JP4997945B2 - Liquid lens array - Google Patents

Description

The present disclosure relates to a liquid lens array , and more particularly, to a liquid lens array capable of improving transmittance and light collection rate.

  2. Description of the Related Art Conventionally, there is a variable focus liquid lens that changes a focal length by using a change in an interface between two liquids whose wettability is changed by applying a voltage. In this conventional variable focus liquid lens, as shown in FIG. 1A, a method of centering the liquid by forming a recess has been proposed (see, for example, Patent Document 1).

  As shown in FIG. 1A, the liquid lens 1 includes a rib 13, a rib 14, a lower electrode 15, a lower electrode 16, an insulating film 17, a nonpolar liquid 18, in a space between the transparent substrate 11 and the transparent top plate 12. A polar liquid 19, an upper electrode 20, and an upper electrode 21 are formed. In addition, the upper electrode 20 and the upper electrode 21 of the liquid lens 1 are connected to the lower electrode 15 and the lower electrode 16 through a power source 31 and a switch 32. That is, when the switch 32 is turned on, the voltage of the power source 31 is applied between the upper electrode 20 and the upper electrode 21 and the lower electrode 15 and the lower electrode 16. Application of this voltage changes the wettability of the polar liquid 19, changes the shape of the interface between the nonpolar liquid 18 and the polar liquid 19, and curves into a convex lens shape. Due to the shape of this interface, the light passing through these two liquid layers is collected. The liquid lens 1 can adjust the curvature of the interface between the two liquids by adjusting the value of the applied voltage, and can change the focal length of the lens.

  In Patent Document 1, it is described that a conical truncated cone or a long narrow groove-shaped recess is formed, and the liquid is centered using the recess. That is, when the liquid lens 1 shown in FIG. 1A is viewed from the transparent top plate 12 side, a circular depression 41 is formed as shown in FIG. 1B.

  In addition, as shown in FIG. 1C, there has also been proposed a method in which conventional variable focus liquid lenses are arranged and used in an array (see, for example, Patent Document 2).

Special Table 2002-540464 JP 2000-356708 A

  For example, as described in Patent Document 1, the liquid lenses 1 having the depressions 41 having a circular upper surface are arranged in an array as described in Patent Document 2, and the liquid as shown in FIG. A lens array 51 is formed.

  At this time, of the light incident on the liquid lens array 51, the light incident on the portion indicated by the dotted line 52 passes through the liquid lens 1-1 to the liquid lens 1-3 as shown by the arrows in FIG. 2A. The light is collected.

  However, since the light incident on the portion of the dotted line 53 out of the light incident on the liquid lens array 51 does not pass through the concave portion 41 of the liquid lens 1-4 to the liquid lens 1-6, it is shown in FIG. 2B. It is blocked as indicated by the arrow. Therefore, the light transmittance of the entire liquid lens array 51 may be reduced.

  Therefore, even if the portion that is not the depression 41 of each liquid lens 1 is also formed of a material that transmits light, the light incident on the portion of the dotted line 53 out of the light incident on the liquid lens array 51 is liquid. Since it does not pass through the concave portion 41 of the lens 1-4 to the liquid lens 1-6, it is not condensed as shown by the arrow in FIG. 2C. Therefore, there is a possibility that the light collection rate of the entire liquid lens array 51 may be reduced.

  The present invention has been made in view of such a situation, and is intended to improve the transmittance and condensing rate of the entire liquid lens array even when the liquid lenses are arranged in an array. .

In one aspect of the present disclosure, liquid lenses that control the optical path of transmitted light at the interface are arranged in an array by controlling the shape of the interface between the polar liquid and the nonpolar liquid in the recess by applying a voltage. To the polar liquid, wherein the liquid lens array has an outer shape of the liquid lens and an upper surface of the depression, and each liquid lens is arranged so as to form a honeycomb structure and provided on each side of the depression. This is a liquid lens array in which the electrodes for voltage application are shared by the adjacent liquid lenses.

The depressions between the adjacent liquid lenses can be formed such that the side surfaces are formed by the same electrodes having the insulating film formed on the surface .

By applying a voltage between the electrodes of the liquid lens, the interface can be changed from a concave shape to a convex shape or a flat surface, or the curvature can be reduced while remaining concave .

By applying a voltage between the electrodes of the liquid lens, the interface can be changed from a flat surface to a convex shape, or the curvature can be increased while remaining convex .

In the present disclosure, a liquid lens having a hexagonal outer shape and an upper surface of the recess that controls the optical path of transmitted light at the interface by controlling the shape of the interface between the polar liquid and the nonpolar liquid in the recess by applying a voltage. However, the electrodes for applying a voltage to the polar liquid, which are arranged so as to form a honeycomb structure and are provided on the side surface of the recess, are shared by adjacent liquid lenses.

  According to one aspect of the present invention, light can be collected. In particular, the transmittance and the light collection rate can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a diagram illustrating a configuration example according to an embodiment of a liquid lens to which the present invention is applied.

  FIG. 3A is a perspective view of a liquid lens to which the present invention is applied. As will be described later, the liquid lens 101 shown in FIG. 3A has a recess 102 formed by a side wall or the like, and is injected into the recess 102 and sealed with a top plate from the upper side in the drawing (for example, A lens that controls the optical path of transmitted light that passes through the liquid lens 101 (indentation 102) in the vertical direction in the drawing using the shape of the interface between a polar liquid having polarity and a nonpolar liquid having no polarity. is there. That is, the liquid lens 101 collects or diverges the transmitted light that passes through the interface between the two liquids. For example, when the interface acts as a convex lens for transmitted light due to its shape (for example, when a voltage is applied to the electrode as described later), the transmitted light is focused at a position corresponding to the shape of the interface. It is condensed to. In addition, for example, when the interface acts as a concave lens with respect to the transmitted light due to its shape (for example, when a voltage is not applied to the electrode as described later), the transmitted light is in a range corresponding to the shape of the interface. To be exhaled. As shown in FIG. 3A, the shape of the liquid lens 101 is a hexagonal column shape whose side surfaces are constituted by six planes. 3A, the side surface of the recess 102 is also composed of six planes (the recess 102 is a hexagonal column-shaped space).

  FIG. 3B is a cross-sectional view of the liquid lens 101 of FIG. 3A when viewed from a direction perpendicular to the side surface. In FIG. 3B, the liquid lens 101 includes a transparent substrate 111, a transparent top plate 112, a side wall 113-1, a side wall 113-2, a lower electrode 115-1, a lower electrode 115-2, an insulating film 117, a nonpolar liquid 118, a polarity. A liquid 119 and an upper electrode 120 are provided.

  The transparent substrate 111 and the transparent top plate 112 are made of, for example, a transparent material capable of transmitting light, specifically, quartz glass or the like. In addition, for example, synthetic resins, specifically, esters such as polyethylene naphthalate, polyethylene terephthalate or polycarbonate, cellulose esters such as cellulose acetate, polyvinylidene fluoride or polytetrafluoroethylene and hexafluoropropylene Consists of fluoropolymers such as copolymers, polyethers such as polyoxymethylene, polyolefins such as polyacetal, polystyrene, polyethylene, polypropylene or methylpentene polymer, polyimides such as polyamideimide or polyetherimide, or polyamides May be.

  The side wall 113-1 and the side wall 113-2 shown in FIG. 3B are a part of six surfaces configured as side surfaces of the liquid lens unit 101 as shown in FIG. It is a member for sealing. The side wall 113-1 and the side wall 113-2 are desirably not dissolved in the nonpolar liquid 118 or the polar liquid 119 and do not react, such as an epoxy resin or an acrylic resin. Is a polymer resin, for example, an epoxy resin or an acrylic resin. In the following description, the side wall 113-1 and the side wall 113-2 are referred to as the side wall 113 when it is not necessary to distinguish between them.

As shown in FIG. 3B, the lower electrode 115-1 and the lower electrode 115-2 are one electrode formed inside the side wall 113 (between the side wall 113 and the insulating film 117). In the following, the lower electrode 115-1 and the lower electrode 115-2 are referred to as the lower electrode 115 when it is not necessary to distinguish them from each other. As shown in FIG. 3A, the side wall 113 is composed of six planes. Similarly to the side wall 113, the lower electrode 115 is also formed so as to surround the side surface of the recess 102 with six planes. The lower electrode 115 is, for example, gold (Au), platinum (Pt), chromium (Cr), aluminum (Al), cobalt (Co), palladium (Pd), bismuth (Bi), silver (Ag), or these It is formed from an alloy. In addition, the lower electrode 115 is a transparent film having both high transparency and conductivity, formed by forming a thin film of tin oxide (SnO ₂ ) with a slight amount of fluorine or a thin film of indium tin oxide (ITO) with a slight amount of antimony. It is good also as a transparent electrode comprised with an electroconductive film.

  The upper electrode 120 is an electrode corresponding to the lower electrode 115 formed on the lower surface of the transparent top plate 112. Since the material of the upper electrode 120 is basically the same as that of the lower electrode 115, detailed description thereof is omitted. As shown in FIG. 3B, a part of the lower surface (near the center) of the upper electrode 120 becomes the upper surface of the recess 102 (the upper surface inside the liquid lens 101).

  As shown in FIG. 3B, the upper electrode 120 and the lower electrode 115 are insulated by at least an insulating film 117. The upper electrode 120 and the lower electrode 115 act in pairs with each other, and a predetermined voltage is applied between both electrodes as necessary. That is, as shown in FIG. 3B, the power supply 131 and the switch 132 are connected between the upper electrode 120 and the lower electrode 115. When the switch 132 is turned on, the voltage of the power source 130 is applied between the upper electrode 120 and the lower electrode 115.

  Note that the shapes and the number of electrodes of the upper electrode 120 and the lower electrode 115 are arbitrary.

  The insulating film 117 is a film formed of a material having low conductivity, such as PVdF or PTFE, which is a fluorine-based polymer, or polyparaxylene or polymonochloroparaxylene, and is transparent to the lower electrode 115. It is formed so as to cover the substrate 111. That is, the surface of the insulating film 117 becomes the side surface and the bottom surface of the recess 102 (the side surface and the bottom surface inside the liquid lens 101). As a material of the insulating film 117, a substance having hydrophobicity (water repellency) and a large dielectric constant is desirable. The film thickness of the insulating film 117 is desirably thinner in order to increase the dielectric constant, but it is desirable that the film is thicker from the viewpoint of insulation strength, and the optimum value is determined by a balance between the two. Note that the insulating film 117 may be at least one layer, and may be formed of a plurality of layers such as two layers or three layers. Further, the insulating film 117 may be formed so as to cover at least the lower electrode 115 (so as to insulate the upper electrode 120 and the lower electrode 115), and does not necessarily cover the transparent substrate 111 as shown in FIG. 3B. There is no need.

  This insulating film 117 contributes to lowering the operating voltage and increasing the driving speed. For example, when this insulating film 117 is not provided, when a voltage is applied, a water decomposition reaction occurs and gas is generated. In order to suppress this gas generation, it is necessary to further provide a reference electrode, to have a three-electrode structure, and to limit the potential of the lower electrode 115 to a potential at which no water decomposition reaction occurs. However, such a three-pole structure complicates the manufacturing process and increases the manufacturing cost. Furthermore, since the control circuit becomes extremely complicated, the circuit scale and manufacturing cost increase, which is not desirable.

  On the other hand, when the insulating film 117 is provided as shown in FIG. 3B, since the upper electrode 120 and the lower electrode 115 are structurally insulated, the decomposition of water does not occur even when a high voltage is applied. Therefore, the liquid lens 101 can be easily structured and controlled, can reduce costs, and can be applied with a high voltage because water does not decompose, thereby reducing the electrowetting force. It can be made larger, and faster focus control is possible.

  For the nonpolar liquid 118, a hydrocarbon-based material such as decane, dodecane, hexadecane, or undecane, silicon oil having a high refractive index, or 1,1-diphenylethylene is used. For the polar liquid 119, for example, an aqueous solution in which an electrolyte such as water, potassium chloride, or sodium chloride is dissolved, methyl alcohol having a small molecular weight, or alcohol such as ethyl alcohol is used.

  Of course, the non-polar liquid 118 and the polar liquid 119 may be liquids other than those described above. For example, the polar liquid 119 may be formed by applying a voltage between the upper electrode 120 and the lower electrode 115. The non-polar liquid 118 is not mixed with each other, and its refractive index is significantly different from the refractive index of the non-polar liquid 120.

  In the liquid lens 101 as described above, the side wall 113 surrounds the side surface of the recess 102 with six planes so that the upper surface of the recess 102 has a hexagonal shape. That is, when viewed from above (from the transparent top plate 112 side), the liquid lens 101 has a hexagonal shape as shown by a solid line in FIG. 3C, and the upper surface of the recess 102 has a hexagonal shape as shown by a dotted line. It has become.

  In such a liquid lens 101, when the switch 132 shown in FIG. 3B is opened (in an OFF state), no voltage is applied between the upper electrode 120 and the lower electrode 115. At this time, the polar liquid 119 and the nonpolar liquid 118 are stabilized in a predetermined shape due to the wettability (surface energy) relationship with respect to each insulating film 117.

  When the switch 132 shown in FIG. 3B is connected (turned on), a voltage is applied between the upper electrode 120 and the lower electrode 115, thereby generating a polarization charge in the direction of the electric field in the insulating film 117. Then, charges are accumulated on the surface of the insulating film 117 (charge double layer state). Due to the presence of this electric charge, a Coulomb force is generated only in the polar liquid 119, for example, in the direction of approaching the vicinity of the insulating film 117. That is, the wettability of the polar liquid 119 with respect to the insulating film 117 is changed by applying a voltage to the electrodes. As a result, for example, the contact area between the polar liquid 119 and the insulating film 117 increases, and the contact area between the nonpolar liquid 118 and the insulating film 117 decreases accordingly. As a result, the interface between the nonpolar liquid 118 and the polar liquid 119 is deformed, and the curvature thereof changes.

  Due to the difference in refractive index between the nonpolar liquid 118 and the polar liquid 119, refraction of the transmitted light that passes through the recess 102 of the liquid lens 101 from the bottom to the top in the figure occurs at the interface between the two liquids. The degree and direction of refraction of the transmitted light varies depending on the incident angle to the interface, the degree of difference in refractive index between the nonpolar liquid 118 and the polar liquid 119, and the like. In other words, depending on whether or not voltage is applied,

As the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119 changes, the optical path of the transmitted light changes.

  In the case of the example shown in FIG. 3B, the switch 132 is in the OFF state, and the center part of the interface between the nonpolar liquid 118 and the polar liquid 119 protrudes from the surrounding part (the upper part in the figure). And stable. In this state, for example, if the refractive index of the nonpolar liquid 118 is higher than the refractive index of the polar liquid 119, the transmitted light is emitted from the liquid lens 101 so as to be condensed. That is, in this case, the interface between the nonpolar liquid 118 and the polar liquid 119 acts as a condenser lens for the transmitted light. Conversely, in the state of FIG. 3B, if the refractive index of the nonpolar liquid 118 is lower than the refractive index of the polar liquid 119, the transmitted light is emitted from the liquid lens 101 so as to diverge. That is, in this case, the interface between the nonpolar liquid 118 and the polar liquid 119 acts as a diverging lens for the transmitted light. As described above, the direction and degree of refraction of transmitted light is affected by which one of the refractive index of the nonpolar liquid 118 and the refractive index of the polar liquid 119 is larger.

  In addition, for example, when the switch 132 is turned on, the central portion of the interface between the nonpolar liquid 118 and the polar liquid 119 further protrudes from the state of FIG. When the curvature of the interface between the liquid and the polar liquid 119 is further increased, the transmitted light is further refracted. For example, if the interface between the nonpolar liquid 118 and the polar liquid 119 acts as a diverging lens with respect to the transmitted light when the switch 132 is in the OFF state, the transmitted light is further reduced by the switch 132 being turned on. It is emitted so as to diverge greatly. On the other hand, if the interface between the nonpolar liquid 118 and the polar liquid 119 acts as a condensing lens with respect to the transmitted light when the switch 132 is in the OFF state, the transmitted light is obtained by turning on the switch 132. Is more intensely condensed and emitted so that its focal length becomes shorter.

  On the other hand, for example, when the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119 is reduced by turning on the switch 132, the refraction of the transmitted light is reduced. That is, if the transmitted light diverges when the switch 132 is in the OFF state, the divergence of the transmitted light is weakened by turning the switch 132 to the ON state. Conversely, the transmitted light is transmitted when the switch 132 is in the OFF state. If the light is collected, the switch 132 is turned on, so that the collected light is weakened (the focal length of the transmitted light is increased).

  Further, for example, when the switch 132 is turned on, the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119 becomes “0”, that is, the interface between the nonpolar liquid 118 and the polar liquid 119 is In the case of a flat surface in the horizontal direction in FIG. 3B, the transmitted light is neither condensed nor diverged. Furthermore, when the switch 132 is turned on, the central portion of the interface between the nonpolar liquid 118 and the polar liquid 119 is recessed with respect to the surrounding portion, that is, the interface between the nonpolar liquid 118 and the polar liquid 119. When the bending direction is reversed, the transmitted light that has been diverged is collected, and the collected transmitted light is diverged.

  As described above, the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119 changes depending on the state of the switch 132, that is, whether or not a voltage is applied to the liquid lens 101, thereby changing the optical path of the transmitted light. .

  In other words, the transmitted light is refracted according to the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119. By the way, since the shape of the upper surface of the recess 102 is a hexagon (polygon), the length from the side wall 113 to the center point of the upper surface differs depending on the position of the side wall 113. If this length is different, the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119 changes depending on the location, and the lens is distorted, so that the transmitted light is out of focus or is not condensed. There is a fear.

  However, in reality, the strong surface tension of the nonpolar liquid 118 and the polar liquid 119 acts to act so that the curvature of the interface is substantially constant, so that the curvature of the interface is substantially the same at any position. It becomes. For example, when a voltage is applied to the upper electrode 120 and the lower electrode 115 so that the contact area between the polar liquid 119 and the insulating film 117 is increased, the polar liquid 119 is shown in FIG. In addition, the insulating film 117 serving as the side surface tends to spread along the hexagonal apex portion on the upper surface of the recess 102. Therefore, the interface between the nonpolar liquid 118 and the polar liquid 119 is curved in an arc shape on each of the six planes of the insulating film 117 serving as side surfaces.

  As described above, the curvature of the interface between the nonpolar liquid 118 and the polar liquid 119 is substantially constant regardless of the position.

  This will be described more specifically. For example, as shown in FIG. 5A, for a vertical cross-section 151 of the indentation 102 through the hexagonal diagonal of the top surface of the indentation 102, the interface 152 between the nonpolar liquid 118 and the polar liquid 119 is It is shown as 5B. At this time, the horizontal length of the cross section 151 (the length of the hexagonal diagonal) is d1, and the contact angle between the insulating film 117 and the interface 152 is θ1.

  Further, for example, as shown in FIG. 6A, the nonpolar liquid 118 and the polar liquid 119 are crossed with respect to a cross-section 153 of the depression 102 in the vertical direction in the figure passing through the midpoints of the two opposing planes of the insulating film 117. The interface 152 is shown as in FIG. 6B. At this time, the horizontal length of the cross section 153 is d2, and the contact angle between the insulating film 117 and the interface 152 is θ2.

  At this time, the contact angle θ1 and the contact angle θ2 are constant, but since the length d1 and the length d2 are different, the curvature radius of the interface may be different between the case of FIG. 5 and the case of FIG. For example, if d1 = 1 mm, d2 = 1.32 mm, and θ = 130 °, the radius of curvature R1 of the interface 152 in the case of FIG. 5 is R1 = 0.78 mm, and the interface in the case of FIG. The curvature radius R2 of 152 is R2 = 1.03 mm. Therefore, the curvature of the interface 152 is almost the same between the case of FIG. 5 and the case of FIG. 6, and there is no significant difference. Furthermore, since the strong surface tension acts on the interface 152 as described above, the influence of the surface tension is dominant on the shape of the interface 152. Therefore, the curvature of the interface 152 is substantially constant regardless of the position.

  That is, the liquid lens 101 having such a hexagonal recess 102 on the upper surface can obtain sufficient lens characteristics as in the case of a conventional liquid lens having a circular recess upper surface. In addition, since the upper surface of the recess 102 is a polygon (hexagon), the upper surface of the outer shape of the liquid lens 101 is also a polygon (hexagon) according to the recess 102, so that the liquid lens 101 is The area of the portion other than the depression 102 when viewed from the upper surface can be reduced, and the depression 102 (lens-shaped interface) can occupy almost the entire area. That is, the liquid lens 101 can improve the transmittance and condensing rate of the transmitted light.

  As shown in FIG. 7, the liquid lenses 101 can be arranged in an array to form a liquid lens array 161. The liquid lens array 161 is a liquid lens constituted by a set of small liquid lenses (liquid lens 101) arranged in an array. At this time, by forming the upper surface of the liquid lens 101 of the liquid lens array 161 into a polygonal shape, as shown in FIG. 7, a fine structure with almost no gap between the lenses can be formed. Therefore, the liquid lens array 161 of FIG. 7 in which the liquid lenses 101 are arranged in an array can improve the transmittance and condensing rate of the transmitted light.

  In the liquid lens array 161 of FIG. 7, for example, the side wall 113 may be omitted, and the lower electrode 115 may be shared by the adjacent liquid lenses 101. In this way, not only can the number of components of each liquid lens 101 be reduced, but also by connecting the power supply 131 to the lower electrode 115 of one liquid lens 101 in the liquid lens array 161, The lower electrodes 115 of all the liquid lenses 101 in the lens array 161 can be connected to the power supply 131, and the number of parts such as wiring can be further reduced.

  Therefore, by doing so, the liquid lens array 161 can be further reduced in size, and the manufacturing cost can be reduced.

  The shape of the upper surface of the recess 102 of the liquid lens 101 may be other than a hexagon as long as it is a polygon. For example, as shown in FIG.

  FIG. 8 is a diagram showing another configuration example according to an embodiment of the liquid lens to which the present invention is applied.

  FIG. 8A is a perspective view of a liquid lens to which the present invention is applied. The liquid lens 201 shown in FIG. 8A has a dent 202 formed by a side wall or the like, similar to the liquid lens 101, and is injected into the dent 202 and is sealed with two liquids sealed with a top plate from the upper side in the figure ( For example, by utilizing the shape of the interface between a polar liquid having polarity and a nonpolar liquid having no polarity, the optical path of transmitted light that passes through the liquid lens 201 (indent 202) in the vertical direction in the figure is controlled. It is a lens. That is, the liquid lens 201 collects or diverges the transmitted light that passes through the interface between the two liquids. For example, when the interface acts as a convex lens for transmitted light due to its shape (for example, when a voltage is applied to the electrode as described later), the transmitted light is focused at a position corresponding to the shape of the interface. It is focused on. In addition, for example, when the interface acts as a concave lens with respect to the transmitted light due to its shape (for example, when a voltage is not applied to the electrode as described later), the transmitted light is in a range corresponding to the shape of the interface. To be exhaled. As shown in FIG. 8A, the shape of the liquid lens 201 is a quadrangular prism shape whose side surfaces are constituted by four planes. Note that, as shown by a dotted line in FIG. 8A, the side surface of the depression 202 is also constituted by four planes (the depression 202 is a square columnar space).

  FIG. 8B is a cross-sectional view of the liquid lens 201 of FIG. 8A when viewed from a direction perpendicular to the side surface. In FIG. 8B, the liquid lens 201 basically has the same configuration as the liquid lens 101, and includes a transparent substrate 211, a transparent top plate 212, a side wall 213-1, a side wall 213-2, a lower electrode 215-1, and a lower electrode. 215-2, the insulating film 217, the nonpolar liquid 218, the polar liquid 219, and the upper electrode 220 are included.

  The transparent substrate 211 is formed of the same material as the transparent substrate 111. The transparent top plate 212 is also made of the same material as the transparent top plate 112. The side wall 213-1 and the side wall 213-2 are a part of four surfaces configured as side surfaces of the liquid lens unit 201 as shown in FIG. 8A, and seal the nonpolar liquid 218 and the polar liquid 219. It is a member. The side wall 213-1 and the side wall 213-2 are formed of the same material as the side wall 113. In the following description, the side wall 213-1 and the side wall 213-2 are referred to as the side wall 213 when it is not necessary to distinguish between them.

  The lower electrode 215-1 and the lower electrode 215-2 are electrodes formed of the same material as the lower electrode 115. As shown in FIG. 8B, the inner side of the side wall 213 (between the side wall 213 and the insulating film 217). ) Is one electrode formed. Hereinafter, the lower electrode 215-1 and the lower electrode 215-2 are referred to as the lower electrode 215 when it is not necessary to distinguish them from each other. As shown in FIG. 8A, the side wall 213 is constituted by four planes. Similarly to the side wall 213, the lower electrode 215 is also formed so as to surround the side surface of the recess 202 with four planes.

  The upper electrode 220 is an electrode corresponding to the lower electrode 215 formed on the lower surface of the transparent top plate 212. The upper electrode 220 is formed of the same material as the upper electrode 120. As shown in FIG. 8B, a part of the lower surface (near the center) of the upper electrode 220 becomes the upper surface of the recess 202 (the upper surface inside the liquid lens 201).

  As shown in FIG. 8B, the upper electrode 220 and the lower electrode 215 are insulated by at least an insulating film 217. The upper electrode 220 and the lower electrode 215 act in pairs with each other, and a predetermined voltage is applied between both electrodes as necessary. That is, as shown in FIG. 8B, the power source 231 and the switch 232 are connected between the upper electrode 220 and the lower electrode 215. When the switch 232 is turned on, the voltage of the power source 230 is applied between the upper electrode 220 and the lower electrode 215.

  Note that the shapes and the number of electrodes of the upper electrode 220 and the lower electrode 215 are arbitrary.

  The insulating film 217 is a film formed of the same material as that of the insulating film 117, is formed so as to cover the lower electrode 215 and the transparent substrate 211, and obtains the same effect as the insulating film 117. Note that the insulating film 217 may be formed so as to cover at least the lower electrode 215 (so as to insulate the upper electrode 220 and the lower electrode 215), and does not necessarily cover the transparent substrate 211 as shown in FIG. 8B. There is no need.

  As the nonpolar liquid 218, a liquid similar to the nonpolar liquid 118 is used. For the polar liquid 219, the same liquid as the polar liquid 119 is used.

  In the liquid lens 201 as described above, the side wall 213 surrounds the side surface of the recess 202 with four planes so that the upper surface of the recess 202 is a quadrangle. That is, when viewed from above (from the transparent top plate 212 side), the liquid lens 201 has a quadrangular shape as indicated by a solid line in FIG. 8C, and the upper surface of the recess 202 has a rectangular shape as indicated by a dotted line. It has become.

  In such a liquid lens 201, when the switch 232 shown in FIG. 8B is open (in an OFF state), no voltage is applied between the upper electrode 220 and the lower electrode 215. At this time, the polar liquid 219 and the nonpolar liquid 218 are stabilized in a predetermined shape because of the wettability (surface energy) relationship with respect to each insulating film 217.

  When the switch 232 shown in FIG. 8B is connected (turned on), a voltage is applied between the upper electrode 220 and the lower electrode 215, as in the case of the liquid lens 101, thereby the insulating film 217. Polarization charges are generated in the electric field direction, and charges are accumulated on the surface of the insulating film 217 (charge double layer state). Due to the presence of this electric charge, a Coulomb force is generated only in the polar liquid 219, for example, in a direction to approach the insulating film 217. That is, the wettability of the polar liquid 219 with respect to the insulating film 217 is changed by applying a voltage to the electrodes. As a result, for example, the contact area between the polar liquid 219 and the insulating film 217 increases, and the contact area between the nonpolar liquid 218 and the insulating film 217 decreases accordingly. As a result, the interface between the nonpolar liquid 218 and the polar liquid 219 is deformed, and the curvature thereof changes.

  Due to the difference in refractive index between the nonpolar liquid 218 and the polar liquid 219, refraction of transmitted light that passes through the recess 202 of the liquid lens 201 from the bottom to the top in the figure occurs at the interface between the two liquids. The degree and direction of refraction of the transmitted light varies depending on the incident angle to the interface, the degree of difference in refractive index between the nonpolar liquid 218 and the polar liquid 219, and the like. That is, the optical path of the transmitted light is changed by changing the curvature of the interface between the nonpolar liquid 218 and the polar liquid 219 depending on whether or not a voltage is applied.

  In the case of the example shown in FIG. 8B, the switch 232 is in the OFF state, and the central part of the interface between the nonpolar liquid 218 and the polar liquid 219 protrudes from the surrounding part (as shown in the upper side in the figure). And stable. In this state, for example, if the refractive index of the nonpolar liquid 218 is higher than the refractive index of the polar liquid 219, the transmitted light is emitted from the liquid lens 201 so as to be condensed. That is, in this case, the interface between the nonpolar liquid 218 and the polar liquid 219 acts as a condenser lens for the transmitted light. 8B, if the refractive index of the nonpolar liquid 218 is lower than the refractive index of the polar liquid 219, the transmitted light is emitted from the liquid lens 201 so as to diverge. That is, in this case, the interface between the nonpolar liquid 218 and the polar liquid 219 acts as a diverging lens for the transmitted light. As described above, the direction and degree of refraction of transmitted light is affected by which one of the refractive index of the nonpolar liquid 218 and the refractive index of the polar liquid 219 is larger.

  Further, for example, when the switch 232 is turned on, the central portion of the interface between the nonpolar liquid 218 and the polar liquid 219 further protrudes from the state of FIG. 8B with respect to the surrounding portion, that is, the nonpolar liquid 218. When the curvature of the interface between the liquid and the polar liquid 219 is further increased, the transmitted light is further refracted. For example, if the interface between the nonpolar liquid 218 and the polar liquid 219 acts as a diverging lens with respect to the transmitted light when the switch 232 is in the OFF state, the transmitted light is further reduced by the switch 232 being turned on. It is emitted so as to diverge greatly. On the other hand, if the interface between the nonpolar liquid 218 and the polar liquid 219 acts as a condensing lens with respect to the transmitted light when the switch 232 is in the OFF state, the transmitted light is transmitted by the switch 232 being turned on. Is more intensely condensed and emitted so that its focal length becomes shorter.

  On the contrary, for example, when the curvature of the interface between the nonpolar liquid 218 and the polar liquid 219 is reduced by turning on the switch 232, the refraction of the transmitted light is reduced. That is, if the transmitted light diverges when the switch 232 is in the OFF state, the divergence of the transmitted light is weakened by turning on the switch 232, and conversely, the transmitted light is transmitted when the switch 232 is in the OFF state. If the light is collected, the switch 232 is turned on, so that the collected light is weakened (the focal length of the transmitted light is increased).

  Further, for example, when the curvature of the interface between the nonpolar liquid 218 and the polar liquid 219 becomes “0” due to the switch 232 being turned on, that is, the interface between the nonpolar liquid 218 and the polar liquid 219 is In the case of a flat surface in the horizontal direction in FIG. 8B, the transmitted light is neither condensed nor diverged. Furthermore, when the switch 232 is turned on, the central portion of the interface between the nonpolar liquid 218 and the polar liquid 219 is recessed with respect to the surrounding portion, that is, the interface between the nonpolar liquid 218 and the polar liquid 219 is When the bending direction is reversed, the transmitted light that has been diverged is collected, and the collected transmitted light is diverged.

  As described above, the curvature of the interface between the nonpolar liquid 218 and the polar liquid 219 changes depending on the state of the switch 232, that is, whether or not a voltage is applied to the liquid lens 201, thereby changing the optical path of the transmitted light. .

  In other words, the transmitted light is refracted according to the curvature of the interface between the nonpolar liquid 218 and the polar liquid 219. By the way, since the shape of the upper surface of the recess 202 is a quadrangle (polygon), the length from the side wall 213 to the center point of the upper surface differs depending on the position of the side wall 213. If this length is different, the curvature of the interface between the nonpolar liquid 218 and the polar liquid 219 changes depending on the location, and the lens is distorted, so that the transmitted light is out of focus or is not condensed. There is a fear.

  However, even in the case of this liquid lens 201, in reality, the strong surface tension of the nonpolar liquid 218 and the polar liquid 219 acts to act so that the curvature of the interface is substantially constant. The curvature of the interface is substantially the same. For example, when a voltage is applied to the upper electrode 220 and the lower electrode 215 so that the contact area between the polar liquid 219 and the insulating film 217 increases, the polar liquid 219 has a surface tension as shown in FIG. In addition, the insulating film 217 serving as the side surface tends to spread along the quadrangular vertex of the upper surface of the recess 202. Therefore, the interface between the nonpolar liquid 218 and the polar liquid 219 is curved in an arc shape in each of the four planes of the insulating film 217 that forms the side surfaces.

  That is, for example, as shown in FIG. 10A, an interface between the nonpolar liquid 218 and the polar liquid 219 with respect to a cross-section 251 of the depression 202 in the vertical direction in the figure passing through the midpoints of the two opposing planes of the side wall 213. 252 is shown as in FIG. 10B. At this time, the horizontal length of the cross section 253 is d3, and the contact angle between the side wall 213 and the interface 252 is θ3.

  Further, for example, as shown in FIG. 11A, the interface 252 between the nonpolar liquid 218 and the polar liquid 219 is about the cross section 253 in the vertical direction in the drawing of the depression 202 passing through the square diagonal line on the upper surface of the depression 202. As shown in FIG. 11B. At this time, the horizontal length of the cross section 253 (the length of the diagonal line of the quadrangle) is d4, and the contact angle between the side wall 213 and the interface 252 is θ4.

  At this time, the contact angle θ3 and the contact angle θ4 are constant, but since the length d3 and the length d4 are different, the curvature radius of the interface may be different between the case of FIG. 10 and the case of FIG. However, as in the case of FIGS. 5 and 6 described above, the difference is not large. Furthermore, since strong surface tension acts on the interface 252 as described above, the influence of the surface tension is dominant on the shape of the interface 252. Therefore, the curvature of the interface 252 is substantially constant regardless of the position.

  In other words, the liquid lens 201 having such a depression 202 having a rectangular upper surface can obtain sufficient lens characteristics as in the case of a conventional liquid lens having a circular depression. In addition, since the upper surface of the recess 202 in the liquid lens 201 is polygonal (square), the upper surface of the outer shape of the liquid lens 201 is also made polygonal (square) in accordance with the recess 202, so that the liquid lens 201 is removed from the upper surface. The area of the portion other than the recess 202 when viewed can be reduced, and the recess 202 (lens-shaped interface) can occupy substantially the entire area. That is, the liquid lens 201 can improve the transmittance and condensing rate of the transmitted light.

  The liquid lenses 201 can be arranged in an array to form a liquid lens array 261 as shown in FIG. The liquid lens array 261 is a liquid lens configured by a set of small liquid lenses (liquid lenses 201) arranged in an array. At this time, by forming the upper surface of the liquid lens 201 of the liquid lens array 261 in a polygonal shape, a fine structure with almost no gap between the lenses can be formed as shown in FIG. Therefore, the liquid lens array 261 in FIG. 12 in which the liquid lenses 201 are arranged in an array can improve the transmittance and condensing rate of the transmitted light.

  In the liquid lens array 261 of FIG. 12, for example, the side wall 213 may be omitted, and the adjacent liquid lenses 201 may share the lower electrode 215. In this way, not only can the number of components of each liquid lens 201 be reduced, but only by connecting the power source 231 to the lower electrode 215 of one liquid lens 201 in the liquid lens array 261, The lower electrodes 215 of all the liquid lenses 201 in the liquid lens array 261 can be connected to the power source 231 and the number of parts such as wiring can be further reduced.

  Therefore, by doing so, the liquid lens array 261 can be further reduced in size, and the manufacturing cost can be reduced.

  A liquid lens array in which liquid lenses as described above are arranged in an array form, for example, a polygon having a top surface with a pentagonal liquid lens and a hexagonal liquid lens in combination to be arranged in an array. You may make it combine the liquid lens of the shape of multiple types made into the shape of these.

  The liquid lens 101 described above is configured so that the shape of the interface between the two liquids of the nonpolar liquid 118 and the polar liquid 119 is changed in accordance with the voltage application between the upper electrode 120 and the lower electrode 115. The shape (curvature) of the interface between the two liquids when no voltage is applied between these electrodes and the magnitude of the voltage applied between these electrodes are both arbitrary.

  That is, for example, when a voltage is applied between the upper electrode 120 and the lower electrode 115 of the liquid lens 101 described above, the interface between the two liquids of the nonpolar liquid 118 and the polar liquid 119 changes from concave to convex. It may be changed, may be changed from a concave shape to a flat surface, may be concave and may have a small curvature, or may be changed from a flat surface to a convex shape. Alternatively, the curvature may be increased while remaining convex.

  The shape (curvature) of the interface between the two liquids and the amount of change are applied between the type, amount, and temperature of the two liquids, the size and shape of the depression 102 (liquid lens 101), and between the electrodes. It is determined by the magnitude of the voltage to be determined.

  Similarly, the liquid lens 201 described above is configured such that the shape of the interface between the two liquids of the nonpolar liquid 218 and the polar liquid 219 changes in accordance with the voltage application between the upper electrode 220 and the lower electrode 215. As in the case of the liquid lens 101, the shape (curvature) of the interface between the two liquids of the nonpolar liquid 218 and the polar liquid 219 when no voltage is applied between these electrodes, and between these electrodes The magnitude of the applied voltage is arbitrary.

  That is, in the case of the liquid lens 201, for example, when a voltage is applied between the upper electrode 220 and the lower electrode 215 of the liquid lens 201 described above, the interface between the two liquids of the nonpolar liquid 218 and the polar liquid 219 is obtained. However, it may be changed from a concave shape to a convex shape, may be changed from a concave shape to a flat surface, may be concave and may have a small curvature, or may be changed from a flat surface to a convex shape. Alternatively, the curvature may be increased while maintaining the convex shape.

  The shape (curvature) of the interface between the two liquids and the amount of change are applied between the type, amount, and temperature of the two liquids, the size and shape of the depression 202 (liquid lens 201), and between the electrodes. It is determined by the magnitude of the voltage to be determined.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a figure explaining the structural example of the conventional focus variable liquid lens. It is a figure explaining the mode of permeation | transmission of the light in the conventional focus variable liquid lens. It is a figure which shows the structural example which concerns on one Embodiment of the liquid lens to which this invention is applied. It is a figure explaining the example of the mode of the interface at the time of applying a voltage in the liquid lens of FIG. It is a figure explaining the curvature of the interface in the liquid lens of FIG. It is a figure explaining the curvature of the interface in the liquid lens of FIG. It is a figure which shows the structural example of the liquid lens array using the liquid lens of FIG. It is a figure which shows the other structural example which concerns on one Embodiment of the liquid lens to which this invention is applied. It is a figure explaining the example of the mode of the interface at the time of applying a voltage in the liquid lens of FIG. It is a figure explaining the curvature of the interface in the liquid lens of FIG. It is a figure explaining the curvature of the interface in the liquid lens of FIG. It is a figure which shows the structural example of the liquid lens array using the liquid lens of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 Liquid lens, 102 Indentation, 111 Transparent substrate, 112 Transparent top plate, 113-1 and 113-2 Side wall, 115-1 and 115-2 Lower electrode, 117 Insulating film, 118 Nonpolar liquid, 119 Polar liquid, 120 Upper part Electrode, 131 power supply, 132 switch, 151 cross section, 152 interface, 153 cross section, 161 liquid lens array, 201 liquid lens, 202 depression, 211 transparent substrate, 212 transparent top plate, 213-1 and 213-2 side wall, 215-1 And 215-2 lower electrode, 217 insulating film, 218 nonpolar liquid, 219 polar liquid, 220 upper electrode, 231 power supply, 232 switch, 251 cross section, 252 interface, 253 cross section, 261 liquid lens array

Claims (4)

By controlling the shape of the interface between the polar liquid and the nonpolar liquid in the recess by applying a voltage, the liquid lens that controls the optical path of the transmitted light of the interface is a liquid lens array,
The outer shape of the liquid lens and the upper surface of the recess are hexagonal, and each liquid lens is arranged so as to form a honeycomb structure,
A liquid lens array in which electrodes for applying a voltage to the polar liquid provided on each side surface of the depression are shared by the adjacent liquid lenses. The liquid lens array according to claim 1, wherein the recesses between adjacent liquid lenses have the same side surface formed by the electrodes having the same surface and an insulating film formed thereon. The liquid lens array according to claim 1 , wherein the interface changes from a concave shape to a convex shape or a flat surface by applying a voltage between the electrodes of the liquid lens, or the curvature remains small while remaining in the concave shape . When a voltage is applied between the electrodes of the liquid lens, the interface changes from a flat surface to a convex shape, or the curvature remains large while remaining convex.
The liquid lens array according to claim 1 .

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