JP2007212735A - Illuminating optical system and image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminating optical system in which brightness on an illuminated surface is almost uniform even though the angle distribution of a luminous flux on a specific cross-section is made small, and which is hardly affected by the nonuniform luminance of a light source and is high in the availability of light ray. <P>SOLUTION: The illuminating optical system divides a luminous flux from a light source 1 into a plurality of first luminous fluxes at least in a first cross-section (XZ cross-section), and causes the plurality of first luminous fluxes to overlap one another on an illuminated surface. The optical system that divides the luminous flux from the light source includes, in order from the light source side, a first lens array 6 and a second lens array 7, each having a plurality of eccentric lens cells. The first and second lens array have refractive powers the signs of which are the same. In addition, the faces in which the lens cells of the first and second lens arrays are formed are directed in the same direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination optical system that illuminates a surface to be illuminated using a light beam from a light source, and more particularly to an image projection apparatus that projects an image by illuminating a light modulation element such as a liquid crystal panel with light from the illumination optical system. The present invention relates to a suitable illumination optical system.

  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 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. For this reason, when an optical element with sensitive angular characteristics, particularly an optical element having a dichroic film or a polarization separation film inclined with respect to the optical axis, is disposed in the optical system, brightness unevenness (color unevenness) and contrast decrease. Degradation of image quality occurs.

  In order to prevent such image quality degradation, there is an asymmetric optical system in which the angular distribution of the light beam is reduced in the direction sensitive to the angular distribution in the optical element and the angular distribution of the light beam is increased in the direction insensitive to the angular distribution. Proposed.

  For example, Patent Document 1 discloses an optical system using a cylindrical lens array in which cylindrical lens cells are arranged in a one-dimensional direction as an optical integrator. In this optical system, color unevenness is reduced by using Koehler illumination with respect to the bending direction of a light beam by an optical element having high angle sensitivity such as a dichroic mirror.

In Patent Document 2, a diaphragm is arranged at the pupil position in a direction where the angle sensitivity of the thin film optical element is high, thereby reducing the angle distribution in one cross-sectional direction of the light beam and improving the contrast. .
Japanese Patent Laid-Open No. 06-75200 (paragraphs 0017 to 0018, FIG. 1, etc.) Japanese Unexamined Patent Publication No. 2004-45907 (paragraphs 0012 to 0013, FIG. 1, etc.)

  However, in the optical system disclosed in Patent Document 1, since the cylindrical lens array does not perform superimposing illumination in a section where the cylindrical lens array does not have refractive power (Kohler illumination section), the illuminance distribution on the liquid crystal panel surface is uneven. Is likely to occur. Accordingly, only a relatively flat region of the uneven illumination distribution must be used for panel illumination, and the light utilization efficiency is low.

  Further, in the optical system disclosed in Patent Document 1, since the luminous flux from the light source to the condensing lens (field lens) disposed immediately before the liquid crystal panel has a small angular distribution, the distance between the light source and the condensing lens is small. Degradation of the image quality at the dichroic mirror arranged in is reduced. However, since the light flux is converged by the condensing lens immediately before the liquid crystal panel, image quality deterioration due to an optical element having high angle sensitivity such as a liquid crystal panel and a dichroic mirror disposed behind the liquid crystal panel is inevitable.

  Furthermore, in the cross section where no overlapping illumination is performed, when the light source has uneven brightness due to fluctuations in the light source (arc jump, deterioration, etc.), the illuminance distribution on the liquid crystal panel also fluctuates and bright on the projected image It appears as samurai.

  Further, in the optical system disclosed in Patent Document 2, since the illumination is superimposed on two orthogonal cross sections, it is difficult to be affected by the light source. Is significantly reduced.

  Further, in Patent Document 2, instead of the diaphragm, the principal point position of the optical system between the lens array and the liquid crystal panel is made different between the two cross sections, whereby the angular distributions in the two cross sections are made different from each other. There is a description. However, in the method of changing the principal point of the collimator lens described in the example of Patent Document 2, the boundary of the illumination area on the liquid crystal panel surface becomes unclear, resulting in reduced brightness and uneven illuminance. In addition, the telecentric condition on the panel side of the illumination optical system, that is, the condition that the exit pupil is sufficiently distant from the panel surface is broken, resulting in a decrease in contrast and color unevenness.

  The present invention provides illumination optics that reduces the angular distribution of the light flux in a specific cross section, has almost uniform brightness on the surface to be illuminated, is not easily affected by luminance unevenness of the light source, and has high light use efficiency. An object is to provide a system and an image projection apparatus including the system.

  An illumination optical system according to one aspect of the present invention divides a light beam from a light source into a plurality of first light beams at least in a first cross section, and superimposes the plurality of first light beams on an illuminated surface. It is an optical system. The optical system that splits the light flux from the light source includes a first lens array and a second lens array that are arranged in order from the light source side and each have a plurality of eccentric lens cells. The lens arrays have the same refracting power, and the surfaces of the first and second lens arrays on which the lens cells are formed are oriented in the same direction.

  According to the present invention, it is possible to realize an illumination optical system in which the angular distribution of the light flux in at least the first cross section is small, the surface to be illuminated can be illuminated almost uniformly, and the light utilization efficiency is high. By configuring the optical system of the image projection apparatus using the illumination optical system, it is possible to project a bright, uniform image with high contrast.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show the configuration of an illumination optical system that is Embodiment 1 of the present invention. The illumination optical system illuminates a reflective liquid crystal panel (however, may be a transmissive type) 11 as a light modulation element disposed on an illuminated surface via an optical block 10. The illumination optical system of this embodiment is used in a projector that displays an image by projecting a light beam that has been image-modulated by the liquid crystal panel 11.

  In this embodiment, the optical axis of the illumination optical system (for example, defined by an axis line from the center of the liquid crystal panel 11 through the center of the condenser lens 8 to the lamp) is defined as the Z axis, and a direction parallel to the Z axis is defined. The optical axis direction.

  FIG. 1 is a cross section of YZ having a wider angle distribution of incident light flux on the panel surface of the liquid crystal panel 11 among the YZ plane and the XZ plane which are two planes including the Z axis and orthogonal to the Z axis. The optical structure in a surface (2nd cross section) is shown. The YZ plane is a cross section parallel to the direction in which the long side of the liquid crystal panel 11 extends. FIG. 2 shows an optical configuration on an XZ plane (first cross section) which is a cross section having a narrower angle distribution of incident light beams on the panel surface. The XZ plane is a cross section parallel to the direction in which the short side of the liquid crystal panel 11 extends.

  In these figures, only basic components of the illumination optical system are not shown, but in reality, a polarization conversion element that converts non-polarized light from the light source into linearly polarized light, a mirror that bends the optical path, and a heat ray cut filter Various optical elements such as polarizing plates are also arranged.

  On the YZ plane shown in FIG. 1, the light beam emitted from the arc tube 1 such as a high-pressure mercury discharge tube is emitted into a parallel light beam by the paraboloid reflector 2. The arc tube 1 and the reflector 2 constitute a light source lamp.

  The parallel luminous flux from the lamp is divided into a plurality of luminous fluxes by the third cylindrical lens array 3 whose perspective view is shown in FIG. 3, and each of the divided luminous fluxes is condensed. Each split light beam is condensed toward the position of the incident surface of the fourth cylindrical lens array 4 or the vicinity thereof, and forms a secondary light source image here.

  The state of the secondary light source image formed by the action of the third cylindrical lens array 3 in the present embodiment is shown in FIG. FIG. 4 shows the intensity distribution of the secondary light source image on a plane orthogonal to the optical axis direction. In FIG. 4, the YZ plane is a plane indicated by a one-dot chain line in the drawing. The width of the region where the secondary light source image is formed on the YZ plane is W1.

  The width W1 of the light source image forming region at the position where the secondary light source image is formed is the largest of the widths of the region obtained when the light source image forming region is cut in various cross sections parallel to the YZ plane. Or it is set as the width | variety obtained when it cuts with a YZ surface.

  Since the third and fourth cylindrical lens arrays 3 and 4 have a refractive power only in a direction parallel to the YZ plane, the light flux is not substantially affected in the XZ plane orthogonal to the YZ plane.

  On the other hand, the positive lens 5 that constitutes a part of the compression optical system on the XZ plane, the first cylindrical lens array 6, the second cylindrical lens array 7, and the cylindrical lens 9 do not have refractive power on the YZ plane. . Accordingly, the divided light beam emitted from the fourth cylindrical lens array 4 is collected by the condenser lens 8 without being affected by these optical elements on the YZ plane. The compression optical system is preferably an afocal optical system that emits a parallel light beam while narrowing the beam diameter of the parallel light beam, and the afocal compression optical system is also used in this embodiment. This will be described later.

  In FIG. 1, a plurality of split light beams emitted from the condenser lens 8 are superimposed on each other on the reflective liquid crystal panel 11 via the optical block 10. Thereby, on the YZ plane, the reflective liquid crystal panel 11 is overlaid with a plurality of divided light beams.

  Here, the optical block 10 indicates a so-called color separation / synthesis optical system. In the color separation optical system 10, an optical element having an optical film surface (multilayer film surface) disposed to be inclined with respect to the optical axis direction of the illumination optical system is disposed. For example, a polarization beam splitter having a polarization separation film surface, a dichroic mirror and a dichroic prism having a dichroic film surface. The inclination of the optical film surface with respect to the optical axis direction is generally set to 45 degrees and is often set in the range of 42 to 48 degrees.

  The polarization beam splitter (polarization separation film) has a separation characteristic depending on 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). 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.

  In the XZ plane shown in FIG. 2, the light beam emitted from the lamp as a parallel light beam is not affected by the third and fourth cylindrical lens arrays 3 and 4, and is a positive lens that is a part of the afocal compression optical system. 5, the first cylindrical lens array 6 is reached. FIG. 6 shows a perspective view of the first cylindrical lens array 6.

  As shown in FIG. 6, one surface of the first cylindrical lens array 6 has a shape in which a plurality of cylindrical lens cells 6a are formed on a concave surface having a concave shape only in the XZ plane. In other words, the first cylindrical lens array 6 is an optical element having both a negative lens function and a lens array function (light beam splitting function). The surface on which the plurality of cylindrical lens cells 6 a are formed is referred to as a lens cell formation surface of the first cylindrical lens array 6.

  Here, “the function of the negative lens” means that the light beam incident on the center of each lens cell of the cylindrical lens array exhibits the same characteristics as the negative lens. In other words, the center of curvature of each lens cell (the optical axis of each lens cell) is shifted outward (outside the optical axis of the illumination optical system) with respect to the center of each lens cell. This constitutes a cylindrical lens array. If comprised in this way, a cylindrical lens array will function as a negative lens with respect to the light which injects into the center of each lens cell.

  Each lens cell of the cylindrical lens array has a positive refractive power in order to have a function of dividing incident light into partial light beams (light beam dividing function).

  FIG. 7 shows a side view of the first cylindrical lens array 6. The first cylindrical lens array 6 plays the role of a negative lens as a whole by decentering the apex 6c of the lens cell 6a from the center 6b of each cylindrical lens cell 6a.

  The afocal compression optical system includes a positive lens 5 and a first cylindrical lens array 6 in order from the light source side. A parallel light beam from the lamp is compressed by the afocal compression optical system and is divided into a plurality of light beams by the first cylindrical lens array 6. Each split light beam is condensed toward the position of the incident surface of the second cylindrical lens array 7 or the vicinity thereof to form a secondary light source image.

  FIG. 5 shows a state of the secondary light source image formed by the action of the first cylindrical lens array 6 in the present embodiment. FIG. 5 shows the intensity distribution of the secondary light source image on a plane orthogonal to the optical axis direction. In FIG. 5, the XZ plane is a plane indicated by a one-dot chain line in the drawing. In the XZ plane, the width of the region where the secondary light source image is formed is W2.

As can be seen by comparing FIG. 4 and FIG. 5, the width W2 of the light source image forming area on the XZ plane is narrower than the width W1 of the light source image forming area on the YZ plane. The magnitude relationship (ratio) between W1 and W2 becomes the magnitude relationship (ratio) of the angle distribution in the polarization beam splitter as it is. For this reason,
W2 <W1
Preferably,
1 <W2 / W1 <0.8 (1)
It is desirable to satisfy this condition.

  In this conditional expression (1), if W2 / W1 exceeds the upper limit, effects such as an increase in contrast cannot be obtained sufficiently. If W2 / W1 falls below the lower limit value, the light beam divided and condensed by an arbitrary lens cell 6a of the first cylindrical lens array 6 does not enter the corresponding lens cell of the second cylindrical lens array 7 and does not correspond. The rate of incidence on the lens cell increases. The light beam that has not entered the corresponding lens cell reaches a position outside the effective area (light modulation area in the liquid crystal panel) on the surface to be illuminated, and thus does not become an effective light beam as an illumination light beam. And if the ratio of the light beam that does not reach the effective area of the illuminated surface increases, the brightness of the projected image is greatly reduced. If the lower limit value of conditional expression (1) is thus exceeded, the light utilization efficiency decreases, which is not preferable.

  Here, W1 and W2 may be the light beam diameter on the YZ plane of the light beam incident on the fourth cylindrical lens array 4 and the light beam diameter on the XZ surface of the light beam incident on the second cylindrical lens array 7, respectively.

  The split luminous flux emitted from the second cylindrical lens array 7 is collected by the cylindrical lens 9 and is superimposed on the reflective liquid crystal panel 11 through the color separation optical system 10 including a polarization beam splitter and the like. Thereby, on the XZ plane, the reflective liquid crystal panel 11 is superimposedly illuminated with a plurality of divided light beams.

  Similarly to the first cylindrical lens array 6 shown in FIGS. 6 and 7, the second cylindrical lens array 7 has a plurality of cylindrical lens cells (FIG. 9) on a concave surface having a concave shape only in the XZ plane. 7a) is arranged. The second cylindrical lens array 7 also serves as a negative lens as a whole by decentering the apex of the lens cell from the center of each cylindrical lens cell. That is, the second cylindrical lens array 7 is also an optical element having both a negative lens function and a lens array function. The surface on which the plurality of cylindrical lens cells are formed is referred to as a lens cell forming surface of the second cylindrical lens array 7.

  The negative lens action of the second cylindrical lens array 7 and the cylindrical lens 9 that is a positive lens constitute a retrofocus type superimposing optical system. By making the superimposing optical system a retrofocus type, the back focus becomes longer and the color separation optical system 10 can be easily arranged.

  In the present embodiment, the condenser lens 8 does not have a refractive power on the XZ plane, and therefore does not substantially affect the light flux. However, the condenser lens 8 may be a spherical lens, and the superimposing optical system may be configured including the condenser lens 8.

  In this embodiment, the lens cell forming surfaces of the first and second cylindrical lens arrays 6 and 7 are both directed to the illuminated surface side, that is, the liquid crystal panel 11 side. Hereinafter, this technical reason will be described in detail with reference to FIGS.

  FIG. 8 shows a schematic diagram of an illumination optical system using a conventional lens array. The light beam is divided by the lens array A51 and the lens array B52, and the divided light beam is superimposed by the condenser lens 53 to illuminate the liquid crystal panel 54. In this case, each lens cell of the lens array A53 acts to superimpose the illumination light beam on the liquid crystal panel 54.

Here, the cell pitch of the lens array A53 is a, the focal length of the condenser lens 53 is f, the distance between the corresponding lens cell surfaces of the lens array A53 and the lens cell B54 is d, and the size (height) of the liquid crystal panel 54 is B. Then,
B = a × (f / d) (2)
The relational expression of

  From this equation (2), it can be seen that the illumination area becomes narrower as the distance d between the lens cell surfaces becomes longer, and the illumination area becomes wider as it becomes shorter.

In the first and second cylindrical lens arrays 6 and 7 having the shape shown in FIG. 6 of the present embodiment and having the function of a negative lens, the thickness increases toward the outer lens cell when viewed from the center of the cylindrical lens array. When the light beam is split by the lens array having such a shape, the lens cell forming surfaces of the first and second cylindrical lens arrays 6 and 7 are preferably directed in the same direction as shown in FIG. This is because the difference between the lens cell surface distances d can be reduced in the plurality of corresponding lens cells in the first and second cylindrical lens arrays 6 and 7.

As shown in FIG. 10, when the lens cell formation surfaces of both cylindrical lens arrays are directed in opposite directions, the difference in the distance d between the lens cell surfaces in a plurality of corresponding lens cells becomes large. For this reason, the illumination area formed by the outer lens cell is narrower than the central lens cell, and the size of the entire illumination area on the liquid crystal panel is insufficient, or the illumination area formed by the outer lens cell is smaller. The amount of light may decrease due to widening.

With the above configuration, as shown in FIGS. 1 and 2, the angular distribution of the illumination light beam after passing through the last optical element having refractive power in the illumination optical system is narrower in the XZ plane than in the YZ plane. .

  The polarizing beam splitter included in the color separation optical system 10 disposed in front of the reflective liquid crystal panel 11 bends a part of the optical path of the incident light beam on the XZ plane. A polarization beam splitter having a general dielectric multilayer film as a polarization separation film performs polarization separation using a difference in reflectance with respect to P-polarized light and S-polarized light at the Brewster angle. For this reason, polarized light separation becomes insufficient as the light beam deviates from the Brewster angle. That is, when an illumination light beam having a wide angular distribution is incident on the polarization separation film, the polarized light to be transmitted is reflected or the polarized light to be reflected is transmitted. As a result, polarized light (leakage light) different from the desired polarized light is incident on the liquid crystal panel or the like, thereby reducing the contrast of the image.

  In this embodiment, a cross section in which a desired effect such as polarization separation is not sufficiently obtained when the angle distribution of the incident light beam is wide is referred to as a cross section sensitive to the angle distribution in this embodiment. A cross section in which a desired effect is sufficiently obtained even when the angle distribution of the incident light beam is wide is called a cross section insensitive to the angle distribution.

  On the other hand, in this embodiment, the angular distribution in the cross section (XZ plane) sensitive to the angular distribution of the light beam is made smaller than the angular distribution in the cross section (YZ plane) insensitive to the angular distribution. For this reason, the amount of leakage light generated in the cross section sensitive to the angular distribution of the luminous flux is suppressed, and as a result, a high contrast image can be obtained. Moreover, the light utilization efficiency is high.

  In this embodiment, the diameter of the light source image forming region is made different between the first and second cross sections by compressing the diameter of the light flux from the lamp in the first cross section without compressing the diameter of the light flux from the lamp in the second cross section. Let However, the present invention is not limited to such a configuration. For example, the beam diameter may be compressed in both the first cross section and the second cross section. Further, the light beam diameter may be compressed in one cross section and the light beam diameter may be expanded in the other cross section. Furthermore, the beam diameter may be enlarged in both the first and second cross sections. Further, the light beam diameter may be compressed by using an elliptical reflector instead of the parabolic reflector 2. That is, the width of the light source image forming area is different between the first cross section and the second cross section, and the width of the light source image forming area in the cross section sensitive to the angular distribution of the light beam is in the cross section insensitive to the angular distribution. Any configuration may be used as long as the configuration is smaller than the width.

  In a projector, a polarization conversion element (an element in which a polarization beam splitter is configured in an array) may be disposed near the lens array in order to increase the light utilization efficiency. In the present embodiment, although not shown, it is desirable to dispose on the rear side of the fourth cylindrical lens array 4 or the rear side of the second cylindrical lens array 7. In particular, when the polarization conversion element is disposed on the rear side of the second cylindrical lens array 7 through which the compressed light beam passes, the polarization conversion element can be reduced in size as compared with the conventional case. As a result, the entire optical system and projector can be reduced in size and cost.

  In the present embodiment, the case where both the lens cell forming surfaces of the first and second cylindrical lens arrays 6 and 7 are directed to the illuminated surface side is described, but both may be directed to the light source side.

  In this embodiment, the case where two cylindrical lens arrays each having power in the cross section are provided for each cross section (XZ plane, YZ plane) may be provided.

  FIG. 11 shows an illumination optical system that is Embodiment 2 of the present invention. The configuration in which the lens cell surfaces of the pair of lens arrays described in the first embodiment are directed in the same direction is not only the case where the configuration of the optical system is different between the first cross section and the second cross section as in the first embodiment, but also the first This is also effective when the cross section and the second cross section have the same optical system configuration. That is, the configuration of the optical system shown in FIG. 11 is common to the first cross section and the second cross section.

  The light beam emitted from the arc tube 21 is emitted as a light beam focused by the ellipsoidal reflector 22. The arc tube 21 and the reflector 22 constitute a light source lamp.

  The luminous flux from the lamp is divided by the first lens array 23 into a plurality of luminous fluxes in which the central luminous flux advances in parallel, and each divided luminous flux is condensed toward the incident surface of the second lens array 24 or the vicinity thereof. One side of each of the first and second lens arrays 23 and 24 has a shape in which a plurality of lens cells 23a and 24a are formed on a concave surface having a concave shape in the first and second cross sections. In each lens array, the lens cells are arranged in a two-dimensional direction. Each split light beam emitted from the first lens array 23 forms a secondary light source image on or near the incident surface of the second lens array 24.

  In this embodiment, the compression optical system is configured by the functions of the elliptical reflector 22 and the negative lens of the first lens array 23. Thereby, the size from the lamp to the first and second lens arrays 23 and 24 is reduced.

  A plurality of split light beams emitted from the second lens array 24 are collected by the condenser lens 25 and illuminate the reflective liquid crystal panel 27 in a superimposed manner through a color separation optical system 26 including a polarization beam splitter and the like.

  The second lens array 24 also has the same shape as the first lens array 23 as described above, and has both a negative lens function and a lens array function.

  In this embodiment, a retrofocus type superposition optical system is configured by the function of the negative lens of the second lens array 24 and the function of the condenser lens 25 as a positive lens. As in the first embodiment, by using a retrofocus type superimposing optical system, the back focus becomes longer and the color separation optical system 26 can be easily arranged.

  Further, by directing the lens array forming surfaces of the first and second lens arrays 23 and 24 in the same direction, the difference in distance between the lens cell surfaces in a plurality of corresponding lens cells can be reduced as in the first embodiment. It is possible to make the brightness uniform in the illumination area and improve the brightness.

  In the present embodiment, the first and second lens arrays 23 and 24 have a negative lens function, but the present invention is not limited to this. For example, one surface of both lens arrays may have a shape in which a plurality of lens cells are arranged on a convex surface, and the lens array may have a positive lens function. In this case, for example, a compression optical system having a positive and positive refractive power configuration is configured by the elliptical reflector and the first lens array, and the second lens array is configured to handle all or part of the positive refractive power of the condenser lens. be able to.

  FIG. 12 shows a configuration of a liquid crystal projector (image projection apparatus) using the illumination optical system described in the first embodiment. FIG. 12 shows a configuration in a cross section including the XZ plane in the first embodiment.

  In the figure, 41 is an arc tube that emits white light in a continuous spectrum, and 42 is a reflector that collects light from the arc tube 41 in a predetermined direction. A light source lamp 40 is configured by the arc tube 41 and the reflector 42.

  Reference numeral 100 denotes the illumination optical system described in the first embodiment.

  Reference numeral 58 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). Reference numeral 59 denotes a G 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 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 red wavelength plate, a green wavelength plate, and a blue wavelength plate, 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. Reference numeral 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 58 to the third polarizing beam splitter 69 constitute a color separation / synthesis optical system 200.

  Reference numeral 70 denotes a projection lens, and the illumination optical system 100, the color separation / synthesis optical system 200, and the projection lens 70 constitute an image display optical system.

  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 58 enters the incident side polarizing plate 59. The G light remains S-polarized light after being decomposed by the dichroic mirror 58. The G light exits from the incident-side polarizing plate 59, 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 liquid crystal drive circuit 250 drives each reflective liquid crystal panel based on image (video) information input from the image supply device 300, and forms an original image for each color. 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 58 enter the incident side polarizing plate 64. The R and B lights remain S-polarized 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 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 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, and is reflected by the G-use 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. For this reason, it is reflected again by the polarization separation surface of the first polarization beam splitter 60, passes through the incident side polarizing plate 59, returns 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 58 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. Accordingly, the R light remains as S-polarized light even after being reflected by the R reflective liquid crystal panel 61R. 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. Thereby, black display is performed.

  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.

  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.

The figure which shows the structure (2nd cross section) of the illumination optical system which is Example 1 of this invention. 1 is a diagram illustrating a configuration (first cross section) of an illumination optical system according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating a cylindrical lens array of the illumination optical system according to the first embodiment. FIG. 3 is a diagram showing a light source image forming region by the cylindrical lens array of Example 1. FIG. 3 is a diagram illustrating a light source image forming region by a cylindrical lens array in the first embodiment. 1 is a perspective view of a cylindrical lens array in Embodiment 1. FIG. 2 is a side view of a cylindrical lens array in Embodiment 1. FIG. 1 is a schematic diagram of a general illumination optical system using a lens array. The figure which shows the effect in case the direction of a lens array is the same direction. The figure which shows the fault when the direction of a lens array is a reverse direction. The figure which shows the structure (1st, 2 cross section) of the illumination optical system which is an Example of this invention. FIG. 6 is a diagram illustrating a configuration of a projector that is Embodiment 3 of the present invention.

Explanation of symbols

1, 2, 41, Light-emitting tube 2, 22, 42 Reflector 3 Third cylindrical lens array 4 Fourth cylindrical lens array 5 Positive lens 6 First cylindrical lens array 7 Second cylindrical lens array 8 Condenser lens 9 Cylindrical lenses 10, 26, 200 Color separation / synthesis optical system 11, 27, 61R, 61G, 61B Reflective liquid crystal panel 23 First lens array 24 Second lens array 25 Condenser lens 100 Illumination optical system

Claims (9)

An illumination optical system that divides a light beam from a light source into a plurality of first light beams and superimposes the plurality of first light beams on an illuminated surface at least in a first cross section,
The optical system for splitting the light flux from the light source includes a first lens array and a second lens array, which are arranged in order from the light source side and each have a plurality of eccentric lens cells,
The first and second lens arrays have the same refractive power as each other;
An illumination optical system, wherein surfaces of the first and second lens arrays on which the lens cells are formed are oriented in the same direction.   2. The illumination optical system according to claim 1, wherein a surface of the first and second lens arrays on which the lens cells are formed faces the direction of the illumination target. In the first cross section, the illumination optical system compresses the light beam from the light source and then divides the light beam into the plurality of first light beams, and superimposes the plurality of first light beams on the illuminated surface,
The optical system for compressing the light beam from the light source is an afocal system including a first optical element having a positive refractive power and a first lens array having a negative refractive power, which are arranged in order from the light source side. Yes,
The optical system for superimposing the first light beam includes the second lens array having negative refractive power and the second optical element having positive refractive power, which are arranged in order from the light source side. The illumination optical system according to claim 1 or 2. In a second cross section orthogonal to the first cross section, the illumination optical system includes:
A third and a fourth lens array, which are arranged in order from the light source side, and divide the light beam from the light source into a plurality of second light beams;
The illumination optical system according to claim 3, further comprising: a third optical element having a positive refractive power that superimposes the plurality of second light beams on the surface to be illuminated.   5. The illumination optical system according to claim 1, wherein in each of the first and second lens arrays, each of the lens cells has a positive refractive power.   The width of the light beam incident on the first lens array in the first cross section is smaller than the width of the light beam incident on the third lens array in the second cross section. The illumination optical system described. The illumination optical system according to any one of claims 1 to 6,
A light modulation element illuminated by a light beam from the illumination optical system;
An optical system comprising: a projection optical system that projects a light beam from the light modulation element. An optical element having an optical film is disposed between the illumination optical system and the light modulation element,
The optical system according to claim 7, wherein the first cross section is a surface parallel to an optical axis direction of the illumination optical system and a direction in which a normal line of the optical film extends. An image projection apparatus comprising the optical system according to claim 7.