Image analysis – Image transformation or preprocessing – Image storage or retrieval
Reexamination Certificate
1998-07-21
2003-01-28
Couso, Jose L. (Department: 2621)
Image analysis
Image transformation or preprocessing
Image storage or retrieval
C382S312000, C250S553000
Reexamination Certificate
active
06512858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image sensor array technology for use in electronic cameras employing solid state pixel sensor arrays. More particularly, the present invention relates to image scanning techniques for displaying a high-resolution image sensor pixel array onto a viewscreen of lower resolution.
2. The Prior Art
Active pixel sensor arrays are well known in the prior art. Readout techniques for active pixel sensor arrays combine pixel sensor addressing schemes with scanning circuitry suitable for reading solid state sensor arrays. Exemplary scanning circuitry suitable for vertical and horizontal scanning is described in Analog VLSI and Neural Systems, by Carver A. Mead, Addison Wesley Publishing Co., 1989, at pp. 263-267.
Pictures from active pixel sensor arrays are often displayed onto viewscreens which have a lower resolution than the active pixel sensor array itself does. In order to fit the picture onto the viewscreen, some pixels are not displayed. Two known methods of skipping some of the pixel sensors in the array are panning and zooming. Panning involves changing the start location of readout along the vertical or horizontal active pixel sensor array axis. Zooming involves mapping an image of higher resolution onto a viewscreen of lower resolution. Such zooming is accomplished by selectively displaying only a portion of the total rows and columns of active pixel sensor array data.
The prior art pixel sensor addressing schemes employed by scanning circuitry for active pixel sensor arrays are generally capable of either the random access of individual pixel sensors, or the sequential access of pixel sensors. The random accessing of pixel sensors allows for the readout of any individual pixel sensor in the active pixel sensor array. Sequential access allows for the readout of all of the pixel sensors in an active pixel sensor array, where each frame is scanned out one line at a time.
Some prior art imaging systems read out the entire active pixel sensor array and store the image data in memory. Subsequent manipulations are performed on the memory to access selected portions of the image data for display onto a viewscreen of lower resolution. Such imaging systems necessitate reading out the entire active pixel sensor array regardless of what image data is actually desired.
Other prior art imaging systems use off-chip processing circuitry to determine which portions of pixel sensor data are desired for display. The entire active pixel sensor array is read out sequentially. While readout is occurring, a timing controller selectively transfers only the pixel sensor data desired to the viewscreen display. Such imaging systems also necessitate reading out the entire active pixel sensor array.
Still other prior art imaging systems can be adjusted to change the number of pixel sensors read out at a given time. Such imaging systems are able to read out multiple pixel sensors simultaneously to produce a single average value. This technique increases the scanning speed of the imaging system while decreasing the resolution of the sensor array data. However, such systems involve additional circuitry to average the pixel sensor values.
In prior-art systems using random-access imager arrays, external logic could be used to select rows and columns for pan and zoom, but this requires high-speed address busses and added logic which may be a speed bottleneck.
In the art of color electronic imaging, it is necessary to resolve the incoming image into three color channels. Prior art active pixel sensor arrays are typically combined with a color separation prism, which splits the incoming image into three separate images, one in each wavelength range. Three separate active pixel sensor arrays are used in conjunction with the color separation prism, each capturing the image from one wavelength range. When the image data from the three separate active pixel sensor arrays are recombined, they form the basis of a color image.
Prior art color separation prisms such as that disclosed in U.S. Pat. No. 4,084,180, issued Apr. 11, 1978 to Stoffels et al., resolve an incoming image into three separate color beams. All beams exiting the color separation prism have the same image orientation, and thus none of the three-color separation beams are mirrored compared to the other color beams. However, this type of color separation prism has the disadvantage of requiring an air gap within the prism itself to achieve the same image orientation for all three-color separation beams. Such prisms can be difficult to manufacture properly.
A second type of color separation prism, such as that disclosed in U.S. Pat. No. 4,072,405, issued Feb. 7, 1978 to Ozeki, avoids the necessity of having an air gap within the prism. However, this color separation prism produces three different color beams wherein one beam's orientation is a mirror image as compared to the other two color beams' orientations. The active pixel sensor array receiving this mirrored color beam should be able to reverse its image readout direction to match the image orientation of the other two color beams.
It is an object of the present invention to provide scanning circuitry for an active pixel sensor array with row and column addressability that can combine the features of an arbitrary pixel sensor readout starting location with a sequential pixel sensor addressing mode. Different scanning modes with different image resolutions are achieved by counting pixel sensor rows in steps of Kn for row addressability and counting pixel sensor columns in steps of Km for column addressability, allowing for selective pixel sensor skipping. Selective pixel sensor skipping allows for increased scanning speed and decreased image resolution, producing an image suitable for viewing on a low-resolution viewscreen.
It is another object of the present invention to provide on-chip scanning logic for row and column addressing to perform sequential pixel sensor addressing with pan and zoom modes.
Yet another object of the present invention is to provide easy panning control, which changes the start readout location along the vertical and horizontal dimensions of the active pixel sensor array. Each sequential pixel sensor addressing mode allows for an arbitrary pixel sensor readout starting point.
Yet another object of the present invention is to provide a means for storing several values of Kn and Km on-chip, to provide for several different image resolutions.
Yet another object of the present invention is to provide a means for selectively complementing the row or column pixel sensor address counting sequence during pixel sensor selection. This feature is useful when the active pixel sensor arrays are used with a color-separation prism whereby some prism outputs may be mirrored. The pixel sensor address complementing feature returns the mirrored prism output to the standard output orientation. The complementing feature is available for both the row and column pixel sensor selection. This allows the active pixel sensor arrays receiving each color separation beam to be placed in any orientation (all vertical or all horizontal, with 180-degree rotation being allowed).
BRIEF DESCRIPTION OF THE INVENTION
The present invention describes an apparatus and a method for scanning an active pixel sensor array that provides multiple pixel sensor addressing modes. The apparatus and method are used in conjunction with a solid state active pixel sensor array for use in either a still or video digital camera. A preferred active pixel sensor array with which the present invention may be used comprises a plurality of integrating photosensors placed in rows and columns. Each photosensor on a row is connected to a common row select line. Each photosensor on a column is connected to a common column output line. Illustrative different types of active pixel sensor arrays suitable for use with the scanning apparatus disclosed herein are described in U.S. Pat. Application Ser. No. 08/969,383, “INTRA-PIXEL FRAME STORAGE ELEME
Lyon Richard F.
Merrill Richard B.
Turner Richard M.
Couso Jose L.
Foveon, Inc.
Patel Kanji
Sierra Patent Group Ltd.
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