Fiducial routine uncertainty With the vacuum stand x

Fiducial routine uncertainty • With the vacuum stand, δx = 0. 5μm δy = 1. 7μm δθ = 0. 01 rads • Each routine takes about 15 s. 12/22/2021

Needle tip finding A modified webcam is used to locate the dispenser needle tip. A certain illumination and background setup is required to extract the needle when applying a threshold. Eventually, two webcams will locate the x, y and z position of the middle of the needle tip. The procedure is similar to the fiducial finding. First, focus on the tip. Second, extract the needle tip. Third, locate the middle point. 12/22/2021

Determination of the width and the middle point • Method 1: Equivalent rectangle (full extraction 1920*1080) a*b = Area 2(a+b) = Perimeter a < b The needle width in pixel is approximately a. • Method 2: Equivalent rectangle (partial extraction 200*200) Similar to Method 1 but smaller area. The error should be larger. • Method 3: Slope calculation (partial extraction 200*200) w = c * sin(θ) 12/22/2021

Determination of the width and the middle point Red - Method 1 Green - Method 2 Blue - Method 3 The fluctuation (uncertainty) of the method 3 is the smallest. More robust against the bad focus quality. 12/22/2021

Focus on the needle • It is almost impossible to focus on the whole needle. Practically, can only focus on a small portion of the needle, assuming the needle is arbitrarily tilted. • Step 1: Without any focusing, extract the needle out in the field of view. Use the Method 1 find the rough position of the tip middle point. Move the tip into the 200*200 box. • Step 2: After the conversion to the greyscale, FFT the 200*200 image and use the chosen frequency domain (370 – 400) to find the focus with the best quality. • Step 3: Use the Method 3 to find the exact position of the middle point. Move the needle such that the mid point is at the center of the field of view. 12/22/2021

Preview of the complete program Show the 3 D position of the needle tip mid point. Specify the realworld width of the needle to convert the pixel to mm 12/22/2021 Initial position to find the focus. With an increment of 0. 1 mm, specify the number of steps.

Potential problem Webcam is of low quality … Glitch appears now and then. This line may cause troubles in focusing. 12/22/2021