Illuminating device and projector using it and built-in display unit

An illuminating device comprising a light source for emitting a plurality of light beams (207, 208, 209) of different colors, a plurality of rotating beam scanners (102, 103, 104) and a plurality of scanning lenses (109, 110, 111). The beam scanners have spiral reflection surfaces (102, 103, 204) formed on the outer peripheries of cylindrical bodies, Each colored light beam is shone onto each reflection surface from a direction parallel to a rotating axis, and magnified by each scanning lens after reflected to scan an illuminated area with a plurality of beams of different colors one after another. Accordingly, the illuminating device can enhance scanning linearity, reduce noise due to a minimal windage loss, and decrease costs and power consumption.

TECHNICAL FIELD

The present invention relates to an illumination optical system that performs sequential scanning with a plurality of different colors of light, a projection video system using the illumination optical system, and an integral-type video display using the projection video system.

BACKGROUND ART

An apparatus for magnifying and projecting an image by sequentially scanning a light valve with a plurality of different colors of light has been known from JP 6(1994)-319148 A. The apparatus includes first, second and third polygonal prisms that are arranged coaxially and shifted relative to one another by a rotation angle of 30 degrees with respect to the rotation axis. The polygonal prisms are rotated, so that the different colors of light entering the respective prisms are refracted to scan the light valve sequentially.

As described above, the rotating polygonal prism is used to deflect light incident thereon by refraction. Thus, scanning linearity depends on the number of surfaces of the prism. To improve the linearity, it is necessary to increase the number of surfaces of the prism. However, a predetermined size of each surface of the prism for receiving light has to be ensured. Therefore, an increase in the number of surfaces inevitably leads to an increase in size of the prism. Moreover, to rotate a large prism, a motor or the like, acting as a rotation system, requires a large rotation torque. When a prism having edges is rotated, the chance of wind resistance occurring increases, and thus a larger rotation torque is needed. These bring about a rise in the cost and in the power consumption. In addition, the occurrence of wind resistance causes noise, which becomes a major obstacle to showing pictures.

DISCLOSURE OF INVENTION

Therefore, with the foregoing in mind, it is an object of the present invention to provide an illumination optical system that can achieve the improvement in scanning linearity and the reductions in wind resistance, cost, power consumption and noise, a projection video system, and an integral-type video display.

A first illumination optical system of the present invention includes the following: a light source for emitting a plurality of different colors of light; a plurality of optical scanners; rotation systems for rotating the optical scanners; and at least one scanning lens. Each of the optical scanners has a reflecting surface defined by the path traced by a segment that tilts at a predetermined angle with respect to a rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. The different colors of light enter the respective reflecting surfaces of the optical scanners, are reflected therefrom, and pass through the scanning lenses, so that a region to be illuminated is scanned sequentially with the different colors of light.

A second illumination optical system of the present invention includes the following: a light source for emitting a plurality of different colors of light; a combined optical scanner; a rotation system for rotating the combined optical scanner; and at least one scanning lens. The combined optical scanner has a plurality of reflecting surfaces in the direction of a rotation axis, each reflecting surface being defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. The different colors of light enter the respective reflecting surfaces of the combined optical scanner, are reflected therefrom, and pass through the scanning lens, so that a region to be illuminated is scanned sequentially with the different colors of light.

A third illumination optical system of the present invention includes the following: a light source for emitting white light; a combined optical scanner; a rotation system for rotating the combined optical scanner; and at least one scanning lens. The combined optical scanner has a plurality of dichroic mirror surfaces in the direction of a rotation axis, each dichroic mirror surface being defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. The white light enters successively the dichroic mirror surfaces of the combined optical scanner and is separated into a plurality of different colors of light, and then the different colors of light are reflected from the respective dichroic mirror surfaces and pass through the scanning lens, so that a region to be illuminated is scanned sequentially with the different colors of light.

A fourth illumination optical system of the present invention includes the following: a light source for emitting a plurality of different colors of light; a combined optical scanner having a hollow portion; a plurality of third reflecting surfaces placed in the hollow portion of the combined optical scanner; a rotation system for rotating the combined optical scanner; and at least one scanning lens. The combined optical scanner has a plurality of first and second reflecting surfaces arranged in the direction of a rotation axis. Each of the first reflecting surfaces is defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. Each of the second reflecting surfaces is defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and rotates around the rotation axis. The different colors of light enter the respective third reflecting surfaces in the direction substantially parallel to the rotation axis, then are reflected in the direction substantially perpendicular to the rotation axis, reflected from the second reflecting surfaces, reflected further from the first reflecting surfaces, and pass through the scanning lens, so that a region to be illuminated is scanned sequentially with the different colors of light.

A fifth illumination optical system of the present invention includes the following: a light source for emitting white light; a combined optical scanner having a hollow portion; a plurality of dichroic mirror surfaces placed in the hollow portion of the combined optical scanner; a rotation system for rotating the combined optical scanner; and at least one scanning lens. The combined optical scanner has a plurality of first and second reflecting surfaces arranged in the direction of a rotation axis. Each of the first reflecting surfaces is defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. Each of the second reflecting surfaces is defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and rotates around the rotation axis. The white light enters successively the dichroic mirror surfaces in the direction substantially parallel to the rotation axis of the combined optical scanner and is separated into a plurality of different colors of light, and then the different colors of light are reflected from the respective dichroic mirror surfaces in the direction substantially perpendicular to the rotation axis, reflected from the second reflecting surfaces, reflected further from the first reflecting surfaces, and pass through the scanning lens, so that a region to be illuminated is scanned with the different colors of light.

A sixth illumination optical system of the present invention includes the following: a light source for emitting a plurality of different colors of light; a combined optical scanner having a hollow portion; a plurality of second reflecting surfaces placed in the hollow portion of the combined optical scanner; a rotation system for rotating the combined optical scanner; a plurality of third reflecting surfaces; and at least one scanning lens. The combined optical scanner has a plurality of first reflecting surfaces in the direction of a rotation axis, each first reflecting surface being defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. The different colors of light enter the respective second reflecting surfaces in the direction substantially parallel to the rotation axis of the combined optical scanner, then are reflected in the direction substantially perpendicular to the rotation axis, reflected from the third reflecting surfaces, reflected further from the first reflecting surfaces, and pass though the scanning lens, so that a region to be illuminated is scanned sequentially with the different colors of light.

A seventh illumination optical system of the present invention includes the following: a light source for emitting white light; a combined optical scanner having a hollow portion; a plurality of dichroic mirror surfaces placed in the hollow portion of the combined optical scanner; a rotation system for rotating the combined optical scanner; a plurality of second reflecting surfaces; and at least one scanning lens. The combined optical scanner has a plurality of first reflecting surfaces in the direction of a rotation axis, each first reflecting surface being defined by the path traced by a segment that tilts at a predetermined angle with respect to the rotation axis and moves in the direction of the rotation axis while rotating around the rotation axis. The white light enters successively the dichroic mirror surfaces in the direction substantially parallel to the rotation axis of the combined optical scanner and is separated into a plurality of different colors of light, and then the different colors of light are reflected from the respective dichroic mirror surfaces in the direction substantially perpendicular to the rotation axis, reflected from the second reflecting surfaces, reflected further from the first reflecting surfaces, and pass through the scanning lens, so that a region to be illuminated is scanned sequentially with the different colors of light.

Next, a projection video system of the present invention includes any one of the first to the seventh illumination optical system, a light modulator, an electronic circuit for driving the light modulator, and a projection optical system.

An integral-type video display of the present invention includes the above projection video system, a screen, and a case for housing the projection video system and the screen.

According to the illumination optical system of the present invention, the optical scanner or the combined optical scanner can provide favorable scanning linearity, which simplifies the configuration of an electronic circuit that constitutes the projection video system. Moreover, since the illumination optical system can achieve reduction both in wind resistance and noise, a smaller rotation torque is needed to rotate the optical scanner or the combined optical scanner. Therefore, they can be driven by a small motor, resulting in low cost and low power consumption. Thus, the present invention can provide an illumination optical system that can achieve good scanning linearity and the reductions in wind resistance, cost, power consumption and noise, a projection video system, and an integral-type video display.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1is an elevation view showing an illumination optical system101of Embodiment 1 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light. An optical scanner102for scanning red light207, an optical scanner103for scanning green light208, and an optical scanner104for scanning blue light209are rotated by rotation systems (not shown) in the directions of arrows106,107and108, respectively. The red, green and blue light thus scanned are magnified in the direction of the width of the region105through the respective scanning lenses109,110and111, and at the same time, they scan the region105vertically with respect to the drawing sheet for illumination.

FIG. 2is a front view showing the configurations of the optical scanners102,103and104inFIG. 1. Reflecting surfaces204,205and206, each having a collar shape, are formed around cylindrical rotating bodies201,202and203while moving in the direction of rotation axes213,214and215, i.e., the reflecting surfaces are provided in helical fashion. Specifically, each of the reflecting surfaces204,205and206is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to the rotation axis and moves in the direction of the rotation axis at constant velocity while rotating around the same. In other words, those reflecting surfaces are similar in shape to a tooth flank cut on an external thread, such as a bolt, or a helical ridge formed on a screw. Each of the reflecting surfaces204,205and206is formed over an angular range that is slightly smaller than the perimeter (i.e., 360 degrees) of the rotating body.

A light source (not shown) emits red, green and blue light. Such a light source can be composed, e.g., of a white light source and a well-known means for separating white light into its spectral components.

The red light207enters the reflecting surface204in the direction parallel to the rotation axis213and is reflected in the direction perpendicular to the axis. Similarly, the green light208enters the reflecting surface205in the direction parallel to the rotation axis214and is reflected in the direction perpendicular to the axis. The blue light209enters the reflecting surface206in the direction parallel to the rotation axis215and is reflected in the direction perpendicular to the axis.

The optical scanners102,103and104are rotated by motors210,211and212, acting as rotation systems. Consequently, the incident positions of the red, green and blue light on the reflecting surfaces204,205and206of the optical scanners are changed in the direction of the rotation axis (i.e., the direction of height), so that each color of light is scanned. Then, they pass through the scanning lenses109,110and111, thereby scanning and illuminating the region105.

In this case, scanning linearity becomes perfect when each optical scanner rotates at constant velocity and has such a configuration that the rotation angle of each optical scanner is proportional to the amount of change in the corresponding reflecting surface in the direction of height, i.e., there is a linear relationship between the angular velocity of the segment, which defines the reflecting surface and tilts with respect to the rotation axis, rotating around the rotation axis and the velocity of the segment moving in the direction of the rotation axis.

Moreover, sequential scanning of the region105without overlapping colors can be achieved in the following manner: each of the optical scanners102,103and104is formed to have the same shape and rotated while maintaining a predetermined phase difference, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

In the above example, the number of scanning lenses is equal to that of optical scanners, and the scanning lenses are arranged to have one-to-one correspondence with the optical scanners. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from the reflecting surfaces of a plurality of optical scanners. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the reflecting surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

In the above example, the motors210,211and212, acting as rotation systems, have one-to-one correspondence with the optical scanners102,103and104. However, the present invention is not limited to this configuration. For example, a single motor can be used to produce a driving force that is distributed by a well-known driving force distribution method to rotate the respective optical scanners102,103and104.

FIG. 3is a cross-sectional view showing an illumination optical system301of Embodiment 2 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light.

A combined optical scanner302has the same configuration as that obtained when the optical scanners102,103and104of Embodiment 1 are connected coaxially in the direction of the rotation axis. The combined optical scanner302is rotated around a rotation axis310by a motor303, acting as a rotation system. The combined optical scanner302includes a cylindrical rotating body311having a plurality of reflecting surfaces304,305and306on its side face. Each of the reflecting surfaces304,305and306is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to the rotation axis and moves along the rotation axis while rotating around the same. Moreover, the three reflecting surfaces304,305and306are formed on the rotating body311so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

A light source (not shown) emits red, green and blue light. Such a light source can be composed, e.g., of a white light source and a well-known means for separating white light into its spectral components.

Blue light307enters the reflecting surface304in the direction parallel to the rotation axis310and is reflected in the direction perpendicular to the axis. Green light308enters the reflecting surface305in the direction parallel to the rotation axis310and is reflected in the direction perpendicular to the axis. Red light309enters the reflecting surface306in the direction parallel to the rotation axis310and is reflected in the direction perpendicular to the axis.

The combined optical scanner302is rotated by the motor303, acting as a rotation system. Consequently, the incident positions of blue, green and red light on the reflecting surfaces304,305and306of the combined optical scanner302are changed in the direction of the rotation axis (i.e., the direction of height), so that each color of light is scanned. Then, they pass through the scanning lenses109,110and111, thereby scanning and illuminating the region105.

In this case, scanning linearity becomes perfect when the reflecting surfaces are formed so that the rotation angle is proportional to the amount of change in the reflecting surfaces in the direction of height (i.e., the direction of the rotation axis310).

Moreover, sequential scanning of the region105without overlapping colors can be achieved since the reflecting surfaces304,305and306are formed integrally with the rotating body311so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

In the above example, the number of scanning lenses is equal to that of reflecting surfaces, and the scanning lenses are arranged to have one-to-one correspondence with the reflecting surfaces. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from a plurality of reflecting surfaces. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the reflecting surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

FIG. 4is a front view showing an illumination optical system401of Embodiment 3 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light, andFIG. 5is a cross-sectional view thereof.

A combined optical scanner402is rotated by a motor303, acting as a rotation system. The combined optical scanner402includes a cylindrical rotating body407having three dichroic mirror surfaces403,404and405on its side face. Each of the dichroic mirror surfaces is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to a rotation axis310and moves along the rotation axis while rotating around the same. Moreover, the three dichroic mirror surfaces403,404and405are formed integrally with the rotating body407so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis, thus constituting the combined optical scanner402.

White light406from a white light source (not shown) enters the dichroic mirror surface403in the direction parallel to the rotation axis310, where the blue light component is reflected in the direction perpendicular to the rotation axis310. The blue light then scans and illuminates the region105through a scanning lens109. The light, after the blue light component has been filtered out, enters the dichroic mirror surface404, where the green light component is reflected in the direction perpendicular to the rotation axis310. The green light then scans and illuminates the region105through a scanning lens110. The remaining light, after the blue and green light components have been filtered out, enters the dichroic mirror surface405, where the red light component is reflected in the direction perpendicular to the rotation axis310. The red light then scans and illuminates the region105through a scanning lens111.

In this case, scanning linearity becomes perfect when the dichroic mirror surfaces are formed so that the rotation angle of the combined optical scanner402is proportional to the amount of change in the dichroic mirror surfaces in the direction of height (i.e., the direction of the rotation axis310).

Moreover, sequential scanning of the region105without overlapping colors can be achieved since the dichroic mirror surfaces403,404and405are formed integrally with the rotating body407so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

As described above, the order of arrangement of the dichroic mirror surfaces from the white light incident side, i.e., the order of spectral reflection characteristics is blue, green, and red. This makes it possible to suppress unnecessary spectral components in red light, which is separated lastly, with a small number of layers of the dichroic mirror surfaces. Thus, an illumination optical system that achieves higher color purity can be provided at low cost.

Moreover, the efficiency of utilization of a red light component can be increased by arranging the spectral reflection characteristics in the order of red, green, and blue. Therefore, an illumination optical system that achieves higher light utilization efficiency can be provided even if a high-pressure mercury lamp is used, whose emission spectrum is low in the red light component.

The dichroic mirror surface405, on which the light is incident lastly, may be replaced by a general reflecting surface, as long as the incident light does not contain unnecessary spectral components. The use of such a reflecting surface can provide the same illumination optical system as that described above.

In the above example, the number of scanning lenses is equal to that of dichroic mirror surfaces, and the scanning lenses are arranged to have one-to-one correspondence with the dichroic mirror surfaces. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from a plurality of dichroic mirror surfaces. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the dichroic mirror surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

FIG. 6is a cross-sectional view showing an illumination optical system601of Embodiment 4 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light.

A combined optical scanner602is rotated by a motor303, acting as a rotation system. The combined optical scanner602includes a cylindrical rotating body603having three first reflecting surfaces604,605and606and three second reflecting surfaces607,608and609on its side face, the first and second reflecting surfaces being provided alternately. Like the reflecting surfaces304,305and306in Embodiment 2, each of the first reflecting surfaces604,605and606is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to a rotation axis310and moves along the rotation axis while rotating around the same. Each of the second reflecting surfaces607,608and609is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to the rotation axis310and rotates around the rotation axis in a plane perpendicular to the rotation axis so as to form part of a conical surface. Moreover, the first reflecting surfaces604,605and606are formed on the rotating body603so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

There are three third reflecting surfaces610,611and612in the central space of the hollow-cylindrical rotating body603. Each of the third reflecting surfaces tilts at a predetermined angle with respect to the rotation axis310.

A light source (not shown) emits red, green and blue light. Such a light source can be composed, e.g., of a white light source and a well-known means for separating white light into its spectral components.

Blue light613enters in the direction parallel to the rotation axis310and is reflected from the third reflecting surface610in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface607. The blue light reflected therefrom enters the first reflecting surface604, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens109, thus scanning and illuminating the region105. Similarly, green light614enters in the direction parallel to the rotation axis310and is reflected from the third reflecting surface611in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface608. The green light reflected therefrom enters the first reflecting surface605, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens110, thus scanning and illuminating the region105. Also, red light615enters in the direction parallel to the rotation axis310and is reflected from the third reflecting surface612in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface609. The red light reflected therefrom enters the first reflecting surface606, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens111, thus scanning and illuminating the region105.

In this case, scanning linearity becomes perfect when the first reflecting surfaces604,605and606are formed so that the rotation angle is proportional to the amount of change in the first reflecting surfaces in the direction of height (i.e., the direction of the rotation axis310).

Moreover, sequential scanning of the region105without overlapping colors can be achieved since the first reflecting surfaces604,605and606are formed integrally with the rotating body603so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

It is preferable that the member of the combined optical scanner with a hollow portion (i.e., the rotating body603) can transmit light and has a light transmittance of 70% or more to improve the efficiency of light utilization. This is because lower light transmittance increases loss resulting from the light absorption, which in turn reduces the light utilization efficiency.

In the above example, the number of scanning lenses is equal to that of first reflecting surfaces, and the scanning lenses are arranged to have one-to-one correspondence with the first reflecting surfaces. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from a plurality of first reflecting surfaces. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the first reflecting surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

FIG. 7is a cross-sectional view showing an illumination optical system701of Embodiment 5 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light.

A combined optical scanner602is rotated by a motor303, acting as a rotation system. The combined optical scanner602includes a cylindrical rotating body603having three first reflecting surfaces604,605and606and three second reflecting surfaces607,608and609on its side face, the first and second reflecting surfaces being provided alternately. Like the reflecting surfaces304,305and306in Embodiment 2, each of the first reflecting surfaces604,605and606is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to a rotation axis310and moves along the rotation axis while rotating around the same. Each of the second reflecting surfaces607,608and609is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to the rotation axis310and rotates around the rotation axis in a plane perpendicular to the rotation axis so as to form part of a conical surface. Moreover, the first reflecting surfaces604,605and606are formed on the rotating body603so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

There are three dichroic mirror surfaces703,704and705in the central space of the hollow-cylindrical rotating body603. Each of the dichroic mirror surfaces tilts at a predetermined angle with respect to the rotation axis310, and they are arranged on a straight line.

White light702from a white light source (not shown) is incident on the center of the rotating body603in the direction parallel to the rotation axis and enters the dichroic mirror surface703, where the blue light component is reflected in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface607. The blue light reflected therefrom enters the first reflecting surface604, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens109, thus scanning and illuminating the region105. Similarly, the light, after the blue light component has been filtered out, enters the dichroic mirror surface704, where the green light component is reflected in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface608. The green light reflected therefrom enters the first reflecting surface605, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens110, thus scanning and illuminating the region105. Also, the remaining light, after the blue and green light components have been filtered out, enters the dichroic mirror surface705, where the red light component is reflected in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface609. The red light reflected therefrom enters the first reflecting surface606, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens111, thus scanning and illuminating the region105.

In this case, scanning linearity becomes perfect when the first reflecting surfaces604,605and606are formed so that the rotation angle is proportional to the amount of change in the first reflecting surfaces in the direction of height (i.e., the direction of the rotation axis310).

Moreover, sequential scanning of the region105without overlapping colors can be achieved since the first reflecting surfaces604,605and606are formed integrally with the rotating body603so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

It is preferable that the member of the combined optical scanner with a hollow portion (i.e., the rotating body603) can transmit light and has a light transmittance of 70% or more to improve the efficiency of light utilization. This is because lower light transmittance increases loss resulting from the light absorption, which in turn reduces the light utilization efficiency.

As described above, the order of arrangement of the dichroic mirror surfaces from the white light incident side, i.e., the order of spectral reflection characteristics is blue, green, and red. This makes it possible to suppress unnecessary spectral components in red light, which is separated lastly, with a small number of layers of the dichroic mirror surfaces. Thus, an illumination optical system that achieves higher color purity can be provided at low cost.

Moreover, the efficiency of utilization of a red light component can be increased by arranging the spectral reflection characteristics in the order of red, green, and blue. Therefore, an illumination optical system that achieves higher light utilization efficiency can be provided even if a high-pressure mercury lamp is used, whose emission spectrum is low in the red light component.

The dichroic mirror surface705, on which the light is incident lastly, may be replaced by a general reflecting surface, as long as the incident light does not contain unnecessary spectral components. The use of such a reflecting surface can provide the same illumination optical system as that described above.

In the above example, the number of scanning lenses is equal to that of first reflecting surfaces, and the scanning lenses are arranged to have one-to-one correspondence with the first reflecting surfaces. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from a plurality of first reflecting surfaces. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the first reflecting surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

FIG. 8is a cross-sectional view showing an illumination optical system801of Embodiment 6 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light.

A combined optical scanner802is rotated by a motor303, acting as a rotation system. The combined optical scanner802includes a cylindrical rotating body803having three first reflecting surfaces804,805and806on its side face. Like the reflecting surfaces304,305and306in Embodiment 2, each of the first reflecting surfaces804,805and806is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to a rotation axis310and moves along the rotation axis while rotating around the same. Moreover, the first reflecting surfaces804,805and806are formed integrally with the rotating body803so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis, thus constituting the combined optical scanner.

There are three second reflecting surfaces807,808and809in the central space of the hollow-cylindrical rotating body803. Each of the second reflecting surfaces tilts at a predetermined angle with respect to the rotation axis310.

In addition, three third reflecting surfaces810,811and812are located at the positions opposite to the first reflecting surfaces804,805and806of the combined optical scanner.

A light source (not shown) emits red, green and blue light. Such a light source can be composed, e.g., of a white light source and a well-known means for separating white light into its spectral components.

Blue light813enters the second reflecting surface807in the direction parallel to the rotation axis310and is reflected in the direction substantially perpendicular to the rotation axis310onto the third reflecting surface810. The blue light reflected therefrom enters the first reflecting surface804, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens109, thus scanning and illuminating the region105. Similarly, green light814enters the second reflecting surface808in the direction parallel to the rotation axis310and is reflected in the direction substantially perpendicular to the rotation axis310onto the third reflecting surface811. The green light reflected therefrom enters the first reflecting surface805, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens110, thus scanning and illuminating the region105. Also, red light815enters the second reflecting surface809in the direction parallel to the rotation axis310and is reflected in the direction substantially perpendicular to the rotation axis310onto the third reflecting surface812. The red light reflected therefrom enters the first reflecting surface806, is reflected in the direction perpendicular to the rotation axis310, and passes through a scanning lens111, thus scanning and illuminating the region105.

In this case, scanning linearity becomes perfect when the first reflecting surfaces804,805and806are formed so that the rotation angle is proportional to the amount of change in the first reflecting surfaces in the direction of height (i.e., the direction of the rotation axis310).

Moreover, sequential scanning of the region105without overlapping colors can be achieved since the first reflecting surfaces804,805and806are formed integrally with the rotating body803so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

It is preferable that the member of the combined optical scanner with a hollow portion (i.e., the rotating body803) can transmit light and has a light transmittance of 70% or more to improve the efficiency of light utilization. This is because lower light transmittance increases loss resulting from the light absorption, which in turn reduces the light utilization efficiency.

In the above example, the number of scanning lenses is equal to that of first reflecting surfaces, and the scanning lenses are arranged to have one-to-one correspondence with the first reflecting surfaces. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from a plurality of first reflecting surfaces. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the first reflecting surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

FIG. 9is a cross-sectional view showing an illumination optical system901of Embodiment 7 of the present invention that illuminates a region105to be illuminated by sequentially scanning the region105with a plurality of colors of light.

A combined optical scanner802is rotated by a motor303, acting as a rotation system. The combined optical scanner802includes a cylindrical rotating body803having three first reflecting surfaces804,805and806on its side face. Like the reflecting surfaces304,305and306in Embodiment 2, each of the first reflecting surfaces804,805and806is defined by the path traced by a segment that tilts at a predetermined angle (e.g., 45 degrees) with respect to a rotation axis310and moves along the rotation axis while rotating around the same. Moreover, the first reflecting surfaces804,805and806are formed on the rotating body803so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

There are three dichroic mirror surfaces703,704and705in the central space of the hollow-cylindrical rotating body803. Each of the dichroic mirror surfaces tilts at a predetermined angle with respect to the rotation axis310, and they are arranged on a straight line.

In addition, three second reflecting surfaces910,911and912are located at the positions opposite to the first reflecting surfaces804,805and806of the optical scanner.

White light702from a white light source (not shown) is incident on the center of the rotating body802in the direction parallel to the rotation axis310and enters the dichroic mirror surface703, where the blue light component is reflected in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface910. The blue light reflected therefrom enters the first reflecting surface804, is reflected in the direction substantially perpendicular to the rotation axis310, and passes through a scanning lens109, thus scanning and illuminating the region105. Similarly, the light, after the blue light component has been filtered out, enters the dichroic mirror surface704, where the green light component is reflected in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface911. The green light reflected therefrom enters the first reflecting surface805, is reflected in the direction substantially perpendicular to the rotation axis310, and passes through a scanning lens110, thus scanning and illuminating the region105. Also, the remaining light, after the blue and green light components have been filtered out, enters the dichroic mirror surface705, where the red light component is reflected in the direction substantially perpendicular to the rotation axis310onto the second reflecting surface912. The red light reflected therefrom enters the first reflecting surface806, is reflected in the direction substantially perpendicular to the rotation axis310, and passes through a scanning lens111, thus scanning and illuminating the region105.

In this case, scanning linearity becomes perfect when the first reflecting surfaces804,805and806are formed so that the rotation angle is proportional to the amount of change in the first reflecting surfaces in the direction of height (i.e., the direction of the rotation axis310).

Moreover, sequential scanning of the region105without overlapping colors can be achieved since the first reflecting surfaces804,805and806are formed integrally with the rotating body803so that each of them has a predetermined phase difference in the rotational direction, i.e., they are shifted relative to one another by a rotation angle (phase) of 120 degrees with respect to the rotation axis.

It is preferable that the member of the combined optical scanner with a hollow portion (i.e., the rotating body803) can transmit light and has a light transmittance of 70% or more to improve the efficiency of light utilization. This is because lower light transmittance increases loss resulting from the light absorption, which in turn reduces the light utilization efficiency.

As described above, the order of arrangement of the dichroic mirror surfaces from the white light incident side, i.e., the order of spectral reflection characteristics is blue, green, and red. This makes it possible to suppress unnecessary spectral components in red light, which is separated lastly, with a small number of layers of the dichroic mirror surfaces. Thus, an illumination optical system that achieves higher color purity can be provided at low cost.

Moreover, the efficiency of utilization of a red light component can be increased by arranging the spectral reflection characteristics in the order of red, green, and blue. Therefore, an illumination optical system that achieves higher light utilization efficiency can be provided even if a high-pressure mercury lamp is used, whose emission spectrum is low in the red light component.

The dichroic mirror surface705, on which the light is incident lastly, may be replaced by a general reflecting surface, as long as the incident light does not contain unnecessary spectral components. The use of such a reflecting surface can provide the same illumination optical system as that described above.

In the above example, the number of scanning lenses is equal to that of first reflecting surfaces, and the scanning lenses are arranged to have one-to-one correspondence with the first reflecting surfaces. However, the present invention is not limited to this configuration. For example, a single scanning lens can be used to receive each color of light reflected from a plurality of first reflecting surfaces. It should be noted that, in such a case, the preferred optical system includes a reflecting mirror or prism for guiding the different colors of light reflected from the first reflecting surfaces to the single scanning lens and a relay lens so that each color of light has an equivalent optical path length.

The reflecting surfaces formed around the optical scanners or the combined optical scanner in Embodiments 1 to 7 can be achieved by evaporating a metallic material such as aluminum on the surface to be a reflecting surface.

FIG. 10shows the configuration of a projection video system1005of Embodiment 8 of the present invention. The projection video system1005includes the following: the illumination optical system1001of the present invention; a light modulator1002to be scanned sequentially and illuminated with different colors of light by the illumination optical system1001; an electronic circuit1003for driving the light modulator1002; and projection optical system1004for projecting light modulated by the light modulator1002. The projection video system1005magnifies and projects video information onto a screen1006. As the illumination optical system1001, any one of the illumination optical systems in Embodiments 1 to 7 can be used. The electronic circuit1003generates a driving signal suitable for the light modulator1002, which is scanned sequentially with different colors of light, in accordance with a video signal, and thus drives the light modulator1002. As the light modulator1002, e.g., a transmission-type liquid crystal panel can be used.

The above configuration can provide a projection video system that is very valuable for industrial use. The reason for this is as follows: the configuration of the electronic circuit1003can be simplified due to the favorable scanning linearity of the illumination optical system1001, the system can perform scanning with a small motor because of its reduced wind resistance, the noise is lowered, and the like.

FIG. 11shows the configuration of an integral-type video display1104of Embodiment 9 of the present invention. The integral-type video display1104includes the projection video system1005of Embodiment 8, a reflecting mirror1101, a transmission-type screen1102, and a case1103for housing the projection video system1005, the reflecting mirror1101, and the screen1102.

The above configuration can provide an integral-type video display that is very valuable for industrial use. The reason for this is as follows: the configuration of the electronic circuit can be simplified due to the favorable scanning linearity of the illumination optical system, the system can perform scanning with a small motor because of its reduced wind resistance, the noise is lowered, and the like.