How can I measure the pixel size

Hi, I have a graduation project called Quality Check in PCB.

I was not able to identify the defects in the three existing holes, and my professor told me that I need to calculate the pixel size.

Does anyone have any idea about this?

Thank you for any help.

Answer 1

[Matt J]

If you know the real world distance D (e.g. in millimeters) between two points on the PCB, and if these points are N pixels apart, then the pixel size would be,

pixel_size = D/N;

[Manar]

how can I determine the real distance between points and the number of pixels? Is there a code that calculates them automatically or something else?"

[Matt J]

To get the real distance, you get a ruler out and measure the distance directly on the PCB. Or, perhaps the product literature for the PCB gives you some relevant dimensions, for example it may tell you how tall/wide the card is.

To get the number of pixels, one way is to use imdistline.

[Manar]

Oh, so this is a problem… I only have an image of the board and there are no documents for it.thx

[Stephen23]

"so this is a problem… I only have an image of the board and there are no documents for it."

Most likely those are standard 0.1" DIP hole spacing (e.g. on the 40-pin DIP, and the 16-pin DIP):

https://en.wikipedia.org/wiki/Dual_in-line_package

You could cross-check the DIP sizes against the pin/lead spacing of the SOP28 footprint too.

So you can easily estimate all sizes on that board.