This application claims the foreign priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2007-170102 filed on Jun. 28, 2007, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid crystal glare-proof mirror used for an inner mirror or an outer mirror of a vehicle, for example.
2. Description of the Related Art
Conventionally, there has been known a liquid crystal glare-proof mirror in which a vertically aligned polarizing plate, a liquid crystal cell, a horizontally aligned polarizing plate and a reflecting mirror are laminated in order (as disclosed in JP Unexamined Patent Publication (Kokai) No. 57-102602).
The liquid crystal glare-proof mirror disclosed in JP Unexamined Patent Publication (Kokai) No. 57-102602 transmits vertically polarized light through a vertically aligned polarizing plate to the liquid crystal cell and switches between a glare-proof mode and a non-glare-proof mode by applying voltage to the liquid crystal cell.
In the conventional liquid crystal glare-proof mirror, there has been a problem that part of reflected light becomes extraordinary rays when voltage is not applied because the behavior of liquid crystal molecules in the liquid crystal cell is disordered when voltage is not applied to the liquid crystal cell.
An object of the present invention is to provide a liquid crystal glare-proof mirror which enables to reduce extraordinary ray generated in a liquid crystal cell.
A first aspect of the present invention provides a liquid crystal glare-proof mirror including a first polarizing plate for transmitting a first polarization component of incident light; a second polarizing plate for transmitting a second polarization component of the incident light; and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate, at least either one of the first polarizing plate and the second polarizing plate being formed of material having refractive index anisotropy exhibiting a different refraction of the incident light that varies depending on an angle at which the incident light comes into the either one of the first polarizing plate and the second polarizing plate.
In the aforementioned liquid crystal glare-proof mirror, the second polarizing plate reflects a third polarization component perpendicular to the second polarizing component, liquid crystal molecules in the liquid crystal cell are aligned in such a manner that the liquid crystal cell exhibits polarization rotatory power on the incident light when voltage is not applied to the liquid crystal molecules and the liquid crystal cell does not exhibit the polarization rotatory power on the incident light when voltage is applied to the liquid crystal molecules, and the first polarizing plate and the second polarizing plate are disposed in such a manner that the first polarization component is perpendicular to the third polarization component and the first polarization component is parallel to the second polarization component.
In the aforementioned liquid crystal glare-proof mirror, an optical absorption member for absorbing the second polarization component transmitted through the second polarizing plate is disposed opposite to the side of the second polarizing plate on which the liquid crystal cell is disposed.
The aforementioned liquid crystal glare-proof mirror further includes a surrounding light detection device for detecting a quantity of light around a vehicle; a back light detection device for detecting a quantity of light coming from a rear side of the vehicle; a liquid crystal cell control device for comparing the quantity of light around the vehicle detected by the surrounding light detection device and the amount of the light coming from the rear side of the vehicle detected by the back light detection device, controlling the liquid crystal glare-proof mirror to be glare-proofed when the quantity of the light coming from the rear side of the vehicle is greater than the quantity of the light around the vehicle at not less than a predetermined value, and controlling the liquid crystal glare-proof mirror not to be glare-proofed when the quantity of the light coming from the rear side of the vehicle is smaller than or equal to the quantity of the light around the vehicle or the quantity of the light coming from the rear side of the vehicle is greater than the quantity of the light around the vehicle in less than the predetermined value.
The aforementioned liquid glare proof mirror further includes a delay unit for delaying a timing at which a detection signal output from the surrounding light detection device and a detection signal output from the back light detection device are input to the liquid crystal cell control device.
In the aforementioned liquid crystal glare-proof mirror, the liquid crystal cell control device includes an oscillation unit for oscillating a control signal which controls the liquid crystal cell.
Other features and advantages of the present invention will become more apparent from the following detailed descriptions of the invention when taken in conjunction with the accompanying drawings.
Embodiment of the present invention is described with reference to the accompanying drawings. The external appearance of a liquid crystal glare-proof mirror 100 is described below with reference to
The liquid crystal glare-proof mirror 100 mainly includes a body 1, a support 2, a bush 3, a plate 4, a screw 5, sensor covers 6A, 6B, a plate circuit 7, a button 8, tapping screws 9, a mirror body 10, a ring 11, a battery cover 12, a seal 13, a battery 14, a stay 15. The liquid crystal glare-proof mirror 100 is assembled by these parts.
The body 1 is a container having an opening 1A which meets the outside shape of the mirror body 10. The body 1 also includes screw holes 1a, 1b, 1c and 1d for fixing the support 2, screw holes 1e, 1f for fixing the plate circuit 7. The body 1 further includes on the bottom surface of the body 1 which is opposed to the opening IA an installation hole 1B into which the stay 15 is inserted, and a hole 1C through which a surrounding light sensor 7C, which is described later, detects surrounding light via the sensor cover 6A. The body 1A is also provided with a storage portion 1D for storing a battery 14.
The support 2, the bush 3 and the plate 4 are members for installing the stay 15. The support 2 includes screw holes 2a, 2b, 2c, 2d corresponding to the screw holes 1a, 1b, 1c, 1d. Four tapping screws 9 are inserted into the screw holes 2a, 2b, 2c, 2d and then screwed into the screw holes 1a, 1b, 1c, 1d to fix the support 2 to the body 1. The support 2 includes an installation hole 2A corresponding to the installation hole 1B. The support 2 also includes a screw hole 2e for fixing the plate 4.
The bush 3 is formed in a substantially hemispheric body having an opening (not show) facing in the direction indicated by an arrow B in
Protrusions 4a, 4b are formed on the plate 4 and are fitted into cutouts (not shown) formed in the support 2. A hole 4c corresponding to the screw hole 2e is also formed in the plate 4. The screw 5 is inserted into the hole 4c and then screwed into the screw hole 2e to fix the plate 4 to the support 2 with the bush 3 sandwiched between the plate 4 and the bush 3. The plate 4 also includes a bush-axis receiving portion which is raised in a substantially hemispheric shape.
The plate circuit 7 includes a circuit for controlling a liquid crystal cell 10b (see
The mirror body 10 is designed to adjust the amount of reflected light by switching between a non-glare-proof mode and a glare-proof mode based on the relationship of the light volume of surrounding light and that of back light. To be more specific, the mirror body 10 is formed by laminating a first polarizing plate (not shown in
A ring 11 is an elastic body for fixing the mirror body 10 to the body 1. The outer circumference of the mirror body 10 meets the inner circumference of the ring 11, and the ring 11 is fixed to the circumferential edge of the body 1. The ring 11 includes a hole 11A through which the button 8 protrudes outside, and a hole 11B through which a backward light sensor 7A detects back light via the sensor cover 6B.
A battery cover 12 covers an opening (not shown) of the storage portion 1D. A seal 13 prevents the battery 14 from being moved in a space of the storage portion 1D. A cable 14A is connected to a terminal of the battery 14 and the other end of the cable 14A is provided with a socket 14B. Although, in this specification, each of the socket 14B and the socket 10B is connected to a connecting terminal (not shown) on the plate circuit 7, wiring is not limited to this as long as both of the socket 14B and the socket 10B are electrically connected.
A stay 15 is for attaching the liquid crystal glare-proof mirror 100 to a ceiling or the like of a vehicle (not shown). An axle-center portion 15a, which is a spherical body, is formed at an end of the stay 15. The axle-center portion 15a is inserted into the installation hole 1B and the installation hole 2A and is gripped by the bush 3. The bush 3 allows the body 1 to be rotatably attached to the stay 15 at a desired angle. An upper surface portion 15B of the stay 15 is closely attached to a ceiling, a front window or the like with an adhesive agent or the like.
As shown in
Internal structure of the mirror body 10 is described below.
The polarizing plate (also referred to as a “first polarizing plate”) 10a ejects to the liquid crystal cell 10b a particular first polarization component of incident light coming from the upper side of
The liquid crystal cell 10b is disposed on the back of the polarizing plate 10a and includes two control areas thereon, each of which can be controlled independently. The liquid crystal cell 10b functions as a shutter which transmits or blocks light. The liquid crystal cell 10b is configured by disposing a liquid crystal 10h between glass substrates 10e and 10f in which the transparent electrodes (not shown) are wired. In this embodiment, the liquid crystal 10h is a TN (Twisted Nematic) liquid crystal. More specifically, the liquid crystal molecules x are aligned in such a manner that incident light is rotated when no voltage is applied to the transparent electrodes (not shown) on the glass substrates 10e and 10f, whereas the incident light is not rotated when voltage is applied to the transparent electrodes. A sealing member (spacer) 10G is also disposed between the glass substrates 10e and 10f.
The reflection polarizing plate (the second polarizing plate) 10c ejects a particular second polarization component of incident light as transmitted light and also ejects a third polarization component which is perpendicular to the second polarization component of the transmitted light as reflected light. In this embodiment, the second polarization component the reflection polarizing plate 10c is a vertical polarization component and the third polarization component is a horizontal polarization component. More specifically, the first polarization component (the vertical polarization component) and the third polarization component (the horizontal polarization component) are perpendicular to each other, and the first polarization component (the vertical polarization component) and the second polarization component (the vertical polarization component) are parallel to each other.
The structure of the reflection polarizing plate 10c is described below.
In this embodiment, the polarizing plate 10a and the reflection polarizing plate 10c are formed of resin layers having refractive index anisotropy. The resin layers having the refractive index anisotropy are formed of materials such as a polyvinyl alcohol iodine system. For example, polyvinyl alcohol is stretched in any direction and then the polyvinyl alcohol molecules are aligned such that a helix structure of the polyvinyl alcohol molecules faces toward any direction so that the refractive index anisotropy is generated. The polyvinyl alcohol is then soaked in iodine solution so that iodine is absorbed in the helix structure. Thus, the resin layers having the refractive index anisotropy and a polarization performance are formed. Furthermore, it is preferable that the resin layers are sandwiched by cellulosic plastic films to increase their durability and the mechanical strength.
The polarizing plate 10a and the reflection polarizing plate 10c makes it possible to separate an ordinary ray from an extraordinary ray whose traveling direction is different from that of the ordinary ray by means of the refractive index anisotropy, whereby only the ordinary ray can be emitted toward eyes of a driver as reflected light. More specifically, even if the transmitted light emitted from the liquid crystal cell 10b includes an extraordinary ray generated by disordered behavior of the liquid crystal molecules, it is possible to exclude the extraordinary ray and to emit only an ordinary ray as reflected light.
Referring back to
An operation of the liquid crystal glare-proof mirror 100 in a non-glare-proof mode and an operation thereof in a glare-proof mode are explained below. The subscript “⊥” is assigned to the vertical polarization component and the subscript “=” is assigned to the horizontal polarization component hereinafter for the convenience of the explanation.
The operation of the liquid crystal glare-proof mirror 100 in the non-glare-proof mode is described.
In the liquid crystal glare-proof mirror 100 shown in
When a light H1 (natural light (especially back light)) enters the polarizing plate 10a, the polarizing plate 10a transmits the vertical polarization component (also referred to as the “first polarization component”) and ejects a light H2⊥ as shown in
The light H3= ejected from the liquid crystal cell 10b enters the reflection polarizing plate 10c and is reflected as a light H5= because the light H3= is the horizontal polarization component (the third polarization component). The light H5= then enters the liquid crystal cell 10b and is rotated by the liquid crystal cell 10b. The light H5= is then ejected from the liquid crystal cell 10b as a light H6⊥, which is the vertical polarization component, and the light H6⊥ is then ejected from the polarizing plate 10a as a light H8⊥. When the behavior of the liquid crystal molecules x in the liquid crystal cell 10b are unstable, an extraordinary ray H7 is ejected together with the light H6⊥. Although the light H7 is generally the same vertical polarization component as the light H6⊥ because the light H7 is a light whose traveling direction is changed from that of the light H6⊥, the light H7 is assumed to include the horizontal polarization component which has not been rotated for the convenience of the explanation.
At the reflection polarizing plate 10c, the light H4=, which is the horizontal polarization component of the light H4, is significantly bent to be separated from the traveling direction of the light H5=. The light H4⊥, which is the horizontal polarization component of the light H4, transmits through the reflection polarizing plate 10c and is absorbed by the optical absorption member 10d. The light H7⊥, which is the vertical polarization component of the light H7 is significantly bent at the polarizing plate 10a to be separated from the traveling direction of the light H6⊥. The light H7=, which is the horizontal polarization component of the light H7 is absorbed by the polarizing plate 10a and then is radiated as heat.
Thus, when the liquid crystal glare-proof mirror 100 is in the non-glare-proof mode, it is possible to remove an extraordinary ray by the polarizing plate 10a and the reflection polarizing plate 10c and to emit only an ordinary ray as reflected light even when the extraordinary ray is generated in the liquid crystal cell 10b, whereby the liquid crystal glare-proof mirror 100 is less affected by the extraordinary ray generated in the liquid crystal cell 10b.
Next, the operation of the liquid crystal glare-proof mirror 100 in the glare-proof mode is described.
In the liquid crystal cell 10b, the liquid crystal molecules x are aligned in the horizontal direction of
Although, in the embodiment, the voltage value applied to the liquid crystal cell 10b is controlled based on the amount of surrounding light and that of back light, a voltage value large enough to align all of the liquid crystal molecules x substantially vertical to the electrodes may always be applied to the liquid crystal cell 10b in the glare-proof mode. In the liquid crystal glare-proof mirror 100, a driver can catch back light even if all incident light is controlled to be absorbed in optical absorption member 10d because practically the back light is reflected by the surface of the polarizing plate 10a and a protective coat (not shown) covering the surface of the polarizing plate 10a. The voltage value may be changed in stages based on the amount of the back light to gradually reduce glare.
In the liquid crystal glare-proof mirror 100 shown in
When a light HI (natural light (especially back light)) enters the polarizing plate 10a, the polarizing plate 10a transmits the vertical polarization component (the first polarization component) and ejects a light H2⊥ as shown in
The light H9 ejected from the liquid crystal cell 10b enters the reflection polarizing plate 10c and is reflected as a light H12= because the light H9= is the horizontal polarization component (the third polarization component). The light H12= then enters the liquid crystal cell 10b and a part of the light H12= is rotated by the liquid crystal cell 10b and ejected from the liquid crystal cell 10b as a light H13⊥, which is the vertical polarization component, and the other part of the light H12= is not rotated and ejected as a light H13=, which is the horizontal polarization component. Both of the light H13⊥ and the light H13= enter the polarizing plate 10a, but only the light H13⊥ is transmitted and ejected as a light H15⊥. When the behavior of the liquid crystal molecules x in the liquid crystal cell 10b are disordered, a light extraordinary ray H14 is ejected together with the light H13⊥ and the light H13=. The light H14 is generally the vertical polarization component which is the same as the polarization component of the light H13⊥ because the light H14 is a light whose traveling direction is changed from that of the light H13⊥, however, the light H11 is also assumed to include the vertical polarization component which has not been rotated for the convenience of the explanation.
The light H11=, which is the horizontal polarization component of the light H11, is significantly bent at the reflection polarizing plate 10c to be separated from the traveling direction of the light H12=. The light H11⊥, which is the vertical polarization component of the light H11 passes through the reflection polarizing plate 10c together with the light H9⊥. The light H11⊥ and the light H9⊥ are absorbed in the optical absorption member 10d. The light H14⊥, which is the vertical polarization component of the light H14, is significantly bent at the polarizing plate 10a to be separated from the traveling direction of the light H13⊥. The light H14=, which is the horizontal polarization component of the light H14, and a light H13= are absorbed in the polarizing plate 10a and radiated as heat.
As described above, when the liquid crystal glare-proof mirror 100 is in the glare-proof mode, it is possible to remove an extraordinary ray by the polarizing plate 10a and the reflection polarizing plate 10c and to eject only an ordinary ray as reflected light even when an extraordinary ray is generated in the liquid crystal cell 10b, whereby the liquid crystal glare-proof mirror 100 is less affected by an extraordinary ray generated in the liquid crystal cell 10b.
Examples 1 and 2 of a liquid crystal cell control circuit (means) for controlling the liquid crystal cell 10b are explained hereinafter.
A switch S of which end is grounded is connected to a direct current power supply E in series, and the positive electrode of the power supply E is connected to a resistance R1 via a branch point J1 and J2 as shown in
A resistance R2 of which an end is grounded is connected via a branch point J4 to the branch point J3 and an input terminal of the circuit SHI1. A capacitor C1 of which an end is grounded is connected via a branch point J5 to the branch point J4 and the input terminal of the circuit SHI1. The resistance R2 and the capacitor C1 functions as a delay circuit (means) for delaying a signal generated by voltage change at the branch point J3 to be input to the input terminal of the circuit SHI1. An output terminal of the circuit SHI1 is connected to an input terminal of a circuit SHI2.
The circuit SHI1 has hysteresis characteristics, and thus the operation condition of the circuit SHI1 is not changed by voltage change within a range set in advance. The negative logic at the circuit SHI1 returns to the positive logic at the circuit SHI2, and voltage change is absorbed by the circuit SHI1 and SHI2 having the hysteresis characteristics.
The output terminal of the circuit SHI2 is connected to an input terminal B of a digital IC1. The digital IC1 and a digital IC2 function as an oscillating circuit (means). Each of the digital IC1 and the digital IC2 includes an input terminal A (negative logic) (although a symbol “−” is assigned at the top of the reference symbol A in
Connected to the branch point J6 between an output terminal of a circuit SHI2 and the input terminal B of the digital IC1 is a resistance R3. A capacitor C2 of which end is grounded is connected to a branch point J7 which is connected to the other end of the resistance R3. The branch point J7 is also connected to a branch point J8, and the branch point J8 is further connected to each CLR terminal of the digital IC1 and the digital IC2. The resistance R3 and the capacitor C2 delays a signal being input to the CLR terminal.
The input terminal B of the digital IC2 is connected via a branch point J10 to a branch point J9 between the output terminal of the circuit SHI2 and the input terminal B of the digital IC1. Thus, the same output from the circuit SHI2 is input to each input terminal B in the digital IC1 and the digital IC2.
An output terminal Q (positive logic) of the digital IC1 is connected to the input terminal A (negative logic) of the digital IC2. The output terminal Q (negative logic) of the digital IC1 is opened. An output terminal Q (positive logic) of the digital IC2 is connected via a branch point J11 to the input terminal A(negative logic) of the digital IC1. Thus, when the input terminals B of the digital IC1 and the digital IC2 are high if the output terminal Q (positive logic) of the digital IC2 is low, the output terminal Q (negative logic) of the digital IC2 becomes low, making the output terminal Q (positive logic) of the digital IC1 high and the output terminal Q (negative logic) which is opened low. When the output terminal Q (positive logic) of the digital IC1 becomes low according to the duty ratio set based on the time constant set by the terminals Rx/Cx, the input terminal A (negative logic) of the digital IC2 becomes low. Then, the output terminal Q (positive logic) of the digital IC2 becomes high and the output terminal Q (negative logic) becomes low. By repeating the above operation, when the input terminal B is high, the digital IC1 and the digital IC2 function as an oscillating circuit (means).
An end of the terminal Cx of the digital IC1 is connected to a branch point J12 between an earth and a capacitor Cx. The other end of the capacitor Cx is connected via a branch point J13 to the terminal Rx/Cx of the digital IC1. The terminal Rx/Cx of the digital IC2 is connected via branch points J14 and J15 to the branch point J13. The terminal Cx of the digital IC2 is grounded. Connected to the branch point J14 is a diode D1 of which negative terminal is disposed at the branch point J14 side. A resistance Rx is also connected to the branch point J15.
A positive electrode of the diode D1 and the other end of the resistance Rx are connected to a branch point J30 and further connected to the positive electrode of the power supply E via the branch point J2. Therefore, when the switch S is switched on, the capacitor Cx is charged via the resistance Rx. When the switch S is switched off, the capacitor Cx starts to discharge electricity to raise the electrical potential of the terminal Cx of the digital IC1. Thus, the capacitor Cx functions as a delay circuit (means), preventing the digital IC1 from being turned off abruptly. When the switch S is switched on, the digital IC1 and the digital IC2 are supplied with electricity from the terminals Rx/Cx.
An input terminal A of a logical circuit NAND1 is connected to a branch point J11. An output terminal C of the logical circuit NAND1 is connected to input terminals A and B of the logical circuit NAND2. An output terminal C of the logical circuit NAND2 is connected to a terminal of the area AR2 on one side of the area AR2. An input terminal B of the logical circuit NAND1 and an input terminal B of the logical circuit NAND3 are connected to a branch point J16.
An input terminal A of the logical circuit NAND3 is connected to the output terminal Q (negative logic) of the digital IC2. An output terminal C of the logical circuit NAND3 is connected to input terminals A and B of the logical circuit NAND4. An output terminal C of the logical circuit NAND4 is connected to a terminal of the AR2 on the other side of the area AR2.
Thus, both of the output terminals C of the logical circuit NAND2 and the logical circuit NAND4 have to be low in order not to apply voltage to the liquid crystal cell 10b. On the other hand, when either one of the output terminals C of the logical circuit NAND 2 and the logical circuit NAND 4 is high and the other one of the output terminals C is low, voltage is applied to the area AR2 of the liquid crystal cell 10b.
In the circuit of example 1 described as above, on/off of the liquid crystal cell 10b is controlled based on the voltage value of the branch point J3 between the surrounding light sensor 7C and the backward light sensor 7A. Operations of the circuit in the non-glare-proof mode and the glare-proof mode are respectively described below.
The operation of the liquid crystal glare-proof mirror when back light comes into the liquid crystal glare-proof mirror while surrounding light is strong is described below. In this case, a driver is not dazzled because the back light is made less glaring by the surrounding light. Thus, the liquid crystal glare-proof mirror is controlled to be the non-glare-proof mode. In this case, even if the received light volume of the backward light sensor 7A is large, because the received light volume of the surrounding light sensor 7C is also large and the output voltage of the surrounding light sensor 7C is large, the voltage value of the branch point J3 does not become large, and thus the input terminal of the circuit SHI1 becomes low. At this time, the output of the circuit SHI1 is high and the output of the circuit SHI2 is low. Thus, each input terminal B and each CLR terminal in the digital IC1 and digital IC2 are low. Each input terminal B in the logical circuit NAND1 and the logical circuit NAND3 is low and thus each output terminal C in the logical circuit NAND1 and the logical circuit NAND3 is high. Therefore, each output terminal C in the logical circuit NAND2 and the logical circuit NAND4 becomes low. Thus, voltage is not applied to the area AR1, and the area AR1 in the liquid crystal glare-proof mirror 10 is not glare-proofed.
When back light comes into the liquid crystal glare-proof mirror while surrounding light is weak, the liquid crystal glare-proof mirror is controlled to be in the glare-proof mode because the back light is emphasized too much and a driver is dazzled. To be more specific, the voltage value of the branch point J3 becomes large in this case because the received light volume of the surrounding light sensor 7C is small, the output voltage thereof is also small, the received light volume of the backward light sensor 7A is large and the output voltage thereof is also large. Therefore, the input terminal of the circuit SHI1 becomes high, making the output voltage of the circuit SHI2 high. Then each input terminal B in the logical circuit NAND1 and the logical circuit NAND3 becomes high. Each input terminal of the digital IC1 and the digital IC2 is also high, and thus the digital IC1 and the digital IC2 starts to function as an oscillating circuit. Thus, the logical circuit NAND1 and the logical circuit NAND 3 repeats an on-off operation according to the output of the digital IC2, causing the logical circuit NAND 2 and the logical circuit NAND 4 to perform an on-off operation corresponding to the on-off operation of the logical circuit NAND1 and the logical circuit NAND 3. Thus, alternating voltage is applied to the liquid crystal cell 10b, and the liquid crystal glare-proof mirror 100 is in the glare-proof mode.
Similarly to the example 1, in the example 2 a switch S of which an end is grounded is connected to a direct current power supply E in series, and the positive electrode of the power supply E is connected to a resistance R1 via a branch point J1 and J2 as shown in
A resistance R2 of which an end is grounded is connected via a branch point J4 to the branch point J3 and an input terminal of the circuit SHI1. A capacitor C1 of which an end is grounded is connected via a branch point J5 to the branch point J4 and the input terminal of the circuit SHI1. The resistance R2 and the capacitor C1 functions as a delay circuit (means) for delaying a signal generated by voltage change at the branch point J3 to be input to the input terminal of the circuit SHI1.
The anode of a diode D4 and the anode of a diode D2 are connected to the output terminal of the circuit SHI1 via a branch point J17. The resistance R3 of which an end is grounded is connected via a branch point J18 to the cathode of the diode D4. Connected to the branch point J18 via a branch point J19 is an input terminal of a circuit SHI 8. An output terminal of the circuit SHI 8 is connected to a terminal of the liquid crystal cell 10b on one side thereof.
A resistance R4 of which an end is grounded is connected to the cathode of the diode D2 via a branch point J20. Connected to the branch point J20 via a branch point J21 is an input terminal of a circuit SHI 7. An output terminal of the circuit SHI7 is connected to a terminal of the area AR2 of the liquid crystal cell 10b on the other side of the area AR2. Therefore, when voltage is not applied to the liquid crystal cell 10b, both output terminals of the circuit SHI7 and the circuit SHI8 are low, whereas when voltage is applied to the liquid crystal cell 10b, each output terminal of the circuit SHI7 and the circuit SHI8 outputs high and low alternately.
An input terminal of the circuit SHI4 is connected to a branch point J22 between the branch point J21 and the circuit SHI7, and an output terminal of the circuit SHI4 is connected to the branch point J19 via a diode D5. Connected to the branch point J21 is the cathode of a diode D3, and the anode of the diode D3 is connected to an output terminal of the circuit SHI6. Connected to an input terminal of the circuit SHI6 via a branch point J23 are an output terminal of the circuit SHI5 and a resistance R5. The resistance R5 is also connected to an input terminal of the circuit SHI5 via a branch point J24, and the input terminal of the circuit SHI5 is connected via the branch point J24 to a capacitor C2 of which an end is grounded.
In the circuit described above, when the liquid crystal glare proof mirror is in the non-glare-proof mode (i.e. when the branch point J3 is low), the output terminal of the circuit SHI1 becomes high, making the diode D2 conduct and its potential on the branch point J21 side high. Thus, reverse voltage is applied to the diode D3, making the potential of the output terminal of the circuit SHI6 low, and thus the potential of the branch point J23 becomes high. The capacitor C2, the circuit SHI5 and the resistance R5 constitutes an astable multivibrator (oscillating circuit (means)). Thus, when the branch point J23 is high, the capacitor C2 is charged through the resistance R5. It is to be noted that the capacitor C2 remains saturated with the branch point J23 kept being high because a trigger voltage of the circuit SHI5 is not exceeded when reverse voltage is applied to the diode D3.
At this time, the input terminal of the circuit SHI8 is high and the output terminal of the circuit SHI8 is low because the diode D4 is conducted in a forward direction. The input terminal of the circuit SHI7 is high and the output terminal of the circuit SHI7 is low because the diode D2 is conducted. Thus, voltage is not applied to the liquid crystal cell 10b, and the liquid crystal glare-proof mirror 100 is in the non-glare-proof mode. Forward voltage is applied to the diode D5 because the input terminal of the circuit SHI4 is high, the output terminal of the circuit SHI4 is low and the branch point J19 is high.
When the non-glare-proof mode is switched to the glare-proof mode (i.e. the branch point J3 becomes high), the output terminal (branch point J51) of the circuit SHI1 becomes low, and thus reverse voltage is applied to the diode D2, causing the potential of the diode D2 on the branch point J21 side to be low through the resistance R4. On the other hand, the low voltage applied to the output terminal of the circuit SHI6 is reduced by the reverse voltage applied to the diode D3, and the capacitor C2 begins to discharge based on a balance between a trigger voltage of the circuit SHI6 and a trigger voltage of the circuit SHI5, causing the capacitor C2 and the circuit SHI5 and the resistance R5 to start oscillation. The oscillation is transmitted to the branch point J22 via the diode D3, and thus the output terminal of the circuit SHI 7 repeats inversion of high and low, and the circuit SHI4 and the circuit SHI8 synchronizes with the circuit SHI7 to repeat inversion of high and low which is reversed from the inversion at the circuit SHI 7. Thus, voltage is applied to the liquid crystal cell 10b, making the liquid crystal glare-proof mirror 100 be in the glare-proof mode.
In the above embodiments, the liquid crystal glare-proof mirror 100 includes both of the surrounding light sensor 7C and the backward light sensor 7A, however, the liquid crystal glare-proof mirror 100 may include at least one of them.
In the above embodiments, the liquid crystal glare-proof mirror 100 includes the TN liquid crystal as a light transmission shutter, however the liquid crystal glare-proof mirror 100 may include any other components as a light transmission shutter as long as the components have a shutter function without limited to the TN liquid crystal.
In the above embodiments, the liquid crystal is used as a light transmission shutter, however, Faraday rotator using a so-called Faraday effect that exhibits a polarization rotatory power when given a magnetic field may be used as a shutter element.
The embodiments according to the present invention have been explained as aforementioned. However, the embodiment of the present invention is not limited to those explanations, and those skilled in the art ascertain the essential characteristics of the present invention and can make the various modifications and variations to the present invention to adapt it to various usages and conditions without departing from the spirit and scope of the claims.
Number | Date | Country | Kind |
---|---|---|---|
2007-170102 | Jun 2007 | JP | national |