ASTM C1652 Optical Distortion measurement in Flat Glass by Digital Photography

Scope:

Standard test method ASTM C1652 is used for inspection of laminated and tempered automotive glass in transmitted light. The digital imaging test method provides accurate data for evaluating the optical properties of the glass being inspected.

Procedure:

In ASTM C1652 test method, the reflected image of the processed glass is photographed, and the photographic image is analyzed to quantify the distortion due to surface waviness. This method works by obtaining a picture of a grid pattern distorted by a transparent object and evaluating this to an undistorted image of the grid pattern. A digital camera records the appearance of a grid pattern that has been reflected from or transmitted through the glass. They are noncontact and measure the entire surface of the glass. Computer software analyzes the digitized images and displays a surface distortion waviness or quantifies the lens power or optical distortion (mdpt) for approximately every square inch (645.16 mm²) of the entire glass surface.

Specimen Size : 

The tolerances range for a ASTM C1652 test specimen = +/- 2 mm to +/- 1mm

Wave pattern = (300-400 mm).

Data:

The following data is calculated in ASTM C1652 test:

Optical Distortion (roll wave peak-to-valley depth and mdpt)

Lens Power (positive and negative).

Conclusion:

The standard method ASTM C1652 covers the optical distortion measurement of heat-strengthened and fully tempered architectural glass substrates.