JP4272446B2 - Projection display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display device applied to an image display device such as a projector or an exposure device.
[0002]
[Prior art]
Many projector devices, which are one type of projection display device, use a liquid crystal spatial light modulator called a liquid crystal light valve as image forming means. A liquid crystal light valve is a kind of image display element in which a large number of fine pixels are arranged, and a projector forms an image with the liquid crystal light valve and projects it onto a screen with a projection lens. The shape of the pixel included in the liquid crystal light valve is a square or a rectangle, and the size is from several tens of μm to several tens of μm or several tens of μm on one side. This pixel size determines the definition of the projected image. The finer the pixel, the higher the definition of the projected image. However, miniaturization of pixels, that is, reduction in size, has a problem in the manufacturing process of the liquid crystal light valve. Also, it is necessary to increase the number of pixels in order to cope with a large screen.
[0003]
Liquid crystal light valves, which are liquid crystal spatial light modulators, are roughly classified into transmissive light valves and reflective light valves. In the transmissive light valve, even if the pixel is miniaturized, it is difficult to miniaturize a portion that does not contribute to image formation, such as a pixel control thin film transistor (TFT), and even if the pixel is miniaturized, it does not contribute to the image formation. There is a problem in that the area of the portion is relatively large with respect to the area of the pixel, and the aperture ratio is reduced. On the other hand, in the reflection type light valve (which is often referred to as LCoS (Liquid Crystal on Silicon) because it is formed on a silicon substrate), a wiring portion is formed under the pixel electrode (reflection electrode). Therefore, the aperture ratio or the reflectance can be improved.
[0004]
However, in the case of a surface stabilization structure using ferroelectric liquid crystal or in a vertical alignment mode using nematic liquid crystal, a liquid crystal layer of about 1 μm is required for switching the liquid crystal layer, and 10 μm A pixel size of the order can be realized. However, it is very difficult to realize a smaller pixel of 5 to 7 μm or less while maintaining the image quality evaluated by contrast, gradation, and uniformity. There is also a method of increasing the number of pixels by increasing the size of the liquid crystal light valve itself, but this increases the cost of the liquid crystal light valve exponentially and at the same time increases the size of the optical system, further increasing the cost. Projection display device.
[0005]
In recent years, as a projection display device applied to a projector, an image display device, etc., there is an increasing demand for a larger screen and higher resolution, but in a method for increasing the number of pixels of image forming means such as a liquid crystal light valve, As described above, there are problems of increase in manufacturing cost and enlargement of the apparatus.
Thus, it has been proposed to realize a high-resolution projection display device by displaying the projection pixels from a plurality of light valves while appropriately shifting the positions on the screen (for example, see Non-Patent Document 1).
[0006]
In addition, a display device has been proposed in which the projection pixel position is moved at high speed using an element that shifts or deflects the optical axis (for example, a wobbling element) to make the number of projection pixels more than the number of pixels of the light valve. Yes. For example, the following Patent Document 1 discloses an image display device that realizes high resolution by increasing the number of pixels in a time division manner by providing an element that shifts the optical axis when projecting light emitted from a liquid crystal light valve. Has been proposed. In this image display device, by using two sets of an optical element capable of rotating the polarization direction and a transparent element having a birefringence effect with the optical axis shift directions orthogonal to each other, the vertical length is doubled and the horizontal width is doubled for a total of 4 times. High resolution images. Patent Document 2 below proposes an apparatus capable of substantially arranging pixels by Δ (delta) by shifting the optical axis. As a wobbling element that shifts and deflects the optical axis, for example, there is an optical element described in Patent Document 3 below.
[0007]
[Patent Document 1]
JP-A-4-113308
[Patent Document 2]
Japanese Patent Laid-Open No. 9-230329
[Patent Document 3]
Japanese Patent No. 32309969
[Non-Patent Document 1]
SID International Symposium Digest of Technical Papers (Vol.XXXIII, No.II) 2002, pp. 1254-1257
[0008]
[Problems to be solved by the invention]
Even when using a plurality of light valves to shift pixels at the projection position to achieve high resolution, such as the projection display device that performs pixel shifting, the pixels are shifted using a wobbling element to increase the resolution. Even when aiming at, the overlap of adjacent projection pixels arises. For this reason, if it is a projection image which displays 1 line, there exists a problem that the blur of an image generate | occur | produces.
[0009]
Therefore, in order to solve this problem, it is necessary to arrange a reduction optical system in the vicinity of the light valve, which is an image forming unit, and reduce the size of the projection pixel so that it does not overlap with the adjacent pixel. In this case, in order to pass through the optical system that reduces all the pixels of the light valve, for example, an optical element having a positive refractive power such as a microlens array is used to reduce the size of the pixels and project an image with the pixels reduced. An optical system that magnifies and projects onto a screen with a lens can be considered.
[0010]
However, as a result of the non-sequential ray tracing simulation by the Monte Carlo method, the present inventors set the back focus of the projection lens near the focal plane of an optical element having a positive refractive power such as a microlens array. It was found that the profile reflected the orientation distribution of the lamp light source and a good projection image could not be obtained.
[0011]
The present invention has been made in view of the above circumstances, and in the case where a reduction optical system is disposed in the vicinity of a light valve that is an image forming unit, and the size of a projection pixel is reduced to an extent that does not overlap adjacent pixels. Another object of the present invention is to provide a projection display device having a configuration capable of reducing the influence of the orientation distribution of the light source, maintaining high resolution performance, and obtaining a good projection image.
[0012]
  More specifically,The present inventionAn object of the present invention is to provide a projection display device having a configuration capable of reducing the influence of the orientation distribution of the light source, maintaining high resolution performance, and reducing the hardness (sharpness) of the image.The
[0013]
[Means for Solving the Problems]
  As means for achieving the above object, the invention according to claim 1 is provided in the vicinity of a light source that emits radiated light, an image forming means that includes a plurality of pixels that allow the radiated light from the light source to enter, and an image forming means. And a projection display device comprising an optical element having a positive refractive power and a projection lens.The back focus length from the projection lens to the object surface is longer than the optical distance from the projection lens to the image forming means.It is characterized by this.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
In order to realize a high-resolution projection display device, the projection pixel pitch is smaller than the product of the pixel pitch of the light valve and the projection magnification of the projection lens. A projection display device that moves the projection pixel position at high speed using a wobbling element that shifts and deflects the optical axis, and makes the number of projection pixels more than the number of pixels of the light valve apparently has been proposed. ing. In these high-resolution projection display devices, when one pixel of the light valve is projected on the screen with the projection lens as it is, an area that overlaps with the projected adjacent pixel is generated, and when a thin line is projected, the pixel blurs. appear. For this reason, if the size of each pixel is reduced without changing the pixel pitch, and these images are projected onto the screen by the projection lens, the blurring between adjacent projection images can be reduced.
[0019]
In order to reduce the size of the pixel, it is necessary to use an optical system corresponding to the pixel pitch of the light valve and having a positive refractive power. As an optical system having positive refractive power, a microlens array, a concave reflecting mirror, or the like can be used. On the focal plane of these optical systems, the illumination angle distribution of the light valve appears as an intensity distribution. Currently, discharge lamps such as metal halide lamps and ultrahigh pressure mercury lamps are often used as light sources for projection display devices. The light intensity orientation distribution of these lamps does not have a peak in the direction where the radiation angle is 0 degrees due to the shadow of the electrode in the lamp tube, and shows the light intensity orientation distribution as shown in FIG. Therefore, when the object plane of the projection lens is made coincident with the focal plane of the optical system having a positive refractive power, there is a problem that the intensity distribution of the projection pixel also becomes a distribution similar to FIG.
[0020]
  ThereforeThe present inventionIn the configuration, the object plane of the projection lens is positioned closer to the image forming means side than the focal plane of the optical system (optical element) having a positive refractive power. The projection pixel profile can reduce the influence of the lamp orientation distribution, even though it can be reduced. Furthermore, since it overlaps with an adjacent projection pixel with small relative intensity and the hardness (sharpness) of a projection image is reduced, it becomes an easy-to-view image.
  Also,The present inventionIs characterized in that the back focus length from the projection lens to the projection lens object surface is longer than the optical distance from the projection lens to the image forming means, and the object surface position viewed from the projection lens side is positively refracted. By further distant from the image forming means placed behind the optical system with power, the influence of the orientation distribution of the light source is reduced, high resolution performance is maintained, and the hardness of the image is reduced. Yes.
[0021]
  furtherThe present inventionThenaboveBy adopting a wobbling element as a pixel shifting means in a projection display device employing an optical system, and arranging a wobbling element between an optical element having a positive refractive power and a projection lens, pixels that are larger than the pixels of the image forming means Can be displayed, the influence of the orientation distribution of the light source can be reduced, high resolution performance can be maintained, and the hardness of the image can be reduced.
[0022]
【Example】
Hereinafter, the configuration, operation, and operation of the present invention will be described in detail based on the illustrated embodiments.
[0023]
  Example 1
  First,The first according to the present inventionExamples will be described.
  FIG. 1 is a schematic configuration diagram of a projection display device showing an embodiment of the present invention. In FIG. 1, the projection display device includes a lamp light source 11, an illumination optical system 12, beam splitters 13a and 13b, folding mirrors 14a and 14b, image forming means 15a and 15b, and an optical element having a positive refractive power. It is composed of elements 16a and 16b and a projection lens 17. Reference numeral 18 denotes a screen which is a projection surface on which an image is projected. As the lamp light source 11, a discharge lamp such as a metal halide lamp or an ultrahigh pressure mercury lamp is used. As the illumination optical system 12, a fly-eye integrator using a fly-eye lens and a condenser lens, a rod lens using internal reflection or a kaleidoscope and a relay lens can be used. The first beam splitter 13a is used for separating the illumination light into two light beams, and the second beam splitter 13b is used for multiplexing the separated light beams. These beam splitters 13a and 13b may be half mirrors or polarization beam splitters. As the optical elements 16a and 16b having positive refractive power, for example, microlenses are two-dimensionally arranged corresponding to the pixel pitch of the image forming means (for example, a transmissive light valve that is a transmissive display element) 15a and 15b. A microlens array can be used.
[0024]
2 shows a transmissive light valve 50 and an optical element having a positive refractive power (an example) used as the image forming means 15a and 15b of the projection display apparatus shown in FIG. 1 and the optical elements 16a and 16b having a positive refractive power. (Macro lens array) 54 as an example. FIG. 2 is an enlarged cross-sectional view of the main parts of the transmissive light valve 50 and the microlens array 54, and only three arrays are shown in the vertical direction of the drawing. In an actual configuration, there are hundreds to more than a thousand arrays. In the transmissive light valve 50, a liquid crystal 53 is sandwiched between two transparent substrates 52a and 52b, and polarizing plates 51a and 51b are disposed outside the transparent substrates 52a and 52b, respectively. Although not shown in FIG. 2, an alignment film, a transparent electrode, and the like are provided between the transparent substrates 52 a and 52 b and the liquid crystal 53. Pixel light from the transmissive light valve 50 is emitted as transmitted light having a spread according to the incident angle distribution of the illumination light. The microlens array 54 has a function of refracting and collecting the light.
[0025]
Next, the operation of optical elements (for example, microlens arrays) 16a and 16b having a positive refractive power will be described with reference to FIG. In the projection display device without the optical elements 16a and 16b, the projection image on the screen 18 is already near the boundary of each projection pixel of the projection image 21 from one light valve 15a as shown in FIG. The position of the light valve is adjusted so that the center of the pixel of the projection image 22 from one light valve 15b comes. This configuration can realize twice the number of pixels in almost the same projection area as compared to a projection display device with one light valve (for example, only 15a). However, when two projection images 21 and 22 are overlapped as shown in FIG. 3A, pixel blurring occurs because there is a region where projection adjacent pixels overlap. In order to reduce this blur, optical elements (for example, microlens arrays) 16a and 16b having a positive refractive power are used. For example, as shown in FIG. 3B, if the projection pixel size is halved by the optical elements 16a and 16b without changing the projection pixel pitch of the projection images 21 and 22 from the light valves 15a and 15b, the adjacent pixels No smearing occurs between them. Further, even if the pixel size is not reduced to the size shown in FIG. 3B, the blur is reduced by setting the pixel size to 0.5 times or more and less than 1.0 times compared to the pixel size shown in FIG. The effect of reducing is manifested.
[0026]
Further, like the projection display device described in Non-Patent Document 1 (however, in Non-Patent Document 1, the light valve is a reflection type), one of the two projection display devices is used in this embodiment (reflection). By arranging an optical element having a positive refractive power in front of the mold light valve (not shown), blurring can be reduced. Further, if an optical element having a positive refractive power is arranged in both of the two projection display devices, it is possible to reduce the blur between the projection pixels of all three colors.
[0027]
  (Example 2)
  nextThe second according to the present inventionExamples will be described.
  FIG. 5 is a schematic configuration diagram of a projection display device showing another embodiment of the present invention. In FIG. 5, this projection display device includes a lamp light source 31, an illumination optical system 32 for uniformly illuminating the emitted light from the lamp light source 31 on the image forming means, and a polarized beam for separating the illumination light and the projection light. A splitter 33, an optical element 34 having a positive refractive power, a reflective display element 35 as an image forming means, a wobbling element 36, and a projection lens 37 are provided. Reference numeral 38 denotes a projection on which an image is projected. Represents a screen that is a surface. As the lamp light source 31, for example, an ultra-high pressure mercury lamp or a metal halide lamp can be used. The illumination optical system 32 can uniformly illuminate the surface of the image forming means 35 by combining a lens array called a fly-eye lens and a condenser lens. Further, in this embodiment, a reflection type light valve which is one of the reflection type display elements is used as the image forming means 35.
[0028]
Next, FIG. 6 shows an example of an optical member in which the optical element 34 having the positive refractive power of the projection display apparatus shown in FIG. FIG. 6 is an enlarged cross-sectional view of a reflective display element (reflective light valve with lens) 60 having a configuration in which an optical element having a positive refractive power is integrated with a reflective light valve. In FIG. 6, an optical element (for example, a microlens array) 61 having a positive refractive power is included in the components of the reflective light valve 60. In the reflective light valve 60 with a lens, the liquid crystal 64 is sandwiched between the transparent substrate 63 and the back plane 65. A microlens array 61 is bonded to the transparent substrate 63 via an adhesive layer 62 as an optical element having a positive refractive power. An alignment film and a transparent electrode are disposed between the transparent substrate 63 and the liquid crystal 64, and an alignment film, a reflective film, or an aluminum mirror is disposed between the liquid crystal 64 and the back plane 65, but these are not shown. . Each array (microlens) of the microlens array 62 is arranged corresponding to the liquid crystal pixel.
[0029]
In FIG. 5, as the wobbling element 36, for example, the optical element described in Patent Document 3 can be used. However, since the method of the wobbling element does not affect the effect of the present invention, a method other than the optical element described in Patent Document 3 may be used. With the wobbling element 36, for example, two-stage subfield images can be obtained in the horizontal and vertical directions, respectively. In the present embodiment, a case of a projection display device that performs two-stage wobbling in the horizontal and vertical directions will be described. However, in the present invention, the effect of the invention is not affected by the number of stages of wobbling.
[0030]
Reflecting plates for pixel display are arranged in an array (not shown) on the liquid crystal layer side of the backplane 65 of the reflective light valve 60 with a lens shown in FIG. The microlens array 61 corresponding to the array pitch is bonded to the transparent substrate 63 made of a parallel plate via an adhesive layer 62. The refractive index of the microlens array 61 and the transparent substrate (parallel plate) 63 is 1.52, the refractive index of the adhesive layer 62 is 1.40, the F number of each microlens of the microlens array 61 is 1.37, and the adhesive layer The thickness (shortest distance) of 62 was 4 μm, and the thickness of the transparent substrate (parallel plate) 63 was 10 μm. Then, non-sequential ray tracing was performed by the Monte Carlo method, and the pixel profile on the projection plane (screen) 38 was calculated. When the continuous pixels having the maximum spatial frequency of the projected image are bright, dark, bright, dark,..., The CTF (Contrast Transfer Function) indicating the resolution performance was 59%. Further, the projection pixel reduction rate (the ratio of the projection pixel size to the projection pixel pitch when only one light valve was projected) was 44%. In this case, the CTF exceeds 50%, which can be said to be high resolution.
[0031]
In the configuration of this embodiment, the object plane (back focus position) of the projection lens 37 is from the image forming surface of the reflective light valve 60 that is the image forming means 35 (the surface of the liquid crystal 64 of the reflective light valve 60 in FIG. 6). Further, it was at a position of 12 μm in the back (further right side of the liquid crystal 64 in FIG. 6) and in the back from the liquid crystal surface. This is in the illumination optical path (path from the lamp light source 31 to the liquid crystal surface of the reflective light valve 35 (60)) further than the reflective surface of the reflective light valve 35 (60) when viewed from the projection lens 37 side. More specifically, this means that there is a projection lens object surface in the adhesive layer 62. Therefore, in the configuration of the present embodiment, the back focus length from the projection lens 37 to the projection lens object surface is longer than the optical distance from the projection lens 37 to the image forming means 35 (the liquid crystal surface of the reflective light valve 60). It will be. With such a configuration, it is possible to reduce image deterioration due to the orientation distribution of the lamp light source while maintaining high resolution performance, and it is possible to reduce the hardness (sharpness) of the image. Further, in this embodiment, since the reflection type light valve having the configuration as shown in FIG. 6 is used as the image forming unit 35, it is suitable for increasing the number of pixels and the resolution.
[0032]
  (Example 3)
  nextThird according to the present inventionExamples will be described.
  In this embodiment, the overall configuration of the projection display device is the same as that shown in FIG. 5, and the optical element 34 having positive refractive power and the image forming means 35 are integrated as in FIG. As in the second embodiment, the optical element having a positive refractive power is composed of a microlens array 61, and this microlens array 61 is bonded to the transparent substrate (parallel plate) 63 of the reflective light valve 60 by an adhesive layer 62. ing. Here, the refractive index of the microlens array 61 and the transparent substrate (parallel flat plate) 63 is 1.63, the refractive index of the adhesive layer 62 is 1.40, and the F number of each microlens of the microlens array 61 is 1.13. The thickness (shortest distance) of the adhesive layer was 4 μm, and the thickness of the transparent substrate (parallel plate) 63 was 10 μm. As a result of performing non-sequential ray tracing by the Monte Carlo method with the configuration of this example and calculating the pixel profile on the projection surface (screen) 38, the CTF of the projection image was a sufficiently high resolution of 83%. The reduction ratio was 65%. In this case, since the reduction ratio is a value larger than 50%, there is an area overlapping with the adjacent projection pixel. However, this projection pixel size is not so large as to degrade the projected image performance.
[0033]
In the configuration of this example, the object plane (back focus position) of the projection lens 37 was about 8 μm from the liquid crystal layer 64 in FIG. 6 to the projection lens side, that is, from the liquid crystal 64 in FIG. The microlens array 61, the adhesive layer 62, and the transparent substrate (parallel flat plate) 63 form an optical system having a positive refractive power. The focal position of this optical system is closer to the projection lens than the curved surface of the microlens array 61. Exists. Accordingly, the object plane of the projection lens 37 is positioned on the image forming means side (the liquid crystal surface side of the reflective light valve 60) from the focal plane. With such a configuration, it is possible to reduce image deterioration due to the orientation distribution of the lamp light source while maintaining high resolution performance, and it is possible to reduce the hardness (sharpness) of the image.
[0034]
  (Example 4)
  next4th according to the present inventionExamples will be described.
  The overall configuration of the projection display apparatus of the present embodiment is the same as that of FIG. 5, but the configurations of the optical element 34 and the image forming means 35 are different from those of the second and third embodiments. FIG. 7 is a view for explaining a reflective light valve 70 with a mirror used as the image forming means 35 in this embodiment. This reflective light valve 70 is a micromirror corresponding to each pixel of the liquid crystal 72 as an optical element. The array substrate 74 is provided on the back side. In FIG. 7, the liquid crystal 72 is disposed between a transparent substrate 71 and a planarization layer 73 for planarizing the concave shape of the micromirror array substrate 74. An alignment film and a transparent electrode are disposed between the transparent substrate 71 and the liquid crystal 72, and an alignment film is disposed between the liquid crystal 72 and the planarizing layer 73, but these are not shown. The radius of curvature of each concave micromirror on the micromirror array substrate 74 was 13.6 times the array pitch P, and the refractive index of the transparent substrate 71 and the planarizing layer 73 was 1.83. In the configuration of the present embodiment, the focal position of each array (concave micromirror) on the micromirror array substrate 74 is 6.7P (P is the length of the array pitch) on the projection lens side from the position of the liquid crystal 72, that is, on the left side in FIG. That is). However, the back focus position of the projection lens 37 is set to 3.6P from the liquid crystal 72 position to the projection lens side.
[0035]
In this embodiment, the non-sequential ray tracing by the Monte Carlo method is performed, and the pixel profile on the projection surface (screen) 38 is calculated. As a result, the CTF of the projection image is 83%, and the width of one projected pixel (full width at half maximum) ) Was 50% with respect to the projection pixel pitch. In this case, the CTF representing the projection resolution performance greatly exceeds 50%, indicating that the resolution is high. Further, the projection pixel width is half that of the adjacent projection image. When the wobbling element 36 displays two-stage subfield images in the horizontal and vertical directions, a good projection image can be obtained. In addition, the projection pixel width is shown by the full width at half maximum, and a pixel region having an intensity equal to or less than half of the pixel peak intensity intersects with an adjacent pixel. However, since the relative intensity is low, the resolution performance is not deteriorated, and since the image is superimposed with an appropriate intensity, it has an effect of reducing the hardness (sharpness) of the image. Therefore, in this embodiment, image deterioration due to the orientation distribution of the light source can be reduced while maintaining high resolution performance, the hardness of the image can be reduced, and an optical element having a positive refractive power can be obtained. Since the micromirror array is used as the element, the optical element can be made more compact.
[0036]
  (Example 5)
  nextThe fifth aspect of the present inventionExamples will be described.
  The overall configuration of the projection display apparatus of the present embodiment is the same as that of FIG. FIG. 8 is a diagram for explaining the image forming unit of this embodiment and an optical system having a positive refractive power. In this embodiment, the optical system having a positive refractive power is a configuration of the image forming unit. It is shared with some of the elements, and is a reflective light valve 80 with a lens. In the optical system having a positive refractive power, two microlens arrays 81 and 83 are bonded via an adhesive layer 82, and one microlens array 83 is transparent for sandwiching the liquid crystal 84 of the image forming unit 80. Used as a substrate. The liquid crystal 84 is sandwiched between a microlens array 83 and a backplane 85 mainly made of silicon. Further, an alignment film and a transparent electrode are provided between the microlens array substrate 83 and the liquid crystal 84, and an alignment film and a pixel electrode are provided between the liquid crystal 84 and the back plane 85, but these are not shown. .
[0037]
The configuration of this embodiment has a microlens array structure having a plurality of curved surfaces along the optical axis direction of each pixel of the image forming means 80. If the number of curved surfaces increases, the degree of freedom in design increases when the same positive refractive power is caused to function in the microlens array unit. In addition, if the microlens array portion is designed so that the focal positions are the same, the radius of curvature can be made larger than that of a single microlens, which facilitates processing. In the present embodiment, good projection performance can be obtained by setting the object position of the projection lens 37 closer to the liquid crystal side than the focal position of the combination lens of the two microlens arrays 81 and 83 (this operation is the same as in the embodiment). The description is omitted because it is equivalent to 2.) Therefore, in this embodiment, it is possible to reduce image deterioration due to the orientation distribution of the light source while maintaining high resolution performance, to reduce the hardness of the image, and further along the optical axis direction. By using a microlens array having a plurality of curved surfaces, the light condensing performance of an optical element having a positive refractive power can be enhanced.
[0038]
  (Example 6)
  nextThe sixth aspect of the present inventionExamples will be described.
  In the present embodiment, description will be made on a projection display device having a configuration using a transmissive light valve as shown in FIGS. In the projection display device configured as shown in FIGS. 1 and 2, when the magnification of the optical elements 16a and 16b having positive refractive power is ½, the angle magnification is twice the reciprocal. Here, when the image forming units 15a and 15b are transmissive light valves 50 configured as shown in FIG. 2, the incident angle spread of the illumination light to the transmissive light valve 50 in FIG. Degree to maximum θ). Similarly, the spread of the light beam angle of the light emitted from the transmissive light valve 50 is from 0 degree to a maximum θ. When these light rays are refracted by the microlens array 54 and the magnification of the microlens array 54 is ½, the angle magnification is doubled, so the spread of the light emitted from the microlens array 54 is from 0 degree to 2θ. Become. Therefore, when the F number of the illumination optical system 12 of the projection display device is defined as F1, and the F number of the projection lens 17 is defined as F2, the F number F1 of the illumination optical system 12 and the F number F2 of the projection lens 17 are
  F2 ≦ F1 / 2
If the condition is satisfied, the light beam reaches the screen 18 efficiently.
[0039]
Furthermore, if a wobbling element or the like is arranged between the optical elements 16a and 16b and the projection lens 17, and the maximum value of the number of horizontal or vertical wobbling steps by the wobbling element or the like is m,
F2 ≦ F1 / m
By satisfying the above, the light use efficiency of the projection display device can be increased. Further, as described in the above-described embodiment, in this embodiment as well, the object plane position of the projection lens 17 is closer to the image forming means 15a, 15b side than the focal plane position of the optical elements 16a, 16b having positive refractive power. In addition, the resolution performance can be improved by installing further on the back side than the image forming means surface. Therefore, in this embodiment, image degradation due to the orientation distribution of the light source can be reduced while maintaining high resolution performance, the hardness of the image can be reduced, and the light utilization efficiency of the entire apparatus can be reduced. Can be increased.
[0040]
  (Example 7)
  nextThe seventh aspect of the present inventionExamples will be described.
  The overall configuration of the projection display apparatus of this embodiment is the same as that shown in FIG. FIG. 9 is a diagram showing a configuration example of a wobbling element used as the wobbling element 36 of the projection display device of FIG. The wobbling element 90 is sandwiched between two transparent substrates 91a and 91b on which a plurality of strip-shaped electrodes 92a, 92b, 92c, 92d, 92e, 92f, and 92g are formed, and the two transparent substrates 91a and 91b. The liquid crystal layer 93 is made of a ferroelectric liquid crystal. Although alignment films are provided between the transparent substrate 91a and the liquid crystal layer 93 and between the transparent substrate 91b and the liquid crystal layer 93, illustration is omitted. The normal line of the transparent substrates 91a and 91b is taken as the Z axis, and the X axis and the Y axis are determined as shown in FIG. When no voltage is applied, the ferroelectric liquid crystal molecules are oriented so as to face the Z-axis. The voltage application direction is a direction perpendicular to the Z axis, that is, in the XY plane. In the case of FIG. 9, the direction of the electrodes is the Y axis, and these electrodes are arrayed in the X axis direction. These electrodes may be metal or transparent electrodes (ITO). By increasing (or decreasing) the applied voltage in the order of the electrodes 92a, 92b, 92c, 92d, 92e, 92f, and 92g, a voltage gradient can be generated along the X axis. By switching the polarity of this voltage gradient, the molecular direction of the liquid crystal molecules 94a (94b) can be switched from + θ to −θ and from −θ to + θ at high speed. Note that the electrode structure of this embodiment is an example, and any electrode structure can affect the effect of the present invention as long as the voltage gradient can be switched in a plane perpendicular to the Z axis. Absent.
[0041]
By such voltage control, the liquid crystal molecules 94a (94b) can switch the molecular direction from the Z axis in the XZ plane at high speed from + θ to -θ, and from -θ to + θ, and the liquid crystal molecules 94a (94b) can be switched to the Z axis. Lean from. At this time, when linearly polarized light having a polarization direction in the X direction enters the wobbling element 90, in the case of the liquid crystal molecules 94a, the optical path is deflected in the + X direction by the birefringence effect. In the state of the liquid crystal molecules 94b, the optical path is deflected in the -X direction. In the configuration of this embodiment, the two alignment states 94a and 94b of the liquid crystal molecules are symmetric with respect to the optical axis (Z-axis), so both optical path deflection states have symmetry. For this reason, symmetry is also maintained in the projected image. Furthermore, in order to perform wobbling in two stages in each of the horizontal and vertical directions, for a total of four subfields, two wobbling elements 90 are prepared and arranged so that the electrode directions of the front and rear wobbling elements are orthogonal to each other. Just do it.
[0042]
  As described above, in this embodiment, the wobbling element 90 using a ferroelectric liquid crystal is provided.Example 2~Example 6In the projection display device described in the above, it is possible to reduce the influence of the orientation distribution of the light source, maintain high resolution performance, and reduce the hardness (sharpness) of the image. Further, high-speed wobbling is possible due to the characteristics of the ferroelectric liquid crystal, and flicker between subfields can be reduced.
[0043]
  (Example 8)
  nextEighth according to the present inventionExamples will be described.
  The overall configuration of the projection display apparatus of this embodiment is the same as that shown in FIG. FIG. 10 is a diagram showing a configuration example of the wobbling element 100 used as the wobbling element 36 of the projection display device of FIG. The wobbling element 100 has a configuration in which a liquid crystal layer 102 made of a ferroelectric liquid crystal is disposed between a sawtooth substrate 101a and a parallel plate 101b. An alignment film is provided between the sawtooth substrate 101a and the liquid crystal layer 102, and between the liquid crystal layer 102 and the parallel plate 101b, but the illustration is omitted. Here, the Z axis is determined along the normal direction of the parallel plate 101b, and the X and Y axes are selected as shown in FIG. Further, the refractive index of the sawtooth substrate 101a is n1, the refractive index of the parallel plate 101b is n2, and the ordinary light refractive index no of the liquid crystal layer 102 is approximately equal to n1, and the extraordinary light refractive index ne is approximately equal to n2. . Note that the difference between the ordinary light refractive index no of the liquid crystal 102 and the refractive index n1 of the sawtooth substrate 101a, and the difference between the extraordinary light refractive index ne and the refractive index n2 of the parallel plate 101b can be made smaller than the value of ne-no. desirable.
[0044]
When the electric field to the liquid crystal layer 102 is controlled and the direction of the liquid crystal molecules is aligned along the Y-axis direction as indicated by 103a, a refractive index difference occurs at the interface between the sawtooth substrate 101a and the liquid crystal layer 102. If the X position is taken on the horizontal axis and the phase of the light beam passing through the wobbling element 100 is taken on the vertical axis, the phase distribution becomes a sawtooth shape as shown in FIG. For this reason, since the wobbling element 100 of this embodiment is a blazed diffraction grating, it has a function of deflecting light at a diffraction angle represented by a function of the sawtooth pitch and wavelength. On the other hand, when the electric field applied to the liquid crystal layer 102 is changed so that the direction of the liquid crystal molecules is the X-axis direction as indicated by 103b, there is no difference in refractive index at the interface between the sawtooth substrate 101a and the liquid crystal layer 102. For this reason, since the wobbling element 90 has the same characteristics as a simple parallel plate, the light travels straight. In this way, by switching the electric field applied to the liquid crystal layer 102, the traveling direction of the outgoing light from the wobbling element 100 is easily switched by causing the moment when the phase distribution in the wobbling element has a sawtooth shape. be able to.
[0045]
Furthermore, if two wobbling elements 100 of this embodiment are prepared and arranged so that the groove directions of the sawtooth substrate 101a are orthogonal, the optical path for an image of two stages in the horizontal and vertical directions, that is, four subfields. Can be switched. The wobbling element 100 of this embodiment is formed of a liquid crystal functional element using the sawtooth substrate 101a. However, the wobbling element 100 may have a structure in which the orientation angle of liquid crystal molecules is periodically changed from place to place in the liquid crystal layer.
[0046]
  As described above, in this embodiment, the wobbling element 100 having a moment when the phase distribution has a sawtooth shape in the element is obtained.Example 2~Example 6By incorporating it in the projection display device described in 1), the influence of the orientation distribution of the light source can be reduced, high resolution performance can be maintained, and the hardness (sharpness) of the image can be reduced. Furthermore, if a ferroelectric liquid crystal is used as the liquid crystal, wobbling can be performed at high speed, and flickering of the projected image can be reduced.
[0047]
【The invention's effect】
  As explained above,According to the present inventionIn the projection display device, image deterioration due to the orientation distribution of the light source can be reduced while maintaining high resolution performance, and the hardness (sharpness) of the image can be reduced.
  Also,According to the present inventionIn the projection display device, pixels exceeding the number of pixels of the image forming means can be displayed using a wobbling element, and image degradation due to the orientation distribution of the light source can be reduced while maintaining high resolution performance. The hardness of the image can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a projection display device showing an embodiment of the present invention.
2 is a cross-sectional view of a transmissive light valve and a macro lens array having a positive refractive power used as an image forming unit and an optical element having a positive refractive power of the projection display device shown in FIG. 1;
FIG. 3 is an explanatory diagram of a method of superimposing projection images from two light valves and doubling the number of pixels in a projection area.
FIG. 4 is a diagram showing a light intensity orientation distribution (a relation between a radiation angle and an intensity) of a lamp light source.
FIG. 5 is a schematic configuration diagram of a projection display device showing another embodiment of the present invention.
FIG. 6 is an enlarged cross-sectional view of a reflective light valve with a lens having a configuration in which an optical element having a positive refractive power is integrated with an image forming unit.
FIG. 7 is an enlarged cross-sectional view of a reflective light valve with a mirror in which a micromirror array is integrated with a reflective light valve.
FIG. 8 is an enlarged cross-sectional view of a reflective light valve with a lens having a configuration in which an optical system (two microlens arrays) having a positive refractive power is shared with some of the components of an image forming unit. .
FIG. 9 is a schematic perspective view showing a main part of a configuration example of a wobbling element used in the projection display device of the present invention.
FIG. 10 is a schematic perspective view showing a main part of another configuration example of the wobbling element used in the projection display device of the present invention.
11 is a diagram showing a phase distribution of light rays passing through the wobbling element shown in FIG.
[Explanation of symbols]
11: Lamp light source
12: Illumination optical system
13a, 13b: Beam splitter
14a, 14b: Folding mirror
15a, 15b: Transmission type light valve (image forming means)
16a, 16b: optical elements having positive refractive power
17: Projection lens
18: Screen (projection surface)
21, 22: Projected image
31: Lamp light source
32: Illumination optical system
33: Polarizing beam splitter
34: Optical element having positive refractive power
35: Reflective light bulb
36: Wobbling element
37: Projection lens
38: Screen (projection surface)
50: Transmission type light valve
51a. 51b: Polarizing plate
52a, 52b: Transparent substrate
53: Liquid crystal
54: Microlens array
60: Reflective light valve with lens
61: Microlens array
62: Adhesive layer
63: Transparent substrate (parallel plate)
64: Liquid crystal
65: Backplane
70: Reflective light valve with mirror
71: Transparent substrate
72: Liquid crystal
73: Planarization layer
74: Mirror array substrate (micromirror array)
80: Reflective light valve with lens
81, 83: Microlens array
82: Adhesive layer
84: Liquid crystal
85: Backplane
90: Wobbling element
91a, 91b: transparent substrate
92a, 92b, 92c, 92d, 92e, 92f, 92g: electrodes
93: Liquid crystal layer
100: Wobbling element
101a: serrated substrate
101b: parallel plate
102: Liquid crystal layer

Claims (1)

Projection composed of a light source that emits radiated light, an image forming unit having a plurality of pixels on which radiated light from the light source is incident, an optical element that is installed near the image forming unit and has positive refractive power, and a projection lens In the display device,
A projection display device characterized in that a back focus length from the projection lens to the projection lens object surface is longer than an optical distance from the projection lens to the image forming means .

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