USB character size measurement of camera module

The character height of a particular character font should be measured as the distance between the baseline and the upper limit line of the font, as shown in Figure a.1. The character "H" should be used to define the character height.

The character width of a particular character font should be measured as the distance between the appropriate parallel edges of the character "H", as shown in Figure a.1.

For the purpose of size rather than optical measurement, the edge of a character is defined as a point extending to 50% of the luminance difference between the character and the background. The 50% point is determined by measuring the character brightness distribution. The measuring equipment should be able to reliably measure the minimum uniform area of the character.