Optical module with movable carriage having mirror

An optical module with movable reflective mirrors is provided in the invention. The optical module, which is set in a scanner for the scanning of documents, comprises the following elements: a first carriage comprising a first reflective mirror, a lens and a photoelectric sensing device, wherein the first carriage moves along the scanning direction to scan the document to be scanned; a second carriage comprising a second reflective mirror, a lens and a photoelectric sensing device, wherein the second carriage can make relative movement corresponding to the first carriage along the scanning direction; and a third carriage comprising a third reflective mirror, a lens and an photoelectric sensing device, wherein the third carriage can make relative movement corresponding to the first carriage along the scanning direction. Of which, the first carriage is situated between the second carriage and the third carriage with the distance between the second carriage and the third carriage being fixed at a constant value during the course of scanning, while the image light of the document to be scanned forms an image on the photoelectric sensing device via the focusing of the lens after having been reflected via the first reflective mirror, the second reflective mirror, and the third reflective mirror sequentially.

This application claims the benefit of Taiwan application Serial No. 91138175, filed Dec. 31, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to an optical module, and more particularly, to an optical module with movable reflective mirrors.

2. Description of the Related Art

Of the many peripherals of a personal computer, the scanner can be said to be essential equipment. Generally speaking, the scanners in today's market have only little difference in terms of function and image scanning quality. Therefore, how to further shrink the size and volume of a scanner to improve the convenience of use has become a focus for R&D engineers in the field of scanners.

Please refer toFIG. 1, a schematic diagram for a conventional optical module. The conventional optical module100comprises a carriage110and a guiding piece120, wherein the carriage110is equipped with a reflective mirror set, a lens and a photoelectric sensing device (not shown in the diagram).

The carriage110, which is coupled to the guiding piece120, can move back and forth along the scan direction D.

In the course of scanning, the image light130of the document to be scanned, the reflecting light or the penetrating light of the document to be scanned for instance, enters into the carriage110. The image light130, reflected by the reflective mirror set composed of plural reflective mirrors, will be focused via a lens and received by the photoelectric sensing device.

Each reflective mirror of the reflective mirror set, the lens and the photoelectric sensing device are all fixed in the carriage110. The purpose is to keep both the front optical path and the rear optical path at a fixed value such that a clear and quality scan image can be obtained. The front optical path is the path traveled by the image light, emitted by the document to be scanned, reflected via various reflective mirrors, arriving at the lens lastly. The rear optical path refers to the path from the lens to the photoelectric sensing device, The carriage10, having to accommodate all reflective mirrors, the lens and the photoelectric sensing device, is undesirably large.

It can be understood from the above disclosure that an over-sized carriage110will affect the scanner, which the carriage110is installed therein. The consequence is that the overall volume of the scanner cannot be effectively reduced. Moreover, a conventional scanning module whose back focus cannot be enlarged cannot be used to scan large-sized documents.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an optical module with movable reflective mirrors. The purpose is to effectively reduce the overall volume of a scanner, availing the convenience of use and the scanning of lager-sized documents.

According to the above object, an optical module with movable reflective mirrors is provided in the present invention. The optical module, which is set in a scanner for the scanning of documents, comprises the following elements: a first carriage comprising a first reflective mirror, a lens and a photoelectric sensing device, wherein the first carriage moves along the scanning direction to scan the document to be scanned; a second carriage comprising a second reflective mirror, a lens and a photoelectric sensing device, wherein the second carriage can make relative movement corresponding to the first carriage along the scanning direction; and a third carriage comprising a third reflective mirror, a lens and an photoelectric sensing device, wherein the third carriage can make relative movement corresponding to the first carriage along the scanning direction. Of which, the first carriage is situated between the second carriage and the third carriage with the distance between the second carriage and the third carriage being fixed at a constant value during the course of scanning, while the image light of the document to be scanned forms an image on the photoelectric sensing device via the focusing of the lens after having been reflected via the first reflective mirror, the second reflective mirror, and the third reflective mirror sequentially.

DETAILED DESCRIPTION OF THE INVENTION

The optical module with movable reflective mirrors according to the present invention differs with a conventional optical module in that the former has three carriages while the latter has only one single but bigger carriage. The optical module according to the invention reduces the volume of the scanner in which the carriage is accommodated. Without increasing the volume of the carriage on which a lens and a photoelectric sensing device are installed, a reflective mirror is installed between the lens and the photoelectric sensing device to increase the back focus so the scanner can scan larger documents via such optical module.

Please refer toFIG. 2A, a structural diagram for an optical module with movable reflective mirrors according to the preferred embodiment of the invention, andFIG. 2B, a side view thereof. The optical module200, which can be set in a scanner for the scanning of documents to be scanned, comprises carriages210,220and230, a guiding piece and a firmware250.

The carriage210comprises a reflective mirror212, a lens214and a photoelectric sensing device216, wherein the carriage210, being coupled to the guiding piece240, moves on the guiding piece240along the scanning direction D (the pivotal direction of the guiding piece214) to scan documents.

The carriage220comprises reflective mirrors222and224, wherein the carriage220, being coupled to the guiding piece240, makes relative movement corresponding to the carriage210and moves on the guiding piece240along the scanning direction D.

By the same analogy, the carriage230, coupled to the guiding piece240, comprises two reflective mirrors232and234, makes relative movement corresponding to the carriage210and moves on the guiding piece240along the scanning direction D.

As illustrated inFIG. 2AandFIG. 2B, the image light of the document to be scanned is reflected via reflective mirrors212,222,224,232and234sequentially then forms an image on the photoelectric sensing device via the focusing of the lens214.

The image light260follows an optical characteristic of keeping the front light path unchanged, i.e., the sum of the distance between reflective mirrors222and212, the distance between reflective mirrors232and224, and the distance between the lens214and the reflective mirror234must be kept at a fixed value. The purpose of keeping the front light path of the image light260unchanged can be achieved by installing the carriage210between carriages220and230, meanwhile, keeping the distance between carriages220and230at a fixed value during the course of scanning. A fixed distance between carriages220and230can be achieved by connecting the firmware250between them. As shown in the diagram, the firmware250, passing through the carriage210, connects carriages220and230. While the carriage210can make relative movement corresponding to carriages220and230on the firmware250, carriages220and230can not make relative displacement due to the connection of the firmware250during the course of scanning.

Please refer toFIG. 3AandFIG. 3B, schematic diagrams illustrating relative positions between each carriage corresponding to the optical module according to the invention ofFIG. 2during scanning processes. As is shown in the diagrams, all carriages210,220and230can move back and forth along the scanning direction D during the course of scanning. The carriage220and the carriage230always remain a distance of X+Y, which can be achieved by means of the firmware250ofFIG. 2. When the distance between carriages210and230is increased from X to X+a (fromFIG. 3AtoFIG. 3B), the distance between carriages10and220will be reduced from Y to Y−a (fromFIG. 3AtoFIG. 3B).

Please refer to bothFIG. 2andFIG. 4, a side view for another reflective mirror layout of the optical module with reflective mirrors according to the preferred embodiment of the invention. Under the circumstance of keeping the front optical path unchanged, the original two-piece designed reflective mirrors222and224of the carriage220can be replaced by a single piece reflective mirror422while the original two-piece designed reflective mirrors232and234of the carriage230can be replaced by a single piece reflective mirror432. Such layout of reflective mirrors reduces not only the number of reflective mirrors but also the volume of the carriage in which the reflective mirrors are installed.

Please refer toFIG. 5AandFIG. 5B, two structural diagrams for the optical module with reflective mirrors according to the preferred embodiment of the invention when back focus is large. Normally, when a larger document is to be scanned, a larger back focus is needed. That is to say, the distance between the lens and the photoelectric sensing device needs to be enlarged. This can be achieved by means of the structure shown inFIG. 5AandFIG. 5B.

Under the circumstance of not increasing the volume of the carriage210, the locations for the lens214and the photoelectric sensing device216can be adjusted with an additional reflective mirror512being installed on the carriage210as is illustrated inFIG. 5A. Another design as is shown inFIG. 5Bis to install reflective mirrors514and516on the two lateral sides of the carriage210respectively to reflect the image light260, which has been focused via the lens216, onto the photoelectric sensing device216. So the back focus can be effectively enlarged permitting the scanning of larger documents.

In the above disclosure, the scanner can be a reflection-type image scanner or a penetration-type image scanner; the guiding piece240can be a pivotal shaft or any other elements which enable the carriage to move back and forth along the scanning direction D; the firmware250can be any element, which, connecting carriages220and230, prevents relative displacement between carriages220and230without impeding the movement of the carriage210between carriages220and230; the photoelectric sensing device can be a charged coupled device (CCD) or a complementary mental oxide semiconductor sensor (CMOS sensor).

When compared with a conventional optical module having only one large carriage, the scanning direction of the carriage210according to the invention needs only a thinner thickness because a number of reflective mirrors have been moved to carriages220and230. Being equipped with reflective mirrors only, the thickness for carriages220and230can also be reduced. When compared with the carriage in a conventional optical module, all the carriages inFIG. 2Bare shorter in terms of the height while the carriages inFIG. 4can be even shorter. With the installation of reflective mirrors on the carriage210, the back focus can be enlarged enabling the scanning of larger documents.

The optical module with movable reflective mirrors according to the preferred embodiment of the invention is featured by the advantages of effectively reducing the volume of the scanner in which the optical module is installed, enhancing the convenience of use and enabling the scanning of larger documents.