JP2008256979A - Illumination optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination optical system for providing illuminating luminous flux having isotropic NA distribution with compact constitution equipped with a laser array light source. <P>SOLUTION: The illumination optical system IL1 for illuminating the image display surface 10a of a display element 10 has a laser array light source 1 which emits illuminating light having a flat beam cross section, and a rod integrator 8 whose cross-sectional shape is quadrate and which uniformizes spatial energy distribution of the illuminating light. When the illuminating light is made incident on the rod integrator 8, the longitudinal direction of the beam cross section of the illuminating light and the side direction of the cross-sectional shape of the rod integrator 8 form a predetermined angle which is neither parallel nor perpendicular on a cross section perpendicular to the incident direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an illumination optical system. For example, in an image projection apparatus using a digital micromirror device or LCD (liquid crystal display) as a display element, the image display surface of the display element is illuminated. The present invention relates to an illumination optical system.

  Surface emitting semiconductor laser arrays are attracting attention as light sources for projectors. Since the light source array of this semiconductor laser array is often a very flat array, for example, 1 column or 2 columns × 10 columns, when illumination is performed with such a laser array light source, the NA (numerical aperture) of the illumination light is increased. ) Will vary greatly depending on the direction. On the other hand, an optical system such as a projection lens used in a projector has an isotropic NA.

  With illumination light with a flat NA as described above, if the optical system is adjusted to a smaller NA, the NA component with the larger illumination light cannot be transmitted. On the other hand, if the optical system is adjusted to the larger NA, the overall size of the optical system may be increased, resulting in poor efficiency. Further, when the optical system is adjusted to an NA having a larger illumination light with an appropriate NA (for example, NA = 0.2), the NA in the smaller direction of the illumination light becomes considerably smaller (for example, NA = 0.025). The smaller resolution cannot be obtained. Thus, when the laser array light source is used, there is a problem that the NA distribution becomes flat.

Examples of the illumination optical system using a light source having a flat NA distribution include those described in Patent Documents 1 to 3.
US Pat. No. 6,856,727 US Pat. No. 5,704,700 JP-A-2005-300823

  The light source described in Patent Document 1 is not a laser array light source, but a tapered rod is used in the illumination optical system in order to correct a flat NA distribution to an isotropic NA distribution. However, it is difficult to manufacture a tapered rod as an integrator, and its use increases the cost and causes the entire illumination optical system to increase in size. For this reason, there is a demand for an illumination optical system that can provide high illumination efficiency even when a rod integrator having a general quadrangular prism shape (a rectangular parallelepiped shape or the like) is used.

  In the illumination optical system described in Patent Document 2, a laser array is used as a light source, and a uniform illuminance distribution is obtained by a pair of lens arrays. However, the isotropy of NA is not taken into consideration, and the problems caused by the flat NA distribution are not solved.

  The illumination optical system described in Patent Document 3 has a configuration in which a light beam from a laser array is incident on a rod integrator via an optical fiber. Then, an optical fiber is disposed obliquely with respect to the rod incident surface and is incident from an oblique direction, thereby taking a countermeasure against return light. However, the isotropy of NA is not taken into consideration, and the problems caused by the flat NA distribution are not solved.

  The present invention has been made in view of such a situation, and an object thereof is to provide an illumination light beam having an isotropic NA distribution while having a laser array light source and a compact configuration. It is to provide an optical system.

  In order to achieve the above object, an illumination optical system according to a first aspect of the present invention is an illumination optical system for illuminating an image display surface of a display element, and includes a laser array light source that emits illumination light having a flat light beam section, The cross-sectional shape is a quadrilateral and has a rod integrator that uniformizes the spatial energy distribution of the illumination light, and when the illumination light is incident on the rod integrator, in a cross section perpendicular to the incident direction, The longitudinal direction of the cross section of the luminous flux of the illumination light and the side direction of the cross section of the rod integrator form a predetermined angle that is neither parallel nor perpendicular.

  The illumination optical system according to a second aspect is characterized in that, in the first aspect, the predetermined angle is 20 ° to 70 °.

  The illumination optical system according to a third aspect is characterized in that, in the first aspect, the predetermined angle is 45 ° or substantially 45 °.

  The illumination optical system according to a fourth aspect of the present invention further includes a lens for diverging or condensing the illumination light from the laser array light source so as to be incident on the rod integrator in any one of the first to third aspects of the invention. It is characterized by.

  The illumination optical system according to a fifth aspect of the present invention is characterized in that, in the fourth aspect of the invention, a central axis of the light beam of the illumination light and a central axis of the lens are relatively decentered.

  The illumination optical system according to a sixth aspect of the present invention is characterized in that, in the fifth aspect, the decentering direction is a short direction of a cross section of the luminous flux of the illumination light.

  The illumination optical system according to a seventh aspect of the present invention is the illumination optical system according to any one of the first to sixth aspects, wherein all light beams having a maximum NA in the longitudinal direction of the light beam cross section of the illumination light constitute the inner surface of the rod integrator. Each surface is reflected twice or more.

  An illumination optical system according to an eighth invention is the illumination optical system according to any one of the first to seventh inventions, wherein the rod integrator includes two rod integrators, a first rod integrator and a second rod integrator, sequentially from the laser array light source side. When the illumination light is incident on the first rod integrator, the longitudinal direction of the light beam cross section of the illumination light and the side direction of the cross sectional shape of the first rod integrator when the illumination light is incident on the first rod integrator Are formed in a predetermined angle that is neither parallel nor vertical, and in a cross section perpendicular to the incident direction of the illumination light to the second rod integrator, the side direction of the cross-sectional shape of the first rod integrator, and the second The side direction of the cross-sectional shape of the rod integrator forms a predetermined angle that is neither parallel nor perpendicular.

  The illumination optical system according to a ninth aspect of the present invention is the illumination optical system according to the eighth aspect, wherein a light beam incident on the second rod integrator has a cross section perpendicular to the incident direction of the illumination light to the second rod integrator. The longitudinal direction and the side direction of the cross-sectional shape of the second rod integrator form a predetermined angle that is neither parallel nor perpendicular.

  In the illumination optical system according to a tenth aspect, in the eighth aspect, α is a predetermined angle formed by the long direction of the cross section of the light flux of the illumination light and the side direction of the cross section of the first rod integrator. When a predetermined angle formed by the side direction of the cross-sectional shape of the first rod integrator and the side direction of the cross-sectional shape of the second rod integrator is β, α = 45 ° and β = 22. 5 ° or α = 22.5 ° and β = 45 °.

  An illumination optical system according to an eleventh aspect of the present invention is the optical system according to any one of the first to tenth aspects, wherein the two laser array light sources are provided so that the illumination light emitted from each laser array light source travels in the same direction. A light beam combining member for combining the light beams, and in a cross section perpendicular to the traveling direction of the two light beams combined by the light beam combining member, the longitudinal direction of the cross sections of the two light beams has a predetermined angle that is not parallel. It is characterized by making.

  An illuminating optical system according to a twelfth aspect is characterized in that, in the eleventh aspect, the light beam combining member is a polarization beam splitter.

  The illumination optical system according to a thirteenth aspect of the present invention is the illumination system according to the eleventh or twelfth aspect, wherein a predetermined angle formed by the longitudinal direction of the cross section of the two light beams is γ, When a predetermined angle formed by the side direction of the cross-sectional shape of the rod integrator is δ, γ = 90 ° and δ = 22.5 °, or γ = 45 °, and It is characterized by δ = 45 °.

  The illumination optical system according to a fourteenth aspect of the present invention is the illumination optical system according to any one of the first to thirteenth aspects, wherein the laser array light source includes three laser array light sources that respectively emit illumination light of three primary colors R, G, and B The rod integrator further comprising an optical path synthesis member that synthesizes the illumination light emitted from each laser array light source into the same optical path, and the three light beams synthesized by the optical path synthesis member have the same divergence or condensing degree. It is characterized by being optically arranged so as to be incident on.

  The illumination optical system of the fifteenth aspect of the invention is characterized in that, in the fourteenth aspect of the invention, the optical path lengths from the laser array light sources to the rod integrator are equal.

  An image projection apparatus according to a sixteenth aspect includes the illumination optical system according to any one of the first to fifteenth aspects.

  According to the first invention, when the illumination light is incident on the rod integrator, the longitudinal direction of the light beam cross section of the illumination light and the side direction of the cross-sectional shape of the rod integrator are perpendicular to the incident direction. Since it is configured to form a predetermined angle that is neither parallel nor vertical, a flat NA distribution can be converted more isotropically. For example, when illumination light having a flat light beam cross section is incident with the predetermined angle α, the illumination light is emitted from the rod integrator in a state where the direction of large NA becomes two directions forming the angle 2α. . That is, the flat NA direction can be increased by one more direction, whereby the flat NA distribution can be converted into a more isotropic distribution. An illumination beam having an isotropic NA distribution can be obtained with a laser array light source and a compact configuration, so that a uniform illuminance distribution can be obtained while maintaining high illumination efficiency and high resolution. . Moreover, when illumination light with a flat beam cross section is incident on the rod integrator at a predetermined angle as described above, it can be easily reflected even on the reflecting surface in the short side direction of the cross section of the rod integrator. It becomes easier to obtain a proper illuminance distribution.

  Therefore, if the characteristic illumination optical system is used in an image projection apparatus (rear projector, front projector, etc.) as in the sixteenth aspect, the problems caused by the flat NA distribution unique to the laser array light source can be solved. Thus, the image projector can be greatly contributed to downsizing, cost reduction, high brightness, high performance, high functionality, and the like. An apparatus to which the illumination optical system according to the present invention is applied is not limited to an image projection apparatus. Any device that requires illumination light with an isotropic NA distribution is applicable.

  According to the second invention, when the illumination light is incident on the rod integrator, the longitudinal direction of the light beam cross section of the illumination light and the side direction of the cross-sectional shape of the rod integrator are perpendicular to the incident direction. Since the angle is 20 ° to 70 °, conversion to an isotropic NA distribution can be performed more effectively.

  Further, according to the third invention, when the illumination light is incident on the rod integrator, in the cross section perpendicular to the incident direction, the longitudinal direction of the light beam cross section of the illumination light, the side direction of the cross sectional shape of the rod integrator, Is configured to form an angle of 45 ° or approximately 45 °, and as a result of orthogonality of the direction of large NA, the most isotropic NA distribution can be achieved.

  According to the fourth aspect of the invention, the illumination light from the laser array light source is diverged or condensed by the lens, so that it is incident on the rod integrator at an angle. Therefore, the number of reflections in the rod integrator can be increased, and a uniform illuminance distribution can be obtained more easily.

  Further, according to the fifth invention, since the central axis of the luminous flux of the illumination light and the central axis of the lens are relatively decentered, the illumination light having a flat luminous flux section bends in an oblique direction and enters the rod integrator. Become. Since the NA increases in the oblique direction, the flat NA distribution can be converted more isotropically.

  For example, as in the sixth aspect of the invention, if the eccentric direction is set to the short direction of the cross section of the luminous flux of the illumination light, the illumination light incident on the rod integrator is inclined in a direction with a small NA, so that the NA in that direction increases and the NA The flatness of is more relaxed. In addition, if the lens is used without any eccentricity, it is difficult to make an angle in the direction of small NA. However, if the incident angle to the rod integrator is increased by decentering the lens in the direction of small NA, the rod integrator in the direction of small NA. Since the incident light on the surface is inclined, the number of reflections on the inner surface of the rod integrator in that direction can be increased. Therefore, it becomes easier to obtain a uniform illuminance distribution.

  According to the seventh aspect, the light beam having the maximum NA in the longitudinal direction of the cross section of the illumination light beam is reflected twice or more (that is, eight times or more on four surfaces) on all surfaces constituting the inner surface of the rod integrator. Therefore, it is possible to superimpose with five or more secondary light sources in each of the two directions (that is, five or more in the direction of small NA). Therefore, a uniform illuminance distribution can be obtained effectively.

  According to the eighth invention, since the rod integrator is composed of two parts, the first rod integrator and the second rod integrator, the first rod integrator increases the flat NA direction by one, and the second rod integrator Two more flat NA directions can be added. Therefore, the NA distribution can be made more isotropic. Also, in the case of a projector using a digital micromirror device, normally, when a light beam is incident at an angle of 45 ° in the side direction of the rod integrator cross section, the direction with a large NA is obliquely 45 ° to the projection screen. Become. However, since the pixel array is in the vertical and horizontal directions, the NA in this direction is relatively small, and the resolution may not be sufficient. If another function is added by dividing the rod integrator into two parts, the NA can be increased in the vertical and horizontal directions. In addition, since the light beam incident on the second rod integrator has two directions with a large NA, the number of reflections in the second rod integrator increases, and a uniform illuminance distribution is more easily obtained.

  Further, according to the ninth aspect, in the cross section perpendicular to the incident direction of the illumination light to the second rod integrator, for all light beams incident on the second rod integrator, the long direction of the light beam cross section, Since the side direction of the cross-sectional shape of the rod integrator forms a predetermined angle that is neither parallel nor perpendicular, the conversion to the isotropic NA distribution by the second rod integrator is performed more reliably and effectively. be able to.

  For example, as in the tenth invention, if α = 45 °, β = 22.5 °, or α = 22.5 °, β = 45 °, the NA increases in the direction of 45 ° every 4 °. Because of the direction, a more isotropic NA distribution can be achieved. In addition, when a digital micromirror device is used, the resolving power in the pixel arrangement direction can be ensured.

  According to the eleventh aspect of the invention, there are two laser array light sources, and the light beam combining member is configured to combine the light beams so that the illumination light emitted from each laser array light source travels in the same direction. Conversion to a square NA distribution can be performed more effectively. By using two laser array light sources in this way, a more isotropic NA distribution can be obtained as in the case of using two rod integrators. In addition, in this case, since the brightness can be doubled, the illumination optical system according to the present invention is most suitable for a high-power projector for cinema or the like. In addition, since the longitudinal direction of the cross-sections of the two light beams synthesized by the light beam combining member is incident on the rod integrator at a predetermined angle, the number of reflections in the rod integrator is increased, resulting in a uniform illuminance distribution. Becomes easier to obtain.

  For example, as in the twelfth aspect, if a polarization beam splitter is used as the light beam combining member, the light beams can be combined efficiently. Since the light beam emitted from the laser array light source is linearly polarized in the array direction, coaxial beam combining can be performed easily and efficiently by using a polarizing beam splitter.

  For example, as in the thirteenth invention, if γ = 90 ° and δ = 22.5 °, or γ = 45 ° and δ = 45 °, the direction of large NA is in four directions every 45 °. Therefore, a more isotropic NA distribution can be achieved. In addition, when a digital micromirror device is used, the resolving power in the pixel arrangement direction can be ensured.

  According to the fourteenth aspect of the invention, there are three laser array light sources that respectively emit the illumination lights of the three primary colors R, G, and B, and the illumination light emitted from each laser array light source is combined into the same optical path by the optical path combining member. Because it is configured, it is possible to illuminate in full color. Further, since the three light beams combined by the optical path combining member are optically arranged so as to enter the rod integrator with the same degree of divergence or concentration, the occurrence of color unevenness can be suppressed. Therefore, illumination with a uniform illuminance distribution substantially equal for each color light can be achieved more reliably.

  Further, as in the fifteenth aspect, if an optical arrangement having the same optical path length from each laser array light source to the rod integrator is employed, the occurrence of color unevenness can be prevented with a simple configuration. When a light source device that emits light with the same minute divergence angle as a point light source such as a laser light source is used, the difference in the optical path length becomes the difference in the light beam width in the optical component as it is. Accordingly, if the optical path lengths from the R, G, and B laser array light sources to the rod integrator are different, the difference in luminous flux width becomes the difference in divergence angle, resulting in color unevenness due to the difference in NA generated for each color. Become. By adopting an optical arrangement in which the optical path lengths from the R, G, and B laser array light sources to the rod integrator are equal, the risk of such color unevenness can be eliminated.

  Hereinafter, embodiments of an illumination optical system and an image projection apparatus using the illumination optical system according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is mutually attached | subjected to the part which is the same in each embodiment etc., and the corresponding part, and duplication description is abbreviate | omitted suitably.

<< First Embodiment (FIGS. 1 to 3, FIG. 16, FIG. 17)>
FIG. 1A shows a main optical arrangement of the image projection apparatus including the illumination optical system IL1 according to the first embodiment from the upper surface side. This image projection apparatus enlarges and projects a display element 10, an illumination optical system IL1 for illuminating the image display surface 10a, and an image displayed on the image display surface 10a onto a screen (not shown). A projection optical system PO. The illumination optical system IL1 includes a laser array light source 1R, 1G, 1B; a reflection mirror 3R, 3G, 3B; a dichroic mirror 4R, 4G; a concave lens 7a; a rod integrator 8; The optical configuration after that, that is, the relay optical system 9, the display element 10, the TIR (Total Internal Reflection) prism 11, and the projection lens 12 have the same configuration as a general image projection apparatus using a discharge lamp. ing.

  Red (R) illumination light is emitted from the laser array light source 1R, green (G) illumination light is emitted from the laser array light source 1G, and blue (B) illumination light is emitted from the laser array light source 1B. The That is, the three laser array light sources 1R, 1G, and 1B that emit the illumination lights of the three primary colors R, G, and B are sequentially blinked, and the display element 10 displays an image corresponding to the color of the illumination light on the image display surface 10a. By doing so, a color image is displayed.

  The light source arrays of the laser array light sources 1R, 1G, and 1B are all flat (for example, one row or two rows × ten rows). For this reason, the illumination light emitted from each laser array light source 1R, 1G, 1B has a flat light beam cross section. The three laser array light sources 1R, 1G, and 1B are arranged so that the longitudinal direction of the cross section of each illumination light beam is substantially linear, and is common to the three laser array light sources 1R, 1G, and 1B. The heat sink 2 is attached. FIG. 1C shows the heat sink 2 attached to the laser array light sources 1R, 1G, and 1B from the side surface (that is, the arrow D2 side in FIG. 1A).

  As shown in FIG. 1A, a cooling fan 6 is disposed on the side surface of the heat sink 2, and wind 6a is sent from the cooling fan 6 to the heat sink 2 to cool the laser array light sources 1R, 1G, and 1B. It is configured to be. As can be seen from FIG. 1C, the heat sink 2 has a plurality of fins 2a. The wind 6a from the cooling fan 6 is guided by the fins 2a so as to flow along the arrangement direction of the three laser array light sources 1R, 1G, and 1B. This cooling configuration can be adopted by arranging the laser array light sources 1R, 1G, and 1B in a straight line. In other words, by arranging the layout of the laser array light sources 1R, 1G, and 1B in a straight line, it becomes possible to use a common cooling mechanism, and only one cooling point is required, and cooling can be performed very efficiently. Become. In particular, when a light source such as a semiconductor laser or an LED (light emitting diode) is handled, the layout has an important point in the illumination optical system because the cooling affects the light emission amount.

  As shown in FIG. 1A, the terminals 5R, 5G, and 5B for driving each of the R, G, and B laser arrays are arranged in the same plane and in the same direction, and a control board (not shown). It is easy to connect with. When a light source such as a semiconductor laser or an LED is used, a large current flows. Therefore, it is important to arrange the laser array light sources 1R, 1G, and 1B in the above layout from the viewpoint of efficiency and safety. is there.

  The R illumination light emitted from the laser array light source 1R is reflected by the reflection mirror 3R and then reflected by the dichroic mirror 4R. Since the dichroic mirror 4R reflects the R illumination light and transmits the G and B illumination lights, the R illumination light is reflected by the dichroic mirror 4R, so that it has the same optical axis as the G and B illumination lights. Optical path synthesis. The R illumination light after the optical path synthesis enters the concave lens 7a and diverges. The G illumination light emitted from the laser array light source 1G is reflected by the reflection mirror 3G and then reflected by the dichroic mirror 4G. Since the dichroic mirror 4G reflects the G illumination light and transmits the B illumination light, the G illumination light is reflected by the dichroic mirror 4G, so that the optical path is synthesized with the same optical axis as the B illumination light. . The G illumination light after the optical path synthesis is transmitted through the dichroic mirror 4R, is incident on the concave lens 7a, and is diverged. The B illumination light emitted from the laser array light source 1B is reflected by the reflection mirror 3B, and then sequentially passes through the dichroic mirrors 4G and 4R, so that the optical paths are combined on the same optical axis as the R and G illumination lights. . The B illumination light after the optical path synthesis is incident on the concave lens 7a and diverged.

  As described above, the R, G, and B illumination lights are combined into the same optical path by the three reflection mirrors 3R, 3G, and 3B and the two types of dichroic mirrors 4R and 4G. By this optical path synthesis (that is, color synthesis), the R, G, and B illumination lights are coaxial, and the optical path lengths from the respective light emitting surfaces to the rod integrator 8 are equal to each other. As a result, the beam cross sections on the same surface after the optical path synthesis are substantially equal. This will be described in detail later.

  The R, G, and B illumination lights after the optical path synthesis are diverged by the concave lens 7 a and then enter the rod integrator 8. The rod integrator 8 is a hollow rod type light intensity equalizing means formed by bonding four plane mirrors. The illumination light incident from the incident end face is mixed by being repeatedly reflected by the side surface (that is, the inner wall surface) of the rod integrator 8, and the spatial energy distribution of the illumination light is made uniform and emitted from the exit end face. To do. The shape of the incident end face and the exit end face of the rod integrator 8 is a quadrangle substantially similar to the image display surface 10 a of the display element 10, and the exit end face of the rod integrator 8 is relative to the image display surface 10 a of the display element 10. Is conjugated. Therefore, the luminance distribution at the emission end face is made uniform by the mixing effect, so that the display element 10 is efficiently and uniformly illuminated.

  The rod integrator 8 is not limited to a hollow rod, but may be a glass rod made of a quadrangular prism-shaped glass body. Further, as long as it matches the shape of the image display surface 10a of the display element 10, the side surfaces are not limited to four. That is, the cross-sectional shape is not limited to a quadrilateral such as a rectangle. Therefore, examples of the rod integrator 8 to be used include a hollow cylinder formed by combining a plurality of reflection mirrors, and a polygonal columnar glass body.

  As described above, the illumination light emitted from each laser array light source 1R, 1G, 1B has a flat beam cross section. In FIG. 1A showing the main optical arrangement from the upper surface side, the concave lens 7a and the rod integrator 8 are shown as seen from the side with the larger light beam width. FIG. 1B shows a state in which the concave lens 7a and the rod integrator 8 are viewed from the arrow D1 side in FIG. In this illumination optical system IL1, as can be seen from FIGS. 1A and 1B, the light beam P is angled by the concave lens 7a so as to be easily reflected in the rod integrator 8. As described above, if the configuration is such that the illumination light from the laser array light sources 1R, 1G, and 1B is diverged by the concave lens 7a (or condensed by the convex lens 7b (FIGS. 4, 6, and 9) described later), the rod integrator 8 is incident at an angle (that is, the incident angle with respect to the incident end face is large), the number of reflections in the rod integrator 8 is increased, and a uniform illuminance distribution is more easily obtained.

  However, since the light beam cross section of the illumination light has a flat shape, the refraction angles U1 and U2 of the light beam differ depending on the difference between the light beam width S1 and the light beam width S2, as shown in FIG. That is, the angle S 2 with a smaller beam width is less angled with respect to the rod integrator 8 than the beam S 1 with a larger beam width. For this reason, in the rod integrator 8, the number of reflections in that direction is reduced, and it is difficult to obtain a uniform illuminance distribution and an isotropic NA distribution.

  In the illumination optical system IL1, in order to eliminate the above problems, when illumination light is incident on the rod integrator 8, the longitudinal direction of the light beam cross section of the illumination light and the rod integrator 8 The long side direction of the cross-sectional shape forms a predetermined angle that is neither parallel nor perpendicular (45 ° in this illumination optical system IL1). FIG. 2A shows the relationship between the cross section of the luminous flux P of the illumination light and the cross section of the rod integrator 8. The rod integrator 8 is arranged such that the long side direction of the cross-sectional shape forms an angle α = 45 ° with respect to the long direction of the cross section of the light flux P. Since the cross-sectional shape of the light beam P substantially coincides with the NA distribution when the light beam P enters the rod integrator 8, when the light beam P having a flat cross section is incident at an angle α = 45 °, FIG. As shown, the light beam P is emitted from the rod integrator 8 in a state where the direction of large NA (that is, the long direction of the cross section of the light beam P) is two directions forming an angle θ = 2α = 90 °. In other words, the flat NA direction can be increased by another direction, whereby the flat NA distribution can be converted into a more isotropic distribution.

  According to the configuration of the illumination optical system IL1, the illumination light beam having the isotropic NA distribution can be obtained while having the laser array light sources 1R, 1G, and 1B and having a compact configuration. A uniform illuminance distribution can be obtained while maintaining the resolving power. In addition, when illumination light having a flat light beam cross section is incident on the rod integrator 8 at a predetermined angle as described above, it can be easily reflected even on the reflection surface in the short side direction of the cross section of the rod integrator 8. This makes it easier to obtain a uniform illuminance distribution. Therefore, by providing the illumination optical system IL1 in the image projection apparatus, it is possible to greatly contribute to downsizing, cost reduction, high performance, high functionality, and the like.

  As shown in FIG. 2A, when the illumination light beam P is incident on the rod integrator 8, the longitudinal direction of the cross section of the illumination light beam P and the cross-sectional shape of the rod integrator 8 in the cross section perpendicular to the incident direction. When the long side direction forms an angle α = 45 ° or approximately 45 °, the most isotropic NA distribution can be achieved as a result of the orthogonal direction of the large NA. However, the effective angle α for increasing the isotropy of NA is not limited to 45 ° or approximately 45 °. In practice, if the configuration is such that the angle α = 20 ° to 70 °, conversion to an isotropic NA distribution can be performed more effectively.

  For example, as shown in FIG. 3A, when the illumination light beam P is incident on the rod integrator 8, in the cross section perpendicular to the incident direction, the longitudinal direction of the cross section of the illumination light beam P and the cross-sectional shape of the rod integrator 8 The long side direction may be arranged such that the angle α = 30 °. When a light beam P having a flat cross section is incident at an angle α = 30 °, the direction in which the NA is large (that is, the longitudinal direction of the cross section of the light beam P) is an angle θ = 2α as shown in FIG. Since the light beam P is emitted from the rod integrator 8 in the two directions of = 60 °, the flat NA distribution is converted into a more isotropic distribution. As described above, when the light beam P having a flat NA distribution is incident on the rod integrator 8 at a predetermined angle α, the flatness degree of the NA distribution can be improved according to the inclination degree.

  In this embodiment and other embodiments described later, the angle formed by the long direction of the flat light beam cross section is defined with respect to the long side direction of the cross sectional shape of the rod integrator (for example, parallel or vertical). However, the angle is not limited to the angle formed with respect to the long side direction, and is not parallel to or perpendicular to the side direction of the quadrilateral. If so, the flat NA distribution can be converted into a more isotropic distribution.

  The illumination optical system IL1 is configured such that a light beam having a maximum NA in the longitudinal direction of the cross section of the illumination light beam P is reflected twice or more on all surfaces constituting the inner surface of the rod integrator 8. If the light beam having the maximum NA in the longitudinal direction of the cross section of the illumination light beam P is reflected twice or more on all surfaces constituting the inner surface of the rod integrator 8 (that is, eight times on four surfaces), 2 Overlapping with five or more secondary light sources in each direction (that is, five or more even in the direction of small NA) is possible. Therefore, a uniform illuminance distribution can be obtained effectively.

  By the way, as shown in FIG. 17, a light beam emitted from a light source close to a point light source such as a laser light source has a divergence angle of the same minute angle Δ, and the difference between the optical path lengths T1 and T2 remains as it is. Then, the difference in the luminous flux width at the concave lens 7a). For this reason, if the optical path lengths T1 and T2 from the R, G, and B laser array light sources 1R, 1G, and 1B are different, the ratio of the difference in the luminous flux width in the concave lens 7a becomes relatively large, and the concave lens 7a has different colors. A large difference occurs in the divergence angles V1 and V2. Therefore, a difference in NA occurs for each color, resulting in color unevenness. In the illumination optical system IL1 shown in FIG. 1, since the three light beams of R, G, and B combined in the optical path are optically arranged so as to enter the rod integrator 8 with the same degree of divergence, the above color unevenness is caused. The risk that arises is eliminated. Further, by suppressing the occurrence of color unevenness, it is possible to more reliably achieve illumination with a uniform illuminance distribution that is substantially equal for each color light. Further, by adopting an optical arrangement in which the optical path lengths from the laser array light sources 1R, 1G, and 1B to the rod integrator 8 are equal, it is possible to prevent the occurrence of color unevenness with a simpler configuration.

  As shown in FIG. 1A, the illumination light emitted from the rod integrator 8 enters the TIR prism 11 through the illumination relay optical system 9. The illumination light incident on the TIR prism 11 is totally reflected by the air gap surface 11a of the TIR prism 11, and then uniformly illuminates the image display surface 10a of the display element 10. At this time, the relay optical system 9 relays the illumination light to form an image on the output end surface of the rod integrator 8 on the image display surface 10 a of the display element 10. That is, an image of the emission end face of the rod integrator 8 is formed on the image display surface 10a of the display element 10.

  On the image display surface 10a of the display element 10, a two-dimensional image is formed by intensity modulation of illumination light. Here, a digital micromirror device is assumed as the display element 10. However, the display element 10 used is not limited to this, and other non-light emitting / reflective (or transmissive) display elements (for example, liquid crystal display elements) suitable for the projection optical system PO may be used. When a digital micromirror device is used as the display element 10, the incident light is spatially modulated by being reflected by each micromirror in the ON / OFF state (for example, ± 12 ° tilt state). Is done. At that time, only the light reflected by the micromirror in the ON state passes through the air gap surface 11a of the TIR prism 11 without total reflection, enters the projection lens 12, and is projected on the screen. On the other hand, the light reflected by the micro mirror in the OFF state is largely deflected to the side opposite to the illumination light entrance side of the TIR prism 11 and therefore does not enter the projection lens 12. Thus, the display image on the image display surface 10a is enlarged and projected on the screen by the power of the projection lens 12 constituting the projection optical system PO.

<< Second Embodiment (FIGS. 4 and 5) >>
FIG. 4 shows an enlarged view of a main part of the illumination optical system IL2 according to the second embodiment. FIG. 4 shows the portions from the laser array light sources 1R, 1G, and 1B to the rod integrator 8 as seen from the side of the flat illumination light beam P with the smaller light beam width. The illumination optical system IL2 is characterized in that it has a convex lens 7b that condenses the illumination light from the laser array light sources 1R, 1G, and 1B and enters the rod integrator 8 in an eccentric state, and the convex lens 7b is the concave lens 7a. The configuration is the same as that of the first embodiment except for the above.

  The illumination light beam P after the optical path synthesis is condensed by the convex lens 7 b and enters the rod integrator 8. Even if the convex lens 7b is used instead of the concave lens 7a, the illumination light beam P can be angled as in the first embodiment. Therefore, the illumination light beam P is easily reflected in the rod integrator 8 due to condensing by the convex lens 7b, and a uniform illuminance distribution is easily obtained by increasing the number of reflections in the rod integrator 8.

  Since the central axis PX of the illumination light beam P and the central axis AX of the convex lens 7 b are relatively decentered, the illumination light beam P bends in an oblique direction and is inclined with respect to the incident end face of the rod integrator 8. FIG. 5A shows the relationship between the cross section of the illumination light beam P and the cross section of the rod integrator 8 at that time. Since the decentering direction of the convex lens 7b is set to the short direction of the section of the illumination light beam P (that is, the direction in which the light beam width is small), the light beam P incident on the rod integrator 8 is inclined in the direction of small NA. The rod integrator 8 is arranged such that the long side direction of the cross-sectional shape forms an angle α = 45 ° with respect to the long direction of the cross section of the light flux P. Therefore, as shown in FIG. Direction (that is, the longitudinal direction of the cross section of the light beam P) is two directions forming an angle θ = 2α = 90 °, and the NA increases in the oblique deflection direction by the convex lens 7b. The light is emitted from the rod integrator 8 in a state where the degree is further improved.

  Further, when the lens is used without any eccentricity, it is difficult to make an angle in the direction of small NA, but in this embodiment, the incident angle to the rod integrator 8 is set large due to the eccentricity of the lens in the direction of small NA. For this reason, the number of reflections on the inner surface of the rod integrator 8 in that direction increases as the incident light on the rod integrator 8 is inclined in the direction of small NA. Therefore, it becomes easier to obtain a uniform illuminance distribution.

<< Third Embodiment (FIGS. 6 to 8) >>
FIG. 6A shows a main optical arrangement of the image projection apparatus including the illumination optical system IL3 according to the third embodiment from the upper surface side. The main feature of the illumination optical system IL2 is that the rod integrator 8 is composed of two parts of a first rod integrator 8a and a second rod integrator 8b in order from the laser array light sources 1R, 1G, and 1B. Further, a convex lens 7b is provided instead of the concave lens 7a, two reflection mirrors 3R and 3G are provided, a cooling pump 13 is provided instead of the cooling fan 6, and a liquid cooling pipe 2b is provided on the heat sink 2 as a fin. The structure is the same as that of the first embodiment (FIG. 1) except that it is attached instead of 2a.

  Red (R) illumination light is emitted from the laser array light source 1R, green (G) illumination light is emitted from the laser array light source 1G, and blue (B) illumination light is emitted from the laser array light source 1B. The That is, the three laser array light sources 1R, 1G, and 1B that emit the illumination lights of the three primary colors R, G, and B are sequentially blinked, and the display element 10 displays an image corresponding to the color of the illumination light on the image display surface 10a. By doing so, a color image is displayed.

  The light source arrays of the laser array light sources 1R, 1G, and 1B are all flat (for example, one row or two rows × ten rows). For this reason, the illumination light emitted from each laser array light source 1R, 1G, 1B has a flat light beam cross section. The three laser array light sources 1R, 1G, and 1B are arranged so that the longitudinal direction of the cross section of each illumination light beam is substantially linear, and is common to the three laser array light sources 1R, 1G, and 1B. The heat sink 2 is attached. FIG. 6B shows the cooling pump 13, the liquid cooling pipe 2b, and the heat sink 2 from the bottom side (that is, the side opposite to the side where the laser array light sources 1R, 1G, and 1B are provided).

  As shown in FIG. 6 (A), a cooling pump 13 is disposed on the side surface of the heat sink 2, and a cooling liquid is flowed from the cooling pump 13 to the liquid cooling pipe 2 b to take heat away from the heat sink 2. The array light sources 1R, 1G, and 1B are cooled. As can be seen from FIG. 6B, the liquid cooling pipe 2b is arranged so that the cooling liquid flows along the arrangement direction of the three laser array light sources 1R, 1G, 1B. This cooling configuration can be adopted by arranging the laser array light sources 1R, 1G, and 1B in a straight line. In other words, by arranging the layout of the laser array light sources 1R, 1G, and 1B in a straight line, it becomes possible to use a common cooling mechanism, and only one cooling point is required, and cooling can be performed very efficiently. Become. In particular, when a light source such as a semiconductor laser or an LED (light emitting diode) is handled, the layout has an important point in the illumination optical system because the cooling affects the light emission amount.

  As shown in FIG. 6A, the terminals 5R, 5G, and 5B for driving each of the R, G, and B laser arrays are arranged in the same plane and in the same direction, and a control board (not shown). It is easy to connect with. When a light source such as a semiconductor laser or an LED is used, a large current flows. Therefore, it is important to arrange the laser array light sources 1R, 1G, and 1B in the above layout from the viewpoint of efficiency and safety. is there.

  The R illumination light emitted from the laser array light source 1R is reflected by the two reflecting mirrors 3R and then reflected by the dichroic mirror 4R. Since the dichroic mirror 4R reflects the R illumination light and transmits the G and B illumination lights, the R illumination light is reflected by the dichroic mirror 4R, so that it has the same optical axis as the G and B illumination lights. Optical path synthesis. The R illumination light after the optical path synthesis is incident on the convex lens 7b and collected. The G illumination light emitted from the laser array light source 1G is reflected by the two reflecting mirrors 3G and then reflected by the dichroic mirror 4G. Since the dichroic mirror 4G reflects the G illumination light and transmits the B illumination light, the G illumination light is reflected by the dichroic mirror 4G, so that the optical path is synthesized with the same optical axis as the B illumination light. . The G illumination light after the optical path synthesis passes through the dichroic mirror 4R, enters the convex lens 7b, and is condensed. The B illumination light emitted from the laser array light source 1B is reflected by the reflection mirror 3B, and then sequentially passes through the dichroic mirrors 4G and 4R, so that the optical paths are combined on the same optical axis as the R and G illumination lights. . The illumination light B after the optical path synthesis enters the convex lens 7b and is condensed.

  As described above, the R, G, and B illumination lights are combined in the same optical path by the five reflection mirrors 3R, 3G, and 3B and the two types of dichroic mirrors 4R and 4G. By this optical path synthesis (that is, color synthesis), the R, G, and B illumination lights are coaxial, and the optical path lengths from the respective light emitting surfaces to the rod integrator 8 are equal to each other. As a result, the beam cross sections on the same surface after the optical path synthesis are substantially equal. In this regard, the same effect as that of the first embodiment described above can be obtained. That is, a light beam emitted from a light source close to a point light source, such as a laser light source, with a divergence angle of the same minute angle becomes a difference in the light beam width of the optical component as it is. If the optical path lengths from the R, G, and B laser array light sources 1R, 1G, and 1B are different, the ratio of the difference in the light beam width at the convex lens 7b becomes relatively large, and the divergence angle for each color differs greatly at the convex lens 7b. Occurs. For this reason, a difference in NA occurs for each color, resulting in color unevenness. In the illumination optical system IL3 shown in FIG. 6, since the three light fluxes R, G, and B combined in the optical path are optically arranged so as to enter the rod integrator 8 with the same divergence degree, the above-described color unevenness is caused. The risk that arises is eliminated. Further, by suppressing the occurrence of color unevenness, it is possible to more reliably achieve illumination with a uniform illuminance distribution that is substantially equal for each color light. Further, by adopting an optical arrangement in which the optical path lengths from the laser array light sources 1R, 1G, and 1B to the rod integrator 8 are equal, it is possible to prevent the occurrence of color unevenness with a simpler configuration.

  The R, G, and B illumination lights after the optical path synthesis are collected by the convex lens 7b and then enter the rod integrator 8 composed of two parts, the first rod integrator 8a and the second rod integrator 8b. The first and second rod integrators 8a and 8b are hollow rod type light intensity uniformizing means each formed by bonding four plane mirrors. The illumination light incident from each incident end face is the first and second rod integrators. The two-rod integrators 8a and 8b are mixed by being repeatedly reflected by the side surfaces (that is, the inner wall surfaces), and the spatial energy distribution of the illumination light is made uniform and emitted from each emission end face.

  The shape of the incident end face and the exit end face of the second rod integrator 8b is a quadrangle substantially similar to the image display face 10a of the display element 10, and the exit end face of the second rod integrator 8 is the image display face 10a of the display element 10. It is conjugate with respect to. Therefore, the luminance distribution at the emission end face is made uniform by the mixing effect, so that the display element 10 is efficiently and uniformly illuminated. On the other hand, the cross-sectional shape of the first rod integrator 8a is a square. Since the exit end face of the first rod integrator 8a is not conjugated to the image display face 10a of the display element 10, the exit end face of the first rod integrator 8a needs to be similar to the image display face 10a of the display element 10. There is no.

  The first and second rod integrators 8a and 8b are not limited to hollow rods, but may be glass rods made of a rectangular columnar glass body. Further, the side surface of the first rod integrator 8a is not limited to four surfaces, and the side surface of the second rod integrator 8b is not limited to four surfaces as long as it matches the shape of the image display surface 10a of the display element 10. That is, the cross-sectional shape of the first and second rod integrators 8a and 8b is not limited to a quadrangle such as a rectangle. Accordingly, examples of the first and second rod integrators 8a and 8b to be used include a hollow cylinder formed by combining a plurality of reflecting mirrors, a polygonal columnar glass body, and the like.

  The illumination optical system IL3 is configured such that the light beam having the maximum NA in the longitudinal direction of the cross section of the illumination light beam P is reflected twice or more on all surfaces constituting the inner surface of the rod integrator 8. If the light beam having the maximum NA in the longitudinal direction of the cross section of the illumination light beam P is reflected twice or more on all surfaces constituting the inner surface of the rod integrator 8 (that is, eight times on four surfaces), 2 Overlapping with five or more secondary light sources in each direction (that is, five or more even in the direction of small NA) is possible. Therefore, a uniform illuminance distribution can be obtained effectively. In this illumination optical system IL3, the rod integrator 8 is divided into two parts, the first and second rod integrators 8a and 8b. However, the number of reflections sufficient for the illumination light to have a homogeneous distribution in the rod integrator 8 as a whole is as described above. If secured in this way, the number of divisions may be increased to three or more than four.

  As described above, the illumination light emitted from each laser array light source 1R, 1G, 1B has a flat beam cross section. In this illumination optical system IL3, as can be seen from FIG. 6A, the light beam P is angled by the convex lens 7b so as to be easily reflected in the rod integrator 8. If the illumination light from the laser array light sources 1R, 1G, and 1B is thus collected by the convex lens 7b, it is incident on the rod integrator 8 at an angle (that is, the incident angle with respect to the incident end face). Therefore, the number of reflections in the rod integrator 8 increases, and a uniform illuminance distribution is more easily obtained.

  However, since the cross section of the light beam of the illumination light has a flat shape, as described above (FIG. 16), the refraction angles U1 and U2 of the light beam differ depending on the difference between the light beam width S1 and the light beam width S2. That is, the angle S 2 with a smaller beam width is less angled with respect to the rod integrator 8 than the beam S 1 with a larger beam width. For this reason, in the rod integrator 8, the number of reflections in that direction is reduced, and it is difficult to obtain a uniform illuminance distribution and an isotropic NA distribution.

  In the illumination optical system IL3, in order to solve the above problems, when illumination light enters the first rod integrator 8a, in the cross section perpendicular to the incident direction, the longitudinal direction of the light beam cross section of the illumination light, and the first The long side direction of the cross-sectional shape of the rod integrator 8a forms a predetermined angle that is neither parallel nor perpendicular (45 ° in the illumination optical system IL3), and is perpendicular to the incident direction of the illumination light to the second rod integrator 8b. In a simple cross section, the long side direction of the cross-sectional shape of the first rod integrator 8a and the long side direction of the cross-sectional shape of the second rod integrator 8b are not parallel or perpendicular to each other (in this illumination optical system IL3, 22.2. 5 °).

  FIG. 7A shows the relationship between the cross section of the luminous flux P of the illumination light and the cross section of the first rod integrator 8a. The rod integrator 8a has an angle α = 45 ° with respect to the longitudinal direction of the cross section of the light beam P when the long side direction of the cross sectional shape (in this embodiment, the cross sectional shape is square is the direction of one side). It is arranged to make. Since the cross-sectional shape of the light beam P substantially coincides with the NA distribution when the light beam P enters the rod integrator 8, when the light beam P having a flat cross section is incident at an angle α = 45 °, FIG. As shown, the light beam P is emitted from the first rod integrator 8a in a state where the direction of large NA (that is, the longitudinal direction of the cross section of the light beam P) is two directions forming an angle θ = 2α = 90 °. Become. Accordingly, the NA distribution is converted to isotropic by the amount of increase in the flat NA direction by another direction, and the light beam P emitted from the first rod integrator 8a enters the second rod integrator 8b.

  FIG. 7C shows the relationship between the cross sections of the two illumination light beams P emitted from the first rod integrator 8a and the cross sections of the first and second rod integrators 8a and 8b. The second rod integrator 8b is arranged such that the long side direction of the cross-sectional shape forms an angle β = 22.5 ° with respect to the direction of one side of the cross-sectional shape of the first rod integrator 8a. The cross-sectional shapes of the two light beams P substantially coincide with the NA distribution when the two light beams P are incident on the second rod integrator 8b. Therefore, when the two light beams P having a flat cross section are incident on the second rod integrator 8b, As shown in FIG. 7D, in the state where the direction of large NA (that is, the longitudinal direction of the cross section of the light beam P) is the four directions forming the angle θ = 45 °, the four types of light beams P are reflected by the second rod. The light is emitted from the integrator 8b. Therefore, the NA distribution is converted into an isotropic one by the increase of the flat NA direction by two more directions, and the light flux P is emitted from the second rod integrator 8b in a state where the flatness of the NA distribution is further improved. Will do.

  As described above, since the rod integrator 8 is composed of two parts, the first rod integrator 8a and the second rod integrator 8b, the flat NA direction is increased by one in the first rod integrator 8a, and the second rod integrator In 8b, the flat NA direction can be further increased by two. Therefore, the NA distribution can be made more isotropic. Also, in the case of a projector using a digital micromirror device, usually, when a light beam is incident at an angle of 45 ° in the long side direction of the rod integrator cross section, the direction with a large NA is the direction of 45 ° oblique to the projection screen. become. However, since the pixel array is in the vertical and horizontal directions, the NA in this direction is relatively small, and the resolution may not be sufficient. If another function is added by dividing the rod integrator into two parts, the NA can be increased in the vertical and horizontal directions. In addition, since the light flux incident on the second rod integrator 8b has two directions with a large NA, the number of reflections in the second rod integrator 8b increases, and a uniform illuminance distribution is more easily obtained.

  In this embodiment, with respect to a light beam incident on the second rod integrator 8b in a cross section perpendicular to the incident direction of the illumination light to the second rod integrator 8b, the longitudinal direction of the light beam cross section and the second rod integrator 8b Since the long side direction of the cross-sectional shape forms a predetermined angle that is neither parallel nor perpendicular, the conversion to the isotropic NA distribution by the second rod integrator 8b is performed more reliably and effectively. be able to.

  In this embodiment, α = 45 ° and β = 22.5 ° as shown in FIG. 7, but α = 22.5 ° and β = 45 ° as shown in FIG. Good. As shown in FIG. 8A, when the illumination light beam P is incident on the first rod integrator 8a, the light beam P having a flat cross section is incident at an angle α = 22.5 °. As shown in FIG. 2, the light flux P is emitted from the first rod integrator 8a and enters the second rod integrator 8b in a state where the direction of large NA is two directions forming an angle θ = 2α = 45 °. . As shown in FIG. 8C, the second rod integrator 8b is arranged so that the long side direction of the cross-sectional shape forms an angle β = 45 ° with respect to the direction of one side of the cross-sectional shape of the first rod integrator 8a. Therefore, when the two light beams P are incident on the second rod integrator 8b, as shown in FIG. 8D, in the state where the direction of large NA becomes four directions forming an angle θ = 45 °, The kind of light flux P is emitted from the second rod integrator 8b.

  Therefore, according to the configuration of the rod integrator 8 shown in FIG. 8, like the configuration of the rod integrator 8 shown in FIG. 7, the NA distribution is converted to isotropic, and the luminous flux P has a more flat degree of the NA distribution. The light is emitted from the second rod integrator 8b in a further improved state. If α = 45 ° and β = 22.5 ° or α = 22.5 ° and β = 45 ° as described above, the direction of large NA becomes four directions every 45 °. A more isotropic NA distribution can be achieved, and when a digital micromirror device is used, the resolving power in the pixel arrangement direction can be ensured.

  As shown in FIG. 6A, the illumination light emitted from the second rod integrator 8b enters the TIR prism 11 through the relay optical system 9 for illumination. The illumination light incident on the TIR prism 11 is totally reflected by the air gap surface 11a of the TIR prism 11, and then uniformly illuminates the image display surface 10a of the display element 10. At this time, the relay optical system 9 relays the illumination light to form an image of the emission end face of the second rod integrator 8b on the image display surface 10a of the display element 10. That is, an image of the emission end surface of the second rod integrator 8b is formed on the image display surface 10a of the display element 10.

  On the image display surface 10a of the display element 10, a two-dimensional image is formed by intensity modulation of illumination light. Here, a digital micromirror device is assumed as the display element 10. However, the display element 10 used is not limited to this, and other non-light emitting / reflective (or transmissive) display elements (for example, liquid crystal display elements) suitable for the projection optical system PO may be used. When a digital micromirror device is used as the display element 10, the incident light is spatially modulated by being reflected by each micromirror in the ON / OFF state (for example, ± 12 ° tilt state). Is done. At that time, only the light reflected by the micro mirror in the ON state is transmitted through the air gap surface 11a of the TIR prism 11 without total reflection, enters the projection lens 12, and is projected onto the screen (not shown). On the other hand, the light reflected by the micro mirror in the OFF state is largely deflected to the side opposite to the illumination light entrance side of the TIR prism 11 and therefore does not enter the projection lens 12. Thus, the display image on the image display surface 10a is enlarged and projected on the screen by the power of the projection lens 12 constituting the projection optical system PO.

<< Fourth Embodiment (FIGS. 9 and 10) >>
FIG. 9 is an enlarged view of a main part of the illumination optical system IL4 according to the fourth embodiment. FIG. 9 shows the portions from the laser array light sources 1R, 1G, and 1B to the rod integrator 8 as viewed from the side with the smaller luminous flux width of the flat illumination luminous flux P. This illumination optical system IL4 has the characteristics of both the illumination optical systems IL2 and IL3 described above. That is, the third embodiment is characterized in that it has the convex lens 7b in an eccentric state (FIG. 4), and the other configuration is the same as that of the third embodiment.

  The illumination light flux P after the optical path synthesis is condensed by the convex lens 7 b and enters the rod integrator 8. Since the illumination light beam P is easily reflected in the rod integrator 8 by condensing by the convex lens 7b, a uniform illuminance distribution is easily obtained by increasing the number of reflections in the rod integrator 8. Further, since the central axis PX of the illumination light beam P and the central axis AX of the convex lens 7b are relatively decentered, the illumination light beam P is bent in an oblique direction and is incident on the incident end surface of the first rod integrator 8a. It will be. FIG. 10A shows the relationship between the cross section of the illumination light beam P and the cross section of the first rod integrator 8a.

  Since the eccentric direction of the convex lens 7b is set to the short direction of the cross section of the illumination light beam P (that is, the direction in which the light beam width is small), the light beam P incident on the first rod integrator 8a is inclined in the direction of small NA. Since the first rod integrator 8a is arranged such that the direction of one side of its cross-sectional shape forms an angle α = 45 ° with respect to the longitudinal direction of the cross section of the light beam P, as shown in FIG. , The direction in which the NA is large (that is, the longitudinal direction of the cross section of the light beam P) is two directions forming an angle θ = 2α = 90 °, and the NA increases in the oblique deflection direction by the convex lens 7b. In a state where the degree of flatness is further improved, the light exits from the first rod integrator 8a and enters the second rod integrator 8b.

  FIG. 10C shows the relationship between the cross sections of the four illumination light beams P emitted from the first rod integrator 8a and the cross sections of the first and second rod integrators 8a and 8b. The second rod integrator 8b is arranged such that the long side direction of the cross-sectional shape forms an angle β = 22.5 ° with respect to the direction of one side of the cross-sectional shape of the first rod integrator 8a. The cross-sectional shapes of the four light beams P substantially coincide with the NA distribution when the four light beams P are incident on the second rod integrator 8b. Therefore, when the four light beams P having a flat cross section are incident on the second rod integrator 8b, As shown in FIG. 10D, in the state where the direction of large NA (that is, the longitudinal direction of the cross section of the light beam P) is four directions forming an angle θ = 45 °, the eight kinds of light beams P are The light is emitted from the integrator 8b. Accordingly, the NA distribution is converted to isotropic by the amount of increase in the flat NA direction by two more directions, and the light flux P is emitted from the second rod integrator 8b in a state where the flatness of the NA distribution is greatly improved. Will do.

  Further, when the lens is used without any eccentricity, it is difficult to make an angle in the direction of small NA, but in this embodiment, the incident angle to the rod integrator 8 is set large due to the eccentricity of the lens in the direction of small NA. For this reason, the number of reflections on the inner surface of the rod integrator 8 in that direction increases as the incident light on the rod integrator 8 is inclined in the direction of small NA. Therefore, it becomes easier to obtain a uniform illuminance distribution.

<< 5th Embodiment (FIGS. 11-13) >>
FIG. 11 is an enlarged view of a main part of the illumination optical system IL5 according to the fifth embodiment. FIG. 11 shows the optical arrangement before the illumination light emitted from the laser array light sources 1R, 1G, and 1B enters the concave lens 7a (FIG. 1) or the convex lens 7b (FIGS. 4, 6, and 9). They are shown as viewed from (A) and the side (B). This illumination optical system IL5 has two light source sets 21, 22 each consisting of three laser array light sources 1R, 1G, 1B, and two light beams in a cross section perpendicular to the traveling direction of the two combined light beams. This is characterized in that the longitudinal direction of the cross section forms a predetermined angle (90 ° in the illumination optical system IL5) that is not parallel, and the other configuration is the same as that of the first embodiment.

  The light source arrays of the laser array light sources 1R, 1G, and 1B are all flat (for example, one row or two rows × ten rows). For this reason, the illumination light emitted from each laser array light source 1R, 1G, 1B has a flat light beam cross section. The three laser array light sources 1R, 1G, and 1B in each of the light source sets 21 and 22 are arranged so that the longitudinal direction of the light beam cross section of each illumination light is substantially linear, and the two light source sets 21, 22 are arranged in parallel along the same plane. Further, as shown in FIG. 11B, a common heat sink 2 is attached to the back surface of a total of six laser array light sources 1R, 1G, and 1B included in the two light source sets 21 and 22. The cooling using the heat sink 2 is performed by the cooling fan 6 as in the first embodiment (FIG. 1).

  As shown in FIG. 11A, the first light source set 21 emits light in a direction perpendicular to the paper surface, and optical path synthesis (that is, color synthesis) is performed in a plane perpendicular to the paper surface. The color synthesis is performed in the same manner as in the first embodiment (FIG. 1), and the R, G, B illumination lights are made coaxial by the color synthesis and the optical path lengths from the respective light emitting surfaces to the rod integrator 8 are equal to each other. Become. The color-synthesized illumination light beam P1 from the first light source set 21 is deflected by the reflection mirror 16 toward the polarization beam splitter 17. On the other hand, as shown in FIG. 11A, the second light source set 22 emits light in a direction perpendicular to the paper surface, and the illumination light beam P2 is a surface parallel to the paper surface by the long reflecting mirror 15. And optical path synthesis (that is, color synthesis) is performed in a plane parallel to the paper surface. The color synthesis is performed in the same manner as in the first embodiment (FIG. 1), and the R, G, B illumination lights are made coaxial by the color synthesis and the optical path lengths from the respective light emitting surfaces to the rod integrator 8 are equal to each other. Become. Then, the illumination light beam P <b> 2 from the second light source set 22 that has undergone color synthesis travels toward the polarization beam splitter 17.

  The illumination light beams P1 and P2 color-combined by the first and second light source sets 21 and 22 are both linearly polarized light depending on the flat direction of the light beam cross section. In the polarization beam splitter 17, the longitudinal directions of the cross sections of the illumination light beams P1 and P2 are in a relationship of 90 ° with each other. Therefore, the illumination light beams P1 and P2 can be easily combined on the same optical axis by reflecting one light beam P1 and transmitting the other light beam P2 by the polarization beam splitter 17. If the polarization beam splitter 17 is subjected to processing such as polarization of at least one of the illumination light beams P1 and P2 in an arbitrary polarization direction using a wave plate or the like before the polarization synthesis, the polarization beam splitter 17 is moved to the first direction. It is possible to easily arrange the light source set 21, change the traveling direction after the polarization synthesis, or change the layout of the image projection apparatus according to convenience.

  FIG. 12A shows the cross-sectional shapes of illumination light beams P1 and P2 that are polarized and synthesized on the same optical axis. As can be seen from FIG. 12 (A), the two illumination beams P1 and P2 synthesized by polarization have an angle γ = 90 ° in the longitudinal direction of the cross-sectional shape in a cross section perpendicular to the traveling direction. . Then, in such a state where the light beams are combined, the light is incident on the rod integrator 8 via the concave lens 7a (FIG. 1) or the convex lens 7b (FIGS. 4, 6, and 9). The configuration from the rod integrator 8 to the projection lens 12 is the same as that of the first embodiment (FIG. 1).

  FIG. 12B shows the relationship between the cross sections of the illumination light beams P 1 and P 2 and the cross section of the rod integrator 8. The rod integrator 8 is arranged such that the long side direction of the cross-sectional shape forms an angle δ = 22.5 ° with respect to the symmetry axis of the two illumination light beams P1 and P2 after synthesis. Since the sectional shapes of the illumination light beams P1 and P2 substantially coincide with the NA distribution when the illumination light beams P1 and P2 enter the rod integrator 8, the illumination light beams P1 and P2 having a flat cross section have an angle δ = 22.5 °. When entering the rod integrator 8, as shown in FIG. 12C, the direction in which the NA is large (that is, the longitudinal direction of the cross section of the light beams P1 and P2) is the four directions forming the angle θ = 2δ = 45 °. Thus, four types of illumination light beams P1 and P2 are emitted from the rod integrator 8. Therefore, the NA distribution is converted to isotropic by the increase of the flat NA direction by two directions, and the illumination light beams P1 and P2 are emitted from the rod integrator 8 in a state where the flatness of the NA distribution is further improved. Will do.

  As described above, the illumination optical system IL5 has two laser array light sources 1R, 1G, and 1B of the same color, and the luminous flux emitted from the laser array light sources 1R, 1G, and 1B travels in the same direction. Since P1 and P2 are combined, conversion to an isotropic NA distribution can be performed more effectively. Thus, by using two laser array light sources 1R, 1G, and 1B as the light source sets 21 and 22, the rod integrator 8 in the third embodiment including the two portions 8a and 8b (FIG. 6) can be used. Similarly, a more isotropic NA distribution can be obtained. In addition, in this case, since the brightness can be doubled by simultaneous emission of the same color, the illumination optical system IL5 having this configuration is optimal for a high-power projector for cinema or the like. In addition, since the longitudinal directions of the cross sections of the two light beams synthesized are incident on the rod integrator 8 at a predetermined angle, the number of reflections in the rod integrator 8 is increased, and a uniform illuminance distribution is obtained. It becomes easier to obtain.

  In the illumination optical system IL5, since the polarization beam splitter 17 is used as the light beam combining member, the light beams can be combined efficiently. Since the light beams emitted from the laser array light sources 1R, 1G, and 1B are linearly polarized in the arrangement direction of the array, by using the polarization beam splitter 17, coaxial light beam synthesis can be performed easily and efficiently.

  In this embodiment, γ = 90 ° and δ = 22.5 ° as shown in FIG. 12, but γ = 45 ° and δ = 45 ° may be used as shown in FIG. If the angle of the long reflecting mirror 15 of the second light source set 22 is changed, the color composition direction is set to 45 ° with respect to the paper surface of FIG. Polarization synthesis as shown in FIG. 13 (A) is also possible. As shown in FIG. 13B, when the illumination light beams P1 and P2 are incident on the rod integrator 8 with an angle δ = 45 °, the direction in which the NA is large is the angle θ = Four kinds of light beams P are emitted from the rod integrator 8 in the four directions of 45 °.

  Therefore, according to the configuration of the rod integrator 8 shown in FIG. 13, like the configuration of the rod integrator 8 shown in FIG. 12, the NA distribution is converted to isotropic, and the illumination light beams P1 and P2 are flattened in the NA distribution. The light is emitted from the rod integrator 8 in a state where the degree is further improved. As described above, if γ = 90 ° and δ = 22.5 °, or γ = 45 ° and δ = 45 °, the direction of large NA becomes four directions every 45 °. A square NA distribution can be achieved. In addition, when a digital micromirror device is used, the resolving power in the pixel arrangement direction can be ensured.

<< Sixth Embodiment (FIGS. 14 and 15) >>
FIG. 14 is an enlarged view of a main part of the illumination optical system IL6 according to the sixth embodiment. FIG. 14 shows the optical arrangement before the illumination light emitted from the laser array light sources 1R, 1G, and 1B enters the concave lens 7a (FIG. 1) or the convex lens 7b (FIGS. 4, 6, and 9). They are shown as viewed from (A) and the side (B). This illumination optical system IL6 has four light source sets 21, 22, 23, 24 each consisting of three laser array light sources 1R, 1G, 1B, and in a cross section perpendicular to the traveling direction of the four synthesized light beams. The two light beams are characterized in that they form a predetermined angle (90 ° in the illumination optical system IL6) in which the longitudinal direction of the cross-section is not parallel to the other two light beams. The configuration is the same as that of the embodiment.

  The light source arrays of the laser array light sources 1R, 1G, and 1B are all flat (for example, one row or two rows × ten rows). For this reason, the illumination light emitted from each laser array light source 1R, 1G, 1B has a flat light beam cross section. The three laser array light sources 1R, 1G, and 1B in each of the light source sets 21 to 24 are arranged so that the longitudinal direction of the light beam cross section of each illumination light is substantially linear. The first and second light source sets 21 and 22 are arranged in parallel along the same plane. As shown in FIG. 14B, a common heat sink is provided on the back surface of each of the laser array light sources 1R, 1G, and 1B. The 1st light source unit 31 is comprised in the state in which 2 was attached. Similarly, the third and fourth light source sets 23 and 24 are arranged in parallel along the same plane. As shown in FIG. 14B, the laser array light sources 1R, 1G, and 1B are arranged on the rear surface. The second light source unit 32 is configured with the common heat sink 2 attached. The cooling using the heat sink 2 in each of the light source units 31 and 32 is performed by the cooling fan 6 as in the first embodiment (FIG. 1).

  The first light source set 21 emits light in a direction perpendicular to the paper surface of FIG. 14A (a direction parallel to the paper surface of FIG. 14B), and its illumination light beam P1 is a long reflecting mirror. 15 is deflected along a plane parallel to the paper surface of FIGS. 14 (A) and 14 (B). Similarly, the second light source set 22 emits light in a direction perpendicular to the paper surface of FIG. 14A (a direction parallel to the paper surface of FIG. 14B), and the illumination light beam P2 is long. The reflection mirror 15 deflects in the same direction as the illumination light beam P1 along a plane parallel to the paper surface of FIGS. 14 (A) and 14 (B). At this time, as shown in FIG. 14B, since the arrangement heights of the long reflecting mirrors 15 are different, the illumination light beams P1 and P2 are arranged in parallel. These parallel illumination light beams P1 and P2 are color-synthesized (that is, optical path synthesis) by a common color synthesis mechanism. The color synthesis is performed in the same manner as in the first embodiment (FIG. 1), and the R, G, B illumination lights are made coaxial by the color synthesis and the optical path lengths from the respective light emitting surfaces to the rod integrator 8 are equal to each other. Become. The illumination light beam P1 and the illumination light beam P2 travel toward the polarization beam splitter 17 in parallel. This is the configuration of the first light source unit 31.

  The third light source set 23 and the fourth light source set 24 emit light in a direction perpendicular to the paper surface of FIG. 14A (a direction parallel to the paper surface of FIG. 14B). The illumination light beam P3 from the third light source set 23 is reflected by the two long reflecting mirrors 15, and the optical path is changed so that the vicinity of the illumination light beam P4 from the fourth light source set 24 is parallel. . These parallel illumination light beams P3 and P4 are color-synthesized (that is, optical path synthesis) by a common color synthesis mechanism. The color synthesis is performed in the same manner as in the first embodiment (FIG. 1), and the R, G, B illumination lights are made coaxial by the color synthesis and the optical path lengths from the respective light emitting surfaces to the rod integrator 8 are equal to each other. Become. Then, as shown in FIG. 14A, the illumination light beam P 3 and the illumination light beam P 4 are deflected by the reflection mirror 16 toward the polarization beam splitter 17. This is the configuration of the second light source unit 32.

  The illumination light beams P1 and P2 emitted from the first light source unit 31 and the illumination light beams P3 and P4 emitted from the second light source unit 32 are linearly polarized light depending on the flat direction of the light beam cross section. Further, in the polarization beam splitter 17, the illumination light beams P1 and P2 and the illumination light beams P3 and P4 have a relationship in which the longitudinal direction of the light beam cross section forms 90 °. Therefore, the illumination light beams P1 to P4 can be easily combined with the same optical axis by transmitting one of the light beams P1 and P2 and reflecting the other light beams P3 and P4 with the polarization beam splitter 17. Further, if the polarization beam splitter 17 is subjected to a process such as polarization of at least one illumination light beam P1 to P4 in an arbitrary polarization direction using a wave plate or the like before the polarization synthesis, the arrangement of the polarization beam splitter 17; It is possible to easily change the traveling direction after the polarization synthesis, the layout as the image projection apparatus, and the like according to convenience.

  FIG. 15A shows the cross-sectional shapes of illumination light beams P1 to P4 polarized and synthesized on the same optical axis. As can be seen from FIG. 15 (A), the four illumination beams P1 to P4 that have been combined with each other have a longitudinal direction of an angle γ = 90 ° in a cross section perpendicular to the traveling direction. . Then, in such a state where the light beams are combined, the light is incident on the rod integrator 8 via the concave lens 7a (FIG. 1) or the convex lens 7b (FIGS. 4, 6, and 9). The configuration from the rod integrator 8 to the projection lens 12 is the same as that of the first embodiment (FIG. 1).

  FIG. 15B shows the relationship between the cross sections of the illumination light beams P <b> 1 to P <b> 4 and the cross section of the rod integrator 8. The rod integrator 8 is arranged such that the long side direction of the cross-sectional shape forms an angle δ = 22.5 ° with respect to the symmetry axis of the two illumination light beams P1 and P2 after synthesis. Since the sectional shapes of the illumination light beams P1 to P4 substantially coincide with the NA distribution when the illumination light beams P1 to P4 enter the rod integrator 8, the illumination light beams P1 to P4 having a flat cross section are at an angle δ = 22.5 °. When entering the rod integrator 8, as shown in FIG. 15C, the direction in which the NA is large (that is, the longitudinal direction of the cross section of the light beams P1 to P4) is the four directions forming the angle θ = 2δ = 45 °. Thus, four types of illumination light beams P <b> 1 to P <b> 4 are emitted from the rod integrator 8. Therefore, the NA distribution is converted to isotropic by the increase of the flat NA direction by two directions, and the illumination light beams P1 to P4 are emitted from the rod integrator 8 with the flatness of the NA distribution being greatly improved. Will do.

  As described above, the illumination optical system IL6 has four laser array light sources 1R, 1G, and 1B of the same color, and the luminous flux emitted from each laser array light source 1R, 1G, and 1B travels in the same direction. Since it is configured to synthesize P1 to P4, conversion to an isotropic NA distribution can be performed more effectively. Thus, by using four laser array light sources 1R, 1G, and 1B as the light source sets 21 to 24, in the case of the fourth embodiment (FIG. 9) (that is, the rod integrator 8 has two portions 8a, As is the case with the configuration having the convex lens 7b in an eccentric state), a very isotropic NA distribution can be obtained. In addition, in this case, since the brightness can be quadrupled by simultaneous emission of the same color, the illumination optical system IL6 having this configuration is optimal for a high-power projector for cinema or the like. Further, since the longitudinal directions of the cross sections of the four light beams synthesized are incident on the rod integrator 8 at a predetermined angle that is neither parallel nor perpendicular, the number of reflections in the rod integrator 8 increases, and the uniform The illuminance distribution can be obtained more easily.

  In the illumination optical system IL6, as in the illumination optical system IL5, the polarization beam splitter 17 is used as the light beam combining member, so that the light beams can be efficiently combined. Since the light beams emitted from the laser array light sources 1R, 1G, and 1B are linearly polarized in the arrangement direction of the array, by using the polarization beam splitter 17, coaxial light beam synthesis can be performed easily and efficiently. Further, if γ = 90 °, δ = 22.5 °, or γ = 45 °, δ = 45 ° as described above, the direction of large NA becomes four directions every 45 °. A more isotropic NA distribution can be achieved. In addition, when a digital micromirror device is used, the resolving power in the pixel arrangement direction can be ensured.

1 is a schematic configuration diagram showing an image projection apparatus according to a first embodiment. The figure which shows the change of NA distribution by the rod integrator ((alpha) = 45 degrees) in 1st Embodiment by the positional relationship with a rod cross section. The figure which shows the change of NA distribution by the rod integrator ((alpha) = 30 degrees) in 1st Embodiment by the positional relationship with a rod cross section. The front view which shows the principal part of the image projector which concerns on 2nd Embodiment. The figure which shows the change of NA distribution by the rod integrator ((alpha) = 45 degrees) in 2nd Embodiment by the positional relationship with a rod cross section. The schematic block diagram which shows the image projector which concerns on 3rd Embodiment. The figure which shows the change of NA distribution by the rod integrator ((alpha) = 45 degrees, (beta) = 22.5 degrees) in 3rd Embodiment by the positional relationship with a rod cross section. The figure which shows the change of NA distribution by the rod integrator ((alpha) = 22.5 degrees, (beta) = 45 degrees) in 3rd Embodiment by the positional relationship with a rod cross section. The front view which shows the principal part of the image projector which concerns on 4th Embodiment. The figure which shows the change of NA distribution by the rod integrator ((alpha) = 45 degrees, (beta) = 22.5 degrees) at the time of decentering a convex lens in 4th Embodiment by the positional relationship with a rod cross section. The schematic block diagram which shows the principal part of the illumination optical system which concerns on 5th Embodiment. The figure which shows the change of NA distribution by the rod integrator ((gamma) = 90 degrees, (delta) = 22.5 degrees) in 5th Embodiment by the positional relationship with a rod cross section. The figure which shows the change of NA distribution by the rod integrator ((gamma) = 45 degrees, (delta) = 45 degrees) in 5th Embodiment by the positional relationship with a rod cross section. The schematic block diagram which shows the principal part of the illumination optical system which concerns on 6th Embodiment. The figure which shows the change of NA distribution by the rod integrator ((gamma) = 90 degrees, (delta) = 22.5 degrees) in 6th Embodiment by the positional relationship with a rod cross section. The optical path figure for demonstrating the difference of the refraction angle produced by the difference of the light beam width with respect to a rod integrator. The optical path figure for demonstrating the difference of the refraction angle which arises by the difference of the optical path length to a rod integrator, and a light beam width.

Explanation of symbols

IL1 to IL6 Illumination optical system PO Projection optical system 1R Red light emitting laser array light source 1G Green light emitting laser array light source 1B Blue light emitting laser array light source 3R R reflecting mirror 3G G reflecting mirror 3B B reflecting mirror 4R R reflection dichroic mirror (light path combining member)
Dichroic mirror for 4G G reflection (light path combining member)
7a Concave lens 7b Convex lens 8 Rod integrator 8a First rod integrator 8b Second rod integrator 10 Display element 10a Image display surface 12 Projection lens (projection optical system)
17 Polarizing beam splitter
21-24 Light source set 31, 32 Light source unit P Illumination light beam PX Illumination light beam central axis AX Lens central axis

Claims (16)

  An illumination optical system for illuminating an image display surface of a display element, a laser array light source for emitting illumination light having a flat light beam cross section, and a spatial energy distribution of the illumination light having a quadrangular cross section A uniform rod integrator, and when the illumination light is incident on the rod integrator, in a cross section perpendicular to the incident direction, the longitudinal direction of the light beam cross section of the illumination light, and the cross sectional shape of the rod integrator An illumination optical system characterized by forming a predetermined angle that is neither parallel nor perpendicular to the side direction of   The illumination optical system according to claim 1, wherein the predetermined angle is 20 ° to 70 °.   The illumination optical system according to claim 1, wherein the predetermined angle is 45 ° or approximately 45 °.   The illumination optical system according to any one of claims 1 to 3, further comprising a lens for diverging or condensing illumination light from the laser array light source and causing the light to enter the rod integrator.   5. The illumination optical system according to claim 4, wherein a central axis of the luminous flux of the illumination light and a central axis of the lens are relatively decentered.   6. The illumination optical system according to claim 5, wherein the direction of the eccentricity is a short direction of a cross section of the light beam of the illumination light.   The light beam having the maximum NA in the longitudinal direction of the cross section of the luminous flux of the illumination light is reflected at least twice on all surfaces constituting the inner surface of the rod integrator. The illumination optical system described.   The rod integrator is composed of two parts of a first rod integrator and a second rod integrator in order from the laser array light source side, and when illumination light is incident on the first rod integrator, the rod integrator is perpendicular to the incident direction. In the cross section, the long direction of the cross section of the light beam of the illumination light and the side direction of the cross sectional shape of the first rod integrator form a predetermined angle that is neither parallel nor perpendicular, and the illumination light to the second rod integrator In a cross section perpendicular to the incident direction, the side direction of the cross-sectional shape of the first rod integrator and the side direction of the cross-sectional shape of the second rod integrator form a predetermined angle that is neither parallel nor perpendicular. The illumination optical system according to any one of claims 1 to 7.   In a cross section perpendicular to the incident direction of the illumination light to the second rod integrator, for the light beam incident on the second rod integrator, the longitudinal direction of the light beam cross section, and the side direction of the cross-sectional shape of the second rod integrator, 9. The illumination optical system according to claim 8, wherein the angle is a predetermined angle that is neither parallel nor vertical.   A predetermined angle formed by the longitudinal direction of the cross section of the luminous flux of the illumination light and the side direction of the cross-sectional shape of the first rod integrator is α, the side direction of the cross-sectional shape of the first rod integrator, and the second direction If β is a predetermined angle formed by the side direction of the cross-sectional shape of the rod integrator, α = 45 ° and β = 22.5 °, or α = 22.5 °, and The illumination optical system according to claim 8, wherein β = 45 °.   The two laser array light sources further include a light beam combining member that combines light beams so that illumination light emitted from each laser array light source travels in the same direction, and the two light beams combined by the light beam combining member 11. The illumination optical system according to claim 1, wherein in a cross section perpendicular to a traveling direction of the light beam, a long angle of the cross sections of the two light beams forms a predetermined angle that is not parallel.   The illumination optical system according to claim 11, wherein the light beam combining member is a polarization beam splitter.   A predetermined angle formed by the longitudinal direction of the cross section of the two light beams is γ, and a predetermined angle formed by the symmetry axis of the two light beams after synthesis and the side direction of the cross-sectional shape of the rod integrator is δ. The illumination optics according to claim 11, wherein γ = 90 ° and δ = 22.5 ° or γ = 45 ° and δ = 45 °. system.   As the laser array light source, there are three laser array light sources that emit illumination lights of three primary colors R, G, and B, respectively, and an optical path combining member that combines the illumination lights emitted from the respective laser array light sources into the same optical path. 14. The optical arrangement according to any one of claims 1 to 13, wherein the three light beams combined by the optical path combining member are optically arranged so as to enter the rod integrator with the same divergence or condensing degree. The illumination optical system described in 1.   15. The illumination optical system according to claim 14, wherein the optical path length from each laser array light source to the rod integrator is equal.   An image projection apparatus comprising the illumination optical system according to claim 1.

Images