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Machine Vision Lighting Tips for Overdriving LEDs Cheat Sheet (DRAFT) by [deleted]

This is a draft cheat sheet. It is a work in progress and is not finished yet.


Lighting is a vital element of an optimized inspection using machine vision. Even the best camera can capture what it can see, and the best image processing software relies on good results from the camera. Illumi­nation consis­tency, intensity, and resolution will have an effect on the final accuracy of an applic­ation. Despite this, lighting histor­ically has not been an integrated part of a machine vision system.

A fundam­ental element of a successful and effective vision system is the visibility of the target object to be inspected, especially the specific objectives for an inspec­tion: missing parts, color differ­ent­iation, blemishes, character recogn­ition, or sizing, for example. The starting point for the quality of these source images is the suitab­ility and effect­iveness of the lighting for a machine vision system to perform consis­tently. The primary images need to be consis­tent, making undefi­nable variations in lighting unacce­ptable.
Credit: http:/­/ww­w.c­ont­rol­­m/s­ing­le-­art­icl­e/m­ach­ine­-vi­sio­n-l­igh­tin­g-t­ips­-fo­r-o­ver­dri­vin­g-l­eds­/bd­389­34e­e18­87b­f01­452­570­b98­ca5­295.html
Edited by Mark T. Hoske, content manager, Control Engine­ering, CFE Media, mhoske­@cf­eme­ from an April 22 article, "­Seeing the light,­" posted by Control Engine­ering Europe

Five LED overdr­iving tips

Most machine vision applic­ations are short of light, so overdr­iving light-­emi­tting diodes (LEDs) is a common practi­ce–it allows users to increase intensity from LED lights for a short, defined, period of time (with up to 1,000% overdr­iving capabi­lity). However, LED overdr­iving limits are based on genera­lized parameters that are considered safe for all LEDs so are usually set lower than is possible in reality for a specific light.

1. Ensure generation of maximum brightness

Ensure generation of maximum brightness from a light. This is achieved by having data readily available on the actual light being used, therefore enabling the overdr­iving of a particular light to its safe optimized limits.

2. Calibrate lighting brightness

Calibrate lighting brightness to allow more repeat­ability of lighting intensity.

3. Set thresholds

Set thresholds and feature detection to be more sensitive, while mainta­ining good repeat­ability and reliab­ility of detection

4. Use actual temper­atures

Overdrive limits also are based on the maximum operating temper­ature, but most lights run at a lower temper­ature. So, by measuring the actual temper­ature of the light, it is possible to allow for more overdrive in systems which run below the maximum temper­ature.

5. Pay attention to timing

Some systems need to capture many images of each product item in a sequence of varying lighting requir­ements. With applic­ati­on-­level visibility of the timing of the system, and a fully featured lighting contro­ller, such systems are easier to set up, monitor, and maintain.