Electronic focusing lens

Abstract

The present application relates to the technical field of optical lenses, and specifically relates to an electronic focusing lens. The electronic focusing lens comprises a first lens unit, a second lens unit, a liquid lens module, and a third lens unit which are sequentially disposed in an optical path direction; the first lens unit has negative focal power, and the second lens unit and the third lens unit have positive focal power; the liquid lens module comprises a first window pane and a second window pane which are disposed in parallel, a sealed chamber is formed between the first window pane and the second window pane, a separation film is disposed in the sealed chamber, a first liquid is encapsulated between the separation film and the first window pane, a second liquid is encapsulated between the separation film and the second window pane, and a voltage is applied between the first window pane and the second window pane to change the radius of curvature of the separation film. By means of the above means, the lens has a simple structure, and can perform electronic focusing in real time at different object distances, thereby increasing an observable object distance range, and improving the resolution.

Description

Electric focusing lens TECHNICAL FIELD

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

[0002] In the field of industrial slits, pipeline monitoring and detection, and medical minimally invasive surgery observation, due to the large size of various monitoring lenses and industrial lenses commonly used in the market, they cannot be inserted into small spaces, so electronic endoscopes with small size are mainly used to freely enter and exit various small holes. However, due to the size limitation, various types of motors cannot be installed on the endoscope, and the electric focusing function cannot be realized by driving the lens group to move. Therefore, after the endoscope is installed, the focusing object distance is fixed and cannot be changed, and in a small space, different object distances cannot be observed at will, which limits the observation range.

[0003] In order to avoid the inconvenience of observation caused by the above problems, the traditional endoscopes on the market often use a small aperture system with an aperture greater than 5.0 to improve the depth of field range of the lens. In this way, even if the lens is not focused, a larger object distance range can be observed at the same time. However, this way of improving the depth of field is also limited, and the clear object distance range is only tens of millimeters. Moreover, the small aperture system introduces new problems. On the one hand, the light amount is too small, and strong light compensation is needed. On the other hand, due to the influence of diffraction effect, the resolution of the lens is limited, which is not conducive to observing clear images.

[0004] SUMMARY

[0005] The technical problem to be solved by the embodiments of the present application is to provide an electric focusing lens which can realize real-time electric focusing for different object distances, improve the observation object distance range, and improve the resolution.

[0006] The present application discloses an electric focusing lens, which comprises a first lens unit, a second lens unit, a liquid lens module and a third lens unit arranged in sequence along the optical path direction. The first lens unit has negative focal power, the second lens unit and the third lens unit have positive focal power, the liquid lens module comprises a first window sheet and a second window sheet 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, and a second liquid is encapsulated between the diaphragm and the second window sheet. A voltage is applied between the first window sheet and the second window sheet to change the radius of curvature of the diaphragm.

[0007] Optionally, the first lens unit is a first single lens with negative focal power, and the first single lens is a meniscus lens.

[0008] Optionally, the second lens unit is a second single lens with positive focal power.

[0009] Optionally, the second lens unit is a parallel flat glass with no focal power and a second single lens with positive focal power corresponding to the parallel flat glass.

[0010] Optionally, the second lens unit is a combination lens group of a turning prism and a second single lens with positive focal power corresponding to the turning prism.

[0011] Optionally, the turning prism comprises a first prism, a second prism and a third prism, the first prism and the second prism are respectively provided with an incident area and a first reflection area on the upper and lower parts of the abutting surface, and the third prism is provided with a second reflection area on the abutting surface of the second prism, so that the light emitted by the first lens unit is incident on the incident area, is sequentially reflected by the second reflection area and the first reflection area, and 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.

[0012] Optionally, the third lens unit is a first cemented lens with positive focal power, or the third lens unit comprises a first cemented lens and a second cemented lens with positive focal power arranged oppositely.

[0013] Optionally, the object distance range of the electric focusing lens is 20mm to 150mm, and the electric focusing lens satisfies the following conditional formula:

[0014] -1.3 < fG1 / f < -0.9 (1)

[0015] 1.6 < fG2 / f < 2.6 (2)

[0016] 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 focusing lens when the object distance is 150mm.

[0017] Optionally, the electric focusing lens also satisfies the following conditional formula:

[0018] 1.76 < nG1 < 2.06 (3)

[0019] Wherein, nG1 is the refractive index of the first single lens.

[0020] Optionally, the electric focusing lens further comprises a lens barrel, the first lens unit, the second lens unit, the liquid lens module and the third lens unit are located in the lens barrel, and the outer diameter of the lens barrel is less than or equal to 8.5mm.

[0021] Compared with existing technologies, the beneficial effects of the electrically adjustable focusing lens provided in this application are as follows: Real-time electric focusing is achieved by utilizing a liquid lens module; the outer surface of the structure has no protrusions such as motors or gears, and requires no moving parts, making it simple and compact, thus achieving miniaturization of the electrically adjustable focusing lens. Simultaneously, the use of a negative optical power first lens unit forms a reverse telephoto optical structure, resulting in a large field of view. Since the electrically adjustable focusing lens can focus at different object distances at any time, a large depth of field is not necessary in the optical path design, allowing the lens aperture to reach F4.0 or even larger, helping to reduce the influence of diffraction effects. Compared to lenses with fixed focusing object distances, it possesses higher resolution. Attached Figure Description

[0022] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0023] Figure 1 is one of the structural schematic diagrams of the electrically adjustable focusing lens provided in an embodiment of this application;

[0024] Figure 2 is a second schematic diagram of the structure of the electrically adjustable focusing lens provided in the embodiment of this application;

[0025] Figure 3 is a third structural schematic diagram of the electrically adjustable focusing lens provided in the embodiment of this application;

[0026] Figure 4 is a fourth structural schematic diagram of the electrically adjustable focusing lens provided in the embodiment of this application;

[0027] Figure 5 is the fifth structural schematic diagram of the electrically adjustable focusing lens provided in the embodiments of this application.

[0028] Figure 6 is a graph showing the spherical aberration, astigmatism, and optical distortion curves when the object distance is 20 mm in the structure shown in Figure 1.

[0029] Figure 7 is a graph showing the spherical aberration, astigmatism, and optical distortion curves when the object distance is 150 mm in the structure shown in Figure 1.

[0030] Figure 8 is a graph showing the spherical aberration, astigmatism, and optical distortion curves when the first single lens in the structure shown in Figure 2 is a spherical lens and the object distance is 20 mm.

[0031] Figure 9 is a graph of spherical aberration, astigmatism, and optical distortion when the first single lens in the structure shown in Figure 2 is a spherical lens and the object distance is 150 mm.

[0032] Figure 10 is a graph showing the spherical aberration, astigmatism, and optical distortion curves when the first single lens in the structure shown in Figure 2 is an aspherical lens and the object distance is 20 mm.

[0033] Figure 11 is a graph of spherical aberration, astigmatism, and optical distortion when the first single lens in the structure shown in Figure 2 is an aspherical lens and the object distance is 150 mm.

[0034] Fig. 12 is a curve diagram of spherical aberration, astigmatism and optical distortion when the object distance is 20mm in the structure shown in Fig. 4;

[0035] Fig. 13 is a curve diagram of spherical aberration, astigmatism and optical distortion when the object distance is 150mm in the structure shown in Fig. 4.

[0036] The various reference signs in the drawings represent the following:

[0037] 100, electric focusing lens; 110, first lens unit; 112, first single lens; 120, second lens unit; 122, second single lens; 124, parallel flat glass; 126, turning prism; 1262, first prism; 1264, second prism; 1266, third prism; 130, liquid lens module; 132, first window sheet; 134, second window sheet; 136, diaphragm; 140, third lens unit; 142, first cemented lens; 144, second cemented lens. DETAILED DESCRIPTION

[0038] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The preferred embodiments of the present application will be described in detail with reference to the drawings.

[0039] As shown in Figs. 1-5, the electric focusing lens 100 provided by the embodiments of the present application comprises 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 light path direction, wherein the first lens unit 110 has negative focal power, the second lens unit 120 and the third lens unit 140 have positive focal power, the liquid lens module 130 comprises a first window sheet 132 and a second window sheet 134 arranged in parallel, a sealed chamber is formed between the first window sheet 132 and the second window sheet 134, a diaphragm 136 is arranged in the sealed chamber, a first liquid is encapsulated between the diaphragm 136 and the first window sheet 132, a second liquid is encapsulated between the diaphragm 136 and the second window sheet 134, and a voltage is applied between the first window sheet 132 and the second window sheet 134 to change the radius of curvature of the diaphragm 136.

[0040] Specifically, the first lens unit 110 is arranged to have a negative focal power, so that the motorized focusing lens 100 forms a retrofocus structure. The large-angle incident light rays outside the field of view are deflected in angle after passing through the first lens unit 110, and the included angle with the optical axis is reduced, so that the aberration correction of the rear light path is facilitated, and the motorized focusing lens 100 has a larger field of view. The second lens unit 120 has a positive focal power, and mainly corrects the spherical aberration of the motorized focusing lens 100. The first liquid and the second liquid are different in material and are separated by the diaphragm 136. In order to ensure the normal transmission of light, the diaphragm 136 needs to be transparent. When the voltage applied between the first window sheet 132 and the second window sheet 134 changes, the curvature of the diaphragm 136 changes by using the electrowetting effect. The curvature and the applied voltage have a clear corresponding relationship, so the focusing distance of the lens and the voltage also have a one-to-one corresponding relationship. The focal power of the liquid lens module 130 can be adjusted by the voltage. The third lens unit 140 has a positive focal power, and is used for correcting the chromatic aberration of the motorized focusing lens.

[0041] The motorized focusing lens 100 provided by the embodiment of the present application realizes the real-time motorized focusing of the motorized focusing lens 100 by using the liquid lens module 130. The structure has no protrusions such as motors and gears on the outer surface, and does not need any movable parts, so it is simple, small and compact, and achieves the miniaturization of the motorized focusing lens 100. At the same time, the first lens unit 110 with a negative focal power forms a retrofocus optical structure, and has a larger field of view. Since the motorized focusing lens 100 can focus on different object distances at any time, it is not necessary to consider the large depth of field in the light path design. The lens aperture can be F4.0 or even larger, which helps to reduce the influence of diffraction effect, and has higher resolution compared with the lens with an unchangeable focusing object distance. By using the above form, the observation object distance range of the lens can be improved, and the resolution can be improved.

[0042] As shown in FIGS. 1-5, the first lens unit 110 is a negative focal power first single lens 112, and the first single lens 112 is a meniscus lens.

[0043] Specifically, the first lens unit 110 adopts the first single lens 112 with a negative focal power, which is beneficial to increase the field of view while ensuring the required imaging effect. In actual application, a meniscus lens can be used, which can be in the form of a spherical lens or an aspherical lens, and the embodiment of the present application does not make specific limitation on this.

[0044] When the first single lens 112 adopts an aspherical lens, the optical distortion of the system can be reduced, and more image information can be retained at the edge of the field of view, which is very valuable for medical observation. The surface shape of the aspherical surface satisfies the following formula:

[0045] Wherein, c = 1 / R, R represents the curvature radius of the reference sphere of the aspheric surface, r represents the radial coordinate of the aspheric surface lens from the optical axis, z represents the corresponding sag of the aspheric surface lens at the radial coordinate r, k represents the conic coefficient, and A, B, C, D, E and F represent the aspheric surface coefficients of different orders respectively.

[0046] As shown in Fig. 1, the second lens unit 120 is a second single lens 122 with positive focal power.

[0047] Specifically, the second single lens 122 can be a plano-convex lens or a double-convex lens to correct the spherical aberration of the motorized focusing lens 100.

[0048] The motorized focusing lens 100 is constructed by using the scheme shown in Fig. 1, and the lens data used is shown in the following table:

[0049] It should be noted that the 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, the parameters of D(6), D(7) and R(7) change as shown in the following table when the object distance is 20 mm and 150 mm respectively:

[0050] Wherein, when the embodiment shown in Fig. 1 is used, 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%.

[0051] As shown in Figs. 2 and 4, the second lens unit 120 is a parallel flat glass 124 with no focal power, and a combination lens group of the second single lens 122 with positive focal power corresponding to the parallel flat glass 124.

[0052] Specifically, when the second single lens 122 is a double-convex lens, there can be a certain distance between the second single lens 122 and the parallel flat glass 124 (see Fig. 2). When the second single lens 122 is a plano-convex lens, the parallel flat glass 124 and the second single lens 122 can be directly glued together (see Fig. 4), at this time, there is no air gap between the parallel flat glass 124 and the second single lens 122, and one spacer ring can be omitted, and the assembly steps are more simple.

[0053] The motorized focusing lens 100 is constructed by using the scheme shown in Fig. 2, and the lens data used is shown in the following table when the first single lens 112 is a spherical lens:

[0054] It should be noted that the surface number 1 to the surface number 14 are the numbers of the optical surfaces arranged in order from the object side to the image side. In addition, the parameter changes of D(8), D(9) and R(9) when the object distance is 20mm and 150mm respectively are shown in the following table:

[0055] In which, the corresponding optical indexes (when the object distance is 150mm) are as follows: focal length f: 2.92mm; aperture Fno: F4.1; half field angle ω: 40° optical distortion: -18.5%.

[0056] When the electric focusing lens 100 is composed of the scheme shown in Fig. 2 and the first single lens 112 is a non-spherical lens, the lens data used are shown in the following table:

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

[0058] In which, the non-spherical lens uses the parameters in the following table:

[0059] In the above table, the surface number 1 and the surface number 2 are the numbers of the two optical surfaces of the first single lens 112 arranged in order from the object side to the image side.

[0060] At this time, the corresponding optical indexes (when the object distance is 150mm) are as follows: focal length f: 2.66mm; aperture Fno: F4.1; half field angle ω: 40° optical distortion: -10.0%.

[0061] In the embodiments of Fig. 2 and Fig. 4, the parallel flat glass 124 has no optical power and does not participate in the correction of aberration in the system. In actual application, it can be transformed into a turning prism 126 with the same optical path as the parallel flat glass 124 by the method of prism expansion.

[0062] As shown in Fig. 3 and Fig. 5, in the alternative embodiments of the present application, the second lens unit 120 is a turning prism 126, and a combination of the second single lens 122 with positive optical power corresponding to the turning prism 126.

[0063] Specifically, by cooperating the turning prism 126 with the second single lens 122, the optical axis direction of the optical path is changed, so that the motorized focusing lens 100 can have different angle of view angles. In this way, the change of the lens angle of view is realized, and the demand of different observation angles is met. When the lens is in a small space, only rotating around the optical axis can observe the view in different directions.

[0064] As shown in FIG. 3, the turning prism 126 includes a first prism 1262, a second prism 1264 and a third prism 1266 which are glued together. The upper and lower parts of the bonding surface of the first prism 1262 and the second prism 1264 are respectively provided with a first reflection area and an incident area. The bonding surface of the third prism 1266 and the second prism 1264 is provided with a second reflection area. The light emitted by the first lens unit 110 is incident to the incident area of the first prism 1262, and then is reflected by the second reflection area and the first reflection area in turn, and is emitted from the second prism 1264 to the rear optical path. The direction of the light incident to the turning prism 126 and the direction of the light emitted from the turning prism 126 form a preset angle.

[0065] Specifically, the incident area can not be coated with any functional film. After the light emitted by the first lens unit 110 is incident to the incident area, the light can directly pass through the first prism 1262 and the second prism 1264 to the second reflection area. Alternatively, an anti-reflection film can be coated on the incident area to improve the utilization rate of the light. After the light is incident to the second reflection area, the light is reflected to the first reflection area. In this case, the bonding surface of the third prism 1266 and the second prism 1264 is entirely provided with a reflection film to improve the utilization rate of the light when reflected. After the light is reflected to the first reflection area, the light is finally emitted from the second prism 1264. In this way, the direction of the light incident to the turning prism 126 and the direction of the light emitted from the turning prism 126 form a preset angle, so that the optical axis direction of the optical path is changed, and the lens has different angle of view angles. For example, the first lens unit 110 can be set to have a certain angle of view, such as 30°.

[0066] As shown in FIGS. 1-5, the third lens unit 140 is a first glued lens 142 with positive focal power, or the third lens unit 140 includes a first glued lens 142 and a second glued lens 144 with positive focal power which are oppositely arranged.

[0067] Specifically, the first cemented lens 142 can be formed by cementing a positive lens and a negative lens, the positive lens being 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 lens and a negative lens, the positive lens being 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 are combined, the aberrations such as spherical aberration and chromatic aberration in the optical system can be reduced, and the imaging quality and definition of the optical system can be improved.

[0068] When the electric focusing lens 100 is formed by using the scheme shown in FIG. 4, the lens data used is shown in the following table:

[0069] It should be noted that the 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 distances are 20 mm and 150 mm respectively, the parameters of D(7), D(8) and R(8) change as shown in the following table:

[0070] At this time, the corresponding optical indexes (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%.

[0071] In an optional embodiment of the present application, the electric focusing lens 100 can focus on the object distance range of 20 mm to 150 mm, and the electric focusing lens 100 satisfies the following conditional expressions:

[0072] -1.3 < fG1 / f < -0.9 (1)

[0073] 1.6 < fG2 / f < 2.6 (2)

[0074] 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 focusing lens 100 when the object distance is 150 mm.

[0075] Specifically, by 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, clear focusing can be achieved in the object distance range of 20mm to 150mm, so as to improve the observation effect. As shown in FIGS. 6 to 13, the spherical aberration, astigmatism and optical distortion of the electric focusing lens 100 in different structural forms are shown. The Spherical Aberration is the spherical aberration, the ordinate represents the height of the light on the stop, the Astigmatic Field Curves is the astigmatic field curve, the ordinate is the image height, and the Distortion is the optical distortion, and the ordinate is also the image height. It can be seen that the various aberrations of the electric focusing lens 100 at different object distances are well corrected, and the electric focusing lens 100 has high-definition imaging capability in a large working object distance range.

[0076] In an optional embodiment of the present application, the electric focusing lens 100 also satisfies the following conditional expression:

[0077] 1.76 < nG1 < 2.06 (3)

[0078] Wherein, nG1 is the refractive index of the first single lens 112.

[0079] By the above form, the large-angle incident light outside the field of view is deflected in angle after passing through the first single lens 112, and the included angle with the optical axis is small, which is convenient for aberration correction of the rear light path, so that the system has a larger field of view. In addition, the height of the light on the first single lens 112 can be compressed, which is beneficial to control the diameter of the lens and ensure the compactness of the overall diameter of the electric focusing lens 100.

[0080] The conditional expression values corresponding to the embodiments of the present application are as follows:

[0081] In an optional embodiment of the present application, the electric focusing lens 100 further comprises a lens barrel, and the first lens unit 110, the second lens unit 120, the liquid lens module 130 and the third lens unit 140 are located in the lens barrel, and the outer diameter of the lens barrel is less than or equal to 8.5mm.

[0082] Specifically, by the above method, in actual application, the overall diameter of the electric focusing lens 100 is small, which can easily enter the small hole and the cavity, and can electrically focus at different object distances, thereby expanding the observation range of the electric focusing lens 100, and being beneficial to application in the endoscope and other miniature lenses.

[0083] It should be understood that the above examples are only used to illustrate the technical solutions of the present application, but not limit them. Those skilled in the art can modify, scale or equivalently replace part of the technical features of the technical solutions described in the above examples; and all the modifications, scaling and replacement should belong to the protection scope of the claims of the present application.

Claims

1. An electrically motorized focusing lens, characterized in that, The electric focusing lens comprises a first lens unit, a second lens unit, a liquid lens module and a third lens unit arranged in sequence along the optical path direction, wherein the first lens unit is negative, the second lens unit and the third lens unit are positive, the liquid lens module comprises a first window sheet and a second window sheet arranged in parallel, a sealed cavity is formed between the first window sheet and the second window sheet, a diaphragm is arranged in the sealed cavity, 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 motorized focus lens of claim 1, wherein, The first lens unit is a first single lens with negative focal length, and the first single lens is a meniscus lens.

3. The motorized focus lens of claim 2, wherein, The second lens unit is a second single lens with positive focal length.

4. The motorized focus lens of claim 2, wherein, The second lens unit is a combination lens group of a parallel flat glass with no focal length and a second single lens with positive focal length corresponding to the parallel flat glass.

5. The motorized focus lens of claim 2, wherein, The second lens unit is a combination lens group of a turning prism and a second single lens with positive focal length corresponding to the turning prism.

6. The motorized focus lens of claim 5, wherein, The turning prism comprises a first prism, a second prism and a third prism which are glued, the upper and lower parts of the bonding surface 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 by the first lens unit is incident to the incident area, is reflected in sequence through the second reflection area and the first reflection area, and is emitted from the second prism, and the direction of the light incident to the turning prism and the direction of the light emitted from the turning prism form a preset included angle.

7. The motorized focus lens of any of claims 2-6, wherein, The third lens unit is a first glued lens with positive focal length, or the third lens unit comprises a first glued lens and a second glued lens with positive focal length arranged oppositely.

8. The motorized focus lens of claim 7, wherein, The focusing range of the electric focusing lens is 20mm to 150mm, and the electric focusing lens satisfies the following conditional expressions: -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 focusing lens when the object distance is 150mm.

9. The motorized focus lens of claim 8, wherein, The electric focusing lens also satisfies the following conditional expression: 1.76 < nG1 < 2.06 (3) Wherein, nG1 is the refractive index of the first single lens.

10. The motorized focus lens of any of claims 1-6, wherein, The electric focusing lens further comprises a lens barrel, the first lens unit, the second lens unit, the liquid lens module and the third lens unit are located in the lens barrel, and the outer diameter of the lens barrel is less than or equal to 8.5mm.

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