JPH11149124A - Rear projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an inexpensive super-thin rear projection type display device by which a projected picture is not deteriorated, the temperature characteristic of a display device is stable, whose reliability is high. SOLUTION: An illuminator 8, a light valve 9, and a projecting lens are arranged inside a cabinet 1, the projecting lens is arranged along the bottom surface of the cabinet 1, and the illuminator 8 is arranged between the side surface of the cabinet 1 and the outside of the outermost side surface of an image luminous flux 12 toward a screen 3 from a fourth reflecting mirror 7. A partitioning plate 15 is set between the outermost side surface of the image luminous flux 12 and the illuminator 8. An intake fan 16 is provided on the bottom surface of the cabinet 1, air introduced inside the cabinet 1 from the fan 16 is guided in the height direction of the cabinet 1, and discharged from the front surface of the cabinet 1 by a ventilating fan 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection display device, and more particularly to a rear projection display device suitable for enlarging and projecting video images, computer images, and the like.

[0002]

2. Description of the Related Art In recent years, a CRT (Cathode Ray) has been developed.
(Tube) High-quality and large-screen displays, including direct-view displays, are being rapidly developed. But C
The RT direct view type is said to have a limit of about 40 inches due to manufacturing problems, and is heavy. Liquid crystal, EL,
A flat display such as a plasma is also being developed to have a large area in terms of technical problems in manufacturing and cost.

[0003] In such a situation, attention has been paid to 1
LCD panel of about 5 inches or CR of about 5 to 9 inches
This is a projection display device that enlarges and projects the T image. Projection display devices are classified into a front projection type and a rear projection type. The front projection type has the advantage that the screen size can be freely obtained, but has the disadvantage that the image cannot be viewed unless the room is darkened and that a screen is required separately from the display device. On the other hand, in the rear projection type, although the screen size cannot be changed, it is possible to view the image in an arbitrary place and even in a bright room with a large screen like a CRT direct view type.

[0004] Such a display device is required to have a large screen and be small and lightweight. An ultra-thin display, such as a wall-mounted TV, is a dream for the future.

Under the circumstances described above, Japanese Unexamined Utility Model Publication No. 1-85778 and the technical report of the Television Society of Japan (1989 Vol. 13 No. 53 55-60)
Page) etc.
There has been provided a rear projection display device of a type in which projection is performed with a vertical optical axis. This type of rear projection display device
If the image is not projected with an optical axis perpendicular to the screen, the image will be distorted due to trapezoidal distortion, etc., which greatly restricts the installation conditions of the reflection mirror, and the volume occupied by the enlarged projection optical system, especially the screen There is a problem that the dimension in the depth direction (the thickness of the cabinet) increases, so that a rear projection display device using a thin cabinet cannot be provided. The size and weight have been reduced by reducing the projection distance by widening the angle of the projection lens and by reducing the size of the image forming unit such as a CRT and liquid crystal. However, the size and weight have not been significantly reduced.

Therefore, an oblique projection system has been proposed as a means for making the cabinet thin. In general, an image of a tilted object by a lens is described in US Pat. As shown by Scheimpflug, trapezoidal distortion occurs. In FIG. 17, the inclined object surface 31 is
An image is formed on the inclined image plane 33 by the lens 32. As shown in FIG. 17, the relationship between the object surface 31 and the lens 3
2 and the extension of the image plane 33 become coincident. Assuming that the point of intersection between the image plane 33 and the perpendicular to the optical axis Z of the image-side focal point F of the lens 32 is g, the image on the square object plane shown in FIG. An image is formed on 33 in a trapezoidal shape.

In order to remove this trapezoidal distortion, as shown in FIG. 19, the light valve 9, the first projection lens 34 and the second
Of the projection lens 36 and the screen 3 are inclined with respect to the Z axis. Here, the image-side focal point f of the first projection lens 34
1, the intersection line s between the plane parallel to the first projection lens 34 and the image plane 35 having a trapezoidal distortion, and the object side focal point f2 of the second projection lens 36 and parallel to the second projection lens 36. The intersection line s ′ between the surface and the image plane 35 having the trapezoidal distortion is matched.

At this time, for example, the image of the square light valve shown in FIG.
Although the image has a trapezoidal distortion shown in FIG. 1, the image is formed on the screen 3 by the second projection lens 36 into an image without the trapezoidal distortion shown in FIG. Therefore, as shown in FIG. 20, if this projection optical system is folded and accommodated in the cabinet 1 by the first mirror 37 and the second mirror 38, the dimension in the depth direction is reduced, and a thin rear projection display device is obtained. Can be configured.

[0009]

In the above-mentioned conventional rear projection type display device, the inside of the cabinet is roughly divided into a space for an image light beam and a component area such as a lighting device and a display device. These two regions are laid out with little sharing. In particular, there are no components disposed near the image light beam region (the image light beam portion in the space for the image light beam), and the space utilization efficiency is poor. This was one of the problems that the cabinet became large.

In addition, since the apparatus is designed to be thinner, the components must be arranged in the width direction, and the cabinet becomes larger in the width direction.

As described above, the large size of the apparatus has a problem that the price of the apparatus is high because the parts are large and parts for securing the strength of the apparatus are required.

In addition, there is a problem that light leaks from a lighting device or a display device and is incident on a screen, whereby the contrast of an image is reduced, flares or shadows of components appear, and the image is significantly deteriorated.

Further, in such a rear projection display device, a large amount of heat is generated, so that forced cooling is required. However, since the heat generating portion in the apparatus was in an open state, heat was conducted to the entire apparatus, and the inside of the apparatus was at a high temperature.
Further, since the size of the device is large, it takes time until the temperature inside the device reaches an equilibrium state. As described above, the fact that an effective cooling method has not been taken means that display devices such as light valves having a change in characteristics with respect to temperature cause display deterioration,
This is a cause of low reliability of the apparatus, for example, a component such as a reflection mirror distorts an image due to thermal distortion.

The present invention has been made to solve the above-mentioned conventional problems. The object of the present invention is to prevent image deterioration due to a decrease in contrast or flare, to provide high cooling efficiency and high reliability. It is an object of the present invention to provide a rear projection display device which is much thinner and cheaper than the conventional one.

[0015]

In order to solve the above-mentioned problems, a rear projection type display device according to the present invention is provided with an image forming means and an original image of the image forming means which are enlarged and projected on a screen in a cabinet. Projection means, and at least one reflection means for guiding the image light flux projected from the projection means to the screen, and a screen, the image light flux from the reflection means closest to the screen on the optical axis to the screen In a rear projection display device in which a central optical axis is obliquely inclined with respect to the screen, the projection unit converts an image generated by the image forming unit into an intermediate image having trapezoidal distortion. A projection optical system, and a second projection optical system for converting the intermediate image having the trapezoidal distortion into a regular image having no trapezoidal distortion on the screen, wherein the image forming unit includes: It is located outside the outermost surface of the image light flux from the reflection means closest to the screen on the optical axis toward the screen, and is arranged in an area surrounded by the front, back, side, top and bottom surfaces of the cabinet. And

[0016] The optical axis of the image forming means may be in the lateral direction of the screen, or in the front-rear direction, or both directions, with respect to the axis connecting the center of the upper end and the center of the lower end of the screen. It is characterized by being inclined at a required angle to approach it.

Further, the image forming means has a structure capable of adjusting the inclination angle of the optical axis.

Further, the image forming means has a structure in which rotation can be adjusted with its optical axis as a rotation center axis.

Further, a separating means is provided between the image forming means and the outermost surface of the image light beam.

Further, the isolation means is made of metal or resin, and the outer surface is black or a dark color close to black.

A cooling device is arranged on the bottom and front surfaces of the cabinet (screen installation surface), and a cooling structure that draws in air from the bottom surface of the cabinet and discharges air from the front surface, or a cooling structure that draws air from the front surface of the cabinet and discharges air from the bottom surface. It is characterized by having a structure.

Further, a cooling device is arranged above the cabinet and has a cooling structure for exhausting air from above.

Further, in the cabinet, there is provided an image forming means, a projecting means for enlarging and projecting an original image of the image forming means on a screen, and at least one image projecting means for projecting an image light beam projected from the projecting means onto a screen. A rear projection display device, comprising: two reflecting means, and a screen, wherein a central optical axis of an image light flux directed from the reflecting means closest to the screen on the optical axis toward the screen is obliquely inclined with respect to the screen. Wherein the projection unit converts the image generated by the image forming unit into an intermediate image having trapezoidal distortion, and the intermediate image having trapezoidal distortion has no trapezoidal distortion on the screen. A second projection optical system for converting the image into a regular image, and a screen of an image display unit in the image forming means (for an enlarged image plane projected on the screen, Te, short side direction of the object surface) corresponding via the projection lens, so that the substantially same direction as the depth direction of the cabinet, wherein said image forming means is disposed.

[0024]

(Embodiment 1) The present invention will be described below with reference to an embodiment shown in the drawings.

As shown in FIG. 1, a rear projection type display device according to an embodiment of the present invention includes a thin cabinet 1 and a lighting device 8 and a polarizing device 11 which are components of image forming means. An image forming optical system 10 including three light valves 9, a projection lens 2 as a projection unit, and a rear projection screen 3 provided on a front surface of the cabinet 1;
First, second, third, and third reflecting means for guiding the image light beam from the projection lens 2 to the rear surface of the screen 3
And fourth reflecting mirrors 4, 5, 6, and 7.

First, the configuration of the oblique projection optical system used in this embodiment will be described. FIG. 9 shows the layout. The basic concept is the same as the above-described principle of the conventional oblique projection. FIG. 10 shows the light valve 9 in FIG.
11 shows an intermediate image with trapezoidal distortion on the intermediate image plane 23 in FIG. 9, and FIG. 12 shows an image without trapezoidal distortion on the screen 3 in FIG.

In FIG. 9, the optical axis of the first lens 21 of the first projection optical system, the optical axis of the second lens 22, the optical axis of the second projection optical system 24, the normal of the light valve 9, and the screen 3 Are on the same plane.

The first lens 21 and the second lens 21 of the first projection optical system
The lenses 22 are tilted from each other by an angle ψ, and the first lens 21
The intersection line between the image-side focal plane and the object-side focal plane of the second lens 22 is
It is arranged so as to pass substantially on the Z axis. Intermediate image plane 23 and second
The projection optical system 24 and the screen 3 are arranged such that their extended surfaces intersect on a straight line.

The light beam emitted from the illumination device 8 illuminates the light valve 9 substantially in parallel. Therefore, the light valve 9
The light flux enters at substantially the same angle, and uniform brightness and contrast can be obtained on the entire surface of the light valve 9. The image of the light valve 9 shown in FIG. 10 forms an intermediate image having a trapezoidal distortion as shown in FIG. 11 by the first lens 21 and the second lens 22 inclined with respect to each other. As shown in FIG. 13, the image-side focal plane of the first lens 21 and the second lens 22
A plane parallel to the Z-axis including the line of intersection of the main plane
And the line of intersection with g. When g and the line passing through the object-side focal point of the second projection optical system 24 and parallel to the second projection optical system 24 and the intersection line g ′ of the intermediate image plane 23 are matched as shown in FIG. The intermediate image distorted into a trapezoid as shown in FIG. 11 is formed on the screen 3 by the second projection optical system 24 as an image without trapezoidal distortion as shown in FIG.

The projection lens 2 used this time is composed of the first lens 21, the second lens 22, and the second projection optical system 24 of the first projection optical system. The light valve 9 uses an active matrix type liquid crystal panel.

The screen 3 can be made of a resin base material containing a diffusing agent, a lenticular lens and a Fresnel lens sheet in combination to improve the light distribution characteristics. However, as shown in FIG. 14, a part of the light beam projected obliquely (for example, at an incident angle of 60 °) from the rear surface of the screen 3 is not transmitted in the extension direction.
It is desirable to use a screen whose light distribution characteristics are good for oblique projection by combining a prism total reflection sheet for directing the incident light beam in a direction substantially perpendicular to the front surface of the screen 3 with a sheet of a lenticular lens. .

The image light flux 12 projected from the projection lens 2
The reflection system for optical path conversion for guiding the light to the back of the screen 3 has a triangular shape A as shown in FIG.
When considering BC, it is understood that the minimum depth is to bend the optical path so as to form an isosceles triangle with the line segment AB as the base. That is, when X is without a reflection mirror,
Y indicates an optical path in the case of single reflection, and Z indicates an optical path in the case of double reflection.

At this time, the angle φ between the line segments AB and BC is expressed by φ = (π / 2) -α-θ.

Tan φ = 1 / tan (α + θ) From the figure, H / 2D = tan (α + θ) Therefore, tan φ = 2D / H Now, (H / D) is 3, that is, depth D is 3 of height H.
In order to make it 1/1/2, if θ = 12 °, α = tan−1 (3/2) −θ = 56.3 ° −12 ° =
44.3 ゜. If α = 60 °, the depth dimension D can be further reduced and a thin configuration can be achieved.

The above description is the same in the case of three or more reflections, and may be bent not only three-dimensionally but also three-dimensionally as shown in FIG.

Referring to the embodiment shown in FIG. 1, in this case, the light beam emitted from the lighting device 8 of the cabinet 1 is
In the polarizer 11, only single polarized light selectively passes. The transmitted light flux is subjected to optical path conversion using a mirror or the like, and is guided to the image forming optical system 10. In the image forming optical system 10,
The light is modulated in each light valve 9 and enters the projection lens 2. The inside of the projection lens 2 is as described above. The image light flux 12 that has passed through the projection lens 2 travels while expanding, and the optical path is changed upward by the first reflection mirror 4 to the cabinet, and is incident on the second reflection mirror 5 that receives the reflected light from the first reflection mirror 4. I do. Further, the image light flux 12 is reflected by the second reflection mirror 5 and guided to the third reflection mirror 6 installed at the lower part of the screen 3.
A fourth reflection mirror 7 receiving the light reflected from the reflection mirror 6 is placed on the rear inner surface facing the screen 3 substantially in parallel with the rear surface of the screen 3, and the fourth reflection mirror 7 is inclined from the fourth reflection mirror 7 to the rear surface of the screen 3. By projecting, the image formed on the light valve 9 is projected on the screen 3 as an enlarged image.

By adopting the above arrangement structure, even when obliquely projecting from the back of the screen 3, trapezoidal distortion does not occur in the enlarged image formed on the screen 3, and a regular image can be projected. The depth of the cabinet 1 can be greatly reduced, and a thin, large-screen display device can be obtained.

FIG. 2 is a front view of the rear projection display device of FIG. In the apparatus of the present embodiment, a space above the first and third reflecting mirrors 4 and 6 and below the upper end of the screen 3 is a space for image light flux. In the space, a quadrangular pyramid-shaped image light beam 12 intersects the space. However, since only the image light flux 12 does not completely fill the space,
Although the form is complicated, there is an area where the image light flux does not exist.

FIG. 3 is a top view of the rear projection display device in FIG. As shown in the figure, the outermost surface of the image light flux 12 (the surface including the light rays 13) from the fourth reflection mirror 7 closest to the screen 3 on the optical axis toward the screen 3, and the front surface of the cabinet 1 (the screen 3 installation surface) ), A narrow area of a trapezoidal column shape surrounded by the back surface, the side surface, the top surface, and the bottom surface extends long in the height direction of the cabinet. Therefore, since there is no image light beam here, a narrow component can be arranged in the vertical (height) direction. Also,
In the present invention, a configuration in which the state in which FIG. 2 is rotated by 90 ° is a front view is also possible. In that case, this FIG.
Is a side view of the rear projection display device. At this time, the trapezoidal narrow region surrounded by the outermost surface of the image light flux 12 and the front, back, top (or bottom), and side surfaces of the cabinet 1 extends in the width direction of the cabinet, so that the width and the installation posture are large. Although there is a limit, components can be installed. Of course, when installing,
The image light flux 12 must not be blocked. Since it is difficult to visually recognize the light beam, the boundary between the regions is not clear, so special care is required.

On the other hand, the first lens 21, the second lens 22, and the second projection optical system 24 of the first projection optical system which constitute the projection lens 2 are arranged as shown in FIG. This lens group is not a single lens but a combination of several lenses in order to reduce the aberration that causes deterioration and the amount of distortion correction. Accordingly, as can be seen from FIGS. 1 and 2, the projection lens 2 is considerably long.
Such an apparatus requires at least an illumination device 8 and an image forming optical system 10 in addition to the projection lens 2. Therefore,
If these are arranged linearly on the optical axis, a long and wide space is required in the width direction.

Further, in order to maintain good image quality, the first and second lenses 21 and 22 and the second projection optical system 24 are required.
The inclination of each lens inside must be small. For that purpose, it is necessary to increase the projection distance.

In this embodiment, the fourth reflecting mirror 7
The optical axis is bent in a region outside the outermost surface of the image light flux 12 traveling from the front to the screen 3 and surrounded by the front surface, the back surface, the side surface, the top surface, and the bottom surface of the cabinet 1, and the illumination device 8, the polarizing device 11, and the image. The forming optical system 10 is arranged. Since the optical axis is bent based on the same concept as the installation of each reflection mirror, the flow of projection described with reference to FIG. 1 is not changed at all.

With this arrangement, the necessary projection distance can be ensured, and the projection lens 2, the illumination device 8, and the polarization device 11 can be secured.
And the image forming optical system 10 can be arranged without difficulty.
The cabinet can be reduced in size without impairing the function as a rear projection display device. In particular, the width direction is reduced.

When good image quality can be maintained even when the projection distance is slightly short due to the improvement of the projection lens 2, as shown in FIG.
A configuration in which only the illuminating device 8 is disposed below the region outside the outermost surface of the image light beam 12 traveling from the front to the screen 3 and surrounded by the front surface, the back surface, the left side surface, and the bottom surface of the cabinet 1 is also possible.

(Embodiment 2) FIG. 5 is a partially enlarged front view of a rear projection display apparatus according to an embodiment of the present invention. As is clear from FIG. 5, the illuminating device 8 and the polarizing device 11 are arranged to be inclined with respect to an axis connecting the center of the upper end and the center of the lower end of the screen 3 in FIG. The reason will be described below.

The projection type display device is arranged such that
Projects with a certain angle of view. Therefore, the same applies to the rear projection display device. In the figure, since the image light beam 12 traveling from the fourth reflection mirror 7 to the screen 3 travels while expanding, the image light beam 12 is outside the outermost surface of the image light beam 12 described above, and is the front, back, side, top, and bottom of the cabinet 1. The area surrounded by is narrowed toward the upper surface side and the front side of the cabinet 1. Therefore, if the illuminating device 8 and the polarizing device 11 are arranged with a sufficient margin to avoid the image light flux 12, the width direction of the cabinet 1 becomes large. Therefore, in order to further reduce the width of the cabinet 1, the illuminating device 8 and the polarizing device 11 need to be closer to the side of the image light flux 12, and the axis connecting the center of the upper end and the center of the lower end of the screen 3 is It becomes the arrangement of the inclined posture. In this embodiment, the inclination angle is 8 ° in the left-right direction of the screen 3 and 7 ° in the front-rear direction. The optimum value of the tilt angle differs depending on the projection angle of view and the projection angle with respect to the screen. With this arrangement, the width direction can be further reduced, and the cabinet can be configured with a minimum width of (screen width) + (width of parts holding the screen).

Further, in this area, a part of the projection lens can be bent and arranged, and the projection distance can be extended.

(Embodiment 3) FIG. 6 is a configuration diagram of a rear projection type display apparatus according to another embodiment of the present invention. In this embodiment, three CRTs 14 are used as image forming means. The arrangement of the projection lens 2, the first, second, third, and fourth reflection mirrors 4, 5, 6, 7, and the screen 3 in the cabinet is the same as that in the first embodiment. In particular, a CRT is a device that is elongated in the optical axis direction except for an image display unit, and thus is suitable for installation in the narrow and long region described above. An apparatus using a light valve is more advantageous for miniaturization (thinning). However, even when a CRT is used, a normal image can be projected by projecting the image light flux 12 obliquely onto the screen 3, but the depth is greatly reduced. In addition, the CRT 14 is disposed outside the outermost surface of the image light beam 12 traveling from the fourth reflection mirror 7 toward the screen 3 and is surrounded by the front, back, side, top, and bottom surfaces of the cabinet 1, so that the width becomes wider. Can be reduced. In addition, a minimum lateral width can be achieved by arranging them at an angle.

(Embodiment 4) In the case where the illuminating device 8 and the polarizing device 11 are arranged to be inclined as in Embodiment 2 described above, it is desirable to have a tilt angle adjusting mechanism.
When a projection lens such as the projection lens 2 described in the first embodiment is used, alignment of the optical axis is particularly important. When the optical axis is tilted, the brightness and contrast are reduced on the screen, the illuminance ratio is deteriorated, and the like, and the display quality is significantly impaired. In some cases, the design value of the installation angle may not be satisfied due to the accumulation of component accuracy and assembly accuracy. Therefore, an angle adjusting mechanism is required to maintain good display image quality.

When a TN type liquid crystal panel is used for the display device, a single polarization component is selected and the transmittance is controlled. Therefore, the polarization of the film polarizing plate placed near the liquid crystal panel is controlled. The relationship between the axis and the polarization axis of the polarizer is important. For example, when a film polarizer is placed on the light incident side of a liquid crystal panel, the polarization axis (transmission axis or absorption axis) of the polarizer and the polarization axis (transmission axis or absorption axis) of the film polarizer match. The maximum amount of light is incident on the liquid crystal panel. When this shifts from 1 ° to 2 °, the amount of incident light decreases. Therefore, the brightness on the screen is reduced as described above. The light use efficiency of the currently available projection-type liquid crystal display device with respect to the output of the light source is very low at 1 to 3%, so it goes without saying that a shift of 1 ° or 2 ° greatly affects the brightness. . Further, if the positional relationship between the polarization axis of the film polarizer placed on the light emission side of the liquid crystal panel and the polarization axis of the polarizer is lost, the brightness and the contrast are reduced. Therefore, a mechanism for adjusting the polarization axis is required. FIG. 7A shows an example of a tilt angle adjusting mechanism of the illumination device 8, and FIG.
An example of a rotation adjusting mechanism of the polarization axis with the optical axis as the central axis is shown.

In FIG. 7A, the lighting device 8 includes the first
It is fixed to the plate 25. The first plate 25 and the second plate 26 have a hinge structure. By rotating the adjustment screw 27 attached to the first plate 25, the inclination angle can be adjusted.

In FIG. 7B, the polarizing device 11 is fixed to a third plate 28. When the protrusion of the third plate 28 is moved as indicated by an arrow 30, the columnar boss provided on the fourth plate 29 can be rotated and adjusted along the elongated hole provided on the third plate.

(Embodiment 5) FIG. 8 is a partially enlarged side view of the periphery of the illumination device 8 in FIG. Here, the lighting device 8
A black partition plate 15 made of aluminum, which is an isolation means, is provided between the image light flux 12 and the image light flux 12. As described above, the image beam 12 must be installed so as not to block it. As is clear from this figure, it is understood that the light beam 13 is not in contact with the lighting device 8 and the partition plate 15. Ray 13
Is a light beam from the fourth reflection mirror 7 toward the lower left corner of the screen, that is, the outermost light beam of the image light flux 12. From the above, it can be proved that the illumination device 8, the polarization device 11, and the partition plate 15 can be installed without affecting the image light flux 12.

The installation of the partition plate 15 makes it possible to block direct leakage light or diffusely reflected light from around the lighting device 8, the polarizing device 11, and the light valve 9 from entering the screen. Therefore, it is possible to prevent a decrease in contrast and a flare or a shadow of a component from appearing on the screen, so that it is possible to provide a high-quality image without image degradation.

The partition plate 15 and the third reflecting mirror 6 form a space in the cabinet in which the lighting device 8 and the light valve 9 are half-isolated. As shown in the figure, the intake fan 16 and the exhaust fan 1
If the device 7 is installed, the heat generated from the lighting device 8 and the wind that has cooled the lighting device 8 and the light valve 9 can be immediately discharged to the outside as indicated by an arrow 18.

At this time, on the front and the bottom of the cabinet 1,
It is clear that the same effect can be obtained even if the intake fan 16 and the exhaust fan 17 are arranged in reverse.

Here, on the front and the bottom of the cabinet 1,
The reason why the intake fan 16 and the exhaust fan 17 are provided is as follows.

Such a thin rear projection display device has
The installation environment differs depending on the user. For example, it is fully expected that it will be installed in close proximity to walls, bookshelves, and other furniture. At this time, if the intake or exhaust fan is installed on the back or side of the cabinet, the ventilation holes will be blocked, and the cooling capacity will decrease or the noise will increase.
In contrast, the front of the cabinet is not affected unless intentionally placed by obstacles, and the bottom can secure the necessary space with the floor at the design stage, so it is always stable regardless of the installation environment. The obtained cooling effect is obtained.

As described above, since efficient and stable cooling has become possible, the influence of heat on the entire apparatus is small, the temperature rise in the apparatus can be reduced, and the time for the temperature to reach an equilibrium state can be reduced. Can be significantly reduced. Therefore, components such as reflection mirrors do not distort the image due to thermal distortion,
Since the temperature characteristics of the light valve are stable and display deterioration does not occur, a highly reliable device can be realized.

(Embodiment 6) In the rear projection type display apparatus shown in FIG. 6, an exhaust fan 19 is arranged above the cabinet 1. A rear projection display device using a CRT does not require an illuminating device, and the CRT itself does not require as much cooling as a light valve.

Since the heat rises to the upper part in the cabinet 1 by the convection effect, the exhaust fan 19 provided at the upper part
Thereby, heat can be efficiently released outside the cabinet 1.
Therefore, a rise in temperature inside the device is suppressed, and a stable state is achieved.

When this embodiment is combined with the cooling structure described in the fifth embodiment, more efficient cooling is possible in a rear projection display device using a light valve.

(Embodiment 7) Referring to FIGS. 1 and 8, one light valve 9 is arranged such that the short side of the screen of the image display section is substantially the same as the depth direction of the cabinet.

Normally, a rear projection display device for displaying a video image or the like is horizontally long such that the screen has an aspect ratio of 3: 4. In the arrangement of the components shown in FIG. 1, if the installation angles of the first reflection mirror 4, the second reflection mirror 5, and the third reflection mirror 6 are selected, the short side of the screen of the image display unit in the light valve 9, Regardless of the long side, any direction may be arranged in the same direction as the depth direction of the cabinet 1 so that the screen 3 can be configured to be a horizontally long screen.

However, the direction of the long side of the screen is the cabinet 1
When the direction is substantially the same as the depth direction of the first and second
The dimensions of the reflection mirrors 4 and 5 themselves in the depth direction are increased. Further, since the image is twisted by about 90 °, the first and second reflection mirrors 4 and 5 are installed in a posture rotated around the optical axis, so that the size of the cabinet 1 in the depth direction is increased. Therefore, when the short side direction of the screen of the image display unit of the light valve 9 is arranged in the substantially same direction as the depth direction of the cabinet 1, the size of the first reflection mirror 4 and the second reflection mirror 5 in the depth direction becomes small. Since there is almost no need to rotate about the optical axis, the size in the depth direction is further reduced, so that the cabinet becomes thin.

When the image forming optical system 10 is configured by arranging the short side of the image display section of the light valve 9 in the same direction as the depth direction of the cabinet 1, the image forming optical system 10 Thinner. Compared to a configuration in which the long side direction of the screen is the same as the depth direction of the cabinet 1, it can be configured to be about 30% thinner. Using this configuration, in a rear projection display device having an aspect ratio of 3: 4 and a screen size of 50 inches, a depth dimension of 25
An unprecedented thickness of up to 30 cm can be achieved. Further, when the aspect ratio becomes horizontally long such as 9:16, this difference becomes more remarkable.

It is obvious that the same effect is obtained even if the display device is a CRT.

Therefore, it is possible to realize an even thinner, ultra-thin rear projection display device.

[0069]

As described above, according to the present invention, the size of the cabinet can be reduced by disposing the illuminating device, the polarizing device, and the like near the image light beam in the space for the image light beam.
In particular, the width can be reduced.

Further, by arranging the illuminating device and the polarizing device at a required angle with respect to an axis connecting the center of the upper end and the center of the lower end of the screen and disposing the illuminating device and the polarizing device near the image light beam, the lateral width can be further reduced.

Further, by arranging the short side direction of the screen of the image display unit in the light valve or the CRT in substantially the same direction as the depth direction of the cabinet, the depth dimension of the cabinet thinned by oblique projection can be further reduced. effective.

As described above, since the width and the depth are reduced, the number of large-sized parts and parts for securing the strength are reduced, so that there is an effect that the price of the apparatus is reduced.

Further, by providing a tilt angle adjusting mechanism or a polarization axis rotation adjusting mechanism in the illumination device or the polarizing device, it is possible to prevent the optical axis shift or the polarization axis shift, so that a good image can be maintained.

Further, by providing the partition plate, it is possible to prevent a decrease in contrast and the incidence of an image other than the regular image on the screen, thereby obtaining a good projected image. In addition, a black or near-dark colored partition plate is more effective because it absorbs stray light and prevents diffuse reflection.

In addition, by installing a partition plate and providing an intake or exhaust fan on the front and bottom surfaces or the upper portion of the cabinet, it is possible to prevent a rise in the temperature inside the device, and to achieve efficient and stable cooling, thereby enabling image display components. This has the effect that the temperature characteristics are stable and display deterioration does not occur, and image distortion due to thermal distortion does not occur in components such as the reflection mirror. These effects greatly improve the reliability of the device.

Therefore, a highly reliable, low-cost, ultra-thin rear-projection display device can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a rear projection type display device using a light valve as one embodiment of the present invention.

FIG. 2 is a front view of the rear projection display device of FIG. 1;

FIG. 3 is a top view of the rear projection display device of FIG. 1;

FIG. 4 is a front view of a rear projection display device in which a good image can be maintained even when the projection distance is short, as another embodiment of the present invention.

FIG. 5 is an enlarged front view of a rear projection display device in which an illuminating device and a polarizing device are arranged obliquely as another embodiment of the present invention.

FIG. 6 is a perspective view of a rear projection display device using a CRT as another embodiment of the present invention.

FIG. 7 is an explanatory view showing an example of a tilt angle adjustment mechanism and a polarization axis rotation adjustment mechanism.

8 is an enlarged side view of a part around the lighting device of FIG. 5;

FIG. 9 is a layout diagram of an oblique projection optical system.

FIG. 10 is an explanatory diagram of an image on the light valve in FIG. 9;

FIG. 11 is an explanatory diagram of the intermediate image of FIG. 9;

FIG. 12 is an explanatory view showing image formation on the screen of FIG. 9;

FIG. 13 is an explanatory diagram of an arrangement of a first projection optical system in FIG. 9;

FIG. 14 is an enlarged cross-sectional view of a part of a screen due to total reflection of a prism.

FIG. 15 is a principle explanatory diagram of the arrangement relationship of the reflection mirrors.

FIG. 16 is a configuration diagram illustrating an example of a first projection optical system.

FIG. 17 is an explanatory view of an inclined object surface.

FIG. 18 is an image plane diagram of the image plane of FIG. 17;

FIG. 19 is a diagram illustrating the principle of an oblique projection optical system.

FIG. 20 is an optical path diagram of a conventional oblique projection optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cabinet 2 Projection lens 3 Screen 4 First reflection mirror 5 Second reflection mirror 6 Third reflection mirror 7 Fourth reflection mirror 8 Illumination device 9 Light valve 10 Image forming optical system 11 Polarizing device 12 Image light flux 14 CRT 15 Partition plate 16 Intake fan 17 Exhaust fan 19 Exhaust fan

[Procedure amendment]

[Submission date] September 9, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

In order to solve the above-mentioned problems, a rear projection type display device according to the present invention comprises: an image forming means;
A projection unit for projecting an image formed by the image forming unit on a screen, and at least one reflection unit for guiding an image projected by the projection unit to a screen, are provided in a cabinet; A rear projection display device in which the screen is disposed on a front surface, wherein an isolation unit is disposed between the image forming unit and an outermost surface of an image light beam projected by the projection unit. Features.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Further, the isolation means is made of metal or resin, and the outer surface is black or a dark color close thereto.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

Further, a cooling structure for taking in air from the bottom of the cabinet and exhausting it from the front is provided.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

Further, a cooling structure for taking in air from the front of the cabinet and exhausting from the bottom is provided.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

Further, a cooling device is provided at an upper portion of the cabinet, and a cooling structure for exhausting air from an upper portion of the cabinet is provided.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

An image forming means, a projecting means for projecting an image formed by the image forming means on a screen, and at least one reflecting means for guiding the image projected by the projecting means to a screen. In a cabinet, wherein the screen is arranged on the front surface of the cabinet, and a cooling structure for taking in air from the bottom surface of the cabinet and exhausting air from the front surface.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

Further, the rear projection type display device of the present invention comprises an image forming means, a projection means for projecting the image formed by the image forming means on a screen, and a screen for projecting the image projected by the projection means. At least one reflecting means for guiding to the inside of the cabinet,
A rear-projection display device in which the screen is arranged on a front surface of the cabinet, comprising a cooling structure that takes in air from the front surface of the cabinet and exhausts air from the bottom surface.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

Further, the rear projection type display device of the present invention comprises an image forming means, a projection means for projecting an image formed by the image forming means on a screen, and a screen for projecting the image projected by the projection means. At least one reflecting means for guiding to the inside of the cabinet,
A rear projection display device in which the screen is disposed on a front surface of the cabinet, wherein a cooling device is disposed on an upper portion of the cabinet, and a cooling structure for exhausting air from an upper portion of the cabinet is provided.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Deleted

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Deleted

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Deleted

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Deleted

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0070

[Correction method] Deleted

[Procedure amendment 15]

[Document name to be amended] Statement

[Correction target item name] 0071

[Correction method] Deleted

[Procedure amendment 16]

[Document name to be amended] Statement

[Correction target item name] 0072

[Correction method] Deleted

[Procedure amendment 17]

[Document name to be amended] Statement

[Correction target item name] 0073

[Correction method] Deleted

[Procedure amendment 18]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0074]

As described above, according to the present invention, the installation of the partition plate can prevent a decrease in contrast and prevent a non-regular image from being incident on the screen, thereby obtaining a good projected image. In addition, a black or near-dark colored partition plate is more effective because it absorbs stray light and prevents diffuse reflection.

[Procedure amendment 19]

[Document name to be amended] Statement

[Correction target item name] 0075

[Correction method] Change

[Correction contents]

Further, by providing a cooling structure for exhausting air to the front, bottom, or upper part of the cabinet, it is possible to prevent a rise in the temperature inside the apparatus, to enable efficient and stable cooling, and to stabilize the temperature characteristics of the image display parts. This has the effect of preventing display degradation and preventing image distortion due to thermal distortion in components such as a reflection mirror. These effects greatly improve the reliability of the device.

Claims (9)

[Claims] An image forming means in a cabinet, a projection means for enlarging and projecting an original image of the image forming means on a screen, and at least one for guiding an image light beam projected from the projection means to a screen. Reflection means;
A rear projection display device, comprising: a screen; and a central optical axis of an image light beam traveling from the reflection unit closest to the screen on the optical axis to the screen, the center optical axis of the image light flux being obliquely inclined with respect to the screen. Comprises: a first projection optical system that converts an image generated by the image forming unit into an intermediate image having trapezoidal distortion;
A second projection optical system for converting the intermediate image having the trapezoidal distortion into a regular image having no trapezoidal distortion on the screen, wherein the image forming unit comprises a reflecting unit closest to the screen on the optical axis. Outside the outermost surface of the image light beam toward the screen, the front, back, side,
A rear projection display device, wherein the rear projection display device is arranged in a region surrounded by a top surface and a bottom surface. 2. An image forming apparatus according to claim 1, wherein the optical axis of the image forming unit is close to the side of the image light beam in the left-right direction, the front-back direction, or both directions with respect to an axis connecting the center of the upper end and the center of the lower end of the screen. 2. The rear projection display device according to claim 1, wherein the rear projection display device is inclined at a required angle to approach the display device. 3. The rear projection display device according to claim 2, wherein said image forming means has a structure capable of adjusting an inclination angle of an optical axis thereof. 4. The rear projection type display device according to claim 2, wherein said image forming means has a structure capable of adjusting rotation with its optical axis as a rotation center axis. 5. The rear projection display device according to claim 1, wherein a separating unit is disposed between the image forming unit and an outermost surface of the image light beam. 6. The rear projection type display device according to claim 5, wherein the isolation means is made of metal or resin, and has an outer surface of black or a dark color close to black. 7. A cooling structure is provided on the bottom and front surfaces (screen installation surface) of the cabinet, and a cooling structure that takes in air from the bottom surface of the cabinet and exhausts air from the front surface, or cools air from the front surface of the cabinet and exhausts air from the bottom surface. The rear projection display device according to claim 1, wherein the display device has a structure. 8. The rear projection display device according to claim 1, wherein a cooling device is disposed above the cabinet, and has a cooling structure that exhausts air from above the cabinet. 9. In a cabinet, there is provided an image forming means, a projecting means for enlarging and projecting an original image of the image forming means on a screen, and at least one image projecting means for projecting an image light beam projected from the projecting means onto a screen. A rear projection display device, comprising: two reflecting means, and a screen, wherein a central optical axis of an image light flux directed from the reflecting means closest to the screen on the optical axis toward the screen is obliquely inclined with respect to the screen. In the above, the projection means, a first projection optical system for converting the image generated by the image forming means into an intermediate image having a trapezoidal distortion,
A second projection optical system for converting the intermediate image having the trapezoidal distortion into a regular image having no trapezoidal distortion on the screen,
The short side direction of the screen of the image display unit (the object surface corresponding to the enlarged image plane projected on the screen via the projection lens) in the image forming unit is substantially the same as the depth direction of the cabinet. A rear projection display device, wherein the image forming unit is disposed.