Television – Special applications – Observation of or from a specific location
Reexamination Certificate
2001-04-27
2004-05-11
Rao, Andy (Department: 2632)
Television
Special applications
Observation of or from a specific location
C701S301000, C701S302000, C382S284000, C348S036000, C348S152000
Reexamination Certificate
active
06734896
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image processing technique for generating a synthesized image from images taken with a plurality of cameras. In particular, the present invention relates to a technique that can be effectively applied to monitoring systems used as an assist in ensuring safety driving of a vehicle and the like.
In recent years, with widespread use of car-mounted displays and cost reduction in video equipment such as cameras, devices for monitoring the surroundings of a vehicle with cameras to assist safety driving have been commercialized and are now becoming popular.
As an example of such conventional vehicle surroundings monitoring devices, the following construction is known. That is, a camera is placed at a position on a vehicle where an image of a blind area for the driver, such as the rear of the vehicle, can be taken with the camera, and the image taken (camera image) is shown on a display for monitoring.
For example, Japanese Laid-Open Patent Publication No. 58-110334 discloses the following construction. A plurality of cameras are placed at different positions on a vehicle. A plurality of camera images taken with the cameras are modified and synthesized, to generate a synthesized image as is viewed from the above of the vehicle with the vehicle in the center and display the synthesized image on an in-car display. Using this vehicle surroundings monitoring device, the driver sitting on the driver's seat can monitor on the display a blind area of which direct view is not possible. This contributes to avoiding an accident that would otherwise have occurred, and also facilitating the driving.
[Problems to be Solved]
However, the inventors of the present invention have found from experiments and examinations that the conventional construction has the following problems.
FIGS. 22A
to
22
C illustrate examples of image synthesis performed when a vehicle is moving. In the case of using cameras for interlaced scanning, an input image as shown in
FIG. 22A
is obtained when the vehicle is moving. That is, every other horizontal line is displaced resulting in comb-shaped appearance. This input image is not particularly strange as long as it is displayed as it is on a display for interlaced scanning. However, when this input image is modified for synthesis, the comb-shaped displacement is also modified during the image modification as shown in
FIG. 22B
, and this causes a lag between the image-taking timing and the displaying timing. The resultant image makes the observer feel strange. That is, so-called interlace noise appears on the synthesized image more significantly.
The unnaturalness as described above does not appear when a one-field synthesized image is generated from one-field input images. However, the resolution of an input image is low in this per-field synthesis, compared with per-frame synthesis. Therefore, when an image of two fields is observed as a frame image as shown in
FIG. 22C
, comb-shaped displacement occurs due to an error in quantization of coordinate values even when the image is still. This deteriorates the image quality, especially in the area of a synthesized image where an input image has been enlarged, when the vehicle is standing still.
That is, as the first problem, when a one-frame synthesized image is generated from one-frame (two-field) input images, the synthesized image is unnatural when the vehicle is moving and when a moving image is taken. When a one-field synthesized image is generated from one-field input images, the resolution of the synthesized image is low.
As the second problem, in modification of a camera image, the input image may be contracted depending on the composition of a synthesized image. As a result, aliasing distortion may partially be generated in the synthesized image.
As the third problem, the junctures of input images on a synthesized image may be unnatural. For example, because white balancing and the like are adjusted separately for the respective cameras, the brightness and the tint may fail to match at the junctures as shown in FIG.
23
A. Also, in some image synthesis methods, the junctures of images may be displaced due to calculation error, erroneous detection of the position of an object, and the like, as shown in FIG.
23
B.
SUMMARY OF THE INVENTION
An object of the present invention is providing an image processor for generating a synthesized image from a plurality of camera images, which can generate a more natural synthesized image compared with the conventional processors.
Specifically, the image processor of the present invention, which receives camera images taken with a plurality of cameras capturing the surroundings of a vehicle and generates a synthesized image from the camera images, includes a parameter generation section constructed to be able to generate a plurality of image synthesis parameter groups each representing the correspondence between the camera images and the synthesized image and having different spatial or temporal resolution relations, wherein the synthesized image is generated from the camera images according to the image synthesis parameter group generated by the parameter generation section, and the parameter generation section switches the image synthesis parameter group to be generated according to an output of a vehicle motion detection section for detecting the motion of the vehicle.
According to the invention described above, it is possible to switch the image synthesis parameter group used for generation of a synthesized image according to the motion of the vehicle. This makes it possible to reduce the unnaturalness of the synthesized image observed when the vehicle is moving and when an image of a moving object is taken, and also prevent the reduction in resolution observed when the vehicle is standing still.
In the image processor of the present invention, the parameter generation section preferably includes: a parameter storage section for storing the plurality of image synthesis parameter groups; and a parameter selection section for selecting at least one among the plurality of image synthesis parameter groups stored in the parameter storage section according to the output of the vehicle motion detection section.
In the image processor of the present invention, preferably, the camera images are interlaced images, and the plurality of image synthesis parameter groups include at least a frame-base image synthesis parameter group and a field-base image synthesis parameter group. Preferably, the parameter generation section generates the field-base image synthesis parameter group when the motion of the vehicle detected by the vehicle motion detection section is relatively fast, and generates the frame-base image synthesis parameter group when the motion of the vehicle is relatively slow.
In the image processor of the present invention, the vehicle motion detection section preferably detects the motion of the vehicle from the camera images.
In the image processor of the present invention, preferably, the plurality of cameras are constructed to be able to switch a capture pattern according to an input switch signal, and the parameter generation section sends the switch signal to the cameras, together with generating the image synthesis parameter group, according to the output of the vehicle motion detection section, to switch the capture patterns of the cameras. Preferably, the parameter generation section selects the image synthesis parameter group and switches the capture patterns of the cameras according to an output of a vehicle status detection section for detecting brightness of the surroundings of the vehicle, in addition to the output of the vehicle motion detection section.
In the image processor of the present invention, preferably, the parameter generation section generates the image synthesis parameter group according to an output of a vehicle status detection section for detecting the vehicle status such as an operation by a driver of the vehicle or whether or not an obstacle exists in the surroun
Ishii Hirofumi
Nakagawa Masamichi
Nobori Kunio
Okamoto Shusaku
Harness & Dickey & Pierce P.L.C.
Matsushita Electric - Industrial Co., Ltd.
Parsons Charles E
Rao Andy
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