JP2015172609A - Projection lens and projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection lens configured to have a wide angle of view and to be compact, satisfactorily correcting various aberrations and having high projection performance, and a projection type display device including the projection lens.SOLUTION: The projection lens includes, in order from the enlargement side: a first lens group G1 having negative refractive power; and a second lens group G2 having positive refractive power. The first lens group G1 includes three or more negative lenses. In the first lens group G1, an aspherical lens is arranged at the side closest to the enlargement side. In the first lens group G1, a meniscus lens whose reduction side surface is aspheric and whose concave surface is directed toward the reduction side in the vicinity of the optical axis is arranged at the side closest to the reduction side. A spherical lens which is arranged closest to the enlargement side in the whole system and has positive refractive power is the lens closest to the enlargement side in the second lens group G2. The projection lens satisfies a predetermined conditional expression.

Description

  The present invention relates to a projection lens and a projection display device, for example, a projection lens suitable for enlarging and projecting an original image formed by a light valve on a screen, and a projection display device equipped with the projection lens. is there.

  In recent years, with the spread of personal computers, projection display devices generally called projectors are becoming widespread, and the market is also expanding. In this type of projection display device, the projection light beam is light-modulated by a light valve such as a liquid crystal display element or DMD (Digital Micromirror Device: registered trademark) on the basis of the video signal, and is applied to the screen via a projection lens. Generally, an image is displayed.

  Examples of conventionally known projection lenses include those described in Patent Documents 1 to 3 below. Patent Documents 1 to 3 below describe a lens system in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are arranged in order from the magnification side.

Japanese Patent Application Laid-Open No. 2012-256022 JP 2013-88804 A US Pat. No. 7,924,508

  A projection lens applied to the projection display apparatus as described above is required to have a wider angle of view in order to enable projection of a large screen at a shorter projection distance in a narrow room. In addition to this requirement, a compact configuration is also required in recent years due to an increase in demand for mobile applications.

  However, the projection lenses disclosed in Patent Documents 1 to 3 all have an angle of view of about 110 ° to 115 °, and further widening is desired in order to meet recent demands. In addition, the projection lenses disclosed in Patent Documents 1 to 3 cannot sufficiently correct various aberrations, and further improvement in performance is desired.

  The present invention has been made in view of the above circumstances, and has a wide-angle but compact configuration, and various projections are well corrected to provide high projection performance, and a projection display including the projection lens. The object is to provide an apparatus.

The projection lens of the present invention includes, in order from the magnification side, substantially two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power. The group has three or more negative lenses, an aspherical lens is disposed on the most enlargement side of the first lens group, and a reduction side surface is an aspherical surface on the most reduction side of the first lens group. A spherical lens having a positive refractive power disposed on the most magnified side in the entire system is a lens on the most magnified side of the second lens group, and a second lens. When the sum of the center thicknesses of the lenses constituting the group is Σct2, and the distance on the optical axis from the most enlargement side surface to the most reduction side surface of the second lens group is TL2, the following conditional expression (1) Is satisfied.
0.75 <Σct2 / TL2 (1)
However,
Σct2: Sum of center thicknesses of the lenses constituting the second lens group TL2: Distance on the optical axis from the most enlargement side surface to the most reduction side surface of the second lens group

In the projection lens of the present invention, it is preferable to satisfy any one of the following conditional expressions (2) to (6), (1 ′) to (4 ′), and (6 ′), or any combination. .
0.85 <Σct2 / TL2 (1 ′)
−3.5 <f1 / f <−0.6 (2)
−2.5 <f1 / f <−0.9 (2 ′)
120 ° <2ω (3)
130 ° <2ω (3 ')
1.5 <f2 / f <9.0 (4)
2.5 <f2 / f <7.0 (4 ′)
2.5 <Bf / f (5)
−4.0 <(R1r + R2f) / (R1r−R2f) <0.0 (6)
−3.0 <(R1r + R2f) / (R1r−R2f) <0.0 (6 ′)
However,
f: focal length of the entire system f1: focal length of the first lens group f2: focal length of the second lens group 2ω: maximum full angle of view on the enlargement side when the projection distance is infinite Bf: reduction side as the back side The back focal length R1r of the entire system at the air-converted distance in this case: Paraxial radius of curvature of the lens surface on the most reduced side of the first lens group R2f: Radius of curvature of the lens surface on the most magnified side of the second lens group

  In the projection lens of the present invention, the first to third lenses from the magnification side of the second lens group are respectively a positive lens having a convex surface on the reduction side, a biconcave lens, and a positive lens having a convex surface on the magnification side. You may comprise so that it is. In that case, a three-piece cemented lens may be configured by the first to third lenses from the magnification side of the second lens group.

In the projection lens of the present invention, it is preferable that the most magnified lens of the first lens group is made of a plastic material and satisfies the following conditional expression (7).
4.0 <| fp / f | (7)
However,
fp: Focal length of the most magnified lens in the first lens group f: Focal length of the entire system

  The projection display apparatus of the present invention is the above-described invention as a light source, a light valve on which light from the light source is incident, and a projection lens for projecting an optical image by light modulated by the light valve onto a screen. Projection lens.

  The “enlarged side” means the projected side (screen side), and the screen side is also referred to as the enlarged side for the sake of convenience when performing reduced projection. On the other hand, the “reduction side” means the original image display area side (light valve side), and the light valve side is also referred to as the reduction side for the sake of convenience when performing reduced projection.

  The sign of the refractive power of the above-mentioned lens or lens group is considered in the paraxial region unless otherwise specified. A composite aspheric lens (a lens composed of a spherical lens and an aspherical film superimposed on the spherical lens) is not regarded as a cemented lens but is treated as a single lens. Note that the sign of the radius of curvature is positive when the shape is convex toward the object side, and negative when the shape is convex toward the image side.

  According to the present invention, in a two-group lens system in which a negative lens group and a positive lens group are arranged in order from the magnification side, the configuration of lenses included in each lens group is preferably set, and a predetermined conditional expression is set. Because it is configured so as to satisfy, a projection lens that has a wide angle and is small in size, has various projections corrected well, and has high projection performance, and a projection display device equipped with the projection lens are realized. can do.

It is sectional drawing which shows the lens structure and optical path of the projection lens of Example 1 of this invention. It is sectional drawing which shows the lens structure and optical path of the projection lens of Example 2 of this invention. It is sectional drawing which shows the lens structure and optical path of the projection lens of Example 3 of this invention. It is sectional drawing which shows the lens structure and optical path of the projection lens of Example 4 of this invention. FIG. 4 is a diagram illustrating various aberrations of the projection lens according to Example 1 of the present invention, and is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification in order from the left. FIG. 5 is a diagram illustrating various aberrations of the projection lens according to Example 2 of the present invention, and is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification in order from the left. FIG. 6 is a diagram illustrating various aberrations of the projection lens according to Example 3 of the present invention, and is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification in order from the left. FIG. 10 is a diagram illustrating various aberrations of the projection lens according to Example 4 of the present invention, and is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification in order from the left. 1 is a schematic configuration diagram of a projection display device according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 4 are sectional views showing the lens configuration of the projection lens according to the embodiment of the present invention and the optical paths of the axial light beam 4 and the light beam 5 having the maximum field angle, and Examples 1 to 4 described later are respectively shown. Compatible with any projection lens. The basic configuration of the example shown in FIGS. 1 to 4 is the same, and the illustration method of FIGS. 1 to 4 is also the same. Therefore, in the following, the embodiment of the present invention is mainly described with reference to FIG. The projection lens will be described.

  This projection lens is mounted on, for example, a projection display device, and can be used as a projection lens that projects image information displayed on a light valve onto a screen. In FIG. 1, assuming that the left side of the drawing is an enlargement side and the right side is a reduction side and is mounted on a projection display device, an optical member 2 in the form of a plane parallel plate assuming various filters, cover glasses, and the like, The image display surface 1 of the light valve located on the reduction side surface of the optical member 2 is also shown.

  In the projection display device, a light beam given image information on the image display surface 1 is incident on the projection lens via the optical member 2 and is arranged on the left side of the paper surface by the projection lens ( (Not shown).

  In the configuration shown in FIG. 1, an example is shown in which the position of the reduction-side surface of the optical member 2 and the position of the image display surface 1 coincide with each other, but the configuration is not necessarily limited thereto. Further, in FIG. 1, only one image display surface 1 is shown for simplification of the drawing, but in the projection display device, the light flux from the light source is separated into three primary colors by a color separation optical system, Three light valves may be provided for primary colors so that a full color image can be displayed.

  The projection lens in the example shown in FIG. 1 includes, in order from the enlargement side, substantially two lens groups, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. Become. This retrofocus lens system is advantageous for widening the angle.

  For example, in the example illustrated in FIG. 1, the first lens group G1 includes four lenses L11 to L14 in order from the magnification side, and the second lens group G2 includes lenses L21 to L30 in order from the magnification side. It consists of 10 lenses. As shown in FIGS. 1 to 4, in the projection lens of the present invention, for example, the first lens group G1 is composed of 3 to 5 lenses, and the second lens group G2 is composed of 10 lenses. However, it is also possible to configure with a different number of lenses from the examples shown in FIGS.

  In the projection lens according to the present embodiment, the first lens group G1 is configured to have three or more negative lenses. Thereby, the negative refractive power required for the first lens group G1 can be shared by these negative lenses, and the amount of aberration generated can be suppressed.

  In the projection lens according to the present embodiment, the aspherical lens is arranged on the most enlargement side of the first lens group G1, and the reduction side surface is aspherical on the most reduction side of the first lens group G1. A meniscus lens having a concave surface facing the reduction side in the paraxial region is arranged. By using an aspherical lens as the most magnified lens where the height of off-axis light becomes high, it is possible to effectively correct distortion that is a problem when widening the angle. At the same time, the lens surface on the most reduction side of the first lens group G1 is aspherical and has a meniscus shape with the concave surface on the reduction side, so that distortion can be more effectively corrected and the image surface can be corrected. Curvature can also be corrected appropriately.

  In the projection lens according to the present embodiment, the spherical lens having the positive refractive power disposed on the most magnification side in the entire system is the most magnification side lens of the second lens group G2. By placing the positive lens on the most magnifying side of the second lens group G2, when the light beam traveling from the magnifying side to the reducing side is seen, the light enters the second lens group G2 from the first lens group G1, which is a negative lens group. The luminous flux to be converged can be suitably converged and guided to the subsequent lens of the second lens group G2. Further, in the second lens group G2, the lens on the most enlargement side of the second lens group G2 whose lens diameter tends to be large can be a spherical lens, so that the cost can be reduced.

  The first to third lenses from the magnification side of the second lens group G2 are preferably a positive lens having a convex surface facing the reduction side, a biconcave lens, and a positive lens having a convex surface facing the magnification side. By arranging such three lenses on the most magnified side of the second lens group G2, it is possible to satisfactorily correct lateral chromatic aberration.

  When the first to third lenses from the magnification side of the second lens group G2 are a positive lens having a convex surface facing the reduction side, a biconcave lens, and a positive lens having a convex surface facing the magnification side, these three lenses Are preferably joined to form a three-piece cemented lens. By constructing a three-piece cemented lens, the lateral chromatic aberration can be corrected more satisfactorily. In addition, the tolerance for assembly error of a single lens is reduced with widening the angle, but by using a cemented lens, the tolerance for assembly error can be increased compared to the case where a cemented lens is not used, and productivity is increased. It can be improved.

In addition, the projection lens according to the present embodiment is configured to satisfy the following conditional expression (1).
0.75 <Σct2 / TL2 (1)
However,
Σct2: Sum of center thicknesses of the lenses constituting the second lens group TL2: Distance on the optical axis from the most enlargement side surface to the most reduction side surface of the second lens group

In a lens system designed to widen the angle, the lens diameter of the first lens group G1, which is the lens group on the enlargement side, tends to increase, but it is configured so that it does not fall below the lower limit of conditional expression (1). The increase in the lens diameter of the first lens group G1 can be suppressed, and it is possible to achieve both a wide angle and a reduction in size. In order to enhance the effect related to conditional expression (1), it is preferable to satisfy the following conditional expression (1 ′).
0.85 <Σct2 / TL2 (1 ′)

Furthermore, it is preferable that the projection lens according to the present embodiment satisfies any one of the following conditional expressions (2) to (6), or any combination.
−3.5 <f1 / f <−0.6 (2)
120 ° <2ω (3)
1.5 <f2 / f <9.0 (4)
2.5 <Bf / f (5)
−4.0 <(R1r + R2f) / (R1r−R2f) <0.0 (6)
However,
f: focal length of the entire system f1: focal length of the first lens group f2: focal length of the second lens group 2ω: maximum full angle of view on the enlargement side when the projection distance is infinite Bf: reduction side as the back side The back focal length R1r of the entire system at the air-converted distance in this case: Paraxial radius of curvature of the lens surface on the most reduced side of the first lens group R2f: Radius of curvature of the lens surface on the most magnified side of the second lens group

Conditional expression (2) is a conditional expression for correcting various aberrations necessary for widening the angle. By configuring so as not to be less than or equal to the lower limit of conditional expression (2), it is possible to avoid the power of the first lens group G1 from becoming too weak, and it becomes easy to satisfactorily correct lateral chromatic aberration. By configuring so that the upper limit of conditional expression (2) is not exceeded, it is possible to avoid the power of the first lens group G1 from becoming too strong, and it is possible to satisfactorily correct various aberrations such as spherical aberration and astigmatism. It becomes easy. In order to enhance the effect related to conditional expression (2), it is more preferable to satisfy the following conditional expression (2 ′).
−2.5 <f1 / f <−0.9 (2 ′)

By configuring so as not to be less than or equal to the lower limit of conditional expression (3), it is possible to meet the demand for wide angle. In order to enhance the effect related to conditional expression (3), it is more preferable to satisfy the following conditional expression (3 ′).
130 ° <2ω (3 ')

By configuring so as not to be less than or equal to the lower limit of conditional expression (4), it is possible to avoid the power of the second lens group G2 from becoming too strong, and it is possible to ensure an appropriate length of back focus. By configuring so that the upper limit of conditional expression (4) is not exceeded, it is possible to avoid the power of the second lens group G2 from becoming too weak and easily correct various aberrations such as spherical aberration and coma. In addition, the overall length of the lens system can be suppressed. In order to enhance the above effect related to conditional expression (4), it is more preferable to satisfy the following conditional expression (4 ′).
2.5 <f2 / f <7.0 (4 ′)

  By configuring so that it does not fall below the lower limit of conditional expression (5), a long back focus can be secured, and in the projection display apparatus, the projection lens and the illumination optical system are arranged to provide a suitable apparatus configuration. Easy to do. More specifically, in the projection display apparatus described later as shown in FIG. 9, the illumination optical system and the projection lens interfere with each other, or the illumination is not performed below the lower limit of the conditional expression (5). Problems such as the projection lens shielding the illumination light from the optical system and unnecessary reflected light from the DMD pixel being switched off can be avoided.

By satisfying conditional expression (6), the air lens formed by the most demagnifying side lens surface of the first lens group G1 and the most enlarging side lens surface of the second lens group G2 can have a suitable shape. It is possible to suppress the enlargement of the entire lens system and to easily correct the curvature of field. In order to enhance the above effect related to conditional expression (6), it is more preferable to satisfy the following conditional expression (6 ′).
−3.0 <(R1r + R2f) / (R1r−R2f) <0.0 (6 ′)

In the projection lens according to the present embodiment, it is preferable that the most enlarged lens in the first lens group G1 is made of a plastic material and satisfies the following conditional expression (7).
4.0 <| fp / f | (7)
However,
fp: Focal length of the most magnified lens in the first lens group f: Focal length of the entire system

  Since the lens on the most enlarged side of the wide-angle projection lens has a large diameter, it is preferable to use a plastic material to reduce cost and weight. However, the plastic lens changes its focus position when the temperature changes. It tends to be larger than glass lenses. Therefore, by configuring so as not to be less than or equal to the lower limit of conditional expression (7), it is possible to suppress the refractive power of the most aspherical plastic aspherical lens in the first lens group G1, and to reduce the focal length when the temperature changes. Change can be suppressed.

  In the projection lens according to the present embodiment, it is preferable that the F number is smaller than 3.0. In the projection lens according to the present embodiment, it is preferable that the distortion is in the range of -2% to + 2%.

  The projection lens according to the present embodiment may be configured to perform focusing by moving only a part of the entire system in the optical axis direction. For example, in the example shown in FIG. 1, focusing is performed by moving only one lens L24, which is the fourth lens from the magnification side of the second lens group G2, in the optical axis direction.

  It should be noted that the preferred configurations and possible configurations described above are preferably selectively employed as appropriate in accordance with the matters desired for the projection lens.

  According to the projection lens according to the embodiment of the present invention described above, various aberrations such as distortion, curvature of field, etc., which can be configured in a small size and are likely to cause problems when widening the angle, although being a wide-angle lens system. Can be corrected well, and a lens system having high optical performance can be realized. This embodiment can be suitably applied to, for example, a projection lens having a maximum full field angle of 130 ° or more when the projection distance is infinity.

  Next, a projection display apparatus according to an embodiment of the present invention will be described with reference to FIG. A projection display device 100 shown in FIG. 9 includes a light source 101, an illumination optical system 102, a DMD 103 as a light valve, and a projection lens 104 according to an embodiment of the present invention. A light beam emitted from the light source 104 is selectively converted in time series into light of three primary colors (R, G, B) by a color wheel (not shown), and is perpendicular to the optical axis Z1 of the light beam by the illumination optical system 102. After uniforming the light amount distribution in a simple cross section, the light enters the DMD 103. In the DMD 103, modulation switching to the color light is performed according to the color switching of the incident light. The light modulated by the DMD 103 enters the projection lens 104. The projection lens 104 projects an optical image of the light-modulated light on the screen 105.

  The projection display device of the present invention is not limited to the above-described configuration. For example, the light valve used and the optical member used for light beam separation or light beam synthesis are not limited to the above-described configuration, and various types are available. It is possible to change the mode. For example, in the projection display device of the present invention, other light modulation means such as a reflective liquid crystal display element and a transmissive liquid crystal display element can be used as the light valve.

  Next, specific examples of the projection lens of the present invention will be described. Note that all of the examples described below are in a standardized state in which the focal length of the entire system is 1.00 when the projection distance is infinity.

<Example 1>
The lens configuration diagram of the projection lens of Example 1 is shown in FIG. The projection lens of Example 1 includes, in order from the magnification side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first lens group G1 includes four lenses L11 to L14 arranged in order from the magnification side. The lenses L11 to L13 have a negative meniscus shape in the paraxial region, and the lens L14 has a positive meniscus shape in the paraxial region. The second lens group G2 is formed by arranging ten lenses L21 to L30 in order from the magnification side. Focusing is possible by moving only the lens L24 in the optical axis direction.

  Table 1 shows basic lens data of Example 1 when the projection distance is infinite, and Table 2 shows aspherical coefficients. In each table shown below, a numerical value rounded by a predetermined digit is shown. In the upper part outside the frame in Table 1, the specifications regarding the d-line are shown. In the specifications of Table 1, f is the focal length of the entire system, Bf is the back focus of the entire system at the air conversion distance when the reduction side is the back side, FNo. Is the F number, and 2ω is the maximum full angle of view (in degrees) on the enlargement side.

  In the column of Si in Table 1, the i-th (i = i = n) when the surface of the component is numbered so as to increase sequentially toward the reduction side with the enlargement-side surface of the most enlargement-side component being first. 1, 2, 3,...), The Ri column indicates the radius of curvature of the i-th surface, and the Di column indicates the optical axis Z between the i-th surface and the i + 1-th surface. The distance between the surfaces is shown, and the N-jj (j = 1, 2, 3,...) Component d-line (wavelength 587) increases sequentially toward the reduction side with the most magnified component as the first in the Ndj column. .6 nm), and the column νdj indicates the Abbe number of the j-th component relating to the d-line. However, the sign of the radius of curvature is positive when the surface shape is convex on the enlargement side, and negative when the surface shape is convex on the reduction side. The basic lens data includes the optical member 2.

In Table 1, the surface numbers of the aspheric surfaces are marked with *, and the paraxial curvature radius values are entered in the column of curvature radius of these aspheric surfaces. Table 2 shows the aspheric coefficient of each aspheric surface. The numerical value “E−n” (n: integer) of the aspheric coefficient in Table 2 means “× 10 ⁻ⁿ ”. The aspheric coefficient is a value of each coefficient KA, Am (m is an integer of 3 or more, and a value taken by a surface is different) in the aspheric expression represented by the following expression. In the following formula, Σ is the sum of m.
However,
Zd: Depth of aspheric surface (length of a perpendicular line dropped from a point on the aspherical surface of height h to a plane perpendicular to the optical axis where the aspherical vertex is in contact)
h: Height (distance from the optical axis to the lens surface)
C: Paraxial curvature KA, Am: Aspheric coefficient

  FIG. 5 shows, in order from the left, each aberration diagram of the spherical aberration, astigmatism, distortion (distortion), and chromatic aberration of magnification (chromatic aberration of magnification) of the projection lens of Example 1 when the projection distance is 141.1. . In FIG. 5, in the spherical aberration diagram, aberrations relating to the d-line (wavelength 587.6 nm), the C-line (wavelength 656.3 nm), and the F-line (wavelength 486.1 nm) are indicated by a solid line, a long broken line, and a short broken line, respectively. In the point aberration diagram, the sagittal and tangential d-line aberrations are indicated by solid lines and short broken lines, respectively, in the distortion diagram, the d-line aberration is indicated by solid lines, and in the lateral chromatic aberration diagram, the C-line and F-line aberrations are illustrated. Aberrations are indicated by a long broken line and a short broken line, respectively. FNo. Means F number, and ω in other aberration diagrams means half value (half field angle) of the maximum full field angle on the enlargement side when the projection distance is infinite.

  Since the symbols, meanings, and description methods of various data described in the description of the first embodiment are the same for the following embodiments unless otherwise specified, the duplicate description is omitted below.

<Example 2>
A lens configuration diagram of the projection lens of Example 2 is shown in FIG. The projection lens of Example 2 includes, in order from the magnification side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first lens group G1 includes three lenses L11 to L13 arranged in order from the magnification side. The lenses L11 to L13 have a negative meniscus shape in the paraxial region. The lens L13 is a compound aspheric lens. The second lens group G2 is formed by arranging ten lenses L21 to L30 in order from the magnification side. Focusing is possible by moving only the lens L24 in the optical axis direction.

  Table 3 shows basic lens data of the projection lens of Example 2 when the projection distance is infinity, and Table 4 shows aspheric coefficients. FIG. 6 shows, in order from the left, each aberration diagram of the spherical aberration, astigmatism, distortion (distortion), and lateral chromatic aberration (chromatic aberration of magnification) of the projection lens of Example 2 when the projection distance is 141.2. .

<Example 3>
The lens configuration diagram of the projection lens of Example 3 is as shown in FIG. The projection lens of Example 3 includes, in order from the enlargement side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first lens group G1 includes five lenses L11 to L15 arranged in order from the magnification side. The lenses L11 to L14 have a negative meniscus shape in the paraxial region, and the lens L15 has a positive meniscus shape in the paraxial region. The second lens group G2 is formed by arranging ten lenses L21 to L30 in order from the magnification side. Focusing is possible by moving only the lens L24 in the optical axis direction.

  Table 5 shows basic lens data of the projection lens of Example 3 when the projection distance is infinity, and Table 6 shows aspheric coefficients. FIG. 7 shows, in order from the left, each aberration diagram of the spherical aberration, astigmatism, distortion (distortion), and lateral chromatic aberration (chromatic aberration of magnification) of the projection lens of Example 3 when the projection distance is 147.2. .

<Example 4>
The lens configuration diagram of the projection lens of Example 4 is as shown in FIG. The projection lens of Example 4 includes, in order from the magnification side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first lens group G1 includes five lenses L11 to L15 arranged in order from the magnification side. The lenses L11 to L15 have a negative meniscus shape in the paraxial region. The second lens group G2 is formed by arranging ten lenses L21 to L30 in order from the magnification side. Focusing is possible by moving only the lens L24 in the optical axis direction.

  Table 7 shows basic lens data of the projection lens of Example 4 when the projection distance is infinite, and Table 8 shows aspheric coefficients. FIG. 8 shows, in order from the left, each aberration diagram of the spherical aberration, astigmatism, distortion (distortion), and chromatic aberration of magnification (chromatic aberration of magnification) of the projection lens of Example 4 when the projection distance is 146.3. .

  Table 9 shows the corresponding values of the conditional expressions (1) to (7) of Examples 1 to 4 and the values related to the conditional expressions. The values shown in Table 9 are for the d line when the projection distance is infinite.

  As can be seen from the above data, the projection lenses of Examples 1 to 4 have a total angle of view in the range of 130 ° to 140 °, a wide angle is achieved, a compact configuration, and a back focus ratio (Bf / fw). ) Is in the range of 3.3 to 4.2, has a long back focus, and various aberrations are well corrected to achieve high optical performance.

  The present invention has been described with reference to the embodiments and examples. However, the projection lens of the present invention is not limited to the above examples, and various modifications can be made. It is possible to appropriately change the curvature radius, the surface interval, the refractive index, and the Abbe number.

DESCRIPTION OF SYMBOLS 1 Image display surface 2 Optical member 4 Axial light beam 5 Light beam of the maximum field angle 100 Projection type display apparatus 101 Light source 102 Illumination optical system 103 DMD
104 Projection lens 105 Screen G1 First lens group G2 Second lens group L11-L15, L21-L30 Lens Z, Z1 Optical axis

Claims (15)

In order from the magnifying side, the first lens group having a negative refractive power and a second lens group having a positive refractive power are substantially composed of two lens groups,
The first lens group has three or more negative lenses,
An aspherical lens is disposed on the most magnifying side of the first lens group, and a meniscus-shaped lens having an aspherical surface on the reduction side and a concave surface on the reduction side on the most reduction side of the first lens group. Arranged,
A spherical lens having positive refractive power arranged on the most magnification side in the entire system is the most magnification side lens of the second lens group,
When the sum of the center thicknesses of the respective lenses constituting the second lens group is Σct2, and the distance on the optical axis from the most enlargement side surface to the most reduction side surface of the second lens group is TL2, A projection lens satisfying conditional expression (1).
0.75 <Σct2 / TL2 (1) The projection lens according to claim 1, wherein the following conditional expression (1 ′) is satisfied.
0.85 <Σct2 / TL2 (1 ′) The projection lens according to claim 1 or 2, wherein the following conditional expression (2) is satisfied, where f1 is a focal length of the first lens group and f is a focal length of the entire system.
−3.5 <f1 / f <−0.6 (2) The projection lens according to claim 3, wherein the following conditional expression (2 ′) is satisfied.
−2.5 <f1 / f <−0.9 (2 ′) 5. The projection lens according to claim 1, wherein the following conditional expression (3) is satisfied when the maximum total angle of view on the magnification side when the projection distance is infinity is 2ω.
120 ° <2ω (3) The projection lens according to claim 5, wherein the following conditional expression (3 ′) is satisfied.
130 ° <2ω (3 ') The projection lens according to claim 1, wherein the following conditional expression (4) is satisfied, where f2 is a focal length of the second lens group and f is a focal length of the entire system.
1.5 <f2 / f <9.0 (4) The projection lens according to claim 7, wherein the following conditional expression (4 ′) is satisfied.
2.5 <f2 / f <7.0 (4 ′) The system according to any one of claims 1 to 8, which satisfies the following conditional expression (5), where Bf is the back focus of the entire system at the air conversion distance when the reduction side is the back side, and f is the focal length of the entire system. A projection lens according to claim 1.
2.5 <Bf / f (5) When the paraxial radius of curvature of the lens surface closest to the reduction side of the first lens group is R1r and the radius of curvature of the lens surface closest to the magnification side of the second lens group is R2f, the following conditional expression (6) is satisfied. The projection lens according to claim 1.
−4.0 <(R1r + R2f) / (R1r−R2f) <0.0 (6) The projection lens according to claim 10, wherein the following conditional expression (6 ′) is satisfied.
−3.0 <(R1r + R2f) / (R1r−R2f) <0.0 (6 ′)   The first to third lenses from the magnification side of the second lens group are a positive lens having a convex surface facing the reduction side, a biconcave lens, and a positive lens having a convex surface facing the magnification side, respectively. The projection lens according to item 1.   The projection lens according to claim 12, wherein a three-piece cemented lens is constituted by the first to third lenses from the magnification side of the second lens group. The most magnified lens of the first lens group is made of a plastic material,
The following conditional expression (7) is satisfied, where fp is the focal length of the lens on the most magnifying side of the first lens group and f is the focal length of the entire system. Projection lens.
4.0 <| fp / f | (7)   15. The light source, a light valve into which light from the light source is incident, and a projection lens that projects an optical image by light modulated by the light valve onto a screen. A projection display device comprising a projection lens.