JP2003131189A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the white balance of a video camera mounted with an electric dimming element composed of dichroic guest-host (GH) liquid crystal under a use temperature condition of -20 to 80 deg.C. SOLUTION: A photography optical system 1 of this video camera is composed of a 1st lens group L1, a 2nd lens group L2, a 3rd lens group L3, a 4th lens group L4, a solid-state imaging element 2, a low-pass filter 3, a filter 4, a motor 5, an iris blade 6, an electric driving iris system 7, etc. The filter 4 is constituted of an IR cutting filter 4a and an IR cutting coat layer 4b having an IR cutting coating laminated on the infrared-light cutting filter 4a. The IR cutting filter 4a is a filter which is used for a video camera mounted with a mechanical iris system before. The IR cutting coating layer 4b is formed by laminating 16 layers of IR cutting coatings having an infrared-light cutting function with a 630±50 nm half-value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to an image pickup apparatus in which the amount of light incident on a solid-state image pickup element is adjusted by an electric light control element.

[0002]

2. Description of the Related Art In recent years, the resolution of images from electronic cameras such as video cameras and digital still cameras has increased.
The demand for smaller size is increasing. In order to meet this demand, high-density CC is used as a solid-state image sensor for electronic cameras.
It has been proposed to reduce the optical system of the electronic camera by mounting a D (Charge Coupled Device) and downsizing a lens mounted in the electronic camera.

However, when the optical system of the electronic camera is downsized as in the above-mentioned proposal, the image quality deterioration due to the diffraction phenomenon becomes more and more remarkable. This is because the aperture area of the aperture is reduced by reducing the size of the optical system.

Further, in the conventional electronic camera, the limitation of size is faced due to the mechanical size limitation. In conventional electronic cameras, this is an iris system that adjusts the amount of light entering the solid-state image sensor.
This is because an iris system (hereinafter, mechanical iris system) that mechanically drives a plurality of diaphragm blades by a motor to adjust the opening area of the opening is used.

Therefore, in order to solve the above-mentioned problems, instead of the mechanical iris system, an electric dimming element made of an electrochemical material such as liquid crystal or EC (electrochromic) is used, and the amount of light incident on the solid-state image pickup element is increased. An iris system (hereinafter, referred to as an electric drive iris system) for adjusting the electric field has been proposed (see JP-A-7-20529 and JP-A-11-326894).

[0006]

By the way, in the electronic camera equipped with the electric drive iris system described above,
It is required that the white balance can be adjusted under the operating temperature condition of 20 ° C. to 80 ° C., but the electronic camera equipped with the conventional electric drive iris system is not sufficient to meet this demand.

Therefore, an object of the present invention is to provide an image pickup device having an electric drive iris system and capable of adjusting white balance under a use temperature condition of a temperature range of -20 ° C to 80 ° C.

[0008]

In order to solve the above problems, the invention of claim 1 adjusts the amount of light incident on a solid-state image pickup device by an electric light control device made of liquid crystal containing at least a dye-based pigment. The image pickup apparatus according to claim 1, further comprising a removing unit that removes at least a near-infrared region of the light that enters the solid-state image sensor, in the optical path of the light that enters the solid-state image sensor.

According to the image pickup apparatus of the present invention configured as described above, the removing means for removing at least the near-infrared region of the light entering the solid-state image sensor is included in the optical path of the light entering the solid-state image sensor. -20 ℃ to 80 ℃ because it is equipped
In such a use environment temperature, the light intensity of the light incident on the solid-state image sensor can be made constant in the visible band.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. The present inventor has conducted earnest studies in order to solve the above-mentioned problems of the prior art. The outline will be described below.

According to the knowledge of the inventor of the present invention, in a video camera equipped with an electric drive iris system, -20 ° C
The white balance cannot be adjusted under the operating temperature condition of -80 ° C because the electrochemical material showing the same physical property value is used as the material of the electrochromic device under the operating temperature condition of -20 ° C-80 ° C. Because it was not.

Further, according to the knowledge of the present inventor, in a video camera equipped with an electrically driven iris system,
The reason why the white balance cannot be adjusted under the operating temperature condition of 20 ° C. to 80 ° C. is to study the white balance adjusting method by using all the materials of the electric dimming device such as liquid crystal and EC in a lump. This is also because
-105219 and JP-A-6-148593).
That is, according to the inventor's knowledge, it is difficult to find a white balance adjusting method that can be applied to all materials, because the physical properties are different for each material used for the electric dimming element. It is necessary to study the white balance adjustment method for each material used for the optical element.

Therefore, first, the inventor of the present invention has a temperature of -20.degree.
In order to find an electrochemical material having the same physical property value under the use temperature condition of 0 ° C., investigation was conducted on the electrochemical material such as liquid crystal and EC. As a result, the present inventor recalls that it is preferable to use a dichroic guest-host liquid crystal (dichroic GH (Guest Host) liquid crystal) in which a liquid crystal is blended with a dye, as the electrochemical material of the electrochromic device. Came to.

Next, a thorough examination was made on a white balance adjusting method for a video camera equipped with an electric light control device using the dichroic GH liquid crystal. This is because, according to the knowledge of the present inventor, a white balance adjusting method for a video camera equipped with an electric light control element made of dichroic GH liquid crystal has not been clarified yet.

According to the knowledge of the present inventor, the spec required for the dichroic GH liquid crystal in order to adjust the white balance of the video camera is that the spectrum is stable in the visible region of 400 nm to 700 nm. is there. Specifically, the spectrum of each wavelength in 400 nm to 700 nm is within ± 5% regardless of the applied voltage.

Therefore, the present inventor diligently conducted experiments to investigate the spectral characteristics of the dichroic GH liquid crystal. As a result, in the dichroic GH liquid crystal, the spectrum is almost constant at 400 nm to 630 nm, whereas it is 630 nm to 700 n.
We have come to understand the property that the spectrum floats in the near infrared region of m. Further, it has been clarified that the floating of the spectrum becomes more severe as the applied voltage applied to the dichroic GH liquid crystal is increased.

As a result of repeated studies as described above, the present inventor can suppress the floating of the spectrum in the near-infrared region (630 nm to 700 nm) of the light incident on the solid-state image pickup device mounted on the video camera. It came to the mind that the white balance of a video camera can be adjusted under operating temperature conditions of -20 ° C to 80 ° C.

The present invention has been devised based on the above examination. An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the schematic arrangement of a photographing optical system 1 of a video camera according to an embodiment of the present invention. As shown in FIG. 1, the photographing optical system 1 of this video camera includes a lens first group L1, a lens second group L2, a lens third group L3, a lens fourth group L4, a solid-state image sensor 2, a low-pass filter 3, It is composed of a filter 4, a motor 5, an iris blade 6, an electric light control element 7, and the like.

The first lens unit L1 and the third lens unit L3
Is a fixed lens. The second lens unit L2 is a zoom lens. The fourth lens group is a focusing lens.

The solid-state image pickup device 2 converts the incident light into an electric signal and supplies it to a signal processing unit (not shown). The solid-state image sensor 2 is, for example, a CCD or the like.

The low-pass filter 3 is for suppressing a false signal (moire) generated when a striped image close to the pixel pitch is taken, and is made of, for example, artificial quartz.

The filter 4 cuts the infrared region of the light incident on the solid-state image pickup device 2 and also controls the near infrared region (630n).
It suppresses the floating of the spectrum from m to 700 nm), and the visible range (40
This is for making the light intensity of 0 nm to 700 nm uniform. The filter 4 includes an infrared light cut filter (hereinafter, IR cut filter) 4a and an IR cut coat layer 4b formed by laminating an IR cut coat on the IR cut filter 4a. Where I
The R cut coat layer 4b is formed, for example, on at least one of the surface of the IR cut filter 4a on the subject side and the surface of the IR filter 4a on the solid-state image pickup device 2 side. It is formed on the surface of the subject side.

The IR cut filter 4a is a filter having a transmittance as shown in FIG. The IR cut filter 4a is a filter that has been conventionally used in a video camera equipped with a mechanical iris system. By mounting this filter, the solid-state imaging device 2 such as a CCD detects infrared light and the brightness is increased. It is possible to prevent a large error in reproducibility and color reproducibility. Where I
The thickness of the R cut filter 4a is 0.8 mm to 1.2 m.
It is selected from the range of m.

On the other hand, the IR cut coat layer 4b is a coat layer having an infrared light cut function (hereinafter, IR cut function). This IR cut coat layer 4b is 650 ± 10
nm half value, preferably 630 ± 50 nm half value IR cut coat having an IR cut function is formed by laminating a predetermined layer, 16 layers in one embodiment of the present invention. Here, the thickness of the IR cut coat is selected from several hundred Å, that is, from 0.1 μm to 1 μm.

In one embodiment of the present invention, by stacking an IR cut coat on the IR cut filter 4a, the floating of the spectrum of light incident on the solid-state image pickup device 2 in the near infrared region (630 nm to 700 nm) is prevented. An example of suppressing is shown, but the solid-state imaging device 2 is
Near-infrared region (630 nm to 700 nm) of light incident on
It may be possible to suppress the floating of the spectrum of. For example, 650 ± 10 nm half value, preferably 630 ± 50 nm
By attaching a half-value infrared light cut filter or the like to the above-mentioned IR cut filter 4a, the near-infrared region (630 nm to 700 n) of light incident on the solid-state imaging device 2
The floating of the spectrum of m) may be suppressed.

In one embodiment of the present invention,
An example of applying the IR cut coat on the IR cut filter 4a is shown, but the place where the IR cut coat is applied is not limited to this. For example, the surface of the electric dimming element 7 on the subject side, the surface of the electric dimming element 7 on the solid-state imaging element 2 side,
The surface of the low-pass filter 3 on the subject side, the surface of the low-pass filter 3 on the solid-state image sensor 2 side, the surface of the IR-cut filter 4a on the subject side, the surface of the IR-cut filter 4a on the solid-state image sensor 2 side, and the first lens group L1. The surface on the object side, the surface on the solid-state image sensor 2 side of the first lens group L1, the surface on the object side of the second lens group L2, the surface on the solid-state image sensor 2 side of the second lens group L2, and the third lens group L3. Object side surface, third lens unit L
An IR cut coat is applied to at least one of the surface of the third lens group 3 on the solid-state image sensor 2 side, the surface of the fourth lens group L4 on the subject side, and the fourth lens group L4 on the solid image sensor side. I don't care.

The motor 5 moves the fourth lens unit L4 based on a control signal supplied from a control unit (not shown). The iris blade 6 is for adjusting the amount of light incident on the solid-state image sensor 2, and is driven by a motor (not shown).

The electric light control device 7 is for adjusting the amount of light incident on the solid-state image pickup device 2. The electric dimming element 7 is an electric dimming element made of liquid crystal containing at least a dye-based pigment, and in one embodiment of the present invention,
It is an electric light control device made of dichroic GH liquid crystal.

FIG. 3 is a graph showing the spectral characteristics of the dichroic GH liquid crystal used as the material of the electric light control device 7. The spectral characteristics shown in FIG. 3 are standardized at 540 nm. As for the spectrum of the dichroic GH liquid crystal, as shown in FIG. 3, the spectrum is almost constant in the 400 nm to 630 nm region, whereas the spectrum floats in the near infrared region of 630 nm to 700 nm. Also, the floating of this spectrum is
It becomes more severe as the applied voltage applied to the dichroic GH liquid crystal is increased. By mounting the above-mentioned filter 4 on a video camera, the floating of the spectrum in the near-infrared region (630 nm to 700 nm) of the light incident on the solid-state imaging device 2 is suppressed, and the light intensity in the visible region (400 nm to 700 nm) is suppressed. Can be made almost uniform. That is, by mounting the filter 4 on the video camera, the white balance of the video camera equipped with the electric light control device 7 can be adjusted.

The present inventor evaluated the white balance adjustment of the video camera having the above-mentioned configuration using a vector scope. Specifically, 0
White balance adjustment was evaluated by applying rectangular waves of v, ± 2.3v, ± 3v, and ± 5v to the electric dimming element 7 and observing a vectorscope screen for each applied voltage. The object to be captured by the video camera when observing the vectorscope screen is an all-white monitor.

FIG. 4 shows an example of the vectorscope screen. Here, the evaluation method of the white balance adjustment using the vector scope according to the embodiment of the present invention will be described with reference to FIG. The white balance point is located at the center of the screen. If the white balance point is located near the center of the vector scope screen at each of the applied voltages described above, the visible light of the light incident on the solid-state image sensor 2 is within the range of 0 v to ± 5 v regardless of the applied voltage. It shows that the spectrum of the band (400 nm to 700 nm) is stable. That is, it indicates that the white balance of the video camera is in the range of 0v to ± 5v regardless of the applied voltage. On the other hand, when the white balance point is not located near the center of the vectorscope screen at each applied voltage described above, the applied voltage is 0 v.
It is shown that the spectrum of the light incident on the solid-state image sensor 2 in the visible region (400 nm to 700 nm) is not stable within the range of ± 5 v. That is, it indicates that the white balance of the video camera is not balanced within the applied voltage range of 0 v to ± 5 v.

Further, at each applied voltage, by measuring the distance from the center point of the vector scope screen to the white balance point, the incident light enters the solid-state image sensor 2 within the range of 0 v to ± 5 v regardless of the applied voltage. Visible range of light (4
It is possible to quantitatively evaluate whether or not the spectrum of (00 nm to 700 nm) is stable. That is, it is possible to quantitatively evaluate whether or not the white balance of the video camera is taken. According to the knowledge of the present inventor, in the video camera according to the embodiment of the present invention, if the distance from the center point to the white balance point is within 1 mm, the spectrum of each wavelength in the visible range (400 nm to 700 nm) is obtained. Is ± 5%
Within. In the vector scope used in this experiment, the length from the central point to the outermost point (referred to as burst length) is 38 mm.

Below, the electric light control device 7 of the video camera is used.
Fig. 5 shows the vector scope screens when rectangular waves of 0v, ± 2.3v, ± 3v, and ± 5v are applied.
A, 5B, 5C, and 5D.

FIG. 5A shows an electric light control element 7 of a video camera.
A vector scope screen when a 0 V rectangular wave is applied is shown in FIG. The white balance point is located almost in the center of the vector scope screen, specifically, within 1 mm from the center point. Therefore, when the 0v rectangular wave is applied to the electric light control device 7 of the video camera, the solid-state image pickup device 2
Visible band of light incident on (400nm-700nm)
Can be stabilized. That is, when a 0v rectangular wave is applied to the electric light control element 7 of the video camera,
The white balance of the video camera can be adjusted.

FIG. 5B shows an electric light control device 7 of a video camera.
A vector scope screen when a ± 2.3v rectangular wave is applied is shown in FIG. The white balance point is located almost in the center of the vector scope screen, specifically, within 1 mm from the center point. Therefore, when a ± 2.3v rectangular wave is applied to the electric light control element 7 of the video camera, the visible light band (400 nm to 7 nm) of the light incident on the solid-state image sensor 2 is applied.
00 nm) can be stabilized. That is, when a ± 2.3v rectangular wave is applied to the electric light control element 7 of the video camera, the white balance of the video camera can be obtained.

FIG. 5C shows an electric light control element 7 of a video camera.
A vector scope screen when a ± 3v rectangular wave is applied is shown in FIG. The white balance point is located almost in the center of the vector scope screen, specifically, within 1 mm from the center point. Therefore, when a ± 3v rectangular wave is applied to the electric light control element 7 of the video camera, the visible light band (400 nm to 700 n) of the light incident on the solid-state image sensor 2 is applied.
m) can be stabilized. That is, when a ± 3v rectangular wave is applied to the electric light control element 7 of the video camera, the white balance of the video camera can be obtained.

FIG. 5D shows an electric light control device 7 of a video camera.
A vectorscope screen when a ± 5v rectangular wave is applied is shown in FIG. The white balance point is located almost in the center of the vector scope screen, specifically, within 1 mm from the center point. Therefore, when a ± 5 v rectangular wave is applied to the electric light control element 7 of the video camera, the visible light band (400 nm to 700 n) of the light incident on the solid-state image sensor 2 is applied.
m) can be stabilized. That is, when a ± 5v rectangular wave is applied to the electric light control element 7 of the video camera, the white balance of the video camera can be obtained.

As described above, in the range of 0 v to ± 5 v, the visible light band (400
nm-700 nm) can be stabilized. Specifically, in the range of 0v to ± 5v, the spectroscopy of each wavelength can be made within ± 5% regardless of the applied voltage. That is, in the range of 0 v to ± 5 v, the white balance of the video camera can be taken regardless of the applied voltage.

As described above, according to the embodiment of the present invention, in the optical path of the light incident on the solid-state image sensor 2,
IR cut filter 4a and this IR cut filter 4
Since the filter 4 including the IR cut coat layer 4b formed by laminating the IR cut coat on the surface a is provided, the spectrum can be stabilized in the visible band of 400 nm to 700 nm. Specifically, 400 nm
Spectroscopy of each wavelength in the visible region of ~ 700 nm
Within the range of ± 5 v, the voltage can be suppressed within ± 5% regardless of the applied voltage of the electric light control element 7. Therefore, 0
In the range of v to ± 5v, the white balance of the video camera can be taken regardless of the applied voltage.

Next, another embodiment of the present invention will be described. In the above-described one embodiment of the present invention, an example in which an IR cut coat is laminated on the IR cut filter 4a has been shown, but in another embodiment of the present invention,
The IR cut filter 4a is removed, and an IR cut coat is laminated on the low pass filter 3. Specifically, 650
An IR cut coat having an infrared light cut function of ± 10 nm half-value, preferably 630 ± 50 nm half-value, is provided in a predetermined layer, in another embodiment of the present invention, 48 to 52 layers,
It is laminated on the low-pass filter 4. Here, the IR cut coat is formed on, for example, at least one of the surface of the low-pass filter 3 on the object side and the surface of the low-pass filter 3 on the solid-state image sensor 2 side. In another embodiment of the present invention, the IR-cut coat of the low-pass filter 3 is formed. It is formed on the surface of the subject side.

In another embodiment of the invention, IR
By applying a cut coat to the low pass filter 3,
An example of suppressing the near-infrared region of the light incident on the solid-state image pickup device 2 will be shown.
Near-infrared region (630 nm to 700 nm) of light incident on
It may be possible to suppress the floating of the spectrum of. For example, 650 ± 10 nm half value, preferably 630 ± 50 nm
By attaching a half-value infrared light cut filter to the above-mentioned low-pass filter, floating of the spectrum of light entering the solid-state imaging device 2 in the near-infrared region (630 nm to 700 nm) may be suppressed.

In another embodiment of the present invention, an example in which the IR cut coat is applied to the low pass filter 3 is shown, but the place where the IR cut coat is applied is not limited to this. For example, the surface of the electric light control element 7 on the object side, the surface of the electric light control element 7 on the solid-state image sensor 2 side, the surface of the low pass filter 3 on the object side, the low pass filter 3
Surface of the solid-state imaging device 2 side, surface of the first lens unit L1 facing the subject, surface of the first lens unit L1 facing the solid-state imaging device 2, surface of second lens unit L2 facing the subject, second lens unit L2 Of the solid-state image sensor 2 side, the surface of the third lens unit L3 on the subject side,
The surface of the third lens unit L3 on the solid-state imaging device 2 side, the fourth lens unit
An IR cut coat may be applied to at least one of the surface of the group L4 on the subject side and the surface of the fourth lens unit L4 on the solid-state imaging element 2 side.

The configuration of the video camera other than this is substantially the same as that of the above-described embodiment, and therefore the description thereof is omitted here.

The same advantages as those of the above-described embodiment of the present invention can be obtained in other embodiments of the present invention.

The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, in the above-described embodiment, when the red sensitivity of the video camera is low, the thickness of the filter 4, specifically, the IR cut filter 4a or the IR cut coat layer 4b is reduced. It doesn't matter if you do so.

Further, in the other embodiments described above, when the red sensitivity of the video camera is lowered, the thickness of the IR cut coat layer may be reduced.

[0049]

As described above, according to the present invention, in the image pickup apparatus in which the amount of light incident on the solid-state image pickup element is adjusted by the electric light control element made of liquid crystal containing at least a dye-based pigment, -20 ° C. It is possible to make the light intensity of the light incident on the solid-state image sensor constant in the visible band under the use temperature condition of -80 ° C. Therefore, the white balance can be adjusted under the use temperature condition of −20 ° C. to 80 ° C.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a photographing optical system of a video camera according to an embodiment of the present invention.

FIG. 2 is a graph showing the transmittance of the IR cut filter according to the embodiment of the present invention.

FIG. 3 is a graph showing a spectral characteristic of a dichroic GH liquid crystal used as an electric light control element material of a video camera according to another embodiment of the present invention.

FIG. 4 is an example of a vector scope screen for explaining white balance adjustment evaluation of a bidet camera according to an embodiment of the present invention.

FIG. 5 shows a vector scope screen when a predetermined voltage is applied to the electric light control device of the video camera according to the embodiment of the present invention.

[Explanation of symbols]

L1 ... Lens first group, L2 ... Lens second group, L
3 ... Lens third group, L4 ... Lens fourth group, 2 ...
..Solid-state image sensor, 3 ... Low-pass filter, 4 ...
・ Filter, 5 ・ ・ ・ Motor, 6 ・ ・ ・ Iris blade,
7 ... Electric light control element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03B 11/00 G03B 11/00 5C022 H04N 5/238 H04N 5/238 Z 5C024 5/335 5/335 VF Terms (reference) 2H048 AA03 AA06 AA16 AA18 AA24 EA03 EA07 EA12 2H049 BA05 BA46 BC21 2H083 AA04 AA15 2H088 EA32 GA02 GA03 GA13 HA11 JA06 MA20 2H091 FA01X CG55 AC51 C52 AC54 C54 AC54 554022 AB13 AB05

Claims (6)

[Claims] 1. An image pickup device for adjusting the amount of light incident on a solid-state image pickup device by a light control device made of a liquid crystal containing at least a dye-based pigment, wherein the solid-state image pickup device is provided in an optical path of light incident on the solid-state image pickup device. An image pickup apparatus comprising: a removing unit that removes at least a near-infrared region of light incident on an element. 2. The image pickup device according to claim 1, wherein the liquid crystal is a dichroic guest-host liquid crystal. 3. The image pickup device according to claim 1, wherein the removing unit is provided between the solid-state image pickup element and the light control element. 4. The image pickup device according to claim 1, wherein the removing unit is an infrared light cut filter. 5. The image pickup device according to claim 4, wherein the infrared light cut filter is a filter having a half-value infrared light cut function of 630 ± 50 nm. 6. The image pickup device according to claim 4, wherein the infrared light cut filter is a filter having an infrared light cut function of 650 ± 10 nm half value.