CN110161674A - Liquid lens - Google Patents

Abstract

The present invention provides a liquid lens, comprising: a main body, the main body is provided with a lens cavity in the shape of a through hole; a liquid is accommodated in the lens cavity, and the liquid includes a first conductive liquid, an insulating liquid and a second conductive liquid; encapsulating glass, matched with the main body to seal the lens cavity; define the refractive index of the first conductive liquid as n ₁ , the refractive index of the insulating liquid as n ₂ , and the second The refractive index of the conductive liquid is n ₃ , when there is a difference between n ₁ and n ₂ , the first curved interface formed by the first conductive liquid and the insulating liquid is used to adjust the focal length of the liquid lens; when n ₂ When there is a difference between n and ₃ , the second curved interface formed by the insulating liquid and the second conductive liquid is used to adjust the phase of the light beam entering the liquid lens. Compared with the prior art, the liquid lens of the present invention can not only adjust the focal length, but also adjust the phase, and can also be modified to take into account a large adjustment range and high adjustment accuracy as required.

Description

liquid lens

technical field

The invention relates to a liquid lens, which belongs to the technical fields of imaging control optical technology and optical information processing devices.

Background technique

The liquid zoom lens based on electrowetting of dielectrics (EWOD) uses an external voltage to adjust the curvature of the liquid surface, thereby changing the focal length of the lens in a wide range.

Generally, the lens material of a liquid zoom lens is composed of two kinds of conductive aqueous solutions and non-conductive oils with different refractive indices and immiscible with each other. The interface of these two liquids can form a stable contact surface and play the role of a lens. . However, under normal circumstances, the adjustment of the liquid contact surface is used for zooming, and it is not suitable for phasing.

In view of this, it is indeed necessary to improve the existing liquid lens to solve the above problems.

Contents of the invention

The object of the present invention is to provide a liquid lens, which has the functions of focusing and phase adjustment.

To achieve the above object, the present invention provides a liquid lens, comprising:

The main body part is provided with a lens chamber in the shape of a through hole;

a liquid contained in the lens cavity, the liquid includes a first conductive liquid, an insulating liquid and a second conductive liquid placed in sequence;

an encapsulating glass matched with the main body to seal the lens cavity;

Define the refractive index of the first conductive liquid as n ₁ , the refractive index of the insulating liquid as n ₂ , and the refractive index of the second conductive liquid as n ₃ , when there is a difference between n ₁ and n ₂ , the first The first curved interface formed by the conductive liquid and the insulating liquid is used to adjust the focal length _of the liquid lens; when there is a difference between _n2 and n3, the second curved interface formed by the insulating liquid and the second conductive liquid Used to adjust the phase of the light beam entering the liquid lens.

Optionally, the difference between the refractive index n1 of the first conductive liquid and the refractive index _{n2 of} the insulating liquid is between 0.01-1.

Optionally, the difference between the refractive index n ₂ of the insulating liquid and the refractive index n ₃ of the second conductive liquid is between 0.0001-0.01.

Optionally, in the axial direction of the lens chamber, the main body is made of conductive material to serve as a common electrode of the liquid lens; the packaging glass is transparent conductive glass to lead out the liquid lens the control electrode.

Optionally, when the difference between the refractive index n1 of the first conductive liquid and the refractive index _{n2 of} the insulating liquid is between 0.001 and 0.01, at the same time, the refractive index _n2 of the insulating liquid and the second conductive liquid When the difference between the refractive indices n _of the liquid is between 0.0001 and 0.001, the first curved interface is used for coarse adjustment of the phase of the beam, and the second curved interface is used for fine adjustment of the phase of the beam .

Optionally, the first conductive liquid, the insulating liquid and the second conductive liquid are immiscible with each other.

Optionally, the inner surface of the main body is coated with an insulating dielectric layer, so as to form a capacitive structure between the main body and the first conductive liquid, and between the main body and the second conductive liquid, so as to control the Describe the shapes of the first curved interface and the second curved interface.

Optionally, a surface active layer is provided on the second curved interface.

Optionally, the focal length of the liquid lens is given by the formula

Calculated, where a is the inner diameter of the lens cavity, _θ0 is the initial contact angle between the second conductive liquid and the inner wall of the lens cavity when the applied voltage U is zero, and _εr is the relative permittivity of the first conductive liquid and the insulating liquid , γ ₁₂ is the interfacial tension between the first conductive liquid and the insulating liquid, and e is the thickness of the dielectric layer.

Optionally, the relationship between the applied voltage U and the contact angle θ between the second conductive liquid and the inner wall of the lens cavity satisfies the relational expression:

The beneficial effects of the present invention are: the present invention designs the liquid to be composed of the first conductive liquid, the insulating liquid and the second conductive liquid placed in sequence, so that when there is a difference between the refractive index of the first conductive liquid and the refractive index of the insulating liquid, When , the first curved interface formed by the first conductive liquid and the insulating liquid can be used to adjust the focal length; and when there is a difference between the refractive index of the insulating liquid and the second conductive liquid, the insulating liquid and the second conductive liquid The formed second curved interface can be used to adjust the phase, realizing the function that the liquid lens can adjust both the focal length and the phase.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the liquid lens of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to Fig. 1, the present invention provides a liquid lens, which can be applied to an optical system with focusing and phase modulation functions, to achieve focusing while taking into account phase modulation compensation, or to take into account a large phase adjustment range at the same time High adjustment accuracy occasions. For example: optical synthetic aperture imaging, camera, mobile phone lens, etc.

The liquid lens includes a main body (not shown), a liquid accommodated in the main body, and an encapsulating glass (not shown) for cooperating with the main body. The main body is provided with a through-hole-shaped lens cavity; the main body is made of conductive material and used as a common electrode of the liquid lens. The liquid is accommodated in the lens cavity, and includes a first conductive liquid 1 , an insulating liquid 2 and a second conductive liquid 3 placed in sequence.

The encapsulating glass covers the outside of the lens cavity to seal the lens cavity. Preferably, the packaging glass is transparent conductive glass and two pieces are provided to respectively seal the two ends of the lens chamber, the first conductive liquid 1 is in contact with one piece of packaging glass, and the second conductive The liquid 3 is in contact with another piece of packaging glass, so that the two control electrodes in the liquid lens can be led out from the two pieces of packaging glass respectively.

The first conductive liquid 1, the insulating liquid 2 and the second conductive liquid 3 are immiscible with each other, so that a first curved interface 4 can be formed between the first conductive liquid 1 and the insulating liquid 2, and the insulating liquid 2 and the second conductive liquid 3 form a second curved interface 5 . In the axial direction of the lens cavity, define the thickness of the first conductive liquid 1 as L ₁ , the thickness of the insulating liquid 2 as L ₂ , and the thickness of the second conductive liquid 3 as L ₃ , then L ₂ >L ₃ >L ₁ ; but should not be limited to this.

Define the refractive index n 1 of the first conductive liquid 1, the refractive index n ₂ of the insulating liquid 2, and the refractive index n ₃ of the second conductive liquid ₃ , when there is a difference between n ₁ and n ₂ and the difference When the value is large, the first curved interface 4 formed by the first conductive liquid 1 and the insulating liquid 2 can be used to adjust the focal length of the liquid lens; when there is a difference between n ₂ and n ₃ and the difference is small, The second curved interface 5 formed by the insulating liquid 2 and the second conductive liquid 3 can be used to adjust the phase of the light beam entering the liquid lens.

Specifically, when the difference between the refractive index n 1 of the first conductive liquid 1 and the refractive index n ₂ of the insulating liquid ₂ is between 0.01 and 1, the first curved interface 4 plays a role in focusing role. When the difference between the refractive index n 2 of the insulating liquid 2 and the refractive index n ₃ of the second conductive liquid ₃ is between 0.0001-0.01, the second curved interface 5 plays a role of phase modulation.

In order to improve the phase modulation accuracy, generally, it can be realized by further reducing the initial contact angle between the second curved interface 5 and the inner wall of the lens cavity, and at the same time, a surface active layer is provided on the second curved interface 5 . During specific work, the focal length of the liquid lens should be adjusted by using the first curved interface 4 first, and then the phase of the light beam should be adjusted by the second curved interface 5 after the focal length is adjusted.

It should be noted that the phase adjustment function is only to complete the fine-tuning and matching of the phase. Under normal circumstances, the adjustment range will not be greater than 100λ, otherwise the accuracy will be difficult to meet the requirements, so the phase adjustment effect of the second bending interface 5 is not for the first bending Phase compensation after focusing on interface 4.

Of course, if you want to achieve a wide range of phase adjustment while taking into account the adjustment accuracy, you can make the first curved interface 4 function as a coarse phase adjustment by reasonably distributing the refractive index difference between the liquids, while the second curved interface 5 plays the function of fine phase adjustment. At this time, the difference between the refractive index n1 of the first conductive liquid ₁ and the refractive index n2 of the insulating liquid ₂ is between 0.001 and 0.01, and at the same time, the refractive index n2 of the insulating liquid ₂ and the second The difference between the refractive indices n ₃ of the conductive liquid 3 is between 0.0001-0.001. It can be seen that the present invention can adjust the size of the difference between n ₁ and n ₂ and n ₂ and n ₃ according to actual needs to realize the focusing or phase adjustment function of the first curved interface 4 and the function of the second curved interface 5 Phasing function.

The focal length of the liquid lens is given by the formula

Calculated, where a is the inner diameter of the lens cavity, _θ0 is the initial contact angle between the second conductive liquid 3 and the inner wall of the lens cavity when the applied voltage U is zero, _εr is the relative angle between the first conductive liquid 1 and the insulating liquid 2 Dielectric coefficient, γ ₁₂ is the interfacial tension between the first conductive liquid 1 and the insulating liquid 2, and e is the thickness of the dielectric layer.

Wherein, the relationship between the applied voltage U and the contact angle θ between the second conductive liquid 3 and the inner wall of the lens cavity satisfies the relation:

It can be seen from the above formula (1): if other conditions remain unchanged, when the difference between the refractive index _n1 and the refractive index _n2 is relatively large (for example, greater than 0.01, especially greater than 0.1), the first curved interface 4 exerts a modulation Focusing effect _; and when the difference between the refractive index n3 and the refractive index _n2 is very small (such as less than 0.01, especially less than 0.0001), the second curved interface 5 does not perform the focusing function, but is used to adjust the light beam entering the lens cavity , and under the action of the electrowetting effect, adjust the phase Φ variation of the beam transmitted along the axis of the lens cavity (δΦ=2π/λ*δ△, δ△=(n ₂ -n ₃ )*δh, δh is the displacement change amount of the apex of the second curved interface 5).

The inner surface of the main body is coated with an insulating dielectric layer to form a capacitive structure between the main body and the first conductive liquid 1, and between the main body and the second conductive liquid 3, so that after applying a voltage , the capacitive structure is charged and discharged, thereby facilitating the control of the shapes of the first curved interface 4 and the second curved interface 5 .

When used as a lens, the inner wall of the lens cavity needs to be treated with hydrophobic treatment to increase the initial contact angle between the liquid and the inner wall, so that the liquid lens has a larger adjustment range; when used as a phase modulation, the inner wall of the lens cavity should be selected properly Insulating dielectric layer to reduce the initial contact angle between the liquid and the inner wall, or add a surface active layer on the second curved interface 5 to further reduce the initial contact angle between the liquid and the inner wall, so that the liquid lens has a higher High phase adjustment accuracy.

The phase modulation principle of the liquid lens of the present invention is as follows: respectively apply control voltages to the main body and the two pieces of packaging glass, so that the interfacial tension between the second conductive liquid 3 and the inner wall of the lens cavity is reduced due to the electrowetting effect, thereby The shape of the second curved interface 5 is changed, and the second curved interface 5 is moved along the axial direction of the lens cavity by a displacement of δh. In a preferred embodiment, after selecting a suitable insulating dielectric layer material or applying a surface active layer, the contact angle θ between the second conductive liquid 3 and the inner wall of the lens cavity can be made less than 95°, and the control accuracy of δh is less than 0.1mm. When the refractive index difference |n ₂ -n ₃ | is selected in the range of 0.0001~0.01, the optical path adjustment accuracy δ△=(n ₂ -n ₃ )*δh can be controlled between 0.01~1μm, which meets the needs of different occasions.

Similarly, if the first curved interface 4 is also used for phase modulation, when the refractive index difference |n ₁ -n ₂ | is selected from the range of 0.001 to 0.01, the optical path adjustment accuracy δ△=(n ₂ -n ₃ )* δh can be controlled between 0.1 and 1 μm, which can be used as a coarse phase adjustment to increase the phase modulation range. Combined with the fine adjustment of the second curved interface 5, it can meet the large-scale and high-precision phase modulation requirements.

The following specification part will describe the present invention in detail with specific examples.

Embodiment 1: the first conductive liquid 1 selects 10% NaCl aqueous solution, or LiCL aqueous solution, or NaSO4 aqueous solution, the refractive index is about 1.34; the insulating liquid 2 selects turpentine, and the refractive index at normal temperature is 1.4721, so, the first curved interface 4 It plays the role of focusing; the second conductive liquid 3 chooses the ionic liquid [P666(14)][Deca], the refractive index at room temperature is 1.47242, which is 0.00032 different from the refractive index of the insulating liquid 2, when δh is 0.1mm, the second The phase modulation (dimming range) accuracy of the curved interface 5 can reach 0.03 μm, and for green light with λ=0.55 μm, it can reach 0.06λ, which can meet the requirements of most imaging occasions.

Example 2: The first conductive liquid 1 is mixed with 5% NaCl aqueous solution + 60% sugar solution, and the refractive index is about 1.462; the insulating liquid 2 is turpentine, and the refractive index at room temperature is 1.4721, which is the same as the refractive index of the first conductive liquid 1 The phase difference is 0.01. When δh is 0.1 mm, the first curved interface 4 constitutes a liquid phase modulator with a phase modulation accuracy of 1 μm. At this time, although the adjustment accuracy is relatively coarse, the phase modulation range is greatly increased. Two, the fine phase adjustment function of the curved interface 5, the two can be combined into a liquid phase adjuster with a large adjustment range and high adjustment accuracy.

Embodiment 3: choose turpentine for insulating liquid 2; choose the same conductive liquid for first conductive liquid 1 and second conductive liquid 3, such as ionic liquid [EM2N(CH2)2OH][ESO4], and the refractive index is 1.47303 at room temperature. However, the thickness of the first insulating dielectric layer contacted by the first curved interface 4 is much smaller than the thickness of the second insulating dielectric layer contacted by the second curved interface 5, for example, the thickness of the first insulating dielectric layer is 3um , the thickness of the second insulating dielectric layer is 10um, then according to the formula (2), it can be seen that the contact angle adjustment sensitivity of the first curved interface 4 is about 10 times higher than that of the second curved interface 5 . Therefore, the adjustment accuracy of δh of the second curved interface 5 is 10 times higher than that of the first curved interface 4, and the first curved interface 4 can be used as a coarse adjustment phase, while the second curved interface 5 can be used as a fine adjustment phase.

Of course, according to the nonlinear relationship between δh and the initial contact angle of the liquid-inner wall, different initial contact angles of the first curved interface 4 and the second curved interface 5 can be set to complete the distribution of coarse and fine adjustment roles, for example, the first The liquid-inner wall contact surface of the curved interface 4 is coated with a hydrophobic layer to make the initial contact angle greater than 120°, which is used as a coarse phase adjustment; the liquid-inner wall contact surface of the second curved interface 5 is not coated with a hydrophobic layer, and even added surface active agent (sodium lauryl sulfate, etc.), so that the initial contact angle is less than 95° (greater than 90°), and used as a fine-tuning phase.

The present invention combines microfluidic optical technology with modern optical technology, and designs a method based on liquid lens that can not only adjust the focal length, but also adjust the phase. At the same time, it can also be transformed into a large adjustment range and high adjustment accuracy according to needs. scheme. The liquid lens of the present invention has the advantages of simple structure, easy manufacture, low cost, etc., and has economic and technical value. It is used in mobile phones, digital cameras, micro cameras, endoscopes and other products.

In summary, the liquid lens of the present invention is designed to consist of the first conductive liquid 1, the insulating liquid 2 and the second conductive liquid 3 placed in sequence, so that when the refractive index n of the first conductive liquid ₁ is equal to the insulating When there is a difference between the refractive index n of the liquid ₂ and the difference is large, the first curved interface 4 formed by the first conductive liquid 1 and the insulating liquid 2 can be used to adjust the focal length; and when the refractive index of the insulating liquid 2 When there is a difference between n ₂ and the refractive index n ₃ of the second conductive liquid 3 and the difference is small, the second curved interface 5 formed by the insulating liquid 2 and the second conductive liquid 3 can be used to adjust the phase, realizing liquid The lens can not only adjust the focal length, but also adjust the phase function.

The above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. A liquid lens, characterized in that, comprising: The main body part is provided with a lens chamber in the shape of a through hole; a liquid contained in the lens cavity, the liquid includes a first conductive liquid, an insulating liquid and a second conductive liquid placed in sequence; an encapsulating glass matched with the main body to seal the lens cavity; Define the refractive index of the first conductive liquid as n ₁ , the refractive index of the insulating liquid as n ₂ , and the refractive index of the second conductive liquid as n ₃ , when there is a difference between n ₁ and n ₂ , the first The first curved interface formed by the conductive liquid and the insulating liquid is used to adjust the focal length _of the liquid lens; when there is a difference between _n2 and n3, the second curved interface formed by the insulating liquid and the second conductive liquid Used to adjust the phase of the light beam entering the liquid lens. 2 . The liquid lens according to claim 1 , wherein the difference between the refractive index n _{1 of the first conductive liquid and the refractive index n 2 of} the insulating liquid is between 0.01-1. 3 . The liquid lens according to claim 1 , wherein the difference between the refractive index n ₂ of the insulating liquid and the refractive index n ₃ of the second conductive liquid is between 0.0001˜0.01. 4. The liquid lens according to claim 1, characterized in that: the main body is made of conductive material to serve as the common electrode of the liquid lens; the packaging glass is transparent conductive glass to lead out the Control electrode of the liquid lens. 5. The liquid lens according to claim 1, characterized in that: when the difference between the refractive index n1 of the first conductive liquid and the refractive index _{n2 of} the insulating liquid is between 0.001 and 0.01, at the same time the When the difference between the refractive index n ₂ of the insulating liquid and the refractive index n ₃ of the second conductive liquid is between 0.0001 and 0.001, the first curved interface is used to roughly adjust the phase of the beam, and the second The two curved interfaces are used for fine adjustment of the phase of the beam. 6 . The liquid lens according to claim 1 , wherein the first conductive liquid, the insulating liquid and the second conductive liquid are incompatible with each other. 7. The liquid lens according to claim 1, characterized in that: the inner surface of the main body is coated with an insulating dielectric layer, so that between the main body and the first conductive liquid, and between the main body and the first conductive liquid, A capacitive structure is formed between the two conductive liquids to control the shapes of the first curved interface and the second curved interface. 8. The liquid lens according to claim 1, wherein a surface active layer is provided on the second curved interface. 9. liquid lens according to claim 1, is characterized in that: the focal length of described liquid lens is by formula Calculated, where a is the inner diameter of the lens cavity, _θ0 is the initial contact angle between the second conductive liquid and the inner wall of the lens cavity when the applied voltage U is zero, and _εr is the relative permittivity of the first conductive liquid and the insulating liquid , γ ₁₂ is the interfacial tension between the first conductive liquid and the insulating liquid, and e is the thickness of the dielectric layer. 10. The liquid lens according to claim 9, wherein the relationship between the applied voltage U and the contact angle θ between the second conductive liquid and the inner wall of the lens cavity satisfies the relational expression: