JP5948781B2 - Camera with water drop removal function - Google Patents

Description

  The present invention relates to a water droplet removal technique for a camera used outdoors.

  In recent years, cameras used outdoors such as in-vehicle cameras and security cameras are increasing. There is a possibility that water drops such as rain may adhere to these cameras used outdoors, and if water drops adhere to the lens, an image of sufficient quality cannot be taken. Various techniques have been proposed to solve this problem.

  For example, Patent Document 1 describes a technique in which hydrophilic processing is performed on an upper portion of an outer surface of a camera lens and water repellent processing is performed on a lower portion. When raindrops hit this lens, most of the raindrops hit the upper part of the lens subjected to the hydrophilic treatment, and the raindrops flow downward and are repelled by the lower part of the lens subjected to the water repellent treatment. This prevents raindrops from adhering to the lens surface.

  Patent Document 2 discloses a technique for directly joining a disk-shaped or ring-shaped piezoelectric member to the inner surface of a camera lens. In the technique of Patent Document 2, the lens is vibrated in the optical axis direction by vibrating the piezoelectric element, and water droplets attached to the lens are removed.

  As a technique for removing water droplets directly attached to the lens, for example, Patent Document 3 discloses a technique in which a lens washer that injects a cleaning liquid onto the lens surface and an air injection mechanism that injects air are provided. . In the technique of Patent Document 3, when a predetermined condition is satisfied, a lens washer and an air injection mechanism are activated, and the cleaning liquid and air directly act on the water droplets adhering to the lens surface to remove the water droplets.

JP 2009-265473 A JP 2007-082062 A JP 2009-220719 A

  When the lens is subjected to a hydrophilic treatment as in the technique of Patent Document 1 described above, small mist-like water droplets may penetrate the lens, and if the amount of raindrops is large, the water droplets may become large.

  On the other hand, in the technique of Patent Document 2, since the water droplets are shaken off by applying vibration to the lens, it is considered that the ability of removing water drops is higher than that of the technique of Patent Document 1. However, in Patent Document 2, a disk-shaped or ring-shaped piezoelectric element is used, and in the case of a disk-shaped piezoelectric element, there is a possibility that the image taken because light passes through the piezoelectric element may be distorted. In the case of a piezoelectric element having a shape, there is a problem that the manufacturing cost increases. Furthermore, since the vibration direction of the lens is the optical axis direction, there is a possibility that sufficient force does not act on the water droplets.

  On the other hand, in the technique of Patent Document 3, since the cleaning liquid and air are directly applied to the water droplets, it is considered that the ability of removing the water droplets is higher than the techniques of Patent Documents 1 and 2. However, in the technique of Patent Document 3, it is necessary to provide a special mechanism such as a lens washer or an air injection mechanism, which increases the manufacturing cost. In addition, since an operation such as lens cleaning is performed only when a predetermined condition is satisfied, there is a possibility that water droplets or the like may penetrate into the lens and be difficult to remove.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a camera with a water droplet removal function that can remove water droplets attached to a lens with a simple structure.

In order to solve the above problems, a camera with a water droplet removal function according to the present invention includes an imaging unit including a lens, a lens holder that holds the lens , and an imaging device that photoelectrically converts light transmitted through the lens, and power feeding A vibration unit that is connected to a circuit and vibrates the entire imaging unit in a direction in which the optical axis of the lens swings; and the vibration unit based on a frequency that is set according to the size of a foreign substance attached to the lens. And a controller for controlling the power feeding circuit so as to drive.

  In this configuration, the imaging unit is configured to vibrate in the direction in which the optical axis of the lens is swung. That is, the imaging unit vibrates in a state of swinging. Due to this vibration, water droplets attached to the surface of the lens can be shaken off. In addition, since the entire imaging unit is vibrated, the positional relationship between the lens and other engineering components can be prevented from shifting compared to the case where only the lens is vibrated.

  As described above, in order to shake the image pickup unit and drop the water droplets, it is desirable to increase the amplitude of the vibration. Therefore, in one of the preferred embodiments of the camera with a water droplet removal function of the present invention, the imaging unit includes an imaging device, and the fulcrum of the swing is retracted to the imaging device side from the center of the lens. Is set to

  In one preferable embodiment of the camera with a water droplet removal function of the present invention, the vibration unit causes the imaging unit to have different accelerations in a first direction and a second direction opposite to the first direction. Swing with.

  If the acceleration when swinging in the first direction is larger than the acceleration when swinging in the second direction, the acceleration in the first direction is large enough to shake off water droplets attached to the lens surface. It is desirable that the acceleration in the direction is set to a magnitude that allows the water droplets attached to the lens surface to move in the first direction. When the acceleration is set in this way, when the imaging unit is swung in the second direction, water droplets attached to the lens surface move in the first direction. Thereafter, when the imaging unit is swung in the first direction, water droplets gathered in the first direction are shaken off. At this time, if the action of gravity is taken into consideration, it is preferable that the first direction and the second direction be the vertical direction with respect to the direction of gravity. Further, the vibration unit may be configured by a plurality of vibration members, and the plurality of vibration members may be connected to the power feeding circuit, respectively.

It is a perspective view of the vehicle carrying the camera with a water droplet removal function of this invention. It is a schematic diagram of the principal part side cross section of the camera with a water droplet removal function of this invention. It is a figure showing the time change of the voltage applied to a piezoelectric element. It is a figure which shows arrangement | positioning of the piezoelectric element in another embodiment.

〔Constitution〕
The camera with a water droplet removal function of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a vehicle V equipped with a camera with a water droplet removal function of the present invention. The vehicle V is equipped with a camera with a water droplet removal function of the present invention as a rear camera C that captures the rear of the vehicle V. The rear camera C has its optical axis directed downward (for example, 30 ° downward from the horizontal) above the license plate behind the vehicle V and at a position offset laterally from the central axis in the left-right direction of the vehicle V. is set up. The rear camera C includes, for example, a wide-angle lens with a viewing angle of 110 to 120 °, and can capture an area up to about 8 m behind the vehicle V. In the present embodiment, the rear camera C is configured by a digital camera that can capture a two-dimensional image of 15 to 30 frames per second.

  Further, as shown in the figure, a display D for performing various displays is provided in the vehicle V. In the present embodiment, the display D also serves as a monitor device for the navigation system.

  An image photographed by the rear camera C is displayed on the display D and can be used for rearward monitoring of the vehicle V. Further, an image in which an auxiliary line or the like is superimposed can be displayed on the display D and used as a parking assistance image.

  FIG. 2 is a cross-sectional side view of a main part of the rear camera C. As shown in the figure, the rear camera 1 includes an imaging unit 1 that performs imaging and a vibration unit 2 that vibrates the imaging unit 1. The imaging unit 1 includes a lens 11, a lens holder 12 that holds the lens 11, and an imaging element 13 that photoelectrically converts light transmitted through the lens 11. As the image sensor 13, a charge coupled device (CCD), a CMOS image sensor (CIS), or the like can be used.

  The lens 11 is preferably formed by using a water-repellent material rather than applying a water-repellent coating because the coating does not peel off. In addition, raindrops are likely to roll on the surface of the lens 11 and easily fall off due to the vibration of the imaging unit 1 described above.

  The vibration unit 2 vibrates the imaging unit 1 in a direction in which the optical axis of the lens 11 swings. In the present embodiment, the vibration unit 2 includes two piezoelectric elements 2a and 2b, and the piezoelectric elements 2a and 2b are arranged near the upper end and the lower end of the back surface of the imaging unit 1, respectively, as shown in the figure. Yes. Further, the piezoelectric elements 2a and 2b are arranged so as to protrude and retract in the optical axis direction of the lens 11. When voltages periodically changing with respect to the piezoelectric elements 2a and 2b arranged in this way are applied to the positive phase and the reverse phase, respectively, the imaging unit 1 has the optical axis of the lens 11 in the vertical direction (the first of the present invention). And the second direction). At this time, it is preferable that the center of oscillation is positioned rearward (image sensor 13 side) at a predetermined distance from the front-rear direction position of the center of the lens 11 because the amplitude of vibration of the lens 11 is increased.

Although not shown, a power supply circuit that supplies a driving voltage is connected to the piezoelectric elements 2a and 2b, and a control unit that controls a voltage supplied by the power supply circuit is connected to the power supply circuit. . This control unit can be configured by an electronic control unit (ECU) configured with a memory and other peripheral circuits with a central processing unit (CPU) as a core. The control unit may be incorporated in the rear camera C or may be separated from the rear camera C.

(Water drop removal function)
When raindrops or the like hit the surface of the lens 11 (the surface exposed to the outside of the imaging unit 1), water droplets adhere to the surface of the lens 11. With the water droplets attached to the surface of the lens 11 as described above, the water droplets can be shaken off by vibrating the imaging unit 1 so that the optical axis of the lens 11 swings in the vertical direction as described above.

  In the present embodiment, a sawtooth waveform voltage as shown in FIG. 3 is used as the voltage applied to the piezoelectric elements 2a and 2b. Therefore, there is a difference between the acceleration when the piezoelectric element 2a expands and the acceleration when the piezoelectric element 2a contracts. As a result, a difference occurs between the acceleration when the imaging unit 1 swings upward and the acceleration when the imaging unit 1 swings downward.

  In the present embodiment, the acceleration when the imaging unit 1 swings upward is set larger than the acceleration when the imaging unit 1 swings downward. At this time, water droplets adhering to the surface of the lens 11 move downward due to the upward swing of the imaging unit 1, and the water droplets gathered downward due to the downward swing of the imaging unit 1 are shaken. It is preferable to set each acceleration to such an extent that it can be dropped. The acceleration when the imaging unit 1 swings upward may be larger than the acceleration when the imaging unit 1 swings downward.

  According to the research of the inventors of the present invention, it has been found that the ease of dropping of water droplets attached to the lens 11 depends on the frequency of vibration applied to the imaging unit 1 and the size of the water droplets. Therefore, the control part of this embodiment is comprised so that the frequency of the voltage waveform which a electric power feeding circuit supplies can be changed.

  For example, in the case of granular water droplets (large water droplets), since the resonance frequency is low, it is easy to drop when low-frequency vibration is applied to the imaging unit 1. Therefore, in the case of normal rain or the like, the control unit controls the power feeding circuit so as to apply a low-frequency sawtooth voltage.

  On the other hand, in the case of mist-like water droplets (small water droplets), the resonance frequency is high, and even if low-frequency vibration is applied, it is difficult to drop. Further, in the case of mist-like water droplets, the mass is small, so even if a vibration at a resonance frequency is applied, it does not fall as much as granular water droplets. However, when vibration at a resonance frequency is applied to the mist-like water droplets, the water droplets move, and the mist-like water droplets are combined to form a granular water droplet. Therefore, in the present embodiment, when a mist-like water droplet is attached to the lens 11, first, a high-frequency vibration near the resonance frequency of the mist-like water droplet is applied, and then a low-frequency vibration is applied. At this time, vibration that gradually changes from a high frequency to a low frequency may be applied. Thereby, vibration can be effectively applied to water droplets of various sizes.

  It is desirable that the vibration frequency be higher than the frequency that can be perceived by human vision.

  Further, the control unit may perform control so as to change the height of the voltage supplied by the power feeding circuit.

  In the present embodiment, when the driver of the vehicle V operates the touch panel formed on the surface of the display D, the operation content is transmitted to the control unit, and the imaging unit 1 is vibrated. Therefore, a signal line is provided between the control unit and the display D.

  For example, along with the image photographed by the rear camera C on the display D, buttons “large water droplet” and “small water droplet” are displayed. The driver looks at the size of the water droplet in the image and selects “large water droplet” if the water droplet is granular, and selects “small water droplet” if the water droplet is foggy. This selection result is transmitted to the control unit via the touch panel, and when “large water droplet” is selected, the control unit controls the power feeding circuit so as to generate low-frequency vibration. On the other hand, when “small water droplets” is selected, the control unit controls the power feeding circuit to generate low-frequency vibration after high-frequency vibration as described above.

  In the present embodiment, the driver explicitly gives the vibration application. However, it may be configured to recognize the water droplet in the image by image processing and to control the vibration application according to the recognition result. Absent. The image processing at this time may be performed by an image processing circuit incorporated in the rear camera C, or an ECU such as a parking assistance ECU installed in the vehicle V may be used.

  Further, a rain sensor may be provided, and vibration control (voltage control) may be performed according to an output signal of the rain sensor, or control may be performed according to an operating state of a wiper or the like.

[Another embodiment]
(1) In the above-described embodiment, the two piezoelectric elements 2a and 2b are arranged on the back side of the image pickup unit 1 so that the direction of withdrawal is the optical axis direction of the lens 11, but the image pickup unit 1 is vibrated. The configuration is not limited to this, and for example, the following modified configurations are possible.

  (A) The piezoelectric elements 2a and 2b may be provided on the upper surface and the lower surface as shown in FIG. In this case, the piezoelectric elements 2a and 2b are arranged so as to face each other so that the exit / retreat direction is the vertical direction.

  (B) In the above-described embodiment or the configuration of (a), only one piezoelectric element 2a may be provided. In this case, the piezoelectric element 2a and the outer surface of the imaging unit 1 are connected, and the force when the piezoelectric element 2a is advanced and the force when the piezoelectric element 2a is retracted are applied to the imaging unit 1.

  (C) In the above-described embodiment or the configuration of (a), an elastic member may be used instead of the piezoelectric element 2b. In this case, the piezoelectric element 2a applies a force at the time of advancement to the image pickup unit 1, and the elastic member is elastically deformed by the force, and the force is applied to the image pickup unit 1 when elastically restored. Good. In this case, an elastic member having an elastic modulus (spring constant) may be used so that the acceleration when the imaging unit 1 swings downward is larger than the acceleration when the imaging unit 1 swings upward.

  (2) In the above-described embodiment or another embodiment, the entire imaging unit 1 is swung by the piezoelectric element 2a or the like. However, as shown in FIG. 4B, only the lens 11 may be swung. Absent. Also in this case, the same modifications as in the above (a) to (c) are possible. In this case, the positional relationship between the optical axis of the lens 11 and the image sensor 13 is temporarily shifted due to the swinging, so that there is a possibility that the captured image may be distorted. On the other hand, since the force for vibrating the lens 11 is small, there is an advantage that a piezoelectric element that operates at a low voltage can be used.

  (3) In the above-described embodiment or another embodiment, the piezoelectric element 2a or the like is used to swing the lens 11. However, instead of this, a device capable of controlling the exit and withdrawal of an actuator or the like may be used. .

  (4) In the above-described embodiment, the imaging unit 1 is vibrated so that the optical axis of the lens 11 swings in the vertical direction. However, the swinging direction may be other directions such as right and left and diagonal.

  (5) In the above-described embodiment, the imaging unit 1 is vibrated in the direction in which the optical axis of the lens 11 is swung, but may be configured to vibrate in a direction orthogonal to the optical axis of the lens 11.

  (6) Although the present invention is applied to the vehicle-mounted rear camera in the above-described embodiment, it can also be applied to a front camera, a side camera, and the like. Further, the present invention is not limited to an in-vehicle camera, and can be applied to a camera that is installed outdoors and may be exposed to water droplets when exposed to rain or the like.

  The present invention can be applied to an in-vehicle camera, a security camera, or the like that is used outdoors and in which water drops such as rain may adhere.

C: Rear camera (camera with water droplet removal function)
1: Imaging unit 11: Lens 12: Lens holder 13: Imaging device 2: Vibration unit 2a: Piezoelectric element 2b: Piezoelectric element

Claims (5)

An imaging unit having a lens, a lens holder that holds the lens , and an imaging device that photoelectrically converts light transmitted through the lens ;
A power feeding circuit is connected, and a vibration unit that vibrates the entire imaging unit in a direction in which the optical axis of the lens swings;
A camera with a water droplet removal function, comprising: a control unit that controls the power feeding circuit so that the vibration unit is driven based on a frequency set in accordance with a size of a foreign substance attached to the lens. Before fulcrum of KiYurado is, the lens according to claim 1 water droplet removal function with a camera according set in the retracted position to the imaging element side than the center of.   3. The camera with a water droplet removal function according to claim 1, wherein the vibration unit swings the imaging unit at a different acceleration in a first direction and a second direction opposite to the first direction.   The camera with a water droplet removal function according to claim 3, wherein the first direction and the second direction are vertical directions with respect to the direction of gravity.   The camera with a water droplet removal function according to any one of claims 1 to 4, wherein the vibration unit includes a plurality of vibration members, and each of the plurality of vibration members is connected to the power feeding circuit.

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