JP2009175539A - Liquid prism and projector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid prism (variable optical axis element) in which the refraction angle of emitting light is made larger with respect to incident light. <P>SOLUTION: The voltage applied between a conductive liquid and electrodes is so controlled in the liquid prism that a liquid boundary plane becomes flat, and the maximum tilt line of the liquid boundary plane passes through two corners which are mostly separated from each other among corners of a vessel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid prism that refracts light using a liquid interface, and more particularly, to a liquid prism configured to drive a liquid interface by electrowetting.

  The liquid prism is an optical element that utilizes the refraction of light at the interface between two liquids or the interface between a liquid and a gas, which have different refractive indexes and are not mixed with each other. The tilt angle and the maximum tilt direction of the interface are driven by electrowetting. Electrowetting is a phenomenon in which an apparent contact angle of a liquid with respect to an electrode is changed by applying a potential difference between the electrode and the liquid (Non-Patent Document 1). By changing the inclination angle and the maximum inclination direction of the interface, the refraction angle and refraction direction of light can be changed. Conventional examples of the liquid prism are described in Patent Document 2, Non-Patent Document 2, and the like. Patent Document 1 describes an example of a projector for a portable device.

JP 2005-148459 Special Table 2006-509263 Frieder Mugele and Jean-Christophe Baret, “Electrowetting: from basics to applications”, J. Phys .: Condens. Matter 17 (2005) R705-R774. Neil R. Smith, Don C. Abeysinghe, Joseph W. Haus, and Jason Heikenfeld, “Agile wide-angle beam steering with electrowetting microprisms”, OPTICS EXPRESS, Vol. 14, No. 14, pp.6557-6563.

  In the liquid prism, the tilt angle and the maximum tilt direction of the interface are changed by electrowetting. However, in electrowetting, the variable range of the contact angle of the liquid surface with respect to the electrode surface is limited. Therefore, there is a limit to the inclination angle of the interface with respect to the optical axis. Therefore, there is a limit to the refraction angle of the outgoing light with respect to the incident light.

  An object of the present invention is to provide a liquid prism (optical axis variable element) capable of increasing the refraction angle of outgoing light with respect to incident light.

In the liquid prism of the present invention, the voltage applied between the conductive liquid and the electrode is controlled so as to satisfy the following condition.
(1) The liquid interface is a plane.
(2) The maximum inclination line of the liquid interface passes through two corners farthest from each other among the corners of the container. Thus, the maximum slope of the liquid interface passes through the two corners of the container but not through the side of the container. When the cross section of the container is a figure having a major axis and a minor axis perpendicular to each other, the liquid interface is a surface obtained by rotating the cross section of the container around the minor axis, and the maximum inclination line of the liquid interface is the cross section of the cross section. It is a line obtained by rotating the major axis around the minor axis.

  According to the liquid prism of the present invention, the refraction angle of outgoing light with respect to incident light can be increased.

  The liquid prism of the present invention will be described with reference to FIG. The liquid prism of the present invention has a container 100, and a conductive liquid 10 and an insulating liquid 11 sealed therein. The conductive liquid 10 and the insulating liquid 11 are in contact with each other at the interface 12. The conductive liquid 10 and the insulating liquid 11 are not mixed with each other and have different refractive indexes.

  The container 100 includes a first surface 101, a second surface 102, and at least three side surfaces (only two side surfaces 103a and 103c are shown in FIG. 1). The optical axis 200 of the liquid prism is set along the central axis of the container 100 passing through the first surface 101 and the second surface 102 as shown.

  The shape of the cross section obtained by cutting the container 100 along a plane perpendicular to the optical axis 200 may be a point-symmetrical figure such as a square, a rectangle, a rhombus, or a polygon, but an astigmatic figure such as a right-angled triangle or an isosceles triangle. It may be. The first surface 101 and the second surface 102 are arranged perpendicular to the optical axis 200. The plurality of side surfaces 103 a and 103 c may be arranged in parallel to the optical axis 200. In this case, the cross-sectional shapes of the containers are all the same when cut along a plurality of surfaces perpendicular to the optical axis. However, the plurality of side surfaces 103 a and 103 c may not be parallel to the optical axis 200. In this case, when the cross-sectional shape of the container is cut along a plurality of planes perpendicular to the optical axis, they are similar to each other but have different dimensions. For example, you may comprise so that the cross section of a container may become small along the direction from the 1st surface 101 to the 2nd surface 102. FIG. An example of the shape of the container will be described later.

  Electrodes (only two electrodes 104a and 104c are shown in FIG. 1) are provided on the inner surfaces of the plurality of side surfaces 103a and 103c, respectively. Insulating films (only two insulating films 106a and 106c are shown in FIG. 1) are provided on the inner surfaces of the electrodes so as to cover the electrodes. Further, a water-repellent film (only two water-repellent films 107a and 107c are shown in FIG. 1) is provided on the inner surface of the insulating film so as to cover the insulating film. When the water repellent film has sufficient insulating properties, the insulating film is unnecessary. A common electrode 105 is provided on the inner surface of the first surface 101. The common electrode 105 is in contact with the conductive liquid 10.

  A power source (only two power sources 108a and 108c are shown in FIG. 1) is connected between the common electrode 105 and the plurality of electrodes 104a and 104c. A voltage is applied between the conductive liquid 10 in contact with the common electrode 105 and the electrodes 104a and 104c by the power source. The contact angle of the conductive liquid 10 with respect to the side surface of the container 100 is changed by electrowetting. By adjusting the voltages from the power supplies 108a and 108c, the contact angle of the conductive liquid 10 on each of the side surfaces of the container 100 can be changed to a desired value. Thus, the inclination angle and the maximum inclination direction of the interface 12 with respect to the optical axis 200 can be set to desired values. As shown in the drawing, the light incident along the optical axis 200 via the second surface 102 is refracted at the interface 12 and is emitted via the first surface 101. The angle formed by the outgoing light 202 with respect to the incident light 201, that is, the refraction angle α depends on the refractive index of the conductive liquid 10 and the insulating liquid 11 and the inclination angle of the liquid interface 12.

  In the liquid prism of this example, the conductive liquid 10 is disposed on the first surface 101 side so as to contact the common electrode 105. That is, the conductive liquid 10 is separated from the insulating liquid 11 and is in contact with the common electrode 105 regardless of the rotation direction and rotation position in the three-dimensional space. , Disposed on the first surface 101 side. In order to arrange the conductive liquid 10 on the first surface 101 side, an arbitrary physical phenomenon, for example, an adhesive force may be used. In this case, as the material of the first surface 101, a material having a large adhesion force of the conductive liquid 10 is selected, and as the material of the second surface 102, a material having a large adhesion force of the insulating liquid 11 is selected.

The material of the constituent member of the liquid prism of this example will be described. The material of the first surface 101 and the second surface 102 may be any material as long as it can transmit the incident light 201 to the liquid prism. For example, when the incident light 201 is visible light, the first surface 101 and the second surface 102 may be made of glass or acrylic. The insulating films 106a and 106c may be formed by depositing SiO ₂ , parylene (trade name) or the like by CVD. The water-repellent films 107a and 107c may be formed by dip-coating or spin-coating CYTOP (trade name) or AF1601 (trade name), which is a fluorine-based material.

  The conductive liquid 10 and the insulating liquid 11 may be liquids that do not cross each other and have different refractive indexes. For example, the conductive liquid 10 may be an aqueous solution in which an electrolyte such as water or potassium chloride is dissolved. The insulating liquid 11 may be an oil such as silicone oil or fluorine oil, or an organic solvent such as decane or dodecane. Further, the conductive liquid 10 and the insulating liquid 11 are materials that transmit the wavelength of the incident light 201, as in the first surface 101 and the second surface 102.

  The features of the present invention will be described in detail with reference to FIG. FIG. 2A is a perspective view showing only the side surface of the container 100 of the liquid prism of this example, and the conductive liquid 10 and the insulating liquid 11 housed in the container. The container 100 of this example has four side surfaces 103a, 103b, 103c, and 103d, and the cross section of the container cut along a plane perpendicular to the optical axis 200 is a quadrilateral. The electrodes 104a, 104b, 104c, 104d, the insulating films 106a, 106b, 106c, 106d, the water repellent films 107a, 107b, 107c, 107d, and the common electrode 105 are not shown.

  The contact angle of the conductive liquid 10 will be described. The four sides of the interface 12, that is, the contact lines where the interface 12 contacts the four side surfaces 103a, 103b, 103c, and 103d are defined as 12a, 12b, 12c, and 12d, respectively. The contact angle of the conductive liquid 10 is defined as the angle formed by the interface 12 and the side surface at the four contact lines of the interface 12. As illustrated, the contact angles of the conductive liquid 10 with respect to the side surfaces 103a, 103b, 103c, and 103d are θa, θb, θc, and θd, respectively. For example, the contact angle θa of the conductive liquid 10 with respect to the side surface 103a is an angle formed by the interface 12 and the side surface 103a in the contact line 12a. When the container 100 is cut by a plane perpendicular to the contact line 12a, the angle formed by the interface 12 and the side surface 103a on the cut surface is the contact angle θa of the conductive liquid 10 on the side surface 103a. Other contact angles θb, θc, and θd are obtained in the same manner.

  Each of the contact angles θa, θb, θc, and θd depends on the relative dielectric constant and thickness of each of the insulating films 106a, 106b, 106c, and 106d and the water-repellent films 107a, 107b, 107c, and 107d. Furthermore, each of the contact angles θa, θb, θc, and θd depends on the voltage applied between the conductive liquid 10 and the electrodes 104a, 104b, 104c, and 104d, respectively.

  FIG. 2B shows a cross-sectional shape of the container 100 cut along a plane perpendicular to the optical axis 200. As shown, the cross section of the container 100 is a diamond having four vertices 14a, 14b, 14c, 14d. The cross section of the container 100 has a short diagonal line 13a along the short axis of the rhombus and a long diagonal line 13b along the long axis, and the optical axis 200 passes through the intersection of both. The angle formed by the two side surfaces 103b and 103c sandwiching the vertex 14b, that is, the vertex angle is β.

  FIG. 2C shows a cross section of the container 100 cut by a plane passing through both the long diagonal 13b of the container 100 and the optical axis 200C. An inclination angle of the liquid interface 12 with respect to a plane perpendicular to the optical axis 200 is φ. The liquid interface 12 is a plane in which the cross section of the container 100 is inclined around a short diagonal line 13a. The maximum inclination line of the liquid interface 12 is a line obtained by inclining the long diagonal line 13b around the short diagonal line 13a. Incident light 201 to the liquid prism enters from the second surface 102 along the optical axis 200 of the liquid prism, is refracted by the liquid interface 12, passes through the first surface 101, and exits from the liquid prism. . The refraction angle of the outgoing light 202 with respect to the incident light 201 is α.

  When voltages are respectively applied to the four electrodes 104a, 104b, 104c, and 104d, the contact angles θa, θb, θc, and θd are changed by electrowetting. That is, the angle φ of the liquid interface 12 with respect to the optical axis 200 can be manipulated by the voltages of the power supplies 108a, 108b, 108c, and 108d. A desired refraction angle α can be obtained by adjusting the angle φ of the liquid interface 12.

According to the present invention, the maximum value of the inclination angle φ of the liquid surface 12 can be made larger than that of a conventional liquid prism. According to the present invention, the liquid interface has the following conditions.
(1) The liquid interface is a plane.
(2) The maximum inclination line of the liquid interface passes through two corners farthest from each other among the corners of the container. Thus, the maximum slope of the liquid interface passes through the two corners of the container but not through the side of the container. When the cross section of the container is a figure having a major axis and a minor axis perpendicular to each other, the liquid interface is a surface obtained by rotating the cross section of the container around the minor axis, and the maximum inclination line of the liquid interface is the cross section of the cross section. It is a line obtained by rotating the major axis around the minor axis.

The conditions necessary for satisfying these two liquid level conditions will be described. In this example, the cross section of the container 100 is a rhombus. Accordingly, the contact angles θa and θb with respect to the two adjacent side surfaces 103a and 103b on both sides of the vertex 14a are equal, and the contact angles θc and θd with respect to the two adjacent side surfaces 103c and 103d on both sides of the vertex 14c are equal.
θa = θb and θc = θd Equation 1

Further, the sum of the contact angles θb and θc for the two adjacent side surfaces 103b and 103c on both sides of the vertex 14b is 180 °, and the sum of the contact angles θa and θd for the two adjacent side surfaces 103a and 103d on both sides of the vertex 14d is 180 °.
θb + θc = θa + θd = 180 ° Equation 2

  Thus, the above-mentioned two conditions are satisfied by setting the contact angle. The relative dielectric constants and thicknesses of the insulating films 106a, 106b, 106c, 106d mounted on the four side surfaces 103a, 103b, 103c, 103d are all equal, and the relative dielectric constants and thicknesses of the water-repellent films 107a, 107b, 107c, 107d. Are all equal. In order for the contact angles on the four side surfaces to satisfy the relationship of Equations 1 and 2, the same voltage may be applied to the electrode 104a and the electrode 104b, and the same voltage may be applied to the electrode 104c and the electrode 104d. Thus, electrowetting on each side surface can be controlled by applying a predetermined voltage to the four electrodes. That is, each contact angle can be adjusted by electrowetting. Thereby, a liquid interface satisfying the above two conditions can be obtained.

  The relationship between the cross-sectional shape of the container and the inclination angle φ of the liquid surface 12 will be described with reference to FIG. The cross section of the container 100 is a quadrilateral, and when the apex angle β is 90 °, 120 °, 150 °, and 180 °, the contact angle θa of the conductive liquid 10 with respect to the side surface 103a and the inclination angle of the liquid interface The relationship of φ was calculated. FIG. 3A is a diagram showing the relationship between the contact angle θa and the inclination angle φ of the liquid interface. The horizontal axis represents the contact angle θa at the side surface 103a, and the vertical axis represents the tilt angle φ of the liquid interface. The minimum value of the contact angle θa is 60 °. That is, the contact angle θa is variable in the range of 60 ° to 180 °.

  It can be seen that when the contact angle θa on the side surface 103a is set to a predetermined value and the apex angle β of the container is larger than 90 °, the inclination angle φ of the liquid interface increases. For example, the contact angle θa is 60 °. When the vertex angle β of the container is 90 °, the inclination angle φ of the liquid interface is 45 °. That is, when the cross section of the container is square and the contact angle θa on the side surface 103a is 60 °, the inclination angle φ of the liquid interface is 45 °.

  However, when the apex angle β of the container is 120 °, that is, when the cross section of the container is rhombus, the inclination angle φ of the liquid interface is 45 ° or more (or 90 °). When the contact angle θa is 90 °, the inclination angle φ of the liquid interface is 0 °. Further, when the tilt angle φ of the liquid interface is a negative value, the liquid interface 12 is tilted from the lower left to the upper right in the cross-sectional view of FIG. 2C.

  FIG. 3B is a diagram showing the relationship between the voltage applied between the conductive liquid 10 and the electrode and the tilt angle φ of the liquid interface. The horizontal axis represents the applied voltage V between the electrode 104a mounted on the side surface 103a and the conductive liquid 10, and the vertical axis represents the tilt angle φ of the liquid interface. The cross section of the container 100 is a quadrilateral, and the relationship between the applied voltage V and the inclination angle φ of the liquid interface was calculated for four cases where the apex angle β was 90 °, 120 °, 150 °, and 180 °. The relationship between the contact angle of the liquid with respect to the electrode surface and the potential difference between the liquid and the electrode is described in Non-Patent Document 1.

  As materials for the insulating films 106a, 106b, 106c, and 106d and the water-repellent films 107a, 107b, 107c, and 107d, materials having no charge may be used, but materials having charges may be used.

  When the insulating films 106a, 106b, 106c, and 106d and the water repellent films 107a, 107b, 107c, and 107d have no charge, the potential difference between the conductive liquid 10 and the electrode, that is, the applied voltage V is the power supply ( In FIG. 1, only two power supplies 108a and 108c are shown. When the power supply voltage is Vb, V = Vb.

  In this example, the water repellent film also serving as an insulating film is a Cytop having a relative dielectric constant of 2.1 and a thickness of 300 nm, and the contact angle θa of the conductive liquid 10 with respect to the side surface 103a when the applied voltage V is zero is 180 °. The interfacial tension between the liquid 10 and the insulating liquid 11 was calculated as 40 mN / m.

  When the insulating films 106a, 106b, 106c, and 106d and the water-repellent films 107a, 107b, 107c, and 107d have electric charges, the applied voltage V is the sum of the potential difference between the insulating film and the water-repellent film and the power supply voltage. equal. When the potential difference between the insulating film and the water repellent film is Vi, V = Vi + Vb. The insulating films 106a, 106b, 106c, 106d or the water repellent films 107a, 107b, 107c, 107d can be formed of electrets. The electret has a charge. Let the electret potential be Vel. The applied voltage V is V = Vel + Vb. When the power supply voltage is zero (Vb = 0), an electret potential is applied between the conductive liquid 10 and the electrode. When the applied voltage V is equal to the electret potential, that is, when the power supply voltage is zero (Vb = 0), it is assumed that the contact angle of the conductive liquid 12 with respect to the side surface is 90 °. When the power supply voltage is zero (Vb = 0), the liquid interface 12 is perpendicular to the incident light 201, and when the power supply voltage is not zero (Vb ≠ 0), the liquid interface 12 is inclined.

  Returning to FIG. 3B again. Regardless of the vertex angle β being 90 °, 120 °, 150 ° or 180 °, there is a voltage at which the inclination angle φ of the liquid interface becomes 0 °. In this example, when the applied voltage is 37.5 volts, the inclination angle φ of the liquid interface is 0 °. The voltage at which the inclination angle φ of the liquid interface becomes 0 ° depends on the relative dielectric constant and thickness of the insulating film and the water repellent film. Further, when the applied voltage V is increased, the tilt angle φ of the liquid interface increases. Furthermore, as the vertex angle β is larger, the increasing rate of the tilt angle φ of the liquid interface with respect to the applied voltage V is larger.

  3A and 3B, it can be seen that the inclination angle φ of the liquid interface can be increased when the apex angle β of the container is larger than 90 °. For example, when the cross section of the container is a square, the rhomboid can increase the inclination angle φ of the liquid interface.

  As long as the above liquid level conditions are satisfied, the cross section of the container may not be square or rhombus. Below, the case where the cross section of a container is not a square or a rhombus is demonstrated.

  FIG. 4 shows a second example of a liquid prism according to the present invention. FIG. 4 shows a cross-sectional shape obtained by cutting the container 100 of this example along a plane perpendicular to the optical axis 200. As shown, the cross section of the container 100 is a quadrilateral having four apexes 14a, 14b, 14c, 14d, but the lengths of the four sides are not the same. The cross section of the container 100 has a short diagonal line 13a connecting the two apexes 14b and 14d and a long diagonal line 13b connecting the two apexes 14a and 14c, and they are orthogonal to each other. The optical axis 200 passes through the intersection of the two. The cross section of the container 100 is a quadrilateral symmetrical with respect to the long diagonal line 13b. Accordingly, the two side surfaces 103a and 103b sandwiching the ridge line passing through the vertex 14a have the same dimension, and the two side surfaces 103c and 103d sandwiching the ridge line passing through the vertex 14c have the same dimension.

  The liquid interface 12 is a plane in which the cross section of the container 100 is inclined around a short diagonal line 13a. The intersecting line of the liquid interface 12 and the plane passing through both the long diagonal line 13b and the optical axis 200 is the maximum inclination line of the liquid interface 12. That is, the maximum inclination line of the liquid interface 12 is a straight line connecting between a ridge line passing through the vertex 14a and a ridge line passing through the vertex 14c.

  The contact angles of the conductive liquid 10 on the four side surfaces are set so as to satisfy the above-described liquid interface conditions. In this example, the above-described Expression 1 is satisfied, but Expression 2 is not satisfied. However, instead of Equation 2, a relationship of θa + θd = θb + θc is established. Thus, in the liquid prism of this example, the inclination angle φ of the liquid interface 12 can be increased.

  FIG. 5 shows a third example of a liquid prism according to the present invention. FIG. 5 shows a cross-sectional shape of the container 100 of this example cut along a plane perpendicular to the optical axis 200. As shown, the cross section of the container 100 is a hexagon having six apexes 14a, 14b, 14c, 14d, 14e, and 14f, but the lengths of the six sides are not the same. The container of this example is obtained by dividing a container having a diamond-shaped cross section shown in FIG. 2 into two and inserting two parallel side surfaces therebetween. The cross section of the container 100 has a diagonal line 13b connecting the two apexes 14a and 14d, and the optical axis 200 passes through the midpoint. The cross section of the container 100 is a hexagon symmetrical with respect to the diagonal line 13b. Accordingly, the two side surfaces 103a and 103b sandwiching the ridge line passing through the vertex 14a have the same dimension, and the two side surfaces 103c and 103d sandwiching the ridge line passing through the vertex 14d have the same dimension. The two side surfaces 103e and 103f on both sides are parallel to each other and have the same dimensions.

  On the cross section of the container 100, an axis 13a passing through the midpoint of the diagonal line 13b and orthogonal to the diagonal line 13b is set. The liquid interface 12 is a plane in which the cross section of the container 100 is inclined around the axis 13a. The intersecting line of the liquid interface 12 and the plane passing through both the long diagonal line 13b and the optical axis 200 is the maximum inclination line of the liquid interface 12. That is, the maximum inclination line of the liquid interface 12 is a straight line connecting the ridge line passing through the vertex 14a and the ridge line passing through the vertex 14d.

  The contact angles of the conductive liquid 10 on the six side surfaces are set so as to satisfy the above-described liquid interface conditions. It is assumed that the side surfaces 103e and 103f are parallel to the optical axis 200. In this case, the contact angle of the conductive liquid 10 with respect to the side surfaces 103e and 103f is set to 90 °. The contact angle of the conductive liquid 10 with respect to the other side surfaces 103a, 103b, 103c, and 103d is set in the same manner as in the example shown in FIG. Thus, in the liquid prism of this example, the inclination angle φ of the liquid interface 12 can be increased.

  Here, the cross section of the container 100 is a hexagon, but it can be a polygon having more sides. In this case, each of the side surfaces 103e and 103f may be constituted by a plurality of side surfaces. For example, by replacing each of the side surfaces 103e and 103f with a triangular prism, the cross section of the container 100 can be an octagon.

  FIG. 6 shows a fourth example of a liquid prism according to the present invention. FIG. 6 shows a cross-sectional shape of the container 100 of this example cut along a plane perpendicular to the optical axis 200. As shown, the cross section of the container 100 is an isosceles triangle having three vertices 14a, 14b, 14c. The container of this example is obtained by cutting the diamond-shaped container shown in FIG. 2 by a plane passing through both the long diagonal line 13b and the optical axis 200C. The two side surfaces 103b and 103c sandwiching the ridge line passing through the vertex 14b have the same dimensions. On the cross section of the container 100, the perpendicular line 13a is lowered from the vertex 14b to the midpoint of the bottom connecting the two vertices 14a and 14c. The optical axis 200 passes through the midpoint of the perpendicular 13a.

  The liquid interface 12 is a plane in which the cross section of the container 100 is inclined around the axis 13a. The maximum inclination line of the liquid interface 12 is a straight line connecting between a ridge line passing through the vertex 14a and a ridge line passing through the vertex 14c. That is, the maximum inclination line of the liquid interface 12 is a contact line where the liquid interface 12 contacts the side surface 103a.

  The contact angles of the conductive liquid 10 on the three side surfaces are set so as to satisfy the above-described liquid interface conditions. It is assumed that the side surface 103a is parallel to the optical axis 200. In this case, the contact angle of the conductive liquid 10 with respect to the side surface 103a is set to 90 °. The contact angle of the conductive liquid 10 with respect to the other side surfaces 103b and 103c is set in the same manner as in the example shown in FIG. Thus, in the liquid prism of this example, the inclination angle φ of the liquid interface 12 can be increased.

  FIG. 7 shows a fourth example of a liquid prism according to the present invention. FIG. 7A shows the top surface of the container 100 of this example. As shown, the upper surface of the container 100 is a diamond having four vertices 14a, 14b, 14c, 14d. The upper surface of the container 100 has a short diagonal line 13a connecting the two vertices 14b and 14d and a long diagonal line 13b connecting the two vertices 14a and 14c, and the optical axis 200 passes through the intersection of both.

  FIG. 7B shows a cross section of the container 100 cut by a plane that passes through both the long diagonal 13b of the container 100 and the optical axis 200. FIG. In this example, the four side surfaces are inclined with respect to the optical axis 200. The cross section of the container 100 cut by a plane perpendicular to the optical axis 200 is a rhombus, but the size of the rhombus changes depending on the cutting position. An inclination angle of the liquid interface 12 with respect to a plane perpendicular to the optical axis 200 is φ.

  On the cross section of the container 100, an axis 13c parallel to the diagonal line 13a is set. The liquid interface 12 is a plane in which the cross section of the container 100 is inclined around the axis 13c. The intersecting line of the liquid interface 12 and the plane passing through both the long diagonal line 13b and the optical axis 200 is the maximum inclination line of the liquid interface 12. That is, the maximum inclination line of the liquid interface 12 is a straight line connecting between a ridge line passing through the vertex 14a and a ridge line passing through the vertex 14c.

  The contact angles of the conductive liquid 10 on the four side surfaces are set so as to satisfy the above-described liquid interface conditions. Thereby, the inclination angle φ of the liquid interface 12 can be increased.

  An example of a liquid prism array according to the present invention will be described with reference to FIG. The liquid prism array of this example includes a plurality of liquid prisms formed on the substrate 110 and wiring 109 connecting them. Each liquid prism includes a container 100 and electrodes 104a to 104d. Inside the container 100, a conductive liquid and an insulating liquid are sealed. In all liquid prisms, the direction of incident light, the angle of refraction, and the direction of outgoing light are the same. That is, in all the liquid prisms, incident light along the optical axis is incident from the first surface and refracted at a predetermined refraction angle, and the emitted light is emitted through the second surface.

  The liquid prism is formed on the substrate 110 by application of semiconductor microfabrication technology. Therefore, the size of the container 100 can be reduced. In addition, it is possible to reduce the mass of the conductive liquid 10 and the insulating liquid 11 that are driving units and increase the response speed of the change in the tilt angle of the liquid interface 12. In this example, since the cross-sectional area of the container 100 is small, the amount of incident light 201 incident on the liquid prism is small. Therefore, if a plurality of liquid prisms are arranged, the total amount of incident light can be increased. In this case, the liquid interfaces of all the liquid prisms are driven in the same direction. Accordingly, the same voltage is applied to the corresponding electrodes in all the liquid prisms. The wiring 109 to all the liquid prisms can be comb-shaped as shown in the figure. When the container 100 is formed on the same substrate, the wiring 109 can be formed on the first surface of the substrate.

  Single crystal silicon can be used for the substrate 110. In the case of single crystal silicon, when the side surface of the container is formed by wet etching, the side surface of the container is formed along the crystal interface. For example, a hole having a diamond shape in cross section shown in FIG. 2A can be formed, and the apex angle β between the two side surfaces is 109.5 °.

  Referring to FIG. 9, the configuration of a projector using a liquid prism according to the present invention is shown. The projector of this example includes a light source 301, a vertical scanning liquid prism 302, a horizontal scanning liquid prism 303, and a housing 300 for housing them. The projector of this example further includes a drive circuit 320 that drives the light source and the liquid prism, and a power source 321. The drive circuit 320 includes an image data conversion circuit 323 that converts the image data 322 into a control signal, a control circuit 324 that outputs a drive signal for the light source and the liquid prism in accordance with an output signal converted from the image signal, and an output signal of the control circuit The light source driving driver 331 for applying a driving voltage to the light source 301 based on the above, and the liquid prism driving drivers 332 and 333 for supplying the driving voltage to the liquid prisms 302 and 303 based on the output signal of the control circuit.

  The emitted light 301a of the light source 301 is scanned in the vertical direction by the vertical scanning liquid prism 302, is scanned in the horizontal direction by the horizontal scanning liquid prism 303, and is raster scanned on the screen. An image is formed by controlling the light amount of the light source 301 in accordance with the scanning position.

  As the light source 301, a semiconductor laser, an LED, or the like can be used. In particular, when an LED is used as the light source 301, an optical system for adjusting the light from the light source is necessary because the divergence angle of the light emitted from the light source is large.

  FIG. 10 shows an example of an optical system that adjusts light from a light source. The optical system of this example includes a light source 301, a condensing lens 304, a vertical scanning liquid prism 302, a horizontal scanning liquid prism 303, a collimating lens 305, and a housing 300. The light emitted from the light source 301 is condensed by the condenser lens 304 and enters the liquid prisms 302 and 303, respectively. Light emitted from the liquid prisms 302 and 303 is narrowed by the collimating lens 305 and emitted as parallel rays.

  Referring to FIG. 11, a configuration of another example of a projector using a liquid prism according to the present invention is shown. Although the projector of FIG. 10 is a single color, the projector of this example can display full color. The projector of this example includes light sources 301A, 301B, and 301C of three colors of red, green, and blue. A horizontal scanning liquid prism 302A and a vertical scanning liquid prism 303A are provided for the red light source 301A. Similarly, a horizontal scanning liquid prism 302B and a vertical scanning liquid prism 303B are provided for the green light source 301B, and a horizontal scanning liquid prism 302C and a vertical scanning liquid prism 303C are provided for the blue light source 301C. Is provided. These three color liquid prisms are housed in a housing 300.

  In the three-color horizontal scanning liquid prisms 302A, 302B, and 302C, the direction of incident light, the refraction angle, and the direction of outgoing light are the same. That is, in the three-color horizontal scanning liquid prism, the incident light along the optical axis is incident from the first surface, refracted at a predetermined refraction angle, and the emitted light is emitted through the second surface. .

  In the three-color vertical scanning liquid prisms 303A, 303B, and 303C, the direction of incident light, the refraction angle, and the direction of outgoing light are the same. That is, in the three-color vertical scanning liquid prism, incident light along the optical axis is incident from the first surface, refracted at a predetermined refraction angle, and emitted light is emitted through the second surface. .

  In this example, the liquid interface angles of the respective liquid prisms are adjusted according to the wavelengths of the light sources 301A, 301B, and 301C so that light from the light sources of the three colors is irradiated to one point on the screen. In this case, an image is formed by light scanning by general raster scanning.

  The example of the present invention has been described above. However, the present invention is not limited to the above-described example, and various modifications can be easily made by those skilled in the art within the scope of the invention described in the claims. Will be understood.

  The liquid prism of the present invention can be used in the field of portable devices.

It is a figure which shows the structure of the liquid prism by this invention. It is a figure explaining the contact angle of the liquid interface of the liquid prism by this invention. It is a figure explaining the relationship between the contact angle or applied voltage of the liquid prism by this invention, and the inclination angle of a liquid interface. It is a figure which shows the structure of the 2nd example of the liquid prism by this invention. It is a figure which shows the structure of the 3rd example of the liquid prism by this invention. It is a figure which shows the structure of the 4th example of the liquid prism by this invention. It is a figure which shows the structure of the 5th example of the liquid prism by this invention. It is a figure which shows the example of the liquid prism array by this invention. It is a figure which shows the structure of the projector using the liquid prism by this invention. It is a figure which shows the structure of the monochromatic light source device of the projector by this invention. It is a figure which shows the structure of the light source device of 3 colors of the projector by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Conductive liquid, 11 ... Insulating liquid, 12 ... Liquid interface, 13a ... Short diagonal of the cross section of a container, 13b ... Long diagonal of the cross section of a container, 100 ... Container, 103a, 103b, 103c, 103d, 103e, 103f ... Side, 104, 104a, 104b, 104c, 104d ... Electrode, 105 ... Common electrode, 106a, 106b, 106c, 106d ... Insulating film, 107a, 107b, 107c, 107d ... Water repellent film, 108a, 108b, 108c, 108d DESCRIPTION OF SYMBOLS ... Power supply, 109 ... Wiring, 200 ... Optical axis, 201 ... Incident light, 202 ... Refraction light, 300 ... Housing, 301 ... Light source, 301a ... Light emitted from light source 14, 301A ... Light source (red), 301B ... Light source ( Green), 301C ... Light source (blue), 302A ... Light source (red) vertical scanning liquid prism, 302B ... Light source (green) vertical scanning liquid Prism, 302C ... Light source (blue) vertical scanning liquid prism, 303A ... Light source (red) horizontal scanning liquid prism, 303B ... Light source (green) horizontal scanning liquid prism, 303C ... Light source (blue) horizontal scanning liquid prism, 304 ... Condenser lens, 305 ... Collimator lens, 320 ... Drive circuit, 321 ... Power supply, 322 ... Image data, 323 ... Image data conversion circuit, 324 ... Control circuit, 331 ... Light source drive driver, 332, 333 ... Liquid prism drive driver

Claims (15)

A first surface through which incident light passes, a second surface through which outgoing light opposite to the first surface passes, at least three side surfaces arranged between the first surface and the second surface, the first surface, A container having an optical axis passing through the second surface; an electrode disposed on each inner surface of the side surface; and a conductive liquid and an insulating liquid which are enclosed in the container and are not mixed with each other and have different refractive indexes; In a liquid prism having a power supply device that changes a potential difference between each of the electrodes and the conductive liquid in order to change a contact angle of the conductive liquid on each of the side surfaces,
In the power supply device, a liquid interface between the conductive liquid and the insulating liquid is a flat surface, and a maximum inclined line of the liquid interface passes through two corners farthest from each other among corners of the container. A liquid prism that changes a potential difference between each of the electrodes and the conductive liquid.   2. The liquid prism according to claim 1, wherein a cross section of the container cut by a plane perpendicular to the optical axis is a quadrilateral having a major axis and a minor axis perpendicular to each other, and the maximum inclination line of the liquid interface is A liquid prism characterized by passing through two corners of the container through which the long axis of the quadrilateral passes.   2. The liquid prism according to claim 1, wherein a cross section obtained by cutting the container along a plane perpendicular to the optical axis is a rhombus having a major axis and a minor axis, and a maximum inclination line of the liquid interface is a major axis of the rhombus. A liquid prism, characterized in that it passes through two corners of the container.   4. The liquid prism according to claim 3, wherein one of the vertex angles of the cross section is 109.5 [deg.].   4. The liquid prism according to claim 3, wherein one of the vertex angles of the cross section is 90 degrees.   6. The liquid prism according to claim 1, wherein a side surface of the container has a taper from the first surface toward the second surface.   2. The liquid prism according to claim 1, wherein a cross section of the container taken along a plane perpendicular to the optical axis is a triangle, and a maximum inclination line of the liquid interface passes through the longest side of the triangle. A liquid prism characterized by passing through the two corners.   2. The liquid prism according to claim 1, wherein a cross section of the container cut by a plane perpendicular to the optical axis is a hexagon, and a maximum inclination line of the liquid interface is the container through which the longest diagonal line of the hexagon passes. A liquid prism characterized by passing through the two corners.   2. The liquid prism according to claim 1, wherein a dielectric film having a predetermined potential is formed on each of the electrodes, and a potential difference caused by the power supply device and the dielectric between each of the electrodes and the conductive liquid. A liquid prism characterized by being provided with a potential difference that is the sum of the potentials of the membrane.   10. The liquid prism according to claim 9, wherein the dielectric film is formed of an electret, and the potentials of the dielectric films are all equal.   10. The liquid prism according to claim 9, wherein a contact angle of the conductive liquid with respect to the side surface is 90 ° when a potential difference by the power supply device is zero. In a liquid prism array having a substrate, a plurality of liquid prisms formed on the substrate, and wiring formed on the substrate,
Each of the liquid prisms includes at least three surfaces disposed between a first surface through which incident light passes, a second surface through which outgoing light on the opposite side of the first surface passes, and the first and second surfaces. A container having an optical axis passing through a side surface, the first surface and the second surface; an electrode disposed on each inner surface of the side surface; and a conductive liquid which is enclosed in the container and does not mix with each other and has a different refractive index. And an insulating liquid, and a power supply device that changes a potential difference between each of the electrodes and the conductive liquid in order to change a contact angle of the conductive liquid on each of the side surfaces,
In the power supply device, a liquid interface between the conductive liquid and the insulating liquid is a flat surface, and a maximum inclined line of the liquid interface passes through two corners farthest from each other among corners of the container. A liquid prism array that changes a potential difference between each of the electrodes and the conductive liquid.   13. The liquid prism array according to claim 12, wherein the substrate is made of single crystal silicon, and one of the vertex angles of a cross section obtained by cutting the container along a plane perpendicular to the optical axis is 109.5 °. Liquid prism array. In a projector having a plurality of light sources, and a horizontal scanning liquid prism and a vertical scanning liquid prism provided in each of the light sources,
Each of the liquid prisms includes at least three surfaces disposed between a first surface through which incident light passes, a second surface through which outgoing light on the opposite side of the first surface passes, and the first and second surfaces. A container composed of a side surface; an electrode disposed on an inner surface of each of the side surfaces; a conductive liquid and an insulating liquid which are sealed in the container and are not mixed with each other and have different refractive indexes; A power supply device that changes a potential difference between each of the electrodes and the conductive liquid to change a contact angle of the conductive liquid;
In the power supply device, a liquid interface between the conductive liquid and the insulating liquid is a flat surface, and a maximum inclined line of the liquid interface passes through two corners farthest from each other among corners of the container. A projector that changes a potential difference between each of the electrodes and the conductive liquid.   The projector according to claim 14, wherein the light from the plurality of light sources is scanned so that the directions of the light emitted from the liquid prism are all the same.

Images