PtGrey Blackfly Lense - Seanmatthews/rowboat1 GitHub Wiki

Lenses for Point Grey Mono USB3 camera BFLY-U3-23S6M-C

Optical Format (Sensor Size)

The camera has an unusual optical format of 1/1.2", and not many lenses for the format exist. Though a larger optical format may be used, but there will likely be a loss of resolution. For our purposes, we can viably consider the next size up, which is 1". It looks like some manufacturers (see SENKO lense below) have success in using their 2/3" lenses with the 1/1.2" format, but I'm wary of potential cropping.

FOV

Field of view (FOV) is determined by the lense focal length as well as the size of the particular dimension of the sensor. That is, for horizontal FOV, HFOV = 2 * tan^-1(h/2f) where f is the focal length and h is the horizontal size of the sensor. See the resource link below for more technical details.

For our application, imagine that the camera is angled forward-down at some angle, and views the sea floor from a range of ~two feet. At 80deg angular FOV, the camera will see a width of sea floor of 1.68ft (and in front of itself), only slightly wider than the sub itself. At 1920 pixels wide, that means the image produced will represent each millimeter with almost 4 pixels! Pretty good. We could even have the sub move over the ground from a little higher up, but then we'd obtain less resolute picture details and would need to increase the lumen output from the lights (expensive in both power and pecuniary budgets).

Megapixel Resolution

With megapixel sensors, we need to ensure that the lense have a MP rating that meets or exceeds that of the sensor. A lense with a higher MP rating has optical components capable of projecting images onto the sensor at a resolution high enough for it.

Candidates

Resources