JP2008015242A - Rear projection screen and rear projection display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projection screen capable of preventing image quality from degrading due to reflection of outdoor light and to provide a rear projection display apparatus. <P>SOLUTION: The rear projection screen 1 has a Fresnel lens sheet 11. The optical center of the Fresnel lens sheet 11 is at a position eccentric in an upward direction from the center of the rear projection screen 1. In the mounted state of the rear projection screen 1, the amount by which the optical center is eccentric is 10% or more to the width in the vertical dimension. The rear projection display apparatus has such a rear projection screen 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rear projection type screen and a rear projection type display device.

  2. Description of the Related Art Conventionally, there is a rear projection type projection television as an apparatus for observing an image by enlarging and projecting image light from an image projection device from the back onto a screen. As a video projection apparatus, there is a CRT type, and in recent years, a micro display such as a liquid crystal display (LCD) or a micro mirror device (DMD) is also used.

  The rear projection type screen has a configuration in which two sheets of a Fresnel lens sheet and a lenticular lens sheet are overlapped. Furthermore, a front sheet may be provided on the observation side. These screen sheets are often mixed with a light diffusing material for the purpose of reducing ghost light or for widening the viewing angle. In order to prevent a decrease in contrast due to external light reflection, a light-shielding pattern, so-called black stripe, is provided on the observation side of the lenticular lens sheet.

  The lens sheet on which the rear projection type screen is superimposed is used by being mounted on a frame or the like of the display device set. The usage pattern of such a screen will be described with reference to FIG. FIG. 10A is a side view of the screen observed from the lateral direction, and FIG. 10B is a top view of the screen observed from above (ceiling). As shown in FIG. 10A, in general, the rear projection type screen is used indoors, and the indoor lighting is often arranged on the ceiling. The outside light from the room illumination enters the screen from above the observer and is reflected by the Fresnel lens. Since the Fresnel lens is a convex lens on the observation side, external light incident on the upper part of the screen is reflected toward the vicinity of the position of the observer on the upper part of the screen. On the other hand, the external light incident on the central part or the lower part is reflected downward from the position of the observer at the central part or the lower part, and is not reflected toward the observer.

  As shown in FIG. 10B, since the Fresnel lens is a lens convex to the observation side, external light is reflected near the position of the observer at the center of the screen. On the other hand, external light incident on the left and right ends is reflected rightward or leftward from the observation position at these left and right ends. Further, when the external light reflected in the rightward or leftward oblique direction is incident on the lenticular lens, a part of the light beam is blocked by the light shielding pattern.

  Thus, as shown in FIG. 11, when an observer views the screen from the front, a portion where external light reflection is conspicuous under indoor lighting on the ceiling (hereinafter, sometimes referred to as out-of-frame light reflection). Is observed only near the center of the screen. Since this occurs at the center of the screen or at a position that is horizontally upward from this position, this conspicuous reflection from the forehead is a serious problem in viewing the video. As a result, the image quality of the rear projection display device is greatly reduced.

  On the other hand, there is a technique for deflecting the emission angle by shifting the projection system optical axis of the projection lens and the optical axis of the Fresnel lens. For example, Patent Document 1 discloses a technique using a Fresnel lens sheet whose optical center is decentered upward. In this technique, incident light is incident obliquely on the entire surface of the Fresnel lens, and the outgoing direction of the incident light is also deflected upward. In addition, this technology proposes such a configuration in order to reduce the viewing angle dependency and realize a vivid display.

Further, for example, Patent Document 2 discloses a configuration in which a Fresnel lens is decentered upward in a rear projection screen combining a lenticular lens, a Fresnel lens, and a linear Fresnel lens. In this technique, oblique incident light is deflected by a linear Fresnel lens, and parallel light is emitted to the Fresnel lens. Also, this technology proposes such a configuration in order to reduce the vertical height of the screen.
Japanese Utility Model Publication No. 60-129780 JP-A-5-333432

As described above, in the conventional rear projection type screen, external light reflection from room illumination is observed near the center of the screen, so that the screen is difficult to see depending on the observer viewed from the front, and the image quality is degraded. is there.
The present invention has been made in view of such a problem, and an object of the present invention is to provide a rear projection type screen and a rear projection type display device capable of preventing image quality from being deteriorated by external light reflection. .

The rear projection screen according to the present invention is a rear projection screen provided with a Fresnel lens sheet, the optical axis of the Fresnel lens sheet coincides with the optical axis of a projection lens for projecting video light, The optical center of the Fresnel lens sheet is arranged at a position deviated upward from the center of the rear projection type screen, and the amount of decentration is 10% with respect to the width in the vertical direction with the rear projection type screen attached. That's it.
In such a configuration, the peak of reflection outside the forehead can be shifted upward, so that the reflection of outside light from the interior lighting can be made inconspicuous. Therefore, it is possible to prevent the image quality from being deteriorated by external light reflection.

  Further, the projection light is incident at right angles to the sheet surface at the optical center of the Fresnel lens sheet. Thereby, the emitted light from a Fresnel lens sheet can be made into parallel light.

On the other hand, the rear projection screen according to the present invention is a rear projection screen provided with a Fresnel lens sheet, and the optical center of the Fresnel lens sheet is arranged at a position deviated upward from the center of the rear projection screen. The projected light is incident at a right angle to the sheet surface at the optical center of the Fresnel lens sheet.
In such a configuration, the peak of reflection outside the forehead can be shifted upward, so that the reflection of outside light from the interior lighting can be made inconspicuous. Therefore, it is possible to prevent the image quality from being deteriorated by external light reflection.

  Preferably, the amount of eccentricity is 15% or more with respect to the width in the vertical direction with the rear projection screen attached. Thereby, external light reflection can be made more inconspicuous.

  More preferably, the amount of eccentricity is 25% or more with respect to the width in the vertical direction with the rear projection screen attached. Thereby, external light reflection can be made more inconspicuous.

  More preferably, the amount of eccentricity is 35% or more with respect to the width in the vertical direction with the rear projection screen attached. Thereby, it can prevent reliably that external light reflection is conspicuous.

  Furthermore, the amount of eccentricity is 50% or less with respect to the width in the vertical direction with the rear projection screen attached. Thereby, the emitted light from a Fresnel lens sheet can be made into parallel light more reliably.

The rear projection display device according to the present invention includes such a rear projection screen.
In such a configuration, the peak of reflection outside the forehead can be shifted upward, so that the reflection of outside light from the interior lighting can be made inconspicuous. Therefore, it is possible to prevent the image quality from being deteriorated by external light reflection.

  Furthermore, the rear projection type display device according to the present invention includes a projection device that projects image light onto the rear projection type screen, and the optical axis of the projection lens of the projection device is the optical axis of the Fresnel lens sheet. Match.

  According to the present invention, it is possible to provide a rear projection type screen and a rear projection type display device that can prevent image quality from being deteriorated due to external light reflection.

The best mode for carrying out the present invention will be described below with reference to the drawings.
First, the configuration of a rear projection type screen according to the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a structural example of a rear projection screen according to the present invention. Here, FIG. 1 is a schematic view of the rear projection screen observed from the side.
As shown in FIG. 1, the rear projection screen 1 includes a Fresnel lens sheet 11, a lenticular lens sheet 12, and a front sheet 13. A Fresnel lens sheet 11, a lenticular lens sheet 12, and a front sheet 13 are sequentially arranged from the image light projection side to the image light emission side.

  The Fresnel lens sheet 11 is an example of an optical sheet having a function of collecting incident light in the direction of an observer. The Fresnel lens sheet 11 has a Fresnel lens 112 on one surface of a base material 111, and the Fresnel lens 112 is composed of a sawtooth-shaped Fresnel lens with a sharp tip. The Fresnel lens 112 is uneven toward the image light emitting side.

The lenticular lens sheet 12 is an example of an optical sheet having a function of diffusing light emitted from the Fresnel lens sheet 11 in the horizontal direction and the vertical direction. The lenticular lens sheet 12 has a lenticular lens 122 on one surface of a base material 121, and the lenticular lens 122 is formed of a bowl-shaped convex lenticular lens. The lenticular lens 122 is uneven toward the image light projection side. Accordingly, the lenticular lens 122 of the lenticular lens sheet 12 faces the Fresnel lens 112 of the Fresnel lens sheet 11.
The light shielding pattern 123 that blocks light is arranged in parallel on a flat surface opposite to the lens surface of the lenticular lens 122, and is formed in a non-condensing region where image light does not pass.
The front sheet 13 has a function of diffusing emitted light and protecting the front surface of the screen. The front sheet 13 is laminated on the surface of the light shielding pattern 123 via an adhesive or adhesive for optical use.

Next, the rear projection type screen 1 according to the present invention will be described in detail with reference to FIG. FIG. 2 shows only the Fresnel lens sheet 11 in the rear projection screen 1 according to the present invention, and the lenticular lens sheet 12 and the front sheet 13 are omitted for easy understanding of the features of the present invention.
As shown in FIG. 2, the optical center of the Fresnel lens sheet 11 is deviated from the center of the rear projection screen 1. Specifically, the optical center of the Fresnel lens sheet 11 is decentered upward from the center of the rear projection screen 1 in a state where the rear projection screen 1 is attached.

  The amount of eccentricity of the optical center of the Fresnel lens sheet 11 can be 10% or more of the height in the vertical direction of the screen with the rear projection screen 1 attached. That is, the amount of eccentricity can be set to 10% or more of the vertical width of the screen in order to avoid that the forehead light reflection is clearly noticeable. The amount of eccentricity can be preferably 15% or more of the screen vertical width, more preferably 25% or more of the screen vertical width. In this case, the out-of-frame light reflection can be made less noticeable. Furthermore, the amount of eccentricity is preferably 35% or more of the screen vertical width, and in this case, the reflection of the extraneous light can be made inconspicuous.

  Further, the amount of eccentricity is preferably 50% of the vertical width of the screen in consideration of a decrease in transmittance at the peripheral portion of the Fresnel lens sheet 11, particularly at the left and right ends of the lower portion of the sheet. In general, it is preferable that the outgoing side focal length of the Fresnel lens sheet 11 is infinite, that is, the outgoing light beam is parallel light. Since the Fresnel lens sheet 11 in the present invention is decentered, the configuration in which the emitted light is collected is not preferable because the emitted light is deflected and the vertical viewing angle is biased. Therefore, the amount of eccentricity is preferably 50% or less of the screen vertical width.

  The optical axis of the Fresnel lens sheet 11 coincides with the projection system optical axis. Here, the projection system optical axis is a substantial optical axis of the projection lens provided in the projection device 20. For example, when a reflection sheet or the like that changes the direction of the projection light is disposed between the projection device 20 and the Fresnel lens sheet 11, the optical axis of the projection lens disposed at a virtual position. In other words, the coincidence of the optical axis of the Fresnel lens sheet 11 and the projection system optical axis indicates that the projection light is incident at a right angle to the sheet surface at the optical center of the Fresnel lens sheet 11.

  In the rear projection type screen 1 according to the present invention, the projection light emitted from the projection device 20 is incident on the entire surface of the Fresnel lens sheet 11. Specifically, at the optical center of the Fresnel lens sheet 11, the projection light is incident on the sheet surface at a right angle, and is emitted through an optical path perpendicular to the sheet surface. On the other hand, when the incident light is incident on the side where the optical center is decentered in the Fresnel lens sheet 11, the incident light is refracted by the Fresnel lens 112 disposed at a position close to the optical center and refracted in the Fresnel lens 112. While exiting. On the other hand, when the light enters the side opposite to the side where the optical center is decentered in the Fresnel lens sheet 11, the light is incident while being refracted by the Fresnel lens 112 arranged at a position far from the optical center, and is refracted in the Fresnel lens 112. Exit.

  At this time, the projection light incident at a position far from the optical center of the Fresnel lens sheet 11 is refracted and emitted so as to have a smaller angle than the projection light incident at a position near the optical center. In other words, the projection light is largely refracted as the position of the Fresnel lens 11 on which the projection light is incident moves away from the optical center of the Fresnel lens sheet 11. Thereby, when the Fresnel lens sheet 11 and the projection optical axis coincide, the projection light is emitted from the Fresnel lens sheet 11 as parallel light.

  As described above, the rear projection screen 1 according to the present invention decenters the optical center of the Fresnel lens sheet 11 as a result of considering the position and viewing position of the external light source, the angle of the Fresnel lens, and the like. As a result, the position of the forehead light reflection can be shifted from the center of the screen, and the amount of reflection can be suppressed. In particular, the optical center of the Fresnel lens sheet 11 can be decentered upward. In this case, the amount of reflection outside the forehead by the indoor lighting installed on the ceiling can be shifted upward to suppress the amount of reflection. In this way, it is possible to prevent the image quality from being deteriorated due to external light reflection.

FIG. 3A shows a configuration example of a conventional Fresnel lens sheet. As shown in FIG. 3 (a), a technique for deflecting the emission angle by generally shifting the projection system optical axis and the optical axis of the Fresnel lens sheet is known. In this technique, since the projection optical axis and the Fresnel optical axis do not coincide with each other, the outgoing light is deflected upward, so that the vertical viewing angle is biased upward.
For example, Patent Document 1 discloses a technique using a Fresnel lens sheet whose optical center is decentered upward. In this technique, incident light is incident obliquely on the entire surface of the Fresnel lens, and the outgoing direction is also deflected upward. Therefore, similarly to the configuration shown in FIG. 3A, the emitted light is changed and the vertical viewing angle is biased.
On the other hand, as shown in FIG. 2, in the rear projection screen 1 according to the present invention, the optical axis of the projection system and the optical axis of the Fresnel lens sheet 11 coincide. Therefore, the emitted light can be emitted perpendicular to the screen plane, and the vertical viewing angle can be prevented from being biased.

Further, in the Fresnel lens sheet shown in FIG. 3A, in consideration of adverse effects such as distortion, the amount of eccentricity in the Fresnel lens sheet is within about 5% of the height in the vertical direction of the screen. In this case, the effects of the present invention as described above cannot be exhibited, and deterioration in image quality due to external light reflection cannot be prevented.
Patent Document 2 discloses a configuration in which a Fresnel lens is decentered upward in a screen combining a lenticular lens, a Fresnel lens, and a linear Fresnel lens. FIG. 3B shows an example of this configuration. In this technique, oblique incident light is deflected by a linear Fresnel lens, and parallel light is emitted to the Fresnel lens. However, it is different from the configuration in which the projection optical axis and the Fresnel optical axis coincide with each other as in the present invention. The amount of eccentricity is not clear.

ただしθは垂直方向の拡散角、ａ＝０．００２２、ｂ＝１．８５、ｃ＝２．７である（図６参照）。 FIG. 4 shows an arrangement configuration of the rear projection type screen 1 in the present embodiment, FIG. 4 (a) is a schematic side view, and FIG. 4 (b) is a schematic top view. In this example, the intensity of reflection outside the forehead when the rear projection type screen 1 is arranged and observed as shown in FIGS. 4A and 4B was simulated. Here, the simulation was performed by changing various illumination positions, illumination intervals, illumination heights, and Fresnel eccentricity. Conditions common to each of these simulations are as follows.
<Common conditions>
Center height of screen screen: Equal to viewing height, 1.1 (m)
Screen observation position: Screen center front view position: 3.0 (m) from the screen
Screen vertical dimension: 800 (mm)
External light source: Three small area light sources are arranged at equal intervals. The light distribution characteristic is a circle in contact with the light source as shown in FIG. 5 and is maximum when φ = 0 ° and becomes zero when φ = ± 90 °.
Screen vertical diffusion characteristic: The diffusion characteristic represented by the formula (1) is shown for the entire screen on the observation side from the Fresnel lens sheet. The vertical diffusing action was taken into account when entering from the observation side and when reflecting from the Fresnel lens surface and exiting to the observation side.

Where θ is the vertical diffusion angle, a = 0.0002, b = 1.85, and c = 2.7 (see FIG. 6).

ただし、ｒ：光学中心からの距離（ｍｍ）、Ａ２、Ａ４、Ａ６、Ａ８、Ａ１０は以下の表に示された係数である。

The Fresnel lens shape is a shape represented by Equation (2).

However, r: distance (mm) from the optical center, A2, A4, A6, A8, and A10 are coefficients shown in the following table.

Reflected light intensity calculation: A light ray in a plane passing through the center in the horizontal direction of the screen was taken into consideration.
A light beam emitted from each external light source is diffused and transmitted through the screen, reflected by the Fresnel lens surface, and then diffused again to the viewer side to be emitted, and a reflected light intensity distribution is calculated.
Then, the intensity at a position on a straight line passing through the central portion in the horizontal direction of the screen, which is emitted in the direction of the viewing position, is expressed from the reflected light intensity distribution.

<Example 1> (In a general household)
Lighting height: 3.3 (m)
Viewing distance: 2.0 (m)
Illumination position: 1.0 (m)
Lighting interval: 1.0 (m)

<Example 2> (In the case of a hall with a high ceiling)
Illumination height: 4.0 (m)
Viewing distance: 3.0 (m)
Lighting position: 2.0 (m)
Lighting interval: 2.0 (m)

For Examples 1 and 2, the results of calculating the Fresnel eccentricity from 0 (mm) to 300 (mm) upward every 50 (mm) are shown in FIGS. In addition, the perspective schematic view of FIG. 7 shows the positional relationship between the screen and the intensity of the forehead light reflection three-dimensionally.
As can be seen from FIGS. 8 and 9, when the shift amount is 0 (mm), a peak of the forehead reflection intensity distribution appears near the center of the screen. On the other hand, when the shift amount is 100 (mm) and 13% of the height in the vertical direction of the screen, the peak is greatly deviated from the center of the screen, so that it becomes difficult to notice.
When the shift amount is 150 (mm) and 19% of the height in the vertical direction of the screen, the peak deviates more from the center of the screen, and part of the forehead reflection intensity distribution is outside the screen, so the forehead is more conspicuous. Hateful.
When the shift amount is 200 (mm) and 25% of the height in the vertical direction of the screen, the peak is at the top edge of the screen, and many parts of the forehead reflection intensity distribution are outside the screen, so the forehead is even more noticeable. Hateful.
When the shift amount is 300 (mm) and the height in the vertical direction of the screen is 38%, the forehead is hardly noticeable because most of the forehead reflection intensity distribution is outside the screen.

  In consideration of such an effect of suppressing the reflection of out-of-frame light, when the vertical width of the screen is 800 (mm), the amount of eccentricity is preferably 150 mm above the screen, and more preferably 200 mm or more. In consideration of a decrease in transmittance in the peripheral part of the Fresnel lens (particularly, the lower left and right ends), the amount of eccentricity is preferably 400 mm or less.

  As described above, the optical axis of the projection system coincides with the Fresnel optical axis, the optical center of the Fresnel lens is decentered upward from the center of the screen, and the amount of decentering is 10% or more of the height in the vertical direction of the screen. As a result, the intensity of reflection outside the forehead could be suppressed.

It is a cross-sectional schematic diagram which shows one structural example of the rear projection type screen which concerns on this invention. It is a cross-sectional schematic diagram which shows one structural example of the rear projection type screen which concerns on this invention. It is a cross-sectional schematic diagram which shows one structural example of the conventional rear projection type screen. It is a schematic diagram which shows an example of the arrangement configuration of the rear projection type screen which concerns on this invention. It is a graph which shows an example of the light distribution characteristic of the illumination light source in the rear projection type screen which concerns on this invention. It is a graph which shows an example of the diffusion characteristic of the diffusion plate in the rear projection type screen which concerns on this invention. It is a schematic diagram which shows an example of the intensity | strength of out-of-frame light reflection in the rear projection type screen which concerns on this invention. It is a graph which shows an example of the intensity | strength of the forehead light reflection in the rear projection type screen which concerns on this invention. It is a graph which shows an example of the intensity | strength of the forehead light reflection in the rear projection type screen which concerns on this invention. It is a schematic diagram which shows an example of the arrangement configuration of the conventional rear projection type screen. It is a schematic diagram which shows an example of the forehead light reflection in the conventional rear projection type screen.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Back projection type screen, 11 ... Fresnel lens sheet, 111 ... Base material, 112 ... Fresnel lens, 12 ... Lenticular lens sheet, 121 ... Base material, 122 ... Lenticular lens, 123 ... Light-shielding pattern, 13 ... Front sheet

Claims (9)

A rear projection screen equipped with a Fresnel lens sheet,
The optical center of the Fresnel lens sheet is arranged at a position deviated upward from the center of the rear projection screen,
The amount of eccentricity is 10% or more with respect to the width | variety of a perpendicular direction in the state in which the said rear projection type screen was attached.   The rear projection screen according to claim 1, wherein the projection light is incident at a right angle to the sheet surface at the optical center of the Fresnel lens sheet. A rear projection screen equipped with a Fresnel lens sheet,
The optical center of the Fresnel lens sheet is arranged at a position deviated upward from the center of the rear projection screen,
The projection light is a rear projection screen that is incident at a right angle to the sheet surface at the optical center of the Fresnel lens sheet.   The rear projection screen according to any one of claims 1 to 3, wherein the amount of eccentricity is 15% or more with respect to a width in a vertical direction in a state where the rear projection screen is attached.   The rear projection screen according to any one of claims 1 to 3, wherein the amount of eccentricity is 25% or more with respect to a width in a vertical direction in a state where the rear projection screen is attached.   The rear projection screen according to any one of claims 1 to 3, wherein the amount of eccentricity is 35% or more with respect to a width in a vertical direction in a state where the rear projection screen is attached.   The rear projection screen according to any one of claims 1 to 3, wherein the amount of eccentricity is 50% or less with respect to a width in a vertical direction in a state where the rear projection screen is attached.   A rear projection display device comprising the rear projection screen according to claim 1. A projection device for projecting image light onto the rear projection screen;
9. The rear projection type display device according to claim 8, wherein an optical axis of a projection lens of the projection device coincides with an optical axis of the Fresnel lens sheet.

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