Lighting Archives - Page 2 of 4 - 1stVision Inc.

June 26, 2023June 26, 2023

Learn how an Allied Vision Mako camera can control your LED light source

In this article we discuss when and why one might want to strobe a light instead of using continuous lighting. While strobing traditionally required a dedicated controller, we go on to introduce that CCS and AVT have published an Application Note showing how the Allied Vision Mako camera can serve as the controller!

While LED lights are often used for continuous lighting, since that’s an easy mode of deployment, sometimes an application is best served with a well-timed strobe effect. This might be for one or more of the following reasons:

to “freeze motion” via light timing rather than shutter control alone;
to avoid the heat buildup from continuously-on lights
overwhelm ambient lighting
maximize lamp lifetime

Let’s suppose you’ve already decided that you require strobe lighting in your application. You’re past “whether” and on to “how to”.

Since you are moving into the realm tight timing tolerances, it’s clear that the following are going to need to be coordinated and controlled:

the strobe light start and stop timing, possibly including any ramp-up delays to full intensity
the camera shutter or exposure timing, including any signal delays to start and stop
possibly the physical position of real world objects or actuators or sensors detecting these

Traditionally, one used and external controller, an additional device, to control both the camera and the lighting. It’s a dedicated device that can be programmed to manage the logical control signals and the appropriate power, in the sequence required. This remains a common approach today – buy the right controller and configure it all, tuning parameters through calculations and empirical testing.

Effilux pulse controller: controls up to 4 lights; output current can reach up to 1A @ 30V in continuous and 10A @ 200V in strobe mode – courtesy Effilux

Call us if you want help designing your application and choosing a controller matched to your camera and lighting requirements.

But wait! Sometimes, thanks to feature-rich lighting equipment and cameras, with the right set of input/output (I/O) connections, and corresponding firmware-supported functionality, one can achieve the necessary control – without a separate controller. That’s attractive if it can reduce the number of components one needs to purchase. Even better, it can reduce the number of manuals one has to read, the number of cables to connect, and the overall complexity of the application.

Let’s look at examples of “controller free” applications, or more accurately, cameras and lights that can effect the necessary controls – without a separate device.

Consider the following timing diagram, which shows the behavior of the Effi-Ring when used in auto-strobe mode. That doesn’t mean it strobes randomly at times of its own choosing! Rather it means that when triggered, it strobes at 300% of continuous intensity until the trigger pulse falls low again, OR 2 seconds elapse, whichever comes first. Then if steps down to continuous mode at 100% intensity. This “2 seconds max” feature, far longer than most strobed applications require, is a design feature to prevent overheating.

OK, cool. So where to obtain that nice square wave trigger pulse? Well, one could use a controller as discussed above. But in the illustration below, where’s the controller?!? All we see are the host computer, an Allied Vision Mako GigE Vision camera, an Effilux LED, a power supply, and some cabling.

Camera exposure signal controls strobe light – courtesy Allied Vision Technologies

How is this achieved without a controller? In this example, the AVT Mako camera and the Effilux light are “smart enough” to create the necessary control. While neither device is “smart” in the sense of so-called smart cameras that eliminate the host computer for certain imaging tasks, the Mako is equipped with opto-isolated general purpose input output (GPIO) connections. These GPIOs are programmable along with many other camera features such as shutter (exposure), gain, binning, and so forth. By knowing the desired relationship between start of exposure, start of lighting, and end of exposure, and the status signals generated for such events, one can configure the camera to provide the trigger pulse to the light, so that both are in perfect synchronization.

Note: During application implementation, it can be helpful to use an oscilloscope to monitor and tune the timing and duration of the triggers and status signals.

Whether your particular application is best served with a controller, or with a camera that doubles as a controller, depends on the application and camera options available. 1stVision carries a wide range of Effilux LED lights in bar, ring, backlight, and dome configurations, together with the ability to be used on continuous or strobe modes.

1st Vision’s sales engineers have over 100 years of combined experience to assist in your camera and components selection. With a large portfolio of lenses, cables, NIC card and industrial computers, we can provide a full vision solution!

May 16, 2023May 18, 2023

Machine vision lights as important as sensors and optics

Lighting matters as much or more than camera (sensor) selection and optics (lensing). A sensor and lens that are “good enough”, when used with good lighting, are often all one needs. Conversely, a superior sensor and lens, with poor lighting, can underperform. Read further for clear examples why machine vision lights are as important as sensors and optics!

Assorted white and color LED lights – courtesy of Advanced Illumination

Why is lighting so important? Contrast is essential for human vision and machine vision alike. Nighttime hiking isn’t very popular – for a reason – it’s not safe and it’s no fun if one can’t see rocks, roots, or vistas. In machine vision, for the software to interpret the image, one first has to obtain a good image. And a good image is one with maximum contrast – such that photons corresponding to real-world coordinates are saturated, not-saturated, or “in between”, with the best spread of intensity achievable.

Only with contrast can one detect edges, identify features, and effectively interpret an image. Choosing a camera with a good sensor is important. So is an appropriately matched lens. But just as important is good lighting, well-aligned – to set up your application for success.

What’s the best light source? Unless you can count on the sun or ambient lighting, or have no other option, one may choose from various potential types of light:

Fluorescent
Quartz Halogen – Fiber Optics
LED – Light Emitting Diode
Metal Halide (Mercury)
Xenon (Strobe)

By far the most popular light source is LED, as it is affordable, available in diverse wavelengths and shapes (bar lights, ring lights, etc.), stable, long-life, and checks most of the key boxes.

The other light types each have their place, but those places are more specialized. For comprehensive treatment of the topics summarized here, see “A Practical Guide to Machine Vision Lighting” in our Knowledgebase, courtesy of Advanced Illumination.

Lighting geometry and techniques: There’s a tendency among newcomers to machine vision lighting to underestimate lighting design for an application. Buying an LED and lighting up the target may fill up sensor pixel wells, but not all images are equally useful. Consider images (b) and (c) below – the bar code in (c) shows high contrast between the black bars and the white field. Image (b) is somewhere between unusable or marginally usable, with reflection obscuring portions of the target, and portions of the (should be) white field appearing more grey than white.

As shown in diagram (a) of Figure 22 above, understanding bright field vs dark field concepts, as well as the specular qualities of the surface being imaged, can lead to radically different outcomes. A little bit of lighting theory – together with some experimentation and tuning, is well worth the effort.

Now for a more complex example – below we could characterize images (a), (b), (c) and (d) as poor, marginal, good, and superior, respectively. Component cost is invariant, but the outcomes are sure different!

To learn more, download the whitepaper or call us at (978) 474-0044.

Color light – above we showed monochrome examples – black and white… and grey levels in between. Many machine vision applications are in fact best addressed in the monochrome space, with no benefit from using color. But understanding what surfaces will reflect or absorb certain wavelengths is crucial to optimizing outcomes – regardless of whether working in monochrome, color, infrared (IR), or ultraviolet (UV).

Beating the same drum throughout, it’s about maximizing contrast. Consider the color wheel shown below. The most contrast is generated by taking advantage of opposing colors on the wheel. For example, green light best suppresses red reflection.

On can use actual color light sources, or white light together with well-chosen wavelength “pass” or “block” filters. This is nicely illustrated in Fig. 36 below. Take a moment to correlate the configurations used for each of images (a) – (f), relative to the color wheel above. Depending on one’s application goals, sometimes there are several possible combinations of sensor, lighting, and filters to achieve the desired result.

Filters – can help. Consider images (a) and (b) in Fig. 63 below. The same plastic 6-pack holder shown is shown in both images, but only the image in figure (b) reveals stress fields that, were the product to be shipped, might cause dropped product, reduced consumer confidence in one’s brand. By designing in polarizing filters, this can be the basis for a value-added application, automating quality control in a way that might not have been otherwise achievable – or not at such a low cost.

For more comprehensive treatment of filter applications, see either or both Knowledgebase documents:

Powering the lights – should the be voltage-driven or current-driven? How are LEDs powered? When to strobe vs running in continuous modes? How to integrate light controller with the camera and software. These are all worth understanding – or having someone in your team – whether in-house or a trusted partner – who does.

For comprehensive treatment of the topics summarized here, see Advanced Illumination’s “A Practical Guide to Machine Vision Lighting” in our Knowledgebase:

This blog is intended to whet the appetite for interest in lighting – but it only skims the surface. Machine vision lights as important as sensors and optics. Please download the guide linked just above – to deepen your knowledge. Or if you want help with a specific application, you may draw on the experience of our sales engineers and trusted partners.

March 28, 2023July 21, 2023

Effilux LED bar lights for machine vision – adjustable and modular!

Effective machine vision outcomes depend upon getting a good image. A well-chosen sensor and camera are a good start. So is a suitable lens. Just as important is lighting, since one needs photons coming from the object being imaged to pass through the lens and generate charges in the sensor, in order to create the digital image one can then process in software. Elsewhere we cover the full range of components to consider, but here we’ll focus on lighting.

While some applications are sufficiently well-lit without augmentation, many machine vision solutions are only achieved by using lighting matched to the sensor, lens, and object being imaged. This may be white light – which comes in various “temperatures”; but may also be red, blue, ultra-violet (UV), infra-red (IR), or hyper-spectral, for example.

LED bar lights are a particularly common choice, able to provide bright field or dark field illumination, according to how they are deployed. The illustrations below show several different scenarios.

LED light bars conventionally had to be factory assembled for specific customer requirements, and could not be re-configured in the field. The EFFI-Flex LED bar breaks free from many of those constraints. Available in various lengths, many features can be field-adapted by the user, including, for example:

Color of light emitted
Emitting angle
Optional polarizer
Built-in controller – continuous vs. strobed option
Diffuser window opacity: Transparent, Semi-diffusive, Opaline

EFFI-Flex user-configurable LED bar

While the EFFI-Flex offers maximum configurability, sister products like the EFFI-Flex-CPT and EFFI-Flex-IP69K offer IP67 and IP69 protection, respectively, ideal for environments requiring more ruggedized or washdown components.

**SWIR LED bar, backlight, and ringlight**

Do you have an application you need tested with lights? Contact us and we can get your parts in the lab, test them and send images back. If your materials can’t be shipped because they are spoilable foodstuffs, hazmat items, or such, contact us anyway and we’ll figure out how to source the items or bring lights to your facility.

**Test and optimize lighting with customer materials**

November 2, 2022November 2, 2022

Components needed for machine vision and industrial imaging systems

Machine vision and industrial imaging systems are used in various applications ranging from automated quality control inspection, bottle filling, robot pick-and-place applications, autonomous drone or vehicle guidance, patient monitoring, agricultural irrigation controls, medical testing, metrology, and countless more applications.

Imaging systems typically include a least a camera and lens, and often also include one or more of specialized lighting, adapter cards, cables, software, optical filters, power supply, mount, or enclosure.

At 1stVision we’ve created a resource page is intended to make sure that nothing in a planned imaging application has been missed. There are many aspects on which 1stVision can provide guidance. The main components to consider are indicated below.

Cameras: There are area scan cameras for visible, infrared, and ultraviolet light, used for static or motion situations. There are line scan cameras, often used for high-speed continuous web inspection. Thermal imaging detects or measures heat. SWIR cameras can identify the presence or even the characteristics of liquids. The “best” camera depends on the part of the spectrum being sensed, together with considerations around motion, lighting, surface characteristics, etc.

**An assortment of lens types and manufacturers**

Lens: The lens focuses the light onto the sensor, mapping the targeted Field of View (FoV) from the real world onto the array of pixels. One must consider image format to pair a suitable lens to the camera. Lenses vary by the quality of their light-passing ability, how close to the target they can be – or how far from it, their weight (if on a robot arm it matters), vibration resistance, etc. See our resources on how to choose a machine vision lens. Speak with us if you’d like assistance, or use the lens selector to browse for yourself.

Lighting: While ambient light is sufficient for some applications, specialized lighting may also be needed, to achieve sufficient contrast. And it may not just be “white” light – Ultra-Violet (UV) or Infra-Red (IR) light, or other parts of the spectrum, sometimes work best to create contrast for a given application – or even to induce phosphorescence or scatter or some other helpful effect. Additional lighting components may include strobe controllers or constant current drivers to provide adequate and consistent illumination. See also Lighting Techniques for Machine Vision.

Optical filter: There are many types of filters that can enhance application performance, or that are critical for success. For example a “pass” filter only lets certain parts of the spectrum through, while a “block” filter excludes certain wavelengths. Polarizing filters reduce glare. And there are many more – for a conceptual overview see our blog on how machine filters create or enhance contrast.

Don’t forget about interface adapters like frame grabbers and host adapters; cables; power supplies; tripod mounts; software; and enclosures. See the resource page to review all components one might need for an industrial imaging system, to be sure you haven’t forgotten anything.