JP5361145B2 - Illumination optical system, image projection optical system, and image projection apparatus - Google Patents

Abstract

An optical system for image projection is disclosed which is easy to be manufactured and designed and capable of projecting a bright image with high contrast. The optical system includes an illumination optical system introducing a luminous flux emitted from a light source to an image-forming element through an optical surface having a light-splitting function, and a projection optical system projecting the luminous flux from the image-forming element through the optical surface onto a projection surface. The illumination optical system includes a conversion system which respectively convertsthe widths of the luminous flux in first and second cross-sections into widths different from those before entering thereinto. Conversion rates in the first and second cross-sections are different from each other.

Description

  The present invention relates to an optical system used in an image projection apparatus using an image forming element such as a liquid crystal panel.

  In the image projection apparatus as described above, it is important that a bright and high-contrast image can be projected, and that the projection image has almost uniform brightness throughout.

  In an illumination optical system of an image projection apparatus (projector) using a reflective image forming element such as a reflective liquid crystal panel, a light beam emitted from a light source is emitted as substantially parallel light by a parabolic reflector. This parallel light beam is divided and condensed by the first fly-eye lens, and each divided light beam is condensed near the second fly-eye lens to form a light source image (secondary light source image). The microlenses (lens cells) constituting each fly-eye lens have a rectangular shape that is similar to the liquid crystal panel that is the illuminated surface.

  The plurality of split light beams emitted from the second fly-eye lens are collected by a condenser lens and superimposed on the liquid crystal panel via a color separation / synthesis optical system to illuminate the liquid crystal panel. In the color separation / synthesis optical system, an optical element (such as a dichroic prism or a polarization beam splitter) provided with a dichroic film or a polarization separation film is used.

  In such an image projecting device, when trying to increase the utilization efficiency of light from the light source, the angular distribution of the light flux generally tends to increase. Therefore, when an optical element with sensitive angular characteristics, that is, an optical element having a dichroic film or a polarization separation film inclined with respect to the optical axis is arranged in the color separation / synthesis optical system, uneven brightness (color unevenness) or Degradation of image quality such as a decrease in contrast occurs.

  20 and 21 show examples of angle-dependent characteristics (transmittance characteristics and reflectance characteristics) of the polarization separation film, respectively. Compared to the characteristics for light incident on the polarization separation film at 45 °, the characteristics for the light incident on the polarization separation film at 47 ° or 49 ° are lower. The greater the deviation of the incident angle from 45 °, the more the degree of deterioration of the characteristics. Is big. This deterioration in characteristics causes so-called leakage light and lowers the contrast. When the dichroic film is used, if the incident angle is deviated, it appears as uneven color (change in color), so that an image is displayed in a color different from the color originally intended to be displayed.

  In Patent Document 1, in order to prevent such a decrease in image quality, the angle distribution of the incident light beam is reduced in a direction sensitive to the angle distribution in the optical element, and the angle distribution of the incident light beam is displayed in a direction insensitive to the light beam angle distribution. A large asymmetric optical system is disclosed.

In Patent Document 1, the lens cell constituting the first fly-eye lens is decentered so that the first fly-eye lens has a positive power as a whole in a direction sensitive to the luminous flux angle distribution in the optical element. Yes. On the other hand, in the same direction, the lens cells constituting the second fly-eye lens are decentered so that the second fly-eye lens has a negative power as a whole. In this way, by compressing the light beam emitted from the reflector only in the direction sensitive to the light beam angle distribution, the angle distribution of the light beam incident on the optical element becomes asymmetric between the direction sensitive to the light beam angle distribution and the insensitive direction. ing.
Japanese Unexamined Patent Publication No. 7-181392 (paragraph 0019, FIG. 3 etc.)

  However, when compressing the light beam emitted from the reflector, only by compressing one of the cross sections including the optical axis, the angle of incidence distribution on the polarization separation film in the other cross section (the cross section perpendicular to the above-mentioned one cross section). The image quality cannot be reduced, making it difficult to improve the image quality. Further, if the reflector is made small in order to reduce the diameter of the emitted light beam, it will become dark, so the outer diameter of the reflector needs to be increased to some extent in order to ensure brightness.

  Therefore, the present invention provides an optical system capable of projecting a bright and high-contrast image that is easy to manufacture and design, and an image projection apparatus having the optical system.

An optical system according to one aspect of the present invention includes a polarization beam splitter including a polarization separation surface formed of a multilayer film in which a light beam emitted from a light source and reflected by a reflector is inclined with respect to the optical axis of the illumination optical system. This is an illumination optical system that leads to the image forming element via the. The illumination optical system is disposed between the light source and the polarization beam splitter, and includes a polarization conversion element that converts non-polarized light into linearly polarized light. The normal line of the polarization separation surface of the polarization beam splitter and the image forming element when entering the exit surface normals of the first cross-section of a cross section parallel to the cross section perpendicular to the first cross section including the optical axis of the illumination optical system and the second cross section, between the light source and the polarization conversion element And a compression system that compresses the light beam width in each of the first cross section and the second cross section to a light beam width different from that before incidence, and the compression ratio of the light beam width in the first cross section by the compression system is When α is β and the compression ratio of the light beam width in the second cross section is β, α / β <1 is satisfied, and the compression systems are different from each other in the first cross section and the second cross section in order from the light source side. The first optical element having the following optical power is different from each other in the first cross section and the second cross section. The have a second optical element having optical power, the light source-side surface of the first optical element is a surface in which a plurality of lens cells are formed, the surface of the image forming device side is a plane, the A first fly-eye lens having positive optical power by decentering at least some of the plurality of lens cells by different amounts in the first cross section and the second cross section, and the second optical The surface on the light source side of the element is a flat surface, the surface on the image forming element side is a surface on which a plurality of lens cells are formed, and at least some of the plurality of lens cells have a first cross section and a first cross section. The second fly-eye lens has a negative optical power by being decentered by different amounts in the two cross sections .

  ADVANTAGE OF THE INVENTION According to this invention, the optical system which can project a bright image can be implement | achieved, suppressing the contrast fall.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[ Reference Example 1]

1 and 2 show the configuration of an illumination optical system used in an image projection optical system that is Reference Example 1 of the present invention. The illumination optical system illuminates a reflective liquid crystal panel (hereinafter simply referred to as a liquid crystal panel) 8 as a reflective image forming element disposed on an illuminated surface through a polarizing beam splitter 7 using a light beam from a light source 1. To do.

However, light (image light) that has been image-modulated by the liquid crystal panel 8 is guided again to a projection lens (not shown) via the polarization beam splitter 7 and projected onto a projection surface such as a screen. As described above, the illumination optical system of this reference example also includes a function of detecting image light with the polarization beam splitter 7 and guiding it to the projection lens.

In this reference example, the optical axis of the illumination optical system (for example, defined by an axis passing through the center of the condenser lens 6 and the center of the panel surface of the liquid crystal panel 8) is the Z axis, and the direction parallel to the Z axis is the optical axis. The direction. The direction along the Z-axis in which the light beam from the light source lamp LP travels toward the liquid crystal panel 8 via the condenser lens 6 and the polarization beam splitter 7 is also referred to as the light traveling direction.

  FIG. 1 shows an XZ cross section and a YZ cross section, which are two planes that include the Z axis (parallel to the Z axis) and are orthogonal to each other, and have a wider angle distribution of the incident light beam with respect to the panel surface of the liquid crystal panel 8. The optical structure in the XZ cross section (1st cross section) which is is shown. This XZ cross section is a cross section parallel to the direction of the long side of the liquid crystal panel 8 (the direction in which the long side extends).

  FIG. 2 shows an optical configuration in a YZ section (second section), which is a section having a narrower angle distribution of incident light beams with respect to the panel surface. The YZ plane is a cross section parallel to the direction of the short side of the liquid crystal panel 8 (the direction in which the short side extends).

  As shown in FIG. 3, the YZ cross section is a cross section parallel to the plane (paper surface of FIG. 3) including the optical axis (Z axis) and the normal line (N) of the polarization splitting surface 7a of the polarizing beam splitter 7. is there. The YZ cross section can be rephrased as a cross section parallel to the normal line N of the polarization separation surface 7a and the normal line NP of the panel surface (incident / exit surface) 8a of the liquid crystal panel 8.

Further, it can be said that the XZ section is a section perpendicular to the YZ section and parallel to the Z axis (optical axis). The meanings of these Z-axis, XZ cross-section, and YZ cross-section are the same in Examples 3 and 4 and Reference Examples 2 and 5 described below.

  In these drawings, only basic components of the illumination optical system are shown, but actually, various optical elements such as a mirror for bending an optical path from a light source, a heat ray cut filter, and a polarizing plate are also arranged.

  A luminous flux emitted radially from a light source 1 such as a high-pressure mercury discharge tube is converted into a convergent luminous flux by an elliptical reflector (elliptical mirror) 2. The light source 1 and the reflector 2 constitute a light source lamp LP. Here, the elliptical reflector may be replaced with a parabolic reflector and a convex lens.

  The reflected light reflected by the elliptical reflector 2 is divided into a plurality of light beams by the first fly-eye lens 3, and the plurality of divided light beams are in the vicinity of the second fly-eye lens 4 and the polarization conversion element 5. The secondary light source image is formed.

  The light beam that forms each secondary light source image is converted into linearly polarized light (light beam having a uniform polarization state) having a predetermined polarization direction by the polarization conversion element 5 and then enters the condenser lens 6. The polarization conversion element 5 includes a plurality of polarization separation surfaces, a plurality of reflection surfaces, and a plurality of half-wave plates. Specifically, the polarization conversion element 5 here is configured as one polarization conversion element unit with a polarization separation surface, a reflection surface (or polarization separation surface) and a half-wave plate, and this polarization conversion element unit. Is an array-shaped optical element in which a plurality of are arranged in a direction substantially perpendicular to the optical axis. Therefore, the polarization conversion element here may be referred to as a polarization conversion element array.

  In the polarization conversion element 5, the polarized light component having a predetermined polarization direction among the light incident on each polarization separation film is transmitted through the polarization conversion element 5 and emitted from the polarization conversion element 5.

  On the other hand, of the light incident on each polarization separation film, a polarization component having a polarization direction orthogonal to the predetermined polarization direction is reflected by the polarization separation surface and further reflected by the reflection surface. Then, the polarization direction is converted by 90 degrees by the half-wave plate and emitted from the polarization conversion element 5. Thus, the polarization conversion element 5 converts the incident non-polarized light into linearly polarized light having a predetermined polarization direction.

  Here, the half-wave plate may be disposed only on the optical path of the light transmitted through the polarization separation film. Moreover, this polarization conversion element should just make unpolarized light into linearly polarized light for every color (each wavelength range corresponding to each panel), and the direction of those linearly polarized light does not necessarily need to be the same.

  That is, only the red light is made S-polarized with respect to the polarizing beam splitter 7 in the subsequent stage, and the green light and the blue light are made P-polarized with respect to the polarized beam splitter 7. The polarization directions of the two color lights may be orthogonal to each other.

  Specifically, the polarization splitting surface described above reflects green light, blue light S-polarized light, and red light P-polarized light, and transmits green light, blue light P-polarized light, and red light S-polarized light. A half-wave plate may be disposed on the optical path of the light beam reflected by the polarization splitting surface.

  A plurality of split light beams emitted from the condenser lens 6 pass through the polarization separation surface (optical film surface, optical surface) 7 a of the polarization beam splitter 7 and are superimposed on the liquid crystal panel 8. As a result, the liquid crystal panel 8 is illuminated with an illumination light beam having a uniform intensity distribution.

The polarization separation surface 7a has a light separation function. The light modulated and reflected by the liquid crystal panel 8 is reflected by the polarization separation surface 7a of the polarization beam splitter 7 and guided to a projection lens (not shown). In this reference example, only one liquid crystal panel 8 is shown. However, in an actual general projector, three liquid crystal panels corresponding to R, G, and B are provided. The polarization beam splitter 7 constitutes a part of a so-called color separation / synthesis optical system that guides R, G, and B color illumination light to these three liquid crystal panels and synthesizes each color image light from the three liquid crystal panels. To do.

  The polarization beam splitter 7 includes a polarization separation film (polarization separation surface) 7a formed of a multilayer film that is disposed to be inclined with respect to the optical axis (Z axis) of the illumination optical system. The inclination of the polarization splitting surface 7a with respect to the optical axis Z is generally set to 45 degrees and is often set in the range of 42 to 48 degrees.

  The polarization separation film has a separation action according to the polarization direction with respect to light in at least a part of the wavelength region in the visible light region (for example, a wavelength region having a width of 10 nm or more, preferably 40 nm or more). Generally, 80% or more of light having the first polarization direction is reflected among light incident at a specific angle, and 80% or more of light having the second polarization direction orthogonal to the first polarization direction is transmitted.

  Each of the first and second fly-eye lenses 3 and 4 has a plurality of lens cells in a two-dimensional direction (so that a plurality of lens cells are arranged in a first direction perpendicular to the optical axis and a second direction perpendicular thereto). It is arranged and configured. The center line direction of each fly-eye lens is parallel to the Z axis.

  As described above, the light beam emitted from the light source 1 in the vicinity of the first focal position of the elliptical reflector 2 is reflected and collected by the elliptical reflector 2 and travels toward the first fly-eye lens 3 as a convergent light beam.

  In the XZ cross section shown in FIG. 1, as shown in FIG. 4, the vertexes of the lens cells other than the central lens cell among the plurality of lens cells 3a of the first fly-eye lens 3 are decentered outward in the X direction. For this reason, the first fly-eye lens 3 has a negative (concave) lens action as a whole with respect to the light flux from the elliptical reflector 2.

  This will be described in detail with reference to FIG. FIG. 5 shows a central lens cell 3a0 of the first fly-eye lens 2 in the XZ section and two lens cells (outer lens cells) 3a1 and 3a2 adjacent to this in the X direction.

  The vertices of the outer lens cells 3a1 and 3a2 (dotted lines shown in the figure, that is, positions on the optical axes o1 and o2 of the two lens cells) are on the centers (dotted lines o1 'and o2' in the figure). Is eccentric to the outside. When an even number of lens cells are arranged in each of the X direction and the Y direction, it is desirable to decenter the apexes of all the lens cells outward with respect to the center of each lens cell.

  In FIG. 5, the focal length f of the first fly-eye lens 3 is a, and a position (incident side focal position) that is separated from the first fly-eye lens 3 (center lens cell 3a0) by the distance a toward the elliptical reflector 2 side. Indicated by line A.

  In this case, when the light beams L1 and L2 that have passed through the intersections Q1 and Q2 with the line A on the optical axes o1 and o2 of the outer lens cells 3a1 and 3a2 pass through the centers of these outer lens cells 3a1 and 3a2, Ejected as parallel rays traveling along.

  Here, the light beams L1 and L2 are light beams that pass through the centers of the outer lens cells 3a1 and 3a2, respectively. Further, although not shown, the apex of the central lens cell 3a0 is positioned at the center of the central lens cell 3a0, and the light incident on the center of the central lens cell 3a0 also becomes a light that travels in parallel along the Z axis. Eject from the fly-eye lens.

  That is, the first fly-eye lens 3 has a function of converting a light beam incident on the center of each lens cell into a light beam parallel to the optical axis (Z axis). In other words, the first fly-eye lens divides the convergent light beam from the elliptical reflector into a plurality of light beams (parallel light beams) parallel to the optical axis, and then condenses each of the plurality of divided light beams to generate a light source. It has a function of forming an image.

  The first fly-eye lens acts as a lens with negative optical power on the entire convergent light beam from the elliptical reflector to convert it into a parallel light beam, and is positive for each divided light beam. It acts as an optical power lens and condenses each split light beam. The optical power is the reciprocal of the focal length and can be rephrased as refractive power.

  As described above, the first fly-eye lens 3 has a concave lens function that emits the convergent light beam from the elliptical reflector 2 as a plurality of light beams parallel to the optical axis in the XZ section.

  On the other hand, in the YZ cross section shown in FIG. 2, as shown in FIG. 6, the apexes of the lens cells other than the central lens cell among the plurality of lens cells 4a of the second fly-eye lens 4 are decentered outward in the Y direction. Thereby, the light beam reflected by the elliptical reflector 2 and incident on the second fly-eye lens 4 becomes a parallel light beam. That is, the second fly-eye lens 4 has a negative (concave) lens action as a whole with respect to the light beam from the elliptical reflector 2 in the YZ section. This lens action is obtained in the same manner as the first fly-eye lens 3.

  7 and 8 show an enlarged optical path from the elliptical reflector 2 to the polarization conversion element 5 shown in FIGS. 1 and 2. The convergent light beam reflected by the elliptical reflector 2 is converted into a parallel light beam by the first fly-eye lens 3 in the XZ section, and is converted into a parallel light beam by the second fly-eye lens 4 in the YZ section.

  That is, in the XZ section, by the compression system constituted by the elliptical reflector 2 and the first fly eye lens 3, and in the YZ section by the compression system constituted by the elliptical reflector 2 and the second fly eye lens 4. Each of the beams is compressed.

Here, the compression of the light beam refers to the process from the reduction of the light beam diameter (in other words, the light beam width) to the parallel light beam. In addition, the parallel light beam referred to in this reference example includes not only a completely parallel light beam but also a light beam that can be regarded as parallel in terms of optical performance.

  Specifically, the compression system includes, in order from the light source side, a first optical element having a positive optical power and second and second optical powers having different first and second negative optical powers in the XZ and YZ cross sections. It is a combination with a third or second optical element. The first optical element can be constituted by an elliptical reflector, a convex lens, or the like. The second and third optical elements can be constituted by a concave lens or a fly-eye lens (lens array) having a concave lens action. Of course, even if a combination of an optical element having a positive power (such as an elliptical reflector and a convex lens) and an optical element having a positive power (such as a convex lens) is used, the light beam emitted from the compression system is a parallel light beam. I do not care. In the case where the compression system is configured only by a lens system, it is desirable that the compression system be configured by an afocal system.

  Thus, the compression system emits from the compression system more than the diameter (light beam width) of the light beam before entering the compression system (incident on the reflector) in both the XZ cross section and the YZ cross section (one and the other cross section). The diameter of the light flux is narrowed.

Here, the compression system of the present reference example has a light source (light emitting unit) and a pupil position of the illumination optical system (a position where a light source image is formed, a position of the light emitting unit) in the illumination optical system that guides the light flux from the light source to the liquid crystal panel. (Position where an image is formed).

In this reference example, the pupil position of the illumination optical system is located in the vicinity of a polarization conversion element (configured by arranging a plurality of small polarization conversion elements in an array). It may be positioned on the liquid crystal panel side with two or more optical elements interposed therebetween.

  The XZ cross-section compression system that compresses the light beam diameter in the XZ cross-section and the YZ cross-section compression system that compresses the light flux in the YZ cross-section may be configured by the same optical element, or a part of the optical element. May be overlapped, or may be composed of separate optical elements that do not overlap each other.

The compression system in this reference example is disposed between the light source and the polarization conversion element, and compresses the light beam diameter when reflected by the reflector in the XZ section and the YZ section.

  In this way, the diameter of the light beam at the pupil position (light source image forming position) of the illumination optical system that guides the light from the light source to the liquid crystal panel can be reduced.

  Then, in the XZ and YZ cross-sections, the arrangement of the optical elements and / or the arrangement of these optical elements so that the powers of these optical elements are different from each other, whereby the light beam diameter at the stage of entering the polarization conversion element (stage of exiting the compression system) Are different from each other in the XZ cross section and the YZ cross section. That is, the compressibility is different between the XZ cross section and the YZ cross section.

  Here, the case where the compression system is arranged on the light source side mainly from the polarization conversion element is described, but the compression system is arranged on the liquid crystal panel (projection optical system) side than the polarization conversion element as described above. It doesn't matter.

In that case, an XZ cross-section compression system that compresses the light beam diameter of the XZ cross-section is disposed closer to the light source than the pupil position (light source image forming position) of the illumination optical system in the XZ cross-section. Further, a YZ cross-section compression system that compresses the light beam diameter of the YZ cross-section may be disposed closer to the light source than the pupil position (light source image forming position) of the illumination optical system in the YZ cross-section. The same applies to other examples and reference examples described later.

Here, the compression rate of the light beam is determined based on the outer diameter of the light beam when exiting (reflecting) from the elliptical reflector 2 and the outer diameter of the light beam immediately after exiting from the compression system (or the outer diameter of the light beam incident on the polarization conversion element 5). ) And the ratio. Specifically, in Examples 3 , 4 and Reference Examples 1, 2 , and 5, the compression rate is the outer diameter of the light beam immediately after being emitted from the compression system. It means the value divided by. The definition of the compression rate in Examples 3 and 4 and Reference Examples 1, 2 , and 5 is opposite to the definition of the compression rate in Reference Example 7 and later. Details will be described in Reference Example 7 and later.

In this reference example, since the light beams emitted from the fly-eye lenses 3 and 4 enter the polarization conversion element 5 as parallel light beams, the compression rate is eventually determined by the distance between the elliptical reflector 2 and the fly-eye lenses 3 and 4 (hereinafter, It is determined by the compression distance).

  As shown in FIG. 7, in the XZ section, the compression distance is B because the light beam is compressed by the elliptical reflector 2 and the first fly-eye lens 3.

  Further, as shown in FIG. 8, in the YZ section, the compression distance is C because the light beam is compressed by the elliptical reflector 2 and the second fly's eye lens 4.

That is, in this reference example, the compression rate of the light beam is different between the XZ section and the YZ section. Specifically, since B / C <1, the light beam compression rate in the YZ cross section is larger than the light beam compression rate in the XZ cross section.

In other words, if the compression ratio in the XZ section is α and the compression ratio in the YZ section is β, then α ≠ β,
α / β <1
(Α ≠ 0, β ≠ 0, preferably α, β> 1)
It has become.

  Here, as described above, the compression ratios represented by α and β are values obtained by dividing the outer diameter of the light beam at the time of emission from the elliptical reflector 2 by the outer diameter of the light beam immediately after being emitted from the compression system. That is, if the light beam is compressed by the compression system, the compression ratios α and β are necessarily larger than 1.

  Here, α and β will be described with reference to FIGS. 1 and 2. First, Lr shown in FIGS. 1 and 2 indicates the width of the light beam reflected by the elliptical reflector (the width in the direction perpendicular to the optical axis). Lx is the width of the light beam (perpendicular to the optical axis) immediately before the polarization conversion element (between the polarization conversion element and the optical element closest to the polarization conversion element on the light source side) in the XZ section. The width in the correct direction).

  In the YZ cross section, Ly is the width of the light beam (perpendicular to the optical axis) immediately before the polarization conversion element (between the polarization conversion element and the optical element closest to the polarization conversion element on the light source side of the polarization conversion element). The width in the correct direction).

  Here, α and β can be expressed as follows.

α = Lr / Lx
β = Lr / Ly

Further, α and β can be paraphrased as follows. When the light ray incident on the center of the lens cell arranged off-axis in the fly-eye lens is reflected by the reflector at the height (distance from the optical axis) Hr, and the light ray enters the polarization conversion element The height of each is Hx (XZ cross section) and Hy (YZ cross section). At this time, α and β can be expressed as follows.

α = Hr / Hx
β = Hr / Hy
Here, the light ray incident on the center of the lens cell arranged off-axis among the above-described fly-eye lenses is arranged off-axis with respect to both the first fly-eye lens and the second fly-eye lens. It is desirable that the light is incident on the center of the lens cell. Further, the light beam enters the polarization conversion element perpendicularly (in a state parallel to the optical axis).

  Here, Lx and Ly are the light beam diameters at the position immediately before the polarization conversion element, but they may be the light beam diameters immediately after exiting the compression system.

In the reference examples shown in FIGS. 1 and 2, α = 1.21 and β = 1.67, α and β are different from each other, and α / β = 0.72 (<1 )

As described above, in this reference example, a convergent light beam is emitted from the elliptical reflector 2, and a light beam larger than the XZ cross section is obtained by using the distance difference between the elliptical reflector 2 and the first and second fly-eye lenses 3 and 4. The compression rate is obtained in the YZ section.

  For this reason, it is necessary to increase the amount of eccentricity of the lens cells constituting each fly-eye lens as compared with the conventional example in which the light beam is rapidly compressed between the first fly-eye lens and the second fly-eye lens. Absent.

  Therefore, an increase in thickness of each fly eye lens in the optical axis direction can be suppressed. As a result, the aberration generated in each fly-eye lens can be reduced, and the required luminous flux compression ratio can be realized in the YZ section without greatly reducing the illumination efficiency. As a result, a bright image can be projected while reducing the light beam angle distribution in the direction sensitive to the light beam angle distribution (YZ cross-sectional direction) in the polarization beam splitter 7 to suppress uneven brightness and contrast reduction.

Moreover, by reducing the light beam angle distribution in the direction insensitive to the light beam angle distribution in the polarizing beam splitter 7 (XZ cross-sectional direction), the brightness unevenness and the contrast decrease as compared with the case where the light beam angle distribution in this direction is large. It can contribute to suppression of the above.
[ Reference Example 2]

9 and 10 show an illumination optical system that is Reference Example 2 of the present invention. 9 shows an XZ section of the illumination optical system, and FIG. 10 shows a YZ section.
White light emitted from the light source 11 is emitted as a parallel light beam by a parabolic reflector (parabolic mirror) 12. The light source 11 and the parabolic reflector 12 constitute a light source lamp LP. The parallel light beam is focused by the convex lens 13, passes through the first concave cylindrical lens 14, and enters the first fly-eye lens 15.

  The light beam incident on the first fly-eye lens 15 is divided into a plurality of light beams, and each of the divided light beams is collected. The light beam emitted from the first fly-eye lens 15 passes through the second concave cylindrical lens 16 and then forms a secondary light source image in the vicinity of the second fly-eye lens 17 and the polarization conversion element 18.

A plurality of split light beams (linearly polarized light having a predetermined polarization direction) emitted from the polarization conversion element 18 are collected by the condenser lens 19, transmitted through the polarization beam splitter 20, and superimposed on the reflective liquid crystal panel 21. The polarization beam splitter 20 is provided with a polarization separation film (optical surface, optical film surface) 20a similar to that described in Reference Example 1.

  Each of the first and second fly-eye lenses 15 and 17 is configured by arranging a plurality of lens cells in a two-dimensional direction.

  FIGS. 11 and 12 show an enlarged optical path from the parabolic reflector 12 to the polarization conversion element 18 shown in FIGS. 9 and 10. The parallel light beam emitted from the parabolic reflector 12 is converted into a convergent light beam by the convex lens 13, and then converted into a parallel light beam by the first concave cylindrical lens 14 having a concave lens action in the XZ section.

  On the other hand, in the YZ section, the convergent light beam from the convex lens 13 is converted into a parallel light beam by the second concave cylindrical lens 16 having a concave lens action.

  That is, in the XZ section, the light beam is compressed by a compression system including the convex lens (first optical element) 13 and the first concave cylindrical lens (second optical element) 14. In the YZ section, the light beam is compressed by a compression system including the convex lens 13 and the second concave cylindrical lens (third optical element) 16.

  Here, the compression rate of the light beam is defined as a value obtained by dividing the outer diameter of the light beam at the time of emission from the parabolic reflector 12 by the outer diameter of the light beam immediately after being emitted from the compression system, as described above.

In this reference example, a parallel light beam enters the convex lens 13 from the parabolic reflector 12, and a light beam emitted from the concave cylindrical lenses 14 and 16 enters the polarization conversion element 18 as a parallel light beam. Therefore, the compression rate is determined by the distance (compression distance) between the convex lens 13 and the concave cylindrical lenses 14 and 16.

  As shown in FIG. 11, since the compression of the light beam in the XZ section is performed by the convex lens 13 and the first concave cylindrical lens 14, the compression distance is D. Further, as shown in FIG. 12, the compression distance is E because the light beam is compressed in the YZ section by the convex lens 13 and the second concave cylindrical lens 16.

That is, in this reference example, the compression rate of the light beam is different between the XZ section and the YZ section. Specifically, since D / E <1, the light beam compression rate in the YZ cross section is larger than the light beam compression rate in the XZ cross section.

In other words, if the compression ratio in the XZ section is α and the compression ratio in the YZ section is β,
α / β <1
(Α ≠ 0)
It has become.

As described above, in this reference example, the parallel light beam emitted from the parabolic reflector 12 is converted into a convergent light beam by the convex lens 13, and the distance difference from the convex lens 13 to the first and second concave cylindrical lenses 14 and 16 is used. A larger beam compressibility than that of the XZ section is obtained in the YZ section.

As a result, similar to Reference Example 1, the required luminous flux compression ratio is realized in the YZ section while suppressing an increase in the thickness of the first and second fly-eye lenses 15 and 17 and a reduction in illumination efficiency associated therewith. Can do. As a result, a bright image can be projected while the light beam angle distribution in the direction sensitive to the light beam angle distribution (YZ cross-sectional direction) in the polarization beam splitter 20 is reduced to suppress uneven brightness and a decrease in contrast.

  In addition, by reducing the light beam angle distribution in the direction insensitive to the light beam angle distribution in the polarizing beam splitter 20 (XZ cross-sectional direction), the brightness unevenness and the contrast decrease as compared with the case where the light beam angle distribution in this direction is large. It can contribute to suppression of the above.

In this reference example, the case where the concave cylindrical lens is used as a lens different from the fly-eye lens has been described. However, a concave cylindrical surface may be provided on the surface of the fly-eye lens opposite to the lens cell surface. Good.
[Example 3]

  13 and 14 show an illumination optical system that is Embodiment 3 of the present invention. FIG. 13 shows an XZ section of the illumination optical system, and FIG. 14 shows a YZ section.

  White light emitted from the light source 31 is emitted as a parallel light beam by the parabolic reflector 32. The light source 31 and the parabolic reflector 32 constitute a light source lamp LP. The parallel light beam is made into a convergent light beam by the biconvex toric lens 33, further passes through the biconcave toric lens 34, and enters the first fly-eye lens 35. Here, the biconvex toric lens 33 may be a plano-convex shape or a meniscus shape. The biconcave toric lens 34 may be plano-concave or meniscus.

  The light beam incident on the first fly-eye lens 35 is divided into a plurality of light beams, and each of the divided light beams is collected. The light beam emitted from the first fly-eye lens 35 forms a secondary light source image in the vicinity of the second fly-eye lens 36 and the polarization conversion element 37.

A plurality of split light beams (linearly polarized light having a predetermined polarization direction) emitted from the polarization conversion element 37 are collected by the condenser lens 38, transmitted through the polarization beam splitter 39, and superimposed on the reflective liquid crystal panel 40. The polarization beam splitter 39 is provided with a polarization separation film (optical surface) 39a similar to that described in Reference Example 1.

  Each of the first and second fly's eye lenses 35 and 36 is configured by arranging a plurality of lens cells in a two-dimensional direction.

  FIGS. 15 and 16 show an enlarged optical path from the parabolic reflector 32 to the polarization conversion element 37 shown in FIGS. 13 and 14.

  The light beam that has passed through the biconvex toric lens 33 is a convergent light beam, but is converted into a parallel light beam by the biconcave toric lens 34 having a concave lens action in the XZ and YZ cross sections.

  That is, in both the XZ section and the YZ section, the light flux is compressed by the compression system including the biconvex toric lens (first optical element) 33 and the biconcave toric lens (second optical element) 34. .

  Here, the compression rate of the light beam is defined as a value obtained by dividing the outer diameter of the light beam at the time of emission from the parabolic reflector 32 by the outer diameter of the light beam immediately after being emitted from the compression system.

  In the present embodiment, a parallel light beam enters the biconvex toric lens 33 from the parabolic reflector 32, and a light beam emitted from the biconcave toric lens 34 enters the polarization conversion element 37 as a parallel light beam. Therefore, the compression rate is determined by the focal lengths of the biconvex toric lens 33 and the biconcave toric lens 34 in the XZ section and the YZ section. That is, also in this embodiment, the light beam compression rate α in the XZ section and the light beam compression ratio β in the YZ section are different from each other.

  Here, the focal length in the XZ section of the biconvex toric lens 33 is T1x, and the focal length in the YZ section is T1y. The focal length of the biconcave toric lens 34 on the XYZ cross section is T2x, and the focal length on the YZ cross section is T2y.

in this case,
T1x / T1y> 1
T2x / T2y> 1
Are in a relationship. The compression ratios α and β in each cross section are
α = T1x / T2x> 1
β = T1y / T2y> 1
It becomes. Here, the luminous flux compression ratio β in the YZ section is larger than the luminous flux compression ratio α in the XZ section.

In other words, the relationship between the compression ratio α in the XZ section and the compression ratio β in the YZ section is:
α / β <1
(Α ≠ 0)
It has become.

  Thus, in the present embodiment, the parallel light beam emitted from the parabolic reflector 32 is converted into a convergent light beam by the biconvex toric lens 33. Then, by using the difference in focal length between the XZ cross section and the YZ cross section of the biconvex toric lens 33 and the biconcave toric lens 34, a luminous flux compressibility larger than that of the XZ cross section is obtained in the YZ cross section.

As a result, as in Reference Example 1, the required luminous flux compression ratio is realized in the YZ section while suppressing an increase in thickness of the first and second fly-eye lenses 35 and 37 and a decrease in illumination efficiency associated therewith. Can do. As a result, a bright image can be projected while reducing the light beam angle distribution in the direction sensitive to the light beam angle distribution (YZ cross-sectional direction) in the polarization beam splitter 39 to suppress uneven brightness and contrast reduction.

In addition, by reducing the light beam angle distribution in the direction insensitive to the light beam angle distribution in the polarization beam splitter 39 (XZ cross-sectional direction), brightness unevenness and contrast decrease compared to the case where the light beam angle distribution in this direction is large. It can contribute to suppression of the above.
[Example 4]

17 and 18 show an illumination optical system that is Embodiment 4 of the present invention. 17 shows an XZ section of the illumination optical system, and FIG. 18 shows a YZ section.

  White light emitted from the light source 51 is reflected by the elliptical reflector 52 to become a convergent light beam. The convergent light beam enters the first fly-eye lens 53. The light source 51 and the elliptical reflector 52 constitute a light source lamp LP. Instead of the elliptical reflector 52, a parabolic reflector may be used.

In the present embodiment , each of the plurality of lens cells constituting the first fly-eye lens 53 (excluding the central lens cell) is decentered by a different amount in the XZ section and the YZ section, so that the first fly-eye lens 53 is decentered. The biconvex toric lens action as a whole is added.

  The light beam incident on the first fly-eye lens 53 is divided into a plurality of light beams, and each of the divided light beams is collected. The light beam emitted from the first fly-eye lens 53 forms a secondary light source image in the vicinity of the second fly-eye lens 54 and a polarization conversion element (not shown).

Here, in this embodiment , each of the plurality of lens cells constituting the second fly's eye lens 54 (excluding the central lens cell) is decentered by a different amount in the XZ cross section and the YZ cross section, and the second fly eye lens 54 is decentered. A biconcave toric lens action as a whole is added to the eye lens 54.

  A plurality of split light beams (linearly polarized light having a predetermined polarization direction) emitted from the polarization conversion element are collected by the condenser lens 55 and transmitted through the polarization separation film (optical surface) 56a of the polarization beam splitter 56 to be reflected liquid crystal. Overlaid on the panel 57.

  The relationship between the focal length of the first fly-eye lens 53 on the XZ section and the YZ section as a biconvex toric lens, and the focal length of the second fly-eye lens 54 on the XZ section and the YZ section as a biconcave toric lens. This relationship is the same as in the third embodiment.

That is, if the compression ratio in the XZ section is α and the compression ratio in the YZ section is β,
α / β <1
(Α ≠ 0)
It has become.

In this embodiment , the same effect as that of the third embodiment can be obtained.

In the above embodiments and reference examples, the illumination optical system using the polarization beam splitter has been described. However, the light beam compression configuration of the present embodiment is applied to an illumination optical system using a dichroic prism or a dichroic mirror having a dichroic film surface having a color separation action arranged inclined with respect to the optical axis of the illumination optical system. You can also.

Table 1 below is a table in which values of compression ratios α, β, and α / β were calculated for Examples 3 and 4 and Reference Examples 1 and 2 described above. However, even if the numerical value here is changed within the range of the conditional expression, the effect of the present application is not impaired. Therefore, the compression rate of Reference Example 1 may be applied to other examples, and the reverse effect does not impair the effect of the present application. In addition, the compression ratios described in Table 1 may be applied to Examples and Reference Examples after Reference Example 5.

  Here, α / β <1. More preferably, α / β <0.95, and even more preferably α / β <0.90. The lower limit value is preferably α / β> 0.3, more preferably α / β> 0.5, and still more preferably α / β> 0.7.

Of course, α> 1, but more preferably α> 1.05, and even more preferably α> 1.10. Further, β is naturally β> 1, but more desirably β> 1.10, and further desirably β> 1.25.
[ Reference Example 5]

In each of the above embodiments and reference examples , the illumination optical system has been described in which a compression system is provided on the light source side of the polarization conversion element so that the compression rate of the light beam varies between the XZ section and the YZ section. However, a compression system having the same function may be provided on the side of the polarization beam splitter with respect to the polarization conversion element.

  Also in this case, the compression system is configured such that the compression rate in the YZ section is larger than the compression rate in the XZ section.

According to each example and reference example described above, it is possible to realize an image projection optical system capable of projecting a bright image while suppressing a decrease in contrast.

For the above Examples 3 , 4 and Reference Examples 1, 2 and 5, the compression rate is the light flux diameter before entering the compression system (immediately after exiting from the reflector) and the light flux diameter immediately after exiting from the compression system. Defined as divided value. However, the terms “compression rate” and “decompression rate” (hereinafter also referred to as “conversion rate”) used in Reference Example 7 and later are opposite to this definition. That is, the “compression rate” and “extension rate” (conversion rate) used in Reference Example 7 and after are the light beam diameter immediately after being emitted from the compression system and the light flux before being incident on the compression system (immediately after being emitted from the reflector). It is defined as the value divided by the diameter. Of course, the “compression rate” and the “expansion rate” (conversion rate) may be defined using the focal length of the optical system in the compression system, as will be described in detail in Reference Example 7 and later.

In addition, the XZ cross section and YZ cross section in Examples 3 , 4 and Reference Examples 1, 2 , and 5 and the XZ cross section and YZ cross section in Reference Examples 7 to 15 indicate cross sections (cross sections opposite to each other). That is, the XZ cross section in Reference Examples 7 to 15 is a cross section parallel to the normal line of the optical surface (polarization separation surface), and the YZ cross section is a cross section perpendicular to the XZ cross section. Of course, both the XZ section and the YZ section are parallel to the Z axis (that is, the optical axis of the illumination optical system).

Thus, based on the definition of “compression ratio” and “extension ratio” (conversion ratio) used in Reference Example 7 and later, the section parallel to the normal line of the optical surface (polarization separation surface) (implementation) The conversion rate in Examples 3 , 4 and YZ cross sections in Reference Examples 1, 2 , and 5) is γ (gamma). Moreover, let delta (delta) be the conversion rate in the cross section (XZ cross section in Examples 3 , 4 and Reference Examples 1, 2 and 5) perpendicular to the cross section. At that time, Table 1 above can be rewritten as Table 1A below.

In Table 1A, it is natural that γ is less than 1, but γ is preferably less than 0.90, more preferably less than 0.75. Naturally, δ is also less than 1, but δ is preferably less than 0.95, more preferably less than 0.90. The same can be said for the reference examples 7 to 11 as well as the examples 3 and 4 and the reference examples 1, 2 and 5. However, in Reference Examples 12 to 15, both γ and δ are larger than 1 in order to extend the light flux.

Also, γ / δ is naturally less than 1, but it is preferably less than 0.95, more preferably less than 0.90. Further, it is desirable that γ / δ is a value greater than 0.3, more preferably greater than 0.5 (more preferably 0.6 or more). The same can be said for the reference examples 7 to 15 as well as the examples 3 and 4 and the reference examples 1, 2 and 5.

In Reference Example 7 and later, a cross section parallel to the normal line of the optical surface (polarized light separation surface) is defined as an XZ cross section, and a cross section perpendicular thereto is defined as a YZ cross section (Examples 3 and 4 , Reference Examples). (The opposite of 1, 2 , 5). That is, γ in Table 1A corresponds to the conversion rate (compression rate, elongation rate) in the XZ section after Reference Example 7, and δ in Table 1A corresponds to YZ after Reference Example 7 It is the conversion rate in a cross section. In other words, γ in Table 1A is α after Reference Example 7 or parallelization magnification HX, and δ in Table 1A is β after Reference Example 7 or parallelization magnification HY. Therefore, γ / δ in Table 1A is the same as α / β or HX / HY described in Reference Example 7 and the following, and it is desirable that the numerical range be in the same range.

FIG. 19 shows a configuration of a liquid crystal projector (image projection apparatus) using the illumination optical system described in the first reference example. FIG. 19 shows a configuration in a cross section including the YZ plane in Reference Example 1. In this liquid crystal projector, the illumination optical system may be replaced with those described in the third and fourth embodiments and the second and fifth reference examples.

  In the figure, 1 is a light source that emits white light with a continuous spectrum, and 2 is an elliptic reflector that condenses light from the light source 1 in a predetermined direction. The light source 1 and the reflector 2 constitute a light source lamp LP.

Reference numeral 100 denotes a portion of the illumination optical system described in Reference Example 1 excluding the light source lamp LP and the polarization beam splitter 7.

  Reference numeral 158 denotes a dichroic mirror that reflects light in the wavelength region of blue (B: 430 to 495 nm) and red (R: 590 to 650 nm) and transmits light in the wavelength region of green (G: 505 to 580 nm). The wavelength regions of blue, red, and green are not limited to the above description, and any wavelength region having a width of 40 nm or more may be used. Reference numeral 159 denotes an incident-side polarizing plate for G in which a polarizing element is attached to a transparent substrate, and transmits only S-polarized light. Reference numeral 60 denotes a first polarization beam splitter that transmits P-polarized light and reflects S-polarized light on a polarization separation surface constituted by a multilayer film.

  61R, 61G, and 61B are a reflective liquid crystal panel for red, a reflective liquid crystal panel for green, and a reflective liquid crystal panel for blue as light modulation elements (or image forming elements) that reflect incident light and modulate the image, respectively. is there. 62R, 62G, and 62B are a quarter wavelength plate for red, a quarter wavelength plate for green, and a quarter wavelength plate for blue, respectively.

  Reference numeral 64 denotes an incident-side polarizing plate for RB in which a polarizing element is attached to a transparent substrate, and transmits only S-polarized light.

  Reference numeral 65 denotes a first color-selective retardation plate that converts the polarization direction of the B light by 90 degrees and does not convert the polarization direction of the R light. Reference numeral 66 denotes a second polarization beam splitter that transmits P-polarized light and reflects S-polarized light on the polarization separation surface. 67 denotes a second color-selective phase difference plate that converts the polarization direction of the R light by 90 degrees and does not convert the polarization direction of the B light.

  Reference numeral 68 denotes an exit-side polarizing plate (polarizing element) for RB, which transmits only S-polarized light. Reference numeral 69 denotes a third polarization beam splitter that transmits P-polarized light and reflects S-polarized light on the polarization separation surface.

  The above-described optical elements from the dichroic mirror 158 to the third polarizing beam splitter 69 constitute a color separation / synthesis optical system 200.

  Reference numeral 70 denotes a projection lens (projection optical system), and the illumination optical system 100, the color separation / synthesis optical system 200, and the projection lens 70 constitute an image projection optical system. Here, the projection lens may of course have both a mirror and a lens, or may be composed of only a mirror. Of course, a diffractive optical element or the like may be included.

  Next, the optical action after passing through the illumination optical system 100 will be described. First, the G optical path will be described.

  The G light transmitted through the dichroic mirror 158 enters the incident side polarizing plate 159. The G light remains S-polarized light after being decomposed by the dichroic mirror 158. The G light exits from the incident-side polarizing plate 159, then enters the first polarizing beam splitter 60 as S-polarized light, is reflected by the polarization separation surface, and reaches the G reflective liquid crystal panel 61G. .

  An image supply device 300 such as a personal computer, a DVD player, or a TV tuner is connected to the liquid crystal driving circuit 250 of the projector. The projector and the image supply device 300 constitute an image display system. The liquid crystal driving circuit 250 drives each reflective liquid crystal panel based on image information (video information) input from the image supply device 300, and forms an original image for each color on them. Thereby, the light incident on each reflective liquid crystal panel is reflected and modulated (image modulation) according to the original image.

  The S-polarized component of the image-modulated G light is reflected again by the polarization separation surface of the first polarization beam splitter 60, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized component of the image-modulated G light passes through the polarization separation surface of the first polarization beam splitter 60 and travels to the third polarization beam splitter 69 as projection light. At this time, in a state where all the polarization components are converted to S-polarized light (a state where black is displayed), a quarter-wave plate provided between the first polarizing beam splitter 60 and the G-use reflective liquid crystal panel 61G. The slow axis of 62G is adjusted in a predetermined direction. Thereby, the influence of the disturbance of the polarization state generated in the first polarizing beam splitter 60 and the G-use reflective liquid crystal panel 61G can be suppressed to a low level.

  The G light emitted from the first polarization beam splitter 60 enters the third polarization beam splitter 69 as P-polarized light, passes through the polarization separation surface of the third polarization beam splitter 69, and enters the projection lens 70. It reaches.

  On the other hand, the R and B lights reflected by the dichroic mirror 158 enter the incident side polarizing plate 64. The R and B lights remain S-polarized after being decomposed by the dichroic mirror 158. Then, the R light and the B light are emitted from the incident side polarizing plate 64 and then incident on the first color selective phase difference plate 65. The first color-selective retardation plate 65 has a function of rotating the polarization direction of only B light by 90 degrees, whereby the B light becomes P-polarized light and the R light becomes S-polarized light. 66 is incident. The R light incident on the second polarization beam splitter 66 as S-polarized light is reflected by the polarization separation surface of the second polarization beam splitter 66 and reaches the R-use reflective liquid crystal panel 61R.

  Further, the B light incident on the second polarization beam splitter 66 as P-polarized light passes through the polarization separation surface of the second polarization beam splitter 66 and reaches the B-use reflective liquid crystal panel 61B.

  The R light incident on the R reflective liquid crystal panel 61R is image-modulated and reflected. The S-polarized component of the image-modulated R light is reflected again by the polarization separation surface of the second polarization beam splitter 66, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized component of the image-modulated R light passes through the polarization separation surface of the second polarization beam splitter 66 and travels toward the second color selective phase plate 67 as projection light.

  Further, the B light incident on the reflective liquid crystal panel 61B for B is image-modulated and reflected. The P-polarized component of the image-modulated B light is transmitted again through the polarization separation surface of the second polarization beam splitter 66, returned to the light source side, and removed from the projection light. On the other hand, the S-polarized component of the image-modulated B light is reflected by the polarization separation surface of the second polarization beam splitter 66 and travels toward the second color selective phase plate 67 as projection light.

  At this time, by adjusting the slow axis of the quarter wave plates 62R and 62B provided between the second polarizing beam splitter 66 and the reflective liquid crystal panels 61R and 61B for R and B, the case of G In the same manner as described above, the black display of each of R and B can be adjusted.

  The R light out of the R light and B light emitted from the second polarization beam splitter 66 in this way is combined into one light beam, and its polarization direction is rotated 90 degrees by the second color selective phase plate 67 so that it is S polarized light. Become an ingredient. Further, the R light is analyzed by the exit-side polarizing plate 68 and enters the third polarizing beam splitter 69.

  Further, the B light passes through the second color-selective phase plate 67 as it is as S-polarized light, is further analyzed by the exit-side polarizing plate 68, and enters the third polarizing beam splitter 69. The R- and B-projected lights are analyzed by the exit-side polarizing plate 68, so that the second polarizing beam splitter 66, the R and B reflective liquid crystal panels 61R and 61B, and the quarter wavelength plate 62R. , 62B, ineffective components generated by passing through the light are cut.

  The R and B projection light incident on the third polarization beam splitter 69 is reflected by the polarization separation surface of the third polarization beam splitter 69, and is combined with the G light to reach the projection lens 70.

  The combined R, G, B projection light (color image) is enlarged and projected by a projection lens 70 onto a projection surface such as a screen.

  Since the optical path described above is for the case where the reflective liquid crystal panel displays white, the optical path for the case where the reflective liquid crystal panel displays black will be described below.

  First, the G optical path will be described. The S-polarized light of G light that has passed through the dichroic mirror 158 enters the incident-side polarizing plate 159, and then enters the first polarizing beam splitter 60 and is reflected by the polarization separation surface, and is reflected by the G reflective liquid crystal panel 61G. It leads to. However, since the reflective liquid crystal panel 61G is in the black display state, the G light is reflected without being image-modulated. Therefore, the G light remains S-polarized light even after being reflected by the reflective liquid crystal panel 61G. Therefore, the light is again reflected by the polarization separation surface of the first polarization beam splitter 60, passes through the incident side polarizing plate 159, is returned to the light source side, and is removed from the projection light.

  Next, the R and B optical paths will be described. S-polarized light of R and B light reflected by the dichroic mirror 158 enters the incident-side polarizing plate 64. Then, the R light and the B light are emitted from the incident side polarizing plate 64 and then incident on the first color selective phase difference plate 65. The first color-selective phase difference plate 65 has an action of rotating the polarization direction of only B light by 90 degrees, whereby the B light becomes P-polarized light and the R light becomes S-polarized light. Is incident on.

  The R light incident on the second polarization beam splitter 66 as S-polarized light is reflected by the polarization separation surface of the second polarization beam splitter 66 and reaches the R-use reflective liquid crystal panel 61R. Further, the B light incident on the second polarization beam splitter 66 as P-polarized light passes through the polarization separation surface of the second polarization beam splitter 66 and reaches the B-use reflective liquid crystal panel 61B.

  Here, since the R reflective liquid crystal panel 61R is in a black display state, the R light incident on the R reflective liquid crystal panel 61R is reflected without being image-modulated. Therefore, even after being reflected by the reflective liquid crystal panel 61R for R, the R light remains S-polarized light. Therefore, the light is again reflected by the polarization separation surface of the second polarization beam splitter 66, passes through the incident-side polarizing plate 64, returns to the light source side, and is removed from the projection light.

  On the other hand, the B light incident on the B reflective liquid crystal panel 61B is reflected without being image-modulated because the B reflective liquid crystal panel 61B is in the black display state. Therefore, even after being reflected by the reflective liquid crystal panel 61B for B, the B light remains as P-polarized light. Therefore, the light is again transmitted through the polarization separation surface of the second polarization beam splitter 66, converted to S-polarized light by the first color-selective retardation plate 65, transmitted through the incident-side polarizing plate 64, and returned to the light source side. Removed from the projection light. Thereby, black display is performed.

  In this embodiment, in the color separation / synthesis system 200, the wavelength selective phase difference plate is used, but this may be eliminated. In this case, the polarization beam splitter arranged in the color separation / synthesis system 200 functions as a polarization beam splitter for a specific wavelength region in the visible region, and transmits to other wavelength regions regardless of the polarization direction. Or what is necessary is just to set it as the structure which has the polarization separation film which has the characteristic to reflect.

  Further, a ¼ phase difference plate is disposed between the color separation / synthesis system 200 and the projection lens 70, and the light reflected and returned by the lens surface in the projection lens 70 is re-reflected, again in the screen direction. You may make it prevent returning to.

  Further, in this embodiment, the case where three liquid crystal panels are used has been described. However, in the present invention, one, two, or four or more may be used.

In addition, what is described as a fly-eye lens in the present embodiment may be replaced with a lens in which two cylindrical lenses are arranged close to each other or a lens that is bonded together.
[ Reference Example 7]

22 and 23 are schematic views of a main part of a projector (image projection apparatus) using the illumination optical system according to Reference Example 7 of the present invention. In the following examples, the definition of the XZ cross section and the YZ cross section and the meaning of the compression rate are different from those of Examples 3 , 4 and 6, and Reference Examples 1, 2 and 5.

  22 and 23, reference numeral 401 denotes light source means such as a high-pressure mercury discharge tube. Reference numeral 402 denotes an elliptic reflector (elliptical mirror) as a light beam condensing means. The light emitting surface 401 a of the light source 401 is disposed at the first focal point P <b> 1 of the elliptical reflector 402.

  The light beam emitted radially from the light source 401 is converted into a light beam (converged light) that is converged by the elliptical reflector 402 and is collected at the second focal point P <b> 2 of the elliptical reflector 402.

  The elliptical reflector 402 may be replaced with a parabolic reflector and a positive lens.

  A distance fp from the vertex T of the elliptical reflector 402 to the second focal point P2 corresponds to the focal length of the light beam condensing means 402. That is, the elliptical reflector (light flux condensing means) 402 condenses the light flux from the light source at the position of the second focal point on the light source side with respect to the first lens array 403. Here, the second focus is a position where the light beam emitted from the light source is collected, and may be simply referred to as a condensing point (condensing position) when the elliptical reflector is not used. .

  The light beam from the second focal point P2 is divided into a plurality of light beams by the first lens array 403 disposed on the polarization conversion element side with respect to the second focal point. The plurality of split light beams form a plurality of secondary light source images near the polarization conversion element 405 or on the light incident side or light exit side via the second lens array 404.

  The light beam that forms each secondary light source image is converted into linearly polarized light having a predetermined polarization direction by the polarization conversion element 405 and then enters the condenser lens 406.

  The plurality of split light beams emitted from the condenser lens 406 are transmitted through the polarization separation surface 407a of the polarization beam splitter 407 and superimposed on the liquid crystal panel 408 provided on the irradiated surface. As a result, the liquid crystal panel 408 is illuminated with an illumination light beam having a uniform intensity distribution.

Light modulated and reflected by the liquid crystal panel 408 is reflected by the polarization separation surface 407 a of the polarization beam splitter 407 and guided to the projection lens 409. In this reference example, only one liquid crystal panel 408 is shown. However, in an actual general color projector, three liquid crystal panels corresponding to R, G, and B color light are provided as image forming elements. The polarization beam splitter 407 constitutes a part of a so-called color separation / synthesis optical system that guides R, G, and B color illumination light to these three liquid crystal panels and synthesizes each color image light from the three liquid crystal panels. To do.

  FIG. 22 shows a first section (XZ plane) including the normal line of the polarization separation surface 407a of the polarization beam splitter 407 and the optical axis o of the illumination optical system.

  Here, the optical axis o is defined by an axis passing through the center of the condenser lens 406 and the center of the panel surface of the liquid crystal panel 408, for example. The optical axis o corresponds to the Z axis.

  FIG. 23 shows a second cross section (YZ plane) orthogonal to the first cross section including the optical axis o of the illumination optical system.

  FIG. 22 is a cross section of the rectangular liquid crystal panel 408 parallel to the short side direction.

  FIG. 23 is a cross section parallel to the long side direction of the liquid crystal panel 408.

In other words, the XZ section can be referred to as a section parallel to the normal line of the polarization separation surface 407a and the normal line of the panel surface (incident / exit surface) of the liquid crystal panel 408. Further, it can be said that the YZ cross section is a cross section perpendicular to the XZ cross section and parallel to the Z axis (optical axis). The meanings of these Z axis, XZ cross section, and YZ cross section are the same in the following reference examples.

  The illumination optical system includes a reflective liquid crystal panel (liquid crystal panel) 408 as a rectangular reflective image forming element disposed on the surface to be illuminated by the illumination light beam via the polarization beam splitter 407 using the light beam from the light source means. Lighting up. The light (image light) that has been image-modulated by the liquid crystal panel 408 is guided again to the projection lens (projection optical system) 409 via the polarization beam splitter 407 and projected onto a projection surface such as a screen.

  In the first cross section of FIG. 22, the light incident side of the first lens array 403 is formed of a cylindrical surface having a positive refractive power only in the first cross section. The light exit surface of the first lens array 403 is constituted by a lens array surface. The incident surface of the second lens array 404 is constituted by a lens array surface. The light exit surface of the second lens array 404 has no refractive power.

  In the second cross section of FIG. 23, the light incident surface of the first lens array 403 is a surface having no refractive power. The light emission side of the first lens array 403 is constituted by a lens array surface. The light incident surface of the second lens array 404 is constituted by a lens array surface. The light exit surface of the second lens array 404 is constituted by a cylindrical surface having a positive refractive power only in the second cross section.

  In the first cross section, when the focal length of the cylindrical surface of the first lens array 403 is fx, the distance from the second focus P2 to the first lens array 403 is fx. The divergent light beam from the second focal point P2 becomes a parallel light beam after passing through the first lens array 403, passes through the second lens array 404 and the polarization conversion element 405 in the state of the parallel light beam, and enters the condenser lens 406.

The parallel light beam referred to in this reference example includes not only a completely parallel light beam but also a light beam that can be regarded as parallel in terms of optical performance.

  In FIG. 22, the dotted line is a light beam that passes through the center (on the optical axis) of the first lens array 403. A solid line is a light beam that passes through other than the center of the first lens array 403. A state where the light beam of the solid line is superimposed on the liquid crystal panel 408 is shown. In the first cross section, the first lens array 403 constitutes a collimating means.

  In the second cross section of FIG. 23, let fy be the focal length of the light exit surface of the second lens array 404 on the cylindrical surface.

  At this time, the air equivalent value of the distance from the second focal point P2 to the second lens array 404 is fy.

  For this reason, of the divergent light beam from the second focal point P2, the light beam that has passed through the center of the cylindrical surface of the light exit surface of the first lens array 403 and the center of the cylindrical surface of the light incident surface of the second lens array 404 is the second lens. When exiting from the light exit surface of the array 404, it becomes a parallel light flux.

  A plurality of light source images are formed by the lens array surfaces provided on the light emitting surface of the first lens array 403 and the light incident surface of the second lens array 404. The plurality of light source images are formed on the focal plane of the condenser lens 406.

  Light beams from the plurality of light source images are superimposed on the liquid crystal panel 408 by the condenser lens 406 via the polarization conversion element 405.

  Within the second cross section, the second lens array 404 constitutes a collimating means.

  FIG. 39 is an explanatory diagram of a part of the polarization conversion element 405.

  The polarization conversion element 405 is used by being provided in the light exit side of the collimating means or in its optical path.

  The polarization conversion element 405 includes a plurality of polarization separation surfaces 405a, a plurality of reflection surfaces 405b, and a plurality of half-wave plates 405c. Specifically, the polarization conversion element 405 includes a polarization separation surface 405a, a reflection surface (or polarization separation surface) 405b, and a half-wave plate 405c as one polarization conversion element unit. The polarization conversion element 405 is an arrayed optical element in which a plurality of polarization conversion element units are arranged in a direction substantially orthogonal to the optical axis. Therefore, the polarization conversion element 405 here may be referred to as a polarization conversion element array.

  In this polarization conversion element 405, the polarized light component having a predetermined polarization direction out of the light incident on each polarization separation surface 405 a is transmitted therethrough and emitted from the polarization conversion element 405.

  On the other hand, of the light incident on each polarization separation surface 405a, a polarization component having a polarization direction orthogonal to the predetermined polarization direction is reflected by the polarization separation surface 405a and further reflected by the reflection surface 405b. Then, the polarization direction is converted by 90 degrees by the half-wave plate 405 c and emitted from the polarization conversion element 405. Thus, the polarization conversion element 405 converts the incident non-polarized light into linearly polarized light having a predetermined polarization direction.

  Here, the half-wave plate 405c may be disposed only on the optical path of the light transmitted through the polarization separation surface 405a. In addition, the polarization conversion element 5 only needs to convert the non-polarized light into linearly polarized light for each color (for each wavelength region corresponding to each panel), and the directions of the linearly polarized light are not necessarily the same.

  That is, only the red light is made S-polarized with respect to the polarization beam splitter 407 in the subsequent stage, and the green light and the blue light are made P-polarized with respect to the polarization beam splitter 407, and the polarization direction and the remaining of one color light among the three color lights. The polarization directions of the two color lights may be orthogonal to each other.

  Specifically, the polarization splitting surface 405a reflects green light, blue light S-polarized light, and red light P-polarized light, and transmits green light, blue light P-polarized light, and red light S-polarized light. The half-wave plate 405c may be disposed on the optical path of the light beam reflected by the polarization separation surface 405a.

In this reference example, the convergent light beam (converged light) reflected by the elliptical reflector (first optical element) 402 is converted into a parallel light beam by the first lens array (second optical element) 403 in the XZ section of FIG. . Further, in the YZ section of FIG. 23, the second lens array (third optical element) 404 forms a parallel light beam. That is, in the XZ section, the light beam is compressed by the compression system constituted by the elliptical reflector 402 and the first lens array 403.

  In the YZ section, the light beam is compressed by a compression system constituted by the elliptical reflector 402 and the second fly-eye lens 404.

As described above, in this reference example, the convergent light beam is emitted from the elliptical reflector 402, and the difference in the distance from the elliptical reflector 402 to the first and second lens arrays 403 and 404 is used to compress the light beam larger than the YZ cross section. The rate (parallelization magnification) is obtained in the XZ cross section.

  For this reason, it is not necessary to increase the amount of eccentricity of the lens cells constituting each lens array, compared to the conventional example in which the light beam is rapidly compressed between the first lens array 403 and the second lens array 404. . Therefore, an increase in the thickness of each lens array in the optical axis direction can be suppressed. As a result, the aberration generated in each lens array can be reduced. In addition, a required light beam compression rate (parallelization magnification) can be realized in the XZ section without greatly reducing the illumination efficiency. As a result, a bright image is projected while the light beam angle distribution in the direction sensitive to the light beam angle distribution (XZ cross section) in the polarization beam splitter 407 is reduced to suppress uneven brightness and a decrease in contrast.

  By reducing the light beam angle distribution even in the direction insensitive to the light beam angle distribution in the polarization beam splitter 407 (YZ cross section), it contributes to uneven brightness and lower contrast than when the light beam angle distribution in this direction is large. be able to.

In this reference example, the angle distribution of the incident light beam with respect to the panel surface of the liquid crystal panel 408 is larger in the long side direction in FIG. 23 than in the XZ cross section (first cross section) parallel to the short side direction of the liquid crystal panel 408 in FIG. The parallel YZ section (second section) is larger.

  Parallelizing means (second and second) provided between the light source 401 and the polarization beam splitter 407 and compressing the light beam in the first cross section (XZ cross section) and the second cross section (YZ cross section) orthogonal to each other in the illumination optical system. 3 optical elements) 403 and 404. The light beam compression rate (parallelization magnification) by the collimating means 403 and 404 is different between the first cross section and the second cross section.

  Note that the compression of the light beam refers to the process from the reduction of the light beam diameter (in other words, the light beam width) by the light beam condensing unit 402 to the parallel light beam conversion by the parallelizing units 403 and 404.

  The compression rate is the light beam diameter L (Lx, Ly) after passing through the collimating means 403, 404 with respect to the light beam diameter (width in the direction perpendicular to the optical axis) Lr reflected by the light beam condensing means 402. The ratio L / Lr.

  The compression rate of the light beam in the first cross section is α, and the compression rate of the light beam in the second cross section is β.

At this time,
α = Lx / Lr
β = Ly / Lr
It is. here,
α ≠ β
α <1, β <1
α <β
α / β <1
It is.

  That is, the light beam compression rate α in the first cross section in FIG. 22 is smaller than the light beam compression rate β in the second cross section in FIG.

For example,
α = 0.6
β = 0.83
α / β = 0.72
It is.

In this reference example,
α / β ≦ 0.75
Each element is set to be

More preferably,
0.5 <α / β ≦ 0.75
It is trying to become.

  Here, the compression rate (conversion rate) α in the first cross section, the compression rate (conversion rate) β in the second cross section, and the ratio α / β between them are respectively expressed as parallelization magnifications HX and HY in the first and second cross sections. , HX / HY may be substituted. Therefore, HX and HY described below have substantially the same meaning as compression ratios (conversion ratios) α (γ) and β (δ), and α (γ), β (δ), α / β (γ / δ). It is assumed that the conditional expressions defined for) are applicable to HX, HY, and HX / HY. Therefore, as well as the numerical range of γ / δ, it is natural that HX / HY is also less than 1, but preferably less than 0.95, more preferably less than 0.90, and further as described above. Thus, it is desirable that it is 0.75 or less. Further, HX / HY is desirably larger than 0.5 (more preferably 0.6 or more) as described above, but it should be larger than at least 0.3, similarly to γ / δ.

Here, in this reference example, the parallelization magnifications HX and HY in the first cross section (XZ plane) and the second cross section (YZ plane) refer to the following.

The first parallelization magnification (light beam compression ratio) HX in the first cross section (FIG. 22) is:
HX = | fx / fp |
It is.

Similarly, the second parallelization magnification HY in the second cross section (FIG. 23) is
HY = | fy / fp |
It is.

Since the second lens array 404 is arranged at a position farther from the second focal point P2 than the first lens array 403 from FIGS.
| Fy |> | fx |
It is.

Therefore,
HY> HX
Will be satisfied.

  Thereby, the light flux from the light flux condensing means 402 is compressed at different compression rates in the first and second cross sections, and converted into light fluxes having different widths (diameters) in the first and second cross sections.

Here, in this reference example, the polarization conversion element 405 constitutes an array of polarization conversion units in the second cross section of FIG. 23 where the light beam is wide, and the polarization beam splitter 407 has a polarization separation surface in the first cross section direction where the light beam is narrow. Bending by 407a is performed. According to this, the polarization separation surface 407a can improve contrast without impairing brightness.

  The parallelizing means for XZ section that compresses the light beam diameter in the XZ section and the parallelizing means for YZ section that compresses the light beam in the YZ section may be configured by the same optical element. Further, a part of the optical elements may be overlapped so as to have the collimating means depending on the arrangement of the lens array, or may be constituted by separate optical elements that do not overlap each other.

The collimating means in the present reference example is disposed between the light source and the polarization conversion element, and compresses the light beam diameter when reflected by the reflector in the XZ section and the YZ section. In this way, the diameter of the light beam at the pupil position (light source image forming position) of the illumination optical system that guides the light from the light source to the liquid crystal panel can be reduced.

  In the XZ cross section and the YZ cross section, at least one of the arrangement of the optical elements and the arrangement of the power of these optical elements being different from each other, the stage of entering the polarization conversion element (the stage of emitting the collimating means) The beam diameters are different from each other in both cross sections. That is, the compressibility is different between the XZ cross section and the YZ cross section.

  Here, the case where the collimating means is arranged on the light source side with respect to the polarization conversion element is mainly described, but the collimating means is arranged on the liquid crystal panel (projection optical system) side with respect to the polarization conversion element. It doesn't matter.

  In that case, YZ cross-section collimating means for compressing the light beam diameter of the YZ cross-section may be arranged closer to the light source than the pupil position (light source image forming position) of the illumination optical system in the YZ cross-section. Further, XZ cross-section collimating means for compressing the beam diameter of the XZ cross-section may be arranged closer to the light source than the pupil position (light source image forming position) of the illumination optical system in the XZ cross-section.

The same applies to other reference examples described later.

As another reference example, instead of compressing the light beam by the collimating means 403 and 404 in this reference example, the incident light beam may be elongated at different ratios in the first cross section and the second cross section, contrary to the compression. Good. In this case, instead of the compression system in the above-described embodiments and reference examples , a beam divergence unit having negative refractive power (optical power), that is, a beam divergence action, and a beam emitted from the beam divergence unit are parallel. An extension system constituted by a collimating means having a positive refractive power is used. When the outer diameter of the light source and the reflector that reflects the light flux from the light source is small (smaller than the size of the image forming element such as a liquid crystal panel or smaller than half), a configuration using a light flux diffusing means is desirable.

  In this case, the extension ratios of the light beams in the first cross section and the second cross section are HXX and HYY, respectively. At this time, if the elongation rate of the light beam in the second cross section is made larger than that in the first cross section, the same effect as that obtained by compressing the light beam can be obtained.

That is,
HXX <HYY
And it is sufficient.

Here, the expansion rate and the compression rate can be referred to as a conversion rate as a rate at which the light beam diameter (light beam width) is converted. The decompression system and the compression system can be referred to as a conversion system. These are exactly the same in each reference example described later.

  In addition, what is necessary is just to use the value defined as follows for the focal distance in each cross section when calculating | requiring the parallelization magnifications HX and HY.

  In FIGS. 22 and 23, the first and second lens arrays 403 and 404 have a cylindrical surface on one surface and a lens array surface on the other surface. However, the cylindrical surface and the lens array surface are integrated. It may be in the form.

  FIG. 24 shows an example of an integrated lens array A. Here, a plurality of decentered micro lens surfaces (lens cells LA1, LA2, LA2 ′) are arranged on one optical surface of the lens array A.

  At this time, the focal length of the lens array A (optical surface) is calculated, as shown in FIG. 24, by the light beam passing through the center of the lens cell LA1 at the center of the lens array and the center of the lens cell LA2 or LA2 ′ adjacent thereto. It can be defined from the condensing point of the light beam passing through.

  When each lens cell constituting the lens array A is arranged perpendicular to a reference axis (optical axis of the illumination optical system) o as a reference, each lens cell (LA1, LA2, LA2 ′, etc.) parallel to the reference axis o The surface normal can be regarded as the optical axis (o1, o2, o2 ′) of each lens cell.

  Therefore, in FIG. 24, when a ray parallel to the reference axis o passing through the center (o1, o2, o2 ′) of each lens cell LA1, LA2, LA2 ′ is traced, the ray is refracted in the lens cell LA2, LA2 ′. It intersects the optical axis of the central lens cell LA1 at a predetermined position Q.

  The distance fg from the lens surface of the lens cell LA1 to the point Q is the focal length of the lens array A in each cross section.

  When the lens cells LA2 and LA2 ′ are symmetric with respect to the reference axis o, the light beam passing through the centers of the lens cells LA2 and LA2 ′ intersects the optical axis of the central lens cell LA1 at one point, and is asymmetric. Sometimes cross at different positions. In this case, the focal length of the lens array A may be defined using the middle of different intersections.

  Further, when there is no lens cell on the reference axis o as shown in FIG. 25, the same drawing is performed on the two lens cells LA3, LA3 ′ in the vicinity of the reference axis o, so that the lens cells LA3, LA3 ′ The focal length fg ′ can be defined from the intersection point Q ′ of two rays passing through the center.

  FIG. 26 shows an example in which the light beam condensing means is configured by a combination of a parabolic reflector (objective mirror) 402 a and a positive lens 420 used in place of an elliptical reflector (elliptical mirror). The light beam from the light source 401 is reflected by the parabolic reflector 402 a to become a parallel light beam and enters the positive lens 420.

  By making the focal position of the positive lens 420 coincide with the second focal position P2 of FIGS. 22 and 23, the light beam that has passed through the positive lens 420 is condensed on the second focal point P2. As a result, the effects described above can be obtained similarly.

In this case the light beam condensing means comprises parabolic reflector 402a and the positive lens 420, the focal length of the light beam focusing means is a focal length f ₂₀ of the positive lens 420 also positive and parabolic reflector 402b as shown in FIG. 27 When the lens 420b is combined, it may be defined as follows.

That is, it is assumed that there is a lens having a focal length fp at the vertex T1 of the parabolic reflector 402b, and that there is a positive lens (focal length = f ₂₀ ) 420b spaced from the vertex T1 by an air interval d. What is necessary is just to define the focal distance of a means.

The light beam condensing means may be composed of an elliptical reflector and a condensing lens.
[ Reference Example 8]

28 and 29 are cross-sectional views of the essential parts of the illumination optical system of Reference Example 8 of the present invention.

  28 shows a first cross section (XZ plane), and FIG. 29 shows a second cross section (YZ plane).

Reference Example 8 differs from Reference Example 7 described in FIGS. 22 and 23 only in that a rotationally symmetric negative lens 423 is disposed between the elliptical reflector 421 and the first lens array 424. Other configurations are the same.

  28 and 29, the same members as those in FIGS. 22 and 23 are denoted by the same reference numerals.

  28 and 29, 401 is a light source, 421 is an elliptical reflector, 423 is a negative lens, 424 is a first lens array, and 425 is a second lens array. 405 is a polarization conversion element, 406 is a condenser lens, 407 is a polarization beam splitter (PBS), 408 is a reflective liquid crystal panel, 409 is a projection lens, and 410 is a phase plate.

  28 and 29, a point P2 'where a virtual image of the light source 401 is formed by the elliptical reflector 421 and the negative lens 423 corresponds to the second focal point P2 in FIGS.

Therefore, in this reference example, basically, the point P2 ′ in FIGS. 28 and 29 may be handled as the second focal point P2 in FIGS.

In this reference example, the light emitting point of the light source 401 is disposed at the first focal point P1 of the elliptical reflector 421, and the light beam from the light source 401 is condensed at the second focal point P2 of the elliptical reflector 421. The elliptical reflector 421 constitutes a light beam condensing means.

  At this time, the distance from the vertex T of the elliptical reflector 421 to the second focal point P2 is the focal length fp of the light beam condensing means.

  A negative lens 423 is provided between the elliptical reflector 421 and the second focal point P2, and the second focal point (object point) P2 is imaged at a point P2 'by the negative power of the negative lens 423. The light beam becomes a light beam diverging from the point P2 '.

  The incident side surface of the first lens array 424 has a lens array shape having a positive power in the XZ section of FIG. Here, unlike FIG. 26, the lens cells are arranged so that there is no level difference, but the method of obtaining the positive power focal length in the lens array is the same as in FIG.

  The focal length of the first lens array 424 obtained in this shape is fx, and the first lens array 424 is arranged at a position away from P2 ′ by fx, thereby having the effect of collimating the light beam in this cross section.

  Therefore, the negative lens 423 and the first lens array 424 constitute a collimating unit for the first cross section XZ.

  The focal length of the collimating means in the first cross section (XZ plane) is determined by the focal length f23 of the negative lens 423 and the focal length fx1 of the first lens array 424.

In the first cross section of FIG. 28, the air equivalent distance from the main plane position of the negative lens 423 on the lens array side to the first lens array surface 424 is L1. The combined focal length of the negative lens 423 and the first lens array 424 is
fx = 1 / (1 / f23 + 1 / fx1-L1 / f23 / f1)
It becomes.

  The exit side of the second lens array 425 has a lens array shape having positive power in the cross section YZ of FIG.

  The focal length of the second lens array 425 obtained in this shape is fy1, and the second lens array 425 is arranged at a position away from the point P2 ′ by a distance fy in terms of air, thereby collimating the light beam in this cross section YZ. Has an effect.

  Therefore, the negative lens 423 and the second lens array 425 serve as a means for collimating the second cross section YZ.

  The focal length of the collimating means in the second cross section (YZ plane) is determined by the focal length f23 of the negative lens 423 and the focal lengths fy1 of the respective lens arrays 424 and 425.

In the second cross section (FIG. 29), if the distance from the lens array side main plane position of the negative lens 423 to the second lens array surface 425 is L2, the combined focal length of the negative lens 423 and the second lens array 425 is ,
fy = 1 / (1 / f23 + 1 / fy1-L2 / f23 / fy1)
It becomes.

At this time, the first parallelization magnification HX in the first cross section (FIG. 28) is:
HX = | fx / fp |
It is.

Similarly, the second parallelization magnification HY in the second cross section (FIG. 29) is
HY = | fy / fp |
It is.

28 and 29, since the second lens array 425 is disposed at a position farther from the second focal point P2 than the first lens array 424,
| Fy |> | fx |
It is. Therefore,
HY> HX
Thus, the light flux from the light flux condensing means is compressed at different compression rates in the first and second cross sections, and converted into light fluxes having different widths (diameters) in the first and second cross sections.

For example, if f23 = −50 mm, fx = 150 mm, L1 = 50 mm, fy = 200 mm, L2 = 100 mm,
fx = −150 mm
fy = −200 mm
It becomes.

here,
HX / HY = | fx / fy | = 0.75
It becomes.
(Modification of Reference Example 8)
30 and FIG. 31 are modifications of the reference example 8, and correspond to FIG. 28 and FIG.

  30 and 31, reference numeral 401 denotes a light source, 421a denotes an elliptical reflector, 423a denotes a rotationally symmetric negative lens, 424a denotes a first lens array, and 425a denotes a second lens array. 405 is a polarization conversion element, 406 is a condenser lens, 407 is a polarization beam splitter (PBS), 408 is a reflective liquid crystal panel, and 409 is a projection lens.

  In FIG. 30, the light source 401 is disposed in the vicinity of the first focal point P1 of the elliptical reflector 421a, and the light flux from the light source 401 is condensed at the second focal point P2 of the elliptical reflector 421a. .

  At this time, the distance from the vertex T of the elliptical reflector 421a to the second focal point P2 is the focal length fp of the light beam condensing means.

  A negative lens 423a is provided between the elliptical reflector and the second focal point P2, and the light beam is collimated by the negative power of the negative lens 423.

  In the first cross section of FIG. 30, the first lens array 424a and the second lens array 425a do not have power (a lens array in which lens cells are uniformly arranged). Therefore, the negative lens 423a becomes the parallelizing means in the first direction.

  In the second cross section of FIG. 31, the first lens array 424a has a shape of a lens array having negative power, and the second lens array 425a has a shape of a lens array having positive power.

  The focal lengths of the first lens array 424a and the second lens array 425a obtained in this shape are assumed to be fy1 and fy2, respectively. Then, the first lens array 424a and the second lens array 425a are arranged so that the respective focal positions corresponding to fy1 and fy2 coincide at the point R1. Thereby, in the second cross section, after the light beam is diverged by the first lens array 424a, the second lens array 425a has the effect of collimating the light beam again.

  Therefore, the negative lens 423a, the first lens array 424a, and the second lens array 425a serve as a collimating unit in the second cross section.

  The focal lengths fx and fy of the collimating means are determined by the focal length f23 of the negative lens 423a and the focal lengths fy1 and fy2 of the lens arrays 424a and 425a, respectively.

In the first cross section (FIG. 30), it is the same as the focal length of the negative lens 423a,
fx = f23
It becomes.

In FIG. 31, the focal length of the first lens array 424a is fy1, and the focal length of the second lens array 425a is fy2. At this time, in the second cross section (FIG. 31), from the combined focal length of the three optical elements 423a, 424a, 425a,
fy = f23 * | fy2 / fy1 |
It becomes.

At this time, the first parallelization magnification HX in the first cross section (FIG. 30) is:
HX = | fx / fp |
It is.

Similarly, the second parallelization magnification HY in the second cross section (FIG. 31) is
HY = | fy / fp |
It is.

From FIG. 31, because | fy2 |> | fy1 |
| Fy |> | fx |
It is. Therefore,
HY> HX
Thus, the light beam from the light beam condensing means 421a is compressed at different compression rates in the first and second cross sections, and converted into light beams having different widths (diameters) in the first and second cross sections.
[ Reference Example 9]

32 and 33 are cross-sectional views of a main part of the illumination optical system according to Reference Example 9 of the present invention.

  32 shows a first cross section (XZ plane), and FIG. 33 shows a second cross section (YZ plane).

  32 and 33, the same members as those in FIGS. 22 and 23 are denoted by the same reference numerals.

  32 and 33, 401 is a light source, 432 is an elliptic reflector, 433 is a first lens array, and 434 is a second lens array. 405 is a polarization conversion element, 406 is a condenser lens, 407 is a polarization beam splitter (PBS), 408 is a reflective liquid crystal panel, 409 is a projection lens, and 410 is a phase plate.

In the figure, a one-dot chain line o is a reference axis (optical axis) of the illumination optical system and coincides with the rotational symmetry axis of the elliptical reflector 432 and the optical axis of the condenser lens 406. (However, these do not necessarily need to match.)
The light source 401 is disposed in the vicinity of the first focal point P1 of the elliptical reflector 432, and the light beam from the light source 401 is condensed on the second focal point P2 of the elliptical reflector 432. The elliptical reflector 432 serves as a light beam condensing unit.

  At this time, the distance from the vertex T of the elliptical reflector 432 to the second focal point P2 is the focal length fp of the light beam condensing means.

  The incident side of the second lens array 434 has a cylindrical shape having negative lens power in the cross section of FIG.

  Let fx be the focal length of the second lens array 434 obtained in this shape. By disposing the second lens array 434 at a position away from the second focal point P2 by the distance fx, the second lens array 434 has an effect of collimating the light beam in this cross section.

  Therefore, the second lens array 434 serves as a collimating unit in the first cross section.

  The exit side of the first lens array 433 has a cylindrical shape having negative lens power in the cross section of FIG.

  The focal length of the first lens array 433 obtained in this shape is assumed to be fy, and the first lens array 433 is arranged at a position away from the second focal point P2 by a distance fy in terms of air, so that the light flux can be emitted in this section. Has the effect of collimating.

  Therefore, the first lens array 433 serves as a collimating unit in the second cross section.

The first parallelization magnification HX in the first cross section (FIG. 32) is
HX = | fx / fp |
It is.

Similarly, the second parallelization magnification HY in the second cross section (FIG. 33) is
HY = | fy / fp |
It is.

32 and 33, the first lens array 433 is disposed at a position farther from the second focal point P2 than the second lens array 434.
| Fy |> | fx |
It is. Therefore,
HY> HX
Thus, the light flux from the light flux condensing means is compressed at different compression rates in the first and second cross sections, and converted into light fluxes having different widths (diameters) in the first and second cross sections.

Here, when fp = 200 mm, fx = 90 mm, and fy = 150 mm,
HX = 0.45, HY = 0.75, and HX / HY = 0.6.
[ Reference Example 10]

FIG. 34 is a schematic diagram of a main part when the illumination optical systems of Reference Examples 7 to 9 are applied to a color projector (image projection apparatus) using three reflective liquid crystal panels.

As shown in FIG. 34, the projector of this reference example is provided with a color separation element 501 between the condenser lens 406 and the PBSs 471 and 472, and a color composition element 502 between the polarization beam splitters 471 and 472 and the projection lens 409. This is a three-plate projector.

  34, the same members as those shown in FIGS. 22 and 23 are denoted by the same reference numerals.

  In FIG. 34, reference numerals 503, 504, and 505 denote reflection type image forming elements for G, R, and B color lights, respectively. Reference numerals 506, 507, and 508 denote half-phase plates for G, R, and B color lights, respectively. Reference numeral 471 denotes a PBS for G color light. Reference numeral 472 denotes an RB color light PBS. Reference numeral 509 denotes a color selective phase plate.

  Further, the image forming element is not limited to the reflective type, and may be a transmissive type. In the case of the transmissive type, it is preferable to set a direction in which the ratio of the compressed light beam width is small in the two orthogonal cross-sectional directions with respect to the relatively low contrast characteristic in the image forming element.

In each of the embodiments and the reference examples , the beam collimating means is preferably handled as a constant focal length regardless of the direction when calculating the compression ratio of the beam, and the optical system from the reflector to the common positive power optical element. May be considered as a light beam compression system.
[ Reference Example 11]

  FIGS. 35 and 36 show a case where the light from the parabolic reflector RF is collected by the toric lens TL having different positive powers (fx, fy) in two cross sections (XZ plane, YZ plane).

  FIG. 37 and FIG. 38 are schematic diagrams of the refractive power arrangement of FIG. 35 and FIG.

  In this optical system, as shown in FIGS. 37 and 38, the focal length (fy) on the side with a small positive power is the common focal length for the XZ section and the YZ section. Also, in the XZ cross section of FIG. 37, the focal length (fx) on the strong positive power side is formed by arranging a positive lens with a focal length fy and a positive lens with a focal length fx ′ at an interval of zero. It is thought that.

At this time, if the focal length fx ′ is considered as a part of the collimating means and the combined focal length is calculated, the conditions of the embodiments and the reference examples can be applied as they are.

With a high-intensity light source, the size of the reflector cannot be reduced due to thermal problems. For this reason, for example, when using a lamp having a luminance higher than 30 W and using a small image forming element having a diagonal of 1 inch or less, it is effective to increase the efficiency to narrow the luminous flux from the reflector. In this case, the parallelization magnification HY is
HY <1
It is good to make it become.

As described above, according to each embodiment and reference example , an illumination optical system capable of projecting a bright and high-contrast image and an image projection apparatus having the illumination optical system can be obtained.
[ Reference Example 12]

A schematic diagram of Reference Example 12 of the present invention is shown in FIGS. 40A and 40B. This Reference Example 12 is a reference example in which the diameter of the light beam emitted from the light source (or reflector) is extended. The reference example for extending the light beam diameter in this way is particularly effective when the outer diameter of the light source or the reflector is small.

As the light source, a high-pressure mercury lamp may be used as in the above-described reference example, but it is particularly suitable when a light source that is easily downsized using a xenon lamp, a laser light source, or the like is used. Specifically, when the outer diameter of the reflector and the laser oscillation area of the laser light source are smaller than the effective area (image display area) of the image forming element, the outer diameter of the reflector and the laser oscillation of the laser light source are particularly large (within each cross section). This is suitable when the area is not more than half of the effective area of the image forming element.

  Here, FIG. 40A is an XZ cross-sectional view, which is a cross section parallel to the short side direction of a liquid crystal panel (liquid crystal display element, image forming element), and has a lower luminous flux extension rate than a YZ cross section described later (conversion rate is low). (Small) cross section. FIG. 40B is a YZ cross-sectional view, which is a cross-section parallel to the long side direction of the liquid crystal panel, and is a cross-section having a higher light beam elongation rate (higher conversion rate) than the cross-section of FIG. 40A.

  Reference numeral 1001 denotes a light source (light emitting point) which emits light radially. Reference numeral 1002 denotes a parabolic reflector (parabolic mirror) that converts a light beam emitted from a light source into a parallel light beam. A concave lens (first optical element) 1003 converts a parallel light beam emitted from the reflector into a divergent light beam. Here, the paraboloid reflector 1002 may be an elliptical reflector, and the position of the light source and the position of the reflector may be set so that the light beam reflected from the reflector 1002 becomes a divergent light beam. .

  In the cross section of FIG. 40A, that is, the XZ cross section, 1004 includes a plurality of minute lens cells (minute cylindrical lens cells) and divides a divergent light beam into a plurality of divided light beams while making them parallel (converting them into parallel light beams). 1 is a lens array. Reference numeral 1005 denotes a second lens array that includes a plurality of minute lens cells as in the case of 1004 and guides a plurality of divided light beams to the polarization conversion element array 1006 at the subsequent stage.

Reference numeral 1007 is a condenser lens, 1008 is a polarization separation element (polarization beam splitter), 1009 is a quarter-wave plate, 1010 is a liquid crystal panel, and 1011 is a projection lens, and the description of these functions is the same as the above-described reference example. Omitted.

  In the cross section of FIG. 40B, that is, the YZ cross section, reference numeral 1004 denotes a first lens array that includes a plurality of microlenses (microcylindrical lenses) and emits a divergent light beam as a divergent light beam (no collimating action). . The first lens array simultaneously divides the divergent light beam into a plurality of divided light beams.

Reference numeral 1005 denotes a second lens array that includes a plurality of minute lens cells as in the case of 1004 and guides the divergent light beam to the subsequent polarization conversion element 1006 while making it parallel (converting it into a parallel light beam). Since 1007 to 1011 have the same functions as those of the reference example described above, as in the cross section (XZ cross section) of FIG. 40A, description thereof is omitted here.

In this reference example, the angle distribution of the incident light beam with respect to the panel surface of the liquid crystal panel 1010 is larger in the long side direction of FIG. 40B than the XZ cross section (first cross section) parallel to the short side direction of the liquid crystal panel 1010 of FIG. The parallel YZ section (second section) is larger.

  Parallelizing means (second and second) provided between the light source 1001 and the polarizing beam splitter 1008 and extending the light beam in the first cross section (XZ cross section) and the second cross section (YZ cross section) orthogonal to each other in the illumination optical system. 3 optical elements) 1004 and 1005. The collimating means 1004, 1005 can be said to be an extension system. And the expansion | extension rate (parallelization magnification) of the light beam by the collimating means 1004 and 1005 is mutually different in the 1st cross section and the 2nd cross section.

  Note that the extension of the light beam means that the light beam diverging means 1003 expands the light beam diameter (light beam width) and then the light beams are parallelized by the parallelizing means 1004 and 1005.

  The elongation rate is the diameter after passing through the collimating means 1004 and 1005 with respect to the light beam diameter (width in the direction perpendicular to the optical axis) Lr expanded by the light beam diverging means 1003 and L (Lx, Ly). It refers to the ratio L / Lr.

  Let α be the elongation rate of the light beam in the first cross section, and β be the elongation rate of the light beam in the second cross section.

At this time,
α = Lx / Lr
β = Ly / Lr
It is. here,
α ≠ β
α> 1, β> 1
α <β
α / β <1
It is.

  That is, the light beam elongation rate α in the first cross section in FIG. 40A is smaller than the light beam elongation rate β in the second cross section in FIG. 40B.

Here, for example, if Lr = 30 mm, Lx = 12 mm, and Ly = 18 mm,
α = 0.4
β = 0.6
α / β = 0.67
It becomes.
[ Reference Example 13]

41 and 42 are diagrams showing an XZ section and a YZ section of an optical system for image projection including an illumination optical system that is Reference Example 13 of the present invention.

  In FIG. 41, 701 is a light source unit that emits divergent light, 703 is a first lens array, 704 is a second lens array, 705 is a polarization conversion element, 706 is a condenser lens, and 707 is a polarization beam splitter (PBS). is there. Reference numeral 708 denotes a reflective liquid crystal panel, 709 denotes a projection lens, and 710 denotes a phase plate.

  The light source unit 701 includes a light source unit 714 having a light emitting element such as a xenon lamp in which electrodes 711 and 712 that emit light are integrally formed with a parabolic mirror 713, and a light source unit 714 that emits light from the light source unit 714. And a concave lens 715 provided on the radiation side. The light beam emitted from the light source unit 714 is converted into a divergent light beam by the concave lens 715.

  An alternate long and short dash line o in the drawing is a reference axis of the illumination optical system and coincides with the rotational symmetry axis of the parabolic mirror 713 and the optical axis of the condenser lens 706 (however, they do not necessarily have to coincide).

  The incident side of the first lens array 703 has a cylindrical shape having positive optical power in the XZ section of FIG.

  The focal length of this shape is fx, and the focal position is substantially located at the focal position of the concave lens 715, thereby having the effect of collimating the light beam in this cross section.

  A light beam indicated by a thick dotted line in the figure represents a light beam passing through the center of the lens array, and the light beam is collimated. A thin solid line shown after the first lens array 703 represents a state in which the divided light beams overlap on the reflective liquid crystal panel 708. The first lens array 703 serves as a collimating unit in the XZ section.

  The exit side of the second lens array 704 has a cylindrical shape having positive optical power in the YZ section of FIG.

  The focal length of this shape is fy, and the focal position is substantially located at the focal position of the concave lens 715, thereby having the effect of collimating the light beam in this cross section. That is, the second lens array 704 serves as a collimating unit in the YZ section.

41 and 42, the second lens array 704 is disposed at a position farther from the concave lens 715 than the first lens array 703.
| Fy |> | fx |
It is. Therefore, the light beam from the elliptical reflector 713 as the light beam condensing means is converted into a light beam having a different width (diameter) in the XZ cross section and the YZ cross section.

  Here, in the polarization conversion element 705, an array of polarization conversion elements is formed in the second cross-sectional direction having a wide light beam width. In the polarization beam splitter 707, the light beam is bent by the polarization separation surface in the first cross-sectional direction having a narrow light beam width. Thereby, contrast can be improved without impairing brightness.

Here, FIG. 41 and FIG. 42 show the case where each lens array has a cylinder shape on one surface and a lens array shape on the other surface. It may be provided on the surface.
[ Reference Example 14]

FIG. 43 shows a light source unit in an illumination optical system that is Reference Example 14 of the present invention.

The light source unit 721 of this reference example has a configuration in which light emitted from a light source 722 on a chip such as an LED or LD is converted into light having a small divergence angle by a convex lens 723 and emitted. In FIG. 43, the emitted light is represented by a thin solid line.

  Such a light source unit 721 is preferably used as a light source unit 731 in which a plurality of light sources are arranged as shown in FIG.

45 and 46 show an XZ section and a YZ section of an image projection optical system including an illumination optical system using the light source unit 731 shown in FIG. Since it is the same as Reference Example 13 except for the light source unit, the same reference numerals are given and description thereof is omitted.

As the light source of the optical system of this reference example, a discharge light source having no electrode may be used.
[ Reference Example 15]

FIG. 47 shows still another light source unit used in the illumination optical system that is Reference Example 15 of the present invention.

In this reference example, parallel light beams emitted from a plurality of light sources 842 are once condensed by a lens array 843 having a plurality of lens cells corresponding to the plurality of light sources 842, respectively, and then diverged light beams to the illumination optical system. Lead. The luminous flux is shown by a thin solid line.

XZ sectional drawing of the illumination optical system used for the optical system for image projections which is the reference example 1 of this invention. FIG. 6 is a YZ sectional view of the illumination optical system of Reference Example 1. FIG. 6 is a YZ sectional view showing a polarizing beam splitter used in Reference Example 1. FIG. 6 is a perspective view of a first fly eye lens used in Reference Example 1. The figure explaining the optical effect | action of the said 1st fly eye lens. The perspective view of the 2nd fly eye lens used in the reference example 1. FIG. The XZ cross-sectional enlarged view of the optical path from the reflector in the reference example 1 to a polarization conversion element. The YZ cross-section enlarged view of the optical path from the reflector in the reference example 1 to a polarization conversion element. XZ sectional drawing of the illumination optical system used for the optical system for image projections which is the reference example 2 of this invention. FIG. 6 is a YZ sectional view of the illumination optical system of Reference Example 2. The XZ cross-section enlarged view of the optical path from the reflector in the reference example 2 to a polarization conversion element. The YZ cross-sectional enlarged view of the optical path from the reflector in the reference example 2 to a polarization conversion element. XZ sectional drawing of the illumination optical system used for the optical system for image projections which is Example 3 of this invention. FIG. 6 is a YZ sectional view of the illumination optical system of Example 3. FIG. 10 is an XZ cross-sectional enlarged view of an optical path from a reflector to a polarization conversion element in Example 3. FIG. 9 is an enlarged YZ cross-sectional view of an optical path from a reflector to a polarization conversion element in Example 3. XZ cross-sectional view of an illumination optical system used for an optical system for image projection that is Embodiment 4 of the present invention. FIG. 6 is a YZ sectional view of the illumination optical system of Example 2. A YZ cross section showing an optical configuration of a liquid crystal projector that is Embodiment 6 of the present invention using the image projecting optical systems of Embodiments 3 , 4 and Reference Examples 1, 2 , and 5. The figure which shows the transmittance | permeability characteristic example of a polarizing beam splitter. The figure which shows the reflectance characteristic example of a polarizing beam splitter. XZ sectional drawing of the illumination optical system used for the optical system for image projections of the reference example 7 of this invention. FIG. 11 is a YZ sectional view of the illumination optical system of Reference Example 7. Explanatory drawing of the modification of a part of FIG. Explanatory drawing of the modification of a part of FIG. XZ sectional drawing of the modification of the reference example 7. FIG. FIG. 11 is a YZ sectional view of a modification of Reference Example 7. XZ sectional drawing of the illumination optical system used for the optical system for image projections of the reference example 8 of this invention. FIG. 12 is a YZ sectional view of the illumination optical system of Reference Example 8. FIG. 10 is an XZ sectional view of a modification of the illumination optical system of Reference Example 8. FIG. 11 is a YZ sectional view of a modification of the illumination optical system of Reference Example 8. XZ sectional drawing of the illumination optical system of the reference example 9 of this invention. FIG. 11 is a YZ sectional view of the illumination optical system of Reference Example 9. The YZ cross section which shows the optical structure of the liquid crystal projector which is the reference example 10 of this invention using the optical system for image projection of the reference examples 7-9. XZ sectional drawing of a part of optical system which is the reference example 11 of this invention. A YZ sectional view of a part of the optical system of Reference Example 11. FIG. FIG. 10 is a schematic diagram of an XZ cross section showing a refractive power arrangement in the optical system of Reference Example 11. The schematic diagram of the YZ cross section which shows refractive power arrangement | positioning in the optical system of the reference example 11. FIG. Explanatory drawing of the polarization conversion element of a reference example. XZ sectional drawing of the illumination optical system of the reference example 12 of this invention. FIG. 14 is a YZ sectional view of the illumination optical system of Reference Example 12. XZ sectional drawing of the illumination optical system of the reference example 13 of this invention. A YZ sectional view of the illumination optical system of Reference Example 13. FIG. Sectional drawing which shows the light source unit used for the illumination optical system of the reference example 14 of this invention. The figure which shows the light source unit using two or more light source units shown in FIG. XZ sectional drawing of the illumination optical system of the reference example 14. FIG. A YZ sectional view of the illumination optical system of Reference Example 14. FIG. Sectional drawing which shows the light source unit used for the illumination optical system of the reference example 15 of this invention.

Explanation of symbols

1, 11, 31, 51, 401 Light source 2, 12, 32, 52, 402 Reflector 3, 15, 35, 53, 403 First fly-eye lens 4, 17, 36, 54, 404 Second fly-eye lens 5, 18, 37, 405 Polarization conversion element 6, 19, 38, 55, 406 Condenser lens 7, 20, 39, 56, 407 Polarization beam splitter 8, 21, 40, 57, 408 Reflective liquid crystal panel 13 Convex lens 14, 16 Concave cylindrical lens 33 Biconvex toric lens 34 Biconcave toric lens

Claims (4)

An illumination optical system that guides a light beam emitted from a light source and reflected by a reflector to an image forming element via a polarization beam splitter having a polarization separation surface composed of a multilayer film arranged to be inclined with respect to the optical axis of the illumination optical system Because
A polarization conversion element that is disposed between the light source and the polarization beam splitter and converts non-polarized light into linearly polarized light;
A cross section parallel to the normal of the polarization separation surface of the polarization beam splitter and the normal of the incident / exit surface of the image forming element is a first cross section, and includes the optical axis of the illumination optical system and is orthogonal to the first cross section. When the cross section is the second cross section ,
Disposed between the front Symbol light source and the polarization conversion element, respectively the light beam width in the first section and the second section has a compression system for compressing a different beam width from the previous incident,
When the compression ratio of the light beam width in the first cross section by the compression system is α, and the compression ratio of the light beam width in the second cross section is β,
α / β <1
Satisfied,
The compression system includes, in order from the light source side, a first optical element having different positive optical power with the previous SL first section in the second section, in the second section and the first section have a second optical element having different negative optical power from each other,
The surface on the light source side of the first optical element is a surface on which a plurality of lens cells are formed, the surface on the image forming element side is a flat surface, and at least some of the lens cells among the plurality of lens cells Is a first fly-eye lens having a positive optical power by decentering different amounts in the first cross section and the second cross section,
The surface on the light source side of the second optical element is a flat surface, the surface on the image forming element side is a surface on which a plurality of lens cells are formed, and at least a part of the lens cells among the plurality of lens cells. Is a second fly's eye lens having negative optical power by decentering the first cross section and the second cross section by different amounts . The illumination optical system according to claim 1 ;
An image projection optical system comprising : a projection optical system that projects a light beam from the image forming element onto a projection surface. An image projection apparatus comprising the optical system for image projection according to claim 2 . An image projection apparatus according to claim 3 ;
The image display system characterized by having an image supply equipment for supplying image information to the image projection apparatus.