JP3797100B2 - projector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projector (projection display device) that projects an image.
[0002]
[Prior art]
As a display device having a large screen, a projector that enlarges and projects an image on a screen is often used. As the projector, a front projector that projects projection light onto a reflective screen and a rear projector that projects projection light onto a transmission screen are known. Examples of the rear projector include those described in JP-A-10-307332.
[0003]
A rear projector reflects projection light emitted from a projector that projects an image on one or a plurality of reflecting mirrors and projects it onto a screen.
[0004]
[Problems to be solved by the invention]
The image displayed by the projector is preferably brighter and better in image quality. For this reason, it is desired that the reflection mirror provided in the rear projector has a high reflectivity with respect to the reflected projection light to reduce the light loss.
[0005]
Further, as disclosed in Japanese Patent Laid-Open No. 10-307332, it is known that a thin rear projector having a short apparatus depth can be configured by arranging the projector in a direction substantially parallel to the screen. Yes. However, in that case, since at least two mirrors are arranged at the twisted position, when the polarization state of the projection light is matched with the reflection characteristic of one reflection mirror, the other reflection mirror is consistent with the reflection characteristic. May decrease, resulting in optical loss.
[0006]
Furthermore, a cross dichroic prism is used as the color light combining optical system of the projector, the polarization direction of the color light reflected by the cross dichroic prism is s-polarized light, and the polarization direction of the transmitted color light is p-polarized light. A configuration for increasing photosynthesis efficiency is known (for example, Japanese Patent Publication No. 6-8985). In this case, however, the polarization directions of the three color lights constituting the projection light are not uniform, and this may cause a deterioration in the color balance of the projection light in consideration of the reflection characteristics of the reflection mirror.
[0007]
The present invention has been made to solve the above-described problems in the prior art, and by setting the polarization direction of the projection light incident on the reflection mirror in consideration of the optical characteristics of the reflection mirror provided in the projector. An object of the present invention is to provide a technique capable of improving the light use efficiency of projection light and realizing a bright projection image.
[0008]
[Means for solving the problems and their functions and effects]
In order to solve at least a part of the problems described above, a first projector according to the present invention includes:
Screen,
A projection unit for emitting projection light representing an image reproduced by a plurality of color lights;
An optical path changing unit for directing projection light emitted from the projection unit toward the screen,
The optical path changing unit has a plurality of reflection mirrors that sequentially reflect the projection light emitted from the projection unit,
The incident surface of the specific reflecting mirror of the plurality of reflecting mirrors is in an arrangement relationship perpendicular to the incident surface of the reflecting mirror disposed immediately before the specific reflecting mirror along the optical path of the projection light. Yes,
The optical path changing unit has a polarization direction perpendicular to an incident surface of each reflection mirror when at least one color light among the plurality of color lights included in the projection light enters each reflection mirror. First polarized light that is configured to be s-polarized light and at least rotates the polarization direction of the projection light emitted from the reflection mirror disposed immediately before and incident on the specific reflection mirror by 90 degrees. A surface rotation element is provided.
[0009]
In general, s-polarized light having a polarization direction perpendicular to the incident surface of the reflecting mirror has high reflectance, and p-polarized light having a polarization direction parallel to the incident surface has low reflectance. Here, the “incident surface of the reflecting mirror” means a plane determined by the normal line of the reflecting surface of the reflecting mirror and the optical axis of the incident light beam.
[0010]
According to the projector of the present invention, when at least one color light among the plurality of color lights included in the projection light sequentially enters the plurality of reflection mirrors, the projector has a polarization direction perpendicular to the incident surface of each reflection mirror. Since it is configured to be polarized light, loss of at least one color light can be reduced. As a result, the utilization efficiency of the projection light projected on the screen can be improved, and a bright projection image can be realized.
[0011]
Here, the optical path changing unit includes at least a first polarization plane rotating element that rotates the polarization direction of the projection light emitted from the reflection mirror disposed immediately before and incident on the specific reflection mirror by 90 degrees. It is preferable.
[0012]
The light that is s-polarized with respect to the reflection mirror disposed immediately before becomes p-polarized light with respect to a specific reflection mirror having an incident surface perpendicular to the incident surface of the immediately preceding reflection mirror. However, according to the above configuration, at least one color light included in the projection light incident on the specific reflecting mirror having an incident surface perpendicular to the incident surface of the immediately preceding reflecting mirror among the plurality of reflecting mirrors. Can be converted from p-polarized light to s-polarized light.
[0013]
Furthermore, a second polarization plane rotation element that rotates the polarization direction of the projection light incident on the optical path changing unit by 90 degrees may be provided between the projection unit and the optical path changing unit.
[0014]
Such a configuration is convenient when the polarization direction of the projection light immediately after being emitted from the projection unit is p-polarized light with respect to the incident surface of the first reflection mirror of the optical path changing unit. Alternatively, in a case where only part of the color light is configured to be s-polarized light having a polarization direction perpendicular to the incident surface of the reflection mirror of the optical path changing unit, the part of the color light immediately after being emitted from the projection unit This is also convenient when the polarization direction is p-polarized light with respect to the incident surface of the first reflecting mirror of the optical path changing unit.
[0015]
Further, at this time, the second polarization plane rotation element may be configured to rotate only the polarization direction of the specific color light constituting the projection light by 90 degrees.
[0016]
If such a second polarization plane rotation element is used for a projector having a projection unit equipped with a color light combining optical system that combines color light that is p-polarized light and color light that is s-polarized light, the light is emitted from the projection unit. The polarization direction of the projection light incident on the optical path changing unit can be made to be substantially one type among all color lights. Therefore, it is possible to set the polarization direction of all the color lights incident on the reflection mirror of the optical path changing unit to s-polarized light having a polarization direction perpendicular to the incident surface, increasing the use efficiency of the projection light, and realizing a bright projection image can do.
[0017]
On the other hand, when only a part of the colored light is configured to be s-polarized light having a polarization direction perpendicular to the incident surface of the reflecting mirror of the optical path changing unit, the reflected light becomes s-polarized light. The colored light is preferably blue light.
[0018]
By so doing, it is possible to reduce the loss of blue light among the plurality of color lights included in the projection light. This adjusts the balance with other color lights when the intensity of blue light is relatively small among the multiple color lights contained in the projection light, for example, when a metal halide lamp is used as the light source included in the projection unit. can do.
[0019]
Further, in the case where only a part of the color light is configured to be s-polarized light having a polarization direction perpendicular to the incident surface of the reflection mirror of the optical path changing unit, red light among a plurality of color lights included in the projection light When the intensity of the light source is relatively small, for example, when a high-pressure mercury lamp is used as the light source included in the projection unit, the color light that becomes the s-polarized light for each reflection mirror may be red light. preferable.
[0020]
In this way, loss of red light among a plurality of color lights included in the projection light can be reduced, and the balance with other color lights can be adjusted.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described based on the following examples. In the following embodiments, the same reference numerals are given to the same components unless otherwise described. Further, x, y, and z indicate three axes that are orthogonal to each other.
[0026]
A. First embodiment:
FIG. 1 is a perspective view showing a schematic configuration of a rear projector (a rear projection display device) as a first embodiment. The projector 10C includes a transmissive screen SCR, a projection unit PJ that projects an image, and two reflection mirrors MR1 and MR2. The first polarization plane rotation plate PR1 is provided between the projection unit PJ and the first reflection mirror MR1, and the second polarization plane rotation plate PR2 is provided between the first reflection mirror and the second reflection mirror. It has. Here, in order to arrange the projection unit PJ in a direction substantially parallel to the screen SCR, the two reflection mirrors MR1 and MR2 are arranged such that their respective incident surfaces are perpendicular to each other.
[0027]
Here, the first polarization plane rotation plate PR1 corresponds to the second polarization plane rotation element of the present invention, and the second polarization plane rotation plate PR2 corresponds to the first polarization plane rotation element of the present invention. The two reflecting mirrors MR1, MR2 and the polarization plane rotating plate PR2 correspond to the optical path changing unit of the present invention. The second reflection mirror MR2 corresponds to the main reflection mirror.
[0028]
The projection light emitted from the projection unit PJ passes through the first polarization plane rotation plate PR1, is reflected by the first reflection mirror MR1, passes through the second polarization plane rotation plate PR2, and further passes through the second polarization plane rotation plate PR2. Is reflected by the reflecting mirror MR2 and enters the screen SCR. Thereby, an image is formed on the screen SCR.
[0029]
The projection light emitted from the projection unit PJ is set to light (p-polarized light) having a polarization direction parallel to the incident surface of the first reflection mirror MR1. The “incident surface of the reflecting mirror” means a plane determined by the normal line of the reflecting surface and the optical axis of the incident light beam.
[0030]
The first polarization plane rotating plate PR1 rotates the polarization direction of the incident projection light by 90 degrees to convert it into light (s-polarized light) having a polarization direction perpendicular to the incident plane of the first reflection mirror MR1. . The first polarization plane rotating plate PR1 is constituted by, for example, a λ / 2 phase difference plate.
[0031]
As the first and second reflection mirrors MR1 and MR2, for example, those produced by coating a glass plate with a metal film or a dielectric multilayer film are used.
[0032]
Here, in general, the reflectance of the reflecting mirror has polarization dependency. Specifically, s-polarized light having a polarization direction perpendicular to the incident surface has a relatively high reflectance, and p-polarized light having a polarization direction parallel to the incident surface has a relatively low reflectance.
[0033]
Therefore, by arranging the first polarization plane rotating plate PR1 on the incident side of the first reflecting mirror MR1, the projection light incident on the first reflecting mirror MR1 is directed to the incident surface of the first reflecting mirror MR1. To be s-polarized light. For this reason, since the reflectance of the projection light can be increased as compared with the case of the non-polarized projection light and the p-polarized projection light, the loss in the first reflection mirror MR1 is reduced and a bright projection image is displayed on the screen. Can be projected on top.
[0034]
In addition, since the first and second reflection mirrors MR1 and MR2 are arranged so that the respective incident surfaces are perpendicular to each other, the projection light that has been s-polarized with respect to the first reflection mirror MR1 is For the second reflecting mirror MR2, the projection light is p-polarized light. Therefore, a second polarization plane rotation plate PR2 having the same function as the first polarization plane rotation plate PR1 is disposed between the first reflection mirror MR1 and the second reflection mirror MR2, and the incident projection light is transmitted. The polarization direction is rotated 90 degrees. Thereby, the projection light incident on the second reflection mirror MR2 is also set to s-polarized light having a polarization direction perpendicular to the incident surface, so that the reflectance of the projection light can be increased. Thereby, it is possible to reduce the loss in the second reflecting mirror MR2 and project a bright projected image on the screen.
[0035]
As described above, since the projection light incident on the first and second reflection mirrors MR1 and MR2 is set to s-polarized light having a polarization direction perpendicular to the respective incident surfaces, reflection of the projection light is performed. The rate can be increased. Thereby, it is possible to reduce the loss in the reflection mirror and project a bright projected image on the screen.
[0036]
When the projection light emitted from the projection unit PJ is set to s-polarized light with respect to the first reflection mirror MR1, the polarization plane rotating plate PR1 can be omitted.
[0037]
FIG. 2 is an explanatory diagram showing projection light emitted from the projection unit PJ. As shown in the perspective view of FIG. 2, the projection unit PJ includes a cross dichroic prism 500 that is a color light combining optical system, and three light valves 400R, 400G, and 400B. Also, an illumination optical system for illuminating the three light valves 400R, 400G, and 400B, a color light separation optical system that separates the illumination light into three color lights, and a projection lens that projects light emitted from the cross dichroic prism 500 It has. However, the illumination optical system, the color light separation optical system, and the projection lens are omitted for ease of explanation.
[0038]
The three light valves 400R, 400G, and 400B correspond to the color signals (image information) corresponding to the three color lights of red light (R light), green light (G light), and blue light (B light) respectively incident thereon. The modulated light is emitted as transmitted light. As such a transmissive light valve, a transmissive liquid crystal panel is used.
[0039]
The three colored lights emitted from the three light valves 400R, 400G, and 400B are incident on the incident side surfaces 500R, 500G, and 500B of the corresponding cross dichroic prism 500, respectively.
[0040]
The cross dichroic prism 500 has two dichroic surfaces 510R and 510B provided in a substantially X shape. First dichroic surface 510R reflects R light and transmits B light and G light. Second dichroic surface 510B reflects B light and transmits R light and G light. As shown in FIG. 2A, the R light incident from the incident side surface 500R is reflected by the first dichroic surface 510R and emitted from the emission side surface 500O. As shown in FIG. 2B, the G light incident from the incident side surface 500G passes through the first and second dichroic surfaces 510R and 501B and is emitted from the emission side surface 500O. As shown in FIG. 2C, the B light incident from the incident side surface 500B is reflected by the second dichroic surface 510B and emitted from the emission side surface 500O. Accordingly, the three color lights modulated by the light valves 400R, 400G, and 400B for the respective colors are combined by the cross dichroic prism 500. The combined light is emitted as projection light by a projection optical system (not shown) in the direction of the first reflection mirror MR1, and a color image is displayed on the screen SCR.
[0041]
The liquid crystal panels used in the light valves 400R, 400G, and 400B emit linearly polarized modulated light having a specific polarization direction. Therefore, if the color light emitted from each of the light valves 400R, 400G, and 400B is set as p-polarized light with respect to the first reflecting mirror MR1, the polarization direction is rotated by 90 degrees by the polarization plane rotating plate PR1, and eventually Since the s-polarized light is incident on one reflection mirror MR1, the projector 10C having the configuration shown in FIG. 1 can be realized. Specifically, a liquid crystal panel of a type that emits s-polarized light to the incident surfaces of the first and second dichroic surfaces 510R and 510B is used as the light valves 400R, 400G, and 400B. If the color light emitted from each of the light valves 400R, 400G, and 400B is set to s-polarized light with respect to the first reflection mirror MR1, the first polarization plane rotating plate PR1 can be omitted as described above. it can. Specifically, as the light valves 400R, 400G, and 400B, liquid crystal panels that emit p-polarized light to the incident surfaces of the first and second dichroic surfaces 510R and 510B are used.
[0042]
Incidentally, as shown in FIG. 2A, the R light is set to be s-polarized light with respect to the incident surface of the first dichroic surface 510R in order to increase the reflectance at the first dichroic surface 510R. May be. In addition, as shown in FIG. 2C, the B light is also set to be s-polarized light with respect to the incident surface of the second dichroic surface 510B in order to increase the reflectance at the second dichroic surface 510B. May be. On the other hand, as shown in FIG. 2B, the G light is incident on the incident surfaces of the first and second dichroic surfaces 510R and 510B in order to increase the transmittance of the first and second dichroic surfaces 510R and 510B. On the other hand, it may be set to be p-polarized light.
[0043]
When set as described above, the polarization direction of the projection light emitted from the projection unit PJ differs depending on the color light included.
[0044]
Since the incident surfaces of the first and second dichroic surfaces 510R and 510B and the incident surface of the first reflecting mirror MR1 are perpendicular to each other, they are s-polarized with respect to the first and second dichroic surfaces 510R and 510B. Is p-polarized light with respect to the reflection mirror MR1, and p-polarized light is s-polarized light with respect to the reflection mirror MR1. Therefore, the R light and B light emitted from the projection unit PJ become p-polarized light with respect to the first reflecting mirror MR1, while the G light becomes s-polarized light.
[0045]
As described above, the first polarization plane rotating plate PR1 has a function of rotating the polarization direction of incident light by 90 degrees, and can be configured by a λ / 2 phase difference plate. The λ / 2 phase difference plate is an element that gives a phase change of λ / 2 to light of a specific wavelength or wavelength range, and the target color light changes depending on the wavelength range that gives the phase change. For example, there is a narrow-band λ / 2 phase difference plate that rotates the polarization direction of specific color light by 90 degrees, and a broadband λ / 2 phase difference plate that rotates the polarization direction of white light by 90 degrees. Therefore, if a narrow-band λ / 2 phase difference plate corresponding to only G light is used as the polarization plane rotating plate PR1, all the color lights emitted from the cross dichroic prism 500 can be aligned with s-polarized light having the same polarization direction. Therefore, the reflectance in the reflection mirror MR1 can be increased.
[0046]
On the other hand, if a broadband λ / 2 phase difference plate that rotates the polarization direction of white light by 90 degrees is used as the polarization plane rotation plate PR1, among the colored light contained in the projection light, R light and B light are transmitted to the reflection mirror MR1. On the other hand, it is converted into s-polarized light, and G light is converted into p-polarized light. Therefore, as shown in FIG. 2, when the polarization directions are different depending on the three color lights of R, G, and B included in the projection light, the reflectances of the R, G, and B color lights in the first reflection mirror MR1 are set. It cannot be increased. However, when the projection light includes a plurality of color lights having different polarization directions, the following effects can be obtained. That is, a metal halide lamp or a high-pressure mercury lamp is used as a light source included in an illumination optical system (not shown) of the projection unit PJ. In these lamps, for example, a metal halide lamp has a characteristic that the intensity of B light is relatively weak, and a high-pressure mercury lamp has a characteristic that the intensity of R light is relatively weak. Therefore, when a metal halide lamp or a high-pressure mercury lamp is used as the light source in this embodiment, the color balance is reduced by reducing the loss of the B light and the R light in the first reflection mirror MR1 compared to the G light. An excellent image can be displayed.
[0047]
In the above description using FIG. 2, the projection light emitted from the projection unit PJ is described focusing on the first polarization plane rotating plate PR1 and the first reflection mirror MR1, but the second The same applies to the polarization plane rotating plate PR2 and the second reflecting mirror MR2.
[0048]
As can be seen from the above description, the polarization direction of the projection light shown in FIG. 1 indicates the polarization direction common to a plurality of color lights included in the projection light, or the polarization direction of at least one color light whose loss is to be reduced. Yes. In addition, the polarization direction of the projection light shown in the following embodiments also indicates the polarization direction common to a plurality of color lights included in the projection light or the polarization direction of at least one color light whose loss is to be reduced.
[0049]
In the example of the projection unit PJ shown in FIG. 2, the case where the R light and the B light are s-polarized light with respect to the first reflection mirror MR1 is described as an example. However, the present invention is not limited to this. is not. When the R light is weak, a configuration in which at least the R light becomes s-polarized light with respect to the first reflection mirror MR1 is also applicable. In addition, when the G light is weak, a configuration in which at least the G light becomes s-polarized light with respect to the first reflection mirror MR1 is also applicable. In addition, when the B light is weak, a configuration in which at least the B light becomes s-polarized light with respect to the first reflection mirror MR1 is also applicable. For example, when a metal halide lamp is used as the light source, at least B light may be s-polarized light with respect to the first reflection mirror MR1. When a high-pressure mercury lamp is used, at least the R light may be s-polarized light with respect to the first reflecting mirror MR1. These modifications can be realized by devising the configuration of the cross dichroic prism 500, the arrangement of the three light valves 400R, 400G, and 400B, the type of liquid crystal panel to be used, and the like.
[0050]
B. Second embodiment:
FIG. 3 is a perspective view showing a schematic configuration of a rear projector as a second embodiment. The projector 10D has a configuration in which projection light emitted from the projection unit PJ is sequentially reflected by the three reflection mirrors MR1, MR2, and MR3 and projected onto the screen SCR.
[0051]
The first polarization plane rotation plate PR1 corresponds to the second polarization plane rotation element of the present invention, and the second polarization plane rotation plate PR2 corresponds to the first polarization plane rotation element of the present invention. The three reflecting mirrors MR1, MR2, MR3 and the polarization plane rotating plate PR2 correspond to the optical path changing unit of the present invention. The reflection mirror MR3 corresponds to the main reflection mirror.
[0052]
The projection light emitted from the projection unit PJ is transmitted through the first polarization plane rotation plate PR1, reflected by the first reflection mirror, transmitted through the second polarization plane rotation plate PR2, and then the second polarization plane. Then, the light is sequentially reflected by the third reflecting mirrors MR2 and MR3 and enters the screen SCR. Thereby, an image is formed on the screen SCR.
[0053]
Since the projection light emitted from the projection unit PJ is set to p-polarized light, the projection light is converted by the first polarization plane rotating plate PR1 to become s-polarized light with respect to the first reflection mirror MR1. Is done.
[0054]
The second reflection mirror MR2 is arranged such that the incident surface of the first reflection mirror MR1 and the incident surface of the second reflection mirror MR2 are perpendicular to each other. In this arrangement, as described in the first embodiment, the projection light that has been s-polarized with respect to the first reflection mirror MR1 is projected with p-polarization with respect to the second reflection mirror MR2. It becomes light. Therefore, a polarization plane rotating plate PR2 is disposed between the first reflection mirror MR1 and the second reflection mirror MR2, and the polarization direction of the incident projection light is rotated by 90 degrees. Thereby, the projection light incident on the second reflecting mirror MR2 also becomes s-polarized light having a polarization direction perpendicular to the incident surface.
[0055]
The third reflection mirror MR3 is arranged so that the incident surface of the second reflection mirror MR2 and the incident surface of the third reflection mirror MR3 are on the same plane. When arranged in this way, the polarization direction of the projection light incident on the third reflection mirror MR3 is the same as the polarization direction of the projection light reflected by the second reflection mirror MR2. Thereby, the projection light incident on the third reflection mirror MR3 is also set to s-polarized light having a polarization direction perpendicular to the incident surface. Therefore, it is not necessary to arrange a polarization plane rotating plate between the second reflecting mirror MR2 and the third reflecting mirror MR3.
[0056]
As described above, the projector 10D according to the present embodiment converts the projection light incident on the first to third reflection mirrors MR1, MR2, and MR3 into s-polarized light having a polarization direction perpendicular to the respective incident surfaces. Since it is set, the reflectance of the projection light can be increased. Thereby, it is possible to reduce the loss in the reflection mirror and project a bright projected image on the screen.
[0057]
In the present embodiment, the first and second reflecting mirrors MR1 and MR2 are arranged so that their incident surfaces are perpendicular to each other, and the second and third reflecting mirrors MR2 and MR3 are the same on each other. The case where they are arranged to be flat has been described as an example, but the first and second reflecting mirrors MR1, MR2 are arranged so that their incident surfaces are on the same plane, and the second and third reflecting mirrors MR2 are arranged. , MR3 may be arranged in such a manner that their incident surfaces are perpendicular to each other. However, in the latter case, it is preferable to dispose the polarization plane rotating plate between the second and third reflection mirrors MR2 and MR3, not between the first and second reflection mirrors MR1 and MR2.
[0058]
In this embodiment, the second and third reflection mirrors MR2 and MR3 are described as an example where the incident surfaces are arranged on the same plane. However, the second and third reflection mirrors are described. MR2 and MR3 may also be arranged so that their incident surfaces are perpendicular to each other. However, in such a case, it is preferable to arrange a polarization plane rotating plate between the second and third reflecting mirrors MR2 and MR3.
[0059]
Furthermore, in this embodiment, the case where three reflection mirrors are provided is described as an example, but the same applies to the case where four or more reflection mirrors are provided. That is, it is preferable that the projection light incident on each of the plurality of reflection mirrors is set to be s-polarized light with respect to each incident surface. In this case, if the projection light emitted from the projection unit is p-polarized light with respect to the first reflection mirror, a polarization plane rotating plate may be disposed in front of the first reflection mirror. In addition, in the two reflection mirrors that are sequentially reflected, when the incident surfaces are perpendicular to each other, a polarization plane rotating plate may be disposed between the reflection mirrors.
[0060]
C. Third embodiment:
FIG. 4 is a perspective view showing the configuration of a rear projector as a third embodiment. The projector 10E includes a transmissive screen SCR, a projection unit PJ that projects an image, and a reflection mirror MR1a. Further, a polarization plane rotating plate PR1 is provided between the projection unit PJ and the reflection mirror MR1. The reflection mirror MR1a corresponds to the main reflection mirror of the present invention, and the polarization plane rotation plate PR1 corresponds to the polarization plane rotation element. The portion of the reflection mirror MR1a corresponds to the optical path changing unit of the present invention.
[0061]
The projection light emitted from the projection unit PJ passes through the polarization plane rotating plate PR1, is reflected by the reflection mirror MR1a, and enters the screen SCR. Thereby, an image is formed on the screen SCR.
[0062]
This projector 10E is characterized in that the reflection mirror MR1a is formed of a film-like mirror.
[0063]
A film-like mirror is a mirror made by coating a metal film such as silver or aluminum on a resin film formed by stretching a resin material, compared to a reflective mirror using a glass plate, etc. Can be reduced in weight. However, in order to prevent oxidation of the metal film, the metal film generally adopts a structure sandwiched between resin films, so that most film-like mirrors have a reflective surface. The rear surface mirror is formed with a transparent medium. When polarized light enters the back mirror with such a structure, the light passes through the transparent medium. If the transparent medium is not optically uniform, the polarization state of the light passing therethrough is changed and projected. This may cause coloring or uneven color in the image. The resin film produced through the stretching process develops optical anisotropy by stretching, so when handling polarized light with a film-like mirror using this type of film, the optical anisotropy and polarization of the film It is necessary to set the relationship with the state appropriately.
[0064]
In consideration of the above points, the reflection mirror MR1a is arranged so that the extending direction of the resin film (indicated by a broken arrow in the figure) is perpendicular to the incident surface, and is orthogonal to the incident surface. S-polarized light or parallel p-polarized light enters as projection light. As a result, it is possible to suppress the occurrence of uneven color or coloring in the image caused by the reflected projection light. As a result, a high-quality projected image without color unevenness can be projected on the screen.
[0065]
If attention is paid only to suppression of color unevenness or the like, the projection light incident on the reflection mirror MR1a does not need to be s-polarized light. However, in consideration of the reflectance of the reflection mirror MR1a, it is preferable that the projection light incident on the reflection mirror MR1a is s-polarized light.
[0066]
In this embodiment, the case where the reflection mirror of the projector including only the main reflection mirror is configured as a film-like mirror is described as an example. However, a plurality of reflection mirrors are used as in the first and second embodiments. Similarly, in the projector provided, the main reflection mirror can be a reflection mirror composed of a film-like mirror.
[0067]
D. Fourth embodiment:
FIG. 5 is a perspective view showing the configuration of a rear projector as a fourth embodiment. This projector 10F shows an example in which the first and second reflecting mirrors MR1 and MR2 in the projector 10C (FIG. 1) of the first embodiment are configured by film-like mirrors. Since the two reflection mirrors MR1a and MR2a are formed of film-like mirrors in the project 10F of the present embodiment, compared to the case where only the main reflection mirror is formed of a film-like mirror as in the third embodiment, Thus, the weight of the apparatus can be reduced.
[0068]
The two reflection mirrors MR1a and MR2a are arranged so that the extending direction of each resin plate is perpendicular to the incident surface. Accordingly, it is possible to suppress the occurrence of color unevenness, coloring, and the like in the image caused by the reflected projection light.
[0069]
In the present embodiment, a polarization plane rotating plate PR2a is disposed between the first and second reflecting mirrors MR1a and MR2a. This is due to the following reason. FIG. 6 is a schematic side view showing an enlarged cross-sectional structure of the first reflecting mirror MR1a. The linearly polarized projection light incident on the first reflection mirror MR1a is transmitted through the resin film PF, reflected by the metal film MF, and again transmitted through the resin film PF and emitted. At this time, a part of the projected light emitted changes its polarization state corresponding to the optical anisotropy of the resin film PF, and is usually emitted as slightly elliptically polarized light.
[0070]
If attention is paid only to suppression of color unevenness or the like, the projection light incident on the second reflection mirror MR2a may be elliptically polarized light. However, considering the reflectance of the second reflection mirror MR2a, it is preferable that the projection light incident on the reflection mirror MR2a be s-polarized light. Therefore, in this embodiment, the polarization plane rotating plate PR2a is disposed between the first and second reflection mirrors MR1a and MR2a, and the projection light partially elliptically polarized by the first reflection mirror MR1a is again s-polarized. Returning to the light, the light is incident on the second reflecting mirror MR2a. For example, a λ / 4 phase difference plate is used as the polarization plane rotating plate PR2a that converts elliptically polarized light into linearly polarized light (s-polarized light).
[0071]
In this embodiment, the case where the incident surfaces of the two reflecting mirrors are arranged so as to be perpendicular to each other is described as an example. However, the projector is arranged such that the incident surfaces are parallel to each other. The same applies to. In this embodiment, the projector including two reflecting mirrors has been described as an example, but the same applies to a projector including three or more reflecting mirrors. At this time, it is not always necessary to configure all of the plurality of reflecting mirrors with film-like mirrors. Of the plurality of reflection mirrors, a part of the reflection mirrors including the main reflection mirror may be constituted by a film-like mirror.
[0072]
E. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0073]
For example, in the present embodiment, the projection unit PJ, the polarization plane rotating plate PR1, and the reflection mirror MR1 or MR1a are separated, but these may be arranged inside the projection unit PJ. For example, the polarization plane rotating plate PR1 may be disposed immediately before the projection lens constituting the projection unit PJ, and the reflection mirror MR1 or MR1a may be disposed inside the projection lens. In this embodiment, as shown in FIG. 2, a projection unit including three light valves composed of a transmissive liquid crystal panel and a cross dichroic prism is described as an example. However, the projection unit is not a cross dichroic prism. The projection unit may include a cross dichroic mirror. Further, a projection unit that does not include such a cross dichroic prism or a cross dichroic prism may be used. Further, it may be a projection unit provided with a reflective liquid crystal panel as a light valve. Furthermore, the configuration of the present invention is not limited to a rear projection type projector, and can basically be applied to a front projection type projector.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a rear projector as a first embodiment.
FIG. 2 is an explanatory diagram showing projection light emitted from a projection unit PJ.
FIG. 3 is a perspective view showing a schematic configuration of a rear projector as a second embodiment.
FIG. 4 is a perspective view showing a schematic configuration of a rear projector as a third embodiment.
FIG. 5 is a perspective view showing a schematic configuration of a rear projector as a fourth embodiment.
FIG. 6 is a schematic side view showing an enlarged cross-sectional structure of the first reflecting mirror MR1a.
[Explanation of symbols]
10C ... Projector
10D ... Projector
10E ... Projector
10F ... Projector
PJ ... Projector
MR1, MR2, MR3 ... reflection mirror
PR1, PR2 ... Polarizing plane rotating plate
SCR ... Screen
400R, 400G, 400B ... Light valve
500 ... Cross dichroic prism
500R, 500G, 500B ... Incident side surface
500O ... Injection side
510R, 510B ... Dichroic surface
MR1a, MR2a ... reflection mirror
PR2a: Polarizing plane rotating plate
PF ... resin film
MF ... Metal film
OF ... Protective film

Claims (5)

A projector for projecting an image,
Screen,
A projection unit for emitting projection light representing an image reproduced by a plurality of color lights;
An optical path changing unit for directing projection light emitted from the projection unit toward the screen,
The optical path changing unit has a plurality of reflection mirrors that sequentially reflect the projection light emitted from the projection unit,
The incident surface of the specific reflecting mirror of the plurality of reflecting mirrors is in an arrangement relationship perpendicular to the incident surface of the reflecting mirror disposed immediately before the specific reflecting mirror along the optical path of the projection light. Yes,
The optical path changing unit has a polarization direction perpendicular to an incident surface of each reflection mirror when at least one color light among the plurality of color lights included in the projection light enters each reflection mirror. First polarized light that is configured to be s-polarized light and at least rotates the polarization direction of the projection light emitted from the reflection mirror disposed immediately before and incident on the specific reflection mirror by 90 degrees. A projector comprising a surface rotating element. The projector according to claim 1, wherein
A projector comprising a second polarization plane rotation element that rotates a polarization direction of projection light incident on the optical path changing unit by 90 degrees between the projection unit and the optical path changing unit. The projector according to claim 2, wherein
The second polarization plane rotation element is a projector that rotates only a polarization direction of specific color light constituting the projection light by 90 degrees. The projector according to claim 1, wherein
The projector, wherein the color light that is s-polarized light with respect to each of the reflection mirrors is blue light. The projector according to claim 1, wherein
The color light that is s-polarized light with respect to each of the reflection mirrors is a red light.

Images