Photocell array sensor for projectile position detection

A projectile sensor comprising:

• (a) a photocell detector having a substantially planar surface with a photosensitive active area substantially in the form of a plurality of parallel elements and at least one diagonal element interposed between two adjacent said parallel elements, said parallel and diagonal elements being substantially long and narrow
• (b) a lens means of forming a substantially focused image on said photocell detector, said image substantially covering said photosensitive active area and representing the field of view of said lens means
• (c) a support means for holding said lens means and said photocell detector, such that said photosensitive active area is substantially normal to and centered on the optical axis of said lens means
• whereby said sensor is oriented such that a projectile transiting said field of view of said lens means appears in said image and transits said active area substantially normal to said parallel elements and falls once upon each of all said elements producing a plurality of brief electrical responses equal to the number of all said elements, such that the times of said responses when captured by a threshold detection means, define time periods between responses, the duration and ratios of said time periods relating to said projectile's velocity, position, and path through space.