JP2020042103A - Projection optical system and image projection device - Google Patents

Abstract

To provide a projection optical system that uses a refractive/reflective optical element that is inexpensive and easily manufactured.SOLUTION: A projection optical system enlarges and projects an image displayed on an image display surface of an image display element on a projection target surface as a projection image, and has a dioptric system and a refractive/reflective optical element sequentially arranged from a display surface side toward a projection target surface side. The dioptric system consists of a plurality of lenses; the refractive/reflective optical element has a reflective surface member having a reflective surface and a refractive medium part arranged in close contact with the reflective surface; the reflective surface member and the refractive medium part are formed as a single optical element joined on a boundary surface; the refractive medium part is formed with an incident surface and an emission surface for an image forming light beam emitted from the dioptric system; the reflective surface is a curved face having a refractive power. In the dioptric system and the refractive/reflective optical element, one or more intermediate images of an image displayed on the image display surface are formed, and between the incident surface and the emission surface of the refractive/reflective optical element, one or more intermediate images of the image displayed on the image display surface are formed.SELECTED DRAWING: Figure 2

Description

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

2. Description of the Related Art In an optical device such as an image projection device using a reflection type projection optical system represented by a camera or a projector, miniaturization of a mirror has been an issue in pursuit of further miniaturization.
As means for solving such a problem, for example, a refraction / reflection element having both the properties of a lens having a refractive power and a curved mirror is known (for example, see Patent Documents 1 and 2).
However, in such a refraction / reflection element, generally, the reflection surface of the curved mirror is an aspheric surface, and the entrance surface and the exit surface side, which are the lens side, have the same spherical surface. Thus, there is a problem that the cost is increased.

  The present invention has been made in view of the above-described problems, and has as its object to provide a projection optical system that uses an inexpensive refracting and reflecting element that is easy to produce.

  In order to solve the above-described problem, 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 as a projection image on a projection surface, and From the side of the display surface to the side of the projection surface, a refractive optical system and a refractive optical element are sequentially arranged, and the refractive optical system is configured by a plurality of lenses, and the refractive optical element is Has a reflection surface member having a reflection surface, and a refraction medium portion disposed in close contact with the reflection surface, and a single optical element in which the reflection surface member and the refraction medium portion are joined at a boundary surface. An incident surface and an exit surface of an image forming light beam emitted from the refracting optical system are formed in the refracting medium portion, and the reflecting surface is a curved surface having a refracting power; In the optical element, the image display surface One or more intermediate images of the displayed image are formed, and one or more intermediate images of the image displayed on the image display surface are formed between the incident surface and the reflective surface of the refractive optical element. .

  According to the present invention, an easy and inexpensive refraction / reflection element can be manufactured.

FIG. 1 is a diagram illustrating an example of a configuration of an image projection device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a configuration of a lens unit according to the first embodiment of the present invention. FIG. 4 is an aberration diagram in the first example of the present invention. FIG. 3 is a coma aberration diagram in the first example of the present invention. FIG. 6 is a diagram showing a second embodiment of the present invention. FIG. 9 is a diagram illustrating a third embodiment of the present invention. FIG. 11 is a diagram illustrating a fourth embodiment of the present invention. FIG. 11 is a diagram showing a fifth embodiment of the present invention.

FIG. 1 shows an example of the configuration of an image projection device as one embodiment of the present invention.
The image projection apparatus 100 includes a light source 101 that emits a light beam L0 serving as 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. are doing.
The image projection device 100 also controls a lens unit 200 including a projection optical system for projecting an image on a projection surface 104 as a projection surface, and an image display element 102 for displaying an image to be projected on the projection surface 104. And a control unit that performs the control.

The light source 101 emits white light substantially in parallel using a halogen lamp, which is a light emitting source that emits light. Here, a metal halide lamp, a high-pressure mercury lamp, or an LED may be used as the light source.
The light source 101 is a white light source, but uses a plurality of monochromatic light sources such as a laser light source, and combines a converted light into a wavelength corresponding to one or more basic colors such as R, G, and B, or The light source may be a combination of the converted light and the monochromatic light of the laser light source.

  The image display element 102 is an image display unit that transmits image light that is incident thereon, imparts spatial modulation, emits the light, and gives image information. It is a reflective spatial light modulator. Note that the image display element 102 may be a liquid crystal panel or a self-luminous light emitting element array. The image display element 102 may display an image input from an external device such as a computer, or may display image data configured by a control unit disposed inside the image projection apparatus. There may be.

The configuration of the lens unit 200 will be described.
The optical axis of the light incident on the lens unit 200, that is, the lens optical axis, is defined as the Z axis, and among the directions perpendicular to the Z axis, the axis parallel to the vertical direction in FIG. 2 is defined as the Y axis. The vertical axis is defined as the X axis. Note that, with respect to the directions of the X axis, the Y axis, and the Z axis, the directions of the arrows shown in FIG.

As illustrated in FIG. 2, the lens unit 200 projects a plurality of lenses LN <b> 1 to LN <b> 11 that are arranged on the Z-axis and configures the refractive optical system 10, and is located downstream of the lens LN <b> 11 in the Z direction and forms an image forming light beam. And a cemented lens 20, which is a refracting and reflecting optical element for projecting toward the surface 104.
That is, in the present embodiment, the lens unit 200 constitutes a projection optical system that “arranges a refractive optical system and a refractive reflective optical element sequentially from the image display surface side to the projection surface 104 side”. I have.

  The refractive optical system 10 is a refractive optical system including a plurality of lenses LN1 to LN11, and may be a cemented lens in which two or more of these lenses are cemented to each other. In the present embodiment, a configuration using eleven lenses will be described. However, 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 image forming light beam L1 from the refractive optical system 10 is incident, a reflecting surface 20B functioning as a concave mirror, and an image forming light beam L1 reflected by the reflecting surface 20B as a projection light beam L2. And an emission surface 20C from which the light is emitted.
In the cemented lens 20, the reflection surface member 21 and the refraction medium portion 22 are formed close to each other at the boundary surface 23, and the reflection surface member 21 and the refraction medium portion 22 are integrally formed. It is configured as an “optical element”.

The imaging light flux L1 emitted from the refracting optical system 10 enters from the incident surface 20A of the cemented lens 20, and is reflected from the refracting medium portion 22 via the reflecting surface member 21 by the reflecting surface 20B. The light is emitted toward the projection surface 104 serving as the projection surface.
Here, among the incident surface 20A, the reflecting surface 20B, and the outgoing surface 20C of the cemented lens 20, at least the reflecting surface 20B is a “curved surface having a refractive power”, and at least one of the incident surface 20A and the outgoing surface 20C has a refractive power. Can have. Here, in the case where it has a refractive power, it may have either a positive or negative refractive power. What is the shape of the surface having such refractive power? In addition to a spherical shape such as a convex spherical surface or a concave spherical surface, an aspherical shape, an anamorphic shape such as a cylinder surface, or a free-form surface may be used.
The image display surface of the image display element 102 and the projected image magnified and projected on the projection surface 104 have a conjugate relationship by the projection optical system. Further, such a projection optical system is displayed on the image display surface in the cemented lens 20, in other words, at least one or more positions in the optical path from the incidence on the incident surface 20A to the emission on the emission surface 20C. An "intermediate image" of the image is formed.
Further, at this time, since one or more intermediate images are formed inside the cemented lens 20, the intermediate image may be formed once in the refractive optical system 10. Therefore, one or more intermediate images are formed in the entire projection optical system.

The reflection surface member 21 has a concave, aspherical reflection surface 20B on the inner surface side, and is disposed on the + Z direction side of the refraction medium portion 22. In the present embodiment, the boundary surface 23 with the refraction medium portion 22 is a plane parallel to the XY plane, but is not limited to such a configuration.
The refraction medium portion 22 is made of an optical material such as glass or plastic. The lower surface of FIG. 2 on the −Z direction side has an incident surface 20A and the upper surface has an emission surface 20C on the same spherical surface.
By joining the reflective surface member 21 and the refraction medium portion 22 at the boundary surface 23, the cemented lens 20 is refracted such that the surface on the −Z direction side is spherical and the surface on the + Z direction side is aspherical. Functions as a reflective optical element.

Generally, in an optical element, lens polishing, molding using a mold, or the like is used.
However, such reflection and refraction are difficult because the lens thickness increases.
By integrally forming the reflection surface member 21 and the refraction medium portion 22 as in this embodiment, it is possible to manufacture a refraction / reflection optical element which is easier to manufacture and inexpensive.

However, simply joining the two optical elements together may cause a decrease in optical performance due to foreign matter or the like adhering on the boundary surface 23.
Therefore, in the present embodiment, as shown in the main optical path diagram in FIG. 2, the intermediate image Im1 is provided inside the cemented lens 20, specifically, between the incident surface 20A and the reflecting surface 20B of the cemented lens 20. At least one.

  Thus, by arranging the intermediate image Im1 inside the cemented lens 20, it is possible to suppress the influence of a defect such as a foreign matter entering the boundary surface 23.

  Now, in such a lens unit 200, numerical examples will be shown together with specific optical system data.

As shown in FIG. 2, the refractive optical system 10 according to the numerical example includes eleven lenses LN <b> 1 to LN <b> 11 sequentially arranged from the object side to the image side. The three lenses LN2 to LN4 are cemented, and an aperture stop S is disposed 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 “biconvex lens shape”, the entrance surface 20A and the exit surface 20C are the same lens surface, and the reflection surface 20B is formed by using a reflection film deposited on the lens surface as a “reflection surface member”. I have.

In the numerical examples, the “oblique light beam” is used as the image forming light beam L1. That is, as shown in FIG. 2, the image displayed on the image display element 102 is shifted in the + Y direction side with respect to the lens optical axis of the projection optical system. The oblique light beam as the image forming light beam L1 forms an intermediate image Im1 as an inverted image inside the refraction medium portion 22 by the refractive optical system 10 and the positive refractive power of the incident surface 20A of the cemented lens 20.
With the intermediate image Im1 as an object, the projection image is enlarged and projected toward the projection surface 104 by the positive refractive power between the reflection surface 20B and the emission surface 20C. In the following embodiments, illustration of the projection surface 104 is omitted.
Of the lenses LN5 to LN11 located on the image side of the aperture stop S, the lenses LN9 to LN11 have their unused lens portions cut off so that the imaging light flux L1 reflected by the reflecting surface 20B is "blurred". It may be shaped (for example, shaped like a D-cut lens).

The projection optical system according to the first embodiment converts the image displayed on the image display surface of the image display element 104 having the number of pixels of 1920 × 1080 and the pitch of 5.4 μm into a 94.7-inch image. An aspect of enlarging and projecting on a projection surface 104 having a diagonal length is assumed.
The object height in image formation 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) to the enlargement side, “S0” where the image display surface is an object surface, and a screen as a projection surface. Is "Si".
"R" represents the radius of curvature of each surface including the surface of the aperture stop S and the color combining prism P (the paraxial radius of curvature for an aspheric surface).
“D” represents a surface interval on the optical axis.
"Nd" and "Vd" represent the refractive index and the Abpe number of each lens material at d-line.
“Effective diameter” indicates the optical effective diameter of each surface. The unit of the quantity having the dimension of length is “mm” unless otherwise specified.
The surface marked with (*) in the column of radius of curvature: R is "aspherical surface".
The aspherical surface has an aspherical surface amount: Z, a height from the optical axis: r, a conical constant: k, an even-order aspherical coefficient of the second to twentieth order: A, B,..., G, H, J And is represented by the following formula.

  Table 1 shows the optical system data of the examples.

"Aspheric data"
Table 2 shows the aspherical surface data.
In the data of the aspherical surface, for example, “−1.392830E−17” 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 surfaces”, and the reflective surface (S29) is “with respect to the optical axis. Rotationally symmetric aspherical surface ".

FIGS. 3 and 4 show aberration diagrams of the example.
FIG. 3 is a diagram of spherical aberration, astigmatism, and distortion. FIG. 4 is a diagram of coma aberration.

  In the figure of astigmatism, a “bold line” relates to a “meridional ray”, and a “thin line” relates to a “sagittal ray”. As is clear from FIGS. 3 and 4, the aberration is well corrected, and the projection optical system of the embodiment has high performance.

  FIG. 5 shows a second example of the embodiment shown in FIG. 2 as an explanatory diagram. In the following embodiments, components that do not seem to be confused are denoted by the same reference numerals as those in FIG. 2 and description thereof is omitted as appropriate. In particular, it is assumed that the shape of each lens surface of the refractive optical system 10 conforms to the configurations shown in Tables 1 and 2.

In the second embodiment shown in FIG. 5, the position where the intermediate image Im1 is formed does not overlap with the boundary surface 23, and the position where the main light rays of the image forming light beam L1 are concentrated is Are also arranged inside the refraction medium part 22 of the cemented lens 20.
With this configuration, since the intermediate image Im1 does not cross the boundary surface 23, it is possible to manufacture an easier and less expensive refracting and reflecting element.
In this way, by arranging the boundary surface 23 of the cemented lens 20 so that the position where the intermediate image Im1 is formed does not overlap, it is possible to further reduce the influence of dirt and foreign matter on the boundary surface 23.
In addition, since the light beam is concentrated at the image forming position of the intermediate image Im1, it is expected that the temperature will be high. If such a temperature rise causes a difference in thermal expansion between the refraction medium portion 22 of the cemented lens 20 and the reflection surface member 21, the optical performance is greatly affected. However, by setting the position inside the cemented lens 20 and not overlapping the boundary surface 23, it is easy to reduce the influence of the concentration of the light beam and the temperature rise associated therewith, which is preferable. Further, it is preferable that the lens unit 200 is not likely to touch near the light condensing position when assembling the lens unit 200 or the like.

  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 surface curved with respect to the XY plane.
With such a configuration, it is possible to adjust in consideration of the refracting power of the boundary surface 23, and it is possible to perform joining by considering the shape of the refraction medium portion 22 and the shape of the reflection surface member 21 depending on the shape of the boundary surface 23. The lens 20 can be further downsized, and can be manufactured more easily and inexpensively.

FIG. 7 shows a lens unit 300 as a fourth embodiment of the present invention. In the lens unit 300, the same components as those of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
In the lens unit 300, the cemented lens 30 has a first reflection surface 30B and a second reflection surface 30C between the entrance surface 30A and the exit surface 30D.
The cemented lens 30 has a reflective surface member 31 having a first reflective surface 30B, and a refraction medium portion 32 disposed in close contact with the reflective surface member 31. The boundary between the reflective surface member 31 and the refraction medium portion 32 is provided. It is configured as a single optical element joined at the surface 33.
In addition, “an entrance surface 30A and an exit surface 30D of the image forming light beam L1 emitted from the refraction optical system 10 are formed in the refraction medium portion 32, and an image display surface is provided between the entrance surface 30A and the reflection surface 30B of the cemented lens 30. At least one intermediate image Im1 of the image displayed on the screen. "

That is, in other words, the cemented lens 30 in the present embodiment has a plurality of reflecting surfaces. In addition, of these two reflecting surfaces, the first reflecting surface 30B has a curved shape as shown in FIG. 7, and has a refractive power. On the other hand, the second reflection surface 30C has a planar shape parallel to the ZX plane and has no refractive power.
That is, in the present embodiment, "the refractive / reflective optical element has a second reflective surface extending in a direction parallel to the optical axis of the lens of the refractive optical system".

As described above, since the cemented lens 30 has a plurality of reflection surfaces, the distance of the optical path passing through the refraction medium portion 32 is extended. Therefore, even if a material having a small refractive index is used for the refraction medium portion 32, The size can be reduced while maintaining the overall refractive power. That is, it contributes to cost reduction and size reduction of the lens unit 300.
In addition, according to at least one of the plurality of reflecting surfaces of the cemented lens 30 being the second reflecting surface 30C extending in a direction parallel to the optical axis of the lens, the second reflecting surface of the cemented lens 30 is formed. This is more preferable because the influence of the power of the surface 30C can be suppressed.

Now, a configuration as shown in FIG. 8 will be described as a fifth embodiment of the present invention.
In the fifth embodiment, a D-cut lens 40 as a refracting and reflecting optical element is used instead of the cemented lens 30 used in the fourth embodiment. The refracting optical system 10 has the same configuration as that of the first embodiment and a description thereof will be omitted to avoid complication of the description.
As shown in FIG. 8, the D-cut lens 40 in the present embodiment is configured as a single optical element. That is, it is a single optical element having no boundary surface.
Further, the D-cut lens 40 has an entrance surface 40A and an exit surface 40D, is disposed on an optical path between the entrance surface 40A and the exit surface 40D, and has a first reflection surface 40B having a curved surface shape and an XZ plane. And a second reflection surface 40C having a parallel plane shape.

In such a configuration, the material of the D-cut lens 40 is desirably, for example, the optical material used as the refraction medium unit 22 in the first embodiment.
Further, in the present embodiment, the surface on the + Z direction side of the D-cut lens 40 has a function as the first reflection surface 40B, and with such a configuration, an easy and inexpensive refraction / reflection element can be manufactured. .
In the present embodiment, the first reflection surface 40B is a metal thin film formed on the surface on the + Z direction side of the D-cut lens 40, but is not limited to such a configuration.
In the present embodiment, the second reflecting surface 40C is a flat reflecting surface having no refracting power parallel to the XZ plane. However, the present invention is not limited to such a configuration. It is only necessary that one of the two reflection surfaces 40C has a refractive power.

In the third embodiment, “a refracting optical system and a refracting and reflecting optical element are sequentially arranged from the image display surface side to the projection surface side, and the refraction optical system includes a plurality of lenses. Wherein the refraction-reflection optical element is configured as a single optical element having a first reflection surface, a second reflection surface, and a refraction medium portion disposed in close contact with the reflection surface. An entrance surface and an exit surface of an image forming light beam emitted from the refraction optical system are formed in the medium portion, and at least one of the first reflection surface and the second reflection surface is a curved surface having a refractive power, and the refraction is performed. In the optical system and the refraction / reflection optical element, one or more intermediate images of the image displayed on the image display surface are formed, and the image is formed between the entrance surface and the reflection surface of the refraction / reflection optical element. Form one or more intermediate images of the image displayed on the display surface That "has a configuration.
In general, an optical material having a higher refractive index is desirable because a required refractive power can be realized by a small lens, but such a high refractive index optical material has problems such as being expensive and difficult to process. It is known. However, in the present embodiment, it is possible to reflect the image forming light flux L1 between the first reflection surface 40B and the second reflection surface 40C, and to lengthen the optical path length inside without changing the size of the refraction / reflection optical element. Accordingly, the desired optical performance can be given to the lens unit 300 even if the optical unit is further downsized or an optical material having a relatively low refractive index is used.
According to such a configuration, the intermediate image Im1 is formed inside the refraction / reflection optical element and is reflected a plurality of times. Therefore, a long optical path length can be ensured, and the cost and size of the D-cut lens 40 can be reduced. And contribute to.

As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to the specific embodiments described above, and unless otherwise specified in the above description, the invention described in the claims. Various modifications and changes are possible within the scope of the spirit of the present invention.
For example, a refractive optical element is a "single optical element", while a "single" is morphological. Although the case where the refraction medium portion has a single structure has been described above, the structure of the refraction medium portion is not limited to this. For example, a composite structure of two or more different optical media such as a cemented lens form It may be. When the refraction medium section is constituted by a plurality of optical media as described above, parameters for adjusting the performance of the projection optical system are increased, so that the design of the projection optical system is facilitated.

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

102 image display device 10 refractive optical system
20 Refractive / reflective optical element (Joint lens)
20A Incident surface of refracting and reflecting optical element
20B Reflective surface of refractive / reflective optical element
20C Refraction / reflection optical element exit surface
21 Reflective surface member
22 Refraction medium part
23 boundary surface 30 refractive / reflective optical element (joint lens)
30A Incident surface of refractive / reflective optical element 30B First reflective surface of refractive / reflective optical element 30C Second reflective surface of refractive / reflective optical element 30D Exit surface of refractive / reflective optical element 31 Reflective surface member
32 Refraction medium part
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 for enlarging and projecting an image displayed on an image display surface of an image display element as a projection image on a projection target surface,
From the side of the image display surface to the side of the projection surface, sequentially arranged a refractive optical system and a refractive reflective optical element,
The refractive optical system is configured by a plurality of lenses,
The refractive / reflective optical element has a reflective surface member having a reflective surface, and a refractive medium portion disposed in close contact with the reflective surface, and the reflective surface member and the refractive medium portion are joined at a boundary surface. Is formed as a single optical element, an entrance surface and an exit surface of an image forming light beam emitted from the refractive optical system are formed in the refractive medium portion, and the reflection surface is a curved surface having a refractive power,
In the refractive optical system and the refractive reflective optical element, one or more intermediate images of the image displayed on the image display surface are formed,
A projection optical system that forms one or more intermediate images of an image displayed on the image display surface between the incident surface and the reflection surface of the refraction / reflection optical element. The projection optical system according to claim 1, wherein
The projection optical system, wherein the boundary surface is a plane. The projection optical system according to claim 1, wherein
The projection optical system, wherein the boundary surface is a curved surface. The projection optical system according to claim 1, wherein:
The 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 claim 1, wherein:
The projection optical system, wherein the refractive optical element has a second reflective surface extending in a direction parallel to an optical axis of a lens of the refractive optical system. A projection optical system for enlarging and projecting an image displayed on an image display surface of an image display element as a projection image on a projection target surface,
From the side of the image display surface to the side of the projection surface, sequentially arranged a refractive optical system and a refractive reflective optical element,
The refractive optical system is configured by a plurality of lenses,
The refraction-reflection optical element is configured as a single optical element having a first reflection surface, a second reflection surface, and a refraction medium portion disposed close to the reflection surface,
An entrance surface and an exit surface of an image forming light beam emitted from the refractive optical system are formed in the refractive medium portion, and at least one of the first reflection surface and the second reflection surface is a curved surface having a refractive power. A projection optical system, wherein at least one intermediate image of an image displayed on the image display surface is formed between the incident surface and the reflection surface of the refraction / reflection optical element. A projection optical system according to any one of claims 1 to 6,
Light source,
An image display element for displaying an image on the image display surface,
An image projection device having:

Images