JP2002062588A - Smoothing optical element and illumination optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the formation of a shape by the chipping at the edge of an exit end face of a columnar smoothing element which smoothes the intensity distribution of an exit luminous flux by reflecting an incident optical flux at its flank and the foreign matter on the exit end face and to make the F-number of the exit luminous flux larger than the F-number of the incident optical flux. SOLUTION: The smoothing element is composed of a packing section made of glass and a cylindrical hollow section continuous therewith and is so formed as to totally reflect the luminous flux at the flank of the packing section and to reflect the luminous flux at the flank on the inner side of the hollow section as well. The end face of the packing section is formed as an incident end face and the end face of the hollow section as the exit end face, by which the possibility of the occurrence of the chipping at the exit end face and the adhesion of the foreign matter thereto is completely obviated. The F-number of the exit luminous flux is increased by providing the flank with a microstructure to make the reflection angle larger than the incident angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smoothing optical element for smoothing the intensity distribution of a light beam, and an illumination optical system having the smoothing optical element.

[0002]

2. Description of the Related Art Illumination light is guided to a display element such as an LCD (Liquid Crystal Display) or a DMD (Digital Micromirror Device), and the illumination light is modulated by an image displayed on the display element. There is a projection-type image display device that displays an image on a screen by projecting light after modulation by a projection optical system.
In a projection-type image display device, it is necessary to illuminate a display element with a light beam having a uniform intensity distribution in order to provide an image with uniform brightness. However, generally, the intensity of the light beam emitted from the light source is high at the center and low at the peripheral portions, and does not have a uniform distribution. For this reason, the illumination optical system that supplies illumination light to the display element includes a smoothing optical system for smoothing (uniformizing) the intensity distribution of the light flux from the light source.

There are several types of smoothing optical systems, and the so-called integrator rod has the simplest configuration and is frequently used. The integrator rod is a transparent prismatic element that is provided with convergent light on one end face (incident end face), totally reflects the incident light beam on the side face, guides it to the other end face (emission end face), and emits it as divergent light. The number of times of total reflection on the side surface varies depending on the angle of incidence on the incident end face, and light having various numbers of reflections arrives at any position on the exit end face. In other words, the light at the central portion and the light at the peripheral portion of the light beam before incidence are mixed at the exit end face, whereby the intensity distribution of the light beam becomes uniform.

The angle formed by the light contained in the light beam emitted from the exit end face with respect to the optical axis of the integrator rod (a straight line connecting the center of the incident end face and the center of the exit end face) is as follows. Angle equal to Therefore, light emitted from the same point on the exit end face is separated due to a difference in angle with respect to the optical axis, and the uniform intensity distribution on the exit end face becomes more non-uniform as the distance from the exit end face increases.

[0005] Therefore, the integrator rod is used in combination with a relay optical system that forms a conjugate relationship between the emission end face and the display element and forms an image of a light beam emitted from the emission end face on a plane including the display element. Light emitted from the same point on the emission end face is incident on the same point on the display element regardless of the angle with respect to the optical axis, whereby the intensity distribution of the light beam becomes uniform on the display element.

[0006] In order to display a bright image, the integrator rod is given a high intensity light beam. Therefore, the integrator rod is made of glass having excellent heat resistance. However, since such glass is vulnerable to mechanical shock, the edge of the integrator rod is likely to be chipped. If the edge of the emission end face is chipped, the chip forms a clear shadow on the display element because the emission end face and the display element are in a conjugate positional relationship. This shadow will appear as a clear shadow on the projected screen.

FIG. 10 shows a configuration proposed as a method for solving this inconvenience. In FIG. 10, 71 is an integrator rod, and 72 is a light source. The light source 72
It comprises a lamp 72a and a reflector 72b. The reflector 72b is a spheroidal mirror, and has a lamp 7 at its first focal point.
2a is arranged. The integrator rod 71
The incident end face 71a is arranged so as to be located on the second focal point of the reflector 72b, and receives convergent light from the light source 72.

[0010] A mask 73 having an opening smaller than the emission end face 71 b is provided on the emission end face 71 b, and a peripheral portion of the light flux emitted from the emission end face 71 b is blocked by the mask 73. The size of the opening of the mask 73 is set so as to correspond to the size of the display element, and the light beam passing through the mask 73 forms an image on the entire surface of the display element. Therefore, even if the edge of the emission end face 71b is chipped, no shadow is formed on the display element.

The efficiency and accuracy of modulation of illumination light by a display element such as an LCD or DMD increases as the F-number of the illumination light increases, that is, as the illumination light approaches parallel rays. Also,
The projection optical system for projecting the modulated light beam has the F
The larger the number, the smaller the caliber can be. For this reason, the relay optical system is set so as to guide a light beam having a large F number to the display element, and the F number of the light beam that can be captured by the relay optical system has a substantially lower limit.

In order to brightly illuminate the display element, the light beam from the integrator rod must be guided only to the display element so that there is no portion passing beside the display element. Therefore, the relay optical system needs to have a magnification determined by the ratio of the size of the display element to the size of the exit end face of the integrator rod. However, since there is a lower limit to the F number of the light beam that can be captured, the magnification of the relay optical system cannot be set very freely, and as a result, the upper limit is imposed on the size of the exit end face of the integrator rod.

On the other hand, the F number of the light beam emitted from the integrator rod is equal to the F number of the light beam before entering the integrator rod, that is, the F number of the light beam emitted from the light source. However, if the F number of the light beam emitted from the light source is increased, it is necessary to increase the distance from the light source to the integrator rod in order to make the entire light beam incident on the integrator rod, and the configuration becomes large.

A high-output light source has a large light-emitting portion and thus does not have very high convergence performance, and has a large light beam diameter even at the convergence position. Therefore, if a high-output light source is used to display a bright image, the entire light flux from the light source cannot be incident on the integrator rod, and a light amount loss occurs.

Under the restriction that there is an upper limit to the size of the exit end face, as a method of causing the light flux from the light source to enter the integrator rod as much as possible, as shown in FIG. It has been proposed to form a tapered shape having a large width at the emission end face side. In this way, the entire light beam with a large F number can be made incident on the integrator rod without causing the light source 72 to be largely separated from the integrator rod 71, and the entire light beam from a high-output light source with low convergence performance can be made incident. You can also.

As a method of making the F-number of the light beam emitted from the integrator rod larger than the F-number of the light beam from the light source, as shown in FIG. It has been proposed to adopt a shape having a wide taper portion. In this configuration, each time the light incident on the integrator rod 71 is totally reflected by the side surface of the tapered portion, the light approaches parallel to the optical axis, and the F number of the emitted light flux increases.

It has also been proposed to provide two light sources to display a bright image. This configuration is shown in FIG. The two light sources 72 are arranged symmetrically with respect to the optical axis of the integrator rod 71, and both supply a light beam to the integrator rod 71 from a direction oblique to the optical axis.

[0016]

The configuration shown in FIG. 10 in which the mask is provided on the emission end face of the integrator rod can prevent the lack of the edge of the emission end face from forming a shadow on the display element. However, since a part of the light beam emitted from the integrator rod is blocked by the mask, it is inevitable that a light amount loss occurs. In addition, since the intensity distribution is uniform at the exit end face, a large amount of light is lost, which is not a preferable configuration for displaying a bright image. Further, not only chipping of the edge but also foreign matter such as dust attached to the emission end face forms a clear shadow on the display element. However, the configuration of FIG. 10 cannot prevent the shadow of the foreign matter.

In the configuration shown in FIG. 11 in which the integrator rod is tapered, it is possible to cause the entire light beam from the light source to enter the integrator rod. However, since the angle of the light beam with respect to the optical axis increases each time the light is reflected by the side surface, the F number of the emitted light beam is equal to the F number of the light beam from the light source.
Light that is smaller than the number and is not taken into the relay optical system occurs. Therefore, the effect of displaying a bright image is small.

In the integrator rod having a tapered portion shown in FIG. 12, although the F number of the emitted light beam can be made larger than the F number of the light beam from the light source, the convergence performance of the light source is reduced because the incident end face becomes smaller. If it is not good, light quantity loss occurs. That is, light is incident not from the incident end face but from the side face of the tapered portion, and the angle of this light with respect to the optical axis becomes large due to refraction at the time of incidence, and is not taken into the relay optical system after emission. Therefore, even if a high-output light source is used to display a bright image, its performance cannot be fully utilized.

As shown in FIG. 13, the configuration having two light sources is effective for displaying a bright image. However, since each light source gives a light beam from a direction oblique to the optical axis of the integrator rod, the F number of the emitted light beam becomes smaller in the direction away from the light source, and light that is not taken into the relay optical system occurs. For this reason, 2 of the configuration provided with one light source
It is not possible to display an image with twice the brightness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a smoothing element which is not affected by chipping of an edge of an emission end face or a foreign substance attached to the emission end face, and an F number of a light flux after emission. It is an object of the present invention to provide a smoothing element that can be made larger than the F number of a light beam before incidence. It is another object of the present invention to provide an illumination optical system that does not form a shadow on a surface to be illuminated and an illumination optical system with a small loss of light amount.

[0021]

According to the present invention, in order to achieve the above object, the present invention has a columnar outer shape and reflects a light beam incident from one end face to a side face and guides it to the other end face, thereby smoothing the intensity distribution. A smoothing element that emits as a light beam, filled with a translucent material, and a column-shaped filling portion that totally reflects light on the side surface;
It is composed of a cylindrical hollow portion that is continuous with the filling portion and reflects light on the side facing inward.

This smoothing element has a configuration in which a hollow portion is added to a filling portion similar to the conventional integrator rod. This smoothing element can be used in a form in which a light beam is made incident from the filling portion side and emitted from the hollow portion side.
In this use mode, the area of the air surrounded by the edge of the hollow portion becomes the emission end face of the smoothing element, and no foreign matter adheres to the smoothing element, and chipping does not occur at the edge. Therefore, even when combined with a relay optical system that forms an image of a light beam emitted from the emission end face, there is no possibility that a shadow of a foreign substance or a chip will occur on the image formation surface. Conversely, it may be used in a form in which a light beam is made incident from the hollow part side and emitted from the filling part side.

According to the present invention, a light beam having a columnar outer shape, which is incident from one end face, is reflected by the side face and guided to the other end face,
In the smoothing element that emits a light beam having a smoothed intensity distribution, at least a part of the side surface has a fine structure that makes the reflection angle larger than the incident angle.

Each time light is reflected by the side surface having the fine structure, it approaches parallel to the optical axis of the smoothing element.
Therefore, the F number of the outgoing light beam can be made larger than the F number of the incoming light beam without having a tapered outer shape.

In order to achieve the above object, the present invention also provides the above-described smoothing element having a filling portion and a hollow portion, and a light beam having a converging position near one end face of the smoothing element to the smoothing element. An illumination optical system is configured by a light source and a relay optical system that forms a light flux emitted from the other end surface of the smoothing element on a plane. The smoothing element may be arranged so that the filling portion is located on the light source side, or may be arranged such that the hollow portion is located on the light source side.

When the smoothing element is arranged so that the filling portion is located on the light source side and the hollow portion is located on the relay optical system side, a light beam enters the smoothing element from the filling portion side and is emitted from the hollow portion side. In addition, it is possible to guide the illuminating light to the flat surface to be illuminated without chipping of the edge of the emission end face of the smoothing element and shadow of the foreign matter.

In this arrangement, the total length of the smoothing element is L0,
The length of the hollow part of the smoothing element is represented by L1, the width of the filling part of the smoothing element is represented by d, the refractive index of the filling part of the smoothing element is represented by n, and the F number of the light beam given to the smoothing element by the light source is represented by F1. When Equation 1
It is preferable to satisfy the relationship of Expression 3. ^{d · (4 · n 2 ·} F1 2 -1) 1/2 ≦ L0 ≦ 10 · d · (4 · n 2 · F1 2 -1) 1/2 ... Formula 1 (1/4) · d · ( 4 · N ² · F 1 ² -1) ^1/2 ≤ L 1 ≤ (1/2) · L 0 ... Equation 2 0.8 ≤ F 1 ≤ 2.0 ... Equation 3

Equation 1 shows that the outermost light of the light flux from the light source is
It is ensured that the light is reflected once or more and not more than 10 times on the side surface of the smoothing element. Equation 2 stipulates that the hollow portion has a certain length or more, but not more than half of the entire length of the smoothing element. Equation 3 shows the range of the F number of a light beam from a general light source. By satisfying these expressions, it is possible to suppress the light amount loss due to incomplete reflection on the side surface of the hollow portion while realizing the smoothing of the intensity distribution of the light beam and the prevention of the shadow on the illumination target surface.

It is preferable that at least a part of the side surface of the smoothing element has a fine structure that makes the reflection angle larger than the incident angle. Even if the F number of the light beam from the light source is small, the F number of the light beam emitted from the smoothing element can be increased, and the entire light beam can be easily taken into the relay optical system. As a microstructure for making the reflection angle larger than the incident angle, for example, there is a diffraction grating.

The side surface having the fine structure of the smoothing element may be the side surface of the filling portion or the side surface of the hollow portion.

In order to achieve the above object, the present invention further provides a smoothing element as described above, wherein at least a part of the side surface has a fine structure that makes the reflection angle larger than the incident angle, and the vicinity of one end face of the smoothing element. An illumination optical system is composed of a light source that supplies a light beam at a converging position to the smoothing element and a relay optical system that forms a light beam emitted from the other end surface of the smoothing element on a plane.

In this illumination optical system, the F-number of the light beam emitted from the smoothing element can be made larger than the F-number of the light beam from the light source, and the entire light beam can be easily taken into the relay optical system. . Also, by increasing the magnification of the relay optical system, it is possible to increase the output end face and the input end face of the smoothing element, and even if a light source having a low convergence performance and a high output is used, the light from the light source can be reduced. The entire light beam can be easily incident on the smoothing element.

Here, the total length of the smoothing element is L0, the length of the side having the fine structure on the side surface of the smoothing element is L2, the width of the smoothing element is d, the refractive index of the smoothing element is n, and the light source is When the F number of the light beam given to the smoothing element is represented by F1 and the minimum F number of the light beam that can be captured by the relay optical system is represented by F2, it is preferable to satisfy the relations of Expressions 4 to 6. d · (4 · n ² · F ^{2 2} −1) ^1/2 ≦ L0 ≦ 10 · d · (4 · n ² · F ^{2 2} −1) ^1/2 Equation 4 (1/4) · d · (4 · N ² · F 1 ² -1) ^1/2 ≤ L2 ≤ L0 ... Equation 5 0.8 ≤ F2 ≤ 2.0 ... Equation 6

Equation 4 guarantees that the outermost light of the light beam taken in by the relay optical system is reflected at least once and at most 10 times on the side surface of the smoothing element. Equation 5 specifies that the length of the portion having the fine structure on the side surface is equal to or more than １ ／ of the length of once reflecting the outermost light of the light flux from the light source. Equation 6 shows the range of the F number of the light beam that can be captured by a general relay optical system. By satisfying these equations, it is possible to realize that the entire light beam is incident on the relay optical system while smoothing the intensity distribution of the light beam.

In an illumination optical system having a fine structure in which the side surface of the smoothing element makes the reflection angle larger than the incident angle, the light source is
It is also possible to provide a configuration in which each light source provides a light flux to the smoothing element from a direction oblique to a straight line connecting the center of the one end face and the center of the other end face of the smoothing element. When the light source gives a light beam obliquely to the optical axis of the smoothing element, the F
Although the number decreases, the F number can be increased by the fine structure of the smoothing element, so that the entire light beam can be taken into the relay optical system.

In this case, the side surface of the smoothing element includes a plane perpendicular to a plane including a straight line connecting the center of one end face of the smoothing element and the center of the other end face and the light source. Only one of them may have a fine structure. Since the fine structure is provided only in the direction in which the F number is small, the manufacture of the smoothing element becomes easy.

Also, at least one pair of light sources may be configured to apply a light beam to the smoothing element from directions opposite to each other with respect to a straight line connecting the center of the one end face and the center of the other end face of the smoothing element. That is, the paired light sources can be arranged on a plane including the optical axis of the smoothing element and on the opposite side with respect to the optical axis.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a smoothing optical element and an illumination optical system according to the present invention will be described below with reference to the drawings. FIG. 1 shows a main part of an illumination optical system 1 according to the first embodiment. The illumination optical system 1 includes a smoothing element 11, a light source 1,
2, and a relay optical system (not shown). The light source 12 includes a lamp 12a and a reflector 12b. The reflector 12b is a spheroidal mirror, and the lamp 12a is disposed at the first focal point.

The smoothing element 11 has a rectangular column shape with a rectangular cross section, and includes a filling portion 11f and a hollow portion 11e. The filling portion 11f is made of transparent glass and is filled with a glass material. Although the hollow portion 11e is also made of glass, the inside is not filled with a glass material and has a cylindrical shape. Filling section 11
f and the hollow portion 11e are continuous, and the inner side surface 11c 'of the hollow portion 11e is on the extension of the side surface 11c of the filling portion 11f. A reflection film is provided on the entire side surface 11c 'of the hollow portion 11e.

The two end surfaces 11a and 11b of the filling portion 11f
Is perpendicular to the side surface 11c. A straight line connecting the center of the end face 11a and the center of the end face 11b is defined as the optical axis A of the smoothing element 11.
It is called x. The smoothing element 11 is such that the optical axis Ax is
It is arranged so as to coincide with the optical axis (rotation axis) of 2b and the end face 11a of the filling portion 11 is located on the second focal point of the reflector 12b. The end face 11a of the filling portion 11f is the entrance end face of the smoothing element 11, and the face 11d where only air surrounded by the edge of the end of the hollow section 11e exists is the smoothing element 1
1 is an emission end face.

The light emitted from the lamp 12a is reflected by the reflector 12
b, and becomes a convergent light flux having the center of the end face 11a of the filling portion 11f as a converging position and enters the filling portion 11f. The light included in the light beam incident on the filling portion 11f from the end face 11a is totally reflected by the side face 11c while being reflected on the end face 11c.
b, and penetrates into the hollow portion 11e. The light entering the hollow portion 11e reaches the end face 11d of the hollow portion 11 while being reflected by the side surface 11c ', and is emitted from the smoothing element 11 as a divergent light beam.

The side surface 11c, 1
Various light beams having different numbers of reflections by 1c ′ arrive, and the light beam from the light source 12 having the non-uniform intensity distribution
On 1d, the light flux has a smoothed intensity distribution. End face 1
The light beam emitted from 1d is imaged by a relay optical system (not shown) on a plane conjugate with the end face 11d. This plane is the surface to be illuminated, and the surface to be illuminated has a shape similar to that of the end face 11d and is uniformly illuminated in a range of a size corresponding to the magnification of the relay optical system.

The edge of the filling portion 11f is easily chipped, but even if the edge of the end face 11b is chipped, the end face 11b is not conjugate to the surface to be illuminated. Absent. Even if foreign matter such as dust adheres to the end face 11b, no shadow of the foreign matter appears on the illumination target surface for the same reason. Since only air is present on the emission end face 11d, there is no possibility that foreign matter will adhere or chip there, and there is no possibility that a shadow will be formed on the illumination target surface.

The smoothing element 11 is preferably set so as to satisfy the following equations (1) to (3). d · (4 · n ² · F 1 ² -1) ^1/2 ≦ L0 ≦ 10 · d · (4 · n ² · F 1 ² -1) ^1/2 Equation 1 (represented) (1/4) · d · (4 · n ² · F1 ² -1) ^1/2 ≤ L1 ≤ (1/2) · L0 ... Equation 2 (reprinted) 0.8 ≤ F1 ≤ 2.0 ... Equation 3 (reprinted)

Here, L0 is the filling portion 11f and the hollow portion 11f.
e, the total length of the smoothing element 11 including e, L1 is the length of the hollow part 11e, d is the width (thickness) of the filling part 11f, and n is the filling part 11
The refractive index of f, F1, is the F number of the light beam provided by the light source 12 to the smoothing element 11.

Equation 1 defines the total length of the smoothing element 11. If the outermost light of the light beam from the light source 12 is short enough not to be reflected at all, the smoothing element 11 cannot exhibit the function of smoothing the intensity distribution. d ・ (4 ・ n ²・ F1 ² −
1) ^1/2 is the distance in the direction of the optical axis Ax until the outermost light of the light flux from the light source 12 enters near the edge of the end face 11a and reaches the opposite side face 11c. Therefore,
The inequality sign on the left indicates that the outermost light of the light beam from the light source 12 is reflected at least once by the side surfaces 11c and 11c 'regardless of where the light enters the end face 11a. This ensures a smoothing function. On the other hand, if the outermost light is long enough to be reflected ten times, the intensity distribution becomes sufficiently uniform, and it is meaningless to make the smoothing element 11 longer than that. The inequality sign on the right indicates that the number of reflections is suppressed to 10 or less.

Equation 2 defines the length of the hollow portion 11e. If the hollow portion 11 is too short, the end surface 11b of the filling portion 11f
Becomes closer to a position conjugate with the illumination target surface, and chipped edges and shadows of foreign substances easily appear on the illumination target surface. Such a situation does not occur if the length of the hollow portion 11e is equal to or more than １ ／ of the distance at which the outermost light is reflected at least once. The inequality sign on the left sets this as the lower limit. Although the reflective film provided on the side surface 11c 'of the hollow portion 11e is set to have a high reflectance, the reflectance is not as high as the side surface 11c of the filling portion 11f that totally reflects light.
Therefore, the longer the hollow portion 11e, the greater the light amount loss. The inequality on the right indicates that the length of the hollow portion 11e is limited to less than half of the entire length of the smoothing element 11 to avoid this.

Equation 3 shows the range of the F number of the light beam emitted by a general light source. Therefore, unless a special light source is used as the light source 12, the illumination optical system 1 in which the smoothing element 11 satisfies the relations of Expressions 1 to 3 should smooth the intensity distribution and not form a shadow on the illumination target surface. And the loss of light quantity in the smoothing element 11 can be suppressed to an extremely low level.

FIG. 2 shows a main part of the illumination optical system 2 according to the second embodiment. The illumination optical system 2 includes a smoothing element 21 instead of the smoothing element 11 of the illumination optical system 1 described above. Like the smoothing element 11, the smoothing element 21 includes a filling portion 21f and a hollow portion 21e, but is arranged in the opposite direction, and an end face 21d surrounded by an edge of an end of the hollow portion 21e is a reflector. 12b is located on the second focal point.
The entire side surface 21c 'of the hollow portion 21e is not only provided with a reflective film but also formed with a fine structure that makes the reflection angle larger than the incident angle. This microstructure is
It is a diffraction grating of a binary type or a blazed type.

The light contained in the light beam incident on the hollow portion 21e from the end face 21d is reflected by the side face 21c ', and is brought closer to the optical axis Ax by its fine structure.
This light enters the filling portion 21f from the end face 21b,
The light is totally reflected at 1c and reaches the end face 21a. The intensity distribution of the light beam on the end face 21a is smoothed. The F of the light beam emitted from the end face 21a is reflected by the side face 21c '.
The number is larger than the F number of the light beam before entering the end face 21d. Therefore, as the relay optical system, a relay optical system having a smaller minimum F-number than the relay optical system of the illumination optical system 1 can be used.

FIG. 3 shows a main part of the illumination optical system 3 of the third embodiment. The illumination optical system 3 has a magnification of the relay optical system higher than that of the illumination optical system 2 and a smoothing element 21.
Instead of this, a smoothing element 31 having a wider width between the filling portion 31f and the hollow portion 31e is provided. Similarly, a microstructure for increasing the reflection angle to the incident angle is formed on the side surface 31c 'of the hollow portion 31e.

Since the F number of the light beam emitted from the end face 31a can be increased by the fine structure, it is possible to increase the magnification of the relay optical system while maintaining the F number of the light beam to the irradiation target surface. I have. As a result, the smoothing element 3
1, the width of the incident end face 31 together with the exit end face 31a is increased.
It is also possible to increase d.

In the illumination optical system 3 including the smoothing element 31 having a large incident end face 31d, even if a light source 12 having a low convergence performance and a high output having a large luminous flux diameter at the convergence position is used, the entire luminous flux is smoothed. Incident on the chemical element 31. Therefore, it is possible to brightly illuminate a wide range.

FIG. 4 shows a main part of an illumination optical system 4 according to the fourth embodiment. This illumination optical system 4 is obtained by adding one light source 12 to the illumination optical system 2 of the second embodiment. 4A and 4B are cross-sectional views in two orthogonal directions.

The two light sources 12 have the same configuration and are arranged symmetrically with respect to the optical axis Ax of the smoothing element 21.
Therefore, the light source 12 gives a light beam to the smoothing element 21 from a direction oblique to the optical axis Ax. Smoothing element 21
Of the four side surfaces 11c is such that the opposing set is the optical axis Ax
Perpendicular to the plane containing the lamp 12a and the other 1
The pairs are arranged in parallel.

In this configuration, the F number of the light beam from the light source incident on the smoothing element 21 depends on the direction of separation of the light source 12 (X in FIG. 4).
Direction), a direction orthogonal to this (Y direction in FIG. 4)
Less than half. However, the side surface 21 of the hollow portion 21e
Since the F number of the emitted light beam can be increased by the fine structure formed in c ′, the entire emitted light beam can be taken into the relay optical system. Therefore, there is no light quantity loss, and the effect of providing two light sources 12 is not reduced at all.

In this configuration, a fine structure that makes the reflection angle larger than the incident angle is formed by the four side surfaces 2 of the hollow portion 21e.
It is not necessary to provide it on all of 1c ', and it is sufficient to provide it only on the side surface perpendicular to the direction (X direction) where the F number of the light beam from the light source 12 is small. This makes it easy to manufacture the smoothing element 21 and makes it possible to make the F number of the emitted light beam the same in two orthogonal directions.

FIG. 5 shows a main part of an illumination optical system 5 according to the fifth embodiment. The illumination optical system 5 includes a light source 1
2 is obtained by adding two more. 5A and 5B are cross-sectional views in two orthogonal directions.

The added two light sources 12 are arranged at positions where the other two light sources 12 are rotated by 90 ° with respect to the optical axis Ax of the smoothing element 21. Microstructures that make the reflection angle larger than the incident angle are provided on all four side surfaces 21c '. Also in the illumination optical system 5, the entire light beam emitted from the smoothing element 21 can be taken into the relay optical system, and there is no light amount loss.

FIG. 6 shows a main part of an illumination optical system 6 according to the sixth embodiment. This illumination optical system 6 is different from the illumination optical system 4 of the fourth embodiment in that the smoothing element 21 is replaced with another smoothing element 4.
1 is provided. The smoothing element 41 has only a filling part made of glass, and a fine structure that makes the reflection angle larger than the incident angle is formed on a part 41p of the side surface 41c. The microstructure is formed only on the two side surfaces perpendicular to the direction in which the light source 12 is separated.

The illumination optical system 6 can also increase the F number of the light beam emitted from the smoothing element 41 by the fine structure. For this reason, the entire emitted light beam can be taken into the relay optical system, and there is no light amount loss.

It is preferable that the smoothing element 41 be set so as to satisfy the following equations (4) to (6). d · (4 · n ² · F ^{2 2} -1) ^1/2 ≦ L0 ≦ 10 · d · (4 · n ² · F ^{2 2} −1) ^1/2 Equation 4 (represented) (1/4) · d · (4 · n ² · F 1 ² -1) ^1/2 ≤ L ² ≤ L 0 ... Equation 5 (represented) 0.8 ≤ F 2 ≤ 2.0 ... Equation 6 (represented)

Here, L2 is the length of the portion 41p having the fine structure of the side surface 41c, and F2 is the minimum F number of the light beam that can be captured by the relay optical system. L0, d, and n are the overall length, width, and refractive index of the smoothing element 41, respectively, as described above. Note that F1 is the F number of the entire light beam that the two light sources 12 give to the smoothing element 41.

Equation 4 defines the total length of the smoothing element 41, and the outermost light of the light beam taken into the relay optical system is reflected once or more and not more than 10 times on the side surface 41c. Is shown. Equation 5 specifies that the length of the portion 41p having the fine structure of the side surface 41c is equal to or more than ４ of the length of reflecting the outermost light of the light beam from the light source 12 at least once. Equation 6 shows the range of the F number of the light beam that can be captured by a general relay optical system. By satisfying these expressions, it is possible to realize that the entire light beam is taken into the relay optical system while smoothing the intensity distribution of the light beam.

Here, the fine structure is provided in a portion near the incident end face 41a.
It may be provided anywhere between 1a and the emission end face 41b. Also, as shown by the equal sign on the right side of Equation 5, the incident end face 41
A fine structure may be provided over the entire range from a to the emission end face 41b.

FIG. 7 shows a main part of an illumination optical system 7 according to the seventh embodiment. The illumination optical system 7 is configured such that the direction of the smoothing element 21 of the illumination optical system 4 of the fourth embodiment is reversed,
The end face 21a of 1f is located on the second focal point of the light source 12. The microstructure has a separation direction (X) between the two light sources 12 among the four side surfaces 21c 'of the hollow portion 21e.
Direction) is provided only on the side surface perpendicular to the direction.

The illumination optical system 7 has the feature of the illumination optical system 4 that all the light beams from the two light sources 12 can be taken into the relay optical system, as well as the end face 2 of the filling portion 21f.
The feature of the illumination optical system 1 is that the foreign matter 1b or the shadow of the chipped edge is not formed on the irradiation target surface.

FIG. 8 shows the configuration of a projection type video display device 8 according to the eighth embodiment. The image display device 8 includes the illumination optical system 7, the plane mirror 51, the two prisms 52 and 53, the display element 54, and the projection optical system 55 of the seventh embodiment. The illumination optical system 7 includes a smoothing element 21, a light source 12, and two convex lenses 13 a forming a relay optical system 13.
13b is included.

The mirror 51 reflects the light beam from the smoothing element 21 between the lenses 13a and 13b and bends the optical path. The mirror 51 is provided to reduce the size of the entire configuration, and may be omitted.

The display element 54 is a DMD in which a large number of minute mirror elements whose angles are variable are arranged two-dimensionally. Each mirror element selectively reflects the illumination light in one of two predetermined directions according to its angle. An image is displayed on the DMD by controlling the angle of each mirror element according to a signal representing the image, with each mirror element as a pixel. The illumination light is modulated by being reflected in two directions, one of which becomes light representing an image, and the other of which becomes unnecessary light.

The two prisms 52 and 53 guide the light from the illumination optical system 7 to the display element 54 and
The reflected light representing the image from 4 is guided to the projection optical system 55. The prisms 52 and 53 are arranged such that the opposing surfaces 52a and 53a form a minute gap therebetween, and guide the light from the illumination optical system 7 to the display element 54 by totally reflecting the light from the surface 52a. The reflected light from the display element 54 is
The light is guided to the projection optical system 55 by transmitting a.

The projection optical system 55 projects the reflected light, which has passed through the prisms 52 and 53 and represents the image from the display element 55, toward a screen (not shown) and forms an image on the screen. Although the prisms 52 and 53 also transmit unnecessary light from the display element 54, the unnecessary light does not go to the projection optical system 55,
Discarded.

When a color image is displayed on the image display device 8, a color wheel having a color filter for selectively transmitting red light, green light and blue light is mounted on the smoothing element 2.
The light is illuminated on the display element 54 by being arranged near one of the entrance end face or the exit end face. In addition, the display element 54 displays a red component, a green component, and a blue component of the image corresponding to the illumination light in synchronization with the switching of the illumination light.

The output end face 21d of the smoothing element 21 and the display element 54 are in a conjugate positional relationship by the relay optical system 13, and the display element 54 is a light beam having the same uniform intensity distribution as the intensity distribution at the output end face 21d, without shadow. Illuminated. Moreover, the illumination optical system 7 includes two light sources 12, and the display element 54 is brightly illuminated. Further, since the F number of the illumination light is large, light representing an image and unnecessary light are reliably separated, and the modulation accuracy by the display element is high. Further, the projection optical system 55
Since the F number of the light flux guided to the projection optical system 55 is also large, a small projection optical system 55 having a small aperture can be used.
Thus, the image display device 8 can provide a bright and high-quality image despite its small size.

FIG. 9 shows the configuration of a projection display 9 according to a ninth embodiment. The image display device 9 includes the illumination optical system 7 and the polarization separation (PBS) prism 5 of the seventh embodiment.
6, a display element 57, and a projection optical system 55.

The display element 57 is a reflection type LCD, and modulates linearly polarized light given as illumination light by partially rotating it by 90 ° according to the image displayed on the liquid crystal layer.

The PBS prism 56 is manufactured by joining two triangular prisms, and a PBS film 56a is provided on the joining surface. The PBS film 56a is set so as to reflect a polarized light component incident as S-polarized light and transmit a polarized light component incident as P-polarized light. PBS prism 5
6 reflects linearly polarized light that becomes S-polarized light with respect to the PBS film 56a among the unpolarized light from the illumination optical system 7 and guides the linearly polarized light to the display element 57, and among the light reflected by the display element 57, The linearly polarized light serving as the P-polarized light is transmitted through the PBS film 56a and guided to the projection optical system 55.

The projection optical system 55 projects the reflected light representing the image from the display element 57 transmitted through the PBS prism 56 toward a screen (not shown) and forms an image on the screen. The video display device 9 can also display a color video as described above. As with the image display device 8, it is possible to provide a bright and high-quality image despite its small size.

In the eighth and ninth embodiments, the configuration including the illumination optical system 7 has been described as an example.
Needless to say, any of the above 6 may be provided. Further, although a reflective type is used as the display element here, a transmissive type LCD may be used. In that case, an LCD may be arranged between the illumination optical system and the projection optical system, and a polarizing plate may be arranged between the illumination optical system and the LCD and between the LCD and the projection optical system.

[0080]

According to the smoothing element of the present invention having the filling portion and the hollow portion, the light beam is made incident on the filling portion side and emitted from the hollow portion side, so that the edge of the output end face is not chipped. It is possible to provide a light flux which not only has a uniform intensity distribution but also is not affected by chipping or foreign matter. Also,
It is also possible to provide a predetermined function to the side surface of the hollow portion, and it is useful even when the light beam is incident on the hollow portion side and emitted from the filling portion side.

In the smoothing element of the present invention in which at least a part of the side surface has a fine structure in which the reflection angle is larger than the incident angle, it is possible to make the light contained in the incident light flux close to parallel to the optical axis. That is, even if the entrance end face and the exit end face have the same size, the F number of the light flux after emission can be made larger than the F number of the light flux before incidence.

The illumination optical system of the present invention including the smoothing element having such features, a light source, and a relay optical system includes:
A light beam having no shadow on the illumination target surface or a light beam having a large F number can be guided. Therefore, it is suitable for illumination of the display element of the projection type video display device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a main part of an illumination optical system according to a first embodiment.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a main part of an illumination optical system according to a second embodiment.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of a main part of an illumination optical system according to a third embodiment.

FIG. 4 is a cross-sectional view illustrating a schematic configuration of a main part of an illumination optical system according to a fourth embodiment.

FIG. 5 is a sectional view showing a schematic configuration of a main part of an illumination optical system according to a fifth embodiment.

FIG. 6 is a sectional view illustrating a schematic configuration of a main part of an illumination optical system according to a sixth embodiment.

FIG. 7 is a sectional view showing a schematic configuration of a main part of an illumination optical system according to a seventh embodiment.

FIG. 8 is a cross-sectional view illustrating a schematic configuration of a projection display apparatus according to an eighth embodiment.

FIG. 9 is a sectional view illustrating a schematic configuration of a projection display apparatus according to a ninth embodiment;

FIG. 10 is a sectional view showing a schematic configuration of a main part of a conventional illumination optical system including an integrator rod.

FIG. 11 is a cross-sectional view illustrating a schematic configuration of a main part of another conventional illumination optical system including an integrator rod.

FIG. 12 is a cross-sectional view illustrating a schematic configuration of a main part of still another conventional illumination optical system including an integrator rod.

FIG. 13 is a sectional view showing a schematic configuration of a main part of another conventional illumination optical system including an integrator rod.

[Explanation of symbols]

 1-7 Illumination optical system 8,9 Projection type video display device 11,21,31,41 Smoothing element 11f, 21f, 31f Filling part 11e, 21e, 31e Hollow part 11a, 21a, 31a Filling part end face 11b, 21b, 31b Filling part end face 11c, 21c, 31c, 41c Filling part side face 11c ', 21c', 31c 'Hollow part side face 11d, 21d, 31d Hollow part end face 12 Light source 12a Lamp 12b Reflector 13 Relay optical system 13a, 13b Convex lens 51 Mirror 52 , 53 prism 54 DMD (display element) 55 projection optical system 56 PBS prism 56 a PBS film 57 LCD (display element)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiro Takamoto 2-3-1-13 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Yuichiro Otori 2-3-3 Azuchicho, Chuo-ku, Osaka City No. 13 Osaka International Building Minolta Co., Ltd. F-term (reference) 2H038 AA54 BA07 BA08 2H052 BA02 BA03 BA07 BA09 BA14

Claims (11)

[Claims] 1. A smoothing element having a columnar outer shape, which reflects a light beam incident from one end surface on a side surface, guides the light beam to the other end surface, and emits the light beam as a light beam having a smoothed intensity distribution. A smoothing element comprising: a column-shaped filling portion that is filled and totally reflects light on a side surface; and a cylindrical hollow portion connected to the filling portion and reflecting light on a side surface facing inward. 2. A smoothing element which has a columnar outer shape, reflects a light beam incident from one end surface on a side surface, guides the light beam to the other end surface, and emits the light beam as a light beam having a smoothed intensity distribution. A smoothing element having a fine structure that makes the reflection angle larger than the incident angle. 3. A smoothing element according to claim 1, a light source for supplying a light beam having a convergence position near one end face of the smoothing element to the smoothing element, and a light beam emitted from the other end face of the smoothing element as a plane. An illumination optical system comprising: a relay optical system that forms an image on the illumination optical system. 4. The smoothing element is arranged such that the filling portion is located on the light source side and the hollow portion is located on the relay optical system side, and the total length of the smoothing element is L0, and the length of the hollow portion of the smoothing element is L0. Where L1 is the width of the filling portion of the smoothing element, d is the refractive index of the filling portion of the smoothing element, and F1 is the F number of the light beam given to the smoothing element by the light source. ² · F1 ² -1) ^1/2 ≦ L0 ≦ 10 ・ d ・ (4 ・ n ²・
F1 ² -1) ^1/2 (1/4) · d · (4 · n ² · F1 ² -1) ^1/2 ≦ L1 ≦ (1 /
2) The illumination optical system according to claim 3, wherein a relationship of L0 0.8 ≦ F1 ≦ 2.0 is satisfied. 5. At least a part of the side surface of the smoothing element is:
5. The illumination optical system according to claim 3, wherein the illumination optical system has a fine structure that makes the reflection angle larger than the incident angle. 6. A side face having a fine structure of a smoothing element,
The illumination optical system according to claim 5, wherein the illumination optical system is a side surface of the hollow portion. 7. A smoothing device according to claim 2, a light source for providing a light beam having a convergence position near one end surface of the smoothing device to the smoothing device, and a light beam emitted from the other end surface of the smoothing device as a plane. An illumination optical system comprising: a relay optical system that forms an image on the illumination optical system. 8. The total length of the smoothing element is L0, the length of the side of the smoothing element having a fine structure is L2, the width of the smoothing element is d, the refractive index of the smoothing element is n, and the light source is smooth. When the F number of the luminous flux given to the optical element is represented by F1, and the minimum F number of the luminous flux that can be captured by the relay optical system is represented by F2, d · (4 · n ² · F ^{2 2} −1) ^1/2 ≦ L0 ≦ 10 · d ・ (4 ・ n ²・
F2 ² -1) ^1/2 (1/4) · d · (4 · n ² · F1 ² -1) ^1/2 ≤ L2 ≤ L0 0.8 ≤ F2 ≤ 2.0 The illumination optical system according to claim 7, wherein 9. A light source comprising two or more light sources, wherein each light source applies a light beam to the smoothing element from a direction oblique to a straight line connecting the center of the one end face and the center of the other end face of the smoothing element. The illumination optical system according to any one of claims 5 to 8, wherein: 10. A side surface of the smoothing element includes a plane perpendicular to a plane including a straight line connecting the center of one end face of the smoothing element and the center of the other end face and the light source, and only this plane is included. 10. The illumination optical system according to claim 9, wherein has a fine structure. 11. The smoothing element according to claim 9, wherein at least one pair of light sources applies a light beam to the smoothing element from directions opposite to each other with respect to a straight line connecting the center of the one end face and the center of the other end face of the smoothing element. Alternatively, the illumination optical system according to claim 10.