Optical system

Abstract

This optical system comprises: a light source that emits a light beam; a first sub-optical system that converges the light beam; a first scanning element that scans the light beam in a first direction; a second sub-optical system that includes a plurality of optical surfaces including a first refraction surface, a second refraction surface, and one or more reflection surfaces; and a second scanning element that scans the light beam emitted from the second refraction surface in a second direction orthogonal to the direction of the optical path of the light beam and the first direction. The optical path of the light beam emitted by the light source is in the order of the first sub-optical system, the first scanning element, the second sub-optical system, and the second scanning element. Any one of the plurality of optical surfaces has a rotationally asymmetric shape, and has, with respect to the light beam, diverging power in the first direction and converging power in the second direction.

Description

optical system

[0001] The present disclosure relates to an optical system that scans light emitted from a light source using a scanning element.

[0002] Patent Document 1 discloses an optical system having two scanning elements that scan an irradiated laser beam in two directions. A prism is disposed between the two scanning elements. A two-dimensional image is projected by scanning the laser beam in two directions.

[0003] International Publication No. 2020 / 218035

[0004] There is a demand for further reduction in the size of optical systems.

[0005] The present disclosure provides a miniaturized optical system.

[0006] The optical system disclosed herein includes a light source that emits a light beam, a first sub-optical system that converges the light beam, a first scanning element that scans the light beam in a first direction, a second sub-optical system having a plurality of optical surfaces including a first refractive surface, a second refractive surface, and one or more reflective surfaces, and a second scanning element that scans the light beam emitted from the second refractive surface in a second direction that is orthogonal to the direction of the optical path of the light beam and the first direction. The optical path of the light beam emitted from the light source is in the order of the first sub-optical system, the first scanning element, and the second sub-optical system. Any one of the plurality of optical surfaces has a rotationally asymmetric shape and has diverging power in the first direction and converging power in the second direction with respect to the light beam.

[0007] Another optical system of the present disclosure is an optical system in which a light beam is incident from a first scanning element that scans the light beam in a first direction, the optical system having a plurality of optical surfaces including a first refractive surface, a second refractive surface, and one or more reflecting surfaces, any one of the plurality of optical surfaces having a rotationally asymmetric shape and having diverging power with respect to the light beam in the first direction and converging power in a second direction that is orthogonal to the direction of the optical path of the light beam and the first direction.

[0008] The optical system in the present disclosure can provide a compact optical system.

[0009] 1 is a perspective view showing the configuration of an optical system according to embodiment 1; FIG. 2 is a cross-sectional view in the YZ plane showing the configuration of the optical system; FIG. 3 is a cross-sectional view in the XZ plane showing the configuration of the optical system; FIG. 4 is an explanatory view showing the difference between the shape of the first refractive surface of the second sub-optical system along the first direction and the shape of the first refractive surface along the second direction; FIG. 5 is a cross-sectional view in the YZ plane of the periphery of the first refractive surface; FIG. 6 is a cross-sectional view in the XZ plane showing the first scanning element before and after scanning; FIG. 7 is a cross-sectional view of the first refractive surface in the YZ plane; 15 is a cross-sectional view in the YZ plane showing the first scanning element before and after scanning; FIG. 16 is an explanatory diagram showing the positional relationship of SAG(Xi, 0); FIG. 17 is an explanatory diagram showing the positional relationship of SAG(Xi, -Yis); FIG. 18 is a plot showing the relationship between (SAG(Xi, -Yis) - SAG(Xi, 0)) / Yis and scanning distortion; FIG. 19 is an explanatory diagram showing the optical path when the first refracting surface is concave in the V-axis direction when the first scanning element is not scanned and when it is scanned; FIG. 19 is an explanatory diagram showing the footprint on the first reflecting surface when the first refracting surface is concave; FIG. 20 is an explanatory diagram showing the optical path when the first refracting surface is flat in the V-axis direction; FIG. 1 is an explanatory diagram showing a footprint in an optical path when the first refracting surface is convex in the V-axis direction; FIG. 2 is an explanatory diagram showing a footprint on the first reflecting surface when the first refracting surface is convex; FIG. 3 is an explanatory diagram showing a light path when the first refracting surface is concave in the H-axis direction; FIG. 4 is an explanatory diagram showing a light path when the first refracting surface is flat in the H-axis direction; FIG. 5 is an explanatory diagram showing a light path when the first refracting surface is convex in the H-axis direction;

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the inventor(s) provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] 1 to 22. In this embodiment, as shown in Fig. 2, for example, the Z direction is the direction in which the light ray Lg emitted from the light source 2 travels, the X direction and the Y direction are perpendicular to each other, and the Z direction is the direction perpendicular to the XY plane.

[0012] [1-1. Configuration] Fig. 1 is an overall view showing the configuration of an optical system 1 according to embodiment 1. Fig. 2 is a cross-sectional view in the YZ plane showing the configuration of the optical system 1 according to embodiment 1. Fig. 3 is a cross-sectional view in the XZ plane (including the first direction) showing the configuration of the optical system 1 according to embodiment 1.

[0013] The optical system 1 includes a light source 2, a first sub-optical system 3, a first scanning element 4, a second sub-optical system 5, a third sub-optical system 6, and a second scanning element 7.

[0014] The light source 2 emits a light beam Lg toward the first sub-optical system 3. The light source 2 is, for example, a semiconductor laser. The light beam Lg emitted from the light source 2 is parallel light. The light beam Lg has multiple wavelengths or wavelength ranges, for example, red (R), green (G), and blue (B). The light source 2 may emit a light beam Lg in which red, green, and blue light are mixed into a single beam, or may sequentially emit light beams Lg in the wavelength ranges of each color.

[0015] The first sub-optical system 3 converges the light beam Lg and emits it toward the first scanning element 4. The first sub-optical system 3 includes a lens element with a converging effect. The first sub-optical system 3 has an entrance surface S1, a cemented surface S2, and an exit surface S3. The first sub-optical system 3 is, for example, a positive lens. Note that the first sub-optical system 3 may also be an element with a converging effect, such as a reflective element or a diffractive element. By converting the parallel light beam Lg from the light source 2 into a converging beam in the first sub-optical system 3, the optical path length of the entire optical system 1 can be shortened. The light beam Lg, which has been converted into a converging beam by the first sub-optical system 3, is scanned in the H-axis direction by the first scanning element 4 and reflected toward the second sub-optical system 5. In FIG. 1 , the first sub-optical system 3 is composed of two lens elements, but this is not limited thereto and may be composed of one lens element or three or more lens elements.

[0016] As shown in FIGS. 1 to 3 , the first scanning element 4 scans the incident light beam Lg in the H-axis direction, which is a first direction. The H-axis direction is the lateral direction (horizontal direction) in a viewing area where the light beam Lg is visible as a two-dimensional image. The first scanning element 4 is, for example, a MEMS (Micro Electro Mechanical System) scanner having a mirror S5 that is driven to rotate around a rotation axis tilted from the Y-axis direction by piezoelectric driving. The mirror S5 has a rotation axis that is perpendicular to the first direction, and the light beam Lg is diffused in the H-axis direction. The light beam Lg scanned in the H-axis direction is incident on a first refractive surface S7 of the second sub-optical system 5.

[0017] The second sub-optical system 5 performs aberration correction on the light beam Lg expanded in the first direction by the first scanning element 4. The second sub-optical system 5 has multiple optical surfaces, including a first refractive surface S7 which is an entrance surface and a second refractive surface S10 which is an exit surface. The second sub-optical system 5 further has one or more reflective surfaces along the optical path from the first refractive surface S7 to the second refractive surface S10. In this embodiment, the second sub-optical system 5 has, for example, a first reflective surface S8 and a second reflective surface S9. The second sub-optical system 5 is, for example, a prism made of resin or glass. When the second sub-optical system is a prism, the spaces between the first refracting surface S7, the first reflective surface S8, the second reflective surface S9, and the second refracting surface S10 are filled with resin or glass material.

[0018] The first refractive surface S7 faces the first scanning element 4, and the light ray Lg scanned in the H-axis direction by the first scanning element 4 passes through the first refractive surface S7 and enters the second sub-optical system 5. The first refractive surface S7 and the first reflecting surface S8 face each other, and the light ray Lg incident on the first refractive surface S7 is reflected by the first reflecting surface S8 into the second sub-optical system 5.

[0019] Refer to FIG. 4. FIG. 4 is an explanatory diagram showing the difference between the shape of the first refractive surface S7 of the second sub-optical system 5 along the first direction and the shape along the second direction. FIG. 4 shows the amount of sag, with the negative value being in the traveling direction of the light ray Lg and the positive value being in the direction opposite to the traveling direction of the light ray Lg. The first refractive surface S7 has a rotationally asymmetric shape and has diverging power in the H-axis direction with respect to the light ray Lg incident on the first refractive surface S7 from the first scanning element 4, i.e., when viewed in the direction of the optical path, and has converging power in the V-axis direction, which is perpendicular to the optical path direction of the light ray Lg and the H-axis direction. For example, the first refractive surface S7 has a concave optical surface shape in the H-axis direction and a convex optical surface shape in the V-axis direction with respect to the light ray Lg incident on the first refractive surface S7 from the first scanning element 4, i.e., when viewed in the direction of the optical path.

[0020] Because the first refracting surface S7 has a rotationally asymmetric shape, it is possible to perform appropriate aberration correction in both the first and second directions. Because the first refracting surface S7 has a concave shape in the H-axis direction, it is possible to suppress lateral chromatic aberration and achieve high performance. Furthermore, because the first refracting surface S7 has a convex shape in the V-axis direction, it is possible to reduce the luminous flux of the light ray Lg at the first reflecting surface S8, which is the second surface in the second sub-optical system 5. This allows the diameter of the first reflecting surface S8 to be reduced, thereby achieving a compact second sub-optical system 5. Furthermore, it is possible to achieve good spherical aberration correction for the light ray Lg, which is a convergent light beam, incident on the second sub-optical system 5.

[0021] The first reflecting surface S8 reflects the light ray Lg that has traveled from the first refracting surface S7 toward the second reflecting surface S9.

[0022] The second reflecting surface S9 reflects the light ray Lg that has traveled from the first reflecting surface S8 toward the second refracting surface S10.

[0023] The light ray Lg reflected by the first reflecting surface S8 is reflected again by the second reflecting surface S9, which is arranged opposite the second refractive surface S10, into the second sub-optical system 5. The light ray Lg reflected by the second reflecting surface S9 proceeds to the second refractive surface S10 and is emitted from the second refractive surface S10 to the outside of the second sub-optical system 5.

[0024] The first refractive surface S7, the first reflecting surface S8, the second reflecting surface S9, and the second refractive surface S10 each have a different curvature in the H-axis direction and the V-axis direction, and therefore have a free-form surface shape.

[0025] The first reflecting surface S8 and the second reflecting surface S9 each have a concave shape with respect to the incident light.

[0026] The second refractive surface S10 of the second sub-optical system 5 may also have a configuration similar to that of the first refractive surface S7. As shown in Fig. 4, for example, the second refractive surface S10 has a curvature along the V-axis direction along which the second scanning element 7 scans, and has a concave portion directed toward the inside of the second sub-optical system 5.

[0027] The third sub-optical system 6 converges the light beam Lg incident from the second sub-optical system 5 onto the second scanning element 7. The first sub-optical system 3 includes a lens element having a converging effect. The third sub-optical system 6 has an incident surface S12, a cemented surface S13, and an exit surface S14. The third sub-optical system 6 is, for example, a positive lens. Note that the third sub-optical system 6 may also be a reflective surface having a converging effect.

[0028] The second scanning element 7 scans and reflects the light beam Lg emitted from the emission surface S14 of the third sub-optical system 6 in the V-axis direction, which is the second direction. The second scanning element 7 is, for example, a MEMS scanner having a mirror S16 that is driven to rotate around the X-axis direction by piezoelectric driving. The light beam Lg is diffused in the V-axis direction with the rotation axis being a direction perpendicular to the second direction. The second scanning element 7 also scans in synchronization with the first scanning element 4, which allows a two-dimensional image to be projected onto the projection surface 19.

[0029] The optical system 1 in this embodiment is arranged, in order on the optical path from the light source 2, the first scanning element 4, the first refractive surface S7 of the second sub-optical system 5, the first reflective surface S8 of the second sub-optical system 5, the second reflective surface S9 of the second sub-optical system 5, the second refractive surface S10 of the second sub-optical system 5, and the second scanning element 7. Therefore, the second sub-optical system 5 is arranged on the optical path from the first scanning element 4 to the second scanning element 7.

[0030] As shown in Figure 2, within the second sub-optical system 5, the intermediate imaging position Ph where the H-axis component of the light beam of ray Lg forms an intermediate image and the intermediate imaging position Pv where the V-axis component of the light beam of ray Lg forms an intermediate image are located at different positions.

[0031] The intermediate imaging position Ph is located, for example, between the first reflecting surface S8 and the second reflecting surface S9, and is located, for example, within half the distance from the first reflecting surface S8 to the first reflecting surface S8 and the second reflecting surface S9, which is the optical surface onto which the light reflected by the first reflecting surface S8 is incident.

[0032] The intermediate image position Pv is located, for example, between the first refractive surface S7 and the first reflecting surface S8. The intermediate image position Pv is located, for example, at a position from the first reflecting surface S8 within half the distance between the first refractive surface S7 and the first reflecting surface S8.

[0033] The intermediate imaging position Ph of the H-axis component of the light ray Lg is not at the same position as the intermediate imaging position Pv of the V-axis component of the light ray Lg. As a result, the pupil diameter of the light ray Lg at the intermediate imaging position Ph has a linear shape extending in the V-axis direction. As a result, it is possible to prevent the pupil diameter of the light ray Lg from disappearing even if dust or a scratch is present at the intermediate imaging position Ph.

[0034] Furthermore, at the intermediate imaging position Pv of the V-axis direction component of the light ray Lg, the pupil diameter of the light ray Lg exists before the H-axis direction component of the light ray Lg forms an image. In this way, the pupil diameter of the light ray Lg at the intermediate imaging position Pv also has a linear shape extending in the H-axis direction. As a result, it is possible to prevent the pupil diameter of the light ray Lg from disappearing even if dust or a scratch is present at the intermediate imaging position Pv.

[0035] Next, the shape of the first refractive surface S7 will be described in more detail with reference to Fig. 5. Fig. 5 is a YZ cross-sectional view of the periphery of the first refractive surface S7.

[0036] Let Yi be the radius of the light beam size in the H-axis direction on the first refracting surface S7, SAG(0,Yi) be the amount of sag at the coordinate (0,Yi) on the first refracting surface S7, and SAG(Yi,0) be the amount of sag at the coordinate (Yi,0) on the first refracting surface S7. In other words, SAG(0,Yi) is the amount of sag in the V-axis direction on the first refracting surface S7, and SAG(Yi,0) is the amount of sag in the H-axis direction on the first refracting surface S7. The first refracting surface S7 satisfies the relationship: SAG(0,Yi) / SAG(Yi,0)<0 (1).

[0037] The beam size radius Yi will now be described. In FIG. 5 , a virtual convergent light Lg1 is assumed when the first scanning element 4 is not present, and the relationship between the virtual convergent light Lg reflected by the first scanning element 4 and the beam size radius Yi will now be described. The effective diameter at the exit surface S3 of the first sub-optical system 3 is Rd, the total distance of the distance S4 from the first sub-optical system 3 to the first scanning element 4 and the distance S6 from the first scanning element 4 to the first refractive surface S7 is La, and the exit angle of the beam Lg from the first sub-optical system 3, i.e., the exit angle of the convergent light Lg1, is Yd. The exit angle Yd is the angle between the optical axis and the marginal ray. The distance between the outer diameter of the effective diameter at the exit surface S3 of the first sub-optical system 3 and the beam size radius Yi of the virtual convergent light Lg1 is r2. The relationship between the distance r2, the total distance La, and the angle Yd is approximately expressed by the following equation (2): r2 / La=tan(Yd) (2) Transforming equation (2) leads to equation (3): r2=La×tan(Yd) (3) Furthermore, the relationship between the beam size radius Yi of the convergent light Lg1, the effective diameter Rd, and the distance r2 is expressed by the following equation (4): Yi=Rd−r2 (4) Therefore, the beam size radius Yi of the convergent light Lg1 can be approximated from equations (3) and (4) by the following equation (5): Yi=Rd−La×tan(Yd) (5)

[0038] Since formula (1) is satisfied, the first refractive surface S7 has a concave shape in the H-axis direction, which can suppress lateral chromatic aberration, thereby achieving high performance. Furthermore, the first refractive surface S7 has a convex shape in the V-axis direction, which can suppress the light beam size at the first reflecting surface S8, thereby contributing to the miniaturization of the second sub-optical system 5.

[0039] Next, the shape of the first refractive surface S7 will be described in more detail with reference to Fig. 6. Fig. 6 is a cross-sectional view in the XZ plane showing the first scanning element 4 before and after scanning. In Fig. 6, the first scanning element 4 before scanning is shown by a solid line, and the first scanning element 4 at maximum scanning is shown by a dotted line.

[0040] In FIG. 6, if Xi is the position of the chief ray in the X direction on the first refracting surface S7 and SAG(Xi, 0) is the amount of sag at (Xi, 0) on the first refracting surface S7, the first refracting surface S7 satisfies the relationship SAG(Xi, 0) / Xi>0 (6).

[0041] If the distance between the first scanning element 4 and the first refractive surface S7 is Lb, the X-direction emission angle from the first scanning element 4 when the first scanning element 4 is not scanning is Xfza, and the X-direction emission angle from the first scanning element 4 when the first scanning element 4 is scanning at maximum is Xfzz, the X-direction chief ray position Xi can be approximated by the following equation: Xi / Lb=tan(Xfzz-Xfza) (7) Transforming equation (7) yields equation (8): Xi=Lb×tan(Xfzz-Xfza) (8)

[0042] When the formula (6) is satisfied, the first refractive surface S7 has a concave shape in the H-axis direction, so that chromatic aberration of magnification can be suppressed.

[0043] Next, the shape of the first refracting surface S7 will be described in more detail with reference to Fig. 7. Fig. 7 is a cross-sectional view of the first refracting surface S7 in the YZ plane.

[0044] In FIG. 7, if AveSAG(0, Yi) is the average value of the sag amounts (0, Yi) and (0, −Yi) on the first refractive surface S7, the ratio of AveSAG(0, Yi) to the light beam size radius Yi satisfies the relationship Emin<AveSAG(0, Yi) / Yi<Emax (9).

[0045] Figure 8A is a plot diagram showing the relationship between AveSAG(0, Yi) / Yi and the footprint size FP_Y at the first reflecting surface S8. Figures 8B to 8D are plot diagrams showing the relationship between AveSAG(0, Yi) / Yi and the footprint size FP_|Y| at the first reflecting surface S8, with the footprint size FP_Y in Figure 8A shown as an absolute value. Figure 8A shows a region Rg1 of AveSAG(0, Yi) / Yi where the condition of equation (9) (AveSAG(0, Yi) / Yi<0.00) is satisfied when Emin has no value (no lower limit) and Emax = 0.00. If AveSAG(0, Yi) / Yi is a value within this region Rg1, the refractive power of the first refractive surface S7 has a positive (convex) power, which reduces the diameter of the light beam at the first reflecting surface S8 and contributes to the miniaturization of the first reflecting surface S8.

[0046] See FIG. 8B . In region Rg2 of FIG. 8B , when AveSAG(0,Yi) / Yi is equal to or greater than the upper limit Emax=0.00, this means that AveSAG(0,Yi) is relatively large or the beam size radius Yi is relatively small. When AveSAG(0,Yi) is relatively large in region Rg2, the refractive power of the first refractive surface S7 becomes negative (concave), making aberration correction difficult. To correct this, the number of reflective surfaces of the second sub-optical system 5 must be increased, which increases the size of the second sub-optical system 5. Furthermore, when the beam size radius Yi is relatively small in region Rg2, the beam size is too small to be practical. Region Rg3 in Figure 8B indicates the range of AveSAG(0, Yi) / Yi where the condition of equation (9) (AveSAG(0, Yi) / Yi<0.00) is satisfied when Emin has no value (no lower limit) and Emax = 0.00. Region Rg4 in Figure 8B indicates the range of AveSAG(0, Yi) / Yi where the condition of equation (9) (AveSAG(0, Yi) / Yi<-0.022) is satisfied when Emin has no value (no lower limit) and Emax = -0.022. Within the range of region Rg4, an intermediate imaging position Pv of the V-axis direction component of light ray Lg is provided between first refractive surface S7 and first reflecting surface S8. When AveSAG(0, Yi) / Yi is below the upper limit Emax=-0.022, and AveSAG(0, Yi) is relatively small, the positive refractive power of the first refractive surface S7 can be increased, the distance between the intermediate imaging positions Pv and Ph can be increased, and the effects of dust and scratches can be reduced. In region Rg4 of Figure 8B, when the light beam size radius Yi is appropriate so that AveSAG(0, Yi) / Yi is below the upper limit Emax=-0.022, the light beam size becomes more appropriate and aberration correction becomes easier.

[0047] Next, reference is made to FIG. 8C . FIG. 8C shows a region Rg5 of AveSAG(0, Yi) / Yi where the condition of equation (9) is satisfied when Emin = −0.08 and Emax = 0.00. When AveSAG(0, Yi) / Yi is equal to or less than the lower limit Emin = −0.08, this occurs when AveSAG(0, Yi) is a negative value and the light beam size radius Yi is relatively small, or when AveSAG(0, Yi) is small. When AveSAG(0, Yi) is relatively small in region Rg5, the positive refractive power of first refractive surface S7 is too large, and the light beam size at first reflecting surface S8 is increased. Furthermore, the distance between intermediate imaging positions Ph and Pv is too great, making it difficult for the light ray Lg to coincide with the intermediate imaging positions Ph and Pv. Furthermore, it would be necessary to increase the number of reflective surfaces of the second sub-optical system 5, which would increase the size of the second sub-optical system 5. Furthermore, if the light beam size radius Yi is small in region Rg5, the light beam size would be too small to be practical. FIG. 8C also shows region Rg6 of AveSAG(0, Yi) / Yi where the condition of equation (9) is satisfied when Emin = -0.08 and Emax = -0.022. Region Rg6 provides both the effect of AveSAG(0, Yi) / Yi being smaller than the upper limit value Emax = -0.022 and the effect of AveSAG(0, Yi) / Yi being larger than the lower limit value Emin = -0.08. Next, refer to FIG. 8D. 8D shows a region Rg7 of AveSAG(0, Yi) / Yi where the condition of equation (9) is satisfied when Emin = -0.06 and Emax = 0.00, and a region Rg8 of AveSAG(0, Yi) / Yi where the condition of equation (9) is satisfied when Emin = -0.06 and Emax = -0.022. In region Rg7, the effect of AveSAG(0, Yi) / Yi being smaller than the upper limit Emax = -0.00 described above is achieved. Furthermore, because AveSAG(0, Yi) / Yi is greater than the lower limit Emin = -0.06, in addition to the effect of being greater than the lower limit Emin = -0.08, AveSAG(0, Yi) does not become too small relatively in region Rg7, and therefore the light beam size does not become too large, making aberration correction easier.In the region Rg8, the effect obtained when AveSAG(0, Yi) / Yi is smaller than the upper limit value Emax=-0.022 and the effect obtained when AveSAG(0, Yi) / Yi is larger than the lower limit value Emin=-0.06 are both achieved.

[0048] Next, scanning distortion that occurs when the first scanning element 4 is scanned will be described with reference to Fig. 9. Fig. 9 is an explanatory diagram showing optical surfaces through which the scanned light beam Lg transmits or reflects. The optical surface through which the scanned light beam Lg transmits is, for example, the first refractive surface S7, and the optical surface from which the scanned light beam Lg is reflected is, for example, the first reflecting surface S8.

[0049] Scanning distortion occurs when the light ray Lg is obliquely incident on the first refractive surface S7 or the first reflecting surface S8. For example, when the first scanning element 4, which corresponds to the reflecting surface, is scanned in the horizontal direction, the light ray Lg does not become horizontal but is distorted into a smile. The larger the angle of incidence on the first scanning element 4 and the larger the scanning angle, the greater the distortion in the direction perpendicular to the scanning direction.

[0050] As shown in Figure 9, for example, when light ray Lg2 scanned in the H-axis direction by the first scanning element 4 enters the first refractive surface S7 or the first reflecting surface S8, scanning distortion Ds occurs in the V-axis direction, which is perpendicular to the scanned H-axis direction.

[0051] As the scanning distortion Ds increases, the footprint on the first reflecting surface S8 increases. The scanning distortion Ds is caused by the refractive power in the V-axis direction that the first refracting surface S7 has on the light ray Lg2 after scanning, and a positive (convex) refractive power is required to reduce the footprint.

[0052] The shape of the first refractive surface S7 will be described with reference to Fig. 10 and Figs. 11A and 11B. Fig. 10 is a cross-sectional view in the YZ plane showing the first scanning element 4 before and after scanning. In Fig. 10, the light ray Lg before scanning is shown by a solid line, and the light ray Lg during scanning is shown by a dotted line. Fig. 11A is an explanatory diagram showing the positional relationship of SAG(Xi, 0). Fig. 11B is an explanatory diagram showing the positional relationship of SAG(Xi, -Yis).

[0053] If the Y-direction exit angle from the first scanning element 4 when the first scanning element 4 is not scanning is Yfza, and the Y-direction exit angle from the first scanning element 4 when the first scanning element 4 is scanning at maximum is Yfzz, the Y-direction chief ray position Yis on the first refracting surface S7 can be approximated by the following equation: Yis=Lb×tan(Yfzz−Yfza) (10)

[0054] If AveSAG(Xi, -Yis) is the amount of sag at (Xi, -Yis) on the first refractive surface S7 and SAG(Xi, 0) is the amount of sag at (Xi, 0) on the first refractive surface S7, then the ratio of SAG(Xi, -Yis) - SAG(Xi, 0) to the Y-direction chief ray position Yis on the first refractive surface S7 satisfies the relationship: 0.0 < (SAG(Xi, -Yis) - SAG(Xi, 0)) / Yis < 0.2 ... (11)

[0055] The sign of SAG is negative in the direction of travel of ray Lg with respect to the surface vertex, and positive in the direction opposite to the direction of travel of ray Lg. If the first refracting surface S7 is concave in the H-axis direction (horizontal direction), SAG(Xi, 0) is positive. If the first refracting surface S7 is convex in the V-axis direction (vertical direction), SAG(0, -Yis) is negative.

[0056] In the first embodiment, the first scanning element 4 also receives a positive refractive power with respect to the light beam Lg after scanning, i.e., it also has a convex shape with respect to the light beam in the V-axis direction (vertical direction). The coordinates through which the light beam Lg passes after scanning are (Xi, -Yis), and a convex shape is necessary to receive a positive refractive power. Furthermore, since SAG(Xi, -Yis) is affected by SAG(Xi, 0), the sign can be either positive or negative. Therefore, in equation (11), by subtracting the concave shape in the H-axis direction (horizontal direction) as SAG(Xi, -Yis) - SAG(Xi, 0), the positive refractive power received during scanning is expressed as a relational expression.

[0057] By setting (SAG(Xi, -Yis) - SAG(Xi, 0)) / Yis to a value within a predetermined range that satisfies formula (11), it is possible to reduce scanning distortion. Accordingly, it is possible to reduce the spread of the image in the V-axis direction during scanning on the first scanning element 4, which contributes to a smaller diameter of the first reflecting surface S8.

[0058] FIG. 12 is a plot diagram showing the relationship between (SAG(Xi,-Yis)-SAG(Xi,0)) / Yis and scanning distortion D. The diagram shows the range of (SAG(Xi,-Yis)-SAG(Xi,0)) / Yis for which the condition of equation (11) is satisfied. If the value satisfies equation (11), the scanning distortion D can be reduced, and accordingly, the spread of the image in the V-axis direction when the first scanning element 4 is scanned can be reduced, which contributes to a smaller diameter of the first reflecting surface S8.

[0059] This occurs when (SAG(Xi, -Yis) - SAG(Xi, 0)) / Yis is equal to or greater than the upper limit, that is, when SAG(Xi, -Yis) - SAG(Xi, 0) is relatively large, or when the Y-direction chief ray position Yis is relatively small. When SAG(Xi, -Yis) - SAG(Xi, 0) is relatively large, the positive power becomes too large, causing overcorrection and scanning distortion D in the reverse direction. This requires adjustment at another optical surface, increasing the cost of the second sub-optical system. Furthermore, the Y-direction chief ray position Yis is a value determined by the tilt of the first scanning element 4 and the distance between the first scanning element 4 and the first refractive surface S7. Therefore, the Y-direction chief ray position Yis becomes small when the tilt of the first scanning element 4 is small, or when the distance between the first scanning element 4 and the first refractive surface S7 is small. If the tilt of the first scanning element 4 is reduced, interference occurs between the first sub-optical system 3 and the second sub-optical system 5, which makes manufacturing difficult. If the distance between the first scanning element 4 and the first refractive surface S7 is reduced, there is a possibility that the light beam emitted from the first sub-optical system 3 will interfere with the second sub-optical system 5, which makes manufacturing difficult.

[0060] This occurs when (SAG(Xi,-Yis)-SAG(Xi,0)) / Yis is equal to or less than the lower limit, that is, when SAG(Xi,-Yis)-SAG(Xi,0) is relatively small, or when the Y-direction chief ray position Yis is relatively large. When SAG(Xi,-Yis)-SAG(Xi,0) is relatively small, a concave surface region is formed, which increases scanning distortion D and increases the light beam size at the first reflecting surface S8. Furthermore, when the Y-direction chief ray position Yis is relatively large, the difficulty of aberration correction increases, which increases the number of surfaces in the second sub-optical system 5 and the size of the second sub-optical system 5.

[0061] Table 1 is a table showing the parameter values ​​of the surfaces S1 to S16 in embodiment 1. It shows the radius of curvature r, the surface spacing d, the refractive index nd, and the Abbe number vd of each surface.

[0062]

[0063] The free-form surface shapes of the first refracting surface S7, the first reflecting surface S8, the second reflecting surface S9, and the second refracting surface S10 are defined by the following formula (12): In formula (12), Z is the sag of the surface parallel to the reference axis, c is the curvature at the vertex of the surface, k is the conic constant, r is the distance from the origin on the reference axis in a plane perpendicular to the origin, and cj is a coefficient of the xy polynomial.

[0064] [Equation 1]

[0065] Here, the relationship expressed by the following equation (13) holds between j, p, and q in equation (12).

[0066] [Equation 2]

[0067] Tables 2 and 3 show the free-form surface shape data of the first refracting surface S7, the first reflecting surface S8, the second reflecting surface S9, and the second refracting surface S10.

[0068]

[0069]

[0070] According to the optical system 1 of the first embodiment, the influence of the scanning angle of the first scanning element 4 can be reduced, and the light rays Lg of each color reflected by the second scanning element 7 can be made closer to parallel rays. Fig. 13 shows the shapes of the light beams of the red light ray RL, the blue light ray BL, and the green light ray GL on the second scanning element 7 when the first scanning element 4 is not scanned and when it is scanned at 15 degrees. Fig. 13 also shows the shapes of the light beams of the red light ray RL, the blue light ray BL, and the green light ray GL at a position 100 mm away from the second scanning element 7 in the direction of the projection surface 19 when the first scanning element 4 is not scanned and when it is scanned at 15 degrees.

[0071] At a position 0 mm from the second scanning element 7, i.e., on the second scanning element 7, the shape and size of the light beams of each color RL, BL, GL are almost the same, and are approximately circular, whether the first scanning element is not scanning or is scanning at 15 degrees.

[0072] The shapes and sizes of the light beams of each color RL, BL, and GL at a position 100 mm from the second scanning element 7 are almost the same and substantially circular when the first scanning element is not scanning. This means that the light beams of each color RL, BL, and GL from the second scanning element 7 do not expand, and the light beams of each color RL, BL, and GL are substantially parallel. Furthermore, when the first scanning element scans at 15 degrees, the light beams of each color RL, BL, and GL are substantially circular, with only slight differences in size. Therefore, even when the first scanning element scans at 15 degrees, the light beams of each color RL, BL, and GL from the second scanning element 7 are prevented from expanding and becoming diffused light. Because the light beams of each color RL, BL, and GL from the second scanning element 7 are not diffused light, the two-dimensional image formed appears to be infinitely far away.

[0073] Next, the effect of the first refracting surface S7 being convex in the V-axis direction will be described with reference to Figures 14 to 19. Figure 14 is an explanatory diagram showing the optical path when the first refracting surface S7 is concave in the V-axis direction, and Figure 15 is an explanatory diagram showing the footprint FP on the first reflecting surface S8 when the first refracting surface S7 is concave. Figure 16 is an explanatory diagram showing the optical path when the first refracting surface S7 is flat in the V-axis direction, and Figure 17 is an explanatory diagram showing the footprint FP on the first reflecting surface S8 when the first refracting surface S7 is flat. Figure 18 is an explanatory diagram showing the optical path when the first refracting surface S7 is convex in the V-axis direction, and Figure 19 is an explanatory diagram showing the footprint FP on the first reflecting surface S8 when the first refracting surface S7 is convex.

[0074] As shown in Fig. 14, when the first refracting surface S7 has a shape that has divergence power in the V-axis direction, such as a concave shape in the V-axis direction, for the light ray Lg, which is a convergent light, the light beam of the light ray Lg diverges, and the footprint FP on the first reflecting surface S8 becomes large as shown in Fig. 15. This increases the influence of spherical aberration.

[0075] As shown in Fig. 16, when the first refracting surface S7 has a shape that does not have power with respect to the convergent light beam Lg, such as a flat shape in the V-axis direction, the footprint FP on the first reflecting surface S8 is determined by the convergent light beam Lg incident on the first refracting surface S7, as shown in Fig. 17. becomes large. This increases the influence of spherical aberration.

[0076] As shown in Fig. 18, when the first refracting surface S7 has a shape that has a converging power, such as a convex shape in the V-axis direction, for a convergent light ray Lg, the light beam converges, and the footprint FP on the first reflecting surface S8 becomes relatively small, as shown in Fig. 19. This reduces the influence of spherical aberration.

[0077] 14 to 19, by arranging the first refracting surface S7 whose surface shape in the V-axis direction has positive power in the V-axis direction, incident light is converged and the light beam becomes smaller, which contributes to a smaller diameter of the first reflecting surface S8 itself. Furthermore, the first refracting surface S7 is arranged so that when a light ray Lg, which is convergent light, is incident on the first refracting surface S7, the light ray Lg is incident in a nearly aplanatic state with respect to the first refracting surface S7, which is the incident surface, thereby suppressing the occurrence of spherical aberration.

[0078] Next, the effect of the first refracting surface S7 being concave in the H-axis direction will be described with reference to Fig. 20 to Fig. 22. Fig. 20 is an explanatory diagram showing the optical path when the first refracting surface S7 is concave in the H-axis direction. Fig. 21 is an explanatory diagram showing the optical path when the first refracting surface S7 is flat in the H-axis direction. Fig. 22 is an explanatory diagram showing the optical path when the first refracting surface S7 is convex in the H-axis direction.

[0079] 20 , when the first refracting surface S7 has divergence power in the H-axis direction, for example, by having a concave shape in the H-axis direction, the difference in refraction angle for each wavelength of the light ray Lg incident on the first refracting surface S7 is small for the light ray Lg scanned in the H-axis direction by the first scanning element 4. Since the difference in refractive index among the light rays RL, BL, and GL of each color at the first refracting surface S7 is small, chromatic aberration of magnification can be suppressed.

[0080] 21 , for a light ray Lg scanned in the H-axis direction by the first scanning element 4, when the first refracting surface S7 is, for example, flat in the H-axis direction, the difference in refraction angle for each wavelength of the light ray Lg when it is incident on the first refracting surface S7 becomes larger than when the first refracting surface S7 is concave in the H-axis direction, and therefore the chromatic aberration of magnification becomes larger.

[0081] 22 , for the light ray Lg scanned in the H-axis direction by the first scanning element 4, when the first refracting surface S7 has a convex shape in the H-axis direction, the difference in refraction angle for each wavelength of the light ray Lg when it is incident on the first refracting surface S7 becomes larger than when the first refracting surface S7 has a concave shape in the H-axis direction, and therefore the chromatic aberration of magnification becomes larger.

[0082] As shown in Figures 20 to 22, by arranging the first refractive surface S7 having a concave shape in the H-axis direction, the difference in refraction angle for each wavelength of the light ray Lg when it is incident on the first refractive surface S7 can be reduced, and chromatic aberration of magnification can be suppressed.

[0083] Although the optical system 1 of embodiment 1 has a third sub-optical system 6, the third sub-optical system 6 may be omitted by providing a converging effect to the second refractive surface S10 of the second sub-optical system 5.

[0084] In this embodiment, the first scanning element 4 is a horizontal scanner and the second scanning element 7 is a vertical scanner, but the first scanning element 4 may be a vertical scanner and the second scanning element 7 may be a horizontal scanner.

[0085] [1-2. Effects, etc.] The optical system 1 according to the first embodiment includes a light source 2 that emits a light ray Lg, a first sub-optical system 3 that converges the light ray Lg, a first scanning element 4 that scans the light ray Lg in an H-axis direction that is a first direction, and a second sub-optical system 5 that has a plurality of optical surfaces including a first refractive surface S7, one or more reflecting surfaces (first reflecting surfaces S8), and a second refractive surface S10. One of the plurality of optical surfaces (first refractive surface S7) has a rotationally asymmetric shape and has divergence power with respect to the light ray Lg in the H-axis direction and convergence power in a V-axis direction that is a second direction that is orthogonal to the direction of the optical path of the light ray Lg and the H-axis direction.

[0086] Furthermore, the second sub-optical system 5 according to the first embodiment has a plurality of optical surfaces including a first refractive surface S7, one or more reflecting surfaces (first reflecting surface S8), and a second refractive surface S10. Any one of the plurality of optical surfaces (first refractive surface S7) has a rotationally asymmetric shape, and has diverging power with respect to the light ray Lg in the H-axis direction, which is a first direction, and has converging power with respect to the light ray Lg in the V-axis direction, which is a second direction perpendicular to the optical path direction of the light ray Lg and the H-axis direction.

[0087] In the optical system 1 and the second sub-optical system 5 according to embodiment 1, the first refractive surface S7, which is one of the optical surfaces in the second sub-optical system 5, has diverging power in the H-axis direction with respect to the light ray Lg. This reduces the difference in the refraction angle for each wavelength of the light ray Lg when it is incident on the first refractive surface S7, thereby suppressing lateral chromatic aberration. Furthermore, the first refractive surface S7, which is one of the optical surfaces in the second sub-optical system 5, has converging power in the V-axis direction with respect to the light ray Lg. This converges the incident light ray Lg and reduces the light flux, thereby contributing to a reduction in the diameter of the first reflecting surface S8 itself. This makes it possible to reduce the size of the second sub-optical system 5 and the optical system 1 themselves.

[0088] Furthermore, the light beam Lg emitted by the light source 2 passes through each optical system, whereby aberrations are corrected and a two-dimensional image can be drawn on the projection surface. Furthermore, it is possible to accommodate various positional requirements, such as the distance at which the two-dimensional image is projected and the positional relationship between the incident light and the projected image.

[0089] (Embodiment 2) Next, embodiment 2 will be described using Fig. 23. Fig. 23 is a cross-sectional view in the YZ plane showing the configuration of an optical system 1A in embodiment 2. While the second sub-optical system 5 of the optical system 1 in embodiment 1 has four optical surfaces, in the optical system 1A in embodiment 2, as shown in Fig. 23, the second sub-optical system 5A has three optical surfaces. Apart from this difference, the optical system 1 according to embodiment 1 and the optical system 1A in embodiment 2 have the same configuration.

[0090] The second sub-optical system 5A has a first refractive surface S7, a first reflecting surface S8, and a second refractive surface S10. Note that although the optical system 1A omits the third sub-optical system 6, it may have the same as the optical system 1.

[0091] The optical system 1A of the second embodiment can also suppress chromatic aberration of magnification, similar to the optical system 1 of the first embodiment, and furthermore, can realize a reduction in the size of the optical system 1A itself.

[0092] (Embodiment 3) Next, embodiment 3 will be described using Fig. 24. Fig. 24 is a cross-sectional view in the YZ plane showing the configuration of an optical system 1B in embodiment 3. While the second sub-optical system 5 of the optical system 1 in embodiment 1 has four optical surfaces, in the optical system 1B in embodiment 3, as shown in Fig. 24, the second sub-optical system 5B has five optical surfaces. Apart from this difference, the optical system 1 according to embodiment 1 and the optical system 1B in embodiment 3 have the same configuration.

[0093] The second sub-optical system 5B has a first refractive surface S7, a first reflecting surface S8, a second reflecting surface S9, a third reflecting surface S21, and a second refractive surface S10. The third reflecting surface S21 reflects the light ray Lg traveling from the second reflecting surface S9 and directs it toward the second refractive surface S10. Note that although the optical system 1B omits the third sub-optical system 6, it may have the same as the optical system 1.

[0094] The optical system 1B of the third embodiment can also suppress chromatic aberration of magnification, similar to the optical system 1 of the first embodiment, and furthermore, can realize a reduction in the size of the optical system 1B itself.

[0095] (Fourth Embodiment) Next, a fourth embodiment will be described using Fig. 25. Fig. 25 is a cross-sectional view in the YZ plane showing the configuration of an optical system 1C according to the fourth embodiment. Whereas the second sub-optical system 5 of the optical system 1 of the first embodiment is a prism having four optical surfaces, the optical system 1C of the fourth embodiment is composed of a lens element 21 having a free-form surface and a mirror, as shown in Fig. 25. Apart from this difference, the optical system 1 according to the first embodiment and the optical system 1C of the third embodiment have the same configuration.

[0096] The second sub-optical system 5C includes a lens element 21 having a first refractive surface S7 and a second refractive surface S10. The first reflecting surface S8 and the second reflecting surface S9 are each a reflecting mirror. A light ray LG transmitted through the first refractive surface S7 travels to the first reflecting surface S8, where it also passes through the second refractive surface S10. A light ray Lg reflected by the first reflecting surface S8 travels to the second reflecting surface S9 and is reflected by the second reflecting surface S9. Although the optical system 1B omits the third sub-optical system 6, it may also include the third sub-optical system 6, as in the optical system 1.

[0097] The optical system 1C of the fourth embodiment can also suppress chromatic aberration of magnification, similar to the optical system 1 of the first embodiment, and furthermore, can realize a reduction in the size of the optical system 1C itself.

[0098] (Other Embodiments) As described above, embodiments 1 to 4 have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Therefore, other embodiments will be described below as examples.

[0099] In the above-described embodiments, the first refractive surface S7 has divergent power in the first direction (H-axis direction) and convergent power in the second direction (V-axis direction), but this is not limited thereto. The first reflecting surface S8 or the second reflecting surface S9 may have divergent power in the first direction (H-axis direction) and convergent power in the second direction (V-axis direction). In this case, the first reflecting surface S8 or the second reflecting surface S9 has a convex optical surface shape in the first direction when viewed from the direction of the optical path, which enables aberration correction, and the concave optical surface shape in the second direction, which enables spherical aberration correction and the effect of reducing the size of the second sub-optical system 5.

[0100] Furthermore, the components described in each embodiment can be combined to form a new embodiment.

[0101] As described above, the embodiments have been described as examples of the technology of the present disclosure. For this purpose, the accompanying drawings and detailed description have been provided. Therefore, the components described in the accompanying drawings and detailed description may include not only components essential for solving the problem, but also components that are not essential for solving the problem in order to exemplify the technology. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0102] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0103] (Summary of Embodiments) (1) An optical system disclosed herein includes a light source that emits a light beam, a first sub-optical system that converges the light beam, a first scanning element that scans the light beam in a first direction, a second sub-optical system having a plurality of optical surfaces including a first refractive surface, a second refractive surface, and one or more reflective surfaces, and a second scanning element that scans the light beam emitted from the second refractive surface in a second direction that is orthogonal to the direction of the optical path of the light beam and the first direction. The optical path of the light beam emitted from the light source is in the order of the first sub-optical system, the first scanning element, the second sub-optical system, and the second scanning element, and any one of the plurality of optical surfaces has a rotationally asymmetric shape and has diverging power in the first direction and converging power in the second direction with respect to the light beam.

[0104] Since one of the optical surfaces in the second sub-optical system has diverging power in the first direction with respect to light rays, the difference in refraction angle for each wavelength of the light rays can be reduced, and lateral chromatic aberration can be suppressed. Furthermore, since one of the optical surfaces in the second sub-optical system has converging power in the second direction with respect to light rays, the incident light rays are converged and the luminous flux is reduced, which contributes to a reduction in the diameter of the reflecting surface itself. This makes it possible to achieve a reduction in the size of the second sub-optical system and the optical system itself.

[0105] (2) In the optical system of (1), the first sub-optical system includes a lens element having a converging effect. The lens element forms convergent light, thereby contributing to shortening the optical path length of the entire optical system.

[0106] (3) In the optical system of (1) or (2), the second sub-optical system is a prism element in which the spaces between the optical surfaces are filled with glass material, thereby contributing to miniaturization by shortening the optical path length in the optical system.

[0107] (4) In the optical system of any one of (1) to (3), the first refractive surface has a rotationally asymmetric shape, thereby making it possible to perform appropriate aberration correction in both the first direction and the second direction.

[0108] (5) In the optical system of (4), the first refractive surface has a concave shape in a first direction and a convex shape in a second direction when viewed from the direction of the optical path. The concave shape in the first direction can achieve high performance by suppressing chromatic aberration of magnification, and the convex shape in the second direction can contribute to miniaturization by suppressing the light beam size at the reflecting surface.

[0109] (6) In the optical system of (4) or (5), where Yi is the radius of the beam size in the first direction on the first refractive surface, SAG(0,Yi) is the amount of sag at (0,Yi) on the first refractive surface, and SAG(Yi,0) is the amount of sag at (Yi,0) on the first refractive surface, the first refractive surface satisfies the relationship: SAG(0,Yi) / SAG(Yi,0)<0. The concave shape in the first direction can achieve high performance by suppressing chromatic aberration of magnification, and the convex shape in the second direction contributes to miniaturization by suppressing the beam size on the reflective surface.

[0110] (7) In the optical system of any one of (4) to (6), where Xi is the position of the chief ray in the X direction on the first refracting surface, and SAG(Xi, 0) is the amount of sag at (Xi, 0) on the first refracting surface, the first refracting surface satisfies the relationship SAG(Xi, 0) / Xi>0. The concave surface shape in the first direction can suppress chromatic aberration of magnification.

[0111] (8) In the optical system of (4) or (5), if Yi is the radius of the beam size in the first direction on the first refractive surface, and AveSAG(0, Yi) is the average value of the sag amounts of (0, Yi) and (0, −Yi) on the first refractive surface, the first refractive surface satisfies the relationship AveSAG(0, Yi) / Yi<0. By setting AveSAG(0, Yi) to a value within a predetermined range, an intermediate imaging position in the second direction is provided between the first refractive surface and the reflecting surface, while the diameter of the beam on the reflecting surface is reduced, contributing to the miniaturization of the reflecting surface.

[0112] (9) In the optical system of (4) or (5), where Xi is the position of the X-direction chief ray on the first refracting surface, Yis is the position of the Y-direction chief ray on the first refracting surface, SAG(Xi,0) is the amount of sag at (Xi,0) on the first refracting surface, and SAG(Xi,-Yis) is the amount of sag at (Xi,0) on the first refracting surface, the first refracting surface satisfies the relationship: 0.0<(SAG(Xi,-Yis)-SAG(Xi,0)) / Yi<0.2. By setting (SAG(Xi,-Yis)-SAG(Xi,0)) / Yi to a value within a predetermined range, scanning distortion can be reduced. As a result, the spread of the image in the second direction during scanning can be reduced, contributing to a smaller diameter of the reflecting surface.

[0113] (10) In the optical system of any one of (4) to (9), the second refractive surface has a rotationally asymmetric shape, whereby aberrations generated by the first refractive surface and the reflecting surface can be appropriately corrected in the first direction and the second direction, respectively.

[0114] (11) In the optical system of any one of (1) to (10), the second refracting surface has a concave shape in the first direction and a convex shape in the second direction when viewed from the direction of the optical path, thereby enabling miniaturization and suppression of chromatic aberration of magnification due to convergence of light rays that have diverged in the first direction, and enabling expansion of the light beam in the second direction.

[0115] (12) In the optical system of any one of (1) to (11), a reflecting surface having a concave shape is provided, whereby light spread by the first scanning element can be converged.

[0116] (13) The optical system of (12) has a reflecting surface that has a rotationally asymmetric shape, thereby making it possible to perform appropriate aberration correction in both the first and second directions.

[0117] (14) In the optical system of (12) or (13), a reflecting surface having a stronger power in the second direction than in the first direction is provided, which has the effect of converging the light beam expanded by the first scanning element in the first direction, and can appropriately correct aberrations in the second direction.

[0118] (15) In the optical system of any one of (1) to (14), the light beam propagating through the plurality of optical surfaces forms intermediate images at positions different from each other in the first direction and the second direction. By making the positions of the intermediate images in the first direction and the second direction different, it is possible to reduce the possibility of vignetting or disappearance of the image due to a foreign object or the like.

[0119] (16) In the optical system of (15), an intermediate image in the second direction is formed between the first refractive surface and the reflecting surface, and an intermediate image in the first direction is formed between the reflecting surface and an optical surface onto which the light reflected from the reflecting surface is incident. By forming an intermediate image between the first refractive surface and the reflecting surface, and forming an intermediate image in the first direction between the reflecting surface and an optical surface onto which the light reflected from the reflecting surface is incident, it is possible to further reduce the possibility of image vignetting or disappearance due to foreign matter, etc.

[0120] (17) In the optical system of (16), the intermediate image in the second direction is located within half the distance from the reflecting surface to the first refracting surface, thereby reducing the size of the light beam at the reflecting surface.

[0121] (18) In the optical system of any one of (15) to (17), the intermediate image in the first direction is located within half the distance from the reflecting surface to the optical surface onto which the reflected light from the reflecting surface is incident. This allows the size of the reflecting surface to be reduced.

[0122] (19) An optical system according to the present disclosure is an optical system in which a light beam is incident from a first scanning element that scans the light beam in a first direction. The optical system includes a plurality of optical surfaces including a first refractive surface, a second refractive surface, and one or more reflecting surfaces. Any one of the plurality of optical surfaces has a rotationally asymmetric shape and has diverging power with respect to the light beam in the first direction and converging power in a second direction that is orthogonal to the direction of the optical path of the light beam and the first direction.

[0123] Since one of the optical surfaces has diverging power in a first direction with respect to light rays, the difference in refraction angle for each wavelength of the light rays can be reduced, and lateral chromatic aberration can be suppressed. Furthermore, since one of the optical surfaces has converging power in a second direction with respect to light rays, the incident light rays are converged and the luminous flux is reduced, which contributes to a reduction in the diameter of the reflecting surface itself. This makes it possible to achieve a miniaturization of the optical system itself.

[0124] The present disclosure is applicable to optical devices that use refractive optical systems.

[0125] 1, 1A, 1B Optical system 2 Light source 3 First sub-optical system 4 First scanning element 5, 5A, 5B Second sub-optical system 6 Third sub-optical system 7 Second scanning element 19 Projection surface 21 Lens element S1 Incident surface S2 Cemented surface S3 Exit surface S4 Distance S5 Mirror S6 Distance S7 First refractive surface S8 First reflecting surface S9 Second reflecting surface S10 Second refractive surface S11 Distance S12 Incident surface S13 Cemented surface S14 Exit surface S15 Distance S16 Mirror S21 Third reflecting surface Lg Light ray Pv, Ph Intermediate image position

Claims

1. An optical system comprising: a light source that emits a light beam; a first sub-optical system that converges the light beam; a first scanning element that scans the light beam in a first direction; a second sub-optical system having a plurality of optical surfaces including a first refractive surface, a second refractive surface, and one or more reflecting surfaces; and a second scanning element that scans the light beam emitted from the second refractive surface in a second direction that is perpendicular to the direction of the optical path of the light beam and the first direction, wherein the optical path of the light beam emitted by the light source is in the order of the first sub-optical system, the first scanning element, the second sub-optical system, and the second scanning element, and wherein any one of the plurality of optical surfaces has a rotationally asymmetric shape and has diverging power in the first direction and converging power in the second direction for the light beam.

2. The optical system according to claim 1, wherein the first sub-optical system includes a lens element having a converging effect.

3. The optical system according to claim 1, wherein the second sub-optical system is a prism element in which the spaces between the plurality of optical surfaces are filled with glass material.

4. The optical system according to claim 1, wherein the first refractive surface has a rotationally asymmetric shape.

5. The optical system according to claim 4, wherein the first refractive surface has a concave shape in the first direction and a convex shape in the second direction when viewed in the direction of the optical path.

6. The optical system according to claim 4, wherein, when Yi is a beam size radius in the first direction at the first refractive surface, SAG(0,Yi) is a sag amount at (0,Yi) at the first refractive surface, and SAG(Yi,0) is a sag amount at (Yi,0) at the first refractive surface, the first refractive surface satisfies the relationship: SAG(0,Yi) / SAG(Yi,0)<0.

7. The optical system according to claim 4, wherein, when Xi is the position of a chief ray in the X direction on said first refractive surface, and SAG(Xi, 0) is the amount of sag at (Xi, 0) on said first refractive surface, said first refractive surface satisfies the relationship: SAG(Xi, 0) / Xi>0.

8. The optical system according to claim 4, wherein, when Yi is a luminous flux size radius in the first direction at the first refractive surface, and AveSAG(0,Yi) is an average value of sag amounts of (0,Yi) and (0,-Yi) at the first refractive surface, the first refractive surface satisfies the relationship AveSAG(0,Yi) / Yi<0.

9. The optical system according to claim 4, wherein Xi is the position of the X-direction chief ray on said first refracting surface, Yis is the position of the Y-direction chief ray on said first refracting surface, SAG(Xi, 0) is the amount of sag at (Xi, 0) on said first refracting surface, and SAG(Xi, -Yis) is the amount of sag at (Xi, 0) on said first refracting surface, said first refracting surface satisfies the relationship: 0.0<(SAG(Xi, -Yis) - SAG(Xi, 0)) / Yi<0.

2.

10. The optical system according to claim 4, wherein the second refractive surface has a rotationally asymmetric shape.

11. The optical system according to claim 4, wherein the second refractive surface has a concave shape in the first direction and a convex shape in the second direction when viewed in the direction of the optical path.

12. The optical system according to claim 1, having a reflecting surface that is concave in shape.

13. The optical system according to claim 12, having a reflecting surface that has a rotationally asymmetric shape.

14. The optical system according to claim 12, further comprising a reflecting surface having a stronger power in the second direction than in the first direction.

15. The optical system according to claim 1, wherein the light beams propagating through the plurality of optical surfaces form intermediate images at different positions in the first direction and the second direction.

16. The optical system according to claim 15, wherein an intermediate image in the second direction is formed between the first refractive surface and the reflecting surface, and an intermediate image in the first direction is formed between the reflecting surface and an optical surface onto which the light reflected by the reflecting surface is incident.

17. The optical system according to claim 16, wherein the intermediate image in the second direction is located at a position within 1 / 2 of the distance from the reflecting surface to the first refractive surface and the reflecting surface.

18. The optical system according to claim 16, wherein the intermediate image in the first direction is located at a position within half the distance from the reflecting surface between the reflecting surface and an optical surface onto which the light reflected by the reflecting surface is incident.

19. An optical system in which a light beam is incident from a first scanning element that scans the light beam in a first direction, the optical system having a plurality of optical surfaces including a first refractive surface, a second refractive surface, and one or more reflecting surfaces, any one of the plurality of optical surfaces having a rotationally asymmetric shape and having diverging power with respect to the light beam in the first direction and converging power in a second direction that is perpendicular to the direction of the optical path of the light beam and the first direction.

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