JP5229955B2 - Projection lens and projection display device using the same - Google Patents

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.

  In addition, 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, there is a demand for a significant cost reduction with a very simple configuration as well as a demand for the above-mentioned miniaturization, 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 magnifying side, a first lens having a positive refractive power, a second lens having a negative refracting power having a concave surface on the magnifying side, a third lens having a positive refracting power having a convex surface on the reducing side, and a positive lens It is composed of a fourth lens having refractive power,
The fourth 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 (3) are satisfied.
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
20 <S / OBJ <65 (3)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m)

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 magnifying side, a first lens having a positive refractive power, a second lens having a negative refracting power having a concave surface on the magnifying side, a third lens having a positive refracting power having a convex surface on the reducing side, and a positive lens It is composed of a fourth lens having refractive power,
The following conditional expressions (1), (2), (3) and (4) are satisfied.
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
20 <S / OBJ <65 (3)
TH <IH (4)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m)
IH: Maximum effective luminous flux height at the reduction side conjugate position TH: Maximum effective luminous flux height at the lens excluding the most reduction side lens

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 magnifying side, a first lens having a positive refractive power, a second lens having a negative refracting power having a concave surface on the magnifying side, a third lens having a positive refracting power having a convex surface on the reducing side, and a positive lens It is composed of a fourth lens having refractive power,
The fourth 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), (3 ′) and (5) are satisfied.
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
35 <S / OBJ <140 (3 ')
3.0 <S <10.0 (5)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m)

  The projection lenses are preferably telecentric on the reduction side.

  In addition, it is preferable that an opening that restricts the passage of a light beam is disposed between the first lens and the second lens.

  The fourth lens preferably has an aspherical surface.

Moreover, it is preferable that the following conditional expressions (6) and (7) are satisfied.
ν _d12 <45 (6)
40 <ν _d34 (7)
here,
ν _d12 : Abbe number of each of the first lens and the second lens ν _d34 : Abbe number of each of the third lens and the fourth lens

  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.

  According to the projection lens of the present invention, by satisfying conditional expression (1), it is possible to improve the illumination efficiency and increase the screen definition while suppressing the increase in size of the apparatus.

  Further, by satisfying conditional expression (2), the back focus on the reduction side is ensured, which facilitates separation of illumination light and projection light, synthesis of color light, and the like. 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 lens diameter on the reduction side is prevented from becoming too large by making the fourth lens arranged on the most reduction side into a non-circular shape and cutting a predetermined area other than the area necessary for light beam passage. Like to do.

  Further, the conditional expression (3) is satisfied according to the first and second projection lenses, and the conditional expression (3 ′) and the conditional expression (5) are simultaneously satisfied according to the third projection lens. By doing so, the projection screen size (maximum length) and the projection distance can be set to appropriate values, respectively.

  Further, according to the second projection lens, it is possible to prevent the brightness of the projection screen from becoming too dark at the time of short-distance projection, compared to the first projection lens. That is, by satisfying conditional expression (5), the size of the light valve is not too small, and the projection screen can be set to a size that is not too dark.

  Further, according to the second projection lens, by satisfying conditional expression (4), the lens shape of the lens excluding the fourth lens on the most reduction side can be a non-circular shape including the effective light beam passage region. At least, the cross section may be circular, and the cost can be improved.

  Further, the above conditional expressions are satisfied by the configuration of four lenses, so that the system can be made extremely simple and compact, 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. It is a figure showing the structure of the projection lens which concerns on Example 4 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; FIG. 9 is a diagram illustrating all aberrations of the projection lens according to Example 4; 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.

  Embodiments of the present invention will be described below with reference to the 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 has a positive refractive power in order from the enlargement side. L ₁ , a second lens L ₂ having a negative refractive power having a concave surface on the enlargement side, a third lens L ₃ having a positive refractive power having a convex surface on the reduction side, and a fourth lens L having a positive refractive power _4, the lens arranged on the most reduction side has a non-circular shape including an effective light beam passage region, and further satisfies the following conditional expressions (1), (2) and (3) To do.
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
20 <S / OBJ <65 (3)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m)

In addition to the configuration of the first projection lens, the second projection lens according to the present embodiment satisfies the following conditional expression (4). In the second projection lens, the lens arranged closest to the reduction side does not necessarily have to be a non-circular shape including the effective light beam passage region.
TH <IH (4)
here,
IH: Maximum effective luminous flux height at the reduction side conjugate position TH: Maximum effective luminous flux height at the lens excluding the most reduction side lens

The third projection lens according to the present embodiment satisfies the following conditional expression (3 ′) and conditional expression (5) instead of the configuration of conditional expression (3) of the first projection lens.
35 <S / OBJ <140 (3 ')
3.0 <S <10.0 (5)
here,
S: Maximum length of the enlarged image (inch)
OBJ: Expansion side projection distance (m)

  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, the light beam incident from the right side of the paper and provided with image information on the image display surface 1 of the light valve is covered with the glass block 2a, various filters such as a low-pass filter and an infrared cut filter, and the cover of the light valve. The light enters the projection lens through the glass 2b and is enlarged and projected in the left direction of the paper by the projection lens. Furthermore, in the lens system, it is possible to provide an aperture (in particular, one or a plurality of apertures between the first lens L ₁ and the second lens L _{2. Further} , the aperture on the most reduction side is a stop. Is possible). 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 2a. Is possible.

  In addition, when using one light valve, the glass block 2a etc. are omissible (refer Example 2 mentioned later).

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 fourth lens L ₄ arranged on the most reduction side is configured to have an aspheric surface.

  In the projection lens according to the present embodiment, the second lens and the third lens from the reduction side can be joined to each other to improve chromatic aberration, particularly lateral chromatic aberration.

Furthermore, in the projection lens of this embodiment, it is preferable that the following conditional expressions (6) and (7) are satisfied.
ν _d12 <45 (6)
40 <ν _d34 (7)
here,
ν _d12 : Abbe number of each of the first lens L ₁ and the second lens L ₂ ν _d34 : Abbe number of each of the third lens L ₃ and the fourth lens L ₄

In the projection lens according to the present embodiment, it is preferable that the following conditional expressions (8) and (9) are satisfied.
2ω> 60 degrees (8)
BH> FH (9)
here,
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 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.

  If the lower limit of conditional expression (2) is not reached, the reduction-side back focus is not ensured, and it becomes difficult to separate illumination light and projection light, and to combine color light.

  In addition, when trying to ensure the telecentricity on the reduction side, the lens diameter on the reduction side becomes too large as the back focus becomes longer. The non-circular shape is included, and unnecessary lens portions are not provided (so-called D-cut is applied) to prevent the lens diameter on the reduction side from becoming too large.

  Further, if it falls outside the range of the conditional expression (3), it becomes difficult to set the projection screen size and the projection distance to appropriate values. Furthermore, by replacing the conditional expression (3) with the configuration satisfying the conditional expression (3 ′) and the conditional expression (5), for example, an ultra-compact projection image apparatus that can be held by hand. It can be suitable when mounted.

  If the conditional expression (5) is not satisfied, it is difficult to obtain a light bulb size of an appropriate size. That is, it is difficult to make the size of the light valve not too small and the projection image not too dark.

Furthermore, by replacing the conditional expression (3) with a configuration that satisfies the following conditional expression (3 ″), it is possible to achieve better effects when the conditional expression (3) is satisfied. .
30 <S / OBJ <65... (3 ″)

  Further, if the conditional expression (4) is not satisfied, the back focus on the reduction side is not secured, and it becomes difficult to separate illumination light and projection light, combine color light, and the like.

  Further, by satisfying the conditional expressions (6) and (7), chromatic aberration such as lateral chromatic aberration can be made better.

  It should be noted that if it is below the lower limit of the conditional expression (8), it is difficult to make the image size sufficiently large when performing short-distance projection.

  Further, if the conditional expression (9) is not satisfied, it is difficult to suppress the diameter of the magnifying side lens from becoming too large with the widening of the angle.

  Next, an embodiment of a projection display device according to the present invention will be described. FIG. 9 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. 9, the illumination optical system 10 includes, as described above, transmissive liquid crystal panels 11a to 11c as light valves, dichroic mirrors 12 and 13 for color separation, and cross dichroic for color synthesis. 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 first and third projecting lens, the fourth lens L ₄ 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, this in addition to, or other lenses instead of this, the first lens L ₁ which is arranged, for example, the most magnification side, may have a non-circular shape including an effective light beam passage region.

  As the non-circular shape, the lens shape when viewed from the light beam traveling direction can be various shapes different from the circle, but 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.

As shown in FIG. 1, the projection lens according to Example 1 has a first lens L ₁ composed of a biconvex lens, an aperture 3 a and an aperture (or aperture) 3 b, and a concave surface directed toward the magnification side in order from the magnification side. negative and the second lens L ₂ formed of a meniscus lens, a third lens L _3, which is a positive meniscus lens having a convex surface on the reduction side, the fourth lens has been aspherical on the optical axis Z a biconvex lens L consisting of _4.

Further, the fourth lens L ₄ arranged on the most reduction side is formed into a non-circular shape including an effective light beam passage region, and an unnecessary lens portion (portion located above the drawing) L _4A is not provided (so-called D To prevent the lens diameter on the reduction side from becoming too large.

Aspherical shape of the both surfaces of the fourth lens L ₄ are defined by the aspheric expression below.

  The projection lens according to Example 1 is configured to satisfy the conditional expressions (1) to (4), (6), (7), (9), and (3 ″).

  FIG. 1 also shows an image display surface 1 of the light valve, a glass block 2a, various filters such as a low-pass filter and an infrared cut filter, and a cover glass 2b of the light valve.

The radius of curvature R of each lens surface of the projection lens according to Example 1, the center thickness of each lens, the air space between the lenses (hereinafter referred to as “axial surface space”) D, and the refractive index N _d of each lens at the d-line. The values of Abbe number ν _d are shown in the upper part of Table 1. In Table 1 and the following table, the surface number numbers indicate the order from the enlargement side, and the surface marked with * on the right side of the surface number is an aspheric surface. The lower part of Table 1 shows aspheric coefficients representing the respective aspheric surfaces.

  Further, in Example 1 and Examples 2 to 4 below, the curvature radius R of these aspheric surfaces is shown as the value of the curvature radius R on the optical axis Z in each table. In order to make the drawing easier to see, the leader line is not necessarily drawn from the intersection with the optical axis Z.

  As shown in Table 5, the projection lens of Example 1 satisfies the conditional expressions (1) to (4), (6), (7), (9), and (3 ″).

  In Example 1, the focal length f of the entire system is set to 10.6, the F number Fno. Is set to 3.01, and the total angle of view 2ω is set to 48.2 (degrees).

The configuration of the projection lens according to Example 2 is as shown in FIG. 2, and the lens configuration itself is substantially the same as that of Example 1. However, since the light valve is configured to correspond to those of a single plate, between the image display surface 1 of the fourth lens L ₄ and the light valve, for color synthesis as in Example 1 The glass block 2a is not arranged. In addition, various filters such as a low-pass filter and an infrared cut filter and a cover glass 2b of the light valve are also omitted.

The fourth lens L ₄ arranged on the most reduction side has a non-circular shape including an effective light beam passage region, and an unnecessary lens portion (portion positioned in the vertical direction in the drawing) L _4A is not provided (so-called (D cut) to prevent the lens diameter on the reduction side from becoming too large.

Moreover, the aspherical shape of the both surfaces of the fourth lens L ₄ are defined by the aspheric expression shown above.

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 5, the projection lens according to Example 2 is configured to satisfy the conditional expressions (1) to (9), (3 ′), and (3 ″).

  In Example 2, the focal length f of the entire system is set to 5.9, the F number Fno. Is 2.51, and the total angle of view 2ω is 61.8 (degrees).

  The configuration of the projection lens according to Example 3 is as shown in FIG. 3, and the lens configuration itself is substantially the same as that of Example 1.

  In addition, what is called D cut in the said Example 1 is not given.

Moreover, the aspherical shape of the both surfaces of the fourth lens L ₄ are defined by the aspheric expression shown above.

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 5, the projection lens according to Example 3 is configured to satisfy the conditional expressions (1) to (4), (6), (7), (9), and (3 ″). Has been.

  In Example 3, the focal length f of the entire system is set to 9.9, the F number Fno. Is set to 2.51, and the total angle of view 2ω is set to 45.4 (degrees).

The configuration of the projection lens according to Example 4 is as shown in FIG. 4, and the lens configuration itself is substantially the same as that of Example 1. However, the third lens L ₃ is a biconvex lens.

The fourth lens L ₄ arranged on the most reduction side has a non-circular shape including an effective light beam passage region, and an unnecessary lens portion (portion positioned in the vertical direction in the drawing) L _4A is not provided (so-called (D cut) to prevent the lens diameter on the reduction side from becoming too large.

Moreover, the aspherical shape of the both surfaces of the fourth lens L ₄ are defined by the aspheric expression shown above.

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 4 are shown in the upper part of Table 4. In addition, the lower part of Table 4 shows the aspheric coefficients representing the respective aspheric surfaces.

  As shown in Table 5, the projection lens according to Example 4 satisfies the above conditional expressions (1) to (3), (6), (7), (9), and (3 ″). It is configured as follows.

  In Example 4, the focal length f of the entire system is set to 9.9, the F number Fno. Is set to 2.51, and the total angle of view 2ω is set to 45.4 (degrees).

  5 to 8 are aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the projection lenses according to Examples 1 to 4. 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. 5 to 8, in the projection lenses according to Examples 1 to 4, 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.

DESCRIPTION OF SYMBOLS 1 Image display surface 2a Glass block 2b Various filters, such as a low-pass filter, and cover glass of a light valve 3a, 3b Aperture (stop)
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 ₄ lens R ₁ to R etc. ₁₄ lens surface curvature radius D ₁ to D ₁₃ lens spacing (lens thickness)
Z optical axis

Claims (10)

A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the magnifying side, a first lens having a positive refractive power, a second lens having a negative refracting power having a concave surface on the magnifying side, a third lens having a positive refracting power having a convex surface on the reducing side, and a positive lens It is composed of a fourth lens having refractive power,
The fourth 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 (3).
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
20 <S / OBJ <65 (3)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m) A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the magnifying side, a first lens having a positive refractive power, a second lens having a negative refracting power having a concave surface on the magnifying side, a third lens having a positive refracting power having a convex surface on the reducing side, and a positive lens It is composed of a fourth lens having refractive power,
A projection lens satisfying the following conditional expressions (1), (2), (3) and (4):
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
20 <S / OBJ <65 (3)
TH <IH (4)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m)
IH: Maximum effective luminous flux height at the reduction side conjugate position TH: Maximum effective luminous flux height at the lens excluding the most reduction side lens A projection lens for projecting image information displayed at a reduction-side conjugate position to an enlargement-side conjugate position,
In order from the magnifying side, a first lens having a positive refractive power, a second lens having a negative refracting power having a concave surface on the magnifying side, a third lens having a positive refracting power having a convex surface on the reducing side, and a positive lens It is composed of a fourth lens having refractive power,
The fourth 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), (3 ′) and (5).
2.5 <β / S <10.0 (1)
0.8 <Bf / f (2)
35 <S / OBJ <140 (3 ')
3.0 <S <10.0 (5)
here,
β: Magnification S: Maximum length of the enlarged image (inch)
Bf: Reduction side back focus f: Total system focal length OBJ: Enlargement side projection distance (m)   The projection lens according to claim 1, wherein the reduction side is telecentric.   The projection lens according to any one of claims 1 to 4, wherein an opening for restricting the passage of a light beam is disposed between the first lens and the second lens.   The projection lens according to claim 1, wherein the fourth lens has an aspherical surface. The projection lens according to claim 1, wherein the following conditional expressions (6) and (7) are satisfied.
ν _d12 <45 (6)
40 <ν _d34 (7)
here,
ν _d12 : Abbe number of each of the first lens and the second lens ν _d34 : Abbe number of each of the third lens and the fourth lens   The minimum portion 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 a light beam from the light source to the plurality of light valves, and a projection lens according to any one of claims 1 to 8, comprising: 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 a light beam from the light source to the light valve, and a projection lens according to any one of claims 1 to 8, 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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