Transcript:
Okay, so let’s jump right in. We know you’re out there working hard in quality control, aerospace, food and beverage, you name it. And you’ve got to be on top of your game. You need to understand machine vision lighting, like yesterday. You got it, no time to waste. So consider this your crash course. We’re diving deep into machine vision illumination. Deep dives right. And we’re going to focus on what really matters to you. The main lighting types, the color wheel.
and how to use those filters effectively. Yeah, we’re going to cut through the noise and give you those aha moments that’ll help you level up your inspection game. Exactly. Flexible vision is leading the way here. And we’re going to explore those core concepts that make illumination so powerful. Think of it as your toolkit for seeing the unseen, for revealing those critical details that can make or break your product quality. Yeah, you’ve got to catch those errors before they become, well, expensive problems. Exactly.
So how do we even begin to make those features visible to a machine vision system? What’s the foundation here? It all boils down to contrast. You know, the name of the game is creating enough contrast between the thing you want to see, the feature, and everything else around it, the background. Right. Without contrast, your fancy camera system is basically working blindfolded. It’s like trying to spot a scratch in a mirror. Exactly. It’s the difference in light and shadow, or maybe in color, that makes that scratch pop out. OK.
How do we strategically create that contrast using different lighting techniques? What are the go-to methods? Well, there are a few key players here, each with their own strengths and weaknesses. Let’s start with bright field illumination. Bright field, OK. This one’s pretty straightforward. You shine a light directly onto the object. Direct light, got it. It’s great for highlighting those surface details that are easy to see. So like a desk lamp on a piece of paper? Yeah.
Exactly. It makes the text really clear. You see all the details. Right. So this is your go-to for spotting those obvious defects, know, surface markings, things like that. There’s always a but, right? Right. Especially in your world with all that polished metal and aerospace or the glossy packaging and food and beverage, bright field can backfire. Too much shine. Yeah. It can create glare and glare can hide those subtle flaws. OK, that makes sense. Yeah.
So what do we do when we’re dealing with glare or we’re hunting for those really tiny imperfections? We bring in the dark field illumination. Dark field, interesting. Instead of shining light directly at the object, you use a light that grazes the surface. So it’s kind of skimming across the surface at a low angle. Yeah, exactly. And the magic here is that it can reveal even the tiniest imperfections on surfaces that look smooth or reflective. I see.
Think about shining a flashlight almost parallel to a table. Suddenly you see all those dust particles that were invisible before. right. You can suddenly see all that texture. Exactly. So in aerospace, this is huge for finding those micro scratches or blemishes on crucial components. Makes sense. And in food and beverage, it can show you imperfections on packaging films or even if a seal is compromised. Any little bump or break on the surface will scatter that light and it’ll pop out as a bright spot against a dark back.
That’s pretty clever. Now what if we’re less concerned with the surface details and more interested in the overall shape of the object or if a part is even there at all? In that case, we switch to backlighting. Backlighting, okay. As the name suggests, you put the light source behind the object opposite the camera. Got it. And this creates a silhouette. so you’re looking at the outline. Exactly. And silhouettes are perfect for figuring out if parts are present or absent.
or for measuring dimensions and profiles really precisely. I see. In food and beverage, this is used all the time to check fill levels in bottles, you making sure those bottles are actually full. Right, right. You can see exactly where the liquid level is. Yeah, or to make sure all the components are in a prepackaged meal. that’s interesting. And that clear outline is also essential for really accurate dimensional checks, which is important for both aerospace and food and beverage. So we’ve got direct light.
for general visibility, low angle light for tiny defects, and light from behind for shape and presence. What about those tricky surfaces though? You know, the curved or super reflective ones that are tough to inspect. yeah, those can be a real headache. That’s where diffuse lighting comes in. Diffuse lighting. Right. The goal here is to minimize that pesky glare and create a nice even illumination across the whole object.
even if it’s curved or shiny. Exactly. It doesn’t matter what the shape is or how reflective it is. So it’s like that soft light you get on a cloudy day. Yeah. Perfect analogy. The shadows are basically gone. Right. And we achieve this by scattering the light before it hits the object. Scattering the light. OK. Two popular ways to do this are dome lights and on-axis diffuse lights. OK. Tell me more about those. So a dome light is shaped like, well, a dome, half a sphere.
And the light shines onto the inside of the dome, scattering it everywhere and creating a really uniform illumination. It spreads the light out nicely. Yeah, it’s perfect for inspecting complex shapes like those molded parts in aerospace or making sure labels are applied evenly on curved hood containers. Okay, that makes sense for those tricky shapes. Now what about on-axis diffuse lighting?
That one uses a beam splitter to project light along the same path as the camera. so the light is basically traveling with the camera. Yeah, you got it. And the advantage here is that it minimizes shadows on flat, reflective surfaces. That’s handy. So it’s great for inspecting things like sheets of polished metal or smooth packaging materials. So dome diffuse for complex shapes, on axis diffuse for flat and shiny. That’s a helpful distinction. Right.
Now, are there any other lighting tricks we should know about for those more specialized situations? absolutely. There’s also coaxial lighting, which is similar to on-axis diffuse in that it projects light along the camera’s axis. But instead of diffusing the light, it uses a mirror or a prism. It’s really good at illuminating flat, highly reflective surfaces and seeing those tiny details right on them, like inspecting a silicone wafer for those microscopic defects. Coaxial lighting is a real work.
for that kind of thing. And then there are ring lights, which mount right around the camera lens. Ring lights, okay. If you have them near axial, they give you a pretty shadow-free frontal illumination. For more general purposes. Yeah, but you can also use them off axis to highlight those surface irregularities. Right. And then we have strobe lights, which emit these super short, intense bursts of light. Strobe lights, those are for capturing things that are moving fast, right? Exactly. You need that burst of light to freeze the motion and get a…
clear image on a production line. Makes sense. And finally, there’s projection lighting, which uses structured light to project patterns onto objects. So you’re projecting a pattern of light. Yeah, and that lets you do some really detailed shape and surface analysis. Wow, OK. So we’ve covered the main lighting types, their strengths, when to use them. But light isn’t just about brightness and direction, right? Color plays a role, too. Let’s talk about the color wheel and how it fits into machine vision. Absolutely.
The color wheel, with its spectrum of warm and cool colors, it’s a powerful tool for controlling contrast. You’ve got your warm colors, red, orange, yellow, and your cool colors, violet, blue, green. Like a rainbow. Exactly. And the key to using this in machine vision is understanding how different colors of light interact with objects of different colors. So how does that interaction work? It comes down to reflection and absorption.
Okay. An object will reflect a lot of light that’s the same color as it is. So it’ll look brighter under that color of light. Exactly. But it’ll absorb light that’s the opposite color on the color wheel. So it’ll look darker under that opposite color. You got it. So the trick is to choose the right color of light to enhance the visibility of whatever you’re inspecting. Interesting. So you can make certain features pop out or disappear depending on the color of the light you use. Yeah. It’s like a visual magic trick. Can you give us some examples of how this might be used in,
aerospace or food and beverage? Sure. Imagine you’re in food and beverage and you have a product with blue lettering on red packaging. Okay, I can picture that. And your vision system is struggling to read that blue text. It’s blending in with the red. Exactly. But if you illuminate that package with red light, the red background will reflect a ton of light and become really bright.
But the blue lettering will stay dark. Exactly. It’ll absorb most of that red light and really stand out against the bright background, making it much easier for the camera to read. that’s clever. Or in aerospace, you might have components made from materials that are slightly different shades of, say, gray. Subtle color differences. Yeah. By choosing the right color of light, you can exaggerate that contrast and make it easy for the system to tell them apart. Even if they look almost identical under white light.
Exactly. So you can use color to guide your inspection process. Like a visual cue. Yeah. And while white light contains all the colors and gives you a general level of contrast, using monochromatic light, you know, just one color or a very narrow band of wavelengths, gives you a lot more control over the contrast. So it’s a more focused approach. Exactly. It’s about being deliberate with the wavelengths of light you’re using. OK, that makes sense. Yeah. So how do monochrome cameras play into this whole strategy of
using colored light for contrast. Monochrome cameras are actually ideal for this. Because they see in black and white. Yeah, shades of gray. And they’re really good at measuring the intensity of the light that comes back to them. OK. So if you shine a red LED on something and look at it with a monochrome camera, any red parts will show up as bright gray. And anything that absorbs red light, like green, will be darker gray. so you’re still getting that contrast based on color. Exactly. But you’re not dealing with the complexity of processing
full color images. That’s efficient. It is. Okay, that clears up the connection between colored lights and monochrome cameras. Now let’s move on to filters. We can control the type and color of the light source, but how do filters give us even more control? Filters are like fine-tuning tools for your light. Okay. They’re these special optical components that you put in the light path, usually right in front of the camera lens. Got it. And they let you control the wavelength of the light and sometimes even the polarization. So they’re refining the light.
that reaches the sensor. Precisely. And that makes a big difference in image quality and contrast. OK, so what are the main types of filters? Well, we’ve got pass filters and polarizing filters. OK, let’s start with pass filters. How do they work? Pass filters selectively allow certain wavelengths of light to pass through while blocking others. You’ve got short pass filters, which let the shorter wavelengths through, like blue and violet, and block the longer ones, like red and infrared. And then you’ve got long pass filters, which
do the opposite. They let through the longer wavelengths. Yeah, and then there are bandpass filters, which are the real specialists. They only let a very specific band of wavelengths through. Glocking everything else. Right. And the beauty of these filters is that they can really enhance contrast and get rid of unwanted ambient light. Can you give us an example of how these might be used in, say, an aerospace or food and beverage setting? Sure. Imagine you’re on a food production line.
and you’re using a red LED to inspect some feature on a package. But the factory has these big fluorescent lights overhead, and that ambient light can mess with your inspection, creating noise and reducing the contrast of your red illuminated feature. It’s like trying to read a book in a disco. Yeah, kind of. Too many distracting lights. Exactly. But if you put a red bandpass filter in front of your camera lens, you’re only letting through the specific red light that’s bouncing off your target.
And blocking up those other wavelengths from the fluorescent lights. Exactly. And that makes a huge difference. The red feature pops out, and it’s much easier for the vision system to analyze. So it’s like cleaning up the visual clutter. Yeah. And this works in aerospace, too, where you might have all sorts of light sources interfering with your inspection. Makes sense. And bandpass filters are also critical in fluorescence applications. right. Where a material emits light at a specific wavelength.
when you hit it with, say, UV light. So you need to isolate that emitted light. Exactly. The bandpass filter helps you see that faint glow against all the other background noise. That’s fascinating. OK. OK, so we’ve tackled pass filters. What about polarizing filters? You mentioned they help with glare, like in photography. How do they work in machine vision?
Polarizing filters block light waves that are vibrating in a specific direction. And glare, you that annoying reflection you get off shiny surfaces, is often polarized light. Like on polished metal parts or glossy packaging? Exactly. So if you put a polarizing filter on your light source and another one on your camera lens and you orient them perpendicular to each other, you can dramatically reduce or even eliminate that glare. So you’re not just trying to overpower the glare with more light.
you’re actually blocking it at the source. Exactly. And that lets you see the surface details that were hidden underneath. I see. And this is particularly useful in both aerospace and food and beverage. Right. You’ve got those shiny metal components and those glossy films. Yeah. But there’s another cool trick with polarizing filters. If you use them on transparent materials like
plastic packaging or certain aerospace composites, you can actually see internal stresses. Wow, really? Yeah, these stresses show up as colorful patterns when you view them through crossed polarizers. It’s called birefringence, and it can tell you a lot about the integrity of the material. So you can see if there are any weaknesses or potential points of failure? Exactly. But it’s worth noting that sometimes simply adjusting the angles of your light source and camera can also be a really effective way to minimize glare.
So a more geometrical approach. Yeah, and that might be the preferred method in some cases. It really depends on the situation and how bad the glare is. OK, that makes sense. So choosing the right filter or combination of filters involves thinking about the light source, the object, and the effect you want to achieve. Absolutely. It’s about matching the filter to the task. This has been a really insightful look into the world of machine vision illumination. We’ve covered the main lighting types, each with its own specialty.
We’ve seen how the color wheel can be used to manipulate contrast by choosing specific colors of light. And we’ve learned how filters, both pass and polarizing, can be used to refine the light, boost contrast, and eliminate glare. And as you’re thinking about all of this, remember that flexible vision has a whole range of illumination solutions designed with these concepts in mind. So you go back to your work, whether it’s ensuring the precision of aerospace components or the safety of food packaging, consider this.
With this knowledge of how light interacts with materials and how color and filters can be used to reveal hidden details, how might you approach a particularly tricky inspection you’re facing right now? Yeah, think about it. Could a different lighting setup, a strategically chosen color of light, or even a simple polarizing filter be the key to making your inspection process more effective and more reliable? It’s definitely worth exploring. It’s all about using the right tools for the job.
Exactly. And we encourage you to take these principles and experiment, you know, see how you can apply them to your own unique challenges. Because often, even small tweaks to your lighting and filtering can make a big difference. You might be surprised at what you discover. Absolutely. It’s all about seeing things in a new light. And that’s what machine vision is all about.
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