JP2002303850A - Dimming device and its driving method, and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance, picture quality, and reliability of a dimming device and an image pickup device more by speedily and accurately judging ambient temperature and smoothly starting alignment variation of liquid crystal or its relaxation according to the ambient temperature even when a liquid crystal element for dimming is driven for halftones in low-temperature environment. SOLUTION: The dimming device 23 has a liquid crystal element (GH cell) 12. The liquid crystal element 12 is driven and controlled by a control part 64 including a temperature decision part 65 which detects the light transmissivity when the liquid crystal element 12 is in a transparent and/or in a shading state during actual use and decides the ambient temperature of the liquid crystal element 12 according to the detected value.

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, a driving method thereof, and an image pickup apparatus 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. 24 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 has an operating electrode and a liquid crystal alignment film (the same applies hereinafter). In the GH cell 2, positive liquid crystal molecules 3 and positive dichroic dye molecules 4 are sealed.

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. 24A 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. 24A, the polarization direction coincides with the molecular long axis direction of the positive dichroic dye molecules 4, so that light is absorbed by the positive dichroic dye molecules 4 and the light of the GH cell 2 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. 24, as shown in FIG. 25, 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 light control device shown in FIG. 24, 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]

In driving a light control device using a conventional liquid crystal element, a drive pulse is changed in a step-like manner when the light transmittance is changed. , The response speed is reduced.
In particular, the light transmittance is slightly reduced as compared with a step response (or a large step response from light-shielded to transparent) with a large change width from transparent (maximum light transmittance) to light-shielded (minimum light transmittance). The response time at the time of halftone driving in the case of changing to is longer due to the influence of the environmental temperature, which is problematic in terms of the response speed.

[0011] This is a problem that can be said to be a fate when using a physical element such as a liquid crystal cell.
There is an urgent need to establish a means for responsively operating a liquid crystal element at a speed required as a dimmer.

As one of the countermeasures, the inventor of the present invention has a device for detecting the ambient temperature of the element, such as a thermistor,
In addition, Japanese Patent Application No. 2000-311502 has already proposed an invention of improving the transient response speed of a liquid crystal light control device at a low temperature by a multi-step driving method in which a control driving pulse corresponding to the detected environmental temperature is inserted. did.

That is, the light control device, the image pickup device, and the method of driving the light control device according to the prior application include a light control device using a liquid crystal optical element, which is provided with a device environmental temperature detecting section, thereby detecting the element environmental temperature and providing a liquid crystal display. When the light transmittance of the element is slightly changed from the current transmittance to the target transmittance in a halftone, before the drive pulse corresponding to the target transmittance is given, the device is completely shaded (minimum transmittance) or completely transparent ( Control pulses of a voltage corresponding to the maximum transmittance) are appropriately inserted in advance in a number of pulses corresponding to the detected element ambient temperature, so that a drive pulse corresponding to the target transmittance is simply given in a step-like manner. Compared with the conventional driving method, the change in the orientation of the liquid crystal (or the relaxation thereof) rises more smoothly, and the response time until the target transmittance is reached can be greatly reduced.

However, as a result of further studies by the present inventor, as a result, a method capable of more effectively detecting an element environment temperature without intentionally providing an external sensor such as a thermistor as described in the prior application. And discovered the device.

That is, an object of the present invention is to quickly and accurately determine the environmental temperature even when driving a dimming liquid crystal element in a low-temperature environment to perform a halftone driving, and to perform a change in the orientation of the liquid crystal or a relaxation thereof. An object of the present invention is to further improve the performance, image quality, and reliability of the light control device and the image pickup device by allowing the light control device and the image pickup device to start up more smoothly in accordance with the temperature.

[0016]

That is, the present invention has a liquid crystal element, and detects the light transmittance of the liquid crystal element when it is transparent and / or when it is shielded from light before use. The present invention relates to a dimming device in which the driving of the liquid crystal element is controlled by a control unit including a temperature determination unit that determines an environmental temperature of the liquid crystal element.

According to the present invention, there is also provided an image pickup apparatus in which a light control device including a liquid crystal element is disposed in an optical path of an image pickup system, wherein the light control device includes a liquid crystal element;
A control unit that detects a light transmittance of the liquid crystal element when it is transparent and / or shields light, and that includes a temperature determination unit that determines an environmental temperature of the liquid crystal element from the detected value. It is.

The present invention also relates to a method for driving a light control device comprising a liquid crystal element, wherein when changing the transmittance of light emitted from the liquid crystal element from the current light transmittance to the target light transmittance, At least before giving a drive pulse corresponding to the target transmittance, a control drive pulse corresponding to the minimum light transmittance or the maximum light transmittance is determined according to the environmental temperature determined from the light transmittance of the liquid crystal element before actual use. And a method for driving the light control device, which is inserted in advance.

According to the present invention, since the light transmittance of the liquid crystal element before actual use is detected and the environmental temperature is determined from the detected value, the optical system and circuit system originally included in the dimmer itself are directly used. The temperature can be determined simply by detecting the light transmittance using the temperature control, and the temperature can be detected quickly and accurately, and the temperature can be detected in a circuit by omitting the temperature detector. It is relatively simple and can be downsized.

As a result, for example, when the light transmittance of the liquid crystal element is slightly changed in halftone from the current light transmittance to the target light transmittance, before the drive pulse corresponding to the target light transmittance is given, It is possible to appropriately insert a control drive pulse corresponding to the time of light shielding (minimum light transmittance) or completely transparent (maximum light transmittance) at a value controlled in accordance with the determined use environment temperature. Yes, compared to the case where the driving pulse corresponding to the target light transmittance is simply given in a step shape and driven.
The change in the orientation of the liquid crystal or the relaxation thereof can be started more smoothly, and the response time until the target light transmittance is reached can be greatly reduced.

This solves the problem that can be said to be a fate when using a physical element such as a liquid crystal cell, and enables the liquid crystal element to perform a response operation at a speed required as a dimmer even in a low-temperature environment.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when changing the transmittance of light emitted from a liquid crystal element from a current light transmittance to a target light transmittance, a driving pulse corresponding to at least the target light transmittance is given. It is desirable to provide a pulse control unit that inserts a control drive pulse corresponding to the minimum light transmittance or the maximum light transmittance in advance according to the environmental temperature determined by the temperature determination unit.

Further, the control drive pulse has at least a controlled pulse voltage and a controlled number of pulses, and the pulse voltage is equal to or equal to the pulse voltage that produces the minimum light transmittance or the maximum light transmittance. It may be a value between a voltage and a pulse voltage that produces the target light transmittance.

Further, the control drive pulse has at least a controlled pulse width and a controlled number of pulses, and the pulse width is equal to or smaller than the pulse width that produces the minimum light transmittance or the maximum light transmittance. It may be a value between a width and a pulse width that produces the target light transmittance.

The control drive pulse can be controlled not only by the above-described pulse voltage or pulse width, but also by pulse density, and also by a combination of these.

It is preferable that the liquid crystal element is a guest-host type liquid crystal element using negative liquid crystal as a host material and a dichroic dye as a guest material.

Such a liquid crystal device is based on the prior invention of Japanese Patent Application No. 11-322186 already filed by the present applicant. According to this prior invention, a liquid crystal device and a polarizing plate arranged in the optical path of light incident on the liquid crystal device constitute a dimmer, and further, a guest-host type using a negative type liquid crystal as a host material. By using liquid crystal, the ratio of the absorbance between when no voltage is applied and when a voltage is applied (that is, the ratio between optical densities) is improved, and the contrast ratio of the light control device is increased. Can be performed normally.

Hereinafter, preferred embodiments of the present invention will be described in detail.

In this embodiment, as shown in FIG. 23, information on the correlation between the light transmittance of the liquid crystal optical element when it is transparent and / or when it is shielded from light and the ambient temperature of the element (the constituent material of the liquid crystal cell and the cell). Is determined in advance in the memory of the temperature determination circuit 65 of the GH cell drive control circuit section 62, and the liquid crystal cell 12 is driven before the imaging device is actually used. By changing the light transmittance and comparing the measured value of the light transmittance in the transparent state and / or the light-shielded state with the correlation data input to the memory of the temperature determination circuit 65 in advance, it is possible to detect the element environment temperature. It was found that even without the external sensor, the ambient temperature of the liquid crystal optical element could be almost accurately and quickly determined from the light transmittance of the mounted liquid crystal cell.

In actual use, when the light transmittance of the liquid crystal optical element is slightly changed from the current transmittance to the target transmittance in halftone, before the drive pulse corresponding to the target transmittance is given, The control drive pulse corresponding to the time of complete light shielding (minimum transmittance) and / or the time of complete transparency (maximum transmittance) is determined according to the element environment temperature determined in advance by the temperature determination circuit 65 from the previous light transmittance. By changing the pulse voltage and the number of pulses appropriately beforehand, the orientation change (or relaxation) of the liquid crystal cell can be made smoother in an optimal form according to the operating temperature of the light control device equipped with the liquid crystal element. And the transient response time until the target transmittance is reached can be greatly reduced.

This solves the problem that the response speed of the light transmittance in the halftone is slow when using a physical element such as a liquid crystal cell. The liquid crystal optical element can be responsively operated at the required speed.

Next, in the guest-host type liquid crystal cell (GH cell) 2 shown in FIG. 24, 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 the transmittance is measured, as shown in FIG. 25, the average light transmittance of the 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. (= 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, in the prior invention, as shown in FIG. 16, in the guest-host type liquid crystal cell (GH cell) 12, as the host material 13, the dielectric anisotropy (Δε) was used.
Is a negative liquid crystal MLC-6 manufactured by Merck
608 is used as an example, the polarizing plate 11 is arranged on the incident side of the GH cell 12 by using D5 manufactured by BDH, which is a positive type dye having dichroism, as an example of the guest material 4, and a rectangular wave is formed. When the change in the light transmittance when the operating voltage was applied was measured as a drive waveform, as shown in FIG.
Is reduced from the maximum light transmittance of about 75% to several percent, and the change in light transmittance is 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. 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.

As described above, in the present invention, when the GH cell is formed using the negative type host material, the light transmittance (particularly when transparent) is improved, and the position of the GH cell is fixed in the imaging optical system as it is. This makes it possible to realize a compact light control device that can be used as a light control device. In this case, by arranging the 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 the voltage is applied (that is, the ratio of the optical density) is further improved,
The contrast ratio of the light control device is further increased, and the light control operation can be performed more normally from a bright place to a dark place.

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

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

The light control device 2 including the GH cell 12 described above
The lens 3 is disposed between a front lens group 15 and a rear lens group 16 including a plurality of lenses such as a zoom lens, as shown in FIG. 18, for example. The light transmitted through the front lens group 15 is linearly polarized through the polarizing plate 11, and then enters the GH cell 12. 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 of the light incident on the GH cell 12 in the same manner as in the above-mentioned prior invention by the present applicant. Specifically, by moving the polarizing plate 11 to a position indicated by a virtual line, the light can be emitted out of the effective optical path. As a means for taking in and out the polarizing plate 11, FIG.
A mechanical iris as shown at 0 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. 19, 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. 20 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.
Accordingly, as shown in FIG. 20A, 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. Accordingly, 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 the 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. 20B).

At this time, the GH cell 12 is in a state of not absorbing light (because of 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
Is covered (FIG. 20C). 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. 20).
(A)).

Also, as shown in FIGS. 8 to 20, the polarizing plate 11 (transmittance, for example, 40% to 50%) can go out of the effective optical path 20 of 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.

Further, since the polarizing plate 11 is moved in and out by using a mechanical iris which has been put to practical use in a digital still camera or the like, a dimming 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, this light control device can increase the contrast ratio between light and dark and can maintain the light amount distribution substantially uniform.

The present embodiment relates to a liquid crystal element applied in, for example, the field of manufacturing electronic equipment, and more particularly, to a dimming device using the liquid crystal element and disposing it in an optical path of an imaging system. The present invention relates to an imaging device and a method for driving these devices.

In this light control device, before the actual use, the light transmittance of the liquid crystal optical element when it is transparent and / or when it is shielded is detected by a detecting means in advance, and the detected value is used to determine the light transmittance of the liquid crystal element. It is characterized by having a mechanism for determining the environmental temperature.

Further, the light control device includes a liquid crystal element, a detecting unit for detecting light transmittance, and a light emitted from the liquid crystal element upon receiving an element environment temperature determined before actual use from the detected value. When changing the transmittance from the current transmittance to the target transmittance, before giving a drive pulse corresponding to the target transmittance,
Pulse control in which control drive pulses corresponding to complete light shielding (minimum transmittance) or complete transparency (maximum transmittance) are inserted in advance by the number of pulses corresponding to the element environmental temperature determined from the light transmittance of the liquid crystal element. And a unit.

Further, this method of driving the light control device corresponds to a method for driving the liquid crystal element, in which the transmittance of light emitted from the liquid crystal element is changed from the current transmittance to the target transmittance. Before providing a drive pulse to be applied, a control drive pulse corresponding to complete light shielding (minimum transmittance) or complete transparency (maximum transmittance) is a pulse corresponding to the element ambient temperature determined from the light transmittance of the liquid crystal element. It is characterized in that it is inserted in advance by a number.

In the light control device and the driving method, the driving pulse of the light control device is controlled by at least a pulse voltage.

In the light control device and the driving method, the driving pulse of the light control device is controlled at least by a pulse width.

Further, this light control device is characterized in that the liquid crystal element is a guest-host type liquid crystal element using negative liquid crystal molecules as a host material and dichroic dye molecules as a guest material.

In the light control device and the image pickup device according to the present invention, it is preferable that 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 to the drive electrode, the collective control of the light transmittance can be performed with high accuracy over the entire effective optical path width.

According to the present embodiment, since the light transmittance of the liquid crystal element before actual use is detected and the environmental temperature is determined from the detected value, the optical system and circuit originally owned by the light control device itself are used. The temperature can be determined simply by detecting the light transmittance using the system as it is, and the temperature can be detected quickly and accurately.
In addition, the temperature detection unit can be omitted, and the temperature can be detected in a circuit manner, so that the structure of the light control device can be made relatively simple and the size can be reduced.

As a result, for example, when slightly changing the light transmittance of the liquid crystal element from the current light transmittance to the target light transmittance in halftone, before giving a drive pulse corresponding to the target light transmittance, A control drive pulse corresponding to complete light shielding (minimum light transmittance) or complete transparency (maximum light transmittance) is appropriately inserted in advance at a value controlled according to the determined use environment temperature. As compared to the case where the driving pulse corresponding to the target light transmittance is simply given in a step-like manner, the change in the orientation of the liquid crystal or the relaxation thereof rises more smoothly, and until the target light transmittance is reached. Response time can be greatly reduced.

This solves the problem that can be said to be a fate when using a physical element such as a liquid crystal cell, and makes it possible to operate the liquid crystal element responsively at a speed required as a dimmer even in a low-temperature environment.

That is, since the use environment temperature of the liquid crystal element is determined from its light transmittance, a temperature detection unit (for example, a thermistor, etc.) is not required. Is omitted, and the detection can be performed quickly.

Also, due to the deterioration of the operation characteristics and performance, etc.,
It is not necessary to always transmit a proper detection signal, and the temperature detection unit is omitted, and the detection value of the light transmittance previously stored and the detection value of the current light transmittance are compared in the temperature determination circuit. Since the temperature is detected in a specific manner, the temperature can be accurately detected.

[0065]

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

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

This light control device has a G
It comprises an H cell 12 and a polarizing plate 11. The GH cell 12 is provided between two glass substrates (both not shown) on each of which a transparent electrode and an alignment film are formed, and a negative liquid crystal molecule (host material) and a positive or negative two-color liquid crystal molecule. A mixture with a chromatic dye molecule (guest material) is enclosed.

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 dimmer 23 including the GH cell 12
For example, as shown in FIG. 18, 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 through the polarizing plate 11, and then enters the GH cell 12. 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 is similar to the above-mentioned prior invention by the present applicant.
The light can enter and exit the effective optical path of the light incident on the GH cell 12.

Specifically, by moving the polarizing plate 11 to the position indicated by the imaginary line, the light can be out of the effective optical path. As a means for taking the polarizing plate 11 in and out, a mechanical iris shown in FIG. 17 may be used.

When a rectangular wave was input as a driving waveform into the GH cell 12 and the change in light transmittance when the operating voltage was applied was measured (FIG. 16), as shown in FIG. As a result, the average light transmittance (in air) of visible light was reduced from the maximum light transmittance of about 75% to several percent. Depending on the liquid crystal cell structure and constituent materials used, the GH cell 12
Reached almost the minimum light transmittance when a pulse voltage of ± 5 V (1 kHz) or more was applied.

However, when the state is changed from the transparent state to the completely light-shielded state or from the completely light-shielded state to the transparent state as in the case of 0V → ± 5V and ± 5 → 0V, the light transmittance responds at a somewhat high speed. However, when trying to slightly change the light transmittance in a halftone, a response time several times as long as the case may be required.

For example, at an environmental temperature of 25 ° C., 0V → ± 5
When the light transmittance responds at 23.4 ms as shown in FIG. 6A to the drive voltage change of V, when the halftone driving is performed at ± 2 → ± 3 V as shown in FIG. , Response time 8
It deteriorated to about 7.4 ms.

Further, the response speed is greatly affected by the environmental temperature. Under a low temperature environment, the response time increases because the movement of the liquid crystal molecules decreases.

For example, when the environmental temperature drops to 0 ° C.,
As shown in FIG. 7A, the response time of the light transmittance is slowed down to 90 ms with respect to the drive voltage change from 0 V to ± 5 V. As shown in b), the response time further deteriorated to about 305 ms.
When an image pickup device is to be realized by using a liquid crystal cell as a light control element, such a decrease in response speed impairs automatic exposure adjustment.

Further, for example, when the environmental temperature reaches 10 ° C., even if the driving voltage changes from 0 V to ± 5 V, as shown in FIG.
As shown in FIG. 8A, the response time of the light transmittance is slowed down to 44.5 ms. However, when halftone driving is performed at ± 2 → ± 3 V, the response time is further increased to 158.5 ms as shown in FIG. Degraded to a degree.

Further, for example, at an environmental temperature of 40 ° C., 0
As shown in FIG. 9 (a), when the light transmittance responds to the drive voltage change of V → ± 5V at 13.8 ms, ± 2V
→ When driving at halftone at ± 3V, as shown in FIG.
The response time deteriorated to about 52.9 ms.

In order to solve these problems, the present inventor has made intensive efforts. Even when driving in a halftone, first, a driving waveform corresponding to a completely light-shielded state (minimum light transmittance) is set to a target transmittance. It has been found that the response time can be significantly shortened by inserting a suitable number of pulses according to the environmental temperature before the driving waveform giving.

That is, the inventors of the present invention have made intensive studies, and found that the liquid crystal element is not used as a light control device of an image pickup device, and the liquid crystal element is determined based on the value of the light transmittance in a transparent state and / or in a light-shielded state. The element environment temperature of the dimmer equipped with the cell is grasped, and even when driving in the halftone, the control drive pulse waveform corresponding to the completely light-shielded state (minimum transmittance) is first given the target transmittance. It has been found that the transient response time can be greatly reduced by inserting an appropriate pulse voltage and pulse number in accordance with the previously determined element environment temperature before the drive waveform.

For example, as shown in FIG.
When driving from ± 2V to ± 3V under the ambient temperature of ± 5V, first insert a ± 5V rectangular wave corresponding to a completely light-shielded state (minimum light transmittance) for 12ms before the ± 3V driving waveform. As a result, the response time of the light transmittance was greatly reduced from 87.4 ms to 11.0 ms.

For example, as shown in FIG.
When driving from ± 2 V to ± 3 V under an environment temperature of 0 ° C., ± first corresponds to a completely light-shielded state (minimum light transmittance).
When a 5 V rectangular wave was inserted for 41 ms before the driving waveform of ± 3 V, the response time of the light transmittance was 305 ms.
From 41.0 ms to 41.0 ms.

For example, as shown in FIG.
When driving from ± 2 V to ± 3 V under an environment temperature of 10 ° C., ± first corresponds to a completely light-shielded state (minimum light transmittance).
When a 5 V rectangular wave was inserted for 21 ms before the driving waveform of ± 3 V, the response time of the light transmittance was 158.5.
from 1 ms to 19.0 ms.

For example, as shown in FIG.
When driving from ± 2 V to ± 3 V at an environment temperature of 40 ° C., ± first corresponds to a completely light-shielded state (minimum light transmittance).
When a 5 V rectangular wave was inserted for 7 ms before the driving waveform of ± 3 V, the response time of the light transmittance was 52.9 ms.
From 6.8 ms to 6.8 ms.

Similarly, as shown in FIG.
When driving from ± 3V to ± 2V under the environment temperature of ° C,
First, when a rectangular wave of 0 V corresponding to a completely transparent state (maximum light transmittance) is inserted by 18 ms before a driving waveform of ± 2 V, the response time of the light transmittance is 51.4 ms to 18.8 ms. , Could be greatly reduced.

For example, as shown in FIG. 11C, when driving from ± 3 V to ± 2 V at an environmental temperature of 0 ° C., it corresponds to a completely transparent state (maximum light transmittance) first. When a rectangular wave of 0 V was inserted for 88 ms before the driving waveform of ± 2 V, the response time of the light transmittance was 190 ms.
To 67.0 ms.

For example, as shown in FIG. 12C, when driving from ± 3 V to ± 2 V at an environment temperature of 10 ° C., it corresponds to a completely transparent state (maximum light transmittance) first. When a 0 V rectangular wave was inserted by 55 ms before the ± 2 V drive waveform, the response time of the light transmittance was 98.5.
ms to 41.5 ms.

For example, as shown in FIG. 13 (c), when driving from ± 3V to ± 2V under an environment temperature of 40 ° C., the first state corresponds to a completely transparent state (maximum light transmittance). When a rectangular wave of 0 V was inserted for 11 ms before the driving waveform of ± 2 V, the response time of the light transmittance was 40.4.
ms to 13.1 ms.

In the present embodiment, the time width and the voltage of the waveform to be inserted in the middle can be freely selected to some extent so as to be easily controlled. However, the response of the light transmittance is insufficient if the pulse application time is too short as shown in FIG. 14A, and the target value is too small as shown in FIG. 14C because the pulse application time is too long. Settings that cause overshoot are not preferred. Therefore, it is preferable to set an appropriate pulse as shown in FIG.

That is, there is an optimum value for the time width of the control pulse inserted intermediately according to the element environment temperature according to each element environment temperature, and the transient response of the light transmittance overshoots the target value. Is not preferable.

Next, FIG. 2 shows the relationship between the light transmittance and the applied driving voltage measured at different environmental temperatures.

According to this graph, the environmental temperature (for example,
-5 ° C, 22 ° C, 65 ° C, etc.), the behavior of the liquid crystal molecules changes, and the higher the ambient temperature, the stronger the effect of the fluctuations of the liquid crystal molecules in the steady state becomes. Decreases (light transmittance decreases), and when a voltage is applied, the degree of light blocking decreases (light transmittance increases).

In particular, as shown in FIG. 3, when a voltage equal to or higher than the threshold voltage is applied, a large difference in light transmittance depending on the environmental temperature appears.

Then, as shown in FIGS. 2 and 3, the relationship between the light transmittance and the ambient temperature, which was measured in advance when the film was transparent and / or when the light was shielded, was grasped and stored in correspondence with the applied voltage. By comparing this stored value with the actual light transmittance detection value with respect to the applied voltage before actual use, the actual environmental temperature of the mounted liquid crystal optical element can be accurately recognized.

FIG. 1 shows the results of a study on the improvement of the response speed under various environmental temperatures when driving in the halftone of (A) ± 2V → ± 3V and (B) ± 3V → ± 2V. ,
The average optimal time width of the above-mentioned intermediate insertion waveform is shown.

Therefore, the optimum time width of the intermediate insertion waveform according to the environmental temperature before actual use recognized by comparison with the data of FIGS. 2 and 3 can be obtained by FIG. That is, by inserting the control drive pulse intermediately with this optimum time width, as shown in FIGS. 4 and 5, the transient response at the time of halftone drive is optimally adjusted to the environmental temperature where the liquid crystal optical element is used. It can be seen that the speed can be greatly improved.

FIGS. 4 and 5 further show that the response speed of halftone driving can be greatly improved under any environmental temperature.

Embodiment 2 In this embodiment, the driving method of the liquid crystal cell is changed from pulse voltage modulation (PHM) described in Embodiment 1 to pulse width modulation (PWM).

For example, if the basic pulse generation cycle is 100
By controlling the pulse width in this basic period as μs, as shown in FIG. 15, the average light transmittance of visible light (in air ) Decreased from a maximum light transmittance of about 75% to several percent.

Then, the pulse peak value is fixed at 5 V, the pulse width is controlled, and 0 μs → 100 μs, 100 μs →
When changing from a transparent state to a completely light-shielded state or from a completely light-shielded state to a transparent state as in 0 μs, the light transmittance responds to a certain high-speed, but slightly changes the light transmittance in a halftone. In this case, several times as much response time was required.

For example, in response to a change in the driving pulse width from 0 μs to 100 μs, when the light transmittance responds at about 20 ms, when the halftone driving is performed from 20 μs to 40 μs, the response time deteriorates to about 90 ms.

Furthermore, the response speed is greatly affected by the environmental temperature, and in a low-temperature environment, the response time increases because the movement of the liquid crystal molecules decreases.

For example, when the environmental temperature is lowered to 10 ° C., the response time of the light transmittance is reduced to about 45 ms even when the driving pulse width changes from 0 μs to 100 μs.
When halftone driving was performed from 20 μs to 40 μs, the response time further deteriorated to about 160 ms. When an image pickup apparatus is to be realized by using a liquid crystal cell as a light control element, such a decrease in response speed hinders automatic exposure adjustment and the like.

To solve this, pulse width modulation (P
Also in the case of halftone driving in WM), according to the present invention, the drive waveform corresponding to the completely light-shielded state (minimum light transmittance) is first determined based on the environment determined in advance before the drive waveform providing the target transmittance. It has been found that the response time can be significantly reduced by inserting several pulses having an appropriate pulse width according to the temperature.

That is, the inventor of the present invention has made intensive studies, and found that even in the case of halftone driving by pulse width modulation (PWM), before driving the liquid crystal element as a dimming device, the first and second embodiments were used. Similarly, by detecting the light transmittance before actual use, the ambient temperature of the light control device in which the liquid crystal cell is mounted is determined, and when the light control device is driven in a halftone, first, the light control device is completely shaded (minimum light transmittance). It has been found that the transient response time can be significantly reduced if the corresponding control drive waveform is inserted with an appropriate pulse width in accordance with the previously determined element environment temperature before the drive waveform that provides the target transmittance.

For example, 20 μs at an environmental temperature of 25 ° C. →
When driving with a pulse width change of 40 μs, first, a rectangular wave having a pulse width of 100 μs corresponding to a completely light-shielded state (minimum light transmittance) is inserted by 12 ms before a drive waveform having a pulse width of 40 μs. The response time of the light transmittance could be greatly reduced from about 90 ms to about 10 ms.

Similarly, at an ambient temperature of 25 ° C., 40 μs →
In the case of driving with a pulse width change of 20 μs, first, a driving waveform of 0 μs corresponding to a completely transparent state (maximum light transmittance) is inserted by 18 ms before a driving waveform of a pulse width of 20 μs. Response time of transmittance is about 55m
s to about 18 ms.

Also, for example, at an environmental temperature of 10 ° C.,
When driving with a pulse width change of 0 μs → 40 μs,
First, 100 corresponding to a completely light-shielded state (minimum light transmittance)
When a rectangular wave having a pulse width of μs was inserted by 21 ms before a drive waveform having a pulse width of 40 μs, the response time of the light transmittance was able to be significantly reduced from about 160 ms to about 20 ms.

Similarly, 40 μs at an environment temperature of 10 ° C.
→ When driving with a pulse width change of 20 μs, a drive waveform of 0 μs corresponding to a completely transparent state (maximum light transmittance) is first inserted by 55 ms before a drive waveform of a pulse width of 20 μs. The response time of light transmittance is about 10
The time could be reduced from 0 ms to about 40 ms.

In this embodiment as well, the time width and voltage of the intermediately inserted waveform can be freely selected to some extent so as to be easily controlled. However, as described above, setting such that the response of the light transmittance overshoots the target value is not preferable.

Further, in this embodiment, since the driving is performed by using the pulse width modulation, the threshold voltage is lower than that of the pulse voltage modulation of the first embodiment, and the characteristics are shifted to the lower voltage side as a whole. Therefore, low voltage control is possible and power consumption can be reduced. Further, since the change in light transmittance is relatively gradual, the transmittance can be easily controlled by the voltage, and the gradation is improved.

Embodiment 3 FIG. 21 shows that the dimming device 23 according to the above embodiment is a CCD (Ch
5 shows an example in which the camera is incorporated into an arge coupled device 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 and the rear lens group 16 are arranged along the optical axis indicated by a dashed line. Corresponding third-group lens 53 and fourth-group lens (for focusing) 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, The CCD image sensor 55c is housed.

Between the second lens group 52 and the third lens group 53, the G lens according to the present invention described above is disposed near the third lens group 53.
A light control device 23 composed of the H cell 12 and the polarizing plate 11 is mounted on the same optical path for light amount adjustment (light amount stop). The fourth lens group 54 for focusing is disposed so as to be movable between the third lens group 53 and the CCD package 55 along the optical path by a linear motor 57, and the second lens group 52 for zooming is disposed in the optical path. Along the first lens group 51 and the light control device 23, it is movably disposed.

FIG. 22 shows an algorithm of a light transmittance control sequence by the light control device 23 in this camera system.

According to this embodiment, the second group lenses 52 and 3
Since the dimming 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 reduced in size, and the size of the optical path can be substantially reduced. Can be downsized. Therefore, CC
It is possible to reduce the size of the D camera. Also,
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.

FIG. 23 is a block diagram of a driving circuit of the above-mentioned CCD camera. According to this, the drive circuit unit 60 of the CCD image sensor 55c arranged on the light emission side of the light control device 23
The output signal of the CCD image sensor 55c is processed by the Y / C signal processing unit 61, and GH is output as luminance information (Y signal).
The signal is fed back to the cell drive control circuit 62. Further, according to the present invention, the light transmittance before actual use is detected by the CCD image sensor 55c,
To calculate the light transmittance-temperature correlation previously stored as described above and the above-described detected value, thereby accurately recognizing the environmental temperature before actual use, A control signal is supplied from control circuit section 62 to pulse generation circuit 63 so as to generate an intermediate insertion pulse corresponding to this. That is, by the control signal, as described above, in synchronization with the basic clock of the CCD drive circuit unit 60,
A drive pulse whose pulse voltage or pulse width is controlled is obtained from the pulse generation circuit section 63. Note that the control circuit unit 62, the pulse generation circuit unit 63, and the temperature determination circuit 65 constitute a GH liquid crystal drive control unit 64 for controlling a pulse voltage or a pulse width.

In a system different from this camera system, for example, the light emitted from the dimmer 23 is received by a photodetector (or photomultiplier), and the luminance information of the emitted light is fed back to the control circuit 62 from here. , GH
In synchronization with a clock of a cell drive circuit unit (not shown), a drive pulse whose pulse voltage or pulse width is controlled can be obtained from the pulse generation circuit unit.

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, it goes without saying that the sample structure, the materials used, the driving method of the liquid crystal cell, the form of the light control device, and the like can be appropriately selected without departing from the gist 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, and the configuration of the control circuit can be variously changed. The driving waveform is a square wave,
It can be driven by trapezoidal wave, triangular wave, 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.

Further, the light control device and the image pickup device according to 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 to the electrodes, the collective 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. 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.

Further, 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 first. 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, the invention 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.

The light control device according to the present invention can be used in combination with another known filter material (for example, an organic electrochromic material, liquid crystal, electroluminescent material, etc.).

Further, the light control device according to the present invention can be used not only for the optical stop of an image pickup device such as a CCD camera as described above but also for adjusting the light amount of various optical systems, for example, an electrophotographic copying machine or an optical communication device. Is also widely applicable. Further, the light control device according to 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.

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.

The above-mentioned temperature determining means may be other than the temperature determining circuit 65 using a comparison amplifier. or,
In the temperature determination circuit 65, the type, the number, the installation position,
The size and the like may be freely changed as long as a predetermined effect is obtained.

In the pulse signal generated from the pulse generation circuit 63, if a predetermined purpose is achieved when the signal is generated in response to the signal from the control circuit unit 62, the values of the pulse voltage, the pulse width, and the like are changed. You can change it freely.

The control information of the drive pulse output from the GH cell drive control circuit 62 through the temperature determination circuit 65 may be used for controlling the CCD image sensor 55c. Thereby, it is considered that the driving of the CCD image sensor 55c is stabilized.

In the above-described embodiment, the CCD image pickup device 55c may be replaced with another device if a predetermined effect is obtained. For example, it may be replaced with a normal photosensitive material and adapted to this image exposure. Further, it may be replaced with a photoelectric conversion element.

The mechanism of the above embodiment can be applied to optical devices such as a camera and a telescope. For example, when using a telescope, it is not preferable that a change in light amount occurs due to a change in outside air temperature. However, according to the mechanism of the above embodiment, since the light transmittance can be controlled quickly and reliably, the light amount can be kept constant and stabilized.

[0137]

According to the present invention, the light transmittance of the liquid crystal element before actual use is detected, and the environmental temperature is determined from the detected value. The temperature can be determined simply by detecting the light transmittance using the circuit system as it is, and the temperature can be detected quickly and accurately.
In addition, the temperature detection unit can be omitted, and the temperature can be detected in a circuit manner, so that the structure of the light control device can be made relatively simple and the size can be reduced.

As a result, for example, when slightly changing the light transmittance of the liquid crystal element from the current light transmittance to the target light transmittance in halftone, before giving a drive pulse corresponding to the target light transmittance, A control drive pulse corresponding to complete light shielding (minimum light transmittance) or complete transparency (maximum light transmittance) is appropriately inserted in advance at a value controlled according to the determined use environment temperature. As compared to the case where the driving pulse corresponding to the target light transmittance is simply given in a step-like manner, the change in the orientation of the liquid crystal or the relaxation thereof rises more smoothly, and until the target light transmittance is reached. Response time can be greatly reduced.

As a result, it is possible to solve the problem which can be said to be a fate when using a physical element such as a liquid crystal cell, and to operate the liquid crystal element responsively at a speed required as a dimmer even in a low temperature environment.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an appropriate insertion time of an intermediate pulse for improving a response speed of a halftone and an ambient temperature according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between an applied voltage, a light transmittance, and an ambient temperature for improving halftone response.

FIG. 3 is a graph showing a relationship between light transmittance and environmental temperature for improving halftone response.

FIG. 4 is a graph summarizing the effect of improving the response speed of halftone driving at each environmental temperature.

FIG. 5 is a graph summarizing the effect of improving the response speed of halftone driving at each environmental temperature.

FIG. 6 is a graph showing an example of an improvement result of a halftone response speed according to the embodiment of the present invention.

FIG. 7 is a graph showing another example of the result of improving the response speed of the halftone.

FIG. 8 is a graph showing another example of the improvement result of the response speed of the halftone.

FIG. 9 is a graph showing another example of the improvement result of the response speed of the halftone.

FIG. 10 is a graph showing an example of an improvement result of a response speed of a halftone.

FIG. 11 is a graph showing an example of an improvement result of the response speed of the halftone.

FIG. 12 is a graph showing another example of the result of improving the response speed of the halftone.

FIG. 13 is a graph showing another example of the improvement result of the response speed of the halftone.

FIG. 14 is a graph showing an example of drive pulse control for improving the response speed of halftones.

FIG. 15 is a graph and a drive pulse waveform diagram showing a relationship between a light transmittance and a pulse width of a drive pulse of a light control device according to another embodiment of the present invention.

FIG. 16 is a schematic diagram showing the operation principle of an example of the light control device according to the present invention.

FIG. 17 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.

FIG. 18 is a schematic side view of the light control device using the liquid crystal optical element.

FIG. 19 is a front view of a mechanical iris of the light control device.

FIG. 20 is a schematic partial enlarged view showing the operation of a mechanical iris near the effective optical path of the light control device.

FIG. 21 is a schematic cross-sectional view of a camera system incorporating the light control device.

FIG. 22 shows an algorithm of light transmittance control in the camera system.

FIG. 23 is a block diagram of a camera system including a drive circuit.

FIG. 24 is a schematic view showing the operation principle of a conventional light control device.

FIG. 25 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 liquid crystal molecules, 15: front lens group, 16: rear lens group, 17: imaging surface, 18, 19 ... iris blade, 20 ...
Effective optical path (cell middle or central part), 21... Operating direction,
Reference numeral 22: opening, 23: dimmer, 24: peripheral part of cell, 3
1A, 31B: glass substrate, 32A, 32B: transparent (operating) electrode, 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, 55
c: 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 section, 64: pulse voltage or pulse width control section (GH liquid crystal drive control device), 65: temperature determination circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 FA12 GA13 MA02 MA09 2H093 NC54 NC59 NC63 ND03

Claims (14)

[Claims] 1. A liquid crystal device having a liquid crystal element, in a state before actual use, detecting a light transmittance of the liquid crystal element in a transparent state and / or a light-shielded state, and judging an environmental temperature of the liquid crystal element from the detected value. A dimmer in which the liquid crystal element is driven and controlled by a control unit including a temperature determination unit. 2. An image pickup apparatus wherein a light control device comprising a liquid crystal element is disposed in an optical path of an image pickup system, wherein the light control device comprises: a liquid crystal element; A control unit that detects a light transmittance at the time of transparency and / or light shielding and determines a temperature of the liquid crystal element from the detected value. 3. When the transmittance of light emitted from the liquid crystal element is changed from the current light transmittance to the target light transmittance, a minimum light transmittance is provided at least before a drive pulse corresponding to the target light transmittance is given. A control drive pulse corresponding to a rate or a maximum light transmittance, a pulse control unit is inserted in advance in accordance with the environmental temperature determined by the temperature determination unit,
An apparatus according to claim 1. 4. The control drive pulse according to claim 1, wherein the control pulse has at least a controlled pulse number and a pulse voltage.
Or the apparatus described in 2. 5. The pulse voltage of the control drive pulse is:
5. The apparatus according to claim 4, wherein the pulse voltage is equal to or a value between the pulse voltage that causes the minimum light transmittance or the maximum light transmittance or the pulse voltage that causes the target light transmittance. 6. The apparatus according to claim 1, wherein the control drive pulse has at least a controlled number of pulses and a controlled pulse width. 7. The pulse width of the control drive pulse is equal to the pulse width that produces the minimum light transmittance or the maximum light transmittance, or is between this pulse width and the pulse width that produces the target light transmittance. 7. The device according to claim 6, which is a value. 8. The device according to claim 1, wherein the liquid crystal element is a guest-host type liquid crystal element using a negative liquid crystal as a host material and a dichroic dye as a guest material. 9. A method of driving a light control device including a liquid crystal element, wherein when changing the transmittance of light emitted from the liquid crystal element from a current light transmittance to a target light transmittance, at least the target light Before giving the drive pulse corresponding to the transmittance, a control drive pulse corresponding to the minimum light transmittance or the maximum light transmittance is previously inserted according to the environmental temperature determined from the light transmittance of the liquid crystal element before actual use. A method for driving a light control device. 10. The method according to claim 9, wherein the control drive pulse is controlled by at least a pulse voltage and a pulse number. 11. The pulse voltage of the control drive pulse is equal to the pulse voltage that produces the minimum light transmittance or the maximum light transmittance, or is between this pulse voltage and the pulse voltage that produces the target light transmittance. The method of driving a light control device according to claim 9, wherein the value is a value. 12. The method according to claim 9, wherein the control drive pulse is controlled by at least a pulse width and a pulse number. 13. The pulse width of the control drive pulse is:
The driving of the light control device according to claim 12, wherein the pulse width that generates the minimum light transmittance or the maximum light transmittance is equal to or a value between this pulse width and the pulse width that generates the target light transmittance. Method. 14. A guest device comprising a negative liquid crystal as a host material and a dichroic dye as a guest material as the liquid crystal element.
The method for driving a light control device according to claim 9, wherein a host-type liquid crystal element is used.