WO2021131122A1

WO2021131122A1 - Droplet removal device and imaging unit

Info

Publication number: WO2021131122A1
Application number: PCT/JP2020/028252
Authority: WO
Inventors: 宣孝岸
Original assignee: 株式会社村田製作所
Priority date: 2019-12-26
Filing date: 2020-07-21
Publication date: 2021-07-01

Abstract

The present invention provides a droplet removal device and an imaging unit, the droplet removal device being able to efficiently remove droplets adhering to a translucent cover. This droplet removal device is provided with a translucent cover, a vibration unit that vibrates the translucent cover, and a control unit that controls the vibration unit. The translucent cover has a droplet removal region for removing droplets adhering to the surface of the translucent cover, and the droplet removal region includes a portion having the largest vibration generated by the vibration unit on the surface of the translucent cover.

Description

Droplet remover and imaging unit

The present invention relates to an imaging unit including a droplet removing device and a droplet removing device.

In cameras used outdoors such as in-vehicle cameras or surveillance cameras, the lens is covered with a translucent body cover to prevent foreign matter such as raindrops or mud from adhering. However, when foreign matter such as raindrops or mud adheres to the translucent body cover, the foreign matter adhering to the translucent body cover is reflected in the image captured by the camera, and it is difficult to acquire a clear image.

Therefore, as in Patent Document 1, a dome-type surveillance camera system that determines whether or not foreign matter has adhered to the surface of the dome-shaped cover and vibrates the dome-shaped cover to remove the foreign matter when the foreign matter adheres. Are known.

Japanese Unexamined Patent Publication No. 2012-138768

However, the system described in Patent Document 1 has a problem that the droplets adhering to the cover may not be completely removed.

Therefore, an object of the present invention is to provide a droplet removing device and an imaging unit capable of efficiently removing droplets adhering to the translucent body cover.

The droplet removing device according to one aspect of the present invention is
With a translucent cover,
The vibrating part that vibrates the translucent cover and
A control unit that controls the vibrating unit and
With
The translucent cover has a droplet removal region for removing droplets adhering to the surface of the translucent cover.
The droplet removal region includes the portion of the surface of the translucent body cover that is most vibrated by the vibrating portion.

The image pickup unit according to one aspect of the present invention includes the above-mentioned droplet removing device and an image pickup device.

According to the present invention, it is possible to provide a droplet removing device and an imaging unit capable of efficiently removing droplets adhering to a translucent body cover.

It is a perspective view which shows the structure of the image pickup unit which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the structure of the image pickup unit of FIG. It is a block diagram for demonstrating the control of the image pickup unit of FIG. It is an enlarged view of a part of the translucent body cover arranged in the droplet removal apparatus of the image pickup unit of FIG. It is a schematic diagram for demonstrating the water contact angle in this embodiment. It is a flowchart explaining operation of a droplet removal apparatus. It is a graph which shows the distribution of the vibration displacement in a translucent body cover. It is a figure explaining the viewing angle in a translucent body cover. It is a graph which shows the relationship between the water contact angle on the surface of a translucent body cover, and the time until a droplet is removed from the surface of a translucent body cover by vibration. It is a figure which shows the modification of the droplet removal region of the droplet removal apparatus of FIG. FIG. 5 is an enlarged cross-sectional view of a part of a translucent body cover arranged in the droplet removing device according to the second embodiment. 9A is a view of the translucent body cover of FIG. 9A viewed from another angle. FIG. 5 is an enlarged cross-sectional view of a part of a translucent body cover of a modified example of the droplet removing device according to the second embodiment.

(Background to the present invention)
For example, a camera used outdoors such as an in-vehicle camera, a surveillance camera, or a camera mounted on a drone is provided with a cover made of glass or transparent plastic so as to cover the lens because it is exposed to wind and rain. However, if a liquid such as water droplets or muddy water or a foreign substance adheres to the cover, the liquid or the like may be reflected in the image captured by the camera, and a clear image may not be obtained.

Therefore, a system for removing liquid or foreign matter by vibrating the cover when liquid or foreign matter adheres to the dome-shaped cover, such as the surveillance camera system described in Patent Document 1, is being studied.

The magnitude of vibration of the cover varies depending on the location, and the effect of removing droplets is high in locations with large vibration. For this reason, the present inventors have devised to form a droplet removal region on the surface of the cover where the vibration is greatest. It was also found that the effect of removing droplets differs depending on the surface condition of the cover. The surface state of the cover is, for example, the water contact angle on the surface of the cover, and the present inventors have investigated a method of optimizing the water contact angle of the droplet removal region and removing droplets more efficiently. , The following inventions have been reached.

According to this configuration, the droplets adhering to the translucent body cover can be efficiently removed.

The droplet removal region may include at least the central portion of the translucent body cover.

According to this configuration, the droplet removal region can be arranged in the central portion of the translucent body cover having a high effect of removing droplets by vibration, and the droplets can be removed more efficiently.

The water contact angle of the droplet removal region may be 50 ° or more.

According to this configuration, the time required for removing droplets can be shortened.

The water contact angle of the droplet removal region may be 110 ° or less.

According to this configuration, the time required for removing droplets can be further shortened.

The droplet removal region may have a water-repellent coating layer formed on the surface of the translucent cover.

The water-repellent coating layer may be formed of a fluororesin or a silicon resin.

According to this configuration, a water-repellent coating layer can be easily formed from a fluororesin or a silicon resin.

The droplet removal region may have a plurality of protrusions formed on the surface of the translucent body.

According to this configuration, since a plurality of protrusions are formed on the surface of the translucent body cover, deterioration during use such as an increase in the water contact angle can be suppressed.

The translucent body cover may have a hydrophilic region having a lower water contact angle than the droplet removing region around the droplet removing region.

According to this configuration, droplets can be easily removed by setting a portion having a low effect of removing droplets due to vibration as a hydrophilic region.

The hydrophilic region may have a hydrophilic coating layer on the surface of the translucent cover.

According to this configuration, the hydrophilic region can be easily formed by the coating agent.

The hydrophilic coating layer may be formed of at least one of alkoxysilane, polyethylene glycol, photocatalyst, and organosiloxane.

further,
A discharge unit that is controlled by the control unit and discharges at least one of a cleaning liquid and a coating agent onto the surface of the translucent cover.
May be provided.

According to this configuration, cleaning can be performed by discharging a cleaning liquid onto the surface of the translucent body cover. In addition, a coating agent can be applied to maintain a water-repellent or hydrophilic effect.

The imaging unit of the present invention
With the above-mentioned droplet removal device,
An image sensor arranged inside the droplet removing device and
May be provided.

According to this configuration, droplets and / or foreign matter adhering to the translucent body cover can be efficiently removed, so that it is possible to prevent the field of view of the image sensor from becoming unclear due to raindrops, muddy water, or the like.

Hereinafter, Embodiment 1 according to the present invention will be described with reference to the accompanying drawings. Further, in each figure, each element is exaggerated for easy explanation.

(Embodiment 1)
FIG. 1 is a perspective view showing a configuration of an imaging unit 100 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the imaging unit 100 of FIG. FIG. 3 is a block diagram for explaining the control of the image pickup unit 100 of FIG. FIG. 4 is an enlarged view of a part of the translucent body cover 2 arranged in the droplet removing device 200 of the imaging unit 100 of FIG.

[overall structure]
As shown in FIGS. 1 and 2, the imaging unit 100 includes a droplet removing device 200 and an imaging unit 5 arranged inside the droplet removing device 200. The droplet removing device 200 and the imaging unit 5 are held in the housing 1 to form the imaging unit 100.

As shown in FIG. 2, the image pickup unit 5 is supported by the main body member 4 and is fixed to the base plate 4a fixed to a part of the housing 1. Further, a circuit 6 including an image pickup element is built in the image pickup unit 5. A lens unit 7 including a plurality of lenses 9 is fixed in the imaging direction of the imaging unit 5. The structure of the imaging unit 5 is not particularly limited as long as it can image an imaging object located in front of the lens 9.

The housing 1 is formed in a tubular shape and is made of, for example, metal or synthetic resin. In the present embodiment, as shown in FIG. 1, the housing 1 is formed in a square tubular shape, but it may have another shape such as a cylindrical shape. The base plate 4a is fixed to one end side of the housing 1. Further, on the other end side of the housing 1, the translucent body cover 2 of the droplet removing device 200 is arranged so as to be exposed to the outside.

The droplet removing device 200 is a device that removes droplets and / or foreign matter adhering to the translucent body cover 2 by vibration. In the present embodiment, the droplet means, for example, a liquid deposit such as raindrop or muddy water, and the foreign substance means a solid deposit such as mud. In the droplet removing device 200, the droplets are atomized by vibration, and the foreign matter is shaken off by vibration and removed from the translucent cover 2. In the following description, a case where the droplets are mainly atomized and removed will be described.

The droplet removing device 200 includes a translucent body cover 2, a vibrating unit 12, and a control unit 20 (see FIG. 3). The droplet removing device 200 may further include a ejection unit 3. Each component constituting the droplet removing device 200 will be described below.

<Vibration part>
The vibrating unit 12 vibrates the translucent body cover 2. The vibrating portion 12 has a cylindrical shape. As shown in FIG. 2, the vibrating unit 12 includes a first tubular member 13, a second tubular member 14, and a piezoelectric vibrator 15. In the vibrating unit 12, the piezoelectric vibrator 15 is sandwiched between the first tubular member 13 and the second tubular member 14. In the present embodiment, the first tubular member 13, the second tubular member 14, and the piezoelectric vibrator 15 are each formed in a cylindrical shape.

The piezoelectric vibrator 15 includes two

piezoelectric plates

16 and 17. In the thickness direction of the two

piezoelectric plates

16 and 17, the polarization direction of one piezoelectric plate and the polarization direction of the other piezoelectric plate are opposite to each other. The terminal 18 is sandwiched between the

piezoelectric plates

16 and 17, and the terminal 19 is sandwiched between the piezoelectric plate 16 and the second tubular member 14. That is, the piezoelectric plate 17, the terminal 18, the piezoelectric plate 16, and the terminal 19 are laminated in this order to form the piezoelectric vibrator 15. Therefore, the piezoelectric vibrator 15 is in contact with the first tubular member 13 and the terminal 19 of the piezoelectric vibrator 15 is in contact with the second tubular member 14. It is sandwiched between the tubular member 13 and the second tubular member 14. Further, the piezoelectric vibrator 15 is formed in a ring shape.

The shape of the vibrating portion 12 and each component constituting the vibrating portion 12 is not limited to a cylindrical shape or a ring shape, and may be another shape such as a square cylinder shape. Preferably, a cylindrical, or ring-shaped, shape is used.

The

piezoelectric plates

16 and 17 can be formed of lead zirconate titanate-based piezoelectric ceramics. Further, other piezoelectric ceramics such as (K, Na) NbO _{3 may be used.} Further, a piezoelectric single crystal such as _{LiTaO 3 may be used.}

Electrodes (not shown) are formed on both sides of the

piezoelectric plates

16 and 17. The electrode has, for example, a laminated structure of Ag / NiCu / NiCr. The terminal 18 is arranged so as to be in contact with an electrode formed inside the

piezoelectric plates

16 and 17 in the stacking direction. The terminal 18 can be formed by using any conductive material. As the conductive material, for example, Cu, Al, Ag, or an alloy mainly composed of these can be used.

The first tubular member 13 is fixed to the piezoelectric plate 17 side of the piezoelectric vibrator 15. The first tubular member 13 is made of metal and has conductivity. As the metal forming the first tubular member 13, for example, duralumin, stainless steel, Kovar or the like can be used. Alternatively, the first tubular member 13 may be formed of a conductive semiconductor such as Si.

The second tubular member 14 is arranged on the terminal 18 side of the piezoelectric vibrator 15. The second tubular member 14 is made of metal and has conductivity. As the metal forming the second tubular member 14, for example, duralumin, stainless steel, Kovar or the like can be used. Alternatively, the second tubular member 14 may be formed of a conductive semiconductor such as Si.

By applying an AC electric field between the terminal 18 and the terminal 19, the piezoelectric vibrator 15 can be vibrated vertically or horizontally.

Since the threaded portion 14a is formed on a part of the inner peripheral surface of the second tubular member 14, the first tubular member 13 is screwed into the inside of the second tubular member 14, and the first tubular member 14 is screwed into the first tubular member 14. The member 13 is fixed to the second tubular member 14. Therefore, the first tubular member 13 is pressure-welded to the piezoelectric plate 17 side of the piezoelectric vibrator 15, and a part of the second tubular member 14 is pressure-welded to the terminal 19 side of the piezoelectric vibrator 15.

Therefore, the vibration generated in the piezoelectric vibrator 15 can efficiently vibrate the entire vibrating portion 12. In the present embodiment, the vibrating portion 12 is efficiently excited by the vertical effect or the horizontal effect. The horizontal effect means that stress is generated in the direction perpendicular to the direction of the electric field, and the vertical effect means that stress is generated in the direction parallel to the direction of the electric field.

The second tubular member 14 is provided with a flange portion 14b overhanging to the outside. As shown in FIG. 2, the flange portion 14b is placed and fixed in the recess formed in the housing 1.

Further, a flange portion 14c is provided at an end portion of the second tubular member 14 opposite to the piezoelectric vibrator 15. The portion connected between the flange portion 14b and the flange portion 14c is a thin-walled portion 14d. The thickness of the thin portion 14d is thinner than the thickness of the first tubular member 13. Therefore, when the vibration of the vibrating portion 12 generated by the piezoelectric vibrator 15 is transmitted to the translucent body cover 2, the thin-walled portion 14d functions to convert the vibration mode and expand the vibration.

<Control unit>
The vibrating unit 12 and the discharging unit 3 are controlled by the control unit 20 shown in FIG. The control unit 20 is composed of a CPU (Central Processing Unit) or the like as a control center. Further, the control unit 20 has a ROM (Read Only Memory) for storing a program or control data for operating the CPU, a RAM (Random Access Memory) that functions as a work area of the CPU, and signal consistency with peripheral devices. It has an input / output interface, etc.

<Translucent body cover>
As shown in FIG. 2, the translucent body cover 2 is fixed to the flange portion 14c of the second tubular member 14. The translucent body cover 2 is a cover for protecting the image pickup unit 5 and the lens unit 7 from adhesion of droplets or foreign matter. The translucent body cover 2 is formed by a cover main body 2a and a water-repellent coating layer 21a (see FIG. 4) formed on the surface of the cover main body 2a. In FIG. 2, the water-repellent coating layer 21a is not shown.

The translucent body cover 2 has a hemispherical dome shape and has an opening on the bottom surface 2b. The bottom surface 2b is joined to the flange portion 14c of the second tubular member 14. The translucent body cover 2 and the second tubular member 14 can be joined, for example, by using an adhesive or a brazing material. Alternatively, thermocompression bonding, anode bonding, or the like can also be used.

The image pickup unit 5 and the lens unit 7 are arranged inside the translucent body cover 2, and an external image pickup object is imaged through the translucent body cover 2. The shape of the translucent body cover 2 is not limited to the hemispherical dome shape, and may be, for example, a shape in which cylinders are connected to the hemisphere, a curved shape smaller than the hemisphere, or a shape having a flat surface.

The translucent body cover 2 has translucency as a whole, and in the present embodiment, the translucent body cover 2 has a cover body 2a formed of glass and a water repellent formed on the surface thereof. It has a coating layer 21a. The cover body 2a may be made of synthetic resin, translucent ceramics, or the like. Further, by forming the cover body 2a with tempered glass, it is possible to increase the strength of the translucent body cover 2.

As shown in FIG. 4, the translucent body cover 2 has a droplet removal region 21. The droplet removal region 21 includes the portion of the surface of the translucent body cover 2 that is most vibrated by the vibrating portion 12, which will be described later. On the surface of the translucent body cover 2, the portion having the largest vibration is the portion having the largest vibration displacement (amplitude).

In the present embodiment, the droplet removal region 21 is formed over the entire translucent body cover 2. The droplet removal region 21 does not necessarily have to be formed over the entire translucent body cover 2, and may include at least the central portion of the translucent body cover 2.

The droplet removing region 21 is a region for removing droplets adhering to the surface of the translucent body cover 2 and has water repellency. The droplets are liquid deposits adhering to the translucent body cover 2 that are formed into granular liquid masses due to surface tension. The fact that the droplet removing region 21 has water repellency means that the water contact angle of the surface of the translucent body cover 2 is 50 ° or more in the droplet removing region 21. The water contact angle will be described later. Since the droplet removing region 21 has the water-repellent coating layer 21a, it is possible to realize a water contact angle capable of removing droplets in the droplet removing region 21.

In the present embodiment, the droplet removal region 21 has a water-repellent coating layer 21a formed on the surface of the cover body 2a. The water-repellent coating layer 21a can be formed of, for example, a fluororesin such as PTFE (polytetrafluoroethylene), a silicon resin, or the like. The water-repellent coating layer 21a can be formed by a well-known coating method such as wet coating, vacuum deposition, and sputtering.

FIG. 5 is a schematic view for explaining the water contact angle in the present embodiment. In the present embodiment, the water contact angle θ is an angle when 2 μl of water droplet L is attached to the surface (droplet removal region 21) of the translucent body cover 2. When the surface of the transparent body cover 2 by adhering water droplets L, the tangent T ₁ drawn on the surface of the water droplet L from the portion in contact and the water droplet L and the transparent body cover 2, the surface of the transparent body cover 2 The angle θ with the drawn tangent T ₂ is the water contact angle.

In the present embodiment, the water contact angle of the droplet removal region 21 is 50 ° or more. More preferably, the water contact angle of the droplet removal region 21 is 50 ° or more and 110 ° or less.

<Discharge part>
As shown in FIG. 2, the discharge unit 3 has a cleaning nozzle 31 and an opening 32 provided in the housing 1 of the imaging unit 100. The discharge unit 3 is controlled by the control unit 20 and discharges at least one of the cleaning liquid and the coating agent to the surface of the translucent body cover 2. The cleaning nozzle 31 and the opening 32 are outside the imaging range (field of view) of the imaging unit 5, and the cleaning nozzle 31 and the opening 32 are arranged at positions where they are not reflected in the image captured by the imaging unit 5. That is, as shown in FIG. 2, the discharge portion 3 is arranged so that the opening 32 of the discharge portion 3 is located in the range R between the bottom surface 2b of the translucent body cover 2 and the top of the translucent body cover 2. It should be done.

When the droplet removing device 200 has the ejection portion 3, for example, when the water-repellent coating layer 21a is peeled off due to aged deterioration due to long-term use, the coating agent is applied from the ejection portion 3 to the translucent body cover 2. Can be sprayed. When spraying the coating agent, it is desirable to reduce the amplitude of vibration by the vibrating portion 12 so that the coating agent does not atomize. Due to the vibration having a small amplitude, the sprayed coating agent stays on the surface of the translucent body cover 2 for a long time without being atomized, so that the coating agent can be easily fixed to the translucent body cover 2.

The peeling of the water-repellent coating layer 21a can be detected by, for example, image processing. When the droplets adhering to the surface of the translucent body cover 2 cannot be completely removed and remain, the image captured by the imaging unit 5 is distorted or the like. For example, the control unit 20 automatically detects the distortion of the image generated at this time, and when the distortion of the image is detected, it is determined that the water-repellent coating layer 21a has peeled off, and the coating agent is automatically used. May be discharged. Alternatively, the coating agent may be discharged periodically.

Further, when dirt containing a solid component such as mud adheres to the translucent body cover 2, the cleaning liquid is discharged from the discharge unit 3 to wash away the solid component adhering to the translucent body cover 2 with the cleaning liquid, and the surface thereof is washed away. The cleaning liquid remaining in the water can be atomized by vibration. Even when dirt containing a solid component adheres to the translucent body cover 2, for example, it may be detected by image processing by the control unit 20 and the cleaning liquid may be automatically discharged.

In the present embodiment, the cleaning nozzle 31 and the opening 32 are arranged so that the cleaning liquid or the coating agent is discharged to the top of the translucent cover 2, but the positions of the cleaning nozzle 31 and the opening 32 are the same. Not limited to. Further, a plurality of cleaning nozzles may be arranged.

In the present embodiment, it is preferable that the discharge portion is arranged so that the cleaning liquid or the coating liquid is discharged near the top of the translucent body cover 2. This is because the coating is easily peeled off in the vicinity of the top of the translucent body cover 2 because the vibration amplitude becomes large, as will be described later.

[motion]
Next, with reference to FIG. 6, the operation of removing the droplets adhering to the translucent body cover 2 by the droplet removing device 200 will be described. FIG. 6 is a flowchart illustrating the operation of the droplet removing device 200.

An AC electric field is applied to the piezoelectric vibrator 15 to drive the piezoelectric vibrator 15. The AC electric field applied to the piezoelectric vibrator 15 is not particularly limited, but a current such as a sine wave sufficient to remove water droplets is applied. When the piezoelectric vibrator 15 is driven, it vibrates due to longitudinal vibration or lateral vibration. Along with this, the vibrating portion 12 having the first tubular member 13 and the second tubular member 14 sandwiching the piezoelectric vibrator 15 vibrates due to a vertical effect or a horizontal effect (step S101).

In the present embodiment, the vibrating unit 12 vibrates in the respiratory vibration mode due to the lateral effect. The vibration of the vibrating portion 12 is converted into the bending vibration mode by the thin-walled portion 14d of the second tubular member 14, and the amplitude is expanded and transmitted to the translucent body cover 2. The distribution of the vibration displacement on the surface of the translucent body cover 2 at this time is shown in FIG. 7A. The respiratory vibration mode is a mode in which the ring-shaped piezoelectric vibrator 15 naturally vibrates in the radial direction. The bending vibration mode is a mode in which the piezoelectric vibrator 15 vibrates naturally in the thickness direction.

FIG. 7A is a graph showing the distribution of vibration displacement in the translucent body cover 2. FIG. 7B is a diagram illustrating a viewing angle in the translucent body cover 2.

As shown in FIG. 7B, the viewing angle on the horizontal axis of the graph of FIG. 7A indicates the viewing angle of the camera (lens unit 7) when the top of the translucent cover 2 is 0 °. That is, the top of the translucent cover 2 serves as the optical axis of the lens unit 7, and the viewing angle approaches 90 ° from the top of the translucent cover 2 toward the outer periphery. The vertical axis of the graph of FIG. 7A indicates the vibration displacement, that is, the magnitude of the amplitude on the surface of the translucent body cover 2.

From the vibration displacement D shown in the graph of FIG. 7A, the acceleration α for atomizing the foreign matter can be obtained. The acceleration α can be calculated by ^{α = ω 2 × D.} 7A, the maximum acceleration was about 3.5 × 10 ⁵ G. The values of the frequency f and the acceleration α of the piezoelectric vibrator 15 depend on the design of the piezoelectric vibrator 15. Further, the vibration displacement D can be adjusted by the voltage V applied to the piezoelectric vibrator 15. For water contact angle to atomize the foreign matter in the range of less than 110 degrees 50 degrees, may acceleration α is approximately 1 × 10 5 ^G. More preferably, may acceleration α is at 3 × 10 ⁵ G.

In order to realize the above-mentioned value of acceleration α, the frequency f of the piezoelectric vibrator 15 is 20 to 100 kHz, the applied voltage V is 20 to 80 Vpp, the mechanical quality coefficient Q of the piezoelectric vibrator is 40 to 2500, and the piezoelectric vibrator is piezoelectric. It is desirable that the constant d is 7 to 300 pc / N.

As shown in FIG. 7A, the magnitude of vibration on the surface of the translucent body cover 2 is largest in the portion where the viewing angle is 0 °. Here, the magnitude of vibration is the magnitude of vibration displacement (amplitude), and on the surface of the translucent body cover 2, the portion (top) having a viewing angle of 0 ° is the portion having the largest vibration.

On the surface of the translucent body cover 2, the maximum amplitude is not limited to the top portion, but may be other portions. Further, the portion where the magnitude of the amplitude is maximized may differ depending on the shape of the translucent body cover. For example, when the translucent body cover is formed in a flat plate shape, the magnitude of the amplitude may be maximized at the central portion of the translucent body cover.

In the translucent body cover 2, the droplets adhering to the surface move as droplets from the portion where the vibration is small to the portion where the vibration is large (step S102). This is because a larger acceleration acts on a portion having a large amplitude.

The atomized region A (see FIG. 7B) including the portion with the largest vibration is atomized by vibration and removed from the surface of the translucent body cover 2 (step S103). In the above steps, the droplet removing device 200 removes the droplets adhering to the surface of the translucent body cover 2.

Here, the atomized region A of the translucent body cover 2 is, for example, a region in which the viewing angle of the translucent body cover 2 is 0 ° or more and less than 30 °, as shown in FIG. 7B. Further, as shown in FIG. 7B, the region other than the atomization region A is referred to as a movement region B in which the droplet moves toward the atomization region A. In the present embodiment, the droplet removal region 21 includes both the atomization region A and the movement region B, but the droplet removal region 21 may include at least the atomization region A.

In order for the droplets adhering to the translucent body cover 2 to move to the atomization region A or to be atomized in the atomization region A, the energy given to the droplets by vibration is applied to the droplets due to surface tension. It suffices to be greater than the force that tends to stay on the surface of the translucent body cover 2. For that purpose, it is desirable to balance the force of vibration energy and surface tension.

FIG. 8 is a graph showing the relationship between the water contact angle on the surface of the translucent body cover 2 and the time until droplets are removed from the surface of the translucent body cover 2 by vibration. This is a measurement of the time required for the droplets to be removed by vibration by adhering 5 μl of water (droplets) to any five positions on the surface of the translucent body cover 2. In FIG. 8, what is plotted in a circle indicates that all the droplets were atomized at the indicated time. Further, in FIG. 8, what is plotted as a quadrangle indicates that the unatomized droplets remained on the surface of the translucent body cover 2 at the displayed time and were not further atomized. Shown.

As shown in the graph of FIG. 8, when the water contact angle is 50 ° or more and 110 ° or less, the droplets can be atomized about twice as fast as in the case of other water contact angles. You can see that. Therefore, it can be seen that when the water contact angle is 50 ° or more and 110 ° or less, the droplets adhering to the surface of the translucent body cover 2 can be efficiently removed.

When the water contact angle is smaller than 50 °, that is, when the contact area between the droplet and the translucent cover 2 is large, the droplet moves on the surface of the translucent cover 2 although the vibration energy is transmitted to the droplet. The resistance of the time increases. Therefore, when the water contact angle is less than 50 °, it can be seen that the droplets may not be removed to the end.

On the other hand, when the water contact angle is larger than 110 °, that is, when the contact area between the droplet and the translucent cover 2 is small, the vibration energy is not efficiently transmitted to the droplet. Therefore, when the water contact angle is larger than 110 °, it takes time for the droplets to move to the atomization region A, or it takes time for the droplets to atomize in the atomization region A. When the water contact angle is larger than 110 °, it takes time to move the droplet to the atomization region A or atomize in the atomization region A, but the droplet is finally atomized.

Therefore, the droplet removal region 21 should have a water contact angle of 50 ° or more. More preferably, the water contact angle is 50 ° or more and 110 ° or less.

[effect]
According to the droplet removing device 200 and the imaging unit 100 according to the first embodiment, the following effects can be obtained.

The imaging unit 100 includes a droplet removing device 200 and an imaging unit 5. The droplet removing device 200 includes a translucent body cover 2, a vibrating unit 12, and a control unit 20. The translucent body cover 2 has a droplet removing region 21 for removing droplets adhering to the surface, and the droplet removing region 21 covers the portion of the surface of the translucent body cover 2 that is most vibrated by the vibrating portion 12. Including. Therefore, the droplets adhering to the translucent body cover 2 can be efficiently atomized by the vibration of the vibrating unit 12.

Further, since the water contact angle of the droplet removing region 21 is 50 ° or more, more preferably 50 ° or more and 110 ° or less, it is possible to quickly remove the droplets adhering to the translucent body cover 2. is there.

Further, when the droplet removing device 200 further includes the ejection unit 3, for example, when the water-repellent coating layer 21a of the translucent body cover 2 is peeled off, the coating agent is ejected and the water-repellent coating layer 21a is peeled off. Can be repaired. Therefore, deterioration of the function of the water-repellent coating layer 21a can be prevented.

Although the configuration in which the droplet removing device 200 has the ejection unit 3 has been described in the first embodiment, the ejection unit 3 is not an essential configuration in the droplet removing device 200.

FIG. 9 is a diagram showing a modified example of the droplet removing region 21 of the droplet removing device 200 according to the first embodiment. The droplet removing region 21 may have a plurality of protrusions formed on the surface of the cover body 2a instead of the water-repellent coating layer 21a described in the first embodiment. For example, as shown in FIG. 9, the surface of the cover main body 2a may be regularly provided with irregularities having a size (for example, a diameter or a side length) of about several μm. In this case, the size and height of the concave portion and the convex portion are both preferably about several μm. By forming the plurality of protrusions in this way, it is possible to realize a water contact angle capable of removing droplets.

(Embodiment 2)
The droplet removing apparatus according to the second embodiment of the present invention will be described.

The second embodiment mainly describes the differences from the first embodiment. In the second embodiment, the same or equivalent configurations as those in the first embodiment will be described with the same reference numerals. Further, in the second embodiment, the description overlapping with the first embodiment is omitted.

The second embodiment is different from the first embodiment in that the translucent body cover 24 has a hydrophilic region 22 having a water contact angle lower than that of the droplet removing region 21 around the droplet removing region 21. Other configurations are the same as those of the droplet removing device 200 and the imaging unit 100 described in the first embodiment.

FIG. 10A is an enlarged cross-sectional view of a part of the translucent body cover 24 arranged in the droplet removing device according to the second embodiment. FIG. 10B is a view of the translucent body cover 24 of FIG. 10A viewed from another angle. As shown in FIGS. 10A and 10B, the translucent body cover 24 has a hydrophilic region 22 around the droplet removing region 21 having a lower water contact angle than the droplet removing region 21. The hydrophilic region 22 has a hydrophilic coating layer 22a. The hydrophilic coating layer 22a can be formed of, for example, alkoxysilane, polyethylene glycol, a photocatalyst (TiO ₂ ), organosiloxane, or the like. The hydrophilic coating layer 22a can be formed by a well-known coating method such as wet coating, vacuum deposition, and sputtering.

As shown in FIG. 7A described above, the vibration displacement by the vibrating portion 12 becomes small in the portion where the viewing angle of the translucent body cover 24 is close to 90 °. Therefore, in the portion where the viewing angle of the translucent body cover 24 is close to 90 °, the effect of removing droplets by vibration is reduced. Therefore, in the present embodiment, the droplet removing region 21 is formed in the central portion of the translucent body cover 24 having a small viewing angle, and the hydrophilic region 22 is formed around the droplet removing region 21 having a large viewing angle. ..

Since the hydrophilic region 22 has a lower water contact angle than the droplet removal region 21, the attached droplets spread like a film in the hydrophilic region 22. Therefore, the outflow of droplets can be promoted in the hydrophilic region 22. Further, since the droplets spread like a film, it is possible to suppress the occurrence of distortion of the image captured by the imaging unit 5 even when the droplets remain in the hydrophilic region 22.

[effect]
According to the droplet removing device according to the second embodiment, the following effects can be obtained.

The translucent body cover 24 has a hydrophilic region 22 having a lower water contact angle than the droplet removing region 21 around the droplet removing region 21. The hydrophilic region 22 is formed in the translucent body cover 24 at a portion where the effect of removing droplets due to vibration of the vibrating portion 12 is low. Therefore, in the hydrophilic region 22, distortion in the captured image can be suppressed by spreading the attached droplets like a film.

Further, since the translucent body cover 24 has the hydrophilic region 22, it is possible to promote the outflow of droplets that cannot be completely removed by vibration.

In the second embodiment, the configuration in which the hydrophilic region 22 has the hydrophilic coating layer 22a has been described, but the present invention is not limited to this.

FIG. 11 is an enlarged cross-sectional view of a part of the translucent body cover 25 of the modified example of the droplet removing device according to the second embodiment. As shown in FIG. 11, the hydrophilic region 22 may not have the hydrophilic coating layer 22a formed. In the present embodiment, the cover body 2a of the translucent body cover 25 is made of glass. Generally, since the surface of the glass has a low water contact angle, the water contact angle is lower than that of the droplet removal region 21 even if the hydrophilic coating layer 22a is not formed. Therefore, the water-repellent coating layer 21a of the droplet removal region 21 or the region where a plurality of protrusions are not formed can be designated as the hydrophilic region 22.

The imaging unit and the droplet removing device of the present invention can be applied to an in-vehicle camera, a surveillance camera, or an optical sensor such as LiDAR used outdoors.

2, 24, 25 Translucent body cover 3 Discharge unit 5 Image pickup unit (image sensor)
12 Vibration unit 20 Control unit 21 Droplet removal area 21a Water-repellent coating layer 22 Hydrophilic area 22a Hydrophilic coating layer 100 Imaging unit 200 Droplet removal device

Claims

With a translucent cover,
The vibrating part that vibrates the translucent cover and
A control unit that controls the vibrating unit and
With
The translucent cover has a droplet removal region for removing droplets adhering to the surface of the translucent cover.
The droplet removal region includes the portion of the surface of the translucent body cover that is most vibrated by the vibrating portion.
Droplet remover.
The droplet removal region includes at least the central portion of the translucent cover.
The droplet removing device according to claim 1.
The droplet removal region has a water contact angle of 50 ° or more.
The droplet removing device according to claim 1 or 2.
The droplet removal region has a water contact angle of 110 ° or less.
The droplet removing device according to claim 3.
The droplet removal region has a water repellent coating layer formed on the surface of the translucent cover.
The droplet removing device according to any one of claims 1 to 4.
The water-repellent coating layer is made of a fluororesin or a silicone resin.
The droplet removing device according to claim 5.
The droplet removal region has a plurality of protrusions formed on the surface of the translucent cover.
The droplet removing device according to any one of claims 1 to 4.
The translucent cover has a hydrophilic region around the droplet removal region, which has a lower water contact angle than the droplet removal region.
The droplet removing device according to any one of claims 1 to 7.
The hydrophilic region has a hydrophilic coating layer on the surface of the translucent cover.
The droplet removing device according to claim 8.
The hydrophilic coating layer is formed of at least one of alkoxysilane, polyethylene glycol, photocatalyst, or organosiloxane.
The droplet removing device according to claim 9.
further,
A discharge unit that is controlled by the control unit and discharges at least one of a cleaning liquid and a coating agent onto the surface of the translucent cover.
To prepare
The droplet removing device according to any one of claims 1 to 10.
The droplet removing device according to any one of claims 1 to 11.
An image sensor arranged inside the droplet removing device and
To prepare
Imaging unit.