Changes In Illumination Level Research Articles

Perubahan Tahap Pencahayaan dalam Bilik Darjah di Sebuah Sekolah Pendidikan Khas Cacat Penglihatan dan Perbandingan Tahap Pencahayaan di bawah Keadaan Pencahayaan yang Berbeza

Illumination is one of the important physical aspects that influences comfortability during learning session particularly among visually impaired students. The purpose of this study was to determine changes in illumination level in classrooms during learning session at Sekolah Menengah Pendidikan Khas (SMPK), Setapak. The second objective was to compare the illumination level in the classrooms under three different lighting conditions: daylight only, with additional artificial light and with removal of obstructions to daylight. Illumination levels in 17 classrooms was measured at one hour interval, between 8 am to 1 pm for the first stage and 19 classrooms under three different lighting conditions from 11 am to 12 noon for the second stage, using ILM1335 (ISO-TECH, Taiwan) digital luxmeter. Illumination level increased significantly from 8 am to 11 am (One-Way Repeated Measures ANOVA: F(2.14, 34.26)=76.49, p<0 .001) and was maximum at 1 pm. The illumination level was highest for the condition of daylight with additional artificial light (One-Way Repeated Measures ANOVA: F(2,34)=110.51, p<0.001) compared to other conditions. Illumination levels for daylight without obstruction was significantly higher than daylight only (pairwise comparison: p=0.001). Classroom illumination level was lowest in the early morning. However, classroom illumination can be increased either by removing the obstructions to daylight or with additional artificial lighting.

A gestalt account of lightness illusions.

Illusions of lightness offer valuable clues to how lightness values are computed by the visual system. The traditional domain of lightness illusions must be expanded to include failures of constancy, as there is no distinction between these categories. Just as lightness is (relatively) constant in the face of changes in illumination level, so it is equally constant in the face of changes in background reflectance. Simultaneous lightness contrast, the most familiar lightness illusion, is fairly weak, and represents a failure of background-independent lightness constancy. It is argued that a combination of the highest-luminance rule of anchoring plus the Kardos idea of codetermination can account for most lightness illusions. Kardos suggested that the lightness value of a target surface is partly determined relative to the field of illumination (or framework) in which it is embedded, and partly relative to the neighboring field of illumination. Although Kardos did not apply his principle of codetermination to failures of background-independent constancy such as the simultaneous contrast illusion, this can be done rather easily by defining a framework as a perceptual group instead of identifying it strictly with an objective field of illumination.

Stereovision Safety System for Identifying Workers’ Presence: Results of Tests

This article presents the results of extensive tests of a stereovision safety system performed using real and artificial images. A vision based protective device (VBPD) analyses images from 2 cameras to calculate the position of a worker and moving parts of a machine (e.g., an industrial robot’s arm). Experiments show that the stereovision safety system works properly in real time even when subjected to rapid changes in illumination level. Experiments performed with a functional model of an industrial robot indicate that this safety system can be used to detect dangerous situations at workstations equipped with a robot, in human–robot co-operation. Computer-generated artificial images of a workplace simplify and accelerate testing procedures, and make it possible to compare the effectiveness of VBPDs and other protective devices at no additional cost.

Eyeing the Camera

Imaging systems are compared to the human eye in terms of acquisition, spectral sensitivity, transmission, and display. Although the performance of imaging systems is generally of a high standard, there is still room for improvement. At the acquisition stage, the use of flash, or infra-red lighting, results in images with some unnatural features, and there is a general absence of systems that give monochrome images at very low light levels, as are provided by the rod system in the eye. The overlapping nature of the spectral sensitivities of the cones results in unwanted cone stimulations which reduce reproduction gamuts; in printing, extra colorants, such as orange, green, and violet, can be used to extend the gamut and reduce metamerism. Commercially available imaging systems incorporate spectral sensitivities that do not usually exactly match a set of color matching functions, which is a requirement for special applications where high colour accuracy is important. The transmission of image signals in broadcast television makes use of the important luminance/chrominance principle, but full benefit is not achieved because of gamma correction, and only one system makes use of the reduced resolution of the yellowness-blueness channel of the eye. Successful bit reduction in digital images is achieved by taking advantage of the reduced contrast sensitivity of the eye at high spatial frequencies and other effects, but a reduction in the consequent artefacts is desirable. In the visual system, the display is in the cortex, which has an enormous ability to interpret the retinal signals so as to recognise objects, including very efficient compensation for changes in illumination level and color; some improvements in the similar compensation provided in imaging systems are desirable, together with increases in the dynamic ranges available, especially in display devices. Automatic image-enhancement adjustments can be included when making images, but there is room for more sophisticated techniques that avoid impairing some types of scene. A low-cost image-display device for the mass market that is more convenient than the cathode-ray tube remains an important challenge.

人感センサによってコントロールされた明るさ変動と主観的評価

人感センサによってコントロールされた明るさ変動と主観的評価

Directed forgetting of elements in compound samples.

Pigeons were trained in a delayed matching-to-sample procedure in which the sample stimuli consisted of a compound of color (red or green) and spatial location (left or right). A postsample cue (houselight on or off) signaled whether color matching or location matching would be required following the delay. In Experiment 1, the reduction in performance on probe trials (in which the houselight condition was reversed relative to that on regular trials) was greater for location matching than for color matching. The birds showed overt mediational behavior during the delays on location-matching trials. On color-matching trials, the birds exhibited behavior during delays that might have interfered with that mediational behavior. In Experiment 2, the houselight condition was changed shortly before presentation of the comparison stimuli on probe trials. Accuracy of location matching was reduced when the cue initially signaled color matching and was then changed to signal location matching, whereas matching accuracy was not reduced by a change in the opposite direction. Accuracy of color matching was reduced by a change in illumination level from dark to light, regardless of type of the relevant dimension signaled by houselight illumination. Discussion of these findings focuses on the variables critical to establishment of an effective cue to forget.

Sources of visual interference in delayed matching-to-sample with pigeons.

In two experiments, independent groups of pigeons were trained on an identity matching task involving line orientations as sample and comparison stimuli. For some birds an overhead houselight was illuminated continuously throughout each training session. For other birds the houselight was never illuminated during training sessions. During subsequent testing, the lighting conditions during the delay were the same as in training on some trials, but on other trials they were opposite those of training during either the entire delay (Experiment 1) or during a portion of the delay (Experiment 2). In birds trained with the houselight off, turning the houselight on during the delay produced a large and enduring disruption in matching accuracy. On the other hand, in birds trained with the houselight on, turning the houselight off during the delay produced only a moderate and temporary disruption in matching accuracy. These findings are inconsistent with the prevailing view that retroactive interference in pigeons is a function of a change in illumination level relative to that which prevailed during training. In pigeons, as in monkeys, sustained retoactive interference effects obtain only when the level of illumination is increase during the delay interval.

Simultaneous constancy, lightness, and brightness.

An achromatic surface in a complex scene has both an apparent reflectance attribute (lightness) and an overall intensitive attribute (brightness). We studied changes of these two attributes as a function of changes in illumination level and pattern complexity. Subjects observed simultaneously two arrays of simulated achromatic surfaces with identical reflectance distributions. The left-hand array (standard) was always illuminated at a moderate level. The right-hand array (test) had different illuminances from trial to trial. The subjects adjusted patches in the test array to match the corresponding patches in the standard array in either lightness or brightness. In complex patterns (32 grays) lightness constancy was nearly perfect; test reflectance settings were invariant over illuminance. In disk/annulus patterns (two grays), the lightness-match data confirmed previously published reports. At high illuminances, the standard patches could be matched with a smaller range of test-array reflectances than at low illuminances, i.e., lightness constancy was imperfect. Brightness matches varied substantially as a function of illuminance in all conditions.

Feedback synaptic interaction in the dragonfly ocellar retina.

The intracellular response of the ocellar nerve dendrite, the second order neuron in the retina of the dragonfly ocellus, has been modified by application of various drugs and a model developed to explain certain features of that response. Curare blocked the response completely. Both picrotoxin and bicuculline eliminated the "off" overshoot. Bicuculline also decreased the size of response and the sensitivity. gamma-Aminobutyric acid (GABA), however, increased the size of response. The evidence indicates the possibility that the receptor transmitter is acetylcholine and is inhibitory to the ocellar nerve dendrite whereas the feedback transmitter from the ocellar nerve dendrite may be GABA and is facilitory to receptor transmitter release. The model of synaptic feedback interaction developed to be consistent with these results has certain important features. It suggests that the feedback transmitter is released in the dark to increase input sensitivity from receptors in response to dim light. This implies that the dark potential of the ocellar nerve dendrite may be determined by a dynamic equilibrium established by synaptic interaction between it and the receptor terminals. Such a system is also well suited to signalling phasic information about changes in level of illumination over a wide range of intensities, a characteristic which appears to be a significant feature of the dragonfly median ocellar response.

A Max-Min Measure for Image Texture Analysis

A new technique for image texture analysis is described which uses the relative frequency of local extremes in grey level as the principal measure. This method is invariant to multiplicative gain changes (such as caused by changes in illumination level or film processing) and is invariant to image resolution and sampling rate if the image is not undersampled. The algorithm described is computationally simple and can be implemented in hardware for real-time analysis. Comparisons are made between this new method and the spatial dependence method of texture analysis using 49 samples of each of eight textures. The new method seems just as accurate and considerably faster.

Surface-state density and surface potential in MIS capacitors by surface photovoltage measurements. II

This paper describes a surface photovoltage method which is complementary to the one reported in part I. The present method relies on the fact that a change in illumination level causes a change in electron occupancy of some of the surface states. It involves only moderate light intensity and yields results for the surface-state density from the slope of the surface-photovoltage against log-of-light-intensity curve. The limits of surface potential within which the method is valid as well as the range of surface-state densities measurable will be examined. Results are presented and are compared with those obtained by other methods. The possible advantage in measurements at low temperatures is also discussed.