A Colonial Williamsburg staff cabinet maker made the wood frame copying an antique Zograscope. Laurel Industries was commissioned to replicate the 18th century lens. No drawings were available; Laurel Industries worked with Colonial Williamsburg to reverse engineer this antique lens. Their craftsman initially stated this lens’s focal length was approximately 20 inches. While the image focused 20 i
nches from the lens, this was not the effective focal length of the lens. Carl Lambrecht, from Laurel Industries, advised taking this lens outside to use the sun as an object at infinity. One person positioned a yard stick until there was no shadow from the sun. A second person holding the lens perpendicular against the yard stick while focusing the sun’s light to a spot size. When the sun was in sharp focus, they measured effective focal length from lens edge to sun’s focussed image at 32 inches. Laurel Industries determined the type of glass used to make this lens during the 18th century. Using the refractive index of this glass and the effective focal length, a lens radius was calculated. This radius and a measured diameter of six inches, this was enough information to begin manufacturing this lens. Our lens arrived in Williamsburg one day before the start of the exhibition of this exhibit. Two weeks my daughter and two granddaughters visited Williamsburg to test this lens in action to make this a special tour of Colonial Williamsburg. This is an example of Laurel Industries capability to work with a client. We are not usually working on a project to reproduce an instrument over two centuries old. We regularly make lenses from 1 mm to 300 mm diameter and larger. We have been involved with LEDs since 1968. At that time we evaluated a fragile, expensive $800 LED which was loaned to Carl Lambrecht from the Pentagon. We are developing proprietary products for our clients using LEDs as a light source. Laurel Industries has refine engineered customer prototypes to ease manufacturing and reducing cost by 50% at full production.
