14Dec/092
Communicating with TSL202R
Last time I talked about my USB device that I’m creating. I’ve connected the TSL202R Linear Array Photodiode sensor. It has 128 photodiodes(pixels) that tells us how much light there is on each one of them. This is very useful. It can be used for example for OCR, measuring the angle of a light source etc. I’m interesting in measuring the dimensions of object. It’s actually a simple method. Take a look at this figure:
We have a source of light then an optic system and the sensor. When we put an object in front of the light we get his shadow on the sensor. By measuring the size of the shadow we can calculate the size of the object.
Here’s how the sensor looks like and a simple result of it’s output in my application:
December 22nd, 2009 - 00:36
It looks very good, but what are the dimensions of the grid(the application’s one)?
December 22nd, 2009 - 10:36
One vertical line corresponds to 1 pixel (photo diode) + the space to the other one – 70um + 55um = 125um. The maximum of the graph is 3V. However that is not important as I’ll mainly measure vertically. In horizontal I need to measure in % and that’s easy if I take into account the min and the max… If designed and programmed well I should be able to archive an accuracy of about +/- 3um.