Coverglass

Most biological specimens on slides are protected by a coverglass. This means that light from specimens must always pass through a coverglass, making this thin piece of glass an important part of the microscope process.

Specifications for coverglass made in Japan are determined by the Japan Industrial Standards (JIS). Here is one example of particular optical interest:

Refraction index:

ne=1.5255±0.0015

Abbe number:

υe=56±2

Flatness:

0.010mm

Thickness:

Name:	Thickness range:
No.1	0.12-0.17
No.1-S	0.15-0.18

So we see that coverglass is manufactured according to strict standards, which also determine the design of objectives (usually 0.17 mm thick). The first step in correct use of a microscope is using a coverglass that meets these standards.