Electric focusing lens

Abstract

The invention relates to the technical field of optical lenses, in particular to an electric focusing lens. The electric focusing lens comprises a first lens unit, a second lens unit, a liquid lens module and a third lens unit which are sequentially arranged in the light path direction, the first lens unit is of negative focal power, the second lens unit and the third lens unit are of positive focal power, and the liquid lens module and the third lens unit are of positive focal power. The liquid lens module comprises a first window piece and a second window piece which are arranged in parallel, a sealed cavity is formed between the first window piece and the second window piece, a diaphragm is arranged in the sealed cavity, first liquid is packaged between the diaphragm and the first window piece, second liquid is packaged between the diaphragm and the second window piece, and the first window piece and the second window piece are arranged in a sealed mode. And voltage is applied between the first window sheet and the second window sheet so as to change the curvature radius of the diaphragm. By the adoption of the mode, the lens is simple in structure, real-time electric focusing can be conducted on different object distances, the object distance observation range is widened, and the resolution ratio is improved.

Description

Technical Field

[0001] The present application relates to the technical field of optical lenses, and in particular to an electric focusing lens. Background Art

[0002] In the field of industrial slits, pipeline monitoring and detection, and medical minimally invasive surgery observation, since the various types of monitoring lenses and industrial lenses commonly used in the market are large and cannot be inserted into small spaces, small electronic endoscopes are mainly used. In order to freely enter and exit various tiny holes, but precisely because of this size limitation, various types of motors cannot be installed on the endoscope, and the motor cannot be used to drive the lens group to move to achieve the electric focusing function. Therefore, when the endoscope is installed, its focusing distance is fixed and cannot be changed. In a small space, objects with different distances cannot be observed at will, which limits its observation range.

[0003] In order to avoid the observation inconvenience caused by the above problems, traditional endoscopes on the market today often use a small aperture system with an aperture greater than 5.0 to increase the depth of field of the lens, so that even if the lens is not focused, a larger object distance range can be observed at the same time. However, this method has limited improvement in depth of field, and the clear object distance range is only a few dozen millimeters. In addition, the small aperture system introduces new problems. First, the amount of light entering is too small, requiring strong fill light. On the other hand, affected by the diffraction effect, the resolution of the lens is limited, which is not conducive to seeing a clear image. Summary of the invention

[0004] The technical problem to be solved by the embodiments of the present application is to provide an electric focusing lens that can perform real-time electric focusing for different object distances, increase the observation object distance range, and improve the resolution.

[0005] The present application discloses an electric focus lens, comprising a first lens unit, a second lens unit, a liquid lens module and a third lens unit which are sequentially arranged along an optical path direction, wherein the first lens unit has a negative optical focal length, the second lens unit and the third lens unit have a positive optical focal length, the liquid lens module comprises a first window sheet and a second window sheet which are arranged in parallel, a sealed chamber is formed between the first window sheet and the second window sheet, a diaphragm is arranged in the sealed chamber, a first liquid is encapsulated between the diaphragm and the first window sheet, a second liquid is encapsulated between the diaphragm and the second window sheet, and a voltage is applied between the first window sheet and the second window sheet to change the radius of curvature of the diaphragm.

[0006] Optionally, the first lens unit is a first single lens with negative optical power, and the first single lens is a meniscus lens.

[0007] Optionally, the second lens unit is a second single lens with positive optical power.

[0008] Optionally, the second lens unit is a combination lens group of a parallel flat glass with no optical power and a second single lens with positive optical power corresponding to the parallel flat glass.

[0009] Optionally, the second lens unit is a combination lens group of a turning prism and a second single lens with positive optical power corresponding to the turning prism.

[0010] Optionally, the turning prism includes a first prism, a second prism and a third prism that are glued together, and the upper and lower parts of the bonding surfaces of the first prism and the second prism are respectively provided with an incident area and a first reflection area, and the bonding surfaces of the third prism and the second prism are provided with a second reflection area, so that the light emitted from the first lens unit is incident on the incident area, and after being reflected by the second reflection area and the first reflection area in sequence, it is emitted from the second prism, and the direction of the light incident on the turning prism and the direction of the light emitted from the turning prism form a preset angle.

[0011] Optionally, the third lens unit is a first cemented lens with positive refractive power, or the third lens unit includes a first cemented lens and a second cemented lens with positive refractive power which are arranged opposite to each other.

[0012] Optionally, the electric focus lens can focus on an object distance range of 20 mm to 150 mm, and the electric focus lens satisfies the following conditional formula:

[0013] -1.3 <fG1 / f<-0.9 (1)

[0014] 1.6 <fG2 / f<2.6 (2)

[0015] Wherein, fG1 is the focal length of the first lens unit, fG2 is the focal length of the second lens unit, and f is the total focal length of the electric focus lens when the object distance is 150 mm.

[0016] Optionally, the electric focus lens also satisfies the following conditional formula:

[0017] 1.76 <nG1<2.06 (3)

[0018] Wherein, nG1 is the refractive index of the first monomer lens.

[0019] Optionally, the electric focus lens further includes a lens barrel, the first lens unit, the second lens unit, the liquid lens module and the third lens unit are all located in the lens barrel, and the outer diameter of the lens barrel is less than or equal to 8.5 mm.

[0020] Compared with the prior art, the beneficial effect of the electric focus lens provided by the embodiment of the present application is that the real-time electric focus of the electric focus lens is achieved by utilizing a liquid lens module, the outer surface of the structure does not have any protrusions of motors, gears or other structures, does not require any moving parts, is simple and compact, and achieves the purpose of miniaturization of the electric focus lens. At the same time, a first lens unit with negative optical focal length is adopted to form a reverse telephoto optical structure with a large field of view. Since the electric focus lens can focus on different object distances at any time, it is not necessary to consider a large depth of field in the optical path design, and the lens aperture can be F4.0 or even larger, which helps to reduce the influence of the diffraction effect and has a higher resolution than a lens with an immutable focusing object distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The technical solution of the present application will be further described in detail below with reference to the accompanying drawings and embodiments, in which:

[0022] Figure 1 This is one of the structural schematic diagrams of the electric focus lens provided in the embodiment of the present application;

[0023] Figure 2 This is the second structural schematic diagram of the electric focus lens provided in the embodiment of the present application;

[0024] Figure 3 This is the third structural schematic diagram of the electric focus lens provided in the embodiment of the present application;

[0025] Figure 4 This is the fourth structural schematic diagram of the electric focus lens provided in the embodiment of the present application;

[0026] Figure 5 This is the fifth structural schematic diagram of the electric focus lens provided in the embodiment of the present application;

[0027] Figure 6 yes Figure 1 Spherical aberration, astigmatism, and optical distortion curves when the object distance is 20 mm in the structure shown;

[0028] Figure 7 yes Figure 1 Spherical aberration, astigmatism, and optical distortion curves when the object distance is 150mm in the structure shown;

[0029] Figure 8 yes Figure 2 The spherical aberration, astigmatism and optical distortion curves when the first single lens in the structure shown is a spherical lens and the object distance is 20 mm;

[0030] Fig. 9 yes Figure 2 The spherical aberration, astigmatism and optical distortion curves when the first single lens in the structure shown is a spherical lens and the object distance is 150 mm;

[0031] Fig.10 yes Figure 2 The spherical aberration, astigmatism and optical distortion curves when the first single lens in the structure shown is an aspherical lens and the object distance is 20 mm;

[0032] Fig.11 yes Figure 2 The spherical aberration, astigmatism and optical distortion curves when the first single lens in the structure shown is an aspherical lens and the object distance is 150 mm;

[0033] Fig.12 yes Figure 4 Spherical aberration, astigmatism, and optical distortion curves when the object distance is 20 mm in the structure shown;

[0034] Fig.13 yes Figure 4 Spherical aberration, astigmatism, and optical distortion curves when the object distance is 150mm in the structure shown.

[0035] The reference numerals in the figures are:

[0036] 100, electric focus lens; 110, first lens unit; 112, first monomer lens; 120, second lens unit; 122, second monomer lens; 124, parallel plate glass; 126, turning prism; 1262, first prism; 1264, second prism; 1266, third prism; 130, liquid lens module; 132, first window plate; 134, second window plate; 136, diaphragm; 140, third lens unit; 142, first cemented lens; 144, second cemented lens. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, a detailed description of the preferred embodiments of the present application is given.

[0038] like Figures 1 to 5 As shown, an embodiment of the present application provides an electric focus lens 100, comprising a first lens unit 110, a second lens unit 120, a liquid lens module 130 and a third lens unit 140 arranged in sequence along the optical path direction, wherein the first lens unit 110 has a negative optical focal length, the second lens unit 120 and the third lens unit 140 have a positive optical focal length, the liquid lens module 130 comprises a first window 132 and a second window 134 arranged in parallel, a sealed chamber is formed between the first window 132 and the second window 134, a diaphragm 136 is arranged in the sealed chamber, a first liquid is encapsulated between the diaphragm 136 and the first window 132, a second liquid is encapsulated between the diaphragm 136 and the second window 134, and a voltage is applied between the first window 132 and the second window 134 to change the curvature radius of the diaphragm 136.

[0039] Specifically, the first lens unit 110 is set to have a negative optical focal length, which can enable the electric focus lens 100 to form a reverse telephoto structure. The large-angle incident light outside the field of view is deflected after passing through the first lens unit 110, and the angle between it and the optical axis becomes smaller, which is convenient for the rear optical path to perform aberration correction, so that the electric focus lens 100 has a larger field of view. The second lens unit 120 has a positive optical focal length, which is mainly responsible for correcting the spherical aberration of the electric focus lens 100. The first liquid and the second liquid are made of different materials and are separated by a diaphragm 136. In order to ensure the normal transmission of light, it is necessary to ensure that the diaphragm 136 is made of a transparent material. When the voltage applied between the first window 132 and the second window 134 changes, the curvature of the diaphragm 136 will change by using the electrowetting effect, and the curvature and the applied voltage have a clear corresponding relationship. Therefore, there is also a one-to-one corresponding relationship between the focusing object distance of the lens and the voltage, and the optical focal length of the liquid lens module 130 can be adjusted by voltage. The third lens unit 140 has positive refractive power and is used to correct the chromatic aberration of the electric focus lens.

[0040] The electric focusing lens 100 provided in the embodiment of the present application realizes real-time electric focusing of the electric focusing lens 100 by utilizing a liquid lens module 130. The outer surface of the structure does not have any protrusions of structures such as motors and gears, does not require any moving parts, is simple and compact, and achieves the purpose of miniaturization of the electric focusing lens 100. At the same time, a first lens unit 110 with negative optical focal length is adopted to form a reverse telephoto optical structure with a larger field of view. Since the electric focusing lens 100 can focus on different object distances at any time, it is not necessary to consider a large depth of field in the optical path design. The lens aperture can be F4.0 or even larger, which helps to reduce the influence of the diffraction effect and has a higher resolution compared to a lens with an immutable focusing object distance. The above-mentioned form can increase the observation object distance range of the lens and improve the resolution.

[0041] like Figures 1 to 5 As shown, the first lens unit 110 is a first single lens 112 with negative optical power, and the first single lens 112 is a meniscus lens.

[0042] Specifically, the first lens unit 110 uses a first single lens 112 with a negative optical focal length, which is beneficial to increase the field of view and ensure the desired imaging effect. In practical applications, a meniscus lens can be used, and the meniscus lens can be in the form of a spherical lens or an aspherical lens, which is not specifically limited in the present embodiment.

[0043] When the first single lens 112 is in the form of an aspherical lens, the optical distortion of the system can be reduced, so that the edge of the field of view retains richer image information, which is very valuable for medical observation. The surface shape of the aspherical surface satisfies the following formula:

[0044]

[0045] Among them, c=1 / R, R represents the curvature radius of the reference sphere of the aspheric surface, r represents the radial coordinate of the aspheric lens starting from the optical axis, z represents the vector height corresponding to the radial coordinate r of the aspheric lens, k represents the cone coefficient, and A, B, C, D, E, and F represent aspheric coefficients of different orders respectively.

[0046] like Figure 1 As shown, the second lens unit 120 is a second single lens 122 with positive optical power.

[0047] Specifically, the second single lens 122 may be a plano-convex lens or a bi-convex lens to correct the spherical aberration of the electric focus lens 100 .

[0048] use Figure 1 The scheme shown constitutes an electric focus lens 100, and the lens data used are shown in the following table:

[0049] Face number Curvature radius R(mm) Thickness interval d(mm) Refractive index nd Abbe coefficient vd 1 9.697 0.85 1.9108 35.26 2 2.1 3.835 3 16.95 3.3 1.9004 37.37 4 6.17 0.66 5 ∞ 0.4 1.5233 54.52 6 ∞ D(6) 1.4882 38.39 7 R(7) D(7) 1.4293 62.16 8 ∞ 0.5 1.5233 54.52 9 ∞ 0.5 10 8.11 1.509 1.6968 56.2 11 -3.0 0.51 1.9460 17.94 12 -9.4 4.83

[0050] It should be noted that surface numbers 1 to 12 are the numbers of the optical surfaces arranged in order from the object side to the image side. In addition, when the object distance is 20 mm and 150 mm respectively, the parameter changes of D(6), D(7) and R(7) are shown in the following table:

[0051] Object distance(mm) 20 150 D(6) 0.35 0.28 D(7) 0.45 0.52 R(7) -12.03 42.06

[0052] Among them, the use of Figure 1 In the embodiment shown, the corresponding optical indicators (when the object distance is 150 mm) are as follows: focal length f: 2.65 mm; aperture Fno: F4.1; half field angle ω: 45°; optical distortion: -24.0%.

[0053] like Figure 2 and Figure 4 As shown, the second lens unit 120 is a combination lens group of a parallel plate glass 124 with no optical power and a second single lens 122 with positive optical power corresponding to the parallel plate glass 124 .

[0054] Specifically, when the second monomer lens 122 is a biconvex lens, a certain distance may be provided between the second monomer lens 122 and the parallel plate glass 124 (see Figure 2 When the second monomer lens 122 is a plano-convex lens, it can be directly glued and connected to the parallel flat glass 124 (please refer to Figure 4 ), at this time, there is no air gap between the parallel flat glass 124 and the second monomer lens 122, and a spacer can be omitted in the structure, and the assembly steps are simpler.

[0055] use Figure 2 The scheme shown constitutes the electric focus lens 100, and when the first monomer lens 112 is a spherical lens, the lens data used are shown in the following table:

[0056] Face number Curvature radius R(mm) Thickness interval d(mm) Refractive index nd Abbe coefficient vd 1 16.75 1.0 2.0010 29.13 2 2.44 0.47 3 ∞ 8.6 1.9108 35.26 4 ∞ 0.11 5 7.852 1.25 1.9108 35.26 6 -10.665 0.643 7 ∞ 0.4 1.5233 54.52 8 ∞ D(8) 1.4882 38.39 9 R(9) D(9) 1.4293 62.16 10 ∞ 0.5 1.5233 54.52 11 ∞ 0.3 12 9.954 1.756 1.5928 68.62 13 -2.589 0.53 1.9229 20.88 14 -7.051 5.55

[0057] It should be noted that surface numbers 1 to 14 are the numbers of the optical surfaces arranged in order from the object side to the image side. In addition, when the object distance is 20 mm and 150 mm respectively, the parameter changes of D(8), D(9) and R(9) are shown in the following table:

[0058] Object distance(mm) 20 150 D(8) 0.35 0.28 D(9) 0.45 0.52 R(9) -13.02 62.03

[0059] Among them, the use of Figure 2 In the embodiment shown, the corresponding optical indicators (when the object distance is 150 mm) are as follows: focal length f: 2.92 mm; aperture Fno: F4.1; half field angle ω: 40°; optical distortion: -18.5%.

[0060] use Figure 2 The scheme shown constitutes the electric focus lens 100, and when the first monomer lens 112 is an aspherical lens, the lens data used are shown in the following table:

[0061]

[0062]

[0063] It should be noted that surface numbers 1 to 14 are the numbers of the optical surfaces arranged in order from the object side to the image side. In addition, when the object distance is 20 mm and 150 mm respectively, the parameter changes of D(8), D(9) and R(9) are shown in the following table:

[0064] Object distance(mm) 20 150 D(8) 0.34 0.29 D(9) 0.46 0.51 R(9) -13.818 50.122

[0065] Among them, the aspheric lens adopts the parameters in the following table:

[0066] Face number k A B C D E F 1 0 6.0245E-03 3.5537E-03 -2.6859E-03 7.8835E-04 -1.0951E-04 5.8310E-06 2 -3.1587E-01 2.8378E-03 3.7565E-02 -3.9933E-02 2.1796E-02 -5.7326E-03 5.5118E-04

[0067] In the above table, surface number 1 and surface number 2 are the numbers of two optical surfaces of the first monomer lens 112 arranged in sequence from the object side to the image side.

[0068] At this time, the corresponding optical indicators (when the object distance is 150 mm) are as follows: focal length f: 2.66 mm; aperture Fno: F4.1; half field angle ω: 40° optical distortion: -10.0%.

[0069] exist Figure 2 and Figure 4In the embodiment, the parallel plate glass 124 has no optical focal length and does not participate in correcting the aberration in the system. In practical applications, it can be transformed into a turning prism 126 with the same optical path as the parallel plate glass 124 by the method of prism expansion.

[0070] like Figure 3 and Figure 5 As shown, in an optional embodiment of the present application, the second lens unit 120 is a combination lens group of a turning prism 126 and a second single lens 122 with positive optical power corresponding to the turning prism 126 .

[0071] Specifically, by cooperating with the steering prism 126 and the second monomer lens 122, the optical axis direction of the optical path is changed, so that the electric focus lens 100 can have different viewing angles. The above method is conducive to realizing the change of the lens viewing angle and meeting the needs of different observation angles. When the lens is in a small space, it only needs to rotate around the optical axis to observe the field of view in different directions.

[0072] like Figure 3 As shown, the turning prism 126 includes a first prism 1262, a second prism 1264 and a third prism 1266 which are glued together, and the upper and lower parts of the bonding surfaces of the first prism 1262 and the second prism 1264 are respectively provided with a first reflection area and an incident area, and the bonding surfaces of the third prism 1266 and the second prism 1264 are provided with a second reflection area, so that the light emitted from the first lens unit 110 is incident on the incident area of ​​the first prism 1262, and then after being reflected by the second reflection area and the first reflection area in sequence, it is emitted from the second prism 1264 to the rear light path, and the direction of the light incident on the turning prism 126 and the direction of the light emitted from the turning prism 126 form a preset angle.

[0073] Specifically, the incident area may not be coated with any functional film. After the light emitted from the first lens unit 110 is incident on the incident area, it can directly pass through the first prism 1262 and the second prism 1264 to the second reflection area, or an anti-reflection film can be coated on the incident area to improve the utilization rate of the light. After the light is incident on the second reflection area, the light is reflected to the first reflection area, wherein the bonding surfaces of the third prism 1266 and the second prism 1264 are all provided with a reflective film to improve the utilization rate of the light during reflection. After the light is reflected to the first reflection area, it is finally emitted from the second prism 1264. With the above form, the direction of the light incident on the steering prism 126 and the direction of the exit steering prism 126 are at a preset angle to change the optical axis direction of the light path so that the lens has a viewing angle of different angles. For example, the first lens unit 110 can be set to a certain deflection angle as needed, such as a 30° viewing angle.

[0074] like Figures 1 to 5As shown, the third lens unit 140 is a first cemented lens 142 with positive optical power, or the third lens unit 140 includes a first cemented lens 142 and a second cemented lens 144 with positive optical power that are arranged opposite to each other.

[0075] Specifically, the first cemented lens 142 can be formed by cementing a positive power lens and a negative power lens, and the positive power lens is made of ultra-low dispersion glass, which helps to correct the chromatic aberration of the system. In addition, the second cemented lens 144 is also formed by cementing a positive power lens and a negative power lens, and the positive power lens is also made of ultra-low dispersion glass, which helps to further correct the chromatic aberration of the system. When the first cemented lens 142 and the second cemented lens 144 cooperate, the aberrations in the optical system, such as spherical aberration, chromatic aberration, etc., can be reduced, and the imaging quality and clarity of the optical system can be improved.

[0076] use Figure 4 When the scheme shown constitutes the electric focus lens 100, the lens data used are shown in the following table:

[0077] Face number Curvature radius R Thickness interval d Refractive index nd Abbe coefficient vd 1 17.086 0.75 2.0010 29.13 2 2.52 0.488 3 ∞ 8.6 1.9108 35.26 4 ∞ 1.142 1.9537 32.32 5 -6.258 1.021 6 ∞ 0.4 1.5233 54.52 7 ∞ D(7) 1.4882 38.39 8 R(8) D(8) 1.4293 62.16 9 ∞ 0.5 1.5233 54.52 10 ∞ 0.29 11 3.65 1.332 1.5928 68.62 12 64.02 0.54 1.7618 26.61 13 3.614 0.13 14 6.333 2.611 1.5928 68.62 15 -2.4 0.695 1.9037 31.32 16 -5.281 4.27

[0078] It should be noted that surface numbers 1 to 16 are the numbers of the optical surfaces arranged in order from the object side to the image side. In addition, when the object distance is 20 mm and 150 mm respectively, the parameter changes of D(7), D(8) and R(8) are shown in the following table:

[0079] Object distance 20 150 D(7) 0.34 0.29 D(8) 0.46 0.51 R(8) -13.011 170.02

[0080] At this time, the corresponding optical indicators (when the object distance is 150 mm) are as follows: focal length f: 2.89 mm; aperture Fno: F4.05; half field angle ω: 40° optical distortion: -17.3%.

[0081] In an optional embodiment of the present application, the object distance range that the electric focus lens 100 can focus on is 20 mm to 150 mm, and the electric focus lens 100 satisfies the following conditional formula:

[0082] -1.3 <fG1 / f<-0.9 (1)

[0083] 1.6 <fG2 / f<2.6 (2)

[0084] Wherein, fG1 is the focal length of the first lens unit 110, fG2 is the focal length of the second lens unit 120, and f is the total focal length of the electric focus lens 100 when the object distance is 150 mm.

[0085] Specifically, through the cooperation of the first lens unit 110, the second lens unit 120 and the third lens unit 140, and relying on the electric focusing of the liquid lens module 130, it is possible to clearly focus within the object distance range of 20mm to 150mm to improve the observation effect. Figures 6 to 13 As shown in the figure, the spherical aberration, astigmatism and optical distortion diagrams of the electric focus lens 100 in different structural forms are shown. Among them, Spherical Aberration is the spherical aberration, and its ordinate represents the height of the light on the aperture, Astigmatic Field Curves is the astigmatic field curve, and its ordinate represents the image plane height, Distortion is the optical distortion, and its ordinate is also the image plane height. It can be seen that the various aberrations of the electric focus lens 100 at different object distances are well corrected, and it has the ability of high-definition imaging in a large working object distance range.

[0086] In an optional embodiment of the present application, the electric focus lens 100 also satisfies the following conditional formula:

[0087] 1.76 <nG1<2.06 (3)

[0088] Wherein, nG1 is the refractive index of the first monomer lens 112 .

[0089] With the above-mentioned form, the incident light outside the field of view at a large angle is deflected after passing through the first monomer lens 112, and the angle between the light and the optical axis becomes smaller, which is convenient for the aberration correction of the rear optical path, so that the system has a larger field of view. In addition, the height of the light on the first monomer lens 112 can be compressed, which is conducive to controlling the diameter of the lens and ensuring the compactness of the overall diameter of the electric focus lens 100.

[0090] The conditional values ​​corresponding to the embodiments of the present application are summarized as follows:

[0091]

[0092]

[0093] In an optional embodiment of the present application, the electric focus lens 100 further includes a lens barrel, the first lens unit 110, the second lens unit 120, the liquid lens module 130 and the third lens unit 140 are all located in the lens barrel, and the outer diameter of the lens barrel is less than or equal to 8.5 mm.

[0094] Specifically, by adopting the above method, in actual applications, the electric focusing lens 100 has a small overall diameter and can easily enter tiny holes and cavities to perform electric focusing on different object distances, thereby expanding the observation range of the electric focusing lens 100 and facilitating its application in micro lenses such as endoscopes.

[0095] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present application rather than to limit them. For those skilled in the art, the technical solutions described in the above embodiments can be modified, scaled, or some of the technical features can be replaced by equivalents; and all these modifications, scaling and replacements should fall within the scope of protection of the claims attached to the present application.

Claims

1. An electric focus lens, characterized in that: The invention comprises a first lens unit, a second lens unit, a liquid lens module and a third lens unit which are sequentially arranged along the optical path direction, wherein the first lens unit has a negative optical focal length, the second lens unit and the third lens unit have a positive optical focal length, the liquid lens module comprises a first window sheet and a second window sheet which are arranged in parallel, a sealed chamber is formed between the first window sheet and the second window sheet, a diaphragm is arranged in the sealed chamber, a first liquid is encapsulated between the diaphragm and the first window sheet, a second liquid is encapsulated between the diaphragm and the second window sheet, and a voltage is applied between the first window sheet and the second window sheet to change the radius of curvature of the diaphragm.

2. The electric focus lens according to claim 1, characterized in that: The first lens unit is a first single lens with negative optical power, and the first single lens is a meniscus lens.

3. The electric focus lens according to claim 2, characterized in that: The second lens unit is a second single lens with positive refractive power.

4. The electric focus lens according to claim 2, characterized in that: The second lens unit is a combination lens group of a parallel flat glass with no optical power and a second single lens with positive optical power corresponding to the parallel flat glass.

5. The electric focus lens according to claim 2, characterized in that: The second lens unit is a turning prism and a combined lens group of a second single lens with positive optical power corresponding to the turning prism.

6. The electric focus lens according to claim 5, characterized in that: The turning prism includes a first prism, a second prism and a third prism that are glued together. The upper and lower parts of the bonding surfaces of the first prism and the second prism are respectively provided with a first reflection area and an incident area. The bonding surface of the third prism and the second prism is provided with a second reflection area, so that the light emitted from the first lens unit is incident on the incident area, and after being reflected by the second reflection area and the first reflection area in sequence, it is emitted from the second prism, and the direction in which the light is incident on the turning prism and the direction in which the light is emitted from the turning prism form a preset angle.

7. The electric focus lens according to any one of claims 2 to 6, characterized in that: The third lens unit is a first cemented lens with positive refractive power, or the third lens unit includes a first cemented lens and a second cemented lens with positive refractive power that are arranged opposite to each other.

8. The electric focus lens according to claim 7, characterized in that: The object distance range that the electric focus lens can focus on is 20mm to 150mm, and the electric focus lens satisfies the following conditional formula: -1.3 <fG1 / f<-0.9 (1) 1.6 <fG2 / f<2.6 (2) Wherein, fG1 is the focal length of the first lens unit, fG2 is the focal length of the second lens unit, and f is the total focal length of the electric focus lens when the object distance is 150 mm.

9. The electric focus lens according to claim 8, characterized in that: The electric focus lens also satisfies the following conditional formula: 1.76 <nG1<2.06 (3) Wherein, nG1 is the refractive index of the first monomer lens.

10. The electric focus lens according to any one of claims 1 to 6, characterized in that: The electric focus lens also includes a lens barrel, the first lens unit, the second lens unit, the liquid lens module and the third lens unit are all located in the lens barrel, and the outer diameter of the lens barrel is less than or equal to 8.5 mm.

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