JP5909334B2 - Light beam scanning device and image display device using the same - Google Patents

Description

  The present invention relates to a light beam scanning device and an image display device using the same, and in particular, by projecting and displaying an image on a predetermined projection screen surface, for example, by scanning a light beam two-dimensionally with a predetermined light beam deflecting means. The present invention relates to the optical device.

  In recent years, a light beam emitted from a predetermined light source is projected on a predetermined screen, and the light beam is two-dimensionally deflected by a predetermined deflecting means, thereby causing the light beam to be two-dimensionally projected on the projection screen. Various light beam scanning devices or scanning image display devices having a function of projecting and displaying a two-dimensional image on the screen by the afterimage effect are proposed.

  In such a scanning image display device, as a deflecting means for deflecting the light beam emitted from the light source in a two-dimensional manner, a galvanometer mirror or MEMS (Micro Electro-Mechanical Systems) which has attracted considerable attention in recent years. ) Reflective light beam deflection scanning elements or apparatuses typified by MEMS mirror devices using technology are widely used.

  However, on the other hand, when a light beam is scanned two-dimensionally using such a reflection type light beam deflection scanning element or device, an ideal on the projection screen is obtained by a combination of a horizontal deflection angle and a vertical deflection angle. There is a problem that a deviation occurs with respect to a typical scanning line, and as a result, a large image distortion occurs in the two-dimensional image projected on the screen.

  That is, in order to display the two-dimensional image with high quality in the light beam scanning apparatus or the scanning type image display apparatus as described above, it is necessary to satisfactorily remove or correct the image distortion caused by the light beam scanning as described above. This means is essential.

  As such an image distortion correcting means or device, for example, disclosed in Patent Document 1 is “a deflector having a sine wave drive in the first scanning direction, and one optical surface constituting the scanning optical system is The second-order differential value in the first scanning direction changes in a direction to diverge the deflected light beam from the center in the first scanning direction toward the periphery, and the shape is continuous with the second running direction. There is a characteristic optical scanning device.

JP 2006-178346 A

  Although the conventional image distortion correction technique as disclosed in the known example can be expected to have a certain effect with respect to the reduction of the image distortion, three optical elements having a free-form surface as an optical system for distortion correction. A reflective surface or lens surface is required, and its size and complexity are inevitable.

  In view of the circumstances as described above, the present invention provides a light beam scanning device that realizes the image distortion correction with a very simple optical system configuration and an image display device using the same.

The object can be achieved by the invention described in the claims.

  According to the present invention, by using a small and very simple optical element, it is possible to realize a light beam scanning apparatus that can satisfactorily correct the image distortion as described above and an image display apparatus using the same.

1 is a schematic side view showing a first embodiment of a light beam scanning image display apparatus according to the present invention. The top view which showed an example of the image projected with the conventional light beam scanning type image display apparatus A diagram showing an example of the relationship between the elevation angle of the initial reflection optical axis from the deflecting mirror, the distortion rate RMS value D, and the optimum apex angle δ of the image distortion correction prism The top view which showed an example of the image projected with the light beam scanning type image display apparatus carrying the image distortion correction prism of this invention A diagram showing an example of the relationship between the initial incident angle of the deflecting mirror incident optical axis, the optimal elevation angle of the deflecting mirror initial reflecting optical axis, and the optimal apex angle δ of the image distortion correcting prism Schematic side view showing a second embodiment of the image distortion correcting prism of the present invention. Schematic side view showing a third embodiment relating to an image distortion correcting prism of the present invention and a light beam scanning image display device equipped with the prism. Schematic side view showing a fourth embodiment relating to an image distortion correcting prism of the present invention and a light beam scanning image display device equipped with the prism. The diagram which showed the example regarding optical performances, such as the specific example regarding the combination of the vertex angle of each wedge-shaped prism in 4th Example of this invention, and image distortion correction performance

  Embodiments of the present invention will be described below with reference to the drawings. As a matter of course, the present invention is not limited to the configurations of the embodiments described below.

  FIG. 1 is a schematic side view showing a first embodiment of a light beam scanning device and an image display device using the same according to the present invention. Note that the one-dot chain line in the figure represents the optical axis of the light beam.

  The light beam scanning device in this embodiment includes a light source unit 100 that generates and emits a light beam for image display, a deflection mirror device 9 that deflects and scans the light beam in two dimensions, and an image distortion correction as described later. The wedge-shaped prism 10 is configured as a main optical component.

  First, the configuration of the light source unit 100 will be briefly described. In the light source unit 100, three laser light sources 1, 2, and 3 having different wavelengths are arranged.

  Reference numeral 1 denotes a semiconductor laser light source that emits a green light beam having a wavelength of 520 nm, for example. The green light beam emitted from the semiconductor laser light source 1 is converted into a substantially parallel light beam by the collimator lens 4 and then enters the flat mirror 7.

  Reference numeral 2 denotes a semiconductor laser light source that emits a red light beam having a wavelength of 640 nm, for example. Similarly to the green light beam emitted from the semiconductor laser light source 1, the red light beam emitted from the semiconductor laser light source 2 is converted into a substantially parallel light beam by the collimator lens 5 and then enters the flat mirror 7.

  The flat mirror 7 has a function of transmitting the green light beam emitted from the semiconductor laser light source 1 with a predetermined transmittance and reflecting the red light beam emitted from the semiconductor laser light source 2 with a predetermined reflectance. Each of the light beams transmitted or reflected by the flat mirror 7 travels along substantially the same optical path and enters the flat mirror 8.

  On the other hand, 3 is a semiconductor laser light source that emits a blue light beam having a wavelength of 440 nm, for example. The blue light beam emitted from the semiconductor laser light source 3 is converted into a substantially parallel light beam by the collimator lens 6 and then enters the flat mirror 8.

  The flat mirror 8 is a second wavelength-selective mirror having a function of transmitting the green light beam and the red light beam with a predetermined transmittance and reflecting the blue light beam with a predetermined reflectance.

  The green, red, and blue light beams respectively transmitted or reflected by the second wavelength selective mirror 8 have their respective optical axes so that their light beam cross sections overlap each other and travel as substantially the same light beam. The light source unit 100 exits the light source unit 100 in a state in which the tilt and position are strictly adjusted, and enters the deflection mirror device 9 for light beam scanning.

  Naturally, the light source unit 100 is not limited to the above-described configuration, and any configuration is possible as long as the light source unit has a function of emitting a light beam for projecting and displaying an image by deflection scanning. It does not matter.

  Next, the deflecting mirror device 9 for scanning the light beam reflects the light beam incident on a predetermined reflecting mirror arranged in the device, and projects the reflected light beam at a predetermined distance from the deflecting mirror device 9. While projecting on the screen 20, the reflecting mirror surface itself is formed with a predetermined rotation axis 91 substantially perpendicular to the paper surface, that is, substantially parallel to the Y axis in the drawing, and parallel to the paper surface, that is, the XZ axis in the drawing. It has a function of performing high-speed repetitive deflection driving at a predetermined angle around a predetermined rotation axis 92 substantially parallel to the plane.

  As a result, the reflected light beam projected on the projection screen 20 is high-speed two-dimensionally in the horizontal direction (Y-axis direction in the figure) and in the vertical direction (Z-axis direction in the figure) on the projection screen 20 surface. Scanned.

  At this time, the optical output of each of the laser light sources 1, 2 and 3 is independently modulated in synchronization with the scanning position of the reflected light beam on the projection screen 20, thereby utilizing the afterimage phenomenon of the human eye. A two-dimensional color image is projected and displayed on the projection screen 20.

  By the way, in this embodiment, as described above, the deflecting mirror device 9 for scanning the light beam is composed of one reflecting mirror that is driven to be repeatedly deflected at high speed around the rotation axes 30 and 31 perpendicular to each other. The deflection mirror device 9 having such a configuration is generally referred to as a biaxial single-surface type deflection mirror device.

  The use of such a biaxial single-sided deflection mirror device is extremely advantageous from the viewpoint of downsizing the scanning image display device or reducing the number of optical components, and may be widely used in the future. The invention is not limited to the scanning type image display device using such a biaxial single-surface type deflection mirror device. For example, high-speed repetitive deflection driving is performed around one rotation axis that is substantially perpendicular to each other. Other deflection methods and configurations, such as a device generally called a uniaxial, two-surface type deflection mirror device, which has an independent two-surface deflection mirror and a configuration in which the incident light beam is sequentially reflected by the two-surface deflection mirror. The present invention can also be applied to a light beam scanning device using a light beam scanning deflection mirror device and an image display device using the same.

  Examples of the configuration of the mirror driving unit in the above-described light beam scanning deflection mirror device 9 include, for example, Micro Electro Mechanical Systems (abbreviated as MEMS), an electromagnetically driven galvanometer mirror, and the like. The specific configuration of the deflecting mirror device driving unit is not directly related to the present invention, and a detailed description thereof will be omitted.

  By the way, in the first embodiment of the present invention shown in FIG. 1, the wedge-shaped prism 10 is arranged in the reflected light beam optical path between the light beam scanning deflection mirror device 9 and the projection screen 20. The wedge-shaped prism 10 is an optical prism for correcting image distortion, which is the core of the present invention.

  In this embodiment, the wedge-shaped prism 10 for correcting image distortion is provided with a relative inclination angle between the optical surface 11 on the light beam incident side and the optical surface 12 on the light beam exit side as shown in the figure. The prism apex angle δ is defined, and the optical surface 12 on the light beam emission side is arranged so as to be substantially parallel to the vertical direction (Z-axis direction in the drawing).

  Hereinafter, a specific configuration of the image distortion correcting prism and its image distortion correcting effect will be described.

  First, an image distortion problem in a conventional light beam scanning image display apparatus that does not include any image distortion correcting means as in the present invention will be described.

  For example, FIG. 2 uses a deflection mirror device 9 for scanning a light beam having a function of repeatedly deflecting a reflection mirror at a high speed with a deflection angle of ± about 14 degrees in the horizontal direction and ± about 7 degrees in the vertical direction. When a simple rectangular frame is displayed on the projection screen 20 having a screen surface parallel to the vertical direction at a position 1 m away from 9, an image actually drawn is reproduced by computer simulation.

  When reproducing and displaying an image by computer simulation, the light beam incident on the deflection mirror device 9 is parallel to the horizontal direction (X-axis direction in FIG. 1) and is in the initial state, that is, the reflection mirror in the deflection mirror device 9. The simulation was performed by setting the incident angle of the incident light beam to the reflecting mirror surface (β in FIG. 1) to 15 degrees when is in a neutral state. In this case, the elevation angle (α in FIG. 1) from the horizontal direction (X-axis direction in FIG. 1) of the initial reflected light beam 50 reflected from the deflection mirror device 9 and traveling toward the origin O of the projection screen 20 is necessarily 30. It is a degree.

  Further, in order to reproduce the performance of a conventional light beam scanning image display apparatus, this figure shows an image when no means for correcting image distortion is provided.

  In this figure, the horizontal axis represents the image size in the horizontal direction (corresponding to the Y-axis direction in FIG. 1), and the vertical axis represents the image size in the vertical direction (corresponding to the Z-axis direction in FIG. 1).

  Further, the solid line in the figure indicates an image of a rectangular frame that is actually displayed, and the broken line indicates an image of an ideal rectangular frame that should be originally displayed.

  As is clear from this figure, the image of the rectangular frame displayed by scanning the light beam two-dimensionally with the deflecting mirror device 9 is trapezoidal because the lengths of the upper side and the lower side are different, for example. In addition, each side that should be originally drawn as a straight line has become an arc-shaped curve.

  As a result, a large distortion occurs in the display image, and the display positions of the four corner vertices C1, C2, C3, and C4 of the displayed rectangular frame are ideal display positions, that is, 4 of the ideal rectangular frame image represented by a broken line. It has shifted greatly from the corner apex position.

  If there is such a large image distortion, the shape of the display image is naturally not displayed correctly, and the image quality is greatly impaired. Therefore, it is desirable to delete or correct such image distortion as much as possible.

  Therefore, first, an evaluation index for quantitatively grasping the magnitude of such image distortion is defined as follows. That is, as shown in the figure, among the shift amounts from the ideal display positions of the four corner vertices C1, C2, C3, and C4 of the rectangular frame image, the horizontal shift components are Hc1, Hc2, Hc3, and Hc4, respectively. The vertical shift components are represented by Vc1, Vc2, Vc3, and Vc4, respectively. Then, each shift component is divided by the horizontal width Lh or vertical width Lv of the ideal rectangular frame image, and each shift component is expressed as a ratio to the display width of the ideal rectangular frame. Then, the root mean square (RMS value for short) D of each deviation component ratio is defined. That is,

(Equation 1)
D = SQRT [(Hc1 / Lh) ² + (Hc2 / Lh) ² + (Hc3 / Lh) ²
+ (Hc4 / Lh) ² + (Vc1 / Lv) ² + (Vc2 / Lv) ²
+ (Vc3 / Lv) ² + (Vc4 / Lv) ² ]

By using the distortion rate RMS value D expressed by the above [Equation 1], it is possible to quantitatively grasp the magnitude of image distortion that occurs. That is, the larger the distortion rate RMS value D, the larger the image distortion. Conversely, the closer the D value is to zero, the smaller the image distortion and the closer to the ideal display image. For example, the display image on the conventional image display device shown in FIG. 2 has a distortion factor RMS value D of about 8.4%.

  In the present invention, as an optical means for significantly reducing the distortion rate RMS value D and favorably reducing or correcting the image distortion of the display image, as shown in FIG. A wedge-shaped prism 10 for correcting image distortion (hereinafter referred to as a distortion correcting prism for the sake of simplicity) is disposed in the reflected light beam optical path 20.

  3 shows the relationship between the elevation angle α from the horizontal direction (X-axis direction in FIG. 1) of the initial optical axis 50 of the reflected light beam emitted from the deflecting mirror device 9 in FIG. 1 and the distortion factor RMS value D. It is the graph which plotted the case where the distortion correction prism 10 is arrange | positioned like this invention, and the case where no image distortion correction means is arrange | positioned like the past. A diagram 501 in the figure shows a case where the distortion correction prism 10 of the present invention is arranged, and a diagram 502 shows a case where no image distortion correction means is arranged.

  In the case where the distortion correction prism 10 is disposed, the optimum prism apex angle δ of the distortion correction prism 10 at which the distortion rate RMS value D takes the minimum value Dmin is searched, and the Dmin is plotted, and the optimum prism apex angle δ is plotted. Is plotted as a diagram 503 in the same graph.

  In this figure, it is assumed that the initial incident angle β of the light beam incident on the reflecting mirror in the deflecting mirror device 9 is 15 degrees as in FIG.

  Further, it is assumed that the distortion correction prism 10 used in FIG. 3 is configured by BK-7 (refractive index nd = 1.51633) which is a general glass material for optical parts as an example.

  As is apparent from this figure, the distortion rate RMS value D changes depending on the initial elevation angle α of the reflected light beam emitted from the deflection mirror device 9 regardless of the presence or absence of the distortion correction prism 10, and is minimized at a predetermined elevation angle. Takes a value.

  For example, in the case of a conventional configuration in which the distortion correction prism 10 is not disposed, the value D is the minimum value of 5.4% at the point A in the diagram 502, that is, the elevation angle α = 0 degrees.

  On the other hand, when the distortion correcting prism 10 is installed, the D value is clearly lower than the conventional configuration in which the distortion correcting prism 10 is not installed as shown in the diagram 501. Further, in this case, the D value becomes the minimum value at the point B in the figure, that is, in the vicinity of the initial elevation angle α = 22 degrees, and the value is about 1.5%.

  That is, as shown in the embodiment of FIG. 1, the distortion correction prism 10 is arranged and the elevation angle is set to the optimum angle, so that the distortion rate RMS value D is significantly reduced to about 30% of the conventional value. It is possible.

  The optimum apex angle δ of the distortion correction prism 10 for the D value to be about 1.5% is about 14 degrees. As a result of computer simulation, if the apex angle δ of the distortion correcting prism 10 is within a range of 14 degrees ± 3 degrees, the distortion rate RMS value D is 2.0% or less, and image distortion is sufficiently reduced. I know that.

  FIG. 4 shows a projection screen when the distortion correction prism 10 having the prism apex angle δ = 14 degrees as described above is arranged in the reflected light path from the deflecting mirror device 9 and the initial elevation angle α is set to 22 degrees. The rectangular frame image drawn on 20 is reproduced by computer simulation. Various conditions other than the parameters described above were the same as in FIG.

  As is clear from comparison between FIG. 2 and FIG. 2, the distortion correction prism 10 is installed in the reflected light path, and the initial elevation angle α and prism apex angle δ of the reflected light beam optical axis 50 incident on the prism are optimally designed. Thus, the generated image distortion can be greatly reduced, and an image quality almost equivalent to the ideal display image can be obtained.

  Meanwhile, the optimum value of the initial elevation angle α of the reflected light beam optical axis 50 that minimizes the distortion rate RMS value D and the optimum apex angle δ of the distortion correction prism 10 are the light beams incident on the reflecting mirror in the deflection mirror device 9. Depending on the initial angle of incidence β.

  FIG. 5 plots the relationship between the initial incident angle β of the incident light beam, the optimum value of the initial elevation angle α of the reflected light beam that minimizes the distortion rate RMS value D, and the optimum apex angle δ of the distortion correcting prism 10. It is a graph. In the figure, the horizontal axis represents the initial incident angle β, and the vertical axis represents the optimum value of the initial elevation angle α and the optimum apex angle δ of the distortion correcting prism. Various conditions other than those described above are the same as the conditions set in FIGS.

  A diagram 601 in the figure shows the relationship between the initial incident angle β and the optimum value of the initial elevation angle α, and a diagram 602 shows the relationship between the initial incident angle β and the optimum apex angle δ of the distortion correcting prism. Show.

  Both diagrams are almost straight lines, indicating that β and α and β and δ are in a proportional relationship. In addition, formulas representing the respective straight lines are shown in the figure.

  That is, in all of the embodiments of FIGS. 1 to 4, the case where the initial incident angle β is 15 degrees is described, but it goes without saying that the present invention can be applied even when the initial incident angle β is other than 15 degrees. In this case, the optimum value of the initial elevation angle α of the reflected light beam and the optimum apex angle δ of the distortion correction prism 10 can be easily calculated using, for example, the results shown in FIG.

  In the embodiments of FIGS. 1 to 5, it is assumed that BK-7, which is a general glass material for optical parts, is used as the glass material constituting the distortion correcting prism 10, but of course other glass materials are used. Even if the prism is configured by using, it does not matter.

  In general, the refractive index of a glass material slightly changes according to the wavelength of an incident light beam. As an index indicating the magnitude of the wavelength change, there is an index called a refractive index dispersion value or an Abbe number. A glass material having a larger Abbe number has a smaller refractive index dispersion value and a smaller rate of change in the refractive index with respect to the wavelength of the incident light beam. As a result, when the incident light beam is refracted by the prism, the change in the refraction angle caused by the difference in the refractive index generated according to the wavelength of the incident light beam can be suppressed to a small level.

  Therefore, for example, by constituting the distortion correction prism 10 with a glass material having an Abbe number larger than that of the BK-7 and thus a refractive index dispersion value, red, green and blue image display light beams are incident on the distortion correction prism. The relative deviation of the refraction angle at the time of refraction can be reduced, and as a result, the relative pixel deviation (color deviation) of the three primary colors on the projection screen can be minimized.

  In this case, the refractive index of the newly used glass material naturally has a refractive index different from the refractive index of the BK-7 (nd = 1.51633). Accordingly, the reflected light beam optical axis is accordingly increased. The optimum value of the initial elevation angle α and the optimum apex angle δ of the distortion correction prism 10 are also different from those of the distortion correction prism configured using BK-7.

  1 to 5, the distortion correction prism 10 is a wedge-shaped prism having a predetermined apex angle δ, and the optical surface (surface 12 in FIG. 1) of the prism is the light beam emission side. Although the description has been limited to an example in which it is arranged in a direction that is substantially parallel to the vertical direction (Z-axis direction in the drawing), it is of course not limited to prisms of this shape and arrangement. Any shape and arrangement as long as the optical prism has a predetermined inclination angle δ between the incident side optical surface (corresponding to the surface 11 in FIG. 1) and the light beam emitting side optical surface (corresponding to the surface 12 in FIG. 1). Even if it is a prism, it does not matter.

  In the following [Embodiment 2], another configuration example of the distortion correcting prism 10 will be introduced.

  FIG. 6 is a schematic side view of a prism body showing a second embodiment relating to the distortion correcting prism 10 of the present invention. The light beam scanning apparatus and the image display apparatus using the same in the present embodiment are the same as those in the embodiment of FIG. 1 except for the distortion correction prism 10, and thus the drawings and detailed description thereof are omitted.

  The distortion correcting prism 10 in the present embodiment is composed of at least two types of glass materials having different refractive indexes or refractive index dispersion values or Abbe numbers, and each has a predetermined apex angle δ1 and δ2, respectively. As shown in the figure, a composite prism in which 10a and the second wedge-shaped prism 10b are bonded together is formed.

  By combining a plurality of prisms made of different glass materials in this way, the relative deviation of the refractive angles of the red, green and blue image display light beams generated by the refractive index dispersion characteristics of each prism can be reduced. The prisms can be set to compensate for each other. As a result, good image distortion correction is achieved, and the relative pixel shift (color shift) of the three primary colors on the projection screen 20 that could not be completely removed by a single prism is almost a problem in performance. It can be reduced to the extent that it is not.

  For example, when a rectangular frame as shown in FIG. 4 is displayed, a single wedge-shaped prism composed only of the glass material BK-7 as shown in the first embodiment of the present invention is replaced with a distortion correcting prism 10. In this case, the relative pixel shift (color shift) of the three primary colors of red, green, and blue occurs at the maximum of about 1 mm at the four corners of the display figure.

  On the other hand, for example, this distortion correction prism 10 is made up of a first prism 10a made of a glass material BK-7 (nd = 1.51633, Abbe number νd = 64.1) and an apex angle δ1 = 20 degrees, and a high refractive index and high dispersion. The above-mentioned distortion is caused by a composite prism in which a second prism 10b made of a glass material L-LAH83 (nd = 1.864, Abbe number νd = 40.6) and apex angle δ2 = 14.5 degrees is bonded as shown in FIG. By configuring the correction prism 10, the relative pixel shift (color shift) of the three primary colors can be reduced to 0.2 mm or less at the maximum.

  Note that a composite prism in which so-called color misregistration is satisfactorily reduced by the composite prism configuration as described above is generally referred to as an achromatic prism. Of course, the distortion correcting prism of the present invention having such an achromatic effect is described above. It is not limited to such a combination of glass material BK-7 and L-LAH83, and can be realized by a combination of other glass materials.

  However, in the case of a combination of other glass materials, naturally, the optimum prism apex angle combination that provides the best image distortion correction effect depends on the refractive index of each glass material and the combination thereof. For example, the design method disclosed in the present invention Must be optimally designed.

The image distortion correcting prism described above is disposed, for example, in a light beam exit opening of a light beam scanning device and an image display device using the same, and the opening portion prevents dust and dirt from entering the device. The image distortion correction prism can be used also as a dustproof transparent window member.

  FIG. 7 is a schematic side view showing another embodiment of the light beam scanning apparatus and the image display apparatus using the same according to the present invention. Note that the one-dot chain line in the figure represents the optical axis of the light beam. In this figure, the same reference numerals are assigned to the same components as those in the first embodiment of the present invention shown in FIG.

  This embodiment has structural features different from those of the first embodiment of the present invention shown in FIG. 1 as described below.

  First, the first feature is that a composite prism formed by bonding two wedge-shaped prisms made of predetermined glass materials having different refractive indexes or refractive index dispersion values as shown in FIG. 6 is a prism for correcting image distortion. It is a point used as.

  As a specific example of the constituent glass material and the shape, the first prism 10a constituting the composite distortion correcting prism 10 in the drawing has a glass material name BK-7 (refractive index nd = 1.51633, Abbe as a glass material). Number vd = 64.1), and the apex angle δ1 is 20 degrees.

  On the other hand, the second prism 10b constituting the composite distortion correcting prism 10 is constituted by a glass material name N-F2 (refractive index nd = 1.62004, Abbe number vd = 36.3) as a glass material, and the apex angle thereof. The angle of δ2 is 10 degrees.

  Next, the second feature of the present embodiment is that the outgoing light beam that is emitted from the light source unit 100 and incident on the deflecting mirror device 9 for scanning the light beam and the deflecting mirror device 9 are reflected and directed to the projection screen 20. The composite distortion correction prism 10 is disposed immediately before the deflection mirror device 9 so that both the return light beams pass through the composite distortion correction prism 10.

  As a specific example of the arrangement, the center optical axis 48 of the outward light beam emitted from the light source unit 100 travels in a substantially horizontal direction (a direction substantially parallel to the X axis in the drawing), and first, composite distortion correction is performed. The light enters the incident surface 12 in the prism 10 from a substantially right angle direction, that is, a direction where the incident angle is approximately 0 degrees. The prisms 10b and 10a constituting the composite distortion correcting prism 10 are sequentially transmitted in this order and emitted from the surface 11.

  Next, the forward light beam 49 emitted from the composite distortion correcting prism 10 enters the deflecting mirror device 9 for scanning the light beam, reflects the reflecting mirror in the deflecting mirror device 9, and then becomes a return light beam again. The light enters the composite distortion correcting prism 10 from the surface 11 side. At this time, when the deflection mirror device 9 is in the initial state (neutral state), the incident angle of the central optical axis 50 of the return path light beam with respect to the incident surface 11 (the surface normal of the surface 11 and the center optical axis of the return path light beam). The reflection mirror in the deflection mirror device 9 is installed at a predetermined installation angle so that the angle α formed by 50 is about 27 degrees.

  Then, the return light beam incident on the composite distortion correcting prism 10 again from the incident surface 11 is sequentially transmitted through the prisms 10a and 10b constituting the composite distortion correcting prism 10 in this order, and is emitted from the surface 12 again. Thereafter, the light travels toward the projection screen 20 as a return light beam 51.

  As in this embodiment, when the distortion correcting prism 10 is a composite prism and both the forward light beam and the backward light beam are incident on the distortion correcting prism 10 from substantially opposite directions, image distortion is caused. In addition, it is possible to satisfactorily compensate for the relative pixel shift (color shift) due to the difference in the wavelengths of the RGB three primary colors on the projection screen 20 and to set the distortion correction prism 10 immediately before the light beam scanning deflection mirror device 9. As a result, the light beam scanning device of the present invention or the image display device using the same can be greatly reduced in size.

  Of course, the specific parameters relating to the configuration and shape of the distortion correcting prism 10 and the arrangement thereof in the [Embodiment 3] of the present invention as described above are merely examples of the parameters. It is not limited to.

  Using a composite distortion correction prism composed of a plurality of prisms made of different glass materials, an outward light beam that exits the light source unit and enters the deflection mirror device, and a return light that reflects from the deflection mirror device and travels toward the projection screen Any configuration may be used as long as the light beam scanning device in which the distortion correction prism is arranged so that both beams pass through the distortion correction prism or an image display device using the same.

  FIG. 8 is a schematic side view showing another embodiment of the light beam scanning apparatus and the image display apparatus using the same according to the present invention. Note that the one-dot chain line in the figure represents the optical axis of the light beam. In this figure, the same reference numerals are assigned to the same components as those of the embodiments of the present invention shown in FIGS.

  As shown below, the present embodiment has structural features different from those of the first, second, and third embodiments of the present invention described above.

  First, the first feature of this embodiment is that the two wedge-shaped prisms 10a and 10b constituting the distortion correcting prism 10 are arranged at positions separated by a predetermined distance. The wedge-shaped prisms 10a and 10b are made of predetermined glass materials having different refractive indices or refractive index dispersion values as in the second and third embodiments.

  Next, as a second feature of the present embodiment, two wedge-shaped prisms constituting the distortion correcting prism 10 are formed by the outward light beam that is emitted from the light source unit 100 and incident on the deflecting mirror device 9 for scanning the light beam. 1 is transmitted through only one of the prisms (the prism 10a in the example in the figure) and then enters the deflection mirror device 9. On the other hand, the return light beam reflected by the deflection mirror device 9 and directed to the projection screen 20 is reflected. The point is that the two wedge-shaped prisms 10a and 10b are sequentially transmitted.

  FIG. 9 is a graph for explaining a specific configuration example of this embodiment and an example of its optical performance.

  As a specific configuration example of the present embodiment, the first wedge-shaped prism 10a is made of a glass material (refractive index nd = 1.51633, Abbe number vd = 64.1) generally called a glass material name BK-7. A prism having an isosceles triangle shape with an apex angle δ1, and the second wedge-shaped prism 10b is a glass material generally called a glass material name N-F2 (refractive index nd = 1.62004, Abbe number vd = 36.3). Assume that the prism has a shape of a right triangle with a vertical angle δ2 using (1) (a vertical surface is disposed on the side facing the deflection mirror device 9 as shown in FIG. 8).

  FIG. 9 shows a case where the distortion correcting prism 10 as shown in FIG. 8 is configured using such two wedge-shaped prisms, and the apex angle δ1 of the first wedge-shaped prism 10a is taken as the horizontal axis, and each δ1 , The optimum angle of the apex angle δ2 of the second wedge-shaped prism 10b for minimizing the minimum of the distortion factor RMS value D, the value of the distortion factor RMS value D at that time, and the wavelengths of the RGB three primary colors 5 is a graph in which the relationship between the respective parameters is plotted with the maximum value of the relative pixel shift (color shift) amount on the projection screen 20 accompanying the vertical axis as the vertical axis.

  In FIG. 9, it is assumed that the distance from the light beam scanning device on which the deflection mirror device 9 and the distortion correction prism 10 are mounted to the projection screen 20 is 40 cm.

  In addition, the reflection mirror provided in the deflection mirror device 9 can swing two-dimensionally with a deflection angle of ± about 14 degrees in the horizontal direction and ± about 7 degrees in the vertical direction, as in the case of FIG. The reflection mirror is arranged so as to be substantially parallel to the vertical direction. Further, in the initial state, the incident angle β of the forward light beam incident on the deflection mirror device 9 is defined as 15 °.

  In this way, in order to regulate the incident angle β of the forward light beam incident on the deflection mirror device 9 to 15 °, the forward light beam emitted from the light source unit 100 and incident on the first wedge-shaped prism 10a. The incident angle γ must be set to an optimum angle according to the value of the apex angle δ1 of the first wedge prism 10a.

  Further, the maximum value of the relative pixel shift (color shift) amount on the projection screen 20 is the optical axis tilt in the initial state of each RGB light beam in order to make the relative pixel shift at the center of the image zero. When the reflection mirror provided in the deflecting mirror device 9 is driven to be two-dimensionally deflected to form an image after the adjustment, the relative pixel shift remaining at the four corners of the image, that is, the residual color shift amount The maximum value is shown. Further, in order to make the graph easy to see, values obtained by multiplying the maximum residual pixel shift (color shift) amount by 10 are plotted in FIG.

  As is apparent from the figure, a proportional relationship is established between the apex angle δ1 of the first prism 10a and the optimal apex angle δ2 of the second prism 10b that fits the apex angle δ1, and the relationship is approximately the following relational expression: It is represented by

(Expression 2) δ2≈0.94 × δ1 + 14.5
Further, when the relationship between the apex angle δ1 of the first wedge-shaped prism 10a and the apex angle δ2 of the second wedge-shaped prism 10b satisfies the relationship shown in FIG. 9 or [Equation 2], the apex angle δ1. Is about 35 ° or less, the image distortion rate RMS value D on the projection screen can be 2% or less, and if the apex angle δ1 is between 25 ° and 30 °, The maximum light beam residual pixel deviation amount can be suppressed to 0.1 mm or less.

  As described above, by adopting the configuration as in this embodiment, as in the second and third embodiments, relative to the image distortion and the wavelength of the RGB three primary colors on the projection screen 20 are different. In addition to excellent pixel misalignment (color misregistration), the degree of freedom in designing the arrangement of the light source unit 100, the light beam scanning deflection mirror device 9 and the distortion correcting prism 10 is increased. Further miniaturization of the beam scanning device or the image display device using the beam scanning device can be realized.

  However, the relationship between the apex angle δ1 of the first wedge-shaped prism 10a and the apex angle δ2 of the second wedge-shaped prism 10b as represented by FIG. This is merely an example of the configuration and shape of the distortion correction prism 10 in [Embodiment 4], or the arrangement thereof, and it should be understood that the present invention is not limited to this.

  That is, an optical member for correcting image distortion composed of a plurality of wedge-shaped prisms each made of a predetermined glass material different from each other and having a predetermined apex angle is reflected at least on the deflection mirror device and travels toward the projection screen. Any configuration may be used as long as it is a light beam scanning device or an image display device using the light beam scanning device characterized by being arranged in the optical path of the beam.

DESCRIPTION OF SYMBOLS 1, 2, 3 ... Semiconductor laser light source, 4, 5, 6 ... Collimating lens, 7, 8 ... Wavelength selective mirror, 9 ... Deflection mirror device for light beam scanning, 10 ... Prism for image distortion correction, 20 ... Projection screen

Claims (4)

A light source and a predetermined optical reflecting surface that repeatedly drives to deflect in two directions substantially orthogonal to each other;
In a light beam scanning apparatus having a function of deflecting and scanning a light beam emitted from the light source and reflected from the optical reflecting surface in a first scanning direction and a second scanning direction substantially orthogonal thereto,
In the optical path of the light beam reflected the optical reflecting surface, arranged wedge or trapezoidal prism with a result and predetermined apex angle from transparent optical glass or optical component plastics having a predetermined refractive index ,
The light beam incident on the optical reflecting surface and the light beam reflected by the optical reflecting surface are arranged so as to pass through the optical prism,
The wedge-shaped or trapezoidal prism is disposed in the light beam emission opening of the beam scanning device or an image display device using the beam scanning device, and the prism is sealed with the prism, thereby allowing the prism to be transparent for dust prevention. A light beam scanning device characterized by being used also as a member .   The apex angle of the wedge-shaped or trapezoidal optical prism is an angle formed by an incident surface and an output surface on which the light beam reflected by the optical reflecting surface enters the optical prism, and the apex angle is 14 ° ± 3. 2. The light beam scanning device according to claim 1, wherein the light beam scanning device is in a range of °. A light source and a predetermined optical reflecting surface that repeatedly drives to deflect in two directions substantially orthogonal to each other;
In a light beam scanning apparatus having a function of deflecting and scanning a light beam emitted from the light source and reflected from the optical reflecting surface in a first scanning direction and a second scanning direction substantially orthogonal thereto,
In the optical path of the light beam reflected from the optical reflecting surface,
A wedge-shaped or trapezoidal first optical prism made of transparent optical glass or a plastic for optical parts having a predetermined refractive index and a predetermined Abbe number, and having a predetermined apex angle; and at least the first optical prism; Is composed of optical glass having a predetermined Abbe number different from each other or a plastic for optical parts, and a composite prism obtained by bonding together a second optical prism having a predetermined apex angle,
The light beam incident on the optical reflecting surface and the light beam reflected by the optical reflecting surface are disposed so as to pass through the composite prism ,
The composite prism is disposed in a light beam exit opening of the beam scanning device or an image display device using the beam scanning device, and the opening is sealed with the prism, so that the prism is also used as a dustproof transparent window member. light beam scanning apparatus which is characterized in that is.   An image display device comprising the light beam scanning device according to claim 1.

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