JP2015001579A - Projection optical system, and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce performance degradation due to a manufacturing error while adopting a lens having a free-form surface.SOLUTION: There is provided a projection optical system of an image projection device that projects an image on a projection target surface to be enlarged and displayed, and includes a rotationally asymmetric free-form surface lens 10 and a curved surface mirror 4, where the free-form surface lens 10 and curved surface mirror 4 are held by a single holding member 20. Of a plurality of lens groups, lenses other than the free-form surface lens 10 are held in a lens barrel 30 so that all optical axes coincide with each other. The holding member 20 holds the lens barrel 30.

Description

  The present invention relates to a projection optical system that projects and enlarges an image on a projection surface, and an image projection apparatus that includes the projection optical system.

  In image projection apparatuses such as liquid crystal projectors, the resolution of liquid crystal panels is improved, the brightness is improved and the price is lowered in accordance with the efficiency of light source lamps.

  In addition, small and lightweight image projection apparatuses using DMD (Digital Micro-mirror Device) are widely used. Small and light image projection apparatuses are widely used not only in offices and schools, but also at home.

  In recent years, image projection apparatuses have been required to reduce the size and weight of the main body and shorten the projection distance. For example, a projector having a projection optical system using a reflective imaging optical system has been developed to reduce the size and weight of the main body of the image projection apparatus and shorten the projection distance.

  Here, a technique having a configuration in which a projection optical system is combined with a concave free-form curved mirror is disclosed for an image projection apparatus having a projection optical system (see, for example, Patent Document 1). In the technique disclosed in Patent Document 1, an intermediate image of an image display element is connected by an optical system, and the intermediate image is enlarged and projected by a free-form curved mirror.

  Further, for an image projection apparatus having a projection optical system, a technique is disclosed in which an intermediate image is created by the projection optical system and the intermediate image is enlarged and projected using a rotationally symmetric concave aspherical mirror (for example, Patent Documents 2 and 3). reference).

  In the technique disclosed in Patent Document 2, a lens closest to the aspherical mirror and a free-form surface are used for the aspherical mirror, and each lens is miniaturized while maintaining each aberration.

  In the technique disclosed in Patent Document 3, distortion correction is performed using a free-form surface lens as one of the lenses constituting the projection optical system.

  As in this technique, in an image projection apparatus that generates an intermediate image with a projection optical system and enlarges and projects it with a curved mirror, the distance from the projection optical system to the curved mirror is large, or the height direction of the projection optical system The size of the curved mirror is larger than the size of.

  Here, in the projection optical system of an ultra-close-type image projection apparatus in which the distance from the image projection apparatus to the projection surface is extremely close, principal rays (projection surfaces) corresponding to each angle of view are used to correct distortion. The principal ray corresponding to each predetermined position above is reflected at a desired angle. That is, in the projection optical system of the very close-up type image projection apparatus, the surface shape of the curved mirror is set to a surface shape corresponding to the principal ray.

  In order to realize such a surface shape of the curved mirror, it is desirable that each principal ray is separated as much as possible on the curved mirror. For this reason, in the projection optical system of an extremely close-up type image projection apparatus in which the distance from the image projection apparatus to the projection surface is extremely close, the distance from the projection optical system to the curved mirror is long, and the dimension of the curved mirror is set large. ing.

  In the projection optical system of the image projection apparatus, as the distance between the screen and the curved mirror becomes shorter, that is, as it becomes extremely close, the difference in the light ray angle (reflection angle at the mirror) between the principal rays increases. In the projection optical system of such an image projection apparatus, the distance from the projection optical system to the curved mirror is further increased, and the size of the curved mirror is further increased.

  Further, in the techniques of Patent Documents 1 and 3, the use of a free-form surface lens in the projection optical system supplements the distortion correction function by the free-form surface mirror, but the curved mirror remains large in either technique. .

  Furthermore, when a free-form surface is used for the lens or curved mirror of the projection optical system, high accuracy with respect to the position is required at the time of attachment, but this problem is not considered in any document.

  It is an object of the present invention to provide a projection optical system of an image projection apparatus that can reduce performance deterioration due to manufacturing errors while employing a free-form surface lens.

  The present invention is a projection optical system of an image projection apparatus that projects an image on a projection surface and displays the enlarged image, and includes a rotationally asymmetric free-form surface lens and a curved mirror, and the free-form surface lens and the curved surface The mirror is held by a common holding member.

  According to the present invention, it is possible to reduce performance degradation due to manufacturing errors while employing a free-form surface lens.

It is an optical arrangement | positioning figure which shows embodiment of the projection optical system which concerns on this invention. 1 is an optical arrangement diagram showing an embodiment of an image projection apparatus according to the present invention. It is an optical arrangement | positioning figure which shows the 1st optical system of the said projection optical system. FIG. 2 is an optical layout diagram of the image projection apparatus. It is a figure which shows the relationship between distance D1 and D2 of the said projection optical system. It is a figure which shows the relationship of the distance D3 of the said projection optical system. It is a schematic diagram which shows the view angle number of the image display area displayed on an image display element. It is a figure which shows the beam spot diameter ratio on a screen about the case where the projection image size of the said projection optical system is 80 inches, 60 inches, and 48 inches. In the said projection optical system, it is a figure which shows the distortion on a screen when a 60-inch size projection image is projected. It is a block diagram which shows the housing of embodiment of the said projection optical system. It is a block diagram which shows the housing of another embodiment of the said projection optical system. It is a block diagram which shows the housing of another embodiment of the said projection optical system. It is a perspective view which shows a free-form surface lens. It is a perspective view which shows the coordinate position in the lens surface of a free-form surface lens. It is a figure which shows embodiment of the image projection apparatus which concerns on this invention. It is a figure which shows another embodiment of the image projection apparatus which concerns on this invention.

  Embodiments of a projection optical system and an image projection apparatus according to the present invention will be described below with reference to the drawings.

● Projection optics ●
First, an embodiment of a projection optical system according to the present invention will be described.

  FIG. 1 is an optical layout diagram showing an embodiment of a projection optical system according to the present invention.

  The projection optical system 100 includes a first optical system 2, a folding mirror 3, and a free curved mirror 4 having, for example, a rotationally asymmetric shape with a concave surface facing the first optical system 2. Here, the projection optical system 100 is arranged on the optical axis A of the first optical system 2 in the above order from the image display element 1 side (left side in FIG. 1).

  Here, in the following description, the surface on which the image display element 1 is arranged is defined as a surface including the Y-axis direction and the X-axis orthogonal thereto, and the direction orthogonal to this surface is the Z-axis direction (through the paper surface of FIG. 1). Direction).

  The image display element 1 displays an image according to an image signal given from an external device (not shown). The image display element 1 is irradiated with illumination light from an illumination optical system (not shown). The intensity of the illumination light is two-dimensionally modulated by the image displayed on the image display element 1 and enters the first optical system 2. In the image display element 1, the long side direction corresponds to the X-axis direction, and the short side direction corresponds to the Y-axis direction.

  The imaging light beam emitted from the first optical system 2 is incident on the folding mirror 3, the optical path is folded, and is incident on the free-form surface mirror 4.

  Here, the folding mirror 3 and the free-form surface mirror 4 constitute a second optical system according to the present invention.

  The folding mirror 3 is a plane mirror disposed in the optical path between the free-form surface lens 10 and the free-form surface mirror 4, and has a function of folding the optical path of the imaging light beam in a predetermined direction.

  Note that the folding mirror 3 is not limited to a plane mirror, and may be formed of a curved surface, for example, and may have an optical function.

  The imaging light beam emitted from the first optical system 2 forms an image of the image displayed on the image display element 1, that is, an intermediate image by the first optical system 2. In FIG. 1, the intermediate image is formed in the optical path between the folding mirror 3 and the free-form surface mirror 4.

  The intermediate image formed by the first optical system 2 is enlarged by the free-form surface mirror 4 and projected as an enlarged image on a screen (not shown).

  FIG. 2 is an optical layout diagram showing an embodiment of an image projection apparatus according to the present invention. The image projection apparatus 1000 includes the projection optical system 100 and the dustproof glass 5. This figure shows a state in which an imaging light beam by the projection optical system 100 of the image projection apparatus 1000 forms an image on the screen (projected surface) 6 and an enlarged image is displayed on the screen 6 in an enlarged manner.

  The dustproof glass 5 is disposed in the optical path between the free-form curved mirror 4 and the screen 6. Here, the dustproof glass 5 closes the inside of the image projection apparatus 1000 together with a casing (not shown), and seals the inside of the image projection apparatus 1000 to prevent dust.

  Here, the optical axis A of the first optical system 2 is extended to the screen 6 side, and the optical axis of the imaging light beam from the first optical system 2 sequentially folded by the folding mirror 3 and the free-form surface mirror 4 is projected optically. Let it be the optical axis of the system 100.

  Further, an arbitrary angle counterclockwise from the Z axis in the plane including the optical axis of the projection optical system 100 (a plane parallel to the paper surface of FIG. 2) is α.

  FIG. 3 is an optical layout diagram showing the first optical system 2. As shown in the figure, the first optical system 2 is composed of 13 lenses in 5 groups. In the figure, (a) shows the lens position of 48 inches, and (b) shows the lens position of 80 inches.

  The projection optical system 100 is a zoom system, and the third to fifth groups are displaced to positions indicated by arrows, so that the diagonal size of the projected image is changed from 48 inches in (a) to 80 inches in (b). The focus is adjusted accordingly.

  A surface S0 on which an image of the image display element 1 is displayed is an object surface with respect to the projection optical system 100.

  Here, each surface (lens surface and aperture stop surface) of the first optical system 2 is defined as surfaces S1, S2,... S25 in order from the left to the right in FIG. Of the above surfaces, the surface S10 is a surface of an aperture stop.

  In FIG. 3, the left side of the first optical system 2 is the object side (reduction side). The right side of the first optical system 2 is the image side (enlargement side).

  Each of the 13 lenses constituting the first optical system 2 is referred to as a lens L1, a lens L2,..., A lens L13 in order from the object side to the image side.

  Here, the lens L1 to the lens L8 are a first lens group. The lens L9 is a second lens group. The lens L10 is a third lens group. The lens L11 and the lens L12 are a fourth lens group. Further, the lens L13 is a fifth lens group. Here, the lens L13 is the free-form surface lens 10 shown in FIG. 1 (the same applies in the following description).

  The aperture stop is disposed between the lens L5 and the lens L6.

  Therefore, the first optical system 2 is composed of five lens groups and is composed of thirteen lenses.

  In the first group, the lens L3 and the lens L4 are cemented. In the first group, the lens L7 and the lens L8 are also cemented.

  The object-side numerical aperture of the first optical system 2 is 0.195.

  The size of the image displayed on the image display element 1 that is the surface S0 is a ratio of 10:16 in the vertical direction (Y direction): horizontal direction (X direction), and the expansion length is 0.65 inches (165 mm). It is.

  A protective glass for the image display element 1 is disposed on the right side of the surface S0.

  The optical axis of the first optical system 2 is shifted by 1.541 mm in the −Y direction (downward in FIG. 3) with respect to the center of the surface S0 (image surface).

  The lens L1 and the lens L12 are aspheric lenses, and both the object-side and image-side lens surfaces are aspheric. The lens L1 and the lens L12 are both rotationally symmetric aspheric lenses.

  FIG. 4 is an optical layout diagram of the image projection apparatus 1000. As shown in the figure, in the image projection apparatus 1000, the mirror surface of the folding mirror 3 is S26, and the mirror surface (reflective surface) of the free-form curved mirror 4 is S27.

  Further, in the image projection apparatus 1000, the reduction-side surface of the dust-proof glass 5 is S28, the enlargement-side surface is S29, and the screen 6 is S30.

Example of Projection Optical System A specific example of the projection optical system 100 described above is shown below as an example of the projection optical system 100.

  In the data shown below, the unit of the quantity having a length dimension is mm unless otherwise specified.

  The data of the examples are shown in Table 1.

  In Table 1, the surface numbers are S0 to S30 described above. The refractive index and dispersion are both based on the d line.

  The projection optical system of the embodiment is a zoom system, and as shown in FIG. 3, the third to fifth groups are displaced to the positions indicated by arrows, and the diagonal size of the projected image is adjusted to the projection size from 48 inches to 80 inches. To adjust the focus.

  The surface interval at which the group interval changes during focus adjustment is described as variable in Table 1.

  Table 2 shows the surface spacing for the diagonal size of the projected image of 80 inches, 60 inches, and 48 inches.

  Table 3 shows layout data of the folding mirror 3, the free-form mirror 4, and the dustproof glass 5.

  Table 3 shows each surface (S27, S28, S29, S30) of the folding mirror 3, the free-form mirror 4, and the dust-proof glass 5 when the surface vertex of S1 is defined as a reference (Y, Z) = (0, 0). The Y-axis coordinate and the Z-axis coordinate of the surface vertex are shown.

  The aspherical shape has a height from the optical axis of h, a paraxial radius of curvature of R, a conic coefficient of k, an aspherical coefficient of Ai, an aspherical quantity of Z (h), and a free-form surface quantity of Z (x, y). ), Where the free-form surface coefficient is Cj, and is expressed by the following equations (1) and (2).

Z (h) = (1 / R) h2 / [1 + √ {1- (1 + k) (h / R) 2} + ΣAihi (1)
+ ΣCjxmyn (2)

  Note that the directions of coordinates: x and y are parallel to the X-axis and Y-axis coordinates, respectively, and the positive direction is the same as the X-axis and Y-axis coordinates.

  Table 4 shows the aspheric coefficients of S1, S2, S22, and S23.

  Table 5 shows the free-form surface coefficients of S24, S25, and S27.

  In the free-form surface coefficient shown in Table 5, for example, C14: x ^ 4 * y ^ 2 represents that the free-form surface coefficient: C14 is a coefficient of x4y2.

  Next, the size of the projection optical system 100 and the projection distances D1, D2, and D3 will be described.

  The distance D1 is a distance on the optical axis from the image display element 1 to the vertex of the lens surface farthest from the image display element 1 of the first optical system 2.

  The distance D2 is a distance on the optical axis from the vertex of the lens surface farthest from the image display element 1 to the free-form surface mirror 4 in the first optical system 2.

  The distance D3 is the shortest projection distance of the projection optical system 100.

  FIG. 5 is a diagram showing the relationship between the distances D1 and D2 of the projection optical system 100. As shown in FIG. FIG. 6 is a diagram showing the relationship of the distance D3 of the projection optical system 100. In FIG. 5, since D2 is a distance on the optical axis, an optical system in which the folding mirror 3 is omitted is shown.

  As shown in FIG. 5, the distance D1 is larger than the distance D2. Further, as shown in FIG. 6, the shortest projection distance D3 is smaller than the sum of the distance D1 and the distance D2.

That is, the relationship between the distances D1, D2, and D3 is
D1 + D2> D3
It is.

  Here, the shortest projection distance D3 is a projection distance when a 48-inch projection image is projected in the embodiment.

  Table 6 shows values of the distances D1, D2, D3 and D1 + D2 in the examples.

  As shown in Table 6, the distance D2 from the first optical system 2 to the free-form curved mirror 4 is smaller than the distance D1 from the image display element 1 to the most image side surface of the first optical system 2 in the embodiment.

  With the configuration as described above, the projection optical system 100 according to the embodiment can realize downsizing of the entire optical system and the image projection apparatus 1000.

  Further, as shown in Table 6, the shortest projection distance l3 is smaller than the distance D1 + D2 from the image display element 1 to the free-form curved mirror 4 in the embodiment.

  Here, in order to shorten the shortest projection distance D3, an optical system having a wide projection angle of view is necessary. On the other hand, in general, as the projection angle of view becomes wider, the size of the projection optical system tends to increase.

  When the relationship between the distances D1, D2, and D3 satisfies the above-described conditions, the projection optical system 100 and the image projection apparatus 1000 according to the embodiment can reduce the configuration and the projection distance. Can do.

  Next, the optical performance of the projection optical system 100 of the embodiment will be described.

  FIG. 7 is a schematic diagram showing the angle of view number of the image display area displayed on the image display element 1. In the figure, the field angle number of the image display area has the lens optical axis of the first optical system 2 as the origin.

  Table 7 shows the coordinates of the image display area corresponding to the angle of view number. Since the X-axis direction is symmetric with respect to the Y-axis, only X ≧ 0 is evaluated in Table 7.

  FIG. 8 is a diagram showing the beam spot diameter ratio on the screen when the projection image size of the projection optical system 100 is 80 inches, 60 inches, and 48 inches. In the figure, the horizontal axis represents the field angle number shown in FIG. 7, and the vertical axis represents the beam spot diameter ratio.

  Here, one pixel on the screen is one pixel with a resolution of WXGA (1280 × 800). The beam spot diameter ratio is an RMS spot diameter for one pixel on the screen. The RMS spot diameter is σ2 calculated by the following equation (3).

σ2 = Σ {Wλ∫∫ [(x (λ; xp, yp) − [x]) 2
+ (Y (λ; xp, yp) − [y]) 2] dxpdyp} / ΣWλ (3)

  In equation (3), x (λ; xp, yp) is the x coordinate of the image plane that passes through the pupil point (xp, yp) and is tracked at wavelength λ. [X] is an average value of x.

  In equation (3), y (λ; xp, yp) is the y coordinate of the image plane that passes through the pupil point (xp, yp) and is tracked at the wavelength λ. [Y] is an average value of y.

  In Expression (3), Wλ is a weight attached to the wavelength λ. The sum Σ is calculated for each of the three wavelengths of red, green, and blue of wavelength λ.

  In the embodiment, for the projected image sizes of 80 inches, 60 inches, and 48 inches, the beam spot diameters on the screen are 1.58 mm, 1.18 mm, and 0.95 mm, respectively.

  Here, when the beam spot diameter ratio is approximately 1.0 or less, it can be said that each aberration is corrected well.

  As shown in FIG. 8, in the embodiment, the beam spot diameter ratio is 0.4 to 1.0 at a projection image size of 48 to 80 inches. That is, in the example, it can be said that each aberration is corrected satisfactorily.

  FIG. 9 is a diagram showing distortion on the screen when a projection image of a 60 inch size is projected in the projection optical system 100. In the figure, an ideal screen size is indicated by a broken line, and distortion on the screen is indicated by a solid line.

  Table 8 shows the amount of distortion at each projection size.

  As shown in FIG. 8 and Table 8, the projection optical system 100 of the example can reduce the distortion of the projected image.

● Housing configuration of projection optical system (1)
Next, the structure of the projection optical system housing according to the present invention will be described.

  When a curved mirror having power is arranged downstream from the free curved lens 10 in the optical path, the free curved lens 10 is greatly deteriorated in optical characteristics due to mounting errors. In the present embodiment, the free-form surface mirror 4 is used as the curved surface mirror. However, the curved surface mirror in the present invention is not limited to the free-form surface mirror 4, and may be a rotationally symmetric spherical or aspherical concave mirror, convex surface mirror, or the like. Good.

  FIG. 10 is a block diagram showing the housing of the embodiment of the projection optical system according to the present invention. As shown in the figure, the housing 20 of the projection optical system 100 is a common holding member that holds at least the free-form surface lens 10 and the free-form surface mirror 4 that is an example of a curved mirror.

  The housing 20 is one member in which the holding portion of the free-form surface lens 10 and the holding portion of the free-form surface mirror 4 are integrally formed.

  In the case where the holding portion of the free-form surface lens 10 and the holding portion of the free-form surface mirror 4 are separate members, it is difficult to actually position the free-form surface lens 10 and the free-form surface mirror 4 with high accuracy, resulting in an error. In this case, the optical characteristics are deteriorated.

  The housing 20 also holds a lens barrel 30 that holds lenses other than the image display element 1 and the free-form surface lens, and the folding mirror 3.

  The lens barrel 30 can satisfy the desired performance of the projection optical system 100 by holding the lens in the lens barrel 30 at an appropriate position so that the optical axis can be adjusted. The lens barrel 30 matches the optical axis of the first optical system 2.

  The adjusted lens barrel 30, free-form surface lens 10, folding mirror 3, and free-form surface mirror 4 are integrally held by a housing 20 made with high precision. The variation in position can be reduced.

  Here, the housing 20 is a method capable of integrally molding the holding portion of the free-form surface lens 10 and the holding portion of the free-form surface mirror 4 as described above, that is, resin molding, aluminum die casting, magnesium die casting, or the like. It is formed by metal molding.

  The housing 20 holds the lens barrel 30 and the free-form surface lens 10 separately, so that the optical axis can be adjusted only by the lens barrel 30 that holds a rotationally symmetric lens system. That is, in the projection optical system 100, the optical axis adjustment can be simplified.

  In the projection optical system 100, the lens barrel 30 can be rotationally adjusted in the optical axis direction with respect to the housing 20 by forming the lens barrel 30 in a rotationally symmetric outer shape. That is, by forming the lens barrel 30 in a rotationally symmetric outer shape, the optical axis of the lens barrel 30 can be adjusted with respect to the housing 20 in the projection optical system 100.

  In the projection optical system 100, the dust-proof glass 5 is also integrally attached to the housing 20 in order to prevent dust from entering the optical system.

● Housing configuration of projection optical system (2)
Next, the structure of the housing of another embodiment of the projection optical system according to the present invention will be described. In the following description, only differences from the projection optical system 100 described above will be described.

  FIG. 11 is a configuration diagram showing a housing of another embodiment of the projection optical system according to the present invention. As shown in the figure, in the projection optical system 200 according to the present embodiment, unlike the projection optical system 100, the dust-proof glass 5 is not provided, that is, the projection direction of the free-form curved mirror 4 is open.

● Housing configuration of projection optical system (3)
Next, the structure of the housing of still another embodiment of the projection optical system according to the present invention will be described. In the following description, only differences from the projection optical system 100 described above will be described.

  FIG. 12 is a configuration diagram showing a housing of still another embodiment of the projection optical system according to the present invention. As shown in the figure, the projection optical system 300 according to the present embodiment is different from the projection optical system 100 described above in that the folding mirror 3 is not provided, and accordingly, the shape of the housing 21 is different.

  Since the folding mirror 3 has only the role of optically folding the optical path, the optical characteristics of the projection optical system 300 are not different from those of the projection optical system 100 even when the folding mirror 3 is not provided.

  By adopting a configuration without the folding mirror 3, the projection optical system 300 can reduce the dimension of the optical system in the height direction (Y-axis direction).

  The housing 21 is the same as the housing 20 described above in that it is one member that integrally forms the holding portion of the free-form curved lens 10 and the holding portion of the free-form curved mirror 4.

Next, the free-form surface lens used in the projection optical systems 100, 200, and 300 described above will be described.

  FIG. 13 is a perspective view showing the free-form surface lens 10. As shown in the figure, the free-form surface lens 10 includes a free-form surface lens surface 10a and a rib 10b outside the free-form surface lens surface 10a.

  The rib 10b is bonded and fixed to a free curved lens fixing portion (not shown). The free-form surface lens fixing portion is held by the housings 20 and 21 when being fixed to the projection optical systems 100, 200, and 300.

  The free-form surface lens 10 is positioned on the housings 20 and 21 at two positions on both ends in the X-axis direction. Here, the free-form surface lens 10 has a symmetric shape in the X-axis direction and an asymmetric free-form shape in the Y-axis direction. That is, the free-form surface lens 10 has a rotationally asymmetric shape with respect to the Z axis. For this reason, the free-form surface lens 10 has a large deterioration in optical characteristics (MTF (Modulation Transfer Function), distortion) due to an attachment error of the γ component (component in the rotation direction with the Z-axis direction in FIG. 13 as the rotation axis).

  That is, in the projection optical systems 100, 200, and 300, the free-form surface lens 10 can be accurately positioned and attached to the housings 20 and 21.

  The free-form surface lens fixing portion is a lens holder having a mechanism capable of adjusting the positional relationship between the free-form surface lens 10 and the housings 20 and 21, such as a cam configuration.

  With this configuration, the free-form surface lens fixing unit can realize focus adjustment by moving the free-form surface lens 10 alone.

  In addition, when the structure which does not move the free-form curved lens 10 is employ | adopted, you may function the housings 20 and 21 as a free-form curved lens fixing | fixed part. That is, in this case, the free-form surface lens 10 is directly fixed to the housings 20 and 21.

  FIG. 14 is a perspective view showing the coordinate position on the lens surface of the free-form surface lens 10.

  In this free-form surface, the curvature in the X-axis direction according to the position in the X-axis direction is not constant at any position in the Y-axis direction, and according to the position in the Y-axis direction at any position in the X-axis direction. It also refers to an anamorphic surface where the curvature in the Y-axis direction is not constant.

  As shown in FIG. 14, in the free-form surface lens 10, at the position of Y = 0, the lens surface position (X, Y) = (0, 0) and the lens surface position (X, Y) = (− X1,0). ) And the X-axis direction curvature are different.

  Further, the curvature in the Y-axis direction differs between the lens surface position (X, Y) = (0, 0) and the lens surface position (X, Y) = (0, −Y2) at the position of X = 0.

  Further, the curvatures in the X-axis direction and the Y-axis direction are different at the lens surface position (X, Y) = (0, 0), and the lens surface position (X, Y) = (0, −Y2) is also different from the X-axis direction. The curvature in the Y-axis direction is different.

  The definition of the free-form surface described above is not limited to the lens surface of the free-form surface lens 10 but can be applied to an optical member such as the free-form surface mirror 4.

  Table 9 shows the focal lengths in the X-axis direction and the Y-axis direction at the coordinate positions in FIG.

  In FIG. 14, the effective range of the free-form surface lens 10 is ± 16.0 mm in the X-axis direction and 0 to −20.7 mm in the Y-axis direction. Further, in FIG. 14, four points of the lens effective range, six points of the lens surface reference point (X, Y) = (0, 0) and the lower side center (X, Y) = (0, −20.7). The coordinate position is shown.

  Table 9 shows that positions 4 and 6 at the lens outermost periphery with respect to the lens surface reference point have a short focal length in the Y-axis direction (strong positive refractive power).

  Here, referring to FIG. 1, the light beam in the periphery of the lens is incident on the free-form surface lens 10 while being inclined in a direction spreading from the lens optical axis.

  Although not shown in FIG. 1, the light beam at the lens peripheral portion has the largest inclination in the lens peripheral portion, particularly in the X-axis direction.

  That is, the free-form surface lens 10 increases the positive refractive power in the outermost Y-axis direction rather than the positive refractive power at the center, so that the angle of the light beam after passing through the free-form surface lens 10 spreads from the optical axis. It is possible to prevent bending in the direction. For this reason, according to the free-form surface lens 10, the effective range of the free-form surface mirror 4 of the projection optical systems 100, 200, and 300 can be suppressed small.

  However, when the refractive power at the lens periphery is increased, if the free-form curved mirror 4 having power is arranged downstream from the free-form curved lens 10 in the optical path, it is inevitably against the mounting position error of the free-form curved lens 10. Sensitivity increases (the accuracy of lens alignment becomes strict. In particular, the accuracy of the positional relationship between the free-form surface mirror 4 and the free-form surface lens 10 becomes strict), which leads to distortion and deterioration of the MTF. In particular, it was found that the sensitivity to the mounting position error of the free-form surface lens 10 is high in the rotation direction around the optical axis.

  Therefore, the present inventors integrate the lens barrel 30, the free-form surface lens 10, and the free-form surface mirror 4 with a common housing 20, 21, as in the projection optical systems 100, 200, 300 described above. Found to hold on. That is, in the projection optical systems 100, 200, and 300, each component is positioned with the accuracy inherent in the housings 20 and 21, so that even if the lens shape is high in sensitivity to the mounting position error like the free-form surface lens 10, the image quality is high. Degradation can be reduced.

  Further, in the projection optical system according to the present invention, the free curved mirror 4 is not limited to being directly attached to the housings 20 and 21, but the free curved mirror 4 is attached to the housings 20 and 21 via a free curved mirror holder (not shown). Also good. Here, the free-form surface mirror holder can be provided with a member for adjusting the inclination of attachment such as a screw.

  With this configuration, in the projection optical system according to the present invention, it is possible to adjust the mounting error due to the dimensional variation of parts and the like according to the position of the free-form curved mirror 4, so that high image quality can be achieved.

● Image projection device (1) ●
Next, the image projection apparatus according to the present invention will be described.

  FIG. 15 is a diagram showing an embodiment of an image projection apparatus according to the present invention. As shown in the figure, an image projection apparatus 1100 includes an illumination light source 1101, a reflector 1102, a relay lens 1103, a polarization conversion element 1104, an illuminance uniformizing unit 1105, a color wheel 1106, and a polarization separating unit 1108. Have The projection optical system 1109 is the projection optical system 100, 200, 300 described above. The image display element 1107 corresponds to the image display element 1.

  The illumination light source 1101 irradiates the image display element 1 with illumination light. Here, as the illumination light source 1101, a halogen lamp, a xenon lamp, a metal halide lamp, an ultra-high pressure mercury lamp, an LED (Light Emitting Diode), or the like can be used.

  The reflector 1102, the relay lens 1103, the polarization conversion element 1104, and the illuminance uniformizing means 1105 constitute an illumination optical system. The illumination optical system enables the illumination light source 1101 to obtain highly efficient illumination efficiency. Here, an appropriate optical system can be adopted as the illumination optical system according to the type of the light source.

  The reflector 1102 is disposed in the vicinity of the illumination light source 1101 and reflects the light from the illumination light source 1101.

  The polarization conversion element 1104 converts the polarization of the light from the illumination light source 1101.

  The illuminance uniformizing means 1105 is an integrator optical system. The illuminance uniformizing means 1105 irradiates the surface of the image display element 1107 with light having directivity reflected by the reflector 1102 so as to obtain a uniform illumination distribution.

  The color wheel 1106 colors the illumination light.

  Note that the image projection apparatus 1100 may project a color image enlarged on the screen by controlling the image of the image display element 1107 in synchronization with the color wheel 1106.

For example, the polarization separation means 1108 is a polarization beam splitter (PBS: Polarization).
illumination beam path and projection beam path combined with beam splitter). The polarized light separating means 1108 can provide efficient illumination when a reflective liquid crystal image display element is used as the image display element 1107.

Further, as the polarization separation means 1108, DMD (Digital
In the case of mounting a (Mirror Device) panel, optical path separation using a total reflection prism can be employed.

Advantages of Embodiment According to the image projection apparatus 1100 described above, since the free-form surface lens and the free-form surface mirror use a projection optical system that is integrally held by a housing made with high accuracy, While adopting a lens, it is possible to reduce performance degradation due to manufacturing errors.

● Image projection device (2) ●
Next, another embodiment of the image projection apparatus according to the present invention will be described. In the following description, only differences from the image projection apparatus 1100 described above will be described.

  FIG. 16 is a diagram showing another embodiment of the embodiment of the image projection apparatus according to the present invention. As shown in the figure, the image projection apparatus 1200 is different from the image projection apparatus 1100 described above in that the image display element 1207 uses a plurality (three in FIG. 16) of red, green, and blue. To do.

  In the image projection apparatus 1200, the illumination light is separated by the color separation unit 1206, and the illumination light of each color is synthesized by the color synthesis unit 1209. The image projection apparatus 1200 can project a color image on the screen 1211 by causing the combined light to enter the projection optical system 1210.

  Here, the distance from the image display element 1207 to the first surface of the first optical system of the projection optical system 1210 needs to be a long distance by including the polarization separation unit 1208 and the color synthesis unit 1209.

  In this case, in the image projection apparatus 1200, the dimension of the projection optical system 1210 may be extended or shortened by matching the distance from the image display element 1207 to the first optical system with the size of the color synthesizing unit 1209.

Effects of the Embodiment According to the image projection apparatus 1200 described above, since the free-form surface lens and the free-form surface mirror use a projection optical system that is integrally held by a housing made with high accuracy, While adopting a lens, it is possible to reduce performance degradation due to manufacturing errors.

1: Image display element 2: First optical system 3: Folding mirror 4: Free-form curved mirror 5: Dust-proof glass 6: Screen 10: Free-form curved lens 20: Housing 21: Housing 100: Projection optical system 200: Projection optical system 300: Projection optical system 1000: Image projection apparatus 1100: Image projection apparatus 1101: Illumination light source 1102: Reflector 1103: Relay lens 1104: Polarization conversion element 1105: Illuminance uniformizing means 1106: Color wheel 1107: Image display element 1108: Polarization separation means 1200 : Image projection device 1206: Color separation means 1207: Image display element 1208: Polarization separation means 1209: Color composition means

Japanese Patent No. 4223936 JP 2009-251457 A JP 2011-33738 A

Claims (11)

A projection optical system of an image projection apparatus that projects an image onto a projection surface and displays the enlarged image,
A rotationally asymmetric free-form lens,
A curved mirror,
Having
The free curved lens and the curved mirror are held by a common holding member,
A projection optical system characterized by that. The curved mirror is a free curved mirror,
The projection optical system according to claim 1. An image display element for forming the image;
When the long side direction of the image display element is the X axis and the short side direction is the Y axis,
The free-form surface lens has a symmetric shape in the X-axis direction and an asymmetric free-form surface shape in the Y-axis direction,
In the X-axis direction or the Y-axis direction, the positive refractive power at the peripheral portion of the free-form surface lens is larger than the positive refractive power at the center portion of the free-form surface lens.
The projection optical system according to claim 1 or 2. In the Y-axis direction, the free-form surface lens has a positive refracting power at the periphery of the free-form surface lens that is greater than the positive refracting power at the center of the free-form surface lens.
The projection optical system according to claim 3. In the free-form surface lens, in the X-axis direction and the Y-axis direction, the positive refractive power at the peripheral portion of the free-form surface lens is larger than the positive refractive power at the center portion of the free-form surface lens.
The projection optical system according to claim 3. A plurality of lens groups;
A first optical system that forms an image on the image display element as an intermediate image;
A second optical system that forms the intermediate image on the projection surface;
Have
The first optical system includes a lens barrel that holds the plurality of lens groups and the free-form surface lens,
The second optical system is the curved mirror;
The curved mirror has a rotationally asymmetric shape with a concave surface facing the first optical system,
The projection optical system according to claim 3. Lenses other than the free-form surface lens among the plurality of lens groups are held by the lens barrel so that all optical axes coincide with each other,
The free-form surface lens is held at a position optically closest to the free-form surface mirror;
The holding member integrally holds the lens barrel, the free-form surface lens, and the free-form surface mirror;
The projection optical system according to claim 5 or 6. The free-form surface lens moves alone with respect to the plurality of lens groups;
The projection optical system according to claim 5. A folding mirror that folds an optical path disposed in an optical path between the free-form surface lens and the free-form surface mirror;
The folding mirror is held by the holding member;
The projection optical system according to claim 5. The holding member includes dust-proof glass,
The housing is hermetically sealed by the image display element, the lens barrel, the free-form surface lens, the folding mirror, the free-form surface lens, and the dust-proof glass.
The projection optical system according to claim 9. An image projection apparatus having a projection optical system for projecting and projecting an image onto a projection surface,
The projection optical system is the projection optical system according to any one of claims 1 to 10.
An image projection apparatus characterized by that.