Monday, January 27, 2014

USB3 Vision: A force not to be reckoned with

The birth of modern vision industry happened during the 90s computer boom . With personal computer becoming cheaper and faster during that era, running machine vision algorithm no longer requires expensive investment in hardware development such as DSP and FPGA. Back then machine vision related companies were mushrooming in every corner of the developed world.

The digital evolution of industrial camera is fuelled by the ever growing appetite for higher resolution and faster frame rate. The machine vision industry looks towards digital interface when traditional analogue standards can no longer coped with the increasing demand.

During that period, with no single standard digital format, interoperability was near impossible. In October 2000, the very first digital standard known as Camera Link was introduced. It was, and still is, an expensive technology, but semiconductor equipment makers embraced it quickly as the need for quality inspection technologies exceed the cost it incurred. Unnoticeable by some, the Camera Link standard has actually fired off the first servo in the race for dominance in the digital age of modern machine vision .

Within a year after the induction of Camera Link, Pointgrey and AVT pioneered the firewire standard (1394A) developing range of successful low cost digital format cameras for the industry. The salient of this new technological front are AVT’s Dolphin series and Pointgrey’s Firefly series. Almost immediately, these cameras enter the industry like a welcoming storm from a long drought, shaking up the mainstream and low end machine market. Applications that require higher resolution and yet at a lower speed now have an alternative solution, Firewire instead of Camera Link. With the success of Firewire, industry innovators are now in two camps. With one camp tirelessly looking into high end dedicated imaging interfaces (deriving today HS-link and Coaxpress standard), predicting that this is the future industry needs.  While the other believes that there should be a low cost solution and ploughs ahead with commercial standards.

In 2006, the GigE Vision standard was inaugurated; it provided a much larger bandwidth and at the same time eliminated the limitation of cabling distance of firewire technology. Among the early adopters of this technology was Basler. The Basler Pilot series with Kodak sensor together with their Scout series with Sony sensor was first introduced in 2006. The impact of GigE Vision became apparent when Basler launches her Ace product near the end of 2009. Its success lies not only in her indigenous design but also the strategic alliances with major industry partners such as National Instruments and Cognex .

Today, USB3 Vision emerged as the new mainstream digital standard. Unlike its predecessors (GigE Vision and Firewire), USB3 Vision is more than a replacement technology for the earlier mainstream market. It has the great potential to penetrate into the untouchable high end area scan market that had been continuously dominated by Camera Link technology for the last 10 years.

Camera Link Base interfaces with a bandwidth of 255Mbyte/sec makes up the major demand for area scan Camera Link market. USB3 Vision with its 400Mbyte/sec bandwidth provides a competitive alternative to Camera Link Base. There is one major drawback in earlier technology such as GigE or Firewire, CPU loading for camera acquisition gets significant with increasing amount of data steamed to PC. USB3 is different from such earlier consumer technology, thanks to the use of DMA (Direct Memory Access), CPU loading becomes negligible.

Camera Link Base
GigE Vision
USB3 Vision
CPU Loading
Triggering Concurrency on multiple cameras

Most OEM equipment makers are now keeping a keen eye on this technology and are seeking for the perfect moment to adopt the change. In 2 to 3 years time, the proliferation of USB 3.0 hardware on PC will become prevalence and in tandem, development in the consumers industry is working towards an overwhelming bandwidth of 10GB/s with USB 3.5. Already a Taiwanese chip maker, ASMedia, has planned to release her first USB 3.5 host controller by 2014. There are definitely plenty of rooms for improvement in the USB vision technology. A whole new world will emerge for machine vision as the evolution of USB technology in the consumer industry continues to advance. It is indeed an exciting time for the future of the industry.

Tuesday, January 21, 2014

IMX174, Sony's ground-breaking global shutter CMOS sensor for machine vision

Without a shadow of a doubt, Sony is among the big names in the imaging sensor industry. In the dusk of 2013, it releases its first global shutter CMOS sensor IMX174. With its Exmor CMOS technology, it possess unprecedented dynamic range of more than 70dB as a CMOS sensor. Fix pattern noise that is commonly found on CMOS is basically non existence. The read noise is exceptionally low with only ~6 electrons. Coupled with its large pixel size of 5.68um, this sensor is extremely sensitive to light and it deliver up to a maximum of ~160fps at 1920 x 1200 resolutions.

In the past, KAI series sensor based cameras from Truesense have always been the obvious choice for most OEM equipment makers that have requirement less than 4 Mpx resolution in high speed (~50 to >100fps) defects inspection.  The wind of change is blowing, with the prevailing Exmor technology from IMX174 even the most recent KAI-2170 Truesense sensor is being eclipsed by this Sony technology .

Linear Dynamic Range (est)
Read Noise
12 e
6.83 e
Full Well
Pixel Size
7.4 x 7.4 um
5.68 x 5.68um
Maximum Quantum efficiency
52% @ 500nm
76% @525nm
1920 x 1080
1920 x 1200
Maximum frame rate
Quad Output @ 60 fps
8 LVDS Output @ ~160fps
Interline CCD; Progressive Scan
Exmor CMOS read out technology
68 pin PGA
118pin - LGA

It is unfortunate that current IMX174 sensor based cameras only comes with USB3.0 interface (Pointgrey). Market adaptation to this interface is still uncommon due to various reasons. Most OEM equipment makers at this moment still prefer the traditional Cameralink technology. 

Existing machine vision lighting and lens technology prove to be sufficient when working with Truesense based cameras. There is no pressing need at this moment to address the sensitivity or the dynamic range issues on existing equipment.

Also, if IMX174 serves only machine vision application it will do no justice to the specification it possess. The wide dynamic range in combination of its HD format, delineate a perfect blueprint for high end outdoor daylight camera.

IMX174 is an excellent product and the landscape for less than 4Mpx industry cameras will definitely be redefined. 

Monday, January 20, 2014

CMOS technology that equals CCD image quality

Traditional machine vision imaging had been dominated by the CCD technology. CMOS was used either in simple inspections or very specialize applications that usually uses rolling shutters.

The CMV4000 image sensor introduced by CMOSIS changes the believe that CMOS sensors are low in dynamic range and noisy. CMV4000 is a highly sensitive global shutter CMOS image sensor with pixel size of 5um and a resolution of 2048 x 2048.

Based on an eight transistor pixel architecture, its state of the art correlated double sampling (CDS) reduces the dark current noise and fixed pattern noise.

It is high speed, with 16LVDS output @ 480Mhz, this equates to about 180 frame per seconds at full frame rate. At about 60dB, its dynamic range tails tightly behind the high end CCD sensor. There is no doubt that CMOSIS have set a new bar for the imaging industry.