WO2023283810A1

WO2023283810A1 - Low refractive power zoom lens and optical system thereof

Info

Publication number: WO2023283810A1
Application number: PCT/CN2021/106132
Authority: WO
Inventors: Yasuhide Nihei; Takumi Matsui
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2021-07-14
Filing date: 2021-07-14
Publication date: 2023-01-19
Also published as: CN117642667A

Abstract

A super-telephoto zoom lens comprising, from an object side to an image side along a first optical axis (OA1) and a second optical axis (OA2), a first lens group (G1) having a positive refractive power, a second lens group (G2) having a positive refractive power, a third lens group (G3) having a negative refractive power, a fourth lens group (G4) having a negative refractive power, and a fifth lens group (G5) having a positive refractive power, wherein, when zooming, at least the third lens group (G3) and the fourth lens group (G4) is moved along the second optical axis (OA2) while the first lens group (G1) is fixed along the first optical axis (OA1), and the first lens group (G1) comprises a reflective optical element (L2) for bending an optical path from the object side by 90 degrees to the image side.

Description

LOW REFRACTIVE POWER ZOOM LENS AND OPTICAL SYSTEM THEREOF

FIELD OF THE DISCLOSURE

The present invention relates to a zoom lens composed of a plurality of lenses and a plurality of lens groups, and more particularly to a super-telephoto zoom lens which is compact and has a long focal length. The present application also relates to an electronic device such as a mobile communication terminal equipped with an image pickup lens device including such a super-telephoto zoom lens.

BACKGROUND OF THE DISCLOSURE

In recent years, mobile terminal devices have become widespread, and specifications in which a compact imaging unit is built into these devices have become common. Further, in recent years, a device having a plurality of camera units including a wide-angle lens for normal shooting and also a telephoto lens having a relatively long focal length and an angle of view of about 30 degrees has appeared.

For such telephoto lenses, there are demand for so-called super-telephoto lens, which have a longer focal length than a regular telephoto lens, in order to meet the demand for zooming subjects from a longer distance.

It is more desirable that such an optical system is a zoom lens whose focal length can be varied by one camera unit.

For example, the refractive power of an inner focus type lenses. However it is too high to reduce the manufacturing error sensitivity in order to improve mass productivity, and as a result, the focusing stroke becomes too long.

The telephoto zoom lens that is suitable for demand for miniaturization, for example, bending the optical axis has been proposed in which the optical axis is bended at 90 degrees by a reflecting optical element.

However, in the bending optical system, the configuration in prior art increases the total length of the optical system. Therefore, it is not suitable for a super-telephoto zoom lens in a size that can be mounted on a mobile device.

A bending optics system has a configuration suitable for miniaturization of a device capable of arranging a telephoto zoom lens perpendicular to the thickness direction of the housing of a mobile device by arranging the reflection optical element on the most object side. Since the first lens group of the telephoto zoom lens has a negative refractive power, the total length becomes too long when the angle of view at the telephoto end of the zoom lens is reduced to about 7 degrees or less to make it super telephoto.

For the above reasons, the problem to be solved by the present invention cannot be resolved by conventional bending type zoom lenses.

Therefore, the present invention aims to provide a so-called super-telephoto zoom lens in a size that can be mounted on a mobile device, in which the telephoto optical system is provided with a zooming function and the focal length is extended until the angle of view at the telephoto end becomes about 7 degrees or less.

SUMMARY OF THE DISCLOSURE

The present invention mitigates and/or obviates the afore-mentioned disadvantages.

The primary objective of the focusing system of the present disclosure is to provide a super-telephoto zoom lens in a size that can be mounted on a mobile device, in which the telephoto optical system is provided with a zooming function and the focal length is extended until the angle of view at the telephoto end becomes about 7 degrees or less.

According to a first aspect, a super-telephoto zoom lens is provided. The super-telephoto zoom lens comprises, in order from the object side along a first optical axis and a second optical axis, a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power.

By making the first lens group and the second lens group have a positive refractive power and the third lens group and the fourth lens group having a negative refractive power, a so-called telephoto configuration is obtained, and the TTL of the super-telephoto zoom lens is obtained while the restrained and it becomes possible to increase the focal length, and miniaturized super-telephoto zoom lens.

According to one aspect of the present super-telephoto zoom lens, the first lens group is fixed while zooming, and comprises a first lens element and a reflective optical element. The first optical axis is an optical axis of the first lens element, and the second optical axis is an optical axis of the second lens group, the third lens group, the fourth lens group and the fifth lens group, and the second optical axis is perpendicular to the first optical axis. The first lens element and the reflective optical element are disposed in order along the first optical axis from the object side, and the reflective optical element is configured to bend an optical path from the object side by 90 degrees to the image side.

By bending the optical path by 90 degrees by the reflective optical element of the first lens group, the length of the super-telephoto zoom lens in the direction along the second optical axis can be reduced even though it is a super-telephoto zoom lens.

According to one aspect of the present super-telephoto zoom lens, when zooming from a wide angle end to a telephoto end, the third lens group is moved towards the image side along the second optical axis, and the fourth lens group is moved towards the object side along the second optical axis. When FW is the focal length of the super-telephoto zoom lens at its wide position, F1 is the focal length of the first lens group, F4 is the focal length of the fourth lens group, and F5 is the focal length of the fifth lens group, it satisfies the following conditions:

(i) 1.25 < |F1/FW| < 1.85;

(ii) 0.15 < |F4/FW| < 0.75; and

(iii) 0.3 < |F5/FW| < 0.6.

Conditions (i) , (ii) and (iii) keep the focal lengths of the first lens group, the fourth lens group, and the fifth lens group in an appropriate range.

If the upper limit of Condition (i) is exceeded, since the refractive power of the first lens group becomes too strong, large aberrations such as spherical aberration occur, which makes it difficult to correct the aberration in the entire zoom range. In addition, the magnification of the lens groups on the image side of the second lens group becomes larger, which enlarge the aberration of the first lens group, and the aberration of the entire optical system is deteriorated. If it is less than the lower limit of Condition (1) , the refractive power of the first lens group becomes too weak and the total length of the optical system becomes large, which is not preferable

If it is less than the lower limit of Condition (ii) , the refractive power of the fourth lens group becomes too strong and the amount of aberration generated in the fourth lens group becomes large, so that the variation of the aberration becomes large when zooming, which is not preferable. Further, if the upper limit of Condition (ii) is exceeded, the refractive power of the fourth lens group is weakened, so that the amount of movement for zooming increases, which leads to an increase in the overall length of the optical system.

If it is less than the lower limit of Condition (iii) , the refractive power of the fifth lens group becomes too strong and the aberration including curvature of field becomes too large in the fifth lens group, and it becomes difficult to correct the aberration in the entire zoom range. If the upper limit of Condition (iii) is exceeded, the refractive power of the fifth lens group becomes too weak, so that the aberration correction effect of the fifth lens group becomes too weak, and it becomes difficult to correct the aberration in the entire zoom range.

According to one aspect of the present super-telephoto zoom lens, when TTL is a distance from the optical surface on the most object side of the zoom lens to the image plane along the first optical axis and the second optical axis, ST3 is an amount of movement of the third lens group along the second optical axis when zooming from the wide angle end to the telephoto end, and ST4 is an amount of movement of the forth lens group along the second optical axis when zooming from the wide angle end to the telephoto end, it satisfies the conditions:

(iv) 0.03 < |ST3/TTL| < 0.23; and

(v) 0.15 < |ST4/TTL| < 0.45.

Conditions (iv) and (v) keep the amount of movement of the third lens group and the fourth lens group within an appropriate range. If it is less than the lower limit of each condition, the refractive power of each lens group becomes too strong, and it becomes difficult to correct aberrations such as spherical aberration and curvature of field in each of the lens groups. In addition, if the upper limit of the condition is exceeded, the refractive power becomes too weak, which leads to an increase in the overall length of the zoom lens since the amound ffo movement for zooming increases.

According to one aspect of the super-telephoto zoom lens, when focusing from infinity to a short distance, at least the second lens group is moved toward the object side along the second optical axis. When FC2 is the ratio of the movement amount of the focal position to the movement amount of the second lens group, and F2 is the focal length of the second lens group, it satisfies the relation:

(vi) 0.4 < |FC2| < 0.58; and

(vii) 0.7 < |F2/FW| < 1.9.

Condition (vi) keeps the focusing sensitivity of the second lens group within an appropriate range. If it falls below the lower limit of the condition, the sensitivity becomes too low and at least the amount of movement of the second lens group during focusing becomes large, which slows down the focusing speed and causes an increase in the size of the optical system. If the upper limit of the condition is exceeded, the sensitivity becomes too high, the mechanical accuracy required for focusing becomes too high, and at least it becomes a constraint of the actuator for moving the second lens group.

Condition (vii) keeps the focal length of the second lens group within an appropriate range. If it falls below the lower limit of the condition, spherical aberration and axial chromatic aberration become large, resulting in deterioration of optical performance. If the upper limit of the condition is exceeded, the refractive power becomes too weak, which leads to an increase in the size of the optical system.

According to one aspect of the present super-telephoto zoom lens, each of the third lens group and the fourth lens group has at least one lens with a positive refractive power and one lens with a negative refractive power. When AB3 is an abbe number of either negative lens of the third lens group, and AB4 is an abbe number of either negative lens of the fourth lens group, it satisfies the relation:

(viii) 60 < AB3;

(ix) 60 < AB4.

Conditions (viii) and (ix) keep the Abbe number of lenses having a positive refractive power in each of the third lens group and the fourth lens group in an appropriate range. If it falls below the lower limit of the condition, the ability to correct chromatic aberration decreases, and as a result, it becomes difficult to correct axial chromatic aberration. [0028] According to one aspect of the present super-telephoto zoom lens, when zooming and focusing, the fifth lens group is fixed along the second optical axis. When FT is the focal length of the zoom lens at the tele end, they satisfy the relation:

(x) 1.0 < |FT/TTL| < 1.3.

Condition (x) keeps the ratio of the TTL of the super-telephoto zoom lens to the focal length at the telephoto end of the super-telephoto zoom lens in an appropriate range. If it falls below the lower limit of the condition, sufficient miniaturization cannot be achieved. If the upper limit of the condition is exceeded, the total optical length becomes too short with respect to the focal length at the telephoto end, and it becomes difficult to suppress axial chromatic aberration, which is not suitable.

According to a second aspect, a camera is provided. The camera comprises the super-telephoto zoom lens and an image sensor. The image sensor is disposed on the image side of the zoom lens. The zoom lens is configured to form an optical signal of a photographed object and reflect the optical signal to the image sensor, and the image sensor is configured to convert the optical signal corresponding to the photographed object into an image signal. The camera can be applied to small cameras for mobile devices such as mobile phones and tablets..

According to a third aspect, a terminal is provided. The terminal comprises a camera, which is the camera provided in the second aspect, and a Graphic Processing Unit (GPU) . The GPU is connected to the camera. The camera is configured to obtain image data and input the image data into the GPU, and the CPU is configured to process the image data received from the camera. The terminal can be applied to small cameras for mobile devices such as mobile phones and tablets.

The present disclosure will be presented in further detail from the following descriptions with accompanying drawings, which show, for purpose of illustration only, the preferred embodiments in accordance with the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood from the following detailed description of non-limiting embodiments thereof, and on examining the accompanying drawings, in which:

FIG 1-1 shows a cross-sectional illustration of a super-telephoto zoom lens in accordance with a first embodiment of the present disclosure at the wide angle end.

FIG 1-2 shows a cross-sectional illustration of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the telephoto end.

FIG 1-3 shows a longitudinal spherical aberration, an astigmatic field curves, and a distortion of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the wide angle end.

FIG 1-4 shows a longitudinal spherical aberration, an astigmatic field curves, and a distortion of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the telephoto end.

FIG 1-5 shows a lateral aberration of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the wide angle end.

FIG 1-6 shows a lateral aberration of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the telephoto end.

FIG 2-1 shows a cross-sectional illustration of a super-telephoto zoom lens in accordance with a second embodiment of the present disclosure at the wide angle end.

FIG 2-2 shows a cross-sectional illustration of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the telephoto end.

FIG 2-3 shows a longitudinal spherical aberration, an astigmatic field curves, and a distortion of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the wide angle end.

FIG 2-4 shows a longitudinal spherical aberration, an astigmatic field curves, and a distortion of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the telephoto end.

FIG 2-5 shows a lateral aberration of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the wide angle end.

FIG 2-6 shows a lateral aberration of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the telephoto end.

FIG 3-1 shows a cross-sectional illustration of a super-telephoto zoom lens in accordance with a third embodiment of the present disclosure at the wide angle end.

FIG 3-2 shows a cross-sectional illustration of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the telephoto end.

FIG 3-3 shows a longitudinal spherical aberration, an astigmatic field curves, and a distortion of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the wide angle end.

FIG 3-4 shows a longitudinal spherical aberration, an astigmatic field curves, and a distortion of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the telephoto end.

FIG 3-5 shows a lateral aberration of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the wide angle end.

FIG 3-6 shows a lateral aberration of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the telephoto end.

FIG 4 shows an implementation of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following embodiments of the super-telephoto zoom lens system of the present disclosure will be described with reference to the figures and the optical data. This super-telephoto zoom lens system can be applied to small cameras for mobile devices such as a mobile-phones and tablets.

The super-telephoto zoom lens according to the present invention has five lens groups, i.e., in order from the object side along a first optical axis and a second optical axis, a first lens group having a positive refractive power and including a reflective optical element for bending an optical path along the first optical axis by 90 degrees, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. In this super-telephoto zoom lens, zooming from the wide end to the tele end is realized by moving at least the third lens group towards the image side and the fourth lens group towards the object side along the second optical axis. In addition, focusing from infinity to a short distance is realized by moving at least the second lens group toward the object side along the second optical axis.

First Embodiment

FIG 1-1 shows a cross-sectional illustration of a super-telephoto zoom lens system in accordance with a first embodiment of the present disclosure at the wide angle end.

The super-telephoto zoom lens system comprises five lens groups G1, G2, G3, G4, and G5 from the object side along a first optical axis OA1 and a second optical axis OA 2, and the first lens group G1 comprises a first lens element L1 and a reflective optical element L2 from the object side along the first optical axis OA1. The reflective optical element L2 is a right-angled prism to bend an optical path along the first optical axis OA 1 from the object side by 90 degrees to the image side along the second optical axis OA2 in this embodiment, the second lens group G2 comprises a third lens element L3 and a fourth lens elements L4, the third lens group G3 comprises a fifth lens element L5 and a sixth lens element L6, the forth lens group G4 comprises a seventh lens element L7 and an eighth lens element L8, and the fifth lens group G5 comprises a ninth lens element L9. The first lens group G1 has a positive refractive power. The second lens group G2 has a positive refractive power. The third lens group G3 has a negative refractive power. The forth lens group G4 has a negative refractive power. The fifth lens group G5 has a positive refractive power.

The super-telephoto zoom lens system also comprises an image sensor IS, and a cover glass CG may be arranged on the image sensor IS.

FIG 1-2 shows a cross-sectional illustration of a super-telephoto zoom lens system in accordance with a first embodiment of the present disclosure at the telephoto end. For the telephoto end, the third lens group G3 is moved towards the image side along the second optical axis OA2, and the forth lens group G4 is moved towards the object side along the second optical axis OA2.

FIGs 1-1 and 1-2 show that only the third lens group G3 is moved towards the image side along the second optical axis OA2, and the forth lens group G4 is moved towards the object side along the second optical axis OA2 when zooming from the wide angle end to the telephoto end. Therefore, the zooming mechanism can be easily designed.

Table 1-1 shows the radius of curvature (R) and the thickness or separation (D) for each of the optical surfaces, and the refractive index (nd) and the Abbe number (vd) at wavelength 587.65nm for each of the lens elements of the super-telephoto zoom lens system of the first embodiment. Opposite surfaces of each lens element are respectively referred to as surface S1, surface S2, …, surface S19, and surface S20 in order form the objet side to the image side. Denotation “*” indicates that the surface is aspheric.

Table 1-1

Table 1-2 shows the thickness or separation (D) for D4, D8, D12, and D16 in the Table 1-1 at the wide angle end and the telephoto end. In Table 1-2, the wide angle end is referred to “Wide” , the telephoto end is referred to “Tele” .

Table 1-2

position	D4	D8	D12	D16
Wide	1.000	0.781	11.706	0.800
Tele	1.000	4.460	0.700	8.127

Table 1-3 shows the aspheric coefficients for each of the optical surfaces of the low refractive inner focusing lens system, wherein numbers 4 and 6 represent the higher order aspheric coefficients. The equation of the aspheric surface profiles is expressed as follows:

wherein:

X: the height of a point on the aspheric surface at a distance Y from the optical axis relative to the tangential plane at the aspheric surface vertex;

Y: the distance from a point on the curve of the aspheric surface to the optical axis;

k: the conic coefficient;

Ai: the aspheric coefficient of order i.

Table 1-3

surface	k	A4	A6
S5	0	-1.84532E-04	-1.30265E-06
S7	0	-6.65251E-05	6.50411E-07
S8	0	-2.90841E-04	1.21888E-06
S10	0	-3.49180E-04	-1.11733E-07
S11	0	-5.43298E-04	0.00000E+00
S12	0	-1.91583E-04	-2.56420E-07
S13	0	8.34997E-05	1.05577E-05
S15	0	-2.09993E-03	7.74787E-05
S16	0	-2.14527E-03	8.31715E-05
S17	0	6.75671E-04	3.28558E-05

FIG 1-3 shows a longitudinal spherical aberration for each wavelength, an astigmatic field curves where the amount of d-line aberration on the sagittal image plane S is shown by a solid line, and the amount of d-line aberration on the tangential image plane T is shown by a broken line., and a distortion where the amount of aberration on the d-line is shown by a solid line, of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the wide angle end.

FIG 1-5 shows a lateral aberration for each wavelength on the sagittal image plane and the tangential image plane, of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the wide angle end.

FIG 1-6 shows a lateral aberration for each wavelength on the sagittal image plane and the tangential image plane, of the super-telephoto zoom lens in accordance with the first embodiment of the present disclosure at the telephoto end.

It can be seen from the diagrams that each aberration is satisfactorily corrected.

Second Embodiment

FIG 2-1 shows a cross-sectional illustration of a super-telephoto zoom lens system in accordance with a second embodiment of the present disclosure at the wide angle end.

The super-telephoto zoom lens system comprises five lens groups G1, G2, G3, G4, and G5 from the object side along a first optical axis OA1 and a second optical axis OA2, and the first lens group G1 comprises a first lens element L1 and a reflective optical element L2 from the object side along the first optical axis OA1. The reflective optical element L2is a right-angled prism to bend an optical path along the first optical axis OA1 from the object side by 90 degrees to the image side along the second optical axis OA2in this embodiment, the second lens group G2 comprises a third lens element L3 and a fourth lens element L4, the third lens group G3 comprises a fifth lens element L5 and a sixth lens element L6, the fourth lens group G4 comprises lens a seventh element L7 and an eighth lens element L8, and the fifth lens group G5 comprises a ninth lens element L9. The first lens group G1 has a positive refractive power. The second lens group G2 has a positive refractive power. The third lens group G3 has a negative refractive power. The forth lens group G4 has a negative refractive power. The fifth lens group G5 has a positive refractive power.

FIG 2-2 shows a cross-sectional illustration of a super-telephoto zoom lens system in accordance with the second embodiment of the present disclosure at the telephoto end. For the telephoto end, the third lens group G3 is moved towards the image side along the second optical axis OA2, and the forth lens group G4 is moved towards the object side along the second optical axis OA2.

FIGs 2-1 and 2-2 show that only the third lens group G3 is moved towards the image side along the second optical axis OA2, and the forth lens group G4 is moved towards the object side along the second optical axis OA2 when zooming from the wide angle end to the telephoto end. Therefore, the zooming mechanism can be easily designed.

Table 2-1 shows the radius of curvature (R) and the thickness or separation (D) for each of the optical surfaces, and the refractive index (nd) and the Abbe number (vd) at wave length 587.65 nm for each of the lens elements of the super-telephoto zoom lens system of the second embodiment. Opposite surfaces of each lens element are respectively referred to as surface S1, surface S2, …, surface S19, and surface S20 in order form the objet side to the image side. Denotation “*” indicates that the surface is aspheric.

Table 2-1

Table 2-2 shows the thickness or separation (D) for D4, D8, D12, and D16 in the Table 2-1 at the wide angle end and the telephoto end. In Table 2-2, the wide angle end is referred to “Wide” , the telephoto end is referred to “Tele” .

Table 2-2

position	D4	D8	D12	D16
Wide	1.000	0.700	15.279	0.800
Tele	1.000	6.303	0.700	9.776

Table 2-3 shows the aspheric coefficients for each of the optical surfaces of the low refractive inner focusing lens system, wherein numbers 4 and 6 represent the higher order aspheric coefficients.

Table 2-3

surface	k	A4	A6
S5	0	-7.73375E-05	2.14441E-06
S6	0	1.46586E-04	9.67961E-07
S7	0	-1.82761E-04	7.62159E-06
S8	0	-3.85987E-04	9.57419E-06
S10	0	-2.05848E-04	-6.21794E-06
S11	0	1.73306E-04	0.00000E+00
S12	0	2.79377E-04	2.65873E-06
S13	0	-1.22148E-03	1.61674E-04
S14	0	1.26678E-03	8.49097E-05
S15	0	4.38869E-04	-3.86405E-05
S16	0	-5.54815E-03	6.53957E-05
S17	0	3.56076E-04	-7.30209E-07

FIG 2-3 shows a longitudinal spherical aberration for each wavelength, an astigmatic field curves where the amount of d-line aberration on the sagittal image plane S is shown by a solid line, and the amount of d-line aberration on the tangential image plane T is shown by a broken line., and a distortion where the amount of aberration on the d-line is shown by a solid line, of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the wide angle end.

FIG 2-5 shows a lateral aberration for each wavelength on the sagittal image plane and the tangential image plane, of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the wide angle end.

FIG 2-6 shows a lateral aberration for each wavelength on the sagittal image plane and the tangential image plane, of the super-telephoto zoom lens in accordance with the second embodiment of the present disclosure at the telephoto end.

Third Embodiment

FIG 3-1 shows a cross-sectional illustration of a super-telephoto zoom lens system in accordance with a third embodiment of the present disclosure at the wide angle end.

The super-telephoto zoom lens system comprises five lens groups G1, G2, G3, G4, and G5 from the object side along a first optical axis OA1 and a second optical axis OA2, and the first lens group G1 comprises a first lens element L1 and a reflective optical element L2 from the object side along the first optical axis OA1. The reflective optical element L2 is a right-angled prism to bend an optical path along the first optical axis OA1 from the object side by 90 degrees to the image side along the second optical axis OA2 in this embodiment, the second lens group G2 comprises a third lens element L3 and a fourth lens element L4, the third lens group G3 comprises a fifth lens element L5 and a sixth lens element L6, the forth lens group G4 comprises a seventh lens element L7, an eighth lens element L8, and a ninth lens element L9, and the fifth lens group G5 comprises a tenth lens element L10. The first lens group G1 has a positive refractive power. The second lens group G2 has a positive refractive power. The third lens group G3 has a negative refractive power. The forth lens group G4 has a negative refractive power. The fifth lens group G5 has a positive refractive power.

FIG 3-2 shows a cross-sectional illustration of a super-telephoto zoom lens system in accordance with the third embodiment of the present disclosure at the telephoto end. For the telephoto end, the third lens group G3 is moved towards the image side along the second optical axis OA2, and the forth lens group G4 is moved towards the object side along the second optical axis OA2.

FIGs 3-1 and 3-2 show that only the third lens group G3 is moved towards the image side along the second optical axis OA2, and the forth lens group G4 is moved towards the object side along the second optical axis OA2 when zooming from the wide angle end to the telephoto end. Therefore, the zooming mechanism can be easily designed.

Table 3-1 shows the radius of curvature (R) and the thickness or separation (D) for each of the optical surfaces, and the refractive index (nd) and the Abbe number (vd) at wave length 587.65 nm for each of the lens elements of the super-telephoto zoom lens system of the third embodiment. Opposite surfaces of each lens element are respectively referred to as surface S1, surface S2, …, surface S21, and surface S22 in order form the objet side to the image side. Denotation “*” indicates that the surface is aspheric.

Table 3-1

Table 3-2 shows the thickness or separation (D) for D4, D8, D12, and D16 in the Table 3-1 at the wide angle end and the telephoto end. In Table 3-2, the wide angle end is referred to “Wide” , the telephoto end is referred to “Tele” .

Table 3-2

position	D4	D8	D12	D18
Wide	1.000	0.600	17.927	0.800
Tele	1.000	3.526	0.700	15.102

Table 3-3 shows the aspheric coefficients for each of the optical surfaces of the low refractive inner focusing lens system, wherein numbers 4 and 6 represent the higher order aspheric coefficients.

Table 3-3

surface	k	A4	A6
S5	0	-2.75776E-04	-7.69934E-07
S7	0	-2.36441E-04	1.34682E-07
S8	0	-3.81750E-04	-1.35671E-07
S10	0	-2.18458E-04	7.03695E-07
S11	0	-2.25439E-04	0.00000E+00
S12	0	-2.31546E-05	2.95455E-07
S13	0	1.30992E-04	1.68328E-06
S15	0	-2.72763E-04	-2.32214E-05
S16	0	3.60913E-03	5.51616E-05
S18	0	-7.73080E-03	1.15102E-05
S19	0	-1.29812E-03	-8.47906E-06

FIG 3-3 shows a longitudinal spherical aberration for each wavelength, an astigmatic field curves where the amount of d-line aberration on the sagittal image plane S is shown by a solid line, and the amount of d-line aberration on the tangential image plane T is shown by a broken line., and a distortion where the amount of aberration on the d-line is shown by a solid line, of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the wide angle end.

FIG 3-5 shows a lateral aberration for each wavelength on the sagittal image plane and the tangential image plane, of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the wide angle end.

FIG 3-6 shows a lateral aberration for each wavelength on the sagittal image plane and the tangential image plane, of the super-telephoto zoom lens in accordance with the third embodiment of the present disclosure at the telephoto end.

As shown in the optical data of the first, second, and third embodiments, the super-telephoto zoom lens systems according to the present disclosure comprise five lens groups, i.e., in order from the object side along a first optical axis and a second optical axis, a first lens group having a positive refractive power and including a reflective optical element for bending an optical path from the object side by 90 degrees to the image side, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. In this super-telephoto zoom lens, zooming from wide to tele is realized by moving at least the third lens group towards the image side and the fourth lens group towards the object side along the second optical axis. In addition, focusing from infinity to a short distance is realized by moving at least the second lens group toward the object side along the second optical axis. The super-telephoto zoom lens in the present invention can be in a size that can be mounted on a mobile device, in which the telephoto optical system is provided with a zooming function and the focal length is extended until the angle of view at the telephoto end becomes about 7 degrees or less. The above-mentioned advantages are accomplished when it satisfies the following relations:

(i) 1.25 < |F1/FW| < 1.85,

where FW is the focal length of the super-telephoto zoom lens at its wide position, F1 is the focal length of the first lens group.

(ii) 0.15 < |F4/FW| < 0.75,where F4 is the focal length of the fourth lens group.

(iii) 0.3 < |F5/FW| < 0.6,

where F5 is the focal length of the fifth lens group.

(iv) 0.03 < |ST3/TTL| < 0.23; and

where TTL is a distance from the optical surface on the most object side of the zoom lens to the image plane along the first optical axis and the second optical axis, ST3 is an amount of movement of the third lens group along the second optical axis.

(v) 0.15 < |ST4/TTL| < 0.45;

where ST4 is an amount of movement of the forth lens group along the second optical axis.

(vi) 0.4 < |FC2| < 0.58,

where FC2 is the ratio of the movement amount of the focal position to the movement amount of the second lens group.

(vii) 0.7 < |F2/FW| < 1.9,

where F2 is the focal length of the second lens group.

(viii) 60 < AB3,

where AB3 is an abbe number of either negative lens of the third lens group.

(ix) 60 < AB4,

where AB4 is an abbe number of either negative lens of the fourth lens group.

(x) 1.0 < |FT/TTL| < 1.3,

Where FT is the focal length of the zoom lens at the tele end

If the upper limit of Condition (i) is exceeded, since the refractive power of the first lens group becomes too strong, large aberrations such as spherical aberration occur, which makes it difficult to correct the aberration in the entire zoom range. In addition, the magnification of the lens groups on the image side of the second lens group becomes larger, which enlarge the aberration of the first lens group, and the aberration of the entire optical system is deteriorated. If it is less than the lower limit of Condition (1) , the refractive power of the first lens group becomes too weak and the total length of the optical system becomes large, which is not preferable.

Conditions (viii) and (ix) keep the Abbe number of lenses having a positive refractive power in each of the third lens group and the fourth lens group in an appropriate range. If it falls below the lower limit of the condition, the ability to correct chromatic aberration decreases, and as a result, it becomes difficult to correct axial chromatic aberration.

Table 4 shows the values of the parameters used in the above-mentioned conditions from the first, second and third embodiments. In addition, F#W is F-number at the wide-angle end, F#T is F-number at the telephoto end, and Y is the maximum image height.

Table 4

By satisfying these conditions, the height of the super-telephoto zoom lens in the direction of bending 90 degrees can be reduced even though it is a super-telephoto zoom lens. Further, the first lens group and the second lens group have a positive refractive power, and the third lens group and the fourth lens group have a negative refractive power, thereby forming a so-called telephoto configuration. It is possible to extend the focal length of the zoom lens while keeping the TTL small, realizing a compact super-telephoto zoom lens.

Further, a camera is provided. The camera in the present disclosure comprises the super-telephoto zoom lens of the present disclosure and an image sensor. The super-telephoto zoom lens is configured to input light, which is used to project an image to the image sensor; and the image sensor is configured to convert the image into a digital image data.

FIG. 4 shows a terminal 1000 disclosed in the present disclosure. The terminal 1000 comprises cameras 100 provided in the above implementations and a Graphic Processing Unit (GPU) 200. The camera 100 is configured to convert an image through a super-telephoto zoom lens of the present disclosure to digital image data and input the digital image data into the GPU 200, and the GPU 200 is configured to process the image data received from the camera.

In FIG. 4, the terminal comprises two cameras 100. However, the terminal may comprise a single camera or two or more cameras and it (or they) could be connected to the single GPU 200. One of the cameras 100 can be combined with the super-telephoto zoom lens of the present disclosure, and other of the cameras 100 can be combined with a different type of lens such as a Single focus wide-angle lens.

Although the lens system according to the present disclosure can be applied especially to mobile phone cameras, it can also be applied to cameras in any mobile device such as tablet type devices and wearable devices

Although preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims.

Claims

A zoom lens comprising, from an object side to an image side along a first optical axis and a second optical axis:

a first lens group having a positive refractive power;

a second lens group having a positive refractive power;

a third lens group having a negative refractive power;

a fourth lens group having a negative refractive power; and

a fifth lens group having a positive refractive power,

when zooming from a wide angle end to a telephoto end, the third lens group is moved towards the image side along the second optical axis, and the fourth lens group is moved towards the object side along the second optical axis;

the first lens group is fixed while zooming, and comprises a first lens element and a reflective optical element; the first optical axis is an optical axis of the first lens element, the second optical axis is an optical axis of the second lens group, the third lens group, the fourth lens group and the fifth lens group, and the second optical axis is perpendicular to the first optical axis;

the first lens element and the reflective optical element are disposed in order along the first optical axis from the object side, and the reflective optical element is configured to bend an optical path from the object side by 90 degrees to the image side ; and

the following conditions are satisfied:

(i) 1.25 < |F1/FW| < 1.85;

(ii) 0.15 < |F4/FW| < 0.75; and

(iii) 0.3 < |F5/FW| < 0.6,

where FW is a focal length of the zoom lens at the wide angle end, F1 is a focal length of the first lens group, F4 is a focal length of the fourth lens group, and F5 is a focal length of the fifth lens group.
The zoom lens as claimed in claim 1, wherein the following conditions are satisfied:

(iv) 0.03 < |ST3/TTL| < 0.23; and

(v) 0.15 < |ST4/TTL| < 0.45;

where TTL is a distance from an optical surface on the most object side of the zoom lens to an image plane along the first optical axis and the second optical axis, ST3 is an amount of movement of the third lens group along the second optical axis when zooming from the wide angle end to the telephoto end, and ST4 is an amount of movement of the forth lens group along the second optical axis when zooming from the wide angle end to the telephoto end.
The zoom lens as claimed in claim 1 or 2, wherein, when focusing from infinity to a short distance, the second lens group is moved towards the object side along the second optical axis, and the following conditions are satisfied:

(vi) 0.4 < |FC2| < 0.58; and

(vii) 0.7 < |F2/FW| < 1.9;

where FC2 is a ratio of a movement amount of a focal position to a movement amount of the second lens group, and F2 is a focal length of the second lens group.
The zoom lens as claimed in one of claims 1 to 3, wherein each of the third lens group and the fourth lens group has at least one positive lens and one negative lens, and

wherein the following conditions are satisfied:

(viii) 60 < AB3; and

(ix) 60 < AB4,

where AB3 is an abbe number of either negative lens of the third lens group, and AB4 is an abbe number of either negative lens of the fourth lens group.
The zoom lens as claimed in one of claims 1 to 4, wherein, when zooming and focusing, the fifth lens group is fixed along the second optical axis, and

wherein the following condition is satisfied:

(x) 1.0 < |FT/TTL| < 1.3;

where FT is a focal length of the zoom lens at the telephoto end, TTL is a distance from an optical surface on the most object side of the zoom lens to an image plane along the first optical axis and the second optical axis.
A camera module, comprising the zoom lens according to any one of claims 1 to 5, further comprising an image sensor, wherein the image sensor is disposed on the image side of the zoom lens, the zoom lens is configured to form an optical signal of a photographed object and reflect the optical signal to the image sensor, and the image sensor is configured to convert the optical signal corresponding to the photographed object into an image signal.
A terminal, comprising the camera module according to claim 6 and a Graphic Processing Unit (GPU) , wherein the GPU is connected with the camera module to receive and process the image signal.