JP4380200B2 - Projection lens - Google Patents

Description

【００２８】
［実施例２］ 第２実施例について数値例を表２に示す。また、図３はそのレンズ構成図、図４はその諸収差図である。
【表 ２】

【００２９】
［実施例３］ 第３実施例について数値例を表４に示す。また、図５はそのレンズ構成図、図６はその諸収差図である。本実施例におけるバックフォーカスｂ_f は広角端における第２レンズ群ＬＧ２を構成する第５レンズＬ２５のライトバルブ側面Ｓ２９から像面までの距離の空気換算距離である。
【表 ３】

【００３０】
次に第１実施例から第３実施例に関して条件式（１）から条件式（１５）に対応する値を、まとめて表４に示す。
【表 ４】

表４から明らかなように、第１実施例から第３実施例の各実施例に関する数値は条件式（１）から条件式（１５）を満足しているとともに、各実施例における収差図からも明らかなように、各収差とも良好に補正されている。
【００３１】
【発明の効果】
本発明によれば、ＤＭＤなどのライトバルブの特性に適した結像性能が高くコンパクトで画角が広い投影レンズを実現し、コンパクトで明るく、高画質のプロジェクタ装置を提供することが出来る。
【図面の簡単な説明】
【図１】本発明によるコンパクトな広角投影用ズームレンズの第１実施例のレンズ構成図。
【図２】第１実施例のレンズの諸収差図。
【図３】本発明によるコンパクトな広角投影用ズームレンズの第２実施例のレンズ構成図。
【図４】第２実施例のレンズの諸収差図。
【図５】本発明によるコンパクトな広角投影用ズームレンズの第３実施例のレンズ構成図。
【図６】第３実施例のレンズの諸収差図。[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a projection lens that projects an image from a light valve that forms an image by changing the reflection direction of light, such as DMD, onto a screen or the like.
[0002]
[Prior art]
Conventionally, a liquid crystal panel has been often used as a light valve of a projector for a long time. Recently, however, DMDs (digital micromirrors) that display images by arranging microscopic micromirrors (mirror elements) on a plane in correspondence with pixels and mechanically controlling the angle of each mirror surface using micromachine technology. Device) has been put into practical use, has a response speed faster than a liquid crystal panel, and provides a bright image, and is suitable for realizing a small, high-brightness, high-quality projector that is portable. Therefore, it shows signs of widespread use (see, for example, prior document 1).
[0003]
[Patent Document 1]
JP 2001-511195 A
[0004]
[Problems to be solved by the invention]
When a DMD is used as a light valve in a projector device, the projection lens is restricted by DMD. The first limitation is related to the F value of the projection lens. At present, in the DMD, when the image is generated, the turning angle of the micromirror is ± 12 °, thereby switching between the effective reflected light (effective light) and the invalid reflected light (ineffective light). Accordingly, in a projector using a DMD as a light valve, it is necessary to capture effective light and not to capture invalid light. From this condition, the F value of the projection lens can be derived, that is, F = 2.4. Become. Actually, there is a demand to increase the amount of light as much as possible. Therefore, in many cases, a projection lens with F = 2.0 is considered in consideration of a decrease in contrast in a range where there is no actual harm. In addition, since such a condition is established under the condition that the position of the pupil on the light valve side of the projection lens is constant, if the pupil position of the zoom lens or the like moves, In general, it is necessary to consider such as optimizing the pupil position at the wide-angle end where brightness tends to be a problem.
[0005]
The second restriction is a restriction due to the positional relationship with the light source system. Since the image circle of the projection lens is desired to be as small as possible for miniaturization, the arrangement of the light source system for inputting the projection light beam to the DMD is limited, and the effective light from the DMD is input to the projector lens. In this case, the light source system is installed in substantially the same direction (adjacent) as the projector lens. In addition, the projection lens and the light source system use the space between the light valve side lens and the light valve (that is, the back focus) of the projection lens, and the projection lens must have a large back focus. At the same time, it is necessary to design a small lens system on the light valve side in order to secure a light guide space from the light source. From the standpoint of optical design of the projection lens, this means that the pupil position on the light valve side is designed near the rear of the projection lens. On the other hand, in order to improve the performance of the projection lens, it is necessary to combine a large number of lenses. When a large number of lenses are arranged, the total length of the projection lens is required, and the total length of the projection lens is reduced. If the length is longer, the lens having the entrance pupil position on the rear side naturally has a problem that the front lens diameter is increased.
[0006]
Despite these development limitations, projector devices that employ DMD as a light valve are considered to be more advantageous than other methods for miniaturization, and are now portable, mainly for data projectors. Things are widespread. In order to make the device itself compact, it is a matter of course that there is a great demand for compactness in the projection lens used, and there is also a demand for multiple functions. In addition to being fully satisfied, zooming is also possible for convenience, and a zoom lens having a large angle of view at the wide-angle end and a large zoom ratio has been demanded.
[0007]
In view of the circumstances described above, the present invention realizes a compact and wide-angle projection lens with high imaging performance suitable for the characteristics of a light valve that forms an image by changing the reflection direction of light such as DMD. An object of the present invention is to provide a high-quality projector device that can project a large screen even in a limited space such as a bright and small meeting room.
[0008]
[Means for Solving the Problems]
  The projection lens of the present invention is a projection lens that enlarges and projects an image from a light valve of a projection display device onto a screen or other wall surface, and has a negative refracting power as a whole in order from the screen side. The lens group and the second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole, depending on the relationship between the type of light valve used and the specifications of the illumination optical system, etc. The second lens group includes a first lens that is a lens having a positive refractive power (hereinafter, positive lens), and a second lens that is a negative meniscus lens having a negative refractive power that is convex on the screen side (hereinafter, negative lens). A third lens that is a negative lens, a fourth lens that is a positive lens and joined to the third lens that constitutes the second lens group, and a fifth lens that is a positive lens. The following conditional expression (1) is satisfied with respect to the power of the second lens group, the following conditional expression (2) is satisfied with respect to the power of the first lens constituting the second lens group, and the second The following formula (3) is satisfied with respect to the power of the fifth lens constituting the lens group.The zooming is performed by moving the positions of the first lens group and the second lens group.It is characterized by that. (Claim 1, Claim 2)
(1) 0.55 <f_W/ F_II <0.7
(2) 1.1 <f_II/ F_2,1 <1.6
(3) 0.3 <f_II/ F_2,5 <0.8
However,
f_W : Total focal length of the entire lens system at the wide-angle end
f_II : Composite focal length of the second lens group
f_2,1: Focal length of the first lens constituting the second lens group
f_2,5: Focal length of the fifth lens constituting the second lens group
[0009]
Conditional expression (1) relates to appropriate distribution of power to the second lens group having positive refractive power. This is a necessary condition for balancing the size of the entire optical system and the conditions for appropriately correcting various aberrations. Further, a space for arranging an optical system for illuminating a light valve such as a DMD is defined as a back focus portion (in the case of having a third lens group, the air interval between the second lens group and the third lens group is this space. In order to secure the back focus, it is necessary to distribute appropriate power to the first lens group. At the same time, the power of the second lens group must be appropriate. This is based on a balance including the relationship with aberration. For this reason, if the upper limit is exceeded, the positive power of the second lens group becomes large, and accordingly, the negative power of the first lens group must be strengthened. Getting worse. On the other hand, if the lower limit is exceeded, the air gap from the first lens group must be increased, and the overall size of the optical system increases, which contradicts the purpose of miniaturization, or the back focus can be secured. Disappear.
[0010]
Subsequently, conditional expressions (2) and (3) are conditional expressions relating to correction of various monochromatic aberrations in the second lens group. The basis for correcting various monochromatic aberrations in the second lens group is that a relatively strong positive power is given to the first lens and the fifth lens in the second lens group, so that the second lens group for each aberration. As the power balance is established, it cannot be greatly destroyed. Among them, the first lens in particular needs to converge the divergent light from the first lens group, so that stronger power is given, and this is expressed by conditional expression (2). Therefore, if the upper limit of conditional expression (2) is exceeded, the power of the first lens is increased, and conversely, the power of the fifth lens must be decreased, and various aberrations deteriorate. Conversely, if the lower limit of conditional expression (2) is exceeded, the diverging light from the first lens group in the first lens cannot be sufficiently converged, and the converging action must not be shared by lenses other than the first lens. As a result, the overall aberration balance is lost. Similarly, the conditional expression (3) is expressed for the fifth lens. If the upper limit is exceeded, the convergence of the first lens will be reduced. Conversely, if the lower limit is exceeded, sufficient aberrations will be obtained. The power to correct is lost.
[0011]
Further, the following conditional expression (4) is satisfied regarding the radius of curvature of the screen side surface of the first lens constituting the second lens group, and the screen side surface of the first lens and the second lens constituting the second lens group are satisfied. The following conditional expression (5) is satisfied with respect to the radius of curvature of the light valve side surface of the fifth lens constituting the group, and the following conditional expression regarding the radius of curvature of the light valve side surface of the second lens constituting the second lens group ( 6) is satisfied, and the following conditional expression (7) is satisfied with respect to the curvature radius of the light valve side surface of the second lens constituting the second lens group and the screen side surface of the third lens constituting the second lens group. Projection lens characterized by satisfaction. (Claim 3)
(4) 1.1 <f_II/ R_{twenty one} <1.5
(5) -1.1 <r_{twenty one}/ R₂₉ <-0.6
(6) 1.1 <f_II/ R_{twenty four} <1.9
(7) -1.5 <r_{twenty four}/ R_{twenty five} <-0.8
However,
r_{twenty one}: Curvature radius of screen side surface of first lens constituting second lens group
r_{twenty four}: Curvature radius of the light valve side surface of the second lens constituting the second lens group
r_{twenty five}: Curvature radius of the screen side surface of the third lens constituting the second lens group
r₂₉: Radius of curvature of the light valve side surface of the fifth lens constituting the second lens group
[0012]
Conditional expression (4) relates to the shape of the first lens constituting the second lens group. In particular, the screen side surface must converge strong divergent light from the first lens group and correct spherical aberration, and requires strong surface power. That is, when the upper limit of conditional expression (4) is exceeded, the convergence effect is sufficient, but under spherical aberration remains, and conversely, when the lower limit is exceeded, the power for convergence is insufficient, and thus the convergence effect is reduced. The other lenses must be shared, and various aberrations will deteriorate. Conditional expression (5), together with conditional expression (4), is a condition for correcting spherical aberration and other aberrations in a well-balanced manner. If the upper limit is exceeded, it is difficult to correct various aberrations. Conversely, if the lower limit is exceeded, spherical aberration cannot be corrected. Conditional expression (6) is a conditional expression related to the shape of the second lens constituting the second lens group. In particular, the shape of the side surface of the light valve is important, and the coma aberration is corrected by correcting the under spherical aberration caused by the first lens of the second lens group and concentrating the diaphragm.
[0013]
Therefore, when the upper limit is exceeded, that is, when the radius of curvature of the light valve side surface of the second lens becomes too large, it becomes difficult to correct coma, and when the lower limit is exceeded, it is difficult to correct spherical aberration. Conditional expression (7) relates to the shape of the light valve side surface of the second lens of the second lens group and the side surface of the screen of the third lens. The two surfaces are concentric and symmetrical with respect to the so-called stop. , Which acts to prevent the occurrence of off-axis aberrations in the second lens group, that is, the amount of occurrence of off-axis aberrations as the second lens group increases even if the upper limit is exceeded or the lower limit is exceeded, The balance of various aberrations as a whole system is lost.
[0014]
Furthermore, it is preferable that the shape of at least one refracting surface of the screen side surface of the first lens constituting the second lens group and the light valve side surface of the fifth lens constituting the second lens group is an aspherical shape. . (Claim 4)
This is permitted in terms of cost since the screen side surface of the first lens and the light valve side surface of the fifth lens constituting the second lens group are both surfaces having a large influence on correction of spherical aberration and coma aberration. If it is within the range, making these parts aspherical is advantageous mainly for correction of spherical aberration and coma aberration, and it is possible to further reduce the size or improve the performance.
[0015]
Further, the first lens group includes a first lens that is a negative lens having a meniscus shape convex to the screen side, a second lens that is a lens having positive or negative refractive power, a third lens that is a negative lens, and the third lens. The lens is composed of a fourth lens, which is a positive lens, and a fifth lens, which is a negative lens, arranged so as to be cemented or separated, and satisfies the following conditional expression (8) with respect to the power of the first lens group. In addition, the following formula (9) is satisfied with respect to the power of the first lens constituting the first lens group, and in addition, the radius of curvature of the side surface of the light valve of the first lens constituting the first lens group is satisfied. The following conditional expression (10) is satisfied with respect to the curvature radius of the screen side surface of the fifth lens constituting the first lens group, and the following conditional expression (11) is satisfied with respect to the radius of curvature of the screen constituting the first lens group. That is, the following conditional expression (12) is satisfied with respect to the Abbe number of the glass material used for the lens excluding the second lens, and the refractive index of the glass material used for the fourth lens constituting the first lens group is as follows. Conditional expression (13) is satisfied, the second lens constituting the first lens group is made of a resin material, and at least the side surface of the light valve has an aspherical shape. It is preferable that the following conditional expression (14) is satisfied with respect to the power of the two lenses. (Claim 5)
(8) 0.6 <f_W/ | F_I | <1.0 (the absolute value is f_I<Because it is 0)
(9) 0.45 <f_I / F_1,1 <0.75
(10) −1.6 <f_I / R₁₂ <-1.0
(11) 1.1 <f_I / R₁₉ <1.5
(12) 20 <(ν_1,1+ Ν_1,3+ Ν_1,5) / 3-ν_1,4
(13) 1.7 <n_1,4
(14) | f_I / F_1,2| <0.3
However,
f_W: Total focal length of the entire lens system at the wide-angle end
f_I: Composite focal length of the first lens group
f_1,1: Focal length of the first lens constituting the first lens group
r₁₂: Curvature radius of the light valve side surface of the first lens constituting the first lens group
r₁₉: Curvature radius of screen side surface of fifth lens constituting first lens group
ν_1,1: Abbe number of the first lens constituting the first lens group
ν_1,3: Abbe number of the third lens constituting the first lens group
ν_1,4: Abbe number of the fourth lens constituting the first lens group
ν_1,5: Abbe number of the fifth lens constituting the first lens group
n_1,4: Refractive index at the d-line of the fourth lens constituting the first lens group
f_1,2: Focal length of the second lens constituting the first lens group
[0016]
Conditional expression (8) relates to appropriate distribution of power to the first lens unit having negative refractive power. This is a necessary condition for balancing the size of the entire optical system and the conditions for appropriately correcting various aberrations. Further, a space for arranging an optical system for illuminating a light valve such as a DMD is defined as a back focus portion (in the case of having a third lens group, the air interval between the second lens group and the third lens group is this space. And the purpose of ensuring the back focus. Therefore, if the upper limit is exceeded, the negative power of the first lens group becomes large, and accordingly, the positive power of the second lens group and the third lens group must be increased, and various aberrations are balanced. Becomes difficult and performance deteriorates. On the other hand, if the lower limit is exceeded, the air gap from the second lens group must be increased, and the overall size of the optical system increases, which contradicts the purpose of miniaturization, or the back focus cannot be secured. . Conditional expression (9) relates to power distribution in the first lens group based on conditional expression (8). That is, in order to increase the back focus and secure a balance of various aberrations, it is particularly important to give an appropriate negative power to the first lens constituting the first lens group. If the upper limit is exceeded, it is easy to satisfy the back focus conditions and the like, and it becomes easy to balance various aberrations, but on the other hand, it is not preferable because it becomes difficult to manufacture and increases costs. If the lower limit is exceeded, on the contrary, the back focus cannot be secured, and the balance of various aberrations becomes difficult.
[0017]
The following conditional expression (10) is a condition for reducing the occurrence of coma and distortion under the negative power condition distributed to the first lens of conditional expression (9). That is, when these two conditional expressions are satisfied, the first lens has a meniscus shape having a strong negative power. If the upper limit of conditional expression (10) is exceeded, coma and distortion cannot be sufficiently suppressed. If the lower limit is exceeded, it is effective to suppress the occurrence of aberrations, but the curved shape of the meniscus negative lens becomes too strong, making manufacture difficult. Conditional expression (11) affects the spherical aberration and coma aberration correction in the first lens group and the effective diameter (hereinafter referred to as the front lens diameter) of the first lens constituting the first lens group. The specifications of this zoom lens require that the angle of view at the wide-angle end is wide and at the same time the front lens diameter is designed to be small. Usually, these two conditions often exist as contradictory ones. In order to satisfy each aberration correction and simultaneously reduce the front lens diameter, a light beam corresponding to an image point having a large image height is passed through a position where the light beam height is lower in the lens disposed on the screen side of the first lens group. It is necessary. The third lens and the fifth lens practice this in the first lens group. Particularly characteristic is the fifth lens. Although the power given to the fifth lens is small, the object is achieved by forming a meniscus shape that is largely convex on the light valve side.
[0018]
On the other hand, the spherical aberration and coma aberration correction in the first lens group is balanced, and if the upper limit is exceeded, that is, the radius of curvature is too small, this case relates to correction of spherical aberration and coma aberration. The degree of freedom will be insufficient, and if the lower limit is exceeded, the diameter of the front lens must be increased. Conditional expression (12) relates to the distribution of the Abbe numbers of the negative lens and the positive lens constituting the first lens group. This is a conditional expression for maintaining good correction of chromatic aberration of the first lens group, and selection of the glass material of the negative lens and the positive lens constituting the first lens group is performed under the condition as in the conditional expression (12). As a result, proper power distribution is achieved and chromatic aberration can be corrected well. If the lower limit is exceeded, the power of each lens becomes excessive for correcting chromatic aberration, and various aberrations deteriorate. Conditional expression (13) is a condition relating to the control of curvature of field, that is, the Petzval sum. The fourth lens, which is the only lens with positive power in the first lens group, is very important in controlling the Petzval sum, increasing the power, that is, increasing the refractive index. Reduce Petzval sum. Therefore, if the lower limit is exceeded, the Petzval sum increases, the field curvature increases, and it becomes difficult to control the image plane at the peripheral image height.
[0019]
For the purpose of correcting distortion, it is considered that the aspherical shape is effective for both the first lens and the second lens, but the effective diameter of these lenses is more effective. Even the second lens having a small diameter is about φ32.6 mm to φ34.8 mm according to the design example adopted in the embodiment, which is disadvantageous in terms of cost when manufactured by the current glass mold manufacturing method. If an aspheric lens made of a resin material is used, the problem of cost is solved. However, if a surface scratch or the like is taken into consideration, an aspheric surface made of a resin material is used for the second lens rather than the first lens exposed on the exterior surface. It is preferable to employ a lens. Therefore, the conditional expression (14) shows a range of conditions for maintaining the performance as a projection lens when the second lens is made of a resin material. When manufacturing lenses with resin materials, it is necessary to keep in mind that the refractive index changes due to temperature changes and humidity changes are kept within a safe range, and in order to improve moldability, the wall thickness is evenly distributed. It is to give consideration to. In order to satisfy these conditions, it is necessary to reduce the power distributed to the resin lenses. Therefore, if the lower limit of conditional expression (14) is exceeded, the power distributed to the second lens is too large to maintain the performance as a projection lens, and good performance is obtained when the environment or the like changes as described above. It can no longer be maintained.
[0020]
Furthermore, it is preferable that the third lens group includes only a first lens that is a positive lens, and the following conditional expression (15) is satisfied with respect to the power of the third lens group. (Claim 6)
(15) 0.22 <f_W/ F_III <0.29
However,
f_III: Composite focal length of the third lens group
[0021]
In order to efficiently form the light bundle from the DMD on the screen surface, the principal ray angle of the light bundle between the third lens group and the DMD must be set in accordance with the characteristics of the illumination optical system. In many cases, it is almost telecentric. In order to ensure telecentricity during this period, the focal position of the third lens group needs to be near the exit pupil of the second lens group, and the power of the third lens group within the range of conditional expression (16). It is possible to achieve the purpose. Therefore, even if the upper limit is exceeded or the lower limit is exceeded, pupil matching cannot be achieved and various aberrations deteriorate.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described with respect to specific numerical examples. The following first embodimentSecond embodimentIn the compact zoom lens for wide-angle projection, the first lens group LG1 and the second lens group LG2 are sequentially arranged from the screen side.Subsequently, the third lens group LG3 arrangedIs composed of the thirdExampleInFrom the first lens group LG1 and the second lens group LG2Composed. The first lens group LG1 has a negative refractive power, a first lens L11 which is a lens having a negative meniscus shape convex to the screen side (hereinafter referred to as a negative lens), and has a positive or negative refractive power. The second lens L12, the third lens L13 which is a negative lens, and the third lens which is a lens having a positive refractive power which is arranged to be bonded or separated (hereinafter referred to as a positive lens) is a fourth lens L14 and a negative lens. The fifth lens L15 is arranged.
[0023]
The second lens group has a positive refractive power, a first lens L21 that is a positive lens, a second lens L22 that is a negative lens with a meniscus shape convex to the screen side, a third lens L23 that is a negative lens, a positive lens A fourth lens L24 that is a lens and is joined to the third lens that constitutes the second lens group, and a fifth lens L25 that is a positive lens are arranged. The third lens group has a positive refractive power and is configured by arranging only the first lens L31 which is a positive lens. Further, zooming is performed by moving the positions of the first lens group LG1 and the second lens group LG2. Of the lens intervals, those relating to the focus are shown as an example when the projection distance from the screen side surface of the first lens L11 to the screen is 2 m. A cover glass CG, which is a component of the light valve such as DMD, is disposed between the third lens group LG3 and the light valve surface with an air gap.
[0024]
The names of the refracting surfaces of each lens are S11 for the screen side of the first lens L11 constituting the first lens group LG1, S12 for the side of the light valve, S13 for the screen side of the second lens L12, and S14 for the side of the light valve. The screen side of the third lens L13 is S15, the side of the light valve is S16, the side of the screen of the fourth lens L14 is S17, the side of the light valve is S18, the side of the screen of the fifth lens L15 is S19, and the side of the light valve is S20. The screen side surface of the first lens L21 constituting the second lens group LG2 is S21, the side surface of the light valve is S22, the screen side surface of the subsequent second lens L22 is S23, the side surface of the light valve is S24, and the screen side surface of the third lens L23 is S25, the light valve side (joint surface with the fourth lens) is S2 The light valve side surface of the fourth lens L24 is S27, the screen side surface of the fifth lens L25 is S28, and the light valve side surface is S29, and the first lens constituting the third lens group LG3 in the embodiments other than the third embodiment. The screen side surface of L31 is S31, the light valve side surface is S32, the screen side surface of the cover glass CG is S41, and the light valve side surface is S42.
[0025]
As is well known, the aspherical surface used in each embodiment has an aspherical formula when taking the Z axis in the optical axis direction and the Y axis in the direction orthogonal to the optical axis:
Z = (Y²/ R) [1 + √ {1- (1 + K) (Y / r)²}]
+ A ・ Y^Four+ B ・ Y⁶+ C ・ Y⁸+ D ・ Y^Ten+ ...
Is a curved surface obtained by rotating the curve given by around the optical axis, and the shape is defined by giving paraxial curvature radius: r, conic constant: K, and higher-order aspheric coefficients: A, B, C, D To do. In the notation of the conic constant and the higher-order aspheric coefficient in the table, “E and the number following it” represent “power of 10”. For example, “E-4” is 10^{− Four}This value can be multiplied by the previous value.
[0026]
Example 1 Table 1 shows numerical examples of the first example of the compact zoom lens for wide-angle projection according to the present invention. FIG. 1 is a diagram showing the lens configuration, and FIG. 2 is a diagram showing various aberrations thereof.
In the tables and drawings, f is the focal length of the entire zoom lens system, F_noIs the F number, 2ω is the full angle of view of the zoom lens, b_fRepresents the back focus. Back focus b in the first and second embodiments_fIs the air equivalent distance of the distance from the light valve side surface S32 of the first lens L31 constituting the third lens group LG3 at the wide angle end to the image plane. R is the radius of curvature, D is the lens thickness or lens spacing, N_dIs the refractive index of d-line, ν_dIndicates the Abbe number of the d line. CA1, CA2, CA3, and CA4 in the various aberration diagrams are aberration curves at wavelengths of CA1 = 550.0 nm, CA2 = 486.1 nm, CA3 = 640.0 nm, and CA4 = 435.8 nm, respectively. S represents sagittal and M represents meridional.
[0027]
[Table 1]

[0028]
[Example 2] Table 2 shows numerical examples of the second example. FIG. 3 is a diagram showing the lens configuration, and FIG. 4 is a diagram showing various aberrations thereof.
[Table 2]

[0029]
[Example 3] Table 4 shows numerical examples of the third example. FIG. 5 is a lens configuration diagram, and FIG. Back focus b in this embodiment_fIs the air equivalent distance of the distance from the light valve side surface S29 of the fifth lens L25 constituting the second lens group LG2 at the wide angle end to the image plane.
[Table 3]

[0030]
Next, Table 4 collectively shows values corresponding to the conditional expressions (1) to (15) with respect to the first to third embodiments.
[Table 4]

As is clear from Table 4, the numerical values related to the first to third embodiments satisfy the conditional expressions (1) to (15) and also from the aberration diagrams in the respective embodiments. As is apparent, each aberration is well corrected.
[0031]
【The invention's effect】
According to the present invention, a compact projection lens having a wide imaging angle and a high imaging performance suitable for the characteristics of a light valve such as a DMD can be realized, and a compact, bright and high-quality projector apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a lens configuration diagram of a first embodiment of a compact wide-angle projection zoom lens according to the present invention;
FIG. 2 is a diagram illustrating various aberrations of the lens of the first example.
FIG. 3 is a lens configuration diagram of a second embodiment of a compact wide-angle projection zoom lens according to the present invention;
FIG. 4 is a diagram illustrating various aberrations of the lens of the second example.
FIG. 5 is a lens configuration diagram of a third example of a compact wide-angle projection zoom lens according to the present invention;
FIG. 6 is a diagram illustrating various aberrations of the lens of the third example.

Claims (6)

A projection lens for enlarging and projecting an image from a light valve of a projection display device onto a screen or other wall surface, in order from the screen side, a first lens group having a negative refractive power as a whole and a positive as a whole is composed of two groups from the second lens group having a refractive power, the second lens group, the first lens is a lens having a positive refractive power (hereinafter positive lens), a negative on the screen side at a convex meniscus shape A second lens that is a lens having a refractive power (hereinafter referred to as a negative lens), a third lens that is a negative lens, and a third lens that is a positive lens and that constitutes the second lens group. The fourth lens and the fifth lens, which is a positive lens, are arranged, satisfy the following conditional expression (1) with respect to the power of the second lens group, and the first lens constituting the second lens group Power of Regard is satisfied the following matters formula (2), satisfies the following matters formula (3) with respect to a power of the fifth lens constituting the second lens group, the first lens group and the second lens group A projection lens characterized in that zooming is performed by moving the position .
(1) 0.55 <f _W / f _II <0.7
(2) 1.1 <f _II / f _2,1 <1.6
(3) 0.3 <f _II / f _2,5 <0.8
However,
f _W : Total focal length f _{II of the} entire lens system at the wide angle end : Synthetic focal length f _{2,1 of} the second lens group: Focal length f _2,5 of the first lens constituting the second lens group: Focal length of the fifth lens constituting the second lens group A projection lens for enlarging and projecting an image from a light valve of a projection display device onto a screen or other wall surface, in order from the screen side, a first lens group having a negative refractive power as a whole and a positive as a whole is composed of three groups from the third lens group having positive refractive power in the second lens group and the whole having a refractive power, the second lens group, the first lens is a positive lens meniscus convex to the screen side A second lens that is a negative lens, a third lens that is a negative lens, a fourth lens that is a positive lens and is joined to the third lens that constitutes the second lens group, and a positive lens that is a positive lens. 5 lenses are arranged, the following conditional expression (1) is satisfied regarding the power of the second lens group, and the following expression (2) regarding the power of the first lens constituting the second lens group: Satisfied And which satisfies the following matters formula (3) with respect to a power of the fifth lens constituting the second lens group, a zooming formed by moving the position of the first lens group and the second lens group projection lenses, characterized by being.
(1) 0.55 <f _W / f _II <0.7
(2) 1.1 <f _II / f _2,1 <1.6
(3) 0.3 <f _II / f _2,5 <0.8
However,
f _W : Total focal length f _{II of the} entire lens system at the wide angle end : Synthetic focal length f _{2,1 of} the second lens group: Focal length f _2,5 of the first lens constituting the second lens group: Focal length of the fifth lens constituting the second lens group The following conditional expression (4) is satisfied with respect to the curvature radius of the screen side surface of the first lens constituting the second lens group, and the screen side surface of the first lens and the second lens group constituting the second lens group. The following conditional expression (5) is satisfied with respect to the curvature radius of the light valve side surface of the fifth lens constituting the second lens group, and the following conditional expression (6 with respect to the curvature radius of the light valve side surface of the second lens constituting the second lens group is satisfied. In addition, the following conditional expression (7) is satisfied with respect to the radius of curvature of the light valve side surface of the second lens constituting the second lens group and the screen side surface of the third lens constituting the second lens group: The projection lens according to claim 1, wherein the projection lens is a projection lens.
(4) 1.1 <f _II / r ₂₁ <1.5
(5) −1.1 <r ₂₁ / r ₂₉ <-0.6
(6) 1.1 <f _II / r ₂₄ <1.9
(7) -1.5 <r ₂₄ / r ₂₅ <-0.8
However,
r ₂₁ : radius of curvature of the screen side surface of the first lens constituting the second lens group r ₂₄ : radius of curvature r ₂₅ of the surface of the second lens constituting the second lens group on the light valve side r ₂₅ : second lens group Radius of curvature r ₂₉ of the surface on the screen side of the third lens constituting the lens: radius of curvature of the surface on the light valve side of the fifth lens constituting the second lens group The shape of at least one refracting surface of the screen side surface of the first lens constituting the second lens group and the side surface of the light valve of the fifth lens constituting the second lens group is an aspheric shape. The projection lens according to claim 1. The first lens group includes a first lens that is a negative meniscus lens convex toward the screen, a second lens that is a lens having a positive or negative refractive power, a third lens that is a negative lens, and the third lens. Is arranged with a fourth lens that is a positive lens and a fifth lens that is a negative lens, which are arranged to be joined or separated, and satisfies the following conditional expression (8) with respect to the power of the first lens group: The following condition (9) is satisfied with respect to the power of the first lens constituting the first lens group, and the following condition is satisfied with respect to the radius of curvature of the light valve side surface of the first lens constituting the first lens group. Expression (10) is satisfied, the following conditional expression (11) is satisfied with respect to the radius of curvature of the screen side surface of the fifth lens constituting the first lens group, and the second of the lenses constituting the first lens group is satisfied. The following conditional expression (12) is satisfied with respect to the Abbe number of the glass material used for the lens excluding the lens, and the following conditional expression (13 with respect to the refractive index of the glass material used for the fourth lens constituting the first lens group) ), The second lens constituting the first lens group is made of a resin material, and at least the side surface of the light valve has an aspherical shape, and the power of the second lens is The projection lens according to claim 1, wherein the following conditional expression (14) is satisfied.
(8) 0.6 <f _W / | f _I | <1.0 (because the absolute value is f _I <0)
(9) 0.45 <f _I / F _1,1 <0.75
(10) −1.6 <f _I / R ₁₂ <-1.0
(11) 1.1 <f _I / R ₁₉ <1.5
(12) 20 <(ν _1,1 + ν _1,3 + ν _1,5 ) / 3−ν _1,4
(13) 1.7 <n _1,4
(14) | f _I / F _1,2 | <0.3
However,
f _W : Total focal length of the entire lens system at the wide angle end f _I : Composite focal length of the first lens group f _1,1 : Focal length r ₁₂ of the first lens constituting the first lens group: First lens group Radius of curvature r _{19 of} the first lens constituting the light valve side surface: radius of curvature ν _1,1 of the surface of the fifth lens constituting the first lens group on the screen side: first lens constituting the first lens group Abbe number ν _{1,3 of} the third lens constituting the first lens group ν _1,4 : Abbe number of the fourth lens constituting the first lens group ν _1,5 : constituting the first lens group Abbe number n _1,4 of the fifth lens: refractive index f _{1,2 at} the d-line of the fourth lens constituting the first lens group: focal length of the second lens constituting the first lens group The said 3rd lens group is comprised only by the 1st lens which is a positive lens, and satisfies the following conditional expression (15) regarding the power of the said 3rd lens group, The Claim 1 thru | or 5 characterized by the above-mentioned. Projection lens.
(15) 0.22 <f _W / f _III <0.29
However,
f _III: composite focal length of the third lens group

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