Abstract:
A light source mechanism for an imaging apparatus comprises at least a point light source and a light shield. The point light source located at one end of the light shield is used for providing illumination to the imaging apparatus during a scanning process. The light shield is a hollow pipe structure and further includes a long slot lying along an axial longitudinal direction thereof for allowing lights to leave the light shield. An inner surface of the light shield is made as a diffusion surface for evenly diffusing lights inside the light shield, by which a homogeneous line light source for the scanning process is formed at the long slot of the light shield.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention relates to a light source mechanism for an imaging apparatus, and more particularly to a combination which integrate a point light source with a light shield for producing a line light source with enhanced homogeneous illumination. 
     (2) Description of the Prior Art 
     An imaging apparatus or a scanner is one of popular computer peripherals. In an imaging apparatus, an internal light source is used to generate an image from a document rested upon a document plate. The image is then forwarded through a plurality of lenses and experiencing a proper travel path to reach a CCD for being transformed into digital signals. The digital signals are then sent to a computer for further image processing. 
     Referring now to FIG.  1 A and FIG. 1B, a perspective and a side views of a conventional light source mechanism are shown, respectively. The light source mechanism  1  mainly comprises a fluorescent tube  12  and a light housing  14 . The fluorescent tube  12  for providing illumination during an imaging process has a length substantially equal to the width of the document rested upon the document plate of the imaging apparatus. The light housing  14  provides a lengthy internal accommodation room  141  thereof for installing therein the fluorescent tube  12 . The accommodation room  141  as shown includes a lengthy aperture  142  for allowing the light of the fluorescent tube  12  to pass therethrough. The inner surface of the light housing  14 , formed as a reflection surface for collecting and reflecting the light to enhance the illumination of the light source mechanism  1 , can be preferably embodied as an arc surface or a parabolic surface. 
     Nevertheless, the conventional light source mechanism  1  as discussed generally has several disadvantages as follows. 
     1. In the conventional light source mechanism, a fluorescent tube is usually used as the light source. Yet, it is well known that the fluorescent tube can only provide lights limited to a narrow wave length range, and generally within the range of visible lights. However, some imaging apparatus are designed to proceed the scanning by invisible lights. Under such an arrangement, it is obvious that the fluorescent tube cannot provide the required light source to perform the scanning. 
     2. The conventional fluorescent tube is generally a product of short-life term and is vulnerable to be broken as well as invaded by gas. 
     3. The illumination provided by the conventional fluorescent tube is sometimes unstable and consequently affects the scanning quality of the imaging apparatus. 
     4. The unit price of the conventional fluorescent tube is usually high, so that the cost of the imaging apparatus cannot be reduced to a competitive level. 
     To resolve the aforesaid disadvantages of the conventional imaging apparatus using the fluorescent tube as the light source, additional effort in the industry to develop an improved light source mechanism is definitely necessary for producing an imaging apparatus with low cost, long life term, quality performance and wide-ranged application. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to provide a light source mechanism for an imaging mechanism, in which a point light source is applied to provide improved imaging quality and advantages of low cost, stable illumination, long life term and a wider application range. 
     The light source mechanism for an imaging apparatus in accordance with the present invention includes at least a point light source and a light shield. The light source of the present invention for the imaging apparatus to perform the document scanning, preferably includes two point light sources located respectively at both ends of the light shield. The light shield, having a shape of lengthy hollow pipe structure, provides an internal mounting element at each end thereof for installing thereinside the respective point light source. One feature of the present invention is that the light shield includes a long slot located along a longitudinal direction thereof for transforming the lights provided by the inside point light sources into a line light source for performing the illuminating of a document. In addition, the interior wall surface of the light shield is formed as a diffusion surface for evenly diffusing the lights emitted by the point light sources, and thus a homogeneous line light source can be provided through the long slot to perform the document illuminating. 
     According to the present invention, the diffusion surface inside the light shield can be formed by a plurality of ring protrusions. In theory of optics, the ring protrusion can provide even diffusion upon the incoming point light source, so that homogeneous line light source can be produced through the long slot, even though point light sources does be applied as the real light source inside the light shield. In the present invention, the lights emitted by the point light sources might travel a substantial period and experience several diffusion inside the light shield before leaving the light shield through the long slot, so that the light quality provided by the light source mechanism of the present invention can be better than that provided by the conventional light source; though two separate point light sources might be used inside the light shield of the present invention. 
     All these objects are achieved by the light source mechanism for an imaging apparatus machine described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which 
     FIG.  1 A and FIG. 1B show respectively a perspective and a side view of a conventional light source mechanism for an imaging apparatus; 
     FIG. 2 is an exploded perspective view of a first embodiment of the light source mechanism for an imaging apparatus in accordance with the present invention; 
     FIG. 3 is an enlarged perspective view of the ring protrusions for light diffusion inside the upper half of the light shield; and 
     FIG. 4 is an exploded perspective view of a second embodiment of the light source mechanism for an imaging apparatus in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention disclosed herein is directed to a light source mechanism for an imaging apparatus. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instance, well-known components are not described in detail in order not to unnecessarily obscure the present invention. 
     Referring now to FIG. 2, a first embodiment of the light source mechanism for an imaging apparatus in accordance with the present invention is shown explodedly. 
     The light source mechanism  2  as shown includes a single point light source  21  and a light shield  22 . The point light source  21  can be a light emitting diode (LED) which has advantages of low cost, longer life term, stable illumination and a wider wave range for application. To meet the requirement of the line light source for scanning the document, the light source mechanism  2  of the present invention utilizes the light shield  22  to transform the lights of the point light source  21  into an applicable line lights. 
     As shown in FIG. 2, the light shield  22  of the present invention, shaped as a long hollow pipe structure, includes an upper half  221  and a mating lower half  222 . The light shield  22  can be preferably made of opaque materials. One end of the light shield  22  includes a mounting element  223  for installing the point light source  21 . One feature of the present invention is that the lower half  222  of the light shield  22  further includes a long slot  224  lying along the axial longitudinal direction of the light shield  22 . The long slot  224  has a length approximately equal to an ordinary width of a document for whole scale scanning. The interior surface of the light shield  22  can be formed as a diffusion surface  225  for evenly diffusing the lights emitted by the point light source  21  inside the light shield  22 , in order to prevent from localized illumination phenomenon of a point light. Therefore, under such an arrangement of the present invention, quality line light source can be obtained from the long slot  224  which provides homogeneous line lights from the diffused lights inside the light shield  22 , though the point light source  21  is applied. 
     Referring now to FIG. 3, the diffusion surface  225  inside the light shield  22  can include a plurality of ring protrusions  226  located at the upper half  221  and a high reflection layer located at the lower half  222 . Methods for forming the high reflection layer (not shown in the figure) can be any injection method or any electroplating. In the optics theory, the ring protrusions  226  can have an excellent diffusion ability. Therefore, the lights emitted by the point light source  21  can be evenly diffused inside the light shield  22 , and then a homogeneous line light source can be constructed through the long slot  224 . 
     Though the point light source  21  of the present invention is mounted at one end of the light shield  22 , yet localized illumination of the light source mechanism adjacent to the point light source  21  can be avoided because lights through the long slot  224  might have experienced several diffusions inside the light shield  22 . 
     Though the light source mechanism  2  of the present invention can utilize the light shield  22  to perform a homogeneous line light source through the long slot  224  for further illuminating upon the document, yet it is still believed that slight localized illumination phenomenon might exist at the area close to the point source  21  inside the light shield  22 . Also, the phenomenon will become vague as the distance from the point light source  21  increases. 
     To resolve the aforesaid problem and to obtain a much improved quality line light source from the long slot  224 , one of the solutions is to increase the diffusion ability of the ring protrusion  226  as its respective distance from the point light source  21  increases. Under such an arrangement, the illumination adjacent to the point light source  21  will be decreased a little bit due to the decrease in the diffusion ability of the ring protrusions  226  therearound. On the other hand, the illumination of the location distant from the point light source  21  will be increased slightly due to the increase in the diffusion ability of the ring protrusions  226  therearound. By proper adjustment upon the diffusion ability of the ring protrusions  226 , the line light quality from the long slot  224  of the light shield  22  can be improved further, and so as the scanning quality. 
     Referring now to FIG. 4, a second embodiment of the light source mechanism for an imaging apparatus in accordance with the present invention is shown explodedly. 
     In the second embodiment, the light source mechanism  2   a  can include two point light source  21   a  and  21   b , and a light shield  22   a . The point light source  21   a  or  21   b  can be a light emitting diode (LED) which, as said in previous description, has advantages of low cost, longer life term, stable illumination and a wider wave range for application. These two point light sources  21   a  and  21   b  are preferably mounted to opposing ends of the light shield  22   a.    
     As shown in FIG. 4, the light shield  22   a  of the present invention, shaped as a long hollow pipe structure, includes an upper half  221   a  and a mating lower half  222   a . The light shield  22   a  can be preferably made of opaque materials. Each of both ends of the light shield  22   a  can include a respective mounting element  223   a  or  223   b  for installing the respective point light source  21   a  or  21   b . One feature of the present invention is that the lower half  222   a  of the light shield  22   a  further includes a long slot  224   a  lying along the axial longitudinal direction of the light shield  22   a . The long slot  224   a  has a length approximately equal to an ordinary width of a document for whole scale scanning. The interior surface of the light shield  22   a  can be formed as a diffusion surface  225   a  for evenly diffusing the lights emitted by the point light sources  21   a  and  21   b  inside the light shield  22   a , by which localized illumination phenomenon of the point lights  21   a  and  21   b  can be prevented. Therefore, under such an arrangement of the present invention, quality line light source can be obtained from the long slot  224   a  which provides homogeneous line lights from the diffused lights inside the light shield  22   a , though the point light sources  21   a  and  21   b  are applied. 
     Referring now again back to FIG. 3, just like the first embodiment in previous description, the inner wall of the light shield  22   a  and the diffusion surface  225  includes a plurality of the ring protrusions  226  and the high reflection layer. Methods for forming the high reflection layer (not shown in the figure) can be any injection method or any electroplating. In the optics theory, the ring protrusions  226  can have an excellent diffusion ability. Therefore, the lights emitted by the point light sources  21   a  and  21   b  can be evenly diffused inside the light shield  22   a , and then a homogeneous line light source can be constructed through the long slot  224   a.    
     Nevertheless, illustration adjacent to the point light sources  21   a  and  21   b  are still higher than that in the middle of the light shield  22   a . To overcome such localized illumination problem of the light source mechanism  2   a , the diffusion ability of the ring protrusions  226  adjacent to the point light sources  21   a  and  21   b  can be reduced and, on the other hand, that of the ring protrusions  226  in the middle of the light shield  22   a  can be increased. Under such an arrangement, the illumination adjacent to the point light sources  21   a  and  21   b  will be decreased a little bit due to the decrease in the diffusion ability of the ring protrusions  226  therearound. On the other hand, the illumination of the middle portion of the light shield  22   a  will be increased slightly due to the increase in the diffusion ability of the ring protrusions  226  therearound. By proper adjustment upon the diffusion ability of the ring protrusions  226 , the line light quality from the long slot  224   a  of the light shield  22   a  can be improved further, and so as the scanning quality. 
     While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.