Patent Description:
<CIT> describes an imaging device including an image sensor, a lens, a control module designed to trigger a plurality of shots by the image sensor at successive instants, so as to acquire a respective plurality of images having a given spatial resolution, and an analysis module designed to produce a super-resolved image presenting a spatial resolution greater than the given spatial resolution of the separate images.

<CIT> discloses a shooting method comprising, in response to a shot release: - the capture of a first image, according to a first shooting field, using a camera equipped with a variable focus lens set to a first focal length, - the automatic search in the first image of interest zones, and when at least one interest zone is found, - the automatic modification of the focal length to tighten the shooting field around the interest zone, - the automatic capture of at least one second image according to the tightened shooting field, and - the automatic creation of a composite image by combining the first image and the second image.

<CIT> discloses a variable focus lens comprising a chamber filled with a first liquid, a drop of a second liquid being disposed at rest on a region of a first surface of an insulating wall of the chamber, the first and second liquids being non miscible, of different optical indexes and of substantially same density. The first liquid is conductive and the second liquid is insulating. The lens further comprises means for applying a voltage between the conductor liquid and an electrode placed on the second surface of said wall; and centering means for maintaining the centering of the edge of the drop while the voltage is applied and for controlling the shape thereof.

<CIT> describes a 3D image capture apparatus that uses digital images of an object from multiple view points, which can be used to generate a 3D image of the object. The apparatus includes an image sensor, a lens adjacent the image sensor, and an active optical component adjacent the lens and opposite the image sensor. An aperture component is located between the active optical component and the lens, and the aperture component has an aperture for allowing passage of light to the image sensor. The active optical component is changeable between first and second shapes. The first shape provides a first optical wavefront through the aperture and lens to the image sensor from a first view angle of an object, and the second shape provides a second optical wavefront through the aperture and lens to the image sensor from a second view angle of the object. The second optical wavefront is shifted by the active optical component on the image sensor with respect to the first optical wavefront in order to provide multiple view-angle images along a single optical channel.

<CIT> describes a network camera and a photographing method thereof. The network camera includes a lens module comprising a plurality of lenses having incident paths different from each other, a prism reflecting light incident through the lens module, a prism driving module rotating the prism, and a controller controlling the prism through the prism driving module. The prism reflects lights incident through the incident paths different from each other by performing a rotation operation according to a control of the prism driving module.

<NPL> describes a tunable wedge prism by electrowetting actuation. The prism can shift the field of view to the left or to the right and is useful for small cameras and endoscopes because its field of view can be changed without the need for large instruments. It consists of two plates that face each other, and a liquid is sandwiched between them. The liquid and plates form a wedge when the angle between the plates is changed. Electrowetting is used to change the angle between the plates. The wedge prism is small because the liquid driven by electrowetting works as a prism. In addition, the prism produces a clear field of view because its optical flatness is determined by the flatness of the plates.

The present invention is defined by independent claim <NUM>. Particular embodiments are defined in the dependent claims.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

Automotive cameras are used for a wide variety of functions in a vehicle. Such uses include control of vehicle equipment to supplementing a driver's vision of the environment surrounding the vehicle. Cameras that supplement a driver's vision include rearward-facing cameras such as a camera for a reverse camera display (RCD) system and a camera for a full display mirror (FDM) system. Cameras for RCD systems and FDM systems may be aimed in approximately the same direction but have different fields of view (FOV) and focal points. Thus, in a vehicle that provides both RCD and FDM systems, two cameras have been mounted to the rear of the vehicle with each camera providing images for different ones of the two systems.

Automotive cameras tend to be much lower resolution than consumer products due to reliability requirements. For example, the latest automotive-grade parts are 2MP, with recent announcements of <NUM>. 5MP sensors coming in <NUM>. The reason for the increase in resolution is to handle the NCAP requirements for <NUM> in Europe where forward-facing sensors must have enough resolution to see pedestrians at the side of the vehicle and still have enough resolution in the center. A similar problem exists in the rearward direction where requirements of <NUM> ppi over <NUM> degrees, with <NUM> pixels wide, implies a 24MP sensor necessary for <NUM>° FOV surround system with a standard fixed-focus lens. Thus, digital high definition (HD) cameras have been used to provide these higher resolutions. However, these digital HD cameras require expensive serializer/deserializer pairs and associated connectors (coaxial connectors). As used herein an HD camera/image sensor has a signal to noise ratio of at least about 90dB.

The inventors have discovered that by using a variable focus lens, the wide FOVs desired for some automotive applications can be obtained while using a camera with a lower resolution. Thus, an analog HD camera isused with a variable focus lens. Analog HD cameras provide the benefit of not requiring expensive serializer/deserializer pairs and associated connectors of their digital counterparts. Thus, less expensive twisted pair cables and conventional crimp and snap connector systems may be used. A suitable analog encoder is available from Techpoint Inc. of San Jose, California.

<FIG> shows an example of an imaging system <NUM> having a HD image sensor <NUM>, a variable focus lens such as an electrowetting lens <NUM> positioned in front of the image sensor <NUM> and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor <NUM>, and a controller <NUM> coupled to the variable focus lens <NUM> and configured to select a field of view of the image sensor <NUM> by selecting the electrical stimulus to be applied to the variable focus lens <NUM>. The variable focus lens <NUM> may also be used for auto-focusing.

The variable focus lens <NUM> may take any form known in the art including the forms shown in <FIG> and <FIG>. In general, as shown in <FIG>, the variable focus lens <NUM> is an electrowetting lens, which includes an oil lens <NUM> that may take various shapes to form a variable lens in response to the application of an electrical stimulus such as the application of a selected voltage to one or more electrodes <NUM> within the electrowetting lens <NUM>. The lens <NUM> may include two glass substrates 35a and 35b that combine with electrodes 34a, 34b and insulating member 36a to form a chamber in which the oil lens <NUM> is disposed. The remainder of the chamber in which the oil lens <NUM> is located is filled with another fluid such as water <NUM> that does not mix with the oil lens <NUM>. Note that the electrode 34b that contacts the oil lens <NUM> may be coated with an insulator material. <FIG> show three examples of the shapes the oil lens <NUM> may form in response to two different voltages applied to electrodes 34a and 34b. In <FIG>, the oil lens <NUM> takes the shape of a convex glass lens and the electrowetting lens <NUM> functions as a bi-convex lens. In <FIG>, the oil lens <NUM> takes the shape of a concave glass lens and the electrowetting lens <NUM> functions as a bi-concave lens. In <FIG>, the oil lens <NUM> takes a tilted or rotated shape so that the electrowetting lens <NUM> shifts the field of view to one direction (i.e., left, right, up, or down). By changing the shape of oil lens <NUM>, the focal length may be changed as may the direction of the optical axis. When placed in front of an image sensor <NUM>, the electrowetting lens <NUM> may be used to change the field of view of the image sensor <NUM> as well as to pan the field of view across the imaging surface of the image sensor <NUM>. Such a capability would provide many advantages in imaging systems used in vehicles as well as in security cameras and mobile devices, such as smartphones, notebooks, and laptop computers.

The electrowetting lens 30a shown in <FIG> is similar to that shown in <FIG> except that the configuration of electrode 34b is different and rear glass substrate 35b includes a spherical recess with the electrode 34b coated over the entire surface of substrate 35b. An insulating layer 36b is provided across the entire surface of electrode 34b and fills the electrode-coated spherical recess in substrate 35b. Further, an annular glass ring 35c may be provided about the periphery of the chamber between substrates 35a and 35b. In this lens configuration, a drop of oil is centered by a gradient in the electric field applied through electrodes 34a and 34b to form oil lens <NUM>.

One example of an application for imaging system <NUM> not encompassed by the claimed invention would be a rear vision camera 10a of a vehicle <NUM> as shown in <FIG>. In this application, the field of view 15a of the rear vision camera 10a could be dynamically changed without reducing the resolution of the image output from the rear vision camera 10a. For example, the field of view could be shifted to keep the image of any detected vehicle within the image. Further, the field of view could be widened or narrowed as shown in <FIG> depending upon whether the vehicle was in reverse (for RCD) or driving forward (for FDM), or depending upon the forward speed of the vehicle or the type of road upon which the vehicle is traveling. Thus, a single camera may be used for both RCD and FDM applications. Note that the rear vision camera 10a may be located at the rear of the vehicle or at the sides of the vehicle as cameras 10a' and 10a" with respective variable fields of view 15a' and 15a". The images captured by the rear vision cameras 10a, 10a', and 10a" may be displayed on a display located in the rearview mirror <NUM> or other location in the instrument panel or console. Additionally or alternatively, the images may be processed for use in autonomous vehicle control or a driver assist function, such as parking assist, blind spot detection, rear collision warning, lane departure warning, lane keeping assist, etc..

Another example of a vehicle application for imaging system <NUM> not encompassed by the claimed invention would be as a forward vision camera 10b as shown in <FIG>. Such forward vision cameras 10b may be mounted at or near the rearview mirror <NUM> to capture images forward of the vehicle through its windshield. Images captured by the forward vision camera 10b may be used for a number of different driver assist functions or autonomous vehicle control functions. For example, the images may be used for headlamp control, lane departure warning, parking assist, adaptive cruise control, lane keeping assist, forward collision warning, object detection, pedestrian detection, and traffic sign recognition. However, it may be desirable to use a wider or narrower field of view 15b for each of these functions so as to limit the information in the captured images to that information that is relevant for the particular function. Accordingly, the provision of the electrowetting lens <NUM> in a forward vision camera 10b provides the advantage of changing the field of view for a selected function without a loss in resolution. Further, the ability of the electrowetting lens to shift the field of view 15b left or right allows the forward vision camera 10b to look in the direction of an upcoming turn.

When used for headlamp control, the forward vision camera 10b may advantageously maintain a high pixel count per degree of field of view when the field of view is narrowed to focus on distant objects. This allows for more accurate detection of vehicles and other objects at greater distances. Likewise, the field of view may be changed to look ahead in the direction of an upcoming turn so that vehicles on the turn may be detected more quickly and accurately.

Another example of a vehicle application for imaging system <NUM> according to the claimed invention is an interior vision camera 10c as shown in <FIG>. Such interior vision cameras 10c may be mounted at or near the rearview mirror <NUM>, an upper console, or reading light assembly in order to capture images inside the vehicle and display the images to the driver or other occupants. For example, such a camera 10c may be mounted to view back seat passengers and display the images to the driver on a display that may be mounted in the rearview mirror <NUM> or other location in the instrument panel or console. This is particularly useful if one of the passengers is a baby and even more advantageous if the baby is in a car seat facing rearward. By employing an electrowetting lens in the interior vision camera 10c, the field of view 15c may be shifted around the interior of the vehicle so as to view a particular passenger or location in the vehicle. The field of view 15c may also be widened or narrowed to capture front seat passengers or focus on rear seat passengers. Such a change in the field of view 15c is effectuated by automated control. Automated control may be used for video conferences so as to shift the field of view to whichever vehicle occupant is speaking.

By using the variable focus lens <NUM> in imaging systems <NUM> used in a vehicle, one can avoid having to only rely upon digital zooming for changing a field of view, which results in a reduction in the resolution of the images captured by the system. Further, to the extent one intends to avoid this by providing a mechanical zoom lens, such a mechanical zoom lens is much more complex to make and subject to breakage.

If the variable focus lens <NUM>, 30a was oscillated between two or more images or fields of view, a first image stream having a first field of view could be supplied to a first display 50a and a second image stream having a different second field of view may be supplied to a second display 50b and thus two or more different image streams could be captured and displayed in real time. The different image streams could also be displayed in different display areas of one display 50a. Using one camera to collect multiple images is an advantage over using multiple cameras. For example, if the camera was set to oscillate between two images at <NUM>, one could update two different images on two different displays or two different display zones at <NUM>.

The imaging system <NUM> may also find advantageous application in security cameras, particularly for those applications where two separate image sensors are used to capture retinal images of both a person's eyes. By using the electrowetting lens <NUM>, the field of view may be shifted from one eye to the other and thereby eliminate the need for two separate cameras. Further, the field of view may be initially set to wide to capture a person's face and identify the location of their eyes and then zoom in on each eye. This would make it more practical to implement biometric screening security measures (particularly retinal imaging) in mobile devices, which typically only have one camera aimed in any one direction.

Security cameras having an electrowetting lens with a variable field of view may be used in home security systems as well as in smoke detectors and strobe light fixtures. Similarly, a vehicle camera such as camera 10c may be used for security purposes to scan the irises of the driver prior to starting the vehicle. The imaging system may also be used for scanning of a person's face for a facial recognition system.

Although imaging system <NUM> is shown as having just an electrowetting lens <NUM> in front of image sensor <NUM>, additional conventional lenses may be used in combination with the electrowetting lens <NUM> to obtain the desired fields of view and focus. Further, other forms of variable focus lenses may be used in combination with the HD image sensor <NUM>. An example of an electrowetting lens that may be used is available from Invenios of Santa Barbara, California. Such a lens can provide a <NUM>° FOV for RCD applications and a <NUM>° FOV for FDM applications with crisp images.

It should further be noted that the controller <NUM> may include various forms of control logic and image processing circuitry. In order to properly handle both FDM and RCD FOVs, a dewarp engine may be provided in controller <NUM>. In order to use an analog HD image sensor <NUM>, one may want to lower the resolution transmitted so that image signal processing (ISP) may be performed in the camera module (HDR reconstruct, windowing, etc.). Therefore, an ISP processor with dewarp, e.g. GEO Semi GW5, may be provided in the camera module portion of the imaging system <NUM>, which would include HD image sensor <NUM>, variable focus lens <NUM>, and controller <NUM>, with an analog output from the camera.

Claim 1:
A vehicle comprising an imaging system (<NUM>), the imaging system (<NUM>) comprising:
an image sensor (<NUM>);
an electrowetting lens (<NUM>; 30a) positioned in front of the image sensor (<NUM>) and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor; and
a controller (<NUM>) coupled to the electrowetting lens (<NUM>; 30a) and configured to select a field of view (15c) of the image sensor (<NUM>) by selecting the electrical stimulus to be applied to the electrowetting lens (<NUM>; 30a),
the imaging system (<NUM>) characterized in that the imaging system (<NUM>) is an interior vision camera (10c) of the vehicle, wherein the controller (<NUM>) selects two different electrical stimuli so as to alternate the field of view of the image sensor (<NUM>) back and forth to obtain a first image stream with a first field of view and a second image stream with a second field of view,
wherein the controller (<NUM>) either supplies the first image stream to a first display (50a) and supplies the second image stream to a second display (50b), or supplies the first image stream and the second image stream to the first display (50a) to be displayed simultaneously in different display areas of the first display (50a),
wherein the interior vision camera (10c) is configured to capture images inside the vehicle and to display the first image stream and the second image stream to a driver or occupants of the vehicle, and
wherein a change in the field of view (15c) is effectuated by automatic control.