Image Quality Of Camera Research Articles

Image Tuning

Nazneen A looks at the fundamentals of camera image quality tuning

Binder-endowed thermal stability of diimmonium dye-based near-infrared (NIR) absorbing films

The near-infrared (NIR) absorbing film is a film to block unnecessary near-infrared light. The NIR absorbing film is one of the main components to improve the image quality of digital cameras. In this work, we studied the stability of NIR absorbing films made of NIR absorbing dyes by varying the kind of transparent polymeric binders, which have different thermal stability. We analyzed the optical properties, thermal stability, and microscopic morphology of the NIR absorbing films and investigated the change of these properties by the heat. The NIR absorbing films using dithiolene dye showed good thermal stability. The diimmonium dyes showed discoloration and decomposition in the films using binders with low thermal stability because of the change of molecular arising from the dissociation of counter anions arrangement. Consequently, we could improve the stability of diimmonium dye-based NIR absorbing films by applying thermally stable binders to the NIR absorbing films.

Ambient temperature effect on the imaging quality of an aspherical airborne camera: theoretical and experimental analysis.

The ambient temperature is one of the important factors that affects the imaging quality of aspherical airborne camera. In order to evaluate the imaging quality of an airborne camera under the effect of ambient temperature and predict the influence of the ambient temperature on the modulation transfer function (MTF) of the airborne camera, on the basis of the imaging principle and the material properties of lenses of the airborne camera, this study integrates theoretical analysis, simulation analysis, and experimental tests to study the influence of ambient temperature on the imaging performance of airborne cameras. The imaging performance of an airborne camera is characterized by using the MTF. First, a mathematical model is presented to analyze the effect of ambient temperature on the MTF of the airborne camera. Then the simulation analysis and experiment tests are, respectively, proposed. The results of the mathematical model are compared, respectively, with the results of the simulation analysis and experimental test, and the comparison shows that the variation trends of the mathematical model results are in line with the simulation results and the experimental results, respectively. Therefore, the mathematical model presented in this study is effective for analyzing the influence of ambient temperature variation on the MTF of airborne cameras.

Handheld fundus camera performance, image quality and outcomes of diabetic retinopathy grading in a pilot screening study

To compare the performance and image quality of the handheld fundus camera to standard table-top fundus cameras in diabetic retinopathy (DR) screening. The reliability and diagnostic accuracy of DR grading performed by an ophthalmologist and a photographer reader were evaluated. 157 patients with diabetes, attending screening or follow-up of DR, were evaluated by fundus photographs taken in mydriasis by Optomed Aurora and Canon or Zeiss Visucam fundus cameras. The image quality and the severity of DR were evaluated independently by an ophthalmologist and experienced photographer. The sensitivity, specificity and reliability of the assessments were determined. 1884 fundus images from 314 eyes were analysed. In 53% of all eyes, DR was not present. 10% had mild non-proliferative diabetic retinopathy (NPDR), 16% moderate NPDR, 6% severe NPDR and 16% proliferative diabetic retinopathy (PDR). The DR grading outcomes by Aurora highly equalled to those of Canon or Zeiss (κ = 0.93, 95% CI 0.91 to 0.94), and there was almost perfect agreement in grading between the ophthalmologist and photographer (κ = 0.96, 95% CI 0.95 to 0.97). The image quality of Aurora was sufficient for reliable assessment according to both graders in 84-88% of the cases. The Optomed Aurora fundus camera seems appropriate for DR screening. The sufficient image quality and high diagnostic accuracy for DR grading are supportive for a less expensive and easily transportable screening system for DR. Immediate image grading carried out by a photographer would further improve and speed up the screening process in all settings.

Modeling and experimental analysis on the effect of carrier aircraft vibration on the imaging quality of an aspherical aerial camera

As one of the important factors, the vibration of the carrier aircraft has its impact on the imaging quality of an aspherical aerial camera. To analyze the imaging quality of the aspherical aerial camera under the vibration of the carrier aircraft, a mathematical model is established in this paper based on the theory of the transfer function and the carrier aircraft vibration principle to describe the influence of the carrier aircraft vibration on the modulation transfer function (MTF) of the aspherical optical system. The imaging quality of the aerial camera is based on MTF, and the effect of carrier aircraft vibration on the MTF of the aspherical aerial camera is investigated by simulation analysis and experiment analysis respectively. As per the results of both analyses, the variation trend of the results is in good agreement with the outcome of the mathematical model, and the mathematical model is validated. Therefore, the mathematical model is available to investigate the effect of carrier aircraft vibration on the MTF of the aspherical aerial camera, and provide theoretical guidance for aerial camera optimization design.

14.4: Diffraction Simulation of Camera Under Display

This paper provided a method to simulate diffraction of Camera Under Display (CUD). To balance the display performance of CUD area and front camera image quality, special panel lamination was designed to meet the requirement. Due to the micro level size of pixel texture, strong optical diffraction effect was caused and image on CMOS was blurred. This paper built a way to simulate the Modulation Transfer Function of different pixel patterns display and promote promising research direction for camera under display.

Understanding the importance of Artistic Aspect of Camera Image Quality Tuning and Quantifying the Artistic Attributes by using Scientific Principles

The camera tuning process contains multiple stages under the image signal processing (ISP) pipeline through which the RAW image gets processed and displayed. The objective image quality is well defined and important when tuning the color imaging pipeline in the Camera. The ISP pipeline is tuned by optimizing objective criteria, resulting image and video may not be aesthetically appealing to end-users and may not be sufficient to provide the best visual experience. There are certain key artistic factors affecting the overall user experience in the process of ISP pipeline tuning. However, currently there is no industry standard for artistic image quality (IQ) quantification and is mostly based on expert based subjective evaluation. In this paper, we emphasize the importance of artistic attributes and to quantify them with two studies. First study focusses on importance of artistic attribute by two alternate forced choice pairwise comparison user study on artistic vs objective tuning. Based on this study, artistic tuning is statistically significantly better than objective tuning with 95% confidence interval based on fisher least significant difference test. Second study develop a method to quantify holistic IQ. The novel mathematical equation has been formulated to calculate the weight of different IQ attributes which are impacting on overall IQ as a first step. Rank based user study was performed on expert and nonexpert users to find their preference on different attributes with the use of novel mathematical equation. In this equation, user preferences were converted into weights of artistic attributes in the holistic IQ. The study shows that color saturation and memory color attributes have higher impact for both expert and non-expert user with weightage of 14.04% and 13.62% in holistic IQ, respectively. This study validates the importance of the artistic approach and our first step to quantify these artistic attributes in a scientific way. It also exhibits the need of a novel image quality assessment criteria to tune and validate the final visual experience of the consumer camera. Especially, in the era of Artificial Intelligence (AI), quantifying artistic attributes is far more important than ever.

Image quality and diagnostic accuracy of a handheld nonmydriatic fundus camera: Feasibility of a telemedical approach in screening retinal diseases.

Background:A suitable fundus camera for telemedicine screening can expand the scale of eye care service. The purpose of this study was to compare a handheld nonmydriatic digital fundus camera and a conventional mydriatic fundus camera according to the image quality of their photographs and usability of those photographs to accurately diagnose various retinal diseases.Methods:A handheld nonmydriatic fundus camera and conventional fundus camera were used to take fundus photographs of outpatients at an ophthalmic clinic before and after pupillary dilation. Image quality and diagnostic agreement of the photos were graded by two masked and experienced retinal specialists.Results:A total of 867 photographs of 393 eyes of 200 patients were collected. Approximately 80% of photos taken under nonmydriasis status using the handheld nonmydriatic fundus camera had good (55.7%) or excellent (22.7%) image quality. The overall agreement of diagnoses between the doctors was more than 90%. When the handheld nonmydriatic fundus camera was used after mydriasis, the proportion of images with good (45%) or excellent (49.7%) quality reached 94.7% and diagnostic agreement was 93.4%. Lens opacity was associated with the quality of images obtained using the handheld camera (p = 0.041), and diagnosis disagreement for handheld camera images was associated with preexisting diabetes diagnosis (p = 0.009). Approximately 40% of patients expressed preference for use of the handheld nonmydriatic camera.Conclusion:This study demonstrated the effectiveness of the handheld nonmydriatic fundus camera in clinical practice and its feasibility for telemedicine screening of retinal diseases.

A Novel Method of Image Denoising: New Variant of Block Matching and 3D

The demand of accurate and visually fair images is increasing with the passage of time and bang of the number of digital images especially in the domain of medical and healthcare systems. The visual image quality of modern cameras affected due to edges, textures and sharp structures noise. Though research community has introduced several techniques such as BM3D (Block Matching and 3D) for image denoising. However, edges and texture preservation capabilities remain issues due to hard thresholds values and captured image diversity. In order to address these issues, we propose a new variant of BM3D namely BM3DMA (Block Matching and 3D with Mahalanobis and Adaptive filter) which is employed through the use of Mahalanobis distance measure (for diversity coverage) and adaptive filter (for soft thresholds). We used two widely known datasets consist of set of standard and medical images. We observe 5% to 10% enhancement in the performance of BM3DMA as compared to BM3D in terms of improving the PSNR (Peak Signal to Noise Ratio) value. The promising experimental result indicates the effectiveness of BM3DMA in terms preserving the edge and texture image noise.

Spectral ghost imaging camera with super-Rayleigh modulator

A spectral camera based on ghost imaging via sparsity constraints (GISC) acquires a spectral data-cube (x,y,λ) through a single exposure. The noise immunity of the system is one of the important factors affecting the quality of the reconstructed images, especially at low sampling rates. Tailoring the intensity to generate super-Rayleigh speckle patterns which have superior noise immunity offer an effective route to promote the imaging quality of GISC spectral camera. According to the structure of GISC spectral camera, we propose a universal method for generating super-Rayleigh speckle patterns based on the principle of reversibility of light. Simulation and experimental results demonstrate that, within a wide imaging spectral bandwidth, GISC spectral camera with super-Rayleigh modulator not only has superior noise immunity, but also has higher imaging quality at low sampling rates. This work will promote the application of GISC spectral camera by improving the quality of imaging results, especially in weak-light illumination.

SweepCam - Depth-Aware Lensless Imaging Using Programmable Masks.

Lensless cameras, while extremely useful for imaging in constrained scenarios, struggle with resolving scenes with large depth variations. To resolve this, we propose imaging with a set of mask patterns displayed on a programmable mask, and introduce a computational focusing operator that helps to resolve the depth of scene points. As a result, the proposed imager can resolve dense scenes with large depth variations, allowing for more practical applications of lensless cameras. We also present a fast reconstruction algorithm for scene at multiple depths that reduces reconstruction time by two orders of magnitude. Finally, we build a prototype to show the proposed method improves both image quality and depth resolution of lensless cameras.

Development of an Aspherical Aerial Camera Optical System

The aerial camera lens largely determines the performance of the camera. It is necessary to further optimize the lens to satisfy the requirements of small-scale and lightweight aircraft camera systems. The optical system design is the primary prerequisite. Therefore, considering the image quality and working environment of the aerial camera, an aspherical aerial camera optical system is developed by studying the aerial camera optical system. The work presented in this paper decreases the overall weight of the aerial camera by using an aspherical lens instead of a spherical lens, which reduces the number of lenses and improves the image quality. The athermalization of the optical system ensures that the camera has good temperature adaptability in the temperature range of −60 °C∼60 °C. The definition of the aspherical surface shape is detected by a ZYGO digital interferometer. The root mean square (RMS) of the system is 0.0403λ(λ = 632 nm), and the peak value (PV) is 0.354λ, which ensures the image quality of the camera. The research results verify that the aspherical lens can be well applied to the camera optical system, improving the image quality of the system and reducing the weight of the camera.

Endoscopic Pan/Tilt Camera for Thorax Interventions – Design and first results

Abstract Minimally invasive surgery in some cases suffers from a limited view because certain areas are obscured by others. In this paper, a system is described, which can be used in minimally invasive procedures as an addition to a standard endoscope to improve the range of view. Through FEM simulation a magnetic circuit was designed to position the camera head. Subsequently, a camera positioning system was set up that includes an extracorporeal and an intracorporeal unit. The first controls the intracorporeal system. The latter has a camera inclination angle of up to 65° and an additional vertically downward viewing angle when aligned in parallel (inclination angle 0°). The panning angle is 360°. The camera system was evaluated in lab and cadaver trials. It has been found that the size of the intracorporeal system (16 × 10 × 150 mm) represents a major problem. Future work will focus of the reduction of the system’s size, the improvement of the camera image quality, and design changes considering mechanical stability.

Stabilization of Removal Rate in Small Tool Polishing of Glass Lenses

The demand for improving the image quality of cameras has increased significantly, especially in industrial fields such as broadcasting, on-vehicle, security, factory automation, and medicine. The surface of glass lenses as a key component of cameras is formed and finished by polishing using small tools. The existing polishing technologies, however, exhibit serious problems including an unstable material removal rate over time. In our previous work, the mechanism of time variation in material removal rate was clarified. Based on the findings, a vibration-assisted polishing method using polishing pads containing titanium dioxide particles was developed for improving the stability of the material removal rate with the accumulated polishing time. Our experiments revealed that the proposed polishing method suppressed the time variation significantly in the material removal rate. The developed polishing pads, however, possessed a short life because of their poor wear resistance; as such, they could not be applied to the mass-production process of lenses. In this study, we applied the vibration-assisted polishing method to the polishing process using commercial polishing pads that exhibit sufficient wear resistance for practical use. To investigate the effect of vibration on the stability of the material removal rate, polishing experiments and the observation of slurry flow on the surface of the polishing pads during the vibration-assisted polishing process were conducted. Based on the findings, a new polishing method utilizing a large-amplitude high-frequency vibration applied to the polishing pressure was developed. In addition, a new polishing method utilizing the overhang of a polishing pad, where the polishing pad was moved to hang over the edge of the workpiece for incorporating periodic dressing processes of the polishing pad surface during the polishing process, was also developed. Our polishing experiments revealed that both the proposed polishing methods improved the stability of the material removal rate significantly over the course of the polishing process.

Development of a prototype for referees to monitor whip use in horse racing

There is no standard surveillance system for modern flat horse racing in Sweden, so the surveillance camera placement and image quality varies between tracks. Reported whip misuse and unauthorised whipping often occur outside of the camera’s view and are therefore unrecorded. Thorough investigation of the current monitoring system used in Sweden revealed concerns about whether the stewards have enough time to estimate the number of whip strikes per horse, even when camera quality is sufficient, and has led to the development of an enhanced whip system. The system prototype offers a technical solution for the supervision of whip use in modern horse racing, and it would be useful in countries where there are regulations limiting the number of strikes. Current specifications allow the system to record the attributes and number of strikes and to relay the data contemporaneously to the stewards. The system does not interfere with the operation of the camera monitoring system. Since the number of strikes is reported with total accuracy, stewards are afforded more time to focus on matters of interference and actions that are important to the final result list. The prototype is a whip with a custom-made force sensor placed on both sides of the cushion pad. The sensors measure an area 24mm wide by 275mm long and cover the entire padded part of the approved race whip. The sensor is constructed of polyester that is 0.203mm thick. The force sensor is connected to a microcontroller mounted in the handle of the whip. The microcontroller processes the sensor data and sends the information via radio waves up to 1.7km in outdoor conditions to a second microcontroller located in the steward’s office. The whip strike sensor prototype is able to distinguish between a wave of the arm that leads to no impact and a strike. The software allows the force of each strike impact to be recorded. The intention is to embed the whip strike sensor within the body of whips used in a range of equestrian disciplines in which whip use is permitted. The possibility to register the properties of whip strikes will help to safeguard the welfare of horses used in these disciplines and provide information to the equestrian community that could change the way whips are used in training and racing. Lay person message: The whipping of horses in racing leads to concerns about animal welfare globally. A whip strike sensor prototype has been developed that will facilitate detailed exploration of the effect whips have on horses and allow stewards to accurately assess the number of strikes made and forces used. It is intended to integrate strike sensors into whips used in disciplines where whipping is allowed; this will help to safeguard the welfare of horses used in these disciplines.

Stabilization of removal rate in small tool polishing of glass lenses

Demand for improving image quality of cameras has largely grown, especially in industrial fields such as broadcasting, on-vehicle, security, factory automation and medicine. Surface of glass lenses as a key component of cameras is formed and finished by polishing using small tools. The existing polishing technologies, however, have serious problems including an unstable material removal rate over time. In this study, we investigated mechanism of the variation in the material removal rate, specifically the low material removal rate at the beginning of polishing process. Based on the findings, we clarified that surface of polishing pad with high wettability is effective in stabilizing the removal rate.

Analysis of the Spatial Errors of the Scanning Mirrors in Complex Optical and Mechanical Systems

In recent years, in order to improve the imaging performance of complex optical and mechanical components in complex working environments, scanning mirrors are used as main optical components that precisely control the direction of beam propagation. They can not only expand the range of photography, but also suppress the shift error caused by attitude changes. So scanning mirrors are widely used in the fields of aerial cameras, satellite remote sensing and military investigation. In the process of machining and assembling the scanning mirror platform, pointing error will be produced which directly affects the imaging quality of the camera which acquires the ground image by the reflection of the scanning mirrors. Taking the two-axis scanning mirror as an example, the global error model is established based on the homogeneous coordinate transformation theory. The simulation analysis is carried out to compare the influence of each error to the pointing error of the scanning mirror. In the process of designing and processing scanning mirror, the error items which have great influence to the pointing error of the scanning mirror should be strictly controlled or taken some corresponding measures. It is very important to improve the pointing accuracy of scanning mirror to enhance the imaging quality of the aerial camera.

Technical Note: Automated quantitative analysis of planar scintigraphic resolution with the ACR SPECT phantom.

Evaluating gamma camera image quality is a routine task required for annual physics surveys and laboratory accreditation. A common method is visual assessment of a planar view of the American College of Radiology (ACR) phantom, for which a satisfactory result is to resolve 7.9 mm diameter cold rods with high contrast. The objective was to investigate an automated quantitative measure of planar image quality for more precise evaluation of gamma camera performance. Planar images were automatically co-registered to a template of the phantom's cold rod pattern. Contrast-to-noise ratio (CNR) was measured for each cold rods sector by automatic placement of regions of interests on each rod and on each gap between rods. A quadratic fit to CNR vs. rod diameter yielded the Minimum Detectable Rod Diameter (MDRD) corresponding to a CNR threshold of 4. This methodology was applied to planar images acquired on a variety of gamma cameras according to ACR guidelines and also to planar images generated by Monte Carlo simulation. The automated MDRD analysis had reproducibility of 0.1 mm in repeat phantom scans with random repositioning between scans. The MDRD was 5.8 mm for modern fully digital gamma cameras and 6.2 mm for an older analog gamma camera, whereas visual assessment was identical for all cameras. Simulated Monte Carlo images had MDRD of 5.6 mm using the following parameters: 3.5 mm FWHM intrinsic detector resolution, LEHR collimators, 9.0% FWHM energy resolution, and 15% energy window. Further simulations revealed that collimator design and detector resolution have a substantial impact on MDRD but that energy window width and energy resolution have a minor or negligible impact. The small difference between the Monte Carlo simulations and the modern fully digital gamma cameras was attributed to nonlinearities associated with event positioning and depth-of-interaction effects, which were not modeled in the simulations. Automated MDRD analysis of planar phantom images is a robust technique that provides more precise and meaningful evaluation of camera performance than visual assessment. MDRD is a suitable measure for quality assurance and for annual physics surveys of gamma cameras.

The use of low cost compact cameras with focus stacking functionality in entomological digitization projects.

Digitization of specimen collections has become a key priority of many natural history museums. The camera systems built for this purpose are expensive, providing a barrier in institutes with limited funding, and therefore hampering progress. An assessment is made on whether a low cost compact camera with image stacking functionality can help expedite the digitization process in large museums or provide smaller institutes and amateur entomologists with the means to digitize their collections. Images of a professional setup were compared with the Olympus Stylus TG-4 Tough, a low-cost compact camera with internal focus stacking functions. Parameters considered include image quality, digitization speed, price, and ease-of-use. The compact camera’s image quality, although inferior to the professional setup, is exceptional considering its fourfold lower price point. Producing the image slices in the compact camera is a matter of seconds and when optimal image quality is less of a priority, the internal stacking function omits the need for dedicated stacking software altogether, further decreasing the cost and speeding up the process. In general, it is found that, aware of its limitations, this compact camera is capable of digitizing entomological collections with sufficient quality. As technology advances, more institutes and amateur entomologists will be able to easily and affordably catalogue their specimens.

An efficient and effective blind camera image quality metric via modeling quaternion wavelet coefficients

As an extension of Discrete and Complex Wavelet Transform, Quaternion Wavelet Transform (QWT) has attracted extensive attention in the past few years, because it can provide better analytic representation for 2D images. The QWT of an image consists of four parts, i.e., one magnitude part and three phase parts. The magnitude is nearly shift-invariant, which characterizes features at any spatial location, and the three phases represent the structure of these features. This indicates that QWT is more powerful in representing image structures, and thus is suitable for image quality evaluation. In this paper, an efficient and effective Camera Image Quality Metric (CIQM) is proposed based on QWT, which is utilized to describe the intrinsic structures of an image. For an image, it is first decomposed by QWT with three scales. Then, for each scale, the magnitude and entropy of the subband coefficients, and natural scene statistics of the third phase are calculated. The magnitude is utilized to describe the generalized spectral behavior, and the entropy is used to encode the generalized information of distortions. Since the third phase of QWT is considered to be texture feature, the natural scene statistics of the third phase of QWT is used to measure structure degradations in the proposed method. All these features reflect the self-similarity and independency of image content, which can effectively reflect image distortions. Finally, random forest is utilized to build the quality model. Experiments conducted on three camera image databases and two multiply distorted image databases have proved that CIQM outperforms the relevant state-of-the-art models for both authentically distorted images and multiply distorted images.