Zoom lens, projection display device, and imaging device

Abstract

To provide a zoom lens which is configured to form an intermediate image and offers suppressed variation in aberrations while zooming, a high zoom ratio and high performance, and to provide a projection display device and an image capturing device equipped with the zoom lens.SOLUTION: A zoom lens provided herein comprises a first unit, second unit, third unit, fourth unit, and fifth unit, arranged in order from the magnification side, and is configured to form an intermediate image. The first unit consists of a single lens group having positive refractive power. The second unit consists of two lens groups configured to move while zooming and has negative refractive power as a whole at the wide-angle end. The third unit comprises one or more lens groups configured to move while zooming. The fourth unit comprises one or more lens groups configured to move while zooming.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 technology]

[0002] The lens systems described in Patent Documents 1 and 2 below are known as zoom lenses that can be used in projection display devices or imaging devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5378162 specification [Patent Document 2] Japanese Patent Publication No. 2020-118807 Summary of the Invention [Problem to be solved by the invention]

[0004] Zoom lenses that form an intermediate image are required to have high magnification, suppress aberration fluctuations during zooming, and maintain high optical performance. These requirements are becoming higher every year.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a zoom lens that forms an intermediate image, has a high magnification, suppresses aberration fluctuations during magnification change, and maintains high optical performance, a projection-type display device that includes this zoom lens, and an imaging device that includes this zoom lens. [Means for solving the problem]

[0006] A zoom lens according to one embodiment of the present disclosure is a zoom lens that forms an intermediate image at a position conjugate with a reduction-side image plane and re-images the intermediate image on a magnification-side image plane, and is composed of, in order from the magnification side to the reduction side along an optical path, a first unit, a second unit, a third unit, a fourth unit, and a fifth unit. If a group whose spacing in the optical axis direction with an adjacent group changes during magnification is considered to be one lens group, the first unit is composed of one lens group having positive refractive power, and the second unit is composed of two lens groups whose spacing changes during magnification. The lens consists of three lens groups, and has negative refractive power overall at the wide-angle end, the third unit includes one or more lens groups that move when changing magnification, and the fourth unit includes one or more lens groups that move when changing magnification, and if, of the intersections of the chief ray of the maximum angle of view at the wide-angle end and the optical axis on the enlargement side on the optical path are defined as the first intersection and the intersection on the reduction side are defined as the second intersection, at the wide-angle end the third unit includes a lens group with positive refractive power that is located closest to the first intersection, and at the wide-angle end the fifth unit includes the second intersection within it.

[0007] The zoom lens of the above aspect is preferably configured so that the reduction side is telecentric.

[0008] When the radius of the effective image circle on the reduction side is Ymax, and the reduction side is the exit side in a state where the magnification side image plane is at infinity, the distance on the optical axis from the reduction side image plane at the wide-angle end to the paraxial exit pupil position is exPw, the zoom lens of the above aspect has the following characteristics: 0 <Ymax / |exPw|<0.1 (1) It is preferable to satisfy conditional expression (1) below.

[0009] Of the two lens groups in the second unit, if the lens group on the enlargement side in the optical path is the 2A lens group and the lens group on the reduction side is the 2B lens group, it is preferable that the 2A lens group has negative refractive power and the 2B lens group has positive refractive power. Furthermore, it is preferable that the 2B lens group moves to the enlargement side and then to the reduction side when changing magnification from the wide-angle end to the telephoto end.

[0010] Of the two lens groups in the second unit, the lens group on the enlargement side in the optical path is the 2A lens group, and the lens group on the reduction side is the 2B lens group. If the focal length of the 2A lens group is f2A and the focal length of the 2B lens group is f2B, the zoom lens of the above aspect will have the following characteristics: -0.5 <f2A / f2B<0 (2) It is preferable to satisfy conditional expression (2) below.

[0011] The fourth unit preferably comprises, in order from the magnification side to the reduction side along the optical path, a 4A lens group having positive refractive power and a 4B lens group having positive or negative refractive power, and the 4A lens group and the 4B lens group preferably move while changing the distance between them during magnification. If the focal length of the 4A lens group is f4A and the focal length of the 4B lens group is f4B, the zoom lens of the above aspect has the following characteristics: -2 <f4A / f4B<1 (3) It is preferable to satisfy conditional expression (3) below.

[0012] When the average value of the Abbe numbers of all the positive lenses included in the fourth lens unit based on the d-line is taken as ν4pave, the zoom lens of the above embodiment has the following: 60<ν4pave (4) It is preferable to satisfy conditional expression (4) below.

[0013] The intermediate image is preferably located within the fifth unit.

[0014] When the optical system on the enlargement side of the intermediate image is the first optical system, and the optical system on the reduction side of the intermediate image is the second optical system, and the focal length of the first optical system at the wide-angle end is fS1w, and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above aspect has the following characteristics: 0.8 <fS1w / |fw| (5) It is preferable to satisfy conditional expression (5) below.

[0015] When the optical system on the enlargement side of the intermediate image is the first optical system and the optical system on the reduction side of the intermediate image is the second optical system, it is preferable that the first optical system corrects the field curvature that occurs in the second optical system and re-images the intermediate image on the enlargement side image plane.

[0016] The intermediate image is located on the reduction side of the second unit, the optical system on the enlargement side of the intermediate image is the first optical system, and the optical system on the reduction side of the intermediate image is the second optical system. If the distance on the optical axis from the lens surface of the first optical system on the most enlargement side to the lens surface of the first optical system on the most reduction side at the wide-angle end is ThS1, and the distance on the optical axis from the lens surface of the zoom lens on the most enlargement side to the lens surface of the zoom lens on the most reduction side at the wide-angle end is ThZL, then the zoom lens of the above aspect will have the following characteristics: 0.4 <ThS1 / ThZL<0.7 (6) It is preferable to satisfy conditional expression (6) below.

[0017] When the air-equivalent distance on the optical axis from the lens surface closest to the reduction side of the zoom lens at the wide-angle end to the reduction-side focal position of the zoom lens is Bfw and the focal length of the zoom lens at the wide-angle end is fw, the zoom lens of the above embodiment has the following characteristics: 1 <Bfw / |fw| (7) It is preferable to satisfy conditional expression (7) below.

[0018] The zoom lens of the above aspect preferably includes an optical path bending member that bends the optical path to a position adjacent to the intermediate image. The optical path bending member may be configured to bend the optical path by 90 degrees.

[0019] During focusing, it is preferable that one or more lenses in at least one of the fourth unit and the fifth unit move.

[0020] A projection display device according to another aspect of the present disclosure includes a light valve that outputs an optical image and the zoom lens of the above aspect, and the zoom lens of the above aspect projects the optical image output from the light valve onto a screen.

[0021] An imaging device according to yet another aspect of the present disclosure includes the zoom lens of the above aspect.

[0022] In this specification, the terms "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, other optical elements than lenses, such as lenses having substantially no refractive power, apertures, masks, filters, cover glasses, flat mirrors, and prisms, as well as mechanical parts such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms, may also be included. Furthermore, a "lens group" may include optical elements other than lenses, such as apertures, masks, filters, cover glasses, flat mirrors, and prisms, in addition to lenses.

[0023] In this specification, "a lens group having positive refractive power" and "the lens group has positive refractive power" mean that the lens group as a whole has positive refractive power. Similarly, "a lens group having negative refractive power" and "the lens group has negative refractive power" mean that the lens group as a whole has negative refractive power. This also applies when "group" is replaced with "unit." Unless otherwise specified, the sign of the refractive power of a lens including an aspherical surface is considered in the paraxial region. In this specification, the "lens group" is not limited to a configuration consisting of multiple lenses, and may be a configuration consisting of only one lens.

[0024] The "focal length" used in the conditional expressions is the paraxial focal length. The "distance on the optical axis" used in the conditional expressions is the geometric distance unless otherwise specified. The values ​​used in the conditional expressions are values ​​based on the d-line when the magnification-side image plane is at infinity.

[0025] The terms "d-line," "C-line," and "F-line" used in this specification are emission lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line as 656.27 nm (nanometers), and the wavelength of the F-line as 486.13 nm (nanometers). [Effects of the Invention]

[0026] According to the present disclosure, it is possible to provide a zoom lens that forms an intermediate image, has a high magnification, suppresses aberration fluctuations during magnification change, and maintains high optical performance, a projection-type display device equipped with this zoom lens, and an imaging device equipped with this zoom lens. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a cross-sectional view showing the configuration, light beams, and movement locus of a zoom lens according to an embodiment, which corresponds to the zoom lens of Example 1. FIG. [Figure 2] 2A to 2C are diagrams illustrating the configuration and light beams in each magnification state of the zoom lens of Example 1. [Figure 3] 4A to 4C are diagrams showing aberrations of the zoom lens of Example 1 when the projection distance is at infinity. [Figure 4] 4A to 4C are diagrams showing aberrations of the zoom lens of Example 1 when the projection magnification is 150 times. [Figure 5] FIG. 4 is an astigmatism diagram of the second optical system of the zoom lens of Example 1. [Figure 6] 4 is a cross-sectional view showing the configuration and light beam of a zoom lens according to a modified example of the first embodiment. FIG. [Figure 7] 10 is a cross-sectional view showing the configuration, light beam, and movement locus of a zoom lens according to a second embodiment. [Figure 8] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 2 when the projection distance is at infinity. [Figure 9] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 2 when the projection magnification is 150 times. [Figure 10] FIG. 10 is a cross-sectional view showing the configuration and light beams of a zoom lens according to a modified example of the second embodiment. [Figure 11] 10 is a cross-sectional view showing the configuration, light beam, and movement locus of a zoom lens according to a third embodiment. [Figure 12] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 3 when the projection distance is at infinity. [Figure 13] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 3 when the projection magnification is 150 times. [Figure 14]FIG. 10 is a cross-sectional view showing the configuration and light beams of a zoom lens according to a modified example of the third embodiment. [Figure 15] 10 is a cross-sectional view showing the configuration, light beam, and movement locus of a zoom lens according to a fourth embodiment. [Figure 16] 10A to 10C are diagrams showing various aberrations of the zoom lens according to the fourth embodiment when the projection distance is at infinity. [Figure 17] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 4 when the projection magnification is 150 times. [Figure 18] 10 is a cross-sectional view showing the configuration, light beam, and movement locus of a zoom lens according to a fifth embodiment. [Figure 19] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 5 when the projection distance is at infinity. [Figure 20] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 5 when the projection magnification is 150 times. [Figure 21] 10 is a cross-sectional view showing the configuration, light beam, and movement locus of a zoom lens according to a sixth embodiment. [Figure 22] 10A to 10C are diagrams showing various aberrations of the zoom lens according to the sixth embodiment when the projection distance is at infinity. [Figure 23] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 6 when the projection magnification is 150 times. [Figure 24] FIG. 13 is a cross-sectional view showing the configuration and light beam of a zoom lens according to a modified example of the sixth embodiment. [Figure 25] 10 is a cross-sectional view showing the configuration, light beam, and movement locus of a zoom lens according to a seventh embodiment. [Figure 26] 13A and 13B are diagrams illustrating the configuration and light beams of a zoom lens in each variable magnification state according to a seventh embodiment. [Figure 27] 13A to 13C are diagrams showing various aberrations of the zoom lens according to Example 7 when the projection distance is at infinity. [Figure 28] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 7 when the projection magnification is 150 times. [Figure 29] FIG. 13 is a cross-sectional view showing the configuration and light beams of a zoom lens according to a modified example of the seventh embodiment. [Figure 30] 1 is a schematic configuration diagram of a projection display device according to an embodiment. [Figure 31]FIG. 10 is a schematic configuration diagram of a projection display device according to another embodiment. [Figure 32] FIG. 10 is a schematic configuration diagram of a projection display device according to yet another embodiment. [Figure 33] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 34] FIG. 34 is a perspective view of the rear side of the imaging device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0029] FIG. 1 shows a cross-sectional view of the configuration and luminous flux of a zoom lens according to an embodiment of the present disclosure at the wide-angle end, with the movement trajectory shown below. In FIG. 1, the luminous flux is represented by an axial luminous flux Ka and a luminous flux Kb at the maximum angle of view. FIG. 2 shows a cross-sectional view of the configuration and luminous flux of this zoom lens in each zooming state. In FIG. 2, the wide-angle end state is shown in the top row labeled "Wide-Angle End," the first intermediate focal length state is shown in the second row from the top labeled "First Intermediate," the second intermediate focal length state is shown in the third row from the top labeled "Second Intermediate," and the telephoto end state is shown in the bottom row labeled "Telephoto End." The example shown in FIGS. 1 and 2 corresponds to the zoom lens of Example 1, which will be described later. In FIGS. 1 and 2, the left side is the magnification side, and the right side is the reduction side. Below, the zoom lens according to an embodiment of the present disclosure will be described primarily with reference to FIG. 1.

[0030] The zoom lens of the present disclosure can be mounted in a projection display device to form an image to be projected on a screen as a projection optical system, or can be mounted in an imaging device to form an image of an object as an imaging optical system. The following description will be given assuming that the zoom lens is used as a projection optical system.

[0031] Figure 1 shows an example in which an optical element PP and an image display surface Sim of a light valve are placed on the reduction side of the zoom lens, assuming that the zoom lens will be installed in a projection display device. The optical element PP is a component that is assumed to be a filter, cover glass, color synthesis prism, etc. The optical element PP is a component that does not have refractive power, and it is possible to omit the optical element PP in a configuration.

[0032] In a projection display device, a light beam that has been given image information on an image display surface Sim is incident on a zoom lens via an optical member PP, and is then projected onto a screen (not shown) by the zoom lens. In this case, the image display surface Sim corresponds to the reduction-side image formation surface, and the screen corresponds to the enlargement-side image formation surface. In this specification, the term "screen" refers to an object onto which the projection image formed by the zoom lens is projected. The screen may be a dedicated screen, or may be a wall, floor, ceiling, or exterior wall of a building, etc.

[0033] In addition, in the explanation of this specification, the "enlargement side" means the screen side on the optical path, and the "reduction side" means the image display surface Sim side on the optical path. In this specification, the "enlargement side" and the "reduction side" are determined along the optical path, and this also applies to zoom lenses that form a folded optical path. In the following, to avoid redundant explanation, "in sequence along the optical path from the enlargement side to the reduction side" may be expressed as "in sequence from the enlargement side to the reduction side."

[0034] The zoom lens of the present disclosure is configured to form an intermediate image MI at a position conjugate with the reduction-side image formation plane and re-image the intermediate image MI on the enlargement-side image formation plane. In FIG. 1, only a portion of the intermediate image MI near the optical axis is shown by a dotted line for simplicity. The intermediate image MI in FIG. 1 indicates its position on the optical axis and does not show its exact shape. Hereinafter, among the optical systems constituting the zoom lens, the optical system on the enlargement side of the intermediate image MI will be referred to as the first optical system, and the optical system on the reduction side of the intermediate image MI will be referred to as the second optical system. In a projection display device, the second optical system forms an intermediate image MI of an image displayed on an image display surface Sim, and the first optical system projects this intermediate image MI onto a screen to form a projected image. An optical system that forms an intermediate image MI in this manner has the advantages of shortening the back focus of the first optical system and reducing the lens diameter on the enlargement side of the first optical system.

[0035] The zoom lens of the present disclosure can be considered to be composed of, in order from the magnification side to the reduction side along the optical path, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5. Each unit is configured as follows:

[0036] The first unit U1 consists of one lens group with positive refractive power. By locating a group with positive refractive power on the most magnifying side, it is possible to include a teleconverter-like configuration, which is advantageous for achieving high magnification. The first unit U1 may be fixed or may move during magnification variation. If the first unit U1 is fixed during magnification variation, the overall length of the optical system can be kept constant even when the magnification is changed. If the first unit U1 moves during magnification variation, this is advantageous for suppressing aberration fluctuations during magnification variation.

[0037] In this specification, a lens group is defined as a group whose distance from adjacent groups in the optical axis direction changes during magnification. In other words, a "lens group" in this specification is a component of a zoom lens that includes at least one lens and is separated by an air gap that changes during magnification. During magnification, each lens group is moved or fixed individually, and the distance between lenses within each lens group does not change.

[0038] The second unit U2 has an overall negative refractive power at the wide-angle end. With this configuration, the second unit U2 is primarily responsible for varying magnification. The second unit U2 also consists of two lens groups that move while varying the distance between them during magnification. This configuration of the second unit U2 makes it possible to suppress aberration fluctuations during magnification. In an optical system that forms an intermediate image MI, the above-described configuration of the second unit U2 reduces distortion, which is a problem at the wide-angle end, while minimizing the lens diameter on the magnification side. It also minimizes changes in distortion due to magnification. Hereinafter, of the two lens groups that make up the second unit U2, the lens group on the magnification side in the optical path will be referred to as the second-A lens group U2A, and the lens group on the reduction side will be referred to as the second-B lens group U2B.

[0039] FIG. 1 shows two intersections between the optical axis Z and the chief ray Kb1 of the maximum angle of view at the wide-angle end. Of these two intersections, the intersection on the magnification side on the optical path is referred to as the first intersection P1, and the intersection on the reduction side is referred to as the second intersection P2. The third unit U3 is configured as a unit including a lens group having positive refractive power that is located closest to the first intersection P1 at the wide-angle end. Here, "closest" means closest in terms of order on the optical path, not closest in terms of distance. Furthermore, if there is a lens group including the first intersection P1, that lens group is referred to as the lens group located closest to the first intersection P1.

[0040] The third unit U3 is configured to include one or more lens groups that move during zooming. In addition to the above configuration of the second unit U2, the third unit U3 includes one or more lens groups that move during zooming, which can contribute to suppressing aberration fluctuations during zooming. All of the lens groups included in the third unit U3 may be configured to move during zooming. The third unit U3 may also be configured to have positive refractive power overall at the wide-angle end. In this case, the negative refractive power of the second unit U2 can be strengthened, which is advantageous for achieving high magnification while suppressing the size of the lens system.

[0041] The fourth unit U4 is configured to include one or more lens groups that move during magnification. This configuration of the fourth unit U4 allows the fourth unit U4 to have a magnification-varying function in addition to the magnification-varying function of the second unit U2, enabling even higher magnification. It also makes it easier to ensure telecentricity throughout the entire magnification range. All of the lens groups included in the fourth unit U4 may be configured to move during magnification.

[0042] The fifth unit U5 is configured as a unit that includes the second intersection point P2 inside at the wide-angle end. The fifth unit U5 may be configured to consist of one lens group or multiple lens groups. If the fifth unit U5 consists of one lens group, it may be configured to be fixed during magnification. If the fifth unit U5 consists of multiple lens groups, it may be configured so that the lens group on the most reduction side of the fifth unit U5 is fixed during magnification. Fixing the lens group on the most reduction side during magnification makes it easier to maintain telecentricity on the reduction side.

[0043] As an example, in the example of FIG. 1, each unit is configured as follows: The first unit U1 consists of one lens group. The second unit U2 consists of two lens groups, a second-axis lens group U2A and a second-axis lens group U2B, arranged in order from the enlargement side to the reduction side. The third unit U3 consists of two lens groups, a third-axis lens group U3A and a third-axis lens group U3B, arranged in order from the enlargement side to the reduction side. The fourth unit U4 consists of two lens groups, a fourth-axis lens group U4A and a fourth-axis lens group U4B, arranged in order from the enlargement side to the reduction side. The fifth unit U5 consists of one lens group.

[0044] In the example of Fig. 1, the intermediate image MI is located inside the fifth unit U5. Also, in the example of Fig. 1, at the wide-angle end, the lens group having positive refractive power located closest to the first intersection point P1 is the 3B lens group U3B, and the second intersection point P2 is located inside the fifth unit U5. The position of the second intersection point P2 coincides with the position of the aperture stop St. The aperture stop St in Fig. 1 does not indicate the shape or size, but rather its position in the optical axis direction.

[0045] In the example of Figure 1, the first unit U1 and the fifth unit U5 are fixed during magnification variation, and the second-A lens group U2A, the second-B lens group U2B, the third-A lens group U3A, the third-B lens group U3B, the fourth-A lens group U4A, and the fourth-B lens group U4B move along the optical axis Z while changing the spacing between adjacent lens groups. In Figure 1, straight dotted lines are drawn below the lens groups that are fixed during magnification variation, and solid lines are drawn below the lens groups that move during magnification variation to show the movement trajectory when changing magnification from the wide-angle end to the telephoto end.

[0046] More preferred and possible configurations of the zoom lens of the present disclosure will be described below. In the following, to avoid redundant explanation, the "zoom lens of the present disclosure" will also be referred to simply as the "zoom lens."

[0047] It is preferable that the reduction side of a zoom lens be telecentric. For example, projection display devices that project high-definition images often use a so-called three-plate system, which is equipped with image display elements corresponding to the wavelengths of blue, green, and red. To accommodate this system, it is preferable that the reduction side be telecentric.

[0048] Note that the above phrase "the reduction side is configured to be telecentric" includes a practically acceptable error in the technical field to which the technology of the present disclosure pertains. The error may be, for example, ±3 degrees. In a system that does not include an aperture stop St, when a light beam is viewed in the direction from the enlargement side to the reduction side, telecentricity may be determined by using the bisector angle between the upper and lower maximum rays in the cross section of the light beam that converges at a point on the reduction-side image plane as a substitute for the chief ray.

[0049] The zoom lens preferably satisfies the following conditional expression (1). Here, the radius of the effective image circle on the reduction side is defined as Ymax. Also, in a state where the image formation plane on the telephoto side is at infinity, when the reduction side is the emission side, the distance on the optical axis from the reduction-side image formation plane at the wide-angle end to the paraxial exit pupil position is defined as exPw. As an example, Fig. 1 shows the radius Ymax of the effective image circle. The effective image circle is a so-called image circle. When calculating exPw, for an optical member having no refractive power, the air-equivalent distance is used. Regarding the lower limit of the conditional expression (1), since Ymax > 0 and |exPw| > 0, 0 < Ymax / |exPw| holds. By ensuring that the corresponding value of the conditional expression (1) does not exceed the upper limit, it becomes easy to ensure telecentricity while obtaining a desired effective image circle size. 0 < Ymax / |exPw| < 0.1 (1)

[0050] It is preferable that the second A lens group U2A has a negative refractive power and the second B lens group U2B has a positive refractive power. In this case, the second A lens group U2A can preferably perform the zooming action, and the second B lens group U2B can perform the action of correcting aberrations associated with zooming, which is advantageous for increasing the magnification. <​​​​​​

[0052] The second-subgroup U2B may be configured to move first to the enlargement side and then to the reduction side when changing magnification from the wide-angle end to the telephoto end. This arrangement increases the stroke of the second-subgroup U2A when changing magnification. This is advantageous for achieving higher magnification and also suppresses fluctuations in aberrations during magnification, particularly fluctuations in distortion at the wide-angle end during magnification.

[0053] The fourth unit U4 preferably comprises, in order along the optical path from the magnification side to the reduction side, a fourth-a lens group U4A having positive refractive power and a fourth-b lens group U4B having positive or negative refractive power. In this configuration, it is preferable that the fourth-a lens group U4A and the fourth-b lens group U4B move while varying the distance between them during magnification. This configuration allows the fourth-a lens group U4A to perform the magnification change function, while the fourth-b lens group U4B can correct aberrations associated with magnification change, which is advantageous for achieving higher magnification. It also makes it easier to ensure telecentricity throughout the entire magnification range.

[0054] In a configuration in which the fourth lens unit U4 is composed of the above-mentioned fourth-a lens group U4A and fourth-b lens group U4B, where the focal length of the fourth-a lens group U4A is f4A and the focal length of the fourth-b lens group U4B is f4B, it is preferable that the zoom lens satisfy the following conditional expression (3): By ensuring that the corresponding value of conditional expression (3) is not below the lower limit, the negative refractive power of the fourth-b lens group U4B relative to the refractive power of the fourth-a lens group U4A is not excessively strong. By ensuring that the corresponding value of conditional expression (3) is not above the upper limit, the positive refractive power of the fourth-b lens group U4B relative to the refractive power of the fourth-a lens group U4A is not excessively strong. Satisfying conditional expression (3) is advantageous for suppressing aberration fluctuations during magnification change and for ensuring telecentricity. To obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (3-1): -2 <f4A / f4B<1 (3) -1.5 <f4A / f4B<0.8 (3-1)

[0055] If the average Abbe number of all the positive lenses included in the fourth unit U4 based on the d-line is ν4pave, it is preferable that the zoom lens satisfy the following conditional expression (4). By ensuring that the corresponding value of conditional expression (4) is not below the lower limit, correction of longitudinal chromatic aberration becomes easier. It is more preferable that the zoom lens satisfy the following conditional expression (4-1). By ensuring that the corresponding value of conditional expression (4-1) is not below the lower limit, correction of longitudinal chromatic aberration becomes easier. By ensuring that the corresponding value of conditional expression (4-1) is not above the upper limit, it is advantageous for reducing the cost of the lens. 60<ν4pave (4) 65<ν4pave<90 (4-1)

[0056] It is preferable that the first optical system corrects the curvature of field generated in the second optical system and re-images the intermediate image MI on the magnification-side image-forming plane. By using an optical system that corrects the curvature of field generated at the position of the intermediate image MI, it is advantageous for reducing the size and increasing the magnification of the entire lens system.

[0057] If the focal length of the first optical system at the wide-angle end is fS1w and the focal length of the zoom lens at the wide-angle end is fw, it is preferable that the zoom lens satisfy the following conditional expression (5). By ensuring that the corresponding value of conditional expression (5) is not below the lower limit, the F-number of the first optical system does not need to be excessively small, which is advantageous for correcting spherical aberration and astigmatism. It is more preferable that the zoom lens satisfy the following conditional expression (5-1). By ensuring that the corresponding value of conditional expression (5-1) is not below the lower limit, the effect described above regarding the lower limit of conditional expression (5) can be further enhanced. By ensuring that the corresponding value of conditional expression (5-1) is not above the upper limit, the relay magnification when forming the intermediate image MI at a position conjugate with the reduction-side image formation surface does not become too large, which allows the size of the intermediate image MI to be reduced. This prevents the first optical system from becoming too large and is advantageous for correcting distortion and field curvature in the first optical system. 0.8 <fS1w / |fw| (5) 1 <fS1w / |fw|<2 (5-1)

[0058] When the intermediate image MI is located on the reduction side of the second unit U2, it is preferable that the zoom lens satisfy the following conditional expression (6). Here, ThS1 is the axial distance from the most magnifying lens surface of the first optical system to the most reducing lens surface of the first optical system at the wide-angle end. Also, ThZL is the axial distance from the most magnifying lens surface of the zoom lens to the most reducing lens surface of the zoom lens at the wide-angle end. By ensuring that the value corresponding to conditional expression (6) is not below the lower limit, the overall length of the first optical system, which has a large zooming effect, does not become too short, which is advantageous for achieving high magnification. By ensuring that the value corresponding to conditional expression (6) is not above the upper limit, the overall length of the first optical system does not become too long, which prevents the overall length of the second optical system from becoming too short. This prevents aberrations such as field curvature and distortion occurring in the second optical system from becoming excessive, which is advantageous for correcting these aberrations occurring in the second optical system with the first optical system to obtain a good image at the magnification-side image plane. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (6-1). 0.4 <ThS1 / ThZL<0.7 (6) 0.5 <ThS1 / ThZL<0.65 (6-1)

[0059] It is preferable that the intermediate image MI be located within the fifth unit U5. In this case, the intermediate image MI can be formed at a position relatively close to the second intersection point P2, thereby reducing the size of the intermediate image MI. This prevents the first optical system from becoming too large and is advantageous for correcting distortion and field curvature in the first optical system.

[0060] If the air-equivalent distance on the optical axis from the lens surface closest to the reduction side of the zoom lens at the wide-angle end to the reduction-side focal position of the zoom lens is Bfw and the focal length of the zoom lens at the wide-angle end is fw, it is preferable that the zoom lens satisfy the following conditional expression (7). Bfw is the back focus in air-equivalent distance of the zoom lens at the wide-angle end. By ensuring that the corresponding value of conditional expression (7) is not below the lower limit, the back focus does not become too short, making it easy to arrange a color synthesis prism or the like. It is more preferable that the zoom lens satisfy the following conditional expression (7-1). By ensuring that the corresponding value of conditional expression (7-1) is not below the lower limit, the effect described above regarding the lower limit of conditional expression (7) can be further enhanced. By ensuring that the corresponding value of conditional expression (7-1) is not above the upper limit, it is possible to prevent the entire optical system, including the back focus, from becoming larger. 1 <Bfw / |fw| (7) 1.3 <Bfw / |fw|<4 (7-1)

[0061] The zoom lens may be configured to include an optical path bending member that bends the optical path at a position adjacent to the intermediate image MI. Here, "including an optical path bending member that bends the optical path at a position adjacent to the intermediate image MI" means that there is no member with refractive power, such as a lens, in the optical path between the intermediate image MI and the bending member. A relatively large air gap can be secured at a position adjacent to the intermediate image MI, making it easy to arrange the optical path bending member. Including an optical path bending member can contribute to the miniaturization of the entire lens system. The optical path bending member can be, for example, a member with a reflective surface, such as a mirror.

[0062] The angle at which the optical path of the optical path bending member is bent can be set arbitrarily, but may be, for example, 90 degrees. Setting the bending angle to 90 degrees allows for a structure that is easy to manufacture. Note that this "90 degrees" includes a practically acceptable margin of error in the technical field to which the technology of the present disclosure pertains. The margin of error may be, for example, ±5 degrees.

[0063] It is preferable for a zoom lens to have a focusing function. For example, one or more lenses in at least one of the fourth unit U4 and the fifth unit U5 may be configured to move during focusing. By focusing on a relatively reduced focal length, the lens group that moves during focusing can be configured to be small, which is advantageous for reducing the load on the drive system, downsizing the device, and speeding up focusing. Hereinafter, the lens group that moves during focusing will be referred to as the focus group. In the example of Figure 1, the focus group is the fourth-subgroup lens U4B. The horizontal double arrow above the fourth-subgroup lens U4B in Figure 1 indicates that the focus group is the fourth-subgroup lens U4B.

[0064] Note that the example shown in Fig. 1 is just one example, and various modifications are possible without departing from the spirit of the technology of the present disclosure. For example, in the technology of the present disclosure, the number of lens groups included in the third unit U3, the fourth unit U4, and the fifth unit U5 may be different from that in the example of Fig. 1. Furthermore, in the technology of the present disclosure, the number of lenses included in each lens group may also be different from that in the example of Fig. 1.

[0065] The above-described preferred and possible configurations, including those related to the conditional expressions, can be combined in any desired manner, and are preferably selectively adopted as appropriate according to the required specifications. Note that the conditional expressions that the zoom lens of the present disclosure preferably satisfies are not limited to those written in the form of an expression, but include all conditional expressions obtained by arbitrarily combining lower and upper limits from among the preferred and more preferred conditional expressions.

[0066] Next, examples of the zoom lens of the present disclosure will be described with reference to the drawings. Note that the reference symbols assigned to the units and lens groups in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanations and drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the configuration is the same.

[0067] [Example 1] The configuration of the zoom lens of Example 1 and a cross-sectional view of the light beam are shown in Figure 1. The illustration method and configuration are as described above, so some redundant explanation will be omitted here. The zoom lens of Example 1 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0068] The first unit U1 consists of one lens group with positive refractive power. The second unit U2 consists, from the magnification side to the reduction side, of a secondA lens group U2A with negative refractive power and a secondB lens group U2B with positive refractive power. The third unit U3 consists, from the magnification side to the reduction side, of a thirdA lens group U3A with negative refractive power and a thirdB lens group U3B with positive refractive power. The fourth unit U4 consists, from the magnification side to the reduction side, of a fourthA lens group U4A with positive refractive power and a fourthB lens group U4B with negative refractive power. The fifth unit U5 consists of one lens group. The zoom lens of Example 1 consists of eight lens groups.

[0069] During magnification variation, the lens groups of the first unit U1 and the fifth unit U5 are fixed, and the other lens groups change the spacing between themselves and move along the optical axis Z. The focus group is made up of the fourth lens group U4B.

[0070] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0071] For the zoom lens of Example 1, basic lens data is shown in Tables 1A and 1B, specifications are shown in Table 2, and variable surface spacing is shown in Table 3. Here, to avoid making one table too long, the basic lens data is shown in two tables, Table 1A and Table 1B. Table 1A shows the first optical system, and Table 1B shows the second optical system and optical member PP.

[0072] The table of basic lens data is written as follows. The Sn column shows the surface number, with the surface closest to the enlargement side designated as surface 1 and the numbers increasing by one as you move toward the reduction side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and the surface adjacent to it on the reduction side. The Nd column shows the refractive index for the d-line of each component element. The νd column shows the Abbe number for each component element based on the d-line.

[0073] In the basic lens data table, the sign of the radius of curvature of a surface with a convex surface facing the enlargement side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the reduction side is negative. In Table 1B, the surface number and the term (St) are entered in the column for the surface corresponding to the aperture stop St. The value in the bottom column of D in Table 1B is the distance between the surface on the most reduction side in the table and the image display surface Sim. In the basic lens data table, the symbol DD[ ] is used for variable surface distances, and the surface number on the enlargement side of this distance is entered in the [ ] in the D column.

[0074] Table 2 shows the zoom magnification Zr, absolute value of focal length |f|, F-number FNo., and maximum full angle of view 2ω, based on the d-line. The [°] in the 2ω column indicates that the unit is degrees. The values ​​shown in Tables 1 and 2 are those when the projection distance is at infinity. Note that in the embodiments of the present disclosure, the projection distance at infinity is synonymous with the magnification-side image plane being at infinity. In Table 2, the values ​​for the wide-angle end state, first intermediate focal length state, second intermediate focal length state, and telephoto end state are shown in the "wide-angle end," "first intermediate," "second intermediate," and "telephoto end" columns, respectively. This also applies to Table 3, described below.

[0075] Table 3 shows the variable surface distance for each magnification state. In Table 3, the value when the projection distance is infinite is shown in the table labeled "Infinity," and the value when the projection magnification is 150x is shown in the table labeled "Projection magnification 150x."

[0076] In the data in each table, degrees are used as the unit of angle and mm (millimeters) as the unit of length, but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table below, values ​​are listed rounded to a certain number of decimal places.

[0077] [Table 1A]

[0078] [Table 1B]

[0079] [Table 2]

[0080] [Table 3]

[0081] FIG. 3 shows aberration diagrams of the zoom lens of Example 1 when the projection distance is at infinity. In FIG. 3, the top row labeled "Wide-Angle End" shows aberration diagrams at the wide-angle end, the second row labeled "First Intermediate" shows aberration diagrams at the first intermediate focal length state, the third row labeled "Second Intermediate" shows aberration diagrams at the second intermediate focal length state, and the bottom row labeled "Telephoto End" shows aberration diagrams at the telephoto end. From left to right, FIG. 3 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In the spherical aberration diagrams, aberrations for the d-line, C-line, and F-line are shown by solid lines, long-dashed lines, and short-dashed lines, respectively. In the astigmatism diagrams, aberrations for the d-line in the sagittal direction are shown by solid lines, and aberrations for the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagrams, aberrations for the d-line are shown by solid lines. In the lateral chromatic aberration diagram, aberrations for the C-line and F-line are shown with long-dashed and short-dashed lines, respectively. In the spherical aberration diagram, the F-number value is shown after "FNo.=". In the other aberration diagrams, the maximum half angle of view value is shown after "ω=".

[0082] Fig. 4 shows aberration diagrams for the zoom lens of Example 1 when the projection magnification is 150x. The illustration method for Fig. 4 is the same as Fig. 3. In the data in Fig. 4, the projection distances at the wide-angle end, the first intermediate focal length state, the second intermediate focal length state, and the telephoto end are 2.1 m (meters), 4.1 m (meters), 8.6 m (meters), and 15.1 m (meters), respectively. The projection distance is the distance on the optical axis from the lens surface on the most enlargement side to the enlargement-side image plane.

[0083] FIG. 5 shows an astigmatism diagram of the second optical system of Example 1 alone. FIG. 5 shows an astigmatism diagram on the reduction-side image plane when the object distance is the distance on the optical axis from the lens surface on the magnification side of the second optical system to the paraxial image position of the intermediate image MI. The top of the graph in FIG. 5 corresponds to the maximum half angle of view. While the astigmatism is large in FIG. 5, the astigmatism in FIGS. 3 and 4 is much smaller than that in FIG. 5. This shows that the first optical system of the zoom lens of Example 1 effectively corrects the field curvature generated in the second optical system and re-images the intermediate image MI on the magnification-side image plane.

[0084] FIG. 6 shows the configuration and light beam at the wide-angle end of a zoom lens according to a modified example of Example 1. The zoom lens of FIG. 6 is composed of, in order along the optical path from the magnification side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5R. The fifth unit U5R differs from the fifth unit U5 of the zoom lens of Example 1 in that it includes a mirror R1, which is an optical path bending member, located adjacent to the intermediate image MI, and the optical path is bent by the mirror R1. The rest of the configuration of the zoom lens of FIG. 6 is the same as that of the zoom lens of Example 1. Bending the optical path enables a compact configuration.

[0085] The symbols, meanings, notation methods, and illustration methods of each piece of data relating to the above-mentioned first embodiment and the modified examples are basically the same in the following embodiments unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0086] [Example 2] 7 shows a cross-sectional view of the configuration and light beam of the zoom lens of Example 2. The zoom lens of Example 2 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0087] The first unit U1 consists of one lens group with positive refractive power. The second unit U2 consists, from the magnification side to the reduction side, of a secondA lens group U2A with negative refractive power and a secondB lens group U2B with positive refractive power. The third unit U3 consists, from the magnification side to the reduction side, of a thirdA lens group U3A with negative refractive power and a thirdB lens group U3B with positive refractive power. The fourth unit U4 consists, from the magnification side to the reduction side, of a fourthA lens group U4A with positive refractive power and a fourthB lens group U4B with negative refractive power. The fifth unit U5 consists of one lens group. The zoom lens of Example 2 consists of eight lens groups.

[0088] When varying magnification, the lens groups in the first unit U1 and the fifth unit U5 are fixed, while the other lens groups change the spacing between themselves and move along the optical axis Z. The focus group consists of a single lens, the second from the magnification side of the fifth unit U5.

[0089] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0090] For the zoom lens of Example 2, basic lens data is shown in Tables 4A and 4B, specifications are shown in Table 5, and variable surface spacing is shown in Table 6. Also, each aberration diagram when the projection distance is at infinity is shown in Fig. 8, and each aberration diagram when the projection magnification is at 150x is shown in Fig. 9. In the data in Fig. 9, the projection distances at the wide-angle end, first intermediate focal length state, second intermediate focal length state, and telephoto end are 2.1 m (meters), 4.1 m (meters), 8.5 m (meters), and 14.7 m (meters), respectively.

[0091] [Table 4A]

[0092] [Table 4B]

[0093] [Table 5]

[0094] [Table 6]

[0095] FIG. 10 shows the configuration and light beam at the wide-angle end of a zoom lens according to a modified example of Example 2. The zoom lens of FIG. 10 is composed of, in order along the optical path from the magnification side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5R. The fifth unit U5R differs from the fifth unit U5 of the zoom lens of Example 2 in that it includes a mirror R1, which is an optical path bending member, located adjacent to the intermediate image MI, and the optical path is bent by the mirror R1. The rest of the configuration of the zoom lens of FIG. 10 is the same as that of the zoom lens of Example 2. Bending the optical path enables a compact configuration.

[0096] [Example 3] 11 shows a cross-sectional view of the configuration of the zoom lens of Example 3 and the light beam. The zoom lens of Example 3 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0097] The first unit U1 consists of one lens group with positive refractive power. The second unit U2 consists, from the magnification side to the reduction side, of a secondA lens group U2A with negative refractive power and a secondB lens group U2B with positive refractive power. The third unit U3 consists, from the magnification side to the reduction side, of a thirdA lens group U3A with negative refractive power and a thirdB lens group U3B with positive refractive power. The fourth unit U4 consists, from the magnification side to the reduction side, of a fourthA lens group U4A with positive refractive power and a fourthB lens group U4B with negative refractive power. The fifth unit U5 consists of one lens group. The zoom lens of Example 3 consists of eight lens groups.

[0098] During magnification variation, the lens groups of the first unit U1 and the fifth unit U5 are fixed, and the other lens groups change the spacing between themselves and move along the optical axis Z. The focus group is made up of the fourth lens group U4B.

[0099] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0100] For the zoom lens of Example 3, basic lens data is shown in Tables 7A and 7B, specifications are shown in Table 8, variable surface spacing is shown in Table 9, and aspherical coefficients are shown in Table 10.

[0101] In the basic lens data, aspherical surface numbers are marked with an *, and the paraxial radius of curvature is listed in the aspherical radius of curvature column. In Table 10, the Sn row shows the aspherical surface number, and the KA and Am (m = 3, 4, 5, 6, 7, 8) rows show the numerical values ​​of the aspherical coefficients for each aspherical surface. The numerical values ​​of the aspherical coefficients in Table 10, "E±n" (n: integer), are expressed as "×10 ±n KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial curvature radius KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0102] [Table 7A]

[0103] [Table 7B]

[0104] [Table 8]

[0105] [Table 9]

[0106] [Table 10]

[0107] For the zoom lens of Example 3, each aberration diagram when the projection distance is infinity is shown in Fig. 12, and each aberration diagram when the projection magnification is 150x is shown in Fig. 13. In the data in Fig. 13, the projection distances at the wide-angle end, the first intermediate focal length state, the second intermediate focal length state, and the telephoto end are 1.8 m (meters), 3.5 m (meters), 7.3 m (meters), and 12.8 m (meters), respectively.

[0108] FIG. 14 shows the configuration and light beam at the wide-angle end of a zoom lens according to a modified example of Example 3. The zoom lens of FIG. 14 comprises, in order along the optical path from the magnification side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5R. The fifth unit U5R differs from the fifth unit U5 of the zoom lens of Example 3 in that it includes a mirror R1, which is an optical path bending member, located adjacent to the intermediate image MI, and the optical path is bent by the mirror R1. The rest of the configuration of the zoom lens of FIG. 14 is the same as that of the zoom lens of Example 3. Bending the optical path enables a compact configuration.

[0109] [Example 4] 15 shows a cross-sectional view of the configuration of the zoom lens of Example 4 and the light beam. The zoom lens of Example 4 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0110] The first unit U1 consists of one lens group having positive refractive power. The second unit U2 consists of, from the magnification side to the reduction side, a secondA lens group U2A having negative refractive power and a secondB lens group U2B having positive refractive power. The third unit U3 consists of one lens group having positive refractive power. The fourth unit U4 consists of, from the magnification side to the reduction side, a fourthA lens group U4A having positive refractive power and a fourthB lens group U4B having positive refractive power. The fifth unit U5 consists of one lens group. The zoom lens of Example 4 consists of seven lens groups.

[0111] When varying magnification, the lens groups in the first unit U1 and the fifth unit U5 are fixed, while the other lens groups change the spacing between themselves and move along the optical axis Z. The focus group consists of a single lens in the fifth unit U5, which is on the magnification side.

[0112] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0113] For the zoom lens of Example 4, basic lens data is shown in Tables 11A and 11B, specifications are shown in Table 12, and variable surface spacing is shown in Table 13. Also, each aberration diagram when the projection distance is at infinity is shown in Fig. 16, and each aberration diagram when the projection magnification is at 150x is shown in Fig. 17. In the data in Fig. 17, the projection distances at the wide-angle end, first intermediate focal length state, second intermediate focal length state, and telephoto end are 2.7 m (meters), 5.3 m (meters), 10.9 m (meters), and 13.6 m (meters), respectively.

[0114] [Table 11A]

[0115] [Table 11B]

[0116] [Table 12]

[0117] [Table 13]

[0118] [Example 5] 18 shows a cross-sectional view of the configuration of the zoom lens of Example 5 and the light beam. The zoom lens of Example 5 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0119] The first unit U1 consists of one lens group having positive refractive power. The second unit U2 consists of, from the magnification side to the reduction side, a secondA lens group U2A having negative refractive power and a secondB lens group U2B having positive refractive power. The third unit U3 consists of one lens group having positive refractive power. The fourth unit U4 consists of, from the magnification side to the reduction side, a fourthA lens group U4A having positive refractive power and a fourthB lens group U4B having positive refractive power. The fifth unit U5 consists of one lens group. The zoom lens of Example 5 consists of seven lens groups.

[0120] When varying magnification, the lens groups in the first unit U1 and the fifth unit U5 are fixed, while the other lens groups change the spacing between themselves and move along the optical axis Z. The focus group consists of a single lens in the fifth unit U5, which is on the magnification side.

[0121] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0122] For the zoom lens of Example 5, basic lens data is shown in Tables 14A and 14B, specifications are shown in Table 15, and variable surface spacing is shown in Table 16. Also, each aberration diagram when the projection distance is at infinity is shown in Fig. 19, and each aberration diagram when the projection magnification is at 150x is shown in Fig. 20. In the data in Fig. 20, the projection distances at the wide-angle end, first intermediate focal length state, second intermediate focal length state, and telephoto end are 2.7 m (meters), 5.3 m (meters), 10.9 m (meters), and 13.6 m (meters), respectively.

[0123] [Table 14A]

[0124] [Table 14B]

[0125] [Table 15]

[0126] [Table 16]

[0127] [Example 6] 21 shows a cross-sectional view of the configuration of the zoom lens of Example 6 and the light beam. The zoom lens of Example 6 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0128] The first unit U1 consists of one lens group with positive refractive power. The second unit U2 consists, from the magnification side to the reduction side, of a second-A lens group U2A with negative refractive power and a second-B lens group U2B with positive refractive power. The third unit U3 consists, from the magnification side to the reduction side, of a third-A lens group U3A with negative refractive power and a third-B lens group U3B with positive refractive power. The fourth unit U4 consists, from the magnification side to the reduction side, of a fourth-A lens group U4A with positive refractive power and a fourth-B lens group U4B with negative refractive power. The fifth unit U5 consists of one lens group. The zoom lens of Example 6 consists of eight lens groups.

[0129] During magnification variation, the lens groups included in the fifth unit U5 are fixed, and the other lens groups change the spacing between adjacent groups and move along the optical axis Z. The focus group is made up of the fourth lens group U4B.

[0130] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0131] For the zoom lens of Example 6, basic lens data is shown in Tables 17A and 17B, specifications are shown in Table 18, and variable surface spacing is shown in Table 19. Also, each aberration diagram when the projection distance is at infinity is shown in Fig. 22, and each aberration diagram when the projection magnification is at 150x is shown in Fig. 23. In the data in Fig. 23, the projection distances at the wide-angle end, first intermediate focal length state, second intermediate focal length state, and telephoto end are 2.1 m (meters), 4.1 m (meters), 8.6 m (meters), and 15.1 m (meters), respectively.

[0132] [Table 17A]

[0133] [Table 17B]

[0134] [Table 18]

[0135] [Table 19]

[0136] FIG. 24 shows the configuration and light beam at the wide-angle end of a zoom lens according to a modified example of Example 6. The zoom lens of FIG. 24 is composed of, in order along the optical path from the magnification side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5R. The fifth unit U5R differs from the fifth unit U5 of the zoom lens of Example 6 in that it includes a mirror R1, which is an optical path bending member, located adjacent to the intermediate image MI, and the optical path is bent by the mirror R1. The rest of the configuration of the zoom lens of FIG. 24 is the same as that of the zoom lens of Example 6. Bending the optical path enables a compact configuration.

[0137] [Example 7] FIG. 25 shows a cross-sectional view of the configuration and light beam of the zoom lens of Example 7. FIG. 26 shows a cross-sectional view of the configuration and light beam of the zoom lens of Example 7 in each magnification state. The illustration method in FIG. 26 is the same as that in FIG. 2. The zoom lens of Example 7 is composed of, in order from the enlargement side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5.

[0138] The first unit U1 consists of one lens group with positive refractive power. The second unit U2 consists, from the magnification side to the reduction side, of a second-A lens group U2A with negative refractive power and a second-B lens group U2B with positive refractive power. The third unit U3 consists, from the magnification side to the reduction side, of a third-A lens group U3A with negative refractive power and a third-B lens group U3B with positive refractive power. The fourth unit U4 consists, from the magnification side to the reduction side, of a fourth-A lens group U4A with positive refractive power and a fourth-B lens group U4B with negative refractive power. The fifth unit U5 consists, from the magnification side to the reduction side, of a fifth-A lens group U5A, a fifth-B lens group U5B, a fifth-C lens group U5C, a fifth-D lens group U5D, a fifth-E lens group U5E, and a fifth-F lens group U5F. The zoom lens of Example 7 is made up of 13 lens groups.

[0139] When changing magnification from the wide-angle end to the second intermediate focal length state, the lens groups of the first unit U1 and the lens groups of the fifth unit U5 are fixed, while the other lens groups move along the optical axis Z while changing the spacing between them. When changing magnification from the second intermediate focal length state to the telephoto end, the 5B lens group U5B, the 5C lens group U5C, the 5D lens group U5D, and the 5E lens group U5E move along the optical axis Z while changing the spacing between them, while the other lens groups are fixed. The focus group consists of the 4B lens group U4B.

[0140] The intermediate image MI is located inside the fifth unit U5. At the wide-angle end and the telephoto end, the first optical system has a positive refractive power as a whole, and the second optical system has a positive refractive power as a whole.

[0141] For the zoom lens of Example 7, basic lens data is shown in Tables 20A and 20B, specifications are shown in Table 21, and variable surface spacing is shown in Table 22. Also, each aberration diagram when the projection distance is at infinity is shown in Fig. 27, and each aberration diagram when the projection magnification is at 150x is shown in Fig. 28. In the data in Fig. 28, the projection distances at the wide-angle end, first intermediate focal length state, second intermediate focal length state, and telephoto end are 2.1 m (meters), 4.1 m (meters), 10.8 m (meters), and 15.1 m (meters), respectively.

[0142] [Table 20A]

[0143] [Table 20B]

[0144] [Table 21]

[0145] [Table 22]

[0146] FIG. 29 shows the configuration and light beam at the wide-angle end of a zoom lens according to a modified example of Example 7. The zoom lens of FIG. 29 comprises, in order along the optical path from the magnification side to the reduction side, a first unit U1, a second unit U2, a third unit U3, a fourth unit U4, and a fifth unit U5R. The fifth unit U5R differs from the fifth unit U5 of the zoom lens of Example 7 in that it includes a mirror R1, which is an optical path bending member, located adjacent to the intermediate image MI, and the optical path is bent by the mirror R1. The rest of the configuration of the zoom lens of FIG. 29 is the same as that of the zoom lens of Example 7. Bending the optical path enables a compact configuration.

[0147] Table 23 shows the corresponding values ​​of conditional expressions (1) to (7) and the radius Ymax of the effective image circle for the zoom lenses of Examples 1 to 7. Table 23 shows values ​​based on the d-line. The corresponding values ​​of the Examples shown in Table 23 may be used as the upper or lower limits of the conditional expressions to set preferred ranges for the conditional expressions.

[0148] [Table 23]

[0149] The zoom lenses of Examples 1 to 7 have a high zoom magnification of 3 or more, more specifically 5 or more, and also have high optical performance with suppressed aberration fluctuations during zooming and excellent correction of each aberration.

[0150] Projection optical systems used in projection display devices require excellent aberration correction commensurate with the resolution of the light valves of the projection display devices. Furthermore, in recent years, as light valves have become increasingly brighter, projection optical systems are required to cover a wide focal length range in order to utilize projection display devices in a variety of situations. While efforts have been made to achieve this, achieving both high magnification and excellent aberration correction is not easy, and zoom magnifications have typically remained at around 2x. Conventionally, a method has been adopted in which multiple projection optical systems with zoom magnifications of around 1x to 2x are prepared for each focal length range, and a wide focal length range is covered by replacing the projection optical systems. However, this method has drawbacks, such as the introduction of dust when replacing the projection optical systems, the laborious replacement process, and the need to prepare a new projection optical system for each usage situation. In contrast, the zoom lenses of Examples 1 to 7 above achieve sufficiently high zoom magnifications and excellent aberration correction, even when changing the magnification, thereby eliminating the aforementioned drawbacks.

[0151] Next, a projection display device according to an embodiment of the present disclosure will be described. FIG. 30 is a schematic diagram of a projection display device according to an embodiment of the present disclosure. The projection display device 100 shown in FIG. 30 includes a zoom lens 10 according to an embodiment of the present disclosure, a light source 15, transmissive display elements 11a-11c as light valves corresponding to the respective colors of light, dichroic mirrors 12 and 13 for color separation, a cross dichroic prism 14 for color synthesis, condenser lenses 16a-16c, and total reflection mirrors 18a-18c for deflecting the optical path. Note that FIG. 30 only shows the zoom lens 10 in a schematic manner. An integrator is disposed between the light source 15 and the dichroic mirror 12, but is not shown in FIG. 30.

[0152] White light from light source 15 is separated into three colored light beams (green light, blue light, and red light) by dichroic mirrors 12 and 13, and then passes through condenser lenses 16a to 16c, where the colored light beams are incident on transmissive display elements 11a to 11c corresponding to the colored light beams and modulated there. After being color-synthesized by cross dichroic prism 14, the colored light beams are incident on zoom lens 10. Zoom lens 10 projects an optical image based on the modulated light modulated by transmissive display elements 11a to 11c onto screen 105.

[0153] Fig. 31 is a schematic diagram of a projection display device according to another embodiment of the present disclosure. The projection display device 200 shown in Fig. 31 includes a zoom lens 210 according to an embodiment of the present disclosure, a light source 215, DMD (Digital Micromirror Device: registered trademark) elements 21a-21c as light valves corresponding to the respective colors of light, TIR (Total Internal Reflection) prisms 24a-24c for color separation and color synthesis, and a polarization separation prism 25 that separates illumination light and projection light. Note that Fig. 31 only shows a schematic view of the zoom lens 210. An integrator is disposed between the light source 215 and the polarization separation prism 25, but is not shown in Fig. 31.

[0154] White light from light source 215 is reflected by a reflective surface inside polarization separation prism 25, and then separated into three colored light beams (green light, blue light, and red light) by TIR prisms 24a-24c. Each separated colored light beam enters and is modulated by the corresponding DMD elements 21a-21c, travels again in the opposite direction through TIR prisms 24a-24c, and is color-synthesized. Then, it passes through polarization separation prism 25 and enters zoom lens 210. Zoom lens 210 projects an optical image based on the modulated light modulated by DMD elements 21a-21c onto screen 205.

[0155] Fig. 32 is a schematic diagram of a projection display device according to yet another embodiment of the present disclosure. The projection display device 300 shown in Fig. 32 includes a zoom lens 310 according to an embodiment of the present disclosure, a light source 315, reflective display elements 31a-31c as light valves corresponding to the respective colors of light, 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 separation prisms 35a-35c. Note that Fig. 32 only shows the zoom lens 310 in a simplified manner. An integrator is disposed between the light source 315 and the dichroic mirror 32, but is not shown in Fig. 32.

[0156] White light from light source 315 is separated into three colored light beams (green light, blue light, and red light) by dichroic mirrors 32 and 33. Each separated colored light beam passes through polarization separation prisms 35a to 35c, enters and is modulated by reflective display elements 31a to 31c corresponding to the colored light beam, and is color-synthesized by cross dichroic prism 34 before entering zoom lens 310. Zoom lens 310 projects an optical image based on the modulated light by reflective display elements 31a to 31c onto screen 305.

[0157] 33 and 34 are external views of a camera 400, which is an imaging device according to an embodiment of the present disclosure. Fig. 33 shows a perspective view of the camera 400 as seen from the front, and Fig. 34 shows a perspective view of the camera 400 as seen from the rear. The camera 400 is a mirrorless single-lens digital camera to which an interchangeable lens 48 is removably attached. The interchangeable lens 48 is a zoom lens 49 according to an embodiment of the present disclosure housed within a lens barrel.

[0158] The camera 400 includes a camera body 41, and a shutter button 42 and a power button 43 are provided on the top surface of the camera body 41. 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 the image was captured.

[0159] A photographic opening through which light from the subject to be photographed enters is provided in the center of the front of the camera body 41, and a mount 47 is provided at a position corresponding to the photographic opening, and an interchangeable lens 48 is attached to the camera body 41 via the mount 47.

[0160] Inside the camera body 41, there are provided an imaging element (not shown) such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 48, a signal processing circuit (not shown) that processes the imaging signal output from the imaging element to generate an image, and a recording medium (not shown) for recording the generated image. With the camera 400, it is possible to take a still image or a video by pressing the shutter button 42, and the image data obtained by this shooting is recorded on the recording medium.

[0161] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0162] Furthermore, the projection display device according to the technology of the present disclosure is not limited to the above configuration, and for example, the optical members and light valves used for light beam separation or light beam combination can be modified in various ways. The light valve is not limited to a configuration in which light from a light source is spatially modulated by an image display element and output as an optical image based on image data, but may be a configuration in which light itself output from a self-luminous image display element is output as an optical image based on image data. Examples of self-luminous image display elements include image display elements in which light-emitting elements such as LEDs (Light Emitting Diodes) or OLEDs (Organic Light Emitting Diodes) are two-dimensionally arranged.

[0163] Furthermore, the imaging device according to the technology of the present disclosure is not limited to the above configuration, and can take various forms, such as cameras other than mirrorless cameras, film cameras, video cameras, and cinema cameras. [Explanation of symbols]

[0164] 10, 49, 210, 310 zoom lenses 11a to 11c Transmissive display element 12, 13, 32, 33 Dichroic mirror 14, 34 Cross dichroic prism 15, 215, 315 light source 16a~16c Condenser Lens 18a~18c, 38 Total reflection mirror 21a~21c DMD elements 24a~24c TIR Prism 25, 35a-35c Polarization separation prism 31a to 31c reflective display elements 41 Camera Body 42 Shutter button 43 Power button 44, 45 Operation section 46 Display section 47 Mount 48 Interchangeable Lenses 100, 200, 300 Projection display device 105, 205, 305 screens 400 cameras Ka On-axis luminous flux Kb Maximum angle of view luminous flux Kb1 chief ray MI intermediate image PP optical components P1 1st intersection P2 2nd intersection R1 Mirror Sim image display surface St aperture stop U1 1st Unit U2 2nd Unit U2A 2A lens group U2B 2B lens group U3 3rd Unit U3A 3A lens group U3B 3B lens group U4 4th Unit U4A 4A lens group U4B 4B lens group U5 5th Unit U5A 5A lens group U5B 5B lens group U5C 5C lens group U5D 5D lens group U5E 5E lens group U5F 5F lens group U5R 5th Unit Ymax Radius of the effective image circle Z optical axis

Claims

1. A zoom lens that forms an intermediate image at a position conjugate with a reduction-side image-forming surface and re-images the intermediate image at an enlargement-side image-forming surface, The lens comprises a first unit, a second unit, a third unit, a fourth unit, and a fifth unit, arranged in this order along the optical path from the magnification side to the reduction side, If a lens group whose spacing in the optical axis direction with respect to its adjacent group changes during magnification is considered to be one lens group, then: the first unit is made up of one lens group having positive refractive power, the second unit is made up of two lens groups that move while changing the distance between them during magnification, and has a negative refractive power as a whole at the wide-angle end; the third unit is composed of one or two lens groups, the fourth unit is composed of two lens groups, When changing magnification from the wide-angle end to the telephoto end, all of the lens groups in the third unit and the two lens groups in the fourth unit move while changing the intervals between adjacent groups in the optical axis direction, and the lens group on the most enlargement side in the fifth unit is fixed, Of the intersections between the chief ray of the maximum angle of view at the wide-angle end and the optical axis, if the intersection on the enlargement side on the optical path is defined as a first intersection and the intersection on the reduction side is defined as a second intersection, at a wide-angle end, the third unit includes a lens group having positive refractive power located nearest to the first intersection point, at the wide-angle end, the fifth unit includes the second intersection therein, of the two lens groups of the second unit, the lens group on the enlargement side on the optical path is designated as a second-A lens group, and the lens group on the reduction side is designated as a second-B lens group, The focal length of the second A lens group is f2A, When the focal length of the second lens group B is f2B, -0.5<f2A / f2B<0 (2) A zoom lens that satisfies conditional expression (2) expressed as follows:

2. A zoom lens that forms an intermediate image at a position conjugate with a reduction-side image-forming surface and re-images the intermediate image at an enlargement-side image-forming surface, The lens comprises a first unit, a second unit, a third unit, a fourth unit, and a fifth unit, arranged in this order along the optical path from the magnification side to the reduction side, If a lens group whose spacing in the optical axis direction with respect to its adjacent group changes during magnification is considered to be one lens group, then: the first unit is made up of one lens group having positive refractive power, the second unit is made up of two lens groups that move while changing the distance between them during magnification, and has a negative refractive power as a whole at the wide-angle end; the third unit is composed of one or two lens groups, the fourth unit comprises, in order along the optical path from the enlargement side to the reduction side, a fourth A lens group having positive refractive power and a fourth B lens group having positive or negative refractive power; When changing magnification from the wide-angle end to the telephoto end, all of the lens groups of the third unit, the fourth A lens group, and the fourth B lens group move while changing the intervals between adjacent groups in the optical axis direction, and the lens group on the most enlargement side of the fifth unit is fixed, Of the intersections between the chief ray of the maximum angle of view at the wide-angle end and the optical axis, if the intersection on the enlargement side on the optical path is defined as a first intersection and the intersection on the reduction side is defined as a second intersection, at a wide-angle end, the third unit includes a lens group having positive refractive power located nearest to the first intersection point, at the wide-angle end, the fifth unit includes the second intersection therein, The focal length of the fourth lens group A is f4A, When the focal length of the 4B lens group is f4B, -2<f4A / f4B<1 (3) A zoom lens that satisfies conditional expression (3) expressed as follows:

3. 3. The zoom lens according to claim 1, wherein the reduction side is configured to be telecentric.

4. The radius of the effective image circle on the reduction side is Ymax, When the enlargement-side image-forming surface is at infinity and the reduction side is the exit side, the distance on the optical axis from the reduction-side image-forming surface at the wide-angle end to the paraxial exit pupil position is denoted by exPw. 0<Ymax / |exPw|<0.1 (1) 4. The zoom lens according to claim 1, which satisfies conditional expression (1) expressed as follows:

5. When the lens group on the enlargement side in the optical path of the two lens groups of the second unit is the 2A lens group and the lens group on the reduction side is the 2B lens group, 5. The zoom lens according to claim 1, wherein the second-A lens group has negative refractive power, and the second-B lens group has positive refractive power.

6. 6. The zoom lens according to claim 5, wherein the second lens group B moves to the enlargement side and then to the reduction side when varying magnification from the wide-angle end to the telephoto end.

7. When the average value of the Abbe numbers of all the positive lenses included in the fourth unit based on the d-line is ν4pave, 60<ν4pave (4) 7. The zoom lens according to claim 1, which satisfies conditional expression (4) expressed as follows:

8. The zoom lens according to claim 1 , wherein the intermediate image is located within the fifth unit.

9. an optical system on the enlargement side of the intermediate image is a first optical system, and an optical system on the reduction side of the intermediate image is a second optical system; The focal length of the first optical system at the wide-angle end is fS1w, When the focal length of the zoom lens at the wide-angle end is fw, 0.8<fS1w / |fw| (5) 9. The zoom lens according to claim 1, which satisfies conditional expression (5) expressed as follows:

10. When the optical system on the enlargement side of the intermediate image is the first optical system and the optical system on the reduction side of the intermediate image is the second optical system, 10. The zoom lens according to claim 1, wherein the first optical system corrects curvature of field occurring in the second optical system to re-image the intermediate image onto the enlargement-side image-forming plane.

11. the intermediate image is located on the reduction side of the second unit, an optical system on the enlargement side of the intermediate image is a first optical system, and an optical system on the reduction side of the intermediate image is a second optical system; ThS1 is the distance on the optical axis from the lens surface of the first optical system closest to the enlargement side to the lens surface of the first optical system closest to the reduction side at the wide-angle end, When the distance on the optical axis from the lens surface on the most enlargement side of the zoom lens to the lens surface on the most reduction side of the zoom lens at the wide-angle end is ThZL, 0.4<ThS1 / ThZL<0.7 (6) 11. The zoom lens according to claim 1, which satisfies conditional expression (6) expressed as follows:

12. Bfw is the air-equivalent distance on the optical axis from the lens surface on the most reduction side of the zoom lens at the wide-angle end to the reduction-side focal position of the zoom lens, When the focal length of the zoom lens at the wide-angle end is fw, 1<Bfw / |fw| (7) 12. The zoom lens according to claim 1, which satisfies conditional expression (7) expressed as follows:

13. 13. The zoom lens according to claim 1, further comprising an optical path bending member that bends the optical path to a position adjacent to the intermediate image.

14. 14. The zoom lens according to claim 13, wherein the optical path bending member bends the optical path by 90 degrees.

15. 15. The zoom lens according to claim 1, wherein one or more lenses in at least one of the fourth unit and the fifth unit move during focusing.

16. a light valve for outputting an optical image; and the zoom lens according to any one of claims 1 to 15, The zoom lens projects the optical image output from the light valve onto a screen.

17. An imaging device comprising the zoom lens according to any one of claims 1 to 15.

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