JP4893015B2 - Fresnel lens sheet and rear projection screen using the same - Google Patents

Description

  The present invention relates to a Fresnel lens sheet used for a rear projection television and the like, and a rear projection screen using the same.

  As shown in FIG. 2, the rear projection screen 3 for rear projection television is generally constituted by a combination of a light diffusion sheet 2 disposed on the viewer side and a Fresnel lens sheet 1 positioned on the light source side. . A Fresnel lens sheet having unit lenses arranged concentrically serves to project the image light of 5 from a small projector called an engine as a substantially parallel light and project it onto the light diffusion sheet via the mirror 4. The light diffusing sheet serves to emit display light to the observer side as directional light in the horizontal or vertical direction due to the characteristic of the inherent lens group. There is.

Rear projection screens used in rear projection televisions are required to faithfully reproduce the image light from the engine, and in recent years, with the higher definition of the engine, the screen must also be able to faithfully reproduce high-definition images. ing.
In order to achieve high definition of the screen, it is required to make the lens pitch of the light diffusing sheet finer, and the pitch of the combined Fresnel lens sheet is made finer than the lens pitch of the light diffusing sheet, so It is possible to reduce moire that causes deterioration.

  If the Fresnel lens pitch is set to 50 μm or less, a rainbow appears due to reflection on the rise surface, causing image degradation. For example, as described in Patent Documents 1 to 3, it is possible to reduce the rainbow by using a technique similar to the suppression of ghost light, but a light absorber or a light diffusing material can be separately applied. Since the rise surface is processed, labor and cost are generated. Although it is possible to roughen the rise surface by increasing the number of times of cutting, when the Fresnel lens pitch becomes fine, the number of times of cutting increases, resulting in an increase in the cutting time of the mold.

  Further, for example, as disclosed in Patent Document 4, it is known to reduce moire by making the Fresnel lens pitch irregular, but regarding the specific Fresnel lens pitch and the lens pitch of the light diffusion sheet to be combined, Neither listed nor suggested.

Patent documents are as follows.
JP 2002-49100 A JP 2002-62591 A JP 2002-277614 A JP 2002-196421 A

  The present invention has been made in consideration of the above background, and when the lens pitch of the light diffusing sheet to be combined is made fine, even if the Fresnel lens pitch to be combined is made fine, the rise angle is made irregular by making the rise angle irregular. It is possible to reduce the rainbow by dispersing the reflected light, to reduce the moire generated between the light diffusion sheet and the Fresnel lens sheet, and to further reduce the cutting time than before. An object of the present invention is to provide a rear projection screen using the same.

According to the present invention, in order to achieve the above object, the invention according to claim 1 is mainly for a rear projection screen used in a form in which a light diffusion sheet is arranged on the observer side and a Fresnel lens sheet is arranged on the light source side. A Fresnel lens sheet,
The angle formed by the normal to the rise surface of the Fresnel lens sheet is defined as the rise angle (θ), and the rainbow caused by the reflection of the rise surface is reduced by making the rise angle (θ) irregular. It is a Fresnel lens sheet.

The invention according to claim 2 is a Fresnel lens sheet for a rear projection screen used mainly in a form in which a light diffusion sheet is arranged on the observer side and a Fresnel lens sheet is arranged on the light source side,
The angle between the rise surface and the normal line of the Fresnel lens sheet is defined as a rise angle (θ), and by making the rise angle (θ) irregular, the Fresnel lens pitch is made random, thereby the light diffusion sheet. 2. The Fresnel lens sheet according to claim 1, wherein moiré generated between the two is reduced.

The invention according to claim 3 is a Fresnel lens sheet for a rear projection screen used mainly in a form in which a light diffusion sheet is arranged on the observer side and a Fresnel lens sheet is arranged on the light source side,
When the lens pitch (PF) of the Fresnel lens sheet is defined as a value obtained by dividing the unit length (Pl) by the number of lenses (Pn) (PF = Pl / Pn), the lens pitch (PF) is 50 μm or less. The Fresnel lens sheet according to claim 1 or 2, wherein

The invention according to claim 4 is a rear projection screen mainly used in a form in which a light diffusion sheet is arranged on the observer side and a Fresnel lens sheet is arranged on the light source side,
4. The rear projection screen according to claim 1, wherein the light diffusion sheet combined with the Fresnel lens sheet has a lens pitch of 75 [mu] m or less.

  The present invention has been made in consideration of the above background, and when the lens pitch of the light diffusing sheet to be combined is made fine, even if the Fresnel lens pitch to be combined is made fine, the rise angle is made irregular by making the rise angle irregular. It is possible to reduce the rainbow by dispersing the reflected light, to reduce the moire generated between the light diffusion sheet and the Fresnel lens sheet, and to further reduce the cutting time than before. In addition, a rear projection screen using the same can be provided.

  Hereinafter, an embodiment as a preferred example of the present invention will be described with reference to the drawings.

  FIG. 3 is a schematic view showing an example of a Fresnel lens sheet according to the present invention, and FIG. 1 is an enlarged view of a portion A thereof. As shown in FIG. 1, Fresnel lenses P1, P2,... Exist from the center. At this time, since the rise angle (θ) exists for the first time at the position P2, the rise angle in the nth Fresnel lens (Pn) is the (n−1) th. The rise angles adjacent from the 1st to the (n-1) th show different angles, and the pitch of the adjacent Fresnel lenses is also different. A distance from the first Fresnel lens to the nth Fresnel lens (Pn) from the center is defined as Pl, and PF can be defined as Pl / Pn.

  For example, when Pl is 500 mm and Pn is 10,000, the lens pitch PF is 0.05 mm (50 μm).

  The rear projection screen of the present invention is not limited to the above-described configuration.

  The cause of moiré occurs when two or more gratings having periodicity and a regular frequency are overlapped to generate a new stripe pattern. In the case of a rear projection screen used for a projection television, moire appears due to three factors: the lens pitch of the light diffusion sheet, the lens pitch of the Fresnel lens sheet, and the pixel pitch of the projected image.

  In particular, the moiré that appears at the lens pitch of the light diffusing sheet and the lens pitch of the Fresnel lens sheet is observed as being particularly strong. Therefore, in order to faithfully reproduce the image, it is effective to make the moiré inconspicuous here. is there.

  Therefore, according to the present invention, the regularity with the light diffusing sheet can be eliminated by making the Fresnel lens pitch random by making the rise angle irregular, and the moire can be made inconspicuous.

  In addition, by making the rise angle irregular as in the Fresnel lens sheet of the present invention, the reflected light on the rise surface can be made irregular, and post-processing is separately applied to the rise surface or the number of times of cutting is increased. Thus, it is possible to reduce the rainbow without making the rise surface rough. Therefore, even if the pitch becomes fine, the post-process and the cutting time do not increase extremely, and the tact time is shortened.

  The present invention is particularly preferably applied to a lens pitch of 50 μm or less where the rainbow is easily noticeable, and the unit length is preferably set to a diagonal where the number of concentric lenses is the largest.

  When considering moire, it is theoretically said that moire can be reduced by making each pitch 2/3 or 3/2. The light diffusion sheet combined with the Fresnel lens sheet of the present invention is preferably larger than the lens pitch of the Fresnel lens sheet, and considering the rainbow of the Fresnel lens sheet, the Fresnel lens pitch is 50 μm or less. The lens pitch is desirably 75 μm or less.

  Moreover, in order to shorten the cutting time and reduce the rainbow, it is possible to respond by increasing the lens pitch of the Fresnel lens sheet than the light diffusion sheet to be combined, but in this case, it appears between the light diffusion sheet and the Fresnel lens sheet. Moire becomes large, and as a result, it becomes difficult to reduce moire.

It is the model enlarged view which showed the Fresnel lens sheet of this invention. It is the schematic cross section which showed the general rear projection type screen. It is the schematic cross section which showed the Fresnel lens sheet of this invention.

Explanation of symbols

1. Fresnel lens sheet 2. Light diffusion sheet 3. Rear projection screen 4. Mirror 5. Projector A. Enlarged portion .theta.1 as shown in FIG. 1 exists in the second Fresnel lens from the center. Rise angle θn−1... Rise angle P1 in the n-th (Pn) Fresnel lens from the center, the first Fresnel lens P2 from the center, the second Fresnel lens Pn from the center,. Nth Fresnel lens Pl from the center Unit length

Claims (1)

A Fresnel lens sheet for a rear projection screen used in a form in which a light diffusion sheet is arranged on the observer side and a Fresnel lens sheet is arranged on the light source side,
The Fresnel lens sheet is characterized in that an angle formed by a normal to the rise surface of the Fresnel lens sheet is defined as a rise angle (θ), and the rise angle (θ) is irregular.

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