JP3383082B2 - Projection type image display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for displaying an image by making light from a light source incident on a transmissive display element or the like and projecting the transmitted light on a screen.

[0002]

2. Description of the Related Art A transmissive display panel does not emit light by itself, but its transmissivity is changed by a drive signal, and an intensity of light from a light source is modulated to display an image or a character. Examples of such a transmissive display panel include a liquid crystal display panel, an electrochromic display, and a PLZT (Plumbum Lanthanum Zirconium Titanium).
oxide) and other transparent ceramics. Among them, liquid crystal display panels are widely and generally used for pocketable TVs, word processors, and the like.

In such a liquid crystal display panel, a minimum display unit called a picture element is regularly arranged, and by applying an independent driving voltage to each of the picture elements, the optical characteristics of the liquid crystal are improved. It changes, which causes images and characters to be displayed. As a method of applying an independent drive voltage to each picture element, a simple matrix method and an active matrix method are known.

According to the above active matrix system, each pixel is provided with a thin film transistor or an MI of a diode.
It is necessary to provide an element such as M (Metal Insulator Metal) and to provide a line for supplying a driving signal to these elements between the picture elements. Therefore, the ratio of the picture element area in the screen (called the aperture ratio) becomes small. Further, of the light emitted to the liquid crystal display panel, the light incident on the area other than the pixel area is not modulated by the display signal. In a display panel in which the display operation mode is a normally black mode (an operation mode in which light does not pass through when an electric field is not applied to the liquid crystal layer), light incident on a region other than the pixel region does not pass through the liquid crystal display panel. Does not penetrate. In a liquid crystal display panel in which the display operation mode is a normally white mode (an operation mode in which light is transmitted when an electric field is not applied to the liquid crystal layer), the light incident on the area other than the pixel area is the liquid crystal display panel. , The black level of the display screen rises and the contrast decreases.

In order to prevent the deterioration of the contrast, a light-shielding mask (Blackout Mask) is provided in a matrix form in a region other than the picture elements as necessary to absorb or reflect light which does not contribute to display. Is known to do. Therefore, when this panel is projected, stripes due to the light-shielding mask are conspicuous on the screen, and the image quality is significantly deteriorated. Therefore, a diffraction grating is inserted in the light path on the exit side of the liquid crystal display panel to diffract the light emitted from the liquid crystal display panel and pass through the picture element aperture of the liquid crystal display panel at the position where the light-shielding mask should be focused on the screen. It is possible to form an image of the formed light so that the light-shielding mask is not conspicuous, for example, JP-A-59-214825 and JP-A-63-114.
It is disclosed in Japanese Patent Laid-Open No. 475,475 and Japanese Patent Laid-Open No. 3-148622.

According to the color display device (first prior art) disclosed in Japanese Patent Laid-Open No. 59-214825, a front surface of a pixel group in which three types of pixels corresponding to three primary colors are linearly arranged alternately. In addition, a transmissive plane diffraction grating is provided, and the light emitted from each pixel is diffracted by this diffraction grating and divided into three (0th-order diffracted light and ± 1st-order diffracted light).
Therefore, a real image and two virtual images of each pixel can be seen. Therefore, even if pixels of a single color are scattered (even if the pixels are arranged at a low density), they do not appear to be scattered but appear to be dense. In addition, when two or more pixels emit light, it appears that the pixels of the combined color emit light, and the image becomes clear. Similar technology
It is also disclosed in Japanese Patent Laid-Open No. 3-148622.

According to the image display device (second prior art) disclosed in Japanese Patent Laid-Open No. 63-114475, an optical low-pass filter having a diffraction grating is provided between the image display and the eyepiece. It is arranged at a predetermined position on the optical axis and at a predetermined angle with respect to a plane perpendicular to the optical axis (may be integrally formed on the surface of the image display). The image display has dot-shaped display segments arranged two-dimensionally, and an optical low-pass filter cuts frequency components of (1 / 2p) or more (the pitch of the display segments is p).
Therefore, only the information regarding the display image is displayed. Therefore, the roughness due to the dot pitch is eliminated, and an easily viewable image can be reproduced. The optical low-pass filter only needs to have a blurring effect, and examples thereof include a polished glass and a milky white resin plate.

In addition, as a third conventional technique, a plurality of projection type image display devices are used so that an opening of a picture element of one liquid crystal display panel overlaps a light-shielding mask of a picture element of another display panel. When superimposing images, it is known to insert a parallel plate element into the entire optical path near the projection lens and change the tilt angle to make fine adjustments (picture element matching) of multiple images on the screen. (For example, Japanese Patent Laid-Open No.
-123868 gazette).

[0009]

However, according to the above-mentioned first and second prior arts, both use diffraction gratings. In this case, the diffraction angle β of light is as shown in FIG.
, The diffracted light is largely dependent on the order of the diffracted light, so that the diffracted light of each order (0th, 1st, and 2nd order diffracted light) is formed on the screen according to each diffraction angle. To be imaged.

Further, the diffraction angle of light largely depends on the grating spacing of the diffraction grating, as shown in the following equation (1). That is, if the lattice spacing is D, α is the angle formed by the incident light with respect to the optical axis, β is the angle formed by the diffracted light with respect to the optical axis, m is the order of the diffracted light, and λ is the wavelength of the incident light. Formula (1)
Is established.

Sinα−sinβ = m · λ / D (1) Therefore, it is necessary to prepare a specific diffraction grating having a corresponding grating interval for each display panel having a different pixel pitch. In this case, since the manufacturing cost of the diffraction grating is high, there is a problem that the cost of the device equipped with this diffraction grating increases.

Further, according to the above-mentioned third conventional technique, since all the light projected from one projection type image display device onto the screen is shifted, the images of a plurality of projection type image display devices are simultaneously displayed on the screen. This is effective only in the case of projection, causes a significant increase in cost, and makes the configuration of the apparatus itself complicated and large-scale.

From the above, the present invention has been made in view of the above problems, and an object thereof is to maintain a fineness of a display panel and obtain a smooth and natural image at a low cost. To provide a device.

[0014]

In order to solve the above-mentioned problems, the projection-type image display device according to the present invention forms an image of the transmitted light from the liquid crystal display means in which picture elements are arranged in a matrix on a screen. The following means are taken in the projection-type image display device that displays an image.

That is, the above projection type image display device includes a projection lens between the liquid crystal display means and the screen,
Provided in a part of the pupil position of the projection lens refracts incident light, and the optical path shifting means for shifting the optical path of the incident light, the light a pupil position of the projection lens
On the part where the road shifting means is not provided ,
An optical path difference correction means that is a transparent parallel plate parallel to the liquid crystal display means, and an image formed through the optical path difference correction means and an image formed through the optical path shift means. It corrects the optical path difference between these images is superposed
To be projected on the screen.

In order to solve the above-mentioned problems, the projection type image display device according to a second aspect of the present invention is the structure of the first aspect, wherein the optical path shifting means is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis. It is a transparent parallel plate element, and the optical path difference correcting means is glass.

Further , the projection type image display device of the present invention is a projection type image display device for displaying an image by forming an image of transmitted light from a liquid crystal display means in which picture elements are arranged in a matrix on a screen. Then, in order to solve the above problems, provided on the optical path between the liquid crystal display means and the screen, by refracting the incident light, an optical path shift means for shifting the optical path of the incident light, The above-mentioned optical path shifting means has a plurality of surfaces, and each surface is a polygonal frustum whose surface normals form an angle symmetrical to the optical axis. This is a configuration in which the prime number increases.

The above-mentioned projection type image display device is a projection type image display device for displaying an image by forming an image of transmitted light from a liquid crystal display means in which picture elements are arranged in a matrix on a screen. In order to solve the above, a projection lens between the liquid crystal display means and the screen, and the projection
An optical path shift unit provided at a part of the pupil position of the lens for refracting incident light to shift the optical path of the incident light is provided, and the optical path shift unit has a polygonal pyramid shape. be able to.

Further, the projection type image display device of the present invention, in order to solve the above problems, a shift amount of the optical path by the upper Kihikariro shifting means, the configuration is set to be substantially half of the pixel pitch Is.

[0020]

According to the structure of the first aspect, the transmitted light from the liquid crystal display means is projected on the screen through the optical path shifting means, and is also projected on the screen without passing through the optical path shifting means. In other words, an image based on the liquid crystal display means (an image formed without passing through the optical path shift means) and an image based on the liquid crystal display means that is displaced in parallel by a predetermined shift amount (via the optical path shift means). The projected image is projected onto the screen so that it is superposed.

[0021] At this time, the light passing through the light path shift unit is provided between the not pass light, the optical path difference is generated, the optical path difference by the optical path difference correction means is corrected. Therefore, on the screen, between the image formed through the optical path difference correcting means without passing through the optical path shifting means and the image formed by shifting in parallel by a predetermined amount through the optical path shifting means. Has no optical path difference and is projected on the screen so that these images are superimposed.

According to the structure of claim 2, the optical path shift means
Is a transparent parallel plate element, and the optical path difference correction means is a parallel plate
Because it is glass, you can obtain smooth images at low cost.

According to the configuration of the present invention, the number of picture elements formed is increased and a smooth image can be obtained.

[0024]

According to the structure of the present invention , since the shift amount of the optical path is approximately half the pixel pitch, the pixel becomes a double image on the screen, and a smooth image can be obtained.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS. 1 to 8.

Reference Example 1 A projection type image display device of this reference example is as shown in FIG.
The light source 4 that emits light for projection, the parabolic mirror 3 that collimates the light emitted from the light source 4 and guides it to the liquid crystal display panel 2 (liquid crystal display means), and the transmitted light of the liquid crystal display panel 2 It has a field lens 5 that guides it to the projection lens 6 and a projection screen 7 (screen) for focusing the light from the projection lens 6.

In the present projection type image display device, a parallel plate glass 1 (optical path shifting means) is further provided on at least a part of the optical path between the liquid crystal display panel 2 and the projection screen 7. For example, parallel plate glass 1
Is provided on the optical axis l between the liquid crystal display panel 2 and the projection screen 7, as shown in FIG. 1, and has a predetermined angle θ with respect to the normal line of the incident surface (see FIG. 2). The optical path of the incident light is shifted only by tilting. The shift amount of the optical path differs depending on the thickness of the parallel plate glass 1, the refractive index, and the angle θ.

In this reference example , the liquid crystal display panel 2 having the following specifications was used. That is, the diagonal line of the display screen is 75 mm, the pixel pitch is 160 μm × 130 μm in length × width, the pixel region is 80 μm × 75 μm in length × width, and the aperture ratio (the size of the pixel region in the screen is The ratio) is 29%. Although the twisted nematic is used as the operation mode of the liquid crystal, it is also possible to use other modes.

Examples of the light source 4 include a metal halide lamp, a xenon lamp, a halogen lamp and the like.

According to the above structure, the light emitted from the light source 4 is collimated by the parabolic mirror 3 and then is incident on the liquid crystal display panel 2, and is further transmitted to the projection lens 6 via the field lens 5. Be guided. Here, since the parallel plate glass 1 is obliquely arranged at a part of the pupil position of the projection lens 6, the parallel plate glass 1 refracts the incident light as shown in FIG.

That is, as shown in FIG. 2, the light incident on the point A at an angle of θ with respect to the normal to the plane of incidence of the parallel flat glass 1 is refracted in the parallel flat glass 1 according to Snell's law. After that, go out from point B into the air. At this time, the incident light and the outgoing light of the parallel flat plate glass 1 are parallel to each other, and a predetermined shift amount d is generated between them.

Here, referring to FIG. 2, the shift amount d generated between the incident light and the outgoing light of the parallel flat plate glass 1 will be obtained.

As described above, the incident angle of the incident light on the parallel flat plate glass 1 is θ, the refraction angle in the parallel flat plate glass 1 is α, the thickness of the parallel flat plate glass 1 is D, and the refraction of the parallel flat plate glass 1 is made. When the ratio is n, α = sin ⁻¹ (1 / n · sin θ) (2), and the line segment AB corresponding to the length of the optical path in the parallel plate glass 1 is AB = D / cos (sin ⁻¹ (1 / n · sin θ)) (3), and the shift amount d of the light generated by the incident light passing through the parallel flat glass 1 is d = AB · sin (θ−α) = D · sin (θ− It is expressed by sin ^-1 (1 / n · sin θ)) / cos (sin ⁻¹ (1 / n · sin θ)) (4).

The thickness d of the parallel plate glass 1 and the tilt angle of the parallel plate glass 1 are adjusted so that the shift amount d is approximately half the pixel pitch of the liquid crystal display panel 2, and the projection lens 6 is used.
It is preferable to dispose near the pupil position. With this setting, the picture element is formed as a double image on the projection screen 7, so that the stripes due to the light shielding mask become inconspicuous.

As described above, when the parallel flat plate glass 1 is viewed from the projection lens 6 side, it seems that the liquid crystal display panel 2 is shifted by d. Therefore, on the projection screen 7, an image based on the original liquid crystal display panel 2 (an image based on transmitted light that does not pass through the parallel flat plate glass 1) and an image based on the liquid crystal display panel 2 (parallel plate based on the transmitted light that does not pass through the parallel flat plate glass 1). Glass 1
The image based on the transmitted light that has passed through) was projected so as to be superimposed, and a smooth image was obtained.

Specifically, from the above equations (2) to (4), d
When the thickness D of the parallel flat plate glass 1 is set to 1.3 mm, the incident angle θ is set to 10 °, and the refractive index n is set to 1.52 so as to be approximately half the pixel pitch (about 80 μm in this reference example ), Figure 3
As shown in FIG. 3, the image of the picture element aperture portion is superposedly formed at the position where the image of the light-shielding mask is originally formed (see the shaded portion in FIG. 3A) (see the shaded portion in FIG. 3B). ), The stripes due to the light-shielding mask became inconspicuous, and a smooth image was obtained. 3 (a) shows the state of the projection screen 7 before the parallel flat plate glass 1 is arranged, and FIG. 3 (b) shows the state of the projection screen 7 after the parallel flat plate glass 1 is arranged (picture element image). Is shown.

In the present reference example , as described above, the case where the parallel flat plate glass 1 is arranged so as to be inclined with respect to the vertical direction (the plane perpendicular to the optical axis 1) of the liquid crystal display panel 2 has been described . is not limited to being this, for example, it may be arranged so as to be oblique to the horizontal direction and the diagonal direction of the liquid crystal display panel 2, or the vertical direction of the liquid crystal display panel 2, left and right directions The parallel flat plate glass 1 may be provided in each.

[0039] EXAMPLES herein, the embodiments of the present invention with reference to FIG. 4, described below. The members having the same functions as those in Reference Example 1 are designated by the same reference numerals, and detailed description thereof will be omitted here.

As shown in FIG. 4, in the projection type image display apparatus of this embodiment, the incident light is incident at a predetermined angle with respect to the normal to the incident surface, as in Reference Example 1. The parallel plate glass 1 (optical path shifting means) is arranged on one side of the optical axis l (upper side from the optical axis l in FIG. 4), and is parallel to the liquid crystal display panel 2 on the other side of the optical axis l. Direction (Fig. 4
In the above, the case where the parallel flat plate glass 8 (optical path difference correction means) is arranged below the optical axis 1 is illustrated, but the other configurations are the same as those of the reference example 1.

According to the configuration of the first reference example, the side on which the parallel flat plate glass 1 is disposed (the upper side from the optical axis 1) and the side on which the parallel flat plate glass 1 is not disposed with the optical axis 1 as a boundary ( Optical axis l
From the lower side).

This is because the light passing through the parallel flat plate glass 1 has a longer optical path than that of the light not passing through the parallel flat plate glass 1 due to refraction, resulting in an optical path difference. Defocusing occurs in the image formed on the projection screen 7 based on the optical path difference thus generated. In order to correct the out-of-focus condition, in the present embodiment, a parallel plate glass 8 for correcting the optical path difference is provided on the portion where the parallel plate glass 1 is not provided, as shown in FIG. It is provided parallel to the panel 2.

In this embodiment, the parallel flat plate glass 1 is used.
Is arranged at a part of the pupil position of the projection lens 6 at a predetermined angle (for example, 10 °) with respect to the perpendicular of the optical axis l, and the parallel plate glass 8 is vertically downward from the optical axis l. It is provided in the direction. Since the parallel flat glass 1 has a small inclination angle of 10 °, the thickness of the parallel flat glass 8 and the thickness of the parallel flat glass 1 are set to be the same so that the optical path length is the same (the optical path difference is zero). There is.

According to the above construction, since the light passing through the parallel flat plate glass 1 and the light passing through the parallel flat plate glass 8 both have the same optical path length, there is no optical path difference between them. As a result, the light passing through the parallel plate glass 1
The light that has passed through the parallel plate glass 8 is condensed and imaged on the projection screen 7 in a state where there is no optical path difference, so that a smooth and defocused image is obtained.

Incidentally, as the optical path shifting means and the optical path difference correcting means, in addition to the parallel plate glass shown in the reference example 1 and the example , for example, FIGS. 5 (a), 5 (b) and 6 (a) are used. It is also possible to use a quadrangular pyramid as shown in (b), a polygonal pyramid such as a quadrangular pyramid, and a polygonal pyramid. The polygonal pyramid shape has a common feature that it has a plurality of surfaces, and the surface normal of at least one surface is not parallel to the optical axis l. The polygonal frustum shape has a plurality of surfaces, and each surface has a common feature that the normal to the surface forms a symmetrical angle with respect to the optical axis.

When a quadrangular pyramid shaped one as shown in FIGS. 5A and 5B is used as the parallel plate glass 1 (or the parallel plate glass 8), an image is formed as shown in FIG. 5C. The number of picture elements is increased from 1 (the number in the case where the parallel flat glass 1 is not used) to 4 which is equal to the number of picture elements around the same, and along with this, a smooth image can be obtained. Also, FIG.
When a rectangular truncated pyramid shape as shown in (a) and (b) is used as the parallel flat plate glass 1 or the parallel flat plate glass 8,
As shown in FIG. 6C, the number of picture elements to be imaged is increased from one (when the parallel flat glass 1 is not used) to five, which is equal to the number of picture elements in the surrounding area. Along with this, a smooth image is obtained. Note that FIGS. 5B and 6B are FIGS. 5A and 6A, respectively.
FIG.

Reference Example 2 Here, another reference example will be described below with reference to FIGS. 7 and 8. The members having the same functions as those in Reference Example 1 are designated by the same reference numerals, and detailed description thereof will be omitted here.

In this reference example , as shown in FIG.
Instead of the parallel plate glass 1 of Reference Example 1, a birefringent element 9 (birefringent substance) is orthogonal to the optical axis l (parallel to the liquid crystal display panel 2), and the upper side and the lower side of the optical axis l. It differs from Reference Example 1 in that it is provided over the side.

Liquid crystal display panel 2 utilizing polarization of light
In this case, since polarizing plates (both not shown) are provided on the light incident side and the light emitting side, respectively, the light passing through the liquid crystal display panel 2 becomes linearly polarized light vibrating in a specific direction. Therefore, the vibration direction of this linearly polarized light and the axial direction of the birefringent element are set to be inclined by 45 °, or the emitted light from the liquid crystal display panel 2 is converted into circularly polarized light via a wave plate (not shown), Birefringence effect when incident on the birefringent element 9 (eg, Tetsuo Sueda "How to Use Optical Components and Points to Note")
(See pages 69 to 86 of Optronics Co., Ltd.), the ordinary ray and the extraordinary ray are separated, and the same effect as that of the parallel flat glass 1 of Reference Example 1 is obtained.

The birefringent element 9 of this reference example is made of a Savart plate. Specifically, a uniaxial crystal such as quartz or calcite is cut from an oblique direction with respect to the optical axis of the crystal and finished into a parallel plate. Although the birefringent element 9 is used in this reference example , this utilizes a phenomenon that the traveling direction of the extraordinary ray changes when the Savart plate makes the light obliquely incident on the optical axis. Is.

When the angle between the normal line of the Savart plate and the optical axis of the crystal is θ, the light incident on the Savart plate at the angle of θ is split into two polarizations P and Q orthogonal to each other. At this time, the polarized light Q corresponding to the extraordinary ray (the wavefront and the light traveling direction are not perpendicular) travels obliquely in the Savart plate against the Snell's law and is emitted from the Savart plate. On the other hand, the polarized light P corresponding to an ordinary ray (where the wavefront and the traveling direction of the light are perpendicular to each other) goes straight through the Savart plate and is emitted from the Savart plate. Both of these separated polarizations P
The separation width d between −Q is obtained as follows.

As shown in FIG. 8, as described above, the angle between the normal of the Savart plate and the optical axis of the crystal is θ, the refractive index for ordinary rays is n _o, and the refractive index for extraordinary rays is n.
_{Assuming e} , the separation width d between the extraordinary ray and the ordinary ray is represented by d = [(b ² −a ² ) / 2c ² ] · t · sin 2θ (5). _{Here, a = 1 / n e,} b = 1 / n o, and ^{c 2 = a 2 sin 2 θ} + b 2 cos 2 θ, and t is the thickness of the Savaru plate.

According to the above configuration, when the transmitted light of the liquid crystal display panel 2 is incident on the birefringent element 9, the birefringent element 9
The ordinary ray and the extraordinary ray pass through different optical paths in the inside, and are separated into two polarizations P and Q.
Image on top, respectively. As a result, when the birefringent element 9 is viewed from the projection lens 6 side, it is as if the liquid crystal display panel 2
Appears to have shifted by d. Therefore, on the projection screen 7, the original image by the liquid crystal display panel 2 and d
The image on the liquid crystal display panel 2 which was displaced by a certain amount was projected so as to be superimposed, and a smooth image was obtained.

[0054] In this case, calcite _{(n e = 1.6584, n o} =
If the thickness of the Savart plate (θ = 45 °) created from 1.4864) is set to 0.37 mm, the separation width d between the polarized light P and Q is approximately
The thickness was 80 μm, and similar to Reference Example 1 , a smooth image without out-of-focus was obtained.

[0055] birefringent element 9 has been described as being disposed at the pupil position of the present embodiment in the projection lens 6, is not limited to this, a emission side of the liquid crystal display panel 2, It may be provided on a part of the optical path.

In the above-mentioned embodiments and the reference examples 1 and 2 , the case where the image shift amount is set to half the picture element pitch has been described, but the shift amount may be any value as long as the resolution is not lowered. It does not matter if the elements partially overlap.

Further, although the embodiment and the reference examples 1 and 2 adopt the telecentric illumination as the illumination method, the present invention can be applied to other illumination methods such as critical illumination and Koehler illumination system.

Further, in the examples and the reference examples 1 and 2 , the case of the single plate type has been described for convenience of explanation, but the present invention is not limited to this, and can be applied to a three plate type projection type image display device. Applicable.

[0059]

As described above, the projection type image display apparatus according to the first aspect of the present invention has a projection lens between the liquid crystal display means and the screen.
And an optical path shift means provided at a part of the pupil position of the projection lens for refracting incident light to shift the optical path of the incident light, and a pupil position of the projection lens.
A transparent parallel plate parallel to the liquid crystal display means, provided in a portion where the optical path shifting means is not provided.
That an optical path difference corrector performs the image formed through the optical path difference corrector, correction of optical path difference between the image formed through the optical path shifting means, these images Piled up
The image is projected on the screen so as to be combined .

[0060] Therefore, regardless of the picture element pitch, it can provide a low-cost projection-type image display apparatus. Further, an image based on the liquid crystal display means (an image formed without passing through the optical path shift means) and an image based on the liquid crystal display means displaced by a predetermined shift amount (an image formed via the optical path shift means). ) Is projected on the screen so that
Similar to the case where the conventional diffraction grating is used, the effect is obtained that the stripes due to the light-shielding mask become inconspicuous and a smooth image is obtained. Further, since the optical path difference correction means corrects the optical path difference generated by the optical path shift means, the transmitted light from the liquid crystal display device is imaged on the screen without any optical path difference without complicating the configuration . By this
Ri, smooth image is obtained without focus blur, so together effect that can cope with the liquid crystal display panel of any pixel pitch.

As described above, in the projection type image display device according to a second aspect of the present invention, in the configuration of the first aspect, the optical path shifting means is a transparent parallel plate which is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis. It is a flat plate element, and the optical path difference correction means is made of glass.

Therefore, in addition to the effect of claim 1,
Effect of providing a low-cost projection-type image display device
Is also played.

As described above, the projection type image display device of the present invention is provided on the optical path between the liquid crystal display means and the screen, refracts the incident light, and shifts the optical path of the incident light. The optical path shifting means includes a plurality of surfaces, and each surface is a polygonal truncated pyramid whose surface normal forms an angle symmetrical with respect to the optical axis. The number of picture elements to be imaged is increased.

Therefore, the number of picture elements to be imaged increases.
With the effect that a smoother image can be obtained
Play.

[0065] The projection type image display apparatus, as described above, provided part of the optical path between the liquid crystal display unit and the screen, refracts incident light shifts the optical path of the incident light An optical path shift means may be provided, and the optical path shift means may be configured in a polygonal pyramid shape.

Therefore, the number of picture elements to be imaged increases.
With the effect that a smoother image can be obtained
Play.

[0067] a projection type image display device of the present invention, as described above, the shift amount of the optical path by the upper Kihikariro shift means has a configuration that is set to be substantially half of the pixel pitch .

Therefore, the picture element becomes a double image on the screen.
As a result, the stripes due to the shading mask become less noticeable,
The effect is that a smoother image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a configuration example of a main part of a projection-type image display device according to a reference example and an example of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between incident light and outgoing light of the parallel flat plate glass when the parallel flat plate glass is used as the optical path shifting means in FIG.

3A and 3B are explanatory views showing a state of stripes by a light-shielding mask based on the presence or absence of the parallel flat plate glass of FIG. 1, and FIG. 3A shows a state of a projection screen before disposing the parallel flat plate glass,
(B) shows the state of the projection screen after the parallel flat glass is arranged.

FIG. 4 is an explanatory diagram showing a configuration example of a main part of a projection-type image display device according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing changes in the number of picture elements to be imaged when a quadrangular pyramid is used as the optical path shifting means of the present invention.

FIG. 6 is an explanatory view showing a change in the number of picture elements to be imaged when a quadrangular truncated pyramid is used as the optical path shifting means of the present invention.

FIG. 7 is an explanatory diagram showing a configuration example of a main part of a projection-type image display device according to still another reference example of the present invention.

FIG. 8 is an explanatory diagram showing a relationship between incident light and outgoing light of the birefringent element when the optical path shift means is composed of the birefringent element in FIG.

FIG. 9 is an explanatory diagram for explaining a problem of the conventional technique.

[Explanation of symbols]

1 parallel flat plate glass (optical path shifting means) 2 liquid crystal display panel (liquid crystal display means) 3 parabolic mirror 4 light source 5 field lens 6 projection lens 7 projection screen (screen) 8 parallel flat glass (optical path difference correcting means )

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Claims (2)

(57) [Claims] 1. A projection type image display device for displaying an image by forming an image of transmitted light from liquid crystal display means in which picture elements are arranged in a matrix on a screen, wherein the liquid crystal display means and the screen are provided. Between the projection lens, a part of the pupil position of the projection lens, which refracts the incident light, and shifts the optical path of the incident light, and the pupil position of the projection lens. The above optical path shifting means
The liquid crystal display means provided in a portion not provided
Optical path difference correction means that is a transparent parallel plate parallel to
Comprising performs a image formed through the optical path difference corrector, correction of optical path difference between the image formed through the optical path shifting means, so that these images are superposed A projection type image display device characterized by being projected on a screen. 2. The optical path shift means is a transparent parallel plate element tilted at a predetermined angle with respect to a plane perpendicular to the optical axis, and the optical path difference correction means is glass. 1. The projection type image display device according to 1.