JP2010197604A - Projection lens and projection type display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection lens which can be suitable for a projection type display device excellent in portability, has a wide angle so as to make the size of an image large even in close-distance projection and can provide an extremely simple inexpensive system, while having excellent projection performance and to provide the projection type display device using the projection lens. <P>SOLUTION: The projection lens includes, in order from an enlargement side, a negative lens L<SB>1</SB>having a concave surface on a reduction side, a negative lens L<SB>2</SB>having a concave surface on the reduction side, a positive lens L<SB>3</SB>having a convex surface on the reduction side, a negative lens L<SB>4</SB>, a positive lens L<SB>5</SB>having a convex surface on the reduction side, and a positive lens L<SB>6</SB>. The projection lens satisfies conditional expressions (1) to (4): 2.5<β/S<10.0 (1), 20<S/OBJ<140 (2), 60°<2ω (3), FH<BH (4), wherein β is an enlargement magnification, S is the maximum length (inch) of an enlargement-side image, OBJ is an enlargement-side projection distance (m), 2ω is an enlargement-side field angle, FH is the maximum effective luminous flux height in a lens surface on the most enlargement side, and BH is the maximum effective luminous flux height in a lens surface on the most reduction side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a projection lens for enlarging and projecting display information from a light valve such as a transmissive or reflective liquid crystal display element or DMD (digital micromirror device), and in particular, a so-called portable type having excellent portability. The present invention relates to a projection lens suitable for the projection display apparatus and a projection display apparatus using the same.

  Projection-type display devices using light valves such as liquid crystal display devices and DMD display devices are widely used. However, along with the popularization of personal computers, the light valves are rapidly becoming smaller and more precise. Since the demand for giving presentations using such a projection display device is also increasing, in recent years, a particularly small projection display device having excellent portability has been demanded. In the future, it may be possible to handle a projection display device as if it were a mobile phone or a flashlight. To that end, it is essential to further promote portability.

  As a measure that can meet the above requirements, it is particularly effective to reduce the thickness so as to be smaller in the direction perpendicular to the optical axis of the projection optical system, generally in the thickness direction of the apparatus housing. It is important to reduce the outer diameter of all the lenses.

  For the purpose of enhancing the portability of the apparatus, as a conventional technique for reducing the size of the projection lens, for example, the reduction side is made telecentric, as in the projection lenses described in Patent Documents 1 and 2, and color synthesis is performed. In addition, there is known a configuration in which a certain amount of space is secured in the lens back in order to separate illumination light and projection light.

Japanese Patent No. 3508011 JP-A-2005-84456

  However, those described in Patent Documents 1 and 2 are difficult to project so that the angle of view is as small as about 50 degrees and the image size is large at a short distance.

  Further, as described above, in Patent Documents 1 and 2, the reduction side is telecentric, and the lens back is secured to some extent. No measures for reducing the size of the lens are taken, and no positive measures for reducing the effective luminous flux are taken, including the reduction side lens and the enlargement side lens.

  In addition to the demand for downsizing, there is also a demand for a significant cost reduction with an extremely simple configuration, and those described in Patent Documents 1 and 2 do not necessarily meet such a demand. It is not.

  Further, in order to promote the portability, it is effective to reduce the size of the light valve, but no proposal is made from such a viewpoint.

  The present invention has been made in view of such circumstances, and can be adapted to a projection display device having excellent portability, and has a wide angle so as to increase the image size even in short-distance projection. An object of the present invention is to provide a projection lens that has a projection performance and can be a very simple and inexpensive system, and a projection display device using the projection lens.

The first projection lens according to the present invention is:
A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the enlargement side, the first lens having negative refractive power having a concave surface on the reduction side, the second lens having negative refractive power having a concave surface on the reduction side, and the first lens having positive refractive power having a convex surface on the reduction side. 3 lenses, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power whose convex side is a reduction side, and a sixth lens having a positive refractive power,
Furthermore, the following conditional expressions (1), (2), (3) and (4) are satisfied.
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
60 degrees <2ω ··· (3)
FH <BH (4)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
2ω: Magnification-side angle of view FH: Maximum effective luminous flux height on the most magnified lens surface BH: Maximum effective luminous flux height on the most demagnifying lens surface

The second projection lens according to the present invention is:
A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the enlargement side, the first lens having negative refractive power having a concave surface on the reduction side, the second lens having negative refractive power having a concave surface on the reduction side, and the first lens having positive refractive power having a convex surface on the reduction side. 3 lenses, a fourth lens having negative refracting power, a fifth lens having positive refracting power whose convex side is a reduction side, and a sixth lens having positive refracting power,
The sixth lens arranged on the most reduction side has a non-circular shape including an effective light beam passage region,
Furthermore, the following conditional expressions (1), (2) and (5) are satisfied.
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
0.8 <Bf / f (5)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
Bf: Back focus on the reduction side f: Total system focal length

The third projection lens according to the present invention is
A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the enlargement side, the first lens having negative refractive power having a concave surface on the reduction side, the second lens having negative refractive power having a concave surface on the reduction side, and the first lens having positive refractive power having a convex surface on the reduction side. 3 lenses, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power whose convex side is a reduction side, and a sixth lens having a positive refractive power,
Furthermore, the following conditional expressions (1), (2), (5) and (6) are satisfied.
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
0.8 <Bf / f (5)
TH <IH (6)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
Bf: Back focus on the reduction side f: Focal length of the entire system TH: Maximum effective light flux height in a lens except the most reduction side lens IH: Maximum effective light flux height at the reduction side conjugate position

In addition, it is preferable that any one of the projection lenses according to the present invention satisfies the following conditional expression (7).
3.0 <S <10.0 (7)
here,
S: Maximum length of the enlarged image (inch)

  The projection lenses are preferably telecentric on the reduction side.

  Further, it is preferable that an opening for restricting the passage of the light beam is provided between the third lens and the fourth lens.

  In addition, it is preferable that the second lens and / or the sixth lens have an aspherical surface.

  Further, it is preferable that the fourth lens and the fifth lens are cemented together to form a cemented lens.

Moreover, it is preferable that the following conditional expression (8) is satisfied.
35 <ν _d5 -ν _d4 (8)
here,
ν _d5 : Abbe number of the fifth lens at the d-line ν _d4 : Abbe number of the fourth lens at the d-line

  Further, it is preferable that the minimum portion of all the lens elements constituting the projection lens in the lens radial direction perpendicular to the optical axis is set to 15 mm or less.

  In addition, a first projection display device of the present invention includes a light source, a plurality of light valves, an illumination optical unit that guides a light beam from the light source to the plurality of light valves, and any one of the above projection lenses. The light beams from the light source are each light-modulated by the plurality of light valves, and the light-modulated lights are combined and projected onto the screen by the projection lens.

  In addition, a second projection display device of the present invention includes a light source, one light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and any one of the above projection lenses, The light beam from the light source is light-modulated by the light valve and then projected onto the screen by the projection lens.

The “aperture” described above only needs to have a function of restricting the passage of light flux, and includes a variable stop.
The “non-circular shape” means that the shape of each lens viewed from the light beam traveling direction is not circular.

  Furthermore, in the present specification, the terms “convex surface” or “concave surface” used to define the shape of the lens surface are used in the vicinity of the optical axis and the paraxial region of the lens surface when the lens surface is aspherical. It shall represent the shape of

  According to all the projection lenses according to the present invention, by satisfying conditional expression (1), it is possible to improve the illumination efficiency and increase the definition of the screen while suppressing an increase in the size of the apparatus. By satisfying Expression (2), the projection screen size (maximum length) and the projection distance can be set to appropriate values.

  Further, according to the first projection lens, when the conditional expression (3) is satisfied, the angle of view on the enlargement side is defined to be larger than 60 degrees, and the image size is increased even in short-distance projection. Configured as follows. Further, by satisfying conditional expression (4), the maximum effective light flux height on the most enlargement side lens surface is configured to be smaller than the maximum effective light flux height on the most reduction side lens surface. It is possible to prevent the diameter of the magnifying side lens from becoming too large with the increase in the size.

  Further, according to the second and third projection lenses, the reduction-side back focus is secured by satisfying the conditional expression (5), thereby separating the illumination light and the projection light, Color light synthesis and the like are facilitated. On the other hand, if the telecentricity on the reduction side is to be secured as the back focus becomes longer, the lens diameter on the reduction side becomes too large. Therefore, the sixth lens arranged closest to the reduction side has a non-circular shape and a predetermined region other than the region necessary for light beam passage is cut to prevent the lens diameter on the reduction side from becoming too large. Like to do.

  Further, according to the third projection lens, by satisfying the conditional expression (6), in the lens excluding the lens on the most reduction side, the lens shape does not have to be a non-circular shape including the effective light beam passage region. The cross section may be circular, which is advantageous in terms of cost.

  Further, the above conditional expressions are satisfied by the six-lens configuration, so that a simple and compact system can be obtained, and the cost can be greatly reduced.

  In addition, the projection display device of the present invention can be a simple and inexpensive projection display device that is excellent in portability by using the projection lens of the present invention. A wide angle is set so that the size is sufficiently large, and favorable projection performance can be obtained.

It is a figure showing the structure of the projection lens which concerns on Example 1 of this invention. It is a figure showing the structure of the projection lens which concerns on Example 2 of this invention. It is a figure showing the structure of the projection lens which concerns on Example 3 of this invention. FIG. 4 is a diagram illustrating various aberrations of the projection lens according to Example 1. FIG. 6 is a diagram illustrating various aberrations of the projection lens according to Example 2. FIG. 9 is a diagram illustrating all aberrations of the projection lens according to Example 3; It is a figure showing the schematic structure of the principal part of the projection type display apparatus of this invention. It is the schematic which shows the specific example of the non-circular shape of a lens when it sees from a light beam advancing direction.

  Hereinafter, embodiments of the present invention will be described with reference to the above-mentioned drawings. FIG. 1 shows a projection lens according to the present invention, and is a lens configuration diagram of Example 1 to be described later. In the figure, Z represents the optical axis.

The first projection lens according to the present embodiment is a projection lens that projects image information displayed at the reduction-side conjugate position to the enlargement-side conjugate position, and negative refraction with the reduction side made concave in order from the enlargement side. A first lens L ₁ having a power, a second lens L ₂ having a negative refractive power having a concave surface on the reduction side, a third lens L ₃ having a positive refractive power having a convex surface on the reduction side, and a negative refractive power the fourth lens L _4, it is configured by the sixth lens L ₆ having a fifth lens L _5, and positive refractive power having a positive refractive power reduction side is a convex surface, further, the following conditional expression with ( 1), (2), (3) and (4) are satisfied.
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
60 degrees <2ω ··· (3)
FH <BH (4)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
2ω: Magnification-side angle of view FH: Maximum effective luminous flux height on the most magnified lens surface BH: Maximum effective luminous flux height on the most demagnifying lens surface

Further, in the second projection lens according to the present embodiment, in addition to the configuration of the first projection lens, the sixth lens L ₆ arranged on the most reduction side has a non-circular shape including an effective light beam passage region. In addition, the following conditional expression (5) is satisfied instead of the conditional expressions (3) and (4) of the first projection lens.
0.8 <Bf / f (5)
here,
Bf: Back focus on the reduction side f: Total system focal length

The third projection lens according to the present embodiment satisfies the following conditional expressions (5) and (6) instead of the conditional expressions (3) and (4) of the first projection lens. .
0.8 <Bf / f (5)
TH <IH (6)
here,
Bf: Back focus on the reduction side f: Focal length of the entire system TH: Maximum effective light flux height in a lens except the most reduction side lens IH: Maximum effective light flux height at the reduction side conjugate position

Incidentally, in the first and third projection lenses, most reduction the disposed side sixth lens L ₆ is, may not be a non-circular shape necessarily including an effective light beam passage region.

  Further, in a projection lens that projects the image information displayed at the reduction-side conjugate position to the enlargement-side conjugate position, the length in the lens radial direction that is perpendicular to the optical axis of all lens elements constituting the projection lens Among these, it is preferable that the minimum portion is set to 15 mm or less in order to make the lens system compact.

  Here, the value of the “minimum portion of the length in the lens radial direction” is preferably set to “12 mm or less”, and more preferably “10 mm or less” instead of the “15 mm or less”.

  The “maximum length” means the longest distance in the enlarged image, and is generally a diagonal length.

In the projection lens of FIG. 1, a light beam incident from the right side of the paper and given image information on the image display surface 1 of the light valve is a glass block (various filters such as a low-pass filter and an infrared cut filter, and a cover glass of the light valve). 2), and is enlarged and projected in the left direction on the paper surface by the projection lens. Further, in the lens system, the aperture (in particular, can be provided between the third lens L ₃ and the fourth lens L ₄₎ 3 is disposed. Although only one image display surface 1 is shown in FIG. 1, in a projection display device, a light beam from a light source is separated into three primary color lights by a color separation optical system, and three light beams for each primary color light are used. It is possible to arrange a light valve so that a full color image can be displayed. Further, it is desirable that the reduction side is telecentric.

  Specifically, a color synthesizing means (glass block) such as a cross dichroic prism, a DMD prism for separating illumination light and projection light, an LCOS PBS, and the like are disposed at the position of the glass block 2. Is possible.

  In addition, when using one light valve, the glass block 2 etc. are omissible.

In addition, it is desirable that the projection lens of the present embodiment has at least one aspherical surface, so that the resolution can be improved while reducing the number of lenses. In particular, it is preferable that the sixth lens L ₆ which is disposed in the second lens L ₂ and / or the most reduction side are configured to have aspherical (in addition to this, other lens is to have a non-spherical surface Is possible).

In the projection lens of the present embodiment, the second and third lenses (fourth lens L ₄ and fifth lens L ₅ ) from the reduction side are joined to each other so that chromatic aberration, particularly lateral chromatic aberration, is good. Can be.

In the projection lens of this embodiment, it is preferable that the following conditional expression (7) is satisfied.
3.0 <S <10.0 (7)
here,
S: Maximum length of the enlarged image (inch)

Furthermore, in the projection lens according to the present embodiment, it is preferable that the following conditional expression (8) is satisfied.
35 <ν _d5 -ν _d4 (8)
here,
ν _d4 : Abbe number of the fourth lens L _{4 at} the d line ν _d5 : Abbe number of the fifth lens L _{5 at} the d line

The technical significance of each conditional expression will be described below.
That is, when it falls outside the range of the conditional expression (1), it is difficult to improve the illumination efficiency and increase the screen definition while suppressing the increase in size of the apparatus.

  Further, if it falls outside the range of the conditional expression (2), it becomes difficult to set the projection screen size and the projection distance to appropriate values.

Furthermore, by replacing the conditional expression (2) with the configuration satisfying the following conditional expression (2 ′), the operational effects when the conditional expression (2) is satisfied can be more satisfactorily achieved.
20 <S / OBJ <65 (2 ')

  It should be noted that if it is below the lower limit of the conditional expression (3), it is difficult to make the image size sufficiently large when performing short-distance projection.

  Further, if the conditional expression (4) is not satisfied, it is difficult to suppress the diameter of the magnifying side lens from becoming too large as the angle is increased.

  If the lower limit of conditional expression (5) is not reached, the reduction-side back focus is not secured, and it becomes difficult to separate illumination light and projection light, and to combine color light.

  On the other hand, if the telecentricity on the reduction side is to be ensured, the lens diameter on the reduction side becomes too large as the back focus becomes longer. The lens diameter on the reduction side can be prevented from becoming too large by providing a non-circular shape including the effective light beam passage region and not providing unnecessary lens portions (so-called D-cut).

  Further, if the above conditional expression (6) is not satisfied, the lens shape in the lens excluding the lens on the most reducing side may be a circular shape in cross section without being a non-circular shape including the effective light beam passage region. It is difficult to achieve the effect that it can be advantageous.

Further, by satisfying the conditional expression (7), and further satisfying the following conditional expression (2 ″) instead of the conditional expression (2), an ultra-compact projection image apparatus that can be held by hand. It is configured to be more suitable when mounted on.
35 <S / OBJ <140... (2 ″)

  That is, if it falls outside the range of the conditional expression (7), the projection screen size (maximum length) and the projection distance cannot be set to appropriate values, and if it falls outside the range of the conditional expression (2 ″), it is appropriate. It becomes difficult to obtain a large light valve size.

  Further, by satisfying the conditional expression (8), it is possible to improve chromatic aberration such as lateral chromatic aberration.

  Next, an embodiment of a projection display device according to the present invention will be described. FIG. 7 is a configuration diagram showing an example of a main part (illumination optical system 10) of the projection display apparatus according to an embodiment of the present invention.

  As shown in FIG. 7, the illumination optical system 10 includes the transmissive liquid crystal panels 11a to 11c as light valves, the dichroic mirrors 12 and 13 for color separation, and the cross dichroic for color composition as described above. A prism 14, condenser lenses 16a to 16c, and total reflection mirrors 18a to 18c are provided. Although the illustration of the front stage of the dichroic mirror 12 is omitted, the white light from the light source passes through the illumination optical unit and the liquid crystal panels 11a to 11c respectively correspond to the three color light beams (G light, B light, and R light). Then, the light is modulated and projected onto the screen by the projection lens.

  Since this projection display apparatus uses the projection lens according to the present invention, it is possible to obtain a high-resolution large screen in which various aberrations are favorably corrected with a compact size.

  In order to promote further compactness, the light valve is a single plate, for example, RGB color images are sequentially displayed on the light valve, and in synchronization with this, corresponding color light is emitted from a light source composed of RGB color LEDs. It is preferable to output. Thereby, the dichroic mirrors 12 and 13 for color separation, the cross dichroic prism 14 for color synthesis, the total reflection mirrors 18a to 18c, and the like described above can be omitted.

Further, in the second projection lens, the sixth lens L ₆ arranged closest to the reduction side, although a non-circular shape including an effective light beam passage region, as the projection lens of the present invention, in addition to , or instead of this, (in the following examples 1, in addition to the sixth lens L _6, the first lens L ₁ and the fifth lens L ₅₎ another lens as a non-circular shape including an effective light beam passage region Also good.

  As the non-circular shape, the lens shape when viewed from the light beam traveling direction can be various shapes different from the circle. For example, when viewed from the optical axis direction as shown in FIG. The shape of the lens is one obtained by cutting one arcuate region from a circle (A), one obtained by cutting two opposing arcuate regions from a circle (B), and one more arcuate region cut from the shape of (B) It can be a thing (C) or the like.

  Specific examples of the projection lens according to the present invention will be described below. In addition, in each Example, the same code | symbol is attached | subjected about the member which makes mutually the same effect.

Negative projection lens according to Example 1 is as shown in FIG. 1, toward the order from the magnification side, a first lens L ₁ composed of a negative meniscus lens having a convex surface facing the magnification side, a concave surface on the reduction side a second lens L ₂ formed of double-sided aspheric lens of the meniscus shape, a third lens L _3, which is a biconvex lens, an aperture 3 (or variable aperture), a negative meniscus lens having a concave surface facing the reduction side a fourth lens L ₄ and the cemented lens formed by cementing a fifth lens L ₅ which is a biconvex lens, made by arranging a sixth lens L ₆ comprising a positive bi-aspherical lens.

The sixth lens L ₆ arranged on the most reduction side, the first lens L ₁ arranged on the most enlargement side, and the fifth lens L ₅ have a non-circular shape including an effective light beam passage region, which is unnecessary. The lens portion (portion located in the upper or lower direction of the drawing) L _6A , L _1A , and L _5A is not provided (so-called D-cut is applied) to prevent the lens diameter on the reduction side from becoming too large. ing.

Both surfaces aspheric shape of the second lens L ₂ and the sixth lens L ₆ are defined by the aspheric equation shown below.

  FIG. 1 shows an image display surface 1 of a light valve and a glass block (including a filter unit such as a low-pass filter) 2.

The values of the curvature radius R of each lens surface, the axial top surface distance D, the refractive index N _d of each lens at the d-line and the Abbe number ν _d of the projection lens according to Example 1 are shown in the upper part of Table 1. In addition, the lower part of Table 1 shows the aspheric coefficients representing the respective aspheric surfaces.

As shown in Table 4, the projection lens according to Example 1 satisfies the conditional expressions (1) to (5), (8), (2 ′), and (2 ″).
In Example 1, the focal length f of the entire system is set to 6.4, the F number Fno. Is set to 3.00, and the total angle of view 2ω is set to 73.0 (degrees).

Structure of a projection lens according to Example 2 is as shown in FIG. 2, is substantially the same manner as in Example 1, is mainly, second lens L ₂ is a biconcave aspherical lens Point, the fourth lens L ₄ is a biconcave lens, and two apertures (or variable diaphragms) 3 a and 3 b are provided between the third lens L ₃ and the fourth lens L _4. Are different.

Both surfaces aspheric shape of the second lens L ₂ and the sixth lens L ₆ are defined by the aspheric equation shown above.
2 shows an image display surface 1 of a light valve and a glass block (including a filter unit such as a low-pass filter) 2.

Table 2 shows the values of the radius of curvature R of each lens surface, the axial top surface distance D, the refractive index N _d of each lens at the d-line, and the Abbe number ν _d of the projection lens according to Example 2. In addition, the lower part of Table 2 shows the aspheric coefficients representing the respective aspheric surfaces.

As shown in Table 4, the projection lens according to Example 2 satisfies the conditional expressions (1) to (6), (8), (2 ′), and (2 ″).
In Example 2, the focal length f of the entire system is set to 6.5, the F number Fno. Is set to 3.00, and the total angle of view 2ω is set to 71.8 (degrees).

The structure of a projection lens according to Example 3, is as shown in FIG. 3, is similar to the second embodiment, primarily, both surfaces of the negative meniscus second lens L ₂ is that a concave surface facing the reduction side non It is different in that it is a spherical lens.

Both surfaces aspheric shape of the second lens L ₂ and the sixth lens L ₆ are defined by the aspheric equation shown above.
3 shows a light valve image display surface 1 and a glass block (including a filter unit such as a low-pass filter) 2.

Table 3 shows values of the curvature radius R of each lens surface, the axial top surface distance D, the refractive index N _d of each lens at the d-line, and the Abbe number ν _d of the projection lens according to Example 3. In addition, the lower part of Table 3 shows the aspheric coefficients representing the respective aspheric surfaces.

As shown in Table 4, the projection lens according to Example 3 satisfies the conditional expressions (1) to (8), (2 ′), and (2 ″).
In Example 3, the focal length f of the entire system is set to 7.6, the F number Fno. Is set to 3.00, and the total angle of view 2ω is set to 63.6 (degrees).

  4 to 6 are aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the projection lenses according to Examples 1 to 3. FIG. In these aberration diagrams, ω represents a half angle of view, the aberration diagram of spherical aberration shows aberration curves of d-line, F-line, and C-line, and the aberration diagram of lateral chromatic aberration shows F-line (dotted line: Aberration curves of C-line (two-dot chain line: same below) are shown. As shown in FIGS. 4 to 6, in the projection lenses according to Examples 1 to 3, each aberration including distortion and lateral chromatic aberration is well corrected.

  The projection lens according to the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the curvature radius R and the lens interval (or lens thickness) D of each lens can be changed as appropriate. Is possible.

  Further, the projection display device of the present invention is not limited to the above-described configuration, and various device configurations including the projection lens of the present invention are possible. As the light valve, for example, a transmissive or reflective liquid crystal display element, or a micro mirror element in which a large number of micro mirrors capable of changing the inclination are formed on a substantially flat surface (for example, manufactured by Texas Instruments). Digital micromirror device) can be used. Also, as the illumination optical system, an appropriate configuration corresponding to the type of light valve can be adopted.

1 Image display surface 2 Glass block 3, 3a, 3b Aperture (aperture)
10 illumination optics 11a~11c transmissive liquid crystal panel 12, 13 dichroic mirror 14 cross dichroic prism 16a~16c condenser lens 18a~18c total reflection mirror L ₁ ~L ₆ lens R ₁ to R etc. ₁₆ lens surface curvature radius D ₁ to D ₁₅ lens spacing (lens thickness)
Z optical axis

Claims (13)

A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the enlargement side, the first lens having negative refractive power having a concave surface on the reduction side, the second lens having negative refractive power having a concave surface on the reduction side, and the first lens having positive refractive power having a convex surface on the reduction side. 3 lenses, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power whose convex side is a reduction side, and a sixth lens having a positive refractive power,
Furthermore, the projection lens characterized by satisfying the following conditional expressions (1), (2), (3) and (4).
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
60 degrees <2ω ··· (3)
FH <BH (4)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
2ω: Magnification-side angle of view FH: Maximum effective luminous flux height on the most magnified lens surface BH: Maximum effective luminous flux height on the most demagnifying lens surface A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the enlargement side, the first lens having negative refractive power having a concave surface on the reduction side, the second lens having negative refractive power having a concave surface on the reduction side, and the first lens having positive refractive power having a convex surface on the reduction side. 3 lenses, a fourth lens having negative refracting power, a fifth lens having positive refracting power whose convex side is a reduction side, and a sixth lens having positive refracting power,
The sixth lens arranged on the most reduction side has a non-circular shape including an effective light beam passage region,
Furthermore, the projection lens characterized by satisfying the following conditional expressions (1), (2) and (5).
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
0.8 <Bf / f (5)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
Bf: Back focus on the reduction side f: Total system focal length A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the enlargement side, the first lens having negative refractive power having a concave surface on the reduction side, the second lens having negative refractive power having a concave surface on the reduction side, and the first lens having positive refractive power having a convex surface on the reduction side. 3 lenses, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power whose convex side is a reduction side, and a sixth lens having a positive refractive power,
Furthermore, the projection lens characterized by satisfying the following conditional expressions (1), (2), (5) and (6).
2.5 <β / S <10.0 (1)
20 <S / OBJ <140 (2)
0.8 <Bf / f (5)
TH <IH (6)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)
Bf: Back focus on the reduction side f: Focal length of the entire system TH: Maximum effective light flux height in a lens except the most reduction side lens IH: Maximum effective light flux height at the reduction side conjugate position The projection lens according to claim 1, wherein the following conditional expression (7) is satisfied.
3.0 <S <10.0 (7)
here,
S: Maximum length of the enlarged image (inch)   5. The projection lens according to claim 1, wherein the reduction side is telecentric.   The projection lens according to claim 1, wherein an opening that restricts passage of a light beam is disposed between the third lens and the fourth lens.   The projection lens according to claim 1, wherein the second lens has an aspherical surface.   The projection lens according to claim 1, wherein the sixth lens has an aspherical surface.   The projection lens according to claim 1, wherein the fourth lens and the fifth lens are cemented together to form a cemented lens. The projection lens according to claim 1, wherein the following conditional expression (8) is satisfied.
35 <ν _d5 -ν _d4 (8)
here,
ν _d5 : Abbe number of the fifth lens at the d-line ν _d4 : Abbe number of the fourth lens at the d-line   The minimum part of the length in the lens radial direction perpendicular to the optical axis of all the lens elements constituting the projection lens is set to 15 mm or less. The projection lens according to any one of claims.   A light source, a plurality of light valves, an illumination optical unit that guides light beams from the light sources to the plurality of light valves, and a projection lens according to any one of claims 1 to 11, A projection-type display device, wherein a light beam is modulated by each of the plurality of light valves, and the light-modulated lights are combined and projected onto a screen by the projection lens.   A light source, one light valve, an illumination optical unit that guides the light beam from the light source to the light valve, and the projection lens according to claim 1, wherein the light beam from the light source is A projection display apparatus, wherein light is modulated by the light valve and then projected onto a screen by the projection lens.

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