CN101685171A - Mechanically Driven Refractive-Diffractive Hybrid Zoom Liquid Lens - Google Patents

Abstract

A mechanically driven refraction-diffraction hybrid zoom liquid lens, including a substrate frame, and also includes a substrate and a transparent elastic film whose periphery is embedded in an annular groove inside the substrate frame and sealed with the substrate frame. The substrate is a diffractive surface substrate, and the substrate The sealed cavity formed by the transparent elastic film is filled with a filling liquid, and the sealed cavity communicates with the cavity of the control piston. The invention solves the technical problem in the background art that the common liquid lens has no degree of design freedom and cannot perform aberration optimization on a single liquid lens. In the present invention, the plane substrate of the liquid lens is directly used as a diffractive optical surface, and the design freedom of aberration correction is provided for the liquid lens without increasing the weight and volume of the liquid lens and without affecting the structure and stability of the liquid lens. According to the requirements of imaging and zooming, different diffraction surface parameters can be reasonably designed, and the image quality optimization design of the liquid lens can be carried out according to the needs, so as to improve the imaging quality of a single liquid lens.

Description

Mechanically Driven Refractive-Diffractive Hybrid Zoom Liquid Lens

technical field

The invention relates to a liquid zoom lens, in particular to a mechanically driven refraction-diffraction hybrid zoom liquid lens.

Background technique

The liquid zoom lens is a new type of optical element based on the principle of bionics in the world. It mainly includes the variable focus lens using the change of the contact angle of the electrowetting fluid and the variable focus lens based on the change of the surface curvature of the filled liquid. They have wide The tunable range, strong zoom ability, smooth zoom, low cost, easy processing and other characteristics have a good application prospect.

Ordinary liquid lenses, whether it is a variable-focus lens that uses the change of the contact angle of the electrowetting fluid or a variable-focus lens based on the change of the surface curvature of the filled liquid, according to the aberration equation, once the required optical power is determined, the surface curvature of the lens or two The curvature of the interface between two immiscible liquids is then determined. Therefore, when the required optical power is determined, a single liquid lens itself does not have the freedom to correct aberrations, which makes the lens unable to image clearly during the imaging process. When a liquid lens is used in the design of a zoom system, since the liquid lens itself cannot correct aberrations, if the system is required to image clearly, the system will be complicated and the number of lenses will increase, which is not conducive to the miniaturization and dexterity of the zoom system.

Referring to FIG. 1 , an existing common mechanically driven liquid lens is mainly composed of a base glass plate 111 , a filling liquid 112 , a transparent elastic film 113 , a frame 114 , a cavity body 116 and a piston 115 . It generally uses a stepping motor or air pressure, hydraulic pressure, etc. to drive the piston 115 to move, so that the volume distribution of the filling liquid 112 in the cavity body 116 changes, causing the curvature radius R of the surface of the transparent elastic film 113 to change, so that the mechanically driven liquid lens The focal length f changes. The change of focal length f satisfies the following equations:

$\mathrm{<span\; class="notranslate">\; \&Phi;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; ;</span>$

$\mathrm{<span\; class="notranslate">\; \&Delta;V</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\sqrt{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; +</span>\sqrt{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; ;</span>$

Wherein, Φ is the focal power of the liquid lens, f is the focal length of the liquid lens, n is the refractive index of the liquid 112 filled in the cavity body 116, R is the radius of curvature of the surface of the transparent elastic film 113, r ₀ is the effective passage of the liquid lens The radius of the light aperture, ΔV is the volume change caused by the movement of the piston 115 . Corresponding to a certain optical power Φ, since the base glass plate 111 on one surface of the mechanically driven liquid lens is a plane, the radius of curvature R of the transparent elastic film 113 on the other surface must be constant, so that the required optical power Φ can be realized. Therefore, the degree of freedom for image quality optimization in optical design is zero.

In recent years, the research on this type of element has mostly focused on the verification of the imaging principle and the lens structure and stability. There have been no research reports on the improvement and perfection of the lens imaging quality.

At present, Philips, Samsung, Lucent Technology Co., Ltd., etc. have made rapid progress in the design and research of liquid lenses. Some research institutions, such as Florida Central University, have also carried out research on mechanically driven liquid lenses, mainly including liquid The structural form of the lens, the filling liquid, the control method, etc. However, as a single variable focus element, how to correct the aberration of the liquid lens, improve the imaging quality of the lens, and obtain high-quality imaging quality with the smallest weight and volume have not been reported so far. Domestic University of Shanghai for Science and Technology, Tsinghua University, etc. have also carried out research on liquid lenses in recent years, but most of them are researches on the imaging mechanism and manufacturing process of liquid lenses, and there are no reports on improving the imaging quality of a single liquid lens.

Contents of the invention

The purpose of the present invention is to provide a mechanically driven refraction-diffraction hybrid zoom liquid lens, which solves the technical problem in the background art that ordinary liquid lenses have no design freedom and cannot perform aberration optimization on a single liquid lens.

Design scheme of the present invention is as follows:

A mechanically driven refraction-diffraction hybrid zoom liquid lens, including a substrate frame 214, and also includes a substrate 211 and a transparent elastic film 213 whose periphery is embedded in an annular groove 216 inside the substrate frame 214 and sealed with the substrate frame 214. The sealing cavity 217 formed by the substrate 211 and the transparent elastic film 213 is filled with the filling liquid 212, and the sealing cavity 217 communicates with the cavity of the control piston 215; the special feature is that the substrate 211 is the diffractive substrate.

The base of the above-mentioned diffractive surface substrate may be a glass material substrate or an optical plastic substrate.

The above-mentioned filling liquid 212 in the sealed cavity 217 is a transparent liquid that is incompatible with the transparent elastic film 213 and does not undergo chemical reactions.

The filling liquid 212 in the above-mentioned sealed cavity 217 can be water or oil.

The present invention has the following advantages:

1. The degree of freedom in the design of liquid lenses is increased, so that a single liquid lens can realize achromatic and spherical aberration.

2. The present invention uses the plane base of the liquid lens directly as the diffractive optical surface, and provides the design freedom of aberration correction for the liquid lens without increasing the weight and volume of the liquid lens and without affecting the structure and stability of the liquid lens. According to According to different imaging and zoom requirements, different diffraction surface parameters can be reasonably designed, and the image quality optimization design of the liquid lens can be carried out according to the needs, so as to improve the imaging quality of a single liquid lens.

3. The present invention directly integrates the diffractive optical element into the liquid lens substrate, so that the liquid lens can be applied to the design of a miniature and smart zoom system, and has the characteristics of good imaging quality, small size, light weight, simple manufacture, and easy control.

4. Adopting the present invention can make the zoom optical system have a smaller volume and weight, making it possible to realize a perfect imaging zoom system by simply using one or two refraction-diffraction hybrid liquid lenses.

5. It can be widely extended to various systems that have high requirements on imaging quality and strict requirements on system size, which can ensure the miniaturization of the system.

Description of drawings

FIG. 1 is a schematic structural diagram of a conventional mechanically driven liquid lens.

Fig. 2 is a schematic diagram of the system structure of the refraction-diffraction hybrid mechanically driven liquid lens of the present invention.

FIG. 3 is a schematic diagram of a modulation transfer function (MTF) curve of a conventional mechanically driven liquid lens at a short focal length.

FIG. 4 is a schematic diagram of the modulation transfer function (MTF) curve of the refraction-diffractive hybrid mechanically driven liquid lens at a short focal length according to the present invention.

FIG. 5 is a schematic diagram of a modulation transfer function (MTF) curve of a conventional mechanically driven liquid lens at a long focal length.

6 is a schematic diagram of the modulation transfer function (MTF) curve of the refraction-diffractive hybrid mechanically driven liquid lens at a long focal length according to the present invention.

Fig. 7 is a schematic diagram of the change of the focal length of a common mechanically driven liquid lens at different wavelengths.

Fig. 8 is a schematic diagram of the focal length variation of the refraction-diffraction hybrid mechanically driven liquid lens at different wavelengths according to the present invention.

Description of drawings: 111-base glass plate, 112-filling liquid, 113-transparent elastic film, 114-frame, 115-piston; 116-cavity; 211-substrate, 212-filling liquid, 213-transparent elastic Membrane, 214-substrate frame, 215-control piston, 216-groove, 217-sealed cavity.

Detailed ways

In the present invention, the ordinary flat glass substrate in the existing ordinary liquid lens is designed as a diffractive optical element, that is, a diffractive surface substrate, and a diffractive optical surface is added by using a diffractive optical element, and a phase function of a binary surface is introduced:

$\mathrm{<span\; class="notranslate">\; \&phi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; )</span>$

The introduction of the binary phase function makes the formation of the Seder aberration sum of the liquid lens into the following form:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \{</span>{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; [</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 32</span>}\mathrm{<span\; class="notranslate">\; m\&lambda;</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \{</span>\frac{{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \}</span>$

S _III = H ² (φ _r +φ _d ) = H ² φ

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; IV</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>$

S _V =0

Among them, S _I -S _V are the five aberrations and numbers of the lens, which respectively reflect the size of spherical aberration, coma, astigmatism, field curvature and distortion. φ _r is the optical power borne by the lens shape formed by the filling liquid; φ _d is the optical power borne by the diffractive optical surface; y is the distance from the intersection point of the marginal ray and the lens to the optical axis; n is the refractive index of the filling liquid; H is the Lagrangian invariant; C _r and C _d are the conjugate coefficients of the lens shape and the diffraction surface formed by the filling liquid, respectively, which are determined by the incident and outgoing aperture angles when the light passes through the lens shape or the diffraction surface formed by the filling liquid; m is the corresponding diffraction order (usually m=1 if not specified); λ is the corresponding wavelength; A ₂ is the quartic term coefficient in the phase function of the binary surface, that is, the fourth-order aspheric coefficient.

After the design of the diffractive optical surface is added to the mechanically driven liquid lens system, a fourth-order aspheric coefficient A ₂ appears in the sum of Sieder aberrations. This aspheric coefficient gives the liquid lens system a degree of design freedom, enabling aberration-optimized design of a single liquid lens. The fourth-order aspheric coefficients can be used for spherical aberration correction of liquid lenses. At the same time, due to the negative dispersion characteristics of the diffractive surface, it is also possible to realize the achromatic aberration of the mechanically driven liquid lens.

In the present invention, the diffractive optical element is directly integrated on the base of the liquid lens, that is, the diffractive optical surface is used as a main structural component of the liquid lens. This method can provide aberration correction for the liquid lens without changing the weight, size, and stability of the liquid lens. Design freedom, so that the image quality optimization design of the liquid lens can be carried out according to the needs, and the imaging quality of the liquid lens can be improved. The invention makes it possible to realize a perfect imaging zoom system by simply using one or two refraction-diffraction hybrid liquid lenses. According to different imaging and zoom requirements, different diffraction surface parameters can be reasonably designed.

2 is a schematic diagram of the structure of the system using a refraction-diffraction hybrid mechanically driven liquid lens according to the present invention. There is an annular groove 216 inside the substrate frame 214, and the periphery of the substrate 211 and the transparent elastic film 213 are embedded in the annular groove 216. And it is sealingly connected with the substrate frame 214 . The transparent elastic film 213 adopts an optically transparent elastic film, which is required to be immiscible with the filling liquid 212 and have no chemical reaction. The sealed cavity 217 formed by the substrate 211 and the transparent elastic film 213 is filled with a filling liquid 212 , and the filling liquid 212 is generally a transparent liquid that is incompatible with the transparent elastic film 213 and does not undergo a chemical reaction, such as water or oil. The sealed cavity 217 communicates with the cavity of the control piston 215 . The substrate 211 is a diffractive surface substrate, and the diffractive surface substrate is a diffractive optical element. Specifically, a glass material substrate or other optical material substrates, such as optical plastics, can be used. The diffractive surface substrate of the present invention can partially eliminate the spherical aberration and primary chromatic aberration of the refraction-diffraction hybrid mechanically driven liquid lens, so that the refraction-diffractive hybrid mechanically driven liquid lens can obtain a more perfect image on the image plane.

The comparison of the modulation transfer function (MTF) between the focal length change of the refraction-diffraction hybrid liquid lens of the present invention and the common liquid lens during the focal length change process is shown in Figs. 3, 4, 5 and 6. It can be seen that after adding the diffraction surface, the modulation transfer function (MTF) of the system at different focal lengths is significantly improved, and the imaging quality is optimized.

See Figures 7 and 8 for the comparison of the chromatic aberration between the focal length change of the refraction-diffractive hybrid liquid lens of the present invention and the common liquid lens during the focal length change process. It can be seen that after the diffraction surface is added, the focal length change curves of the system overlap well at the three wavelengths, and the chromatic aberration of the system is significantly reduced.

Claims (4)

1. mechanical driven hybrid refractive-diffractive zooming liquid lens, comprise base panel frame (214), also comprise substrate (211) and transparent elastic film (213) that periphery is embedded in the inboard annular recess (216) of base panel frame (214), is tightly connected with base panel frame (214), be filled with filling liquid (212) in the seal chamber (217) that described substrate (211) and transparent elastic film (213) constitute, described seal chamber (217) is connected with the cavity of control piston (215); It is characterized in that: described substrate (211) is the diffraction surfaces substrate.

2. mechanical driven hybrid refractive-diffractive zooming liquid lens according to claim 1 is characterized in that: described diffraction surfaces substrate is glass material substrate or optical plastic substrate.

3. mechanical driven hybrid refractive-diffractive zooming liquid lens according to claim 1 and 2 is characterized in that: the filling liquid (212) in the described seal chamber (217) is immiscible and the transparency liquid of chemical reaction do not take place with transparent elastic film (213).

4. mechanical driven hybrid refractive-diffractive zooming liquid lens according to claim 3 is characterized in that: the filling liquid (212) in the described seal chamber (217) is water or oil.

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