Super-Spherotronic Highly Accurate PC-controlled
is an automatic three ball contacting spherometer designed to meet the highest test plate
calibration requirements. Super-Spherotronic can measure the radius of curvature to an
accuracy of 0.01%.
To ensure that the highest available accuracy values of radius measurement are
obtained, all Super- Spherotronic components have been optimized and perfected so that
residual errors are negligible:
- The mainframe components locating the probe are made of massive stainless steel,
hardened and fine ground on machine tools to the highest achievable accuracy.
Concentricity of mainframe components to the probe is less than 1 micron (0.00004").
- The spherometer rings represent one of the key components of the Super-Spherotronic
including an incredible amount of work to eliminate any possible error source. Made of
heat-treated high quality stainless steel, the rings are machined on high accuracy
grinding machine tools and finally fine-lapped. An ingenious design combined with a
special electro-erosion procedure allows the ball and the ball location site to be matched
with highest accuracy. Each ring is delivered with a calibration certificate. The
measuring accuracy is directly traceable to NIST standards.
- The supporting balls are also concentrically positioned with an extreme accuracy of less
than 1 micron (0.00004"). This highly accurate positioning of the ring balls is an
essential and distinctive feature of the Super-Spherotronic, ensuring excellent
repeatability. To avoid any thermal and mechanical deformation, the supporting balls are
made of wolfram carbide (an extremely hard metal), while the probe center is an
ultra-precision ruby ball. This completely eliminates any errors introduced by metallic
probe centers used in other spherometers.
- The probe itself is a high precision Heidenhain encoder, specifically selected for this
use, having a total systematic and random error of less than 0.2 microns (0.000008").
- The test plates used for calibration of the instrument are manufactured to high quality
standards to an accuracy better than 1/10 wave for sphericity. The test plates are
certified by NIST of USA, so that the accuracy of Super-Spherotronic is directly traceable
to international standards.
The fitting of ring
diameters to test plates diameters has c significant influence on the measurement
accuracy. As a general rule, to obtain best accuracy, a test plate must be measured with
the ring having the largest possible diameter still fitting the test plate. In this case
the largest saggital height is measured and the smallest relative error results.
The Super-Spherotronic is equipped with a standard set of 6 precision rings with
diameters ranging from 7.8 to 120mm. An additional set of precision rings is also
available: diameters 14mm, 28mm, 47mm and 75mm.
Normally the standard rings set is sufficient for most of applications. However, when
the highest possible accuracy is required or most of the measuring test plates do not fit
optimally with the standard rings set, the use of the additional rings set or individual
rings belonging to this set ore recommended.
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
Equipped with special rings, it can even measure radius of cylindrical surfaces.
Compared with other radius measuring methods (e.g. interferometers) the spherometric
measuring method provides a multitude of advantages:
- 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.
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 '95 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
- 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
- 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.
Technical Specifications Super-Spherotronic
- Radius (Convex): +3mm to (+0.1 " to )
- Radius (Concave): -6mm to (-0.2" to )
- Travel of linear encoder: ±15mm (±0.6")
- Diameter of part under test: 6mm to 500mm (0.25" to 20")
- Resolution of linear encoder: 0.5 µm
- Absolute accuracy of linear encoder: ± 0.2 µm
- Accuracy of measurement of radius of curvature: 0.01 %
Precision Ball Rings
- Standard set of high precision ball rings in wooden box ranging in sizes (diameters)
7.8 mm, 20 mm, 38 mm, 60 mm, 90 mm, 120 mm
- Optional: 150 mm, 225 mm (6", 8¾")
- Position accuracy of balls:
±0.5 microns for diameters up to 60 mm;
±1 micron for diameters exceeding 60 mm.
- High precision hard metal balls:
Sphericity less than ±0.1 microns
Dimensions and Weights
- Mainframe: Dia. 90 x 260 mm (6.5Kg)
- Digital display: 240 x 240 x 70 mm
- Wooden box incl. ring set: 380 x 300 x 70 mm