We have developed an optical method to monitor the activity of the ON and OFF channels in the anuran retina. The change in the fraction of near infrared that is transmitted transversely through the retina in an eyecup slice is monitored during stimulation by visible, green light. Near-infrared transmission increases both at the onset and at the termination of a step stimulus. This “ON/OFF” response is maximal in the neural retina. Sodium L-aspartate, which blocks the light-evoked activity of post-photoreceptor neurons, abolishes the “ON/OFF” response. L-AP4, used as a selective blocker of the ON channel, reduces the “ON” component and has little or no effect on the “OFF” component. The “ON” and “OFF” processes observed optically are distinct from those that generate the b– and d–waves of the electroretinogram, and the “ON” and “OFF” components may be superior to the b– and d–waves as indicators of ON and OFF channel activity. The optical method is almost as simple as electroretinography and has the advantage that responses can be spatially localized with ease.

La rétro-conception géométrique est un processus permettant l'obtention d'un modèle numérique à partir d'un objet réel préexistant. Le processus de prise de mesures est l'étape initiale conditionnant cette démarche. Plusieurs solutions commerciales performantes existent, mais sont trop souvent des boîtes noires pour l'utilisateur. Les limites inhérentes aux principes physiques utilisés ne sont pas directement perceptibles. Dans le cadre de travaux pratiques de rétro-conception, les étudiants expérimentent la mesure 3D d'un élément de carrosserie avec un montage simple qui se compose d'un vidéoprojecteur et d'un appareil photo numérique. La méthode testée est celle de la lumière structurée avec codage en binaire réfléchi de la position des franges. À partir de la disposition spatiale du dispositif expérimental et des prises de vue, les étudiants doivent analyser le contenu 3D des images à l'aide de logiciels génériques non dédiés. Ceci leur permet d'estimer les sources d'erreurs expérimentales ou de traitement des images. L'étape ultime est l'intégration des données numérisées dans une solution CAO où une comparaison avec un modèle numérique est possible.

This paper describes a micro-optical three-axis tactile sensor capable of sensing not only normal force, but also shearing force. The normal force was detected from the integrated gray-scale values of bright pixels emitted from the contact area of conical feelers. The conical feelers were formed on a rubber sheet surface that maintains contact with an optical waveguide plate. The shearing force was detected from horizontal displacement of the conical feeler. In the experiments, a precise multi-axial loading machine was developed to measure sensing characteristics of the present sensor. Results show that the normal force was specified uniquely under combined force conditions and that the shearing force was specified by modifying the relationship between the shearing force and the horizontal displacement on the basis of normal force. We formulated a set of expressions to derive the normal force and the shearing force by taking into account this modification. Furthermore, calibration coefficients were identified for transforming the integration of gray-scale values into the normal force and for transforming the horizontal displacement into the shearing force. This result suggests that the expressions can estimate the normal force and the shearing force in wide-load regions.

This paper describes precision enhancement of an optical three-axis tactile sensor capable of detecting both normal force and tangential force. The sensor's single cell consists of a columnar feeler and 2-by-2 conical feelers. We have derived equations to precisely estimate the three-axis force from the area-sum and area-difference of the conical feelers' contact areas by taking into account wrench-length shrinkage caused by a vertical force. To evaluate the equations and determine constants included in the equations, we performed a series of calibration experiments using a manipulator-mounted tactile sensor and a combined load-testing machine. Subsequently. to evaluate the tactile sensor's practicality. it was mounted on the end of a robotic manipulator which rubbed flat specimens such as brass plates with step-heights of δ=0.05, 0.1, 0.2 mm and a brass plate with no step-height. We showed from the experimental data that the optical three-axis tactile sensor can detect not only the step-heights but also the distribution of the coefficient of friction, and that the sensor can detect fine plate inclination with accuracy to about ±0.4°.