JP5163347B2 - Lens system with a small aperture and projector device using the same - Google Patents

Description

  The present invention relates to a compact zoom lens having a small lens aperture for enlarging and projecting an image from a light valve for forming an image mainly by changing the reflection direction of light such as DMD.

  In recent years, DMD (digital micromirror device) displays images by arranging microscopic micromirrors (mirror elements) on a plane corresponding to pixels and mechanically controlling the angle of each mirror surface using micromachine technology. ) Has been put to practical use, and is characterized by a faster response speed and a brighter image than a liquid crystal panel that has been widely used in this field. It is rapidly spreading because it is suitable for realizing.

  When a DMD is used as a light valve in a projector device, a DMD-specific restriction occurs for a projection lens that is used simultaneously. The first restriction relates to the F value of the projection lens, which is considered to be the largest restriction in developing a small projector device. Currently, in the DMD, when the image is generated, the turning angle to represent ON and OFF of the micromirror is ± 12 °, which enables effective reflected light (effective light) and invalid reflected light (ineffective light). ). Therefore, in a projector apparatus using a DMD as a light valve, it is necessary to capture effective light and not to catch invalid light. From this condition, the F value of the projection lens can be derived, that is, F = 2. 4 Actually, there is a demand for capturing a light amount as much as possible, and therefore, a smaller F value is often required 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, the amount of light Since loss or the like occurs, it is generally necessary to consider such as optimizing the pupil position at the wide-angle end where brightness tends to be a problem. The second restriction relates to the arrangement 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. In order to input effective light from the DMD to the projection lens, the light source system is installed in substantially the same direction (adjacent) as the projection lens. In addition, the projection lens and the light source system are used between the light valve side lens of the projection lens and the light valve (in general, the back focus), and the projection lens has a large back. In addition to providing a focus, 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 is a constraint that the pupil position on the light valve side is located 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, and if a large number of lenses are arranged, the total length of the projection lens needs to be a certain length. If the total length of the lens is increased, the lens having the entrance pupil position on the rear side becomes a problem contrary to the size reduction in which the front lens diameter is naturally increased.

  In this way, although there are major restrictions on development, a projector device that employs DMD as a light valve is advantageous over other methods in terms of miniaturization, and is now convenient for presentations. Portable portable compact projectors have become widespread, centering on new data projectors. In addition, in order to make the device itself compact, it is natural that there is a strong demand for miniaturization of the projection lens used, and on the other hand, there is also a demand for multi-function, and correction of various aberrations. In addition to satisfying the specifications of the DMD used as a result of the image quality performance as a result of the above, not only zooming is possible in terms of convenience, but the center of the DMD and the optical axis of the projection lens are In order to adopt a shifted so-called shift configuration, a lens with a large image circle is required, and a lens with a large angle of view at the wide-angle end and a lens with a large zoom ratio have been required. . In the projection lens developed with such specifications, the aperture of the front lens group tends to be larger than desired, which greatly affects the thickness of the projector device. However, it is important to reduce the thickness of a projector device that is assumed to be portable, and it is the most important factor for projector devices that are often used with laptop personal computers. It can also be said. As a means for solving this problem, there is an example of a compact design method for a projection lens. (For example, refer to Patent Document 1).

JP 2004-271668 A

  In the technique described in the above-mentioned technical document 1, when the 0.7-inch DMD is used, the effective diameter of the front lens is 39 mm to 42 mm, and at least the thickness of the projector device cannot be 50 mm or less. When this thickness is actually carried with a notebook type personal computer or the like, the thickness is still unsatisfactory.

  In view of the above-described circumstances, the present invention is suitable for the characteristics of a light valve that forms an image by changing the reflection direction of light, such as DMD, and enlarges and projects an image from the light valve on a screen or other wall surface. A compact zoom lens with high imaging performance and a small lens aperture in applications, is compact and bright, and has a high image quality that can project a large screen even in a limited space such as a small conference room. An object of the present invention is to provide a projector device.

According to the first aspect of the present invention, in order from the magnification side, the first lens group having a negative refractive power as a whole, the second lens group having a positive refractive power as a whole, and the third lens having a positive refractive power as a whole The first lens group includes four lenses, a negative meniscus lens having a negative refractive power, a negative lens, a negative lens, and a lens having a positive refractive power in order from the magnifying side. The second lens group is configured by arranging five lenses of a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens in order from the magnification side, and the third lens group includes: A zoom lens capable of zooming comprising a single positive lens, wherein the third lens group is fixed during zooming operation, and the first lens group is enlarged from the wide-angle end to the middle range. From the side to the reduction side, and from the middle range to the telephoto end, the reduction side The second lens unit is zoomed from the wide-angle end to the telephoto end, moving from the reduction side to the enlargement side, and zooming the entire lens system. The following conditional expression (1) is satisfied with respect to the distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens group at the wide angle end to the in-focus position, and the second condition at the wide angle end is satisfied. The following conditional expression (2) is satisfied with respect to the positional relationship between the lens group and the third lens group, and the following conditional expression (3) is satisfied with respect to the magnification at the wide angle end of the second lens group. A compact zoom lens that satisfies the following conditional expression (4) with respect to the power of one lens group and satisfies the following conditional expression (5) with respect to the magnification at the telephoto end of the second lens group. is there.
(1) 7.0 <TL / _fw <10.0
(2) 1.8 < _dIIw / _fw <2.5
(3) −1.0 <m _{II w} <−0.5
_{(4) -1.0 <f w /} f I <-0.55
(5) 1.4 <m _{II T} / m _{II w} <2.8
However,
TL: Distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens unit at the wide angle end to the in-focus position (according to the magnifying side object distance of 1700 mm from the magnifying side most of the first lens unit) Out of focus)
f _w : Combined focal length of the entire lens system at the wide-angle end (focused state on the enlargement side object distance of 1700 mm from the most enlargement side surface of the first lens group)
d _{II w} : Air distance between the second lens group and the third lens group at the wide angle end f _I : Composite focal length m _{II w} of the first lens group m 2 _T : Magnification m _{II T} of the second lens group at the wide angle end Magnification of the second lens group at the end

According to a second aspect of the present invention, in the compact zoom lens according to the first aspect, the following conditional expression (6) is satisfied with respect to the dimension on the optical axis of the first lens group, and the first lens group The following conditional expression (7) is satisfied with respect to the power of the lens arranged closest to the enlargement side, and the following conditional expression (8) is satisfied with respect to the shape of the reduction side surface of the lens arranged closest to the enlargement side in the first lens group. The following conditional expression (9) is satisfied with respect to the dispersion characteristics of the glass material used for each lens constituting the first lens group.
_{(6) 1.4 <L I /} f w <2.2
_{(7) -0.8 <f w /} f 1 <-0.2
_{(8) 0.9 <f w /} r 2 <1.4
(9) 25 <(V ₁ + V ₂ + V ₃ ) / 3−V ₄
However,
L _I : Distance f ₁ on the optical axis between the enlargement side surface of the lens arranged closest to the enlargement side in the first lens group and the reduction side surface of the lens arranged closest to the reduction side in the first lens group f ₁ : first lens group The focal length r _{2 of} the lens arranged closest to the magnification side: radius of curvature V ₁ of the reduction side of the lens arranged closest to the magnification side in the first lens group V ₁ : negative arranged closest to the magnification side in the first lens group Lens Abbe number V ₂ : Abbe number V _{3 of the} negative lens arranged on the second lens from the magnification side in the first lens group V ₃ : Abbe number of the negative lens arranged on the _third lens from the magnification side in the first lens group V ₄ : Abbe number of the positive lens arranged closest to the reduction side in the first lens group

According to a third aspect of the present invention, in the compact zoom lens according to the first and second aspects, the focusing operation is achieved by moving the first lens group in the optical axis direction, and the first lens group is configured. Conditional expression (10) is satisfied with respect to the second lens disposed in the first lens group, and at least one surface of the second lens disposed in the first lens group is aspherical. It is characterized by that.
(10) −0.25 <f _w / f ₂
However,
f ₂ : Focal length of the second lens from the magnification side in the first lens group

According to a fourth aspect of the present invention, in the compact zoom lens according to the first aspect, the second lens group includes five lenses of a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens in order from the magnification side. In addition, the following conditional expression (11) is satisfied with respect to the shape of the magnifying side of the lens that is arranged closest to the magnifying side among the lens groups that constitute the second lens group, and the five lenses that constitute the second lens group. The following conditional expression (12) is satisfied with respect to the dispersion characteristic of the glass material used for each lens, and the following conditional expression (13) is satisfied with respect to the dispersion characteristic of the glass material arranged on the most reduction side of the second lens group. It is characterized by.
_{(11) 0.2 <f w /} r II 1 <0.4
_{(12) 25 <(V 5} + V 7 + V 9) / 3- (V 6 + V 8) / 2
(13) 69 <V ₉
However,
r _{II 1} : radius of curvature V ₅ of the magnifying side surface of the lens arranged closest to the magnifying side of the second lens group V ₅ : Abbe number V _{6 of the} positive lens arranged maximally on the magnifying side of the second lens group In the second lens group, the Abbe number V _{7 of} the second lens arranged from the magnifying side: The Abbe number V _{8 of the} positive lens arranged third from the magnifying side in the second lens group: From the magnifying side in the second lens group Abbe number V _{9 of the} negative lens arranged in the fourth lens: Abbe number of the positive lens arranged closest to the reduction side in the second lens group

According to a fifth aspect of the present invention, in the compact zoom lens according to the fourth aspect of the present invention, the surface on the magnification side of the fourth lens arranged from the magnification side of the second lens group is an aspherical surface, and the lens The following conditional expression (14) is satisfied with respect to the power of the lens, and the following conditional expression (15) is satisfied with respect to the shape of the reduction-side surface of the lens disposed on the most reduction side of the second lens group. It is characterized by.
_{(14) -0.8 <f w /} f 8 <-0.3
(15) −0.2 <f _w / r _{II 10} <−0.4
However,
f ₈ : Focal length r _{II 10 of the} lens arranged on the fourth lens from the magnification side of the second lens group, radius of curvature of the reduction side surface of the lens arranged closest to the reduction surface of the second lens group

  A sixth aspect of the present invention is a projector device including the compact zoom lens according to at least one of the first to fifth aspects.

  According to the present invention, a compact zoom lens with high imaging performance suitable for the characteristics of a light valve such as DMD can be realized, and a compact, bright and high-quality projector can be provided.

The zoom lens of the present invention includes, in order from the magnification side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole. The first lens group includes four lenses of a meniscus lens having a negative refractive power convex to the enlargement side, a negative lens negative lens, and a lens having a positive refractive power in order from the enlargement side. The second lens group is composed of five lenses, a positive lens, a positive lens, a negative lens, a positive lens and a convex meniscus negative lens on the enlargement side in order from the enlargement side. The third lens group is a zoom lens capable of zooming comprising a single positive lens, and the third lens group is fixed during zooming operation, and the first lens group is From the wide-angle end to the middle range, from the enlargement side to the reduction side direction, From the intermediate region to the telephoto end, the lens moves on the optical axis from the reduction side to the enlargement side, and the second lens group moves from the wide angle end to the telephoto end on the optical axis from the reduction side to the enlargement side. The entire system is zoomed, and the following conditional expression (1) is satisfied with respect to the distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens unit at the wide angle end to the in-focus position. The following conditional expression (2) is satisfied regarding the positional relationship between the second lens group and the third lens group at the wide-angle end, and the following conditional expression regarding the magnification at the wide-angle end of the second lens group ( 3) is satisfied, the following conditional expression (4) is satisfied regarding the power of the first lens group, and the following conditional expression (5) is satisfied regarding the magnification at the telephoto end of the second lens group. It is characterized by that.
(1) 7.0 <TL / _fw <10.0
(2) 1.8 < _dIIw / _fw <2.5
(3) −1.0 <m _{II w} <−0.5
_{(4) -1.0 <f w /} f I <-0.55
(5) 1.4 <m _{II T} / m _{II w} <2.8
However,
TL: Distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens unit at the wide angle end to the in-focus position (according to the magnifying side object distance of 1700 mm from the magnifying side most of the first lens unit) Out of focus)
f _w : Combined focal length of the entire lens system at the wide-angle end (focused state on the enlargement side object distance of 1700 mm from the most enlargement side surface of the first lens group)
d _{II w} : Air distance between the second lens group and the third lens group at the wide angle end f _I : Composite focal length of the first lens group at the wide angle end (magnification side object distance from the most magnifying side of the first lens group) Focused on 1700mm)
m _{II w} : magnification of the second lens group at the wide angle end m _{II T} : magnification of the second lens group at the telephoto end

  Conditional expression (1) is a condition of the distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens group at the wide-angle end to the in-focus position, and is a condition for reducing the size and diameter. . If the upper limit is exceeded, the distance from the magnifying side of the lens arranged closest to the magnifying side in the first lens group at the wide-angle end to the in-focus position becomes large, and the lens becomes a large aperture, which impairs the reduction in size and size. If the lower limit is exceeded, it becomes difficult to balance various aberrations.

  Conditional expression (2) is an interval condition at the wide-angle end of the second lens group and the third lens group. As described above, it is necessary to secure this space because of the space of the illumination system of the light valve. If the upper limit is exceeded, the space for the illumination system can be secured, but the lens becomes larger, and if the upper limit is exceeded, the space for the illumination system is insufficient and design becomes difficult.

  Conditional expression (3) corresponds to the magnification of the second lens group, and is a condition for reducing the size of the entire lens system over the zooming range. If the lower limit is exceeded, the total length at the reduction magnification becomes longer, and if the upper limit is exceeded, enlargement occurs. The total length at the magnification becomes longer.

  Conditional expression (4) is a condition regarding the power of the first lens group. The first lens group has a strong negative power and has a purpose of securing a space for arranging an optical system for illuminating a light valve such as a DMD in an air space portion between the second lens group and the third lens group. ing. When the upper limit is exceeded, the negative power of the first lens group becomes small, and it becomes difficult to secure the air gap between the second lens group and the third lens group. When the upper limit is exceeded, the negative power increases and the second power increases. The positive power of the lens group must be strengthened, making it difficult to balance various aberrations.

Conditional expression (5) is a conditional expression regarding the magnification at the wide-angle end of the second lens group and the magnification at the telephoto end of the second lens group, and corresponds to the variable magnification of the zoom lens system. If the upper limit is exceeded, a lens system with a large zoom ratio can be obtained, but the amount of movement of the second lens group increases and the size of the second lens group increases, and the fluctuation in performance also increases. However, the zoom ratio itself becomes small, and the small and high zoom lens according to the present invention cannot be obtained.
In the first lens group, the following conditional expression (6) is satisfied with respect to the dimension on the optical axis of the first lens group, and the following conditional expression (7) is satisfied with respect to the power of the lens arranged on the most magnified side. The following conditional expression (8) is satisfied with respect to the shape of the reduction side surface of the lens arranged closest to the magnification side in the first lens group, and the dispersion characteristics of the glass material used for each lens constituting the first lens group: It is preferable that the following conditional expression (9) is satisfied.
_{(6) 1.4 <L I /} f w <2.2
_{(7) -0.8 <f w /} f 1 <-0.2
_{(8) 0.9 <f w /} r 2 <1.4
(9) 25 <(V ₁ + V ₂ + V ₃ ) / 3−V ₄
However,
L _I : Distance f ₁ on the optical axis between the enlargement side surface of the lens arranged closest to the enlargement side in the first lens group and the reduction side surface of the lens arranged closest to the reduction side in the first lens group f ₁ : first lens group The focal length r _{2 of} the lens arranged closest to the magnification side: radius of curvature V ₁ of the reduction side of the lens arranged closest to the magnification side in the first lens group V ₁ : negative arranged closest to the magnification side in the first lens group Lens Abbe number V ₂ : Abbe number V _{3 of the} negative lens arranged on the second lens from the magnification side in the first lens group V ₃ : Abbe number of the negative lens arranged on the _third lens from the magnification side in the first lens group V ₄ : Abbe number of the positive lens arranged closest to the reduction side in the first lens group

Conditional expression (6) is a conditional expression related to the dimension on the optical axis of the first lens group, and is a condition for correcting various aberrations with a small number of lenses.
In order to increase the length corresponding to the back focus between the second lens group and the third lens group, it is particularly effective to increase the negative power of the lens arranged closest to the enlargement side in the first lens group. However, when the negative power is excessive, it is difficult to correct various aberrations. This can be solved by increasing the distance on the optical axis of the first lens group, or by increasing the number of lenses in order to disperse the negative power of the first lens group. The first lens group has to be long to some extent. If the upper limit of conditional expression (6) is exceeded, the dimension in the optical axis direction becomes too large and it is difficult to satisfy the specifications, and there is no point in downsizing, and if the lower limit is exceeded, it is difficult to reduce the aperture.

  Conditional expression (7) is a condition regarding the power of the lens arranged closest to the magnification side of the first lens group, and increases the negative power of the lens arranged closest to the magnification side of the first lens group as described above. This is effective for ensuring the air space between the second lens unit and the third lens unit at the wide-angle end and reducing the size. However, if the upper limit of conditional expression (7) is exceeded, the negative power of the lens increases. Chromatic aberration and curvature of field occur, making it difficult to correct the aberration. If the lower limit is exceeded, the negative power of the lens becomes weak, and a portion corresponding to the back focus between the second lens group and the third lens group is made long. Becomes difficult.

Conditional expression (8) is a conditional expression for correcting distortion and coma aberration of the entire lens system.
This relates to the shape of the lens on the reduction side of the lens arranged closest to the magnifying side of the first lens group. While giving a strong power, the shape is substantially concentric with the light beam on the magnifying side. The shape is suppressed. Therefore, when the upper limit is exceeded, spherical aberration and coma aberration are undercorrected, and when the lower limit is exceeded, overcorrection is conversely performed.

Conditional expression (9) is a condition for correcting chromatic aberration in the first lens group. In order to correct the monochromatic aberration, it is necessary that the power of each lens does not become excessive. To that end, it is necessary that the Abbe numbers of the positive lens and the negative lens satisfy the conditional expression (9). When the lower limit is exceeded, it becomes difficult to correct chromatic aberration.
The focusing operation is achieved by moving the first lens group in the direction of the optical axis, and a conditional expression regarding the second lens from the magnifying side in the first lens group constituting the first lens group. (10) is satisfied, and it is preferable that at least one surface of the second lens disposed in the first lens group has an aspherical shape.
(10) −0.25 <f _w / f ₂
However,
f ₂ : Focal length of the second lens arranged from the magnification side in the first lens group As described above, increasing the negative power of the lens arranged closest to the magnification side in the first lens group is a wide angle. The air gap between the second lens group and the third lens group at the end is ensured and effective for miniaturization. However, since it is difficult to correct various aberrations including curvature of field in the spherical shape, the first lens By using an aspherical lens having weak negative power that satisfies the conditional expression (10) as the second lens arranged from the magnification side of the group, various aberrations including field curvature can be corrected.

Setting a weak negative power that satisfies the conditional expression (10) can use a plastic material, which is a glass material having a low refractive index, and thus can reduce weight and cost.
The second lens group is composed of five lenses of a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens in order from the magnifying side, and is arranged on the most magnifying side among the lens groups constituting the second lens group. The following conditional expression (11) is satisfied with respect to the shape on the magnification side of the lens, and the following conditional expression (12) is satisfied with respect to the dispersion characteristics of the glass material used for each of the five lenses constituting the second lens group. It is preferable that the following conditional expression (13) is satisfied with respect to the dispersion characteristics of the lens arranged closest to the reduction side of the second lens group.
_{(11) 0.2 <f w /} r II 1 <0.4
_{(12) 25 <(V 5} + V 7 + V 9) / 3- (V 6 + V 8) / 2
(13) 69 <V ₉
However,
r _{II 1} : radius of curvature V ₅ of the magnifying side surface of the lens arranged closest to the magnifying side of the second lens group V ₅ : Abbe number V _{6 of the} positive lens arranged maximally on the magnifying side of the second lens group In the second lens group, the Abbe number V _{7 of} the second lens arranged from the magnifying side: The Abbe number V _{8 of the} positive lens arranged third from the magnifying side in the second lens group: From the magnifying side in the second lens group Abbe number V _{9 of the} negative lens arranged in the fourth lens: Abbe number of the positive lens arranged closest to the reduction side in the second lens group

  Conditional expression (11) is a conditional expression related to the shape of the magnifying side surface of the positive lens arranged closest to the magnifying side of the second lens group. The lens arranged on the magnifying side in the second lens group needs to be a lens having a strong positive power for guiding the divergent light beam emitted from the first lens group to a converged state. In order to generate chromatic aberration, it is necessary to have a shape that allows aberration correction with the second and subsequent lenses of the second lens group. When the upper limit of conditional expression (11) is exceeded, the surface power increases and under spherical aberration increases, and when the lower limit is exceeded, the surface power decreases and over spherical aberration increases, making correction difficult.

  Conditional expression (12) is a condition for correcting chromatic aberration in the second lens group. In order to correct the monochromatic aberration, it is necessary that the power of each lens does not become excessive. To that end, it is necessary that the Abbe numbers of the positive lens and the negative lens satisfy the conditional expression (12). When the lower limit is exceeded, it becomes difficult to correct chromatic aberration.

Conditional expression (13) is a condition for correcting the lateral chromatic aberration. Since the second lens group has a strong positive power, it has a great influence on the lateral chromatic aberration. In particular, the influence of the positive lens arranged closest to the reduction side having the strongest positive power in the second lens group is large, and if the lower limit of conditional expression (13) is exceeded, aberration correction becomes difficult.
The surface on the magnification side of the fourth lens from the magnification side of the second lens group is an aspherical surface, and satisfies the following conditional expression (14) regarding the power of the lens, and the second lens It is preferable that the following conditional expression (15) is satisfied with respect to the shape of the surface on the reduction side of the lens disposed on the most reduction side of the group.
_{(14) -0.8 <f w /} f 8 <-0.3
(15) −0.2 <f _w / r _{II 10} <−0.4
However,
f ₈ : Focal length r _{II 10 of the} lens arranged on the fourth lens from the magnification side of the second lens group, radius of curvature of the reduction side surface of the lens arranged closest to the reduction surface of the second lens group

  Conditional expression (14) is a condition for correcting the divergent light beam from the first lens group, ensuring a large aperture ratio, and correcting spherical aberration and coma aberration. The second lens group has a strong positive power for guiding the diverging beam bundle exiting the first lens group into a focused state, and various aberrations such as spherical aberration occur. The lenses constituting the second lens group are three lenses, a positive lens, a negative lens, and a positive lens from the magnifying surface side, and various aberrations are corrected as a triplet structure, but the positive power of the second lens group is strong. Therefore, the aberration correction becomes insufficient, so that the aberration correction is made possible by disposing a negative lens on the reduction side of the triplet configuration lens. When the upper limit of conditional expression (14) is exceeded, under spherical aberration increases, and when the lower limit is exceeded, over spherical aberration increases, resulting in significant coma in the periphery, making it difficult to correct aberrations. The spherical shape may result in insufficient aberration correction, but the large lens diameter ratio of the entire lens system is ensured by making the magnifying side of the lens arranged on the fourth lens from the magnifying side of the second lens group aspherical. In addition, it is possible to reduce the diameter of the entire lens system and correct spherical aberration and the like.

Conditional expression (15) is a conditional expression for finely correcting spherical aberration and coma aberration in the entire lens system. From the enlarged side surface of the second lens group, the remaining four spherical aberrations and coma aberration are corrected by the four lenses. When the upper limit is exceeded, the correction is insufficient, and when the lower limit is exceeded, the correction is excessive.
Thus, by mounting the compact zoom lens according to the present invention on the projector device, the entire device can be reduced in size, and a thin projector device that is convenient for carrying can be provided.

  Hereinafter, the present invention will be described with respect to specific numerical examples. In the following compact zoom lenses of the first to fourth embodiments, in order from the magnification side, a first lens group LG1 having a negative refractive power as a whole, a second lens group LG2 having a negative refractive power as a whole, and The first lens group LG1 is composed of a third lens group LG3 having a positive refractive power as a whole. The first lens group LG1 has a negative meniscus lens having a negative refractive power convex to the enlargement side in order from the enlargement side (lens name L11, Enlarged side surface 101, reduced side surface 102) (hereinafter negative lens), negative lens (lens name L12, enlarged side surface 103, reduced side surface 104), negative lens (lens name L13, enlarged side surface 105, reduced side surface 106), and positive refractive power (Lens name L14, enlargement side surface 107, reduction side surface 108) (hereinafter referred to as a positive lens), and the second lens group LG2 includes three positive lenses and two lenses. The third lens group includes five lenses including a negative lens (lens names are L21, L22,... In order from the enlargement side, and surface names are 201, 202, etc. in order from the enlargement side). LG3 is configured by arranging one positive lens (the lens name is L31, the name of the enlarged side surface is 301, and the name of the reduced side surface is 302). In addition, a cover glass CG (C01 is an enlarged side surface and C02 is a reduced side surface) which is a component of a light valve such as a DMD with a slight air gap between the reduced side of the third lens group LG34 and the light valve surface. ) Is arranged. The third lens group LG3 is fixed during zooming operation, and the first lens group LG1 is enlarged from the wide-angle end to the intermediate area from the enlargement side to the reduction side, and from the intermediate area to the telephoto end is enlarged from the reduction side. The second lens unit LG2 moves on the optical axis in the lateral direction, and the entire lens system is zoomed by moving on the optical axis from the reduction side to the enlargement side from the wide-angle end to the telephoto end.

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 回 り around the optical axis, giving a paraxial radius of curvature: r, conic constant: K, and higher order aspherical coefficients: A, B, C, D, etc. Define 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.

[Example 1]
Table 1 shows numerical examples of the first embodiment of the compact 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 is the focal length of the zoom lens system, F _no is the F-number, 2 [omega a total angle of view of the zoom lens. Further, r is a radius of curvature, d is a lens thickness or a lens interval, n _d is a refractive index with respect to the d line, and ν _d is an Abbe number of the d line (however, a numerical value that changes due to the focusing operation in the table is 101 plane) The numerical value in the in-focus state with the object distance from 1700 mm). CA1, CA2, and CA3 in the spherical aberration diagrams in the various aberration diagrams are aberration curves at wavelengths of CA1 = 550.0 nm, CA2 = 450.0 nm, and CA3 = 620.0 nm, respectively. In the astigmatism diagram, S indicates sagittal and M indicates meridional. In addition, unless otherwise specified throughout, the wavelength used for calculation of various values is CA1 = 550.0 nm.

[Example 2]
Table 2 shows numerical examples of the second embodiment of the compact zoom lens according to the present invention. FIG. 3 is a diagram showing the lens configuration, and FIG. 4 is a diagram showing various aberrations thereof.

[Example 3]
Table 3 shows numerical examples of the third embodiment of the compact zoom lens according to the present invention. FIG. 5 is a diagram showing the lens configuration, and FIG. 6 is a diagram showing various aberrations.

  Next, Table 4 collectively shows values corresponding to the conditional expressions (1) to (14) with respect to the first to third embodiments.

  As is apparent from Table 4, the numerical values for the first to fourth embodiments satisfy the conditional expressions (1) to (14) and are also apparent from the aberration diagrams in the respective embodiments. Thus, each aberration is corrected well.

1 is a lens configuration diagram of a first embodiment of a compact zoom lens according to the present invention. Various aberration diagrams of the lens of the first example Lens configuration diagram of a second embodiment of a compact zoom lens according to the present invention Various aberration diagrams of the lens of the second example Lens configuration diagram of a third embodiment of a compact zoom lens according to the present invention Various aberration diagrams of the lens of the third example

Claims (6)

The first lens group having a negative refractive power as a whole, the second lens group having a positive refractive power as a whole, and the third lens group having a positive refractive power as a whole in order from the magnification side, The lens group includes four lenses, a meniscus lens having a convex negative meniscus shape on the magnifying side, a negative lens, a negative lens, and a lens having a positive refracting power. The two lens group is composed of five lenses, a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens in order from the enlargement side, and the third lens group includes one positive lens. The zoom lens is configured to be zoomed, and the third lens group is fixed during zooming operation, and the first lens group extends from the wide-angle end to the intermediate range from the enlargement side to the reduction side direction, and On the optical axis from the reduction side to the enlargement side from the intermediate range to the telephoto end The second lens group moves on the optical axis from the reduction side to the enlargement side direction from the wide-angle end to the telephoto end, thereby changing the magnification of the entire lens system. The following conditional expression (1) is satisfied regarding the distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side to the in-focus position, and the second lens group and the third lens group at the wide-angle end are The following conditional expression (2) is satisfied with respect to the positional relationship, the following conditional expression (3) is satisfied with respect to the magnification at the wide-angle end of the second lens group, and the following conditional expression is satisfied with respect to the power of the first lens group: A compact zoom lens that satisfies (4) and satisfies the following conditional expression (5) with respect to the magnification at the telephoto end of the second lens group.
(1) 7.0 <TL / _fw <10.0
(2) 1.8 < _dIIw / _fw <2.5
(3) −1.0 <m _{II w} <−0.5
_{(4) -1.0 <f w /} f I <-0.55
(5) 1.4 <m _{II T} / m _{II w} <2.8
However,
TL: Distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens unit at the wide angle end to the in-focus position (according to the magnifying side object distance of 1700 mm from the magnifying side most of the first lens unit) Out of focus)
f _w : Combined focal length of the entire lens system at the wide-angle end (focused state on the enlargement side object distance of 1700 mm from the most enlargement side surface of the first lens group)
d _{II w} : Air distance between the second lens group and the third lens group at the wide angle end f _I : Composite focal length m _{II w} of the first lens group m 2 _T : Magnification m _{II T} of the second lens group at the wide angle end Magnification of the second lens group at the end 2. The compact zoom lens according to claim 1, wherein the following conditional expression (6) is satisfied with respect to the dimension on the optical axis of the first lens group, and the first lens group is arranged on the most magnified side. The following conditional expression (7) is satisfied with respect to the power of the lens, and the following conditional expression (8) is satisfied with respect to the shape of the reduction side surface of the lens disposed on the most magnifying side in the first lens group. It is characterized in that the following conditional expression (9) is satisfied with respect to the dispersion characteristics of the glass material used for each lens constituting one lens group.
_{(6) 1.4 <L I /} f w <2.2
_{(7) -0.8 <f w /} f 1 <-0.2
_{(8) 0.9 <f w /} r 2 <1.4
(9) 25 <(V ₁ + V ₂ + V ₃ ) / 3−V ₄
However,
L _I : Distance f ₁ on the optical axis between the enlargement side surface of the lens arranged closest to the enlargement side in the first lens group and the reduction side surface of the lens arranged closest to the reduction side in the first lens group f ₁ : first lens group The focal length r _{2 of} the lens arranged closest to the magnification side: radius of curvature V ₁ of the reduction side of the lens arranged closest to the magnification side in the first lens group V ₁ : negative arranged closest to the magnification side in the first lens group Lens Abbe number V ₂ : Abbe number V _{3 of the} negative lens arranged on the second lens from the magnification side in the first lens group V ₃ : Abbe number of the negative lens arranged on the _third lens from the magnification side in the first lens group V ₄ : Abbe number of the positive lens arranged closest to the reduction side in the first lens group 3. The compact zoom lens according to claim 1, wherein a focusing operation is achieved by moving the first lens group in an optical axis direction, and 2 in the first lens group constituting the first lens group. Conditional expression (10) is satisfied with respect to the lens arranged on the first sheet, and at least one surface of the second lens arranged in the first lens group is aspherical.
(10) −0.25 <f _w / f ₂
However,
f ₂ : Focal length of the second lens from the magnification side in the first lens group 2. The compact zoom lens according to claim 1, wherein the second lens group includes five lenses of a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens in order from the magnification side. The following conditional expression (11) is satisfied with respect to the shape of the magnifying side of the lens arranged closest to the magnifying side in the constituting lens group, and the glass material used for each of the five lenses constituting the second lens group The following conditional expression (12) is satisfied with respect to the dispersion characteristics, and the following conditional expression (13) is satisfied with respect to the dispersion characteristics of the glass material disposed on the most reduction side of the second lens group.
_{(11) 0.2 <f w /} r II 1 <0.4
_{(12) 25 <(V 5} + V 7 + V 9) / 3- (V 6 + V 8) / 2
(13) 69 <V ₉
However,
r _{II 1} : radius of curvature V ₅ of the magnifying side surface of the lens arranged closest to the magnifying side of the second lens group V ₅ : Abbe number V _{6 of the} positive lens arranged maximally on the magnifying side of the second lens group In the second lens group, the Abbe number V _{7 of} the second lens arranged from the magnifying side: The Abbe number V _{8 of the} positive lens arranged third from the magnifying side in the second lens group: From the magnifying side in the second lens group Abbe number V _{9 of the} negative lens arranged in the fourth lens: Abbe number of the positive lens arranged closest to the reduction side in the second lens group 5. The compact zoom lens according to claim 4, wherein a surface on the enlargement side of the lens disposed on the fourth lens from the enlargement side of the second lens group is an aspherical surface, and the following conditional expression ( 14), and the following conditional expression (15) is satisfied with respect to the shape of the reduction side surface of the lens arranged closest to the reduction side of the second lens group.
_{(14) -0.8 <f w /} f 8 <-0.3
(15) −0.2 <f _w / r _{II 10} <−0.4
However,
f ₈ : Focal length r _{II 10 of the} lens arranged on the fourth lens from the magnification side of the second lens group, radius of curvature of the reduction side surface of the lens arranged closest to the reduction surface of the second lens group   A projector device comprising the compact zoom lens according to claim 1 mounted thereon.

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