JP2006011076A - Fresnel lens, transmission screen and rear projection display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely suppress the occurrence of moire, even in the case of a fresnel lens having a periodical structure having a prescribed optical function on one side of the lens main body. <P>SOLUTION: Regarding a relation of a pitch Pi of the periodical structure arranged on the incident surface side of the lens body 31 of the fresnel lens 30, a pitch Pf of the fresnel lens part 33 arranged on the exit surface side of the lens body 31 of the fresnel lens 30, a pitch Pl of a diffusing lens part 44 of a lenticular lens sheet 40, and a pitch Pg of a pixel 21 of an image displayed on a transmission type screen 20, the following relations are satisfied; Pi≤Pf×3/4 or Pi≥Pf×4/3, also, Pi≤Pl×3/4 or Pi≥Pl×4/3, also, Pi≤Pg×3/4 or Pi≥Pg×4/3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a Fresnel lens used for a transmissive screen of a rear projection display device such as a rear projection television.

  2. Description of the Related Art Conventionally, a rear projection television known as a rear projection display device equipped with a transmissive screen is a transmissive screen that has a substantially rectangular flat plate shape by reflecting video light projected from a projector as a light source by a reflecting mirror. By making the light incident on the rear surface, an observer positioned on the front surface side of the transmissive screen can observe the image light transmitted through the transmissive screen and emitted.

  The transmission type screen has a Fresnel lens having a Fresnel lens portion that adjusts the direction of incident light to be emitted light, and a lenticular lens having a diffusion lens portion that diffuses light emitted from the Fresnel lens in the left-right direction (horizontal direction) of the screen. A lens sheet (diffuse lens sheet) and a diffusion layer that diffuses light emitted from the lenticular lens sheet in the vertical direction (vertical direction) of the screen are provided.

The lens body of the Fresnel lens used for the transmission type screen has, for example, a Fresnel lens portion made up of a plurality of unit lenses arranged concentrically on one side of the lens substrate facing the lenticular lens sheet side, on the exit surface side of the lens body. The optical axis of this Fresnel lens (the center of a concentric circle formed by a plurality of unit lenses) is made to coincide with the center of the lens body.
In addition, the sheet body of the lenticular lens sheet used for the transmission type screen has a diffuser lens portion composed of a plurality of cylindrical lenses (unit lenses) arranged substantially in parallel on one surface facing the Fresnel lens side of the sheet substrate. It is provided and configured to be located on the incident surface side.

  Image light incident on the back surface of such a transmissive screen is first converted into substantially parallel light by the Fresnel lens, and then diffused in the horizontal direction of the screen by the lenticular lens sheet and diffused in the vertical direction of the screen by the diffusion layer. Thereby, the viewing angles in the horizontal direction and the vertical direction of the screen are controlled.

Here, the Fresnel lens portion of the Fresnel lens has a periodic structure in which a plurality of unit lenses are arranged concentrically, and the diffusion lens portion of the lenticular lens sheet also has a plurality of cylindrical lenses arranged in parallel. In addition, the image pixels displayed on the transmissive screen also have a kind of periodic structure.
Therefore, when these periodic structures overlap each other, interference fringes called moire may be observed on the transmission screen, and various attempts have been made to solve this problem ( For example, see Patent Document 1).
JP 2003-280106 A

  By the way, about the Fresnel lens used for the above transmissive screens, a periodic structure having a predetermined optical function is provided on the incident surface side opposite to the exit surface side provided with the Fresnel lens portion in the lens body. Sometimes.

Recently, a transmissive screen has been constructed using a Fresnel lens whose optical axis deviates from the center of the lens body, rather than the Fresnel lens whose optical axis and the center of the lens body coincide with each other. Since it is considered to reduce the thickness of the rear projection television by making it incident obliquely at an incident angle, the need for a periodic structure having the predetermined optical function is increasing.
In other words, as the incident angle of the image light with respect to the lens body of the Fresnel lens increases, the ratio that the image light is reflected on the substantially flat incident surface increases, and the loss of the image light increases. For this reason, for example, a periodic structure such as a prism portion is required to eliminate a problem caused by a reflection loss of image light.

However, conventionally, with respect to a Fresnel lens in which such a periodic structure having a predetermined optical function is provided on the incident surface side of the lens body, the moiré caused by the overlap between the periodic structure and the periodic structure formed by the Fresnel lens portion is caused. At present, no consideration was given to the occurrence.
It is a total reflection type Fresnel lens that is provided so that the Fresnel lens part is located on the incident surface side of the lens body, and the incident light is totally reflected by the Fresnel lens part so that the direction of the incident light is adjusted to be outgoing light. Even in such a case, when a periodic structure having a predetermined optical function is provided on the exit surface side, a moire problem occurs as described above.

  The present invention has been made in view of the above problems, and even when a periodic structure having a predetermined optical function is provided on one side of a lens body, a Fresnel lens can reliably suppress the occurrence of moire. Another object of the present invention is to provide a transmission screen using the Fresnel lens and a rear projection display device using the transmission screen.

In order to solve the above-described problems and achieve such an object, the Fresnel lens according to the present invention is provided with a Fresnel lens portion that adjusts the direction of incident light to be output light and is provided on one surface side. A Fresnel lens having a lens body in which a periodic structure having an optical function is provided on the other surface side, and the relationship between the pitch Pi of the periodic structure and the pitch Pf of the Fresnel lens portion is Pi ≦ Pf · 3 / 4 or Pi ≧ Pf · 4/3 is satisfied.
The transmission screen according to the present invention includes the Fresnel lens according to the present invention and a diffusion lens sheet having a sheet main body provided with a diffusion lens portion that diffuses the emitted light from the Fresnel lens. It is said.
A rear projection display device according to the present invention includes the transmission screen according to the present invention, and a light source that is disposed on the optical axis of the Fresnel lens and that projects image light onto the Fresnel lens. Yes.

In the Fresnel lens of the present invention, the pitch Pf of the Fresnel lens portion, which is a periodic structure provided on one surface side of the lens body, and a periodic structure having a predetermined optical function provided on the other surface side of the lens body. By setting the relationship between the pitch Pi and the pitch Pi so as to satisfy the above-described formula, these periods are kept away from each other.
Therefore, in the rear projection display device constituted by the transmission type screen provided with the Fresnel lens, it is possible to reliably generate moiré due to the overlap between the periodic structure having the predetermined optical function and the periodic structure formed by the Fresnel lens unit. Therefore, it is possible to eliminate a major problem on the video display.

In the transmissive screen of the present invention, the relationship between the pitch Pi of the periodic structure and the pitch Pl of the diffusing lens portion satisfies Pi ≦ Pl · 3/4 or Pi ≧ Pl · 4/3. Preferably, in the rear projection display device of the present invention, the relationship between the pitch Pi of the periodic structure and the pixel pitch Pg of the image displayed on the transmission screen is Pi ≦ Pg · 3. / 4 or Pi ≧ Pg · 4/3 is preferably satisfied.
With such a configuration, not only the generation of moire due to the overlap between the periodic structure having the predetermined optical function and the periodic structure formed by the Fresnel lens portion, but also the periodic structure having the predetermined optical function and the diffusing lens portion. The generation of moire due to the overlapping of the periodic structure formed by the pixel and the periodic structure formed by the pixel can be suppressed, and a major problem on video display can be more reliably eliminated.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the rear projection television 10 as a rear projection display device according to the present embodiment exposes the casing 11 and the front side (right side in FIG. 1) to the outside of the casing 11 and the rear side. A transmissive screen 20 having a substantially rectangular flat plate shape (left side in FIG. 1) exposed to the inside of the housing 11, and image light is projected on the back surface of the transmissive screen 20 disposed in the housing 11. The projector 12 as a light source to be used, and the two reflecting mirrors 13 and 14 that are disposed in the housing 11 and deflect the optical path of the image light projected from the projector 12 are provided.

As shown in FIG. 2, the transmissive screen 20 has a Fresnel lens 30 having a Fresnel lens portion 33 that adjusts the direction of incident light and outputs the light, and the light emitted from the Fresnel lens 30 in the horizontal direction of the screen (horizontal A lenticular lens sheet (diffusing lens sheet) 40 having a diffusing lens portion 44 that diffuses in the direction), and a diffusion layer 50 that diffuses light emitted from the lenticular lens sheet 40 in the vertical direction (vertical direction) of the screen. Yes.
The Fresnel lens 30, the lenticular lens sheet 40, and the diffusion layer 50 are sequentially arranged from the back side (left side in FIG. 2) to the front side (right side in FIG. 2) of the transmissive screen 20, and are substantially parallel to each other. It is arranged to become.

  As shown in FIGS. 2 and 3, the lens body 31 of the Fresnel lens 30 is on one side facing the lenticular lens sheet 40 side (one side facing the front side of the transmissive screen 20) in the lens substrate 32 having a substantially rectangular flat plate shape. The Fresnel lens portion 33 is provided so as to be positioned on the exit surface side (one surface side) of the lens body 31 and has a predetermined optical function on one side facing the back side of the transmissive screen 20 in the lens substrate 32. The periodic structure 34 is provided and configured to be positioned on the incident surface side (the other surface side) of the lens body 31.

The Fresnel lens unit 33 is formed by concentrically arranging a plurality of unit lenses 35. Each unit lens 35 refracts image light projected from a projector 12 described later to adjust the direction of the image light. And has a refracting surface 35A for emitting substantially parallel light.
In the present embodiment, the direction along the normal of the lens body 31 through the center of the concentric circle formed by the plurality of unit lenses 35 of the Fresnel lens portion 33, that is, the optical axis P1 of the Fresnel lens 30 is as shown in FIG. In the direction along the short side of the lens body 31 that passes through the center P2 of the lens body 31 (the screen vertical direction), the lens body 31 is disposed so as to pass through a position outside the lens body 31 outside the long side of the lens body 31.

For example, the periodic structure 34 having a predetermined optical function is a prism portion 34A in which a plurality of unit prisms 36 are arranged concentrically, for example, and each unit prism 36 is projected from a projector 12 described later. An incident surface 36A for allowing the image light to be incident substantially vertically. Further, the center of the concentric circle formed by the plurality of unit prisms 36 of the prism portion 34A is substantially aligned with, for example, the optical axis P1.
That is, the predetermined optical function of the periodic structure 34, which will be described later, actually constitutes the prism portion 34A for image light that appears to be incident on the lens body 31 of the Fresnel lens 30 at a large incident angle. The function is to make the incidence on the incident surfaces 36A of the plurality of unit prisms 36 substantially perpendicular to reduce the loss of image light caused by reflection as much as possible.

Furthermore, when the plurality of unit prisms 36 are viewed in a radial cross section centered on the center of the concentric circle formed by them, the apex angles of the unit prisms 36 are substantially right angles, and each unit prism 36 is perpendicular to the cross section. It has a triangular shape.
In the present embodiment, the pitch Pi of the periodic structure 34 (prism portion 34A), that is, the arrangement pitch Pi of the plurality of unit prisms 36 constituting the prism portion 34A, and the pitch Pf of the Fresnel lens portion 33, that is, the Fresnel lens portion. The relationship with the arrangement pitch Pf of the plurality of unit lenses 35 constituting 33 satisfies the following expression (1).
Pi ≦ Pf · 3/4 or Pi ≧ Pf · 4/3 (1)

The Fresnel lens 30 configured as described above is provided in the transmissive screen 20 so that its optical axis P1 is positioned on the lower side, for example.
Then, when the image light projected from the projector 12 is incident on the back surface of the transmissive screen 20, that is, when the image light projected from the projector 12 is incident on the Fresnel lens 30 positioned on the back surface side of the transmissive screen 20, The Fresnel lens 30 adjusts the direction of the incident image light to be substantially parallel light, and then emits the light toward the lenticular lens sheet 40.

Here, considering the state in which the optical path of the image light projected from the projector 12 is not deflected by the reflecting mirrors 13 and 14, the projector 12 is disposed on the optical axis P1 of the Fresnel lens 30, so that FIG. As indicated by a two-dot chain line in the middle, the state is arranged in a region deviated downward, for example, from a region facing the rear surface of the transmission screen 20.
Then, the optical path of the image light projected from the projector 12 having such an arrangement is disposed so as to face the back surface of the transmissive screen 20 and to be substantially parallel to the transmissive screen 20. By deflecting by the mirror 14 and another reflecting mirror 13, the projector 12 is disposed in the housing 11 in a region deviated from the region between the transmissive screen 20 and the reflecting mirror 14, for example, downward. ing.

Further, as can be understood from FIG. 1 as seen in a cross section in the vertical direction of the screen including the center P2 of the lens body 31 of the Fresnel lens 30, the lens body of the Fresnel lens 30 is projected from the projector 12 disposed on the optical axis P1. The maximum incident angle θmax of the image light incident on the lens 31, that is, one of the long sides of the lens body 31 away from the optical axis P 1 (corresponding to the upper end of the transmission screen 20 in FIG. 1). The inclination angle θmax formed by the image light incident on the optical axis P1 satisfies, for example, θmax ≧ 60 °.
The prism section 34A causes the image light incident on the lens body 31 of the Fresnel lens 30 at such a maximum incident angle θmax to be incident substantially perpendicular to the incident surface 36A of the unit prism 36, and The Fresnel lens portion 33 is refracted by the refracting surface 35A of the unit lens 35 to adjust the direction and emit as substantially parallel light.

  2 and 3, the sheet body 41 of the lenticular lens sheet 40 is on one side facing the Fresnel lens 30 side (one side facing the back side of the transmissive screen 20) in the sheet substrate 42 having a substantially rectangular flat plate shape. The light-shielding portion 45 is provided on one side of the sheet substrate 42 facing the diffusion layer 50 side (one side facing the front side of the transmissive screen 20).

The diffusing lens portion 44 is formed by arranging a plurality of cylindrical lenses (unit lenses) 43 having a substantially semi-cylindrical shape so as to be substantially parallel to each other, and is positioned on the incident surface side of the sheet main body 41.
The plurality of cylindrical lenses 43 constituting the diffusing lens portion 44 have their length directions substantially aligned with the vertical direction (vertical direction) of the screen, and the image light emitted from the Fresnel lens 30 is applied to the lenticular lens sheet 40. When incident, the lenticular lens sheet 40 collects and diffuses the incident video light in the left-right direction (horizontal direction) of the screen to form striped light and then emits it toward the diffusion layer 50. In FIG. 2, for ease of explanation, the length direction of the cylindrical lens 43 is shown to substantially coincide with the horizontal direction (horizontal direction) rather than the vertical direction (vertical direction) of the screen.

In the present embodiment, the pitch Pi of the periodic structure 34 (prism portion 34A) provided on the incident surface side of the lens body 31 of the Fresnel lens 30 and the pitch Pl of the diffusing lens portion 44, that is, the diffusing lens portion 44 are defined. The relationship with the arrangement pitch Pl of the plurality of cylindrical lenses 43 constituting the structure satisfies the following expression (2).
Pi ≦ Pl · 3/4 or Pi ≧ Pl · 4/3 (2)

The light shielding part (BS = black stripe) 45 is positioned on the exit surface side of the sheet main body 41 so as to shield the stripe-shaped non-condensing part by the plurality of cylindrical lenses 43.
On the other hand, the region corresponding to the stripe-shaped condensing part by the plurality of cylindrical lenses 43 is a passing part 46 positioned on the exit surface side of the sheet main body 41, and the image condensed by the cylindrical lens 43. Light is diffused so as to pass through the passage 46.

  The diffusion layer 50 is configured by dispersing and diffusing a diffusing material in a substrate having a substantially rectangular flat plate shape. When image light emitted from the lenticular lens sheet 40 enters the diffusion layer 50, the diffusion layer 50 is formed. 50 diffuses the incident video light in the vertical direction (vertical direction) of the screen and then emits the light toward the front side of the transmissive screen 20.

Furthermore, in the present embodiment, the pitch Pi of the periodic structure 34 (prism portion 34A) provided on the incident surface side of the lens body 31 of the Fresnel lens 30 and the image displayed on the transmission screen 20 as described above. The pitch Pg of the pixels 21 (indicated by dotted lines in FIG. 3), that is, the image light projected from the projector 12 is imaged on the transmission screen 20 by the action of the Fresnel lens 30 and the lenticular lens sheet 40. The relationship with the pitch Pg of the pixels 21 satisfies the following expression (3).
Pi ≦ Pg · 3/4 or Pi ≧ Pg · 4/3 (3)

In the rear projection television 10 according to the present embodiment configured as described above, first, the short side of the lens body 31 in which the optical axis P1 of the Fresnel lens 30 used in the transmission screen 20 passes through the center P2 of the lens body 31. Is disposed so as to pass through a position deviated from the lens body 31.
Therefore, when the projector 12 disposed on the optical axis P1 of the Fresnel lens 30 is not deflecting the optical path of the image light by the reflecting mirrors 13 and 14, for example, the lower side from the region facing the rear surface of the transmissive screen 20 It can be placed in the area outside.

Therefore, in the rear projection television 10 according to the present embodiment, when the optical path of the image light projected from the projector 12 is deflected by the reflecting mirror 14 disposed opposite to the back surface of the transmissive screen 20, the reflecting mirror 14 is used as the transmissive screen. Even if the projector 12 is substantially parallel to the back surface of the projector 20, the projector 12 can be disposed in a region that is off, for example, the lower side from the region between the transmissive screen 20 and the reflecting mirror 14.
As described above, if the reflecting mirror 14 disposed opposite to the back surface of the transmissive screen 20 can be disposed so as to be substantially parallel to the transmissive screen 20, conventionally, the reflecting mirror 14 is inclined. Therefore, the depth of the housing 11 that is only required is unnecessary, and the rear projection television 10 can be further reduced in thickness.

Here, by using the Fresnel lens 30 with the optical axis P1 decentered as described above, the incident angle of the image light incident on the lens body 31 of the Fresnel lens 30 is large. The incident angle θmax is 60 ° or more.
However, in the present embodiment, the incident angle is increased by providing the prism portion 34A, which is a periodic structure 34 having a predetermined optical function, on the incident surface side of the lens body 31 of the Fresnel lens 30. The problem of image light reflection loss can be solved.

That is, image light that appears to be incident on the lens body 31 at a large incident angle is actually incident substantially perpendicularly to the incident surfaces 36A of the plurality of unit prisms 36 constituting the prism portion 34A. Therefore, the loss of image light caused by reflection can be reduced as much as possible to prevent a dark image from being displayed on the transmissive screen 20.
Here, “substantially vertical” means that when the image light is incident on the incident surface 36A of the unit prism 36, the crossing angle between the image light and the incident surface 36A is within a range of 90 ° ± 5 °. It is in the range.

Further, since the apex angle of each of the plurality of unit prisms 36 constituting the prism portion 34A is substantially a right angle, between the image lights incident on the incident surface 36A of the adjacent unit prism 36, It is possible to eliminate the generation of invalid light and to reduce the loss of image light.
Here, “substantially right angle” means that the apex angle 36B of the unit prism 36 is within the range of 90 ° ± 5 °.

In this embodiment, the pitch Pi of the periodic structure 34 (prism portion 34 </ b> A) provided on the incident surface side of the lens body 31 of the Fresnel lens 30 and the Fresnel provided on the exit surface side of the lens body 31 of the Fresnel lens 30. The pitch Pf of the lens unit 33, the pitch Pl of the diffusing lens unit 44 of the lenticular lens sheet 40, and the pitch Pg of the image pixels 21 displayed on the transmissive screen 20 satisfy the above expressions (1) to (3). Yes.
In other words, the period of the periodic structure 34 (prism portion 34A) provided on the incident surface side of the lens body 31 of the Fresnel lens 30 is the Fresnel lens portion 33 provided on the exit surface side of the lens body 31 of the Fresnel lens 30. The period of the periodic structure formed by the lens, the period of the periodic structure formed by the diffusion lens portion 44 of the lenticular lens sheet 40, and the period of the periodic structure formed by the pixels 21 of the image displayed on the transmissive screen 20 are sufficiently separated. is there.

  Therefore, in the rear projection television 10 according to the present embodiment, the periodic structure 34 having a predetermined optical function provided on the incident surface side of the lens body 31 of the Fresnel lens 30, and the exit surface side of the lens body 31 of the Fresnel lens 30. Moire caused by overlapping with the periodic structure formed by the provided Fresnel lens section 33, the periodic structure formed by the diffusion lens section 44 of the lenticular lens sheet 40, and the periodic structure formed by the pixels 21 of the image displayed on the transmissive screen 20. Can be reliably suppressed, and it is possible to eliminate a major problem on the video display.

  Here, since it is not preferable that the pitch Pi of the periodic structure 34 is too large, Pi ≦ Pf · 3/4 is satisfied in the equation (1), and Pi ≦ Pl · 3 / in the equation (2). 4 is preferably satisfied so that Pi ≦ Pg · 3/4 is satisfied in the above expression (3).

A specific example of the pitches Pi, Pf, Pl, and Pg satisfying the equations (1) to (3) will be described. The pitch Pg of the pixels 21 of the image displayed on the transmission screen 20 is 0.800 mm. When the pitch Pf of the Fresnel lens portion 33 of the Fresnel lens 30 is 0.062 mm and the pitch Pl of the diffusion lens portion 44 of the lenticular lens sheet 40 is 0.098 mm, the pitch Pi of the periodic structure 34 of the Fresnel lens 30 is 0.046 mm. It is preferable that the following is set.
Note that the smaller the pitch Pi of the periodic structure 34 is, the higher processing accuracy is required when processing the periodic structure 34, resulting in an increase in processing cost. The pitch Pi of 34 is preferably set to about 0.045 mm, for example.

In the present embodiment, the prism portion 34A is cited as an example of the periodic structure 34 provided on the incident surface side of the lens body 31 of the Fresnel lens 30, but the prism portion 34A is not limited thereto. Or the periodic structure 34 which consists of a diffraction grating pattern, an uneven | corrugated | grooved part, etc. may be sufficient.
The predetermined function of the periodic structure 34 is not limited to the function of reducing the reflection loss of the image light. For example, the incident angle of the image light incident on the lens body 31 of the Fresnel lens 30 is reduced. The function of deflecting the image light, the function of expanding (controlling) the viewing angle in the vertical direction or the horizontal direction of the screen, and the function of preventing a ghost image caused by the reflection of the image light may be used. .

  As described above, various periodic structures 34 are conceivable. In particular, when the periodic structure 34 and the periodic structure formed by the diffusion lens portion 44 of the lenticular lens sheet 40 have a relationship that is substantially orthogonal to each other, Since there is no moiré caused by overlapping with the periodic structure formed by the diffusing lens unit 44, it is only necessary to set the pitches Pi, Pf, and Pg so as to satisfy the expressions (1) and (3). .

  Further, in the present embodiment, the Fresnel lens 30 in which the periodic structure 34 is provided on the incident surface side of the lens body 31 is described, but the present invention is not limited to this. For example, the Fresnel lens part 33 is provided so as to be positioned on the incident surface side of the lens body 31, and the incident light is totally reflected by the Fresnel lens part 33 so that the direction of the incident light is adjusted to be emitted light. Even in the case of the Fresnel lens 30, when the periodic structure 34 having a predetermined optical function is provided on the exit surface side, the pitches Pi, Pf, and Pl are satisfied so as to satisfy the above expressions (1) to (3). , Pg can be set to eliminate the moire problem.

  Furthermore, in the present embodiment, a plurality of cylindrical lenses (unit lenses) 43 are arranged substantially in parallel as a diffusing lens sheet in which the transmissive screen 20 diffuses light emitted from the Fresnel lens 30 in the horizontal direction of the screen. The lenticular lens sheet 40 having the diffusing lens portion 44 is provided, and the diffusing layer 50 is provided as diffusing means for diffusing the light emitted from the Fresnel lens 30 in the vertical direction of the screen. It is not limited to only lens sheets.

  For example, the transmissive screen 20 has a plurality of unit lenses arranged in a matrix as a diffusion lens sheet that diffuses light emitted from the Fresnel lens 30 in the horizontal direction (horizontal direction) and the vertical direction (vertical direction) of the screen. A microlens sheet having a diffusing lens portion (pitch Pl) may be provided. Further, for example, a plurality of cylindrical lenses (unit lenses) are used as a diffusing lens sheet in which the transmissive screen 20 diffuses light emitted from the Fresnel lens 30 in the horizontal direction (horizontal direction) and the vertical direction (vertical direction) of the screen. The first lens array arranged substantially in parallel and the second lens array in which a plurality of cylindrical lenses (unit lenses) are arranged substantially in parallel have the same plane so that the length directions of the cylindrical lenses intersect each other. You may make it provide the cross wrench lens sheet | seat which has the diffused lens part (pitch Pl) arrange | positioned on the top. Even in these cases, the transmissive screen 20 may include the diffusion layer 50 as necessary.

  Further, for example, a plurality of unit lenses that reflect and diffuse image light are arranged as a diffusing lens sheet in which the transmissive screen 20 diffuses light emitted from the Fresnel lens 30 in the left-right direction (horizontal direction) of the screen. A diffusing layer 50 as a diffusing means for diffusing light emitted from the Fresnel lens 30 in the vertical direction (vertical direction) of the screen. Good. Note that the diffusion layer 50 is not necessarily required depending on the shape and arrangement of the plurality of unit lenses in the prism lens sheet.

It is a schematic sectional drawing which shows an example of the rear projection television by embodiment of this invention. It is a schematic sectional drawing which shows an example of the transmission type screen by embodiment of this invention. It is a schematic sectional drawing which shows the principal part of an example of the transmission type screen by embodiment of this invention.

Explanation of symbols

10 Rear projection television (rear projection type display device)
12 Projector (light source)
DESCRIPTION OF SYMBOLS 20 Transmission type screen 21 Pixel 30 Fresnel lens 31 Lens main body 32 Lens substrate 33 Fresnel lens part 34 Periodic structure 34A Prism part 35 Unit lens 35A Refraction surface 36 Unit prism 36A Incidence surface 40 Lenticular lens sheet (diffuse lens sheet)
43 Cylindrical lens (unit lens)
44 Diffusion lens part 50 Diffusion layer P1 Optical axis of Fresnel lens P2 Center of lens body of Fresnel lens

Claims (5)

A Fresnel lens having a lens body in which a periodic structure having a predetermined optical function is provided on one surface side and a Fresnel lens portion that arranges the direction of incident light to be emitted light is provided on one surface side,
The relationship between the pitch Pi of the periodic structure and the pitch Pf of the Fresnel lens portion is as follows:
Pi ≦ Pf · 3/4 or Pi ≧ Pf · 4/3
A Fresnel lens characterized by satisfying A Fresnel lens according to claim 1;
A transmission type screen comprising: a diffusion lens sheet having a sheet main body provided with a diffusion lens part for diffusing the emitted light from the Fresnel lens. The transmissive screen according to claim 2,
The relationship between the pitch Pi of the periodic structure and the pitch Pl of the diffusing lens portion is as follows:
Pi ≦ Pl · 3/4 or Pi ≧ Pl · 4/3
A transmission screen characterized by satisfying The transmissive screen according to claim 2 or 3,
A rear projection display device, comprising: a light source disposed on an optical axis of the Fresnel lens, and projecting image light onto the Fresnel lens. The rear projection type display device according to claim 4,
The relationship between the pitch Pi of the periodic structure and the pixel pitch Pg of the image displayed on the transmissive screen is as follows:
Pi ≦ Pg · 3/4 or Pi ≧ Pg · 4/3
The rear projection type display device characterized by satisfying the above.

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