1. Field of the Invention
The present invention relates, generally, to methods and systems for capturing and processing images, and particularly, to capturing and processing images while varying the exposure times for capturing monochrome image data and color image data and then combining the image data to produce color images.
2. Description of Related Art
Two types of light-sensitive photoreceptor cells are found in the human retina. These two types are referred to as “rod cells” and “cone cells.” It is understood that these two types of cells differ in function. Rod cells are believed to contribute to the ability to see at night under very dim light conditions. Cone cells are believed to be primarily function to distinguish between colors under normal lighting conditions.
However, studies have shown that for every 20 rod cells there is approximately only 1 cone cell. This variation in the relative number of rod and cone cells was recognized by Dr. Ynjiun Wang when developing the optic arrays disclosed in U.S. patent application Ser. No. 11/174,447 filed on Jun. 30, 2005 [herein “the '447 application”], now U.S. Pat. No. 7,780,089 (other patents pending), marketed under the term “MonoColor” imaging. The MonoColor image array is designed to mimic human optic receptors. For example, in MonoColor imaging there may be 15 monochrome pixels in the sensor array for every one color pixel in the array.
The optical sensor arrays disclosed in the '447 application provide a way to efficiently obtain both monochrome and color images in a single sensor. As described herein, and as will be understood by those in the art digital imaging, the term “monochrome” means that the sensor or image detects or contains shades of gray between white and black. The term “grayscale” is also associated with monochrome digital imaging.
Aspects of the present invention provide systems, devices, and methods that overcome the limitations of the prior art.
The present inventors have shown through experimentation that, with post processing, monochrome and color image data can be used to generate color images by employing the systems and methods disclosed in the '447 application. In conventional methods, “noise,” for example, due to lower pixel sensitivity and lower pixel resolution can negatively affect the quality of color image sensing and display, including the detection of what are known as “Bayer pattern” sensors. However, when employing the teachings of the '447 application, red-green-blue (RGB) color filters are significantly outnumbered by monochrome filters whereby pixel sensitively and pixel resolution may be increased thus producing much brighter and much sharper color images given the amount of exposure time under a dim light condition.
It is also recognized by the inventors that movement of the optical sensor, for example, due to hand motion by the operator, can interfere with the quality of the image detected. Blurred pictures due to an unsteady hand are the bane of even professional photographers. This issue is not only problematic for digital imaging, but also to symbol detection and decoding, for example, of bar codes or quick response (QR) codes, among others.
The present inventors recognized two observations concerning the imaging, for example, photographing, of color images: (1) a shorter exposure time leads to a sharper image with more contrast and details, and (2) when capturing a color image, a longer exposure time is typically required. Shortening the exposure time can result in an image that retains better edge or contour information of the objects being imaged. Longer exposure time for color images can preserve better color content, but the longer time can be susceptible to hand motion blur.
Accordingly, the present inventors have developed a novel approach to improve color signal quality when digitally capturing images in color-sensitive applications. According to aspects of the invention, a first monochrome image is taken over a relatively short exposure time to minimize the effect of motion and provide the desired sharper image with more contrast, details, and better edge or contour information of the objects being imaged. A second color image is taken over a relatively longer exposure time to provide better color content. The image data are combined through digital image data processing to provide high quality color images.
According to aspects of the invention, monochrome photo sensors, for example, monochrome pixels, may be provided with a shorter exposure time while color-filtered photo sensors, for example, color-filtered pixels, may be provided with a longer exposure time. The monochrome image data from the short exposure time are combined with the color image data for the longer exposure time to produce color images. Typically, two exposure instances or frames—one monochrome and one color—may be used to implement aspects of the invention. The monochrome image data and the color image data may be combined using the methods and procedures disclosed in the '447 application, the disclosure of which is incorporated by reference herein in its entirety, among others. By employing aspects of the invention, high quality color images can be obtained.
One embodiment of the present invention is an image processing apparatus comprising: a two-dimensional solid state image sensor array comprising: a first set of monochrome pixels that are devoid of wavelength selective filter elements; and a second set of color sensitive pixels that include wavelength selective filter elements; wherein the image processing apparatus is adapted to expose the image sensor array for a first exposure time e0 and generate first image data, and to expose the image sensor array for a second exposure time e1 greater than the first exposure time e0 and generate second image data; and wherein the image processing apparatus is adapted to combine the first image data and the second image data to produce combined image data. In one aspect, the time e1 is at least 50% greater than time e0, for example, is at least 100% greater than time e0. For example, in one aspect, time e1 is greater than 10 milliseconds and time e0 is less than 5 milliseconds.
In one aspect, the first exposure time e0 and the second exposure time e1 are initiated at substantially simultaneously. In another aspect, the first exposure time e0 is initiated at first time t0 and the second exposure time e1 is initiated at a second time t1, and wherein the first time t0 leads the second time t1. In another aspect, the first time t0 lags the second time t1. For example, in one aspect, first time t0 may be a start time for a first frame and second time t1 may be a start time for a second frame, and the first exposure time e0 may be the exposure time for the first frame and the second exposure time e1 may be the exposure time of the second frame.
Another embodiment of the invention is a portable data collection device comprising the image processing apparatus described above.
Another embodiment of the invention is a method of processing image data comprising or including the steps of: (a) sensing a monochrome image for an exposure time e0, and generating monochrome image data; b) sensing a color image for an exposure time e1 greater than e0, and generating color image data; and (c) processing the monochrome image data and the color image data to produce combined color image data. In one aspect, sensing the monochrome image may be practiced with a set of monochrome pixels that are devoid of wavelength selective filter elements; and sensing the color image may be practiced with a set of color sensitive pixels having a wavelength selective filter element. In another aspect, sensing the monochrome image and sensing the color image may be practiced with a set of monochrome pixels that are devoid of wavelength selective filter elements and a set of color sensitive pixels having a wavelength selective filter element, and wherein the monochrome image data is extracted from the set of monochrome pixels and the color image data is extracted from the set of color-sensitive pixels. Again, in one aspect, the time e1 may be at least 50% greater than time e0, for example, at least 100% greater than time e0. In one aspect, processing may comprise decoding, demosaicking, and/or fusioning.
A still further embodiment is a method of collecting electromagnetic radiation, said method comprising or including (a) sensing of electromagnetic radiation having a first range of wavelength, for example, monochrome, with a first set of sensors for an exposure time e0, and generating a first electrical signal corresponding to the sensed radiation; (b) sensing electromagnetic radiation having a second range of wavelength different from the first range of wavelength, for example, a color image, with a second set of sensors for an exposure time e1 greater than e0, and generating a second electrical signal corresponding to the sensed radiation; and (c) processing the first electrical signal and the second electrical signal to produce a third electrical signal corresponding to a combined first sensed radiation and second sensed radiation. The first set of sensors and the second set of sensors may comprise the same set of sensors. In one aspect, the first set of sensors comprise monochrome sensors and the second set of sensors comprise at least one color sensor. In another aspect, at least one color sensor comprises at least one color filter and at least one photo sensor, such as, a photodiode. In another aspect, the monochrome sensors comprise monochrome pixels and the at least one color sensor comprises color pixels. In one aspect, the electromagnetic radiation having the first range of wavelength and the electromagnetic radiation having the second range of wavelength comprise one or more of microwave radiation, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays, gamma ray radiation, and radio waves.
A still further embodiment of the invention is an apparatus for processing electromagnetic radiation comprising or including: a first set of sensors adapted to detect electromagnetic radiation having a first range of wavelength for an exposure time e0, and to generate a first electrical signal corresponding to the detected radiation; a second set of sensors adapted to detect electromagnetic radiation having a second range of wavelength different from the first range of wavelength for an exposure time e1 greater than e0, and to generate a second electrical signal corresponding to the detected radiation; wherein the apparatus is adapted to process the first electrical signal and the second electrical signal to produce a third electrical signal corresponding to the combined first detected radiation and second detected radiation. The first set of sensors and the second set of sensors may comprise the same set of sensors. In one aspect, the first set of sensors comprises monochrome sensors and the second set of sensors comprise at least one color sensor. In another aspect, the at least one color sensor comprises at least one color filter and at least one photo sensor, such as, a photodiode. In a further aspect, the monochrome sensors comprise monochrome pixels and the at least one color sensor comprises color pixels. In one aspect, the electromagnetic radiation may be any of the forms of electromagnetic radiation listed above.
Details of these embodiments and aspects of the invention, as well as further aspects of the invention, will become more readily apparent upon review of the following drawings and the accompanying claims.
The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention will be readily understood from the following detailed description of aspects of the invention taken in conjunction with the accompanying drawings in which:
The details and scope of the aspects of the present invention can best be understood upon review of the attached figures and their following descriptions. As noted previously, aspects of the presented invention are related to what is disclosed in U.S. patent application Ser. No. 11/174,447 filed on Jun. 30, 2005 [herein “the '447 application”], now U.S. Pat. No. 7,780,089 (other patents pending), the disclosure of which is incorporated by reference herein in its entirety.
Aspects of the present invention disclosed herein may be implemented in any one or more of the structures, devices, systems, software, or processes, disclosed in the '447 application, including, but not limited to, the optical readers; the hardware, such as, the displays, graphical user interfaces (GUIs), and other I/O devices; the software; the image sensor arrays, including polarizer image sensor arrays; the imaging modules; the sensors, including monochrome and color-sensitive pixels; the integrated circuits and chips; the circuits; the controls; the flow diagrams; the routines, including decoding, demosaicking, and fusioning routines; the timing diagrams; the frames of image data; the block diagrams; the curvelent detector maps; the histograms; and the image data segmentation processes, among other disclosures of the '447 application.
In one aspect, the first exposure time e0 and the second exposure time e1 may be established depending upon or as a function of the presence of ambient light or external illumination. For example, in the presence of outdoor sunlight at or about noon time, that is, under highly illuminated conditions, the first exposure time e0 may be about 100 μs and the second exposure time e1 may range from about 200 μs to about 400 μs. However, according to one aspect of the invention, regardless of the absolute lengths of exposure times e0 and e1, second exposure time e1 may be greater than first exposure time e0, for example, e1 may be at least twice as long as eo and may be at least three times as long as eo. Though not shown in
Aspects of the invention may be implemented in any form of image processing device, for example, in the devices shown in and described with respect to
Reader 40 includes an image sensor array 42, for example, a solid state image sensor array 42. Sensor array 42 may be incorporated on an image sensor integrated circuit chip 44 shown in
Image sensor array 42 typically includes a two-dimensional grid of interconnects which are in electrical communication with respective column circuitry 47 and row circuitry 49. Row circuitry 49 and column circuitry 47 typically enable processing and operational tasks, such as, selectively addressing pixels 45M, 45C; decoding pixels 45M, 455C; amplification of signals, analog-to-digital conversion, applying timing, read out and reset signals, and the like.
Monochrome pixels 45M may comprise the same design and construction of the monochrome pixel 250M shown in
Reader 40 may further include a processor IC chip 46 and a control circuit 48. Control circuit 48 as shown in the embodiment of
As also shown in
Reader 40 may further include a field programmable gate array (FPGA) 64. Operating under the control of control circuit 48, FPGA 64 receives digital image data from image sensor IC chip 44 and transfers that image data into RAM 56 so that the image data can be further processed (for example, by the decoding of a bar code symbol). Processor IC chip 46 can include an integrated frame grabber. For example, processor IC chip 46 may be an XSCALE PXA27X processor IC chip with “Quick Capture Camera Interface” available from INTEL, or its equivalent. When processor IC chip 46 includes an integrated frame grabber, the integrated frame grabber may provide the frame acquisition functionality of FPGA 60.
Reader 40 may typically further include an illumination assembly 66 and a trigger 68, for example, a manual trigger. Image sensor IC chip 44 in the embodiment of
According to aspects of the invention, reader 40 may include a radio frequency (RF) communication interface 78. Radio frequency communication interface 78 may include one or more radio transceivers, for example, radio frequency communication interface 78 may include one or more of an 802.11 radio transceiver, a Bluetooth radio transceiver, a GSM/GPS radio transceiver or a WIMAX (802.16) radio transceiver. Radio frequency communication interface 78 may facilitate wireless communication of data between device 40 and a distal, remote, or spaced apart device (not shown). Reader 40 may also include an I/O communication interface 80. Interface 80 may include one or more serial or parallel hard-wired communication interfaces facilitating communication with a spaced apart device (not shown). I/O communication interface 80 may include one or more of an Ethernet communication interface, a universal serial bus (USB) interface, or an RS-232 communication interface. Optical reader 40 may further include a keyboard 82 for entering data, a pointer mover 84 for moving a pointer of a graphical user interface (GUI) and a trigger 68 for initiating bar code reading and/or picture taking. Optical reader 40 may also include a display 86 for displaying image data, such as, a monochrome or color LED display and a touch screen 88 overlaid over display 86.
An image sensor array 42 which is incorporated into optical reader 40 may take a variety of forms. In
All of the components of
Solid state image sensor array 120 includes a plurality of pixels formed in a plurality of, typically, adjacent rows. In the aspect shown in
In one example of the invention, image sensor array 120 may be provided by including an appropriately designed color filter array on an image sensor array of an MT9M111 Digital Clarity SOC 1.3 megapixel CMOS image sensor IC chip of the type available from Micron, Inc.; an MT9V022 image sensor IC chip also available from Micron, Inc.; a VV6600 1.3 megapixel CMOS image sensor IC chip of the type available from STMicroelectronics; a Jade MonoColor sensor having part number is EV76C454BMT-EQV provided by e2V; or their equivalent. Other image sensor IC chips which can be utilized to provide image sensor array 120 include MT9M413 image sensor IC chip available from Micron, Inc., a KAC-0311 image sensor IC chip manufactured by Kodak, Inc. a KAI-0340 image sensor IC chip also manufactured by Kodak, Inc., or their equivalent. Operational aspects of the referenced KAI-0340 image sensor IC chip are described further the '447 application. Various manufacturer product description materials respecting certain of the above image sensor IC chips are appended to provisional patent applications cited in the '447 application. The above commercially sold image sensor IC chips can be utilized (with additions or replacements of filter elements as are necessary) to provide any one of image sensor arrays 120 and others described herein and in the '447 application.
As shown in
Typical exposure control timing pulses, read out control timing pulse, and reset control timing pulse that may be used for aspects of the invention are shown in
The image data captured by aspects of the invention may be processed, for example, demosaicked, decoded, fused, or combined, by, for example, any one or more of the methods or routines disclosed in the '447 application. For example, monochrome image data captured by monochrome pixels 45M and color sensitive pixels 45C may be processed by one or more of the processes described and illustrated with respect to
Though aspects of the invention have been disclosed herein as almost exclusively dealing with the handling of visual image data. According to aspects of the invention, any form of electromagnetic radiation may be captured and processed with the methods, systems, and devices disclosed herein and in the '447 application. For example, the methods, systems, and devices disclose herein may capture and manipulate image data related to one or more of microwave radiation, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays, gamma ray radiation, and radio waves.
Aspects of the present invention provide devices and methods for digital color imaging that minimize the effect of sensor motion and cross talk between sensors. As will be appreciated by those skilled in the art, features, characteristics, and/or advantages of the various aspects described herein, may be applied and/or extended to any embodiment (for example, applied and/or extended to any portion thereof).
Although several aspects of the present invention have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.