Patent Application
20090153814
The present invention relates generally to scan head assemblies for use in imaging devices, such as printers, multi-function printers (MFP's), all-in-ones, fax machines, copiers and scanners. In particular, it relates to a scan head assembly for use in an imaging device for scanning media that uses a cooling mechanism, such as a fan to simultaneously cool an optical system located within the scan head assembly and remove contamination particles from the scan head assembly.
An imaging device for scanning media is a device that optically scans images, text and the like from documents and other media and converts it to a digital image that can be replicated. Imaging devices for scanning media can perform duplex document scanning, which involves scanning both sides of a media and/or simplex document scanning wherein only one side of the media is scanned (usually a front side of the media).
Generally, there are two types of imaging devices for scanning media. The first type uses a single scan head assembly. The single scan head assembly is shared by both a flatbed scanner and an automatic document feeder (ADF). The flatbed scanner is usually composed of a transparent flat platen, which is used to receive the media being scanned. Under the platen is a light source, such as a xenon lamp, to illuminate the media being scanned. Further, the flatbed scanner has mirrors to direct reflected light from the media to an image sensor, such as a charge-coupled device (CCD) module to capture the image via a lens to focus the light. The single scan head assembly can be used for duplex document scanning wherein a recirculating media feed path is used, so both sides of the media are scanned or simplex document scanning wherein a direct single pass feed path is used.
The second type of imaging device for scanning media uses a direct single pass media feed path with two scan head assemblies located on each side of the media feed path. In this arrangement, a first scan head assembly is shared by the flatbed scanner and the ADF for scanning the top or “face-up” side of the media. The first scan head assembly typically located below the media feed path is similar to the single scan head assembly discussed above for the flatbed scanner. Further, a second scan head assembly typically located above the media feed path is used for scanning the bottom or “backside” of the media. The second scan head assembly or “backside” scan head assembly has similar components as the first scan head assembly, such as a light source, mirrors, CCD module and lens. Instead of having a platen at a top surface of the scan head assembly, a transparent plate made of glass or other similar rigid material is located at a bottom part of the second scan head assembly.
In both types of imaging devices for scanning media, operating temperature control and contamination control are two primary issues governing the design of the device. Generally, the temperature of an optical system located in the scan head assembly is relatively high because high intensity illumination is needed to meet the speed requirement of the imaging device. As a result, a cooling mechanism to control temperature under adequate operating temperature, which is usually required to be less than fifty degrees Celsius (50° C.) should be provided. Moreover, the scan head assembly should be configured to clean and prevent contamination within the optical system, which causes image quality issues including artifacts and overall stray light induced quality issues.
The traditional approach to prevent contamination in the scan head assembly is to eliminate openings within the scan head assembly, including the optical system and provide a clean environment for the optical system to operate. As a result, the scan head assembly is a closed or sealed system, which prevents contamination particles from entering into the optical system. Although a closed scan head assembly is simple and economically feasible for low temperature imaging devices for scanning media, it is not as effective for imaging devices using a high intensity light source to meet the need for higher scan speed because it is difficult to cool the optical system. Moreover, it is nearly impossible to prevent contamination particles from accumulating in the scan head assembly even with a closed system. Even if the scan head assembly was assembled under ideal conditions, aging and vibration creates contamination particles. Further, the media travels along the media feed path through the ADF making it difficult to prevent contamination particles from entering the scan head assembly.
An alternative to the closed scan head assembly, is to use a fan in the scan head assembly to cool the optical system. Typically, the fan is orientated within the scan head assembly to transfer air from inside the scan head assembly to the outside. In this arrangement, it is necessary to have a dedicated inlet and exhaust for the scan head assembly. However, since the scan head assembly is not a closed system due to the dedicated inlet and exhaust, contamination particles are more prevalent in this system. As a result of contamination particles existing in the optical system, the quality of the scanned image decreases, such as false vertical lines in the scanned image.
Accordingly, the art of imaging devices for scanning media has a need for a scan head assembly that allows effective cooling of the optical system while preventing contamination particles from accruing in the scan head assembly and cleaning existing contamination particles in the scan head assembly.
The above-mentioned and other problems become solved by applying the principles and teachings associated with the hereinafter described self-cleaning scan head assembly.
In a basic sense, an imaging device for scanning media has a first chamber housing enclosing a first scan head assembly in a location below a media feed path. The first scan head assembly has a first optical system having a light source to illuminate a media being scanned and a charged-coupled device (CCD) module to capture the image via a lens from the media. Preferably, the first optical system is cooled to prevent thermal damage. Further, the first scan head assembly, including the first optical system must be free from any contamination to prevent any blocking of the optical path, which decreases quality in the scanned image. As a result, it is necessary to provide the first scan head assembly with effective cooling and cleaning.
In one embodiment, the invention teaches the first chamber housing enclosing the first scan head assembly having a first inlet, such as an air vent in fluid communication with the first scan head assembly and atmosphere. The first scan head assembly has the first optical system and a first cooling mechanism, such as a fan located adjacent to the first inlet. During use, the first cooling mechanism directs fluid particles, such as air, from the atmosphere through the first inlet across the first scan head assembly to provide cooling and cleaning to the first scan head assembly, including the first optical system. Further, the first scan head assembly may have a filter located between the first inlet and the first cooling mechanism. The filter is configured to prevent fluid particles of a certain size in the atmosphere from entering the first scan head assembly.
In other aspects of the invention, a second chamber housing enclosing a second scan head assembly in a location above the media feed path is disclosed. Further, the second chamber housing has a second inlet such as an air vent in fluid communication with the second scan head assembly and atmosphere. The second scan head assembly has a second optical system and a second cooling mechanism located adjacent to the second inlet. Further, the second scan head assembly may have a duct located adjacent to the second cooling mechanism. During use, the second cooling mechanism directs fluid particles from the atmosphere through the second inlet, then through the duct and across the second scan head assembly to provide cooling and cleaning to the second scan head assembly, including the second optical system.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in the description which follows, and in part will become apparent to those of ordinary skill in the art by reference to the following description of exemplary embodiments of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained according to the following description and as particularly pointed out in the appended claims.
The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:
In the following detailed description of the drawings, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and like numerals represent like details in the various figures. Also, it is to be understood that other embodiments may be utilized and that process or other changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and their equivalents. In accordance with the present invention, a self-cleaning scan head assembly is hereinafter described.
With reference to
In one embodiment, the first inlet 60 is an air vent, which is substantially rectangular with a plurality of parallel slots 170 exposed to the atmosphere to allow fluid particles from the atmosphere to enter the first scan head assembly 30. The second chamber housing 290 having a second dedicated inlet 120 is located above the media feed path 20. The second scan head assembly 90 contained within the second chamber housing 290 is used for scanning a back side of the media. The second inlet 120 is also in the form of an air vent, which is substantially square-shaped with a plurality of parallel slots 180 exposed to the atmosphere to allow fluid particles from the atmosphere to enter the second scan head assembly 90.
Turning to
The first optical system 40 of the first scan head assembly 30 is of a kind generally known in the art. Skilled artisans will appreciate that it has a light source 150 to illuminate a media being scanned and a CCD module (not shown) to capture the image via a lens (not shown) from the media. During use, the first cooling mechanism 80, such as a fan, directs fluid particles from the atmosphere through the first inlet 60 across the first scan head assembly 30 to provide cooling and cleaning to the first scan head assembly 30, including the first optical system 40. Further, the first scan head assembly 30 has at least one opening 50 positioned above the light source 150 of the first optical system 40 such that a negative pressure system exists to prevent contamination from accruing in the first scan head assembly 30, including the first optical system 40.
This invention offers a number of advantages not disclosed in the prior art. Specifically, the scan head assembly is designed to provide effective cooling to the optical system while using the same air flow for cooling to clean the scan head assembly, including the optical system. The cooling mechanism, such as a fan introduces filtered fluid particles through the dedicated inlet of the chamber housing. Since the chamber housing enclosing the scan head assembly is not completely sealed, the air pressure within the chamber housing increases until it escapes through a plurality of openings in the chamber housing. Air is pushed through the plurality of openings of the housing chamber, which creates a positive air pressure system to prevent unfiltered fluid particles from entering the scan head assembly from any of the plurality of openings in the chamber housing (fluid particles may only enter the scan head assembly through the dedicated inlet) while allowing contamination particles to exit the scan head assembly.
Additionally, a negative air pressure system is created to prevent contamination particles from depositing in the scan head assembly, including within the optical system. To create the negative air pressure system when the cooling fluid particles pass through the scan head assembly, the scan head assembly is adequately sealed except for the at least opening facing the airflow. As the airflow from the fan pass over the at least one opening in the top of the mainly sealed scan head assembly, it creates a negative air pressure system at this point to pull the contamination particles away from the optical system. Moreover, the airflow passing through the scan head assembly helps prevent any depositing of contamination particles in the scan head assembly, including the optical system.
Turning to
The first cooling mechanism 80 directs fluid particles from the atmosphere through the first inlet 60 into the first scan head assembly 30 to the first optical system 40. The first cooling mechanism 80 is able to direct fluid particles from the atmosphere into the first scan head assembly 30 pursuant to Bernoulli's principle. Bernoulli's principles provides that for an ideal fluid, an increase in velocity occurs simultaneously with a decrease in pressure. Accordingly, velocity and pressure are inversely related. Further, it is well known that fluid particles, such as air, move from high pressure to low pressure. During use, the fan creates an increase in velocity (and a corresponding decrease in pressure) at the first inlet 60 and, therefore, fluid particles from the atmosphere enter the first scan head assembly 30 through the first inlet 60.
The first scan head assembly 30 also has a filter 70 located between the first inlet 60 and the first cooling mechanism 80 to control the size of fluid particles entering the first scan head assembly 30. The filter 70 is configured to prevent fluid particles of a certain size in the atmosphere from entering the scan head assembly 30 through the first inlet 60. The filter 70 may be designed in variable densities depending on the fluid particle removal efficiency necessary in the first scan head assembly 30. Specifically, the filter 70 may be designed to block particles in the micron size range, but still provide sufficient airflow to cool and clean the first scan head assembly, including the first optical system 40. The filter 70 is made of a foam porous material.
As shown in
In another embodiment, a second housing chamber 290 enclosing a second scan head assembly 90 is disclosed as shown in
The second scan head assembly 90 has a second cooling mechanism 130. The second cooling mechanism 130 is a fan, which may be of the type previously described. Again, the size and speed of the fan will depend upon various factors related to the type of imaging device used. The second cooling mechanism is located adjacent to the second inlet 120, such as an air vent. The second cooling mechanism 130 directs fluid particles from the atmosphere through the second inlet 120 into the second scan head assembly 90 to the second optical system 100. The second cooling mechanism 130 is able to direct fluid particles from the atmosphere into the second scan head assembly 90 pursuant to Bernoulli's principle as described above. The air pressure within the second scan head assembly 90 increases until fluid particles escape through another plurality of smaller openings 200 located in the second housing chamber 290.
The second optical system 100 including a second light source 210 are located below the second cooling mechanism 130. In order to direct fluid particles from the atmosphere to the second optical system 100, a duct 140 is positioned between the second cooling mechanism 130 and the second optical system 100. The duct 140 is substantially rectangular shaped and is in contact with the second cooling mechanism 130. The type of duct used will depend upon the corresponding type of fan used. As a result of this arrangement, the fluid particles are directed to the hottest component of the second optical system 100, the second light source 210, to effectively cool the second optical system 100 and to prevent contamination particles from collecting on the optics and glass surface of the second optical system 100. Due to the orientation of the second scan head assembly, gravity helps prevent contamination particles from floating upwards into the second optical system 100. Further, the airflow created by the second cooling mechanism 130 and the duct 140 create a negative air pressure system across the at least one opening 110 in the second scan head assembly 90 to further prevent contamination particles from collecting in the second optical system 100. The at least one opening 110 in the second scan head assembly is located below the second optical system 100.
In an alternative embodiment, the imaging device for scanning media may have a first scan head assembly located above the media feed path without a second scan head assembly located below the media feed path is contemplated. In this embodiment, the imaging device may perform duplex scanning wherein a recirculating media feed path is used to scan both sides of the media or simplex scanning wherein the media feed path is C-shaped and only the top-side of the media is scanned. In simplex scanning, the media being fed should be properly orientated so that the correct side of the media (i.e., the side having the image) is scanned as known in the art.
In addition, the imaging device for scanning media may also have a first scan head assembly located below the media feed path without a second scan head assembly located above the media feed path is contemplated. In this embodiment, the imaging device may perform duplex scanning wherein a recirculating media feed path is used to scan both sides of the media or simplex scanning wherein the media feed path is C-shaped and only the top-side of the media is scanned. In simplex scanning, the media being fed should be properly orientated so that the correct side of the media (i.e., the side having the image) is scanned as known in the art.
The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.
