Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-01-28
2001-04-03
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S234000, C358S484000
Reexamination Certificate
active
06211508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to image sensing systems and more particularly relates to an image sensing module using a lensless optical system to produce digital images.
2. Description of the Related Art
It is not uncommon to see a whiteboard in every meeting room of a corporate in America. The whiteboard provides an informal medium for meeting attendees to communicate effectively and interactively. Like a scratch paper but more presentable, a whiteboard allows a speaker to use colorful markers to write, erase, draw, and modify what is being discussed and agreed upon among meeting attendees.
Whiteboards offer several advantages over chalkboards including a clean white surface which provides for greater contrast over the traditional green background of chalkboards. In addition, writing on a whiteboard is easier for many than on the traditional chalkboard. For example, the smooth writing surface of the whiteboard allows easy use of the erasable felt tip markers used on whiteboards, whereas the chalkboard surface provides a somewhat scratchy surface to hold the chalk used for writing on such surfaces. In addition, many users prefer a whiteboard to a chalkboard simply because the marker may be gripped easier than the chalk and does not mark the user's hand when gripped.
Recently, whiteboards have been developed to allow the user writings and notations entered upon the whiteboard to be printed or stored to a digital computer for storage, display and manipulation. A whiteboard, called Plus Boardfax, from Plus Corporation is designed to provide the capabilities to capture the information presented in the whiteboard.
FIG. 1
illustrates an exemplary whiteboard
100
. It includes a frame
102
and a rotatable canvas or writing surface (sheet)
104
for writing. When a page of writing is done, sheet
104
is caused to rotate towards an image scanning module
106
that is typically concealed in frame
102
. As sheet
104
moves across image scanning module
106
, marks or anything in writing are scanned by image scanning module
106
that subsequently generates an image thereof. The image can be then printed on a sheet of paper
108
by a concealed thermal printer for distribution or permanent record.
The basic principles of whiteboard
100
are the use of an image scanning module or system that comprises an image sensor, an optical lens and an illumination system. The image sensor comprises an array of photodetectors responsive to reflected light focused by the lens and from writing sheet
102
. Each of the photodetectors produces an electronic signal representing the intensity of the reflected light. The electronic signals from all the photodetectors are then readout for printout or processing.
It can be perceived that the cost of the image scanning system goes up dramatically as the size of scanning width (i.e. the height of sheet
102
) increases, so as the whiteboard
100
. One of the factors in the cost is the complicated design of the optical system that must linearly focus light from sheet
102
onto the image sensor in the image scanning system. To reduce the cost of designing such optical system, multiple image scanning modules are sometimes used, namely each of the image scanning modules is responsible for a predefined area of sheet
102
, signals from all the image scanning modules are then stitched together to form a complete signal for subsequent processing and output. Nevertheless, the use of multiple image scanning modules introduces a complicated process of aligning all the multiple image scanning modules, namely image scanning modules must be aligned precisely to avoid overlapping between two adjacent image scanning modules so as to alleviate data analysis and processing due to the overlapping. There is, therefore, a desire to have a cost-effective optical system in an image scanning system so that there would be no need for multiple image scanning modules.
One of the benefits and advantages of the whiteboard over the traditional chalkboard is the use of powderless markers, and the whiteboard has begun to appear in education facilities and even in many families for children's educational activities. Further the whiteboard can potentially be used for discussion between two people and generates images to be reviewed by a third party in a remote site through the Internet. With the increased applications and popularity of the whiteboard, there is indeed a great demand for a low-cost image scanning system that can be used in applications like the whiteboard.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above described problems and needs and has particular applications to recordation of a large presentational board, such as whiteboards in educational and meeting facilities. Employing the current invention, the cost of the electronic presentational boards can be dramatically reduced so as to enhance the popularity of such boards. It will become apparent to those skilled in the art that the present invention may be utilized in many image sensing modules that do not have to produce high resolution images but are demanded of low cost.
According to one aspect of the present invention, an image sensing module comprises an image sensor and a plurality of tubes closely affixed together in parallel and mounted above and sufficiently covering the image sensor. All of the tubes are identical and can be made and molded out of a plastic material. Each of the tubes includes an opening at the end that faces a scanning object. When the scanning object is illuminated and passes through the image sensing module, openings of all the tubes capture incident light reflected from the scanning object and the captured light passes the tubes and subsequently impinges onto the image sensor. An image of the scanning object is produced when the image sensor is activated.
The lensless optical system disclosed herein works perfectly for those applications that provide sufficient illumination and require no high resolution images. The whiteboard application demanding the imaging capabilities is one of the examples in which the present invention can be practiced. The advantages and benefits of the image sensing module employing the lensless optical system are numerous, one of which is the cost that is now significantly reduced comparing to the traditional lens-based optical system. Another one may be appreciated to those skilled in the art that the cost of the lensless optical system is not directly related to the size thereof. Typically the size of an optical system is one of the factors that determines the cost while the size in the present optical system is no longer the factor as the lensless optical system is simply made with an array of plastic tubes.
According to another aspect of the present invention, each of the tubes has an inner wall surface that is preferably dark and of rough surface. The reason behind the design features is to minimize possible ambient light coming through the openings of the tubes to affect the image sensor.
Objects and other advantages and benefits, together with the foregoing are attained in the exercise of the invention in the following description and resulting in the embodiment illustrated in the accompanying drawings.
REFERENCES:
patent: 4742240 (1988-05-01), Yamanishi et al.
patent: 5859421 (1999-01-01), Onishi et al.
Le Que T.
Syscan Inc.
Zheng Joe
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