JP4158432B2 - Projection zoom lens - Google Patents

Description

【００２９】
[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】

【００３０】
［実施例３］ 第３実施例について数値例を表３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。
【表 ３】

【００３１】
［実施例４］ 第４実施例について数値例を表４に示す。また、図７はそのレンズ構成図、図８はその諸収差図である。
【表 ４】

【００３２】
[実施例５] 第５実施例について数値例を表５に示す。また、図９はそのレンズ構成図、図１０はその諸収差図である。
【表 ５】

【００３３】
［実施例６］ 第６実施例について数値例を表６に示す。また、図１１はそのレンズ構成図、図１２はその諸収差図である。
【表 ６】

【００３４】
次に実施例１から実施例６に関して条件式（１）から条件式（１３）に対応する値を、まとめて表７に示す。
【表 ７】

表７から明らかなように、実施例１から実施例６の各実施例に関する数値は条件式（１）から（１３）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。
【００３５】
【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な投影用ズームレンズを実現し、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
【図７】本発明によるコンパクトな投影用ズームレンズの第４実施例のレンズ構成図
【図８】第４実施例のレンズの諸収差図
【図９】本発明によるコンパクトな投影用ズームレンズの第５実施例のレンズ構成図
【図１０】第５実施例のレンズの諸収差図
【図１１】本発明によるコンパクトな投影用ズームレンズの第６実施例のレンズ構成図
【図１２】第６実施例のレンズの諸収差図[0001]
[Field of the Invention]
The present invention relates to a projection zoom lens that mainly 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.
[0003]
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, and F = 2.4. . 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.
[0004]
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.
[0005]
[Problems to be solved by the invention]
Under such circumstances, projector devices that employ DMDs as light valves are considered advantageous for miniaturization, and at present, portable and compact projectors are becoming widespread, centering on data projectors. 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, there is a demand for a zoom lens that can be zoomed in terms of convenience and that has a large zoom ratio.
[0006]
In view of the circumstances described above, the present invention realizes a compact projection zoom lens having 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, and is compact and bright. An object of the present invention is to provide a high-quality projector device.
[0007]
[Means for Solving the Problems]
The zoom lens for projection according to the present invention is a projection lens that magnifies and projects onto a light valve and a screen or other wall surface of a projection display device. The projection zoom lens is a first lens group, a second lens group, and a The first lens group is composed of three lens groups, and the first lens group has a negative refractive power and has a negative meniscus lens having a negative refractive power on the screen side (hereinafter referred to as a negative lens). A second lens that is a negative lens with a convex meniscus shape, a third lens that is a convex meniscus shape with a positive refractive power (hereinafter, positive lens), and a fourth lens that is a negative lens are arranged on the screen side. The second lens group has a positive refractive power, and is a fifth lens that is a positive lens, a sixth lens that is a positive lens, and a negative lens that is used in a joined state with the sixth lens. A seventh lens, an eighth lens that is a negative lens, a ninth lens that is a positive lens, and a tenth lens that is a positive lens. The third lens group has a positive refractive power and is positive. In the projection zoom lens which is configured by arranging an eleventh lens which is a lens, and which performs zooming by moving the positions of the first lens group and the second lens group, the first lens group The following conditional expression (1) is satisfied with respect to the power of the second lens group, and the distance between the light valve side surface of the tenth lens constituting the second lens group and the screen side surface of the eleventh lens constituting the third lens group The following conditional expression (2) is satisfied with respect to the distance, and the following conditional expression (3) is satisfied with respect to the dimension of the entire lens system in the optical axis direction at the wide-angle end, and at the wide-angle end of the second lens group. Below for magnification And satisfies conditional expression (4). (Claim 1)
[0008]
(1) 1.3 <| f _I | / f _w <2.0 (because the absolute value is f _I <0)
(2) 1.5 < _d20W / _fw <1.9
(3) 5.0 <TL _W / f _w <7.0
(4) -0.8 <M _IIW <-0.5
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 d _20W : Distance TL between the light valve side surface of the tenth lens and the screen side surface of the eleventh lens at the wide angle end _W : Distance from the screen side of the first lens to the light bulb at the wide-angle end when the projection distance is ∞ (however, the cover glass part is the air equivalent distance)
M _IIW : Composite magnification of the second lens unit at the wide angle end
Conditional expression (1) relates to appropriate distribution of power to the first lens group 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. If the lower limit is exceeded, the negative power of the first lens group becomes large. Accordingly, the positive power of the second lens group and the third lens group must be increased, and various aberrations must be balanced. It becomes difficult and performance deteriorates. On the other hand, if the upper limit is exceeded, the air gap from the second lens group must be increased, which increases the overall size of the optical system and contradicts the purpose of downsizing.
[0010]
Conditional expression (2) corresponds to a condition relating to the size of the back focus. Actually, since the third lens group is arranged on the light valve side of the interval expressed by the conditional expression (2), it cannot be called back focus, but as described above, the projection lens and the light valve such as DMD are not connected. A light guide space from the light source is required between them, and the illumination condition is secured by widening the distance between the second lens group and the third lens group for this light guide space. Therefore, the third lens group is characterized in that it is used not only in the projection lens but also in the light guiding optical system. Therefore, as a conditional expression, when the upper limit of conditional expression (2) is exceeded, both the negative power of the first lens group and the positive power of the second lens group increase, and various aberrations deteriorate. On the other hand, if the lower limit is exceeded, the space for guiding light cannot be secured. This leads to loss of illumination light, and as a result, a high-quality projector cannot be provided.
[0011]
Conditional expression (3) shows the total length of the zoom lens at the wide-angle end. The total lens length at the wide-angle end is larger than when used at any other focal length. That is, it shows the result of miniaturization of the zoom lens of the present invention. Exceeding the upper limit is advantageous for aberration correction, but contradicts the size reduction characteristic of the zoom lens of the present invention. On the other hand, if the lower limit is exceeded, the power of each lens must be increased, leading to deterioration of various aberrations such as distortion and chromatic aberration, deterioration of sensitivity, and the like, which are not suitable for the actual situation.
[0012]
Conditional expression (4) is a condition relating to proper selection of the composite magnification at the wide-angle end of the second lens group, and is a condition for downsizing the entire lens system. Since the arrangement of power of each group in an optimized optical system such as a zoom lens is based on the balance of aberration correction, it is difficult to greatly change this. Moreover, it cannot be operated alone. That is, in the case of the projection zoom lens according to the present invention, by appropriately selecting the composite magnification at the wide-angle end of the second lens group within the range of conditional expression (4), the size of the entire lens system and the power of each lens group can be determined. Optimization can be achieved. When the upper limit is exceeded, the entire lens system becomes large. Conversely, when the lower limit is exceeded, the power of the second lens group becomes excessive, and the balance with the other lens groups is lost, making it difficult to correct aberrations.
[0013]
Next, in the zoom lens for projection according to the present invention, the side surface of the light valve of the second lens constituting the first lens group is aspherical, and the lens having negative refractive power constituting the first lens group. It is preferable that the following conditional expression (5) is satisfied with respect to the Abbe number and the following conditional expression (6) is satisfied with respect to the power of the third lens. (Claim 2)
(5) 45 <(ν ₁ + ν ₂ + ν ₄ ) / 3
(6) 2.5 <f ₃ / f _w <5.0
However,
ν ₁ : Abbe number ν ₂ of the first lens : Abbe number ν ₄ of the second lens : Abbe number f ₃ of the fourth lens : Focal length of the third lens
The side surface of the light valve of the second lens is preferably aspherical in order to satisfactorily correct distortion. Conditional expression (5) relates to the distribution of the Abbe number of the negative lenses constituting the first lens group. This is a conditional expression for maintaining good correction of chromatic aberration of the first lens group. By designing the negative lens constituting the first lens group under the condition such as conditional expression (5), an appropriate power can be obtained. This makes it possible to correct chromatic aberration. If the lower limit is exceeded, the power of each lens becomes excessive for correcting chromatic aberration, and various aberrations deteriorate. Conditional expression (6) is a conditional expression regarding the power of the third lens, which is the only positive lens constituting the first lens group. This is a condition for optimizing the distribution of positive power and negative power of the lenses constituting the first lens group. When the upper limit is exceeded, the positive power is insufficient. Conversely, when the lower limit is exceeded, the positive power is too strong. In both states, the chromatic aberration correction state deteriorates, and the Petzval sum. Deviates from the proper value, and the field curvature cannot be corrected.
[0015]
Next, in the zoom lens for projection according to the present invention, the material of the second lens is made of a resin material, and the side surface of the light valve is aspherical, and the following conditional expression ( It is preferable that 7) is satisfied. (Claim 3)
(7) 3.0 <| f ₂ | / f _w (because the absolute value is f ₂ <0)
However,
f ₂ : Focal length of the second lens
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 φ33.8 mm to φ39.8 mm, which is a size that is considerably 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 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, conditional expression (7) 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 value of the conditional expression (7) is exceeded, the power distributed to the second lens is too large to maintain the performance as a projection lens, causing the above-described adverse effects.
[0017]
Next, in the zoom lens for projection according to the present invention, the glass side surface of the lens having the positive refractive power in which the screen side surface of the fifth lens constituting the second lens group is aspherical and the second lens group is constituted. The following conditional expression (8) is satisfied with respect to the refractive index of the second lens group, the following conditional expression (9) is satisfied with respect to the distribution of the Abbe number of each lens constituting the second lens group, and the following conditional expression with respect to the power of the fifth lens: (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 and the light valve side surface of the tenth lens, and the light valve side surface of the seventh lens and the eighth lens It is preferable that the following conditional expression (12) is satisfied with respect to the radius of curvature of the screen side surface of the lens. (Claim 4)
[0018]
(8) 1.65 <(n ₅ + n ₆ + n ₉ + n ₁₀ ) / 4
(9) 15 <(ν ₅ + ν ₆ + ν ₉ + ν ₁₀ ) / 4- (ν ₇ + ν ₈ ) / 2 <22
(10) 1.1 <f ₅ / f _w <1.9
(11) 1.0 <(r ₁₀ −r ₂₀ ) / (2 * f _w ) <2.0
(12) 0.7 <(r ₁₄ −r ₁₅ ) / (2 * f _w ) <1.5
However,
n ₅ : Refractive index n _{6 at} the d-line of the fifth lens : Refractive index n _{9 at} the d-line of the sixth lens : Refractive index n _{10 at} the d-line of the ninth lens: Refractive index ν _{5 at} the d-line of the tenth lens : Abbe number ν ₆ of the fifth lens : Abbe number ν ₇ of the sixth lens : Abbe number of the seventh lens ν ₈ : Abbe number ν ₉ of the eighth lens : Abbe number ν ₁₀ of the ninth lens: Abbe number f _{5 of} the tenth lens : Focal length r _{10 of} fifth lens: radius of curvature r ₁₄ of screen surface of fifth lens r ₁₄ : radius of curvature r ₁₅ of light valve side surface of seventh lens: radius of curvature of screen side surface of eighth lens r ₂₀ : radius of curvature of the light valve side surface of the tenth lens
In order to satisfactorily correct spherical aberration, coma aberration, etc., the screen side surface of the fifth lens is preferably aspherical. Conditional expression (8) relates to the selection of the refractive index of the glass material used for the positive lens among the lenses constituting the second lens group. This is a condition for satisfactorily correcting curvature of field and astigmatism while keeping Petzval sum small. Therefore, when the lower limit is exceeded, the Petzval sum increases, making it difficult to correct curvature of field. Conditional expression (9) is a conditional expression related to the distribution of the Abbe numbers of the positive lens and the negative lens used in the second lens group. This is a condition for maintaining a balance with each aberration while satisfactorily correcting chromatic aberration. When the upper limit is exceeded, that is, when the Abbe number of the positive lens is increased, the respective refractive indexes are decreased, and the Petzval sum is increased, which is disadvantageous for correction of field curvature. On the other hand, when the lower limit is exceeded, the power of each lens increases for correcting chromatic aberration, which is disadvantageous for correcting spherical aberration and coma aberration.
[0020]
Conditional expression (10) is a conditional expression regarding appropriate distribution of positive power given to the fifth lens arranged closest to the screen of the second lens group. If the lower limit is exceeded, it indicates that the power of the fifth lens is excessive, and if the upper limit is exceeded, the power to the sixth lens, the ninth lens, and the tenth lens, which are other positive lenses constituting the second lens group. This shows that the distribution is excessive, and in either case, spherical aberration and coma aberration are excessive and cannot be corrected. Conditional expression (11) and conditional expression (12) are conditional expressions for correcting spherical aberration and coma that are likely to occur in a large aperture ratio lens, similar to conditional expression (10). Conditional expression (11) shows a method of distributing the surface power of the light valve side surface of the tenth lens located closest to the light valve side of the second lens group and conversely the screen side surface of the fifth lens located closest to the screen side. ing. The light valve side surface of the tenth lens converges the divergent light beam incident on the third lens group from the light valve, and the screen side surface of the fifth lens condenses the light beam diverged in the second lens group again. Both have strong surface power, but it is necessary to appropriately distribute them within the range of the condition of the conditional expression (11). Conditional expression (12) shows a method of distributing the surface power between the light valve side surface of the seventh lens and the screen side surface of the eighth lens, which is a diverging surface disposed substantially at the center of the second lens group. A strong negative surface power is given to both the light valve side surface of the seventh lens and the screen side surface of the eighth lens, and it is also necessary to distribute the power within the range of the conditional expression. If neither the conditional expression (11) nor the conditional expression (12) satisfies the conditional expressions, it is impossible to create a good spherical aberration and coma aberration state.
[0021]
Next, in the projection zoom lens according to the present invention, it is preferable that the light valve side surface of the tenth lens has an aspherical shape. (Claim 5) This is mainly for correction of spherical aberration and coma aberration. It will be advantageous. If it is within a range that is allowed in terms of cost, it is possible to further reduce the size or improve the performance by making this part aspherical.
[0022]
Finally, it is preferable that the projection zoom lens of the present invention satisfies the following conditional expression (13) with respect to the power of the third lens group. (Claim 6)
_{(13) 0.4 <d 20W /} f III <0.6
However,
f _III: composite focal length [0023] of the third lens group
Conditional expression (13) indicates that the distance between the light valve side surface of the tenth lens constituting the second lens group and the screen side surface of the eleventh lens constituting the third lens group and the focal length of the eleventh lens at the wide-angle end. It is a conditional expression showing the relationship. Ideally, light incident on the lens from the light valve should exit the light valve vertically. This needs to be incident on the pupil position of the second lens group by the third lens group. Actually, since the second lens moves due to zooming, it is not always possible to maintain this emission condition, but it must be avoided to change greatly. That is, when the upper limit is exceeded, the pupil condition on the telephoto side becomes poor, and when the lower limit is exceeded, the pupil condition on the wide-angle side becomes poor. In either state, it becomes impossible to sufficiently capture the illumination light beam at those zoom positions.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with respect to specific numerical examples. The following projection zoom lenses according to the first to sixth embodiments include a first lens group LG1, a second lens group LG2, and a third lens group LG3 in order from the screen side, and the first lens group LG1 is negative. A first lens L1 having a refractive power and a negative meniscus lens having a negative refractive power on the screen side (hereinafter referred to as a negative lens); a second lens L2 having a negative meniscus shape negative on the screen side; A third lens L3, which is a convex meniscus lens having a positive refractive power (hereinafter referred to as a positive lens), and a fourth lens L4, which is a negative lens, are arranged on the screen side. It has a positive refractive power, the dummy surface DS is arranged on the most screen side, the fifth lens L5 as a positive lens, the sixth lens L6 as a positive lens, and the sixth lens L6 as a negative lens. The third lens group includes a seventh lens L7 used in a cemented state, an eighth lens L8 that is a negative lens, a ninth lens L9 that is a positive lens, and a tenth lens L10 that is a positive lens. Has a positive refracting power and is composed of an eleventh lens L11, which is a positive lens, and performs zooming by moving the positions of the first lens group LG1 and the second lens group LG2. ing. Further, 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.
[0025]
The name of the refracting surface of each lens is S1 on the screen side of the first lens L1, S2 on the side of the light valve, similarly S3 on the screen side of the second lens L2, S4 on the side of the light valve, and the screen side of the third lens L3. S5, the side surface of the light valve is S6, the screen side surface of the fourth lens L4 is S7, the side surface of the light valve is S8, and a virtual surface DS (S9) for limiting the marginal ray is disposed immediately before the fifth lens L5. The screen side surface of the fifth lens L5 is S10, the side surface of the light valve is S11, the screen side surface of the subsequent sixth lens L6 is S12, the joint surface of the sixth lens L6 and the seventh lens L7 is S13, and the side surface of the light valve of the seventh lens L7 S14, the screen side of the eighth lens L8 is S15, the side of the light valve is S16, and the screen side of the ninth lens L9 is 17. The light valve side is S18, the screen side of the tenth lens L10 is S19, the light valve side is S20, the screen side of the eleventh lens L11 is S21, the light valve side is S22, and the screen side of the cover glass CG is S23. The side surface of the light valve is S24.
[0026]
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 = (Y ² / r) [1 + √ {1− (1 + K) (Y / r) ² }] + A · Y ⁴ + B · Y ⁶ + C · Y ⁸ + D · Y ¹⁰ +
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” means 10 ⁻⁴ , and this numerical value may be multiplied by the immediately preceding numerical value.
[0027]
Example 1 Table 1 shows numerical examples of the first example of the compact projection zoom lens 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 table and drawings, f denotes represents a focal length of the zoom lens system, F _no is the F-number, 2 [omega is full angle of the zoom lens, a b _f is the back focus. The back focus b _f is an air equivalent distance of the distance from the light valve side surface of the eleventh lens constituting the third lens group to the image plane. Further, R is a radius of curvature, D is a lens thickness or a lens interval, N _d is a refractive index of the d line, and ν _d is an Abbe number of the d line. As for the distance between the lenses, the distance between the groups is shown as an example when the projection distance from the screen side surface of the first lens L1 to the screen is 2 m. Therefore, when the first lens group LG1 is used for focus adjustment, the dimension between the first lens group LG1 and the second lens group LG2 changes if the projection distance is other than 2 m. D, g, and C in the various aberration diagrams are aberration curves at respective wavelengths. S represents sagittal and M represents meridional.
[0028]
[Table 1]

[0029]
[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]

[0030]
[Example 3] Table 3 shows numerical examples of the third example. FIG. 5 is a lens configuration diagram, and FIG.
[Table 3]

[0031]
[Example 4] Table 4 shows numerical examples of the fourth example. FIG. 7 is a lens configuration diagram, and FIG.
[Table 4]

[0032]
[Example 5] Table 5 shows numerical examples of the fifth example. FIG. 9 is a lens configuration diagram, and FIG. 10 is a diagram showing various aberrations.
[Table 5]

[0033]
[Example 6] Table 6 shows numerical examples of the sixth example. FIG. 11 is a lens configuration diagram, and FIG.
[Table 6]

[0034]
Next, Table 7 collectively shows values corresponding to the conditional expressions (1) to (13) regarding the first to sixth embodiments.
[Table 7]

As is clear from Table 7, the numerical values related to the examples of Examples 1 to 6 satisfy the conditional expressions (1) to (13), and are also apparent from the aberration diagrams in the examples. Each aberration is corrected well.
[0035]
【The invention's effect】
According to the present invention, a compact projection zoom lens having 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 example of a compact projection zoom lens according to the present invention. FIG. 2 is a diagram showing various aberrations of the lens of the first example. FIG. 4 is a diagram showing various aberrations of the lens of the second embodiment. FIG. 5 is a lens construction diagram of the third embodiment of the compact projection zoom lens according to the present invention. FIG. 7 is a diagram showing the lens arrangement of a fourth example of a compact projection zoom lens according to the present invention. FIG. 8 is a diagram showing various aberrations of the lens of the fourth example. FIG. 10 is a diagram illustrating various aberrations of the lens of the fifth embodiment. FIG. 11 is a diagram of a lens of the sixth embodiment of the compact projection zoom lens according to the present invention. [FIG. 12] Ren of the sixth embodiment Aberration diagrams of

Claims (6)

A projection lens for enlarging and projecting onto a light valve and a screen or other wall surface of a projection display device, comprising a first lens group, a second lens group, and a third lens group in order from the screen side, One lens group has a negative refractive power, a first lens that is a negative meniscus lens having a negative refractive power on the screen side (hereinafter, a negative lens), and a negative meniscus negative lens having a convex side on the screen side. A second lens, a third lens that is a positive meniscus lens having a positive refractive power (hereinafter referred to as a positive lens) and a fourth lens that is a negative lens. A fifth lens that has a positive refractive power and is a positive lens, a sixth lens that is a positive lens, a negative lens that is used in a joined state with the sixth lens, and a negative lens. A third lens group having a positive refractive power and an eleventh lens that is a positive lens; and a ninth lens that is a positive lens and a tenth lens that is a positive lens. In the projection zoom lens in which zooming is performed by moving the positions of the first lens group and the second lens group, the following conditional expression (1) is satisfied with respect to the power of the first lens group: The following formula (2) is satisfied with respect to the distance between the light valve side surface of the tenth lens constituting the second lens group and the screen side surface of the eleventh lens constituting the third lens group. The following conditional expression (3) is satisfied with respect to the dimension of the entire lens system in the optical axis direction at the wide angle end, and the following conditional expression (4) is satisfied with respect to the magnification at the wide angle end of the second lens group. Specially Projection zoom lens to be.
(1) 1.3 <| f _I | / f _w <2.0 (because the absolute value is f _I <0)
(2) 1.5 <d _{20 W} / f _w <1.9
(3) 5.0 <TL _W / f _w <7.0
(4) -0.8 <M _IIW <-0.5
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 d _20W : Distance TL between the light valve side surface of the tenth lens and the screen side surface of the eleventh lens at the wide angle end _W : Distance from the screen side of the first lens to the light valve surface at the wide-angle end when the projection distance is ∞ (however, the cover glass part is the air equivalent distance)
M _IIW : Composite magnification of the second lens unit at the wide angle end 2. The projection zoom lens according to claim 1, wherein a side surface of a light valve of the second lens constituting the first lens group is aspherical and has a negative refractive power constituting the first lens group. A projection zoom lens characterized by satisfying the following conditional expression (5) with respect to the Abbe number of the lens and satisfying the following conditional expression (6) with respect to the power of the third lens.
(5) 45 <(ν ₁ + ν ₂ + ν ₄ ) / 3
(6) 2.5 <f ₃ / f _w <5.0
However,
ν ₁ : Abbe number ν ₂ of the first lens : Abbe number ν ₄ of the second lens : Abbe number f ₃ of the fourth lens : Focal length of the third lens 3. The projection zoom lens according to claim 2, wherein the second lens is made of a resin material, and a light valve side surface has an aspherical shape, and the following conditional expression ( 7) A zoom lens for projection characterized by satisfying 7).
(7) 3.0 <| f ₂ | / f _w (because the absolute value is f ₂ <0)
However,
f ₂ : Focal length of the second lens 2. The projection zoom lens according to claim 1, wherein a screen side surface of the fifth lens constituting the second lens group has an aspherical shape, and has a positive refractive power constituting the second lens group. The following conditional expression (8) is satisfied with respect to the refractive index of the glass material, the following conditional expression (9) is satisfied with respect to the distribution of the Abbe number of each lens constituting the second lens group, and the power of the fifth lens is described below. Conditional expression (10) is satisfied, the following conditional expression (11) is satisfied with respect to the curvature radius of the screen side surface of the fifth lens and the light valve side surface of the tenth lens, and the light valve side surface of the seventh lens and A projection zoom lens characterized in that the following conditional expression (12) is satisfied with respect to a radius of curvature of a screen side surface of the eighth lens.
(8) 1.65 <(n ₅ + n ₆ + n ₉ + n ₁₀ ) / 4
(9) 15 <(ν ₅ + ν ₆ + ν ₉ + ν ₁₀ ) / 4- (ν ₇ + ν ₈ ) / 2 <22
(10) 1.1 <f ₅ / f _w <1.9
(11) 1.0 <(r ₁₀ −r ₂₀ ) / (2 * f _w ) <2.0
(12) 0.7 <(r ₁₄ −r ₁₅ ) / (2 * f _w ) <1.5
However,
n ₅ : Refractive index n _{6 at} the d-line of the fifth lens : Refractive index n _{9 at} the d-line of the sixth lens : Refractive index n _{10 at} the d-line of the ninth lens: Refractive index ν _{5 at} the d-line of the tenth lens : Abbe number ν ₆ of the fifth lens : Abbe number ν ₇ of the sixth lens : Abbe number of the seventh lens ν ₈ : Abbe number ν ₉ of the eighth lens : Abbe number ν ₁₀ of the ninth lens: Abbe number f _{5 of} the tenth lens : Focal length r _{10 of} fifth lens: radius of curvature r ₁₄ of screen surface of fifth lens r ₁₄ : radius of curvature r ₁₅ of light valve side surface of seventh lens: radius of curvature of screen side surface of eighth lens r ₂₀ : radius of curvature of the light valve side surface of the tenth lens 5. The projection zoom lens according to claim 4, wherein the light valve side surface of the tenth lens is aspherical. 5. The projection zoom lens according to claim 1, wherein the following conditional expression (13) is satisfied with respect to the power of the third lens group.
_{(13) 0.4 <d 20W /} f III <0.6
However,
f _III: composite focal length of the third lens group

Images