Depth of field adjustable objective based on liquid lens

Abstract

This invention proposes a depth-of-field adjustable objective lens based on a liquid lens. The objective lens includes: a solid lens group 1, an aperture stop, a liquid lens group, a solid lens group 2, and an image sensor. The liquid lens in the liquid lens group can have its interface curvature controlled by an external actuator, thereby changing the focal length. The effective light-passing diameter of the aperture stop is D. In state 1, the liquid lens group is not driven, and the image captured by the image sensor is blurry and indistinguishable. Adjusting the curvature of the liquid lens in the liquid lens group makes the image captured by the image sensor clear. In state 2, the shooting distance changes, and the curvature of the liquid lens in the liquid lens group is adjusted again, making the image captured by the image sensor clear again. That is, when the shooting distance changes, the adaptive depth-of-field adjustment function of the depth-of-field adjustable objective lens can be realized by controlling the focal length of the liquid lens in the liquid lens group.

Description

Technical Field

[0001] This invention relates to a depth-of-field adjustable objective lens technology, and more specifically, to a depth-of-field adjustable objective lens based on a liquid lens. Background Technology

[0002] An objective lens is a lens group composed of several lenses. The purpose of using them in combination is to overcome the imaging defects of a single lens and improve the optical quality of the objective lens. Whether in microscopes, telescopes, or photographic equipment, the objective lens is an indispensable and important optical component. Currently, objectives mainly consist of multiple groups of solid lenses with a fixed focal length. To obtain good image quality, 6-8 lenses are generally required, which increases the size of the objective lens and seriously affects the integration and lightweight design of optical instruments or equipment. Furthermore, once the objective lens system is designed, its depth of field is fixed and cannot be adjusted. However, in practical optical applications, it is often necessary to adjust the depth of field to achieve multi-layer depth scanning or depth fusion. Current methods only allow adjusting the aperture or moving the distance between the instrument and the subject, which is extremely inconvenient and limits the accuracy of depth scanning. In recent years, emerging liquid lenses have adaptive zoom capabilities, providing new design ideas for the lightweighting and miniaturization of optical systems. Based on the mechanically motion-free zoom characteristics of liquid lenses, it is hoped that adjustable depth of field of the objective lens can be achieved. Summary of the Invention

[0003] This invention proposes a depth-of-field adjustable objective lens based on a liquid lens. The depth-of-field adjustable objective lens includes: a solid lens group 1, an aperture stop, a liquid lens group, a solid lens group 2, and an image sensor. The liquid lens in the liquid lens group can change the focal length by controlling the interface curvature of the liquid through an external actuator; the effective light-passing diameter of the aperture stop is D.

[0004] As attached Figure 1 As shown, in state 1, the shooting distance is F1, the liquid lens group is not driven, and the image captured by the image sensor is blurry and indistinguishable. Adjusting the curvature of the liquid lens in the liquid lens group makes the image sensor capture a clear image, with the maximum tolerance size of the blur spot being δ. At this time, the effective focal length of the depth-of-field adjustable objective is f1, the aperture number N1 is f1 / D, the foreground depth of field is ∆L1, and the background depth of field is ∆L2. Then, in this state, the depth of field ∆L of the depth-of-field adjustable objective is:

[0005]

[0006]

[0007] Where Ф1, Ф2, and Ф3 represent the optical power of solid lens group 1, liquid lens group, and solid lens group 2, respectively, under state 1. Ф1 and Ф3 can be directly measured by an optical power measuring instrument. The optical power Ф2 of the liquid lens group is determined by the applied voltage value of each liquid lens in the group, therefore:

[0008]

[0009] Among them, U1, U2, U3, ... U M These represent the voltage values ​​applied to the M liquid lenses in the liquid lens group.

[0010] In state 2, when the shooting distance changes from F1 to F2, the curvature of the liquid lens in the liquid lens group is readjusted to make the image sensor re-image clear. Since the same image sensor is used in both imaging processes, the maximum tolerance size of the blur spot remains δ. Figure 2 As shown. At this time, the effective focal length of the depth-of-field adjustable objective lens is f2, the aperture number N2 is f2 / D, the foreground depth of field is ∆L3, and the background depth of field is ∆L4. Therefore, the depth of field ∆L' of this depth-of-field adjustable objective lens in this state is:

[0011]

[0012]

[0013] Where Ф1, Ф'2, and Ф3 represent the optical power of solid lens group 1, liquid lens group, and solid lens group 2, respectively, under state 2. Ф1 and Ф3 are fixed values ​​and remain unchanged. The optical power Ф'2 of the liquid lens group is determined by the applied voltage value of each liquid lens in this group under this state, therefore:

[0014]

[0015] Among them, U'1, U'2, U'3,...U' M These are the voltage values ​​applied to the M liquid lenses in the liquid lens group under state 2.

[0016] That is, when the shooting distance changes, the adaptive depth-of-field adjustment function of the depth-of-field adjustable objective lens can be realized by controlling the focal length of the liquid lens in the liquid lens group. The depth-of-field adjustable objective lens of the present invention has the advantages of simple structure, lightweight and high resolution.

[0017] Preferably, in the depth-of-field adjustable objective lens based on a liquid lens, the solid lens group 1, the aperture, the liquid lens group, and the solid lens group 2 are coaxially arranged, and the image sensor is located on the focal plane of the depth-of-field adjustable objective lens.

[0018] Preferably, the liquid lens group is located between the solid lens group 1 and the solid lens group 2; the aperture is located between the solid lens group 1 and the liquid lens group.

[0019] Preferably, the liquid lens in the liquid lens group can be: an electrowetting-driven liquid lens, a dielectric force-driven liquid lens, a mechanically driven elastic thin film liquid lens, a magnetically controlled liquid lens, or an electronically driven liquid lens.

[0020] Preferably, the number of solid lenses in solid lens group 1 is M. G1 ≥ 1, the number of liquid lenses M in the liquid lens group ≥ 1, the number of solid lenses M in the solid lens group 2 G2 ≥ 1. Attached Figure Description

[0021] Appendix Figure 1 This is a schematic diagram of the structure of the depth-of-field adjustable objective lens in this invention when the effective focal length is f1 and the shooting distance is F1.

[0022] Appendix Figure 2 This is a schematic diagram of the structure of the depth-of-field adjustable objective lens in this invention when the effective focal length is f2 and the shooting distance is F2.

[0023] Appendix Figure 3 This is a simulation diagram of an adjustable depth-of-field objective lens provided in an embodiment of the present invention.

[0024] Appendix Figure 4 Visible light dot plots provided for an embodiment of the present invention when the depth-of-field adjustable objective lens has a shooting distance of 40.76 mm.

[0025] Appendix Figure 5 Visible light dot plots at a shooting distance of 222.00 mm provided for an embodiment of the present invention using a depth-of-field adjustable objective lens.

[0026] The figure labels in the above figures are as follows:

[0027] (1) Solid lens group 1, (2) Aperture, (3) Liquid lens group, (4) Solid lens group 2, (5) Image sensor.

[0028] It should be understood that the above figures are only schematic and are not drawn to scale. Detailed Implementation

[0029] The following detailed description of an embodiment of a depth-of-field adjustable objective lens based on a liquid lens, as proposed in this invention, further illustrates the invention. It is important to note that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of protection of this invention. Any non-essential improvements and adjustments made to this invention by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0030] This invention proposes a depth-of-field adjustable objective lens based on a liquid lens, as shown in the attached figure. Figure 3 As shown, solid lens group 1 is a positive meniscus lens; the effective aperture of the aperture is 1 mm; the liquid lens group is a liquid lens from Optotune, Switzerland; solid lens group 2 consists of three solid lenses, namely a positive biconvex lens, a positive biconvex lens, and a negative biconcave lens, wherein the negative biconcave lens and its adjacent positive biconvex lens are cemented together to form a cemented doublet. The image sensor used has a blur tolerance size of 0.045 mm; when the shooting distance changes, adjusting the focal length of the liquid lens can keep the image plane position unchanged, and adaptive adjustment of the depth of field of the depth-of-field adjustable objective lens can be achieved.

[0031] The following are the specific parameters of this embodiment, where the radius of curvature and thickness are in mm.

[0032]

[0033] As attached Figure 4 The shooting distance shown is 40.76 mm, the field of view is 60°, and the curvature radius of the liquid lens is adjusted to -30 mm. The average blur pattern in each field of view is smaller than the Airy disk radius of 18.42 μm. According to formulas (1) and (2), the depth of field at this time is calculated to be 15.27 mm; as shown in the attached figure. Figure 5 The shooting distance shown is 222.00 mm, the full field of view is 60°, the curvature radius of the liquid lens is adjusted to 30 mm, and the average blur pattern of the dot plot under each field of view is less than the Airy disk radius of 18.50 μm. According to formula (1) and formula (2), the depth of field at this time is calculated to be 950.21 mm.

Claims

1. A depth-of-field adjustable objective lens based on a liquid lens, the depth-of-field adjustable objective lens comprising: Solid lens group 1, aperture, liquid lens group, solid lens group 2, and image sensor; The liquid lens in the liquid lens group can change the focal length by controlling the curvature of the liquid interface through an external actuator; the effective light-passing diameter of the aperture is D. In state 1, the shooting distance is F1, the liquid lens group is not driven, and the image captured by the image sensor is blurry and indistinguishable; Adjusting the curvature of the liquid lens in the liquid lens group to achieve a clear image from the image sensor, with a maximum tolerance size of δ for the blur spot, and given an effective focal length of f1, an aperture number N1 of f1 / D, a foreground depth of field of ∆L1, and a background depth of field of ∆L2, the depth of field ∆L of this adjustable objective in this state is: Where Ф1, Ф2, and Ф3 represent the optical power of solid lens group 1, liquid lens group, and solid lens group 2 under state 1, respectively; Ф1 and Ф3 can be directly measured by an optical power measuring instrument, and the optical power Ф2 of the liquid lens group is determined by the applied voltage value of each liquid lens in the group, then: Among them, U1, U2, U3, ... U M These represent the voltage values ​​applied to the M liquid lenses in the liquid lens group; In state 2, when the shooting distance changes from F1 to F2, the curvature of the liquid lens in the liquid lens group is adjusted again to make the image sensor re-image clear. Since the same image sensor is used in both imaging processes, the maximum tolerance size of the blur spot remains δ. At this time, the effective focal length of the depth-of-field adjustable objective lens is f2, the aperture number N2 is f2 / D, the foreground depth of field is ∆L3, and the background depth of field is ∆L4. Then, the depth of field ∆L' of the depth-of-field adjustable objective lens in this state is: Where Ф1, Ф'2, and Ф3 represent the optical power of solid lens group 1, liquid lens group, and solid lens group 2 respectively under state 2; Ф1 and Ф3 are fixed values ​​and remain unchanged, while the optical power Ф'2 of the liquid lens group is determined by the applied voltage value of each liquid lens in this group under this state, thus: Among them, U'1, U'2, U'3,...U' M These represent the voltage values ​​applied to the M liquid lenses in the liquid lens group under state 2; that is, when the shooting distance changes, the adaptive depth-of-field adjustment function of the depth-of-field adjustable objective lens can be realized by controlling the focal length of the liquid lenses in the liquid lens group.

2. The depth-of-field adjustable objective lens based on a liquid lens according to claim 1, characterized in that, Solid lens group 1, aperture, liquid lens group and solid lens group 2 are coaxially arranged, and the image sensor is located on the focal plane of the depth-adjustable objective lens.

3. The depth-of-field adjustable objective lens based on a liquid lens according to claim 1, characterized in that, The liquid lens group is located between the solid lens group 1 and the solid lens group 2; the aperture is located between the solid lens group 1 and the liquid lens group.

4. The depth-of-field adjustable objective lens based on a liquid lens according to claim 1, characterized in that, The liquid lens in the liquid lens group can be: an electrowetting-driven liquid lens, a dielectrophoretic-driven liquid lens, a mechanically driven elastic thin-film liquid lens, a magnetically controlled liquid lens, or an electromuscle-driven liquid lens.

5. The depth-of-field adjustable objective lens based on a liquid lens according to claim 1, characterized in that, The number of solid lenses in solid lens group 1 is M G1 ≥ 1, the number of liquid lenses M in the liquid lens group; ≥ 1, the number of solid lenses M in the solid lens group 2. G2 ≥ 1.

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