Camera interface standards

It's my impression that the machine vision industry has pretty much standardized on one interface. It’s GigE for area or matrix cameras, leaving USB3 to the scientific/medical community and falling back on CameraLink for linescan applications. (Though I notice Dalsa now has a family of GigE linescan cameras.) However, I know other industries like other formats.

So, when I saw a post on the excellent Adimec blog asking, “Which digital video interface is best for global security systems?” I didn’t expect to learn much. But there were a couple of interesting snippets.

First, regarding GigE, “Processing required to pack and unpack video generates additional heat and uncertain latency…” Now that is news to me. Yes I have noticed a couple of my favorite GigE cameras seem to run very hot, but I hadn’t compared them with USB3 equivalents. Now I think I will.

Second, someone seems to have a bit of a downer on USB3:

“Cons

• Large connector and interface driver
• Maximum throughput unpredictable (chipset, PC motherboard and driver dependent)
• Sustainable speed is much lower than theoretical limit
• Unreliable operation with longer cables (>3 m)”

Interesting points. There’s been so much hype over USB3 that the downsides seem to have been forgotten. Good to see Adimex removing the rose-tinted specs.

This is why it’s important to keep reading the machine vision blogs. You never know quite what you’ll learn. (And kudos to Adimec for providing consistently good content.)

Newsflash: Machine Vision Camera-maker Thinks You Should Buy More Machine Vision Cameras!

This comes from Basler, who suggest it’s time to ditch Firewire/1394 for USB 3.0. A White Paper on their website sets out their reasoning, some of which makes sense and some of which I would question.

Four arguments are presented: 1394 hardware will disappear, Windows 8 doesn’t support it, the bandwidth is insufficient, and it will save you money.

The first two of these I agree with completely. Indeed, it’s been several years since I developed anything with Firewire, preferring to use GigE instead. So yes, new systems should not be developed with this outdated interface. But if the system is in-service and working well, why would you change?

The bandwidth argument makes no sense, and how will replacing cameras that still work save money?

Bottom line: if you’re developing applications with Firewire interfaces you’re building-in obsolescence. But if your old Firewire systems still perform the way you need, stay with them.

I suppose I should add one caveat: smart engineers will be looking ahead at how they would replace the old systems when they do fail.

USB3 cable lengths

USB3 is attracting attention from machine vision users, and for some cable length is a concern. Back in August (“USB3 Vision Clarification”), I said I understood the maximum length to be 3m, but Andy Wilson has provided an update.

If you read “USB 3 Vision: Extending camera to computer interfaces” you’ll learn that “Alysium-Tech has tested passive USB 3.0 Vision industrial cables … running at distances of up to 8m.”

That’s helpful, but it may not be enough. If that’s the case, Andy suggests you use an active USB3 cable, such as those available from Components Express or Icron. Those, apparently, will get you up to 100m, using fiber, which should be enough for most users.

If you need longer, there are other camera interface formats.

USB3 Vision Clarification

If you read the Comments my ramblings sometimes attract you’ll see that “USB3 Vision versus GigE Vision” drew some questions. As the writers took the time to read what I had to say I’d like to pay them the courtesy of a reply.

First off, I should have cited my sources. Most of my information came from the Basler paper referenced in “Understanding USB3 Vision” although I did pick up a few other points from Stemmer and others. Regrettably, I didn’t save the links but if you Google “Advantages of USB3” or some similar phrase you’ll find the pages I used. Lesson learned.

And now, to the questions (or should that be answers?):

• Regarding USB3 cable length – yes I’m sure you can use repeaters but everything I’ve seen says the effective limit is around 3m.
• On cable security – I meant the provision of screw-in connectors, but I also included immunity to noise. It’s my understanding that USB3 cables offer superior construction in this regard.
• On how I calculated the CPU load scores for USB and GigE – confession time – I didn’t calculate anything. It was a subjective assessment again based on what I read in the Basler paper. In my defense, my intention was to highlight relative strengths and weaknesses rather than assign absolute scores, and I think I accomplished that.

If anyone has any different information that runs counter to what I’ve said, I’d be glad to hear from them.

USB3 Vision versus GigE Vision

If you couldn’t wade through the presentation I offered in my last post, “Understanding USB3 Vision” here’s a graphical comparison of the two interface formats.

I think the message here is that USB3 is a good choice when you have large images from single camera systems and you don’t need a long cable length. However, most single camera machine vision applications are, in my humble opinion, best met with smart cameras. If you go towards a PC solution you’re probably using either linescan or multiple cameras, in which case I think you’ll want CameraLink or GigE.

In other words, I’m still on the fence about the benefits of USB3 in machine vision.

Understanding USB3 Vision

Machine vision camera companies are starting to really push their USB3 products, (yes Point Grey, I am talking about you,) so you may be wondering if it’s time to pay attention.

If you are interested in getting a better understanding of the technology and what it means, here’s a link for you. “USB 3 Vision” is a presentation given by Dr Joachim Linkemann, Product Manager at Basler, at the NH Conference Center Koningshof, Veldhoven, May 22^nd, 2013. That means it’s about as current as can be, and also that it opens up as a pretty sizeable pdf document.

Naturally, the document does “plug” Basler cameras, but you can overlook that and just focus on the technical “meat”, of which there is plenty. I’d go so far as to say this document should be required reading for anyone contemplating using a USB3 camera.

Good results from Basler

It’s good to see German camera-maker Basler doing well. There was a period when their results were kind of flat, but that’s certainly not been the case in 2013. In fact, with sales up 28% to €32.2m at the half and earnings up 77% you could say business is booming. The only fly in the ointment would seem to be the cash flow, down 30%. But as that probably stems from the sales growth I doubt it’s really a problem (in my unqualified opinion anyway.)

As for why business is so good, well Basler management points to three factors: strong demand for GigE cameras, growth in Asia, and a pruning of end-of-life models. I’d suggest there’s a fourth factor at work too. Now they’ve got out of the “Solutions” business they’re able to focus just on making cameras.

There were a couple of other points in the reports that I’d like to share. R&D spend was up 7%, but actually fell as a percentage of sales. I can understand a reluctance to twist the R&D tap based on just six months of sales, but assuming the volume of business remains stable, or even continues to grow, I would hope to see more R&D investment in 2014.

And second, a comment I found interesting was, “… we see our expectations confirmed predicting that GigE Vision and USB3 Vision will be the dominant interface technologies for industrial cameras in the years to come.”

I would agree that GigE has clearly become the default choice and has left FireWire for dead, but USB3? Personally, I think the jury is still out. I’m not even sure if there’s room for two “mainstream” interfaces. Isn’t that just going to create additional complexity and cost?

But leaving that debate for another time, it’s good to see Basler looking healthy. It bodes well for our industry.

One less barrier to using USB

There are a number of USB machine vision cameras on the market. (Lumenera is one such manufacturer.) But the concern I have is about cable security. Those push-in, pull-out connectors are fine and dandy when I’m connecting my Nikon DSLR at home, but in the factory I need something more robust.

Recognizing this need, B&B Electronics has introduced a “high-retention” USB port. You’ll find it on their Four Port USB 2.0 Hub, and other products, and if you want to see it in action, watch the video here.

Now being an engineer of sorts, I’d prefer data to just watching a dude pull the cable out, but it sure looks like the cables are held tight.

If you’re thinking of using a USB camera out on the factory floor, this is one less barrier to deal with.

Camera trends

The love-fest that is Vision 2012 is less than a month away and already vendors are giving us sneak-peeks at their latest and greatest. Some of the most intriguing come from camera-maker AVT who, besides some ho-hum range extensions, have an entirely new product, the Mako.

As I write this, the Mako page on the AVT website doesn’t have any content, so instead I will direct you their press release. Now this camera looks much like the reliable old Guppy, but whereas that was a FireWire camera, this will be offered with both GigE and USB3 interfaces.

I see that as highly significant. In fact I’d go so far as to say it means FireWire is on its death-bed, at least in the machine vision world. Some years back AVT saw how the wind was blowing when they snapped up Prosilica, thereby gaining a GigE product line up, and now they’re backing the new USB standard. I’d say that means the future is GigE and USB3, for everything except really large sensor formats and very high data rates.

Just out of curiosity, does anyone think we’ll see a linescan USB3 camera before the year end?

USB 3 Camera from Ximea

I’m getting more interested in what USB 3 can do for us in machine vision. A month ago I mentioned that Point Grey had some good info on their website, (“Everything you ever wanted to know about USB3.0”,) and now I’ve found that relative newcomer Ximea has a camera that runs even faster.

Curiously though, I didn’t learn this from Ximea themselves. It was the Polish RkBlog, specializing in “Python, Linux, Astronomy”, that drew my attention to the xiQ013MG-E2. (Boy how I love those snappy names the techies come up with!)

I’m not going to tell you about the camera, because RkBlog has done a pretty decent first-pass review, so take a look at what they had to say under “Testing fast USB3 camera - Ximea xiQ MQ013MG-E2”. I will mention though some intelligent discussion about what interface card to use. (Hint: don’t plug the cam into the motherboard and expect everything to work.)

Another twist to camera interfaces

With various groups making plays for their preferred new standard – USB 3.0, CameraLink HS and CoaXPress – camera interfaces are in the news of late. Everyone talks about data rates and cable lengths - I’ve done my part, with “King of the (camera interface speed) hill” and “Everything you ever wanted to know about USB3.0” – but writing in the Adimec blog, Gretchen Alper offers another factor to consider: the cost of the cables. (“How to save cabling costs with new machine vision interfaces” August 29^th, 2012.)

Now I knew that CameraLink cables were expensive, but I hadn’t appreciated just how expensive in comparison to GigE, FireWire, USB 3.0 and CoaXPress. (Read Gretchen’s blog post to see the actual numbers.) CoaxPress is of course just plain old co-ax cable, which is why it’s so cheap. As backers of this new standard, Adimec aren’t exactly neutral, so I would expect them to have done their best to ‘spin’ the cable cost issue, but even so, the numbers are pretty startling.

I wonder if this might change your choice of interface next time you spec out a system?

Everything you ever wanted to know about USB3.0

If you read my post “King of the (camera interface speed) hill” you’ll have noticed the new USB 3.0 interface offers seriously fast data transfer. While 3.0 isn’t supported by Windows 7 (I believe it will be part of 8,) you may still be curious about how to take advantage of it in your machine vision applications.

Canadian camera-maker Point Grey has been at the forefront of USB3.0 imaging, and to help smooth the way for early adopters they’ve posted a pile of info on their website. To make your life easy, here’s a link that takes you straight to their USB 3.0 Technology Updates page.

You’re welcome.

King of the (camera interface speed) hill

Most of us were happy with FireWire-b and had no need of faster data rates. Then along came GigE and the bits flowed faster. If we needed real speed, like for those occasional linescan projects, there was always CameraLink.

But just as racing drivers always want more, so too do some machine vision people. Many of these are in the high speed web inspection niche, and they were starting to think that good old CameraLink might not be up to the job in a few years. So Dalsa started work on an interface they called “HSLink”.

This showed a lot of promise, but as Mike Miethig of Dalsa discusses in “Vision Market Touts Camera Link HS in Boston, Beyond” (Quality magazine, August 7^th, 2012,) it never really gained traction.

Fortunately for the speed freaks though, it did set the scene for CameraLink HS, which promises speeds of up to 2.1Gbytes/sec. Now that number might be hard to grasp, so I’ve put together a little graphic to show just how much faster than the older standards that is.

 

 

Now there are some important caveats. CameraLink speeds are complicated because they depend on whether it’s Base, Medium, or Full configuration. CameraLinkHS is much the same: there are three speed flavors, starting at a relatively paltry 300Mbytes/sec. And then, missing from my table, is CoaXpress.

CoaXpress boasts of up to 6.25Gbps, (which I suspect is gigabits rather than bytes,) so it’s not a s fast as CameraLink HS. More importantly, it’s not an AIA standard – it’s supported by the Japan Industrial Imaging Association – so whether it will prosper remains to be seen.

And what does this mean for the regular machine vision user? It means there’s virtually no limit to how fast you can shove those pixels down the pipe. The only question to consider is, how deep are your pockets?

Interesting new camera

Point Grey has just announced an 8.8 Mp version of their compact Flea 3 USB 3.0 camera. Inevitably, packing an array of 4096 by 2160 pixels into a C-mount format sensor means the pixels are pretty darned small, and that’s where this is interesting.

This hi-res Flea 3 is using a Sony IMX121 color sensor with pixels just 1.75 microns in size. On learning that, my first thought is “poor sensitivity and high noise,” but that might not be the case. Sony are making a big deal of their “Exmor R” CMOS sensor technology that effectively switches the positions of the internal wiring and the photon-capturing silicon. (Click the link to see a great animation of how it works.)

This, it is claimed, increases sensitivity by 6db and reduces noise by 2db. Those might not seem big numbers but remember that it’s all logarithmic. Sony has one comparison image posted on their site; it would be interesting to see a few more.

Two last points to mention: the camera puts out 21fps at full resolution, which is a pretty impressive number. Good thing USB 3.0 offers 5Gbits per second of bandwidth! And pricing? $945, which seems like a bargain.

Yet another camera communication standard

FireWire, GigE, USB 3.0 … do we need another standard? Well some machine vision users do, yes.

The problem is that every standard has its strengths and weaknesses. I touched on this last month under the heading of “Pros and Cons” (take a look for details,) so some users want something that does better – “better” usually meaning higher speeds over long cable lengths.

That’s where CameraLink High Speed (CLHS) comes in. Promoted by Teledyne Dalsa, this aims to be “future proof” so as you upgrade to ever higher resolution cameras the infrastructure can remain unchanged. Personally I think this is more of an issue in traffic and surveillance applications, but it’s something we industrial/manufacturing types should be aware of.

So how do you learn more? Well as always, you click the link I shall provide. In this case it takes you to “Vision & Sensors: Machine Vision Standards”, published on the Vision & Sensors site, March 8^th 2012.

Be aware though that CLHS may not be the last word in camera interfaces: there’s CoaXPress too.

Pros and Cons

“Mr. Grey,” the email began. Oh how I love that olde worlde formality. “I see some machine vision cameras now use the USB3.0 interface. Should I switch from 1394?”

If only I could offer a clear-cut yes or no answer, but unfortunately the world doesn’t work like that. Instead, I have to go with the standard integrator response of “It depends.”

USB3.0 has some attractive features for machine vision, most notably speed approaching that of CameraLink and power through the same cable, but in other regards it’s less than ideal. Cable length is limited, though you can add repeaters, and while it’s less of a CPU-hog than USB2.0 it’s still not as good as 1394b. A bigger concern in my view though is lack of Windows support. It’s my understanding we’ll have to wait for Windows 8 to take full advantage of the 3.0 ports now appearing on PC’s.

For those interested in learning more, there’s a great FAQ on the website of camera-maker Point Grey (no, we’re not related.) If you scroll through the Q’s you’ll eventually come to a table comparing the merits of the various interfaces (the latest high-speed systems have been omitted.) Now bearing in mind that Point Grey are in the 1394 and USB camera business, what surprised me is that 1394 still seems a good choice for run-of-the-mill applications where the speed demands aren’t extreme. On the other hand, while USB3.0 seems not to excel at anything, it clearly has the potential to be a good choice overall.

So to answer my email friend’s question – should you switch from 1394 to USB3.0? Right now I would say no, unless you want to be at the cutting edge. Personally, I’ve been cut enough over the years, so I’m going to hang back and let others iron out the bugs. But ask me again in twelve months and I may have a different answer.

Aspect ratios and wine bottles

Despite all the growth, machine vision is still a niche industry. We’re not big enough to have the semiconductor guys make sensors just for us (leaving the linescan sub-niche out of the discussion,) so instead we have to make do with what’s churned out for consumer applications. Most of the time this isn’t a problem, but there are times when I find I’m throwing away a whole bunch of pixels.

Example? Well imagine viewing a wine bottle from the side. This has an aspect ratio something like 16:4 so to get the whole thing on a typical 16:9 aspect ratio sensor I have to include a whole lot of empty space in my image. Wouldn’t it be useful to have a long thin sensor?

Well, while I was reading up on Ximea’s USB3 cameras I spotted such a thing. Their sexily-named MQ022MG-CM has a CMV2000 sensor of 2048 x 1088 pixels. Now this sensor may be used by other camera vendors too, I haven’t bothered looking. It just struck me, while downing a glass of merlot, that long, thin sensors would be a useful thing to have.

Size wars

If you took the time to follow my links to USB3 camera manufacturers, you might have noticed something interesting. Point Grey have been very eager to boast of their Flea3 being “the world’s smallest and fastest USB 3.0 cameras…”). And at 29 x 29 x 30mm, it is pretty darned small. But along comes Ximea with their MQ series of “Ultra-compact USB 3.0 camera[s]”. Dimensions on this are 26.4 x 26.4 x 19.1mm, so it’s smaller.

Now I struggle to imagine an industrial application where the Flea would be too big, but it’s amusing all the same. For some folks, size is very important.

And that’s all I have to say about that.

USB3 fit for machine vision?

USB cameras have never really been adopted for machine vision. Yes there are some products on the market – Lumenera seems to be leading the pack – but they’ve failed to break through. As I understand it, this is mainly due to the way USB tends to hog more CPU time than does FireWire or GigE, and because it’s difficult to have more than a single camera per PC.

Things seem different with USB3. This interface seems to be building a head of steam with vendors such as Point Grey, Ximea, and Basler all launching USB3 cameras.

What does that mean for we end-users? I think it means life just got a little more complicated. There I was, getting to grips with GigE, learning how to address the cameras (not as easy as the vendors would have you believe,) and now they expect me to try something else. And what does USB3 give that GigE doesn’t?

I’m not sure I know. Speeds are broadly comparable and cable lengths are plenty long enough for my industrial needs. One difference might be that USB3 supplies power, so I can save on a separate power supply. Yes, I could go PoE but that doesn’t really seem to have broken through, so camera choices are limited.

I don’t know about you, but I think I’ll hang back and watch how this all pans out.

USB 3.0 for machine vision

A little over a year ago Point Grey started talking about their USB 3.0 cameras. Around the same time the AIA started to explore what might be the most appropriate protocols for machine vision USB 3.0. So what’s happened since?

On paper, and as discussed in this excellent article from Advanced Imaging magazine from March 2010, USB 3.0 has a lot going for it as a machine vision interface. Obviously, it’s going to provide fast data transfer, which will help as resolutions and frame rates continue to rise, but it also offers more power, which makes life easier for camera designers and those users who want only a single cable. But we’re approaching the middle of 2011 and I’m not sensing a groundswell of support for 3.0. Frankly, both consumers and the machine vision industry seem pretty uninterested.

My feeling, and I’d like to hear your views on this, is that with GigE, CameraLink, CameraLink HS and CoaXPress we have more than enough options. (And that’s not forgetting that FireWire still has a lot to recommend it for lower-end applications.) In other words, for machine vision USB 3.0 is something of a dead end.

Unless something was to come along to change that, which I think might happen.

I have to wonder if there’s a new and improved version of the Kinect in the works. This would provide higher resolution and higher speed, which would in turn require bigger and faster camera sensors. Follow that line of thought and you’ll see that Kinect II might have to be a USB 3.0 device. If that happens, expect to see vision integrators using it for robot guidance applications, with the costs of such systems tumbling.

USB 3.0 for regular machine vision? No, but for 3D work it may be the way forward.