Patent Application
20060279807
1. Field of the Invention
The present invention relates to a flat bed scanner, especially to a flat bed scanner using Light Emitting Diodes (LEDs) as a light source.
2. The Related Art
Flat bed scanners are applied widely by people in their daily life and work. The flat bed scanners can quickly scan papers, photos or pictures to get the image information and further input the image information into a computer.
When scanning, the flat bed scanners project light beams radiated from light sources over the objects that wait for scanning. And then the objects further reflect the light beams over Charge Coupled Devices (CCDs). The CCDs convert the light signals into corresponding electrical signals in order to get the image information of the objects.
Conventional flat bed scanners generally use Cold Cathode Fluorescent Lamps (CCFLs) as light sources. In order to make the CCFLs radiate light beams, a step-up circuit is needed to bring a high voltage to the CCFLs. During the period for the step-up circuit to turn a low voltage into a high voltage, the step-up circuit will product high frequency signal that can interfere the Charge Coupled Devices (CCDs) and other electrical devices of the flat bed scanners to make the flat bed scanners work unstably. Furthermore, security problems can not be omitted, because the flat bed scanners are work under high voltages.
U.S. Pat. Publication No. 2004/0095620 discloses a flat bed scanner, which uses a Light Emitting Diode (LED) as a light source. The flat bed scanner further has a half-cylinder optical element. The LED is beside the half-cylinder optical element. A part of the light beam radiated from the LED is reflected/refracted from the top of the half-cylinder optical element and converged into a light strip over the objects that wait for scanning along the extending direction of the half-cylinder optical element.
Because the LED is beside the half-cylinder optical element, the light-intensity distribution of the light strip along the extending direction of the half-cylinder optical element is not evenly. Furthermore, because the light-intensity distribution of LED is also not evenly, the light-intensity distribution in the width becomes more uneven. Therefore, the image produced by the flat bed scanner has streaks.
An object of the present invention is to provide a flat bed scanner that balances the light-intensity distribution of the light beam projected over the objects waiting for scanning, accordingly to enhance the quality of the image produced by the flat bed scanner.
To achieve the above object, the present invention provides a flat bed scanner comprises a transparent platform and a scanning mechanism. The transparent platform is used to support the objects that are waiting for scanning. The scanning mechanism is movably placed under of the transparent platform along the length direction of the transparent platform. The scanning mechanism includes a plurality of LEDs, a camera lens, a CCD and a diffuser. The LEDs are arranged in a line along the width direction of the transparent platform. The diffuser is set over the LEDs and has the same width with the transparent platform. The diffuser diffuses the light beams radiated from the LEDs and then projects the light beams being diffused over the objects that wait for scanning. The camera lens receives the light beams reflected from the objects, then the light beams being further projected over the CCD.
According to the flat bed scanner of the present invention, a plurality of LEDs are arranged in a line along the width direction of the transparent platform radiates light beams, and a diffuser diffuses the light beams to balance the light-intensity distribution of the light beams. Accordingly, the quality of the scanned image is enhanced.
With reference to
The transparent platform 100 is made of a kind of high-transparent material for supporting objects which wait for scanning, such as papers, photos, and pictures.
The scanning mechanism 200 includes a plurality of Light Emitting Diodes (LEDs) 210, a transparent plastic slice 220, a camera lens 240, a plurality of Charge Coupled Devices (CCDs) 250 and a housing 260. Furthermore, the scanning mechanism 200 further has reflection devices 230 in order to reflect lights. An accommodating space is enclosed by the housing 260 to accommodate the reflection devices 230, the camera lens 240 and the CCDs 250.
Please refer to
When scanning, a light beam radiated from the LEDs 210 is projected to the transparent plastic slice 220. The light beam is diffused by the transparent plastic slice 220 in the direction of the length and width direction of the transparent platform 100, and then the light beam being diffused is projected over the objects that are waiting for scanning. Consequently, the light-intensity distribution in the scanning zone is balanced, so that the shortcoming that the light-intensity distribution is not even in the prior art is overcome. The light beam is further reflected over the reflection devices 230 from the objects that are waiting for scanning. And then the light beam is further reflected to the camera lens 240, and further to the CCDs 250. Finally, the CCDs 250 convert the light signal into the corresponding electrical signal.
In order to get the full image information of the objects that wait for scanning, the flat bed scanner 10 of the present invention further includes a driving mechanism 300 and a control circuit 400 (shown in
According to the present invention, the transparent plastic slice 220 of the flat bed scanner 10 is used to diff-use light beams, so that other diffusers can be used to replace the transparent plastic slice 220. For example, a strip-shaped concave lens 220′ can be used to replace the transparent plastic slice 220 as shown in
As the above mentioned, by the LEDs 210 arranged in a line along the width direction of the transparent platform 100 and a diffuser such as the transparent plastic slice 220 or the strip-shaped concave lens 220′ diffusing the light beams radiated from the LEDs 210, the light-intensity distribution of the light beam projected in the scanning zone is balanced, accordingly, the quality of the scanned image is enhanced.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations as they are outlined within the description above and within the claims appended hereto. While the preferred embodiment and application of the invention have been described, it is apparent to those skilled in the art that the objects and features of the present invention are only limited as set forth in the claims appended hereto.
