![]() In practice, the optimal index of refraction may be lower than n i + 1 ≅ 2 due to several factors. In that case, the sphere surface behaves as a concave spherical mirror with the required curvature for retroreflection. In the paraxial approximation, this effect can be achieved with lowest divergence with a single transparent sphere when the refractive index of the material is exactly one plus the refractive index n i of the medium from which the radiation is incident (n i is around 1 for air). These two types have similar optical properties.Ī large relatively thin retroreflector can be formed by combining many small corner reflectors, using the standard hexagonal tiling.Ĭat's eye Eyeshine from retroreflectors of the transparent sphere type is clearly visible in this cat's eyesĪnother common type of retroreflector consists of refracting optical elements with a reflective surface, arranged so that the focal surface of the refractive element coincides with the reflective surface, typically a transparent sphere and (optionally) a spherical mirror. The second form uses mutually perpendicular flat mirrors bracketing an air space. In this structure, the reflection is achieved either by total internal reflection or silvering of the outer cube surfaces. In the more common form, the corner is literally the truncated corner of a cube of transparent material such as conventional optical glass. ![]() Therefore, as the ray reflects first from side x then side y and finally from side z the ray direction goes from to to to and it leaves the corner with all three components of its direction exactly reversed.Ĭorner reflectors occur in two varieties. When the ray reflects from the first side, say x, the ray's x-component, a, is reversed to − a, while the y- and z-components are unchanged. The three corresponding normal vectors of the corner's sides form a basis ( x, y, z) in which to represent the direction of an arbitrary incoming ray. I will be out of town fron Aug 6th-9th, so if pmt arrives after Aug 5th shipping will have to wait till Aug 11th.A set of three mutually perpendicular reflective surfaces, placed to form the internal corner of a cube, work as a retroreflector. Ask about shipping to Canada via International 1st Class. Do not send pmt till I send you an invoice after the sale is over. ![]() With Pay Pal or Money Order payments, Items shipped within 2 business days.Payments by personal check: checks will need to clear my bank prior to shipment. Payment by check, money order, or Pay Pal. Shipping in lower 48 states $9.00,, Plus insurance. This sale is only for the 22 clear glass reflectors. See my other sales to view these 15 scarce yellow ones. ![]() T are 15 of these Vaseline reflectors in this separate later sale. I also show in the last photo 2 different color reflectors, I am listing the yellow or, true VASELINE glass reflectors in a separate sale. I'm sure someone needs these to complete their vintage sign w some are missing. These were used in vintage 1920's-1940's Railroad Signal, Crossing signs, & in a variety of different Road/ Highway signs. I'm not sure how these mounted into the holes in old signs, possibly they just pressed into the holes?One photo shows the back side of one, I cleaned a bit with steel to reveal the name, it reads " Patent Pending, SIGNAL 1 " inside a circle & a stop sign shaped figure. The metal housing seem to be a plated brass, with very minor dents on 3 or 4. They are 1 inch tall & measure between 7/8"-1" diameter, all are the same size & brand. Some of these have some white paint on the metal rim around the glass "eyes". These 22 reflectors all have been used, but donâe(tm)t have any type of real damage, no chips, or cracks. 22 RAILROAD, or HIGHWAY SIGNAL SIGN REFLECTORS CLEAR MARBLE CAT'S EYE are 22 vintage 1920's-40's, clear glass cat's eye, or marble type signal / sign reflectors.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |