JP2005189768A - Projection optical system, image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system which consists of free-form surface mirrors and makes variable magnification possible. <P>SOLUTION: The projection optical system consists of the plurality of free-form surface mirrors and projects the light from a image display device to a screen surface. The system has mirror groups consisting, successively from the image display device side, of a positive first group, a negative second group and a positive third group, and drives the second group and third group when the magnification is varied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The apparatus relates to a focusing mechanism such as a projector apparatus that projects an image on a large screen screen in presentations such as a meeting or appreciation of a movie in a general home.

  As a projection optical system using a reflection system, there is one disclosed in the republished patent patent WO97 / 01787 shown in FIG. As shown in this example, the image displayed on the image display element is a so-called rear projection that is projected on a screen by an imaging optical system configured by a combination of free-form curved reflectors and viewed from the back side of the screen. In the case of such an apparatus, since the distance between object images is fixed, once this is adjusted at the time of manufacture of the apparatus, it is not necessary to adjust every time it is used. The focus adjustment need not be executed on the user side unless the image focus once adjusted shifts due to a change with time (expansion due to temperature, etc.) or a vibration shock during transportation. On the other hand, since the liquid crystal projector of the front projection type is installed under different conditions every time it is used, it is necessary to adjust the focus and the like each time. The distance to the screen is usually different for each installation. Therefore, when the focus to the screen is adjusted, there is a problem that the screen size changes according to the projection distance. For this reason, conventionally, a refractive projection lens is usually equipped with a zoom mechanism having a low zoom magnification of about 1.2 to 1.3 times. Using this zoom mechanism, the variation in the projected image size is adjusted depending on the variation in the projection distance, and the change in the image size can be absorbed to some extent and used. However, since the projection optical system configured by combining free-form surface reflecting mirrors is an enlargement imaging optical system, it is very sensitive to the decentering of each component mirror and it is very difficult to construct a zoom system.

  As an attempt of a zoom optical system using a free-form surface reflecting mirror, a coaxial refractive optical system and a free-form surface reflection in an imaging device disclosed in Japanese Patent Application Laid-Open No. 10-20196 shown in FIG. This is a reduction optical system combined with an imaging system using a mirror and used as an imaging optical system. In this example, a zoom function is to be realized by moving an image forming system using a free-form curved reflecting mirror and a coaxial refractive optical system. In this example, since a refractive optical element is included, the occurrence of chromatic aberration occurring in the system is unavoidable, and high-precision achromaticity cannot be performed.

  Further, there is an example in which only a reflection optical system is combined as in the imaging apparatus disclosed in Japanese Patent Laid-Open No. 9-258106 shown in FIG. 10, but in this example, a moving group + a fixed group + It is a moving group configuration, and a fixed group must be sandwiched between them. As will be described later, the projection optical system requires a group that deflects the optical axis emitted from the image display and illumination optical system to the optical axis that projects upward, and thus the deflected light beam is thus moved group + fixed group If it is configured to change the magnification by three groups as in the + moving group, the total number of groups becomes four, and the entire optical system becomes very large. Further, as in the embodiment in the publication, further increase in size is inevitable if each group has a surface configuration of 4 to 5 surfaces.

Further, what is common to the disclosed embodiments of both Japanese Patent Application Laid-Open No. 10-20196 and Japanese Patent Application Laid-Open No. 9-258106 is that each group of the imaging system based on a combination of free-form curved mirrors is made transparent. Since the free curved surface is formed on the surface of the refracting member and the light beam passes through the transparent member, all the free curved surface reflectors are configured by the back surface reflecting mirror. For this reason, there are an entrance surface and an exit surface to the transparent member, and refraction occurs on these surfaces and chromatic aberration occurs. Under imaging conditions determined by a certain object distance and image distance, it is possible to take a configuration that cancels out chromatic aberration generated on the entrance surface and the exit surface. However, since the partial imaging magnification of each of these groups changes due to the zooming operation, it is difficult to determine a condition that can always completely cancel out the occurrence of chromatic aberration on the entrance surface and exit surface.
WO97 / 01787 Japanese Patent Laid-Open No. 10-20196 JP 09-258106 A

  In general, when a free-form curved mirror is combined to form an imaging system, the relative positional relationship between the mirrors is very important. In the case of a reflective imaging system, the effect of surface deformation is doubled compared to a refractive imaging system, so once the imaging system is assembled, each reflector is fixed very strongly so that it does not move. Or, as disclosed in Japanese Patent Application Laid-Open Nos. 10-20196 and 9-258106, a bulk member surface of a transparent member in which a light beam propagates while reflecting backside. As a back reflector, the relative position is prevented from moving.

  Unlike the state assumed at the time of design, the passing point of each light ray on the mirror surface is different from the state assumed at the time of design due to the movement of the reflecting mirror surface itself. In other words, at the time of design, a certain ray passes through a predetermined point on the Nth specular surface, that is, is reflected and deflected, collides with a point at a predetermined position on the next N + 1th specular surface, and is reflected and deflected again there. By repeating this reflection deflection, each ray emitted from a certain point on the object reaches the image plane and converges to a certain point on the image plane corresponding to the point on the object. However, when the passing point of the light beam deviates from a predetermined position on the Nth surface, in the case of a mirror having a curved surface, the deflection angle generally changes because the local mirror tilt angle is different. As a result, the light beam that has passed through the Nth mirror reaches a position on the next N + 1th mirror that is different from the position where the light beam originally intended to pass, and as a result, the local light beam at the position where the light beam reached again. Since the angle of the mirror is different from the originally assumed state, the light beam reflected and deflected there travels in a direction different from the original direction. This deviation increases with each passing through the surface, and thus affects the imaging performance of the entire light beam that has passed through the optical system.

  When configuring a zoom optical system, it is necessary to move at least two groups. It is necessary to play a role of so-called variator and compensator, which changes the magnification by moving one group and keeps the distance between the object and the screen constant by moving the other group. Because. In the case of an optical system having a risk that the relative shift of the optical elements greatly impairs the imaging performance, such as the decentered reflection optical system of the present invention, it is necessary to adopt the following configuration.

  First, in the present optical system, one optical axis originating from the center of the image display panel as an object is defined as a reference axis ray. The reference axis ray reaches the center of the image plane while reflecting and passing through a vertex serving as a reference for each surface (hereinafter, this point is referred to as a hit point of the reference axis ray).

  The problems to be solved by the present invention based on the above points are summarized below.

  First, it is preferable that the position of the center of the image projected on the screen does not change when the relative positional relationship of the optical elements changes due to zooming. This is not preferable because the projection screen may move up and down on the screen according to the zooming operation.

  Second, in this optical system, if the passing position of the reference axis ray is shifted with respect to the hit point due to the eccentricity or movement of some free-form curved reflectors, the reflection angle or space of the reference axis ray there The position of the upper deflection point will change. As a result, as described above, the hit point where the reference axis ray should pass does not pass even on the subsequent reflecting surfaces. Accordingly, there is a concern that the image formation relationship of each light beam that reaches the image plane while passing through a predetermined hit point on each surface is greatly changed, and the original image formation performance is greatly impaired. Therefore, even if group movement occurs due to zooming, it is preferable that the hit points on each surface of the reference axis ray do not move, and the surrounding ray group moves in the direction of expanding or reducing the beam diameter around the reference axis ray. .

  Third, it is desirable to realize these with a minimum group configuration as a projection optical system.

  Fourth, it is desirable that the imaging optical system configured by combining free-form surface reflecting mirrors has a hollow configuration.

  An object of the present invention is to provide a projection optical system capable of solving the above-described problems.

  In order to solve the above problems, a projection optical system according to the present invention is a projection optical system that has a plurality of curved reflecting mirrors and projects light from at least one image display element onto a projection surface. It is characterized by having a function. Here, it is preferable that the projection optical system includes only a reflective surface.

  A plurality of the image display elements; a color combining optical system for combining light beams from the plurality of image display elements; and a light beam emitted from the color combining optical system on the projection surface. It is preferable to project.

  In zooming, it is preferable that the center position of the projection image projected on the projection surface does not substantially move.

  Moreover, it is preferable that the position of the center of the projection image is less than 1% of the diameter of the smallest circle that can surround the projection image projected on the projection surface.

  It is preferable that the center position of the projection image is less than 0.5% of the diameter of the smallest circle that can surround the projection image projected on the projection surface.

  It is preferable that two optical units move during zooming, and each of the two optical units has at least two reflecting mirror surfaces.

  Further, it is preferable that the two optical units move during zooming, and each of the two optical units includes at least two reflecting mirror surfaces.

  And a fixed deflection group for deflecting the reference axis ray upward when the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projection image of the projection surface is a reference axis ray. In zooming, it is preferable that the two optical units move along the direction of the reference axis light beam emitted from the fixed deflection group.

  Two optical units move during zooming, and the direction in which the two optical units move is inclined with respect to a straight line connecting the center of the image display element and the center of the projected image of the projection surface. preferable.

  It is preferable that two optical units move during zooming, and focus adjustment is possible by moving an optical unit close to the projection surface of the two optical units.

  When the two optical units move at the time of zooming, and the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projected image on the projection surface is used as a reference axis light beam, The direction cosines of the reference axis ray incident on at least one of the two optical units and the reference axis ray emitted from the optical unit close to the projection surface of the two optical units are substantially parallel and have the same sign. preferable.

  When the two optical units move at the time of zooming, and the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projected image on the projection surface is used as a reference axis light beam, The direction cosines of the reference axis ray incident on at least one of the two optical units and the reference axis ray emitted from the optical unit close to the projection surface of the two optical units may be substantially parallel to each other and have opposite signs. preferable.

  Further, when the two optical units move during zooming, and there are three reflecting surfaces constituting either of the two optical units, it is preferable that the power of the three surfaces is positive or negative.

  Further, when the two optical units move during zooming and there are two reflecting surfaces constituting either of the two optical units, it is preferable that the powers of the two surfaces are both positive.

  In addition, two optical units move during zooming, and among the two optical units, the optical units close to the image display element have opposite powers between adjacent surfaces, and the power of the final surface continues. Preferably it is the opposite of the power of the first face of the group.

  The projection optical system according to claim 1, wherein at least one of the plurality of curved reflecting mirrors has a non-rotationally symmetric curved shape.

  An image projection apparatus according to another aspect of the present invention includes at least one image display element, an illumination optical system that illuminates the at least one image display element with light from a light source, and the at least one image display element. It has the above-mentioned projection optical system which projects the light beam of this to a to-be-projected surface, It is characterized by the above-mentioned. Here, the at least one image display element is a plurality of image display elements, and includes a color synthesis optical system that synthesizes light beams emitted from the plurality of image display elements, and the projection optical system includes the color synthesis optical system. It is desirable to project the light beam emitted from the system onto the projection surface.

  According to the present invention, an image projection imaging optical system configured by combining a plurality of free-form surface mirrors of a projection apparatus, a system capable of performing zooming adjustment and focus adjustment by partially moving a zoom group and a focus adjustment group. It can be realized.

  Prior to the description of the present embodiment, description will be given of how to represent the configuration specifications of the embodiment and common matters of the entire embodiment.

  In the embodiment of the present invention, the m-th surface is defined as the m-th surface in the order of arrival of rays traveling from the object side to the image plane. Each reflecting surface is a surface reflecting mirror in which a reflecting film or the like is attached to a surface shape formed of glass, plastic or the like, and the medium filling the space between the mirrors is air. Therefore, all the examples are so-called hollow types. On the other hand, a configuration in which a plurality of free curved surfaces are formed on the surface of a glass or plastic bulk, a reflective film is attached, and a light beam propagates through the medium as a back mirror.

  In order to describe the embodiment, first, three items of a reference axis ray, a global coordinate system, and a local coordinate system are defined and described.

  Since the optical system of the present invention is an off-axial optical system, the surfaces constituting the optical system do not have a common optical axis. To repeat, in the embodiment of the present invention, a light beam that is first emitted from the image display element, which is an object, reaches the image plane while following the imaging optical system, and passes through the center of the stop of the optical system. The light beam to be used is regarded as a reference, and the light beam is defined as a reference axis light beam. The reference axis ray has a direction (orientation). The direction is the direction in which the reference ray travels during imaging. The reference axis ray passes through the center of the stop and finally reaches the center of the image plane while changing its direction in accordance with the law of reflection along the set order of each surface. Here, there may be one image display element or a plurality (preferably three for red, blue, and green). However, in the case of having a plurality of image display elements, a color synthesis optical system (a prism described in FIG. 1, FIG. 3, etc.) for synthesizing a plurality of light beams from the plurality of image display elements is provided. The light beam emitted from the projector is projected onto a projection surface such as a screen by a projection optical system.

Next, consider a global coordinate system (global coordinates are expressed by capital letters XYZ) with the origin at the center point of the object plane that is the image display element. Each axis of the global coordinate system is defined as follows, and FIG. It explains using. The coordinate system is a right-handed system.
(1) Z-axis: As shown in FIG. 1, the direction from the object plane toward the first mirror through the global origin is positive.
(2) Y axis: A straight line passing through the global origin and forming 90 ° with respect to the Z axis as shown in FIG. In FIG. 1, the upper side of the drawing is the positive sign direction of the Y axis. In the present invention, it is assumed that the reference axis ray exists in the YZ plane. Accordingly, all the curved mirrors constituting the reflective imaging optical system of each embodiment of the present invention are tilted in the YZ plane. In each figure of each embodiment of the present invention, the paper surface coincides with the YZ plane. The coordinate system is common in the drawings of the embodiments of the present invention, and the positive direction of the Y-axis is the upper side of the drawing.
(3) X axis: A straight line passing through the origin and perpendicular to the Z and Y axes. That is, it is a straight line in a direction perpendicular to the paper surface of each figure. Since it is a right-handed system, the positive is the back side of the page.

In order to express the surface shape of the m-th surface constituting the optical system, the local coordinate system using the point moved on the reference axis ray by the surface distance as the local origin rather than describing the shape of the surface in the global coordinate system (Local coordinates are expressed in lower case xyz), and the surface shape of the surface in the local coordinate system corresponding to each surface is easier to understand when recognizing the shape. The surface shape is expressed in the local coordinate system (right hand system). The tilt of the surface is also expressed by tilting the local coordinate system corresponding to each surface with respect to the global coordinate system. The tilt angle in the YZ plane of the local coordinate system corresponding to the m-th plane is represented by an angle θm (unit [°]) with the counterclockwise direction being positive with respect to the Z axis of the global coordinate system. Therefore, as a matter of course, in the embodiment of the present invention, the origins of the local coordinates of each surface are all on the YZ plane. There is no surface eccentricity in the XZ and XY planes. Furthermore, the y and z axes of the local coordinates (x, y, z) of the m-th plane are inclined at an angle θm in the YZ plane with respect to the global coordinate system (X, Y, Z). Set as follows.
(1) z-axis: a straight line that passes through the origin of local coordinates and forms an angle θm counterclockwise in the YZ plane with respect to the Z direction of the global coordinate system.
(2) y-axis: a straight line that passes through the origin of local coordinates and forms 90 ° counterclockwise in the YZ plane with respect to the z direction.
(3) x-axis: a straight line passing through the origin of local coordinates and perpendicular to the YZ plane.
(4) Lm is a scalar quantity that represents the distance between the origins of the local coordinates of the mth and m + 1th planes. (Unit [mm])
However, for the final surface, the distance from the local origin of the surface to the center of the image surface is shown.
The optical system of the present invention has at least one rotationally asymmetric aspheric surface, and the shape thereof is represented by the following equation (1) on the local coordinate system:
However, C02, C20, C03, C21, C04, C22, C40, C05, C23, C41, C06, C24, C42, and C60 are aspherical coefficients.
^{z (x, y) = C02y} 2 + C20x 2 + C03y 3 + C21x 2 y + C04y 4 + C22x 2 y 2 + C40x 4 + C05y 5 + C23x 2 y 3 + C41x 4 y + C06y 6 + C24x 2 y 4 + C42x 4 y 2 + C60x 6 ‥‥ (1)

Since the curved surface (1) represents a rotationally asymmetric surface based on a plane and is only an even-order term with respect to x, the curved surface defined by the curved surface equation has a plane-symmetric shape with the yz plane as a symmetry plane. is there. Furthermore, when the following conditions are satisfied, it represents a symmetrical shape with respect to the xz plane.
C03 = C21 = C05 = C23 = C41 = 0
Furthermore, C02 = C20, C04 = C40 = C22 / 2, C06 = C60 = C24 / 3 = C42 / 3
Represents a rotationally symmetric shape. When the above conditions are not satisfied, the shape is non-rotationally symmetric.

  Next, each embodiment of the present invention will be described.

  First, the optical system is arranged and configured so that the hit points on each surface of the reference axis ray do not move by the zooming operation of the projection imaging optical system. Since the free-form curved reflecting surface according to the present invention does not have a first-order term in the expression for each surface, the inclination in a minute region near the hit point of the reference axis ray is the aspheric coefficient of the surface. Even when the surface shape changes due to the change, it is constant (always in the minute region). Therefore, a basic skeleton for designing this optical system is constructed, and even if a relative position change between each group occurs due to a zooming operation, if this reference axis does not move, the projected image will also be centered on this reference axis ray. Since the image is enlarged or reduced, the center position of the projection image does not move.

  As is well known, in the case of a projection optical system, the image display element and a part constituting an illumination system that illuminates the image display element and two parts of an image forming optical system that are connected to the image display element and project an image of the image display element on a screen are enlarged. However, in many cases, the optical paths of the image display element and the illumination system are often parallel to the surface of a table or table on which the apparatus is placed. On the other hand, since the screen projected from the apparatus is generally placed at a place higher than the installation position, the optical path of the imaging optical system has an oblique optical axis having an elevation angle vertically upward. Therefore, in the present invention, one or two free-form surface mirrors for deflecting the optical axis from the image display element and the illumination device to the optical axis having the upward projection elevation angle are required, and the optical path is moved upward by these mirrors. A zoom projection imaging system is configured by arranging a mirror group having a deflected light beam functioning as a variator and a compensator. The group of the variator and the compensator has a configuration in which the incident reference axis light beam is emitted as it is in the same sign direction or in parallel in the opposite sign direction. When the relative positional relationship between the optical elements is changed by zooming due to the movement of the variator and the compensator group by these combinations, the position of the center of the image projected on the screen does not change. Further, although it is preferable that the center position of the image projected on the screen does not change due to focusing, the compensator group is also used for focusing. As a result, the image does not move due to focusing.

  Each of the above variator and compensator groups constitutes one group with two or three mirrors, and each group is repeated, but each group has its incident axis and exit axis coincide with each other, and the projection optical axis also has it. Therefore, the hit point of the reference axis ray in each plane does not move due to the movement of each group.

  In addition, since these mirrors are all configured with a hollow structure by combining surface reflection mirrors, chromatic aberration does not occur.

  FIGS. 1 and 2 are a diagram of a mirror portion of a free-form surface reflection imaging optical system and a diagram of the entire optical path to a projection screen (projection image). FIG. 1 is a schematic view of a main part of a first embodiment of a projection display device using the projection optical system of the present invention. Although an illumination optical system for illuminating the image display element using light from the light source is not shown here, it is of course preferable to provide it.

  This embodiment is a projection optical system using an off-axial system for projecting light whose intensity is modulated by an image display element onto a projection screen and forming an image on the projection screen surface. FIG. 2 is an overall view of the projection optical system of FIG.

In FIG. 1, the object plane coincides with the plane of the image display element. The image display element is illuminated from the back side by an illumination system (not shown). The illumination system (not shown) includes a lamp, a condenser lens, a filter for selecting a wavelength, and the like. In the present embodiment, three RGB image display elements are used and a RGB color image is synthesized and projected using a color synthesis prism, but the two image display elements are not shown. An image display element and a color synthesis prism are shown. This is common for all examples,
(1) The total number of reflection curved surfaces is 6 (2) The distance from the object surface to the color synthesis prism: 11.0
(3) Color composition prism thickness: 28.0
(4) Nd: 1.872690, νd: 32.33
(5) Distance from the prism exit end face to the local coordinate origin of the first mirror: 30.0
(Unit [mm]).

  1 and 2, the reflective imaging optical system includes a first mirror (concave surface), a diaphragm, a second mirror (convex surface), a third mirror (concave surface), a fourth mirror (in order of passage of light rays from the image display element). Convex surface), 5th mirror (concave surface), and 6th surface mirror (concave surface). All the reflection surfaces are symmetrical with respect to only the YZ plane. Here, an image formed by the image display element is intermediately formed between the fourth mirror and the fifth mirror, and the diaphragm is formed at a position after the sixth mirror.

  In all embodiments in the proposal, the image display element is 0.7 inches diagonal (10.7 × 14.2 mm), and the projection screen size is 70 inches diagonal (1067 × 10) with an aspect ratio of 3: 4. 1422 mm). Further, the normal line of the projection screen is inclined by 40 degrees with respect to the reference axis light beam immediately before entering the projection screen. The image display element is a so-called XGA (1024 × 768 pixels), the pixel pitch is 1.4 mm on the screen side, and the spatial cutoff frequency at this time is 1 / 2.8 = 0.36 lines / mm.

  An example of an installation configuration that takes into account the actual use state of the apparatus, such that the plane of the projection screen is parallel to the vertical direction, and a plane including all the reference axis rays is within the vertical plane perpendicular to the projection screen. When the device is installed so that the projection distance is measured in the horizontal direction from the final reflection surface of the device to the screen, the projection distance is L6 × Cos 40 ° = 2837 mm × Cos 40 ° = 2173 mm.

  Table 1 below shows design values of the first embodiment. In the configuration data, each surface from the panel surface to the image surface (projection screen surface) is numbered sequentially. The F value on the object side is 2.8.

  In the first embodiment, in order from the image display element side (reduction conjugate side, reduction side), the first and second mirrors are the first optical unit (mirror group, optical group), and the third and fourth mirrors are the second optical unit. The unit, the fifth and sixth mirrors are the third optical unit, and a projection optical system having three positive and negative optical units. Here, the second optical unit, that is, the third surface and the fourth surface is composed of the variator, and the third optical unit, that is, the fifth surface and the sixth surface is composed of the compensator. A group. In addition, a group composed of two of the fifth surface and the sixth surface is also a focus group. Here, the tilt angle θ5 of the fifth surface and the tilt angle θ6 of the sixth surface are 5 ° and 5 °, respectively, and are equal. The angle formed by the reference axis ray incident on the variator / compensator group with respect to the Z axis of the global coordinate system is 40 °, and the angle formed by the reference axis ray emitted from the variator / compensator group with respect to the global Z axis is The angle is also 40 °. The focus group has a scaling function and a focus adjustment function by moving in parallel with a direction axis that is parallel to the optical axis and forms an angle of 40 ° with the global Z axis.

  Next, FIGS. 3 to 4 are a diagram of the mirror part of the free-form surface reflection imaging optical system of the second embodiment in the present invention and a diagram of the entire optical path to the projection screen (projection image).

  This embodiment is a projection optical system using an off-axial system for projecting light whose intensity is modulated by an image display element onto a projection screen and forming an image on the projection screen surface. FIG. 4 is an overall view of the projection optical system of FIG. Although an illumination optical system for illuminating the image display element using light from the light source is not shown here, it is of course preferable to provide it.

  FIG. 3 is a schematic view of a main part of a second embodiment of a projection display device using the projection optical system of the present invention. In the second embodiment, the positions of the mirrors in the three states of wide, middle, and tele are shown in an overlapping manner. In the case of this display, since the three states overlap each other, the drawing becomes complicated. However, since there are also aspects that make it easy to grasp the three states at once, the second embodiment is an enlarged view and an overall view of the optical system in FIG. 4 will be described using a diagram in which the three states of wide, middle, and tele are displayed in an overlapping manner.

In FIG. 3, the object plane coincides with the plane of the image display element. The image display element is illuminated from the back side by an illumination system (not shown). The illumination system (not shown) includes a lamp, a condenser lens, a filter for selecting a wavelength, and the like. In the present embodiment, three RGB image display elements are used and a RGB color image is synthesized and projected using a color synthesis prism, but the two image display elements are not shown. An image display element and a color synthesis prism are shown. This is common for all examples,
(1) The total number of reflection curved surfaces is 6 (2) The distance from the object surface to the color synthesis prism: 11.0
(3) Color composition prism thickness: 28
(4) Nd: 1.872690, νd: 32.33
(5) Distance from the prism exit end face to the local coordinate origin of the first mirror: 30.0
(Unit [mm]).

  3 and 4, the reflective imaging optical system includes a first mirror (concave surface), a second mirror (convex surface), an aperture, a third mirror (concave surface), a fourth mirror (in order of passage of light rays from the image display element). Convex surface), 5th mirror (concave surface), 6th surface (convex surface), 7th surface (concave surface). All the reflection surfaces are symmetrical with respect to only the YZ plane. Here, an image formed by the image display element is intermediately formed between the fourth mirror and the fifth mirror, and the diaphragm is formed at a position after the sixth mirror.

  In all embodiments in the proposal, the image display element is 0.7 inches diagonal (10.7 × 14.2 mm), and the projection screen size is 70 inches diagonal (1067 × 10) with an aspect ratio of 3: 4. 1422 mm). Further, the normal line of the projection screen is inclined by 40 degrees with respect to the reference axis light beam immediately before entering the projection screen. The image display element is a so-called XGA (1024 × 768 pixels), the pixel pitch is 1.4 mm on the screen side, and the spatial cutoff frequency at this time is 1 / 2.8 = 0.36 lines / mm.

  An example of an installation configuration that takes into account the actual use state of the apparatus, such that the plane of the projection screen is parallel to the vertical direction, and a plane including all the reference axis rays is within the vertical plane perpendicular to the projection screen. When the device is installed so that the projection distance is measured in the horizontal direction from the final reflection surface of the device to the screen, the projection distance is L7 × Cos 40 ° = 2300 mm × Cos 40 ° = 1760 mm. This horizontal projection distance is a reference for design.

The design values of the second embodiment are shown below. In the configuration data, each surface from the panel surface to the image surface (projection screen surface) is numbered sequentially.
The F value on the object side is 3.3.

  In the second embodiment, in order from the image display element side (reduction conjugate side, reduction side), the first and second mirrors are the first optical unit (mirror group, optical group), and the third and fourth mirrors are the second optical unit. The unit, the fifth and sixth mirrors are the third optical unit, and a projection optical system having three positive and negative optical units. Here, the second optical unit, that is, the third surface and the fourth surface is a variator, and the third optical unit, that is, the fifth surface and the sixth surface is a compensator.

  In the second embodiment, a variator is constituted by the third surface and the fourth surface, and a compensator is constituted by the three surfaces of the fifth surface, the sixth surface and the seventh surface. A group composed of three surfaces of the fifth surface, the sixth surface, and the seventh surface is also a compensator / focus group. The angle formed by the reference axis ray incident on the focus group with respect to the Z axis of the global coordinate system is 40 °, and the angle formed by the reference axis ray emitted from the compensator / focus group with respect to the global Z axis is the same 40 °. The compensator / focus group has a focus adjustment function by moving parallel to a direction axis that is parallel to the optical axis and forms an angle of 40 ° with the global Z axis. 5 to 7 show the defocus characteristics and distortion of the wide end, middle and tele end of the MTF at each point on the image plane at the above-mentioned projection distance of 1760 mm which is the reference of the second embodiment. In the figure, the horizontal axis is the amount of focus, and the point 0 is the position of the reference image plane (reference projection position). The focus amount is measured along the horizontal direction in which the above-described reference projection distance is measured. The spatial frequency at this time is 0.36 lines / mm on the projection screen side determined from the pixel pitch of the image display element.

  This example can be described as follows.

  The projection optical system of the present invention is a projection optical system that has a plurality of curved reflection mirrors and projects light from at least one image display element onto a projection surface, and has a zooming function. . Here, it is preferable that the projection optical system includes only a reflective surface. A plurality of the image display elements; a color combining optical system for combining light beams from the plurality of image display elements; and a light beam emitted from the color combining optical system on the projection surface. It is preferable to project. In zooming, it is preferable that the center position of the projection image projected on the projection surface does not substantially move. Moreover, it is preferable that the position of the center of the projection image is less than 1% of the diameter of the smallest circle that can surround the projection image projected on the projection surface. It is preferable that the center position of the projection image is less than 0.5% of the diameter of the smallest circle that can surround the projection image projected on the projection surface. It is preferable that two optical units move during zooming, and each of the two optical units has at least two reflecting mirror surfaces. Further, it is preferable that the two optical units move during zooming, and each of the two optical units includes at least two reflecting mirror surfaces. And a fixed deflection group for deflecting the reference axis ray upward when the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projection image of the projection surface is a reference axis ray. In zooming, it is preferable that the two optical units move along the direction of the reference axis light beam emitted from the fixed deflection group.

  Two optical units move during zooming, and the direction in which the two optical units move is inclined with respect to a straight line connecting the center of the image display element and the center of the projected image of the projection surface. preferable.

  It is preferable that two optical units move during zooming, and focus adjustment is possible by moving an optical unit close to the projection surface of the two optical units.

  When the two optical units move at the time of zooming, and the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projected image on the projection surface is used as a reference axis light beam, The direction cosines of the reference axis ray incident on at least one of the two optical units and the reference axis ray emitted from the optical unit close to the projection surface of the two optical units are substantially parallel and have the same sign. preferable.

  When the two optical units move at the time of zooming, and the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projected image on the projection surface is used as a reference axis light beam, The direction cosines of the reference axis ray incident on at least one of the two optical units and the reference axis ray emitted from the optical unit close to the projection surface of the two optical units may be substantially parallel to each other and have opposite signs. preferable.

  Further, when the two optical units move during zooming, and there are three reflecting surfaces constituting either of the two optical units, it is preferable that the power of the three surfaces is positive or negative.

  Further, when the two optical units move during zooming and there are two reflecting surfaces constituting either of the two optical units, it is preferable that the powers of the two surfaces are both positive.

  In addition, two optical units move during zooming, and among the two optical units, the optical units close to the image display element have opposite powers between adjacent surfaces, and the power of the final surface continues. Preferably it is the opposite of the power of the first face of the group.

  It is desirable that at least one of the plurality of curved reflection mirrors has a non-rotationally symmetric curved shape.

  At least one of the curved reflecting mirrors is preferably a surface reflecting mirror. In addition, it is desirable that at least one of the above curved surface reflecting mirrors is made of resin or glass and has a surface with a highly reflective coating. It is desirable that at least one of the above curved surface reflecting mirrors is obtained by applying a highly reflective coating to the surface of a metal sheet that has been press-molded to transfer a predetermined shape. It is desirable that at least one of the curved surface reflecting mirrors has a highly reflective coating on a surface obtained by grinding and polishing a metal.

  An image projection apparatus according to another aspect of the present invention includes at least one image display element, an illumination optical system that illuminates the at least one image display element with light from a light source, and the at least one image display element. And the above-described projection optical system for projecting the luminous flux onto the projection surface. Here, the at least one image display element is a plurality of image display elements, and includes a color synthesis optical system that synthesizes light beams emitted from the plurality of image display elements, and the projection optical system includes the color synthesis optical system. It is desirable to project the light beam emitted from the system onto the projection surface.

Schematic diagram of essential parts of the projection optical system of the first embodiment of the present invention Overview of the projection imaging optical system of the first embodiment of the present invention Projection optical system main part schematic of 2nd Example of this invention Overview of the projection imaging optical system of the second embodiment of the present invention MTF-defocus characteristic and distortion characteristic at the Tele end of the second embodiment of the present invention MTF-defocus characteristic and Distortion characteristic at the Middle end of the second embodiment of the present invention MTF-defocus characteristic and distortion characteristic at the wide end of the second embodiment of the present invention Conventional example disclosed in International Publication No. WO97 / 01787 Conventional example of zoom projection imaging system with a refracting system Conventional example of reflecting mirror zoom projection imaging system limited to moving group + fixed group + moving group configuration

Claims (19)

  A projection optical system having a plurality of curved reflecting mirrors and projecting light from at least one image display element onto a projection surface, the projection optical system having a zooming function.   The projection optical system according to claim 1, wherein the projection optical system includes only a reflecting surface. A plurality of the image display elements;
A color combining optical system for combining light beams from the plurality of image display elements;
The projection optical system according to claim 1, wherein a light beam emitted from the color synthesis optical system is projected onto the projection surface.   4. The projection optical system according to claim 1, wherein a position of a center of a projection image projected on the projection surface does not substantially move during zooming. 5.   The projection optical system according to claim 4, wherein a position of a center of the projection image is less than 1% of a diameter of a minimum circle that can surround the projection image projected on the projection surface. .   6. The center position of the projected image is less than 0.5% of the diameter of the smallest circle that can surround the projected image projected on the projection surface. Projection optical system.   7. The projection optical system according to claim 1, wherein two optical units move during zooming, and each of the two optical units has at least two reflecting mirror surfaces.   7. The projection optical system according to claim 1, wherein two optical units move at the time of zooming, and each of the two optical units includes at least two reflecting mirror surfaces.   When the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projection image of the projection surface is a reference axis ray, the fixed deflection group deflects the reference axis ray upward. 9. The projection optical system according to claim 1, wherein the two optical units move along the direction of the reference axis light beam emitted from the fixed deflection group during zooming.   Two optical units move at the time of zooming, and the direction in which these two optical units move is inclined with respect to a straight line connecting the center of the image display element and the center of the projected image of the projection surface. The projection optical system according to claim 1, wherein the projection optical system is a projection optical system.   11. The focus adjustment is possible by moving two optical units at the time of zooming and moving an optical unit close to the projection surface of the two optical units. The projection optical system described in 1.   When the two optical units move at the time of zooming, and the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projected image on the projection surface is used as a reference axis light beam, The direction cosines of the reference axis ray incident on at least one of the two optical units and the reference axis ray emitted from the optical unit close to the projection surface of the two optical units are substantially parallel and have the same sign. The projection optical system according to claim 1, wherein the projection optical system is a projection optical system.   When the two optical units move at the time of zooming, and the optical path of the principal ray of the light beam passing through the center of the image display element and the center of the projected image on the projection surface is used as a reference axis light beam, The direction cosines of the reference axis ray incident on at least one of the two optical units and the reference axis ray emitted from the optical unit close to the projection surface of the two optical units are substantially parallel to each other and have opposite signs. The projection optical system according to claim 1, wherein the projection optical system is a projection optical system.   The two optical units move at the time of zooming, and when there are three reflecting surfaces constituting either of the two optical units, the power of the three surfaces is positive or negative. The projection optical system according to any one of the above.   The two optical units move at the time of zooming, and when there are two reflecting surfaces constituting either of the two optical units, the powers of the two surfaces are both positive. The projection optical system according to any one of the above.   Two optical units move during zooming, and among the two optical units, an optical unit close to the image display element is a group in which the powers of the adjacent surfaces are opposite to each other and the power of the final surface continues. 16. The projection optical system according to claim 1, wherein the projection optical system has a power opposite to that of the first surface.   The projection optical system according to claim 1, wherein at least one of the plurality of curved reflecting mirrors has a non-rotationally symmetric curved shape.   The at least one image display element, an illumination optical system that illuminates the at least one image display element with light from a light source, and a light beam from the at least one image display element is projected onto a projection surface. 16. An image projection apparatus comprising: the projection optical system according to any one of 16 above. The at least one image display element is a plurality of image display elements;
A color synthesizing optical system for synthesizing light beams emitted from the plurality of image display elements;
The image projection apparatus according to claim 18, wherein the projection optical system projects a light beam emitted from the color synthesis optical system onto the projection surface.

Images