JP4135001B2 - Video display device - Google Patents

Description

  The present invention uses a light valve element such as a liquid crystal panel or a reflective video display element to project an image on a screen, for example, a liquid crystal projector apparatus, a reflective video display projector apparatus, a liquid crystal television, The present invention relates to a technology such as a projection display device.

  2. Description of the Related Art There is known a projection display apparatus such as a liquid crystal projector that projects light on a liquid crystal panel by applying light from a light source such as a light bulb to a light valve element such as a liquid crystal panel.

  This type of video display device adjusts light from a light source by changing it to light and dark for each pixel with a light valve element, and projects it onto a screen or the like. For example, a twisted nematic (TN) type liquid crystal display element, which is a typical example of a liquid crystal display element, has a polarization direction before and after a liquid crystal cell formed by injecting liquid crystal between a pair of transparent substrates having a transparent electrode film. The two polarizing plates are arranged so that they are different from each other by 90 °. By combining the action of rotating the polarization plane by the electro-optic effect of the liquid crystal and the selection of the polarizing component of the polarizing plate, Image information is displayed by controlling the amount of transmitted light. In recent years, in such a transmissive or reflective video display element, the element itself has been miniaturized and the performance such as resolution has been rapidly improved.

  For this reason, a display device using the image display element has been improved in size and performance, and not only simply performing image display by a video signal or the like as in the prior art, but also a projection image display device as an image output device of a personal computer. Has also been proposed. This type of projection-type image display device is particularly required to be small in size and to obtain bright images at every corner of the screen. However, the conventional projection-type video display device has a problem that it is large-sized or has insufficient performance such as brightness and image quality of the finally obtained image.

  For example, to reduce the size of the entire liquid crystal display device, it is effective to reduce the size of the light valve, that is, the liquid crystal display element itself. If the liquid crystal display element is reduced in size with respect to the amount of luminous flux, the area irradiated by the illumination means is reduced, so the ratio of the luminous flux on the liquid crystal display element to the total luminous flux emitted by the light source (hereinafter referred to as light utilization efficiency) This causes problems such as lowering and darkness in the periphery of the screen. Furthermore, since the liquid crystal display element can use only polarized light in one direction, about half of the light from the light source that emits randomly polarized light is not used.

  As an optical system for irradiating a liquid crystal display element with randomly polarized light from a light source aligned in one polarization direction, a polarizing beam splitter (hereinafter referred to as PBS) disclosed in Japanese Patent Laid-Open No. 4-63318 is used. In some cases, random polarized light emitted from a light source is separated into P-polarized light and S-polarized light and synthesized using a prism.

  In addition, with this, in conventional optical systems, particularly in an illumination optical system using a reflective liquid crystal display device, the above-mentioned PBS and reflective liquid crystal display device are combined for ON / OFF and gradation expression of an image. Accordingly, the light is analyzed by changing the polarization direction, and then the image is projected onto the screen by the projection lens. In this case, color unevenness and contrast reduction caused by PBS are regarded as problems.

  That is, since the characteristics of the transmittance of the P-polarized light and the reflectance of the S-polarized light with respect to the incident angle of light change, the transmittance and reflectance unevenness of the PBS occur with respect to the light at a predetermined angle of the illumination system. As a result, the image quality projected on the screen is degraded.

  A transparent material sandwiching a PB film as disclosed in Japanese Patent Application Laid-Open No. 09-054213 is made of PBS made of a glass material whose absolute value of photoelastic coefficient is 1.5 × 10 −8 cm 2 / N or less. Some reduce the birefringence in the PBS glass and improve the contrast on the screen.

  However, in the present invention, no consideration is given to the distortion at the time of bonding at the bonding site and the distortion at the bonding site due to temperature change, and the birefringence phenomenon due to this distortion is not considered.

  Further, no measures are taken against the light use efficiency deterioration and the color unevenness phenomenon due to the characteristic change due to the incident light angle of the PB film itself.

  Therefore, although the birefringence phenomenon of only the prism glass material itself has been reduced, the effect of reducing the birefringence phenomenon of the entire PBS or dichroic prism is insufficient. Furthermore, since measures for reducing the light utilization efficiency and the extinction ratio due to the angle characteristics are not taken, brightness, color unevenness, and contrast tend to be insufficient.

  Further, the boundary surface on which the PB film is provided is limited, and there are two or more types of dielectric multilayer films, such as a PB film and an adjustment AR film, and the structure of a PBS or a dichroic prism having a characteristic of providing a plurality of layer pairs. It is impossible. Therefore, it is impossible to increase the polarization purity and improve the accuracy of the image quality performance by stacking a plurality of layers of the PB film and the adjustment AR film as a pair.

  From the above, it is necessary to take measures from the two viewpoints of improving the brightness and image quality of the video display device.

JP-A-4-63318 JP 09-054213 A

  Summarizing the above issues in the prior art, there is a problem of how to ensure the performance of the video display device in terms of brightness and image quality, and technologies for addressing issues related to brightness and image quality improvement are issues. Yes. That is, in order to ensure brightness, improve contrast, and reduce color unevenness, improving the light efficiency of PBS and further reducing birefringence are problems.

  An object of the present invention is to provide a projection display technique capable of ensuring high brightness and image quality and miniaturizing with respect to the above-described problems in the prior art.

  A part of the outgoing light A from the light source unit is transmitted to the transmission prism means along the transmission optical axis, and the remaining part of the outgoing light B from the light source unit is reflected by the reflecting means such as a mirror or a total reflection prism. Converted to the outgoing optical axis side, this reflected light B is reflected by an inclined surface provided through an air gap substantially parallel to the inclined surface of the transmitting prism means and through which the outgoing light A is transmitted, The light beam compression means is composed of a transmission prism means and a reflection means for aligning the optical axis of the outgoing light B substantially in the same optical axis direction as A and compressing the light in the vertical direction or the horizontal direction with respect to the optical axis of the illumination system.

  As a result, the light beam width can be compressed vertically or horizontally while preserving the angle of the light, so that it is possible to prevent the problem of lens aberration due to compression and the deterioration of the illumination system efficiency due to the spread of the divergence angle. Good light beam compression is possible.

  Further, in this light beam compression means, the angle θ1 formed with the orthogonal plane of the transmission optical axis, which is the inclination of the first inclined surface of the transmission prism means of the light beam compression means, is equal to or smaller than the critical angle θ01 of the optical member of the transmission prism, that is, θ01. > Θ1, for example, BK7 is set to be close to ± 41 ° or less. As a result, even various glass materials such as BK7 can transmit the outgoing light A using the total reflection angle. Further, the BK7 can constitute the transmission prism means of the light beam compression means, so that the cost can be reduced.

  Further, in this light beam compressing means, the angle formed by the third inclined surface of the reflecting means and the orthogonal plane of the transmission optical axis of the transmission prism is θ1 = θ4, and the normal line, the incident optical axis and the normal line The angle θ3 formed by the reflection optical axis is set to be not less than the critical angle θ02 of the optical member of the reflection synthesizing means, that is, θ02 <θ3, for example, in the vicinity of ± 41 ° or more for BK7. As a result, the first inclined surface of the transmission prism means and the third inclined surface of the reflection combining means can be joined via a predetermined gap, and can be joined to each other by an adhesive, a spacer, a thin film, printing, or the like outside the effective area. Manufacturing becomes easy.

  Further, since the incident optical axis and the outgoing optical axis do not change with respect to the transmitted light, the later illumination system can be easily designed. Naturally, light flux compression with high light utilization efficiency is possible.

  Further, the inclination θ2 of the second inclined surface of the reflection combining unit is an angle formed with the plane perpendicular to the optical axis of the light incident on the reflection combining unit, and θ2 = (θ1 + θ3) / 2, for example, θ3 = ± in BK7. In the case of 41 °, θ2 is in the vicinity of ± 41.5 °.

  As a result, even with the glass material of BK7, it is possible to reflect the outgoing light B by total reflection using the total reflection angle. Further, since this light beam compression means can be constituted by BK7, it is possible to further reduce the cost.

  Furthermore, light flux compression with high light utilization efficiency is possible.

  Further, the reflecting means of the light beam compressing means has a prism configuration, and the prism glass material has a refractive index different from that of the transmission prism glass material. Thus, by adjusting the angle of the first inclined surface of the reflecting prism, the light of the light totally reflected by the second inclined surface of the reflecting prism arranged in parallel with the inclined surface of the transmitting prism via the air gap It is possible to make the axis coincide with the transmission optical axis of the transmission prism.

  Thereby, it is also possible to improve the light use efficiency in the whole illumination system.

  Further, a reflection type video display element of a light valve means for forming an optical image corresponding to a video signal from light emitted from a light source unit, an illumination optical system for irradiating light on the reflection type video display element, and the reflection type A projection type optical engine or a video display device configured to project light emitted from the video display element, wherein the light incident on the reflective video display element is polarized and the reflective type Illumination having a polarization conversion element for detecting reflected light whose polarization has been converted by an image display element, and color separation / synthesis means for reflecting or transmitting light entering / exiting the reflection image display element or the polarization conversion element only in a specific wavelength range In this illumination optical system, an up-and-down direction f value that is perpendicular to the optical axis surface of the polarization conversion element and / or the color separation / synthesis means, and a left-right direction that is orthogonal Relationship between the values constitute the vertical f value> illumination optical system is a relationship in the lateral direction f value.

  This compresses the light in a direction that is disadvantageous in the angular performance of the polarization conversion element and reduces the angle, so that high-precision optical performance can be maintained, and the angular characteristics, light utilization efficiency, or analysis efficiency can be maintained. Improvement and reduction of birefringence can be achieved with ease.

  Further, in the projection type optical engine or image display device, the light source compression unit for the light emitted from the light source unit and the light source unit is, for example, a combination of convex and concave cylindrical lenses, or a combination of eccentric lenses, and / or a prism. Or a combination of mirrors and / or combinations of polarization conversion elements, having a vertical light compression means that is perpendicular to the optical axis surface of the illumination optical system, or a horizontal light compression means that is horizontal. It was.

  With such a configuration, it is possible to reduce extinction ratio deterioration due to inclined light, which occurs in the dielectric multilayer film of the PBS or the color separation prism, and to reduce color unevenness in image quality and change in contrast characteristics due to temperature change.

  Thereby, the extinction ratio of PBS is improved, and the light detection efficiency and color separation efficiency by polarization separation can be improved. In addition, this configuration can increase the polarization purity and improve the accuracy of image quality performance.

  In addition, by mounting the illumination optical system on a projection-type image display device, it is possible to achieve both brightness and contrast performance that could not be realized conventionally.

  According to the present invention, the light beam width can be compressed in the vertical and horizontal directions while maintaining the angle of the light, so that it is possible to prevent lens aberration problems due to compression and the spread of the angle, thereby enabling efficient light beam compression. Therefore, it is possible to provide an image display device that achieves both the miniaturization of the optical system and the brightness performance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an optical configuration diagram of an embodiment of a projection type liquid crystal display device according to the present invention. In the embodiment of FIG. 1, a total of three reflective liquid crystal display elements 2 corresponding to the three primary colors R (red), G (green), and B (blue) are used as liquid crystal light valves. A three-plate projection display device is shown.

  In FIG. 1, the projection type liquid crystal display device has a light source 1, and the light source 1 is a white lamp such as an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, or a halogen lamp. The light source 1 includes at least one reflecting surface mirror 5 having a circular or polygonal exit aperture, and light emitted from the light source 1 passes through a liquid crystal display element 2 which is a light valve element and travels toward a projection lens 3 to be screened. 4 is projected.

  The light emitted from the light bulb of the light source 1 is collected by the ellipsoidal, parabolic or aspherical reflector 5 and enters the light beam compression means 26, where the light beam width of either the left or right or top and bottom is compressed. The That is, the f value of the illumination system is converted. In the case of FIG. 1, the light flux width in the depth direction is compressed from the front of the figure. It is composed of a plurality of condensing lenses provided in a rectangular frame of approximately the same size as the exit aperture of the light beam compression means 26, and condenses the light emitted from the lamp unit to form a plurality of secondary light source images. The first array lens 6 is made up of a plurality of condensing lenses, arranged in the vicinity of the plurality of secondary light source images, and is arranged on the liquid crystal display element 2. It passes through the second array lens 7 for forming the individual lens images. The emitted light is incident on a row of rhomboid prisms of approximately ½ size of each lens width arranged so as to match the pitch in the horizontal direction of each lens optical axis of the second array lens 7. The prism surface is provided with a polarizing beam splitter 8. The incident light is separated into P-polarized light and S-polarized light by the polarizing beam splitter 8. The P-polarized light passes through the polarization beam splitter 8 as it is, and the polarization direction is rotated by 90 ° by the λ / 2 phase difference plate 9 provided on the exit surface of this prism, and is converted into S-polarized light and emitted. The On the other hand, the S-polarized light is reflected by the polarization beam splitter 8, reflected once again in the original optical axis direction in the adjacent rhomboid prism, and then emitted as S-polarized light. The emitted light enters the condenser lens 10.

  In a projection type liquid crystal display device using a conventional reflective liquid crystal display element, the amount of reflected light is halved because only one direction of polarized light is reflected by the combination of the incident polarizing plate and the reflective liquid crystal display element. However, since the polarization beam splitter 8 is used, the polarization direction of the randomly polarized light emitted from the light source 1 is aligned and incident on the reflective liquid crystal display element 2, so that it is ideally twice that of a conventional projection liquid crystal display device. Can be obtained.

  In addition, the array lenses 6 and 7 have an effect that an individual image of each lens cell is superimposed on the liquid crystal display element 2 and uniform image quality is obtained.

  The condenser lens 10 has at least one structure, has a positive refractive power, has a function of further condensing the S-polarized light, and the light that has passed through the condenser lens 10 is reflected mirrors 11 and 12. The optical axis direction is converted by 90 ° in a predetermined direction. Thereafter, in order to illuminate the three reflective liquid crystal display elements 2R, 2G, and 2B for each color RGB, the light is divided into G light, R light, and B light by a color separation mirror 13 or a color separation prism (not shown). The light is divided and incident on PBSs 16G and 16RB, which are polarization conversion elements dedicated to the respective colors. That is, the G light is incident on the G-dedicated PBS 16G according to the present invention, and is then S-polarized light, so that it is reflected toward the G-dedicated reflective liquid crystal display element 2G and irradiates this panel. Further, the B light and the R light pass through the B-R light-dedicated polarizing plate 14, enter the RB-dedicated PBS 16 RB according to the present invention, and then pass through the specific wavelength selection wavelength plate 17 that converts the polarization direction only in a specific wavelength region. Then, the polarization of either B light or R light is converted from S polarization light to P polarization light. For example, the B light that is P polarization light whose polarization has been converted passes through the PBS 16RB dedicated to RB. The B-only reflective liquid crystal display element 2B is irradiated. On the other hand, since the R light is S-polarized light, it is reflected by the R-B dedicated PBS 16RB, and then irradiates the R-only reflective liquid crystal display element 2R. Of course, the above example is one specific example, and the embodiment is not limited to this. R may be converted into P-polarized light, and apart from this, the polarized light of the original illumination system is P-polarized light. There is also a configuration in which one RGB color is converted to S-polarized light and the remaining two colors are P-polarized light. Further, an RB-dedicated incident polarizing plate 14 and a G-dedicated incident polarizing plate 15 that transmit S-polarized light are disposed on the incident side of the reflective liquid crystal display elements 2R, 2G, and 2B dedicated to each color, and the degree of polarization and / or color of each color is arranged. It is also possible to increase the purity. Thereafter, the polarized light is converted by the reflection type image display element 2 dedicated to each color, the light again enters the PBSs 15 and 16 dedicated to each color, the S-polarized light is reflected, and the P-polarized light is transmitted.

  The reflective image display element 2 is provided with a number of liquid crystal display units corresponding to the pixels to be displayed (for example, 1024 horizontal pixels by 768 vertical pixels). Then, the polarization angle of each pixel of the liquid crystal display element 2 changes according to a signal driven from the outside, and finally light that is orthogonal to the incident polarization direction is emitted. Analyzed. The amount of light passing through the PBS and the amount of light detected for the light having polarized light at an intermediate angle are determined in relation to the degree of polarization of the PBS 2. In this way, an image according to a signal input from the outside is projected. At this time, the polarization conversion elements that are the G-dedicated PBS 16G and the RB-dedicated PBS 16RB of the present invention have the same polarization direction as that of the incident light when the reflective image display elements 2R, 2G, and 2B perform black display. As it is, it is returned to the light source side along the incident optical path. However, if the detection efficiency, which is the polarization degree and extinction ratio of PBS, is the conventional illumination system, the light in the weak direction of PBS film becomes slightly polarized or distorted polarized light and passes through PBS. The light passes through the color synthesizing mirror 19 or the color synthesizing prism on the emission side and is irradiated to the projection lens 20 side, and a slight brightness is detected on the screen during black display. As a result, the contrast performance is lowered, which has been a problem in the past. Therefore, according to the present invention, in the illumination optical system, the f value in the vertical direction (depth direction in FIG. 1) which is perpendicular to the optical axis plane of the PBS or the color separation / combination means, and the horizontal direction orthogonal to the f value. (Depicted in the vertical direction in FIG. 1) The illumination optical system in which the relationship of the f value is the relationship of the vertical f value> the horizontal f value allows the light beam angle in the weakest direction of the PBS film characteristics to be Since it is made smaller with respect to the axis, there is an effect that it is possible to reduce the color unevenness in the image quality and the change in the contrast characteristic due to the PBS angle dependency. As a result, the polarization purity can be improved and the accuracy of the image quality performance can be improved. Therefore, it is possible to improve light utilization efficiency, extinction ratio, brightness, color unevenness, and contrast due to angle characteristics that have been insufficient in the past.

  Therefore, it is possible to provide a reflective liquid crystal display device that achieves both high-precision color reproducibility, high brightness, and high-efficiency contrast.

  Thereafter, the light of each color of RGB, which is an image, is color-combined again by the dichroic mirror 19 or a dichroic prism (not shown), and the light passes through the projection means 20 such as a zoom lens and reaches the screen. . The images formed on the reflective liquid crystal display elements 2R, 2G, and 2B by the projection means 20 are enlarged and projected on a screen to function as a display device. In the reflection type liquid crystal display device using the three reflection type liquid crystal display elements, a power source 21 drives a lamp and a panel.

  Therefore, in the conventional reflective liquid crystal display device, the brightness can be improved by improving the contrast, and further the performance improvement such as color unevenness can be realized at the same time.

  FIG. 2 is a diagram showing an embodiment of the first light beam compression means according to the present invention.

  FIG. 6A shows a transmission prism means 32 having an inclined surface that transmits a part of the outgoing light A from the light source units 1 and 5 of the present invention along the transmission optical axis, and the remaining light source units 1 and 5. The output light B in the range is bent to the transmission optical axis side by a first inclined surface of the reflection means 31, for example, a mirror or a total reflection prism, and this reflection light B is emitted from the transmission prism means 32. The reflected light is reflected by the second inclined surface of the reflecting means 31 provided substantially parallel to the inclined surface through the air gap, and the outgoing light B is reflected in the optical axis direction substantially the same as the outgoing light A. The optical axis is aligned, and the light beam compression means 26 is composed of the transmission prism means 32 and the reflection means 31 that compress the D-width light flux of the light source units 1 and 5 into the d-width light flux in the vertical direction or the left-right direction with respect to the optical axis of the illumination system. Configure.

  In this light beam compression means 26, the angle θ1 between the inclination of the inclined surface of the transmission prism means 32 and the surface orthogonal to the transmission optical axis is ± 41 ° or less.

  Further, the angle θ2 between the inclination of the first inclined surface of the reflecting means 31 of the light beam compressing means 26 and the surface orthogonal to the incident optical axis is set to ± 41.5 ° or less.

  As a result, even with the glass material of BK7, it is possible to totally reflect the outgoing light B on the second inclined surface using the total reflection angle. Further, since the light beam compressing means 26 can be configured by the BK7, it is possible to further reduce the cost.

  Thus, the light beam width can be compressed vertically or horizontally while the angle of the light is preserved, so that the problem of lens aberration due to compression and the spread of the angle can be prevented, thereby enabling efficient light beam compression.

  As a result, it is possible to improve light utilization efficiency, extinction ratio improvement, brightness improvement, color unevenness reduction, and contrast due to angle characteristics of PBS in front of the panel, which was insufficient in the past.

  On the other hand, FIG. (B) shows an embodiment of a light beam compression means different from that in FIG.

  The present embodiment is a cylindrical lens, and light beams emitted from the light source units 1 and 5 are compressed to the optical axis side by a first cylindrical lens 33 having a positive refractive power, and then a second cylindrical lens having a negative refractive power. , And is compressed to a predetermined light flux width d substantially parallel to the optical axis direction. Thereby, the light beam compressing means 26 for compressing the light beam vertically and horizontally can be provided by a combination of simple cylindrical lenses 33 and 34.

  However, in this case, it is necessary to design in a direction to reduce aberrations as much as possible.

  FIG. 3C shows an example of another light beam compressing means.

  The light beam emitted from the light source unit forms a secondary light source image by the lens array 35, and is arranged in a strip shape at this image plane position, and a plurality of PBSs (polarization conversion elements) arranged on the optical axis of the lens array 35. 36, and the polarization directions are aligned with the P-polarized light or the S-polarized light by the ½λ wave plates 9 arranged in every other row, and all the light is aligned in one of the polarization directions. Thereafter, the emitted light is incident on the polarization conversion element (PBS) 37 again. At this time, for example, if all of the outgoing light from the preceding PBS 36 is S-polarized light, the PBS 37 transmitted light is converted into P-polarized light by the 1 / 2λ wavelength plate 9 again, and the reflected light passes through the PBS 37 reflection optical path. The light is used as S-polarized light. At this time, the outgoing light beam width of the PBS 37 is compressed to the d width. As described above, the light beam compressing means 26 includes the array lens 35 and the two-stage PBSs 36 and 37.

  Even in this case, the beam width can be compressed in the vertical and horizontal directions while preserving the angle of the light, preventing problems of lens aberration due to compression, widening of the angle, and slight optical axis deviation of reflected light with respect to the transmitted optical axis. As a result, efficient light beam compression is possible.

  Therefore, light utilization efficiency such as PBS, dichroic prism or polarizing plate or liquid crystal panel on the downstream side of the illumination system due to angular characteristics that was insufficient in the past, as well as improved extinction ratio, improved brightness, reduced color unevenness and Contrast can be improved. This method is effective when a reflective image display element that does not depend on polarization, such as a micromirror device, is used as the image display element.

  In addition, the embodiments of (a), (b), and (c) are not limited to one direction, and can be combined and compressed vertically and horizontally or in the other direction.

  Further, when a plurality of light source units are arranged, for example, when two or more light source units are arranged with their emission openings arranged in parallel, the light flux compressing means shown in the embodiments of (a), (b) and (c) is used. The compression of the light emitted from the light source unit can be easily realized.

  FIG. 3 is a diagram showing details of the light beam compression means as the first embodiment according to the present invention.

  Transmitting prism means 32 having an inclined surface that transmits a part of the outgoing light A from the light source units 1 and 5 along the transmission optical axis, and reflecting means for the remaining outgoing light B from the light source units 1 and 5 A first inclined surface 31 of, for example, a mirror or a total reflection prism, the optical axis is bent toward the transmission optical axis, and the reflected light B is transmitted through the outgoing light A of the transmission prism means 32; The light reflected from the second inclined surface of the reflecting means 31 provided in parallel via an air gap or the like is aligned with the optical axis of the outgoing light B in the optical axis direction substantially the same as the outgoing light A, and the light of the illumination system The light beam compression means 26 is constituted by the transmission prism means 32 and the reflection means 31 for compressing the D-width light flux of the light source units 1 and 5 with respect to the axis into the d-width light flux in the vertical direction or the left-right direction.

  In this light beam compression means 26, the angle θ1 between the inclination of the inclined surface of the transmission prism means 32 and the surface orthogonal to the transmission optical axis is ± 41 ° or less.

  Further, the angle θ2 between the inclination of the first inclined surface of the reflecting means 31 of the light beam compressing means 26 and the surface orthogonal to the incident optical axis is set to ± 41.5 ° or less.

  This value is a case where a glass material of BK7 is used for the transmission prism 32 and the reflection prism 31, and the reflection of the outgoing light B can be totally reflected on the second inclined surface using the total reflection angle. . Further, since the light beam compressing means 26 can be configured by the BK7, it is possible to further reduce the cost. In addition, in the case of a refractive index near 1.474 such as Pyrex, the angle corresponding to this, that is, θ1 is 42 ° or less, and θ2 is 42.5 ° or less. Conversely, if the glass material has a refractive index of 1.523, θ1 is 40 ° or less, θ2 is 42 ° or less, and if the glass material has a refractive index of 1.6, θ1 is 38 ° or less, and θ2 is 38.5 ° or less. The conditions are slightly different. Accordingly, θ1 is equal to or smaller than the critical angle obtained by θ01 = sin−1 (1 / n2), that is, θ1 <sin−1 (1 / n2), and transmitted light is transmitted from the medium of the transmission prism 32 to the first inclined surface. 40 and the third inclined surface 39 are in such a condition that total reflection does not occur. Conversely, the reflected light is adjusted on the second inclined surface 38 of the reflection combining prism 31, and θ 2 and θ 4 are set so as to be totally reflected by the third inclined surface 39. At this time, θ4 is θ1 = θ4, and θ3, which is an angle formed by the normal line of the third inclined surface 39 and the incident optical axis, and the normal line and the reflected optical axis, is the critical angle of the optical member of the reflection combining prism 31 θ02 and critical angle θ02 = sin −1 (1 / n1). That is, θ3> sin−1 (1 / n1), that is, θ02 <θ3, for example, in BK7, a relationship of about ± 41 ° or more is established. However, this is one embodiment of the present invention, and the transmission prism and the reflection combining prism use different glass materials, or the first inclined surface 40 and the third inclined surface 39 are not parallel, that is, θ1 ≠. A configuration of θ4 is also conceivable. As a result, the optical axes of the transmitted light and the reflected light can be substantially aligned with the transmitted optical axis. That is, only one of the optical axis angle deviations is shared by the transmitted optical axis and the reflected optical axis, thereby reducing the absolute value of the optical axis angular deviation and improving the efficiency.

  Of course, the first inclined surface 40 of the transmission prism 32 is provided with an antireflection film and an AR coat. Thus, the light beam width can be compressed vertically or horizontally while the angle of the light is preserved, so that the problem of lens aberration due to compression and the spread of the angle can be prevented, thereby enabling efficient light beam compression.

  Further, a configuration in which the reflecting means of the light beam compressing means has a prism configuration and the prism glass material has a refractive index different from that of the transmission prism glass material is also conceivable. This is possible because of the illumination system. For example, when the refractive index of the glass material of the reflecting means 31 is n1, and the refractive index of the glass material of the transmission prism 32 is n2, the second inclined surface is obtained when n1> n2. The optical axis of the light totally reflected at 39 can finally be made almost coincident with the optical axis of the transmitted light. In this case, the selection of the refractive indexes of n1 and n2 is important, but in general, when the refractive index of the glass material of the transmission prism 32 and the reflection prism 31 is changed, the optical axis of the transmitted light is slightly refracted. It is necessary to consider a combination of glass materials that has the highest light utilization efficiency of the entire illumination system. As an example, it is conceivable that θ1 = 38 ° and θ2 = 39.5 ° using the glass material of n2 = 1.5168 for the transmission prism 32 and n1 = 1.56883 for the reflection prism 31.

  Thus, the light beam width can be compressed vertically or horizontally while the angle of the light is preserved, so that the problem of lens aberration due to compression and the spread of the angle can be prevented, thereby enabling efficient light beam compression.

  FIG. 4 is a view showing an embodiment of the first light beam compression means according to the present invention.

  FIG. 1A shows a configuration in which a plurality of light source units 1 and 5 of the present invention are arranged and arranged, and the emitted light beam is compressed. In the case of FIG. 1 (a), the light source units 1 and 5 are arranged in a row, and the light flux in one direction, in this case, the vertical direction, that is, the direction in which the light source units 1 and 5 are aligned is compressed. The figure is shown.

  As a result, the luminous flux of the light source can be compressed while the angle of the luminous flux is preserved, the size of the optical illumination system can be reduced, and more than two light source units can be used, so that the brightness is improved. .

  FIGS. (B) and (c) show an example of a configuration that uses two or more of the present invention and compresses the luminous flux width of the illumination system both vertically and horizontally. In this case, the light beam compression means 26 after the light source units 1 and 5 can be sequentially subjected to vertical compression and horizontal compression so that the compression directions are orthogonal to each other in a plane orthogonal to the respective transmission optical axes. In this configuration, a plurality of light beam compression means 26 are arranged.

  Thus, even if a plurality of light source units 1 and 5 are arranged, two (b) are arranged in parallel, and (c) shows four arranged light sources, but this corresponds to the arrangement of the light sources. However, it can be compressed in any direction, and the final luminous flux diameter of the illumination system can be compressed. Therefore, it is possible to provide an image display device that achieves both the miniaturization of the optical system and the brightness performance.

1 is a configuration diagram of a projection type liquid crystal display device as a first embodiment of the present invention. It is a figure which shows the 1st embodiment of this invention. It is a figure which shows the 1st embodiment of this invention. It is a figure which shows the 2nd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source, 2G, 2R, 2B ... Reflective type image display element, 5 ... Reflector, 6 ... 1st array lens, 7 ... 2nd array lens, 8 ... Polarization beam splitter (PBS), 10 ... Condenser lens, DESCRIPTION OF SYMBOLS 11 ... Reflection mirror, 13 ... Dichroic mirror, 14 ... Incident polarizing plate, 16 ... PBS for exclusive use of G, PBS for exclusive use of RB, 17 ... Specific wavelength selection polarized light conversion element, 20 ... Projection lens, 22 ... Optical member, 23 ... Prism Glass material 25... Dielectric multilayer film 26. Light flux compression means 31. Reflection synthesis means 32. Transmission prism means

Claims (2)

An illumination optical system having at least one light source unit and at least a polarization beam splitter, and emitting light from the light source unit via the polarization beam splitter, and light from the illumination optical system according to a video signal A video display device including a video display element that modulates the optical image, and a projection unit that projects light from the video display element,
In the illumination optical system, a first f value in a direction orthogonal to a plane including the optical axis of the light source unit and the optical axis of the illumination optical system is parallel to the plane, and the optical axis of the light source unit And a second f value in a direction orthogonal to the image display device. The video display device according to claim 1,
The illumination optical system has first and second cylindrical lenses,
An image display device, wherein the first and second cylindrical lenses make the first f value larger than the second f value.

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