Visual Field Light Research Articles

Relationship between photon flow and the perception of light field under simple lighting environments

In our previous study we proposed a new method, “photon flow”, to visualise the light propagation in space. Theoretically the photon flow depicts the physically correct light distribution, however, it was yet unclear whether people could correctly read the physical light field in actual spaces by observing the photon flow. Therefore, in this study we verified the relationship between the light field perceived in the real space (visual light field) and the one estimated by observing the photon flow. The experiment was conducted using the method of a white sphere, on which shade represents the light field at that point. We clarified the characteristics of the perceived light field in a simple rectangular space with one spotlight or two. The perceived light field when observing the photon flow was basically similar to the physical light field when there is one spotlight in the space. However, under the more complex scene, the subjects sometimes could not predict the physical light field well when seeing the photon flow. Basically, the perceived light field when observing the photon flow was close to the visual light field than expected. In future work we would like to clarify under which conditions people can estimate the correct physical light field by observing the photon flow and compare the difference between experienced and naïve observers.

Retina 3D Perception Reconstruction Algorithm Based on Visual Light Field Image

As an important part of the eye, the retina is very important to the human body. At present, the diagnosis and treatment of patients with retinal damage or detached blindness in clinical medicine rely on medical imaging technology and ophthalmological equipment. However, the three-dimensional image of the retina constructed by the existing imaging equipment has major defects, which is not conducive to the medical staff's treatment of the lesion, careful observation and precise judgment. Therefore, this article proposes a three-dimensional perceptual reconstruction of the retina based on visual light field images. Computer vision lighting technology is used to create four-dimensional spaces for retinal images, and to enable this, four-dimensional light data is connected to the three-dimensional retinal reconstruction. The resulting retinal image not only contains three-dimensional information, but also has four-dimensional optical shapes, providing physicians with well-thought-out and accurate images for diagnosing and treating diseases. This article first collected a large amount of data through the literature survey method, introduced in detail the related theories and algorithm processes of computer vision, light field imaging technology and 3D reconstruction technology, laying a sufficient theoretical foundation for the 3D perception reconstruction of the retina. Combining the light field imaging technology with 3D reconstruction technology, a 3D reconstruction based on visual light field images is proposed, taking 10 retinal images from the ophthalmology department of the Provincial Hospital as an example, the 3D perception of the retina based on visual light field images is carried out. Finally, a comprehensive comparison and analysis of several algorithms in the process of retina 3D perception reconstruction found that the logarithmic transformation method is better than the histogram equalization method in the enhanced image contrast algorithm; compared with the traditional median filter denoising algorithm, the adaptive weighted median filter denoising method proposed in this article has better effect; in the retinal image registration algorithm, the Powell algorithm handles the details of the image more in place, preserves the edge of the image intact, and the image quality is better; and the inter-layer interpolation algorithm. In this article, the image obtained by the adaptive optimization interpolation algorithm proposed is better than the image obtained by the nearest neighbor interpolation and linear interpolation algorithm.

The global structure of the visual light field and its relation to the physical light field.

Human observers have been demonstrated to be sensitive to the local (physical) light field, or more precisely, to the primary direction, intensity, and diffuseness of the light at a point in a space. In the present study we focused on the question of whether it is possible to reconstruct the global visual light field, based on observers' inferences of the local light properties. Observers adjusted the illumination on a probe in order to visually fit it in three diversely lit scenes. For each scene they made 36 settings on a regular grid. The global structure of the first order properties of the light field could then indeed be reconstructed by interpolation of light vectors coefficients representing the local settings. We demonstrate that the resulting visual light fields (individual and averaged) can be visualized and we show how they can be compared to physical measurements in the same scenes. Our findings suggest that human observers have a robust impression of the light field that is simplified with respect to the physical light field. In particular, the subtle spatial variations of the physical light fields are largely neglected and the visual light fields were more similar to simple diverging fields than to the actual physical light fields.

The visual light field in real scenes.

Human observers' ability to infer the light field in empty space is known as the “visual light field.” While most relevant studies were performed using images on computer screens, we investigate the visual light field in a real scene by using a novel experimental setup. A “probe” and a scene were mixed optically using a semitransparent mirror. Twenty participants were asked to judge whether the probe fitted the scene with regard to the illumination intensity, direction, and diffuseness. Both smooth and rough probes were used to test whether observers use the additional cues for the illumination direction and diffuseness provided by the 3D texture over the rough probe. The results confirmed that observers are sensitive to the intensity, direction, and diffuseness of the illumination also in real scenes. For some lighting combinations on scene and probe, the awareness of a mismatch between the probe and scene was found to depend on which lighting condition was on the scene and which on the probe, which we called the “swap effect.” For these cases, the observers judged the fit to be better if the average luminance of the visible parts of the probe was closer to the average luminance of the visible parts of the scene objects. The use of a rough instead of smooth probe was found to significantly improve observers' abilities to detect mismatches in lighting diffuseness and directions.

The Visual Light Field

Human observers are sensitive to the '(physical) light field' in the sense that they have expectations of how a given object would appear if it were introduced in the scene in front of them at some arbitrary location. Thus the 'visual light field' is defined even in the 'empty space' between objects. In that sense the light field is akin to visual space considered as a 'container'. The visual light field at any given point can be measured in psychophysical experiments through the introduction of a suitable 'gauge object' at that position and letting the observer adjust the appearance of that gauge object (eg through suitable computer rendering) so as to produce a 'visual fit' into the scene. The parameters of the rendering will then be considered as the measurement result. We introduced white spheres as gauge objects at various locations in stereoscopically presented photographic scenes. We measured the direction ('direction of the light'), diffuseness ('quality of the light' as used by photographers and interior decorators), and intensity of the light field. We used three very different scenes, with very different physical light fields. The images were geometrically and photometrically calibrated, so we were in a position to correlate the observations with the physical 'ground truth'. We report that human observers are quite sensitive to various parameters of the physical light field and generally arrive at close to veridical settings, although a number of comparatively minor systematic deviations from veridicality can be noted. We conclude that the visual light field is an entity whose existence is at least as well defined as that of visual space, despite the fact that the visual light field hardly appears as prominently in vision science as it does in the visual arts.

Colour vision and light sensitivity in tunnel workers previously exposed to acrylamide and N-methylolacrylamide containing grouting agents

Objectives The aim of the study was to examine possible persisting visual system effects in tunnel workers previously exposed to acrylamide and N-methylolacrylamide during grouting work. Material and methods Visual field light sensitivity threshold and colour vision has been examined among 44 tunnel workers 2–10 years after exposure to acrylamide and N-methylolacrylamide containing grouting agents. Forty-four tunnel workers not involved in grouting operations served as control group. Information on exposure and background variables was obtained for all participants from a questionnaire. Visual light sensitivity threshold was measured using Humphrey Visual Field Static Perimeter 740, program 30-2 Fastpack, with red stimuli on white background, and colour vision, using Lanthony D-15 Desaturated Color test. Based on D-15d test results, colour confusion index (CCI), and a severity index (C-index) was calculated. Results The exposed group had a significantly higher threshold for detecting single stimuli in all parts of the inner 30° of the visual field compared to the control group. The foveal threshold group difference was 1.4 dB ( p = 0.002) (mean value, both eyes). On the Lanthony 15 Hue Desaturated test, the exposed subjects made more errors in sorting blue colours, and a statistically significant increase in C-index was observed. Surrogate measures for duration and intensity of exposure gave no further improvement of the model. Conclusions The results indicate slightly reduced light sensitivity and reduced colour discrimination among the exposed subjects compared to the controls. The findings may be due to previous exposure to acrylamide containing grouts among the tunnel workers.

Differential Effects of Aging on the Functions of the Corpus Callosum

Several structural imaging studies have revealed atrophy in regions of the corpus callosum due to normal aging. We examined the performance of young and senior adults on 2 behavioral measures of interhemispheric interactions to test for possible functional consequences of callosal decline. In a simple reaction time task, the efficiency of sensorimotor transfer was assessed by comparing response times from conditions that required interhemispheric transfer (e.g., the left hand responding to a right visual field light) to those from conditions that did not require transfer (e.g., the left hand responding to a left visual field light). Older adults were selectively slower when interhemispheric transfer was required. In the second task, participants matched letters presented within the same visual field or in opposite visual fields. This task is thought to index attentional functions of the corpus callosum, in particular, callosal contributions to resource allocation (Banich, 1998). For more difficult tasks, older participants showed a performance advantage on bilateral conditions requiring transfer compared to unilateral conditions that did not require transfer. This advantage equaled or exceeded that observed in younger adults. Together these results suggest that age does not have uniform effects on callosal function. Whereas sensorimotor functions show age-related decline, attentional functions of the corpus callosum may be relatively preserved and assume a more prominent role in the aging brain.