Evaluation of Detection Performance for Safety-Related Sensors in Low-Visibility Environments

Abstract

This paper addresses the evaluation of object detection performance for non-contact safety-related sensors in low-visibility environments due to adverse weather conditions. An evaluation metric, MOT (Minimum Object-detectable Transmittance), is proposed to quantitatively evaluate the influence of the low-visibility environments on the object detection performance. Traditionally, the Meteorological Optical Range (MOR) has been used for this purpose. However, MOR is not appropriate for the sensor evaluation because it is a meteorological metric which is optimized for human eyes to estimate the distance at which a person can see clearly through an atmosphere. On the other hand, MOT is a physical and optical measure that quantifies the relationship between the spatial transmittance and the distance at which a sensor can detect a specified object. It is specialized for the sensor evaluation and can express the sensor characteristics in the low-visibility environments at each measurement distance. The usefulness of MOT will be demonstrated by presenting the experimental results of MOT measurements for various sensor devices in a fog space reproduced with environmental simulator equipment.

Impact of Rainfall on the Detection Performance of Non-Contact Safety Sensors for UAVs/UGVs

“…The effect of wind on rain and drizzle, while potentially significant, is not treated here and is left for future study. This paper focuses on the evaluation of non-contact safety sensors based on optical principles, similar to those discussed in our previous paper [3]. Specifically, we examine "depth cameras" (also known as 3D cameras, distance imaging cameras, or RGBD sensors).…”

“…However, its suitability for technical evaluation of sensor performance is questionable because MOR is tailored to the characteristics of the human eye, as evidenced by the use of different c 0 values for rainfall and other conditions. Therefore, in our previous work, we demonstrated the advantages of using spatial transmittance over MOR for such evaluations [3].…”

“…These findings led us to question the suitability of the commonly used visibility metric, MOR, for evaluating sensor performance. As an alternative, we proposed MOT, Minimum Object-detectable Transmittance, a novel metric based on spatial transmittance [3].…”

“…Sensor performance should be evaluated based on the physical characteristics of the space, i.e., the "visibility". To quantitatively evaluate the visibility, this paper adopts the spatial transmittance T d at distance d [m] intended for sensor use, as introduced in a previous study [3]. To evaluate the visibility of the rainfall space itself without relying on a specific sensor, we use T 5 , which uses 5 m as a representative distance.…”

“…To provide information to sensor users, such as safety sensor system integrators, a description based on the intended maximum operating distance and its spatial transmittance, as suggested in our previous paper [3], should be used. For example, the user manual should state: "This sensor is designed for use in rainfall with a spatial transmittance greater than 80% at a sensing distance of 5 m".…”