Liquid lens focusing micro-microscope

Abstract

The utility model discloses a kind of liquid lens focusing miniature microscope, including first lens, second lens, field stop, third lens, fourth lens, fifth lens, sixth lens and seventh lens sequentially arranged from object plane to image plane along optical axis, wherein, first lens and second lens are glued into glued lens, glued lens has positive focal power;Third lens is liquid lens, including two pieces of window sheet and two kinds of liquid, focusing is realized by changing the curvature of liquid surface;Fourth lens, fifth lens and sixth lens have positive focal power, and seventh lens has negative focal power.The system has 500 μm wide field, and numerical aperture is 0.6, while meeting high-resolution wide-field imaging performance, 100 μm axial detection depth is realized by liquid lens focusing, can be focused to different depth tissue information, and small in size, light in weight, can be used with fiber bundle, with wide application prospect.

Description

Technical Field

[0001] This utility model relates to the field of optical design technology, specifically to a miniature microscope objective with liquid lens focusing. Background Technology

[0002] In the field of minimally invasive surgery, high-resolution microscope objectives are indispensable tools, providing surgeons with clear and detailed images of tissue structures, thus significantly improving the precision and safety of the procedure. However, existing high-resolution microscope objectives have a significant limitation: a small depth of field. This problem is particularly pronounced in surgical procedures within confined spaces. To observe tissue structures at different distances, surgeons need to switch endoscopes with different focal lengths, which not only increases the complexity of the surgery but also increases patient discomfort. This significantly limits the efficiency of the procedure.

[0003] To address this issue, existing technologies employ traditional mechanical zoom to achieve greater depth of field. However, current tilt-shift lenses typically contain a large number of lenses, resulting in complex structures that increase system weight and size, limiting their application in minimally invasive medical surgery and making them difficult to adapt to confined spaces. Furthermore, in minimally invasive surgery, due to the limited system aperture, various types of motors cannot be installed on the endoscope, thus preventing the use of motors to drive the endoscope assembly and achieve mechanical zoom.

[0004] A liquid lens is a lens that achieves zoom by changing the curvature of a liquid surface. It has advantages such as small size and fast focusing speed, meeting the needs of equipment miniaturization. Prior to this practical innovation, the literature "Design and Research of a Liquid Lens Zoom Optical System for Laparoscopy" (Chinese Journal of Lasers 50.21(2023):181-189) reported a laparoscopic optical system using a liquid lens as the core component for zooming. This system utilizes a liquid lens to replace the mechanical zoom structure, achieving zoom functionality, reducing the overall size of the laparoscope, and improving operational convenience. However, the maximum object-space numerical aperture of this system is only 0.1, making it impossible to achieve high-resolution imaging and obtain complex details and precise location information of tissues. Furthermore, the fixed object distance cannot meet the practical needs of observing tissues at different depths. Thirdly, the system's total length is 45mm and its outer diameter is 10mm, making it too large to be inserted into the human body through the endoscope tube for observation. Therefore, this system suffers from many shortcomings, including low imaging resolution, small axial observation range, and excessive size, limiting its practical application in the medical field. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a miniature microscope imaging objective with high imaging resolution, a large field of view, a large axial observation range, fast zoom speed, and a compact structure.

[0006] The technical solution to achieve the purpose of this invention is to provide a liquid lens focusing micro microscope objective, wherein a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially along the optical axis from the object plane to the image plane; the aperture stop of the system is located on the rear surface of the second lens.

[0007] The first lens and the second lens are cemented together to form a cemented lens. The first lens is a spherical mirror with negative optical power, and the second lens is a spherical mirror with positive optical power. According to the incident direction of light, the radii of curvature of the surfaces of each lens are R11, R12 and R13 respectively, which satisfy the conditions that R11 is infinite, 2.6mm≤R12≤2.8mm, and -2.85mm≤R13≤-2.87mm respectively. The refractive index n1 of the material of the first lens (1) is in the range of 1.9≤n1≤2.0, and the Abbe number v1 is in the range of 17≤v1≤18. The refractive index n2 of the material of the second lens (2) is in the range of 1.9≤n2≤2.0, and the Abbe number v2 is in the range of 32≤v2≤33.

[0008] The third lens is a liquid lens;

[0009] The fourth lens has positive optical power, its front surface is aspherical and its rear surface is spherical, and the radii of curvature of the front and rear surfaces are R31 and R32 respectively, satisfying the conditions 4.7mm≤R31≤4.8mm and -5.9mm≤R32≤-5.8mm respectively; the refractive index n3 of its material is in the range of 1.7≤n3≤1.8, and the Abbe number v3 is in the range of 53.7≤v3≤55.4.

[0010] The fifth lens has positive optical power, its front surface is spherical and its rear surface is aspherical, and the radii of curvature of the front and rear surfaces are R41 and R42 respectively, satisfying the conditions 2.2mm≤R31≤2.3mm and 5.3mm≤R32≤5.5mm respectively; the refractive index n4 of its material is in the range of 1.5≤n4≤1.7, and the Abbe number v4 is in the range of 67.7≤v4≤69.4.

[0011] The sixth lens is a spherical mirror with positive optical power, and the radii of curvature of its front and rear surfaces are R51 and R52 respectively, satisfying the conditions 2.0mm≤R51≤2.1mm and 26mm≤R52≤28mm respectively; the refractive index n5 of its material is in the range of 1.7≤n5≤1.8, and the Abbe number v5 is in the range of 54≤v5≤55; the seventh lens (7) is a spherical mirror with negative optical power, and the radii of curvature of its front and rear surfaces are R61 and R62 respectively, satisfying the conditions -15mm≤R61≤-14mm and 1.0mm≤R62≤1.1mm respectively; the refractive index n6 of its material is in the range of 1.6≤n6≤1.8, and the Abbe number v6 is in the range of 40.6≤v6≤42.2.

[0012] The third lens, a liquid lens, as described in this utility model, comprises, in sequence according to the direction of light incidence, a first window, a first liquid, a second liquid, and a second window. The first window is a parallel glass plate, with a refractive index n7 ranging from 1.7 to 1.9 and an Abbe number v7 ranging from 37 to 38. The second window is also a parallel glass plate, with a refractive index n8 ranging from 1.7 to 1.9 and an Abbe number v8 ranging from 37 to 38. The first liquid is a conductive liquid, with a refractive index n9 ranging from 1.3 to 1.4 and an Abbe number v9 ranging from 54 to 59. The second liquid is an insulating non-polar liquid with a refractive index n7 ranging from 1.3 to 1.4 and an Abbe number v9 ranging from 54 to 59. 10 The range of values ​​for is 1.5 ≤ n 10 ≤1.7, Abbe number v 10 The range of values ​​for v is 37 ≤ v 10 ≤45.

[0013] The aspherical surfaces described on the front surface of the fourth lens and the rear surface of the fifth lens of this invention are constructed in a Cartesian rectangular coordinate system with the intersection of the lens surface and the optical axis as the origin. The incident direction of the light is the positive Z-axis, the positive Y-axis is upward, and the positive X-axis is perpendicular to the paper and inward. The equation for the sag Z of the even-order aspherical surface is:

[0014]

[0015] Where c is the curvature; r is the radius; k is the quadratic surface coefficient; a i It is the coefficient of the monomial;

[0016] The front surface of the fourth lens, 0≤k≤1, and the coefficients of each monomial satisfy the following conditions: a1=0, -3×10 -2 ≤a2≤-1×10 -2 3×10 -4 ≤a3≤5×10 -4 -3×10 -4≤a4≤-2×10 -4 -5×10 -5 ≤a5≤-4×10 -5 -3×10 -5 ≤a6≤-1×10 -5 ;

[0017] On the rear surface of the fifth lens, 0 ≤ k ≤ 1, the coefficients of each monomial satisfy the following conditions: a1 = 0, -4 × 10 -2 ≤a2≤-2×10 -2 7×10 -3 ≤a3≤9×10 -3 7×10 -3 ≤a4≤9×10 -3 -6×10 -3 ≤a5≤-4×10 -3 6×10 -3 ≤a6≤8×10 -3 .

[0018] The present invention discloses a liquid lens focusing micro microscope objective with an object-side numerical aperture of 0.6, an image-side numerical aperture of 0.3, an object-side field of view (FOV) ranging from 0 mm to 0.50 mm, and a detection depth (L) ranging from 50 μm to 150 μm.

[0019] The micro microscope objective with liquid lens focusing described in this utility model has a total system length T ranging from 11.5mm to 12.5mm.

[0020] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0021] 1. This invention aims to achieve a miniature microscope objective with a large axial observation range. However, due to the contradiction between high numerical aperture and large depth of field, a high numerical aperture inevitably leads to a smaller depth of field, which in turn reduces the axial observation range. Therefore, a voltage-driven liquid lens focusing method is adopted. Under the condition of an object-side numerical aperture of 0.6, a detection depth of 100 μm in the visible light range is achieved, which can observe cell structures in the range of 50 μm to 150 μm below the tissue surface, covering the effective penetration depth of visible light in tissues and possessing a large axial observation range. At the same time, since this miniature objective has a magnification of about 2 times and an image-side numerical aperture of 0.3, it can be well combined with fiber optic bundles to achieve the observation of tissue cells.

[0022] 2. This invention aims to achieve high-resolution microscopic imaging. Through research on first-order aberration theory and aberration characteristics, the position of the aspherical surface was investigated. It was found that placing the aspherical lens after the liquid lens effectively suppresses aberrations introduced by the liquid lens during zooming. The selection of the aspherical surface position enhances the system's ability to balance various geometric aberrations. Spherical aberration and distortion of the optical system were corrected, effectively improving the overall imaging resolution of the system. For the commonly used 3μm pixel size in visible light detectors, this invention achieves an optical transfer function greater than 0.6 across the entire operating band and field of view at 167 lp / mm, demonstrating excellent imaging quality.

[0023] 3. This utility model addresses the design requirements of miniature microscope objectives. Under the premise of system aperture limitations, the structure is optimized by placing the liquid lens used for zooming after the aperture stop, effectively reducing the system's outer diameter. Furthermore, compared to mechanically compensated zooming, the outer surface of the structure requires no protrusions such as motors or gears, and no moving parts. It is simple and compact, with a total length of only 12mm, meeting the miniaturization requirements of human endoscopy while still satisfying various optical performance requirements during diagnosis. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the liquid lens focusing micro microscope objective provided in this embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of the liquid lens focusing micro microscope objective provided in this embodiment of the present invention under different focal lengths.

[0026] Figure 3 This is a series of focused light spots of the liquid lens focusing miniature microscope objective provided in this embodiment of the present invention under different focal lengths and in the full field of view and working wavelength.

[0027] Figure 4 This is a transfer function (MTF) curve of the liquid lens focusing micro microscope objective provided in this embodiment of the present invention.

[0028] Figure 5 This is a distortion curve of a liquid lens focusing microscope objective provided in an embodiment of this utility model.

[0029] In the diagram, 1 is the first lens; 2 is the second lens; STO is the aperture stop; 3 is the third lens (liquid lens); L1 is the first window; L2 is the first liquid; L3 is the second liquid; L4 is the second window; 4 is the fourth lens; 5 is the fifth lens; 6 is the sixth lens; and 7 is the seventh lens. Detailed Implementation

[0030] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0031] Example 1:

[0032] This embodiment provides a miniature microscope objective with liquid lens focusing. The optical system consists of five lenses and a liquid lens. The object-side numerical aperture of the optical system is 0.6, the image-side numerical aperture is 0.3, the working wavelength is 480–550 nm, the detection depth is 50–150 μm, the field of view is 500 μm, and the total length of the system is 12 mm.

[0033] The performance parameters of the zoom optical system provided in this embodiment are shown in Table 1.

[0034] Table 1:

[0035] Operating wavelength (nm) 480～550 Numerical aperture of material 0.6 Image numerical aperture 0.3 Field of view (μm) 500 Detection depth (μm) 50～150 Total system length (mm) 12

[0036] See appendix Figure 1 It is a miniature microscope objective with liquid lens focusing provided in this embodiment, which is arranged in the following order from the object plane to the image plane according to the incident direction of light: first lens 1, second lens 2, aperture stop STO, third lens 3, fourth lens 4, fifth lens 5, sixth lens 6 and seventh lens 7.

[0037] In this embodiment, the third lens 3 is a liquid lens, including a first window L1, a first liquid L2, a second liquid L3, and a second window L4. The first liquid L2 is a conductive liquid sodium chloride solution with a refractive index of 1.39 and an Abbe number of 58.1. The second liquid L3 is an insulating non-polar liquid silicone oil with a refractive index of 1.50 and an Abbe number of 34.6.

[0038] In this embodiment, the front surface of the fourth lens 4 and the rear surface of the fifth lens 5 are aspherical surfaces. A Cartesian coordinate system is constructed with the intersection of the lens surface and the optical axis as the origin. The incident direction of the light is the positive Z-axis, the positive Y-axis is upward, and the positive X-axis is perpendicular to the paper and inward. The equation for the sag Z of the even-order aspherical surface is:

[0039]

[0040] Where c is the curvature; r is the radius; k is the quadratic surface coefficient; a i These are the coefficients of the monomials; where the front surface of the third lens 3 has k = 1, and the coefficients of each monomial are a1 = 0, a2 = -1 × 10⁻⁶. -2 a3 = 5 × 10 -4 a4 = -2 × 10 -4 a5 = -4 × 10 -5 a6=-1×10 -5The rear surface of the fourth lens 4 has k=1, and the coefficients of each monomial are: a1=0, a2=-2×10. -2 a3 = 9 × 10 -3 a4 = 9 × 10 -3 a5 = -4 × 10 -3 a6 = 8 × 10 -3 .

[0041] The parameters of each optical element in this embodiment are shown in Table 2.

[0042] Table 2:

[0043]

[0044]

[0045] See appendix Figure 2 This is a schematic diagram of the liquid lens focusing micro microscope objective provided in this embodiment under three different detection depths; in the figure, (a), (b) and (c) correspond to the optical path structure of the micro microscope objective provided in this embodiment under detection depths of 50μm, 100μm and 150μm, respectively.

[0046] The liquid surface curvature parameters of the liquid lens under different detection depths for the liquid lens focusing micro microscope objective provided in this embodiment are shown in Table 3.

[0047] Table 3:

[0048] Detection depth (μm) Liquid surface curvature 50 -0.048 100 -0.136 150 -0.223

[0049] See appendix Figure 3 It is a ray tracing dot plot of light passing through the micro microscope objective focused by the liquid lens provided in this embodiment. The root mean square radius of the dot plots for each focal length corresponding to the four fields of view in the figure is less than 1.34 μm, and the average geometric radius of the dot plots is less than 5.95 μm, indicating good imaging quality.

[0050] See appendix Figure 4 This figure shows the MTF (Mean Transfer Function) curves of the liquid lens focusing micromicroscope objectives provided in this embodiment for each field of view on the corresponding image plane. In the figure, (a), (b), and (c) correspond to the MTF curves of all fields of view on the corresponding image planes of the micromicroscope objectives provided in this embodiment at detection depths of 50 μm, 100 μm, and 150 μm, respectively. Figure 4 It can be seen that the optical transfer function of the entire working band and field of view within the zoom range of 167 lp / mm is greater than 0.6, close to the diffraction limit, and the curve is smooth and compact, indicating that the system has clear and uniform imaging and good imaging quality in the entire band and field of view.

[0051] See appendix Figure 5 This figure shows the distortion curves of the liquid lens focusing micromicroscope objective provided in this embodiment at three different detection distances. Figures (a), (b), and (c) correspond to the distortion curves on the image plane of the micromicroscope objective provided in this embodiment at detection depths of 50 μm, 100 μm, and 150 μm, respectively. The vertical axis represents the normalized field of view, and the horizontal axis represents the percentage of image distortion at each field of view. Distortion deforms the image; a smaller percentage of distortion indicates less image distortion. Figure 5 It can be seen that the maximum distortion of the zoom optical system in the normalized field of view does not exceed 0.4% under different focal lengths.

Claims

1. A miniature microscope objective with liquid lens focusing, characterized in that: The system consists of a first lens (1), a second lens (2), an aperture stop, a third lens (3), a fourth lens (4), a fifth lens (5), a sixth lens (6), and a seventh lens (7) arranged sequentially from the object plane to the image plane along the optical axis; the aperture stop of the system is located on the rear surface of the second lens (2); The first lens (1) and the second lens (2) are cemented together to form a cemented lens. The first lens (1) is a spherical mirror with negative optical power, and the second lens (2) is a spherical mirror with positive optical power. According to the incident direction of light, the radii of curvature of the surfaces of each lens are R11, R12 and R13 respectively, which satisfy the conditions that R11 is infinite, 2.6mm≤R12≤2.8mm, and -2.85mm≤R13≤-2.87mm respectively. The refractive index n1 of the material of the first lens (1) is in the range of 1.9≤n1≤2.0, and the Abbe number v1 is in the range of 17≤v1≤18. The refractive index n2 of the material of the second lens (2) is in the range of 1.9≤n2≤2.0, and the Abbe number v2 is in the range of 32≤v2≤33. The third lens (3) is a liquid lens; The fourth lens (4) has positive optical power. Its front surface is aspherical and its rear surface is spherical. The radii of curvature of the front and rear surfaces are R31 and R32, respectively, satisfying the conditions 4.7mm≤R31≤4.8mm and -5.9mm≤R32≤-5.8mm. The refractive index n3 of its material is in the range of 1.7≤n3≤1.8, and the Abbe number v3 is in the range of 53.7≤v3≤55.

4. The fifth lens (5) has positive optical power. Its front surface is spherical and its rear surface is aspherical. The radii of curvature of the front and rear surfaces are R41 and R42, respectively, satisfying the conditions 2.2mm≤R31≤2.3mm and 5.3mm≤R32≤5.5mm. The refractive index n4 of its material is in the range of 1.5≤n4≤1.7, and the Abbe number v4 is in the range of 67.7≤v4≤69.

4. The sixth lens (6) is a spherical mirror with positive optical power. The radii of curvature of the front and rear surfaces are R51 and R52, respectively, satisfying the conditions 2.0mm≤R51≤2.1mm and 26mm≤R52≤28mm. The refractive index n5 of its material is in the range of 1.7≤n5≤1.8, and the Abbe number v5 is in the range of 54≤v5≤55. The seventh lens (7) is a spherical mirror with negative optical power. The radii of curvature of the front and rear surfaces are R61 and R62, respectively, satisfying the conditions -15mm≤R61≤-14mm and 1.0mm≤R62≤1.1mm. The refractive index n6 of its material is in the range of 1.6≤n6≤1.8, and the Abbe number v6 is in the range of 40.6≤v6≤42.

2.

2. The miniature microscope objective with liquid lens focusing according to claim 1, characterized in that: The third lens (3), a liquid lens, comprises, in order of light incident direction, a first window (L1), a first liquid (L2), a second liquid (L3), and a second window (L4); the first window (L1) is a parallel glass plate, the refractive index n7 of which ranges from 1.7 to 1.9, and the Abbe number v7 of which ranges from 37 to 38; the second window (L4) is a parallel glass plate, the refractive index n8 of which ranges from 1.7 to 1.9, and the Abbe number v8 of which ranges from 37 to 38; the first liquid (L2) is a conductive liquid, the refractive index n9 of which ranges from 1.3 to 1.4, and the Abbe number v9 of which ranges from 54 to 59; the second liquid (L3) is an insulating non-polar liquid, the refractive index n... 10 The range of values ​​for is 1.5 ≤ n 10 ≤1.7, Abbe number v 10 The range of values ​​for v is 37 ≤ v 10 ≤45.

3. A miniature microscope objective with liquid lens focusing according to claim 1, characterized in that: The aspherical surfaces described on the front surface of the fourth lens (4) and the rear surface of the fifth lens (5) are used to construct a Cartesian coordinate system with the intersection of the lens surface and the optical axis as the origin. The incident direction of the light is the positive Z-axis, the positive Y-axis is upward, and the positive X-axis is perpendicular to the paper and inward. The equation for the sag Z of the even-order aspherical surface is: , Where c is the curvature; r is the radius; k is the quadratic surface coefficient; a i It is the coefficient of the monomial; The front surface of the fourth lens (4) has 0≤k≤1, and the coefficients of each monomial satisfy the following conditions: , , , , , ; The rear surface of the fifth lens (5) has 0≤k≤1, and the coefficients of each monomial satisfy the following conditions: , , , , , .

4. A miniature microscope objective with liquid lens focusing according to claim 1, characterized in that: The system has an object-side numerical aperture of 0.6, an image-side numerical aperture of 0.3, and an object-side field of view (FOV) ranging from 0 mm to 0.50 mm. The detection depth (L) ranges from 50 μm to 150 μm.

5. A miniature microscope objective with liquid lens focusing according to claim 1, characterized in that: The total system length T ranges from 11.5mm ≤ T ≤ 12.5mm.

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