Traceable radius of curvature measurements on a micro-interferometer

Karodkar, Devendra; Gardner, Neil; Bergner, Brent C.; Davies, Angela

doi:10.1117/12.506416

Cited by 3 publications

(2 citation statements)

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“…The methods by which error motions were measured and uncertainties estimated are described elsewhere. 12 Our displacement gauge is a linear voltage displacement transducer (LVDT), and the final analysis shows that the dominant uncertainty components are the z positions of the stage at confocal and cat's eye, which are reflected in the uncertainties u d ce and u dz ce. Bias corrections to dz cf and d ce are small in our case compared with the final uncertainties and are therefore negligible.…”

Section: Illustration With An Examplementioning

confidence: 99%

Correcting for stage error motions in radius measurements

Davies¹,

Schmitz

2005

Appl. Opt.

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Traceable radius of curvature measurements are critical for precision optics manufacturing. An optical bench measurement is repeatable and is the preferred method for low-uncertainty applications. With an optical bench, the displacement of the optic is measured as it is moved between the cat's eye and the confocal positions, each identified using a figure measuring interferometer. The translated distance is nominally the radius of curvature; however, errors in the motion of the stage add a bias to the measurement, even if the error motions are zero on average. Estimating the bias and resulting measurement uncertainty is challenging. We have developed a new mathematical definition of the radius measurand that intrinsically corrects for error motion biases and also provides a means of representing other terms such as figure error-correction, wave-front aberration biases, displacement gauge calibration and their uncertainties. With this formalism, it is no long necessary to design a high-quality radius bench to carry out a precision measurement; rather a lower quality is adequate, provided that error motions are repeatable and characterized and error motion measurement uncertainties are estimated.

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Section: Illustration With An Examplementioning

confidence: 99%

Correcting for stage error motions in radius measurements

Davies¹,

Schmitz

2005

Appl. Opt.

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“…To overcome these challenges, this paper presents an innovative approach that utilizes an interferometer for measuring the radius of curvature and form error. Interferometers are highly accurate and flexible measurement devices that can measure different radii of workpieces with precision 7 . Compared to the traditional method, this approach can measure the radius of curvature and form errors at different stages of polishing, leading to a significant reduction in production costs and time.…”

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confidence: 99%

An innovative approach to measuring radius of curvature and form error of spherical optics with an interferometer

Singh¹,

Chen²

2023

Digital Optical Technologies 2023

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Quality control is a critical aspect in the manufacturing of high-quality optical components. However, the traditional metrology techniques of sag meters and test plates are often performed as the final step in the polishing process, leading to an increased number of defective parts and increased production costs caused by the need for many test plates. In this paper, we present an innovative approach to measuring the radius of curvature and form error using an interferometer. The traditional method needs a pair of test plates for each curvature radius. This could cause very high costs in storage and maintenance for long-term use. In contrast, an interferometer can measure different radii of workpieces and is highly accurate. The measured data can be used in a closed-loop feedback system to compensate for form error and radius errors in CNC-controlled polishing machines. This innovative approach will significantly improve flexibility and reduce the costs of the polishing process.

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Absolute interferometry for fast and precise radius measurement

et al. 2021

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A novel radius of the curvature measurement method for optical spherical surfaces using absolute interferometry is proposed. A measurement setup is designed and built around a common-path Fizeau interferometer. The cavity length (volume of air between reference and tested surfaces) can be measured by the absolute wavelength tuning interferometry. An interconnection of data from three different tunable laser diodes (central wavelengths 780, 785 and 852 nm) allows us to measure the cavity length with uncertainty from tens to hundreds of nanometres. Once the reference radius of curvature is known/measured/calibrated, the radius of surface under test can be computed applying the value of the cavity length. The radius of curvature is measured directly in confocal position of the interferometer with relative precision of about 10 ppm. Moreover, unlike standard radius measurement by interferometry, the uncertainty of the introduced method can be optimized by selecting a suitable transmission sphere. In the paper, the method is described, tested, and verified by measuring several specimens featuring different radii of curvature. The results are analysed and furthermore compared to other measurement device.

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Traceable radius of curvature measurements on a micro-interferometer

Cited by 3 publications

References 0 publications

Correcting for stage error motions in radius measurements

Correcting for stage error motions in radius measurements

An innovative approach to measuring radius of curvature and form error of spherical optics with an interferometer

Absolute interferometry for fast and precise radius measurement

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