Wide-Angle Foveation for All-Purpose Use

Abstract

Abstract-This paper proposes a model of a wide-angle spacevariant image that provides a guide for designing a fovea sensor. First, an advanced wide-angle foveated (AdWAF) model is formulated, taking all-purpose use into account. This proposed model uses both Cartesian (linear) coordinates and logarithmic coordinates in both planar projection and spherical projection. Thus, this model divides its wide-angle field of view into four areas, such that it can represent an image by various types of lenses, flexibly. The first simulation compares with other lens models, in terms of image height and resolution. The result shows that the AdWAF model can reduce image data by 13.5%, compared to a log-polar lens model, both having the same resolution in the central field of view. The AdWAF image is remapped from an actual input image by the prototype fovea lens, a wide-angle foveated (WAF) lens, using the proposed model. The second simulation compares with other foveation models used for the existing log-polar chip and vision system. The third simulation estimates a scale-invariant property by comparing with the existing fovea lens and the log-polar lens. The AdWAF model gives its planar logarithmic part a complete scale-invariant property, while the fovea lens has 7.6% error at most in its spherical logarithmic part. The fourth simulation computes optical flow in order to examine the unidirectional property when the fovea sensor by the AdWAF model moves, compared to the pinhole camera. The result obtained by using a concept of a virtual cylindrical screen indicates that the proposed model has advantages in terms of computation and application of the optical flow when the fovea sensor moves forward.Index Terms-Active sensing, all-purpose use, biomimetics, fovea sensor, image processing, wide-angle foveation (WAF).

Eccentricity Compensator for Log-Polar Sensor

“…(10). , (10) where N is the number of the points (x' di , y' di ) Figure 9 shows the image CF by eq. (10).…”

“…One is by a special CCD or CMOS log-polar chip, where united size of each photosensitive element increases as going to periphery [5]- [7]. The other is by a special fovea lens, such as a Wide-Angle Foveated (WAF) lens, where a projected image is distorted geometrically [8]- [10].…”

“…One of the most remarkable advantages of the log-polar image is to give us rotation and scale-invariant (RS-invariant) property [5] [10], because its image resolution distributes isotropically and changes logarithmically from the image center towards the periphery. Assume a situation where a view direction (that is, the optical axis) of the fovea sensor is perpendicular to a planar target image (that is, without shear).…”

Development of wide angle fovea telescope

“…The author has repeatedly enhanced that the WAF lens method has an advantage of higher resolution compared to the above other methods because the WAF lens magnifies an projected image optically in the central FOV (when the photosensitive element density of the vision chip used for each method is the same in the central FOV, i.e., attention area) [10].…”

“…Here, the human eye is wellknown for its visual acuity distribution, i.e., as keeping a 120degree (in case of a single eye) wide FOV horizontally, the visual acuity is the highest in the central FOV (this means the human eye has an obvious attention area in the FOV) and decreases rapidly towards the peripheral FOV. The vision sensors, inspired from this knowledge, have been developed and reported [1]- [10]. The human eye is a smart sensory organ having the following 2 functions; (1) not to miss the target out of the wide FOV, (2) to observe it in detail in the central FOV.…”