Sunday, December 10, 2017

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USB3.0 Challenges Mainstream Camera Interfaces

Courtesy of Andy Wilson, Editor in Chief, Vision Systems Design

The dizzying number of competing camera interface standards might leave many engineers wondering which one, if any, might emerge over the next few years as a clear leader. For Arndt Bake, COO at Basler (Ahrensburg, Germany; www.baslerweb.com), the choice is clear - USB 3.0, and its faster successor USB 3.1, will start to dominate the world of computer vision after 2020.

Bake explains that his company views the camera market in three segments - high end, mainstream and entry level. At present, each of these segments is served by a number of camera interface standards.

USB 2.0 - an interface standard widely used in the computer peripheral market is capable of an effective throughput of 280Mbit/sec, Bake claims, will be superseded by the new "superspeed" USB 3.0 interface which, with its faster 4Gbit/s data rate, will dominate the entry level market and take a substantial share of the mainstream market. Not only that, but

Bake also believes that cameras based on the new "superspeed" USB 3.0 will totally replace those based on the Firewire standard by the year 2020, despite the fact that the latest incarnation of the Firewire specification (IEEE 1394-2008) can theoretically deliver an effective throughput of up to 3.2 Gbits/s - speeds that could potentially mean that the standard would compete directly with USB 3.0. Bake believes, however, that USB will dominate the market, due to its high bandwidth and its cost which will reduce as the number of consumer products that adopt it increases.

At the top end of the mainstream camera market, the dominant computer to camera interface at the present time is Camera Link, which is offered in Base, Medium, Full and Extended Full configurations with data transfer speeds of up to 6.8Gbits/s. However, Bake thinks that, over the long haul, even the Camera Link standard will face stiff competition from USB, since once the newer USB 3.1 standard is adopted, with its data transfer speeds up to 10Gbit/s, many existing Camera Link applications will migrate to this standard.

At the very high-end, Bake admits that one camera interface standard - CoaXPress - has come to dominate, having stolen the thunder from the competing Camera Link HS standard which has failed to gain a foothold. But CoaXPress is a standard that he believes will also eventually come under threat from USB 3.1. At the present time, the CoaXPress interface enables cameras to be connected to frame grabbers at bit rates from 1.25 Gbit/s to 6.25 Gbit/s per cable - up to 25Gbit/s if systems integrators employ frame grabbers and cameras with four cables. At 10Gbit/s, however, USB 3.1 could mean that all but those computer vision systems that demand the very highest speed could find themselves using a USB interface.

To enable its customers to quickly upgrade their camera-based systems from one interface standard to another, Basler has developed a suite of software called Pylon. Based on the GenApi module of the GenICam reference implementation, it offers a single generic programming interface for programming the functionality of any Basler camera with a Windows or Linux PC. No matter what interface technology the cameras are using or what features they are implementing, the application programming interface (API) remains the same, easing the task of the systems integrator.

For its part, Basler appears to have no intentions, at present time at least, to compete in the high end camera market served by CoaXPress. Its position is to continue to serve its customers in the mainstream factory automation, ITS and medical and life sciences fields. To do so, it will consolidate its position supporting the Camera Link and GigE interfaces while looking to the future by developing a suite of USB based cameras.

 

 


Evaluating Machine Vision Cameras versus Comparing Camera Specification Documents

Evaluating Machine Vision Cameras versus Comparing Camera Specification Documents

 

Many of our customers ask us how they should evaluate cameras in order to find the best solution for their application. There are several reasons why we feel the Photon Transfer Curve (PTC) is useful, especially if you are trying to get the most out of your imaging system such as when detecting small differences between images or using the pixel information as data for measurements. We have shared some detailed information on how to measure the Photon Transfer Curve for CCD or CMOS machine vision cameras because we feel it is an important part of camera evaluation and selection.

Camera vendors provide a lot of detailed specifications about their cameras, but as we have discussed it is challenging to connect all of the camera specifications to the image details you require and to know how the camera will perform under your system settings.  The biggest advantage of measuring the Photon Transfer Curve of different cameras yourself is that you can verify the camera performance with your own equipment and environment such as integration time, illumination conditions (continuous/strobed, spectral range), optics, filters, etc. which can all have an effect on the performance.  You are then not only comparing cameras under the same conditions, but also comparing them under conditions that are relevant to your system/application.

Should you have some questions about how to perform the measurements, there are many resources or courses available. 

As you could read in an earlier blog, the EMVA 1288 standard provides details on how to accurately measure many camera parameters in a controlled environment.  This can be very useful for camera manufacturers as guidelines to present specifications or for qualifying cameras during development. (Note that the Photon Transfer Curve is measured by EMVA 1288 too!)

But instead of using the EMVA 1288 test setup, you can also use your own system to gather the measurement data needed to construct the PTC and derive important camera parameters like full well capacity, read noise, dynamic range and linearity.

If you are a customer that wants to get the most out of your system, we strongly suggest that you invest in testing and understanding camera performance.

Testing of a camera using your specific imaging conditions may show behavior and image artifacts that are not seen under "standard" conditions that are used during camera testing in the factory of the camera vendor. In practice we've often identified significant differences in camera behavior from different vendors - even between cameras that are using the same image sensor!

There is no camera in the world that that will be an optimal fit for your application.  Your competitive advantage depends on your electro-optical system, measurements algoirthm, etc. being unique.  Therefore, to summarize the top 3 reasons for measuring the PTC are so you can:

  • Verify and compare camera performance under the relevant system conditions.
  • Better communicate questions to the supplier or understand customization requirements.
  • Go beyond megapixels/second to quantify image quality to parameterize the outgoing inspection at the supplier or incoming inspection needed to have consistency in series production. 
 


IVS Imaging is a distributor & manufacturer of machine vision cameras, lenses, cabling, monitors, filters, interface boards & more. IVS is your one stop shop for all your vision needs. IVS Imaging is known across the USA for carrying imaging products from leading manufactures, including Sony Cameras and Accessories, Basler Industrial Cameras, Hitachi Surveillance Cameras, Toshiba Network-based IP Cameras, and Sentech Advanced Digital and OEM cameras. Contact IVS Imaging for all your imaging products, parts, and accessories needs.

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