Project Title:

Measuring Instruments for Aspherical and Free-form Optical Surfaces

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Project no.: TA03010893Provider: Technology Agency of the Czech Republic Realization period: 1st January 2013 – 31st December 2016

The aim of the project, which was completed in cooperation with Meopta - optika, s.r.o. and the Tech-nical University of Liberec, was research and development into systems and technologies for mea-suring the shape of aspherical and free-form optical surfaces which meet current requirements of industry and are more affordable and more effective than instruments available on the market.

Within the project, a team consisting of representatives of all the institutions involved developed two instruments as functional samples – an interferometric and a holographic one. The interfero-metric instrument is a six-axis automatic measurement system that combines information from measurements at two wavelengths, which makes it possible to measure aspherical surfaces with high precision. The holographic gauge for free-form surfaces is a three-axis system that illumina-tes the measured surface from 16 directions and uses digital holography with frequency sweep of the laser source developed at the TOPTEC Centre.

The development of these measuring systems involved their mechanical design, design and im-plementation of an innovative optical system, and software development. Both instruments were tested and the results compared with reference systems.

The basic parameters of the two instruments are summarized in the table:

Instrument V005 - Interferometer V004 – Holographical systemAutomatic positioning and calibration

YES YES

Axis travel range X ± 120 mmY ± 10 mmZ 1250 mmA 360°B ± 60°C ± 7°

X ± 12.5 mmY ± 12.5 mmZ ± 12.5 mm(+ rough manual shift)

Output aperture 4“ NA (Field of view is defined by camera – element distance)

Wavelength 780 nm, 850 nm 780 nm, 850 nmMaximum measurable diameter < 100 mm < 250 mmMaximum surface slope 6.5 mrad (with respect to BFS*) NABFS deviation 90 µm Not limitedMeasurement repeatability (RMS) λ/50 λ/40Camera resolution 2048x2048 pixels 2016x2016 pixels

*(BFS – best fit sphere) = best matching spherical wavefront

RESEARCH CENTRE FOR SPECIAL OPTICS AND OPTOELECTRONIC SYSTEMS

WWW.TOPTEC.EU

INSTITUTE OF PLASMA PHYSICSOF THE CZECH ACADEMY OF SCIENCES

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Among the scientific outputs of the project, besides several publications, there are also two utility models and a patent (No. PS4069CZ: An interferometric device for measurement of shape deviati-ons of optical elements).

a) b) c)

d) e) f)

V

POS

Figure 1: Aspherical interferometer without cover: a) detailed view of the measuring unit; (b) a general view of the device; (c) a de-tailed view of the mounted measured element and the transmission sphere (TS); (d) passive vibration damping system; e) vacuum hydro-expansion chuck (V); f) drive (P) and gauge system (OS).

Figure 2: Deviation measured by a commercial subaperture interferometer (left) and by the newly-developed aspherical interferome-ter (right). Both measurement results are in agreement within the uncertainties of both systems.

RESEARCH CENTRE FOR SPECIAL OPTICS AND OPTOELECTRONIC SYSTEMS

WWW.TOPTEC.EU

INSTITUTE OF PLASMA PHYSICSOF THE CZECH ACADEMY OF SCIENCES

TS