Zoom lens, projection display device, and image capturing device

Abstract

To provide a high-performance zoom lens which offers a wide angle of view, a high zoom ratio and compactness, and nicely suppresses variation in aberrations while zooming and focusing, and to provide a projection display device having such zoom lens, and an image capturing device having such zoom lens.SOLUTION: A zoom lens is provided, consisting of a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, an intermediate group comprising one or more lens groups, and a final lens group having positive refractive power, arranged in order from the magnification side to the reduction side. The first lens group consists of a 1A sub-group having negative refractive power, a 1B sub-group, and a 1C sub-group arranged in order from the magnification side to the reduction side. Distances between the 1B sub-group and adjacent sub-groups change while focusing. A distance between the second lens group and the third lens group is shorter at the telephoto end than at the wide-angle end.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology of the present disclosure relates to a zoom lens, a projection display device, and an imaging device.

Background Art

[0002] Patent Documents 1 and 2 below describe an optical system applicable to an image projection device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a demand for a zoom lens that has a wide angle, a high magnification ratio, is compactly configured, has good suppression of aberration variation during zooming and focusing, and has high optical performance. These required levels are increasing year by year.

[0005] The present disclosure provides a zoom lens that has a wide angle, a high magnification ratio, is compactly configured, has good suppression of aberration variation during zooming and focusing, and has high optical performance, a projection display device including this zoom lens, and an imaging device including this zoom lens.

Means for Solving the Problems

[0006] One aspect of the present disclosure is a zoom lens, which comprises, in order from the telephoto side to the wide-angle side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, an intermediate group including one or more lens groups, and a final lens group having a positive refractive power. The first lens group comprises, in order from the telephoto side to the wide-angle side, a first A subgroup having a negative refractive power, a first B subgroup, and a first C subgroup. During focusing, the distance between the first A subgroup and the first B subgroup changes, and the distance between the first B subgroup and the first C subgroup changes. During zooming, the first lens group and the final lens group are stationary, and the second lens group, the third lens group, the fourth lens group, and all the lens groups within the intermediate group change the distance in the optical axis direction from the adjacent lens groups and move along the optical axis. The distance between the second lens group and the third lens group at the telephoto end is shorter than the distance between the second lens group and the third lens group at the wide-angle end.

[0007] When the distance between the second lens group and the third lens group at the telephoto end is D23t and the distance between the second lens group and the third lens group at the wide-angle end is D23w, the zoom lens of the above aspect satisfies the conditional expression (1) represented by D23t / D23w < 1 (1) preferably.

[0008] When the combined lateral magnification of the second lens group and the third lens group at the telephoto end is β23t and the combined lateral magnification of the second lens group and the third lens group at the wide-angle end is β23w, the zoom lens of the above aspect satisfies the conditional expression (2) represented by 1.4 < β23t / β23w < 3 (2) preferably.

[0009] When the focal length of the fourth lens group is fG4 and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect satisfies the conditional expression (3) represented by -15 < fG4 / fw < -1 (3) preferably.

[0010] When the focal length of the first A subgroup is fG1A and the focal length of the first C subgroup is fG1C, the zoom lens of the above aspect is -0.5 < fG1A / fG1C < 0.5 (4) Preferably, the conditional expression (4) represented by is satisfied.

[0011] When the focal length of the first A subgroup is fG1A and the focal length of the first B subgroup is fG1B, the zoom lens of the above aspect is 0 < |fG1A / fG1B| < 0.3 (5) Preferably, the conditional expression (5) represented by is satisfied.

[0012] When the focal length of the first lens group is fG1 and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect is -4 < fG1 / fw < -1 (6) Preferably, the conditional expression (6) represented by is satisfied.

[0013] During focusing, the first C subgroup may be configured to be stationary.

[0014] In a configuration where the first C subgroup includes at least one negative lens, when the average value of the Abbe numbers of all the negative lenses included in the first C subgroup with respect to the d line is νave, the zoom lens of the above aspect is νave > 50 (7) Preferably, the conditional expression (7) represented by is satisfied.

[0015] Preferably, the zoom lens of the above aspect is telecentric on the reduction side.

[0016] When the focal length of the second lens group is fG2 and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect is 2 < fG2 / fw < 10 (8) Preferably, the conditional expression (8) represented by is satisfied.

[0017] When the focal length of the third lens group is fG3 and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect satisfies: 4 < fG3 / fw < 12 (9) It is preferable to satisfy the conditional expression (9) represented by.

[0018] When the focal length of the final lens group is fGE and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect satisfies: 3 < fGE / fw < 8 (10) It is preferable to satisfy the conditional expression (10) represented by.

[0019] When the back focus on the reduction side in terms of the air equivalent distance of the zoom lens is Bf and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect satisfies: 2 < Bf / fw (11) It is preferable to satisfy the conditional expression (11) represented by.

[0020] It is preferable that the intermediate group includes, on the reduction side in order from the magnification side, a cemented lens in which a negative lens and a positive lens are cemented, at the most reduction side.

[0021] The first C subgroup may be configured to include, in order from the magnification side to the reduction side, a negative lens and a positive lens.

[0022] Another aspect of the present disclosure is a projection display device including the zoom lens of the above aspect.

[0023] Still another aspect of the present disclosure is an imaging device including the zoom lens of the above aspect.

[0024] In this specification, "consisting of" and "comprising" are intended to include, in addition to the recited components, lenses having substantially no refractive power, optical elements other than lenses such as diaphragms, masks, filters, cover glasses, plane mirrors, and prisms, and mechanical parts such as lens flanges, lens barrels, imaging elements, and shake correction mechanisms.

[0025] The "group having positive refractive power" in this specification means having positive refractive power as a whole group. Similarly, the "group having negative refractive power" means having negative refractive power as a whole group. The "lens having positive refractive power" and the "positive lens" are synonymous. The "lens having negative refractive power" and the "negative lens" are synonymous. The "~lens group" and the "focusing group" in this specification are not limited to a configuration consisting of a plurality of lenses, and may also be a configuration consisting of only one lens.

[0026] A compound aspherical lens (a lens in which a lens (e.g., a spherical lens) and an aspherical film formed on the spherical lens are integrally configured and function as one aspherical lens as a whole) is not regarded as a cemented lens and is treated as one lens. For the sign of the refractive power of a lens including an aspherical surface, unless otherwise specified, the value in the paraxial region is used. The "focal length" used in the conditional expression is the paraxial focal length. The values used in the conditional expression are values based on the d-line.

[0027] The "d-line", "C-line", and "F-line" described in this specification are spectral lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line is treated as 656.27 nm (nanometers), and the wavelength of the F-line is treated as 486.13 nm (nanometers).

Advantages of the Invention

[0028] According to the present disclosure, it is possible to provide a zoom lens having a wide angle, a high magnification ratio, a compact configuration, excellent suppression of aberration variation during zooming and focusing, and high optical performance, a projection display device including this zoom lens, and an imaging device including this zoom lens.

Brief Description of the Drawings

[0029]

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Embodiments for Carrying Out the Invention

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0031] FIG. 1 shows the configuration of a zoom lens, a cross-sectional view of a light beam, and a movement locus according to an embodiment of the present disclosure. In FIG. 1, as the light beams, an on-axis light beam K0 and a light beam K1 with the maximum half field angle are shown. Further, FIG. 2 shows a cross-sectional view of the configuration in each zoom state of the zoom lens of FIG. 1. In FIG. 2, the upper stage marked with "WIDE" shows the wide-angle end state, the middle stage marked with "MIDDLE" shows the intermediate focal length state, and the lower stage marked with "TELE" shows the telephoto end state. The configuration examples shown in FIGS. 1 and 2 correspond to Example 1 described later. In FIGS. 1 and 2, the left side is the magnification side and the right side is the reduction side. Hereinafter, the description will be mainly made with reference to FIG. 1.

[0032] The zoom lens of the present disclosure can be a projection optical system mounted on a projection display device to form an image projected onto a screen, or can also be an imaging optical system mounted on an imaging device to form an image of an object. Hereinafter, the case where the zoom lens is used for the purpose of a projection optical system will be assumed for description. Also, hereinafter, in order to avoid redundant description, "the zoom lens of the present disclosure" may be simply referred to as "the zoom lens".

[0033] In FIG. 1, an example is shown in which an optical member PP and an image display surface Sim of a light valve are arranged on the reducing side of a zoom lens, assuming that the zoom lens is mounted on a projection display device. The optical member PP is a member assuming a filter, a cover glass, a color combining prism, etc. The optical member PP is a member having no refractive power, and a configuration in which the optical member PP is omitted is also possible. The light valve outputs an optical image, and this optical image is displayed as an image on the image display surface Sim.

[0034] In a projection display device, a light beam given image information at the image display surface Sim is incident on the zoom lens through the optical member PP, and is projected onto a screen (not shown) by the zoom lens. In this case, the image display surface Sim corresponds to the reducing-side conjugate surface, and the screen corresponds to the magnifying-side conjugate surface. Note that in this specification, the "screen" means an object onto which a projection image formed by the zoom lens is projected. As the screen, in addition to a dedicated screen, a wall surface of a room, a floor surface, a ceiling, an outer wall of a building, etc. may be used.

[0035] Note that in the description of this specification, the "magnifying side" means the screen side on the optical path, and the "reducing side" means the image display surface Sim side on the optical path. In this specification, the "magnifying side" and the "reducing side" are determined along the optical path, and this also applies to the case of a zoom lens having a bent optical path. "The most magnifying side of ~" means the most magnifying side in the order on the optical path, and does not mean the closest to the screen in terms of distance. Hereinafter, in order to avoid making the description redundant, "in order along the optical path from the magnifying side to the reducing side" is described as "in order from the magnifying side to the reducing side".

[0036] The zoom lens of the present disclosure includes, in order from the wide-angle side to the telephoto side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, an intermediate group GM including one or more lens groups, and a final lens group GE having a positive refractive power. By making the lens group on the most wide-angle side a negative refractive power group, it becomes possible to reduce the diameter of the lens on the most wide-angle side and ensure sufficient back focus, which is advantageous for miniaturization. The second lens group G2 and the third lens group G3 having positive refractive powers can bear the main action of zooming. The fourth lens group G4 and the intermediate group GM can bear image plane correction. In particular, by making the fourth lens group G4 a negative refractive power group, it becomes possible to correct aberrations from the wide-angle end to the telephoto end caused by an increase in the movement amount of the lens group accompanying a high zoom ratio. By configuring the intermediate group GM to be capable of being divided into multiple groups, it is advantageous for achieving a high zoom ratio and high performance. The final lens group GE, by having a positive refractive power, can bear an imaging action and telecentricity on the telephoto side.

[0037] During zooming, the first lens group G1 and the final lens group GE are stationary, and the second lens group G2, the third lens group G3, the fourth lens group G4, and all the lens groups in the intermediate group GM move along the optical axis Z by changing the intervals in the optical axis direction between adjacent lens groups. Here, the phrase "During zooming, ~ stationary" means being fixed with respect to the conjugate surface on the telephoto side during zooming. By making the first lens group G1 on the most wide-angle side stationary during zooming, it is advantageous for suppressing fluctuations in the center of gravity position during zooming. By making the final lens group GE stationary during zooming, it becomes easy to ensure the imaging action and telecentricity on the telephoto side.

[0038] In this specification, a group whose distance in the optical axis direction from an adjacent group changes during zooming is regarded as one lens group. During zooming, the distance between adjacent lenses within one lens group does not change. That is, a "lens group" is a component of a zoom lens, and is a part including at least one lens separated by an air interval that changes during zooming. During zooming, each lens group is moved or fixed in units of lens groups. Note that a "lens group" may include components other than lenses having no refractive power, such as diaphragms, masks, filters, cover glasses, plane mirrors, etc.

[0039] As an example, the zoom lens of FIG. 1 includes, in order from the wide-angle side to the telephoto side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. In the example of FIG. 1, the intermediate group GM consists of the fifth lens group G5, and the final lens group GE consists of the sixth lens group G6. In FIG. 1, below each lens group that moves during zooming, the schematic movement locus of each lens group during zooming from the wide-angle end to the telephoto end is indicated by a solid arrow.

[0040] As an example, each group of FIG. 1 is configured as follows. The first lens group G1 consists of six lenses L11 to L16 in order from the wide-angle side to the telephoto side. The second lens group G2 consists of one lens L21. The third lens group G3 consists of one lens L31. The fourth lens group G4 consists of one lens L41. The fifth lens group G5 consists of six lenses L51 to L56 in order from the wide-angle side to the telephoto side. The sixth lens group G6 consists of one lens L61.

[0041] In the zoom lens of the present disclosure, the distance between the second lens group G2 and the third lens group G3 at the telephoto end is configured to be shorter than the distance between the second lens group G2 and the third lens group G3 at the wide-angle end. By configuring the distance between the second lens group G2 and the third lens group G3, which is mainly responsible for the zooming action, as described above, an increase in the overall lens length is suppressed, and while suppressing an increase in the diameter of the lenses of the lens group that moves during zooming, it is advantageous for ensuring the zoom ratio and correcting spherical aberration on the telephoto side.

[0042] Further, in the zoom lens of the present disclosure, the first lens group G1 is composed of a first A subgroup G1A having a negative refractive power, a first B subgroup G1B, and a first C subgroup G1C in order from the magnification side to the reduction side. During focusing, the distance between the first A subgroup G1A and the first B subgroup G1B changes, and the distance between the first B subgroup G1B and the first C subgroup G1C changes. That is, in the present disclosure, focusing is performed by moving the subgroups within the first lens group G1 along the optical axis Z. Hereinafter, the group that moves during focusing is referred to as the focusing group. By arranging the focusing group in the first lens group G1 that does not move during zooming, an operation that separates zooming and focusing becomes possible. Also, in a projection optical system, performance changes when the projection distance changes due to wide-angle conversion tend to be a problem. However, as in the present disclosure, since focusing is performed by changing the distances between the first B subgroup G1B and the adjacent magnification side and reduction side, it is advantageous for suppressing performance changes when the above-mentioned projection distance changes. In this specification, the "projection distance" means the distance on the optical axis from the conjugate surface on the magnification side to the lens surface on the most magnified side of the zoom lens.

[0043] In the present disclosure, during focusing, only the first B subgroup G1B may move, or the first A subgroup G1A and the first B subgroup G1B may move while changing the mutual distance therebetween, or the first B subgroup G1B and the first C subgroup G1C may move while changing the mutual distance therebetween, or the first A subgroup G1A, the first B subgroup G1B, and the first C subgroup G1C may move while changing the distance from an adjacent group. The first B subgroup G1B may be a group having a positive refractive power or a group having a negative refractive power. The first C subgroup G1C may be a group having a positive refractive power or a group having a negative refractive power.

[0044] As an example, in the zoom lens of FIG. 1, the first A subgroup G1A is composed of lenses L11 to L13, the first B subgroup G1B is composed of lens L14, and the first C subgroup G1C is composed of lenses L15 to L16. In the example of FIG. 1, during focusing, only the first B subgroup G1B moves, and the first A subgroup G1A and the first C subgroup G1C are stationary. That is, in the example of FIG. 1, the focusing group is composed of the first B subgroup G1B. In FIG. 1, double arrows in the left - right direction are marked below the focusing group. By keeping the first C subgroup G1C stationary during focusing, the configuration can be simplified and cost reduction can be contributed. By keeping the first A subgroup G1A stationary during focusing, the configuration can be simplified and cost reduction can be contributed. Further, by keeping the first A subgroup G1A having a large lens diameter stationary, it is advantageous for reducing the load on the drive system.

[0045] The intermediate group GM preferably includes, on the most reduced - side, a cemented lens in which a negative lens and a positive lens are cemented in order from the enlarged - side to the reduced - side. In this case, it is advantageous for correcting magnification chromatic aberration, particularly for correcting magnification chromatic aberration during variable magnification.

[0046] The zoom lens of the present disclosure preferably has a telecentric configuration on the reduction side. For example, in a projection display device that projects a high-definition image, a so-called three-panel system in which image display elements corresponding to the wavelengths of each of blue, green, and red are provided is often adopted. In order to cope with such a system, it is preferable that the reduction side is configured to be telecentric. In an optical system that is strictly configured to be telecentric on the reduction side, the chief ray from the most reduced-side surface of the optical system toward the reduction-side conjugate surface is parallel to the optical axis Z.

[0047] However, "the reduction side is telecentric" in the technology of the present disclosure is not limited to the case where the angle of the chief ray with respect to the optical axis Z is 0 degree, and includes errors that are practically acceptable in the technical field to which the technology of the present disclosure belongs. The error may be, for example, in the range where the angle of the chief ray with respect to the optical axis Z is -3 degrees or more and +3 degrees or less. In a system that does not include an aperture stop, when viewing the light beam in the direction from the enlargement side to the reduction side, the telecentricity may be determined using the bisector of the upper maximum ray and the lower maximum ray in the cross section of the light beam converging at a point on the reduction-side conjugate surface as a substitute for the chief ray.

[0048] Next, a preferable configuration regarding the conditional expressions of the zoom lens of the present disclosure will be described. In the following description of the conditional expressions, in order to avoid redundant explanations, the same symbols are used for those having the same definitions, and the duplicate explanations of the symbols are omitted.

[0049] The zoom lens preferably satisfies the following conditional expression (1). Here, the distance between the second lens group G2 and the third lens group G3 at the telephoto end is denoted as D23t, and the distance between the second lens group G2 and the third lens group G3 at the wide-angle end is denoted as D23w. As an example, Fig. 2 shows the above distances D23t and D23w. When attempting to achieve a high magnification ratio, it is likely to cause an increase in the overall lens length and an increase in the diameter of the lenses of the lens groups that move during zooming. However, by ensuring that the corresponding value of conditional expression (1) does not exceed the upper limit value, it is advantageous for securing a high magnification ratio without causing an increase in the overall lens length and an increase in the diameter of the lenses of the lens groups that move during zooming. Also, when attempting to suppress an increase in the overall lens length, it is likely to cause the inconvenience that it becomes difficult to correct good spherical aberration on the telephoto side. However, by ensuring that the corresponding value of conditional expression (1) does not exceed the upper limit value, the above inconvenience can also be avoided. D23t / D23w < 1 (1)

[0050] The zoom lens preferably satisfies the following conditional expression (1-1). By ensuring that the corresponding value of conditional expression (1-1) does not fall below the lower limit value, it is possible to prevent the third lens group G3 from getting too close to the second lens group G2 at the telephoto end. This facilitates maintaining a mechanical holding structure such that the lenses do not come into contact with each other, or facilitates maintaining the interval of the grooves of the cam that suspends the moving lens groups. 0.05 < D23t / D23w < 1 (1-1)

[0051] To obtain better characteristics, the upper limit values of conditional expression (1) and conditional expression (1-1) are preferably set to 0.9.

[0052] The zoom lens preferably satisfies the following conditional expression (2). Here, the combined lateral magnification of the second lens group G2 and the third lens group G3 at the telephoto end is denoted as β23t, and the combined lateral magnification of the second lens group G2 and the third lens group G3 at the wide-angle end is denoted as β23w. Note that β23t and β23w are values in a state where the projection distance is infinite. By ensuring that the corresponding value of the conditional expression (2) does not fall below the lower limit value, it is advantageous for securing the zoom ratio. More specifically, by ensuring that the corresponding value of the conditional expression (2) does not fall below the lower limit value, it is advantageous for securing the zoom ratio while suppressing an increase in the overall lens length. The conditional expression (2) indicates the magnitude of the zooming action of the second lens group G2 and the third lens group G3. If the zooming action of the second lens group G2 and the third lens group G3 becomes too large, a lens group on the reduction side from the third lens group G3 has to bear a large zooming action that cancels out a part of this zooming action. In that case, there arises the inconvenience that aberration correction accompanying zooming becomes difficult. By ensuring that the corresponding value of the conditional expression (2) does not exceed the upper limit value, the zooming action of the second lens group G2 and the third lens group G3 does not become too large, so the above inconvenience can be avoided, and thereby, it is advantageous for aberration correction. 1.4 < β23t / β23w < 3 (2)

[0053] In order to obtain better characteristics, it is more preferable that the lower limit value of the conditional expression (2) is 1.5. Also, in order to obtain better characteristics, it is more preferable that the upper limit value of the conditional expression (2) is 2.5.

[0054] When the focal length of the fourth lens group G4 is fG4 and the focal length of the zoom lens at the wide-angle end is fw, it is preferable that the zoom lens satisfies the following conditional expression (3). Note that fw is the value in the state where the projection distance is infinite. By ensuring that the corresponding value of conditional expression (3) does not fall below the lower limit value, the negative refractive power of the fourth lens group G4 does not become too weak, so it is possible to have a great effect on aberration correction at the wide-angle end and the telephoto end, and it is easy to ensure a sufficiently long back focus. By ensuring that the corresponding value of conditional expression (3) does not exceed the upper limit value, the negative refractive power of the fourth lens group G4 does not become too strong, which is advantageous for spherical aberration correction. -15 < fG4 / fw < -1 (3)

[0055] To obtain better characteristics, it is more preferable that the lower limit value of conditional expression (3) is -12. Also, to obtain better characteristics, it is more preferable that the upper limit value of conditional expression (3) is -1.5.

[0056] When the focal length of the first subgroup G1A is fG1A and the focal length of the first subgroup G1C is fG1C, it is preferable that the zoom lens satisfies the following conditional expression (4). By ensuring that the corresponding value of conditional expression (4) does not fall below the lower limit value, the positive refractive power of the first subgroup G1C with respect to the first subgroup G1A does not become too strong, so it is easy to maintain a good balance of refractive power within the first lens group G1, which is advantageous for suppressing performance changes associated with changes in the projection distance. By ensuring that the corresponding value of conditional expression (4) does not exceed the upper limit value, the negative refractive power of the first subgroup G1C with respect to the first subgroup G1A does not become too strong, so it is possible to maintain the required negative refractive power of the first lens group G1 without causing an increase in the diameter of the first subgroup G1A. This is advantageous for miniaturization. -0.5 < fG1A / fG1C < 0.5 (4)

[0057] In order to obtain better characteristics, it is more preferable that the lower limit value of conditional expression (4) is -0.28. Also, in order to obtain better characteristics, it is more preferable that the upper limit value of conditional expression (4) is 0.22.

[0058] When the focal length of the first subgroup G1B is fG1B, it is preferable that the zoom lens satisfies the following conditional expression (5). Regarding the lower limit of conditional expression (5), since |fG1A / fG1B| is an absolute value, 0 < |fG1A / fG1B|. By ensuring that the corresponding value of conditional expression (5) does not exceed the upper limit value, the refractive power of the first subgroup G1B with respect to the first subgroup G1A does not become too strong, so it is advantageous for suppressing fluctuations in various aberrations accompanying fluctuations in the projection distance, particularly for suppressing fluctuations in field curvature. As a result, it becomes easier to achieve both wide-angle and high magnification ratios. 0 < |fG1A / fG1B| < 0.3 (5)

[0059] In order to obtain better characteristics, it is more preferable that the upper limit value of conditional expression (5) is 0.1.

[0060] When the focal length of the first lens group G1 is fG1, it is preferable that the zoom lens satisfies the following conditional expression (6). Note that fG1 is the value in the state where the projection distance is infinite. By ensuring that the corresponding value of conditional expression (6) does not fall below the lower limit value, the refractive power of the first lens group G1 does not become too weak, so it becomes easier to ensure the desired back focus and suppress an increase in the overall lens length. By ensuring that the corresponding value of conditional expression (6) does not exceed the upper limit value, the refractive power of the first lens group G1 does not become too strong, so it is advantageous for correcting distortion aberration and field curvature, which are problems in wide-angle conversion. -4 < fG1 / fw < -1 (6)

[0061] In order to obtain better characteristics, it is more preferable that the lower limit value of conditional expression (6) is -3. Also, in order to obtain better characteristics, it is more preferable that the upper limit value of conditional expression (6) is -1.5.

[0062] The first sub-group G1C may be configured to include at least one negative lens. In the configuration where the first sub-group G1C includes at least one negative lens, it is preferable that the zoom lens satisfies the following conditional expression (7). Here, the average value of the Abbe numbers of all the negative lenses included in the first sub-group G1C based on the d-line is denoted as νave. By ensuring that the corresponding value of the conditional expression (7) does not fall below the lower limit value, it is advantageous for correcting the magnification chromatic aberration, which is a problem in wide-angle conversion. νave>50 (7)

[0063] Also, it is preferable that the zoom lens satisfies the following conditional expression (7-1). By ensuring that the corresponding value of the conditional expression (7-1) does not exceed the upper limit value, it is possible to suppress the increase in the price of the lens, which is advantageous for cost reduction. 50<νave<100 (7-1)

[0064] To obtain better characteristics, it is preferable that the lower limit values of the conditional expressions (7) and (7-1) are set to 65.

[0065] When the focal length of the second lens group G2 is denoted as fG2, it is preferable that the zoom lens satisfies the following conditional expression (8). By ensuring that the corresponding value of the conditional expression (8) does not fall below the lower limit value, the refractive power of the second lens group G2 does not become too strong, which is advantageous for aberration correction during zooming. By ensuring that the corresponding value of the conditional expression (8) does not exceed the upper limit value, the movement amount of the second lens group G2 during zooming can be suppressed, which is advantageous for miniaturization. 2<fG2 / fw<10 (8)

[0066] To obtain better characteristics, it is more preferable that the lower limit value of the conditional expression (8) is set to 4. Also, to obtain better characteristics, it is more preferable that the upper limit value of the conditional expression (8) is set to 8.

[0067] When the focal length of the third lens group G3 is fG3, the zoom lens preferably satisfies the following conditional expression (9). By preventing the corresponding value of the conditional expression (9) from falling below the lower limit value, the refractive power of the third lens group G3 does not become too strong, which is advantageous for aberration correction during zooming. By preventing the corresponding value of the conditional expression (9) from exceeding the upper limit value, the movement amount of the third lens group G3 during zooming can be suppressed, which is advantageous for miniaturization. 4 < fG3 / fw < 12 (9)

[0068] To obtain better characteristics, it is more preferable that the lower limit value of the conditional expression (9) is 5. Also, to obtain better characteristics, it is more preferable that the upper limit value of the conditional expression (9) is 9.

[0069] When the focal length of the final lens group GE is fGE, the zoom lens preferably satisfies the following conditional expression (10). By preventing the corresponding value of the conditional expression (10) from falling below the lower limit value, the refractive power of the final lens group GE does not become too strong, which is advantageous for both maintaining telecentricity and ensuring an appropriate back focus length. By preventing the corresponding value of the conditional expression (10) from exceeding the upper limit value, the back focus does not become too long, which is advantageous for miniaturization of the entire lens system including the back focus. 3 < fGE / fw < 8 (10)

[0070] To obtain better characteristics, it is more preferable that the lower limit value of the conditional expression (10) is 4. Also, to obtain better characteristics, it is more preferable that the upper limit value of the conditional expression (10) is 7.

[0071] When the back focus on the reduction side in terms of the air equivalent distance of the zoom lens is Bf, the zoom lens preferably satisfies the following conditional expression (11). Note that Bf is the value in the state where the projection distance is infinite. By preventing the corresponding value of the conditional expression (11) from falling below the lower limit value, the back focus does not become too short, which makes it easier to arrange a color combining prism or the like. 2 < Bf / fw (11)

[0072] Further, it is preferable that the zoom lens satisfies the following conditional expression (11-1). By preventing the corresponding value of the conditional expression (11-1) from exceeding the upper limit value, it is advantageous for downsizing the entire lens system including the back focus. 2 < Bf / fw < 8 (11-1)

[0073] In order to obtain better characteristics, it is preferable that the lower limit values of the conditional expression (11) and the conditional expression (11-1) be 2.5.

[0074] Note that the example shown in FIG. 1 is just an example, and various modifications are possible without departing from the gist of the technology of the present disclosure.

[0075] For example, the first subgroup G1A may be configured to consist of three negative lenses. The first subgroup G1B may be configured to consist of one lens, or may be configured to consist of two lenses. When the first subgroup G1B consists of one lens, the lens may be a positive lens or a negative lens. When the first subgroup G1B consists of two lenses, for example, it may be configured to consist of a negative lens and a positive lens. The first subgroup G1C may be configured to consist of a negative lens and a positive lens in order from the telephoto side to the wide-angle side. When the first subgroup G1C is configured in this way, it is advantageous for correcting longitudinal chromatic aberration.

[0076] The focusing group may be configured to consist of one lens, or may be configured to consist of two lenses. By minimizing the number of lenses constituting the focusing group, it is advantageous for downsizing and weight reduction of the focusing group.

[0077] The second lens group G2 may be configured to consist of one positive lens. The third lens group G3 may be configured to consist of one positive lens. The fourth lens group G4 may be configured to consist of one lens, or may be configured to consist of two lenses, or may be configured to consist of four lenses.

[0078] The intermediate group GM may be configured to consist of one lens group or may be configured to consist of two lens groups.

[0079] The final lens group GE may be configured to consist of one positive lens.

[0080] In order to absorb the tilt error and / or position error of the attachment mount between the zoom lens and the projection display device, etc., the lenses on the telephoto side of the focusing group may be configured to be movable as a back adjustment group. For example, in the example of FIG. 1, although the lens L14 is the focusing group, the lenses L11 to L13 may be configured to be movable as the back adjustment group.

[0081] The above-described preferred configurations and possible configurations can be combined arbitrarily within a non-conflicting range, and it is preferable to selectively adopt them as appropriate according to the required specifications.

[0082] As an example, a preferred aspect of the zoom lens of the present disclosure includes, in order from the telephoto side to the wide-angle side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, an intermediate group GM including one or more lens groups, and a final lens group GE having a positive refractive power. The first lens group G1 includes, in order from the telephoto side to the wide-angle side, a first A subgroup G1A having a negative refractive power, a first B subgroup G1B, and a first C subgroup G1C. During focusing, the interval between the first A subgroup G1A and the first B subgroup G1B changes, and the interval between the first B subgroup G1B and the first C subgroup G1C changes. During zooming, the first lens group G1 and the final lens group GE are stationary, and the second lens group G2, the third lens group G3, the fourth lens group G4, and all the lens groups in the intermediate group GM change the interval in the optical axis direction with the adjacent lens groups and move along the optical axis Z. The interval between the second lens group G2 and the third lens group G3 at the telephoto end is shorter than the interval between the second lens group G2 and the third lens group G3 at the wide-angle end.

[0083] Next, an embodiment of the zoom lens of the present disclosure will be described with reference to the drawings. Note that the group of cross-sectional views of each embodiment and the reference numerals attached to the lenses are used independently for each embodiment in order to avoid the complexity of explanations and drawings associated with the increase in the number of digits of the reference numerals. Therefore, even if the same reference numeral is attached to the drawings of different embodiments, they are not necessarily the same configuration.

[0084] [Embodiment 1] The configuration of the zoom lens of Embodiment 1 in a state where the projection distance is infinite and the cross-sectional view of the light beam are shown in FIG. 1. Since the illustration method and configuration are as described above, redundant explanations are partially omitted here. The zoom lens of Embodiment 1 includes, in order from the wide-angle side to the telephoto side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. The first lens group G1 includes, in order from the wide-angle side to the telephoto side, a first A subgroup G1A having a negative refractive power, a first B subgroup G1B having a positive refractive power, and a first C subgroup G1C having a positive refractive power.

[0085] For the zoom lens of Embodiment 1, the basic lens data is shown in Table 1, the specifications and the variable surface intervals during zooming are shown in Table 2, the aspherical coefficients are shown in Table 3, and the variable surface intervals during focusing are shown in Table 4.

[0086] The table of the basic lens data is described as follows. The column of "Sn" shows the surface number when the surface on the most wide-angle side is defined as the first surface and the numbers are incremented one by one toward the telephoto side. The column of "R" shows the curvature radius of each surface. The column of "D" shows the surface interval on the optical axis between each surface and the surface adjacent to it on the telephoto side. The column of "Nd" shows the refractive index of each component with respect to the d-line. The column of "νd" shows the Abbe number of each component based on the d-line.

[0087] In the table of the basic lens data, the sign of the radius of curvature of the surface facing the convex shape on the magnification side is positive, and the sign of the radius of curvature of the surface facing the convex shape on the reduction side is negative. The value in the bottom column of the D column in the table is the distance between the surface on the most reduction side in the table and the image display surface Sim. In the table of the basic lens data, for the variable surface interval during zooming, the symbol DD[] is used, and the surface number on the magnification side of this interval is attached in [] and entered in the D column. Table 1 shows the data in the state where the projection distance is infinite.

[0088] Table 2 shows the zoom ratio Zr, focal length f, F-number FNo., and maximum total angle of view 2ω based on the d-line standard. The [°] in the column of 2ω indicates that the unit is degrees. In Table 2, the values at the wide-angle end are shown in the "WIDE" column, the values in the state of the intermediate focal length are shown in the "MIDDILE" column, and the values at the telephoto end are shown in the "TELE" column.

[0089] In the basic lens data, an asterisk is attached to the surface number of the aspherical surface, and the value of the paraxial radius of curvature is described in the column of the radius of curvature of the aspherical surface. In Table 3, the row of Sn shows the surface number of the aspherical surface, and the rows of KA and Am show the numerical values of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more and varies depending on the surface. For example, in the first surface of Example 1, m = 3, 4, 5, ···, 16. The "E±n" (n: integer) of the numerical value of the aspherical coefficient in Table 3 means "×10 ±n ". KA and Am are the aspherical coefficients in the aspherical formula represented by the following formula. Zd = C × h 2 / {1+(1 - KA × C 2 × h 2 ) 1 / 2}+ ΣAm × h m However, Zd: Aspherical depth (the length of the perpendicular line dropped from the point on the aspherical surface with height h to the plane perpendicular to the optical axis Z where the aspherical vertex touches) h: Height (the distance from the optical axis Z to the lens surface) C: Reciprocal of the paraxial radius of curvature KA, Am: Aspherical coefficients And Σ in the aspherical formula means the sum with respect to m.

[0090] Table 4 shows the distances between the first subgroup G1A and the first subgroup G1B, and between the first subgroup G1B and the first subgroup G1C, in the states where the projection distance is infinity, 1370 mm (millimeters), and 1000 mm (millimeters).

[0091] In the data of each table, degrees are used as the unit of angle and millimeters are used as the unit of length. However, since the optical system can be used even if it is proportionally enlarged or reduced, other appropriate units can also be used. Also, in each of the tables shown below, the numerical values are rounded to a predetermined number of digits.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] [Table 4]

[0096] FIG. 3 shows aberration diagrams of the zoom lens according to Example 1 in a state where the projection distance is infinite. In FIG. 3, aberration diagrams at the wide-angle end are shown in the upper row labeled "WIDE", aberration diagrams in the intermediate focal length state are shown in the middle row labeled "MIDDILE", and aberration diagrams at the telephoto end are shown in the lower row labeled "TELE". In FIG. 3, from left to right, spherical aberration, astigmatism, distortion, and chromatic aberration of magnification are shown. In the spherical aberration diagram, aberrations related to the d-line, C-line, and F-line are shown by solid line, long dashed line, and short dashed line, respectively. In the astigmatism diagram, the aberration related to the d-line in the sagittal direction is shown by a solid line, and the aberration related to the d-line in the tangential direction is shown by a short dashed line. In the distortion diagram, the aberration related to the d-line is shown by a solid line. In the chromatic aberration of magnification diagram, aberrations related to the C-line and F-line are shown by a long dashed line and a short dashed line, respectively. In the spherical aberration diagram, the value of the F-number is shown after "FNo.=". In the other aberration diagrams, the value of the maximum semi-aperture angle is shown after "ω=".

[0097] FIG. 4 shows aberration diagrams of the zoom lens according to Example 1 in a state where the projection distance is 1370 mm (millimeters). The illustration method in FIG. 4 is the same as that in FIG. 3.

[0098] The symbols, meanings, description methods, and illustration methods of the respective data related to the above Example 1 are basically the same in the following examples unless otherwise specified, so duplicate explanations are omitted below.

[0099] [Example 2] FIG. 5 shows a cross-sectional view of the configuration and light beam of the zoom lens according to Example 2. The zoom lens according to Example 2 includes, in order from the magnification side to the reduction side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. The intermediate group GM consists of the fifth lens group G5, and the final lens group GE consists of the sixth lens group G6. During zooming, the first lens group G1 and the sixth lens group G6 are stationary, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move along the optical axis Z by changing the interval in the optical axis direction between adjacent lens groups.

[0100] The first lens group G1 consists of a first subgroup G1A having a negative refractive power, a first subgroup G1B having a positive refractive power, and a first subgroup G1C having a positive refractive power, in order from the wide-angle side to the telephoto side. The first subgroup G1A consists of three lenses, lenses L11 to L13, in order from the wide-angle side to the telephoto side. The first subgroup G1B consists of one lens, lens L14. The first subgroup G1C consists of two lenses, lenses L15 to L16, in order from the wide-angle side to the telephoto side. During focusing, only the first subgroup G1B moves, and the first subgroup G1A and the first subgroup G1C remain stationary.

[0101] The second lens group G2 consists of one lens, lens L21. The third lens group G3 consists of one lens, lens L31. The fourth lens group G4 consists of four lenses, lenses L41 to L44, in order from the wide-angle side to the telephoto side. The fifth lens group G5 consists of three lenses, lenses L51 to L53, in order from the wide-angle side to the telephoto side. The sixth lens group G6 consists of one lens, lens L61.

[0102] Regarding the zoom lens of Example 2, the basic lens data is shown in Table 5, the specifications and the variable surface intervals during zooming are shown in Table 6, the aspherical coefficients are shown in Table 7, and the variable surface intervals during focusing are shown in Table 8. Also, regarding the zoom lens of Example 2, each aberration diagram in the state where the projection distance is infinite is shown in FIG. 6, and each aberration diagram in the state where the projection distance is 1370 mm (millimeters) is shown in FIG. 7.

[0103]

Table 5

[0104]

Table 6

[0105]

Table 7

[0106]

Table 8

[0107] [Embodiment 3] The configuration of the zoom lens of Embodiment 3 and the cross-sectional view of the light beam are shown in Fig. 8. The zoom lens of Embodiment 3 includes, in order from the wide-angle side to the telephoto side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. The intermediate group GM consists of the fifth lens group G5, and the final lens group GE consists of the sixth lens group G6. During zooming, the first lens group G1 and the sixth lens group G6 are stationary, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move along the optical axis Z by changing the interval in the optical axis direction between adjacent lens groups.

[0108] The first lens group G1 includes, in order from the wide-angle side to the telephoto side, a first A subgroup G1A having a negative refractive power, a first B subgroup G1B having a positive refractive power, and a first C subgroup G1C having a negative refractive power. The first A subgroup G1A consists of three lenses L11 to L13 in order from the wide-angle side to the telephoto side. The first B subgroup G1B consists of two lenses L14 to L15 in order from the wide-angle side to the telephoto side. The first C subgroup G1C consists of two lenses L16 to L17 in order from the wide-angle side to the telephoto side. During focusing, only the first B subgroup G1B moves, and the first A subgroup G1A and the first C subgroup G1C are stationary.

[0109] The second lens group G2 consists of a single lens L21. The third lens group G3 consists of a single lens L31. The fourth lens group G4 consists of two lenses L41 to L42 in order from the wide-angle side to the telephoto side. The fifth lens group G5 consists of six lenses L51 to L56 in order from the wide-angle side to the telephoto side. The sixth lens group G6 consists of a single lens L61.

[0110] For the zoom lens of Example 3, the basic lens data is shown in Table 9, the specifications and the variable surface intervals during zooming are shown in Table 10, the aspherical coefficients are shown in Table 11, and the variable surface intervals during focusing are shown in Table 12. Also, for the zoom lens of Example 3, each aberration diagram in the state where the projection distance is infinite is shown in Fig. 9, and each aberration diagram in the state where the projection distance is 1370 mm (millimeters) is shown in Fig. 10.

[0111]

Table 9

[0112]

Table 10

[0113]

Table 11

[0114]

Table 12

[0115] [Example 4] The configuration of the zoom lens of Example 4 and the cross-sectional view of the light beam are shown in Fig. 11. The zoom lens of Example 4 consists of, in order from the wide-angle side to the telephoto side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, a sixth lens group G6, and a seventh lens group G7. The intermediate group GM consists of two lens groups, the fifth lens group G5 and the sixth lens group G6. The final lens group GE consists of the seventh lens group G7. During zooming, the first lens group G1 and the seventh lens group G7 are stationary, and the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 move along the optical axis Z by changing the intervals in the optical axis direction with adjacent lens groups.

[0116] The first lens group G1 consists of a first A subgroup G1A having a negative refractive power, a first B subgroup G1B having a positive refractive power, and a first C subgroup G1C having a negative refractive power, in order from the wide-angle side to the telephoto side. The first A subgroup G1A consists of three lenses, lenses L11 to L13, in order from the wide-angle side to the telephoto side. The first B subgroup G1B consists of one lens, lens L14. The first C subgroup G1C consists of two lenses, lenses L15 to L16, in order from the wide-angle side to the telephoto side. During focusing, only the first B subgroup G1B moves, and the first A subgroup G1A and the first C subgroup G1C remain stationary.

[0117] The second lens group G2 consists of one lens, lens L21. The third lens group G3 consists of one lens, lens L31. The fourth lens group G4 consists of one lens, lens L41. The fifth lens group G5 consists of four lenses, lenses L51 to L54, in order from the wide-angle side to the telephoto side. The sixth lens group G6 consists of two lenses, lenses L61 to L62, in order from the wide-angle side to the telephoto side. The seventh lens group G7 consists of one lens, lens L71.

[0118] For the zoom lens of Example 4, the basic lens data is shown in Table 13, the specifications and the variable surface intervals during zooming are shown in Table 14, the aspherical coefficients are shown in Table 15, and the variable surface intervals during focusing are shown in Table 16. Also, for the zoom lens of Example 4, each aberration diagram in the state where the projection distance is infinite is shown in FIG. 12, and each aberration diagram in the state where the projection distance is 1370 mm (millimeters) is shown in FIG. 13.

[0119]

Table 13

[0120]

Table 14

[0121]

Table 15

[0122]

Table 16

[0123] [Example 5] The configuration of the zoom lens of Example 5 and a cross-sectional view of the light beam are shown in Fig. 14. The zoom lens of Example 5 comprises, in order from the wide-angle side to the telephoto side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. The intermediate group GM consists of the fifth lens group G5, and the final lens group GE consists of the sixth lens group G6. During zooming, the first lens group G1 and the sixth lens group G6 are stationary, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move along the optical axis Z by changing the interval in the optical axis direction between adjacent lens groups.

[0124] The first lens group G1 comprises, in order from the wide-angle side to the telephoto side, a first subgroup G1A having a negative refractive power, a first subgroup G1B having a negative refractive power, and a first subgroup G1C having a positive refractive power. The first subgroup G1A consists of three lenses L11 to L13. The first subgroup G1B consists of one lens L14. The first subgroup G1C consists of two lenses L15 to L16. During focusing, only the first subgroup G1B moves, and the first subgroup G1A and the first subgroup G1C are stationary.

[0125] The second lens group G2 consists of one lens L21. The third lens group G3 consists of one lens L31. The fourth lens group G4 consists of one lens L41. The fifth lens group G5 consists of six lenses L51 to L56. The sixth lens group G6 consists of one lens L61.

[0126] For the zoom lens of Example 5, the basic lens data is shown in Table 17, the specifications and the variable surface intervals during zooming are shown in Table 18, the aspherical coefficients are shown in Table 19, and the variable surface intervals during focusing are shown in Table 20. Also, for the zoom lens of Example 5, each aberration diagram in the state where the projection distance is infinity is shown in FIG. 15, and each aberration diagram in the state where the projection distance is 1370 mm (millimeters) is shown in FIG. 16.

[0127]

Table 17

[0128]

Table 18

[0129]

Table 19

[0130]

Table 20

[0131] Table 21 shows the corresponding values of conditional expressions (1) to (11) for the zoom lenses of Examples 1 to 5. The values shown in Table 21 are based on the d-line. The preferable ranges of the conditional expressions may be set using the corresponding values of the examples shown in Table 21 as the upper or lower limits of the conditional expressions.

[0132]

Table 21

[0133] The zoom lenses of Examples 1 to 5 are configured to be small, but have a maximum total angle of view at the wide-angle end of 75 degrees or more, a zoom ratio of 1.4 times or more, and achieve a wide angle and a high zoom ratio. Also, the zoom lenses of Examples 1 to 5 have each aberration well corrected, and further, the aberration variation during zooming and focusing is well suppressed, realizing high optical performance.

[0134] Next, a projection display device according to an embodiment of the present disclosure will be described. FIG. 17 is a schematic configuration diagram of a projection display device according to an embodiment of the present disclosure. The projection display device 100 shown in FIG. 17 includes a zoom lens 10 according to an embodiment of the present disclosure, a light source 15, and transmissive display elements 11a to 11c as light valves that output optical images corresponding to respective color lights. The projection display device 100 also includes dichroic mirrors 12 and 13 for color separation, a cross-dichroic prism 14 for color synthesis, condenser lenses 16a to 16c, and total reflection mirrors 18a to 18c for deflecting an optical path. In FIG. 17, the zoom lens 10 is schematically illustrated. An integrator is disposed between the light source 15 and the dichroic mirror 12, but its illustration is omitted in FIG. 17.

[0135] The white light from the light source 15 is decomposed into three color light beams (blue light, green light, and red light) by the dichroic mirrors 12 and 13, and then enters the transmissive display elements 11a to 11c corresponding to the respective color light beams through the condenser lenses 16a to 16c, is modulated, color-synthesized by the cross-dichroic prism 14, and then enters the zoom lens 10. The zoom lens 10 projects an optical image based on the modulated light modulated by the transmissive display elements 11a to 11c onto the screen 105.

[0136] FIG. 18 is a schematic configuration diagram of a projection display device according to another embodiment of the present disclosure. The projection display device 200 shown in FIG. 18 includes a zoom lens 210 according to an embodiment of the present disclosure, a light source 215, and DMD (Digital Micromirror Device: registered trademark) elements 21a to 21c as light valves that output optical images corresponding to respective color lights. The projection display device 200 also includes TIR (Total Internal Reflection) prisms 24a to 24c for color separation and color synthesis, and a polarization separation prism 25 for separating illumination light and projection light. In FIG. 18, the zoom lens 210 is schematically illustrated. An integrator is disposed between the light source 215 and the polarization separation prism 25, but its illustration is omitted in FIG. 18.

[0137] The white light from the light source 215 is reflected by the reflecting surface inside the polarization beam splitter prism 25 and then decomposed into three color light beams (blue light, green light, and red light) by the TIR prisms 24a to 24c. Each of the decomposed color light beams is incident on the corresponding DMD elements 21a to 21c for modulation, travels back through the TIR prisms 24a to 24c in the reverse direction for color synthesis, and then passes through the polarization beam splitter prism 25 and is incident on the zoom lens 210. The zoom lens 210 projects an optical image based on the modulated light modulated by the DMD elements 21a to 21c onto the screen 205.

[0138] FIG. 19 is a schematic configuration diagram of a projection display device according to still another embodiment of the present disclosure. The projection display device 300 shown in FIG. 19 includes a zoom lens 310 according to an embodiment of the present disclosure, a light source 315, and reflective display elements 31a to 31c as light valves that output optical images corresponding to respective color lights. Further, the projection display device 300 includes dichroic mirrors 32 and 33 for color separation, a cross-dichroic prism 34 for color synthesis, a total reflection mirror 38 for optical path deflection, and polarization beam splitter prisms 35a to 35c. Note that in FIG. 19, the zoom lens 310 is schematically illustrated. Also, although an integrator is disposed between the light source 315 and the dichroic mirror 32, its illustration is omitted in FIG. 19.

[0139] The white light from the light source 315 is decomposed into three color light beams (blue light, green light, and red light) by the dichroic mirrors 32 and 33. Each of the decomposed color light beams passes through the polarization beam splitter prisms 35a to 35c, is incident on the corresponding reflective display elements 31a to 31c for modulation, is color-synthesized by the cross-dichroic prism 34, and then is incident on the zoom lens 310. The zoom lens 310 projects an optical image based on the modulated light modulated by the reflective display elements 31a to 31c onto the screen 305.

[0140] Figures 20 and 21 are external views of a camera 400 which is an imaging device according to an embodiment of the present disclosure. FIG. 20 shows a perspective view of the camera 400 seen from the front side, and FIG. 21 shows a perspective view of the camera 400 seen from the back side. The camera 400 is a mirrorless single-lens digital camera to which an interchangeable lens 48 is detachably attached. The interchangeable lens 48 houses a zoom lens 49 according to an embodiment of the present disclosure in a lens barrel.

[0141] The camera 400 includes a camera body 41, and a shutter button 42 and a power button 43 are provided on the upper surface of the camera body 41. Further, an operation unit 44, an operation unit 45, and a display unit 46 are provided on the back surface of the camera body 41. The display unit 46 displays the captured image and the image within the angle of view before being captured.

[0142] A photographing aperture through which light from a photographing object enters is provided at the center of the front surface of the camera body 41, and a mount 47 is provided at a position corresponding to the photographing aperture. The interchangeable lens 48 is attached to the camera body 41 via the mount 47.

[0143] An imaging element 50 is provided inside the camera body 41. The imaging element 50 outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 48. As the imaging element 50, for example, a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or the like is used. A signal processing circuit (not shown), a recording medium (not shown), and the like are provided inside the camera body 41. The signal processing circuit processes the imaging signal output from the imaging element 50 to generate an image. The recording medium is for recording the generated image. In the camera 400, it is possible to take a still image or a moving image by pressing the shutter button 42, and the image data obtained by this photographing is recorded on the above recording medium.

[0144] The above has described the technology of the present disclosure by way of embodiments and examples. However, the technology of the present disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, surface interval, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values shown in the above examples, and other values can be taken.

[0145] Also, the projection display device according to the technology of the present disclosure is not limited to the one having the above configuration. For example, the optical members used for beam separation or beam combination, and the light valve can be changed in various ways. The light valve is not limited to the mode of spatially modulating the light from the light source by the image display element and outputting it as an optical image based on the image data, and may be a mode of outputting the light itself output from the self-luminous type image display element as an optical image based on the image data. Examples of the self-luminous type image display element include an image display element in which light emitting elements such as LEDs (Light Emitting Diodes) or OLEDs (Organic Light Emitting Diodes) are two-dimensionally arranged.

[0146] Also, the imaging device according to the technology of the present disclosure is not limited to the one having the above configuration. For example, it can be in various forms such as cameras other than the mirrorless type, film cameras, video cameras, security cameras, and movie cameras.

[0147] Regarding the above embodiments and examples, the following additional notes are further disclosed. [Appendix 1] It consists of a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, an intermediate group including one or more lens groups, and a final lens group having a positive refractive power, in order from the magnification side to the reduction side. The first lens group consists of a first A subgroup having a negative refractive power, a first B subgroup, and a first C subgroup, in order from the magnification side to the reduction side. When focusing, the interval between the first A subgroup and the first B subgroup changes, and the interval between the first B subgroup and the first C subgroup changes. During zooming, the first lens group and the final lens group are stationary, and the second lens group, the third lens group, the fourth lens group, and all the lens groups within the intermediate group move along the optical axis by changing the intervals in the optical axis direction between adjacent lens groups. A zoom lens in which the distance between the second lens group and the third lens group at the telephoto end is shorter than the distance between the second lens group and the third lens group at the wide-angle end. [Appendix 2] Let the distance between the second lens group and the third lens group at the telephoto end be D23t, when the distance between the second lens group and the third lens group at the wide-angle end is D23w, D23t / D23w < 1 (1) The zoom lens according to Appendix 1 that satisfies the conditional expression (1) represented by the above. [Appendix 3] Let the combined lateral magnification of the second lens group and the third lens group at the telephoto end be β23t, when the combined lateral magnification of the second lens group and the third lens group at the wide-angle end is β23w, 1.4 < β23t / β23w < 3 (2) The zoom lens according to Appendix 1 or Appendix 2 that satisfies the conditional expression (2) represented by the above. [Appendix 4] Let the focal length of the fourth lens group be fG4, when the focal length of the zoom lens at the wide-angle end is fw, -15 < fG4 / fw < -1 (3) The zoom lens according to any one of Appendices 1 to 3 that satisfies the conditional expression (3) represented by the above. [Appendix 5] Let the focal length of the first A subgroup be fG1A, when the focal length of the first C subgroup is fG1C, -0.5 < fG1A / fG1C < 0.5 (4) The zoom lens according to any one of Appendices 1 to 4 that satisfies the conditional expression (4) represented by the above. [Appendix 6] Let the focal length of the first A subgroup be fG1A, When the focal length of the first partial group 1B is fG1B, 0 < |fG1A / fG1B| < 0.3 (5) The zoom lens according to any one of Appendices 1 to 5 that satisfies the conditional expression (5) represented by [Appendix 7] When the focal length of the first lens group is fG1, When the focal length of the zoom lens at the wide-angle end is fw, The zoom lens according to any one of Appendices 1 to 6 that satisfies the conditional expression (6) represented by -4 < fG1 / fw < -1 (6). [Appendix 8] When focusing, the first partial group 1C is stationary. The zoom lens according to any one of Appendices 1 to 7. [Appendix 9] The first partial group 1C includes at least one negative lens. When the average value of the Abbe numbers of all the negative lenses included in the first partial group 1C based on the d-line is νave, νave > 50 (7) The zoom lens according to any one of Appendices 1 to 8 that satisfies the conditional expression (7) represented by [Appendix 10] The zoom lens according to any one of Appendices 1 to 9 in which the telecentricity is on the telephoto side. [Appendix 11] When the focal length of the second lens group is fG2, When the focal length of the zoom lens at the wide-angle end is fw, 2 < fG2 / fw < 10 (8) The zoom lens according to any one of Appendices 1 to 10 that satisfies the conditional expression (8) represented by [Appendix 12] When the focal length of the third lens group is fG3, When the focal length of the zoom lens at the wide-angle end is fw, 4 < fG3 / fw < 12 (9) The zoom lens according to any one of Appendices 1 to 11 that satisfies the conditional expression (9) represented by [Appendix 13] When the focal length of the final lens group is fGE, When the focal length of the zoom lens at the wide-angle end is fw, 3 < fGE / fw < 8 (10) The zoom lens according to any one of Appendices 1 to 12 that satisfies the conditional expression (10) represented by [Appendix 14] Let Bf be the back focus on the reduction side at the air equivalent distance of the zoom lens, When the focal length of the zoom lens at the wide-angle end is fw, 2 < Bf / fw (11) The zoom lens according to any one of Appendices 1 to 13 that satisfies the conditional expression (11) represented by [Appendix 15] The intermediate group includes, on the most reduction side, a cemented lens in which a negative lens and a positive lens are cemented in order from the magnification side to the reduction side. The zoom lens according to any one of Appendices 1 to 14 [Appendix 16] The first C partial group consists of, in order from the magnification side to the reduction side, a negative lens and a positive lens. The zoom lens according to any one of Appendices 1 to 15 [Appendix 17] A projection display device including the zoom lens according to any one of Appendices 1 to 16 [Appendix 18] An imaging device including the zoom lens according to any one of Appendices 1 to 16

Explanation of Signs

[0148] 10 Zoom lens 11a~11c Transmission display element 12 Dichroic mirror 13 Dichroic mirror 14 Cross-dichroic prism 15 Light source 16a~16c Condenser lens 18a~18c Total reflection mirror 21a~21c DMD element 24a~24c TIR prism 25 Polarizing beam splitter prism 31a~31c Reflective display element 32 Dichroic mirror 33 Dichroic mirror 34 Cross-dichroic prism 35a~35c Polarizing beam splitter prism 38 Total reflection mirror 41 Camera body 42 Shutter button 43 Power button 44 Operation unit 45 Operation unit 46 Display unit 47 Mount 48 Interchangeable lens 49 Zoom lens 50 Image sensor 100 Projection display device 105 Screen 200 Projection display device 205 Screen 210 Zoom lens 215 Light source 300 Projection display device 305 Screen 310 Zoom lens 315 Light source 400 Camera D23t interval D23w interval G1 First lens group G1A First A subgroup G1B First B subgroup G1C First C subgroup G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group G7 Seventh lens group GE Final lens group GM Intermediate group K0 On-axis light beam K1 Light beam with maximum semi-field angle L11~L71 Lenses PP Optical member Sim Image display surface Z Optical axis

Claims

1. It consists of a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, an intermediate group including one or more lens groups, and a final lens group having a positive refractive power, in order from the wide-angle side to the telephoto side. The first lens group consists of a first A subgroup having a negative refractive power, a first B subgroup, and a first C subgroup, in order from the wide-angle side to the telephoto side. When focusing, the distance between the first A subgroup and the first B subgroup changes, and the distance between the first B subgroup and the first C subgroup changes. When zooming, the first lens group and the final lens group are stationary, and the second lens group, the third lens group, the fourth lens group, and all the lens groups within the intermediate group move along the optical axis by changing the distance in the optical axis direction between adjacent lens groups. A zoom lens in which the distance between the second lens group and the third lens group at the telephoto end is shorter than the distance between the second lens group and the third lens group at the wide-angle end.

2. When the distance between the second lens group and the third lens group at the telephoto end is D23t, and the distance between the second lens group and the third lens group at the wide-angle end is D23w, D23t / D23w < 1 (1) The zoom lens according to Claim 1, which satisfies the conditional expression (1) represented by the above.

3. When the combined lateral magnification of the second lens group and the third lens group at the telephoto end is β23t, and the combined lateral magnification of the second lens group and the third lens group at the wide-angle end is β23w, 1.4 < β23t / β23w < 3 (2) The zoom lens according to Claim 1, which satisfies the conditional expression (2) represented by the above.

4. When the focal length of the fourth lens group is fG4, and the focal length of the zoom lens at the wide-angle end is fw, -15 < fG4 / fw < -1 (3) The zoom lens according to Claim 1, which satisfies the conditional expression (3) represented by the above.

5. When the focal length of the first A subgroup is fG1A, and the focal length of the first C subgroup is fG1C, -0.5 < fG1A / fG1C < 0.5 (4) The zoom lens according to Claim 1, which satisfies the conditional expression (4) represented by the above.

6. When the focal length of the first A subgroup is fG1A, and the focal length of the first B subgroup is fG1B, 0 < |fG1A / fG1B| < 0.3 (5) The zoom lens according to Claim 1, which satisfies the conditional expression (5) represented by the above.

7. Let the focal length of the first lens group be fG1, when the focal length of the zoom lens at the wide-angle end is fw, -4 < fG1 / fw < -1 (6) The zoom lens according to claim 1, which satisfies the conditional expression (6) represented by.

8. The zoom lens according to claim 1, wherein the first C subgroup is stationary during focusing.

9. The first C subgroup includes at least one negative lens, when the average value of the Abbe numbers of all the negative lenses included in the first C subgroup based on the d line is νave, νave > 50 (7) The zoom lens according to claim 1, which satisfies the conditional expression (7) represented by.

10. The zoom lens according to claim 1, wherein the reduction side is telecentric.

11. Let the focal length of the second lens group be fG2, when the focal length of the zoom lens at the wide-angle end is fw, 2 < fG2 / fw < 10 (8) The zoom lens according to claim 1, which satisfies the conditional expression (8) represented by.

12. Let the focal length of the third lens group be fG3, when the focal length of the zoom lens at the wide-angle end is fw, 4 < fG3 / fw < 12 (9) The zoom lens according to claim 1, which satisfies the conditional expression (9) represented by.

13. Let the focal length of the final lens group be fGE, when the focal length of the zoom lens at the wide-angle end is fw, 3 < fGE / fw < 8 (10) The zoom lens according to claim 1, which satisfies the conditional expression (10) represented by.

14. Let the back focus on the reduction side of the zoom lens in terms of air equivalent distance be Bf, when the focal length of the zoom lens at the wide-angle end is fw, 2 < Bf / fw (11) The zoom lens according to claim 1, which satisfies the conditional expression (11) represented by.

15. The zoom lens according to claim 1, wherein the intermediate group includes, on the most reduction side, a cemented lens in which a negative lens and a positive lens are cemented in order from the magnification side to the reduction side.

16. The zoom lens according to claim 1, wherein the first C subgroup consists of a negative lens and a positive lens in order from the magnification side to the reduction side.

17. A projection display device including the zoom lens according to any one of claims 1 to 16.

18. An imaging device including the zoom lens according to any one of claims 1 to 16.

Images