There has been a recent discussion on power meters of which I have some relevant information as we have used power meters on a confocal microscope routinely for the last few years . I have excepted a section from an upcoming publication that will appear in Cytometry in the next few months ( Zucker and Price-- Evaluation of confocal microscopy system performance Cytometry 4: 2001. I hope it helps as this is a very relevant test and this piece of equipment is very useful for power measurements. Power meter The power meter used to measure light on the microscope stage was a Lasermate Q (Coherent, Auburn, California) with visible (LN36) and UV detectors (L818). A power meter (1830C) from Newport Corporation with an SL 818 visible wand detector can also be used for power measurements. A remote control box for the Coherent UV Enterprise laser was used to regulate UV laser power (0163-662-00, Coherent, Santa Clara, California). The power test is done using a low magnification lens (2.5x-10x) in the following manner: The lens is raised to its maximum specified height. The detector is secured on the stage and grossly centered using either laser light or mercury fluorescent light. The detector position is then more accurately adjusted to achieve maximum signal intensity by using the microscope's x/y joystick. The CLSM zoom factor is set from 8-32 to reduce the beam scan and to focus the beam into the "sweet spot" of the detector. The scanner is set at bi-directional-slow speed to reduce the time period that the power meter is reading "0". The power derived from this measurement is dependent on the lens type, lens magnification, and lens NA. On most confocal systems there is a 10-x lens: Zeiss uses a 10x Plan Neofluar (NA 0.3) and a Leica has a 10x Plan Fluortar (NA 0.3). Robert M. Zucker, PhD U.S. Environmental Protection Agency MD 72 National Health and Environmental Effects Research Laboratory Research Triangle Park, North Carolina, 27711 Tel: 919-541-1585; fax 919-541-4017 e-mail: zucker.robert@epa.gov
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