JP6199082B2 - Projection optical system - Google Patents

Description

  The present invention relates to a projection optical system.

  More specifically, the present invention relates to a projection optical system used in an image display apparatus that projects an image for projection displayed on an image display surface of an image display element onto a projection surface by oblique light and displays the enlarged image.

  An image display device that projects an image for projection displayed on an image display surface of an image display element onto a projection surface and displays the image on an enlarged scale is widely used as a projector device or the like.

  In such an image display apparatus, various types of projection optical systems have been proposed for forming an image for projection as a “projection image” on a projection surface (usually a screen).

  As a genre of the projection optical system, “a configuration including a lens system and a curved mirror” is known (Patent Documents 1 to 4).

  In the projection optical systems described in these patent documents, the light beam from the image display surface is incident on the lens system, and the light beam emitted from the lens system is reflected by the curved mirror and guided to the projection surface.

  With such a configuration, the curved surface mirror can also share the imaging function, so the lens system can be easily designed.

  Further, by using a curved mirror having a large mirror surface area, the angle of view of the projection light can be increased without difficulty, and the arrangement position of the projection optical system can be brought close to the projection surface.

  In the projection optical system disclosed in FIG. 12 of Patent Document 4, a light beam emitted from a lens system is reflected by a reflecting mirror having a “substantially planar reflecting surface” and is incident on a concave mirror.

  In the projection optical systems described in Patent Documents 1 to 3, the projection surface is orthogonal to the optical axis of the lens system. However, in the projection optical system of Patent Document 4, the projection surface is substantially parallel to the lens system optical axis. is there.

  For this reason, the projection optical system of Patent Document 4 can “place the lens system closer to the projection surface”.

  By the way, in order to bring the projection surface close to the projection optical system and to increase the size of the projection image, the projection optical system needs to have a wide angle.

  In the projection optical systems described in Patent Documents 1 to 4, in order to realize a wide angle, the lens diameter on the most curved mirror side of the lens system is increased to increase the divergence of the light beam emitted from the lens.

  Moreover, since the divergence of the light beam emitted from the lens is large, the mirror surface area of the curved mirror is also large, making it difficult to make the projection optical system and the image display device compact.

  In view of the circumstances described above, an object of the present invention is to realize a projection optical system that can effectively suppress an increase in the diameter of the lens system and an increase in the area of the mirror surface of the concave mirror.

The projection optical system according to the present invention is a projection optical system used in an image display device that projects an image for projection displayed on an image display surface of an image display element onto a projection surface by oblique light and displays the enlarged image. A lens system, a concave mirror, and a reflecting mirror having a substantially planar reflecting surface, and sequentially projecting light from the image display surface to the projection surface in the order of the lens system, the concave mirror, and the reflecting mirror; The second and third lenses from the magnifying side among the plurality of lenses that guide the light and form an image on the projection surface mainly by the imaging action of the lens system and the concave mirror. , A lens having a coaxial aspherical surface, the enlargement-side surface of the second lens is concave, and the reduction-side surface of the third lens is convex near the optical axis and concave at the periphery and wherein the der Rukoto.

  In the projection optical system of the present invention, the light beam emitted from the lens system is first reflected by the concave mirror and enters the reflecting mirror.

  For this reason, the distance between the lens system and the concave mirror can be increased in the optical axis direction of the lens system, the divergence of the light beam emitted from the lens system can be suppressed, and the increase in the area of the concave mirror can also be suppressed.

It is a figure for demonstrating one Embodiment of a projection optical system. 1 is a diagram illustrating a configuration of a projection optical system according to Example 1. FIG. FIG. 3 is a diagram showing a spot diagram of the projection optical system of Example 1. FIG. 6 is a diagram illustrating a configuration of a projection optical system of Example 2. FIG. 6 is a diagram showing a spot diagram of the projection optical system of Example 2.

  Embodiments of the invention will be described below.

  FIG. 1 is a diagram for explaining one embodiment of a projection optical system for an image display apparatus.

  In FIG. 1, reference numeral 10 denotes a lens system, reference numeral 20 denotes a concave mirror, and reference numeral 30 denotes a reflecting mirror.

  An image display element (not shown) is arranged on the left side (also referred to as a reduction side) of the lens system 10 in the figure, and the image display surface is shifted downward in the figure with respect to the optical axis AX of the lens system 10.

  As the image display element, a liquid crystal light valve having one or three liquid crystal panels, a DMD (digital mirror device), or the like can be used as appropriate.

  The projection image is displayed on the image display surface. For example, in the case of DMD, the two-dimensionally arranged micromirrors are displayed by being tilted according to the projection image.

  The projection light from the image display surface is called “projection light beam”.

  As shown in FIG. 1, the principal light beam of the projected light beam is “an oblique light beam that rises diagonally to the right” with respect to the lens system optical axis AX.

  The projected light beam exits from the lens system 10 as a “right-up divergent light beam” with respect to the optical axis AX, and first enters the concave mirror 20.

  In the figure, light fluxes FL1 and FL2 are light fluxes formed at both ends of the projected image on the screen, and the symbol: θ is an angle formed by the light fluxes FL1 and FL2 and is a “divergence angle of the projected light flux”.

  The projected light beam reflected by the concave mirror 20 enters the reflecting surface of the reflecting mirror 30 while being focused by the positive power of the concave mirror 20.

  Then, the light is reflected upward in the figure and directed to a screen which is a projection surface (not shown), and the projection image is enlarged and displayed as a projection image.

  That is, the projection light beam that is the projection light is sequentially guided to the screen side in this order by the lens system 10, the concave mirror 20, and the reflecting mirror 30.

  In the embodiment being described, the reflecting mirror 30 is a “plane mirror”, and the shape of the reflecting surface is “substantially plane”.

  Therefore, the projected image projected on the screen is imaged by “imaging action by the lens system 10 and the concave mirror 20”.

  As shown in the figure, the distance on the optical axis AX from the exit surface of the projection light beam on the most magnified side (right side in the figure) of the lens system 10 to the concave mirror 20 is L1.

  Further, the “size in the direction orthogonal to the optical axis AX” of the concave mirror 20 is L2 as shown in the figure. The length of the reflecting mirror 30 in the optical axis AX direction is L3.

  Consider three quantities with these length dimensions: L1, L2, L3.

  What determines the size of the projection optical system shown in FIG. 1 in the vertical direction (direction perpendicular to the optical axis AX) in the drawing is the size of the concave mirror 20: L2.

  Also, what determines the size of the projection optical system in the optical axis AX direction is the distance: L1.

  Considering making the projection optical system compact by reducing the size in both directions, it is conceivable to reduce both the distance L1 and the size L2.

  First, considering that the distance L1 is reduced, the concave mirror 20 approaches the lens system 10 in this case.

  In this situation, if the divergence angle: θ of the projection light beam emitted from the lens system 10 is not changed, the portion where the projection light beam enters the concave mirror 20 is also reduced.

  Accordingly, the size L2 of the mirror surface area of the concave mirror 20 can be reduced, and the projection optical system becomes compact.

  However, in that case, if the “wide angle property” required for the projection optical system is to be ensured, the “optical function for ensuring the wide angle property of the projection optical system” imposed on the concave mirror 20 becomes severe.

  For this reason, the mirror surface shape of the concave mirror 20 becomes complicated, and it is very difficult to realize this complicated mirror surface shape with a small mirror surface area.

  As a measure to avoid this, it is conceivable to increase the divergence angle: θ of the projection light beam emitted from the lens system 10 without reducing the size L2 of the concave mirror 20.

  However, if this is done, it is necessary to provide the lens system 10 with a “widening function”, and the lens diameter of the lens on the enlargement side of the lens system 10 tends to increase.

  By setting the distance: L1 “large to some extent”, an increase in the divergence angle: θ can be suppressed, and the complexity of the optical function imposed on the concave mirror 20 can also be suppressed.

  In addition, since the distance L1 is “somewhat large”, the arrangement of the reflecting mirror 30 is facilitated.

  By suppressing the increase in the divergence angle: θ, the design conditions of the lens system 10 are also relaxed.

  In the projection optical systems described in Patent Documents 1 to 4, the projection light beam reflected by the curved mirror is directed toward the screen as it is, and the distance between the curved mirror and the screen is large.

  In the projection optical system of the present invention, the projected light beam reflected by the concave mirror 20 goes to the screen via the reflecting mirror 30.

  For this reason, the distance between the concave mirror 20 and the screen can be “gained inside the projection optical system”, and “the installation distance from the screen” of the projection optical system can be reduced.

  In the example of FIG. 1, the reflecting mirror 30 is a plane mirror as described above, but is not limited thereto, and the mirror surface shape of the reflecting mirror 30 may be a “substantially planar curved surface”.

  In this way, although power is generated in the reflecting mirror 30 even though it is weak, this weak power can be used in an auxiliary or correction manner for the imaging function of the entire projection optical system.

  That is, it is possible to apply weak power to the reflecting mirror 30 to adjust the imaging magnification and correct various aberrations. If necessary, the surface shape of the reflecting mirror 30 may be an aspherical surface or a free curved surface.

  In the example shown in the figure, the reflecting mirror 30 is arranged with the reflecting surface "parallel to the optical axis AX of the lens system 10".

  The arrangement of the reflecting mirror 30 is not limited to such an arrangement state, but the “state substantially parallel or nearly parallel to the optical axis AX of the lens system 10” is preferable because the position adjustment is easy.

  In the example shown in the figure, it is assumed that the optical axes AX of the screen and the lens system 10 are parallel to each other, but the present invention is not limited to this.

  By adjusting the arrangement of the lens system 10, the concave mirror 20, and the reflecting mirror 30, the angle formed by the optical axis AX of the lens system 10 and the screen can be set as appropriate.

  However, it is preferable that the optical axis AX of the screen and the lens system 10 be parallel to each other because the projection optical system can be installed close to the screen.

  In the example shown in the drawing, the reflecting mirror 30 is disposed with its reflecting surface aligned with the optical axis AX of the lens system 10. Of course, the arrangement of the reflecting mirror 30 is not limited to this.

  When the reflecting surface is parallel to the optical axis AX, the reflecting mirror 30 can be arranged at a position shifted downward or upward from the position shown in the figure.

  When the reflecting mirror 30 is shifted upward from the position shown in FIG. 1, it is necessary to prevent the luminous flux FL <b> 2 from being vignetted by the reflecting mirror 30.

  When the reflecting mirror 30 is arranged at a position where the light beams FL1 and FL2 reflected by the concave mirror 20 intersect, the length L3 can be minimized.

  The reflector 30 can be shifted downward from the position shown in FIG. 1 to reduce the length L3. However, if the shift amount increases, the size of the projection optical system may increase in the vertical direction of the figure.

  Therefore, the arrangement position of the reflecting mirror 30 is preferably set by balancing the shortening of the length L3 and the increase in the size of the entire projection optical system.

  The arrangement position shown in the drawing in which the reflecting surface is made to coincide with the optical axis AX of the lens system 10 is preferable in that the accuracy of the assembly position can be easily obtained.

  In order to suppress the increase in the divergence angle: θ of the projection light beam emitted from the lens system 10, the embodiment of FIG.

  That is, the lens on the most magnifying side of the lens system 10 is a “positive meniscus lens with the concave surface facing the magnifying side”, and the divergence of the projected light beam emitted from the lens system 10 is suppressed.

  A positive meniscus lens having a concave surface directed toward the enlargement side has a function of refracting transmitted light toward the optical axis AX, and this function suppresses an increase in the divergence angle: θ.

"Example"
Two specific examples of the projection optical system described with reference to FIG. 1 will be given below.

  The lens system 10 is composed of a plurality of lenses.

Specifically, as shown in the drawing, the lens system 10 is composed of 12 lenses.
These twelve lenses are counted from the reduction side to form a first lens, a second lens,.

  The second lens (biconvex lens) and the third lens (biconcave lens) are cemented with each other, and the fourth lens and the fifth lens are also cemented with each other.

  An aperture stop is disposed between the fifth lens and the sixth lens.

Hereinafter, the radius of curvature of the i-th surface (including the surface of the aperture stop and the surface of the concave mirror 20) counted from the reduction side is Ri, and the surface interval on the optical axis between the i-th and i + 1-th surfaces is Di. And
Further, the refractive index and Abbe number of the material of the jth lens (j = 1 to 12) counted from the reduction side are Nj and νj, respectively.

  The twelve lenses constituting the lens system 10 include an aspheric lens, and the mirror surface shape of the concave mirror 20 is a “free-form surface”, but only “paraxial curvature radius” is shown below for simplicity.

  The focal length of the projection optical system is indicated by f (mm), the half angle of view is indicated by ω (degrees), and the F number is indicated by F.

"Example 1"
The configuration of the projection optical system of Example 1 is shown in FIG. The meanings of the reference numerals of the respective parts are the same as those shown in FIG.

f = 17.28, F = 2.27, ω = 67.8
The data of Example 1 is shown below.

i j Ri Di Nj νj
1 * 1 193.59 4.87 1.739 49.0
2 * -24.92 0.2
3 2 17.09 6.91 1.497 81.5
4 3-24.87 0.97 1.904 31.3
5 24.76 0.3
6 4 12.51 5.79 1.497 81.5
7 -33.64 0.2
8 5-80.25 5.47 1.847 23.8
9 6-13.23 2.97 1.881 40.1
10 39.92 2.42
11 ∞ 1.89
12 * 7-66.87 3.26 1.739 49.0
13 * -22.17 3.99
14 8 57.9 0.80 1.689 31.1
15 22.85 0.34
16 9 26.92 4.07 1.583 46.4
17-17.81 2.37
18 * 10 34.98 2.41 1.530 55.9
19 * 26.05 1.70
20 * 11 -33.93 2.20 1.530 55.7
21 * 12.93 1.54
22 12 26.74 3.03 1.487 70.2
23 279.94 70.39
24 † 72.15-577.17
25 ∞
"Aspherical data"
In the above data, the surface marked with “*” has an aspherical shape.

  The aspheric shape is assumed to be a well-known expression.

Z = (H ² / R) / [1 + √ {1- (1 + k) (H / R) ² }]
^{_{+ Σ (A 2m H 2m)}} (m = 2~9).

  In this equation, Z is an aspheric surface shape.

H is a distance from the optical axis, R is a paraxial radius of curvature, k is a conic constant, A _2m is a 2m-order aspherical coefficient, and the sum takes “from 1 to 9 for m”.

  Therefore, the aspherical shape is specified by giving the above K, A, and R (paraxial curvature radius of the i-th lens surface).

In the notation of the paraxial radius of curvature: R, conic constant: k, and aspherical coefficient: A _2m , Ri, ki, and Ai are used, where i is the number of the lens surface (the number of the surface marked with “*”).

  Aspherical data are shown below.

"First side"
k1 = 0
A1 ₄ = 1.021313 × 10 ⁻⁵
A1 ₆ = −1.777040 × 10 ⁻⁷
A1 ₈ = 1.346978 × 10 ⁻¹⁰
A1 ₁₀ = −7.970685 × 10 ⁻¹²
A1 ₁₂ = −1.883968 × 10 ⁻¹⁵
A1 ₁₄ = 2.566833 × 10 ⁻¹⁶
A1 ₁₆ = −5.376428 × 10 ⁻¹⁹
A1 ₁₈ = 0.

"Second side"
k2 = 0
A2 ₄ = 1.332956 × 10 ⁻⁵
A2 ₆ = −7.3345798 × 10 ⁻⁸
A2 ₈ = −7.054116 × 10 ⁻¹⁰
A2 ₁₀ = −1.2228184 × 10 ⁻¹²
A2 ₁₂ = −4.075513 × 10 ⁻¹⁶
A2 ₁₄ = 8.5570573 × 10 ⁻¹⁷
A2 ₁₆ = −2.288666 × 10 ⁻¹⁹
A2 ₁₈ = 0.

"Twelfth surface"
k12 = 0
A12 ₄ = −3.544941 × 10 ⁻⁴
A12 ₆ = −7.777781 × 10 ⁻⁶
A12 ₈ = 4.777114 × 10 ⁻⁸
A12 ₁₀ = −4.037179 × 10 ⁻⁸
A12 ₁₂ = 1.395533 × 10 ⁻⁹
A12 ₁₄ = −2.058120 × 10 ⁻¹¹
A12 ₁₆ = 0
A12 ₁₈ = 0.

"13th page"
k13 = 0
A13 ₄ = −2.309137 × 10 ⁻⁴
A13 ₆ = −4.312556 × 10 ⁻⁶
A13 ₈ = 1.665018 × 10 ⁻⁷
A13 ₁₀ = −8.77710 × 10 ⁻⁹
A13 ₁₂ = 1.997169 × 10 ⁻¹⁰
A13 ₁₄ = -1.922258 × 10 ⁻¹²
A13 ₁₆ = 0.

A13 ₁₈ = 0
"18th page"
k18 = 0
A18 ₄ = −6.224124 × 10 ⁻⁴
A18 ₆ = -1.8048483 × 10 ⁻⁶
A18 ₈ = 2.4786679 × 10 ⁻⁸
A18 ₁₀ = 8.231628 × 10 ⁻¹⁰
A18 ₁₂ = −4.414106 × 10 ⁻¹¹
A18 ₁₄ = 9.157316 × 10 ⁻¹³
A18 ₁₆ = −7.473187 × 10 ⁻¹⁵
A18 < ₁₈ > = 1.965664 * 10 < ^-17 >.

"19th page"
k19 = 0
A19 ₄ = −6.967451 × 10 ⁻⁴
A19 ₆ = 2.037914 × 10 ⁻⁶
A19 ₈ = -1.972424 × 10 ⁻⁸
A19 ₁₀ = 7.754886 × 10 ⁻¹⁰
A19 ₁₂ = −3.876020 × 10 ⁻¹²
A19 ₁₄ = −1.659231 × 10 ⁻¹³
A19 ₁₆ = 3.4377787 × 10 ⁻¹⁵
A19 ₁₈ = −1.892756 × 10 ⁻¹⁷ .

"20th page"
k20 = 0
A20 ₄ = 1.405532 × 10 ⁻⁴ ,
A20 ₆ = -1.970503 × 10 ⁻⁶
A20 ₈ = 5.243846 × 10 ⁻⁹
A20 ₁₀ = 1.288428 × 10 ⁻¹⁰
A20 ₁₂ = 1.653534 × 10 ⁻¹²
A20 ₁₄ = −2.701872 × 10 ⁻¹⁴
A20 ₁₆ = 1.166830 × 10 ⁻¹⁶
A20 < ₁₈ > = -4.427992 * 10 < ^-19 >.

"21st page"
k21 = 0
A21 ₄ = −6.208192 × 10 ⁻⁵
A21 ₆ = −1.222986 × 10 ⁻⁶
A21 ₈ = 6.125845 × 10 ⁻⁹
A21 ₁₀ = 6.132913 × 10 ⁻¹²
A21 ₁₂ = −3.774013 × 10 ⁻¹³
A21 ₁₄ = 2.414910 × 10 ⁻¹⁵
A21 ₁₆ = 4.361710 × 10 ⁻¹⁸
A21 < ₁₈ > = -9.100180 * 10 < ^-20 >.

"Free-form surface data"
The surface marked with “†” is a free-form surface, and the shape is expressed by the following equation.

Z = {(x ² + y ² ) / R} / [1 + √ {1- (1 + k) (x ² + y ² ) / R ² }]
+ Σ (A _{m, n} · x ^m · y ⁿ ) (m = 1 to 10, n = 1 to 10)
Z is a free-form surface, x, y coordinates from the origin, R represents the radius of curvature near the origin, k is a conic _{constant, A m, n} are the coefficients of ^(x m · ^{y n).}

Therefore, the shape is specified by giving these R, k, _{Am, and n} .

Since in Example 1 24th surface (i = 24) is a free-form _surface, k, _{A m,} a _n, k24, _{A24 m,} denoted as _n.

  The free surface shape data is shown below.

k24 = 0
A24 _1,0 = 0
A24 _0,1 = 0
A24 _2,0 = -1.8777791 × 10 ⁻²
A24 _1,1 = 0
A24 _0,2 = −1.580502 × 10 ⁻²
A24 _3,0 = 0
A24 _2,1 = 1.277255 × 10 ⁻⁴
A24 _{1, 2} = 0
A24 _0,3 = 7.653722 × 10 ⁻⁵
A24 _4,0 = -5.139766 × 10 ⁻⁷
A24 _3,1 = 0
A24 _2,2 = -3.921281 × 10 ⁻⁶
A24 _1,3 = 0
A24 _0,4 = −2.279286 × 10 ⁻⁶
A24 _5,0 = 0
A24 _4,1 = −1.775925 × 10 ⁻⁸
A24 _3,2 = 0
A24 _2,3 = 3.258345 × 10 ⁻⁸
A24 _1,4 = 0
A24 _0,5 = 4.019291 × 10 ⁻⁸
A24 _6,0 = −5.594684 × 10 ⁻¹⁰
A24 _5,1 = 0
A24 _4,2 = 9.074996 × 10 ⁻¹⁰
A24 _3,3 = 0
A24 _2,4 = 3.2231729 × 10 ⁻⁹
A24 _1,5 = 0
A24 _0,6 = −5.618965 × 10 ⁻¹⁰
A24 _7,0 = 0
A24 _6,1 = 1.626391 × 10 ^-11
A24 _5,2 = 0
A24 _4,3 = −2.586640 × 10 ⁻¹¹
A24 _3,4 = 0
A24 _2,5 = −1.697428 × 10 ⁻¹⁰
A24 _1,6 = 0
A24 _0,7 = −1.520897 × 10 ⁻¹¹
A24 _8,0 = 4.538138 × 10 ⁻¹³
A24 _7,1 = 0
A24 _6,2 = −7.849576 × 10 ⁻¹³
A24 _5,3 = 0
A24 _4,4 = −2.518447 × 10 ⁻¹²
A24 _3,5 = 0
A24 _2,6 = −6.333761 × 10 ⁻¹²
A24 _1,7 = 0
A24 _0,8 = 5.249754 × 10 ⁻¹²
A24 _9,0 = 0
A24 _8,1 = -3.913047 × 10 ⁻¹⁵
A24 _7,2 = 0
A24 _6,3 = 2.099527 × 10 ⁻¹⁴
A24 _5,4 = 0
A24 _4,5 = 2.177817 × 10 ⁻¹³
A24 _3,6 = 0
A24 _2,7 = 5.768204 × 10 ⁻¹³
A24 _1,8 = 0
A24 _0,9 = −3.354014 × 10 ⁻¹³
A24 _10,0 = -2.361854 × 10 ⁻¹⁶
A24 _9,1 = 0
A24 _8,2 = 1.523443 × ^{10 -16}
A24 _7,3 = 0
A24 _6,4 = −2.66661438087972 × 10 ⁻¹⁶
A24 _5,5 = 0
A24 _4,6 = -4.6774086 × 10 ⁻¹⁵
A24 _3,7 = 0
A24 _2,8 = −9.979307 × 10 ⁻¹⁵
A24 _1,9 = 0
A24 _0,10 = 6.238107 × 10 ⁻¹⁵ .

  A spot diagram of the projection optical system of Example 1 is shown in FIG. This figure shows a spot diagram of a portion on one side from the center of the enlarged image displayed on the screen.

  The top and bottom in the figure correspond to the top and bottom of the enlarged image, and the spot row at the right end is the spot row at the center in the left-right direction.

"Example 2"
The structure of the projection optical system of Example 2 is shown in FIG. The meanings of the reference numerals of the respective parts are the same as those shown in FIG.

f = 17.61, F = 2.27, ω = 69.5
The data of Example 2 is shown below.

i j Ri Di Nj νj
1 * 1 34.90 4.93 1.670 55.4
2 * -38.29 0.2
3 2 15.60 4.93 1.497 81.5
4 3 272.60 1.03 1.904 31.3
5 4 13.03 5.71 1.497 81.5
6-32.65 1.07
7 5 29.62 4.02 1.805 25.4
8 6 -14.55 2.71 1.834 37.2
9 11.31 4.27
10 ∞ 0.72
11 * 7 51.31 2.64 1.542 62.9
12 * -17.71 4.25
13 8 31.97 0.75 1.847 23.8
14 16.12 0.73
15 9 27.43 3.27 1.596 39.2
16-21.97 5.67
17 * 10 53.01 2.20 1.530 55.9
18 * 19.24 5.06
19 * 11 46.95 2.2 1.530 55.9
20 * 14.66 2.3
21 12 42.74 2.13 1.740 28.3
22 159.33 67.26
23 † 149.23 529.95
24 ∞.

"Aspherical data"
Aspherical data are shown below.

"First side"
k1 = −10.394056
A1 ₄ = 7.598164 × 10 ⁻⁶
A1 ₆ = −1.108165 × 10 ⁻⁷
A1 ₈ = 1.290063 × 10 ⁻¹⁰
A1 ₁₀ = −7.348591 × 10 ⁻¹³
A1 ₁₂ = 7.173937 × 10 ⁻¹⁵
A1 ₁₄ = 1.161755 × 10 ⁻¹⁶
A1 ₁₆ = −2.117537 × 10 ⁻¹⁹
A1 ₁₈ = 0.

"Second side"
k2 = 0.670158
A2 ₄ = 8.9337161 × 10 ⁻⁶
A2 ₆ = −1.093306 × 10 ⁻⁸
A2 ₈ = −4.010256 × 10 ⁻¹⁰
A2 ₁₀ = 5.637324 × 10 ⁻¹³
A2 ₁₂ = 2.957128 × 10 ⁻¹⁴
A2 ₁₄ = −1.461469 × 10 ⁻¹⁶
A2 ₁₆ = 5.821829 × 10 ⁻¹⁹
A2 ₁₈ = 0.

"Eleventh side"
k11 = -21.996036
A11 ₄ = −1.117763 × 10 ⁻⁴
A11 ₆ = −5.17338 × 10 ⁻⁶
A11 ₈ = 3.989827 × 10 ⁻⁷
A11 ₁₀ = −3.804510 × 10 ⁻⁸
A11 ₁₂ = 1.431401 × 10 ⁻⁹
A11 ₁₄ = −2.271013 × 10 ⁻¹¹
A11 ₁₆ = 0
A11 ₁₈ = 0.

"Twelfth surface"
k12 = 1.923841
A12 ₄ = −9.334418 × 10 ⁻⁵
A12 ₆ = −7.496360 × 10 ⁻⁶
A12 ₈ = 5.77144 × 10 ⁻⁷
A12 ₁₀ = −3.757877 × 10 ⁻⁸
A12 ₁₂ = 1.099761 × 10 ⁻⁹
A12 ₁₄ = −1.392181 × 10 ⁻¹¹
A12 ₁₆ = 0
A12 ₁₈ = 0.

“Seventeenth”
k17 = 6.4440728
A17 ₄ = −5.5116689139259 × 10 ⁻⁴
A17 ₆ = 5.008006 × 10 ⁻⁶
A17 ₈ = −7.883733408608656 × 10 ⁻⁸
A17 ₁₀ = 2.069271 × 10 ⁻⁹
A17 ₁₂ = −4.881745 × 10 ⁻¹¹
A17 ₁₄ = 6.952967 × 10 ⁻¹³
A17 ₁₆ = −5.685057 × 10 ⁻¹⁵
A17 < ₁₈ > = 1.9965633 * 10 < ^-17 >.

"18th page"
k18 = −0.091885
A18 ₄ = −6.493919164416247 × 10 ⁻⁴
A18 ₆ = 5.815737 × 10 ⁻⁶
A18 ₈ = −6.421628 × 10 ⁻⁸
A18 ₁₀ = 3.674345 × 10 ⁻¹⁰
A18 ₁₂ = 3.734873 × 10 ⁻¹²
A18 ₁₄ = −1.139610 × 10 ⁻¹³
A18 ₁₆ = 9.819580 × 10 ⁻¹⁶
A18 < ₁₈ > = -3.02211411631982 * 10 < ^-18 >.

"19th page"
k19 = 11.5503806
A19 ₄ = 1.129629 × 10 ⁻⁵
A19 ₆ = −1.609669 × 10 ⁻⁶
A19 ₈ = 1.537380 × 10 ⁻⁸
A19 ₁₀ = −5.652252 × 10 ⁻¹¹
A19 ₁₂ = -3.951371 × 10 ⁻¹³
A19 ₁₄ = 1.565348 × 10 ⁻¹⁵
A19 ₁₆ = 2.922001 × 10 ⁻¹⁷
A19 < ₁₈ > = -1.684395 * 10 < ^-19 >.

"20th page"
k20 = 0.316724
A20 ₄ = −7.599634 × 10 ⁻⁵
A20 ₆ = −7.889512 × 10 ⁻⁷
A20 ₈ = 5.882468 × 10 ⁻⁹
A20 ₁₀ = −1.475999 × 10 ⁻¹²
A20 ₁₂ = −3.019701 × 10 ⁻¹³
A20 ₁₄ = −1.820263 × 10 ⁻¹⁵
A20 ₁₆ = 3.912666 × 10 ⁻¹⁷
A20 < ₁₈ > = -1.498600 * 10 < ^-19 >.

"Free-form surface data"
In Example 2, since the surface No. 23 (i = 23) is a free-form surface, _{k, A m,} and _n, denoted as k23, _{A23 m, n.}

  The free surface shape data is shown below.

k23 = 0,
A23 _1,0 = 0
A23 _0,1 = 0
A23 _2,0 = −1.546445 × 10 ⁻²
A23 _1,1 = 0
A23 _0,2 = -1.187789 × 10 ⁻²
A23 _3,0 = 0
A23 _2,1 = 1.486013 × 10 ⁻⁴
A23 _{1, 2} = 0
A23 _0,3 = 8.229945 × 10 ⁻⁵
A23 _4,0 = −1.039594 × 10 ⁻⁷
A23 _3,1 = 0
A23 _2,2 = −3.531029 × 10 ⁻⁶
A23 _1,3 = 0
A23 _0,4 = −1.84545 × 10 ⁻⁶
A23 _5,0 = 0
A23 _4,1 = −2.768693 × 10 ⁻⁸
A23 _3,2 = 0
A23 _2,3 = 3.024866 × 10 ⁻⁸
A23 _1,4 = 0
A23 _0,5 = 1.997092 × 10 ⁻⁸
A23 _6,0 = −5.598675 × 10 ⁻¹⁰
A23 _5,1 = 0
A23 _4,2 = 5.669689 × 10 ⁻¹⁰
A23 _3,3 = 0
A23 _2,4 = 1.048641 × 10 ⁻⁹
A23 _1,5 = 0
A23 _0,6 = −4.389021 × 10 ⁻¹⁰
A23 _7,0 = 0
A23 _6,1 = 2.3488942 × 10 ⁻¹¹
A23 _5,2 = 0
A23 _4,3 = 1.645431 × 10 ⁻¹¹
A23 _3,4 == 0
A23 _2,5 = −3.415468 × 10 ⁻¹¹
A23 _1,6 = 0
A23 _0,7 = 3.993681 × 10 ⁻¹¹
A23 _8,0 = 3.970472 × 10 ⁻¹³
A23 _7,1 = 0
A23 _6,2 = 2.1839777787646 × 10 ⁻¹⁴
A23 _5,3 = 0
A23 _4,4 = -1.312998 × 10 ⁻¹²
A23 _3,5 = 0
A23 _2,6 = -2.159948 × 10 ⁻¹²
A23 _1,7 = 0
A23 _0,8 = 5.558045 × 10 ⁻¹³
A23 _9,0 = 0
A23 _8,1 = −6.309278 × 10 ⁻¹⁵
A23 _7,2 = 0
A23 _6,3 = −8.9965238 × 10 ⁻¹⁵
A23 _5,4 = 0
A23 _4,5 = 4.713489 × 10 ⁻¹⁵
A23 _3,6 = 0
A23 _2,7 = 1.609646 × 10 ⁻¹³
A23 _1,8 = 0
A23 _0,9 = −1.231889 × 10 ⁻¹³
A23 _10,0 = −1.488532 × 10 ⁻¹⁶
A23 _9,1 = 0
A23 _8,2 = -3.357219 × ^{10 -16}
A23 _7,3 = 0
A23 _6,4 = 3.364255 × 10 ⁻¹⁶
A23 _5,5 = 0
A23 _4,6 = 6.555401 × 10 ⁻¹⁶
A23 _3,7 = 0
A23 _2,8 = −3.051072 × 10 ⁻¹⁵
A23 _1,9 = 0
A23 _0,10 = 2.662806 × 10 ⁻¹⁵ .

  A spot diagram of the projection optical system of Example 2 is shown in FIG. This figure shows a spot diagram of a portion on one side from the center of the enlarged image displayed on the screen.

  The top and bottom in the figure correspond to the top and bottom of the enlarged image, and the spot row at the right end is the spot row at the center in the left-right direction.

  The distances shown in FIG. 1: L1, L2, L3 and the divergence angle of the projected light beam: θ are as follows with respect to Examples 1 and 2.

Example 1 L1 = 75 mm, L2 = 40 mm, L3 = 21 mm, θ = 21.3 degrees Example 2 L1 = 73 mm, L2 = 41 mm, L3 = 25 mm, θ = 23.3 degrees Further, the twelfth lens in the lens system The lens diameter is 23 mm in Example 1 and 25 mm in Example 2.

  In both the first and second embodiments, the reflecting mirror 30 is a “plane mirror”.

  The reflecting mirror 30 is disposed on the optical path between the concave mirror having the free curved surface shape (i = 24 surface in the first embodiment, i = 23 surface in the second embodiment) and the screen.

  The reflecting mirror 30 is disposed so as to face the screen with the reflecting surface matching the optical axis of the lens system.

  In this manner, the relationship among L1, L2, L3, and θ was well balanced, and a “projection optical system in which the increase in the diameter of the lens system and the increase in the area of the mirror surface of the concave mirror were effectively suppressed” was realized.

  The tenth lens which is the third lens from the magnification side in the lens system and the eleventh lens which is the second lens from the magnification side are lenses having a “coaxial aspheric surface”.

The eleventh lens is concave on the magnification side.
The surface on the reduction side of the tenth lens is “a convex surface near the optical axis and a concave surface in the periphery”.

  The twelfth lens arranged on the most enlargement side is a “positive meniscus lens having a concave surface directed toward the enlargement side”.

  By making the shapes of the tenth lens to the twelfth lens as described above, the divergence angle: θ is suppressed by the twelfth lens while improving the divergence of the projected light flux by the tenth lens and the eleventh lens.

  Further, the above-described shapes of the tenth and eleventh lenses contribute to “enhance distortion”.

  The free-form surface shape of the aspherical lens and concave mirror included in the lens system is optimized as shown in the above data.

  As shown in the spot diagrams shown in FIGS. 3 and 5, both Examples 1 and 2 achieve good performance.

10 Lens system 20 Concave mirror
30 Reflector

JP 2009-134254 A JP 2010-181672 A JP 2011-33737 A JP 2004-258620 A

Claims (5)

A projection optical system used in an image display device for projecting an image for projection displayed on an image display surface of an image display element onto a projection surface by oblique light and displaying the enlarged image,
A lens system, a concave mirror, and a reflecting mirror having a substantially planar reflecting surface;
The projection light from the image display surface is sequentially guided to the projection surface in the order of the lens system, the concave mirror, and the reflection mirror, and mainly on the projection surface by the imaging action of the lens system and the concave mirror. Image ,
Of the plurality of lenses constituting the lens system, the second and third lenses from the magnification side are lenses having a coaxial aspheric surface, and the magnification side surface of the second lens is a concave surface, and , reduction side surface of the third lens, the projection optical system near the optical axis to the peripheral portion by a convex surface and said concave der Rukoto. The projection optical system according to claim 1,
A projection optical system characterized in that a reflecting surface of a reflecting mirror having a substantially planar reflecting surface is a flat surface. The projection optical system according to claim 1 or 2,
A projection optical system, characterized in that the reflecting mirror is arranged with a reflecting surface parallel or nearly parallel to the optical axis of the lens system. In the projection optical system according to claim 1, 2 or 3,
A projection optical system, wherein an arrangement of the lens system, the concave mirror, and the reflecting mirror is determined so that a projection surface is substantially parallel to an optical axis of the lens system. In the projection optical system according to any one of claims 1 to 4,
Among the plurality of lenses constituting the lens system, the most magnified lens is a positive meniscus lens having a concave surface facing the magnified side, and suppresses the divergence of the projected light beam emitted from the lens system. Projection optical system.

Images