JP2007041538A - Free-form surface mirror - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily moldable, lightweight and compact free-form surface mirror. <P>SOLUTION: The mirror surface of the free-form surface mirror has an effective area 21 of more than 1,800 mm<SP>2</SP>and is formed with the contour along the circumference of the effective area 21. The corner portions 24a to 24d of the outline are formed to have a radius of curvature larger than the thickness of the corner portions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical system such as a projection image display device such as a rear projection television or a video projector provided with a reflective image forming element such as a DMD (digital micromirror device) or a transmissive image forming element such as a transmissive liquid crystal element. The present invention relates to a free-form surface mirror having good moldability and formed by injection resin molding.

  Conventionally, in order to form a free-form surface mirror with high accuracy, Patent Document 1 describes a mirror in which a difference in thickness of a molded product is reduced. As shown in FIG. 8 of the document 1, this mirror has a quadrangular outer shape with respect to the substantially trapezoidal effective area, and the outer shape near the center upper part and the lower left and right of the reflecting surface has a margin with respect to the effective area. Yes. It also has a gate near the upper center where there is room.

  However, such a curved mirror requires a molding time because the mirror volume is larger than necessary, which is disadvantageous in terms of cost. Further, the outer shape of the mirror is increased, and interference with other components is likely to occur, and it is difficult to reduce the size of the projection unit. In particular, when used in an ultra-thin rear projection television (for example, a 60-inch screen and a thickness of 30 cm or less), the size of the projection unit greatly affects the thickness.

On the other hand, as a holding structure for an optical element, for example, Patent Document 2 discloses a structure in which a dowel is provided on the back surface of a mirror and inserted into a round hole of the housing, and a dowel is provided at an end of the mirror and accommodated in a groove of the housing. Proposed. However, in this structure, since the boss is provided on the back surface of the mirror, the mold becomes complicated, and the shape sink occurs on the mirror surface side during molding. The structure in which this boss is provided cannot be applied to a lens. In addition, biting occurs between the dowel and groove of the mirror during expansion. Furthermore, position correction in the X direction substantially perpendicular to the optical surface is difficult. Patent Document 3 proposes a holder that holds an optical element provided with a clamp that biases the optical element in the X and Y directions and a clamp that biases the optical element in the Z direction. However, in this structure, the restriction surface to the holder and the surface to which the bias is applied by the clamp are located with the optical surface in between, so that there is a problem that the optical surface is distorted by holding.
JP-A-11-125864 JP 2002-341229 A US Pat. No. 6,654,186

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a free-form mirror having a good moldability, light weight and compactness.

In order to solve the above-mentioned problems, the present invention provides a free-form surface mirror having an effective area of a mirror surface of 1800 mm ² or more, wherein an outer shape is formed along an outer periphery of the effective region, and a corner portion of the outer shape is thickened. It is formed with a larger radius of curvature.

  According to this configuration, since the outer shape is formed along the outer periphery of the effective region, the outer shape does not become larger than necessary and there is no waste. Moreover, since the corner | angular part of the external shape was formed with the curvature radius larger than thickness, the fluidity | liquidity of molding resin is good and a moldability becomes favorable.

  Here, when the thickness is t and the radius of curvature is R, it is preferable to have a relationship of 1.5t ≦ R ≦ 6t.

  It is preferable to form a peripheral region outside the effective region with a free-form surface or a surface close thereto. If it does in this way, the fluidity | liquidity of molding resin is good from an effective area | region to a peripheral part, and a moldability becomes favorable.

It is preferable that a flat part is provided in a part of the peripheral region, and an ear part is provided in a part of the flat part so that the plane part and the surface of the ear part on the mirror surface side are flush with each other.
In this case, it is preferable that a transition part is provided between the peripheral region and the flat part, and the transition part is flat.

  It is preferable that an ear portion is provided in a part of the peripheral region, and the surface of the ear portion on the mirror surface side is formed by a free curved surface continuous to the peripheral region or a surface close thereto.

  It is preferable that an ear is provided in a part of the peripheral region, and the surface of the ear on the mirror surface side is flat.

Further, the present invention is a curved mirror used in a projection optical system for projecting an image generated by an image forming element on a screen, the effective area is substantially trapezoid, and forms an outer shape along the effective area, The corner portion of the outer shape is formed with a curvature larger than the wall thickness.
In this case, it is preferable that the curved mirror is arranged on the most screen side among the optical elements having the optical power of the projection optical system.

Another aspect of the present invention relates to the holding structure of the optical element as follows.
(1) A pair of ears of the optical element are arranged at symmetrical positions in the peripheral region, and a lower end surface of the pair of ears is used as an attachment reference in the Y direction (vertical direction) of the optical element. Is located between the centroid of the optical element and a half position between the centroid and the upper end of the optical element.
Thereby, the thermal expansion above the attachment reference can be suppressed, and the occurrence of distortion of the projected image can be suppressed.
(2) The ear portion of the optical element is disposed at the lower end position of the peripheral region, and the side end surface of the ear portion is used as an attachment reference in the Z direction (left-right direction) of the optical element, and the attachment reference is the center line of the optical surface. It is located near.
Thereby, the thermal expansion in the Z direction of the optical element centered on the Z direction mounting reference can be made substantially the same, and the distortion of the projected image can be suppressed by the difference in the thermal deformation of the optical element in the Z direction.
(3) The ear portion of the optical element is disposed at the lower end position of the peripheral region, and the ear portion is used as a gate when the optical element is molded.
As a result, it is not necessary to hold the upper end of the optical element, and it is possible to keep the optical element free. When the optical element is tilted backward and incorporated in a projection type image display apparatus, the thickness of the apparatus can be increased. Absent.
In addition, by using the bottom edge of the optical element as a gate, there is less influence on the optical surface such as undulation of the resin compared to the case where the surface opposite to the optical surface is used as a gate, and molding is performed with high accuracy. be able to.
In the optical element holding structure of (1) to (3), since there is no conventional dowel on the back surface of the optical surface (Patent Document 2), there is no possibility of causing sink marks during molding. It will be easy. In addition, since the ear portion is provided in the peripheral region, it can be applied not only to the reflection type (mirror) but also to the transmission type optical element (lens, correction plate). Further, since the end face of the ear portion is used as the attachment reference in the Y and Z directions, there is no biting during thermal expansion, and position correction in the X direction substantially perpendicular to the optical surface is easy.

  According to the present invention, since the outer shape is formed along the outer periphery of the effective area, the outer shape does not become larger than necessary and there is no waste. Further, since the corners of the outer shape are formed with a radius of curvature larger than the wall thickness, the flowability of the molding resin is good, and the moldability is improved.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the following embodiments, the X direction refers to a direction substantially perpendicular to the optical surface of the optical element (mirror surface in the case of a mirror, lens surface in the case of a lens), and the Y direction is a direction perpendicular to the X direction. The Z direction is a direction perpendicular to the X direction and perpendicular to the Y direction.

  FIG. 1 shows a rear projection television (rear pro TV) 1 which is an embodiment of a projection type image display apparatus provided with a free-form surface mirror of the present invention. In the casing 2 of the rear pro TV 1, a digital micromirror device (DMD) 3 which is an example of a reflective image forming element, an illumination optical system 4 for irradiating the DMD 3 with illumination light, and projection light reflected by the DMD 3, that is, A projection optical system 5 for enlarging and projecting image light is accommodated. Further, a screen 7 on which an image enlarged by the projection optical system 5 is projected via two plane mirrors 6A and 6B is disposed above the front surface of the casing 2.

  The projection optical system 5 includes a concave mirror 8, a variable aperture mechanism 9, a first aberration correction plate 10, a convex mirror 11, a second aberration correction plate 12, a first free-form curved mirror 13, and a second free-form curved surface in order from the DMD 3 side. A mirror 14 is disposed, and image light from the DMD 3 is guided to the screen 7 in this order.

  The DMD 3 and the projection optical system 5 are held in a projection optical system unit 15 shown in FIG. The projection optical system unit 15 includes a lower pedestal component 16 and an upper pedestal component 17. The lower pedestal component 16 holds the concave mirror 8, the variable aperture mechanism 9, the first aberration correction plate 10, the convex mirror 11, and the second aberration correction plate 12, and the upper pedestal component 17 has the first and second aberrations. Free curved surface mirrors 13 and 14 are held. The second free-form curved mirror 14 is held by a holding component 18 attached to the upper pedestal component 17.

  Next, the second free-form curved mirror (hereinafter simply referred to as free-form curved mirror) 14 which is an embodiment of the free-form curved mirror of the present invention will be described in detail.

FIG. 3 shows the free-form curved mirror 14. The free-form surface mirror 14 has a fluidity (MFR; Melt Flow Rate) of 20 or more, heat resistance (glass transition temperature Tg) of 130 ° C. or more, thermal deformation temperature of 115 ° C. or more, and moisture absorption of 0.01% or less. It is made of a thermoplastic resin such as cycloolefin polymer (for example, ZEONEX, ZEONOR (registered trademark of Nippon Zeon)), and is molded into a curved plate having a uniform thickness in the range of 1 mm to 5 mm by injection molding. The surface shape change due to moisture absorption can be suppressed by using a molding material of .01% or less, and the internal stress is removed by annealing the free-form curved mirror 14 after molding. The effective area is 1800 mm ² or more, and 3500 mm ² or more and 5000 mm ² or more is also possible.

  The effective area 21 of the free-form surface mirror 14 is formed of a convex free-form surface, and as shown by a one-dot chain line, the upper side 21a and left and right sides 21b and 21c extending downward from both ends of the upper side 21a. The lower left side 21d extending from the lower end of the left side 21b to the center line obliquely downward to the right and the lower right side 21e extending from the lower end of the right side 21c to the center line obliquely downward to the left and connected to the lower left side 21d is formed. Yes.

  A peripheral region 22 having a substantially constant width is formed outside the effective region 21, and a peripheral region 23 is formed further outside the peripheral region 22. The peripheral region 23 is a free-form surface or a surface close thereto. The outer shape of the peripheral region 23 is formed along the outer periphery of the effective region 21 and has substantially the same pentagon as the effective region 21. The corners 24a, 24b, 24c and 24d of the peripheral region 23 have a radius of curvature R larger than the wall thickness t, preferably 1.5t ≦ R ≦ 6t, and more preferably 2t ≦ R ≦ 4t. Yes. In this embodiment, the thickness is 5 mm, the corners 24a and 24b are R = 15, and the corner 24c is R = 20. For this reason, the fluidity of the molding resin at the corners 24a, 24b, 24c, and 24d is good, and the moldability is good. Further, no ribs perpendicular to the mirror surface are formed at the edge of the peripheral region 23. Such ribs deteriorate the fluidity of the resin and bite into the mold at the time of mold release to lower the accuracy of the molding surface. Since the free-form curved mirror 14 of this embodiment does not have such ribs, the flowability of the molding resin is good and the releasability is good and the surface accuracy of the mirror surface is improved as compared with those having ribs.

  The peripheral region 23 on the left and right sides of the peripheral region 23 is formed wider than the peripheral region 23 on the upper side and the lower left and right sides, and includes an inner free curved surface portion 25 and an outer plane portion 26. The upper end of the free curved surface portion 25 is continuous with the free curved surface of the peripheral region 23 on the upper side, and the lower end of the free curved surface portion 25 is continuous with the peripheral region 23 on the left and right lower sides. As shown in FIG. 4, the free curved surface portion 25 and the flat surface portion 26 are continuous with a smooth surface.

  A rectangular first ear portion 27a and a second ear portion 27b are provided so as to project in the Z direction at the edges of the flat portion 26 of the peripheral region 23 on the left and right sides. The front surfaces of the first ear portion 27a and the second ear portion 27b are made of a plane that is flush with the flat surface portion, and are the first and second X-direction mounting reference surfaces 28a and 28b of the free-form curved mirror 14. Lower end surfaces of the first ear portion 27a and the second ear portion 27b are first and second Y-direction attachment reference surfaces 29a and 29b of the free-form curved mirror 14. The first and second Y-direction mounting reference surfaces 29a and 29b are preferably in a range between the centroid 30 of the effective area 21 and a position 31 that is 1/2 between the centroid 30 and the upper end of the effective area 21. Is located at the centroid 30. As described above, the reason why the first and second Y-direction mounting reference surfaces 29a and 29b are positioned above the effective area 21 is as follows. As shown in FIG. 1, the free-form surface mirror 14 has a higher incident / reflection angle at the upper side than the lower side and is more sensitive, so that a slight displacement of the free-form surface due to thermal expansion during operation distorts the projected image on the screen 7. Cause it to occur. In this embodiment, by providing the first and second Y-direction mounting reference surfaces 29a and 29b above the effective area 21, the thermal expansion above the first and second Y-direction mounting reference surfaces 29a and 29b can be suppressed. The distortion of the projected image on the screen 7 can be suppressed.

  In addition, a rectangular third ear portion 27c protrudes downward from the left and right edges of the peripheral region 23 on the left and right sides. The front surface of the third ear portion 27 c is a flat surface and serves as a third X-direction mounting reference surface 28 c of the free-form surface mirror 14. The left end surface of the third ear portion 27 c is the Z-direction attachment reference surface 32 of the free-form curved mirror 14. By reducing the width of the third ear portion 27c, the Z-direction mounting reference surface 32 can be made as close to the center line as possible so that the left and right thermal expansions are substantially the same, and distortion of the projected image on the screen 7 can be suppressed. The third ear portion 27c is preferably located on the center line and has a width of 5 mm or more and 15 mm or less. The right end surface or the lower end surface of the third ear portion 27c is a gate made of molding resin when the free-form curved mirror 14 is molded. The Y and Z direction attachment reference surfaces 29a, 29b, and 32 of the ear portions 27a, 27b, and 27c are surfaces that pass through substantially the center of the free-form surface mirror 14. Further, the Y and Z direction mounting reference surfaces 29a, 29b, and 32 of the ear portions 27a, 27b, and 27c and the opposite surfaces on the opposite sides are parallel to each other.

  The back surface of the free-form mirror 14 is formed as a concave free-form surface that is substantially complementary to the curved surface of the effective area 21 on the front side.

As described above, since the free-form surface mirror 14 forms an outer shape along the outer periphery of the effective region 21, the outer shape is more than necessary even though the effective region 21 has a large area of 1800 mm ² or more. It doesn't get bigger and there is no waste. In particular, when the effective area of the mirror is a substantially triangular shape or a substantially trapezoidal shape (the substantially pentagonal shape of the present embodiment is also included in the substantially trapezoidal shape), a greater effect can be obtained by forming the outer shape along the effective area. Further, since the corner portions 24a to 24e of the outer shape are formed with a curvature radius larger than the thickness, the flowability of the molding resin is good and the moldability is good.

  FIG. 5 shows another form of the free-form curved mirror 14. In FIG. 5A, the peripheral region 23 on the left and right sides is formed with a free curved surface or a curved surface close to it on the entire width without providing the flat portion 26 in the peripheral region 23 on the left and right sides as in the embodiment shown in FIG. Is. In FIG. 5B, the peripheral regions 23 on the left and right sides of FIG. 5A are further continued to the ear portion 27a, and a part of the front surface of the ear portion 27a is made flat to form the X-direction mounting reference surface 28a. Is. Thus, by eliminating the flat portions in the peripheral regions 23 on the left and right sides, the fluidity of the molding resin can be further improved and the moldability can be improved.

  FIG. 6 shows still another form of the free-form curved mirror 14. This free-form surface mirror 14 is a substantially triangular transition portion indicated by hatching between the lower end region of the free-form surface portion 25 and the lower end region of the plane portion 26 in the peripheral region 23 on the left and right sides of the free-form surface mirror 14 shown in FIG. 33 is provided. This transition part 33 is formed in a plane. In the free-form surface mirror 14 shown in FIG. 3, the free-form surface portion 25 and the flat surface portion 26 have a steep angle between the lower end region of the free-form surface portion 25 and the lower end region of the flat surface portion 26 as shown in FIG. It is the part that intersects. In this portion, as shown in FIG. 7B, a transition portion 33 having a flat surface is provided, thereby avoiding stress concentration and preventing warpage.

  Next, a structure for attaching the free-form curved mirror 14 having the above-described configuration to the holding component 18 will be described.

  In FIG. 8, the holding part 18 of the free-form mirror 14 is made of synthetic resin, and has a base 41, left and right arm parts 42a and 42b extending obliquely rearward from both ends of the base part 41, and the left and right arm parts 42a and 42b. And a reinforcing portion 43 that connects the substantially middle portion of the back surface of the head.

  On the bottom surface of the base 41, as shown in FIG. 9, a projection 44 projects from the center, and a metal mounting plate 45 is attached to the rear. A total of three attachment holes 46 are formed at both ends of the attachment plate 45 and the base 41. A third concave portion 47c in which the third ear portion 27c of the free-form curved mirror 14 is located is formed on the upper surface of the base portion 41, and the front wall of the third concave portion 47c is the third X direction mounting reference surface of the third ear portion 27c. It becomes the 3rd contact surface 48c which 28c contacts. The third contact surface 48c is formed as a convex surface (for example, a spherical surface). Further, a third positioning protrusion 49c protrudes from the third recess 47c, and a third pressing spring (Z-direction pressing spring) 50c is fixed to face the third positioning protrusion 49c. Further, in the vicinity of the third presser spring 50c, a third fixing bracket (X direction presser spring) 51c that presses and fixes the third ear portion 27c to the third contact surface 48c is attached to the screw hole 52c. Yes.

  First and second recesses 47a and 47b in which the first and second ear portions 27a and 27b of the free-form surface mirror 14 are located are formed on the left and right arm portions 42a and 42b, and the first and second recesses are formed. The front walls of 47a and 47b are first and second contact surfaces 48a and 48b with which the first and second X-direction mounting reference surfaces 28a and 28b of the first and second ear portions 27a and 27b abut. The first and second contact surfaces 48a and 48b are also formed as convex surfaces (for example, spherical surfaces). The first and second recesses 47a and 47b are provided with first and second positioning protrusions 49a and 49b. The first and second pressing springs face the first and second positioning protrusions 49a and 49b. (Y direction pressing springs) 50a and 50b are fixed. Further, in the vicinity of the first and second holding springs 50a and 50b, first and second fixing brackets for pressing and fixing the first and second ear portions 27a and 27b against the first and second contact surfaces 48a and 48b. (X direction pressing springs) 51a and 51b are attached to the screw holes 52a and 52b (each at two locations).

  In order to attach the free-form surface mirror 14 to the holding component 18, first, the free-form surface mirror 14 is tilted rearward and inserted into the holding component 18 from above, and the third ear portion 27c is inserted into the third pressing spring of the third recess 47c. It inserts between 50c and the 3rd positioning protrusion 49c. Subsequently, the free-form curved mirror 14 is pushed forward, and the first and second ear portions 27a and 27b are moved to the first and second holding springs 50a and 51b and the first and second positioning projections of the first and second recesses 47a and 47b. 49a and 49b. As a result, the free-form curved mirror 14 is positioned such that the first and second holding springs 50a and 50b face the first and second Y-direction mounting reference surfaces 29a and 29b at the two locations of the first and second ear portions 27a and 27b. The first and second Y-direction mounting reference surfaces 29a and 29b are pressed against the first and second positioning protrusions 49a and 49b to be positioned in the Y direction. Further, the third pressing spring 50c biases the position of the third ear portion 27c facing the Z-direction mounting reference surface 32, whereby the Z-direction mounting reference surface 32 is pressed against the third positioning protrusion 49c. Thus, it is positioned in the Z direction.

  Next, by attaching the first to third fixing brackets 51a to 51c at predetermined positions and biasing the positions of the first to third ear portions 27a to 27c opposite to the X direction reference planes 28a to 28c, the X direction The reference surfaces 28a to 28c are pressed against the first to third contact surfaces 48a to 48c. As a result, the X-direction reference surfaces 28a to 28c are in point contact with the first to third contact surfaces 48a to 48c formed of convex surfaces, and the free-form surface mirror 14 is highly accurate in the X direction with respect to the holding component 18 as shown in FIG. Can be positioned and easily attached.

  As shown in FIG. 2, the free-form surface mirror 14 held by the holding part 18 inserts the protrusion 44 of the base 41 into the long hole 53 of the upper pedestal part 17 and places the three mounting holes 46 on the upper side. It can be fixed to the upper pedestal component 17 by fitting a screw (not shown) so as to match the corresponding mounting hole 54 of the pedestal component 17.

  The free-form curved mirror 14 of the holding part 18 fixed to the upper pedestal part 17 is tilted rearward as shown in FIG. 9, so that the upper side of the holding part 18 is indicated by a two-dot chain line 18 ′. When protruding above the upper end of the mirror 14, the dimension in the thickness direction of the rear pro TV 1 is increased by the amount of protrusion of the holding component 18. Therefore, in the present embodiment, the third ear portion 27c having the third X-direction mounting reference surface 28c and the Z-direction mounting reference surface 32 is provided on the lower side instead of the upper side of the free-form curved mirror 14, and the third side of the lower side is provided. While providing a gate position on the ear portion 27c, the upper side is completely free, so that the upper end of the holding part 18 is positioned below the upper side of the free-form curved mirror 14, and the upper end of the free-form curved mirror 14 is positioned on the rear pro TV 1. The thickness of the rear pro TV 1 is reduced by determining the dimension in the thickness direction.

  In the embodiment shown in FIG. 8, the holding springs 50a, 50b, and 50c and the fixing brackets 51a, 51b, and 51c are formed separately. However, as shown in FIG. , 55b, 55c, the number of parts can be reduced and the mounting work can be simplified. That is, these fixing brackets 55 a, 55 b, and 55 c have a substantially T-shape including a first base 56 that is elongated and a second base 57 that extends perpendicularly from one side in the longitudinal direction of the first base 56. The second base 57 is provided with a pressing spring piece (X-direction pressing spring) 58 that extends from the first base 56 along the second base 57 by forming a slit. One piece of the second base 57 is provided with a fixed spring piece (Y, Z direction pressing spring) 59 extending perpendicularly to the surface of the second base 57. Then, by attaching these fixing brackets 55a, 55b, and 55c to the screw holes 52a, 52b, and 52c of the holding component 18, the free curved mirror 14 can be positioned and fixed in the Y and Z directions simultaneously with respect to the holding component 18. it can.

  Note that the second base portion 57 has not only a base portion on which the fixed spring piece 59 is provided, but also an action of an impact resistant stopper. For example, when an impact due to dropping or the like occurs in the projection optical system unit 15, if there is no second base portion 57, the X-direction pressing spring 58 cannot withstand the weight of the free-form surface mirror 14 and causes plastic deformation, and the free-form surface mirror 14 is There is a possibility of dropping out. In the configuration of the modified example, since the second base portion 57 is more rigid than the X-direction pressing spring 58, the movement of the free-form curved mirror 14 in the X direction is suppressed when an impact occurs, and plastic deformation of the X-direction pressing spring 58 is prevented. Has the effect of In this modification, such a stopper is used only for the X-direction pressing spring 58, but is used for the fixing spring piece 59 and the first to third fixing brackets 51a to 51c of the embodiment of FIG. Also good.

  In the embodiment of FIG. 8 and the modification of FIG. 10, the fixing bracket is separated at three places. As shown in FIG. 11, the second aberration is obtained by using a single fixing member 61 that integrates them. By attaching the correction plate 12 (hereinafter simply referred to as “correction plate”) to the lower pedestal component 16 of the projection optical system unit 15, the number of components can be further reduced and the mounting operation can be simplified.

  Unlike the outer shape of the free-form curved mirror 14, the correction plate 12 is composed of straight lines whose upper side and lower side are parallel to each other, and the left side and the right side are curved so as to protrude outward. Similar to the free-form curved mirror 14, the correction plate 12 is provided with first and second ear portions 62 a and 62 b at the left and right edges and a third ear portion 62 c at the lower edge. As shown in FIGS. 12 and 13, the first, second, and third X-direction mounting reference surfaces 63a, 63b, and 63c are spherically convex on the back surface of the correction plate 12 at the center of the upper side, the lower side of the left side, and the lower side of the right side, respectively. It is formed with parts. A flat protrusion may be used instead of the spherical protrusion. The protrusion amount of these protrusions is preferably 0.5 mm or less. The lower end surfaces of the first and second ear portions 62a and 62b are first and second Y-direction attachment reference surfaces 64a and 64b, and the left end surface of the third ear portion 72c in FIG. . The Y and Z direction attachment reference surfaces 64a, 64b, and 65 of these ear portions 62a, 62b, and 62c are surfaces that pass through substantially the center of the correction plate 12. Further, the Y and Z direction mounting reference surfaces 64a, 64b, 65 of the ear portions 62a, 62b, 62c and the opposite surfaces on the opposite sides thereof are parallel to each other.

  The lower pedestal component 16 has an upper surface inclined, and a holding portion 66 for holding the correction plate 12 is formed. The holding portion 66 has a substantially rectangular shape, and has a small opening 67 similar to the outer shape of the correction plate 12 at the center. The first, first and second X-direction mounting reference surfaces 63a, 63b, 63c are in contact with the upper surface of the center of the upper edge of the opening 67, the upper surface of the lower left edge, and the upper surface of the lower right edge. 2, the third contact surfaces 68a, 68b, 68c are formed as flat or spherical protrusions.

  On the left and right sides of the opening 67, ridges 69a and 69b extending in the Y direction are formed, the tips thereof are formed as cylindrical surfaces, and the first and second Y direction mounting reference surfaces 64a and 64b are in contact with each other. , Second positioning portions 70a and 70b. Further, a protrusion 69c extending in the Z direction is formed below the opening 67, and the tip thereof is formed of a cylindrical surface, which is a third positioning portion 70c with which the Z direction attachment reference surface 65 abuts. .

  A boss 71 on which the fixing member 61 is placed is formed at the four corners of the holding portion 66, and a screw hole 72 for attaching the fixing member 61 is formed at the tip thereof. In the vicinity of the screw holes 72 of the two lower bosses 71, positioning protrusions 73 are formed.

  The fixing member 61 is made of a leaf spring material, is substantially rectangular, and has a small opening 74 similar to the outer shape of the correction plate 12 at the center. A slit is formed in the fixing member 61 at the center of the upper edge, the lower left edge, and the lower right edge of the opening 74 to thereby provide first, second, and third holding springs (X-direction holding springs) 75a, 75b, and 75c. The front end portions of the presser springs 75a, 75b, and 75c connect the first, second, and third X-direction mounting reference surfaces 63a, 63b, and 63c of the correction plate 12 to the first, second, and second portions of the holding portion 66, respectively. 3 is pressed against the contact surfaces 68a, 68b, 68c.

  The left and right edges of the fixing member 61 are formed with bent edges 76a and 76b bent at 90 °, and the upper ends of the bent edges 76a and 76b are further bent at 90 ° as shown in FIG. In addition, fourth and fifth presser springs (Y direction presser springs) 77a and 77b extending in the horizontal direction are provided. Similarly, a bent edge 76c bent at 90 ° is formed at the lower edge of the fixing member 61, and the right end of the bent edge 76c is further bent at 90 ° as shown in FIG. A sixth presser spring (Z direction presser spring) 77c is provided. These first, second, and third presser springs 77a, 77b, and 77c connect the first and second Y-direction mounting reference surfaces 64a and 64b and the Z-direction mounting reference surface 65 of the correction plate 12 to the first and second portions of the holding portion 66, respectively. The second and third positioning portions 70a, 70b, and 70c are pressed.

  Attachment pieces 78 are formed at the four corners of the fixing member 61, and screw holes 79 are formed in the attachment pieces 78. A positioning screw hole 80 is further formed in the vicinity of the screw holes 79 of the two lower mounting pieces 78.

  In order to attach the correction plate 12 to the holding portion 66 of the lower pedestal component 16, first, the correction plate 12 is placed on the inclined surface of the holding portion 66, and the first and second ear portions 62a and 62b are placed in two places. The first and second Y-direction mounting reference surfaces 64a and 64b are brought into contact with the first and second positioning portions 70a and 70b, and the Z-direction mounting reference surface 65 of the third ear portion 62c is brought into contact with the third positioning portion 70c. Further, the first, second and third X direction mounting reference surfaces 63a, 63b and 63c of the correction plate 12 are brought into contact with the first, second and third contact surfaces 68a, 68b and 68c of the holding portion 66. Next, the fixing member 61 is placed on the correction plate 12, and the first, second, and third holding springs 75a, 75b, and 75c are moved to the first, second, and third contact surfaces 68a of the correction plate 12. , 68b and 68c, and the fourth, fifth and sixth holding springs 77a, 77b and 77c are connected to the first first and second ear portions 62a and 62b of the correction plate 12. , The second Y-direction mounting reference surfaces 64a and 64b and the third ear portion 62c are brought into contact with the Z-direction mounting reference surface 65. In this state, the screw 81 is screwed into the screw hole 72 of the holding portion 66 from the screw hole 79 of the fixing member 61 to fix the fixing member 61.

  Thereby, the X direction reference surfaces 63a, 63b, and 63c of the correction plate 12 are moved to the first, second, and third contact surfaces 68a of the holding portion 66 by the first, second, and third pressing springs 75a, 75b, and 75c. By making point contact with 68b and 68c, the correction plate 12 is positioned in the X direction by the holding portion 66. Further, the correction plate 12 has first and second Y-direction mounting reference surfaces 64a and 64b at the first and second Y-direction mounting reference surfaces 64a and 64b by the fourth and fifth pressing springs 77a and 77b. 2 Line-contact with the positioning portions 70a and 70b allows positioning in the Y direction, and the third pressing spring 77c causes one Z-direction mounting reference surface 65 of the third ear portion 62c to move to the third positioning portion 70c. It is positioned in the Z direction by line contact. As a result, as shown in FIG. 15, the correction plate 12 can be positioned and attached to the holding portion 66 with high accuracy in the X direction, Y direction, and Z direction.

  In the holding structure of the free-form surface mirror 14 and the correction plate 12, the X direction substantially perpendicular to the optical surface is received at three points to bias the opposite positions, and the Y and Z directions are received by lines at the end face of the ear portion. Since the opposite positions are biased, the distortion due to holding is small, and the distortion due to thermal expansion is also small.

  Note that the present invention is not limited to a mirror having a free-form surface. For example, even if the shape of the reflecting surface is rotationally symmetric, the mirror does not have a rotationally symmetric axis at the center of the reflecting surface, and the mirror does not have a rotationally symmetric axis within the mirror outer shape. The present invention can also be applied to optical elements such as.

Sectional drawing of the rear projection television which is embodiment of the projection type image display apparatus provided with the free-form surface mirror of this invention. The disassembled perspective view of the projection optical system unit of the rear projection television of FIG. (A) Front view of free-form curved mirror, (b) Right side view, (c) Bottom view. IV-IV sectional view taken on the line of Fig.3 (a). (A) The partial front view of other embodiment of a free-form curved mirror, (b) The partial front view of other embodiment of a free-form curved mirror. (A) Front view of further another embodiment of free-form curved mirror, (b) Bottom view. 6A is a cross-sectional view taken along the line VII-VII in FIG. 6A before forming the transition part, and FIG. 6B is a cross-sectional view taken along the line VII-VII in FIG. 6A after forming the transition part. The disassembled perspective view of the holding | maintenance part of a free-form surface mirror. The side view of the holding component of a free-form curved mirror. The perspective view which shows the fixing metal fitting by the modification of the holding | suppressing spring and fixing metal fitting of FIG. The disassembled perspective view which shows the attachment structure of a correction board. The back view of a correction board. The elements on larger scale of FIG. The back view of a fixing member. The perspective view which shows the state which attached the correction board to the holding | maintenance part of the lower pedestal component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Free-form surface mirror 18 Holding component 21 Effective area 23 Peripheral area | region 24a-24d Corner | angular part 25 Free-form surface part 26 Plane part 27a-27c Ear part 28a-28c X direction attachment reference surface 29a, 29b Y direction attachment reference surface 30 Centric center 32 Z direction mounting reference plane 33 Transition part

Claims (9)

In a free-form curved mirror having an effective area of the mirror surface of 1800 mm ² or more, an outer shape is formed along an outer periphery of the effective region, and a corner portion of the outer shape is formed with a radius of curvature larger than a thickness. Free curved mirror.   2. The free-form surface mirror according to claim 1, wherein when the thickness is t and the radius of curvature is R, the relationship is 1.5t ≦ R ≦ 6t.   The free-form surface mirror according to claim 1 or 2, wherein a peripheral region outside the effective region is formed by a free-form surface or a surface close thereto.   A flat part is provided in a part of the peripheral region, and an ear part is provided in a part of the flat part so that the plane part and the surface of the ear part on the mirror surface side are flush with each other. The free-form surface mirror according to claim 3.   The free-form curved mirror according to claim 4, wherein a transition part is provided between the peripheral region and the flat part, and the transition part is made flat.   The ear portion is provided in a part of the peripheral region, and the surface on the mirror surface side of the ear portion is formed by a free curved surface continuous with the peripheral region or a surface close thereto. Free curved mirror.   The free-form curved mirror according to claim 3, wherein an ear portion is provided in a part of the peripheral region, and a surface of the ear portion on the mirror surface side is flat.   A curved mirror used in a projection optical system for projecting an image generated by an image forming element onto a screen, wherein an effective area is substantially trapezoidal, forms an outer shape along the effective area, and corners of the outer shape are formed. A curved mirror characterized by being formed with a curvature larger than the wall thickness.   9. The curved mirror according to claim 8, wherein the curved mirror is disposed on the most screen side among optical elements having optical power of the projection optical system.

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