JP2007047767A - Projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection device of an oblique projection type capable of employing an intermediate optical system that can be efficiently manufactured at a low cost. <P>SOLUTION: The projection device which converts an image having a rectangular shape in the display body on which light from an optical source is made incident into an intermediate image having trapezoidal distortion, makes the intermediate image obliquely incident on a screen, and magnifies and projects an image without trapezoidal distortion onto the screen, comprises: a first projecting optical system of forming the intermediate image with the light emitted from the display body; a second projecting optical system of magnifying and projecting the intermediate image onto the screen while correcting the trapezoidal distortion; and an intermediate optical system of combining respective pupils of the first projecting optical system and the second projecting optical system, deflecting the light emitted from the first projecting optical system and guiding the light to the second projecting optical system, wherein each of the first projecting optical system and the second projecting optical system is constituted to be substantially telecentric toward the intermediate side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projection apparatus that projects a display image of a display body obliquely on a screen via a trapezoidal intermediate image.

  2. Description of the Related Art Conventionally, an oblique projection type projection apparatus that projects an image displayed on a display body obliquely on a screen without causing trapezoidal distortion is known. In the present specification, the simple term “projection device” refers to an oblique projection type. In general, the projection apparatus is configured to place each optical member with respect to the optical axis so that the Scheinproof law is established between the display body, the display-side optical system and the intermediate image, and between the intermediate image, the screen-side optical system and the screen. Thus, the display image of the display body is projected obliquely on the screen without causing trapezoidal distortion. As such a projection apparatus, for example, a configuration disclosed in Patent Document 1 below is known.

JP-A-6-265814

  In general, the projection apparatus as described above has an intermediate optical system for guiding an intermediate image formed by the display body side optical system to the screen side optical system. The intermediate optical system needs to have the following three optical performances. The first is the ability to efficiently capture light emitted from the display-side optical system. The second is the ability to adjust the spread of the diverging light so that the diverging light after exiting the intermediate optical system is efficiently taken into the screen side optical system. Third, it is a performance as a prism that bends incident light in the vertical direction of the projector in a normal use state.

  Here, each member is arranged in a state inclined with respect to the optical axis. In each optical system on the display body side and the screen side, a straight line including the most cores of the optical surface is defined as the optical axis of each optical system. However, when all the centers of the optical surfaces are displaced, a straight line passing through the core of the optical surface closest to the pupil is defined as the optical axis of the optical system. Due to the configuration of the projection apparatus in which each member is arranged to be inclined with respect to the optical axis, the light emitted from the display-body-side optical system in the first optical performance and the intermediate optical system in the second optical performance after being emitted. In the vicinity of the intermediate optical system, the divergence of the light differs in directions corresponding to the vertical direction and the horizontal direction of the image projected on the screen of the projector in the normal use state. Therefore, in order to obtain the first and second optical performances, the intermediate optical system is required to have different power depending on directions. When using optical systems having different powers depending on directions, it is necessary to suppress the occurrence of various asymmetric aberrations.

  Therefore, in the above-mentioned Patent Document 1, an intermediate optical system including two Fresnel lenses is adopted, and each lens is decentered to exhibit the above three optical performances while suppressing the occurrence of various aberrations. Yes.

  However, the intermediate optical system of Patent Document 1 needs to design a very high performance Fresnel lens with high accuracy. Moreover, the Fresnel lens is used in an eccentric state. Therefore, it is necessary to manufacture the lens end portion, which is usually difficult to obtain high accuracy, so as to have high performance. Therefore, the manufacturing cost increases and the yield is pointed out.

  In view of the above circumstances, an object of the present invention is to provide an oblique projection type projection apparatus that can employ an intermediate optical system that can be manufactured inexpensively and efficiently.

  In order to solve the above-described problem, the projection apparatus according to claim 1 converts a rectangular image on a display body on which light from a light source is incident into an intermediate image having trapezoidal distortion, and converts the intermediate image to a screen. A projection apparatus for enlarging and projecting an image having no trapezoidal distortion on a screen by being incident obliquely on the screen, the first projection optical system forming an intermediate image by light emitted from the light source and passing through a display body And the second projection optical system that magnifies and projects the intermediate image on the screen while correcting the trapezoidal distortion, and the first projection optical system and each pupil of the second projection optical system are combined and emitted from the first projection optical system. An intermediate optical system that deflects the reflected light and guides it to the second projection optical system, and the first projection optical system and the second projection optical system are respectively substantially telecentric on the intermediate image side. And

  According to the projection device of the first aspect, regarding the intermediate optical system, the burden on the first and second effects among the three optical performances is effectively reduced. That is, the intermediate optical system according to the present invention only needs to have the third optical performance. Therefore, the difficulty and cost required at the time of manufacturing can be suppressed, and the manufacturing efficiency can be improved.

  According to the projection device of the second aspect, the first projection optical system is emitted from the lowermost end of the display body in the cross section of the first projection optical system and the second projection optical system including the respective optical axes. The first angle difference, which is the difference between the angle between the principal ray of the reflected light and the optical axis, and the angle between the principal ray of the light emitted from the top end of the display body and the optical axis is the approximate center of the display body. The second projection optical system is configured to be smaller than the convergence angle of a light beam incident while converging on the intermediate optical system via the first projection optical system. A second angle difference, which is the difference between the angle formed by the light beam and the optical axis, and the angle formed by the principal ray of the light emitted from the uppermost end of the display body and the optical axis, is emitted from the approximate center of the display body and is intermediate It is configured to be smaller than the divergence angle of the light beam emitted while diverging from the optical system.

  More specifically, according to the projection apparatus of the third aspect, the absolute value of the tilt angle of the screen with respect to the plane orthogonal to the optical axis of the second projection optical system is θ, and the projection magnification of the projection apparatus is M. Then, the first angle difference and the second angle difference are both configured to be θ / M or more.

  As described above, it is possible to satisfactorily correct axial chromatic aberration and spherical aberration generated in the intermediate optical system by providing a wide telecentricity for each projection optical system.

  By configuring as described above, the intermediate optical system can be configured by at least one prism. That is, an inexpensive and efficient manufacturing prism can be used as the intermediate optical system. Further, the intermediate optical system can have a chromatic aberration correcting action.

  As described above, according to the present invention, the optical performance required for the intermediate optical system is reduced by making the intermediate image side of the two projection optical systems disposed with the intermediate optical system interposed therebetween substantially telecentric. be able to. Therefore, according to the present invention, there is provided a projection apparatus that can employ an intermediate optical system constituted by an optical member that can be manufactured inexpensively and efficiently, such as a prism.

  FIG. 1 is a diagram illustrating a schematic configuration of an oblique projection type projection apparatus 100 according to an embodiment. The projection apparatus 100 includes a projection optical system 10, a first mirror 20, a second mirror 30, and a screen S in a housing 50.

  FIG. 2 is an enlarged view showing the projection optical system 10 while developing the optical path in the projection apparatus 100. In FIG. 2, the first mirror 20 and the second mirror 30 are not shown. As shown in FIG. 2, the projection optical system 10 includes a first projection optical system 1, a second projection optical system 2, an intermediate optical system 3, and a display body 4. In FIG. 2, AX1 represents the optical axis of the first projection optical system 1, and AX2 represents the optical axis of the second projection optical system 2. In each figure, optical axes AX1 and AX2 are indicated by alternate long and short dash lines. That is, FIG. 2 is a cross-sectional view of the projection optical system 10 on a plane including the optical axes AX1 and AX2. The plane including the optical axes AX1 and AX2 bisects the screen S by a straight line extending in the vertical direction through the center of the screen. In the text, for convenience of explanation, a plane including the optical axes AX1 and AX2 is referred to as a reference plane.

  In the actual projection apparatus 100, not only the first mirror 20 and the second mirror 30 but also a mirror (not shown) in the projection optical system 10 is provided depending on the shape of the housing 50 and the positional relationship with other members. The optical path may be bent. However, in the following, each member will be described on the assumption that the optical path is bent by each of the mirrors and that the optical path is expanded, in other words, all the members are arranged on the reference plane.

  In the projection apparatus 100 of the present embodiment, the lenses (or some optical surfaces) constituting the projection optical systems 1 and 2 have aberrations and distortions that cannot be sufficiently corrected by a rotationally symmetric optical system. They are eccentric to each other for the purpose of correction. Therefore, in the present text, in each of the projection optical systems 1 and 2, a straight line including the most cores of the optical surface is defined as the optical axis of each optical system. However, in a specific projection optical system, when the centers of the optical surfaces are all displaced, a straight line passing through the core of the optical surface closest to the pupil is defined as the optical axis of the optical system.

  The display body 4 displays an image that is enlarged and projected onto the screen S using light emitted from a light source (not shown) arranged in front of the display body 4. Examples of the display body 4 include a transmissive liquid crystal element, a reflective liquid crystal element, and DMD (registered trademark). Light emitted from the display body 4 (more specifically, light reflected by the display body 4 or light transmitted through the display body 4) forms an intermediate image via the first projection optical system 1. Here, the intermediate image is not necessarily formed well. That is, even if various aberrations remain in the intermediate image stage or the Scheinproof law is not accurately established, it can be compensated by the second projection optical system 2 in the subsequent stage. no problem. In the present embodiment, the image plane P of the intermediate image substantially matches the surface of the intermediate optical system 3 closest to the first projection optical system 1. The intermediate optical system 3 is an optical system that combines the pupils of the projection optical systems 1 and 2. The intermediate optical system 3 deflects the light forming the intermediate image and guides it to the second projection optical system 2. The second projection optical system 2 diverges light incident through the intermediate optical system 3. The divergent light emitted from the second projection optical system 2, that is, the projection optical system 10 is sequentially reflected by the first mirror 20 and the second mirror 30, and then the back surface of the screen S (that is, the surface inside the apparatus). Incident obliquely. Thereby, the image displayed on the display body 4 is projected on the screen S in an enlarged manner.

  1 and the subsequent drawings, the principal ray Lu of the light beam forming the uppermost end of the image on the straight line passing through the center of the screen S in the vertical direction (cross section at the reference plane) is the principal ray Lu, and the center of the image. Is the principal ray Lc, and the principal ray of the luminous flux forming the lowermost end of the image is the principal ray Ld. In the following description, the uppermost end and the lowermost end of the image mean the uppermost end and the lowermost end of the image on a straight line that passes through the center of the screen S and extends in the vertical direction.

  A thin film-like Fresnel lens (not shown) is attached to the screen S. Therefore, the light incident obliquely on the back surface of the screen S is emitted from the surface of the screen S (that is, the surface on the user (observer) side) at a substantially right angle.

  FIG. 3 is a diagram for explaining the positional relationship between the members constituting the screen S and the projection optical system 10. In FIG. 3, for convenience of explanation, each of the projection optical systems 1 and 2 is simplified and shown as a single lens. In the projection apparatus 100, the display body 4, the first projection optical system 1, and the image plane P of the intermediate image are arranged to be inclined with respect to each other so as to satisfy the Scheinproof law. That is, the display body 4, the first projection optical system 1, and the extended surfaces of the image plane P intersect at the same straight line (hereinafter referred to as a first reference straight line) L1. Specifically, the display body 4 is tilted with respect to a virtual plane (hereinafter referred to as a first virtual plane) P1 orthogonal to the optical axis AX2 of the first projection optical system 1. Similarly, the image plane P of the intermediate image is tilted with respect to the first virtual plane P1.

  The screen S, the second projection optical system 2, and the image plane P of the intermediate image are also inclined with respect to each other so as to satisfy the Scheinproof law. That is, the screen S, the main plane of the second projection optical system 2, and the extended surfaces of the image plane P intersect at the same straight line (hereinafter referred to as a second reference straight line) L2. Specifically, the image plane P of the intermediate image is not limited to the first virtual plane P1 but also a virtual plane (hereinafter referred to as a second virtual plane) P2 orthogonal to the optical axis AX2 of the second projection optical system 2. Even tilted. The screen S is also tilted with respect to the second virtual plane P2.

  As described above, in the projection apparatus 100, the light emitted from the display body 4 that displays a rectangular image is subjected to trapezoidal distortion via the first projection optical system 1 by applying the Scheinproof law twice. Tie an intermediate image. Then, the light connecting the intermediate image having the trapezoidal distortion forms on the screen S a rectangular enlarged image in which the trapezoidal distortion is corrected by the second projection optical system 2. That is, the user (observer) can observe an enlarged image without trapezoidal distortion.

  The projection apparatus 100 of the present embodiment is arranged and configured so that the intermediate image side of the first projection optical system 1 and the intermediate image side of the second projection optical system 2 are substantially telecentric. Thereby, the intermediate optical system 3 can be configured to have only an optical performance of bending the optical path. In this embodiment, as shown in FIG. 2, the intermediate optical system 3 is configured using three triangular prisms that can be manufactured inexpensively and efficiently.

  When the intermediate optical system 3 is composed of a plurality of triangular prisms, the aberration that may occur in the intermediate optical system 3 is limited to so-called basic aberrations such as axial chromatic aberration and spherical aberration. Therefore, aberration correction becomes easier as compared with the conventional configuration in which aberration due to decentration or the like has occurred. However, if the intermediate image side of each of the projection optical systems 1 and 2 is completely telecentric, there is a possibility that the axial chromatic aberration and spherical aberration cannot be effectively corrected in the intermediate optical system 3.

  Therefore, in the present embodiment, in order to provide the intermediate optical system 3 with a function of correcting axial chromatic aberration, spherical aberration, and the like, the intermediate image side of each of the projection optical systems 1 and 2 is telecentric with a predetermined allowable range. The term “substantially telecentric” is used in the sense of a simple configuration (that is, it is not necessarily strictly telecentric, even a configuration having a slight divergence tendency). The intermediate optical system 3 is given an action of correcting chromatic aberration of angular magnification by appropriately selecting the refractive index and Abbe number of each triangular prism constituting the intermediate optical system 3. Note that the chromatic aberration correcting action can be imparted to the intermediate optical system 3 also by providing a diffraction element in combination with a combination of refractive index and Abbe number, or independently of the combination.

  Next, the arrangement configuration relating to the intermediate optical system 3 will be described in detail with reference to FIG. FIG. 4 is a diagram showing an optical path in the vicinity of the intermediate optical system 3. FIG. 4 shows not only the main light beam Lc but the entire light beam only for the light beam C forming the center of the image among the light forming the image projected onto the screen S. For the light beams forming the uppermost and lowermost edges of the image, only the principal rays Lu and Ld are shown. The dotted line a1 is a line parallel to the optical axis AX1, and the dotted line a2 is a line parallel to the optical axis AX2.

  The first projection optical system 1 includes an angle difference between the angle φ1 formed by the principal ray Ld and the dotted line a1 (that is, the optical axis AX1) and the angle φ2 formed by the principal ray Lu and the dotted line a1 (that is, the optical axis AX1). (Angle difference) | φ1-φ2 | is configured to be smaller than the convergence angle φ3 of the light beam C that converges on the image plane P. That the intermediate image side of the first projection optical system 1 is substantially telecentric means the configuration as described above. The convergence angle is defined as an angle formed by a light beam emitted from the exit pupil of the first projection optical system 1 on the reference plane.

  The second projection optical system 2 has an angle difference between the angle φ4 formed by the principal ray Ld and the dotted line a2 (that is, the optical axis AX2) and the angle φ5 formed by the principal ray Lu and the dotted line a2 (that is, the optical axis AX2). (Angle difference) | φ4-φ5 | is configured to be smaller than the divergence angle φ6 of the light beam C emitted from the image plane P. That the intermediate image side of the second projection optical system 2 is substantially telecentric means the configuration as described above. The divergence angle is defined as an angle formed by a light beam that diverges toward the entrance pupil of the second projection optical system on the reference plane.

  When importance is attached to correction of axial chromatic aberration and spherical aberration, each of the projection optical systems 1 and 2 assumes that the projection magnification of the projection apparatus 100 is M and the tilt angle of the screen S with respect to the second virtual plane P2 is θ. The first angle difference | φ1-φ2 | and the second angle difference | φ4-φ5 | are both arranged and configured to be equal to or larger than θ / M. Thereby, the correction of each aberration can be easily performed in the intermediate optical system 3.

  Next, specific examples of the projection apparatus 100 according to this embodiment will be described.

  Table 1 shows specific numerical examples of the projection apparatus according to the embodiment. The tilt angle (unit: deg) of each member in Table 1 is the amount of tilt from the planes P1 and P2 orthogonal to the optical axes AX1 and AX2. The tilt amount is expressed with the counterclockwise direction as positive with respect to the optical axes AX1 and AX2. The shift amount of each member in Table 1 refers to the shift amount in a state where the tilt amount with respect to each optical axis is maintained. The shift amount represents the direction away from the reference straight lines L1 and L2 with respect to the optical axes AX1 and AX2 on the reference plane as positive.

  Surface number 0 indicates screen S. Surface numbers 1 to 21 indicate the second projection optical system 2. Surface numbers 22 to 28 indicate the intermediate optical system 3. Surface numbers 29 to 44 indicate the first projection optical system 1. The surface number 45 indicates the display body 4.

  Surface numbers 1, 2, 5, 6, 22-24, 29-32, and 44 are virtual surfaces (eccentricity defining surfaces) provided to define an eccentric state such as a shift or tilt of the immediately following surface. . Surface numbers 25 to 27 are surfaces of three triangular prisms constituting the intermediate optical system 3 and are also decentering definition surfaces. The coordinate system after the eccentricity is a relative coordinate determined based on the state on the eccentricity definition plane. However, the surface numbers 24 to 27 do not consider the change in coordinates due to the tilting, and follow the coordinate system based on the state at the surface number 21.

As shown in Table 1, the surface numbers 3, 4, 33, 34, 42, and 43 are rotationally symmetric aspheric surfaces. The shape of the aspherical surface is the distance (sag amount) from the tangent plane on the rotationally symmetric axis of the aspherical surface to the coordinate point on the aspherical surface where the height from the rotationally symmetric axis is h, and X (h) Where the curvature (1 / r) on the rotational symmetry axis is C, the conic coefficient is K, the aspherical coefficients are A ₄ and A ₆ , and is expressed by the following equation.

  In the aspherical coefficient shown in Table 1, the notation E represents a power with 10 as the radix and the right number of E as the exponent. Further, in the examples, the conic coefficient K and the aspheric coefficient not specified are 0 for all surfaces.

  Here, the display body 4 is 10.46 mm in length (height) in a direction corresponding to the vertical direction of the image projected on the screen S in the normal use state, and the horizontal of the image projected on the screen S. A length (width) dimension in a direction corresponding to the direction is assumed to be 18.85 mm.

  On the intermediate image side of the first projection optical system 1, the first angle difference | φ1−φ2 | is 3.17 °, whereas the convergence angle φ3 shown in FIG. 4 is 6.59 °. On the intermediate image side of the second projection optical system 2, the second angle difference | φ4-φ5 | is 5.53 °, whereas the divergence angle φ6 shown in FIG. 4 is 10.7 °. is there. That is, it can be seen that the projection optical systems 1 and 2 of the present embodiment are both substantially telecentric on the intermediate image side.

  In the projection apparatus 100 of the present embodiment, the projection magnification M is 71.43, and the tilt angle θ of the screen S with respect to the second virtual plane P2 is 34.3 °. Therefore, θ / M = 0.48 °, and it can be seen that the first angle difference | φ1-φ2 | and the second angle difference | φ4-φ5 | are larger. In other words, the intermediate optical system 3 of the present embodiment reduces the axial chromatic aberration and the spherical aberration asymmetry during transmission through the intermediate optical system 3 by increasing the telecentricity of the projection optical systems 1 and 2 on the intermediate image side. Can do.

  FIG. 5 is a diagram illustrating a degree of distortion of an image actually projected by the projection apparatus 100 according to the embodiment. In FIG. 5, the solid line shows an image actually projected on the screen S, and the broken line shows an ideal image without distortion. It can be seen that the projected image shown by the solid line in FIG. 5 is an image that is very close to an ideal image with good distortion reduction. Thus, in the embodiment, the intermediate optical system 3 configured by combining three triangular prisms that can be manufactured inexpensively and easily by making the intermediate image side of each of the projection optical systems 1 and 2 substantially telecentric. Can be used. Further, it can be seen that even when the intermediate optical system 3 is used, good performance is exhibited and a high-quality image is projected on the screen.

  The above is the embodiment of the present invention. The projector optical system according to the present invention is not limited to the above embodiment. For example, in each triangular prism constituting the intermediate optical system 3, the surface facing each projection optical system 1 or 2 is processed into a cylindrical surface for adjusting the aspect ratio or correcting curvature of field. May be. In addition to the prism, an optical member having power for ensuring telecentricity may be incorporated in the intermediate optical system. Further, in the above-described embodiment, the intermediate optical system is configured by combining three prisms, but may be configured by combining one or two, or four or more optical members.

It is a figure showing the schematic structure of the projection apparatus of embodiment of this invention. It is a figure which expands and shows a projection optical system, developing the optical path in the projection apparatus of embodiment. It is a figure for demonstrating the arrangement | positioning relationship of each member which comprises a screen and a projection optical system. It is a figure which shows the optical path in the intermediate optical system vicinity of embodiment. It is a figure which shows the distortion condition of the image actually projected by the projection apparatus of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st projection optical system 2 2nd projection optical system 3 Intermediate optical system 4 Display body 10 Projection optical system 100 Projection apparatus S Screen

Claims (5)

By converting a rectangular image on the display body on which light from the light source is incident into an intermediate image having trapezoidal distortion, and incident obliquely on the intermediate image screen, an image having no trapezoidal distortion on the screen is obtained. A projection device for enlarging projection,
A first projection optical system that irradiates from the light source and forms the intermediate image by light through the display body;
A second projection optical system that magnifies and projects the intermediate image on the screen while correcting trapezoidal distortion;
An intermediate optical system that couples the pupils of the first projection optical system and the second projection optical system and guides the light emitted from the first projection optical system to the second projection optical system,
The projection apparatus, wherein the first projection optical system and the second projection optical system are respectively substantially telecentric on the intermediate image side. In the cross section at the plane including each optical axis of the first projection optical system and the second projection optical system,
The first projection optical system includes an angle formed between a principal ray of light emitted from the lowermost end of the display body and an optical axis, and an angle formed between the principal ray of light emitted from the uppermost end of the display body and the optical axis. A first angle difference that is a difference between and is configured to be smaller than a convergence angle of a light beam that is emitted from a substantially center of the display body and is incident on the intermediate optical system through the first projection optical system.
The second projection optical system includes an angle formed between the principal ray of light emitted from the lowermost end of the display body and an optical axis, and an angle formed between the principal ray of light emitted from the uppermost end of the display body and the optical axis. The second angle difference that is a difference between the first and second display elements is configured to be smaller than a divergence angle of a light beam emitted from a substantially center of the display body and emitted from the intermediate optical system. The projection apparatus described in 1. The screen is tilted at a predetermined angle with respect to a plane orthogonal to the optical axis of the second projection optical system,
The first angle difference and the second angle difference are both θ / M or more, where θ is an absolute value of the predetermined angle and M is a projection magnification of the projection apparatus. The projection apparatus according to 2.   The projection apparatus according to claim 1, wherein the intermediate optical system includes at least one prism. The projection apparatus according to claim 1, wherein the intermediate optical system has a chromatic aberration correction function.

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