Optical image scanning device with fluorescent layer as back light

1. An optical image scanning device comprising:

a casing having a light-transmittable document supporting plate;

a top cover movably mounted to the casing for removably covering the document supporting plate, the top cover having an underside surface facing the document supporting plate, a layer of fluorescent material being formed on the underside surface of the top cover; and

an optic module arranged inside the casing, the optic module comprising a light source for projecting an exciting light onto the fluorescent layer whereby the fluorescent material of the layer is excited by the exciting light to emit a scanning light, and an image sensing unit for receiving the scanning light;

when a light-transmittable document comprising image formed thereon is positioned on the document supporting plate, the exciting light generated by the light source and projected onto the fluorescent layer causes the fluorescent material to emit the scanning light transmitting through the light-transmittable document and thus projecting the image onto the image sensing unit.

2. The optical image scanning device as claimed in claim 1 , wherein the light source comprises an ultraviolet light generator to generate an ultraviolet light as the exciting light and wherein the fluorescent material is excited by the ultraviolet light to emit the scanning light.

3. The optical image scanning device as claimed in claim 2 , wherein the ultraviolet light generated by the light source has a wavelength of 250–260 nm.

4. The optical image scanning device as claimed in claim 2 , wherein the ultraviolet light generated by the light source has a wavelength of 360–370 nm.

5. The optical image scanning device as claimed in claim 2 , wherein the ultraviolet light generator comprises at least one ultraviolet light emitting diode emitting an ultraviolet light having a wavelength of 370–400 nm.

6. The optical image scanning device as claimed in claim 2 , wherein the fluorescent material comprises Halo Calcium Phosphate.

7. The optical Image Scanning Device as claimed in claim 2 , wherein the fluorescent material comprises rear earth based fluorescent materials.

8. The optical image scanning device as claimed in claim 2 , wherein the fluorescent material is excited by the ultraviolet light generated by the ultraviolet light generator to emit a light source comprising a blue light, a green light, an orange light, and a red light, the light source being further mixed to form a white light.

9. The optical image scanning device as claimed in claim 1 , wherein the light source comprises a light generator that generates a blue light, the blue light being projected to the fluorescent layer to cause the fluorescent material to emit a yellow light whereby a white light is formed by combination thereof.

10. The optical image scanning device as claimed in claim 9 , wherein the light generator that generates a blue light comprises at least one InGaN based blue light emitting diode, the blue light generated by the blue light emitting diode having a wavelength of 460–480 nm.

11. The optical image scanning device as claimed in claim 9 , wherein the fluorescent material comprises Yttrium Aluminum Garnet that generates a yellow light of wavelength 555 nm.

12. The optical image scanning device as claimed in claim 1 , further comprising a reflective type light source mounted on the optic module for projecting a light onto a document formed on a non-transmissive medium, the light being reflected by the document and received by the image sensing unit.