Tuesday, August 12, 2008

Micrometer Thin Precision Marking with Modulation of Contrast


Marking a variety of materials is one of the strengths of Lenox Laser, Inc. Marking and engraving is required for both industrial and scientific purposes. In industry, marking and engraving is required for accounting and parts discrimination, for making delivery channels in materials for the delivery of liquids and powders, for mechanical engagement of micro-parts, etc. For scientific purposes, when used in the optical systems, precision and methods of marking can be crucial for the whole system performance. In this case, the positioning tolerances and the width and depth of marking define the contrast ratios and ability of the marked parts to serve as fiducials. These fiducials are used to align opto-mechanical systems and to perform telemetry light intensity analysis. Being able to modulate the contrast is a very important task for space born systems similar to the Hubble Telescope where available photon counts are low. NASA commissioned Lenox Laser to fabricate precise crosshair fiducials for the Hubble Telescope.

CONTRAST = (BRIGHTEST - DARKEST) / (BRIGHTEST + DARKEST)

(where brightest and darkest refer to the intensities of the light reflected from a surface)


In the case of large differences between brightest and darkest this formula reduces to a simple ratio:

CONTRAST RATIO = BRIGHTEST / DARKEST


Lenox Laser, Inc. has developed a method of maximizing and modulating the contrast of marking for a given material and pattern geometry. The process of alignment and orientation of slits or pinholes in front of the light beam can be simplified by engraving the fiducials on the holder. This technique allow one to engrave lines as wide as a few micrometers with very high or customer requested contrast.

Lenox Laser offers different standard or custom shapes of patterns. Negative or positive marking on most opaque and transparent materials are readily available and produced. Marking a periodic structure such as a set of lines spaced with variable or constant period on a surface turns the material into grading or optronic crystal. The efficiency of these devices highly deepens the accuracy and precision of the manufacturing process. It is for this reason the Lenox Laser engineering and production teams are constantly improving their tools and processing methods.