A low-distortion high-resolution liquid automatic zoom imaging system

Abstract

The application discloses a low-distortion high-resolution liquid automatic zoom imaging system, which is composed of a front lens group with positive focal length, a liquid lens, a diaphragm, a rear lens with positive focal length, a filter and a chip cover glass arranged in sequence from an object plane to an image plane. f Satisfies: 16mm≤f f ≤25mm, the focal length f b of the rear lens group satisfies: 12mm≤f b ≤17.5mm, the focal length f of the imaging system satisfies: 15mm≤f≤17mm, the working F number F# of the imaging system satisfies: 4≤F#≤5, the total optical length TTL of the imaging system satisfies: 25mm≤TTL≤32mm, the relationship between the total optical length TTL and the focal length f satisfies: 1.5≤|TTL / f|≤2.2, and the low-distortion high-resolution liquid automatic zoom imaging system has the advantages that each lens is designed and the focal length is reasonably set, specific optical parameters are selected, the zoom function of the liquid lens is combined, the distortion is greatly reduced, and high-resolution imaging of a far field, a middle field and a near field is realized.

Description

Technical Field

[0001] This invention relates to an automatic zoom imaging system, and more particularly to a low-distortion, high-resolution liquid automatic zoom imaging system. Background Technology

[0002] The current trend in image sensors is to shrink pixel size and increase pixel count. In this context, an automatic zoom system is essential to maximize the use of the image sensor. Liquid lenses exhibit different refractive powers under different driving voltages without altering their mechanical structure. They offer advantages such as low power consumption, high shock resistance, and fast zoom, making them widely used in the field of automatic zoom. Liquid lenses employing the electrowetting principle have a main structure of five layers. The outermost two layers are glass windows, one is a conductive phase, and the other two are adjacent and made of liquid. The radius of curvature at their interface changes with the driving voltage, thus achieving zoom. Liquid lenses can be assembled into imaging modules or combined as accessories with independent fixed-focus imaging lenses to maximize their utilization.

[0003] However, some existing automatic zoom imaging systems that include liquid lenses suffer from problems such as an imbalance in imaging quality between the near and far fields and low overall image quality.

[0004] Patent CN112505891A adopts an eight-element structure design and combines a liquid lens to achieve rapid identification and detection over a wide range, but its imaging quality is poor and the distortion is large.

[0005] Patent CN113296242A adopts a seven-element structure design, which reduces the number of lenses and the size of the lens by using liquid lenses. It achieves high-quality imaging over a large field of view by using large-aperture aspherical lenses. However, it uses multiple aspherical lenses, which increases the cost and causes greater distortion. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a low-distortion, high-resolution liquid autofocus imaging system with good imaging quality stability in the far field, mid field and near field, low distortion and high resolution.

[0007] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a low-distortion, high-resolution liquid auto-zoom imaging system, comprising a front lens group with positive optical power, a liquid lens, an aperture stop, a rear lens with positive optical power, a filter, and a chip cover glass group arranged sequentially from the object plane to the image plane. The aperture stop is close to the liquid lens, and the focal length f of the front lens group is... f Satisfies: 16mm≤f f ≤25mm, the focal length f of the rear lens group b Satisfy: 12mm≤f bThe focal length f of the imaging system satisfies: 15mm≤f≤17mm, the working F-number F# of the imaging system satisfies: 4≤F#≤5, the total optical length TTL of the imaging system satisfies: 25mm≤TTL≤32mm, and the relationship between the total optical length TTL and the focal length f is 1.5≤|TTL / f|≤2.2.

[0008] Preferably, the front lens group consists of a first lens L1, a second lens L2, and a third lens L3 arranged in sequence. The first lens L1 has a convex object side and positive optical power. The second lens L2 has a convex object side and a concave image side and positive optical power. The third lens L3 has a convex object side and a concave image side and negative optical power.

[0009] In one preferred embodiment, the rear lens group can be composed of three lenses arranged in sequence: a fourth lens L4, a fifth lens L5, and a sixth lens L6. The fourth lens L4 has a concave object side and a convex image side, and has a negative optical power. The fifth lens L5 has a concave object side and a convex image side, and has a positive optical power. The sixth lens L6 has a convex object side and a concave image side, and has a positive optical power.

[0010] In a second preferred embodiment, the rear lens group can also be composed of four lenses arranged in sequence: a fourth lens L4, a fifth lens L5, a seventh lens L7, and a sixth lens L6. The fourth lens L4 has a concave object side and a concave image side, and has a negative optical power. The fifth lens L5 has a convex object side and a convex image side, and has a positive optical power. The sixth lens L6 has a convex object side and a concave image side, and has a positive optical power. The seventh lens L7 has a convex object side and a convex image side, and has a positive optical power.

[0011] In the third preferred embodiment, the rear lens group consists of three lenses arranged in sequence: a fourth lens L4, a fifth lens L5, and a sixth lens L6. The fourth lens L4 is a biconcave lens with negative optical power, the fifth lens L5 is a biconvex lens with positive optical power, and the sixth lens L6 has a convex surface on the object side, a concave surface on the image side, and positive optical power.

[0012] The sixth lens L6 can be an even-order aspherical lens.

[0013] Preferably, the diopter of the liquid lens is controlled by a driving voltage, and the dynamic range of diopter variation is -5 to +20 dpt.

[0014] Compared with the prior art, the advantages of the present invention are that the invention adopts a six- or seven-element optical structure, designs and reasonably sets the optical power of each lens, selects specific optical parameters, and combines the zoom function of the liquid lens to achieve high-quality imaging over a wide working object distance range, greatly reducing distortion and achieving high-resolution imaging in the far field, mid field and near field. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the optical system structure of Embodiment 1 of the present invention;

[0016] Figure 2 This is a transfer function curve of Embodiment 1 of the present invention at an object distance of 400 mm;

[0017] Figure 3 This is a transfer function curve of Embodiment 1 of the present invention at an object distance of 100 mm;

[0018] Figure 4 This is a transfer function curve of embodiment 1 of the present invention at infinity object distance;

[0019] Figure 5 This is the field curvature diagram of Embodiment 1 of the present invention at an object distance of 400 mm;

[0020] Figure 6 This is a distortion diagram of Embodiment 1 of the present invention at an object distance of 400 mm;

[0021] Figure 7 This is a schematic diagram of the optical system structure of Embodiment 2 of the present invention;

[0022] Figure 8 This is a transfer function curve of Embodiment 2 of the present invention at an object distance of 400 mm;

[0023] Figure 9 This is a transfer function curve of Embodiment 2 of the present invention at an object distance of 100 mm;

[0024] Figure 10 This is a transfer function curve of the object distance at infinity in Embodiment 2 of the present invention;

[0025] Figure 11 This is the field curvature diagram of Embodiment 2 of the present invention at an object distance of 400 mm;

[0026] Figure 12 This is a distortion diagram of Embodiment 2 of the present invention at an object distance of 400 mm;

[0027] Figure 13 This is a schematic diagram of the optical system structure of Embodiment 3 of the present invention;

[0028] Figure 14This is a transfer function curve of Embodiment 3 of the present invention at an object distance of 400 mm;

[0029] Figure 15 This is a transfer function curve of Embodiment 3 of the present invention at an object distance of 100 mm;

[0030] Figure 16 This is a transfer function curve of embodiment 3 of the present invention at infinity object distance;

[0031] Figure 17 This is the field curvature diagram of Embodiment 3 of the present invention at an object distance of 400 mm;

[0032] Figure 18 This is a distortion diagram of Embodiment 3 of the present invention at an object distance of 400 mm. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The drawings are for reference and illustration only and do not constitute a limitation on the scope of protection of the present invention.

[0034] Example 1:

[0035] The structure of this embodiment 1 is as follows: Figure 1 As shown, from the object plane to the image plane, the components are, in order: front lens group 1 with positive optical power, liquid lens 2, aperture 6, rear lens group 3 with positive optical power, filter 4, and chip cover glass 5. The aperture 6 is placed between the front lens group 1 and the rear lens group 3, close to the rear side of the liquid lens 2.

[0036] The front lens group 1 is a three-element structure, consisting of a first lens L1, a second lens L2, and a third lens L3 arranged sequentially. The first lens L1 is a biconvex lens with positive optical power. The second lens L2 is a positive lens with a convex object-side surface and a concave image-side surface, and also has positive optical power. The third lens L3 is a negative lens with a convex object-side surface and a concave image-side surface, and also has negative optical power.

[0037] The rear lens group is a three-element structure, consisting of a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged sequentially. The fourth lens L4 is a negative lens with a concave object-side surface and a convex image-side surface, possessing negative optical power. The fifth lens L5 is a positive lens with a concave object-side surface and a convex image-side surface, possessing positive optical power. The sixth lens L6 is a positive lens with a convex object-side surface and a concave image-side surface, possessing positive optical power.

[0038] The focal length f of the front lens group f =19.02mm, the focal length f of the rear lens group b =14.91mm.

[0039] The sixth lens, L6, is an even-order aspherical lens, and its surface shape satisfies the following equation:

[0040]

[0041] y represents the radial coordinate value of the lens perpendicular to the optical axis, and Z is the sag of the aspherical lens at a height of y along the optical axis from the vertex of the aspherical surface. c = 1 / R, where R represents the radius of curvature of the center of the corresponding aspherical lens surface, k represents the conic coefficient, and parameters A, B, C, D, E, F, ... are higher-order aspherical coefficients.

[0042] The physical optical parameters of this embodiment 1 are as follows:

[0043]

[0044]

[0045] In this embodiment, both surfaces of the sixth lens L6 are even-order aspherical surfaces, and their higher-order terms are (K: conic coefficient; B: 4th-order term; C: 6th-order term; D: 8th-order term; E: 10th-order term):

[0046] k B C D E L6 First Page -1.75 -6.00E-5 3.76E-6 -1.42E-7 3.88E-9 L6 Second Side 35.28 -9.71E-5 -2.33E-6 2.05E-7 -3.39E-9

[0047] Embodiment 1 of this invention employs a six-element structure to achieve low-distortion, high-resolution zoom imaging with a maximum field of view of approximately 30°. From Figure 2 As can be seen, in Example 1, the object imaging MTF at an object distance of 180 lp / mm and 400 mm is greater than 0.3. From... Figure 6 As can be seen from the data, the distortion of Example 1 at an object distance of 400 mm is less than 1%.

[0048] Example 2:

[0049] The structure of this embodiment 2 is as follows: Figure 7 As shown, from the object plane to the image plane, the components are, in order: front lens group 1 with positive optical power, liquid lens 2, aperture 6, rear lens group 3 with positive optical power, filter 4, and chip cover glass 5. The aperture 6 is placed between the front lens group 1 and the rear lens group 3, close to the rear side of the liquid lens 2.

[0050] The front lens group has a three-element structure, consisting of a first lens L1, a second lens L2, and a third lens L3 arranged sequentially. The first lens L1 is a biconvex lens with positive optical power. The second lens L2 is a positive lens with a convex object-side surface and a concave image-side surface, and also has positive optical power. The third lens L3 is a negative lens with a convex object-side surface and a concave image-side surface, and also has negative optical power.

[0051] The rear lens group is a four-element structure, consisting of the fourth lens L4, the fifth lens L5, the seventh lens L7, and the sixth lens L6 arranged sequentially from left to right along the optical axis and symmetrical about the optical axis. The fourth lens L4 is a biconcave lens with negative optical power. The fifth lens L5 is a biconvex lens with positive optical power. The seventh lens L7 is a biconvex lens with positive optical power. The sixth lens L6 is a positive lens with a convex object-side surface and a concave image-side surface, and also has positive optical power.

[0052] The focal length f of the front lens group f =24.74mm, the focal length f of the rear lens group b =12.24mm.

[0053] The physical optical parameters of this embodiment 2 are as follows:

[0054]

[0055]

[0056] Embodiment 2 of this invention employs a seven-element structure to achieve low-distortion, high-resolution zoom imaging with a maximum field of view of approximately 30°. From... Figure 8 As can be seen, in Example 2, the object imaging MTF at an object distance of 180 lp / mm and 400 mm is greater than 0.3. From... Figure 12 As can be seen from the data, the distortion in Example 2 at an object distance of 400 mm is about 1%.

[0057] Example 3:

[0058] The structure of embodiment 3 is as follows: Figure 13 As shown, from the object plane to the image plane, the components are, in order: front lens group 1 with positive optical power, liquid lens 2, aperture 6, rear lens group 3 with positive optical power, filter 4, and chip cover glass 5. The aperture 6 is placed between the front lens group 1 and the rear lens group 3, close to the rear side of the liquid lens 2.

[0059] The front lens group has a three-element structure, consisting of a first lens L1, a second lens L2, and a third lens L3 arranged sequentially. The first lens L1 is a positive lens with a convex object-side surface and a concave image-side surface, and has positive optical power. The second lens L2 is a positive lens with a convex object-side surface and a concave image-side surface, and also has positive optical power. The third lens L3 is a negative lens with a convex object-side surface and a concave image-side surface, and has negative optical power.

[0060] The rear lens group is a three-element structure, consisting of a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged sequentially. The fourth lens L4 is a biconcave lens with negative optical power. The fifth lens L5 is a biconvex lens with positive optical power. The sixth lens L6 is a positive lens with a convex object-side surface and a concave image-side surface, and also has positive optical power.

[0061] The focal length f of the front lens group f =16.16mm, the focal length f of the rear lens group b =17.18mm.

[0062] The physical optical parameters of this embodiment 3 are as follows:

[0063]

[0064]

[0065] Embodiment 3 of this invention employs a six-element structure to achieve low-distortion, high-resolution zoom imaging with a maximum field of view of approximately 27°. Figure 14 As can be seen, in Example 3, the object imaging MTF at an object distance of 180 lp / mm and 400 mm is around 0.4. From... Figure 18 As can be seen, the distortion in Example 3 is less than 0.2% at an object distance of 400mm.

[0066] The main optical parameters of the above embodiments are shown in the table below:

[0067] Serial Number project Example 1 Example 2 Example 3 1 System focal length f / mm 15.96 15.97 16.12 2 entrance pupil diameter / mm 3.54 3.63 3.66 3 TTL / mm 31.01 30.99 26.18 4 FOV / ° (Field of View) 30° 30° 27° 5 F# 4.5 4.4 4.4 6 400mm object distance liquid lens diopter / dpt 0 0 0 7 100mm object distance liquid lens diopter / dpt 15.4 17.4 16.4 8 Infinity object distance liquid lens diopter / dpt -3.8 -4.3 -4.3 9 Maximum distortion at 400mm object distance / % 0.71 1.04 0.13

[0068] In the above embodiment, the front lens group 1 has a three-piece structure with positive optical power, and collects the light beam into the effective aperture of the liquid lens 2 with a diameter of 2.5 mm.

[0069] The front lens group 1 and the rear lens group 3 are asymmetrical structures with a double Gaussian structure, which can reduce distortion and lateral chromatic aberration.

[0070] The second surface of the first lens L1 and the second surface of the second lens L2 have larger radii of curvature, which can reduce distortion.

[0071] The second surface of the third lens L3 is concave, and its optical power is positive, which can reduce field curvature and distortion.

[0072] The aperture 6 is placed between the front lens group 1 and the rear lens group 3, close to the rear side of the liquid lens 2. This can reduce distortion and facilitate lens assembly and engineering production.

[0073] The first surface of the fourth lens L4 is concave and has a negative optical power, while the second surface has a large radius of curvature, which can reduce distortion and astigmatism.

[0074] In the following Example 1, the first and second surfaces of the sixth lens L6 are both designed as even-order aspherical surfaces, which can reduce spherical aberration, coma, and astigmatism.

[0075] In Example 2, the rear lens group 3 has a four-element structure, which can correct spherical aberration, coma and astigmatism, and improve imaging quality.

[0076] In Example 2, the seventh lens L7 is a biconvex lens with positive optical power, which allows light to transition more naturally to the next surface and reduces the sensitivity of the imaging system.

[0077] Compared with Example 1, Examples 2 and 3 show that the distance between the first surface of the fourth lens L4 and the aperture 6 is reduced, which can reduce astigmatism.

[0078] Compared with Example 1, Examples 2 and 3 show a reduced distance between the rear lens group 3 and the liquid lens 2, which can reduce vignetting and wavefront error.

[0079] Compared with Examples 1 and 2, Example 3 has a smaller field of view, which can reduce distortion, reducing the maximum distortion of imaging at a 400mm object distance from about 1% to about 0.1%.

[0080] Compared with Examples 1 and 2, Example 3 has a three-piece structure for the rear lens group 3, all of which are spherical lenses, thus reducing costs.

[0081] The above-described embodiments are merely individual examples of the present invention and do not limit the scope of protection of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A low-distortion, high-resolution liquid auto-zoom imaging system, comprising a front lens group with positive optical power, a liquid lens, an aperture stop, a rear lens group with positive optical power, a filter, and a chip cover glass arranged sequentially from the object plane to the image plane, wherein the aperture stop is located close to the liquid lens, characterized in that... The focal length f of the front lens group f Satisfies: 16mm≤f f ≤25mm, the focal length f of the rear lens group b Satisfy: 12mm≤f b The focal length f of the imaging system satisfies: 15mm≤f≤17mm, the working F-number F# of the imaging system satisfies: 4≤F#≤5, the total optical length TTL of the imaging system satisfies: 25mm≤TTL≤32mm, and the relationship between the total optical length TTL and the focal length f is 1.5≤|TTL / f|≤2.

2.

2. The low-distortion, high-resolution liquid auto-zoom imaging system as described in claim 1, characterized in that... The front lens group consists of a first lens L1, a second lens L2, and a third lens L3 arranged in sequence. The first lens L1 has a convex object side and a positive optical power. The second lens L2 has a convex object side and a concave image side and a positive optical power. The third lens L3 has a convex object side and a concave image side and a negative optical power.

3. The low-distortion, high-resolution liquid auto-zoom imaging system as described in claim 2, characterized in that... The rear lens group consists of a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged in sequence. The fourth lens L4 has a concave object side and a convex image side, and has a negative optical power. The fifth lens L5 has a concave object side and a convex image side, and has a positive optical power. The sixth lens L6 has a convex object side and a concave image side, and has a positive optical power.

4. The low-distortion, high-resolution liquid auto-zoom imaging system as described in claim 2, characterized in that... The rear lens group consists of a fourth lens L4, a fifth lens L5, a seventh lens L7, and a sixth lens L6 arranged in sequence. The fourth lens L4 has a concave object side and a concave image side, and has a negative optical power. The fifth lens L5 has a convex object side and a convex image side, and has a positive optical power. The sixth lens L6 has a convex object side and a concave image side, and has a positive optical power. The seventh lens L7 has a convex object side and a convex image side, and has a positive optical power.

5. The low-distortion, high-resolution liquid auto-zoom imaging system as described in claim 2, characterized in that... The rear lens group consists of a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged in sequence. The fourth lens L4 is a biconcave lens with negative optical power, the fifth lens L5 is a biconvex lens with positive optical power, and the sixth lens L6 has a convex surface on the object side and a concave surface on the image side, with positive optical power.

6. A low-distortion, high-resolution liquid autofocus imaging system as described in claim 3, 4, or 5, characterized in that... The sixth lens L6 is an even-order aspherical lens.

7. The low-distortion, high-resolution liquid autofocus imaging system as described in claim 1, characterized in that... The diopter of the liquid lens is controlled by the driving voltage, and the dynamic range of diopter variation is -5 to +20 dpt.

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