JP2011257645A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector capable of displaying a stereoscopic image and keeping the brightness of a projected image, without an increase in its size and its manufacturing cost.SOLUTION: A projector 1 comprises: a light source 2; a plurality of light modulation elements 6R, 6G and 6B having a first writing region for writing first image data corresponding to an image for a left eye and a second writing region for writing second image data corresponding to an image for a right eye, for modulating respective colored light beams based on the respective image data; a light combination optical system 7; a polarization switching element 9 having a first region which a light beam from the first writing region of the light modulation element enters and a second region which a light beam from the second writing region of the light modulation element enters, for changing the polarization status of a light beam emitted from the first region and a light beam emitted from the second region; a light transmission optical system 8 for transmitting the modulated light beam to the polarization switching element to form an intermediate image thereon; and a projection optical system 10.

Description

  The present invention relates to a projector, and more particularly to a projector capable of viewing a projected image in three dimensions using polarized glasses.

  A technique for three-dimensionally expressing a display image using a projector capable of displaying a large screen has been developed and put into practical use. In stereoscopic image display using a projector, a parallax-based method is generally used in which a left-eye image and a right-eye image are projected on a screen, and the respective images are observed by the left eye and the right eye. At this time, it is necessary for an observer to selectively observe an image corresponding to each eye. As one of the methods, a polarizing projector using polarizing glasses is known.

  In a polarizing projector, a left-eye image and a right-eye image including parallax information are simultaneously displayed on a screen while changing the polarization state between the two images. Alternatively, the image for the left eye and the image for the right eye are alternately and continuously displayed for each frame arranged in time series while changing the polarization state between the two images. At this time, the observer selects only two eyes corresponding to the two types of images by viewing the left-eye image and the right-eye image displayed in different polarization states through polarizing glasses having polarization selectivity. Therefore, the display image can be viewed in three dimensions.

  As one measure for simultaneously displaying a left-eye image and a right-eye image having different polarization states on the screen, the left-eye image is displayed by the first projector, and the left-eye image is displayed by the second projector. A stereoscopic image display device using two projectors has been proposed (see Patent Document 1 below). In the stereoscopic image display device described in Patent Document 1, in order to eliminate the inconvenience of preparing two projectors having different polarization states of projection light, two projectors having the same polarization state of projection light are used. By switching the polarization state of the projection light from the projector with a polarization switching element made of a reflecting mirror, a left-eye image and a right-eye image with different polarization states are generated.

  In addition, as another measure for simultaneously displaying on the screen a left-eye image and a right-eye image having different polarization states, two sets of display panels for left-eye image formation and right-eye image formation are provided. A projection-type stereoscopic display device has been proposed (see Patent Document 2 below). In the projection display device described in Patent Document 2, after a specific color component is selected in a time-sharing manner from light emitted from a light source using a color selection filter, each color component is separated according to a polarization state by a wire grid. Then, the separated lights having different polarization states are modulated in the first display panel for image formation for the left eye and the second display panel for image formation for the right eye, respectively.

  On the other hand, the method of displaying left-eye images and right-eye images having different polarization states alternately in time series has the advantage that the display image can be expressed in three dimensions with only one projector. In addition, a projection display device of this system has also been proposed (see Patent Document 3 below). In the projection type display device described in Patent Document 3, the image for the left eye is projected by projecting the light emitted from the liquid crystal light valve via the polarization control means including the liquid crystal cell and the phase difference plate whose polarization states are alternately switched. And right-eye images are displayed alternately in time series.

JP 2003-202520 A JP 2004-205919 A JP-A-2005-115276

  However, in the method using two projectors as in the stereoscopic image display device described in Patent Document 1, the characteristics of the display image such as brightness and hue are adjusted and the projection position is adjusted between the two projectors. The problem that it is difficult to do. Further, since two projectors are used, there are problems in terms of downsizing and usability.

  In addition, the projection type stereoscopic display device described in Patent Document 2 modulates light of different colors that are sequentially incident in time series in a time-division manner in a single spatial light modulation element, and displays a color image. This is a projection type display device of a so-called field sequential method. In the case of a general field sequential type projection display device, it is only necessary to have one spatial light modulation element. However, in the case of this projection type stereoscopic display device, each light path of light separated by the polarization separation optical system is provided. It is necessary to provide spatial light modulation elements for the left eye and right eye respectively. For this reason, there is a problem that the apparatus configuration becomes complicated and the apparatus becomes larger and the product cost increases.

  Further, in the projection display device described in Patent Document 3, left eye images and right eye images are alternately generated in a time-division manner, and left eye using shutter glasses provided with optical shutters that open and close in time series. Stereoscopic viewing is enabled by switching between visual recognition by the right eye and visual recognition by the right eye in a time-sharing manner. However, since the left eye and the right eye are alternately shielded by the shutter glasses, there is a problem that the brightness of the image visually recognized by the observer is substantially halved with respect to the output of the projection display device. . Further, the polarization switching element used for the shutter glasses is expensive, and it is necessary to provide the glasses with a power source for driving the polarization switching element, which is inconvenient.

  The present invention has been made in view of such circumstances, and is a projector that displays a left-eye image and a right-eye image with different polarization states to display a stereoscopic image, and the size of the apparatus is increased. It is an object of the present invention to provide a projector that can ensure the brightness of a projected image without causing an increase in manufacturing cost.

  In order to achieve the above object, a projector according to the present invention includes a light source, a first writing area in which first image data corresponding to a left-eye image is written, and second image data corresponding to a right-eye image. A plurality of light modulation elements that respectively modulate a plurality of color lights having different wavelength ranges emitted from the light source based on the first image data and the second image data, A light combining optical system configured to combine a plurality of color lights modulated by the plurality of light modulation elements; a first region into which light from the first writing region of the light modulation element is incident; and the first of the light modulation elements. Incident light so that the light emitted from the first area and the light emitted from the second area are in different polarization states. Polarization switching element that switches the polarization state of A light transmission optical system that transmits a plurality of color lights modulated by the plurality of light modulation elements to the polarization switching element and forms an image on the position of the polarization switching element, and the polarization switching element A projection optical system for projecting the intermediate image formed thereon.

  In the projector according to the aspect of the invention, the plurality of light modulation elements modulate the plurality of color lights having different wavelength ranges based on the first image data corresponding to the left eye image and the second image data corresponding to the right eye image, respectively. Then, an optical image corresponding to the image for the left eye and the image for the right eye is formed. The light transmission optical system transmits a plurality of color lights modulated by the plurality of light modulation elements to the polarization switching element, forms an image, and forms an intermediate image of the left eye image and the right eye image on the polarization switching element. . Here, the polarization switching element has a first area where light from the first writing area of the light modulation element is incident and a second area where light from the second writing area is incident, The polarization state of the incident light is switched so that the emission light from the first region and the emission light from the second region are in different polarization states.

  Thus, on the polarization switching element, the image for the left eye by the light emitted from the first region and the image for the right eye by the light emitted from the second region are mixed, and the image for the left eye and the image for the right eye are mixed. An intermediate image in which the polarization state is different from that of the image is formed. Therefore, the observer can selectively observe the two types of images only with the corresponding eyes by looking at the left-eye image and the right-eye image displayed in different polarization states through the polarizing glasses. The displayed image can be viewed three-dimensionally. In the present invention, only one projector is required, and it is not necessary to separately provide the left-eye and right-eye spatial light modulation elements, so that the size of the apparatus and the production cost are not increased, A compact, inexpensive projector capable of stereoscopic viewing can be realized. In addition, the left eye image and the right eye image are not temporally separated by shielding light with shutter glasses or the like, but the left eye image and the right eye image are always visually recognized. Therefore, it is possible to ensure the brightness of the projected image corresponding to the output of.

  In addition, since the light transmission optical system generally has wavelength dependency, there may be a case where a plurality of colored lights having different wavelength regions modulated by a plurality of light modulation elements do not form an image at the same position. In that case, there is a possibility that problems such as color unevenness occur in the display image and color reproducibility deteriorate. On the other hand, according to the projector of the present invention, the light transmission optical system forms an intermediate image by forming all of the plurality of color lights modulated by the plurality of light modulation elements at the position of the polarization switching element. Thus, a display image having no color unevenness and excellent color reproducibility can be obtained.

In the projector according to the aspect of the invention, the light modulation element includes a plurality of pixels arranged in a matrix, and the first writing area and the second writing area are each a plurality arranged in the horizontal direction of the screen. It is possible to adopt a configuration in which the pixel is composed of one row of pixels and arranged alternately.
According to this configuration, the left-eye image and the right-eye image can be evenly incorporated into one frame image, and a high-quality display image can be obtained.

In the projector according to the aspect of the invention, it is possible to employ a configuration in which the sum of the first region and the second region in the polarization switching element is equal to the number of rows of the plurality of pixels in the light modulation element.
According to this configuration, each row of pixels into which each image data is written in the light modulation element and each of the first area and the second area in the polarization switching element have a one-to-one correspondence. In this case, since the writing position of each image data in the light modulation element and the switching position of the polarization state in the polarization switching element are completely coincident with each other, a higher quality stereoscopic image display can be realized.

In the projector according to the aspect of the invention, it is possible to employ a configuration in which the sum of the first region and the second region in the polarization switching element is smaller than the number of rows of the plurality of pixels in the light modulation element.
In the case of this configuration, each row of pixels in which each image data is written in the light modulation element does not have a one-to-one correspondence between the first area and the second area in the polarization switching element, so each image data is written in the light modulation element. The position and the switching position of the polarization state in the polarization switching element do not completely match. Therefore, the local polarization state of the projected image is disturbed, and as a result, the local stereoscopic state is slightly disturbed. However, if the size of the region where the polarization state is disturbed is very small compared to the size of the entire image, there is almost no problem in practical use. According to this configuration, the configuration of the polarization switching element can be simplified, and the cost can be reduced.

In the projector according to the aspect of the invention, it is preferable that the light transmission optical system has telecentricity at least on the light modulation element side. It is more desirable if both the light modulation element side and the polarization switching element side have telecentricity.
An optical system having telecentricity is an optical system in which a principal ray passes through an image side or object side focal point. By using a light transmission optical system composed of such an optical system, the size and shape of the transmitted image do not change even if the light modulation element or the polarization switching element is displaced in the optical axis direction. Therefore, alignment of both elements is easy, and accurate image transmission can be realized.

In the projector according to the aspect of the invention, it is possible to employ a configuration in which the light transmission optical system is an equal magnification transmission optical system.
According to this configuration, accurate image transmission can be realized by using the polarization switching element having the first area and the second area having the same size and shape as the pixel area of the light modulation element.

In the projector according to the aspect of the invention, the light transmission optical system may be a reduction transmission optical system.
According to this configuration, the polarization switching element and the projection optical system can be reduced in size, and the entire projector can be easily reduced in size and cost.

In the projector according to the aspect of the invention, it is possible to employ a configuration in which the light transmission optical system is an enlarged transmission optical system.
According to this configuration, it is easy to align the intermediate image transmitted to the polarization switching element and the polarization switching element, and it is easy to ensure the placement accuracy of the polarization switching element.

In the projector according to the aspect of the invention, it is possible to employ a configuration including a position adjusting mechanism that adjusts the position of the polarization switching element by moving the polarization switching element in at least the arrangement direction of the first region and the second region.
According to this configuration, since the alignment between the intermediate image transmitted to the polarization switching element and the polarization switching element, particularly the alignment in the arrangement direction of the first region and the second region, becomes easy, Therefore, it is easy to obtain a high-quality display image.

In the projector according to the aspect of the invention, it is possible to employ a configuration in which a polarization compensation optical system that compensates for a disturbance in the polarization state is provided on the optical path between the light transmission optical system and the polarization switching element. Or the structure provided with the light absorption type or light reflection type polarizing element arrange | positioned at the incident side of the said polarization switching element is employable.
According to these configurations, since the degree of polarization of polarized light incident on the polarization switching element can be increased, the polarization state of the projection light can be accurately switched by the polarization switching element, and high-quality stereoscopic image display can be realized.

1 is a schematic configuration diagram of a projector according to a first embodiment of the invention. It is a figure which shows the polarization switching element of the projector of 1st Embodiment. It is a figure for demonstrating the correspondence of a polarization switching element and image light. It is a figure which shows the other example of a polarization switching element. It is a figure which shows the other example of a polarization switching element. It is a figure which shows the other example of a polarization switching element. It is a figure which shows the other example of a polarization switching element. It is a figure which shows some structural examples of a light transmission optical system. It is a figure which shows the structural example which added the optical path length correction | amendment optical system to the light transmission optical system. It is a figure which shows the other structural example which correct | amends the optical path length in a light transmission optical system. It is a figure which shows the structural example which added the polarization compensation optical system to the light transmission optical system. It is a figure which shows the polarization switching element of the projector of 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, a so-called three-plate liquid crystal projector using three sets of transmissive liquid crystal light valves as light modulation elements is illustrated. Further, the projector according to the present embodiment employs a line sequential method as a writing mode of image data.
FIG. 1 is a schematic configuration diagram of a projector according to the present embodiment. 2A and 2B are diagrams showing the polarization switching element of the projector according to the present embodiment. FIG. 2A is an xy plan view viewed from the z-axis direction, and FIG. 2B is the x-axis direction. It is yz plane sectional drawing seen from. 3A to 3C are diagrams for explaining the correspondence between the polarization switching element and the image light. 4 to 7 are diagrams showing other examples of the polarization switching element. FIGS. 4A, 5A, 6A, and 7A are xy viewed from the z-axis direction. FIG. 4B, FIG. 5B, FIG. 6B, and FIG. 7B are yz plan sectional views as seen from the x-axis direction. 8A to 8E are diagrams showing some configuration examples of the light transmission optical system. FIG. 9 is a diagram illustrating a configuration example in which an optical path length correction optical system is added to the light transmission optical system. FIG. 10 is a diagram showing another configuration example for correcting the optical path length in the light transmission optical system. FIG. 11 is a diagram illustrating a configuration example in which a polarization compensation optical system is added to the light transmission optical system.
It should be noted that in all of the following drawings, in order to make each component easy to see, the scale of dimensions may be different depending on the component.

  As shown in FIG. 1, the projector 1 according to the present embodiment includes a light source 2, an integrator optical system 3, a color light separation optical system 4, an optical path length correction relay optical system 5, and three liquid crystals that modulate each color light. It mainly includes light valves 6R, 6G, and 6B (light modulation elements), a color light combining optical system 7, a light transmission optical system 8, a polarization switching element 9, and a projection optical system 10. In the configuration of this embodiment, since there are two light transmission optical systems, the “optical path length correcting relay optical system 5”, which is used for the purpose of correcting the optical path length of the illumination optical path, is generated by the liquid crystal light valve. The method of using the image light for the purpose of transmitting to the polarization switching element is referred to as “light transmission optical system 8” (corresponding to “light transmission optical system” in the claims) and distinguished.

Hereinafter, each component of the projector 1 will be described.
The light source 2 includes an ultra-high pressure mercury lamp, a xenon lamp, and the like, and includes a light source lamp 12 that emits white light and a reflector 13 that reflects the light from the light source lamp 12 and emits the light toward the integrator optical system 3. is doing. The integrator optical system 3 includes a first lens array 14 and a second lens array 15 made of fly-eye lenses and the like, and a superimposing lens 16. The integrator optical system 3 has a function of making the illuminance distribution of the light emitted from the light source 2 substantially uniform on each of the liquid crystal light valves 6R, 6G, 6B.

  The color light separation optical system 4 includes dichroic mirrors 18 and 19 and a reflection mirror 20. The dichroic mirrors 18 and 19 are formed by, for example, laminating a dielectric multilayer film on a glass surface, selectively reflect colored light in a predetermined wavelength band included in incident white light, and emit colored light in other wavelength bands. It has the property of transmitting. The dichroic mirror 18 reflects the green light LG and the blue light LB and transmits the red light LR. The dichroic mirror 19 reflects the green light LG among the color lights reflected by the dichroic mirror 18 and transmits the blue light LB. The reflection mirror 20 reflects the red light LR transmitted through the dichroic mirror 18 toward the collimating lens 21 of the liquid crystal light valve 6R for red light modulation.

  The optical path length correcting relay optical system 5 includes an incident side lens 23, a relay lens 24, and reflection mirrors 25 and 26, and the blue light LB is a liquid crystal light valve compared to the other color lights LR and LG. It has a function of correcting optical loss due to the long optical path length up to 6B. The incident side lens 23 has a function of making light incident on the relay lens 24 efficiently. The relay lens 24 has a function of transmitting light in the vicinity of the incident side lens 23 to the blue light modulating liquid crystal light valve 6B through the collimating lens 21. The optical path length correcting relay optical system 5 causes the blue light LB incident on the incident side lens 23 to enter the spatially separated liquid crystal light valve 6B with almost no light loss in a state where the light intensity distribution is substantially preserved. Communicated.

  Each of the liquid crystal light valves 6R, 6G, and 6B includes a pair of substrates and a liquid crystal sandwiched between the substrates, and has a configuration in which a plurality of pixels whose transmittance can be independently controlled are arranged in a matrix. . In the light transmission region, a plurality of scanning lines and a plurality of data lines are provided so as to intersect each other, and image data is supplied to the plurality of data lines, while the plurality of scanning lines are sequentially scanned from one to the other. Thus, the image data is written to a plurality of pixels arranged in the row direction (horizontal direction of the screen) corresponding to each scanning line. For example, the liquid crystal light valve 6R for modulating red light modulates the incident red light substantially parallelized by the collimating lens 21 based on the image data, and emits image light containing an optical image. The operations of the liquid crystal light valve 6G for modulating green light and the liquid crystal light valve 6B for modulating blue light are the same as those of the liquid crystal light valve 6R for modulating red light. In the following description, a row composed of a plurality of pixels arranged in the row direction may be referred to as a “line”.

  In the case of the present embodiment, the image data is composed of first image data corresponding to the left eye image and second image data corresponding to the right eye image. The first image data is from the upper side to the lower side of the screen with respect to the odd lines of the liquid crystal light valves 6R, 6G, 6B, for example, the top row, the third row from the top, the fifth row from the top,. Are written in a line sequential manner. On the other hand, the second image data is displayed on the screen for the even lines of the liquid crystal light valves 6R, 6G, 6B, for example, the second row from the top, the fourth row from the top, the sixth row from the top, and so on. Are written in a line sequential manner from the upper side to the lower side. In the line-sequential method, image data is written simultaneously to all of a plurality of pixels arranged in the row direction, and the image data is written to all the pixels by sequentially moving the pixel group in the column direction (vertical direction of the screen). One frame image is completed.

  That is, each of the liquid crystal light valves 6R, 6G, and 6B has a first writing area including odd lines in which the first image data corresponding to the left-eye image is written, and second image data corresponding to the right-eye image. And a second writing area composed of even lines to be written. Therefore, each of the first writing area and the second writing area corresponds to a line composed of a plurality of pixels arranged in the row direction. As described above, the first image data and the second image data are sequentially written to the liquid crystal light valves 6R, 6G, and 6B, and this writing operation is repeated for each frame. Each of the liquid crystal light valves 6R, 6G, and 6B modulates incident light based on the written first image data and second image data.

  The color light combining optical system 7 includes a cross dichroic prism 28 and a wavelength selection phase plate 29. The cross dichroic prism 28 has a structure in which four triangular prisms are bonded to each other. The surface to be bonded in the triangular prism becomes the selective reflection surface of the cross dichroic prism 28. On the inner surface of the cross dichroic prism 28, a selective reflection surface that reflects the red light LR and transmits the green light LG and a selective reflection surface that reflects the blue light LB and transmits the green light LG are formed orthogonal to each other. Yes. The green light LG incident on the cross dichroic prism 28 is emitted as it is through the selective reflection surface, and the red light LR and the blue light LB are selectively reflected by the selective reflection surface and have the same emission direction as the green light LG. Injected in the direction.

  The wavelength selection phase plate 29 selectively converts the polarization state of the color light in a specific wavelength band in the incident light. For example, Color Select (a product name of Color Link) or the like can be used. That is, the image light emitted from each of the liquid crystal light valves 6R, 6G, and 6B is linearly polarized light that has passed through an exit side polarizing plate (not shown), and the efficiency at the cross dichroic prism 28 that is the color light combining optical system 7 is increased. Considering this, the green light LG is incident on the cross dichroic prism 28 in the P-polarized state, the red light LR, and the blue light LB in the state of S-polarized light, and is combined with the image light that forms a color image and emitted. The image light emitted from the cross dichroic prism 28 is incident on the wavelength selection phase plate 29, and only the polarization direction of the green light LG is rotated by 90 degrees to become S-polarized light, and is composed of three color lights having the same polarization state. It is emitted from the wavelength selection phase plate 29 as image light. In this way, when the polarization states of all the color lights are aligned, it is easy to align the transmission characteristics between the color lights in the light transmission optical system 8 described later, and it is easy to realize high transmission efficiency. Of course, each of the color light beams LR, LG, and LB emitted from the liquid crystal light valves 6R, 6G, and 6B through the exit side polarizing plate (not shown) is linearly polarized light (for example, S-polarized light) in the same state. In this case, the wavelength selection phase plate 29 is not necessary.

  The light transmission optical system 8 includes an incident side lens 31, a relay lens 32, and an emission side lens 33. The light transmission optical system 8 has a function of transmitting image light emitted from the liquid crystal light valves 6R, 6G, and 6B to the polarization switching element 9 and forming an image at the position of the polarization switching element 9 to form an intermediate image. is doing. The light transmission optical system 8 of the present embodiment employs an equal magnification transmission optical system, but may employ a reduction transmission optical system or an enlargement transmission optical system. The imaging magnification of the light transmission optical system 8 will be described later.

  The incident side lens 31 is disposed between the liquid crystal light valves 6R, 6G, and 6B and the cross dichroic prism 28. The incident side lens 31 has a function of causing the image light from each of the liquid crystal light valves 6R, 6G, and 6B to efficiently enter the relay lens 32. The relay lens 32 has a function of transmitting the image light in the vicinity of the incident side lens 31 into one through the cross dichroic prism 28 while forming an image on the polarization switching element 9 and forming an intermediate image. Have. Since the color light composition characteristic of the cross dichroic prism 28 is incident angle dependent, the incident side lens 31 is not disposed on the exit side of each of the liquid crystal light valves 6R, 6G, and 6B, and one incident side lens is cross dichroic. The prism 28 may be disposed close to the exit end surface. In such a configuration, it is possible to reduce color unevenness that easily occurs during color light synthesis. The emission side lens 33 has a function of causing the image light emitted from the relay lens 32 to efficiently enter the polarization switching element 9.

  The light transmission optical system 8 is desirably an optical system that generates less optical aberrations such as distortion and lateral chromatic aberration, and the same applies to the relay lens 32. From this point of view, it is effective to adopt means such as a relay lens 32 composed of a plurality of lenses, an aspheric lens, or a low-dispersion glass material. The light transmission optical system 8 is not limited to a lens, and may be configured by using a reflection mirror or a combination of a lens and a reflection mirror. The incident side lens 31 and the emission side lens 33 are effective in terms of improving transmission efficiency, but are not essential optical elements, and the characteristics and light of image light emitted from the liquid crystal light valves 6R, 6G, and 6B. This may not be necessary depending on the configuration of the transmission optical system.

  The optical transmission optical system 8 is preferably an optical system that generates less optical aberrations. More specifically, the optical transmission optical system 8 is preferably an optical system having a small wavelength dependency of image transmission characteristics. The reason is that in each of the liquid crystal light valves 6R, 6G, and 6B, an image for red light, an image for green light, and an image for blue light are formed by light having different wavelength ranges, and these images are formed by one light transmission optical system 8. Because it is handled. For this purpose, it is desirable to use an optical material having zero dispersion or low dispersion. When an optical system having zero or small wavelength dependence of image transmission characteristics is used as the light transmission optical system 8, all of the red light image, the green light image, and the blue light image with light having different wavelength ranges are polarization switching elements. An intermediate image is formed by forming an image at the installation position 9.

  Alternatively, as another means for reducing the wavelength dependence of the image transfer characteristics, as shown in FIG. 9, an optical path length correction optical system is arranged on the exit side of each liquid crystal light valve 6R, 6G, 6B, and each optical path. It is possible to adopt a method for correcting the optical path length. Here, as an example of the optical path length correction optical system, a case where three plano-convex lenses 35R, 35G, and 35B having different lens characteristics (for example, curvature and material) are used for each optical path is shown. By optimizing the lens characteristics for each optical path, the wavelength dependency during image transmission can be reduced. Alternatively, as shown in FIG. 10, measures such as changing the distance DR, DG, DB between the liquid crystal light valves 6R, 6G, 6B and the polarization switching element 9 to correct the optical path length for each optical path are adopted. it can. In FIG. 10, in order to make the drawing easy to see, arrows indicating the distances DR, DG, and DB are drawn only from the liquid crystal light valves 6R, 6G, and 6B to the emission optical axis.

  Further, in the configuration including a plurality of liquid crystal light valves, the above-described light transmission optical system 8 is used to reliably transmit the image light of each of the liquid crystal light valves 6R, 6G, and 6B to the polarization switching element 9 while accurately superimposing them. It is necessary to set the optical distance between each of the liquid crystal light valves 6R, 6G, 6B and the polarization switching element 9 to a predetermined relationship in consideration of the optical characteristics. That is, it is necessary to accurately set the positions of the liquid crystal light valves 6R, 6G, and 6B in the direction of the projection optical axis. However, this is not easy. Therefore, it is desirable to use a light transmission optical system having telecentricity at least on one side of the liquid crystal light valves 6R, 6G, 6B, preferably on both sides of the liquid crystal light valves 6R, 6G, 6B and the polarization switching element 9 side. . An optical system having telecentricity is an optical system in which a principal ray passes through an image side focal point or an object side focal point. By using such an optical system, even if the liquid crystal light valves 6R, 6G, 6B and the polarization switching element 9 are displaced in the optical axis direction, the size and shape of the transmitted image do not change. Therefore, the alignment of both elements becomes easy, and accurate image transmission can be realized.

  Several examples of such a light transmission optical system having telecentricity are shown in FIGS. FIG. 8A shows an example of a lens-type double-sided telecentric light transmission optical system, which includes two lenses 37A and 37B and one optical aperture 38. FIG. 8B shows an example of a mirror-type double-side telecentric light transmission optical system, which includes three reflecting mirrors 39A, 39B, and 39C. FIG. 8C shows an example of a both-side telecentric light transmission optical system using a lens / mirror combination system, and two pairs of mirrors 40A, 40B, 41A, and 41B include two pairs and one lens 42. . FIG. 8D shows an example of a double-sided telecentric reduction transmission optical system, which includes two lenses 43A and 43B and one optical aperture 44. FIG. 8E shows an example of an object side telecentric light transmission optical system, which includes one lens 45 and one optical aperture 46.

  Note that the cross dichroic prism 28 which is the color light combining optical system 7 is also preferably an element with little occurrence of optical aberration, similarly to the light transmission optical system 8, and is configured using an optical material having zero dispersion or low dispersion. It is desirable.

  As shown in FIGS. 2A and 2B, the polarization switching element 9 includes a support substrate 43 and a polarization element 46 formed of two types of wavelength plates, a first wavelength plate 44 and a second wavelength plate 45. Have. The support substrate 43 is made of a transparent substrate having no polarization such as quartz glass. The polarizing element 46 has a configuration in which a plurality of first wave plates 44 and a plurality of second wave plates 45 are alternately arranged in the short direction of each wave plate. The first wave plate 44 and the second wave plate 45 are elongated rectangular plates having the same dimensions and shape, and are fixed to one surface of the support substrate 43 by, for example, an optical adhesive. In addition, since the image light from each liquid crystal light valve is transmitted to the polarization switching element 9 and light having high light intensity is incident, the polarization switching element 9 has a photoelastic coefficient from the viewpoint of not disturbing the polarization state of the image light. It is desirable to use a material having a small size.

  The polarization switching element 9 includes a first region where light from the odd lines (first writing region) of the liquid crystal light valves 6R, 6G, and 6B is incident and an even line (second second) of the liquid crystal light valves 6R, 6G, and 6B. And a second region into which light from the (writing region) is incident. The first region is a region where the first wave plate 44 is disposed, and the second region is a region where the second wave plate 45 is disposed. The polarization switching element 9 uses the difference in the arrangement of the optical axes of the first wave plate 44 and the second wave plate 45, which will be described later, to generate light emitted from the first region and light emitted from the second region. It has a function of switching the polarization state of incident light so that the polarization states are different from each other.

  In the present embodiment, as described above, a configuration in which the optical image on the liquid crystal light valves 6R, 6G, 6B is transmitted to the polarization switching element 9 at approximately the same magnification by the light transmission optical system 8 is adopted. Therefore, the shape, the longitudinal direction, and the short dimension of each wave plate 44, 45 are the shape, the longitudinal direction, and the short direction of the pixel group composed of a plurality of pixels arranged in the row direction of the liquid crystal light valves 6R, 6G, 6B. It is almost the same as the dimensions of. Further, the sum of the first wave plate 44 and the second wave plate 45 in the polarization switching element 9, that is, the sum of the first region and the second region, is the number of rows of pixels in the liquid crystal light valves 6R, 6G, 6B (line). Number). The total sum of the first wave plate 44 and the second wave plate 45 in the polarization switching element 9 may not necessarily match the number of pixel rows in the liquid crystal light valves 6R, 6G, and 6B. This point will be described later.

  In the present embodiment, the first wave plate 44 and the second wave plate 45 are both quarter wave plates and have a function of converting linearly polarized light into circularly polarized light. The first wave plate 44 and the second wave plate 45 differ only in the arrangement of the optical axis (fast axis or slow axis). That is, as shown in FIG. 2 (A), the first wave plate 44 is arranged in an oblique 45 degree direction whose fast axis (indicated by arrow PA) connects the upper left direction and the lower right direction. The second wave plate is disposed in a direction in which the fast axis (indicated by an arrow PB) is orthogonal to the fast axis of the first wave plate, that is, in an oblique 45 degree direction connecting the lower left direction and the upper right direction. Each of the wave plates 44 and 45 includes a birefringent optical crystal, a laminate thereof, a polymer film obtained by stretching a polymer, and an optical anisotropy, a laminate thereof, and an inorganic material having anisotropy. It is possible to use a multilayer film structure in which the optical anisotropy is expressed by stretching the structure, a structure in which the structural birefringence is expressed by forming a periodic fine structure, and the like.

  As shown in FIG. 1, the polarization switching element 9 is held by a holding member 48, and the holding member 48 is provided with a position adjusting mechanism 49 for adjusting the position of the polarization switching element 9. With this configuration, the polarization switching element 9 can be adjusted in position in all the x-axis direction, y-axis direction, and z-axis direction. The light transmission optical system 8 has a one-to-one correspondence between the pixel groups arranged in the row direction of the images formed on the liquid crystal light valves 6R, 6G, and 6B and the first region and the second region of the polarization switching element 9. It is necessary to accurately transmit the images of the liquid crystal light valves 6R, 6G, and 6B to a predetermined position of the polarization switching element 9. Therefore, by providing the above-described position adjustment mechanism 49, the light transmission optical system 8 and the polarization switching element 9 can be easily adjusted (positioned).

  The polarization switching element 9 is preferably position-adjustable in all directions of the x-axis direction, the y-axis direction, and the z-axis direction, but at least the arrangement direction of the first region and the second region ( It is desirable that position adjustment is possible in the y-axis direction). According to this configuration, it is easy to align the intermediate image transmitted to the polarization switching element 9 and the first region and the second region of the polarization switching element 9 in the arrangement direction. The local polarization state disorder of the projected image that occurs when the alignment of the first and second regions of the polarization switching element 9 in the arrangement direction is insufficient can be prevented, and a high-quality display image can be easily obtained.

  Hereinafter, the state in which image light from the liquid crystal light valves 6R, 6G, and 6B is converted into image light having a predetermined polarization state by the polarization switching element 9 and emitted is used with reference to FIGS. I will explain. 3A shows the state of the image light incident on the polarization switching element 9, FIG. 3B shows the state of the polarization switching element 9, and FIG. 3C exits from the polarization switching element 9. The state of image light is shown.

  When the image light incident on the polarization switching element 9 is viewed in detail, the image is continuous line by line corresponding to the writing of the image data in the line sequential scanning in the vertical direction of the liquid crystal light valves 6R, 6G, 6B. Has been rewritten. In other words, the intermediate image formed by the image light incident on the polarization switching element 9 is, as shown in FIG. 3 (A), at a certain point in time, the image of the previous frame and the image of the current frame newly rewritten. Coexist with a predetermined boundary position X in between. In each frame image, the first image data corresponding to the left-eye image L and the second image data corresponding to the right-eye image R are alternately arranged in line units. That is, the left eye image L corresponding to the first image data appears on the odd lines, and the right eye image R corresponding to the second image data appears on the even lines.

  As shown in FIG. 3B, the first wave plate 44 of the polarization switching element 9 is arranged in an oblique 45-degree direction (the direction of the arrow PA) whose fast axis connects the upper left direction and the lower right direction. The second wave plate 45 is disposed in a 45-degree oblique direction (in the direction of the arrow PB) whose fast axis connects the lower left direction to the upper right direction. Here, the image light from the liquid crystal light valves 6R, 6G, and 6B is incident on the polarization switching element 9 in the state of linearly polarized light, for example, S-polarized light having a vibration direction in the y-axis direction in FIG. In this case, the image light incident on the first wave plate 44 is set in a 45-degree oblique direction connecting the upper left direction and the lower right direction with the fast axis of the first wave plate 44, so It becomes and is injected. On the other hand, the image light incident on the second wave plate 45 becomes clockwise circularly polarized light because the fast axis of the second wave plate 45 is set in an oblique 45 degree direction connecting the lower left direction and the upper right direction. It is injected.

  Therefore, as shown in FIG. 3C, in the state where the image of the previous frame and the image of the current frame coexist with the predetermined boundary position X in between, all the left-eye images are in the first polarization state. Is converted into counterclockwise circularly polarized light, and all right-eye images are converted into clockwise circularly polarized light that is the second polarization state. In this way, the left-eye image or the right-eye image can be selectively converted into a predetermined polarization state, and the left-eye image and the right-eye image can be in different polarization states.

  The observer displays a projection image in which a left-eye image and a right-eye image having different polarization states are mixed, a polarizing element that transmits only counterclockwise circularly polarized light for the left eye, and clockwise for the right eye. Observation is performed through polarizing glasses each having a polarizing element that transmits only the circularly polarized light. Then, the left-eye image and the right-eye image are accurately separated, and the observer can visually recognize the left-eye image only with the left eye and the right-eye image with only the right eye. In this way, a favorable stereoscopic state can be obtained.

  As described above, according to the present embodiment, only one projector is required, and it is not necessary to provide the left-eye and right-eye spatial light modulation elements, respectively, which increases the size of the apparatus and the manufacturing cost. A small and inexpensive projector capable of stereoscopic viewing can be realized without incurring. Also, by shielding light using shutter glasses or the like, the left-eye image and the right-eye image are not temporally separated, and the left-eye image and the right-eye image are stereoscopically viewed at all times. Since the image is viewed, the overall brightness of the projected image can be ensured.

  If a light transmission optical system having wavelength dependency is used, R light, G light, and B light modulated by the three liquid crystal light valves 6R, 6G, and 6B may not form an image at the same position. There is a risk that problems such as occurrence of color unevenness in the display image and deterioration in color reproducibility may occur. On the other hand, according to the projector 1 of the present embodiment, the light transmission optical system 8 switches all the R light, G light, and B light modulated by the three sets of liquid crystal light valves 6R, 6G, and 6B. Since an intermediate image is formed by forming an image at the position of the element 9, a display image having no color unevenness and excellent color reproducibility can be obtained.

[Other configuration example 1 of polarization switching element]
4A and 4B show another configuration example of the polarization switching element applicable to the projector 1 of the present embodiment.
The polarization switching element 9 shown in FIGS. 2A and 2B has a configuration in which a first wave plate 44 and a second wave plate 45 are attached to a support substrate 43, respectively. Instead of this configuration, the polarization switching element 51 of this configuration example includes a first wave plate 44 and a second wave plate 45 inside a frame-shaped support body 52 as shown in FIGS. Are configured to be alternately fitted. The inside of the support body 52 is hollowed out, and the first wave plate 44 and the second wave plate 45 are substantially exposed from the support body 52 except for an end portion supported by the support body 52. . In addition, when the polarization switching element 51 is viewed along the x-axis direction, the first wave plate 44 and the second wave plate 45 disposed therein may be invisible depending on the light transmittance of the frame-shaped support body 52. In FIG. 4 (B), the case where the frame-like support body 52 has a light transmitting property is illustrated. FIG. 7B described later is also drawn from the same viewpoint.

  In the polarization switching element 9 shown in FIGS. 2A and 2B, the image light emitted from the liquid crystal light valves 6R, 6G, and 6B is added to the first wave plate 44 or the second wave plate 45 and the support substrate. 43. In contrast, in the polarization switching element 51 of this configuration example shown in FIGS. 4A and 4B, there is no support substrate, and the image light emitted from the liquid crystal light valves 6R, 6G, and 6B has the first wavelength. Since it is the structure which permeate | transmits only the plate 44 or the 2nd wavelength plate 45, it is preferable at the point which does not have the structural member which has a bad influence on the polarization state of image light.

[Other configuration example 2 of polarization switching element]
Still another configuration example of the polarization switching element applicable to the projector 1 of the present embodiment is shown in FIGS.
In the polarization switching element 9 shown in FIGS. 2A and 2B, the first wave plate 44 and the second wave plate 45 formed of two types of quarter wave plates having different optical axis arrangements are provided on the support substrate 43. It was provided. Instead of this configuration, in the polarization switching element 55 of this configuration example shown in FIGS. 5A and 5B, a wave plate 56 made of one kind of half-wave plate is stuck on the support substrate 43. . The polarization switching element 55 has a configuration in which a plurality of wave plates 56 are spaced apart from each other in the y-axis direction at a pitch that is twice the dimension in the short direction of the wave plate 56. Between the wave plates 56 arranged at a predetermined interval, a transparent member 57 made of glass or the like having no polarizing property is arranged. In this configuration example, the installation position of the wave plate 56 is set as a first area where the image for the left eye is incident, and the installation position of the transparent member 57 is set as a second area where the image for the right eye is incident.

  Or it is good also as an air layer, without arrange | positioning the transparent member 57 in a 2nd area | region. In this configuration, the transparent member 57 can be reduced, and the cost of the polarization switching element 55 can be reduced.

  Assume that image light, for example, S-polarized light having a vibration direction in the y-axis direction in FIG. 5A is incident on the polarization switching element 55 having the above configuration. In this case, the image light incident on the wave plate 56 is set in an oblique 45 degree direction (the direction indicated by the arrow PA or the lower left direction and the upper right direction may be used) in which the fast axis of the wave plate connects the upper left direction and the lower right direction. Therefore, the polarization direction is P-polarized light rotated by 90 degrees, and is emitted from the polarization switching element 55. On the other hand, the image light incident on the transparent member 57 is emitted in the S-polarized state similar to that at the time of incidence without receiving the action of polarization rotation. Therefore, all the left-eye images are P-polarized light that is the first polarization state, and all the right-eye images are S-polarized light that is the second polarization state. Thus, the left-eye image or the right-eye image can be selectively converted into a predetermined polarization state, and the left-eye image and the right-eye image can be in different polarization states.

  An observer transmits a projection image in which a left-eye image and a right-eye image having different polarization states are mixed, a polarizing element that transmits only P-polarized light for the left eye, and only S-polarized light for the right eye. Observe through polarizing glasses each equipped with a polarizing element. Then, the left-eye image and the right-eye image are accurately separated, and the observer can visually recognize the left-eye image only with the left eye and the right-eye image with only the right eye. Thereby, a favorable stereoscopic state can be obtained.

[Other configuration example 3 of polarization switching element]
In the case of using a transparent member such as glass having no polarizing property in addition to the wave plate as in the above configuration, it is necessary to use a transparent member having an optical thickness (optical distance) substantially the same as that of the wave plate. desirable. For example, when the refractive index of the transparent member 80 is larger than the refractive index of the wave plate 81 as in the polarization switching element 59 shown in FIGS. The thickness is made smaller than the physical thickness and adjusted so that the optical thickness of the transparent member 80 and the optical thickness of the wave plate 81 are substantially the same. As described above, when the physical thickness of the transparent member 80 and the physical thickness of the wave plate 81 are different, the transparent member 80 and the wave plate 81 are disposed on the support substrate 43, so that the thickness direction (z-axis direction). Since the one end face is arranged with the transparent member 80 and the wave plate 81, this end face can be made flat. It is desirable that the flat surface be an image transmission surface from the liquid crystal light valves 6R, 6G, 6B. This facilitates the alignment of the intermediate image with respect to the arrangement of the wave plates 81 of the polarization switching element 59.

  Thus, when the optical thickness of the wave plate 81 and the transparent member 80 is approximately the same, the intermediate image transmitted onto the polarization switching element 59 is projected and displayed on the projection plane (screen) by the projection optical system 10. At this time, the optical distance between the polarization switching element 59 and the projection optical system 10 is constant at any position in the intermediate image plane transmitted onto the polarization switching element 59. Therefore, a projection optical system having a relatively shallow depth of focus can be used, and the projection optical system can be easily reduced in size and cost.

[Other configuration example 4 of polarization switching element]
Alternatively, instead of the configuration using the support substrate 43, the wave plates 81 and the transparent members 80 are alternately arranged inside the frame-shaped support body 52, as in the polarization switching element 63 shown in FIGS. 7A and 7B. It is good also as a structure inserted in. Also in this case, one end surface in the thickness direction of the transparent member 80 and the wave plate 81 is abutted against and aligned with a virtual plane defined by the support 52, and the flat surface is made into a flat surface, and the liquid crystal light valves 6R, 6G, It is desirable to use the transmission surface of the image from 6B. Alternatively, the wavelength plate 81 and the transparent member 80 are arranged so that the thicknesses (dimensions in the z-axis direction) are the same before and after the virtual plane, and the virtual planes from the liquid crystal light valves 6R, 6G, and 6B are arranged. It may be an image transmission surface.

[Other configuration example 5 of polarization switching element]
The total sum of the first region and the second region in the polarization switching element 9 is preferably the same as the number of pixels (number of lines) in the liquid crystal light valves 6R, 6G, 6B, but is not limited thereto. is not. When the sum of the first region and the second region of the polarization switching element 9 does not match the number of rows of pixels of the liquid crystal light valves 6R, 6G, 6B, a pixel group in the row direction of the liquid crystal light valves 6R, 6G, 6B And the respective regions of the polarization switching element 9 do not have a one-to-one correspondence, so that the boundary position of each image data in the liquid crystal light valves 6R, 6G, 6B and the boundary position of the region where the polarization state in the polarization switching element 9 is different Does not match exactly. Therefore, for example, the local polarization state of the projected image is slightly disturbed, for example, a light beam that should originally be in the first polarization state in the vicinity of the boundary position is emitted as the second polarization state. However, if the size of the region where the polarization state is disturbed is very small compared to the size of the entire image, there is almost no problem in practical use.

  From this viewpoint, the total of the first region and the second region of the polarization switching element 9 may be smaller than the number of rows (number of lines) of pixels of the liquid crystal light valves 6R, 6G, and 6B. If the number of first regions and second regions that are about ½ or more of the number of rows of pixels of the liquid crystal light valves 6R, 6G, and 6B is formed, the polarization switching element 9 has almost a desired effect. can get. In the case where the sum of the first region and the second region of the polarization switching element 9 is smaller than the number of rows of pixels of the liquid crystal light valves 6R, 6G, 6B, the number of wave plates to be used can be reduced, thereby reducing the cost. Can be planned.

[Other configuration examples of optical transmission optical system]
In the above-described embodiment, the light transmission optical system 8 is an equal magnification transmission optical system. However, the optical image on the liquid crystal light valves 6R, 6G, 6B may be similarly reduced or enlarged and transmitted. That is, the light transmission optical system 8 may be a reduction transmission optical system or an enlargement transmission optical system. In the configuration in which the optical image formed by the liquid crystal light valves 6R, 6G, and 6B is reduced and transmitted to the polarization switching element 9, the polarization switching element 9 and the projection optical system 10 can be reduced in size. Cost is easy to achieve. Conversely, in the configuration in which the optical image formed by the liquid crystal light valves 6R, 6G, and 6B is enlarged and transmitted to the polarization switching element 9, the alignment between the transmitted image and the polarization switching element 9 becomes easy, and the polarization switching is performed. It is easy to ensure the arrangement accuracy of the element 9.

  In the case of the above embodiment, the polarization switching element 9 is disposed at the focal position of the projection optical system 10, and there is no inclusion other than air between the polarization switching element 9 and the projection optical system 10. An extremely short projection optical system can be used. As the back focus length becomes shorter, the high-performance projection optical system 10 can be realized more easily despite the small F value and the large aperture. Therefore, even when the magnification of image transmission in the light transmission optical system 8 is set to other than equal magnification, the projection optical system 10 corresponding to this configuration can be realized relatively easily.

[Configuration example using a polarizing element]
In order to switch the polarization state of the image light accurately by the polarization switching element 9, it is desirable that the image light incident on the polarization switching element 9 is linearly polarized light having a high degree of polarization. Alternatively, depending on the configuration of the wave plate or the like in the polarization switching element 9, circularly polarized light with high roundness may be used. The image light emitted from the liquid crystal light valves 6R, 6G, and 6B through the unillustrated exit side polarizing plate is linearly polarized light having a high degree of polarization, but the color light combining optical system 7 existing on the way to the polarization switching element 9, for example, Polarization is disturbed by the cross dichroic prism 28 having a dichroic film formed of a dielectric multilayer film and the light transmission optical system 8 including lenses having curvature, and the degree of polarization is lowered.

  Therefore, a polarizing element for increasing the degree of polarization of image light incident on the polarization switching element 9 may be disposed between the light transmission optical system 8 and the polarization switching element 9. Polarizing elements include light-absorbing polarizing elements using stretched polymer materials, light-absorbing polarizing elements with orienting light-absorbing fine particles, light-absorbing or light-reflecting polarized light utilizing structural birefringence An element or the like can be used. However, since these polarization elements are elements that improve the degree of polarization of image light by absorbing or reflecting light of unnecessary polarization components, the polarization elements immediately before the polarization switching element 9 (liquid crystal light valve 6R). , 6G, 6B side). Considering the limited installation space, light-absorbing polarization elements are easy to use, but reflection-type polarization elements are used to transmit and eliminate unnecessary polarization components and to polarize reflected image light. A configuration may be adopted in which the light is incident on the switching element 9.

  By disposing these polarizing elements immediately before the polarization switching element 9 (on the liquid crystal light valves 6R, 6G, 6B side), the degree of polarization of the image light at the stage from the liquid crystal light valves 6R, 6G, 6B to the polarization switching element 9 Even in the case of a decrease, the degree of polarization of linearly polarized light incident on the polarization switching element 9 is increased. Therefore, the polarization switching element 9 can accurately switch the polarization state of the image light, and a high-quality stereoscopic state can be realized.

[Example of configuration using polarization compensation optics]
In the measures using the light absorption type or light reflection type polarizing element, since the polarizing element is an element that increases the degree of polarization of the image light by eliminating light of an unnecessary polarization component, the light amount of the image light is reduced. Inevitable. Therefore, as another measure for increasing the degree of polarization of image light incident on the polarization switching element, a configuration using a polarization compensation optical system that compensates for polarization disturbance caused by the color light combining optical system 7 and the light transmission optical system 8 is used. Can be adopted. In the polarization compensation optical system, light having an unnecessary polarization characteristic can be compensated and converted to light having a useful polarization characteristic without causing a large light loss, so that a reduction in the amount of image light can be suppressed to a small level.

  Specifically, as shown in FIG. 11, it is desirable to dispose the polarization compensation optical system 53 on the optical path between the relay lens 32 of the light transmission optical system 8 and the polarization switching element 9. According to this configuration, since the degree of polarization of polarized light can be increased immediately before entering the polarization switching element 9, the polarization switching element 9 can accurately switch the polarization state of the projection light, realizing high-quality stereoscopic image display. it can.

  A known rectifier can be used as the polarization compensation optical system 53. The rectifier includes a half-wave plate 71 and a lens 72 having no refractive power. The lens 72 having no refractive power is constituted by a combination of a convex lens 73 and a concave lens 74 having a pair of strong refractive surfaces. The lens 72 having no refractive power can cause a difference in transmittance between the P-polarized component and the S-polarized component of the transmitted light, and can rotate the polarization plane. The degree of polarization rotation can be adjusted over a wide range by adjusting the curvature radius and the glass refractive index of the curved surface. Further, by forming a dielectric multilayer film that generates a desired retardation on the surface of the half-wave plate 71 and each surface of the lens 72 having no refractive power, the desired retardation is imparted to the transmitted light. Can do.

  Polarization changes caused by the polarization of each color emitted from the liquid crystal light valves 6R, 6G, and 6B passing through the cross dichroic prism 28 and the relay lens 32 are not completely the same. In the cross dichroic prism 28, green light (G light) is transmitted through the R light reflecting surface and the B light reflecting surface. Red light (R light) is reflected by the R light reflecting surface and transmitted through the B light reflecting surface. Blue light (B light) is transmitted through the B light reflecting surface and reflected by the B light reflecting surface. Therefore, the retardation received by each color light in the dielectric multilayer film (R light reflecting dichroic film, B light reflecting dichroic film) on the R light reflecting surface and the B light reflecting surface is different. In the relay lens 32, the degree of rotation of the polarization plane differs for each color light due to chromatic dispersion of the glass refractive index.

  For the above reasons, it is difficult to completely reverse the polarization change over the entire wavelength range with the rectifier, and in order to realize this, the polarization compensation optical system may become larger, more complicated, and the cost may increase significantly. There is. In this case, for example, the rectifier may be configured with an emphasis on polarization compensation of G light having the highest human visibility. Specifically, the curvature radius of the dielectric multilayer film of the rectifier and the lens 72 having no refractive power and the glass material are adjusted so as to minimize the retardation received by the G light and the rotation of the polarization plane. By doing so, the polarization compensation optical system 53 (rectifier) can be compensated for the polarization state of the image light most effectively while avoiding an increase in size, complexity, and cost. Can be displayed. When a mercury lamp such as an ultra-high pressure mercury lamp is used as the light source 2, it is desirable to minimize retardation and polarization plane rotation in the vicinity of the e-line (546.1 nm) having the highest intensity in the G light wavelength region. .

  The place where the polarization compensation optical system 53 can be disposed is after the color lights from the liquid crystal light valves 6R, 6G, 6B are combined by the cross dichroic prism 28 (on the side of the polarization switching element 9) due to space restrictions or the like. It is limited to a position close to the polarization switching element 9. Also, in each optical path of red light, green light, and blue light, the optical characteristics of the intervening dichroic element and the like are different, and the degree of polarization in each optical path is reduced due to the fact that the optical material used has wavelength dispersion. The degree is not uniform. Therefore, the degree of polarization of the image light incident on the polarization switching element 9 cannot be compensated over the entire wavelength range. Therefore, in this configuration, it is desirable to adopt a method of setting the polarization compensation amount according to the color light with the greatest decrease in the degree of polarization. Alternatively, it is desirable to adopt a method of setting the polarization compensation amount so that the decrease in the degree of polarization is averaged among the three color lights.

  In this example, the dielectric multilayer film for compensating for the retardation generated in the cross dichroic prism 28 and the relay lens 32 is formed on at least one surface of the optical element constituting the rectifier. However, the formation position of the dielectric multilayer film is not limited to the rectifier, and may be formed on the surface of another optical element as long as it performs an equivalent function. Specifically, the light emission surface of the cross dichroic prism 28 and each lens surface of the relay lens 32 are mentioned. Furthermore, antireflection films are usually formed on these surfaces, but it is also possible to effectively generate retardation for compensation by not forming an antireflection film on at least one of these surfaces. is there.

    Further, the arrangement position of the rectifier is not limited to the rear stage (light emission side) of the relay lens 32 but may be the front stage (light incident side) of the relay lens 32. In this case, for example, among the rectifiers shown in FIG. 11, the lens 72 having no refractive index may be arranged at the front stage, and the half-wave plate 71 may be arranged at the rear stage.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment, a transmissive liquid crystal light valve is used as the light modulation element. However, in the projector according to the present embodiment, a configuration example using a reflective liquid crystal light valve as the light modulation element will be described.
FIG. 12 is a schematic configuration diagram of the projector according to the present embodiment. In FIG. 12, the same components as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the projector 61 of the present embodiment, as shown in FIG. 12, dichroic mirrors 63 and 64 that are color light separation optical systems 62 are provided on the exit side of the superimposing lens 16 constituting the integrator optical system 3. The dichroic mirror 63 reflects the green light LG and the blue light LB and transmits the red light LR. The dichroic mirror 64 transmits the green light LG and the blue light LB and reflects the red light LR. A reflection mirror 65 and a dichroic mirror 66 are provided on the optical paths of the green light LG and the blue light LB reflected by the dichroic mirror 63. The dichroic mirror 66 reflects the green light LG among the green light LG and the blue light LB reflected by the dichroic mirror 63 and transmits the blue light LB.

The red light LR reflected by the dichroic mirror 64 is reflected by the reflection mirror 67 and enters the polarization separation prism 68 through the collimating lens 21. The polarization separation prism 68 includes a polarization separation surface that transmits, for example, P-polarized light and reflects S-polarized light, and the red light LR is reflected into a specific polarization state, for example, P-polarized light by the polarization separation surface. The light enters the light valve 69R. Light that has been modulated into different polarization states by the liquid crystal light valve 69R, for example, S-polarized light, is reflected by the polarization separation surface of the polarization separation prism 68 and enters the dichroic prism 28 that is a color light combining optical system. The behavior of the green light LG reflected by the dichroic mirror 66 and the blue light LB transmitted through the dichroic mirror 66 is the same as that of the red light LR, and the description thereof is omitted. Other configurations and operations are the same as those in the first embodiment.
In this configuration example, the incident side lens 31 of the light transmission optical system 8 is disposed between the polarization separation prism 68 and the cross dichroic prism 28, but the polarization separation prism 68 and the liquid crystal light valves 69R, 69G, and 69B. You may arrange | position between. Further, the three incident side lenses 31 may be aggregated and arranged on the exit side of the cross dichroic prism 28.

  In this embodiment, the same effect as that of the first embodiment can be obtained in that a small, inexpensive, and bright projector capable of displaying a stereoscopic image can be realized.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example in which a wavelength plate (or a transparent member) having a shape and dimensions corresponding to a plurality of pixels arranged in the row direction in the pixel array of the liquid crystal light valve is used as the polarization switching element. A wave plate (or a transparent member) having a shape and dimensions corresponding to a plurality of pixels arranged in the column direction may be used. Further, as the light modulation element, a light modulation element using a dot sequential image data writing method may be employed instead of the line sequential method. In addition, the specific configuration of each part of the projector of the above embodiment is not limited to the above embodiment, and can be changed as appropriate.

  DESCRIPTION OF SYMBOLS 1,61 ... Projector, 2 ... Light source, 6R, 6G, 6B, 69R, 69G, 69B ... Liquid crystal light valve (light modulation element), 7 ... Color light synthesis optical system, 8 ... Light transmission optical system, 9, 51, 55 , 59, 63 ... polarization switching elements, 10 ... projection optical system, 49 ... position adjustment mechanism, 53 ... polarization compensation optical system.

Claims (11)

A light source;
A first writing area in which first image data corresponding to the image for the left eye is written and a second writing area in which second image data corresponding to the image for the right eye is written; A plurality of light modulation elements that respectively modulate a plurality of color lights having different wavelength ranges based on the first image data and the second image data;
A light combining optical system for combining a plurality of color lights modulated by the plurality of light modulation elements;
A first region where light from the first writing region of the light modulation element is incident; and a second region where light from the second writing region of the light modulation element is incident; A polarization switching element that switches a polarization state of incident light so that light emitted from one region and light emitted from the second region have different polarization states;
A light transmission optical system that transmits a plurality of color lights modulated by the plurality of light modulation elements to the polarization switching element and forms an intermediate image by forming an image at the position of the polarization switching element;
A projection optical system that projects the intermediate image formed on the polarization switching element;
A projector characterized by comprising: The light modulation element has a plurality of pixels arranged in a matrix,
2. The first writing area and the second writing area are each composed of one row composed of a plurality of pixels arranged in the horizontal direction of the screen, and are alternately arranged. Projector.   The projector according to claim 2, wherein a total sum of the first region and the second region in the polarization switching element is equal to the number of rows of the plurality of pixels in the light modulation element.   The projector according to claim 2, wherein a total sum of the first region and the second region in the polarization switching element is smaller than a number of rows of the plurality of pixels in the light modulation element.   The projector according to claim 1, wherein the light transmission optical system has telecentricity at least on the light modulation element side.   The projector according to claim 1, wherein the light transmission optical system is an equal magnification transmission optical system.   The projector according to claim 1, wherein the light transmission optical system is a reduction transmission optical system.   The projector according to claim 1, wherein the light transmission optical system is an enlarged transmission optical system.   The position adjusting mechanism for adjusting the position of the polarization switching element by moving the polarization switching element in at least the arrangement direction of the first region and the second region. The projector according to any one of the above.   The polarization compensation optical system that compensates for disturbance of polarization state is provided on an optical path between the light transmission optical system and the polarization switching element, according to any one of claims 1 to 9. projector.   10. The projector according to claim 1, further comprising a light absorption type or a light reflection type polarization element disposed on an incident side of the polarization switching element. 11.

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