The invention relates in general to electronic imaging devices that are capable of compensating for defective sensor elements contained therein.
Electronic imaging devices having an array of sensor elements that convert incident scene light to electrical signals are utilized in a variety of products. For example, linear electronic imaging devices, which include a plurality of sensor elements configured in a line, are commonly used in scanning devices, such as facsimile machines, to scan an original document on a line-by-line basis in order to generate electrical signals that correspond to the image of the original document. The electrical signals can then be used to reproduce the image of the original document in either hard copy or electronic form.
It is desirable to reproduce the image of the original document with a high degree of resolution. Thus, the electronic imaging device employed to scan the document should preferably have a large number of sensor elements. It is difficult and expensive, however, to produce high resolution electronic imaging devices without defective sensor elements. Present manufacturing methods form of a large number of electronic imaging devices on a semiconductor wafer and then use a sorting process to identify those devices on the wafer that do not have sensor element defects. The percentage yield of good devices, however, generally decreases with increasing resolution, as higher resolution devices necessarily require a greater surface area which increases the chance that a defect in the wafer will fall within the structure of a particular device. A great deal of effort and material is wasted if the percentage yield of good devices from each wafer is low.
One approach to increasing the yield of devices that can be utilized is to provide redundant sensor elements within the structure of the electronic imaging device to compensate for defective sensor elements. U.S. Pat. No. 4,661,713 issued to Besson et al., for example, discloses a photovoltaic diode detection device that includes two diode arrays. Each of the diode arrays includes defective diode elements. A programmed memory is used to control two switches to accomplish a winding or serpentine readout of the arrays, wherein the signals from only the good diode elements in each of the arrays are readout. A disadvantage of this approach, particularly in a color scanning system having separate red, green and blue arrays of sensor elements, is that total redundancy of sensor elements is required.
It is an object of the invention to provide an improved electronic imaging device that utilizes redundant sensor elements to provide defect compensation for defective sensor elements, and to provide an improvement in the overall response of the electronic imaging device. It is a further object of the invention to provide an improved electronic imaging device that does not require total redundancy of all sensor elements in a color scanning system.