Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Utility Patent
1998-11-03
2001-01-02
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S823000, C358S474000, C358S483000
Utility Patent
active
06169622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical scanner, and more particularly, to an optical scanner with a distance adjusting device.
2. Description of the Prior Art
Flatbed scanners are commonly used for converting document data into image signals. The most critical component within a flatbed scanner is the optical scanning module. A scanning module usually comprises a casing with an opening for receiving light from the document, an optical sensing device installed within the casing for converting light from the document into corresponding image signals, and a lens installed in front of the optical sensing device for converging light from the document onto the optical sensing device.
The scanning module has a fixed resolution determined both by the image amplification of the optical scanning module and the resolving power of the optical sensing device. The image amplification of the scanning module is determined by its lens, the object distance between the document and the lens, and the image distance between the lens and the optical sensing device. If errors of the object and image distances are generated during the installation of the scanning module, the resolution of the scanning module will be affected.
In general, there are two types of scanners: transmitted type and reflective type. In a transmitted-type scanner, the document is defined as a transmitted document and the light source is positioned behind this document. Light travels from the light source to the document, then travels to the optical sensing device to be converted into image signals. Conversely, in a reflective-type scanner, the document is defined as a reflective document and the light source is positioned in front of this document. In this scheme, light is reflected by the document and then passed to the optical sensing device.
A flatbed scanner usually further comprises a document holder for fixing transmitted documents. To scan a transmitted document, the document holder is mounted on the transparent window of the flatbed scanner. The transmitted document is fixed onto the document holder. However, to scan a reflective document, the reflective document is placed directly onto the transparent window of the flatbed window. The document holder has a set thickness of approximately 2 mm to 5 mm and so the object distance of a transmitted document is 2 mm to 5 mm longer than that of a reflective document. This difference between the object distances in high resolution scanning modules often exceeds the tolerance of the lens of the scanning module. The image of a transmitted document thus cannot be accurately focused onto the optical sensing device.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide an optical flatbed scanner with an object distance adjusting device to solve the above mentioned problem.
In a preferred embodiment, the present invention provides an optical scanner comprising a housing, a transparent platform installed on the housing for placing a reflective document; and a document holder with a transparent window for placing a transmitted document. The scanner further comprises a scanning module movably installed in the housing under the transparent platform for scanning a transmitted document or a reflective document. The scanning module comprises:
a casing with a transparent window for receiving light from the document;
an optical sensing device installed in the casing for converting the light from the document into corresponding image signals;
three reflective mirrors installed in the casing for passing light from the document to the optical sensing device;
a lens installed between the reflective mirrors and the optical sensing device for converging light from the document onto the optical sensing device;
a plastic housing installed within the casing for mounting the lens and optical sensing device; and
an adjusting device for adjusting the object distance between the document and the lens by moving the attached plastic housing.
The scanner further comprises a driving device for driving the scanning module, and a control device for controlling the scanning module and the driving device.
It is an advantage of the present invention that the object distance adjusting device can adjust the object distance between the document and the lens and the flatbed scanner is able to scan documents placed at different heights over the transparent platform of the scanner.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.
REFERENCES:
patent: 5621563 (1997-04-01), Brook et al.
patent: 5633745 (1997-05-01), Chen et al.
Chen Bill
Tsai Jern-Tsair
Cherry Euncha
Hsu Winston
Mustek Systems Inc.
Spyrou Cassandra
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