Patent Application
20100245937
1. Field of the Invention
The present invention relates generally to image forming devices, and more particularly, to a method and system for improving the output quality of the image forming devices.
2. Description of the Related Art
An image forming device produces an image of an object or a document containing text, graphics, or a combination thereof. A scanner is an example of an image forming device. Such devices include a light source and an optical system within a bar or a carriage assembly, also referred to as a scan bar assembly. A scan bar in the scan bar assembly traverses the object or document for generating image data corresponding to the object or the document being scanned. The scan bar assembly also includes an image sensor circuit to gather the image data. The image sensor converts the generated optical image into an electrical signal. This electrical signal is then converted into digital information resulting in the formation of an image of the document. Examples of image sensors include, but are not limited to, Contact Image Sensors (CIS), Charge-Coupled Devices (CCD) and Complementary Metal-Oxide Semiconductor (CMOS) sensors. Accordingly, the scan bar may be or otherwise include a CCD array, a CIS array or a CMOS array.
CIS scan bars include an internal light guide that projects light from a Light Emitting Diode (LED) source on the object at an angle. Light reflected from the object passes through a lens on the scan bar assembly onto the CIS, placed in close proximity to the object being scanned. The CIS gathers the image data and converts it into a digital signal(s) corresponding to the digital image of the object scanned.
CIS scan bars are generally more cost effective in comparison with CCD scan bars. However, the CIS scan bars have a low depth of field. In other words, the quality of images of three-dimensional (3-D) objects produced by an image forming device employing a CIS scan bar is sometimes not of an acceptable quality. Further, CIS scan bars often do not effectively scan documents having different kinds of textures such as a textured-surface photo print. Different textures of the surface of documents or objects cause irregular reflections of light from a light guide of the scan bar assembly onto the lens. Such irregular light reflections often result in the digital image of the scanned object including a number of small, white spots, referred to as speckle. As can be seen, the occurrence of speckle degrades the output quality of the digital image.
The intensity of the speckle depends on the type of texture of the object, the construction of the scan bar in the device assembly and the angle of the light guide with respect to the object.
Some other contemporary image forming devices include a “despeckle” photo software tool solution for minimizing the speckle effect. Although the photo tool solution removes the speckle, it also diminishes other image details in the output.
Embodiments of the present invention overcome shortcomings in prior image forming devices and thereby satisfy a need for a method and system to improve the output quality of the image forming device by minimizing the speckle in the produced image. The image forming devices according to the embodiments of the present invention do not diminish image details in any way and are cost effective.
According to exemplary embodiments of the present invention, there is provided a method including capturing one or more images through an image capture assembly, determining an amount of speckle in the images and comparing the speckle amount with a predefined amount of speckle. Further, the method may indicate, based upon the comparison, whether adjustment of an angle of inclination of the image capture assembly is required for reducing the amount of speckle in the images to an acceptable level. Embodiments of the present invention may include a mechanism for modifying the angle of inclination of the image capture assembly with respect to a transparent surface on which an object scanned is placed. In an embodiment of the present invention, the mechanism may include a height-adjustable spacer assembly that may be adjusted to induce an adjustment of an angle of inclination of the image capture assembly. The adjustment in the angle of inclination may result in a variation in the amount of speckle appearing in the images. Accordingly, the angle of inclination may be adjusted such that the amount of speckle in the images is reduced to a value less than or equal to the predefined amount of speckle thereby improving the output quality of the image forming device. Further, the spacers or the spacer assembly may be advantageously provided by the manufacturer of the image forming device instead of the manufacturer of the image capture assembly. Therefore, the spacers or the spacer assembly may be included in the image forming device without increasing the design cost of the image capture assembly.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
In addition, it should be understood that embodiments of the invention include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical and electrical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative configurations are possible.
Embodiments of the present invention provide a method and system for improving the output quality of an image forming device that produces one or more images of one or more objects. Examples of an image forming device include, but are not limited to, a scanner, a camera scan assembly or other imaging devices which incorporate same. Typically, scanners capture an object or a document image by capturing a one pixel-wide line per color plane at a time. Camera scan assemblies may be image capture systems that capture more than one pixel-wide line per color plane at a time. In other words, camera scan assemblies capture an X by Y pixel-sized image in one or more color planes at a time. For instance, camera-scan assemblies might include a digital still camera imaging system with a light source, mounted in a housing at some distance away from an object or a document position. Camera scan assemblies may be used for imaging the document at a faster rate than a line scanner.
According to an exemplary embodiment of the present invention, there is shown a method which includes capturing one or more images of an object or a document through an image capture assembly. Thereafter, an amount of speckle present in the images is determined. The determined speckle amount is then compared with a predefined amount of speckle. Further, based on the comparison, an indication is made whether an adjustment of an angle of inclination of the image capture assembly is required for improving the output quality of the images. The adjustment of the angle of inclination may include modifying the height of at least one of a plurality of spacers of a spacer assembly utilized in the image forming device for supporting the image capture assembly. The adjustment of the angle of inclination results in a variation in the angle of incidence of light projected on the objects thereby reducing the amount of speckle in the images and improving the output quality of the image forming device.
In an embodiment of the present invention, the entropy value of an image may be calculated using Shannon Entropy measurement. Shannon entropy measurement is a measure of the degree of uncertainty of a discrete random variable. In this case, the value of an image pixel may be considered to be the discrete random variable. The value of the image pixel may be calculated as follows:
P(i)≈h(i)/N
In another embodiment of the present invention, speckle may be determined by using a gray-level co-occurrence matrix (GLCM). The method includes taking counts for intensity of pairs of neighboring pixels and placing the counts in a bin. In yet another embodiment of the present invention, speckle may be determined manually by a user by visually examining the image.
Further, at 106, the speckle determined in the images is compared with a predefined amount of speckle. If the determined amount of speckle is less than or equal to the predefined amount of speckle, then at 108, the image quality of the images is deemed acceptable and the images are produced by the image forming device. If the amount of speckle determined in the images is more than the predefined amount of speckle, then at 110, an angle of inclination of an image capture assembly in the image forming device is adjusted. The adjustment of the angle of inclination may include modifying the height of at least one of a plurality of spacers of a spacer assembly in the image forming device supporting the image capture assembly. The adjustment results in a variation of the effective angle of incidence of light projected on the objects for capturing the images of the objects, thereby resulting in a variation in the image data gathered by the image sensor. Thus, the adjustment of the angle of inclination induces a variation in the amount of speckle determined in the images.
It is understood that prior to adjusting the angle of inclination of the image capture assembly, the image forming device may indicate to a user, for example, that adjustment of the angle of inclination is warranted. Thereafter, the angle may be manually adjusted at 110. In an alternative embodiment of the present invention, following a determination that the amount of speckle in the image(s) captured exceeds the predefined speckle amount at 106, the angle of inclination of the image capture assembly may be automatically adjusted by the image forming device without providing a user indication.
Thereafter, the method is repeated until the amount of speckle determined in the images is less than or equal to the predefined amount of speckle. The method results in an improvement of the output quality of the image forming device by reducing the amount of speckle.
The predefined amount of speckle may be determined through empirical analysis. In various embodiments of the present invention, the predefined amount of speckle may vary according to the type of image forming device used or the type of texture of the object or the document to be scanned. The type of image forming device depends on the hardware components used and the construction of the scan bar assembly in the image forming device. An amount of speckle is determined in the images of the object or the document at different angles of inclination of the image capture assembly of the image forming device. Accordingly, the predefined amount of speckle may be viewed as an acceptable level of the amount of speckle determined in the images. In an embodiment of the present invention, the predefined amount of speckle may be a level acceptable to a user and therefore may vary among different users of the image forming device.
A plurality of images generated by image forming device 200 are provided as input to speckle determination module 202. Speckle determination module 202 determines an amount of speckle in the images. In an embodiment of the present invention, speckle determination module 202 may determine entropy values for the images in order to determine the amount of speckle. In another embodiment of the present invention, entropy values may be determined only for one or more dark regions of the images in order to facilitate a faster and more accurate measurement of entropy in the images. Thereafter, speckle comparison module 204 compares the determined amount of speckle corresponding to the images with a predefined amount of speckle. In an embodiment of the present invention, speckle comparison module 204 may compare the entropy values with a predefined entropy value. In an embodiment of the present invention, the predefined entropy value may be in the range of about 0.0 to about 2.5.
If the amount of speckle determined in the images is more than the predefined amount of speckle, angle estimation module 206 may determine one or more angles of inclination of the image capture assembly. The angles of inclination are used to adjust the image capture assembly relative to a transparent surface, such as a glass surface, on which the documents to be processed by the image forming device are placed. In an embodiment of the present invention, the image capture assembly may be adjusted by the manufacturer while manufacturing the image forming device. In another embodiment of the invention, the image capture assembly may be adjusted manually by a user of the image forming device. Following adjustment of the image capture assembly, new image data is generated from the documents using the image capture assembly and speckle determination module 202 again measures the amount of speckle in the new image data and speckle comparison module 204 again compares the predefined amount of speckle with the amount of speckle determined from the new image data. The variation in the angle of inclination results in a variation in the angle of incidence of light projected on the documents thereby resulting in a variation in the amount of speckle. Thus, the one or more angles of inclination of the image capture assembly may be used to reduce the amount of speckle to a value less than or equal to the predefined amount of speckle.
It is understood that portions of the method of
Light emitted by light source 308 is projected on document 302 through transparent surface 304 and is represented by 314a. Further, the projected light is reflected back by document 302. The reflected light then passes through array of lens 310 onto CIS chip 312 and is represented by 314b. CIS chip 312 receives the optical image of document 302 generated by array of lens 310 and converts the optical image to an electrical signal. Thereafter, the electrical signal is converted into a digital image of the document. CIS chip 312 may contain a plurality of sensor elements.
Scan bar assembly 300 is tilted with respect to transparent surface 304 such that a line normal to CIS chip 312 is at a non-zero angle to a line normal to transparent surface 304. The height of at least one spacer 320b is larger than the height of at least one other spacer 320a so as to provide scan bar assembly 300 with the desired tilt and non-zero angle between the normal to CIS chip 312 and the normal to surface 304. In an exemplary embodiment of the present invention, the heights of spacers 320a and 320b are fixed. In another exemplary embodiment of the present invention, the height of spacer(s) 320b is capable of being adjusted in order to vary the amount of tilt of scan bar assembly 300. This results in a selective variation in the angle of incidence of light projected on document 302 thereby resulting in a variation in the amount of speckle appearing in the image of the document. By suitably adjusting the height of one or more spacers 320, such as spacer 320b, the amount of speckle in the generated image may be reduced for a number of documents 302 having differing degrees of texture, to a value less than or equal to the predefined amount of speckle. As a result, the output quality of the image forming device is improved.
It is understood that in order to tilt scan bar housing 306 so as to vary the angle of inclination of scan bar assembly 300 relative to transparent surface 304, scan bar housing 306 may be urged upwardly towards transparent surface 304 within the imaging device until spacers 320 contact transparent surface 304. The imaging device may, for example, include a spring or other biasing mechanism to so urge scan bar assembly 300 upwardly. In this way, scan bar housing 306 may be relatively easily tilted as desired to achieve a desirably low amount of speckle in the image of the document scanned.
As stated above, the height of one or more spacers 320b may be adjusted to vary the angle of inclination between scan bar housing 306 and transparent surface 304. Accordingly, the amount of speckle in the captured images of document 302 may be reduced to a desired value less than or equal to the predefined amount of speckle. In an embodiment of the present invention, the height of one or more spacers 320 may be adjusted by a user. In another embodiment of the invention, the height of spacers 320 may be pre-set to an optimum level that minimizes the amount of speckle in the images of widely used textured media types.
Access door 506 is provided in image forming device 500 to enable a user to adjust the height of at least one spacer 510 of spacer assembly 502. Spacer assembly 502 may include a plurality of spacers, such as spacers 510a and 510b, and a height adjustment mechanism. The height adjustment mechanism enables the user to modify the angle of inclination of scan bar assembly 514 with respect to a transparent surface (not shown in
In another embodiment of the present invention, a screw may be provided for adjusting the height of spacer 510a.
In an embodiment of the present invention, the user-accessible leveler-type spacer assembly may be used in conjunction with a scan preview procedure. The user may adjust the height of spacer assembly 502 and check the scan preview simultaneously. If the scan result is not as desired, the user may further adjust the height of spacer assembly 502. In an embodiment of the present invention, the image forming device 500 may provide a range of the angle of inclination to the user for adjusting spacer assembly 502.
When scan bar assembly 802 is driven into ratcheting lever 804 in the direction represented by 812, gear 806 engages with ratcheting lever 804. This engagement rotates gear 806 in a first direction which moves spacer 810a in the vertical direction to the next rest position. Each rest position is at a different spacer height. In various embodiments of the present invention, at least one spacer 810 is enmeshed with gear 806. As gear 806 moves along sidewall 808 passing over ratcheting lever 804, the spring mechanism inside ratcheting lever 804 makes ratcheting lever 804 return to the original position.
When scan bar assembly 802 is then driven in the direction represented by 814, gear 806 passes over ratcheting lever 804 thereby pushing ratcheting lever 804 such that it retracts into sidewall 808 without rotating gear 806. Thus, spacers 810 retain their original positions. When scan bar assembly 802 is again moved in the direction as represented by 812, spacer 810a moves to the next rest position. In an embodiment of the present invention, spacers 810 may return to the original position after attaining several intermediate rest positions.
A biasing mechanism, such as a spring (not shown in the figure), may be placed under the scan bar housing so as to exert an upward pressure on spacers 810 thereby holding spacers 810 in their rest positions. Thus, the ratcheting drive mechanism allows a one-way drive for moving spacers 810 in the vertical direction. The movement of spacers 810 in the vertical direction induces an angle of inclination of the scan bar assembly 802 with respect to a transparent surface on which an object is placed for scanning by image forming device 800.
In an embodiment of the present invention, the leveler-type spacer assembly may be placed outside the scan bar assembly 802.
Spacers 902a and 902b have different heights such that scan bar assembly 802 is inclined at a non-zero angle relative to the transparent surface of the imaging device. Gear 904 may be used for driving the spacer 902b in the vertical direction into several rest positions. Peg 906 rides on circular cam surface 912 of inner shaft 910 of scan bar assembly 802 to enable spacer 902b to come to a rest position. As gear 904 rotates, peg 906 moves along circular cam surface 912 into a resting position. When gear 904 rotates again, peg 904 moves into the next resting position. Thus, height of spacer 902b may be varied.
Spring 908 induces an upward pressure on spacers 902 thereby pressing spacers 902 against the transparent surface. The spacer assembly is designed such that spacers 902 may return to the original positions owing to the upward pressure of spring 908 on spacers 902.
The rotational movement of gear 904 causes peg 906 to rotate while riding along circular cam surface 912. For example, peg 906 may come to a resting position at rest divot 1002a on circular cam surface 912. Rest divots 1002 are at unique resting positions. When gear 904 is rotated further, peg 906 moves to the next rest divot position, for example, peg 906 may move to rest divot 1002b, which is at a different vertical position. In various embodiments of the present invention, peg 906 may return to the original position, such as rest divot 1002a, after attaining a series of intermediate positions of different heights, such as rest divot 1002b, 1002c and 1002d as depicted in
Experimental results reveal that the angle at which light is projected on the object to be scanned is a critical parameter in reducing speckle in the image of the object. Experiments were conducted using a black matte photo paper and entropy values of the images were measured for a set of angles of inclination of the scan bar assembly. The table below depicts the measured entropy of the scanned images for a range of angles of inclination of the scan bar assembly in accordance with an embodiment of the present invention.
In accordance with various embodiments of the present invention, the minimum entropy or minimum speckle in the scanned images occurs when the angle of inclination of the scan bar assembly is varied within the range of 0° to 2.5°. The angle of inclination of the scan bar assembly may be varied in order to minimize the speckle appearing in the scanned images, thereby improving the output quality of the image forming device.
It is understood that the exemplary embodiments described above may be used in conjunction with a scan preview procedure. Specifically, the user may adjust the height of the one or more spacers and then check the scan preview substantially immediately following a scan of the document. If the scan image has an undesirably high amount of speckle, the user may further adjust the height of the spacer assembly. In an embodiment of the present invention, the image forming device may provide a range of the angle of inclination to the user for adjusting the spacer assembly.
The foregoing description of several methods and an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.
