JP5087765B2 - Projection system - Google Patents

Description

The present invention relates to a projection system using a diffusion film.

In recent years, as the demand for projection displays has increased, there has been a demand for wide viewing angles, high contrast, and high resolution of screens. As a conventional technique for these, there is a technique based on a combination of a Fresnel lens, a lenticular lens, and a diffusion plate made of fine particles for wide viewing angle. For high contrast, an external light control technique using a black mask is used. Yes (for example, Non-Patent Document 1), and a technique for forming the lenticular lens pitch with high definition is known (for example, Non-Patent Document 1).
SID 2005, p.1914-1917, 'A Super Fine-Pitch Screen for Rear Projection TV.'; S.Iwata etc.; Toppan Printing Co., Ltd.

  As the projection system becomes larger and thinner, the angle of incident light at the screen position changes greatly. In order to deliver these lights to the observer side, the conventional technique first aligns the light traveling direction in the normal direction of the screen with a Fresnel lens, then diffuses in the lateral direction with a lenticular lens, and then adds a black mask at the focal point. Measures against external light by (stripes) and finally diffusion in the vertical direction is realized by a diffusion plate made of fine particles or the like.

  In the above prior art, the functions required for the screen are made by stacking four different optical devices (a Fresnel lens, a lenticular lens, a black mask, a diffusion plate made of fine particles, etc.), and each layer of the optical device performs the function. Since this is realized by sharing, multiple images are generated by multiple reflection at the interface of the stacked optical devices. In order to avoid this, in the prior art, a Fresnel lens or a lenticular lens contains fine particles and is blurred to make a multiple image invisible. Therefore, it is difficult in principle to display a high-resolution image with a wide viewing angle with the screen according to this conventional technique. Further, in the case of a diffusion plate (particulate diffusion for short) with fine particles or the like, the wider the viewing angle, the more backscattering occurs and the contrast deteriorates (resolution deteriorates).

Therefore, in the present invention, the function required for the screen is not shared by a plurality of stacked optical devices, but is realized by only one optical device, and fine particles are not used at all for the physical mechanism of diffusion. by the optical system, in the prior art difficult, and an object thereof is to provide a projection system using a spread-fill beam capable image display wide viewing angle and high contrast at high resolution.

  An optical device (or optical system) in which the surface (and / or the back surface) of only one film is partially covered with a thin film of a medium other than the film medium is also counted as one sheet.

The inventors have determined that in order to avoid resolution degradation due to multiple images and fine particle diffusion, the function required for the screen needs to be realized by only one thin micro-optical system film.
First, combining the functions of a Fresnel lens and a lenticular lens requires a system that exhibits a certain diffusion characteristic even when the incident angle changes. As a diffusion characteristic, it is desirable to have a top-hat-like diffusion that diffuses uniformly within a certain diffusion angle region, and does not spread energy, and is bright in the diffusion angle region. Moreover, if the optical system has the same structure at different locations in the screen, it is very easy to manufacture. In order to make the physical mechanism of diffusion small in backscattering, diffusion based on the surface shape rather than fine particles is excellent. Therefore, only one optical system (an optical system consisting of a single optical film) that diffuses only by the surface shape, and that forms a screen having the same surface shape at different locations in the plane is very It is thought that it has excellent characteristics and is easy to manufacture.

As a result of intensive studies based on the above-described new concept, the inventors have made the present invention.
That is, the present invention is as follows.
[Claim 1] A projection system obtained by applying the diffusion film according to any one of the following reference items 1 to 15 to a rear projection system or a front projection system, wherein the diffusion film according to the reference item 14 or 15 is applied. On the other hand, a projection system characterized in that incident light corresponding to each of two or more different incident angle regions of the diffusion film is incident from separate projectors.
Serial a single film to be emitted by diffusing Reference claim 1 incident light, the diffusion is realized only by the surface shape of the film, the emitted light angle of incidence within the incident angle region of the incident light A diffusion film characterized by having a substantially constant top-hat-like diffusion characteristic of diffusing with a substantially constant light intensity within an exit diffusion angle region corresponding to the incident angle region regardless of the difference .

The surface shape design of the Reference claim 2 wherein the film, diffusion film as described in Reference claim 1, characterized in that the size of the size and emission diffusion angle region of the incident angle region can be controlled independently of each other.
[ Reference Item 3] The reference item 1 or 2, wherein the angle of the center direction of the incident angle region and the angle of the center direction of the outgoing diffusion angle region can be controlled independently of each other by the surface shape design of the film. The diffusion film described in 1.
[ Reference Item 4] The diffusion film according to any one of Reference Items 1 to 3, wherein the surface shape on both the incident side and the emission side is a microlens array shape or a lenticular lens shape.

[ Reference Item 5] The size of the incident angle region and the size of the exit diffusion angle region are determined by the surface shape design of the film, the NA of the incident side microlens or lenticular lens, and the exit side microlens or lenticular lens. diffusion film described in reference claim 4 in by the NA adjusting respectively, characterized in that it is controlled independently of each other.
[ Reference Item 6] The angle in the center direction of the incident angle region and the angle in the center direction of the exit diffusion angle region are determined depending on the surface shape design of the film, and the incident side microlens or lenticular lens and the exit side microlens. Alternatively, the diffusion film according to Reference Item 4 or 5, wherein the diffusion film can be controlled independently of each other by adjusting the shift amount of the optical axis and the selection range of the partial shape with both of the lenticular lenses.

[ Reference Item 7] The diffusion film according to any one of Reference Items 4 to 6, wherein a lens having a microlens array shape or a lenticular lens shape on the incident side is of a total reflection type.
[ Reference Item 8] A diffusion film obtained by coating a part of a lens surface having a microlens array shape or a lenticular lens shape on the incident side of the diffusion film according to any one of Reference Items 4 to 6 with a reflection medium.

[ Reference Item 9] The diffusion film according to any one of Reference Items 1 to 3, wherein a surface shape for realizing diffusion is formed only on one side of the film.
[ Reference Item 10] The surface shape for realizing diffusion formed only on one side of the film is an optical element array shape in which a lens and a mirror are combined, and is equivalent to the control according to any one of claims 4 to 6. 10. The diffusion film according to Reference Item 9, which can be controlled.

[ Reference Item 11] A diffusion film obtained by coating the mirror portion in the optical element array shape of the diffusion film according to Reference Item 10 with a reflection medium.
[ Reference Item 12] A part of the surface of one or both of the incident side and the output side of the diffusion film according to any one of Reference Items 1 to 11 is covered with a black mask for measures against external light. Diffusion film characterized by

[ Reference Item 13] A diffusion film obtained by adding a polarizing plate or a circularly polarizing plate for measures against external light to the diffusion film according to any one of Reference Items 1 to 12.
[ Reference Item 14] There are a plurality of sets of incident angle regions and corresponding exit diffusion angle regions, each set of incident angle regions does not overlap with the other set, and each set of exit diffusion angle regions is The diffusion film according to any one of Reference Items 1 to 8, which does not overlap with other sets.

[ Reference Item 15] A diffusion film characterized in that a reflection plate is added to the diffusion film according to any one of Reference Items 1 to 14 to obtain a reflection type film .

  According to the present invention, a function required for a projection system screen can be realized by only the surface shape and by only one optical device, and high-resolution image display is possible. Further, there is no scattering mechanism for fine particles and the like, and a high-contrast image display can be obtained. In addition, a uniform and wide viewing angle characteristic with a constant top-hat-like diffusion characteristic that does not depend on the incident angle is possible, and the size of the angle region and The ability to control the direction allows a wide range of applications in ultra-thin rear projection displays and the like.

The diffusion film according to the present invention (hereinafter also referred to as a new D-film) has only a surface shape of one thin optical system film, and exhibits a function that combines the functions of a Fresnel lens, a lenticular lens, and a diffusion plate. However, it is ideal for high-resolution, high-contrast image display, and it is ideal for manufacturing to have a uniform structure at different locations. The best mode is to correspond to the reference section 1～3,8, the surface shape of the requirements of the new D-film corresponds to the reference section 4～7,9.

First, Reference Item 4 which is the best surface shape for expressing the diffusion characteristics described in Reference Item 1, which is a basic function of the new D-film, will be described. 1A and 1B are diagrams for explaining the principle of the diffusion film described in Reference Item 4. FIG. 1A shows the structure of the optical system, and FIG. 1B shows the function. Consider a two-lens lens optical system as shown in FIG. Let the focal lengths of the two lenses 1 and 2 be f ₁ and f ₂ , respectively. Here, consider a case where f ₁ = f ₂ , the optical axes of both lenses (lens optical axes) coincide, and the distance between lenses = f ₁ (= f ₂ ). The lens diameter is the same d for both lenses. The light beams 102 and 105 are vertically incident light incident in parallel to the lens optical axis, and are collected by the lens 1 at a focal position on the optical axis. Since the optical axis of the lens 2 coincides with the optical axis of the lens 1 and the distance between the principal planes of the lens 1 and the lens 2 is f ₁ = f ₂ , the light beams 102 and 105 are collected at the center (node) of the lens 2. Therefore, the direction of the light beam passes through the lens 2 without changing. At this time, the light rays 102 and 105 are emitted at an angle ± θ ₁ represented by the following expression with respect to the optical axis.

次に、レンズ光軸上方θ₁の角度で入射してくる光線101,104を考える。この光はレンズ１によってレンズ１の焦点面に集光するが、この焦点面に設置されたレンズ２の作用によって、光軸と±θ₁の角をなして出射することになる。この拡散特性は、光線102,105と同じである。理由は後述する。次に、レンズ光軸下方θ₁の角度で入射してくる光線106,103を考える。この光も光線102,105と同様に、レンズ１によってレンズ１の焦点面に集光し、レンズ２によって、光軸と±θ₁の角をなして出射することになる。次に、この光学的メカニズムを説明する。

Next, consider the rays 101 and 104 incident at an angle θ ₁ above the lens optical axis. This light is condensed on the focal plane of the lens 1 by the lens 1, and is emitted at an angle of ± θ ₁ with the optical axis by the action of the lens 2 installed on the focal plane. This diffusion characteristic is the same as that of the light beams 102 and 105. The reason will be described later. Next, consider the light rays 106 and 103 incident at an angle θ ₁ below the lens optical axis. Similarly to the light rays 102 and 105, this light is condensed on the focal plane of the lens 1 by the lens 1, and is emitted by the lens 2 at an angle of ± θ ₁ with the optical axis. Next, this optical mechanism will be described.

Now, pay attention to the upper end point of the lens 1 in FIG. From this point, light rays 101, 102, 103 are emitted toward the lens 2. Since the distance between the lens principal planes is f ₂ (= f ₁ ), when these light rays 101, 102, 103 are viewed from the lens 2, light emitted from one point on the front focal plane of the lens 2 enters the lens 2. Therefore, the light rays 101, 102, 103 are parallel to each other on the exit side of the lens 2. Similarly, paying attention to the lower end point of the lens 1, the light beams 104, 105, and 106 are incident on the lens 2 from one point on the front focal plane of the lens 2, and thus are parallel to each other on the exit side of the lens 2.

Now, if the rays 105 and 102 are emitted at ± θ ₁ with respect to the optical axis, and the rays 101, 102, and 103 are parallel to each other on the emission side, and the rays 104, 105, and 106 are parallel to each other on the emission side, the rays 101 and 104 are ± θ _{1 with} respect to the optical axis. The light rays 103 and 106 are emitted at ± θ ₁ with respect to the optical axis.
The above discussion is for the case where the incident light angle to the lens 1 is only 0 ° and ± θ _1, but the incident angle θ _in to the lens 1 is continuous between −θ ₁ ≦ θ _in ≦ + θ _1. The focal point on the main plane of the lens 2 only changes from -d / 2 to + d / 2, and the angle of the outgoing light is in any case in the optical axis. On the other hand, it is ± θ ₁ and a constant angle.

Next, the incident position of incident light will be discussed. Now, paying attention to the rays 101 and 104 whose incident angle is θ ₁ above the optical axis, consider a ray parallel to the rays 101 and 104 and having an incident position between the rays 101 and 104. These rays, depending on the incident position, the exit angle between -θ ₁ ~ + θ _1, the direction of light is changed, to spread, it is clear from FIG. Therefore, a parallel beam whose incident angle is above the optical axis with the light beams 101 and 104 as the upper and lower ends of the beam is diffused and emitted from the lower end of the lens 2 on the emission side by −θ ₁ to + θ ₁ . Similarly, considering a vertically incident parallel beam having the light rays 102 and 105 as the upper and lower ends, light is diffused at −θ ₁ to + θ ₁ from the center position of the lens 2 on the exit side, and the light rays 103 and 106 are set as the upper and lower ends. The parallel beam whose incident angle is θ ₁ below the optical axis is diffused and emitted from the upper end of the lens 2 on the emission side at −θ ₁ to + θ ₁ .

It is clear that the above argument holds true for all parallel beams whose incident angles continuously change from −θ ₁ to + θ ₁ and whose upper and lower ends are the upper and lower ends of the beam. FIG. 1B shows the above characteristics in a graph. As shown in the upper part of FIG. 1B, the parallel beam incident at the incident angles −θ ₁ to + θ ₁ becomes a δ function on the graph, and the incident angle region −θ ₁ ≦ θ _in depending on the incident angle. ≦ + [delta] function between the theta ₁ is decided to move. The characteristic for the emission angle is the lower graph, and even if the δ function in the upper graph moves, the emitted light shows a constant top-hat diffusion characteristic, and the angle −θ _{1 at} the left end and the right end of the output diffusion angle region , + Θ ₁ indicates that there is no change.

  From the above discussion, a micro optical system array that is finer than the resolution that requires the size of the optical system in FIG. 1A (shown for each beam incident angle in FIGS. 2A to 2C) is used as a film. When the surface shape is on both the front and back surfaces, a diffusion film 3 as shown in FIG. 2 (d) is obtained. The diffusion film 3 corresponds to claim 4, and the front and back surfaces are filled with a film medium. The front and back surfaces of the diffusion film 3 have a plano-convex lens corresponding to the lenses 1 and 2 on the front and back surfaces. The air interface side has a shape in which a plurality of optical axes coincide with each other, and the thickness of the film is determined by the focal length of the lens in the medium. The size of the lens is below the required resolution. According to this, a top hat type diffusion characteristic equivalent to that shown in FIG. When the top-hat diffusion characteristic is two-dimensional, the film double-sided shape is a microlens array shape, and the one-dimensional case is a lenticular lens array shape.

  The top-hat diffusion characteristic is ideally “constant”, but may deviate from constant due to an approximation error, a manufacturing error, or the like. However, if the deviation is within an allowable range, there is no particular problem. Therefore, in order to include such a case, the top hat diffusion characteristic of the diffusion film according to the present invention is “almost constant”. As an allowable range of deviation from the constant, the size of the half value region of the light intensity distribution in the exit diffusion angle region is 50% or more (of course 100% or less) of the entire exit diffusion angle region, and Within the half-value region, the variation range of the light intensity is preferably within ± 50% of the average value of the light intensity.

Next, the diffusion film described in Reference Item 5 that realizes the function described in Reference Item 2 will be described. FIG. 3A shows an optical system having a two-lens configuration for realizing this function, and FIG. 3B shows its function. Basically, it operates on the same principle as the mechanism of the optical system shown in FIG. 1, but by changing the NA (F number) of the incident side lens and the NA (F number) of the exit side lens, the incident angle is changed. It differs from the optical system of FIG. 1 in that the size of the region and the size of the exit diffusion angle region are controlled.

FIG. 3 shows a case where the exit diffusion angle region is made larger than the incident angle region. In this case, the NA of the entrance-side lens 1 may be reduced and the NA of the exit-side lens 2 may be increased. Since the lens diameter d is the same, f ₁ > f ₂ . Here, f ₁ and f ₂ are the focal lengths of the lenses 1 and 2, respectively. The optical axes of the lenses 1 and 2 are matched, and the distance between the main planes of the lenses 1 and ₂ is f2. The range of the incident angle θ _in is −θ ₁ ≦ θ _in ≦ + θ ₁ from θ ₁ expressed by the equation (1), but the range of the outgoing diffusion angle θ _out is determined by θ ₂ expressed by the following equation: −θ ₂ ≦ θ _out ≦ + θ ₂ .

光学的メカニズムは、図１の光学系とほぼ同等である。今、光線109,110に着目しよう。光線109,110は入射角±θ₁でレンズ１の端に入射し、レンズ１の前焦点面と光軸との交点を通過する光であるから、レンズ１を通過後は光軸と平行になり、レンズ２を通過後は、レンズ２の光軸上の後焦点に集光する。よって、光線109,110の出射角は±θ₂となる。次に、レンズ１の上端点に着目すると、光線107,108,109はこの１点からレンズ２へ入射している。レンズ１はレンズ２の前焦点面に設置してあるから、光線107,108,109はレンズ２を通過後は互いに平行となる。光線110,111,112についても同じ理由で、レンズ２を通過後は互いに平行となる。よって、光線112,109で決まる拡散角は±θ₂であり、光線111,108で決まる拡散角も±θ₂となる。同様に、光線110,107で決まる拡散角も±θ₂となる。

The optical mechanism is almost the same as that of the optical system of FIG. Now let's focus on the rays 109,110. Since the light rays 109 and 110 are incident on the end of the lens ₁ at an incident angle ± θ ₁ and pass through the intersection of the front focal plane of the lens 1 and the optical axis, the light rays 109 and 110 are parallel to the optical axis after passing through the lens 1. After passing through the lens 2, the light is condensed at the rear focal point on the optical axis of the lens 2. Therefore, the emission angles of the light beams 109 and 110 are ± θ ₂ . Next, focusing on the upper end point of the lens 1, the light beams 107, 108 and 109 are incident on the lens 2 from this one point. Since the lens 1 is installed on the front focal plane of the lens 2, the light beams 107, 108, and 109 are parallel to each other after passing through the lens 2. For the same reason, the rays 110, 111, and 112 are parallel to each other after passing through the lens 2. Therefore, the diffusion angle determined by the light beams 112 and 109 is ± θ ₂ , and the diffusion angle determined by the light beams 111 and 108 is also ± θ ₂ . Similarly, the diffusion angle determined by the light beams 110 and 107 is ± θ ₂ .

The characteristics of this optical system are shown in a graph as shown in FIG. The light incident in the angle range of −θ ₁ to + θ ₁ exhibits a constant top hat diffusion characteristic regardless of the incident angle, and ± θ ₂ which is the left and right ends of the top hat diffusion characteristic does not change. The theta ₁ and theta ₂ and, (1), (2) from equation, the following relationship is established.

(3a)式は、レンズ１のf₁とレンズ２のf₂を設定することにより、入射角度領域の大きさと出射拡散角度領域の大きさを互いに独立に制御できることを意味している。
そこで、図３（ａ）の光学系（図４（ａ）〜（ｃ）にビーム入射角度ごとに示した）のサイズを必要とする解像度よりも細かくしたマイクロ光学系アレイを、フィルムの表裏両面側の表面形状とすると、図３（ｄ）に示すような拡散フィルム３が得られる。これは、参考項５に対応するものであり、表裏面間がフィルム媒体で埋まっており、表裏面形状は、表,裏にそれぞれレンズ１,２に対応する平凸レンズが凸面側を空気界面側として光軸を一致させて複数配置された形状にしてあり、フィルムの厚さは、媒体中のレンズ２の焦点距離f₂で決まる。レンズの大きさは必要とする解像度以下である。これによれば、図３（ｂ）と同等なトップハット的拡散特性が得られる。トップハット的拡散特性が２次元的の場合、フィルム両面形状はマイクロレンズアレイ形状であり、１次元的の場合がレンティキュラレンズアレイ形状である。

Equation (3a) means that the size of the incident angle region and the size of the exit diffusion angle region can be controlled independently of each other by setting f ₁ of the lens ₁ and f ₂ of the lens 2.
Therefore, a micro optical system array having a finer resolution than that which requires the size of the optical system in FIG. 3A (shown for each beam incident angle in FIGS. 4A to 4C) is provided on both the front and back sides of the film. If it is set as the surface shape of the side, the diffusion film 3 as shown in FIG.3 (d) will be obtained. This corresponds to Reference Item 5, where the front and back surfaces are filled with film media, and the front and back surfaces of the front and back surfaces of the plano-convex lenses corresponding to the lenses 1 and 2 are the convex surface side and the air interface side. the optical axis to coincide as shown here on more than one arranged shape, the thickness of the film is determined by the focal length f ₂ of the lens 2 in the medium. The size of the lens is below the required resolution. According to this, a top hat type diffusion characteristic equivalent to that shown in FIG. When the top-hat diffusion characteristic is two-dimensional, the film double-sided shape is a microlens array shape, and the one-dimensional case is a lenticular lens array shape.

Next, Reference Item 6 will be described. First, the angle in the center direction of the incident angle region and the angle in the center direction of the exit diffusion angle region are controlled independently of each other by adjusting the selection range of the partial shape of the lens on the entrance side and the exit side in Reference Item 6. Explain the principle of the requirement that it is possible.
FIG. 5A shows an optical system that realizes this control function, and FIG. 5B shows the function in a graph. This optical system has a two-lens configuration, and the optical axes of the lenses 1 and 2 on the input side (incident side) and output side (outgoing side) coincide with each other. The effective portion of the lens principal plane exists in a region where the distance is d ₁ to d ₂ . That is, the lens 2 selects and uses only a part of the entire lens. Of course, it is possible to function even if only a part of the lens 1 is selected or only a part of each of the lenses 1 and 2 is selected.

FIG. 5 shows an example in which a part of the lens 2 is selected. The distance between the main planes of the two lenses is f ₂ (f ₂ = f ₁ ). The mechanism of this optical system is basically the same as that of the optical system shown in FIG. Since only the vicinity of the optical axis of the lens 2 is not used, it is easy to change the incident angle of the beam incident on the optical system in FIG. 1A to the range where the lens 2 in FIG. The function is understandable. Due to the function of the optical system of FIG. 1, even if the incident angle is changed, the top hat diffusion characteristic does not change, and therefore the top hat diffusion characteristic of FIG. 5 does not change. Therefore, the top-hat diffusion characteristic on the emission side is a characteristic fixed within the same range of −θ ₁ to + θ ₁ as that of FIG. When the optical system of FIG. 3A is modified in the same manner as the modification from FIG. 1A to FIG. 5A, it is within the same range of −θ ₂ to + θ ₂ as that of FIG. It becomes a fixed characteristic.

The incident angle region is determined by the incident angle at which the parallel light that has passed through the lens 1 can pass through the lens 2. Therefore, the light beam 119 that is the center of the parallel beam with the light beams 113 and 116 as the upper and lower ends, and the light beams 115 and 118 as the upper and lower ends. It is determined by the incident angle of the light beam 120 that becomes the center of the parallel beam. Since the rays 119 and 120 pass through the center (node) of the lens 1, the direction does not change in the lens 1. Therefore, the incident angles of the light beams 119 and 120 are θ ₃ and θ ₄ represented by the following equations, as shown in the figure.

よって、この光学系にθ₃〜θ₄の範囲内の平行ビームを入射しても、図５（ｂ）の上部分に示すように、常に一定のトップハット的拡散特性が発現する。θ₃とθ₄は、ｄ₁とｄ₂によって制御できるため、θ1を固定したまま、つまり、出射拡散角度領域を固定したまま、独立に入射角度領域を制御できることを意味している。

Therefore, even if a parallel beam in the range of θ ₃ to θ ₄ is incident on this optical system, a constant top-hat diffusion characteristic is always exhibited as shown in the upper part of FIG. Since θ ₃ and θ ₄ can be controlled by d ₁ and d ₂ , this means that the incident angle region can be controlled independently while θ 1 is fixed, that is, the outgoing diffusion angle region is fixed.

Therefore, a micro optical system array having a finer resolution than the size required for the size of the optical system in FIG. 5A (shown for each beam incident angle in FIGS. 6A to 6C) is provided on both the front and back sides of the film. If it is set as the surface shape of the side, the diffusion film 3 as shown in FIG.6 (d) will be obtained. This corresponds to claim 6 and the front and back surfaces are filled with a film medium. The front and back surfaces of the front and back are plano-convex lenses (parts) corresponding to the lenses 1 and 2, respectively. Is a shape in which a plurality of optical axes coincide with each other on the air interface side, and the thickness of the film is the focal length f ₂ of the lens 2 in the medium. The size of the lens is below the required resolution. According to this, a top-hat type diffusion characteristic equivalent to that shown in FIG. When the top-hat diffusion characteristic is two-dimensional, the film double-sided shape is a microlens array shape, and the one-dimensional case is a lenticular lens array shape.

Next, the angle in the center direction of the incident angle region and the angle in the center direction of the exit diffusion angle region are controlled independently of each other by adjusting the shift amount of the optical axes of the lenses on the entrance side and the exit side in Reference Item 6. Explain the principle of the requirement that it is possible.
FIG. 7A shows an optical system that realizes this control function, and FIG. 7B shows the function in a graph. This optical system has a two-lens configuration, and the optical axes of the lenses 1 and 2 on the input side (incident side) and output side (exit side) are shifted from each other by a distance a. The distance between the main planes of the lenses 1 and 2 is the focal length f ₂ of the lens ₂ (assuming that f ₂ = f ₁ ). The mechanism of this optical system is basically the same as that of the optical system in FIG.

First, consider the light rays 123 and 126 that are incident parallel to the light rays passing through the centers (nodes) of the lenses 1 and 2. Since this light beam is focused on the center (node) of the lens 2, the direction of the light does not change in the lens 2. Therefore, from the figure, the outgoing angles θ ₅ and θ ₆ of the light beams 123 and 126 are given by the following equations.

次に、レンズ１への入射角が変化した場合を考える。レンズ１の上端点に着目する。この点から光線121,122,123がレンズ２へ入射しているが、レンズ１はレンズ２の前焦点面に設置されているので、光線121,122,123はレンズ２を通過後互いに平行となり、それらの出射角は全てθ₅となる。同様に、レンズ１の下端点に着目すると、光線124,125,126は、レンズ２通過後は互いに平行になるから、それらの出射角は全てθ₆となる。

Next, consider a case where the incident angle to the lens 1 changes. Attention is paid to the upper end point of the lens 1. From this point, the light rays 121, 122, 123 are incident on the lens 2. However, since the lens 1 is placed on the front focal plane of the lens 2, the light rays 121, 122, 123 are parallel to each other after passing through the lens 2, and their exit angles are all θ. ₅ Similarly, paying attention to the lower end point of the lens 1, the light rays 124, 125, and 126 become parallel to each other after passing through the lens 2, so that their emission angles are all θ ₆ .

Therefore, as shown in FIG. 7B, the parallel beams input within the range of incident angles −θ ₁ to + θ ₁ (incident angle region) are not related to the incident angle, but range of θ ₅ to θ ₆ ( It exhibits a certain top-hat-like diffusion characteristic within the exit diffusion angle region). Equations (5) and (6) indicate that θ ₅ and θ ₆ can be controlled independently of θ 1 by adjusting the optical axis deviation amount a.
In order to make the optical system of FIG. 7 (a) into one film, a space between a plurality of lenses 1 and 2 arranged in the vertical direction is filled with a film medium (the same material as the lens), and the surface shape of both surfaces of the film is The lens array may be formed by an array on the convex side of the plano-convex lens portion with one surface being the lens 1 and the other surface being the lens 2 (FIGS. 2D, 4D, and 6D). ), But the illustration is omitted). The thickness of the film is the focal length f ₂ of the lens 2 in the medium. The optical axes of the lens 1 and the lens 2 are shifted by a. The size of the lens is below the required resolution. According to this, a top hat type diffusion characteristic equivalent to that of FIG. 7B is obtained. When the top-hat diffusion characteristic is two-dimensional, the film double-sided shape is a microlens array shape, and the one-dimensional case is a lenticular lens array shape.

In any one of the reference items 4 to 6, the lens on the incident side is of a total reflection type (that is, a surface shape in which light incident on the lens from a predetermined incident angle region is totally reflected on the inner surface of the lens). (Corresponding to the reference item 7) or a part of the lens surface forming the microlens array shape or the lenticular lens shape on the incident side of the diffusion film according to any one of the reference items 4 to 6 is coated with a reflection medium (Corresponding to Reference Item 8), when the incident-side surface shape is converted into a reflective optical element array shape, the above-mentioned top-hat diffusion characteristics can be exhibited even at a larger incident angle. It is expected to contribute to further thinning.

Here, for coating with a reflection medium, an aluminum coat, a silver coat or the like can be preferably used.
Next, the best mode of the diffusion film described in Reference Items 9 and 10 will be described. The diffusion films described in Reference Items 1 to 8 described so far have a lens shape on both sides of the film, and accuracy is required for mutual alignment between one surface shape of the both surfaces and the other surface shape. It is. In this regard, in the diffusion film described in Reference Item 9, since the surface shape that realizes diffusion is formed only on one side of the film, the alignment is not required at all, and the manufacturing is excellent.

The diffusion film according to the reference section 10, in the reference section 8, which is formed only on the film one side, the surface shape to achieve the diffusion, an optical element array shape which is a combination of lenses and mirrors, moreover reference term As in 4 to 6, since the incident angle region and the outgoing diffusion angle region can be controlled independently from each other in size and direction, the oblique incident light with a larger incident angle is added to the advantage of excellent manufacturability. Can be diffused and emitted in a desired direction and size range, and therefore can be applied to the screen of an ultra-thin rear projection display and the like very advantageously.

  Here, as a basic optical system in an optical element array shape in which a lens and a mirror are combined, a combination of a lens and a non-axial paraboloidal mirror can be mentioned. This basic optical system is the one shown in FIGS. 1 (a), 3 (a), 5 (a), and 7 (a). Instead of a mirror, this is rearranged to the input side and integrated with the lens 1. Examples of this basic optical system are shown in FIGS. 8A to 8F.

As a representative of these drawings, FIG. 8D1 in which light rays are described in more detail in FIG. 8D in which a 90 ° non-axial parabolic mirror 4D is used as an alternative to the lens 2 in FIG. 1 will be described.
As in FIG. 1, the focal length of the lens 1 is f ₁ . The 90 ° non-axis parabolic mirror 4D has a quadratic function described by the equation: y = (1 / (4f ₂ )) x ² in the xy coordinate system (the origin O is called Vertex) in the figure. The xy coordinate system is set so that the focal point F (0, f ₂ ) of the paraboloid is at the center of the lens 1. The distance between the focal point F and the origin O of the paraboloid is called PFL (Parent Focal Length), here a PFL = f _2. In the case of 90 ° non-axis, the y-axis of the paraboloid coordinate system is set to be included in the principal plane of the lens 1. Further, the focal length f ₁ of the lens ₁ is matched with the REFL (Reflected Effective Focal Length;) of the 90 ° non-axis paraboloidal mirror 4D.

Of the light rays incident on this optical system, light rays 8-4, 8-5 and 8-6 parallel to the optical axis of the lens 1 are first considered. These rays are condensed at an intersection C between the rear focal plane of the lens 1 and the optical axis of the lens 1. Since this point C is exactly on the 90 ° non-axial parabolic mirror 4D, the principal ray 8-5 changes its direction by 90 ° and is reflected, and at this point C, relative to the optical axis of the lens 1 (ie, the principal ray 8). The light rays 8-4 and 8-6 that are incident at ± θ ₁ are also ± 5 with respect to the principal ray 8-5 whose direction is changed by 90 ° by the 90 ° non-axial parabolic mirror 4D. Reflected at θ ₁ . Therefore, a parallel beam parallel to the optical axis of the lens 1 and having the light beams 8-4 and 8-6 at the upper and lower ends is diffused by ± θ ₁ by changing the 90 ° direction as in the optical system of FIG. .

Next, light rays 8-1, 8-2, and 8-3 that are incident on the optical axis of the lens 1 at θ ₁ from above and light beams 8-7 and ₈ that are incident at θ ₁ from below. Consider 8,8-9. Consider principal rays 8-2,8-8 of the center of the collimated beam coming incident at the ± theta _1. Since these lights pass through the center (node) of the lens with respect to the lens 1 on the incident side, the direction of the light does not change. For the 90 ° non-axis parabolic mirror 4D, the principal rays 8-2 and 8-8 are incident from the optical axis direction of the lens 1 because they pass through the focal point F (0, f ₂ ) of the paraboloid. It will be reflected parallel to the principal ray 8-5 of the beam. Therefore, even if light incident at ± θ ₁ is diffused by this optical system, the principal ray of the diffused light coincides with the principal ray of light diffused at ± θ ₁ that is the output of 0 ° incident light. ing.

As is clear from the figure, the incident angle does not have to be discrete at 0 ° and ± θ _1, and the range of the incident angle also includes -θ ₁ to + θ ₁ (the absolute value of the upper and lower limits of the range is Even if it is θ ₁ or more), the chief ray of diffused light that has entered the optical system and diffused by changing the 90 ° direction is always in the y-axis direction regardless of the incident angle.
Next, the diffusion angle width from the chief ray will be described. As in the explanation of the principle of the optical system in FIG. 1, attention is paid to the upper end and the lower end of the lens 1. Now, it is assumed that the upper and lower ends of the lens are in the vicinity of the focal point F (0, f ₂ ) of the 90 ° non-axial parabolic mirror 4D. Therefore, the light beams 8-1, 8-4, and 8-7 emitted from the upper end of the lens to the 90 ° non-axial parabolic mirror 4D are substantially parallel to each other after being reflected by the 90 ° non-axial parabolic mirror 4D. Light. Since the light ray 8-4 is emitted at an angle of + θ ₁ with respect to the y axis, the light rays 8-1 and 8-7 are also emitted at an angle of + θ ₁ with respect to the y axis. If a similar argument is made for the light beams 8-3, 8-6, and 8-9 emitted from the lower end of the lens to the 90 ° non-axial parabolic mirror 4D, these light beams are also 90 ° non-axial parabolic mirror 4D. After being reflected by the light, the light becomes substantially parallel to each other. Since light 8-6 it is emitted at an angle of - [theta] ₁ with respect to the y axis, will be emitted at an angle of - [theta] ₁ with respect to substantially y-axis also light 8-3,8-9.

From the above discussion, the parallel light incident at the upper θ ₁ of the lens diffuses like a top hat within a range of approximately ± θ ₁ with respect to the y axis, and the parallel light incident at the lower θ ₁ of the lens is similarly y With respect to the axis, it diffuses like a top hat within a range of approximately ± θ ₁ . As is clear from the figure, the incident angle is established even if it is not discrete as ± θ _1. Therefore, for all continuous incident angles of −θ ₁ to + θ ₁ , approximately ± θ _{1 with} respect to the y axis. The top hat diffusion characteristic within the range of

  The above is the explanation of the principle of the optical system when the 90 ° non-axial parabolic mirror 4D is used in place of the lens 2. 8A, 8B, 8C, 8E, and 8F show the basic configuration of the optical system in some cases using a non-axis parabolic mirror whose non-axis angle is other than 90 °. Among these basic configurations, when an ultra-thin rear projection system is considered, an important configuration is a configuration using a 100 ° non-axial parabolic mirror 4F shown in FIG. 8F. As shown in FIG. 8G, when the chief ray angle with an incident angle of 80 ° is considered with respect to the screen 20, the system using a 100 ° non-axial parabolic mirror emits the normal direction of the screen. This is because it can coincide with the direction of the principal ray of the diffused light (preferably non-axial angle = 90 ° −incident angle + 90 ° = 180 ° −incident angle). Therefore, in the case of an ultra-thin rear projection system that operates at an oblique incidence of 70 ° to 90 °, a system using a 110 ° to 90 ° non-axial parabolic mirror is suitable.

The optical system using the 100 ° non-axial parabolic mirror 4F shown in FIG. 8F is shown in more detail in FIG. 8F1. This is basically the same operating principle as the optical system of FIG. 8D1. The structural difference is that the y-axis of the 100 ° non-axial parabolic mirror 4F is inclined 10 ° with respect to the main plane of the lens 1.
The above is the basic configuration and principle of the diffusion film described in Reference Items 9 and 10. Next, means for realizing the functions of the reference items 2 and 3 with the optical system shown in FIGS. 8A to 8F will be described. As is clear from FIGS. 8D1 and 8F1 in which the light beam is described in more detail, the size of the input angle region and the angle in the center direction of the input region are controlled by a quadratic function y in the installation range of the non-axial parabolic mirror to be used. It can be controlled by which part of = (1 / (4f ₂ )) x ² is used. 8A to 8F, 8D1, and 8F1 are all set so that the focal point of the non-axial parabolic mirror 4 is the center (node) of the lens 1. By shifting within the lens principal plane and shifting the optical axis, the range of the non-axis parabolic mirror to be used can be fixed and the angle in the center direction of the input angle region can be controlled (not shown). .

Next, control of the size of the exit diffusion angle region and the angle in the center direction of the region will be described. As described in the principle explanation of FIG. 8D1, since the exit diffusion angle region is ± θ ₁ with respect to the y-axis, the magnitude is 2θ ₁ , and θ ₁ = tan ⁻¹ (d / (2f ₁ )) The lens 1 can be controlled by the focal length f ₁ and the diameter d. In addition, the control of the angle in the center direction of the exit diffusion angle region is such that the direction of the principal ray, which is the center direction of the diffused light, is always parallel to the y axis of the non-axial parabolic mirror regardless of the incident angle. If the direction of the axis is controlled, it can be controlled independently of the incident angle region. In the above description, it has been shown that the functions of Reference Items 1 to 3 can be realized by the optical system shown in FIGS. 8A to 8F, 8D1, and 8F1.

Next, the point that the optical system shown in FIGS. 8A to 8F, 8D1, and 8F1 can be formed only on one side of the film (requirements of the reference items 9 and 10) will be described. The diffusion films described in Reference Items 9 and 10 are intended for use with ultra-thin rear-pro screens, and incident light is obliquely incident on the screen at a large angle. Therefore, the optical system shown in FIGS. 8A to 8F is installed substantially parallel to the film. Therefore, the lens 1 and the non-axial parabolic mirror 4 exist only on one side (incident side) of the diffusion film.

When an optical element array in which the lens 1 and the non-axial paraboloidal mirror 4 are combined on one side of the film is mounted (corresponding to the reference item 10), a shape as simple as possible is advantageous in manufacturing. Therefore, the space between the lens 1 and the non-axial parabolic mirror 4 is filled with a film medium to form one device shape. The non-axis parabolic mirror 4 can be operated only with the surface shape if it is designed to satisfy the total reflection condition. When the total reflection condition is not satisfied, the same operation is possible if the reflecting surface is covered with a reflecting medium such as an aluminum coat or a silver coat (corresponding to Reference Item 11).

The lens 1 on the input side is easily manufactured as a spherical lens, and a part of the upper half of the hemispherical lens is used. First, the input hemisphere lens is analyzed. FIG. 9 shows an operation of a part of the upper half of the hemispherical lens 5. The hemispherical lens 5 has a refractive index of n ₂ , and the right side of the hemispherical lens 5 is a medium (film) having a refractive index of n ₂ . The left side of the hemispherical lens 5 is a medium (air) having a refractive index n ₁ . Set the origin O of the xy coordinate system at the center of the hemisphere. The x axis is the lens optical axis. Light rays 9-1 and 9-2 are light incident parallel to the optical axis. Ray 9-1 is refracted at the intersection A with the surface of the hemispherical lens, and intersects the x-axis and the point A ′. Similarly, the light ray 9-2 is refracted at the intersection B with the surface of the hemispherical lens, and intersects at the x-axis and the point B ′. Also, the point of intersection between the x-axis and the hemispherical lens surface is taken as point C.

In Figure _{9, ∠AOC = θ 11, ∠BOC} = θ 21, ∠OAA '= θ 12, ∠OBB' When _{= θ 22, ∠AA'O = θ 11} -θ 12, ∠BB'O = θ 21 the -θ _22. When Snell's law is applied to points A and B, the following equation is established.

△OAA'と△OBB'に正弦定理を適用すると、次式が成立する。

Applying the sine theorem to △ OAA 'and △ OBB', the following equation holds.

ここで、ｒは半球レンズの球面の半径、f₁は線分OA’の長さ、f₂は線分OB'の長さである。(7),(9)式より、次式が成立する。

Here, r is the radius of the spherical surface of the hemispherical lens, f ₁ is the length of the line segment OA ′, and f ₂ is the length of the line segment OB ′. From the equations (7) and (9), the following equation is established.

(8),(10)式より、次式が成立する。

From the equations (8) and (10), the following equation is established.

光線9-1が半球レンズ表面で屈折した後の方程式は、θ₁₁，ｎ₁，ｎ₂，ｒが決まれば、(11),(12)式のf₁とθ₁₂を用いて次式で表せる。

The equation after the light ray 9-1 is refracted on the surface of the hemispherical lens is as follows using θ ₁ , θ ₁₂ , and f ₁ and θ ₁₂ when θ ₁₁ , n ₁ , n ₂ , and r are determined. I can express.

同様に光線9-2についても次式で表せる。

Similarly, the ray 9-2 can be expressed by the following equation.

(15),(16)式を連立させて解くと、光線9-1と光線9-2との交点座標(x_f,y_f)が導出でき、次式で表せる。

By solving the equations (15) and (16) simultaneously, the intersection coordinates (x _f , y _f ) of the light beam 9-1 and the light beam 9-2 can be derived and expressed by the following equations.

半球レンズ５において、光線9-1,9-2の間の部分のみを使用することを考えると、(17),(18)式が、同レンズの焦点座標を与えることになる。今、光線9-1,9-2の間の中央の主光線が半球レンズ表面に対し、入射角がほぼ45°となる部分を考える。この入射角45°に対し、±5°の範囲を考えると、光線9-1の半球レンズ表面に対する入射角θ₁₁＝40°、光線9-2の半球レンズ表面に対する入射角θ₂₁＝50°となる。ｎ₁＝1.0（空気の屈折率）、ｎ₁＝1.5（ガラス又はフィルム媒体の屈折率）とすると、(17),(18)式より、x_f＝1.10ｒ,y_f＝0.155ｒとなる。以上の結果より、レンズ表面に対し45°の入射角近傍で、球面レンズの焦点は、入射側の球面を出射側まで考えた場合、この球面と、入射光と平行で球の中心を通る光軸との交点近傍に存在することになる。

Considering that only the portion between the light rays 9-1 and 9-2 is used in the hemispherical lens 5, the equations (17) and (18) give the focal coordinates of the lens. Now, let us consider a portion where the central chief ray between the light rays 9-1 and 9-2 is approximately 45 ° with respect to the hemispherical lens surface. Considering the range of ± 5 ° with respect to this incident angle of 45 °, the incident angle θ ₁₁ = 40 ° with respect to the hemispherical lens surface of the light ray 9-1 and the incident angle θ ₂₁ = 50 ° with respect to the hemispherical lens surface of the light ray 9-2 It becomes. Assuming that n ₁ = 1.0 (refractive index of air) and n ₁ = 1.5 (refractive index of glass or film medium), x _f = 1.10r, y _f = 0.155r from the equations (17) and (18). . From the above results, in the vicinity of the incident angle of 45 ° with respect to the lens surface, the focal point of the spherical lens is that light passing through the center of the sphere in parallel with the incident light when considering the incident side spherical surface to the output side. It exists in the vicinity of the intersection with the axis.

In order to make the optical system shown in FIGS. 8A to 8F function, this focal position (x _f , y _f ) exists on the surface of the non-axial parabolic mirror and the focal position of the non-axial parabolic mirror. Is set at the intersection of the central principal ray between the rays 9-1 and 9-2 and the hemispherical lens surface. FIG. 10 shows an optical design example in which such setting is performed in the case of FIG. 8F (in the case of the 100 ° non-axial parabolic mirror 4F). In the same figure, rays 10-1 and 10-2 are shown when the incident angles are 20 ° and 70 ° with respect to the surface of the spherical lens 6, respectively.

FIG. 11 shows the shape of FIG. 10 formed on one side of a film medium 11, arranged as a two-dimensional array, and provided with a black mask 23 for measures against external light, This is an example of design. This example is also an example of Reference Item 12. 11A is a rear view of the screen, and FIG. 11B is a cross-sectional view. With a large oblique incidence from the optical engine X, an image is formed on the back surface (back surface) of the screen 20. The screen 20 has the function shown in FIG. 8F1, and does not depend on the incident angle with respect to light having an incident angle different from the polar angle and the azimuth angle. FIG. 11 shows that a top-hat characteristic that faces the normal direction of the surface can be expressed.

As described above, the screen 20 constituted by the new D-film 3 can realize the function required for the screen only by the surface shape of one side, so that the image is hardly blurred and a high-resolution image display is possible. Become. Further, in this screen 20, backscattering generated in a screen composed of a normal diffusion film does not occur. In addition, a black mask 23 on the back surface of the screen and an antireflection film 24 on the screen surface as shown in the figure. Even in a bright environment, most of the outside light is absorbed, and high-contrast image display can be expected. The advantages of the screen 20 constituted by the new D-film 3 are schematically shown in FIG. This is the end of the description of the best mode of the diffusion film described in Reference Items 9 and 10.

Next, reference item 12 will be described. When the diffusion film described in Reference Items 1 to 11 is applied as a screen to a rear projection system (rear pro for short) or the like, a measure against external light is required to obtain a high-contrast image display in a bright environment. There is a black mask as one means for countermeasures against this external light. This black mask is also effective for the diffusion film according to the present invention. Basically, when the diffusion film according to the present invention is incorporated into a system and operated, if a black mask can be installed on all surfaces through which light does not pass, a very large external light countermeasure effect can be expected. Particularly , the diffusion film (screen) according to the present invention has a device surface in the vicinity of the focal plane of the two lenses. Therefore, if a black mask is attached to the surface of the surface through which light does not pass, the effect is extremely high. Big.

FIGS. 13 and 14 are part of examples in which the black mask 23 is added to the diffusion film 3 described in Reference Items 1 to 8 as the rear pro screen 20, and each of FIGS. A film obtained by adding a black mask 23 to the diffusion film 3 is shown. In addition, in the example shown in FIG. 11 as an example in which a black mask is added to the diffusion film described in Reference Items 9 and 10, the reflective surface of the non-axial parabolic mirror does not have a black mask. As shown in the example of FIG. 14, there is no problem even if a black mask is added to the surface where the light beam is not reflected. Therefore, on this surface, the entire surface excluding the hole 25 of the pinhole-like black mask is provided. A black mask 23 can be added. Therefore, further external light countermeasure effects can be expected.

Next, reference item 13 will be described. When the diffusion film according to the present invention is used as a screen for a rear pro and the optical engine uses polarized light such as LCD or LCOS, a polarizer or a circular polarizer can be applied as a countermeasure against external light. Conceivable. Physical diffusion mechanism of diffusion film according to the present invention, partially due to scattering rather is only reflected by the refraction or mirror (reflecting surface) by the lens, thus the polarization retention, than the diffusion film of the prior art generally much better It is thought that.

Therefore, only by adding the polarizing plate to the diffusion film (or the screen using the same) according to the present invention , half of the external light can be absorbed without substantially reducing the light utilization efficiency.
Furthermore, if a circularly polarizing plate is used, even if the external light that has entered the interior of the rear pro is reflected by the internal mirror and exits to the outside of the rear pro, it can be effectively blocked, so a further external light countermeasure effect can be expected. In this case, a λ / 4 plate is installed on the optical engine side in such a direction as to cancel the action of the λ / 4 plate (quarter wave plate) in the circularly polarizing plate added to the screen. Ensure usage efficiency. The above is the description of Reference Item 13. The external light countermeasure using the black mask of Reference Item 12 and the external light countermeasure using the polarizing plate or the circularly polarizing plate of Reference Item 13 do not cause any problems even when used together, and when used together, further countermeasures against external light are obtained. The effect can be expected.

Embodiment of the diffusion film according to the present invention which has been described so far, a modified embodiment to the rear projection of the diffusion film. On the other hand, the reference items 14 and 15 correspond to application forms to the front projection system. First, reference item 14 will be described. The basic structure of the diffusion film described in Reference Item 14 is the same as that of Reference Items 1-6. An example having the same basic configuration as that shown in FIG. 1 will be described.

FIG. 15 is an explanatory diagram of the principle of the n-th order fixed top-hat diffusion characteristic expressed in the diffusion film described in Reference Item 14, wherein (a) and (b) show the basic optical system, and (c) show its function. ing. FIG. 15A shows the 0th-order fixed top-hat diffusion similar to FIG. 1, and FIG. 15B shows n = 1 of the n-th fixed top-hat diffusion that did not appear in FIG. Represents the case. The zero-order fixed top hat-like diffusion is manifested by light passing through two lenses 1 and 2 having the same optical axis in the incident side lens 1 and the outgoing side lens 2, whereas the primary fixed top In the hat-like diffusion, the lenses 1 ′ and 2 ′ which are adjacent to the lenses 1 and 2 on the entrance side and the exit side, respectively share the main plane with the lenses 1 and 2 and share the optical axis with each other, In the optical system added to 1 and 2, it is expressed by the light passing through the two lenses 1 and 2 ′.

The primary fixed top hat diffusion mechanism developed by these two lenses 1 and 2 'is almost the same as that of the optical system shown in FIG. Lenses 1 'main plane distance between each other, the lens 2' is the focal length f ₂ of the. In FIG. 15, this f ₂ is made to coincide with the focal length f ₁ of the lens 1. Consider now rays 15-3 and 15-6 incident in parallel to a straight line connecting two points, which are the centers (nodes) of the lenses 1 and 2 '. Since these light rays pass through the lens 1 and are condensed on the center (node) of the lens 2 ′, the light direction is emitted from the lens 2 ′ without changing. From the figure, the emission angle of ray 15-3 is

であり、光線15-6の出射角は、図より、

From the figure, the emission angle of ray 15-6 is

である。
次に、レンズ１の上端からレンズ２’へ向かう光線15-2,15-3,15-4に着目する。これらの光線は、レンズ２’の前焦点面内の同じ点から出ているので、レンズ２’を通過後互いに平行となる。同様に、レンズ１の下端からレンズ２’へ向かう光線15-5,15-6,15-7も、レンズ２’の前焦点面内の同じ点から出ているので、レンズ２’を通過後互いに平行となる。よって、光線15-2,15-4の出射角は光線15-3の出射角（＝−θ_1-1）に等しく、光線15-5,15-7の出射角は光線15-6の出射角（＝−θ_1-0）に等しい。レンズ１の中心（節）とレンズ２’の下端を結ぶ直線に平行に入射する光線15-2,15-5の入射角は、図より、−θ_1-1であり、レンズ１の中心（節）とレンズ２’の上端を結ぶ直線に平行に入射する光線15-4,15-7の入射角は、図より、−θ_1-0である。従って、入射側のレンズ１と出射側のレンズ２’とをペアにした光学系に、−θ_1-1〜−θ_1-0の入射角度領域内から入射する平行光は、入射角によらずに、−θ_1-1〜−θ_1-0の出射拡散角度領域内で固定したトップハット的拡散特性を発現する。以上が、図１５（ｂ）の１次固定トップハット的拡散特性の発現メカニズムである。

It is.
Next, attention is paid to light rays 15-2, 15-3, and 15-4 from the upper end of the lens 1 toward the lens 2 ′. Since these light rays are emitted from the same point in the front focal plane of the lens 2 ′, they are parallel to each other after passing through the lens 2 ′. Similarly, the rays 15-5, 15-6, and 15-7 from the lower end of the lens 1 to the lens 2 ′ are also emitted from the same point in the front focal plane of the lens 2 ′, so that they pass through the lens 2 ′. They are parallel to each other. Therefore, the exit angles of the rays 15-2 and 15-4 are equal to the exit angle of the ray 15-3 (= −θ _1-1 ), and the exit angles of the rays 15-5 and 15-7 are the exit of the ray 15-6. It is equal to the angle (= −θ _1-0 ). From the figure, the incident angle of the light rays 15-2 and 15-5 incident parallel to the straight line connecting the center (node) of the lens 1 and the lower end of the lens 2 ′ is −θ _1-1 , and the center of the lens 1 ( The incident angle of rays 15-4 and 15-7 incident in parallel to the straight line connecting the upper end of the lens 2 ′ and the lens 2 ′ is −θ _1-0 from the figure. Accordingly, the parallel light incident on the optical system in which the incident side lens 1 and the outgoing side lens 2 ′ are paired from within the incident angle region of −θ _1-1 to −θ _1-0 depends on the incident angle. In addition, the top-hat diffusion characteristic fixed in the emission diffusion angle region of −θ _1-1 to −θ _1-0 is exhibited. The above is the mechanism by which the primary fixed top-hat diffusion characteristic of FIG.

  The order of the above-described fixed top-hat diffusion is not limited to the first order, and generally ± n-order fixed top hat diffusion exists. The range of the incident angle θin-n of the n-th order fixed top hat diffusion characteristic, that is, the incident angle region is expressed by the following equation.

又、ｎ次固定トップハット的拡散特性の出射角度θout-nの範囲すなわち出射拡散角度領域は、次式で表される。

Further, the range of the emission angle θout-n of the nth-order fixed top hat diffusion characteristic, that is, the emission diffusion angle region is expressed by the following equation.

(19),(20)式より、n-1次固定トップハット的拡散における入射角度領域,出射拡散角度領域の上限値は、ｎ次固定トップハット的拡散における対応（同名の）領域の下限値と完全に一致しており、入射角度領域，出射拡散角度領域のそれぞれが、n-1次とｎ次とで互いに重複することなく、かつ、とぎれることもないことがわかる。これが参考項１４での限定特性である。この特性は、参考項３，６に記載の拡散フィルムにも付与でき、複数の入射角度領域の中心方向の角度と、複数の出射拡散角度領域のそれとを、互いに独立に制御可能である。

From equations (19) and (20), the upper limit value of the incident angle region and the outgoing diffusion angle region in the n-1st order fixed top hat type diffusion is the lower limit value of the corresponding (same name) region in the nth order fixed top hat type diffusion. It can be seen that the incident angle region and the outgoing diffusion angle region do not overlap with each other in the n−1 order and the n order, and are not interrupted. This is the limiting characteristic in Reference Item 14. This characteristic can also be imparted to the diffusion film described in Reference Items 3 and 6, and the angle in the center direction of the plurality of incident angle regions and that of the plurality of outgoing diffusion angle regions can be controlled independently of each other.

Note that the diffusing film described in Reference Items 2 and 5 can also be imparted with the limiting characteristics in Reference Item 14, but in this case, if the incident side NA <the output side NA, then there will be overlap in the output diffusion angle region. On the contrary, if NA on the incident side> NA on the outgoing side, then there will be a break in the outgoing diffusion angle region. This completes the description of Reference Item 14.
Next, reference item 15 will be described. Reference item 15 is a reflection type diffusion film obtained by adding a reflector such as a mirror to the diffusion film of any one of reference items 1 to 14, and is mainly applied to a front projection system. Corresponding to As an example of this, FIG. 16 shows an optical system in which, in the diffusion film described in Reference Item 14, f ₁ = f ₂ and a mirror 30 is installed at the center between the input and output side lens principal planes. According to this, because of the action of the mirror 30, the input side lens also becomes the output side lens, and the limiting characteristic in the reference item 14 is manifested only by the surface shape on the one side of the film. The alignment of the shaft is unnecessary, and the manufacturing becomes very easy.

  Further, in the application form of the front projection system to the screen 20 as shown in FIG. 16, there is an external light suppression function as a great advantage. As shown in the figure, this screen 20 is excellent in that there is no overlap between input / output angle regions (n-order input / output angle regions) of different n-th order fixed top hat diffusions and is completely quantized. When this characteristic is applied, a strong external light suppression function is exhibited. In other words, when the projector X is installed in the 0th-order input / output angle area and the image projected on the screen is viewed in this area, the projector light is uniformly diffused only in the 0th-order input / output angle area. On the other hand, outside light that exists outside the 0th-order input / output angle region never diffuses into the 0th-order input / output angle region, so that a high-contrast image can be viewed even in a bright environment. It is. When the projector is installed in the m-th order input / output angle region other than the 0th order, the same effect can be obtained if the image is viewed in the −m-th order input / output angle region.

As another type of the diffusion film described in Reference Item 15 (and a screen to which the diffusion film is applied), there is the one shown in FIG. The screen 20 is for a front projection system capable of oblique incidence at a large angle. The function of the screen 20 is equivalent to that of FIG. 1, and a large-angle oblique incident light is condensed by a total reflection type reflector 18 having the same function as the lens 1 of FIG. The light is reflected by the mirror 30 and is focused on the main plane of the lens 19 having the same function as that of the lens 2 in FIG. 1 to develop a fixed top-hat diffusion characteristic. If the optical axis of the total reflection type reflecting mirror 18 and the optical axis of the lens 19 are made to coincide with each other, the fixed top-hat diffusion characteristic with the screen normal direction as the principal ray direction is always used regardless of the incident angle. To express. If the technique described in any one of the reference items 1 to 6 is applied to this screen, independent control on the input side and the output side with respect to the NA and the angle in the central direction can be realized. The black mask 23 added to the back surface of the film has a great effect on suppressing external light. This completes the description of Reference Item 15.

Finally, the projection system according to claim 1 is an application of the diffusion film (new D-film) according to the present invention to a rear projection system or a front projection system. and has, by the effect obtained by the various embodiments of the new D-film, with the structure of ultra-thin, Ru can be a high-contrast and high-resolution image display system capable of.

FIG. 6 is a diagram illustrating the principle of the function of the diffusion film described in Reference Item 4. (A)-(c) is explanatory drawing which supplements FIG. 1, (d) is a conceptual diagram of the diffusion film of the reference item 4. FIG. It is a principle explanatory view of the function of the diffusion film described in Reference Item 5. (A)-(c) is explanatory drawing which supplements FIG. 3, (d) is a conceptual diagram of the diffusion film of the reference item 5. FIG. FIG. 10 is a principle explanatory diagram of one requirement in Reference Item 6. (A)-(c) is explanatory drawing which supplements FIG. 5, (d) is a conceptual diagram of the diffusion film of the reference item 6. FIG. It is a principle explanatory view of another requirement in Reference Item 6. It is an example of the basic optical system used for the diffusion film described in Reference Item 10, and is a configuration diagram showing an arrangement using a 60 ° non-axial paraboloidal mirror and a lens. It is an example of the basic optical system used for the diffusion film of Reference Item 10, and is a configuration diagram showing an arrangement using a 120 ° non-axial parabolic mirror and a lens. It is an example of the basic optical system used for the diffusion film of Reference Item 10, and is a configuration diagram showing an arrangement using a 30 ° non-axial parabolic mirror and a lens. It is an example of the basic optical system used for the diffusion film of Reference Item 10, and is a configuration diagram showing an arrangement using a 90 ° non-axial parabolic mirror and a lens. It is an operation principle explanatory view of the optical system of FIG. 8D. It is an example of the basic optical system used for the diffusion film described in Reference Item 10, and is a configuration diagram showing an arrangement using a 150 ° non-axial parabolic mirror and a lens. It is an example of the basic optical system used for the diffusion film of Reference Item 10, and is a configuration diagram showing an arrangement using a 100 ° non-axial parabolic mirror and a lens. It is an operation principle explanatory view of the optical system of FIG. 8F. It is explanatory drawing of the suitable non-axis angle of the non-axis paraboloid mirror in the diffusion film of the reference term 10 applied to this screen corresponding to the incident angle to a screen. It is a principle explanatory view of operation (optical behavior) of a hemispherical lens. It is sectional drawing which shows the optical design example of the diffusion film of reference item 10. It is the rear view (a) and sectional drawing (b) which show the example of the screen comprised using the diffusion film of FIG. It is a schematic diagram which shows the advantage of the screen (for rear pros) comprised with the new type D-film. It is the schematic which shows a part of example which added the black mask to what used the diffusion film of FIG. 4 as a screen for rear pros. It is the schematic which shows a part of example (corresponding to the reference item 12) which added the black mask to what used the diffusion film of FIG. 5 as a screen for rear pros. It is a principle explanatory view of the n order fixed top hat diffusion characteristic which expresses with the diffusion film of referential paragraph 14. It is a schematic diagram which shows one example (application example to a front projection system) of the diffusion film of the reference item 15. It is a schematic diagram which shows one example (application example to a front projection system; another form from the previous example) of the diffusion film of the reference item 15.

Explanation of symbols

1, 1 ', 2, 2' Lens 3 Diffusion film (New D-film)
4 Non-axis parabolic mirror (the attached alphabetical code corresponds to the non-axis angle)
5 Hemispherical lens 6 Spherical lens 7 Film surface
8-1 to 8-9, 9-1, 9-2, 10-1 to 10-3, 15-1 to 15-7, 101 to 126 rays (or chief rays)
11 Film media
18 Total reflection type reflector having the same function as the lens 1 of FIG.
19 Lens having the same function as lens 2 in FIG.
20 screens
21 Input lens surface
22 Reflective surface of non-axis parabolic mirror
23 Black mask
24 Anti-reflective coating
25 Black mask hole
26 Micro lens array
30 mirror (plane mirror)
X Optical engine (projector)

Claims (1)

A projection system obtained by applying the diffusion film according to any one of the following reference items 1 to 15 to a rear projection system or a front projection system , wherein the diffusion film is different from the diffusion film according to the reference item 14 or 15. A projection system characterized in that incident light corresponding to each of two or more different incident angle regions of the projector is incident from separate projectors .
Record
[Reference Item 1]
A single film that diffuses and emits incident light, wherein the diffusion is realized only by the surface shape of the film, and the incident light is incident on the incident light regardless of an incident angle within an incident angle region of the incident light. A diffusion film characterized by having a substantially constant top-hat diffusion characteristic of diffusing at a substantially constant light intensity within an exit diffusion angle region corresponding to the angle region.
[Reference item 2]
The diffusion film according to claim 1, wherein the size of the incident angle region and the size of the outgoing diffusion angle region can be controlled independently of each other by the surface shape design of the film.
[Reference item 3]
The diffusion film according to claim 1 or 2, wherein an angle in the center direction of the incident angle region and an angle in the center direction of the outgoing diffusion angle region can be controlled independently of each other by the surface shape design of the film. .
[Reference item 4]
4. The diffusion film according to any one of Reference Items 1 to 3, wherein the surface shape on both the incident side and the emission side is a microlens array shape or a lenticular lens shape.
[Reference Item 5]
The size of the incident angle region and the size of the exit diffusion angle region are determined by determining the NA of the incident side microlens or lenticular lens and the NA of the exit side microlens or lenticular lens, respectively, depending on the surface shape design of the film. 5. The diffusion film according to item 4, wherein the diffusion film can be controlled independently by adjusting.
[Reference Item 6]
The angle in the center direction of the incident angle region and the angle in the center direction of the exit diffusion angle region are determined by the surface shape design of the film, and the incident side microlens or lenticular lens, and the exit side microlens or lenticular lens 6. The diffusion film according to item 4 or 5, wherein the diffusion film can be controlled independently of each other by adjusting the shift amount of the optical axis and the selection range of the partial shape.
[Reference Item 7]
7. The diffusion film according to any one of Reference Items 4 to 6, wherein the lens having the shape of the incident side microlens array or the lenticular lens is of a total reflection type.
[Reference Item 8]
A diffusion film obtained by coating a part of a lens surface having a microlens array shape or a lenticular lens shape on the incident side of the diffusion film according to any one of Reference Items 4 to 6 with a reflection medium.
[Reference Item 9]
4. The diffusion film according to any one of Reference Items 1 to 3, wherein a surface shape for realizing diffusion is formed only on one side of the film.
[Reference Item 10]
The surface shape that realizes diffusion formed only on one side of the film is an optical element array shape that combines a lens and a mirror, and control equivalent to the control described in any one of Reference Items 4 to 6 is possible. 10. The diffusion film according to Reference Item 9, wherein
[Reference Item 11]
A diffusion film obtained by coating the mirror portion in the optical element array shape of the diffusion film according to Reference Item 10 with a reflection medium.
[Claim 12]
Diffusion characterized in that a part of the surface of either or both of the incident side and the outgoing side of the diffusion film according to any one of Reference Items 1 to 11 is covered with a black mask for measures against external light. the film.
[Claim 13]
A diffusion film obtained by adding a polarizing plate for preventing external light or a circularly polarizing plate to the diffusion film according to any one of Reference Items 1 to 12.
[Reference Item 14]
There are a plurality of sets of incident angle areas and corresponding exit diffusion angle areas, each set of incident angle areas does not overlap with the other set, and each set of exit diffusion angle areas is the other set. The diffusion film according to any one of Reference Items 1 to 8, which does not overlap.
[Reference Item 15]
A diffusion film, wherein a reflection plate is added to the diffusion film according to any one of Reference Items 1 to 14 to form a reflection type film.

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