From daniel@cfar.umd.edu Mon Sep 26 13:02:02 1994 Date: 17 May 1994 15:35:47 GMT From: Daniel DeMenthon To: sci-virtual-worlds@uunet.uu.net Newsgroups: sci.virtual-worlds Subject: Lens for 3D mouse Hello all, Here at the Computer Vision Lab we are developing a camera for use as a position tracker for a 3D mouse (and later for head tracking) [1]. Several infrared LEDs are attached to the mouse; the camera picks up the bright spots in the image and sends their centroids to the computer using the serial port 60 times per second (field rate). Then the computer uses these centroids to get the pose of the mouse. The principles are not new, I know; our contribution is mainly in the fast methods to compute the pose from the centroids, and some hardware tricks to do things in real time. Our present prototype is built around a small board-level Chinon camera [2], and analyzes the NTSC signal to get the centroids using programmable logic and an 8051 microcontroller (which also takes care of the serial output). But NTSC limits the pose rate to 60 per second, and we don't care much about the interlace feature either :-) In the new prototype we are designing, we are trying to compute 100 to 200 poses per second, by driving a new Texas Instruments CCD chip directly with programmable logic, and analyzing the signal out of the chip without going through NTSC at all. This type of camera sending elementary image processing results to an RS232 port is also useful for a small robot trying to find beacons or just trying to go straight. The problem we are having now is simply buying a lens assembly. What I call lens assembly is a small box (20 mm x 20 mm) that is screwed on the printed board with a couple of screws and encloses the CCD chip. A threaded barrel is mounted on that box like a miniature C-mount lens to position the lens above the sensitive surface of the CCD and to allow adjusting of the focal length. So lens assembly = lens + barrel + box + screws. TI sells its CCD chips without a lens assembly, and we couldn't get any help from them. Other companies such as Sanyo sell their chips with a lens for mounting on a PCB, ($40, $14 in quantity) but of course they don't sell the lens by itself. For the next prototype we are going to buy a Sanyo CCDs + lens combination, and use the lens with the TI chip (the Sanyo chip seems a bit harder to drive), but we would hate to do that for each of the systems we want to build. There is some hint in the Sanyo literature that the manufacturer of the lens is Minolta, but we haven't found a distributor for Minolta. Do you know any manufacturer or distributor of small lens assemblies similar to the ones used on board-level cameras? Many thanks for any suggestions. Daniel DeMenthon, Assistant Research Scientist, Computer Vision Lab (CVL), Center for Automation Research (CfAR), U. of Maryland, College Park daniel@cfar.umd.edu, FAX (301) 314-9115 [1] with a State of Maryland MIPS grant to CVL, and to Data Design Corp., Gaithersburg, MD, FAX (301) 926-6441. [2] Chinon CX 103, with a 3 mm lens (wide angle; they also have a 4mm lens). Dimensions are less than 2" x 2" x 2". Price is $139 in single quantity. Great glass optics on board-mounted lens for this price and dimensions. Coordinates: Chinon America, P.O. Box 1248, Mountainside, NJ