LED illumination system for a scanner including a UV light emitting device
View Patent ↗An illumination system for a scanner according to one example embodiment includes an array of visible light emitting diodes including a red, a blue and a green light emitting diode and an ultraviolet light emitting device configured to emit light predominantly in the ultraviolet region of the electromagnetic spectrum. During a scan sequence of the red, blue and green light emitting diodes, at least one of the visible light emitting diodes and the ultraviolet light emitting device are positioned to simultaneously illuminate an object being scanned. In one form, during the sequence, the blue light emitting diode and the ultraviolet light emitting device are simultaneously illuminated while in another the red light emitting diode and the ultraviolet light emitting device are simultaneously illuminated.
1. An illumination system for a scanner, comprising:
an array of visible light emitting diodes having a red light emitting diode, a blue light emitting diode and a green light emitting diode;
an ultraviolet light emitting device for emitting light predominantly in the ultraviolet region of the electromagnetic spectrum, the array of the visible light emitting diodes and the ultraviolet light emitting device being positioned to illuminate an object to be scanned; and
a controller operatively connected to the array of visible light emitting diodes and the ultraviolet light emitting device, wherein, during illuminating the object to be scanned, the controller is configured to operate the red, blue and green light emitting diodes in a sequence to illuminate the object being scanned and, during the sequence, the ultraviolet light emitting device is operated so that the ultraviolet light emitting device and at least one of the red light emitting diode, the blue light emitting diode and the green light emitting diode are simultaneously operated to illuminate the object being scanned.
2. The illumination system of claim 1 , wherein the ultraviolet light emitting device is a light emitting diode.
3. The illumination system of claim 2 , wherein the array of visible light emitting diodes and the ultraviolet light emitting diode are operatively mounted on a common printed circuit board assembly.
4. The illumination system of claim 1 , wherein the array of visible light emitting diodes and the ultraviolet light emitting device are mounted in a housing of the scanner on a scan head frame that is movable in a reciprocating manner.
5. The illumination system of claim 1 , wherein the array of visible light emitting diodes and the ultraviolet light emitting device are mounted in a stationary position in a housing of the scanner and an integrating light pipe is positioned to receive light emitted by the array of visible light emitting diodes and the ultraviolet light emitting device and to transmit the received light onto the object being scanned.
6. The illumination system of claim 1 , wherein the array of visible light emitting diodes further includes a white light emitting diode.
7. The illumination system of claim 1 , wherein the intensity of the ultraviolet light emitting device is adjusted so that the spectral distribution of the illumination system matches the spectral distribution of one of sunlight, conventional fluorescent office light and conventional white light.
8. The illumination system of claim 1 wherein the controller is further configured to perform gamma correction of the ultraviolet light emitting device.
9. The illumination system of claim 1 wherein the controller is further configured to simultaneously operate the ultraviolet light emitting device and the blue light emitting diode during the sequence.
10. The illumination system of claim 1 wherein the controller is further configured to simultaneously operate the ultraviolet light emitting device and the red light emitting diode during the sequence.
11. A document scanner, comprising:
a housing having a transparent imaging window positioned thereon for supporting a document to be scanned;
an illumination system disposed within the housing and positioned to illuminate the transparent imaging window, the illumination system including a printed circuit board assembly having an array of light emitting diodes operatively mounted thereto, the array of light emitting diodes including:
a red light emitting diode, a blue light emitting diode and a green light emitting diode for emitting light predominantly in the visible region of the electromagnetic spectrum; and
an ultraviolet light emitting diode for emitting light predominantly in the ultraviolet region of the electromagnetic spectrum;
an image sensor positioned to sense light from the array of light emitting diodes reflected from the document being scanned; and
a controller operatively connected to the array of diodes and the image sensor, wherein, during illuminating the document to be scanned, the controller is configured to operate the red, blue and green light emitting diodes in a sequence to illuminate the document being scanned and, during the sequence, the ultraviolet light emitting device is operate so that the ultraviolet light emitting diode and at least one of the red light emitting diode, the blue light emitting diode and the green light emitting diode are simultaneously operated to illuminate the object being scanned.
12. The document scanner of claim 11 , wherein the printed circuit board assembly is mounted in the housing of the document scanner on a scan head frame that is movable in a reciprocating manner.
13. The document scanner of claim 11 , wherein the printed circuit board assembly is mounted in a stationary position in the housing of the document scanner and an integrating light pipe is positioned to receive light emitted by the array of light emitting diodes and to transmit the received light onto substantially the entire imaging window at one time to illuminate substantially the entire document being scanned at one time.
14. The document scanner of claim 11 , wherein the printed circuit board assembly includes a plurality of printed circuit board assemblies each having an array of light emitting diodes operatively mounted thereto; each printed circuit board assembly is mounted in a stationary position in the housing of the document scanner; and a plurality of integrating light pipes are each positioned to receive light emitted by a respective array of light emitting diodes and to collectively transmit the received light onto substantially the entire imaging window at one time to illuminate substantially the entire document being scanned at one time.
15. The document scanner of claim 11 , wherein the controller is programmed to turn off the ultraviolet light emitting diode when a lid of the document scanner is in an open position.
16. The document scanner of claim 11 , wherein the intensity of the ultraviolet light emitting device is adjusted so that the spectral distribution of the illumination system matches the spectral distribution of one of sunlight, conventional fluorescent office light and conventional white light.
17. The document scanner of claim 11 wherein the controller is further configured to perform gamma correction of the ultraviolet light emitting diode.
18. The document scanner of claim 11 wherein the controller is further configured to simultaneously operate the ultraviolet light emitting diode and the blue light emitting diode during the sequence.
19. The document scanner of claim 11 wherein the controller is further configured to simultaneously operate the ultraviolet light emitting diode and the red light emitting diode during the sequence.
20. A method for scanning an object to reduce the occurrence of metameric failure associated with the scan, comprising:
illuminating the object being scanned by activating in a sequence an array of light emitting diodes that emit predominantly visible light, the array having a red light emitting diode, a blue light emitting diode and a green light emitting diode and,
during the sequence, activating a light emitting device that emits predominantly ultraviolet light simultaneously with one of the red, blue and green light emitting diodes;
sensing during the sequence the light reflected from an the object being scanned using an image sensor; and
processing the sensed reflected light to form an image of the scanned object.
21. The method of claim 20 further comprising simultaneously illuminating the blue light emitting diode and the ultraviolet light emitting device during the sequence.
22. The method of claim 20 further comprising simultaneously illuminating the red light emitting diode and an ultraviolet light emitting device during the sequence.
23. The method of claim 20 further comprising performing gamma correction to linearize the ultraviolet light emitted by the ultraviolet light emitting device.