Patent Application
20080012953
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
The detailed description of the present invention is presented largely in terms of procedures, steps, logic blocks, processing, or other symbolic representations that directly or indirectly resemble the operations of devices or systems contemplated in the present invention. These descriptions and representations are typically used by those skilled in the art to most effectively convey the substance of their work to others skilled in the art.
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Significantly different from
Bayer uses twice as many green elements as red or blue to mimic the human eye's greater resolving power with green light. These elements are referred to as samples, and become pixels after interpolation. The raw output of a Bayer sensor is referred to as a Bayer pattern image. Since each pixel is filtered to record only one of the three colors, two-thirds of the color data is missing from each point. To obtain a full-color image, various demosaicing algorithms can be used to reconstruct a set of complete red, green, and blue values for each point.
Different algorithms of image reconsruction requiring various amounts of computing power result in varying-quality final images. The sensor 106 of
In one embodiment, the compressor 206 is based on ADPCM, short for Adaptive Differential Pulse Code Modulation. ADPCM is a form of pulse code modulation (PCM) that produces a digital signal with a lower bit rate than standard PCM. ADPCM produces a lower bit rate by recording only the difference between samples and adjusting the coding scale dynamically to accommodate large and small differences. Depending on implementation, ADPCM can be implemented in one or two dimentions.
As a result, the compressor 206 produces compressed Bayer pattern image that is much smaller in size and applicable for transferring via the USB 208. It is understood that because each pixel in a Bayer pattern image is filtered to record only one of the three colors, two-thirds of the color data is missing from each point. Accordingly, the Bayer pattern image is only about one third of a color image that is otherwise reconstructed from the Bayer pattern image as the image sensor 102 of FIG. 1 does. With the compressor 206, the Bayer pattern image is further reduced in size. Depending on the image quality requirement, the Bayer pattern image can be compressed by another 25%˜40%.
According to one embodiment, the USB 208 is based on the Universal Serial Bus 2.0, an overhaul of the Universal Serial Bus input/output bus protocol which allows much higher speeds than the older USB 1.1 standard does. USB 1.1 allows a maximum transfer rate of 12 Mbits/second while USB 2.0 (high speed) is capable of a much faster 480 Mbits/second. Even with the requirement of 60 frames per second from the sensor array 202, USB 2.0 is sufficient for transferring compressed Bayer pattern images for sensors of most commonly used resolutions, and uncompressed Bayer pattern images for sensors of certain resolutions.
A compressed Bayer pattern image from the USB 208 is essentially an un-interpolated data image where each pixel corresponds to only one specific color value. In order to get a color image, the colors have to be “reconstructed” based on the Bayer data. Traditionally, the reconstruction is done in hardware to accommodate the required speed. As seen above, the compressed Bayer pattern image has now been read out from the USB 208, a sufficient computing resource has to be allocated to perform the reconstruction.
Nowdays many computing devices are equipped with a powerful processor. For example, most of the latest laptop computers are equipped with either a Pentium 4 processor from Intel or a Turion 64 processor from AMD, both are sufficient to provide the necessary computation power to perform the reconstruction of a color image from a compressed Bayer pattern image. Alternatively, some computing devices are equipped with a graphics chip that may be also used to supplement the computing power needed to perform the reconstruction of a color image from a compressed Bayer pattern image. Before the reconstruction of the color image starts, the compressed Bayer pattern image is first uncompressed to recover the Bayer pattern image.
Also interfaced to the data bus 420 is a display interface 426, a network interface 428, a printer interface 440 and a disk drive interface 448. Generally, a compiled and linked version, an executable version, or a software module performing the reconstruction of a color image from a compressed Bayer pattern image is loaded into the storage space 446 through the disk drive interface 438, the network interface 428, the device interface 424 or other interfaces coupled to the data bus 420.
The main memory 442 such as random access memory (RAM) is also interfaced to the data bus 420 to provide the CPU 422 with the instructions and access to storage space 446 for data and other instructions, applications or services. In particular, when executing stored application program instructions, such as the software module of the present invention, the CPU 422 is caused to decompress the compressed Bayer pattern image received from the device interface 424 and proceed with the reconstruction of the color image from the uncompressed Bayer pattern image. The color image may be subsequently displayed on a display screen (not shown) via a display interface 426.
The ROM (read only memory) 444 is provided for storing invariant instruction sequences such as a basic input/output operation system (BIOS) for operation of the keyboard 440, the display 426 and the pointing device 442, if there are any. In general, the system 418 is coupled to a network and configured to provide one or more resources to be shared with or executed by another system on the network or simply as an interface to receive data and instructions from a human being. In one application, the reconstructed image can be transported to another site via the network.
Those skilled in the art can appreciate that the image sensor 200 of
Although exemplary embodiments of the present invention have been disclosed in detail, it will be apparent to those skilled in the art that various changes and modifications may be made to achieve the advantage of the invention. It will be obvious to those skilled in the art that some components may be substituted with another component providing same function. For example, a USB interface has been used throughout the description. In practice, other types of interface may be used. Likewise, other type of sensors as well as compressors may be used. In addition, a Bayer pattern is used in the described embodiments. Those skilled in the art can appreciate that other optical filter configurations may be used. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description of embodiments.
