Compact Digital Spherometer with High Precision Encoder

SPHEROCOMPACT is an extremely accurate and easy to use instrument designed for saggita measurement of both concave and convex surfaces.

  • SPHEROCOMPACT is the first hand held spherometer with a high precision linear encoder which features bright digital readout, micron resolution and excellent absolute accuracy.
  • The calibrated rings have precision grinded reference surfaces and are machined of high quality stainless steel. Ultraprecision RUBY BALLS guarantee highest hardness and unsurpassed thermal stability. The deviation from sphericity is less than 1/10 of a micron.
  • The diameter of each ring is certified and the instrument is calibrated using test plates with Certified Radius, traceable to NIST. The calibration is done for both concave and convex spherical surfaces. The radius difference between the concave and convex test plates used in calibration is smaller than lambda/10.
  • Easily removable rings of different diameters increase the versatility of the instrument and feature a very large measuring range covering almost all applications in optical manufacturing.
  • The Spherocompact can be used either as a hand-held instrument to take measurements directly on the machine or as a stand-alone instrument in the laboratory.

Spherocompact is the first hand held spherometer with a high precision linear encoder. It features bright digital readout, micron resolution and excellent absolute accuracy.

This inexpensive and highly accurate instrument can be used either for in- process measurement of lenses and polishing tools or for the calibration of test plates.

Operation Principle

A precision flat is put on the selected spherometer ring. This is the reference (zero) position for the subsequent sample measurement. In the second step the lens or test plate is put on the ring. The spherometer measures the saggital height of the curved surface of the lens.

The radius of curvature can be quickly derived using the relationship between sag and radius:

The values of D and d are determined with extreme accuracy during the calibration procedure and are certified in the individual calibration sheet supplied with the instrument.


Due to its extreme accuracy and repeatability Super-Spherotronic is primarily used for calibration of master test plates, but also for any measuring problem requiring high precision evaluation of radius of curvature:

  • Concave/convex optical parts
  • Ground or polished optical parts
  • Spheres and balls

Super-Spherotronic can also be used to measure both concave and convex polishing tools, assuring quality standards of  tools and thus reducing subsequent rejected elements.

Spherocompact which is an affordable but accurate instrument, can be used either for in-process measurement of lenses and polishing tools or for the calibration of test plates.


  • the precision spherometers offer for comparable accuracy dramatically reduced costs.
  • the measurement time for PC-controlled spherometers is a fraction of the time
  • needed to set up, to align and to take a measurement with interferometers.
  • since the measuring procedure is so simple, no highly qualified personnel is required.
  • when it comes to measure large aperture optics or radii longer than 1 m, the interferometers become impractical due to the high costs or impossibility to realize the extra-long mechanical set up.
  • using spherometers the radius can be accurately measured before polishing, when a correction of the lenses is still possible.
  • the accuracy of measurement is directly traceable to international standards, since Trioptics spherometers are calibrated with (NIST and NPL) certified test plates.

Advanced Software

Super-Spherotronic and Spherocompact represent not only the most accurate but also the most useful and efficient spherometers available today. User-oriented software has been developed to really meet the requirements of an easy, quick and errorless measurement.

  • The SPHEROWIN-Software package runs under Windows XP, 2000, and 98 in German and English. The measurement results can be displayed in ,,mm” or,,inch”.
  • Only this software package automatically recognizes when measuring convex and concave surfaces and also records automatically the difference when measuring pairs of test plates or individual lenses.This significantly speeds up the measuring procedure and avoids measurement errors.
  • The sagittal height, radius of curvature, the current number of the measurement and the type of surfaces (convex/concave) will be automatically displayed and printed out as a certificate of measurement errors.
  • It provides a statistic evaluation of the measurements including mean value and standard deviation.
  • Easy selection of the rings. Calibration data of the rings can be easily stored, displayed or modified.
  • On-line help shows the necessary steps to take a measurement.


Measurement range

  • Radius convex: +2.5mm to
  • Radius concave: -4mm to (-.2″ to )
  • Diameter of parts under test: 7mm to 500mm
  • Travel of linear encoder: ±12.5mm

Measurement Accuracy

  • Resolution of the linear encoder: 0.1 µm
  • Absolute accuracy of the linear encoder: ± 0.2 µm
  • Accuracy of measurement of radius of curvature: 0.01%

Precision Ruby Ball Rings

  • Standard diameter: 6mm,12.5mm, 25mm, 50mm, 75mm,100mm, 125mm
  • Special diameters: 150mm, 225mm

Further Features

  • Instantly selectable units mm/inch
  • Zero reset at any probe position

Dimensions and Weight

  • Mainframe: 180 x 70 x 56 mm
  • Mainframe Weight: 400 g.