JPH0527326A - Rear projection type display device - Google Patents

Abstract

PURPOSE:To realize a rear projection type display device which is provided with many functions on the front surface side of a cabinet, which can be operated from the front surface side and which is made super thin. CONSTITUTION:A projecting lens 13 is arranged on the rear surface side of a cabinet 1. Besides, multi-functional components are arranged on the front surface side of the cabinet 1. Then, the luminous flux of an image emitted from the lens 13 is reflected by a first, a second, a third and a fourth reflecting mirrors 4, 5, 6 and 7 and guided to the rear surface of a screen 3. At this time, the respective reflecting mirrors are set and arranged so as to obliquely project it with respect to the screen 3.

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, CRT (Cathode Ray)
The direct-view type display, such as Tube, has rapidly been improved in image quality and screen size. But C
The RT direct-view type is said to have a limit of about 40 inches due to manufacturing problems, and is heavy. LCD, EL,
Flat displays such as plasma are also in the process of being developed into a large area in terms of manufacturing technical problems and costs.

Under such circumstances, 1 is attracting attention.
~ 5 inch LCD panel or 5 ~ 9 inch CR
It is a projection display device for enlarging and projecting an image of T. The projection display device is 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 drawbacks that the image cannot be seen unless the room is dark and 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 large screen in a bright room at an arbitrary position as if it were a CRT direct-view type.

Such a display device is required to have a large screen and a small size and light weight. Ultra-thin displays are a dream for the future, as typified by wall-mounted TVs.

Under the circumstances as described above, the technical report of the Literature Television Society (1989 Vol. 13) has been published so far.
No. 53 53-60),
There is provided a rear projection display device of a type that projects with an optical axis perpendicular to a screen. For downsizing and weight reduction, shortening the projection distance by widening the angle of the projection lens,
Although it has been achieved by downsizing the image forming unit such as a CRT or a liquid crystal, it has not been significantly thinned and reduced in size and weight.

[0006]

However, in the conventional rear projection display device described above, the image is distorted due to trapezoidal distortion or the like unless the image is projected with an optical axis perpendicular to the screen. As a result, the volume occupied by the magnifying projection optical system (composed of the display device, the projection lens, the image light flux and the reflection mirror), especially the dimension in the depth direction with respect to the screen (cabinet thickness) increases. Therefore, there is a problem that the rear projection type display device cannot be formed by a thin cabinet.

[0007] In addition to the above-mentioned, the recent television is based on the development of satellite broadcasting, CATV (Cable T
popularization of AV and AV (Audio ・ Vi)
Each company is becoming multi-functional due to its “sual” orientation, and sales are increasing in the market. Therefore, it can be said that a multifunctional rear projection display device is a matter of course.

A CRT direct-viewing type television, which is widely used in homes, is usually mounted on a rack made of wood or the like, and AV equipment such as a video deck and a tuner is housed in the rack. And space is being used effectively. Needless to say, such a thing is also required for the rear projection display device, and the above function is attached to the lower part of the screen of the rear projection display device (the lower part of the front side of the cabinet), which corresponds to this rack part, It is desirable to be able to operate from the front side.

However, since the magnifying projection optical system is laid out in the cabinet due to the restrictions on the installation conditions of the reflecting mirrors described above, the space in the cabinet is filled with only the magnifying projection optical system which is the minimum necessary component. However, even if there was a space, it could not be used on the back side of the cabinet, or it was not used effectively because it was small. Therefore, the AV function and the like are not incorporated, and there is a problem that it is merely a monitor that takes in a video signal from outside the device and simply projects it.

Further, since securing the space for enhancing the function of the device is focused on making the device thin, a method of enlarging the device at the expense of the width and height is adopted, and the overall size and weight are small. There was also a problem that it was not made into a product.

The present invention solves the above-mentioned conventional problems. The object of the present invention is to reduce the width and height in order to add functions, while being much thinner than the devices currently on the market. It is an object of the present invention to provide a rear projection display device that is compact and lightweight without sacrificing the overall size and weight of the device, has a large number of various functions, and can be operated from the front side of the cabinet.

[0012]

A rear projection display device according to the present invention includes at least one display means in a cabinet, projection means for enlarging and projecting an original image of the display means on a screen, and The projection means is provided with at least one reflecting means for guiding the image light flux projected to the back surface of the screen installed on the front surface of the cabinet and projecting the image light flux obliquely with respect to the back surface of the screen at a required inclination angle. By arranging on the side opposite to the installation surface (cabinet front surface) (cabinet back surface side), the cabinet is made smaller, particularly thin, and the device is made multifunctional.

[0013]

【Example】

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

The rear projection display device of the present invention is a rear projection device provided in the front of the cabinet 1 with a projection optical system 2 in a thin cabinet 1 as shown in a perspective view of the device of one embodiment in FIG. Type screen 3 and first, second, third and fourth reflection mirrors 4 which are reflection means for guiding the image light flux from the projection optical system 2 to the back surface of the screen 3.
It is equipped with 5, 6, and 7.

Projection optical system 2 used in the present invention
4A illustrates a transmission type optical system and FIG. 4B illustrates a reflection type optical system, the lighting device 8, an example light valve 9 as a display unit, and a projection unit. , A projection lens 13 including a first lens 10, an image plane 11 and a second lens 12.

The light valve 9 uses a transmissive or reflective dot matrix liquid crystal and is installed at a predetermined angle with respect to the optical axis 14 of the first lens 10. The light valve 7 with respect to the optical axis 14 is located at a position where an image of the bulb 9 is formed.
The imaging surface 11 is installed so as to be inclined on the side opposite to. In the case of the transmissive type, as shown in FIG. 4A, the second lens 12 having the optical axis 15 bent on the image forming surface 11 with respect to the optical axis 14 of the first lens 10 is arranged with the image forming surface 11 in between. Was
The first lens 10 and the second lens 12 are arranged in a V shape. The second lens 12 is the first lens
The image formed on the image forming surface 11 by the lens 10 is the optical axis 1
It has an optical function of enlarging and projecting it on the screen 3 which is arranged on the side opposite to the inclination of the image forming surface 11 with respect to 5. Further, in the case of the reflection type, as shown in FIG.
1 is a reflection mirror, and the second lens 12 is on the reflection optical path.
And has an optical function of obliquely projecting on the screen 3.

The image light flux on the first reflecting mirror 4 is reflected, and the optical path is changed by the second and third reflecting mirrors 5 and 6, respectively, and is guided to the fourth reflecting mirror 7. The image light flux further reflected by the fourth reflecting mirror 7 is projected on the rear surface of the screen 3 with an inclination angle α (for example, 60 °).

The screen 3 has an incident light flux as shown in a partially enlarged view in FIG. 10 so that a light flux projected obliquely (incident angle 60 °) from the back surface of the screen 3 does not pass through in its extension direction. A prism total reflection screen is used which directs the screens in a direction substantially perpendicular to the front surface of the screen 3.

The image plane 11 used in the transmission type is
For example, as shown in FIG.
In the depth direction, a structure is used in which a large number of narrow minute reflecting surfaces 16, 16, ... Are arranged in the vertical direction, and the light from the first lens 10 is reflected by the minute reflecting surfaces 16, 16 ,. It is reflected by and goes toward the second lens 12. If such a reflecting structure is used as the imaging surface 11, light amount loss due to reflection is small, which is preferable, but when the area of the screen 3 is not so large (when the enlargement ratio is small) or when the light amount of the illumination device 8 is large. A transmissive screen can also be used.

When the projection optical system 2 is viewed geometrically as shown in FIG. 6, on the first lens 10 side, the light valve 9 and the image forming surface 11 are image forming positions A ₁ , A of the first lens as shown in FIG. ₂ , the extension line 17 of the light valve 9 and the extension line 18 of the imaging plane 11 pass through the center of the first lens 10 and the optical axis 14
It intersects at the point O on the line 19 which is perpendicular to. At this time, enlargement ratio m
Is m = f / (χ ₁ −f) = (χ ₂ −f) / f = χ ₂ / χ ₁ . In other words, it can be expressed by m = tan α ₂ / tan α ₁ (Scheinfulf's law).

By satisfying the above conditions, the image of the light valve 9 can be formed on the image forming surface 11 by the first lens 10. However, the image formed on the image forming surface 11 is a trapezoidally distorted image in the case where the original image is a regular quadrangle as shown in FIG.

The second lens 12 is also arranged such that the image plane 11 and the screen 3 are arranged in the same relationship as the case of the first lens 10, so that the image on the image plane 11 is changed to the second lens 12. The image is enlarged by and is focused on the screen 3. Since the distortion caused by the first lens 10 is corrected by the second lens 12, this image becomes a normal image as shown in FIG. 8, and the magnification obtained by multiplying the magnification of the first lens 10 and the magnification of the second lens 12 is used. Image is formed.

The reflection system for changing the optical path for guiding the image light beam projected from the projection lens 13 to the back surface of the screen 3 has a triangle AB as shown in the principle explanatory view in FIG.
When considering C, it can be seen that the minimum depth is obtained by bending the optical path so as to form an isosceles triangle whose base is the line segment AB. That is, X is Y when there is no reflection mirror.
Indicates the optical path in the case of single reflection, and Z represents the optical path in the case of double reflection.

At this time, the angle φ formed by the line segments AB and BC is represented 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 one-half, if θ = 12 °, α = tan ⁻¹ (3/2) −θ = 56.3 ° −12 ° = 44.3 ° from the above equation. If α = 60 ° as shown in FIG. 2, the depth dimension D can be further reduced, and the device can be made thin.

The above description applies to the case of three or more reflections. Further, not only the plane bending as shown in FIG. 9 but also the three-dimensional bending may be performed.

With reference to the embodiment shown in FIG. 1, in this case, the luminous flux emitted from the lighting device 8 placed in the lower part of the cabinet 1 is light-modulated by the light valve and installed at the bottom of the cabinet 1 on the back side. Projection lens 13
Incident on. The image light flux that has passed through the projection lens 13 travels while expanding, and is subjected to optical path conversion to the upper side of the cabinet by the first reflection mirror 4 and enters the second reflection mirror 5 that receives the reflected light from the first reflection mirror 4. .. Further, this image light flux is reflected by the second reflection mirror 5, guided to the third reflection mirror 6 installed under the screen 3, and the fourth reflection mirror 7 receives the reflected light from the third reflection mirror 6.
Is placed substantially parallel to the back surface of the screen 3 on the rear inner surface facing the screen 3 and projected from the fourth reflecting mirror 7 to the back surface of the screen 3 from an oblique direction.
The image formed on the light valve 9 is projected on the screen 3 as an enlarged image.

Even if the above-mentioned arrangement structure is adopted and a diagonal image is projected from the rear surface of the screen 3, a magnified image formed on the screen 3 does not have trapezoidal distortion and a normal image can be displayed. The depth dimension of the cabinet 1 can be significantly reduced, and an ultrathin display device with a large screen can be obtained.

Further, in the present invention, by disposing the projection lens 13 on the lower portion on the rear side of the cabinet, it is possible to incorporate a BS tuner, various converters and the like on the lower portion on the front side of the cabinet, and it becomes a multifunctional TV monitor. Needless to say, functions such as VCR, laser disc, compact disc, and center speaker can also be built in. Therefore, the advantages of a large screen, a thin shape, and a small installation area can be further utilized, and not only simple video images and computer image monitors but also AV integrated devices such as karaoke can be realized. Further, a device compatible with multimedia is possible.

The reason why the projection lens 13 can be arranged on the back side of the cabinet 1 will be described below.

FIG. 2 is a side view of the rear projection display device of the present invention. The incident angle of the optical axis 20 on the screen 3 is α,
Fourth reflection mirror 7 with optical axis 21 (reflection optical axis of third mirror)
The angle of incidence on is β. Since the screen 3 and the fourth reflecting mirror 7 are arranged in parallel here, β is equal to α.
The angle between the optical axis 21 and the optical axis 22 (the reflected optical axis of the second reflecting mirror) is 2ψ, the angle between the axis parallel to the Z axis and the optical axis 22 is γ, and the axis parallel to the Z axis and the optical axis. Letting δ be the angle formed by 23 (the reflection optical axis of the first reflection mirror), the inclination angle of the third reflection mirror 6 (the angle formed by the reflection surface and the axis parallel to the X axis) is (γ
+ Ψ). The inclination angle of the second reflection mirror 5 (the angle formed by the reflection surface and the axis parallel to the X axis) is (δ−
γ) / 2. Therefore, if α and β are fixed, distortion and vignetting will not occur if care is taken to prevent the image light flux from being eclipsed by the components and not to break the relationship between γ, δ, and ψ described above. Γ, because a normal image is obtained
δ and ψ can be arbitrarily selected. The tilt angle (δ−γ) / 2 of the second reflecting mirror 5 so that the optical axis 23 faces the cabinet back side.
Is set and the inclination angle of each reflection mirror is adjusted in accordance therewith, the projection lens 13 can be arranged on the back side of the cabinet.

FIG. 3 is a front view of the rear projection display device of the present invention. The inclination angle (angle formed by the reflection surface and the axis parallel to the Y axis) ζ of the first reflection mirror 4 and the inclination angle (angle formed by the reflection surface and the axis parallel to the Y axis) η of the second reflection mirror 5 are Since the above-mentioned settings of γ, δ, and ψ can be changed as needed, there is no difficulty in the configuration of arranging the projection lens 13 on the back side of the cabinet. The first lens 10 and the second lens 12 constituting the projection lens 13 are not a single lens but a lens group in which a plurality of lenses are combined in order to reduce the aberration that causes image deterioration and the distortion correction amount. is there. Further, as can be seen from the figure, the projection lens 13 is elongated in the width direction of the cabinet. Therefore, it is obvious that the inside of the cabinet can be effectively used by disposing the projection lens 13 on the back side of the cabinet. For example, in this embodiment, the VCR 24, the center speaker 25, and the BS tuner 26 can be installed in the lower portion of the front side of the cabinet.

FIG. 11 is a block diagram of a rear projection display device according to another embodiment of the present invention.

In this embodiment, the CRT 2 is used as the display means.
7 is used. In the cabinet, the projection lens 13, the first, second, third and fourth reflection mirrors 4, 5, 6,
The arrangement of 7 and the screen 3 is similar to that of the embodiment shown in FIG. A device that uses a light valve requires a lighting device, but a CRT does not require a lighting device.
Even if the CRT is large, it is possible to install the CRT if the space of this lighting device is used. A device using a light valve is more advantageous for downsizing (thinning), but it is also possible to use a CRT by projecting the image light beam obliquely on the screen and arranging the projection lens on the back side of the screen. The depth of the cabinet can be greatly reduced.

[0035]

As described above, according to the present invention, by arranging the projection lens on the back side of the cabinet,
It is possible to arrange components having various functions on the front side of the cabinet without increasing the width and height. Therefore, the device can be made compact and multifunctional, and can be operated from the front side. Further, the image light flux from the projection lens can be projected obliquely to the screen by changing the required angle optical path by each reflection mirror, so that the depth of the cabinet can be greatly reduced. Therefore, it is possible to realize an ultra-thin rear projection display device which is multifunctional and can be operated from the front side.

[Brief description of drawings]

FIG. 1 is a perspective view of a rear projection display device showing an embodiment of the present invention.

FIG. 2 is a side view showing the arrangement and configuration of optical axes and mirrors in one embodiment of FIG.

FIG. 3 is a front view showing the arrangement and configuration of optical axes and mirrors in one embodiment of FIG.

FIG. 4 is an optical layout diagram showing the principle of the projection optical system in FIG.

5 is an enlarged schematic cross-sectional view of a part of the image plane in FIG.

FIG. 6 is an explanatory view showing the relationship between the first lens of the projection optical system, the light valve, and the image plane in FIG. 4 by geometrical optics.

FIG. 7 is an explanatory diagram showing distortion of an image formed by the first lens.

FIG. 8 is an explanatory diagram showing an image corrected by a second lens.

FIG. 9 is a principle explanatory view of the arrangement relationship of the reflection mirrors.

FIG. 10 is an enlarged cross-sectional view of a part of the screen.

FIG. 11 is a configuration diagram of a rear projection display device according to another embodiment of the present invention.

[Explanation of symbols]

 1 Cabinet 2 Projection Optical System 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 First Lens 11 Image Forming Surface 12 Second Lens 13 Projection Lens 27 CRT

Claims (1)

Claim: What is claimed is: 1. In a cabinet, at least one display means, projection means for enlarging and projecting an original image of this display means on a screen, and an image light flux projected from this projection means. Is installed on the front side of the screen and is provided with at least one reflecting means for projecting obliquely with respect to the back side of the screen at a required inclination angle, said projection means facing the screen installation surface (the front side of the cabinet). A rear projection display device characterized in that the rear projection display device is arranged on the side where it is closed (on the back side of the cabinet).