Image analysis – Image transformation or preprocessing – Combining image portions
Reexamination Certificate
1998-11-05
2002-04-16
Mehta, Bhavesh (Department: 2621)
Image analysis
Image transformation or preprocessing
Combining image portions
C382S294000, C345S629000
Reexamination Certificate
active
06373995
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and apparatus for processing image data acquired by an optical scanning device and, more particularly, to an image processing system which receives overlapping image data acquired by an optical scanning device and which reconstructs an original image from the overlapping images.
BACKGROUND OF THE INVENTION
Image scanning devices such as, for example, flat bed image scanners and sheet feed image scanners, are commonly used to scan documents containing image information to convert the image information contained on the document into a digital representation of the document. Image scanning devices typically utilize a linear imaging device which is scanned across a document being imaged to produce multiple one-dimensional (1-D) slices of the image which are subsequently processed and combined to produce a two-dimensional (2-D) digital representation of the image contained on the document.
A light source comprised by the image scanning device projects light onto the document being scanned and the light reflected from the document is focused by imaging optics onto the linear imaging device. The linear imaging device comprises one or more photosensor which convert the light reflected from the document into analog signals. The analog signals are then converted by an analog-to-digital converter into a digital representation. The digital representation is then processed by a processing circuit such as, for example, a microprocessor or a digital signal processor in accordance with a predetermined algorithm to produce an output. The output may be, for example, a reproduction of the original image scanned.
Generally, image scanning devices can be categorized into two categories, namely, image scanning devices which utilize an optical reduction system in combination with a single photosensor and image scanning devices which utilize a contact image sensor comprised of a plurality of photosensor in combination with an array of optical fibers which function as the imaging optics. In a reduction system of an image scanning device, a single, relatively small, high-resolution linear image sensor is used to capture an image of the object (e.g., a document) being scanned. Since the image sensor is relatively small, reduction optics are used to reduce the size of the images contained on the object into smaller images which fit onto the photosensor.
An advantage of image scanning devices which utilize reduction systems is that only a small image sensor, i.e., a single photosensor, is required for capturing an image of the object being scanned, which is normally relatively inexpensive to manufacture. One disadvantage of image scanning devices which utilize reduction systems is that the reduction optics require a relatively long optical path in order to focus the object image onto the single photosensor, which, consequently, increases the overall size of the image scanning device. Although attempts have been made to “fold” the optical path by incorporating a plurality of mirrors into the imaging optics in order to reduce the size of the image scanning device, additional mirrors increase light loss and increase the cost of the imaging optics. Another disadvantage of image scanning devices which utilize reduction systems is that producing relative motion between the object being scanned and the photosensor often involves substantial mechanical difficulty and, consequently, can lead to malfunctions and increased maintenance costs.
A typical contact image sensor utilized in an image scanning device has a length equal to the length of the 1-D scan to be performed. Typically, the contact image sensor comprises an array of photosensor, rather than a single photosensor, because a single photosensor having a length equal to the 1-D length of the scan to be performed is extremely difficult and expensive to manufacture. Therefore, a plurality of photosensor are closely aligned with each other in a linear array so that the photosensor are in contact with each other and so that no gaps exist between the photosensor.
In order to focus the image of the object being scanned onto the array, an array of optical fibers is utilized as the imaging optics for focusing the light from the object being scanned onto the contact image sensor. A one-to-one relationship is required between the photosensor of the array and the optical fibers of the imaging optics due to the fact that the fields of views of the optical fibers with respect to their respective photosensor overlap. If a one-to-one relationship is not maintained between the optical fibers and the photosensor, the original object image will not be capable of being accurately reconstructed from the individual 1-D images focused onto the photosensor by the optical fibers.
One advantage of implementing a contact image sensor in an image scanning device is that the optical path of the imaging optics is relatively short, which reduces the overall size of the image scanning device. A disadvantage of utilizing a contact image sensor is that the array of photosensor must have a length equal to the length of the 1-D scan being performed. Also, it is a difficult and expensive process to place the individual photosensor in the array and align them since this task must be performed monolithically in silicon.
In order to create an photosensor array of this length, full-sized photosensor must be used in the array, which typically are expensive due to the fact that they are monolithically manufactured in silicon and require a relatively large amount of silicon area. The photosensor cannot be fabricated in the same dice. A separate dice must be used for each photosensor. Therefore, each dice must be cut to precise tolerances and then all of the dice must be carefully placed in alignment to create a long line which matches the length of the object (e.g., the document) being scanned. This is a difficult and expensive process. In fact, the alignment process is so difficult that it generally is done by hand, often leading to alignment errors which require that the entire array be discarded, or scrapped. This loss significantly increases the overall cost of the image scanning device since the die are typically the largest percentage of the overall cost of the contact image sensor.
Accordingly, a need exists for an image scanning device having a relatively short optical path and which is capable of utilizing an image sensor which is relatively inexpensive to manufacture.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for constructing a representation of an original image scanned with an optical scanning device. The apparatus of the present invention comprises a processing device for generating an electrical representation of the original image scanned with the optical scanning device and for processing the electrical representation to obtain a representation of the original image.
Preferably, the scanning device used with the processing device of the present invention comprises an illumination device for projecting light onto an original image being scanned and an optical image sensing device disposed to receive light reflected from the original image. The processing device is in communication with the optical image sensing device for receiving electrical signals produced by the optical sensors of the optical image sensing device and for processing the electrical signals. The optical image sensing device comprises a plurality of optical sensors. Each optical sensor has a field and at least two of the optical sensors have fields of view which at least partially overlap. Each optical sensor generates electrical signals relating to the portion of the original image within the field of view of the respective optical sensor.
The processing device processes the image data obtained by the optical sensors and determines the amount of overlap of the images obtained by adjacent optical sensors. Once the amount of overlap has been determined, the processing device uses the determined amount of ove
Agilent Technologie,s Inc.
Kassa Yosef
Mehta Bhavesh
Neudeck Alex J.
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