JP7317252B2 - Magnification optical system and imaging device - Google Patents

Description

The technology of the present disclosure relates to a variable power optical system and an imaging device.

As a catadioptric variable magnification optical system, one described in Japanese Patent Application Laid-Open No. 2019-148790 is known.

There is a demand for a compact catadioptric variable power optical system that has less light loss, a wider angle of view, and good optical performance.

In view of the above circumstances, the technology of the present disclosure is capable of widening the angle of view while suppressing light loss, miniaturization, and a catadioptric variable power optical system having good optical performance. An object of the present invention is to provide an image pickup apparatus having a variable magnification optical system.

A variable power optical system according to one aspect of the technology of the present disclosure changes the distance between a first group that forms an intermediate image and a group that is arranged on the optical path on the image side of the intermediate image and is adjacent to the intermediate image during zooming. The first group includes a first mirror with a spherical concave reflecting surface facing the object side, and a first mirror that reflects light directed toward the object side toward the image side. , and a second mirror having a convex reflecting surface facing the image side. During zooming, the first mirror and the second mirror are fixed with respect to the image plane and pass through the vertex of the optical surface of the zooming group. When the ray is used as a reference ray, the absolute value of the angle formed by the reference ray and the normal to the reflection surface of the first mirror at the intersection of the reflection surface of the first mirror and the reference ray is 2 degrees or more, and the angle from the object is of the light reflected by the first mirror and then reflected by the second mirror all pass radially outside the outer edge of the first mirror, the focal length of the first mirror is f1, and the reflecting surface of the first mirror and the reference ray to the intersection of the reflecting surface of the second mirror and the reference ray is DL12,
0.4<DL12/|f1|<0.99 (4)
The conditional expression (4) expressed by is satisfied .

Within the first group, there are arranged correction lens groups composed only of one or more refracting lenses located on the optical path from the first mirror to the second mirror and on the optical path from the second mirror to the intermediate image. preferably .

When the angle formed by the reference ray incident on the first mirror and the reference ray emitted from the first mirror is Ang1, the zoom optical system of the above aspect preferably satisfies the following conditional expression (1). , more preferably satisfies the following conditional expression (1-1).
4<|Ang1|<30 (1)
6<|Ang1|<20 (1-1)

When the angle formed by the reference ray incident on the second mirror and the reference ray emitted from the second mirror is Ang2, the zoom optical system of the above aspect preferably satisfies the following conditional expression (2). , the following conditional expression (2-1) is more preferably satisfied.
5<|Ang2|<50 (2)
10<|Ang2|<40 (2-1)

When the angle formed by the reference ray incident on the first mirror and the reference ray emitted from the second mirror is Ang3, the zoom optical system of the above aspect preferably satisfies the following conditional expression (3). , more preferably satisfies the following conditional expression (3-1).
4<|Ang3|<30 (3)
6<|Ang3|<25 (3-1)

The variable power optical system of the above aspect preferably satisfies the following conditional expression (4-1) .
0 . 6<DL12/|f1|<0.95 (4-1)

The variable-power optical system of the above aspect includes a first group and a second group disposed closer to the image side than the intermediate image in order from the object side to the image side along the optical path, the second group comprising: including a second A subgroup having positive power and a second B subgroup having negative power in order from the most object side to the image side along the optical path, the second A subgroup and the second B subgroup may be arranged non-coaxially with respect to each other.

When the variable magnification optical system of the aspect described above includes the second group, the second group is fixed with respect to the image plane during zooming, and the second group sequentially moves along the optical path from the object side to the image side, It may comprise a second A subgroup, a second B subgroup, and a second C subgroup, and the second B subgroup and the second C subgroup may be arranged non-coaxially with each other. When the focal length of the 2A subgroup is fG2A and the focal length of the 2B subgroup is fG2B, the zoom optical system of the above aspect preferably satisfies the following conditional expression (5). It is more preferable to satisfy (5-1).
-1<fG2A/fG2B<-0.01 (5)
-0.75<fG2A/fG2B<-0.02 (5-1)

When the variable magnification optical system of the aspect described above includes the second group, the second group is fixed with respect to the image plane during zooming, and the second group sequentially moves along the optical path from the object side to the image side, comprising a second A subgroup, a second B subgroup and a second C subgroup, the second B subgroup and the second C subgroup being arranged non-coaxially with each other, the second C subgroup being a positive power refractive It may be configured to be an optical system.

In the variable power optical system of the above aspect, the first group, the second group arranged closer to the image side than the intermediate image, and the negative power group are arranged in order from the object side to the image side along the optical path as groups having power. a third group that is a refractive optical system with positive power, a fourth group that is a refractive optical system with positive power, and a trailing group; The subgroup closest to the image side of the second group on the optical path has positive power. The fourth group may be configured to move in directions opposite to each other.

In the configuration in which the variable power optical system of the above mode includes the third group and the fourth group, when the focal length of the third group is fG3 and the focal length of the fourth group is fG4, the variable power optical system of the above mode is , preferably satisfies the following conditional expression (6).
-10<fG4/fG3<-1 (6)

The variable power optical system of the above aspect preferably includes a diaphragm that is fixed with respect to the image plane during variable power. In that case, the stop may be arranged on the image side of the surface of the most object-side variable magnification group on the optical path, which is closest to the image side. Alternatively, the stop may be arranged on the optical path between the most object side surface of the most object side variable magnification group and the most image side surface of the most image side variable magnification group.

An imaging device according to another aspect of the technology of the present disclosure includes the variable power optical system of the above aspect.

In addition, "consisting of" and "consisting of" in this specification refer to lenses other than the listed components, lenses that have substantially no power, and lenses such as apertures, filters, and cover glasses. and mechanical parts such as lens flanges, lens barrels, imaging elements, and image stabilization mechanisms.

In this specification, "having positive power" for a group means that the group as a whole has positive power. Similarly, "has negative power" for a group means that the group as a whole has negative power. "Has power" means that the reciprocal of the focal length is not zero. "Power" as used in reference to lenses is synonymous with refractive power.

A compound aspherical lens (a lens that functions as a single aspherical lens as a whole by integrally forming a spherical lens and an aspherical film formed on the spherical lens) is not considered a cemented lens. treated as a single lens. The signs of power and surface shapes for optical elements including aspheric surfaces are considered in the paraxial region.

The "focal length" used in the conditional expression is the paraxial focal length. The value of the conditional expression is the value when the d-line is used as a reference when an object at infinity is focused. The "d-lines," "C-lines," "F-lines," and "s-lines" referred to herein are emission lines. In this specification, the wavelength of the d-line is 587.56 nm (nanometers), the wavelength of the C-line is 656.27 nm (nanometers), the wavelength of the F-line is 486.13 nm (nanometers), and the wavelength of the s-line is Treat as 852.11 nm (nanometers).

According to the technology of the present disclosure, a catadioptric variable-power optical system capable of widening the angle of view while suppressing light loss, miniaturization, and excellent optical performance, and this variable-magnification optical system An imaging device with the system can be provided.

FIG. 2 is a cross-sectional view showing a configuration and a reference ray at the wide-angle end of a variable power optical system according to an embodiment, corresponding to the variable power optical system of Example 1; 2A and 2B are cross-sectional views showing the configuration and light beams of the variable-magnification optical system in FIG. 1 in each variable-power state; FIG. 4 is a partially enlarged view for illustrating Ang2 and Ang3; FIG. 10 is a partial cross-sectional view showing the configuration and light beams of a comparative example in which an aperture stop is arranged between the 2C partial group and the 3rd group; FIG. 10 is a partial cross-sectional view showing the configuration and light beams of an example in which an aperture stop is arranged between the third group and the fourth group; 4 is a lateral aberration diagram at the wide-angle end of the variable power optical system of Example 1. FIG. 4 is a lateral aberration diagram at the telephoto end of the variable power optical system of Example 1. FIG. FIG. 10 is a cross-sectional view showing the configuration and light beams at the wide-angle end of the variable power optical system of Example 2; FIG. 11 is a lateral aberration diagram at the wide-angle end of the variable magnification optical system of Example 2; FIG. 10 is a lateral aberration diagram at the telephoto end of the variable magnification optical system of Example 2; FIG. 10 is a cross-sectional view showing the configuration and light beams at the wide-angle end of the variable-magnification optical system of Example 3; FIG. 11 is a lateral aberration diagram at the wide-angle end of the variable magnification optical system of Example 3; FIG. 11 is a lateral aberration diagram at the telephoto end of the variable magnification optical system of Example 3; FIG. 12 is a cross-sectional view showing the configuration and light beams at the wide-angle end of the variable-magnification optical system of Example 4; FIG. 11 is a lateral aberration diagram at the wide-angle end of the variable-magnification optical system of Example 4; FIG. 11 is a lateral aberration diagram at the telephoto end of the variable power optical system of Example 4; FIG. 12 is a cross-sectional view showing the configuration and light beams at the wide-angle end of the variable-magnification optical system of Example 5; FIG. 11 is a lateral aberration diagram at the wide-angle end of the variable-magnification optical system of Example 5; FIG. 11 is a lateral aberration diagram at the telephoto end of the variable power optical system of Example 5; FIG. 12 is a cross-sectional view showing the configuration and light beams at the wide-angle end of the variable-magnification optical system of Example 6; FIG. 11 is a lateral aberration diagram at the wide-angle end of the variable-magnification optical system of Example 6; FIG. 12 is a lateral aberration diagram at the telephoto end of the variable power optical system of Example 6; 1 is a schematic configuration diagram of an imaging device according to an embodiment; FIG.

An example of an embodiment according to the technology of the present disclosure will be described below with reference to the drawings. FIG. 1 shows a cross-sectional view of the configuration at the wide-angle end of a variable power optical system according to an embodiment of the present disclosure. FIG. 2 shows a cross-sectional view of the configuration and light beams in each variable magnification state of this variable magnification optical system. In FIG. 2 , the upper stage labeled “Wide” shows the wide-angle end state, the middle row labeled “Middle” shows the intermediate focal length state, and the lower row labeled “Tele” shows the telephoto end state. In order to avoid complication of the drawing, reference numerals are attached only to the upper drawing. 1 and 2 show a state in which an object at infinity is in focus. The examples shown in FIGS. 1 and 2 correspond to a variable-magnification optical system of Example 1, which will be described later. This variable-magnification optical system is applicable to, for example, surveillance cameras. The variable magnification optical system in FIG. 1 forms a bent optical path, the upper left side of FIG. 1 is the object side, and the lower right side of FIG. 1 is the image side.

This variable power optical system includes a first group G1 having two mirrors and a plurality of variable power groups arranged on the optical path closer to the image side than the first group G1. The variable power group is a group that moves while changing the distance between adjacent groups during variable power. Zooming is performed by moving these zooming groups.

As an example, the variable-magnification optical system in the example of FIG. It is a zoom optical system including G3, fourth group G4, and fifth group G5. In this example, the third group G3 and the fourth group G4 are zooming groups, and when zooming from the wide-angle end to the telephoto end, the third group G3 moves toward the image side, and the fourth group G4 moves toward the object. move to the side. In FIG. 1, below the third group G3 and the fourth group G4, the locus of movement of each group during zooming from the wide-angle end to the telephoto end is schematically indicated by arrows.

As an example, each group in the example of FIG. 1 is configured as follows. The first group G1 consists of a first mirror M1, a lens L11, a lens L12, and a second mirror M2. The second group G2 consists of, in order from the object side to the image side, a second A subgroup G2A, a second B subgroup G2B, and a second C subgroup G2C. The 2A subgroup G2A is composed of two lenses La1 to La2 in order from the object side to the image side. The 2B subgroup G2B is composed of three lenses Lb1 to Lb3 in order from the object side to the image side. The second C subgroup G2C consists of six lenses Lc1 to Lc6 in order from the object side to the image side. The third group G3 is composed of four lenses L31 to L34 in order from the object side to the image side. The fourth group G4 is composed of five lenses L41 to L45 in order from the object side to the image side. The fifth group G5 is composed of nine lenses L51 to L59 in order from the object side to the image side.

In the example of FIG. 1, an aperture stop St is arranged between the third group G3 and the fourth group G4. Note that the aperture diaphragm St in FIG. 1 does not indicate the shape and size, but indicates the position in the light traveling direction. This illustration method for the aperture stop St is the same in other drawings.

FIG. 1 shows an example in which a parallel plate-like optical member PP is arranged between the variable power optical system and the image plane Sim, assuming that the variable power optical system is applied to an imaging apparatus. The optical member PP is a member assuming various filters, cover glasses, and the like. Various filters are, for example, a low-pass filter, an infrared cut filter, and a filter that cuts a specific wavelength band. The optical member PP is a member having no power. It is also possible to configure the imaging device without the optical member PP.

In the example of FIG. 1, light entering the variable power optical system from an object is first reflected toward the object side by the first mirror M1, passes through the lenses L11 and L12 in this order, and is reflected by the second mirror M2 toward the image side. and passes through the lenses L12 and L11 in this order, and then reaches the image plane Sim via the second group G2, the third group G3, the fourth group G4, the fifth group G5, and the optical member PP. .

In the following description, the light ray passing through the vertex of the optical surface of the variable power group will be referred to as the reference light ray 2 . However, if the optical surfaces forming the variable power group include a plane, the plane is not included in the plane defining the reference light ray 2 . The optical surface of the lens is the lens surface. In the example of FIG. 1, the reference ray 2 passes through the surface vertices of all the lens surfaces of the variable power group. When the optical surface of the variable power group is concave, the bottommost point on the optical surface, that is, the vertex when viewed from the optical element side to the air side, is referred to as the vertex of the optical surface for convenience. Let us define the reference ray 2 as

In addition, the X-axis, Y-axis, and Z-axis that are orthogonal to each other will be used in the following description. The direction of the reference light ray 2 incident on the first group G1 from the object side is defined as the Z-axis direction. A plane that includes both the reference ray 2 incident on the first group G1 from the object side and the reference ray 2 that passes between the two mirrors of the first group G1 is defined as a YZ plane. That is, the paper plane of FIG. 1 is the YZ plane. In FIG. 1, the horizontal direction is the Z-axis direction, the vertical direction is the Y-axis direction, and the direction perpendicular to the paper surface is the X-axis direction. The positive direction of the Z-axis is the direction from left to right, the positive direction of the Y-axis is the direction from bottom to top, and the positive direction of the X-axis is the direction from the back side to the front side of the paper.

The first group G1 includes a first mirror M1 having a concave reflecting surface facing the object side. By condensing the incident light beam on the concave reflecting surface of the first mirror M1 instead of the refracting optical system, it is possible to suppress the occurrence of longitudinal chromatic aberration without using an expensive cemented lens with a large diameter.

The first group G1 includes, in addition to the first mirror M1 configured as described above, a second mirror M2 that reflects light traveling from the first mirror M1 toward the object side to the image side. The second mirror M2 has a convex reflecting surface facing the image side. According to the two mirrors configured as described above, the light flux deflected to the object side by the reflection by the first mirror M1 is reflected by the second mirror M2 having a convex shape and is deflected again to the image side, thereby turning the optical path. be able to. Therefore, by folding back the optical path while forming a telephoto type configuration with the combination of the first mirror M1 and the second mirror M2, it is possible to suppress an increase in the total length of the optical system in the Z direction due to telephoto. In addition, since mirrors do not contribute to chromatic aberration, the use of the two mirrors is advantageous in terms of chromatic aberration, which tends to be a problem in long focal length optical systems.

A point where the reflecting surface of the first mirror M1 and the reference ray 2 intersect is defined as an intersection point P1. In FIG. 1, the normal to the reflecting surface of the first mirror M1 at the intersection point P1 is indicated by a dashed line. The angle formed by this normal line and the reference ray 2 is defined as Ang0. The variable magnification optical system of this embodiment is configured so that the absolute value of Ang0 is 2 degrees or more. In the variable magnification optical system of this embodiment, the first mirror M1 and the second mirror M2 are arranged non-coaxially with each other. These points are significantly different from the optical system described in JP-A-2019-148790.

Here, as a comparative example, an optical system described in Japanese Patent Application Laid-Open No. 2019-148790 will be described. The optical system of this comparative example includes a first mirror M1 and a second mirror M2 whose reflecting surfaces are arranged to face each other. The first mirror M1 and the second mirror M2 of the comparative example have a common optical axis, and the second mirror M2 is arranged in the optical path of the first mirror M1. Therefore, the first mirror M1 is configured in a ring shape having an aperture, and the second mirror M2 shields the central portion of the light beam incident on the variable-magnification optical system, resulting in loss of light quantity. In addition, the comparative example has the following drawbacks regarding the widening of the angle of view. In general, the wider the angle of view, the smaller the diameter of the incident light beam, that is, the diameter of the entrance pupil. Therefore, in the comparative example in which the central portion of the incident light beam is blocked by the second mirror M2, when an attempt is made to widen the angle of view, the ratio of the light beam blocked by the second mirror M2 to the diameter of the incident light beam increases. put away. Due to these circumstances, it is difficult in the comparative example to widen the angle of view while ensuring the desired illuminance.

On the other hand, in the variable magnification optical system of this embodiment shown in FIG. 1, the absolute value of Ang0 is 2 degrees or more. After being reflected by the 1-mirror M1, it can be emitted in a direction deviated from the incident optical path. As a result, as shown in FIG. 2, unlike the comparative example, the second mirror M2 located closer to the object side than the first mirror M1 can be placed at a position where it does not block the light beam incident on the variable-magnification optical system. becomes.

According to the above arrangement, it is possible to configure the second mirror M2 not to block the incident light flux on the wide-angle side, which is advantageous for widening the angle of view. In addition, even on the telephoto side where the diameter of the incident light beam is large, the central portion of the incident light beam is not blocked, so that the light amount loss that occurs in the comparative example does not occur. Therefore, when compared with the same incident beam diameter, the configuration of this embodiment can capture more light than the comparative example.

In addition, in the variable power optical system of the present embodiment, as shown in FIG. 2, all of the light from the object that is reflected by the first mirror M1 and then reflected by the second mirror M2 is reflected by the first mirror M1. passes radially outward from the outer edge of The radial direction here means the radial direction of the reflecting surface of the first mirror M1 centering on the intersection point P1. In the comparative example, since the light reflected by the second mirror M2 passes through the inside of the first mirror M1, the first mirror M1 is provided with an opening for passing the light flux in the center. On the other hand, unlike the comparative example, the first mirror M1 of the present embodiment does not need to be provided with an opening for passing the light flux, so when compared with the same incident light flux diameter, a larger amount of light can be obtained than the comparative example. be able to.

Assuming that the angle formed by the reference ray 2 incident on the first mirror M1 and the reference ray 2 emitted from the first mirror M1 is Ang1, it is preferable to satisfy the following conditional expression (1). By ensuring that the lower limit of conditional expression (1) is not reached, it is possible to prevent the light flux entering the first mirror M1 from being blocked by the second mirror M2. By not exceeding the upper limit of conditional expression (1), the occurrence of coma caused by the inclination of the normal to the reflecting surface of the first mirror M1 at the intersection point P1 with respect to the reference ray 2 is suppressed. be able to. In order to obtain better characteristics, the variable power optical system more preferably satisfies the following conditional expression (1-1), and even more preferably satisfies the following conditional expression (1-2).
4<|Ang1|<30 (1)
6<|Ang1|<20 (1-1)
8<|Ang1|<15 (1-2)

Assuming that the angle formed by the reference ray 2 incident on the second mirror M2 and the reference ray 2 emitted from the second mirror M2 is Ang2, it is preferable to satisfy the following conditional expression (2). The point where the reflecting surface of the second mirror M2 and the reference ray 2 intersect is defined as an intersection point P2. As an example, FIG. 3 shows a partially enlarged view around the intersection P2 and Ang2. By ensuring that the conditional expression (2) does not fall below the lower limit, it is possible to suppress the light rays emitted from the first mirror M1 to the second mirror M2 from being blocked by the constituent elements on the image side of the first group G1. can be done. By not exceeding the upper limit of conditional expression (2), the occurrence of coma aberration due to the inclination of the normal to the reflecting surface of the second mirror M2 at the intersection point P2 with respect to the reference ray 2 is suppressed. can do. In order to obtain better characteristics, the variable magnification optical system more preferably satisfies the following conditional expression (2-1), and even more preferably satisfies the following conditional expression (2-2).
5<|Ang2|<50 (2)
10<|Ang2|<40 (2-1)
15<|Ang2|<35 (2-2)

Assuming that the angle between the reference ray 2 incident on the first mirror M1 and the reference ray 2 emitted from the second mirror M2 is Ang3, it is preferable to satisfy the following conditional expression (3). As an example, FIG. 3 shows Ang3. In FIG. 3, an extension line on the second mirror side of the reference light beam 2 emitted from the second mirror M2 is indicated by a chain double-dashed line. In FIG. 3, the solid line above the second mirror M2 indicates the reference light ray 2 incident on the first mirror M1. FIG. 3 is a schematic diagram for showing angles, and the distance between the second mirror M2 and the reference ray 2 incident on the first mirror M1 in FIG. 3 is not accurate. By ensuring that the conditional expression (3) does not fall below the lower limit, the light beam emitted from the first mirror M1 to the second mirror M2 is blocked by the component arranged in the optical path closer to the image side than the first group G1. can be suppressed. By ensuring that the upper limit of conditional expression (3) is not exceeded, an increase in the size of the optical system in the Y-axis direction can be suppressed. In order to obtain better characteristics, the variable magnification optical system more preferably satisfies the following conditional expression (3-1), and even more preferably satisfies the following conditional expression (3-2).
4<|Ang3|<30 (3)
6<|Ang3|<25 (3-1)
9<|Ang3|<20 (3-2)

The first mirror M1 may be an optical element positioned closest to the object side on the optical path among the optical elements having power included in the variable magnification optical system. In this case, the concerns described below can be avoided. If a refractive optical system is placed in the optical path on the object side of the first mirror M1, the refractive optical system will have a large aperture. In this case, the center of gravity of the variable-magnification optical system may be biased toward the distal end, resulting in poor weight balance and high cost.

During zooming, the first mirror M1 and the second mirror M2 are configured to be fixed with respect to the image plane Sim. Since the first mirror M1 has a size that covers the diameter of the entrance pupil on the telephoto side, it is a large component. By adopting a configuration in which the first mirror M1 is fixed during zooming, a mechanism for moving the first mirror M1 becomes unnecessary, and an increase in the size of the apparatus can be avoided. By adopting a configuration in which the second mirror M2 is fixed during zooming, the mechanical structure around the second mirror M2 can be simplified. This makes it easier to prevent the mechanical parts around the second mirror M2 from blocking the imaging light flux, which is advantageous for suppressing the loss of the amount of light.

During zooming, the first group G1 is preferably fixed with respect to the image plane Sim. That is, it is preferable that all optical elements constituting the first group G1, including elements other than mirrors, be fixed with respect to the image plane Sim during zooming. This arrangement is advantageous in simplifying the configuration of the device.

As shown in FIG. 2, the first group G1 is configured to form an intermediate image Im inside the variable magnification optical system. The intermediate image Im is re-imaged on the image plane Sim via a group on the image side of the intermediate image Im on the optical path. By using the variable magnification optical system as the re-imaging optical system, it is advantageous to reduce the diameter of each group. In the variable magnification optical system of this embodiment, an intermediate image Im is formed on the optical path between the first group G1 and the second group G2. In FIGS. 1 and 2, only a part of the intermediate image Im is simply represented by dotted lines.

Two or more variable magnification groups are arranged on the optical path on the image side of the intermediate image Im. By arranging the variable power group on the image side of the intermediate image Im, a mechanical structure is provided for moving the variable power group without blocking the light beams returned by the first mirror M1 and the second mirror M2. becomes easier.

The first group G1 may be configured to include a correction lens group Gh. The correction lens group Gh is preferably arranged in the first group G1 so as to be positioned on the optical path from the first mirror M1 to the second mirror M2 and on the optical path from the second mirror M2 to the intermediate image Im. . In this case, the light beam passes through the correction lens group Gh twice. By arranging the correction lens group Gh at the above position, it becomes easy to correct the coma aberration caused by the absolute value of Ang0 being 2 degrees or more.

The correction lens group Gh preferably consists of only one or more refractive lenses. If a mirror is used in place of the correcting lens group Gh to perform similar correction, a folded optical path is formed, which may cause light blocking due to interference between the light flux and the member. Alternatively, there is a risk that the size of the optical system will increase in order to arrange the members so as not to cause this light blocking. In this specification, the "refracting lens" is also simply referred to as "lens".

As an example, the correction lens group Gh in FIG. 1 consists of a lens L11 that is a negative lens and a lens L12 that is a positive lens. Lenses L11 and L12 in the example of FIG. 1 are spherical lenses. By arranging the correcting lens group Gh at a position through which light rays pass twice as described above, it becomes easy to satisfactorily correct various aberrations even when the correcting lens group Gh does not include an aspherical lens.

When the first group G1 includes the correction lens group Gh, it is preferable that the reflecting surface of at least one of the first mirror M1 and the second mirror M2 has a spherical shape. According to the configuration in which the correction lens group Gh arranged at the above position and the spherical mirror are combined, the coma aberration caused by the absolute value of Ang0 being 2 degrees or more and the spherical aberration caused by the spherical mirror It becomes easier to correct aberrations. In addition, according to the configuration of the above combination, it is easy to configure a variable power optical system capable of achieving the object of the present invention without using an expensive aspherical mirror.

In a configuration in which the reflecting surface of the first mirror M1 has a spherical shape, if the focal length of the first mirror M1 is f1 and the distance from the intersection point P1 to the intersection point P2 is DL12, the following conditional expression (4) can be satisfied. preferable. The intersection point P1 and the intersection point P2 are each the intersection points defined above. By ensuring that the lower limit of conditional expression (4) is not exceeded, it is possible to suppress an increase in the distance from the second mirror M2 to the intermediate image Im, so it is possible to suppress an increase in size mainly in the Z-axis direction. can. By not exceeding the upper limit of conditional expression (4), the intermediate image Im does not come too close to the second mirror M2. can avoid interference with the end of the group (in the example of FIG. 1, the upper end of the 2A subgroup G2A) arranged continuously. In order to obtain better characteristics, the variable power optical system more preferably satisfies the following conditional expression (4-1), and even more preferably satisfies the following conditional expression (4-2).
0.4<DL12/|f1|<0.99 (4)
0.6<DL12/|f1|<0.95 (4-1)
0.75<DL12/|f1|<0.92 (4-2)

The variable power optical system in FIG. 1 includes a first group G1 and a second group G2 arranged closer to the image side than the intermediate image Im in order from the object side to the image side along the optical path. The second group G2 may be composed of a plurality of subgroups, adjacent subgroups being arranged non-coaxially with each other. Since the first mirror M1 and the second mirror M2 are arranged non-coaxially with each other, coma aberration occurs due to decentration. By arranging the subgroups in the second group G2 non-coaxially with each other, it is advantageous to correct the coma associated with this decentration.

For example, the second group G2 includes a second A subgroup G2A having positive power and a second B subgroup G2B having negative power, consecutively from the most object side to the image side along the optical path, The second A subgroup G2A and the second B subgroup G2B may be arranged non-coaxially with each other. This configuration is advantageous in correcting the above-described coma aberration due to decentration. Further, by arranging the second A partial group G2A having a positive power at a position where the light beam diverges on the image side of the intermediate image Im, the divergence of the light beam can be suppressed. This is advantageous for reducing the diameter of the group closer to the image side than the 2A partial group G2A. Arranging the second B subgroup G2B, which has power opposite in sign to that of the second A subgroup G2A, following the second A subgroup G2A is advantageous for correcting aberrations.

More specifically, the second group G2 includes, in order from the object side to the image side along the optical path, a second A subgroup G2A having positive power, a second B subgroup G2B having negative power, and a positive power subgroup G2B. and a second C subgroup G2C having power. In that case, the second A partial group G2A and the second B partial group G2B are arranged non-coaxially with each other, and the second B partial group G2B and the second C partial group G2C are arranged non-coaxially with each other. good too. This configuration is advantageous in correcting the above-described coma aberration due to decentration. Further, by arranging the subgroups so that the powers of the subgroups adjacent to each other have opposite signs, it is advantageous for correction of aberrations. Furthermore, by arranging the second C subgroup G2C having a positive power closest to the image side of the second group G2, it is possible to give a convergence action to the divergent light flux directed from the intermediate image Im toward the image side. This is advantageous for reducing the diameter of the group closer to the image side than the second group G2.

When the second group G2 consists of the three subgroups described above, the second A subgroup G2A and the second C subgroup G2C may be arranged non-coaxially with each other or coaxially with each other. good. Further, the 2A partial group G2A and the variable power group may be arranged non-coaxially with each other, or may be arranged coaxially with each other. The second B subgroup G2B and the zooming group may be arranged non-coaxially with each other. The second C subgroup G2C and the zooming group may be arranged coaxially with each other.

The second A subgroup G2A may be configured to be a refractive optical system. The second B subgroup G2B may be configured to be a refractive optical system. The second C subgroup G2C may be configured to be a refractive optical system. In this specification, the term "refractive optical system" refers to an optical system that does not include reflective optical elements having power, and includes only refractive lenses as optical elements having power. When a reflective optical element is used, the optical path is turned back, which may cause a problem of light blocking due to interference between the light flux and the member. Alternatively, there is a risk that the size of the optical system will increase in order to arrange the members so as not to cause this light blocking. By using refractive optics, it is possible to avoid this problem.

In a configuration in which the second group G2 includes a second A subgroup G2A having positive power and a second B subgroup G2B having negative power in order from the most object side to the image side along the optical path, Assuming that the focal length of the 2A subgroup G2A is fG2A and the focal length of the 2B subgroup G2B is fG2B, it is preferable to satisfy the following conditional expression (5). Abiding by the lower limit of conditional expression (5) prevents the positive power of the 2A subgroup G2A from becoming too weak, which is advantageous for correcting the coma associated with decentration. Also, since the negative power of the second B subgroup G2B does not become too strong, a group (in the example of FIG. 1, the second C subgroup G2C) can be suppressed from increasing in outer diameter. By not exceeding the upper limit of conditional expression (5), the positive power of the 2A subgroup G2A does not become too strong, so that it is possible to suppress the occurrence of spherical aberration on the telephoto side. In addition, since the negative power of the 2B subgroup G2B does not become too weak, it is advantageous in correcting the coma aberration due to decentering. In order to obtain better characteristics, the variable magnification optical system more preferably satisfies the following conditional expression (5-1), and even more preferably satisfies the following conditional expression (5-2).
-1<fG2A/fG2B<-0.01 (5)
-0.75<fG2A/fG2B<-0.02 (5-1)
-0.5<fG2A/fG2B<-0.04 (5-2)

During zooming, the second group G2 is preferably fixed with respect to the image plane Sim. In this case, a mechanism for moving the second group G2 becomes unnecessary, and an increase in size of the apparatus can be suppressed. Further, by fixing the second group G2 close to the first group G1, the mechanical structure around the second group G2 can be simplified. This is advantageous in avoiding blocking of light beams directed from the first mirror M1 to the second mirror M2 by mechanical parts around the second group G2.

As a preferred aspect of the variable magnification optical system, for example, the following configuration can be adopted. The variable power optical system has, in order from the object side to the image side along the optical path, a first group G1, a second group G2 arranged closer to the image side than the intermediate image Im, and a third group G3 as groups having power. , the fourth group G4, and the subsequent group. The second group G2 consists of a plurality of subgroups in which adjacent subgroups are arranged non-coaxially with each other. G2C) has positive power. The third group G3 is a refractive optical system with negative power, and the fourth group G4 is a refractive optical system with positive power. During zooming, the second group G2 is fixed with respect to the image plane Sim, and the third group G3 and the fourth group G4 move in directions opposite to each other. In this configuration, the subgroups closest to the image side of the second group G2, the third group G3, and the fourth group G4 have positive, negative, and positive power, respectively. In this way, by arranging adjacent subgroups so that their powers have opposite signs, each group can have strong power. As a result, the amount of movement of the third group G3 and the fourth group G4 during zooming can be suppressed, which is advantageous for miniaturization of the optical system. Further, by converging the light beam diverged by the negative power third group G3 by the positive power fourth group G4 on the image side, it is possible to suppress the increase in the outer diameter of the subsequent group. .

In a configuration in which the variable-magnification optical system includes the third group G3 and the fourth group G4, when the focal length of the third group G3 is fG3 and the focal length of the fourth group G4 is fG4, the following conditional expression (6) is preferably satisfied. By ensuring that the lower limit of conditional expression (6) is not exceeded, the power of the fourth group G4 does not become too weak, so that the amount of movement of the fourth group G4 during zooming can be suppressed. As a result, it is possible to suppress an increase in the size of the optical system mainly in the Z-axis direction. Also, since the power of the third group G3 does not become too strong, spherical aberration occurring in the third group G3 can be suppressed. By not exceeding the upper limit of conditional expression (6), the power of the third group G3 does not become too weak, so the amount of movement of the fourth group G4 during zooming can be suppressed. As a result, it is possible to suppress an increase in the size of the optical system mainly in the Z-axis direction. Also, since the power of the fourth group G4 does not become too strong, it is possible to suppress spherical aberration occurring in the fourth group G4. In order to obtain better characteristics, the variable magnification optical system more preferably satisfies the following conditional expression (6-1), and even more preferably satisfies the following conditional expression (6-2).
-10<fG4/fG3<-1 (6)
-7<fG4/fG3<-1.5 (6-1)
-5<fG4/fG3<-2 (6-2)

The subsequent group consists of the fifth group G5 in the example of FIG. However, the subsequent group is not limited to a configuration consisting of one group. The trailing group may consist of two groups, or three or more groups, the mutual spacing of which changes during magnification. When the trailing group consists of a plurality of groups, the group closest to the image side of the trailing groups may be configured to be fixed during zooming. This arrangement is advantageous in simplifying the configuration of the device.

The aperture stop St is preferably fixed with respect to the image plane Sim during zooming. It is preferable that the aperture diameter of the aperture stop St is variable in order to cope with various photographing conditions. In particular, it is preferable that the opening diameter be variable in surveillance camera applications in which photography is performed regardless of whether it is day or night. By adopting a configuration in which the aperture stop St is fixed during zooming, the arrangement of the aperture mechanism for changing the aperture diameter is facilitated. Also, if the aperture diaphragm St is configured to move when the magnification is changed, a lead wire for supplying power to the drive components for driving the aperture stop St is required, and there is a risk that the lead wire will break. occurs. On the other hand, in the configuration in which the aperture diaphragm St is fixed during zooming, such a risk does not occur, and therefore, the durability, which is important for monitoring applications, can be maintained at a higher level.

The aperture stop St may be arranged on the image side of the most image side surface of the most object side variable magnification group on the optical path. In this case, the arrangement of the diaphragm mechanism is facilitated, and it is advantageous for miniaturization of the diaphragm mechanism. In the example of FIG. 1, the most image side surface of the most object side variable magnification group is the object side surface of the lens L34 of the third group G3.

Alternatively, the aperture stop St is arranged on the optical path between the most object side surface of the most object side variable magnification group and the most image side surface of the most image side variable magnification group. may In the example of FIG. 1, the most object side surface of the most object side variable power group is the object side surface of the lens L31 of the third group G3, and the most image side surface of the most image side variable power group is , the object-side surface of the lens L45 of the fourth group G4.

In the example of FIG. 1, the aperture stop St is arranged in the air space between the third group G3 and the fourth group G4. It is preferable to arrange the aperture diaphragm St at a position such that part of the imaging area is not blocked when the aperture diaphragm St is closed. For this reason, the position of the aperture stop St is set so that the lower ray of the axial luminous flux and the lower ray of the off-axis luminous flux are separated from the point where the upper ray of the axial luminous flux and the upper ray of the off-axial luminous flux intersect (hereinafter referred to as point P3). is preferably within a range up to a point (hereinafter referred to as point P4) where the two intersect with. Here, a luminous flux whose principal ray is the reference ray 2 is referred to as an on-axis luminous flux, and a luminous flux whose principal ray is not the reference ray 2 is referred to as an off-axis luminous flux.

As a comparative example, FIG. 4A shows an example in which an aperture stop St is arranged between the second C subgroup G2C and the third group G3. Also shown in FIG. 4A are the on-axis beam 3a, the off-axis beam 3b, points P3 and P4 above. When the aperture stop St is arranged between the second C partial group G2C and the third group G3, the range from the point P3 to the point P4 is near the third group G3 as shown in FIG. 4A. At the wide-angle end, the distance between the second C subgroup G2C and the aperture stop St becomes wider than when the aperture stop St is arranged between G3 and the fourth group G4. Therefore, the distance between the second C partial group G2C and the third group G3 is also widened, resulting in an increase in the total optical length.

FIG. 4B shows an example in which the aperture stop St is arranged between the third group G3 and the fourth group G4. In this case, the off-axis light flux 3b emerging from the second C partial group G2C and entering the third group G3 is diverged by the negative power third group G3. Therefore, the angle of inclination of the off-axis light flux 3b emitted from the third group G3 with respect to the optical axis Z is smaller than the angle of inclination with respect to the optical axis Z of the off-axis light flux 3b emitted from the second C partial group G2C. Therefore, the points P3 and P4 are located closer to the image side than when the aperture stop St is arranged between the second C partial group G2C and the third group G3. When the aperture stop St is arranged between the third group G3 and the fourth group G4 as shown in FIG. 4B, unlike the example of FIG. 4A, there is no aperture stop St on the object side of the third group G3. The distance between the second C subgroup G2C and the third group G3 at the wide-angle end can be shortened, and at the same time, the amount of movement of the third group G3 required for zooming can be secured.

Arranging the aperture stop St closer to the object side than the surface closest to the image side of the zoom lens unit closest to the image side is advantageous in suppressing an increase in size in the radial direction. If the aperture stop St were arranged closer to the image side than the most image side surface of the most image side variable magnification group, more of the off-axis light beams on the lower side would have to pass through. There is a risk that the outer diameter of the group G3 will increase.

Although FIG. 1 shows an example of a preferred embodiment, the variable power optical system of the present disclosure can be modified in various ways without departing from the gist of the technology of the present disclosure. For example, the number of optical elements included in each group and the number of variable power groups can be arbitrarily selected. Each group is not limited to the configuration composed of a plurality of optical elements, and may be composed of one optical element. Moreover, although the example of FIG. 1 is a zoom optical system, the variable magnification optical system of the present disclosure may be a variable focal optical system.

The preferred and possible configurations described above can be arbitrarily combined, and are preferably selectively employed as appropriate according to required specifications.

Numerical examples of the variable magnification optical system of the present disclosure will now be described.
[Example 1]
Cross-sectional views of the variable magnification optical system of Example 1 are shown in FIGS. 1 and 2, and the configuration and illustration method thereof are as described above, so redundant description is partially omitted here. The variable-magnification optical system of Example 1 includes a first group G1, a second group G2, a third group G3, an aperture stop St, and a fourth group in order from the object side to the image side along the optical path. It is a zoom optical system consisting of G4 and a fifth group G5. An intermediate image Im is formed on the optical path between the first group G1 and the second group G2. During zooming from the wide-angle end to the telephoto end, the third group G3 moves toward the image side, the fourth group G4 moves toward the object side, and the other groups and the aperture stop St are fixed with respect to the image plane Sim. It is The first group G1 consists of a first mirror M1, a second mirror M2, and a correction lens group Gh. The correction lens group Gh consists of a lens L11 and a lens L12. The second group G2 consists of, in order from the object side to the image side, a second A subgroup G2A, a second B subgroup G2B, and a second C subgroup G2C. The 2A subgroup G2A is composed of two lenses La1 to La2 in order from the object side to the image side. The 2B subgroup G2B is composed of three lenses Lb1 to Lb3 in order from the object side to the image side. The second C subgroup G2C consists of six lenses Lc1 to Lc6 in order from the object side to the image side. The second A subgroup G2A, the second B subgroup G2B, and the second C subgroup G2C are arranged non-coaxially with each other. The second C subgroup G2C, the third group G3, the aperture stop St, the fourth group G4 and the fifth group G5 are arranged coaxially with each other. The third group G3 is composed of four lenses L31 to L34 in order from the object side to the image side. The fourth group G4 is composed of five lenses L41 to L45 in order from the object side to the image side. The fifth group G5 is composed of nine lenses L51 to L59 in order from the object side to the image side.

Tables 1A and 1B show the basic lens data, Table 2 shows the coordinate data of the variable power group, and Table 3 shows the specifications of the variable magnification optical system of Example 1. Here, the basic lens data are divided into two tables, Table 1A and Table 1B, and displayed in order to avoid making one table too long. Table 1A shows the first group G1 and the second group G2, and Table 1B shows the third group G3, the aperture stop St, the fourth group G4, the fifth group G5, and the optical member PP.

Each table shows values in an XYZ coordinate system using the above-described X, Y, and Z axes with the point O shown in FIG. 1 as the origin. Tables 1A and 1B show the components along the optical path. Each column will be described below. The column of "surface number" shows the surface number when the plane including the point O and perpendicular to the Z-axis is defined as the first surface, and the number is incremented one by one toward the image side along the optical path. The symbol "(St)" is also entered in the "surface number" column of the surface corresponding to the aperture stop St.

The column of "radius of curvature" shows the radius of curvature of each surface. As for the sign of the radius of curvature, the sign of the surface with the convex surface facing the object side is positive, and the sign of the surface with the convex surface facing the image side is negative. The columns of "X", "Y", and "Z" of "coordinates" respectively indicate the coordinates of the center of curvature of each surface in the XYZ coordinate system with the point O as a reference.

In the columns of "X-axis component" and "Y-axis component" of "Normal angle component", the angle formed by the normal line of the surface at the center of curvature of each surface with the X-axis direction and the angle with the Y-axis direction are shown. show. As for the sign of the angle, the angle in the clockwise direction is positive and the angle in the counterclockwise direction is negative in the positive direction of each axis. The column of "nd" indicates the refractive index of each component at the d-line. The column of "νd" indicates the d-line reference Abbe number of each component. However, "reflecting surface" is written in the column of nd and νd of the surface corresponding to the reflecting surface. The name of each group is shown in the "group name" column.

Since the coordinates of the third group G3 and the fourth group G4 change with zooming, Table 2 shows the coordinates of the surfaces of the third group G3 and the fourth group G4 for each zoom position. In Tables 2 and 3, the values at each zoom position in the wide-angle end state, intermediate focal length state, and telephoto end state are shown in columns labeled "Wide", "Middle", and "Tele", respectively.

In Table 3, the column of "axial beam diameter" shows the diameter of the axial beam incident on the variable power optical system. In the following description, the principal rays of the maximum angle of view that are incident above and below the reference ray 2 on the image plane Sim will be referred to as the upper principal ray and the lower principal ray, respectively. In Table 3, θ1 is the incident angle of the upper principal ray, that is, the angle formed by the upper principal ray and the reference ray 2 . θ2 is the incident angle of the lower chief ray, that is, the angle formed by the lower chief ray and the reference ray 2 . When calculating the angle of view, consider a rectangular imaging area with a length of 7.76 mm (mm) in the X direction and a length of 4.36 mm (mm) in the Y direction. Calculate by position. The aspect ratio of this rectangle is 16:9. The zoom ratio is calculated from the ratio between the value of tan(|θ1|)+tan(|θ2|) at the wide-angle end and the value of tan(|θ1|)+tan(|θ2|) at each zoom position. there is

In the data in each table, degrees are used as units for angles and mm (millimeters) are used as units for coordinates, but since the optical system can be used even if it is proportionally enlarged or reduced, other appropriate units are used. can also be used. Also, in each table shown below, numerical values rounded to predetermined digits are described.

FIG. 5 shows a lateral aberration diagram at the wide-angle end of the variable-magnification optical system of Example 1. As shown in FIG. In FIG. 5, the left column shows the aberration in the sagittal direction, and the right column shows the aberration in the tangential direction. Aberrations at the d-line, F-line, C-line, and s-line are indicated by a solid line, a long dashed line, a dashed-dotted line, and a dotted line, respectively. The unit of the vertical axis is μm (micrometer).

In the lateral aberration diagrams, coordinates are expressed using an xyz coordinate system different from the above-described XYZ coordinate system. In the xyz coordinate system, the origin is the intersection of the reference ray 2 and the image plane Sim, and x, y, and z axes, which are described below and are orthogonal to each other, are used. The direction of the reference light ray 2 incident on the image plane Sim from the variable-magnification optical system is the z-axis direction, the plane of FIG. 1 is the yz-plane, and the direction perpendicular to the plane of FIG. The positive direction of the z-axis is the direction from the variable power optical system to the image plane Sim, the positive direction of the y-axis is the direction in which the first mirror M1 is located with respect to the reference light ray 2 incident on the image plane Sim, and the x-axis The positive direction is the direction from the back side to the front side of the paper. FIG. 5 shows the aberration at each coordinate of the xyz coordinate system, and the value of each coordinate is written after (x, y)= in each aberration diagram.

FIG. 6 shows a lateral aberration diagram at the telephoto end of the variable magnification optical system of Example 1. In FIG. Also in FIG. 6, the left column shows the aberration in the sagittal direction, and the right column shows the aberration in the tangential direction. The drawing method of FIG. 6 is basically the same as that of FIG. Figures 5 and 6 show the aberrations in focus on an infinite object.

Unless otherwise specified, the symbol, meaning, description method, and illustration method of each data relating to Example 1 above are basically the same in the following Examples, and therefore redundant explanations will be omitted below.

[Example 2]
FIG. 7 shows a cross-sectional view and light beams at the wide-angle end of the variable-magnification optical system of Example 2. As shown in FIG. The variable-magnification optical system of Example 2 includes a first group G1, a second group G2, a third group G3, an aperture stop St, and a fourth group in order from the object side to the image side along the optical path. It is a zoom optical system consisting of G4 and a fifth group G5. An intermediate image Im is formed on the optical path between the first group G1 and the second group G2. During zooming from the wide-angle end to the telephoto end, the third group G3 moves toward the image side, the fourth group G4 moves toward the object side, and the other groups and the aperture stop St are fixed with respect to the image plane Sim. It is The first group G1 consists of a first mirror M1, a second mirror M2, and a correction lens group Gh. The correction lens group Gh consists of two lenses. The second group G2 consists of, in order from the object side to the image side, a second A subgroup G2A, a second B subgroup G2B, and a second C subgroup G2C. The second A subgroup G2A consists of two lenses. The second B subgroup G2B consists of three lenses. The second C subgroup G2C consists of six lenses. The second A subgroup G2A, the second B subgroup G2B, and the second C subgroup G2C are arranged non-coaxially with each other. The second C subgroup G2C, the third group G3, the aperture stop St, the fourth group G4 and the fifth group G5 are arranged coaxially with each other. The third group G3 consists of four lenses. The fourth group G4 consists of five lenses. The fifth group G5 consists of nine lenses. The above is the outline of the variable-power optical system of the second embodiment.

Regarding the variable power optical system of Example 2, basic lens data are shown in Tables 4A and 4B, coordinate data of the variable power group are shown in Table 5, specifications are shown in Table 6, and lateral aberration diagrams at the wide-angle end are shown in FIG. FIG. 9 shows lateral aberration diagrams at the telephoto end.

[Example 3]
FIG. 10 shows a cross-sectional view and light beams at the wide-angle end of the variable-magnification optical system of Example 3. As shown in FIG. The variable-power optical system of Example 3 has a configuration similar to that of the variable-power optical system of Example 2. FIG. Regarding the variable magnification optical system of Example 3, the basic lens data are shown in Tables 7A and 7B, the coordinate data of the variable magnification group are shown in Table 8, the specifications are shown in Table 9, and the lateral aberration diagram at the wide-angle end is shown in FIG. FIG. 12 shows lateral aberration diagrams at the telephoto end.

[Example 4]
FIG. 13 shows a cross-sectional view and light beams at the wide-angle end of the variable-magnification optical system of Example 4. As shown in FIG. The variable-power optical system of Example 4 has a configuration similar to that of the variable-power optical system of Example 2. FIG. Regarding the variable magnification optical system of Example 4, basic lens data is shown in Tables 10A and 10B, coordinate data of the variable magnification group is shown in Table 11, specifications are shown in Table 12, and lateral aberration diagrams at the wide-angle end are shown in FIG. FIG. 15 shows lateral aberration diagrams at the telephoto end.

[Example 5]
FIG. 16 shows a cross-sectional view and light beams at the wide-angle end of the variable-magnification optical system of Example 5. As shown in FIG. The variable-power optical system of Example 5 has a configuration similar to that of the variable-power optical system of Example 2. FIG. Regarding the variable power optical system of Example 5, basic lens data are shown in Tables 13A and 13B, coordinate data of the variable power group are shown in Table 14, specifications are shown in Table 15, and lateral aberration diagrams at the wide-angle end are shown in FIG. FIG. 18 shows lateral aberration diagrams at the telephoto end.

[Example 6]
FIG. 19 shows a cross-sectional view and light beams at the wide-angle end of the variable-magnification optical system of Example 6. In FIG. The variable-magnification optical system of Example 6 comprises a first group G1, a second group G2, a third group G3, an aperture stop St, and a fourth group in order from the object side to the image side along the optical path. It is a zoom optical system consisting of G4, fifth group G5, and sixth group G6. An intermediate image Im is formed on the optical path between the first group G1 and the second group G2. During zooming from the wide-angle end to the telephoto end, the third group G3 moves toward the image side, the fourth group G4 moves toward the object side, the fifth group G5 moves toward the image side, and the other groups and The aperture stop St is fixed with respect to the image plane Sim. The first group G1 consists of a first mirror M1, a second mirror M2, and a correction lens group Gh. The correction lens group Gh consists of two lenses. The second group G2 consists of, in order from the object side to the image side, a second A subgroup G2A, a second B subgroup G2B, and a second C subgroup G2C. The second A subgroup G2A consists of two lenses. The second B subgroup G2B consists of three lenses. The second C subgroup G2C consists of six lenses. The second A subgroup G2A, the second B subgroup G2B, and the second C subgroup G2C are arranged non-coaxially with each other. The second C subgroup G2C, the third group G3, the aperture stop St, the fourth group G4, the fifth group G5, and the sixth group G6 are arranged coaxially with each other. The third group G3 consists of four lenses. The fourth group G4 consists of five lenses. The fifth group G5 consists of six lenses. The sixth group G6 consists of three lenses.

Tables 16A and 16B show basic lens data, Tables 17A and 17B show coordinate data of the variable power group, Table 18 shows specifications, and lateral aberration diagrams at the wide-angle end of the variable power optical system of Example 6 are shown in Tables 17A and 17B. 20, lateral aberration diagrams at the telephoto end are shown in FIG.

Table 19 shows the corresponding values of |Ang0| and conditional expressions (1) to (6) for the variable magnification optical systems of Examples 1 to 6. The values shown in Table 19 are based on the d-line.

The variable power optical systems of Examples 1 to 6 have a variable power ratio of 6.5 times or more, and particularly the variable power optical systems of Examples 2 to 6 have a variable power ratio of 10 times or more. The variable-magnification optical systems of Examples 1 to 6 achieved such a high variable-magnification ratio while suppressing loss in the amount of light, achieved a wide angle of view, had a compact configuration, and were capable of capturing light near the visible light range. Various aberrations are corrected satisfactorily over a wide range up to the infrared light region, providing high optical performance. In addition, the variable power optical systems of Examples 1 to 6 are designed to reduce the load on the object side portion, and achieve a telescopic catadioptric variable power optical system with a low cost structure.

Next, an imaging device according to an embodiment of the present disclosure will be described. FIG. 22 shows a schematic configuration diagram of an imaging device 10 using the variable magnification optical system 1 according to the embodiment of the present disclosure as an example of the imaging device of the embodiment of the present disclosure. Examples of the imaging device 10 include surveillance cameras, video cameras, and electronic still cameras.

An imaging apparatus 10 includes a variable magnification optical system 1, a filter 4 arranged on the image side of the variable magnification optical system 1, an image sensor 5 arranged on the image side of the filter 4, and an output signal from the image sensor 5. A signal processing unit 6 for arithmetic processing and a variable power control unit 7 for controlling variable power of the variable power optical system 1 are provided.

The imaging device 5 converts an optical image formed by the variable magnification optical system 1 into an electrical signal. As the imaging element 5, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) can be used. The imaging element 5 is arranged so that its imaging plane coincides with the image plane of the variable magnification optical system 1 . Although only one imaging device 5 is shown in FIG. 22, the imaging device 10 may be configured to include a plurality of imaging devices.

Although the technology of the present disclosure has been described above with reference to the embodiments and examples, the technology of the present disclosure is not limited to the above-described embodiments and examples, and various modifications are possible. For example, the radius of curvature, coordinates, refractive index, Abbe number, etc. of each optical element are not limited to the values shown in the above numerical examples, and may take other values.

All publications, patent applications and technical standards mentioned herein are to the same extent as if each individual publication, patent application and technical standard were specifically and individually noted to be incorporated by reference. incorporated herein by reference.

Claims (18)

a first group that forms an intermediate image; and a plurality of variable magnification groups that are arranged on the optical path on the image side of the intermediate image and move while changing the distance between adjacent groups during magnification,
The first group includes a first mirror having a spherical concave reflecting surface facing the object side, and a convex reflecting surface facing the image side for reflecting light traveling from the first mirror toward the object side to the image side. a second mirror directed to
During zooming, the first mirror and the second mirror are fixed with respect to the image plane,
When a ray passing through the vertex of the optical surface of the variable power group is used as a reference ray,
an absolute value of an angle formed by a normal to the reflecting surface of the first mirror at an intersection of the reflecting surface of the first mirror and the reference beam and the reference beam is 2 degrees or more;
All of the light from the object that has been reflected by the first mirror and then reflected by the second mirror passes through the outer edge of the first mirror in the radial direction,
the focal length of the first mirror is f1;
When the distance from the intersection of the reflecting surface of the first mirror and the reference ray to the intersection of the reflecting surface of the second mirror and the reference ray is DL12,
0.4<DL12/|f1|<0.99 (4)
A variable-magnification optical system that satisfies conditional expression (4) . In the first group, located on the optical path from the first mirror to the second mirror and on the optical path from the second mirror to the intermediate image, and composed only of one or more refractive lenses 2. The variable magnification optical system according to claim 1, further comprising a correction lens group. When the angle formed by the reference ray incident on the first mirror and the reference ray emitted from the first mirror is Ang1,
4<|Ang1|<30 (1)
3. A variable power optical system according to claim 1 , which satisfies conditional expression (1) expressed by: When the angle formed by the reference ray incident on the second mirror and the reference ray emitted from the second mirror is Ang2,
5<|Ang2|<50 (2)
4. The variable power optical system according to any one of claims 1 to 3 , wherein conditional expression (2) represented by is satisfied. When the angle formed by the reference ray incident on the first mirror and the reference ray emitted from the second mirror is Ang3,
4<|Ang3|<30 (3)
5. The variable magnification optical system according to claim 1, wherein the conditional expression ( 3 ) is satisfied. including the first group and a second group arranged on the image side of the intermediate image in order from the object side to the image side along the optical path;
The second group includes a 2A subgroup having positive power and a 2B subgroup having negative power, successively in order from the most object side to the image side along the optical path,
6. The variable power optical system according to claim 1, wherein the second A partial group and the second B partial group are arranged non-coaxially with each other. During zooming, the second group is fixed with respect to the image plane,
The second group consists of the second A subgroup, the second B subgroup, and the second C subgroup in order from the object side to the image side along the optical path,
the second B subgroup and the second C subgroup are arranged non-coaxially with each other;
the focal length of the second A subgroup is fG2A;
When the focal length of the second B subgroup is fG2B,
-1<fG2A/fG2B<-0.01 (5)
7. A variable magnification optical system according to claim 6 , which satisfies conditional expression (5) represented by: During zooming, the second group is fixed with respect to the image plane,
The second group consists of the second A subgroup, the second B subgroup, and the second C subgroup in order from the object side to the image side along the optical path,
the second B subgroup and the second C subgroup are arranged non-coaxially with each other;
8. The variable magnification optical system according to claim 6 , wherein said second C partial group is a refractive optical system having positive power. In order from the object side to the image side along the optical path, as groups having power, the first group, the second group arranged on the image side of the intermediate image, and the refractive optical system having negative power. 3 groups, a fourth group that is a refractive optical system having positive power, and only a subsequent group,
the second group comprises a plurality of subgroups in which adjacent subgroups are arranged non-coaxially with each other, and the subgroup closest to the image side of the second group on the optical path has positive power;
9. A zoom lens according to any one of claims 1 to 8 , wherein the second group is fixed with respect to the image plane, and the third group and the fourth group move in directions opposite to each other during zooming. Optical system. the focal length of the third group is fG3;
When the focal length of the fourth group is fG4,
-10<fG4/fG3<-1 (6)
10. A variable magnification optical system according to claim 9 , which satisfies conditional expression (6) represented by: including an aperture that is fixed with respect to the image plane during zooming,
11. The variable power optical system according to any one of claims 1 to 10 , wherein the stop is disposed closer to the image side than the surface closest to the image side of the variable power group closest to the object on the optical path. including an aperture that is fixed with respect to the image plane during zooming,
10. The stop is arranged on the optical path between the most object side surface of the zooming group closest to the object side and the most image side surface of the zooming group closest to the image side. The variable power optical system according to any one of . 6<|Ang1|<20 (1-1)
4. A variable power optical system according to claim 3 , which satisfies conditional expression (1-1) expressed by: 10<|Ang2|<40 (2-1)
5. A variable power optical system according to claim 4 , which satisfies conditional expression (2-1) represented by: 6<|Ang3|<25 (3-1)
6. A variable power optical system according to claim 5 , which satisfies conditional expression (3-1) represented by: 0.6<DL12/|f1|<0.95 (4-1)
2. A variable power optical system according to claim 1 , which satisfies conditional expression (4-1) expressed by: -0.75<fG2A/fG2B<-0.02 (5-1)
8. A variable magnification optical system according to claim 7 , which satisfies conditional expression (5-1) represented by: An imaging apparatus comprising the variable magnification optical system according to any one of claims 1 to 17 .