Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-05-03
2001-03-06
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C348S294000, C297S440200, C250S214100
Reexamination Certificate
active
06198087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image sensing systems. More particularly, the present invention relates to CMOS image sensing systems.
2. Description of the Prior Art and Related Information
Imaging systems are being incorporated into a variety of new products and employed in new applications due in large part to cost reductions associated with improved CMOS (Complimentary Metal Oxide Semiconductor) imaging technology as well as the increased availability of low cost processing power to process the resulting image data. For example, automotive applications employing such CMOS imaging systems have been recently introduced. One such automotive application is a lane tracking and lane departure warning system which images the roadway to detect when the vehicle deviates from a lane and issues a lane departure warning. Other automotive as well as other outdoor imaging system applications have been proposed. Such applications have the potential to expose the imaging system to bright sunlight at a variety of different angles and intensities. Also, automobile applications may be exposed to bright headlights shining directly into the imaging system.
In such outdoor applications, and in particular in an automobile lane tracking application using commercially available CMOS image sensors a distorted image output has been experienced under certain lighting conditions. In particular, an undesirable vertical striping effect has been experienced in the CMOS image sensor output under various combinations of daylight brightness and angle of the sun relative to the image sensor. Such distortions of the image output make it more difficult for the associated image processing system, for example a lane tracking system, to identify the relevant portion of the image and perform the image processing function. This in turn can impact on the reliability of the system which is very significant in many applications including the above-noted lane tracking applications.
Accordingly, the increased use of CMOS imaging systems in outdoor environments has created a need for an improved imaging system which is not susceptible to image distortion due to certain outdoor ambient lighting conditions. There is a further need for such an improved imaging system which is not associated with significantly increased costs or difficulty in manufacturing and assembly.
SUMMARY OF THE INVENTION
The present invention provides an improved CMOS imaging system which is not subject to distortions in image output in outdoor lighting environments. Furthermore, the present invention provides an improved CMOS imaging system which may be provided without substantial increase in cost over conventional CMOS imaging systems.
In particular, the present invention provides an imager sensor comprising an array of CMOS sensing elements corresponding to a plurality of image pixels and a read out circuit configured adjacent the array of sensing elements, at least a portion of the read out circuit including light sensitive circuitry. A light blocking layer is configured over at least the light sensitive portion of the read out circuit but not over the array of sensing elements. The light blocking layer may be provided on top of the glass top package containing the image sensor chip or may be provided as part of the chip manufacturing process. To accommodate typical dimensions and layouts of CMOS imaging chips, the light blocking layer is preferably spaced apart from the light sensing element by 0.006 inches or less.
The present invention exploits the observation that the distortions in output images experienced by conventional CMOS imaging systems under certain outdoor lighting conditions are caused by light sensitive circuitry associated with the readout and amplification of the output of the sensing elements (pixels) of the imager. Such light sensitive circuit elements will cause distortion in the output when bright light present in certain outdoor applications reaches these elements. The present invention shields these circuits without blocking the light sensing elements of the sensor itself. This is achieved by precise alignment of masking material over the light sensitive circuitry but spaced apart from the imaging elements themselves. This thus provides an inexpensive solution to the above-noted problem associated with conventional CMOS imaging systems.
Further features and advantages of the present invention will be appreciated by review of the following detailed description of the invention.
REFERENCES:
patent: 4354104 (1982-10-01), Chikamura et al.
patent: 4369372 (1983-01-01), Yoshioka et al.
patent: 4583002 (1986-04-01), Knondo et al.
patent: 5841126 (1998-11-01), Fossum et al.
Allen Stephone B.
Iteris, Inc.
Myers Dawes & Andras LLP
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