2-Inch LAZER GRAZER

  Why Grazing Incidence?

  Fizeau Interferometers

  Infrared Interferometers

  Dual Wavelength 
  Interferometers

  How Phase works

  Tutorials

Principle of Operation
When a rough surface is examined at a low grazing angle, it appears to be highly reflective. The LAZER GRAZER utilizes this principle to produce high contrast interferograms of unpolished surfaces.  A grazing angle of 14.48 degrees was selected since at that angle, each interference fringe equals one wavelength.  With a normal incidence Fizeau Interferometer, each fringe equals one half wavelength. Clicking on the link at the left will provide further information on the subject of Grazing Incidence Interferometers.

Model 4GRP Phase-Shifting LAZER GRAZER
Although, in a double-pass grazing system we trade-off some sensitivity for the capability 
of measuring unpolished parts, one wavelength per fringe is usually more than adequate sensitivity  for such samples. 

If you don't need the 4-inch aperture of the Model 4 GRP, please look at our Models 2GRP and 2GRPL. The principle is the same... the size and the cost are different.

Our 4-inch aperture LAZER GRAZER, Model 4GRP Interferometer operates under the control of Durango Interferometry Software which provides a live interferogram on the computer monitor.  The user can select from a rich palette of graphics, text files and reports.  For further Information click on Durango.

Typical Durango Screen, shown below, showing live interferogram, histogram, and OPD plot. Durango permits the user to select from a wide array of graphics, text files and customized reports.

Note that the live image shows interference fringes on the surface of the test sample while providing a 3-D image of the part. 

This is a unique display is a feature available only with Graham's Grazing Incidence Interferometers!  This capability is of enormous value in the interpretation of test pieces with complex geometry.

Measure flatness 
                   ...before polishing!
The ability to measure flatness of unpolished parts opens the door to examining surfaces which would be difficult if not impossible for a normal incidence interferometer.  This permits the operator to check parts for flatness while still in the grinding stage. For some operations, this is all that is needed since the finished parts do not require polishing. GRAHAM's LAZER GRAZER  puts an end to all of those “tricks” using wax and china markers to increase reflectivity of the surface.

Difficult substrates easily tested
With the LAZER GRAZER, matte, semi-matte, or polished surfaces can be checked for flatness of virtually any material. Very difficult substrates such as ceramics, graphite, tungsten carbide and silicon carbide can be evaluated with ease.  Even machined metal surfaces can be tested.  The high contrast fringes produced by Lazer GRAZER will assist in fine-tuning the production process and increasing both quality and through-put. 

Comparison of Normal Incidence 
and Grazing Incidence Interferograms
The Upper drawing shows the interferogram of a part using a normal incidence interferometer.  The interferogram shows 8 fringes. 

With a normal incidence Fizeau interferometer, 
2 fringes = 1 wave. This part is therefore shown to be either concave or convex by:  8 fringes = 4 waves = 2.53 microns

The Lower drawing shows the interferogram of the same part using a grazing incidence Fizeau interferometer. 

With a grazing angle of 14.48 degrees, 1 fringe = 1 wave.  The grazing incidence interferogram shows that the part is either concave or convex by: 4 fringes = 4 waves = 2.53 microns

Because of the wide variation in sample thickness encountered, it is essential to make provision for the sample surface to be totally covered by the incident laser beam. By providing a height adjustment for the tilt table, samples of various thickness can be examined.  After the appropriate tip-tilt adjustment has been made, the tilt-table may be raised or lowered as required for the sample to fully encounter the beam.

Because of the low grazing angle of the incident light, the illuminated area of the tilt-table is much elongated with the result that a long ellipse of light, in this case 4 times the interferometer's aperture is available for evaluating  long narrow parts.  It can also be used to look at parts substantially larger than the interferometer's aperture by examining a narrow swath across the substrate and then rotating the sample to look at another swath.

Non-contacting Grazing Incidence Interferometers like the 4GRP series of instruments open the door for the flatness measurement of semi-matte and matte finished surfaces -- surfaces which otherwise are not reflective enough to evaluate with an interferometer.

The Model 4GRP PhaseShiftingLAZER GRAZERis available now.  This turnkey system is complete with 3 GHz Pentium 4 Computer, 17-inch Flat Panel LCD Monitor, data acquisition board, phase-shift control board, and Durango Interferometry Software.
 
 

GENERAL SPECIFICATIONS	BENEFITS
Grazing Incidence Interferometer	Measures matte, semi-matte, and polished surfaces
Rugged Construction	For high stability even in vibration areas
4-inch aperture (101.6 mm)	Measures a swath across a 16-inch test piece
1/20 wave fused silica reference surface	High accuracy
Dithered HeNe Laser source (632.8 nM)	Sharp, speckle-free images
No video monitor required	Live interferogram on computer monitor
Remote control	Focus, Zoom, Iris, Intensity, Mode  <ALIGN> <VIEW>
Sturdy Integral Tip/Tilt Table	Fine adjustment for easy adjustment Adjustable height to accommodate thick samples
Two Spot Alignment	For easy alignment of Tip/Tilt
Piezo-electric Phase Shifter	For highest precision measurements
CCD Camera 768(H) x 494(V) pixels	High resolution for maximum data capture and image sharpness
Durango Universal Interferometry Software	For high repeatability For high reproducibility For high speed data reduction For excellent colorful graphics
3 GHz Computer	Durango Software, Image Acquisition Board, Data Acquisition Board all installed and configured for the Model 2GRP
19-inch TFT Flat Screen Monitor	For easy viewing
Power Requirements	117 Volts 60 Hz or 240 Volts 50 Hz
Small Footprint	Low Cost

Durango and Universal Interferometry Software are Trademarks of Diffraction International.  Visit their website where you can download a FREE Demonstration copy of Durango Interferometry Software.

Then send us some of your samples.  We will evaluate them with our LAZER GRAZER interferometer and Durango Software, put the files on a CD and send it to you so that you can see what a great job the LAZER GRAZER and Durango can do for you!

For high contrast, ultra-sharp interferograms, you can't beat GRAHAM Interferometers!

GENERAL FEATURES AND SPECIFICATIONS OF MODEL 4GRP LAZER GRAZER
   Rugged Construction for use in high vibration areas 
   Open Top for ease of use
   Low Profile for high stability and increased vibration immunity

   Grazing angle of 14.48 degrees yields a sensitivity of one fringe per wavelength.
   4-inch Aperture (101.6 mm)
   1/20 wave fused silica reference flat

   HeNe Laser Source operating at 632.8 nm
   Live fringe output on computer monitor for quick inspection
   High resolution CCD camera:  768 (H) x 494(V) pixels
   Dithered illumination for sharp images that are speckle-free 
   Pupil imaging: continuous Zoom 

   Integral tilt-table with ultra-fine adjustment for easy alignment
   Rack and Pinion sample stage for convenient vertical positioning of sample
   Controls:   Remote control of Zoom, Focus and  Illumination 

   3 GHz Pentium 4 Computer with 17-inch TFT Flat Screen Monitor
   Piezo-electric phase-shifting
 ..Durango Universal Interferometry Software*
   Image acquisition board, and Data acquisition board installed in computer
   Software installed and configured for LAZER GRAZER Interferometer

   Dimensions (W x H x D):   32 x 21 x 9 inches     (81.3 x 53.3 x 22.9 cm)
   Weight:  approx.            150 lb. (68 kg)
   Power requirements:      115 Volts 60 Hz or 250 Volts 50 Hz 
   Warm-up time :             ~20 minutes

For even rougher surfaces, the Model 4GRP Interferometer can be configured with an infrared source at 
1.55 micron wavelength.  Please inquire..