To: Naggrachi who wrote (39181 ) 12/10/1997 2:02:00 PM From: Naggrachi Respond to of 58324
TO ALL, A MUST READ OFF THE MOTLEY FOOL: >>Subject: Re: Counting Stars by Candlelight Date: Tue, Dec 9, 1997 00:47 EST From: IraS1 Good digging Clay. Clay posted: << Check out claim 12 from patent 5,638,228 and recall that this patent was filed Feb 14, 1995. 5638228.tif Page 10 "...a textured lens for said, detector, said textured lens discriminating against light reflected from other than a retroreflector material by distorting light reflected from other than a retroreflective material..." >> Moving back 2 pages in the patent, in the section titled "Description of the Preferred Embodiment", we find the following which explains the patent claim Clay cited: "Features may be added to the lens prism which help frustrate the use of other types of reflective materials and also the use of a lens in conjunction with other reflective materials. For example, surface roughness or waviness of the top of the lens prism which has a spatial frequency of less than the pitch of the retroreflective elements (0.006") will be corrected by optically using the retroreflective cartridge marker. This will frustrate the use of both ordinary mirrors and reflectors used in conjunction with lenses. Just putting an angular surface on the front face of the prism lens will frustrate the use of polished mirrors if the angle is made large enough. The corrective polished mirror that would be required is of such a large tilt angle that it would be difficult, if not impossible, to locate on a cartridge. If a mirror is oriented just right, some light will get back to the receiver, but this amount decreases in an exponential manner as the mirror is moved away from the source. This is not the case with the retroreflective material. The decrease with distance is linear with a very gradual slope." In the middle of the next column: "Hence, the differences in the return of light from the two retroreflective materials, Reflexite and a molded acrylic tag, are basically in the diameter of the returned spot of illumination. With the Reflexite, the retroreflected spot is about 12 mils. in diameter and requires the "Lens prism" to redirect light to the detector for sensing. It should also be noted that by getting rid of the "lens prism" some of the modes of discriminating against other types of light directing tags has been reduced." So....(my hypotheses follow)... leave out the prism in early production - save money. Lure competition. "Put back" prism, eliminate competition. >> Zead