Manufacturers produce either silver- or copper-coated prisms to reflect laser wavelengths, but what's the difference?
In the early days of electronic distance measurement (EDM), in the mid to late-20th century, there was a school of thought that copper-coated prisms better reflected the laser wavelength of the instrument and not as much of the visual wavelengths. This may have been true back then when EDM instruments had very weak light sources when compared to today's standards. Today's EDMs have much stronger lasers and narrower bandpass filters on the receiver, making any difference negligible.
The simple answer is that a lot of it comes down to history, and in the case of Trimble®, silver-coated prisms have been the standard for decades. Let's explore why.
The graph below shows the reflectivity of different metals as far as Trimble instruments are concerned, where the gold line (Ag) is silver and the red line (Cu) is copper. As you can see, silver and copper practically have the same reflectivity.
