Method and apparatus for preventing debris contamination of optical elements used for imaging
View Patent ↗The imaging debris produced by imaging a media with a higher power laser is prevented from accumulating on an optical imaging element by establishing a substantially non-turbulent fluid flow across the optical element. The non-turbulent flow forms a barrier between the optical element and the imaging environment such that debris is not able to reach a surface of the optical element during an imaging operation.
1. An apparatus for preventing the contamination of an optical element in an imaging head for imaging a media that produces imaging debris, the apparatus comprising:
an imaging head comprising an exposed optical element and a source of an imaging beam directed through the optical element to image a media, the imaging beam creating imaging debris upon interaction with the media;
a pressurized fluid source;
an orifice for directing fluid from the fluid source across the front surface of the optical element;
a flow collimating element, interposed in a path of the fluid for producing a substantially non-turbulent fluid flow in front of the optical element;
a vacuum sink connected to a source of vacuum, the vacuum sink operative to remove the imaging debris from the imaging area in combination with the substantially non-turbulent fluid flow; and,
a fluid jet directed towards the surface of the media, the jet for directing the imaging debris towards the vacuum sink.
2. The apparatus of claim 1 wherein the flow collimating element comprises plurality of parallel passages segmenting the orifice.
3. The apparatus of claim 2 wherein the parallel passages are hexagonal in cross section.
4. The apparatus of claim 2 wherein, in cross section, the parallel passages comprise an array of rectangular passages.
5. The apparatus of claim 4 wherein the parallel passages comprise a regular array of holes in the flow collimating element.
6. The apparatus of claim 1 wherein the flow collimating element comprises a substantially straight channel leading up to the orifice, the channel having a length in the direction of the fluid flow greater than at least one of the dimensions of the orifice.
7. The apparatus of claim 6 wherein the substantially straight channel is tapered.
8. The apparatus of claim 1 comprising a fluid reservoir for equalizing fluid pressure, the reservoir located before the flow collimating element, the reservoir fed by the fluid source.
9. The apparatus of claim 1 wherein the optical element comprises at least one of: a transparent window; and, an imaging lens.
10. The apparatus of claim 1 wherein the fluid source comprises a source of a gas.
11. The apparatus of claim 10 wherein the gas comprises air.
12. The apparatus of claim 10 wherein the gas is ionized.
13. The apparatus of claim 1 comprising a rounded protrusion located between the exposed optical element and the vacuum sink.
14. The apparatus of claim 1 wherein the vacuum sink comprises an inlet passage oriented generally in a direction of the substantially non-turbulent flow.
15. A method for preventing the contamination of an optical element in an imaging head for imaging a media that produces imaging debris, the method comprising:
collimating a flow of fluid from a source of pressurised fluid to produce a substantially non-turbulent fluid flow;
directing the non-turbulent fluid flow across an optical element such that the fluid flow forms a barrier between the optical element and the imaging debris;
vacuuming the imaging debris away from the imaging area using a vacuum sink; and,
directing a fluid jet at the surface of the media to direct the imaging debris toward the vacuum sink.