KR102225501B1 - Vari-focal liquid lens capable of controlling aberration - Google Patents

Abstract

Disclosed is a variable focus liquid lens capable of controlling aberration.
In this liquid lens, the chamber contains a liquid that acts as a lens in a hydraulic liquid lens. A lower substrate is mounted in the chamber to seal the lower portion of the liquid, and a surface film is mounted in the chamber to cover the upper portion of the liquid. A first elastic layer is mounted in the chamber to apply pressure to the liquid, and a driving unit drives the first elastic layer.

Description

Variable focus liquid lens with aberration control {VARI-FOCAL LIQUID LENS CAPABLE OF CONTROLLING ABERRATION}

The present invention relates to a variable focus liquid lens capable of controlling aberration.

In an optical system, the optical properties of a lens are a very important factor in determining the quality of an image. When such a lens is used, if aberration is not corrected, the image is not properly formed on the image pickup surface, resulting in image deterioration, and the desired image cannot be obtained clearly.

In general, an optical system requires a plurality of solid lenses to correct aberrations, and each lens is designed as a lens group or aspheric lenses are used to minimize aberrations. In the case of a high-performance aspherical lens, it is manufactured based on the Rayleigh standard, which has a root mean square (RMS) wavefront error value of about 0.07 times (λ/14) of the wavelength.

However, in the case of an aspherical lens, it is difficult to manufacture a surface profile required for high performance and the cost is high. In addition, since the focal length is fixed even when an aspherical lens is used, when a variable focal length optical system is manufactured, the distance between the lens groups must be mechanically adjusted by combining several lenses. For this reason, in the case of a solid lens, aberration is low only at one specific focal length due to the characteristics of the lens, and aberration increases when the focal length is changed. Currently, since these aberrations are compensated using lenses with a fixed focal length, sacrifices such as volume and speed are inevitable in designing an optical system.

On the other hand, a representative method that can change focus without mechanical movement is a method using a liquid lens. Here, the liquid lens is a technology capable of manufacturing a lens using a liquid and changing the focal length by changing the surface curvature of the lens.

Because liquid lenses change their focus at high speed, they can overcome the limitations of conventional optical systems composed of solid lenses, so various companies such as Optotune, Corning Varioptic, and Bosch are forming the variable focus lens market.

As a driving method of such a liquid lens, there are typically an electrowetting method, a hydraulic method, and the like. In the case of a liquid lens of the electrowetting method, focus can be adjusted at high speed, but because it can be manufactured only with a small lens due to its operating characteristics, a hydraulic method is advantageous in order to implement a liquid lens of various sizes. In the case of a hydraulic liquid lens, the focus is adjusted by injecting liquid to change the shape of the surface film corresponding to the lens surface.

Despite these advantages, a variable focus liquid lens has not been widely used, and the main reason is a reliability problem due to aberration. Liquid lenses that are currently commercially available basically have a spherical surface because they use the surface shape of the liquid as it is, and thus, aberrations are considerably higher than that of solid lenses. In addition, since the shape of a liquid may change, the shape of the liquid changes under the influence of gravity, and when the liquid lens is used upright, a large y-axis coma aberration occurs. Accordingly, there is a disadvantage in that image deterioration occurs due to performance degradation due to such aberration and cannot be widely used in a field requiring a high-quality image.

Accordingly, there is a demand for a lens with less aberration while maintaining the high-speed focus variable characteristic of the conventional liquid lens.

The technical problem to be achieved by the present invention is to provide a variable focus liquid lens capable of controlling aberration with little aberration while maintaining a high-speed focus variable characteristic.

A variable focus liquid lens according to one feature of the present invention,

A chamber for accommodating a liquid serving as a lens in a hydraulic liquid lens; A lower substrate mounted in the chamber to seal a lower portion of the liquid; A surface film mounted in the chamber to cover the upper portion of the liquid; A first elastic film mounted in the chamber to apply pressure to the liquid; And a driving unit for driving the first elastic film.

Here, the driving unit includes a voice coil for focus adjustment and a magnet for a voice coil mounted in the chamber to drive the first elastic film by supplying a driving current.

In addition, the variable focus liquid lens, the second elastic film mounted in the chamber to apply a tension to the surface film; And a voice coil mounted in the chamber and configured to drive the second elastic film by supplying a driving current.

In addition, the second elastic film is composed of two elastic films, the aberration correction liquid is accommodated in the space formed by the two elastic films and the chamber, and one of the two elastic films is the voice for adjusting aberration. Driven by a coil and a magnet for voice coil to pressurize the aberration correction liquid, and the other elastic film of the two elastic films other than the one elastic film is pressed by the aberration correction liquid to apply tension to the surface film. .

In addition, the surface film is formed in a circular shape, and is formed to decrease in thickness from the center to the edge of the surface film.

In addition, the surface film has the same refractive index as that of the liquid.

In addition, the surface layer, the first elastic layer, and the second elastic layer are made of a polymer-based polydimethylsiloxane (PDMS) material.

In addition, the thickness and shape of the surface film are adjusted according to the intensity of the driving current supplied to the focus control voice coil.

In addition, as the intensity of the driving current supplied to the voice coil for focus adjustment increases, the surface film becomes more convex, so that the focal length of the liquid lens is shorter.

In addition, the strength of the tension applied to the surface film is controlled according to the strength of the driving current supplied to the voice coil for adjusting the aberration.

In addition, when the surface film is formed in a circular shape, it is possible to control the strength of the tension applied to the edge of the circular surface film to be different for each position.

In addition, when the liquid lens is erected so that the surface film is in a vertical state, driving supplied to the voice coil for adjusting aberration so that the tension applied to the lower edge of the surface film is greater than the tension applied to the upper edge of the surface film The current is controlled.

In addition, the chamber is formed in a circular shape, the lower substrate is formed in a circular shape to seal a lower portion of the circular chamber, the surface film is formed in a circular shape to seal the upper portion of the liquid, and the first elastic film is It is formed in a ring shape to pressurize from the bottom.

According to the present invention, when a system for variable focal length is manufactured, an efficient aberration can be controlled with a small number of lenses, and since no mechanical movement is required, the entire optical system can be remarkably miniaturized.

In addition, since the aberration can be removed only by controlling the surface film, the manufacturing cost can be drastically reduced.

In addition, by improving the optical properties of the existing liquid lens, it replaces the solid lens of the existing optical system to make the optical design flexible, and it can be applied to applications equipped with functions such as time division shooting and real-time focus tracking, which are impossible with the existing solid lens have.

1 is a plan view of a variable focus liquid lens according to an embodiment of the present invention.
FIG. 2 is a front cross-sectional view of the variable focus liquid lens shown in FIG. 1 based on AA′.
FIG. 3 is a diagram showing a focus control principle of the liquid lens shown in FIG. 2, and shows a case in which the focal length is long due to low pressure.
FIG. 4 is another diagram showing a focus control principle of the liquid lens shown in FIG. 2, and shows a case in which the focal length is short due to high pressure.
5 is a diagram illustrating an optical path of parallel rays according to the presence or absence of aberration of a general lens.
6 is a view showing a principle of adjusting the aberration of the liquid lens shown in FIG. 2, (a) is a diagram showing a state before aberration adjustment, and (b) is a view showing a state after aberration adjustment.
7 is a view showing a form before aberration adjustment when a variable focus liquid lens is erected according to an exemplary embodiment of the present invention.
8 is a view showing a form after aberration adjustment when a variable focus liquid lens is erected according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary. In addition, terms such as "... unit", "... group", and "module" described in the specification mean a unit that processes at least one function or operation, which can be implemented by hardware or software or a combination of hardware and software. have.

Hereinafter, a variable focus liquid lens according to an embodiment of the present invention will be described with reference to the drawings.

1 is a plan view of a variable focus liquid lens according to an embodiment of the present invention, and FIG. 2 is a front cross-sectional view of the variable focus liquid lens shown in FIG. 1 based on AA′.

1 and 2, a liquid lens 100 according to an exemplary embodiment of the present invention is a hydraulic liquid lens, and is accommodated in a ring-shaped chamber 105 to serve as a lens. The circular surface film 102 covering the upper part of 101), the circular lower substrate 106 sealing the lower part of the liquid 101, the ring-shaped elastic film 103 and voice coil 104 used for aberration control , It includes a ring-shaped elastic film 110 and a voice coil 111 and a magnet 112 for a voice coil used for focus adjustment.

The liquid 101 serving as a lens is surrounded by the chamber 105, the surface film 102, the elastic films 103 and 110, and the lower substrate 106 and is accommodated in the chamber 105.

The ring-shaped elastic membrane 103 is supported by the chamber 105, and the surface membrane 102 is inserted and supported between the elastic membranes 103.

The elastic film 103 is formed so that the surface where the surface film 102 is not in contact with the chamber 105 accommodates the aberration correction liquid 107.

The liquid 101 and the surface film 102 have the same or similar refractive indices to minimize diffuse reflection or additional optical aberration.

In the case of the surface layer 102, a material such as a polymer-based polydimethylsiloxane (PDMS) having a low elastic modulus is used. At this time, the surface layer 102 is formed so that the center portion of the lens 100 is thick and thinner toward the edge. In this way, when the thickness of the surface film 102 is different, in particular, when the thickness of the center portion is thicker than the edge, when the same hydraulic pressure is applied, the surface film 102 of the lens 100 swells in the shape of an aspherical lens. It becomes possible to climb.

Since the elastic film 110 for adjusting focus and the elastic film 103 for adjusting aberration must also use a property of bending according to hydraulic pressure, a polymer-based material such as PDMS may be used.

FIG. 3 is a view showing the principle of focusing the liquid lens shown in FIG. 2, showing a case where the focal length is long due to low pressure, and FIG. 4 is another diagram showing the principle of focusing the liquid lens shown in FIG. 2 , This indicates a case where the focal length is short due to high pressure.

Referring to FIG. 3, in the case of focus adjustment, when the elastic film 110 is bent in a direction applying pressure to the liquid 101 by using the voice coil magnet 112 and the focus control voice coil 111, the liquid ( Pressure is applied to 101, and as a result, the surface film 102 covering the upper portion of the liquid 101 swells. At this time, the focal length changes according to the degree of swelling of the surface layer 102, which can be freely deformed. That is, in the case of FIG. 3, when the driving current supplied to the voice coil 111 is low so that a low pressure is applied to the liquid 101, the pressure applied by the elastic film 110 is weak, and the surface film 102 swells. The smaller the degree, the longer the focal length.

On the other hand, referring to FIG. 4, when the driving current supplied to the voice coil 111 is high so that a high pressure is applied to the liquid 101, the pressure applied by the elastic film 110 increases, resulting in a large amount of the surface film 102. It swells up and shortens the focal length.

As described above, in the embodiment of the present invention, the degree of bending of the elastic film 110 is adjusted by using the magnet 112 for voice coil and the voice coil 111 for focus adjustment, so that the pressure applied to the liquid 101 is adjusted accordingly. Thus, the focal length of the lens 100 can be adjusted. That is, a liquid lens 100 capable of variable focus may be provided.

On the other hand, when indicating the performance due to the aberration of the lens, as shown in Fig. 5, the wavefront error rate is measured for each location, the wavefront error is calculated as RMS (Root M0ean Square) value, and the ratio to the wavelength is calculated to be less than λ/14 When it becomes, it is said to be'the anhydrous level'.

In the case of a general hydraulic type liquid lens, since a lens surface film having a constant thickness is used, aberrations are minimized only at a specific focal point, and aberrations are greatly increased as the focal length is varied. In addition, when the lens is erected due to gravity, the liquid is focused to the lower part of the lens, which causes the wavefront to be distorted, and the light rays passing through the lens do not collect at one point, resulting in aberration.

6 is a view showing the principle of aberration adjustment of the liquid lens shown in FIG. 2, (a) is a diagram showing a state before aberration adjustment, and (b) is a diagram showing a state after aberration adjustment.

Referring to (a) of FIG. 6, as described with reference to FIG. 4, by applying a high pressure to the liquid 101 using a magnet 112 for voice coil and a voice coil 111 for focus adjustment, the surface film 102 After focusing is performed so that the focal length is shortened by swelling, the aberration can be controlled by changing the thickness and shape of the surface film 102.

Referring to FIG. 6B, in the case of aberration control, the elastic membrane 103, specifically the elastic membrane 103-1, is aberration using the voice coil magnet 112 and the aberration control voice coil 104. When the correction liquid 107 is bent in a direction in which pressure is applied, pressure is applied to the aberration correction liquid 107, which causes the elastic film 103-2 to bend in the form of applying tension to the surface film 102. The thickness and shape of the film 102 may be modified.

At this time, the tension applied to the surface film 102 is adjusted by adjusting the magnitude of the voltage applied to the voice coil 104 for aberration adjustment, and as a result, the aberration can be freely adjusted. That is, a liquid lens 100 capable of adjusting aberration may be provided.

In the above case, the surface film 102 of the liquid lens 100 is removed in the horizontal direction. Thus, a case where the outer side of the ring-shaped elastic film 103 is controlled equally centered on the center portion of the surface film 102 has been described. That is, it means the case where the wavefront of the liquid lens 100 formed by the surface layer 102 is not twisted.

However, as shown in FIG. 7, when the liquid lens 100 is erected, that is, when the surface film 102 is placed in a vertical direction, the liquid 101 is pulled downward by gravity and the surface film ( The shape of the lower part of 102) swells more and becomes thinner than the upper part, resulting in a large y-axis coma aberration.

Therefore, in this case, as shown in FIG. 8, the aberration control voice coil 104-1 positioned at the upper part of the liquid lens 100 and the aberration control voice coil 104-2 positioned at the lower part of the liquid lens 100 When different currents are supplied to each of the aberration correction liquids 107-1 and 107-2 located at the lower and upper portions, different hydraulic pressures are applied to each of the upper and lower portions of the surface film 102. Different tensions can be applied to each part.

By using this, when the liquid lens 100 is erected, a large amount of current is supplied to the voice coil 104-1 for aberration correction located at the upper part to cause a lot of deformation of the elastic film 103-11, and the lower part If a small amount of current is supplied to the voice coil 104-2 for aberration correction located in the elastic film 103-21 so that the deformation of the elastic film 103-21 occurs only a little, as a result, the aberration correction liquid 107-1 located in the upper part and the lower part are A high tension is applied to the upper part of the surface film 102 due to the pressure difference between the located aberration correction liquid 107-2, and a low tension is applied to the lower part, so that aberration due to gravity is applied even though the surface film 102 is erected. Can be controlled. That is, even when the liquid lens 100 is erected, the wavefront of the liquid lens 100 formed by the surface film 102 is formed by differently adjusting the tension of the upper part and the lower part applied to the surface film 102 By preventing twisting, it is possible to prevent aberration caused by the rays passing through the lens not gathering at one point.

Meanwhile, when the circular surface layer 102 is erected, the tension applied to the edge of the circular surface layer 102 at 360 degrees may be different from each other. Therefore, the voltage applied to the ring-shaped aberration correction voice coil 104 must be set in advance in order to apply tension to each of the 360-degree edges of the surface film 102 according to the design shape or characteristics of the liquid lens 100. It will be easily understood by those of ordinary skill in the art.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (13)

A chamber for accommodating a liquid serving as a lens in a hydraulic liquid lens;
A lower substrate mounted in the chamber to seal a lower portion of the liquid;
A surface film mounted in the chamber to cover the upper portion of the liquid;
A first elastic film mounted in the chamber to apply pressure to the liquid; And
A driving unit for driving the first elastic film;
A second elastic film mounted in the chamber to directly apply tension to the surface film in order to directly deform the shape of the surface film; And
A voice coil for adjusting aberration that is mounted in the chamber and drives the second elastic film to directly apply tension to the surface film by supplying a driving current
Variable focus liquid lens comprising a. The method of claim 1,
The driving unit,
Comprising a focus adjustment voice coil and a magnet for a voice coil mounted in the chamber to drive the first elastic film by supplying a driving current,
Variable focus liquid lens. delete The method of claim 2,
The second elastic membrane is composed of two elastic membranes,
A liquid for correcting aberration is accommodated in the space formed by the two elastic films and the chamber,
One of the two elastic membranes is driven by the aberration adjusting voice coil and the voice coil magnet to pressurize the aberration correction liquid,
The elastic film other than the one of the two elastic films is pressed by the aberration correction liquid to apply tension to the surface film,
Variable focus liquid lens. The method of claim 4,
The surface film is formed in a circular shape, the focus variable liquid lens formed so as to decrease in thickness from the center to the edge of the surface film. The method of claim 5,
The surface film has the same refractive index as the liquid,
Variable focus liquid lens. The method of claim 5,
The surface layer, the first elastic layer, and the second elastic layer are made of a polymer-based polydimethylsiloxane (PDMS) material,
Variable focus liquid lens. The method of claim 2,
Adjusting the thickness and shape of the surface film according to the intensity of the driving current supplied to the focus control voice coil,
Variable focus liquid lens. The method of claim 8,
As the intensity of the driving current supplied to the focus adjusting voice coil increases, the surface film becomes more convex, so that the focal length of the liquid lens becomes shorter,
Variable focus liquid lens. The method of claim 2,
The strength of the tension applied to the surface film is controlled according to the strength of the driving current supplied to the voice coil for adjusting the aberration,
Variable focus liquid lens. The method of claim 9,
When the surface film is formed in a circular shape, it is possible to control the strength of the tension applied to the edge of the circular surface film to be different for each position,
Variable focus liquid lens. The method of claim 11,
When the liquid lens is erected so that the surface film is in a vertical state, the driving current supplied to the voice coil for adjusting aberration is higher so that the tension applied to the lower edge of the surface film is greater than the tension applied to the upper edge of the surface film. Controlled,
Variable focus liquid lens. The method of claim 1,
The chamber is formed in a circular shape, the lower substrate is formed in a circular shape to seal the lower part of the circular chamber, the surface film is formed in a circular shape to seal the upper portion of the liquid, and the first elastic film contains the liquid in the lower part. Formed in a ring shape to pressurize in,
Variable focus liquid lens.

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