Patent Application
20180054569
This disclosure generally relates to a dual-focus camera, and more particularly relates to equipping the camera with a negative-meniscus-lens configured to focus a portion of an image at a distance independent from the distance at which the remainder of the image is focused.
It is known to install a camera behind a windshield of a vehicle to view an area proximate to, e.g. forward of, the vehicle to detect objects in or adjacent to the travel-path of the vehicle. It is also known to use camera technology to detect raindrops on a windshield for the purpose of controlling automated windshield wipers. However, since the focus-distance necessary to detect objects is much different than the focus-distance used to detect raindrops on the windshield are so different, the typical solution is to utilize two separate cameras.
In accordance with one embodiment, a dual-focus camera suitable for use on an automated vehicle is provided. The camera includes an imager, a lens-assembly, and a negative-meniscus-lens (NML). The imager is used to detect an image of a field-of-view. The lens-assembly is used to direct the image from the field-of-view toward the imager. The lens-assembly is characterized as focused at a first-distance in the field-of view. The negative-meniscus-lens is interposed between the imager and the lens-assembly. The negative-meniscus-lens is configured to focus a portion of the image onto the imager. The portion is characterized as less than a whole of the image and focused at a second-distance in the field-of-view independent from the first-distance.
Further features and advantages will appear more clearly on a reading of the following detailed description of the preferred embodiment, which is given by way of non-limiting example only and with reference to the accompanying drawings.
The present invention will now be described, by way of example with reference to the accompanying drawings, in which:
The camera 20 also includes a lens-assembly 26 used to direct the image 24 from the field-of-view 14 toward the imager 22. The lens-assembly 26 may be any of many types of commercially available lens-assemblies known to be suitable for this application, having relatively few or numerous lens elements. In general, for the application suggested by
As previously mentioned, camera based technology is used by various vehicle safety systems to detect objects proximate to a vehicle, and by automated wiper systems to detect raindrops on the windshield 12 of the vehicle. Prior solutions for image detection at such disparate ranges (e.g. 35 m for object detection and 25 mm for raindrop detection) required two cameras. However, the camera 20 described herein is able to do both tasks because the camera 20 is equipped with a negative-meniscus-lens 30, hereafter referred to as the NML 30, which is interposed between the imager 22 and the lens-assembly 26. The NML 30 is generally configured to focus a portion 32 of the image onto the imager 22, where the portion 32 is characterized as less than a whole of the image 24. Furthermore, the portion 32 is characterized as focused at a second-distance 34 in the field-of-view 14 independent from the first-distance 28. For example, the second-distance 34 may be twenty-five millimeters (25 mm) so raindrops on the windshield 12 while the first-distance 28 may be thirty-five meters, as previous suggested. As used herein, the term negative-meniscus-lens is used to indicate any type of an optical-element design or a lens-element that could be interposed between the lens-assembly 26 and the imager 22 that could effectively change the focus-distance of the lens-assembly 26 from the first-distance 28 to the second-distance 34.
In one embodiment, the NML 30 is configured to have a fixed focal-length, i.e. is not adjustable. It is recognized in view of the image 24 that having a fixed focal-length may make it difficult to detect, identify, and/or classify distant objects within the portion 32. However, it is contemplated that distance objects in the remainder 38 may be readily detected, identified, and/or classified, and that objects moving through the remainder 38 toward the portion 32 may be detected by safety system more quickly than would be the case if the portion 32 occupied the entire image as is the case when a camera is only used for raindrop detection, i.e. when all of the field-of-view 14 is focused at the second-distance 34.
Preferably, the NML 30 is configured to have an adjustable focal-length. It is further preferable that the adjustable focal-length is characterized by a range of adjustability, and the range is selected such that the second-distance 34 can be adjusted to be equal the first-distance 28. The technology used to provide for the adjustable focal-length is preferably fast enough so that the variable focus-distance in the portion 32 provided by the NML 30 allows the focus-distance of the portion 32 to be quickly switched between the first-distance and the second-distance so both object detection and raindrop detection can be performed by a single instance of the camera 20.
In order to optimize the detection of the raindrops 36 in the portion 32 and distant objects in the remainder 38, it may be advantageous if the camera 20 includes a filter 42 configured so light that passes through the NML 30 is filtered different from light that does not pass through the negative-meniscus-lens. By way of example and not limitation, it may be preferable if the filter 42 for light from the portion that passes through NML 30 is characterized as a near-infrared (NIR) filter as most rain sensing uses active NIR LEDs whose light is directed at the windshield 12, and a reflected signal from the windshield 12 is sensed, where the LED NIR wavelength spectrum is about 800-1000 nm. The outer area of the filter 42 where light for the remainder 38 passes could be either a visible color or visible monochrome filter depending upon the outer field camera function. It is also recognized that using an outer field visible color filter camera allows better discrimination for some object characteristics, e.g.—traffic lighting, lane marking colors.
Accordingly, a dual-focus camera (the camera 20) is provided. The camera 20 provides for raindrop detection and object detection using a single camera.
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
