JP2007232811A - Projection type display device and rear projection type display device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type display device capable of being more easily manufactured. <P>SOLUTION: The projection type display device includes a polarized light changing part which arranges light passing through a first lens element in a desired polarization direction, and has a first color separation part which separates light from a light source to a first primary color light beam and second and third primary color light beams, and a second color separation part which separates the second and the third primary color light beams. Optical distances from the first lens element to video display elements arranged corresponding to the respective primary color light beams are designed to be equal, and a polarizing plate is arranged between the polarized light changing part and the first color separation part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention irradiates a video display element in which pixels having means for separating light from a light source into three primary color lights and modulating the light intensity of the light according to the amplitude of the video signal corresponding to each primary color light are arranged in a matrix. The present invention relates to a projection display device that modulates the intensity of each primary color light in accordance with a video signal by the video display element, and then enlarges and projects an image obtained by combining with a cross prism on a screen.

  In Patent Document 1 below, an illumination optical system having a light source that emits illumination light and an illuminance uniformizing means that uniformizes the illuminance distribution of the light emitted from the light source, and a plurality of illumination lights emitted from the illumination optical system are disclosed. A color separation optical system that separates the color illumination light, a plurality of electro-optic modulation devices that respectively modulate the illumination lights of the plurality of colors separated by the color separation optical system, and the modulation emitted from each of the electro-optic modulation devices A color combining optical system for combining light, a projection optical system for projecting the combined light emitted from the color combining optical system as a display image, and at least one of a plurality of colors of illumination light separated by the color separation optical system A configuration of a projector including a relay optical system positioned in the path of the illumination light is disclosed.

  In Patent Document 2 below, a light source and a light beam emitted from the light source are incident, and this light beam is separated into a first primary color light and a second and third primary color light with a separation angle of 180 ° from each other. A cross dichroic mirror to be separated, a first mirror for deflecting the first primary color light that has passed through the cross dichroic mirror by 90 °, and a first primary color light deflected by the first mirror by 90 °, A second mirror that transmits through the image display panel and is incident on the first incident surface of the color combining prism; a third mirror that deflects the second and third primary color light that has passed through the cross dichroic mirror by 90 °; The second and third primary color light deflected by the third mirror is separated into the second primary color light and the third primary color light, and the second primary color light travels straight, and the third primary color light is 90%. Deflection dichroic mirror The fourth mirror that deflects the second primary color light that has passed through the dichroic mirror by 90 °, transmits the second primary color light through the second image display panel, and enters the second incident surface opposite to the first incident surface of the color combining prism. The third primary color light deflected by the dichroic mirror is deflected by 90 °, transmitted through the third image display panel, and perpendicular to the first and second incident surfaces of the color synthesis prism. A fifth mirror that is incident on the incident surface, and the color synthesis prism synthesizes each primary color light transmitted through each video display panel and enters the projection lens, and each video display panel corresponding to the light source of each primary color light A configuration of a projector apparatus is disclosed in which the optical path lengths up to are substantially equal to each other.

JP 2004-226814 A JP-A-8-234156

  In Patent Document 1, the optical path length to the liquid crystal panel for B light is longer than the optical path length of the liquid crystal panel for R and G light. Therefore, the B light forms an image having a size equal to the effective dimension of the panel halfway up to the liquid crystal panel, and this aerial image is inverted by the relay lens and formed again on the liquid crystal panel. . For this reason, the direction of the image of the B light in the liquid crystal panel for B light is opposite to that of the R and G light that directly forms an image having a size equal to the effective size of the liquid crystal panel. There is a problem that uneven brightness and uneven color occur.

  Also, in Patent Document 1, in order to make the light quantity distribution on the liquid crystal panel uniform, the light from the light source is divided by the first lens array, and the obtained plurality of divided lights are superimposed on the second lens array. The lens is superimposed on the liquid crystal panel. However, in order to overlap and project on the liquid crystal panel, high shape accuracy and positional accuracy are required for the first lens array and the second lens array, and there is a problem of high cost. Further, when polarizing plates are required on the incident side and the emission side of the liquid crystal panel, there is a problem that the cost of the illumination optical unit is increased.

  In Patent Document 2, the first and second mirrors and the third and fourth mirrors are arranged at symmetrical positions with respect to the cross dichroic mirror, and further, the fourth mirror and the fifth mirror are provided. By disposing at symmetrical positions with respect to the dichroic mirror, the optical distance from the light source to the video display panel corresponding to each primary color light is made equal, and in principle, color unevenness is suppressed. However, since the cross dichroic mirror used for color separation is arranged at a position away from the video display panel, the sensitivity of the image position change on the video display panel to the angle change of the cross dichroic mirror becomes high, and a highly accurate holding method There is a problem that is necessary. Further, at the intersection of the cross dichroic mirrors, there is a problem that the dichroic mirror to be combined in an X shape (cross shape) has a predetermined thickness, so that color separation cannot be performed in the crossed region and desired characteristics cannot be obtained. Similar to Patent Document 1, in the projector device of Patent Document 2, the illumination optical unit such as a lens array is required to have high shape accuracy and position accuracy, and there is a problem of high cost. Furthermore, when polarizing plates are required on the incident side and the emission side of the video display panel, there is a problem that the cost of the illumination optical unit is increased.

  The present invention has been made in view of the above-described problems, and its purpose is not to use a cross dichroic mirror as a color separation unit, and in principle, color unevenness and brightness unevenness do not occur, and a lens array is not used. Then, it is providing the projection type display apparatus with easy manufacture.

  In one aspect of the present invention, a polarization conversion unit that aligns light having passed through the first lens element in a desired polarization direction is provided, and light from the light source is converted into first primary color light and second and third primary color light. An image display element having a first color separation unit for separating and a second color separation unit for separating the second and third primary color lights, and arranged corresponding to each primary color light from the first lens element And the polarizing plate is disposed between the polarization conversion unit and the first color separation unit.

  ADVANTAGE OF THE INVENTION According to this invention, the projection type display apparatus with easy manufacture can be provided.

  Hereinafter, the best mode of the present invention will be described with reference to the drawings. In addition, in each figure, the element which has the same function is attached | subjected and shown, and the overlapping description is abbreviate | omitted about what was once demonstrated. In the following description, a liquid crystal panel is used as the video display element.

  FIG. 1 is a schematic diagram of an optical system of a projection display apparatus showing Example 1. FIG.

  In the figure, reference numeral 101 denotes a lamp tube as a light source. As the light source, for example, an ultra-high pressure mercury lamp, a xenon lamp, a metal haloid lamp, or the like can be used. The reflector 102 has a function of reflecting the light emitted from the lamp tube 101 and condensing it in the illumination system, and the reflection surface shape of the inner surface thereof is a free-form surface shape shown in Equation 1 described later. Then, by the mutual lens action with the first lens element 104 having the same free-form surface shape, the shape of the light emitted from the lamp tube (the light shape in the cross section perpendicular to the optical axis is a circular shape) The light is converted into rectangular light having a shape similar to the effective display area of the liquid crystal panel 115 (115R, 115G, 115B). The light shape conversion will be described later.

  The ultraviolet reflection filter 103 disposed between the light source and the first lens element 104 functions to reflect light in the ultraviolet region (for example, a wavelength region of 430 nm or less) out of the light emitted from the lamp tube 101. .

  The rectangular light emitted from the first lens element 104 is incident on a polarization conversion unit 105 that performs polarization conversion that aligns unpolarized light (unbiased light) from the light source in a predetermined polarization direction.

  The polarization conversion unit 105 includes a prism block 105a, a reflection mirror 105b, and a λ / 2 plate 105c.

  In the prism block 105a, as shown in the figure, a polarization separation film S105a of a dielectric multilayer film or an organic multilayer film is formed on the C-shaped joint surface of the three prism blocks. The polarization separation film S105a has a polarization separation function of reflecting a desired polarization component (for example, S wave) and transmitting P wave. The S wave reflected by the polarization separation film S105a passes through the λ / 2 plate 105c, is converted into a P wave, and is emitted along the optical axis by the action of the reflection mirror 105b. The reflection mirror 105b may be a total reflection mirror, but a mirror having a dielectric multilayer film or a metal reflection film formed on the reflection surface may be selected depending on desired characteristics.

  The field lens 123 is a second lens element having an effect of causing the P-wave rectangular light emitted from the polarization conversion unit 105 to efficiently enter the liquid crystal panel 115.

  The first polarizing plate 106 arranged on the emission side of the field lens 123 is arranged to improve the degree of polarization of the light whose polarization direction is aligned with the P wave by the polarization conversion unit 105. The first polarizing plate 106 is preferably a polarizing plate formed of an inorganic material as a high light-resistant material because light before spectroscopy (before color separation) passes therethrough. In order to further reduce damage due to light, it is desirable to select a reflective polarizing plate to obtain higher reliability. As shown in FIG. 1, when the reflective inorganic polarizing plate is arranged perpendicular to the optical axis, the reflected light returns to the lamp tube 101 as it is, and there is a risk of damaging the lamp. In such a case, the reflection-type inorganic polarizing plate may be disposed so as to be inclined with respect to the optical axis so that the light does not return directly to the lamp tube. There is no loss of lamp life.

  The light whose degree of polarization is increased by the first polarizing plate 106 enters the first dichroic mirror 107. The first dichroic mirror 107 is a first color separation unit that separates the first primary color light and the second and third primary color lights. Generally, a dichroic mirror is formed by depositing a dielectric multilayer film on a glass substrate by vapor deposition or sputtering. Here, it has a characteristic of reflecting blue light (first primary color light).

  The blue light (also referred to as B light) reflected from the first dichroic mirror 107 is guided to the B light liquid crystal panel 115B through the total reflection mirror 112 and the third lens element 120B.

  As shown in FIG. 1, the first dichroic mirror 107 has an optical axis of reflected light (also referred to as a reflected optical axis) that is a positive direction of an optical axis of incident light (also referred to as an incident optical axis). ) With a predetermined angle α (for example, 110 degrees or more). That is, the incident optical axis and the normal line of the first dichroic mirror 107 are set to be an angle smaller than 45 degrees (35 degrees when the angle α is 110 degrees) (the reason will be described later). .

  On the other hand, the second primary color light and the third primary color light transmitted through the first dichroic mirror 107 have their optical axes bent by 90 degrees by a total reflection mirror 109 disposed at an inclination of 45 degrees with respect to the optical axis, The light enters the second dichroic mirror 110.

  The second dichroic mirror 110 is a second color separation unit that separates the second primary color light and the third primary color light and is disposed at an inclination of 45 degrees with respect to the optical axis. Here, it has a characteristic of reflecting green light (second primary color light).

  The green light (also referred to as G light) that is the second primary color light reflected from the second dichroic mirror 110 has its optical axis bent by 90 degrees, and the optical axis of the total reflection mirror 111 is bent by 90 degrees. The light is guided to the liquid crystal panel 115G for G light through the third lens element 120G. Further, red light (also referred to as R light), which is the third primary color light transmitted through the second dichroic mirror 110, is bent 90 degrees in the optical axis by the total reflection mirror 113 and passes through the third lens element 120R. Then, the light is guided to the liquid crystal panel 115R for R light.

  The third lens element 120 (120R, 120G, 120B) reduces the light ray angle of light incident on the periphery of the screen of the liquid crystal panel 115 (115R, 115G, 115B) corresponding to each primary color light and improves the contrast performance. Has a function. Here, the third lens element 120 is formed by a single lens, but is not limited to this. For example, a plurality of (for example, two) lenses are used to correct aberrations. May be formed.

  Conventionally, a polarizing plate is disposed on the incident side of the liquid crystal panel 115. However, in Example 1, since the degree of polarization is increased by the first polarizing plate 106, the incident-side polarizing plate is omitted. Thereby, cost reduction can be achieved.

  Here, the optical path length from the intersection M between the first dichroic mirror 107 and the optical axis to the liquid crystal panel 115B for B light, and from the M point to the liquid crystal panel 115R for R light and the liquid crystal panel 115G for G light. I will talk about the optical path length.

  As is apparent from FIG. 1, the optical path length of the R optical path and the optical path length of the G optical path are equal. On the other hand, as already described, in the first embodiment, the first dichroic mirror 107 has an angle α of 110 degrees between the optical axis of incident light (incident optical axis) and the optical axis of reflected light (reflected optical axis). It arrange | positions so that it may become the above. Accordingly, the angle formed between the optical axis of the incident light (incident optical axis) and the normal line of the first dichroic mirror 107 is 35 degrees or less, and the optical path length of the B optical path from the point M is increased. Thereby, the optical path length of the B optical path can be made equal to the optical path length of the R optical path and the optical path length of the G optical path. In other words, the angle α is set to a predetermined value so as to be equal to the optical path lengths of the other primary color optical paths. However, if the optical path length of the optical path length of the R optical path, the optical path length of the G optical path, and the optical path length of the B optical path is within ± 5%, color unevenness does not occur in practice.

  Each color light incident on each liquid crystal panel 115 is subjected to light intensity modulation (also simply referred to as modulation) according to a video signal of each color (not shown) by a drive circuit (not shown) to form an optical image. The optical image of each color light formed by each liquid crystal panel 115 is incident on the cross prism 118 via the output side polarizing plate 116 (116R, 116G, 116B).

  In the first embodiment, the output-side polarizing plate 116 is directly attached to the cross prism 118 using an adhesive or an adhesive. At this time, in order to further improve the cooling efficiency, the polarizing plate is attached to sapphire, a quartz substrate, etc. having a higher thermal conductivity than glass, and further, these are attached to the cross prism 118 using an adhesive or an adhesive. good.

  A cross prism 118 which is a color synthesis unit (also referred to as a light synthesis unit) synthesizes optical images of the respective color lights to form a color image. The color image is enlarged and projected on a screen (not shown) by a projection lens 117 which is a projection optical unit.

  Next, light shape conversion by the reflector 101 and the first lens element 104 will be described with reference to FIGS.

  FIG. 7 shows the arrangement of optical components when the design of the illumination optical system for guiding the light from the light source to the liquid crystal panel according to Example 1 is actually performed, with the optical path bent linearly replaced. It is sectional drawing containing an axis | shaft. FIG. 8 is a perspective view of FIG. FIG. 9 is a diagram illustrating the free curved surface shapes of the reflector and the first lens element according to the first embodiment. FIG. 10 is a diagram illustrating the shape of light obtained in the effective display area of the liquid crystal panel according to the first embodiment. FIG. 11 is a diagram illustrating a result of light quantity distribution obtained by ray tracing obtained on the liquid crystal panel according to the first embodiment. FIG. 12 is a diagram illustrating lens data of the illumination optical system according to the first embodiment. In addition, in each figure, the same code | symbol is attached | subjected to what has the same effect | action as the component shown in FIG.

  8 and 9, the third lens element 120 includes two lenses, a lens element 120a and a lens element 120b, in order to focus light from the light source in accordance with the shape of the effective display area of the liquid crystal panel 115 without aberration. It is divided into In addition, although the polarization conversion unit 105 is not illustrated, this is the optical distance (distance between two surfaces × refractive index of the medium) of the surface distance from the exit surface of the first lens element 104 to the field lens 123. This is because the design is converted into equivalent air (refractive index 1.0). In Example 1, the surface distance from the exit surface of the first lens element 104 to the field lens 123 is set to 58.6239 mm in terms of a converted value (see FIG. 12 for details).

  The reflector 102 has a function of reflecting the light emitted from the lamp tube 101 and condensing it in the illumination system. In order to convert light having a circular shape (circular light) emitted from the lamp tube into rectangular light having a rectangular shape similar to the effective display area of the liquid crystal panel, the reflection surface shape of the inner surface of the reflector 102 The surface shape of the first lens element is a free-form surface shape shown in Formula 1.

  Here, in order to facilitate the following description, an orthogonal coordinate system is introduced. The optical axis 100 of the illumination optical system is the Z axis, and the direction parallel to the long side of the rectangle of the effective display area of the liquid crystal panel is the X axis direction within the plane orthogonal to the Z axis, and is parallel to the short side of the rectangle. The direction is defined as the Y-axis direction.

  In the first embodiment, the shape of the reflector 102 has different cross-sectional shapes in the XZ cross section and the YZ cross section, as shown in FIGS. 8 and 9A. Similarly, as shown in FIGS. 8 and 9B, the first lens element 104 has a free-form surface having different cross-sectional shapes in the XZ cross section and the YZ cross section. That is, the reflector 102 and the first lens element 104 have a free-form surface that is rotationally asymmetric with respect to the optical axis 100 of the illumination optical system including the light emission center of the light source.

  The light from the lamp tube reflected by the reflecting surface of the rotationally asymmetric free curved surface of the reflector 102 and subjected to the rotationally asymmetric reflecting action is further reflected by the first lens element 104 having the rotationally asymmetric free curved surface shape, Receives rotationally asymmetric refraction. As a result, the shape of the light is converted into rectangular light having a shape similar to the shape of the effective display area of the liquid crystal panel 115 by the mutual lens action of the reflector 102 and the first lens element 104. The rectangular light emitted from the first lens element 104 intersects the optical axis 100, is refracted by the field lens 123 and the third lens element 120 (120a, 120b), and is applied to the liquid crystal panel 115.

  Here, “crossing the optical axis” means that a light beam reflected by the reflector 102 and incident on the first lens element 104, undergoes a refraction action at the first lens element 104, and travels toward the field lens 123. When projected onto the plane formed by the intersection of the light beam emitted from the lamp tube 101 at the reflector 102 and the optical axis 100, it reaches the opposite region divided by the optical axis 100 beyond the optical axis 100. It means that.

  That is, in the first embodiment, the light beam emitted from the lamp tube 101, for example, the light beam reflected by the reflector 102 reaches the point of the liquid crystal panel 115 in a point-symmetrical direction with respect to the optical axis 100. A mapping method in which points on 102 and points on the liquid crystal panel 115 are associated is employed.

  The coefficients that can be taken by the first embodiment corresponding to Equation 1 are shown in FIG.

但し、ｊ＝｛（ｍ＋ｎ）^２＋ｍ＋３ｎ｝／２＋１
ｒ^２＝ｘ^２＋ｙ^２
ここで Ｚ：Ｚ軸方向のサグ量,Ｃ：頂点の曲率，ｋ：コーニング係数
Ｃｊ：多項式のｘ^ｍｙ^ｎの係数

However, j = {(m + n) ² + m + 3n} / 2 + 1
r ² = x ² + y ²
Where Z: sag amount in the Z-axis direction, C: curvature of vertex, k: Corning coefficient Cj: coefficient of x ^m y ⁿ of polynomial

  How to read FIG. 12 will be described. From the figure, the distance from the light source to the reflector reflecting surface which is the first surface S1 is 6.5 mm, and the origin of the reflector reflecting surface with respect to the light source is the negative direction of the Z axis (negative) in the coordinate system shown in FIG. Direction), ie backwards. The first surface S1 is a reflecting surface of the reflector, has a radius of curvature of 14.1992 mm, and has a free-form surface shape having a coefficient corresponding to Equation 1 as well as a spherical system.

  The second surface S2 is an incident surface of the ultraviolet reflection filter 103 shown in FIGS. 7 and 8, and has an infinite radius of curvature, that is, a plane, along the optical axis from the reflector reflecting surface to the incident surface (second surface). The distance is 33.681 mm. Further, the distance between the second surface S2 and the third surface S3, that is, the thickness of the ultraviolet reflection filter 103 is 1.1 mm, and the glass material is B270 (manufactured by Corning).

  The third surface S3 is an exit surface of the ultraviolet reflection filter 103, has an infinite radius of curvature, that is, a flat surface, has a distance of 10 mm to the incident surface of the first lens element 104, which is the fourth surface S4, and a glass material (medium). Is air. In addition, the medium when there is no description in the glass material column is air (refractive index 1.0).

  The fourth surface S4 is an incident surface of the first lens element 104 and has an infinite curvature radius, that is, a plane. The shape of the fourth surface S4 is not only a spherical system but also a free-form surface having a coefficient corresponding to Equation 1. The glass material (medium) is K-VC79 (manufactured by Sumita Optical Co., Ltd.). The above is the description of the data of Example 1 shown in FIG.

  FIG. 10 shows the shape of light obtained in the effective display area of the liquid crystal panel based on the lens data described in FIG. A light source such as a high-pressure mercury lamp has an arc size of a finite size because it emits light between two electrodes. However, in the design, the light source was designed as a point light source, and the position of the point light source was moved back and forth for evaluation. FIG. 10B shows a ray tracing result at the design center (the light emission center position of the lamp tube). FIG. 10 (a) shows the result when ray tracing is performed by moving the point light source position by 0.5 mm from the light emission center position to the reflector side (minus direction of the Z-axis). On the other hand, FIG. 10C shows the result when the ray tracing is performed by moving the point light source position by 0.5 mm in the direction farther from the reflector side than the light emission center position (the positive direction of the Z axis). .

  As is apparent from FIGS. 10B and 10C, the light beam emitted from the design center position and a position far from the reflector by 0.5 mm from the design center position passes through the effective display area of the liquid crystal panel indicated by the solid rectangular frame. It can be seen that the rectangular shape is irradiated. Further, it can be confirmed that the light beam emitted from the position closer to the 0.5 mm reflector than the design center position covers the effective display area of the liquid crystal panel. That is, according to the first embodiment, even when the light source is finite, there is little blur on the image plane, and the light source with an arc length of 1.0 mm can be sufficiently handled.

  In FIG. 11A, as described above, the number of evaluation light beams is increased at three types of light source positions to perform light ray tracing, and the respective results are overlapped to calculate the light amount distribution on the liquid crystal panel surface that is the evaluation surface. It is obtained and displayed with an equal light intensity line.

  FIG. 11B is a two-dimensional display of the light amount distribution in the A-A ′ cross section and the a-a ′ cross section of the equi-light line display shown in FIG. Similarly, FIG. 11C is a two-dimensional display of the light amount distribution in the B-B ′ cross section and the b-b ′ cross section of the equal light amount display shown in FIG.

  As can be seen from the evaluation results of the light quantity distributions in FIGS. 11A, 11B, and 11C, according to the first embodiment, the light quantity distribution in the image plane is uniform and the arc length is 1 even if the light source has a finite length. It can sufficiently handle a light source of 0 mm. That is, although a pair of lens arrays as an integrator is not used, a uniform light amount distribution is realized.

  As described above, in the projection display device according to the first embodiment, the reflecting surface shape of the reflector, which is the reflecting portion that reflects the light from the light source and enters the first lens element, and the first lens element Is a rotationally asymmetric free-form surface, so that the shape of the light distribution emitted from the light source (circular shape) can be converted into a rectangular shape having a shape similar to the effective display area of the video display element. Therefore, a pair of lens arrays existing in the conventional illumination system is not necessary, and cost reduction can be realized. In addition, since the first polarizing plate that increases the degree of polarization is disposed before color separation, the incident-side polarizing plate that is conventionally disposed on the incident side of each liquid crystal panel can be omitted, and the cost can be reduced accordingly.

  Further, by setting the angle formed by the optical axis of the reflected light from the dichroic mirror 107 to 110 degrees or more with respect to the optical axis of the illumination system, the optical path lengths from the light source to the liquid crystal panel corresponding to each primary color light can be made equal to each other. . Accordingly, it is possible to reduce color unevenness and luminance unevenness generated in an image enlarged and projected on the screen by the projection lens after color synthesis. Further, by setting the equal optical path length, it is not necessary to use a relay lens optical system, and a compact illumination optical system can be realized.

  Furthermore, by using an illumination optical system that does not use a lens array, an inexpensive illumination optical system can be realized, and it is not necessary to maintain the relative position of the pair of lens arrays with high precision even on the manufacturing surface, making projection easy to assemble. A mold display device can be provided.

  FIG. 2 is an explanatory diagram of the second embodiment. Components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals.

  The projection display device according to the second embodiment shown in FIG. 2 has a field lens 123 having an effect of efficiently entering the liquid crystal panel 115 with respect to the projection display device according to the first embodiment shown in FIG. The third lens element 120 corresponding to the panel is omitted.

  Depending on the level that does not impede practical use, or the application to be applied, the field lens or the third lens element may be deleted as a method for reducing the uniformity of the light intensity distribution and reducing the cost. It is possible.

  According to the second embodiment, further cost reduction can be realized.

  FIG. 3 is an explanatory diagram of the third embodiment. Components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals.

  The difference between the third embodiment shown in FIG. 3 and the first embodiment shown in FIG. 1 is that the output side polarizing plate 116 (116R, 116G, 116B) is made of blue plate glass, white plate glass, sapphire having high thermal conductivity, a quartz substrate, or the like. And is disposed between the liquid crystal panel and the cross prism so that both sides of the output side polarizing plate and the substrate can be cooled, thereby improving the efficiency of forced air cooling.

  FIG. 4 is an explanatory diagram of the fourth embodiment. Components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals.

  In the fourth embodiment, in the third embodiment shown in FIG. 3, the polarization which is the second polarizing plate between the first color separation unit (dichroic mirror 107) and the second color separation unit (dichroic mirror 110). A plate 121 is additionally arranged.

  As a result, it is possible to further increase the degree of polarization of green and red light having a high specific visibility, so that the contrast performance of an enlarged image obtained on a screen (not shown) is improved.

  Since light in the wavelength range from green to red passes through the polarizing plate 121, the energy density is high, and an organic polarizing plate or an inorganic polarizing plate made of a highly light-resistant material is desirable. In order to reduce damage caused by light, it is desirable to select a reflective polarizing plate to obtain higher reliability.

  As shown in FIG. 4, when a reflective inorganic polarizing plate as the polarizing plate 121 is disposed perpendicular to the optical axis, the reflected light may return to the lamp tube as it is and damage the lamp. . In such a case, the reflection-type inorganic polarizing plate may be disposed so as to be inclined with respect to the optical axis so that the light does not return directly to the lamp tube. There is no loss of lamp life.

  Next, a description will be given of a fifth embodiment in which the projection display devices of the first to fourth embodiments are applied to a rear projection display device.

  FIG. 5 is a front view showing a rear projection display device using the projection display devices of Examples 1 to 4. In FIG. 5, 11 is an illumination optical system, 12 is a projection optical unit, 15 is a housing, 16 is a screen, and 17 is an optical path folding mirror. Reference numeral 14 denotes an optical unit that irradiates light from a light source onto a video display element (not shown) by the illumination optical system 11 and enlarges and projects an image formed by the video display element in accordance with the video signal by the projection optical unit 12. Show. By arranging the optical unit 14 at the center of the screen of the set, the signal circuit board 8a, the power supply circuit board 8b, and the like are incorporated in the left and right spaces generated to form a rear projection type display device. As shown in FIG. 5, the optical unit 11 is disposed at the center lower portion of the housing 15, and the image light projected therefrom is directly projected from the back side of the screen 16.

  FIG. 6 is a side view showing a rear projection display device using the projection display devices according to the first to fourth embodiments. In the figure, the same components as those shown in FIG.

  In order to reduce the depth and height of the rear projection type display device, a projection optical unit (projection lens) provided with an optical path turning part inside the lens barrel is becoming mainstream. The image light magnified by the projection optical unit 12 is once folded by the optical path folding mirror 17 disposed on the back cover 18 side of the apparatus, and then projected onto the screen 16, so that a compact rear projection display device is provided. Can be realized.

1 is a schematic diagram illustrating an optical system of a projection display device according to Embodiment 1. FIG. FIG. 6 is a layout diagram illustrating an illumination optical system of a projection display device according to a second embodiment. FIG. 6 is a layout diagram illustrating an illumination optical system of a projection display device according to a third embodiment. FIG. 7 is a layout diagram illustrating an illumination optical system of a projection display device according to a fourth embodiment. FIG. 10 is a front view showing a rear projection display device according to a fifth embodiment. FIG. 10 is a side view showing a rear projection display device according to a fifth embodiment. FIG. 3 is an explanatory diagram illustrating an illumination optical system of the projection display device according to the first embodiment. 1 is a perspective view of an illumination optical system of a projection display device according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating free-form surface shapes of the reflector and the first lens element according to the first embodiment. FIG. 6 is a diagram showing a result of ray tracing on an image display element by the illumination optical system of Example 1. FIG. 5 is a diagram illustrating a result of light amount distribution obtained by ray tracing obtained on the image display element by the illumination optical system according to the first embodiment. FIG. 3 is a diagram showing lens data of the illumination optical system of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Illumination optical system, 12 ... Projection optical unit, 14 ... Optical unit, 8a ... Signal circuit board, 8b ... Power supply circuit board, 15 ... Case, 16 ... Screen, 17 ... Optical path folding mirror, 18 ... Back cover, 100 DESCRIPTION OF SYMBOLS ... Optical axis, 101 ... Lamp tube, 102 ... Reflector, 103 ... Ultraviolet reflection filter, 104 ... First lens element, 105 ... Polarization converter, 123 ... Field lens, 106 ... First polarizing plate, 107 ... First 1 dichroic mirror, 109, 111, 112, 113... Optical path folding mirror, 110... 2 dichroic mirror, 120... Third lens element, 115. 118: Cross prism, 121: Polarizing plate.

Claims (12)

A light source that emits light;
A reflector that reflects light from the light source;
A first lens element that transmits light from the reflector;
A polarization converter that aligns light from the first lens element in a desired polarization direction;
A first color separation unit that separates light from the light source into first primary color light and second and third primary color light;
A second color separation unit that separates the second and third primary color lights separated by the first color separation unit;
First, second, and third video display elements disposed corresponding to each of the first, second, and third primary color lights;
A cross prism for synthesizing light from the first, second and third video display elements;
A projection lens for projecting light from the cross prism;
A polarizing plate disposed between the polarization conversion unit and the first color separation unit,
The projection display device, wherein optical distances from the first lens element to the image display elements corresponding to the primary color lights are equal. The projection display device according to claim 1,
The projection display device, wherein the first polarizing plate is a reflective polarizing plate. The projection display device according to claim 1,
The projection display device, wherein the first polarizing plate is formed of an inorganic material. A light source that emits light;
A reflector that reflects light from the light source;
A first lens element that transmits light from the reflector;
A polarization converter that aligns light from the first lens element in a desired polarization direction;
A first color separation unit that separates light from the light source into first primary color light and second and third primary color light;
A second color separation unit that separates the second and third primary color lights separated by the first color separation unit;
First, second, and third video display elements disposed corresponding to each of the first, second, and third primary color lights;
A cross prism for synthesizing light from the first, second and third video display elements;
A projection lens for projecting light from the cross prism;
A first polarizing plate disposed between the polarization conversion unit and the first color separation unit;
A second polarizing plate disposed between the first color separation unit and the second color separation unit,
The projection display device, wherein optical distances from the first lens element to the image display elements corresponding to the primary color lights are equal. The projection display device according to claim 1,
The projection display device, wherein the first and second polarizing plates are reflective polarizing plates. The projection display device according to claim 1,
The projection display device, wherein the first and second polarizing plates are formed of an inorganic material.   5. The projection type display device according to claim 4, wherein a polarizing plate is disposed between the first color separation means and the image display element corresponding to the first primary color light. The projection type display device according to claim 1,
The first lens element is:

However, j = {(m + n) ² + m + 3n} / 2 + 1
r ² = x ² + y ²
Where Z: sag amount in the Z-axis direction, C: curvature of vertex, k: Corning coefficient Cj: coefficient of x ^m y ⁿ of polynomial

A projection-type display device having a shape defined by the formula: The projection display device according to claim 1, wherein
The reflector is

However, j = {(m + n) ² + m + 3n} / 2 + 1
r ² = x ² + y ²
Where Z: sag amount in the Z-axis direction, C: curvature of vertex, k: Corning coefficient Cj: coefficient of x ^m y ⁿ of polynomial

A projection-type display device having a shape defined by the formula: The projection display device according to claim 1, wherein
An angle formed by the first primary color light separated by the first color separation unit and the second and third primary color lights is 110 degrees or more. The projection display device according to claim 1,
The projection type display device, wherein the light source is any one of an ultra-high pressure mercury lamp, a xenon lamp, and a metal haloid lamp. A projection display device according to claim 1;
A folding mirror that folds the optical path of the light from the projection display device;
A rear projection display device having a screen for displaying light from the folding mirror.

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