Optical detection of objects having irregular surfaces

A method for autonomously operating a photosensing object detector that includes an illumination source and a photosensor, the method comprising:

• performing a baseline characterization of a background surface, the background characterization including:
• measuring of distance between the object detector and the background surface;
• measuring a characteristic of the background surface using a modality that is different from the distance;
• performing an initial detection of any presence of at least a portion of an object within a target area between the object detector and a background surface, the initial detection being based at least in part on a distance measurement of a first difference between the object detector and any surface within the target area;
• and
• performing multi-modal testing of any presence of at least a portion of an object within the target area, the multi-modal testing including:
• performing a verification of continued presence at least a portion of the object within the target area, including applying off-state testing criteria that includes a measure of a second difference between any surface within the target area and the background surface, the measure of the second difference being in a measurement modality that is different from the distance measurement,
• wherein the baseline characterization further includes computing a measure of dispersion of a set of reflection-intensity measurements of the background surface, including the reflection-intensity measurement of the background surface, the dispersion of the set of reflection-intensity measurements representing variability within the set of reflection-intensity measurements, wherein the measure of dispersion of the reflection-intensity measurement information is compared against a reflection-intensity measurement dispersion threshold representing a defined degree of variability of the set of reflection-intensity measurements which is different, by a given margin, from a baseline degree of variability of a set of reflection- intensity measurements corresponding to the background surface, and wherein satisfaction of the reflection-intensity measurement threshold is indicative of the presence of at least a portion of the object within the target area;
• and
• wherein applying the off-state testing criteria includes determining the measure of the second difference as determining the presence of at least a portion of the object within the target area based on the measure of dispersion of the set of reflection-intensity measurements.

A system for autonomously operating a photosensing object detector that includes an illumination source and a photosensor, the system comprising:

• means for performing a baseline characterization of a background surface including:
• means for measuring a distance between the object detector and the background surface;
• means for measuring a characteristic of the background surface using a modality that is different from the distance;
• and
• means for performing a multi-modal detection of any presence of at least a portion of an object within a target area between the object detector and a background surface, including:
• means for measuring distance between the object detector and any surface within the target area to produce a distance measurement;
• means for determining a first difference between the distance measurement and the distance between the object detector and the background surface as measured in the baseline characterization, wherein the first difference is indicative of a trigger event for verification of the presence of at least a portion of the object within the target area;
• and
• means for performing the verification of at least a portion of the object within the target area in response to the trigger event, including means for applying detection verification decision criteria that includes a measure of a second difference between any surface within the target area and the background surface, the measure of the second difference being in a measurement modality that is different from the distance measurement including at least:
• a measure of dispersion of a set of reflection-intensity measurements of the background surface, including the reflection-intensity measurement of the background surface, the dispersion of the set of reflection-intensity measurements representing variability within the set of reflection-intensity measurements, wherein the measure of dispersion of the reflection-intensity measurement information is compared against a reflection-intensity measurement dispersion threshold representing a defined degree of variability of the set of reflection-intensity measurements which is different, by a given margin, from a baseline degree of variability of a set of reflection-intensity measurements corresponding to the background surface, and wherein satisfaction of the reflection-intensity measurement threshold is indicative of the presence of at least a portion of the object within the target area.