JP5163794B2 - Projection type image display device - Google Patents

Description

    The present invention relates to a projection type image display apparatus.

  In a projection-type image display apparatus that projects an image at a predetermined angle (for example, from below the screen) with respect to the normal of the screen main plane, the output optical component of the projection optical system includes an aspherical surface. A free-form curved mirror is used. In general, these mirrors are made of resin in consideration of mass productivity and are manufactured by vapor deposition of aluminum or silver. However, since they are easily charged, they are easily contaminated with dust and dirt in the air. When dust or dirt adhering to the mirror surface is wiped off, hairline-like scratches are generated on the mirror surface, which contains dust and dirt harder than the coating material on the mirror surface. These scratches not only lead to a decrease in the contrast of the image, but also have the disadvantage that moisture enters from the scratches and rusts the deposited film of the mirror.

  In order to deal with such problems, the projection optical system is housed in a casing with an open window, and a flat transparent plate made of a glass plate or the like is disposed between the projection optical system and the screen, thereby mirroring with dust or dust. Techniques for preventing surface contamination have been proposed (see, for example, Patent Document 1).

JP 2002-082387 A

  However, in such a projection optical system, importance is attached to compactness, and the projection distance is greatly shortened by using an aspherical or free-form mirror for the outgoing optical component. For this reason, since the angle of view is extremely wide, the angle at which the image light at both ends of the screen is incident on the transparent plate increases depending on the above technique, and both ends of the screen become dark due to reflection loss on the transparent plate. It was.

  An object of the present invention is to provide a technique capable of protecting an optical component from dust and dirt in the air while suppressing deterioration in image quality.

  In order to solve the above problems, a transparent member that covers the outgoing optical component is provided.

  According to the present invention, it is possible to protect the optical component from dust and dirt in the air while suppressing deterioration in image quality.

It is a schematic sectional side view of the projection type image display apparatus concerning this Embodiment. It is a side view which shows the structure of the principal part of the optical system of the projection type image display apparatus which concerns on this Embodiment. It is XZ sectional drawing which shows arrangement | positioning and an optical path of the optical system of the projection type image display apparatus concerning this Embodiment. It is YZ sectional drawing which shows the structure and optical path of the optical system of the projection type image display apparatus concerning this Embodiment. It is a figure showing the distortion performance of the projection type image display apparatus concerning this Embodiment. It is a figure explaining the surface number of the optical component of the projection type image display apparatus which concerns on this Embodiment. It is a figure showing the spot performance of the projection type image display apparatus concerning this Embodiment. It is a perspective view showing the principal part of the projection type image display apparatus which concerns on this Embodiment. It is a perspective view showing the principal part of the projection type image display apparatus which concerns on this Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the illustrated example.

  FIG. 1 is a schematic side sectional view of a projection type image display apparatus 1 according to the present embodiment, and FIG. 2 is a side view showing a configuration of a main part of an optical system of the projection type image display apparatus.

  1 and 2 show the configuration of the main part of the optical system in the YZ section in the XYZ orthogonal coordinate system. Here, it is assumed that the origin of the XYZ orthogonal coordinate system is the center of the display screen of the image display element 10 constituting the image generation source 8 described later, and the Z axis is parallel to the normal line of the screen 20 described later. The Y axis is assumed to be parallel to the short side direction of the screen 20, that is, the vertical direction of the screen 20, and the X axis is parallel to the long side direction of the screen 20, ie, the horizontal direction of the screen 20. Shall.

  As shown in FIG. 1, the projection type image display device 1 includes an image generation source 8 for displaying an image on a bottom plate 6 attached to a stand 4 having casters 2. The image generation source 8 includes, for example, a light modulation element such as a reflective or transmissive liquid crystal panel or an image display element 10 having a plurality of minute mirrors, and a lamp for irradiating the light modulation element. It is. Further, the image display element 10 may be a method of combining a plurality of images like a so-called three-plate type, and in this case, a combining optical system such as a combining prism is provided. The image generation source may include a projection type cathode ray tube.

  In the light emitting direction of the image display element 10, a projection lens 12 constituting the first optical system is disposed. The projection lens 12 includes a front group 12 that includes a plurality of refractive lenses having a rotationally symmetric surface shape, and a lens having a free-form surface having at least one surface that is rotationally asymmetric (hereinafter, “free-form surface lens”). A rear group 16 composed of a plurality of lenses. The front group 12 is disposed on the traveling direction side of the light emitted from the image display element 10, and the rear group 16 is disposed on the traveling direction side of the light emitted from the front group 12.

  On the traveling direction side of the light emitted from the rear group 16, there is at least one reflecting mirror (hereinafter referred to as a “free curved mirror”) having a rotationally asymmetric free curved surface forming the second optical system. Has been placed. A screen 20 is arranged in the traveling direction of the light reflected by the free-form curved mirror 18. In the present embodiment, an aspherical mirror may be used as the second optical system.

  In the present embodiment, the lenses constituting the projection lens 12 are linearly arranged. However, as shown in FIG. 3, the free-form surface mirror 18 and the rear group 16 of the projection lens 12 are arranged. The reflection mirror 15 may be arranged so that the optical axis of the projection lens 12 is bent in the X-axis direction. As a result, it is possible to prevent the overall length of the projection type image display apparatus from becoming long. Further, in order to prevent the total length of the projection type image display apparatus from being increased, the reflection mirror 15 may be disposed between the front group 12 and the rear group 16 of the projection lens 12 or in the middle of the front group 12. .

  In the present embodiment, as shown in FIG. 2, the light beam L1 emitted from the lower end portion P1 of the projection lens 12 is reflected by the lower end portion P3 of the free-form curved mirror 18 and guided to the lower end portion P6 of the screen 20. It has become. Further, the light beam L2 emitted from the upper end portion P2 of the projection lens 12 is reflected by the upper end portion P5 of the free-form curved mirror 18 and guided to the upper end portion P8 of the screen 20.

  As shown in FIG. 2, the image display element 10 is arranged so that the center of the display screen is located on the optical axis of the projection lens 12. Accordingly, a light beam L3 that passes through the center of the display screen of the image display element 10 and passes through the center of the entrance pupil of the projection lens 12 toward the screen center on the screen 20 (hereinafter referred to as “screen center light beam”) is substantially projected. Proceed along the optical axis of the lens. The screen center ray L3 is reflected at a point P4 on the reflection surface of the free-form surface mirror 18, and has a predetermined angle with respect to the normal line L4 of the screen at a point P7 at the screen center on the screen 20 (that is, obliquely). (An angle formed by the screen center ray L3 and the normal L4 (hereinafter referred to as “oblique incident angle”) is θs).

  As described above, when the light beam emitted from the projection lens 12 is obliquely incident on the screen 20, various aberrations that are not rotationally symmetric with respect to the optical axis in addition to the so-called trapezoidal distortion in which the projected rectangular shape becomes trapezoidal. Occurs. In the present embodiment, these are corrected by the rear group 16 of the projection lens 12 and the reflecting surface of the second optical system (free-form curved mirror 18).

  As shown in FIG. 2, the optical path length of the light beam 22 from the point P5 to the point P8 is longer than the optical path length of the light beam 23 from the point P3 to the point P6. This means that the image point P8 on the screen is farther than the image point P6 when viewed from the projection lens 12.

  Therefore, an object point (a point on the display screen) corresponding to the image point P8 on the screen is located closer to the projection lens 12, and an object point corresponding to the image point P6 is located farther from the projection lens 12. By doing so, the inclination of the image screen is corrected. Specifically, the normal vector at the center of the display screen of the image display element 1 is inclined in the direction in which the free-form surface mirror 18 is located in the YZ plane.

  In order to obtain an image plane tilted with respect to the optical axis, the method of tilting the object plane is well known, but at an angle of view of a practical size, the image plane due to the tilt of the object plane is asymmetrical with respect to the optical axis Is difficult to correct with a rotationally symmetric projection lens.

  In this regard, in the present embodiment, since the rotationally asymmetric free-form surface lens 22 and the free-form surface mirror 18 are used in the projection optical system, it is possible to cope with asymmetric image plane deformation. For this reason, by tilting the object plane, distortion of a low-order image plane can be greatly reduced, which is effective in assisting aberration correction by a free-form surface lens or a free-form surface mirror.

  Hereinafter, correction of trapezoidal distortion and aberration will be described in detail. The projection lens 12 that is the first optical system is a main lens whose front group 12 projects the display screen of the image display element 10 onto the screen 20, and corrects basic aberrations in the rotationally symmetric optical system. . The rear group 16 of the projection lens 12 includes a rotationally asymmetric free-form surface lens 22. Here, in the present embodiment, the free-form surface lens 22 closest to the free-form surface mirror 18 is formed to be curved so as to face a concave with respect to the light exit direction. The second optical system includes a free curved surface mirror 18 having a rotationally asymmetric free curved surface shape.

  The free-form curved mirror 18 is a rotationally asymmetric convex mirror that is curved so that a part thereof is convex with respect to the light reflection direction. Specifically, the free-form surface mirror 18 is formed so that the curvature of the portion that reflects light traveling downward of the screen 20 is larger than the curvature of the portion that reflects light traveling upward of the screen 20. In addition, the portion of the free-form curved mirror 18 that reflects the light downward toward the screen 20 has a convex shape in the light reflection direction, and the portion that reflects the light upward toward the screen 20 is concave in the light reflection direction. You may form in a shape.

  By the action of the free-form surface lens of the first optical system and the free-form surface mirror 18 of the second optical system, correction of aberrations caused by oblique incidence is mainly performed. That is, in the present embodiment, the second optical system mainly corrects trapezoidal distortion, and the rear group 16 of the projection lens 12 that is the first optical system mainly corrects asymmetric aberrations such as distortion of the image plane. It has become.

  Further, by using the free-form surface lens 22 and the free-form surface mirror 18 in the projection optical system in this way, in the projection lens 12 having a refracting surface, the number of lenses can be increased without causing decentration of the lens and an increase in the lens diameter. Without correction, it is possible to correct trapezoidal distortion due to oblique incidence.

  As described above, in the present embodiment, the first optical system includes at least one rotationally asymmetric free-form surface lens, and the second optical system includes at least one rotationally asymmetric free-form surface mirror, thereby generating a trapezoid generated by oblique projection. Both distortion and aberration can be corrected.

  The above description is based on the embodiment shown in FIG. However, the same idea as in the above-described embodiment can be applied even when the direction of bending of the optical path by the mirror is in the plane including the long side of the screen, contrary to FIG.

  Next, the optical system according to the present embodiment will be described with specific numerical values. One of the numerical examples of the present invention will be described with reference to FIGS. 3 to 6 and Tables 1 to 4. FIG.

  3 and 4 show ray diagrams of the optical system according to the present invention based on numerical examples. In the XYZ orthogonal coordinate system described above, FIG. 3 shows an XZ cross-sectional view, and 4 shows a YZ cross-sectional structure. FIG. 3 shows an example in which a bending mirror 15 is installed in the middle of the front group 12 of the projection lens 12 and the optical path is bent once in the X-axis direction. In FIG. 4, the bending mirror 15 is omitted, and the optical system is shown expanded in the Z-axis direction. The bending mirror has a certain degree of arbitrary installation position and angle, and does not affect the function of each optical element. Therefore, in the following description, the bending mirror 15 is omitted.

  In this example, the light emitted from the image display element 10 displayed on the lower side of FIG. 4 is, first, a front group 12 configured by only lenses having only a rotationally symmetric surface among projection lenses including a plurality of lenses. Pass through. Then, the light passes through the rear group 16 including a rotationally asymmetric free-form surface lens, is reflected by the reflection surface of the free-form surface mirror 18 that is the second optical system, and then enters the screen 20.

  Here, the front group 14 of the projection lens 12 is composed of a plurality of lenses each having a rotationally symmetric refracting surface, two of the refracting surfaces being rotationally symmetric aspherical surfaces, and the other being spherical surfaces. It is. The rotationally symmetric aspherical surface used here is expressed by the following equation using a local cylindrical coordinate system for each surface.

Here, r is the distance from the optical axis, and Z represents the sag amount. C is the curvature at the apex, k is the conic constant, and A to J are coefficients of the power of r.
The free-form surface lens in the rear group 16 of the projection lens 12 uses a local orthogonal coordinate system (x, y, z) with the surface vertex of each surface as the origin, and includes the following equations including X and Y polynomials. Represented.

  Here, Z represents the sag amount of the shape of the free-form surface in the direction perpendicular to the X and Y axes, c is the curvature at the vertex, r is the distance from the origin in the plane of the X and Y axes, k Is a conic constant and C (m, n) is a coefficient of a polynomial.

  In Table 1, Rd is the radius of curvature of each surface, and in the figure, when the center of curvature is on the left side of the surface, it is expressed as a positive value, and in the opposite case, it is expressed as a negative value. In Table 1, TH is the inter-surface distance, and indicates the distance from the apex of the lens surface to the apex of the next lens surface. When a next lens surface is located on the left side with respect to a certain lens surface, the inter-surface distance is represented by a positive value, and when located on the right side, it is represented by a negative value. In Table 1, S5, S6, S16, and S17 are rotationally symmetric aspherical surfaces. In Table 1, * is shown beside the surface number. Table 2 shows the coefficients of these four aspheric surfaces. In Table 1, M indicates the position of the bending mirror provided in the front group 12 of the projection lens. Actually, the optical axis is bent at the position of this mirror, but in FIG. 6, for the sake of simplicity, only the position of the mirror is shown, and the optical axis is not bent. Further, S23 is a screen 20, which is not shown in FIG.

  In Table 1, S18 to S21 are refracting surfaces of the free-form surface lens, and S22 is a reflecting surface of the free-form surface mirror 18, which is indicated by # next to the surface number. Table 3 shows values of coefficients representing the shapes of these five free-form surfaces.

  In Table 3, the names and values of the coefficients are displayed side by side as a set of frames, the values on the right side are the values of the coefficients, the left side is the name and the two sets of numbers separated by commas in parentheses are given in Equation 2. The indicated values of m and n are shown.

  Table 4 shows the inclination or eccentricity of the local coordinate system of each surface in this example. In Table 4, the angle of inclination and the value of eccentricity are shown on the right side of the surface number, and ADE is the magnitude of the inclination in a plane parallel to the cross section of the figure. The direction of inclination is positive in the direction rotating counterclockwise in the cross section of the figure. YDE is the magnitude of the eccentricity, and the eccentricity is set in a direction perpendicular to the optical axis in the cross section of the figure, and the downward eccentricity in the cross section of the figure is positive.

  The numerical values in Tables 1 to 4 above are an example in the case where an image in the range of 12.16 × 6.84 on the object plane is projected to a size of 1841.9 × 1036.1 on the image plane. The graphic distortion at that time is shown in FIG. The vertical direction in FIG. 5 is the vertical direction in FIG. 4 and is the Y-axis direction. The horizontal direction in FIG. 5 is a direction perpendicular to the Y axis on the screen 20, and the center of the rectangle in the figure is the center of the screen. The figure shows the state of figure distortion by displaying the state of straight line bending in which the vertical direction of the screen is divided into four and the horizontal direction is divided into eight.

  A spot diagram of this numerical example is shown in FIG. In FIG. 7, (6.08, 3.42), (0, 3.42), (3.65, 2.05), (X, Y coordinate values on the display screen of the video display element 11. 6.08,0), (0,0), (3.65, -2.05), (6.08, -3.42), and (0, -3.42) The spot diagrams are shown in order from the top. The unit is mm. The horizontal direction of each spot diagram is the X direction on the screen, and the vertical direction is the Y direction on the screen. Thus, both maintain good performance.

  Since S0 to S20 shown in FIG. 6 are housed in a container such as a chassis or a lens barrel (not shown), it is possible to sufficiently take measures against dust and dirt.

  On the other hand, among the lenses constituting the projection lens 12, the free-form surface lens 22 and the free-form surface mirror 18 arranged closest to the free-form surface mirror 18 are covered with a transparent cover 24 having light transmittance. The transparent cover 24 is a curved member, and has a circular arc whose center is the point of intersection with the Z-axis of the lens surface S21 of the free-form surface lens 22 on the free-form surface mirror 18 side and the reflection surface S22 of the free-form surface mirror 18. It is formed as follows.

  One end of both ends of the transparent cover 24 formed in a curved shape is attached to a lens rod 26 provided on the free-form surface lens 22, and the other end of both ends formed in the curved shape is a mirror rod 28 of the free-form surface mirror 18. Is attached. Further, the end portion that is not curved is attached in close contact with the bottom plate 6. Therefore, the lens surface S21 of the free-form surface lens 22 facing the free-form surface mirror 18 and the reflection surface S22 of the free-form surface mirror 18 are housed in a sealed space formed in the projection image display device 1 and are blocked from the outside air. .

  Since the transparent cover 24 is curved, light rays emitted from the free-form surface mirror 18 do not have a large incident angle with respect to the transparent cover. For this reason, the problem that the image light is reflected by the transparent cover 24 and the peripheral portion of the image becomes dark does not occur. In the present embodiment, the incident angle of the light incident on the transparent cover 24 is about 20 ° at the peripheral portion of the image, and the maximum incident angle is 33 ° at the lowermost portion of the image center. In this case, the transmittance of the image light is 89%, which is sufficient for practical use, and the transmittance may be improved by further performing a transparency increasing process.

  Moreover, there is no restriction | limiting in particular in the material of the material which the transparent cover 24 forms, For example, it is preferable to use the plastics excellent in flexibility. By forming the transmission cover with the plastic material, it is possible to easily fix the lens cover 26, the mirror cover 28, and the bottom plate 6. In addition, by forming a transparent cover with such a plastic material, the replacement becomes easy even when the transparent cover is damaged or dirty.

  FIG. 9 is a perspective view showing another embodiment of the transparent cover 24. In FIG. 9, the light beam 22 and the light beam 23 shown in FIG. 2 are added. In FIG. 2, only one light beam is shown because the light beams overlap each other in FIG. 2. However, since FIG. 9 is a perspective view, two light beams are displayed on the left and right. These four rays indicate the rays at the four corners of the image.

  The transparent cover 24 only needs to be transparent only in the range of the image light projected on the screen 20, and the portion other than the range through which the range surrounded by the light beam 22 and the light beam 23 passes may be shielded. The light shielding of the transparent cover is performed, for example, by painting or printing on the surface of the transparent cover 24.

  The lightness of the light-shielded portion is preferably as low as possible, and it is particularly preferable to use a black paint or the like. Further, for example, the inside of the light shielding area of the transparent cover 24 may be painted with a black paint or the like, and the outside may be painted with a color considering the design of the entire projection type image display apparatus. In this way, the contrast of the video can be improved by preventing external light from entering the projection type image display device 1 as much as possible.

  Next, the operation of the projection type image display apparatus 1 according to the present embodiment will be described.

  When the projection-type image display device 1 according to this embodiment is turned on, image light is emitted from the image generation source 8 and projected onto the projection lens 12. The image light projected on the projection lens 12 is transmitted through the lenses constituting the projection lens 12, emitted from the free-form surface lens 22, projected onto the free-form surface mirror 18, and reflected on the free-form surface mirror 18.

  The image light reflected by the free-form surface mirror 18 is applied to the transparent cover 24. At this time, since the image light is irradiated to the transparent portion of the transparent cover 24, the image is displayed after being transmitted to the screen 20 after passing through the transparent portion. Since the transparent cover 24 is curved, there is almost no loss of image light projected from the free-form surface mirror 18, and the screen 20 is irradiated through the transparent cover 24. Further, since the light outside the projection type image display device 1 is shielded by the shielded portion of the transparent cover 24, the entrance of external light into the projection type image display device 1 is prevented.

  Further, since the light reflecting surface of the free-form curved mirror 18 and the light exit surface of the free-form curved lens 22 are housed in a sealed space isolated from the outside of the projection-type image display device 1 by the transparent cover 24, the projection-type image display is performed. Even if the free-form surface mirror 18 and the free-form surface lens 22 are charged when the apparatus 1 is driven, dust or dirt in the outside air does not adhere.

  As described above, according to the present embodiment, since the free-form curved mirror 18 and the free-form curved lens 22 are covered by the transparent cover 24, they are not contaminated by dust or dirt in the air. In addition, since the transparent cover 24 is formed in a curved shape, the maximum incident angle of light incident on the transparent cover 24 does not increase, and there is no inconvenience that both ends of the screen become dark due to reflection loss at the transparent cover.

DESCRIPTION OF SYMBOLS 1 ... Projection type image display apparatus, 2 ... Caster, 4 ... Stand, 6 ... Bottom plate, 8 ... Image generation source, 10 ... Image display element, 12 ... Projection lens, 14 ... Front group, 15 ... Reflection mirror, 16 ... Rear Group: 18 ... Free-form surface mirror, 20 ... Screen, 22 ... Free-form surface lens, 24 ... Transparent cover, 26 ... Lens cage, 28 ... Mirror cage, L1 ... Ray, L2 ... Ray, L3 ... Screen center ray, L4 ... Method line

Claims (8)

A projection lens including a plurality of lenses for enlarging and projecting the image of the image display element on the screen;
A reflective optical system for reflecting an image from the projection lens ;
A member that covers an optical path between the light emitting surface of the first lens and the light reflecting surface of the reflective optical system disposed at a position closest to the reflective optical system among the plurality of lenses;
The first lens is a free-form surface lens;
The reflective optical system is a free-form surface mirror or an aspherical mirror,
When the plane of the screen is defined as the XY plane, the horizontal direction of the screen is defined as the X axis, the direction perpendicular to the X axis is defined as the Y axis, and the direction perpendicular to the XY plane is defined as the Z axis, The projection display device in which the portion passing through the apexes at both ends of the member is a straight line, and the straight line is substantially parallel to the YZ plane.   The projection display device according to claim 1, wherein an area other than an area through which an image reflected by the reflection optical system of the member passes is a light shielding area.   The projection display device according to claim 2, wherein the light shielding region is formed by painting or printing.   The projection display device according to claim 1, wherein the reflection optical system has a convex shape with respect to a direction in which the image is reflected. The projection lens is housed in a container;
A first flange formed at an end of the container on the reflective optical system side;
A second collar formed on a side edge of the reflective optical system;
The projection display apparatus according to claim 1, wherein both ends of the member are attached to the first and second collar parts, respectively.   The projection display device according to claim 1, wherein the member has flexibility.   The projection display device according to claim 1, wherein the member is transparent.   The projection display device according to claim 1, wherein a transmittance of the image light with respect to the member is 89% or more.

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