Haofeng Hu

• Professor
• Professor at Tianjin University

In underwater imaging scenarios, the scattering media could cause severe image degradation due to the backscatter veiling as well as signal attenuation. In this paper, we consider the polarization effect of the object, and propose a method of retrieving the objects radiance based on estimating the polarized-difference image of the target signal. We...

The underwater imaging could be severely degraded by the scattering media because of the backscattered light and signal attenuation, especially in the case of strong scattering for dense turbid medium. In this paper, we propose an improved method for recovering the underwater image combining the histogram stretching and polarimetric recovery in a p...

Based on measuring the polarimetric parameters which contain specific physical information, polarimetric imaging has been widely applied to various fields. However, in practice, the noise during image acquisition could lead to the output of noisy polarimetric images. In this paper, we propose, for the first time to our knowledge, a learning-based m...

Imaging in scattering media has been a challenging and important subject in optical science. In scattering media, the image quality is often severely degraded by the scattering and absorption effects owing to the small particles and the resulting nonuniform distribution of the intensity or polarization properties. This study reviews the recent deve...

The occurrence of Phaeocystis globosa blooms poses a potential hazard to both human society and the ecological environment, particularly concerning the safety of cooling systems in coastal nuclear power plants. However, current ecological monitoring techniques fail to dynamically detect the densities of solitary cells of Phaeocystis globosa prior t...

In underwater imaging, the influence of light absorption and scattering in the water medium could cause image details blurring and color distortion, which can compromise the effectiveness of intelligent computer vision systems for visual inspection, environment perception, and object detection and recognition. To address these challenges, this pape...

In this paper we present a magnetic probe structure based on magneto-fluidic and laser internal cavity modulation. We used a single-mode-no-core-single-mode fiber structure coated by a magnetic fluid as a sensing element, and inserted the sensing element in the inner cavity of a laser. Highly sensitive, high signal-to-noise ratio (SNR), narrow half...

In infrared small target detection (ISTD), a common challenge for neural network methods is that as the network deepens, the sparse information of small targets becomes even more diffuse in the deeper layers, limiting the ability to extract high-level semantic features. To address this issue, we propose the Orthogonal Inputs Perception Fusion (OIPF...

Due to the scattering and absorption of light, underwater imaging yields suboptimal results characterized by low brightness, diminished image contrast, and the loss of details. Current learning-based underwater image enhancement (UIE) methods mainly focus on addressing these issues in the spatial domain, with limited attention to the Fourier freque...

In this Letter, we introduce a self-supervised depth estimation method based on polarization binocular imaging. First, an end-to-end disparity estimation network is utilized to estimate the left and right disparities from the stereo view images. Next, we design loss functions that facilitate self-supervised training of the network, eliminating the...

In this Letter, we introduce a self-supervised depth estimation method based on polarization binocular imaging. First, an end-to-end disparity estimation network is utilized to estimate the left and right disparities from the stereo view images. Next, we design loss functions that facilitate self-supervised training of the network, eliminating the...

In this Letter, we introduce a self-supervised depth estimation method based on polarization binocular imaging. First, an end-to-end disparity estimation network is utilized to estimate the left and right disparities from the stereo view images. Next, we design loss functions that facilitate self-supervised training of the network, eliminating the...

In this Letter, we introduce a self-supervised depth estimation method based on polarization binocular imaging. First, an end-to-end disparity estimation network is utilized to estimate the left and right disparities from the stereo view images. Next, we design loss functions that facilitate self-supervised training of the network, eliminating the...

Optical imaging and vision technology have become crucial research topics in the field of underwater and ocean scenes. These technologies play a vital role in advancing underwater exploration, scientific research, and smart aquaculture. Despite their importance, optical systems face substantial challenges in complex water environments, especially i...

Underwater optical imaging is widely used in various marine exploration tasks. However, the scattering of light by suspended particles in water will result in poor contrast to underwater images. Underwater polarimetric imaging could effectively suppress the influence of scattered light. However, apart from scattering, the absorption and poor illumi...

Polarimetric imaging technology plays a crucial role in de-scattering, particularly in the field of underwater image restoration. Circularly polarized light (or the underlying circular polarization memory effect) has been proven to better preserve the polarization characteristics of detected light. Utilizing circularly polarized light as illuminati...

Advanced sensors and signal processing algorithms are significant for remote-operated vehicles (ROVs) and autonomous underwater vehicles (AUVs). The distance/length measurement is the basis of many sensing functions, including positioning, tracking, surface reconstruction, and pose determination. Optical-based ranging sensors have been proven as a...

Due to its insensitivity to light intensity and the capability to capture multidimensional information, polarimetric imaging technology has been proven to have advantages over traditional intensity-based imaging techniques for object detection tasks in adverse environmental conditions, particularly in road traffic scenarios. Recently, with the rapi...

In a scattering environment, the quality of obtained optical images is severely degraded, with reduced contrast in details, which greatly limits the application of optical imaging technology in various fields. Due to the partial polarization characteristics of scattered light, polarization-based scatter removal techniques have received widespread a...

Although deep learning-based methods have achieved great success in various polarimetric imaging tasks, the performance and the generalization ability are strongly dependent on massive training data, which is a critical limitation and limits the practical applications. In this paper, for the first time to our knowledge, we present a deep transfer l...

When light traverses through water, it undergoes influence from the absorption and scattering of particles, resulting in diminished contrast and color distortion within underwater imaging. These effects further constrain the observation of underwater environments and the extraction of features from submerged objects. To address these challenges, we...

In this Letter, we present a self-supervised method, polarization to polarization (Pol2Pol), for polarimetric image denoising with only one-shot noisy images. First, a polarization generator is proposed to generate training image pairs, which are synthesized from one-shot noisy images by exploiting polarization relationships. Second, the Pol2Pol me...

Special Issue “Advanced Techniques for Water-Related Remote Sensing" Deadline for manuscript submissions: 30 November 2023 “Water-related” refers to anything related to water, such as oceans, rivers, lakes, floods, clouds, rain, mist, snow, and ice. The research objects of water-related remote sensing cover all water bodies that serve as either l...

Color polarimetric imaging could provide multi-dimensional information that provides physical properties related to object shape, surface roughness, etc. Therefore, it has been widely used in various instrumentation and measurement applications, such as 3D measurement, surface detection, and navigation. However, compared to conventional color image...

Polarization can provide information largely uncorrelated with the spectrum and intensity. Therefore, polarimetric imaging (PI) techniques have significant advantages in many fields, e.g., ocean observation, remote sensing (RS), biomedical diagnosis, and autonomous vehicles. Recently, with the increasing amount of data and the rapid development of...

Reduced resolution of polarized images makes it difficult to distinguish detailed polarization information and limits the ability to identify small targets and weak signals. A possible way to handle this problem is the polarization super-resolution (SR), which aims to obtain a high-resolution polarized image from a low-resolution one. However, comp...

Underwater images always suffer from color distortion, contrast decrease, and detail blur due to the selective absorption and scattering of water, which significantly limits their applications. In this article, we introduce an effective underwater image enhancement method to improve image quality, i.e., correcting color distortion, enhancing contra...

Underwater images always suffer from low contrast and color distortion due to the wavelength-dependent scattering and absorption effects caused by particles existing in turbid water, especially in high turbidity conditions. Based on the polarization properties of the backscattering light, polarimetric methods can estimate the intensity level of the...

The imaging process of polarization images in the natural environment is easily affected by noise, which not only causes the acquisition of relevant polarization parameters to deviate from their real values but also affects the further processing of subsequent polarization information. The denoising method based on deep learning can significantly r...

The polarization characteristics is significantly crucial for tasks in various fields, including the remote sensing of oceans and atmosphere, as well as the polarization LIDAR and polarimetric imaging in scattering media. Many polarimetric metrics (such as the degree of polarization, diattenuation, and depolarization) were proposed to enrich the ch...

Utilizing the polarization analysis in underwater imaging can effectively suppress the scattered light and help to restore target signals in turbid water. Neural network-based solutions can also boost the performance of polarimetric underwater imaging, while most of the existing networks are pure data driven which suffer from ignoring the physical...

In this Letter, we present a Stokes imaging-based method to restore objects and enhance image contrast in turbid water. In the system, a light source illuminates the objects with two orthometric polarization states; based on a new Stokes decomposition model, the recorded images are converted to Stokes maps and subsequently restored to a clear image...

In this Letter, we propose an attention-based neural network specially designed for the challenging task of polarimetric image denoising. In particular, the channel attention mechanism is used to effectively extract the features underlying the polarimetric images by rescaling the contributions of channels in the network. In addition, we also design...

Polarimetric imaging has prominent advantages in scattering media. Emerging learning-based polarimetric technologies has succeeded but heavily relied on paired data corresponding to the same scenes. In this paper, we propose an unsupervised method for the unpaired underwater-image recovery with a polarimetric generative adversarial network, named U...

This presentation aims to show that the proposed IPLNet network can enhance the quality of both intensity and polarization images in continuously changed outdoor scenes effectively.

Temperature cross-sensitivity is the main obstacle to the practical application of fiber current sensors based on the garnet crystal Faraday rotator. In this paper, a temperature compensation method is proposed and experimentally demonstrated. By introducing an appropriate static bias to the sensor, temperature compensation can be realized by simpl...

We demonstrate a fiber Bragg grating (FBG) pressure sensor based on a spring-diaphragm elastic structure (SDES) for measuring ultimate pressure. The spring-diaphragm elastic structure model can effectively prevent the fiber Bragg grating from being broken under large pressure situations. The geometrical parameters of the sensor are optimally optimi...

The temporal response, especially characteristics of luminescence intensity decay, of lanthanide ions (Ln3+) doped upconversion materials has attracted much attention for its significance in understanding upconversion mechanisms and developing fluorescence lifetime-based applications. However, a detailed explanation concerning the temporal response...

Mid-infrared (mid-IR) microring resonators (MRRs) have been extensively studied for biochemical sensing. However, the temperature fluctuation is an undesirable cross-sensitive effect for refractive index (RI) sensing. Here, we study an electric-field-assisted resonance scanning (EARS) spectroscopic technique based on a graphene-on-silicon dual-mode...

Low illuminated images make it challenging to conduct anomaly detection on material surface. Adding polarimetric information helps expand pixel range and recover background structure of network inputs. In this letter, an anomaly detection method in low illumination is proposed which utilizes polarization imaging and patch-wise Support Vector Data D...

Previous polarization underwater imaging methods based on the physical scattering model usually require background region included in the image and the prior knowledge, which hinders its practical application. In this paper, we analyze and optimize the physically feasible region and propose an improved method by degenerating intermediate variables,...

We propose a new super-resolution microscopy, named frequency interferometric localization microscopy (FILM). FILM is implemented by incorporating a Michelson interferometer into wide-field fluorescence microscope, which introduces coherence time as a new auxiliary axis to obtain the spectral information of individual fluorophores. After the time–w...

Luminescence properties of upconverting nanomaterials are significantly influenced by host structures. Even though previous studies have demonstrated various modulation approaches of host structures on upconversion luminescence, in-situ host transition has been hardly realized. In this paper, we demonstrate in-situ host-transition-induced upconvers...

Polarimetric imaging is an effective way for enhancing the image quality in underwater environments. Previous polarization-based methods for underwater imaging actually involve both optical and digital processing, while compared with digital processing, the importance of the optical method is not clear. In this paper, we propose a polarimetric meth...

Polarization information is valuable for image de-scattering in turbid media. Previous polarimetric image de-scattering methods tend to employ the illumination with a fixed polarization state, while the effect of the polarization state of active illumination on the target is less considered. In this paper, a computational polarization differential...

Surface-enhanced Raman spectroscopy (SERS) based on two-dimensional (2D) materials has attracted great attention over the past decade. Compared with metallic materials, which enhance Raman signals via the surface plasmon effect, 2D materials integrated on silicon substrates are ideal for use in the fabrication of plasmon-free SERS chips, with the a...

Stimulus-triggered drug delivery systems (DDSs) based on lanthanide-doped upconversion nanoparticles (UCNPs) have attracted intensive attention for treating cancers due to the merits of high drug availability, precisely controlled drug release, and low side-effects. However, such DDSs usually exhibit a single stimulus-response, which may limit the...

Full Stokes imaging can be performed with a continuously rotating retarder in front of a fixed polarizer and a standard camera (RRFP) or a division of a focal plane polarization camera (RRDOFP). We determine the optimal number and duration of intensity measurements through a cycle of the retarder for these two types of setups as a function of instr...

Underwater images always suffer low contrast and inaccurate colors due to the scattering and absorption by the particles when the target light propagates through the turbid water. In this paper, we first found that a lot of intensity space is occupied by fewer pixels called "tails" on both sides of the histograms for RGB channels of the image. Base...

Water sensing is of great importance in wide applications of biomedicine, precision agriculture, chemical industrial processes, and food inspection. As a promising probe to detect water molecules, lanthanide-doped upconversion nanoparticles have drawn rapidly increasing research interest with the merits of the high photostability, fast response, an...

In extreme environments such as deep space and abysmal sea, the characteristics of low-temperature, vacuum, electromagnetic interference will significantly affect the performance of measuring instruments. With merits of anti-electromagnetic interference, corrosion resistance, compact size and so on, optical fiber sensing systems can accurately meas...

Deep learning is a powerful technique based on neural networks, which has distinct advantages in terms of finding the relation between the input and the label, and it has shown the superior performance for image recovery in complex and strong noise environment than other methods. We employ the deep learning method for polarimetric imaging in turbid...

Imaging in low light is significant but challenging in many applications. Adding the polarization information into the imaging system compromises the drawbacks of the conventional intensity imaging to some extent. However, generally speaking, the qualities of intensity images and polarization images cannot be compatible due to the characteristic di...

Mode division multiplexing (MDM) silicon photonic integrated circuits (PICs) have been widely developed for achieving high-speed optical interconnects and communications. As an excellent nonlinear optical platform, silicon PICs also receive great attention in applications of optical parametric devices and nonlinear optical signal processing. Howeve...

Full Stokes polarimetric images can be obtained from two acquisitions with a microgrid polarization camera equipped with a retarder. When the retardance is imperfectly known, it can be calibrated from the measurements, but this requires three image acquisitions and may cause divergence of estimation variance at a low signal-to-noise ratio. We deter...

Mode-division multiplexing (MDM) has attracted broad attention as it could effectively boost up transmission capability by utilizing optical modes as a spatial dimension in optical interconnects. In such a technique, different data channels are usually modulated to the respective carriers over different spatial modes by using individual parallel el...

Mid-infrared microring resonators have been extensively studied for biochemical sensing applications. To characterize such resonators, a tunable laser or spectrometer has usually been utilized in previous studies. However, it is challenging to integrate these bulky instruments on a chip, ineluctably limiting practical applications. Here, we study a...

We propose a general theory of simultaneous estimation of Stokes vector and instrumental autocalibration of polarization imagers. This theory is applicable to any polarization imager defined by its measurement matrix. We illustrate it on the example of retardance autocalibration in a large class of polarization imagers based on rotating retarders a...

The variation of environment temperature is a crucial problem for optical magnetic field sensors based on the magneto-optical crystal. In this paper, we propose a novel temperature compensation method for optical alternating magnetic field measuring by analyzing the demodulation principle and establishing the temperature compensation model, which c...

Calibration by hydrogen cyanide (HCN) absorption spectrum can make the fiber Bragg grating (FBG) demodulation system immune to environment temperature changes. The transmittance function of Fabry-Perot (F-P) filter will result in the distortion of the HCN absorption peaks. A demodulation scheme based on deconvolution is proposed to eliminate the im...

The measurement of linearly-polarized Stokes vector can be extended to the measurement of full Stokes vector (FSV) by placing a phase retarder, such as a waveplate, in front of the division-of-focal-plane (DoFP) polarization camera. In this study, we propose two optimization strategies to estimate FSV by matrix-decomposition and pseudo-inverse mode...

Due to the backscattered light and signal attenuation, the underwater imaging could be severely degraded by the scattering media, especially in the case of strong scattering for dense turbid medium. Considering the circular polarization light can persist better its polarization property during propagating through turbid media compared with the line...

A linear division-of-focal-plane camera combined with a controllable polarization modulator constitutes a versatile full-Stokes imager with four possible sampling rate modes, depending on the number of acquisitions. Considering several polarization modulator architectures, we determine the parameter settings that minimize estimation variance in eac...

In this paper, a surface plasmon resonance (SPR) fiber sensor based on a multimode-no-core-multimode (MNM) structure for refractive index (RI) measurement is proposed and experimentally investigated. The influence of the diameter and length of the no-core fiber on the performance of the sensor are studied. The results show that the sensitivity incr...

This publisher’s note contains corrections to Opt. Lett. 44, 5410 (2019)OPLEDP0146-959210.1364/OL.44.005410.

We investigate the validity domain and precision of retardance autocalibration in full-Stokes imaging polarimeters based on a linear division-of-focal-plane polarization camera. We demonstrate that the level of precision of autocalibration in these systems gets worse as the degree of linear polarization of input Stokes vector approaches zero. Autoc...