4-5 輝度クリップ特性差による立体映像の劣化の評価

Investigations on the radiometric and geometric characteristics of IKONOS Geo satellite imagery and its use for orthoimage generation and 3D building reconstruction are reported. The paper first starts with an analysis of the radiometric quality of IKONOS Geo images of varying preprocessing and type, focussing on noise, edge quality and definition, and various artefacts. A noise estimation method is presented and results from various IKONOS Geo images, showing an intensity-dependent noise of 1.5-10.5 grey levels, which is high considering the effectively 8-9 bit data. Methods will be presented that reduce noise, enhance edges and contrast and optimally reduce 11-bit to 8-bit, without leading to loss of small, but still important, image details. Next, the topic of the geometric potential of IKONOS Geo images using the Rational Polynomial Coefficients (RPCs) and a possible improvement will be discussed. The geometric analysis makes use of stereo images and testfield data provided by the University of Melbourne with 28 well defined and distributed GCPs with 1-2 dm accuracy in object and image space. It will be shown that the RPCs have moderate absolute accuracy (large systematic bias, conforming to the Geo product accuracy specifications of 25 m RMS) but sub-metre relative accuracy. With the help of 4-8 accurate and well-distributed GCPs and a simple translation (bias removal), 0.4-0.5 m and 0.6-0.8 m absolute accuracies in planimetry and height can be achieved with the full set of 60 RPCs per image, or reduced RPCs omitting the higher-order terms (down to 22 coefficients). Even when using just one GCP to remove the bias, the accuracy is at worst ca. 2 m. In a related paper (Fraser et al., 2001b), it is shown that other simple sensor models (including affine projection) can produce similar or better accuracy than the RPCs with similar GCP requirements. This is shown also in this work, but with a different 3D spatial resection, using relief-corrected affine transformation and down to just 3 GCPs. Results from generation of orthoimages from three projects using own methods will be shown, including quantitative analysis, and showing how with simple and fast methods the 1-2 m accuracy of the much more expensive IKONOS Precision and Precision Plus can be achieved. With 1-2 dm accurate GCPs and depending on DTM accuracy and sensor elevation, sub-metre planimetric accuracy can be achieved. Buildings of the University of Melbourne Campus were measured manually and stereoscopically. After measuring a point cloud, 3D points were automatically structured and visualised with the system CCModeler, including texture mapping. The point accuracy was evaluated using GPS measurements of building corners and was found to be in the meter range. The completeness of the data and their limits regarding modelling roof details were evaluated: (a) qualitatively and (b) quantitatively through a comparison to a 3D model that was generated from aerial images. The results of this assessment are summarised, these highlighting both the high metric potential of IKONOS and difficulties to be anticipated in building reconstruction when the modelling should be complete and detailed.

An Internet browser-based annotation system can be used to identify and describe features in digitalized retinal images, in multicentric clinical trials, in real time. In this web-based annotation system, the user employs a mouse to draw and create annotations on a transparent layer, that encapsulates the observations and interpretations of a specific image. Multiple annotation layers may be overlaid on a single image. These layers may correspond to annotations by different users on the same image or annotations of a temporal sequence of images of a disease process, over a period of time. In addition, geometrical properties of annotated figures may be computed and measured. The annotations are stored in a central repository database on a server, which can be retrieved by multiple users in real time. This system facilitates objective evaluation of digital images and comparison of double-blind readings of digital photographs, with an identifiable audit trail. Annotation of ophthalmic images allowed clinically feasible and useful interpretation to track properties of an area of fundus pathology. This provided an objective method to monitor properties of pathologies over time, an essential component of multicentric clinical trials. The annotation system also allowed users to view stereoscopic images that are stereo pairs. This web-based annotation system is useful and valuable in monitoring patient care, in multicentric clinical trials, telemedicine, teaching and routine clinical settings.

To assess agreement between evaluations of monoscopic and stereoscopic digital images versus stereo film photographs in diabetic macular edema (DME). A 152-eye group of digital monoscopic macular images (seven-field sets and wide-angle mosaics) were compared with digital stereoscopic images (uncompressed and compressed seven-field sets) and stereo 35-mm film photos (Early Treatment Diabetic Retinopathy Study protocol) for the presence of hard exudates (HE), retinal thickening (RT), clinically significant macular edema (CSME), and RT at the center of the macular (RTCM). Agreement, according to the κ statistic, was almost perfect in identifying HE and RT between all digital formats and stereo film (HE, κ = 0.81-0.87; RT, κ = 0.87-0.92). Distribution in all digital formats was not significantly different from that in film (Bhapkar test: HE, P = 0.20-0.40; RT, P = 0.06-1.0). CSME and RTCM grading differences were either significant or trended toward significance. The readers detected CSME and RTCM in film images more often than in digital formats. In identifying DME features, agreement between evaluations of monoscopic digital formats and film was similar to that between stereo digital formats and film, and the performance of uncompressed images versus film was similar to that of compressed images versus film. Repeatability between readers was similar in evaluations of film and all digital formats. Repeatability in identifying RTCM was lower than that of other DME components in film and all digital formats. Stereoscopic digital formats are equivalent to monoscopic for DME evaluation, but digital photography is not as sensitive as film in detecting CSME and RTCM.

Imaging is a valuable tool in the assessment of glaucoma and glaucoma progression. Although glaucoma is a clinical diagnosis—there is no blood test or definitive genetic test, for example, for the disease—the diagnosis has traditionally been subjective albeit based on certain physical characteristics of the patient. Over the years, the diagnosis has gone from a hard, blind, painful eye; to palpation indicating a hard eye associated with sudden pain or slow, painless visual loss; to a specifically described progressive optic neuropathy with characteristic neural damage and visual loss, sometimes associated with elevated intraocular pressure (IOP). In the mid-19th century, Helmholtz and Von Graefe enabled clinical assessment of the optic nerve head (ONH); later, fundus photography permitted objective recording of this physical parameter.1,2 Nevertheless, despite objective photographs of the ONH, subjective interpretation on the part of the clinician was necessary for identification of glaucomatous damage or progression. Different clinicians would provide discrepant interpretations of the optic nerve, and even the same observer would frequently characterize the disc differently on separate viewings of the same photograph.3 Measurement of ocular function is and has been similarly crude and subjective. From discriminating finger movement in different quadrants to discerning white objects on a black background to map the visual field in tangent screen perimetry, the patient must tell the examiner when a light or object is seen. The same is true of kinetic and static perimetry, both manual and automated. The patient must detect the object (or light) on the retina, realize that a light or object has been seen, and then inform the examiner of this fact. The evaluation is difficult as best, often tedious, and fraught with problems in reproducibility of findings. For these reasons, clinicians, scientists, and engineers have sought to objectively measure optic nerve structure and function both quantitatively and reproducibly, preferably without the requirement for patient input. In the assessment of optic nerve function, this has meant multifocal electroretinography,4 pattern electroretinography,5,6 multifocal visual evoked potential, and pattern visual evoked potential,7,8 among other tests.9 Unfortunately, none of these objective functional tests has been validated to the level of perimetry, which remains the clinical gold standard, despite its shortcomings. Automated objective, quantitative characterization of the optic nerve has been more successful. As mentioned above, the first step in this direction was optic nerve photography, particularly stereoscopic disc photography. This method enables objective recording, but still requires subjective interpretation. More sophisticated techniques, invented and/or developed in the past quarter century, include confocal scanning laser ophthalmoscopy (CSLO), scanning laser polarimetry (SLP), and optical coherence tomography (OCT). These systems capture, in different ways, objective, accurate, and precise quantitative information about optic nerve and retinal structure that does not require subjective input for measurement. Although there is objective image and segmentation algorithm quality evaluation, subjective quality assessment is still necessary to ensure that the image acquired is adequate for evaluation and that the analysis algorithm has functioned properly.

The NGA has initiated a program to evaluate high resolution commercial sensors developed by Space Imaging, DigitalGlobe, Orbimage and others. Recent evaluations have involved QuickBird panchromatic products including the Basic 1B, Ortho-Ready Standard 2A, orthorectified, and Basic Stereo Pair products. This paper presents the results of an additional geo-positional accuracy evaluation of multispectral QuickBird Ortho-Ready Standard 2A images. These products were compared to a globally distributed set of Ground Control Points (GCPs), and the calculated geo-positional accuracy was compared to the published QuickBird specifications and to the panchromatic Ortho-Ready Standard 2A product. The results of the panchromatic and multispectral bands are compared, and the band-to-band registration of the multispectral arrays is evaluated.

Recently, various studies of human factors have been conducted to reveal stereoscopic characteristics of the human visual system and visual fatigue. In this paper, we investigate the effect of vergence-accommodation conflict and parallax difference on binocular fusion for random dot stereograms. The aim of this paper is to provide a study on visual fatigue induced by the conflict. We measured the time required for fusion under various conditions that include foreground parallax, background parallax, focal distance, aperture size, and corrugation frequency. The results show that foreground parallax and parallax difference between foreground parallax and background parallax have significant influences on fusion time. In addition, we verify the relationship between fusion time and visual fatigue by conducting a subjective evaluation of stereoscopic images.

This paper presents a new metric for the quality evaluation of stereoscopic images. The proposed metric is inspired from the simple and complex cells response, in which the matching of the left and right retinal images is performed, in the visual cortex. In order to estimate the binocular energy, we used the bandelet transform which is computed on complex wavelet transform. By using the complex wavelet transform, we were able to model the behavior of the simple and complex cells. The proposed model allows the estimation of the degradation of the binocular energy according to the impairments of the right and the left images. Subjective tests have been performed to validate the results obtained by our metric. The results shows a high correlation between the predicted score and the human judgement.

Because sentinel lymph nodes (SLNs) of esophageal cancer can be widely located between the neck and the upper abdomen, lymphoscintigraphy plays an important role in their detection, but some modifications are required to clearly visualize their locations. Recently, we applied the stereoscopic imaging method by adding the 10-degree oblique view to the conventional lymphoscintigraphy for SLNs, so that we could better determine SLN locations on the basis of depth information. In this report, we describe a case in which the oblique view of the lymphoscintigram contributed to improving the visualization of a mediastinal SLN of esophageal cancer. Evaluation of the patient's chest CT image validated the notion that gamma rays from SLN are less absorbed by the surrounding soft tissues and the sternum in acquisition from the oblique view than from the true anterior view. The additional oblique view of the lymphoscintigram is useful for evaluation of the SLNs of esophageal cancer.