Opto Engineering is known and respected for high-performance lenses in machine vision, medical, and related fields. The new TCSE series are telecentric lenses designed for large sensor formats (4/3″, APS-C, APS-H). Each provides high resolution with low distortion.
Who needs a telecentric lens?
Before inviting you to some of the TCSE series features, let’s offer readers who aren’t already telecentric-savvy a brief motivation for this category of lens. If you are doing precise gauging applications – measuring via optics and software – your tolerances may require a telecentric lens. A telecentric lens eliminates perspective error. They have very low distortion. And, if paired with collimated light, they enhance edge definition.
TCSE lenses are available for applications using light in either the visible spectrum or near-infrared (NIR) wavelengths. Currently there are 8 members in the TCSE product family.
Image circle diameter
The TCSE Series offers image circle diameter options from 24 – 45mm.
A key parameter in telecentric imaging is the level of magnification available. The 8 members of the TCSE Series offer magnification ranging from 0.36 through 2.75 times the original object size.
The working distance (WD), from the front of the lens to the object being imaged, varies by lens model across the TCSE Series. The shortest WD offered is 160mm, spanning distances up to 240mm. These long working distances allow space for lighting and/or robotic arms.
While typically “plug and play” once mounted on your camera, it’s worth noting that the TCSE lenses offer back focal length adjustment, should one choose to fine tune.
Telecentric lenses are the core business for Opto Engineering, who have more than 20 years expertise in research, development, and production. 1stVision, North America’s largest stocking distributor, works to understand each customer’s application requirements, to help you select the ideal lens, camera, or other imaging component(s). Call us at 978-474-0044.
While a standard lens is adequate or even ideal for many machine vision applications, there is inherent distortion in a standard lens, often in the range of 1 – 2%. Telecentric lenses achieve distortion of 0.1% or less. They also provide constant magnification and no perspective error.
If you “just” need presence/absence detection, or counting discreet non-occluded objects, a conventional lens may be fine. But if you need highly accurate contactless measurement, telecentric lenses offer remarkable performance.
Let’s take a brief look at what qualifies a lens as telecentric, and why you might want (or need) one. Subsequently we’ll summarize Edmund Optics SilverTLTM and CobaltTLTM lens series.
Telecentric lenses only accept incoming light rays that are parallel to the optical axis of the lens. It’s not that the oblique rays don’t reach the outer edge of the telecentric lens. Rather, it’s about the optical design of the lens in terms of what it passes on through the other lens elements and onto the sensor focal plane.
Hmm, but the telecentric lens must have a narrower Field of View (FoV) – and I have to pay a premium for that? Well yes – and yes. There are certain benefits.
Let’s get to an example. In the image immediately below, labeled “Setup”, we see a pair of cubes positioned with one forward of the other. This image was made with a conventional (entocentric) lens, whereby all three dimensions appear much the same as for human vision. It looks natural to us because that’s what we’re used to. And if we just wanted to count how many orange cubes are present, the lens used to make the setup image is probably good enough.
But suppose we want to measure the X and Y dimensions of the cubes, to see if they are within rigorous tolerance limits?
An object-space telecentric lens focuses the light without the perspective of distance. Below, the image on the left is the “straight on” view of the same cubes positioned as in “Setup” above, taken with a conventional lens. The forward cube appears larger, when in fact we know it to be exactly the same size.
The rightmost image below was made with a telecentric lens, which effectively collapses the Z dimension, while preserving X and Y. If measuring X and Y is your goal, without regard to Z, a telecentric lens may be what you need.
Depth of Field can be “pushed”
You are likely familiar with Depth of Field (DoF), the range in the Z dimension in which objects in the FoV are in focus. With a conventional lens, if an object moves out of focus, the induced blur is asymmetrical, due to parallax (aka. perspective error).
But with a telecentric lens, there is no parallax error, since the FoV is constant and non-angular. A benefit of this is that even if the target image is somewhat defocused with a telecentric lens, the image may still be perfectly usable.
In the two images below, the “sharp transition” edge is clearly optimal. But when measuring tolerances in a manufacturing environment, with mechanized conveyors, vibration, etc., target objects may not always be ideally positioned. So the “shallow transition” image from the object just out of focus is entirely acceptable to identify the center of mass for the circular object, since the transition is symmetrical at all positions.
Edmund Optics is widely recognized for their range of standard products – and their expertise in custom lens design when needed. The SilverTLTM and CobaltTLTM lens series each offer 10+ members, where all lenses are high-resolution and bi-telectric. Some additionally offer inline illumination options.
Noteworthy characteristics of both the SilverTL and CobaltTL series include:
Aperture controls often not available in competitor products
“Fast” ==> lower F# options than in many competitor products (so can work effectively with less light)
Conform to narrowly specified engineering tolerances
Pricing identical with or without in-line illumination via coax port
Edmund Optics SilverTLTM series
The SilverTL series pairs with C-mount sensors up to 7.5 MegaPixels, ideal with 2.8 µm pixel size. Magnification options range from 0.16X to 4X.
Edmund Optics CobaltTLTM series
For C-mount sensors up to 20 MegaPixels, and pixel size 2.2 µm, choose the CobaltTL series.
What type of lens is best for my application?
Machine vision is a broad field, with a lot of variables across wavelengths, application goals, sensor, software, and lens choices. If you are a seasoned veteran, you may know from experience exactly what you need. Or you may want to review our on-line knowledge base or online blogs. Easier yet – just phone us at 978-474-0044. You’ll speak with one of our sales engineers, who put customer success first. Customers with successful outcomes – who return to us project after project – is our goal.
Who needs 360° optics? Granted, it’s specialized stuff. Innovative lenses in Opto Engineering’s series enable single-camera inspection of objects many users might not have thought possible! For example, a Bi-Telecentric system uses mirrors to image all 4 sides of an object at once, without moving the camera or the object. Or a boroscope gets the optics and a light inside a tight space, creating a panoramic view of the interior.
Even experienced machine vision professionals may never have seen or heard of some of these specialized optics. Unless one knows of such lens systems, one might try to design a multi-camera system for an application, when in fact a single camera could have been used!
In the segments below, we highlight categories for which there are lens series available, together with representative images, diagrams, and texts. The goal here is not a master class in optics – just an overview to raise awareness.
Opto Engineering provides pericentric lenses, allowing 360° by 180° FOV from a position above an object. That provides 360° top and lateral views with a single camera. The PC Series, with five choices, are designed to perform complete inspection of objects up to 60 mm in diameter. Typical applications include bottleneck thread inspection and data matrix reading – the code will always be properly imaged regardless of its position.
Suppose you produce and pack a product in a plastic container such as the one shown here. Quality control inspections may require verifying each container is labeled with print, graphical, and/or coded information. Image courtesy Opto Engineering.
Below we see the top and sides imaged in a single exposure, using a PC lens:
The PCCD Series, with four members, enables the 360° side view of small objects (sample diameter 7 – 35 mm). Perfect for bottle cap and can inspection.
Above, the top image is generated from a lens that uses both reflection and refraction to image the vial’s interior as well as the exterior “shoulder”. The interior check is for any impurities before filling, and the exterior aspect is to obtain OCR characters or bar codes for tracking.
Hole inspection lenses
The PCHI Series includes 10 members, covering a range of sensor sizes, and includes a liquid lens option for adjustable focus control. Unlike a common lens with a flat field of view (FOV), these lenses provide a focused view of both the cavity bottom as well as the interior sidewalls! Perfect for thread inspection or cavity checks for contamination from above the cavity entrance.
PCHI Series hole inspection lenses and applications – Image courtesy Opto Engineering.
Bi-Telecentric lens systems
Many are familiar with telecentric lenses, which hold magnification constant, regardless of an object’s distance or position in the field of view. Consider Opto Engineering’s Bi-Telecentric Series, TCCAGE. Using multiple mirrors, parts can be measured and inspected horizontally from each 90, with no rotation required. Two different illumination devices are built into the system to provide either backlight or direct part illumination. In the example to the right, syringes are inspected for length and angle from all 4 directions.
Image courtesy of Opto Engineering.
A boroscope gets the optics into tight spaces, for panoramic cavity imaging from the inside. The PCBP series includes built-in compact illumination. It’s ideal for 360 degree inspection of interiors with static parts.
Image courtesy of Opto Engineering.
In addition to fixed focus and manual focus (with lockring) options, some lenses in the PCHI and PCBP Series include Adjustable Focus (AF) features. With liquid lens technology, using AF these lenses with varying product sizes and dimensions just got easier. With millisecond repositioning, it allows extremely fast changes to focus to allow you to dial in the exact position on multiple size products or sizes for inspection of an even wider range of SKU with a single system.
If your imaging application can be solved with more conventional lenses, lucky you. But if your requirements might otherwise be impossible to address, or seemingly need two or more separate cameras, or complex rotation controls and multiple exposures, call us at 978-474-0044. You might not have realized there are specialized optics designed precisely for your type of application!
Short wave infrared (SWIR) imaging is a specialized segment of machine vision, applying automated imaging outside the human-visible spectrum. Able to see through opaque plastic bottles to verify or control fill levels, inspect fruit for bruising, sort recyclables, inspect silicon wafers, etc., SWIR applications require SWIR-specific sensors, cameras, and lenses.
Visible vs SWIR image of same targets – image courtesy of TAMRON
TAMRON Wide Band SWIR lenses are designed for Sony IMX990 / Sony IMX991 sensors and other sensors with a 5µm pixel-pitch. These wide band lenses feature the capability to work in a wide range of wavelengths from the visible range to Short-Wave Infrared Range (SWIR 400 – 1700nm). In addition, TAMRON’s new proprietary eBAND anti-reflection lens coating technology provides 80% constant spectrum transmittance over the whole visible to SWIR spectrum.
Tamron wide-band SWIR lens series – Image courtesy of TAMRON
Vein imaging application overlays SWIR image of veins into visible image of patient forearm – Image courtesy TAMRON
Monitor moisture levels in crops from airborne drone – Image courtesy TAMRON
Banknote under visible light (left) and SWIR (right) – Images courtesy of Allied Vision
Opaque and clear plastic bottles in visible light (left) and SWIR (right) – Images courtesy of Allied Vision
Cool applications! Would 1stVision happen to carry any cameras that utilize the SONY sensors for which these TAMRON lenses are designed? Yes, of course:
So far we’ve got SWIR lenses, sensors and cameras, the latter with several interface and performance options. How about SWIR lighting, to create the proper contrast? We’ve got that too. Call us at 978-474-0044.