Asymmetrical optical lenslet array realized by spatial light modulator for measuring toroidal surfaces

Zhao, Liping; Bai, N.; Li, X.

doi:10.1364/ao.47.006778

Cited by 4 publications

(5 citation statements)

References 7 publications

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“…1. Also, in the digital SHWS system, using a spatial light modulator (SLM) as a flexible lenslet array to better focus a wavefront with varying curvatures [15] increases the noise due to the zero and high-order diffraction.…”

Section: A Noisementioning

confidence: 99%

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Adaptive centroid-finding algorithm for freeform surface measurements

et al. 2013

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Wavefront sensing systems measure the slope or curvature of a surface by calculating the centroid displacement of two focal spot images. Accurately finding the centroid of each focal spot determines the measurement results. This paper studied several widely used centroid-finding techniques and observed that thresholding is the most critical factor affecting the centroid-finding accuracy. Since the focal spot image of a freeform surface usually suffers from various types of image degradation, it is difficult and sometimes impossible to set a best threshold value for the whole image. We propose an adaptive centroid-finding algorithm to tackle this problem and have experimentally proven its effectiveness in measuring freeform surfaces.

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Section: A Noisementioning

confidence: 99%

“…6) are toroidal surfaces with different radii in two directions, and are manufactured from programmable diamond turning. These aspheric surfaces have wide applications in the optics and manufacturing industries [15]. Table 1 shows the detailed specifications of the two samples.…”

Section: B Samplesmentioning

confidence: 99%

Adaptive centroid-finding algorithm for freeform surface measurements

et al. 2013

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“…Normally, a freeform surface is measured in a digital wavefront sensing system 5 . The use of the spatial light modulator (SLM) as a flexible lenslet array to better focus a wavefront with varying curvatures increases the noise due to the zero and high order diffraction, as shown in Fig.…”

Section: Dynamic Focal Spots Registration Algorithm 21 Challengesmentioning

confidence: 99%

Dynamic focal spots registration algorithm for freeform surface measurement

Guo¹,

Zhao²,

Chen³

2013

SPIE Proceedings

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In a wavefront sensing system, the raw data for surface reconstruction, either the slope matrix or curvature matrix, is obtained through centroiding on the focal spot images. Centroiding is to calculate the first moment within a certain area of interest, which encloses the focal spot. As the distribution of focal spots is correlated to the surface sampling condition, while a uniform rectangular grid is good enough to register all the focal spots of a uniformly sampled near flat surface, the focal spots of aspherical or freeform surfaces have varying shapes and sizes depending on the surface geometry. In this case, the normal registration method is not applicable. This paper proposed a dynamic focal spots registration algorithm to automatically analyze the image, identify and register every focal spot for centroiding at one go. Through experiment on a freeform surface with polynomial coefficients up to 10 th order, the feasibility and effectiveness of the proposed algorithm is proved

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“…From the working principle of the SHWS, the lenslet array samples the incoming wavefront reflected back from the sample surface, and forms individual focal spots on the detector plane. However, due to the different curvatures in two perpendicular dimensions of a toroidal surface, it is impossible to sample the wavefront in two directions simultaneously with the normal lenslet array 5 .…”

Section: Challenges In Using Shws For Toroidal Surface Measurementsmentioning

confidence: 99%

“…With the great flexibility provided by the SLM, various parameters of the designed lenslet array can be easily adjusted. Elliptical lenslets provide different optical powers in two directions 5 . When the parameters are designed properly, this kind of digital SHWS can sample the wavefront of a toroidal surface properly.…”

Section: Elliptical Lenslet Array Designmentioning

confidence: 99%

Toroidal surface measurement with elliptical lenslet array

2013

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Toroidal surfaces have wide applications in optics and manufacturing industry. Due to the strong aspherical surface profile of a toroidal surface, there are few optical measurement techniques proposed or reported for its measurement. This paper proposed digital Shack Hartmann wavefront sensor (SHWS) with extendable dynamic range. Instead of the traditional spherical lenslet array, which cannot sample the wavefront in two directions simultaneously, an elliptical lenslet array realized by a spatial light modulator (SLM), which provides different optical powers in two directions, is used in the system. With the incorporation of the extended version of the traditional SHWS, the reference-free wavefront sensor (RFWS), curvature matrix is measured, which can be further reconstructed into the surface profile. Both numerical simulation and experimental study has been conducted and the feasibility of measuring toroidal surfaces in the RFWS system with an elliptical lenslet array is proven.

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Asymmetrical optical lenslet array realized by spatial light modulator for measuring toroidal surfaces

Cited by 4 publications

References 7 publications

Adaptive centroid-finding algorithm for freeform surface measurements

Adaptive centroid-finding algorithm for freeform surface measurements

Dynamic focal spots registration algorithm for freeform surface measurement

Toroidal surface measurement with elliptical lenslet array

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