Determining inventory levels using rotatable counting devices and visual imagery

A method comprising:

• capturing, by a camera, a first image at a first time,
• wherein a first counting device is within a field of view of the camera,
• wherein the first counting device is provided in association with a first shelf,
• wherein a first portion of the first counting device having a first visible pattern thereon is configured to rotate about a first axis in response to changes in position of a first pusher slidably disposed in a first track on the first shelf, and
• wherein a first plurality of items is provided between a first contact face of the first pusher and the first end of the shelf at the first time;
• determining a first orientation of the first visible pattern within the first image;
• capturing, by the camera, a second image at the second time;
• determining a second orientation of the first visible pattern within the second image;
• determining a change in position of the first pusher between the first time and the second time based at least in part on a difference between the first orientation and the second orientation;
• calculating a number of the first plurality of items based at least in part on the change in position;
• and
• determining that an interaction involving the number of the first plurality of items occurred between the first time and the second time.

A counting device comprising:

• a front panel having a visible pattern thereon;
• a spring;
• a reel, wherein a first end of the second spring is coupled to the reel;
• a tether, wherein a first end of the tether is coupled to the reel, and wherein at least a first portion of the tether is coiled around the reel;
• a housing, wherein the housing has a shape of a cylinder having an open first end and a closed second end, wherein a bore extends through the second end, and wherein at least a second portion of the tether is extended through the bore, and wherein a second end of the spring is coupled to the housing;
• wherein the front panel is joined to the reel with the spring therebetween to form a subassembly;
• wherein the subassembly is configured to rotate within the housing about an axis defined by the bore in a first rotational direction or a second rotational direction;
• and
• wherein the spring supplies bias to the subassembly in one of the first rotational direction or the second rotational direction.