The glass changes it's shapes by heated and molded duringmanufacturing
process. Regardless of how excellent shape and color is, the optical strain
can occur within the glass invisibly if proper annealing* is not carried
out.
**annealing: the process of heating up to an appropriate temperature, then
holding at that temperature then followed by slowly cooling. By this process,
it removes residual stresses, reducing hardness, improving machinability,
enhancing cold working, and adjusting crystal structure, etc
Products with optical strains are fragile and can easily break with even
a slight impact. In extreme cases, the unevenness can naturally cause curvature
or cracks. Optical strain tester can easily identify these imperfections
in inadequately annealed products. Another distinctive feature of this
product is the ability to observe the striae caused by refractive index
imbalances.
The rotating frame has markings distributed from 0° to 100°. With 0°representing
the normal state and the most intense colors of optical strain appearing
at the 90°position.
For the inspection, the acceptable quality limit is set by the number appears
on the rotating frame. Based on that, it can be judged that the annealing
is insufficient if the color of optical strain can be observed at a lower
value on the scale than where the acceptable quality limit begins to show
color. (If the annealing process is sufficient, optical strains will not
be visible. If the annealing is insufficient, the more intense the colors
will appear. Additionally, the appearance of optical strains can vary slightly
depending on the sample.) |
