JP4525052B2 - projector - Google Patents

Description

  The present invention relates to a projector, and more particularly to a projector that generates four types of color light from light source light and forms a projected image using the four types of color light.

  A projector that enlarges and projects an image emitted from an optical system using a light valve such as a liquid crystal display device onto a screen through a projection lens has been put into practical use. When a video image centered on a natural image is displayed on a projector, this type of video image generally has many dark tones, and thus the projector is required to have an excellent dark part expression capability. At the same time, a high peak luminance is required in the white display portion in order to express the flash feeling and the metallic luster feeling well. However, in conventional projectors, the displayable gradation range (dynamic range) is fixed depending on the display performance of the light valve, so it is generally difficult to achieve both improvement in dark area expression and high peak luminance. There are challenges.

  As one solution to the problem of such a projector, that is, as a method of extending the dynamic range in the white display portion, an optical system that independently modulates white light has been proposed (for example, see Patent Document 1).

JP-A-9-212384 (FIG. 1)

  In the optical system introduced in Patent Document 1, in addition to the three light valves corresponding to the three primary color lights (blue light B, green light G, and red light R), a light valve that independently modulates white light. By providing the above, the brightness improvement and the image quality improvement of the projected image are realized. However, since this type of optical system has dedicated light valves for the three primary color light and the white light, four light valves are required, and it is inevitable to increase the size of the apparatus and it is difficult to reduce the cost. is there. Further, in order to obtain a display image free from brightness unevenness and color unevenness, it is important to set the lengths of the illumination light paths between the colored lights to be equal in the illumination system, but in order to align the lengths of the four illumination light paths. Has to adopt a three-dimensional optical path arrangement, which makes the configuration more complicated and makes it difficult to realize a thin device.

  Therefore, the present invention has been made in view of the above-described problems, and the object thereof is to realize high peak luminance while improving the expressibility of dark parts, and further, downsizing and cost reduction of the apparatus are possible. It is to provide a projector.

  To achieve the above object, a projector according to the present invention includes a light source that emits light including three primary color lights, a first color separation optical element that separates light emitted from the light source into two color lights, and Of the two color lights separated by the first color separation optical element, one is separated into white light and first color light, and the other is separated into second color light and third color light. A third color separation optical element, a first light modulation device that modulates white light and first color light, a second light modulation device that modulates second color light and third color light, and the two light modulations The polarization rotation element that rotates the polarization direction of at least one of the emitted lights and the four types of color lights modulated by the first and second light modulation devices so that the polarization directions of the emitted light from the apparatus are substantially orthogonal to each other. A projector having a color synthesis optical system to synthesize And features. The second color separation optical element is arranged so that the white light and the first color light are incident on the first light modulation device from different directions, and the third color separation optical element is the second color light and the third color light. The colored light is arranged to enter the second light modulation device from different directions. Further, the first and second light modulation devices include a pair of substrates, an electro-optical material sandwiched between the pair of substrates, and a microlens array provided on a light incident side substrate of the pair of substrates. And a plurality of subpixel electrodes formed on the other substrate, wherein the plurality of subpixels are arranged corresponding to the respective microlenses of the microlens array.

  According to the present invention, since the first and second light modulation devices capable of independently modulating two kinds of color light are provided, four kinds of color light of white light and three primary color lights can be independently modulated. A projection image with a wide color expression range can be formed. As the white illumination light is generated, the intensity of the three primary color lights is relatively reduced, and it is possible to achieve both the improvement of the black-side tone expression and the realization of a high peak luminance in an image close to white. Further, since two types of color light are modulated by one light modulation device, the number of light modulation devices required is two even though the four types of color light are independently modulated. It is easy to realize miniaturization, weight reduction, and cost reduction. The light modulation device of the present invention is provided with two adjacent sub-pixels in a matrix to independently modulate two types of color light, and condenses the two types of sub-pixels to make light incident. This is a light modulation device called a so-called spatial pixel array type having a configuration in which microlenses are provided in an array on the incident side. Two types of color light whose traveling directions are separated (direction separated) by the second and third color separation optical elements are incident on this light modulation device and modulated independently for each sub-pixel. It is not necessary to use a color filter or the like for generation, and high light utilization efficiency can be realized. Therefore, it is possible to achieve both high brightness of the projected image and expansion of the color expression area.

  In the second color separation optical element, the direction of the white light and the first color light is separated. In this case, the white light is reflected from the second color separation optical element and separated from the first color light. It is desirable. At this time, it is desirable that the color light having a relatively high light intensity among the color lights emitted from the light source is the first color light, and specifically, the green light and the blue light are desirable.

  Since the color light separated by transmission through the second color separation optical element passes through the second color separation optical element again through a reflection mirror installed at a later stage, a part of the light is lost due to reflection in the process. Decreases the light intensity as transmitted light. On the other hand, the color light reflected and separated by the second color separation optical element hardly causes light loss. Therefore, if the light constituting the white light is separated by reflection, and the color light separated by transmission is a color light having a relatively high light intensity among the color lights emitted from the light source, the light is transmitted between the other color lights. It becomes easy to balance the intensity, and the color expression as a projector can be improved while minimizing the decrease in light utilization efficiency. For example, when a high-pressure mercury lamp or a metal halide lamp is used as the light source lamp, green light and blue light are excessive in comparison with red light in terms of color balance, so that they pass through the second color separation optical element. It is desirable to set green light or blue light as the first color light to be separated. If the first color light is blue light, the spectral characteristics of the second color separation optical element are simplified, and the second color separation optical element can be easily manufactured. In the third color separation optical element, the second color light and the third color light are direction-separated. In this case, the color light separated by reflection by the third color separation optical element is converted into the color light emitted from the light source. Of these, it is desirable to set the color light having a relatively low light intensity, and specifically, it is desirable to use red light.

  The first to third color separation optical elements can be elements having higher reflection characteristics than transmission characteristics by the element structure. Therefore, if the color light reflected and separated by the third color separation optical element is a color light having a relatively low light intensity among the color lights emitted from the light source, for example, red light, the light of the color light is used. Since the loss can be reduced, it is easy to balance the light intensity with other color lights, and the color expression as a projector can be improved while minimizing the decrease in light utilization efficiency.

  In the projector according to the invention, the polarization conversion optical system for converting the non-polarized light emitted from the light source into light having the same polarization direction between the light source and the first and second light modulation devices. Can be provided. In this case, it is desirable that the light having the same polarization direction emitted from the polarization conversion optical system is S-polarized light with respect to the light separation surface of the first color separation optical element.

  As a light modulation device for a projector according to the present invention, a liquid crystal panel that requires polarized light for image display is assumed. Therefore, by adopting the above-described configuration, it is possible to significantly improve the light use efficiency from the light source, and to realize further higher brightness of the projected image. In addition, by making the light emitted from the polarization conversion optical system S-polarized light, the reflectance on the color light separation surface (dichroic surface) of the color separation optical system can be increased, so that the light use efficiency is improved and the projected image is improved. Further increase in brightness can be realized.

  According to the projector according to the present invention as described above, a display image is formed by independently modulating four types of color light of three primary color light and white light, so that a projection image having a wide color expression range can be formed. In particular, the white illumination light that can be modulated independently can improve the expressiveness in the sense of brightness, such as metallic luster and flash. In addition, the intensity of the three primary colors is relatively smaller than that of a projector using only the three primary colors because of the generation of white illumination light, and image display using only these three primary colors is possible. In the case where it is performed, it is possible to improve the black side gradation expression. Therefore, it is possible to achieve both improvement of dark area expression and realization of high peak luminance, and it is suitable for display of video images having a large overall dark color tone.

  In addition, since a configuration in which two types of color light are modulated by a single two-color modulation liquid crystal panel is adopted, two types of color light can be modulated by two liquid crystal panels, and the device can be reduced in size and cost. It is easy to realize. Furthermore, since the illumination light paths of four types of color light can be arranged symmetrically, illumination light paths having the same length can be configured at a short distance. In this respect as well, it is easy to reduce the size and thickness of the device. As described above, according to the present invention, it is possible to realize a projector having relatively high light utilization efficiency, high brightness of a projected image, excellent size and cost reduction of the apparatus, and excellent image expression.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 shows a schematic configuration of the projector according to the first embodiment of the present invention. The projector 1 includes a light source 10 that emits light including three primary color lights, a color separation optical system 30 that separates light from the light source into four types of color lights having different wavelength ranges, and light that is modulated based on image information from the outside. A light modulation optical system 60 that forms an optical image every time, a color synthesis optical system 70 that combines the formed optical images to form one color image, and projects the formed color image onto a projection surface (not shown). A projection optical system 90 for displaying is generally configured.

  The light source 10 includes a light source lamp 11 that emits substantially white light including three primary color lights radially, and a reflector 12 that emits light emitted from the light source lamp 11 in one direction. As the light source lamp 11, a high-pressure mercury lamp, a metal halide lamp, a halogen lamp, a xenon lamp, or the like can be used. As the reflector 12, a parabolic reflector, an ellipsoidal reflector, a spherical reflector, or the like can be used.

  The color separation optical system 30 includes a dichroic mirror 40 that is a first color separation optical element, a dichroic mirror 50W and a reflection mirror 56 that are second color separation optical elements, and a dichroic mirror 55R that is a third color separation optical element. A reflection mirror 57 is provided. The three types of dichroic mirrors 40, 50W, and 55R are mirrors having wavelength selectivity that transmits or reflects color light in a specific wavelength range at a predetermined ratio. For example, a dielectric multilayer film on a transparent substrate such as glass It is realized by forming. The reflection mirrors 56 and 57 can be formed by forming a metal film such as silver or aluminum on a transparent substrate such as glass, but may be dichroic mirrors that can easily realize high reflectivity. An example of the spectral characteristics of the dichroic mirrors 40, 50W, and 55R is shown in FIGS. 2A shows the spectral characteristics of the dichroic mirror 40, FIG. 2B shows the dichroic mirror 50W, and FIG. 2C shows the spectral characteristics of the dichroic mirror 55R. In FIG. 2 and FIG. 5, in consideration of the readability of the graph, the reflectance is drawn as a value other than 0 in a wavelength region where the reflectance should be essentially 0.

  The light emitted from the light source 10 can be regarded as white light (W, W = B + G + R) containing blue light (B), green light (G), and red light (R) at a predetermined ratio. Here, light of a wavelength range of approximately 380 nm to 495 nm is assumed as blue light, light of a wavelength range of approximately 495 nm to 585 nm is assumed as green light, and light in a wavelength range of approximately 585 nm to 780 nm is assumed as red light. It is not limited to this.

  The white light (W) emitted from the light source 10 is finally output by the color separation optical system 30 into four types of blue light (B1), green light (G1), red light (R1), and white light (W2). Separated into colored light. Hereinafter, the separation process will be described in detail.

  First, the white light (W) incident on the dichroic mirror 40 from the light source 10 is a part of the blue light (B2) transmitted through the dichroic mirror 40 and all the green light according to the spectral characteristics shown in FIG. (G1 + G2) and a part of red light (R2), and the remaining blue light (B1) reflected from the dichroic mirror 40 and the remaining red light (R1) are separated.

  Next, the light transmitted through the dichroic mirror 40 is a part of green light (G1) that passes through the dichroic mirror 50W and the remaining green light that reflects off the dichroic mirror 50W according to the spectral characteristics shown in FIG. It is separated into light (G2), blue light (B2) and red light (R2). Here, the light intensity ratio of the blue light (B2) reflected by the dichroic mirror 50W, the green light (G2), and the red light (R2) is the blue light (B) and green light (G The spectral characteristics of the dichroic mirror 40 and the dichroic mirror 50W are set so as to substantially coincide with the light intensity ratio of the red light (R). Thereby, the light composed of the blue light (B2), the green light (G2), and the red light (R2) reflected by the dichroic mirror 50W can be regarded as white light (W2). For this purpose, for example, ignoring the light loss in the reflection mirror 56 and assuming the reflectance in the wavelength range of the blue light (B) and red light (R) of the dichroic mirror 40 to be x, the green light of the dichroic mirror 50W ( The reflectance in the wavelength range of G) is preferably set to 1-x. Of course, the spectral characteristics shown here are merely examples, and should be appropriately set according to the spectral distribution of the light emitted from the light source 10. Furthermore, in order to form a high-quality color image, there is a considerable need to correct the spectral distribution of light emitted from the light source 10 (for example, the intensity of green light is often reduced to make the color balance appropriate. ), It is not always necessary to set the spectral characteristics of the dichroic mirrors 40, 50W and the like to the above values. For example, a color filter or the like is arranged on the incident side of the light modulation optical system 60, and white light (W2 ), The color balance with other color lights, the color balance between other color lights, and the like may be adjusted.

  Then, the green light (G1) transmitted through the dichroic mirror 50W is changed in the traveling direction by the reflecting mirror 56, and then transmitted again through the dichroic mirror 50W, together with white light (W2), a first two-color modulation liquid crystal panel described later. 61 (light modulation optical system 60). Here, since the green light (G1) reflected by the reflection mirror 56 is transmitted again through the dichroic mirror 50W on the way to the first two-color modulation liquid crystal panel 61, the green light (G) depends on the spectral characteristics of the dichroic mirror 50W. ) Is reflected, and the light intensity of the transmitted light decreases (G1 ′). In a high-pressure mercury lamp often used in projectors, the light intensity of green light tends to be too high compared to other color lights. Therefore, even if a part of green light is lost when passing through the dichroic mirror 50W, the second light is lost. The color balance with other color light incident on the two-color modulation liquid crystal panel 62 is not lost. Therefore, it is desirable that the color light passing through this optical path is a color light having the highest light intensity among the color lights emitted from the light source. For this reason, in this embodiment, green light (G) is set in this optical path. ing. As a result, it becomes easy to achieve a color balance of the color light incident on the light modulation optical system 60, and it is possible to improve the color expression and light utilization efficiency as a projector.

  On the other hand, the light reflected from the dichroic mirror 40 is separated into red light (R1) reflected from the dichroic mirror 55R and blue light (B1) transmitted through the dichroic mirror 55R in accordance with the spectral characteristics shown in FIG. Is done. The blue light (B1) transmitted through the dichroic mirror 55R changes its traveling direction by the reflection mirror 57 and enters the second two-color modulation liquid crystal panel 62 (light modulation optical system 60) described later together with the red light (R1). Since green light does not enter the dichroic mirror 55R, spectral characteristics that change sharply in the wavelength region corresponding to the green light are not required. Therefore, by adopting an optical path arrangement (setting of colored light) in which the colored light (that is, green light) positioned between the three primary color light wavelengths is not incident on the dichroic mirror 55R, the dichroic mirror 55R can be easily realized and the cost can be reduced. Easy to plan. Further, since the reflectance is easy to increase in the dichroic mirror 55R, it is desirable that the color light reflected by the dichroic mirror 55R is the color light having the lowest light intensity among the color lights emitted from the light source. As a result, it becomes easy to achieve a color balance of the color light incident on the light modulation optical system 60, and it is possible to improve the color expression and light utilization efficiency as a projector.

  The dichroic mirror 50W and the reflection mirror 56 are arranged so that light from the dichroic mirror 40 is incident at different angles. Specifically, a virtual axis Q1 is set so as to form 45 ° with respect to the central axis of incident light on the XZ plane, and the dichroic mirror 50W and the reflection mirror 56 are not parallel to each other with this axis Q1 as the axis of symmetry. (In FIG. 1, the interval between the two is narrower in the + X and + Z directions). Therefore, the white light (W2) reflected by the dichroic mirror 50W and the green light (G1 ′) reflected by the reflection mirror 56 are separated in two slightly different directions on the XZ plane, which will be described later. The light enters the first two-color modulation liquid crystal panel 61 (light modulation optical system 60).

  Similarly, the dichroic mirror 55R and the reflection mirror 57 also set a virtual axis Q2 that forms 45 ° with respect to the central axis of the incident light beam on the XZ plane, and are not parallel to each other with this axis Q2 as the axis of symmetry. It is arranged with. Accordingly, the red light (R1) reflected by the dichroic mirror 55R and the blue light (B1) reflected by the reflection mirror 57 are also separated in two slightly different directions on the XZ plane, and will be described later. Is incident on the two-color modulation liquid crystal panel 62 (light modulation optical system 60). The arrangement state of the dichroic mirror 50W and the reflection mirror 56, and the dichroic mirror 55R and the reflection mirror 57 is not limited to the above. In FIG. 1, the arrangement is such that the distance between the two becomes narrower in the + X and + Z directions, but conversely, the arrangement may be made such that the distance between both becomes larger in the + X and + Z directions. In that case, the relationship of the incident angles between the respective color lights with respect to the two-color modulation liquid crystal panel is opposite to that in the present embodiment. In short, the dichroic mirrors 50W and 55R and the reflection mirrors 56 and 57 are arranged so that each color light enters the light modulation optical system 60 at a predetermined angle in correspondence with the optical configuration of the light modulation optical system 60 described later. Just do it.

  Next, the light modulation optical system 60 includes two light modulation devices that modulate color light, that is, a first two-color modulation liquid crystal panel 61 (first light modulation device) and a second two-color modulation liquid crystal panel 62 (first light modulation device). 2 light modulation devices). The first and second two-color modulation liquid crystal panels 61 and 62 are basically the same liquid crystal panel, and are distinguished by the difference in color light to be modulated. In the present embodiment, the first two-color modulation liquid crystal panel 61 uses white light (W2) and green light (G1 ′), and the second two-color modulation liquid crystal panel 62 uses red light (R1) and blue light (B1). Are modulated respectively.

  The two-color modulation liquid crystal panels 61 and 62 independently modulate the two types of incident color light based on image information from the outside (not shown) to form an optical image, and modulate from the side opposite to the incident side. FIG. 3 shows a sectional structure of a transmissive liquid crystal panel that emits light. FIG. 3 shows the first two-color modulation liquid crystal panel 61 as an example. The schematic structure of the two-color modulation liquid crystal panels 61 and 62 is sub-pixels 616A1 and 616A2 to be described later (sub-pixels are pixels driven by sub-pixel electrodes to be described later, and are therefore given the same numbers as the sub-pixel electrodes). Except for the fact that it has a micro lens corresponding to it, it is almost the same as a general monochrome liquid crystal panel. That is, a twisted nematic (TN) liquid crystal 613 that is an electro-optic material is sealed between two transparent substrates (a counter substrate 611 and a TFT substrate 612) made of glass or the like, and a common electrode is formed on the counter substrate 611. 614 and a black matrix 615 for blocking unnecessary light, and two kinds of subpixel electrodes 616A1 and 616A2 and a thin film transistor (TFT) 617 as a switching element are formed on the TFT substrate 612. When a voltage is applied to the sub-pixel electrodes 616A1 and 616A2, the liquid crystal 613 sandwiched between the common electrode 614 is driven. Of course, the sub-pixel electrodes 616A1 and 616A2 can be controlled independently of each other.

  Further, a microlens array 630 including a plurality of unit microlenses 631 arranged in a matrix is disposed on the incident side of the counter substrate 611. The unit micro lens 631 is formed on a glass plate by etching or the like, and is bonded to the counter substrate 611 via a resin layer (adhesive) 632 having a refractive index different from that of the glass plate on which the micro lens array is formed. . The microlens array 630 condenses two types of color lights whose emission directions are separated by the dichroic mirror 50W and the reflection mirror 56, or the dichroic mirror 55R and the reflection mirror 57, respectively, and corresponding sub-states in a spatially separated state. The light is incident on the pixels 616A1 and 616A2. That is, the microlens array 630 is arranged so that one unit microlens 631 corresponds to a pair of subpixels 616A1 and 616A2 arranged in the Z direction. Therefore, the direction in which the pair of sub-pixels 616A1 and 616A2 are arranged is the direction in which the emission direction of the colored light is separated by the dichroic mirror 50W and the reflection mirror 56 (or the dichroic mirror 55R and the reflection mirror 57) (direction on the XZ plane in FIG. 1). ) Is set.

  Here, the width dimension in the Z direction of the unit microlens 631 is substantially equal to the sum of the width dimension in the Z direction of the subpixel 616A1 and the width dimension in the Z direction of the subpixel 616A2, and the length dimension in the Y direction is the subpixel 616A1. , 616A2 (the length dimensions of the two sub-pixels are equal to each other) are set to be substantially equal to the length dimension in the Y direction. In addition, the width dimension in the Z direction of the sub-pixels 616A1 and 616A2 is set to approximately ½ of the length dimension in the Y direction. This is because a display form in which one picture element (dot) is expressed by the pair of sub-pixels 616A1 and 616A2 is employed, but the dimensional shape of the sub-pixels 616A1 and 616A2 is not limited to the above.

  Polarizers 642 and 641 are disposed on the light emission side of the TFT substrate 612 and the light incident side of the microlens array 630, respectively. Note that as the liquid crystal 613, not only a TN type but also a ferroelectric type, an antiferroelectric type, a horizontal alignment type, a vertical alignment type, and the like can be used.

  As shown in FIGS. 1 and 3, the white light (W2) and the green light (G1 ′), the emission directions of which are separated by the dichroic mirror 50W and the reflection mirror 56, are converted into respective colors on the first two-color modulation liquid crystal panel 61. The light enters the unit micro lens 631 at different angles. The white light (W2) and the green light (G1 ′) incident on each unit microlens 631 are emitted from the unit microlens 631 at different angles, collected separately for each color light, and paired in the Z direction. The light enters the sub-pixels 616A1 and 616A2. The white light (W2) and the green light (G1 ′) are modulated by the respective sub-pixels 616A1 and 616A2, and then orthogonal to the light beam incident end face of the first two-color modulation liquid crystal panel 61 (FIG. 3). Injected at substantially symmetric angles with respect to (X direction). Similarly, the blue light (B1) and the red light (R1) whose emission directions are separated by the dichroic mirror 55R and the reflection mirror 57 are also modulated by the respective sub-pixels 616A1 and 616A2 of the second two-color modulation liquid crystal panel 62. After that, the light beams are emitted at substantially symmetric angles with respect to the direction orthogonal to the light beam incident end face.

  FIG. 4 shows the arrangement of the sub-pixels in the first and second two-color modulation liquid crystal panels 61 and 62 and the relative correspondence of the sub-pixels between the first and second two-color modulation liquid crystal panels 61 and 62. Show. FIG. 4 shows an arrangement relationship of sub-pixels when the two-color modulation liquid crystal panels 61 and 62 are both viewed from the light incident side. In the first two-color modulation liquid crystal panel 61, an image forming region (sub pixel) 616W on which white light (W2) is incident and an image forming region (sub pixel) 616G on which green light (G1 ′) is incident are also displayed. In the two-color modulation liquid crystal panel 62, the image forming area (sub-pixel) 616R where the red light (R1) is incident and the image forming area (sub-pixel) 616B where the blue light (B1) is incident are respectively in a checkered pattern. Is arranged. Between the two two-color modulation liquid crystal panels 61 and 62, an image forming region (sub pixel) 616W and an image forming region (sub pixel) 616R, and an image forming region (sub pixel) 616G and an image forming region are provided. (Sub-pixels) 616B are arranged so as to correspond to each other (spatially overlap). However, the correspondence relationship of the sub-pixels between the two two-color modulation liquid crystal panels 61 and 62 is not limited to the above. Corresponding to the arrangement relationship between the pixels, the arrangement relationship between the dichroic mirror 50W and the reflection mirror 56, and the dichroic mirror 55R and the reflection mirror 57 is set.

  Returning to FIG. 1, a polarization rotation element 80 is disposed on the exit side of the first two-color modulation liquid crystal panel 61, and the polarization direction of the light emitted from the first two-color modulation liquid crystal panel 61 is rotated by 90 degrees. As the polarization rotation element, for example, a λ / 2 phase difference plate can be used. As a result, the polarization directions of the light emitted from the two two-color modulation liquid crystal panels 61 and 62 are different from each other by 90 degrees. For example, the light emitted from the polarization rotation element 80 is P-polarized light, and the light emitted from the second two-color modulation liquid crystal panel 62 is S-polarized light. The arrangement position of the polarization rotation element 80 is not limited to the above, and it may be arranged on the exit side of the second two-color modulation liquid crystal panel 62, or the incident-side polarization of the two-color modulation liquid crystal panels 61 and 62. As long as it is closer to the projection lens than the plate 641, it can be arranged on the incident side of the two-color modulation liquid crystal panel. In short, the polarization rotation element 80 may be appropriately arranged so that light treated as reflected light by the color synthesis optical system 70 is at least S-polarized light.

  Light emitted from the two two-color modulation liquid crystal panels 61 and 62 is combined into one light by the polarization beam splitter 70 which is a color combining optical system. The polarization beam splitter 70 has a cubic shape in which a polarization separation / synthesis film 71 is sandwiched between two substantially triangular prism-shaped transparent media (for example, glass and resin), and two types of polarized light (P The polarization separation / combination film 71 that transmits the P-polarized light and reflects the S-polarized light is formed on the diagonal portion of the square in plan view. The polarization separation / synthesis film 71 can be realized by, for example, a dielectric multilayer film. As a result, the color light from the first two-color modulation liquid crystal panel 61 that is P-polarized light and the color light from the second two-color modulation liquid crystal panel 62 that is S-polarization use the difference in their polarization directions to produce one light. Synthesized with light to form a color image. The color image synthesized by the polarization beam splitter 70 is emitted from a projection lens (projection optical system) 90 and is projected and displayed on a screen (not shown).

  According to this embodiment, there are the following effects. Since the light modulation optical system 60 includes the first and second two-color modulation liquid crystal panels 61 and 62, a projection image having a wide color expression range can be obtained using four kinds of color light of three primary colors and white light. Can be formed. In particular, since white light can be modulated independently, white display with a relatively high brightness can be achieved compared to a projector using only conventional three primary color lights, and the expression in brightness such as metallic luster and flash can be improved. . In addition, since white illumination light is generated, the intensity of the three primary color lights is relatively smaller than that of a projector using only the conventional three primary color lights. Therefore, when image display is performed using only these three primary color lights, the gradation expression on the black side can be improved. As a result, it is possible to achieve both improvement in dark area expression and realization of high peak luminance, and it is suitable for display of video images with many dark colors overall.

  In addition, since a configuration in which two kinds of color light are modulated by one two-color modulation liquid crystal panel 61, 62 is adopted, it is possible to cope with two liquid crystal panels in spite of modulation of four kinds of color light, and the size of the apparatus is small. Easy to realize and cost reduction. Furthermore, since the illumination light paths of four types of color light can be arranged symmetrically, illumination light paths having the same length can be configured at a short distance. In this respect as well, it is easy to reduce the size and thickness of the device.

Further, the dichroic mirror 50W employs a form that transmits green light. Light that has passed through the dichroic mirror 50W passes through the reflecting mirror 56 and then loses light when it passes through the dichroic mirror 50W again. However, in a high-pressure mercury lamp that is often used in projectors, the light intensity of green light is higher than that of other color lights. Since it is relatively large, the color light transmitted through the dichroic mirror 50W is green light, so that it is easy to balance the light intensity with other color light, and it is easy to realize a bright projected image with excellent color balance.
(Modification of the first embodiment)
The spectral characteristics of the dichroic mirrors 40, 50W, and 55R in the color separation optical system 30 are not limited to those in the first embodiment, and the spectral characteristics are determined by the setting of the color light with respect to the optical path. For example, when blue light (B1) and red light (R1) are separated from white light (W) by transmission through the dichroic mirror 40, the dichroic mirror 40 having spectral characteristics as shown in FIG. That's fine. Further, when white light (W2) is separated by transmission through the dichroic mirror 50W, the reflectance of blue light or red light in FIG. 5A is set to y, and the spectral characteristics as shown in FIG. 5B are obtained. A dichroic mirror 50W can be used. Here, since the green light (G2) reflected by the reflection mirror 56 is transmitted again through the dichroic mirror 50W on the way to the first two-color modulation liquid crystal panel 61, the green light (G2) depends on the spectral characteristics of the dichroic mirror 50W. ) Is reflected, and the light intensity of the transmitted light is reduced. Therefore, in order to maintain the color balance of the white light incident on the first two-color modulation liquid crystal panel 61, the reflectance in the wavelength region corresponding to the green light is set to 1-√y in consideration of the light loss. Furthermore, when the blue light (B1) is separated by reflection by the dichroic mirror 55R, a dichroic mirror 55R having spectral characteristics as shown in FIG. 5C may be used. Of course, the spectral characteristics shown here are merely examples, and should be appropriately set according to the spectral distribution of the light emitted from the light source 10. Furthermore, in the first embodiment, the color separation optical system 30 is configured by using a plate-like dichroic mirror or reflection mirror, but the dichroic film or reflection film is sandwiched by a transparent medium such as glass or resin. You may comprise using a prism or a reflective prism. In the former case, it is easy to reduce the weight and cost of the projector, and in the latter case, it is easy to improve optical characteristics such as color light separation efficiency and reflectance. Further, although the color combining optical system 70 is configured using a prism-shaped polarizing beam splitter, a plate-shaped polarizing beam splitter may be used. In the former case, the incident angle of light with respect to the polarization separation / combination film can be made relatively small, so it is possible to reduce the occurrence of color unevenness during efficient synthesis and synthesis of colored light. There is a feature that it is easy to reduce the cost.
[Second Embodiment]
Next, FIG. 6 shows a schematic configuration of a projector according to the second embodiment of the present invention. The projector 2 has substantially the same configuration as the projector 1 of the first embodiment, but the polarization conversion optical system 20 that converts light from the light source 10 into specific polarized light, and the illumination light into the light modulation optical system 60. The main difference from the projector 1 is that a collimating lens 65 is provided for efficient incidence. Therefore, portions having the same functions or operations as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

  Between the light source 10 and the dichroic mirror 40 which is a first color separation optical element, a first lens array 21, a second lens array 22, a polarization beam splitter array 23, a phase difference plate array 24, and a superimposing lens 25 are provided. A polarization conversion optical system 20 including the above is disposed. Note that the polarization conversion optical system 20 used here is a known technique whose details are disclosed in, for example, a patent publication (Japanese Patent Laid-Open No. H8-304739), and thus detailed description thereof is omitted.

  A non-polarized light beam emitted from the light source 10 is separated into a P-polarized light beam group and an S-polarized light beam group whose polarization directions are orthogonal by the first and second lens arrays 21 and 22 and the polarization beam splitter array 23. The separated P-polarized light beam group is rotated by the phase difference plate array 24 to be converted into an S-polarized light beam group. Since the S-polarized light beam group is not subjected to the rotating action of the polarization direction by the phase difference plate array 24, all the light beams emitted from the phase difference plate array 24 are aligned with the S-polarized light. These polarized light beams are directed by the superimposing lens 25 in the direction of emission to the first and second two-color modulation liquid crystal panels 61 and 62 to be illuminated, pass through the collimating lens 65, and each two-color modulation liquid crystal panel. 61 and 62 are overlap-coupled.

  A collimating lens 65 is disposed on each exit side of the dichroic mirror 50W and the dichroic mirror 55, and the respective polarized light beams emitted from the superimposing lens 25 are condensed with respect to the central axis, and in a state of being substantially parallelized. The light enters the first and second two-color modulation liquid crystal panels 61 and 62. In general, a liquid crystal panel has an incident angle dependency on display characteristics. However, the arrangement of the collimating lens 65 narrows the angular distribution of light beams incident on the first and second two-color modulation liquid crystal panels 61 and 62. . As a result, the incident angle dependency of the display characteristics is reduced, and high image quality and high brightness of the projected image are realized. Further, the light condensing property by the unit microlens 631 is improved, and a smaller light condensing spot can be formed. Therefore, it is possible to prevent the occurrence of color mixing caused by unnecessary color light incident on other adjacent sub-pixels. Excellent color image without bleeding can be displayed.

  Light that is incident on the color separation optical system 30 by the polarization conversion optical system 20 is S-polarized light. Therefore, since the dichroic mirrors 40, 50W, and 55R can have spectral characteristics specialized for S-polarized light, it is easy to achieve efficient color light separation. In particular, the dichroic mirror 55R is configured to reflect S-polarized red light, and when a light source lamp (for example, a part of a metal halide lamp or a high-pressure mercury lamp) having a relatively small intensity of red light is used as a light source. However, red light can be used without waste. This makes it easy to balance the light intensity with other color lights, and the color expression range can be expanded without reducing the light utilization efficiency, and a bright projected image with excellent color balance can be realized.

  Each color light direction-separated by the dichroic mirror 50W and the reflection mirror 56, and the dichroic mirror 55R and the reflection mirror 57 is incident on the first or second two-color modulation liquid crystal panels 61 and 62 as in the case of the projector 1. The light is independently modulated on the basis of external image information (not shown), and is partially converted into P-polarized light according to the image information and emitted. Here, unlike the case of the first embodiment, a polarization rotation element 80 for rotating the polarization direction by approximately 90 degrees is arranged on the exit side of the second two-color modulation liquid crystal panel 62, and the second two-color modulation liquid crystal panel 62 is arranged. The modulated P-polarized light from the liquid crystal panel 62 is converted into S-polarized light and then enters the color synthesis optical system 70.

  The color combining optical system 70 combines the four types of modulated color light emitted from the first and second two-color modulation liquid crystal panels 61 and 62 to form a color image. At this time, the color light from the first two-color modulation liquid crystal panel 61 is combined as transmitted light, and the color light from the second two-color modulation liquid crystal panel 62 is combined as reflected light. The arrangement of the polarization rotation element 80 is not limited to this embodiment. That is, when the light from the color synthesis optical system 70 is emitted in the Z-axis direction, the polarization rotation element 80 is disposed on the emission side of the first two-color modulation liquid crystal panel 61, and the polarization rotation element 80 receives the S-polarized light. May be configured to be injected. Further, since the light incident on the two two-color modulation liquid crystal panels 61 and 62 by the polarization conversion optical system 70 is polarized light, the two-color modulation liquid crystal is used instead of the emission side of the two-color modulation liquid crystal panels 61 and 62. You may arrange | position to the incident side of the panels 61 and 62. FIG. In short, the polarization rotation element 80 may be appropriately arranged so that the light beam treated as reflected light by the color synthesis optical system 70 is at least S-polarized light.

  According to the second embodiment, in addition to the effects described in the first embodiment, there are the following effects. In other words, non-polarized illumination light is converted into specific polarized light that can be efficiently used on a liquid crystal panel to produce illumination light, so that the light use efficiency from the light source can be greatly improved and the brightness of the projected image is further increased Can be realized. In addition, by making the light incident on the color separation optical system 30 S-polarized light, high-precision and high-efficiency color separation is realized, and high image quality and high brightness of the projected image are realized. Since none of the light source lamps currently in practical use has an ideal color balance, it is necessary to reduce the intensity of specific color light and to balance the color at the expense of brightness. According to the configuration, since the light use efficiency at the time of color separation can be increased, it is possible to achieve both the improvement of dark area expression and the realization of high peak luminance while minimizing the sacrifice of brightness.

Unlike the present embodiment, the light incident on the color separation optical system 30 from the polarization conversion optical system 20 can be P-polarized light. However, in that case, it is necessary to appropriately change the arrangement of the polarization rotation element 80, the color synthesis optical system 70, the projection lens 90, and the like.
(Modification of the second embodiment)
The arrangement place of the collimating lens 65 is not limited to the second embodiment. For example, it may be arranged on each incident side of the dichroic mirrors 50W and 55R. According to this arrangement, the parallelism of the light incident on the dichroic mirrors 50W and 55R can be increased, so that the separation accuracy and efficiency of the color light in the dichroic mirrors 50W and 55R can be easily improved, and the cost can be reduced.

Further, the arrangement of the polarization conversion optical system 20 is not limited to the second embodiment. For example, the first lens array 21 is disposed on the incident side of the dichroic mirror 40, and the second lens array 22, the polarization beam splitter array 23, the phase difference plate array 24, the superimposing lens 25, and the like are disposed on the two exit sides. It is good also as a form to arrange. In this case, although the number of parts to be used increases, the distance between the light source 10 and the light modulation optical system 60 can be shortened, so that the optical system can be downsized. Further, compared to the configuration of the second embodiment, the wavelength range of the color light incident on the two polarizing beam splitter arrays 23 and the phase difference plate array 24 is limited and narrowed. It can be relaxed and polarization conversion can be realized with higher efficiency. In the second embodiment, the polarization conversion optical system 20 having a lens array is used. Instead, a rod-like (eg, glass rod) or tubular (eg, tubular reflection mirror) light guide is provided. Alternatively, a polarization conversion optical system may be used.
(Other variations)
The present invention is not limited to the above-described embodiments, and includes modifications as described below. In each of the above-described embodiments, the first two-color modulation liquid crystal panel 61 is configured to modulate white light (W2) and green light (G1 ′), but instead of green light (G1 ′), blue light (B1 ) Or red light (R1) may be modulated. In that case, it is easy to manufacture the dichroic mirror 40 and the dichroic mirror 50W. Taking the dichroic mirror 40 as an example, the spectral characteristics are such that the reflectance in the wavelength region located on the short wavelength side or the long wavelength side in the wavelength region of the three primary colors is 0, and the reflectance in the other wavelength regions is x. Therefore, as compared with the dichroic mirror having the spectral characteristics shown in FIG. 2A, the method of changing the spectral characteristics is simple, and it is easy to manufacture and the cost can be reduced. In each of the above-described embodiments, light incident on the color synthesis optical system from the two two-color modulation liquid crystal panels is converted into linearly polarized light orthogonal to each other by the polarization rotation element. Depending on the case, for example, polarization rotation elements may be disposed at two locations, and conversion may be performed so that the circularly polarized light has different rotation directions (for example, counterclockwise circularly polarized light and clockwise circularly polarized light). In short, the polarization rotation element only needs to have a function of converting at least one polarized light so that the polarization states thereof are different so that colored light from two directions can be efficiently combined by the color combining optical system. .

  Further, in each of the above-described embodiments, the first and second two-color modulation liquid crystal panels using TFTs as switching elements are employed as the light modulation optical system. However, the present invention is not limited to this. That is, even if it is the same liquid crystal panel, what used TFD (thin film diode) as a switching element may be used. Furthermore, a projector that can be expected to have the same effect even if a PDLC (Polymer Dispersed Liquid Crystal) panel is used can be configured. In short, various projectors equipped with a light modulation optical system that modulates the light beam emitted from the light source. The present invention can be applied to other projectors. Further, in each of the above embodiments, the pixel arrangement of the first and second two-color modulation liquid crystal panels is set in a matrix form, but not limited to this, various pixel arrangements such as a stripe type and a triangle type are adopted. May be.

In addition, the specific structure, shape, and the like when implementing the present invention may be other structures as long as the object of the present invention can be achieved.

It is a schematic diagram showing schematic structure of the projector 1 which concerns on 1st Embodiment of this invention. It is a figure which shows the spectral characteristic of the dichroic mirror in 1st Embodiment, (A) is the spectral characteristic of the dichroic mirror 40, (B) is the spectral characteristic of the dichroic mirror 50W, (C) is the spectral characteristic of the dichroic mirror 55R. Is shown. 3 is a cross-sectional view illustrating a schematic structure of a first two-color modulation liquid crystal panel 61 in the first embodiment. FIG. FIG. 6 is an explanatory diagram illustrating a pixel arrangement of first and second two-color modulation liquid crystal panels 61 and 62 in the first embodiment and a correspondence relationship of pixels between the two two-color modulation liquid crystal panels 61 and 62. It is a figure which shows the spectral characteristic of the dichroic mirror as a modification of 1st Embodiment, (A) shows the other spectral characteristic of the dichroic mirror 40, (B) shows the other spectral characteristic of the dichroic mirror 50W, (C ) Shows another spectral characteristic of the dichroic mirror 55R. It is a schematic diagram showing schematic structure of the projector 2 which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Projector 10 Light source 20 Polarization conversion optical system 21 1st lens array 22 2nd lens array 23 Polarization beam splitter array 24 Phase difference plate array 25 Superimposition lens 30 Color separation optical system 40 Dichroic mirror (1st color separation) Optical element)
50W dichroic mirror (second color separation optical element)
55R Dichroic mirror (third color separation optical element)
56, 57 Reflection mirror 60 Light modulation optical system 61 First two-color modulation liquid crystal panel (first light modulation device)
62 Second two-color modulation liquid crystal panel (second light modulation device)
616A1, 616A2 Subpixel (Subpixel electrode)
630 Microlens arrays 641 and 642 Polarizing plate 65 Parallelizing lens 70 Polarizing beam splitter (color synthesis optical system)
71 Polarization Separation / Synthesis Film 80 Polarization Rotating Element 90 Projection Lens (Projection Optical System)

Claims (10)

A light source;
A first color separation optical element that separates light emitted from the light source into two color lights, and one of the two color lights separated by the first color separation optical element is white light and first color light. A second color separation optical element that separates the light into a second color light and a third color separation optical element that separates the other into a second color light and a third color light,
A first light modulation device that modulates the white light and the first color light; a second light modulation device that modulates the second color light and the third color light;
A polarization rotation element that rotates the polarization direction of at least one of the emitted lights so that the polarization directions of the emitted lights from the first and second light modulation devices are substantially orthogonal to each other;
A projector comprising: a color synthesizing optical system that synthesizes four kinds of color lights modulated by the first and second light modulation devices. In claim 1,
The second color separation optical element is arranged so that the white light and the first color light are incident on the first light modulation device from different directions,
The projector, wherein the third color separation optical element is arranged so that the second color light and the third color light are incident on the second light modulation device from different directions. In claim 1,
The first and second light modulation devices include a pair of substrates, an electro-optical material sandwiched between the pair of substrates, and a microlens array provided on a light incident side of the pair of substrates. And a plurality of subpixel electrodes formed on the other substrate, wherein the plurality of subpixel electrodes are arranged corresponding to the respective microlenses of the microlens array. In claims 1 to 3,
The projector according to claim 2, wherein the second color separation optical element separates white light from the first color light by reflection. In Claims 1 to 4,
The projector according to claim 1, wherein the first color light is a color light having a relatively high light intensity among the color lights emitted from the light source. In claims 1 to 3,
The color light separated by reflection by the third color separation optical element is a color light having a relatively low light intensity among the color lights emitted from the light source. In claim 5,
The projector according to claim 1, wherein the first color light is green light or blue light. In claim 6,
The projector, wherein the color light separated by reflection by the third color separation optical element is red light. In Claims 1 to 6,
A polarization conversion optical system for converting non-polarized light emitted from the light source into light having a uniform polarization direction is provided between the light source and the first and second light modulation devices. Projector. In claim 9,
The projector is characterized in that the light having the same polarization direction emitted from the polarization conversion optical system is S-polarized light with respect to the light separation surface of the first color separation optical element.

Images