OptiCentric | Goniometer | PrismMaster

PrismMaster High Precision Automatic Goniometer

The system also includes an autocollimator mounted on a tillable base. Unlike other goniometers which are using a visual autocollimator, the PrismMaster is equipped with a computerized autocollimator featuring a resolution of 0.1 arcsec. The autocollimator image is taken by a  CCD-camera and further processed via framegrabber, PC and specific software.

The fine rotary adjustment of the table is given by a high precision micrometer. A digital display provides an angle indication with a resolution of 0.36/0,036 arcsec. The software provides easy operation, records of measurement data to a file and print out of the measurement certificate.

Operation

Since the PrismMaster is using a computerized autocollimator no precise, difficult and time consuming alignment procedures are necessary.

The tilt table is simply rotated until the autocollimator is approximately square to the first surface of the prism or polygon. To achieve this, the operator is rotating the table until the reflected image of the autocollimator appears on the PC-monitor within a defined range area. The same procedure is repeated to obtain a reading from the second surface of the prism. The tiresome and difficult visual alignment becomes obsolete.

This is not only incomparably easier and comfortable for the operator, but very important for the overall accuracy of the instrument. In other goniometers the overall accuracy - even when using an accurate encoder- is decisively limited by the ability of the operator to visually and repeatedly align the autocollimator perfectly square to the sample surface. Certainly the alignment error can be reduced repeating the measurement several times and calculating the mean value, however, this is inefficient and dependent on the ability and the degree of tiredness of the operator.

Measurement in reflection mode

The measurement starts using the mouse or pressing a PC-key. The position of the autocollimator reticle and of the rotary encoder is automatically recorded. Following up the angle indication on the digital display, the table is rotated until the reflected image on the second surface of the prism appears on the monitor within the range area. This range area is designated by a red coloured rectangle on the PC-Monitor. A mouse click completes the measurement and the angle value is displayed on the monitor.

Measurement in transmission mode

For measurements in transmission mode the PrismMaster uses a tillable mirror attached to the tilt table of the goniometer. The tilt table is rotated until the mirror is approximately square to the autocollimator i.e. the reflected image is seen on the monitor within the range area. This reference position is recorded.

The tilt table is rotated at the expected angle following the angular indication of the digital display. The sample is placed on the table and positioned so that the reflected image goes through the prism and returns to the autocollimator. Since the beam is reflected by the mirror a double measurement sensitivity results.

Advantages

• extremely quick and easy measurement procedure since the sample does not need to be perfectly square to the autocollimator axis
• significantly increased accuracy due to
  - the use of the computerized autocollimator instead of the visual autocollimator
  - the use of the air bearing with a radial run out of 0.05,um which allows the encoder to deliver highest accuracy
• measurement accuracy is not dependent on the operator qualification or tiredness
• It enables the measurement of small or anti-reflex coated samples since the HR-CCD is able to process weak images
• double measurement sensitivity in transmission mode
• dramatically improved accuracy for pyramidal error due to the extremely small
  axial run out of the air bearing (0.05 µm)
• advanced software under WINDOWS 95 / NT with full capabilities to store, export, print out the data and produce measurement certificates.

Ordering Information

The PrismMaster is available in several versions:

• PrismMaster - Standard Version / Air Bearing
• PrismMaster HR - High Resolution / Air
  Bearing
• PrismMaster C-Compact Version / Rotary
  Table

Specifications

Goniometer

• Measuring range: 0-360°
• Resolution of the CCD-Autocollimator: 0.1 arcsec
• Diameter of the tilt table 130mm
• Measurement mode: reflection and transmission
• Software runs under WINDOWS 95/ NT
• Language: free selectable in German and English
• System requirements: Pentium PC with PCI bus min. 16MB

Air bearing

• Air bearing axial run out: 0.05 µm
• Air bearing radial run out: 0.05 µm
• Diameter: 200mm
• Air consum: 35 I/min

Precision Rotary Table

• Diameter: 270 mm
• Axial run out: less 3µm

Autocollimator:

• EFL 300 or 500 mm
• Free aperture: 50mm
• HR-CCD, 1 /3" or 2/3"