is always constant. Become. Accordingly, the amount of change in the moment of inertia is constant regardless of the position in the longitudinal direction of the mass body. Therefore, it is possible to easily control the amount of change in the moment of inertia when the width of the mass body is reduced.

  Further, the connecting portion may extend from the beam portion in the first direction, and the mass body may extend symmetrically with respect to the connecting portion from an end portion of the connecting portion.

  According to this optical scanner, the connecting portion extends from the beam portion in the first direction. Therefore, the mass body is reliably separated from the beam portion, the mirror portion, and the outer edge portion. In addition, since the mass body extends symmetrically with respect to the connecting portion, the distribution of mass is kept symmetrical with respect to the connecting portion, and stable oscillation of the mirror portion becomes possible.

  Moreover, you may make it the said connection part and the said mass body provide a pair symmetrically with respect to the said beam part.

  According to this optical scanner, a pair of the connecting portion and the mass body are provided symmetrically with respect to the beam portion. Therefore, even if a connection part and a mass body are added, the distribution of mass is kept symmetrical with respect to the beam part. Therefore, it is possible to swing the mirror part stably.

  Further, the mass body and the connecting portion may be provided on both the first torsion beam and the second torsion beam.

  According to this optical scanner, the mass body and the connecting portion are provided on both the first torsion beam and the second torsion beam. Therefore, when the mass body and the connecting portion are provided, it is possible to suppress the position of the center of gravity from being biased to one of the first torsion beam and the second torsion beam with respect to the mirror portion. For this reason, it is possible to swing the mirror part stably.

  The mass body and the connecting portion may be provided on both the first torsion beam and the second torsion beam so as to be symmetric with respect to the mirror portion.

  According to this optical scanner, the mass body and the connecting portion are provided on both the first torsion beam and the second torsion beam so as to be symmetric with respect to the mirror portion. Therefore, even if the mass body and the connecting portion are provided, the position of the center of gravity is maintained on the mirror portion. Therefore, the mirror part can be more stably swung.

  Another aspect of the present invention includes the above-described optical scanner, a light source for supplying light to the optical scanner, and a light guide unit that guides light scanned by the optical scanner to a projection surface. This is an image projection apparatus characterized by this.

  According to this, an image projection apparatus using an optical scanner capable of suppressing variations in resonance frequency is provided. Therefore, since the yield of the optical scanner is increased, an image projection apparatus can be provided at a low cost.

  According to the present invention, it is possible to suppress variations in the resonance frequency of the scanner even when a manufacturing error or the like occurs due to variations in the etching rate, for example.

(A) The top view of the optical scanner 10, (B) AA sectional drawing of the optical scanner 10, (C) BB sectional drawing of the optical scanner 10. FIG. The top view which expanded the periphery of the mirror part 101 of the structure 100. FIG. The figure which shows the ratio of the measured value with respect to the size of a design value at the time of performing an etching process with respect to three samples of the structure 100. FIG. The figure explaining the dispersion | variation in the resonant frequency with respect to the dispersion | variation in the size by an etching process. The figure explaining the structure of the retinal scanning display 1. FIG. The figure explaining the structure of the laser display.

  Embodiments reflecting one aspect of the present invention will be described below in detail with reference to the drawings. One aspect of the present invention is not limited to the configuration described below, and various configurations can be employed in the same technical idea. For example, in each configuration described below, a predetermined configuration may be omitted or replaced with another configuration. Moreover, you may make it include another structure.

[Configuration of Optical Scanner 10]
As shown in FIG. 1, the optical scanner 10 includes a structure 100, a piezoelectric drive unit 110 provided in the structure 100, and a pedestal 120 to which the structure 100 is fixed. In the optical scanner 10, the piezoelectric drive unit 110 periodically expands and contracts at the resonance frequency of the structure 100, thereby exciting plate wave vibration in the structure 100. The plate-wave vibration is transmitted through the structure 100 and the mirror portion 101 of the structure 100 is swung, so that the optical scanner 10 is resonantly driven. Hereinafter, individual configurations of the optical scanner 10 will be described.

  As shown in FIGS. 1 and 2, the structure 100 includes a mirror part 101, a first torsion beam 102, a second torsion beam 103, an outer edge part 104, first mass bodies 105a and 105b, a second mass body 106a, 106b, 1st connection part 107a, 107b, and 2nd connection part 108a, 108b. The structure 100 is manufactured by forming each of the above-described structures on a metal plate such as stainless steel or titanium having a thickness of several tens to several hundreds of micrometers using a removal process such as an etching process or a press process. . However, the structure 100 may be formed of a non-metallic material such as a silicon wafer. In this case, a conductive layer such as a metal thin film is preferably provided on the surface of the nonmetallic material. In FIG. 1, the thickness direction of the structure 100 is defined as the Z direction, the direction parallel to the swing axis L1 of the mirror unit 101 is defined as the Y direction, and the direction perpendicular to the Z direction and the Y direction is defined as the X direction. .

  The mirror unit 101 swings about the swing axis L1. The mirror unit 101 has a circular shape in plan view. However, the mirror unit 101 may have another shape such as a quadrangle or a polygon. The surface of the mirror unit 101 is mirror-polished so as to reflect incident light. However, instead of mirror polishing, a metal thin film having a high reflectance with respect to visible light, such as aluminum or silver, may be provided on the surface of the mirror unit 101 by vapor deposition or sputtering.

  A first torsion beam 102 is connected to the Y direction positive side of the mirror unit 101. The first torsion beam 102 extends in a direction away from the mirror unit 101 in parallel with the swing axis L1. A second torsion beam 103 is connected to the negative side of the mirror unit 101 in the Y direction. The second torsion beam 103 is parallel to the swing axis L1 and extends in the direction opposite to the first torsion beam 102. The mirror unit 101 is supported on both sides by the first torsion beam 102 and the second torsion beam 103. In addition, when not distinguishing the 1st twisted beam 102 and the 2nd twisted beam 103, it only calls a beam part.

  The outer edge portion 104 includes a first ear portion 104a1, a second ear portion 104a2, a main body portion 104b, and a fixed portion 104c. The first ear portion 104a1 is connected to the end of the first twisted beam 102 on the Y direction positive side. The second ear portion 104a2 is connected to the Y-direction negative end of the second torsion beam 103. The first ear portion 104a1 and the second ear portion 104a2 extend in the X direction negative side from the position where the first torsion beam 102 and the second torsion beam 103 are connected. The first ear portion 104a1 is connected to the end portion on the positive side in the Y direction on the side on the positive side in the X direction of the main body portion 104b. The second ear portion 104a2 is connected to the end portion on the Y direction negative side on the X direction positive side of the main body portion 104b. The main body portion 104 b is located at the central portion of the structure 100. A fixed portion 104c is connected to one end of the main body portion 104b on the X direction negative side. The fixed portion 104c is connected to one end of the main body portion 104b at the center in the longitudinal direction. The fixed portion 104 c is fixed to the pedestal 120.

  The piezoelectric drive unit 110 that functions as a drive source is provided on the surface on the positive side in the Z direction of the main body portion 104b. For example, the piezoelectric drive unit 110 is a laminate of 0.2 μm to 0.6 μm of gold, platinum, or the like as electrodes on both sides of a piezoelectric material such as lead zirconate titanate formed into a plate shape having a thickness of 30 μm to 100 μm. It is formed by doing. The piezoelectric drive part 110 and the main-body part 104b are adhere | attached with a conductive adhesive. This conductive adhesive, for example, disperses a disc-shaped metal filler composed of silver, gold, copper, etc. in a base made of a thermosetting epoxy resin, acrylic resin, silicon resin or the like. It has been made. First, the piezoelectric drive unit 110 is placed on the conductive adhesive applied to the main body portion 104b. In this state, the conductive adhesive is thermally cured to bond the piezoelectric driving unit 110 and the main body portion 104b. Since the structure 100 is formed of a metal plate, an AC voltage corresponding to the resonance frequency of the optical scanner 10 is applied between the structure 100 and the positive side of the piezoelectric drive unit 110 in the Z direction, so that the optical scanner 10 Resonant drive is possible.

The pedestal 120 is made of a metal material such as stainless steel or titanium. The fixed portion 104 c is fixed to the surface on the positive side in the Z direction of the pedestal 120. For fixing the pedestal 120 and the fixing portion 104c, for example, bonding with an adhesive, welding with a laser, or clamping with a predetermined jig is used.

  The first mass bodies 105a and 105b and the first connecting portions 107a and 107b have an H-shaped structure provided in the first torsion beam 102 in plan view. The first mass bodies 105 a and 105 b are separated from the first torsion beam 102, the mirror part 101, and the outer edge part 104 between the mirror part 101 and the ear part 104 a 1 of the outer edge part 104. The first connecting portions 107 a and 107 b connect the first mass bodies 105 a and 105 b and the first torsion beam 102. Specifically, the first connecting portion 107a extends from the first torsion beam 102 to the X direction positive side. The first mass body 105a extends from the end on the X direction positive side of the first connecting portion 107a to both sides in the Y direction symmetrically with respect to the first connecting portion 107a. The first connecting portion 107b and the first mass body 105b are provided symmetrically with respect to the first torsion beam 102 with respect to the first connecting portion 107a and the first mass body 105a. That is, the first connecting portion 107b extends from the first torsion beam 102 to the X direction negative side. And the 1st mass body 105b is extended from the edge part of the X direction negative side of the 1st connection part 107b to the both sides of the Y direction symmetrically with respect to the 1st connection part 107b.

  The second mass bodies 106a and 106 and the second connecting portions 108a and 108b also have an H-shaped structure in plan view. The second mass bodies 106a and 106b and the second connecting portions 108a and 108b are symmetrical with the first mass bodies 105a and 105b and the first connecting portions 107a and 107b with respect to the mirror portion 101. 103. The second mass bodies 106a and 106 and the second connecting portions 108a and 108b are positioned between the mirror portion 101 and the ear portion 104a2, except that the first mass bodies 105a and 105b and the first connecting portions 107a, It is the same shape as 107b. Therefore, description of the shape is omitted. In addition, when not distinguishing 1st mass body 105a, 105b and 2nd mass body 106a, 106, it only calls a mass body. Moreover, when not distinguishing 1st connection part 107a, 107b and 2nd connection part 108a, 108b, it only calls a connection part.

[Size variation due to processing]
When mass production efficiency is considered, it is preferable to form a plurality of structures 100 by etching simultaneously from one large metal plate. However, when a plurality of structures 100 are etched at the same time, an individual whose etching shape is progressing with respect to the design shape and an individual who is behind are necessarily generated. 2 and 3, how much the size varies due to variations in the etching rate when the structure 100 is formed will be described. FIG. 2 shows a location where the size was measured after the structure 100 was etched. The resonance frequency of the optical scanner 10 is determined by the moment of inertia of the swinging portion and the rigidity of the beam portion. The rigidity is determined by the shape (length, width, thickness) of the beam portion. The beam portion has a sufficiently small width in the X direction with respect to the length in the Y direction. Therefore, even if the sizes in the X direction and the Y direction change by the same amount due to variations in the etching rate, the change in the width in the X direction greatly affects the rigidity. Therefore, as shown in FIG. 2, the width of the structure 100 in the X direction was measured.

  As shown in FIG. 3, three structural bodies 100 were prepared, and the width in the X direction of each part was measured for each sample (No. 1, No. 2, No. 3). In FIG. 3, the width in the X direction is shown as a ratio to the design value. No. 1, no. In the sample of 2, the etching process is almost as designed. However, in the beam portions (A to D), there is a variation in width in the X direction of about ± 1%. Moreover, about the mass bodies (E-L), the width | variety of the X direction was narrow about 5 to 10% with respect to the design value. On the other hand, no. In the sample No. 3, in the beam portions (A to D), the width in the X direction was narrowed by about 5% with respect to the design value. Further, regarding the mass bodies (E to L), the width in the X direction was narrowed by about 15% with respect to the design value.

[Effect of mass body]
As described above, when the structure 100 is formed by etching, the width in the X direction that affects the rigidity of the beam portion varies due to variations in the etching rate. This variation in rigidity leads to variations in the resonance frequency of the optical scanner 10. However, in the present embodiment, variation in the resonance frequency is suppressed by providing the first mass bodies 105a and 105b and the second mass bodies 106a and 106b. The reason will be described below.

  The resonance frequency in a structure having a mirror and both support beams like the structure 100 is expressed by the above (Equation 2). As described above, since the torsional elastic constant K changes due to variations in the etching rate, the resonance frequency also changes.

  Strictly speaking, the size of the mirror portion 101, that is, the moment of inertia I also changes due to variations in the etching rate. However, when the width of the beam portion is sufficiently narrow with respect to the mirror portion 101 as in the structure 100 of the present embodiment, the amount of inertia of the beam portion is larger than the amount of change in the inertia moment I due to the size change of the mirror portion 101. The amount of change in the torsional elastic constant K due to the width change in the X direction is larger. As a result, the resonance frequency changes due to variations in the etching rate. Here, from (Equation 1), if the amount of change in the moment of inertia I due to the variation in the etching rate is approximately the same as the amount of variation in the torsional elastic constant K, it is considered that the variation in the resonance frequency is suppressed. In the present embodiment, the mass body is coupled to the beam portion via the coupling portion. Since this mass body is separated from the beam by a predetermined distance, the mass body contributes greatly to the moment of inertia of the swinging portion. That is, when the variation in the etching rate occurs, the amount of change in the moment of inertia I increases due to the change in the size of the mass body. As a result, the amount of change in the inertia moment I is approximately the same as the amount of change in the torsional elastic constant K, and variations in resonance frequency are suppressed. Only from the viewpoint of increasing the amount of change of the inertia moment I, the mass body may be provided in the mirror portion 101. However, when the mass body is provided in the mirror unit 101, the mirror distortion increases when the mirror unit 101 swings. As a result, the optical characteristics are deteriorated such that the wavefront shape of the reflected light changes. In the present embodiment, since the mass body is provided in the beam portion, variations in resonance frequency are suppressed without deteriorating the optical characteristics of the mirror portion 101.

  This is expressed by Equation (1) above. In this embodiment, (Equation 1) indicates that “I1” is the moment of inertia about the swing axis L1 of the mirror portion 101, and “I2” is the moment of inertia about the swing axis L1 of the mass body. “K” corresponds to the torsional elastic constant of the beam portion. Strictly speaking, a change in the mass of the beam portion and the connecting portion caused by variations in the etching rate also changes the moment of inertia. However, the beam portion and the connecting portion are sufficiently close to the swing axis L1 as compared with the mirror portion 101 and the mass body. Therefore, the influence of the mass change of the beam part and the connecting part on the moment of inertia is sufficiently small to be negligible compared to the influence of the mass change of the mirror part 101 and the mass body on the moment of inertia. Therefore, in the above (Equation 1), the effects of the beam portion and the connecting portion are ignored. As described above, since the mass body is formed so as to satisfy (Equation 1), variation in resonance frequency is suppressed. The mass body preferably satisfies the above (Equation 3). Thus, the change amount of the moment of inertia I in the entire optical scanner system caused by the variation in the etching rate is balanced with the change amount of the torsional elastic constant K. As a result, variations in resonance frequency are suppressed.

[Change in resonance frequency]
With reference to FIG. 4, how much the variation in the resonance frequency is suppressed by providing the mass body will be described. The vertical axis in FIG. 4 represents the measured value of the resonance frequency of the optical scanner 10 created using the processed structure 100 and the value of the resonance frequency in the optical scanner 10 having the structure 100 having a size as designed. Is the ratio. The horizontal axis in FIG. 4 represents the ratio between the measured value of the width in the X direction of the beam portion of the structure 100 after processing and the value of the width in the X direction of the beam portion of the structure 100 at the design value. 4, the data of this embodiment indicated by circles and solid lines indicate the three samples (No. 1, No. 2, No. 3) described in FIG. The value on the horizontal axis of the data indicated by the circle and the solid line is a value obtained by averaging the widths in the X direction in A to D of FIG. On the other hand, the data indicated by the cross and the broken line is obtained by removing the first mass bodies 105a and 105b, the second mass bodies 106a and 106b, the first connection portions 107a and 107b, and the first connection portions 107a and 107b from the structure 100. This is the value obtained for the three samples. That is, the data indicated by the cross and the broken line can be said to be a comparative example having no features of the present invention.

  In the data of the comparative example, the beam width varies with a width of about 96 to 104%, and there is a variation in resonance frequency of about 96 to 104%. That is, the amount of change in beam width and the amount of change in resonance frequency correspond approximately one to one. On the other hand, in the data of the present embodiment, although the beam width varies in the range of about 93 to 100%, the variation of the resonance frequency is 99 to 100%, which is suppressed to about 1%. That is, by providing the mass body, it is possible to suppress variations in the resonance frequency of the optical scanner 10 even if a manufacturing error occurs in the form that the width of the beam portion varies.

[Configuration of Retina Scanning Display 1]
The optical scanner 10 described above can be used for the retinal scanning display 1 as a configuration for scanning light to form an image. FIG. 5 is a diagram for explaining the overall configuration of the retinal scanning display 1. The retinal scanning display 1 is a device that allows an observer to visually recognize a virtual image by projecting an image on the retina 54 using a light beam incident on the pupil 52 of the observer.

  The retinal scanning display 1 includes a control unit 1a and a head display unit 1b. The control unit 1a and the head display unit 1b are configured separately. The control unit 1a is attached to a user's waist, for example. The head display unit 1b is connected to the control unit 1a by a signal line capable of transmitting electrical and optical signals. The head display unit 1b is mounted on the user's head using, for example, a spectacle-shaped mounting tool as disclosed in, for example, US Patent Application Publication No. 2010/0073262. Of course, the control unit 1a and the head display unit 1b may be configured integrally.

  The control unit 1a includes a video signal processing circuit 3, a light source unit 30, and an optical multiplexing unit 40. The video signal processing circuit 3 generates a B signal, a G signal, an R signal, a horizontal synchronization signal, and a vertical synchronization signal for forming an image based on a video signal supplied from the outside.

The light source unit 30 includes a B laser driver 31, a G laser driver 32, an R laser driver 33, a B laser 34, a G laser 35, and an R laser 36. The B laser driver 31 drives the B laser 34 so as to generate a blue light beam having an intensity corresponding to the B signal from the video signal processing circuit 3. The G laser driver 32 drives the G laser 35 so as to generate a green light beam having an intensity corresponding to the G signal from the video signal processing circuit 3. The R laser driver 33 drives the R laser 36 so as to generate a red light beam having an intensity corresponding to the R signal from the video signal processing circuit 3. The B laser 34, the G laser 35, and the R laser 36 can be configured using, for example, a semiconductor laser or a solid-state laser with a harmonic generation mechanism.

  The optical combining unit 40 includes collimating optical systems 41, 42, and 43, dichroic mirrors 44, 45, and 46 for combining the collimated laser light, and condensing optics for condensing the combined laser light. A system 47. The blue laser light emitted from the B laser 34 is collimated by the collimating optical system 41. The collimated blue laser light is incident on the dichroic mirror 44. The green laser light emitted from the G laser 35 is collimated by the collimating optical system 42. The collimated green laser light is incident on the dichroic mirror 45. The red laser light emitted from the R laser 36 is collimated by the collimating optical system 43. The collimated red laser light is incident on the dichroic mirror 46. The blue, green, and red laser beams respectively incident on the dichroic mirrors 44, 45, and 46 are reflected or transmitted in a wavelength selective manner and are combined as one light beam, and reach the condensing optical system 47. The combined laser light is condensed by the condensing optical system 47 and guided to the head display unit 1b via an optical fiber or the like.

  The head display unit 1b includes a collimating optical system 20, a horizontal scanning driver 23, an optical scanner 10, a relay optical system 24, a vertical scanning driver 25, a vertical scanning scanner 26, and an eyepiece optical system 27.

  The collimating optical system 20 converts the laser light guided from the control unit 1a through an optical fiber or the like into parallel light. The laser light converted into parallel light enters the optical scanner 10.

  The optical scanner 10 scans the laser light from the collimating optical system 20 in the horizontal direction (for example, the left-right direction with respect to the observer's eyes). Specifically, the horizontal scanning driver 23 controls the swing state of the optical scanner 10 in accordance with the horizontal synchronization signal from the video signal processing circuit 3. The horizontally scanned laser light enters the relay optical system 24.

  The relay optical system 24 includes lens systems 24a and 24b having a positive refractive power. The lens system 24a is disposed at a position away from the optical scanner 10 at the focal length of the lens system 24a. Accordingly, the horizontally scanned laser light is refracted by the lens system 24a so that the optical axes thereof are parallel to each other. Further, the horizontally scanned laser light is converted into parallel light by the collimating optical system 20 and is therefore converted as focused light. In FIG. 5, the optical axis of the laser light is indicated by a dotted line, and the light beam of the laser light passing through the centers (= optical axes) of the relay optical system 24 and the eyepiece optical system 27 is indicated by a solid line. The lens system 24b is arranged at a position away from the lens system 24a by the total distance of the focal length of the lens system 24a and the focal length of the lens system 24b. Accordingly, the laser light that has passed through the lens system 24 a is refracted by the lens system 24 b so that the optical axes of the laser beams are focused on one point on the vertical scanner 25. The laser light converted as the focused light when passing through the lens system 24a is converted into parallel light again by the lens system 24b. That is, the relay optical system 24 functions to transfer the optical pupil (= laser beam incident point) formed in the optical scanner 10 onto the vertical scanner 25.

  The vertical scanner 25 scans the laser beam from the relay optical system 24 in the vertical direction (for example, the vertical direction with respect to the eyes of the observer). Specifically, the vertical scanner 25 has a reflecting surface that swings. As the reflecting surface swings, the laser light incident on the reflecting surface is scanned in the vertical direction. The vertical scanner 25 can be composed of, for example, an electromagnetic MEMS mirror that swings using a moving coil method. The vertical scanning driver 26 controls the swing state of the vertical scanner 25 according to the vertical synchronization signal from the video signal processing circuit 3. Here, since the laser light is scanned in the horizontal direction by the optical scanner 10, it becomes image light scanned two-dimensionally by the vertical scanner 25. The two-dimensionally scanned image light enters the eyepiece optical system 27.

  The eyepiece optical system 27 includes lens systems 27a and 27b having a positive refractive power. The eyepiece optical system 27 performs the function of transferring the optical pupil formed in the vertical scanner 25 to the pupil 52 of the observer's eye, like the relay optical system 24. The image light emitted from the eyepiece optical system 27 passes through the pupil 52 of the observer's eye and forms an image on the retina 54. Therefore, the observer visually recognizes the image.

<Modification>
The present invention is not limited to the embodiments described so far, and various modifications and changes can be made without departing from the spirit of the present invention. An example is described below.

  In the embodiment described above, the optical scanner 10 is driven by the piezoelectric drive unit 110. However, for example, an electromagnetic drive system such as a moving coil or a moving magnet, an electrostatic drive system, or the like may be employed. In short, it is sufficient that plate wave vibration is excited in the structure 100 in any method.

  In the above-described embodiment, in the retinal scanning display 1, the laser beam is scanned in the vertical direction after being scanned in the horizontal direction. However, for example, by replacing the optical scanner 10 and the vertical scanner 25, the laser beam may be scanned in the horizontal direction after being scanned in the vertical direction. Alternatively, the horizontal direction may be defined in the up-down direction with respect to the observer's eye, and the vertical direction may be defined in the left-right direction with respect to the observer's eye.

  In the above-described embodiment, the optical scanner 10 is used for the retinal scanning display 1. However, the optical scanner 10 may be used for any other purpose. As an example, the optical scanner 10 may be used in a laser projector 2 that forms an image of scanned laser light on a projection surface as shown in FIG. The laser projector 2 is different from the retinal scanning display 1 in an optical system subsequent to the vertical scanning scanner 25. Therefore, the description regarding the configuration common to the retinal scanning display 1 in the vertical scanning scanner 25 is omitted by adopting the same figure number. The imaging optical system 28 is a lens system having a positive refractive power. The imaging optical system 28 focuses the collimated laser beam from the vertical scanner 25 to form an image on a projection surface such as a screen. It is desirable that the imaging optical system 28 has a predetermined focus adjustment function in order to form an image on a projection surface at an arbitrary distance. Alternatively, if the beam diameter of the laser beam is sufficiently small, the imaging optical system 28 may be omitted. In this case, the parallel laser beam from the vertical scanning scanner 25 is directly imaged on the projection surface. Will be drawn. In this case, the light guide does not exert an optical action on the laser light.

DESCRIPTION OF SYMBOLS 1 Retina scanning display 1a Control unit 1b Head display unit 3 Video signal processing circuit 10 Optical scanner 20,41,42,43 Collimating optical system 23 Horizontal scanning driver 24 Relay optical system 24a, 24b, 27a, 27b Lens system 25 Vertical scanning Scanner 26 Vertical scanning driver 27 Eyepiece optical system 28 Imaging optical system 30 Light source unit 31 B laser driver 32 G laser driver 33 B laser driver 34 B laser 35 G laser 36 R laser 40 Optical multiplexing units 44, 45, 46 Dichroic mirror 47 Condenser optical system 52 Observer's pupil 54 Retina 100 of the observer Structure 101 Mirror part 102 First torsion beam 103 Second torsion beam 104 Outer edge part 104a1 First ear part 104a2 Second ear part 104b Main body part 104c Fixed part 105a , 105b First mass 1 6a, 106b second mass 107a, 107b first connecting portion 108a, 108b second connecting portion 110 piezoelectric driving unit 120 pedestal

Claims (10)

An optical scanner that is resonantly driven at a predetermined resonance frequency and scans incident light in a predetermined direction,
A mirror section that swings around the swing axis at the predetermined resonance frequency;
A beam portion having a first torsion beam coupled to the mirror portion and extending in parallel with the swing axis, and a second torsion beam coupled to the mirror portion and extending in a direction opposite to the first torsion beam. When,
An outer edge to which an end of the first torsion beam and an end of the second torsion beam are coupled;
A drive source for swinging the mirror part;
Between the mirror part and the outer edge part, a mass body spaced from the beam part, the mirror part and the outer edge part,
A connecting portion that connects the mass body and the beam portion;
The mass body is
In the beam portion, the mass body changes the predetermined width due to a change in the resonance frequency caused by a change in rigidity of the beam portion caused by a change in the width in the first direction orthogonal to the swing axis. It is configured to be suppressed by a change in moment of inertia about the swing axis generated by
An optical scanner characterized by that. An optical scanner that is resonantly driven at a predetermined resonance frequency and scans incident light in a predetermined direction,
A mirror section that swings around the swing axis at the predetermined resonance frequency;
A beam portion having a first torsion beam coupled to the mirror portion and extending in parallel with the swing axis, and a second torsion beam coupled to the mirror portion and extending in a direction opposite to the first torsion beam. When,
An outer edge to which an end of the first torsion beam and an end of the second torsion beam are coupled;
A drive source for swinging the mirror part;
Between the mirror part and the outer edge part, a mass body extending along the swing axis in a state of being separated from the beam part, the mirror part and the outer edge part,
A connecting portion that connects the mass body and the beam portion;
The torsional elastic constant in the beam portion is K, the moment of inertia of the mirror portion around the swing axis is I1, the moment of inertia of the mass body around the swing axis is I2,
The amount of change in K that occurs when the width in the first direction perpendicular to the swing axis in the beam portion changes by a predetermined width is ΔK, and the amount of change in I1 that occurs when the mirror portion changes by the predetermined width. ΔI1, when the amount of change of I2 that occurs when the mass body changes by the predetermined width is ΔI2,
The mass body is formed so as to satisfy the following relational expression.
The optical scanner according to claim 2, wherein the mass body is formed to satisfy the following relational expression.
The mass body is
Extending along the direction of the swing axis;
The optical scanner according to claim 1. The mass body is
Extending parallel to the swing axis,
The width in the first direction is formed to be constant.
The optical scanner according to claim 4. The connecting portion extends from the beam portion in the first direction,
The mass body extends symmetrically with respect to the connecting portion from the end of the connecting portion.
The optical scanner according to claim 1. A pair of the connecting portion and the mass body are provided symmetrically with respect to the beam portion;
The optical scanner according to claim 1. The mass body and the connecting portion are provided on both the first torsion beam and the second torsion beam.
The optical scanner according to claim 1. The mass body and the connecting portion are provided on both the first torsion beam and the second torsion beam so as to be symmetric with respect to the mirror portion.
The optical scanner according to claim 8. An optical scanner according to any one of claims 1 to 9, for forming an image by scanning light;
A light source for supplying light to the optical scanner;
An image projection apparatus comprising: a light guide unit that guides light scanned by the optical scanner to a projection surface.