JP2009288407A - Lighting optical system and image projection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To vary contrast without significantly deteriorating brightness of projection images. <P>SOLUTION: A lighting optical system 100 is used for an image projection apparatus for guiding a light flux from a light source 101 to an image display element 110 through the lighting optical system and projecting a light flux from the image display element to a face to be projected. The lighting optical system includes: a light flux division means 106 for dividing the light flux from the light source into a plurality of light fluxes and forming a plurality of light source images on the plurality of the light fluxes; a condensing means 109 for superposing the plurality of the light fluxes from the light flux division means on the image display element; and light flux control optical systems 103-105 arranged closer to a light source side than the condensing means and compressing the light fluxes. The light flux control optical system includes two or more optical elements, and modifies a compression rate of the light fluxes by moving at least the two optical elements of the two or more optical elements in an optical axis direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination optical system used in an image projection apparatus such as a projector.

  The image projection apparatus has an illumination optical system that illuminates an image display element such as a liquid crystal panel with illumination light from a light source, and enlarges and projects the light modulated by the image display element on the screen via the projection optical system.

  In the conventional image projection apparatus, the contrast of the projected image is made variable by cutting a component having a large incident angle with respect to the image display element out of the illumination light directed to the image display element or making it enter the image display element.

For example, Patent Document 1 discloses an illumination optical system having an aperture stop whose aperture size is variable. The variable aperture stop is disposed in the vicinity of the fly eye lens (second fly eye lens) far from the light source among the two fly eye lenses, and the second fly eye lens is moved by moving the four light shielding plates. The incident area of the illumination light to the eye lens is changed. Thereby, the F number of the illumination optical system is changed to change the contrast of the projected image.
JP 2005-017500 A

  However, in the method that allows the contrast to be changed using the variable aperture stop disclosed in Patent Document 1, it is necessary to cut a considerable part of the illumination light when the contrast is greatly increased. As a result, the contrast of the projected image is increased, but the luminance is greatly decreased.

  The present invention provides an illumination optical system capable of making the contrast variable without greatly reducing the brightness of the projected image, and an image projection apparatus using the illumination optical system.

  An illumination optical system according to one aspect of the present invention is used in an image projection apparatus that guides a light beam from a light source to an image display element via the illumination optical system and projects the light beam from the image display element onto a projection surface. It is done. The illumination optical system divides a light beam from a light source into a plurality of light beams and forms a plurality of light source images on the plurality of light beams, and superimposes a plurality of light beams from the light beam splitting unit on the image display element. And a light beam control optical system that is disposed closer to the light source than the light collecting unit and compresses the light beam. The light flux controlling optical system includes two or more optical elements, and changes the compression ratio of the light flux by moving at least two of the two or more optical elements in the optical axis direction. And

  Note that an image projection apparatus including the illumination optical system also constitutes another aspect of the present invention.

  In the present invention, the contrast of the projected image is made variable by changing the compression rate of the light beam in the illumination optical system. As a result, even if the contrast is increased, the illumination light beam is not largely cut, so that a decrease in the brightness of the projected image can be reduced. Therefore, it is possible to realize an image projection apparatus capable of projecting a bright and high-contrast image while the contrast of the projected image is variable.

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

  21A and 21B show an optical configuration of a liquid crystal projector (image projection apparatus) in which an illumination optical system according to each embodiment of the present invention to be described later is used. (A) and (B) are views of the optical configuration viewed from different directions.

  In the figure, reference numeral 41 denotes a discharge arc tube (hereinafter simply referred to as an arc tube) that emits white light of non-polarized light (non-polarized light) in a continuous spectrum. Reference numeral 42 denotes a reflector having a paraboloid for condensing light from the arc tube 41 in a predetermined direction. The light source lamp 1 is constituted by the arc tube 41 and the reflector 42. Most of the light beam emitted from the reflector 42 is a parallel light beam.

  Reference numeral 100 denotes an illumination optical system according to each embodiment, and guides an illumination light beam from the light source lamp 1 to an image display element to be described later via a color separation / synthesis optical system to be described later. A specific configuration of the illumination optical system 100 will be described later. The illumination optical system 100 includes a polarization conversion element that converts non-polarized light from the light source lamp 1 into linearly polarized light (here, S-polarized light) having a specific polarization direction. This polarization conversion element will be described later.

  Reference numeral 47 denotes a reflection mirror for bending the optical axis from the lamp 1 by approximately 90 degrees (more specifically, 88 degrees).

  58 is a dichroic mirror that reflects light in the wavelength region of blue (B: for example 430 to 495 nm) and red (R: for example 590 to 650 nm) and transmits light in the wavelength region of green (G: for example 505 to 580 nm). is there. 59 is an incident side polarizing plate for G in which a polarizing element is bonded to a transparent substrate, and transmits only P-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.

  Each of 61R, 61G, and 61B reflects a red reflective liquid crystal panel, a green reflective liquid crystal panel, and a blue reflective as an image display element (image forming element or spatial light modulator) that reflects and modulates incident light. Type LCD panel. 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.

  A trimming filter 64a returns orange light to the lamp 1 in order to increase the color purity of the R light. Reference numeral 64b denotes an incident-side polarizing plate for RB in which a polarizing element is attached to a transparent substrate and transmits only P-polarized light.

  65 is a 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 66 denotes a second polarization beam splitter that transmits P-polarized light and reflects S-polarized light on the polarization separation surface.

  Reference numeral 68B denotes a B-use exit side polarizing plate (polarizing element) that rectifies only the S-polarized component of the B light. 68G is a G output-side polarizing plate that transmits only the S-polarized light component of the G light. Reference numeral 69 denotes a dichroic prism that transmits R light and B light and reflects G light.

  The above dichroic mirror 58 to dichroic prism 69 constitute a color separation / synthesis optical system.

  In the present embodiment, the polarization conversion element included in the illumination optical system 100 converts the P-polarized component of the non-polarized light into the S-polarized component, and emits the S-polarized light by passing through the S-polarized component as it is. P-polarized light and S-polarized light here are described with reference to the polarization direction of light in the polarization conversion element. On the other hand, the light incident on the dichroic mirror 58 is assumed to be P-polarized light considering the polarization directions in the first and second polarization beam splitters 60 and 66 as a reference. That is, in this embodiment, the light emitted from the polarization conversion element is S-polarized light, but when the same S-polarized light is incident on the dichroic mirror 58, it is defined as P-polarized light.

  Next, the optical action will be described. Here, the optical action in the white display state will be described.

  Light emitted from the arc tube 41 is collected in a predetermined direction by the reflector 42. The reflector 42 has a parabolic concave mirror, and light from the focal position of the paraboloid becomes a light beam parallel to the symmetry axis of the paraboloid. However, since the light source from the arc tube 41 is not an ideal point light source and has a finite size, the condensed light flux includes many light components that are not parallel to the symmetry axis of the paraboloid. ing. These light beams enter the dichroic mirror 58 through the illumination optical system 100 and the reflection mirror 47. The light incident on the dichroic mirror 58 is converted into S-polarized light by a polarization conversion element (which will be described later) included in the illumination optical system 100.

  Hereinafter, the optical path of the G light transmitted through the dichroic mirror 58 will be described.

  The G light transmitted through the dichroic mirror 58 enters the incident side polarizing plate 59. Even after the G light is decomposed by the dichroic mirror 58, it is P-polarized light (S-polarized light when the polarization conversion element is used as a reference). The G light exits from the incident-side polarizing plate 59, then enters the first polarizing beam splitter 60 as P-polarized light, passes through the polarization separation surface, and reaches the G reflective liquid crystal panel 61G.

  Here, an image supply device 80 such as a personal computer, a DVD player, or a TV tuner is connected to the interface 25 of the projector. The control board 11 drives the reflective liquid crystal panels 61R, 61G, and 61B based on the image information input from the image supply device 80 via the interface 25, and forms an original image for each color on them. Thus, the light incident on each reflective liquid crystal panel is reflected and modulated (image modulation) according to the original image. The image supply apparatus 80 and the projector constitute an image display system.

  In the G reflective liquid crystal panel 61G, the G light is image-modulated and reflected. The P-polarized component of the image-modulated G light is again transmitted through 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 S-polarized component of the image-modulated G light is reflected by the polarization separation surface of the first polarization beam splitter 60 and travels toward the dichroic prism 69 as projection light.

  At this time, in a state where all the polarization components are converted to P-polarized light (in a state where black is displayed), a quarter-wave plate 62G provided between the first polarizing beam splitter 60 and the G-use reflective liquid crystal panel 61G. The slow axis is adjusted in a predetermined direction. Thereby, the influence of the disturbance of the polarization state which generate | occur | produces with the 1st polarizing beam splitter 60 and the reflective liquid crystal panel 61G for G can be restrained small.

  The G light emitted from the first polarizing beam splitter 60 enters the dichroic prism 69 as S-polarized light, is reflected by the dichroic film surface of the dichroic prism 69, and reaches the projection lens 5.

  On the other hand, the R light and B light reflected by the dichroic mirror 58 enter the trimming filter 64a. R light and B light are still P-polarized light after being decomposed by the dichroic mirror 58. Then, after the orange light component is cut by the trimming filter 64 a, the R light and the B light are transmitted through the incident-side polarizing plate 64 b and are incident on the color selective phase difference plate 65.

  The color-selective phase difference plate 65 has an action of rotating only the polarization direction of the R light by 90 degrees, so that the R light is incident on the second polarization beam splitter 66 as S-polarized light and the B light is incident on P-polarized light.

  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. The B light incident on the second polarization beam splitter 66 as P-polarized light is transmitted 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 dichroic prism 69 as projection light.

  The B light incident on the B-use reflective liquid crystal panel 61B 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 and returned to the light source side, and is 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 dichroic prism 69 as projection light.

  At this time, by adjusting the slow axes of the quarter-wave plates 62R and 62B provided between the second polarizing beam splitter 66 and the R and B reflective liquid crystal panels 61R and 61B, As in the case, the adjustment in the black display state of each of the R and B lights can be performed.

  The R light and B light that are combined into one light beam and emitted from the second polarization beam splitter 66 are analyzed by the exit-side polarizing plate 68B and enter the dichroic prism 69. Further, the R light is transmitted through the exit-side polarizing plate 68 </ b> B as P-polarized light and enters the dichroic prism 69.

  By being analyzed by the exit-side polarizing plate 68B, the B light is ineffective generated by the B light passing through the second polarizing beam splitter 66, the B reflective liquid crystal panel 61B, and the quarter wavelength plate 62B. The light is cut from the components.

  The R light and B light incident on the dichroic prism 69 pass through the dichroic film surface and are combined with the G light reflected by the dichroic film surface to reach the projection lens 5.

  Then, the combined R, G, B light is enlarged and projected onto a projection surface such as a screen by the projection lens 5.

FIG. 1 shows an XZ section of an illumination optical system 100 that is Embodiment 1 of the present invention. Reference numeral 101 in the figure denotes a light source, which corresponds to the arc tube 41 in FIG. Reference numeral 102 denotes a parabolic reflector, which corresponds to the reflector 42 in FIG.

  Reference numerals 103, 104, and 105 denote a first lens, a second lens, and a third lens as optical elements, respectively, and the first to third lenses 103 to 105 constitute a light flux controlling optical system.

  Reference numeral 106 denotes a first fly-eye lens (lens array) as a light beam splitting means, which is configured by arranging a plurality of lens cells in a two-dimensional direction. The first fly-eye lens 106 divides a light beam from a light source into a plurality of light beams (light beam splitting), and a light source image (secondary light source) near a second fly-eye lens 107 and a polarization conversion element 108 described later. Image). Reference numeral 107 denotes a second fly-eye lens (lens array), which is configured by arranging a plurality of lens cells in a two-dimensional direction.

Reference numeral 108 denotes a polarization conversion element. Reference numeral 109 denotes a condenser lens as a light collecting means. The aforementioned first to third lenses 103 to 105 are arranged on the light source side with respect to the condenser lens 109. Reference numeral 110 denotes a liquid crystal panel (image display element), which corresponds to the reflective liquid crystal panels 61R, 61G, and 61B in FIG. O ₁ represents the optical axis of the illumination optical system 100.

  FIG. 2 shows the structure (XZ cross section) of the polarization conversion element 108. The polarization conversion element 108 includes a plurality of polarization separation surfaces 31, a plurality of reflection surfaces 32, a plurality of half-wave plates 33, a plurality of light shielding plates 34, a plurality of first light-transmissive members 35, and a plurality of The second translucent member 36.

  The first light transmissive member 35 and the second light transmissive member 36 are alternately disposed between the polarization separation surface 31 and the reflection surface 32. The light shielding plate 34 is attached to the incident surface of the first light transmissive member 35. The half-wave plate 33 is affixed to the emission surface of the second light transmissive member 36.

  A plurality of light beams which are light beams from the light source 101 and divided by the first fly-eye lens 106 and passed through the second fly-eye lens 107 are in a column corresponding to the lens cell column of the first fly-eye lens 106. The light enters the second light transmissive member 36. FIG. 2 shows one light beam R31 among the plurality of light beams.

  The light beam R31 incident on the second light transmissive member 36 enters the polarization separation surface 31, and is divided into a P-polarized light component R32 that passes through this and a S-polarized light component R33 that is reflected there. The S-polarized light component R33 reflected by the polarization separation surface 31 is further reflected by the reflection surface 32 and exits from the exit surface. On the other hand, the P-polarized component R32 transmitted through the polarization separation surface 31 is rotated by 90 ° in the polarization direction by the half-wave plate 33 to become an S-polarized component, and is emitted from the exit surface. Thus, the non-polarized light from the light source 101 is converted into S-polarized light having the same polarization direction. That is, the polarization conversion element 108 emits a plurality of light beams as S-polarized light.

  The first lens 103 of the light flux controlling optical system has a positive power (which is the reciprocal of the focal length, also referred to as refractive power), and the second lens 104 and the third lens 105 both have negative power. . Thereby, the light beam control optical system constitutes an afocal optical system that converts an incident light beam as a parallel light beam into an emitted light beam as a parallel light beam having a light beam width smaller than the light beam width, that is, compresses it.

The second lens 104 and the third lens 105 are provided in the direction in which the optical axis O ₁ extends in order to change the width of the emitted light beam, that is, to change the compression ratio of the emitted light beam with respect to the incident light beam (hereinafter simply referred to as light beam). (Referred to as the axial direction) (the position in the optical axis direction changes). The first lens 103 is fixed (the position in the optical axis direction does not change).

The light beam (parallel light beam) from the light source 101 converted into the light beam parallel to the optical axis O ₁ by the paraboloid reflector 102 enters the light beam control optical system. As described above, the light beam control optical system is configured by the lenses 103 to 105 having positive, negative, and negative powers in order from the light source side. Therefore, the parallel light beam incident on the light beam control optical system has the light beam width. It is emitted as a compressed parallel light beam.

  A parallel light beam emitted from the light beam control optical system is divided into a plurality of light beams by a plurality of lens cells included in the first fly-eye lens 106. In addition, the first fly-eye lens 106 has a plurality of secondary light sources in the vicinity of the second fly-eye lens 107 and the polarization conversion element 108 due to the positive power of the plurality of lens cells. Form an image.

  Here, even if the second lens 104 and the third lens 105 move in the optical axis direction (even if the position in the optical axis direction changes), the position in the optical axis direction where a plurality of secondary light source images are formed ( And the position in the plane orthogonal to the optical axis) does not change. This is the same in other embodiments described later.

  The plurality of light beams forming the plurality of secondary light source images are converted into S-polarized light through the polarization conversion element 108 and then enter the condenser lens 109. The condenser lens 109 superimposes a plurality of light beams on the light receiving surface of the liquid crystal panel 10 (that is, on the image display element) to form a uniform illumination area.

  Here, the compression rate α of the light beam in the light beam control optical system is defined as follows.

α = B / A
However, A is the beam width (beam diameter) of the incident beam to the beam control optical system, and B is the beam width (beam diameter) of the exit beam from the beam control optical system.

  FIG. 3 shows an XZ cross section of the illumination optical system 100 when α = 0.85. FIG. 4 shows an XZ cross section of the illumination optical system 100 when α = 0.75. Furthermore, FIG. 5 shows an XZ cross section of the illumination optical system 100 when α = 0.65. As can be seen from these figures, the compression rate α changes by moving the second lens 104 and the third lens 105 in the optical axis direction.

  Note that as the compression ratio increases as the state changes to the state illustrated in FIGS. 3 to 5 (the numerical value of α decreases), the second lens 104 moves along a convex locus toward the light source, and the third The lens 105 moves monotonously toward the liquid crystal panel.

  The smaller the incident angle of the light beam incident on the liquid crystal panel 110, the higher the contrast of the projected image. For this reason, if the focal length of the condenser lens 109 is constant, the smaller the luminous flux diameter incident on the condenser lens 109, the smaller the incident angle incident on the liquid crystal panel 110 and the higher the contrast of the projected image. That is, the contrast can be increased as the light beam compression ratio in the light beam control optical system is increased.

  As described above, in this embodiment, in order to change the contrast of the projection image, the compression rate of the light beam in the light beam control optical system is changed. For this reason, when the contrast is increased, light can be collected at the center of the projected image with high contrast. Therefore, it is possible to reduce the decrease in the brightness of the projected image with respect to the contrast increase rate.

  In the present embodiment, the case where the light flux controlling optical system is configured by the three lenses 103 to 105 and positive, negative, and negative powers are applied to the first to third lenses 103 to 105 has been described. However, the light flux controlling optical system can be constituted by two or more optical elements. Of two or more (for example, four) optical elements, at least one optical element having a positive power and at least one optical element having a negative power (that is, at least two optical elements) are each in the optical axis direction. Just move.

  In the present embodiment, the case where the paraboloid reflector 102 and the first lens 103 are used has been described. Alternatively, an elliptical reflector may be used (the light beam may be compressed by the elliptical reflector).

  6 and 7 respectively show an XZ section and a YZ section of the illumination optical system 100 that is Embodiment 2 of the present invention.

  Reference numeral 151 in the figure denotes a light source, which corresponds to the arc tube 41 in FIG. Reference numeral 152 denotes a parabolic reflector, which corresponds to the reflector 42 in FIG.

  Reference numerals 153 and 154 denote a first lens and a second lens as optical elements, respectively. A first light flux controlling optical system is constituted by the first and second lenses 153 and 154 and a first fly-eye lens described later. The first and second lenses 153 and 154 and the second fly-eye lens described later constitute a second light flux controlling optical system.

  Reference numeral 155 denotes a first fly-eye lens (lens array, optical element), which is configured by arranging a plurality of lens cells in a two-dimensional direction. Reference numeral 156 denotes a second fly-eye lens (lens array, optical element), which is configured by arranging a plurality of lens cells in a two-dimensional direction. The first and second fly-eye lenses 155 and 156 constitute a light beam splitting unit and, as described above, a part of the first and second light flux control optical systems.

  A polarization conversion element 157 has the same structure as the polarization conversion element 108 of the first embodiment. Reference numeral 159 denotes a condenser lens as a light collecting means. The first and second lenses 153 and 154 described above are disposed closer to the light source than the condenser lens 159.

Reference numeral 159 denotes a liquid crystal panel (image display element), which corresponds to the reflective liquid crystal panels 61R, 61G, and 61B in FIG. O ₂ represents the optical axis of the illumination optical system 100.

  As shown in FIG. 8, in the first fly-eye lens 155, the apex of each lens cell is decentered outward in the X direction. Therefore, the first fly-eye lens 155 has a cylinder lens effect that generates negative power as a whole in the XZ cross section shown in FIG.

  In the second fly-eye lens 156, as shown in FIG. 9, the apex of each lens cell is decentered outward in the Y direction. Therefore, the second fly-eye lens 156 has a cylinder lens effect that generates negative power as a whole in the YZ cross section shown in FIG.

  The first lens 153 has a positive power, and the second lens 154 has a negative power.

  In the XZ cross section, the first lens 153 having a positive power, the second lens 154 having a negative power, and the first fly-eye lens 155 having a cylinder lens effect (negative power) A light flux controlling optical system is configured. The first light beam control optical system is an afocal optical system that converts an incident light beam as a parallel light beam into an outgoing light beam as a parallel light beam having a light beam width smaller than the light beam width in the XZ section, that is, a compression. is there.

  In the YZ section, the first lens 153 having a positive power, the second lens 154 having a negative power, and the second fly-eye lens 156 having a cylinder lens effect (positive power) are used. Two light flux controlling optical systems are configured. The second light beam control optical system is an afocal optical system that converts an incident light beam as a parallel light beam into an outgoing light beam as a parallel light beam having a light beam width smaller than the light beam width in the YZ section, that is, a compression. is there.

  The first lens 153 and the second lens 154 move in the optical axis direction in order to change the width of the emitted light beam, that is, to change the compression rate of the emitted light beam with respect to the incident light beam. The first and second fly eye lenses 156 and 157 are fixed.

  The light beam compression ratios β and γ in the XZ section and the YZ section are respectively defined as follows.

β = D / C
γ = F / E
However, C is a light beam width (light beam diameter) of the incident light beam to the first light beam control optical system, and D is a light beam width (light beam diameter) of the light beam emitted from the first light beam control optical system. E is a light beam width (light beam diameter) of a light beam incident on the second light beam control optical system, and F is a light beam width (light beam diameter) of an emitted light beam from the second light beam control optical system.

  10 and 11 show an XZ section and a YZ section of the illumination optical system 100 when β = 0.85 and γ = 0.7. 12 and 13 show an XZ section and a YZ section of the illumination optical system 100 when β = 0.76 and γ = 0.62.

  As can be seen from these figures, the compression ratios β and γ are changed by moving the first lens 153 and the second lens 154 in the optical axis direction.

  The first and second lenses 153 and 154 change as the compression ratio increases from the state shown in FIGS. 10 and 11 to the state shown in FIGS. 12 and 13 (the values of β and γ decrease), respectively. Moves monotonously to the light source.

  In the present embodiment, the following relationship is established.

β / γ = constant Accordingly, the angular distribution of the light beam incident on the liquid crystal panel 159 in the YZ section is smaller than the angular distribution of the light beam incident on the liquid crystal panel 159 in the XZ section. For this reason, when the color separation / synthesis optical system includes a polarization separation surface (polarization beam splitter) or a dichroic surface (dichroic prism) having incident angle dependency, a high light utilization efficiency is achieved, while the projection image The contrast can be changed.

  Further, in this embodiment, since the number of lenses is smaller than that in the first embodiment, it is possible to increase the illumination efficiency and reduce the cost.

  In this embodiment, the light flux controlling optical system is constituted by three optical elements, that is, positive and negative first and second lenses 153 and 154 and a fly-eye lens 156 or 157 having a negative cylinder lens effect. However, the light flux controlling optical system can be constituted by two or more optical elements including at least two optical elements movable in the optical axis direction. Of two or more (eg, four) optical elements, at least one optical element having positive power and at least one optical element having negative power (ie, at least two optical elements) excluding a fly-eye lens May be moved in the optical axis direction.

  FIG. 14 shows an XZ section of the illumination optical system 100 that is Embodiment 3 of the present invention. In this embodiment, a variable aperture stop 171 is added between the first and second fly-eye lenses 106 and 107 in the illumination optical system 100 of Embodiment 1 and close to the second fly-eye lens 107. Have Constituent elements other than the variable aperture stop 171 are denoted by the same reference numerals as in the first embodiment, and are not described.

  The configuration of the variable aperture stop 171 is shown in FIG. Reference numeral 172 denotes two light shielding plates as light shielding means. By moving the two light shielding plates 172 to the opposite sides in the Y direction, the size of the aperture of the variable aperture stop 71 is changed, and the amount of light beam to be cut out of the compressed light beam is kept constant.

  FIG. 15A shows the state of the variable aperture stop 171 when the compression rate of the light beam in the light beam control optical system is α = 0.85. FIG. 15B shows the state of the variable aperture stop 171 when α = 0.75. FIG. 15C shows the state of the variable aperture stop 171 when α = 0.65.

  As can be seen from these figures, the size of the aperture of the variable aperture stop 171 is changed and the amount of light to be cut is increased or decreased by moving the light shielding plate 172 in conjunction with the change in the compression rate α. More specifically, as the compression ratio increases (the numerical value of α decreases) as shown in FIGS. 15A to 15C, the aperture of the variable aperture stop 171 is reduced and cut. The amount of luminous flux to be maintained is kept constant. Here, the amount of light beam cut by the variable aperture stop 171 is smaller than the amount of light beam cut by the variable aperture stop disclosed in Patent Document 1. For this reason, the contrast can be further increased as compared with the first embodiment without greatly reducing the brightness of the projected image.

  Note that the shape of the variable aperture stop 171 (light shielding plate 172) shown in FIG. 15 is merely an example, and other shapes may be employed.

  Further, the position at which the variable aperture stop 171 is disposed may not be the position illustrated in FIG. 14, and may be disposed, for example, between the third lens 105 and the first fly-eye lens 106.

  FIG. 16 shows an XZ section of an illumination optical system 100 that is Embodiment 4 of the present invention. This embodiment has a configuration in which an aperture stop 191 is added between the second lens 104 and the third lens 105 in the illumination optical system 100 of the first embodiment. Constituent elements other than the aperture stop 191 are denoted by the same reference numerals as in the first embodiment, and are not described.

  The aperture stop 191 is provided to be movable in the optical axis direction. The shape of the aperture stop 191 is shown in FIG. A light shielding plate 192 is a light shielding means, and a rhombus opening 192a is formed at the center thereof.

  FIG. 16 shows the position of the aperture stop 191 when the compression ratio of the light beam in the light beam control optical system is α = 0.75. FIG. 18 shows the XZ cross section of the illumination optical system 100 and the position of the aperture stop 191 when α = 0.65.

  As can be seen from these figures, the amount of light beam to be cut is increased or decreased by moving the aperture stop 191 in the optical axis direction in conjunction with the change in the compression rate α. Specifically, as the compression ratio increases from the state shown in FIG. 16 to the state shown in FIG. 18 (the numerical value of α decreases), the aperture stop 191 is moved to the light source side to cut the luminous flux. Keep the amount of water constant.

  Also in this embodiment, the amount of light beam cut by the aperture stop 191 is smaller than the amount of light beam cut by the variable aperture stop disclosed in Patent Document 1. For this reason, the contrast can be further increased as compared with the first embodiment without greatly reducing the brightness of the projected image.

  Note that the shape of the aperture stop 191 (light shielding plate 192) shown in FIG. 17 is merely an example, and other shapes may be adopted.

  Further, the position at which the aperture stop 191 is disposed does not have to be the position illustrated in FIGS. 16 and 18. For example, the aperture stop 191 may be disposed between the first lens 103 and the second lens 104.

  19 and 20 show XZ cross sections of an illumination optical system 100 that is Embodiment 5 of the present invention.

  Reference numeral 201 in the figure denotes a light source, which corresponds to the arc tube 41 in FIG. Reference numeral 202 denotes a parabolic reflector, which corresponds to the reflector 42 in FIG.

  Reference numerals 203, 204, and 205 denote a first lens, a second lens, and a third lens as optical elements, respectively, and the first to third lenses 203 to 205 constitute a light flux controlling optical system.

Reference numeral 206 denotes a rod integrator as a beam splitting unit, 207 denotes a first field lens, 208 denotes a second field lens, and 209 denotes a third field lens. Reference numeral 210 denotes a polarization conversion element, and 211 denotes a condenser lens as a condensing unit. The first to third lenses 203 to 205 described above are arranged on the light source side with respect to the condenser lens 211. Reference numeral 212 denotes a liquid crystal panel (image display element), which corresponds to the reflective liquid crystal panels 61R, 61G, and 61B in FIG. O ₃ represents the optical axis of the illumination optical system 100.

  The first lens 203 has a positive power, and the second lens 204 has a negative power. The third lens 205 has a positive power.

  The second lens 204 and the third lens 205 move in the optical axis direction so as to change the distribution angle of the light beam incident on the rod integrator 206 indicated by φ1 and φ2 (<φ1) in FIGS. 19 and 20, respectively. . Specifically, as the distribution angle of the light beam incident on the rod integrator 206 becomes smaller, each of the second and third lenses 204 and 205 moves monotonously to the light source side. The first lens 203 is fixed.

  Thus, by changing the distribution angle of the light beam incident on the rod integrator 206, the F number of the illumination optical system 100 can be changed, and the contrast of the projected image can be made variable.

  In the first to fourth embodiments described above, reducing the diameter (width) of the incident parallel light beam and emitting it again as a parallel light beam is referred to as light beam compression, but in this embodiment, such light beam compression is performed. Do not do. However, since the diameter of the light beam emitted from the third lens 205 and directed to the rod integrator 206 is smaller than the light beam incident on the first lens 203, this is also included in the light beam compression referred to in the present invention. . Increasing or decreasing the distribution angle of the light beam incident on the rod integrator 206 is equivalent to changing the compression rate of the light beam.

  In this embodiment, the case where the light flux controlling optical system is configured by the three lenses 203 to 205 and positive, negative, and positive powers are applied to the first to third lenses 203 to 205 has been described. However, the light flux controlling optical system can be constituted by two or more optical elements. Of two or more (for example, four) optical elements, at least one optical element having a positive power and at least one optical element having a negative power (that is, at least two optical elements) are each in the optical axis direction. Just move.

  In the present embodiment, the case where the paraboloid reflector 202 and the first lens 203 are used has been described, but an elliptical reflector may be used instead.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

FIG. 3 is an XZ sectional view showing a configuration of an illumination optical system that is Embodiment 1 of the present invention. FIG. 3 is an XZ sectional view showing the structure of a polarization conversion element used in the illumination optical system of Example 1. XZ sectional drawing which shows the structure by (alpha) = 0.85 of the illumination optical system of Example 1. FIG. FIG. 4 is an XZ sectional view showing the configuration of the illumination optical system of Example 1 at α = 0.75. FIG. 6 is an XZ sectional view showing the configuration of the illumination optical system of Example 1 at α = 0.65. XZ section which shows the structure of the illumination optical system which is Example 2 of this invention. FIG. 6 is a YZ cross section showing the configuration of the illumination optical system of Example 2. FIG. 6 is a perspective view of a first fly's eye lens used in the illumination optical system of Example 2. FIG. 6 is a perspective view of a second fly's eye lens used in the illumination optical system of Example 2. XZ sectional drawing which shows the structure by (beta) = 0.85 and (gamma) = 0.70 of the illumination optical system of Example 2. FIG. YZ sectional drawing which shows the structure by (beta) = 0.85 and (gamma) = 0.70 of the illumination optical system of Example 2. FIG. XZ sectional drawing which shows the structure by (beta) = 0.76 and (gamma) = 0.62 of the illumination optical system of Example 2. FIG. YZ sectional drawing which shows the structure by (beta) = 0.76 and (gamma) = 0.62 of the illumination optical system of Example 2. FIG. XZ sectional drawing which shows the structure of the illumination optical system which is Example 3 of this invention. FIG. 10 is a diagram showing the shape of a variable aperture stop used in the illumination optical system of Example 3. XZ sectional drawing which shows the structure by (alpha) = 0.75 of the illumination optical system which is Example 4 of this invention. FIG. 10 is a diagram showing the shape of an aperture stop used in the illumination optical system of Example 4. XZ sectional drawing which shows the structure by (alpha) = 0.65 of the illumination optical system of Example 4. FIG. XZ sectional drawing which shows the structure of the illumination optical system (phi1) which is Example 5 of this invention. XZ sectional drawing which shows the structure of the illumination optical system (phi2) of Example 5. FIG. FIG. 6 is a diagram showing an optical configuration of a liquid crystal projector using the illumination optical system of Examples 1 to 5.

Explanation of symbols

101, 151, 201 Light source 102, 152, 202 Parabolic reflector
103, 153, 203 First lens 104, 154, 204 Second lens 105, 205 Third lens 106, 155 First fly-eye lens 107, 156 Second fly-eye lens 108, 157, 210 Polarization conversion Elements 109, 158, 211 Condenser lenses 110, 159, 212 Liquid crystal panel 31 Polarization separation surface 32 Reflecting surface 33 Half wave plate 34 Light shielding plate 35 First transmissive member 36 Second transmissive member 171 Variable aperture stop 172 192 Shading plate 191 Aperture stop 206 Rod integrator

Claims (7)

The illumination optical system of the image projection apparatus for guiding a light beam from a light source to an image display element via an illumination optical system and projecting the light beam from the image display element onto a projection surface,
A light beam dividing means for dividing a light beam from the light source into a plurality of light beams, and forming a plurality of light source images on the plurality of light beams;
Condensing means for superimposing a plurality of light beams from the light beam dividing means on the image display element;
A light beam control optical system that is disposed closer to the light source than the light collecting means and compresses the light beam;
The light flux controlling optical system includes two or more optical elements, and changes the compressibility of the light flux by moving at least two of the two or more optical elements in the optical axis direction. Illumination optical system.   The light flux controlling optical system includes three or more optical elements, and the compression rate is changed by moving at least two of the three or more optical elements in the optical axis direction. The illumination optical system according to claim 1.   The illumination optical system according to claim 1, wherein the at least two optical elements move so as not to change positions in an optical axis direction where the plurality of light source images are formed.   The illumination optical system according to any one of claims 1 to 3, further comprising a light shielding unit that moves in accordance with movement of the at least two optical elements in an optical axis direction.   5. The illumination optical system according to claim 1, wherein the light beam splitting unit includes a lens array including a plurality of lens cells or a rod integrator. A polarization conversion element that converts non-polarized light from the light source into linearly polarized light having a specific polarization direction;
The illumination optical system according to claim 1, wherein the light flux controlling optical system is provided on a light source side with respect to the polarization conversion element. A light source;
The illumination optical system according to any one of claims 1 to 6,
An image display element to which a light beam from the illumination optical system is guided;
An image projection apparatus comprising: a projection optical system that projects a light beam from the image display element onto a projection surface.