Intensity Compensation Research Articles

Dolphin hearing during echolocation: evoked potential responses in an Atlantic bottlenose dolphin (Tursiops truncatus)

Auditory evoked potential (AEP) responses were recorded during echolocation in an Atlantic bottlenose dolphin (Tursiops truncatus) trained to accept suction-cup EEG electrodes and detect targets by echolocation. AEP recording was triggered by the echolocation clicks of the animal. Three targets with target strengths of -34, -28 and -22 dB were used at a target distance of 2 to 6.5 m for each target. The results demonstrated that the AEP appeared to both outgoing echolocation clicks and echoes during echolocation, with AEP complexes consisting of alternative positive and negative waves. The echo-related AEP amplitudes were obviously lower than the outgoing click-related AEP amplitudes for all the targets at the investigated target distances. However, for targets with target strengths of -22 and -28 dB, the peak-to-peak amplitudes of the echo-related AEPs were dependent on the target distances. The echo-related AEP response amplitudes increased at further target distances, demonstrating an overcompensation of echo attenuation with target distance in the echo-perception system of the dolphin biosonar. Measurement and analysis of outgoing click intensities showed that the click levels increased with target distance (R) by a factor of approximately 10 to 17.5 logR depending on target strength. The results demonstrated that a dual-component biosonar control system formed by intensity compensation behavior in both the transmission and receiving phases of a biosonar cycle exists synchronously in the dolphin biosonar system.

Video Coding Using a Simplified Block Structure and Advanced Coding Techniques

This paper describes a new video coding scheme based on a simplified block structure that significantly outperforms the coding efficiency of the ISO/IEC 14496-10 ITU-T H.264 advanced video coding (AVC) standard. Its conceptual design is similar to a typical block-based hybrid coder applying prediction and subsequent prediction error coding. The basic coding unit is an 8 × 8 block for inter, and an 8 × 8 or a 16 × 16 block for intra, instead of the usual 16 × 16 macroblock. No larger block sizes are considered for prediction and transform. Based on this simplified block structure, the coding scheme uses simple and fundamental coding tools with optimized encoding algorithms. In particular, the motion representation is based on a minimum partitioning with blocks sharing motion borders. In addition, compared to AVC, the new and improved coding techniques include: block-based intensity compensation, motion vector competition, adaptive motion vector resolution, adaptive interpolation filters, edge-based intra prediction and enhanced chrominance prediction, intra template matching, larger trans forms and adaptive switchable transforms selection for intra and inter blocks, and nonlinear and frame-adaptive de-noising loop filters. Finally, the entropy coder uses a generic flexible zero tree representation applied to both motion and texture data. Attention has also been given to algorithm designs that facilitate parallelization. Compared to AVC, the new coding scheme offers clear benefits in terms of subjective video quality at the same bit rate. Objective quality improvements are equally significant. At the same quality, an average bit-rate reduction of 31% compared to AVC is reported.

Compensating for intensity loss in a large-aperture MIMO sonar imaging system

To reduce the computation burden of a large-aperture multiple-input multiple-output(MIMO) sonar imaging system,the phase-shift beamformer(PSBF) is used at the cost of bringing the intensity loss(IL).The cause of the IL is analyzed in detail and a variable termed as IL factor is defined to quantify the loss amount.To compensate for the IL,two methods termed as intensity compensation for the PSBF(IC-PSBF) and the hybrid beamforming(HBF),respectively,are proposed.The IC-PSBF uses previously estimated IL factors to compensate for output intensities of all PSBFs;and the HBF applies the IC-PSBF to the center beam region and the shifted-sideband beamformer(SSBF) to the side beam region,respectively.Numerical simulations demonstrate the effectiveness of the two proposed methods.

Sensor Calibration Based on Incoherent Optical Fiber Bundles (IOFB) Used For Remote Image Transmission

Image transmission using incoherent optical fiber bundles (IOFB) requires prior calibration to obtain the spatial in-out fiber correspondence in order to reconstruct the image captured by the pseudo-sensor. This information is recorded in a Look-Up Table (LUT), used later for reordering the fiber positions and reconstructing the original image. This paper presents a method based on line-scan to obtain the in-out correspondence. The results demonstrate that this technique yields a remarkable reduction in processing time and increased image quality by introducing a fiber detection algorithm, an intensity compensation process and finally, a single interpolation algorithm.

Broadband phase and intensity compensation with a deformable mirror for an interferometric nuller

Nulling interferometry has been proposed for the direct detection of Earth-like planets. Deep stable nulls require careful control of the relative intensity and phase of the beams that are being combined. We present a novel compensator, the Adaptive Nuller, that corrects the intensity and phase as a function of wavelength from 8 to 12 microm using a deformable mirror. This compensator has been used to produce rejection ratios of 82,000:1 over a bandwidth of 3.2 microm centered around 10 microm.

Compensation and Improvement of Intensity and Distribution in Reconstructed Image Using Adaptive Optics in Holographic Data Storage

We applied a genetic algorithm to adaptive optics to improve the intensity and distribution of reconstructed images in holographic data storage. This is a kind of combinatorial optimisation. In holographic data storage, the photopolymer recording medium shrinks during light curing and this shrinkage distorts the recorded interference fringes, which degrades the reconstructed data images. Although it is possible to compensate for the degradation in the reconstructed image by using adaptive optics, it has been difficult to compensate for the shrinkage distortion by using normal feedback control because the relationship between the reconstructed image and deformable mirror input is nonlinear. With our method, the inverse variance coefficient in a reconstructed image with bits that are all “1” increased from 10.3 to 14.7 dB, an improvement of 4.4 dB. Moreover, the intensity average of the reconstructed image with compensation was 1.7 times higher than the average without compensation. These results show that the combination of adaptive optics and a genetic algorithm is very effective for improving reconstructed images.

Block-Coordinate Gauss–Newton Optimization and Constrained Monotone Regression for Image Registration in the Presence of Outlier Objects

In this paper, we propose the block-coordinate Gauss- Newton/regression method in order to conduct a correlation-based registration considering the intensity difference between images in the presence of outlier objects. In the proposed method, the parameters are decomposed into two blocks, one of which is for the spatial registration and the other for the intensity compensation. The two blocks are sequentially updated by the Gauss-Newton update and the polynomial regression, respectively. Because of the separated blocks, we can perform a joint optimization with low computational complexity and high implementation flexibility. For example, we apply separately appropriate scaling techniques to the parameter blocks for a stable and fast convergence of the algorithm. Furthermore, we apply the constrained monotone regression with a robust outlier detection scheme for the intensity compensation block. From numerical results, it is shown that the proposed algorithm more effectively performs a correlation-based registration considering the intensity difference alleviating the influence of the outlier objects compared to the traditional registration algorithms that perform the joint optimization.

A statistical approach for intensity loss compensation of confocal microscopy images

In this paper, a probabilistic technique for compensation of intensity loss in confocal microscopy images is presented. For single-colour-labelled specimen, confocal microscopy images are modelled as a mixture of two Gaussian probability distribution functions, one representing the background and another corresponding to the foreground. Images are segmented into foreground and background by applying Expectation Maximization algorithm to the mixture. Final intensity compensation is carried out by scaling and shifting the original intensities with the help of parameters estimated for the foreground. Since foreground is separated to calculate the compensation parameters, the method is effective even when image structure changes from frame to frame. As intensity decay function is not used, complexity associated with estimation of the intensity decay function parameters is eliminated. In addition, images can be compensated out of order, as only information from the reference image is required for the compensation of any image. These properties make our method an ideal tool for intensity compensation of confocal microscopy images that suffer intensity loss due to absorption/scattering of light as well as photobleaching and the image can change structure from optical/temporal section-to-section due to changes in the depth of specimen or due to a live specimen. The proposed method was tested with a number of confocal microscopy image stacks and results are presented to demonstrate the effectiveness of the method.

Image Processing and Interactive Visualization of Confocal Microscopy Images

The essence and methodology is proposed for image processing and interactive visualization of confocal microscopy images. Firstly, an intensity compensation algorithm is applied to reduce noises resulted from light absorption and scattering by objects and particles in the volume through which light passed. Secondly, a deconvolution algorithm based on Maximum A Posteriori is applied to improve the image stacks' quality. Lastly, the ray-casting algorithm is used to reconstruct the fine details in the volume. Furthermore, interactive control panel is integrated to provide users an intuitive interface to view the cells and its structures through translation, rotation and zoom in/out operations. Experimental results demonstrate that the speed and versatility of the program allows for convenient, fast, interactive examination of unknown cell structures even on commodity PC without any other special hardware. The program is also able to visualize dynamically changing temporary structures conveniently in addition to static images.

Acid-base homeostasis of blood and pH of abomasum in calves fed non-acidified and acidified milk replacer

Experiments were conducted on calves divided into three groups, 6 animals in each, to determine the influence of the intake of non-acidified and acidified milk replacer on the level of acid-base homeostasis in venous blood. The milk replacer was supplied at a dose of 700 g dry matter in 8 l of the liquid in two feedings. The milk replacer was acidified by adding formic acid to ensure the concentration of 0.2% in milk replacer. Venous blood was collected before feeding and 1, 2, 4, and 6 hours after feeding. The samples were analyzed for blood pH, actual bicarbonate HCO<sub>3</sub><sup>-</sup> (mmol/l), base excess BE (mmol/l), partial pressure of carbon dioxide pCO<sub>2</sub> (kPa) and partial pressure of oxygen pO<sub>2</sub> (kPa). Significant changes were observed in calves fed acidified milk of albumin type. The mean daily values of acid-base parameters in these calves were significantly lower in comparison with animals fed non-acidified milk replacer and reached the following levels: pH 7.343 ± 0.032 (<i>P</i> < 0.05), HCO<sub>3</sub> 24.49 ± 2.13 mmol/l (<i>P</i> < 0.01), BE 1.11 ± 1.97 mmol/l (<i>P</i> < 0.001). A similar tendency but of a more pronounced decrease in values was recorded in the group of calves fed acidified milk replacer of casein type: pH 7.312 ± 0.022 (<i>P</i> < 0.01), HCO<sub>3</sub><sup>-</sup> 21.73 ± 0.75 mmol/l (<i>P</i> < 0.001), BE 96 ± 0.86 mmol/l (<i>P</i> < 0.001). In relation to the time after feeding the group of calves fed non-acidified milk replacer showed a rising tendency in the level of metabolic components (HCO<sub>3</sub><sup>-</sup>), compensated by respiratory regulating mechanisms (rise in pCO<sub>2</sub>) conducive to the maintenance of optimum blood pH level. The group of calves fed acidified milk replacer (formic acid 2 ml/l) of the albumin type showed metabolic acidosis with subsequent gradual adjustment and compensation by means of metabolic (HCOHCO<sub>3</sub><sup>-</sup>) rather than respiratory regulation mechanisms. The calves fed acidified casein type milk replacer displayed metabolic acidosis with insufficient metabolic regulation and more intensive respiratory compensation (decrease in pCO<sub>2</sub>). Concurrent investigations of the abomasum acidity and blood acid-base homeostasis reflected the joint action of both the acidifying effect of formic acid and significantly lower production of bicarbonate (HCO<sub>3</sub><sup>-</sup>) related to the intake of acidified milk and the tendency to the development of metabolic acidosis.

Fully automated intensity compensation for confocal microscopic images

One well-recognized problem in three-dimensional (3D) confocal microscopic images is that the intensities in deeper slices are generally weaker than those in shallower slices. The loss of intensity with depth hampers both qualitative observation and quantitative measurement of specimens. Two major types of methods exist to compensate for this intensity loss: the first is based on the geometrical optics inside the specimen, and the second applies an empirical parametric intensity decay function (IDF) of depth. A common feature shared by both methods is that they are parameter-dependent. However, for the optics-based method there are as yet no fully automated parameter-setting approaches; and for the IDF method the traditional profile-fitting approach cannot provide proper parameters if the presumed IDF model does not match the experimental intensity-depth profile of the 3D image. In this paper, we propose a novel maximum-entropy (ME) approach to fully automated parameter-setting. In principle the ME approach is suitable for any compensation method as long as it is parameter-dependent. The basic assumption is that without intensity loss an ideal 3D image should be generally homogeneous with respect to depth and this axial homogeneity can be represented by the entropy of a normalized intensity-depth profile. Experiments on real confocal images showed that such a profile was consistent with visual evaluation of axial intensity homogeneity and that the ME approach could provide proper parameters for both compensation methods mentioned above. Moreover, for the IDF method, experiments on both real and simulated data showed that the ME approach could provide more precise parameters than with traditional profile-fitting. The Appendix provides a proof that under certain conditions the global maximization of the profile-entropy is guaranteed.

Effect of growth conditions, surface orientation, and alloy composition on Cl incorporation and activation in ZnSe and Zn1−xMgxSe grown by molecular beam epitaxy

While chlorine can be incorporated in ZnSe at levels up to about 2×1020cm−3, it is only electrically active at levels up to 1×1019cm−3 with almost complete compensation occurring beyond this point. The doping level at which this compensation occurs coincides with a dramatic decrease in growth rate when using ZnCl2 as the chlorine source during growth by molecular beam epitaxy. The decrease in growth rate is likely due to competition for Zn atoms between growth and the chlorine. Compensation and degradation of photoluminescence edge emission intensity appear to be directly correlated to the reduced growth rate. Surface chemistry effects on point defect formation and surface reaction kinetics are investigated through comparison of growth and Cl doping of ZnSe on (100) and (211)B oriented substrates, and by dramatically modifying Zn-to-Se ratios during growth. It is shown that growth conditions can be modified to overcome Cl-related growth rate reduction, recovering to some extent the optical and electrical properties. ZnMgSe alloys have a higher Cl solubility than ZnSe, increasing the rate of Cl incorporation by an order of magnitude for the same ZnCl2 flux. The growth rate for ZnMgSe was not observed to decrease under high Cl flux. The ZnMgSe alloys were electrically active for roughly an order of magnitude larger Cl concentration than ZnSe. However the increase in band gap with Mg results in a lower net activation of carriers than for equivalently doped ZnSe.

Tensor voting for image correction by global and local intensity alignment

This paper presents a voting method to perform image correction by global and local intensity alignment. The key to our modeless approach is the estimation of global and local replacement functions by reducing the complex estimation problem to the robust 2D tensor voting in the corresponding voting spaces. No complicated model for replacement function (curve) is assumed. Subject to the monotonic constraint only, we vote for an optimal replacement function by propagating the curve smoothness constraint using a dense tensor field. Our method effectively infers missing curve segments and rejects image outliers. Applications using our tensor voting approach are proposed and described. The first application consists of image mosaicking of static scenes, where the voted replacement functions are used in our iterative registration algorithm for computing the best warping matrix. In the presence of occlusion, our replacement function can be employed to construct a visually acceptable mosaic by detecting occlusion which has large and piecewise constant color. Furthermore, by the simultaneous consideration of color matches and spatial constraints in the voting space, we perform image intensity compensation and high contrast image correction using our voting framework, when only two defective input images are given.

Intensity control during target approach in echolocating bats; stereotypical sensori-motor behaviour in Daubenton's bats, Myotis daubentonii.

When approaching a prey target, bats have been found to decrease the intensity of their emitted echolocation pulses, called intensity compensation. In this paper we examine whether intensity compensation in the echolocation of bats is flexible or stereotyped. We recorded the echolocation calls of Daubenton's bats (Myotis daubentonii) while the animals attacked targets of different dimensions. Myotis daubentonii reduced the peak sound pressure level emitted by about 4dB for each halving of distance, irrespective of the target presented (mealworms and two different sizes of spheres). The absolute sound pressure level emitted by the bat is not or only a little affected by target strength. Furthermore, the decrease in emitted intensity over distance shows less scatter than the same intensity over time for the last 20 cm of target approach. The bats matched the emitted intensity to target distance equally well for the spheres (aspect-invariant target strength) as for the mealworms (aspect-dependent echo strength). We therefore conclude that intensity compensation does not rely on feedback information from received intensity, but instead follows a stereotyped pattern.

Method to synthesize polynomial current waveforms and intensity compensation functions for DFB lasers in digital sweep integration gas analyzers

With analysis methods using digital sweep integration of the absorbance function, linear current ramps can produce non-linear laser intensity and wavenumber functions from distributed feedback lasers. These non-linear functions produce offset and gain errors in mole fraction estimates on tunable diode laser gas analyzers. A method is described to synthesize polynomial current waveforms and laser intensity compensation functions to give linear wavenumber functions and to minimize the offset error. Quantitative and qualitative results are presented to evaluate reduction in mole fraction errors.

Focus latitude enhancement of symmetrical phase mask design for deep submicron contact hole patterning

The mechanism of focus latitude enhancement for contact/via hole printing is explained by approximating the axis intensity distribution of an image as a series of cosine functions to characterize the interference between each pair of diffraction beams. It is found that a phase-shifting mask (PSM) with symmetrical assist features improves the depth of focus (DOF) by introducing destructive interference to counterbalance the intensity fluctuation from constructive interference as defocus. A simple formula was derived to represent the capability of focus latitude enlargement. It shows that the extent of enhancement depends on the exposure wavelength and numerical aperture of a projection lens only. Increasing the degree of partial coherence degrades the focal range enlargement because a larger illumination angle elongates the destructive interference pattern in the optical-axis direction to weaken its ability for intensity compensation. On the other hand, the lack of constructive interference in dense hole imaging fails the mask pattern transfer, which limits the application of the phase-shifting method to pattern pitch greater than 2λ/NA. A tiny amount of spherical aberration results in prominent asymmetrical defocus behavior because the wave deformation in the projection lens shifts the distribution of constructive and destructive interference patterns to opposite defocus directions. The printing characteristics of 0.17 μm contact using an 18% transmission, rim-type attenuated phase-shifting mask are investigated to corroborate our analysis of defocus behavior. The dependence of depth of focus on pattern duty is stressed to elucidate the difference in mechanisms of focus latitude improvements for a sparse hole and periodic dense hole.

Color consistency between different printing materials using dot gain and intensity compensation

In a drop-on-demand thermal ink-jet printer, the dot size of an ink droplet expelled from a printer depends on the absorption ratio of the substrate. This causes color differences between output images on different printing materials. A color consistency algorithm for different papers is proposed. To achieve a corresponding color reproduction, dot gain compensation based on saturation was applied to correct the color reproduction of the printer. However, dot gain compensation applied to substrates with different intensity values may still produce unequal intensity values in the output images. Accordingly, intensity compensation is added in order to match the colors of different papers.

An instrument for the measurement of colour and turbidity in natural waters

The development of a sensor to measure colour and turbidity of natural waters is described. Filtration of the water is not required, so maintenance intervals and costs will be reduced. A four-beam intensity compensation technique is used for robust measurement and resistance to fouling. Results of the operation of a prototype at a water treatment works are presented.

Intensity compensation for passive in-fibre Fabry-Perotsensorsin high disturbed environments

A method for compensating intensity variations in passive in-fibre Fabry-Perot sensors is studied. To achieve passive Fabry-Perot sensors for intensity compensations, three read-out cavities are used. Two path-balanced Fabry-Perot read-out cavities are designed for two quadrature signals, and the other path-imbalanced cavity is for eliminating the effect of intensity variations via subtraction from two quadrature signals. Consequently, a compensation method proposed to eliminate intensity variations in the interferometry shows good a result in highly disturbed environments.

An instrument for the measurement of colour and turbidity in natural waters

The development of a sensor to measure colour and turbidity of natural waters is described. Filtration of the water is not required, so maintenance intervals and costs will be reduced. A four-beam intensity compensation technique is used for robust measurement and resistance to fouling. Results of the operation of a prototype at a water treatment works are presented.