WO2016125681A1

WO2016125681A1 - Projection optical system and projection device

Info

Publication number: WO2016125681A1
Application number: PCT/JP2016/052510
Authority: WO
Inventors: 佐野永悟
Original assignee: コニカミノルタ株式会社
Priority date: 2015-02-05
Filing date: 2016-01-28
Publication date: 2016-08-11

Abstract

The present invention comprises, in the following order, an image display element such as a reflecting liquid crystal element 40, a dioptric system Gr1 which has a plurality of lenses, and a catoptric system Gr2 which reflects and guides light that has exited from the dioptric system Gr1 to a screen PS. An intermediate image is formed between the dioptric system Gr1 and the catoptric system Gr2, and the lens disposed closest to the catoptric system Gr2 in the dioptric system Gr1 has a negative power. Moreover, the catoptric system Gr2 is solely constituted by, in the following order from the side of the image display element, a concave mirror M1 having a concave shape and a convex mirror M2 having a convex shape, and satisfies the conditional expression -3.0 < FLlst/FLd < -0.5 … (1) provided that the value FLlst is the focal distance of the lens disposed closest to the catoptric system Gr2 in the dioptric system Gr1, and the value FLd is the focal distance of the dioptric system Gr1.

Description

Projection optical system and projection apparatus

The present invention relates to a projection optical system and a projection apparatus for projecting an image, and more particularly to a wide-angle projection optical system including a mirror and a projection apparatus including the projection optical system.

In recent years, a projection apparatus for enlarging and projecting an image displayed on an image display element on a screen by a projection optical system is desired to have a wide-angle projection optical system that can be projected on a large screen even at a short projection distance while being small and light. ing. In addition, with the increase in resolution of image display elements, there is an increasing demand for higher performance in projection optical systems.

As such a projection optical system, an optical system having a configuration in which a refractive optical system having a plurality of lenses and a reflective optical system including a mirror, such as Patent Document 1, is disclosed.

However, since the optical system of Patent Document 1 has a single mirror with power in the reflective optical system, there is a limit to the enlargement ratio of the optical system, and a large screen can be projected at a sufficiently short distance. I can not say. In addition, the number of lenses in the refractive optical system increases.

Therefore, for example, Patent Document 2 discloses a projection optical system that can project a large screen at a short distance while arranging two mirrors having power in the reflecting optical system to further reduce the number of lenses of the refractive optical system. It is disclosed.

However, the projection optical system described in Patent Document 2 cannot be said to project a sufficiently large screen and has a large optical total length.

Japanese Patent No. 4210314 JP 2007-79524 A

The present invention has been made in view of the problems of the background art described above, and an object of the present invention is to provide a projection optical system capable of projecting a small screen and a large screen and having good optical performance over the entire screen. .

It is another object of the present invention to provide a projection apparatus provided with the above projection optical system.

In order to achieve the above object, a projection optical system according to the present invention is a projection optical system for a projection apparatus that enlarges an image obtained from an image display element and projects it on a screen, in order from the image display element side, It consists of a refractive optical system having a plurality of lenses and a reflective optical system that reflects the light emitted from the refractive optical system and guides it to the screen. An intermediate image is formed between the refractive optical system and the reflective optical system to be refracted. The lens arranged on the most reflective optical system side of the optical system has negative power, and the reflective optical system has a concave mirror having one concave shape and a convex surface having one convex shape in order from the image display element side. It consists only of mirrors and satisfies the following conditional expression.
-3.0 <FLlst / FLd <-0.5 (1)
However, the value FLlst is the focal length of the lens arranged closest to the reflective optical system of the refractive optical system, and the value FLd is the focal length of the refractive optical system.

A projection apparatus according to the present invention includes the above-described projection optical system, an image display element, an illumination optical system that generates illumination light that illuminates the image display element, an element drive circuit that drives the image display element, and illumination. A control circuit for controlling operations of the optical system and the element driving circuit.

It is a figure explaining the structure of the projection apparatus incorporating the projection optical system which concerns on one Embodiment of this invention. It is a figure explaining the projection using the projection optical system shown in FIG. 3A and 3B are diagrams illustrating some parameters representing the characteristics of the projection optical system. FIG. 2 is a diagram illustrating a projection optical system according to Example 1. 5A and 5B are MTF characteristic diagrams showing the performance of the projection optical system of Example 1 on the screen. It is a figure explaining the MTF evaluation point on an image display element. FIG. 6 is a diagram illustrating a projection optical system of Example 2. 8A and 8B are MTF characteristic diagrams showing the performance of the projection optical system of Example 2 on the screen. FIG. 6 is a diagram for explaining a projection optical system according to Example 3. 10A and 10B are MTF characteristic diagrams showing the performance of the projection optical system of Example 3 on the screen. It is a figure explaining the modification of the projection optical system shown in FIG.

Hereinafter, a projection optical system according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a projection apparatus incorporating a projection optical system according to an embodiment of the present invention, and FIG. 2 shows a projection state by the projection optical system. The projection apparatus 100 has a structure in which a projection optical system 10, an illumination optical system 20, a polarizing beam splitter 30, a reflective liquid crystal element 40, an element driving circuit 50, and a control circuit 70 are incorporated.

In the projection apparatus 100, the projection optical system 10 magnifies and projects an image (image displayed on the display surface DD of the reflective liquid crystal element 40) obtained from the reflective liquid crystal element 40, which is an image display element, onto the projection target. To do. The projection optical system 10 includes a refractive optical system Gr1 that is a first optical group and a reflective optical system Gr2 that is a second optical group. The refractive optical system Gr1 close to the reflective liquid crystal element (image display element) 40 has a plurality of lenses, and the reflective optical system Gr2 on the screen PS side far from the reflective liquid crystal element 40 is a refractive optical system (first optical group). ) The light beam emitted from Gr1 is reflected and guided to the screen PS. The refractive optical system Gr1 is composed of nine lenses L1 to L9 in the projection optical system 10 shown in FIG. Among these lenses L1 to L9, in particular, the lens L9 is disposed closest to the reflective optical system (second optical group) Gr2 and has a negative power. Here, power means the reciprocal of the focal length. Each of the lenses L1 to L9 is made of glass or a resin material. The optical surfaces of the lenses L1 to L9 are spherical or aspheric and have a rotationally symmetric shape with respect to the optical axis OA. Of the lenses L1 to L9, a lens close to the reflective liquid crystal element (image display element) 40 has a circular outline when viewed from the optical axis OA direction, but a lens far from the reflective liquid crystal element 40, for example, the lens L9, is An area not used in the optical path may be cut out. The reflective optical system Gr2 includes, in order from the reflective liquid crystal element 40 side, a single concave mirror M1 having a concave shape and a single convex mirror M2 having a convex shape. Both mirrors M1 and M2 may be cut out in a region not used in the optical path.

The projection optical system 10 forms an intermediate image (an intermediate image of an image obtained from the image display element) between the refractive optical system (first optical group) Gr1 and the reflective optical system (second optical group) Gr2. is doing. That is, the projection optical system 10 is a system that re-images an image once formed.

Like the projection optical system 10, the projection optical system 10 includes, in order from the reflective liquid crystal element (image display element) 40 side, a refractive optical system Gr1 that is a first optical group and a reflective optical system Gr2 that is a second optical group. The intermediate image is once formed by the optical system Gr1, and then the intermediate image is enlarged and projected onto the screen PS by the reflection optical system Gr2, so that the image of the reflective liquid crystal element 40 is once formed on the screen PS. Since the magnification ratio can be shared by the refractive optical system Gr1 and the reflection optical system Gr2, compared with the case of magnifying and projecting, the configuration is advantageous as an optical system for large screen projection. In addition, a large screen can be projected from a short distance by making the light beam obliquely incident on the screen PS by the reflective optical system Gr2. In addition, by constructing the reflective optical system Gr2 in order of the concave mirror M1 and the convex mirror M2 from the reflective liquid crystal element 40 side, it is possible to reduce the beam bundle diameter by the concave mirror M1, so that the convex surface disposed behind it. The size of the mirror M2 can be reduced. Further, by configuring each mirror M1, M2 one by one, it is possible to reduce the size of the entire projection optical system 10 while ensuring the assembly of the reflection optical system Gr2 or the mirrors M1, M2. It becomes like this. Further, by setting the lens L9 closest to the reflective optical system Gr2 in the refractive optical system Gr1 as a negative lens, a wider-angle projection optical system can be obtained.

The illumination optical system 20 generates illumination light that illuminates the reflective liquid crystal element 40, and a detailed description thereof is omitted, but includes a light emission source, a condensing optical system, a polarization conversion element, and the like. As the light source, for example, a light source incorporating three color LEDs or the like can be used, and the condensing optical system converts, for example, illumination light from the three color LEDs or the like into substantially parallel light. The polarization conversion element converts the incident light into specific polarization without reducing the amount of incident light.

The polarization beam splitter 30 is obtained by bonding a pair of right-angle prisms, and a reflection surface that reflects linearly polarized light in a predetermined direction incident from the illumination optical system 20 on the inclined surface of one right-angle prism on the bonding surface. (Not shown) is formed. Thereby, the illumination light emitted from the illumination optical system 20 and linearly polarized in a predetermined direction can be reflected and incident on the reflective liquid crystal element 40.

The reflective liquid crystal element 40 is a display element (image display element) that forms image light, and can be said to be a light modulation element in that image light is formed from illumination light by changing the spatial transmittance. The reflective liquid crystal element (image display element) 40 is an image display panel that is a plate-like electronic component. The reflection type liquid crystal element 40 is a micro display also called LCOS (Liquid crystal on silicon), in which a circuit is directly formed on the surface of a silicon chip and a liquid crystal layer is sandwiched between a counter substrate. When a voltage corresponding to a drive signal is applied to a liquid crystal layer for each pixel, the reflective liquid crystal element 40 modulates illumination light by changing the arrangement of liquid crystal molecules and displays a desired image. . The reflective liquid crystal element 40 displays the target image, and the incident light is incident on the reflective liquid crystal element 40 while sequentially switching the emitted light of the red LED, blue LED, and green LED in a short time, thereby corresponding to the target image. Each color image is shifted and reflected on the time axis, thereby forming a color image on the screen PS. Therefore, the color balance can be arbitrarily changed by individually adjusting the light emission amount or the light emission time by changing the drive current and duty ratio of the red LED, blue LED, and green LED (see, for example, JP-A-2007-79402). ).

The element driving circuit 50 is a circuit portion that operates the reflective liquid crystal element 40 based on an image signal. The element driving circuit 50 operates based on a control signal from a control circuit 70 described later, and outputs a driving signal corresponding to the image signal to the reflective liquid crystal element 40 to perform an image display operation.

The control circuit 70 can appropriately operate the illumination optical system 20, the element drive circuit 50, and the like based on a program incorporated therein or an instruction from an operation unit (not shown). The control circuit 70 outputs a drive signal and an image signal to the illumination optical system 20 and the element drive circuit 50 based on a video signal and other signals input from the outside, and performs a display operation on the reflective liquid crystal element 40. Let it be done.

Hereinafter, detailed features of the projection optical system 10 will be described. The projection optical system 10 satisfies the following conditional expression.
-3.0 <FLlst / FLd <-0.5 (1)
However, the value FLlst is the focal length of the lens L9 arranged closest to the reflective optical system Gr2 of the refractive optical system Gr1, and the value FLd is the focal length of the refractive optical system Gr1.

When the conditional expression (1) is satisfied, the size of the entire projection optical system 10 can be reduced. When the value FLlst / FLd of conditional expression (1) exceeds the lower limit value, the negative power of the lens L9 closest to the reflective optical system Gr2 can be appropriately maintained, and the projection optical system 10 having a wider angle can be obtained. Can do. On the other hand, when the value FLlst / FLd is less than the upper limit value, the negative power of the lens L9 closest to the reflective optical system Gr2 is prevented from becoming too strong, and the effective diameter of the concave mirror M1 disposed behind increases. As a result, the overall size of the projection optical system 10 can be reduced.

The projection optical system 10 satisfies the following conditional expression.
1.0 <EDMR1 / EDL <3.0 (2)
However, the value EDMR1 is the maximum height from the optical axis OA of the use area EA of the concave mirror M1, and the value EDL is the lens having the largest outer diameter among the lenses L1 to L9 in the refractive optical system Gr1 (specifically The effective radius of the lens L8). In addition, in FIG. 3A, height EDMR1 was illustrated about the concave mirror M1 shown typically.

The effective area of the concave mirror M1 disposed closer to the refractive optical system Gr1 in the reflective optical system Gr2 is a light beam by a negative lens (specifically, the lens L9) closest to the reflective optical system Gr2 in the refractive optical system Gr1. Is increased by diverging. Since the value EDMR1 / EDL of the conditional expression (2) exceeds the lower limit value, the power of the negative lens (lens L9) closest to the reflective optical system Gr2 in the refractive optical system Gr1 can be appropriately maintained. This is advantageous for correction of surface curvature and distortion. On the other hand, when the value EDMR1 / EDL is less than the upper limit value, the effective area of the concave mirror M1 does not become too large, and the radial size of the entire projection optical system 10 can be kept relatively small.

The projection optical system 10 satisfies the following conditional expression.
1.5 <YDMR2 / YDMR1 <3.0 (3)
However, the value YDMR2 is the size in the diagonal direction of the use area EA of the convex mirror M2, and the value YDMR1 is the size in the diagonal direction of the use area EA of the concave mirror M1. In addition, in FIG. 3A, the size YDMR1 in the diagonal direction of the use area EA is illustrated for the concave mirror M1 schematically shown.

Conditional expression (3) is a conditional expression for appropriately setting the ratio between the size of the concave mirror M1 and the size of the convex mirror M2. When the value YDMR2 / YDMR1 of conditional expression (3) is below the upper limit value, the effective area of the convex mirror M2 does not become too large, and the size of the entire projection optical system 10 in the radial direction can be reduced. Moreover, since the weight of the mirror increases with the size, the weight of the projection optical system 10 can be kept small. Further, if the distance to the screen PS and the size of the projection image are constant, the fact that the size of the convex mirror M2 is kept small means that the magnification of the projection image must be greatly borne by the convex mirror M2. . Therefore, when the value YDMR2 / YDMR1 exceeds the lower limit value, the magnification burden of the convex mirror M2 can be reduced, and the aberration generated by the convex mirror M2 can be suppressed to a small value.

The projection optical system 10 satisfies the following conditional expression.
0.7 <TLMM / TLLM <1.5 (4)
However, when the principal ray that emerges from the screen center of the display surface DD of the reflective liquid crystal element 40 and reaches the screen center of the screen PS is the central principal ray PL, the value TLMM is that the central principal ray PL is the concave mirror M1. Is a distance with respect to the normal direction (specifically, the Z direction) of the display surface DD of the reflective liquid crystal element 40 from the point corresponding to the convex mirror M2, and the value TLLM is the central principal ray PL of the refractive optical system Gr1. The normal direction of the display surface DD of the reflective liquid crystal element 40 from the point passing through the exit surface S92 or the rear surface of the lens L9 closest to the reflective optical system Gr2 or the screen PS side to the point hitting the concave mirror M1 (specifically Is the distance in the Z direction (see FIG. 3B).

Conditional expression (4) is a conditional expression for appropriately setting the ratio between the optical path length from the concave mirror M1 to the convex mirror M2 and the optical path length from the refractive optical system Gr1 to the concave mirror M1. When the value TLMM / TLLM of conditional expression (4) is below the upper limit value, the optical path length from the concave mirror M1 to the convex mirror M2 does not become too large, and the size of the convex mirror M2 can be kept small. On the other hand, when the value TLMM / TLLM exceeds the lower limit, the magnification burden of the convex mirror M2 can be reduced, and the aberration generated in the convex mirror M2 can be suppressed to a small value.

In the projection optical system 10, an optical element having substantially no power can be added to the refractive optical system Gr1 and the reflective optical system Gr2.

The projection optical system 10 described above includes the refractive optical system Gr1 and the reflective optical system Gr2 in order from the reflective liquid crystal element 40, which is an image display element, and once forms an intermediate image with the refractive optical system Gr1. In addition, the intermediate optical image is magnified and projected on the screen PS by the reflective optical system Gr2, so that the magnification rate is refracted rather than the magnified projection of the image of the reflective liquid crystal element 40 on the screen PS at once. The optical system Gr1 and the reflective optical system Gr2 can be divided. As a result, the projection optical system 10 has an advantageous configuration for an optical system for large screen projection. In addition, a large screen can be projected from a short distance by making the light rays obliquely enter the screen PS surface with the reflective optical system Gr2.

In addition, by constructing the reflective optical system Gr2 in order of the concave mirror M1 and the convex mirror M2 from the reflective liquid crystal element 40 side, it is possible to reduce the beam bundle diameter by the concave mirror M1, so that the convex surface disposed behind it. The size of the mirror M2 can be reduced. Further, by configuring each of the mirrors M1 and M2 one by one, it is possible to reduce the size of the entire projection optical system 10 while ensuring the assembly of the mirrors.

Further, the projection optical system 10 having a wider angle can be obtained by using a negative lens as the lens closest to the reflective optical system Gr2 of the refractive optical system Gr1.

〔Example〕
Examples of the projection optical system according to the present invention will be described below. Symbols used in each example are as follows.
R: Paraxial radius of curvature D: Axial surface spacing Nd: Refractive index νd of lens material with respect to d-line: Abbe number of lens material The optical specification values common to the projection optical systems of Examples 1 to 3 are as follows: ing.
F number: F2.80
Image display element size: 13.5mm x 7.6mm

In each embodiment, the surface described with “*” after each surface number (Surf.N) is a surface having an aspherical shape, and the aspherical shape has the apex of the surface as the origin and the optical axis direction. Is expressed by the following “Equation 1” where the height in the direction perpendicular to the optical axis is h. In addition, infinity is represented as “INF”, the display surface of the reflective liquid crystal element 40 is represented as “DD”, and the aperture stop is represented as “ST”.
[Equation 1]

However,
Ai: i-order aspheric coefficient R: radius of curvature K: conic constant

Hereinafter, specific examples of the projection optical system of the present invention will be described.

[Example 1]
Table 1 below shows data such as lens surfaces of the projection optical system of Example 1.
[Table 1]
Surf.N R [mm] D [mm] Nd νd
DD 1.400
1 INF 27.300 1.5187 64.0
2 INF 12.000 1.8396 42.8
3 INF 1.000
4 25.929 5.143 1.8550 23.5
5 -354.502 1.665
6 71.039 3.487 1.4891 70.0
7 -66.541 2.500 1.8550 23.5
8 22.441 1.572
9 17.777 5.521 1.4891 70.0
10 -24.118 1.200 1.8550 23.5
11 56.149 1.207
12 * 24.254 6.489 1.6347 23.9
13 * -66.531 2.899
14 ST INF 30.533
15 -39.401 5.150 1.8550 23.5
16 -34.735 1.000
17 28.562 13.783 1.4891 70.0
18 -62.545 3.150
19 * -28.918 3.000 1.5305 56.0
20 * 61.411 120.000
21 * M1 -55.660 -114.298
22 * M2 -62.676 250.000
PS INF

Table 2 below shows the aspheric coefficients of the aspheric surfaces included in the projection optical system of Example 1.
[Table 2]
12th page
K = 2.1571E + 00, A4 = -6.9109E-06, A6 = 1.6523E-07,
A8 = -6.7297E-10, A10 = 1.8046E-11, A12 = 0.0000E + 00
Side 13
K = -1.7307E + 01, A4 = 4.4902E-05, A6 = 3.5378E-07,
A8 = -1.8972E-09, A10 = 5.4204E-11, A12 = 0.0000E + 00
19th page
K = 0.0000E + 00, A4 = 9.4028E-06, A6 = 1.9792E-08,
A8 = -4.2715E-13, A10 = -8.0667E-14, A12 = 9.7361E-17
20th page
K = 0.0000E + 00, A4 = 3.8404E-06, A6 = 2.6829E-08,
A8 = -3.4872E-11, A10 = 1.1459E-13, A12 = -1.1273E-16
21st page
K = -1.4847E-01, A3 = -4.0358E-06, A4 = 1.9865E-06,
A5 = -1.7979E-08, A6 = 1.1716E-10, A7 = 0.0000E + 00,
A8 = 4.3467E-14, A9 = 0.0000E + 00, A10 = -1.0341E-17,
A11 = 0.0000E + 00, A12 = 3.9834E-21
22nd page
K = -7.1463E + 00, A3 = 8.9723E-06, A4 = -2.7174E-08,
A5 = -1.0619E-10, A6 = -7.6719E-13, A7 = 0.0000E + 00,
A8 = 1.0374E-16, A9 = 0.0000E + 00, A10 = -2.7055E-21,
A11 = 0.0000E + 00, A12 = 0.0000E + 00
In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed by using E (for example, 2.5E-02).

FIG. 4 is a cross-sectional view of the projection optical system 11 and the like of the first embodiment as already described. The projection optical system 11 includes a refractive optical system (first optical group) Gr1 and a reflective optical system (second optical group) Gr2. In the figure, reference symbol Li denotes an i-th lens (i = 1 to 9) constituting the refractive optical system Gr1, and reference symbol ST denotes an aperture stop. The reflective optical system Gr2 has a concave mirror M1 on the reduction side and a convex mirror M2 on the enlargement side. Reference numeral F denotes a parallel plate (in this embodiment, a polarization beam splitter 30) assuming a prism for combining RGB colors when the image display element is a reflective liquid crystal element 40, that is, LCOS. Depending on the type of image display element, the parallel plate F may not be necessary, but the parallel plate F does not have power, so the optical system after the parallel plate F is not changed, and the parallel plate F is excluded. You can also. In that case, it is only necessary to set the air gap between the reflective liquid crystal element 40 as an image display element and the lens L1 at an optimum position.

5A and 5B are MTF (Modulation Transfer Function) characteristic diagrams of the projection optical system 11 of Example 1 on the screen PS instead of the image display element (specifically, the reflective liquid crystal element 40) side. FIG. 5A is an MTF characteristic diagram of points F1 to F3 in the projection range Sc shown in FIG. 6, and FIG. 5B is an MTF characteristic diagram of points F4 to F6 in the projection range Sc shown in FIG. In FIGS. 5A and 5B, Fi-X (i = 1 to 6) indicates the horizontal resolving power at the position Fi, and Fi-Y (i = 1 to 6) indicates the vertical resolving power at the position Fi. Show. The MTF evaluation points are the same as in the first embodiment in the following embodiments. The wavelength weights for calculating the MTF are as follows, and the subsequent examples are the same as those in the first example.
Wavelength weight
656.3nm 34
587.6nm 63
546.1nm 100
486.1nm 83
435.8nm 26
404.7nm 8

(Example 2)
Table 3 below shows data such as lens surfaces of the projection optical system of Example 2.
[Table 3]
Surf.N R [mm] D [mm] Nd νd
DD 1.400
1 INF 27.300 1.5187 64.0
2 INF 12.000 1.8396 42.8
3 INF 2.077
4 617.797 5.367 1.8550 23.5
5 -78.889 0.500
6 36.187 6.291 1.8550 23.5
7 213.861 12.788
8 699.383 8.115 1.5914 60.8
9 -32.880 1.200 1.8550 23.5
10 27.246 0.420
11 22.886 6.866 1.4891 70.0
12 -31.915 0.500
13 -44.425 1.993 1.7617 27.2
14 -396.048 0.748
15 * 51.875 2.780 1.8550 23.5
16 * 496.032 0.552
17 ST INF 140.796
18 -382.164 19.714 1.8550 23.5
19 -141.060 0.500
20 73.115 34.030 1.4891 70.0
21 -1060.931 28.578
22 -131.957 2.500 1.8081 46.3
23 106.474 162.986
24 * M1 -83.633 -132.986
25 * M2 -78.885 230.000
PS INF

Table 4 below shows the aspheric coefficients of the aspheric surfaces included in the projection optical system of Example 2.
[Table 4]
15th page
K = -6.1778E + 00, A4 = -2.5493E-06, A6 = -5.1140E-08,
A8 = -2.0572E-10, A10 = -4.3235E-13, A12 = 0.0000E + 00
16th page
K = -5.0000E + 01, A4 = 3.6952E-07, A6 = -3.4903E-08,
A8 = -2.4392E-10, A10 = 1.3855E-13, A12 = 0.0000E + 00
24th page
K = -1.7621E-01, A3 = 5.1536E-06, A4 = 2.6671E-07,
A5 = -7.9058E-10, A6 = 1.2073E-12, A7 = 0.0000E + 00,
A8 = 6.3460E-15, A9 = 0.0000E + 00, A10 = -9.5268E-19,
A11 = 0.0000E + 00, A12 = 8.5392E-23
25th page
K = -1.4212E + 01, A3 = 1.5289E-06, A4 = 7.7158E-09,
A5 = 4.5956E-11, A6 = -9.8232E-13, A7 = 0.0000E + 00,
A8 = 2.2667E-17, A9 = 0.0000E + 00, A10 = -2.3350E-22,
A11 = 0.0000E + 00, A12 = 0.0000E + 00

FIG. 7 is a sectional view of the projection optical system 12 and the like of the second embodiment. The projection optical system 12 includes a refractive optical system (first optical group) Gr1 and a reflective optical system (second optical group) Gr2. In the drawing, reference symbol Li denotes an i-th lens (i = 1 to 10) constituting the refractive optical system Gr1, and reference symbol ST denotes an aperture stop. The reflective optical system Gr2 has a concave mirror M1 on the reduction side and a convex mirror M2 on the enlargement side. In addition, about the parallel plate F, it can also be set as the structure except this.

8A and 8B are MTF characteristics diagrams of the projection optical system 12 of Example 2 on the screen PS instead of the image display element side. 8A is an MTF characteristic diagram at points F1 to F3 similar to FIG. 6, and FIG. 8B is an MTF characteristic diagram at points F4 to F6 similar to FIG.

(Example 3)
Table 5 below shows data such as lens surfaces of the projection optical system of Example 3.
[Table 5]
Surf.N R [mm] D [mm] Nd νd
DD 1.400
1 INF 27.300 1.5187 64.0
2 INF 12.000 1.8396 42.8
3 INF 1.000
4 30.867 4.632 1.8550 23.5
5 -20974.654 0.500
6 87.201 2.963 1.8470 23.8
7 -369.296 2.050
8 -237.417 7.925 1.6682 54.3
9 -24.883 2.500 1.8470 23.8
10 25.631 1.868
11 22.466 4.415 1.4950 69.0
12 -24.118 1.200 1.7429 27.2
13 -44.257 0.500
14 * 57.176 2.182 1.6347 23.9
15 * 96.266 2.256
16 ST INF 46.967
17 -80.950 6.293 1.8460 24.4
18 -52.367 1.000
19 54.783 9.281 1.4870 70.2
20 2066.262 33.622
21 * -52.760 5.000 1.5305 56.0
22 * 218.326 123.145
23 * M1 -66.197 -136.577
24 * M2 -90.061 250.000
PS INF

Table 6 below shows the aspheric coefficients of the aspheric surfaces included in the projection optical system of Example 3.
[Table 6]
14th page
K = 3.5491E + 01, A4 = -1.0021E-05, A6 = -1.3915E-07,
A8 = -4.7609E-10, A10 = -2.1213E-11, A12 = 0.0000E + 00
15th page
K = 5.0000E + 01, A4 = 2.5526E-05, A6 = 4.4569E-08,
A8 = -8.6429E-10, A10 = 8.7629E-12, A12 = 0.0000E + 00
21st page
K = 0.0000E + 00, A4 = 1.2418E-06, A6 = 9.8647E-10,
A8 = -2.9277E-14, A10 = 2.5698E-15, A12 = -1.8959E-18
22nd page
K = 0.0000E + 00, A4 = -2.1956E-07, A6 = 9.5549E-10,
A8 = 1.2307E-12, A10 = -6.7547E-16, A12 = 8.7661E-19
23rd page
K = -1.6472E-01, A3 = -1.1570E-06, A4 = 9.2981E-07,
A5 = -8.4620E-09, A6 = 7.0157E-11, A7 = 0.0000E + 00,
A8 = 2.0323E-14, A9 = 0.0000E + 00, A10 = -5.7871E-18,
A11 = 0.0000E + 00, A12 = 9.8459E-22
24th page
K = -9.9531E + 00, A3 = 2.7126E-06, A4 = -2.8924E-09,
A5 = 5.7897E-11, A6 = -7.2237E-13, A7 = 0.0000E + 00,
A8 = 1.4781E-17, A9 = 0.0000E + 00, A10 = -1.4333E-22,
A11 = 0.0000E + 00, A12 = 0.0000E + 00

FIG. 9 is a sectional view of the projection optical system 13 and the like of the third embodiment. The projection optical system 13 includes a refractive optical system (first optical group) Gr1 and a reflective optical system (second optical group) Gr2. In the drawing, reference symbol Li denotes an i-th lens (i = 1 to 10) constituting the refractive optical system Gr1, and reference symbol ST denotes an aperture stop. The reflective optical system Gr2 has a concave mirror M1 on the reduction side and a convex mirror M2 on the enlargement side. In addition, about the parallel plate F, it can also be set as the structure except this.

10A and 10B are MTF characteristics diagrams of the projection optical system 13 of Example 3 on the screen PS instead of the image display element side. 10A is an MTF characteristic diagram at points F1 to F3 similar to FIG. 6, and FIG. 10B is an MTF characteristic diagram at points F4 to F6 similar to FIG.

Table 7 below summarizes the values of Examples 1 to 3 corresponding to the conditional expressions (1) to (4) for reference.
[Table 7]

As mentioned above, although this invention was demonstrated according to embodiment and an Example, this invention is not limited to the said embodiment etc. For example, in the projection optical system 10, an optical path bending mirror having no power can be disposed between the refractive optical system Gr1 and the reflective optical system Gr2. In this case, the optical path can be bent in a direction different by 90 °, for example. Therefore, the degree of freedom of the layout of the projection optical system 10 is increased, and as a result, the size of the entire projection optical system 10 can be kept small.

FIG. 11 shows a modification of the projection optical system 10 shown in FIG. 1. In this projection optical system 10, a third plane mirror M3 is arranged as an optical path bending mirror between the lens L9 and the concave mirror M1. is doing. Thereby, the optical path is bent 90 degrees between the refractive optical system Gr1 and the reflective optical system Gr2.

In the above embodiment, the image display element is not limited to the reflective liquid crystal element 40 such as LCOS, but a micromirror device including a micromirror, a transmissive LCD, or the like can be used. In this case, the polarization beam splitter 30 is changed to an optical system suitable for each.

Further, in the above-described embodiment, the reflective liquid crystal element 40 is not limited to being used alone, and an additional reflective liquid crystal element can be disposed facing another side surface of the polarization beam splitter 30.

In the above embodiment, the light source of the illumination optical system 20 is not limited to the LED, and a mercury lamp, a laser, or the like can be used, and these light sources can be used in the same type or different types. In particular, when LEDs or lasers are used as light sources, the number of red, green, and blue light sources may be arbitrarily combined according to the output. Further, it is possible to increase the brightness by adding an optical system for multiplexing and arranging a plurality of light sources for white or a specific color.

Claims

A projection optical system for a projection apparatus that magnifies and projects an image obtained from an image display element on a screen, in order from the image display element side,
A refractive optical system having a plurality of lenses;
A reflective optical system that reflects the light emitted from the refractive optical system and guides it to the screen;
Forming an intermediate image between the refractive optical system and the reflective optical system;
The lens disposed closest to the reflective optical system of the refractive optical system has a negative power,
The projection optical system is composed of only one concave mirror having a concave shape and one convex mirror having a convex shape in order from the image display element side, and satisfies the following conditional expression.
-3.0 <FLlst / FLd <-0.5 (1)
However,
FLlst: focal length of the lens disposed closest to the reflective optical system of the refractive optical system FLd: focal length of the refractive optical system
The projection optical system according to claim 1, wherein the following conditional expression is satisfied.
1.0 <EDMR1 / EDL <3.0 (2)
However,
EDMR1: Maximum height from the optical axis of the use area of the concave mirror EDL: Effective radius of the lens having the largest outer diameter among the lenses in the refractive optical system
The projection optical system according to claim 1, wherein the following conditional expression is satisfied.
1.5 <YDMR2 / YDMR1 <3.0 (3)
However,
YDMR2: size in the diagonal direction of the usage area of the convex mirror YDMR1: size in the diagonal direction of the usage area of the concave mirror
The projection optical system according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.7 <TLMM / TLLM <1.5 (4)
However, when the principal ray that emerges from the center of the screen on the display surface of the image display element and reaches the screen center of the screen surface is the central principal ray,
TLMM: Distance in the normal direction of the display surface of the image display element from the point where the central principal ray hits the concave mirror surface to the point where the central principal ray hits the convex mirror surface. TLLM: The central principal ray is closest to the screen side of the refractive optical system. The distance in the normal direction of the display surface of the image display element from the point passing through the exit surface of the lens arranged at the point to the point hitting the concave mirror surface
The projection optical system according to any one of claims 1 to 4, further comprising an optical path bending mirror having no power between the refractive optical system and the reflective optical system.
The projection optical system according to any one of claims 1 to 5, further comprising an optical element having substantially no power.
A projection optical system according to any one of claims 1 to 6;
An image display element;
An illumination optical system for generating illumination light for illuminating the image display element;

An element driving circuit for driving the image display element;
A control circuit for controlling operations of the illumination optical system and the element driving circuit;
A projection apparatus comprising: