JP6533495B2 - Projection optical system and image display device - Google Patents

Description

  The present invention relates to a projection optical system and an image display apparatus using the optical system.

  There is known an image display device which can be installed near the screen as compared with the prior art. Such an image display device is called a near distance projector. The purpose of the close projector is as follows. First, to avoid glare from entering the eyes of the presenters (or presenters, presenters, etc.) standing near the screen, and secondly, to the listeners who listen to the presenters' explanations the projector exhausts and noises To prevent the influence of

  The projection optical system provided in the close-range projector includes one that shortens the distance to the screen surface by widening the angle of view of the conventional projection optical system (coaxial and rotational symmetry), and one that uses a curved mirror. The extension of the angle of view of the conventional projection optical system can achieve the purpose of close-up projection by extending the prior art. However, the outer diameter of the lens close to the screen needs to be large, and the entire projector becomes large. On the other hand, the method using a curved mirror can perform projection at a close distance although it is compact.

  As a device using a curved mirror, for example, there are inventions described in Patent Document 1 and Patent Document 2. The invention described in Patent Document 1 is a system in which a concave mirror is placed behind a lens optical system for projection. The invention described in Patent Document 2 is a system in which a convex mirror is placed behind a lens optical system for projection. In either method, setting can be performed only by arranging the lens and the mirror in order, so that the arrangement accuracy between the parts can be increased. However, a long distance is required between the lens optical system and the mirror, and the projection optical system becomes large.

  Patent Documents 3 and 4 disclose inventions capable of shortening the distance between the lens and the mirror. In the inventions described in Patent Document 3 and Patent Document 4, a long distance between the lens optical system and the mirror is folded by arranging the folding mirror, thereby miniaturizing the optical system.

  In the invention described in Patent Document 3, miniaturization is achieved by sequentially arranging a concave mirror and a convex mirror next to the lens optical system. In the invention described in Patent Document 4, the miniaturization is achieved 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 further reduce the distance from the screen to the projector main body than in the related art, the length of the optical system main body is an obstacle.

  There is an invention described in Patent Document 5 as a solution to such restrictions on the "size of the optical system itself". Patent Document 5 describes a projection optical system in which the screen surface and the display surface of the image display element are perpendicular to each other. By adopting such a vertical method, the length of the projection optical system itself does not become an obstacle even if the distance between the screen and the projector main body is reduced.

  However, as in the case of the projection optical system described in Patent Document 5, when the projection lens is erected to be parallel to the screen, the projection optical system is compared with the projection optical system of the horizontal projector in which the projection optical system is perpendicular to the screen. The dust easily adheres to the projection lens and the mirror. Further, since the attached dust falls on the vertical projection optical system, it does not come off naturally due to the action of gravity, and if left as it is, the dust is reflected on the screen surface.

  Moreover, since the angle of view of the lens optical system is narrow in the projection optical system described in Patent Document 5, if dust adheres to either of the two mirrors that reflect the projection light flux, the amount of light on the projection surface will be greatly affected. . Even if dustproof glass is disposed between the mirror and the projection surface, it is difficult to prevent the entry of fine dust of 0.01 mm or less.

  The present invention has been made in view of the above problems, and provides a projection optical system used in an image display device, which can prevent the influence of dust on the light amount on the projection surface. With the goal.

The present invention is a projection optical system for use in an image display apparatus which projects a projection image formed by an image display element onto a projection surface, the lens optical system having a plurality of lenses, and a first mirror which is a plane mirror. And a mirror optical system including a second mirror which is a concave mirror, and the lens optical system is a coaxial optical system in which a plurality of lenses all share the optical axis, and the plurality of lenses are directed in the direction of gravity And a first projection light beam that reaches the closest position from the image display surface of the image display element on the projection surface in a plane including the optical axis of the coaxial optical system and perpendicular to the projection surface The second projection light flux reaching the position farthest from the image display surface of the image display element on the projection surface is reflected by the second mirror and temporarily intersects, and then projected onto the projection surface, and after being reflected by the second mirror, a first throw A position where the light flux and the second projection light beam intersect, rather than the second mirror is positioned closer to the first mirror, a lens surface of the lens closest to the first mirror of the plurality of lenses are convex, a coaxial optical The intermediate image of the pixel related to the image display element closest to the optical axis of the system is formed on the optical path from the first mirror to the second mirror, and the middle of the pixel related to the image display element farthest to the optical axis of the coaxial optical system The main feature is that an image is formed on the optical path from the lens optical system to the first mirror.

  According to the invention, it is possible to display a large screen on a screen at an extremely close distance, and to provide a projection optical system which is compact and can reduce the influence on a projection image even if dust adheres to the lens optical system. You can get it.

FIG. 1 is an optical layout diagram schematically showing an example of an image display device according to the present invention. It is a side view which shows the example of the principal part of the projection optical system with which one Example of the said image display apparatus is provided. It is an optical path figure which shows the appearance of the light projected by the said projection optical system. It is a side view which shows the principal part of the projection optical system with which another Example of the said image display apparatus is provided. It is a side view which shows the principal part of the projection optical system with which another Example of the said image display apparatus is provided. It is a ray diagram which shows the locus | trajectory of the light projected by the said projection optical system. 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 side view which shows the example of the lens optical system which the said image display apparatus has.

  Hereinafter, an embodiment of an image display device according to the present invention will be described with reference to the drawings. FIG. 1 is a side view of an essential part of an optical engine provided in an image display apparatus according to the present invention as viewed from one direction. Hereinafter, in this specification, the axis in the optical axis direction of the projection optical system is taken as the Z axis, the axis in the optical axis direction of the illumination optical system is taken as the Y axis, and the axis in the direction orthogonal to both the Z axis and the Y axis is taken as X It is an axis.

  In FIG. 1, the projector 100 is roughly an illumination optical system that illuminates the DMD 7 that is a reflection type image display device by light emitted from the lamp 1 that is a light source, and a projection surface of the light reflected by the DMD 7 And a projection optical system for projecting toward the screen 20. FIG. 1 illustrates only the lens optical system 8 which is a part of the projection optical system.

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

  The illumination optical system of the projector 100 will be described below. The light emitted from the lamp 1, which 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 in which four mirrors are combined to form a tunnel. The light incident on the integrator rod 3 is repeatedly reflected by the mirror surface in the integrator rod 3, and the light amount becomes uniform and uniform at the exit of the integrator rod 3.

  The exit of the integrator rod 3 is captured as a surface light source with uniform light amount and no unevenness, and light from this surface light source is transmitted through the DMD illumination lens 4, the first turning mirror 5, and the second turning mirror 6. It irradiates to the effective image area of DMD 7 which is an image display element. The DMD illumination lens 4 is an optical element for efficiently illuminating the effective image area of the DMD 7. The first turning mirror 5 is a plane mirror, and the second turning mirror 6 is a curved mirror (concave mirror).

  The light emitted from the integrator rod 3 passes through the DMD illumination lens 4, is reflected by the first folding mirror 5 in the obliquely lower right direction in FIG. 1, and travels toward the second folding mirror 6. The light reflected by the second mirror illuminates the surface of the DMD 7. The illumination light is reflected by the micro mirror disposed on the surface of the DMD 7 to form the image projection light. The image projection light passes through the side of the second folding mirror 6 and is incident on the lens optical system 8 constituting the projection optical system, and the image projection light is projected on the screen 20 to display an image. The lamps 1 to the second folding mirror 6 are referred to as an illumination optical system.

  The DMD 7 is illuminated with light having no unevenness in the light amount by the above-described illumination optical system to form a uniform illuminance distribution, and thus the projected image, which is an enlarged image thereof, also has a uniform illuminance distribution.

  The DMD 7 is a device consisting of a large number of micro mirrors, and the angle of each micro mirror can be changed in the range of + 12 ° to -12 °. For example, when the angle of the micromirror is -12 [deg.], The illumination light reflected by the micromirror is made to enter the projection lens. This state is called "ON state". In addition, when the angle of the mirror is + 12 °, the illumination light reflected by the micro mirror is prevented from entering the projection lens. This state is called "OFF state".

  The minute mirrors of the DMD 7 correspond to the pixels of the image displayed on the projection surface. Therefore, by controlling the tilt angle of each micro mirror of the DMD 7, it is possible to project the projection light (projected image light) necessary for forming the image displayed on the screen 20 through the projection optical system.

  In FIG. 1, only the lens optical system 8 is shown as the projection optical system, 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. The lens barrel is omitted in FIG. Further, a mirror optical system (not shown) has a mirror that reflects the light beam projected from the projection lens toward the screen 20.

Example 1
Next, an embodiment of a projection optical system included in the image display apparatus according to the present invention will be described. FIG. 2 is a schematic view enlarging a main part of the projection optical system according to the present embodiment. In FIG. 2, the illumination optical system is not shown. FIG. 2 exemplifies a state in which all the micromirrors provided in the DMD 7 are in the ON state, and the entire effective image area is projected onto the screen 20 which is a 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 passes through the first mirror 9 and the second mirror 10 constituting the mirror optical system to reach the screen 20. It is represented as

  The lens optical system 8 comprises a plurality of lens groups housed in a lens barrel 81. The projected light beam 14 travels to the first mirror 9 while being converged after being converged inside the lens barrel 81. The first mirror 9 is not limited to a plane mirror, but if it is a convex mirror, the projected light flux 14 reflected by the first mirror 9 becomes more divergent. Then, the projected light beam 14 reflected by the first mirror 9 collides with, for example, the lens barrel 81 or the like on the way to the second mirror 10 and the possibility of light being blocked (blocked) becomes high. Therefore, it is desirable that the first mirror 9 be a flat mirror or a concave mirror.

  In addition, the second mirror 10 that reflects the projection light flux 14 reflected by the first mirror 9 toward the screen 20 needs to be a concave mirror. If the second mirror 10 is a plane mirror or a convex mirror, the projected light beam 14 reflected by the second mirror 10 is diffused and is not reflected toward the screen 20.

  That is, the first mirror 9 is a flat mirror or a concave mirror, and the second mirror 10 is a concave mirror, so that the projected light beam 14 reflected by the second mirror 10 is a screen 20 and a second mirror. The light may be collected between 10 and diffused and projected on the screen 20 to display an image.

  In order to make a large screen display while keeping the distance between the projector 100 and the screen 20 very close, the divergence of the light beam entering the mirror optical system from the lens optical system 8 is intensified, and the concave mirror (second It is necessary to condense the projected light flux 14 after being reflected by the mirror 10), and to make the condensing position close to the second mirror 10 far before the screen 20. If the condensing position 15 is not close to the second mirror 10 far in front of the screen 20, the projected light flux 14 from the projector 100 installed at an extremely close distance does not diverge sufficiently, and a large size on the screen 20 It is because it can not display an image.

  For example, as shown in FIG. 3, if the condensing position 15 is at a position near the second mirror 10 far before the screen 20, even if the projector 100 is installed at a close distance to the screen 20, the projected light flux 14 Can be sufficiently diffused to display a greatly magnified image over the screen 20.

  Return to FIG. Since the lens optical system 8 is placed vertically along the direction of gravity, it is desirable that the lens surface of the lens 80 closest to the first mirror 9 be a convex surface. Dust tends to get on the lens surface of the lens 80, but by making the lens surface convex, dust on the lens surface tends to fall naturally along the lens surface by gravity. Further, dust does not enter inside the lens barrel 81, and dust is not easily attached to the lens surface of the lens closest to the DMD 7 among the lenses of the lens optical system 8.

  The projector 100 according to the embodiment described above performs a large screen display even at an extremely close distance by installing the condensing position 15 at a position near the second mirror 10, which is far in front of the screen 20. Furthermore, even if the lens optical system 8 is vertical, dust can be prevented from being reflected in the projection image.

(Example 2)
Next, a projection optical system in another embodiment of the image display device according to the present invention will be described. In the projection optical system shown in FIG. 2, assuming that the area of the first mirror 9 is S1 and the area of the second mirror 10 is S2, the relationship of S1 <S2 is established as illustrated. The smaller the ratio of the area of the mirror to the size of the dust, the greater the influence of the dust and light reduction on the screen (area H). For example, the effect is larger when dust of φ 0.01 mm is attached to the first mirror 9 than when attached to the second mirror 10.

  Therefore, in order to reduce the reflection of dust and the adverse effect of the dust on the light amount without changing the area H of the screen 20, the area S1 of the first mirror 9 may be increased. However, in order to increase the area S1 of the first mirror 9, it is necessary to widen the angle of view of the lens optical system 8. In order to make the entire configuration of the projection optical system compact after expanding the angle of view of the lens optical system 8, the lens group near the first mirror 9 among the lens groups of the lens optical system 8 is a concave lens group The lens group close to the DMD 7 may be a convex lens group having positive refractive power.

  In this case, since the divergence of the projection light flux 14 becomes stronger, there is a possibility that the projection light flux 14 reflected by the first mirror 9 is diffused and hit the lens optical system 8. Therefore, in the optical path reflected by the first mirror 9 toward the second mirror 10, a part of the lens optical system 8 which may be an obstacle is cut away so that the projection light flux 14 is not broken. Therefore, among the lenses constituting the lens optical system 8, the lens closest to the first mirror 9 may be a different lens so that the diverged projection light beam 14 is not blocked.

  FIG. 4 is a side view showing this embodiment of the projection optical system in the case where the lens closest to the first mirror 9 is a modified lens. In FIG. 4, the lens optical system 8a includes an odd-shaped lens 80a disposed closest to the first mirror 9 and a lens barrel 81a for holding the same. As shown in FIG. 4, of the lenses constituting the lens optical system 8a, about half of the lens 80a closest to the first mirror 9 on the second mirror side is cut away, leaving about half. As a result, in the optical path from the first mirror 9 to the second mirror 10, the lens optical system 8a does not become an obstacle, and the projection light flux 14 reflected by the first mirror 9 has a stronger divergence and an optical path Even if it spreads, the second mirror 10 can be reached.

  As described above, by processing the end of the lens 80a closest to the first mirror 9 and the end of the lens barrel 81a to form a notch, the passable optical path of the projection light beam 14 reflected by the first mirror 9 is obtained. As a result, it is possible to obtain a projector 100 capable of reducing the size and weight of the projection optical system and capable of displaying a large screen even at an extremely close distance.

  As apparent from the light rays shown in FIG. 4, since the range of use of the lens 80 a is a portion left on the opposite side to the above-mentioned notched portion, the sharpness and brightness of the image projected on the screen 20 are There is no effect.

  The lens 80a may be a molded lens such as a plastic lens, and may be molded in a partially missing shape.

(Example 3)
Next, the projection optical system of still another embodiment of the image display device according to the present invention will be described. FIG. 5 is a schematic view enlarging the main part of the projection optical system according to the present embodiment, and shows an example in which dustproof glass is added to the projection optical system shown in the first embodiment.

  The dustproof glass 11 is installed on the upper part of the second mirror 10 for the purpose of protecting the second mirror 10 which is a concave mirror and preventing dust from being mixed in the lens optical system 8. The installation of the dustproof glass 11 does not significantly deteriorate the quality of the projected image.

  In the present embodiment, it is desirable that the dustproof glass 11 be as small as possible. The reason is that if the dustproof glass 11 becomes large, the entire projection optical system becomes large, and the projector 100 becomes large.

  The projected light flux 14 directed to the screen 20 (not shown) is reflected by the second mirror 10 and is once condensed and diffused. Therefore, in order to achieve the above purpose without increasing the size of the dustproof glass 11, the light collecting position 15 may be in the vicinity of the dustproof glass 11. As shown in FIG. 5, when the condensing position 15 of the projection light beam 14 is in the vicinity of the dustproof glass 11, there is no need to enlarge the dustproof glass 11, and the projection optical system can be miniaturized. However, since the projection light beam 14 diffuses at once when the condensing position 15 is away from the dustproof glass 11, the dustproof glass 11 must be enlarged.

  That is, the projection light beam 14 directed from the second mirror 10 to the screen 20 is not distorted, the overall size of the projection optical system including the lens optical system 8, the first mirror 9 and the second mirror 10 can be reduced, and dustproof glass Considering the above three points that the size 11 can be made small, it is desirable that the condensing position 15 be a position close to both the dustproof glass 11 and the plane mirror 9 as in the projector 100 according to the present embodiment.

  Further, if there is dust at the light collecting position 15, the light amount at the screen 20 is reduced. Therefore, when the dustproof glass 11 is arranged at the light collecting position 15, it is arranged to be oblique to all the projected light beams 14. Good. For example, as shown in FIG. 5, the dustproof glass may be disposed parallel to the plane of the DMD 7.

(Example 4)
Next, the projection optical system of still another embodiment of the image display device according to the present invention will be described. FIG. 6 is a ray tracing diagram in the case where seven rays are emitted from the fifteen points on the DMD 7 shown in FIG. In FIG. 6, reference numerals 16 and 17 indicate optimum positions where an intermediate image is formed on the light path of the projector 100 according to the present embodiment.

  FIG. 7 is a plan view of the DMD 7. In FIG. 7, among the plurality of points on the plane of the DMD 7, the point 71 at the lower end in the Y-axis direction, which is the middle point in the X-axis direction, is eccentric in the Y-axis direction. The eccentricity is 1.56 mm.

  Return to FIG. FIG. 6 is a ray diagram showing the locus of light projected onto the screen by the projection optical system used in the image display device according to the present invention. As shown in FIG. 6, the projection optical system has two coupling optical systems of a coupling optical system by a lens optical system 8 and a coupling optical system consisting of a second mirror 10 which is a concave mirror. The lens optical system 8 has a function of forming an image of the DMD 7 (creating an intermediate image). The second mirror 10 has a function of connecting the intermediate image of the DMD 7 to the screen 20.

  The projection optical system having two imaging optical systems exhibits the function of connecting the image of the DMD 7 to the screen 20 "cleanly". In this case, the intermediate image may be a "blurred" image. Rather, in order to prevent debris from being reflected on the screen 20, it is preferable for the intermediate image to be a "blurred" image. This is because, when the intermediate image is "clean", the "mirrored intermediate image" is displayed on the screen 20 as "clean" by the second mirror 10.

  If there is dust in the vicinity of the first mirror 9, which is a flat mirror having an intermediate image, this dust image will be clearly displayed on the screen, but if this intermediate image is a "blurred" image Since the "blurred" image is projected on the screen 20 by the second mirror 10, even if the dust is on the first mirror 9, it becomes an image of the "blurred" dust on the screen 20, It is because it is hard to stand out. Therefore, in the lens optical system 8, it is preferable to form a “blurred” intermediate image, and it is preferable that the “blurred” intermediate image be clearly displayed on the screen 20 by the second mirror 10.

  However, since it is difficult to make an intermediate image of pixels close to the optical axis "blurred", in the projection optical system used in the image display apparatus according to the present embodiment, the first mirror which is a plane mirror is used. No intermediate image of pixels close to the optical axis is placed in the image.

  In FIG. 6, a position 16 indicates a position at which an intermediate image of pixels close to the optical axis is formed. The position 17 indicates the position at which the intermediate image of the image far from the optical axis is formed. In the DMD 11, the intermediate image of the pixel farthest from the optical axis of the lens optical system 8 naturally has large aberrations, so the diameter of the light spot on the mirror is large and the reflection of dust on the mirror surface is small.

  The second mirror 10, which is a concave mirror, ties the image of the intermediate image formed in the lens optical system 8 to the screen 20, so if there is dust near the position 16, the image of the dust will be tied to the screen 20 . In particular, when dust is present at the position of the intermediate image where the spot diameter is small (cleanly), the dust image is also clearly seen on the screen 20. On the other hand, when dust is present at the position of the large (blurred) intermediate image of the spot diameter, the dust image is reflected as a “blurred image” even on the screen 20, so the dust image is less noticeable. Therefore, an intermediate image of an image far from the optical axis is formed between the lens optical system 8 and the first mirror 9. As a result, it is possible to obtain an image display device capable of projecting a large screen by taking a large field curvature and bringing the distance between the screen 20 and the projector 100 close.

  The intermediate image formed on the reflective surface of the first mirror 9 by pixels distant from the vicinity of the optical axis to the optical axis is reflected by the second mirror 10 in order to avoid reflection of dust on the first mirror as described above. The spot diameter on the surface is made to be large (the intermediate image is made to be blurred), and the intermediate image is formed between the first mirror 9 and the second mirror.

  The lens on the first mirror 9 side of the lens optical system 8 is a two-piece aspheric lens, and the spot diameter is in an optimum state. In addition, the lens in the vicinity of the stop is an aspheric lens so that the spot diameter of the intermediate image of the pixel close to the optical axis is large and the spot diameter on the projection surface of the screen 20 of the pixel close to the optical axis becomes narrow. .

  The configuration is different from that of the projector 100 according to the present embodiment, and the projected light flux 14 that has passed through the lens optical system 8 hits the second mirror 10 without the projected light flux 14 emitted from the DMD 7 being folded back by the first mirror 9. In the case of a projector in which the projection optical system is disposed, the projector optical system is disposed on the exterior so that the main casing of the projector 100 collides with the screen 20, so the projector can not be installed. That is, as in the projector 100 shown in this embodiment, the first mirror 9 and the second mirror 10 are used to reflect the projected luminous flux 14 having strong divergence and to project it onto the screen 20. It is possible to obtain an image display device capable of close-range projection.

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

  Of the plurality of points on the plane of the DMD 7 shown in FIG. 7, this optical axis and the point 71 at the lower end in the Y-axis direction are eccentric in the Y-axis direction, and the eccentricity is 1.56 mm. That is, in FIG. 8, the optical axis is 1.56 mm lower than the lower end of the DMD 7.

  Further, as shown in FIG. 8, among the plurality of lens groups that constitute the lens optical system 8, the lens group closest to the DMD 11 that is the image display element includes the diaphragm 82. The amount of luminous flux reaching the screen 20 (not shown) from the DMD 11 can be determined by the stop 82, and the angle of view can be widened by including the stop 82 in the lens group closest to the DMD 11. it can. By this, it is possible to enlarge the spread of the light flux at the lens position close to the mirror optical system where the dust is most likely accumulated and the spread of the light flux on the reflection surface of the mirror optical system and reduce the influence of the dust reflection. .

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 surfaces 4, 5, 21, 22, 23 and 24 are aspheric surfaces, and these aspheric coefficients are shown in Table 2.

The equation for calculating the aspheric surface by applying the above aspheric coefficient is shown in Equation 1.

The coefficients for forming the reflection surface of the second mirror 10 are shown in Table 3.

An equation for calculating the reflection surface of the second mirror 10 by applying the above coefficient is shown in Equation 2.

The layout of the first mirror 9, the second mirror 10 and the dustproof glass 11 is shown in Table 4.

  According to the projector 100 having the configuration described above, it is possible to obtain a screen display device capable of displaying a large screen while performing extremely close projection.

  In the description in Table 3, "**" means exponentiation. Also, "*" means multiplication.

  As described above, the image display apparatus according to the present invention adjusts the position at which the intermediate image is formed, thereby reducing the influence of dust reflection and displaying an image of a large screen from a very close distance on the screen. Can do

7 DMD
8 lens optical system 9 first mirror 10 second mirror 14 projection light flux 15 focusing position

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

Claims (7)

A projection optical system used in an image display apparatus that projects a projection image formed by an image display element onto a projection surface,
A lens optical system having a plurality of lenses, and a mirror optical system comprising a first mirror which is a plane mirror and a second mirror which is a concave mirror;
The lens optical system is a coaxial optical system in which the plurality of lenses all share the optical axis, and the plurality of lenses are vertically disposed along the gravity direction.
The image display surface of the image display element is perpendicular to the projection surface,
A first projection light beam that reaches a position closest to the image display surface of the image display element on the projection surface in a plane including the optical axis of the coaxial optical system and perpendicular to the projection surface; The second projected light flux reaching the position farthest from the image display surface of the image display element on the surface is reflected by the second mirror and temporarily intersected, and then projected onto the projection surface,
And, after being reflected by the second mirror, a position at which the first projected light flux and the second projected light flux intersect is a position closer to the first mirror than the second mirror,
The lens surface of the lens closest to the first mirror among the plurality of lenses is a convex surface,
An intermediate image of the pixels relating to the image display element closest to the optical axis of the coaxial optical system is formed on the optical path from the first mirror to the second mirror, and is farthest from the optical axis of the coaxial optical system A projection optical system, wherein an intermediate image of pixels relating to the image display element is formed on an optical path from the lens optical system to the first mirror.   The projection optical system according to claim 1, wherein the lens optical system has an aperture stop adjacent to a lens closest to the image display element among the plurality of lenses. In the lens adjacent to the aperture stop, the spot diameter of the intermediate image of the pixel related to the image display element closest to the optical axis of the coaxial optical system is large, and the spot diameter of the pixel on the projection surface is narrow The projection optical system according to claim 2, characterized in that it is an aspheric lens.   The projection optical system according to any one of claims 1 to 3, wherein the second mirror is a free-form surface mirror. An illumination optical system for irradiating the image display element with light emitted from the light source;
The image display element which emits illumination light from the illumination optical system to form a projection image;
A projection optical system that has a positive refractive power as a whole and projects a projection image formed by the image display element onto a projection surface,
An image display apparatus characterized in that the projection optical system is the projection optical system according to any one of claims 1 to 4. Dustproof glass is provided between the second mirror and the projection surface,
The image display apparatus according to claim 5, wherein the dustproof glass is parallel to a plane of the image display element. The image display device has a plurality of two-dimensionally arranged micro mirrors, and is a reflection type that turns on / off the emission of reflected light by changing the inclination angle of each micro mirror in the on state and the off state. 7. The image display device according to claim 5, which is an image display element.