JP6854439B2 - Projection type display device - Google Patents

Description

The present disclosure relates to a projection type display device having an internal total internal reflection prism.

Patent Document 1 discloses a projector device having a TIR prism (internal total internal reflection prism).

Japanese Unexamined Patent Publication No. 2012-215656

In the internal total internal reflection prism of Patent Document 1, since the shape of the air layer is formed in a wedge shape, the light beam angle changes before and after the incident on the internal total internal reflection prism, and new astigmatism occurs.

An object of the present disclosure is to improve the optical performance of a projection type display device having an internal total internal reflection prism.

The projection type display device of the present disclosure projects the image light emitted from the image generation unit through the internal total internal reflection prism and the projection lens. In the projection type display device, a transmission plate that transmits image light is arranged on the optical path between the internal total internal reflection prism and the projection lens. The internal total reflection prism includes a first prism having a first surface and a second prism having a second surface. The first surface and the second surface are opposed to each other in parallel or substantially parallel to each other through the air layer, and are inclined with respect to a reference plane perpendicular to the optical axis of the image light incident on the internal total internal reflection prism. .. The transmission plate is inclined to the same side as the side on which the first surface and the second surface are inclined with respect to the reference plane.

In the present disclosure, a transmission plate is provided on the optical path between the internal total internal reflection prism and the projection lens so as to be inclined to the same side as the side on which the first surface and the second surface of the internal total internal reflection prism are inclined. Therefore, it is possible to correct the aberration generated in the air layer of the internal total internal reflection prism. Therefore, the optical performance of the projection type display device having the internal total internal reflection prism can be improved.

The figure which shows the structure of the projection type image display device in Embodiment 1. The figure which shows the main part of the projection type image display device in Embodiment 1. The figure explaining the relationship between the angle of a light ray with respect to an optical axis and the optical path length difference.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art.
It should be noted that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 4.

[1-1. Constitution]
[1-1-1. Overview of projection type video display device]
FIG. 1 is a diagram showing a configuration of a projection type image display device 10 according to the first embodiment. The illumination light RL emitted from the light source enters the first prism 101 of the internal total internal reflection prism 100 (hereinafter referred to as “TIR prism 100”) from the third surface 101c, and passes through the first prism 101 to the digital micromirror device 110. (Hereinafter referred to as "DMD110"). The illumination light RL incident on the DMD 110 is reflected by the micromirrors, and when reflected, the orientation of each micromirror is controlled based on the video signal, so that the illumination light RL is modulated into the video light R and emitted. The image light R passes through the first prism 101 and the second prism 102 of the TIR prism 100, then passes through the transmission plate 120, and is incident on the projection lens 130. The projection lens 130 magnifies and projects the image light R on the screen 200.

[1-1-2. Configuration of main parts of projection type image display device]
FIG. 2 is a diagram showing a main part of the projection type image display device 10 according to the first embodiment. The first prism 101 and the second prism 102 are each composed of a triangular prism made of optical glass having a refractive index of 1.516. The first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 are adhered to each other by an adhesive containing glass beads. As a result, the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 face each other in parallel with each other via an air layer 104 (adhesive layer containing glass beads) having a size of about 5 μm. As a result, the illumination light RL incident on the boundary surface (first surface 101a) of the first prism 101 at an angle larger than the critical angle is the difference between the refractive index of the glass constituting the first prism 101 and the refractive index of the air layer 104. Is totally reflected by.

The second surface 101b of the first prism 101 and the second surface 102b of the second prism 102 are arranged in parallel with the exit surface 110a of the DMD 110, respectively. On the other hand, the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 are inclined by an angle α with respect to the exit surface 110a of the DMD 110. The angle α is, for example, 33 degrees. Here, when the description is made based on the central axis of the image light R (hereinafter, appropriately referred to as “optical axis Ac” of the image light R), the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 Can be said to be inclined by an angle α with respect to the reference plane Pp perpendicular to the optical axis Ac of the image light R incident on the TIR prism 100.

The transmission plate 120 is a flat glass having a thickness of 1 mm using a material having a refractive index of 1.516. The transmission plate 120 may be formed by using a material other than glass that transmits light. The transmission plate 120 is provided to correct the optical path length difference caused by the air layer 104 of the TIR prism 100. The transmission plate 120 is inclined at an angle β with respect to the exit surface 110a of the DMD 110. Here, when the description is made based on the optical axis Ac of the image light R, the transmission plate 120 is inclined by an angle β with respect to the reference plane Pp perpendicular to the optical axis Ac of the image light R incident on the TIR prism 100. It can be said. The angle β may be referred to as an inclination angle β. The angle β is, for example, 11 degrees. The transmission plate 120 is inclined to the same side as the side on which the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 are inclined with respect to the reference plane Pp.

The projection lens 130 is a projection lens having an aperture F value of 2.5 based on the effective aperture, and allows incident light having an incident angle of 11.5 degrees with respect to the optical axis Ac of the DMD 110 to reach the screen 200. .. In the present embodiment, the transmission plate 120 is tilted so that the optical path length difference between the light rays Ra and the light rays Rb inside the light rays with an incident angle of 11 degrees is 0, instead of the light rays having an incident angle of 11.5 degrees. The angle β of is set. That is, the angle β is set based on the aperture smaller than the effective aperture. When the angular distribution of the intensity of the image light R is taken into consideration, the light rays Ra and the light rays Rb having an incident angle of 11 degrees slightly inside are corrected rather than the light rays having the maximum incident angle of 11.5 degrees. This is because better optical characteristics can be obtained overall.

Next, the optical path length difference between the light rays included in the image light R will be described in more detail. Since the image light R incident on the TIR prism 100 has a spread, the angle of incidence on the air layer 104 is different between the light rays Ra and the light rays Rb of the image light R. Therefore, the optical path length of the air layer 104 portion (indicated by "ray Ra104" in FIG. 2) in the ray Ra and the optical path length of the air layer 104 portion (indicated by "ray Rb104" in FIG. 2) in the ray Rb are different. It becomes. In the example of FIG. 2, the optical path length of the air layer 104 portion (ray Ra104) in the ray Ra is shorter than the optical path length of the air layer 104 portion (ray Rb104) in the ray Rb.

ここで、
Ｆ：光線Ｒａ，Ｒｂの入射角度（光線Ｒａ，Ｒｂが光軸Ａｃに対してなす角度（上記の例では１１度））、
Ａ：空気層１０４の厚み
α：空気層１０４が基準平面Ｐｐに対してなす角度（第１プリズム１０１の第１面１０１ａ及び第２プリズム１０２の第１面１０２ａが基準平面Ｐｐに対してなす角度）、
ｎ：第１プリズム１０１及び第２プリズム１０２の屈折率（上記の例では１．５１６）である。
これらのうち、Ａ、α、ｎは構造によって決まる。Ｆは任意である。しかし、図３に示すように、光線Ｒａ，Ｒｂが光軸Ａｃに対してなす角度（投写レンズ１３０への入射角度）が大きくなるほど、非点収差の要因となる空気層１０４での光路長差が大きくなる。そのため、入射角度Ｆは、開口Ｆ値によって定まる最大角度よりも一定程度小さい角度とすることが好ましい。なお、射出角θ１１０と最大角度とがほぼ等しいとした場合、射出角θ１１０に基づいて数式３の条件を満たす角度に設定してもよい。

Here, assuming that the optical path length of the air layer 104 portion (ray Ra104) in the ray Ra is LRa104 and the optical path length of the air layer 104 portion (ray Rb104) in the ray Rb is LRb104, the optical path lengths LRa104 and LRb104 are expressed in Equations 1 and 2. Can be obtained by.

here,
F: Incident angle of light rays Ra and Rb (angle formed by light rays Ra and Rb with respect to the optical axis Ac (11 degrees in the above example)),
A: Thickness of the air layer 104 α: Angle formed by the air layer 104 with respect to the reference plane Pp (angle formed by the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 with respect to the reference plane Pp. ),
n: The refractive index of the first prism 101 and the second prism 102 (1.516 in the above example).
Of these, A, α, and n are determined by the structure. F is arbitrary. However, as shown in FIG. 3, the larger the angle formed by the light rays Ra and Rb with respect to the optical axis Ac (the angle of incidence on the projection lens 130), the greater the difference in optical path length in the air layer 104, which causes astigmatism. Becomes larger. Therefore, it is preferable that the incident angle F is a certain degree smaller than the maximum angle determined by the aperture F value. Assuming that the injection angle θ110 and the maximum angle are substantially equal, the angle may be set to satisfy the condition of Equation 3 based on the injection angle θ110.

The optical path length difference Lδ104 when the light rays Ra and the light rays Rb pass through the air layer 104 can be obtained by the formula 4 based on the LRa 104 obtained by the formula 1 and the LRb 104 obtained by the formula 2.

In order to correct the optical path length difference Lδ104, the transmission plate 120 is arranged at an angle β with respect to the reference plane Pp as shown in FIG.

By inclining by the angle β in this way, the angles incident on the transmission plate 120 differ between the light rays Ra and the light rays Rb of the image light R. Therefore, the optical path length of the transmission plate 120 portion (light ray Ra120) in the light ray Ra and the optical path length of the transmission plate 120 portion (light ray Rb120) in the light ray Rb are different. In the example of FIG. 2, the optical path length of the transmission plate 120 portion (ray Ra120) in the ray Ra is longer than the optical path length of the transmission plate 120 portion (ray Rb120) in the ray Rb.

Ｆ：光線Ｒａ，Ｒｂの入射角度（光線Ｒａ，Ｒｂが光軸Ａｃに対してなす角度（上記の例では１１度））、
ｔ：透過板１２０の厚み、
β：透過板１２０が基準平面Ｐｐに対してなす角度、
Ｎ：透過板１２０の屈折率（上記の例では１．５１６）
である。
これらのうち、ｔ、β、Ｎは構造によって決まる。Ｆは、ＴＩＲプリズム１００の空気層１０４での光線Ｒａ，Ｒｂの光路長の計算に使用したものと同一である。 Here, assuming that the air-equivalent optical path length of the transmission plate 120 portion (ray Ra120) in the ray Ra is LRa120 and the air-equivalent optical path length of the transmission plate 120 portion (ray Rb120) in the ray Rb is LRb120, the optical path lengths LRa120 and LRb120. Can be obtained by Equations 5 and 6.

F: Incident angle of light rays Ra and Rb (angle formed by light rays Ra and Rb with respect to the optical axis Ac (11 degrees in the above example)),
t: Thickness of the transparent plate 120,
β: The angle formed by the transmission plate 120 with respect to the reference plane Pp,
N: Refractive index of the transmission plate 120 (1.516 in the above example)
Is.
Of these, t, β, and N are determined by the structure. F is the same as that used for calculating the optical path lengths of the light rays Ra and Rb in the air layer 104 of the TIR prism 100.

The air-equivalent optical path length difference Lδ120 when the light rays Ra and the light rays Rb pass through the transmission plate 120 can be obtained by the mathematical formula 7 based on the LRa 120 obtained by the mathematical formula 5 and the LRb 120 obtained by the mathematical formula 6.

If the inclination angle β of the transmission plate 120 is set so that the size of the Lδ 104 obtained by the formula 4 and the size of the Lδ 120 obtained by the formula 7 are equal to each other, that is, the inclination angle β of the transmission plate 120 is set so as to satisfy the condition of the following formula 8, the air layer 104 The generated optical path length difference Lδ104 can be canceled (corrected) by the optical path length difference Lδ120 generated in the transmission plate 120.

When Equation 4 and Equation 7 are applied to Equation 8, Equation 9 is obtained.

As described above, in the present embodiment, by arranging the transmission plate 120 at an angle β, the optical path length difference Lδ104 between the light rays Ra and the light rays Rb generated when the image light R passes through the air layer 104 can be obtained. It can be canceled by the transparent plate 120 arranged at an angle β tilt. That is, the optical path lengths of the light rays Ra and the light rays Rb can be made as uniform as possible. Therefore, the occurrence of astigmatism due to the difference in optical path length can be suppressed. Therefore, the quality of the projected image can be improved.

[1-1-3. Effect, etc.]
The projection type image display device 10 of the present embodiment projects the image light R emitted from the DMD 110 (an example of the image generation unit) via the TIR prism 100 (internal total internal reflection prism) and the projection lens 130. In the projection type image display device 10, a transmission plate 120 that transmits image light R is arranged on an optical path between the TIR prism 100 and the projection lens 130. The TIR prism 100 includes a first prism 101 (first prism) having a first surface 101a (first surface) and a second prism 102 (second prism) having a first surface 102a (second surface). ) And. The first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 face each other in parallel via the air layer 104 and are perpendicular to the optical axis Ac of the image light R incident on the TIR prism 100. It is inclined with respect to the reference plane Pp. The transmission plate 120 is inclined to the same side as the side on which the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 are inclined with respect to the reference plane Pp.

According to the present embodiment, the first surface 101a of the first prism 101 of the TIR prism 100 and the first surface 102a of the second prism 102 are inclined on the optical path between the TIR prism 100 and the projection lens 130. Since the transmission plate 120 inclined to the same side as the side is provided, it is possible to correct the aberration generated in the air layer 104 of the TIR prism 100. Therefore, the optical performance of the projection type image display device 10 having the TIR prism 100 can be improved.

Further, the inclination angle β of the transmission plate 120 is an angle at which the optical path length difference Lδ104 generated in the air layer 104 between the light rays included in the image light R incident on the TIR prism 100 is canceled by the optical path length difference Lδ120 generated in the transmission plate 120. Is set to. Thereby, the optical path length difference Lδ104 generated when the light rays included in the image light R pass through the air layer 104 can be canceled by the optical path length difference Lδ120 in the transmission plate 120.

The tilt angle β of the transmission plate 120 is set based on a predetermined aperture that is smaller than the effective aperture of the projection lens 130. As a result, aberrations can be suppressed in a well-balanced manner as the entire image light R.

(Other embodiments)
The present disclosure is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit of the present disclosure.

(1) In the projection type image display device 10 of the above embodiment, the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 face each other in parallel. However, in the present disclosure, the first surface 101a of the first prism 101 and the first surface 102a of the second prism 102 may face each other substantially in parallel.

(2) In the projection type image display device 10 of the above embodiment, the inclination angle β of the transmission plate 120 is the optical path length difference generated in the air layer 104 between the light rays Ra and Rb included in the image light R incident on the TIR prism 100. The angle at which Lδ104 is canceled by the optical path length difference Lδ120 generated by the transmission plate 120 is set. However, the inclination angle β of the transmission plate 120 may be set so that the optical path length of the light ray Ra and the optical path length of the light ray Rb between the DMD 110 and the projection lens 130 are equal to each other. The inclination angle in this case may be geometrically obtained in consideration of the refractive index of the medium as in the above embodiment.
(3) In the projection type image display device 10 of the above embodiment, a case where the image light R emitted from the DMD 110 is incident on the TIR prism 100 without passing through another optical system is illustrated. However, the projection type display device of the present disclosure is not limited to this. In the projection type display device of the present disclosure, for example, three color prisms for RGB may be arranged between the TIR prism and the DMD, and three DMDs for RGB may be provided. .. Even in this case, the transmission plate has the first surface of the first prism and the second surface of the second prism with respect to the reference plane perpendicular to the optical axis of the image light incident on the TIR prism. Astigmatism due to the air layer of the TIR prism can be similarly improved by arranging the TIR prism so as to be inclined to the same side as the inclined side.

(4) In the above embodiment, the case where the transmission plate 120 is fixed at a predetermined angle β (11 degrees in the above embodiment) with respect to the optical axis of the image light R is illustrated. However, in the present disclosure, the transmission plate 120 may have a minute tilt angle varied with reference to a position tilted by a predetermined angle β. By varying the tilt angle of the transmission plate 120 by a small angle in this way, it is possible to integrally configure the pixel position moving means for moving the pixel position of the projected image to increase the number of pixels.

As described above, the embodiments considered to be the best mode and other embodiments have been provided by the accompanying drawings and detailed description. These are provided to those skilled in the art to illustrate the subject matter described in the claims by reference to a particular embodiment. Therefore, in the scope of claims or the equivalent thereof, with respect to the above-described embodiment,
Various changes, replacements, additions, omissions, etc. can be made.

The present disclosure is widely applicable to projection type display devices such as projectors.

10 Projection type image display device 100 TIR prism 101 1st prism 101a 1st surface 101b 2nd surface 101c 3rd surface 102 2nd prism 102a 1st surface 102b 2nd surface 104 Air layer 110 DMD
110a Emission surface 120 Transmission plate 130 Projection lens 200 Screen Ac Optical axis Pp Reference plane R Image light Ra Ray Ra104 Ray Ra120 Ray Rb Ray Rb104 Ray Rb120 Ray RL Illumination light

Claims (3)

It is a projection type display device that projects the image light emitted from the image generator through the internal total internal reflection prism and the projection lens.
A transmission plate that transmits the image light is arranged on the optical path between the internal total internal reflection prism and the projection lens.
The internal total reflection prism includes a first prism having a first surface and a second prism having a second surface.
The first surface and the second surface face each other in parallel or substantially parallel to each other via an air layer, and are inclined with respect to a reference plane perpendicular to the optical axis of the image light incident on the internal total internal reflection prism. And
The transmission plate is inclined to the same side as the side on which the first surface and the second surface are inclined with respect to the reference plane.
Projection type display device. The inclination angle of the transmission plate is set to an angle at which the optical path length difference generated in the air layer between the light rays included in the image light incident on the internal total reflection prism is canceled by the optical path length difference generated in the transmission plate. Yes,
The projection type display device according to claim 1. The tilt angle of the transmission plate is set based on a predetermined aperture smaller than the effective aperture of the projection lens.
The projection type display device according to claim 2.

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