Television – Camera – system and detail – Optics
Reexamination Certificate
1997-08-28
2001-11-20
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Optics
C348S113000
Reexamination Certificate
active
06320618
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a semiconductor image sensor which comprises a plurality of photosensitive elements in a two dimensional array and particularly to a semiconductor image sensor which is mounted on a vehicle such as an automobile and is used for monitoring the forward view of the vehicle for the purpose of recognizing the vehicle's forward environment including buildings, other vehicles on the roadway, etc.
BACKGROUND OF THE INVENTION
An image sensor is applied to an automatic navigation system, which is incorporated in a vehicle such as an automobile, for monitoring the forward view of the vehicle so that the automatic navigation system can control such operations of the vehicle as steering to follow a white guiding line which is provided along the roadway by capturing the guiding line with the image sensor or braking appropriately in response to changes in the vehicle's forward environment which may include other vehicles preceding ahead and other objects. In such monitoring, the performance required of the image sensor includes a capacity to detect an obstacle 200 meters or more away ahead of the vehicle. This is especially true for the vehicle to drive on a highway. For this reason, the automatic navigation system has required a camera which incorporates a high-resolution imaging device.
A conventional method for such monitoring has made use of two general television cameras. While one camera equipped with a telephoto lens is used for monitoring distant views in detail, the other camera with an ordinary lens is used for monitoring close views with a wide angle. Another method has utilized the relatively high resolution of a Hi-Vision camera, and views are monitored collectively without any distinction whether they are distant from or close to the vehicle.
However, these methods of the prior art have had problems inherent to the types of camera which are used. One of the problems is that any of the cameras which may be applied as such sensor is so expensive that the hardware of the automatic navigation system which incorporates any of these cameras has been rendered impracticably expensive. Furthermore, if a high-resolution camera such as a Hi-Vision camera is applied as the image sensor for monitoring the forward view of a vehicle, then this image sensor inherently takes in a large amount of information for image formation without any distinction whether the views captured are distant or near. This presents another problem because the images captured by the image sensor can easily overload the image processing capacity of the automatic navigation system. Because of the characteristic of high resolution, Hi-vision cameras are suitable for monitoring distant views. However, when they are used for monitoring near views with the same resolution, they tend to include details which are not really necessary for the object recognition of the automatic navigation system, and the load of image processing required for the recognition of the objects in the views is quite sizable.
It is not necessary for the system to monitor all objects at a constant high resolution. Some objects need to be monitored at a higher resolution. However, it all depends on the condition. For example, in the case shown in
FIG. 1
where a camera is mounted on the front of a vehicle to monitor the forward view, the upper portions of the images which are being monitored generally include distant views of the roadway while the lower portions include near views thereof. Therefore, if the upper portions of the images are captured at a relatively high resolution while the lower portions are captured at a relatively low resolution, then the load of data to be processed or the information extracted from the images in the image processing can be effectively reduced or lightened without jeopardizing the recognition of the condition of the roadway. By realizing this feature for the image sensor, a camera for monitoring the forward view of a vehicle can be produced relatively inexpensively.
SUMMARY OF THE INVENTION
The present invention is conceived to solve the problems mentioned above. It is an object of this invention to provide a semiconductor image sensor which comprises areas of different resolution on a single substrate so that the image sensor can effectively discriminate image information and can omit collection of unnecessary part. This semiconductor image sensor can be effectively used to collect a minimum amount of image data or information necessary for recognition of the road condition for a vehicle to operate. While the image sensor monitors forward views of the vehicle from proximity to distance in such a discriminatory way, the load of image data to be processed can be substantially reduced for the system as a whole. As such, a comparatively inexpensive yet effective imaging can be realized for monitoring forward views of a vehicle.
The above objective is realized by a semiconductor image sensor of the present invention which comprises a plurality of different resolution areas on a single substrate. As examples of construction, a first embodiment of semiconductor image sensor comprises a number of photosensitive elements which are provided as a two dimensional array in a plurality of different resolution areas in a single plane on a single substrate by accommodating a different size or density of photosensitive elements for a respective different resolution area. In this image sensor, an output from each photosensitive element as a pixel composes an image signal.
With this construction, for example, it is possible to obtain an image whose central part is rendered in a relatively high resolution to capture clearly an object which is targetted in the monitoring while the other part is rendered in a low resolution. Likewise, the collection of data for image formation can be carried out effectively by minimizing the collection of image signals to those which are really necessary for a particular purpose of monitoring. Thereby, the load of image data to be processed can be substantially reduced as a whole for the system which incorporates this semiconductor image sensor.
A second embodiment of semiconductor image sensor according to the present invention further comprises, in addition to the construction of the first embodiment, a plurality of different resolution areas in a vertical direction. The area of this semiconductor image sensor which images a distant view (e.g., refer to the upper portion of an image in
FIG. 1
) comprises a high resolution area while areas which image subsequently closer views (e.g., refer to the lower portion of the image in
FIG. 1
) comprise correspondingly lower resolution areas.
If this semiconductor image sensor is to be mounted on the front of a vehicle and to be used as a sensor for monitoring forward views of the vehicle, then the upper portion of the sensor comprises a sensor section for distant monitoring to capture objects in the distance with a high resolution, and the middle portion of the sensor is used to capture objects more than ten meters but less than a hundred meters away with an intermediate resolution, and the lower portion is used to capture relatively large objects near the vehicle with a low resolution. This arrangement is optimal for monitoring forward views from the front of the vehicle because the sensor reduces or minimizes the amount of data collected for the image formation which is required in the monitoring in correspondence with the distance of the view without losing information necessary for the recognition of the road condition. Thus, this minimized amount of image data lightens the load of the subsequent image processing. However, depending on the condition of a particular monitoring or design of the camera incorporating the semiconductor image sensor, the upper portion of the sensor may comprise a low resolution area, and the lower portion may comprise a high resolution area.
A third embodiment of semiconductor image sensor according to the present invention further comprises, in addition to t
Garber Wendy R.
Harrington Alicia M
Honda Giken Kogyo Kabushiki Kaisha
Lyon & Lyon LLP
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