In the field of biomedical optics, optical scattering has traditionally limited the range of imaging within tissue to a depth of one millimetre. A recently developed class of wavefront-shaping techniques now aims to overcome this limit and achieve diffraction-limited control of light beyond one centimetre. By manipulating the spatial profile of an optical field before it enters a scattering medium, it is possible to create a micrometre-scale focal spot deep within tissue. To successfully operate in vivo, these wavefront-shaping techniques typically require feedback from within the biological sample. This Review summarizes recently developed 'guidestar' mechanisms that provide feedback for intra-tissue focusing. Potential applications of guidestar-assisted focusing include optogenetic control over neurons, targeted photodynamic therapy and deep tissue imaging.

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Guidestar-assisted wavefront-shaping methods for focusing light into biological tissue

A cellular-level study of the pathophysiology is crucial for understanding the mechanisms behind human diseases. Recent advances in quantitative phase imaging (QPI) techniques show promises for the cellular-level understanding of the pathophysiology of diseases. To provide important insight on how the QPI techniques potentially improve the study of cell pathophysiology, here we present the principles of QPI and highlight some of the recent applications of QPI ranging from cell homeostasis to infectious diseases and cancer.

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Quantitative phase imaging techniques for the study of cell pathophysiology: from principles to applications.

In a display apparatus and a driving method thereof, a detector determines whether a timing controller is operated in a three-dimensional (3D) mode or a two-dimensional (2D) mode to output a first or second mode signal according to a result of the determination. A compensator compensates for a gamma value of a 3D image to be increased in response to a first mode signal when the 2D mode is converted to the 3D mode and decreases an increased gamma value to a gamma value for a 2D image in response to a second mode signal when the 3D mode is converted to the 2D mode.

Display apparatus and method of driving the same

Light scattering was thought to be the fundamental limitation for the depth at which optical imaging methods can retain their resolution and sensitivity. However, it was shown that light can be focused inside even the most strongly scattering objects by spatially shaping the wavefront of the incident light. This review summarizes recently developed feedback-based approaches for focusing light inside and through scattering objects

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Feedback-based wavefront shaping.

Techniques are described for encoding and decoding digital video data using macroblocks that are larger than the macroblocks prescribed by conventional video encoding and decoding standards. For example, the techniques include encoding and decoding a video stream using macroblocks comprising greater than 16×16 pixels. In one example, an apparatus includes a video encoder configured to encode a coded unit comprising a plurality of video blocks, wherein at least one of the plurality of video blocks comprises a size of more than 16×16 pixels and to generate syntax information for the coded unit that includes a maximum size value, wherein the maximum size value indicates a size of a largest one of the plurality of video blocks in the coded unit. The syntax information may also include a minimum size value. In this manner, the encoder may indicate to a decoder the proper syntax decoder to apply to the coded unit.

Video coding with large macroblocks

An image processing apparatus and image processing method capable of providing a high-resolution image for a desired position by use of light field data are provided. The image processing apparatus may determine a position of a portion of light field data among light field data corresponding to a scene, according to a desired focusing position, generate a refocusing first image by use of the position determined portion of light field data, generate a high-resolution image having a predetermined setting ratio relative to the refocusing first image, determine a ratio for local synthesis between the high-resolution image and an enlarged image of the refocusing first image by use of a similarity with respect to the position determined portion of light field data, and generate a synthesized image by synthesizing the high-resolution image and the enlarged image of the refocusing first image according to the local synthesis ratio.

Image processing apparatus and method

We report on an approach to exploit multiple light scattering by shaping the incident wavefront in optical coherence tomography (OCT). Most of the reflected signal from biological tissue consists of multiply scattered light, which is regarded as noise in OCT. A digital mirror device (DMD) is utilized to shape the incident wavefront such that the maximal energy is focused at a specific depth in a highly scattering sample using a coherence-gated reflectance signal as feedback. The proof-of-concept experiment demonstrates that this approach enhances depth-selective focusing in the presence of optical inhomogeneity, and thus extends the penetration depth in spectral domain-OCT (SD-OCT).

Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography

An apparatus and method for capturing digital images are provided. The digital capturing apparatus includes an image pickup unit obtaining light field data to change a view of a captured image and refocus the captured image, and a data processor generating a refocusing image using the light field data, wherein the image pickup unit performs optical modulation on light beams to obtain light field data of the modulated light beams so that the light beams are identified when two or more of the light beams overlap, and the data processor demodulates the light field data to obtain light field data of the light beams not subjected to the optical modulation.

Apparatus and method for capturing digital images

We report the enhancement in the obtained signal and penetration depth of 2-D depth-resolved images that were taken by shaping the incident wavefront in optical coherence tomography (OCT). Limitations in the penetration depth and signal to noise ratio (SNR) in OCT are mainly due to multiple scattering, which have been effectively suppressed by controlling the incident wavefront using a digital mirror device (DMD) in combination with spectral-domain OCT. The successful enhancements in the penetration depth and SNR are demonstrated in a wide-range of tissue phantoms, reaching depth enhancement of up to 92%. The hidden structures inside a tissue phantom that could not be seen in conventional OCT are clearly revealed through our proposed system. Its 2-D imaging capability, assisted by further optimization of the system for real-time acquisition speed will boost wide-spread use of OCT for in-vivo tissue diagnosis.

Depth-enhanced 2-D optical coherence tomography using complex wavefront shaping

An apparatus for capturing an image of a scene including an image capturing unit and a data processing unit. The image capturing unit may generate light field data and may include a first optical having at least two portions with at least two different fields of view, a sensing unit having a plurality of photosensors, and a second optical unit interposed between the first optical unit and the sensing unit. The data processing unit may perform at least one of change of view of the image and refocusing the generated light field data. The sensing unit may be configured to obtain an image with at least two magnifications corresponding to regions of the scene.

Jae-guyn Lim

Papers

Image processing apparatus and method

Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography

Apparatus and method for capturing digital images

Depth-enhanced 2-D optical coherence tomography using complex wavefront shaping

Apparatus and method of capturing image