FPGA technology for high-speed low-cost adaptive optics

Saunter, Christopher D.; Love, Gordon D.; Johns, Matt; Holmes, J. Fred

doi:10.1117/12.669386

Cited by 17 publications

(12 citation statements)

References 7 publications

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“…For current commercial technology and interfaces, a frame rate of 1kHz is only possible for fields of view of several 10's of square microns. However, high-speed "smart cameras" have recently been developed with integrated signal processing, where a programmable logic array measures the position of each particle [16] and only these positions, rather than the whole image, is passed to the data logging computer. Such systems can simultaneously measure the positions of several trapped particles [17] even when they are positioned far apart in the sample.…”

Section: Discussionmentioning

confidence: 99%

Measuring the accuracy of particle position and force in optical tweezers using high-speed video microscopy

Gibson¹,

Leach²,

Keen³

et al. 2008

Opt. Express

195

161

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Abstract:We assess the performance of a CMOS camera for the measurement of particle position within optical tweezers and the associated autocorrelation function and power spectrum. Measurement of the displacement of the particle from the trap center can also be related to the applied force. By considering the Allan variance of these measurements, we show that such cameras are capable of reaching the thermal limits of nanometer and femtonewton accuracies, and hence are suitable for many of the applications that traditionally use quadrant photodiodes. As an example of a multi-particle measurement we show the hydrodynamic coupling between two particles.

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Section: Discussionmentioning

confidence: 99%

Measuring the accuracy of particle position and force in optical tweezers using high-speed video microscopy

Gibson¹,

Leach²,

Keen³

et al. 2008

Opt. Express

195

161

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“…The proposed method achieves these results in 0.57µs. As a direct comparison, if the proposed method is run at 80 MHz (the same clock speed as the method in [13]) the results are achieved in 0.7125 µs, an improvement of 40%. Specifics of the implementation are not given by Saunter so a comprehensive comparison is not possible but, as above, illustrates the competitive nature of this design.…”

Section: Resultsmentioning

confidence: 99%

“…al, [13] implemented a wavefront reconstruction scheme, producing Zernike coefficients, using an FPGA in approximately 1.19 µs for an 8 × 8 grid of Shack-Hartmann spots, running at 80 MHz. The proposed method achieves these results in 0.57µs.…”

Section: Resultsmentioning

confidence: 99%

An FPGA Architecture for Extracting Real-Time Zernike Coefficients from Measured Phase Gradients

Moser

Lee

Podoleanu

2015

Measurement Science Review

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Zernike modes are commonly used in adaptive optics systems to represent optical wavefronts. However, real-time calculation of Zernike modes is time consuming due to two factors: the large factorial components in the radial polynomials used to define them and the large inverse matrix calculation needed for the linear fit. This paper presents an efficient parallel method for calculating Zernike coefficients from phase gradients produced by a Shack-Hartman sensor and its real-time implementation using an FPGA by pre-calculation and storage of subsections of the large inverse matrix. The architecture exploits symmetries within the Zernike modes to achieve a significant reduction in memory requirements and a speed-up of 2.9 when compared to published results utilising a 2D-FFT method for a grid size of 8 × 8. Analysis of processor element internal word length requirements show that 24-bit precision in precalculated values of the Zernike mode partial derivatives ensures less than 0.5% error per Zernike coefficient and an overall error of <1%. The design has been synthesized on a Xilinx Spartan-6 XC6SLX45 FPGA. The resource utilisation on this device is <3% of slice registers, <15% of slice LUTs, and approximately 48% of available DSP blocks independent of the Shack-Hartmann grid size. Block RAM usage is <16% for Shack-Hartmann grid sizes up to 32×32.

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“…The centroider module is derived from an earlier system for measuring the position of bright spots in a ShackHartmann wavefront sensor 17 for adaptive optics. 18 The centroider measures the optical center of mass of up to 16 user-programmable regions of arbitrary size from 2 × 2 to 256 × 256 pixels and the regions may be overlapping or separate.…”

Section: Smart Cameramentioning

confidence: 99%

Multidepth, multiparticle tracking for active microrheology using a smart camera

Silburn

Saunter

Girkin

et al. 2011

Review of Scientific Instruments

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The quantitative measurement of particle motion in optical tweezers is an important tool in the study of microrheology and can be used in a variety of scientific and industrial applications. Active microheology, in which the response of optically trapped particles to external driving forces is measured, is particularly useful in probing nonlinear viscoelastic behavior in complex fluids. Currently such experiments typically require independent measurements of the driving force and the trapped particle's response to be carefully synchronized, and therefore the experiments normally require analog equipment. In this paper we describe both a specialized camera and an imaging technique which make high-speed video microscopy a suitable tool for performing such measurements, without the need for separate measurement systems and synchronization. The use of a high-speed tracking camera based on a field programmable gate array to simultaneously track multiple particles is reported. By using this camera to simultaneously track one microsphere fixed to the wall of a driven sample chamber and another held in an optical trap, we demonstrate simultaneous optical measurement of the driving motion and the trapped probe particle response using a single instrument. Our technique is verified experimentally by active viscosity measurements on water-ethylene glycol mixtures using a phase-shift technique.

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FPGA technology for high-speed low-cost adaptive optics

Cited by 17 publications

References 7 publications

Measuring the accuracy of particle position and force in optical tweezers using high-speed video microscopy

Measuring the accuracy of particle position and force in optical tweezers using high-speed video microscopy

An FPGA Architecture for Extracting Real-Time Zernike Coefficients from Measured Phase Gradients

Multidepth, multiparticle tracking for active microrheology using a smart camera

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