Detecting part orientation

When you’re assembling components orientation is usually critical. That becomes an even bigger issue when the assembly is automated, but machine vision can of course help out.

European vision components distributor Framos has an interesting example in the Case Studies section of the website, (though it was Vision Systems Design (VSD) that first brought it to my attention.) This describes an application where it was essential to know if one component was tilted. The solution was to …

Click the links to find out more, but I will say it involved projecting a pattern. A classic case of a priori knowledge; knowing what the pattern should be, it’s possible work out why it appears differently.

One side note for you: GigE cameras from Smartek were used. I’d never heard of them so I followed the links from the VSD article. Turns out they’re a newish camera manufacturer based in Croatia. I couldn’t find out pricing on their range of matrix cameras, but I would guess they can undercut Basler by a few Euros.

Building better cameras

Bad news: that $3,000 camera you just bought isn’t perfect. But it’s not just your camera. No camera is really perfect.

As every good mechanical engineer will tell you, tolerances and variation in manufacturing mean that the sensor, (that little square of photon-capturing silicon,) is not going to sit exactly on the optical axis of the lens, and neither will it be perfectly perpendicular.

Depending on just how the sensor is mounted, this means that the image will be slightly out of focus in some areas. Most likely, I’m surmising, across diagonal corners. In most machine vision applications this might not matter, but I suspect that as resolutions increase and pixels get smaller it will become more of an issue.

Good news: Kasalis, who build machines that mount CCD and CMOS sensors, are working on ways to improve sensor positioning. I learnt this from “Adaptive software eases camera lens-to-sensor alignment” published in Laser Focus World, March 2013, but you can find out more by visiting the “Active Alignment” page on the Kasalis website.

If you’re wondering why you should be interested, let me briefly explain. If you use cameras you should (a) know how they work, and (b) understand what differentiates the inferior from the superior. Clearly, one such factor will be the precision of the sensor alignment, for which we will no doubt be charged a premium.

New cameras at Automate

File this under “things to look for in a few months.”

Both JAI and SVS-Vistek spent some time telling about their new cameras. JAI have adopted a color – a jazzy metallic green – and have two new families on the way, the Spark and the Elite. If you know the JAI product line, you’ll realize that this represents a significant change in marketing approach: until now it was a case of “any color you like so long as…” well you know.

SVS-Vistek are also doing some interesting things, most notably their evo-Tracer which has a “Micro four thirds lens mount.” Translation: it’s a bayonet fitting that provides focus control. It looks really cool, but it’s not on their website. Check back later, I guess.

And last but not least, German camera-maker NET had a wireless smart/PC camera on their stand. Dubbed the Corsight, this is one of those PC-in-a-box products, but with wireless capability. I can imagine it being very useful in situations where I don’t want or can’t string an Ethernet cable through the plant. But it’s not on their website yet.

Final thought: it’s good to tease potential customers with next-generation products, but maybe a little more coordination between the webmaster and Marketing would be a good thing?

Who over-engineers their cameras?

There seem to be two schools of thought when it comes to the design and development of new products. One group argues that providing anything more than the minimum needed to meet customer expectations is waste. The opposing view seems to be that the customer should be delighted by all sorts of features he didn’t realize he was getting. Of course, the latter will result in more expensive products, but if customers love them maybe loyalty is higher.

Basler though seem to be opting for the former, minimalist, approach, at least if this movie about their ace camera is any indication.
 

 

Watch closely and you’ll see a little tag line saying “no over-engineering.” I’m curious about this. It sounds as though they’re having a dig at a competitor, but who? When I run through my mental list of camera manufacturers I don’t match any to the phrase “over-engineered.” Whoever can they mean?

A really smart camera

More than once I’ve extolled the merits of liquid lenses that can be focused through software. Now it seems SVS-Vistek has taken this further with their new EVO-Tracer camera.

Accordingly to the press release, (there’s nothing on the SVS-Vistek website as I write this,) “Focus, iris and zoom are now controllable directly from the camera over the GigE Vision interface without any additional cabling.”

I’m hugely excited about this and can’t wait to get my hands on one. If I could get to Vision 2012, where I imagine SVS-Vistek will have a camera on display, I would, but unfortunately I have projects to attend to in other parts of the world.

Camera sales going well

German camera-maker Basler published their third quarter results today, the 6^th, and they look surprisingly good. Well they surprised me. Previous quarters haven’t look too rosy, and with all the talk of a downturn in Europe, plus comments from Cognex to the effect that Q3 is never great, I was expecting a dip in both revenues and income.

To my surprise, I was wrong. (Well it had to happen sometime I suppose.) Comparing the first nine months of 2012 with the same period in ’11, things don’t look so great. Revenue was up just 1% while income (profit, to my British readers,) was down 15% to €14m. But compare Q3 and you see a very different picture with both revenue and income up 26% to €16.6m and €2.4m respectively.

What are we to make of this, dear reader?

Well there are some new products – the runner, pilot and ace all debuted relatively recently – but also, Basler has a strong and growing presence in the traffic marketplace. Basler then, seem to be building momentum, and I think this tells us that machine vision continues to be a technology whose benefits outweigh costs. Thus, even when belts need to be tightened, advanced cameras are still in demand.

Good news for all of us I think.

Camera pricing

Point Grey sent me an email – you probably got it too – saying that the latest additions to their Flea series are priced at $995.

I haven’t purchased a machine camera for a while, but that strikes me as a competitive price for a 2.8Mp GigeE unit with a Sony CCD sensor. Time was I used to calculate the price per megapixel – call it the Grey Index – and just last year I was paying $500 per Mp. This camera, the FL3-GE-28S4C or S4M if you want the monochrome version, works out at $335 per Mp.

Cameras keep getting cheaper.

We need a new camera mounting system

Here’s something to file under “Why, oh why?”: Machine vision cameras need to be mounted on a plate of some kind. To make this possible the manufacturers usually provide a number of small threaded holes – typically M3 – to which a bigger plate can be fitted. But the bigger camera mounting plate typically has a single ¼-20, or possibly M6, screw thread.

This makes no sense to me. Securing a camera with a single screw means it’s going to move. It’s just not a robust, industrial, mounting. So why not put two holes on a 1” or 25mm spacing? Wouldn’t that make for a more depending mounting?

And while we’re at it, let’s go further. Would it be possible to tie down the relationship between sensor mount, the M3 threads in the camera body, and the ¼-20/M6 threads in the mounting plate?

What I’m asking for is that when I engineer a mount I can bolt the camera in to place and know with some certainty that it’s pointing in the right direction. I don’t want to nudge it left and right while watching a monitor until it’s pointing the right way. You know what happens then: I clamp it down and it moves, so I have to repeat the exercise. Can’t cameras be engineered to just bolt right in?

Is this too much to ask?

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.

Let’s hear it for the Swiss

Today, for no other reason than that I think they have an interesting product family, I’d like to give a “shout out” to Leutron Vision. For some thirty years the good people of Leutron been making cameras in their factory near Zurich, yet few in the machine vision world know of them, so let’s change that.

There are two things I find interesting about Leutron.

Number one is that they were one of the pioneers in the field of PC cameras. Today they have Intel Atom-based cameras that will run a variety of vision software products, but they were getting in to this some four or five years ago.

Number two is their Simplon Software Developer Suite. This comes with programming libraries and a set of tools for camera control, but the cool thing is the code generation capability. In other words, use Simplon to set up your application, then turn it into code that actually runs the application. Best of all, and I’m 99% certain about this, Simplon is free.

So here’s the bottom line: if you’re interested in PC cameras, or just want to see what less mainstream camera vendors have to offer, check out Leutron Vision. I think you’ll find it interesting.

New cameras

Over the last few days there’s been a torrent of new product announcements from German camera manufacturer AVT. Might this be connected with the Vision show held last week? How naive do you think I am?

Cynicism aside, these are some interesting products. Let’s start with the 6 Mp Prosilica GX2750. This uses a Dual GigE Vision® interface to deliver full-frame images from its CCD sensor at 19fps. Impressive numbers, to be sure. I have to say though, since I believe the pixels are just 4.5 microns and the cooling fins imply considerable heat generation, I am a little concerned about noise in the images.

Perhaps then I should look at their cooled camera, the AVT Bigeye with Active Cooling. Presumably resulting from the acquisition of VDS, this features a Peltier cooler to reduce noise. I have a feeling this is something we shall see more of as pixels shrink and resolutions grow.

Last off, (and I lack a good segue into this,) is the AVT Bonito. This is an impressively fast camera – 4Mp at 386fps – but what really intrigues me is the interface: CameraLink.

Okay, there’s nothing particularly earth shattering about CameraLink, but it’s new for AVT. They started out with FireWire, moving into GigE with the acquisition of Prosilica. And now CameraLink?

If other camera companies weren’t already paying close attention to AVT before, they should be now.

Trends in machine vision cameras

CameraLink provides the highest robustness and data rates, FireWire has been superseded by GigE, and USB is irrelevant for machine vision. Oh, and by the way, resolutions are going up.

Well that’s what I told an engineer who emailed me a few days ago asking if he should stick with FireWire cameras, but let’s take a moment to dive deeper.

Few in machine vision would argue that CameraLink, for now at least, provides the best overall performance. It can handle the highest data rates, (up to 6Gbps with 2 cables,) works over cable lengths as long as 10 meters, (enough for most industrial applications,) and never misses a frame, but it does have downsides. Chief among these is cost. CameraLink needs a framegrabber, which can easily cost $500 or more. It also needs special or custom cables – yet more cost. And since Power-Over-CameraLink (PoCL) doesn’t seem to have really caught on, perhaps because it’s limited to 4W, figure on running two or three cables out to the camera.

So what about the alternatives? Well let’s start with USB. Every computer has a USB port, so there’s no need for a framegrabber, making it seem attractive. But when you dig down into the details the problems start to emerge. The basic issue is that USB is something of a processor-hog, thanks to its employing a master-slave architecture. There are also bandwidth issues, meaning that a significant proportion of its 480Mbps is not available to transfer image data. For these reasons few manufacturers of industrial cameras have ventured into this standard. (Scientific and astronomical cameras are a different matter of course because they don’t need high data rates.) The maximum cable length of 5m can also be bothersome in many applications.

And then there’s FireWire, IEEE1394, to use its proper name. 1394 cameras, which need no framegrabber and take their power – up to 45W – from the single cable, come in two flavors, a) and b), the difference being speed. Roughly speaking, a) handles 400Mbps while b) hits 800Mbps. That’s more than enough for a 2Mp camera running at 5 fps, so what’s the problem?

Well first, cable length is limited to 4.5m, which can get to be a problem in even the simplest of industrial settings. Second, and I’m speaking from personal experience here, it’s just not totally reliable. I’m not up in all the details of error detection methodologies, but it’s my understanding that 1394 doesn’t have any. That means a frame can be dropped and you’ll never know. Now in many applications that might not be a problem, but if you need to be 100% confident in your system, think carefully before going this way.

That brings us to GigE, strictly speaking, GigE Vision. This uses plain old network cabling, though you should upgrade to the better shielded CAT 6, to transmit up to 1Gbps of image data as far as 100m. You will need to buy a special purpose card for your PC – the regular network card can probably not handle Jumbo Frames and in any case, you need it for internet and intranet access – but these are far less expensive than a CameraLink grabber. And if power cabling is a concern, Power-over-Ethernet (PoE) will deliver up to 13W – enough for most cameras.

Downsides? Well really, just the fact that you’re limited to 1Gbps, which is more than FireWire b) can offer, so it’s enough for run-of-the-mill applications.

As for resolutions going up, well you knew that already, didn’t you?

Advice on selecting a camera – how many pixels?

You’re new to machine vision. You know you’ll need a camera and lens, but when you open the Edmund Optics catalog (or start surfing the web,) you’re overwhelmed by the options. So, in keeping with my mission of providing practical advice to machine vision users, here are a few tips:

The task dictates the hardware. Don’t buy a camera because you like the color, because there’s a pretty girl in the catalog or because it has more megapixels for the buck than any other camera. Start with the task.

Define the field of view – the area that you need to image. Don’t worry about fitting it to the proportions of the sensor (16:9, 4:3 or whatever,) just determine length and width, or diameter if that’s more appropriate. (Incidentally, I prefer to work in metric units – I just find it makes life easier.)

Now, a word of caution: Never plan on using every pixel in the sensor. This is because optical distortion and a fall-off in light intensity make the border pixels less reliable. To avoid using these I suggest adding 10% to the longest dimension you need to view, and calling that the field of view.

Now you need to determine the resolution required, in terms of pixels per millimeter. Okay, this can cause some head-scratching so let’s dive a little deeper.

The drivers for pixels per millimeter are either the smallest feature you need to detect, OR the required measurement resolution. If you need to check the presence of a screw in an assembly, then the smallest feature you need to find is that screw head. But how many pixels does it take to do that?

People have tried to apply some science to the business of how many pixels make a feature detectable but I prefer to rely on old-fashioned heuristics. (That’s “rule-of-thumb” to you!) The absolute minimum number of pixels needed to find a feature is a square measuring 3 pixels by 3. But, if it’s a circular feature you need to find this can result in only the center pixel fully covering the feature. The border pixels will have a grayscale value partway between that of the feature and the background, making detectability difficult. Thus 4 by 4 pixels is better and 5 by 5 better still.

Now, how about measurement resolution? Without going in to how an edge is detected, let’s just say that calculation of edge location depends on the gray levels of the surrounding pixels. And you can’t assume that the edge lines up neatly with the pixels; you’ll never have a white pixel adjacent to a black pixel – there will always be one or two shades of gray in between. So my heuristic for edge detection is that the uncertainty in the measurement will always be 3 pixels.

But before you apply that to the tolerance on the part print, remember this: you almost certainly have two edges to find in your image, so the total uncertainty is 6 pixels, not 3. And how is this related to the part tolerance? Well opinions vary, but I suggest that the measurement uncertainty should be no more than 10% of the tolerance on the dimension. So if you’re measuring a feature that should be 25mm +/- 0.6mm, (I picked those numbers to make the arithmetic easier,) the uncertainty should be 0.060mm, meaning that you’ll want each pixel to span 0.010mm.

 

And with that number, you can calculate how many pixels are needed to image your field of view.

A warning about camera voltages

I noticed a message recently on the AVT website that I thought I should share with you. This related to some older models of Prosilica camera that had an upper voltage limit of 16V. Apparently they’ve now realized that this might not be particularly smart, and have modified newer product to accept 24V. (Here’s a link to the pdf of their announcement.)

If you’re wondering why this is a problem, consider this: pretty much all factory automation runs on 24V. Controls guys, maintenance techs and other plant people tend to assume they can put 24V on all shop floor technology, so it’s understandable that they’d do it to a Prosilica camera. In fact it was probably a nice moneymaker for the repair side of the business, so kudos to AVT for fixing the problem.

It does however beg some questions:

1. How many other cameras are limited to less than 24V?
2. Can older cameras be retrofitted, and will AVT be issuing a recall?
3. Do all those people who paid for repairs to their Prosilica cameras now get refunds? I’m no lawyer but making the design change would seem to imply they recognize there was a design flaw.

Now I’m off to check on all our other cameras.

M&A news

Guppy, Marlin, Pike, Stingray – someone at AVT clearly has a penchant for fishy names. Such a pity then that Dalsa have the Piranha because that would have made a great mascot for the acquisitive German camera company.

The Piranha is of course a voracious carnivore, gobbling up smaller competitors, and that’s what AVT have done with their purchase of VDS Vosskühler. This comes on the heels of the Prosilica acquisition a couple of years back and seems like it should be a good fit. VDS works mainly in the infrared while AVT products are all intended for visible light imaging. I suspect that VDS will also bring some significant technical expertise, so this will only strengthen AVT’s competitive position.

I’d like to claim that I had foreshadowed this in my January 20th posting, “Too many camera manufacturers?” but in all honestly I will admit that VDS wasn’t on my list of mainstream machine vision camera companies. I would like to think though that it shows I have my finger on the pulse of our industry.

Check back soon for my next prediction!

Learning about cameras

Most users of machine vision don’t care too much about how a camera works, just so long as it works, and does so day-in, day-out, without fail, so classes on CCD and CMOS camera technology may not be of much interest. But those of my readers working at the sharp end of camera design and development may want to follow these links.

Fundamentals of CCD and CMOS Imagers and Camera Systems

Applications, Design, and Testing of CMOS and CCD Sensors and Camera Systems

These classes, each of two days, are being put on by the UCLA Extension program, and take place over the period February 28th to March 3rd 2011 in Los Angeles, California. I’ve found it difficult to track down programs that give more than a superficial overview of aspects of imaging technology, so if you could benefit from a more thorough understanding, talk to your boss about these classes.

Don’t forget, the weather’s pretty nice in LA at the end of February too, certainly sunnier than northern Europe or the frozen Midwest, so send me a postcard!

Help with camera selection

Canadian camera manufacturer Point Grey has launched a “Camera Selector Tool” on their website. I applaud the thinking behind this; it’s difficult to figure out which is the best camera for a given application, but I have my doubts about the way this tool has been executed.

The deficiency I observe is that the selection options are all based around camera specifications – model of sensor, type of interface and so on. Now many of us care little about the sensor employed; we just need the camera to work in our application.

What I suggest is needed is a camera guide that takes as inputs details of the task to be performed – field of view and resolution needed, velocity of target and so on – and then outputs a list of cameras that might do the job.

As far as I know, such a “smart” guide doesn’t exist, so perhaps this is an opportunity for some handy programmer to make a name for him or herself.

Incidentally, National Instruments do have their “Camera Advisor,” but that suffers the same weakness of being product rather than application oriented.

Opportunity is knocking.

A lot of pixels in a very small space

That’s what you get with the USB UI-1008XS camera from IDS. This little baby squeezes an 8Megapixel Sony CMOS sensor AND a DSP chip into a one inch cube. And if that’s not good enough for you, there’s an integrated lens with autofocus and even face detection.

Face detection? Yes, I scratched my head over that. I don’t have a lot of industrial applications that need face detection, but there again I tend not to use USB cameras in my applications. Could this be aimed at the security market?

By the way, if you don’t know IDS I would encourage you to visit their website, (which is where I lifted the photo of the diminutive 8Mp USB camera.) They have a fascinating range of USB and GigE camera offerings.

New products from Point Grey

Here’s something I missed in all the clamor around Vision 2009: Point Grey have several interesting new cameras on the way. (Memo to the guys in Richmond, British Columbia: SHOUT LOUDER!)

Okay, the new Grasshopper®2 and Flea®3 don’t set my world on fire, but the Grasshopper Express™ with USB3.0 interface is very interesting, as is the Gazelle™.

The Grasshopper Express™ offers the promise of 2.8 Mp images at 50fps (USB3.0) from a Sony CCD sensor: I can think of quite a few uses for that. The Gazelle™ does even better with 6.2 Mp at 60 fps. Now that I find incredible, although it is using the Sony IMX067 CMOS sensor, which might be a bit of a dampener.

Too early to know about pricing, but my guess is that the Grasshopper Express™ will be under $3,000 and the Gazelle™ perhaps around $5,000. Definitely very competitive products.

Another newbie

Actually I’m not sure just how new Rice Camera Technologies is, but they’re new to me. Based in Billerica, Massachusetts, they offer a large range of matrix, or area, GigE and CameraLink cameras for machine vision and military applications.

At the moment these appear to be private labeled cameras from SVS-Vistek, but the job opening for a Camera Design Engineer would imply that they want to develop their own product line up as quickly as possible.

I just wonder how Jay Rice is going to differentiate his cameras from the plethora of such products in the marketplace.