Lens calibration board

When doing visual recognition , We need a calibration board , Calibration plates can also be purchased , You can also print . But because of the printer , The length and width of the last square are not equal .
You can also purchase finished calibration plates , It usually ranges from dozens to hundreds , It doesn't seem necessary .
So prepare to use mobile phones or tablets to make calibration plates , Because this thing is very accurate , It is used for lens correction with good accuracy .

use Coreldraw Draw one as shown in the figure above , Finally, it was recognized that it was wrong to check the aspect ratio on the screen , Finally, it is found that the length width ratio error of the display .

My main monitor is Samsung , Show the figure above ,6 Grid width , Measure with caliper as 203mm, And the height is 198.2mm, Length width ratio 1.024, That is to say, it is wider 2.4% This is a value that cannot be ignored , Never thought about this before . And I have another one Acer Monitor , Is accurate 1：1.

It seems that when you buy a monitor in the future , I have to go to the physical store to buy , Just bring a caliper .

The flat plate acts as a calibration plate , The effect is very good , And my mobile phone and tablet , The aspect ratio is 1：1, There is no error ：

If you need the original picture, please download it here
https://download.csdn.net/download/13011803189/86227156