Rear projection type projector device

In a rear projection type projector device, a transparent plate-like member is supported so as to incline from a vertical surface, and a lenticular screen and a Fresnel lens are placed on the transparent plate-like member. Accordingly, the lenticular lens and the Fresnel lens are in tight contact with the front plate owing to their own weight, and this makes it unlikely to create spaces between these components.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rear projection type projector device that allows a light image projected from a rear side of a screen member to be viewed from a front side of the screen member.

2. Related Background Art

In recent years, a rear projection type projector device has been proposed which allows a light image projected from a rear side of a screen member to be viewed from a front side of the screen member.

FIG. 5is a sectional view showing an example of the structure of a rear projection type projector device.

Reference numeral1denotes a video source (light image output means) and reference numeral2denotes a reflection mirror (reflecting means). Reference numeral3denotes a lenticular screen (screen member), and reference numeral4denotes a front plate (transparent member). Reference numeral5denotes a Fresnel lens, and reference numeral6is a housing. Reference numeral7denotes a picture frame-like escutcheon, and reference numerals8and9denote members for locating at least the screen member3at an opening in the housing6.

A device D3comprises the video source (light image output means)1that outputs a light image, the reflection mirror (reflecting means) that reflects the light image from the video source1, and the lenticular screen (screen member) on which the light image is reflected by the reflection mirror2. Thus, the light image projected on the lenticular screen3from the rear side (as shown by arrow R) can be viewed from the front side (as shown by arrow F). Reference numeral4denotes the transparent member (hereinafter referred to as the “front plate”) located in front F of the lenticular screen3. Reference numeral5denotes the Fresnel lens.

In spite of its large screen, such a rear projection type projector device requires a smaller depth and a smaller installation area than CRT display devices. Screen device is disclosed, for example, Japanese Patent Application Laid-Open No. H07-209753.

The above described front plate4is composed of a relatively rigid member. However, the lenticular screen3and the Fresnel lens5are only 1 to 2 mm in thickness and are thus not substantially rigid. Furthermore, the lenticular screen3and the Fresnel lens5are conventionally held vertically with only their ends supported on the housing6(see the members denoted by reference numerals8and9). Thus, the lenticular screen3or the Fresnel lens5may be buckled by its own weight to create spaces S between the front plate4and the lenticular screen3and the Fresnel lens5. Consequently, resolution may decrease or the image may be distorted, thus disadvantageously degrading image quality.

SUMMARY OF THE INVENTION

It is thus an object of the present invention to provide a rear projection type projector device that prevents a decrease in resolution and the distortion of an image, thus preventing the degradation of image quality.

Accordingly, the present invention is provided in view of the above circumstances. There is provided a rear projection type projector device comprising light image output means for outputting a light image, reflecting means for reflecting the light image from the light image output means, and a screen member on which the light image reflected by the reflecting means is projected, the device allowing the light image projected from a rear side of the screen member to be viewed from a front side of the screen member, the device further comprising:

a transparent member located so as to incline from a vertical plane,

wherein the screen member is located so as to be placed on the transparent member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below with reference toFIGS. 1 to 4. In the Figures, the same reference numerals denote the same components.

FIG. 1is a sectional view showing an example of the structure of a rear projection type projector device D1according to the present invention, and showing a sectional view along the line1—1ofFIG. 7.FIG. 2is a sectional view showing another example of the structure of a rear projection type projector device D2according to the present invention.FIG. 3is a detailed sectional view illustrating the angles at which a screen member and the like are mounted in the device shown inFIG. 1.FIG. 4is a detailed sectional view illustrating the angles at which the screen member and the like are mounted in the device shown inFIG. 2.

The rear projection type projector device comprises light image output means1for outputting a light image L, reflecting means2for reflecting the light image L from the light image output means1, and a screen member3on which the light image reflected by the reflecting means2is projected. The light image projected from the rear side (shown by arrow R and on which the reflecting means2is located) of the screen member3is viewed from the front side (shown by arrow F) of the screen member3. Then, as illustrated inFIG. 3, a transparent member4is located along the screen member3. However, the transparent member4is located so as to incline from a vertical plane A. Furthermore, almost all the surface of the screen member3is placed on the transparent member4. Here, the vertical plane means a plane (virtual plane) containing a vertical line (this applies to the description below). The expression “screen member3is placed on the transparent member4” means that the screen member3is located on a top surface of the transparent member4located so as to incline from the vertical plane A so that the transparent member4bears the weight of the screen member3. The screen member3and the transparent member4may be in contact with each other or another member (for example, a Fresnel lens5, described later) may be located between the members3and4. InFIGS. 1 and 3, the transparent member4is located on the front side of the screen member3. However, the present invention is not limited to this aspect. The transparent member4may be located on the rear side of the screen member3as shown inFIGS. 2 and 4.

In this case, the Fresnel lens5may be located on the rear side R of the screen member3. Almost all the surface of the Fresnel lens5may be placed on the transparent member4together with the screen member3. Here, the expression “Fresnel lens5is placed on the transparent member4” means that the Fresnel lens5is located on the top surface of the transparent member4located so as to incline from the vertical plane A so that the transparent member4bears the weight of the Fresnel lens5. The Fresnel lens5and the transparent member4may be in contact with each other or another member (for example, the above described screen member3) may be located between the members5and4.

Furthermore, a housing6may be provided to house the light image output means1and the reflecting means2. The screen member3and the transparent member4(and the Fresnel lens5) may be supported on the housing6at least at their upper ends.

Moreover, the above described light image output means1may be composed of a light source that emits light and a light bulb that switches the light from the light source to convert it into a light image.

The transparent member4may be rigid. The screen member3may be a lenticular screen.

In the present invention, the transparent member is a plate and not a frame.

Furthermore, in the present invention, the screen member is thinner than the transparent member. If the transparent member is, for example, a glass plate having a thickness of 3 to 4 mm, then the screen member has a thickness of larger than 0 mm and at most 1.5 mm.

Furthermore, in the present invention, if the above different member is further installed, it is thinner than the transparent member. If the transparent member is, for example, a glass plate having a thickness of 3 to 4 mm, the Fresnel lens, which is the different member, has a thickness of larger than 0 mm and at most 1.5 mm.

Description will be given of how the transparent member ensures the planarity of the screen member in the present invention.

If the transparent member is installed so as to extend vertically, the screen member is inevitably buckled perpendicularly to the plane of the screen member (either upward from the front surface or downward from the back surface) under the effect of the gravity.

The inclination of the transparent member means that the buckling of the screen member is prevented to allow the screen member to follow the surface of the planar member. The planar member means that it is rigid. In the present embodiment, this rigid member corresponds to the transparent member. More specifically, it corresponds to a glass plate of thickness 3 mm or more. The glass plate uses its plane to prevent the buckling of the screen member.

The screen member is also a plate. Owing to its small thickness, the screen member may be buckled when inclined without any supports. The plate can maintain its planarity provided that it is supported on a plane. Any member that fails to take a planar shape when supported on a plane is assumed to be different from the screen member according to the present invention.

In the present invention, the screen member preferably has an inclination θ of larger than 5.5. This will be described below.

An example will be given in which the screen member is used in a rear projection type projector device having a screen for which the ratio of width to length is 16:9, which is comparable to a 64-inch screen. The screen member is composed of methacrylstyrene resin, which is a typical material. The methacrylstyrene has a specific gravity of 1.18. The screen member weighs 1,560 g when its thickness is 1 mm. When the screen member is stood up so that its long horizontal side corresponds to a bottom side and that it is supported from its screen surface to the degree that it does not fall down, it may be bent (buckled) by 20 to 30 mm. If this bending is avoided by pushing the center of the screen member from the screen surface, a load of about 150 g is required.

If the buckling of the screen member is avoided by utilizing the load of the screen member itself without imposing any external loads on it, then it is possible to determine θ=5.5 on the basis of the relationship 1,560×Sin θ=150. θ denotes the angle between the vertical direction and the inclined screen member. Accordingly, it is understandable that the inclination θ is preferably larger than 5.5 if this angle is utilized to avoid the buckling of the screen member itself to maintain its planarity by using the load of the screen member itself without imposing any external loads on the screen member.

FIG. 7is a front view of the rear projection type projector device shown inFIG. 1.FIG. 1is a sectional view taken along line1—1inFIG. 7.FIG. 2is a sectional view showing another example of the structure of a rear projection type projector device. That is,FIGS. 1 and 2are schematic sectional views of a central portion of the rear projection type projector device. The same reference numerals as those in the previously described drawings denote the same components. Reference numerals8a,8b,8cand8ddenote members used to locate the screen member. These members are arranged on the respective sides of the screen member as shown in the figure. The screen member3, the transparent member4, and the Fresnel lens5are arranged between the members8and the escutcheon7. In particular, to provide for the possible thermal expansion of at least one of the screen member3, transparent member4, and Fresnel lens5, the members8other than the lower member8b,that is, the members8a,8cand8d,are provided with a clearance in the direction of the thermal expansion (more specifically, at the end of each of the screen member3, transparent member4, and Fresnel lens5). The clearance is about 0.1 to 0.2 mm. The clearance is preferably provided to avoid the offset of the screen member in addition to the thermal expansion.

The lengths of the members8a,8b,8cand8dmay be individually determined. More specifically, each of the members8a,8b,8cand8dpreferably has a length equal to or larger than two-thirds of one side of the screen member. This does not mean that the plurality of members are considered to be one member having a length equal to or larger than two-thirds of one side of the screen member but that each member has a continuous length equal to or larger than two-thirds of one side of the screen member. Because of the continuity, the load involved in the sandwiching is uniform within one side. Each of the members8a,8b,8cand8dis fixed to the escutcheon using a screw.FIG. 8is a view showing the escutcheon and the members arranged as described above.

The effects of the present embodiment will be described below.

According to the present embodiment, the screen member3is placed and supported on the transparent member4. This makes it unlikely to create a space between the screen member3and the transparent member4. It is thus possible to prevent a decrease in resolution and the distortion of an image, thus preventing the degradation of image quality.

Furthermore, the Fresnel lens5is located on the rear side R of the screen member3. When the Fresnel lens5is placed on the transparent member4together with the screen member3, it is unlikely to create a space between the Fresnel lens5and the screen member3. It is thus possible to prevent a decrease in resolution and the distortion of an image, thus preventing the degradation of image quality.

The present invention will be described in further detail with reference to examples.

In the present example, the rear projection type projector device D1, shown inFIGS. 1 and 3, was produced.

In these figures, reference numeral1denotes a video source (light image output means) and reference numeral2denotes a reflection mirror (reflecting means). Reference numeral3denotes a lenticular screen (screen member), and reference numeral4denotes a front plate (transparent member). Reference numeral5denotes a Fresnel lens. A picture frame-like escutcheon7was attached to an opening in a housing6. The lenticular screen3, the front panel4, and the Fresnel lens5were attached to the escutcheon7using a screw9and a presser plate8. However, the front plate4was located so as to incline through an angle θ1from a vertical surface A (that is, an upper part of the front plate4protrudes toward the front side F). The screen3was located on the rear side R of the front plate4. The Fresnel lens5was further placed on the rear side R of the screen3. Accordingly, the lenticular screen3was supported on the front plate4. However, as shown inFIG. 3, if the weight of the lenticular screen3per unit area is defined as w1, the lenticular screen3is pressed against the front plate4under a force w1sin θ1(in all the portions of the lenticular screen3). This makes it unlikely to create a space between the lenticular screen3and the front plate4. That is, the weight w1of the lenticular screen3can be divided into a component of force w1sin θ1and a component of force w1cos θ1. Here, the component of force w1sin θ1acts in the normal direction of the front plate4. The component of force w1cos θ1acts in the plane direction of the front plate4. The component of force w1sin θ1operates as a force that presses the lenticular screen3itself against the front plate4. The lenticular screen3, which is thin and not rigid, is in tight contact with the front plate4, which is very rigid, so as to rest against and adhere to the front plate4. This also applies to the Fresnel lens5. The Fresnel lens5is in tight contact with the front plate4via the lenticular screen3so as to rest against and adhere to the front plate4.

In the present example, the rear projection type projector device D2, shown inFIGS. 2 and 4, was produced. The front plate4was located so as to incline through an angle θ2from a vertical surface A (that is, a lower part of the front plate4protrudes toward the front side F). The Fresnel lens5was placed on the front side F of the front plate4. The lenticular screen3was further placed on the front side F of the Fresnel lens5. Accordingly, the Fresnel lens5was supported on the front plate4. However, as shown inFIG. 4, if the weight of the Fresnel lens5per unit area is defined as w2, the Fresnel lens5is pressed against the front plate4under a force w2sin θ2(in all the portions of the Fresnel lens5). This makes it unlikely to create a space between the Fresnel lens5and the front plate4. That is, the weight w2of the Fresnel lens5can be divided into a component of force w2sin θ2and a component of force w2cos θ2. Here, the component of force w2sin θ2acts in the normal direction of the front plate4. The component of force w2cos θ2acts in the plane direction of the front plate4. The component of force w2sin θ2operates as a force that presses the Fresnel lent5itself against the front plate4. The Fresnel lens5, which is thin and not rigid, is in tight contact with the front plate4, which is very rigid, so as to rest against and adhere to the front plate4. This also applies to the screen3. The screen3is in tight contact with the front plate4via the Fresnel lens5so as to rest against and adhere to the front plate4.

As described above in the embodiment and examples, according to the present invention, the screen member is placed and supported on the transparent member. This makes it unlikely to create a space between the screen member and the transparent member. It is thus possible to prevent a decrease in resolution and the distortion of an image, thus preventing the degradation of image quality.