JP2003228038A - Dimming device and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dimming device improved in optical functions and to provide an imaging device improved in performance, picture quality, and reliability by arranging the dimming device in an optical path. <P>SOLUTION: The dimming device has a dimming element equipped with a liquid crystal element and a polarizing element, and a polarization eliminating element (depolarizer) which is arranged on the incidence side or/and exitting side of the light of the dimming element. The imaging device has the dimming device composed of the liquid crystal element and polarizing element, in the optical path of an imaging system and the dimming device equipped with the dimming element equipped with the liquid crystal element and polarizing element and the polarization eliminating element (depolarizer) which is arranged on the incidence side or/and the exitting side of the light of the dimming element. <P>COPYRIGHT: (C)2003,JPO

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 and emitting the amount of incident light and an image pickup device using this light control device.

[0002]

2. Description of the Related Art Generally, a dimmer using a liquid crystal cell is
A polarizing plate is used. In this liquid crystal cell, for example, TN
(Twisted Nematic) type liquid crystal cell and guest-host (G
An H (Guest Host) type liquid crystal cell is used.

FIG. 8 is a schematic diagram showing the operating 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 not shown.
It is enclosed between two glass substrates and has a working electrode and a liquid crystal alignment film (the same applies hereinafter). In GH cell 2,
Positive liquid crystal molecules 3 and positive dichroic dye molecules 4 are enclosed.

The positive type dichroic dye molecule 4 is a positive type (p type) dye molecule which has anisotropy in light absorption and absorbs light in the direction of the long axis of the molecule. The positive liquid crystal molecule 3 is
For example, it is a positive type (positive type) having a positive dielectric anisotropy.

FIG. 8A shows the state of the GH cell 2 when no voltage is applied (no voltage is applied). Incident light 5 is
The light is linearly polarized by passing through the polarizing plate 1. Figure 8
In (a), since the polarization direction matches the direction of the long axis of the positive dichroic dye molecule 4, light is absorbed by the positive dichroic dye molecule 4 and the light transmittance of the GH cell 2 is increased. Is reduced.

Then, as shown in FIG. 8B, when a voltage is applied to the GH cell 2, the molecular length of the positive dichroic dye molecule 4 is increased as the positive liquid crystal molecule 3 is oriented in the electric field direction. The axial direction is perpendicular to the polarization direction of linearly polarized light. For this reason,
Incident light 5 is transmitted by the GH cell 2 with almost no absorption.

When a negative type (n-type) dichroic dye molecule that absorbs light in the minor axis direction of the molecule is used, this is the reverse of the case of the positive type dichroic dye molecule 4, and no voltage is applied. Light is not absorbed when applied, and absorbed when voltage is applied.

In the light control device shown in FIG. 8, the ratio of the absorbance when the voltage is applied and when the voltage is not applied, that is, the optical density ratio is about 10. This is a GH cell 2 without using the polarizing plate 1.
It has an optical density ratio about twice as high as that of a light control device composed of only one.

[0009]

However, by using the image pickup device equipped with the light control device including the liquid crystal element as described above, a liquid crystal monitor such as a notebook computer or a thin display, or a water surface where light is reflected or When shooting a subject with polarized light components such as the surface of a window glass, polarized light cannot pass through the polarizing plate depending on the shooting angle, and the image is partially crushed in total darkness or unnatural. It was understood that the image would be an image, and there was a strong desire to improve it.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a dimmer capable of improving an optical function, and the dimmer in the optical path. Another object of the present invention is to provide an image pickup apparatus which can be improved in performance, image quality, and reliability.

[0011]

That is, the present invention provides a dimming element including a liquid crystal element and a polarizing element, and a depolarizing element disposed on the light incident side and / or the outgoing side of the dimming element ( And a depolarizer).

Further, in an image pickup device in which a light control device including a liquid crystal element and a polarization element is arranged in an optical path of an image pickup system, the light control device includes the liquid crystal element and the polarization element. And a depolarizing element (depolarizer) disposed on the light incident side and / or the light emitting side of the light control element;
The present invention relates to an image pickup apparatus including:

According to the present invention, the depolarizer (depolarizer) for canceling the linear polarization of the light is arranged on the light incident side and / or the light exit side of the light control element. Even when shooting a subject with a polarized light component without affecting the dimming operation by the conventional liquid crystal optical element, polarized light can pass through the polarizing element depending on the shooting angle as in the conventional case. Instead, the captured image does not become partially dark, and a more natural image can be captured.

Therefore, the present invention can improve the optical functions of the light control device and the image pickup device, and is extremely effective for improving the performance, image quality, and reliability thereof.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The depolarizing element is arranged anywhere in the effective optical path on the light entrance side and / or the exit side of the light control element unless it is between the liquid crystal element and the polarization element. Although it may be provided, it is particularly preferable to be arranged on the light incident side. Then, as the depolarization element, a ¼λ phase difference plate or the like may be used. For example, the linearly polarized light component forming the circularly polarized light by the ¼λ retardation plate can be selectively transmitted by the polarizing element.

The depolarizing element is preferably integrated on the surface of the liquid crystal element opposite to the polarizing element (hereinafter referred to as a polarizing plate). For example, the liquid crystal element is formed. It may be directly attached on the substrate. Thereby, the optical function of the light control device can be improved in a more compact form without increasing the module unit of the light control element.

When the depolarizing element is installed in the effective optical path at all times, there is a slight light absorption in the depolarizing element when photographing a subject having no polarization component. On the other hand, in the light control device and the image pickup device according to the present invention, since the depolarization element can be provided with a drive mechanism that can be put in and taken out of the effective optical path of light, the depolarization function can be provided only when necessary. Can work. Therefore, when a normal subject having no polarization component is photographed, the slight desorption of light by the depolarization element as described above is eliminated, and a brighter image can be photographed.

Further, when photographing a subject having a polarization component according to preference, the depolarizing element is intentionally removed from the effective optical path to cut the polarization component of the subject, thereby reducing the surface reflection in water or It is also possible to capture the image through the glass window more clearly.

Further, in the liquid crystal element, a guest liquid containing a negative type liquid crystal as a host material and a dichroic dye as a guest material.
It is preferably a host type liquid crystal element.

Such a liquid crystal element is based on the prior invention of Japanese Patent Application No. 11-322186 filed by the present applicant. According to the invention of the prior application, a liquid crystal device and a polarizing plate arranged in the optical path of light incident on the liquid crystal device constitute a light control device, and further, a guest-host type liquid crystal device using a negative liquid crystal as a host material. The use of liquid crystal improves the ratio of absorbance (that is, the ratio of optical density) when voltage is not applied and when voltage is applied, and the contrast ratio of the dimmer is increased. Can be performed normally.

In the guest-host type liquid crystal cell (GH cell) 2 shown in FIG. 8, a positive type liquid crystal having a positive dielectric anisotropy (Δε) is used as the host material 3 and the guest material 4 is used.
Is a positive dye 4 having a positive light absorption anisotropy (ΔA) having dichroism, and the polarizing plate 1 is arranged on the incident side of the GH cell 2.
When a change in light transmittance when an operating voltage is applied is measured using a rectangular wave as a drive waveform, as shown in FIG. 9, the average light transmittance of visible light (in air, in addition to the liquid crystal cell) is increased as the operating voltage is applied. Refer to the transmittance when adding polarizing plates (= 100%)
The following is the same), but the maximum light transmittance when the voltage is increased to 10 V is about 60%,
Moreover, the change in light transmittance is gradual.

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, so that the director of the director is applied even if a voltage is applied. Orientation does not change (or
It is considered that this is because liquid crystal molecules remain (which are difficult to change).

On the other hand, in the prior invention, as shown in FIG. 10, in the guest-host type liquid crystal cell (GH cell) 12, as the host material 13, the dielectric anisotropy (Δε) is used.
Is a negative liquid crystal of negative type MLC-6 manufactured by Merck.
608 is used as an example, and as the guest material 4, D5 manufactured by BDH, which is a positive dye having dichroism, is used as an example, so that the polarizing plate 11 is arranged on the incident side of the GH cell 12 and a rectangular wave is generated. When a change in light transmittance when an operating voltage is applied as a drive waveform is measured, as shown in FIG. 11, the average light transmittance of visible light (in air) is increased as the operating voltage is applied.
The maximum light transmittance decreases from about 75% to several%, and the change of the light transmittance becomes relatively sharp.

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, and therefore light does not flow when no voltage is applied. It is considered that this is 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.

As described above, in the present invention, if the GH cell 12 is formed by using the negative type host material, the light transmittance (particularly when transparent) is improved, and the GH cell 12 is directly used in the image pickup optical system. It becomes possible to realize a more compact light control device that can be used by fixing the position. 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 when no voltage is applied and when voltage is applied (that is, the ratio of optical density)
Is further improved, the contrast ratio of the light control device is further increased, and the light control operation can be normally performed from a bright place to a dark place.

In the present invention, the negative-type liquid crystal of the liquid crystal element preferably has a negative dielectric anisotropy, but the guest material is composed of positive-type or negative-type dichroic dye molecules. You may The host material is preferably a negative type, but a positive type can be used.

In the present invention, the negative (or positive) host material and the positive (or negative) guest material can be selected from known materials and used. However, in the case of actual use, a blended composition may be used which is selected so as to exhibit nematic properties in the actual use temperature range.

The dimmer according to the present invention is the above-mentioned GH.
The light control device includes a cell 12 and a polarizing plate, and the depolarization device disposed on the light incident side and / or the light emission side of the light control device.

For example, as shown in FIG. 1, the dimming element composed of a polarizing plate 11 and a GH cell 12 is composed of a front lens group 15 and a rear lens group 16 composed of a plurality of lenses like a zoom lens. A depolarizing element 33 is disposed between the light control elements and on the light incident side of the light control element. The light that has passed through the front lens group 15 passes through the depolarizer 33 and is then linearly polarized through the polarizing plate 11, and the GH cell 12
Incident on. The light that has passed through the GH cell 12 is condensed by the rear lens group 16 and is displayed as an image on the imaging surface 17.

According to the light control device of the present invention as shown in FIG. 1, the depolarization element 33 for canceling the linear polarization of the light is arranged on the light incident side of the light control element. , Without affecting the dimming operation by the liquid crystal optical element of the invention of the prior application, and even when shooting a subject having a polarization component, the captured image does not become partially dark depending on the shooting angle, A more natural image can be captured and the image quality can be improved.

The depolarizing element 33 can be put in and taken out from the effective optical path 20 of the light entering the GH cell 12. Specifically, by moving the depolarizing element 33 to the position indicated by the imaginary line, it is possible to let the light out of the effective optical path 20. As a result, the depolarization function can be activated only when necessary. For example, when a normal subject having no polarization component is photographed, the depolarization element 33 is used.
Is moved to the position indicated by the virtual line, the depolarizer 3
There is no slight light absorption in 3 and a brighter image can be taken.

A polarizing plate 11 which constitutes this light control device
Can be put in and taken out of the effective optical path 20 of the light incident on the GH cell 12, as in the above-mentioned prior invention by the present applicant. Specifically, by moving the polarizing plate 11 to the position indicated by the imaginary line, it is possible to let the light out of the effective optical path 20. A mechanical iris as shown in FIG. 2 may be used as a means for moving the polarizing plate 11 in and out.

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

As a result, as shown in FIG. 2, the iris blades 18 and 19 are partially overlapped, and when this overlap becomes large, the opening 22 on the effective optical path 20 located near the center of the iris blades 18 and 19 is formed. Is covered with the polarizing plate 11.

FIG. 3 is a partially enlarged view of the mechanical iris near the effective optical path 20. At the same time that the iris blade 18 moves downward, the iris blade 19 moves upward. Along with this, as shown in FIG. 3A, the iris blade 1
The polarizing plate 11 attached to 8 also moves to the outside of the effective optical path 20. On the contrary, 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, the polarizing plate 11 moves to the effective optical path 20,
The opening 22 is gradually covered. When the overlapping of the iris blades 18 and 19 with each other becomes large, as shown in FIG.
The polarizing plate 11 covers the entire opening 20.

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

As the subject (not shown) becomes brighter, as shown in FIG. 3A, the iris blades 18 and 19 that have been opened in the vertical direction are driven by a motor (not shown) to start overlapping. As a result, the polarizing plate 11 attached to the iris blade 18 starts to enter the effective optical path 20 and covers part of the opening 22 (FIG. 3B).

At this time, the GH cell 12 is in a state of not absorbing light (note that due to thermal fluctuation or surface reflection,
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 the same.

Then, the polarizing plate 11 is completely opened 22.
Is covered (FIG. 3 (c)). Furthermore, when the brightness of the subject increases, the voltage to the GH cell 12 is increased,
Light control is performed by absorbing light in the GH cell 12.

On the contrary, when the subject becomes dark,
First, the light absorption effect of the GH cell 12 is eliminated by reducing or not applying the voltage to the GH cell 12. When the subject becomes darker, drive a motor (not shown) to move the iris blade 18 downward.
Further, the iris blade 19 is moved upward. Thus
The polarizing plate 11 is moved out of the effective optical path 20 (see FIG. 3).
(A)).

Further, as shown in FIG.
(For example, the transmittance is 40% to 50%).
The light is not absorbed by the polarizing plate 11 because it can be emitted outside. Therefore, the maximum transmittance of the light control device can be increased to, for example, twice or more. Specifically, when this dimmer is compared with a conventional dimmer composed of a fixedly installed polarizing plate and a GH cell, the maximum light transmittance is approximately doubled. The minimum light transmittance is the same for both.

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

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

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

Example 1 First, an example of a light control device using a guest-host liquid crystal (GH) cell will be described.

As shown in FIG. 1, this light control device includes a light control element having a polarizing plate 11 and a GH cell 12 in this order, and an effective light path 20 on the light incident side of the light control element. And a depolarization element 33 such as a 1 / 4λ retardation plate. The GH cell 12 includes a negative type liquid crystal molecule (host material) and a positive type or negative type two-colored film between two glass substrates (neither of which is shown) on which a transparent electrode and an alignment film are respectively formed. A mixture with a sexual dye molecule (guest material) is encapsulated.

As the liquid crystal molecule, for example, MLC-6608 manufactured by Merck Co., which is a negative type liquid crystal having a negative dielectric anisotropy, is used as an example, and the dichroic dye molecule 4 is anisotropic in light absorption. As an example, D5 manufactured by BDH, which is a positive type dye that has properties and absorbs light in the long axis direction of the molecule, was used.
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 dimming device comprising the polarizing plate 11, the GH cell 12, and the depolarizer 33 is, for example, as shown in FIG. 1, a lens front group 15 and a lens which are composed of a plurality of lenses such as a zoom lens. It was placed between the rear group 16.
The light transmitted through the front lens group 15 passes through the depolarizing element 33, is linearly polarized through the polarizing plate 11, and then enters the GH cell 12. The light that has passed through the GH cell 12 is condensed by the rear lens group 16 and is displayed as an image on the imaging surface 17.

According to the light control device of the present invention as shown in FIG. 1, the effective light path 20 on the light incident side of the light control element is set.
In addition, the depolarizing element 33 for eliminating the linearly polarized light.
Since it is arranged, even if a subject having a polarization component is photographed without affecting the dimming operation of the liquid crystal optical element of the invention of the prior application, the captured image may partially vary depending on the photographing angle. It is possible to capture a more natural image without becoming dark and to improve the image quality.

The depolarizer 33 can be put in and taken out of the effective optical path 20 of the light entering the GH cell 12. Specifically, by moving the depolarizing element 33 to the position indicated by the imaginary line, it is possible to let the light out of the effective optical path 20. As a result, the depolarization function can be activated only when necessary. For example, when a normal subject having no polarization component is photographed, the depolarization element 33 is used.
Is moved to a position indicated by an imaginary line, and there is no slight light absorption in the depolarization element 33, and a brighter image can be taken.

In addition, when photographing an object having a polarization component according to preference, the depolarizing element 33 is intentionally removed from the effective optical path 20 to cut the polarization component of the object, thereby suppressing surface reflection in water. It is now possible to take clearer images such as images through a glass window.

The polarizing plate 1 which constitutes this light control device
1 is the same as the above-mentioned prior invention of the applicant.
The light that enters the cell 12 can be moved in and out of the effective optical path 20.

Specifically, by moving the polarizing plate 11 to the position indicated by the imaginary line, it is possible to let the light out of the effective optical path 20. The mechanical iris shown in FIGS. 2 and 3 may be used as a means for putting in and taking out the polarizing plate 11.

Here, in the above-described light control device according to the present invention, as shown by the alternate long and short dash line in FIG. 1, the depolarizing element 33 is preferably placed in the effective light path 20 on the light emitting side of the GH cell 12. It may be arranged in combination with the depolarizing element on the light incident side of the GH cell 12. In this case, as shown in the figure, G
The depolarizing element 33 may be attached directly to the substrate of the H cell 12 on the side opposite to the polarizing plate 11, and may be disposed integrally with the GH cell 12, or may be disposed at an arbitrary distance from the GH cell 12. You may. When the light control device is arranged integrally with the GH cell 12, the optical function of the light control device can be improved in a more compact form without increasing the module unit of the light control element. GH like this
If the element 33 is arranged on the light emitting side of the cell 12, there is a possibility that the polarization of the light incident on the imaging surface (for example, CCD described later) can be canceled and the color pseudo signal due to the polarization component can be prevented.
This effect is added to the function of preventing the color pseudo signal by cutting the high frequency component by the optical low pass filter. For this reason, it is considered that the optical design of the optical low-pass filter considering the problem of the polarization component becomes easy.

Also in this case, similarly to the above,
The depolarizing element 33 may be provided with a drive mechanism that can move in and out of the effective optical path 20 of light.

Embodiment 2 FIG. 4 shows the light control device according to Embodiment 1 as a CCD (Charge).
coupled device) shows an example incorporated in a camera.

That is, in the CCD camera 50, the first group lens 51 and the second group lens (for zoom) 52 corresponding to the lens front group 15 and the lens rear group 16 are arranged along the optical axis shown by the one-dot chain line. The corresponding third group lens 53, fourth group lens (for focus) 54, and CCD package 55 are arranged in this order at appropriate intervals, and the CCD package 55 has an infrared cut filter 55a, an optical low-pass filter system 55b, A CCD image pickup device 55c is stored.

Between the second lens group 52 and the third lens group 53, the polarizing plate 11 and the GH cell 1 are located near the third lens group 35.
2 is arranged, and further, a depolarizing element 33 is attached on the light incident side of the light control element on the same optical path for adjusting the light quantity (light quantity diaphragm).
The focusing fourth group lens 54 is arranged so as to be movable between the third group lens 53 and the CCD package 55 along the optical path by the linear motor 57, and the zoom second group lens 52 is located in the optical path. It is arranged so as to be movable between the first group lens 51 and the dimmer 23.

FIG. 5 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 lenses 52 and 3 are
Since the light control device 23 according to the present invention is provided between the group lenses 53, the amount of light can be adjusted by applying an electric field as described above, the system can be downsized, and the effective range of the optical path can be substantially achieved. Can be miniaturized. Therefore, CC
It is possible to achieve miniaturization of the D camera. Also,
Since the amount of light can be appropriately controlled by the magnitude of the voltage applied to the patterned electrode, the conventional diffraction phenomenon can be prevented, and a sufficient amount of light can be made incident on the image sensor to eliminate the blurring of the image.

Further, since the depolarizer 33 for canceling the linear polarization of the light is arranged on the light incident side of the light control element, for example, the light control operation by the liquid crystal optical element of the invention of the prior application is affected. Even when a subject having a polarization component is photographed on the image without giving the image, the picked-up image is not partially darkened depending on the photographing angle, and a more natural image can be picked up.

Embodiment 3 This embodiment is different from the previous embodiment 1 in that FIG. 6 and FIG.
As shown in FIG. 2, the GH cell 12 and the polarizing plate 11 that form the light control element are arranged in this order, and the depolarizing element 33 exemplified by a 1 / 4λ phase difference plate or the like forms the GH cell 12. This is that the depolarizing element 33 and the GH cell 12 are integrated by being directly attached to the surface of the glass substrate opposite to the polarizing plate 11. This element 33 is the GH cell 1
In addition to being attached to the GH cell 12, the GH cell 12 may be put in and taken out so as to be in contact therewith.

By arranging the depolarizing element 33 and the GH cell 12 in an integrated manner, the module unit of the light control device can be made even more compact. Even when shooting a subject having a polarization component without affecting the dimming operation, the captured image does not become partially dark depending on the shooting angle, and a more natural image can be captured. .

Further, in the present embodiment, the miniaturization of the light control device unit enables the total image pickup device to be assembled into a smaller size, which further leads to further increase in the commercial value of the image pickup device.

Here, in the light control device according to the present invention described above, the depolarizing element 33 may be arranged at an arbitrary distance from the GH cell 12 as shown by the alternate long and short dash line in FIG. Alternatively, it may be arranged in the effective optical path 20 on the light emitting side of the GH cell 12.

Further, also in the light control device and the image pickup device according to the third embodiment, as in the above-described first embodiment, the depolarizing element 33 is provided with a drive mechanism capable of moving in and out of the effective optical path 20 of light. Good.

The embodiments and examples of the present invention have been described above, but the above examples can be variously modified based on the technical idea of the present invention.

For example, the location of the depolarizer 33 is
If it is not between the GH cell 12 and the polarizing plate 11, it may be basically placed anywhere in the optical path of the image pickup device.
It is desirable to be arranged on the incident side of light. Depolarization element 33
Is a quarter-wave retarder if it can convert incident light from a subject (including liquid crystal display) consisting of linearly polarized light components into random polarized light (circularly polarized light + elliptically polarized light + linearly polarized light) like natural light. However, the present invention is not limited to this, and other optical members having the same function can be used.

It goes without saying that the sample structure, the material used, the driving method of the liquid crystal cell, the form of the light control device, etc. can be appropriately selected without departing from the spirit of the invention.

The structures and materials of the liquid crystal element, the light control device and the polarizing plate, the driving mechanism, the driving circuit, the control circuit, and the like can be variously modified. Further, the drive waveform can be driven by a rectangular wave, and the trapezoid can be driven by any of a triangular wave and a sine wave, and the inclination of the liquid crystal molecules changes according to the potential difference between the two electrodes constituting the liquid crystal cell, and the light transmittance Controlled.

Also, an example in which the pulse voltage modulation (PHM) is used for the driving method of the liquid crystal cell is shown.
It can also be applied when driven by M).

As the GH cell 12, a GH cell having a two-layer structure or the like can be used in addition to the above-mentioned ones. The position of the polarizing plate 11 with respect to the GH cell 12 may be set to an optimum position from the setting conditions of the imaging lens. However,
As described above, the depolarizing element 33 includes the polarizing plates 11 and G.
Since the dimming characteristic of the H cell 12 cannot be obtained, the H cell 12 should not be arranged between the polarizing plate 11 and the GH cell 12.

Then, as the subject becomes brighter, light adjustment is first performed by putting in and out the polarizing plate 11, and then GH
An example of absorbing light by the cell 12 has been shown, but conversely,
The dimming may be performed by the light absorption of the GH cell 12 first. In this case, after the transmittance of the GH cell 12 has decreased to a predetermined value, light adjustment is performed by putting the polarizing plate 11 in and out.

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

Further, the depolarizer 33 and the polarizing plate 11 are
It is preferable that it can be taken in and out of the effective optical path 20, but it is of course possible to fix the position in the effective optical path 20.

The number of iris blades 18 and 19 is not limited to two, and a larger number may be used, or conversely, one. Further, although the iris blades 18 and 19 are stacked by moving in the vertical direction, they may move in other directions and 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.

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

Further, the light control device according to the present invention is used for adjusting the light amount of various optical systems such as electrophotographic copying machines and optical communication devices in addition to the optical aperture of the image pickup device such as the CCD camera described above. Is also widely applicable. Further, in addition to the optical diaphragm and the filter, it can be applied to various image display devices for displaying characters and images.

Further, as the image pickup device, in addition to the CCD (Charge Coupled Device) used in this embodiment,
Of course, application to a CMOS image sensor or the like is also possible.

Further, the light control device of the present invention can be applied to various image display devices for displaying characters and images, in addition to the optical filter.

[0082]

According to the present invention, the depolarizer (depolarizer) for canceling the linearly polarized light is arranged on the light incident side and / or the light emitting side of the light control element. , Even when a subject having a polarization component is photographed without affecting the dimming operation by the above-mentioned conventional liquid crystal optical element, polarized light may cause the polarization element to vary depending on the photographing angle as in the conventional case. It is possible to take a more natural image by preventing the image from being partially darkened because the image cannot be transmitted.

Therefore, the present invention can improve the optical functions of the light control device and the image pickup device, and is extremely effective in improving the performance, image quality, and reliability thereof.

[Brief description of drawings]

FIG. 1 is a schematic side view of an example of a light control device according to an embodiment of the present invention.

FIG. 2 is a front view of a mechanical iris of the light control device.

FIG. 3 is a schematic partial enlarged view showing the operation of the mechanical iris in the vicinity of the effective optical path of the light control device.

FIG. 4 is a schematic cross-sectional view of a camera system incorporating the light control device including the depolarizing element.

FIG. 5 is an algorithm of light transmittance control in the camera system.

FIG. 6 is a schematic side view of another example of the light control device.

FIG. 7 is a schematic cross-sectional view of a camera system incorporating the light control device including the depolarizing element.

FIG. 8 is a schematic diagram showing an operating principle of a conventional light control device.

FIG. 9 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.

FIG. 10 is a schematic view showing the operation principle of the light control device of the invention of the prior application.

FIG. 11 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 type liquid crystal molecules, 15 ... Lens front group, 16 ... Lens rear group, 17 ... Imaging surface, 18, 19 ... Iris blade, 20 ...
Effective optical path (intermediate part or central part of cell), 21 ... Operating direction,
22 ... Opening part, 23 ... Dimmer, 24 ... Cell peripheral part, 3
3 ... Depolarization element, 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, 55
c ... CCD image sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/137 500 G02F 1/137 500 5C022 G03B 9/02 G03B 9/02 E 5C024 9/04 9/04 H04N 5/225 H04N 5/225 D 5/335 5/335 Q VF Term (reference) 2H044 EE01 2H049 BA02 BA07 BA12 BB03 BC22 2H080 AA04 AA20 AA31 CC07 2H088 EA25 EA38 GA02 GA13 HA17 HA18 JA06 KA27 MAX FA08Z FA08Z0808 FAH08 FA08Z FD22 HA08 LA30 MA10 5C022 AB01 AC42 AC54 AC74 5C024 EX22 EX35 EX42 EX51

Claims (6)

[Claims] 1. A light control device comprising a light control element including a liquid crystal element and a polarization element, and a depolarizer (depolarizer) disposed on the light incident side and / or the light output side of the light control element. . 2. A light control device comprising a liquid crystal element and a polarizing element arranged in an optical path of an image pickup system, wherein the light control device includes the liquid crystal element and the polarizing element. An imaging device comprising: a depolarizing element (depolarizer) disposed on the light incident side and / or the light emitting side of the light control element. 3. The depolarizing element is integrated on a surface of the liquid crystal element opposite to the polarizing element.
Or the device described in 2. 4. The apparatus according to claim 1, wherein the depolarization element is provided so as to be able to be put in and taken out from an effective optical path of light which is made to enter or exit the liquid crystal element. 5. The device according to claim 1, wherein the polarizing element is provided so as to be able to be put in and taken out from an effective optical path of light which is made to enter or exit the liquid crystal element. 6. The device according to claim 1, wherein the liquid crystal element is a guest-host type liquid crystal element having a negative liquid crystal as a host material and a dichroic dye as a guest material.