JP2003005132A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection device using a reflection type display element, which solves the problems of crosstalk and color unevenness caused when an optical path modulation system is used and has an excellent high-definition image. SOLUTION: This image projection device is equipped with a lighting means which uniformly irradiates the reflection type image display element with light source light, a polarization beam splitter which is provided in the optical path between the lighting means and image display element, a polarizing means which is arranged having its axis of polarized light transmission in parallel to the polarization axis of the optical axis light of light which is reflected by the image display element and transmitted through the polarization beam splitter, an optical path modulating means which changes the plane of polarization of the light projected by the polarizing means to change the optical axis of the light and projects the light, and a projection lens which projects the light transmitted through the optical path modulating means; and the optical path modulating means is placed in operation synchronously with the timing of an image display by the image display element to project image light which does not have its optical path modulated and image light which has its optical path modulated in time series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection apparatus for observing by projecting a magnified image obtained by enlarging an image of an image display element by a lens system, and is particularly suitable for application to a head mounted display, a projector and the like.

[0002]

2. Description of the Related Art A display device for enlarging and displaying an image of a small image display device such as a liquid crystal through a lens system is called a head mounted display and is mounted in front of the eye or is a type for observing a magnified image. There is a so-called projection type display device which projects an image on a screen and observes the projected image.

Generally, in a display device, the screen resolution is an important factor in determining the display quality, but in the conventional magnified projection type display device, in order to increase the screen resolution, the display of a small image display device is displayed. A method of increasing the number of pixels has been adopted. 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, there is a limit to the miniaturization due to the problem of fine processing technology, wiring resistance, and securing of a transistor region and a wiring region, and such an element becomes high in cost due to a reduction 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 the cost is also increased. In addition, the illumination optical system and the projection optical system are enlarged, and However, the problem of increasing the size and increasing the cost will occur.

On the other hand, Japanese Patent No. 2939826 discloses a projection type display device in which an optical element capable of turning a polarization direction between a display element and a screen (that is, in an emission optical path of the display element) and a transparent element having a birefringence effect. Is disclosed, and a method for realizing high resolution by shifting the projected image is disclosed (see FIG. 23). This method
Since it is possible to realize high resolution by using an inexpensive image display device with a small number of pixels, it is a powerful technique for achieving high definition.

[0005]

Liquid crystal display devices used for magnified display are roughly classified into transmissive type and reflective type. The transmissive type is a structure adopted in the projection display device of Japanese Patent No. 2939826 described above, and a liquid crystal using a substrate in which a transistor and 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 in that, when the density of pixels is increased, the aperture ratio is substantially reduced due to the wiring and transistor regions. This causes a decrease in brightness if the light quantity of the light source is constant, and an increase in the light quantity of the light source, that is, an increase in power consumption, in order to keep the brightness constant.

On the other hand, the reflective type is a liquid crystal element using a substrate in which transistors and wirings are formed on a non-translucent 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 can easily maintain the aperture ratio even when the density is increased,
The feature is that both high definition and light utilization efficiency can be achieved at the same time.

However, Japanese Patent No. 2939826 does not describe the structure when a reflective display element is used. In the reflective type, since the illumination light and the projected light pass through the same optical path in the vicinity of the display element, it is necessary to adopt an optical system different from that of the transmissive type, which causes new problems 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, when a polarization beam splitter is used, the polarization axis changes with respect to light that is obliquely incident,
The spectral transmittance or spectral reflectance may change. Also,
The integrator illumination system is used to make the intensity distribution of light emitted from the light source uniform, and in principle illuminates the display element with illumination light having different incident angles. In such a case, a change in the polarization axis of the obliquely incident light causes crosstalk between adjacent pixels and deteriorates display quality. Spectral transmittance /
Changes in the spectral reflectance are observed as color unevenness on the display.

In view of the above problems, it is an object of the present invention to solve the problems of crosstalk and color unevenness when using the optical path modulation method, and to provide an image projection apparatus having a good high-definition image. .

[0009]

In order to solve the above problems, an image projection apparatus according to claim 1 of the present invention uses an image display element which is a reflection type display element and a light source light to the image display element. Illuminating means for uniformly illuminating, polarization beam splitter, optical path modulating 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, and the optical path modulating means. And a projection lens for projecting light transmitted therethrough, wherein the polarizing beam splitter is provided in an optical path between the illuminating means and the image display element, and the optical path modulating means includes the polarizing beam splitter and the projection lens. The optical path modulating means is provided between the image display element and the optical path modulating means in synchronism with the image display timing of the image display element to emit image light whose optical path is not modulated in time series and image light whose optical path is modulated. The image projection apparatus according to claim 1, characterized in that the polarization means is arranged between the optical path modulation means and the polarization beam splitter such that the polarization transmission axis of the polarization means is parallel to the polarization axis of the projection light. . Therefore, since the polarization direction of the projection light incident on the optical path modulating means can be made constant regardless of the incident angle, crosstalk between the shifted light and the non-shifted light is eliminated, and high contrast and high definition display is performed. Can be made. In addition, since there is no crosstalk, it is possible to enter light with a large incident angle, which makes it possible to design an illumination optical system with a high efficiency of capturing light from a light source, and an image projection apparatus with high light utilization efficiency and low power consumption. Can be realized.

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 modulating means, and the slow axis is an optical axis light. It is characterized by being arranged so as to be orthogonal or parallel to the polarization direction. Therefore, since the polarization planes of the illumination light and the image light can be made to be 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, so that the image with higher efficiency and less color unevenness can be obtained. You can project.

According to a third aspect of the present invention, in the image projection apparatus according to the first or second aspect, there is provided a spectroscopic means for spectrally illuminating and illuminating the image display device with illumination light of different wavelength ranges.
And a synthesizing unit for synthesizing the reflected light from the image display element. Therefore, it is possible to provide a high-definition image projection device with higher light utilization efficiency.

According to a fourth aspect of the present invention, in the image projection apparatus according to the third aspect, one dichroic prism is used to perform both the functions of the spectroscopic means and the synthesizing means. Characterize. Therefore,
The device can be made compact.

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 element with different colored light in time series. Therefore, since the optical system can be configured in a small size, a high-definition color image can be displayed by a small device.

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 modulating means can modulate a polarization direction of incident light into a direction substantially orthogonal to each other. A polarization modulation element and an optical path changing optical element that changes the optical path with respect to one polarization of the polarization modulation element, wherein the polarization transmission axis of the polarization means is a slow axis of the optical path changing optical element or It is characterized in that it is arranged so as to be in the plane formed by the fast axis and the optical axis of the projection light or in the plane orthogonal thereto. Therefore, it is possible to provide a preferable configuration of the optical path modulating means for achieving high definition.

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 modulating means is capable of changing the optical path modulation amount with respect to a specific polarized light. It is characterized by Therefore, it is possible to provide a preferable configuration of the optical path modulating means for achieving high definition.

According to an eighth aspect of the present invention, in the image projection apparatus according to the seventh aspect, the optical path modulating means has a slow axis or a fast axis of the optical path modulating means and the polarization axis and the projection light. The optical path of the incident polarized light is modulated by arranging the optical axis so that it lies in the plane formed by the optical axis and changing the inclination angle of the slow axis or the fast axis with respect to the projected optical axis of the optical axis. It is characterized in that the polarization transmission axis is arranged in a plane formed by the slow axis or the fast axis of the optical path modulating means and the projection light optical axis or in a plane orthogonal thereto.
Therefore, it is possible to provide a preferable configuration of the optical path modulating means for achieving high definition.

According to a ninth aspect of the present invention, in the image projection apparatus according to the seventh aspect, the optical path modulating means has an interface inclined with respect to the optical axis of the projection light, and a material forming the interface. It is characterized in that the optical path of the incident polarized light is modulated by changing the effective refractive index for the incident polarized light. Therefore, it is possible to provide a preferable configuration of the optical path modulating means for achieving high definition.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the image projection apparatus of the present invention will be described in detail below with reference to the drawings. <Embodiment 1> FIG. 1 shows an embodiment 1 of the image projection apparatus of the present invention.
It shows the configuration of. In FIG. 1, Example 1
Is a light source 101, an integrator optical system 103 including a fly-eye lens, a polarization beam splitter 104, an image display element 105 that is a reflective liquid crystal display element, an optical path modulating unit 130, a projection lens 108, an integrator optical system 103 (fly-eye lens). ), A field lens 109 for condensing the light transmitted through the image display element 105 on the image display element 105, and a polarization means 120. Here, the optical path modulator 13
0 functions by combining the polarization modulation element 106 and the optical path changing optical element 107 composed of a birefringent plate. As described above, the first embodiment is described by taking a so-called single-plate type optical system configuration using one liquid crystal display element as an example.

Optical path modulator 130 (polarization modulator 106)
And the birefringent plate 107) is used for the polarization beam splitter 10
4 and the projection lens 108. Polarizing means 12
Zero needs to be arranged so that the polarization transmission axis is parallel to the polarization axis of the optical axis light. The polarization means 120 used here can be used as long as it transmits only a specific linearly polarized light, and for example, a second polarization beam splitter, a prism type polarizer or an absorption type polarizer is used. Among these, it is preferable to use the absorption type polarizer because the incident angle dependency is small.

The polarization beam splitter 104 functions as a polarizer and an analyzer, but unlike an absorption-type polarizing plate, the polarization axis changes with respect to obliquely incident light, and the spectral transmittance or spectral reflection. The rate changes. FIG. 2 schematically shows changes in the plane of polarization in the polarization beam splitter 104. In FIG. 2, 104
F represents a polarization separation film surface of the polarization beam splitter 104 formed of a multilayer film, surface A represents a surface on which an incident light beam is incident,
Incident light is optical axis light L1 and L inclined from the optical axis light
Consider 2 and L3 rays. Such light rays are
Inject each in the plane of. When the incident polarized light is not the optical axis light, the s-polarization direction of the polarization separation film deviates from the incident polarization direction. Therefore, when viewed from the traveling direction of the light, the polarization direction of the emitted light is as shown in FIG. Will have different polarization directions. Although the reflected light is shown in FIG. 2, the polarization plane of the transmitted light also changes depending on the incident angle according to the same principle.

The light beam in FIG. 1 illustrates the illumination area of the central fly-eye lens, and each fly-eye lens illuminates the entire surface of the display element 105 as shown in FIG. The illumination shown in FIG. 1 is used in the integrator optical system 10.
3 shows a general operation of No. 3, and with such a configuration, the intensity distribution of the light source is made uniform on the surface of the display element 105. In FIG. 2, the chief ray and the polarization beam splitter 1
A plane (plane A) orthogonal to the plane formed by the normal line of the separation membrane 04.
Although the angles in the figure are shown, the light beams having various angle components actually enter the polarization beam splitter 104. As described above, with respect to the obliquely incident light beam, the polarization axis of the light emitted from the polarization beam splitter 104 changes depending on the incident angle, so that the entire light beam acts to reduce the degree of polarization. .

FIGS. 4 and 5 are views for explaining the structure and operation of the optical path modulating means 130. Polarization modulator 106
Acts to change the plane of polarization 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 so as to rotate the plane of polarization, and the polarization direction of the incident light is assumed to be the direction shown by the arrow in FIG. The light L4 incident from the polarization beam splitter 104 (PBS, not shown) on the left side of the drawing is transmitted through the polarization modulator 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 its optical axis is one polarization axis of the light emitted from the polarization modulation element 106 (in the first embodiment, The polarization modulation element 106 is in the plane formed by the polarization direction in the vertical direction when the polarization modulation element 106 is off) and the main optical axis of the incident light, and is arranged obliquely with respect to the optical axis of the projection optical system. In such a configuration, the light transmitted through the polarization modulation element 106 is transmitted without undergoing the modulation of the optical path and is incident on the projection lens 108 (not shown).

FIG. 5 shows the polarization modulation element 106 in FIG.
Is off. In this case, the incident light L4 is modulated in the plane of polarization and becomes light polarized in the plane including the optical axis changing direction of the optical path changing optical element 107 (birefringent plate). The optical path of this light is shifted by the optical path changing optical element 107 and emitted. In the first embodiment, the number of pixels is doubled by turning the polarization modulator 106 on / off in synchronization with the switching of the display image. Although only the vertical shift is described in the first embodiment, the number of pixels can be four times larger by adding the shift element in the orthogonal direction.

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 5, it is incident depending on the incident angle. Since the polarization direction of the light L4 becomes different, the plane of polarization of the incident polarized light to the optical path changing optical element 107 deviates from the plane formed by the crystal optical axis of the optical path changing optical element 107 and the projection optical axis. Under such a condition, even in the case where the vertically polarized light whose optical axis is originally shifted is incident on the optical path changing optical element 107 as shown in FIG. 5, the horizontally polarized light component is included and the shifted image does not shift. Images are mixed. This is schematically shown in FIGS. 6 and 7. FIG. 6 shows an image to be originally displayed, where the row C1 is an unshifted image and the row C2 is
Corresponds to the shift image. When the binary display as shown in the figure is performed, as shown in FIG. 7, the data of the adjacent pixels have an influence to cause a density change, and as a result, the contrast is lowered.

The polarizing means 120 in FIG. 1 acts so that the polarization direction of the 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. To do. With such a configuration, it is possible to reliably control whether the incident light undergoes the optical path shift or not, 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.

The polarization modulator 106 can be used as long as it can modulate the polarization direction of incident light by approximately 90 degrees, and it is preferable to use an electro-optic crystal or a liquid crystal cell. Among them, the liquid crystal is particularly preferable because it can realize such a function at a low cost. As the liquid crystal, it is possible to adopt a twisted nematic system twisted by 90 degrees, a birefringence mode utilizing a tilt angle change due to an electric field of a nematic liquid crystal, a ferroelectric liquid crystal system utilizing a tilt angle change of a ferroelectric liquid crystal, and the like. Among them, the ferroelectric liquid crystal system is particularly preferable because high speed response can be obtained.

<Embodiment 2> FIG. 8 shows the construction of Embodiment 2 of the image projection apparatus of the present invention. In the second embodiment, as in the first embodiment, the single plate method will be described as an example. In FIG. 8, in addition to the first embodiment, a quarter wavelength plate 110 is arranged between the polarization beam splitter 104 and the image display element 105. The quarter wave plate 110 needs to be arranged with its slow axis parallel or orthogonal to the polarization direction of the optical axis light. In addition, the 1/4 wavelength plate 110 is 1/2 in a round trip.
It acts as a wave plate, and acts so as to match the polarization direction of the reflected light from the image display element 105 with the p polarization direction or the s polarization direction of the polarization beam splitter 104. With such a configuration, even light obliquely incident on the polarization beam splitter 104 can be utilized with high efficiency, and the wavelength characteristics at oblique incidence can be reduced.

In order to perform color display in the first and second embodiments, different methods are used in which a micro color filter is provided in the image display element or a spectroscopic element such as a hologram element is provided outside the image display element. A method of illuminating the image display element with a group of colored lights can be used.

<Embodiment 3> FIG. 9 shows the construction of Embodiment 3 of the image projection apparatus of the present invention. The components having the same meanings as those in FIGS. 1 and 2 are designated by the same reference numerals. However, the subscripts r, g, and b represent elements or optical elements corresponding to red, green, and blue, respectively. The third embodiment relates to a multi-plate type structure. In FIG. 9, 111 to 113
Is a prism between the prisms 111 and 112 and 1
A dichroic film is formed between the prisms 12 and 113, and constitutes a so-called Phillips prism group. According to the configuration of the third embodiment, each image display element modulates monochromatic light and these are combined again by the prism, so that the light amount loss is smaller than that of the first and second embodiments, and high resolution is achieved. It will be easy. Although the color separating / combining prism is composed of the Phillips prism in the third embodiment, it may be composed of a cross dichroic prism. However, considering the incident angle dependence of the prism, the Phillips prism is preferable.

<Embodiment 4> FIG. 10 shows the construction of an embodiment 4 of the image projection apparatus of the present invention, in which constituent elements having the same meanings as in FIG. 1 and FIG. But,
The subscripts r, g, and b represent elements or optical elements corresponding to red, green, and blue, respectively. In the fourth embodiment, the functions of color separation and color composition are separated to form a three-plate configuration. In FIG. 10, 114 is a cross dichroic prism for color combination, and 115a and 115b are dichroic mirrors for color separation. Reference numeral 116 represents a mirror. Reference numeral 117 is a relay lens for adjusting the optical path length. When the configuration of the fourth embodiment is configured as described above, the device becomes larger than that of the third embodiment, but the optical characteristics of the polarization beam splitter 104 can be optimized for each wavelength region, and thus optical contrast is easily obtained. Become.

<Embodiment 5> FIG. 11 shows the construction of an embodiment 5 of the image projection apparatus of the present invention. Example 5
In addition to the second embodiment, the variable spectroscopic means 118 that switches the color of the illumination light in time series is provided in the optical path of the illumination light. For the variable spectroscopic unit 118, for example, a rotary color filter as shown in FIG. 12 is used. Where 118r and 118
Reference numerals g and 118b denote color filters that transmit red, green, and blue, respectively, and rotate the colors to sequentially switch the colors of illumination light. 119 is 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 by repeating this, color information is temporally superimposed and a color image is projected.

Variable spectroscopic means 118 in the fifth embodiment
In addition to the rotary color filter, for example, it is possible to use a spectral element using a liquid crystal element and a retardation plate, which are commercialized under the name of color switch by Color Link Co., Ltd. In addition, although the method of separating the white light source is adopted in the fifth embodiment, the emission spectrum of the light source itself may change in time series, and as such a light source, a light emitting diode, a solid state laser, a semiconductor Lasers and gas lasers are preferred. At this time, a modulation device such as an acousto-optic element for modulating the light quantity may be provided in the optical path as needed.

When the fifth embodiment is configured 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 the apparatus can be made compact. And it can be constructed at low cost.

<Sixth Embodiment> FIG. 13 shows the structure of a sixth embodiment 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,
Instead of the polarization modulator 106 and the optical path changing optical element 107, the optical path modulator 12 that modulates the optical path of the incident polarized light by changing the inclination angle of the slow axis or the fast axis.
1 is provided in the projection optical path. 14 and 15 illustrate the operation of the sixth embodiment. The optical path modulating means 121 according to the sixth embodiment is configured by sandwiching a light transmissive substrate with a material capable of modulating the direction of the slow axis or the fast axis by an external field such as liquid crystal. In addition, a transparent electrode is formed on this substrate (not shown), and by applying a voltage to the liquid crystal, the alignment direction of the liquid crystal is controlled so that the substrate shown in FIG.
The state of 4 and the state of FIG. 15 are switched. The figure shows an example of the change of the alignment structure between the vertical alignment and the tilted alignment, but it is also possible to use the change of the alignment between the horizontal alignment and the tilted alignment, and the change between the oppositely tilted alignment states. Is. As the liquid crystal, it is preferable to use nematic liquid crystal, ferroelectric liquid crystal, a material obtained by adding a polymer material to these, or the like. In the state of FIG. 14, the incident light L10 has its optical path bent by the liquid crystal, but in FIG. 15, such an action does not occur. Therefore, the optical path of the image light is shifted by switching between these two alignment structures. Is possible. Polarizing means 1
The transmission axis of 20 needs to be parallel to the polarization direction of the light emitted from the polarization beam splitter 104 and parallel to the plane formed by the tilt direction of the liquid crystal and the projection light optical axis.

With the structure of the sixth embodiment, even if the projection light is incident obliquely and the polarization plane is deviated from the optical axis light, the polarization plane coincides with the optical axis light. The display of optical contrast can be performed without affecting adjacent pixels. Further, the configuration can be simplified as compared with the method using the polarization modulation element 106 such as the first embodiment.

<Embodiment 7> FIG. 16 shows another structure of the optical path modulating means 121 in Embodiment 6, which has an interface inclined with respect to the main optical axis and at least a substance forming the interface. The optical path of incident polarized light is modulated by changing one of the refractive indexes. This optical path modulation means 12
1, a material 121c made of a liquid crystal or the like whose optical characteristics change according to an external field is sandwiched between the substrates 121a and 121b, and the interface between the substrate and the liquid crystal is arranged to be inclined with respect to the main optical axis as shown in the drawing. There is. The material 121c reversibly changes between the state of FIG. 16 and the state of FIG. 17, for example, when an electric field is applied. Explaining the case where the material 121c is liquid crystal, when the refractive index of the liquid crystal for ordinary light is no and the refractive index of extraordinary light is ne, the bending of the light incident on the liquid crystal layer is the refractive index ns of the substrate and the effective liquid crystal layer. It is determined by the refractive index. For vertically polarized light,
In FIG. 16, almost the refractive index ne works effectively, and in FIG. 17, the refractive index no becomes effective. In general, since refractive index ne> refractive index no, the degree of bending of the optical path can be controlled by changing the orientation between FIG. 16 and FIG. 17 depending on the external field (in the figure, no = ns for simplification). And).

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, and the optical path is not bent and passes through the element. 18 and 19
Is another configuration obtained by modifying the optical path modulating means 121 (FIGS. 16 and 17) in the above-described sixth embodiment, and is an example in which a slanted interface 121d is formed by forming a sawtooth structure 121d on the inner surface of the substrate. . In addition, FIG.
It is another example of the optical path modulating means 121 shown in (3), and is an example in which a sawtooth structure is formed on the substrates on both sides. In addition, FIG.
Is a further improvement of the optical path modulating means 121 shown in FIG. 18, and is a combination of two elements having an inclined interface. With this configuration, an arbitrary shift amount can be obtained by adjusting the distance between the two elements.

The liquid crystal used as the material includes a liquid crystal element in which a nematic liquid crystal having a negative dielectric anisotropy is vertically aligned, a liquid crystal element in which a nematic liquid crystal having a positive dielectric anisotropy is horizontally aligned, and a ferroelectric liquid crystal having a horizontal alignment. Liquid crystal element or the like is preferable. In the case of the ferroelectric liquid crystal, the change in the alignment state due to the electric field is as shown in FIGS. 18 and 22, and the optical axis shift can be modulated. Particularly, when a ferroelectric liquid crystal is used, high-speed optical path modulation is possible, which is particularly preferable.

In the structure according to the seventh embodiment, the structure for optical path modulation is simplified as compared with the first embodiment. In such a configuration, by providing the polarization means 120 between the polarization beam splitter 104 and the optical path modulation means 121, the effective refractive index acting on the projection light can be made almost constant without depending on the incident angle, and thus the optical path. The incident angle dependence of the shift amount of is reduced, and a more uniform projection image without 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 aligned horizontally, generally the direction of the slow axis. It is preferable to be arranged in parallel to the plane formed by the optical axis of the projection light in order to secure an efficient shift amount.

[0040]

As described above, according to the present invention,
It is possible to solve the problems of crosstalk and color unevenness when using the optical path modulation method, and to realize an image projection apparatus having a good high-definition image.

Further, according to claim 1 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, the cross between the shifted light and the non-shifted light can be achieved. Talk can be eliminated, and high-contrast and high-definition display can be performed. In addition, since there is no crosstalk, it is possible to enter light with a large incident angle, which makes it possible to design an illumination optical system with a high efficiency of capturing light from a light source, and an image projection apparatus with high light utilization efficiency and low power consumption. Can be realized.

According to the second aspect of the present invention, since the polarization planes of the illumination light and the image light can be made the same, the light quantity loss due to the polarization beam splitter and the color change due to the incident angle can be minimized. The image can be projected with higher efficiency and less color unevenness.

Further, according to claim 3 of the present invention, it is possible to provide an image projection apparatus having a higher light utilization efficiency and a higher definition.

According to the fourth aspect of the present invention, the device can be made compact.

According to the fifth aspect of the present invention, since the optical system can be made compact, it is possible to display a high-definition color image with a compact device.

Further, claims 6, 7, 8 and 9 of the present invention.
According to this, it is possible to provide a preferable configuration of the optical path modulating means for achieving high definition.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a change in plane of polarization in a polarization beam splitter.

FIG. 3 is a diagram for explaining that polarization directions differ depending on an incident angle.

FIG. 4 is a diagram for explaining the configuration and action of the optical path modulation means (when the polarization modulator is on).

FIG. 5 is a diagram illustrating the configuration and action 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 the data of adjacent pixels is affected by light having a distribution in the polarization direction.

FIG. 8 is a configuration diagram of a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a third embodiment of the present invention.

FIG. 10 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 11 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 12 is a diagram for explaining a configuration of a variable spectroscopy unit.

FIG. 13 is a configuration diagram of a sixth embodiment 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 modulating means in Example 6 (when the effective refractive index is the refractive index of the liquid crystal with respect to ordinary light).

FIG. 17 shows another configuration of the optical path modulating means in Example 6 (when the effective refractive index is the refractive index of the liquid crystal for extraordinary light).

FIG. 18 shows another configuration in which the optical path modulating means in Example 6 is modified (when the effective refractive index is the refractive index of the liquid crystal with respect to ordinary light).

FIG. 19 shows another configuration in which the optical path modulating means in Example 6 is modified (when the effective refractive index is the refractive index of the liquid crystal for extraordinary light).

FIG. 20 is another example of the optical path modulating means shown in FIG. 18, and is an example in which a sawtooth structure is formed on the substrates on both sides.

FIG. 21 is a configuration in which the optical path modulating means shown in FIG. 18 is further improved.

22 shows a configuration in which a ferroelectric liquid crystal is used for the optical path modulating means in FIG.

FIG. 23 is a configuration diagram of an image projection device according to a conventional technique.

[Explanation of symbols]

101 ... Light source, 103 ... Integrator optical system, 104
... Polarizing beam splitter, 105 ... Image display device, 10
6 ... Polarization modulation element, 107 ... Optical path changing optical element (birefringence plate), 108 ... Projection lens, 109 ... Field lens, 110 ... Quarter wave plate, 111, 112, 113 ...
Prism, 114 ... Cross dichroic prism for color combination, 115a, 115b ... Dichroic mirror for color separation, 116 ... Mirror, 117 ... Relay lens for adjusting optical path length, 118 ... Variable spectroscopic means (rotating color filter), 119 ... Collimating lens, 120 ... Polarizing means,
121, 130 ... Optical path modulating means, 121a, 121b ...
Substrate, 121c ... Material, 121d ... Sawtooth structure.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 9/31 H04N 9/31 C (72) Inventor Ikuo Kato 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company In Ricoh (72) Inventor Kazuya Miyagaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Takanobu Aisaka 1-3-6 Nakamagome, Ota-ku, Tokyo F In Ricoh Co., Ltd. Term (reference) 2H099 AA12 BA09 CA07 CA11 DA09 5C058 AA06 AB03 AB06 BA10 BA35 BB01 EA02 EA11 EA26 EA51 5C060 BA03 BB13 BC01 BD02 BE05 BE10 HB05 HB23 HC09 HC12 HC17 HC22 JA00 JB06

Claims (9)

[Claims] 1. An image display element which is a reflection type display element, an illuminating means for uniformly illuminating the image display element with a light source, a polarizing beam splitter, and an image light reflected by the image display element. The polarization beam splitter is provided with an optical path modulating means for changing the optical path of the light and changing the optical path of the light to be emitted, and a projection lens for projecting the light transmitted through the optical path modulating means. Provided in the optical path between the display elements, the optical path modulation means, provided between the polarization beam splitter and the projection lens, to operate the optical path modulation means in synchronization with the image display timing of the image display element, An image projection device that emits image light whose optical path is not time-modulated and image light whose optical path is modulated, wherein a polarized light is provided between the optical path modulator and the polarization beam splitter. An image projection apparatus, wherein the means is arranged such that its polarization transmission axis is parallel to the polarization axis of the optical axis light of the projection light. 2. The image projection apparatus according to claim 1, wherein a ¼ wavelength plate is provided between the polarization beam splitter and the optical path modulating means, and a slow axis is orthogonal or parallel to a polarization direction of the optical axis light. An image projection apparatus, which is arranged so that 3. The image projection apparatus according to claim 1, wherein the image display element is combined with a spectroscopic unit that separates and illuminates illumination light of different wavelength ranges, and a composite that combines reflected light from the image display element. And an image projection device. 4. The image projection apparatus according to claim 3, wherein one dichroic prism is used to perform the functions of both the spectroscopic unit and the synthesizing unit. 5. The image projection apparatus according to claim 3, wherein the spectroscopic unit sequentially illuminates the image display element with different colored light in time series. 6. The image projection apparatus according to claim 1, wherein the optical path modulation unit is a polarization modulation element capable of modulating the polarization direction of incident light in a direction substantially orthogonal to each other, and the polarization modulation element. An optical path changing optical element for changing an optical path with respect to one polarization of the modulation element, wherein the polarization transmission axis of the polarization means is a slow axis or a fast axis of the optical path changing optical element and a projection optical axis. An image projection apparatus, which is arranged so as to be in a plane formed by or in a plane orthogonal thereto. 7. The image projection apparatus according to claim 1, wherein the optical path modulation unit has a variable optical path modulation amount for specific polarization. . 8. The image projection apparatus according to claim 7, wherein the optical path modulation means has a slow axis or a fast axis of the optical path modulation means in a plane formed by one polarization axis and the projection light 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 light optical axis. An image projection apparatus, wherein the image projection apparatus is arranged so as to be in a plane formed by a slow axis or a fast axis of the means and a projection light optical axis or in a plane orthogonal thereto. 9. The image projection apparatus according to claim 7, wherein the optical path modulation unit has an interface inclined with respect to a projection optical axis, and an effective refractive index of a substance forming the interface with respect to incident polarized light. The image projection apparatus is characterized in that the optical path of incident polarized light is modulated by changing the.