JP2002365621A - Light controlling device and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light controlling device and an imaging device suitable for efficient and stable driving of a guest-host type liquid crystal element. SOLUTION: A light controlling device 23 is provided with a GH cell 12 for controlling light and a UV cutting filter 65 provided on the light incident side of the GH cell 12. Thereby the quantity of UV rays made incident into the GH cell 12 is greatly reduced and the photodecomposition or the photo- deterioration of the constituent materials of a liquid crystal layer in the GH cell 12 is prevented. The imaging device such as a CCD camera 50 has the light controlling device disposed in the light path thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a light control device for adjusting the amount of incident light and emitting the light, and an imaging device using the light control device.

[0002]

2. Description of the Related Art Generally, a light control device using a liquid crystal cell includes:
A polarizing plate is used. In this liquid crystal cell, for example, TN
(Twisted Nematic) type liquid crystal cell and guest-host (GH
(GuestHost) type liquid crystal cells are used.

FIG. 15 is a schematic diagram showing the operation principle of a conventional light control device. This dimmer mainly includes a polarizing plate 1 and a GH
And cell 2. Although not shown, the GH cell 2 is sealed between two glass substrates, and the ITO (In)
It has a working electrode such as dium tin oxide) and a liquid crystal alignment film such as a polyimide film (the same applies hereinafter). In the GH cell 2,
Positive liquid crystal molecules 3 and positive dichroic dye molecules 4 are enclosed.

The positive dichroic dye molecule 4 is a positive (p-type) dye molecule having anisotropy in light absorption and absorbing, for example, light in the longitudinal direction of the molecule. Further, the positive liquid crystal molecules 3
For example, it is a positive type (positive type) having a positive dielectric anisotropy.

FIG. 15A shows a state of the GH cell 2 when no voltage is applied (no voltage is applied). Incident light 5
Are linearly polarized by transmitting through the polarizing plate 1. In FIG. 15A, since the polarization direction coincides with the molecular long axis direction of the positive dichroic dye molecule 4, light is absorbed by the positive dichroic dye molecule 4 and the light of the GH cell 2 is absorbed. The transmittance decreases.

[0006] Then, as shown in FIG.
When a voltage is applied to the cell 2, the direction of the major axis of the positive dichroic dye molecules 4 becomes perpendicular to the polarization direction of the linearly polarized light as the positive liquid crystal molecules 3 are oriented in the direction of the electric field. Therefore, the incident light 5 is transmitted by the GH cell 2 without being absorbed.

In the GH cell 2 shown in FIG. 15, as shown in FIG. 16, the average light transmittance of visible light (in air; a polarizing plate is added in addition to the liquid crystal cell) with the application of the operating voltage. The light transmittance at that time was referred to (= 100%):
Similarly, the maximum light transmittance when the voltage is increased to 10 V is about 60%, and the change in light transmittance is gradual.

When a negative (n-type) dichroic dye molecule that absorbs light in the direction of the minor axis of the molecule is used, the operation is the reverse of the case of the positive dichroic dye molecule 4 described above. When the voltage is applied, the light is not absorbed, and when the voltage is applied, the light is absorbed.

In the dimming device shown in FIG. 15, the ratio of the absorbance between when a voltage is applied and when no voltage is applied, that is, the ratio of the optical density is about 10. This has about twice the optical density ratio as compared to a dimmer that is configured only with the GH cell 2 without using the polarizing plate 1.

[0010]

Now, the conventional guest-
When a host-type liquid crystal cell is used, since dichroic dye molecules are used in a liquid crystal element, there has been a problem that the dye molecules are deteriorated by excessive ultraviolet irradiation.

That is, ultraviolet light enters the light control device from the outside through the effective optical path of the image pickup device, and the dichroic dye molecules contained in the guest-host type liquid crystal element undergo photodecomposition or light deterioration due to the incident ultraviolet light. Ionization (change in physical properties), discoloration or fading, the light absorption function originally possessed deteriorated, and the light absorption effect of the guest-host type liquid crystal element was reduced, and the driving efficiency was also deteriorated.

It is an object of the present invention to provide a light control device and an image pickup device suitable for efficient and stable driving of a guest-host type liquid crystal element.

[0013]

That is, the present invention provides a light-modulating guest-host type liquid crystal element and a filter provided on the light incident side of the liquid crystal element and absorbing at least ultraviolet rays. It relates to an optical device.

According to the present invention, there is further provided a light control device comprising a guest-host type liquid crystal element for light control arranged in an optical path of an image pickup system, and a filter for absorbing at least ultraviolet rays on a light incident side of the liquid crystal element. The present invention relates to an imaging device having a material.

The present invention further comprises a guest-host type liquid crystal element for light control, and at least a filter material absorbing at least ultraviolet light and a reflecting material reflecting at least ultraviolet light are provided on the light incident side of the liquid crystal element. One relates to a light control device in which one is arranged.

According to the present invention, there is further provided a light control device including a guest-host type liquid crystal element for light control in an optical path of an image pickup system, and a filter for absorbing at least ultraviolet rays on a light incident side of the liquid crystal element. Another object of the present invention is to provide an imaging device in which at least one of a material and at least one of a reflecting material that reflects ultraviolet light is disposed.

According to the present invention, at least one of a filter material absorbing at least ultraviolet rays and a reflecting material reflecting at least ultraviolet rays is provided on the light incident side of the guest-host type liquid crystal element. The amount of irradiation of the guest-host type liquid crystal device with the ultraviolet light is greatly reduced, whereby the constituent materials such as dichroic dye molecules in the guest-host type liquid crystal device are not decomposed or degraded by the ultraviolet light, and The element can be driven stably with high efficiency.

[0018]

In the present invention, the filter material or the reflection material is at least one selected from an ultraviolet cut or reflection film, an ultraviolet cut or reflection coated glass, and an ultraviolet absorption or reflection glass. Alternatively, it is desirable that the reflecting material is provided at least in the same region as the effective optical path cross section of the incident light in order to sufficiently cut or reflect the ultraviolet light.

In addition, it is desirable to arrange a polarizing plate in the effective optical path of the incident light to the liquid crystal element and to be able to move the polarizing plate in and out of the effective optical path, as described later, in order to make the light amount uniform.

In the case where the liquid crystal element is arranged so as to be exposed on the outer surface of the device, the filter material or the reflection material is arranged on the light incident side of the liquid crystal element. Preferably, a material or a reflector is provided.

Further, the liquid crystal element is a negative type or a positive type,
In particular, a guest-host type liquid crystal element using a negative type liquid crystal as a host material and a positive or negative type dichroic dye as a guest material is desirable in terms of transmittance and response speed as described later.

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

FIG. 1 shows an example in which the light control device 23 in this embodiment is incorporated in a CCD (charge coupled device) camera 50.

That is, in the CCD camera 50, a third lens group 53 and a fourth lens group (for focusing) 54 corresponding to the rear lens group 16 are provided along an optical axis 66 indicated by a one-dot chain line. , An infrared cut filter 55a, an optical low-pass filter 55b, and a CCD image sensor 55c.

Between the second group lens (for zoom) 52 and the third group lens 53, the GH cell 12 is located near the third group lens 53.
A light control device 23 composed of a light source and a polarizing plate 11 is mounted on the same optical path for light amount adjustment (light amount stop). The fourth group lens 54 for focusing is disposed so as to be movable between the third group lens 53 and the CCD package 55 along the optical path by a linear motor 57, and the second group lens 52 for zooming is Along with the lens group 51 and the light control device 23.

Then, an ultraviolet cut filter 65 is attached to the entire surface of the second lens unit so as to cover the effective optical path 20 at the rear end thereof. However, as long as it is on the effective optical path and closer to the first lens group than the GH cell 12, the installation position may be anywhere. That is, the first group lens 51 to the liquid crystal N in FIG.
Insertion is possible at any position up to the D device (GH cell 12).

The structure of the ultraviolet cut filter 65 is as follows.
Is generally SiO_Two, TiO_Two, Al _TwoO_ThreeChosen from
A multilayer structure of one or several layers can be used
You. For example, a film having a thickness of less than 100
0 to 60 layers are stacked.

In the light control device 23 of the present embodiment, the ultraviolet cut filter is disposed at the end of the lens group. Alternatively, the filter may be attached to the incident surface of the liquid crystal element and integrated. They may be separate or separate, and they are collectively called a dimmer. This light control device may be called a light control system or a light control mechanism.

Further, in the present embodiment, for example, instead of the ultraviolet cut filter 65, an ultraviolet cut coated glass, an ultraviolet absorbing glass or the like may be used.

Although the number of the ultraviolet cut coats varies depending on the number of lenses depending on the apparatus configuration, the number may increase or decrease. However, since there are at least two surfaces per lens, the number of the lenses is 2n surfaces or less for the number n of lenses. Can be applied.

The installation position of the ultraviolet cut filter is as follows.
Any position may be used as long as it is on the light incident side of the liquid crystal element. However, since it is only necessary to cover the effective optical path at a minimum, as shown in FIG. It can be said that this is a preferable installation position because the installation area is limited and a useless portion is not generated.

The closer the installation position is to the liquid crystal element, the more effectively the ultraviolet blocking performance can be used.
In this case, the ultraviolet ray absorbing effect of the lens groups 51 and 52 is added to the ultraviolet ray cutting effect of the ultraviolet ray cut filter 65.

Also, the area of the ultraviolet cut filter should be at least overlapped with the cross-sectional area of the effective optical path and at least this cross-sectional area, and the thickness, material, shape and the like may be freely changed.

In addition, the method of mounting the ultraviolet cut filter may have a function capable of being taken in and out of the effective optical path. In addition, in the method of mounting the ultraviolet cut filter, for example, a form in which the lens itself contains an ultraviolet absorbent, a form in which the ultraviolet absorbent is attached to the lens surface, and a method in which the ultraviolet absorbent is separate from the lens A form provided independently may be used.

In the light control device and the image pickup device according to the embodiment, a negative liquid crystal molecule having a negative dielectric anisotropy is used as a host material of the guest-host type liquid crystal element, and the guest material is a positive type. Or it may consist of negative type dichroic dye molecules.

It is desirable that the polarizing plate be installed in a movable part of a mechanical iris or the like so that it can be put in and out of the effective optical path.

Since the ultraviolet cut filter according to the present embodiment is used for protecting the liquid crystal composition in the liquid crystal element, it can be placed anywhere on the effective optical path as long as it is on the incident light side of the liquid crystal element. Good.

In the present embodiment, since the ultraviolet absorbing material is provided on the light incident side of the guest-host type liquid crystal element, the amount of ultraviolet rays irradiated to the guest-host type liquid crystal element is greatly reduced.

Therefore, the dichroic dye molecules in the guest-host type liquid crystal element are not ionized due to photodecomposition or photodeterioration by ultraviolet rays, so that the light absorption function inherent in the dichroic dye molecules can be sufficiently maintained. As a result, the light absorption effect of the guest-host type liquid crystal element is stabilized, and the driving efficiency is improved.

Further, the deterioration of the liquid crystal composition can be reduced, and the driving reliability of the whole liquid crystal element can be improved.

Next, in the guest-host type liquid crystal cell (GH cell) 2 shown in FIG. 15, a positive type liquid crystal having a positive dielectric anisotropy (Δε) is used as the host material 3, and Is a positive type dye 4 having a dichroic positive light absorption anisotropy (ΔA), a polarizing plate 1 disposed on the incident side of the GH cell 2, a rectangular wave as a driving waveform, and a light when operating voltage is applied. When the change in transmittance is measured, as shown in FIG. 16, the average light transmittance of visible light (in air; see the transmittance when a polarizing plate is added in addition to the liquid crystal cell) with the application of the operating voltage, as shown in FIG. (= 1
00%): The same applies to the following, but the voltage is increased by 1
The maximum light transmittance when the voltage is increased to 0 V is about 60%, and the change in the light transmittance is gentle.

This is because when a positive 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 strong when no voltage is applied. The orientation does not change (or
It is considered that liquid crystal molecules remain (which hardly change).

On the other hand, as shown in FIG.
In the host-type liquid crystal cell (GH cell) 12, as a host material 13, MLC-6608 manufactured by Merck, which is a negative type liquid crystal having a negative dielectric anisotropy (Δε), is used as an example. As an example, a dichroic positive dye D5 manufactured by BDH was used.
The configuration is the same as that of the GH cell 2 of No. 5. In this GH cell 12, the polarizing plate 11 was arranged on the incident side of the GH cell 12, and the change in light transmittance when an operating voltage was applied was measured using a rectangular wave as a driving waveform. As shown in FIG. As a result, the average light transmittance (in air) of visible light decreases from the maximum light transmittance of about 75% to several percent, and the change in light transmittance becomes relatively steep.

This is because, when a negative type host material is used, the interaction between 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 applied when no voltage is applied. This is considered to be because the light is easily transmitted, and the direction of the director of the liquid crystal molecules is easily changed with the application of the voltage.

If the GH cell is formed using the negative type host material in this manner, the light transmittance (especially when the GH cell is transparent) is improved, and the GH cell can be used with its position fixed in the imaging optical system. A compact dimmer can be realized.
In this case, by arranging a polarizing plate in the optical path of the incident light to the liquid crystal element, the ratio of the absorbance between when no voltage is applied and when a voltage is applied (that is, the ratio of the optical density) is further improved, and the contrast of the light control device is improved. The ratio is further increased, and the dimming operation can be performed more normally from a bright place to a dark place.

In the present embodiment, the negative liquid crystal of the liquid crystal element preferably has a negative dielectric anisotropy, but the guest material is made of a positive or negative dichroic dye molecule. It may be. The host material is preferably a negative type, but may be a positive type.

In this embodiment mode, a negative (or positive) host material and a positive (or negative) guest material can be selected from known materials. However,
For actual use, a blended composition selected to exhibit nematicity in the actual use temperature range may be used.

The light control device 2 comprising the GH cell 12 described above
Reference numeral 3 denotes a front lens group 15 and a rear lens group 1 each including a plurality of lenses such as a zoom lens as shown in FIG.
6 is arranged. The light transmitted through the front lens group 15 is linearly polarized by way of the polarizing plate 11, and then the GH cell 1
2 is incident. The light transmitted through the GH cell 12 is condensed by the rear lens group 16 and projected on the imaging surface 17 as an image.

The polarizing plate 11 constituting the light control device 23
Can enter and exit the effective optical path 20 of the light incident on the GH cell 12. Specifically, by moving the polarizing plate 11 to a position indicated by a virtual line, the effective optical path 20 of the light is changed.
You can get out. As a means for taking the polarizing plate 11 in and out, a mechanical iris as shown in FIG. 10 may be used.

This mechanical iris is a mechanical diaphragm device generally used for digital still cameras, video cameras and the like, and mainly includes two iris blades 18 and 19,
The polarizing plate 11 is attached to the iris blade 18.
The iris blades 18, 19 can be moved up and down. The iris blades 18 and 19 are relatively moved using a drive motor (not shown) in the direction indicated by the arrow 21.

As a result, as shown in FIG. 10, the iris blades 18 and 19 are partially overlapped with each other. When the overlap increases, the opening 22 on the effective optical path 20 located near the center of the iris blades 18 and 19 is formed. Is covered by the polarizing plate 11.

FIG. 11 is a partially enlarged view of the mechanical iris near the effective optical path 20. At the same time as the iris blade 18 moves downward, the iris blade 19 moves upward.
Along with this, as shown in FIG. 11A, the polarizing plate 11 attached to the iris blade 18 also moves out of the effective optical path 20. Conversely, by moving the iris blade 18 upward and the iris blade 19 downward, the iris blades 18 and 19 overlap each other. According to this, FIG.
As shown in (b), the polarizing plate 11 moves on the effective optical path 20 and gradually covers the opening 22. Iris feather 18, 1
When the overlapping of the components 9 becomes large, the polarizing plate 11 covers the entire opening 20 as shown in FIG.

Next, the light control operation of the light control device 23 using this mechanical iris will be described.

As the subject (not shown) becomes brighter, the iris blades 18 and 19, which have been opened in the vertical direction, are driven by a motor (not shown) and start overlapping as shown in FIG. As a result, the polarizing plate 11 attached to the iris blade 18 starts to enter the effective optical path 20 and covers a part of the opening 22 (FIG. 11B).

At this time, the GH cell 12 is in a state of not absorbing light (note that, due to thermal fluctuation or surface reflection, etc.
There is some absorption by the GH cell 12. ). For this reason,
The light passing through the polarizing plate 11 and the light passing through the opening 22 are
The intensity distributions are almost equal.

After that, the polarizing plate 11 is completely opened.
Is covered (FIG. 11C). Further, when the brightness of the object increases, the voltage to the GH cell 12 is increased, and the light is adjusted by absorbing the light with the GH cell 12.

On the contrary, if the subject becomes dark,
First, by reducing or not applying a voltage to the GH cell 12, the light absorbing effect of the GH cell 12 is eliminated. Further, when the subject becomes dark, the iris blade 18 is moved downward by driving a motor (not shown).
Further, the iris blade 19 is moved upward. Thus,
The polarizing plate 11 is moved out of the effective optical path 20 (FIG. 11).
(A)).

Further, as shown in FIGS. 9 to 11, the polarizing plate 11 (transmittance, for example, 40% to 50%) can be out of the effective optical path 20 of the light. Not absorbed. Therefore, the maximum transmittance of the light control device can be increased to, for example, twice or more. Specifically, when this light control device is compared with a conventional light control device including a fixedly installed polarizing plate and a GH cell, the maximum transmittance is, for example, about twice. Note that the minimum transmittance is the same for both.

Since the polarizing plate 11 is moved in and out using a mechanical iris that has been put to practical use in a digital still camera or the like, a light control device can be easily realized. Further, since the GH cell 12 is used, dimming can be performed by the GH cell 12 itself absorbing light in addition to dimming by the polarizing plate 11.

In this way, the light control device can increase the contrast ratio between light and dark and can maintain the light amount distribution substantially uniform.

Next, an embodiment of a light control device using a guest-host type liquid crystal (GH) cell will be described.

As shown in FIG. 9, this light control device has a GH
It comprises a cell 12 and a polarizing plate 11. And GH cell 1
Reference numeral 2 denotes a negative liquid crystal molecule (host material) and a positive or negative dichroic dye molecule (between two glass substrates (both not shown) each having a transparent electrode and an alignment film formed thereon). Guest material).

As the liquid crystal molecules, for example, MLC-6608 manufactured by Merck, which is a negative type liquid crystal having a negative dielectric anisotropy, is used as an example. The dichroic dye molecules 4 have anisotropic light absorption. For example, D5 manufactured by BDH, which is a positive dye that absorbs light in the molecular long axis direction, is used as an example.
The light absorption axis of the polarizing plate 11 was orthogonal to the light absorption axis when a voltage was applied to the GH cell 12.

The light control device 23 comprising the GH cell 12
For example, as shown in FIG. 9, is disposed between a front lens group 15 and a rear lens group 16 including a plurality of lenses such as a zoom lens. The light transmitted through the front lens group 15 is linearly polarized by way of the polarizing plate 11, and then the GH cell 1
2 is incident. The light transmitted through the GH cell 12 is condensed by the rear lens group 16 and projected on the imaging surface 17 as an image.

The polarizing plate 11 constituting the light control device 23 can enter and exit the effective optical path 20 of the light incident on the GH cell 12 as described above.

Specifically, by moving the polarizing plate 11 to the position indicated by the imaginary line, the light can be emitted out of the effective optical path 20. As a means for taking the polarizing plate 11 in and out, a mechanical iris shown in FIG. 10 may be used.

Next, FIG. 1 shows an example in which the light control device 23 according to the present embodiment is incorporated in a CCD camera.

That is, in the CCD camera 50, the first lens group 51 and the second lens group (for zoom) 52 corresponding to the front lens group 15, the ultraviolet cut filter 65, the iris blade 18, the dimmer 23, the third lens group 53 corresponding to the lens rear lens group 16
And a fourth group lens (for focusing) 54 and a CCD package 55 are arranged in this order at appropriate intervals.
The CCD package 55 has an infrared cut filter 55a,
Optical low-pass filter system 55b, CCD image sensor 55c
Is stored.

Between the second lens group 52 and the third lens group 53, the light control device 23 composed of the GH cell 12 and the polarizing plate 11 adjusts the light amount (light amount aperture) near the third lens group 53.
For the same optical path. The fourth lens group 54 for focusing is movably arranged 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 5 for zooming is provided.
Reference numeral 2 is movably disposed between the first lens group 51 and the light control device 23 along the optical path.

Here, for convenience, the ultraviolet cut filter 65 is arranged at the end of the second group lens. However, on the effective optical path, any position may be used as long as this is on the first group lens side with respect to the GH cell 12.

FIG. 12 shows an algorithm of a sequence of light transmittance control by the light control device 23 in this camera system.

According to this embodiment, the second group lens 52
Dimming device 23 according to the present invention between the lens and the third group lens 53
Is provided, the amount of light can be adjusted by applying an electric field as described above, the system can be downsized, and the size can be substantially reduced to the size of the effective range of the optical path. Therefore, the size of the CCD camera can be reduced. In addition, since the amount of light can be appropriately controlled depending on the magnitude of the voltage applied to the patterned electrodes, a conventional diffraction phenomenon can be prevented, a sufficient amount of light can be made incident on the image sensor, and blurring of the image can be prevented.

Next, FIG. 2 is a block diagram of a driving circuit of the above-mentioned CCD camera. According to this, it has the CCD drive circuit unit 60 of the CCD image sensor 55c arranged on the light emission side of the dimmer 23, and the output signal of the CCD image sensor 55c is processed by the Y / C signal processing unit 61, Brightness information (Y signal)
To the GH cell drive control circuit 62. In response to the control signal from the GH cell drive control circuit 62, the drive pulse whose pulse voltage or pulse width is controlled as described above is synchronized with the basic clock from the CCD drive circuit 60 as described above. 63. Note that the GH cell drive control circuit 62 and the pulse generation circuit 63 constitute a GH liquid crystal drive control device 64 for controlling a pulse voltage or a pulse width.

In a system different from the camera system, the light emitted from the light control device 23 is received by a photodetector (or photomultiplier), and the luminance information of the emitted light is fed back to the GH cell drive control circuit 62. And
In synchronization with a clock of a GH cell driving circuit (not shown), a driving pulse whose pulse voltage is controlled can be obtained from the pulse generating circuit.

In the structure of the image pickup system, for example, in a single focus lens system, it is difficult to arrange a light control element in a lens group. For example, as shown in FIG.
A set of 1 and 72 and an infrared cut filter 73 are arranged on the light incident side of a solid-state imaging device (CCD) 75, and a light amount adjusting device 83 having the same configuration as the above-described light adjusting device is provided on the outermost side on the light incident side. When the liquid crystal element is exposed, the liquid crystal element is exposed to incident light. As shown in FIG. 14, the liquid crystal element has a UV (ultraviolet) absorbing film 86 ( Or UV reflective film)
The liquid crystal 85 is protected.

According to the GH cell 82, the GH
Similarly to the cell 12, a liquid crystal layer 85 made of a negative liquid crystal and a positive dichroic dye is sealed between the substrates 81a and 81b with a transparent electrode, and a spacer (cum sealing) material 84 is provided around the liquid crystal layer 85. In addition, necessary antireflection films 82a and 82b are provided on the outer surfaces of both substrates 81a and 81b, respectively.
Further, on the light incident side, an ultraviolet absorbing film (or an ultraviolet reflecting film) 8
6 are provided.

Accordingly, since the ultraviolet light of the incident light is absorbed or reflected, it is possible to suppress the light from entering the liquid crystal layer 85,
It is possible to prevent the constituent materials of the liquid crystal layer 85, particularly, the deterioration of the dye molecules. In this case, even when the light control element cannot be disposed in the housing due to a small space in the housing, a sufficient ultraviolet absorbing or reflecting effect can be obtained by the ultraviolet absorbing film (or reflecting film) 86 of the light amount adjusting device 83. .

Such an ultraviolet absorbing film (or reflecting film) 86
The method of forming may be either a wet method or a dry method, for example,
The former is a method of applying a surface coating agent containing an ultraviolet absorber, and the latter is a multilayer film deposition method or a CVD (Chemical vap).
or deposition) film forming method.

When the light amount adjusting device 83 is installed outside the housing as shown in the figure, it is preferable that a similar coating for forming an ultraviolet absorbing or reflecting film is applied to the end face on the device side.

The light control device is preferably a liquid crystal element represented by a guest-host type liquid crystal element.
However, the host material includes a material having a positive dielectric anisotropy (positive type) and a material having a negative dielectric anisotropy (negative type), and any of them may be used. , Negative type dichroic dye molecules may be used.

[0081]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

The above liquid crystal element (GH cell 12) was subjected to a light resistance test (ultraviolet irradiation test) using a xenon lamp. In addition, for those in which the liquid crystal element was irradiated with ultraviolet light for an arbitrary time using a xenon lamp, those provided with an ultraviolet cut film 65 on the light incident side of the effective optical path,
2 without UV cut film 65
The two conditions were compared.

FIG. 3 shows the spectral characteristics of the ultraviolet cut film used.

The UV cut film used herein had the following specifications. As its configuration,
Three layers of SiO ₂ , TiO ₂ and Al ₂ O ₃ × 16 times are repeatedly formed. Since the thickness per single layer is 100 °, the total thickness is 100 ° × 48 layers = 4800 °. Since the position and method of mounting the cut film are for performing a light resistance test, no particular attachment or the like is performed, and the cut film is simply disposed on the light incident side of the GH cell.

The relationship between the applied voltage and the light absorbance of the two samples after the irradiation of the ultraviolet rays was measured and graphed. The result is shown in FIG.

That is, as can be seen from the graph of FIG. 4, when the ultraviolet cut film is used (A), when the applied voltage rises from 2 V to 4 V, the light absorbance rises sharply to 0.
From about 11.5 at an arbitrary scale, and finally, when the applied voltage is increased to 10 V, the light absorbance is about 14.
It became 5.

However, when the ultraviolet cut film was not used (B), when the applied voltage was increased from 2 V to 4 V, the light absorption increased gently and was only from 0 to about 6 on an arbitrary scale. Even when the applied voltage was increased to 10 V, the light absorption was only about 9 on an arbitrary scale.

From these results, it was found that the light-absorbing effect of the film without the ultraviolet-cut film (B) was much lower than that of the light-shielded film with the ultraviolet light cut film (A). It was presumed that some physical property change occurred in the liquid crystal composition.

Next, the effect of the ultraviolet cut film was compared with the above two samples as a change in the amount of ions contained in the liquid crystal composition. To measure the amount of ions, a mutation current measurement method (K. Ono et al .; Jpn. J. Appl.
Phys., 30, 1991, 2832). Then, the results in the case of using the ultraviolet cut film are shown in the graph of FIG. 5, and the results in the case of not using the ultraviolet cut film are shown in the graph of FIG.

According to this, when an ultraviolet cut film is used, when the voltage value is changed to about 10 V to about -10 V (or about -10 V to about 10 V), the current value is changed except when the polarity is inverted. It showed a value of 50 nA or -50 nA, and was relatively stable.

This is considered to be because the dichroic dye molecules in the GH cell 12 do not undergo photolysis or photodegradation because they are not irradiated with ultraviolet rays.

On the other hand, when the ultraviolet cut film is not used, the voltage value is about 10 V to about −10 V (or about −10 V).
10V to about 10V), the current value becomes about 10
It becomes very large at 00 nA or about -1000 nA, and draws an unstable and distorted change curve as a whole.

This is presumably because the dichroic dye molecules in the GH cell were ionized by photodecomposition or photodeterioration due to the irradiation of ultraviolet rays, and the amount of ions increased.

As described above, in a system that does not use an ultraviolet cut film, the amount of ions is extremely increased by the irradiation of ultraviolet light, and it can be recognized that the reliability of the liquid crystal element is reduced.

According to the above results, the deterioration of the liquid crystal composition can be reduced by disposing the ultraviolet cut film as the ultraviolet cut filter on the light incident side of the liquid crystal element according to the present invention, and the entire liquid crystal element can be reduced. Reliability could be improved.

Next, in the GH cell 82 constructed in the same manner as the GH cell 12, the glass substrate of the liquid crystal cell is made of Si.
Assuming that the thickness of a layer formed by repeatedly forming three layers of O ₂ , TiO _2, and Al ₂ O ₃ × 16 times is about 50 nm, the obtained absorption characteristics are, for example, a wavelength of 395 nm (transmittance 0%) to a wavelength of 440 nm.
When the thickness of the ultraviolet absorbing film (or the film made of the ultraviolet reflecting agent) of (transmittance 100%) is 5 to 100 nm, the obtained reflection characteristics are, for example, wavelength 395 nm (reflectance 0%) to wavelength 4
In the case where the 40 nm (reflection film having a reflectance of 100%) 86 was not provided and in the case where it was provided, the cells were exposed to ultraviolet rays, and the performance was checked for the deterioration of the cells. The results shown in the following table were obtained.

[0097]

[Table 1] * Deterioration: Spectral characteristic change (comparison before and after test input) ** No deterioration: No spectral characteristic change (comparison before and after test input)

From these results, the material exposed to ultraviolet light deteriorates regardless of the dielectric anisotropy of the liquid crystal. However, when an ultraviolet absorbing film (or a reflective film) is provided, the material deteriorates even when exposed to ultraviolet light. It was confirmed that it did not occur.

Although the present invention has been described with reference to the embodiments and examples, the above examples can be variously modified based on the technical idea of the present invention.

For example, the structure and material of the liquid crystal element and the light control device, the drive mechanism, the drive circuit, and the configuration of 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.

The light control device and the image pickup device of the present invention are suitable when the drive electrode of the liquid crystal optical element is formed at least over the entire area of the effective light transmitting portion. By controlling the drive pulse, batch control of the light transmittance over the entire effective optical path width can be performed with high accuracy.

As the GH cell, a GH cell having a two-layer structure or the like can be used in addition to the above-described one. Polarizing plate 1
The position of one GH cell 12 with respect to the front lens group 15 and the rear lens group 16 has been described. However, the position is not limited to this arrangement, and may be any position that is optimal from the setting conditions of the imaging lens. That is, unless an optical element such as a retardation film that changes the polarization state is used, the polarizing plate 11
It can be placed at any position on the subject side or the image sensor side, such as between the lens and the rear lens group 16. Furthermore, polarizing plate 1
1 may be arranged before or after a single lens (single lens) instead of the front lens group 15 or the rear lens group 16.

The number of iris blades 18 and 19 is not limited to two, and a larger number may be used.
Conversely, one sheet may be used. Also, the iris blades 18 and 19
Although they are overlapped by moving in the vertical direction, they may move in other directions, or may be narrowed down from the periphery toward the center.

Although the polarizing plate 11 is attached to the iris blade 18, it may be attached to the iris blade 19.

Further, as the subject becomes brighter, the light is adjusted by moving the polarizing plate 11 in and out, and then the light is absorbed by the GH cell 12. Conversely, the light is absorbed by the GH cell 12 Dimming may be performed.
In this case, after the transmittance of the GH cell 12 has decreased to a predetermined value, light adjustment is performed by taking the polarizing plate 11 in and out.

Although a mechanical iris is used as a means for moving the polarizing plate 11 in and out of the effective optical path 20, it is not limited to this. For example, by directly installing the film on which the polarizing plate 11 is stuck on the drive motor, the polarizing plate 1
1 may be taken in and out.

In the above example, the polarizing plate 11 is moved in and out of the effective optical path 20, but it is of course possible to fix the position in the effective optical path.

Further, the light control device of the present invention can be used in combination with other known filter materials (for example, organic electrochromic materials, liquid crystals, electroluminescent materials, etc.).

Further, the dimming device of the present invention has the above-described CC.
In addition to the optical diaphragm of an imaging device such as a D camera, the present invention can be widely applied to various optical systems, for example, for adjusting the light amount of an electrophotographic copying machine or an optical communication device. Further, the light control device of the present invention can be applied to various image display elements for displaying characters and images, in addition to the optical diaphragm and the filter.

As shown in FIG. 3, the spectral characteristics of the ultraviolet cut filter desirably exhibit a spectral characteristic that cuts both the ultraviolet region and the infrared region in order to prevent deterioration by ultraviolet light and infrared light at the same time. However, only the ultraviolet region may be cut. Further, the cut wavelength range may be variously changed.

In addition to forming the above-mentioned ultraviolet absorbing film or reflecting film on the substrate, a similar absorbing member or reflecting member may be arranged on the light incident side. In addition to providing either one of the absorbing film (absorbing material) and the reflecting film (reflecting material), both of them can be stacked or sequentially arranged.

[0112]

According to the present invention, at least one of a filter material absorbing at least ultraviolet rays and a reflecting material reflecting at least ultraviolet rays is provided on the light incident side of the guest-host type liquid crystal element. In addition, the amount of irradiation of the guest-host type liquid crystal element with ultraviolet rays is greatly reduced, and thereby, the constituent materials in the guest-host type liquid crystal element are not decomposed or deteriorated by the ultraviolet rays, and the liquid crystal element is stabilized. And can be driven with high efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a camera system incorporating a light control device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a camera system including a driving circuit.

FIG. 3 is a diagram illustrating an example of spectral characteristics of an ultraviolet cut filter according to an embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the light absorption of the light control device and the applied voltage.

FIG. 5 is a graph showing the relationship between applied voltage and current when using an ultraviolet cut film.

FIG. 6 is a graph showing the relationship between applied voltage and current when an ultraviolet cut film is not used, according to a conventional example.

FIG. 7 is a schematic diagram illustrating an operation principle of an example of the light control device according to the present embodiment.

FIG. 8 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.

FIG. 9 is a schematic side view of a light control device using a liquid crystal optical element.

FIG. 10 is a front view of a mechanical iris of the light control device.

FIG. 11 is a schematic partial enlarged view showing an operation of a mechanical iris near an effective optical path of the light control device.

FIG. 12 shows an algorithm of light transmittance control in the camera system.

FIG. 13 is a schematic cross-sectional view of an imaging device incorporating a light amount adjustment device (light control device) according to the present embodiment.

FIG. 14 is a schematic sectional view of the light amount adjusting device.

FIG. 15 is a schematic diagram illustrating the operation principle of a conventional light control device.

FIG. 16 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.

[Explanation of symbols]

1, 11: polarizing plate, 2, 12: GH cell, 3: positive liquid crystal molecule, 4: positive dichroic dye molecule, 5: incident light, 13
... Negative dichroic liquid crystal molecules, 15: front lens group, 16: rear lens group, 17: imaging surface, 18, 19: iris blade,
Reference numeral 20: effective optical path (cell middle or center), 21: operation direction, 22: opening, 23: dimmer, 24: cell peripheral, 31A, 31B: glass substrate, 32A, 32B: transparent (operation) Electrodes, 33A, 33B: alignment film, 34: liquid crystal material, 35: sealing material, 36: spherical spacer, 37: columnar spacer, 50: CCD camera, 51
... 1 group lens, 52 ... 2 group lens, 53 ... 3 group lens,
54: 4 group lens, 55: CCD package, 55a ...
Infrared cut filter, 55b: optical low-pass filter system, 55c: CCD image pickup device, 60: CCD drive circuit unit, 61: Y / C signal processing unit, 62: GH drive control circuit unit, 63: pulse generation circuit unit, 64 ... Pulse voltage or pulse width control unit (GH liquid crystal drive control device), 65: UV cut filter, 66: optical axis, 71, 72: lens,
73: infrared cut filter, 75: solid-state image sensor, 8
1a, 81b: a substrate with a transparent electrode; 82a, 82b: an antireflection film; 83: a light amount adjusting device; 84: a spacer;
... Liquid layer, 86 ... Ultraviolet absorbing film (or reflecting film)

────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. ⁷ identification mark FI theme Court Bu (reference) G03B 11/00 G03B 11/00 (72) inventor Toshiharu Yanagida Shinagawa-ku, Tokyo Kita 6-chome No. 7 No. 35 Within Sony Corporation (72) Inventor Kawabata Dai 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term within Sony Corporation (reference) 2H048 CA06 CA13 CA17 CA27 FA05 FA07 FA09 FA18 FA24 2H083 AA05 2H088 EA25 EA33 GA13 HA11 HA18 HA24 JA06 MA20 2H091 FA01Z FA07X FA07Z FD06 FD22 HA08 LA03 LA30 MA10

Claims (24)

[Claims] A guest-host type liquid crystal element for dimming;
A light control device provided on a light incident side of the liquid crystal element, the filter including a filter material that absorbs at least ultraviolet rays. 2. The light control device according to claim 1, wherein the filter material is made of at least one selected from an ultraviolet cut film, an ultraviolet cut coat glass, and an ultraviolet absorbing glass. 3. The light control device according to claim 1, wherein the filter material is provided at least in the same area as a cross section of an effective optical path of incident light. 4. The light control device according to claim 1, wherein a polarizing plate is disposed in an effective optical path of light incident on the liquid crystal element. 5. The light control device according to claim 4, wherein the polarizing plate is movable in and out of the effective optical path. 6. The liquid crystal device according to claim 1, wherein the liquid crystal device is a guest-host liquid crystal device using negative or positive liquid crystal as a host material and a positive or negative dichroic dye as a guest material. Dimmer. 7. A dimming device comprising a guest-host type liquid crystal element for dimming is arranged in an optical path of an imaging system, and a filter material for absorbing at least ultraviolet rays is provided on a light incident side of the liquid crystal element. Imaging device. 8. The imaging device according to claim 7, wherein the filter material is made of at least one selected from an ultraviolet cut film, an ultraviolet cut coated glass, and an ultraviolet absorbing glass. 9. The imaging device according to claim 7, wherein the filter material is provided at least in the same region as a cross section of an effective optical path of incident light. 10. The imaging device according to claim 7, wherein a polarizing plate is disposed in an effective optical path of light incident on the liquid crystal element. 11. The imaging device according to claim 10, wherein the polarizing plate is movable in and out of the effective optical path. 12. The liquid crystal device according to claim 7, wherein the liquid crystal device is a guest-host type liquid crystal device using a negative or positive liquid crystal as a host material and a positive or negative dichroic dye as a guest material. Imaging device. 13. A liquid crystal display device comprising a guest-host type liquid crystal element for dimming, and at least one of a filter material that absorbs at least ultraviolet light and a reflective material that reflects at least ultraviolet light is disposed on the light incident side of the liquid crystal element. Dimming device. 14. The light control device according to claim 13, wherein the filter material or the reflection material is made of at least one selected from an ultraviolet cut or reflection film, an ultraviolet cut or reflection coated glass, and an ultraviolet absorption or reflection glass. 15. The light control device according to claim 13, wherein the filter material or the reflection material is provided at least in the same area as a cross section of an effective optical path of incident light. 16. The light control device according to claim 13, wherein the liquid crystal element is disposed so as to be exposed on an outer surface of the device, and the filter material or the reflection material is disposed on a light incident side of the liquid crystal element. 17. The light control device according to claim 16, wherein the filter material or the reflection material is arranged also on a side end surface of the liquid crystal element. 18. The liquid crystal device according to claim 13, wherein the liquid crystal device is a guest-host type liquid crystal device using a negative or positive liquid crystal as a host material and a positive or negative dichroic dye as a guest material. Dimmer. 19. A light control device comprising a guest-host type liquid crystal element for light control is disposed in an optical path of an image pickup system, and a filter material for absorbing at least ultraviolet rays is provided on a light incident side of the liquid crystal element. An imaging device in which at least one of a reflecting material that reflects at least ultraviolet rays is disposed. 20. The imaging device according to claim 19, wherein the filter material or the reflection material is at least one selected from an ultraviolet cut or reflection film, an ultraviolet cut or reflection coated glass, and an ultraviolet absorption or reflection glass. 21. The imaging device according to claim 19, wherein the filter material or the reflection material is provided at least in the same region as a cross section of an effective optical path of incident light. 22. The imaging apparatus according to claim 19, wherein the liquid crystal element is disposed so as to be exposed on an outer surface of the apparatus, and the filter material or the reflection material is disposed on a light incident side of the liquid crystal element. 23. The imaging device according to claim 22, wherein the filter material or the reflection material is arranged also on a side end surface of the liquid crystal element. 24. The liquid crystal device according to claim 19, wherein the liquid crystal device is a guest-host liquid crystal device using a negative or positive liquid crystal as a host material and a positive or negative dichroic dye as a guest material. Imaging device.