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November 2006

Did you know?
Did you know that ramé-hart's DROPimage software is extremely accurate? That accuracy, however, is fully dependant on a successful software calibration. This simple procedure takes less than a minute to perform and once completed will ensure that the software is fully synchronized with the camera and optical subsystem. The calibration is accomplished with the use of a calibration tool. This tool consists of a 4mm ball suspended on Plexiglas which in turn is placed squarely on the forefront of the leveling stage. The camera and light settings are adjusted in order to obtain a perfectly black circle with a solid white background in the image window. With this on screen, the DROPimage calibration command is invoked, the crosshairs are positioned below the center of the circle, and the calibration is then made. The measured values are then stored in the system until a new calibration is performed. All editions of DROPimage include the calibration and show calibration commands. DROPimage Standard and Advanced also include a Check Calibration command. The Check Calibration is run the same way except instead of storing the values, it reports them and compares them with previously stored values. This allows the user to validate the current calibration.

The calibration command reports three values: the vertical and horizontal pixel dimensions in μm (micron) and the aspect ratio. The aspect ration is derived by dividing the vertical pixel dimension by the horizontal value and thus should be close to 1.0000. Typically the analog cameras will produce an aspect ration under 1 (e.g., 0.9973) while the digital cameras will be slightly over 1 (e.g. 1.0008). In all cases, though, the aspect ratio should be 1.0000 +/-0.0050. Any value outside of that range may indicate either an invalid calibration -- or possibly some other environmental problem, such as interference from overhead lighting.

The video below shows how to calibrate using DROPimage CA (Note: This video is also available on our website at http://www.ramehart.com/goniometers/dropimageca.htm.)


The procedure for calibrating with DROPimage Standard and Advanced is very similar.

It's recommended that calibration be performed when the instrument is initially setup, and then, any time it is moved, not used for a long while, or if any of the optical components are replaced or adjusted. On a day-to-day basis, it's not necessary to recalibrate. It's a better practice to check the existing calibration (which should be within 1% deviation of the stored valued).

If you are currently using any version of DROPimage and need help calibrating we have a PDF how to guide available for the asking.

Product of the Month - Vacuum Chuck
Often our customers are attempting to measure the contact angle on and the surface energy of thin films and other substrates which -- by themselves -- have a hard time laying flat. Naturally, it's important to keep both the front and rear edges of any thin test sample flat to allow for the line of sight between the illuminator and the camera to be unobstructed. The ramé-hart Vacuum Chuck is just the answer to this problem.

The Vacuum Chuck is available in two sizes: 6" and 8" diameters with part numbers 100-21-VC6 and 100-21-VC8 respectively. The chuck shown below is our 6" version. An air hose connects to the side and is run to available vacuum. (The vacuum source is required but not included.)

In addition to keeping your film flat on the stage, this option also includes a rotating base with 1° graduations between -90° and +90° for a total of 180° of graduated rotational translation. This option is supported on all legacy Model 100 instruments and all current-generation Model 300 and 500 instruments. It mounts directly on the standard stage top. Note that special optics may be required to view drops at both the outer edge and at the center of the stage. If you are interested in this option, would like to receive a quotation, or need additional information, please contact us. 

2007 and Beyond
The ramé-hart goniometer has been in production for over 40 years. Our original Model A100, based on the work of Dr. William Zisman and Elain Shafrin at the Naval Research Lab, has been refined and modernized over the years. In the spirit of taking advantage of newer technologies, we are planning several new products and upgrades which will become available in 2007. These product announcements will follow in subsequent newsletters. We are also moving and expanding our production facility to a new building. This will give us more room and allow us to continue to fabricate and assemble our existing products while simultaneously providing a more conducive environment for development and prototyping of new products. We're excited about these changes and look forward to 2007 with hope and determination.


Carl Clegg
Director of Sales
Phone 973-448-0305
Contact us