JP2008124941A - Imaging system, and control method of variable filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accomplish an imaging system for photographing a subject even with either visible light or near infrared light while using one solid-state imaging element, without using a mechanism for inserting/ejecting and selecting a filter with mechanical movement. <P>SOLUTION: The imaging system is constituted of: a solid-state imaging element 108 for imaging a subject with visible light and near infrared light; an electrochromic filter 106 disposed between the solid-state imaging element 108 and the subject; voltage sources 109, 110 for applying a control voltage to the electrochromic filter 106; and switches 111, 112. By applying a control voltage in a predetermined direction or a reverse direction between electrodes 101 and 105, a wavelength area of light transmitted through the electrochromic filter 106 is switched to visible light or to near infrared light. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging system and a variable filter control method, and more particularly to a technique for selectively detecting light included in one of a plurality of wavelength bands.

  In recent years, an increasing number of vehicles are equipped with a near-infrared camera in order to increase the safety of driving at night. And by emitting near-infrared light from a near-infrared LED (Light Emitting Diode) or the like mounted at the same time, and recognizing reflected light from a pedestrian or an obstacle in the dark with the near-infrared camera, In order to avoid accidents, the driver is alerted and the car is automatically stopped.

  Such a near-infrared camera generally includes a charge coupled device (CCD) type or a complementary metal oxide semiconductor (CMOS) type solid-state imaging device. The solid-state imaging element is formed on a silicon substrate including a photoelectric conversion element.

  A photoelectric conversion element made on a silicon substrate is sensitive not only to near infrared light but also to visible light. Therefore, a normal color image can be obtained by using the solid-state imaging device together with a color filter. That is, with a single solid-state imaging device, a subject can be converted into a color image with visible light, and a subject can be converted into a monochrome image with near-infrared light.

  When obtaining a color image with visible light, a filter that blocks near-infrared light is used in addition to the color filter in order to improve color reproducibility. For example, a color filter used for obtaining a blue image generally transmits near infrared light in addition to blue light. The transmitted near-infrared light is detected as noise with respect to the blue image by the solid-state imaging device. Therefore, in order to remove near infrared light and improve color reproducibility, it is necessary to use a filter that blocks near infrared light.

  On the other hand, when obtaining a monochrome image with near infrared light, it goes without saying that a filter that blocks near infrared light should be removed in order to obtain sufficient sensitivity. Furthermore, since visible light such as a headlight of an oncoming vehicle can become noise, it is preferable to use a filter that blocks visible light.

  Therefore, conventionally, in an imaging system using one solid-state image sensor, solid-state imaging of incident light is performed in order to achieve both good color reproducibility in color photography using visible light and good sensitivity in monochrome photography using near-infrared light. In an optical system leading to an element, a technique for inserting and removing a filter by mechanical movement is known (see, for example, Patent Documents 1 to 3).

Further, as a similar technique, a technique is known in which a filter having characteristics according to inspection contents is selectively inserted into an optical system for inspecting a solid-state imaging device by mechanical movement (for example, Patent Documents). 4).
JP 2000-059798 A JP 2000-0669463 A JP 2002-077721 A JP 2003-042845 A

  However, according to the conventional technology, a mechanism for mechanically moving the filter is required, which hinders downsizing and cost reduction of the apparatus, and is liable to break down.

  The present invention has been made to solve the above-described problems. Color imaging with visible light and near-infrared light can be performed using one solid-state imaging device without performing filter insertion / extraction and selection by mechanical movement. An object of the present invention is to provide an imaging system that can perform photographing well.

  In order to achieve the above object, an imaging system according to the present invention is arranged between a solid-state imaging device that images a subject with visible light and near-infrared light, the solid-state imaging device and the subject, and transmits light. It comprises a variable filter whose voltage can be controlled, and a control means for applying a control voltage to the variable filter. A light transmitting film, a solid electrolyte that supplies the ions to the light transmitting film, and a second electrode are stacked, and the control unit controls the first and second electrodes in a predetermined direction or in a reverse direction. By applying a voltage, the wavelength region of the light transmitted through the variable filter is switched to visible light or near infrared light.

  According to this configuration, by applying a control voltage in a predetermined direction between the first and second electrodes and injecting ions of the solid electrolyte into the light transmission film, visible light is transmitted through the light transmission film. In addition, by applying a control voltage in the reverse direction and extracting ions of the light transmitting film to the solid electrolyte, the light transmitting film can be made to transmit near infrared light. Thereby, the transmission characteristic of the variable filter can be electrically controlled.

  Therefore, by using the variable filter, it is possible to realize an imaging system for imaging a subject by switching between visible light and near infrared light without using a mechanism for inserting and removing the filter by mechanical movement. This configuration is useful for realizing an imaging system with a small size and low cost.

  In addition, the variable filter is formed by stacking a plurality of individual variable filters, and each individual variable filter has a wavelength range of light that is transmitted according to the first electrode and different ion contents according to different characteristics. A light-transmitting film, a solid electrolyte for supplying the light to the light-transmitting film, and a second electrode, and the control means is provided between the first and second electrodes of the individual variable filter, Independent control voltages may be applied.

  According to this configuration, as a typical example of the different characteristics, in each individual variable filter, the first characteristic that transmits one of red, green, and blue light included in visible light and near-infrared light is transmitted. And the second characteristic that transmits visible light and blocks near-infrared light can be electrically switched.

  When all the individual variable filters are used with the first characteristic, the variable filter blocks visible light and transmits near infrared light. When all the individual variable filters are used with the second characteristic, visible light is transmitted and near infrared light is blocked. Furthermore, when one of the individual variable filters is used for the first characteristic and the other is used for the second characteristic, one of red, green, and blue light is selectively transmitted. That is, the variable filter not only functions as a filter that selectively transmits one of visible light and near infrared light, but also functions as a color separation filter for visible light.

  According to this imaging system, in addition to photographing with visible light and near-infrared light, the visible light can be obtained only by electrically controlling the variable filter without inserting and removing and selecting the filter by mechanical movement. Three-color multiband photography with color separation can be performed.

  In the imaging system, the variable filter may be integrally formed on the solid-state imaging device.

  According to this configuration, the number of parts can be reduced from two to one by integrally forming the solid-state imaging device and the variable filter. Compared to the case where the variable filter is formed on a separate substrate and assembled into a final module together with a solid-state imaging device, it can be mounted in a smaller space. In general, since the manufacturing cost for creating the variable filter on a separate substrate is the same, the manufacturing cost can be reduced by the amount of the assembly process.

  Further, in the imaging system, the control unit applies a pulse voltage in a certain direction whose duration is shorter than the period during the period in which the variable filter tries to obtain a certain light transmission characteristic. You may apply intermittently 1 time or more between two electrodes.

  According to this configuration, an electric field is not continuously applied to the light transmissive film, and deterioration due to an excessive redox reaction of the light transmissive film can be prevented. In addition, since there is no leakage current that continues to flow through the light transmission film, steady power consumption can be kept low. Further, when the application of the control voltage is stopped, ions diffuse between the light transmission film and the solid electrolyte as time passes, and as a result, the characteristics of the variable filter may fluctuate. The intermittent application of the pulse voltage is useful for preventing the diffusion of the ions and reliably obtaining the constant light transmission characteristics while suppressing the deterioration of the light transmission film.

  In the imaging system, the control unit and the solid-state imaging device may be formed on the same semiconductor substrate.

  According to this configuration, the control unit and the solid-state imaging device do not need to be separately formed and assembled, which is useful for reducing manufacturing costs and reducing the size of the apparatus.

  The imaging system may further include a color filter between the solid-state imaging device and the variable filter, or between the variable filter and the subject.

  According to this configuration, since color separation can be performed by the color filter, the variable filter can be used only for switching between visible light and near infrared light. As a result, the application of the control voltage can be suppressed to a minimum number of times. When the transmission characteristics of the light transmission film change and deteriorate each time a voltage is applied, the life of the light transmission film can be extended by suppressing the number of application of the control voltage.

  The present invention can be realized not only as the imaging system but also as a method for controlling the variable filter.

  The imaging system of the present invention uses a variable filter capable of voltage-controlling light transmission characteristics together with a solid-state imaging device that images a subject with visible light and near-infrared light. In the variable filter, visible light is transmitted by applying a control voltage in a predetermined direction, and near-infrared light is transmitted by applying a control voltage in the reverse direction, so that the filter is inserted and removed by mechanical movement. An imaging system that captures an image of a subject by switching between visible light and near infrared light without using a mechanism can be realized. This configuration is useful for realizing an imaging system with a small size and low cost.

<First Embodiment>
An imaging system according to a first embodiment of the present invention will be described with reference to the drawings. This imaging system uses a solid-state imaging device that is sensitive to both visible light and near-infrared light, and an electrochromic filter that can electrically change the wavelength range of transmitted light. Switch between shooting and shooting with near-infrared light.

  FIG. 1 is a schematic diagram showing a characteristic part of the imaging system. The characteristic part of this imaging system includes an electrochromic filter 106, a color filter 107, a solid-state imaging device 108, voltage sources 109 and 110, and switches 111 and 112. The electrochromic filter 106 includes electrodes 101 and 105, a solid electrolyte 103, and an electrochromic film 104.

  The electrochromic filter 106 is electrically controlled by the voltage sources 109 and 110 and the switches 111 and 112 so that a desired one of visible light and near infrared light included in incident light from the subject is transmitted. .

  In this configuration, an example of the variable filter recited in the claims is the electrochromic filter 106, and an example of the control unit is the entirety of the voltage sources 109 and 110 and the switches 111 and 112. An example of the light transmission film described in the claims is the electrochromic film 104.

  The solid-state image sensor 108 has sensitivity to both visible light and near-infrared light, and images a subject by incident light after passing through the electrochromic filter 106.

  An example of a specific configuration of the electrochromic filter 106 will be described in detail according to a manufacturing procedure.

  As the electrode 105, for example, ITO (Indium Tin Oxide) is formed on the color filter 107 to a thickness of about 100 nm. Here, in order to improve the adhesion between the electrode 105 and the color filter 107, a silicon oxide (not shown) may be first formed on the color filter 107, and the electrode 105 may be formed thereon.

  As the electrochromic film 104, for example, β-ZrNCl (β-type zirconium nitride chloride) is formed on the electrode 105 to a thickness of about 100 nm. The electrochromic film 104 is preferably formed so as to have a large surface area, for example, in a porous form in order to promote a reaction described later.

As the solid electrolyte 103, for example, Li _x V ₂ O ₅ (lithium vanadium oxide) is formed to a thickness of about 1000 nm. The solid electrolyte 103 is a source of Li ions implanted into the electrochromic film 104.

  And as the electrode 101, ITO is again formed into a thickness of about 100 nm. Here, the electrodes 101 and 105 are transparent electrodes.

The electrochromic filter 106 configured as described above functions as follows. That is, in the electrochromic film 104, the reaction formula β-ZrNCl + xLi ⁺ + xe ⁻ <=> Li _x ZrNCl
According, beta-ZrNCl is intercalation of Li ions occurs (which is oxidized in a broad sense) changed to Li _x ZrNCl by and Li _x ZrNCl is deintercalation of Li ions occurs (in a broad sense Is reduced to β-ZrNCl.

  Before and after this reaction, the electronic band structure in the electrochromic film 104 changes, so that the wavelength range of transmitted light changes. This phenomenon is known as the chromism phenomenon.

Specifically, Li _x ZrNCl transmits only near-infrared light, and β-ZrNCl transmits most of the wavelength of visible light. Therefore, the electrochromic film 104 functions as a filter for near-infrared light photography in a state where Li ions are intercalated (that is, in an oxidized state), and a state where Li ions are deintercalated (that is, in a state where the Li ions are deintercalated). It functions as a filter that transmits visible light in the reduced state.

  Li ion intercalation and deintercalation are controlled by applying a voltage between electrodes 101 and 105 in a desired direction.

  An electric field in a direction corresponding to the applied voltage is generated in the solid electrolyte 103, and Li ions in the solid electrolyte 103 move in the direction of the generated electric field. Depending on this direction, Li ions can be injected into the electrochromic film 104 to cause intercalation, or Li ions can be extracted from the electrochromic film 104 to cause deintercalation.

  Next, a method for controlling the electrochromic filter 106 in the imaging system of the first embodiment will be described.

  FIG. 2 is a timing chart showing an example of the timing of the control signals for the switches 111 and 112, the output voltage of the voltage source 109, and the output voltage of the voltage source 110. The right direction in the figure corresponds to the passage of time.

  When imaging with visible light, it is necessary to block near infrared light by the electrochromic filter 106 and transmit only visible light. In this case, as shown in the left part of FIG. 2, the switches 111 and 112 are turned on while outputting the ground voltage and the positive voltage from the voltage sources 109 and 110, respectively.

  By doing so, an electric field directed from the electrode 105 to the electrode 101 is generated in the electrochromic filter 106, Li ions are extracted from the electrochromic film 104 to the solid electrolyte 103, and deintercalation of Li ions occurs (in other words, The electrochromic film 104 is reduced). As a result, the electrochromic filter 106 transmits visible light.

  On the other hand, when imaging with near infrared light, only the near infrared light needs to be transmitted by the electrochromic filter 106. In this case, as shown in the right part of FIG. 2, the switches 111 and 112 are turned on while outputting the positive voltage and the ground voltage from the voltage sources 109 and 110, respectively.

  By doing so, an electric field from the electrode 101 to the electrode 105 is generated in the electrochromic filter 106, Li ions are implanted from the solid electrolyte 103 into the electrochromic film 104, and Li ion intercalation occurs (in other words, electro The chromic film 104 is oxidized). As a result, the electrochromic filter 106 transmits only near infrared light. Note that the electrochromic filter 106 in this state absorbs visible light and thus appears black to the naked eye.

  Thus, since the transmission characteristics of a single filter can be electrically changed by using the electrochromic filter 106, one solid-state imaging can be performed without performing filter insertion / removal and selection by mechanical movement. By using the element, an imaging system capable of satisfactorily performing imaging with visible light and imaging with near infrared light can be obtained.

  The switches 111 and 112 may be turned off when the above-described intercalation (oxidation) reaction and deintercalation (reduction) reaction have progressed to a desired level. In other words, in order to change the transmission characteristics of the electrochromic filter 106, a pulse voltage having a predetermined duration may be applied.

  After the duration of the pulse voltage elapses (that is, after application of the control voltage is stopped), the electrochromic filter 106 and the voltage sources 109 and 110 are electrically disconnected, so that an electric field is continuously applied to the electrochromic film 104. Thus, deterioration due to an excessive redox reaction of the electrochromic film 104 can be prevented. In addition, since the leakage current that continues to flow through the electrochromic film 104 is eliminated, the steady power consumption can be kept low.

  When the application of the control voltage is stopped, Li ions diffuse between the electrochromic film 104 and the solid electrolyte 103 over time, and as a result, the characteristics of the electrochromic filter 106 may fluctuate. If it is important to prevent such ion diffusion and maintain a certain transmission characteristic, as shown in FIG. The voltage may continue to be applied.

  FIG. 3 is a timing chart showing an example of other timings of the control signals for the switches 111 and 112, the output voltage of the voltage source 109, and the output voltage of the voltage source 110. As shown in FIG. 3, a pulse voltage in a certain direction having a duration shorter than that period may be intermittently applied throughout a period for obtaining a certain transmission characteristic.

  Then, it is possible to stably maintain desired transmission characteristics of the electrochromic filter 106 while suppressing deterioration of the electrochromic film 104.

<Second Embodiment>
An imaging system according to a second embodiment of the present invention will be described with reference to the drawings. This imaging system is the same as the imaging system in the first embodiment in that a solid-state imaging device having sensitivity to both visible light and near-infrared light is used, but a plurality of light transmission characteristics are different from each other. The difference is that an electrochromic filter is used.

  FIG. 4 is a schematic diagram showing a characteristic part of the imaging system. The characteristic part of this imaging system includes electrochromic filters 206, 207, 208, a color filter 217, a solid-state imaging device 218, voltage sources 209 to 212, and switches 213 to 216. The electrochromic filter 206 includes electrodes 201 and 205, an electrochromic film 203, and a solid electrolyte 204.

  The electrochromic filters 207 and 208 are also composed of two electrodes, a solid electrolyte and an electrochromic film sandwiched between them.

  In FIG. 4, the electrode, the solid electrolyte, and the electrochromic layer are shown with the same design, and the reference numerals of some electrodes, the solid electrolyte, and the electrochromic layer are omitted.

  The electrode 205 is also used as the lower electrode of the electrochromic filter 206 and the upper electrode of the electrochromic filter 207. Similarly, the lower electrode of the electrochromic filter 207 and the upper electrode of the electrochromic filter 208 are also used as one electrode.

  In this configuration, an example of the individually variable filter described in the claims is the electrochromic filters 206, 207, and 208, and an example of the control unit is the whole of the voltage sources 209 to 212 and the switches 213 to 216. An example of the light transmission film described in the claims is an electrochromic film 204.

  The electrochromic filters 206, 207, and 208 are configured to have different characteristics of relative transmittance with respect to the wavelength of light.

  FIG. 5 is a graph showing characteristics of the electrochromic filters 206, 207, and 208 as a typical example. In FIG. 5, characteristics A, B, and C indicate the characteristics of the electrochromic filters 206, 207, and 208, respectively. By having such characteristics, the electrochromic filters 206, 207, and 208 function as filters that transmit near-infrared light together with red, green, and blue light included in the visible light region, respectively.

  The characteristic D shows the overall characteristic when the electrochromic filters 206, 207, 208 are used in layers, in other words, the spectral characteristic when white light is transmitted through all of the electrochromic filters 206, 207, 208. Yes.

  Electrochromic membrane materials for obtaining these individual properties are described in, for example, Gursel Somemez and Hayal B.E. Somemez, “Polymeric electrochromics for data storage”, Journal of Materials Chemistry, 2006, (16), 2473-2477.

  This document includes (A) poly-3-alkylthiophene Poly (3-alkylthiophene), (B) poly (2,3-di (cyan-3-yl) -5,7-di (cyan-2-yl) thieno [ 3,4-b] pyrazine) poly (2,3-di (thien-3-yl) -5,7-di (thien-2-yl) thieno [3,4-b] pyrazine), and (C) It is shown that by using each of the polyethylenedioxythiophene PEDOT as an electrochromic film, an electrochromic filter having the characteristics A, B, and C of FIG. 5 can be obtained in a state where the electrochromic film is reduced. .

  FIG. 6 shows the characteristics of these electrochromic filters when the electrochromic film is oxidized, and is shown in the same document. Correspondence with the characteristics of FIG. 5 is shown with the same reference numerals.

  The redox reaction of the electrochromic film can be electrically controlled by applying a voltage in a desired direction to a pair of electrodes sandwiching the electrochromic film and the solid electrolyte as described in the first embodiment. .

  FIG. 7 is a graph showing a comparison between the overall characteristics at the time of reduction shown in FIG. 5 and the overall characteristics at the time of oxidation shown in FIG. As can be seen in this graph, by using the above-mentioned electrochromic filter in layers, the characteristic that blocks visible light and transmits near infrared light, and the characteristic that transmits visible light and blocks near infrared light It can be seen that a filter that can be electrically switched is realized.

  Note that the material of the electrochromic film of the electrochromic filters 206, 207, and 208 is not limited to the materials described above. Any material may be used as long as it has different transmission characteristics with respect to the wavelength of light.

  Next, a method for controlling the electrochromic filters 206, 207, and 208 in the imaging system of the second embodiment will be described.

  FIG. 8 is a timing chart showing temporal changes in the control signals for the switches 213 to 216 and the output voltages of the voltage sources 209 to 212.

  When imaging with visible light, it is necessary to block near-infrared light by the electrochromic filters 206, 207, and 208 and transmit only visible light. In this case, as shown in the left part of FIG. 8, the switches 213 to 216 are turned on while the ground voltage is output from the voltage sources 209 and 211 and the positive voltage is output from the voltage sources 210 and 212.

  By doing so, an electric field from the electrode 205 to the electrode 201 is generated in the electrochromic filter 206, Li ions are injected from the solid electrolyte 204 to the electrochromic film 203, and Li ion intercalation occurs (that is, electrochromic). The film 203 is oxidized). At this time, the electrochromic film is also oxidized in the electrochromic filters 207 and 208.

  As a result, the electrochromic filters 206, 207, and 208 generally exhibit the characteristics of transmitting visible light (during oxidation in FIG. 7).

  On the other hand, when imaging with near infrared light, it is necessary to block visible light by the electrochromic filters 206, 207, and 208 and transmit only near infrared light. In this case, as shown in the right part of FIG. 8, the switches 213 to 216 are turned on while the positive voltage is output from the voltage sources 209 and 211 and the ground voltage is output from the voltage sources 210 and 212.

  By doing so, an electric field directed from the electrode 201 to the electrode 205 is generated in the electrochromic filter 206, Li ions are extracted from the electrochromic film 203 to the solid electrolyte 204, and deintercalation of Li ions occurs (in other words, The electrochromic film 203 is reduced). At this time, the electrochromic film is also reduced in the electrochromic filters 207 and 208.

  As a result, the electrochromic filters 206, 207, and 208 generally exhibit the characteristics of transmitting near-infrared light (at the time of reduction in FIG. 7).

  In this way, by using the electrochromic filters 206, 207, 208, the overall transmission characteristics of the filter can be electrically changed, so that without inserting and removing and selecting the filter by mechanical movement, By using one solid-state imaging device, an imaging system that can perform imaging with visible light and imaging with near infrared light can be obtained.

  In particular, in a configuration using a plurality of electrochromic filters, it is possible to drive while changing the characteristics of each electrochromic filter individually in order to capture an image with higher resolution.

  For example, if the electrochromic filter 206 is used with the characteristics at the time of reduction (A in FIG. 5) and the electrochromic filters 207 and 208 are used with the characteristics at the time of oxidation (B and C in FIG. 6), only red light is comprehensively obtained. The characteristic of selectively transmitting is obtained. Similarly, it is possible to obtain a characteristic that selectively transmits green light or blue light comprehensively according to other combinations of characteristics.

  That is, the electrochromic filters 206, 207, and 208 not only function as a filter that selectively transmits one of visible light and near-infrared light, but also function as a color separation filter for visible light.

  Therefore, according to this imaging system, in addition to visible light and near-infrared light photography, only the variable filter is electrically controlled without inserting and removing and selecting the filter by mechanical movement. Multiband photography can be performed by color separation of light. Multiband shooting is suitable for capturing a still object such as a starry sky with high resolution.

  The imaging system according to the present invention can be widely used for cameras that perform color imaging using visible light and imaging using near-infrared light, and is particularly suitable for in-vehicle cameras, surveillance cameras for roads, rivers, and security cameras.

Schematic showing the characteristic part of the imaging system in 1st Embodiment The figure which shows an example of the timing of the main control signal in 1st Embodiment. The figure which shows another example of the timing of the main control signal in 1st Embodiment. The schematic diagram showing the characteristic part of the imaging system in 2nd Embodiment The figure which shows the characteristic of the electrochromic filter in 2nd Embodiment The figure which shows the characteristic of the electrochromic filter in 2nd Embodiment The figure which compares the characteristic of the electrochromic filter in 2nd Embodiment The figure which shows an example of the timing of the main control signal in 2nd Embodiment.

Explanation of symbols

101, 105, 201, 205 Electrode 103, 204 Solid electrolyte 104, 203 Electrochromic film 106, 206, 207, 208 Electrochromic filter 107, 217 Color filter 108, 218 Solid-state imaging device 109, 110, 209, 210, 211, 212 Voltage source 111, 112, 213, 214, 215, 216 Switch

Claims (8)

A solid-state image sensor that images a subject with visible light and near-infrared light; and
A variable filter disposed between the solid-state imaging device and the subject and capable of voltage-controlling light transmission characteristics;
A control means for applying a control voltage to the variable filter;
The variable filter is
A first electrode;
A light-transmitting film in which the wavelength region of light that is transmitted according to the ion content changes;
A solid electrolyte for supplying the ions to the light-transmitting film;
The second electrode is laminated,
When the control means applies a control voltage in a predetermined direction or a reverse direction between the first and second electrodes, the wavelength region of light transmitted through the variable filter is switched to visible light or near infrared light. An imaging system. The variable filter is formed by laminating a plurality of individual variable filters.
Each individual variable filter
A first electrode;
A light-transmitting film in which the wavelength range of light that is transmitted according to the ion content changes according to different characteristics;
A solid electrolyte for supplying the ions to the light-transmitting film;
The second electrode is laminated,
The imaging system according to claim 1, wherein the control unit applies independent control voltages between the first and second electrodes of the individual variable filter. The imaging system according to claim 1, wherein the variable filter is integrally formed on the solid-state imaging device. The control means applies a pulse voltage in a certain direction whose duration is shorter than the period during the period for obtaining a certain light transmission characteristic in the variable filter at least once between the first and second electrodes. The imaging system according to claim 1, wherein the imaging system is intermittently applied. The imaging system according to claim 1, wherein the control unit and the solid-state imaging device are formed on the same semiconductor substrate. The imaging system according to claim 1, further comprising a color filter between the solid-state imaging device and the variable filter, or between the variable filter and the subject. A variable formed by laminating a first electrode, a light-transmitting film in which the wavelength region of light transmitted according to the ion content changes, a solid electrolyte that supplies the ions to the light-transmitting film, and a second electrode A method of controlling a filter,
A control method, wherein a voltage in a certain direction is continuously applied between the first and second electrodes during a period of obtaining a certain light transmission characteristic in the variable filter. A variable formed by laminating a first electrode, a light-transmitting film in which the wavelength region of light transmitted according to the ion content changes, a solid electrolyte that supplies the ions to the light-transmitting film, and a second electrode A method of controlling a filter,
A pulse voltage in a constant direction having a duration shorter than the period is intermittently applied between the first and second electrodes during a period of obtaining a constant light transmission characteristic in the variable filter. Control method.

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