JP2010128239A - Separation/synthesis optical system and multi-plate type projector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separation/synthesis optical system which suppresses the influence of chromatic aberration generated in a lighting optical system with a simple optical constitution or to provide a projector using the separation/synthesis optical system, regarding the technology of the separation/synthesis optical system used for a multi-plate type projector. <P>SOLUTION: A synthesis surface 21b of the separation/synthesis optical system (a separation/synthesis prism 18) is constituted at a position where optical path lengths to each of optical modulation devices (an optical modulation device 24 and an optical modulation device 25) from the synthesis surface 21b are equal. Further, a separation surface 21a is constituted as a plane different from the synthesis surface 21b at a position where optical path lengths to each of the optical modulation devices (optical modulation device 24 and optical modulation device 25) from the separation surface 21a are different from each other and satisfy desired lengths. In this way, the influence of the chromatic aberration generated in a lighting optical system 12 can be suppressed with a simple optical constitution. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for a multi-plate projection apparatus, and more particularly to a technique for a separation / synthesis optical system used in a multi-plate projection apparatus.

  Projectors can be broadly classified into single-plate projectors and multi-plate projectors depending on the number of light modulation elements such as micromirror devices. A single-plate projection apparatus is a projection apparatus that displays a color image by changing the wavelength of projection light with time using only one light modulation element. On the other hand, a multi-plate projection apparatus is a projection apparatus that displays a color image by using a plurality of light modulation elements and each light modulation element modulates illumination light having a different wavelength and combines them.

  In a multi-plate projection apparatus, light is separated for each color (wavelength, actually a wavelength range having a certain width), and then a plurality of light modulation elements are illuminated. At this time, it is desirable that the plurality of light modulation elements to be illuminated are illuminated under equal conditions. However, the light of different colors (wavelengths) that illuminates each light modulation element changes the optical path length to the image position for each color due to chromatic aberration, and thus causes a difference in the illumination conditions of each light modulation element. . For this reason, a technique for suppressing the influence of chromatic aberration generated in an illumination optical system that illuminates a light modulation element is required for a multi-plate projection apparatus.

  Various methods have been proposed as methods for suppressing the influence of such chromatic aberration. For example, there is a method of correcting chromatic aberration using a cemented lens (for example, a doublet composed of a convex lens and a concave lens) formed of a plurality of lenses having different refractive indexes and chromatic dispersions.

  However, the illumination optical system is disposed in the vicinity of the light source and is exposed to high temperatures, so that thermal restrictions are severe. In such an environment, it is difficult to use a complicated optical system such as a cemented lens that is cemented using an adhesive or the like because a problem such as a pain on the cemented surface occurs. In general, the demand for cost reduction for the illumination optical system is higher than that of other optical systems, and it is difficult to correct chromatic aberration with the above-described complicated optical configuration even in consideration of cost.

  Furthermore, when a separation / combination prism is used in a multi-plate projector, the optical path in the prism is generally longer. Since the chromatic aberration becomes larger as the optical path length becomes longer, the influence of the chromatic aberration becomes more conspicuous in the multi-plate projection apparatus using the separation / combination prism.

  In view of the above circumstances, an object of the present invention is to provide a separation / synthesis optical system that suppresses the influence of chromatic aberration generated in an illumination optical system having a simple optical configuration, or a projection apparatus using the same.

  According to a first aspect of the present invention, a plurality of light modulation elements, a separation surface that separates illumination light emitted from the illumination optical system toward each of the plurality of light modulation elements, and each of the plurality of light modulation elements A separating / synthesizing unit including a combining surface for combining the modulated light; and a field lens disposed between each of the plurality of light modulation elements and the separating / synthesizing unit. The separating surface is a plane different from the combining surface. A separation / synthesis optical system is provided.

  According to a second aspect of the present invention, in the separation / synthesis optical system according to the first aspect, the optical path lengths between each of the plurality of light modulation elements and the combination surface are equal to each other, and The optical path lengths between the separation surfaces provide different separation / combination optical systems.

  According to a third aspect of the present invention, in the separation / synthesis optical system according to the first or second aspect, the separation surface is located at a position where the influence of chromatic aberration generated in the illumination optical system is suppressed by each of the light modulation elements. A separation / synthesis optical system is provided.

  According to a fourth aspect of the present invention, in the separation / combination optical system according to any one of the first to third aspects, each of the plurality of light modulation elements is generated when the illumination light is separated on the separation surface. The optical path length from the separation surface to each of the light modulation elements that are illuminated with light having different wavelengths provides a longer separation / synthesis optical system as the wavelength of the light incident on the light modulation element is longer.

  According to a fifth aspect of the present invention, in the separation / synthesis optical system according to any one of the first to fourth aspects, the separation / synthesis unit includes the first dichroic film in a region where the illumination light is incident on the separation surface. A separation / synthesis optical system including a second dichroic film in a region where the modulated light is incident on the synthesis surface is provided.

  According to a sixth aspect of the present invention, in the separation / synthesis optical system according to the fifth aspect, the first dichroic film and the second dichroic film are dichroic films optimized for the incident angle of each incident light. A separation / synthesis optical system is provided.

  According to a seventh aspect of the present invention, in the separation / synthesis optical system according to any one of the first to sixth aspects, the pupil position of the illumination optical system is in the vicinity of the separation surface, and the projection optical system projects the modulated light. Provides a separation / synthesis optical system in the vicinity of the synthesis surface.

  According to an eighth aspect of the present invention, in the separation / combination optical system according to any one of the first to seventh aspects, the separation / combination optical system is an object whose principal ray is parallel between the light modulation element and the field lens. This is a side telecentric optical system, and the separation surface and the synthesis surface provide a separation / synthesis optical system in the vicinity of the focal position of the field lens.

  According to a ninth aspect of the present invention, in the separation / synthesis optical system according to any one of the first to eighth aspects, a light beam incident on the separation surface and separated and a light beam incident on the synthesis surface and synthesized are separated. Provided is a separation / synthesis optical system that does not cross each other in the vicinity of a surface and a synthesis surface.

A tenth aspect of the present invention provides the separation / synthesis optical system according to any one of the first to ninth aspects, wherein the separation surface is a plane parallel to the synthesis surface.
According to an eleventh aspect of the present invention, in the separation / synthesis optical system according to any one of the first to tenth aspects, the plurality of light modulation elements are illuminated with light having a red wavelength. And a second light modulation element illuminated with light having green and blue wavelengths, and the first optical path length between the first light modulation element and the separation surface is the second light modulation. Provided is a separation / synthesis optical system longer than a second optical path length between an element and a separation surface.

  A twelfth aspect of the present invention provides a projection apparatus including the separation / synthesis optical system according to any one of the first to eleventh aspects.

  According to the present invention, it is possible to provide a separation / synthesis optical system that suppresses the influence of chromatic aberration generated in an illumination optical system having a simple optical configuration, or a projection apparatus using the same.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating the configuration of a multi-plate projection apparatus according to an embodiment of the invention. The projection device 100 includes a light source 10, a reflector 11, an illumination optical system 12, a polarization conversion optical system 13, a wavelength selective polarization conversion unit 14, a condenser lens 15, and two mirrors (mirror 16 and mirror 17). The separation / combination prism 18, two light modulation elements (light modulation element 24, light modulation element 25), two field lenses (field lens 26, field lens 27), polarizing plate 28, and projection optical system 29. And a wavelength selection polarization conversion means 14 and a control circuit (not shown) for controlling the two light modulation elements.

  The separation / combination prism 18 includes two prisms (prisms 19 and 20) having different shapes and a parallel plate 21 sandwiched between them. The prism 19, the prism 20, and the parallel plate 21 have substantially the same refractive index, and transmitted light hardly refracts at the boundary between the prism 19, the parallel plate 21, and the prism 20.

  A separation dichroic film 22 is disposed on the surface (separation surface 21 a) of the parallel plate 21 that contacts the prism 20, and a synthesis dichroic film 23 is disposed on the surface (combination surface 21 b) that contacts the prism 19. The separation dichroic film 22 and the synthesis dichroic film 23 both reflect light having a red wavelength (hereinafter referred to as R light), and light having blue and green wavelengths (hereinafter referred to as B light and G light respectively). It has a characteristic of transmitting light. That is, the separation / combination prism 18 separates the R light of the incident light toward the light modulation element 24, and separates the B light and the G light toward the light modulation element 25, and from the light modulation element 24 and the light modulation element 25. It functions as a separating and synthesizing means for synthesizing the modulated light.

  The synthesis surface 21b is formed at a position where the optical path lengths from the light modulation element 24 and the light modulation element 25 to the dichroic film 23 (synthesis surface 21b) are equal. On the other hand, the separation surface 21 a is formed at a position where the optical path length from the dichroic film 22 (separation surface 21 a) to the light modulation element 24 is longer than the optical path length from the dichroic film 22 (separation surface 21 a) to the light modulation element 25. Yes. More specifically, the separation surface 21a is formed at a position shifted by a predetermined distance in the positive direction of the optical axis of the illumination light 3 with respect to the synthesis surface 21b. As a result, the optical path length from the dichroic film 22 (separation surface 21a) to the light modulation element 24 becomes longer by the predetermined distance than the case where the dichroic film 22 is formed on the composite surface 21b. The optical path length from 22 (separation surface 21a) to the light modulation element 25 is shortened by the predetermined distance.

  Thus, the main purpose of the configuration in which the separating surface 21a and the combining surface 21b are different planes is to suppress the influence of chromatic aberration caused by the illumination optical system. Hereinafter, the reason why the influence of chromatic aberration can be suppressed by forming the separation surface 21a and the synthesis surface 21b as different planes will be described.

FIG. 2 is a diagram for explaining a method for suppressing the influence of chromatic aberration used in the projection apparatus according to the present embodiment. First, chromatic aberration will be briefly described with reference to FIG. The light including a plurality of colors (wavelengths) emitted from the light source 30 is refracted by the lens action of the optical system 31 and is preferably condensed at one condensing position (image position). However, in actuality, the lens member constituting the optical system 31 has a different refractive index depending on the color (wavelength), and therefore the condensing position (image position) differs for each color. Specifically, the refractive index of the lens member shows a larger value in the order of blue (B), green (G), and red (R) (refractive index for B> refractive index for G> refractive index for R). For this reason, among the light refracted by the optical system 31, the R light 31 r is condensed on the condensing surface 32 farthest from the optical system 31, and the G light 31 g is then condensed from the optical system 31. The B light 31 b is condensed on the condensing surface 34 closest to the optical system 31. That is, the optical path length to the condensing position is different for each color. As described above, a phenomenon in which the condensing position (image position) and the optical path length to the condensing position are different for each color is called chromatic aberration.

  By the way, in a projection apparatus using a light modulation element, it is desirable that the modulation surface of the light modulation element (for example, a mirror plane if the light modulation element is a micromirror device) and the light collection position (image position) are the same. . By using a method of correcting chromatic aberration by the configuration of the optical system 31 (that is, a method of bringing the condensing position of each color light closer to one modulation surface), the deviation between the condensing position of each color light and the modulation surface is reduced. Can do. Thereby, the influence of chromatic aberration is suppressed. However, the optical system 31 in the projection apparatus corresponds to, for example, the illumination optical system 12 of the projection apparatus 100 illustrated in FIG. 1, and an optical system having a complicated configuration cannot be employed for the reason described above. It is difficult to correct chromatic aberration with the above configuration.

  Therefore, in the present embodiment, attention is paid to the fact that in the case of a multi-plate projection device, the optical path length from the light source to the modulation surface can be adjusted for each light modulation element, and different optical path lengths can be obtained. The projection apparatus is configured such that the modulation surface of each light modulation element is located at a position where the deviation of each color (wavelength) incident on the modulation surface from the light collection position (image position) can be minimized. For example, as illustrated in FIG. 2, the modulation surface of the light modulation element 35 on which only the R light 31r is incident is the modulation surface of the light modulation element 36 on which the G light 31g and the B light 31b are incident on the light collection surface 32. Is configured to be positioned on a surface 37 between the light collecting surface 33 and the light collecting surface 34. When configured in this way, the deviations between the condensing position and the modulation surface in each of the R light 31r, the G light 31g, and the B light 31b are 0, distance 38, and distance 39, which can be reduced as a whole. Thereby, the influence of chromatic aberration can be suppressed as compared with the case where the position of the modulation surface is only one. The optical path length 40 and the optical path length 41 illustrated in FIG. 2 indicate the optical path length from the light source 30 to the light modulation element 35 and the optical path length from the light source 30 to the light modulation element 36, respectively. It shows that the optical path length is different.

  That is, this embodiment does not correct the chromatic aberration itself, but makes the optical path length to the modulation surface of each modulation element different from each other according to the color (wavelength) incident on the modulation surface. Suppress.

  In the projection apparatus 100 of this embodiment illustrated in FIG. 1, this is realized by providing the separation surface 21a of the separation / combination prism 18 on a different plane from the synthesis surface 21b. As already described above, the optical path length from each of the light modulation element 24 and the light modulation element 25 to the synthesis surface 21b (dichroic film 23) is equal. On the other hand, the optical path length from the separation surface 21a (dichroic film 22) to the light modulation element 24 and the optical path length from the separation surface 21a (dichroic film 22) to the light modulation element 25 are different. As a result, the optical path lengths from the light source 10 to each of the light modulation element 24 and the light modulation element 25 are also different. More specifically, the optical path length from the light source 10 to the light modulation element 24 is increased by an amount corresponding to the thickness of the parallel plate 21 (for example, twice the thickness of the parallel plate 21). The optical path length to the element 25 is shortened. That is, by changing the thickness of the parallel plate 21, the optical path length to each light modulation element can be adjusted, thereby selecting the optimum optical path length that can suppress the influence of chromatic aberration for each light modulation element. Can do. The above is the reason why the influence of chromatic aberration can be suppressed by forming the separation surface 21a and the synthesis surface 21b as different planes.

In the present embodiment, the separation surface 21a is configured to be shifted in the positive direction of the optical axis of the illumination light 3 with respect to the synthesis surface 21b. However, the present invention is not limited to this. The optical axis is shifted in the positive direction because the color (wavelength) reflected by the separation surface 21a is R light, and the G light and B light that are transmitted are condensed far away. This is because it is necessary to increase the length. For example, if R light is transmitted through the separation surface 21a and G light and B light are reflected, the separation surface 21a needs to be shifted in the negative direction of the optical axis with respect to the composite surface 21b for the same reason. . That is, it is necessary to shift the separation surface 21a with respect to the synthesis surface 21b so that the longer the wavelength of light incident on the light modulation element, the longer the optical path length from the separation surface 21a to each of the light modulation elements.

  Moreover, in this embodiment, although the separation surface 21a and the synthetic | combination surface 21b were comprised as a different plane using the parallel plate 21, it is not limited to this in particular. For example, a wedge-shaped member may be sandwiched between the prism 19 and the prism 20 instead of the parallel plate 21, and the boundary surfaces thereof may be a composite surface and a separation surface, respectively.

  FIGS. 3A and 3B are schematic diagrams for explaining the difference in optical path between the case where a parallel flat plate is provided in the separation / combination prism and the case where a wedge-shaped member is provided. FIG. 3A schematically shows the optical paths of the illumination light and the modulated light at the separation / combination prism when a parallel plate is provided. FIG. 3B schematically shows the optical paths of illumination light and modulated light at the separation / combination prism when the wedge-shaped member is provided. 3A and 3B, the optical system and the optical path are simplified for convenience of explanation.

  As illustrated in FIG. 3A, when the separating surface 21 a and the combining surface 21 b are shifted in the optical axis direction of the illumination light 3 using the parallel plate 21, the illumination that reflects the separating surface 21 a and enters the light modulation element 24. The optical axis of the light 4a is shifted from the center of the light modulation element 24 in a direction (height direction) perpendicular to the optical axis. Accordingly, since it is necessary to illuminate the light modulation element in consideration of the deviation in the height direction, a wider illumination range is required, which may be a factor in reducing the illumination efficiency.

  On the other hand, as illustrated in FIG. 3B, when the separating surface 21a and the combining surface 21b are shifted in the optical axis direction of the illumination light 3 using the wedge-shaped member 42, both surfaces of the wedge-shaped member 42 (the separating surface 21a and the combining surface 21b). ) Form a predetermined angle, the deviation from the center of the light modulation element 24 that occurs when the separation surface 21a is incident is canceled when the light modulation element 24 is incident. More specifically, when the separation surface is in the positive direction of the optical axis from the synthesis surface as shown in FIG. 3B, the separation surface is the synthesis surface so that the incident angle on the separation surface is smaller than the incidence angle on the synthesis surface. In the case where the optical axis is in the negative direction, the incident angle on the separation surface may be larger than the incident angle on the composite surface. Thereby, the shift | offset | difference which arises in a height direction can be negated, and the fall of illumination efficiency can be suppressed. At this time, the chief ray is tilted, but since the tilt angle is a very small amount, the influence on the projected image can be ignored.

  In the present embodiment, the optical path lengths from the respective light modulation elements to the synthesis surface 21b are configured to be equal. As a result, the optical path length from each light modulation element to a screen (projection surface) (not shown) is equal. However, chromatic aberration can also occur in the projection system from each modulation element to the projection surface, as in the illumination system from the light source 10 to each modulation element. For this reason, a method of suppressing the influence of chromatic aberration by varying the optical path length from each light modulation element to the synthesis surface 21b is also conceivable. However, if the projection magnification is different in the projection system, the image of each pixel of each color does not match on the projection plane, which greatly affects the image quality. For this reason, it is necessary to make the projection magnifications exactly the same, and in this embodiment, the optical path lengths from the respective light modulation elements to the projection surface are made equal.

  The light modulation element 24 and the light modulation element 25 illustrated in FIG. 1 are, for example, micromirror devices. The micromirror device includes a plurality of micromirrors, and modulates incident light by controlling the inclination of each micromirror. In the present embodiment, the light modulation element 24 and the light modulation element 25 are described as micromirror devices, but are not particularly limited thereto. Any reflective light modulation element may be used. For example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) may be used.

FIG. 4 is a diagram illustrating the configuration of a wheel-type wavelength selective polarization conversion unit included in the projection apparatus according to this embodiment. The wheel-type wavelength selective polarization conversion means 14 divides the whole into two regions, and converts the polarization direction of the B light only in a wavelength selective manner from the S polarization to the P polarization, and the polarization of the G light. It is configured by combining a specific wavelength polarization conversion element 14b that wavelength-selectively converts only the direction from S-polarized light to P-polarized light. Each specific wavelength polarization conversion element is disposed so as to be perpendicular to the optical axis of the incident light. By configuring in this way, each specific wavelength polarization conversion element can convert the polarization direction with high accuracy, that is, only a desired color (wavelength).

  Further, the wheel-type wavelength selective polarization conversion means 14 is not limited to the configuration illustrated in FIG. 4, and at least one specific wavelength polarization conversion element that wavelength-selectively converts the polarization direction of a specific wavelength. As long as it is configured. Further, the wavelength selective polarization conversion means 14 is not limited to the wheel type illustrated in FIG. Instead of the wheel-type wavelength selective polarization conversion means 14, a so-called drum-type wavelength selective polarization conversion means for switching a specific wavelength polarization conversion element that has a plurality of specific wavelength polarization conversion elements on the cylinder surface and acts by rotation of the cylinder, A so-called slide-type wavelength selective polarization conversion means for switching a specific wavelength polarization conversion element that operates by arranging a plurality of specific wavelength polarization conversion elements in a certain direction and sliding them may be used. In addition, electronic color-specific polarization control that can switch the wavelength component that changes the polarization direction by electrical control, such as color switch of Colorlink and electronic color switch of Rolic Technologies Ltd. in Arschville, Switzerland. Means may be used.

  Hereinafter, the flow until the illumination light 1 emitted from the light source 10 is projected onto a screen (not shown) will be described together with the operation of each component of the projection device 100 with reference to FIGS. 1 and 4.

First, illumination light 1 including a plurality of wavelengths and a plurality of polarization directions emitted from a light source 10 such as a mercury lamp is collected using a reflector 11 and enters an illumination optical system 12.
FIG. 5 is a diagram illustrating a configuration of an illumination optical system used in the projection apparatus according to the present embodiment. As illustrated in FIG. 5, the illumination optical system 12 has a simple configuration including a single lens group that does not include a cemented lens. For this reason, the illumination optical system 12 does not sufficiently correct chromatic aberration.

  The illumination light 1 emitted from the illumination optical system 12 is further incident on a polarization conversion optical system 13 for converting the polarization direction of the incident light into a certain direction. The polarization conversion optical system 13 acts to convert the illumination light 1 into S-polarized light. More specifically, for example, using a polarization element that transmits only P-polarized light, the illumination light 1 is converted into P-polarized light and S-polarized light. By separating the light once and transmitting only the P-polarized light through the 1 / 2λ plate, the incident illumination light 1 is converted to S-polarized light and then output. Although a mercury lamp is assumed here as the light source 10, a laser light source including a plurality of sub light sources may be used. In this case, the polarization conversion optical system 13 can be omitted.

  The illumination light 2 converted to S-polarized light and emitted from the polarization conversion optical system 13 enters the wheel-type wavelength selective polarization conversion means 14. The illumination light 2 incident on the wheel-type wavelength selective polarization conversion unit 14 illustrated in FIG. 4 is only B-polarized by the rotation of the wheel-type wavelength selection polarization conversion unit 14 controlled by a control device (not shown). One of the specific wavelength polarization conversion element 14a for converting to P and the specific wavelength polarization conversion element 14b for converting only the G light into P polarization are alternately transmitted. As a result, the illumination light 3 transmitted through the wheel-type wavelength selective polarization conversion means 14 is transmitted through the specific wavelength polarization conversion element 14a, and only the B light is P polarized (otherwise S polarized), and the specific wavelength polarization conversion element. 14b, and only G light is P-polarized light (otherwise it is S-polarized light), and alternately has two states over time. As will be described in detail later, the light of the wavelength converted here is blocked by the polarizing plate 28 and excluded from the projection optical path.

The illumination light 3 that has passed through the wheel-type wavelength selective polarization conversion means 14 enters the separation / combination prism 18 through the condenser lens 15, the reflection mirror 16, and the reflection mirror 17 in a state where only the B light or the G light is P-polarized. . Hereinafter, a case where only the B light is in the P-polarized state through the specific wavelength polarization conversion element 14a in the wheel type wavelength selective polarization conversion means 14 will be described as an example.

  Only the B light incident on the separating / combining prism 18 is P-polarized illumination light 3 is transmitted through the prism 19 and the combining surface 21b and is incident on the separating surface 21a. A separation dichroic film 22 is disposed in the region of the separation surface 21a on which the luminous flux 3 is incident. Since the dichroic film 22 has characteristics of reflecting R light and transmitting B light and G light, the R light of the illumination light 3 reflects the dichroic film 22, and the B light and G light of the illumination light 3 are dichroic. Permeates through the membrane 22. Thereby, the illumination light 3 is separated into the illumination light 4a of R light and the illumination light 4b of B light and G light.

  The R illumination light 4 a reflected from the dichroic film 22 is totally reflected by the incident surface of the prism 19 and then enters the field lens 26. The field lens 26 acts so that the chief rays of the illumination light 4a are all parallel light. As a result, the illumination light 4a enters the light modulation element 24 at a predetermined angle. On the other hand, the B and G illumination lights 4 b that have passed through the dichroic film 22 pass through the prism 20 and enter the field lens 27. The field lens 27 acts so that the chief rays of the illumination light 4b are all parallel light. As a result, the illumination light 4b enters the light modulation element 25 at a predetermined angle. In other words, the optical system including the separation / combination prism 18, the field lens 26, and the field lens 27 has a principal ray parallel between the field lens 26 and the light modulation element 24 (between the field lens 27 and the light modulation element 25). This is a telecentric optical system.

  In addition, the optical path length from the light source 10 to each modulation element is optimal so that the influence of chromatic aberration is suppressed by disposing the separation surface 21a by a predetermined distance in the positive direction of the optical axis with respect to the synthesis surface 21b. The optical path length is adjusted.

  The R illumination light 4a incident on the light modulation element 24 is modulated by the micromirror of the light modulation element 24 based on a control signal related to red (R) received from a control circuit (not shown), and corresponds to the micromirror. Only the amount of light required for each pixel of the projected image is reflected in the normal direction as modulated light 5a. The modulated light 5a of the R light modulated by the light modulation element 24 passes through the field lens 26, is totally reflected again by the incident surface of the prism 19, and then enters the composite surface 21b. A synthesizing dichroic film 23 is disposed in the area of the synthesizing surface 21b on which the modulated light beam 5a is incident. The dichroic film 23 has a characteristic of reflecting R light, like the dichroic film 22. For this reason, the modulated light 5a of the R light is reflected by the dichroic film 23 and emitted from the separation / combination prism 18 as a part of the combined light 6 combined with the modulated light 5b modulated by the light modulation element 25 described later.

  On the other hand, the illumination light 4b of B light and G light incident on the light modulation element 25 is modulated by each micromirror of the light modulation element 25 based on a control signal related to green (G) received from a control circuit (not shown). Only a necessary amount of light for each pixel corresponding to the micromirror is reflected in the normal direction as modulated light 5b.

  A control circuit (not shown) controls the light modulation element 25 in synchronization with the rotation of the wheel-type wavelength selective polarization conversion means 14. More specifically, the control circuit (not shown) includes a specific wavelength polarization conversion element 14a that converts only the B light into P polarization when the illumination light 2 is switched when the specific wavelength polarization conversion means in the wavelength selective polarization conversion means 14 is switched. When transmitting, the control signal regarding green (G) is transmitted to the light modulation element 25 when transmitting the control signal regarding blue (B) to the specific wavelength polarization conversion element 14b that converts only G light into P polarization. To do. Thereby, in the light modulation element 25, the incident light composed of the B light and the G light is modulated based on the control signal relating to the color (wavelength) whose polarization direction has not been converted by the wavelength selective polarization conversion means 14. .

  The modulated light 5b of B light and G light modulated by the light modulation element 25 passes through the field lens 27 and enters the combining surface 21b. The area of the composite surface 21b where the light beam of the modulated light 5b enters coincides with the area where the light beam of the modulated light 5a enters. Therefore, a synthesizing dichroic film 23 is disposed in a region where the modulated light beam 5b is incident. As a result, the modulated light 5b of B light and G light is transmitted through the dichroic film 23 and emitted from the separating / combining prism 18 as a part of the combined light 6 combined with the modulated light 5a modulated by the light modulation element 24 described above. Is done.

  By the way, in this embodiment, the separation surface 21a and the synthesis surface 21b of the separation / combination prism 18 are configured as different planes, and the separation dichroic film 22 and the synthesis dichroic film 23 are provided separately. This configuration is adopted to suppress the influence of chromatic aberration as described above. In such a configuration, in order for light separation by the dichroic film 22 and light synthesis by the dichroic film 23 to be appropriately performed, the light beam of the illumination light 3 separated by the dichroic film 22 is synthesized by the dichroic film 23. It is necessary that the light beams of the modulated light 5 a and the modulated light 5 b do not overlap on the parallel plate 21. In order to prevent the overlapping of the light beams, the optical system may be configured so that the light beam diameters of the respective light beams become smaller in the vicinity of the parallel plate 21. More specifically, the pupil position of the illumination optical system (illumination light 3) is configured in the vicinity of the dichroic film 22 on the separation surface 21a, and the pupil position of the projection optical system (modulated light 5a and modulated light 5b) is combined with the combined surface 21b. It is constructed in the vicinity of the upper dichroic film 23. Such adjustment of the pupil position is realized by using the field lens 26 and the field lens 27. In this case, considering that the principal ray between the field lens and the light modulation element is a parallel object-side telecentric optical system, the focal positions of the field lens 26 and the field lens 27 are the separation plane and the synthesis plane. It will be in the vicinity.

  The combined light 6 emitted from the separation / combination prism 18 enters the polarizing plate 28. Since the polarizing plate 28 has a characteristic of transmitting only the S-polarized light, the B light converted into the P-polarized light by the wavelength selective polarization converting means 14 in the combined light 6 cannot pass through the polarizing plate 28. Therefore, only the R light and G light modulated by the corresponding color control data in each light modulation element are transmitted through the polarizing plate 28 and are incident on the projection optical system 29 as projection light 7. The projection light 7 is magnified by the projection optical system 29 and projects an image on a screen (not shown). When only the G light is converted into P polarized light by the wavelength selective polarization conversion means 14, only the R light and the B light are transmitted through the polarizing plate 28 and projected. Therefore, by switching the specific wavelength polarization conversion element transmitted by the wavelength selective polarization conversion means 14 with time, the projection light composed of R light and B light and the projection light composed of R light and G light are alternately projected on the screen. As a result, a color image is displayed.

  As described above, in the present embodiment, by using the separation / synthesis optical system in which the separation surface 21a is shifted in the optical axis direction with respect to the synthesis surface 21b, the influence of chromatic aberration generated in the illumination optical system can be reduced without complicating the optical configuration. Can be suppressed. Further, by using the separating surface 21a and the combining surface 21b as different planes and using the separating and combining dichroic films, it is possible to optimize the characteristics of the dichroic film according to the incident angle of incident light. Thereby, the color reproducibility of the projected image is improved. Furthermore, since the separation surface 21a and the synthesis surface 21b are different planes, overlapping of these dichroic films having different characteristics is inevitably prevented. This eliminates the need for advanced management of the region where the dichroic film is formed, and reduces the burden on manufacturing the separation / synthesis optical system.

  Needless to say, the present invention is not limited to the configuration exemplified in the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a figure which illustrates the structure of the multi-plate type projector which concerns on one Embodiment of this invention. It is a figure for demonstrating the method to suppress the influence of the chromatic aberration used with the projector which concerns on one Embodiment of this invention. It is the figure which showed typically the optical path of the illumination light and modulation | alteration light in the isolation | separation synthetic | combination prism provided with the parallel plate used with the projector which concerns on one Embodiment of this invention. It is the figure which showed typically the optical path of the illumination light and the modulation | alteration light in the isolation | separation synthetic | combination prism provided with the wedge-shaped member used with the projector which concerns on one Embodiment of this invention. It is a figure which illustrates the structure of the wheel-type wavelength selective polarization conversion means contained in the projection apparatus which concerns on one Embodiment of this invention. It is the figure which illustrated the structure of the illumination optical system used for the projector which concerns on one Embodiment of this invention.

Explanation of symbols

100 Projectors 1, 2, 3, 4a, 4b Illumination light 5a, 5b Modulated light 6 Combined light 7 Projected light 10, 30 Light source 11 Reflector 12, 31 Illumination optical system 13 Polarization conversion optical system 14 Wavelength selective polarization conversion means 14a , 14b Specific wavelength polarization conversion element 15 Condensing lens 16, 17 Mirror 18 Separating / combining prism 19, 20 Prism 21 Parallel plate 21a Separating surface 21b Combining surface 22, 23 Dichroic films 24, 25, 35, 36 Light modulation elements 26, 27 Field lens 28 Polarizing plate 29 Projection optical system 31r R light 31g G light 31b B light 32, 33, 34 Condensing surface 37 Surface 38, 39 Distance 40, 41 Optical path length 42 Wedge shaped member

Claims (12)

A plurality of light modulation elements;
A separating / combining means including a separating surface for separating the illumination light emitted from the illumination optical system toward each of the plurality of light modulation elements and a combining surface for combining the modulated light from each of the plurality of light modulation elements;
A field lens disposed between each of the plurality of light modulation elements and the separating and synthesizing unit,
The separation / synthesis optical system according to claim 1, wherein the separation surface is a plane different from the synthesis surface. The separation / synthesis optical system according to claim 1,
The optical path length between each of the plurality of light modulation elements and the composite surface is equal,
A separation / synthesis optical system characterized in that optical path lengths between each of the plurality of light modulation elements and the separation surface are different from each other. The separation / synthesis optical system according to claim 1 or 2,
The separation / synthesis optical system, wherein the separation surface is disposed at a position where an influence of chromatic aberration generated in the illumination optical system is suppressed by each of the light modulation elements. The separation / synthesis optical system according to any one of claims 1 to 3,
Each of the plurality of light modulation elements is illuminated with light having different wavelengths generated by the illumination light being separated by the separation surface,
The separation / synthesis optical system characterized in that an optical path length from the separation surface to each of the light modulation elements is longer as a wavelength of light incident on the light modulation element is longer. The separation / synthesis optical system according to any one of claims 1 to 4,
The separation and synthesis means includes
A first dichroic film on a region where the illumination light is incident on the separation surface;
A separation / synthesis optical system comprising a second dichroic film in a region where the modulated light is incident on the synthesis surface. The separation / synthesis optical system according to claim 5,
The separation / synthesis optical system characterized in that the first dichroic film and the second dichroic film are dichroic films optimized for the incident angle of each incident light. The separation / synthesis optical system according to any one of claims 1 to 6,
The pupil position of the illumination optical system is in the vicinity of the separation surface,
A separation / synthesis optical system characterized in that a pupil position of the projection optical system for projecting the modulated light is in the vicinity of the synthesis surface. The separation / synthesis optical system according to any one of claims 1 to 7,
The separation / synthesis optical system is an object side telecentric optical system in which chief rays are parallel between the light modulation element and the field lens,
The separation / synthesis optical system, wherein the separation surface and the synthesis surface are in the vicinity of a focal position of the field lens. The separation / synthesis optical system according to any one of claims 1 to 8,
The separation / synthesis optical system characterized in that the light beam incident on the separation surface and separated and the light beam incident on the synthesis surface and synthesized do not intersect each other in the vicinity of the separation surface and the synthesis surface. The separation / synthesis optical system according to any one of claims 1 to 9,
The separation / synthesis optical system characterized in that the separation surface is a plane parallel to the synthesis surface. The separation / synthesis optical system according to any one of claims 1 to 10,
The plurality of light modulation elements include a first light modulation element illuminated with light having a red wavelength and a second light modulation element illuminated with light having green and blue wavelengths,
Separation characterized in that a first optical path length between the first light modulation element and the separation surface is longer than a second optical path length between the second light modulation element and the separation surface. Synthetic optical system.   A projection apparatus comprising the separation / synthesis optical system according to any one of claims 1 to 11.