Wide field amplitude and phase confocal microscope with speckle illumination

Somekh, Michael Geoffrey; See, C. W.; Goh, Jason Y L

doi:10.1016/s0030-4018(99)00657-4

Cited by 52 publications

(47 citation statements)

References 10 publications

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“…However, the in-line LCHM decouples the fringe density with the field of view and enjoys higher axial resolution by removing the off-axis optical aberration. Interferometric methods using low spatial coherence light sources have been used to impose confocality in reflectance wide-field imaging systems [23][24][25]. Incorporation of low spatial coherence sources into the LCHM may enhance the optical sectioning capability.…”

Section: Discussionmentioning

confidence: 99%

High-speed line-field confocal holographic microscope for quantitative phase imaging

et al. 2016

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Abstract:We present a high-speed and phase-sensitive reflectance linescanning confocal holographic microscope (LCHM). We achieved rapid confocal imaging using a fast line-scan CCD camera and quantitative phase imaging using off-axis digital holography (DH) on a 1D, line-by-line basis in our prototype experiment. Using a 20 kHz line scan rate, we achieved a frame rate of 20 Hz for 512x512 pixels en-face confocal images. We realized coherent holographic detection two different ways. We first present a LCHM using off-axis configuration. By using a microscope objective of a NA 0.65, we achieved axial and lateral resolution of ~3.5 micrometers and ~0.8 micrometers, respectively. We demonstrated surface profile measurement of a phase target at nanometer precision and the digital refocusing of a defocused confocal en-face image. Ultrahigh temporal resolution M mode is demonstrated by measuring the vibration of a PZTactuated mirror driven by a sine wave at 1 kHz. We then report our experimental work on a LCHM using an in-line configuration. In this inline LCHM, the coherent detection is enabled by moving the reference arm at a constant speed, thereby introducing a Doppler frequency shift that leads to spatial interference fringes along the scanning direction. Lastly, we present a unified formulation that treats off-axis and in-line LCHM in a unified joint spatiotemporal modulation framework and provide a connection between LCHM and the traditional off-axis DH. The presented high-speed LCHM may find applications in optical metrology and biomedical imaging.

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Section: Discussionmentioning

confidence: 99%

High-speed line-field confocal holographic microscope for quantitative phase imaging

et al. 2016

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“…An alternative approach to completely parallelize confocal image acquisition is to combine interferometric detection with spatial coherence gating [13][14][15][16][17] However, the main advantage of parallelization-faster image acquisition-has thus far been mitigated by the lack of an appropriate light source. Traditional low-spatial coherence sources (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…line-scan confocal microscopy [8][9][10]) to improve imaging speed, but cross-talk limits this approach to weakly scattering samples [11]. Spectral encoding can provide parallelization in one dimension without cross-talk by using a grating to map different wavelengths to a line on the sample; however, scanning in the second dimension is still required to form an image [12].An alternative approach to completely parallelize confocal image acquisition is to combine interferometric detection with spatial coherence gating [13][14][15][16][17] However, the main advantage of parallelization-faster image acquisition-has thus far been mitigated by the lack of an appropriate light source. Traditional low-spatial coherence sources (e.g.…”

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confidence: 99%

“…Unlike physical pinholes, these virtual pinholes do not require physical separation to avoid cross-talk, enabling parallel acquisition of an entire en face plane in a single snapshot without scanning. Although this type of microscope cannot be used for fluorescence imaging, it has the potential for highspeed, large-area reflectance imaging with confocal resolution and sectioning [14]. However, the main advantage of parallelization-faster image acquisition-has thus far been mitigated by the lack of an appropriate light source.…”

mentioning

confidence: 99%

“…[14][15][16], which consisted of a conventional spatially coherent laser passed through a rotating diffuser. The rotating diffuser caused the speckle patterns illuminating the sample and reference to change over time.…”

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Full-field Interferometric Confocal Microscopy using a VCSEL Array

Redding

Bromberg

Choma

et al. 2014

Imaging and Applied Optics 2014

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We present an interferometric confocal microscope using an array of 1200 VCSELs coupled to a multimode fiber. Spatial coherence gating provides ~18,000 continuous virtual pinholes allowing an entire en face plane to be imaged in a snapshot. This approach maintains the same optical sectioning as a scanning confocal microscope without moving parts, while the high power of the VCSEL array (~5 mW per laser) enables high-speed image acquisition with integration times as short as 100 µs. Interferometric detection also recovers the phase of the image, enabling quantitative phase measurements and improving the contrast when imaging phase objects.Confocal microscopy combines high-resolution with improved contrast and optical sectioning, making it an invaluable tool in developmental biology, clinical medicine, and optical metrology [1,2]. However, traditional confocal microscopes rely on raster scanning, which limits image acquisition speed and increases system complexity. With typical frame rates of a few Hz for 1000×1000 pixel frames, scanning confocal systems are susceptible to motion artifacts and poorly suited for the study of dynamic samples or use in vivo. While video-rate confocal microscopes have been demonstrated using very high speed scanning [3,4], the complexity required to achieve such high scan rates has limited their adoption. Given a fixed lateral scan rate, image acquisition speed can also be improved through parallelization. The most common approach to parallelization is through the use of an array of spatially separated pinholes (i.e. a Nipkow disk) [5]; however, this approach has obvious limitations, since the pinholes must be sufficiently separated to prevent cross-talk [6,7]. Researchers have also proposed sacrificing confocality in one-dimension (i.e. line-scan confocal microscopy [8][9][10]) to improve imaging speed, but cross-talk limits this approach to weakly scattering samples [11]. Spectral encoding can provide parallelization in one dimension without cross-talk by using a grating to map different wavelengths to a line on the sample; however, scanning in the second dimension is still required to form an image [12].An alternative approach to completely parallelize confocal image acquisition is to combine interferometric detection with spatial coherence gating [13][14][15][16][17] However, the main advantage of parallelization-faster image acquisition-has thus far been mitigated by the lack of an appropriate light source. Traditional low-spatial coherence sources (e.g. thermal sources or LEDs) lack sufficient power per mode for high-speed imaging, and methods to reduce the spatial coherence of lasers (e.g. rotating diffusers) require relatively long integration times to achieve sufficiently low spatial coherence.In this work, we use a recently developed vertical cavity surface emitting laser (VCSEL) array [18] which combines high power per mode with low spatial coherence to demonstrate full-field confocal image acquisition with integration times as short as 100 µsec. The VCSEL array con...

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Particle Imaging Using a Transmission Wide‐Field Phase Confocal Microscope

Astrakharchik-Farrimond

Shekunov²,

Sawyer

et al. 2003

Part & Part Syst Charact

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A phase‐sensitive wide field transmission microscope, combining the advantages of both interferometric and confocal techniques, has been developed and applied to analysis of particulates, both in dry powder form and in suspensions. The microscope has also been used in detecting defects in crystals. Confocal operation is achieved by superimposing speckle illumination of a reference beam in a Mach‐Zehnder interferometer with a matched speckle pattern of the object beam. It is shown that the phase measurement enables particle size to be determined even when the particle is smaller than the focal spot size. The data acquisition time is below 1ms, making the system suitable for dynamic process measurement. The experimental results are in good agreement with modelled results giving rise to the possibility of simultaneous determination of both the size and refractive index of small particles.

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Wide field amplitude and phase confocal microscope with speckle illumination

Cited by 52 publications

References 10 publications

High-speed line-field confocal holographic microscope for quantitative phase imaging

High-speed line-field confocal holographic microscope for quantitative phase imaging

Full-field Interferometric Confocal Microscopy using a VCSEL Array

Particle Imaging Using a Transmission Wide‐Field Phase Confocal Microscope

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