JP7148334B2 - Projection optical system and image projection device - Google Patents

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 a means for solving such a problem, for example, a refracting/reflecting element having both properties of a lens having refractive power and a curved mirror is known (see, for example, Patent Documents 1 and 2).
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.

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

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 refracting optical system and a refracting/reflecting optical element are arranged in order from the display surface side toward the projected surface side, the refracting optical system is composed of a plurality of lenses, and the refracting/reflecting optical element has a reflective surface member having a reflective surface and a refractive medium portion disposed in close contact with the reflective surface, wherein the reflective surface member and the refractive medium portion are joined at an interface to form a single optic The refracting medium portion is formed with an incident surface and an exit surface for an imaging light beam emitted from the refracting optical system, the reflecting surface is a curved surface having a refractive power, and the refracting optical system and the refracting/reflecting One or more intermediate images of the image displayed on the image display surface are formed on the optical element, and displayed on the image display surface between the incident surface and the reflective surface of the dioptric/reflection optical element. One or more intermediate images of the image are formed.

ADVANTAGE OF THE INVENTION According to this invention, a refractive reflective element can be manufactured easily and cheaply.

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 an aberration diagram in the first embodiment of the present invention; It is a coma-aberration diagram in the 1st Example of this invention. FIG. 4 is a diagram showing a second embodiment of the present invention; FIG. 13 is a diagram showing a third embodiment of the present invention; FIG. 10 is a diagram showing a fourth embodiment of the present invention; FIG. 10 is a diagram showing a fifth embodiment of the present invention;

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 LN11 arranged on the Z-axis and constituting the refractive optical system 10, and a lens LN11 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 LN11, and may be a cemented lens in which two or more of these lenses are cemented together. In this embodiment, a configuration using 11 lenses will be 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.

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.

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 11 lenses LN1 to LN11 from the object side to the image side. The three lenses LN2 to LN4 are cemented together, and an aperture stop S is arranged between the lens LN4 and the lens LN5.
On the image side of the aperture stop S, seven lenses LN5 to LN11 are arranged.
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.
Of the lenses LN5 to LN11 located closer to the image side than the aperture stop S, the lenses LN9 to LN11 have unused lens portions removed so as not to eclipse the imaging light flux L1 reflected by the reflecting surface 20B. A shape (for example, a shape like a D-cut lens) may be used.

The projection optical system of the first embodiment projects an image displayed on the image display surface of the image display element 104 having 1920×1080 pixels and a pitch of 5.4 μm. A form of enlarged projection onto the projection surface 104 having a diagonal length is assumed.
The object height in imaging is 10 mm and the focal length is 4.28 mm. The numerical aperture NA is 0.2778, the total length of the optical system is 193.28 mm, and the imaging magnification is 201.6 times. The projection distance is "-855 mm" and the projection magnification is "201.6 times".

In the optical system data shown below, the "surface number" is represented by a number counted from the reduction side (image display surface side) toward the enlargement side. is referred to as "Si".
"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.

"Aspheric Data"
Aspheric data are shown in Table 2.
For example, "-1.392830E-17" in aspheric data means "-1.392830×10 ^-17 ".
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 diagram of spherical aberration, astigmatism, and distortion. FIG. 4 is a diagram of coma aberration.

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 shows a second example of the embodiment shown in FIG. 2 as an explanatory diagram. In the following embodiments, the same reference numerals as those in FIG. 2 are assigned to the parts that are not likely to cause confusion, and the explanations thereof are omitted as appropriate. In particular, the shape of each lens surface of the refractive optical system 10 conforms to the configurations shown in Tables 1, 2, and the like.

In the second embodiment shown in FIG. 5, the position where the intermediate image Im1 is formed does not overlap the boundary surface 23, and the position where the principal rays of the imaging light flux L1 concentrate is 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.
Also, the imaging position of the intermediate image Im1 is expected to reach a high temperature because the rays are concentrated there. If such a temperature rise causes a difference in thermal expansion between the refractive medium portion 22 of the cemented lens 20 and the reflecting surface member 21, the optical performance is significantly affected. However, it is preferable to position it inside the cemented lens 20 and not overlap with the boundary surface 23 because it is easier to reduce the effects of such concentration of rays and the associated temperature rise. Also, when assembling the lens unit 200, etc., it is preferable because there is no possibility of touching the vicinity of the condensing position.

FIG. 6 shows a third example of the embodiment shown in FIG. 2 as an explanatory diagram.

In the third embodiment shown in FIG. 6, the boundary surface 23 has a curved shape curved with respect to the XY plane.
With this configuration, the refractive power of the boundary surface 23 can also be considered for adjustment. The lens 20 can be made smaller and manufactured more easily and inexpensively.

A lens unit 300 is shown in FIG. 7 as a fourth 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.
In the lens unit 300, the cemented lens 30 has a first reflecting surface 30B and a second reflecting surface 30C between the entrance surface 30A and the exit surface 30D.
The cemented lens 30 has a reflecting surface member 31 having a first reflecting surface 30B, and a refractive medium portion 32 arranged in close contact with the reflecting surface member 31. The reflecting surface member 31 and the refractive medium portion 32 form a boundary. It is constructed as a single optical element joined at surfaces 33 .
In addition, "the entrance surface 30A and the exit surface 30D of the imaging light flux L1 emitted from the refractive optical system 10 are formed in the refractive medium portion 32, and between the entrance surface 30A and the reflection surface 30B of the cemented lens 30, the image display surface One or more intermediate images Im1 of the image displayed on the image are formed.

In other words, the cemented lens 30 in this embodiment has a plurality of reflecting surfaces. Further, of the two reflecting surfaces, the first reflecting surface 30B has a curved shape and refractive power, as is clear from FIG. On the other hand, the second reflecting surface 30C has a planar shape parallel to the ZX plane and has no refractive power.
That is, in this embodiment, "the dioptric-reflecting optical element has a second reflecting surface extending in a direction parallel to the optical axis of the lens of the dioptric system".

In this way, since the cemented lens 30 has a plurality of reflecting surfaces, the distance of the optical path passing through the refractive medium portion 32 is extended. The size can be reduced while maintaining the overall refractive power. That is, it contributes to cost reduction and miniaturization of the lens unit 300 .
Further, by making at least one of the plurality of reflecting surfaces of the cemented lens 30 the second reflecting surface 30C extending in the direction parallel to the optical axis of the lens, the second reflection in the cemented lens 30 This is more preferable because the influence of the power of the surface 30C can be suppressed.

Now, as a fifth embodiment of the present invention, a configuration as shown in FIG. 8 will be described.
In the fifth embodiment, instead of the cemented lens 30 used in the fourth embodiment, a D-cut lens 40 is used as a refracting/reflecting optical element. To avoid complicating the description, the refractive optical system 10 is assumed to have the same configuration as in the first embodiment, and description thereof will be omitted.
As shown in FIG. 8, the D-cut lens 40 in this embodiment is configured as a single optical element. That is, it is a single optical element with no boundary surface.
The D-cut lens 40 has an entrance surface 40A and an exit surface 40D, and is arranged on the optical path between the entrance surface 40A and the exit surface 40D. and a second reflecting surface 40C having a parallel planar shape.

In such a configuration, the material of the D-cut lens 40 is preferably the optical material used for the refractive medium portion 22 in the first embodiment, for example.
In addition, in this embodiment, the surface of the D-cut lens 40 on the +Z direction side functions as the first reflecting surface 40B, and with such a configuration, it is possible to easily manufacture a refractive-reflecting element at low cost. .
In addition, in the present embodiment, the first reflecting surface 40B is a metal thin film formed on the surface of the D-cut lens 40 on the +Z direction side, but the configuration is not limited to this.
In the present embodiment, the second reflecting surface 40C is a planar reflecting surface that is parallel to the XZ plane and has no refractive power. Any one of the two reflecting surfaces 40C should have refractive power.

In the third embodiment, a refracting optical system and a refracting/reflecting optical element are sequentially arranged from the image display surface side toward the projected surface side, and the refracting optical system is composed of a plurality of lenses. wherein the refractive reflective optical element is configured as a single optical element having a first reflective surface, a second reflective surface, and a refractive medium portion disposed in close contact with the reflective surface; An incident surface and an exit surface for an imaging light beam emitted from the refractive optical system are formed in the medium portion, at least one of the first reflecting surface and the second reflecting surface is a curved surface having a refractive power, and One or more intermediate images of the image displayed on the image display surface are formed in the optical system and the refractive and reflective optical element, and the image is formed between the incident surface and the reflective surface of the refractive and reflective optical element. One or more intermediate images of the image displayed on the display surface are formed.'
In general, the higher the refractive index of the optical material, the more desirable it is because the required refractive power can be achieved with a small lens. However, such high refractive index optical materials are expensive and difficult to process. It is known. However, in this embodiment, it is possible to reflect the imaging light beam L1 between the first reflecting surface 40B and the second reflecting surface 40C, thereby increasing the internal optical path length without changing the size of the refracting/reflecting optical element. Therefore, the desired optical performance can be provided to the lens unit 300 even with further miniaturization and the use of an optical material with a relatively low refractive index.
According to this configuration, the intermediate image Im1 is formed inside the refracting/reflecting optical element, and the image is reflected a plurality of times. contribute to

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".

102 image display element 10 refractive optical system
20 Refractive reflective optical element (bonded 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 30 Refractive reflective optical element (bonded lens)
30A Entrance surface of refractive/reflection optical element 30B First reflecting surface of refractive/reflection optical element 30C Second reflecting surface of refractive/reflection optical element 30D Exit surface of refractive/reflection optical element 31 Reflecting surface member
32 refracting medium
33 Boundary surface 40 Refractive reflective optical element (D cut lens)
LN1 to LN11 lens constituting refractive optical system S aperture stop
Im1 intermediate image

Japanese Patent No. 5274030 Japanese Patent No. 5632782

Claims (7)

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 is composed of a plurality of lenses,
The dioptric-reflective optical element has a reflective surface member having a reflective surface and a refracting medium portion disposed in close contact with the reflective surface, 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/reflective 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 the dioptric-reflection optical element has a second reflecting surface extending in a direction parallel to an optical axis of a lens of the dioptric system. 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 is composed of a plurality of lenses,
The refractive and reflective optical element is configured as a single optical element having a first reflecting surface, a second reflecting surface, and a refractive medium portion disposed in close contact with the reflecting surface,
An incident surface and an exit surface for an imaging light beam emitted from the refractive optical system are formed in the refractive medium portion, the first reflecting surface is a curved surface having a refractive power, and the second reflecting surface is a planar shape, 1. A projection optical system , wherein one or more intermediate images of an image displayed on said image display surface are formed between said incident surface and said reflecting surface of said refractive and reflective optical element. a projection optical system according to any one of claims 1 to 6;
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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