JP2022136517A - Projection optical system and image projection device - Google Patents

Abstract

To provide a projection optical system using a refractive reflection element capable of easily focusing.SOLUTION: A projection optical system enlarges and projects an image displayed on an image display element on a surface to be projected as a projection image. In the projection optical system, a refractive optical system and a refractive reflection optical element are arranged in order from a side of an image display surface to a side of the surface to be projected, the refractive optical system has a plurality of lens groups composed of one or more lenses, lens driving means for moving at least one lens group to an optical axis direction is provided, the refractive reflection optical element is constituted as a single optical element obtained by joining a reflection surface member and a refraction medium portion on a boundary surface, an incident surface and an emission surface of an imaging luminous flux emitted from the refractive optical system to the refraction medium portion are formed, a reflection surface is a curved surface having refractive power, one or more intermediate images are imaged in the refractive optical system and the refractive reflection optical element, and one or more intermediate images of the image displayed on the image display surface between the incident surface and the reflection surface of the refractive reflection optical element.SELECTED DRAWING: Figure 2

Description

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

2. Description of the Related Art In an optical apparatus such as an image projection apparatus using a reflection type projection optical system, which is represented by a camera or a projector, miniaturization of a mirror has become an issue in pursuit of further miniaturization.
As means for solving such a problem, for example, a dioptric-reflecting element having both properties of a lens having refractive power and a curved mirror is known.
However, in such refractive and reflective elements, the reflecting surface of the curved mirror is generally aspherical, and the entrance surface and the exit surface on the lens side are formed of the same spherical surface. However, there is a problem that the cost is increased.
In order to solve these problems, it has been considered to use a single optical element in which a reflecting surface member having a reflecting surface and a refracting medium portion arranged in close contact with the reflecting surface member are joined at the boundary surface. (See, for example, Patent Document 1, etc.).
However, particularly in the projection optical system, it is preferable to perform so-called focusing adjustment, in which the focal length of the entire projection optical system is changed without changing the magnification. In such focusing adjustment, there has been a problem that it is difficult to design an optical system that takes into consideration refractive and reflective optical elements having refractive power.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a projection optical system using refractive and reflective elements that enable easy focusing.

In order to solve the above-described problems, a projection optical system according to the present invention is a projection optical system that enlarges and projects an image displayed on an image display surface of an image display element onto a projection surface as a projection image, wherein the image is A lens group comprising a refracting optical system and a refracting/reflecting optical element arranged in order from the display surface side toward the projected surface side, wherein the refracting optical system is composed of one or a plurality of lenses. and lens driving means for moving at least one of the lens groups in the optical axis direction. a refractive medium portion disposed thereon, wherein the reflecting surface member and the refractive medium portion are configured as a single optical element joined at a boundary surface; An incident surface and an exit surface for an image light beam are formed, the reflecting surface is a curved surface having a refractive power, and an intermediate image of an image displayed on the image display surface is formed by the refractive optical system and the refractive reflection optical element. One or more images are formed, and one or more intermediate images of the image displayed on the image display surface are formed between the entrance surface and the reflection surface of the refractive and reflective optical element.

According to the present invention, it is possible to provide a projection optical system using refractive and reflective elements that enables easy focusing.

It is a figure showing an example of composition of an image projection device in an embodiment of the present invention. It is a figure which shows an example of a structure of the lens unit in 1st Example of this invention. FIG. 4 is a longitudinal aberration diagram in the first embodiment of the present invention; FIG. 4 is a lateral aberration diagram in the first embodiment of the present invention; 3 is a diagram showing an example in which the lens position of the lens unit shown in FIG. 2 is changed to Pos1; FIG. FIG. 6 is a longitudinal aberration diagram in the example shown in FIG. 5; FIG. 6 is a lateral aberration diagram in the embodiment shown in FIG. 5; 3 is a diagram showing an example in which the lens position of the lens unit shown in FIG. 2 is changed to Pos3; FIG. FIG. 9 is a longitudinal aberration diagram in the example shown in FIG. 8; FIG. 9 is a lateral aberration diagram in the example shown in FIG. 8; It is a figure which shows the modification of a structure of the lens unit of this invention. FIG. 4 is a diagram showing a second embodiment of the present invention; FIG. 13 is a longitudinal aberration diagram in the example shown in FIG. 12; FIG. 13 is a lateral aberration diagram in the example shown in FIG. 12; FIG. 13 is a diagram showing a longitudinal aberration diagram when the lens position of the lens unit shown in FIG. 12 is changed to Pos5; FIG. 13 is a diagram showing a longitudinal aberration diagram when the lens position of the lens unit shown in FIG. 12 is changed to Pos5;

FIG. 1 shows an example of the configuration of an image projection apparatus as one embodiment of the present invention.
The image projection apparatus 100 has a light source 101 that emits a light beam L0 that forms an image forming light beam, and an image display element 102 that displays an image to be projected on an image display surface and adds image information to the transmitted light beam. is doing.
The image projection apparatus 100 also controls a lens unit 200 having a projection optical system for projecting an image onto a projection plane 104, which is a surface to be projected, and an image display element 102 for displaying the image to be projected onto the projection plane 104. and a control unit for

The light source 101 uses a halogen lamp, which is a light source for emitting light, to emit white light substantially in parallel. Here, a metal halide lamp, a high-pressure mercury lamp, or an LED may be used as the light source.
Light source 101 is a white light source, but a light source that combines multiple monochromatic light sources, such as laser light sources, converted to wavelengths corresponding to one or more basic colors, such as R, G, B, or It may be a light source that combines the converted light with the monochromatic light of the laser light source.

The image display element 102 is an image display means that gives image information by transmitting incident light beams, imparting spatial modulation to the light beams, and emitting the light beams. It is a reflective spatial light modulator. The image display element 102 may be a liquid crystal panel, or may be a self-luminous light emitting element array. Further, the image display element 102 may display an image input from an external device such as a computer, or display image data configured by a control unit arranged inside the image projection apparatus. It can be.

A configuration of the lens unit 200 will be described.
The optical axis of incident light to the lens unit 200, that is, the lens optical axis, is defined as the Z axis, and the axis that is parallel to the vertical direction of the paper surface in FIG. Define the vertical axis as the X-axis. Regarding the directions of the X-axis, Y-axis, and Z-axis, the direction of the arrow shown in FIG. 2 is defined as the positive direction.

As shown in FIG. 2, the lens unit 200 includes a plurality of lenses LN1 to LN17 arranged on the Z-axis and constituting the refractive optical system 10, and a lens LN17 downstream in the Z direction for projecting an imaging light flux. and a cemented lens 20 which is a refractive and reflective optical element for projecting toward the surface 104 .
That is, in this embodiment, the lens unit 200 constitutes a projection optical system in which a refractive optical system and a refractive reflective optical element are sequentially arranged from the image display surface side toward the projection surface 104 side. there is

The refractive optical system 10 is a refractive optical system composed of a plurality of lenses LN1 to LN17. Also, a cemented lens in which two or more of these lenses are cemented together may be used. In this embodiment, a configuration using 17 lenses is described, but the number of lenses constituting the refractive optical system 10 is not limited, and an appropriate number may be used according to various optical design conditions. good.

The cemented lens 20 has an incident surface 20A on which the imaging light beam L1 from the refractive optical system 10 is incident, a reflecting surface 20B functioning as a concave mirror, and an imaging light beam L1 reflected by the reflecting surface 20B as a projection light beam L2. and an exit surface 20C from which the light is emitted.
The cemented lens 20 has a reflective surface member 21 and a refracting medium portion 22 in close contact with each other at a boundary surface 23, and the reflective surface member 21 and the refracting medium portion 22 are integrally formed to form a "single lens". It is configured as an optical element.

The imaging light flux L1 emitted from the refractive optical system 10 enters from the incident surface 20A of the cemented lens 20, passes through the reflecting surface member 21 from the refractive medium portion 22, and is reflected by the reflecting surface 20B. The light is emitted toward a projection surface 104, which is a projection surface.
Of the entrance surface 20A, the reflection surface 20B, and the exit surface 20C of the cemented lens 20, at least the reflection surface 20B is a "curved surface having refractive power", and at least one of the entrance surface 20A and the exit surface 20C has a refractive power. can have In addition, when it has refractive power here, it may have either positive or negative refractive power. Also, what is the shape of the surface with such refractive power? In addition to a spherical shape such as a convex spherical surface or a concave spherical surface, it may be an aspherical shape, an anamorphic shape such as a cylindrical surface, or a free curved surface.
The image display surface of the image display device 102 and the projection image enlarged and projected onto the projection surface 104 have a conjugate relationship due to the projection optical system. In addition, such a projection optical system is arranged inside the cemented lens 20, in other words, at least at one or more positions in the optical path from the incident surface 20A to the exit surface 20C. Form an "intermediate image" of the image.
In addition, since one or more intermediate images are formed inside the cemented lens 20 at this time, an image may be formed once in the refractive optical system 10 as well. Therefore, one or more intermediate images are formed in the entire projection optical system.

The reflecting surface member 21 has a concave, aspherical reflecting surface 20B on the inner surface side, and is arranged on the +Z direction side of the refractive medium portion 22 . In this embodiment, the interface 23 with the refractive medium portion 22 is parallel to the XY plane, but the configuration is not limited to this.
The refracting medium portion 22 is made of an optical material such as glass or plastic, and has an incident surface 20A on the lower portion in FIG. 2 on the -Z direction side and an output surface 20C on the same spherical surface.
By joining the reflective surface member 21 and the refractive medium portion 22 at the boundary surface 23, the cemented lens 20 has a spherical surface on the −Z direction side and an aspherical surface on the +Z direction side. It functions as a reflective optical element. The “boundary surface” can also be rephrased as a “joint surface” between the reflecting surface member 21 and the refracting medium portion 22 .

In general, optical elements are produced by lens polishing, molding using a mold, or the like.
However, it is difficult to perform reflection as well as refraction because the lens thickness increases.
By integrally forming the reflecting surface member 21 and the refractive medium portion 22 as in this embodiment, it is possible to manufacture a refractive and reflective optical element that is easier to manufacture and is less expensive.

However, if the two optical elements are simply joined together, there is a risk that foreign matter adhering to the boundary surface 23 will cause deterioration in optical performance.
Therefore, in this embodiment, as shown in the main optical path diagram in FIG. at least one is formed in

By arranging the intermediate image Im1 inside the cemented lens 20 in this manner, the influence of defects such as foreign matter entering the boundary surface 23 can be suppressed.

In this embodiment, the projection optical system 10 is composed of a plurality of movable lens groups.
Specifically, it has a first movable lens group 11 composed of a lens LN1, a second movable lens group 12 of LN11, and a third movable lens group 13 of lenses LN12 to LN15.
These lens groups are integrally driven using a first cam 11a, a second cam 12a, and a third cam 13a, which are lens driving means for moving in the ±Z direction, which is the direction of the optical axis. be.

In this embodiment, the first cam 11a, the second cam 12a, and the third cam 13a may all be known lens driving means, and the shape of the cam and the like may be appropriately designed according to the size and weight of the lens. description is omitted.

As for the projection optical system 10, it is desirable that the projection surface 104 can be freely installed within a certain range in terms of design, and the image on the image display surface is projected on the projection surface 104 in a focused state. is required.
In general, it is desirable that the projection optical system 10 has a configuration that allows so-called focus adjustment (focusing) to be performed after the position of the projection plane 104 is determined.
In this embodiment, the first cam 11a, the second cam 12a, and the third cam 13a, the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are arranged in the optical axis direction, respectively. By functioning as lens driving means for moving in the ±Z directions, focus adjustment is possible.

In focus adjustment, the image displayed on the image display surface is formed on the projection surface 104 by changing the focal length of the entire system of the projection optical system 10 without changing the positions of the image display surface and the projection surface 104 . Adjust to
That is, in principle, when adjusting the focus, it is required to prevent angular fluctuations in the emitted light rays emitted from the emission surface 20C to the screen among the principal rays emitted from the image display surface.

In this way, suppressing the angular fluctuations of the emitted light rays emitted from the emission surface 20C to the projection surface 104 is, in other words, the movement of the first movable lens group 11, the second movable lens group 12, and the third lens group 13. It is equivalent to keeping the height of the chief ray from changing before and after . With such a configuration, the image projected on the projection surface 104 should not change in size with respect to the image display element 102 because the position of the projection surface 104 remains unchanged. In other words, it is possible to keep magnification fluctuations low during focus adjustment.

Numerical examples of such a lens unit 200 will be shown together with specific optical system data.

As already shown in FIG. 2, the refractive optical system 10 in the numerical example is constructed by sequentially arranging 17 lenses LN1 to LN17 from the object side to the image side. Four lenses LN3 to LN6 are cemented together, and an aperture stop S is arranged between lens LN8 and lens LN9.
The cemented lens 20 has a "double convex lens shape", the incident surface 20A and the exit surface 20C are the same lens surface, and the reflecting surface 20B is formed by vapor-depositing a reflecting film on the lens surface as a "reflecting surface member". there is

In the numerical examples, the "oblique beam" is used as the imaging beam L1. That is, as shown in FIG. 2, the image displayed on the image display element 102 is shifted in the +Y direction with respect to the lens optical axis of the projection optical system. The oblique luminous flux as the imaging luminous flux L1 forms an intermediate image Im1 as an inverted image inside the refracting medium portion 22 by the refractive optical system 10 and the positive refractive power of the incident surface 20A of the cemented lens 20 .
Using the intermediate image Im1 as an object, the projection image is enlarged and projected toward the projection surface 104 due to the positive refractive power of the reflection surface 20B and the exit surface 20C. It should be noted that the illustration of the projection surface 104 is omitted in the following embodiments.
The lens positioned closer to the image side than the aperture stop has a shape (for example, a D-cut lens) in which an unused lens portion is cut so as not to "blind" the imaging light flux L1 reflected by the reflecting surface 20B. shape).

The projection optical system of the first embodiment projects an image displayed on the image display surface of the image display element 102 having 1920×1080 pixels and a pitch of 7.56 μm. A form of enlarged projection onto the projection surface 104 having a diagonal length is assumed.
When the projection surface 104, which is a screen for enlarged projection, has a surface number S0 and the image display surface of the image display element 102 has a surface number Si, the projection optical system 10 makes the S0 surface and the Si surface optically conjugate with each other.

That is, for example, when the surface distance D of the S0 surface is -554.813, the image projection apparatus 100 is in a state of being "focused" on the projection surface 104 located -554.813 mm ahead. The ratio between the size of the projection surface 104 and the size of the image display element 102 at that time is indicated as "magnification".

Further, the state in which the actual position of the projection surface 104 and the position of the S0 plane are different is the "out of focus" state. The first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are each moved in the ±Z direction by a predetermined amount by using the lens driving means in the out-of-focus state. Adjustment to change the distance from the image projection device 100 to the projection surface 104 so as to match the distance to the S0 surface in the lens system of the projection optical system 10 is "focus adjustment" (focusing).
In this way, considering the actual operation, the image projection apparatus 100 of the present embodiment has the effect that "magnification does not change before and after focus adjustment". Since this movement is equivalent to changing the focal length, the magnification of the projection plane 104 with respect to the image display element 102 changes when each position of Pos1, Pos2, and Pos3, which will be described later, is taken.

As for the surface * shown in Table 1, the aspherical surface represented by Equation 1 is used, and Table 2 shows the coefficients of each aspherical surface.

In the numerical example shown in Table 1, the projection distance is "-554.813 mm" and the projection magnification is "162.7 times" indicated on the surface number S0.

In the optical system data shown below, the "surface number" is expressed by numbers counted from the enlargement side to the reduction side, with "S0" as the surface of the screen to be projected and "Si" as the image display surface.
"R" represents the radius of curvature of each surface including the surface of the aperture stop S and the color synthesizing prism P (the paraxial radius of curvature in the case of an aspherical surface).
"D" represents the interplanar spacing on the optical axis.
"Nd" and "Vd" represent the refractive index and Abbe number for the d-line of the material of each lens.
"Effective diameter" represents the optical effective diameter of each surface. The unit of quantity having a dimension of length is "mm" unless otherwise specified.
Radius of curvature: Surfaces marked with (*) in the column of R are "aspherical surfaces".
Aspherical surface: aspherical amount: Z, height from optical axis: r, conic constant: k, second to 20th even-order aspherical coefficients: A, B, ..., G, H, J is represented by the well-known following equation.

Table 1 shows the optical system data of the example. In Table 1, the portions indicated by .DELTA. A case where the second movable lens group 12 and the third movable lens group 13 are moved is shown.

"Aspheric Data"
Aspheric data are shown in Table 2.
For example, "2.507680E-11" in aspheric data means "2.507680×10 ^-11 ".
As shown in "Table 1", the entrance surface (S28) and the exit surface (S30) of the catadioptric optical element are the same surface and are "convex spherical", and the reflection surface (S29) is " It is a rotationally symmetrical aspherical surface.

Aberration diagrams of the example are shown in FIGS. 3 and 4. FIG.
FIG. 3 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. FIG. 4 is a lateral aberration diagram showing coma.

In the diagrams of astigmatism, the "bold line" relates to the "meridional ray" and the "thin line" relates to the "sagittal ray". As is clear from FIGS. 3 and 4, aberrations are well corrected, and the projection optical system of the example has high performance.

FIG. 5 is a ray diagram at Pos1 where the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are respectively moved from Pos2 shown in FIG.
The position Pos1 of the lens group assumes an aspect in which an image displayed on the image display device 102 is enlarged and projected onto the projection surface 104 having a diagonal length of 305.9 inches.
At this time, as shown in Table 3, the distance S0 at Pos1 of −1632.778 mm represents the actual projection distance, and the image on the image display surface is projected onto the projection surface 104 at a magnification of 466.6.
Aberration diagrams at this time are shown in FIGS.
FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. FIG. 7 is a lateral aberration diagram showing coma.

FIG. 8 is a ray diagram at Pos3 where the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are respectively moved from Pos2 shown in FIG.
The position Pos3 of the lens group assumes an aspect in which an image displayed on the image display element 102 is enlarged and projected onto the projection surface 104 having a diagonal length of 60.7 inches.
At this time, as shown in Table 3, the distance S0 at Pos3 of −306.169 mm represents the actual projection distance, and the image on the image display surface is projected onto the projection surface 104 at a magnification of 92.6.
Aberration diagrams at this time are shown in FIGS. 9 and 10. FIG.
FIG. 9 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. FIG. 10 is a lateral aberration diagram showing coma.

In this way, with Pos2 as a reference position, each lens group can be moved to each position of Pos1 and Pos3, so that the projection distance can be changed from -306.169 to -1632.778 mm This enables focus adjustment and magnified projection from 60.7 inches to 305.9 inches.

By the way, when the position of each lens group is changed from Pos1 to Pos3 using the lens driving means for such focus adjustment, the emission surface of the cemented lens 20 for the principal ray with a maximum object height of 12.5 mm in the image display device 102 If the angle of the ray from 20C toward the projection plane 104 changes, the position of the image on the projection plane 104 will change. In such a case, it becomes necessary to adjust the positional relationship between the screen and the image projection apparatus 100 each time focus adjustment is performed.
Therefore, in this embodiment, when the lens driving means moves the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13, the height of the chief ray of the projection optical system 10 The performance of each lens is determined so that the change in is suppressed within a predetermined range.
In other words, in the present embodiment, the performance of each lens is determined so that the angle of the outgoing light beam is suppressed within a predetermined range before and after the movement for focus adjustment.

Specifically, the ray angle from the emission surface 20C of the cemented lens 20 to the projection surface 104 of the principal ray with the maximum object height of 12.5 mm on the image display element 102 side in this embodiment is Pos1: 74.2259 degrees, Pos2: 74.2532 degrees, Pos3: 74.2652 degrees. That is, the amount of angular variation in the angle of light projected onto the screen is suppressed within the range of -0.0273 to 0.012 degrees, and the variation in magnification is suppressed within -0.18 to 0.08%. there is
In this way, by suppressing the change in magnification before and after movement of the lens group during focus adjustment to within 0.5%, focus adjustment can be performed smoothly.

In addition, in the embodiment of FIG. 2, the cemented lens 20 used as a refracting/reflecting optical element has a flat boundary surface 23 between the refracting medium portion 22 and the reflecting surface member 21. However, the configuration is limited to such a structure. For example, as shown in FIG. 11, the boundary surface 23 may be curved.
Even when the boundary surface 23 is curved as described above, the position where the intermediate image Im1 is formed does not overlap with the boundary surface 23, and the main light rays of the imaging light flux L1 are concentrated. However, it is desirable that both of them are arranged inside the refractive medium portion 22 of the cemented lens 20 .
With such a configuration, the intermediate image Im1 does not straddle the boundary surface 23, so that it is possible to manufacture the refractive-reflective element more easily and inexpensively.
In this way, by arranging the interface 23 of the cemented lens 20 and the position where the intermediate image Im1 is formed so as not to overlap, the influence of dirt, foreign matter, etc. on the interface 23 can be further reduced.

In addition, with such a configuration, it is possible to adjust the refractive power of the boundary surface 23 in consideration of the shape of the boundary surface 23. The cemented lens 20 can be further miniaturized and manufactured more easily and inexpensively.

A lens unit 300 is shown in FIG. 12 as a second embodiment of the present invention. In the lens unit 300, the same reference numerals are given to the same configurations as those of the already described first embodiment, and the description thereof will be omitted as appropriate.
The lens unit 300 is an embodiment in which the number of movable lens groups in the projection optical system 10 shown in FIG. 2 is reduced based on the lens arrangement of Pos2.

In this embodiment, as shown in Table 4, only the third lens group 13 operates, excluding the first movable lens group 11 and the second lens group 12 in the first numerical example. The positions of the surface numbers S9 and S17 change.

Pos2 shown in Table 4 has the same optical performance as Pos2 in the first numerical example, and the description is omitted to avoid duplication.

The position indicated by Pos4 in Table 4 assumes that the image displayed on the image display device 102 is enlarged and projected onto the projection surface 104 having a diagonal length of 115.9 inches.
As shown in Table 4, the S0 interval of −604.813 mm indicates the actual projection distance, and the image is projected onto the projection surface 104 at an image magnification of 176.8 times.
FIG. 13 shows longitudinal aberration diagrams and FIG. 14 shows lateral aberration diagrams in such a positional relationship.

Table 4 also shows each configuration at Pos5 in which the second movable lens group 12 and the third movable lens group 13 are respectively moved from Pos2.
The position Pos5 of the lens group assumes an aspect in which an image displayed on the image display element 102 is enlarged and projected onto the projection surface 104 having a diagonal length of 97.5 inches.
At this time, as shown in Table 4, the distance S0 at Pos5 of −504.813 mm represents the actual projection distance, and the image on the image display surface is projected onto the projection surface 104 at a magnification of 148.7.
Aberration diagrams at this time are shown in FIGS. 15 and 16. FIG.
FIG. 15 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion, similar to FIG. FIG. 16 is a lateral aberration diagram showing coma aberration, similar to FIG.

As described above, with Pos2 as a reference, the third lens moving group 13, which is one lens moving group, can move each lens group to the respective positions of Pos4 and Pos5, thereby reducing the projection distance to -504. It is variable from 813 to -604.813 mm, allows focus adjustment and magnified projection from 97.5 inches to 115.9 inches.

Similarly, in this embodiment, when the lens driving means moves the third movable lens group 13, each lens is arranged so that the change in the height of the principal ray of the projection optical system 10 is suppressed within a predetermined range. The performance of the lens is defined.
In other words, in the present embodiment, the performance of each lens is determined so that the angle of the outgoing light beam is suppressed within a predetermined range before and after the movement for focus adjustment.

Specifically, the ray angle of the principal ray of the maximum object height of 12.5 mm on the side of the image display device 102 in this embodiment from the output surface 20C of the cemented lens 20 to the projection surface 104 is Pos4: 74.2414 degrees, Pos2 : 74.2532 degrees, Pos5: 74.2677 degrees. That is, the amount of angular variation in the angle of light projected onto the screen is suppressed within the range of -0.0118 to 0.0145 degrees, and the variation in magnification is suppressed within -0.08 to 0.10%. there is
In this way, by suppressing the change in magnification of the entire lens unit 300 before and after movement of the lens group during focus adjustment to within 0.5%, focus adjustment can be performed smoothly.

Although the preferred embodiments of the invention have been described above, the invention is not limited to the specific embodiments described above, and the invention described in the scope of claims unless specifically limited in the above description. Various modifications and changes are possible within the scope of the spirit.
For example, a refractive reflective optical element is a "single optical element", but "single" is a morphology. Although the case where the refractive medium portion has a single structure has been described above, the structure of the refractive medium portion is not limited to this. may be When the refracting medium section is composed of a plurality of optical media in this way, the number of parameters for adjusting the performance of the projection optical system increases, so the design of the projection optical system becomes easier.

The effects described in the embodiments of the present invention are merely enumerations of preferred effects resulting from the invention, and the effects of the invention are not limited to "those described in the embodiments".

10 Refractive optics
REFERENCE SIGNS LIST 11 1st movable lens group 12 2nd movable lens group 13 3rd movable lens group 11A, 12A, 13A lens driving means 20 refracting/reflecting optical element (cemented lens)
20A Entrance surface of refractive reflective optical element
20B Reflective surface of refractive reflective optical element
20C exit surface of refractive reflective optical element
21 reflective surface member
22 refracting medium
23 boundary surface 100 image projection device 102 image display element 104 projection surface 200 lens unit 300 lens units LN1 to LN17 lenses constituting refractive optical system Im1 intermediate image

Japanese Patent Application Laid-Open No. 2020-042103

Claims (6)

A projection optical system that enlarges and projects an image displayed on an image display surface of an image display element onto a projection surface as a projection image,
A refracting optical system and a refracting/reflecting optical element are sequentially arranged from the image display surface side toward the projected surface side,
The refractive optical system has a plurality of lens groups each composed of one or more lenses,
A lens driving means for moving at least one of the lens groups in the optical axis direction,
The dioptric-reflection optical element has a reflective surface member having a reflective surface and a refracting medium portion disposed in close contact with the reflective surface member, and the reflective surface member and the refracting medium portion are joined at a boundary surface. an incident surface and an exit surface for an imaging light flux emitted from the refractive optical system are formed in the refractive medium portion, and the reflecting surface is a curved surface having refractive power,
one or more intermediate images of the image displayed on the image display surface are formed in the refractive optical system and the refractive and reflective optical element;
A projection optical system that forms one or more intermediate images of the image displayed on the image display surface between the entrance surface and the reflection surface of the refractive/reflection optical element. The projection optical system according to claim 1,
A projection optical system, wherein the boundary surface is a plane. The projection optical system according to claim 1,
A projection optical system, wherein the boundary surface is a curved surface. The projection optical system according to any one of claims 1 to 3,
A projection optical system, wherein the intermediate image is formed at a position that does not overlap with the boundary surface. The projection optical system according to any one of claims 1 to 4,
A projection optical system, wherein a change in height of a principal ray of the projection optical system is within a predetermined range when the lens driving means moves the lens group. a projection optical system according to any one of claims 1 to 5;
a light source;
an image display element for displaying an image on an image display surface;
An image projection device having

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