JP5213484B2 - Image projection device - Google Patents

Description

  The present invention relates to an image projection apparatus such as a projector using a polarization conversion optical system that converts light from a plurality of light sources into polarized light.

  As an image projection apparatus that modulates light by an image modulation element (spatial light modulation element) such as a liquid crystal panel and projects the modulated light onto a projection surface such as a screen via a projection lens, the three primary colors of RGB are used. There are many so-called three-plate projectors using three corresponding image modulation elements. However, as disclosed in Patent Document 1, a so-called two-plate projector using two liquid crystal panels has also been proposed.

  In the projector disclosed in Patent Document 1, the other two primary color components are extracted using temporal color separation means that sequentially removes one primary color component from the light emitted from the light source as time passes. The two extracted primary color components are each led to the corresponding liquid crystal panel. The two liquid crystal panels perform image modulation corresponding to the primary color components guided there, and project the modulated light onto the screen through the projection lens. With this configuration, a small projector is realized with a simpler configuration than the three-plate projector.

  Patent Documents 2 and 3 disclose projectors using a plurality of light sources that emit light in different wavelength bands and polarization conversion elements.

  In the projector disclosed in Patent Document 2, polarization conversion elements are individually provided for the three RGB light source (LED) arrays, and light emission from the three LED arrays is sequentially switched, thereby three polarization conversion elements. The light from is guided to one liquid crystal panel. Then, the modulated light from the liquid crystal panel is projected onto a screen via a projection lens. In addition, this projector uses a polarization conversion element in which a plurality of polarization conversion cells are arranged with a period equal to the arrangement period of the plurality of LEDs in the LED array. Light emitted from the plurality of LEDs is incident on approximately half of the opening portion of the polarization conversion element, and is converted into linearly polarized light having a single polarization direction by each polarization conversion cell and is emitted.

In the projector disclosed in Patent Document 3, the arrangement period of the plurality of polarization conversion cells in the polarization conversion element is set to double the arrangement period of the plurality of LEDs in the LED array. Light emitted from the plurality of LEDs is incident on almost all opening portions of the polarization conversion element, and light having different polarization directions is emitted depending on the positions of the opening portions. Light from adjacent LEDs in the LED array is emitted from the polarization conversion element as P-polarized light and S-polarized light whose polarization directions are orthogonal to each other. By alternately lighting adjacent LEDs, P-polarized light and S-polarized light are alternately emitted from one polarization conversion element, and are guided to an image modulating element for P-polarized light and S-polarized light. These image modulation elements form original images for P-polarized light and S-polarized light in synchronization with alternating incidence of P-polarized light and S-polarized light, respectively, so that an image is projected onto the screen.
JP 2001-228455 A Japanese Patent Application Laid-Open No. 2002-244211 JP 2004-206046 A

  However, since the projector disclosed in Patent Document 1 removes one primary color component from the light from the light source, the light use efficiency is low and the power consumption of the light source is not efficient.

  Further, in the projector disclosed in Patent Document 2, since the arrangement cycle of the polarization conversion cells in the polarization conversion element is the same as the arrangement cycle of the LEDs in the LED array, there is a limit to increasing the density of the LED array. For this reason, in order to increase the number of LEDs and obtain a high-luminance projection image, the LED array becomes large. Moreover, since the light emission of the RGB LEDs is sequentially switched, the brightness is reduced and a color break occurs.

  Further, in the projector disclosed in Patent Document 3, since the P-polarized light and the S-polarized light are alternately emitted from the polarization conversion element, even if the arrangement period of the LED is twice the arrangement period of the polarization conversion cell, the brightness is Really halved. In addition, since the two image modulation elements operate alternately, the utilization efficiency is poor.

  The present invention has a polarization conversion optical system that converts light from a plurality of light sources into polarized light, and is a compact image projection device that can project high-quality images with high use efficiency of light from light sources and image modulation elements. I will provide a.

  An image projection apparatus according to one aspect of the present invention includes a first light source, a second light source, a third light source, and a first light source that respectively emit first light, second light, third light, and fourth light. Four light sources and first, second, third, and fourth lights from the first, second, third, and fourth light sources are incident from different incident regions, and the first and second light sources The first and second light beams are emitted with their polarization directions aligned with the first polarization direction, and the third and fourth light polarization directions from the third and fourth light sources are defined as the first polarization direction. Is a polarization conversion optical system that emits light in a different second polarization direction, a first image modulation element and a second image modulation element, and first and second lights having a first polarization direction. A light guide optical system for guiding the third and fourth light beams having the second polarization direction to the second image modulation element, and the first and second image modulation elements. A projection optical system for projecting first, second, third and fourth light from the child onto the projection surface; first, second, third and fourth light sources; and first and second image modulations Drive means for driving the element. The driving unit causes the first light source and the second light source to emit light alternately and switches the first image modulation element alternately between a state in which the first light is modulated and a state in which the second light is modulated. In addition, the driving unit causes the third and fourth light sources to emit light alternately and switches the second image modulation element alternately between a state in which the third light is modulated and a state in which the fourth light is modulated. Features.

  Note that an image display system including the image projection apparatus and an image supply apparatus that supplies image information to the image projection apparatus also constitutes another aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the utilization efficiency of the light from a several light source and two image modulation elements is high, and the small image projector which can project a high quality image is realizable.

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

  1 to 6 show a schematic optical configuration of a liquid crystal projector (image projection apparatus) that is Embodiment 1 of the present invention. FIG. 1 shows the configuration of a light source and a polarization conversion optical system of a projector. In this embodiment, an xyz coordinate system is set in the three-dimensional space. The z direction is a direction in which light emitted from the polarization conversion optical system propagates in the illumination optical system. In the following description, R represents red, G represents green, and B represents blue.

  In FIG. 1, a first light source 101 that emits G-band light (first light), which is a first wavelength band, and an R-band light (second light), which is a second wavelength band. Two light sources 102 are arranged adjacent to each other in the y direction. In addition, a third light source 103 that emits light in the B band (third light) that is the third wavelength band, and a fourth light that emits light in the G band (fourth light) that is the fourth wavelength band. The light source 104 faces each other and is disposed in a direction orthogonal to the direction of the first and second light sources 101 and 102.

  In the present embodiment, the first and twenty-fourth wavelength bands are the same wavelength band, and the second and third wavelength bands are different from each other with respect to the first and fourth wavelength bands. However, the first and fourth wavelength bands may be different from each other.

  In the following description, R band light, G band light, and B band light are referred to as R light, G light, and B light, respectively. Further, the G light, R light, B light and G light from the first to fourth light sources 101 to 104 are all unpolarized light.

  Reference numeral 1 denotes a polarization conversion optical system. The polarization conversion optical system 1 uses G, R, B, and G light from the first to fourth light sources 101 to 104 in different incident areas (incidents of a wavelength-selective reflecting element, a phase plate, and a prism, which will be described later). The light is incident from a region where the opening is provided. Then, the polarization conversion optical system 1 emits the first and second lights (G light and R light) with the polarization directions aligned with the P polarization, which is the first polarization direction, and outputs third and fourth lights ( (B light and G light) are emitted with their polarization directions aligned with S polarization, which is a second polarization direction different from the first polarization direction.

  The polarization conversion optical system 1 includes a prism having a first polarization separation surface 131 and a second polarization separation surface 132 that reflect or transmit G light, R light, B light, and G light according to their polarization directions. . In the prism, the first and second polarization separation surfaces 131 and 132 are arranged in different (adjacent) regions so as to extend in directions orthogonal to each other. The first and second polarization separation surfaces 131 and 132 do not intersect each other.

  In the prism, reference numeral 201 denotes a first incident opening formed on the first light source 101 side with respect to the first polarization separation surface 131. Reference numeral 202 denotes a second incident opening formed on the second light source 102 side with respect to the second polarization separation surface 132. Reference numeral 203 denotes a third incident aperture formed on the third light source 103 side with respect to the second polarization separation surface 132. Reference numeral 204 denotes a fourth incident aperture formed on the fourth light source 104 side with respect to the first polarization separation surface 131.

  In the prism, reference numeral 211 denotes a first exit opening formed on the side opposite to the first entrance opening 201 side with respect to the first polarization separation surface 131. Reference numeral 212 denotes a second exit aperture 212 formed on the opposite side of the second polarization separation surface 132 from the second entrance aperture 202 side.

  The first and second polarization separation surfaces 131 and 132 have a characteristic that the transmittance for P-polarized light is 100% or near (higher than 50%), and the transmittance for S-polarized light is 0% or close (lower than 50%). Have The first and second polarization separation surfaces 131 and 132 have a reflectance for S-polarized light of 100% or close (higher than 50%) and a reflectivity for P-polarized light of 0% or close (lower than 50%). ) Characteristics.

  The first and second polarization separation surfaces 131 and 132 are formed of a multilayer film or a wire grid formed on the surface of a glass or acrylic substrate. Further, the first and second polarization separation surfaces 131 and 132 are 45 with respect to the emission optical axes of the first to fourth light sources 101 to 104 (directions from the left side to the right side and from the upper side to the lower side in FIG. 1). Has a slope of degrees.

  Reference numeral 111 denotes a first dichroic mirror as a first wavelength-selective reflecting element, which is disposed between the first polarization separation surface 131 and the first light source 101 so as to face the first incident opening 201. Has been placed. The first dichroic mirror 111 has a characteristic that the reflectivity with respect to the R light is 100% or close to it (higher than 50%), and the reflectivity with respect to other wavelength bands is 0% or close to it (lower than 50%).

  Reference numeral 112 denotes a second dichroic mirror as a second wavelength-selective reflecting element, which is disposed between the second polarization separation surface 132 and the second light source 102 so as to face the second incident opening 202. Has been placed. The second dichroic mirror 112 has a characteristic that the reflectivity for G light is 100% or close to it (higher than 50%), and the reflectivity for other wavelength bands is 0% or close to it (lower than 50%).

  Reference numeral 113 denotes a third dichroic mirror as a third wavelength-selective reflecting element, which is disposed between the second polarization separation surface 132 and the third light source 103 so as to face the third incident opening 203. Has been placed. The third dichroic mirror 113 has a characteristic that the reflectivity with respect to the G light is 100% or close to it (higher than 50%), and the reflectivity with respect to other wavelength bands is 0% or close thereto (lower than 50%).

  Reference numeral 114 denotes a fourth dichroic mirror as a fourth wavelength-selective reflecting element, which is disposed between the first polarization separation surface 131 and the fourth light source 104 so as to face the fourth incident opening 204. Has been placed. The fourth dichroic mirror 114 has a characteristic that the reflectivity with respect to the B light is 100% or close (higher than 50%), and the reflectivity with respect to other wavelength bands is 0% or close (lower than 50%).

  Reference numeral 121 denotes a phase plate (¼ wavelength plate), which is disposed between the first and second polarization separation surfaces 131 and 132 and each dichroic mirror. The phase plate 121 has a function of rotating the polarization direction of the linearly polarized light passing through this phase by 45 degrees.

  An optical member (not shown) that converts a light beam from each light source into a parallel light beam or a convergent light beam that converges toward the polarization separation surfaces 131 and 132 is provided between each light source and the polarization conversion optical system 1. preferable.

  Next, the optical action of the polarization conversion optical system 1 configured as described above will be described.

  The G light emitted from the first light source 101 passes through the first dichroic mirror 111 and the phase plate 121 and enters the prism as P-polarized light 101P and S-polarized light 101S from the first incident opening 201. The P-polarized light 101 </ b> P passes through the first polarization separation surface 131 and exits from the first exit opening 211.

  The S-polarized light 101 </ b> S is reflected by the first polarization separation surface 131, then reflected by the second polarization separation surface 132, and is emitted from the second incident opening 202. Furthermore, after passing through the phase plate 121, the S-polarized light 101S is reflected by the second dichroic mirror 112, and is transmitted through the phase plate 121 again to be converted to P-polarized light 101P. The P-polarized light 101P after this conversion enters the prism again from the second incident aperture 202, passes through the second polarization separation surface 132, and exits from the second exit aperture 212.

  Thus, the G light emitted from the first light source 101 is emitted from the polarization conversion optical system 1 with the polarization direction thereof aligned with the polarization direction of P-polarized light (that is, as P-polarized light).

  The R light emitted from the second light source 102 passes through the second dichroic mirror 112 and the phase plate 121 and enters the prism from the second incident opening 202 as P-polarized light 102P and S-polarized light 102S. The P-polarized light 102 </ b> P passes through the second polarization separation surface 132 and exits from the second exit opening 212.

  The S-polarized light 102 </ b> S is reflected by the second polarization separation surface 132, then reflected by the first polarization separation surface 131, and exits from the first incident opening 201. Furthermore, after passing through the phase plate 121, the S-polarized light 102S is reflected by the first dichroic mirror 111, and is again transmitted through the phase plate 121 to be converted to P-polarized light 102P. The P-polarized light 102P after this conversion enters the prism again from the first incident opening 201, passes through the first polarization separation surface 131, and exits from the first exit opening 211.

  In this way, the R light emitted from the second light source 102 is emitted from the polarization conversion optical system 1 with its polarization direction aligned with the polarization direction of P-polarized light (that is, as P-polarized light).

  The B light emitted from the third light source 103 passes through the third dichroic mirror 113 and the phase plate 121 and enters the prism from the third incident opening 203 as P-polarized light 103P and S-polarized light 103S. P-polarized light 103 </ b> P passes through the second polarization separation surface 132, then passes through the first polarization separation surface 131, and exits from the fourth incident opening 204. Thereafter, the P-polarized light 103P is transmitted through the phase plate 121, reflected by the fourth dichroic mirror 114, and again transmitted through the phase plate 121 to be converted to S-polarized light 103S. The converted S-polarized light 103 </ b> S enters the prism again from the fourth incident opening 204, is reflected by the first polarization separation surface 131, and exits from the first exit opening 211.

  The S-polarized light 103 </ b> S that has entered the prism from the third incident opening 203 is reflected by the second polarization separation surface 132 and is emitted from the second emission opening 212.

  As described above, the B light emitted from the third light source 103 is emitted from the polarization conversion optical system 1 with the polarization direction thereof aligned with the polarization direction of S-polarized light (that is, as S-polarized light).

  The G light emitted from the fourth light source 104 passes through the fourth dichroic mirror 114 and the phase plate 121 and enters the prism from the fourth incident opening 204 as P-polarized light 104P and S-polarized light 104S. The P-polarized light 104 </ b> P passes through the first polarization separation surface 131, then passes through the second polarization separation surface 132, and exits from the third incident opening 203. Thereafter, the P-polarized light 104P is transmitted through the phase plate 121, reflected by the third dichroic mirror 113, and again transmitted through the phase plate 121 to be converted to S-polarized light 104S. The converted S-polarized light 104S enters the prism again from the third incident opening 203, is reflected by the second polarization separation surface 132, and is emitted from the second exit opening 212.

  The S-polarized light 104 </ b> S that has entered the prism from the fourth incident opening 204 is reflected by the first polarization separation surface 131 and is emitted from the first emission opening 211.

  As described above, the G light emitted from the fourth light source 104 is emitted from the polarization conversion optical system 1 with the polarization direction thereof aligned with the polarization direction of S polarization (that is, as S polarization).

  As described above, by passing through the polarization conversion optical system 1, the G light from the first light source 101 and the R light from the second light source 102 are converted into P-polarized light, and B light from the third light source 103. The light and the G light from the fourth light source 104 are converted into S-polarized light.

  Next, the light-emitting element arrays as the first to fourth light sources 101 to 104 will be described with reference to FIGS. FIG. 2 shows a light emitting element array as the third light source 103 as seen from the y direction. Each light-emitting element is indicated by a portion marked with a symbol 103 in a circle. The same applies to FIGS. 3 and 4. In this embodiment, a light emitting diode (LED) is used as the light emitting element.

  FIG. 3 shows a light emitting element array as the first and second light sources 101 and 102 as seen from the z-axis direction. FIG. 4 shows a light emitting element array as the fourth light source 104 as viewed from the −y direction. The x direction is the arrangement direction of the polarization conversion cells when the polarization conversion optical system 1 shown in FIG. 1 is used as one polarization conversion cell.

  In the 1st-4th light sources 101-104, the emitted light quantity from the polarization conversion optical system 1 can be increased by arranging a several light emitting element in an array form in the x direction. Further, it is more preferable that the shape of all exit openings of the polarization conversion optical system 1 is similar to the shape of the illuminated surface described later.

  FIG. 5 shows an optical configuration of a projector using the polarization conversion optical system 1. In addition, at least from the polarization conversion optical system 1 to the condenser lens 23 described later is referred to as an illumination optical system. However, you may include the 1st-4th light sources 101-104 and the polarization separation element 31 mentioned later in an illumination optical system.

  As described above, the polarization conversion optical system 1 emits the G P-polarized light 101P, the R P-polarized light 102P, the B S-polarized light 103S, and the G S-polarized light 104S. Each of the G, R, B, and G light beams is divided into a plurality of light beams by the first fly-eye lens 21 and condensed toward the vicinity of the second fly-eye lens 22, where An image (two-dimensional light source image) is formed. The first and second fly-eye lenses 21 and 22 are configured by arranging a plurality of lens cells in a two-dimensional direction. Each lens cell has a rectangular lens shape similar to a later-described liquid crystal panel (image modulation element) that is an illuminated surface.

  The plurality of split light beams that have passed through the second fly-eye lens 22 are collected by the condenser lens 23 and enter a polarization separation element (polarization beam splitter) 31 that constitutes the light guide optical system.

  The polarization separation element 31 has a polarization separation surface inside, and has an inclination of 45 degrees with respect to the incident optical axis direction (the direction from the left side to the right side in the figure). This polarization splitting surface has the characteristics that the transmittance for P-polarized light is 100% or close (higher than 50%), and the reflectivity for S-polarized light is 100% or close (higher than 50%). The polarization separation surface is formed as a multilayer film inside the prism.

  Of the plurality of split light beams that have passed through the condenser lens 23, the G P-polarized light 101P and the R P-polarized light 102P are transmitted through the polarization separation surface of the polarization separation element 31 to reflect the G and R band reflective liquid crystal panels (first). Image modulation element: hereinafter referred to as P liquid crystal panel) 41. Thus, the P liquid crystal panel 41 is illuminated.

  Of the plurality of split light beams that have passed through the condenser lens 23, the B S-polarized light 103S and the G S-polarized light 104S are reflected by the polarization separation surface of the polarization separation element 31 and reflected in the B and G band reflective liquid crystal panels (second). The image modulation element (hereinafter referred to as “S liquid crystal panel”) 42 is superposed. Thus, the S liquid crystal panel 42 is illuminated.

  Each liquid crystal panel is connected to a drive circuit (drive means) 6. Image information (image signal) from an image supply device 7 such as a personal computer, a DVD player, a video deck, or a TV tuner is input to the drive circuit 6 that is a part of the projector. The projector and the image supply device 7 constitute an image display system.

  The drive circuit 6 drives the liquid crystal panels 41 and 42 corresponding to the respective colors based on the R, G, and B components of the input image signal to form an original image. Accordingly, each liquid crystal panel reflects and modulates incident light in each wavelength band and emits it as image light. The drive circuit 6 is connected to each light source and controls each light source as will be described later. Such a configuration is the same in the following embodiments, though not shown.

  The light that has been image-modulated by the P liquid crystal panel 41 is converted into image light as S-polarized light 101S and 102S and reflected by the polarization separation surface of the polarization separation element 31, and a screen (not shown) (not shown) is projected by the projection lens (projection optical system) 5. Projected onto the projection surface).

  The light modulated by the S liquid crystal panel 42 becomes image light as P-polarized light 103 </ b> P and 104 </ b> P, passes through the polarization separation surface of the polarization separation element 31, and is projected on the screen by the projection lens 5.

  Next, the driving of each light source and each liquid crystal panel in this embodiment will be described with reference to FIG. FIG. 6 shows a time chart of the driving by the driving circuit 6.

  In FIG. 6, “On” of the light source indicates that the light source is turned on, and “Off” indicates that the light source is turned off. “Liquid crystal panel incident light” indicates the wavelength band and polarization direction of light incident on each liquid crystal panel.

  The first and second light sources 101 and 102 are alternately turned on and off. Further, the third and fourth light sources 103 and 104 are alternately turned on and off. Further, the first and fourth light sources 101 and 104 are simultaneously turned on and off, and the second and third light sources 102 and 103 are simultaneously turned on and off.

  Therefore, the G P-polarized light 101P and the R P-polarized light 102P are alternately incident on the P liquid crystal panel 41. In synchronization with this, an original G image and an R original image are alternately formed on the P liquid crystal panel 41. That is, the P liquid crystal panel 41 is alternately switched between a state in which the first light is modulated and a state in which the second light is modulated. The S liquid crystal panel 42 is alternately incident with the B S polarized light 103S and the G S polarized light 104S. In synchronization with this, an original image for B and an original image for G are alternately formed on the S liquid crystal panel 42. That is, the S liquid crystal panel 42 is alternately switched between a state in which the third light is modulated and a state in which the fourth light is modulated. Thereby, an RGB color image is projected on the screen.

  Since the G light component occupies approximately 60 to 80% of the light in the visible wavelength region, the influence of the G light on the brightness of the projected image is large. In this embodiment, since the G light is obtained from twice as many light sources as the R light and B light, the brightness of the projected image is higher than that of a conventional projector that sequentially turns on the RGB light sources. Can be improved.

  Moreover, when using LED as a light emitting element, since there exists time when all the light emitting elements are not always lighted and extinguished in a present Example, the fall of the light emission efficiency by the temperature rise of LED can be suppressed. Conventionally, color breaks occur because the RGB light sources are sequentially turned on. However, in this embodiment, the color breaks are reduced because the G and G light sources and the R and B light sources are turned on alternately. Can be made.

  FIG. 7 shows a driving time chart of each light source and each liquid crystal panel in the projector that is Embodiment 2 of the present invention.

  The configuration of the projector is basically the same as that described in the first embodiment, and the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  Also in this embodiment, G light is emitted from the first light source 101 and G P-polarized light is emitted from the polarization conversion optical system 1. Further, R light is emitted from the second light source 102, and R P-polarized light is emitted from the polarization conversion optical system 1. Further, B light is emitted from the third light source 103, and B S-polarized light is emitted from the polarization conversion optical system 1. Further, G light is emitted from the fourth light source 104 and G S-polarized light is emitted from the polarization conversion optical system 1.

  In FIG. 7, “On” of the light source indicates that the light source is turned on, and “Off” indicates that the light source is turned off. “Liquid crystal panel incident light” indicates the wavelength band and polarization direction of light incident on each liquid crystal panel.

  The first and second light sources 101 and 102 are alternately turned on and off. Further, the third and fourth light sources 103 and 104 are alternately turned on and off. Furthermore, the first and third light sources 101 and 103 are simultaneously turned on and off, and the second and fourth light sources 102 and 104 are simultaneously turned on and off.

  Therefore, the G P-polarized light 101P and the R P-polarized light 102P are alternately incident on the P liquid crystal panel 41. In synchronization with this, an original G image and an R original image are alternately formed on the P liquid crystal panel 41. The S liquid crystal panel 42 is alternately incident with the B S polarized light 103S and the G S polarized light 104S. In synchronization with this, an original image for B and an original image for G are alternately formed on the S liquid crystal panel 42. Thereby, an RGB color image is projected on the screen.

  As described in the first embodiment, the influence of the G light on the brightness of the projected image is large. In this embodiment, since one of the two G light sources 101 and 104 is always turned on, the brightness of the projected image can be improved as compared with a conventional projector that sequentially turns on the RGB light sources. .

  In the conventional projector, a color break occurs because the RGB light sources are sequentially turned on. However, in this embodiment, one of the two G light sources 101 and 104 is always turned on, so that the color break is reduced. Can do.

  According to each of the above embodiments, the polarization conversion optical system 1 that converts light from the plurality of light sources 101 to 104 into polarized light is provided, and the light from each light source and the use efficiency of the liquid crystal panels 41 and 42 are high and bright. A small projector that projects high-quality images with few color breaks can be realized.

  In each of the above embodiments, in the light emitting element arrays shown in FIGS. 2 to 4, light emitting elements having the same wavelength band are arranged in the x direction, but the light emitting elements arranged in the x direction are not necessarily the same. It does not have to be in the wavelength band.

  In each of the above embodiments, the fourth light source 104 uses a light source that emits the same G light as the first light source 101. However, by appropriately changing the characteristics of the dichroic mirror, S-polarized light may be emitted using a light source of a wavelength band other than G, such as cyan.

  In each of the above embodiments, the first wavelength band is G, the second wavelength band is R, the third wavelength band is B, and the fourth wavelength band is G. It is not limited to. Various wavelength bands can be used by appropriately changing the characteristics of the dichroic mirror.

  In each of the above embodiments, the case where each light source is configured by arranging a plurality of LEDs in an array is described. However, a single LED, a single or a plurality of laser diodes, and an organic electroluminescence element are used as the light source. Each light source may be configured by using.

  In each of the above embodiments, the B light, the R light, and the G light can be interchanged. However, in order to obtain white, it is necessary to make the G light component occupy about 60 to 80% of the light in the visible wavelength range, so that the number of the G light sources is larger than the B and R light sources. Is preferred.

  Further, as described above, a polarization separation element in which a multilayer film is formed inside the prism as described above is well known, but a polarization separation element utilizing structural birefringence may be used. Since the polarization separation element using structural birefringence has a wider incident angle range than the polarization separation element using a multilayer film, there is little leakage light and the contrast can be improved.

  In each of the above embodiments, the case where a reflective liquid crystal panel is used as an image modulation element has been described. However, in the present invention, a transmissive liquid crystal panel or a DMD (digital micromirror device) is used as another image modulation element. It may be used.

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

1 is a diagram illustrating a configuration of a light source and a polarization conversion optical system used in a projector that is Embodiment 1 of the present invention. FIG. FIG. 3 is a diagram illustrating a configuration of a third light source in the first embodiment. FIG. 3 is a diagram illustrating a configuration of first and second light sources in the first embodiment. FIG. 4 is a diagram illustrating a configuration of a fourth light source in the first embodiment. FIG. 3 is a diagram illustrating an optical configuration of the projector according to the first embodiment. FIG. 3 is a driving time chart of each light source and each liquid crystal panel in Embodiment 1. FIG. 10 is a drive time chart of each light source and each liquid crystal panel in the projector that is Embodiment 2 of the present invention.

Explanation of symbols

1 Polarization Conversion Optical System 5 Projection Lens
6 Drive circuit 21, 22 Fly eye lens 23 Condenser lens 31 Polarization separation element 41, 42 Reflective liquid crystal panel 101, 102, 103, 104 Light source 111, 112, 113, 114 Wavelength selective reflection element (dichroic mirror)
121 Phase plate 131, 132 Polarization separation surface 201, 202, 203, 204 Entrance opening 211, 212 Exit opening

Claims (9)

A first light source, a second light source, a third light source, and a fourth light source that respectively emit first light, second light, third light, and fourth light;
The first, second, third, and fourth light from the first, second, third, and fourth light sources are incident from different incident areas, and the first and second light sources The polarization directions of the first and second lights are emitted so as to be aligned with the first polarization direction, and the polarization directions of the third and fourth lights from the third and fourth light sources are changed to the first polarization. A polarization conversion optical system that emits light in alignment with a second polarization direction different from the direction;
A first image modulation element and a second image modulation element;
The first and second lights having the first polarization direction are guided to the first image modulation element, and the third and fourth lights having the second polarization direction are converted to the second image modulation. A light guiding optical system leading to the element;
A projection optical system that projects the first, second, third, and fourth light from the first and second image modulation elements onto a projection surface;
The first, second, third and fourth light sources and driving means for driving the first and second image modulation elements;
The driving means alternately causes the first and second light sources to emit light and causes the first image modulation element to alternately modulate a state in which the first light is modulated and a state in which the second light is modulated. Switching, causing the third and fourth light sources to emit light alternately, and switching the second image modulation element alternately between a state in which the third light is modulated and a state in which the fourth light is modulated. A featured image projection apparatus. The polarization conversion optical system is
Emitting the first light in the first polarization direction and the third light in the second polarization direction from a first opening;
The second light in the first polarization direction and the fourth light in the second polarization direction are emitted from a second opening different from the first opening. Item 2. The image projection device according to Item 1. The surface on which the first light source is arranged and the surface on which the third light source is arranged are orthogonal to each other, and the surface on which the second light source is arranged and the surface on which the fourth light source is arranged. The image projection apparatus according to claim 1, wherein the image projection apparatuses are orthogonal to each other. The polarization conversion optical system is
The first light, the second light, the third light, and the fourth light are reflected or transmitted in accordance with the polarization direction of the first light, and are arranged to extend in directions orthogonal to each other in different regions in the polarization conversion optical system. A polarization separation surface and a second polarization separation surface;
A wavelength-selective reflection element that reflects the first, second, third, and fourth light according to a wavelength band thereof, and is disposed between the first polarization separation surface and the first light source. The first wavelength-selective reflecting element, the second wavelength-selective reflecting element disposed between the second polarization separation surface and the second light source, the second polarization separation surface, and the second A third wavelength-selective reflective element disposed between the third light source and a fourth wavelength-selective reflective element disposed between the first polarization separation surface and the fourth light source;
It said first and said first and second polarization separating surface, second, claims 1 to 3, characterized in that it comprises a third and a phase plate disposed between the fourth wavelength selective reflective element The image projection apparatus as described in any one of these . In the polarization conversion optical system,
Of the first light, the light having the first polarization direction passes through the first polarization separation surface and exits from the polarization conversion optical system.
Of the first light, the light having the second polarization direction is reflected by the first and second polarization separation surfaces, passes through the phase plate, and is reflected by the second wavelength selective reflection element. Is then transmitted again through the phase plate and converted into light having the first polarization direction, transmitted through the second polarization separation surface and emitted from the polarization conversion optical system,
Of the second light, the light having the first polarization direction passes through the second polarization separation surface and exits from the polarization conversion optical system.
Of the second light, the light having the second polarization direction is reflected by the second and first polarization separation surfaces, passes through the phase plate, and is reflected by the first wavelength selective reflection element. Then, the light is transmitted through the phase plate again to be converted into light having the first polarization direction, transmitted through the first polarization separation surface, and emitted from the polarization conversion optical system.
Of the third light, the light having the first polarization direction passes through the second and first polarization separation surfaces, passes through the phase plate, and is reflected by the fourth wavelength selective reflection element. Then, the light is transmitted again through the phase plate and converted into light having the second polarization direction, reflected by the first polarization separation surface, and emitted from the polarization conversion optical system,
Of the third light, the light having the second polarization direction is reflected by the second polarization separation surface and emitted from the polarization conversion optical system.
Of the fourth light, the light having the first polarization direction passes through the first and second polarization separation surfaces, passes through the phase plate, and is reflected by the third wavelength selective reflection element. Is transmitted through the phase plate again to be converted into light having the second polarization direction, reflected by the second polarization separation surface, and emitted from the polarization conversion optical system,
5. The image projection according to claim 4 , wherein light having the second polarization direction among the fourth light is reflected by the first polarization separation surface and exits from the polarization conversion optical system. apparatus. The first, second and third lights are lights having different wavelength bands,
The first and fourth light image projection apparatus according to any one of claims 1 to 5, characterized in that the light of the same wavelength bands. The image projection apparatus according to claim 6, wherein the first and fourth lights are lights in a green wavelength band. It said first, second, third and fourth light sources, respectively, the image projection apparatus according to any one of claims 1 to 7, characterized in that a light emitting diode. An image projection apparatus according to any one of claims 1 to 8 ,
An image display system comprising: an image supply device that supplies image information to the image projection device.