JP2008180749A - Rear projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projection device capable of effectively suppressing the fluctuation of a projected image. <P>SOLUTION: A projection lens unit 10 is integrally constituted by assembling a focusing lens barrel 27, a mirror holding frame 22 and a second lens holding frame 13 on a holding member 14 formed of metal or the like. The projection lens unit 10 is attached to the image light generation unit of an optical engine fixed in a device main body by the holding member 14. Accordingly, a focusing optical system 15, a catoptric system, and a diffusion optical system 24 are respectively firmly fixed through the holding member 14. Since the holding member 14 has high rigidity, vibration is effectively suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rear projection apparatus that suppresses vibration of an image displayed on a screen.

  In recent years, a rear projection television has attracted attention as a large screen television. The rear projection television includes a screen incorporated in a housing, a plane mirror installed behind the screen, and an optical engine that has a projector function and projects image light toward the plane mirror. The optical engine consists of an illumination optical system that produces uniform illumination light from the light of a high-intensity light source, and a color separation / combination optical system that separates the illumination light into three colors and combines them with image information provided by image display elements. And a projection optical system having a projection lens unit for enlarging and projecting the image light thus produced onto a plane mirror.

  The rear projection television is required to be thin due to the influence of liquid crystal television and plasma television. In order to satisfy this requirement, it is necessary to use a projection lens with an ultra-short focal point in the rear projection television, but such a lens is large in shape and weight. For this reason, when the lens is housed in a lens barrel made of inexpensive plastic, there is a problem that the lens is vibrated due to the low bass sound generated by the speaker. In particular, when a lens holding frame or the like is connected, this problem is serious because the strength of the connecting portion is insufficient.

  For example, as shown in FIG. 6, the conventional projection lens unit includes a mirror holding frame 54 that holds a reflection mirror 60, a first lens holding frame 52 that holds a first lens 56 that is a projection lens, a second lens 57, and a first lens 57. A projection lens barrel 51 including a third lens 58 and a second lens holding frame 53 that holds the fourth lens 59 and a connecting barrel 62 connected to a focusing lens barrel 66 that holds the focusing lens 55 are integrally formed. It has an attached structure. For this reason, when the first lens holding frame 52 holding the first lens 56 having the maximum size vibrates, the vibration is transmitted to the second lens holding frame 53 holding the second lens 57 to the fourth lens 59. In the worst case, the lens may vibrate to the focusing lens 55 via the mirror holding frame 54 and the connecting cylinder 62. The image light enters the focusing lens 55 from the color separation system / combination optical system of the optical engine along the optical axis L1, is reflected by the reflection mirror 60, and is projected along the optical axis L2 to the four projection lenses 56, 57, and 58. 59, the image is projected onto the screen. When such a vibration is generated, the image displayed on the screen fluctuates and the quality is significantly impaired.

To deal with such a problem, Patent Document 1 proposes a rear projection television that suppresses lens vibration by providing a fastening structure of a projection lens barrel and a focusing lens barrel.
JP 2005-352293 A

  However, only by fastening the lens barrel of the projection lens and the lens barrel of the focusing lens, the vibration of the projection lens is somewhat mitigated, but the fastening member itself is weak in rigidity. The vibration may propagate from the tube to the lens barrel of the focusing lens. In this case, the lenses of the two lens barrels vibrate and eventually the image displayed on the screen fluctuates.

  The present invention has been made to solve the above-described problems, and provides a rear projection device that effectively suppresses fluctuation of an image to be projected.

  In order to solve the above problems, in the rear projection apparatus of the present invention, the projection lens unit includes a focusing optical system that focuses the light beam included in the image light by the focusing lens held in the first holding frame, and a second holding frame. A reflection optical system that reflects the light incident from the focusing optical system in a predetermined direction by the holding reflection mirror, and a diffusion that projects the light incident from the reflection optical system by the projection lens held in the third holding frame An optical system, and integrally configured by assembling the first holding frame, the second holding frame, and the third holding frame to a common holding member formed of a material having a composition such as metal. Has been. Here, the first holding frame and the second holding frame may be fastened by a fastening member formed of sheet metal or the like.

  Further, the rear projection device includes an image light generation unit that is fixed to the apparatus main body, generates the image light, and is connected to the projection lens unit to emit the image light to the focusing optical system. A connecting portion for connecting to the image light generating unit may be provided in the vicinity of the assembled first holding frame.

  In such a rear projection apparatus, since the holding frames of the optical systems constituting the projection lens unit are assembled to a common holding member, the holding frames have high rigidity and can be held in position and posture with high accuracy. At the same time, vibration does not propagate directly between the holding frames. Therefore, vibration can be effectively suppressed. Further, by forming the holding member with metal, the rigidity of the holding member itself can be improved, and the strength and rigidity of the entire projection lens unit can be further increased. Further, the projection lens unit is configured such that the holding frame of the focusing optical system in which image light enters along a predetermined optical axis and the holding frame of the reflective optical system that greatly contributes to image fluctuation are fastened by a fastening member. However, in the vicinity of the first holding frame, by connecting to an image light generation unit that emits image light, the effect of suppressing vibration can be further enhanced.

  In FIG. 1, a rear projection device 1 includes a screen 4 provided on the front surface of a housing 2, a flat mirror 5 provided behind the screen 4, and a bottom portion of the housing 2 that is a device body via a fixing portion 7. And an optical engine 3 fixed to the head. The plane mirror 5 is attached so as to be inclined in a posture closer to parallel to the screen 4 than 45 degrees obliquely. The optical engine 3 is configured by connecting an image generation unit 6 that generates image light and a projection lens unit 10 that projects image light. The optical engine 3 is incorporated with the optical axis of the image light projected from the projection lens unit 10 being inclined with respect to the screen 4, and the image light is reflected by the plane mirror 5 and the image is projected onto the screen 4. . Here, the image is projected on the back side of the screen 4 while being reversed horizontally, but the image is correctly displayed when viewed from the front.

  FIG. 2 is a perspective view showing an outline of the configuration of the optical engine 3. The optical engine 3 includes a light source device 30 that constitutes the image generation unit 6, an illumination optical system 31, a color separation / synthesis optical system 32, and a projection optical system 39 that constitutes the projection lens unit 10. For the light source device 30, a high-intensity light source such as a metal halide lamp, an extra-high pressure mercury lamp, or a xenon lamp is used depending on the application. Light emitted from the light source device 30 passes through the illumination optical system 31 and becomes illumination light with uniform intensity. The illumination optical system 31 includes a fly-eye lens, a polarization conversion element, a condenser lens, and the like.

  The color separation / synthesis optical system 32 includes a dichroic mirror 33, a polarizing prism 34, a dichroic prism 35, a synthesis prism 36, and the like. The dichroic mirror 33 separates the white illumination light into blue illumination light and yellow illumination light. The blue illumination light passes through the dichroic mirror 33 and travels straight, and the yellow illumination light reflects from the dichroic mirror 33 and travels in a right angle direction.

  The polarization prism 34 has a polarization reflection surface 34a inclined at 45 degrees with respect to the traveling direction of the blue illumination light, reflects the blue illumination light transmitted through the dichroic mirror 33 toward the liquid crystal display element 38B, and displays the liquid crystal display. Blue projection light having image information reflected by the element 38B is transmitted.

  The dichroic prism 35 has a dichroic surface 35 a that separates yellow illumination light reflected by the dichroic mirror 33 into red illumination light and green illumination light. The liquid crystal display element 38G modulates the green illumination light reflected from the dichroic surface 35a into green projection light having image information. The liquid crystal display element 38R modulates the red illumination light transmitted through the dichroic surface 35a into red projection light having image information. The green projection light emitted from the liquid crystal display element 38G travels straight through the dichroic surface 35a, and the red projection light emitted from the liquid crystal display element 38R reflects the dichroic surface 35a and travels in a right angle direction. Color projection light is synthesized.

  The combining prism 36 combines the blue projection light incident from the polarizing prism 34 and the red / green projection light incident from the dichroic prism 35 as image light having full-color image information. The combined image light is emitted to the focusing optical system 15 of the projection lens unit 10.

  The liquid crystal display elements 38B, 38G, and 38R are configured by arranging a large number of liquid crystal pixels in a matrix, modulate each color illumination light for each pixel, and provide image information to the illumination light. The illumination light of each color is modulated into projection light having image information by the three liquid crystal display elements. Each liquid crystal display element has a rectangular display screen having an aspect ratio of 16 to 9, for example, and is arranged in a horizontally long posture in which the short sides of the display screens are parallel to each other.

  The projection optical system 39 includes a focusing optical system 15, a reflection optical system (that is, the reflection mirror 20), and a diffusion optical system 24. The projection optical system 39 is connected to the image light generation unit 6 and is combined in the image light generation unit 6. It has a function of projecting image light incident from the prism 36 onto the plane mirror 5. As shown in FIGS. 3, 4, and 5, the focusing optical system 15, the reflection mirror 20, and the diffusion optical system 24 are assembled to the common holding member 14 and integrally configured as the projection lens unit 10.

  The focusing optical system 15 is a focusing lens 25 that is held by a focusing lens barrel 27 that is a lens holding frame. The focusing optical system 15 focuses light rays included in the image light incident from the combining prism 36 along the optical axis L1. The light is emitted to the reflection mirror 20. The reflection mirror 20 is held by a mirror holding frame 22 and reflects image light incident from the focusing optical system 15 along the optical axis L1 so as to enter the diffusion optical system 24 along the optical axis L2. . The focusing optical system 15 and the mirror holding frame 22 are connected by a connecting tube 23 so that the light beam focused by the focusing lens 25 reaches the reflection mirror 20 without leakage. Further, the focusing lens 15 is not limited to a single lens, and is configured with an appropriate type and number of lenses according to the design.

  The diffusion optical system 24 is held by the first lens 16 held by the substantially cylindrical first lens holding frame 12 and the second lens holding frame 13 having a smaller diameter than the first lens holding frame 12. The second lens 17, the third lens 18, and the fourth lens 19, which diffuse the incident light along the optical axis L 2 and project it onto the plane mirror 5. The first lens holding frame 12 and the second lens holding frame 13 are fitted so as to overlap each other's annular portions, and are fixed by a stopper 21 from the side surface side, and the four projection lenses 16 described above. , 17, 18 and 19 function as the projection lens barrel 11. Although the number of projection lenses 16, 17, 18, and 19 is four in this embodiment, the number is not limited to this, and is appropriately determined according to the design of the rear projection apparatus.

  The holding member 14 is configured by combining a first thick plate 14d and a second thick plate 14e made of metal at a right angle. The first thick plate 14d and the second thick plate 14e are provided with openings 14a and 14b, respectively, and the focusing lens barrel 27 and the second lens holding frame 13 are fitted and held therein. Here, a part of the connecting cylinder 23 is fitted into the opening 14 a together with the focusing lens barrel 27. The second lens holding frame 13 is fixed by a stopper 21 at a part of an annular side wall 14c provided at the edge of the opening 14b. Further, below the second lens holding frame 13, a mirror holding frame 22 is attached and held on the lower surface of the second thick plate 14e by means such as screwing or bonding. As described above, the projection lens unit 10 is integrally configured by assembling the focusing lens barrel 27, the mirror holding frame 22, and the second lens holding frame 13 to the holding member 14.

  A flange 14 f is provided around the first thick plate 14 d into which the focusing lens barrel 27 is fitted as a connection portion with the image light generation unit 6. Attachment holes 26 are provided at the four corners of the flange 14f, and are connected to the image light generation unit 6 by means such as screwing. Therefore, the focusing optical system 15 is firmly connected to the image light generation unit 6 in the vicinity of the focusing lens barrel 27, and the reflection optical system and the diffusion optical system 24 are also firmly fixed via the holding member 14, respectively. Furthermore, since the holding member 14 has high rigidity, vibration of the first lens 16 and the like can be effectively suppressed. Further, a reinforcing plate 29 formed of, for example, a sheet metal is fixed to the side surface of the projection lens unit 10 with a plurality of screws 28 as fastening members so as to fasten the mirror holding frame 22 and the focusing lens barrel 27. . Thereby, the intensity | strength of the projection lens unit 10 is further raised. A screw hole 27a for fixing the reinforcing plate 29 with a screw 28 is provided on the side surface of the focusing lens barrel 27 as shown in FIG.

  In the rear projection device 1 configured as described above, the image light combined by the combining prism 36 enters the focusing optical system 15. The image light transmitted through the focusing optical system 15 is reflected by the reflection mirror 20 so that the optical axis direction of the image light is changed from the optical axis L1 to the optical axis L2, and then enters the diffusion optical system 24. The diffusion optical system 24 emits the image light reflected by the reflection mirror 20 toward the plane mirror 5. Thereby, the image light is imaged on the screen 4.

  Such a rear projection apparatus 1 does not have a connection structure between the holding frames of the optical system, and uses the projection lens having a large diameter because the projection lens unit 10 described above has high strength. Vibration can be effectively suppressed, and the projected image on the screen 4 hardly fluctuates. Therefore, the user can view the image comfortably.

It is an internal side view which shows the structure of the optical system of the rear projection apparatus of this invention. It is a structure of the optical system of an optical engine. It is a sectional side view of a projection lens unit. It is a side view of a projection lens unit. It is a perspective view of a projection lens unit. It is side sectional drawing of the conventional projection lens unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rear projection apparatus 2 Case 3 Optical engine 4 Screen 6 Image light generation unit 10 Projection lens unit 11 Projection lens barrel 12 First lens holding frame 13 Second lens holding frame 14 Holding member 14f Flange 15 Focusing optical system 16 First Lens 17 Second lens 18 Third lens 19 Fourth lens 20 Reflective mirror 22 Mirror holding frame 23 Connecting cylinder 24 Diffusing optical system 25 Converging lens 29 Reinforcing plate 30 Light source device 31 Illumination optical system 32 Color separation / combination optical system 39 Projection optical system

Claims (4)

In the rear projection device that projects and displays an image from the projection lens unit on the back of the screen,
The projection lens unit has a focusing optical system for focusing light rays included in image light by a focusing lens held by a first holding frame, and a light beam incident from the focusing optical system by a reflecting mirror held by a second holding frame. A reflecting optical system that reflects in the direction of the light, and a diffusing optical system that diffuses and projects light incident from the reflecting optical system by a projection lens held in a third holding frame, and the first holding frame and the first A rear projection device, wherein the second holding frame and the third holding frame are integrally formed by assembling them to a common holding member.   The rear projection apparatus according to claim 1, wherein the holding member is made of metal.   The rear projection apparatus according to claim 1, wherein the first holding frame and the second holding frame are fastened by a fastening member. An image light generation unit fixed to the apparatus main body and generating the image light and connected to the projection lens unit to emit image light to the focusing optical system,
The rear projection apparatus according to claim 1, wherein the holding member is provided with a connection portion for connecting to the image light generation unit in the vicinity of the assembled first holding frame.

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