JP4707270B2 - Image projection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image projection apparatus that projects and observes an enlarged image obtained by enlarging an image of an image display element with a lens system, and is particularly suitable for application to a head mounted display, a projector, and the like.
[0002]
[Prior art]
A display device that enlarges and displays an image of a small image display device such as a liquid crystal through a lens system is called a head-mounted display. Thus, there is a so-called projection type display device that observes a projected image.
[0003]
In general, in a display device, the screen resolution is an important factor in determining display quality. However, in a conventional enlarged projection display device, the number of display pixels of a small image display device is set to increase the screen resolution. The method of increasing has been taken. As a small image display element, a liquid crystal display element in which a transistor is formed corresponding to each pixel is generally used. In such an element, miniaturization has a limit due to problems of microfabrication technology, wiring resistance, and securing of a transistor region and a wiring region, and such an element is expensive due to a decrease in yield.
In addition, in the method of enlarging the element without changing the pixel density of the element, the productivity of the element is reduced, and in addition to the problem that the cost is increased, the illumination optical system and the projection optical system are enlarged, and the device The problem of larger size and higher cost arises.
[0004]
On the other hand, in Japanese Patent No. 2939826, in a projection type display device, an optical element capable of rotating the polarization direction and a transparent element having a birefringence effect are provided between the display element and the screen (that is, in the emission optical path of the display element). A method for realizing high resolution by shifting a projected image is disclosed (see FIG. 23). This method is an effective method for high definition because high resolution can be realized using an inexpensive image display element with a small number of pixels.
[0005]
[Problems to be solved by the invention]
Liquid crystal display elements used for enlarged display are roughly classified into a transmission type and a reflection type.
The transmissive type is a configuration adopted in the above-mentioned projection display device of Japanese Patent No. 2939826, and is a liquid crystal using a substrate on which a transistor, its wiring, and a pixel electrode are formed on a translucent substrate such as glass. It is an element. In such a transmissive element, there is a problem that when the pixel density is increased, the substantial aperture ratio decreases due to the wiring and transistor regions. This causes a decrease in brightness if the light amount of the light source is constant, and increases the light amount of the light source, that is, increases power consumption in order to make the brightness constant.
[0006]
On the other hand, the reflection type is a liquid crystal element using a substrate in which transistors and wirings are formed on a non-transparent substrate such as a silicon wafer and a reflective electrode is further formed thereon. Due to the characteristics of such a configuration, the reflective liquid crystal display element has the feature that the aperture ratio can be easily maintained even when the density is increased, and both high definition and light utilization efficiency can be achieved. Yes.
[0007]
However, Japanese Patent No. 2939926 does not describe a configuration in the case of using a reflective display element. In the reflection type, illumination light and projection light pass through the same optical path in the vicinity of the display element, so it is necessary to adopt an optical system different from the transmission type, and this causes a new problem to be developed. .
For example, when the configuration of Japanese Patent No. 2939826 is applied to a reflection type, unlike an absorption type polarizing plate, a polarization beam splitter is used to change the polarization axis for obliquely incident light or to change the spectral transmittance. Or the spectral reflectance changes. The integrator illumination system is used to make the intensity distribution of the light emitted from the light source uniform, and in principle, the display element is illuminated with illumination light having different incident angles.
In such a case, the change in the polarization axis of the obliquely incident light becomes crosstalk between adjacent pixels and degrades the display quality. Further, the change in spectral transmittance / spectral reflectance is observed as uneven display color.
[0008]
In view of the above-described problems, an object of the present invention is to solve the problems of crosstalk and color unevenness when an optical path modulation method is used, and to provide an image projection apparatus having a good high-definition image.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, an image projection apparatus according to claim 1 of the present invention includes an image display element which is a reflective display element, and illumination means for uniformly illuminating the image display element with light source light. A polarization beam splitter, an optical path modulation unit that changes the polarization plane of the image light reflected by the image display element, changes the optical path of the light, and emits the light, and a projection lens that projects light transmitted through the optical path modulation unit The polarization beam splitter is provided in an optical path between the illumination means and the image display element, Display light from the image display element passes through the polarization beam splitter, The optical path modulation means is provided between the polarization beam splitter and the projection lens, and operates the optical path modulation means in synchronization with the image display timing of the image display element, so that the optical path is not modulated in time series. An image projection apparatus for emitting image light and image light whose optical path is modulated, wherein the polarizing means is disposed between the optical path modulating means and the polarizing beam splitter, and the polarization transmission axis thereof Display light immediately after exiting from the polarizing beam splitter The optical axis is arranged so as to be parallel to the polarization axis of the light.
Therefore, since the polarization direction of the projection light incident on the optical path modulation means can be made constant regardless of the incident angle, there is no crosstalk between the shifted light and the non-shifted light, and high-contrast and high-definition display is performed. Can be made. In addition, since there is no crosstalk, light with a large incident angle can be incident, so that it is possible to design an illumination optical system with high light source light capture efficiency, and an image projection device with high light utilization efficiency and low power consumption. Can be realized.
[0010]
According to a second aspect of the present invention, in the image projection apparatus according to the first aspect, a quarter wavelength plate is provided between the polarization beam splitter and the optical path modulation means so that the slow axis is in the polarization direction of the optical axis light. They are arranged so as to be orthogonal or parallel to each other.
Therefore, since the polarization planes of the illumination light and the image light can be made the same, it is possible to minimize the light loss due to the polarization beam splitter and the color change due to the incident angle, and the image is more efficient and has less color unevenness. Can project.
[0011]
According to a third aspect of the present invention, in the image projection apparatus according to the first or second aspect, a spectroscopic unit that spectrally illuminates illumination light in a different wavelength range on the image display element, and a reflection from the image display element. And a synthesis means for synthesizing light.
Therefore, it is possible to provide a high-definition image projection apparatus with higher light utilization efficiency.
[0012]
According to a fourth aspect of the present invention, in the image projection apparatus according to the third aspect, the function of both the spectroscopic means and the synthesizing means is achieved by using one dichroic prism. .
Therefore, the apparatus can be made small.
[0013]
According to a fifth aspect of the present invention, in the image projection apparatus according to the third aspect, the spectroscopic means sequentially illuminates the image display elements with different color lights in time series.
Therefore, since the optical system can be made small, a high-definition color image can be displayed with a small device.
[0014]
According to a sixth aspect of the present invention, in the image projection apparatus according to any one of the first to fifth aspects, the optical path modulation means is a polarization modulation capable of modulating the polarization direction of incident light in a direction substantially orthogonal to the incident light. An optical path changing optical element that changes an optical path with respect to one polarization of the polarization modulation element, and the polarizing means has a polarization transmission axis that is a slow axis or a fast axis of the optical path changing optical element. And in a plane formed by the optical axis of the projected light or in a plane perpendicular to the optical axis.
Therefore, it is possible to provide a suitable configuration of the optical path modulation means for high definition.
[0015]
According to a seventh aspect of the present invention, in the image projection apparatus according to any one of the first to fifth aspects, the optical path modulation means has a variable optical path modulation amount with respect to a specific polarization. And
Therefore, it is possible to provide a suitable configuration of the optical path modulation means for high definition.
[0016]
Further, according to an eighth aspect of the present invention, in the image projection apparatus according to the seventh aspect, the optical path modulation unit is configured such that the slow axis or the fast axis of the optical path modulation unit is one of the polarization axis and the projection optical axis. The optical path of the incident polarized light is modulated by changing the tilt angle of the slow axis or the fast axis with respect to the projection optical axis, and the polarizing means has its polarization transmission axis. Is arranged so as to be in the plane formed by the slow axis or the fast axis of the optical path modulation means and the projection optical axis or in a plane orthogonal thereto.
Therefore, it is possible to provide a suitable configuration of the optical path modulation means for high definition.
[0017]
According to a ninth aspect of the present invention, in the image projection device according to the seventh aspect, the optical path modulation means has an interface inclined with respect to the optical axis of the projection light, and the incident polarization of the substance forming the interface The optical path of incident polarized light is modulated by changing the effective refractive index.
Therefore, it is possible to provide a suitable configuration of the optical path modulation means for high definition.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the image projection apparatus of the present invention will be described in detail with reference to the drawings.
<Example 1>
FIG. 1 shows the configuration of Embodiment 1 of the image projection apparatus of the present invention.
In FIG. 1, the first embodiment includes a light source 101, an integrator optical system 103 including a fly-eye lens, a polarizing beam splitter 104, an image display element 105 which is a reflective liquid crystal display element, an optical path modulation means 130, a projection lens 108, an integrator. It comprises a field lens 109 for condensing the light transmitted through the optical system 103 (fly eye lens) on the image display element 105 and a polarizing means 120. Here, the optical path modulation means 130 functions by combining the polarization modulation element 106 and the optical path changing optical element 107 made of a birefringent plate.
As described above, the first embodiment will be described by taking a so-called single-plate optical system configuration using one liquid crystal display element as an example.
[0019]
The optical path modulation unit 130 (the polarization modulation element 106 and the birefringent plate 107) is disposed between the polarization beam splitter 104 and the projection lens 108.
The polarization means 120 needs to be arranged so that the polarization transmission axis is parallel to the polarization axis of the optical axis light. The polarizing means 120 used here can be used as long as it transmits only a specific linearly polarized light. For example, a second polarizing beam splitter, a prism type polarizer, or an absorption type polarizer is used. Of these, it is preferable to use an absorptive polarizer because of its small incident angle dependency.
[0020]
The polarizing beam splitter 104 functions as a polarizer and an analyzer. However, unlike an absorption type polarizing plate, the polarization axis changes or the spectral transmittance or the spectral reflectance changes for light incident from an oblique direction. To do.
FIG. 2 schematically shows the change of the polarization plane in the polarization beam splitter 104. In FIG. 2, 104F represents a polarization separation film surface formed of a multilayer film of the polarization beam splitter 104, surface A represents a surface on which incident light is incident, and incident light is an optical axis light L1 and L2 inclined from the optical axis light. And consider the rays of L3.
Such light rays are respectively emitted into the surface B. When the incident polarized light is not optical axis light, the s-polarization direction of the polarization separation film is shifted from the incident polarization direction. Therefore, the polarization direction of the emitted light is an incident angle as shown in FIG. Have different polarization directions. Although the reflected light is described in FIG. 2, the plane of polarization of the transmitted light changes depending on the incident angle based on the same principle.
[0021]
The light rays in FIG. 1 illustrate the illumination area of the center fly-eye lens, and each fly-eye lens is configured to illuminate the entire surface of the display element 105 as shown in FIG.
The illumination in FIG. 1 shows a general action of the integrator optical system 103. With such a configuration, the intensity distribution of the light source is made uniform on the display element 105 surface. In FIG. 2, the angle in the plane (plane A) orthogonal to the plane formed by the principal ray and the normal of the separation film of the polarization beam splitter 104 is illustrated. The light enters the polarization beam splitter 104. As described above, for a light beam incident obliquely, the polarization axis of the light emitted from the polarization beam splitter 104 changes depending on the incident angle, so that the light beam as a whole acts to reduce the degree of polarization. .
[0022]
4 and 5 are diagrams for explaining the configuration and operation of the optical path modulation means 130. FIG. The polarization modulator 106 acts to change the polarization plane of incident light by approximately 90 °.
FIG. 4 shows the operation when the polarization modulator 106 is on. At this time, the polarization modulator 106 acts to rotate the polarization plane, and the polarization direction of the incident light is assumed to be the direction indicated by the arrow in FIG. Light L4 incident from a polarizing beam splitter 104 (PBS, not shown) on the left side of the drawing is transmitted through the polarization modulation element 106, modulated into polarized light in the direction perpendicular to the paper surface, and incident on the optical path changing optical element 107 formed of a birefringent plate. To do. The optical path changing optical element 107 is a birefringent plate having a crystal optical axis in the direction indicated by 107x, and the optical axis is one polarization axis of light emitted from the polarization modulation element 106 (in the first embodiment, The vertical polarization direction when the polarization modulation element 106 is off) and the plane formed by the main optical axis of the incident light, are inclined with respect to the optical axis of the projection optical system. In such a configuration, the light transmitted through the polarization modulator 106 is transmitted without undergoing optical path modulation, and is incident on the projection lens 108 (not shown).
[0023]
FIG. 5 shows a case where the polarization modulation element 106 in FIG. 4 is off.
In this case, the incident light L4 is modulated in the plane of polarization and becomes light polarized in a plane including the optical axis tilt direction of the optical path changing optical element 107 (birefringent plate). This light is emitted after its optical path is shifted by the optical path changing optical element 107.
In the first embodiment, the number of pixels is doubled by turning on / off the polarization modulator 106 in synchronization with switching of the display image. In the first embodiment, only the shift in the vertical direction has been described, but by adding a shift element in the orthogonal direction, the number of pixels can be increased four times.
[0024]
By the way, the light emitted from the polarization beam splitter 104 becomes light having a distribution in the polarization direction as described above, and when such light is subjected to the action as shown in FIG. 4 or FIG. Since the polarization directions become different, the polarization plane of the polarized light incident on the optical path changing optical element 107 is shifted from the plane formed by the crystal optical axis of the optical path changing optical element 107 and the projection optical axis.
Under such conditions, even in the case where the vertically polarized light as shown in FIG. 5 where the optical axis is originally shifted is incident on the optical path changing optical element 107, the horizontally polarized light component is included, and the shifted image is not shifted. Images will be mixed. FIG. 6 and FIG. 7 schematically show this.
FIG. 6 shows an image to be originally displayed, and row C1 corresponds to a non-shifted image and row C2 corresponds to a shifted image. When the binary display as shown in the figure is performed, as shown in FIG. 7, the data of the adjacent pixels is affected to cause a density change, resulting in a decrease in contrast.
[0025]
The polarizing means 120 in FIG. 1 acts so that the polarization direction of incident light is substantially aligned with the in-plane direction formed by the crystal optical axis of the optical path changing optical element 107 and the projection optical axis, or the direction orthogonal thereto. In such a configuration, it is possible to control whether incident light is reliably subjected to an optical path shift, so that crosstalk as shown in FIG. 7 does not occur and a high contrast display as shown in FIG. 6 can be obtained. it can.
[0026]
The polarization modulator 106 can be used as long as it can modulate the polarization direction of incident light by approximately 90 degrees, and an electro-optic crystal or a liquid crystal cell is preferably used. Among these, liquid crystal is particularly preferable because such a function can be realized at a low cost.
As the liquid crystal, a twisted nematic method twisted by 90 degrees, a birefringence mode using a tilt angle change due to an electric field of the nematic liquid crystal, a ferroelectric liquid crystal method using a tilt angle change of a ferroelectric liquid crystal, etc. may be adopted. However, the ferroelectric liquid crystal method is particularly preferable because high-speed response can be obtained.
[0027]
<Example 2>
FIG. 8 shows the configuration of Embodiment 2 of the image projection apparatus of the present invention. In the second embodiment, similarly to the first embodiment, a single plate method will be described as an example.
In FIG. 8, in addition to the first embodiment, a quarter wavelength plate 110 is disposed between the polarization beam splitter 104 and the image display element 105. The quarter wavelength plate 110 needs to be arranged with its slow axis parallel or orthogonal to the polarization direction of the optical axis light.
The quarter-wave plate 110 acts as a half-wave plate in a reciprocating manner so that the polarization direction of the reflected light from the image display element 105 matches the p-polarization direction or the s-polarization direction of the polarization beam splitter 104. Act on. With such a configuration, even light incident obliquely on the polarization beam splitter 104 can be used with high efficiency, and the wavelength characteristics during oblique incidence can be reduced.
[0028]
In order to perform color display in the first and second embodiments, a method of providing a micro color filter in the image display element or a spectral element such as a hologram element outside the image display element and using different color light groups A method of illuminating the image display element can be used.
[0029]
<Example 3>
FIG. 9 shows the configuration of Embodiment 3 of the image projection apparatus of the present invention. Components having the same meaning as those in FIGS. 1 and 2 are given the same reference numerals, but the subscripts r, g, Each b represents an element or an optical element corresponding to red, green, and blue. The third embodiment relates to a multi-plate configuration.
In FIG. 9, reference numerals 111 to 113 denote prisms, and a dichroic film is formed between the prisms 111 and 112 and between the prisms 112 and 113, forming a so-called Phillips prism group.
With the configuration of the third embodiment, each image display element modulates monochromatic light, and these are recombined by a prism. Therefore, there is less light loss and higher resolution than in the first and second embodiments. It becomes easy.
In the third embodiment, the color separation / combination prism is configured by the Philips prism, but may also be configured by a cross dichroic prism. However, the Philips prism is preferable in consideration of the incident angle dependency of the prism.
[0030]
<Example 4>
FIG. 10 shows the configuration of Embodiment 4 of the image projection apparatus of the present invention. Components having the same meaning as those in FIGS. 1 and 2 are given the same reference numerals, but the subscripts r, g, Each b represents an element or an optical element corresponding to red, green, and blue.
In the fourth embodiment, the functions of color separation and color synthesis are separated, and a three-plate configuration is adopted.
In FIG. 10, reference numeral 114 denotes a cross dichroic prism for color synthesis, and 115a and 115b denote dichroic mirrors for color separation. Reference numeral 116 represents a mirror. 117 is a relay lens for adjusting the optical path length.
When the fourth embodiment has such a configuration, the apparatus is larger than the third embodiment, but the optical characteristics of the polarization beam splitter 104 can be optimized for each wavelength region, so that an optical contrast can be easily obtained. Become.
[0031]
<Example 5>
FIG. 11 shows the configuration of Embodiment 5 of the image projection apparatus of the present invention.
In the fifth embodiment, in addition to the second embodiment, variable spectral means 118 that switches the color of the illumination light in time series is provided in the optical path of the illumination light. For example, a rotating color filter as shown in FIG. Here, 118r, 118g, and 118b are color filters that transmit red, green, and blue, respectively, and the color filters sequentially switch the illumination light as they rotate. Reference numeral 119 denotes a collimating lens. Further, the image display element 105 displays a corresponding color image in synchronization with the color change of the illumination light, and repeats this to superimpose color information temporally and project a color image.
[0032]
In addition to the rotating color filter, the variable spectroscopic means 118 in the fifth embodiment can also use, for example, a spectroscopic element using a liquid crystal element and a phase difference plate, which are commercialized under the name of a color switch by Colorlink. .
Further, although the method of splitting the white light source is adopted in the fifth embodiment, the emission spectrum of the light source itself may change in time series. As such a light source, a light emitting diode, a solid-state laser, a semiconductor, etc. A laser, a gas laser or the like is preferable. At this time, a modulation device such as an acousto-optic element for modulating the amount of light can be provided in the optical path as necessary.
[0033]
By constructing the fifth embodiment in this way, color display can be performed with a small number of image display elements, and the optical system is simpler and smaller than the three-plate type, so that the apparatus is small and inexpensive. Can be configured.
[0034]
<Example 6>
FIG. 13 shows the configuration of Embodiment 6 of the image projection apparatus of the present invention.
The basic configuration of the optical system will be described based on the configuration example 5. In the sixth embodiment, in place of the polarization modulation means 106 and the optical path changing optical element 107, the optical path modulation means 121 for modulating the optical path of the incident polarized light by changing the tilt angle of the slow axis or the fast axis in the projection optical path. Provided.
14 and 15 illustrate the operation of the sixth embodiment.
The optical path modulation means 121 of the sixth embodiment is configured such that a material capable of modulating the direction of the slow axis or the fast axis by an external field made of liquid crystal or the like is sandwiched between the translucent substrates.
Further, a transparent electrode is formed on the substrate (not shown), and the state of FIG. 14 and the state of FIG. 15 are switched by controlling the alignment direction of the liquid crystal by applying a voltage to the liquid crystal. The figure shows an example of the change in the alignment structure between the vertical alignment and the tilted alignment, but it is also possible to use the change in the alignment between the horizontal alignment and the tilted alignment, or between the alignment states tilted in the opposite direction. It is.
As the liquid crystal, it is preferable to use a nematic liquid crystal, a ferroelectric liquid crystal, or a material obtained by adding a polymer material to these. In the state of FIG. 14, the optical path of the incident light L10 is bent by the liquid crystal, but such an action does not occur in FIG. 15, so that the optical path of the image light is shifted by switching between these two alignment structures. Is possible.
The transmission axis of the polarizing means 120 needs to be parallel to the polarization direction of the light emitted from the polarizing beam splitter 104 and parallel to the plane formed by the tilt direction of the liquid crystal and the optical axis of the projection light.
[0035]
By adopting such a configuration of the sixth embodiment, even if the incident light is obliquely incident and the plane of polarization is shifted from the optical axis light, the plane of polarization coincides with the optical axis light. The light contrast can be displayed without affecting the image.
Further, the configuration can be simplified as compared with the method using the polarization modulation element 106 in the first embodiment or the like.
[0036]
<Example 7>
FIG. 16 shows another configuration of the optical path modulation means 121 in the sixth embodiment, which has an interface inclined with respect to the main optical axis and changes the refractive index of at least one of the substances forming the interface. To modulate the optical path of incident polarized light.
In this optical path modulation means 121, a material 121c whose optical characteristics are changed by an external field made of liquid crystal or the like is sandwiched between substrates 121a and 121b, and the interface between the substrate and the liquid crystal is inclined with respect to the main optical axis as shown. Are arranged.
For example, the material 121c reversibly changes between the state of FIG. 16 and the state of FIG. 17 by application of an electric field or the like. The case where the material 121c is a liquid crystal will be described. When the refractive index of liquid crystal with respect to ordinary light is no and the refractive index with respect to extraordinary light is ne, the bending of light incident on the liquid crystal layer is the refractive index ns of the substrate and the effective of the liquid crystal layer. The refractive index is determined. For vertically polarized light, the refractive index ne substantially works effectively in FIG. 16, and the refractive index no becomes effective in FIG. In general,
Refractive index ne> Refractive index no
Therefore, the degree of bending of the optical path can be controlled by changing the orientation between FIG. 16 and FIG. 17 by an external field (in the figure, for simplicity, no = ns).
[0037]
On the other hand, with respect to polarized light in the direction perpendicular to the paper surface, the refractive index no effectively acts in any orientation, so that the optical path is transmitted without being bent.
18 and 19 show another configuration obtained by modifying the optical path modulation means 121 (FIGS. 16 and 17) in the sixth embodiment described above, and an inclined interface is formed by forming a sawtooth structure 121d on the inner surface of the substrate. This is a configured example.
FIG. 20 shows another configuration of the optical path modulation means 121 shown in FIG. 18, which is an example in which a sawtooth structure is formed on the substrates on both sides.
FIG. 21 shows a further improvement of the optical path modulation means 121 shown in FIG. 18, and is a combination of two elements having inclined interfaces. In this configuration, an arbitrary shift amount can be obtained by adjusting the interval between the two elements.
[0038]
The liquid crystal used as a material includes a liquid crystal element in which nematic liquid crystal having negative dielectric anisotropy is vertically aligned, a liquid crystal element in which nematic liquid crystal having positive dielectric anisotropy is horizontally aligned, and a ferroelectric liquid crystal element in which horizontal alignment is performed. Etc. are preferable.
In the case of a ferroelectric liquid crystal, the change in the alignment state due to the electric field is a change as shown in FIG. 18 and FIG. 22, and the optical axis shift can be modulated. In particular, when a ferroelectric liquid crystal is used, it is particularly preferable because high-speed optical path modulation is possible.
[0039]
In the configuration according to the seventh embodiment, the structure for performing optical path modulation is simplified as compared with the first embodiment.
In such a configuration, by providing the polarization unit 120 between the polarization beam splitter 104 and the optical path modulation unit 121, the effective refractive index acting on the projection light can be made almost constant without depending on the incident angle. Dependence of the shift amount on the incident angle is reduced, and a projection image that is more uniform and has no image blur can be obtained.
In the configuration of the seventh embodiment, the transmission axis of the polarization unit 120 is the alignment direction when the liquid crystal molecules in the optical path modulation unit 121 are horizontally aligned, generally optically the direction of the slow axis. In order to ensure an efficient shift amount, it is preferable that the projection optical axis be arranged in parallel to the surface.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to solve the problems of crosstalk and color unevenness when the optical path modulation method is used, and to realize an image projection apparatus having a good high-definition image.
[0041]
According to the first aspect of the present invention, since the polarization direction of the projection light incident on the optical path modulation means can be made constant regardless of the incident angle, there is no crosstalk between the shifted light and the non-shifted light. High-contrast and high-definition display can be performed. In addition, since there is no crosstalk, light with a large incident angle can be incident, so that it is possible to design an illumination optical system with high light source light capture efficiency, and an image projection device with high light utilization efficiency and low power consumption. Can be realized.
[0042]
Further, according to claim 2 of the present invention, since the polarization planes of the illumination light and the image light can be made the same, it is possible to minimize the light amount loss due to the polarization beam splitter and the color change due to the incident angle, It is possible to project an image with higher efficiency and less color unevenness.
[0043]
According to the third aspect of the present invention, it is possible to provide a high-definition image projection apparatus with higher light utilization efficiency.
[0044]
According to the fourth aspect of the present invention, the apparatus can be made compact.
[0045]
According to the fifth aspect of the present invention, since the optical system can be made compact, a high-definition color image can be displayed with a small device.
[0046]
According to the sixth, seventh, eighth and ninth aspects of the present invention, it is possible to provide a suitable configuration of the optical path modulation means for high definition.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of Embodiment 1 of the present invention.
FIG. 2 is a diagram schematically showing a change of a polarization plane in a polarization beam splitter.
FIG. 3 is a diagram for explaining that a polarization direction varies depending on an incident angle.
FIG. 4 is a diagram for explaining the configuration and operation of the optical path modulation means (when the polarization modulation element is on).
FIG. 5 is a diagram for explaining the configuration and operation of the optical path modulation means (when the polarization modulation element is off);
FIG. 6 is a schematic diagram of an image to be originally displayed.
FIG. 7 is a schematic diagram when data of adjacent pixels is affected by light having a distribution in the polarization direction.
FIG. 8 is a configuration diagram of Embodiment 2 of the present invention.
FIG. 9 is a configuration diagram of Embodiment 3 of the present invention.
FIG. 10 is a configuration diagram of Embodiment 4 of the present invention.
FIG. 11 is a configuration diagram of Embodiment 5 of the present invention.
FIG. 12 is a diagram for explaining the configuration of variable spectroscopic means.
FIG. 13 is a configuration diagram of Embodiment 6 of the present invention.
FIG. 14 is a diagram for explaining the operation of the sixth embodiment.
FIG. 15 is a diagram for explaining the operation of the sixth embodiment.
FIG. 16 shows another configuration of the optical path modulator in Example 6 (when the effective refractive index is the refractive index of liquid crystal with respect to ordinary light).
FIG. 17 shows another configuration of the optical path modulation means in the sixth embodiment (when the effective refractive index is a refractive index with respect to extraordinary light of a liquid crystal).
FIG. 18 shows another configuration in which the optical path modulation means in the sixth embodiment is modified (when the effective refractive index is the refractive index of liquid crystal with respect to ordinary light).
FIG. 19 shows another configuration in which the optical path modulation means in the sixth embodiment is modified (when the effective refractive index is a refractive index with respect to extraordinary light of a liquid crystal).
20 is another configuration of the optical path modulation means shown in FIG. 18, and is an example in which a sawtooth structure is formed on the substrates on both sides.
21 is a configuration obtained by further improving the optical path modulation means shown in FIG.
22 is a configuration in the case where a ferroelectric liquid crystal is used for the optical path modulation means of FIG.
FIG. 23 is a configuration diagram of an image projection apparatus according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Light source, 103 ... Integrator optical system, 104 ... Polarization beam splitter, 105 ... Image display element, 106 ... Polarization modulation element, 107 ... Optical path changing optical element (birefringent plate), 108 ... Projection lens, 109 ... Field lens, DESCRIPTION OF SYMBOLS 110 ... 1/4 wavelength plate, 111, 112, 113 ... Prism, 114 ... Cross dichroic prism for color composition, 115a, 115b ... Dichroic mirror for color separation, 116 ... Mirror, 117 ... Relay lens for optical path length adjustment 118, variable spectral means (rotating color filter), 119, collimating lens, 120, polarizing means, 121, 130, optical path modulating means, 121a, 121b, substrate, 121c, material, 121d, serrated structure.

Claims (9)

An image display element which is a reflective display element;
Illuminating means for uniformly illuminating the image display element with light source light;
A polarizing beam splitter;
An optical path modulation means for changing the polarization plane of the image light reflected by the image display element, changing the optical path of the light, and emitting the light;
A projection lens for projecting light transmitted through the optical path modulation means,
The polarization beam splitter is provided in an optical path between the illumination unit and the image display element, and display light from the image display element passes through the polarization beam splitter, and the optical path modulation unit includes the polarization beam splitter and the display unit. Provided between the projection lenses, the optical path modulation means is operated in synchronization with the image display timing of the image display element, and image light in which the optical path is not modulated in time series and image light in which the optical path is modulated An image projection apparatus for emitting,
A polarizing means is disposed between the optical path modulating means and the polarizing beam splitter so that the polarization transmission axis thereof is parallel to the optical axis light of the display light immediately after being emitted from the polarizing beam splitter. An image projection apparatus. The image projection apparatus according to claim 1,
An image projection apparatus, wherein a quarter-wave plate is disposed between the polarization beam splitter and the optical path modulation means so that a slow axis is orthogonal or parallel to a polarization direction of the optical axis light. In the image projection device according to claim 1 or 2,
Spectroscopic means for spectrally illuminating illumination light in different wavelength ranges on the image display element;
An image projection apparatus comprising: a combining unit that combines reflected light from the image display element. The image projection apparatus according to claim 3.
An image projection apparatus characterized in that a single dichroic prism is used to perform the functions of both the spectroscopic means and the combining means. The image projection apparatus according to claim 3.
The image projection device, wherein the spectroscopic unit sequentially illuminates the image display element with different color lights in time series. The image projection apparatus according to any one of claims 1 to 5,
The optical path modulation means includes a polarization modulation element capable of modulating the polarization direction of incident light in a direction substantially orthogonal to
An optical path changing optical element that changes an optical path with respect to one polarization of the polarization modulation element;
The polarizing means is arranged so that a polarization transmission axis thereof is in a plane formed by a slow axis or a fast axis of the optical path changing optical element and a projection optical axis or in a plane orthogonal thereto. An image projection device. The image projection apparatus according to any one of claims 1 to 5,
The image projection apparatus characterized in that the optical path modulation means has a variable optical path modulation amount with respect to a specific polarization. The image projection apparatus according to claim 7,
The optical path modulation means is arranged so that the slow axis or the fast axis of the optical path modulation means is in a plane formed by one polarization axis and the projection optical axis, and the slow axis or the fast axis Modulating the optical path of incident polarized light by changing the tilt angle with respect to the optical axis of the projection light,
The polarization means is arranged so that a polarization transmission axis thereof is in a plane formed by the slow axis or the fast axis of the optical path modulation means and the projection optical axis or in a plane orthogonal thereto. Image projection device. The image projection apparatus according to claim 7,
The optical path modulation means has an interface inclined with respect to the optical axis of the projection light, and modulates the optical path of the incident polarized light by changing the effective refractive index with respect to the incident polarized light of the material forming the interface. An image projection apparatus characterized by the above.

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