Optical Scanning Device

Abstract

To provide an optical scanner with which, while reducing the device size, the quality of an optical beam emitted as scanning light is improved.SOLUTION: An optical scanner 10 comprises: a VCSEL 17 and an MEMS light deflector 20 that are mounted on a same board 15; a planar mirror 23 and a rotary mirror 25 for generating an optical path in which a light beam Lp emitted from the VCSEL 17 is entered to the MEMS light deflector 20; and a condenser lens 19 arranged between the VCSEL 17 and the planar mirror 23. A shield plate 41 has an elliptical aperture 42 and is attached to the planar mirror 23. The light beam Lp from the condenser lens 19 has its cross sectional circumferential edges cut by the elliptical aperture 42.SELECTED DRAWING: Figure 4A

Description

[Technical field]

[0001] The present invention relates to an optical scanning device equipped with a MEMS optical deflector. [Background technology]

[0002] Patent Document 1 discloses an optical scanning device equipped with a MEMS optical deflector. The optical scanning device is attached to one temple of a glasses-type head mount, emits scanning light from the MEMS optical deflector toward a lens and a half mirror arranged toward the front of the glasses, and projects an image onto the user's retina by the scanning light reflected by the half mirror.

[0003] According to the schematic diagram of Patent Document 1, in addition to an optical scanning device, a lens and a half mirror are mounted on the temple. The optical scanning device faces the half mirror with the lens in between. The laser light emitted from the optical scanning device scans along the mirror surface of the half mirror and is reflected by the mirror surface to project an image onto the retina of the user's eye. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6734532 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 does not disclose the specific positional relationship in which the light source, the MEMS optical deflector, and the substrate are mounted within the optical scanning device.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an optical scanning device which improves the quality of the light beam emitted as scanning light. [Means for solving the problem]

[0007] The optical scanning device of the present invention comprises: A substrate; a light source mounted on the substrate and configured to emit a light beam; a MEMS optical deflector mounted on the substrate, the MEMS optical deflector including a mirror portion having an upper surface side thereof as a mirror surface and an actuator for rotating the mirror portion back and forth around an axis; at least one optical path generating mirror that generates an optical path along which the light beam emitted from the light source is incident on the mirror portion of the MEMS optical deflector; a condenser lens disposed between the condenser lens and a light path generating mirror on which the light emitted from the light source is initially incident in the light path; a first shielding plate having a first elliptical aperture, the first shielding plate being disposed on the upstream side of the corresponding optical path generating mirror in the optical path, the corresponding optical path generating mirror being inclined in the same direction as the corresponding optical path generating mirror is inclined with respect to the optical axis of the optical path; Equipped with. Effect of the Invention

[0008] According to the present invention, the shielding plate disposed on the corresponding optical path generating mirror in the optical path has an aperture, whereby the peripheral low brightness area of ​​the optical beam is cut off by the aperture, and as a result, the optical beam can be improved to have a high contrast. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 2 is a plan view of the optical scanning device. [Figure 1B] FIG. 1B is a view taken along the arrow 1B in FIG. 1A. [Figure 1C] FIG. 1C is a view taken along the arrow 1C in FIG. 1A. [Figure 1D] FIG. 1B is a view taken along the arrow 1D in FIG. 1A. [Diagram 2] FIG. [Diagram 3] FIG. 1 is a diagram showing a glasses-type image display device 155 as an application example of an optical scanning device. [Figure 4A] 3 is a detailed diagram showing the positional relationship of optical elements of an optical scanning device arranged in the optical path of a light beam. FIG. [Figure 4B] 4B is a view taken along the arrow 4B in FIG. 4A. [Figure 4C] FIG. 4C is a view taken along the arrow 4C in FIG. 4A. [Figure 4D] FIG. 4D is a view taken along the arrow 4D in FIG. 4A. [Figure 4E] FIG. 4E is a view taken along the arrow 4E in FIG. 4A. [Diagram 5] 1 is a diagram showing the configuration of a main part of an optical scanning device having a concave mirror instead of a plate-shaped mirror. [Figure 6] 1A and 1B are diagrams showing the shape of a light spot when the projection screen is inclined with respect to the optical axis. [Figure 7] This is a schematic diagram of the main parts of an optical scanning device equipped with an RGB VCSEL. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A number of preferred embodiments of the present invention will be described in detail with reference to the drawings. It goes without saying that the present invention is not limited to the following embodiments. The present invention encompasses various configurations within the scope of the technical concept of the present invention in addition to the following embodiments. The same elements are designated by the same reference numerals throughout the drawings.

[0011] (Overall composition) Fig. 1A is a plan view of the optical scanning device 10, Fig. 1B is a view seen from the arrow 1B in Fig. 1A, Fig. 1C is a view seen from the arrow 1C in Fig. 1A, and Fig. 1D is a view seen from the arrow 1D in Fig. 1A. Figs. 1A to 1D show the optical scanning device 10 with the cover 33 (indicated by the dashed dotted line in Fig. 1B) removed.

[0012] The optical scanning device 10 includes a support frame 12. The support frame 12 has an L-shaped cross-sectional profile, and includes a bottom plate portion 13a and an upright plate portion 13b that are vertically coupled to each other. The substrate 15 is rectangular and is placed and fixed on the upper surface of the bottom plate portion 13a.

[0013] For ease of explanation, a three-axis Cartesian coordinate system is defined. The X-axis and Y-axis are defined as axes parallel to the longitudinal direction (direction parallel to the long side) and lateral direction (direction parallel to the short side) of the substrate 15, respectively. The Z-axis is defined as an axis parallel to the direction in which the upright plate portion 13b stands from the substrate 15.

[0014] Lp denotes a light beam. The path of the light beam Lp means the optical path of the light beam Lp. Lc is an optical axis serving as the central axis of the optical path of the light beam Lp. The optical path is static from the VCSEL 17 to the MEMS optical deflector 20. Since the light beam Lp is emitted as scanning light from the MEMS optical deflector 20, the optical path downstream from the MEMS optical deflector 20 becomes dynamic.

[0015] 1B, that is, from the end of the optical scanning device 10 on the negative side in the X-axis direction, the negative and positive sides in the X-axis direction will be referred to as the front and rear of the optical scanning device 10 as appropriate. Also, in the substrate 15, the positive and negative sides in the Z-axis direction are the upper and lower surfaces, respectively, so the positive and negative sides in the Z-axis direction will be defined as the upper and lower sides of the optical scanning device 10 as appropriate.

[0016] The VCSEL 17 and the MEMS optical deflector 20 are mounted on the upper surface of the substrate 15 with the X-axis direction as the aligned direction. The VCSEL 17 has an emission part 18 on its upper surface, and emits laser light from the emission part 18 upward in parallel with the Z-axis direction, i.e., straight up. The MEMS optical deflector 20 has the mirror surface of the rotating mirror 21 facing upward.

[0017] In this embodiment, the MEMS optical deflector 20 is a two-dimensional scanning MEMS optical deflector, but may be a one-dimensional scanning MEMS optical deflector. Various configurations of the MEMS optical deflector are known, and for example, the MEMS optical deflector described in JP 2017-207630 A (two-dimensional scanning MEMS optical deflector) or JP 2014-056020 A (one-dimensional scanning MEMS optical deflector) is selected.

[0018] The condenser lens 19 (FIG. 1B) is disposed close to and directly above the emission section 18. In FIGS. 1A-1D, the VCSEL 17 is shown as a single unit, but in an actual product, it is enclosed in a package (not shown). In the package enclosing the VCSEL 17, the part where the light beam from the emission section 18 is emitted is made of a transparent material such as quartz glass (e.g., Japanese Patent No. 4512330 and Japanese Unexamined Patent Publication No. 2009-027088). The condenser lens 19 is fixed (e.g., glued) to the inner or outer surface of such a transparent material, or the transparent part itself is processed as a condenser lens, and is positioned directly above the emission section 18.

[0019] Fig. 2 is a side view of the support frame 12. The support frame 12, the plate mirror 23, and the rotary mirror 25 will be described with reference to Figs. 1A to 1D and 2.

[0020] The standing plate portion 13b of the support frame 12 has an inclined groove 30 and a through hole 31. The inclined groove 30 has a rectangular cross section and opens obliquely upward and rearward on the side profile of the standing plate portion 13b. The bottom surface of the inclined groove 30 is formed as an inclined surface that is inclined at 45° with respect to the substrate 15. The through hole 31 is formed as a cylindrical hole that penetrates the standing plate portion 13b in the Y-axis direction.

[0021] In the X-axis direction, the center of the width (length in side view in FIG. 1B) of the inclined surface (bottom surface) of the inclined groove 30 is located at the same position as the emission portion 18 of the VCSEL 17. In the X-axis direction, the center line Co of the cylindrical hole of the through-hole 31 is located between the VCSEL 17 and the rotating mirror 21 of the MEMS optical deflector 20 in the X-axis direction. The center of the length of the inclined surface of the inclined groove 30 and the center line of the cylindrical hole of the through-hole 31 are located at the same position in the Z-axis direction, i.e., at the same height from the substrate 15.

[0022] The plate mirror 23 is made of a rectangular plate-like member, and with the lower plate surface serving as the mirror surface, one end of the plate mirror 23 is cantilevered and adhered to the slope of the inclined groove 30 by an adhesive such as resin. The plate thickness of the plate mirror 23 is set to be approximately equal to the depth of the inclined groove 30.

[0023] The plate width of the plate mirror 23 (length in side view in FIG. 1B) is slightly shorter than the width of the inclined groove 30 (length in side view in FIG. 1B). Therefore, before one end of the plate mirror 23 is bonded to the inclined groove 30, i.e., before the one end is fixed, the plate mirror 23 can be slightly displaced in the inclined bottom surface direction within the inclined groove 30, and the rotation angle around an axis parallel to the Y-axis can be changed. This change makes it possible to adjust the orientation of the mirror surface of the plate mirror 23 during the manufacture of the optical scanning device 10. The plate mirror 23 is fixed so that it cannot be displaced by bonding one end of the plate mirror 23 to the inclined groove 30.

[0024] The rotary mirror 25 has a flat mirror section 26 and a cylindrical fitting end 27 that is connected to one end of the mirror section 26 and fits into the through hole 31. The diameter of the fitting end 27 is slightly smaller than the diameter of the through hole 31. Therefore, before the fitting end 27 is bonded to the through hole 31, i.e., before it is fixed, the rotary mirror 25 is rotatable around the center line of the through hole 31 while fitting the fitting end 27 into the through hole 31, and is tiltable within a predetermined tilt angle range from a state in which the center line of the rotary mirror 25 is aligned with the center line Co (FIG. 1B) of the through hole 31. Therefore, the rotary mirror 25 is capable of rotational displacement within a larger angle range than the plate mirror 23. Such a rotatable and tiltable configuration makes it possible to adjust the orientation of the mirror surface as the lower surface of the mirror section 26 during the manufacture of the optical scanning device 10. After the adjustment, the fitting end 27 is bonded with an adhesive such as resin and fixed so that it cannot rotate.

[0025] The rotating mirror 21 of the MEMS optical deflector 20 is located not directly below the rotating mirror 25 but in front of it, that is, on the negative side in the X-axis direction with respect to the rotating mirror 25. In other words, the rotating mirror 21 of the MEMS optical deflector 20 is located obliquely below the rotating mirror 25.

[0026] As described later, this configuration contributes to making the emission direction of the light beam Lp from the optical scanning device 10 obliquely forward rather than perpendicular to the substrate 15. This configuration ensures that when the optical scanning device 10 is attached to the temples of eyeglasses as an eyeglass-type image display device 155 (smart glass image scanning device) which will be described in the following Fig. 3 as an example of use of the optical scanning device 10, the emitted light from the optical scanning device 10 reaches the inner lens surface of the eyeglasses without being interfered with by the user's face through a small gap between the image display device and the user's face.

[0027] 3 is a diagram showing a glasses-type image display device 155 as an application example of the optical scanning device 10. The glasses-type image display device 155 will be briefly described. The glasses-type image display device 155 includes a glasses body 160 and an image generating device 110 detachably attached to the glasses body 160 by an attachment member such as a clip 170. The glasses body 160 includes left and right temples 161a, 161b and a front frame 163 that is connected to the front ends of the left and right temples 161a, 161b at both left and right ends. The front frame 163 further includes left and right lens frame portions 164a, 164b and a bridge 165 that connects the left and right lens frame portions 164a, 164b.

[0028] The optical scanning device 10 is built into the image generating device 110 in a line arrangement along the extension direction of the temples 161b of the eyeglass body 160 together with other elements (e.g., a buffer amplifier for the MEMS sensor and an LDD (laser driver)). In this line arrangement, the optical scanning device 10 is arranged at the forefront, i.e., closest to the lens 167. Thus, the light beam Lp (FIG. 1B or FIG. 4A) emitted from the optical scanning device 10 is reflected by the lens 167. 167b The scanning area 172 is a half mirror, and the light beam Lp is reflected by the scanning area 172 to generate an image on the user's retina, which serves as a screen.

[0029] The cover 33 (FIG. 1B) extends along the contour of the upright plate portion 13b above the substrate 15, covers the upright plate portion 13b from above, and has the periphery of the opening on the lower end side fixed to the periphery of the bottom plate portion 13a. The cover 33 has a transparent portion 34 at least in a portion where a light beam Lp described below is emitted from the optical scanning device 10 as scanning light.

[0030] (Main components) Fig. 4A is a detailed diagram of the positional relationship of the optical elements of the optical scanning device 10 in which the optical path of the light beam Lp is arranged, Fig. 4B is a view taken along the arrow 4B in Fig. 4A, Fig. 4C is a view taken along the arrow 4C in Fig. 4A, Fig. 4D is a view taken along the arrow 4D in Fig. 4A, and Fig. 4E is a view taken along the arrow 4E in Fig. 4A. Fig. 4C is also a view taken along the arrow 4C' in Fig. 4A. Note that the views 4B-4E and 4C' in Fig. 4A are all located on the optical axis Cl.

[0031] In FIG. 4A, the right side on the drawing corresponds to the negative direction of the X axis, ie, the front, and the left side corresponds to the positive direction of the X axis, ie, the rear.

[0032] The condenser lens 19 and the plate mirror 23 are disposed directly above the emission part 18. The mirror surface of the plate mirror 23 faces diagonally downward toward the rotary mirror 25. The shielding plate 41 has an elliptical aperture 42, and is fixed (e.g., glued) to the mirror surface of the plate mirror 23. This allows the light beam Lp to enter and exit only within the range of the elliptical aperture 42 on the mirror surface of the plate mirror 23.

[0033] The focusing lens 19 is located between the exit portion 18 and the plate-shaped mirror 23 in the optical path of the light beam Lp, and after passing through the light beam Lp emitted from the exit portion 18 while expanding radially, the light beam Lp is emitted so as to be focused at a predetermined point downstream of the MEMS optical deflector 20 (in this example, the light spot 51 on the projection screen 50), i.e., so that the light beam Lp progresses while shrinking radially.

[0034] The rotating mirror 25 has the mirror surface of the mirror section 26 facing diagonally downward toward the plate mirror 23. The optical axis Cl extends parallel to the substrate 15 between the plate mirror 23 and the mirror section 26. The shielding plate 45 has an elliptical aperture 46, and is fixed (e.g., glued) to the mirror surface of the mirror section 26. As a result, the light beam Lp is incident on the mirror surface of the mirror section 26 of the rotating mirror 25 only within the range of the elliptical aperture 46. The plate mirror 23 has a mirror surface on the bottom. The shielding plate 41 has an elliptical aperture 42, and is fixed to the mirror surface of the plate mirror 23. As a result, the light beam Lp is incident on and exits from the mirror surface of the plate mirror 23 only within the range of the elliptical aperture 42.

[0035] The light spot 51 is generated on the projection screen 50 as a focal point of the light beam Lp by the condenser lens 19. The projection screen 50 is located at a predetermined distance away from the optical scanning device 10 along the optical path of the light beam Lp. In the optical scanning device 10 installed in the eyeglass-type image display device 155 (FIG. 3), the projection screen 50 serves as the user's retina. The light beam Lp emitted from the emission unit 18 of the VCSEL 17 is laser light that is sufficiently weakened so as not to harm the human eyes.

[0036] (action) The light beam Lp is emitted from the emission portion 18 of the VCSEL 17 perpendicularly to the substrate 15 and upward (positive direction in the Z-axis direction) while expanding in the radial direction. After passing through the condenser lens 19, the light beam Lp advances along the optical path while contracting in the radial direction until it reaches the focusing point of the condenser lens 19 (light spot 51 in this optical scanning device 10). After passing through the condenser lens 19, the light beam Lp then passes through the elliptical aperture 42 of the shielding plate 41 to reach the plate mirror 23.

[0037] In FIG. 4B, the elliptical aperture 42 is an ellipse when viewed from a direction perpendicular to the shielding plate 41 (the direction of the normal to the plate-shaped mirror 23), as shown in FIG. 4B. The shielding plate 41 has a surface inclined with respect to the optical axis Cl, and the elliptical aperture 42 is an ellipse having a major axis in the same direction as the inclination direction of the shielding plate 41 with respect to the optical axis Cl. Note that the inclination direction of the shielding plate 41 here is the direction that appears to overlap with the optical axis Cl of the light beam Lp when viewed from a direction perpendicular to the shielding plate 41 (the normal direction). In FIG. 4B, Da1 and Db1 are defined as the dimensions of the major axis and the minor axis of this ellipse, respectively. Da1 / Db1 is also defined as β1.

[0038] In FIG. 4C, the elliptical aperture 42 is closer to a perfect circle when viewed along the optical axis Cl from the upstream side (the focusing lens 19 side) and downstream side (the rotating mirror 25 side) than when viewed from a direction perpendicular to the shielding plate 41 (the normal direction); that is, the ratio of the major axis to the minor axis in the ellipse in FIG. 4C (in FIG. 4C, the elliptical aperture 42 is an ellipse that includes a perfect circle) is closer to 1 than β1 (1<β1). In FIG. 4C, the vertical axis is the major axis and the horizontal axis is the minor axis. Note that when viewed along the optical axis Cl, the diameter of the circle (the average value of the major and minor axes in the case of an ellipse) is defined as α1.

[0039] The light beam Lp emitted from the emission portion 18 of the VCSEL 17 and collected through the collecting lens 19 has a shape close to a perfect circle when viewed along the optical axis Cl (FIG. 4C). On the other hand, the irradiation shape Lp1 of the shielding plate 41 arranged at an angle with respect to the optical axis Cl becomes an ellipse (FIG. 4B). The elliptical aperture 42 has a shape similar to, but slightly smaller than, the irradiation shape Lp1. The elliptical aperture 42 is included inside the irradiation shape Lp1. In this way, the light beam Lp reflected by the plate mirror 23 and passing through the elliptical aperture 42 maintains a shape close to the original perfect circle when viewed from a direction along the optical axis Cl.

[0040] However, the elliptical aperture 42 becomes almost similar to the irradiation shape Lp1 when the influence of the thickness of the shielding plate 41 is small and does not need to be considered, and when the thickness is considered, the shape becomes slightly deformed. Also, as described above, the tilt angle of the plate mirror 23 is adjusted, so the tilt angle of the fixed shielding plate 41 changes, and the exact shape of the irradiation shape Lp1 is determined after the adjustment. For this reason, the relationship between the shapes of the elliptical aperture 42 and the irradiation shape Lp1 may deviate from similarity, but the directions of the major axes are both inclined directions with respect to the optical axis Cl of the shielding plate 41. Also, the elliptical aperture 42 and the irradiation shape Lp1 overlap so that the center positions of the ellipses, that is, the intersection points of the major and minor axes, coincide (FIG. 4B).

[0041] Here, the illuminance distribution in the cross section of the light beam Lp is considered, and a predetermined value γ1 is defined for the illuminance γ in the cross section. The illuminance γ of the cross section of the light beam Lp is maximum at the center of the cross section, i.e., at the intersection with the optical axis Cl, and decreases as it moves away from the optical axis Cl in the radial direction, eventually becoming illuminance=0. The irradiation shape Lp1 is defined as a region where the illuminance γ is equal to or greater than a predetermined value (the predetermined value (e.g., 0.3 times the maximum value of the illuminance γ) is greater than 0 and less than γ1 (e.g., 0.5 times the maximum value of the illuminance γ)). When simply referring to the irradiation region of the light beam Lp, it refers to a region where the illuminance is equal to or greater than the predetermined value, excluding areas on the irradiation surface of the light beam Lp where the illuminance is less than the predetermined value.

[0042] For ease of explanation, it is assumed that the light rays passing through each position on the cross section maintain the illuminance at that position (although in reality there is a loss) and reach the projection screen 50. The illuminance of the light spot 51 on the projection screen 50 is the illuminance produced when the incident points of the light rays on the projection screen 50 are gathered at the light spot 51.

[0043] By passing through elliptical aperture 42, the light beam Lp has its peripheral region in cross section cut off, in other words, the region in the radially outer direction where the illuminance γ is less than γ1. The region cut off is the region inside irradiation shape Lp1 and outside elliptical aperture 42 in FIG. 4B. As a result, light beam Lp immediately after being reflected by plate mirror 23 and emitted from elliptical aperture 42 becomes a light beam with a circular cross section with illuminance γ of γ1 or more. Light beam Lp then travels along the optical path toward rotary mirror 25.

[0044] The light beam Lp then passes through the elliptical aperture 46 of the shielding plate 45 and reaches the rotating mirror 25. The elliptical aperture 46 is an ellipse along the direction of the optical axis Cl from the direction perpendicular to the shielding plate 45 (the direction of the normal to the rotating mirror 25) like the elliptical aperture 42 of the shielding plate 41 (FIG. 4D). The illumination shape Lp2 of the illumination area of ​​the light beam Lp in the elliptical aperture 46 is an ellipse and is generated inside the ellipse of the elliptical aperture 46.

[0045] The dimensional ratio β between the major axis and the minor axis of the elliptical aperture 46 is β2 (=Da2 / Db2). There is a relationship β1≠β2.

[0046] When viewed along the optical axis direction from the upstream side (the plate mirror 23 side) and the downstream side (the MEMS optical deflector 20 side) (FIG. 4E), the elliptical aperture 46 is closer to a perfect circle than when viewed from a perpendicular direction, that is, a circle with the ratio of the major axis to the minor axis closer to 1 than β2. The diameter α of this circle is defined as α2. α1>α2.

[0047] The elliptical apertures 42, 46 have different inclination angles with respect to the optical axis Cl, and therefore the elliptical shapes are not similar. Therefore, although the elliptical apertures 42, 46 are both circular along the direction of the optical axis Cl, it is possible to set β1 ≠ β2. It is preferable that the major axis of the elliptical apertures 42, 46 of the shielding plates 41, 45 that are arranged at a larger inclination angle with respect to the optical axis Cl of the light beam Lp is longer, i.e., the dimension ratio β is larger.

[0048] The light beam Lp passes through the elliptical aperture 46 and is irradiated with an irradiation shape Lp2 onto the plate mirror 23. The irradiation shape Lp2 is an elliptical shape that is smaller than the elliptical aperture 46.

[0049] Although not shown in Fig. 4, the light beam Lp generates diffracted light when passing through the elliptical aperture 42 of the shielding plate 41. The diffracted light is weak light that spreads over a larger range than the light beam Lp. The shielding plate 45 prevents this diffracted light from being reflected by the plate-shaped mirror 23. In addition, the irradiation shape Lp2 is smaller than the elliptical aperture 46 and is entirely contained inside the elliptical aperture 46, thereby preventing further diffracted light from being generated from the shielding plate 45.

[0050] The light beam Lp emitted from the elliptical aperture 46 travels obliquely downward (in a direction away from the plate mirror 23 in the X-axis direction) and reaches the center of the rotating mirror 21 of the MEMS optical deflector 20.

[0051] The rotating mirror 21 of the MEMS optical deflector 20 rotates around two mutually intersecting axes in a non-resonant and resonant manner. The two axes are parallel to the X-axis and Y-axis, respectively, when the rotating mirror 21 is stationary. The light beam Lp emitted from the rotating mirror 21 becomes a scanning light for two-dimensional scanning due to the reciprocating rotation of the rotating mirror 21 around the two axes. The resonant frequency and the non-resonant frequency are, for example, 14 kHz or more and 60 Hz, respectively. The reciprocating rotation angle (non-concurrent side) of the rotating mirror 21 around the X-axis is smaller than the reciprocating rotation angle (concurrent side) of the rotating mirror 21 around the Y-axis.

[0052] In the embodiment, the reciprocating rotation of the rotating mirror 21 around the resonant axis and the reciprocating rotation of the rotating mirror 21 around the non-resonant axis will be described as corresponding to the horizontal and vertical directions of a projection screen 50, which will be described later, respectively.

[0053] The light beam Lp becomes scanning light by being reflected by the rotating mirror 21, is emitted from the optical scanning device 10, and scans a projection screen 50 outside the optical scanning device 10. A light spot 51 is generated at the irradiation point of the light beam Lp on the projection screen 50. The light spot 51 scanning the projection screen 50 generates a rectangular image area whose long sides are in the horizontal and vertical directions, respectively.

[0054] The area of ​​the upstream elliptical aperture 42 is larger than that of the elliptical aperture 46. Both the elliptical apertures 42, 46 are circular when viewed from the upstream side in the direction of the optical axis Cl, but the diameter of this circle of the upstream elliptical aperture 42 is larger than that of the elliptical aperture 46.

[0055] The effect of shaping the cross section of the light beam Lp can be improved by cutting the periphery of the light beam Lp in two stages, that is, by the elliptical aperture 42 of the shielding plate 41 and the elliptical aperture 46 of the shielding plate 45. In addition, the contrast between the light spot 51 and its surroundings can be increased more than in the case of cutting the periphery in one stage.

[0056] The shielding plates 41 and 45 are attached to the plate-shaped mirror 23 and the rotary mirror 25, respectively, by adhesive or the like.

[0057] 4, it is assumed that the projection screen 50 is a surface perpendicular to the optical axis Cl when the MEMS optical deflector 20 is stationary. The light spot 51 is designed to be ideally a perfect circle with the ratio of its major axis to its minor axis approaching 1.

[0058] However, depending on the application and the arrangement of the components, the projection screen 50 may have a surface that is inclined with respect to the optical axis Cl when the MEMS optical deflector 20 is stopped. In the case of the eyeglass-type image display device 155 in FIG. 3, the retina corresponds to the projection screen 50, but the optical scanning device 10 may be disposed at a position where the optical axis Cl of the light beam Lp when the MEMS optical deflector 20 is stopped is inclined with respect to the expected position of the retina. In that case, ofCompared to a plane perpendicular to the optical axis Cl, the light spot 51 formed is deformed to a shape elongated in the inclination direction of the optical axis Cl of the light beam Lp. Such deformation of the light spot 51 due to the position of the projection screen 50 can also occur in other applications, such as projectors. In the case of a projector, the projection screen 50 can be assumed to be a wall perpendicular to the surface on which the projector is placed.

[0059] Therefore, it is preferable that the cross-sectional shape of the light beam Lp irradiated from the optical scanning device 10 perpendicular to the optical axis Cl is an ellipse having a major axis perpendicular to the inclination direction of the optical axis Cl when the MEMS optical deflector 20 is stopped toward the projection screen 50 as previously assumed.

[0060] 6 is a diagram showing the shape of the light spot 51 when the projection screen 50 is tilted with respect to the optical axis Cl. The tilt direction of the projection screen 50 is the direction that appears to overlap with the optical axis Cl of the light beam Lp when viewed from a direction perpendicular to the projection screen 50 (normal direction). The light beam Lp, whose cross section perpendicular to the optical axis Cl is an ellipse, becomes a perfect circle on the projection screen 50. Even if the light beam Lp does not become an exact perfect circle, it is possible to make the ratio of the major axis to the minor axis of the light spot 51 on the projection screen 50 close to 1 by making the light beam Lp like this.

[0061] The cross-sectional shape of the light beam Lp perpendicular to the optical axis Cl can be shaped by adjusting the shapes of the elliptical aperture 42 of the shielding plate 41 and the elliptical aperture 46 of the shielding plate 45.

[0062] In the optical scanning device 10, the contrast of the light spot 51 on the projection screen 50 is increased by cutting the peripheral edge of the light beam Lp with the elliptical apertures 42 and 46. As a result, the quality of the image viewed by the user can be improved.

[0063] In the above embodiment, the diameter of the cross section perpendicular to the optical axis Cl of the light beam Lp is narrowed by focusing the light beam by the focusing lens 19, but the light beam may be parallel with a constant diameter. Even when the light beam is parallel, the lens is still called the focusing lens 19.

[0064] Furthermore, the number of VCSELs 17 is not limited to one, and for example, three VCSELs 17 of three colors, RGB, may be arranged and used. In this case, a plate-like mirror 23 is provided for each VCSEL 17. Furthermore, by using the plate-like mirror 23 as a dichroic mirror, each VCSEL 17 can be aligned.

[0065] Although two shielding plates, 41 and 45, are used, at least one shielding plate is sufficient.

[0066] 7 is a schematic diagram of the main part of an optical scanning device 61 equipped with RGB VCSELs 17R, G, and B. The VCSELs 17R, G, and B are mounted in a row in the X-axis direction on a common substrate 15 (FIG. 1A). Directly above each of the VCSELs 17R, G, and B, a condenser lens 19 and a dichroic mirror 65 are arranged to face each other.

[0067] The R, G, and B light beams emitted directly upward from the VCSELs 17R, 17G, and 17B pass through the condenser lens 19 and the dichroic mirror 65 to generate an integrated light beam Lp. The light beam Lp travels parallel to the substrate 15 toward the rotating mirror 25, has its peripheral portion cut off by the elliptical aperture 46 of the shielding plate 45, and then travels toward the MEMS optical deflector 20.

[0068] The optical scanning device 61 does not have the shielding plate 41. The elliptical aperture 46 of the shielding plate 45 is smaller than the irradiation area of ​​the light beam Lp on the shielding plate 45 and has the function of shaping the light beam Lp, that is, the same function as the elliptical aperture 42 in the embodiment of FIG.

[0069] (Another embodiment) 5 is a configuration diagram of a main part of the optical scanning device 10 having a concave mirror 53 instead of the plate-like mirror 23. The concave mirror 53 is fixed (e.g., glued) at its periphery to the shielding plate 41 so as to face the elliptical aperture 42 from the upper surface side of the shielding plate 41. The concave mirror 53 can also be manufactured by integral molding with the shielding plate 41, for example, using a predetermined mold. When the concave mirror 53 is used instead of the plate-like mirror 23, one end of the shielding plate 41 is extended toward the inclined groove 30 (FIG. 2, etc.) and is directly fixed to the inclined groove 30.

[0070] (Variations, etc.) In the optical scanning device 10 of the embodiment, a VCSEL 17 is used as the light source. The light source of the present invention is not limited to the VCSEL 17, and other than the VCSEL 17, for example, an edge emitting laser can also be selected.

[0071] In the optical scanning device 10, the VCSEL 17 emits light with the optical axis Cl directly upward. In the optical scanning device of the present invention, the light source does not have to emit the light beam upward (e.g. directly upward). In the optical scanning device of the present invention, even if the light source emits the light beam in a direction other than upward, it is sufficient that the multiple optical path generating mirrors generate optical paths such that the light beam emitted from the light source is incident on the mirror portion of the MEMS optical deflector.

[0072] In the optical scanning device 10, the shading plates 41 and 45 are attached to the plate mirror 23 and the rotary mirror 25, which are the corresponding optical path generating mirrors, by mounting or the like. In the optical scanning device of the present invention, the shading plates can also be arranged on the optical path upstream of the corresponding optical path generating mirror and separated from the corresponding optical path generating mirror. In this case, the shading plate arranged on the optical path upstream of the corresponding optical path generating mirror and separated from the corresponding optical path generating mirror must be arranged so as not to interfere with the optical path downstream of the corresponding optical path generating mirror.

[0073] In the optical scanning device 10, the shielding plates 41 and 45 are disposed parallel to the plate mirror 23 and the rotary mirror 25 as the corresponding optical path generating mirrors. In contrast, the concave mirror 53 in Fig. 5 has a curved mirror surface, so the concept of parallelism with respect to the shielding plate 41 cannot be defined. Including the plate mirror 23, the rotary mirror 25, and the concave mirror 53, a normal line is set at the intersection of the optical axis Cl on the incident side with the shielding plate and the optical path generating mirror, and the normal line of the shielding plate and the optical path generating mirror with respect to the optical axis Cl on the incident side are defined as the inclination angles of the shielding plate and the optical path generating mirror. At that time, the inclination angle of the shielding plate and the inclination angle of the optical path generating mirror are mutually equal. [Explanation of symbols]

[0074] 10,61···Optical scanning device, 17···VCSEL, 19···Condenser lens, 20···MEMS optical deflector, 21···Pivoting mirror, 23···Plate mirror (mirror for generating optical path), 25···Rotary mirror (mirror for generating optical path), 41,45···Shielding plate, 42,46···Elliptical aperture, 53···Concave mirror (mirror for generating optical path).

Claims

1. A substrate; a light source mounted on the substrate and configured to emit a light beam; a MEMS optical deflector mounted on the substrate, the MEMS optical deflector including a mirror portion having an upper surface side thereof as a mirror surface and an actuator for rotating the mirror portion back and forth around an axis; at least one optical path generating mirror that generates an optical path along which the light beam emitted from the light source is incident on the mirror portion of the MEMS optical deflector; a condenser lens disposed between the condenser lens and a light path generating mirror on which the light emitted from the light source is initially incident in the light path; a first shielding plate having a first elliptical aperture, the first ellipsoidal aperture being disposed upstream of the corresponding optical path generating mirror in the optical path, the corresponding optical path generating mirror being inclined in the same direction as the corresponding optical path generating mirror is inclined with respect to the optical axis of the optical path; An optical scanning device comprising:

2. 2. The optical scanning device according to claim 1, the first shielding plate is attached to the corresponding optical path generating mirror; An optical scanning device characterized in that the first elliptical aperture of the first shading plate is circular in shape, when viewed in the optical axis direction from the downstream side of the corresponding optical path generating mirror in the optical path, with a ratio of the major axis to the minor axis closer to 1 than when the first shading plate is viewed from a vertical direction.

3. 3. The optical scanning device according to claim 1, Further, a second shielding plate having a second elliptical aperture is provided on the optical path downstream of the first shielding plate, An optical scanning device, characterized in that the ratios of the major axis and the minor axis of the elliptical apertures in each shielding plate are different from each other.

4. 4. The optical scanning device according to claim 3, An optical scanning device, wherein an aperture area of ​​the elliptical aperture of the second shielding plate is smaller than an aperture area of ​​the elliptical aperture of the first shielding plate.

5. 5. The optical scanning device according to claim 1, 2. An optical scanning device, wherein at least one of the optical path generating mirrors is a concave mirror.

6. 3. The optical scanning device according to claim 1, Further, a second shielding plate having a second aperture is disposed downstream of the first shielding plate on the optical path, The light beam forms an illumination area larger than the first elliptical aperture with respect to the first shielding plate; 2. An optical scanning device according to claim 1, wherein the second shielding plate is disposed at a position where the light beam passes inside a second aperture.

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