• Current Optics and Photonics
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• v.5 no.4
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• pp.351-361
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• 2021

Speckle imaging is capable of dynamic data acquisition at high spatiotemporal resolution, and has played a vital role in the functional study of biological specimens. The presence of various optical scatterers within the tissue causes alteration of speckle contrast. Thus structures like blood vessels can be delineated and quantified. Although laser speckle imaging is frequently used, an optimization process to ensure the maximum speckle contrast has not been available. In this respect, we here report an experimental procedure to optimize speckle contrast via applying different combinations of varying polarization of the illuminating laser light and multiple analyzer angles. Specifically, samples were illuminated by the p-polarization, 45°-polarization, and s-polarization of the incident laser, and speckle images were recorded without and with the analyzer rotated from 0° to 180° (Δ = 30°). Following the baseline imaging of a solid diffuser and a fixed brain sample, laser speckle contrast imaging (LSCI) was successfully performed to visualize in vivo mouse-brain blood flow. For oblique laser illumination, the maximum contrast achieved with p-polarized and s-polarized light was perpendicular to the analyzer's axis. This study demonstrates the optimization process for maximizing the speckle contrast, which can improve blood-flow estimation in vivo.

• Journal of Biomedical Engineering Research
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• v.42 no.3
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• pp.116-124
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• 2021

It is important to differentiate between the target tissue (or organ) and the rest of the tissue before incision during surgery. And when it is necessary to preserve the differentiated tissues, the blood vessels connected to the tissue must be preserved together. Various non-invasive medical imaging methods have been developed for this purpose. We aimed to develop a medical imaging system that can simultaneously apply fluorescence imaging using indocyanine green (ICG) and laser speckle contrast imaging (LSCI) using laser speckle patterns. We designed to collect images directed to the two cameras on a co-axial optical path and to compensate equal optical path length for two optical designs. The light source used for fluorescence and LSCI the same 785 nm wavelength. This system outputs real-time images and is designed to intuitively distinguish target tissues or blood vessels. This system outputs LSCI images up to 37 fps through parallel processing. Fluorescence for ICG and blood flow in animal models were observed throughout the experiment.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.88-93
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• 2016

Recently laser speckle contrast (LSC) imaging has become a widely used optical method for in vivo assessment of blood flow in the animal brain. LSC imaging is useful for monitoring brain hemodynamics with relatively high spatio-temporal resolution. A speckle contrast imaging system has been implemented with electrical sensory stimulation apparatus. LSC imaging is combined with optical intrinsic signal imaging in order to measure changes in cerebral blood flow as well as neural activity in response to electrical sensory stimulation applied to the hindlimb region of the mouse brain. We found that blood flow and oxygen consumption are correlated and both sides of hindlimb activation regions are symmetrically located. This apparatus could be used to monitor spatial or temporal responses of cerebral blood flow in animal disease models such as ischemic stroke or cortical spreading depression.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.91-96
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• 2010

A laser speckle is a random pattern that has a granular appearance produced by reflected light when a coherent laser illuminates an irregular course surface. Laser speckle system has many advantages. It can detect some animals functional parts. Moreover, it relatively consists of simple and in-expensive system. It is very important that detecting micro-vessels through image processed image. Current study is to improve image quality through variable image processing method. But this paper made laser speckle endoscope for miniaturization and commercialization laser speckle system. We had endoscope test through goldfish's tail. We will compare the processed speckle image and halogen image.

• Journal of Biomedical Engineering Research
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• v.28 no.3
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• pp.392-396
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• 2007

In this paper, we develop a new system to visualize the blood flow map in skin tissue, using the technique of Laser Speckle Flowgraphy (LSFG). The measuring unit consists of the laser diode, imaging system, line sensor, scanning mirror, and one-board microcomputer. The speckle signal is analyzed and sent to a PC, where the blood flow in a tissue area of $14mm{\times}26 mm$ is evaluated and displayed in a 2-D color map. It is demonstrated that the new LSFG instrument is useful to evaluate the degree of allergic reaction in patch test.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.1
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• pp.97-102
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• 2010

A laser speckle is a random pattern that has a granular appearance produced by reflected light when a coherent laser illuminates an irregular course surface. Most important property of laser speckle is detecting micro-vascular. Speckle image needs image processing to detect micro-vascular. This paper proposes a new image processing method for laser speckle, adaptive window method that adaptively processes laser speckle images in the spatial. Conventional fixed window based LASCA has shortcoming in that it uses the same window size regardless of target areas. Inherently laser speckle contains undesired noise. Thus a large window is helpful for removing the noise but it results in low resolution of image. Otherwise a small window may detect micro vascular but it has limits in noise removal. To overcome this trade-off, we newly introduce the concept of adaptive window method to conventional laser speckle image analysis. We have compared conventional LASCA and its variants with the proposed method in terms of image quality and processing complexity.

• Journal of the Optical Society of Korea
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• v.20 no.3
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• pp.396-400
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• 2016

Laser speckle patterns were used to monitor variations of thermal voltages of a cathode during a battery discharge. Discharge voltages measured with an oscilloscope were utilized as a figure of merit of thermal voltages in Zn metal. Using an optical imaging system, speckle patterns were taken for zinc metal surface over a time period of 3 minutes. Pixel sum distribution functions (PSDFs) were extracted from speckle patterns. Accumulated pixel sums quantified from PSDFs over an optimized grayscale range strongly correlated with discharge voltages. This suggested that dark matter or particles may have the capability of both absorbing and radiating thermal energies simultaneously. The black body-like properties were able to be validated by identifying coincidences with distinct features of a black body spectrum. The pixels belonging to the grayscale range were confirmed to represent dark matter of a speckle pattern. It was clear that dark matter was part of surface plasmon carriers. The proposed sensing system can be applied to monitor thermal energy variations in any material.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.2
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• pp.65-73
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• 1990

Speckle photography is a simple non-contacting method for analysing surface displacement. In its basic form, the object to be studied is illuminated with a beam of laser light from any convenient direction, and a double exposure photography of the surface recorded on the fine-grain film, the object is undergone the displacement to be measured between exposures. Like this, it allows the strain field to be evaluated in two dimensions. A direct experimental comparison of speckle photography with theoretical value on a notched tensile test specimen showed that serious errors could, however, occur due to local surface tilting and due to aberra- tions of the imaging lens. Methods of minimising these effects and those of the speckle de-correlation which occurs by the various conditions are discussed.

• Current Optics and Photonics
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• v.5 no.4
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• pp.362-369
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• 2021

Absolute position sensors are widely used in machine tools and precision measuring instruments because measurement errors are not accumulated, and position measurements can be performed without initialization. The laser speckle-based absolute position sensor, in particular, has advantages in terms of simple system configuration and high measurement accuracy. Unlike traditional absolute position sensors, it does not require an expensive physical length scale; instead, it uses a laser speckle image database to measure a moving surface position. However, there is a problem that a huge database is required to store information in all positions on the surface. Conversely, reducing the size of the database also decreases the accuracy of position measurements. Therefore, in this paper, we propose a new method to measure the surface position with high precision while reducing the size of the database. We use image stitching and approximation methods to reduce database size and speed up measurements. The absolute position error of the proposed method was about 0.27 ± 0.18 ㎛, and the average measurement time was 25 ms.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.125-133
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• 1993

Electronic Speckle Pattern Interferometry(ESPI) using a CW laser, a video system and image processor was applied to the rotating displacement of rigid body. ESPI require no special surface preparation or attachments and displacements between any two arbitrary points on the surface can be measured. The characteristic speckle pattern formed when imaging a scattering surface illuminated by laser light retains phase information, which can be used for interferometric measurement of surface displacement. The application of this principle to measuring in-plane displacement resolved in one direction is described, together with the novel use of television equipment to detect and process the information contained in the speckle pattern. This is faster, and more convenient and versatile than customary photographic methods.