JP2004144827A - Light control device and image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light control device of which the maximum transmittance in a transparent state is high and the optical density ratio (the contrast ratio) is heightened to a large extent, and an image pickup device with improved performance, picture quality and reliability realized by arranging the light control device in an optical path. <P>SOLUTION: The light control device 6 is constituted of a film shaped liquid crystal optical element (a GH cell) 7 to be inserted into and extracted from an effective optical path and a polarizing plate 11 to be inserted into and extracted from the effective optical path, and the image pickup device has the light control device 6 arranged in an optical path of the image pickup system. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a light control device for adjusting the light transmittance of incident light, and an imaging device using the light control device.
[0002]
[Prior art]
Usually, a polarizing plate is used for a light control device using a liquid crystal optical element (liquid crystal cell). As this liquid crystal cell, for example, a TN (Twisted Nematic) liquid crystal cell or a guest-host (GH (Guest @ Host)) liquid crystal cell is used.
[0003]
FIG. 11 is a schematic diagram illustrating the operation principle of a conventional light control device. This light control device is mainly composed of a polarizing plate 1 and a GH cell 2. Although not shown, the GH cell 2 is sealed between two glass substrates and has an operating electrode and a liquid crystal alignment film. (The same applies hereinafter). In the GH cell 2, liquid crystal molecules 3 and dichroic dye molecules 4 are sealed.
[0004]
The dichroic dye molecules 4 have anisotropy in light absorption, and are, for example, positive (p-type) dye molecules that absorb light in the molecular major axis direction. The liquid crystal molecules 3 are of a positive type (positive type) having a positive dielectric anisotropy.
[0005]
FIG. 11A shows a state of the GH cell 2 when no voltage is applied (no voltage is applied). The incident light 5 is converted into linearly polarized light by passing through the polarizing plate 1. In FIG. 11A, since the polarization direction matches the major axis direction of the dichroic dye molecules 4, the incident light 5 is absorbed by the dichroic dye molecules 4 and the light transmittance of the GH cell 2 is changed. Decreases.
[0006]
Then, as shown in FIG. 11B, when a voltage is applied to the GH cell 2, as the liquid crystal molecules 3 are oriented in the direction of the electric field, the molecular major axis direction of the dichroic dye molecules 4 becomes linearly polarized light. At right angles to the direction. Therefore, the incident light 5 is transmitted by the GH cell 2 without being absorbed.
[0007]
When a negative (n-type) dichroic dye molecule that absorbs light in the direction of the major axis of the molecule is used, the light is reversed when the positive dichroic dye molecule 4 is not applied. Is not absorbed, and light is absorbed when a voltage is applied.
[0008]
In the light control device shown in FIG. 11, the ratio of the absorbance between when the voltage is applied and when no voltage is applied, that is, the ratio of the optical density is about 10. This has approximately twice the optical density ratio as compared with a dimmer that is configured only with the GH cell 2 without using the polarizing plate 1.
[0009]
[Procedure leading to the invention]
However, in the above-described conventional light control device, since the polarizing plate 1 is always fixed and installed in the effective optical path of the light, for example, 50% of the light is always absorbed by the polarizing plate 1, and There is also an effect of surface reflection and the like. Therefore, the maximum light transmittance transmitting through the polarizing plate 1 cannot exceed, for example, 50%, and the amount of light is significantly reduced. This decrease in light quantity has been one of the factors that make it difficult to commercialize a light control device using a liquid crystal cell.
[0010]
As a result of diligent studies on the problems of the prior art as described above, the present applicant has improved the contrast ratio of the dimmer, and has successfully performed the dimming operation in a wide range from a bright place to a dark place. Is proposed in Japanese Patent Application Laid-Open No. 11-326894.
[0011]
That is, according to the invention disclosed in Japanese Patent Application Laid-Open No. 11-326894 (hereinafter referred to as the prior invention), the liquid crystal optical element and the polarizing plate capable of entering and exiting the effective optical path of light incident on the liquid crystal optical element are adjusted. By configuring the light device, the contrast ratio of the light control device is improved, and the light control operation can be performed normally in a wide range from a bright place to a dark place.
[0012]
[Problems to be solved by the invention]
However, the present inventor has found that the prior invention has the above-mentioned excellent features, but still needs to be improved.
[0013]
That is, in the light control device of the prior application, the polarizing plate can be moved in and out of the effective optical path of light, but the GH cell is always fixed and installed in the effective optical path of light. Even when is selected, the light transmittance in the transparent state is reduced by about 20 to 30% (maximum light transmittance: 70 to 80%), and the light control performance in a bright place naturally has a limit.
[0014]
In recent years, as the miniaturization and high definition of an image pickup device (CCD: Charge Coupled Device) have progressed, the imaging sensitivity tends to be relatively low, and from the viewpoint of the minimum illuminance of the subject, the maximum light transmittance in a transparent state is as high as possible. A value is required.
[0015]
Under these circumstances, in order to realize a higher-performance imaging apparatus, it is desired to improve the light transmittance in a transparent state and secure a larger optical density ratio (contrast ratio, dynamic range).
[0016]
The present invention has been made in order to improve the insufficient point while making use of the features of the above-mentioned prior application, and an object of the present invention is to achieve a high maximum light transmittance in a transparent state and an optical density ratio ( It is an object of the present invention to provide a light control device capable of greatly improving contrast ratio) and an imaging device capable of realizing improvement in performance, image quality, and reliability by disposing the light control device in an optical path.
[0017]
[Means for Solving the Problems]
That is, the present invention relates to a light control device including a liquid crystal optical element that can enter and exit the effective optical path of light and a polarizing plate that can enter and exit the effective optical path. The present invention relates to an imaging device arranged in an optical path.
[0018]
According to the dimming device and the imaging device of the present invention, the liquid crystal optical element and the polarizing plate are configured so as to be able to enter and exit the effective optical path of light. The plate can be moved out of the effective optical path, the maximum light transmittance when transparent is high, and the optical density ratio (contrast ratio) can be greatly improved.
[0019]
Therefore, the present invention is extremely effective for improving the performance, image quality, and reliability of a light control device and an image pickup device using the liquid crystal optical element and the polarizing plate.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides a light control device having an improved optical function, which is based on the above-mentioned prior application (Japanese Patent Application No. 11-322186). According to the invention of the prior application, a dimming device is constituted by a liquid crystal optical element and a polarizing plate that is disposed in an effective optical path of light incident on the liquid crystal optical element and that can enter and exit the effective optical path. The liquid crystal optical element has liquid crystal sealed between glass substrates facing each other, each having a transparent electrode and an alignment film, and further, the liquid crystal is a guest-host type liquid crystal optical element using negative type liquid crystal molecules as a host material. It is. According to this, the ratio of absorbance between when no voltage is applied and when a voltage is applied (that is, the ratio between optical densities) is improved, the contrast ratio of the light control device is increased, and the light control operation can be performed from a bright place to a dark place. Enables normal operation.
[0021]
In the guest-host type liquid crystal cell (GH cell) 2 shown in FIG. 11, a positive type liquid crystal molecule having a positive dielectric anisotropy (Δε) is used as the host material 3, and the guest material 4 has dichroism. Using positive dye molecules 4 having positive light absorption anisotropy (ΔA), arranging the polarizing plate 1 on the incident side of the GH cell 2, and changing the light transmittance when applying an operating voltage using a rectangular wave as a driving waveform 12, as shown in FIG. 12, the average light transmittance of visible light (in air; see the light transmittance when a polarizing plate is added in addition to the liquid crystal cell) with the application of the operating voltage (= 100%). ): The same applies hereinafter), but the maximum light transmittance is only about 60% even when the voltage is increased to 10 V, and the change in light transmittance is gradual.
[0022]
This is because when a positive host material is used, the direction of the director changes even when a voltage is applied because the interaction of liquid crystal molecules at the interface with the liquid crystal alignment film of the liquid crystal cell is strong when no voltage is applied. This is probably because liquid crystal molecules that do not (or hardly change) remain.
[0023]
On the other hand, according to the prior invention, as shown in FIG. 13, in the guest-host type liquid crystal cell (GH cell) 12, as the host material 13, negative type liquid crystal molecules having a negative dielectric anisotropy (Δε) are used. By using MLC-6608 manufactured by Merck as an example, and using D5 manufactured by BDH, which is a positive dye molecule having dichroism, as the guest material 4 as an example, the polarizing plate 11 can be used for the GH cell 12. When the change in the light transmittance when the operating voltage was applied was measured using a rectangular wave as a driving waveform and the operating voltage was applied, as shown in FIG. 14, the average light transmittance of visible light ( (In air) decreases from a maximum light transmittance of about 75% to several percent, and the change in light transmittance becomes relatively steep.
[0024]
This is because, when a negative-type host material is used, the interaction of liquid crystal molecules at the interface with the liquid crystal alignment film of the liquid crystal cell is very weak when no voltage is applied, so that light is easily transmitted when no voltage is applied. It is also considered that the direction of the director of the liquid crystal molecules easily changes with the application of the voltage.
[0025]
Thus, in the invention of the prior application, by forming the GH cell 12 using the negative type host material, the light transmittance (especially when transparent) is improved, and the GH cell 12 is positioned in the imaging optical system as it is. A compact light control device that can be fixed and used can be realized. In this case, as shown in FIGS. 13 and 15, the polarizing plate 11 is arranged in the optical path of the incident light to the liquid crystal optical element 12 and the polarizing plate 11 can be moved in and out of the effective optical path of the light, so that no voltage is applied. The ratio of the absorbance between the applied voltage and the applied voltage (that is, the ratio of the optical density) is further improved, the contrast ratio of the dimmer is further increased, and the dimming operation is performed more normally from a bright place to a dark place. Can be.
[0026]
However, according to the dimmer 23 of the prior application, the polarizing plate 11 can be moved in and out of the effective optical path, but the GH cell 12 is always fixed and installed in the effective optical path. Even if the liquid crystal material to be used is selected, the light transmittance when transparent is reduced by about 20 to 30% (maximum light transmittance: 70 to 80%), and the light control performance in a bright place is naturally limited. Was.
[0027]
The inventor of the present invention has intensively studied the further improvement of the characteristics of the light control device using the GH cell 12, and in order to improve the light transmittance in the transparent state and obtain a higher optical density ratio, A liquid crystal optical element that can be moved into and out of the effective optical path of light, and a polarizing plate that includes a polarizing plate that can be moved in and out of the effective optical path, for example, when transparent, the liquid crystal optical element and the polarizing plate are separated from the effective optical path of light. It was found for the first time that it was extremely effective to improve the light transmittance.
[0028]
Here, in the light control device according to the present invention, it is desirable that the liquid crystal optical element is in the form of a lighter film.
[0029]
Further, the film-like liquid crystal optical element has liquid crystal sealed between mutually opposed substrates each having a transparent electrode and an alignment film, and the opposite substrate is replaced with a conventional glass substrate, polycarbonate, polyarylate, polyester. It is preferable that the flexible substrate is made of at least one plastic material selected from sulfone and polyethylene terephthalate as a main raw material.
[0030]
According to this, the weight can be reduced to about 1/4 to 1/5 as compared with a GH cell using a glass substrate as the counter substrate, and the strength can be improved, and a simpler structure can be obtained. The position of the liquid crystal optical element can be made movable by a driving means. Then, the film-like liquid crystal optical element and the polarizing plate are moved in and out of the effective optical path of light, so that it is possible to further improve the light transmittance when transparent, and as a result, the film-like liquid crystal optical element Can greatly improve the dynamic range of a light control device using the light control device.
[0031]
When a normal glass substrate is used as the counter substrate, a method for forming a transparent conductive film on the glass substrate is, for example, using indium tin alloy as a raw material, under a reduced pressure atmosphere containing a little oxygen, A film is formed by a technique such as sputtering, and then baked at about 300 to 500 ° C. to increase transparency and electric conductivity.
[0032]
On the other hand, when the flexible substrate is used as the counter substrate, the plastic film substrate such as the polycarbonate (PC) or the polyester sulfone (PES) (that is, the flexible substrate) has low heat resistance and is heated at a high temperature. Can not.
[0033]
Therefore, on the plastic film substrate held at a low temperature, a black indium lower oxide film is first formed by vapor deposition or ion plating using indium oxide containing a small amount of tin oxide, and then the indium lower oxide film is formed. An alternative process is performed, such as oxidizing for about 1 hour while heating the film at about 170 ° C.
[0034]
The black indium lower oxide has a high specific resistance and poor transparency, but by oxidizing it, it is possible to improve both conductivity and transparency.
[0035]
FIG. 9 shows an example of the relationship between the atmospheric conditions and the conductivity or transparency in this oxidation treatment step. By grasping such characteristics and performing oxidation treatment under appropriate conditions after the low-temperature film formation step, the plastic film It is preferable to perform a practical process for forming a transparent conductive film over the substrate.
[0036]
The light control device according to the present invention is disposed between a front lens group 15 and a rear lens group 16 including a plurality of lenses such as a zoom lens, for example, as shown in FIG. The light transmitted through the front lens group 15 is linearly polarized by way of the polarizing plate 11 and then enters the liquid crystal optical element (GH cell) 7. The light transmitted through the film-shaped GH cell 7 is condensed by the rear lens group 16 and projected on the imaging surface 17 as an image.
[0037]
The film-like GH cell 7 and the polarizing plate 11 constituting the light control device 6 can be moved in and out of an effective optical path of incident light. Specifically, by moving the film-form GH cell 7 and the polarizing plate 11 to positions indicated by phantom lines, the light can be out of the effective optical path of light.
[0038]
FIG. 2 is a schematic sectional view of the film-like liquid crystal optical element (GH cell) constituting the light control device according to the present invention.
[0039]
As shown in FIG. 2, the film-shaped GH cell 7 movable with respect to the effective optical path is a flexible material mainly composed of at least one plastic material selected from polycarbonate, polyarylate, polyester sulfone, and polyethylene terephthalate. A liquid crystal mixture 24 having substrates 8a and 8b and having a liquid crystal mixture 24 sealed therebetween. The liquid crystal mixture 24 has a negative liquid crystal molecule 13 as a host material and a positive dye molecule 4 as a guest material. Type liquid crystal. The space between the flexible substrates 8a and 8b is sealed with a sealant 21. Further, a power source 14 is connected to the film-shaped GH cell 7.
[0040]
The flexible substrates 8a and 8b have transparent electrodes 9a and 9b and alignment films 10a and 10b, respectively.
[0041]
The film-like GH cell 7 uses negative liquid crystal molecules 13 having a negative dielectric anisotropy (Δε) as a host material and dichroic positive dye molecules 4 as a guest material. When no voltage is applied, as shown in FIG. 1A, light passes through the film-shaped GH cell 7 without being absorbed. Conversely, as shown in FIG. 1B, when a voltage is applied, the direction of the director of the liquid crystal molecules changes, light is absorbed by the positive dye molecules 4, and the light transmittance of the film-like GH cell 7 decreases. . In the film-shaped GH cell 7, since the interaction of liquid crystal molecules at the interface with each liquid crystal alignment film 10 of the film-shaped GH cell 7 when no voltage is applied is very weak, light is transmitted when no voltage is applied. The direction of the director of the liquid crystal molecules is easily changed with the application of a voltage, and light is absorbed by the positive dye molecules.
[0042]
Further, the weight of the film-shaped GH cell 7 is reduced to 1/4 to 1/5 of that of a GH cell using a normal glass substrate, and the film-shaped GH cell can be formed by a simpler driving means. 7 can be made movable.
[0043]
Then, by putting the film-shaped GH cell 7 and the polarizing plate 11 into and out of the effective optical path of light, for example, it becomes possible to further improve the light transmittance when transparent, and as a result, the film-shaped GH cell 7 The dynamic range of the used light control device 6 according to the present invention can be greatly improved.
[0044]
In the light control device and the image pickup device according to the present invention, it is desirable that the liquid crystal molecules of the liquid crystal optical element have a negative dielectric anisotropy, but the guest material is a positive or negative dichroic material. It may consist of dye molecules.
[0045]
Further, in the light control device according to the present invention, the polarizing plate is provided in a stop means for adjusting the amount of light passing through the effective optical path, a first driving mechanism for driving the stop means, and the liquid crystal optical element. It is preferable to have at least a second driving mechanism for driving.
[0046]
Specifically, as shown in FIG. 3, the light control device 6 according to the present invention includes a GH cell holding member 29 to which the film-shaped GH cell 7 is fixed, and a GH cell driving device for moving the GH cell holding member 29. A mechanism 30, two diaphragm blades 18, 19 movably arranged in the vertical direction and in opposite directions to each other as the diaphragm means, and a diaphragm blade driving mechanism for moving these diaphragm blades 18, 19 It is preferable to include the polarizing plate 11 and the polarizing plate 11 fixed to the diaphragm blade 18.
[0047]
The film-like GH cell 7 has two plastic film substrates (that is, flexible substrates) each having the transparent electrode and the alignment film as described above, and the liquid crystal mixture is sealed therebetween. The liquid crystal mixture is, for example, a guest-host type liquid crystal in which negative type liquid crystal molecules are used as a host material and positive type dye molecules are used as a guest material.
[0048]
Each of the diaphragm blades 18 and 19 and the GH cell holding member 29 are formed of, for example, a relatively strong film or the like, and the other diaphragm blade 19 and the GH cell holding member 29 sandwich one diaphragm blade 18 therebetween. In the imaging lens system, the diaphragm blades 19 are arranged such that the aperture blade 19 is on the object side and the GH cell holding member 29 is on the image side.
[0049]
Although not shown, the diaphragm blades 18 and 19 and the GH cell holding member 29 are disposed in a rectangular box-shaped housing that is flat in the front-rear direction and long in the vertical direction so as to freely slide in the vertical direction. In addition, a circular light transmitting hole is formed in the housing.
[0050]
The aperture blade 19 has a substantially J-shape when viewed from behind, and a substantially semicircular large opening diameter notch 87 is formed at the upper edge of the lower part thereof. The lower end 87a of the opening diameter notch 87 is , Are formed in a substantially triangular shape.
[0051]
A guided slit 88 is formed at a position near the left edge of the diaphragm blade 19 and extends vertically in the vertical direction, and a guided slit 89 is also formed at the position near the right edge. Further, a connecting slot 90 extending in the left-right direction is formed at a position immediately above the upper guided slit 88 of the diaphragm blade 19.
[0052]
The left two guided slits 88 are provided with two support pins on the left side of the housing (not shown), respectively, and the right guided slit 89 is provided with a support pin located below the right side of the housing. The diaphragm blades 19 are supported by the housing so that they can freely move in the vertical direction.
[0053]
A substantially semicircular opening diameter notch (the upper end of which is substantially triangular) is formed at the lower edge of the diaphragm blade 18 sandwiched between the diaphragm blade 19 and the GH cell holding member 29 in the optical axis direction. The polarizing plate 11 is fixed to the notch for forming the opening diameter. A guided slit 92 is formed at a position closer to the right edge of the aperture blade 18 and is formed so as to be vertically separated from each other and to extend in the vertical direction. A guide slit 93 is formed. Further, a long connecting left and right hole 94 is formed above the right guided slit 92.
[0054]
In the diaphragm blade 18, two guide pins on the right side of the housing (not shown) are provided in the guided slit 92 on the right side, and the lower support pin on the left side of the housing is provided in the guided slit 93 on the left side. Are supported so that they can freely rub.
[0055]
The aperture blades 18 and 19 are configured to move in the vertical direction and in opposite directions, respectively. The apertures are formed by overlapping the opening diameter notch 87 with the polarizing plate 11, and will be described later. In addition, the size of the opening is changed by driving the aperture blade driving mechanism 31.
[0056]
The GH cell holding member 29 has a substantially U-shape that opens upward when viewed from the front, and a film-shaped GH cell 7 is fixed to a central notch so as to cover the notch. The left-right width of each of the aperture blades 18 and 19 is substantially the same as or slightly larger than the left-right width of each of the aperture diameter forming cutouts.
[0057]
Further, a guided slit 98 is formed at a position near the right edge of the film-shaped GH cell 7, and a position immediately below a guided slit 99 provided at a position near the left edge of the film-shaped GH cell 7. A connection elongated hole 100 extending in the left-right direction is formed in the connector.
[0058]
In the GH cell holding member 29, two pins on the right side of the housing (not shown) are provided in the guided slit 98 on the right side, and two pins on the left side of the housing are provided in the guided slit 99 on the left side. The support pins are movably engaged with each other so as to be freely movably supported by the support pins.
[0059]
Next, the diaphragm blade driving mechanism 31 includes a motor 102 disposed above the dimmer 6 and a rotating arm 103 driven by the motor 102. The rotating arm of the motor 102 103 is attached.
[0060]
The rotating arm 103 has a central portion fixed to the rotating shaft of the motor 102, and small connecting pins 104 a and 104 b are provided at both left and right ends of the rotating arm 103 so as to project forward. The connecting pins 104a and 104b are arranged so that the distance from the rotation axis of the motor 102 is the same.
[0061]
The connection pin 104a located at the left end is engaged with the connection elongated hole 90 of the aperture blade 19, and the connection pin 104b located at the right end is engaged with the connection elongated hole 94 of the aperture blade 18 so as to freely rub.
[0062]
Accordingly, when the rotation arm 103 rotates, the connection pins 104a and 104b are displaced in the directions opposite to each other, so that the diaphragm blade 18 and the diaphragm blade 19 move in the directions opposite to each other. In addition, the diaphragm blade 18 and the diaphragm blade 19 that move in different directions move with the same displacement amount (the same speed).
[0063]
When the diaphragm blade 18 and the diaphragm blade 19 move in directions opposite to each other, the polarizing plate 11 fixed to the diaphragm blade 18 and the notch 87 for forming the aperture diameter of the diaphragm blade 19 overlap each other. When the size of the opening changes and the diaphragm blades 19 are located at the upper end in the moving range and the diaphragm blades 18 are positioned at the lower end in the moving range, the openings are all covered with the polarizing plate 11, and When the diaphragm blade 19 is located at the lower end of the moving range and the diaphragm blade 18 is located at the upper end of the moving range, the opening is in the largest state.
[0064]
That is, as shown in FIG. 4, the diaphragm blades 18 and 19 are relatively moved using the diaphragm blade drive mechanism 31 in the direction indicated by the arrow 27.
[0065]
As a result, as shown in FIG. 4, the aperture blades 18 and 19 are partially overlapped, and when the overlap becomes large, the aperture 22 on the effective optical path 20 located near the center of the aperture blades 18 and 19 becomes a polarizing plate. 11 covered.
[0066]
FIG. 5 is a partially enlarged view of the diaphragm means 25 near the effective optical path 20. At the same time as the diaphragm blades 18 move upward, the diaphragm blades 19 move downward. Along with this, as shown in FIG. 5A, the polarizing plate 11 attached to the diaphragm blade 18 also moves out of the effective optical path 20. Conversely, by moving the diaphragm blade 18 downward and the diaphragm blade 19 upward, the diaphragm blades 18 and 19 overlap each other. Accordingly, as shown in FIG. 5B, the polarizing plate 11 moves on the effective optical path 20, and gradually covers the opening 22. When the overlapping of the diaphragm blades 18 and 19 increases, as shown in FIG. 5C, the polarizing plate 11 covers the entire opening 22.
[0067]
Next, the GH cell driving mechanism 30 is provided with a motor 105 disposed below the dimmer 6 and a rotating arm 106 driven by the motor 105. One end of the rotating arm 106 is fixed to the rotating shaft of the motor 105, and a small connecting pin 107 is provided at the other rotating end of the rotating arm 106 so as to protrude forward. ing.
[0068]
The connecting pin 107 is provided so as to freely rub against the connecting elongated hole 100 of the GH cell holding member 29, so that when the rotating arm 106 rotates, the GH cell holding member 29 is moved. Move up and down. In this way, the aperture blade drive mechanism 31 and the GH cell drive mechanism 30 are driven to form the opening 22, and the positional relationship of the film-like GH cell 7 and the polarizing plate 11 with respect to the opening 22 can be defined.
[0069]
Here, the opening area is controlled by the diaphragm means 25 to which the polarizing plate 11 is fixed from an open state located outside the effective optical path to a predetermined open state. It is preferred to have cell 7 enter.
[0070]
For example, as shown in FIGS. 3 to 5, as the subject (not shown) becomes brighter, the movement of the connecting pins 104a and 104b causes the aperture blade 18 which is opened in the vertical direction as shown in FIG. , 19 are driven and begin to overlap. As a result, the polarizing plate 11 attached to the diaphragm blade 18 starts to enter the effective optical path 20 and covers a part of the opening 22 (FIG. 5B).
[0071]
At the same time, by driving the motor 105 and appropriately moving the GH cell holding member 29 upward by the movement of the connecting pin 107, the film-shaped GH cell 7 starts to enter the effective optical path 20.
[0072]
Thereafter, the polarizing plate 11 completely covers the opening 22 (FIG. 5C), and the film-shaped GH cell 7 also covers the opening 22. Further, when the brightness of the subject increases, the voltage to the film-shaped GH cell 7 is increased, and light is adjusted by absorbing the light with the film-shaped GH cell 7.
[0073]
Conversely, when the subject becomes dark, the light absorbing effect of the film-shaped GH cell 7 is eliminated by first reducing or not applying the voltage to the film-shaped GH cell 7. Further, when the subject becomes darker, the motor 102 is driven, and the movement of the connecting pins 104a and 104b moves the diaphragm blade 18 upward and the diaphragm blade 19 downward to move the polarizing plate 11 out of the effective optical path 20. 5 (a), the motor 105 is driven and the GH cell holding member 29 is appropriately moved by the movement of the connecting pin 107 so that a predetermined area of the film-like GH cell 7 is moved to the effective optical path 20. Move outside.
[0074]
According to the light control device 6 according to the present invention, since the film-like GH cell 7 using the flexible substrate is used as the liquid crystal optical element, compared with the GH cell using a normal glass substrate, The weight can be reduced to 1/4 to 1/5, and the position of the film-like GH cell 7 can be moved by simpler driving means as described above.
[0075]
And since it has the film-shaped GH cell 7 and the polarizing plate 11 (light transmittance, for example, 40% to 50%), the film-shaped GH cell 7 itself absorbs light in addition to the light control device using the polarizing plate 11. Thus, light control can be performed.
[0076]
Further, since the film-shaped GH cell 7 and the polarizing plate 11 (light transmittance, for example, 40% to 50%) can be out of the effective optical path 20 for light, the light is absorbed by the film-shaped GH cell 7 and the polarizing plate 11. Not done. Specifically, when the film-forming GH cell 7 and the polarizing plate 11 are completely out of the effective optical path 20 when the GH cell is transparent, the maximum light transmittance of the light control device in which the conventional GH cell is fixed and installed is reduced. The maximum light transmission of the dimmer 6 according to the invention can be about 100%, compared to about 75%. Note that the minimum light transmittance is the same for both.
[0077]
In this manner, the light control device 6 according to the present invention can increase the contrast ratio between light and dark and can maintain the light amount distribution substantially uniform.
[0078]
Here, in the dimming device according to the present invention, instead of the structure as shown in FIG. 3, as shown in FIG. 6, the driving of the diaphragm means, the polarizing plate and the liquid crystal optical element is performed by a common driving mechanism. The structure may be made.
[0079]
Specifically, as shown in FIG. 6, the light control device 6 according to the present invention includes a GH cell holding member 29 to which the film-like GH cell 7 is fixed, and a vertical direction and opposite directions as the diaphragm means. The drive mechanism 109 of the two diaphragm blades 18 (however, the polarizing plate 11 is fixed to the diaphragm blade 18 in the same manner as described above) and 19 are movably disposed on the motor 110 and the motor 110. It comprises a rotating plate 111 driven by 110 and the like.
[0080]
Further, by forming the cam grooves 112, 113 and 114 in the two aperture blades 18 and 19 and the GH cell holding member 29, respectively, the two aperture blades 18 and 19 and the GH cell The holding member 29 can be moved simultaneously and within a predetermined range. Furthermore, by appropriately changing the shapes of the cam grooves 112, 113, and 114, the movements of the aperture blades 18, 19 and the GH cell holding member 29 can be easily controlled.
[0081]
Then, the film-like GH cell 7 has two pieces of the plastic film substrate (that is, a flexible substrate) having the transparent electrode and the alignment film in the same manner as described above, and the liquid crystal mixture is sealed therebetween. Preferably, the liquid crystal mixture is a guest-host type liquid crystal in which, for example, negative type liquid crystal molecules are used as a host material and positive type dye molecules are used as a guest material.
[0082]
Cam grooves 112 and 113 are formed at the lower ends of the aperture blades 18 and 19, respectively, and a cam groove 114 is also formed at the lower end of the GH cell holding member 29.
[0083]
The rotating plate 111 is substantially disk-shaped, and provided with connecting pins 115a, 115b, and 115c protruding forward from predetermined three positions, respectively, and these connecting pins 115a, 115b, and 115c rotate. The connecting pins 115a and 115b are formed at positions shifted by 180 degrees with respect to the center of rotation of the rotating plate 111 by a central angle of 180 degrees. The pin 115c is formed below the line connecting the two connecting pins 115a and 115b with the line connecting the two connecting pins 115a and 115b substantially horizontally, and is formed at a position slightly closer to the connecting pin 115a.
[0084]
The cam groove 112 of the aperture blade 18 is engaged with the connection pin 115a, the cam groove 113 of the aperture blade 19 is engaged with the connection pin 115b, and the cam groove 113 of the GH cell holding member 29 is freely rubbed with the connection pin 115c. Matching.
[0085]
The cam grooves 112 and 113 of the aperture blades 18 and 19 are formed point-symmetrically about the rotation center of the rotating plate 111 in a state where the cam grooves 112 and 113 are engaged with the connection pins 115a and 115b of the rotating plate 111, respectively. The portions 112a and 113a excluding the both ends of the cam grooves 112 and 113 are formed on an arc centered on the rotation center of the rotating plate 111, and the ends 112b and 113b in the direction opposite to the clockwise direction are clockwise. Each is formed so that it may be displaced toward the inner circumference as it goes.
[0086]
Next, as shown in FIG. 6, the positional relationship between the two connecting pins 115a and 115b and the opening (not shown) is such that the line connecting the connecting pins 115a and 115b is slightly clockwise from horizontal. With the rotating plate 111 rotated, the polarizing plate 11 starts to cover the opening. In this state, the connecting pins 115a and 115b are located at the counterclockwise ends 112b and 113b of the cam grooves 112 and 113, respectively.
[0087]
In addition, the cam groove 114 of the GH cell holding member 29 is formed in a flat bow shape convex upward, and is formed so as to be located slightly to the left from the lower end when the opening is in the above state. In this state, the connecting pin 115c is located at the right end 114a of the cam groove 114.
[0088]
Next, as shown in FIG. 7, when the rotating plate 111 is rotated in the clockwise direction, the aperture blade 19 and the GH cell holding member 29 are raised, as indicated by dashed-dotted arrows, respectively. 18, the opening is reduced in diameter. When the connecting pins 115a and 115b engage with the arc-shaped portions 112a and 113a of the cam grooves 112 and 113, the vertical movement of the diaphragm blades 18 and 19 is stopped. At this time, the opening has a predetermined opening diameter. It has become.
[0089]
On the other hand, in the GH cell holding member 29, as shown in FIG. 7, the cam groove 114 with which the connecting pin 115c is engaged is not arc-shaped like the cam grooves 112 and 113. As a result, the film-like GH cell 7 enters the opening having a predetermined opening diameter.
[0090]
When the film-shaped GH cell 7 covers the entire opening having a predetermined opening diameter, the connecting pins 115a and 115b are engaged with the clockwise side ends 112c and 113c of the cam grooves 112 and 113, respectively, almost simultaneously, As a result, the diaphragm blade 19 rises again, the diaphragm blade 18 starts descending, and the diameter of the opening covered by the film-shaped GH cell 7 is reduced, thereby reducing the diameter of each of the cam grooves 112, 113 and 114. When the connecting pins 115a, 115b and 115c are located at the clockwise ends 112c and 113c or the left end 114b, respectively, the motor 110 (not shown) stops and the aperture blades 18 and 19 and the GH cell holding member 29 are stopped. The movement also stops.
[0091]
According to the light control device based on the present invention as shown in FIGS. 6 and 7, the number of drive mechanisms can be reduced, so that the mechanisms can be driven with less components and low power consumption.
[0092]
In addition, since the driving of the aperture blades 18 and 19 and the GH cell holding member 29 and the like are performed by the rotation of one rotating plate 111, the entire driving is synchronized, and the driving is easy and smooth.
[0093]
Further, it goes without saying that the light control device having such a structure also has the same function and effect as the light control device as shown in FIG.
[0094]
【Example】
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0095]
Example 1
First, an example of a light control device using a guest-host type liquid crystal (GH) cell will be described.
[0096]
As shown in FIG. 1, this light control device includes a film-shaped GH cell 7 and a polarizing plate 11, and the film-shaped GH cell 7 and the polarizing plate 11 can be moved in and out of an effective optical path of light.
[0097]
As shown in FIG. 2, the film-shaped GH cell 7 is formed by forming a transparent electrode and an alignment film on a 200 μm-thick flexible film substrate made of a plastic mainly composed of polycarbonate (PC). The two flexible film substrates are attached and aligned, and a mixture of a negative liquid crystal molecule (host material) 13 and a positive dichroic dye molecule (guest material) 4 is placed between the opposing substrates. A sealed liquid crystal optical element (GH cell) was obtained. In addition, the light absorption axis of the polarizing plate 11 was orthogonal to the light absorption axis when a voltage was applied to the film-form GH cell 7.
[0098]
The weight of the film-shaped GH cell 7 thus manufactured is reduced to about 約 to １ ／ of the weight of a conventional GH cell manufactured using a glass substrate having a thickness of about 500 μm. And improved strength.
[0099]
As liquid crystal molecules, for example, MLC-6608 manufactured by Merck, which is a negative type liquid crystal molecule having negative dielectric anisotropy, is used as an example. Dichroic dye molecules have anisotropy in light absorption. For example, DDH manufactured by BDH, which is a positive dye molecule that absorbs light in the molecular long axis direction, was used as an example.
[0100]
The light control device 6 is disposed between a front lens group 15 and a rear lens group 16 including a plurality of lenses such as a zoom lens, for example, as shown in FIG. The light transmitted through the front lens group 15 is linearly polarized through the polarizing plate 11, and then enters the film-shaped GH cell 7. The light transmitted through the film-shaped GH cell 7 is condensed by the rear lens group 16 and projected on the imaging surface 17 as an image. As described above, the film-form GH cell 7 and the polarizing plate 11 can be moved in and out of the effective optical path of light.
[0101]
Specifically, by moving the film-form GH cell 7 and the polarizing plate 11 to positions indicated by phantom lines, the light can be out of the effective optical path of light. The weight of the film-shaped GH cell 7 of the present embodiment can be reduced to about ４ to １ ／ of the weight of a conventional GH cell manufactured using a glass substrate having a thickness of about 500 μm. In addition, since the strength can be improved, for example, a mechanism as shown in FIG. 3 can be manufactured as a means for putting the film-shaped GH cell 7 and the polarizing plate 11 in and out, and a simpler driving means can be used. The positions of the film-form GH cell 7 and the polarizing plate 11 became movable.
[0102]
That is, the GH cell holding member 29 to which the film-shaped GH cell 7 is fixed, the GH cell driving mechanism 30 for moving the GH cell holding member 29, and the up-down movement as the squeezing means in the up-down direction and the opposite directions A dimmer including two freely arranged diaphragm blades 18 and 19, a diaphragm blade driving mechanism 31 for moving the diaphragm blades 18 and 19, a polarizing plate 11 fixed to the diaphragm blade 18, and the like. No. 6 was constructed.
[0103]
In such a light control device 6, a film-shaped GH cell 7 and a polarizing plate 11 fixed to a diaphragm blade 18 as the diaphragm means are appropriately put in and taken out of an effective optical path of light. The GH cell 7 was also removed from the effective optical path of light to completely eliminate the light absorption by these, and the change in light transmittance when a rectangular wave was input as a driving waveform to the film GH cell 7 was measured. As shown in line A of FIG. 8, the average light transmittance in the visible region (400 to 700 nm) changed from about 100% when transparent to about 10% when shielded. On the other hand, the average light transmittance of the conventional light control device which is made of a glass substrate and in which the GH cell is immovable is, as shown by the line B in FIG. The change was up to 10%.
[0104]
Therefore, as is clear from the above, according to the light control device of the present embodiment, the weight can be reduced to about 1/4 to 1/5 by using the film-like GH cell 1 made of the plastic film substrate. 3, the strength of the film-shaped GH cell 7 and the position of the polarizing plate 11 can be moved by simpler driving means as shown in FIG. Can greatly improve the light transmittance, and a dimming device capable of performing a dimming operation in a very wide dynamic range can be realized.
[0105]
Further, the light transmittance in the halftone driving can be improved as compared with the related art. This is because only a part of the film-like GH cell 7 is moved into the effective optical path at the time of the halftone. It is considered that light transmitted through the area where the film-shaped GH cell 7 did not exist.
[0106]
Example 2
The main difference between the present embodiment and the first embodiment is that the film-shaped GH cell 7 made of a plastic film substrate is used as the diaphragm means when the light GH cell 7 is taken in and out of the effective optical path. The drive mechanism of the aperture blades 18 and 19 and the drive mechanism of the GH cell holding member 29 are combined into one drive mechanism.
[0107]
As shown in FIG. 2, the film-like GH cell 7 in this embodiment is formed by forming a transparent electrode and an alignment film on a 200 μm-thick flexible film substrate made of plastic containing polyester sulfone (PES) as a main raw material. The two flexible film substrates provided with the transparent electrode and the alignment film are aligned and bonded to each other, and a negative type liquid crystal molecule (host material) 13 and a positive type dichroic dye molecule (guest material) are provided between the opposing substrates. ) A film-like liquid crystal optical element (GH cell) was obtained by enclosing the mixture with (4). In addition, the light absorption axis of the polarizing plate 11 was orthogonal to the light absorption axis when a voltage was applied to the film-form GH cell 7.
[0108]
The weight of the film-shaped GH cell 7 thus manufactured is reduced to about 約 to １ ／ of the weight of a conventional GH cell manufactured using a glass substrate having a thickness of about 500 μm. And improved strength. Thereby, a mechanism as shown in FIG. 6 can be manufactured as a means for taking the film-shaped GH cell 7 and the polarizing plate 11 in and out, and the position of the film-shaped GH cell 7 and the polarizing plate 11 can be reduced by a simpler driving means. Became mobile.
[0109]
That is, as shown in FIG. 6, the light control device 6 according to the present invention in the present embodiment includes a GH cell holding member 29 to which the film-shaped GH cell 7 is fixed, and The drive mechanism 109 for the two aperture blades 18 (the polarizing plate 11 is fixed to the aperture blades 18 in the same manner as described above) and 19, which are movably disposed in opposite directions, includes a motor 110 and a motor 110. The motor 110 includes a rotating plate 111 and the like.
[0110]
Further, by forming the cam grooves 112, 113 and 114 in the two aperture blades 18 and 19 and the GH cell holding member 29, respectively, the two aperture blades 18 and 19 and the GH cell The holding member 29 could be moved simultaneously and within a predetermined range.
[0111]
In such a light control device 6, a film-shaped GH cell 7 and a polarizing plate 11 fixed to a diaphragm blade 18 as the diaphragm means are appropriately put in and taken out of an effective optical path of light. The GH cell 7 was also removed from the effective optical path of light to completely eliminate the light absorption by the GH cell 7, and the change in light transmittance when a rectangular wave was input as a drive waveform to the film GH cell 7 was measured. As shown in line A of FIG. 8 in the same manner as in Example 1, the average light transmittance in the visible region (400 to 700 nm) changed from about 100% when transparent to about 10% when shielded.
[0112]
In this embodiment, as compared with the first embodiment, the number of driving mechanisms can be reduced, so that the dimmer can be further downsized and the dimming operation can be performed with lower power consumption.
[0113]
Example 3
FIG. 10 shows an example in which the light control device 6 according to the present embodiment is incorporated in a CCD (Charge Coupled Device) camera.
[0114]
That is, in the CCD camera 50, a first lens group 51 and a second lens group (for zoom) 52 corresponding to the front lens group 15, a third lens group 53 corresponding to the rear lens group 16, A fourth group lens (for focus) 54 and a CCD package 55 are arranged in this order at appropriate intervals, and the CCD package 55 accommodates an infrared cut filter 55a, an optical low-pass filter system 55b, and a CCD image sensor 55c. Have been. Between the second group lens 52 and the third group lens 53, the light control device 6 including the movable film-like GH cell 7 and the polarizing plate 11 according to the present invention described above is provided near the third group lens 53, It is mounted on the same optical path for adjustment (light stop). The fourth lens group 54 for focusing is disposed so as to be movable between the third lens group 53 and the CCD package 55 along the optical path by a linear motor 57, and the second lens group 52 for zooming is disposed in the optical path. Along the first lens group 51 and the light control device 6, it is movably disposed.
[0115]
Although the present invention has been described with reference to the embodiment and the examples, the above-described example can be variously modified based on the technical idea of the present invention. It goes without saying that the form of the optical device and the like, as well as the aperture blade driving mechanism and the GH cell driving mechanism can be appropriately selected without departing from the gist of the invention.
[0116]
For example, there is shown a configuration in which connecting elongated holes 90, 94, and 100 are formed on the respective aperture blades 18, 19 and the GH cell holding member 29 side, and connecting pins 104a, 104b, and 107 are formed on the rotating arms 103 and 106 side. However, the locations where the connection pins and the connection slots are formed may be reversed.
[0117]
The aperture blade drive mechanism 31 and the GH cell drive mechanism 30 are not limited to the motors 102 and 105 as described above, but may be a combination of a rack and pinion, a linear motor, or the like.
[0118]
Further, the structure and material of the liquid crystal optical element, particularly the film-like GH cell 7 and the light control device 6, and the configuration of the driving mechanism, the driving circuit, and the control circuit can be variously changed. The driving waveform can be any of a rectangular wave, a trapezoidal wave, a triangular wave, and a sine wave. The inclination of the liquid crystal molecules changes according to the potential difference between the two electrodes, and the light transmittance is controlled.
[0119]
Further, the position of the polarizing plate 11 with respect to the film-like GH cell 7 is set between the front lens group 15 and the rear lens group 16, but is not limited to this arrangement, and is arranged at a position that is optimal from the setting conditions of the imaging lens. Just do it. That is, unless an optical element such as a retardation film that changes the polarization state is used, the polarizing plate 11 is placed at an arbitrary position on the subject side or the imaging element side, for example, between the imaging surface 17 and the rear lens group 16. be able to. Further, the polarizing plate 11 may be arranged before or after a single lens (end lens) instead of the front lens group 15 or the rear lens group 16.
[0120]
Further, the number of diaphragm blades 18 and 19 as the diaphragm means is not limited to two, and a larger number may be used, or one diaphragm blade may be used. The diaphragm blades 18 and 19 are overlapped by moving in the vertical direction, but may move in other directions, or may be narrowed down from the periphery toward the center.
[0121]
Further, the example in which the polarizing plate 11 is fixed to the aperture blade 18 side has been described, but it may be fixed to the aperture blade 19 side, for example.
[0122]
In the above-described embodiment, an example in which pulse voltage modulation (PHM) is used as a driving method of a liquid crystal cell has been described. However, the present invention can be applied to a case where driving is performed by pulse width modulation (PWM).
[0123]
Further, the light control device according to the present invention is widely applied not only to the optical diaphragm of an imaging device such as a CCD camera described above, but also to various light systems, for example, for adjusting the light amount of an electrophotographic copying machine or an optical communication device. Is possible. As an imaging device, of course, in addition to the CCD used in this embodiment, application to a CMOS image sensor or the like is also possible.
[0124]
Further, the light control device according to the present invention can be applied to various image display elements for displaying characters, images, and the like, in addition to the optical filters.
[0125]
Operation and Effect of the Invention
According to the dimming device and the imaging device of the present invention, the liquid crystal optical element and the polarizing plate are configured so as to be able to enter and exit the effective optical path of light. The plate can be moved out of the effective optical path, the maximum light transmittance when transparent is high, and the optical density ratio (contrast ratio) can be greatly improved.
[0126]
Therefore, the present invention is extremely effective for improving the performance, image quality, and reliability of a light control device and an image pickup device using the liquid crystal optical element and the polarizing plate.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a light control device according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a film-like liquid crystal optical element constituting the light control device.
FIG. 3 is an exploded perspective view of the light control device.
FIG. 4 is a front view of an aperture blade constituting the light control device.
FIG. 5 is a schematic partial enlarged view showing an operation of a mechanical iris near an effective optical path of the light control device.
FIG. 6 is an exploded perspective view of another light control device.
FIG. 7 is a front view of the light control device.
FIG. 8 is a graph showing a comparison between the average light transmittance of the light control device according to the embodiment of the present invention and the voltage applied to the film-shaped GH cell.
FIG. 9 is a graph showing an example of a relationship between an atmosphere condition in an oxidation treatment step, conductivity, and transparency when a transparent conductive film is formed on a plastic film substrate according to the present embodiment.
FIG. 10 is a schematic cross-sectional view of a camera system incorporating the light control device.
FIG. 11 is a schematic diagram illustrating the operation principle of a light control device according to a conventional example.
FIG. 12 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.
FIG. 13 is a schematic diagram showing the operating principle of the light control device of the invention of the prior application (Japanese Patent Application No. 11-322186).
FIG. 14 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.
FIG. 15 is a schematic side view of the light control device.
[Explanation of symbols]
4 ... Positive dichroic dye molecules, 5 ... Incident light, 6 ... Dimming device,
7 film GH cell, 8 flexible substrate, 9 transparent electrode,
Reference numeral 10: alignment film, 11: polarizing plate, 13: negative liquid crystal molecule, 14: power supply,
15: front lens group, 16: rear lens group, 17: imaging surface, 18, 19: aperture blade,
Reference numeral 20: effective optical path, 21: sealing material, 22: opening, 24: liquid crystal mixture,
25: throttle means, 29: GH cell holding member, 30: GH cell drive mechanism,
31: aperture blade driving mechanism, 50: CCD camera, 51: one group lens,
52: 2 group lens (for zoom), 53: 3 group lens,
54: 4 group lens (for focus), 55: CCD package,
55a: infrared cut filter; 55b: optical low-pass filter system
55c: CCD imaging device, 57: linear motor,
87, 91 ... notches for forming an opening diameter,
88, 89, 92, 93, 98, 99 ... guided slits,
90, 94, 100 ... connection long hole, 102, 105, 110 ... motor,
103, 106: rotating arm, 104, 107, 115: connecting pin,
109: drive mechanism, 111: rotary plate, 112, 113, 114: cam groove

Claims (9)

A light control device comprising: a liquid crystal optical element capable of entering and exiting an effective optical path of light; and a polarizing plate capable of entering and exiting the effective optical path. The light control device according to claim 1, wherein the liquid crystal optical element has a film shape. The film-like liquid crystal optical element has liquid crystal sealed between substrates facing each other, and the counter substrate is made of at least one plastic material selected from polycarbonate, polyarylate, polyester sulfone, and polyethylene terephthalate as a main raw material. The light control device according to claim 2, wherein the light control device is a flexible substrate. The polarizing plate is provided in a diaphragm unit for adjusting the amount of light passing through the effective optical path, and has at least a first driving mechanism for driving the diaphragm unit and a second driving mechanism for driving the liquid crystal optical element. The light control device according to claim 1. The light control device according to claim 1, wherein driving of the stop unit, the polarizing plate, and the liquid crystal optical element is performed by a common driving mechanism. From the open state located outside the effective optical path to a predetermined open state, the aperture area is controlled by the stop means fixing the polarizing plate, and the liquid crystal optical element is caused to enter the opening in the predetermined open state. The light control device according to claim 4. The light control device according to claim 6, comprising the driving mechanism and a rotating member driven by the driving mechanism. The light control according to claim 1, wherein the liquid crystal optical element is a guest-host type liquid crystal optical element in which a host material is made of negative liquid crystal molecules and a guest material is made of a positive or negative dichroic dye molecule. apparatus. An imaging device, wherein the light control device according to claim 1 is arranged in an optical path of an imaging system.

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