Device interchangeability on anterior chamber depth and white-to-white measurements: a thorough literature review

We have reviewed a set of recently published studies that compared the anterior chamber depth（ACD） and/or white-to-white（WTW） distance obtained by means of different measuring devices.Since some of those studies reached contradictory conclusions regarding device interchangeability,this review was carried out in attempting to clarify which clinical devices can or cannot be considered as interchangeable in clinical practice to measure ACD and/or WTW distance,among these devices：A-scan,ultrasound biomicroscopy,Orbscan and Orbscan Ⅱ（Bausch＆Lomb Surgical Inc.,San Dimas,California,USA）,Pentacam and Pentacam HR（Oculus,Wetzlar,Germany）,Galilei（Ziemer,Switzerland）,Visante optical coherence tomography（Visante OCT,Carl Zeiss Meditec Inc.,Dublin,California,USA）,lOLMaster（Carl Zeiss Meditec,Jena,Germany）,and Lenstar LS 900/Biograph（Haag-Streit AG,Koeniz,Switzerland/Alcon Laboratories Inc.,Ft Worth,Texas,USA）.

New development of hydraulic fracturing technique for in-situ stress measurement at great depth of mines

In-situ stress measurement using the hydraulic fracturing technique was made at Wanfu Coal Mine in Shandong Province, China. To solve problems caused by great measuring depth and extra thick overburden soil layers in the mine, a series of improved techniques were developed for the traditional hydraulic fracturing technique and equipment to increase their pressure-enduring ability and to ensure safe and flexible removal of the sealing packers with other experimental apparatus. Successful in-situ stress measurement at 37 points within 7 boreholes, which were mostly over 1000 m deep, was completed. Through the measurement, detailed information of in-situ stress state has been provided for mining design of the mine. The improved hydraulic fracturing technique and equipment also provide reliable tools for in-situ stress measurement at great depth of other mines.

Cold Atom Cloud with High Optical Depth Measured with Large Duty Cycle

We present a cold atom system with a dark-line two-dimensional magneto-optical trap, to increase the atomic density by suppressing the atomic radiation pressure. Optical depth （OD） and duty cycle are used to evaluate the system performance. We demonstrate a 100% increase in OD with the dark line, and obtain an ultrahigh OD of 264 with 10% for the duty cycle. Also, with an efficient dark line region, the OD could maintain above i00 with duty cycle as high as 30%. The cold atomic ensemble with an ultrahigh OD with a 10%-30% duty cycle is particularly advantageous in quantum i^formation processing and communication.

High performance hardware architecture for depth measurement by using binocular-camera

High performance hardware architecture for depth measurement by using binocular-camera is proposed.In the system,at first,video streams of the target are captured by left and right charge-coupled device(CCD)cameras to obtain an image including the target.Then,two different images with two different view points are obtained,and they are used in calculating the position deviation of the image's pixels based on triangular measurement.Finally,the three-dimensional coordinate of the object is reconstructed.All the video data is processed by using field-programmable gate array(FPGA)in real-time.Hardware implementation speeds up the performance and reduces the power,thus,this hardware architecture can be applied in the portable environment.

3D Depth Measurement for Holoscopic 3D Imaging System

Holoscopic 3D imaging is a true 3D imaging system mimics fly’s eye technique to acquire a true 3D optical model of a real scene. To reconstruct the 3D image computationally, an efficient implementation of an Auto-Feature-Edge (AFE) descriptor algorithm is required that provides an individual feature detector for integration of 3D information to locate objects in the scene. The AFE descriptor plays a key role in simplifying the detection of both edge-based and region-based objects. The detector is based on a Multi-Quantize Adaptive Local Histogram Analysis (MQALHA) algorithm. This is distinctive for each Feature-Edge (FE) block i.e. the large contrast changes (gradients) in FE are easier to localise. The novelty of this work lies in generating a free-noise 3D-Map (3DM) according to a correlation analysis of region contours. This automatically combines the exploitation of the available depth estimation technique with edge-based feature shape recognition technique. The application area consists of two varied domains, which prove the efficiency and robustness of the approach: a) extracting a set of setting feature-edges, for both tracking and mapping process for 3D depthmap estimation, and b) separation and recognition of focus objects in the scene. Experimental results show that the proposed 3DM technique is performed efficiently compared to the state-of-the-art algorithms.

Nonlinear effect of the structured light profilometry in the phase-shifting method and error correction

Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.

Measurement of optical penetration depth and refractive index of human tissue

Experimental techniques for measurement of optical penetration depth and refractive index of human tissue are presented, respectively. Optical penetration depth can be obtained from the measurement of the relative fluencc-depth distribution inside the target tissue. The depth of normal and carcinomatous human lung tissues irradiated with the wavelengths of 406.7, 632.8 and 674.4 nm in vitro are respectively determined. In addition, a novel simple method based on total internal reflection for measuring the refractive index of biotissue in vivo is developed, and the refractive indices of skin from people of different age, sex and skin color are measured. Their refractive indices are almost same and the average is 1.533.

Estimation of particle depth from two defocused images using the Fourier transform

Depth from defocus is one technology for depth estimation.We estimate particle depth information from two defocused images captured simultaneously by two coaxial cameras with different imaging distances.The images are processed with the Fourier transform to obtain the characteristic parameter(i.e.,the standard deviation of the relative blur kernel of these two defocused images).First,we theoretically analyze the functional relationship between the object depth and the standard deviation or variation of the relative blur kernel.Then,we verify the relationship experimentally.We analyze the influence of particle size,window size and image noise on the calibration curves using both numerical simulations and experiments.We obtain the depth range and accuracy of this measurement system experimentally.For the verification experiments,we use a sample of glass microbeads and the irregularly-shaped dust particles on a microscope slide.Both of these experiments present a suitable depth measurement result.Finally,we apply the measuring system to the depth estimation of drops from a small anti-fogging spray.The results show that our system and image processing algorithm are robust for different types of particles,facilitating the in-line three-dimensional positioning of particles.

A reconfigurable 256×256 image sensor controller that is compatible for depth measurement

This paper presents an image sensor controller that is compatible for depth measurement, which is based on the continuous-wave modulation time-of-flight technology. The image sensor controller is utilized to generate reconfigurable control signals for a 256 × 256 high speed CMOS image sensor with a conventional image sensing mode and a depth measurement mode. The image sensor controller generates control signals for the pixel array to realize the rolling exposure and the correlated double sampling functions. An refined circuit design technique in the logic level is presented to reduce chip area and power consumption. The chip, with a size of 700 × 3380 μm2, is fabricated in a standard 0.18 μm CMOS image sensor process. The power consumption estimated by the synthesis tool is 65 mW under a 1.8 V supply voltage and a 100 MHz clock frequency. Our test results show that the image sensor controller functions properly.

Design and calibration of a new high-definition three-dimensional laparoscopic system

We present a high-definition （HD） 3D laparoscopic system including a dual channel optical system, two cameras, a camera control unit （CCU）, and an HD 3D monitor. This laparoscopic system is capable of outputting dual high-definition videos and providing vivid 3D images. A modified pinhole camera model is used for camera calibration and a new method of depth measurement to improve precision. The average error of depth measurement measured by experiment （about 1.13 mm） was small in proportion to the large range in distance of the system （10-150 mm）. The new method is applicable to any calibrated binocular vision system.