JP2018132564A - Projection optical system and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a new projection optical system that includes a dioptric system and a reflection optical system having a refractive power.SOLUTION: A projection optical system enlarges and projects, on a projection target surface, an image displayed on an image forming part of an image display element, and comprises a dioptric system 11 and a reflection optical system 12. The dioptric system includes N(≥4) lens groups, and the reflection optical system includes at least one reflection optical element having a refractive power; the dioptric system has a first lens group I, a second lens group II, and a third lens group III arranged in order from a reduction side to an enlargement side, and has one or more lens groups on the enlargement side of the third lens group, where the first lens group I has the strongest positive refractive force in the dioptric system and the third lens group III has a strong positive refractive force second to the first lens group in the dioptric system; in focusing from a long distance side to a short distance side, the second lens group II is moved to the reduction side, the third lens group III is moved to the enlargement side with respect to the image, and the one or more lens groups on the enlargement side with respect to the third lens group are moved to the reduction side as moving lens groups.SELECTED DRAWING: Figure 1

Description

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

Various types of image display devices (hereinafter also referred to as “projectors”) that display an image displayed on the projection surface by enlarging an image displayed on the image forming unit of the image display element have been known. Yes. As the image display element, various so-called “light valves” such as DMD (digital mirror device) and liquid crystal panel are known. The image forming unit is a “portion on which an enlarged image is displayed” in the light valve.
The projection optical system is an optical system that enlarges and forms an image displayed on the image forming unit on the projection surface, and various types have been proposed. The projected surface is generally a “screen surface”.

  As a configuration of the projection optical system, one that realizes a short projection distance by combining a refractive optical system and a “reflecting optical system having refractive power” is known (Patent Documents 1 to 4, etc.). The “refractive optical system” is an optical system configured by a combination of a plurality of lenses. The projection distance can be shortened by reflecting the imaging light beam that has passed through the refractive optical system toward the projection surface by a reflective optical system having refractive power.

  An object of the present invention is to realize a novel projection optical system having a refractive optical system and a reflective optical system having a refractive power.

  The projection optical system of the present invention is a projection optical system that enlarges and projects an image displayed on the image forming unit of the image display element onto a projection surface, and includes a refractive optical system and a reflective optical system, and the refraction The optical system has N (≧ 4) lens groups, the reflective optical system has at least one reflective optical element having refractive power, and the refractive optical system sequentially moves from the reduction side to the enlargement side. , A first lens group, a second lens group, and a third lens group, and having one or more lens groups on the enlargement side of the third lens group, the first lens group in the refractive optical system It has the strongest positive refractive power, the third lens group has the strongest positive refractive power next to the first lens group in the refractive optical system, and during focusing from the long distance side to the short distance side, The second lens group moves to the reduction side, and the third lens group moves to the image. To move to a fixed or enlargement side, one or more lens groups magnification side than the third lens group is moved to the reduction side as the moving lens group.

  According to the present invention, a novel projection optical system having a refractive optical system and a reflective optical system having a refractive power can be realized.

It is a figure which shows one Embodiment of an image display apparatus explanatoryly. FIG. 3 is a diagram illustrating an example of an image forming unit in an image display device. It is a figure explaining the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. It is a figure for demonstrating the position of the field angle in the image formation part area | region in a to-be-projected surface (screen). It is a figure which shows the spot diagram in the long distance of the projection optical system of Example 1. FIG. FIG. 3 is a diagram showing a spot diagram at a reference distance of the projection optical system of Example 1. FIG. 3 is a diagram showing a spot diagram at a short distance of the projection optical system of Example 1. It is a figure which shows explanatoryally another form of implementation of an image display apparatus. It is a figure for demonstrating the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. It is a figure which shows the spot diagram in the long distance of the projection optical system of Example 2. FIG. FIG. 6 is a diagram showing a spot diagram at a reference distance of the projection optical system of Example 2. FIG. 6 is a diagram showing a spot diagram at a short distance of the projection optical system of Example 2. It is a figure which shows other another form of implementation of an image display apparatus explanatoryly. It is a figure for demonstrating the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. It is a figure which shows the spot diagram in the long distance of the projection optical system of Example 3. FIG. FIG. 10 is a diagram showing a spot diagram at a reference distance of the projection optical system of Example 3. FIG. 10 is a diagram showing a spot diagram at a short distance of the projection optical system of Example 3. It is a figure which shows explanatoryally further another form of implementation of an image display apparatus. It is a figure for demonstrating the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. It is a figure which shows the spot diagram in the long distance of the projection optical system of Example 4. FIG. It is a figure which shows the spot diagram in the reference distance of the projection optical system of Example 4. FIG. It is a figure which shows the spot diagram in the short distance of the projection optical system of Example 4.

Prior to describing specific embodiments, a projection optical system and an image display apparatus of the present invention will be described.
As described above, the projection optical system of the present invention has a refractive optical system and a reflective optical system, the refractive optical system has N (≧ 4) lens groups, and the reflective optical system has “refractive power”. It has at least one “reflective optical element”.
The refractive optical system sequentially arranges a first lens group, a second lens group, and a third lens group from the reduction side to the magnification side, and has one or more lens groups on the magnification side of the third lens group, The first lens group has “the strongest positive refractive power in the refractive optical system”, and the third lens group has “the strongest positive refractive power after the first lens group in the refractive optical system”.
When focusing from the long distance side to the short distance side, the second lens group moves to the reduction side, and the third lens group moves to “fixed to the image displayed on the image forming unit” or to the enlargement side. One or more lens groups on the enlargement side from the third lens group move to the reduction side as “moving lens groups”. The “moving lens group” is a lens group that moves during focusing, the second lens group is also a moving lens group, and the third lens group is a moving lens group when it is “not fixed to the image”.
In addition, in the refractive optical system, the “reduction side” is the “image forming unit side”.

In order to obtain a good magnified projection on the projection surface by changing the projection distance, it is necessary to "correctly correct the position of the image plane", and the refractive power distribution of the lens group in the refractive optical system is displaced during focusing. The configuration of the moving lens group is important.
In general, it is known to perform high-level correction of the image plane position by a configuration that “separates as much as possible” rays of each angle of view incident on the focus group. The outer diameter of the most magnified lens tends to increase.

In the projection optical system according to the present invention, the third lens group is a group having “the next strongest refractive power after the first lens group”, so that “from the third lens group, which is mainly responsible for image plane correction”. In addition, it is possible to suppress the height of the incident light to the “lens group arranged on the enlargement side”, and to effectively reduce the increase in the outer diameter of the enlargement side lens.
Further, when focusing from a long distance to a short distance, the image plane at each projection distance is corrected by moving the “moving lens group on the enlargement side relative to the third lens group” together with the second lens group to the reduction side. It is efficient.
By moving the second lens group to the reduction side, the “angle of the light beam incident on the moving lens group on the enlargement side relative to the third lens group” can be greatly changed according to the projection distance, and compared with the third lens group. It becomes possible to efficiently correct the image plane position in the enlargement side lens group.
Therefore, advanced correction of the image plane position is possible without increasing the outer diameter of the lens on the enlargement side.
Further, by moving the “moving lens group on the enlargement side from the third lens group” to the reduction side, it becomes possible to perform more advanced correction of the image plane position, and good resolution performance up to the corner of the projected image at each projection distance. Can be realized.

  Note that “more advanced image plane position correction” can be performed by moving the third lens group to the enlargement side. However, “the image can be obtained by moving the moving lens group on the enlargement side from the third lens group to the reduction side. Since “advanced correction of the surface position” can be realized, the focusing mechanism can be simplified by “fixing the third lens group to the image”.

  In the projection optical system configured as described above, an increase in the lens diameter of the “lens on the enlargement side” in the refractive optical system is suppressed. Therefore, even if the total length of the refractive optical system is increased, It is difficult to interfere with the system ”, and high resolution performance can be realized at each projection distance.

  In addition, since the projection optical system of the present invention can reduce the lens diameter on the enlargement side, it is possible to adopt a “heat-resistant glass mold lens” for the enlargement side lens, and in a high-luminance image display device In addition, it is possible to suppress performance deterioration due to heat. Further, as described above, since interference between the imaging light beam and the lens or mechanical part is also suppressed, it is possible to reduce the distance between the reflective optical element and the refractive optical system, and the projection optical system and thus the image display device (projector). ) Can greatly contribute to downsizing.

In the above configuration, the projection optical system of the present invention preferably satisfies at least one of the following conditions (1) and (2).
(1) 1.0 <| F2 / F3 | <30.0
(2) 0.1 <FL / F3 <1.0
In these conditions (1) and (2), the meanings of F2, F3, and FL are as follows.
F2: Focal length at the d-line of the second lens group
F3: focal length of the third lens group at the d-line
FL: Focal length at the d-line of the refractive optical system in a focused state where the projected image is maximum.

Condition (1) is a condition that regulates a preferable range of the ratio of refractive power between the second lens group and the third lens group in the refractive optical system.
When the parameter: | F2 / F3 | is below the lower limit value of the condition (1), the refractive power of the third lens group becomes relatively smaller than the refractive power of the second lens group. The height of the light beam to the lens group arranged on the enlargement side increases, the outside diameter of the enlargement side lens tends to be excessive, and the projection optical system tends to be difficult to downsize and improve its performance.
If the parameter: | F2 / F3 | exceeds the upper limit of the condition (1), the positive refractive power of the third lens group becomes excessive, which is advantageous for downsizing and high performance, but manufacturing error sensitivity. Rise, and it is difficult to control the position of the image plane.

The parameter: | F2 / F3 | more preferably satisfies the following condition (1A).
(1A) 2.0 <| F2 / F3 | <25.0.

Condition (2) is a condition for regulating the “appropriate range in the refractive optical system” of the refractive power of the third lens group in the refractive optical system.
When the parameter of condition (2): FL / F3 falls below the lower limit value of condition (2), the positive refractive power of the third lens group becomes small, and “ Since the “divergence angle suppression function” is weakened, the height of the light beam to the lens unit disposed on the enlargement side with respect to the third lens unit is likely to be excessive, and it is easy to increase the diameter of the enlargement side lens. System miniaturization and high performance tend to be difficult.
Condition (2) parameter: If FL / F3 exceeds the upper limit of condition (2), the positive refractive power of the third lens group becomes excessive, which is advantageous for downsizing and higher performance. The manufacturing error sensitivity is likely to increase, and the control of the image plane position is likely to be difficult.
More preferably, the parameter: FL / F3 satisfies the following condition (2A).
(2A) 0.15 <FL / F3 <0.5
It is desirable that at least one of the moving groups arranged on the enlargement side with respect to the third lens group has a negative refractive power. This facilitates “more advanced adjustment” of the image plane position.

Further, if the “most lens group on the enlargement side has negative refractive power”, it becomes easy to widen the angle of the projection optical system. In addition, the light rays on the mirror surface of the reflective optical system are easily separated, and the image plane at each angle of view can be highly adjusted, so-called “ultra-short projection distance” is possible.
Further, if the lens group on the most enlargement side is “fixed to the image display element during focusing”, the focusing mechanism can be simplified and the lens barrel diameter on the enlargement side can be reduced. This makes it easy to avoid interference between the light beam and the lens barrel, and can contribute to the miniaturization and high performance of the projection optical system and thus the projector.

  If there are two “lens groups that move during focusing (moving lens group)” on the magnification side of the third lens group, the image plane of each angle of view can be adjusted to “more advanced” by these movements, Realization of an ultra short projection distance is facilitated.

  A “concave mirror” can be suitably used as the “reflecting optical element having refractive power” of the reflecting optical system that constitutes the projection optical system together with the refractive optical system. The number of reflective optical elements is not limited to one, and a plurality of reflective optical elements can be used. Further, a “plane mirror that bends the optical path” can be appropriately arranged in the projection optical system.

The projection optical system can be configured to form an “image conjugate with an image displayed on the image forming portion of the image display element” between the refractive optical system and the reflective optical element by the refractive optical system.
By forming an image conjugate with the image displayed on the image forming unit of the image display element as an “intermediate image”, the reflective optical element can be made small, and distortion and the like can be corrected efficiently.

All lenses constituting the refractive optical system can be “glass lenses”.
An image display apparatus (projector) according to the present invention is an image display apparatus that displays an image by enlarging and projecting an image displayed on an image forming unit of an image display element on a projection surface by a projection optical system. The projection optical system used is used.
In this image display device, when a concave mirror is used as the reflective optical element, the conditions are:
(3) TR <0.35
(4) 10 <OAL / Y <30
It is preferable to satisfy at least one of the following.
Parameter in condition (3): TR is the object from the intersection point of the concave mirror and the imaging light beam to the projection surface from the “intersection P having the maximum distance to the projection surface in the direction perpendicular to the projection surface”. A ratio between the distance L in the direction perpendicular to the projection surface and the lateral width W of the maximum image projected onto the projection surface is TR (= L / W).
Parameters of condition (4): OAL and Y in OAL / Y are as follows.

OAL: Of the intersections between the concave mirror and the imaging light beam, the intersection P having the maximum distance to the projection surface in the direction perpendicular to the projection surface and the “direction perpendicular to the image formation unit” to the image formation unit The distance at.
Y: the maximum value of the distance between the optical axis of the refractive optical system and the image forming unit.
Supplementally, the refractive optical system has a plurality of optical axis symmetric lenses. When a plurality of these optical axis symmetric lenses share a common optical axis, the shared optical axis is referred to as an “optical axis of a refractive optical system”. Among the plurality of lenses constituting the refractive optical system, there may be one or more “lenses that do not share the optical axis” with other lenses. In such a case, the optical axis shared by the “lens sharing the optical axis” other than such a lens is defined as the “optical axis of the refractive optical system”.

When the above parameter: TR satisfies the condition (3), a projection image having a large size can be displayed with respect to the projection distance regulated by the distance: L, and ultra short distance projection can be easily realized.
The parameter: TR more preferably satisfies the following condition (3A).
(3A) TR <0.30
In addition, the parameter: OAL / Y is the condition (4)
By satisfying the above, a projection image having a large size can be displayed with respect to the length from the image forming unit to the concave mirror (which regulates the size of the image display device), and ultra-short distance projection is easily performed. It is feasible.
The parameter: OAL / Y more preferably satisfies the following condition (4A).

(4A) 10 <OAL / Y <25
Hereinafter, four embodiments of the image display apparatus and the projection optical system will be described.
1, FIG. 8, FIG. 13 and FIG. 19 respectively illustrate embodiments of the image display device. The projection optical system used in these embodiments corresponds to specific Examples 1 to 4 of the projection optical system to be described later in the order shown.
In order to avoid complications, in FIGS. 1, 8, 13, and 19, common symbols are used for those that are not likely to be confused.
In these drawings, symbol H indicates an image display device. Reference numeral LV denotes an “image forming unit” of the image display element, reference numeral LS denotes an “illumination optical system”, reference numeral F denotes a “transparent parallel plate”, reference numeral Pr denotes a “prism”, and reference numeral SC denotes a “non-projection surface”. It shows the screen that makes the actual situation. The transparent parallel flat plate F is assumed to be a cover glass (seal glass) of the image forming unit LV.
Reference numeral 11 in FIG. 1, reference numeral 21 in FIG. 8, reference numeral 31 in FIG. 13, reference numeral 41 in FIG. 19 denotes a “refractive optical system”, reference numeral 12 in FIG. 1, reference numeral 22 in FIG. 8, reference numeral 32 in FIG. In FIG. 19, reference numeral 42 denotes a “reflection optical system”.
Further, reference numeral 13 in FIG. 1, reference numeral 23 in FIG. 8, reference numeral 33 in FIG. 13, and reference numeral 43 in FIG.

  1, 8, 13, and 19 indicates an “aperture stop” disposed in the refractive optical system. In these drawings, the distances indicated by the symbols OAL and L are specific examples of the distances described above in relation to the conditions (3) and (4).

As the image display element, light valves such as “DMD”, “transmission type liquid crystal panel”, and “reflection type liquid crystal panel” can be used as appropriate, and an image is displayed on the image forming unit LV.
The illumination optical system LS is for illuminating an image formed on the image forming unit LV when the image display element does not have a function of emitting light, and the image display element is a “two-dimensional array of light emitting elements”. Thus, it is not necessary to use the “self-emission method having a function of emitting the generated image” as in FIG.

  In the embodiment described below, “DMD” is assumed as an image display element, and an image formed by the inclination of individual micromirrors in a two-dimensional micromirror array in DMD is illuminated from illumination optical system LS. Illuminate with light. The illumination optical system LS preferably has a function of efficiently illuminating the image forming unit LV. For example, a rod integrator or a fly eye integrator can be used to make the illumination more uniform.

  As a light source for illumination, a white light source such as an ultra-high pressure mercury lamp, a xenon lamp, a halogen lamp, or an LED can be used, and a monochromatic light source such as a monochromatic light emitting LED or LD can also be used.

An image display device that will be described below is assumed to project a “color image” on a screen SC, and three DMDs are used as image display elements, and an image forming unit for these three DMDs. In addition, a red component image, a green image component, and a blue image component of a color image are formed and displayed, and these color image components are illuminated with illumination light of corresponding colors.
Each illumination light is modulated by each color image component, is “color synthesized” by the prism Pr, and enters the projection optical system as an imaging light beam.
The imaging light flux is transmitted through the refractive optical systems 11, 21, 31 and 41, reflected by the reflective optical systems 12, 22, 32 and 42, and directed toward the screen SC through the dust-proof glasses 13, 23, 33 and 43. Irradiated to form an enlarged image of color on the screen SC.

"Example of projection optical system"
Hereinafter, specific examples of the projection optical system used in the image display apparatus shown in FIGS. 1, 8, 13, and 19 will be described as Examples 1 to 4.
These projection optical systems of Examples 1 to 4 use “one concave mirror” as a reflection optical system. Each of the refractive optical systems 11, 21, 31, and 41 used in these examples is composed of a plurality of rotationally symmetric lenses, and all the lenses share the optical axis as shown in the figure. doing. As shown in FIGS. 1, 8, 13, and 19, the X axis, the Y axis, and the Z axis that are orthogonal to each other are set. The X axis is a direction orthogonal to the drawing, the Z axis is a direction parallel to the optical axis, and the Y axis is a direction orthogonal to both the X and Z axes. The image forming unit LV and the screen SC shown in the drawing are parallel to the “XY plane”.

  Of the intersections of the concave mirror 12 (22, 32, 42) and the light beam, the optical axis direction (Z-axis direction) between the point P having the maximum distance in the vertical direction (Z-axis direction) to the screen SC and the screen SC. The distance: L is referred to as “projection distance: L”. The distance OAL between the point P and the image forming unit LV is referred to as “optical total length: OAL”.

Here, the image forming unit LV will be described with reference to FIG. 2. The image forming unit LV has a rectangular shape that is long in the X direction, and the center of the image forming unit is from the “optical axis” of the refractive optical system in the Y direction. There is a shift. In the figure, the maximum distance among the distances between the “optical axis” and the image forming unit LV is “Y” in the condition (4), and this distance “Y” is not related to the Y direction.
The specifications of the image forming unit are common in the first to fourth embodiments described below and are as follows.
Dot size: 5.4 μm
Lateral direction (X direction) length: 14.6664 mm
Longitudinal direction (Y direction) length: 8.2512 mm
Distance in the Y direction from the optical axis to the center of the image forming unit (shift amount): 5.5256 mm
In each of the first to fourth embodiments, the light passing through the refractive optical system forms an “intermediate image conjugate with the image formed on the image forming unit LV” as a spatial image on the image forming unit LV side of the reflecting mirror.
The intermediate image does not need to be a planar image, and is formed as a “curved surface image” in Examples 1 to 4. The intermediate image is “magnified and projected by a concave mirror disposed on the most magnified side” and formed on the screen SC. The intermediate image has field curvature / distortion, which can be corrected by “using an aspherical surface for the concave mirror”. Accordingly, the burden of aberration correction of the refractive optical system is reduced, the degree of design freedom is increased, and this is advantageous for downsizing and the like.
The surface shape of the concave mirror is “even aspherical surface with an aspheric coefficient being an even order” in the first to fourth embodiments, but may be “aspherical surface with an aspherical coefficient being an odd order” or “free curved surface”.

The dust-proof glass 13, 23, 33, 43 disposed between the concave mirror and the screen is a “parallel plate glass”, but is not limited thereto, and has a curvature or a lens shape having a refractive power. You can also In each of Examples 1 to 4, the dust-proof glass is disposed so as to be inclined rather than perpendicular to the Y-axis direction, but the inclination angle may be arbitrary and may be orthogonal to the Y-axis direction.
In the first to fourth embodiments, as the projection distance, the size (X direction) of the enlarged image at the reference projection distance is 100 inches, the size at the short distance is 85 inches, and the size at the far distance is 140 inches (Example 2). ) Or 150 inches (Examples 1, 3 and 4), and these sizes are changed by focusing.

  FIG. 3, FIG. 9, FIG. 14, and FIG. 20 show the lens arrangement of the refractive optical system in the projection optical systems of Examples 1, 2, 3, and 4, and how the lens group is displaced by focusing. In these drawings, reference numerals I to IV denote “first lens group to sixth lens group”. That is, in all of Examples 1 to 4, the refractive optical system is composed of six lens groups (N = 6).

In the following description regarding the examples, the meanings of the symbols are as follows.
f: Focal length of the entire system
NA: Numerical aperture
ω: Half angle of view (deg)
R: radius of curvature (for aspheric surfaces, the paraxial radius of curvature)
D: Surface spacing
Nd: Refractive index
νd: Abbe number
K: Aspherical conical constant
Ai: i-th aspherical constant
C: Paraxial curvature (reciprocal of paraxial radius of curvature)
The shape of the aspherical surface is as follows: paraxial curvature: C, height from optical axis: H, conic constant: K, aspheric coefficient of each order: Ai, and X as “aspheric amount in optical axis direction” Well-known formula:
X = CH ² / [1 + √ (1− (1 + K) C ² H ² )] + ΣAiH ⁱ
The shape is specified by giving C, K, and Ai. In addition, regarding the quantity having the dimension of length, the unit is “mm” unless otherwise specified.

"Example 1"
The first embodiment which is the projection optical system of the image display apparatus shown in FIG. 1 includes a refractive optical system 11 and a reflective optical system 12.
As shown in FIG. 3, the refractive optical system 11 includes a first lens group I having a positive refractive power and a second lens group having a positive refractive power in order from the reduction side (object side) to the enlargement side. II, a third lens group III having a positive refractive power, a fourth lens group IV having a positive refractive power, a fifth lens group V having a negative refractive power, and a sixth lens group having a negative refractive power. The lens group VI has a lens group VI. When focusing from the long distance side to the short distance side, the second lens group II, the fourth lens group IV, and the fifth lens group V are reduced on the focusing side. The third lens group III moves to the enlargement side. The first lens group I and the sixth lens group VI do not move during focusing.
With such a “focusing configuration” and appropriate positive refractive power of the third lens group, it is possible to suppress the spread of light rays on the “magnifying side than the third lens group III”, and to reduce the angle of view, particularly around the screen. The image plane of the part can be highly corrected. In addition, this focus method makes it possible to highly correct the image plane of each angle of view, and thus it is possible to use a highly reliable glass molded aspheric lens.

The data of Example 1 of the projection optical system is shown below.
Numerical aperture: 0.22273
The data of Example 1 is shown in Table 1. The surface numbers shown in the leftmost column are the surface number 1 for the image forming unit LV, and the surface numbers 2 to 5 for the surfaces of the transparent parallel flat plate F and the prism Pr. Surface number 6 is the lens surface on the most reduction side of the refractive optical system. This also applies to Examples 2 to 4 below.

“Variable intervals with focusing”
Table 2 shows variable intervals associated with focusing at short distance, reference distance (reference and display), and long distance.

"Aspherical data"
An aspherical surface is a surface obtained by adding “*” to the surface number in the above data (this is the same in other examples below), and the data is shown in Table 3.

In the above notation, for example, “2.8853E-10” means “2.8853 × 10 ⁻¹⁰ ”. The same applies to the following.

"Parameter: TR value"
Table 4 shows the parameter TR with respect to the projection distance.

In Example 1, the lens effective diameter of the most magnified lens of the refractive optical system 11 is 56 mm.
Spot diagrams corresponding to the respective angles of view (F1 to F11) shown in FIG. 4 are shown in FIGS. Each spot diagram shows imaging characteristics (mm) on the screen surface for wavelengths: 638 nm (red), 550 nm (green), and 455 nm (blue). It can be seen that a good image is formed.

"Example 2"
Example 2 is an example of the projection optical system in the image display apparatus whose embodiment is shown in FIG. FIG. 9 shows the lens configuration of the refractive optical system in Example 2 and the displacement of the lens unit accompanying focusing, in accordance with FIG. As shown in FIG. 9, the refractive optical system 21 includes, in order from the reduction side, a first lens group I having a positive refractive power, a second lens group II having a negative refractive power, and a third lens having a positive refractive power. A group III, a fourth lens group IV having a negative refractive power, a fifth lens group V having a negative refractive power, and a sixth lens group IV having a negative refractive power are arranged.

During focusing from the long distance side to the short distance side, the second lens group II, the negative fourth lens group IV, and the fifth lens group V move to the image forming unit side, and the third lens group III moves to the enlargement side. To do. The first lens group I and the sixth lens group VI do not move.
With such a focusing configuration, by making the positive refractive power of the third lens group III appropriate, it is possible to suppress the spread of rays on the enlargement side with respect to the third lens group III, and in particular, at each field angle, particularly at the periphery of the screen. The image plane can be highly corrected. In addition, this focus method makes it possible to highly correct the image plane of each angle of view, so that a highly reliable glass mold aspheric lens can also be used.

The data of Example 2 of the projection optical system is shown below.
Numerical aperture: 0.2222
The data of Example 2 is shown in Table 5.

“Variable intervals with focusing”
Table 6 shows variable intervals associated with focusing at a short distance, a reference distance, and a long distance.

"Aspheric data"
Table 7 shows the aspherical data.

"Parameter: TR value"
Table 8 shows the parameter TR with respect to the projection distance.

In Example 2, the lens effective diameter of the most enlarged lens of the refractive optical system 21 is 44 mm.
The spot diagrams corresponding to the angles of view (F1 to F11) shown in FIG. 4 are shown in FIGS. It can be seen that a good image is formed.

"Example 3"
Example 3 is an example of the projection optical system in the image display apparatus whose embodiment is shown in FIG. FIG. 14 shows the lens configuration of the refractive optical system in Example 3 and the displacement of the lens unit accompanying focusing, in accordance with FIG.
The refracting optical system 31 has a first lens group I having a positive refractive power, a second lens group II having a positive refractive power, and a first lens having a positive refractive power in order from the reduction side to the enlargement side. The third lens group III includes a fourth lens group IV having a negative refractive power, a fifth lens group V having a positive refractive power, and a sixth lens group VI having a negative refractive power.

During focusing from the long distance side to the short distance side, the second lens group II, the fourth lens group IV, and the fifth lens group V move to the image forming unit LV side (reduction side), and the third lens group III Move to the enlargement side. The first lens group I and the negative sixth lens group VI do not move.
While having such a focusing configuration and appropriately setting the positive refractive power of the third lens unit, it is possible to suppress the spread of light on the enlargement side with respect to the third lens unit III while suppressing the angle of view, particularly around the screen. The image plane of the part can be highly corrected.

  This focusing method makes it possible to highly correct the image plane at each angle of view, so that a highly reliable glass mold aspheric lens can also be used.

The data of Example 3 of the projection optical system is shown below.
Numerical aperture: 0.2273
The data of Example 3 is shown in Table 9.

“Variable intervals with focusing”
Table 10 shows variable intervals associated with focusing at a short distance, a reference distance, and a long distance.

"Aspherical data"
Table 11 shows the aspherical data.

"Parameter: TR value"
Table 12 shows the parameter TR with respect to the projection distance.

In Example 3, the lens effective diameter of the most magnified lens of the refractive optical system 31 is 44.2 mm.
Spot diagrams corresponding to the respective angles of view shown in FIG. 4 are shown in FIGS. Each spot diagram shows the imaging characteristics (mm) on the screen surface at wavelengths of 638 nm (red), 550 nm (green), and 455 nm (blue). It can be seen that a good image is formed.

Example 4
Example 4 is an example of the projection optical system in the image display apparatus whose embodiment is shown in FIG. FIG. 19 shows the lens configuration of the refractive optical system in Example 4 and the displacement of the lens unit accompanying focusing, in accordance with FIG.
The refractive optical system 41 includes a first lens group I having a positive refractive power, a second lens group II having a positive refractive power, and a positive lens in order from the image forming unit side (reduction side) to the enlargement side. A third lens group III having a refractive power, a fourth lens group IV having a negative refractive power, a fifth lens group V having a negative refractive power, and a sixth lens group VI having a negative refractive power. It is arranged.
During focusing from the long distance side to the short distance side, the second lens group II, the fourth lens group IV, and the fifth lens group V move to the reduction side, and the third lens group III moves to the enlargement side. The first lens group I and the sixth lens group VI do not move.
By adopting such a focusing configuration and appropriately setting the positive refractive power of the third lens group, it is possible to suppress the spread of the light beam on the enlargement side with respect to the third lens group III, and to reduce the angle of view, particularly at the periphery of the screen The image plane can be highly corrected.
In addition, this focus method makes it possible to highly correct the image plane of each angle of view, so that a highly reliable glass mold aspheric lens can also be used.

The data of Example 4 of the projection optical system is shown below.
Numerical aperture: 0.2273
The data of Example 4 is shown in Table 13.

“Variable intervals with focusing”
Table 14 shows variable intervals associated with focusing at a short distance, a reference distance, and a long distance.

"Aspherical data"
Table 15 shows the aspheric data.

"Parameter: TR value"
Table 16 shows the parameter TR with respect to the projection distance.

In Example 4, the lens effective diameter of the most magnified lens of the refractive optical system 41 is 43.4 mm.
Spot diagrams corresponding to the respective angles of view shown in FIG. 4 are shown in FIGS. Each spot diagram shows the imaging characteristics (mm) on the screen surface at wavelengths of 638 nm (red), 550 nm (green), and 455 nm (blue). It can be seen that a good image is formed.

  Table 17 shows amounts in the parameters relating to the projection optical systems of Examples 1 to 4.

  F4 to F6 are focal lengths (mm) of the fourth lens group to the sixth lens group, respectively.

  Table 18 shows the values of the parameters of the conditions (1) to (4) related to Examples 1 to 4.

  All the examples satisfy the conditions (1) to (4).

  As described above, according to the present invention, the following projection optical system and image display apparatus can be realized.

[1]
A projection optical system for enlarging and projecting an image displayed on an image forming unit (LV) of an image display element on a projection surface (SC), a refractive optical system (11, 21, 31, 41) and a reflective optical system (12, 22, 32, 42), the refractive optical system has N (≧ 4) lens groups (I to VI), and the reflective optical system has a refractive power. The refractive optical system includes a first lens group (I), a second lens group (II), and a third lens group (III) sequentially from the reduction side to the enlargement side, One or more lens groups are provided on the enlargement side of the third lens group, the first lens group has the strongest positive refractive power in the refractive optical system, and the third lens group is the refractive optical system. It has a strong positive refracting power next to the first lens group in the middle, and a focal length from the long distance side to the short distance side. During the singing, the second lens group moves to the reduction side, the third lens group moves to the fixed or enlargement side with respect to the image, and one or more lens groups on the enlargement side move from the third lens group A projection optical system (Examples 1 to 4) that moves to the reduction side as a lens group.

[2]
[1] The projection optical system according to [1], wherein the second lens group (II) has a focal length F2 at the d-line and a third lens group (III) has a focal length F3 at the d-line:
(1) 1.0 <| F2 / F3 | <30.0
Projection optical system satisfying the above (Examples 1 to 4).

[3]
The projection optical system according to [1] or [2], wherein the third lens group (III) has a focal length F3 at the d-line, d of the refractive optical system in a focused state where the projection image is maximum. Focal length at line: FL, condition:
(2) 0.1 <FL / F3 <1.0
Projection optical system satisfying the above (Examples 1 to 4).

[4]
In the projection optical system according to any one of [1] to [3], at least one moving lens group disposed on the enlargement side with respect to the third lens group (III) has a negative refractive power. Projection optical system (Examples 1 to 4).

[5]
The projection optical system according to any one of [1] to [4], wherein the most magnified lens group in the refractive optical system has negative refractive power (Examples 1 to 4).

[6]
The projection optical system according to any one of [1] to [5], wherein the most magnified lens group in the refractive optical system is fixed during focusing (Examples 1 to 4).

[7]
The projection optical system according to any one of [1] to [6],
A projection optical system (Examples 1 to 4) in which the refractive optical system is configured by five or more lens groups, and has two lens groups that move on the enlargement side of the third lens group during focusing.

[8]
The projection optical system according to any one of [1] to [7], wherein an image conjugate with an image displayed on the image forming unit of the image display element is converted into the refractive optical system and the reflective optical element. Projection optical system formed between (Examples 1 to 4).

[9]
The projection optical system according to any one of [1] to [8], wherein all the lenses constituting the refractive optical system are glass lenses (Examples 1 to 4).

[10]
The projection optical system according to any one of [1] to [9], wherein the refractive optical system is sequentially arranged on the enlargement side of the third lens group (III) toward the enlargement side. (IV) A projection optical system (Examples 1 to 4) having a fifth lens group (V) and a sixth lens group (VI).

[11]
The projection optical system according to any one of [1] to [10], wherein the reflective optical elements (12, 22, 32, 42) are concave mirrors (Examples 1 to 4).

[12]
An image display apparatus that displays an image by enlarging and projecting an image displayed on an image forming unit (LV) of an image display element onto a projection surface (SC) by a projection optical system, and [1] to [1] The image display apparatus using the thing as described in any one of [11] (FIG. 1, FIG. 8, FIG. 13, FIG. 18, Examples 1-4).

[13]
[12] The image display device according to [12], wherein the projection optical system described in [11] is used, and among the intersections of the concave mirror (12, 22, 32, 42) and the imaging light ray, In the direction perpendicular to the projection surface (SC), a distance L in the direction perpendicular to the projection surface from the intersection P at which the distance to the projection surface is maximized to the projection surface, and the projection surface The width of the projected maximum image: Ratio to W: TR (= L / W) is the condition:
(3) TR <0.35
Display apparatus satisfying the above (FIGS. 1, 8, 13, and 18, Examples 1 to 4).

[14]
[12] The image display device according to [13], wherein the projection optical system includes [11] the projected surface among the intersection points of the concave mirror (12, 22, 32, 42) and the imaging light beam. The distance P in the direction perpendicular to the image forming unit to the image forming unit (LV): OAL, the optical axis of the refractive optical system, Maximum value of the distance to the image forming unit: Y is a condition:
(4) 10 <OAL / Y <30
Display apparatus satisfying the above (FIGS. 1, 8, 13, and 18, Examples 1 to 4).

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
For example, the number of reflection optical elements constituting the reflection optical system can be two or more.
In Examples 1 to 4, although all the lenses constituting the refractive optical system are glass lenses, the present invention is not limited thereto, and one or more resin lenses may be included.

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

H Image display device
LV image forming unit
F Transparent parallel plate
Pr prism
11 Refraction optical system
12 Reflective optics (concave mirror)
13 Dust-proof glass
S Aperture stop

JP 2007-079524 A JP 2009-251458 A JP 2011-242606 A JP 2012-203139 A

Claims (14)

A projection optical system that enlarges and projects an image displayed on an image forming unit of an image display element on a projection surface,
A refractive optical system and a reflective optical system;
The refractive optical system has N (≧ 4) lens groups,
The reflective optical system has at least one reflective optical element having refractive power,
The refractive optical system includes a first lens group, a second lens group, and a third lens group sequentially from the reduction side to the magnification side, and has one or more lens groups on the magnification side of the third lens group. The first lens group has the strongest positive refractive power in the refractive optical system, and the third lens group has the strongest positive refractive power next to the first lens group in the refractive optical system. And
At the time of focusing from the long distance side to the short distance side, the second lens group moves to the reduction side, the third lens group moves to the fixed side or the magnification side with respect to the image, and enlarges from the third lens group. A projection optical system in which one or more lens groups on the side move to the reduction side as moving lens groups. The projection optical system according to claim 1,
The focal length of the second lens group at the d-line: F2, and the focal length of the third lens group at the d-line: F3 are:
(1) 1.0 <| F2 / F3 | <30.0
Projection optical system that satisfies The projection optical system according to claim 1 or 2,
The focal length at the d-line of the third lens group: F3, and the focal length at the d-line of the refractive optical system in the in-focus state where the projected image is maximized: FL are the conditions:
(2) 0.1 <FL / F3 <1.0
Projection optical system that satisfies The projection optical system according to any one of claims 1 to 3,
A projection optical system in which at least one moving lens group disposed on the enlargement side with respect to the third lens group has a negative refractive power. The projection optical system according to any one of claims 1 to 4,
A projection optical system in which the most magnified lens group in the refractive optical system has a negative refractive power. A projection optical system according to any one of claims 1 to 5,
A projection optical system in which the most magnified lens group in the refractive optical system is fixed during focusing. The projection optical system according to any one of claims 1 to 6,
The refractive optical system is composed of five or more lens groups,
A projection optical system having two lens groups that move during focusing closer to the magnification side than the third lens group. A projection optical system according to any one of claims 1 to 7,
A projection optical system that forms an image conjugate with an image displayed on the image forming unit of the image display element between the refractive optical system and the reflective optical element. A projection optical system according to any one of claims 1 to 8,
A projection optical system in which all the lenses constituting the refractive optical system are glass lenses. The projection optical system according to any one of claims 1 to 9,
A projection optical system in which a refractive optical system includes a fourth lens group, a fifth lens group, and a sixth lens group in order toward the magnification side on the magnification side of the third lens group. A projection optical system according to any one of claims 1 to 10,
A projection optical system in which the reflective optical element is a concave mirror. An image display device that enlarges and projects an image displayed on an image forming unit of an image display element onto a projection surface by a projection optical system, and displays the image.
An image display device using the projection optical system according to any one of claims 1 to 11. The image display device according to claim 12,
The projection optical system according to claim 11 is used.
Of the intersections between the concave mirror and the imaging light beam, the direction perpendicular to the projection surface from the intersection P that maximizes the distance to the projection surface in the direction perpendicular to the projection surface. The ratio of the distance: L to the width of the maximum image projected on the projection surface: W: TR (= L / W) is the condition:
(3) TR <0.35
An image display device that satisfies the requirements. The image display device according to claim 12 or 13,
The projection optical system according to claim 11 is used.
Of the intersections between the concave mirror and the imaging light beam, the intersection P that maximizes the distance to the projection surface in the direction perpendicular to the projection surface and the direction perpendicular to the image formation unit up to the image formation unit Distance: OAL, the maximum distance: Y between the optical axis of the refractive optical system and the image forming unit is:
(4) 10 <OAL / Y <30
An image display device that satisfies the requirements.

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