JPH04310934A - Projection device, projection screen, illumination light source device, and external light shield hood - Google Patents

Abstract

PURPOSE:To improve the contrast of an image and appreciate the projection image in a bright room by setting the directions of two polarizing plates so that the reflection of illumination light on a screen surface is the least. CONSTITUTION:An illumination light source part provided with an illumination cover composed of a polarizing plate and a projection screen provided with a polarizing plate on an observation-side surface are included and the directions of both the polarizing plates 1 are so set that the reflection of the illumination light on the screen surface is the least. Further, the external light shielding hood which is provided at the peripheral part of the projection screen and consists of a polarizing plate and a projection screen provided with a polarizing plate on an observation-side surface are included, and the directions of both the polarizing plates 1 are so set that the reflection of illumination light on the projection screen is the least. Then a polarizing plate is provided on the observation-side surface of the projection screen. Therefore, the reflection factor of the screen surface to external light is extremely reduced, so the contrast of the image is improved and the sharp image can be appreciated in the bright room.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to optical devices for viewing rear or front projection televisions, OHP (overhead projectors), movies, microfilm readers, slides, etc. even in bright rooms. It is.

More specifically, the present invention relates to a projection device, a projection screen, an illumination light source device, and an external light shielding hood used for the projection screen to achieve the above object.

[0003] As used herein, the terms "projection device", "projection screen", "polarizing plate", "retardation plate", "observation side surface", and "illumination light source section" each have the following meanings. shall be taken as a thing.

"Projection device": means a device or system for projecting images, including an illumination light source section, a projection light source section, and a projection screen. "Projection screen": includes a transmissive screen and a reflective screen.

"Polarizing plate": means not only a plate-like polarizer but also a film-like and film-like polarizer, and includes a polarizing beam splitter. "Retardation plate": Includes not only plate-like media but also film-like and membrane-like media for providing a phase difference.

[0006] "Observation side surface": The observation side surface does not refer only to the outermost layer but to the surface layer. That is, it includes cases where a cured film, an antireflection film, etc. are additionally provided as the outermost layer. "Lighting light source": A general term for not only electric lights but also parts that emit light that brightens the room, such as the output part of a light guide, windows, and skylights.

[0007]

2. Description of the Related Art Projection screens are widely used for display purposes in projection televisions, microfilm readers, and the like. This kind of projection screen
The lens is equipped with a predetermined lenticular lens or the like on the entrance surface, the exit surface, or both the entrance surface and the exit surface so that it is bright when viewed from the observation side and the viewing angle is expanded. Normal.

On the other hand, in order to increase the contrast of the image on the projection screen and make it possible to view the projected image even in a bright room, it is proposed, for example, to provide a black stripe on the lenticular lens surface of the projection screen. 8
No. 0241 and Japanese Unexamined Patent Publication No. 2-136846.

[0009] Instead of using black stripes, it is also known to include a coloring agent in the screen substrate or to provide the screen with a canopy. It is also possible to simply use a polarizing plate as a screen plate, as disclosed in JP-A-63.
-4483, JP-A-63-267073, JP-A-2
-187738, Japanese Unexamined Patent Publication No. 2-210488, Japanese Utility Model Application No. 1-38886, and Japanese Utility Model Application No. 1-85778.

0010

[Problems to be Solved by the Invention] However, with conventional methods, it has been difficult to sufficiently increase the contrast of images. Furthermore, when trying to increase the contrast of an image, the loss of light quantity increases, resulting in a decrease in screen brightness.

[0011] Therefore, as a result of considering the above-mentioned drawbacks and proceeding with studies, the present invention attempts to solve the following problems:

(1) In the conventional method, when black stripes are used, it is generally difficult to reduce the external light reflection to 50% or less. (Note that if the amount of black stripes is increased in order to reduce the reflection of external light to 50% or less, problems such as optical path obstruction will occur.)

(2) When a colorant is used, reflection of external light can be reduced to some extent, but the total light transmittance is reduced. (Compared to the rate at which the image contrast improves,
The decrease in light intensity is too large. For example, if a colorant with a total light transmittance of 70% is used, the external light reflection intensity will be halved by 0.7 x 0.7 = 0.49 in the round trip of the light, but with a rear projection screen, the intensity will be reduced by 30%. % of the amount of light loss, and a front-type projection screen causes a loss of 51% of the amount of light. )

0
(3) Using a canopy or the like is effective in blocking direct sunlight, but is not very effective in suppressing reflection of external light and improving image contrast.

[0015]

[Means for Solving the Problems] The present invention first provides (1) an illumination light source section provided with an illumination cover made of a polarizing plate;
) Includes a projection screen with a polarizing plate on the observation side surface,
(3) To provide a projection device that can be used to view a projected image in a bright room, characterized in that the orientation of both of the polarizing plates is set in a direction that minimizes reflection of illumination light on the screen surface. This is what I am trying to do.

Next, the present invention includes (1) an external light shielding hood provided on the periphery of the projection screen and composed of a polarizing plate, and (2) a projection screen provided with a polarizing plate on the observation side surface. (3) A projection device that can be used to view a projected image in a bright room, characterized in that the orientation of both of the polarizing plates is set in a direction that minimizes reflection of illumination light on the screen surface. This is what we are trying to provide.

The present invention also provides a projection screen that can be used in a projection device for viewing projected images in a bright room, characterized in that a polarizing plate is provided on the observation side surface of the projection screen. It is something.

Further, the present invention provides an illumination light source device that can be used as an illumination light source for a projection device for viewing projected images in a bright room, which is characterized by having a lighting cover made of a polarizing plate. It is something.

Furthermore, the present invention provides an external light shielding hood for a projection screen that can be used in a projection device for viewing projected images in a bright room, and is characterized by being composed of a polarizing plate. It is.

As described above, the projection device of the present invention includes an illumination light source section provided with an illumination cover made of a polarizing plate, and a projection screen provided with a polarizing plate on the observation side surface, and the projection device includes a projection screen provided with a polarizing plate on the observation side surface. is set in the direction where the illumination light is least reflected on the screen surface.

[0021] In another embodiment of the projection device of the present invention,
It includes a hood for shielding external light, which is provided around the periphery of the projection screen and is made up of a polarizing plate, and a projection screen that has a polarizing plate on the observation side surface, and the orientation of both polarizing plates is determined by the illumination on the screen surface. Set in the direction that reflects the least amount of light.

In a preferred embodiment, a polarizing plate is also provided in the projection light source section of the projection screen, and the polarizing plate provided in the illumination light source section or the external light shielding hood and the polarizing plate provided in the projection screen are The direction of the screen is set so that the amount of light passing through the screen is maximized.

In the projection screen, a polarizing plate is provided on the observation side surface.

Furthermore, a polarizing beam splitter is used as the illumination cover of the illumination light source section or the polarizing plate of the projection light source section,
Moreover, an illumination light source section or a projection light source section may be used, which is formed so that the polarization direction of the reflected light is rotated by 90 degrees and the reflected light is combined with the straight light from the polarizing beam splitter.

In a projection device, a projection screen, an illumination light source device, and a hood for shielding external light, a polarizing plate may be used in combination with a retardation plate.

In a preferred embodiment, the projection light source section has a
A four-wavelength retardation plate is attached so that it can be rotated freely.

Next, we will explain the principle of the present invention, which has been found as a result of many studies, that is, the main reason why an image with excellent contrast can be obtained and the brightness of the screen does not decrease when the projection device of the present invention is used.

When two or more polarizing plates are overlapped and light is transmitted through them, the polarization angle by the polarizing plates is the same (
When the angles of polarization are perpendicular to each other (
(orthogonal), almost no light is transmitted.

This can also be understood from the graphs shown in FIGS. 1 and 2. The curves in Figures 1 and 2 have a light transmittance of approximately 40%.
, which shows the polarization characteristics of two types of commercially available standard polarizing plates with different characteristics, each having a degree of polarization of about 90%. T1 measures the relationship between the wavelength of light and transmittance when the two polarizing plates are stacked in parallel, and T2 measures the relationship between the wavelength of light and the transmittance when the two polarizing plates are stacked orthogonally. This is what was obtained.

By utilizing this phenomenon, (1) When indoor lighting hits the screen, use polarizing plates so that the above-mentioned orthogonal arrangement is established, so that virtually no illumination light enters the screen. For example, as shown in FIG. 3, when external light passes through a polarizing plate, the amount of light is reduced to about half, and becomes polarized light in one direction.

(2) When light from various projection light sources (projectors) hits the screen, use a polarizing plate to minimize the loss of light so that the above-mentioned parallel arrangement is achieved, especially in the case of liquid crystal projection televisions. Since polarizing plates have been used in projectors from the beginning, the basic idea is that by matching the polarization angle of the indoor lighting with the polarization angle of the projector, it is possible to extremely reduce the loss of light that occurs due to the use of polarizing plates. This is the first basic idea of the invention.

To explain this point more specifically, as shown in FIGS. 4 and 5, the observation side surface (front part) of the rear type or front type screen has a polarizing plate with a polarization angle of 90 degrees compared to the polarizing plate for indoor lighting. By installing another polarizing plate in a different direction, the reflectance of external light at the screen portion can be minimized. In other words, the light transmittance of a single polarizing plate is generally about 30 to 48%, but when two polarizing plates are stacked in an orthogonal arrangement, the light transmittance varies slightly depending on the degree of polarization. The ratio can be kept low to about 0.5 to 5%.

That is, the external light reflection intensity is (0.
005)2 to (0.05)2, which is almost zero. (However, this calculation is based on the assumption that there is no rotation of polarized light on the reflecting surface. In reality, polarized light rotates, but if it is corrected with a retardation plate or the like as described later, the result will be similar to this. )

In FIGS. 4 and 5, (1) is a polarizing plate, (2) is a lenticular lens, (3) is a Fresnel lens, (4) is a diffuse reflection layer, and (5) is a black stripe.

On the other hand, when two polarizing plates are stacked in the same direction, a transmittance of 85 to 90% can be ensured compared to a single polarizing plate.

[0036] In the liquid crystal projection television,
Since a polarizing plate is used inside, if the direction of the polarizing plate provided on the screen surface is set in the same direction as the polarizing direction, the amount of passing projection light can be reduced by 85 to 90% for the reason mentioned above.
It can be done.

[0037] In other words, while the light transmittance of a single polarizing plate is 30 to 48%, the light from an LCD projection television is transmitted by 85 to 90%, and the transmittance appears to increase. It is.

Next, it is well known that when light is reflected, its polarization state changes depending on its angle of incidence. Therefore, when using a reflective screen, mirror, reflective prism, etc., a correction mechanism such as a retardation plate is introduced depending on the degree of change in the polarization state, and the above-mentioned first basic concept of the present invention is implemented. The second way of thinking is to realize this in an ideal situation. (This can target both illumination and projection light sources).

Furthermore, in a full-scale polarizing plate, the light transmittance of the polarizing plate alone is generally 50% or less, and the remaining light is considered to be reflected or absorbed. As it is, the light utilization efficiency is too low, so the third idea of the present invention is to try to improve this.

As shown in FIG. 6, a polarizing plate is placed obliquely to the incident light to function as a beam splitter, and the polarization state of the reflected light is changed (using a phase difference plate, phase shift due to reflection, etc.). After turning the light by 90 degrees using an appropriate method, the light that has passed through the polarizing beam splitter is merged with the light with the same polarization state, thereby improving the efficiency of light utilization. This idea also applies to indoor lighting sources.
It can also be used as a projection light source.

[0041] Furthermore, by rotatably attaching an appropriate retardation plate such as a quarter-wave plate to the projection light source of a liquid crystal projection television, the polarization state can be corrected and adjusted according to the indoor conditions for viewing. The fourth idea of the present invention is to make it easier.

Commercially available products can be used as the projection television, projection screen, illumination light source, polarizing plate, external light shielding hood, retardation plate, etc. used in the projection apparatus of the present invention.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The projection device, projection screen, illumination light source device, and external light shielding hood of the present invention will be explained in more detail by way of embodiments.

[0044]

[Example 1] (Confirmation of the effects of the present invention) As shown in Fig. 7, a slide projector and a slide projector with a width of 2 m x height of 2 m were installed in a dark room.
Place a cloth reflective screen, and place a 30cm x 30cm neutral gray polarizing film made by Sanritz Co., Ltd., part number LL8312 (in the center of the screen).
A color photograph was pasted on the screen (120μ thick, 48% light transmittance, 84% polarization degree) and a color photograph was projected as a slide.

Then, I placed the same polarizing film as above (referred to here as a polarizing plate for illumination) in front of a powerful floodlight lamp that uses four AA batteries, and rotated the polarizing plate for illumination while illuminating the screen. saw.

In most areas where there is no polarizing film on the screen, the screen becomes whitish due to the influence of the floodlights no matter what direction the polarizing plate is in, and it is always difficult to see.
The area in the center of the screen where the polarizing film was stretched was at an angle where the influence of the flood lamp was not felt at all twice during one rotation of the polarizing plate for illumination.

Next, when I turned off the slide and conducted a similar experiment using only a floodlight and a polarizing plate for illumination, the situation became even clearer. In other words, the majority of areas on the screen where there was no polarizing film were whitish with the same brightness even during one rotation of the polarizing plate, but the polarizing plate in the center of the screen was There were places where the lighting turned completely black twice at exactly 180 degree intervals during one rotation of the polarizing plate for illumination.

[0048] This shows that even if there is illumination, the screen image will not be affected at all by an angle of 18.
It has been demonstrated that it exists at every 0 degrees.

[0049]

[Example 2] An experiment was conducted in an AV room with no windows, 8 m wide x 8 m deep, as shown in FIG.

[0050] Four illumination lights were prepared in which the same type of polarizing plate as used in Example 1 was cut into 20 cm diameter pieces and rotatably attached to the emission part of the halogen lamp, and these illumination lights were installed on the ceiling. It was attached at a position corresponding to each corner of a square of 3 m on a side.

[0051] A reflective screen made of cloth with a width of 2 m x a height of 2 m was installed on the wall opposite to the entrance, and on this surface, a roll length of 50 cm in width was wrapped with a polarizing plate of the same type as that used in Example 1. Cut each piece into 2m lengths and cut them into 4 pieces horizontally.
In other words, I pasted them together so that three seams were visible on the sides.

Next, the halogen lighting lamps were turned on one by one, and the direction of the polarizing plate of each lighting lamp was adjusted and fixed so that the screen would be completely black. As a result, it was possible to turn the screen completely black even when all four lights were turned on.

[0053] When we brought a liquid crystal projection television into the AV room prepared in this way, projected an image onto the above screen, and turned on and off the four lighting lights, the images looked the same, depending on whether there was room lighting or not. It felt almost unrelated. (Depending on the model of LCD projection TV, the color may change depending on the orientation of the polarizing plate when used in this way, based on the characteristics of its internal structure.)

[0054]

[Example 3] An overhead projector (OHP) was brought into the AV room of Example 2, and an image was projected in the same manner as in Example 2, and the lighting lights were made to blink. As in Example 2, the results showed that the image was hardly affected by the presence or absence of indoor lighting.

[0055]

[Example 4] A 50-inch rear projection TV manufactured by Mitsubishi Electric Corporation, model number LVP-508DC, was brought into the AV room of Example 2, and the screen exit surface (screen observation side surface) was 50 cm wide x long. Sa100
A neutral gray polarizing film manufactured by Sunritz Co., Ltd., product number LL9818 (thickness 180μ, light transmittance 48%, polarization degree 91%) was pasted on the screen, and the rest of the screen exit surface was intentionally left exposed. Oita.

In this example, since the projection television was placed directly in front of the reflective screen, there was no need to readjust the direction of the polarizing plate for the lighting cover.

[0057] When I flicked on and off the lighting while viewing images from a projection television, I was able to see clear images in the area where the polarizing plate was located, even under the lighting.
When there was a light, the image of the area without the polarizer became whitish and difficult to see.

[0058]

[Effects of the Invention] When the projection device or projection screen of the present invention is used, the reflectance of external light on the screen surface can be extremely reduced, so the contrast of the image is considerably improved, making it possible to enjoy clear images even in a bright room. becomes possible.

[0059]

[Brief explanation of drawings]

[Figure 1] and

FIG. 2 is a graph showing optical characteristics of a polarizing plate.

FIG. 3 is an explanatory diagram showing how external light is transmitted when a polarizing plate is used.

FIG. 4 is a schematic cross-sectional view of a rear projection screen provided with a polarizing plate.

FIG. 5 is a schematic cross-sectional view of a front projection screen provided with a polarizing plate.

FIG. 6 is an explanatory diagram showing the principle of improving the light utilization efficiency using a polarizing beam splitter.

FIG. 7 is a schematic explanatory diagram of a projection device or system used to confirm the effects of the projection device of the present invention.

FIG. 8 is a schematic explanatory diagram showing one projection device or system of the present invention.

[Explanation of sign]

1 Polarizing plate 2. Lenticular lens 3 Fresnel lens 4 Diffuse reflective layer 5 Black stripe

Claims (14)

[Claims] Claim 1: (1) includes an illumination light source section provided with an illumination cover made of a polarizing plate; (2) a projection screen provided with a polarizing plate on the observation side surface; (3) the orientation of both the polarizing plates is A projection device that can be used to view projected images in a bright room, characterized in that the projection device is set in a direction that minimizes reflection of illumination light on the screen surface. Claim 2: (1) a hood for shielding external light provided on the periphery of the projection screen and composed of a polarizing plate; (2) a projection screen provided with a polarizing plate on the observation side surface; ) A projection device that can be used to view a projected image in a bright room, characterized in that the polarizing plates are oriented in a direction that minimizes reflection of illumination light on the screen surface. 3. The projection light source section is also provided with a polarizing plate, and the relative orientation with respect to both of the polarizing plates is set so that the amount of light passing through the screen is maximized.
Or 2 projection device. 4. The projection device according to claim 1, wherein the polarizing plate is used in combination with a retardation plate. 5. A projection screen that can be used in a projection device for viewing projected images in a bright room, characterized in that a polarizing plate is provided on the observation side surface of the projection screen. 6. The projection screen according to claim 5, wherein the polarizing plate is used in combination with a retardation plate. 7. An illumination light source device that can be used as an illumination light source for a projection device for viewing projected images in a bright room, characterized by having a illumination cover made of a polarizing plate. 8. The illumination light source device according to claim 7, wherein the polarizing plate is used in combination with a retardation plate. 9. A hood for shielding external light, which can be used in a projection device for viewing projected images in a bright room, characterized by comprising a polarizing plate. 10. The external light shielding hood according to claim 9, wherein the polarizing plate is used in combination with a retardation plate. 11. A polarizing beam splitter is used as the illumination cover, and the illumination light source section is configured to rotate the polarization direction of the reflected light by 90 degrees so that the reflected light is combined with the straight light from the polarized beam splitter. 2. The projection device according to claim 1, wherein a projection device is formed. 12. A polarizing beam splitter is used as the polarizing plate of the projection light source, and the polarization direction of the reflected light is rotated by 90 degrees so that the reflected light is combined with the straight light from the polarizing beam splitter. 5. The projection device according to claim 3, further comprising a projection light source section. 13. A polarizing beam splitter is used as the polarizing plate, and the polarization direction of the reflected light is rotated by 90 degrees.
9. The illumination light source device according to claim 7, wherein the illumination light source section is formed so that the reflected light is combined with the straight light from the polarizing beam splitter. 14. The projection apparatus according to claim 4, wherein a quarter-wavelength retardation plate is rotatably attached to the projection light source section.