JPH06317765A - Liquid crystal optical device - Google Patents

Abstract

PURPOSE:To effectively remove moire fringes and color false signals from the image output by constituting the liquid crystal optical device of a liquid crystal optical filter injected with a liquid crystal between base bodies and an image pickup element integrated with the liquid crystal optical filter on its front surface side. CONSTITUTION:One sheet of the liquid crystal optical low-pass filter 21 is inserted in place of one sheet of the rock crystal filter which is heretofore arranged on the front surface of the CCD image pickup element 10. The order of the liquid crystal filter 21 and an IR cut filter 12 may be reverse in such a case. The liquid crystal filter 21 is formed by injecting the liquid crystal 22 between two sheets of transparent glass substrates 2 and 2 provided with liquid drystal oriented films on the opposite surfaces and integrating the filter to the front surface side (more specifically, its package 40) of the CCD 10. A transparent glass plate 41 is mounted on the front surface of the package 40. Then, two-point blurs of the high-frequency component of incident light are obtd. by the double refractive index anisotropy of one sheet of the liquid crystal filter 21, by which the performance of the low-pass filter is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal optical device (for example, a CCD image pickup device incorporating an optical low pass filter).

[0002]

2. Description of the Related Art Conventionally, a CCD (charge coupled device) or the like has been used as an image pickup device such as a video camera. But,
Since the light receiving pixel portion of the CCD is discrete, a moire fringe pattern or a color false signal is generated in the image output of the formed image.

In order to prevent this, as shown in FIG. 31, a CC in a light receiving portion of a video camera as an image pickup device is used.
A low-pass filter such as a crystal filter 11 is used on the front surface of the D image pickup device 10 alone or in a laminated manner. Further, a filter 12 for cutting infrared light may be laminated. In the figure, 13 is a diaphragm and 14 is a condenser lens.

As shown in FIG. 32, this low-pass filter is a quartz plate in which, in the case of a single crystal plate, incident light is made into a two-point blur by utilizing its birefringence, and further rotated around the optical axis. By stacking the plates, the two-point image is converted into a four-point image, and in order to further improve the image quality, as shown in FIG.

That is, by blurring the incident light in this way, it is possible to remove a component of image information having a high spatial frequency, and avoid problems such as moire fringes and color false signals. However, in the case of FIG. 32, the high frequency component can be cut or dispersed only in the y direction, but in FIG. 33, the high frequency component can be cut or dispersed in both the x and y directions, and an image of the high frequency component can be obtained while maintaining the sensitivity of the low frequency component. Can be further eliminated.

However, in the quartz plate used for the low-pass filter, the thickness of the plate has to be made considerably large in order to obtain a phase difference, so that reduction of weight and volume ratio, and further reduction of cost are desired. It was

On the other hand, an optical low pass filter using a liquid crystal is known in Japanese Patent Laid-Open Nos. 59-228622 and 61-258570. However, in these, it is not clear about a concrete structure when the liquid crystal low-pass filter is mounted, and a practical structure is not shown.

[0008]

An object of the present invention is to realize a specific mounting structure of a filter using liquid crystal, and
An object of the present invention is to provide a device capable of reducing the volume ratio, the cost, and the like.

[0009]

That is, according to the present invention, a liquid crystal optical filter in which liquid crystal is injected between a first base and a second base facing each other, and this liquid crystal optical filter are integrated on the front side. The present invention relates to a liquid crystal optical device including an image sensor.

According to the present invention, the above-mentioned liquid crystal optical filter is integrated on the front side of the image pickup device (CCD or the like), so that the mounting structure is practical, and the feature of the liquid crystal optical filter is the image pickup device. Can be effectively and realistically exhibited, and moire fringes and color false signals can be effectively removed from the image output.

In this case, it is desirable that the above liquid crystal optical filter is integrated with the package of the image pickup device.

In the liquid crystal optical device of the present invention, the liquid crystal used has a liquid crystal orientation having a spiral axis in a direction along the normal line of the substrate, or an optically uniaxial liquid crystal. It is desirable to have an orientation.

Further, it is preferable that a filter for cutting infrared light and / or ultraviolet light is further provided, or a filter for cutting visible light is further provided. Alternatively, any filter that cuts incident light in the wavelength range of infrared light, ultraviolet light, or visible light may not be provided.

A plurality of the above-mentioned liquid crystal optical filters may be laminated, or a crystal filter may be further provided.

Further, the substrate itself may be an infrared and / or ultraviolet light cut filter and / or a crystal filter.

Further, it is desirable that a liquid crystal alignment film is formed on the surface of the substrate on the liquid crystal injection side, and when the substrates are sandwiched between liquid crystals, the liquid crystal alignment film is preferably formed on both surfaces of the substrate. .

In a conventional low-pass filter using a quartz plate, its birefringence anisotropy Δn = n _e −n _o = 0.00.
Since it is 91, a thickness of about 1 mm is required for each sheet in order to remove moire fringes and color false signals of the CCD image pickup device. Further, in order to improve the image quality, it is necessary to stack three sheets, which further increases the thickness and increases the cost. Therefore, in the present invention, a liquid crystal (Δ
By using n = n _e −n _o ≈0.10 to 0.25), the weight, volume ratio and cost can be reduced.

[0018]

Embodiments of the present invention will now be described with reference to the drawings.

Liquid crystal optical low-pass filters usable in this embodiment are nematic liquid crystals, chiral nematic liquid crystals,
There are those using smectic A liquid crystal, smectic C liquid crystal, chiral smectic C liquid crystal, and the like. These can be roughly divided into two types, one having a uniaxial orientation and the other having a spiral axis in the direction normal to the substrate. First, the mounting structure of both of them will be described with reference to FIGS.

[1] Uniaxially oriented liquid crystal low-pass filter As the uniaxial optical low-pass filter, there are, for example, a nematic liquid crystal type and a smectic liquid crystal type which will be described later. These can be used in the same way as a low-pass filter using a normal crystal filter, and are of a type in which an extraordinary optical axis is changed and laminated.

In the case of two-point blurring As shown in FIG. 1, one liquid crystal optical low-pass filter 21 according to the present example is inserted in place of one crystal filter which is conventionally arranged in front of the CCD image pickup device 10. Here, the order of the liquid crystal filter 21 and the infrared cut filter 12 may be reversed. The liquid crystal filter 21 is formed by injecting a liquid crystal 22 between two transparent glass substrates 2-2 having liquid crystal alignment films (not shown) on opposite surfaces, and the liquid crystal 22 is provided on the front side of the CCD 10 (specifically, its package). 40) is integrated. The package
A transparent glass plate 41 is attached to the front surface of 40.

According to the liquid crystal optical image pickup device constructed as described above, due to the birefringence anisotropy of one liquid crystal filter 21,
Similar to the case shown in FIG. 32, two-point blurring of the high frequency component of the incident light is obtained, and the low pass filter performance is good.

Further, as shown in FIG. 2, a liquid crystal filter
It is also possible to omit the glass substrate 2 on the front side of 21 and integrate it with the infrared cut filter 12 (that is, the infrared cut filter 12 also serves as a substrate). In this case, an alignment film (not shown) is attached to the rear surface of the infrared cut filter 12.

In FIG. 3, the package of the CCD image pickup device 10 is shown.
The glass 41 on the front surface of 40 is omitted and integrated with the package 40 of the CCD image pickup device. Although the order is changed in FIG. 4, the optical characteristics are not changed.

In case of four-point blurring FIG. 5 shows an example in which one crystal filter 11 and a liquid crystal filter 21 are combined. Here, the infrared cut filter 12
And an alignment film is attached to the liquid crystal side surface of the crystal filter 11. As a result, by changing the directions of the abnormal optical axes of the liquid crystal filter 21 and the crystal filter 11, four-point blurring occurs. In this example, the crystal filter 11 also serves as a liquid crystal substrate.

FIG. 6 shows an example in which the glass plate 41 is omitted and the CCD package 40 is integrated. FIG. 7 shows an example in which the order of arrangement of the filters is changed, and in this case also, the optical characteristics are not affected.

FIG. 8 shows an example in which the crystal filter is replaced by the liquid crystal filter 21. Also in this case, the order of the glass substrate and the infrared cut filter does not matter.

In the case of 7-point blurring FIG. 9 shows an arrangement for obtaining 7-point blurring only by using the liquid crystal filter 21, which is directly integrated with the CCD package 40 here. Here again, the order of the glass 2 and the infrared cut filter 12 does not matter.

In this liquid crystal optical image pickup device, the use of three liquid crystal filters 21 makes it possible to obtain the same seven-point blur as shown in FIG.

FIG. 10 shows a case where one crystal filter 11 is left. Further, FIG. 11 shows a case where two crystal filters are left. Further, FIG. 12 shows a case where the glass substrate 2 is entirely removed.

The CCD image pickup device for image pickup in the visible light range, which incorporates the liquid crystal optical low-pass filter using the uniaxial liquid crystal (for example, nematic liquid crystal), has been described above. It can be configured as shown.

That is, the liquid crystal optical image pickup device 70 shown in FIGS. 13 and 14 is a video camera manufactured by Sony: Handycam Sony.
Although the basic structure is the same as TR-900 or TR-1, in FIG. 14, the crystal filter 11 is provided on the front side of the CCD package 40.
-Liquid crystal filter 21-Infrared light cut filter 12-Low-pass filter section consisting of crystal filter 11 (This is the package
It is housed in 42. ) Are integrated.

Here, since the sensitivity range of a semiconductor image pickup device such as a CCD image pickup device is widened to 380 to 1200 nm, when a normal visible light image is taken, it is essentially
Since the near-infrared light region that cannot be sensed by the human eye is imaged, it adversely affects the image. Therefore, it is necessary to insert an infrared cut filter between the subject and the CCD.
In this example, a liquid crystal low-pass filter is combined with an infrared cut filter 12 (cuts wavelengths of 700 nm or more).

As a result of performing a field test with the apparatus of FIG. 13 or FIG. 14, the characteristics of the optical low-pass filter were recognized to some extent, and moire fringes and color false signals could be reduced.

FIG. 15 shows an example of the liquid crystal optical low-pass filter 21 used above.

The optical low-pass filter 21 was manufactured according to the flowchart of FIG. Optical glass (BK7: OHARA CORPORATION) was used as the glass substrate 2, and an alignment film (polyimide type) 4 was formed on one surface of the glass. As the polyimide-based alignment film, for example, U-Varnish A manufactured by Ube Industries, Ltd. or Sunever manufactured by Nissan Chemical Co., Ltd.
The system was used. Further, as the inorganic alignment film, an oblique vapor deposition film of SiO was used.

In forming a polyimide-based alignment film, a polyamic acid diluted in a solvent is applied to a substrate material by a spin casting method and heat-treated at 180 to 240 ° C. for 1 hour to form an imidized thin film (10 to 150 nm) was formed. Further, when performing orientation by rubbing, with respect to the polyimide thin film on the glass substrate formed as described above, while pressing and rotating a roller wrapped with a velvet cloth, by translational movement, the orientation of the polyimide molecules Promoted.

As a method of forming an oblique vapor deposition film of SiO, a substrate is placed vertically above the SiO vapor deposition source in an SiO vacuum vapor deposition apparatus, and the angle formed by the vertical line and the substrate normal is set to 85 degrees. did. After vacuum-depositing SiO at a substrate temperature of 170 ° C, 3
It was baked at 00 ° C. for 1 hour.

A pair of substrates with an alignment film thus produced was assembled so that the alignment treatment directions were anti-parallel on opposite surfaces, and a polyethylene terephthalate film (diamond) having a thickness corresponding to the target gap was used as the spacer. Foil: 50-250 μm) was used. To improve the flatness of polyethylene terephthalate film (PET), it is cut into specified dimensions, sandwiched between glass plates with a thickness of 3 mm, and a constant load of about 100 grams is applied on it, and the temperature is 1 ° C at 100 ° C.
Heat treatment was performed for an hour.

After that, a spacer is sandwiched between two glass substrates to make a gap, and then a liquid crystal injection hole is secured around the cell, and a UV curing type adhesive (UV-1000: manufactured by Sony Chemical Co.). I glued it in. Then, nematic liquid crystal 22 was injected at room temperature or isotropic phase temperature. After removing the liquid crystal on the glass substrate around the injection hole, it was sealed with an epoxy adhesive to fabricate an optical low-pass filter.

Here, ZLI-2008-000 manufactured by Merck was used as the non-chiral nematic liquid crystal material. Z
LI-2008-000 has a melting point of -6 ° C and a nematic phase temperature range of -20 to 64 ° C. Birefringence anisotropy is Δn = n _e
Is a -n _o = 1.707 -1.517 = 0.19. In order to provide the characteristics of an optical low-pass filter using this liquid crystal, it is necessary to achieve a specific tilt of the liquid crystal director (pretilt angle α).

When the smectic liquid crystal is used, the structure illustrated in FIG. 17 can be adopted (23 in the drawing is a spacer around the filter and 24 is an adhesive), which can be produced by the method shown in FIG. Is.

As the organic alignment film, for example, a commercially available polyimide film (Ube Kosan U-Varnish A, Nissan Chemical Co., Ltd., Sun Ever 150, 610, 721) was used. As the inorganic alignment film, a SiO vapor-deposited film was used.

After the transparent glass substrate (BK-7) was washed, a polyamic acid diluted with a solvent was applied to the substrate material by a spin casting method, and the temperature was 80 ° C for 15 minutes.
It is imidized by heat treatment for a period of time to form a thin film (10-15
0 nm) was formed. A roller around which a velvet cloth was wrapped was pressed against the polyimide thin film thus formed on the glass substrate, and while the roller was rotated, the roller was translated to promote the orientation of polyimide molecules.

As a method of forming an oblique vapor deposition film of SiO,
After cleaning the transparent glass substrate (BK-7), the substrate was placed vertically above the SiO vapor deposition source in the SiO vacuum vapor deposition apparatus, and the angle formed by the vertical line and the substrate normal was set to 85 degrees. SiO
Was vacuum-deposited at a substrate temperature of 170 ° C. and then baked at 300 ° C. for 1 hour.

The substrate with the alignment film thus produced was assembled so that the alignment films face each other, and a polyethylene terephthalate film (diafoil: 50 to 250 μm) having a thickness corresponding to the target gap was used as the spacer. I was there. In order to improve its flatness, polyethylene terephthalate film (PET) is cut into a specified size, sandwiched between glass plates with a thickness of 3 mm, and a constant load of about 100 grams is applied on it, and the temperature is kept at 100 ° C for 1 hour. Heat treatment was performed.

After that, a spacer is sandwiched between the two glass substrates to make a gap, and then a liquid crystal injection hole is secured around the cell, and a UV curable adhesive (UV-1000: manufactured by Sony Chemical Co.). I glued it in.

At this time, a combination of facing cells having the same rubbing direction or vapor deposition direction is called a parallel cell, and a combination having opposite rubbing directions or vapor deposition directions is called an antiparallel cell.

After the cell was assembled, a smectic liquid crystal was injected under reduced pressure from the cell injection hole at an isotropic phase temperature or a nematic phase temperature. After completing the liquid crystal injection, return the temperature to room temperature and remove the liquid crystal on the glass substrate around the injection hole,
It was sealed with an epoxy adhesive.

[0050]

## STR00001 ## Cyanobiphenyl compounds, which are well known as smectic A liquid crystals, Was used.

The phase transition temperature of 8CB is Cryst 21, SmA 32.5, N 40, Iso and shows a smectic A phase at room temperature of 25 ° C.

As the smectic C liquid crystal, non-chiral smectic C liquid crystal composition (DFE: tricyclic difluoroester liquid crystal 58 wt%, PPm: phenylpyrimidine liquid crystal 22
wt%, PB: phenyl benzoate type blend of 20 wt%) was used. The phase transition temperature of this liquid crystal composition is Cryst −29.2, SmC 77.5, SmA 93, N 105,
Iso, Smectic C over a wide temperature range including room temperature of 25 ℃
Indicates a phase.

[2] Liquid Crystal Low-Pass Filter Having Spiral Axis in Substrate Normal Direction Liquid crystal low-pass filters having a spiral axis in the substrate normal direction include a chiral nematic liquid crystal type and a chiral smectic liquid crystal type described later. First, taking the chiral smectic liquid crystal 32 as an example, in this case, a two-dimensional isotropic blur is given as shown in FIG. A configuration example of this filter 31 is shown below.

FIG. 20 shows an example of using one spiral-type liquid crystal filter 31 which gives isotropic blur. Also, a spiral type liquid crystal filter 31 and a crystal filter that give isotropic blur
FIG. 21 shows an example in which 11 and 11 are combined. Further, FIG. 22 shows a combination with two crystal filters. Further, instead of these crystal filters, a uniaxial liquid crystal filter or a spiral type liquid crystal filter that gives isotropic blur can be combined, and the order thereof is not limited.

These chiral smectic liquid crystal compositions
A liquid crystal optical low-pass filter 31 using 32 can be constructed as shown in FIG. 23 (30 in the figure is a gap).

Such a chiral smectic liquid crystal itself is a material well known as a ferroelectric liquid crystal, but conventionally, it has been mainly applied as an active electro-optical element. It is known that the chiral smectic liquid crystal has a layered structure as shown in FIGS. 23 and 24 and has a twisted structure in which the layers rotate around the optical axis. Moreover, since the interaction between the layers is small, the inclination of the director in the central portion of the liquid crystal layer should be kept substantially constant. further,
Compared with nematic liquid crystal, it has the property of being less affected by clouding due to light scattering due to thermal fluctuations of the liquid crystal director.

Therefore, in order to realize the low-pass filter characteristics in all the directions shown in FIG. 19, it is possible to rotate the direction of the liquid crystal director around the optical axis so that the liquid crystal has a helical structure. It can be realized by optically utilizing the twisted structure of. Further, if a smectic liquid crystal is used, this inclination can be uniformly maintained in the cell, and further, generation of stray light due to light scattering particularly on the short wavelength side of visible light can be suppressed.

To realize such a chiral smectic liquid crystal helical structure, for example, a liquid crystal alignment method using a vertical alignment film is preferably performed. The cell manufacturing process is shown in FIG.

As the vertical alignment treatment agent, for example, a commercially available polyimide alignment film (San Ever 722 manufactured by Nissan Chemical Co., Ltd.) was used. After the transparent glass substrate (BK-7) was washed, polyamic acid diluted in a solvent was applied to the substrate material by spin casting and heat-treated at 80 ° C for 15 minutes and further at 240 ° C for 1 hour to form an imidized film. (10-150 nm) was formed.

In the case of a vertical alignment film, cells were assembled without rubbing after heat treatment. At the time of assembling the cell, the alignment film forming sides should be opposed to each other, and the above-mentioned P
The cell was assembled using ET film. The method for assembling the cell is the same as described above.

After the cell was assembled, a chiral smectic liquid crystal was injected from the cell injection hole under reduced pressure at an isotropic phase (Iso) temperature or a chiral nematic phase (N ^* ) temperature.
After the liquid crystal injection was completed, the temperature was returned to room temperature, the liquid crystal on the glass substrate around the injection hole was removed, and then the product was sealed with an epoxy adhesive.

Then, as shown in FIG. 26, the vertical alignment film 4 is formed.
Smectic A (S
mA), and further, a phase transition to chiral smectic C (SmC ^* ) and vertical alignment were achieved, and an optical low pass filter 31 was produced.

The phase transition temperature of the SmC ^* liquid crystal that can be used,
The tilt angle, pitch length and refractive index anisotropy in SmC ^* are shown below. CS-1017: Iso 68, N ^* 64, SmA 55, SmC ^*
-20, Cr CS-1015: Iso 78, N ^* 68, SmA 57, SmC ^*
-17, Cr CS-1014: Iso 81, N ^* 69, SmA 54, SmC ^*
-21, Cr CS-3000: Iso 80, N ^* 71, SmA 60, SmC ^*
-37, Cr

[0064]

The results for various chiral smectic liquid crystals are shown below. CS-1017, 1014: Vertical alignment agent [NISSAN CHEMICAL SAN EVER 72
2] was used to attempt the orientation of the SmC ^* phase. In the system coated on a glass substrate, both CS-1007 and CS-10014 have a thickness of 50 μm.
With a gap of m and 100 μm, good alignment was achieved by slow cooling in a vacuum oven after liquid crystal injection. However, in the 250 μm gap, the orientation did not occur in that state, and the orientation was successful by slow cooling from the isotropic phase temperature [−0.2 ° C./min.]. The storage stability was improved by the method using such an alignment film.

CS-3000: CS-3000 was injected into the cell in the Iso phase, cooled to room temperature, and then sealed with an adhesive. This cell is cooled on a hot stage from a temperature of Tiso + 5 ℃ to a cooling rate of 0.1.
Slowly cooled at ° C / min. As a result, the 250 μm gap cell showed good orientation. As a result of observing blurring under the microscope in this 250 μm gap cell, as shown in FIG. 19, two-dimensionally large isotropic blur was confirmed under the microscope.

Furthermore, in each of the above SmC ^* type cells, no change in brightness due to rotation under the cross polarizer was observed, and it was confirmed that the director rotated uniformly. Note that this cell can also be mounted on the CCD image pickup device in the same manner as shown in FIGS.

The following two types can be used as the chiral nematic liquid crystal composition.

(A) ZLI-2008-000 manufactured by Merck & Co.
A mixture of the following chiral agent [1] (chiral liquid crystal).

[Chemical formula 2] Chiral agent for pitch adjustment [1]

The relationship between 1 / P (reciprocal of pitch) and the chiral concentration in the SiO oblique vapor-deposition alignment film showed very good linearity. For example, 2 rotations at 100 μm, ie 50 μm
It was found that 3.23 wt% of chiral concentration is necessary for the pitch of.

(B) Rodic non-chiral liquid crystal RDP-
A mixture of 362 and the following chiral agent [2] (S811).

[Chemical Formula 3] Chiral agent for pitch adjustment [2]: S811 (Merc
k)

When the amount of the chiral agent added is 6 wt%, the pitch length is about 1.6 μm. Refractive index anisotropy of the non-chiral liquid crystal Δn: 0.179, n _o: a 1.507.

After injection of the liquid crystal, in any of the above (a) and (b) chiral nematic (N ^* ) type cells, no change in brightness and darkness due to rotation under a cross-polarizer was observed.
It was confirmed that the director rotated φ.

In the observation of the above-mentioned blur, the blur of the bright spot (about 1 μm diameter) on the surface of the frosted glass was observed using a reflection type microscope system (Nikon Opti-Photo Pol) (see FIG. 27).

[3] In the case of imaging only infrared light By utilizing the sensitivity of the near-infrared light region of a semiconductor image sensor such as a CCD image sensor, only the near-infrared light region that cannot be sensed by the human eye is imaged. can do. Accordingly, the temperature distribution of the subject can be imaged. In this case, it is necessary to insert a visible light cut filter between the subject and the CCD.

Therefore, here, as shown in FIG. 28, the liquid crystal low-pass filter 21 or 31 is provided with a visible light cut filter (760 nm).
An example is the combination of (cut below) 51.

[4] In the case of imaging in the visible and infrared light regions: Utilizing the sensitivity in the visible light region and near infrared light region of a semiconductor image pickup device such as a CCD image pickup device, it cannot be sensed by a bright subject and the human eye. It can also be applied as a low-pass filter for a dark-field camera that can take an image even when it is dark. In this case, a combination without visible light and infrared light cut filters is required.

Therefore, as shown in FIG. 29, combining the liquid crystal low-pass filter 21 or 31 and the crystal filter 11 is an example.

[5] When Inserting Wavelength Band Variable Filter In addition to the above, the wavelength band limiting filter may be made variable as necessary.

For example, as shown in FIG. 30, a knurled wavelength band variable filter 61 and a liquid crystal low pass filter 21 or 31 are used.
And crystal filter 11 are combined. In this case, the variable filter 61 includes a plurality of filters 61A and 61A having different cut wavelengths.
It is composed of B and the like, and can be rotated around the rotation axis 60 as necessary, so that a cut filter required for CCD image pickup can be selected.

Although the embodiments of the present invention have been described above, the above-mentioned embodiments can be further modified based on the technical idea of the present invention.

For example, the above-mentioned liquid crystal optical low-pass filter and the combination filter with other filters are CC
The D package can be integrated by an appropriate method including adhesion.

Further, the material and shape of each component (particularly, the liquid crystal and the alignment film) of the above-mentioned optical low-pass filter, the assembling method, and the like may be variously changed. The substrate is not a glass plate,
Any other optically transparent material may be used. Regarding the liquid crystal, a target liquid crystal phase may be already formed at the temperature of use at the time of injection.

Further, the material of the alignment film and the alignment method can be variously changed. The spiral axis of the above-mentioned spiral orientation does not have to be completely aligned with the normal direction of the substrate,
Within the range of ± 10 degrees, the same effect as described above can be obtained.

The above-mentioned optical low-pass filter can be combined with a number other than those mentioned above to cause various birefringences, or can be combined with a quartz plate. Alternatively, an ultraviolet light cut filter may be used or an infrared light cut filter may be used in combination.

The present invention can also be applied to image pickup devices other than the CCD described above.

[0087]

As described above, according to the present invention, a liquid crystal optical filter in which liquid crystal is injected between a first base and a second base facing each other, and an image pickup device in which the liquid crystal optical filter is integrated on the front side. Since the liquid crystal optical device is composed of and, the mounting structure of the liquid crystal optical filter is practical, and the advantages of the liquid crystal optical filter are exerted to the image sensor in an advantageous and realistic manner. The signal can be effectively removed.

Further, since the liquid crystal having a large anisotropy of birefringence is used, it is possible to reduce the weight, volume ratio and cost which are difficult to expect with quartz.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a liquid crystal optical imaging device according to an embodiment of the present invention.

FIG. 2 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 3 is a schematic diagram of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 4 is a schematic diagram of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 5 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 6 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 7 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 8 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 9 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 10 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 11 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 12 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 13 is a cross-sectional view of a mounting example of an optical low-pass filter according to an example of the present invention.

FIG. 14 is a cross-sectional view of another mounting example of the optical low-pass filter.

FIG. 15 is a schematic cross-sectional view of a liquid crystal optical low-pass filter according to an example of the present invention.

FIG. 16 is a manufacturing flowchart of the same optical low-pass filter.

FIG. 17 is a schematic cross-sectional view of a liquid crystal optical low pass filter according to another embodiment of the present invention.

FIG. 18 is a manufacturing flowchart of the same optical low-pass filter.

FIG. 19 is a schematic diagram showing a state of blurring caused by the optical low-pass filter.

FIG. 20 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 21 is a schematic diagram of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 22 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 23 is a schematic cross-sectional view of a liquid crystal optical low-pass filter according to another embodiment of the present invention.

FIG. 24 is an explanatory diagram of physical property parameters of the liquid crystal.

FIG. 25 is a flow chart of manufacturing a liquid crystal optical low-pass filter according to the same example.

FIG. 26 is a liquid crystal alignment process flow diagram when manufacturing the optical low-pass filter.

FIG. 27 is a schematic diagram of an optical system for explaining measurement of a blur amount of incident light.

FIG. 28 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 29 is a schematic view of a liquid crystal optical imaging device according to another embodiment of the present invention.

FIG. 30 is a schematic view of a liquid crystal optical imaging device according to still another embodiment of the present invention.

FIG. 31 is a schematic diagram of a mounted state of a crystal optical low-pass filter according to a conventional example.

FIG. 32 is a principle diagram illustrating blurring caused by one crystal filter of the same.

FIG. 33 is a principle diagram illustrating a blur caused by three crystal filters of the same.

[Explanation of symbols]

 2 ... Glass substrate 4 ... Alignment film 10 ... CCD (charge coupled device) 11 ... Crystal plate (crystal filter) 12 ... Infrared cut filter 13 ... Aperture 14 ... Lens 20, 30 ... Gap 21, 31 ... Liquid crystal optical low-pass filter 22, 32 ... Liquid crystal molecule (liquid crystal layer) 40 ... CCD package 41 ... Glass plate 42 ... Filter package 51 ...・ Visible light cut filter 70 ・ ・ ・ Liquid crystal optical imaging device

Claims (11)

[Claims] 1. A liquid crystal optical device comprising a liquid crystal optical filter in which liquid crystal is injected between a first base and a second base facing each other, and an image pickup device having the liquid crystal optical filter integrated on the front side. 2. The liquid crystal optical device according to claim 1, wherein the liquid crystal optical filter is integrated with a package of the image pickup device. 3. A liquid crystal having a helical axis in a direction along a normal line of the substrate, the liquid crystal having a liquid crystal orientation being injected.
The liquid crystal optical device described in 1. 4. The liquid crystal optical device according to claim 1, wherein a liquid crystal having an optically uniaxial liquid crystal orientation is injected. 5. The liquid crystal optical device according to claim 1, further comprising a filter that cuts infrared light and / or ultraviolet light. 6. The liquid crystal optical device according to claim 1, further comprising a filter that cuts visible light. 7. The liquid crystal optical device according to claim 1, wherein no filter for cutting incident light in the wavelength range of infrared light, ultraviolet light or visible light is provided. 8. The liquid crystal optical device according to claim 1, wherein a plurality of liquid crystal optical filters are laminated. 9. The liquid crystal optical device according to claim 1, further comprising a crystal filter. 10. The substrate is an infrared light and / or ultraviolet light cut filter and / or a quartz filter,
The liquid crystal optical device according to any one of 1. 11. The liquid crystal optical device according to claim 1, wherein a liquid crystal alignment film is formed on the surface of the substrate on the liquid crystal injection side.