TW200533957A - Variable optical element - Google Patents

Abstract

The invention provides an optical element (204) having a chamber (208) with an entrance window (209), an exit window (210). The chamber comprises two substantially immiscible fluids (212, 213) that are in contact over a meniscus (214). At least one of the entrance window (209) or exit window (210) comprises a surface with a curvature (217,219) that is in contact with one of the fluids. The Abbe-number of the material of this at least one of the entrance and exit windows (209, 210) has a substantial difference with the Abbe-number of the fluid being in contact with the surface having a curvature. By selecting and tuning several optical parameters such as radius, refractive index and Abbe numbers related to these windows and fluids it is possible to design a substantially achromatic optical element or optical lens system.

Description

200533957 IX. Description of the invention: [Technical field to which Dianming belongs] The present invention relates to a variable optical element including a first fluid and a second fluid in contact with a meniscus. Lens System 'pertains to imaging systems including such optical lens systems, and to methods of designing such variable optical elements, lens systems, and optical imaging systems. [Prior art]

A variable lens is a device in which one or more properties of the lens can be adjusted in a controlled manner, such as changing the focal length or position of the lens. The general development trend of the image sensor of the camera group is its continuous resolution

increase. Initially, it was a low-resolution sensor, such as a 100k-pixel CIF image sensor and a 300k-pixel VGA image sensor. At present, there are high-resolution megapixel image sensors. These higher resolutions not only require the focusing function of the optical lens system in order to be able to use high resolution over the entire object distance range (for example, 10 ° to infinity), they also require a lens system including at least two aspherical lenses To meet other optical parameter requirements, such as those related to aberrations. ^ International Patent Application No. WC > Na 938G discloses a kind of electrowetting lens enclosed by a curved lens as a result group of a variable lens system. The applied voltage controls the shape of the surface between the two fluids of the electrowet lens and thus the optical power of the electrowet lens can be controlled. This ‘hunting’ uses this electrowetting lens in the imaging system, and the variable meniscus diameter can meet the 7 meniscus including Zhou Yanben, Qiu ’, so it can eliminate the defocus of the image. Since the meniscus of the wet lens 100100.doc 200533957 will be wpa &, ^, the spheroid is spherical, so it will not eliminate aberrations, such as slitting Adeland, shame aberration, deformation and Spherical aberration

use. Because of the limited number of optical surfaces, the known electrowetting lens has limited potential for magnification, flat field, and aberration reduction. Therefore, this module is only suitable for low-resolution cameras, such as CIF and VGA. For cameras with higher resolution sensors, such as VGA image sensors at 500 k pixels, M pixel and other Lu Xun's XGA image sensor and megapixel device, this performance can not meet the needs. In U.S. Patent Application No. 20001 / 〇17985, a camera lens stack is disclosed that includes an electrowetting lens with flat entrance and exit windows, and includes a difference between before and after the electrowetting lens. Lens group. Focusing is performed by moving the-lens group. The electrowetting lens has a zoom function. It has no effect on the improvement of other optical properties. None of the above disclosures can solve the problem of eliminating chromatic aberration, which is required to achieve excellent optical color correction of the imaging lens system. Eliminating chromatic aberration is to reduce the dispersion optical power of the optical system. Dispersive optical power is due to the dependence of the refractive index of the material of the optical element on the wavelength of light. The py shell number v can express this wavelength dependence. ηΜ-η (λα) ⑴ where nU ,.) is 弋 = 587.6 nm, heart = 486 ″ nm and clip = 656 3 nm at a wavelength of 4. . Dispersion must be well corrected for higher optical quality. Conventional lens systems use grating structures that are easily blurred or expensive double-lens components for color correction. 100130.doc 200533957 ~%% The chromatic aberration can be eliminated by combining a common refraction lens and a diffractive lens. For a complaint lens, the two elements forming the lens usually have substantially the same refractive index = and different Abbe numbers. In order to eliminate chromatic aberration, these two elements are selected ^ Equation: ΚΙ K2-+-= Vi Vi2 Learn power! 〇 2 and Abbe number Vmv2, so that these parameters meet the following formula: (2) Elimination of refraction Another method of chromatic aberration of the lens is to increase the Abbe number of the diffractive lens by only relying on Putian +% ,,, and °. The number depends on the wavelength range used in the application. For camera mode and I $ 夕 ， 士 &一; m 3 452 wide, and the required wavelength # circle " Kebei 4 has a fixed value. Second, two methods for providing a lens system to eliminate chromatic aberration are not suitable for a wet lens. This is because in the "electric private", the mirror first learns the power of the two fluids ^ ♦ the radius of the lunar surface-Jie and Ma: #, cultural and cultural, where the radius of the meniscus depends on the applied The above-mentioned methods are only applicable to lenses with fixed optical power. European Patent Application No. EP 04100100.9 No. 2: Unknown (PHNLG4GGG8) is proposed as follows: Achromatic

Mf lens. It was revealed that by adjusting the optical properties of the liquids involved (eg Abbey, yr, etc.), such as mixing or dissolving carefully selected substances in these liquids, the eccentricity is not uniformly eliminated. The fluid-based variable return lens constitutes a lens system capable of eliminating chromatic aberration. For example, in order to eliminate the interface between these fluids, the refractive indices η and Abbe number V of the fluids "i" and "η" must follow the following relationship: 100130.doc 200533957% -1 For electrowetting lenses with flat entrance and exit window surfaces, this is just enough to make the fluid-fluid interface eliminate chromatic aberration. For electrowetting lenses with curved populations and solid exit surfaces, this can lead to sub-optimal achromatic properties. It is an object of the present invention to provide a variable lens system having substantially achromatic properties. [Summary of the invention] The object of the present invention is achieved by an optical element, wherein the optical element has one to one, the chamber has an entrance window, an exit window, and a longitudinally extending passage: the optical axis of the chamber, A first fluid and a second fluid, the third IL body and the second fluid are in contact on a meniscus extending laterally across the optical axis, 'these fluids are essentially immiscible fluids, the inlet window or outlet The window has included a surface that is in contact with one of the fluids of the second fluid or the second fluid, the surface has a curvature, and the Abbe number of the at least one of the materials in the inlet and outlet windows and the contact has the curvature. The Abbe number of the fluid on the surface is substantially different. When the curved window surface is substantially equal to the Abbe number of the contact fluid, it is impossible to use the interface to eliminate chromatic aberration of the optical element or the entire optical lens system. If the curved window surface is substantially different from the Abbe number of the fluid in contact, the optical properties can be used in the overall design to achieve an optical lens system that substantially eliminates chromatic aberration. The final overall design of an optical lens system is usually the result of optimization of all aspects of imaging to meet, for example, the resolution, field of view, maximum principal ray angle, and optical aberrations (such as distortion, spherical aberration, and chromatic aberration) System 100130.doc 200533957 specifications. Therefore, it is necessary to adjust the optical properties of the fluid and lens materials involved by, for example, selecting appropriate lens materials or mixing or dissolving carefully selected substances in a fluid, so that the entire optical lens system can substantially eliminate chromatic aberration, And avoid using expensive traditional achromatic methods. When the entrance and / or exit window of the electrowetting lens allows the use of curved surfaces, these curvatures can also be adjusted according to the overall optical design of the system to optimize other φ aberrations, such as distortion, spherical aberration, or field curvature . For example, the curved surface can be spherical or aspherical. [Embodiment] FIG. 1 schematically shows an optical lens system according to the present invention. The optical lens system (200) includes two lens groups 201 and 202 and an aperture 203 between the first and second lens groups. The first lens group 201 includes a variable lens, such as an electrowetting lens 204, and functions as a variable focal length lens. The second lens group 202 uses the lens 220 to determine the optical magnification so that the size of the image matches the size of the image sensor 205 located behind the optical lens system. In addition, it also reduces the principal ray angle by the flat field lens 206. A transparent cover 207, such as a flat parallel plate, is used to cover the image sensor 205. The electrowetting lens 204 has a chamber 208 having an entrance window 209 and an exit window 210 and an optical axis 211 extending longitudinally through the chamber. The chamber contains a first fluid 21 3 and a second fluid 212 that are in contact on a meniscus 214 that crosses the optical axis laterally. The radius of curvature of the surface of the entrance window 217 that is in contact with the first fluid 213 has the same sign as the curvature of the meniscus 214 between the? In addition, the curvature of the surface of the outlet window 219 that is in contact with the second fluid 212 has the same sign as the curvature of the meniscus 214 between the first and second fluids. This reduces the height. The windows and the lenses may be made of glass, plastic or other suitable materials. The two fluids 212 and 213 used are essentially immiscible fluids. The first fluid 2 is an electrically insulating fluid, such as silicone oil or olefin (herein referred to as an oil), and the second fluid 212 is a conductive fluid, such as water containing a salt solution. The two fluids preferably have the same density so that the lens is independent of its direction when operating, that is, it does not depend on the effect of gravity on the fluid. According to the requirements of the optical system, it can also be designed according to the following methods, that is, the first stream system is electrically insulated, and the second stream system is conductive fluid. The first-electrode 215 in the chamber is usually a cylinder with a radius of between m2 and 20 mm, but according to the shape and geometry of the chamber, the 电极 -electrode = also has other shapes' such as a conical shape. The electrode us can be electrically insulated from these fluids by an insulating coating, such as poly-xylene_n coated with a hydrophobic top coating of AF-1600. A second electrode 216 (usually ring-shaped) is disposed at the end of the chamber, in this case near the exit window. This second electrode is configured to be at least partially connected to a second fluid 212. The connection may be a direct connection, or it may be a capacitive coupling via a thin insulation layer. When no voltage is applied to the electrodes 215 and 216, the fluids come into contact on the meniscus 214 having a curvature. By applying a voltage to the electrodes, the meniscus can be changed to have a smaller or larger radius of curvature. In addition, according to the configuration of the chamber and the configuration of the electrodes, multiple shapes can be realized: lunar surface. 3 When at least one of the entrance or exit windows uses curved surfaces, the surfaces of the optical element 100130.doc -10- 200533957 may participate in the overall optical design. The curvature of these windows may allow an additional number of degrees of freedom in optical design to optimize the optical performance of the optical lens system. It is possible to adjust the curvature of these windows by applying aspherical surfaces, and eliminating chromatic aberrations by electrowetting lenses, lens groups using them, or even the entire optical lens system to perform aberration correction. This optical element may be used in A-systems that can include more lenses with optical power. It is an object of the present invention that the optical element is used not only as an adjusting or zooming device, but also as an element for reducing chromatic aberration of other elements in an optical lens system. The difference in refractive index between the curved window and the material in contact with the fluid provides the interface with some learning power. A substantially equal refractive index of the two materials results in the interface having substantially no optical power. However, in the above two cases, the difference in Abbe number will result in different optical power due to different wavelengths. The difference in optical power caused by different wavelengths can be used to correct the chromatic aberration of the system. The L # camera lens is designed to use a positive lens, which is made of glass plastic and has a positive radius and contacts the air. Air under normal conditions has a high Abbe number of approximately 90. This only has a positive effect on the color difference. For example, the use of a buried lens-lens interface with a suitable interface radius and refractive index and Abbe number that matches the design in a doublet lens can cause adverse effects on compensation. The number of glasses and plastics that can be used is limited 'and using a doublet lens is not cost effective. -In the present invention, a combination of the optical parameters of the fluid and the optical properties of the window material is used to obtain a cost-effective optical lens system that substantially eliminates chromatic aberration. The optical lens system may include only the optical element, or the I00i30.doc 200533957 optical element and one or more refractive or diffractive elements. Generally, depending on the choice of the oil used as the fluid, the refractive index of the oil may vary between 1.25 and 1.65. Similarly, depending on the type and amount of salt added, a salt solution used as another fluid may have a refractive index that varies between ^^ and 丨 ·%. Similarly, the use of additives in the oil or saline solution can alter the abeloitic of the fluid. This means that it is possible to adjust the optical parameters of the applied fluid within a wide range to meet the design of chromatic aberration.

In order to be able to have sufficient freedom in selecting a suitable lens material and fluid in the design of an optical lens system, it is preferable to allow a wide range of refractive indices. For example, this can lead to a substantial difference in refractive index of the materials used for windows and fluids. The requirement for eliminating chromatic aberration in the formula (3) can also be expressed as: Here Δν is the difference between the Abbe number of the material reading 1 and Δη is the difference between the refractive indices of the materials η and i. Allowing a substantial difference in refractive index also requires a substantial difference in the Abbe number of the window and the fluid 'to optimize the design of an electrowetting lens that substantially eliminates chromatic aberration. It is also possible to choose materials that optimize windows, fluids and bends to substantially eliminate the chromatic aberrations of the entire optical lens system. In this case, Example >, the requirements given in all surface adjustment equations in the optical lens system. The requirements for the uniform design of the Hf mirror are: y ^ L, v -ij such as 丨 -1) where K i is the optical power, and the refractive index and Abbe number existing in the optical system are different.

Vi is the Abbe number of the conventional lens element i, and j calculates the sum of all fluid meniscus. The system of the first fluid is Hj and V ", the refractive index of the second fluid and Abbe's 100130.doc -12- 200533957 are respectively 111 + 1 and \ ^ ·, ^ α Jd, ν ′ · M, and the dome The radius of the face is Ri. Because there is a large difference between the surface with a rough song and the Abbe number in contact with the fluid, it is easier to correct the color difference of the device or system. It also allows the use of smaller radii for surfaces with optical power. Therefore, the difference between the window with a right strand from the surface of Shu Gong curved surface and the Abbe number in contact with the fluid is preferably greater than 5. The difference between a window with a 4-curved surface and an Abbe number in contact with the fluid greater than 10 is more preferable. Figure 1 shows an example of a design according to the invention. It is a f / 2.8, f = 3 97 mm autofocus camera lens with a field of view of 66 degrees, an entrance pupil of 瞳 _, and a height of 6.5 mm. It is used in combination with a megapixel image sensor. All lenses (209, 21, 22, and 20) have aspherical surfaces to optimize the optical quality of the image. The meniscus 214 is essentially spherical. The closed plastic lenses 209 and 21 of the electrowetting lens 204 have an Abbe number of 55.8 and a refractive index of about 1532 at a wavelength of 56 nm. Conductive fluid • 212 includes saline, which has an Abbe number of 38 and a refractive index of 1376 at a wavelength of 56 nm, while the first non-conductive fluid 213 (which is a silicone oil) has an Abbe number of 28 and a wavelength of 560 nm Everywhere! · Refractive index of 552. By properly selecting the lens radius, the optical system can substantially eliminate chromatic aberration. FIG. 2 shows the wavefront aberrations of the optical lens system according to the above design. In the figure, for the three wavelengths of 490 nm, 560 nm & 625 nm, the wavefront aberration W in micrometers is plotted against the normalized entrance pupil coordinates and graphs, respectively. In FIG. 2a, it is displayed for a field angle of 0 degrees, and in FIG. 2 ', it is displayed for a field angle of about 33 degrees. 100130.doc -13-200533957 in the vertical direction of the two figures has a maximum scale of 50 microns. These figures show that the aberrations of different wavelengths have the same trend, and the difference of aberrations between different wavelengths is small enough to obtain an optical lens system that substantially eliminates aberrations. Figure 3 shows the calculated modulus of the polychromatic optical transfer function of the optical lens system based on the above design. It is the result of averaging three corresponding wavelengths of 490 nm, 560 nm, and 625 nm. These modulus and Py and Py The number of lines per millimeter of a digital field angle with a direction up to 33 degrees is a function of function. It shows two groups of lines 301 and 302. The group of lines 30 is 20, and the polychromatic optical transfer function in the direction of "degrees". The group of lines 30 is a multicolored optical transfer function of the Px directions of 0, 10, 20, 29, and 33 degrees and the directions of the angles of 0 and 10 degrees. It shows that modulations up to 75 lines / mm are sufficient for megapixel imaging applications, such as cameras used in mobile phones. In the above example design, all surfaces of both the entrance and exit windows have surface curvatures so that aberrations such as distortion and spherical aberration, and homogeneity can be reduced. Depending on the overall system requirements, it is also possible that only a single surface of the entrance or exit window has curvature to achieve a sufficiently low aberration level and a sufficiently low chromatic aberration. Fig. 4A shows the use of a variable focal length image capturing device 421, which uses the optical lens system according to the present invention. It is possible to obtain measurement signals from the image sensor Erjie 405, such as the focus signal, the image sensor in #. 〇5 The technology used is widely used in cameras using image sensors. The 4 test signal is used as the input signal of the voltage driver 422. The output of this voltage driver is connected to the electrodes 415 and 416 of the electrowetting lens 404 of the optical lens system to control the shape of the meniscus 414. Figure 4B shows an example using integration 100130.doc 200533957. Other integration locations are also available. -By adjusting the optical properties of the fluids and lens materials involved, it is possible to make electrowetting lenses substantially eliminate chromatic aberration and avoid the use of expensive traditional methods of eliminating chromatic aberration. This adjustment can be achieved, for example, by selecting a suitable material for the lens, or by mixing or dissolving a carefully selected substance in a fluid. It is obvious to those skilled in the art that by considering other optical interfaces, this method can also be used to make a lens system including such an electric lens substantially eliminate the difference. This optical element is very suitable for learning money and films for camera applications. For example, these camera applications can be movie or still photo cameras, or mobile phone cameras that can take movies or still photos. You Xuekou and women, at the mouth of the machine, the need for a small size, high light ~ shell, low energy consumption and durable devices: Second, no mechanical moving parts, such as focus and zoom parts, so The invention of the optical element, the light of the piece and the rust. The use of optical elements according to the present invention for lens money and materials can meet these needs. Although the above description is about a camera that swallows a cell phone ... for a small action camera system (such as for other optical systems (such as microscopy), the present invention can also be used to reduce aberrations and heights. In optical storage applications,

u ^, the need for X-ray wavelength item retrieval and recording systems is increased. This is due to the need of 4 brothers, such as ⑶, Wu and 5: 糸, "take and record a variety of discs. For example, all The invention described can be used in 100130.doc '15- 200533957 for wavelength-dependence caused by other optical elements in optical systems, and specific embodiments and examples of M-lens elements using electrohydrogen

Wen bowed the shape of the moon. Of course, other methods of changing the meniscus opening between two fluids along 2 + + X are considered to be within the scope of the present invention

The pump is configured with a conical electrode configured with Α π, J ^ to change the shape and position of the meniscus in a controlled manner.

Month, the present invention may be applied to a fluid-based lens, and the lens is operated by adjusting the bending position without adjusting the shape. [Brief Description of the Drawings] FIG. 1 schematically shows an optical lens system according to the present invention. ° Figures 2A and 2B show the wavefront aberrations designed by the optical lens system according to the present invention. Fig. 3 shows the optical transfer function versus the modulus of different wavelengths designed according to the optical lens system of the present invention.

The compensation is applied by aberrations. Fig. 4, including Figs. 4A and 4B, shows a variable focal length image capturing device including an optical lens system according to a specific embodiment of the present invention. [Description of main component symbols] 200 201 202 203 204 205 Optical lens system Lens group Lens group Aperture Electro-wet lens Image sensor 100130.doc -16-200533957

206 207 208 209 210 211 212 213 214 215 216 217 219 220 400 404 405 414 415 416 421 422 423 Flat field lens transparent cover chamber entrance window exit window optical axis second fluid first fluid meniscus first electrode second electrode Curvature curvature lens optical lens system electrowetting lens image sensor meniscus electrode electrode zoom image capture device voltage driver mobile phone W) 〇130.doc -17-

Claims (1)

200533957 10. Scope of patent application: 1. An optical element (204) having a room (208) having an entrance window (209), an exit window (210), and a light extending longitudinally through the room Axis (2 π); the chamber includes a first fluid (2 13) and a second fluid (212) in contact with a meniscus (214) extending through the optical axis, the fluids being essentially Immiscible fluid -At least one of the entrance or exit window includes a surface (217, 219) in contact with one of the first or second fluids, the surface having a curvature;-and the entrance window and the exit The Abbe-number of the material of the at least one window in the window is substantially different from the Abbe-number of the fluid contacting the surface having curvature. 2. If the optical element of the request, the difference between the ferrites is greater than that of Bu. 3. If the optical element of the request, the difference between the abbe numbers is greater than 10. 4. If requested, the optical element is essentially an achromatic optical element. 5-An optical lens system comprising the light of any one of the preceding claims-an optical lens system comprising an optical element as claimed in the above! The optical lens system is substantially achromatic Optical lens system. : An optical imaging device including an optical element such as item 2, 3, or 4. 8. An optical component including a photon lens system such as item 6, which is also required to be read. 6. An item including, as requested, Item 7 or 7 sΑ, you, or 7 or 8 of ^ imaging device mobile phone. 100130.doc