Dynamic range compression based on illumination compensation

Image enhancement is a crucial pre-processing step for various image processing applications and vision systems. Many enhancement algorithms have been proposed based on different sets of criteria. However, a direct multi-scale image enhancement algorithm capable of independently and/or simultaneously providing adequate contrast enhancement, tonal rendition, dynamic range compression, and accurate edge preservation in a controlled manner has yet to be produced. In this paper, a multi-scale image enhancement algorithm based on a new parametric contrast measure is presented. The parametric contrast measure incorporates not only the luminance masking characteristic, but also the contrast masking characteristic of the human visual system. The formulation of the contrast measure can be adapted for any multi-resolution decomposition scheme in order to yield new human visual system-inspired multi-scale transforms. In this article, it is exemplified using the Laplacian pyramid, discrete wavelet transform, stationary wavelet transform, and dual-tree complex wavelet transform. Consequently, the proposed enhancement procedure is developed. The advantages of the proposed method include: 1) the integration of both the luminance and contrast masking phenomena; 2) the extension of non-linear mapping schemes to human visual system inspired multi-scale contrast coefficients; 3) the extension of human visual system-based image enhancement approaches to the stationary and dual-tree complex wavelet transforms, and a direct means of; 4) adjusting overall brightness; and 5) achieving dynamic range compression for image enhancement within a direct multi-scale enhancement framework. Experimental results demonstrate the ability of the proposed algorithm to achieve simultaneous local and global enhancements.

Medical endoscopic video processing requires real-time execution of color component acquisition, color filter array (CFA) demosaicing, and high dynamic range (HDR) compression under low-light conditions, while adhering to strict thermal constraints within the surgical handpiece. Traditional hardware-aware neural architecture search (NAS) relies on fixed hardware design spaces, making it difficult to balance accuracy, power consumption, and real-time performance. A collaborative “power-accuracy” optimization method is proposed for hardware-aware NAS. Firstly, we proposed a novel hardware modeling framework by abstracting FPGA heterogeneous resources into unified cell units and establishing a power–temperature closed-loop model to ensure that the handpiece surface temperature does not exceed clinical thresholds. In this framework, we constrained the interstage latency balance in pipelines to avoid routing congestion and frequency degradation caused by deep pipelines. Then, we optimized the NAS strategy by using pipeline blocks and combined with a hardware efficiency reward function. Finally, color component acquisition, CFA demosaicing, dynamic range compression, dynamic precision quantization, and streaming architecture are integrated into our framework. Experiments demonstrate that the proposed method achieves 2.8 W power consumption at 47 °C on a Xilinx ZCU102 platform, with a 54% improvement in throughput (vs. hardware-aware NAS), providing an engineer-ready lightweight network for medical edge devices such as endoscopes.

Dynamic Range Compression (DRC) is a key component in all modern Hearing Aids. Attack and Release time constants decide the speed with which the DRC should act to the incoming signal amplitude variation. So an accurate estimation of time constants gives a precise control over the DRC behavior. In this paper we examined various errors that occur in the output of the DRC while using conventional methods which affect attack and release time constants adversely. New methods are proposed for a better estimation of time constants in DRC. Since all the modifications are made in the estimation of attack time, there is no need to change the existing hardware for DRC. The proposed algorithm gives perfect output characteristics with zero error for test signals defined in ANSI S3.22 standards for hearing aid specifications.

Dynamic range compression (DRC) by hexapeptide libraries increases MS/MS-based identification of lower-abundance proteins in complex mixtures. However, two unanswered questions impede fully realizing DRC's potential in shotgun proteomics. First, does DRC enhance identification of post-translationally modified proteins? Second, can DRC be incorporated into a workflow enabling relative protein abundance profiling? We sought to answer both questions analyzing human whole saliva. Addressing question one, we coupled DRC with covalent glycopeptide enrichment and MS/MS. With DRC we identified ∼2 times more N-linked glycoproteins and their glycosylation sites than without DRC, dramatically increasing the known salivary glycoprotein catalog. Addressing question two, we compared differentially stable isotope-labeled saliva samples pooled from healthy and metastatic breast cancer women using a multidimensional peptide fractionation-based workflow, analyzing in parallel one sample portion with DRC and one portion without. Our workflow categorizes proteins with higher absolute abundance, whose relative abundance ratios are altered by DRC, from proteins of lower absolute abundance detected only after DRC. Within each of these salivary protein categories, we identified novel abundance changes putatively associated with breast cancer, demonstrating feasibility and benefits of DRC for relative abundance profiling. Collectively, our results bring us closer to realizing the full potential of DRC for proteomic studies.

Magnetic resonance imaging (MRI) plays a significant role in medical detection technologies but is difficult to avoid suffering from un-uniformity, low brightness and noise pollution. These factors might affect the doctor`s diagnosis and can lead to misdiagnosis in practical applications. In this paper, a new MRI images enhancement strategy is proposed which consists of a dynamic range compression (DRC) operation and a details enhancement (DE) operation. The DRC can efficiently compress the high dynamic range to a suitable range and protect the difference between the pixels, and DE adopts an improved bilateral filtering combined with Laplacian pyramid to remove the noise and enhance the details. A series of experiments results of real MRI images demonstrate that the method is more effective than other methods.

Accurate estimation of decay coefficients for dynamic range compressors in hearing aids and a hardware level comparison of different architectures

Recently we proposed a wavelet-based dynamic range compression algorithm to improve the visual quality of digital images captured in the high dynamic range scenes with non-uniform lighting conditions. The fast image enhancement algorithm which provides dynamic range compression preserving the local contrast and tonal rendition is a very good candidate in aerial imagery applications such as image interpretation for defense and security tasks. This algorithm can further be applied to video streaming for aviation safety. In this paper the latest version of the proposed algorithm which is able to enhance aerial images so that the enhanced images are better then direct human observation, is presented. The results obtained by applying the algorithm to numerous aerial images show strong robustness and high image quality.

Lidar dynamic range compression by using a membrane mirror light shutter

Sensorineural hearing loss is associated with elevated hearing thresholds, reduced dynamic range, and loudness recruitment. Dynamic range compression in the hearing aids is provided for restoring normal loudness of low level sounds without making the high level sounds uncomfortably loud. A sliding-band compression is presented for significantly reducing the temporal and spectral distortions generally associated with the currently used single and multiband compression techniques. It uses a frequency-dependent gain function calculated on the basis of critical bandwidth based short-time power spectrum and the specified hearing thresholds, compression ratios, and attack and release times. It is realized using FFT-based analysis-synthesis and can be integrated with other FFT-based signal processing in hearing aids to save computation. The technique is implemented and tested for satisfactory real-time operation, with sampling frequency of 10 kHz, window length of 25.6 ms with 75% overlap on a 16-bit fixed-point DSP processor with on-chip FFT hardware.

A novel adaptation-based recursive Retinex algorithm is proposed in this paper. The recursive scheme works in a similar way to the first recursive Retinex algorithm proposed by Frankle and McCann. Simulating the spatial response of retinal photoreceptors, the pixel level adaptation is implemented instead of the ratio-product operations. Thus the dynamic range is compressed efficiently without altering the spatial properties of the original image. In addition, the iteration proceeds in a simultaneous manner, thus the spatial distortion over directions is eliminated. Moreover, the sensitivity constant can be tuned for different strength of local contrast enhancement. Finally, global dynamic range compression and local contrast enhancement are achieved simultaneously.

We increase the dynamical range of a scanning tunneling microscope (STM) by actively subtracting dominant current-harmonics generated by nonlinearities in the current-voltage characteristics that could saturate the current preamplifier at low junction impedances or high gains. The strict phase relationship between a cosinusoidal excitation voltage and the current-harmonics allows excellent cancellation using the displacement-current of a driven compensating capacitor placed at the input of the preamplifier. Removal of DC currents has no effect on, and removal of the first harmonic only leads to a rigid shift in differential conductance that can be numerically reversed by adding the known removal current. Our method requires no permanent change of the hardware but only two phase synchronized voltage sources and a multi-frequency lock-in amplifier to enable high dynamic range spectroscopy and imaging.• Active power filter• Dynamic range compression• High gain preamplifier

In this paper we present a new technique for the display of High Dynamic Range (HDR) images on Low Dynamic Range (LDR) displays. The described process has three stages. First, the input image is segmented into luminance zones. Second, the tone mapping operator (TMO) that performs better in each zone is automatically selected. Finally, the resulting tone mapping (TM) outputs for each zone are merged, generating the final LDR output image. To establish the TMO that performs better in each luminance zone we conducted a preliminary psychophysical experiment using a set of HDR images and six different TMOs. We validated our composite technique on several (new) HDR images and conducted a further psychophysical experiment, using an HDR display as reference, that establishes the advantages of our hybrid three-stage approach over a traditional individual TMO.

Cytotoxicity assays in 96-well tissue culture plates allow rapid sample handling for multicondition experiments but have a limited dynamic range. Using DIMSCAN, a fluorescence digital image system for quantifying relative cell numbers in tissue culture plates, we have developed a 96-well cytotoxicity assay with a >4-log dynamic range. To overcome background fluorescence that limits detection of viable cells with fluorescein diacetate, we used 2'4'5'6'-tetrabromofluorescein (eosin Y) to quench background fluorescence in the medium and in nonviable cells to enhance the reduction of background fluorescence achieved with digital image thresholding. The sensitivity and linearity of the new assay were tested with serial dilutions of neuroblastoma and leukemia cell lines. DIMSCAN was compared with other in vitro cytotoxicity assays: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation, and trypan blue dye exclusion. Without background fluorescence reduction, scans produced a nearly flat curve across various cell concentrations from 100 to 10(6) cells per well. Either digital image thresholding or eosin Y dramatically reduced background fluorescence, and combining them achieved a linear correlation (r > 0.9) of relative fluorescence to viable cell number over >4 logs of dynamic range, even in the presence of 4 x 10(4) nonviable cells per well. Cytotoxicity of deferoxamine for neuroblastoma cell lines measured by the DIMSCAN assay achieved dose-response curves similar to data obtained by manual trypan blue counts or colony formation in soft agar but with a wider dynamic range. Long-term cultures documented the clonogenic ability of viable cells detected by DIMSCAN over the entire dynamic range. The cytotoxicity of two drug combinations (buthionine sulfoximine + melphalan or fenretinide + safingol) was tested using both DIMSCAN and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, and the wider dynamic range of DIMSCAN facilitated detection of synergistic interactions. DIMSCAN offers the ability to rapidly and efficiently conduct cytotoxicity assays in 96-well plates with a dynamic range of >4 logs. This assay enables rapid testing of anticancer drug combinations in microplates.

Increasing the flexibility of the LANCE cAMP detection kit.

In color gamut mapping of pictorial images, the lightness rendition of the mapped images plays a major role in the quality of the final image. For color gamut mapping tasks, where the goal is to produce a match to the original scene, it is important to maintain the perceived lightness contrast of the original image. Typical lightness remapping functions such as linear compression, soft compression, and hard clipping reduce the lightness contrast of the input image. Sigmoidal remapping functions were utilized to overcome the natural loss in perceived lightness contrast that results when an image from a full dynamic range device is scaled into the limited dynamic range of a destination device. These functions were tuned to the particular lightness characteristics of the images used and the selected dynamic ranges. The sigmoidal remapping functions were selected based on an empirical contrast enhancement model that was developed for the result of a psychophysical adjustment experiment. The results of this study showed that it was possible to maintain the perceived lightness contrast of the images by using sigmoidal contrast enhancement functions to selectively rescale images from a source device with a full dynamic range into a destination device with a limited dynamic range.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.