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# Autofocus Routine for Camera

IP.com Disclosure Number: IPCOM000035043D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

IBM

## Related People

Kishi, G: AUTHOR [+1]

## Abstract

This article describes a technique for automatically focusing a camera which additionally provides the ability to measure in 3 dimensions the height of a single large object in the image (in our specific usage - a pin sticking through a printed circuit). A camera takes an image that can be described as an array of pixels - the value of each pixel indicating the brightness of the picture at its location. For the purpose of this disclosure, an image is described as the set of I(i,j) where the picture looks something like: I(0,0) I(1,0) I(2,0) I(3,0) ... I(0,1) I(1,1) I(2,1) I(3,1) ... I(0,2) I(1,2) I(2,2) I(3,2) ... ... ... ... ... ...

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Autofocus Routine for Camera

This article describes a technique for automatically focusing a camera which additionally provides the ability to measure in 3 dimensions the height of a single large object in the image (in our specific usage - a pin sticking through a printed circuit). A camera takes an image that can be described as an array of pixels - the value of each pixel indicating the brightness of the picture at its location. For the purpose of this disclosure, an image is described as the set of I(i,j) where the picture looks something like: I(0,0) I(1,0) I(2,0) I(3,0) ...

I(0,1) I(1,1) I(2,1) I(3,1) ...

I(0,2) I(1,2) I(2,2) I(3,2) ...

... ... ... ... ... This
image is filtered: F(i,j) = abs(2*I(i,j) - I(i+1,j) - I(i,j+1) ) The concept behind this filter is that the function (prior to taking the absolute value) gives us the first derivative (or slope) of the image. The absolute value of the first derivative gives us a number that varies from 0 (indicating an image of constant brightness) to 512 (indicating every other pixel is maximum brightness). The filtered image (F) is summed (or integrated) Sum = sum(F(i,j) ) <- called autofocus function This sum gives us a value that indicates the amount of varying intensity in the image. This is a maximum at focus. When the image is out of focus, the image blurs and the image varies less in intensity and the sum is smaller. In our case - inspecting leads sticking through printed circuit cards, we have a plane image (...