JP2008191466A - Projection display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the distortion of a projected image of a waveguide type display which is made thin, with a compact, inexpensive and simple configuration by propagating image projection light by using a waveguide. <P>SOLUTION: The projection optical path of the image projection light which is emitted from a lamp light source 1, spatially modulated by a liquid crystal display element 2 and enlarged by a projection lens 3 is corrected by free-form-surface lenses 4 and 5 having no axial symmetry of two faces, the image projection light is made incident on a same position I on the incident face 6i of a wedge type light guide plate composed of flat faces, the image projection light propagated in the wedge type light guide plate 6 is emitted from a predetermined position of the emission face 6b of the wedge type light guide plate, and displayed on a predetermined position on a screen 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a projection display device, and more specifically, to a light guide type display device that can be made thin by propagating image projection light using a light guide.

  The projection display device is a display device that displays an image displayed on a large screen by enlarging and projecting an image displayed on a small display element such as a liquid crystal display element on a screen by a projection optical system.

  Such a display device can be easily enlarged by increasing the magnification ratio of the projection optical system, and has an excellent feature that can realize a large-screen display device at low cost.

  On the other hand, however, the projection display device has a drawback in that the device becomes large and requires a large installation area in order to secure a sufficient projection optical path for image projection.

In order to improve such a defect, a light guide type display device has been proposed in which projection light is propagated using a light guide, thereby enabling a reduction in thickness and size. (For example, refer to Patent Document 1).
Japanese translation of PCT publication No. 2003-1528356 (paragraphs 0010, 0012 to 0013, FIGS. 1 and 2)

  However, when propagating projection light using a light guide, as described in Patent Document 1 above, there is a problem that distortion is generated in a projected image only by using a light guide constituted by a plane. Occurs. In the above-mentioned patent document 1, in order to eliminate this distortion, the pixel arrangement of the display element is complicated to correct the distortion by a method of configuring the pixel arrangement in a special arrangement so as to correct the distortion caused by the light guide path, or the surface shape of the light guide path. A method for giving a simple shape change is described. However, these methods have a problem in that the cost is high because a special display element arrangement and a complicated light guide path are required.

  In addition, when manufacturing a large-sized light guide, it is extremely high-precision processing and temperature change is small if it is attempted to prevent distortion due to individual differences in the light guide and the occurrence of distortion due to changes in surface shape due to temperature changes. There was a problem that it was necessary to apply a material and the cost was further increased.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a projection display device that has a simple configuration, has no image distortion, and is small and low cost.

A projection display device according to the present invention includes a projection light source that generates projection light, a spatial modulation element that spatially modulates the projection light to generate image projection light, a projection lens that enlarges and projects the image projection light, and A free-form surface lens that corrects a projection angle of image projection light emitted from the projection lens, a wedge-shaped light guide plate that emits image projection light emitted from the free-form surface lens from a position corresponding to the incident angle, and the wedge shape And a screen substantially in close contact with the light guide plate,
The free-form surface lens corrects the projection angle of the image projection light so as to correct image distortion caused by the wedge-shaped light guide plate.

Another projection display device according to the present invention includes a single mode laser that emits intensity-modulated red, green, and blue light, and an optical scanning unit that two-dimensionally scans the light of the single mode laser. A free-form surface lens that corrects the projection angle of the laser light scanned by the optical scanning means, a wedge-shaped light guide plate that emits laser light emitted from the free-form surface lens from a position corresponding to the incident angle, and the wedge-shaped guide With a screen substantially in close contact with the light plate,
The free-form surface lens corrects the projection angle of the laser beam so as to correct image distortion caused by the wedge-shaped light guide plate.

  According to the projection display device of the present invention, the image projection light passes through a free-form surface lens having a three-dimensional curved surface having no axial symmetry of at least two surfaces, and then the inside of the wedge-shaped light guide plate constituted by a plane. Since it is configured to propagate and reach the screen, it is possible to obtain a small-sized and low-cost projection display device with a simple configuration and no image distortion.

  In another projection display device according to the present invention, the single-mode laser light emitting red, green, and blue light that is intensity-modulated and two-dimensionally scanned has at least two planes of axial symmetry. After passing through a free-form surface lens having no three-dimensional curved surface, it is configured to propagate through the planar wedge-shaped light guide plate and reach the screen. A low-cost projection display device can be obtained.

Embodiment 1 FIG.
Hereinafter, the projection type display apparatus according to the first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a projection display apparatus according to Embodiment 1 of the present invention. In the figure, light emitted from a lamp light source 1 is spatially modulated by a liquid crystal display element 2 and is given image information, and is transmitted through a projection lens 3, a first free-form surface lens 4, and a second free-form surface lens 5. Thereafter, the image is displayed on the screen 7 via the wedge-shaped light guide plate 6.

  The light incident on the wedge-shaped light guide plate 6 propagates in the wedge-shaped light guide plate 6 by total reflection, but the propagation angle in the wedge-shaped light guide plate 6 changes every time it is reflected by the inclined surface of the wedge-shaped light guide plate 6. When the propagation angle, in other words, the incident angle on the reflecting surface of the wedge-shaped light guide plate 6 does not satisfy the total reflection angle condition, the light is emitted from the wedge-shaped light guide plate 6 to the screen 7.

Here, the light propagation path in the wedge-shaped light guide plate 6 will be described with reference to FIG.
As shown in FIG. 2, the light incident on the position I on the entrance surface 6i of the wedge-shaped light guide plate determines the light propagation path in the wedge-shaped light guide plate 6 depending on the incident angle, and does not satisfy the total reflection angle condition. The position where light exits from the wedge-shaped light guide plate 6 is also determined. For example, light incident on the wedge-shaped light guide plate 6 at an incident angle α from the incident position I is always emitted from the wedge-shaped light guide plate 6 at the output position A because the propagation path is determined by the shape of the wedge-shaped light guide plate. In the case of the incident angle α, the incident angle and the output position are in a one-to-one relationship, such as the output position A and the output position B in the case of the incident angle β.

  As described above, the light incident on the wedge-shaped light guide plate 6 is emitted from a position corresponding to the incident angle. Therefore, if an intensity distribution corresponding to the incident angle is given to the incident light on the wedge-shaped light guide plate 6, a wedge shape is obtained. Light having an intensity distribution corresponding to the incident angle is emitted from a predetermined position on the exit surface 6d of the light guide plate, deflected in the observation direction by the screen 7, and the viewing angle is adjusted to form an image.

  Next, the projection light angle characteristic of the image projection optical system by the liquid crystal display element 2 and the projection lens 3 will be described with reference to FIG. As shown in FIG. 3, the image projection optical system including the liquid crystal display element 2 and the projection lens 3 performs image transfer of an image displayed on the liquid crystal display element 2 onto a predetermined projection surface by the projection lens 3. It is configured as follows. At that time, the emission angles γ from the projection lens 3 of the light reaching different positions on the projection surface, that is, the light emitted from different pixels of the liquid crystal display element 2 are all different depending on the positions on the projection surface. . Therefore, in the image projection optical system including the liquid crystal display element 2 and the projection lens 3, the light emitted from the projection lens 3 is light having an emission angle intensity distribution according to the image displayed on the liquid crystal display element 2. It has become.

  When image projection light emitted from the image projection optical system including the liquid crystal display element 2 and the projection lens 3 is incident on the wedge-shaped light guide plate 6, light based on the incident angle and intensity distribution of the image projection light is emitted from the wedge-shaped light guide plate 6. Then, an image is formed on the exit surface 6d of the wedge-shaped light guide plate.

  Such a light guide type display device that propagates the image projection light emitted from the image projection optical system by the liquid crystal display element 2 and the projection lens 3 through the inside of the wedge-shaped light guide plate 6 and displays an image has a projection light path. Since it is comprised by the wedge-shaped light-guide plate 6, an extremely small projection type display apparatus is realizable.

  However, when the wedge-shaped light guide plate 6 has a simple wedge shape composed only of a flat surface, the incident angle and the output position of the light incident on the wedge-shaped light guide plate 6 correspond one-to-one, but the incident angle and the output angle. Since the positional relationship is not linear, when a normal display element adopting an orthogonal arrangement is used for the liquid crystal display element 2, the image displayed on the liquid crystal display element 2 and the projected image on the exit surface of the wedge-shaped light guide plate 6 are: There is a problem that distortion does not occur as shown in FIG.

  Such a problem of image distortion can be avoided by making the surface shape of the wedge-shaped light guide plate 6 not a simple flat surface but a complicated curved surface shape for correcting the distortion. Since it is difficult to form a complicated curved surface shape with high accuracy on the surface of the large area, the wedge-shaped light guide plate 6 becomes extremely expensive.

  Also, the problem of image distortion can be avoided by configuring the pixel array of the liquid crystal display element 2 to have a special array so as to correct the distortion caused by the wedge-shaped light guide plate 6. Since an element is required, the cost is similarly increased.

  In the configuration of the first embodiment, a simple wedge-shaped light guide plate 6 configured only by a plane and a liquid crystal display element 2 adopting a normal orthogonal arrangement are used, and an image projection optical system including the liquid crystal display element 2 and the projection lens 3 is provided. By inserting two free-form surface lenses 4 and 5 having a free-form surface which is a three-dimensional curved surface having no axial symmetry on one side and a plane on the opposite side between the wedge-shaped light guide plate 6, Image distortion has been eliminated. Although the free-form surface lens has a complicated curved surface shape, it is an optical element that is smaller than the wedge-shaped light guide plate 6, so that it can be easily manufactured and does not significantly increase the cost.

  With reference to FIG. 5, a configuration for eliminating image distortion by using two free-form surface lenses 4 and 5 will be described. First, distortion generated in the wedge-shaped light guide plate 6 is generated by each pixel of the liquid crystal display element 2, and the angle of the light transmitted through the projection lens 3 is converted into an angle so that the distortion generated in the wedge-shaped light guide plate 6 is corrected. This can be corrected. In the two free-form surface lenses 4 and 5 shown in FIG. 5, the distortion of the image light emitted from each pixel of the liquid crystal display element 2 and transmitted through the projection lens 3 is generated by the wedge-shaped light guide plate 6. The angle is converted so as to correct, and the image projection light enters from the same position I on the entrance surface 6i of the wedge-shaped light guide plate.

  The light emitted from the pixel of the liquid crystal display element 2 and transmitted through the projection lens 3 and emitted from the projection lens at the exit angle δ1 is defined by the exit angle δ1 on the free-form curved surface of the first free-form surface lens 4. Reach position J. On the other hand, when light is made to enter the wedge-shaped light guide plate 6 from the predetermined position I at a predetermined incident angle δ2, the incident light to the wedge-shaped light guide plate 6 is the free curved surface refracting surface of the second free curved lens 5. In the above, it must be emitted from the emission position K.

  The light which has exited the projection lens 3 at the exit angle δ1 and has entered the free-form refracting surface of the first free-form surface lens 4 at the position J is reflected by the free-form surface of the first free-form lens 4 by the second free-form surface. The light is deflected so as to reach the position K on the free curved surface refracting surface of the curved lens 5, and further reaches the position I of the wedge-shaped light guide plate 6 after exiting the position K by the free curved surface refracting surface of the second free curved surface lens 5. By deflecting in this manner, the light emitted from the projection lens 3 at the emission angle δ1 can be converted into light that enters the predetermined position I of the incident surface 6i of the wedge-shaped light guide plate at a predetermined incident angle δ2.

  In the optical system of FIG. 5, the image distortion generated by the wedge-shaped light guide plate 6 is corrected for all image projection light emitted from each display pixel of the liquid crystal display element 2 and transmitted through the projection lens 3. The free-form surface shape of the two free-form surface lenses 4 and 5 is configured so as to be converted into the incident angle and enter the wedge-shaped light guide plate 6 from the same incident position. Can be resolved.

  Generation of image distortion by the wedge-shaped light guide plate 6 is not axially symmetric with respect to the optical axis of the image projection optical system by the liquid crystal display element 2 and the projection lens 3, and therefore the optical system for correcting this is also an axially symmetric aspheric lens. Cannot be corrected, and a free-form surface lens having no axial symmetry is required.

  Moreover, as shown in FIG. 6, even if the incident angle of the image projection light incident on the wedge-shaped light guide plate 6 is the same, if the incident position is shifted to Is, the position emitted from the wedge-shaped light guide plate 6 is shifted to As. In the configuration of the first embodiment, the light emitted from all the pixels of the liquid crystal display element 2 is also incident on the wedge-shaped light guide plate 6 from the same incident position I. Image distortion caused by the difference in position is also eliminated.

  In the first embodiment, the distortion correction optical system is configured by using two independent free-form surface lenses 4 and 5, but at least two surfaces have the effect of eliminating image distortion generated by the wedge-shaped light guide plate 6. It is apparent from the principle of angle conversion that corrects image distortion that it can be similarly realized by using an optical system having a free-form surface. An optical system having two free-form surfaces can be configured using a free-form surface reflecting mirror or a single lens having free-form surfaces on both sides. Furthermore, it is possible to arrange two free-form surfaces in the components of the projection lens 3.

  Regarding the display element and the light source, the liquid crystal display element 2 and the lamp light source 1 are used in the present embodiment, respectively, but it is needless to say that the present invention is not limited to this.

  According to the projection display device of the first embodiment described above, the projection light is propagated by the wedge-shaped light guide plate 6 and the image distortion generated at that time is corrected by the two small free-form curved lenses 4 and 5. As a result, it is possible to realize a projection display device that is extremely small, low-cost, and free from image distortion.

Embodiment 2. FIG.
Next, the projection type display apparatus according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 7 is a diagram showing the configuration of the projection display apparatus according to the second embodiment of the present invention. In the figure, light emitted from single mode lasers 8, 9, and 10 that emit red, green, and blue light whose intensity is modulated based on a video signal is placed on the same optical axis by dichroic mirrors 11, 12 and 13. The images are superimposed, scanned two-dimensionally by the optical scanning device 14, and displayed on the screen 7 through the first free-form surface lens 4, the second free-form surface lens 5, and the wedge-shaped light guide plate 6.

  The red, green, and blue projected laser beams that are two-dimensionally scanned by the optical scanning device 14 after being superimposed on the same optical axis are incident on the first free-form surface lens 4 and the second free-form surface lens 5. Is always corrected and is incident on a predetermined same incident position on the incident surface 6i of the wedge-shaped light guide plate.

  The effect of correcting the light propagation by the wedge-shaped light guide plate 6 and the distortion generated by the wedge-shaped light guide plate 6 by the two free-form surface lenses 4 and 5 is the same as in the first embodiment.

  When the wedge-shaped light guide plate 6 becomes large, there is a possibility that a variation in shape at the time of manufacturing the wedge-shaped light guide plate 6 or a distortion change due to a change in surface shape due to a temperature change may occur. Such a distortion change varies depending on each individual wedge-shaped light guide plate 6 and environmental changes, and may not be corrected by the distortion correction method using the two free-form curved lenses 4 and 5.

  However, in the second embodiment, since the three-color single-mode lasers 8, 9, 10 and the optical scanning device 14 are used for the projection optical system, the change of the scanning condition of the optical scanning device 14 causes the image to be displayed. Distortion can be corrected to some extent. For example, as shown in FIG. 8, a test pattern 15 such as a cross hatch is displayed on the screen 7, and the test pattern 15 is observed by the image pickup device 16, whereby the shape of the wedge-shaped light guide plate 6 varies depending on the individual shape and the temperature change. A distortion change due to a surface shape change is detected, a two-dimensional scanning signal (not shown) generated by the optical scanning controller 17 is corrected, and the optical scanning device 14 is driven by the optical scanning driver 18 to correct the distortion. can do. In this way, by setting the scanning conditions of the optical scanning device 14 in accordance with individual differences of the wedge-shaped light guide plate 6 and environmental changes, it is possible to minimize distortion.

  According to the projection type display apparatus of the second embodiment described above, the projection light is guided in a wedge shape using the image projection optical system composed of the three color single mode lasers 8, 9, 10 and the optical scanning device 14. Image distortion propagated by the optical plate 6 and generated at that time can be corrected by the two small free-form surface lenses 4 and 5, so that the image distortion is extremely small and low-cost, and the environmental distortion can be reduced. It is possible to realize a projection type display device without any problem.

It is a figure which shows the structure of the projection type display apparatus of Embodiment 1 which concerns on this invention. It is a figure which shows the optical path of the light which propagates a wedge-shaped light-guide plate. It is a figure which shows the projection light angle characteristic of the image projection optical system by a liquid crystal display element and a projection lens. It is a figure which shows the image distortion which generate | occur | produces with a wedge-shaped light-guide plate. It is a figure which shows the distortion correction optical system using the free-form surface lens of Embodiment 1 which concerns on this invention. It is a figure which shows the optical path of the light which injects into a wedge-shaped light-guide plate from a different incident position. It is a figure which shows the structure of the projection type display apparatus of Embodiment 2 which concerns on this invention. It is a figure explaining the adaptive distortion correction of the projection type display apparatus of Embodiment 2 which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Lamp light source 2 Liquid crystal display element 3 Projection lens 4 1st free-form surface lens 5 2nd free-form surface lens 6 Wedge light guide plate 7 Screen 8 Red single mode laser 9 Green single mode laser 10 Blue single mode laser, 11 1st dichroic mirror, 12 2nd dichroic mirror, 13 3rd dichroic mirror, 14 optical scanning device.

Claims (6)

A projection light source for generating projection light;
A spatial modulation element that spatially modulates the projection light to generate image projection light;
A projection lens for enlarging and projecting the image projection light;
A free-form surface lens that corrects the projection angle of the image projection light emitted from the projection lens;
A wedge-shaped light guide plate that emits image projection light emitted from the free-form surface lens from a position corresponding to the incident angle;
A screen substantially in close contact with the wedge-shaped light guide plate,
The projection display device, wherein the free-form surface lens corrects a projection angle of the image projection light so as to correct image distortion caused by the wedge-shaped light guide plate.   The projection display apparatus according to claim 1, wherein the image projection light emitted from the free-form surface lens is incident on the same position of the wedge-shaped light guide plate. A single-mode laser that emits intensity-modulated red, green, and blue light;
Optical scanning means for two-dimensionally scanning the light of the single mode laser;
A free-form surface lens that corrects the projection angle of the laser beam scanned by the optical scanning means;
A wedge-shaped light guide plate that emits laser light emitted from a free-form surface lens from a position corresponding to the incident angle;
A screen substantially in close contact with the wedge-shaped light guide plate,
The projection display device, wherein the free-form surface lens corrects a projection angle of the laser light so as to correct image distortion caused by the wedge-shaped light guide plate.   4. The projection display device according to claim 3, wherein the laser light emitted from the free-form surface lens is configured to be incident on the same position of the wedge-shaped light guide plate.   The projection display device according to claim 1, wherein the free-form surface lens has a three-dimensional curved surface having no axial symmetry of at least two surfaces.   The projection display device according to claim 1, wherein an end surface of the wedge-shaped light guide plate is a flat surface.

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