Abstract:
A multi-lenses optical device with high resolution and low cost is provided for converting an image into electronic signals. The optical device includes a plurality of focusing units for focusing a plurality of sections of the image respectively, and correspondingly generating a plurality of focused image sections magnified with the same ratio and having different optical path lengths, a photoelectric conversion unit for converting the plurality of focused image sections to the electronic signals, a switching unit for sequentially having only one of the focused image sections transmitted to the photoelectric conversion unit at an instant, and a light-reflecting unit mounted between the photoelectric conversion unit and the plurality of focusing units for transmitting the plurality of focused image sections to the photoelectric conversion unit.

Description:
FIELD OF THE INVENTION 
     The present invention is related to an optical device, and more particularly to a multi-lenses optical device. 
     BACKGROUND OF THE INVENTION 
     Image processing is often used for photography or movie. As we know, the scanner plays an indispensable role in this field. Increasing the resolution of a scanner is investigated hard in order to get more clear images, but high cost of a scanner with high resolution is not avoidable. The operating principle of the conventional scanner is shown in FIG.  1 . An article is placed on the scanner to be scanned. The article is lit by a light source for generating an optical image  11 . The optical image  11  of the article is focused on a charge coupled device  13  by a lens set  12 , and then is converted to electronic signals to form digital data by the charge coupled device  13 . For obtaining a higher resolution, the number of pixels for the charge coupled device  13  must be increased. However, the cost of the charge coupled device  13  is proportional to the square of the number of pixels for it. Requiring higher resolution will thus cost much since the cost of a charge coupled device  13  is a great part of the production cost of a scanner. Frankly speaking, it is difficult to spend lower cost for obtaining higher resolution in the first prior art. 
     Another method also has been developed to solve the problem of high-cost. Please refer to FIG. 2 showing the operating principle of a scanner according to the second prior art. The optical image of the scanned article is divided into two sections  211  and  212 . There are many corresponding lens sets  221  and  222  and corresponding charge coupled devices  231  and  232  for the optical image sections  211  and  212  in this scanner. Different sections  211  and  212  are converted to electronic signals by the same steps as the first prior art by respective lens sets  221  and  222  and charge coupled devices  231  and  232 . Finally, the electronic signals will be combined together to form a full image. Hence, the number of pixels for a charge coupled device is reduced, but the performance can be still maintained like that of the prior art. The cost can be reduced by this arrangement. However, the cost is proportional to the number of charge coupled devices. Accordingly, we still hope to make an improvement in increasing resolution and decreasing cost. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a multi-lenses optical device with high resolution, but with less pixels for a photoelectric conversion unit. 
     In accordance with the present invention, a multi-lenses optical device for converting an initial image to electronic signals includes a plurality of focusing units, a photoelectric conversion unit, a switching unit, and a light-reflecting unit mounted between the photoelectric conversion unit and the plurality of focusing units. The plurality of focusing units are used for focusing a plurality of sections of the initial image respectively, and correspondingly generating a plurality of focused image sections magnified with the same ratio and having different optical path lengths. The photoelectric conversion unit, e.g. charge coupled device, is used for converting the corresponding focused image sections to electronic signals. The switching unit is used for sequentially having each one of the plurality of focused image sections selected and having the selected focused image section transmitted to the photoelectric conversion unit. The light-reflecting unit is used for transmitting the plurality of focused image sections to the photoelectric conversion unit. 
     In accordance with another aspect of the present invention, the focusing units are lens sets respectively mounted in specific locations for generating the corresponding focused image sections magnified with the same ratio. 
     In accordance with another aspect of the present invention, the light-reflecting unit preferably includes a first dichroic mirror for transmitting the plurality of focused image sections to the photoelectric conversion unit, and a reflective mirror or a second dichroic mirror for transmitting the plurality of focused image sections from the plurality of focusing units to the first dichroic mirror. 
     In accordance with another aspect of the present invention, the number of the plurality of focusing units is from 2 to 4. 
     In accordance with another aspect of the present invention, the switching unit is a light shade set. 
     In accordance with another aspect of the present invention, the light shade set preferably includes a movable light shade. 
     In accordance with another aspect of the present invention, the movable light shade may be mounted within the light paths of the plurality of initial image sections for shading the plurality of focusing units from the respective initial image sections except a selected section of the initial image corresponding to the selected focused image section at the instant. 
     In accordance with another aspect of the present invention, the movable light shade may be mounted between the light-reflecting unit and the plurality of focusing units for shading the light-reflecting unit from the plurality of focused image sections except the selected one generated by a selected focusing unit at the instant. 
     In accordance with another aspect of the present invention, the movable light shade may be mounted within the light-reflecting unit for shading the photoelectric conversion unit from the plurality of focused image sections except the selected one. 
     In accordance with another aspect of the present invention, the light shade set preferably includes a rotatable light shade. 
     In accordance with another aspect of the present invention, the rotatable light shade may be mounted between the light-reflecting unit or within the light-reflecting unit. It is rotated to be in different directions for shading the photoelectric conversion unit from the plurality of focused image sections except the selected one. 
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing the operation of a conventional scanner; 
     FIG. 2 is a schematic diagram showing the operation of another conventional scanner; 
     FIG. 3 is a schematic diagram showing two preferred embodiments of the operation of a scanner according to the present invention; 
     FIG. 4 is a schematic diagram showing a third preferred embodiments of the operation of a scanner according to the present invention; 
     FIG. 5 is a schematic diagram showing a fourth preferred embodiment of the operation of a scanner according to the present invention; and 
     FIG. 6 is a schematic diagram showing a fifth preferred embodiment of the operation of a scanner according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will be described more detailedly with reference to the following embodiments. It is to be noted that the following descriptions of the preferred embodiments of this invention are presented herein for the purpose of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. 
     Please refer to FIG. 3 which is a schematic diagram showing some preferred embodiments of a scanner according to the present invention. As shown in FIG. 3, the scanner has two lens sets  321  and  322  mounted in specific locations so that the ratio of image distance to object distance of the lens set  321  is the same as that of the lens set  322  according to the lens maker&#39;s equation. Hence, the magnifying power of the lens set  321 , defined as a ratio of image distance to object distance, is the same as that of the lens set  322 . An article is placed on the scanner and is lit by a light source to generate an initial image. The initial image is divided into two sections  311  and  312  to be scanned sequentially. The first initial image section  311  is focused by one lens set  321  for generating a first focused image section, while the second initial image section  312  is focused by the other lens set  322  for generating a second focused image section. Since the magnifying power of the lens sets  321  and  322  is the same, the full image will not be distorted when these two focused image sections are combined together. The light-reflecting unit  35  includes a dichroic mirror  351  and a reflective mirror  352 . The so-called dichroic mirror can reflect or transmit light at both sides. The reflectance and the transmittance at each side of the dichroic mirror can be modified according to the requirement of users Hence, the dichroic mirror  351  can transmit the focused image section from the reflective mirror  352  in a transmissive mode and from the lens set  321  in a reflective mode. Certainly, the reflective mirror  352  may be replaced by another dichroic mirror, but a dichroic mirror is more expensive than a reflective mirror. There are two movable light shades  341  and  342  shown in this figure, but only one is needed when this optical device is put into practice. The light shades are defined as “switching unit” because they are used for obstructing undesired initial image sections or undesired focused image sections, in other words, “switching” among the lens sets to have only one initial image section focused by the corresponding lens set or have only one focused image section sensed by the charge coupled device. The two preferred embodiments are described as follows. 
     Embodiment 1 
     A movable light shade  341 , for instance, is equipped in a scanner. First of all, the movable light shade  341  is moved to be located in front of lens set  322  so that the second initial image section  312  can not be focused by the lens set  322  and only the first initial image section  311  can be focused by the lens set  321 . The lens set  321  generates the first focused image section to be transmitted to the charge coupled device  33  through the dichroic mirror  351 . Then, it is sensed and converted to electronic signals by the charge coupled device  33 . Thereafter, the movable light shade  341  is moved to be located in front of lens set  321  so the first initial image section  311  is obstructed by the movable light shade  341 , and only the second initial image section  312  can be focused by the lens set  322 . The lens set  322  generates the second focused image section which is transmitted to the charge coupled device  33  through the reflective mirror  352  and dichroic mirror  351  in sequence. Then, the second focused image section is sensed and converted to electronic signals. At last, all these generated electronic signals are transformed to digital data and a full image is shown on a computer screen or other image processing equipments. Although the optical path lengths of object distance plus image distance of each lens sets are different, the magnifying power of each lens sets is the same. Hence, the combined full image is not distorted. 
     Embodiment 2 
     If the switching unit includes the movable light shade  342 , the scanning principle is a little different. To begin with, the movable light shade  342  is moved to be located in back of the lens set  322  so the second focused image section generated by the lens set  322  responding to the second initial image section  312  can not reach the light-reflecting unit  35 . Only the first focused image section generated by the lens  321  responding to the first initial image section  311  can be transmitted to the charge coupled device  33 . The next in order, the movable light shade  342  is moved leftward to be placed in back of lens set  321  so that the first focused image section is obstructed. Only the second focused image section is sensed by the charge coupled device  33  by way of light-reflecting unit  35 . The following steps and light paths of focused image sections are the same as described in EMBODIMENT 1 and do not explain tautologically. 
     The number of the focusing units can be increased to any requirement, preferable two to four. Their operating functions are similar to the above description. A preferred embodiment of a scanner having three focusing units is described briefly as follows. 
     Embodiment 3 
     Please refer to FIG.  4 . There are three lens sets  421 ,  422 , and  423  corresponding to the left initial image section  411 , the middle initial image section  412 , and the right initial image section  413  respectively. The light-reflecting unit  45  includes two dichroic mirrors  451  and  452  and a reflective mirror  453  corresponding to lens sets  421 ,  422 , and  423 . Each lens set is accompanied by only one movable light shade. In other words, only one of the movable light shades  4411  and  4412  is adopted to match the lens set  421  in the scanner. By the same token, only one of the movable light shades  4421  and  4422 , and only one of the movable light shades  4431  and  4432  are required. All possible movable light shades shown in the diagram are not essential. All the possibilities are indicated in the figure. The switching unit, for example, includes the movable light shades  4411 ,  4421 , and  4431 . First of all, the movable light shades  4411  belonged to the lens set  421  is dislodged from the lens set  421  (hereafter called “non-obstructive state”), and the other movable light shades  4421  and  4431  are provided in front of other lens sets  422  and  423  (hereafter called “obstructive state”). The left initial image section  411  is focused by the lens set  421  to generate a left focused image section. The left focused image section is transmitted through the dichroic mirror  451  and is sensed and converted to electronic signals by the charge coupled device  43 . Secondly, the movable light shade  4421  belonged to lens  422  is in a non-obstructive state and the other movable light shades  4411  and  4431  are in an obstructive state. The middle initial image section  412  is focused by the lens set  422  for generating a middle focused image section. Thereafter, the middle focused image section is transmitted to the charge coupled device  43  through the dichroic mirrors  452  and  451  in sequence, and is converted to electronic signals by the charge coupled device  43 . Afterward, the movable light shade  4431  is in a non-obstructive state and the other movable light shades  4411  and  4421  are in an obstructive state. The right initial image section  413  is focused by the lens set  423  to generate a right focused image section. The right focused image section is then transmitted to the charge coupled device  43  through the reflective mirror  453 , two dichroic mirrors  452  and  451  in sequence and is converted into electronic signals. All these generated electronic signals are transformed to digital data for being processed later. The words “left”, “middle”, and “right” are not used to limit the scope of the present invention, but used to illustrate the preferred embodiment more clearly. The operating sequence also can be modified to make the method more convenient for the manufacturers and users. 
     The feature of above-described preferred embodiments is that the initial image is divided into many sections to be scanned in sequence. Therefore, the resolution can be improved without increasing the number of charge coupled devices or the number of pixels for a charge coupled device. Thus, high resolution and low cost can be achieved at the same time. The costs of some focusing units and a light-reflecting unit required for the embodiment according to the present invention are quite cheaper than that of charge coupled device. Therefore, the cost can be significantly reduced. In addition, the optical elements including lens sets, mirrors, and charge coupled device are kept immobily. It is well known that the precision of a scanner is obviously influenced by the positions of optical elements. Few movable light shades are adopted in the preferred embodiments of the present invention to shade undesired initial image sections and undesired focused image sections at an instant. The movable light shade can be mounted in front of the lens set, between the lens set and the light-reflecting unit, or within the light-reflecting unit just according to one&#39;s requirement. The precision of the scanner according to the present invention keeps unerring because the positions of other optical elements will not be influenced by moving the light shades. The other driving elements provided for the precision according to the prior arts are not needed so that the size and the production cost are significantly reduced. 
     Embodiment 4 
     In stead of movable light shade, a rotatable light shade can also perform well. Please refer to FIG.  5 . This preferred embodiment is similar to the above-described embodiment shown in FIG. 3 except the rotatable light shade  54 . There are two lens sets  521  and  522  mounted in specific locations and the magnifying power of the lens set  521  is the same as that of the lens set  522 . The light-reflecting unit  55  includes a dichroic mirror  551  and a reflective mirror  552  corresponding to lens sets  521  and  522  respectively. The initial image is divided into two sections  511  and  512  to be scanned sequentially. The first initial image section  511  is focused by the lens set  521  for generating a first focused image section and the second initial image section  512  is focused by the lens set  522  for generating a second focused image section. Since the magnifying powers of the lens sets  521  and  522  are the same, the full image will not be distorted when these two focused image sections are combined together. The switching unit includes a rotatable light shade  54 . First of all, the rotatable light shade  54  is rotated to be in a vertical direction between the dichroic mirror  551  and the reflective mirror  552  so that the second focused image section is obstructed. The first focused image section is transmitted to the charge coupled device  53  through the dichroic mirror  551  and is converted to electronic signals by the charge coupled device  53 . Thereafter, the rotatable light shade  54  is rotated to be in a horizontal direction between the lens set  521  and the dichroic mirror  551 . Therefore, the second focused image section, but not the first focused image section, can be received by the charge coupled device  53 . Then, the second focused image section is converted to electronic signals. At last, all these generated electronic signals are transformed to digital data and a full image can be shown on a computer screen or other image processing equipments. It should be noted that the words “horizontal” and “vertical” shown in this paragraph are only used for illustrating this embodiment more clearly. The direction of rotatable light shade is not essential. The only matter borne in mind is that the rotatable light shade must completely obstruct the undesired focused image sections. 
     The number of the focusing units can be increased to meet one&#39;s requirement, especially from two to four. Their operating functions are similar to the ones as described above. A preferred embodiment of a scanner having three focusing units is described briefly as follows. 
     Embodiment 5 
     Please refer to FIG.  6 . There are three lens sets  621 ,  622 , and  623  for focusing the left initial image section  611 , the middle initial image section  612 , and the right initial image section  613  to generate the left focused image section, the middle focused image section, and the right focused image section, respectively. The light-reflecting unit  65  also includes two dichroic mirrors  651 ,  652  and a reflective mirror  653  corresponding to lens sets  621 ,  622 ,  623 . The words “left”, “middle”, and “right” should not be used to limit the scope of the present invention, but used to illustrate the preferred embodiment more clearly. Besides, the operating sequence also can be modified to make the method more convenient for the manufactures and users. At the first step, the rotatable light shade  641  is rotated to be in a vertical direction between the two dichroic mirrors  651  and  652 . The left focused image section is transmitted from the lens set  621  to the charge coupled device  63  through the dichroic mirror  651 , but the other focused image sections are obstructed. Then, the left focused image is converted to electronic signals by the charge coupled device  63 . At the second step, the rotatable light shade  641  is rotated to be in a horizontal direction between the lens set  621  and the dichroic mirror  651 , while the rotatable light shade  642  is rotated to be in a vertical direction between the dichroic mirror  652  and the reflective mirror  653 . The middle focused image section is transmitted from the lens set  622  to the charge coupled device  63  through two dichroic mirrors  652  and  651  in sequence. Thereafter, it is converted to electronic signals by the charge coupled device  63 . With regard to the other focused image sections, they are obstructed by the rotatable light shades  641  and  642 . At the third step, the rotatable light shade  641  kept its position between the lens set  621  and the dichroic mirror  651 , and the other rotatable light shade  642  is rotated to be in a horizontal direction between the lens set  622  and the dichroic mirror  652 . The right focused image section, but not other focused image sections, is transmitted from the lens set  623  to the charge coupled device  63  through the reflective mirror  653  and two dichroic mirrors  652  and  651  in sequence. Thereafter, the right focused image section is received and converted to electronic signals by the charge coupled device  63 . At last, all these electronic signals generated in the first, second, and third instances are transformed to digital data. 
     The feature of these two preferred embodiments is that the initial image is divided into many sections to be scanned in sequence. The number of the charge coupled devices or the pixels for a charge coupled device required for this case can be reduced without changing the resolution. The cost of some lens sets and a light-reflecting unit required for the embodiment according to the present invention are quite cheaper than that of a charge coupled device. Therefore, the cost can be significantly reduced, and the high quality can also be achieved. For instance, if a 600 dpi (dot per inch) resolution of an image is required, the charge coupled device with a 600 dpi must be equipped in the scanner according to the prior art. In the present invention, the charge coupled device with a 300 dpi is sufficient if there are two lens sets equipped in the scanner. Moreover, the charge coupled device with a 200 dpi can provide an image with 600 dpi resolution if there are three lens sets available for the scanner. Besides, another feature of these preferred embodiments is that the optical elements such as lens sets, light-reflecting unit, and the charge coupled device are immobily fixed in the housing. The method of the present invention is to obstruct undesired image sections substituted for capturing the desired image section. The precision of the scanner according to the present invention keeps unerring because the positions of the optical elements will not be affected by rotating the light shades. The other driving elements for the precision according to the prior arts are not required so the size and the production cost can be reduced significantly. Accordingly, the present invention really conforms to the genius of modem technology. 
     While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.