JP6222500B2 - Projection optical system and image display device - Google Patents

Description

The present invention relates to an image display device that projects and displays an enlarged image on a screen , and a projection optical system used in the image display device .

  An image display device capable of displaying an enlarged image even when installed closer to a screen than a conventional one is known. Such an image display device is called a close-range projector. The purpose of the close range projector is as follows. First, in order to avoid glare from entering the eyes of presenters (explainants, presenters, etc.) standing near the screen, secondly, the listener who listens to the presenter's explanations will hear projector exhaust and noise. This is to prevent influence.

  A plurality of types of projection optical systems including a close-range projector are known. For example, there are a type that can shorten the distance from the screen surface by widening the angle of view of a conventional projection optical system (coaxial / rotationally symmetric), a type that uses a curved mirror, and the like. A conventional projection optical system that widens the angle of view can realize close-up projection by extending the prior art. However, since the outer diameter of the lens close to the screen needs to be large, the entire projector becomes large.

  On the other hand, the method using the curved mirror can realize projection at a close distance while reducing the size of the projection optical system. Examples of projectors having a projection optical system using a curved mirror are described in Patent Document 1 and Patent Document 2. In the projection optical system provided in the projector of Patent Document 1, a concave mirror is disposed behind the lens optical system. In the projection optical system provided in the projector described in Patent Document 2, a convex mirror is disposed behind the lens optical system. In either case, setting can be performed simply by arranging the lens and the mirror in order, so that the arrangement accuracy between the parts can be increased. However, since it is necessary to increase the distance between the lens optical system and the mirror, the projection optical system becomes large.

  For example, there are inventions described in Patent Document 3 and Patent Document 4 that can shorten the distance between the lens and the mirror. In the inventions described in Patent Document 3 and Patent Document 4, a folding mirror is arranged to fold a long distance between the lens optical system and the mirror to reduce the size of the projection optical system.

  In the invention described in Patent Document 3, a concave mirror and a convex mirror are arranged in this order next to the lens optical system to achieve miniaturization. Further, the invention described in Patent Document 4 is miniaturized by placing a plane mirror behind the concave mirror.

  However, in any of the optical systems described in Patent Document 3 and Patent Document 4, the distance from the image display element to the curved mirror is long. Therefore, in order to make the distance from the screen to the projector main body closer than before, the length of the optical system main body becomes an obstacle.

  An invention described in Japanese Patent Application Laid-Open No. H10-228561 is available as a solution to such a restriction on “the size of the optical system itself”. Patent Document 5 describes a projection optical system in which a screen surface and a display surface of an image display element are perpendicular to each other. By adopting such a vertical system, the length of the projection optical system itself does not get in the way even if the distance between the screen and the projector body is reduced.

  When a vertical projection optical system such as the projection optical system described in Patent Document 5 is used, in order to perform a large screen projection with ultra-close projection, the divergence of light incident on the mirror optical system from the lens optical system is further increased. It needs to be strong.

  However, when the divergence is increased, the refraction angle of the light beam is increased, so that the quality of the projected image is greatly affected by the positional deviation of the lens optical system and the mirror optical system, and the image quality is deteriorated. In particular, if the positions of the lens optical system and the second mirror (the mirror closest to the screen on the optical path) are shifted, the field curvature largely fluctuates, causing a significant deterioration in image quality.

  The present invention has been made in view of the above problems, and in an image display device having a vertical projection optical system, an image display device capable of preventing quality deterioration of a projected image due to a positional deviation of the optical system. The purpose is to provide.

The present invention relates to a projection optical system used in an image display device that enlarges and displays an image displayed on an image display element on a projection surface , the projection optical system including a lens optical system including a plurality of lens groups, A mirror optical system having one mirror and a second mirror which is a concave mirror, and the lens optical system is a coaxial optical system in which the optical axes of a plurality of lenses are on the same straight line The optical axis of the coaxial optical system and the projection surface are parallel, and an intermediate image of a pixel related to the image display element is formed in the optical path from the lens optical system to the second mirror via the first mirror. The first mirror is held via position adjusting means that can change the optical path of the light beam toward the second mirror without changing the positional relationship between the lens optical system and the second mirror. Three fixed parts that support the mirror at three points and the fixed parts The main feature is that it has a fastening part for fixing each to a back support provided in the image display device, and a spacer inserted between the back of the first mirror and the back support. .

  ADVANTAGE OF THE INVENTION According to this invention, the image display apparatus which can prevent deterioration of the image quality of the projection image by the position shift | offset | difference of an optical system, and can display a big screen on the screen of a short distance can be obtained.

1 is an optical layout diagram schematically illustrating an example of an image display device according to the present invention. It is the schematic which expanded the example of the principal part of the projection optical system with which the example of the said image display apparatus is provided. It is a schematic diagram which shows the example of the principal part and projection surface of a projection optical system with which the example of the said image display apparatus is provided. It is the schematic which expanded the example of the principal part of the projection optical system with which the example of the said image display apparatus is provided. It is the (a) front view which shows the example of the position adjustment means of the 1st mirror with which the said projection optical system is provided, (b) The right view. It is (a) top view and (b) right view which shows another example of the position adjustment means of the 1st mirror with which the said projection optical system is provided. It is a top view which shows the example of the reflection type image display apparatus which the said image display apparatus has. It is a light ray figure which shows the locus | trajectory of the light projected by the said projection optical system. It is a side view which shows the example of the lens optical system which the said image display apparatus has.

  Embodiments of an image display apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a side view of a main part of an optical engine provided in a projector 100 that is an image display apparatus according to the present embodiment as seen from one direction.

  In FIG. 1, a projector 100 is roughly an illumination optical system that illuminates a DMD 7 that is a reflective image display element by light emitted from a lamp 1 that is a light source, and a projection surface that reflects light reflected by the DMD 7. A projection optical system for projecting toward the screen 20. FIG. 1 illustrates only a lens optical system 8 that is a part of the projection optical system. Hereinafter, in this specification, the axis in the optical axis direction of the projection optical system is the Z axis, the axis in the optical axis direction of the illumination optical system is the Y axis, and the axis in the direction perpendicular to both the Z axis and the Y axis is X. Axis.

  In the embodiment described below, a DMD that is a reflective image display element is used as an example of the image display element. However, in the image display device according to the present invention, the element used as the image display element is not limited to the DMD, and other image display elements such as a liquid crystal panel may be used.

  Hereinafter, the illumination optical system included in the projector 100 will be described. The light emitted from the lamp 1 that is a light source is condensed by the reflector 2 at the entrance of the integrator rod 3. The integrator rod 3 is a light pipe formed by combining four mirrors into a tunnel shape. The light incident on the integrator rod 3 is repeatedly reflected on the mirror surface constituting the inner wall of the integrator rod 3. As a result, the light incident on the integrator rod 3 appears at the exit port as light having a uniform light amount and no unevenness.

  The exit port of the integrator rod 3 is regarded as a surface light source with uniform light quantity and no unevenness, and the light from this surface light source is imaged through the DMD illumination lens 4, the first folding mirror 5, and the second folding mirror 6. The effective image area of the DMD 7 that is a display element is irradiated. The DMD illumination lens 4 is an optical element for efficiently irradiating the effective image area of the DMD 7. The first folding mirror 5 is a plane mirror, and the second folding mirror 6 is a free-form curved mirror (concave mirror).

  The light emitted from the surface light source that is the exit of the integrator rod 3 passes through the DMD illumination lens 4, is reflected by the first folding mirror 5 in the diagonally lower right direction in FIG. 1, and travels toward the second folding mirror 6. . The light is reflected by the second mirror toward the surface of the DMD 7 and the surface of the DMD 7 is illuminated. A micromirror is disposed on the surface of the DMD 7. Illumination light is reflected by the micromirrors to form image projection light. The image projection light passes through the side of the second folding mirror 6, enters the lens optical system 8 constituting the projection optical system, and is projected toward the screen 20. The lamp 1 to the second folding mirror 6 are referred to as an illumination optical system.

  With the above illumination optical system, the DMD 7 is illuminated with light having no unevenness in the amount of light, resulting in a uniform illuminance distribution. Therefore, the projected image projected and displayed on the screen 20 also has a uniform illuminance distribution.

  The DMD 7 is a device composed of a large number of micromirrors, and the angle of each micromirror can be changed in the range of + 12 ° to −12 °. For example, when the angle of the micro mirror is −12 °, the illumination light reflected by the micro mirror enters the projection lens. This state is referred to as an “ON state”. When the angle of the mirror is + 12 °, the illumination light reflected by the minute mirror is prevented from entering the projection lens. This state is referred to as “OFF state”.

  The micro mirror of the DMD 7 corresponds to a pixel of an image displayed on the projection surface. Therefore, by controlling the tilt angle of each micromirror of the DMD 7, “ON” and “OFF” control is performed for each pixel, and projection light (projection image light) necessary for forming an image displayed on the screen 20 is generated. An image can be displayed on the screen 20 via the projection optical system.

  In FIG. 1, the projection optical system shows only the lens optical system 8, and the mirror optical system included in the projection optical system is omitted. The lens optical system 8 includes a projection lens composed of a plurality of lenses, and a lens barrel that holds the projection lens. In FIG. 1, the lens barrel is omitted. The mirror optical system (not shown) includes a mirror that reflects the projection light beam from the projection lens toward the screen 20.

  Next, examples of the projection optical system included in the image display apparatus according to the present invention will be described. FIG. 2 is an enlarged schematic view of a main part of the projection optical system according to the present embodiment. In FIG. 2, the illumination optical system is not shown, and the lens optical system 8 and the mirror optical system are shown. FIG. 2 illustrates a state in which all the micromirrors included in the DMD 7 are in the ON state and the entire effective image area is projected onto the screen 20 that is the projection surface.

  In FIG. 2, the projected light beam 14 enters the lens optical system 8 from the end of the effective image area of the DMD 7, and reaches the screen 20 through the first mirror 9 and the second mirror 10 that constitute the mirror optical system. It is expressed as

  The lens optical system 8 includes a plurality of lens groups housed in a lens barrel 81. The projected light beam 14 travels toward the first mirror 9 while diffusing after converging inside the lens barrel 81. The fact that the light traveling from the lens optical system 8 toward the first mirror 9 is a strong divergent light beam as shown in FIG. 2 can project a large screen even when the screen 20 and the projector 100 are at a short distance. It is a condition. Further, the light reflected by the second mirror 10 is condensed at a position closer to the second mirror 10 than the screen 20 and then projected onto the screen 20 while being diffused. This is a condition that enables projection.

  FIG. 3 is a schematic diagram including a main part of the projection optical system according to the present embodiment and a screen which is a projection surface. In FIG. 3, the illumination optical system is not shown, and the lens optical system 8, the mirror optical system, and the screen 20 are illustrated. As shown in FIG. 3, the angle at which the plane obtained by extending the reflecting surface of the DMD 7 in the Y-axis direction and the plane obtained by extending the screen 20 in the Z-axis direction is substantially a right angle. That is, the angle formed by the DMD 7 and the screen 20 is substantially a right angle. The form of the projector 100 in which the DMD 7 that is the image display element and the screen 20 that is the projection surface have the above relationship is referred to as a “vertical projector”.

  In the projector 100 which is a vertical projector, the length of the projection optical system itself is not a restriction on the distance between the screen 20 and the projector 100, and therefore ultra-close projection can be realized.

  There is a possibility that the positional relationship between the lens optical system 8 and the second mirror 10 of the projector 100 may vary greatly. When the positional relationship between the lens optical system 8 and the second mirror 10 varies, it is displayed on the screen 20. Image quality is degraded. Therefore, the projector 100 according to the present embodiment includes a position adjusting unit that can adjust the positional relationship between the lens optical system and the mirror optical system.

  Here, it will be described with reference to FIG. 4 what state the positional relationship between the lens optical system 8 and the first mirror 9 and the second mirror 10 constituting the mirror optical system is “variable”. As shown in FIG. 4, the deviation of the position of the second mirror 10 from the optimum position with respect to the lens optical system 8 in the traveling direction of the light beam is called “variation”. In FIG. 4, the 2nd mirror 10a has shown the example of the position scattered from the 2nd mirror 10 which is a normal position.

  When the projected light beam 14 reflected by the first mirror 9 disposed corresponding to the second mirror 10 at the normal position hits the second mirror 10a that is shifted (varied) from a position different from the normal position, the reflected light is reflected. The projected light beam 14a made of light travels toward the screen through a different optical path from when the second mirror 10 is in the normal position. As a result, the position of the image projected on the screen (not shown) is shifted, or the quality of the image is deteriorated.

  In order to adjust such variations in the optical path, the projector 100 according to the present embodiment holds the first mirror 9 by the position adjusting means. For example, the first mirror 9 is moved in parallel with the moving direction of the light beam (the normal direction of the reflecting surface of the first mirror 9) by the position adjusting means, so that the first mirror 9 is moved to the position (reference numeral 9b) aligned with the second mirror 10a. Can be placed.

  When the positional relationship between the lens optical system 8 and the second mirror 10 varies, when the first mirror 9 is moved to the position indicated by reference numeral 9b, the light beam reflected by the first mirror 9b takes the optical path indicated by reference numeral 14b. . When the projected light beam 14b is reflected by the second mirror 10b, it returns to the same optical path as the projected light beam 14 that is the optical path at the normal position. As described above, the position adjusting unit that holds the first mirror 9 can cancel the variation occurring at the position of the second mirror 10 and prevent the quality of the image displayed on the screen from being deteriorated.

  Next, an embodiment of the position adjusting means for the first mirror 9 will be described with reference to FIG. Fig.5 (a) is the example of the front view which looked at the 1st mirror 9 from the reflective surface side. FIG. 5B is an example of a right side view of the first mirror 9 viewed from the direction of the arrow indicated by the symbol A in FIG. In FIG. 5, the 1st mirror 9 is a plane mirror, Comprising: The external shape has comprised the rectangle.

  The position adjusting unit 90 includes a fixed component 91, a screw 92, and a spacer 93. The first mirror 9 is fixed at a predetermined position on the back support portion 94 with three points supported by fixing parts 91 located near the center of one side of the long side and near both ends of the other long side. That is, the first mirror 9 is held at a predetermined position via the position adjusting means 90.

  The fixed component 91 is a component made of an elastic member for applying pressure to press the first mirror 9 against the back side, and one end of the fixed component 91 is fastened to the back support portion 94 that supports the back side of the first mirror 9. It is fixed by a certain screw 92. The other end of the fixed component 91 is related to the front side (mirror surface side) of the first mirror 9 and supports the first mirror 9 in a predetermined position and a predetermined posture. The back support part 94 is made of a part of the housing of the image display device or a mirror holder.

  Spacers 93 are sandwiched between the first mirror 9 and the back support 94. Each spacer 93 is inserted and disposed at a location where the fixed component 91 presses the first mirror 9 against the back support portion 94 side. The spacer 93 forms a gap between the first mirror 9 and the back support part 94, and the frictional force generated between the back side of the first mirror 9 and the back support part 94 is reduced. It can be moved in the plane direction.

  If the thickness dimensions (thicknesses) of the spacers 93 are all the same, the position can be adjusted by moving the first mirror 9 in a direction perpendicular to the reflecting surface. Further, if the thickness dimensions of the spacers 93 are different, the inclination of the reflection surface of the first mirror 9 with respect to the second mirror 10 can be changed and adjusted.

  As described above, according to the position adjusting means 90 provided in the first mirror 9 of the projector 100 according to the present embodiment, even if the positional relationship between the lens optical system 8 and the second mirror 10 varies, the thickness of the spacer 93 is increased. By adjusting the height dimension, the position and tilt of the first mirror 9 can be arbitrarily adjusted, thereby improving the quality of the image.

  Next, another embodiment of the position adjusting means 90 of the first mirror 9 will be described with reference to FIG. Fig.6 (a) is the example of the front view which looked at the 1st mirror 9 from the reflective surface side. FIG. 6B is an example of a right side view of the first mirror 9 viewed from the direction of the arrow indicated by the symbol A in FIG. As shown in FIG. 6, the position adjusting means 90a of the first mirror 9 inserts a screw 92a into a screw hole 91a formed in the first mirror 9 in advance without using a fixing component 91 (see FIG. 5). The spacer 93 and the back support portion 94 are fixed together. By adjusting the thickness dimension of each spacer 93 individually, the inclination of the first mirror 9 can be adjusted. Further, by making the hole formed in the spacer 93 larger than the diameter dimension of the screw 92a, the first mirror 9 is slid in parallel with the mirror surface direction with respect to the back support portion 94, thereby adjusting the position. In addition, it is possible to adjust the inclination as described above.

  As described above, according to the position adjusting unit 90a included in the first mirror 9 of the projector 100 according to the present embodiment, even if the positional relationship between the lens optical system 9 and the second mirror 10 varies, the thickness of the spacer 93 is increased. By adjusting the height dimension, the position and tilt of the first mirror 9 can be arbitrarily adjusted, thereby improving the quality of the image.

  Next, a projection optical system included in the image display apparatus according to the present invention will be described. FIG. 7 is a plan view of the DMD 7. In FIG. 7, among a plurality of points on the plane of DMD 7, a point 71 at the middle point in the X-axis direction and at the lower end in the Y-axis direction is eccentric in the Y-axis direction. The amount of eccentricity is 1.56 mm. FIG. 8 is a ray tracing diagram when seven rays are emitted from 15 points on the DMD 7 shown in FIG.

  Unlike the conventionally known projection optical system, the projection light beam 14 that has passed through the lens optical system 8 is reflected by the second mirror 10 without the projection light beam 14 emitted from the DMD 7 being folded back by the first mirror 9. If the screen is projected, the exterior portion of the main body protrudes to the screen side due to the arrangement of the projection optical system. Accordingly, the projector cannot be installed unless the distance between the projector and the screen is longer than that of the image display device according to the present invention. That is, as in the projector 100 shown in the present embodiment, the configuration in which the projection light beam 14 having strong divergence is projected toward the screen 20 by the first mirror 9 and the second mirror 10 cannot be realized by the conventional one. Projection at a very close distance is possible.

  FIG. 9 shows a configuration example of the lens optical system 8. In FIG. 9, the optical axis direction of the lens is taken as the Z axis, and two axes orthogonal to it are taken as the X axis and the Y axis. The lens optical system 8 shown in FIG. 9 is a coaxial optical system in which the optical axes of the respective lenses are on the same straight line.

  The optical axis and a point 71 at the lower end in the Y-axis direction among the plurality of points on the plane of the DMD 7 shown in FIG. 7 are eccentric in the Y-axis direction, and the amount of eccentricity is 1.56 mm. That is, in FIG. 9, the optical axis is 1.56 mm below the lower end of the DMD 7.

Next, specific numerical examples of the projection optical system will be shown. Table 1 shows the configuration of the coaxial optical system. In Table 1, the surface numbers 1 and 2 are both surfaces of the cover glass disposed on the front side of the DMD 7. After that, a diaphragm is arranged, and further, lenses indicated by surface numbers 4 to 24 are arranged.

In Table 1, surfaces 4, 5, 21, 22, 23, and 24 are aspheric surfaces, and Table 2 shows their aspheric coefficients.

An expression for calculating the aspheric surface by applying the aspheric coefficient is shown in Expression 1.

Table 3 shows coefficients for forming the reflection surface of the second mirror 10.

Formula 2 for calculating the reflecting surface of the second mirror 10 by applying the above coefficient is shown in Formula 2.

Table 4 shows the layout of the first mirror 9, the second mirror 10, and the dust-proof glass 11.

  According to the projector 100 having the configuration described above, it is possible to obtain a screen display device that can display a large screen while performing ultra-close-up projection.

  In Table 3, “**” means a power operation. “*” Means multiplication.

  As described above, when the positional relationship between the second mirror and the lens optical system varies, the image display device according to the present invention displays the image by offsetting the variation by adjusting the position of the first mirror. The image quality can be improved.

7 DMD
8 Lens optical system 9 First mirror 10 Second mirror 14 Projected light beam 90 Position adjusting means

Japanese Patent No. 4329863 Japanese Patent No. 3727543 JP 2009-157223 A JP 2009-145672 A Japanese Patent No. 4210314

Claims (7)

A projection optical system used in an image display device that enlarges and displays an image displayed on an image display element on a projection surface ,
The projection optical system includes a lens optical system including a plurality of lens groups, and a mirror optical system including a first mirror and a second mirror that is a concave mirror.
The lens optical system is an optical axis of the plurality of lenses is coaxial optical system on the same straight line, wherein the optical axis of the coaxial optical system is parallel to the surface to be projected,
In the optical path from the lens optical system to the second mirror via the first mirror, an intermediate image of the pixel related to the image display element is formed,
The first mirror is held via a position adjusting unit capable of changing an optical path of a light beam toward the second mirror without changing a positional relationship between the lens optical system and the second mirror.
The position adjusting means includes
Three fixed parts for supporting the first mirror at three points;
Fastening parts for fixing each of the fixing parts to a back support provided in the image display device;
A spacer inserted between the back surface of the first mirror and the back surface support portion.
A projection optical system characterized by that.   The projection optical system according to claim 1, wherein the first mirror is a plane mirror.   The projection optical system according to claim 1, wherein the position of the first mirror is adjusted by the thickness of each spacer.   4. The projection optical system according to claim 1, wherein the spacers have the same thickness, and the first mirror is held so that a position in a direction perpendicular to the reflecting surface can be adjusted. 5. .   4. The projection optical system according to claim 1, wherein the spacers have different thicknesses, and the first mirror is held so that the inclination of the reflecting surface can be adjusted. 5.   The projection optical system according to claim 1, wherein the second mirror is a free-form surface mirror. An image display device comprising a projection optical system,
The said projection optical system is an image display apparatus which is a projection optical system in any one of Claims 1 thru | or 6.