A high performance one-dimensional homodyne encoder and the proof of principle of a novel two-dimensional homodyne encoder

Guan, Jun; Köchert, Paul; Weichert, Christoph; Tutsch, Rainer

doi:10.1016/j.precisioneng.2013.05.003

Cited by 24 publications

(12 citation statements)

References 4 publications

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“…Then a series of correlation coefficients by equation (3) are calculated, as is shown in Figure 1. Grating pitch can be evaluated from the adjacent peak-position or valley-position, 1 (j=1,2,3,...) j j j p P P   (5) where Pj denotes the peak position of the curve in Figure 1, and pj is the grating pitch calculated by adjacent peak position.…”

Section: Simulationmentioning

confidence: 99%

“…But, in many situations, environmental stability is not always satisfied, which leads to the accuracy of laser interferometers very sensitive to the temperature, air humidity and wavelength stability. In comparison, optical encoders are drawing more and more attention due to their lower sensitivity to environment [1] . As pitch uniformity determines the precision of encoders, it is essential to evaluate the pitches accurately.…”

Section: Introductionmentioning

confidence: 99%

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Pitch evaluation of high-precision gratings

Zhou

Wei

et al. 2014

SPIE Proceedings

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Optical encoders and laser interferometers are two primary solutions in nanometer metrology. As the precision of encoders depends on the uniformity of grating pitches, it is essential to evaluate pitches accurately. We use a CCD image sensor to acquire grating image for evaluating the pitches with high precision. Digital image correlation technique is applied to filter out the noises. We propose three methods for determining the pitches of grating with peak positions of correlation coefficients. Numerical simulation indicated the average of pitch deviations from the true pitch and the pitch variations are less than 0.02 pixel and 0.1 pixel for these three methods when the ideal grating image is added with salt and pepper noise, speckle noise, and Gaussian noise. Experimental results demonstrated that our method can measure the pitch of the grating accurately, for example, our home-made grating with 20μm period has 475nm peak-to-valley uniformity with 40nm standard deviation during 35mm range. Another measurement illustrated that our home-made grating has 40nm peak-to-valley uniformity with 10nm standard deviation. This work verified that our lab can fabricate high-accuracy gratings which should be interesting for practical application in optical encoders.

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Section: Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pitch evaluation of high-precision gratings

Zhou

Wei

et al. 2014

SPIE Proceedings

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“…Another approach to measuring linear and angular displacements is the usage of encoders or grating interferometer systems [11][12][13][14]. In this case, the influence of the changing refractive index of the air gap is excluded, which is an important advantage of such measuring schemes.…”

Section: Introductionmentioning

confidence: 99%

The use of two-dimensional scales for measuring angle and linear displacement

Korolev

Lukin

Filatov

et al. 2022

Emerging Imaging and Sensing Technologies for Security and Defence VII

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Recently the authors proposed a new angle measurement technology based on the use of the two-dimensional scales. The rotation angle measurement is based on measuring the rotation of the pattern image on the sensor of a digital camera. The report presents the results of generalization of the developed earlier technology of angular measurements using a twodimensional scale to measurements of linear displacements. It is shown that using a simple optical-digital system with a physical resolution, for example, of the order of several micrometers, it is possible to measure angles with an error of one thousandth of an arc second and linear displacements with an error of a fraction of a nanometer.

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“…Compared with homodyne grating interferometers [8,9], heterodyne detection is highly insusceptible to direct current (DC) offset and amplitude variation of the output signals. Although frequency mixing caused by coaxial beams would lead to large periodic non-linearity error in heterodyne interferometric encoders, spatially separated beams can be utilized for this error reduction to tens of picometers typically [10,11,12].…”

Section: Introductionmentioning

confidence: 99%

Two Degree-of-Freedom Fiber-Coupled Heterodyne Grating Interferometer with Milli-Radian Operating Range of Rotation

Yang

Zhang

Zhu

et al. 2019

Sensors

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In the displacement measurement of the wafer stage in lithography machines, signal quality is affected by the relative angular position between the encoder head and the grating. In this study, a two-degree-of-freedom fiber-coupled heterodyne grating interferometer with large operating range of rotation is presented. Fibers without fiber couplers are utilized to receive the interference beams for high-contrast signals under the circumstances of large angular displacement and ZEMAX ray tracing software simulation and experimental validation have been carried out. Meanwhile, a reference beam generated inside the encoder head is adopted to suppress the thermal drift of the interferometer. Experimental results prove that the proposed grating interferometer could realize sub-nanometer displacement measurement stability in both in-plane and out-of-plane directions, which is 0.246 nm and 0.465 nm of 3σ value respectively within 30 s.

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A high performance one-dimensional homodyne encoder and the proof of principle of a novel two-dimensional homodyne encoder

Cited by 24 publications

References 4 publications

Pitch evaluation of high-precision gratings

Pitch evaluation of high-precision gratings

The use of two-dimensional scales for measuring angle and linear displacement

Two Degree-of-Freedom Fiber-Coupled Heterodyne Grating Interferometer with Milli-Radian Operating Range of Rotation

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