JP5752082B2 - Scanning projector - Google Patents

Description

  The present invention relates to a scanning projection apparatus, and is suitably applied to, for example, a scanning projection apparatus in which a distortion correction prism is disposed immediately after a scanning mirror.

  Conventionally, in a scanning projection apparatus, a scanning mirror such as a galvano mirror or a MEMS (Micro Electro-Mechanical Systems) mirror is used as means for two-dimensionally scanning a light beam. When a light beam is scanned two-dimensionally with such a scanning mirror, the angle between the reflection angle of the light beam, which is a combination of the horizontal and vertical angles of the scanning mirror, and the ideal reflection angle of the light beam in the projected image. There is a problem that an error occurs, and as a result, the projected image is distorted.

  As one means for solving such a problem, Patent Document 1 discloses correcting image distortion of a projected image by disposing a distortion correction prism immediately after a scanning mirror.

US Patent Application Publication No. 2010/0060863

  By the way, in the case of a scanning projection apparatus, since one light spot formed on the projection surface by one light beam corresponds to one pixel in the projection image, the shape of the light spot may be accurately circular. desirable.

  However, the distortion correcting prism proposed in Patent Document 1 has different refraction angles in the horizontal direction and the vertical direction with respect to the incident light beam. For this reason, according to the method disclosed in Patent Document 1, a phase difference occurs between the horizontal direction and the vertical direction of the light beam transmitted through the distortion correction prism, and astigmatism occurs in the light beam. Due to this astigmatism, the spot shape of the light beam that has passed through the distortion correction prism becomes an ellipse, and there is a problem that the resolution of the projected image deteriorates.

  The present invention has been made in consideration of the above points, and an object of the present invention is to provide a scanning projection apparatus having a simple configuration that can prevent deterioration in resolution while reducing image distortion of a projected image.

In order to solve this problem, in the present invention, a laser light source that emits a light beam in a scanning projection apparatus that projects a two-dimensional image on the non-projection surface by scanning the light beam on the projection surface. And a first deflection axis and a second deflection axis perpendicular to the first deflection axis, and driving the deflection of the light beam around the first and / or second deflection axis, A scanning mirror that reflects so as to perform two-dimensional scanning on the projection surface, and an angle between the light beam that is installed between the scanning mirror and the projection surface and reflected by the scanning mirror and the projection surface is a predetermined angle. A distortion correction prism that refracts the light beam at a predetermined angle, and an astigmatism correction element that is disposed between the laser light source and the distortion correction prism and generates astigmatism in the light beam. ,Previous Astigmatism correcting element, adds astigmatism that cancels the astigmatism is added to the light beam in advance the light beam in the distortion correcting prism, the distortion correction prism, first and second different refractive index The first wedge-shaped prism is arranged so that both the light beam incident on the scanning mirror and the light beam reflected by the scanning mirror pass through the second wedge-shaped prism. The wedge-shaped prism is arranged on the optical path of the light beam reflected by the scanning mirror and passed through the first wedge-shaped prism .

  ADVANTAGE OF THE INVENTION According to this invention, the scanning-type projection apparatus of the simple structure which can improve the resolution, reducing the image distortion of a projection image is realizable.

It is a basic diagram which shows schematic structure of the scanning projection apparatus by 1st Embodiment. It is a basic diagram with which it uses for description of the astigmatism which generate | occur | produces in the conventional scanning projection apparatus. (A) And (B) is an optical wave-front figure with which it uses for description of the astigmatism which generate | occur | produces in the conventional scanning projection apparatus. It is a basic diagram with which it uses for description of the astigmatism which generate | occur | produces in the conventional scanning projection apparatus. It is a basic diagram with which it uses for description of the astigmatism correction function in the scanning projection apparatus of this Embodiment. (A) And (B) is a light wavefront figure with which it uses for description of the astigmatism correction function in the scanning projection apparatus of this Embodiment. It is a basic diagram with which it uses for description of the astigmatism correction function in the scanning projection apparatus of this Embodiment. It is a basic diagram which shows schematic structure of the scanning projection apparatus by 2nd Embodiment. It is a basic diagram which shows schematic structure of the scanning projection apparatus by other embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) 1st Embodiment In FIG. 1, 1 shows the scanning projection apparatus by 1st Embodiment as a whole. This scanning projection apparatus includes first to third laser light sources 2A to 2C. In FIG. 1, the alternate long and short dash line indicates the optical axis of each light beam to be described later.

  The first laser light source 2A is composed of a semiconductor laser that emits a green light beam L1G in a 520 [nm] band, for example. The green light beam L1G emitted from the first laser light source 2A is converted into a weakly convergent light beam in the first collimator lens 3A, and then enters the first light combining element 4A.

  The second laser light source 2B is composed of a semiconductor laser that emits a red light beam L1R in the 640 [nm] band, for example. The red light beam L1R emitted from the second laser light source 2B is converted into a weakly convergent light beam by the second collimator lens 3B and then enters the first light combining element 4A.

  The third laser light source 2C is composed of a semiconductor laser that emits a blue light beam L1B in a 440 [nm] band, for example. The blue light beam L1B emitted from the third laser light source 2C is converted into a weakly convergent light beam by the third collimator lens 3C and then enters the second light combining element 4B.

  The first to third collimating lenses 3A to 3C are composed of isotropic spherical lenses or aspherical lenses made of glass or plastic for optical parts. Accordingly, the light wavefronts of the green light beam L1G, red light beam L1R, and blue light beam L1B converted into weakly convergent light by the first to third collimating lenses 3A to 3C are isotropic spherical surfaces.

  The first light combining element 4A transmits the green light beam L1G emitted from the first laser light source 2A while reflecting the red light beam L1R emitted from the second laser light source 2B. Composed of sex mirrors. Thus, the green light beam L1G and the red light beam L1R are combined by the first light combining element 4A so that their optical axes substantially coincide with each other, and then enter the second light combining element 4B.

  The second light combining element 4B transmits the green light beam L1G emitted from the first laser light source 2A and the red light beam L1R emitted from the second laser light source 2B, while emitting from the third laser light source 2C. And a wavelength selective mirror having optical characteristics for reflecting the blue light beam L1B. Thus, the green light beam L1G, the red light beam L1R, and the blue light beam L1B are combined by the second light combining element 4B so that their optical axes substantially coincide with each other, and the projection light beam L2 obtained by the combining is obtained. Thereafter, the light enters the astigmatism correction element 5.

  The astigmatism correction element 5 is made of glass or plastic for optical components, and remains in the x direction in the yz plane in FIG. 1 without changing the x direction in FIG. 1 with respect to the light wavefront shape of the incident projection light beam L2. It has a beam shaping function that expands only in the direction perpendicular to it. As such an astigmatism correction element 5, for example, a wedge having a predetermined apex angle in which the x direction in FIG. 1 is perpendicular to the projection light beam L2 and the yz plane direction in FIG. 1 is a slope. A mold or trapezoidal prism can be applied. FIG. 1 shows a configuration example in which a wedge prism that refracts only the yz plane component of the light beam and expands the beam diameter of the projection light beam L2 only in the yz direction is applied as the astigmatism correction element 5. The larger the refraction angle of the projection light beam L2 on the incident surface of the astigmatism correction element 5, the larger the beam diameter enlargement factor (hereinafter referred to as the beam enlargement factor) of the projection light beam L2 on the yz plane. Become.

  The projection light beam L 2 that has passed through the astigmatism correction element 5 enters the scanning mirror 6. The scanning mirror 6 includes a first deflection axis (horizontal scanning axis) parallel to the y direction in FIG. 1 and a second deflection axis (vertical scanning axis parallel to the x direction in FIG. 1) perpendicular to the first deflection axis. ) Or a galvano mirror or the like. By driving the scanning mirror 6 to be deflected around the first and / or second deflection axis, the projection light beam L2 can be reflected so as to be two-dimensionally scanned on the projection surface of the screen 8. The scanning mirror 6 may be configured by a first scanning mirror having a vertical scanning axis and a second scanning mirror having a horizontal scanning axis.

  The projection light beam L 2 reflected by the scanning mirror 6 enters the distortion correction prism 7. The distortion correction prism 7 is composed of a wedge-shaped prism that is parallel to the incident projection light beam L2 in the x direction in FIG. 1 and has a predetermined angle in the yz direction in FIG. As described in Patent Document 1, the distortion correcting prism 7 refracts the scanned projection light beam L2 only in the yz plane component in FIG. 1 so that the deflection angle of the scanning mirror 6 and the ideal deflection angle are refracted. The optical characteristic corrects the distortion of the image caused by the error. However, since the distortion correction prism 7 refracts the projection light beam L2 only in the yz plane component in FIG. 1, the beam shaping function that reduces the light beam diameter only in the yz plane direction in FIG. 1 without changing the x direction in FIG. Also has.

  The green light beam L1G, red light beam L1R, and blue light beam L1B constituting the projection light beam L2 that has passed through the distortion correction prism 7 are respectively at the same position on the screen 8 disposed outside the scanning projection apparatus 1. Three circular light spots are overlaid. That is, on the screen 8, the light spots formed by the green light beam L1G, the red light beam L1R, and the blue light beam L1B can be confirmed as one circular light spot. In the case of the scanning projection apparatus 1 according to the present embodiment, one light spot corresponds to one pixel of the projection image.

  As described above, the scanning projection apparatus 1 according to this embodiment includes at least the first to third laser light sources 2A to 2C, the first to third collimator lenses 3A to 3C, and the first and second light combining elements 4A. 4B, the astigmatism correction element 5, the scanning mirror 6 and the distortion correction prism 7, and an optical element such as a diffraction grating or a wave plate is added in the middle, or the optical path is bent by a mirror. It doesn't matter.

  Next, the beam shaping rate (beam expansion rate and beam reduction rate) of the projection light beam L2 that passes through the astigmatism correction element 5 and the distortion correction prism 7 will be described.

  FIG. 2 shows a partial configuration of a conventional scanning projection apparatus in which the astigmatism correction element 5 is removed from the scanning projection apparatus 1. Here, for simplicity of explanation, only the distortion correction prism 7 and the scanning mirror 6 are described, and other components are omitted. In the figure, the alternate long and short dash line represents the optical axis of the projection light beam L2, and the wavy line represents the outermost periphery of the projection light beam L2. In FIG. 2, regarding the cross section of the projection light beam L2, the direction perpendicular to the x direction in the yz plane is defined as the yz direction.

  An arbitrary position on the optical path of the projection light beam L2 before passing through the distortion correction prism 7 is a position A ′, and an arbitrary position on the optical path of the projection light beam L2 after passing through the distortion correction prism 7 is a position C. ′. Further, regarding the height from the optical axis of the projection light beam L2 to the outermost periphery of the projection light beam L2 in the yz direction of the projection light beam L2, the height at the position A ′ is Hyz1 ′ and the height at the position C ′. Is Hyz3 ′. Further, although not shown in FIG. 2, regarding the height from the optical axis in the x direction of the projection light beam L2 to the outermost periphery of the projection light beam L2, the height at the position A ′ is Hx1 ′ and the position C ′. The height from the optical axis to the outermost periphery of the light beam is Hx3 ′.

When the incident angle of the incident surface 7I of the distortion correcting prism 7 is a1, the refraction angle is a2, the incident angle of the exit surface 70 is a3, and the refraction angle is a4, the beam is calculated based on the height Hyz1 ′ and the height Hyz3 ′. The reduction ratio M1 ′ can be expressed as the following equation.

  On the other hand, when the projection light beam L2 passes through the distortion correction prism 7, the x-direction of the light wavefront of the projection light beam L2 is neither enlarged nor reduced. Accordingly, the projection light beam L2 passing through the distortion correction prism 7 is shaped so that the beam is reduced only in the yz direction, and reaches the screen 8 (FIG. 1) as it is.

  FIG. 3 schematically shows the light wavefront shape of the projection light beam at the positions A ′ and C ′ in FIG. The light wavefront shape in the x direction at the positions A ′ and C ′ of the projection light beam L2 is shown in FIG. 3A, and the light wavefront shape in the yz direction is shown in FIG. 3B. In the following, the curvatures in the x direction at the positions A ′ and C ′ of the projection light beam L2 are Cx1 ′ and Cx3 ′, respectively, and the curvatures in the yz direction of the projection light beam L2 at the positions A ′ and C ′ are respectively. Let them be Cyz1 ′ and Cyz3 ′, respectively.

  As described above, the projection light beam L2 is converted into weakly convergent light by the first to third collimating lenses 3A to 3C which are isotropic spherical lenses or aspherical lenses. Therefore, the light wavefront of the projection light beam L2 at the position A ′ has an isotropic spherical shape, and the height Hx1 ′ and the height Hyz1 ′ are equal to the curvature Cx1 ′ and the curvature Cyz1 ′.

  On the other hand, at the position C ′ that has passed through only the distortion correcting prism 7, only the height Hyz3 ′ is reduced to M1 times with respect to the projection light beam L2, and the height Hyz3 ′ becomes lower than the height Hx3 ′. Further, the curvature Cyz3 ′ of the light wavefront at the position C ′ of the projection light beam L2 becomes larger than the curvature Cx3 ′ as the beam is reduced. That is, when the projection light beam L2 passes through the distortion correction prism 7, astigmatism is given such that the curvature Cyz3 ′ is larger than the curvature Cx3 ′ of the light wavefront.

  FIG. 4 shows how the shape of the light spot changes with respect to the travel distance of the projection light beam L2 emitted from the scanning projection apparatus 1. FIG. The light spot shape of the projection light beam L2 changes according to the distance from the scanning projection apparatus 1 due to astigmatism given when the projection light beam L2 passes through the distortion correction prism 7.

  Specifically, the curvature Cyz3 ′ of the light wavefront in the yz direction at the position C ′ of the projection light beam L2 described above with reference to FIG. 3B is larger than the curvature Cx3 ′ in the x direction of the light wavefront at the position C ′. The focal position in the y direction is in front of the focal position in the x direction.

  Accordingly, the shape of the light spot of the projection light beam L2 in the vicinity of the focal position in the y direction is a horizontally long elliptical shape (reference numeral 11A). Thereafter, as the projection light beam L2 travels, the shape of the light spot continuously changes so that the diameter in the y direction approaches the same length as the diameter in the x direction, and the projection light beam L2 changes to x. The shape of the light spot becomes circular when it has reached the middle position of the focal point in the direction and the y direction (reference numeral 11B).

  Further, thereafter, as the projection light beam L2 advances, the shape of the light spot continuously changes so that the diameter in the y direction becomes larger than the diameter in the x direction, and the projection light beam L2 becomes x. The shape of the light spot becomes a vertically long ellipse when it reaches the vicinity of the focal position in the direction (reference numeral 11C). Thereafter, as the projection light beam L2 proceeds, the light spot spreads while maintaining a vertically long elliptical shape (reference numeral 11D).

  Here, in the scanning projection apparatus, in order to obtain a good resolution, the shape of the light spot is preferably circular. However, in the conventional scanning projection apparatus 200, the point in time when the projection light beam L2 travels to an intermediate position between the focal points in the x direction and the y direction due to the influence of astigmatism applied by the distortion correction prism 7 as described above. Except for this, the light spot of the projection light beam L2 has an elliptical shape. For this reason, when the screen 8 (FIG. 1) is disposed at a position other than the midpoint between the focal points of the projection light beam L2 in the x and y directions, the resolution of the image projected on the screen 8 is degraded.

  FIG. 5 shows a partial configuration of the scanning projection apparatus 1 according to the present embodiment. Here, for the sake of simplicity, only the astigmatism correction element 5, the distortion correction prism 7, and the scanning mirror 6 are described, and other components are omitted. Also in FIG. 5, the alternate long and short dash line represents the optical axis of the projection light beam L2, and the wavy line represents the outermost periphery of the projection light beam L2.

  An arbitrary position on the optical path of the projection light beam L2 before passing through the astigmatism correction element 5 is a position A, and an arbitrary position on the optical path of the projection light beam L2 after passing through the astigmatism correction element 5 Is a position B, and an arbitrary position on the optical path of the projection light beam L2 after passing through the distortion correction prism 7 is a position C. In the light wavefront of the projection light beam L2, the direction perpendicular to the x direction is defined as the yz direction.

  Regarding the height from the optical axis of the projection light beam L2 in the yz direction to the outermost periphery of the projection light beam L2, the height at the position A is Hyz1, the height at the position B is Hyz2, and the height at the position C is Hyz3. And Although not shown in FIG. 5, regarding the height from the optical axis in the x direction of the projection light beam L2 to the outermost periphery of the projection light beam L2, the height at position A is Hx1, and the height at position B is high. Let Hx2 be the height and Hx3 be the height at position C.

On the incident surface 5I of the astigmatism correction element 5, assuming that the incident angle of the light beam is a5 and the refraction angle is a6, the beam expansion ratio M2 calculated based on the height Hyz1 and the height Hyz2 is as follows: Can be represented.

  The exit surface 5O of the astigmatism correction element 5 is set perpendicular to the projection light beam L2 as described above, and the projection light beam L2 passes through as it is.

Similarly, the beam reduction ratio M1 of the distortion correction prism 7 can be expressed as the following equation, similarly to the equation (1).

を満たす場合、次式

が成り立つ場合、非点収差補正素子５及び歪補正プリズム７の双方を通過した後の投射用光ビームＬ２に対するビーム整形効果が打ち消されることが分かる。 Here, from the equations (2) and (3), the relationship between the beam expansion rate M2 and the beam reduction rate M1 is as follows:

If

It is understood that the beam shaping effect on the projection light beam L2 after passing through both the astigmatism correction element 5 and the distortion correction prism 7 is canceled.

  Therefore, in the scanning projection apparatus according to the present embodiment, the incident angle a5 and the refraction angle a6 on the incident surface 5I of the astigmatism correction element 5 are set so as to satisfy the expression (4), thereby the distortion correction prism. 7 cancels the beam reduction effect by the astigmatism correction element 5 (that is, the astigmatism correction element cancels astigmatism added to the projection light beam L2 in the distortion correction prism 7). 5 can be applied in advance to the projection light beam L2.

  FIG. 6 schematically shows the light wavefront shape of the projection light beam L2 at the positions A, B, and C in FIG. FIG. 6A shows the light wavefront shape in the x direction at the positions A, B and C of the projection light beam L2, and FIG. 6B shows the light wavefront shape in the yz direction. In the following, curvatures in the x direction at the positions A, B, and C of the projection light beam L2 are Cx1, Cx2, and Cx3, respectively, and the projection light beam L2 at the positions A, B, and C in the yz direction. Let curvatures be Cyz1, Cyz2, and Cyz3.

  As described above, the light wavefront of the projection light beam L2 at the position A has an isotropic spherical shape, and the height Hx1 and the height Hyz1 are equal to the curvature Cx1 and the curvature Cyz1.

  On the other hand, at the position B that has passed through the astigmatism correction element 5, the projection light beam L2 is expanded M1 times only in the yz direction. Accordingly, the height Hyz2 in the yz direction of the projection light beam L2 at the position B is enlarged to M1 times the height Hyz1 in the yz direction at the position A, and the height Hx2 in the x direction of the projection light beam L2 at the position B. Higher than. Similarly, the curvature Cyz2 in the yz direction of the light wavefront of the projection light beam L2 at the position B also becomes smaller than the curvature Cx2 in the x direction of the light wavefront as the beam diameter increases. That is, when the projection light beam L2 passes through the astigmatism correction element 5, the light wavefront thereof is given astigmatism such that the curvature Cyz2 in the yz direction is smaller than the curvature Cx2 in the x direction.

  On the other hand, at the position C that has passed through the distortion correction prism 7, the yz direction of the light wavefront of the projection light beam L2 at the position B is again reduced to M2 times. That is, the height yz3 of the light wavefront at the position C in the yz direction is reduced to M2 times the height yz2 of the lightwavefront at the position B in the yz direction, and at the same time, the curvature Cyz3 of the light wavefront of the projection light beam L2 at the position C is also obtained. It becomes larger than the curvature Cyz2 of the light wavefront at the position B. That is, astigmatism having a sign opposite to that of the astigmatism correction element 5 is given to the projection light beam L 2 by the distortion correction prism 7.

  In this case, as described above, the relationship between the beam expansion rate M2 of the astigmatism correction element 5 and the beam reduction rate M1 of the distortion correction prism 7 satisfies the equation (4). Therefore, when passing through the distortion correction prism 7, the projection light beam L2 is reduced by the same amount as the beam expansion rate M2 by the astigmatism correction element 5, and the light beam shaping effect is canceled. Therefore, the astigmatism imparted to the projection light beam L2 is canceled and the light wavefront becomes isotropic, and the height Hyz3 in the yz direction and the height Hx3 in the x direction of the light wavefront at the position C, The curvature Cyz3 in the yz direction and the curvature Cx in the x direction of the projection light beam L2 at the position C substantially coincide with each other again.

  FIG. 7 shows how the light spot shape changes with respect to the traveling distance of the projection light beam L2 emitted from the scanning projection apparatus 1 according to the present embodiment. In the case of the present embodiment, since the astigmatism imparted by the distortion correction prism 7 is canceled out in the light beam emitted from the scanning projection apparatus 1, the x direction and y in the light wavefront of the projection light beam L2 are cancelled. The focal position in the direction matches. Therefore, the shape of the light spot in the vicinity of the focal position is circular and minimum (reference numeral 12B), and the light spot diverges before and after the circular shape (reference numerals 12A, 12C, and 12D).

  That is, in the scanning projection apparatus 1 according to the present embodiment, the spot diameter formed on the screen is circular regardless of the screen position, and good resolution can be obtained regardless of the screen position.

  As described above, according to the scanning projection apparatus 1 of the present embodiment, the astigmatism correction element 5 having the beam expansion rate M2 that satisfies the expression (4) with respect to the beam reduction rate M1 of the distortion correction prism 7 is projected. Since the astigmatism having the same amount as the astigmatism generated in the distortion correction prism 7 and having the opposite sign can be given to the light beam, the distortion correction prism 7 Astigmatism given to the light beam can be canceled out. As a result, the light spot shape on the screen can be made circular regardless of the position of the screen, thus realizing a scanning projection apparatus that can prevent image degradation while reducing image distortion of the projected image.

(2) Second Embodiment FIG. 8, which shows components corresponding to those in FIG. 1 with the same reference numerals, shows a scanning projection apparatus 20 according to a second embodiment. This scanning projection apparatus 20 is configured in the same manner as the scanning projection apparatus 1 according to the first embodiment except that the distortion correction prism 21 is configured by two or more parts.

  In practice, in the case of the present embodiment, the distortion correcting prism 21 is composed of first and second wedge prisms 21A and 21B having different refractive indexes. The first wedge prism 21A is arranged so that both the projection light beam L2 incident on the scanning mirror 6 and the projection light beam L2 reflected by the scanning mirror 6 pass therethrough, and the second wedge prism 21A is passed through. The mold prism 21B is disposed on the optical path of the projection light beam L2 reflected by the scanning mirror 6 and passed through the second wedge prism.

  As described above, in the scanning projection apparatus 20 according to the present embodiment, the distortion correcting prism 21 is configured by the two wedge prisms (first and second wedge prisms 21A and 21B) having different refractive indexes. Since the projection light beam L2 is refracted using individual wedge-shaped prisms, the wavelength difference of the green light beam L1G, the red light beam L1R, and the blue light beam L1B constituting the projection light beam L2 is accompanied. The optical axis shift of the green light beam L1G, the red light beam L1R, and the blue light beam L1B can be favorably compensated. Furthermore, in the scanning projection apparatus 20 according to the present embodiment, the first and second wedge-shaped prisms 21A and 21B constituting the distortion correcting prism 21 are arranged apart from each other. Is also possible.

  In this case, such a distortion correction prism 21 is also astigmatic to the passing projection light beam L2 because the refraction angles in the x direction and yz plane direction in FIG. 8 are different in the light wavefront of the projection light beam L2. Aberration is imparted.

  Therefore, in the scanning projection apparatus 20 according to the present embodiment, the distortion correction prism 21 adds the projection light beam L2 that passes through the distortion correction prism 21 (first and second wedge prisms 21A and 21B). The astigmatism correction element 22 is configured so that astigmatism that can cancel the astigmatism that is generated can be given to the projection light beam L2.

  Specifically, the astigmatism correction element 22 applies astigmatism to the projection light beam L2 in the same amount as the astigmatism added to the projection light beam L2 in the distortion correction prism 21, and having the opposite sign. The incident angle and the refraction angle on the incident surface of the astigmatism correction element 22 are set so that they can be added.

  As a result, in the scanning projection apparatus 20 according to the present embodiment, the green light beam L1G and the red light accompanying the difference in wavelength between the green light beam L1G, the red light beam L1R, and the blue light beam L1B constituting the projection light beam L2. While satisfactorily compensating for the optical axis shift of the beam L1R and the blue light beam L1B, it is possible to effectively prevent resolution degradation that can prevent resolution degradation while reducing image distortion of the projected image.

(3) Other Embodiments In the first and second embodiments described above, astigmatism occurs when only the curvature in the yz direction of the light wavefront of the projection light beam L2 increases in the distortion correction prism 7. Although the correction has been described, the present invention is not limited to this, and the present invention can also be applied to the case where only the curvature in the yz direction of the light wavefront of the projection light beam L2 is reduced by the distortion correction prism 7.

  In this case, astigmatism may be added by the astigmatism correction element 5 so that the curvature in the yz direction of the light wavefront of the projection light beam L2 is increased, and thereby the projection light beam L2 traveling to the screen is corrected. Astigmatism can be canceled out. Thus, regardless of the screen position, the light spot formed on the screen 8 by the projection light beam L2 can be made circular, and the resolution of the projected image does not deteriorate.

  In the first and second embodiments described above, the wavelength selective mirror is applied as the light combining elements 4A and 4B that combine the green light beam L1G, the red light beam L1R, and the blue light beam L1B. As described above, the present invention is not limited to this, and as the light combining elements 4A and 4B, a wavelength selective prism may be applied instead of the wavelength selective mirror, or one wavelength selective cross generally used in a liquid crystal projector or the like. You may make it synthesize | combine the green light beam L1G, the red light beam L1R, and the blue light beam L1B using a prism.

  Further, in the first and second embodiments described above, the green light beam L1G and the red light beam L1R are combined, and then the blue light beam L1B is combined with the green light beam L1G and the red light beam L1R. However, the present invention is not limited to this, and the synthesis order of the green light beam L1G, the red light beam L1R, and the blue light beam L1B is other than this. Also good.

  Further, in the first and second embodiments described above, the green light beam L1G, the red light beam L1R, and the blue light beam L1B are each made into a weakly convergent light beam using the first to third collimator lenses 3A to 3C. Although the case of converting is described, the present invention is not limited to this. For example, the green light beam L1G, the red light beam L1R, and the blue light beam L1B are each converted into a weakly convergent light beam by one microlens array. You may do it. In this case, the green light beam L1G, the red light beam L1R, and the blue light beam L1B are combined into one projection light beam L2 and then combined with one microlens array so that the green light beam L1G, the red light beam L1R, and the blue light beam L1B are combined. The light beam L1B may be converted into weakly convergent light.

  Further, in the first and second embodiments described above, the first to third laser light sources 2A to 2C that emit the green light beam L1G, the red light beam L1R, and the blue light beam L1B, respectively, are different packages. However, the present invention is not limited to this, and the first to third laser light sources 2A to 2C are provided in the same package (that is, the green light beam L1G, the red light beam L1R, or the blue light). It is also possible to construct one laser light source that emits the beam L1B.

  Further, in the first and second embodiments described above, the case where the astigmatism correction elements 5 and 22 are configured by wedge prisms has been described. However, the present invention is not limited to this, and for example, FIG. As shown in FIG. 5, the astigmatism correction element is formed by the cylindrical lens 31 having a predetermined curvature in the direction parallel to the projection light beam L2 on the yz plane orthogonal to the plane parallel to the x direction of the cross section. 5 and 22 may be configured. This also makes it possible to expand the projection light beam only in the yz direction perpendicular to the x direction, while maintaining the x direction of the light wavefront of the projection light beam L2.

  The present invention relates to a scanning projection apparatus, and can be widely applied to scanning projection apparatuses having various configurations in which a distortion correction prism is disposed on an optical path of a projection light beam.

  DESCRIPTION OF SYMBOLS 1,20 ... Scanning projection apparatus, 2A-2C ... Laser light source, 3A-3C ... Collimator lens, 4A, 4B ... Photosynthesis element, 5,22 ... Astigmatism correction element, 6 ... Scanning mirror , 7, 21 ... distortion correction prism, 8 ... screen, 21A, 21B ... wedge-shaped prism, 31 ... cylindrical lens.

Claims (4)

In a scanning projection device that projects a two-dimensional image on a projection surface by scanning a light beam on the projection surface,
A laser light source for emitting the light beam;
A first deflection axis and a second deflection axis orthogonal to the first deflection axis, and driving the deflection of the light beam about the first and / or second deflection axis to cause the light beam to be projected A scanning mirror that reflects in a two-dimensional scan above;
Distortion correction that is placed between the scanning mirror and the projection surface and refracts the light beam at a predetermined angle so that the angle between the light beam reflected by the scanning mirror and the projection surface becomes a predetermined angle. Prism,
An astigmatism correction element disposed between the laser light source and the distortion correction prism and generating astigmatism in the light beam,
The astigmatism correction element is
Astigmatism that cancels astigmatism added to the light beam in the distortion correction prism is added to the light beam in advance ,
The distortion correction prism is
It is composed of first and second wedge prisms having different refractive indexes,
The first wedge-shaped prism is
Both the light beam incident on the scanning mirror and the light beam reflected by the scanning mirror pass through,
The second wedge prism is
A scanning projection apparatus, wherein the scanning projection apparatus is disposed on an optical path of the light beam reflected by the scanning mirror and passed through the first wedge prism . The distortion correction prism is
Adding astigmatism to the light beam to enlarge or reduce a predetermined first direction of the light wavefront of the light beam at a predetermined beam shaping rate;
The astigmatism correction element is
2. The scanning projection apparatus according to claim 1, wherein the first direction of the light wavefront of the light beam is reduced or enlarged in the opposite direction by substantially the same amount as the beam shaping rate of the distortion correction prism. . The astigmatism correction element is
The scanning projection apparatus according to claim 1, wherein the scanning projection apparatus is a wedge-shaped or trapezoidal prism made of glass having a predetermined refractive index or plastic for optical parts and having a predetermined apex angle. The astigmatism correction element is
2. The scanning projection apparatus according to claim 1, wherein the first direction of the cross section is a plane, and a second direction orthogonal thereto is a cylindrical lens having a predetermined curvature.

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