JP2007248985A - Liquid crystal lens and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal lens and electronic equipment loaded with the liquid crystal lens, which can detect a focus point at a sufficiently high speed in practical use by forming a heater electrode for directly heating a liquid crystal layer in an outside area of a phase modulation electrode for changing a refractive index of the liquid crystal lens and maintaining the liquid crystal layer at a required temperature and more. <P>SOLUTION: Pattern electrodes constituting the liquid crystal lens comprise a phase modulation electrode for modulating the phase of a first liquid crystal layer by applying modulation voltage, a heater electrode for directly heating the first liquid crystal layer surrounded and formed around the phase modulation electrode, electrode extraction parts having resistance lower than that of the heater electrode and capable of feeding power to the heater electrode, and an electrode extraction branch end formed on the way of the electrode extraction parts. A temperature detection means for sensing the temperature of the first liquid crystal layer is arranged just above the electrode extraction branch end. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal lens and an electronic device, and more particularly to a liquid crystal lens that has a simple configuration but does not decrease a focal movement speed even in a low temperature environment, and an electronic device including the liquid crystal lens.

  Conventionally, as a focusing mechanism for changing the focal length or focal position of an optical system, a method of focusing by moving a lens has been widely used. However, this method requires a lens driving mechanism, and thus has a drawback that the mechanism is complicated and a lens driving motor requires a relatively large amount of electric power. In addition, there is a drawback that the impact resistance is generally low. Thus, as a focusing mechanism that does not require a lens driving mechanism, a method of focusing by changing the refractive index of the liquid crystal lens has been proposed (for example, see Patent Document 1).

  By the way, as an autofocus (automatic focusing) system of a video camera, information corresponding to blurring of an image is directly extracted from a captured video signal, and a contour detection method is used in which a lens is climbed and controlled to minimize this blurring. Various autofocus devices have been proposed (see, for example, Patent Document 2, Patent Document 3, and Patent Document 4).

  Therefore, when the liquid crystal lens in Patent Document 1 is simply applied to the contour detection method for controlling hill climbing shown in Patent Documents 2 to 5, the response speed of the liquid crystal becomes a problem. As described above, it is known that the nematic liquid crystal filled in the liquid crystal lens has a slow response speed due to an increase in viscosity at a low temperature. In order to increase the response speed of the liquid crystal, the response is performed by an alignment method called bend alignment. A method of increasing the speed is used (see Patent Document 5).

  In addition, as a liquid crystal material filled in the liquid crystal lens, a proposal has been made to use a ferroelectric liquid crystal having excellent high-speed response.

  Furthermore, to maintain the temperature of the liquid crystal layer at a desired temperature even in a low temperature environment, rather than as a liquid crystal lens, a liquid crystal panel heater is provided separately from the panel that heats the liquid crystal panel. There has been proposed a method in which the glass substrate is provided by being provided (see, for example, Patent Document 6).

Japanese Patent No. 3047082 (page 3-5, Fig. 1-4) Japanese Utility Model Publication No. 2-44248 (page 4-10, FIG. 7-11) Japanese Patent No. 2742741 (Page 1-2, Figure 5-7) Japanese Patent Publication No. 1-15188 (page 1-3, FIG. 1-5) JP 61-116329 A (page 2-3, FIG. 1) JP-A-6-208100 (page 2-3, FIG. 1-3)

When focusing by controlling the change in the refractive index of the liquid crystal lens by the hill-climbing control method, the responsiveness of the liquid crystal becomes a problem. Especially at low temperatures, the response speed of the liquid crystal significantly decreases due to the increase in the viscosity of the liquid crystal. Therefore, it takes a long time to detect the focal point. For example, suppose that there are 50 positions of the focus position set in advance for the near-distance view, search for a peak of information corresponding to the blur in a certain direction, and an average of 25 positions is required before the peak is found. Thus, the time required to detect the focal point is compared between the method of moving the lens and the method of using the liquid crystal lens.

  In the method of moving the lens, when the lens is moved to a position corresponding to a certain position and information corresponding to the blur at that time is acquired, the lens is moved to a position corresponding to the next position and information corresponding to the blur is obtained. The operation of obtaining is repeated. In this case, since the processing time per position is as short as 67 milliseconds, for example, the average time required to detect the in-focus point is about 1.7 seconds (= 67 milliseconds / position × 25 positions).

  On the other hand, in a method using a liquid crystal lens, the refractive index distribution of the liquid crystal lens is changed by changing a voltage (drive voltage) applied to the liquid crystal lens in order to drive the liquid crystal lens. Therefore, when a driving voltage corresponding to a certain position is applied to the liquid crystal lens and information corresponding to the blur at that time is obtained, a driving voltage corresponding to the next position is applied to the liquid crystal lens and information corresponding to the blur is again obtained. The operation of obtaining may be repeated.

  In the case of a liquid crystal lens, when the processing time per position is, for example, 100 milliseconds at room temperature (20 ° C.), the average is about 2.5 seconds (100 milliseconds / position × 25 positions) until the focal point is detected. .

  In general, however, the response of the liquid crystal to a change in drive voltage is delayed as the viscosity of the liquid crystal increases at low temperatures. Therefore, it is necessary to wait until the response of the liquid crystal becomes stable after changing the drive voltage. Therefore, at a low temperature (0 ° C.), the processing time per position becomes long, for example, 500 milliseconds, and it takes about 12.5 seconds (500 milliseconds / position × 25 positions) on average to detect the focal point. End up. In this case, since the response speed of the liquid crystal is too slow, it is impractical to mount and operate the liquid crystal lens on an electronic device.

  In order to solve this problem, it is conceivable to use the bend alignment capable of high-speed response described in the background and the ferroelectric liquid crystal, but both of them have a small change in the refractive index when the liquid crystal is turned on / off. When the means is used for a liquid crystal lens, there is a problem that the variable focus performance is remarkably inferior.

  In addition, it is difficult to uniformly heat the liquid crystal layer with a simple structure in a method for providing a practical liquid crystal response speed even at low temperatures by providing a heater separate from the panel to heat the liquid crystal panel. Furthermore, if a heater electrode is attached to the periphery of the liquid crystal panel, the thickness of the liquid crystal lens will increase accordingly, or a light blocking body that blocks the light in the area where the lens is formed cannot be formed. Arise.

  Therefore, the present invention provides a heater electrode for directly heating the liquid crystal layer in a region outside the phase modulation electrode for changing the refractive index of the liquid crystal lens in order to eliminate the above-described problems caused by the background art. An object of the present invention is to provide a liquid crystal lens capable of detecting a focal point at a sufficient speed in practical use by maintaining the temperature at a desired temperature or higher, and an electronic apparatus equipped with the liquid crystal lens.

In order to solve the above-described problems and achieve the object, the liquid crystal lens of the present invention basically adopts the following constituent elements.
The liquid crystal lens according to the present invention sandwiches the first liquid crystal layer with the first pattern electrode provided on the first transparent substrate facing the second pattern electrode provided on the second transparent substrate. In the liquid crystal lens, the second pattern electrode is formed by surrounding the periphery of the phase modulation electrode with a phase modulation electrode that modulates the phase of the first liquid crystal layer by applying a modulation voltage. A heater electrode for directly heating the liquid crystal layer, an electrode extraction portion for supplying power to the heater electrode, which has a lower resistance than the heater electrode, and an electrode extraction branch end provided in the middle of the electrode extraction portion; And a temperature detecting means for sensing the temperature of the first liquid crystal layer is provided immediately above the branch end of the electrode.

  According to the above invention, the focal point can be detected in a short time even at a low temperature, and the temperature change of the liquid crystal layer is efficiently propagated to the temperature detecting means through the electrode take-out portion and the electrode take-off branch end. Can be made.

  The liquid crystal lens according to the present invention includes a third pattern electrode provided on the surface of the second transparent substrate opposite to the first liquid crystal layer, and a third pattern electrode provided on the third transparent substrate. 4 is further provided with a structure in which the second liquid crystal layer is sandwiched so as to face the pattern electrode, and the temperature detection means provided at the electrode extraction branch end and the electrode extraction portion provided in the third pattern electrode are It is characterized by being arranged in a wrapping manner.

  According to the above invention, the temperature change of the second liquid crystal layer on the side where the temperature detecting means is not provided is transmitted to the first liquid crystal via the electrode extraction portion provided in the third pattern and the second transparent substrate. It can be efficiently propagated to the temperature detecting means provided on the layer side.

  In addition, the liquid crystal lens according to the present invention is characterized in that the heater electrode further includes heater control means for controlling ON / OFF of the heater heating so that the operating temperature range of the liquid crystal is specified.

  According to the above invention, the liquid crystal lens can be kept in a desired temperature range and operated at a specified response speed.

  The electronic device according to the present invention is characterized in that the above-described liquid crystal lens is mounted.

  An electronic apparatus according to the present invention is characterized in that the liquid crystal lens described above is an autofocus lens, and the autofocus lens is mounted to constitute a camera module.

  In the above-described invention, the camera module can be manufactured as an electronic device having a high impact resistance and a lightweight and small autofocus mechanism.

  According to the present invention, it is possible to obtain a liquid crystal lens capable of detecting a focal point at a sufficiently high speed in practical use under various temperature environments, and an electronic device equipped with the liquid crystal lens.

  Exemplary embodiments of a liquid crystal lens and an electronic apparatus having the liquid crystal lens according to the present invention will be explained below in detail with reference to the accompanying drawings. First, the configuration of the liquid crystal lens of the present invention will be described. 1 and 2 are a front view and a cross-sectional view showing a cell configuration of a liquid crystal lens, respectively.

As shown in FIG. 2, the liquid crystal lens 1 includes, for example, three glass substrates 21 to 23, each of which is provided with pattern electrodes 24 to 27 each having a predetermined pattern formed on the inside thereof. For example, a liquid crystal panel in which liquid crystal layers 28a and 28b of homogeneous orientation are enclosed between 21 and 23 is formed. The glass substrates 21 to 23 correspond to “transparent substrates”.

  In order to realize a variable focus lens by performing phase modulation of light with liquid crystal, a two-layer configuration of a P-wave liquid crystal lens 1a and an S-wave liquid crystal lens 1b is used. Both liquid crystal lenses have the same configuration, but the alignment directions of the liquid crystal layers 28a and 28b differ by 90 °. This is because, when the refractive index distribution of the P-wave liquid crystal lens 1a is changed, light having a polarization plane in the same direction as the orientation direction of the P-wave liquid crystal lens 1a is affected by the change in the refractive index distribution. This is because the light having the polarization plane in the direction orthogonal to the alignment direction of the P-wave liquid crystal lens 1a is not affected by the change in the refractive index distribution. The same applies to the S-wave liquid crystal lens 1b.

  Therefore, two liquid crystal lenses 1 having different orientation directions by 90 °, that is, a P-wave liquid crystal lens 1a and an S-wave liquid crystal lens 1b are required. The P-wave liquid crystal lens 1a and the S-wave liquid crystal lens 1b are driven by a drive voltage having the same waveform. The driving voltage used here is, for example, an AC voltage that has been subjected to pulse height modulation (PHM) or pulse width modulation (PWM).

  As shown in FIGS. 1 and 2, the central portion of the pattern electrodes 24 and 27 constituting the liquid crystal lens 1 is disposed in the lens pattern region 11 whose refractive index changes according to the applied voltage. The heater electrode 15 is provided with a conductor so as to surround the common electrode and the lens pattern region 11. In the central part of the pattern electrodes 25 and 26 facing it, a ring-shaped pattern (not shown here) and a heater electrode 15 are provided, which are arranged facing the common electrode formed on the pattern electrodes 24 and 27, respectively. It has been. The arrangement form of these patterns will be described in detail later. Then, a phase modulation electrode is configured by the common electrode and the ring-shaped pattern, and power is supplied to the liquid crystal sandwiched between the common electrode and the ring-shaped pattern, so that the light incident on the liquid crystal lens 1 is refracted and variable. Operate as a focus lens.

  Further, the peripheral edge portion of the liquid crystal lens 1 is sealed by a seal member 12, and the thicknesses of the liquid crystal layers 28 a and 28 b in the P-wave liquid crystal lens 1 a and the S-wave liquid crystal lens 1 b are scattered in the inner region of the seal member 12. The spacer member (not shown) is kept constant. Furthermore, the common electrode or the ring-shaped pattern disposed on the lens pattern region 11 disposed on the opposing glass substrates 21 to 23, the heater electrode 15, and the electrode lead-out portions 13a and 13b formed by being derived from the heater electrode 15, respectively. , 14a to 14c are connected to an external signal input / output means 17 made of a spring connector or a flexible printed wiring board (FPC). The pattern electrodes 24 and 27 on which the common electrode and the heater electrode 15 are formed are connected to the electrode extraction portions 14 a to 14 c using the common transition electrode 29. Part of the electrode extraction portions 14 a to 14 c is insulated from the pattern electrodes 25 and 26.

  In addition, the heater electrode 15 in the above description surrounds the outer periphery of the lens pattern region 11 as described above, and the liquid crystal existing in the lens pattern region 11, in other words, exists inside the heater electrode 15. The liquid crystal can be heated efficiently. With such a configuration, only the liquid crystal that functions as a lens can be heated locally and efficiently, and can function as a variable focus lens that is always stable in various temperature environments.

And the temperature detection means 80 for sensing temperature is arrange | positioned on the at least one surface of the glass substrate 22 in which the pattern electrodes 25 and 26 were provided. FIG. 2 shows an example in which the temperature detecting means 80 is provided on the surface of the glass substrate 22 on which the pattern electrode 25 is provided. In addition, the electrode take-out portion 13 a can detect the temperature of the liquid crystal existing near the lens pattern region 11 via the heater electrode 15 and the power supply for controlling the temperature of the heater electrode 15.

Although it does not specifically limit in the liquid crystal lens of this invention, The dimension of the liquid crystal lens 1 is shown below as an example.
The length of one side of the glass substrates 21 to 23 is about several mm to several tens of mm, for example, 7 mm. However, the glass substrate 22 on the pattern electrodes 25 and 26 side has dimensions excluding the portions of the pattern electrodes 25 and 26 that cover the electrode extraction portions 13a and 13b. The thickness of the glass substrates 21 to 23 is about several hundred μm, for example, 300 μm. The thickness of the liquid crystal layers 28a and 28b is about several μm to several tens of μm, for example, 25 μm. The diameter of the lens pattern region 11 is about several mm, for example, 3 mm.

  Next, a specific configuration example of the electrode pattern arranged in the lens pattern region 11 constituting the liquid crystal lens 1 of the present invention will be described. FIG. 3 is a front view illustrating a configuration example of the electrode pattern arranged in the lens pattern region 11 in the pattern electrodes 25 and 26 illustrated in FIGS. 1 and 2.

  As shown in FIG. 3, in the lens pattern region 11, a plurality of C-shaped annular electrodes 32, 33 are arranged around a circular central electrode 31 along a plurality of concentric circles having different radii. Pattern. The space between the center electrode 31 and the innermost ring electrode 32 and between the adjacent ring electrodes 32 and 33 are insulated spaces. The central electrode 31, the innermost annular electrode 32, and the adjacent annular electrodes 32, 33 are connected via an annular connection part 34 having a higher resistance than the central electrode 31 and the annular electrodes 32, 33. Are connected to each other.

  From the center electrode 31, the center lead electrode 35 is separated from the other ring electrodes 32, 33 and the ring connection part 34 (that is, in an insulated state) with the outermost ring electrode 33 (hereinafter referred to as “insulated”). It extends to the outside of the outer peripheral electrode 33). On the other hand, from the outer peripheral electrode 33, the outer peripheral lead electrode 36 extends to the outside in a state insulated from other electrodes. The patterns shown in FIG. 3 of the pattern electrodes 25 and 26 are arranged so as to overlap the lens pattern region 11.

  Depending on the voltages applied to the center extraction electrode 35 and the outer periphery extraction electrode 36, the central electrode 31 with respect to the pattern electrodes 24 and 27, which are common electrodes, and between the center electrode 31 and the outer periphery electrode 33, respectively. The voltage values of the annular electrodes 32 and the outer peripheral electrode 33 are different from each other. That is, a voltage distribution is generated in the lens pattern region 11 by the pattern electrodes 25 and 26. By changing this voltage distribution, the refractive index distribution of the liquid crystal lens 1 is changed, so that the liquid crystal lens 1 can be in a convex lens state, a parallel glass state, or a concave lens state.

Here, although it does not specifically limit in the liquid crystal lens of this invention, The dimension and characteristic value of each part of the lens pattern area | region 11 are shown as an example.
The total number of the central electrode 31, the outer peripheral electrode 33, and the annular electrode 32 therebetween is, for example, 30. Further, the diameter of the central electrode 31, the width of each annular electrode 32, and the width of the outer peripheral electrode 33 are selected so that a desired refractive index distribution can be obtained in the lens pattern region 11. The width of the insulated space between adjacent ones of the central electrode 31, the annular electrode 32, and the outer peripheral electrode 33 is, for example, 3 μm. Further, the resistance value of each annular zone connecting portion 34 is, for example, 10 KΩ.

Next, a specific arrangement form of each pattern in the liquid crystal lens 1 of the present invention will be described. 4, 5, and 6 are front views of the pattern electrodes 24 to 27 of FIG. 2 viewed from the light incident direction 204. First, the pattern of the surface on which the pattern electrode 25 is formed will be described with reference to FIG. FIG. 4 shows a configuration example of the pattern electrode 25 including the ring-shaped pattern in FIG. Here, the pattern electrode refers to a ring-shaped pattern or common electrode, the heater electrode 15, the heater wiring part 16, and the electrode extraction parts 13a, 13b, and 14a to 14c.

As shown in FIG. 4, on one surface of the glass substrate 22, there is a heater electrode 15, electrode take-out portions 13a and 13b, and a heater wiring portion connected between the heater electrode 15 and the electrode take-out portions 13a and 13b. 16 and the electrode extraction branch end 100 branched from the electrode extraction portion 13a are both formed of chromium (Cr). And the ring-shaped pattern shown in FIG. 3, which is a pattern other than that, and the center extraction electrode 35, the outer periphery extraction electrode 36 (see FIG. 3), and the electrode extraction portions 14a to 14c connected thereto, It is formed of indium tin oxide (In ₂ O ₅ + SnO ₂ ). In this way, if the heater wiring portion 16 and the electrode lead-out portion 13a are made of a material having high thermal conductivity, for example, the heater electrode 15 and the heater wiring portion 16 are both made of a chromium (Cr) film, the liquid crystal layers 28a and 28b. Is efficiently transmitted to the temperature detecting means 80, and the liquid crystal layers 28a and 28b can be heated.

  The liquid crystal lens of the present invention is arranged to detect the temperature of the liquid crystal positioned directly above the lens pattern region 11 immediately above the electrode lead-out branch end 100 as described with reference to FIGS. Temperature detecting means 80. If comprised in this way, the temperature of the liquid-crystal layer 28a heated with the heater electrode 15 can be detected efficiently via the heater wiring part 16, the electrode extraction part 13a, and the electrode extraction branch end 100. Although FIG. 4 shows a form in which the electrode lead-out branch end 100 is provided in the electrode lead-out portion 13a, the electrode lead-out branch end 100 may be provided in the electrode lead-out portion 13b.

  Next, a configuration example of the pattern electrode 26 shown in FIG. 2 will be described with reference to FIG. FIG. 5 shows a configuration example of the pattern electrode 26 including a ring-shaped pattern.

As shown in FIG. 5, on the surface of the glass substrate 22, the heater electrode 15, the electrode extraction portions 13a and 13b, and the heater wiring portion 16 connected between the heater electrode 15 and the electrode extraction portions 13a and 13b, Are formed of chrome (Cr), and a pattern other than the ring-shaped pattern, a central lead electrode 35, an outer peripheral lead electrode 36 (see FIG. 3), and electrode lead portions 14a to 14a connected thereto. 14c is made of indium tin oxide (In ₂ O ₅ + SnO ₂ ).

  A characteristic of this pattern electrode is that the electrode take-out portion 13a shown in FIG. 5 is provided so as to overlap with the position 50 of the temperature detecting means 80 provided on the glass substrate 22 shown in FIG. It is. If the electrode take-out portion 13a is configured so as to overlap with the position 50 in this way, it is shown in this drawing via the heater wiring portion 16, the electrode take-out portion 13a, and the glass substrate 22 connected to the heater electrode 15. The temperature of the liquid crystal (liquid crystal 28b) in the inner region of the heater electrode 15 can be detected by the temperature detecting means 80 shown in FIG.

  Next, a configuration example of the pattern electrodes 24 and 27 will be described. FIG. 6 shows a configuration example of the pattern electrodes 24 and 27 including the common electrode.

As shown in FIG. 6, the common electrode 40, which is a solid electrode shown in FIG. It is made of tin (In ₂ O ₅ + SnO ₂ ), and the heater electrode 15 is made of chromium (Cr). The common electrode 40 is disposed so as to overlap the lens pattern region 11 in which a ring-shaped pattern is formed. Further, in the region 42, the common electrode 40 includes the electrode extraction portion 44 and the common transition electrode 29 (see FIG. 2). The region 52 (see FIGS. 4 and 5) provided on the opposing glass substrate 22 is connected to the electrode extraction portion 14c.

  In addition, a heater electrode 15 adjacent to the common electrode 40 is formed around the ring-shaped pattern and the common electrode 40 in the same manner as shown in FIGS. 4 and 5, and one end of the heater electrode 15 is The other end of the heater electrode 15 is connected to the electrode extraction portion 43 b via the heater wiring portion 16. Similarly to the routing of the common electrode 40, the electrode extraction portions 43 a and 43 b connected to the heater electrode 15 are connected to the electrode extraction portions 13 a and 13 b provided on the glass substrate 22.

  In the above description, the heater electrode 15 shown in FIGS. 4, 5, and 6 is connected to the electrode extraction portions 13 a and 13 b via the heater wiring portion 16 from the electrode extraction portions 13 a and 13 b. This is because the heat loss due to the film resistance of the heater wiring portion 16 is reduced as much as possible up to 15 and the heater electrode 15 is efficiently heated with less power supply. Therefore, the heater wiring portion 16 is necessary for the heater electrode 15 and the electrode take-out portions 13a and 13b that are close to each other, and those that want to be heated at the same time other than the liquid crystal present in the lens pattern region 11. In particular, when the size of the liquid crystal lens 1 is further reduced, the heater electrode 15 may be directly connected to the electrode extraction portions 13a and 13b.

  The heater electrode 15 described above is provided in a C shape so as to surround the ring-shaped pattern and the common electrode 40, and the resistance value of the heater electrode 15 is determined by the heater wiring portion 16 and the electrode extraction portions 13a, 13b, It is formed to have a higher resistance than the resistance values of 14a to 14c. Thus, the reason why the heater electrode 15 is set to have a higher resistance value than the electrode extraction portions 13a, 13b, and 14a to 14c is that the heater wiring portion 16 described above is set to be higher than the electrode extraction portions 13a, 13b, and 14a to 14c. Based on the same reason that the resistance was reduced.

  As a method of forming the resistance value of the heater electrode 15 to be higher than the resistance values of the electrode extraction portions 13a, 13b, and 14a to 14c, for example, the width of the pattern of the heater electrode 15 is set to the electrode extraction portions 13a, 13b, There are a method of narrowing the width of 14a to 14c, a method of reducing the film thickness of a pattern whose resistance value is to be changed, and a method of changing the film quality.

  The heater electrode 15 is preferably formed so as to have a resistance value that is as uniform as possible. This is because if the resistance value of the heater electrode 15 is not uniform, the heating temperature becomes lower in the portion where the resistance value in the heater electrode 15 is lower than in the portion where the resistance value is high, resulting in uneven heating temperature applied to the liquid crystal. As described above, when the liquid crystal is not heated uniformly in this region and the temperature unevenness (temperature distribution) occurs in the liquid crystal, even if a desired current value is supplied to the heater electrode 15, the light incident on the liquid crystal lens 1 is desired. The refraction of can not be given. Therefore, it is preferable that the heater electrode 15 has a resistance value that is as uniform as possible.

  In this way, the resistance value of the heater electrode 15 is made uniform, and the resistance of the heater electrode 15 is made higher than that of the heater wiring portion 16 and the electrode lead-out portions 13a, 13b, and 14a to 14c. It is possible to efficiently heat the temperature of the liquid crystal enclosed between the ring-shaped pattern disposed on the common electrode 40 and the common electrode 40 and surrounded by the heater electrode 15. Of course, the heater electrode 15 can heat the liquid crystal even when it is formed on only one of the glass substrates 21 and 23 sandwiching the liquid crystal layers 28a and 28b.

  In the present embodiment, the common electrode 40 arranged in the lens pattern region 11 is formed on the outer glass substrates 21 and 23 and the ring-shaped pattern is formed on both surfaces of the glass substrate 22. The common electrode 40 in the region 11 may be formed on both surfaces of the glass substrate 22, and a ring-shaped pattern may be formed on the outer glass substrates 21 and 23.

Here, a driving method of the heater electrode 15 in the liquid crystal lens 1 will be described.
In the liquid crystal lens of the present invention, the liquid crystal is heated at a constant voltage so that the liquid crystal existing in the lens pattern region 11 can be heated to a desired temperature at 13 a and 13 b at the electrode lead-out portions that are connected to the heater electrode 15. Make the power variable. Specifically, by repeatedly providing a power supply period in which the voltage value is, for example, 2.8 V, and a pause period in which power supply is not performed, the amount of power supplied to the heater electrode 15 is changed by changing the duty ratio of each period. The driving method is changed.

Here, the resistance value when the heater electrode 15 is formed of a chromium metal film is shown as an example.
When the thickness of the chromium metal film is about 3200 mm, the width of the heater electrode 15 is 0.2 mm, and the width of the heater wiring portion 16 and the electrode lead-out portions 13a, 13b, and 14a to 14c is 0.4 mm, The resistance value is about 39Ω, the overall resistance of the heater wiring portion 16 and the electrode lead-out portions 13a, 13b, and 14a to 14c is about 30Ω, and the resistance value of the heater electrode 15 is higher than that of the heater wiring portion 16. The diameter of the lens pattern region at this time was 1.56 mm.

  Next, the operation of the liquid crystal lens 1 of the present invention which is a variable focus lens will be described. FIG. 7 is a diagram for explaining a change in refractive index when a voltage is applied to the liquid crystal in a state where light having a polarization plane in the same direction as the alignment direction of the liquid crystal is transmitted through the liquid crystal.

As shown in FIG. 7, when the drive voltage V ₀ is applied to the liquid crystal from the outside (FIG. 7A), the refractive index of the liquid crystal is delayed by a time tf from the rising timing of the drive voltage V _0. a state corresponding to the drive voltage _{V 0} (FIG. (b)). Further, the refractive index of the liquid crystal returns to the original state with a delay of tr time from the falling timing of the drive voltage V ₀ ((b) in the figure). The times tf and tr are periods in which the liquid crystal is in a transient response operation, and the refractive index gradually changes. Here, as described above, the drive voltage V ₀ is, for example, an AC voltage that has been subjected to pulse height modulation (PHM) or pulse width modulation (PWM).

For example, it is assumed that the liquid crystal lens 1 and the lens pattern area 11 having the above-described values for the dimensions and characteristic values of each part are used. Further, as the liquid crystal layers 28a and 28b, nematic liquid crystal having a refractive index ne for extraordinary rays and a refractive index no for ordinary rays of 1.75 and 1.5 and a birefringence Δn of 0.25, respectively, is used. To do. In this case, for example, the driving voltage _{V 0} which liquid crystal response operation time for the rise to 5V from 0V tf, and response operation time tr of the liquid crystal with respect to the falling from 5V driving voltage _{V 0} to 0V, the room temperature (20 ° C.) Both are about 100 milliseconds.

  Next, the relationship between various temperatures and response speeds of the liquid crystal lens 1 of the present invention will be described. FIG. 8 is a graph showing the temperature dependence of the response time of the liquid crystal.

  Curve 71 is measured at 0 ° C., curve 72 is measured at 10 ° C., curve 73 is measured at 20 ° C., curve 74 is measured at 30 ° C., curve 75 is measured at 40 ° C., and curve 76 is 50 ° C. The measured value is shown. From this figure, although the response time of 100 milliseconds or less is obtained to make the refractive index change amount 100% at room temperature (20 ° C.) or more, it deteriorates to about 500 milliseconds at 0 ° C. I understand that.

On the other hand, the liquid crystal lens 1 provided with the heater electrode 15 described above has the following operation. FIG. 9 is a drawing showing measurement results when a voltage is applied to the heater electrode 15 formed around the lens pattern region 11 of the liquid crystal lens 1 to heat the liquid crystal layers 28a and 28b.

  For example, when the heater electrodes 15 are formed on both sides of the glass substrate 22 (see FIG. 2), a voltage of 2.8 V is applied and a current of about 100 milliamperes flows, the temperature at the center of the lens pattern region 11 of the liquid crystal lens 1 is increased. Rises by about 30 ° C. from room temperature (measurement start temperature 28 ° C.) after 7 seconds. That is, by adopting this configuration, even if the liquid crystal lens 1 is in an environment of 0 ° C., the liquid crystal layers 28a and 28b can be in an environment of + 30 ° C., and the response time of the liquid crystal is 0 ° C. It is possible to increase the speed to about ¼ to に 対 し て compared to when operating in an environment. In this way, the relationship between the temperature of the liquid crystal layers 28a and 28b in the liquid crystal lens 1 and the voltage and current value applied to the heater electrode 15 is stored in advance, and the temperature of the liquid crystal layers 28a and 28b at that time is stored. If the heater electrode 15 is controlled, the liquid crystal layers 28a and 28b can be controlled to have a predetermined temperature under various temperature environments.

  Next, the behavior of the variable focus lens in the liquid crystal lens of the present invention will be described. FIG. 10 shows how the refractive index of the liquid crystal changes during the response operation period tf when the drive voltage rises, and how the focal length of the liquid crystal lens 1 changes.

  For example, as shown in FIG. 10A, the refractive index of the liquid crystal changes during the transient response operation period tf and becomes constant when the response operation period tf elapses. Therefore, the center of the liquid crystal lens 1 shown in FIG. The refractive index of the liquid crystal portion corresponding to each of the partial electrode 31, each annular electrode 32, and the outer peripheral electrode 33 is also constant. Therefore, when the transient response operation period tf elapses, the refractive index distribution of the changing liquid crystal lens 1 is determined to have a certain distribution, and as shown in FIG. 10B, the focal length f of the liquid crystal lens 1 is the refractive index distribution. It converges to a certain value according to.

  The lines drawn above and below the horizontal axis in FIG. 10B represent changes in the focal length f when the liquid crystal lens 1 is in a convex lens state and a concave lens state, respectively. In the present embodiment, for convenience of explanation, the focal length f when the liquid crystal lens 1 is in a convex lens state is represented by a positive numerical value, and the focal length f when the liquid crystal lens 1 is in a concave lens state is represented by a negative numerical value. Represents. In other words, when the focal length f of the liquid crystal lens 1 is positive or negative infinity, the liquid crystal lens 1 is in a parallel glass state.

  Next, an autofocus device (autofocus device) which is an electronic device equipped with the liquid crystal lens of the present invention will be described. FIG. 11 is a block diagram showing a schematic configuration of the automatic focusing device.

  As shown in FIG. 11, the automatic focusing apparatus includes a liquid crystal lens system 101, an optical lens system 102, an image sensor 103, a DSP (digital signal processor) 104, an autofocus (AF) controller 105, a liquid crystal lens driver 106, a heater. A control circuit 107 and a temperature sensor 108 are provided. The heater control circuit 107 corresponds to “heater control means”. The liquid crystal lens system 101 is configured by combining a P-wave liquid crystal lens 1a (see FIG. 2) and an S-wave liquid crystal lens 1b (see FIG. 2). The optical lens system 102 includes a diaphragm, a pan focus group lens, and an infrared cut filter. The image sensor 103 includes an image sensor made of a solid-state image sensor such as a CCD or CMOS, and an analog-digital converter. The temperature sensor 108 is, for example, a thermistor, and is disposed in the vicinity thereof in order to detect the temperature of the liquid crystal lens system 101.

An optical image formed through the liquid crystal lens system 101 and the optical lens system 102 is converted into an electrical signal by the image sensor of the image sensor 103. The electrical signal output from the image sensor is converted into a digital signal by an analog-digital converter. The DSP 104 performs image processing on the digital signal output from the analog-digital converter. The autofocus controller 105 samples the image signal output from the DSP 104 after setting a predetermined voltage to the liquid crystal lens, thereby extracting a focus signal (hereinafter referred to as an autofocus signal) corresponding to the degree of focus matching. Then, the autofocus controller 105 controls the driving conditions of the liquid crystal lens system 101 so that the level of the autofocus signal is maximized based on the extracted autofocus signal.

  The autofocus controller 105 includes a microprocessor 1051 and a storage unit 1052 that perform the series of controls described above. The storage unit 1052 includes a read-only memory unit (ROM unit) that stores a program executed by the microprocessor 1051 and various relationships necessary for obtaining an optimum driving voltage, and a write that the microprocessor 1051 uses as a work area. A possible memory unit (RAM unit).

  When the temperature signal output from the temperature sensor 108 falls below a specified value, the liquid crystal lens driver 106 turns the heater electrode 15 provided on the liquid crystal lens 1 on and off when the heater control circuit 107 turns on the liquid crystal lens 1. Is maintained at a response speed equal to or higher than a specified value, and a predetermined voltage is applied to the liquid crystal lens system 101 based on a control signal output from the autofocus controller 105.

  As described above, according to the present embodiment, after the response operation of the liquid crystal lens system 101, the sampling of the image signal and the extraction of the autofocus signal are repeated to detect the in-focus point, which is sufficient for practical use. An automatic focusing device that is an electronic device that can detect the focal point at a high speed is obtained.

  Further, according to the present embodiment, since a movable part such as an actuator for driving the lens is not necessary, the apparatus can be reduced in size. In addition, power consumption can be reduced. Furthermore, since it is excellent in impact resistance, the effect that reliability is high is also acquired. Further, since the liquid crystal lens system 101 also serves as a protective window glass outside the optical lens system 102, the apparatus can be further reduced in size.

  As described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, values such as dimensions, characteristic values, and time described in the embodiments are examples, and the present invention is not limited to these values. The type of liquid crystal is not limited to nematic liquid crystal.

  Further, the transient response operation times tf and tr of the liquid crystal are not about 100 milliseconds at room temperature (20 ° C.). For example, depending on whether the liquid crystal driving method is a pulse height modulation method or a pulse width modulation method, the response speed of the liquid crystal to the rise and fall of the drive voltage changes, so tf and tr change. To do.

  Further, since the characteristics of the liquid crystal differ depending on the liquid crystal material used, the response speed of the liquid crystal with respect to the rise and fall of the drive voltage changes, and tf and tr change. In particular, when TN (twisted nematic) liquid crystal is used, the influence of rotational viscosity or the like is large.

  Liquid crystal alignment methods include homogeneous (horizontal) alignment, homeotropic (vertical) alignment, hybrid alignment, twist alignment, and bend alignment. The rise and fall of the drive voltage depends on the alignment method. The response speed of the liquid crystal to changes, and tf and tr change. Also, tf and tr vary depending on the cell configuration and the like.

Further, the liquid crystal lens driver and the heater control circuit may be integrated in the same IC. Further, the liquid crystal lens driver, the heater control circuit, and the temperature sensor may be integrated in the same IC. In order to efficiently detect the temperature of the liquid crystal lens 1 and reduce the mounting size, it is desirable that the integrated IC is directly mounted on the glass substrate on which the liquid crystal lens 1 is formed.

  As described above, the liquid crystal lens according to the present invention and the electronic device using the liquid crystal lens are useful for an automatic focusing device having an autofocus function, and in particular, for a camera, a digital camera, a movie camera, and a camera-equipped mobile phone. It is suitable for an autofocus function such as a camera unit, a camera mounted on a car or the like and used for a rear confirmation monitor, a camera unit of an endoscope, or glasses having a function of changing the lens degree.

It is a front view which shows the pattern electrode of the liquid crystal lens concerning this invention. It is sectional drawing which shows the structure of the liquid crystal lens concerning this invention. It is a front view which shows the ring-shaped pattern shape formed in the lens pattern area | region of the liquid crystal lens concerning this invention. It is a front view which shows the structural example of the pattern electrode and temperature detection means of the liquid crystal lens concerning this invention. It is a front view which shows the pattern electrode of the liquid crystal lens concerning this invention. It is a front view which shows the pattern electrode of the liquid crystal lens concerning this invention. It is explanatory drawing which shows the change of a refractive index when a voltage is applied to the liquid crystal layer of the liquid crystal lens concerning this invention. It is temperature dependence data which show the refractive index change amount when a voltage is applied to the liquid crystal layer of the liquid crystal lens concerning this invention. It is data which shows the relationship between the heater heating time to the liquid crystal lens concerning this invention, and temperature rise. It is explanatory drawing which shows the change of the refractive index of the liquid crystal in the liquid crystal response operation period of the liquid crystal lens concerning this invention, and the change of the focal distance of a liquid crystal lens. It is a block diagram which shows schematic structure of the automatic focusing apparatus which is an electronic device concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal lens 1a P wave liquid crystal lens 1b S wave liquid crystal lens 11 Lens pattern area | region 12 Seal member 13a, 13b, 14a, 14b, 14c Electrode extraction part 15 Heater electrode 16 Heater wiring part 17 External signal input / output means 21-23 Glass substrate 24-27 Pattern electrode 28a, 28b Liquid crystal layer 29 Common transition electrode 31 Center electrode 32 Ring electrode 33 Ring electrode (outer peripheral electrode)
34 ring zone connection part 35 center part extraction electrode 36 external extraction electrode 40 common electrode 42 region 43a, 43b, 44 electrode extraction part 50 position 52 region 71-76 curve 80 temperature detection means 100 electrode extraction branch end 101 liquid crystal lens system 102 optical Lens system 103 Image sensor 104 DSP
105 Autofocus (AF) Controller 106 Liquid Crystal Lens Driver 107 Heater Control Circuit 108 Temperature Sensor 204 Incident Direction 1051 Microprocessor 1052 Storage Unit

Claims (5)

The first liquid crystal layer is sandwiched between the first pattern electrode provided on the first transparent substrate and the second pattern electrode provided on the second transparent substrate so as to function as a variable focus lens. In liquid crystal lenses,
The second pattern electrode is
A phase modulation electrode for modulating the phase of the first liquid crystal layer by applying a modulation voltage;
A heater electrode for directly heating the first liquid crystal layer formed around the phase modulation electrode;
An electrode take-out portion that is lower in resistance than the heater electrode and that feeds power to the heater electrode from the outside;
An electrode extraction branch end provided in the middle of the electrode extraction portion,
A liquid crystal lens, characterized in that a temperature detecting means for sensing the temperature of the first liquid crystal layer is disposed immediately above the electrode lead-out branch end. The liquid crystal lens includes a third pattern electrode provided on a surface of the second transparent substrate opposite to the first liquid crystal layer, and a fourth pattern electrode provided on a third transparent substrate. Further comprising a configuration in which the second liquid crystal layer is sandwiched by facing each other,
2. The liquid crystal according to claim 1, wherein the temperature detection means provided at the electrode extraction branch end and the electrode extraction portion provided in the third pattern electrode are arranged so as to overlap each other. lens.   The liquid crystal lens according to claim 2, further comprising heater control means for controlling on / off of heater heating in the heater electrode so that the operating temperature range of the liquid crystal is specified.   An electronic apparatus comprising the liquid crystal lens according to any one of claims 1 to 3.   The electronic apparatus according to claim 4, wherein the liquid crystal lens is an autofocus lens, and the camera module is configured by mounting the autofocus lens.

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