Full-field heterodyne interference microscope with spatially incoherent illumination

Pitter, Mark C.; See, C. W.; Somekh, Michael Geoffrey

doi:10.1364/ol.29.001200

Cited by 41 publications

(29 citation statements)

References 9 publications

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“…For point-scanning SH-SLCHM (P-SH-SLCHM), the corresponding frequency shift to achieve 10frames/s with en-face images of 500×500 pixels is ~1900Hz. In fact, use of two AOMs to generate a relative frequency shift between reference and object fields has been well researched in DH [30][31][32], where a frequency shift of several Hz is generated by two AOMs to obtain accurate phase-shifted holograms to achieve the complex field. Their work has demonstrated that it is possible to realize accurate frequency shift as low as several Hertz to milliHertz.…”

Section: Introductionmentioning

confidence: 99%

Spatial heterodyne scanning laser confocal holographic microscopy

Liu

2015

Appl. Opt.

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Scanning laser confocal holographic microscopy using a spatial heterodyne detection method is presented. Spatial heterodyne detection technique employs a Mach-Zehnder interferometer with the reference beam frequency shifted by two acousto-optic modulators (AOM) relative to the object beam frequency. Different from the traditional temporal heterodyne detection technique in which hundreds temporal samples are taken at each scanning point to achieve the complex signal, the spatial heterodyne detection technique generates spatial interference fringes by use of a linear tempo-spatial relation provided by galvanometer scanning in a typical line-scanning confocal microscope or for the slow-scanning on one dimension in a point-scanning confocal microscope, thereby significantly reducing sampling rate and increasing the signal to noise ratio under the same illumination compared to the traditional temporal heterodyne counterpart. The proposed spatial heterodyne detection scheme applies to both line-scanning and point-scanning confocal microscopes. In this paper, we present the mathematical principles of the spatial heterodyne detection method and experimental schemes for both line-scanning and point-scanning confocal microscopes. Computer experiments are provided to demonstrate the validity of this idea. The presented spatial heterodyne scanning laser confocal holographic microscope (SH-SLCHM) can obtain both amplitude and quantitative phase information of the object field without a significant increase in complexity of optical and electronic design on the basis of a traditional scanning laser confocal microscope (SLCM). SH-SLCHM may find applications in optical metrology, in-vivo tissue imaging, and ophthalmic imaging.

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Section: Introductionmentioning

confidence: 99%

Spatial heterodyne scanning laser confocal holographic microscopy

Liu

2015

Appl. Opt.

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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%

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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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“…This arrangement is usually only used in single point interferometers due to the practical challenges associated with capturing widefield time varying fringe patterns. However some systems have been developed to capture real time heterodyne interference patterns in the widefield region at modest modulation frequencies [5][6][7][8][9]. In a previous paper [9], we demonstrated that this could be accomplished for the widefield in the megahertz frequency range using a prototype modulated light camera (MLC).…”

Section: Introductionmentioning

confidence: 99%

Widefield two laser interferometry

Patel¹,

Achamfuo-Yeboah²,

Light³

et al. 2014

Opt. Express

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A novel system has been developed that can capture the widefield interference pattern generated by interfering two independent and incoherent laser sources. The interferograms are captured using a custom CMOS modulated light camera (MLC) which is capable of demodulating light in the megahertz region. Two stabilised HeNe lasers were constructed in order to keep the optical frequency difference (beat frequency) between the beams within the operational range of the camera. This system is based on previously reported work of an ultrastable heterodyne interferometer [Opt. Express 20, 17722 (2012)]. The system used an electronic feedback system to mix down the heterodyne signal captured at each pixel on the camera to cancel out the effects of time varying piston phase changes observed across the array. In this paper, a similar technique is used to track and negate the effects of beat frequency variations across the two laser pattern. This technique makes it possible to capture the full field interferogram caused by interfering two independent lasers even though the beat frequency is effectively random. As a demonstration of the system's widefield interferogram capture capability, an image of a phase shifting object is taken using a very simple two laser interferometer.

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Full-field heterodyne interference microscope with spatially incoherent illumination

Cited by 41 publications

References 9 publications

Spatial heterodyne scanning laser confocal holographic microscopy

Spatial heterodyne scanning laser confocal holographic microscopy

Full-field Interferometric Confocal Microscopy using a VCSEL Array

Widefield two laser interferometry

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