JP2006011176A - Screen for rear projection display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screen for a rear projection display which is provided with simplicity of manufacturing, inexpensiveness of manufacturing cost and image display characteristics of high quality, and can realize a markedly thin shape. <P>SOLUTION: The screen for the rear projection display consists of a diffusion film 2 for diffusing 60% and more of light, made incident at an optional angle in an incident permission angle area (α to β) into a diffusion angle area and a light-outgoing direction control element 1, and 70% and more of projector light whose outgoing direction is controlled by the light-outgoing direction control element 1 satisfies the condition of the outgoing angle θp from the light-outgoing direction control element 1, i.e. (180°-β)≤θp≤(180°-α). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen for a rear projection display, and more particularly to a screen for a rear projection display that can be manufactured easily, has a low manufacturing cost, has high-quality image display characteristics, and can achieve a dramatic reduction in thickness. About.

  In the present specification, as shown in FIG. 7, the reference sign of the angle is a reference line (0 °) below the origin of the orthogonal coordinate vertical axis (corresponding to the screen surface), and is clockwise with respect to the reference line on the incident side. The angle is defined as positive, and the counterclockwise angle with respect to the reference line is defined as positive on the output side.

  The prior art relating to the screen for rear projection display includes the following types I to III.

  (Type I) As a rear projection display screen capable of diffusing projector light incident from a steep angle in the direction of the observer, as shown in FIG. A screen using a prism array 10 that produces an effect equivalent to that of a Fresnel lens, a lenticular lens 11 that is a horizontal diffusion medium, and a fine particle or rough surface diffusion medium 12 that is a vertical diffusion medium (for example, Non-Patent Document 1). Are widely used. Projector light (projection light from the projector 20) enters the screen from the light emission direction control element 10 side.

However, in this screen, the projector light incident angle on the lenticular lens 11 must be vertical, and the conditional expression that the light exit angle θp from the light exit direction control element 10 must satisfy is:
θp = 90 °
Therefore, there is a problem that the light emission direction control element 10 requires strict light emission direction control.

  In addition, there is a limit to the angle of light that can be bent by the light emission direction control element 10, and the projector light incident angle to the light emission direction control element 10 is limited, which is a big factor for thinning the optical system. It is a problem.

  Further, since an air layer exists between the lenticular lens 11 and the light emission direction control element 10 due to the surface shape of the lenticular lens 11, an image ghost is generated due to complex multiple reflection at the air layer interface, and the use efficiency of the projector light is reduced. In addition, there is a problem that the contrast ratio is lowered due to backscattering of external light. In general, an air layer is provided between the lenticular lens 11 and the light emitting direction control element 10, but even if this air layer is filled with a transparent medium having a refractive index n, an interface exists and complicated multiple reflection occurs. That is no different.

  (Type II) A rear projection display using a Fresnel lens as a light emission direction control element and a fine particle or rough surface diffusion medium 13 as a diffusion medium has been proposed (for example, see Non-Patent Document 2).

In the case of this method, the allowable angle region of incident light can be designed widely. That is, if the allowable angle region of incident light is θf-min to θf-max, the conditional expression that the projector light emission angle θp from the Fresnel lens 9 must satisfy as shown in FIG.
(180 ° −θf-max) ≦ θp ≦ (180 ° −θf-min)
Is described. Therefore, the angular width in the light emission direction required for the Fresnel lens 9 is much wider than that of the screen using the lenticular lens 11, and the design conditions and accuracy of the Fresnel lens are greatly relaxed.

  In addition, since the conditions that θp must satisfy are loose, the limitation on the projector light incident angle on the Fresnel lens 9 is relaxed compared to a screen using the lenticular lens 11, and the optical system can be made thinner. it is conceivable that.

  Further, by using the light emission direction control element 10 instead of the Fresnel lens 9, a screen having no air interface with the diffusion medium 13 can be formed. It is possible to avoid problems due to multiple reflections of light.

However, in this screen, in order to widen the diffusion angle region, it is necessary to increase the fine particle density in the fine particle diffusion medium, to increase the fine particle diameter, or to roughen the surface roughness of the rough surface diffusion medium. In principle, it is very difficult to realize a high-quality rear projection display due to problems such as blurring, a decrease in projector light utilization efficiency, and a decrease in contrast ratio due to an increase in external light backscattering.
(Type III) A screen for a rear projection display using a diffusion film that uniformly diffuses light incident from a specific angle region (hereinafter referred to as an allowable incidence angle region) into the diffusion angle region is proposed (for example, see Patent Document 1). In view of the high quality of the displayed image and the uniformity of the diffused light intensity distribution characteristics, expectations are high.

However, at present, the angle range in which projector light is allowed to enter the screen is about 65 ° to 115 °, and the future ultra-thin rear projection in which the projector light incident angle with respect to the screen is very steep. It is not sufficient as a screen constituting a display.
International Publication WO2004 / 034145 Shikama, S.et al.SID02 DIGEST p.1250-1253 http://nippra.com/html/news/news 2003 01.html

  As described above, a conventional high-definition rear projection display screen using a type I light emission direction control element requires strict light emission direction control in the light emission direction control element, and thus the shape becomes complicated. Difficult to manufacture, increase manufacturing cost, limit light output direction control element can be bent, limit optical system thinning, and control light output direction There has been a problem that display image quality is deteriorated due to complicated multiple reflection of projector light and external light due to an air layer interface between the element and the lenticular lens.

  In addition, Type II conventional technology has a problem that it is difficult in principle to realize a high-quality rear projection display in order to relax the conditions that the projector light emission angle must satisfy. The prior art has a problem that it is difficult to achieve a sufficient thickness reduction.

  The present invention provides a rear projection display screen that solves the above-described problems of the prior art, has both ease of manufacturing, low manufacturing cost, and high-quality image display characteristics, and can achieve a dramatic reduction in thickness. For the purpose.

  In order to solve the above problems, in the present invention, while maintaining high-quality image display characteristics, a moderate width is provided in the allowable angle of incidence area for the screen, which has conventionally been required to be strictly controlled, thereby controlling the light emission direction. A rear projection display system has been devised that has a width that satisfies the condition that the projector light emission angle θp from the element must be satisfied.

  Furthermore, in order to further improve the image display characteristics, there is no air layer between the light output direction control element and the diffusion medium in order to eliminate multiple reflection of projector light and external light at the interface inside the screen. A rear projection display system was devised.

  In order to satisfy such a condition, in the present invention, as shown in FIG. 1, a diffusion film 2 that diffuses and transmits 60% or more of light incident at an arbitrary incident angle within the allowable angle range of incidence into the diffusion angle region, And a light emitting direction control element (for example, a prism array, a Fresnel lens, a hologram, a mirror array, etc.) designed to emit most of the projector light by changing the angle so as to be incident on the incident allowable angle region of the diffusion film 2 ) 1 is used to form a screen, and further, since there is no air layer between the light emitting direction control element 1 and the diffusion film 2, a screen having no air interface inside the screen is formed. I thought of that.

That is, the present invention is as follows.
(Invention Item 1) A light emitting direction control comprising a diffusion film and a light emitting direction control element for diffusing 60% or more of light incident at an arbitrary angle within an incident allowable angle region (α to β) into a diffusion angle region. 70% or more of the projector light whose emission direction is controlled by the element is a condition of the emission angle θp from the light emission direction control element (180 ° −β) ≦ θp ≦ (180 ° −α)
A rear projection display screen characterized by satisfying the above requirements.
(Invention 2) The screen for a rear projection display according to Invention 1, wherein there is no air interface between the light emission direction control element and the diffusion film.
(Invention 3) A rear projection display using the screen according to Invention 1 or 2.

  According to the present invention, it is possible to obtain a screen for a rear projection display that has both ease of manufacturing, low manufacturing cost, and high-quality image display characteristics, and can realize a dramatic reduction in thickness. By using the screen, a rear projection display with a significantly reduced thickness can be obtained.

  FIG. 2 is a vertical sectional view showing an example of the screen of the present invention. In this configuration, the light emission direction control element 1 is a prism array, and the diffusion film 2 diffuses and transmits 60% or more of light incident at an arbitrary angle within the allowable incidence angle region θf = α to β as the diffusion medium to the diffusion angle region. The screen is configured using

At this time, the conditional expression of the projector light emission angle θp from the prism array is described as (180 ° −β) ≦ θp ≦ (180 ° −α).

  Here, since the projector light incident from an angle not satisfying the conditional expression is not diffusely reflected in the direction of the observer, 70% or more of the projector light incident on the light emission direction control element 1 is increased in order to improve the utilization efficiency of the projector light. It is necessary to satisfy the conditional expression.

  In addition, when the ratio of light that is incident at an arbitrary angle within the allowable incident angle region is diffused and transmitted to the diffusion angle region is less than 60%, the effect of the present invention does not appear remarkably. Limited.

  Thus, in the light control method of the screen of the present invention (the method of the present invention), the light emission direction control required for the light emission direction control element is not as strict as the conventional method. Therefore, it is possible to obtain a high-definition rear projection display screen that is low in manufacturing cost and has high-quality image display characteristics.

  In addition, since the condition of θp has a width, when the change in the incident angle θps shown in FIG. 2 with respect to the light output direction control element of the projector light is small on the entire screen, it cannot be realized by the conventional control. In addition, it is possible to realize a high-quality rear projection display screen using a light emission direction control element having the same light emission direction control characteristics over the entire screen. In this case, as compared with the case where the light emission direction control element whose characteristics have to be changed for each place is used, the ease of manufacturing and the low manufacturing cost are dramatically improved.

  Furthermore, although there is a limit to the light traveling angle that can be bent by the light emitting direction control element, in the conventional method, the projector light must be bent at θp = 90 °, whereas in the method of the present invention, Since the allowable incident angle region has a width, the conditional expression is satisfied if it is bent to θp ≦ (180 ° −α). When the allowable incident angle region upper limit α <90 °, the light of the projector light is 90 ° −α. It is possible to design the incident angle θps with respect to the emission direction control element to be steep, and the optical system can be significantly thinned.

  In the example of FIG. 2, the case where the present invention is applied to a vertical cross section is shown, but the same effect can be obtained when the present invention is applied to a horizontal cross section or a cross section in any other direction.

  In the example of FIG. 2, an air layer is present between the light emission direction control element 1 and the diffusion film 2, but instead of this, the light emission direction control element 1 and the diffusion film 2 By adopting a configuration in which the mutually facing surfaces are brought into close contact with each other and the air layer between them is eliminated, there is no multiple reflection of projector light and outside light at the air interface inside the screen, and further improvement in image display characteristics can be achieved. preferable.

  As a first embodiment of the present invention, a screen for a high-quality rear projection display using a light emission direction control element having the same light emission direction control characteristics over the entire screen will be described.

  As shown in FIG. 3, a prism array 3 having surface inclinations θp1 and θp2 as light emission direction control elements with respect to the vertical direction of the rear projection display, and an incident allowable angle region (angle region of θf = θf− min to θf-max) Using the diffusion film 2 that diffuses and transmits 90% or more of light incident at an arbitrary angle within the range of 65 ° to 115 ° into the diffusion angle region, the projector light is transmitted to the prism array 3 by θps = 30. Consider the incidence in the range of ° to 65 °.

  In order to bend the projector light incident from such a steep angle by an angle θc in the front direction of the screen, it is necessary to use a total reflection prism array.

  By using a prism array with θp1 = 105 ° and θp2 = 65 °, it is possible to cause the projector light to enter the incident allowable angle region of the diffusing film 2 by 90% or more on the entire screen. At this time, since it is not necessary to change the angle of the prism array depending on the location of the screen, the ease of manufacturing and the low cost of manufacturing cost are dramatically improved.

  In FIG. 3, it is depicted as if there is a gap between the prism array 3 and the diffusion film 2, but in actuality, the opposite surface of the diffusion film 2 is closely attached to the flat surface of the prism array 3 without a gap. Configured the screen.

  As an embodiment 2 of the present invention, an ultra-thin high-quality rear projection display utilizing the fact that the allowable incident angle area of projector light has a width with respect to the screen will be described.

  Here, a light emission direction control element capable of bending the traveling direction of incident light by θc = 55 ° is considered.

  As shown in FIG. 4B, the screen using the conventional lenticular lens 11 must have θp = 90 °, and therefore the minimum incident angle θps-min of the projector light to the light emission direction control element 10 is Guided to 35 °.

  Considering the vertical direction of the rear projection display in which the reflector is not used for simplicity, the screen height is 100 cm, and the projector light is incident on the light emission direction control element at 35 ° to 90 °, it is necessary for the optical system. The thickness is 70 cm from 100 × tan 35 °.

  On the other hand, as shown in FIG. 4 (a), 90% of light incident at an arbitrary angle within an allowable angle range of incidence (angle region of θf = θf-min to θf-max) 65 ° to 115 °. In the screen of the present invention using the diffusion film 2 that diffuses and transmits the light in the diffusion angle region, 65 ° ≦ θp ≦ 115 ° may be satisfied, so that the minimum incident angle θps-min of the projector light with respect to the light emission direction control element 1 Is derived as 10 °.

  Considering the vertical direction of the rear projection display under the same conditions as before, the required thickness of the optical system is 17.6 cm from 100 × tan 10 °.

  In either case of the conventional method or the present invention method, the thickness of the optical system is actually reduced by using a reflector, and the thickness of the projector is added. Therefore, it can be seen that the optical system can be significantly reduced in thickness by using the system of the present invention.

  In FIG. 4, the screen is configured as if there is a gap between the light emission direction control element 1 and the diffusion film 2. .

  The present invention can be used for designing and manufacturing an ultra-thin rear projection display.

It is explanatory drawing which shows the concept which gives the output angle (theta) p from a light-projection direction control element a width | variety using the diffusion film which diffuses and permeate | transmits 60% or more of the light which entered at arbitrary angles in the incident allowable angle area. is there. It is a vertical direction sectional view showing an example of the screen of the present invention. FIG. 3 is a vertical cross-sectional view showing the screen of Example 1. It is a vertical direction sectional view showing a rear projection display (a) of Example 2 in comparison with a conventional one (b). It is a vertical direction sectional view showing the condition of θp in a screen using a lenticular lens. It is a vertical direction sectional view showing the condition of θp in a screen using fine particles or a rough surface diffusion medium. It is definition explanatory drawing of the code | symbol of the angle of an incident side and an output side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emission direction control element 2 The diffusion film which diffuses and permeate | transmits 60% or more of the light which entered at arbitrary angles within the incidence allowable angle area to a diffusion angle area 3 Prism array (light emission direction control element)
9 Fresnel lens (light emission direction control element)
10 Prism array (light emission direction control element) that produces the same effect as a Fresnel lens using total reflection and refraction
11 Lenticular lens (horizontal diffusion medium)
12 Fine particle or rough surface diffusion medium (vertical diffusion medium)
13 Fine particle or rough surface diffusing medium 20 for diffusing incident light over a wide angle region Projector

Claims (3)

It consists of a diffusion film that diffuses 60% or more of light incident at an arbitrary angle within the allowable incidence angle region (α to β) into the diffusion angle region and a light emission direction control element, and the light emission direction control element changes the emission direction. 70% or more of the controlled projector light is a condition (180 ° −β) ≦ θp ≦ (180 ° −α) of the emission angle θp from the light emission direction control element.
A rear projection display screen characterized by satisfying the above requirements.   The rear projection display screen according to claim 1, wherein there is no air interface between the light emission direction control element and the diffusion film.   A rear projection display using the screen according to claim 1.

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