JP5049478B2 - Optical system, image projection optical system, image projection apparatus, and image display system - Google Patents

Description

  The present invention is an optical system that includes a first lens array that divides and collects a light beam from a light source by a plurality of lens cells, and a second lens array that has a plurality of lens cells corresponding to the first lens array. Regarding the system. The present invention also relates to an optical system suitable for illuminating an image forming element such as a liquid crystal panel and an image projection apparatus having the optical system.

For a projector (image projection apparatus) that enlarges and projects a light beam modulated by an image forming element such as a liquid crystal panel onto a projection surface such as a screen by a projection lens, it is important that a bright image can be presented with low power consumption.

  An illumination optical system conventionally used in such a projector is configured as shown in FIGS. 6A and 6B, for example. 6A and 6B, the light beam emitted from the light source 1 is converted into a substantially parallel light beam by the paraboloid reflector 2 and emitted. This parallel light beam is divided by a first fly-eye lens (lens array in which small spherical lenses are two-dimensionally arranged) 3, and each divided light beam is condensed. Each split light beam is condensed in the vicinity of the second fly-eye lens 4 to form a secondary light source image.

  Each small lens constituting the fly-eye lenses 3 and 4 has a rectangular lens shape similar to a liquid crystal panel which is an illuminated surface.

  The plurality of split light beams emitted from the second fly-eye lens 4 are condensed by the condenser lens 6 after the polarization direction is aligned by the polarization conversion element 5, and superimposed on the liquid crystal panel 7 through a color separation / synthesis system (not shown). Illuminate.

  In order to achieve a bright projector with low power consumption, it is important in the illumination optical system to efficiently transfer the light flux from the light source to the liquid crystal panel surface. This luminous flux transfer efficiency is generally called illumination efficiency.

  In the illumination optical system using the fly-eye lenses 3 and 4 as described above, the light beam passing efficiency in each small lens of the second fly-eye lens 4 and the polarization conversion element 5 has the greatest influence on the illumination efficiency.

  This is because the component that does not enter the effective region of the second fly's eye lens 4 or the polarization conversion element 5 of the light flux that forms the secondary light source image cannot reach the panel surface.

  FIG. 7 conceptually shows this. In FIG. 7, the effective area (aperture) of the lens cell constituting the second fly's eye lens 4 and the effective area (incident aperture) of the polarization conversion element 5 are irradiated with respect to the secondary light source image having a certain size. Overlaid in the axial direction.

  In FIG. 7, the light beam component that protrudes from the effective area of the small lens of the second fly-eye lens 4 does not finally enter the liquid crystal panel. Accordingly, the illumination efficiency is reduced. Further, the luminous flux component that does not enter the effective region of the polarization conversion element 5 does not become effective linearly polarized light after polarization conversion, and as a result, is absorbed by a polarizing plate (not shown) before reaching the liquid crystal panel. Accordingly, the illumination efficiency is reduced. As shown in FIGS. 6A, 6B, and 7, a light shielding part may be provided with an aluminum plate or the like outside the effective incident area in the polarization conversion element 5, but a part of the light beam is blocked by this light shielding part. As a result, the illumination efficiency similarly decreases.

  Such a decrease in illumination efficiency, that is, loss of luminous flux is caused by an illumination optical system having a large secondary light source image, for example, an illumination optical system having a dark F number (condensing angle on the panel surface is small) or a surface to be illuminated. It becomes larger when a certain liquid crystal panel is small.

  In order to improve this, Patent Document 1 discloses a method in which the center of gravity of the secondary light source image is moved by decentering each small lens of the first fly-eye lens to reduce the light beam loss at the polarization conversion element. It is disclosed.

Further, Patent Document 2 discloses an illumination optical system that uses a central lens of the second fly-eye lens as a toric lens to reduce brightness unevenness and color unevenness and to achieve uniform brightness on the panel surface. .
Japanese Patent Laid-Open No. 11-183848 (paragraphs 0037 to 0041, FIG. 6) Japanese Patent Laid-Open No. 10-20399 (paragraph 0016)

Recently, however, there is a strong demand for higher brightness for projectors. Therefore, there is a tendency to use higher output light sources. As a result, the vicinity of the position where the secondary light source image is formed becomes very high temperature, and cooling of the polarization conversion element constituted by using a thin film or a film is indispensable. For this reason, it is necessary to provide a certain distance between the second fly's eye lens and the polarization conversion element for allowing cooling air to pass.
Therefore, if the distance between the second fly-eye lens and the polarization conversion element is increased, and the formation position (condensing position) of the secondary light source by the first lens array is in the vicinity of the second fly-eye lens, polarization conversion is performed. Luminous flux loss at the element increases. Further, if the formation position of the secondary light source image is set in the vicinity of the polarization conversion element, the light flux loss in the second fly-eye lens increases.

  In this case, even if the method disclosed in Patent Document 1 is adopted, it is difficult to sufficiently reduce the luminous flux loss. Further, as disclosed in Patent Document 2, the light flux loss cannot be reduced only by using the toric lens at the center.

  SUMMARY An advantage of some aspects of the invention is that it provides an optical system having first and second lens arrays, which can further increase the light use efficiency.

Optical system according to one aspect of the present invention includes a first lens array having a plurality of first lens cells arranged in a two-dimensional direction for focusing the light beam from the light source to split, it is split by the first lens array A second lens array in which second lens cells corresponding to a plurality of light beams are arranged in a two-dimensional direction, and a polarization conversion element that emits light with the polarization directions of the light beams emitted from the second lens array aligned. When two cross sections that are parallel to and orthogonal to the optical axis of the first lens cell are defined as a first cross section and a second cross section, the polarization conversion elements are arranged in a direction that is parallel to the first cross section and orthogonal to the optical axis. A plurality of polarized light separation surfaces. And the condensing position in the 1st cross section by at least 1 1st lens cell among several 1st lens cells is in the position near a polarization conversion element rather than the condensing position in a 2nd cross section, It is characterized by the above-mentioned. To do.

Note that the image projection optical system and an image projection apparatus using the optical system, and even the image display system and an image projection apparatus and the image supply device, constitutes another aspect of the present invention.

  According to the present invention, the shape of the secondary light source image formed by the first lens array can be optimized to realize an optical system with high light use efficiency. By using such an optical system as an optical system for illuminating the image forming element, an image projection optical system or an image projection apparatus capable of projecting a brighter image can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  1A and 1B show the configuration of an illumination optical system that is Embodiment 1 of the present invention. This illumination optical system is used in a projector (image projection apparatus) described in Example 2 later.

  In FIG. 1A and FIG. 1B, 101 is an arc tube as a light source, and 102 is a paraboloid reflector. Reference numeral 103 denotes a first fly-eye lens, which includes a plurality of first lens cells 103a arranged in a two-dimensional direction. In this embodiment, each first lens cell 103a is constituted by a toric lens. This will be described in detail later.

  Reference numeral 104 denotes a second fly-eye lens, which includes a plurality of second lens cells 104 a corresponding to the plurality of first lens cells 103 a of the first fly-eye lens 103 arranged in a two-dimensional direction. In this embodiment, each second lens cell 104a is constituted by a spherical lens.

  Reference numeral 105 denotes a polarization conversion element. As shown in FIG. 1A, the polarization conversion element 105 includes a polarization separation surface 105a, a half-wave plate 105b, and a reflection surface 105c.

  Although not shown in FIGS. 1A and 1B, a condenser lens is disposed at a position away from the traveling direction of the light beam emitted from the polarization conversion element 105.

Here, the optical axis of the illumination optical system, that is, the optical path that the light beam travels through the center of the lens cells 103a and 104a at the center of the first and second fly-eye lenses 103 and 104 and further through the center of the condenser lens is expressed as the Z axis. The direction in which the Z axis extends is the Z direction. Further, FIG. 1A shows a configuration in the YZ section (first section) of the illumination optical system, where the direction in which a plurality of polarization separation surfaces 105a of the polarization conversion element 105 are arranged is the Y direction. Further, FIG. 1B shows a configuration in an XZ section (second section) orthogonal to the YZ section of the illumination optical system, with the direction orthogonal to the Z direction and the Y direction being the X direction.

  The light beam emitted from the arc tube 101 is converted into a substantially parallel light beam by the parabolic reflector 102 and emitted. This parallel light beam is divided by the first fly-eye lens 103, and each divided light beam is condensed to form a secondary light source image and is incident on the second fly-eye lens 104.

  The lens cells 103a and 104a constituting the fly-eye lenses 103 and 104 have a rectangular lens shape similar to a liquid crystal panel (not shown in FIGS. 1A and 1B) that is an object to be illuminated (illuminated surface). Have

  The plurality of split light beams emitted from the second fly-eye lens 104 are incident on the polarization separation surface 105a through the entrance openings corresponding to the columns of the respective light beams. Light shielding plates 105d are arranged on both sides in the Y direction of the respective incident apertures. The polarization separation surface 105a is divided into a transmitting P-polarized component and a reflecting S-polarized component. The reflected S-polarized component is reflected by the reflecting surface 105c and emitted in the same direction as the P-polarized component. On the other hand, the transmitted P-polarized light component is transmitted through the half-wave plate 105c and converted to S-polarized light. As a result, light having the same polarization direction is emitted from the polarization conversion element 105.

  A plurality of split light beams emitted from the polarization conversion element 105 are collected by a condenser lens and illuminate the liquid crystal panel in a superimposed manner through a color separation / synthesis system (not shown).

  Here, when the high-power arc tube 1 is used as a light source, it is necessary to provide a predetermined width interval for passing the cooling air CA between the second fly-eye lens 104 and the polarization conversion element 105. is there. In this case, if the condensing position of the divided light beam by the first fly-eye lens 103 (each first lens cell 103a) is in the vicinity of the polarization conversion element 105 in both the YZ section and the XZ section, the second fly-eye lens 104 is used. The light flux that cannot enter the aperture (effective region) of the second lens cell 104a increases. Further, if the condensing position is set in the vicinity of the second fly-eye lens 104 in both cross sections, the light flux cut by the light shielding plate 105d of the polarization conversion element 105 increases.

  Therefore, in this embodiment, the shape of each first lens cell 103a of the first fly-eye lens 103 is set as shown in FIG. In FIG. 2, C indicates the optical axis (center axis) of the first lens cell 103a. The center view in FIG. 2 shows the shape of the first lens cell 103a as viewed in the optical axis direction, and is rectangular as described above. 2 shows the shape of the YZ section of the first lens cell 103a, and the lower figure shows the shape of the XZ section.

  Here, the first lens cell 103a is formed as a toric lens in which the curvature radius Ry in the YZ section is larger than the curvature radius Rx in the XZ section. For this reason, the condensing position (secondary light source image forming position) in the YZ section by the first lens cell 103a is shifted in the Z + direction from the condensing position in the XZ section. In other words, the focal length in the YZ section of the first lens cell 103a is longer than the focal length in the XZ section.

  In this embodiment, the focal length of the first lens cell 103a in the XZ section is set so that the light condensing position by the first lens cell 103a in the XZ section is in the vicinity of the second fly-eye lens 104. . Further, the YZ of the first lens cell 103a is such that the condensing position by the first lens cell 103a in the YZ section is closer to the polarization conversion element 105 than the condensing position in the XZ section (position in the Z + direction). The focal length in the cross section is set. The position close to the polarization conversion element 105 includes the position inside the polarization conversion element 105 (for example, between the entrance opening of the polarization conversion element 105 and the polarization separation surface 105a).

  The relationship between the light source image at each condensing position at this time, the incident aperture (effective region) of the polarization conversion element 105, and the aperture (effective region) of the second lens cell 104a constituting the second fly-eye lens 104 is shown in FIG. 3A. Conceptually.

  As shown in FIG. 3A, the entrance width of the polarization conversion element 105 has an aperture width in the Y direction partitioned by the light shielding plate 105d that is narrower than the aperture width in the X direction. However, the secondary light source image is formed in a shape compressed in the Y direction by setting the shape of the first lens cell 103a. For this reason, the light beam traveling from the first lens cell 103a to the polarization conversion element 105 via the second lens cell 104a can enter the incident opening of the polarization conversion element 105 with almost no obstruction. That is, light flux loss at the polarization conversion element 105 can be reduced.

  As shown in FIG. 3B, the opening width of the second lens cell 104a is narrower in the X direction than the opening width in the Y direction according to the shape of the liquid crystal panel surface. However, the secondary light source image is formed so as to fit in the opening of the second lens cell 104a by the shape setting of the first lens cell 103a described above. For this reason, it is possible to reduce the light flux loss in the second lens cell 104a.

  Thus, in the present embodiment, 2 formed by each first lens cell 103a constituting the first fly-eye lens 103 so as to reduce the light beam loss in the polarization conversion element 105 and the second fly-eye lens 104. The shape of the next light source image is optimized. Therefore, it is possible to realize an illumination optical system that has higher light utilization efficiency than conventional ones.

  Here, it is desirable to set the curvature radii Rx and Ry so that the focal length fy in the YZ section of the first lens cell 103a and the focal length fx in the XZ section satisfy the following formula (1).

L / 2 <| fx−fy | <2L (1)
However, L is the distance between the lens surface vertex of each second lens cell 104a and the entrance aperture of the polarization conversion element 105, as shown in FIG.

  If | fx−fy | is less than the lower limit of the expression (1), the difference in focal length is too small, and the above effect is hardly expected. Also, if | fx−fy | exceeds the lower limit of the expression (1), the difference in focal length is too large and deviates from the optimum shape of the secondary light source image, which is not preferable.

  In this embodiment, the case where each second lens cell 104a of the second fly-eye lens 104 has a convex shape on the polarization conversion element 105 side has been described. However, the second lens cell is on the first fly-eye lens 103 side. It may have a convex shape.

  In this embodiment, the case where all the first lens cells 103a constituting the first fly-eye lens 103 are toric lenses has been described. However, in the present invention, at least one of the plurality of first lens cells is toric. Including the case of a lens.

  In the present embodiment, the case where the first and second fly-eye lenses 103 and 104 are used as the first and second lens arrays has been described. However, the present invention includes at least one of the first and second lens arrays. It can be applied to an illumination optical system in which one is a fly-eye lens. For example, one lens array may be configured by combining a cylindrical lens array having a plurality of cylindrical lens cells having the Y direction as the generatrix direction and a cylindrical lens array having a plurality of cylindrical lens cells having the X direction as the generatrix direction. .

  FIG. 5 shows a configuration example of a projector using the illumination optical system described in the first embodiment.

  The projector of this embodiment includes a light source unit 100, an illumination optical system α, a color separation / synthesis optical system β, reflective liquid crystal panels (liquid crystal panels) 61R, 61G, 61B, and a projection lens 70. The light source unit 40, the illumination optical system α, the color separation / synthesis optical system β, the reflective liquid crystal panels 61R, 61G, 61B, and the projection lens 70 constitute an image projection optical system.

  In FIG. 5, 101 is an arc tube such as an ultra-high pressure mercury lamp that emits white light in a continuous spectrum, and 102 is a reflector that reflects light from the arc tube 101 and collects it in a predetermined direction. A light source unit 100 is configured by the arc tube 101 and the reflector 102. AXL is an optical axis of the illumination optical system α, the color separation / synthesis optical system β, and the projection lens 70, and indicates the traveling direction of light from the light source unit 100.

  Reference numeral 103 denotes a first fly-eye lens constituted by a plurality of first lens cells each having a refractive power on the paper surface (YZ cross section) of FIG. 5 and a cross section orthogonal thereto. Reference numeral 104 denotes a second fly-eye lens having a plurality of second lens cells corresponding to the individual first lens cells of the first fly-eye lens 103.

  Reference numeral 108 denotes an ultraviolet absorption filter, and reference numeral 105 denotes a polarization conversion element that aligns non-polarized light with light having a predetermined polarization direction.

  Reference numeral 109 denotes a mirror that changes the direction of the optical axis AXL by 90 degrees. Reference numeral 106 denotes a condenser lens. The illumination optical system α is configured as described above.

  Reference numeral 58 denotes a dichroic mirror that reflects light in the blue (B) and red (R) wavelength regions and transmits light in the green (G) wavelength region. Reference numeral 59 denotes a green incident-side polarizing plate 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, and has a polarization separation surface (polarization separation film) between a pair of triangular prism-shaped glass blocks.

  61R, 61G, and 61B are a red reflective liquid crystal panel, a green reflective liquid crystal panel, and a blue reflective liquid crystal panel that reflect incident light and modulate the image, respectively. These liquid crystal panels are also referred to as image forming elements and image modulating elements. The liquid crystal panels 61R, 61G, and 61B are connected to a drive circuit 110 that drives them. An image information supply device 120 such as a personal computer, a DVD player, a video deck, or a TV tuner is connected to the drive circuit 110. It is connected. The drive circuit 110 receives video (image) information from the image information supply device 120 and causes the liquid crystal panels 61R, 61G, and 61B to form original images according to the video information.

  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. 64 is an incident-side polarizing plate for green and blue, 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 phase difference plate that converts the polarization direction of blue light by 90 degrees and does not convert the polarization direction of red light. Reference numeral 66 denotes a second polarization beam splitter that transmits P-polarized light and reflects S-polarized light, and has a polarization separation surface (polarization separation film) between a pair of triangular prism-shaped glass blocks. Reference numeral 67 denotes a second color selective phase difference plate that converts the polarization direction of red light by 90 degrees and does not convert the polarization direction of blue light.

  Reference numeral 68 denotes an exit-side polarizing plate (polarizing element) for red and blue, which transmits only S-polarized light. Reference numeral 69 denotes a third polarization beam splitter as a color synthesis optical member that transmits P-polarized light and reflects S-polarized light, and has a polarization separation surface (polarization separation film) between a pair of triangular prism-shaped glass blocks. .

  The above-described dichroic mirror 58 and the third polarizing beam splitter 69 constitute a color separation / synthesis optical system β.

  Next, the optical action of the image display optical system will be described. Light emitted from the arc tube 101 is reflected by the reflector 102 and collected in a predetermined direction. The reflector 102 has a paraboloid shape, and light from the focal position of the paraboloid becomes a light beam substantially parallel to the axis of symmetry of the paraboloid. However, since the light source from the arc tube 101 is not an ideal point light source but has a finite size, the condensed light flux includes many light components that are not parallel to the symmetry axis of the paraboloid. Yes. These light beams are incident on the first fly-eye lens 103.

  The light beam incident on the first fly-eye lens 103 is divided and condensed into a plurality of light beams corresponding to the plurality of first lens cells. The plurality of light beams pass through the ultraviolet absorption filter 108 and form a secondary light source image in the vicinity of the polarization conversion element 105 in the YZ section and in the vicinity of the second fly-eye lens 104 in the XZ section.

  A plurality of light beams (S-polarized light) emitted with the polarization directions aligned by the polarization conversion element 105 are reflected by 90 degrees by the mirror 109 and overlapped by the condenser lens 106 to form an illumination area with uniform brightness. To do. Reflective liquid crystal panels 61R, 61G, 61B are arranged in this illumination area.

  The light converted to S-polarized light by the polarization conversion element 105 enters the dichroic mirror 58. The dichroic mirror 58 reflects blue (430 to 495 nm) and red (590 to 650 nm) light and transmits green (505 to 580 nm) light.

  Next, the optical path of green light (hereinafter referred to as G light) will be described. The G light transmitted through the dichroic mirror 58 enters the incident side polarizing plate 59. The G light remains S-polarized light after being decomposed by the dichroic mirror 58. Then, the G light exits from the incident-side polarizing plate 59 and then enters the first polarizing beam splitter 60 as S-polarized light, and is reflected by the polarization separation surface of the first polarizing beam splitter 60. To the reflective liquid crystal panel 61G.

  In the reflective liquid crystal panel 61G for G, the G light is image-modulated and reflected. Of the image-modulated G light (reflected light), the S-polarized light component 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.

  Here, in a state where all the polarization components are converted to S-polarized light (in a state where black is displayed), a ¼ wavelength provided between the first polarizing beam splitter 60 and the G reflective liquid crystal panel 61G. The slow axis of the plate 62G is adjusted in a predetermined direction. Thereby, it is possible to suppress 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.

  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, red and blue light reflected by the dichroic mirror 58 (hereinafter, referred to as R light and B light, respectively) enter the incident-side polarizing plate 64. Note that the R light and B light remain S-polarized light even after being decomposed by the dichroic mirror 58. 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 an action of rotating the polarization direction of the B light by 90 degrees, whereby the B light becomes P-polarized light and the R light becomes S-polarized light, and the second polarization beam splitter 66. 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 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 reflective liquid crystal panel 61R for R is image-modulated and reflected. Of the image-modulated R light (reflected light), the S-polarized light component is reflected again by the polarization separation surface of the second polarizing 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 to the second color-selective phase plate 67 as projection light.

  The B light incident on the B reflective liquid crystal panel 61B is image-modulated and reflected. The P-polarized component of the image-modulated B light (reflected 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 light component of the image-modulated B reflected 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, the G light is adjusted by adjusting the slow axes 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. In the same manner as in, the black display of each of the R and B lights can be adjusted.

  Thus, the R light of the R and B projection lights emitted from the second polarization beam splitter 66, which is synthesized into one light beam, is rotated by 90 degrees by the second color selective phase plate 67, and is S-polarized light. It becomes a component, is further analyzed by the exit-side polarizing plate 68, and enters the third polarizing beam splitter 69.

  The B light passes through the second color-selective phase plate 67 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-projection lights are analyzed by the exit-side polarizing plate 68, so that the R and B reflection type liquid crystal panels 61R and 61B and the quarter-wave plates 62R and 62B are reflected on the second polarizing beam splitter 66. 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 reflected by the polarization separation surface described above. The projection lens 70 is reached. Thus, the combined R, G, B projection light is enlarged and projected by the projection lens 70 onto a projection surface such as a screen or a wall surface.

  The optical path described above is for the case where the reflective liquid crystal panel is in the white display state, so the optical action when the reflective liquid crystal panel is in the black display state will be described below.

  First, the optical path of G light will be described. The G light (S-polarized light) transmitted through the dichroic mirror 58 enters the incident-side polarizing plate 59, and then enters the first polarizing beam splitter 60 and is reflected by the polarization separation surface thereof. It reaches 61G. However, since the reflective liquid crystal panel 61G is in the black display state, the G light is reflected without being image-modulated. Therefore, even after being reflected by the reflective liquid crystal panel 61G, the G light remains as S-polarized light, is reflected again by the polarization separation surface of the first polarization beam splitter 60, and passes through the incident-side polarizing plate 59 to be a light source. Back to the side and removed from the projection light.

  Next, the optical paths of R light and B light will be described. The R light and B light (S polarized light) reflected by the dichroic mirror 58 enter the incident side polarizing plate 64. The R light and the B light are emitted from the incident-side polarizing plate 64 and then incident on the first color-selective retardation 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, so that the B light becomes P-polarized light and the R light becomes S-polarized light. The light enters the beam splitter 66.

  The R light incident on the second polarizing beam splitter 66 as S-polarized light is reflected by the polarization separation surface of the second polarizing beam splitter 66 and reaches the R reflective liquid crystal panel 61R. The B light incident on the second polarizing beam splitter 66 as P-polarized light passes through the polarization separation surface of the second polarizing 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 as S-polarized light, is reflected again by the polarization separation surface of the first polarization beam splitter 60, and passes through the incident-side polarizing plate 64. Then, it is returned to the light source side and removed from the projection light. That is, black is displayed on the projection surface.

  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 a 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, passes through the polarization separation surface of the first polarization beam splitter 60 again, and has the first color selectivity. The light is converted into S-polarized light by the phase difference plate 65, passes through the incident-side polarizing plate 64, returns to the light source side, and is removed from the projection light.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist. For example, in this embodiment, an image projection apparatus using a reflective liquid crystal panel has been described, but the present invention can also be applied to an image projection apparatus using a transmissive liquid crystal panel or a digital micromirror device.

1 is a YZ sectional view showing a configuration of an illumination optical system that is Embodiment 1 of the present invention. FIG. FIG. 3 is an XZ cross-sectional view showing the configuration of the illumination optical system of Example 1. 3 is a trihedral view of a lens cell that constitutes the second fly's eye lens of Example 1. FIG. The conceptual diagram which showed the relationship between the secondary light source image in Example 1, and the entrance opening of a polarization conversion element. FIG. 3 is a conceptual diagram showing a relationship between a secondary light source image and an opening of a second fly-eye lens in Example 1. FIG. 3 is a diagram illustrating a distance between a second fly's eye lens and a polarization conversion element in the first embodiment. FIG. 6 is a YZ sectional view showing a configuration of an image projection apparatus that is Embodiment 2 of the present invention. FIG. 6 is a YZ sectional view of a conventional illumination optical system. XZ sectional drawing of the conventional illumination optical system. The conceptual diagram which showed the relationship between the secondary light source image in the conventional illumination optical system, the entrance opening of a polarization conversion element, and the opening of a 2nd fly eye lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light emission tube 102 Reflector 103 1st fly eye lens 104 2nd fly eye lens 105 Polarization conversion element 106 Condenser lens 61R, 61G, 61B Liquid crystal panel

Claims (16)

A first lens array having a plurality of first lens cells arranged in a two-dimensional direction for focusing the light beam to split from a light source,
A second lens array in which second lens cells corresponding to a plurality of light beams divided by the first lens array are arranged in a two-dimensional direction ;
A polarization conversion element that emits light with the same polarization direction of the light beam emitted from the second lens array;
When two cross sections parallel to and orthogonal to the optical axis of the first lens cell are defined as a first cross section and a second cross section,
The polarization conversion element has a plurality of polarization separation surfaces arranged in a direction parallel to the first cross section and perpendicular to the optical axis,
The condensing position in the first cross section by at least one first lens cell among the plurality of first lens cells is located closer to the polarization conversion element than the condensing position in the second cross section. Characteristic optical system. The condensing position in the first cross section, an optical system according to claim 1, characterized in that the interior of the polarization conversion element. 3. The optical system according to claim 1, wherein a condensing position in the second cross section is between a light incident surface of the second lens array and a light emitting surface of the polarization conversion element. The optical system according to claim 3, wherein a condensing position in the second cross section is inside the second lens array. 5. The optical system according to claim 1, wherein an interval having a predetermined width is provided between the second lens array and the polarization conversion element. The optical system according to claim 5, wherein the interval is an interval for passing cooling air. The optical system according to claim 1, wherein a width of the second lens cell in the second cross section is narrower than a width of the first cross section. The optical system according to claim 1, wherein the polarization conversion element includes a plurality of light shielding plates, and an incident opening of the polarization conversion element is formed by the light shielding plates. . The optical system according to claim 1, wherein the optical system includes only one polarization conversion element. Wherein at least a focal length in the first section of one of the first lens cells, optical system according to any one of claims 1 to 9, characterized in that longer than the focal length in the second section . Optical system according to any one of claims 1 to 10, characterized in that the following condition is satisfied.
L / 2 <| fx−fy | <2L
However, L is the distance between the lens surface apex of each said 2nd lens cell and the said polarization conversion element, fx is the focal distance of the said at least 1 1st lens cell in a 1st cross section among the said 2 cross sections, fy is the focal length of the first lens cell in the second cross section of the two cross sections. The optical system according to any one of claims 1 to 11 , wherein the at least one first lens cell is a toric lens. An optical system according to any one of claims 1 to 12 ,
An image projection optical system comprising an image forming element illuminated by a light beam from the optical system. Image projection optical system according to claim 13, characterized in that it comprises an optical system for projecting a light beam from the image forming element on the projection surface. An image projection apparatus comprising the image projection optical system according to claim 13 . An image projection device according to claim 15 ,
An image display system comprising an image information supply device for supplying image information to the image projection device.