JP2006018141A - Optical system and rear projection type display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a rear projection type display apparatus thinner in shape without extremely enlarging a projection angle of image light projected from a light source. <P>SOLUTION: The optical system is provided with a transmission type screen 20 for adjusting the direction of incident light, and also, for diffusing the incident light, a projector 12 as the light source for projecting the image light, a mirror 70 for reflecting the image light, and a half mirror 60 for reflecting and also transmitting the image light, the image light projected from the projector 12 is made incident on the half mirror 60 and reflected, then, made incident on the mirror 70 and reflected, thereafter, made incident on the half mirror 60 again, then, transmitted through the half mirror 60, and then, made incident on the transmission type screen 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical system used for a rear projection display device such as a rear projection television.

Conventionally, for example, a rear projection television 1 as shown in FIG. 5 is known as a rear projection display device provided with such an optical system.
As shown in FIG. 5, the rear projection television 1 reflects the image light projected from a projector 2 as a light source by, for example, two mirrors 3A and 3B to form a substantially rectangular flat plate-like back surface. , The observer positioned on the front side of the transmissive screen 4 can observe the image light transmitted through the transmissive screen 4 and emitted.

The transmissive screen 4 includes a Fresnel lens having a Fresnel lens portion that adjusts the direction of incident light to be emitted light, and a diffusion lens portion that diffuses the emitted light from the Fresnel lens in the left-right direction (horizontal direction) of the screen. A lenticular 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 (see, for example, Patent Document 1).
The image light incident on the back surface of the transmissive screen 4 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.
JP 2002-174703 A

  In the rear projection television 1 as described above, since the space occupied by the optical system for allowing the image light to enter the back surface of the transmission screen 4 is large, for example, the image projected from the projector 2 by the two mirrors 3A and 3B. By deflecting the optical path of the light, the projector 2 is arranged in a region deviating downward from the region between the transmissive screen 4 and the mirror 3B, thereby reducing the depth as much as possible and reducing the thickness. .

By the way, the projector 2 is disposed on the optical axis 5A of the Fresnel lens in the transmissive screen 4, and the optical axis 5A of the Fresnel lens is generally aligned with the center 5B of the lens body of the Fresnel lens. ing.
For this reason, of the mirrors 3A and 3B that deflect the optical path of the image light, the mirror 3B that is opposed to the back surface of the transmissive screen 4 is not tilted at a large tilt angle with respect to the transmissive screen 4, so that 3A cannot be prevented from interfering with the optical path of the image light projected from the projector 2, and as a result, there is a limit in reducing the depth of the rear projection television 1. In other words, the depth of the rear projection television 1 must be secured by the amount of the inclination of the mirror 3B, and this inclination of the mirror 3B is a major obstacle to reducing the thickness of the rear projection television 1. It was.

On the other hand, recently, a transmissive screen 4 is formed using a Fresnel lens arranged so that the optical axis 5A passes through a position deviated from the center 5B of the lens body, and on the optical axis 5A of such a Fresnel lens. It is conceivable that the rear projection television 1 can be thinned by disposing the projector 2 in such a manner that the incident angle of the image light incident on the back surface of the transmissive screen 4 is increased, the inclination of the mirror 3B is made gentle. ing.
However, in such a case, if the incident angle is increased too much in order to further reduce the thickness, the projection angle when the projector 2 projects the image light also increases accordingly. There is a problem that the load applied to the projection lens becomes very large.

  The present invention has been made in view of the above problems, and an optical system capable of reducing the thickness of a rear projection display device without excessively increasing a projection angle when a light source projects image light. An object of the present invention is to provide a rear projection display device using an optical system.

In order to solve the above problems and achieve such an object, an optical system according to the present invention includes a transmissive screen for adjusting the direction of incident light and diffusing the incident light, a light source for projecting image light, and the like. A mirror that reflects the image light and a half mirror that reflects and transmits the image light, and the image light projected from the light source is incident on the half mirror and reflected by the half mirror. After being incident on the mirror and reflected by the mirror, the light is incident again on the half-mirror and transmitted through the half-mirror so as to be incident on the transmissive screen.
A rear projection display device according to the present invention includes the optical system according to the present invention.

In the optical system of the present invention, the image light once incident on and reflected by the half mirror is reflected by the mirror disposed opposite to the back surface of the transmission screen, and then incident again on the same half mirror to be transmitted. It is incident on the back of the mold screen.
Therefore, even if this half mirror is disposed opposite to the rear surface of the transmissive screen and interferes with the optical path of the image light projected from the light source, the function as a rear projection display device is sufficiently obtained. Therefore, it is possible to make the rear projection display device thinner by reducing the inclination of the mirror disposed opposite to the rear surface of the transmissive screen. Further, even if the incident angle of the image light incident on the rear surface of the transmissive screen is not increased too much, that is, the projection angle when the light source projects the image light is not increased too much, the rear projection display device Since the thickness can be reduced, it is possible to make it difficult to apply an excessive load to the projection lens of the light source.

Further, the present invention includes a light shielding means for shielding a transmission component of the video light transmitted through the half mirror when the video light is incident on the half mirror and reflected by the half mirror. Is preferred.
When the image light projected from the light source is once incident on the half mirror and reflected, the transmission component of the image light transmitted through the half mirror may cause a ghost on the screen. By arranging such a light shielding means between the transmissive screen and the half mirror disposed opposite to the rear surface of the transmissive screen, the transmissive component is not incident on the transmissive screen and is observed on the screen. Generation of ghosts can be reliably suppressed.

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 including the optical system according to the present embodiment has a housing 11 and a front side (right side in FIG. 1) to the outside of the housing 11. A transmissive screen 20 having a substantially rectangular plate shape with the back side (left side in FIG. 1) exposed to the inside of the housing 11 and the rear surface of the transmissive screen 20 disposed in the housing 11. The projector 12 as a light source for projecting image light in the same manner, the half mirror 60 and the mirror 70 which are arranged in the housing 11 and deflect the optical path of the image light projected from the projector 12, and also in the housing 11. Arranged and provided with a louver 80 as a light shielding means described later.

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 FIG. 2, the lens body 31 of the Fresnel lens 30 has a Fresnel lens on one side facing the lenticular lens sheet 40 side (one side facing the front side of the transmissive screen 20) in a lens substrate 32 having a substantially rectangular flat plate shape. The portion 33 is provided. The Fresnel lens portion 33 is formed of concentric concavities and convexities and is located on the exit surface side of the lens body 31. That is, the Fresnel lens 30 is so-called that the incident video light passes through the lens substrate 32 and is refracted by the refracting surface of the Fresnel lens portion 33 so that its direction is adjusted and emitted as substantially parallel light. A transmissive Fresnel lens 30 is formed.
In the present embodiment, the direction along the normal line of the lens body 31 through the center of the concentric circle formed by the irregularities 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 passing through the center P <b> 2 of the body 31, the lens body 31 is disposed outside the long side of the lens body 31 and away from the lens body 31.

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.

As shown in FIG. 2, the sheet main body 41 of the lenticular lens sheet 40 has a diffusion lens on one side facing the Fresnel lens 30 side (one side facing the back side of the transmissive screen 20) of the sheet substrate 42 having a substantially rectangular flat plate shape. The light shielding part 45 is provided on one side facing the diffusion layer 50 side of the sheet substrate 42 (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.

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.

Here, in the rear projection television 10 provided with the transmissive screen 20 as described above, when the state in which the optical path of the image light projected from the projector 12 is not deflected by the half mirror 60 and the mirror 70 is considered, In order to be arranged on the optical axis P1 of the Fresnel lens 30, as shown by a two-dot chain line in FIG. It has become.
Then, the optical path of the image light projected from the projector 12 having such an arrangement is deflected by a mirror 70 arranged opposite to the back surface of the transmission screen 20 and a half mirror 60 described later, so that FIG. As shown in the figure, the projector 12 is disposed in a region in the casing 11 that is, for example, deviated downward from the region between the transmissive screen 20 and the mirror 70.

The half mirror (also referred to as a semi-transparent mirror) 60 is configured by forming a vapor deposition film made of, for example, a dielectric or a vapor deposition film made of a metal such as chromium or aluminum on an incident surface on which image light is incident. It has a function of reflecting and transmitting incident video light. Thereby, the image light projected from the projector 12 and incident on the half mirror 60 is divided into a reflection component reflected by the half mirror 60 and a transmission component transmitted through the half mirror 60.
The half mirror 60 is disposed between the transmissive screen 20 and the mirror 70 disposed opposite to the rear surface of the transmissive screen 20, so that the half mirror 60 is disposed opposite to the rear surface of the transmissive screen 20 in the same manner as the mirror 70. ing. For this reason, the mirror 70 disposed opposite to the rear surface of the transmissive screen 20 is actually disposed opposite to the incident surface of the half mirror 60.

Further, between the half mirror 60 and the transmissive screen 20, as shown in FIGS. 1 and 3, the transmission of the image light generated when the image light projected from the projector 12 first enters the half mirror 60. A louver 80 is arranged as a light shielding means for shielding the components.
The louver 80 is configured by arranging a plurality of partition walls 81 extending in the thickness direction in a lattice shape or a concentric shape, for example. The pitch of the plurality of partition walls 81 in the louver 80 is set so that the image light incident on the louver 80 at a predetermined range of incident angles can be absorbed by the partition wall 81 without being transmitted, that is, projected from the projector 12. The transmission component of the image light generated when the image light that has been incident on the half mirror 60 for the first time can be shielded.

Next, an optical path until video light projected at a predetermined projection angle from the projector 12 enters the back surface of the transmissive screen 20 will be described.
As shown in FIGS. 1 and 3, the image light projected from the projector 12 first enters the half mirror 60 disposed opposite to the back surface of the transmissive screen 20. Note that the image light projected from the projector 12 may be first incident on the half mirror 60 after being reflected by at least one mirror. Here, the image light first incident on the half mirror 60 is divided into a reflection component reflected by the half mirror 60 and a transmission component transmitted through the half mirror 60.

The transmissive component of the image light transmitted through the half mirror 60 is incident on the louver 80 disposed between the half mirror 60 and the transmissive screen 20, but is absorbed by the plurality of partition walls 81 in the louver 80. A light transmission component does not enter the back surface of the transmission screen 20.
On the other hand, the reflected component of the image light reflected by the half mirror 60 is incident on the mirror 70 disposed opposite to the incident surface of the half mirror 60 (disposed opposite the rear surface of the transmissive screen 20) and reflected by the mirror 70. To do.

The image light reflected by the mirror 70 is incident on the half mirror 60 again and is transmitted through the half mirror 60, thereby entering the louver 80 disposed between the half mirror 60 and the transmission screen 20.
At this time, the image light incident on the louver 80 has a smaller incident angle on the louver 80 than the transmission component generated when the image light projected from the projector 12 first enters the half mirror 60. All of the light passes through the louver 80 without being absorbed by the partition wall 81. Then, the image light transmitted through the louver 80 is incident on the back surface of the transmissive screen 20.

In the rear projection television 10 equipped with the optical system according to the present embodiment having the above-described configuration, the image light that is once incident on the half mirror 60 and reflected is reflected on the rear surface of the transmission screen 20 by the mirror 70. Then, the light is incident again on the same half mirror 60 and then transmitted, so that it is incident on the back surface of the transmissive screen 20.
Therefore, even if the half mirror 60 is disposed opposite to the rear surface of the transmissive screen 20 and interferes with the optical path of the image light projected from the projector 12, the function as the rear projection television 10 is not impaired. Therefore, the rear projection television 10 can be thinned by making the inclination of the mirror 70 opposed to the rear surface of the transmission screen 20 (opposed to the incident surface of the half mirror 60) very gentle. .

  1 and 3, the mirror 70 is described as being slightly inclined. However, in the present embodiment, the optical axis P1 of the Fresnel lens 30 is disposed so as to pass a position away from the lens body 31. Therefore, it is possible to further reduce the thickness of the rear projection television 10 by arranging the mirror 70 so as to be substantially parallel to the transmission screen 20.

  Further, if the rear projection television 10 can be thinned as described above, it is not necessary to forcibly increase the incident angle of the image light incident on the back surface of the transmissive screen 20, in other words, the projector 12 can display the image. Since it is not necessary to forcibly increase the projection angle when projecting light, it is possible to obtain an effect that an optical system can be designed so that an unreasonable load is not applied to the projection lens of the projector 12.

In addition, since it is not necessary to forcibly increase the incident angle of the image light incident on the back surface of the transmissive screen 20, in this embodiment, when the incident angle of the image light is increased, the transmittance is reduced. However, the transmissive Fresnel lens 30 that is easy to manufacture can be used.
Of course, instead of such a transmission type Fresnel lens 30, the Fresnel lens portion 33 is provided on one side of the lens substrate 32 facing the back side of the transmission type screen 20, that is, the incident surface of the lens body 31. The lens body 31 is configured to be positioned on the side, and the incident image light is totally reflected by the total reflection surface of the Fresnel lens portion 33, so that its direction is adjusted and emitted as substantially parallel light. Alternatively, the Fresnel lens 30 may be used.

Furthermore, in the rear projection television 10 equipped with the optical system according to the present embodiment, the louver 80 for shielding the transmission component generated when the image light first enters the half mirror 60 includes the half mirror 60 and the transmission screen 20. It is arranged between.
Therefore, the transmissive component that may cause a ghost on the screen can be absorbed by the plurality of partition walls 81 in the louver 80 so as not to be incident on the back surface of the transmissive screen 20. It is possible to reliably suppress the occurrence of ghosts observed in (1).

In the present embodiment, the louver 80 is used as the light shielding means for shielding the transmission component of the video light generated when the video light first enters the half mirror 60. However, the present invention is not limited to this. For example, a light shielding means 82 as shown in FIG. 4 may be used.
4 includes a plurality of light absorption layers 84 (corresponding to the plurality of partition walls 81 of the louver 80) extending in the thickness direction inside a light-transmitting substrate 83, for example, a lattice. It is comprised by arranging in the shape of a circle or a concentric circle. Further, the pitch of the plurality of light absorption layers 84 in the light shielding means 82 is set so that the light absorption layer 84 can absorb the image light incident on the light shielding means 82 at an incident angle within a predetermined range without transmitting. That is, it is set so that the transmission component of the image light generated when the image light projected from the projector 12 first enters the half mirror 60 can be shielded.
Even if such a light shielding means 82 is used, the same effect as the above-described embodiment can be obtained. In short, the configuration of the light shielding means is not limited as long as the transmission component of the video light generated when the video light first enters the half mirror 60 can be shielded.

  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 a lens sheet.

  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. You may make it provide the micro lens sheet | seat which has the diffusion lens part which becomes. 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 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 may be provided as diffusing means for diffusing light emitted from the Fresnel lens 30 in the vertical direction (vertical direction) of the screen. 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 principal part expansion 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 another example of a light-shielding means. It is a schematic sectional drawing which shows an example of the conventional rear projection television.

Explanation of symbols

10 Rear projection television (rear projection type display device)
12 Projector (light source)
20 transmissive screen 30 Fresnel lens 40 lenticular lens sheet (diffuse lens sheet)
50 Diffusion layer 60 Half mirror 70 Mirror 80 Louver (light shielding means)
81 Bulkhead 82 Shading means

Claims (3)

A transmission screen for adjusting the direction of incident light and diffusing the incident light; a light source for projecting image light; a mirror for reflecting the image light; and a half mirror for reflecting and transmitting the image light;
The image light projected from the light source is incident on the half mirror and reflected by the half mirror, and then incident on the mirror, reflected by the mirror, and then incident again on the half mirror. An optical system configured to be incident on the transmissive screen by being transmitted through the screen. The optical system according to claim 1,
An optical system comprising: a light shielding means for shielding a transmission component of the video light transmitted through the half mirror when the video light is incident on the half mirror and reflected by the half mirror. . A rear projection display device comprising the optical system according to claim 1.

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